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Revision 1.162 by root, Mon May 26 03:54:40 2008 UTC vs.
Revision 1.337 by root, Sun Oct 31 20:20:20 2010 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
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);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
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
187	=item unsigned int ev_supported_backends ()	213	=item unsigned int ev_supported_backends ()
188		214
189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	215	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
190	value) compiled into this binary of libev (independent of their	216	value) compiled into this binary of libev (independent of their
…		…
192	a description of the set values.	218	a description of the set values.
193		219
194	Example: make sure we have the epoll method, because yeah this is cool and	220	Example: make sure we have the epoll method, because yeah this is cool and
195	a must have and can we have a torrent of it please!!!11	221	a must have and can we have a torrent of it please!!!11
196		222
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		283
257	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<struct ev_loop *>. The library knows two	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
		311
		312	The library knows two types of such loops, the I<default> loop, which
		313	supports child process events, and dynamically created event loops which
		314	do not.
284		315
285	=over 4	316	=over 4
286		317
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		319
289	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
290	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
291	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
292	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
293		330
294	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
295	function.	332	function (or via the C<EV_DEFAULT> macro).
296		333
297	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
300		338
301	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
302	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
303	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
307		363
308	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		366
311	The following flags are supported:	367	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
327	around bugs.	383	around bugs.
328		384
329	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
330		386
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		389
335	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	399	flag.
345		400
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	402	environment variable.
348		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
		423
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		425
351	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	434	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	435	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	436	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	437	readiness notifications you get per iteration.
363		438
		439	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		440	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		441	C<exceptfds> set on that platform).
		442
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	443	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		444
366	And this is your standard poll(2) backend. It's more complicated	445	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	446	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	447	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	448	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	449	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	450	performance tips.
372		451
		452	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		454
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
374		459
375	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	462	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	463	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	464
380	cases and requiring a system call per fd change, no fork support and bad	465	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	466	of the more advanced event mechanisms: mere annoyances include silently
		467	dropping file descriptors, requiring a system call per change per file
		468	descriptor (and unnecessary guessing of parameters), problems with dup,
		469	returning before the timeout value requiring additional iterations and so
		470	on. The biggest issue is fork races, however - if a program forks then
		471	I<both> parent and child process have to recreate the epoll set, which can
		472	take considerable time (one syscall per file descriptor) and is of course
		473	hard to detect.
		474
		475	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		476	of course I<doesn't>, and epoll just loves to report events for totally
		477	I<different> file descriptors (even already closed ones, so one cannot
		478	even remove them from the set) than registered in the set (especially
		479	on SMP systems). Libev tries to counter these spurious notifications by
		480	employing an additional generation counter and comparing that against the
		481	events to filter out spurious ones, recreating the set when required. Last
		482	not least, it also refuses to work with some file descriptors which work
		483	perfectly fine with C<select> (files, many character devices...).
382		484
383	While stopping, setting and starting an I/O watcher in the same iteration	485	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	486	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	487	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	488	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	489	file descriptors might not work very well if you register events for both
388		490	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		491
393	Best performance from this backend is achieved by not unregistering all	492	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	493	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	494	i.e. keep at least one watcher active per fd at all times. Stopping and
		495	starting a watcher (without re-setting it) also usually doesn't cause
		496	extra overhead. A fork can both result in spurious notifications as well
		497	as in libev having to destroy and recreate the epoll object, which can
		498	take considerable time and thus should be avoided.
		499
		500	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		501	faster than epoll for maybe up to a hundred file descriptors, depending on
		502	the usage. So sad.
396		503
397	While nominally embeddable in other event loops, this feature is broken in	504	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	505	all kernel versions tested so far.
		506
		507	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		508	C<EVBACKEND_POLL>.
399		509
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	510	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		511
402	Kqueue deserves special mention, as at the time of this writing, it	512	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	513	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	514	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	515	it's completely useless). Unlike epoll, however, whose brokenness
		516	is by design, these kqueue bugs can (and eventually will) be fixed
		517	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	518	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	519	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	520	system like NetBSD.
409		521
410	You still can embed kqueue into a normal poll or select backend and use it	522	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	523	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		525
414	It scales in the same way as the epoll backend, but the interface to the	526	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	527	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	528	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	529	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	530	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	531	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		532	cases
420		533
421	This backend usually performs well under most conditions.	534	This backend usually performs well under most conditions.
422		535
423	While nominally embeddable in other event loops, this doesn't work	536	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	537	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	538	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	539	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	540	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	541	also broken on OS X)) and, did I mention it, using it only for sockets.
		542
		543	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		544	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		545	C<NOTE_EOF>.
429		546
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	547	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		548
432	This is not implemented yet (and might never be, unless you send me an	549	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	550	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	563	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	564	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	565	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	566	might perform better.
450		567
451	On the positive side, ignoring the spurious readiness notifications, this	568	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	569	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	570	in all tests and is fully embeddable, which is a rare feat among the
		571	OS-specific backends (I vastly prefer correctness over speed hacks).
		572
		573	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		574	C<EVBACKEND_POLL>.
454		575
455	=item C<EVBACKEND_ALL>	576	=item C<EVBACKEND_ALL>
456		577
457	Try all backends (even potentially broken ones that wouldn't be tried	578	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	579	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		581
461	It is definitely not recommended to use this flag.	582	It is definitely not recommended to use this flag.
462		583
463	=back	584	=back
464		585
465	If one or more of these are or'ed into the flags value, then only these	586	If one or more of the backend flags are or'ed into the flags value,
466	backends will be tried (in the reverse order as listed here). If none are	587	then only these backends will be tried (in the reverse order as listed
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	588	here). If none are specified, all backends in C<ev_recommended_backends
468		589	()> will be tried.
469	The most typical usage is like this:
470
471	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473
474	Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:
476
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478
479	Use whatever libev has to offer, but make sure that kqueue is used if
480	available (warning, breaks stuff, best use only with your own private
481	event loop and only if you know the OS supports your types of fds):
482
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484
485	=item struct ev_loop *ev_loop_new (unsigned int flags)
486
487	Similar to C<ev_default_loop>, but always creates a new event loop that is
488	always distinct from the default loop. Unlike the default loop, it cannot
489	handle signal and child watchers, and attempts to do so will be greeted by
490	undefined behaviour (or a failed assertion if assertions are enabled).
491
492	Note that this function I<is> thread-safe, and the recommended way to use
493	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.
495		590
496	Example: Try to create a event loop that uses epoll and nothing else.	591	Example: Try to create a event loop that uses epoll and nothing else.
497		592
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	593	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	594	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	595	fatal ("no epoll found here, maybe it hides under your chair");
501		596
		597	Example: Use whatever libev has to offer, but make sure that kqueue is
		598	used if available.
		599
		600	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		601
502	=item ev_default_destroy ()	602	=item ev_loop_destroy (loop)
503		603
504	Destroys the default loop again (frees all memory and kernel state	604	Destroys an event loop object (frees all memory and kernel state
505	etc.). None of the active event watchers will be stopped in the normal	605	etc.). None of the active event watchers will be stopped in the normal
506	sense, so e.g. C<ev_is_active> might still return true. It is your	606	sense, so e.g. C<ev_is_active> might still return true. It is your
507	responsibility to either stop all watchers cleanly yourself I<before>	607	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	608	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	609	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	610	for example).
511		611
512	Note that certain global state, such as signal state, will not be freed by	612	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	613	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	614	as signal and child watchers) would need to be stopped manually.
515		615
516	In general it is not advisable to call this function except in the	616	This function is normally used on loop objects allocated by
517	rare occasion where you really need to free e.g. the signal handling	617	C<ev_loop_new>, but it can also be used on the default loop returned by
		618	C<ev_default_loop>, in which case it is not thread-safe.
		619
		620	Note that it is not advisable to call this function on the default loop
		621	except in the rare occasion where you really need to free it's resources.
518	pipe fds. If you need dynamically allocated loops it is better to use	622	If you need dynamically allocated loops it is better to use C<ev_loop_new>
519	C<ev_loop_new> and C<ev_loop_destroy>).	623	and C<ev_loop_destroy>.
520		624
521	=item ev_loop_destroy (loop)	625	=item ev_loop_fork (loop)
522		626
523	Like C<ev_default_destroy>, but destroys an event loop created by an
524	earlier call to C<ev_loop_new>.
525
526	=item ev_default_fork ()
527
528	This function sets a flag that causes subsequent C<ev_loop> iterations	627	This function sets a flag that causes subsequent C<ev_run> iterations to
529	to reinitialise the kernel state for backends that have one. Despite the	628	reinitialise the kernel state for backends that have one. Despite the
530	name, you can call it anytime, but it makes most sense after forking, in	629	name, you can call it anytime, but it makes most sense after forking, in
531	the child process (or both child and parent, but that again makes little	630	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
532	sense). You I<must> call it in the child before using any of the libev	631	child before resuming or calling C<ev_run>.
533	functions, and it will only take effect at the next C<ev_loop> iteration.	632
		633	Again, you I<have> to call it on I<any> loop that you want to re-use after
		634	a fork, I<even if you do not plan to use the loop in the parent>. This is
		635	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		636	during fork.
534		637
535	On the other hand, you only need to call this function in the child	638	On the other hand, you only need to call this function in the child
536	process if and only if you want to use the event library in the child. If	639	process if and only if you want to use the event loop in the child. If
537	you just fork+exec, you don't have to call it at all.	640	you just fork+exec or create a new loop in the child, you don't have to
		641	call it at all (in fact, C<epoll> is so badly broken that it makes a
		642	difference, but libev will usually detect this case on its own and do a
		643	costly reset of the backend).
538		644
539	The function itself is quite fast and it's usually not a problem to call	645	The function itself is quite fast and it's usually not a problem to call
540	it just in case after a fork. To make this easy, the function will fit in	646	it just in case after a fork.
541	quite nicely into a call to C<pthread_atfork>:
542		647
		648	Example: Automate calling C<ev_loop_fork> on the default loop when
		649	using pthreads.
		650
		651	static void
		652	post_fork_child (void)
		653	{
		654	ev_loop_fork (EV_DEFAULT);
		655	}
		656
		657	...
543	pthread_atfork (0, 0, ev_default_fork);	658	pthread_atfork (0, 0, post_fork_child);
544
545	=item ev_loop_fork (loop)
546
547	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.
550		659
551	=item int ev_is_default_loop (loop)	660	=item int ev_is_default_loop (loop)
552		661
553	Returns true when the given loop actually is the default loop, false otherwise.	662	Returns true when the given loop is, in fact, the default loop, and false
		663	otherwise.
554		664
555	=item unsigned int ev_loop_count (loop)	665	=item unsigned int ev_iteration (loop)
556		666
557	Returns the count of loop iterations for the loop, which is identical to	667	Returns the current iteration count for the event loop, which is identical
558	the number of times libev did poll for new events. It starts at C<0> and	668	to the number of times libev did poll for new events. It starts at C<0>
559	happily wraps around with enough iterations.	669	and happily wraps around with enough iterations.
560		670
561	This value can sometimes be useful as a generation counter of sorts (it	671	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	672	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	673	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		674	prepare and check phases.
		675
		676	=item unsigned int ev_depth (loop)
		677
		678	Returns the number of times C<ev_run> was entered minus the number of
		679	times C<ev_run> was exited, in other words, the recursion depth.
		680
		681	Outside C<ev_run>, this number is zero. In a callback, this number is
		682	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		683	in which case it is higher.
		684
		685	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		686	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		687	ungentleman-like behaviour unless it's really convenient.
564		688
565	=item unsigned int ev_backend (loop)	689	=item unsigned int ev_backend (loop)
566		690
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	691	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	692	use.
…		…
573	received events and started processing them. This timestamp does not	697	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	698	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	699	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	700	event occurring (or more correctly, libev finding out about it).
577		701
		702	=item ev_now_update (loop)
		703
		704	Establishes the current time by querying the kernel, updating the time
		705	returned by C<ev_now ()> in the progress. This is a costly operation and
		706	is usually done automatically within C<ev_run ()>.
		707
		708	This function is rarely useful, but when some event callback runs for a
		709	very long time without entering the event loop, updating libev's idea of
		710	the current time is a good idea.
		711
		712	See also L<The special problem of time updates> in the C<ev_timer> section.
		713
		714	=item ev_suspend (loop)
		715
		716	=item ev_resume (loop)
		717
		718	These two functions suspend and resume an event loop, for use when the
		719	loop is not used for a while and timeouts should not be processed.
		720
		721	A typical use case would be an interactive program such as a game: When
		722	the user presses C<^Z> to suspend the game and resumes it an hour later it
		723	would be best to handle timeouts as if no time had actually passed while
		724	the program was suspended. This can be achieved by calling C<ev_suspend>
		725	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		726	C<ev_resume> directly afterwards to resume timer processing.
		727
		728	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		729	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		730	will be rescheduled (that is, they will lose any events that would have
		731	occurred while suspended).
		732
		733	After calling C<ev_suspend> you B<must not> call I<any> function on the
		734	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		735	without a previous call to C<ev_suspend>.
		736
		737	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		738	event loop time (see C<ev_now_update>).
		739
578	=item ev_loop (loop, int flags)	740	=item ev_run (loop, int flags)
579		741
580	Finally, this is it, the event handler. This function usually is called	742	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	743	after you have initialised all your watchers and you want to start
582	events.	744	handling events. It will ask the operating system for any new events, call
		745	the watcher callbacks, an then repeat the whole process indefinitely: This
		746	is why event loops are called I<loops>.
583		747
584	If the flags argument is specified as C<0>, it will not return until	748	If the flags argument is specified as C<0>, it will keep handling events
585	either no event watchers are active anymore or C<ev_unloop> was called.	749	until either no event watchers are active anymore or C<ev_break> was
		750	called.
586		751
587	Please note that an explicit C<ev_unloop> is usually better than	752	Please note that an explicit C<ev_break> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	753	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	754	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	755	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	756	of relying on its watchers stopping correctly, that is truly a thing of
		757	beauty.
592		758
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	759	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	760	those events and any already outstanding ones, but will not wait and
595	case there are no events and will return after one iteration of the loop.	761	block your process in case there are no events and will return after one
		762	iteration of the loop. This is sometimes useful to poll and handle new
		763	events while doing lengthy calculations, to keep the program responsive.
596		764
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	765	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	766	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	767	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	768	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	769	user-registered callback will be called), and will return after one
		770	iteration of the loop.
		771
		772	This is useful if you are waiting for some external event in conjunction
		773	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	774	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	775	usually a better approach for this kind of thing.
604		776
605	Here are the gory details of what C<ev_loop> does:	777	Here are the gory details of what C<ev_run> does:
606		778
		779	- Increment loop depth.
		780	- Reset the ev_break status.
607	- Before the first iteration, call any pending watchers.	781	- Before the first iteration, call any pending watchers.
		782	LOOP:
608	* If EVFLAG_FORKCHECK was used, check for a fork.	783	- If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	784	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	785	- Queue and call all prepare watchers.
		786	- If ev_break was called, goto FINISH.
611	- If we have been forked, recreate the kernel state.	787	- If we have been forked, detach and recreate the kernel state
		788	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	789	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	790	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	791	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	792	(active idle watchers, EVRUN_NOWAIT or not having
616	any active watchers at all will result in not sleeping).	793	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	794	- Sleep if the I/O and timer collect interval say so.
		795	- Increment loop iteration counter.
618	- Block the process, waiting for any events.	796	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	797	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	798	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	799	- Queue all expired timers.
622	- Queue all outstanding periodics.	800	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	801	- Queue all idle watchers with priority higher than that of pending events.
624	- Queue all check watchers.	802	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	803	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	804	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	805	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	806	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
629	were used, or there are no active watchers, return, otherwise	807	were used, or there are no active watchers, goto FINISH, otherwise
630	continue with step *.	808	continue with step LOOP.
		809	FINISH:
		810	- Reset the ev_break status iff it was EVBREAK_ONE.
		811	- Decrement the loop depth.
		812	- Return.
631		813
632	Example: Queue some jobs and then loop until no events are outstanding	814	Example: Queue some jobs and then loop until no events are outstanding
633	anymore.	815	anymore.
634		816
635	... queue jobs here, make sure they register event watchers as long	817	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	818	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	819	ev_run (my_loop, 0);
638	... jobs done. yeah!	820	... jobs done or somebody called unloop. yeah!
639		821
640	=item ev_unloop (loop, how)	822	=item ev_break (loop, how)
641		823
642	Can be used to make a call to C<ev_loop> return early (but only after it	824	Can be used to make a call to C<ev_run> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	825	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	826	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	827	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
646		828
647	This "unloop state" will be cleared when entering C<ev_loop> again.	829	This "break state" will be cleared when entering C<ev_run> again.
		830
		831	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
648		832
649	=item ev_ref (loop)	833	=item ev_ref (loop)
650		834
651	=item ev_unref (loop)	835	=item ev_unref (loop)
652		836
653	Ref/unref can be used to add or remove a reference count on the event	837	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	838	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	839	count is nonzero, C<ev_run> will not return on its own.
656	a watcher you never unregister that should not keep C<ev_loop> from	840
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	841	This is useful when you have a watcher that you never intend to
		842	unregister, but that nevertheless should not keep C<ev_run> from
		843	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		844	before stopping it.
		845
658	example, libev itself uses this for its internal signal pipe: It is not	846	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	847	is not visible to the libev user and should not keep C<ev_run> from
660	no event watchers registered by it are active. It is also an excellent	848	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	849	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	850	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	851	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	852	before, respectively. Note also that libev might stop watchers itself
		853	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		854	in the callback).
665		855
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	856	Example: Create a signal watcher, but keep it from keeping C<ev_run>
667	running when nothing else is active.	857	running when nothing else is active.
668		858
669	struct ev_signal exitsig;	859	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	860	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	861	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	862	evf_unref (loop);
673		863
674	Example: For some weird reason, unregister the above signal handler again.	864	Example: For some weird reason, unregister the above signal handler again.
675		865
676	ev_ref (loop);	866	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	867	ev_signal_stop (loop, &exitsig);
678		868
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	869	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		870
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	871	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		872
683	These advanced functions influence the time that libev will spend waiting	873	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	874	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	875	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		876	latency.
686		877
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	878	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	879	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	880	to increase efficiency of loop iterations (or to increase power-saving
		881	opportunities).
690		882
691	The background is that sometimes your program runs just fast enough to	883	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	884	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	885	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	886	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	887	overhead for the actual polling but can deliver many events at once.
696		888
697	By setting a higher I<io collect interval> you allow libev to spend more	889	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	890	time collecting I/O events, so you can handle more events per iteration,
699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	891	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	892	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	893	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		894	sleep time ensures that libev will not poll for I/O events more often then
		895	once per this interval, on average.
702		896
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	897	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	898	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	899	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	900	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	901	value will not introduce any overhead in libev.
708		902
709	Many (busy) programs can usually benefit by setting the I/O collect	903	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	904	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	905	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	906	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	907	as this approaches the timing granularity of most systems. Note that if
		908	you do transactions with the outside world and you can't increase the
		909	parallelity, then this setting will limit your transaction rate (if you
		910	need to poll once per transaction and the I/O collect interval is 0.01,
		911	then you can't do more than 100 transactions per second).
714		912
		913	Setting the I<timeout collect interval> can improve the opportunity for
		914	saving power, as the program will "bundle" timer callback invocations that
		915	are "near" in time together, by delaying some, thus reducing the number of
		916	times the process sleeps and wakes up again. Another useful technique to
		917	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		918	they fire on, say, one-second boundaries only.
		919
		920	Example: we only need 0.1s timeout granularity, and we wish not to poll
		921	more often than 100 times per second:
		922
		923	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		924	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		925
		926	=item ev_invoke_pending (loop)
		927
		928	This call will simply invoke all pending watchers while resetting their
		929	pending state. Normally, C<ev_run> does this automatically when required,
		930	but when overriding the invoke callback this call comes handy. This
		931	function can be invoked from a watcher - this can be useful for example
		932	when you want to do some lengthy calculation and want to pass further
		933	event handling to another thread (you still have to make sure only one
		934	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		935
		936	=item int ev_pending_count (loop)
		937
		938	Returns the number of pending watchers - zero indicates that no watchers
		939	are pending.
		940
		941	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		942
		943	This overrides the invoke pending functionality of the loop: Instead of
		944	invoking all pending watchers when there are any, C<ev_run> will call
		945	this callback instead. This is useful, for example, when you want to
		946	invoke the actual watchers inside another context (another thread etc.).
		947
		948	If you want to reset the callback, use C<ev_invoke_pending> as new
		949	callback.
		950
		951	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		952
		953	Sometimes you want to share the same loop between multiple threads. This
		954	can be done relatively simply by putting mutex_lock/unlock calls around
		955	each call to a libev function.
		956
		957	However, C<ev_run> can run an indefinite time, so it is not feasible
		958	to wait for it to return. One way around this is to wake up the event
		959	loop via C<ev_break> and C<av_async_send>, another way is to set these
		960	I<release> and I<acquire> callbacks on the loop.
		961
		962	When set, then C<release> will be called just before the thread is
		963	suspended waiting for new events, and C<acquire> is called just
		964	afterwards.
		965
		966	Ideally, C<release> will just call your mutex_unlock function, and
		967	C<acquire> will just call the mutex_lock function again.
		968
		969	While event loop modifications are allowed between invocations of
		970	C<release> and C<acquire> (that's their only purpose after all), no
		971	modifications done will affect the event loop, i.e. adding watchers will
		972	have no effect on the set of file descriptors being watched, or the time
		973	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		974	to take note of any changes you made.
		975
		976	In theory, threads executing C<ev_run> will be async-cancel safe between
		977	invocations of C<release> and C<acquire>.
		978
		979	See also the locking example in the C<THREADS> section later in this
		980	document.
		981
		982	=item ev_set_userdata (loop, void *data)
		983
		984	=item ev_userdata (loop)
		985
		986	Set and retrieve a single C<void *> associated with a loop. When
		987	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		988	C<0.>
		989
		990	These two functions can be used to associate arbitrary data with a loop,
		991	and are intended solely for the C<invoke_pending_cb>, C<release> and
		992	C<acquire> callbacks described above, but of course can be (ab-)used for
		993	any other purpose as well.
		994
715	=item ev_loop_verify (loop)	995	=item ev_verify (loop)
716		996
717	This function only does something when C<EV_VERIFY> support has been	997	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	998	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	999	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	1000	is found to be inconsistent, it will print an error message to standard
		1001	error and call C<abort ()>.
721		1002
722	This can be used to catch bugs inside libev itself: under normal	1003	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	1004	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	1005	data structures consistent.
725		1006
726	=back	1007	=back
727		1008
728		1009
729	=head1 ANATOMY OF A WATCHER	1010	=head1 ANATOMY OF A WATCHER
730		1011
		1012	In the following description, uppercase C<TYPE> in names stands for the
		1013	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1014	watchers and C<ev_io_start> for I/O watchers.
		1015
731	A watcher is a structure that you create and register to record your	1016	A watcher is an opaque structure that you allocate and register to record
732	interest in some event. For instance, if you want to wait for STDIN to	1017	your interest in some event. To make a concrete example, imagine you want
733	become readable, you would create an C<ev_io> watcher for that:	1018	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1019	for that:
734		1020
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1021	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	1022	{
737	ev_io_stop (w);	1023	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	1024	ev_break (loop, EVBREAK_ALL);
739	}	1025	}
740		1026
741	struct ev_loop *loop = ev_default_loop (0);	1027	struct ev_loop *loop = ev_default_loop (0);
		1028
742	struct ev_io stdin_watcher;	1029	ev_io stdin_watcher;
		1030
743	ev_init (&stdin_watcher, my_cb);	1031	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1032	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	1033	ev_io_start (loop, &stdin_watcher);
		1034
746	ev_loop (loop, 0);	1035	ev_run (loop, 0);
747		1036
748	As you can see, you are responsible for allocating the memory for your	1037	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	1038	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	1039	stack).
751		1040
		1041	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1042	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1043
752	Each watcher structure must be initialised by a call to C<ev_init	1044	Each watcher structure must be initialised by a call to C<ev_init (watcher
753	(watcher *, callback)>, which expects a callback to be provided. This	1045	*, callback)>, which expects a callback to be provided. This callback is
754	callback gets invoked each time the event occurs (or, in the case of I/O	1046	invoked each time the event occurs (or, in the case of I/O watchers, each
755	watchers, each time the event loop detects that the file descriptor given	1047	time the event loop detects that the file descriptor given is readable
756	is readable and/or writable).	1048	and/or writable).
757		1049
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1050	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	1051	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	1052	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	1053	ev_TYPE_init (watcher *, callback, ...) >>.
762		1054
763	To make the watcher actually watch out for events, you have to start it	1055	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1056	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	1057	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1058	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		1059
768	As long as your watcher is active (has been started but not stopped) you	1060	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	1061	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	1062	reinitialise it or call its C<ev_TYPE_set> macro.
771		1063
772	Each and every callback receives the event loop pointer as first, the	1064	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	1065	registered watcher structure as second, and a bitset of received events as
774	third argument.	1066	third argument.
775		1067
…		…
784	=item C<EV_WRITE>	1076	=item C<EV_WRITE>
785		1077
786	The file descriptor in the C<ev_io> watcher has become readable and/or	1078	The file descriptor in the C<ev_io> watcher has become readable and/or
787	writable.	1079	writable.
788		1080
789	=item C<EV_TIMEOUT>	1081	=item C<EV_TIMER>
790		1082
791	The C<ev_timer> watcher has timed out.	1083	The C<ev_timer> watcher has timed out.
792		1084
793	=item C<EV_PERIODIC>	1085	=item C<EV_PERIODIC>
794		1086
…		…
812		1104
813	=item C<EV_PREPARE>	1105	=item C<EV_PREPARE>
814		1106
815	=item C<EV_CHECK>	1107	=item C<EV_CHECK>
816		1108
817	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1109	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
818	to gather new events, and all C<ev_check> watchers are invoked just after	1110	to gather new events, and all C<ev_check> watchers are invoked just after
819	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1111	C<ev_run> has gathered them, but before it invokes any callbacks for any
820	received events. Callbacks of both watcher types can start and stop as	1112	received events. Callbacks of both watcher types can start and stop as
821	many watchers as they want, and all of them will be taken into account	1113	many watchers as they want, and all of them will be taken into account
822	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1114	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
823	C<ev_loop> from blocking).	1115	C<ev_run> from blocking).
824		1116
825	=item C<EV_EMBED>	1117	=item C<EV_EMBED>
826		1118
827	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1119	The embedded event loop specified in the C<ev_embed> watcher needs attention.
828		1120
829	=item C<EV_FORK>	1121	=item C<EV_FORK>
830		1122
831	The event loop has been resumed in the child process after fork (see	1123	The event loop has been resumed in the child process after fork (see
832	C<ev_fork>).	1124	C<ev_fork>).
833		1125
		1126	=item C<EV_CLEANUP>
		1127
		1128	The event loop is about to be destroyed (see C<ev_cleanup>).
		1129
834	=item C<EV_ASYNC>	1130	=item C<EV_ASYNC>
835		1131
836	The given async watcher has been asynchronously notified (see C<ev_async>).	1132	The given async watcher has been asynchronously notified (see C<ev_async>).
		1133
		1134	=item C<EV_CUSTOM>
		1135
		1136	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1137	by libev users to signal watchers (e.g. via C<ev_feed_event>).
837		1138
838	=item C<EV_ERROR>	1139	=item C<EV_ERROR>
839		1140
840	An unspecified error has occurred, the watcher has been stopped. This might	1141	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	1142	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	1143	ran out of memory, a file descriptor was found to be closed or any other
		1144	problem. Libev considers these application bugs.
		1145
843	problem. You best act on it by reporting the problem and somehow coping	1146	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	1147	watcher being stopped. Note that well-written programs should not receive
		1148	an error ever, so when your watcher receives it, this usually indicates a
		1149	bug in your program.
845		1150
846	Libev will usually signal a few "dummy" events together with an error,	1151	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	1152	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	1153	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	1154	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	1155	programs, though, as the fd could already be closed and reused for another
		1156	thing, so beware.
851		1157
852	=back	1158	=back
853		1159
854	=head2 GENERIC WATCHER FUNCTIONS	1160	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		1161
859	=over 4	1162	=over 4
860		1163
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1164	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1165
…		…
868	which rolls both calls into one.	1171	which rolls both calls into one.
869		1172
870	You can reinitialise a watcher at any time as long as it has been stopped	1173	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1174	(or never started) and there are no pending events outstanding.
872		1175
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1176	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1177	int revents)>.
875		1178
		1179	Example: Initialise an C<ev_io> watcher in two steps.
		1180
		1181	ev_io w;
		1182	ev_init (&w, my_cb);
		1183	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1184
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1185	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
877		1186
878	This macro initialises the type-specific parts of a watcher. You need to	1187	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1188	call C<ev_init> at least once before you call this macro, but you can
880	call C<ev_TYPE_set> any number of times. You must not, however, call this	1189	call C<ev_TYPE_set> any number of times. You must not, however, call this
881	macro on a watcher that is active (it can be pending, however, which is a	1190	macro on a watcher that is active (it can be pending, however, which is a
882	difference to the C<ev_init> macro).	1191	difference to the C<ev_init> macro).
883		1192
884	Although some watcher types do not have type-specific arguments	1193	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1194	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1195
		1196	See C<ev_init>, above, for an example.
		1197
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1198	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1199
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1200	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1201	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1202	a watcher. The same limitations apply, of course.
892		1203
		1204	Example: Initialise and set an C<ev_io> watcher in one step.
		1205
		1206	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1207
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1208	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
894		1209
895	Starts (activates) the given watcher. Only active watchers will receive	1210	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1211	events. If the watcher is already active nothing will happen.
897		1212
		1213	Example: Start the C<ev_io> watcher that is being abused as example in this
		1214	whole section.
		1215
		1216	ev_io_start (EV_DEFAULT_UC, &w);
		1217
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1218	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
899		1219
900	Stops the given watcher again (if active) and clears the pending	1220	Stops the given watcher if active, and clears the pending status (whether
		1221	the watcher was active or not).
		1222
901	status. It is possible that stopped watchers are pending (for example,	1223	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1224	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1225	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1226	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1227	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1228
907	=item bool ev_is_active (ev_TYPE *watcher)	1229	=item bool ev_is_active (ev_TYPE *watcher)
908		1230
909	Returns a true value iff the watcher is active (i.e. it has been started	1231	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1232	and not yet been stopped). As long as a watcher is active you must not modify
…		…
926	=item ev_cb_set (ev_TYPE *watcher, callback)	1248	=item ev_cb_set (ev_TYPE *watcher, callback)
927		1249
928	Change the callback. You can change the callback at virtually any time	1250	Change the callback. You can change the callback at virtually any time
929	(modulo threads).	1251	(modulo threads).
930		1252
931	=item ev_set_priority (ev_TYPE *watcher, priority)	1253	=item ev_set_priority (ev_TYPE *watcher, int priority)
932		1254
933	=item int ev_priority (ev_TYPE *watcher)	1255	=item int ev_priority (ev_TYPE *watcher)
934		1256
935	Set and query the priority of the watcher. The priority is a small	1257	Set and query the priority of the watcher. The priority is a small
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1258	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1259	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1260	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1261	from being executed (except for C<ev_idle> watchers).
940		1262
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1263	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1264	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1265
949	You I<must not> change the priority of a watcher as long as it is active or	1266	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1267	pending.
951		1268
		1269	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1270	fine, as long as you do not mind that the priority value you query might
		1271	or might not have been clamped to the valid range.
		1272
952	The default priority used by watchers when no priority has been set is	1273	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1274	always C<0>, which is supposed to not be too high and not be too low :).
954		1275
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1276	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1277	priorities.
957	or might not have been adjusted to be within valid range.
958		1278
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1279	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1280
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1281	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1282	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1283	can deal with that fact, as both are simply passed through to the
		1284	callback.
964		1285
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1286	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1287
967	If the watcher is pending, this function returns clears its pending status	1288	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1289	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1290	watcher isn't pending it does nothing and returns C<0>.
970		1291
		1292	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1293	callback to be invoked, which can be accomplished with this function.
		1294
		1295	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1296
		1297	Feeds the given event set into the event loop, as if the specified event
		1298	had happened for the specified watcher (which must be a pointer to an
		1299	initialised but not necessarily started event watcher). Obviously you must
		1300	not free the watcher as long as it has pending events.
		1301
		1302	Stopping the watcher, letting libev invoke it, or calling
		1303	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1304	not started in the first place.
		1305
		1306	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1307	functions that do not need a watcher.
		1308
971	=back	1309	=back
972		1310
973
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1311	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1312
976	Each watcher has, by default, a member C<void *data> that you can change	1313	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1314	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1315	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1316	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1317	member, you can also "subclass" the watcher type and provide your own
981	data:	1318	data:
982		1319
983	struct my_io	1320	struct my_io
984	{	1321	{
985	struct ev_io io;	1322	ev_io io;
986	int otherfd;	1323	int otherfd;
987	void *somedata;	1324	void *somedata;
988	struct whatever *mostinteresting;	1325	struct whatever *mostinteresting;
989	}	1326	};
		1327
		1328	...
		1329	struct my_io w;
		1330	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1331
991	And since your callback will be called with a pointer to the watcher, you	1332	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1333	can cast it back to your own type:
993		1334
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1335	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1336	{
996	struct my_io *w = (struct my_io *)w_;	1337	struct my_io *w = (struct my_io *)w_;
997	...	1338	...
998	}	1339	}
999		1340
1000	More interesting and less C-conformant ways of casting your callback type	1341	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1342	instead have been omitted.
1002		1343
1003	Another common scenario is having some data structure with multiple	1344	Another common scenario is to use some data structure with multiple
1004	watchers:	1345	embedded watchers:
1005		1346
1006	struct my_biggy	1347	struct my_biggy
1007	{	1348	{
1008	int some_data;	1349	int some_data;
1009	ev_timer t1;	1350	ev_timer t1;
1010	ev_timer t2;	1351	ev_timer t2;
1011	}	1352	}
1012		1353
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1354	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1355	complicated: Either you store the address of your C<my_biggy> struct
		1356	in the C<data> member of the watcher (for woozies), or you need to use
		1357	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1358	programmers):
1015		1359
1016	#include <stddef.h>	1360	#include <stddef.h>
1017		1361
1018	static void	1362	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1363	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1364	{
1021	struct my_biggy big = (struct my_biggy *	1365	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1366	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1367	}
1024		1368
1025	static void	1369	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1370	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1371	{
1028	struct my_biggy big = (struct my_biggy *	1372	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1373	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1374	}
		1375
		1376	=head2 WATCHER STATES
		1377
		1378	There are various watcher states mentioned throughout this manual -
		1379	active, pending and so on. In this section these states and the rules to
		1380	transition between them will be described in more detail - and while these
		1381	rules might look complicated, they usually do "the right thing".
		1382
		1383	=over 4
		1384
		1385	=item initialiased
		1386
		1387	Before a watcher can be registered with the event looop it has to be
		1388	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1389	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1390
		1391	In this state it is simply some block of memory that is suitable for use
		1392	in an event loop. It can be moved around, freed, reused etc. at will.
		1393
		1394	=item started/running/active
		1395
		1396	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1397	property of the event loop, and is actively waiting for events. While in
		1398	this state it cannot be accessed (except in a few documented ways), moved,
		1399	freed or anything else - the only legal thing is to keep a pointer to it,
		1400	and call libev functions on it that are documented to work on active watchers.
		1401
		1402	=item pending
		1403
		1404	If a watcher is active and libev determines that an event it is interested
		1405	in has occurred (such as a timer expiring), it will become pending. It will
		1406	stay in this pending state until either it is stopped or its callback is
		1407	about to be invoked, so it is not normally pending inside the watcher
		1408	callback.
		1409
		1410	The watcher might or might not be active while it is pending (for example,
		1411	an expired non-repeating timer can be pending but no longer active). If it
		1412	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1413	but it is still property of the event loop at this time, so cannot be
		1414	moved, freed or reused. And if it is active the rules described in the
		1415	previous item still apply.
		1416
		1417	It is also possible to feed an event on a watcher that is not active (e.g.
		1418	via C<ev_feed_event>), in which case it becomes pending without being
		1419	active.
		1420
		1421	=item stopped
		1422
		1423	A watcher can be stopped implicitly by libev (in which case it might still
		1424	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1425	latter will clear any pending state the watcher might be in, regardless
		1426	of whether it was active or not, so stopping a watcher explicitly before
		1427	freeing it is often a good idea.
		1428
		1429	While stopped (and not pending) the watcher is essentially in the
		1430	initialised state, that is it can be reused, moved, modified in any way
		1431	you wish.
		1432
		1433	=back
		1434
		1435	=head2 WATCHER PRIORITY MODELS
		1436
		1437	Many event loops support I<watcher priorities>, which are usually small
		1438	integers that influence the ordering of event callback invocation
		1439	between watchers in some way, all else being equal.
		1440
		1441	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1442	description for the more technical details such as the actual priority
		1443	range.
		1444
		1445	There are two common ways how these these priorities are being interpreted
		1446	by event loops:
		1447
		1448	In the more common lock-out model, higher priorities "lock out" invocation
		1449	of lower priority watchers, which means as long as higher priority
		1450	watchers receive events, lower priority watchers are not being invoked.
		1451
		1452	The less common only-for-ordering model uses priorities solely to order
		1453	callback invocation within a single event loop iteration: Higher priority
		1454	watchers are invoked before lower priority ones, but they all get invoked
		1455	before polling for new events.
		1456
		1457	Libev uses the second (only-for-ordering) model for all its watchers
		1458	except for idle watchers (which use the lock-out model).
		1459
		1460	The rationale behind this is that implementing the lock-out model for
		1461	watchers is not well supported by most kernel interfaces, and most event
		1462	libraries will just poll for the same events again and again as long as
		1463	their callbacks have not been executed, which is very inefficient in the
		1464	common case of one high-priority watcher locking out a mass of lower
		1465	priority ones.
		1466
		1467	Static (ordering) priorities are most useful when you have two or more
		1468	watchers handling the same resource: a typical usage example is having an
		1469	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1470	timeouts. Under load, data might be received while the program handles
		1471	other jobs, but since timers normally get invoked first, the timeout
		1472	handler will be executed before checking for data. In that case, giving
		1473	the timer a lower priority than the I/O watcher ensures that I/O will be
		1474	handled first even under adverse conditions (which is usually, but not
		1475	always, what you want).
		1476
		1477	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1478	will only be executed when no same or higher priority watchers have
		1479	received events, they can be used to implement the "lock-out" model when
		1480	required.
		1481
		1482	For example, to emulate how many other event libraries handle priorities,
		1483	you can associate an C<ev_idle> watcher to each such watcher, and in
		1484	the normal watcher callback, you just start the idle watcher. The real
		1485	processing is done in the idle watcher callback. This causes libev to
		1486	continuously poll and process kernel event data for the watcher, but when
		1487	the lock-out case is known to be rare (which in turn is rare :), this is
		1488	workable.
		1489
		1490	Usually, however, the lock-out model implemented that way will perform
		1491	miserably under the type of load it was designed to handle. In that case,
		1492	it might be preferable to stop the real watcher before starting the
		1493	idle watcher, so the kernel will not have to process the event in case
		1494	the actual processing will be delayed for considerable time.
		1495
		1496	Here is an example of an I/O watcher that should run at a strictly lower
		1497	priority than the default, and which should only process data when no
		1498	other events are pending:
		1499
		1500	ev_idle idle; // actual processing watcher
		1501	ev_io io; // actual event watcher
		1502
		1503	static void
		1504	io_cb (EV_P_ ev_io *w, int revents)
		1505	{
		1506	// stop the I/O watcher, we received the event, but
		1507	// are not yet ready to handle it.
		1508	ev_io_stop (EV_A_ w);
		1509
		1510	// start the idle watcher to handle the actual event.
		1511	// it will not be executed as long as other watchers
		1512	// with the default priority are receiving events.
		1513	ev_idle_start (EV_A_ &idle);
		1514	}
		1515
		1516	static void
		1517	idle_cb (EV_P_ ev_idle *w, int revents)
		1518	{
		1519	// actual processing
		1520	read (STDIN_FILENO, ...);
		1521
		1522	// have to start the I/O watcher again, as
		1523	// we have handled the event
		1524	ev_io_start (EV_P_ &io);
		1525	}
		1526
		1527	// initialisation
		1528	ev_idle_init (&idle, idle_cb);
		1529	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1530	ev_io_start (EV_DEFAULT_ &io);
		1531
		1532	In the "real" world, it might also be beneficial to start a timer, so that
		1533	low-priority connections can not be locked out forever under load. This
		1534	enables your program to keep a lower latency for important connections
		1535	during short periods of high load, while not completely locking out less
		1536	important ones.
1031		1537
1032		1538
1033	=head1 WATCHER TYPES	1539	=head1 WATCHER TYPES
1034		1540
1035	This section describes each watcher in detail, but will not repeat	1541	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1565	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1566	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1567	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1568	required if you know what you are doing).
1063		1569
1064	If you must do this, then force the use of a known-to-be-good backend	1570	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1571	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1572	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1573	descriptors for which non-blocking operation makes no sense (such as
		1574	files) - libev doesn't guarantee any specific behaviour in that case.
1067		1575
1068	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1579	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1580	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1581	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1582	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1584
1077	If you cannot run the fd in non-blocking mode (for example you should not	1585	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1586	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1587	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1588	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1589	does this on its own, so its quite safe to use). Some people additionally
		1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1591	indefinitely.
		1592
		1593	But really, best use non-blocking mode.
1082		1594
1083	=head3 The special problem of disappearing file descriptors	1595	=head3 The special problem of disappearing file descriptors
1084		1596
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1597	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1598	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1599	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1600	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1601	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1602	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1603	fact, a different file descriptor.
1092		1604
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1635	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1636	C<EVBACKEND_POLL>.
1125		1637
1126	=head3 The special problem of SIGPIPE	1638	=head3 The special problem of SIGPIPE
1127		1639
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1640	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1641	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1642	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1643	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1644
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1645	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1646	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1647	somewhere, as that would have given you a big clue).
1137		1648
		1649	=head3 The special problem of accept()ing when you can't
		1650
		1651	Many implementations of the POSIX C<accept> function (for example,
		1652	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1653	connection from the pending queue in all error cases.
		1654
		1655	For example, larger servers often run out of file descriptors (because
		1656	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1657	rejecting the connection, leading to libev signalling readiness on
		1658	the next iteration again (the connection still exists after all), and
		1659	typically causing the program to loop at 100% CPU usage.
		1660
		1661	Unfortunately, the set of errors that cause this issue differs between
		1662	operating systems, there is usually little the app can do to remedy the
		1663	situation, and no known thread-safe method of removing the connection to
		1664	cope with overload is known (to me).
		1665
		1666	One of the easiest ways to handle this situation is to just ignore it
		1667	- when the program encounters an overload, it will just loop until the
		1668	situation is over. While this is a form of busy waiting, no OS offers an
		1669	event-based way to handle this situation, so it's the best one can do.
		1670
		1671	A better way to handle the situation is to log any errors other than
		1672	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1673	messages, and continue as usual, which at least gives the user an idea of
		1674	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1675	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1676	usage.
		1677
		1678	If your program is single-threaded, then you could also keep a dummy file
		1679	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1680	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1681	close that fd, and create a new dummy fd. This will gracefully refuse
		1682	clients under typical overload conditions.
		1683
		1684	The last way to handle it is to simply log the error and C<exit>, as
		1685	is often done with C<malloc> failures, but this results in an easy
		1686	opportunity for a DoS attack.
1138		1687
1139	=head3 Watcher-Specific Functions	1688	=head3 Watcher-Specific Functions
1140		1689
1141	=over 4	1690	=over 4
1142		1691
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1692	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1693
1145	=item ev_io_set (ev_io *, int fd, int events)	1694	=item ev_io_set (ev_io *, int fd, int events)
1146		1695
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1696	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1697	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1698	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1699
1151	=item int fd [read-only]	1700	=item int fd [read-only]
1152		1701
1153	The file descriptor being watched.	1702	The file descriptor being watched.
1154		1703
…		…
1162		1711
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1712	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1713	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1714	attempt to read a whole line in the callback.
1166		1715
1167	static void	1716	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1717	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1718	{
1170	ev_io_stop (loop, w);	1719	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1720	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1721	}
1173		1722
1174	...	1723	...
1175	struct ev_loop *loop = ev_default_init (0);	1724	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1725	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1726	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1727	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1728	ev_run (loop, 0);
1180		1729
1181		1730
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1731	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1732
1184	Timer watchers are simple relative timers that generate an event after a	1733	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1734	given time, and optionally repeating in regular intervals after that.
1186		1735
1187	The timers are based on real time, that is, if you register an event that	1736	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1737	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1738	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1739	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1740	monotonic clock option helps a lot here).
		1741
		1742	The callback is guaranteed to be invoked only I<after> its timeout has
		1743	passed (not I<at>, so on systems with very low-resolution clocks this
		1744	might introduce a small delay). If multiple timers become ready during the
		1745	same loop iteration then the ones with earlier time-out values are invoked
		1746	before ones of the same priority with later time-out values (but this is
		1747	no longer true when a callback calls C<ev_run> recursively).
		1748
		1749	=head3 Be smart about timeouts
		1750
		1751	Many real-world problems involve some kind of timeout, usually for error
		1752	recovery. A typical example is an HTTP request - if the other side hangs,
		1753	you want to raise some error after a while.
		1754
		1755	What follows are some ways to handle this problem, from obvious and
		1756	inefficient to smart and efficient.
		1757
		1758	In the following, a 60 second activity timeout is assumed - a timeout that
		1759	gets reset to 60 seconds each time there is activity (e.g. each time some
		1760	data or other life sign was received).
		1761
		1762	=over 4
		1763
		1764	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1765
		1766	This is the most obvious, but not the most simple way: In the beginning,
		1767	start the watcher:
		1768
		1769	ev_timer_init (timer, callback, 60., 0.);
		1770	ev_timer_start (loop, timer);
		1771
		1772	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1773	and start it again:
		1774
		1775	ev_timer_stop (loop, timer);
		1776	ev_timer_set (timer, 60., 0.);
		1777	ev_timer_start (loop, timer);
		1778
		1779	This is relatively simple to implement, but means that each time there is
		1780	some activity, libev will first have to remove the timer from its internal
		1781	data structure and then add it again. Libev tries to be fast, but it's
		1782	still not a constant-time operation.
		1783
		1784	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1785
		1786	This is the easiest way, and involves using C<ev_timer_again> instead of
		1787	C<ev_timer_start>.
		1788
		1789	To implement this, configure an C<ev_timer> with a C<repeat> value
		1790	of C<60> and then call C<ev_timer_again> at start and each time you
		1791	successfully read or write some data. If you go into an idle state where
		1792	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1793	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1794
		1795	That means you can ignore both the C<ev_timer_start> function and the
		1796	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1797	member and C<ev_timer_again>.
		1798
		1799	At start:
		1800
		1801	ev_init (timer, callback);
		1802	timer->repeat = 60.;
		1803	ev_timer_again (loop, timer);
		1804
		1805	Each time there is some activity:
		1806
		1807	ev_timer_again (loop, timer);
		1808
		1809	It is even possible to change the time-out on the fly, regardless of
		1810	whether the watcher is active or not:
		1811
		1812	timer->repeat = 30.;
		1813	ev_timer_again (loop, timer);
		1814
		1815	This is slightly more efficient then stopping/starting the timer each time
		1816	you want to modify its timeout value, as libev does not have to completely
		1817	remove and re-insert the timer from/into its internal data structure.
		1818
		1819	It is, however, even simpler than the "obvious" way to do it.
		1820
		1821	=item 3. Let the timer time out, but then re-arm it as required.
		1822
		1823	This method is more tricky, but usually most efficient: Most timeouts are
		1824	relatively long compared to the intervals between other activity - in
		1825	our example, within 60 seconds, there are usually many I/O events with
		1826	associated activity resets.
		1827
		1828	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1829	but remember the time of last activity, and check for a real timeout only
		1830	within the callback:
		1831
		1832	ev_tstamp last_activity; // time of last activity
		1833
		1834	static void
		1835	callback (EV_P_ ev_timer *w, int revents)
		1836	{
		1837	ev_tstamp now = ev_now (EV_A);
		1838	ev_tstamp timeout = last_activity + 60.;
		1839
		1840	// if last_activity + 60. is older than now, we did time out
		1841	if (timeout < now)
		1842	{
		1843	// timeout occurred, take action
		1844	}
		1845	else
		1846	{
		1847	// callback was invoked, but there was some activity, re-arm
		1848	// the watcher to fire in last_activity + 60, which is
		1849	// guaranteed to be in the future, so "again" is positive:
		1850	w->repeat = timeout - now;
		1851	ev_timer_again (EV_A_ w);
		1852	}
		1853	}
		1854
		1855	To summarise the callback: first calculate the real timeout (defined
		1856	as "60 seconds after the last activity"), then check if that time has
		1857	been reached, which means something I<did>, in fact, time out. Otherwise
		1858	the callback was invoked too early (C<timeout> is in the future), so
		1859	re-schedule the timer to fire at that future time, to see if maybe we have
		1860	a timeout then.
		1861
		1862	Note how C<ev_timer_again> is used, taking advantage of the
		1863	C<ev_timer_again> optimisation when the timer is already running.
		1864
		1865	This scheme causes more callback invocations (about one every 60 seconds
		1866	minus half the average time between activity), but virtually no calls to
		1867	libev to change the timeout.
		1868
		1869	To start the timer, simply initialise the watcher and set C<last_activity>
		1870	to the current time (meaning we just have some activity :), then call the
		1871	callback, which will "do the right thing" and start the timer:
		1872
		1873	ev_init (timer, callback);
		1874	last_activity = ev_now (loop);
		1875	callback (loop, timer, EV_TIMER);
		1876
		1877	And when there is some activity, simply store the current time in
		1878	C<last_activity>, no libev calls at all:
		1879
		1880	last_activity = ev_now (loop);
		1881
		1882	This technique is slightly more complex, but in most cases where the
		1883	time-out is unlikely to be triggered, much more efficient.
		1884
		1885	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1886	callback :) - just change the timeout and invoke the callback, which will
		1887	fix things for you.
		1888
		1889	=item 4. Wee, just use a double-linked list for your timeouts.
		1890
		1891	If there is not one request, but many thousands (millions...), all
		1892	employing some kind of timeout with the same timeout value, then one can
		1893	do even better:
		1894
		1895	When starting the timeout, calculate the timeout value and put the timeout
		1896	at the I<end> of the list.
		1897
		1898	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1899	the list is expected to fire (for example, using the technique #3).
		1900
		1901	When there is some activity, remove the timer from the list, recalculate
		1902	the timeout, append it to the end of the list again, and make sure to
		1903	update the C<ev_timer> if it was taken from the beginning of the list.
		1904
		1905	This way, one can manage an unlimited number of timeouts in O(1) time for
		1906	starting, stopping and updating the timers, at the expense of a major
		1907	complication, and having to use a constant timeout. The constant timeout
		1908	ensures that the list stays sorted.
		1909
		1910	=back
		1911
		1912	So which method the best?
		1913
		1914	Method #2 is a simple no-brain-required solution that is adequate in most
		1915	situations. Method #3 requires a bit more thinking, but handles many cases
		1916	better, and isn't very complicated either. In most case, choosing either
		1917	one is fine, with #3 being better in typical situations.
		1918
		1919	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1920	rather complicated, but extremely efficient, something that really pays
		1921	off after the first million or so of active timers, i.e. it's usually
		1922	overkill :)
		1923
		1924	=head3 The special problem of time updates
		1925
		1926	Establishing the current time is a costly operation (it usually takes at
		1927	least two system calls): EV therefore updates its idea of the current
		1928	time only before and after C<ev_run> collects new events, which causes a
		1929	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1930	lots of events in one iteration.
1192		1931
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1932	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1933	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1934	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1935	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1936	timeout on the current time, use something like this to adjust for this:
1198		1937
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1938	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1939
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1940	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1941	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1942	()>.
		1943
		1944	=head3 The special problems of suspended animation
		1945
		1946	When you leave the server world it is quite customary to hit machines that
		1947	can suspend/hibernate - what happens to the clocks during such a suspend?
		1948
		1949	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1950	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1951	to run until the system is suspended, but they will not advance while the
		1952	system is suspended. That means, on resume, it will be as if the program
		1953	was frozen for a few seconds, but the suspend time will not be counted
		1954	towards C<ev_timer> when a monotonic clock source is used. The real time
		1955	clock advanced as expected, but if it is used as sole clocksource, then a
		1956	long suspend would be detected as a time jump by libev, and timers would
		1957	be adjusted accordingly.
		1958
		1959	I would not be surprised to see different behaviour in different between
		1960	operating systems, OS versions or even different hardware.
		1961
		1962	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1963	time jump in the monotonic clocks and the realtime clock. If the program
		1964	is suspended for a very long time, and monotonic clock sources are in use,
		1965	then you can expect C<ev_timer>s to expire as the full suspension time
		1966	will be counted towards the timers. When no monotonic clock source is in
		1967	use, then libev will again assume a timejump and adjust accordingly.
		1968
		1969	It might be beneficial for this latter case to call C<ev_suspend>
		1970	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1971	deterministic behaviour in this case (you can do nothing against
		1972	C<SIGSTOP>).
1204		1973
1205	=head3 Watcher-Specific Functions and Data Members	1974	=head3 Watcher-Specific Functions and Data Members
1206		1975
1207	=over 4	1976	=over 4
1208		1977
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	2001	If the timer is started but non-repeating, stop it (as if it timed out).
1233		2002
1234	If the timer is repeating, either start it if necessary (with the	2003	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	2004	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		2005
1237	This sounds a bit complicated, but here is a useful and typical	2006	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	2007	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246		2008
1247	That means you can ignore the C<after> value and C<ev_timer_start>	2009	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249		2010
1250	ev_timer_init (timer, callback, 0., 5.);	2011	Returns the remaining time until a timer fires. If the timer is active,
1251	ev_timer_again (loop, timer);	2012	then this time is relative to the current event loop time, otherwise it's
1252	...	2013	the timeout value currently configured.
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258		2014
1259	This is more slightly efficient then stopping/starting the timer each time	2015	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1260	you want to modify its timeout value.	2016	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2017	will return C<4>. When the timer expires and is restarted, it will return
		2018	roughly C<7> (likely slightly less as callback invocation takes some time,
		2019	too), and so on.
1261		2020
1262	=item ev_tstamp repeat [read-write]	2021	=item ev_tstamp repeat [read-write]
1263		2022
1264	The current C<repeat> value. Will be used each time the watcher times out	2023	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	2024	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	2025	which is also when any modifications are taken into account.
1267		2026
1268	=back	2027	=back
1269		2028
1270	=head3 Examples	2029	=head3 Examples
1271		2030
1272	Example: Create a timer that fires after 60 seconds.	2031	Example: Create a timer that fires after 60 seconds.
1273		2032
1274	static void	2033	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2034	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	2035	{
1277	.. one minute over, w is actually stopped right here	2036	.. one minute over, w is actually stopped right here
1278	}	2037	}
1279		2038
1280	struct ev_timer mytimer;	2039	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2040	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	2041	ev_timer_start (loop, &mytimer);
1283		2042
1284	Example: Create a timeout timer that times out after 10 seconds of	2043	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	2044	inactivity.
1286		2045
1287	static void	2046	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2047	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	2048	{
1290	.. ten seconds without any activity	2049	.. ten seconds without any activity
1291	}	2050	}
1292		2051
1293	struct ev_timer mytimer;	2052	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2053	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	2054	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	2055	ev_run (loop, 0);
1297		2056
1298	// and in some piece of code that gets executed on any "activity":	2057	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	2058	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	2059	ev_timer_again (&mytimer);
1301		2060
1302		2061
1303	=head2 C<ev_periodic> - to cron or not to cron?	2062	=head2 C<ev_periodic> - to cron or not to cron?
1304		2063
1305	Periodic watchers are also timers of a kind, but they are very versatile	2064	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	2065	(and unfortunately a bit complex).
1307		2066
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2067	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	2068	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	2069	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2070	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	2071	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	2072	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		2073
		2074	You can tell a periodic watcher to trigger after some specific point
		2075	in time: for example, if you tell a periodic watcher to trigger "in 10
		2076	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2077	not a delay) and then reset your system clock to January of the previous
		2078	year, then it will take a year or more to trigger the event (unlike an
		2079	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2080	it, as it uses a relative timeout).
		2081
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	2082	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	2083	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	2084	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2085	those cannot react to time jumps.
1320		2086
1321	As with timers, the callback is guaranteed to be invoked only when the	2087	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	2088	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	2089	timers become ready during the same loop iteration then the ones with
		2090	earlier time-out values are invoked before ones with later time-out values
		2091	(but this is no longer true when a callback calls C<ev_run> recursively).
1324		2092
1325	=head3 Watcher-Specific Functions and Data Members	2093	=head3 Watcher-Specific Functions and Data Members
1326		2094
1327	=over 4	2095	=over 4
1328		2096
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2097	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		2098
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2099	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		2100
1333	Lots of arguments, lets sort it out... There are basically three modes of	2101	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	2102	operation, and we will explain them from simplest to most complex:
1335		2103
1336	=over 4	2104	=over 4
1337		2105
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2106	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		2107
1340	In this configuration the watcher triggers an event after the wall clock	2108	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	2109	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2110	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	2111	will be stopped and invoked when the system clock reaches or surpasses
		2112	this point in time.
1344		2113
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2114	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		2115
1347	In this mode the watcher will always be scheduled to time out at the next	2116	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	2117	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	2118	negative) and then repeat, regardless of any time jumps. The C<offset>
		2119	argument is merely an offset into the C<interval> periods.
1350		2120
1351	This can be used to create timers that do not drift with respect to system	2121	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	2122	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	2123	hour, on the hour (with respect to UTC):
1354		2124
1355	ev_periodic_set (&periodic, 0., 3600., 0);	2125	ev_periodic_set (&periodic, 0., 3600., 0);
1356		2126
1357	This doesn't mean there will always be 3600 seconds in between triggers,	2127	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	2128	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	2129	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	2130	by 3600.
1361		2131
1362	Another way to think about it (for the mathematically inclined) is that	2132	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	2133	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	2134	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		2135
1366	For numerical stability it is preferable that the C<at> value is near	2136	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	2137	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	2138	this value, and in fact is often specified as zero.
1369		2139
1370	Note also that there is an upper limit to how often a timer can fire (CPU	2140	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	2141	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	2142	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	2143	millisecond (if the OS supports it and the machine is fast enough).
1374		2144
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2145	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		2146
1377	In this mode the values for C<interval> and C<at> are both being	2147	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	2148	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	2149	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	2150	current time as second argument.
1381		2151
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2152	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	2153	or make ANY other event loop modifications whatsoever, unless explicitly
		2154	allowed by documentation here>.
1384		2155
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2156	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2157	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	2158	only event loop modification you are allowed to do).
1388		2159
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2160	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	2161	*w, ev_tstamp now)>, e.g.:
1391		2162
		2163	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2164	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	2165	{
1394	return now + 60.;	2166	return now + 60.;
1395	}	2167	}
1396		2168
1397	It must return the next time to trigger, based on the passed time value	2169	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	2189	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	2190	program when the crontabs have changed).
1419		2191
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	2192	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		2193
1422	When active, returns the absolute time that the watcher is supposed to	2194	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	2195	to trigger next. This is not the same as the C<offset> argument to
		2196	C<ev_periodic_set>, but indeed works even in interval and manual
		2197	rescheduling modes.
1424		2198
1425	=item ev_tstamp offset [read-write]	2199	=item ev_tstamp offset [read-write]
1426		2200
1427	When repeating, this contains the offset value, otherwise this is the	2201	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2202	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2203	although libev might modify this value for better numerical stability).
1429		2204
1430	Can be modified any time, but changes only take effect when the periodic	2205	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	2206	timer fires or C<ev_periodic_again> is being called.
1432		2207
1433	=item ev_tstamp interval [read-write]	2208	=item ev_tstamp interval [read-write]
1434		2209
1435	The current interval value. Can be modified any time, but changes only	2210	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	2211	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	2212	called.
1438		2213
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2214	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		2215
1441	The current reschedule callback, or C<0>, if this functionality is	2216	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	2217	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	2218	the periodic timer fires or C<ev_periodic_again> is being called.
1444		2219
1445	=back	2220	=back
1446		2221
1447	=head3 Examples	2222	=head3 Examples
1448		2223
1449	Example: Call a callback every hour, or, more precisely, whenever the	2224	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	2225	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	2226	potentially a lot of jitter, but good long-term stability.
1452		2227
1453	static void	2228	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2229	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1455	{	2230	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	2231	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	2232	}
1458		2233
1459	struct ev_periodic hourly_tick;	2234	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2235	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	2236	ev_periodic_start (loop, &hourly_tick);
1462		2237
1463	Example: The same as above, but use a reschedule callback to do it:	2238	Example: The same as above, but use a reschedule callback to do it:
1464		2239
1465	#include <math.h>	2240	#include <math.h>
1466		2241
1467	static ev_tstamp	2242	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2243	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	2244	{
1470	return fmod (now, 3600.) + 3600.;	2245	return now + (3600. - fmod (now, 3600.));
1471	}	2246	}
1472		2247
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2248	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		2249
1475	Example: Call a callback every hour, starting now:	2250	Example: Call a callback every hour, starting now:
1476		2251
1477	struct ev_periodic hourly_tick;	2252	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	2253	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	2254	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	2255	ev_periodic_start (loop, &hourly_tick);
1481		2256
1482		2257
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	2258	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		2259
1485	Signal watchers will trigger an event when the process receives a specific	2260	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	2261	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	2262	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	2263	normal event processing, like any other event.
1489		2264
		2265	If you want signals to be delivered truly asynchronously, just use
		2266	C<sigaction> as you would do without libev and forget about sharing
		2267	the signal. You can even use C<ev_async> from a signal handler to
		2268	synchronously wake up an event loop.
		2269
1490	You can configure as many watchers as you like per signal. Only when the	2270	You can configure as many watchers as you like for the same signal, but
		2271	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2272	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2273	C<SIGINT> in both the default loop and another loop at the same time. At
		2274	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2275
1491	first watcher gets started will libev actually register a signal watcher	2276	When the first watcher gets started will libev actually register something
1492	with the kernel (thus it coexists with your own signal handlers as long	2277	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	2278	you don't register any with libev for the same signal).
1494	watcher for a signal is stopped libev will reset the signal handler to
1495	SIG_DFL (regardless of what it was set to before).
1496		2279
1497	If possible and supported, libev will install its handlers with	2280	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2281	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1499	interrupted. If you have a problem with system calls getting interrupted by	2282	not be unduly interrupted. If you have a problem with system calls getting
1500	signals you can block all signals in an C<ev_check> watcher and unblock	2283	interrupted by signals you can block all signals in an C<ev_check> watcher
1501	them in an C<ev_prepare> watcher.	2284	and unblock them in an C<ev_prepare> watcher.
		2285
		2286	=head3 The special problem of inheritance over fork/execve/pthread_create
		2287
		2288	Both the signal mask (C<sigprocmask>) and the signal disposition
		2289	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2290	stopping it again), that is, libev might or might not block the signal,
		2291	and might or might not set or restore the installed signal handler.
		2292
		2293	While this does not matter for the signal disposition (libev never
		2294	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2295	C<execve>), this matters for the signal mask: many programs do not expect
		2296	certain signals to be blocked.
		2297
		2298	This means that before calling C<exec> (from the child) you should reset
		2299	the signal mask to whatever "default" you expect (all clear is a good
		2300	choice usually).
		2301
		2302	The simplest way to ensure that the signal mask is reset in the child is
		2303	to install a fork handler with C<pthread_atfork> that resets it. That will
		2304	catch fork calls done by libraries (such as the libc) as well.
		2305
		2306	In current versions of libev, the signal will not be blocked indefinitely
		2307	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2308	the window of opportunity for problems, it will not go away, as libev
		2309	I<has> to modify the signal mask, at least temporarily.
		2310
		2311	So I can't stress this enough: I<If you do not reset your signal mask when
		2312	you expect it to be empty, you have a race condition in your code>. This
		2313	is not a libev-specific thing, this is true for most event libraries.
1502		2314
1503	=head3 Watcher-Specific Functions and Data Members	2315	=head3 Watcher-Specific Functions and Data Members
1504		2316
1505	=over 4	2317	=over 4
1506		2318
…		…
1517		2329
1518	=back	2330	=back
1519		2331
1520	=head3 Examples	2332	=head3 Examples
1521		2333
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	2334	Example: Try to exit cleanly on SIGINT.
1523		2335
1524	static void	2336	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2337	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	2338	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	2339	ev_break (loop, EVBREAK_ALL);
1528	}	2340	}
1529		2341
1530	struct ev_signal signal_watcher;	2342	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2343	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	2344	ev_signal_start (loop, &signal_watcher);
1533		2345
1534		2346
1535	=head2 C<ev_child> - watch out for process status changes	2347	=head2 C<ev_child> - watch out for process status changes
1536		2348
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2349	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2350	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2351	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2352	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2353	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2354	forking and then immediately registering a watcher for the child is fine,
		2355	but forking and registering a watcher a few event loop iterations later or
		2356	in the next callback invocation is not.
1542		2357
1543	Only the default event loop is capable of handling signals, and therefore	2358	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2359	you can only register child watchers in the default event loop.
1545		2360
		2361	Due to some design glitches inside libev, child watchers will always be
		2362	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2363	libev)
		2364
1546	=head3 Process Interaction	2365	=head3 Process Interaction
1547		2366
1548	Libev grabs C<SIGCHLD> as soon as the default event loop is	2367	Libev grabs C<SIGCHLD> as soon as the default event loop is
1549	initialised. This is necessary to guarantee proper behaviour even if	2368	initialised. This is necessary to guarantee proper behaviour even if the
1550	the first child watcher is started after the child exits. The occurrence	2369	first child watcher is started after the child exits. The occurrence
1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2370	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1552	synchronously as part of the event loop processing. Libev always reaps all	2371	synchronously as part of the event loop processing. Libev always reaps all
1553	children, even ones not watched.	2372	children, even ones not watched.
1554		2373
1555	=head3 Overriding the Built-In Processing	2374	=head3 Overriding the Built-In Processing
…		…
1559	handler, you can override it easily by installing your own handler for	2378	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2379	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2380	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2381	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2382	that, so other libev users can use C<ev_child> watchers freely.
		2383
		2384	=head3 Stopping the Child Watcher
		2385
		2386	Currently, the child watcher never gets stopped, even when the
		2387	child terminates, so normally one needs to stop the watcher in the
		2388	callback. Future versions of libev might stop the watcher automatically
		2389	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2390	problem).
1564		2391
1565	=head3 Watcher-Specific Functions and Data Members	2392	=head3 Watcher-Specific Functions and Data Members
1566		2393
1567	=over 4	2394	=over 4
1568		2395
…		…
1597	=head3 Examples	2424	=head3 Examples
1598		2425
1599	Example: C<fork()> a new process and install a child handler to wait for	2426	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	2427	its completion.
1601		2428
1602	ev_child cw;	2429	ev_child cw;
1603		2430
1604	static void	2431	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2432	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2433	{
1607	ev_child_stop (EV_A_ w);	2434	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2435	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2436	}
1610		2437
1611	pid_t pid = fork ();	2438	pid_t pid = fork ();
1612		2439
1613	if (pid < 0)	2440	if (pid < 0)
1614	// error	2441	// error
1615	else if (pid == 0)	2442	else if (pid == 0)
1616	{	2443	{
1617	// the forked child executes here	2444	// the forked child executes here
1618	exit (1);	2445	exit (1);
1619	}	2446	}
1620	else	2447	else
1621	{	2448	{
1622	ev_child_init (&cw, child_cb, pid, 0);	2449	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	2450	ev_child_start (EV_DEFAULT_ &cw);
1624	}	2451	}
1625		2452
1626		2453
1627	=head2 C<ev_stat> - did the file attributes just change?	2454	=head2 C<ev_stat> - did the file attributes just change?
1628		2455
1629	This watches a file system path for attribute changes. That is, it calls	2456	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2457	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2458	and sees if it changed compared to the last time, invoking the callback if
		2459	it did.
1632		2460
1633	The path does not need to exist: changing from "path exists" to "path does	2461	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2462	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2463	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2464	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2465	least one) and all the other fields of the stat buffer having unspecified
		2466	contents.
1638		2467
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2468	The path I<must not> end in a slash or contain special components such as
		2469	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2470	your working directory changes, then the behaviour is undefined.
1641		2471
1642	Since there is no standard to do this, the portable implementation simply	2472	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2473	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2474	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2475	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2476	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2477	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2478	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2479	currently around C<0.1>, but that's usually overkill.
1650		2480
1651	This watcher type is not meant for massive numbers of stat watchers,	2481	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2482	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2483	resource-intensive.
1654		2484
1655	At the time of this writing, only the Linux inotify interface is	2485	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2486	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2487	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2488	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2489
1664	=head3 ABI Issues (Largefile Support)	2490	=head3 ABI Issues (Largefile Support)
1665		2491
1666	Libev by default (unless the user overrides this) uses the default	2492	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2493	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2494	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2495	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2496	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2497	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2498	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2499	most noticeably displayed with ev_stat and large file support.
1674		2500
1675	=head3 Inotify	2501	The solution for this is to lobby your distribution maker to make large
		2502	file interfaces available by default (as e.g. FreeBSD does) and not
		2503	optional. Libev cannot simply switch on large file support because it has
		2504	to exchange stat structures with application programs compiled using the
		2505	default compilation environment.
1676		2506
		2507	=head3 Inotify and Kqueue
		2508
1677	When C<inotify (7)> support has been compiled into libev (generally only	2509	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2510	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2511	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2512	watcher is being started.
1681		2513
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2514	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2515	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2516	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2517	there are many cases where libev has to resort to regular C<stat> polling,
		2518	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2519	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2520	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2521	xfs are fully working) libev usually gets away without polling.
1686		2522
1687	(There is no support for kqueue, as apparently it cannot be used to	2523	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2524	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2525	descriptor open on the object at all times, and detecting renames, unlinks
		2526	etc. is difficult.
		2527
		2528	=head3 C<stat ()> is a synchronous operation
		2529
		2530	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2531	the process. The exception are C<ev_stat> watchers - those call C<stat
		2532	()>, which is a synchronous operation.
		2533
		2534	For local paths, this usually doesn't matter: unless the system is very
		2535	busy or the intervals between stat's are large, a stat call will be fast,
		2536	as the path data is usually in memory already (except when starting the
		2537	watcher).
		2538
		2539	For networked file systems, calling C<stat ()> can block an indefinite
		2540	time due to network issues, and even under good conditions, a stat call
		2541	often takes multiple milliseconds.
		2542
		2543	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2544	paths, although this is fully supported by libev.
1690		2545
1691	=head3 The special problem of stat time resolution	2546	=head3 The special problem of stat time resolution
1692		2547
1693	The C<stat ()> system call only supports full-second resolution portably, and	2548	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2549	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2550	still only support whole seconds.
1696		2551
1697	That means that, if the time is the only thing that changes, you can	2552	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2553	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2554	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2555	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2556	stat data does change in other ways (e.g. file size).
1702		2557
1703	The solution to this is to delay acting on a change for slightly more	2558	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2559	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2560	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2561	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2581	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2582	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2583	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2584	path for as long as the watcher is active.
1730		2585
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2586	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2587	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2588	last change was detected).
1734		2589
1735	=item ev_stat_stat (loop, ev_stat *)	2590	=item ev_stat_stat (loop, ev_stat *)
1736		2591
1737	Updates the stat buffer immediately with new values. If you change the	2592	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2593	watched path in your callback, you could call this function to avoid
…		…
1767		2622
1768	=head3 Examples	2623	=head3 Examples
1769		2624
1770	Example: Watch C</etc/passwd> for attribute changes.	2625	Example: Watch C</etc/passwd> for attribute changes.
1771		2626
1772	static void	2627	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2628	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	2629	{
1775	/* /etc/passwd changed in some way */	2630	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	2631	if (w->attr.st_nlink)
1777	{	2632	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2633	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2634	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2635	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	2636	}
1782	else	2637	else
1783	/* you shalt not abuse printf for puts */	2638	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	2639	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	2640	"if this is windows, they already arrived\n");
1786	}	2641	}
1787		2642
1788	...	2643	...
1789	ev_stat passwd;	2644	ev_stat passwd;
1790		2645
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2646	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	2647	ev_stat_start (loop, &passwd);
1793		2648
1794	Example: Like above, but additionally use a one-second delay so we do not	2649	Example: Like above, but additionally use a one-second delay so we do not
1795	miss updates (however, frequent updates will delay processing, too, so	2650	miss updates (however, frequent updates will delay processing, too, so
1796	one might do the work both on C<ev_stat> callback invocation I<and> on	2651	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	2652	C<ev_timer> callback invocation).
1798		2653
1799	static ev_stat passwd;	2654	static ev_stat passwd;
1800	static ev_timer timer;	2655	static ev_timer timer;
1801		2656
1802	static void	2657	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	2658	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	2659	{
1805	ev_timer_stop (EV_A_ w);	2660	ev_timer_stop (EV_A_ w);
1806		2661
1807	/* now it's one second after the most recent passwd change */	2662	/* now it's one second after the most recent passwd change */
1808	}	2663	}
1809		2664
1810	static void	2665	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	2666	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	2667	{
1813	/* reset the one-second timer */	2668	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	2669	ev_timer_again (EV_A_ &timer);
1815	}	2670	}
1816		2671
1817	...	2672	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2673	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	2674	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	2675	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		2676
1822		2677
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2678	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2679
1825	Idle watchers trigger events when no other events of the same or higher	2680	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2681	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2682	as receiving "events").
1828		2683
1829	That is, as long as your process is busy handling sockets or timeouts	2684	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2685	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2686	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2687	are pending), the idle watchers are being called once per event loop
…		…
1843		2698
1844	=head3 Watcher-Specific Functions and Data Members	2699	=head3 Watcher-Specific Functions and Data Members
1845		2700
1846	=over 4	2701	=over 4
1847		2702
1848	=item ev_idle_init (ev_signal *, callback)	2703	=item ev_idle_init (ev_idle *, callback)
1849		2704
1850	Initialises and configures the idle watcher - it has no parameters of any	2705	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2706	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2707	believe me.
1853		2708
…		…
1856	=head3 Examples	2711	=head3 Examples
1857		2712
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2713	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2714	callback, free it. Also, use no error checking, as usual.
1860		2715
1861	static void	2716	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2717	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2718	{
1864	free (w);	2719	free (w);
1865	// now do something you wanted to do when the program has	2720	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2721	// no longer anything immediate to do.
1867	}	2722	}
1868		2723
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2724	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2725	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2726	ev_idle_start (loop, idle_watcher);
1872		2727
1873		2728
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2729	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2730
1876	Prepare and check watchers are usually (but not always) used in tandem:	2731	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2732	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2733	afterwards.
1879		2734
1880	You I<must not> call C<ev_loop> or similar functions that enter	2735	You I<must not> call C<ev_run> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2736	the current event loop from either C<ev_prepare> or C<ev_check>
1882	watchers. Other loops than the current one are fine, however. The	2737	watchers. Other loops than the current one are fine, however. The
1883	rationale behind this is that you do not need to check for recursion in	2738	rationale behind this is that you do not need to check for recursion in
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2739	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2740	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2741	called in pairs bracketing the blocking call.
1887		2742
1888	Their main purpose is to integrate other event mechanisms into libev and	2743	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2744	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2745	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2746	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2747	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2748	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2749	watcher).
1895		2750
1896	This is done by examining in each prepare call which file descriptors need	2751	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2752	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2753	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2754	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2755	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2756	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2757	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2758	nevertheless, because you never know, you know?).
1904		2759
1905	As another example, the Perl Coro module uses these hooks to integrate	2760	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2761	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2762	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2763	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2766	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2767	low-priority coroutines to idle/background tasks).
1913		2768
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2769	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2770	priority, to ensure that they are being run before any other watchers
		2771	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2772
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2773	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2774	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2775	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2776	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2777	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2778	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2779	others).
1923		2780
1924	=head3 Watcher-Specific Functions and Data Members	2781	=head3 Watcher-Specific Functions and Data Members
1925		2782
1926	=over 4	2783	=over 4
1927		2784
…		…
1929		2786
1930	=item ev_check_init (ev_check *, callback)	2787	=item ev_check_init (ev_check *, callback)
1931		2788
1932	Initialises and configures the prepare or check watcher - they have no	2789	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2790	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2791	macros, but using them is utterly, utterly, utterly and completely
		2792	pointless.
1935		2793
1936	=back	2794	=back
1937		2795
1938	=head3 Examples	2796	=head3 Examples
1939		2797
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2806	and in a check watcher, destroy them and call into libadns. What follows
1949	is pseudo-code only of course. This requires you to either use a low	2807	is pseudo-code only of course. This requires you to either use a low
1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2808	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1951	the callbacks for the IO/timeout watchers might not have been called yet.	2809	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2810
1953	static ev_io iow [nfd];	2811	static ev_io iow [nfd];
1954	static ev_timer tw;	2812	static ev_timer tw;
1955		2813
1956	static void	2814	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2815	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2816	{
1959	}	2817	}
1960		2818
1961	// create io watchers for each fd and a timer before blocking	2819	// create io watchers for each fd and a timer before blocking
1962	static void	2820	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2821	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2822	{
1965	int timeout = 3600000;	2823	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2824	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2825	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2826	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2827
1970	/* the callback is illegal, but won't be called as we stop during check */	2828	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2829	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2830	ev_timer_start (loop, &tw);
1973		2831
1974	// create one ev_io per pollfd	2832	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2833	for (int i = 0; i < nfd; ++i)
1976	{	2834	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2835	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2836	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2837	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2838
1981	fds [i].revents = 0;	2839	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2840	ev_io_start (loop, iow + i);
1983	}	2841	}
1984	}	2842	}
1985		2843
1986	// stop all watchers after blocking	2844	// stop all watchers after blocking
1987	static void	2845	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2846	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2847	{
1990	ev_timer_stop (loop, &tw);	2848	ev_timer_stop (loop, &tw);
1991		2849
1992	for (int i = 0; i < nfd; ++i)	2850	for (int i = 0; i < nfd; ++i)
1993	{	2851	{
1994	// set the relevant poll flags	2852	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2853	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2854	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2855	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2856	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2857	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2858
2001	// now stop the watcher	2859	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2860	ev_io_stop (loop, iow + i);
2003	}	2861	}
2004		2862
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2863	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2864	}
2007		2865
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2866	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
2009	in the prepare watcher and would dispose of the check watcher.	2867	in the prepare watcher and would dispose of the check watcher.
2010		2868
2011	Method 3: If the module to be embedded supports explicit event	2869	Method 3: If the module to be embedded supports explicit event
2012	notification (libadns does), you can also make use of the actual watcher	2870	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2871	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2872
2015	static void	2873	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2874	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2875	{
2018	adns_state ads = (adns_state)w->data;	2876	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2877	update_now (EV_A);
2020		2878
2021	adns_processtimeouts (ads, &tv_now);	2879	adns_processtimeouts (ads, &tv_now);
2022	}	2880	}
2023		2881
2024	static void	2882	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2883	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2884	{
2027	adns_state ads = (adns_state)w->data;	2885	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2886	update_now (EV_A);
2029		2887
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2888	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2889	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2890	}
2033		2891
2034	// do not ever call adns_afterpoll	2892	// do not ever call adns_afterpoll
2035		2893
2036	Method 4: Do not use a prepare or check watcher because the module you	2894	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2895	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2896	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2897	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2898	this approach, effectively embedding EV as a client into the horrible
		2899	libglib event loop.
2041		2900
2042	static gint	2901	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2902	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2903	{
2045	int got_events = 0;	2904	int got_events = 0;
2046		2905
2047	for (n = 0; n < nfds; ++n)	2906	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2907	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2908
2050	if (timeout >= 0)	2909	if (timeout >= 0)
2051	// create/start timer	2910	// create/start timer
2052		2911
2053	// poll	2912	// poll
2054	ev_loop (EV_A_ 0);	2913	ev_run (EV_A_ 0);
2055		2914
2056	// stop timer again	2915	// stop timer again
2057	if (timeout >= 0)	2916	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2917	ev_timer_stop (EV_A_ &to);
2059		2918
2060	// stop io watchers again - their callbacks should have set	2919	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	2920	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	2921	ev_io_stop (EV_A_ iow [n]);
2063		2922
2064	return got_events;	2923	return got_events;
2065	}	2924	}
2066		2925
2067		2926
2068	=head2 C<ev_embed> - when one backend isn't enough...	2927	=head2 C<ev_embed> - when one backend isn't enough...
2069		2928
2070	This is a rather advanced watcher type that lets you embed one event loop	2929	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	2935	prioritise I/O.
2077		2936
2078	As an example for a bug workaround, the kqueue backend might only support	2937	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2938	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2939	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2940	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2941	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2942	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2943	C<kevent>, but at least you can use both mechanisms for what they are
		2944	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2945
2086	As for prioritising I/O: rarely you have the case where some fds have	2946	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2947	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2948	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2949	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2950	the rest in a second one, and embed the second one in the first.
2091		2951
2092	As long as the watcher is active, the callback will be invoked every time	2952	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2953	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2954	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2955	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2956	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2957	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2958
2100	As long as the watcher is started it will automatically handle events. The	2959	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2960	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2961
2105	Also, there have not currently been made special provisions for forking:	2962	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2963	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2964	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2965	C<ev_loop_fork> on the embedded loop.
2109		2966
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2967	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2968	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2969	portable one.
2113		2970
2114	So when you want to use this feature you will always have to be prepared	2971	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2972	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2973	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2974	create it, and if that fails, use the normal loop for everything.
		2975
		2976	=head3 C<ev_embed> and fork
		2977
		2978	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2979	automatically be applied to the embedded loop as well, so no special
		2980	fork handling is required in that case. When the watcher is not running,
		2981	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2982	as applicable.
2118		2983
2119	=head3 Watcher-Specific Functions and Data Members	2984	=head3 Watcher-Specific Functions and Data Members
2120		2985
2121	=over 4	2986	=over 4
2122		2987
…		…
2131	if you do not want that, you need to temporarily stop the embed watcher).	2996	if you do not want that, you need to temporarily stop the embed watcher).
2132		2997
2133	=item ev_embed_sweep (loop, ev_embed *)	2998	=item ev_embed_sweep (loop, ev_embed *)
2134		2999
2135	Make a single, non-blocking sweep over the embedded loop. This works	3000	Make a single, non-blocking sweep over the embedded loop. This works
2136	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3001	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2137	appropriate way for embedded loops.	3002	appropriate way for embedded loops.
2138		3003
2139	=item struct ev_loop *other [read-only]	3004	=item struct ev_loop *other [read-only]
2140		3005
2141	The embedded event loop.	3006	The embedded event loop.
…		…
2148	event loop. If that is not possible, use the default loop. The default	3013	event loop. If that is not possible, use the default loop. The default
2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in	3014	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3015	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	3016	used).
2152		3017
2153	struct ev_loop *loop_hi = ev_default_init (0);	3018	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	3019	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	3020	ev_embed embed;
2156		3021
2157	// see if there is a chance of getting one that works	3022	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	3023	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3024	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3025	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	3026	: 0;
2162		3027
2163	// if we got one, then embed it, otherwise default to loop_hi	3028	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	3029	if (loop_lo)
2165	{	3030	{
2166	ev_embed_init (&embed, 0, loop_lo);	3031	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	3032	ev_embed_start (loop_hi, &embed);
2168	}	3033	}
2169	else	3034	else
2170	loop_lo = loop_hi;	3035	loop_lo = loop_hi;
2171		3036
2172	Example: Check if kqueue is available but not recommended and create	3037	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	3038	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	3039	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3040	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		3041
2177	struct ev_loop *loop = ev_default_init (0);	3042	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	3043	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	3044	ev_embed embed;
2180		3045
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3046	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3047	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	3048	{
2184	ev_embed_init (&embed, 0, loop_socket);	3049	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	3050	ev_embed_start (loop, &embed);
2186	}	3051	}
2187		3052
2188	if (!loop_socket)	3053	if (!loop_socket)
2189	loop_socket = loop;	3054	loop_socket = loop;
2190		3055
2191	// now use loop_socket for all sockets, and loop for everything else	3056	// now use loop_socket for all sockets, and loop for everything else
2192		3057
2193		3058
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3059	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		3060
2196	Fork watchers are called when a C<fork ()> was detected (usually because	3061	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	3064	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	3065	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3066	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	3067	handlers will be invoked, too, of course.
2203		3068
		3069	=head3 The special problem of life after fork - how is it possible?
		3070
		3071	Most uses of C<fork()> consist of forking, then some simple calls to set
		3072	up/change the process environment, followed by a call to C<exec()>. This
		3073	sequence should be handled by libev without any problems.
		3074
		3075	This changes when the application actually wants to do event handling
		3076	in the child, or both parent in child, in effect "continuing" after the
		3077	fork.
		3078
		3079	The default mode of operation (for libev, with application help to detect
		3080	forks) is to duplicate all the state in the child, as would be expected
		3081	when I<either> the parent I<or> the child process continues.
		3082
		3083	When both processes want to continue using libev, then this is usually the
		3084	wrong result. In that case, usually one process (typically the parent) is
		3085	supposed to continue with all watchers in place as before, while the other
		3086	process typically wants to start fresh, i.e. without any active watchers.
		3087
		3088	The cleanest and most efficient way to achieve that with libev is to
		3089	simply create a new event loop, which of course will be "empty", and
		3090	use that for new watchers. This has the advantage of not touching more
		3091	memory than necessary, and thus avoiding the copy-on-write, and the
		3092	disadvantage of having to use multiple event loops (which do not support
		3093	signal watchers).
		3094
		3095	When this is not possible, or you want to use the default loop for
		3096	other reasons, then in the process that wants to start "fresh", call
		3097	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3098	Destroying the default loop will "orphan" (not stop) all registered
		3099	watchers, so you have to be careful not to execute code that modifies
		3100	those watchers. Note also that in that case, you have to re-register any
		3101	signal watchers.
		3102
2204	=head3 Watcher-Specific Functions and Data Members	3103	=head3 Watcher-Specific Functions and Data Members
2205		3104
2206	=over 4	3105	=over 4
2207		3106
2208	=item ev_fork_init (ev_signal *, callback)	3107	=item ev_fork_init (ev_fork *, callback)
2209		3108
2210	Initialises and configures the fork watcher - it has no parameters of any	3109	Initialises and configures the fork watcher - it has no parameters of any
2211	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3110	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2212	believe me.	3111	really.
2213		3112
2214	=back	3113	=back
2215		3114
2216		3115
		3116	=head2 C<ev_cleanup> - even the best things end
		3117
		3118	Cleanup watchers are called just before the event loop is being destroyed
		3119	by a call to C<ev_loop_destroy>.
		3120
		3121	While there is no guarantee that the event loop gets destroyed, cleanup
		3122	watchers provide a convenient method to install cleanup hooks for your
		3123	program, worker threads and so on - you just to make sure to destroy the
		3124	loop when you want them to be invoked.
		3125
		3126	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3127	all other watchers, they do not keep a reference to the event loop (which
		3128	makes a lot of sense if you think about it). Like all other watchers, you
		3129	can call libev functions in the callback, except C<ev_cleanup_start>.
		3130
		3131	=head3 Watcher-Specific Functions and Data Members
		3132
		3133	=over 4
		3134
		3135	=item ev_cleanup_init (ev_cleanup *, callback)
		3136
		3137	Initialises and configures the cleanup watcher - it has no parameters of
		3138	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3139	pointless, I assure you.
		3140
		3141	=back
		3142
		3143	Example: Register an atexit handler to destroy the default loop, so any
		3144	cleanup functions are called.
		3145
		3146	static void
		3147	program_exits (void)
		3148	{
		3149	ev_loop_destroy (EV_DEFAULT_UC);
		3150	}
		3151
		3152	...
		3153	atexit (program_exits);
		3154
		3155
2217	=head2 C<ev_async> - how to wake up another event loop	3156	=head2 C<ev_async> - how to wake up an event loop
2218		3157
2219	In general, you cannot use an C<ev_loop> from multiple threads or other	3158	In general, you cannot use an C<ev_run> from multiple threads or other
2220	asynchronous sources such as signal handlers (as opposed to multiple event	3159	asynchronous sources such as signal handlers (as opposed to multiple event
2221	loops - those are of course safe to use in different threads).	3160	loops - those are of course safe to use in different threads).
2222		3161
2223	Sometimes, however, you need to wake up another event loop you do not	3162	Sometimes, however, you need to wake up an event loop you do not control,
2224	control, for example because it belongs to another thread. This is what	3163	for example because it belongs to another thread. This is what C<ev_async>
2225	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3164	watchers do: as long as the C<ev_async> watcher is active, you can signal
2226	can signal it by calling C<ev_async_send>, which is thread- and signal	3165	it by calling C<ev_async_send>, which is thread- and signal safe.
2227	safe.
2228		3166
2229	This functionality is very similar to C<ev_signal> watchers, as signals,	3167	This functionality is very similar to C<ev_signal> watchers, as signals,
2230	too, are asynchronous in nature, and signals, too, will be compressed	3168	too, are asynchronous in nature, and signals, too, will be compressed
2231	(i.e. the number of callback invocations may be less than the number of	3169	(i.e. the number of callback invocations may be less than the number of
2232	C<ev_async_sent> calls).	3170	C<ev_async_sent> calls).
…		…
2237	=head3 Queueing	3175	=head3 Queueing
2238		3176
2239	C<ev_async> does not support queueing of data in any way. The reason	3177	C<ev_async> does not support queueing of data in any way. The reason
2240	is that the author does not know of a simple (or any) algorithm for a	3178	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	3179	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	3180	need elaborate support such as pthreads or unportable memory access
		3181	semantics.
2243		3182
2244	That means that if you want to queue data, you have to provide your own	3183	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	3184	queue. But at least I can tell you how to implement locking around your
2246	queue:	3185	queue:
2247		3186
2248	=over 4	3187	=over 4
2249		3188
2250	=item queueing from a signal handler context	3189	=item queueing from a signal handler context
2251		3190
2252	To implement race-free queueing, you simply add to the queue in the signal	3191	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3192	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	3193	an example that does that for some fictitious SIGUSR1 handler:
2255		3194
2256	static ev_async mysig;	3195	static ev_async mysig;
2257		3196
2258	static void	3197	static void
2259	sigusr1_handler (void)	3198	sigusr1_handler (void)
…		…
2325	=over 4	3264	=over 4
2326		3265
2327	=item ev_async_init (ev_async *, callback)	3266	=item ev_async_init (ev_async *, callback)
2328		3267
2329	Initialises and configures the async watcher - it has no parameters of any	3268	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3269	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	3270	trust me.
2332		3271
2333	=item ev_async_send (loop, ev_async *)	3272	=item ev_async_send (loop, ev_async *)
2334		3273
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3274	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3275	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	3276	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3277	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	3278	section below on what exactly this means).
2340		3279
		3280	Note that, as with other watchers in libev, multiple events might get
		3281	compressed into a single callback invocation (another way to look at this
		3282	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3283	reset when the event loop detects that).
		3284
2341	This call incurs the overhead of a system call only once per loop iteration,	3285	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	3286	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	3287	repeated calls to C<ev_async_send> for the same event loop.
2344		3288
2345	=item bool = ev_async_pending (ev_async *)	3289	=item bool = ev_async_pending (ev_async *)
2346		3290
2347	Returns a non-zero value when C<ev_async_send> has been called on the	3291	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	3292	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	3296	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	3297	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	3298	quickly check whether invoking the loop might be a good idea.
2355		3299
2356	Not that this does I<not> check whether the watcher itself is pending, only	3300	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	3301	only whether it has been requested to make this watcher pending: there
		3302	is a time window between the event loop checking and resetting the async
		3303	notification, and the callback being invoked.
2358		3304
2359	=back	3305	=back
2360		3306
2361		3307
2362	=head1 OTHER FUNCTIONS	3308	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	3312	=over 4
2367		3313
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3314	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		3315
2370	This function combines a simple timer and an I/O watcher, calls your	3316	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	3317	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	3318	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	3319	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	3320	more watchers yourself.
2375		3321
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	3322	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3323	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	3324	the given C<fd> and C<events> set will be created and started.
2379		3325
2380	If C<timeout> is less than 0, then no timeout watcher will be	3326	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3327	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3328	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		3329
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3330	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2386	passed an C<revents> set like normal event callbacks (a combination of	3331	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3332	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2388	value passed to C<ev_once>:	3333	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3334	a timeout and an io event at the same time - you probably should give io
		3335	events precedence.
2389		3336
		3337	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3338
2390	static void stdin_ready (int revents, void *arg)	3339	static void stdin_ready (int revents, void *arg)
2391	{	3340	{
2392	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	3341	if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	3342	/* stdin might have data for us, joy! */;
		3343	else if (revents & EV_TIMER)
		3344	/* doh, nothing entered */;
2396	}	3345	}
2397		3346
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3347	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		3348
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)
2401
2402	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).
2405
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3349	=item ev_feed_fd_event (loop, int fd, int revents)
2407		3350
2408	Feed an event on the given fd, as if a file descriptor backend detected	3351	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	3352	the given events it.
2410		3353
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	3354	=item ev_feed_signal_event (loop, int signum)
2412		3355
2413	Feed an event as if the given signal occurred (C<loop> must be the default	3356	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	3357	loop!).
2415		3358
2416	=back	3359	=back
…		…
2452	you to use some convenience methods to start/stop watchers and also change	3395	you to use some convenience methods to start/stop watchers and also change
2453	the callback model to a model using method callbacks on objects.	3396	the callback model to a model using method callbacks on objects.
2454		3397
2455	To use it,	3398	To use it,
2456		3399
2457	#include <ev++.h>	3400	#include <ev++.h>
2458		3401
2459	This automatically includes F<ev.h> and puts all of its definitions (many	3402	This automatically includes F<ev.h> and puts all of its definitions (many
2460	of them macros) into the global namespace. All C++ specific things are	3403	of them macros) into the global namespace. All C++ specific things are
2461	put into the C<ev> namespace. It should support all the same embedding	3404	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3405	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2496		3439
2497	=over 4	3440	=over 4
2498		3441
2499	=item ev::TYPE::TYPE ()	3442	=item ev::TYPE::TYPE ()
2500		3443
2501	=item ev::TYPE::TYPE (struct ev_loop *)	3444	=item ev::TYPE::TYPE (loop)
2502		3445
2503	=item ev::TYPE::~TYPE	3446	=item ev::TYPE::~TYPE
2504		3447
2505	The constructor (optionally) takes an event loop to associate the watcher	3448	The constructor (optionally) takes an event loop to associate the watcher
2506	with. If it is omitted, it will use C<EV_DEFAULT>.	3449	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	3472	your compiler is good :), then the method will be fully inlined into the
2530	thunking function, making it as fast as a direct C callback.	3473	thunking function, making it as fast as a direct C callback.
2531		3474
2532	Example: simple class declaration and watcher initialisation	3475	Example: simple class declaration and watcher initialisation
2533		3476
2534	struct myclass	3477	struct myclass
2535	{	3478	{
2536	void io_cb (ev::io &w, int revents) { }	3479	void io_cb (ev::io &w, int revents) { }
2537	}	3480	}
2538		3481
2539	myclass obj;	3482	myclass obj;
2540	ev::io iow;	3483	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3484	iow.set <myclass, &myclass::io_cb> (&obj);
		3485
		3486	=item w->set (object *)
		3487
		3488	This is a variation of a method callback - leaving out the method to call
		3489	will default the method to C<operator ()>, which makes it possible to use
		3490	functor objects without having to manually specify the C<operator ()> all
		3491	the time. Incidentally, you can then also leave out the template argument
		3492	list.
		3493
		3494	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3495	int revents)>.
		3496
		3497	See the method-C<set> above for more details.
		3498
		3499	Example: use a functor object as callback.
		3500
		3501	struct myfunctor
		3502	{
		3503	void operator() (ev::io &w, int revents)
		3504	{
		3505	...
		3506	}
		3507	}
		3508
		3509	myfunctor f;
		3510
		3511	ev::io w;
		3512	w.set (&f);
2542		3513
2543	=item w->set<function> (void *data = 0)	3514	=item w->set<function> (void *data = 0)
2544		3515
2545	Also sets a callback, but uses a static method or plain function as	3516	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3517	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		3519
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3520	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3521
2551	See the method-C<set> above for more details.	3522	See the method-C<set> above for more details.
2552		3523
2553	Example:	3524	Example: Use a plain function as callback.
2554		3525
2555	static void io_cb (ev::io &w, int revents) { }	3526	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3527	iow.set <io_cb> ();
2557		3528
2558	=item w->set (struct ev_loop *)	3529	=item w->set (loop)
2559		3530
2560	Associates a different C<struct ev_loop> with this watcher. You can only	3531	Associates a different C<struct ev_loop> with this watcher. You can only
2561	do this when the watcher is inactive (and not pending either).	3532	do this when the watcher is inactive (and not pending either).
2562		3533
2563	=item w->set ([arguments])	3534	=item w->set ([arguments])
2564		3535
2565	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3536	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2566	called at least once. Unlike the C counterpart, an active watcher gets	3537	method or a suitable start method must be called at least once. Unlike the
2567	automatically stopped and restarted when reconfiguring it with this	3538	C counterpart, an active watcher gets automatically stopped and restarted
2568	method.	3539	when reconfiguring it with this method.
2569		3540
2570	=item w->start ()	3541	=item w->start ()
2571		3542
2572	Starts the watcher. Note that there is no C<loop> argument, as the	3543	Starts the watcher. Note that there is no C<loop> argument, as the
2573	constructor already stores the event loop.	3544	constructor already stores the event loop.
2574		3545
		3546	=item w->start ([arguments])
		3547
		3548	Instead of calling C<set> and C<start> methods separately, it is often
		3549	convenient to wrap them in one call. Uses the same type of arguments as
		3550	the configure C<set> method of the watcher.
		3551
2575	=item w->stop ()	3552	=item w->stop ()
2576		3553
2577	Stops the watcher if it is active. Again, no C<loop> argument.	3554	Stops the watcher if it is active. Again, no C<loop> argument.
2578		3555
2579	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3556	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2591		3568
2592	=back	3569	=back
2593		3570
2594	=back	3571	=back
2595		3572
2596	Example: Define a class with an IO and idle watcher, start one of them in	3573	Example: Define a class with two I/O and idle watchers, start the I/O
2597	the constructor.	3574	watchers in the constructor.
2598		3575
2599	class myclass	3576	class myclass
2600	{	3577	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3578	ev::io io ; void io_cb (ev::io &w, int revents);
		3579	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3580	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3581
2604	myclass (int fd)	3582	myclass (int fd)
2605	{	3583	{
2606	io .set <myclass, &myclass::io_cb > (this);	3584	io .set <myclass, &myclass::io_cb > (this);
		3585	io2 .set <myclass, &myclass::io2_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3586	idle.set <myclass, &myclass::idle_cb> (this);
2608		3587
2609	io.start (fd, ev::READ);	3588	io.set (fd, ev::WRITE); // configure the watcher
		3589	io.start (); // start it whenever convenient
		3590
		3591	io2.start (fd, ev::READ); // set + start in one call
2610	}	3592	}
2611	};	3593	};
2612		3594
2613		3595
2614	=head1 OTHER LANGUAGE BINDINGS	3596	=head1 OTHER LANGUAGE BINDINGS
2615		3597
2616	Libev does not offer other language bindings itself, but bindings for a	3598	Libev does not offer other language bindings itself, but bindings for a
…		…
2623	=item Perl	3605	=item Perl
2624		3606
2625	The EV module implements the full libev API and is actually used to test	3607	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3608	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3609	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3610	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3611	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3612	and C<EV::Glib>).
2630		3613
2631	It can be found and installed via CPAN, its homepage is found at	3614	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3615	L<http://software.schmorp.de/pkg/EV>.
		3616
		3617	=item Python
		3618
		3619	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3620	seems to be quite complete and well-documented.
2633		3621
2634	=item Ruby	3622	=item Ruby
2635		3623
2636	Tony Arcieri has written a ruby extension that offers access to a subset	3624	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds file handle abstractions, asynchronous DNS and	3625	of the libev API and adds file handle abstractions, asynchronous DNS and
2638	more on top of it. It can be found via gem servers. Its homepage is at	3626	more on top of it. It can be found via gem servers. Its homepage is at
2639	L<http://rev.rubyforge.org/>.	3627	L<http://rev.rubyforge.org/>.
2640		3628
		3629	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3630	makes rev work even on mingw.
		3631
		3632	=item Haskell
		3633
		3634	A haskell binding to libev is available at
		3635	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3636
2641	=item D	3637	=item D
2642		3638
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3639	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3640	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3641
		3642	=item Ocaml
		3643
		3644	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3645	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3646
		3647	=item Lua
		3648
		3649	Brian Maher has written a partial interface to libev for lua (at the
		3650	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3651	L<http://github.com/brimworks/lua-ev>.
2645		3652
2646	=back	3653	=back
2647		3654
2648		3655
2649	=head1 MACRO MAGIC	3656	=head1 MACRO MAGIC
…		…
2661		3668
2662	This provides the loop I<argument> for functions, if one is required ("ev	3669	This provides the loop I<argument> for functions, if one is required ("ev
2663	loop argument"). The C<EV_A> form is used when this is the sole argument,	3670	loop argument"). The C<EV_A> form is used when this is the sole argument,
2664	C<EV_A_> is used when other arguments are following. Example:	3671	C<EV_A_> is used when other arguments are following. Example:
2665		3672
2666	ev_unref (EV_A);	3673	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	3674	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	3675	ev_run (EV_A_ 0);
2669		3676
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3677	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	3678	which is often provided by the following macro.
2672		3679
2673	=item C<EV_P>, C<EV_P_>	3680	=item C<EV_P>, C<EV_P_>
2674		3681
2675	This provides the loop I<parameter> for functions, if one is required ("ev	3682	This provides the loop I<parameter> for functions, if one is required ("ev
2676	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3683	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2677	C<EV_P_> is used when other parameters are following. Example:	3684	C<EV_P_> is used when other parameters are following. Example:
2678		3685
2679	// this is how ev_unref is being declared	3686	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	3687	static void ev_unref (EV_P);
2681		3688
2682	// this is how you can declare your typical callback	3689	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	3690	static void cb (EV_P_ ev_timer *w, int revents)
2684		3691
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3692	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	3693	suitable for use with C<EV_A>.
2687		3694
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3695	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		3711
2705	Example: Declare and initialise a check watcher, utilising the above	3712	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	3713	macros so it will work regardless of whether multiple loops are supported
2707	or not.	3714	or not.
2708		3715
2709	static void	3716	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	3717	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	3718	{
2712	ev_check_stop (EV_A_ w);	3719	ev_check_stop (EV_A_ w);
2713	}	3720	}
2714		3721
2715	ev_check check;	3722	ev_check check;
2716	ev_check_init (&check, check_cb);	3723	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	3724	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	3725	ev_run (EV_DEFAULT_ 0);
2719		3726
2720	=head1 EMBEDDING	3727	=head1 EMBEDDING
2721		3728
2722	Libev can (and often is) directly embedded into host	3729	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	3730	applications. Examples of applications that embed it include the Deliantra
…		…
2737	=head3 CORE EVENT LOOP	3744	=head3 CORE EVENT LOOP
2738		3745
2739	To include only the libev core (all the C<ev_*> functions), with manual	3746	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	3747	configuration (no autoconf):
2741		3748
2742	#define EV_STANDALONE 1	3749	#define EV_STANDALONE 1
2743	#include "ev.c"	3750	#include "ev.c"
2744		3751
2745	This will automatically include F<ev.h>, too, and should be done in a	3752	This will automatically include F<ev.h>, too, and should be done in a
2746	single C source file only to provide the function implementations. To use	3753	single C source file only to provide the function implementations. To use
2747	it, do the same for F<ev.h> in all files wishing to use this API (best	3754	it, do the same for F<ev.h> in all files wishing to use this API (best
2748	done by writing a wrapper around F<ev.h> that you can include instead and	3755	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	3756	where you can put other configuration options):
2750		3757
2751	#define EV_STANDALONE 1	3758	#define EV_STANDALONE 1
2752	#include "ev.h"	3759	#include "ev.h"
2753		3760
2754	Both header files and implementation files can be compiled with a C++	3761	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	3762	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	3763	as a bug).
2757		3764
2758	You need the following files in your source tree, or in a directory	3765	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	3766	in your include path (e.g. in libev/ when using -Ilibev):
2760		3767
2761	ev.h	3768	ev.h
2762	ev.c	3769	ev.c
2763	ev_vars.h	3770	ev_vars.h
2764	ev_wrap.h	3771	ev_wrap.h
2765		3772
2766	ev_win32.c required on win32 platforms only	3773	ev_win32.c required on win32 platforms only
2767		3774
2768	ev_select.c only when select backend is enabled (which is enabled by default)	3775	ev_select.c only when select backend is enabled (which is enabled by default)
2769	ev_poll.c only when poll backend is enabled (disabled by default)	3776	ev_poll.c only when poll backend is enabled (disabled by default)
2770	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3777	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2771	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3778	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2772	ev_port.c only when the solaris port backend is enabled (disabled by default)	3779	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		3780
2774	F<ev.c> includes the backend files directly when enabled, so you only need	3781	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	3782	to compile this single file.
2776		3783
2777	=head3 LIBEVENT COMPATIBILITY API	3784	=head3 LIBEVENT COMPATIBILITY API
2778		3785
2779	To include the libevent compatibility API, also include:	3786	To include the libevent compatibility API, also include:
2780		3787
2781	#include "event.c"	3788	#include "event.c"
2782		3789
2783	in the file including F<ev.c>, and:	3790	in the file including F<ev.c>, and:
2784		3791
2785	#include "event.h"	3792	#include "event.h"
2786		3793
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	3794	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		3795
2789	You need the following additional files for this:	3796	You need the following additional files for this:
2790		3797
2791	event.h	3798	event.h
2792	event.c	3799	event.c
2793		3800
2794	=head3 AUTOCONF SUPPORT	3801	=head3 AUTOCONF SUPPORT
2795		3802
2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in	3803	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2797	whatever way you want, you can also C<m4_include([libev.m4])> in your	3804	whatever way you want, you can also C<m4_include([libev.m4])> in your
2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3805	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	3806	include F<config.h> and configure itself accordingly.
2800		3807
2801	For this of course you need the m4 file:	3808	For this of course you need the m4 file:
2802		3809
2803	libev.m4	3810	libev.m4
2804		3811
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3812	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3813
2807	Libev can be configured via a variety of preprocessor symbols you have to	3814	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absence of	3815	define before including (or compiling) any of its files. The default in
2809	autoconf is noted for every option.	3816	the absence of autoconf is documented for every option.
		3817
		3818	Symbols marked with "(h)" do not change the ABI, and can have different
		3819	values when compiling libev vs. including F<ev.h>, so it is permissible
		3820	to redefine them before including F<ev.h> without breaking compatibility
		3821	to a compiled library. All other symbols change the ABI, which means all
		3822	users of libev and the libev code itself must be compiled with compatible
		3823	settings.
2810		3824
2811	=over 4	3825	=over 4
2812		3826
		3827	=item EV_COMPAT3 (h)
		3828
		3829	Backwards compatibility is a major concern for libev. This is why this
		3830	release of libev comes with wrappers for the functions and symbols that
		3831	have been renamed between libev version 3 and 4.
		3832
		3833	You can disable these wrappers (to test compatibility with future
		3834	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3835	sources. This has the additional advantage that you can drop the C<struct>
		3836	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3837	typedef in that case.
		3838
		3839	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3840	and in some even more future version the compatibility code will be
		3841	removed completely.
		3842
2813	=item EV_STANDALONE	3843	=item EV_STANDALONE (h)
2814		3844
2815	Must always be C<1> if you do not use autoconf configuration, which	3845	Must always be C<1> if you do not use autoconf configuration, which
2816	keeps libev from including F<config.h>, and it also defines dummy	3846	keeps libev from including F<config.h>, and it also defines dummy
2817	implementations for some libevent functions (such as logging, which is not	3847	implementations for some libevent functions (such as logging, which is not
2818	supported). It will also not define any of the structs usually found in	3848	supported). It will also not define any of the structs usually found in
2819	F<event.h> that are not directly supported by the libev core alone.	3849	F<event.h> that are not directly supported by the libev core alone.
2820		3850
		3851	In standalone mode, libev will still try to automatically deduce the
		3852	configuration, but has to be more conservative.
		3853
2821	=item EV_USE_MONOTONIC	3854	=item EV_USE_MONOTONIC
2822		3855
2823	If defined to be C<1>, libev will try to detect the availability of the	3856	If defined to be C<1>, libev will try to detect the availability of the
2824	monotonic clock option at both compile time and runtime. Otherwise no use	3857	monotonic clock option at both compile time and runtime. Otherwise no
2825	of the monotonic clock option will be attempted. If you enable this, you	3858	use of the monotonic clock option will be attempted. If you enable this,
2826	usually have to link against librt or something similar. Enabling it when	3859	you usually have to link against librt or something similar. Enabling it
2827	the functionality isn't available is safe, though, although you have	3860	when the functionality isn't available is safe, though, although you have
2828	to make sure you link against any libraries where the C<clock_gettime>	3861	to make sure you link against any libraries where the C<clock_gettime>
2829	function is hiding in (often F<-lrt>).	3862	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2830		3863
2831	=item EV_USE_REALTIME	3864	=item EV_USE_REALTIME
2832		3865
2833	If defined to be C<1>, libev will try to detect the availability of the	3866	If defined to be C<1>, libev will try to detect the availability of the
2834	real-time clock option at compile time (and assume its availability at	3867	real-time clock option at compile time (and assume its availability
2835	runtime if successful). Otherwise no use of the real-time clock option will	3868	at runtime if successful). Otherwise no use of the real-time clock
2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3869	option will be attempted. This effectively replaces C<gettimeofday>
2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3870	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3871	correctness. See the note about libraries in the description of
		3872	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3873	C<EV_USE_CLOCK_SYSCALL>.
		3874
		3875	=item EV_USE_CLOCK_SYSCALL
		3876
		3877	If defined to be C<1>, libev will try to use a direct syscall instead
		3878	of calling the system-provided C<clock_gettime> function. This option
		3879	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3880	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3881	programs needlessly. Using a direct syscall is slightly slower (in
		3882	theory), because no optimised vdso implementation can be used, but avoids
		3883	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3884	higher, as it simplifies linking (no need for C<-lrt>).
2839		3885
2840	=item EV_USE_NANOSLEEP	3886	=item EV_USE_NANOSLEEP
2841		3887
2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3888	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2843	and will use it for delays. Otherwise it will use C<select ()>.	3889	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2859		3905
2860	=item EV_SELECT_USE_FD_SET	3906	=item EV_SELECT_USE_FD_SET
2861		3907
2862	If defined to C<1>, then the select backend will use the system C<fd_set>	3908	If defined to C<1>, then the select backend will use the system C<fd_set>
2863	structure. This is useful if libev doesn't compile due to a missing	3909	structure. This is useful if libev doesn't compile due to a missing
2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3910	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2865	exotic systems. This usually limits the range of file descriptors to some	3911	on exotic systems. This usually limits the range of file descriptors to
2866	low limit such as 1024 or might have other limitations (winsocket only	3912	some low limit such as 1024 or might have other limitations (winsocket
2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3913	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2868	influence the size of the C<fd_set> used.	3914	configures the maximum size of the C<fd_set>.
2869		3915
2870	=item EV_SELECT_IS_WINSOCKET	3916	=item EV_SELECT_IS_WINSOCKET
2871		3917
2872	When defined to C<1>, the select backend will assume that	3918	When defined to C<1>, the select backend will assume that
2873	select/socket/connect etc. don't understand file descriptors but	3919	select/socket/connect etc. don't understand file descriptors but
…		…
2875	be used is the winsock select). This means that it will call	3921	be used is the winsock select). This means that it will call
2876	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3922	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2877	it is assumed that all these functions actually work on fds, even	3923	it is assumed that all these functions actually work on fds, even
2878	on win32. Should not be defined on non-win32 platforms.	3924	on win32. Should not be defined on non-win32 platforms.
2879		3925
2880	=item EV_FD_TO_WIN32_HANDLE	3926	=item EV_FD_TO_WIN32_HANDLE(fd)
2881		3927
2882	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3928	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2883	file descriptors to socket handles. When not defining this symbol (the	3929	file descriptors to socket handles. When not defining this symbol (the
2884	default), then libev will call C<_get_osfhandle>, which is usually	3930	default), then libev will call C<_get_osfhandle>, which is usually
2885	correct. In some cases, programs use their own file descriptor management,	3931	correct. In some cases, programs use their own file descriptor management,
2886	in which case they can provide this function to map fds to socket handles.	3932	in which case they can provide this function to map fds to socket handles.
		3933
		3934	=item EV_WIN32_HANDLE_TO_FD(handle)
		3935
		3936	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3937	using the standard C<_open_osfhandle> function. For programs implementing
		3938	their own fd to handle mapping, overwriting this function makes it easier
		3939	to do so. This can be done by defining this macro to an appropriate value.
		3940
		3941	=item EV_WIN32_CLOSE_FD(fd)
		3942
		3943	If programs implement their own fd to handle mapping on win32, then this
		3944	macro can be used to override the C<close> function, useful to unregister
		3945	file descriptors again. Note that the replacement function has to close
		3946	the underlying OS handle.
2887		3947
2888	=item EV_USE_POLL	3948	=item EV_USE_POLL
2889		3949
2890	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3950	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2891	backend. Otherwise it will be enabled on non-win32 platforms. It	3951	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2938	as well as for signal and thread safety in C<ev_async> watchers.	3998	as well as for signal and thread safety in C<ev_async> watchers.
2939		3999
2940	In the absence of this define, libev will use C<sig_atomic_t volatile>	4000	In the absence of this define, libev will use C<sig_atomic_t volatile>
2941	(from F<signal.h>), which is usually good enough on most platforms.	4001	(from F<signal.h>), which is usually good enough on most platforms.
2942		4002
2943	=item EV_H	4003	=item EV_H (h)
2944		4004
2945	The name of the F<ev.h> header file used to include it. The default if	4005	The name of the F<ev.h> header file used to include it. The default if
2946	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4006	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2947	used to virtually rename the F<ev.h> header file in case of conflicts.	4007	used to virtually rename the F<ev.h> header file in case of conflicts.
2948		4008
2949	=item EV_CONFIG_H	4009	=item EV_CONFIG_H (h)
2950		4010
2951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4011	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4012	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2953	C<EV_H>, above.	4013	C<EV_H>, above.
2954		4014
2955	=item EV_EVENT_H	4015	=item EV_EVENT_H (h)
2956		4016
2957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4017	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2958	of how the F<event.h> header can be found, the default is C<"event.h">.	4018	of how the F<event.h> header can be found, the default is C<"event.h">.
2959		4019
2960	=item EV_PROTOTYPES	4020	=item EV_PROTOTYPES (h)
2961		4021
2962	If defined to be C<0>, then F<ev.h> will not define any function	4022	If defined to be C<0>, then F<ev.h> will not define any function
2963	prototypes, but still define all the structs and other symbols. This is	4023	prototypes, but still define all the structs and other symbols. This is
2964	occasionally useful if you want to provide your own wrapper functions	4024	occasionally useful if you want to provide your own wrapper functions
2965	around libev functions.	4025	around libev functions.
…		…
2984	When doing priority-based operations, libev usually has to linearly search	4044	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	4045	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	4046	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	4047	fine.
2988		4048
2989	If your embedding application does not need any priorities, defining these both to	4049	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	4050	both to C<0> will save some memory and CPU.
2991		4051
2992	=item EV_PERIODIC_ENABLE	4052	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4053	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4054	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2993		4055
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	4056	If undefined or defined to be C<1> (and the platform supports it), then
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	4057	the respective watcher type is supported. If defined to be C<0>, then it
2996	code.	4058	is not. Disabling watcher types mainly saves code size.
2997		4059
2998	=item EV_IDLE_ENABLE	4060	=item EV_FEATURES
2999
3000	If undefined or defined to be C<1>, then idle watchers are supported. If
3001	defined to be C<0>, then they are not. Disabling them saves a few kB of
3002	code.
3003
3004	=item EV_EMBED_ENABLE
3005
3006	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.
3008
3009	=item EV_STAT_ENABLE
3010
3011	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.
3013
3014	=item EV_FORK_ENABLE
3015
3016	If undefined or defined to be C<1>, then fork watchers are supported. If
3017	defined to be C<0>, then they are not.
3018
3019	=item EV_ASYNC_ENABLE
3020
3021	If undefined or defined to be C<1>, then async watchers are supported. If
3022	defined to be C<0>, then they are not.
3023
3024	=item EV_MINIMAL
3025		4061
3026	If you need to shave off some kilobytes of code at the expense of some	4062	If you need to shave off some kilobytes of code at the expense of some
3027	speed, define this symbol to C<1>. Currently this is used to override some	4063	speed (but with the full API), you can define this symbol to request
3028	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4064	certain subsets of functionality. The default is to enable all features
3029	much smaller 2-heap for timer management over the default 4-heap.	4065	that can be enabled on the platform.
		4066
		4067	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4068	with some broad features you want) and then selectively re-enable
		4069	additional parts you want, for example if you want everything minimal,
		4070	but multiple event loop support, async and child watchers and the poll
		4071	backend, use this:
		4072
		4073	#define EV_FEATURES 0
		4074	#define EV_MULTIPLICITY 1
		4075	#define EV_USE_POLL 1
		4076	#define EV_CHILD_ENABLE 1
		4077	#define EV_ASYNC_ENABLE 1
		4078
		4079	The actual value is a bitset, it can be a combination of the following
		4080	values:
		4081
		4082	=over 4
		4083
		4084	=item C<1> - faster/larger code
		4085
		4086	Use larger code to speed up some operations.
		4087
		4088	Currently this is used to override some inlining decisions (enlarging the
		4089	code size by roughly 30% on amd64).
		4090
		4091	When optimising for size, use of compiler flags such as C<-Os> with
		4092	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4093	assertions.
		4094
		4095	=item C<2> - faster/larger data structures
		4096
		4097	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4098	hash table sizes and so on. This will usually further increase code size
		4099	and can additionally have an effect on the size of data structures at
		4100	runtime.
		4101
		4102	=item C<4> - full API configuration
		4103
		4104	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4105	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4106
		4107	=item C<8> - full API
		4108
		4109	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4110	details on which parts of the API are still available without this
		4111	feature, and do not complain if this subset changes over time.
		4112
		4113	=item C<16> - enable all optional watcher types
		4114
		4115	Enables all optional watcher types. If you want to selectively enable
		4116	only some watcher types other than I/O and timers (e.g. prepare,
		4117	embed, async, child...) you can enable them manually by defining
		4118	C<EV_watchertype_ENABLE> to C<1> instead.
		4119
		4120	=item C<32> - enable all backends
		4121
		4122	This enables all backends - without this feature, you need to enable at
		4123	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4124
		4125	=item C<64> - enable OS-specific "helper" APIs
		4126
		4127	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4128	default.
		4129
		4130	=back
		4131
		4132	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4133	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4134	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4135	watchers, timers and monotonic clock support.
		4136
		4137	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4138	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4139	your program might be left out as well - a binary starting a timer and an
		4140	I/O watcher then might come out at only 5Kb.
		4141
		4142	=item EV_AVOID_STDIO
		4143
		4144	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4145	functions (printf, scanf, perror etc.). This will increase the code size
		4146	somewhat, but if your program doesn't otherwise depend on stdio and your
		4147	libc allows it, this avoids linking in the stdio library which is quite
		4148	big.
		4149
		4150	Note that error messages might become less precise when this option is
		4151	enabled.
		4152
		4153	=item EV_NSIG
		4154
		4155	The highest supported signal number, +1 (or, the number of
		4156	signals): Normally, libev tries to deduce the maximum number of signals
		4157	automatically, but sometimes this fails, in which case it can be
		4158	specified. Also, using a lower number than detected (C<32> should be
		4159	good for about any system in existence) can save some memory, as libev
		4160	statically allocates some 12-24 bytes per signal number.
3030		4161
3031	=item EV_PID_HASHSIZE	4162	=item EV_PID_HASHSIZE
3032		4163
3033	C<ev_child> watchers use a small hash table to distribute workload by	4164	C<ev_child> watchers use a small hash table to distribute workload by
3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4165	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3035	than enough. If you need to manage thousands of children you might want to	4166	usually more than enough. If you need to manage thousands of children you
3036	increase this value (I<must> be a power of two).	4167	might want to increase this value (I<must> be a power of two).
3037		4168
3038	=item EV_INOTIFY_HASHSIZE	4169	=item EV_INOTIFY_HASHSIZE
3039		4170
3040	C<ev_stat> watchers use a small hash table to distribute workload by	4171	C<ev_stat> watchers use a small hash table to distribute workload by
3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4172	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3042	usually more than enough. If you need to manage thousands of C<ev_stat>	4173	disabled), usually more than enough. If you need to manage thousands of
3043	watchers you might want to increase this value (I<must> be a power of	4174	C<ev_stat> watchers you might want to increase this value (I<must> be a
3044	two).	4175	power of two).
3045		4176
3046	=item EV_USE_4HEAP	4177	=item EV_USE_4HEAP
3047		4178
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4179	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4180	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	4181	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	4182	faster performance with many (thousands) of watchers.
3052		4183
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4184	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3054	(disabled).	4185	will be C<0>.
3055		4186
3056	=item EV_HEAP_CACHE_AT	4187	=item EV_HEAP_CACHE_AT
3057		4188
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4189	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	4190	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4191	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4192	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	4193	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	4194	noticeably with many (hundreds) of watchers.
3064		4195
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4196	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3066	(disabled).	4197	will be C<0>.
3067		4198
3068	=item EV_VERIFY	4199	=item EV_VERIFY
3069		4200
3070	Controls how much internal verification (see C<ev_loop_verify ()>) will	4201	Controls how much internal verification (see C<ev_verify ()>) will
3071	be done: If set to C<0>, no internal verification code will be compiled	4202	be done: If set to C<0>, no internal verification code will be compiled
3072	in. If set to C<1>, then verification code will be compiled in, but not	4203	in. If set to C<1>, then verification code will be compiled in, but not
3073	called. If set to C<2>, then the internal verification code will be	4204	called. If set to C<2>, then the internal verification code will be
3074	called once per loop, which can slow down libev. If set to C<3>, then the	4205	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	4206	verification code will be called very frequently, which will slow down
3076	libev considerably.	4207	libev considerably.
3077		4208
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4209	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3079	C<0.>	4210	will be C<0>.
3080		4211
3081	=item EV_COMMON	4212	=item EV_COMMON
3082		4213
3083	By default, all watchers have a C<void *data> member. By redefining	4214	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	4215	this macro to something else you can include more and other types of
3085	members. You have to define it each time you include one of the files,	4216	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	4217	though, and it must be identical each time.
3087		4218
3088	For example, the perl EV module uses something like this:	4219	For example, the perl EV module uses something like this:
3089		4220
3090	#define EV_COMMON \	4221	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	4222	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	4223	SV *cb_sv, *fh /* note no trailing ";" */
3093		4224
3094	=item EV_CB_DECLARE (type)	4225	=item EV_CB_DECLARE (type)
3095		4226
3096	=item EV_CB_INVOKE (watcher, revents)	4227	=item EV_CB_INVOKE (watcher, revents)
3097		4228
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	4233	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	4234	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4235	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	4236	method calls instead of plain function calls in C++.
3106		4237
		4238	=back
		4239
3107	=head2 EXPORTED API SYMBOLS	4240	=head2 EXPORTED API SYMBOLS
3108		4241
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	4242	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	4243	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	4244	all public symbols, one per line:
3112		4245
3113	Symbols.ev for libev proper	4246	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	4247	Symbols.event for the libevent emulation
3115		4248
3116	This can also be used to rename all public symbols to avoid clashes with	4249	This can also be used to rename all public symbols to avoid clashes with
3117	multiple versions of libev linked together (which is obviously bad in	4250	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvenient to avoid this).	4251	itself, but sometimes it is inconvenient to avoid this).
3119		4252
…		…
3140	file.	4273	file.
3141		4274
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4275	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3143	that everybody includes and which overrides some configure choices:	4276	that everybody includes and which overrides some configure choices:
3144		4277
3145	#define EV_MINIMAL 1	4278	#define EV_FEATURES 8
3146	#define EV_USE_POLL 0	4279	#define EV_USE_SELECT 1
3147	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	4280	#define EV_PREPARE_ENABLE 1
		4281	#define EV_IDLE_ENABLE 1
3149	#define EV_STAT_ENABLE 0	4282	#define EV_SIGNAL_ENABLE 1
3150	#define EV_FORK_ENABLE 0	4283	#define EV_CHILD_ENABLE 1
		4284	#define EV_USE_STDEXCEPT 0
3151	#define EV_CONFIG_H <config.h>	4285	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0
3154		4286
3155	#include "ev++.h"	4287	#include "ev++.h"
3156		4288
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4289	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		4290
3159	#include "ev_cpp.h"	4291	#include "ev_cpp.h"
3160	#include "ev.c"	4292	#include "ev.c"
3161		4293
		4294	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		4295
3163	=head1 THREADS AND COROUTINES	4296	=head2 THREADS AND COROUTINES
3164		4297
3165	=head2 THREADS	4298	=head3 THREADS
3166		4299
3167	Libev itself is completely thread-safe, but it uses no locking. This	4300	All libev functions are reentrant and thread-safe unless explicitly
		4301	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	4302	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	4303	are no concurrent calls into any libev function with the same loop
3170	parameter.	4304	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4305	of course): libev guarantees that different event loops share no data
		4306	structures that need any locking.
3171		4307
3172	Or put differently: calls with different loop parameters can be done in	4308	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	4309	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	4310	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	4311	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	4312	a mutex per loop).
3177		4313
3178	If you want to know which design is best for your problem, then I cannot	4314	Specifically to support threads (and signal handlers), libev implements
		4315	so-called C<ev_async> watchers, which allow some limited form of
		4316	concurrency on the same event loop, namely waking it up "from the
		4317	outside".
		4318
		4319	If you want to know which design (one loop, locking, or multiple loops
		4320	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	4321	help you, but here is some generic advice:
3180		4322
3181	=over 4	4323	=over 4
3182		4324
3183	=item * most applications have a main thread: use the default libev loop	4325	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a separate thread running only the default loop.	4326	in that thread, or create a separate thread running only the default loop.
…		…
3196		4338
3197	Choosing a model is hard - look around, learn, know that usually you can do	4339	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	4340	better than you currently do :-)
3199		4341
3200	=item * often you need to talk to some other thread which blocks in the	4342	=item * often you need to talk to some other thread which blocks in the
		4343	event loop.
		4344
3201	event loop - C<ev_async> watchers can be used to wake them up from other	4345	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	4346	(or from signal contexts...).
		4347
		4348	An example use would be to communicate signals or other events that only
		4349	work in the default loop by registering the signal watcher with the
		4350	default loop and triggering an C<ev_async> watcher from the default loop
		4351	watcher callback into the event loop interested in the signal.
3203		4352
3204	=back	4353	=back
3205		4354
		4355	=head4 THREAD LOCKING EXAMPLE
		4356
		4357	Here is a fictitious example of how to run an event loop in a different
		4358	thread than where callbacks are being invoked and watchers are
		4359	created/added/removed.
		4360
		4361	For a real-world example, see the C<EV::Loop::Async> perl module,
		4362	which uses exactly this technique (which is suited for many high-level
		4363	languages).
		4364
		4365	The example uses a pthread mutex to protect the loop data, a condition
		4366	variable to wait for callback invocations, an async watcher to notify the
		4367	event loop thread and an unspecified mechanism to wake up the main thread.
		4368
		4369	First, you need to associate some data with the event loop:
		4370
		4371	typedef struct {
		4372	mutex_t lock; /* global loop lock */
		4373	ev_async async_w;
		4374	thread_t tid;
		4375	cond_t invoke_cv;
		4376	} userdata;
		4377
		4378	void prepare_loop (EV_P)
		4379	{
		4380	// for simplicity, we use a static userdata struct.
		4381	static userdata u;
		4382
		4383	ev_async_init (&u->async_w, async_cb);
		4384	ev_async_start (EV_A_ &u->async_w);
		4385
		4386	pthread_mutex_init (&u->lock, 0);
		4387	pthread_cond_init (&u->invoke_cv, 0);
		4388
		4389	// now associate this with the loop
		4390	ev_set_userdata (EV_A_ u);
		4391	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4392	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4393
		4394	// then create the thread running ev_loop
		4395	pthread_create (&u->tid, 0, l_run, EV_A);
		4396	}
		4397
		4398	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4399	solely to wake up the event loop so it takes notice of any new watchers
		4400	that might have been added:
		4401
		4402	static void
		4403	async_cb (EV_P_ ev_async *w, int revents)
		4404	{
		4405	// just used for the side effects
		4406	}
		4407
		4408	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4409	protecting the loop data, respectively.
		4410
		4411	static void
		4412	l_release (EV_P)
		4413	{
		4414	userdata *u = ev_userdata (EV_A);
		4415	pthread_mutex_unlock (&u->lock);
		4416	}
		4417
		4418	static void
		4419	l_acquire (EV_P)
		4420	{
		4421	userdata *u = ev_userdata (EV_A);
		4422	pthread_mutex_lock (&u->lock);
		4423	}
		4424
		4425	The event loop thread first acquires the mutex, and then jumps straight
		4426	into C<ev_run>:
		4427
		4428	void *
		4429	l_run (void *thr_arg)
		4430	{
		4431	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4432
		4433	l_acquire (EV_A);
		4434	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4435	ev_run (EV_A_ 0);
		4436	l_release (EV_A);
		4437
		4438	return 0;
		4439	}
		4440
		4441	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4442	signal the main thread via some unspecified mechanism (signals? pipe
		4443	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4444	have been called (in a while loop because a) spurious wakeups are possible
		4445	and b) skipping inter-thread-communication when there are no pending
		4446	watchers is very beneficial):
		4447
		4448	static void
		4449	l_invoke (EV_P)
		4450	{
		4451	userdata *u = ev_userdata (EV_A);
		4452
		4453	while (ev_pending_count (EV_A))
		4454	{
		4455	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4456	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4457	}
		4458	}
		4459
		4460	Now, whenever the main thread gets told to invoke pending watchers, it
		4461	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4462	thread to continue:
		4463
		4464	static void
		4465	real_invoke_pending (EV_P)
		4466	{
		4467	userdata *u = ev_userdata (EV_A);
		4468
		4469	pthread_mutex_lock (&u->lock);
		4470	ev_invoke_pending (EV_A);
		4471	pthread_cond_signal (&u->invoke_cv);
		4472	pthread_mutex_unlock (&u->lock);
		4473	}
		4474
		4475	Whenever you want to start/stop a watcher or do other modifications to an
		4476	event loop, you will now have to lock:
		4477
		4478	ev_timer timeout_watcher;
		4479	userdata *u = ev_userdata (EV_A);
		4480
		4481	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4482
		4483	pthread_mutex_lock (&u->lock);
		4484	ev_timer_start (EV_A_ &timeout_watcher);
		4485	ev_async_send (EV_A_ &u->async_w);
		4486	pthread_mutex_unlock (&u->lock);
		4487
		4488	Note that sending the C<ev_async> watcher is required because otherwise
		4489	an event loop currently blocking in the kernel will have no knowledge
		4490	about the newly added timer. By waking up the loop it will pick up any new
		4491	watchers in the next event loop iteration.
		4492
3206	=head2 COROUTINES	4493	=head3 COROUTINES
3207		4494
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	4495	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	4496	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4497	coroutines (e.g. you can call C<ev_run> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	4498	different coroutines, and switch freely between both coroutines running
3212	loop, as long as you don't confuse yourself). The only exception is that	4499	the loop, as long as you don't confuse yourself). The only exception is
3213	you must not do this from C<ev_periodic> reschedule callbacks.	4500	that you must not do this from C<ev_periodic> reschedule callbacks.
3214		4501
3215	Care has been invested into making sure that libev does not keep local	4502	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	4503	C<ev_run>, and other calls do not usually allow for coroutine switches as
3217	switches.	4504	they do not call any callbacks.
3218		4505
		4506	=head2 COMPILER WARNINGS
3219		4507
3220	=head1 COMPLEXITIES	4508	Depending on your compiler and compiler settings, you might get no or a
		4509	lot of warnings when compiling libev code. Some people are apparently
		4510	scared by this.
3221		4511
3222	In this section the complexities of (many of) the algorithms used inside	4512	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	4513	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	4514	warning options. "Warn-free" code therefore cannot be a goal except when
		4515	targeting a specific compiler and compiler-version.
3225		4516
3226	All of the following are about amortised time: If an array needs to be	4517	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	4518	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	4519	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		4520
3232	=over 4	4521	And of course, some compiler warnings are just plain stupid, or simply
		4522	wrong (because they don't actually warn about the condition their message
		4523	seems to warn about). For example, certain older gcc versions had some
		4524	warnings that resulted in an extreme number of false positives. These have
		4525	been fixed, but some people still insist on making code warn-free with
		4526	such buggy versions.
3233		4527
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4528	While libev is written to generate as few warnings as possible,
		4529	"warn-free" code is not a goal, and it is recommended not to build libev
		4530	with any compiler warnings enabled unless you are prepared to cope with
		4531	them (e.g. by ignoring them). Remember that warnings are just that:
		4532	warnings, not errors, or proof of bugs.
3235		4533
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		4534
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4535	=head2 VALGRIND
3241		4536
3242	That means that changing a timer costs less than removing/adding them	4537	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	4538	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		4539
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4540	If you think you found a bug (memory leak, uninitialised data access etc.)
		4541	in libev, then check twice: If valgrind reports something like:
3246		4542
3247	These just add the watcher into an array or at the head of a list.	4543	==2274== definitely lost: 0 bytes in 0 blocks.
		4544	==2274== possibly lost: 0 bytes in 0 blocks.
		4545	==2274== still reachable: 256 bytes in 1 blocks.
3248		4546
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4547	Then there is no memory leak, just as memory accounted to global variables
		4548	is not a memleak - the memory is still being referenced, and didn't leak.
3250		4549
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4550	Similarly, under some circumstances, valgrind might report kernel bugs
		4551	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4552	although an acceptable workaround has been found here), or it might be
		4553	confused.
3252		4554
3253	These watchers are stored in lists then need to be walked to find the	4555	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	4556	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		4557
3257	=item Finding the next timer in each loop iteration: O(1)	4558	If you are unsure about something, feel free to contact the mailing list
		4559	with the full valgrind report and an explanation on why you think this
		4560	is a bug in libev (best check the archives, too :). However, don't be
		4561	annoyed when you get a brisk "this is no bug" answer and take the chance
		4562	of learning how to interpret valgrind properly.
3258		4563
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	4564	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	4565	I suggest using suppression lists.
3261		4566
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		4567
3264	A change means an I/O watcher gets started or stopped, which requires	4568	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and whether C<ev_io_set> was used).
3267		4569
3268	=item Activating one watcher (putting it into the pending state): O(1)	4570	=head2 GNU/LINUX 32 BIT LIMITATIONS
3269		4571
3270	=item Priority handling: O(number_of_priorities)	4572	GNU/Linux is the only common platform that supports 64 bit file/large file
		4573	interfaces but I<disables> them by default.
3271		4574
3272	Priorities are implemented by allocating some space for each	4575	That means that libev compiled in the default environment doesn't support
3273	priority. When doing priority-based operations, libev usually has to	4576	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276		4577
3277	=item Sending an ev_async: O(1)	4578	Unfortunately, many programs try to work around this GNU/Linux issue
		4579	by enabling the large file API, which makes them incompatible with the
		4580	standard libev compiled for their system.
3278		4581
3279	=item Processing ev_async_send: O(number_of_async_watchers)	4582	Likewise, libev cannot enable the large file API itself as this would
		4583	suddenly make it incompatible to the default compile time environment,
		4584	i.e. all programs not using special compile switches.
3280		4585
3281	=item Processing signals: O(max_signal_number)	4586	=head2 OS/X AND DARWIN BUGS
3282		4587
3283	Sending involves a system call I<iff> there were no other C<ev_async_send>	4588	The whole thing is a bug if you ask me - basically any system interface
3284	calls in the current loop iteration. Checking for async and signal events	4589	you touch is broken, whether it is locales, poll, kqueue or even the
3285	involves iterating over all running async watchers or all signal numbers.	4590	OpenGL drivers.
3286		4591
3287	=back	4592	=head3 C<kqueue> is buggy
3288		4593
		4594	The kqueue syscall is broken in all known versions - most versions support
		4595	only sockets, many support pipes.
3289		4596
3290	=head1 Win32 platform limitations and workarounds	4597	Libev tries to work around this by not using C<kqueue> by default on this
		4598	rotten platform, but of course you can still ask for it when creating a
		4599	loop - embedding a socket-only kqueue loop into a select-based one is
		4600	probably going to work well.
		4601
		4602	=head3 C<poll> is buggy
		4603
		4604	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4605	implementation by something calling C<kqueue> internally around the 10.5.6
		4606	release, so now C<kqueue> I<and> C<poll> are broken.
		4607
		4608	Libev tries to work around this by not using C<poll> by default on
		4609	this rotten platform, but of course you can still ask for it when creating
		4610	a loop.
		4611
		4612	=head3 C<select> is buggy
		4613
		4614	All that's left is C<select>, and of course Apple found a way to fuck this
		4615	one up as well: On OS/X, C<select> actively limits the number of file
		4616	descriptors you can pass in to 1024 - your program suddenly crashes when
		4617	you use more.
		4618
		4619	There is an undocumented "workaround" for this - defining
		4620	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4621	work on OS/X.
		4622
		4623	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4624
		4625	=head3 C<errno> reentrancy
		4626
		4627	The default compile environment on Solaris is unfortunately so
		4628	thread-unsafe that you can't even use components/libraries compiled
		4629	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4630	defined by default. A valid, if stupid, implementation choice.
		4631
		4632	If you want to use libev in threaded environments you have to make sure
		4633	it's compiled with C<_REENTRANT> defined.
		4634
		4635	=head3 Event port backend
		4636
		4637	The scalable event interface for Solaris is called "event
		4638	ports". Unfortunately, this mechanism is very buggy in all major
		4639	releases. If you run into high CPU usage, your program freezes or you get
		4640	a large number of spurious wakeups, make sure you have all the relevant
		4641	and latest kernel patches applied. No, I don't know which ones, but there
		4642	are multiple ones to apply, and afterwards, event ports actually work
		4643	great.
		4644
		4645	If you can't get it to work, you can try running the program by setting
		4646	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4647	C<select> backends.
		4648
		4649	=head2 AIX POLL BUG
		4650
		4651	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4652	this by trying to avoid the poll backend altogether (i.e. it's not even
		4653	compiled in), which normally isn't a big problem as C<select> works fine
		4654	with large bitsets on AIX, and AIX is dead anyway.
		4655
		4656	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4657
		4658	=head3 General issues
3291		4659
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4660	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	4661	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	4662	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4663	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3296	descriptors. This only applies when using Win32 natively, not when using	4664	descriptors. This only applies when using Win32 natively, not when using
3297	e.g. cygwin.	4665	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4666	as every compielr comes with a slightly differently broken/incompatible
		4667	environment.
3298		4668
3299	Lifting these limitations would basically require the full	4669	Lifting these limitations would basically require the full
3300	re-implementation of the I/O system. If you are into these kinds of	4670	re-implementation of the I/O system. If you are into this kind of thing,
3301	things, then note that glib does exactly that for you in a very portable	4671	then note that glib does exactly that for you in a very portable way (note
3302	way (note also that glib is the slowest event library known to man).	4672	also that glib is the slowest event library known to man).
3303		4673
3304	There is no supported compilation method available on windows except	4674	There is no supported compilation method available on windows except
3305	embedding it into other applications.	4675	embedding it into other applications.
		4676
		4677	Sensible signal handling is officially unsupported by Microsoft - libev
		4678	tries its best, but under most conditions, signals will simply not work.
3306		4679
3307	Not a libev limitation but worth mentioning: windows apparently doesn't	4680	Not a libev limitation but worth mentioning: windows apparently doesn't
3308	accept large writes: instead of resulting in a partial write, windows will	4681	accept large writes: instead of resulting in a partial write, windows will
3309	either accept everything or return C<ENOBUFS> if the buffer is too large,	4682	either accept everything or return C<ENOBUFS> if the buffer is too large,
3310	so make sure you only write small amounts into your sockets (less than a	4683	so make sure you only write small amounts into your sockets (less than a
3311	megabyte seems safe, but thsi apparently depends on the amount of memory	4684	megabyte seems safe, but this apparently depends on the amount of memory
3312	available).	4685	available).
3313		4686
3314	Due to the many, low, and arbitrary limits on the win32 platform and	4687	Due to the many, low, and arbitrary limits on the win32 platform and
3315	the abysmal performance of winsockets, using a large number of sockets	4688	the abysmal performance of winsockets, using a large number of sockets
3316	is not recommended (and not reasonable). If your program needs to use	4689	is not recommended (and not reasonable). If your program needs to use
3317	more than a hundred or so sockets, then likely it needs to use a totally	4690	more than a hundred or so sockets, then likely it needs to use a totally
3318	different implementation for windows, as libev offers the POSIX readiness	4691	different implementation for windows, as libev offers the POSIX readiness
3319	notification model, which cannot be implemented efficiently on windows	4692	notification model, which cannot be implemented efficiently on windows
3320	(Microsoft monopoly games).	4693	(due to Microsoft monopoly games).
3321		4694
3322	=over 4	4695	A typical way to use libev under windows is to embed it (see the embedding
		4696	section for details) and use the following F<evwrap.h> header file instead
		4697	of F<ev.h>:
3323		4698
		4699	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4700	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4701
		4702	#include "ev.h"
		4703
		4704	And compile the following F<evwrap.c> file into your project (make sure
		4705	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4706
		4707	#include "evwrap.h"
		4708	#include "ev.c"
		4709
3324	=item The winsocket select function	4710	=head3 The winsocket C<select> function
3325		4711
3326	The winsocket C<select> function doesn't follow POSIX in that it	4712	The winsocket C<select> function doesn't follow POSIX in that it
3327	requires socket I<handles> and not socket I<file descriptors> (it is	4713	requires socket I<handles> and not socket I<file descriptors> (it is
3328	also extremely buggy). This makes select very inefficient, and also	4714	also extremely buggy). This makes select very inefficient, and also
3329	requires a mapping from file descriptors to socket handles. See the	4715	requires a mapping from file descriptors to socket handles (the Microsoft
		4716	C runtime provides the function C<_open_osfhandle> for this). See the
3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	4717	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	4718	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3332		4719
3333	The configuration for a "naked" win32 using the Microsoft runtime	4720	The configuration for a "naked" win32 using the Microsoft runtime
3334	libraries and raw winsocket select is:	4721	libraries and raw winsocket select is:
3335		4722
3336	#define EV_USE_SELECT 1	4723	#define EV_USE_SELECT 1
3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4724	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3338		4725
3339	Note that winsockets handling of fd sets is O(n), so you can easily get a	4726	Note that winsockets handling of fd sets is O(n), so you can easily get a
3340	complexity in the O(n²) range when using win32.	4727	complexity in the O(n²) range when using win32.
3341		4728
3342	=item Limited number of file descriptors	4729	=head3 Limited number of file descriptors
3343		4730
3344	Windows has numerous arbitrary (and low) limits on things.	4731	Windows has numerous arbitrary (and low) limits on things.
3345		4732
3346	Early versions of winsocket's select only supported waiting for a maximum	4733	Early versions of winsocket's select only supported waiting for a maximum
3347	of C<64> handles (probably owning to the fact that all windows kernels	4734	of C<64> handles (probably owning to the fact that all windows kernels
3348	can only wait for C<64> things at the same time internally; Microsoft	4735	can only wait for C<64> things at the same time internally; Microsoft
3349	recommends spawning a chain of threads and wait for 63 handles and the	4736	recommends spawning a chain of threads and wait for 63 handles and the
3350	previous thread in each. Great).	4737	previous thread in each. Sounds great!).
3351		4738
3352	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4739	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3353	to some high number (e.g. C<2048>) before compiling the winsocket select	4740	to some high number (e.g. C<2048>) before compiling the winsocket select
3354	call (which might be in libev or elsewhere, for example, perl does its own	4741	call (which might be in libev or elsewhere, for example, perl and many
3355	select emulation on windows).	4742	other interpreters do their own select emulation on windows).
3356		4743
3357	Another limit is the number of file descriptors in the Microsoft runtime	4744	Another limit is the number of file descriptors in the Microsoft runtime
3358	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4745	libraries, which by default is C<64> (there must be a hidden I<64>
3359	or something like this inside Microsoft). You can increase this by calling	4746	fetish or something like this inside Microsoft). You can increase this
3360	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4747	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3361	arbitrary limit), but is broken in many versions of the Microsoft runtime	4748	(another arbitrary limit), but is broken in many versions of the Microsoft
3362	libraries.
3363
3364	This might get you to about C<512> or C<2048> sockets (depending on	4749	runtime libraries. This might get you to about C<512> or C<2048> sockets
3365	windows version and/or the phase of the moon). To get more, you need to	4750	(depending on windows version and/or the phase of the moon). To get more,
3366	wrap all I/O functions and provide your own fd management, but the cost of	4751	you need to wrap all I/O functions and provide your own fd management, but
3367	calling select (O(n²)) will likely make this unworkable.	4752	the cost of calling select (O(n²)) will likely make this unworkable.
3368		4753
3369	=back
3370
3371
3372	=head1 PORTABILITY REQUIREMENTS	4754	=head2 PORTABILITY REQUIREMENTS
3373		4755
3374	In addition to a working ISO-C implementation, libev relies on a few	4756	In addition to a working ISO-C implementation and of course the
3375	additional extensions:	4757	backend-specific APIs, libev relies on a few additional extensions:
3376		4758
3377	=over 4	4759	=over 4
3378		4760
		4761	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4762	calling conventions regardless of C<ev_watcher_type *>.
		4763
		4764	Libev assumes not only that all watcher pointers have the same internal
		4765	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4766	assumes that the same (machine) code can be used to call any watcher
		4767	callback: The watcher callbacks have different type signatures, but libev
		4768	calls them using an C<ev_watcher *> internally.
		4769
		4770	=item pointer accesses must be thread-atomic
		4771
		4772	Accessing a pointer value must be atomic, it must both be readable and
		4773	writable in one piece - this is the case on all current architectures.
		4774
3379	=item C<sig_atomic_t volatile> must be thread-atomic as well	4775	=item C<sig_atomic_t volatile> must be thread-atomic as well
3380		4776
3381	The type C<sig_atomic_t volatile> (or whatever is defined as	4777	The type C<sig_atomic_t volatile> (or whatever is defined as
3382	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4778	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3383	threads. This is not part of the specification for C<sig_atomic_t>, but is	4779	threads. This is not part of the specification for C<sig_atomic_t>, but is
3384	believed to be sufficiently portable.	4780	believed to be sufficiently portable.
3385		4781
3386	=item C<sigprocmask> must work in a threaded environment	4782	=item C<sigprocmask> must work in a threaded environment
3387		4783
…		…
3396	except the initial one, and run the default loop in the initial thread as	4792	except the initial one, and run the default loop in the initial thread as
3397	well.	4793	well.
3398		4794
3399	=item C<long> must be large enough for common memory allocation sizes	4795	=item C<long> must be large enough for common memory allocation sizes
3400		4796
3401	To improve portability and simplify using libev, libev uses C<long>	4797	To improve portability and simplify its API, libev uses C<long> internally
3402	internally instead of C<size_t> when allocating its data structures. On	4798	instead of C<size_t> when allocating its data structures. On non-POSIX
3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4799	systems (Microsoft...) this might be unexpectedly low, but is still at
3404	is still at least 31 bits everywhere, which is enough for hundreds of	4800	least 31 bits everywhere, which is enough for hundreds of millions of
3405	millions of watchers.	4801	watchers.
3406		4802
3407	=item C<double> must hold a time value in seconds with enough accuracy	4803	=item C<double> must hold a time value in seconds with enough accuracy
3408		4804
3409	The type C<double> is used to represent timestamps. It is required to	4805	The type C<double> is used to represent timestamps. It is required to
3410	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4806	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3411	enough for at least into the year 4000. This requirement is fulfilled by	4807	good enough for at least into the year 4000 with millisecond accuracy
		4808	(the design goal for libev). This requirement is overfulfilled by
3412	implementations implementing IEEE 754 (basically all existing ones).	4809	implementations using IEEE 754, which is basically all existing ones. With
		4810	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3413		4811
3414	=back	4812	=back
3415		4813
3416	If you know of other additional requirements drop me a note.	4814	If you know of other additional requirements drop me a note.
3417		4815
3418		4816
3419	=head1 COMPILER WARNINGS	4817	=head1 ALGORITHMIC COMPLEXITIES
3420		4818
3421	Depending on your compiler and compiler settings, you might get no or a	4819	In this section the complexities of (many of) the algorithms used inside
3422	lot of warnings when compiling libev code. Some people are apparently	4820	libev will be documented. For complexity discussions about backends see
3423	scared by this.	4821	the documentation for C<ev_default_init>.
3424		4822
3425	However, these are unavoidable for many reasons. For one, each compiler	4823	All of the following are about amortised time: If an array needs to be
3426	has different warnings, and each user has different tastes regarding	4824	extended, libev needs to realloc and move the whole array, but this
3427	warning options. "Warn-free" code therefore cannot be a goal except when	4825	happens asymptotically rarer with higher number of elements, so O(1) might
3428	targeting a specific compiler and compiler-version.	4826	mean that libev does a lengthy realloc operation in rare cases, but on
		4827	average it is much faster and asymptotically approaches constant time.
3429		4828
3430	Another reason is that some compiler warnings require elaborate	4829	=over 4
3431	workarounds, or other changes to the code that make it less clear and less
3432	maintainable.
3433		4830
3434	And of course, some compiler warnings are just plain stupid, or simply	4831	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3435	wrong (because they don't actually warn about the condition their message
3436	seems to warn about).
3437		4832
3438	While libev is written to generate as few warnings as possible,	4833	This means that, when you have a watcher that triggers in one hour and
3439	"warn-free" code is not a goal, and it is recommended not to build libev	4834	there are 100 watchers that would trigger before that, then inserting will
3440	with any compiler warnings enabled unless you are prepared to cope with	4835	have to skip roughly seven (C<ld 100>) of these watchers.
3441	them (e.g. by ignoring them). Remember that warnings are just that:
3442	warnings, not errors, or proof of bugs.
3443		4836
		4837	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3444		4838
3445	=head1 VALGRIND	4839	That means that changing a timer costs less than removing/adding them,
		4840	as only the relative motion in the event queue has to be paid for.
3446		4841
3447	Valgrind has a special section here because it is a popular tool that is	4842	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3448	highly useful, but valgrind reports are very hard to interpret.
3449		4843
3450	If you think you found a bug (memory leak, uninitialised data access etc.)	4844	These just add the watcher into an array or at the head of a list.
3451	in libev, then check twice: If valgrind reports something like:
3452		4845
3453	==2274== definitely lost: 0 bytes in 0 blocks.	4846	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3454	==2274== possibly lost: 0 bytes in 0 blocks.
3455	==2274== still reachable: 256 bytes in 1 blocks.
3456		4847
3457	Then there is no memory leak. Similarly, under some circumstances,	4848	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3458	valgrind might report kernel bugs as if it were a bug in libev, or it
3459	might be confused (it is a very good tool, but only a tool).
3460		4849
3461	If you are unsure about something, feel free to contact the mailing list	4850	These watchers are stored in lists, so they need to be walked to find the
3462	with the full valgrind report and an explanation on why you think this is	4851	correct watcher to remove. The lists are usually short (you don't usually
3463	a bug in libev. However, don't be annoyed when you get a brisk "this is	4852	have many watchers waiting for the same fd or signal: one is typical, two
3464	no bug" answer and take the chance of learning how to interpret valgrind	4853	is rare).
3465	properly.
3466		4854
3467	If you need, for some reason, empty reports from valgrind for your project	4855	=item Finding the next timer in each loop iteration: O(1)
3468	I suggest using suppression lists.
3469		4856
		4857	By virtue of using a binary or 4-heap, the next timer is always found at a
		4858	fixed position in the storage array.
		4859
		4860	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4861
		4862	A change means an I/O watcher gets started or stopped, which requires
		4863	libev to recalculate its status (and possibly tell the kernel, depending
		4864	on backend and whether C<ev_io_set> was used).
		4865
		4866	=item Activating one watcher (putting it into the pending state): O(1)
		4867
		4868	=item Priority handling: O(number_of_priorities)
		4869
		4870	Priorities are implemented by allocating some space for each
		4871	priority. When doing priority-based operations, libev usually has to
		4872	linearly search all the priorities, but starting/stopping and activating
		4873	watchers becomes O(1) with respect to priority handling.
		4874
		4875	=item Sending an ev_async: O(1)
		4876
		4877	=item Processing ev_async_send: O(number_of_async_watchers)
		4878
		4879	=item Processing signals: O(max_signal_number)
		4880
		4881	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4882	calls in the current loop iteration. Checking for async and signal events
		4883	involves iterating over all running async watchers or all signal numbers.
		4884
		4885	=back
		4886
		4887
		4888	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4889
		4890	The major version 4 introduced some incompatible changes to the API.
		4891
		4892	At the moment, the C<ev.h> header file provides compatibility definitions
		4893	for all changes, so most programs should still compile. The compatibility
		4894	layer might be removed in later versions of libev, so better update to the
		4895	new API early than late.
		4896
		4897	=over 4
		4898
		4899	=item C<EV_COMPAT3> backwards compatibility mechanism
		4900
		4901	The backward compatibility mechanism can be controlled by
		4902	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4903	section.
		4904
		4905	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4906
		4907	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4908
		4909	ev_loop_destroy (EV_DEFAULT_UC);
		4910	ev_loop_fork (EV_DEFAULT);
		4911
		4912	=item function/symbol renames
		4913
		4914	A number of functions and symbols have been renamed:
		4915
		4916	ev_loop => ev_run
		4917	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4918	EVLOOP_ONESHOT => EVRUN_ONCE
		4919
		4920	ev_unloop => ev_break
		4921	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4922	EVUNLOOP_ONE => EVBREAK_ONE
		4923	EVUNLOOP_ALL => EVBREAK_ALL
		4924
		4925	EV_TIMEOUT => EV_TIMER
		4926
		4927	ev_loop_count => ev_iteration
		4928	ev_loop_depth => ev_depth
		4929	ev_loop_verify => ev_verify
		4930
		4931	Most functions working on C<struct ev_loop> objects don't have an
		4932	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4933	associated constants have been renamed to not collide with the C<struct
		4934	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4935	as all other watcher types. Note that C<ev_loop_fork> is still called
		4936	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4937	typedef.
		4938
		4939	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4940
		4941	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4942	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4943	and work, but the library code will of course be larger.
		4944
		4945	=back
		4946
		4947
		4948	=head1 GLOSSARY
		4949
		4950	=over 4
		4951
		4952	=item active
		4953
		4954	A watcher is active as long as it has been started and not yet stopped.
		4955	See L<WATCHER STATES> for details.
		4956
		4957	=item application
		4958
		4959	In this document, an application is whatever is using libev.
		4960
		4961	=item backend
		4962
		4963	The part of the code dealing with the operating system interfaces.
		4964
		4965	=item callback
		4966
		4967	The address of a function that is called when some event has been
		4968	detected. Callbacks are being passed the event loop, the watcher that
		4969	received the event, and the actual event bitset.
		4970
		4971	=item callback/watcher invocation
		4972
		4973	The act of calling the callback associated with a watcher.
		4974
		4975	=item event
		4976
		4977	A change of state of some external event, such as data now being available
		4978	for reading on a file descriptor, time having passed or simply not having
		4979	any other events happening anymore.
		4980
		4981	In libev, events are represented as single bits (such as C<EV_READ> or
		4982	C<EV_TIMER>).
		4983
		4984	=item event library
		4985
		4986	A software package implementing an event model and loop.
		4987
		4988	=item event loop
		4989
		4990	An entity that handles and processes external events and converts them
		4991	into callback invocations.
		4992
		4993	=item event model
		4994
		4995	The model used to describe how an event loop handles and processes
		4996	watchers and events.
		4997
		4998	=item pending
		4999
		5000	A watcher is pending as soon as the corresponding event has been
		5001	detected. See L<WATCHER STATES> for details.
		5002
		5003	=item real time
		5004
		5005	The physical time that is observed. It is apparently strictly monotonic :)
		5006
		5007	=item wall-clock time
		5008
		5009	The time and date as shown on clocks. Unlike real time, it can actually
		5010	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5011	clock.
		5012
		5013	=item watcher
		5014
		5015	A data structure that describes interest in certain events. Watchers need
		5016	to be started (attached to an event loop) before they can receive events.
		5017
		5018	=back
3470		5019
3471	=head1 AUTHOR	5020	=head1 AUTHOR
3472		5021
3473	Marc Lehmann <libev@schmorp.de>.	5022	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5023	Magnusson and Emanuele Giaquinta.
3474		5024

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