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Revision 1.292 by sf-exg, Mon Mar 22 09:57:01 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	#include <ev.h>	12	#include <ev.h>
12		13
		14	#include <stdio.h> // for puts
		15
		16	// every watcher type has its own typedef'd struct
		17	// with the name ev_TYPE
13	ev_io stdin_watcher;	18	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
15		20
16	/* called when data readable on stdin */	21	// all watcher callbacks have a similar signature
		22	// this callback is called when data is readable on stdin
17	static void	23	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	25	{
20	/* puts ("stdin ready"); */	26	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	27	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	28	// with its corresponding stop function.
		29	ev_io_stop (EV_A_ w);
		30
		31	// this causes all nested ev_loop's to stop iterating
		32	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	33	}
24		34
		35	// another callback, this time for a time-out
25	static void	36	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	38	{
28	/* puts ("timeout"); */	39	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	40	// this causes the innermost ev_loop to stop iterating
		41	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	42	}
31		43
32	int	44	int
33	main (void)	45	main (void)
34	{	46	{
		47	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
36		49
37	/* initialise an io watcher, then start it */	50	// initialise an io watcher, then start it
		51	// this one will watch for stdin to become readable
38	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);
39	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
40		54
		55	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	56	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
44		59
45	/* loop till timeout or data ready */	60	// now wait for events to arrive
46	ev_loop (loop, 0);	61	ev_loop (loop, 0);
47		62
		63	// unloop was called, so exit
48	return 0;	64	return 0;
49	}	65	}
50		66
51	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
52		68
		69	This document documents the libev software package.
		70
53	The newest version of this document is also available as a html-formatted	71	The newest version of this document is also available as an html-formatted
54	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
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	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	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
56		84
57	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	87	these event sources and provide your program with events.
60		88
…		…
70	=head2 FEATURES	98	=head2 FEATURES
71		99
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
76	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
77	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
78	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
80	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
81	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
82		111
83	It also is quite fast (see this	112	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	114	for example).
86		115
87	=head2 CONVENTIONS	116	=head2 CONVENTIONS
88		117
89	Libev is very configurable. In this manual the default configuration will	118	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	119	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	120	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	121	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	122	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		124	this argument.
95		125
96	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
97		127
98	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
100	the beginning of 1970, details are complicated, don't ask). This type is	130	near the beginning of 1970, details are complicated, don't ask). This
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	type is called C<ev_tstamp>, which is what you should use too. It usually
102	to the C<double> type in C, and when you need to do any calculations on	132	aliases to the C<double> type in C. When you need to do any calculations
103	it, you should treat it as some floatingpoint value. Unlike the name	133	on it, you should treat it as some floating point value. Unlike the name
104	component C<stamp> might indicate, it is also used for time differences	134	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	135	throughout libev.
		136
		137	=head1 ERROR HANDLING
		138
		139	Libev knows three classes of errors: operating system errors, usage errors
		140	and internal errors (bugs).
		141
		142	When libev catches an operating system error it cannot handle (for example
		143	a system call indicating a condition libev cannot fix), it calls the callback
		144	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		145	abort. The default is to print a diagnostic message and to call C<abort
		146	()>.
		147
		148	When libev detects a usage error such as a negative timer interval, then
		149	it will print a diagnostic message and abort (via the C<assert> mechanism,
		150	so C<NDEBUG> will disable this checking): these are programming errors in
		151	the libev caller and need to be fixed there.
		152
		153	Libev also has a few internal error-checking C<assert>ions, and also has
		154	extensive consistency checking code. These do not trigger under normal
		155	circumstances, as they indicate either a bug in libev or worse.
		156
106		157
107	=head1 GLOBAL FUNCTIONS	158	=head1 GLOBAL FUNCTIONS
108		159
109	These functions can be called anytime, even before initialising the	160	These functions can be called anytime, even before initialising the
110	library in any way.	161	library in any way.
…		…
119		170
120	=item ev_sleep (ev_tstamp interval)	171	=item ev_sleep (ev_tstamp interval)
121		172
122	Sleep for the given interval: The current thread will be blocked until	173	Sleep for the given interval: The current thread will be blocked until
123	either it is interrupted or the given time interval has passed. Basically	174	either it is interrupted or the given time interval has passed. Basically
124	this is a subsecond-resolution C<sleep ()>.	175	this is a sub-second-resolution C<sleep ()>.
125		176
126	=item int ev_version_major ()	177	=item int ev_version_major ()
127		178
128	=item int ev_version_minor ()	179	=item int ev_version_minor ()
129		180
…		…
142	not a problem.	193	not a problem.
143		194
144	Example: Make sure we haven't accidentally been linked against the wrong	195	Example: Make sure we haven't accidentally been linked against the wrong
145	version.	196	version.
146		197
147	assert (("libev version mismatch",	198	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	199	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	200	&& ev_version_minor () >= EV_VERSION_MINOR));
150		201
151	=item unsigned int ev_supported_backends ()	202	=item unsigned int ev_supported_backends ()
152		203
153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	204	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
154	value) compiled into this binary of libev (independent of their	205	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	207	a description of the set values.
157		208
158	Example: make sure we have the epoll method, because yeah this is cool and	209	Example: make sure we have the epoll method, because yeah this is cool and
159	a must have and can we have a torrent of it please!!!11	210	a must have and can we have a torrent of it please!!!11
160		211
161	assert (("sorry, no epoll, no sex",	212	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	213	ev_supported_backends () & EVBACKEND_EPOLL));
163		214
164	=item unsigned int ev_recommended_backends ()	215	=item unsigned int ev_recommended_backends ()
165		216
166	Return the set of all backends compiled into this binary of libev and also	217	Return the set of all backends compiled into this binary of libev and also
167	recommended for this platform. This set is often smaller than the one	218	recommended for this platform. This set is often smaller than the one
168	returned by C<ev_supported_backends>, as for example kqueue is broken on	219	returned by C<ev_supported_backends>, as for example kqueue is broken on
169	most BSDs and will not be autodetected unless you explicitly request it	220	most BSDs and will not be auto-detected unless you explicitly request it
170	(assuming you know what you are doing). This is the set of backends that	221	(assuming you know what you are doing). This is the set of backends that
171	libev will probe for if you specify no backends explicitly.	222	libev will probe for if you specify no backends explicitly.
172		223
173	=item unsigned int ev_embeddable_backends ()	224	=item unsigned int ev_embeddable_backends ()
174		225
…		…
178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
179	recommended ones.	230	recommended ones.
180		231
181	See the description of C<ev_embed> watchers for more info.	232	See the description of C<ev_embed> watchers for more info.
182		233
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
184		235
185	Sets the allocation function to use (the prototype is similar - the	236	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
187	allocate and free memory (no surprises here). If it returns zero when	238	used to allocate and free memory (no surprises here). If it returns zero
188	memory needs to be allocated, the library might abort or take some	239	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	240	or take some potentially destructive action.
190	function.	241
		242	Since some systems (at least OpenBSD and Darwin) fail to implement
		243	correct C<realloc> semantics, libev will use a wrapper around the system
		244	C<realloc> and C<free> functions by default.
191		245
192	You could override this function in high-availability programs to, say,	246	You could override this function in high-availability programs to, say,
193	free some memory if it cannot allocate memory, to use a special allocator,	247	free some memory if it cannot allocate memory, to use a special allocator,
194	or even to sleep a while and retry until some memory is available.	248	or even to sleep a while and retry until some memory is available.
195		249
196	Example: Replace the libev allocator with one that waits a bit and then	250	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	251	retries (example requires a standards-compliant C<realloc>).
198		252
199	static void *	253	static void *
200	persistent_realloc (void *ptr, size_t size)	254	persistent_realloc (void *ptr, size_t size)
201	{	255	{
202	for (;;)	256	for (;;)
…		…
211	}	265	}
212		266
213	...	267	...
214	ev_set_allocator (persistent_realloc);	268	ev_set_allocator (persistent_realloc);
215		269
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
217		271
218	Set the callback function to call on a retryable syscall error (such	272	Set the callback function to call on a retryable system call error (such
219	as failed select, poll, epoll_wait). The message is a printable string	273	as failed select, poll, epoll_wait). The message is a printable string
220	indicating the system call or subsystem causing the problem. If this	274	indicating the system call or subsystem causing the problem. If this
221	callback is set, then libev will expect it to remedy the sitution, no	275	callback is set, then libev will expect it to remedy the situation, no
222	matter what, when it returns. That is, libev will generally retry the	276	matter what, when it returns. That is, libev will generally retry the
223	requested operation, or, if the condition doesn't go away, do bad stuff	277	requested operation, or, if the condition doesn't go away, do bad stuff
224	(such as abort).	278	(such as abort).
225		279
226	Example: This is basically the same thing that libev does internally, too.	280	Example: This is basically the same thing that libev does internally, too.
…		…
237		291
238	=back	292	=back
239		293
240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
241		295
242	An event loop is described by a C<struct ev_loop *>. The library knows two	296	An event loop is described by a C<struct ev_loop *> (the C<struct>
243	types of such loops, the I<default> loop, which supports signals and child	297	is I<not> optional in this case, as there is also an C<ev_loop>
244	events, and dynamically created loops which do not.	298	I<function>).
245		299
246	If you use threads, a common model is to run the default event loop	300	The library knows two types of such loops, the I<default> loop, which
247	in your main thread (or in a separate thread) and for each thread you	301	supports signals and child events, and dynamically created loops which do
248	create, you also create another event loop. Libev itself does no locking	302	not.
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252		303
253	=over 4	304	=over 4
254		305
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		307
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	311	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		312
262	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
263	function.	314	function.
264		315
		316	Note that this function is I<not> thread-safe, so if you want to use it
		317	from multiple threads, you have to lock (note also that this is unlikely,
		318	as loops cannot be shared easily between threads anyway).
		319
265	The default loop is the only loop that can handle C<ev_signal> and	320	The default loop is the only loop that can handle C<ev_signal> and
266	C<ev_child> watchers, and to do this, it always registers a handler	321	C<ev_child> watchers, and to do this, it always registers a handler
267	for C<SIGCHLD>. If this is a problem for your app you can either	322	for C<SIGCHLD>. If this is a problem for your application you can either
268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270	C<ev_default_init>.	325	C<ev_default_init>.
271		326
272	The flags argument can be used to specify special behaviour or specific	327	The flags argument can be used to specify special behaviour or specific
…		…
281	The default flags value. Use this if you have no clue (it's the right	336	The default flags value. Use this if you have no clue (it's the right
282	thing, believe me).	337	thing, believe me).
283		338
284	=item C<EVFLAG_NOENV>	339	=item C<EVFLAG_NOENV>
285		340
286	If this flag bit is ored into the flag value (or the program runs setuid	341	If this flag bit is or'ed into the flag value (or the program runs setuid
287	or setgid) then libev will I<not> look at the environment variable	342	or setgid) then libev will I<not> look at the environment variable
288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	343	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
289	override the flags completely if it is found in the environment. This is	344	override the flags completely if it is found in the environment. This is
290	useful to try out specific backends to test their performance, or to work	345	useful to try out specific backends to test their performance, or to work
291	around bugs.	346	around bugs.
292		347
293	=item C<EVFLAG_FORKCHECK>	348	=item C<EVFLAG_FORKCHECK>
294		349
295	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	350	Instead of calling C<ev_loop_fork> manually after a fork, you can also
296	a fork, you can also make libev check for a fork in each iteration by	351	make libev check for a fork in each iteration by enabling this flag.
297	enabling this flag.
298		352
299	This works by calling C<getpid ()> on every iteration of the loop,	353	This works by calling C<getpid ()> on every iteration of the loop,
300	and thus this might slow down your event loop if you do a lot of loop	354	and thus this might slow down your event loop if you do a lot of loop
301	iterations and little real work, but is usually not noticeable (on my	355	iterations and little real work, but is usually not noticeable (on my
302	Linux system for example, C<getpid> is actually a simple 5-insn sequence	356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
303	without a syscall and thus I<very> fast, but my Linux system also has	357	without a system call and thus I<very> fast, but my GNU/Linux system also has
304	C<pthread_atfork> which is even faster).	358	C<pthread_atfork> which is even faster).
305		359
306	The big advantage of this flag is that you can forget about fork (and	360	The big advantage of this flag is that you can forget about fork (and
307	forget about forgetting to tell libev about forking) when you use this	361	forget about forgetting to tell libev about forking) when you use this
308	flag.	362	flag.
309		363
310	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
311	environment variable.	365	environment variable.
		366
		367	=item C<EVFLAG_NOINOTIFY>
		368
		369	When this flag is specified, then libev will not attempt to use the
		370	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		371	testing, this flag can be useful to conserve inotify file descriptors, as
		372	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		373
		374	=item C<EVFLAG_SIGNALFD>
		375
		376	When this flag is specified, then libev will attempt to use the
		377	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		378	delivers signals synchronously, which makes it both faster and might make
		379	it possible to get the queued signal data. It can also simplify signal
		380	handling with threads, as long as you properly block signals in your
		381	threads that are not interested in handling them.
		382
		383	Signalfd will not be used by default as this changes your signal mask, and
		384	there are a lot of shoddy libraries and programs (glib's threadpool for
		385	example) that can't properly initialise their signal masks.
312		386
313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	387	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
314		388
315	This is your standard select(2) backend. Not I<completely> standard, as	389	This is your standard select(2) backend. Not I<completely> standard, as
316	libev tries to roll its own fd_set with no limits on the number of fds,	390	libev tries to roll its own fd_set with no limits on the number of fds,
317	but if that fails, expect a fairly low limit on the number of fds when	391	but if that fails, expect a fairly low limit on the number of fds when
318	using this backend. It doesn't scale too well (O(highest_fd)), but its	392	using this backend. It doesn't scale too well (O(highest_fd)), but its
319	usually the fastest backend for a low number of (low-numbered :) fds.	393	usually the fastest backend for a low number of (low-numbered :) fds.
320		394
321	To get good performance out of this backend you need a high amount of	395	To get good performance out of this backend you need a high amount of
322	parallelity (most of the file descriptors should be busy). If you are	396	parallelism (most of the file descriptors should be busy). If you are
323	writing a server, you should C<accept ()> in a loop to accept as many	397	writing a server, you should C<accept ()> in a loop to accept as many
324	connections as possible during one iteration. You might also want to have	398	connections as possible during one iteration. You might also want to have
325	a look at C<ev_set_io_collect_interval ()> to increase the amount of	399	a look at C<ev_set_io_collect_interval ()> to increase the amount of
326	readyness notifications you get per iteration.	400	readiness notifications you get per iteration.
		401
		402	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		403	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		404	C<exceptfds> set on that platform).
327		405
328	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	406	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
329		407
330	And this is your standard poll(2) backend. It's more complicated	408	And this is your standard poll(2) backend. It's more complicated
331	than select, but handles sparse fds better and has no artificial	409	than select, but handles sparse fds better and has no artificial
332	limit on the number of fds you can use (except it will slow down	410	limit on the number of fds you can use (except it will slow down
333	considerably with a lot of inactive fds). It scales similarly to select,	411	considerably with a lot of inactive fds). It scales similarly to select,
334	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	412	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
335	performance tips.	413	performance tips.
336		414
		415	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		416	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		417
337	=item C<EVBACKEND_EPOLL> (value 4, Linux)	418	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		419
		420	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		421	kernels).
338		422
339	For few fds, this backend is a bit little slower than poll and select,	423	For few fds, this backend is a bit little slower than poll and select,
340	but it scales phenomenally better. While poll and select usually scale	424	but it scales phenomenally better. While poll and select usually scale
341	like O(total_fds) where n is the total number of fds (or the highest fd),	425	like O(total_fds) where n is the total number of fds (or the highest fd),
342	epoll scales either O(1) or O(active_fds). The epoll design has a number	426	epoll scales either O(1) or O(active_fds).
343	of shortcomings, such as silently dropping events in some hard-to-detect	427
344	cases and rewiring a syscall per fd change, no fork support and bad	428	The epoll mechanism deserves honorable mention as the most misdesigned
345	support for dup.	429	of the more advanced event mechanisms: mere annoyances include silently
		430	dropping file descriptors, requiring a system call per change per file
		431	descriptor (and unnecessary guessing of parameters), problems with dup and
		432	so on. The biggest issue is fork races, however - if a program forks then
		433	I<both> parent and child process have to recreate the epoll set, which can
		434	take considerable time (one syscall per file descriptor) and is of course
		435	hard to detect.
		436
		437	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		438	of course I<doesn't>, and epoll just loves to report events for totally
		439	I<different> file descriptors (even already closed ones, so one cannot
		440	even remove them from the set) than registered in the set (especially
		441	on SMP systems). Libev tries to counter these spurious notifications by
		442	employing an additional generation counter and comparing that against the
		443	events to filter out spurious ones, recreating the set when required.
346		444
347	While stopping, setting and starting an I/O watcher in the same iteration	445	While stopping, setting and starting an I/O watcher in the same iteration
348	will result in some caching, there is still a syscall per such incident	446	will result in some caching, there is still a system call per such
349	(because the fd could point to a different file description now), so its	447	incident (because the same I<file descriptor> could point to a different
350	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	448	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
351	very well if you register events for both fds.	449	file descriptors might not work very well if you register events for both
352		450	file descriptors.
353	Please note that epoll sometimes generates spurious notifications, so you
354	need to use non-blocking I/O or other means to avoid blocking when no data
355	(or space) is available.
356		451
357	Best performance from this backend is achieved by not unregistering all	452	Best performance from this backend is achieved by not unregistering all
358	watchers for a file descriptor until it has been closed, if possible, i.e.	453	watchers for a file descriptor until it has been closed, if possible,
359	keep at least one watcher active per fd at all times.	454	i.e. keep at least one watcher active per fd at all times. Stopping and
		455	starting a watcher (without re-setting it) also usually doesn't cause
		456	extra overhead. A fork can both result in spurious notifications as well
		457	as in libev having to destroy and recreate the epoll object, which can
		458	take considerable time and thus should be avoided.
360		459
		460	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		461	faster than epoll for maybe up to a hundred file descriptors, depending on
		462	the usage. So sad.
		463
361	While nominally embeddeble in other event loops, this feature is broken in	464	While nominally embeddable in other event loops, this feature is broken in
362	all kernel versions tested so far.	465	all kernel versions tested so far.
		466
		467	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		468	C<EVBACKEND_POLL>.
363		469
364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	470	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
365		471
366	Kqueue deserves special mention, as at the time of this writing, it	472	Kqueue deserves special mention, as at the time of this writing, it
367	was broken on all BSDs except NetBSD (usually it doesn't work reliably	473	was broken on all BSDs except NetBSD (usually it doesn't work reliably
368	with anything but sockets and pipes, except on Darwin, where of course	474	with anything but sockets and pipes, except on Darwin, where of course
369	it's completely useless). For this reason it's not being "autodetected"	475	it's completely useless). Unlike epoll, however, whose brokenness
		476	is by design, these kqueue bugs can (and eventually will) be fixed
		477	without API changes to existing programs. For this reason it's not being
370	unless you explicitly specify it explicitly in the flags (i.e. using	478	"auto-detected" unless you explicitly specify it in the flags (i.e. using
371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	479	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
372	system like NetBSD.	480	system like NetBSD.
373		481
374	You still can embed kqueue into a normal poll or select backend and use it	482	You still can embed kqueue into a normal poll or select backend and use it
375	only for sockets (after having made sure that sockets work with kqueue on	483	only for sockets (after having made sure that sockets work with kqueue on
376	the target platform). See C<ev_embed> watchers for more info.	484	the target platform). See C<ev_embed> watchers for more info.
377		485
378	It scales in the same way as the epoll backend, but the interface to the	486	It scales in the same way as the epoll backend, but the interface to the
379	kernel is more efficient (which says nothing about its actual speed, of	487	kernel is more efficient (which says nothing about its actual speed, of
380	course). While stopping, setting and starting an I/O watcher does never	488	course). While stopping, setting and starting an I/O watcher does never
381	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	489	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
382	two event changes per incident, support for C<fork ()> is very bad and it	490	two event changes per incident. Support for C<fork ()> is very bad (but
383	drops fds silently in similarly hard-to-detect cases.	491	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		492	cases
384		493
385	This backend usually performs well under most conditions.	494	This backend usually performs well under most conditions.
386		495
387	While nominally embeddable in other event loops, this doesn't work	496	While nominally embeddable in other event loops, this doesn't work
388	everywhere, so you might need to test for this. And since it is broken	497	everywhere, so you might need to test for this. And since it is broken
389	almost everywhere, you should only use it when you have a lot of sockets	498	almost everywhere, you should only use it when you have a lot of sockets
390	(for which it usually works), by embedding it into another event loop	499	(for which it usually works), by embedding it into another event loop
391	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	500	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
392	sockets.	501	also broken on OS X)) and, did I mention it, using it only for sockets.
		502
		503	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		504	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		505	C<NOTE_EOF>.
393		506
394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	507	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
395		508
396	This is not implemented yet (and might never be, unless you send me an	509	This is not implemented yet (and might never be, unless you send me an
397	implementation). According to reports, C</dev/poll> only supports sockets	510	implementation). According to reports, C</dev/poll> only supports sockets
…		…
401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	514	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
402		515
403	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	516	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
404	it's really slow, but it still scales very well (O(active_fds)).	517	it's really slow, but it still scales very well (O(active_fds)).
405		518
406	Please note that solaris event ports can deliver a lot of spurious	519	Please note that Solaris event ports can deliver a lot of spurious
407	notifications, so you need to use non-blocking I/O or other means to avoid	520	notifications, so you need to use non-blocking I/O or other means to avoid
408	blocking when no data (or space) is available.	521	blocking when no data (or space) is available.
409		522
410	While this backend scales well, it requires one system call per active	523	While this backend scales well, it requires one system call per active
411	file descriptor per loop iteration. For small and medium numbers of file	524	file descriptor per loop iteration. For small and medium numbers of file
412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	525	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413	might perform better.	526	might perform better.
414		527
415	On the positive side, ignoring the spurious readyness notifications, this	528	On the positive side, with the exception of the spurious readiness
416	backend actually performed to specification in all tests and is fully	529	notifications, this backend actually performed fully to specification
417	embeddable, which is a rare feat among the OS-specific backends.	530	in all tests and is fully embeddable, which is a rare feat among the
		531	OS-specific backends (I vastly prefer correctness over speed hacks).
		532
		533	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		534	C<EVBACKEND_POLL>.
418		535
419	=item C<EVBACKEND_ALL>	536	=item C<EVBACKEND_ALL>
420		537
421	Try all backends (even potentially broken ones that wouldn't be tried	538	Try all backends (even potentially broken ones that wouldn't be tried
422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	539	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
424		541
425	It is definitely not recommended to use this flag.	542	It is definitely not recommended to use this flag.
426		543
427	=back	544	=back
428		545
429	If one or more of these are ored into the flags value, then only these	546	If one or more of the backend flags are or'ed into the flags value,
430	backends will be tried (in the reverse order as listed here). If none are	547	then only these backends will be tried (in the reverse order as listed
431	specified, all backends in C<ev_recommended_backends ()> will be tried.	548	here). If none are specified, all backends in C<ev_recommended_backends
		549	()> will be tried.
432		550
433	The most typical usage is like this:	551	Example: This is the most typical usage.
434		552
435	if (!ev_default_loop (0))	553	if (!ev_default_loop (0))
436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	554	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
437		555
438	Restrict libev to the select and poll backends, and do not allow	556	Example: Restrict libev to the select and poll backends, and do not allow
439	environment settings to be taken into account:	557	environment settings to be taken into account:
440		558
441	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	559	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
442		560
443	Use whatever libev has to offer, but make sure that kqueue is used if	561	Example: Use whatever libev has to offer, but make sure that kqueue is
444	available (warning, breaks stuff, best use only with your own private	562	used if available (warning, breaks stuff, best use only with your own
445	event loop and only if you know the OS supports your types of fds):	563	private event loop and only if you know the OS supports your types of
		564	fds):
446		565
447	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	566	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
448		567
449	=item struct ev_loop *ev_loop_new (unsigned int flags)	568	=item struct ev_loop *ev_loop_new (unsigned int flags)
450		569
451	Similar to C<ev_default_loop>, but always creates a new event loop that is	570	Similar to C<ev_default_loop>, but always creates a new event loop that is
452	always distinct from the default loop. Unlike the default loop, it cannot	571	always distinct from the default loop.
453	handle signal and child watchers, and attempts to do so will be greeted by	572
454	undefined behaviour (or a failed assertion if assertions are enabled).	573	Note that this function I<is> thread-safe, and one common way to use
		574	libev with threads is indeed to create one loop per thread, and using the
		575	default loop in the "main" or "initial" thread.
455		576
456	Example: Try to create a event loop that uses epoll and nothing else.	577	Example: Try to create a event loop that uses epoll and nothing else.
457		578
458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	579	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
459	if (!epoller)	580	if (!epoller)
460	fatal ("no epoll found here, maybe it hides under your chair");	581	fatal ("no epoll found here, maybe it hides under your chair");
461		582
462	=item ev_default_destroy ()	583	=item ev_default_destroy ()
463		584
464	Destroys the default loop again (frees all memory and kernel state	585	Destroys the default loop (frees all memory and kernel state etc.). None
465	etc.). None of the active event watchers will be stopped in the normal	586	of the active event watchers will be stopped in the normal sense, so
466	sense, so e.g. C<ev_is_active> might still return true. It is your	587	e.g. C<ev_is_active> might still return true. It is your responsibility to
467	responsibility to either stop all watchers cleanly yoursef I<before>	588	either stop all watchers cleanly yourself I<before> calling this function,
468	calling this function, or cope with the fact afterwards (which is usually	589	or cope with the fact afterwards (which is usually the easiest thing, you
469	the easiest thing, you can just ignore the watchers and/or C<free ()> them	590	can just ignore the watchers and/or C<free ()> them for example).
470	for example).
471		591
472	Note that certain global state, such as signal state, will not be freed by	592	Note that certain global state, such as signal state (and installed signal
473	this function, and related watchers (such as signal and child watchers)	593	handlers), will not be freed by this function, and related watchers (such
474	would need to be stopped manually.	594	as signal and child watchers) would need to be stopped manually.
475		595
476	In general it is not advisable to call this function except in the	596	In general it is not advisable to call this function except in the
477	rare occasion where you really need to free e.g. the signal handling	597	rare occasion where you really need to free e.g. the signal handling
478	pipe fds. If you need dynamically allocated loops it is better to use	598	pipe fds. If you need dynamically allocated loops it is better to use
479	C<ev_loop_new> and C<ev_loop_destroy>).	599	C<ev_loop_new> and C<ev_loop_destroy>.
480		600
481	=item ev_loop_destroy (loop)	601	=item ev_loop_destroy (loop)
482		602
483	Like C<ev_default_destroy>, but destroys an event loop created by an	603	Like C<ev_default_destroy>, but destroys an event loop created by an
484	earlier call to C<ev_loop_new>.	604	earlier call to C<ev_loop_new>.
…		…
490	name, you can call it anytime, but it makes most sense after forking, in	610	name, you can call it anytime, but it makes most sense after forking, in
491	the child process (or both child and parent, but that again makes little	611	the child process (or both child and parent, but that again makes little
492	sense). You I<must> call it in the child before using any of the libev	612	sense). You I<must> call it in the child before using any of the libev
493	functions, and it will only take effect at the next C<ev_loop> iteration.	613	functions, and it will only take effect at the next C<ev_loop> iteration.
494		614
		615	Again, you I<have> to call it on I<any> loop that you want to re-use after
		616	a fork, I<even if you do not plan to use the loop in the parent>. This is
		617	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		618	during fork.
		619
495	On the other hand, you only need to call this function in the child	620	On the other hand, you only need to call this function in the child
496	process if and only if you want to use the event library in the child. If	621	process if and only if you want to use the event loop in the child. If you
497	you just fork+exec, you don't have to call it at all.	622	just fork+exec or create a new loop in the child, you don't have to call
		623	it at all.
498		624
499	The function itself is quite fast and it's usually not a problem to call	625	The function itself is quite fast and it's usually not a problem to call
500	it just in case after a fork. To make this easy, the function will fit in	626	it just in case after a fork. To make this easy, the function will fit in
501	quite nicely into a call to C<pthread_atfork>:	627	quite nicely into a call to C<pthread_atfork>:
502		628
…		…
504		630
505	=item ev_loop_fork (loop)	631	=item ev_loop_fork (loop)
506		632
507	Like C<ev_default_fork>, but acts on an event loop created by	633	Like C<ev_default_fork>, but acts on an event loop created by
508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	634	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
509	after fork, and how you do this is entirely your own problem.	635	after fork that you want to re-use in the child, and how you keep track of
		636	them is entirely your own problem.
510		637
		638	=item int ev_is_default_loop (loop)
		639
		640	Returns true when the given loop is, in fact, the default loop, and false
		641	otherwise.
		642
511	=item unsigned int ev_loop_count (loop)	643	=item unsigned int ev_iteration (loop)
512		644
513	Returns the count of loop iterations for the loop, which is identical to	645	Returns the current iteration count for the loop, which is identical to
514	the number of times libev did poll for new events. It starts at C<0> and	646	the number of times libev did poll for new events. It starts at C<0> and
515	happily wraps around with enough iterations.	647	happily wraps around with enough iterations.
516		648
517	This value can sometimes be useful as a generation counter of sorts (it	649	This value can sometimes be useful as a generation counter of sorts (it
518	"ticks" the number of loop iterations), as it roughly corresponds with	650	"ticks" the number of loop iterations), as it roughly corresponds with
519	C<ev_prepare> and C<ev_check> calls.	651	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		652	prepare and check phases.
		653
		654	=item unsigned int ev_depth (loop)
		655
		656	Returns the number of times C<ev_loop> was entered minus the number of
		657	times C<ev_loop> was exited, in other words, the recursion depth.
		658
		659	Outside C<ev_loop>, this number is zero. In a callback, this number is
		660	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		661	in which case it is higher.
		662
		663	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		664	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		665	ungentleman behaviour unless it's really convenient.
520		666
521	=item unsigned int ev_backend (loop)	667	=item unsigned int ev_backend (loop)
522		668
523	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	669	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
524	use.	670	use.
…		…
529	received events and started processing them. This timestamp does not	675	received events and started processing them. This timestamp does not
530	change as long as callbacks are being processed, and this is also the base	676	change as long as callbacks are being processed, and this is also the base
531	time used for relative timers. You can treat it as the timestamp of the	677	time used for relative timers. You can treat it as the timestamp of the
532	event occurring (or more correctly, libev finding out about it).	678	event occurring (or more correctly, libev finding out about it).
533		679
		680	=item ev_now_update (loop)
		681
		682	Establishes the current time by querying the kernel, updating the time
		683	returned by C<ev_now ()> in the progress. This is a costly operation and
		684	is usually done automatically within C<ev_loop ()>.
		685
		686	This function is rarely useful, but when some event callback runs for a
		687	very long time without entering the event loop, updating libev's idea of
		688	the current time is a good idea.
		689
		690	See also L<The special problem of time updates> in the C<ev_timer> section.
		691
		692	=item ev_suspend (loop)
		693
		694	=item ev_resume (loop)
		695
		696	These two functions suspend and resume a loop, for use when the loop is
		697	not used for a while and timeouts should not be processed.
		698
		699	A typical use case would be an interactive program such as a game: When
		700	the user presses C<^Z> to suspend the game and resumes it an hour later it
		701	would be best to handle timeouts as if no time had actually passed while
		702	the program was suspended. This can be achieved by calling C<ev_suspend>
		703	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		704	C<ev_resume> directly afterwards to resume timer processing.
		705
		706	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		707	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		708	will be rescheduled (that is, they will lose any events that would have
		709	occured while suspended).
		710
		711	After calling C<ev_suspend> you B<must not> call I<any> function on the
		712	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		713	without a previous call to C<ev_suspend>.
		714
		715	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		716	event loop time (see C<ev_now_update>).
		717
534	=item ev_loop (loop, int flags)	718	=item ev_loop (loop, int flags)
535		719
536	Finally, this is it, the event handler. This function usually is called	720	Finally, this is it, the event handler. This function usually is called
537	after you initialised all your watchers and you want to start handling	721	after you have initialised all your watchers and you want to start
538	events.	722	handling events.
539		723
540	If the flags argument is specified as C<0>, it will not return until	724	If the flags argument is specified as C<0>, it will not return until
541	either no event watchers are active anymore or C<ev_unloop> was called.	725	either no event watchers are active anymore or C<ev_unloop> was called.
542		726
543	Please note that an explicit C<ev_unloop> is usually better than	727	Please note that an explicit C<ev_unloop> is usually better than
544	relying on all watchers to be stopped when deciding when a program has	728	relying on all watchers to be stopped when deciding when a program has
545	finished (especially in interactive programs), but having a program that	729	finished (especially in interactive programs), but having a program
546	automatically loops as long as it has to and no longer by virtue of	730	that automatically loops as long as it has to and no longer by virtue
547	relying on its watchers stopping correctly is a thing of beauty.	731	of relying on its watchers stopping correctly, that is truly a thing of
		732	beauty.
548		733
549	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	734	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
550	those events and any outstanding ones, but will not block your process in	735	those events and any already outstanding ones, but will not block your
551	case there are no events and will return after one iteration of the loop.	736	process in case there are no events and will return after one iteration of
		737	the loop.
552		738
553	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	739	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
554	neccessary) and will handle those and any outstanding ones. It will block	740	necessary) and will handle those and any already outstanding ones. It
555	your process until at least one new event arrives, and will return after	741	will block your process until at least one new event arrives (which could
556	one iteration of the loop. This is useful if you are waiting for some	742	be an event internal to libev itself, so there is no guarantee that a
557	external event in conjunction with something not expressible using other	743	user-registered callback will be called), and will return after one
		744	iteration of the loop.
		745
		746	This is useful if you are waiting for some external event in conjunction
		747	with something not expressible using other libev watchers (i.e. "roll your
558	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	748	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
559	usually a better approach for this kind of thing.	749	usually a better approach for this kind of thing.
560		750
561	Here are the gory details of what C<ev_loop> does:	751	Here are the gory details of what C<ev_loop> does:
562		752
563	- Before the first iteration, call any pending watchers.	753	- Before the first iteration, call any pending watchers.
564	* If EVFLAG_FORKCHECK was used, check for a fork.	754	* If EVFLAG_FORKCHECK was used, check for a fork.
565	- If a fork was detected, queue and call all fork watchers.	755	- If a fork was detected (by any means), queue and call all fork watchers.
566	- Queue and call all prepare watchers.	756	- Queue and call all prepare watchers.
567	- If we have been forked, recreate the kernel state.	757	- If we have been forked, detach and recreate the kernel state
		758	as to not disturb the other process.
568	- Update the kernel state with all outstanding changes.	759	- Update the kernel state with all outstanding changes.
569	- Update the "event loop time".	760	- Update the "event loop time" (ev_now ()).
570	- Calculate for how long to sleep or block, if at all	761	- Calculate for how long to sleep or block, if at all
571	(active idle watchers, EVLOOP_NONBLOCK or not having	762	(active idle watchers, EVLOOP_NONBLOCK or not having
572	any active watchers at all will result in not sleeping).	763	any active watchers at all will result in not sleeping).
573	- Sleep if the I/O and timer collect interval say so.	764	- Sleep if the I/O and timer collect interval say so.
574	- Block the process, waiting for any events.	765	- Block the process, waiting for any events.
575	- Queue all outstanding I/O (fd) events.	766	- Queue all outstanding I/O (fd) events.
576	- Update the "event loop time" and do time jump handling.	767	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
577	- Queue all outstanding timers.	768	- Queue all expired timers.
578	- Queue all outstanding periodics.	769	- Queue all expired periodics.
579	- If no events are pending now, queue all idle watchers.	770	- Unless any events are pending now, queue all idle watchers.
580	- Queue all check watchers.	771	- Queue all check watchers.
581	- Call all queued watchers in reverse order (i.e. check watchers first).	772	- Call all queued watchers in reverse order (i.e. check watchers first).
582	Signals and child watchers are implemented as I/O watchers, and will	773	Signals and child watchers are implemented as I/O watchers, and will
583	be handled here by queueing them when their watcher gets executed.	774	be handled here by queueing them when their watcher gets executed.
584	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	775	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
589	anymore.	780	anymore.
590		781
591	... queue jobs here, make sure they register event watchers as long	782	... queue jobs here, make sure they register event watchers as long
592	... as they still have work to do (even an idle watcher will do..)	783	... as they still have work to do (even an idle watcher will do..)
593	ev_loop (my_loop, 0);	784	ev_loop (my_loop, 0);
594	... jobs done. yeah!	785	... jobs done or somebody called unloop. yeah!
595		786
596	=item ev_unloop (loop, how)	787	=item ev_unloop (loop, how)
597		788
598	Can be used to make a call to C<ev_loop> return early (but only after it	789	Can be used to make a call to C<ev_loop> return early (but only after it
599	has processed all outstanding events). The C<how> argument must be either	790	has processed all outstanding events). The C<how> argument must be either
600	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	791	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
601	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	792	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
602		793
603	This "unloop state" will be cleared when entering C<ev_loop> again.	794	This "unloop state" will be cleared when entering C<ev_loop> again.
604		795
		796	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		797
605	=item ev_ref (loop)	798	=item ev_ref (loop)
606		799
607	=item ev_unref (loop)	800	=item ev_unref (loop)
608		801
609	Ref/unref can be used to add or remove a reference count on the event	802	Ref/unref can be used to add or remove a reference count on the event
610	loop: Every watcher keeps one reference, and as long as the reference	803	loop: Every watcher keeps one reference, and as long as the reference
611	count is nonzero, C<ev_loop> will not return on its own. If you have	804	count is nonzero, C<ev_loop> will not return on its own.
612	a watcher you never unregister that should not keep C<ev_loop> from	805
613	returning, ev_unref() after starting, and ev_ref() before stopping it. For	806	This is useful when you have a watcher that you never intend to
		807	unregister, but that nevertheless should not keep C<ev_loop> from
		808	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		809	before stopping it.
		810
614	example, libev itself uses this for its internal signal pipe: It is not	811	As an example, libev itself uses this for its internal signal pipe: It
615	visible to the libev user and should not keep C<ev_loop> from exiting if	812	is not visible to the libev user and should not keep C<ev_loop> from
616	no event watchers registered by it are active. It is also an excellent	813	exiting if no event watchers registered by it are active. It is also an
617	way to do this for generic recurring timers or from within third-party	814	excellent way to do this for generic recurring timers or from within
618	libraries. Just remember to I<unref after start> and I<ref before stop>	815	third-party libraries. Just remember to I<unref after start> and I<ref
619	(but only if the watcher wasn't active before, or was active before,	816	before stop> (but only if the watcher wasn't active before, or was active
620	respectively).	817	before, respectively. Note also that libev might stop watchers itself
		818	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		819	in the callback).
621		820
622	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	821	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
623	running when nothing else is active.	822	running when nothing else is active.
624		823
625	struct ev_signal exitsig;	824	ev_signal exitsig;
626	ev_signal_init (&exitsig, sig_cb, SIGINT);	825	ev_signal_init (&exitsig, sig_cb, SIGINT);
627	ev_signal_start (loop, &exitsig);	826	ev_signal_start (loop, &exitsig);
628	evf_unref (loop);	827	evf_unref (loop);
629		828
630	Example: For some weird reason, unregister the above signal handler again.	829	Example: For some weird reason, unregister the above signal handler again.
631		830
632	ev_ref (loop);	831	ev_ref (loop);
633	ev_signal_stop (loop, &exitsig);	832	ev_signal_stop (loop, &exitsig);
634		833
635	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	834	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
636		835
637	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	836	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
638		837
639	These advanced functions influence the time that libev will spend waiting	838	These advanced functions influence the time that libev will spend waiting
640	for events. Both are by default C<0>, meaning that libev will try to	839	for events. Both time intervals are by default C<0>, meaning that libev
641	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	840	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		841	latency.
642		842
643	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	843	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
644	allows libev to delay invocation of I/O and timer/periodic callbacks to	844	allows libev to delay invocation of I/O and timer/periodic callbacks
645	increase efficiency of loop iterations.	845	to increase efficiency of loop iterations (or to increase power-saving
		846	opportunities).
646		847
647	The background is that sometimes your program runs just fast enough to	848	The idea is that sometimes your program runs just fast enough to handle
648	handle one (or very few) event(s) per loop iteration. While this makes	849	one (or very few) event(s) per loop iteration. While this makes the
649	the program responsive, it also wastes a lot of CPU time to poll for new	850	program responsive, it also wastes a lot of CPU time to poll for new
650	events, especially with backends like C<select ()> which have a high	851	events, especially with backends like C<select ()> which have a high
651	overhead for the actual polling but can deliver many events at once.	852	overhead for the actual polling but can deliver many events at once.
652		853
653	By setting a higher I<io collect interval> you allow libev to spend more	854	By setting a higher I<io collect interval> you allow libev to spend more
654	time collecting I/O events, so you can handle more events per iteration,	855	time collecting I/O events, so you can handle more events per iteration,
655	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	856	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
656	C<ev_timer>) will be not affected. Setting this to a non-null value will	857	C<ev_timer>) will be not affected. Setting this to a non-null value will
657	introduce an additional C<ev_sleep ()> call into most loop iterations.	858	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		859	sleep time ensures that libev will not poll for I/O events more often then
		860	once per this interval, on average.
658		861
659	Likewise, by setting a higher I<timeout collect interval> you allow libev	862	Likewise, by setting a higher I<timeout collect interval> you allow libev
660	to spend more time collecting timeouts, at the expense of increased	863	to spend more time collecting timeouts, at the expense of increased
661	latency (the watcher callback will be called later). C<ev_io> watchers	864	latency/jitter/inexactness (the watcher callback will be called
662	will not be affected. Setting this to a non-null value will not introduce	865	later). C<ev_io> watchers will not be affected. Setting this to a non-null
663	any overhead in libev.	866	value will not introduce any overhead in libev.
664		867
665	Many (busy) programs can usually benefit by setting the io collect	868	Many (busy) programs can usually benefit by setting the I/O collect
666	interval to a value near C<0.1> or so, which is often enough for	869	interval to a value near C<0.1> or so, which is often enough for
667	interactive servers (of course not for games), likewise for timeouts. It	870	interactive servers (of course not for games), likewise for timeouts. It
668	usually doesn't make much sense to set it to a lower value than C<0.01>,	871	usually doesn't make much sense to set it to a lower value than C<0.01>,
669	as this approsaches the timing granularity of most systems.	872	as this approaches the timing granularity of most systems. Note that if
		873	you do transactions with the outside world and you can't increase the
		874	parallelity, then this setting will limit your transaction rate (if you
		875	need to poll once per transaction and the I/O collect interval is 0.01,
		876	then you can't do more than 100 transations per second).
		877
		878	Setting the I<timeout collect interval> can improve the opportunity for
		879	saving power, as the program will "bundle" timer callback invocations that
		880	are "near" in time together, by delaying some, thus reducing the number of
		881	times the process sleeps and wakes up again. Another useful technique to
		882	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		883	they fire on, say, one-second boundaries only.
		884
		885	Example: we only need 0.1s timeout granularity, and we wish not to poll
		886	more often than 100 times per second:
		887
		888	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		889	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		890
		891	=item ev_invoke_pending (loop)
		892
		893	This call will simply invoke all pending watchers while resetting their
		894	pending state. Normally, C<ev_loop> does this automatically when required,
		895	but when overriding the invoke callback this call comes handy.
		896
		897	=item int ev_pending_count (loop)
		898
		899	Returns the number of pending watchers - zero indicates that no watchers
		900	are pending.
		901
		902	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		903
		904	This overrides the invoke pending functionality of the loop: Instead of
		905	invoking all pending watchers when there are any, C<ev_loop> will call
		906	this callback instead. This is useful, for example, when you want to
		907	invoke the actual watchers inside another context (another thread etc.).
		908
		909	If you want to reset the callback, use C<ev_invoke_pending> as new
		910	callback.
		911
		912	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		913
		914	Sometimes you want to share the same loop between multiple threads. This
		915	can be done relatively simply by putting mutex_lock/unlock calls around
		916	each call to a libev function.
		917
		918	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		919	wait for it to return. One way around this is to wake up the loop via
		920	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		921	and I<acquire> callbacks on the loop.
		922
		923	When set, then C<release> will be called just before the thread is
		924	suspended waiting for new events, and C<acquire> is called just
		925	afterwards.
		926
		927	Ideally, C<release> will just call your mutex_unlock function, and
		928	C<acquire> will just call the mutex_lock function again.
		929
		930	While event loop modifications are allowed between invocations of
		931	C<release> and C<acquire> (that's their only purpose after all), no
		932	modifications done will affect the event loop, i.e. adding watchers will
		933	have no effect on the set of file descriptors being watched, or the time
		934	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		935	to take note of any changes you made.
		936
		937	In theory, threads executing C<ev_loop> will be async-cancel safe between
		938	invocations of C<release> and C<acquire>.
		939
		940	See also the locking example in the C<THREADS> section later in this
		941	document.
		942
		943	=item ev_set_userdata (loop, void *data)
		944
		945	=item ev_userdata (loop)
		946
		947	Set and retrieve a single C<void *> associated with a loop. When
		948	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		949	C<0.>
		950
		951	These two functions can be used to associate arbitrary data with a loop,
		952	and are intended solely for the C<invoke_pending_cb>, C<release> and
		953	C<acquire> callbacks described above, but of course can be (ab-)used for
		954	any other purpose as well.
		955
		956	=item ev_loop_verify (loop)
		957
		958	This function only does something when C<EV_VERIFY> support has been
		959	compiled in, which is the default for non-minimal builds. It tries to go
		960	through all internal structures and checks them for validity. If anything
		961	is found to be inconsistent, it will print an error message to standard
		962	error and call C<abort ()>.
		963
		964	This can be used to catch bugs inside libev itself: under normal
		965	circumstances, this function will never abort as of course libev keeps its
		966	data structures consistent.
670		967
671	=back	968	=back
672		969
673		970
674	=head1 ANATOMY OF A WATCHER	971	=head1 ANATOMY OF A WATCHER
		972
		973	In the following description, uppercase C<TYPE> in names stands for the
		974	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		975	watchers and C<ev_io_start> for I/O watchers.
675		976
676	A watcher is a structure that you create and register to record your	977	A watcher is a structure that you create and register to record your
677	interest in some event. For instance, if you want to wait for STDIN to	978	interest in some event. For instance, if you want to wait for STDIN to
678	become readable, you would create an C<ev_io> watcher for that:	979	become readable, you would create an C<ev_io> watcher for that:
679		980
680	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	981	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
681	{	982	{
682	ev_io_stop (w);	983	ev_io_stop (w);
683	ev_unloop (loop, EVUNLOOP_ALL);	984	ev_unloop (loop, EVUNLOOP_ALL);
684	}	985	}
685		986
686	struct ev_loop *loop = ev_default_loop (0);	987	struct ev_loop *loop = ev_default_loop (0);
		988
687	struct ev_io stdin_watcher;	989	ev_io stdin_watcher;
		990
688	ev_init (&stdin_watcher, my_cb);	991	ev_init (&stdin_watcher, my_cb);
689	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	992	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
690	ev_io_start (loop, &stdin_watcher);	993	ev_io_start (loop, &stdin_watcher);
		994
691	ev_loop (loop, 0);	995	ev_loop (loop, 0);
692		996
693	As you can see, you are responsible for allocating the memory for your	997	As you can see, you are responsible for allocating the memory for your
694	watcher structures (and it is usually a bad idea to do this on the stack,	998	watcher structures (and it is I<usually> a bad idea to do this on the
695	although this can sometimes be quite valid).	999	stack).
		1000
		1001	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1002	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
696		1003
697	Each watcher structure must be initialised by a call to C<ev_init	1004	Each watcher structure must be initialised by a call to C<ev_init
698	(watcher *, callback)>, which expects a callback to be provided. This	1005	(watcher *, callback)>, which expects a callback to be provided. This
699	callback gets invoked each time the event occurs (or, in the case of io	1006	callback gets invoked each time the event occurs (or, in the case of I/O
700	watchers, each time the event loop detects that the file descriptor given	1007	watchers, each time the event loop detects that the file descriptor given
701	is readable and/or writable).	1008	is readable and/or writable).
702		1009
703	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1010	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
704	with arguments specific to this watcher type. There is also a macro	1011	macro to configure it, with arguments specific to the watcher type. There
705	to combine initialisation and setting in one call: C<< ev_<type>_init	1012	is also a macro to combine initialisation and setting in one call: C<<
706	(watcher *, callback, ...) >>.	1013	ev_TYPE_init (watcher *, callback, ...) >>.
707		1014
708	To make the watcher actually watch out for events, you have to start it	1015	To make the watcher actually watch out for events, you have to start it
709	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1016	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
710	*) >>), and you can stop watching for events at any time by calling the	1017	*) >>), and you can stop watching for events at any time by calling the
711	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1018	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
712		1019
713	As long as your watcher is active (has been started but not stopped) you	1020	As long as your watcher is active (has been started but not stopped) you
714	must not touch the values stored in it. Most specifically you must never	1021	must not touch the values stored in it. Most specifically you must never
715	reinitialise it or call its C<set> macro.	1022	reinitialise it or call its C<ev_TYPE_set> macro.
716		1023
717	Each and every callback receives the event loop pointer as first, the	1024	Each and every callback receives the event loop pointer as first, the
718	registered watcher structure as second, and a bitset of received events as	1025	registered watcher structure as second, and a bitset of received events as
719	third argument.	1026	third argument.
720		1027
…		…
729	=item C<EV_WRITE>	1036	=item C<EV_WRITE>
730		1037
731	The file descriptor in the C<ev_io> watcher has become readable and/or	1038	The file descriptor in the C<ev_io> watcher has become readable and/or
732	writable.	1039	writable.
733		1040
734	=item C<EV_TIMEOUT>	1041	=item C<EV_TIMER>
735		1042
736	The C<ev_timer> watcher has timed out.	1043	The C<ev_timer> watcher has timed out.
737		1044
738	=item C<EV_PERIODIC>	1045	=item C<EV_PERIODIC>
739		1046
…		…
778		1085
779	=item C<EV_ASYNC>	1086	=item C<EV_ASYNC>
780		1087
781	The given async watcher has been asynchronously notified (see C<ev_async>).	1088	The given async watcher has been asynchronously notified (see C<ev_async>).
782		1089
		1090	=item C<EV_CUSTOM>
		1091
		1092	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1093	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1094
783	=item C<EV_ERROR>	1095	=item C<EV_ERROR>
784		1096
785	An unspecified error has occured, the watcher has been stopped. This might	1097	An unspecified error has occurred, the watcher has been stopped. This might
786	happen because the watcher could not be properly started because libev	1098	happen because the watcher could not be properly started because libev
787	ran out of memory, a file descriptor was found to be closed or any other	1099	ran out of memory, a file descriptor was found to be closed or any other
		1100	problem. Libev considers these application bugs.
		1101
788	problem. You best act on it by reporting the problem and somehow coping	1102	You best act on it by reporting the problem and somehow coping with the
789	with the watcher being stopped.	1103	watcher being stopped. Note that well-written programs should not receive
		1104	an error ever, so when your watcher receives it, this usually indicates a
		1105	bug in your program.
790		1106
791	Libev will usually signal a few "dummy" events together with an error,	1107	Libev will usually signal a few "dummy" events together with an error, for
792	for example it might indicate that a fd is readable or writable, and if	1108	example it might indicate that a fd is readable or writable, and if your
793	your callbacks is well-written it can just attempt the operation and cope	1109	callbacks is well-written it can just attempt the operation and cope with
794	with the error from read() or write(). This will not work in multithreaded	1110	the error from read() or write(). This will not work in multi-threaded
795	programs, though, so beware.	1111	programs, though, as the fd could already be closed and reused for another
		1112	thing, so beware.
796		1113
797	=back	1114	=back
798		1115
799	=head2 GENERIC WATCHER FUNCTIONS	1116	=head2 GENERIC WATCHER FUNCTIONS
800
801	In the following description, C<TYPE> stands for the watcher type,
802	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
803		1117
804	=over 4	1118	=over 4
805		1119
806	=item C<ev_init> (ev_TYPE *watcher, callback)	1120	=item C<ev_init> (ev_TYPE *watcher, callback)
807		1121
…		…
813	which rolls both calls into one.	1127	which rolls both calls into one.
814		1128
815	You can reinitialise a watcher at any time as long as it has been stopped	1129	You can reinitialise a watcher at any time as long as it has been stopped
816	(or never started) and there are no pending events outstanding.	1130	(or never started) and there are no pending events outstanding.
817		1131
818	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1132	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
819	int revents)>.	1133	int revents)>.
820		1134
		1135	Example: Initialise an C<ev_io> watcher in two steps.
		1136
		1137	ev_io w;
		1138	ev_init (&w, my_cb);
		1139	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1140
821	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1141	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
822		1142
823	This macro initialises the type-specific parts of a watcher. You need to	1143	This macro initialises the type-specific parts of a watcher. You need to
824	call C<ev_init> at least once before you call this macro, but you can	1144	call C<ev_init> at least once before you call this macro, but you can
825	call C<ev_TYPE_set> any number of times. You must not, however, call this	1145	call C<ev_TYPE_set> any number of times. You must not, however, call this
826	macro on a watcher that is active (it can be pending, however, which is a	1146	macro on a watcher that is active (it can be pending, however, which is a
827	difference to the C<ev_init> macro).	1147	difference to the C<ev_init> macro).
828		1148
829	Although some watcher types do not have type-specific arguments	1149	Although some watcher types do not have type-specific arguments
830	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1150	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
831		1151
		1152	See C<ev_init>, above, for an example.
		1153
832	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1154	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
833		1155
834	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1156	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
835	calls into a single call. This is the most convinient method to initialise	1157	calls into a single call. This is the most convenient method to initialise
836	a watcher. The same limitations apply, of course.	1158	a watcher. The same limitations apply, of course.
837		1159
		1160	Example: Initialise and set an C<ev_io> watcher in one step.
		1161
		1162	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1163
838	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1164	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
839		1165
840	Starts (activates) the given watcher. Only active watchers will receive	1166	Starts (activates) the given watcher. Only active watchers will receive
841	events. If the watcher is already active nothing will happen.	1167	events. If the watcher is already active nothing will happen.
842		1168
		1169	Example: Start the C<ev_io> watcher that is being abused as example in this
		1170	whole section.
		1171
		1172	ev_io_start (EV_DEFAULT_UC, &w);
		1173
843	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1174	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
844		1175
845	Stops the given watcher again (if active) and clears the pending	1176	Stops the given watcher if active, and clears the pending status (whether
		1177	the watcher was active or not).
		1178
846	status. It is possible that stopped watchers are pending (for example,	1179	It is possible that stopped watchers are pending - for example,
847	non-repeating timers are being stopped when they become pending), but	1180	non-repeating timers are being stopped when they become pending - but
848	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1181	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
849	you want to free or reuse the memory used by the watcher it is therefore a	1182	pending. If you want to free or reuse the memory used by the watcher it is
850	good idea to always call its C<ev_TYPE_stop> function.	1183	therefore a good idea to always call its C<ev_TYPE_stop> function.
851		1184
852	=item bool ev_is_active (ev_TYPE *watcher)	1185	=item bool ev_is_active (ev_TYPE *watcher)
853		1186
854	Returns a true value iff the watcher is active (i.e. it has been started	1187	Returns a true value iff the watcher is active (i.e. it has been started
855	and not yet been stopped). As long as a watcher is active you must not modify	1188	and not yet been stopped). As long as a watcher is active you must not modify
…		…
871	=item ev_cb_set (ev_TYPE *watcher, callback)	1204	=item ev_cb_set (ev_TYPE *watcher, callback)
872		1205
873	Change the callback. You can change the callback at virtually any time	1206	Change the callback. You can change the callback at virtually any time
874	(modulo threads).	1207	(modulo threads).
875		1208
876	=item ev_set_priority (ev_TYPE *watcher, priority)	1209	=item ev_set_priority (ev_TYPE *watcher, int priority)
877		1210
878	=item int ev_priority (ev_TYPE *watcher)	1211	=item int ev_priority (ev_TYPE *watcher)
879		1212
880	Set and query the priority of the watcher. The priority is a small	1213	Set and query the priority of the watcher. The priority is a small
881	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1214	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
882	(default: C<-2>). Pending watchers with higher priority will be invoked	1215	(default: C<-2>). Pending watchers with higher priority will be invoked
883	before watchers with lower priority, but priority will not keep watchers	1216	before watchers with lower priority, but priority will not keep watchers
884	from being executed (except for C<ev_idle> watchers).	1217	from being executed (except for C<ev_idle> watchers).
885		1218
886	This means that priorities are I<only> used for ordering callback
887	invocation after new events have been received. This is useful, for
888	example, to reduce latency after idling, or more often, to bind two
889	watchers on the same event and make sure one is called first.
890
891	If you need to suppress invocation when higher priority events are pending	1219	If you need to suppress invocation when higher priority events are pending
892	you need to look at C<ev_idle> watchers, which provide this functionality.	1220	you need to look at C<ev_idle> watchers, which provide this functionality.
893		1221
894	You I<must not> change the priority of a watcher as long as it is active or	1222	You I<must not> change the priority of a watcher as long as it is active or
895	pending.	1223	pending.
896		1224
		1225	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1226	fine, as long as you do not mind that the priority value you query might
		1227	or might not have been clamped to the valid range.
		1228
897	The default priority used by watchers when no priority has been set is	1229	The default priority used by watchers when no priority has been set is
898	always C<0>, which is supposed to not be too high and not be too low :).	1230	always C<0>, which is supposed to not be too high and not be too low :).
899		1231
900	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1232	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
901	fine, as long as you do not mind that the priority value you query might	1233	priorities.
902	or might not have been adjusted to be within valid range.
903		1234
904	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1235	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
905		1236
906	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1237	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
907	C<loop> nor C<revents> need to be valid as long as the watcher callback	1238	C<loop> nor C<revents> need to be valid as long as the watcher callback
908	can deal with that fact.	1239	can deal with that fact, as both are simply passed through to the
		1240	callback.
909		1241
910	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1242	=item int ev_clear_pending (loop, ev_TYPE *watcher)
911		1243
912	If the watcher is pending, this function returns clears its pending status	1244	If the watcher is pending, this function clears its pending status and
913	and returns its C<revents> bitset (as if its callback was invoked). If the	1245	returns its C<revents> bitset (as if its callback was invoked). If the
914	watcher isn't pending it does nothing and returns C<0>.	1246	watcher isn't pending it does nothing and returns C<0>.
915		1247
		1248	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1249	callback to be invoked, which can be accomplished with this function.
		1250
		1251	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1252
		1253	Feeds the given event set into the event loop, as if the specified event
		1254	had happened for the specified watcher (which must be a pointer to an
		1255	initialised but not necessarily started event watcher). Obviously you must
		1256	not free the watcher as long as it has pending events.
		1257
		1258	Stopping the watcher, letting libev invoke it, or calling
		1259	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1260	not started in the first place.
		1261
		1262	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1263	functions that do not need a watcher.
		1264
916	=back	1265	=back
917		1266
918		1267
919	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1268	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
920		1269
921	Each watcher has, by default, a member C<void *data> that you can change	1270	Each watcher has, by default, a member C<void *data> that you can change
922	and read at any time, libev will completely ignore it. This can be used	1271	and read at any time: libev will completely ignore it. This can be used
923	to associate arbitrary data with your watcher. If you need more data and	1272	to associate arbitrary data with your watcher. If you need more data and
924	don't want to allocate memory and store a pointer to it in that data	1273	don't want to allocate memory and store a pointer to it in that data
925	member, you can also "subclass" the watcher type and provide your own	1274	member, you can also "subclass" the watcher type and provide your own
926	data:	1275	data:
927		1276
928	struct my_io	1277	struct my_io
929	{	1278	{
930	struct ev_io io;	1279	ev_io io;
931	int otherfd;	1280	int otherfd;
932	void *somedata;	1281	void *somedata;
933	struct whatever *mostinteresting;	1282	struct whatever *mostinteresting;
934	}	1283	};
		1284
		1285	...
		1286	struct my_io w;
		1287	ev_io_init (&w.io, my_cb, fd, EV_READ);
935		1288
936	And since your callback will be called with a pointer to the watcher, you	1289	And since your callback will be called with a pointer to the watcher, you
937	can cast it back to your own type:	1290	can cast it back to your own type:
938		1291
939	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1292	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
940	{	1293	{
941	struct my_io *w = (struct my_io *)w_;	1294	struct my_io *w = (struct my_io *)w_;
942	...	1295	...
943	}	1296	}
944		1297
945	More interesting and less C-conformant ways of casting your callback type	1298	More interesting and less C-conformant ways of casting your callback type
946	instead have been omitted.	1299	instead have been omitted.
947		1300
948	Another common scenario is having some data structure with multiple	1301	Another common scenario is to use some data structure with multiple
949	watchers:	1302	embedded watchers:
950		1303
951	struct my_biggy	1304	struct my_biggy
952	{	1305	{
953	int some_data;	1306	int some_data;
954	ev_timer t1;	1307	ev_timer t1;
955	ev_timer t2;	1308	ev_timer t2;
956	}	1309	}
957		1310
958	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1311	In this case getting the pointer to C<my_biggy> is a bit more
959	you need to use C<offsetof>:	1312	complicated: Either you store the address of your C<my_biggy> struct
		1313	in the C<data> member of the watcher (for woozies), or you need to use
		1314	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1315	programmers):
960		1316
961	#include <stddef.h>	1317	#include <stddef.h>
962		1318
963	static void	1319	static void
964	t1_cb (EV_P_ struct ev_timer *w, int revents)	1320	t1_cb (EV_P_ ev_timer *w, int revents)
965	{	1321	{
966	struct my_biggy big = (struct my_biggy *	1322	struct my_biggy big = (struct my_biggy *)
967	(((char *)w) - offsetof (struct my_biggy, t1));	1323	(((char *)w) - offsetof (struct my_biggy, t1));
968	}	1324	}
969		1325
970	static void	1326	static void
971	t2_cb (EV_P_ struct ev_timer *w, int revents)	1327	t2_cb (EV_P_ ev_timer *w, int revents)
972	{	1328	{
973	struct my_biggy big = (struct my_biggy *	1329	struct my_biggy big = (struct my_biggy *)
974	(((char *)w) - offsetof (struct my_biggy, t2));	1330	(((char *)w) - offsetof (struct my_biggy, t2));
975	}	1331	}
		1332
		1333	=head2 WATCHER PRIORITY MODELS
		1334
		1335	Many event loops support I<watcher priorities>, which are usually small
		1336	integers that influence the ordering of event callback invocation
		1337	between watchers in some way, all else being equal.
		1338
		1339	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1340	description for the more technical details such as the actual priority
		1341	range.
		1342
		1343	There are two common ways how these these priorities are being interpreted
		1344	by event loops:
		1345
		1346	In the more common lock-out model, higher priorities "lock out" invocation
		1347	of lower priority watchers, which means as long as higher priority
		1348	watchers receive events, lower priority watchers are not being invoked.
		1349
		1350	The less common only-for-ordering model uses priorities solely to order
		1351	callback invocation within a single event loop iteration: Higher priority
		1352	watchers are invoked before lower priority ones, but they all get invoked
		1353	before polling for new events.
		1354
		1355	Libev uses the second (only-for-ordering) model for all its watchers
		1356	except for idle watchers (which use the lock-out model).
		1357
		1358	The rationale behind this is that implementing the lock-out model for
		1359	watchers is not well supported by most kernel interfaces, and most event
		1360	libraries will just poll for the same events again and again as long as
		1361	their callbacks have not been executed, which is very inefficient in the
		1362	common case of one high-priority watcher locking out a mass of lower
		1363	priority ones.
		1364
		1365	Static (ordering) priorities are most useful when you have two or more
		1366	watchers handling the same resource: a typical usage example is having an
		1367	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1368	timeouts. Under load, data might be received while the program handles
		1369	other jobs, but since timers normally get invoked first, the timeout
		1370	handler will be executed before checking for data. In that case, giving
		1371	the timer a lower priority than the I/O watcher ensures that I/O will be
		1372	handled first even under adverse conditions (which is usually, but not
		1373	always, what you want).
		1374
		1375	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1376	will only be executed when no same or higher priority watchers have
		1377	received events, they can be used to implement the "lock-out" model when
		1378	required.
		1379
		1380	For example, to emulate how many other event libraries handle priorities,
		1381	you can associate an C<ev_idle> watcher to each such watcher, and in
		1382	the normal watcher callback, you just start the idle watcher. The real
		1383	processing is done in the idle watcher callback. This causes libev to
		1384	continously poll and process kernel event data for the watcher, but when
		1385	the lock-out case is known to be rare (which in turn is rare :), this is
		1386	workable.
		1387
		1388	Usually, however, the lock-out model implemented that way will perform
		1389	miserably under the type of load it was designed to handle. In that case,
		1390	it might be preferable to stop the real watcher before starting the
		1391	idle watcher, so the kernel will not have to process the event in case
		1392	the actual processing will be delayed for considerable time.
		1393
		1394	Here is an example of an I/O watcher that should run at a strictly lower
		1395	priority than the default, and which should only process data when no
		1396	other events are pending:
		1397
		1398	ev_idle idle; // actual processing watcher
		1399	ev_io io; // actual event watcher
		1400
		1401	static void
		1402	io_cb (EV_P_ ev_io *w, int revents)
		1403	{
		1404	// stop the I/O watcher, we received the event, but
		1405	// are not yet ready to handle it.
		1406	ev_io_stop (EV_A_ w);
		1407
		1408	// start the idle watcher to ahndle the actual event.
		1409	// it will not be executed as long as other watchers
		1410	// with the default priority are receiving events.
		1411	ev_idle_start (EV_A_ &idle);
		1412	}
		1413
		1414	static void
		1415	idle_cb (EV_P_ ev_idle *w, int revents)
		1416	{
		1417	// actual processing
		1418	read (STDIN_FILENO, ...);
		1419
		1420	// have to start the I/O watcher again, as
		1421	// we have handled the event
		1422	ev_io_start (EV_P_ &io);
		1423	}
		1424
		1425	// initialisation
		1426	ev_idle_init (&idle, idle_cb);
		1427	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1428	ev_io_start (EV_DEFAULT_ &io);
		1429
		1430	In the "real" world, it might also be beneficial to start a timer, so that
		1431	low-priority connections can not be locked out forever under load. This
		1432	enables your program to keep a lower latency for important connections
		1433	during short periods of high load, while not completely locking out less
		1434	important ones.
976		1435
977		1436
978	=head1 WATCHER TYPES	1437	=head1 WATCHER TYPES
979		1438
980	This section describes each watcher in detail, but will not repeat	1439	This section describes each watcher in detail, but will not repeat
…		…
1004	In general you can register as many read and/or write event watchers per	1463	In general you can register as many read and/or write event watchers per
1005	fd as you want (as long as you don't confuse yourself). Setting all file	1464	fd as you want (as long as you don't confuse yourself). Setting all file
1006	descriptors to non-blocking mode is also usually a good idea (but not	1465	descriptors to non-blocking mode is also usually a good idea (but not
1007	required if you know what you are doing).	1466	required if you know what you are doing).
1008		1467
1009	If you must do this, then force the use of a known-to-be-good backend	1468	If you cannot use non-blocking mode, then force the use of a
1010	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1469	known-to-be-good backend (at the time of this writing, this includes only
1011	C<EVBACKEND_POLL>).	1470	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1471	descriptors for which non-blocking operation makes no sense (such as
		1472	files) - libev doesn't guarentee any specific behaviour in that case.
1012		1473
1013	Another thing you have to watch out for is that it is quite easy to	1474	Another thing you have to watch out for is that it is quite easy to
1014	receive "spurious" readyness notifications, that is your callback might	1475	receive "spurious" readiness notifications, that is your callback might
1015	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1476	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1016	because there is no data. Not only are some backends known to create a	1477	because there is no data. Not only are some backends known to create a
1017	lot of those (for example solaris ports), it is very easy to get into	1478	lot of those (for example Solaris ports), it is very easy to get into
1018	this situation even with a relatively standard program structure. Thus	1479	this situation even with a relatively standard program structure. Thus
1019	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1480	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1020	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1481	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1021		1482
1022	If you cannot run the fd in non-blocking mode (for example you should not	1483	If you cannot run the fd in non-blocking mode (for example you should
1023	play around with an Xlib connection), then you have to seperately re-test	1484	not play around with an Xlib connection), then you have to separately
1024	whether a file descriptor is really ready with a known-to-be good interface	1485	re-test whether a file descriptor is really ready with a known-to-be good
1025	such as poll (fortunately in our Xlib example, Xlib already does this on	1486	interface such as poll (fortunately in our Xlib example, Xlib already
1026	its own, so its quite safe to use).	1487	does this on its own, so its quite safe to use). Some people additionally
		1488	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1489	indefinitely.
		1490
		1491	But really, best use non-blocking mode.
1027		1492
1028	=head3 The special problem of disappearing file descriptors	1493	=head3 The special problem of disappearing file descriptors
1029		1494
1030	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1495	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1031	descriptor (either by calling C<close> explicitly or by any other means,	1496	descriptor (either due to calling C<close> explicitly or any other means,
1032	such as C<dup>). The reason is that you register interest in some file	1497	such as C<dup2>). The reason is that you register interest in some file
1033	descriptor, but when it goes away, the operating system will silently drop	1498	descriptor, but when it goes away, the operating system will silently drop
1034	this interest. If another file descriptor with the same number then is	1499	this interest. If another file descriptor with the same number then is
1035	registered with libev, there is no efficient way to see that this is, in	1500	registered with libev, there is no efficient way to see that this is, in
1036	fact, a different file descriptor.	1501	fact, a different file descriptor.
1037		1502
…		…
1066	To support fork in your programs, you either have to call	1531	To support fork in your programs, you either have to call
1067	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1532	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1068	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1533	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1069	C<EVBACKEND_POLL>.	1534	C<EVBACKEND_POLL>.
1070		1535
		1536	=head3 The special problem of SIGPIPE
		1537
		1538	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1539	when writing to a pipe whose other end has been closed, your program gets
		1540	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1541	this is sensible behaviour, for daemons, this is usually undesirable.
		1542
		1543	So when you encounter spurious, unexplained daemon exits, make sure you
		1544	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1545	somewhere, as that would have given you a big clue).
		1546
		1547	=head3 The special problem of accept()ing when you can't
		1548
		1549	Many implementations of the POSIX C<accept> function (for example,
		1550	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1551	connection from the pending queue in all error cases.
		1552
		1553	For example, larger servers often run out of file descriptors (because
		1554	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1555	rejecting the connection, leading to libev signalling readiness on
		1556	the next iteration again (the connection still exists after all), and
		1557	typically causing the program to loop at 100% CPU usage.
		1558
		1559	Unfortunately, the set of errors that cause this issue differs between
		1560	operating systems, there is usually little the app can do to remedy the
		1561	situation, and no known thread-safe method of removing the connection to
		1562	cope with overload is known (to me).
		1563
		1564	One of the easiest ways to handle this situation is to just ignore it
		1565	- when the program encounters an overload, it will just loop until the
		1566	situation is over. While this is a form of busy waiting, no OS offers an
		1567	event-based way to handle this situation, so it's the best one can do.
		1568
		1569	A better way to handle the situation is to log any errors other than
		1570	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1571	messages, and continue as usual, which at least gives the user an idea of
		1572	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1573	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1574	usage.
		1575
		1576	If your program is single-threaded, then you could also keep a dummy file
		1577	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1578	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1579	close that fd, and create a new dummy fd. This will gracefully refuse
		1580	clients under typical overload conditions.
		1581
		1582	The last way to handle it is to simply log the error and C<exit>, as
		1583	is often done with C<malloc> failures, but this results in an easy
		1584	opportunity for a DoS attack.
1071		1585
1072	=head3 Watcher-Specific Functions	1586	=head3 Watcher-Specific Functions
1073		1587
1074	=over 4	1588	=over 4
1075		1589
1076	=item ev_io_init (ev_io *, callback, int fd, int events)	1590	=item ev_io_init (ev_io *, callback, int fd, int events)
1077		1591
1078	=item ev_io_set (ev_io *, int fd, int events)	1592	=item ev_io_set (ev_io *, int fd, int events)
1079		1593
1080	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1594	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1081	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1595	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1082	C<EV_READ | EV_WRITE> to receive the given events.	1596	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1083		1597
1084	=item int fd [read-only]	1598	=item int fd [read-only]
1085		1599
1086	The file descriptor being watched.	1600	The file descriptor being watched.
1087		1601
…		…
1095		1609
1096	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1610	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1097	readable, but only once. Since it is likely line-buffered, you could	1611	readable, but only once. Since it is likely line-buffered, you could
1098	attempt to read a whole line in the callback.	1612	attempt to read a whole line in the callback.
1099		1613
1100	static void	1614	static void
1101	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1615	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1102	{	1616	{
1103	ev_io_stop (loop, w);	1617	ev_io_stop (loop, w);
1104	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1618	.. read from stdin here (or from w->fd) and handle any I/O errors
1105	}	1619	}
1106		1620
1107	...	1621	...
1108	struct ev_loop *loop = ev_default_init (0);	1622	struct ev_loop *loop = ev_default_init (0);
1109	struct ev_io stdin_readable;	1623	ev_io stdin_readable;
1110	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1624	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1111	ev_io_start (loop, &stdin_readable);	1625	ev_io_start (loop, &stdin_readable);
1112	ev_loop (loop, 0);	1626	ev_loop (loop, 0);
1113		1627
1114		1628
1115	=head2 C<ev_timer> - relative and optionally repeating timeouts	1629	=head2 C<ev_timer> - relative and optionally repeating timeouts
1116		1630
1117	Timer watchers are simple relative timers that generate an event after a	1631	Timer watchers are simple relative timers that generate an event after a
1118	given time, and optionally repeating in regular intervals after that.	1632	given time, and optionally repeating in regular intervals after that.
1119		1633
1120	The timers are based on real time, that is, if you register an event that	1634	The timers are based on real time, that is, if you register an event that
1121	times out after an hour and you reset your system clock to last years	1635	times out after an hour and you reset your system clock to January last
1122	time, it will still time out after (roughly) and hour. "Roughly" because	1636	year, it will still time out after (roughly) one hour. "Roughly" because
1123	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1637	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1124	monotonic clock option helps a lot here).	1638	monotonic clock option helps a lot here).
		1639
		1640	The callback is guaranteed to be invoked only I<after> its timeout has
		1641	passed (not I<at>, so on systems with very low-resolution clocks this
		1642	might introduce a small delay). If multiple timers become ready during the
		1643	same loop iteration then the ones with earlier time-out values are invoked
		1644	before ones of the same priority with later time-out values (but this is
		1645	no longer true when a callback calls C<ev_loop> recursively).
		1646
		1647	=head3 Be smart about timeouts
		1648
		1649	Many real-world problems involve some kind of timeout, usually for error
		1650	recovery. A typical example is an HTTP request - if the other side hangs,
		1651	you want to raise some error after a while.
		1652
		1653	What follows are some ways to handle this problem, from obvious and
		1654	inefficient to smart and efficient.
		1655
		1656	In the following, a 60 second activity timeout is assumed - a timeout that
		1657	gets reset to 60 seconds each time there is activity (e.g. each time some
		1658	data or other life sign was received).
		1659
		1660	=over 4
		1661
		1662	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1663
		1664	This is the most obvious, but not the most simple way: In the beginning,
		1665	start the watcher:
		1666
		1667	ev_timer_init (timer, callback, 60., 0.);
		1668	ev_timer_start (loop, timer);
		1669
		1670	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1671	and start it again:
		1672
		1673	ev_timer_stop (loop, timer);
		1674	ev_timer_set (timer, 60., 0.);
		1675	ev_timer_start (loop, timer);
		1676
		1677	This is relatively simple to implement, but means that each time there is
		1678	some activity, libev will first have to remove the timer from its internal
		1679	data structure and then add it again. Libev tries to be fast, but it's
		1680	still not a constant-time operation.
		1681
		1682	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1683
		1684	This is the easiest way, and involves using C<ev_timer_again> instead of
		1685	C<ev_timer_start>.
		1686
		1687	To implement this, configure an C<ev_timer> with a C<repeat> value
		1688	of C<60> and then call C<ev_timer_again> at start and each time you
		1689	successfully read or write some data. If you go into an idle state where
		1690	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1691	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1692
		1693	That means you can ignore both the C<ev_timer_start> function and the
		1694	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1695	member and C<ev_timer_again>.
		1696
		1697	At start:
		1698
		1699	ev_init (timer, callback);
		1700	timer->repeat = 60.;
		1701	ev_timer_again (loop, timer);
		1702
		1703	Each time there is some activity:
		1704
		1705	ev_timer_again (loop, timer);
		1706
		1707	It is even possible to change the time-out on the fly, regardless of
		1708	whether the watcher is active or not:
		1709
		1710	timer->repeat = 30.;
		1711	ev_timer_again (loop, timer);
		1712
		1713	This is slightly more efficient then stopping/starting the timer each time
		1714	you want to modify its timeout value, as libev does not have to completely
		1715	remove and re-insert the timer from/into its internal data structure.
		1716
		1717	It is, however, even simpler than the "obvious" way to do it.
		1718
		1719	=item 3. Let the timer time out, but then re-arm it as required.
		1720
		1721	This method is more tricky, but usually most efficient: Most timeouts are
		1722	relatively long compared to the intervals between other activity - in
		1723	our example, within 60 seconds, there are usually many I/O events with
		1724	associated activity resets.
		1725
		1726	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1727	but remember the time of last activity, and check for a real timeout only
		1728	within the callback:
		1729
		1730	ev_tstamp last_activity; // time of last activity
		1731
		1732	static void
		1733	callback (EV_P_ ev_timer *w, int revents)
		1734	{
		1735	ev_tstamp now = ev_now (EV_A);
		1736	ev_tstamp timeout = last_activity + 60.;
		1737
		1738	// if last_activity + 60. is older than now, we did time out
		1739	if (timeout < now)
		1740	{
		1741	// timeout occured, take action
		1742	}
		1743	else
		1744	{
		1745	// callback was invoked, but there was some activity, re-arm
		1746	// the watcher to fire in last_activity + 60, which is
		1747	// guaranteed to be in the future, so "again" is positive:
		1748	w->repeat = timeout - now;
		1749	ev_timer_again (EV_A_ w);
		1750	}
		1751	}
		1752
		1753	To summarise the callback: first calculate the real timeout (defined
		1754	as "60 seconds after the last activity"), then check if that time has
		1755	been reached, which means something I<did>, in fact, time out. Otherwise
		1756	the callback was invoked too early (C<timeout> is in the future), so
		1757	re-schedule the timer to fire at that future time, to see if maybe we have
		1758	a timeout then.
		1759
		1760	Note how C<ev_timer_again> is used, taking advantage of the
		1761	C<ev_timer_again> optimisation when the timer is already running.
		1762
		1763	This scheme causes more callback invocations (about one every 60 seconds
		1764	minus half the average time between activity), but virtually no calls to
		1765	libev to change the timeout.
		1766
		1767	To start the timer, simply initialise the watcher and set C<last_activity>
		1768	to the current time (meaning we just have some activity :), then call the
		1769	callback, which will "do the right thing" and start the timer:
		1770
		1771	ev_init (timer, callback);
		1772	last_activity = ev_now (loop);
		1773	callback (loop, timer, EV_TIMER);
		1774
		1775	And when there is some activity, simply store the current time in
		1776	C<last_activity>, no libev calls at all:
		1777
		1778	last_actiivty = ev_now (loop);
		1779
		1780	This technique is slightly more complex, but in most cases where the
		1781	time-out is unlikely to be triggered, much more efficient.
		1782
		1783	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1784	callback :) - just change the timeout and invoke the callback, which will
		1785	fix things for you.
		1786
		1787	=item 4. Wee, just use a double-linked list for your timeouts.
		1788
		1789	If there is not one request, but many thousands (millions...), all
		1790	employing some kind of timeout with the same timeout value, then one can
		1791	do even better:
		1792
		1793	When starting the timeout, calculate the timeout value and put the timeout
		1794	at the I<end> of the list.
		1795
		1796	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1797	the list is expected to fire (for example, using the technique #3).
		1798
		1799	When there is some activity, remove the timer from the list, recalculate
		1800	the timeout, append it to the end of the list again, and make sure to
		1801	update the C<ev_timer> if it was taken from the beginning of the list.
		1802
		1803	This way, one can manage an unlimited number of timeouts in O(1) time for
		1804	starting, stopping and updating the timers, at the expense of a major
		1805	complication, and having to use a constant timeout. The constant timeout
		1806	ensures that the list stays sorted.
		1807
		1808	=back
		1809
		1810	So which method the best?
		1811
		1812	Method #2 is a simple no-brain-required solution that is adequate in most
		1813	situations. Method #3 requires a bit more thinking, but handles many cases
		1814	better, and isn't very complicated either. In most case, choosing either
		1815	one is fine, with #3 being better in typical situations.
		1816
		1817	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1818	rather complicated, but extremely efficient, something that really pays
		1819	off after the first million or so of active timers, i.e. it's usually
		1820	overkill :)
		1821
		1822	=head3 The special problem of time updates
		1823
		1824	Establishing the current time is a costly operation (it usually takes at
		1825	least two system calls): EV therefore updates its idea of the current
		1826	time only before and after C<ev_loop> collects new events, which causes a
		1827	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1828	lots of events in one iteration.
1125		1829
1126	The relative timeouts are calculated relative to the C<ev_now ()>	1830	The relative timeouts are calculated relative to the C<ev_now ()>
1127	time. This is usually the right thing as this timestamp refers to the time	1831	time. This is usually the right thing as this timestamp refers to the time
1128	of the event triggering whatever timeout you are modifying/starting. If	1832	of the event triggering whatever timeout you are modifying/starting. If
1129	you suspect event processing to be delayed and you I<need> to base the timeout	1833	you suspect event processing to be delayed and you I<need> to base the
1130	on the current time, use something like this to adjust for this:	1834	timeout on the current time, use something like this to adjust for this:
1131		1835
1132	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1836	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1133		1837
1134	The callback is guarenteed to be invoked only when its timeout has passed,	1838	If the event loop is suspended for a long time, you can also force an
1135	but if multiple timers become ready during the same loop iteration then	1839	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1136	order of execution is undefined.	1840	()>.
		1841
		1842	=head3 The special problems of suspended animation
		1843
		1844	When you leave the server world it is quite customary to hit machines that
		1845	can suspend/hibernate - what happens to the clocks during such a suspend?
		1846
		1847	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1848	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1849	to run until the system is suspended, but they will not advance while the
		1850	system is suspended. That means, on resume, it will be as if the program
		1851	was frozen for a few seconds, but the suspend time will not be counted
		1852	towards C<ev_timer> when a monotonic clock source is used. The real time
		1853	clock advanced as expected, but if it is used as sole clocksource, then a
		1854	long suspend would be detected as a time jump by libev, and timers would
		1855	be adjusted accordingly.
		1856
		1857	I would not be surprised to see different behaviour in different between
		1858	operating systems, OS versions or even different hardware.
		1859
		1860	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1861	time jump in the monotonic clocks and the realtime clock. If the program
		1862	is suspended for a very long time, and monotonic clock sources are in use,
		1863	then you can expect C<ev_timer>s to expire as the full suspension time
		1864	will be counted towards the timers. When no monotonic clock source is in
		1865	use, then libev will again assume a timejump and adjust accordingly.
		1866
		1867	It might be beneficial for this latter case to call C<ev_suspend>
		1868	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1869	deterministic behaviour in this case (you can do nothing against
		1870	C<SIGSTOP>).
1137		1871
1138	=head3 Watcher-Specific Functions and Data Members	1872	=head3 Watcher-Specific Functions and Data Members
1139		1873
1140	=over 4	1874	=over 4
1141		1875
1142	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1876	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1143		1877
1144	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1878	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1145		1879
1146	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1880	Configure the timer to trigger after C<after> seconds. If C<repeat>
1147	C<0.>, then it will automatically be stopped. If it is positive, then the	1881	is C<0.>, then it will automatically be stopped once the timeout is
1148	timer will automatically be configured to trigger again C<repeat> seconds	1882	reached. If it is positive, then the timer will automatically be
1149	later, again, and again, until stopped manually.	1883	configured to trigger again C<repeat> seconds later, again, and again,
		1884	until stopped manually.
1150		1885
1151	The timer itself will do a best-effort at avoiding drift, that is, if you	1886	The timer itself will do a best-effort at avoiding drift, that is, if
1152	configure a timer to trigger every 10 seconds, then it will trigger at	1887	you configure a timer to trigger every 10 seconds, then it will normally
1153	exactly 10 second intervals. If, however, your program cannot keep up with	1888	trigger at exactly 10 second intervals. If, however, your program cannot
1154	the timer (because it takes longer than those 10 seconds to do stuff) the	1889	keep up with the timer (because it takes longer than those 10 seconds to
1155	timer will not fire more than once per event loop iteration.	1890	do stuff) the timer will not fire more than once per event loop iteration.
1156		1891
1157	=item ev_timer_again (loop)	1892	=item ev_timer_again (loop, ev_timer *)
1158		1893
1159	This will act as if the timer timed out and restart it again if it is	1894	This will act as if the timer timed out and restart it again if it is
1160	repeating. The exact semantics are:	1895	repeating. The exact semantics are:
1161		1896
1162	If the timer is pending, its pending status is cleared.	1897	If the timer is pending, its pending status is cleared.
1163		1898
1164	If the timer is started but nonrepeating, stop it (as if it timed out).	1899	If the timer is started but non-repeating, stop it (as if it timed out).
1165		1900
1166	If the timer is repeating, either start it if necessary (with the	1901	If the timer is repeating, either start it if necessary (with the
1167	C<repeat> value), or reset the running timer to the C<repeat> value.	1902	C<repeat> value), or reset the running timer to the C<repeat> value.
1168		1903
1169	This sounds a bit complicated, but here is a useful and typical	1904	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1170	example: Imagine you have a tcp connection and you want a so-called idle	1905	usage example.
1171	timeout, that is, you want to be called when there have been, say, 60
1172	seconds of inactivity on the socket. The easiest way to do this is to
1173	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1174	C<ev_timer_again> each time you successfully read or write some data. If
1175	you go into an idle state where you do not expect data to travel on the
1176	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1177	automatically restart it if need be.
1178		1906
1179	That means you can ignore the C<after> value and C<ev_timer_start>	1907	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1180	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1181		1908
1182	ev_timer_init (timer, callback, 0., 5.);	1909	Returns the remaining time until a timer fires. If the timer is active,
1183	ev_timer_again (loop, timer);	1910	then this time is relative to the current event loop time, otherwise it's
1184	...	1911	the timeout value currently configured.
1185	timer->again = 17.;
1186	ev_timer_again (loop, timer);
1187	...
1188	timer->again = 10.;
1189	ev_timer_again (loop, timer);
1190		1912
1191	This is more slightly efficient then stopping/starting the timer each time	1913	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1192	you want to modify its timeout value.	1914	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1915	will return C<4>. When the timer expires and is restarted, it will return
		1916	roughly C<7> (likely slightly less as callback invocation takes some time,
		1917	too), and so on.
1193		1918
1194	=item ev_tstamp repeat [read-write]	1919	=item ev_tstamp repeat [read-write]
1195		1920
1196	The current C<repeat> value. Will be used each time the watcher times out	1921	The current C<repeat> value. Will be used each time the watcher times out
1197	or C<ev_timer_again> is called and determines the next timeout (if any),	1922	or C<ev_timer_again> is called, and determines the next timeout (if any),
1198	which is also when any modifications are taken into account.	1923	which is also when any modifications are taken into account.
1199		1924
1200	=back	1925	=back
1201		1926
1202	=head3 Examples	1927	=head3 Examples
1203		1928
1204	Example: Create a timer that fires after 60 seconds.	1929	Example: Create a timer that fires after 60 seconds.
1205		1930
1206	static void	1931	static void
1207	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1932	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1208	{	1933	{
1209	.. one minute over, w is actually stopped right here	1934	.. one minute over, w is actually stopped right here
1210	}	1935	}
1211		1936
1212	struct ev_timer mytimer;	1937	ev_timer mytimer;
1213	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1938	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1214	ev_timer_start (loop, &mytimer);	1939	ev_timer_start (loop, &mytimer);
1215		1940
1216	Example: Create a timeout timer that times out after 10 seconds of	1941	Example: Create a timeout timer that times out after 10 seconds of
1217	inactivity.	1942	inactivity.
1218		1943
1219	static void	1944	static void
1220	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1945	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1221	{	1946	{
1222	.. ten seconds without any activity	1947	.. ten seconds without any activity
1223	}	1948	}
1224		1949
1225	struct ev_timer mytimer;	1950	ev_timer mytimer;
1226	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1951	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1227	ev_timer_again (&mytimer); /* start timer */	1952	ev_timer_again (&mytimer); /* start timer */
1228	ev_loop (loop, 0);	1953	ev_loop (loop, 0);
1229		1954
1230	// and in some piece of code that gets executed on any "activity":	1955	// and in some piece of code that gets executed on any "activity":
1231	// reset the timeout to start ticking again at 10 seconds	1956	// reset the timeout to start ticking again at 10 seconds
1232	ev_timer_again (&mytimer);	1957	ev_timer_again (&mytimer);
1233		1958
1234		1959
1235	=head2 C<ev_periodic> - to cron or not to cron?	1960	=head2 C<ev_periodic> - to cron or not to cron?
1236		1961
1237	Periodic watchers are also timers of a kind, but they are very versatile	1962	Periodic watchers are also timers of a kind, but they are very versatile
1238	(and unfortunately a bit complex).	1963	(and unfortunately a bit complex).
1239		1964
1240	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1965	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1241	but on wallclock time (absolute time). You can tell a periodic watcher	1966	relative time, the physical time that passes) but on wall clock time
1242	to trigger "at" some specific point in time. For example, if you tell a	1967	(absolute time, the thing you can read on your calender or clock). The
1243	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1968	difference is that wall clock time can run faster or slower than real
1244	+ 10.>) and then reset your system clock to the last year, then it will	1969	time, and time jumps are not uncommon (e.g. when you adjust your
1245	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1970	wrist-watch).
1246	roughly 10 seconds later).
1247		1971
1248	They can also be used to implement vastly more complex timers, such as	1972	You can tell a periodic watcher to trigger after some specific point
1249	triggering an event on each midnight, local time or other, complicated,	1973	in time: for example, if you tell a periodic watcher to trigger "in 10
1250	rules.	1974	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1975	not a delay) and then reset your system clock to January of the previous
		1976	year, then it will take a year or more to trigger the event (unlike an
		1977	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1978	it, as it uses a relative timeout).
1251		1979
		1980	C<ev_periodic> watchers can also be used to implement vastly more complex
		1981	timers, such as triggering an event on each "midnight, local time", or
		1982	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1983	those cannot react to time jumps.
		1984
1252	As with timers, the callback is guarenteed to be invoked only when the	1985	As with timers, the callback is guaranteed to be invoked only when the
1253	time (C<at>) has been passed, but if multiple periodic timers become ready	1986	point in time where it is supposed to trigger has passed. If multiple
1254	during the same loop iteration then order of execution is undefined.	1987	timers become ready during the same loop iteration then the ones with
		1988	earlier time-out values are invoked before ones with later time-out values
		1989	(but this is no longer true when a callback calls C<ev_loop> recursively).
1255		1990
1256	=head3 Watcher-Specific Functions and Data Members	1991	=head3 Watcher-Specific Functions and Data Members
1257		1992
1258	=over 4	1993	=over 4
1259		1994
1260	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1995	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1261		1996
1262	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1997	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1263		1998
1264	Lots of arguments, lets sort it out... There are basically three modes of	1999	Lots of arguments, let's sort it out... There are basically three modes of
1265	operation, and we will explain them from simplest to complex:	2000	operation, and we will explain them from simplest to most complex:
1266		2001
1267	=over 4	2002	=over 4
1268		2003
1269	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2004	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1270		2005
1271	In this configuration the watcher triggers an event at the wallclock time	2006	In this configuration the watcher triggers an event after the wall clock
1272	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	2007	time C<offset> has passed. It will not repeat and will not adjust when a
1273	that is, if it is to be run at January 1st 2011 then it will run when the	2008	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1274	system time reaches or surpasses this time.	2009	will be stopped and invoked when the system clock reaches or surpasses
		2010	this point in time.
1275		2011
1276	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2012	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1277		2013
1278	In this mode the watcher will always be scheduled to time out at the next	2014	In this mode the watcher will always be scheduled to time out at the next
1279	C<at + N * interval> time (for some integer N, which can also be negative)	2015	C<offset + N * interval> time (for some integer N, which can also be
1280	and then repeat, regardless of any time jumps.	2016	negative) and then repeat, regardless of any time jumps. The C<offset>
		2017	argument is merely an offset into the C<interval> periods.
1281		2018
1282	This can be used to create timers that do not drift with respect to system	2019	This can be used to create timers that do not drift with respect to the
1283	time:	2020	system clock, for example, here is an C<ev_periodic> that triggers each
		2021	hour, on the hour (with respect to UTC):
1284		2022
1285	ev_periodic_set (&periodic, 0., 3600., 0);	2023	ev_periodic_set (&periodic, 0., 3600., 0);
1286		2024
1287	This doesn't mean there will always be 3600 seconds in between triggers,	2025	This doesn't mean there will always be 3600 seconds in between triggers,
1288	but only that the the callback will be called when the system time shows a	2026	but only that the callback will be called when the system time shows a
1289	full hour (UTC), or more correctly, when the system time is evenly divisible	2027	full hour (UTC), or more correctly, when the system time is evenly divisible
1290	by 3600.	2028	by 3600.
1291		2029
1292	Another way to think about it (for the mathematically inclined) is that	2030	Another way to think about it (for the mathematically inclined) is that
1293	C<ev_periodic> will try to run the callback in this mode at the next possible	2031	C<ev_periodic> will try to run the callback in this mode at the next possible
1294	time where C<time = at (mod interval)>, regardless of any time jumps.	2032	time where C<time = offset (mod interval)>, regardless of any time jumps.
1295		2033
1296	For numerical stability it is preferable that the C<at> value is near	2034	For numerical stability it is preferable that the C<offset> value is near
1297	C<ev_now ()> (the current time), but there is no range requirement for	2035	C<ev_now ()> (the current time), but there is no range requirement for
1298	this value.	2036	this value, and in fact is often specified as zero.
1299		2037
		2038	Note also that there is an upper limit to how often a timer can fire (CPU
		2039	speed for example), so if C<interval> is very small then timing stability
		2040	will of course deteriorate. Libev itself tries to be exact to be about one
		2041	millisecond (if the OS supports it and the machine is fast enough).
		2042
1300	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2043	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1301		2044
1302	In this mode the values for C<interval> and C<at> are both being	2045	In this mode the values for C<interval> and C<offset> are both being
1303	ignored. Instead, each time the periodic watcher gets scheduled, the	2046	ignored. Instead, each time the periodic watcher gets scheduled, the
1304	reschedule callback will be called with the watcher as first, and the	2047	reschedule callback will be called with the watcher as first, and the
1305	current time as second argument.	2048	current time as second argument.
1306		2049
1307	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2050	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1308	ever, or make any event loop modifications>. If you need to stop it,	2051	or make ANY other event loop modifications whatsoever, unless explicitly
1309	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	2052	allowed by documentation here>.
1310	starting an C<ev_prepare> watcher, which is legal).
1311		2053
		2054	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		2055	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		2056	only event loop modification you are allowed to do).
		2057
1312	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	2058	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1313	ev_tstamp now)>, e.g.:	2059	*w, ev_tstamp now)>, e.g.:
1314		2060
		2061	static ev_tstamp
1315	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2062	my_rescheduler (ev_periodic *w, ev_tstamp now)
1316	{	2063	{
1317	return now + 60.;	2064	return now + 60.;
1318	}	2065	}
1319		2066
1320	It must return the next time to trigger, based on the passed time value	2067	It must return the next time to trigger, based on the passed time value
1321	(that is, the lowest time value larger than to the second argument). It	2068	(that is, the lowest time value larger than to the second argument). It
1322	will usually be called just before the callback will be triggered, but	2069	will usually be called just before the callback will be triggered, but
1323	might be called at other times, too.	2070	might be called at other times, too.
1324		2071
1325	NOTE: I<< This callback must always return a time that is later than the	2072	NOTE: I<< This callback must always return a time that is higher than or
1326	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	2073	equal to the passed C<now> value >>.
1327		2074
1328	This can be used to create very complex timers, such as a timer that	2075	This can be used to create very complex timers, such as a timer that
1329	triggers on each midnight, local time. To do this, you would calculate the	2076	triggers on "next midnight, local time". To do this, you would calculate the
1330	next midnight after C<now> and return the timestamp value for this. How	2077	next midnight after C<now> and return the timestamp value for this. How
1331	you do this is, again, up to you (but it is not trivial, which is the main	2078	you do this is, again, up to you (but it is not trivial, which is the main
1332	reason I omitted it as an example).	2079	reason I omitted it as an example).
1333		2080
1334	=back	2081	=back
…		…
1338	Simply stops and restarts the periodic watcher again. This is only useful	2085	Simply stops and restarts the periodic watcher again. This is only useful
1339	when you changed some parameters or the reschedule callback would return	2086	when you changed some parameters or the reschedule callback would return
1340	a different time than the last time it was called (e.g. in a crond like	2087	a different time than the last time it was called (e.g. in a crond like
1341	program when the crontabs have changed).	2088	program when the crontabs have changed).
1342		2089
		2090	=item ev_tstamp ev_periodic_at (ev_periodic *)
		2091
		2092	When active, returns the absolute time that the watcher is supposed
		2093	to trigger next. This is not the same as the C<offset> argument to
		2094	C<ev_periodic_set>, but indeed works even in interval and manual
		2095	rescheduling modes.
		2096
1343	=item ev_tstamp offset [read-write]	2097	=item ev_tstamp offset [read-write]
1344		2098
1345	When repeating, this contains the offset value, otherwise this is the	2099	When repeating, this contains the offset value, otherwise this is the
1346	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2100	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2101	although libev might modify this value for better numerical stability).
1347		2102
1348	Can be modified any time, but changes only take effect when the periodic	2103	Can be modified any time, but changes only take effect when the periodic
1349	timer fires or C<ev_periodic_again> is being called.	2104	timer fires or C<ev_periodic_again> is being called.
1350		2105
1351	=item ev_tstamp interval [read-write]	2106	=item ev_tstamp interval [read-write]
1352		2107
1353	The current interval value. Can be modified any time, but changes only	2108	The current interval value. Can be modified any time, but changes only
1354	take effect when the periodic timer fires or C<ev_periodic_again> is being	2109	take effect when the periodic timer fires or C<ev_periodic_again> is being
1355	called.	2110	called.
1356		2111
1357	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2112	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1358		2113
1359	The current reschedule callback, or C<0>, if this functionality is	2114	The current reschedule callback, or C<0>, if this functionality is
1360	switched off. Can be changed any time, but changes only take effect when	2115	switched off. Can be changed any time, but changes only take effect when
1361	the periodic timer fires or C<ev_periodic_again> is being called.	2116	the periodic timer fires or C<ev_periodic_again> is being called.
1362		2117
1363	=item ev_tstamp at [read-only]
1364
1365	When active, contains the absolute time that the watcher is supposed to
1366	trigger next.
1367
1368	=back	2118	=back
1369		2119
1370	=head3 Examples	2120	=head3 Examples
1371		2121
1372	Example: Call a callback every hour, or, more precisely, whenever the	2122	Example: Call a callback every hour, or, more precisely, whenever the
1373	system clock is divisible by 3600. The callback invocation times have	2123	system time is divisible by 3600. The callback invocation times have
1374	potentially a lot of jittering, but good long-term stability.	2124	potentially a lot of jitter, but good long-term stability.
1375		2125
1376	static void	2126	static void
1377	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2127	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1378	{	2128	{
1379	... its now a full hour (UTC, or TAI or whatever your clock follows)	2129	... its now a full hour (UTC, or TAI or whatever your clock follows)
1380	}	2130	}
1381		2131
1382	struct ev_periodic hourly_tick;	2132	ev_periodic hourly_tick;
1383	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2133	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1384	ev_periodic_start (loop, &hourly_tick);	2134	ev_periodic_start (loop, &hourly_tick);
1385		2135
1386	Example: The same as above, but use a reschedule callback to do it:	2136	Example: The same as above, but use a reschedule callback to do it:
1387		2137
1388	#include <math.h>	2138	#include <math.h>
1389		2139
1390	static ev_tstamp	2140	static ev_tstamp
1391	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2141	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1392	{	2142	{
1393	return fmod (now, 3600.) + 3600.;	2143	return now + (3600. - fmod (now, 3600.));
1394	}	2144	}
1395		2145
1396	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2146	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1397		2147
1398	Example: Call a callback every hour, starting now:	2148	Example: Call a callback every hour, starting now:
1399		2149
1400	struct ev_periodic hourly_tick;	2150	ev_periodic hourly_tick;
1401	ev_periodic_init (&hourly_tick, clock_cb,	2151	ev_periodic_init (&hourly_tick, clock_cb,
1402	fmod (ev_now (loop), 3600.), 3600., 0);	2152	fmod (ev_now (loop), 3600.), 3600., 0);
1403	ev_periodic_start (loop, &hourly_tick);	2153	ev_periodic_start (loop, &hourly_tick);
1404		2154
1405		2155
1406	=head2 C<ev_signal> - signal me when a signal gets signalled!	2156	=head2 C<ev_signal> - signal me when a signal gets signalled!
1407		2157
1408	Signal watchers will trigger an event when the process receives a specific	2158	Signal watchers will trigger an event when the process receives a specific
1409	signal one or more times. Even though signals are very asynchronous, libev	2159	signal one or more times. Even though signals are very asynchronous, libev
1410	will try it's best to deliver signals synchronously, i.e. as part of the	2160	will try it's best to deliver signals synchronously, i.e. as part of the
1411	normal event processing, like any other event.	2161	normal event processing, like any other event.
1412		2162
		2163	If you want signals to be delivered truly asynchronously, just use
		2164	C<sigaction> as you would do without libev and forget about sharing
		2165	the signal. You can even use C<ev_async> from a signal handler to
		2166	synchronously wake up an event loop.
		2167
1413	You can configure as many watchers as you like per signal. Only when the	2168	You can configure as many watchers as you like for the same signal, but
		2169	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2170	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2171	C<SIGINT> in both the default loop and another loop at the same time. At
		2172	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2173
1414	first watcher gets started will libev actually register a signal watcher	2174	When the first watcher gets started will libev actually register something
1415	with the kernel (thus it coexists with your own signal handlers as long	2175	with the kernel (thus it coexists with your own signal handlers as long as
1416	as you don't register any with libev). Similarly, when the last signal	2176	you don't register any with libev for the same signal).
1417	watcher for a signal is stopped libev will reset the signal handler to	2177
1418	SIG_DFL (regardless of what it was set to before).	2178	If possible and supported, libev will install its handlers with
		2179	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
		2180	not be unduly interrupted. If you have a problem with system calls getting
		2181	interrupted by signals you can block all signals in an C<ev_check> watcher
		2182	and unblock them in an C<ev_prepare> watcher.
		2183
		2184	=head3 The special problem of inheritance over fork/execve/pthread_create
		2185
		2186	Both the signal mask (C<sigprocmask>) and the signal disposition
		2187	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2188	stopping it again), that is, libev might or might not block the signal,
		2189	and might or might not set or restore the installed signal handler.
		2190
		2191	While this does not matter for the signal disposition (libev never
		2192	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2193	C<execve>), this matters for the signal mask: many programs do not expect
		2194	certain signals to be blocked.
		2195
		2196	This means that before calling C<exec> (from the child) you should reset
		2197	the signal mask to whatever "default" you expect (all clear is a good
		2198	choice usually).
		2199
		2200	The simplest way to ensure that the signal mask is reset in the child is
		2201	to install a fork handler with C<pthread_atfork> that resets it. That will
		2202	catch fork calls done by libraries (such as the libc) as well.
		2203
		2204	In current versions of libev, the signal will not be blocked indefinitely
		2205	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2206	the window of opportunity for problems, it will not go away, as libev
		2207	I<has> to modify the signal mask, at least temporarily.
		2208
		2209	So I can't stress this enough: I<If you do not reset your signal mask when
		2210	you expect it to be empty, you have a race condition in your code>. This
		2211	is not a libev-specific thing, this is true for most event libraries.
1419		2212
1420	=head3 Watcher-Specific Functions and Data Members	2213	=head3 Watcher-Specific Functions and Data Members
1421		2214
1422	=over 4	2215	=over 4
1423		2216
…		…
1432		2225
1433	The signal the watcher watches out for.	2226	The signal the watcher watches out for.
1434		2227
1435	=back	2228	=back
1436		2229
		2230	=head3 Examples
		2231
		2232	Example: Try to exit cleanly on SIGINT.
		2233
		2234	static void
		2235	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		2236	{
		2237	ev_unloop (loop, EVUNLOOP_ALL);
		2238	}
		2239
		2240	ev_signal signal_watcher;
		2241	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		2242	ev_signal_start (loop, &signal_watcher);
		2243
1437		2244
1438	=head2 C<ev_child> - watch out for process status changes	2245	=head2 C<ev_child> - watch out for process status changes
1439		2246
1440	Child watchers trigger when your process receives a SIGCHLD in response to	2247	Child watchers trigger when your process receives a SIGCHLD in response to
1441	some child status changes (most typically when a child of yours dies).	2248	some child status changes (most typically when a child of yours dies or
		2249	exits). It is permissible to install a child watcher I<after> the child
		2250	has been forked (which implies it might have already exited), as long
		2251	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2252	forking and then immediately registering a watcher for the child is fine,
		2253	but forking and registering a watcher a few event loop iterations later or
		2254	in the next callback invocation is not.
		2255
		2256	Only the default event loop is capable of handling signals, and therefore
		2257	you can only register child watchers in the default event loop.
		2258
		2259	Due to some design glitches inside libev, child watchers will always be
		2260	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2261	libev)
		2262
		2263	=head3 Process Interaction
		2264
		2265	Libev grabs C<SIGCHLD> as soon as the default event loop is
		2266	initialised. This is necessary to guarantee proper behaviour even if the
		2267	first child watcher is started after the child exits. The occurrence
		2268	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		2269	synchronously as part of the event loop processing. Libev always reaps all
		2270	children, even ones not watched.
		2271
		2272	=head3 Overriding the Built-In Processing
		2273
		2274	Libev offers no special support for overriding the built-in child
		2275	processing, but if your application collides with libev's default child
		2276	handler, you can override it easily by installing your own handler for
		2277	C<SIGCHLD> after initialising the default loop, and making sure the
		2278	default loop never gets destroyed. You are encouraged, however, to use an
		2279	event-based approach to child reaping and thus use libev's support for
		2280	that, so other libev users can use C<ev_child> watchers freely.
		2281
		2282	=head3 Stopping the Child Watcher
		2283
		2284	Currently, the child watcher never gets stopped, even when the
		2285	child terminates, so normally one needs to stop the watcher in the
		2286	callback. Future versions of libev might stop the watcher automatically
		2287	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2288	problem).
1442		2289
1443	=head3 Watcher-Specific Functions and Data Members	2290	=head3 Watcher-Specific Functions and Data Members
1444		2291
1445	=over 4	2292	=over 4
1446		2293
…		…
1472		2319
1473	=back	2320	=back
1474		2321
1475	=head3 Examples	2322	=head3 Examples
1476		2323
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	2324	Example: C<fork()> a new process and install a child handler to wait for
		2325	its completion.
1478		2326
		2327	ev_child cw;
		2328
1479	static void	2329	static void
1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2330	child_cb (EV_P_ ev_child *w, int revents)
1481	{	2331	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	2332	ev_child_stop (EV_A_ w);
		2333	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1483	}	2334	}
1484		2335
1485	struct ev_signal signal_watcher;	2336	pid_t pid = fork ();
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2337
1487	ev_signal_start (loop, &sigint_cb);	2338	if (pid < 0)
		2339	// error
		2340	else if (pid == 0)
		2341	{
		2342	// the forked child executes here
		2343	exit (1);
		2344	}
		2345	else
		2346	{
		2347	ev_child_init (&cw, child_cb, pid, 0);
		2348	ev_child_start (EV_DEFAULT_ &cw);
		2349	}
1488		2350
1489		2351
1490	=head2 C<ev_stat> - did the file attributes just change?	2352	=head2 C<ev_stat> - did the file attributes just change?
1491		2353
1492	This watches a filesystem path for attribute changes. That is, it calls	2354	This watches a file system path for attribute changes. That is, it calls
1493	C<stat> regularly (or when the OS says it changed) and sees if it changed	2355	C<stat> on that path in regular intervals (or when the OS says it changed)
1494	compared to the last time, invoking the callback if it did.	2356	and sees if it changed compared to the last time, invoking the callback if
		2357	it did.
1495		2358
1496	The path does not need to exist: changing from "path exists" to "path does	2359	The path does not need to exist: changing from "path exists" to "path does
1497	not exist" is a status change like any other. The condition "path does	2360	not exist" is a status change like any other. The condition "path does not
1498	not exist" is signified by the C<st_nlink> field being zero (which is	2361	exist" (or more correctly "path cannot be stat'ed") is signified by the
1499	otherwise always forced to be at least one) and all the other fields of	2362	C<st_nlink> field being zero (which is otherwise always forced to be at
1500	the stat buffer having unspecified contents.	2363	least one) and all the other fields of the stat buffer having unspecified
		2364	contents.
1501		2365
1502	The path I<should> be absolute and I<must not> end in a slash. If it is	2366	The path I<must not> end in a slash or contain special components such as
		2367	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1503	relative and your working directory changes, the behaviour is undefined.	2368	your working directory changes, then the behaviour is undefined.
1504		2369
1505	Since there is no standard to do this, the portable implementation simply	2370	Since there is no portable change notification interface available, the
1506	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2371	portable implementation simply calls C<stat(2)> regularly on the path
1507	can specify a recommended polling interval for this case. If you specify	2372	to see if it changed somehow. You can specify a recommended polling
1508	a polling interval of C<0> (highly recommended!) then a I<suitable,	2373	interval for this case. If you specify a polling interval of C<0> (highly
1509	unspecified default> value will be used (which you can expect to be around	2374	recommended!) then a I<suitable, unspecified default> value will be used
1510	five seconds, although this might change dynamically). Libev will also	2375	(which you can expect to be around five seconds, although this might
1511	impose a minimum interval which is currently around C<0.1>, but thats	2376	change dynamically). Libev will also impose a minimum interval which is
1512	usually overkill.	2377	currently around C<0.1>, but that's usually overkill.
1513		2378
1514	This watcher type is not meant for massive numbers of stat watchers,	2379	This watcher type is not meant for massive numbers of stat watchers,
1515	as even with OS-supported change notifications, this can be	2380	as even with OS-supported change notifications, this can be
1516	resource-intensive.	2381	resource-intensive.
1517		2382
1518	At the time of this writing, only the Linux inotify interface is	2383	At the time of this writing, the only OS-specific interface implemented
1519	implemented (implementing kqueue support is left as an exercise for the	2384	is the Linux inotify interface (implementing kqueue support is left as an
1520	reader). Inotify will be used to give hints only and should not change the	2385	exercise for the reader. Note, however, that the author sees no way of
1521	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2386	implementing C<ev_stat> semantics with kqueue, except as a hint).
1522	to fall back to regular polling again even with inotify, but changes are
1523	usually detected immediately, and if the file exists there will be no
1524	polling.
1525		2387
1526	=head3 Inotify	2388	=head3 ABI Issues (Largefile Support)
1527		2389
		2390	Libev by default (unless the user overrides this) uses the default
		2391	compilation environment, which means that on systems with large file
		2392	support disabled by default, you get the 32 bit version of the stat
		2393	structure. When using the library from programs that change the ABI to
		2394	use 64 bit file offsets the programs will fail. In that case you have to
		2395	compile libev with the same flags to get binary compatibility. This is
		2396	obviously the case with any flags that change the ABI, but the problem is
		2397	most noticeably displayed with ev_stat and large file support.
		2398
		2399	The solution for this is to lobby your distribution maker to make large
		2400	file interfaces available by default (as e.g. FreeBSD does) and not
		2401	optional. Libev cannot simply switch on large file support because it has
		2402	to exchange stat structures with application programs compiled using the
		2403	default compilation environment.
		2404
		2405	=head3 Inotify and Kqueue
		2406
1528	When C<inotify (7)> support has been compiled into libev (generally only	2407	When C<inotify (7)> support has been compiled into libev and present at
1529	available on Linux) and present at runtime, it will be used to speed up	2408	runtime, it will be used to speed up change detection where possible. The
1530	change detection where possible. The inotify descriptor will be created lazily	2409	inotify descriptor will be created lazily when the first C<ev_stat>
1531	when the first C<ev_stat> watcher is being started.	2410	watcher is being started.
1532		2411
1533	Inotify presense does not change the semantics of C<ev_stat> watchers	2412	Inotify presence does not change the semantics of C<ev_stat> watchers
1534	except that changes might be detected earlier, and in some cases, to avoid	2413	except that changes might be detected earlier, and in some cases, to avoid
1535	making regular C<stat> calls. Even in the presense of inotify support	2414	making regular C<stat> calls. Even in the presence of inotify support
1536	there are many cases where libev has to resort to regular C<stat> polling.	2415	there are many cases where libev has to resort to regular C<stat> polling,
		2416	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2417	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2418	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2419	xfs are fully working) libev usually gets away without polling.
1537		2420
1538	(There is no support for kqueue, as apparently it cannot be used to	2421	There is no support for kqueue, as apparently it cannot be used to
1539	implement this functionality, due to the requirement of having a file	2422	implement this functionality, due to the requirement of having a file
1540	descriptor open on the object at all times).	2423	descriptor open on the object at all times, and detecting renames, unlinks
		2424	etc. is difficult.
		2425
		2426	=head3 C<stat ()> is a synchronous operation
		2427
		2428	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2429	the process. The exception are C<ev_stat> watchers - those call C<stat
		2430	()>, which is a synchronous operation.
		2431
		2432	For local paths, this usually doesn't matter: unless the system is very
		2433	busy or the intervals between stat's are large, a stat call will be fast,
		2434	as the path data is usually in memory already (except when starting the
		2435	watcher).
		2436
		2437	For networked file systems, calling C<stat ()> can block an indefinite
		2438	time due to network issues, and even under good conditions, a stat call
		2439	often takes multiple milliseconds.
		2440
		2441	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2442	paths, although this is fully supported by libev.
1541		2443
1542	=head3 The special problem of stat time resolution	2444	=head3 The special problem of stat time resolution
1543		2445
1544	The C<stat ()> syscall only supports full-second resolution portably, and	2446	The C<stat ()> system call only supports full-second resolution portably,
1545	even on systems where the resolution is higher, many filesystems still	2447	and even on systems where the resolution is higher, most file systems
1546	only support whole seconds.	2448	still only support whole seconds.
1547		2449
1548	That means that, if the time is the only thing that changes, you might	2450	That means that, if the time is the only thing that changes, you can
1549	miss updates: on the first update, C<ev_stat> detects a change and calls	2451	easily miss updates: on the first update, C<ev_stat> detects a change and
1550	your callback, which does something. When there is another update within	2452	calls your callback, which does something. When there is another update
1551	the same second, C<ev_stat> will be unable to detect it.	2453	within the same second, C<ev_stat> will be unable to detect unless the
		2454	stat data does change in other ways (e.g. file size).
1552		2455
1553	The solution to this is to delay acting on a change for a second (or till	2456	The solution to this is to delay acting on a change for slightly more
1554	the next second boundary), using a roughly one-second delay C<ev_timer>	2457	than a second (or till slightly after the next full second boundary), using
1555	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2458	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1556	is added to work around small timing inconsistencies of some operating	2459	ev_timer_again (loop, w)>).
1557	systems.	2460
		2461	The C<.02> offset is added to work around small timing inconsistencies
		2462	of some operating systems (where the second counter of the current time
		2463	might be be delayed. One such system is the Linux kernel, where a call to
		2464	C<gettimeofday> might return a timestamp with a full second later than
		2465	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2466	update file times then there will be a small window where the kernel uses
		2467	the previous second to update file times but libev might already execute
		2468	the timer callback).
1558		2469
1559	=head3 Watcher-Specific Functions and Data Members	2470	=head3 Watcher-Specific Functions and Data Members
1560		2471
1561	=over 4	2472	=over 4
1562		2473
…		…
1568	C<path>. The C<interval> is a hint on how quickly a change is expected to	2479	C<path>. The C<interval> is a hint on how quickly a change is expected to
1569	be detected and should normally be specified as C<0> to let libev choose	2480	be detected and should normally be specified as C<0> to let libev choose
1570	a suitable value. The memory pointed to by C<path> must point to the same	2481	a suitable value. The memory pointed to by C<path> must point to the same
1571	path for as long as the watcher is active.	2482	path for as long as the watcher is active.
1572		2483
1573	The callback will be receive C<EV_STAT> when a change was detected,	2484	The callback will receive an C<EV_STAT> event when a change was detected,
1574	relative to the attributes at the time the watcher was started (or the	2485	relative to the attributes at the time the watcher was started (or the
1575	last change was detected).	2486	last change was detected).
1576		2487
1577	=item ev_stat_stat (ev_stat *)	2488	=item ev_stat_stat (loop, ev_stat *)
1578		2489
1579	Updates the stat buffer immediately with new values. If you change the	2490	Updates the stat buffer immediately with new values. If you change the
1580	watched path in your callback, you could call this fucntion to avoid	2491	watched path in your callback, you could call this function to avoid
1581	detecting this change (while introducing a race condition). Can also be	2492	detecting this change (while introducing a race condition if you are not
1582	useful simply to find out the new values.	2493	the only one changing the path). Can also be useful simply to find out the
		2494	new values.
1583		2495
1584	=item ev_statdata attr [read-only]	2496	=item ev_statdata attr [read-only]
1585		2497
1586	The most-recently detected attributes of the file. Although the type is of	2498	The most-recently detected attributes of the file. Although the type is
1587	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2499	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1588	suitable for your system. If the C<st_nlink> member is C<0>, then there	2500	suitable for your system, but you can only rely on the POSIX-standardised
		2501	members to be present. If the C<st_nlink> member is C<0>, then there was
1589	was some error while C<stat>ing the file.	2502	some error while C<stat>ing the file.
1590		2503
1591	=item ev_statdata prev [read-only]	2504	=item ev_statdata prev [read-only]
1592		2505
1593	The previous attributes of the file. The callback gets invoked whenever	2506	The previous attributes of the file. The callback gets invoked whenever
1594	C<prev> != C<attr>.	2507	C<prev> != C<attr>, or, more precisely, one or more of these members
		2508	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2509	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1595		2510
1596	=item ev_tstamp interval [read-only]	2511	=item ev_tstamp interval [read-only]
1597		2512
1598	The specified interval.	2513	The specified interval.
1599		2514
1600	=item const char *path [read-only]	2515	=item const char *path [read-only]
1601		2516
1602	The filesystem path that is being watched.	2517	The file system path that is being watched.
1603		2518
1604	=back	2519	=back
1605		2520
1606	=head3 Examples	2521	=head3 Examples
1607		2522
1608	Example: Watch C</etc/passwd> for attribute changes.	2523	Example: Watch C</etc/passwd> for attribute changes.
1609		2524
1610	static void	2525	static void
1611	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2526	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1612	{	2527	{
1613	/* /etc/passwd changed in some way */	2528	/* /etc/passwd changed in some way */
1614	if (w->attr.st_nlink)	2529	if (w->attr.st_nlink)
1615	{	2530	{
1616	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2531	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1617	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2532	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1618	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2533	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1619	}	2534	}
1620	else	2535	else
1621	/* you shalt not abuse printf for puts */	2536	/* you shalt not abuse printf for puts */
1622	puts ("wow, /etc/passwd is not there, expect problems. "	2537	puts ("wow, /etc/passwd is not there, expect problems. "
1623	"if this is windows, they already arrived\n");	2538	"if this is windows, they already arrived\n");
1624	}	2539	}
1625		2540
1626	...	2541	...
1627	ev_stat passwd;	2542	ev_stat passwd;
1628		2543
1629	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2544	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1630	ev_stat_start (loop, &passwd);	2545	ev_stat_start (loop, &passwd);
1631		2546
1632	Example: Like above, but additionally use a one-second delay so we do not	2547	Example: Like above, but additionally use a one-second delay so we do not
1633	miss updates (however, frequent updates will delay processing, too, so	2548	miss updates (however, frequent updates will delay processing, too, so
1634	one might do the work both on C<ev_stat> callback invocation I<and> on	2549	one might do the work both on C<ev_stat> callback invocation I<and> on
1635	C<ev_timer> callback invocation).	2550	C<ev_timer> callback invocation).
1636		2551
1637	static ev_stat passwd;	2552	static ev_stat passwd;
1638	static ev_timer timer;	2553	static ev_timer timer;
1639		2554
1640	static void	2555	static void
1641	timer_cb (EV_P_ ev_timer *w, int revents)	2556	timer_cb (EV_P_ ev_timer *w, int revents)
1642	{	2557	{
1643	ev_timer_stop (EV_A_ w);	2558	ev_timer_stop (EV_A_ w);
1644		2559
1645	/* now it's one second after the most recent passwd change */	2560	/* now it's one second after the most recent passwd change */
1646	}	2561	}
1647		2562
1648	static void	2563	static void
1649	stat_cb (EV_P_ ev_stat *w, int revents)	2564	stat_cb (EV_P_ ev_stat *w, int revents)
1650	{	2565	{
1651	/* reset the one-second timer */	2566	/* reset the one-second timer */
1652	ev_timer_again (EV_A_ &timer);	2567	ev_timer_again (EV_A_ &timer);
1653	}	2568	}
1654		2569
1655	...	2570	...
1656	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2571	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1657	ev_stat_start (loop, &passwd);	2572	ev_stat_start (loop, &passwd);
1658	ev_timer_init (&timer, timer_cb, 0., 1.01);	2573	ev_timer_init (&timer, timer_cb, 0., 1.02);
1659		2574
1660		2575
1661	=head2 C<ev_idle> - when you've got nothing better to do...	2576	=head2 C<ev_idle> - when you've got nothing better to do...
1662		2577
1663	Idle watchers trigger events when no other events of the same or higher	2578	Idle watchers trigger events when no other events of the same or higher
1664	priority are pending (prepare, check and other idle watchers do not	2579	priority are pending (prepare, check and other idle watchers do not count
1665	count).	2580	as receiving "events").
1666		2581
1667	That is, as long as your process is busy handling sockets or timeouts	2582	That is, as long as your process is busy handling sockets or timeouts
1668	(or even signals, imagine) of the same or higher priority it will not be	2583	(or even signals, imagine) of the same or higher priority it will not be
1669	triggered. But when your process is idle (or only lower-priority watchers	2584	triggered. But when your process is idle (or only lower-priority watchers
1670	are pending), the idle watchers are being called once per event loop	2585	are pending), the idle watchers are being called once per event loop
…		…
1681		2596
1682	=head3 Watcher-Specific Functions and Data Members	2597	=head3 Watcher-Specific Functions and Data Members
1683		2598
1684	=over 4	2599	=over 4
1685		2600
1686	=item ev_idle_init (ev_signal *, callback)	2601	=item ev_idle_init (ev_idle *, callback)
1687		2602
1688	Initialises and configures the idle watcher - it has no parameters of any	2603	Initialises and configures the idle watcher - it has no parameters of any
1689	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2604	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1690	believe me.	2605	believe me.
1691		2606
…		…
1694	=head3 Examples	2609	=head3 Examples
1695		2610
1696	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2611	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1697	callback, free it. Also, use no error checking, as usual.	2612	callback, free it. Also, use no error checking, as usual.
1698		2613
1699	static void	2614	static void
1700	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2615	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1701	{	2616	{
1702	free (w);	2617	free (w);
1703	// now do something you wanted to do when the program has	2618	// now do something you wanted to do when the program has
1704	// no longer anything immediate to do.	2619	// no longer anything immediate to do.
1705	}	2620	}
1706		2621
1707	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2622	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1708	ev_idle_init (idle_watcher, idle_cb);	2623	ev_idle_init (idle_watcher, idle_cb);
1709	ev_idle_start (loop, idle_cb);	2624	ev_idle_start (loop, idle_watcher);
1710		2625
1711		2626
1712	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2627	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1713		2628
1714	Prepare and check watchers are usually (but not always) used in tandem:	2629	Prepare and check watchers are usually (but not always) used in pairs:
1715	prepare watchers get invoked before the process blocks and check watchers	2630	prepare watchers get invoked before the process blocks and check watchers
1716	afterwards.	2631	afterwards.
1717		2632
1718	You I<must not> call C<ev_loop> or similar functions that enter	2633	You I<must not> call C<ev_loop> or similar functions that enter
1719	the current event loop from either C<ev_prepare> or C<ev_check>	2634	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1722	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2637	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1723	C<ev_check> so if you have one watcher of each kind they will always be	2638	C<ev_check> so if you have one watcher of each kind they will always be
1724	called in pairs bracketing the blocking call.	2639	called in pairs bracketing the blocking call.
1725		2640
1726	Their main purpose is to integrate other event mechanisms into libev and	2641	Their main purpose is to integrate other event mechanisms into libev and
1727	their use is somewhat advanced. This could be used, for example, to track	2642	their use is somewhat advanced. They could be used, for example, to track
1728	variable changes, implement your own watchers, integrate net-snmp or a	2643	variable changes, implement your own watchers, integrate net-snmp or a
1729	coroutine library and lots more. They are also occasionally useful if	2644	coroutine library and lots more. They are also occasionally useful if
1730	you cache some data and want to flush it before blocking (for example,	2645	you cache some data and want to flush it before blocking (for example,
1731	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2646	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1732	watcher).	2647	watcher).
1733		2648
1734	This is done by examining in each prepare call which file descriptors need	2649	This is done by examining in each prepare call which file descriptors
1735	to be watched by the other library, registering C<ev_io> watchers for	2650	need to be watched by the other library, registering C<ev_io> watchers
1736	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2651	for them and starting an C<ev_timer> watcher for any timeouts (many
1737	provide just this functionality). Then, in the check watcher you check for	2652	libraries provide exactly this functionality). Then, in the check watcher,
1738	any events that occured (by checking the pending status of all watchers	2653	you check for any events that occurred (by checking the pending status
1739	and stopping them) and call back into the library. The I/O and timer	2654	of all watchers and stopping them) and call back into the library. The
1740	callbacks will never actually be called (but must be valid nevertheless,	2655	I/O and timer callbacks will never actually be called (but must be valid
1741	because you never know, you know?).	2656	nevertheless, because you never know, you know?).
1742		2657
1743	As another example, the Perl Coro module uses these hooks to integrate	2658	As another example, the Perl Coro module uses these hooks to integrate
1744	coroutines into libev programs, by yielding to other active coroutines	2659	coroutines into libev programs, by yielding to other active coroutines
1745	during each prepare and only letting the process block if no coroutines	2660	during each prepare and only letting the process block if no coroutines
1746	are ready to run (it's actually more complicated: it only runs coroutines	2661	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1749	loop from blocking if lower-priority coroutines are active, thus mapping	2664	loop from blocking if lower-priority coroutines are active, thus mapping
1750	low-priority coroutines to idle/background tasks).	2665	low-priority coroutines to idle/background tasks).
1751		2666
1752	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2667	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1753	priority, to ensure that they are being run before any other watchers	2668	priority, to ensure that they are being run before any other watchers
		2669	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2670
1754	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2671	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1755	too) should not activate ("feed") events into libev. While libev fully	2672	activate ("feed") events into libev. While libev fully supports this, they
1756	supports this, they will be called before other C<ev_check> watchers	2673	might get executed before other C<ev_check> watchers did their job. As
1757	did their job. As C<ev_check> watchers are often used to embed other	2674	C<ev_check> watchers are often used to embed other (non-libev) event
1758	(non-libev) event loops those other event loops might be in an unusable	2675	loops those other event loops might be in an unusable state until their
1759	state until their C<ev_check> watcher ran (always remind yourself to	2676	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1760	coexist peacefully with others).	2677	others).
1761		2678
1762	=head3 Watcher-Specific Functions and Data Members	2679	=head3 Watcher-Specific Functions and Data Members
1763		2680
1764	=over 4	2681	=over 4
1765		2682
…		…
1767		2684
1768	=item ev_check_init (ev_check *, callback)	2685	=item ev_check_init (ev_check *, callback)
1769		2686
1770	Initialises and configures the prepare or check watcher - they have no	2687	Initialises and configures the prepare or check watcher - they have no
1771	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2688	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1772	macros, but using them is utterly, utterly and completely pointless.	2689	macros, but using them is utterly, utterly, utterly and completely
		2690	pointless.
1773		2691
1774	=back	2692	=back
1775		2693
1776	=head3 Examples	2694	=head3 Examples
1777		2695
1778	There are a number of principal ways to embed other event loops or modules	2696	There are a number of principal ways to embed other event loops or modules
1779	into libev. Here are some ideas on how to include libadns into libev	2697	into libev. Here are some ideas on how to include libadns into libev
1780	(there is a Perl module named C<EV::ADNS> that does this, which you could	2698	(there is a Perl module named C<EV::ADNS> that does this, which you could
1781	use for an actually working example. Another Perl module named C<EV::Glib>	2699	use as a working example. Another Perl module named C<EV::Glib> embeds a
1782	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2700	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1783	into the Glib event loop).	2701	Glib event loop).
1784		2702
1785	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2703	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1786	and in a check watcher, destroy them and call into libadns. What follows	2704	and in a check watcher, destroy them and call into libadns. What follows
1787	is pseudo-code only of course. This requires you to either use a low	2705	is pseudo-code only of course. This requires you to either use a low
1788	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2706	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1789	the callbacks for the IO/timeout watchers might not have been called yet.	2707	the callbacks for the IO/timeout watchers might not have been called yet.
1790		2708
1791	static ev_io iow [nfd];	2709	static ev_io iow [nfd];
1792	static ev_timer tw;	2710	static ev_timer tw;
1793		2711
1794	static void	2712	static void
1795	io_cb (ev_loop *loop, ev_io *w, int revents)	2713	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1796	{	2714	{
1797	}	2715	}
1798		2716
1799	// create io watchers for each fd and a timer before blocking	2717	// create io watchers for each fd and a timer before blocking
1800	static void	2718	static void
1801	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2719	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1802	{	2720	{
1803	int timeout = 3600000;	2721	int timeout = 3600000;
1804	struct pollfd fds [nfd];	2722	struct pollfd fds [nfd];
1805	// actual code will need to loop here and realloc etc.	2723	// actual code will need to loop here and realloc etc.
1806	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2724	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1807		2725
1808	/* the callback is illegal, but won't be called as we stop during check */	2726	/* the callback is illegal, but won't be called as we stop during check */
1809	ev_timer_init (&tw, 0, timeout * 1e-3);	2727	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1810	ev_timer_start (loop, &tw);	2728	ev_timer_start (loop, &tw);
1811		2729
1812	// create one ev_io per pollfd	2730	// create one ev_io per pollfd
1813	for (int i = 0; i < nfd; ++i)	2731	for (int i = 0; i < nfd; ++i)
1814	{	2732	{
1815	ev_io_init (iow + i, io_cb, fds [i].fd,	2733	ev_io_init (iow + i, io_cb, fds [i].fd,
1816	((fds [i].events & POLLIN ? EV_READ : 0)	2734	((fds [i].events & POLLIN ? EV_READ : 0)
1817	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2735	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1818		2736
1819	fds [i].revents = 0;	2737	fds [i].revents = 0;
1820	ev_io_start (loop, iow + i);	2738	ev_io_start (loop, iow + i);
1821	}	2739	}
1822	}	2740	}
1823		2741
1824	// stop all watchers after blocking	2742	// stop all watchers after blocking
1825	static void	2743	static void
1826	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2744	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1827	{	2745	{
1828	ev_timer_stop (loop, &tw);	2746	ev_timer_stop (loop, &tw);
1829		2747
1830	for (int i = 0; i < nfd; ++i)	2748	for (int i = 0; i < nfd; ++i)
1831	{	2749	{
1832	// set the relevant poll flags	2750	// set the relevant poll flags
1833	// could also call adns_processreadable etc. here	2751	// could also call adns_processreadable etc. here
1834	struct pollfd *fd = fds + i;	2752	struct pollfd *fd = fds + i;
1835	int revents = ev_clear_pending (iow + i);	2753	int revents = ev_clear_pending (iow + i);
1836	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2754	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1837	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2755	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1838		2756
1839	// now stop the watcher	2757	// now stop the watcher
1840	ev_io_stop (loop, iow + i);	2758	ev_io_stop (loop, iow + i);
1841	}	2759	}
1842		2760
1843	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2761	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1844	}	2762	}
1845		2763
1846	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2764	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1847	in the prepare watcher and would dispose of the check watcher.	2765	in the prepare watcher and would dispose of the check watcher.
1848		2766
1849	Method 3: If the module to be embedded supports explicit event	2767	Method 3: If the module to be embedded supports explicit event
1850	notification (adns does), you can also make use of the actual watcher	2768	notification (libadns does), you can also make use of the actual watcher
1851	callbacks, and only destroy/create the watchers in the prepare watcher.	2769	callbacks, and only destroy/create the watchers in the prepare watcher.
1852		2770
1853	static void	2771	static void
1854	timer_cb (EV_P_ ev_timer *w, int revents)	2772	timer_cb (EV_P_ ev_timer *w, int revents)
1855	{	2773	{
1856	adns_state ads = (adns_state)w->data;	2774	adns_state ads = (adns_state)w->data;
1857	update_now (EV_A);	2775	update_now (EV_A);
1858		2776
1859	adns_processtimeouts (ads, &tv_now);	2777	adns_processtimeouts (ads, &tv_now);
1860	}	2778	}
1861		2779
1862	static void	2780	static void
1863	io_cb (EV_P_ ev_io *w, int revents)	2781	io_cb (EV_P_ ev_io *w, int revents)
1864	{	2782	{
1865	adns_state ads = (adns_state)w->data;	2783	adns_state ads = (adns_state)w->data;
1866	update_now (EV_A);	2784	update_now (EV_A);
1867		2785
1868	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2786	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1869	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2787	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1870	}	2788	}
1871		2789
1872	// do not ever call adns_afterpoll	2790	// do not ever call adns_afterpoll
1873		2791
1874	Method 4: Do not use a prepare or check watcher because the module you	2792	Method 4: Do not use a prepare or check watcher because the module you
1875	want to embed is too inflexible to support it. Instead, youc na override	2793	want to embed is not flexible enough to support it. Instead, you can
1876	their poll function. The drawback with this solution is that the main	2794	override their poll function. The drawback with this solution is that the
1877	loop is now no longer controllable by EV. The C<Glib::EV> module does	2795	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1878	this.	2796	this approach, effectively embedding EV as a client into the horrible
		2797	libglib event loop.
1879		2798
1880	static gint	2799	static gint
1881	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2800	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1882	{	2801	{
1883	int got_events = 0;	2802	int got_events = 0;
1884		2803
1885	for (n = 0; n < nfds; ++n)	2804	for (n = 0; n < nfds; ++n)
1886	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2805	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1887		2806
1888	if (timeout >= 0)	2807	if (timeout >= 0)
1889	// create/start timer	2808	// create/start timer
1890		2809
1891	// poll	2810	// poll
1892	ev_loop (EV_A_ 0);	2811	ev_loop (EV_A_ 0);
1893		2812
1894	// stop timer again	2813	// stop timer again
1895	if (timeout >= 0)	2814	if (timeout >= 0)
1896	ev_timer_stop (EV_A_ &to);	2815	ev_timer_stop (EV_A_ &to);
1897		2816
1898	// stop io watchers again - their callbacks should have set	2817	// stop io watchers again - their callbacks should have set
1899	for (n = 0; n < nfds; ++n)	2818	for (n = 0; n < nfds; ++n)
1900	ev_io_stop (EV_A_ iow [n]);	2819	ev_io_stop (EV_A_ iow [n]);
1901		2820
1902	return got_events;	2821	return got_events;
1903	}	2822	}
1904		2823
1905		2824
1906	=head2 C<ev_embed> - when one backend isn't enough...	2825	=head2 C<ev_embed> - when one backend isn't enough...
1907		2826
1908	This is a rather advanced watcher type that lets you embed one event loop	2827	This is a rather advanced watcher type that lets you embed one event loop
…		…
1914	prioritise I/O.	2833	prioritise I/O.
1915		2834
1916	As an example for a bug workaround, the kqueue backend might only support	2835	As an example for a bug workaround, the kqueue backend might only support
1917	sockets on some platform, so it is unusable as generic backend, but you	2836	sockets on some platform, so it is unusable as generic backend, but you
1918	still want to make use of it because you have many sockets and it scales	2837	still want to make use of it because you have many sockets and it scales
1919	so nicely. In this case, you would create a kqueue-based loop and embed it	2838	so nicely. In this case, you would create a kqueue-based loop and embed
1920	into your default loop (which might use e.g. poll). Overall operation will	2839	it into your default loop (which might use e.g. poll). Overall operation
1921	be a bit slower because first libev has to poll and then call kevent, but	2840	will be a bit slower because first libev has to call C<poll> and then
1922	at least you can use both at what they are best.	2841	C<kevent>, but at least you can use both mechanisms for what they are
		2842	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1923		2843
1924	As for prioritising I/O: rarely you have the case where some fds have	2844	As for prioritising I/O: under rare circumstances you have the case where
1925	to be watched and handled very quickly (with low latency), and even	2845	some fds have to be watched and handled very quickly (with low latency),
1926	priorities and idle watchers might have too much overhead. In this case	2846	and even priorities and idle watchers might have too much overhead. In
1927	you would put all the high priority stuff in one loop and all the rest in	2847	this case you would put all the high priority stuff in one loop and all
1928	a second one, and embed the second one in the first.	2848	the rest in a second one, and embed the second one in the first.
1929		2849
1930	As long as the watcher is active, the callback will be invoked every time	2850	As long as the watcher is active, the callback will be invoked every
1931	there might be events pending in the embedded loop. The callback must then	2851	time there might be events pending in the embedded loop. The callback
1932	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2852	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
1933	their callbacks (you could also start an idle watcher to give the embedded	2853	sweep and invoke their callbacks (the callback doesn't need to invoke the
1934	loop strictly lower priority for example). You can also set the callback	2854	C<ev_embed_sweep> function directly, it could also start an idle watcher
1935	to C<0>, in which case the embed watcher will automatically execute the	2855	to give the embedded loop strictly lower priority for example).
1936	embedded loop sweep.
1937		2856
1938	As long as the watcher is started it will automatically handle events. The	2857	You can also set the callback to C<0>, in which case the embed watcher
1939	callback will be invoked whenever some events have been handled. You can	2858	will automatically execute the embedded loop sweep whenever necessary.
1940	set the callback to C<0> to avoid having to specify one if you are not
1941	interested in that.
1942		2859
1943	Also, there have not currently been made special provisions for forking:	2860	Fork detection will be handled transparently while the C<ev_embed> watcher
1944	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2861	is active, i.e., the embedded loop will automatically be forked when the
1945	but you will also have to stop and restart any C<ev_embed> watchers	2862	embedding loop forks. In other cases, the user is responsible for calling
1946	yourself.	2863	C<ev_loop_fork> on the embedded loop.
1947		2864
1948	Unfortunately, not all backends are embeddable, only the ones returned by	2865	Unfortunately, not all backends are embeddable: only the ones returned by
1949	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2866	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1950	portable one.	2867	portable one.
1951		2868
1952	So when you want to use this feature you will always have to be prepared	2869	So when you want to use this feature you will always have to be prepared
1953	that you cannot get an embeddable loop. The recommended way to get around	2870	that you cannot get an embeddable loop. The recommended way to get around
1954	this is to have a separate variables for your embeddable loop, try to	2871	this is to have a separate variables for your embeddable loop, try to
1955	create it, and if that fails, use the normal loop for everything.	2872	create it, and if that fails, use the normal loop for everything.
1956		2873
		2874	=head3 C<ev_embed> and fork
		2875
		2876	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2877	automatically be applied to the embedded loop as well, so no special
		2878	fork handling is required in that case. When the watcher is not running,
		2879	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2880	as applicable.
		2881
1957	=head3 Watcher-Specific Functions and Data Members	2882	=head3 Watcher-Specific Functions and Data Members
1958		2883
1959	=over 4	2884	=over 4
1960		2885
1961	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2886	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1964		2889
1965	Configures the watcher to embed the given loop, which must be	2890	Configures the watcher to embed the given loop, which must be
1966	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2891	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1967	invoked automatically, otherwise it is the responsibility of the callback	2892	invoked automatically, otherwise it is the responsibility of the callback
1968	to invoke it (it will continue to be called until the sweep has been done,	2893	to invoke it (it will continue to be called until the sweep has been done,
1969	if you do not want thta, you need to temporarily stop the embed watcher).	2894	if you do not want that, you need to temporarily stop the embed watcher).
1970		2895
1971	=item ev_embed_sweep (loop, ev_embed *)	2896	=item ev_embed_sweep (loop, ev_embed *)
1972		2897
1973	Make a single, non-blocking sweep over the embedded loop. This works	2898	Make a single, non-blocking sweep over the embedded loop. This works
1974	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2899	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1975	apropriate way for embedded loops.	2900	appropriate way for embedded loops.
1976		2901
1977	=item struct ev_loop *other [read-only]	2902	=item struct ev_loop *other [read-only]
1978		2903
1979	The embedded event loop.	2904	The embedded event loop.
1980		2905
…		…
1982		2907
1983	=head3 Examples	2908	=head3 Examples
1984		2909
1985	Example: Try to get an embeddable event loop and embed it into the default	2910	Example: Try to get an embeddable event loop and embed it into the default
1986	event loop. If that is not possible, use the default loop. The default	2911	event loop. If that is not possible, use the default loop. The default
1987	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2912	loop is stored in C<loop_hi>, while the embeddable loop is stored in
1988	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2913	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
1989	used).	2914	used).
1990		2915
1991	struct ev_loop *loop_hi = ev_default_init (0);	2916	struct ev_loop *loop_hi = ev_default_init (0);
1992	struct ev_loop *loop_lo = 0;	2917	struct ev_loop *loop_lo = 0;
1993	struct ev_embed embed;	2918	ev_embed embed;
1994		2919
1995	// see if there is a chance of getting one that works	2920	// see if there is a chance of getting one that works
1996	// (remember that a flags value of 0 means autodetection)	2921	// (remember that a flags value of 0 means autodetection)
1997	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2922	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1998	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2923	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1999	: 0;	2924	: 0;
2000		2925
2001	// if we got one, then embed it, otherwise default to loop_hi	2926	// if we got one, then embed it, otherwise default to loop_hi
2002	if (loop_lo)	2927	if (loop_lo)
2003	{	2928	{
2004	ev_embed_init (&embed, 0, loop_lo);	2929	ev_embed_init (&embed, 0, loop_lo);
2005	ev_embed_start (loop_hi, &embed);	2930	ev_embed_start (loop_hi, &embed);
2006	}	2931	}
2007	else	2932	else
2008	loop_lo = loop_hi;	2933	loop_lo = loop_hi;
2009		2934
2010	Example: Check if kqueue is available but not recommended and create	2935	Example: Check if kqueue is available but not recommended and create
2011	a kqueue backend for use with sockets (which usually work with any	2936	a kqueue backend for use with sockets (which usually work with any
2012	kqueue implementation). Store the kqueue/socket-only event loop in	2937	kqueue implementation). Store the kqueue/socket-only event loop in
2013	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2938	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2014		2939
2015	struct ev_loop *loop = ev_default_init (0);	2940	struct ev_loop *loop = ev_default_init (0);
2016	struct ev_loop *loop_socket = 0;	2941	struct ev_loop *loop_socket = 0;
2017	struct ev_embed embed;	2942	ev_embed embed;
2018		2943
2019	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2944	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2020	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2945	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2021	{	2946	{
2022	ev_embed_init (&embed, 0, loop_socket);	2947	ev_embed_init (&embed, 0, loop_socket);
2023	ev_embed_start (loop, &embed);	2948	ev_embed_start (loop, &embed);
2024	}	2949	}
2025		2950
2026	if (!loop_socket)	2951	if (!loop_socket)
2027	loop_socket = loop;	2952	loop_socket = loop;
2028		2953
2029	// now use loop_socket for all sockets, and loop for everything else	2954	// now use loop_socket for all sockets, and loop for everything else
2030		2955
2031		2956
2032	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2957	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2033		2958
2034	Fork watchers are called when a C<fork ()> was detected (usually because	2959	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2037	event loop blocks next and before C<ev_check> watchers are being called,	2962	event loop blocks next and before C<ev_check> watchers are being called,
2038	and only in the child after the fork. If whoever good citizen calling	2963	and only in the child after the fork. If whoever good citizen calling
2039	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2964	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2040	handlers will be invoked, too, of course.	2965	handlers will be invoked, too, of course.
2041		2966
		2967	=head3 The special problem of life after fork - how is it possible?
		2968
		2969	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2970	up/change the process environment, followed by a call to C<exec()>. This
		2971	sequence should be handled by libev without any problems.
		2972
		2973	This changes when the application actually wants to do event handling
		2974	in the child, or both parent in child, in effect "continuing" after the
		2975	fork.
		2976
		2977	The default mode of operation (for libev, with application help to detect
		2978	forks) is to duplicate all the state in the child, as would be expected
		2979	when I<either> the parent I<or> the child process continues.
		2980
		2981	When both processes want to continue using libev, then this is usually the
		2982	wrong result. In that case, usually one process (typically the parent) is
		2983	supposed to continue with all watchers in place as before, while the other
		2984	process typically wants to start fresh, i.e. without any active watchers.
		2985
		2986	The cleanest and most efficient way to achieve that with libev is to
		2987	simply create a new event loop, which of course will be "empty", and
		2988	use that for new watchers. This has the advantage of not touching more
		2989	memory than necessary, and thus avoiding the copy-on-write, and the
		2990	disadvantage of having to use multiple event loops (which do not support
		2991	signal watchers).
		2992
		2993	When this is not possible, or you want to use the default loop for
		2994	other reasons, then in the process that wants to start "fresh", call
		2995	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2996	the default loop will "orphan" (not stop) all registered watchers, so you
		2997	have to be careful not to execute code that modifies those watchers. Note
		2998	also that in that case, you have to re-register any signal watchers.
		2999
2042	=head3 Watcher-Specific Functions and Data Members	3000	=head3 Watcher-Specific Functions and Data Members
2043		3001
2044	=over 4	3002	=over 4
2045		3003
2046	=item ev_fork_init (ev_signal *, callback)	3004	=item ev_fork_init (ev_signal *, callback)
…		…
2075	=head3 Queueing	3033	=head3 Queueing
2076		3034
2077	C<ev_async> does not support queueing of data in any way. The reason	3035	C<ev_async> does not support queueing of data in any way. The reason
2078	is that the author does not know of a simple (or any) algorithm for a	3036	is that the author does not know of a simple (or any) algorithm for a
2079	multiple-writer-single-reader queue that works in all cases and doesn't	3037	multiple-writer-single-reader queue that works in all cases and doesn't
2080	need elaborate support such as pthreads.	3038	need elaborate support such as pthreads or unportable memory access
		3039	semantics.
2081		3040
2082	That means that if you want to queue data, you have to provide your own	3041	That means that if you want to queue data, you have to provide your own
2083	queue. And here is how you would implement locking:	3042	queue. But at least I can tell you how to implement locking around your
		3043	queue:
2084		3044
2085	=over 4	3045	=over 4
2086		3046
2087	=item queueing from a signal handler context	3047	=item queueing from a signal handler context
2088		3048
2089	To implement race-free queueing, you simply add to the queue in the signal	3049	To implement race-free queueing, you simply add to the queue in the signal
2090	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3050	handler but you block the signal handler in the watcher callback. Here is
2091	some fictitiuous SIGUSR1 handler:	3051	an example that does that for some fictitious SIGUSR1 handler:
2092		3052
2093	static ev_async mysig;	3053	static ev_async mysig;
2094		3054
2095	static void	3055	static void
2096	sigusr1_handler (void)	3056	sigusr1_handler (void)
2097	{	3057	{
2098	sometype data;	3058	sometype data;
2099		3059
2100	// no locking etc.	3060	// no locking etc.
2101	queue_put (data);	3061	queue_put (data);
2102	ev_async_send (DEFAULT_LOOP, &mysig);	3062	ev_async_send (EV_DEFAULT_ &mysig);
2103	}	3063	}
2104		3064
2105	static void	3065	static void
2106	mysig_cb (EV_P_ ev_async *w, int revents)	3066	mysig_cb (EV_P_ ev_async *w, int revents)
2107	{	3067	{
…		…
2125		3085
2126	=item queueing from a thread context	3086	=item queueing from a thread context
2127		3087
2128	The strategy for threads is different, as you cannot (easily) block	3088	The strategy for threads is different, as you cannot (easily) block
2129	threads but you can easily preempt them, so to queue safely you need to	3089	threads but you can easily preempt them, so to queue safely you need to
2130	emply a traditional mutex lock, such as in this pthread example:	3090	employ a traditional mutex lock, such as in this pthread example:
2131		3091
2132	static ev_async mysig;	3092	static ev_async mysig;
2133	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;	3093	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2134		3094
2135	static void	3095	static void
…		…
2138	// only need to lock the actual queueing operation	3098	// only need to lock the actual queueing operation
2139	pthread_mutex_lock (&mymutex);	3099	pthread_mutex_lock (&mymutex);
2140	queue_put (data);	3100	queue_put (data);
2141	pthread_mutex_unlock (&mymutex);	3101	pthread_mutex_unlock (&mymutex);
2142		3102
2143	ev_async_send (DEFAULT_LOOP, &mysig);	3103	ev_async_send (EV_DEFAULT_ &mysig);
2144	}	3104	}
2145		3105
2146	static void	3106	static void
2147	mysig_cb (EV_P_ ev_async *w, int revents)	3107	mysig_cb (EV_P_ ev_async *w, int revents)
2148	{	3108	{
…		…
2162	=over 4	3122	=over 4
2163		3123
2164	=item ev_async_init (ev_async *, callback)	3124	=item ev_async_init (ev_async *, callback)
2165		3125
2166	Initialises and configures the async watcher - it has no parameters of any	3126	Initialises and configures the async watcher - it has no parameters of any
2167	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3127	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2168	believe me.	3128	trust me.
2169		3129
2170	=item ev_async_send (loop, ev_async *)	3130	=item ev_async_send (loop, ev_async *)
2171		3131
2172	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3132	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2173	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3133	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2174	C<ev_feed_event>, this call is safe to do in other threads, signal or	3134	C<ev_feed_event>, this call is safe to do from other threads, signal or
2175	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3135	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2176	section below on what exactly this means).	3136	section below on what exactly this means).
2177		3137
		3138	Note that, as with other watchers in libev, multiple events might get
		3139	compressed into a single callback invocation (another way to look at this
		3140	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3141	reset when the event loop detects that).
		3142
2178	This call incurs the overhead of a syscall only once per loop iteration,	3143	This call incurs the overhead of a system call only once per event loop
2179	so while the overhead might be noticable, it doesn't apply to repeated	3144	iteration, so while the overhead might be noticeable, it doesn't apply to
2180	calls to C<ev_async_send>.	3145	repeated calls to C<ev_async_send> for the same event loop.
		3146
		3147	=item bool = ev_async_pending (ev_async *)
		3148
		3149	Returns a non-zero value when C<ev_async_send> has been called on the
		3150	watcher but the event has not yet been processed (or even noted) by the
		3151	event loop.
		3152
		3153	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		3154	the loop iterates next and checks for the watcher to have become active,
		3155	it will reset the flag again. C<ev_async_pending> can be used to very
		3156	quickly check whether invoking the loop might be a good idea.
		3157
		3158	Not that this does I<not> check whether the watcher itself is pending,
		3159	only whether it has been requested to make this watcher pending: there
		3160	is a time window between the event loop checking and resetting the async
		3161	notification, and the callback being invoked.
2181		3162
2182	=back	3163	=back
2183		3164
2184		3165
2185	=head1 OTHER FUNCTIONS	3166	=head1 OTHER FUNCTIONS
…		…
2189	=over 4	3170	=over 4
2190		3171
2191	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3172	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2192		3173
2193	This function combines a simple timer and an I/O watcher, calls your	3174	This function combines a simple timer and an I/O watcher, calls your
2194	callback on whichever event happens first and automatically stop both	3175	callback on whichever event happens first and automatically stops both
2195	watchers. This is useful if you want to wait for a single event on an fd	3176	watchers. This is useful if you want to wait for a single event on an fd
2196	or timeout without having to allocate/configure/start/stop/free one or	3177	or timeout without having to allocate/configure/start/stop/free one or
2197	more watchers yourself.	3178	more watchers yourself.
2198		3179
2199	If C<fd> is less than 0, then no I/O watcher will be started and events	3180	If C<fd> is less than 0, then no I/O watcher will be started and the
2200	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3181	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2201	C<events> set will be craeted and started.	3182	the given C<fd> and C<events> set will be created and started.
2202		3183
2203	If C<timeout> is less than 0, then no timeout watcher will be	3184	If C<timeout> is less than 0, then no timeout watcher will be
2204	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3185	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2205	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3186	repeat = 0) will be started. C<0> is a valid timeout.
2206	dubious value.
2207		3187
2208	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3188	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2209	passed an C<revents> set like normal event callbacks (a combination of	3189	passed an C<revents> set like normal event callbacks (a combination of
2210	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3190	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2211	value passed to C<ev_once>:	3191	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3192	a timeout and an io event at the same time - you probably should give io
		3193	events precedence.
2212		3194
		3195	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3196
2213	static void stdin_ready (int revents, void *arg)	3197	static void stdin_ready (int revents, void *arg)
2214	{	3198	{
2215	if (revents & EV_TIMEOUT)
2216	/* doh, nothing entered */;
2217	else if (revents & EV_READ)	3199	if (revents & EV_READ)
2218	/* stdin might have data for us, joy! */;	3200	/* stdin might have data for us, joy! */;
		3201	else if (revents & EV_TIMER)
		3202	/* doh, nothing entered */;
2219	}	3203	}
2220		3204
2221	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3205	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2222		3206
2223	=item ev_feed_event (ev_loop *, watcher *, int revents)
2224
2225	Feeds the given event set into the event loop, as if the specified event
2226	had happened for the specified watcher (which must be a pointer to an
2227	initialised but not necessarily started event watcher).
2228
2229	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3207	=item ev_feed_fd_event (loop, int fd, int revents)
2230		3208
2231	Feed an event on the given fd, as if a file descriptor backend detected	3209	Feed an event on the given fd, as if a file descriptor backend detected
2232	the given events it.	3210	the given events it.
2233		3211
2234	=item ev_feed_signal_event (ev_loop *loop, int signum)	3212	=item ev_feed_signal_event (loop, int signum)
2235		3213
2236	Feed an event as if the given signal occured (C<loop> must be the default	3214	Feed an event as if the given signal occurred (C<loop> must be the default
2237	loop!).	3215	loop!).
2238		3216
2239	=back	3217	=back
2240		3218
2241		3219
…		…
2257		3235
2258	=item * Priorities are not currently supported. Initialising priorities	3236	=item * Priorities are not currently supported. Initialising priorities
2259	will fail and all watchers will have the same priority, even though there	3237	will fail and all watchers will have the same priority, even though there
2260	is an ev_pri field.	3238	is an ev_pri field.
2261		3239
		3240	=item * In libevent, the last base created gets the signals, in libev, the
		3241	first base created (== the default loop) gets the signals.
		3242
2262	=item * Other members are not supported.	3243	=item * Other members are not supported.
2263		3244
2264	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3245	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2265	to use the libev header file and library.	3246	to use the libev header file and library.
2266		3247
2267	=back	3248	=back
2268		3249
2269	=head1 C++ SUPPORT	3250	=head1 C++ SUPPORT
2270		3251
2271	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3252	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2272	you to use some convinience methods to start/stop watchers and also change	3253	you to use some convenience methods to start/stop watchers and also change
2273	the callback model to a model using method callbacks on objects.	3254	the callback model to a model using method callbacks on objects.
2274		3255
2275	To use it,	3256	To use it,
2276		3257
2277	#include <ev++.h>	3258	#include <ev++.h>
2278		3259
2279	This automatically includes F<ev.h> and puts all of its definitions (many	3260	This automatically includes F<ev.h> and puts all of its definitions (many
2280	of them macros) into the global namespace. All C++ specific things are	3261	of them macros) into the global namespace. All C++ specific things are
2281	put into the C<ev> namespace. It should support all the same embedding	3262	put into the C<ev> namespace. It should support all the same embedding
2282	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3263	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2316		3297
2317	=over 4	3298	=over 4
2318		3299
2319	=item ev::TYPE::TYPE ()	3300	=item ev::TYPE::TYPE ()
2320		3301
2321	=item ev::TYPE::TYPE (struct ev_loop *)	3302	=item ev::TYPE::TYPE (loop)
2322		3303
2323	=item ev::TYPE::~TYPE	3304	=item ev::TYPE::~TYPE
2324		3305
2325	The constructor (optionally) takes an event loop to associate the watcher	3306	The constructor (optionally) takes an event loop to associate the watcher
2326	with. If it is omitted, it will use C<EV_DEFAULT>.	3307	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2349	your compiler is good :), then the method will be fully inlined into the	3330	your compiler is good :), then the method will be fully inlined into the
2350	thunking function, making it as fast as a direct C callback.	3331	thunking function, making it as fast as a direct C callback.
2351		3332
2352	Example: simple class declaration and watcher initialisation	3333	Example: simple class declaration and watcher initialisation
2353		3334
2354	struct myclass	3335	struct myclass
2355	{	3336	{
2356	void io_cb (ev::io &w, int revents) { }	3337	void io_cb (ev::io &w, int revents) { }
2357	}	3338	}
2358		3339
2359	myclass obj;	3340	myclass obj;
2360	ev::io iow;	3341	ev::io iow;
2361	iow.set <myclass, &myclass::io_cb> (&obj);	3342	iow.set <myclass, &myclass::io_cb> (&obj);
		3343
		3344	=item w->set (object *)
		3345
		3346	This is an B<experimental> feature that might go away in a future version.
		3347
		3348	This is a variation of a method callback - leaving out the method to call
		3349	will default the method to C<operator ()>, which makes it possible to use
		3350	functor objects without having to manually specify the C<operator ()> all
		3351	the time. Incidentally, you can then also leave out the template argument
		3352	list.
		3353
		3354	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3355	int revents)>.
		3356
		3357	See the method-C<set> above for more details.
		3358
		3359	Example: use a functor object as callback.
		3360
		3361	struct myfunctor
		3362	{
		3363	void operator() (ev::io &w, int revents)
		3364	{
		3365	...
		3366	}
		3367	}
		3368
		3369	myfunctor f;
		3370
		3371	ev::io w;
		3372	w.set (&f);
2362		3373
2363	=item w->set<function> (void *data = 0)	3374	=item w->set<function> (void *data = 0)
2364		3375
2365	Also sets a callback, but uses a static method or plain function as	3376	Also sets a callback, but uses a static method or plain function as
2366	callback. The optional C<data> argument will be stored in the watcher's	3377	callback. The optional C<data> argument will be stored in the watcher's
…		…
2368		3379
2369	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3380	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2370		3381
2371	See the method-C<set> above for more details.	3382	See the method-C<set> above for more details.
2372		3383
2373	Example:	3384	Example: Use a plain function as callback.
2374		3385
2375	static void io_cb (ev::io &w, int revents) { }	3386	static void io_cb (ev::io &w, int revents) { }
2376	iow.set <io_cb> ();	3387	iow.set <io_cb> ();
2377		3388
2378	=item w->set (struct ev_loop *)	3389	=item w->set (loop)
2379		3390
2380	Associates a different C<struct ev_loop> with this watcher. You can only	3391	Associates a different C<struct ev_loop> with this watcher. You can only
2381	do this when the watcher is inactive (and not pending either).	3392	do this when the watcher is inactive (and not pending either).
2382		3393
2383	=item w->set ([args])	3394	=item w->set ([arguments])
2384		3395
2385	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3396	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2386	called at least once. Unlike the C counterpart, an active watcher gets	3397	called at least once. Unlike the C counterpart, an active watcher gets
2387	automatically stopped and restarted when reconfiguring it with this	3398	automatically stopped and restarted when reconfiguring it with this
2388	method.	3399	method.
2389		3400
2390	=item w->start ()	3401	=item w->start ()
…		…
2414	=back	3425	=back
2415		3426
2416	Example: Define a class with an IO and idle watcher, start one of them in	3427	Example: Define a class with an IO and idle watcher, start one of them in
2417	the constructor.	3428	the constructor.
2418		3429
2419	class myclass	3430	class myclass
2420	{	3431	{
2421	ev::io io; void io_cb (ev::io &w, int revents);	3432	ev::io io ; void io_cb (ev::io &w, int revents);
2422	ev:idle idle void idle_cb (ev::idle &w, int revents);	3433	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2423		3434
2424	myclass (int fd)	3435	myclass (int fd)
2425	{	3436	{
2426	io .set <myclass, &myclass::io_cb > (this);	3437	io .set <myclass, &myclass::io_cb > (this);
2427	idle.set <myclass, &myclass::idle_cb> (this);	3438	idle.set <myclass, &myclass::idle_cb> (this);
2428		3439
2429	io.start (fd, ev::READ);	3440	io.start (fd, ev::READ);
2430	}	3441	}
2431	};	3442	};
		3443
		3444
		3445	=head1 OTHER LANGUAGE BINDINGS
		3446
		3447	Libev does not offer other language bindings itself, but bindings for a
		3448	number of languages exist in the form of third-party packages. If you know
		3449	any interesting language binding in addition to the ones listed here, drop
		3450	me a note.
		3451
		3452	=over 4
		3453
		3454	=item Perl
		3455
		3456	The EV module implements the full libev API and is actually used to test
		3457	libev. EV is developed together with libev. Apart from the EV core module,
		3458	there are additional modules that implement libev-compatible interfaces
		3459	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		3460	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3461	and C<EV::Glib>).
		3462
		3463	It can be found and installed via CPAN, its homepage is at
		3464	L<http://software.schmorp.de/pkg/EV>.
		3465
		3466	=item Python
		3467
		3468	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3469	seems to be quite complete and well-documented.
		3470
		3471	=item Ruby
		3472
		3473	Tony Arcieri has written a ruby extension that offers access to a subset
		3474	of the libev API and adds file handle abstractions, asynchronous DNS and
		3475	more on top of it. It can be found via gem servers. Its homepage is at
		3476	L<http://rev.rubyforge.org/>.
		3477
		3478	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3479	makes rev work even on mingw.
		3480
		3481	=item Haskell
		3482
		3483	A haskell binding to libev is available at
		3484	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3485
		3486	=item D
		3487
		3488	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		3489	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3490
		3491	=item Ocaml
		3492
		3493	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3494	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3495
		3496	=item Lua
		3497
		3498	Brian Maher has written a partial interface to libev for lua (at the
		3499	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3500	L<http://github.com/brimworks/lua-ev>.
		3501
		3502	=back
2432		3503
2433		3504
2434	=head1 MACRO MAGIC	3505	=head1 MACRO MAGIC
2435		3506
2436	Libev can be compiled with a variety of options, the most fundamantal	3507	Libev can be compiled with a variety of options, the most fundamental
2437	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3508	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2438	functions and callbacks have an initial C<struct ev_loop *> argument.	3509	functions and callbacks have an initial C<struct ev_loop *> argument.
2439		3510
2440	To make it easier to write programs that cope with either variant, the	3511	To make it easier to write programs that cope with either variant, the
2441	following macros are defined:	3512	following macros are defined:
…		…
2446		3517
2447	This provides the loop I<argument> for functions, if one is required ("ev	3518	This provides the loop I<argument> for functions, if one is required ("ev
2448	loop argument"). The C<EV_A> form is used when this is the sole argument,	3519	loop argument"). The C<EV_A> form is used when this is the sole argument,
2449	C<EV_A_> is used when other arguments are following. Example:	3520	C<EV_A_> is used when other arguments are following. Example:
2450		3521
2451	ev_unref (EV_A);	3522	ev_unref (EV_A);
2452	ev_timer_add (EV_A_ watcher);	3523	ev_timer_add (EV_A_ watcher);
2453	ev_loop (EV_A_ 0);	3524	ev_loop (EV_A_ 0);
2454		3525
2455	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3526	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2456	which is often provided by the following macro.	3527	which is often provided by the following macro.
2457		3528
2458	=item C<EV_P>, C<EV_P_>	3529	=item C<EV_P>, C<EV_P_>
2459		3530
2460	This provides the loop I<parameter> for functions, if one is required ("ev	3531	This provides the loop I<parameter> for functions, if one is required ("ev
2461	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3532	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2462	C<EV_P_> is used when other parameters are following. Example:	3533	C<EV_P_> is used when other parameters are following. Example:
2463		3534
2464	// this is how ev_unref is being declared	3535	// this is how ev_unref is being declared
2465	static void ev_unref (EV_P);	3536	static void ev_unref (EV_P);
2466		3537
2467	// this is how you can declare your typical callback	3538	// this is how you can declare your typical callback
2468	static void cb (EV_P_ ev_timer *w, int revents)	3539	static void cb (EV_P_ ev_timer *w, int revents)
2469		3540
2470	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3541	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2471	suitable for use with C<EV_A>.	3542	suitable for use with C<EV_A>.
2472		3543
2473	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3544	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2474		3545
2475	Similar to the other two macros, this gives you the value of the default	3546	Similar to the other two macros, this gives you the value of the default
2476	loop, if multiple loops are supported ("ev loop default").	3547	loop, if multiple loops are supported ("ev loop default").
		3548
		3549	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3550
		3551	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3552	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3553	is undefined when the default loop has not been initialised by a previous
		3554	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3555
		3556	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3557	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2477		3558
2478	=back	3559	=back
2479		3560
2480	Example: Declare and initialise a check watcher, utilising the above	3561	Example: Declare and initialise a check watcher, utilising the above
2481	macros so it will work regardless of whether multiple loops are supported	3562	macros so it will work regardless of whether multiple loops are supported
2482	or not.	3563	or not.
2483		3564
2484	static void	3565	static void
2485	check_cb (EV_P_ ev_timer *w, int revents)	3566	check_cb (EV_P_ ev_timer *w, int revents)
2486	{	3567	{
2487	ev_check_stop (EV_A_ w);	3568	ev_check_stop (EV_A_ w);
2488	}	3569	}
2489		3570
2490	ev_check check;	3571	ev_check check;
2491	ev_check_init (&check, check_cb);	3572	ev_check_init (&check, check_cb);
2492	ev_check_start (EV_DEFAULT_ &check);	3573	ev_check_start (EV_DEFAULT_ &check);
2493	ev_loop (EV_DEFAULT_ 0);	3574	ev_loop (EV_DEFAULT_ 0);
2494		3575
2495	=head1 EMBEDDING	3576	=head1 EMBEDDING
2496		3577
2497	Libev can (and often is) directly embedded into host	3578	Libev can (and often is) directly embedded into host
2498	applications. Examples of applications that embed it include the Deliantra	3579	applications. Examples of applications that embed it include the Deliantra
…		…
2505	libev somewhere in your source tree).	3586	libev somewhere in your source tree).
2506		3587
2507	=head2 FILESETS	3588	=head2 FILESETS
2508		3589
2509	Depending on what features you need you need to include one or more sets of files	3590	Depending on what features you need you need to include one or more sets of files
2510	in your app.	3591	in your application.
2511		3592
2512	=head3 CORE EVENT LOOP	3593	=head3 CORE EVENT LOOP
2513		3594
2514	To include only the libev core (all the C<ev_*> functions), with manual	3595	To include only the libev core (all the C<ev_*> functions), with manual
2515	configuration (no autoconf):	3596	configuration (no autoconf):
2516		3597
2517	#define EV_STANDALONE 1	3598	#define EV_STANDALONE 1
2518	#include "ev.c"	3599	#include "ev.c"
2519		3600
2520	This will automatically include F<ev.h>, too, and should be done in a	3601	This will automatically include F<ev.h>, too, and should be done in a
2521	single C source file only to provide the function implementations. To use	3602	single C source file only to provide the function implementations. To use
2522	it, do the same for F<ev.h> in all files wishing to use this API (best	3603	it, do the same for F<ev.h> in all files wishing to use this API (best
2523	done by writing a wrapper around F<ev.h> that you can include instead and	3604	done by writing a wrapper around F<ev.h> that you can include instead and
2524	where you can put other configuration options):	3605	where you can put other configuration options):
2525		3606
2526	#define EV_STANDALONE 1	3607	#define EV_STANDALONE 1
2527	#include "ev.h"	3608	#include "ev.h"
2528		3609
2529	Both header files and implementation files can be compiled with a C++	3610	Both header files and implementation files can be compiled with a C++
2530	compiler (at least, thats a stated goal, and breakage will be treated	3611	compiler (at least, that's a stated goal, and breakage will be treated
2531	as a bug).	3612	as a bug).
2532		3613
2533	You need the following files in your source tree, or in a directory	3614	You need the following files in your source tree, or in a directory
2534	in your include path (e.g. in libev/ when using -Ilibev):	3615	in your include path (e.g. in libev/ when using -Ilibev):
2535		3616
2536	ev.h	3617	ev.h
2537	ev.c	3618	ev.c
2538	ev_vars.h	3619	ev_vars.h
2539	ev_wrap.h	3620	ev_wrap.h
2540		3621
2541	ev_win32.c required on win32 platforms only	3622	ev_win32.c required on win32 platforms only
2542		3623
2543	ev_select.c only when select backend is enabled (which is enabled by default)	3624	ev_select.c only when select backend is enabled (which is enabled by default)
2544	ev_poll.c only when poll backend is enabled (disabled by default)	3625	ev_poll.c only when poll backend is enabled (disabled by default)
2545	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3626	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2546	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3627	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2547	ev_port.c only when the solaris port backend is enabled (disabled by default)	3628	ev_port.c only when the solaris port backend is enabled (disabled by default)
2548		3629
2549	F<ev.c> includes the backend files directly when enabled, so you only need	3630	F<ev.c> includes the backend files directly when enabled, so you only need
2550	to compile this single file.	3631	to compile this single file.
2551		3632
2552	=head3 LIBEVENT COMPATIBILITY API	3633	=head3 LIBEVENT COMPATIBILITY API
2553		3634
2554	To include the libevent compatibility API, also include:	3635	To include the libevent compatibility API, also include:
2555		3636
2556	#include "event.c"	3637	#include "event.c"
2557		3638
2558	in the file including F<ev.c>, and:	3639	in the file including F<ev.c>, and:
2559		3640
2560	#include "event.h"	3641	#include "event.h"
2561		3642
2562	in the files that want to use the libevent API. This also includes F<ev.h>.	3643	in the files that want to use the libevent API. This also includes F<ev.h>.
2563		3644
2564	You need the following additional files for this:	3645	You need the following additional files for this:
2565		3646
2566	event.h	3647	event.h
2567	event.c	3648	event.c
2568		3649
2569	=head3 AUTOCONF SUPPORT	3650	=head3 AUTOCONF SUPPORT
2570		3651
2571	Instead of using C<EV_STANDALONE=1> and providing your config in	3652	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2572	whatever way you want, you can also C<m4_include([libev.m4])> in your	3653	whatever way you want, you can also C<m4_include([libev.m4])> in your
2573	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3654	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2574	include F<config.h> and configure itself accordingly.	3655	include F<config.h> and configure itself accordingly.
2575		3656
2576	For this of course you need the m4 file:	3657	For this of course you need the m4 file:
2577		3658
2578	libev.m4	3659	libev.m4
2579		3660
2580	=head2 PREPROCESSOR SYMBOLS/MACROS	3661	=head2 PREPROCESSOR SYMBOLS/MACROS
2581		3662
2582	Libev can be configured via a variety of preprocessor symbols you have to define	3663	Libev can be configured via a variety of preprocessor symbols you have to
2583	before including any of its files. The default is not to build for multiplicity	3664	define before including (or compiling) any of its files. The default in
2584	and only include the select backend.	3665	the absence of autoconf is documented for every option.
		3666
		3667	Symbols marked with "(h)" do not change the ABI, and can have different
		3668	values when compiling libev vs. including F<ev.h>, so it is permissible
		3669	to redefine them before including F<ev.h> without breaking compatibility
		3670	to a compiled library. All other symbols change the ABI, which means all
		3671	users of libev and the libev code itself must be compiled with compatible
		3672	settings.
2585		3673
2586	=over 4	3674	=over 4
2587		3675
2588	=item EV_STANDALONE	3676	=item EV_STANDALONE (h)
2589		3677
2590	Must always be C<1> if you do not use autoconf configuration, which	3678	Must always be C<1> if you do not use autoconf configuration, which
2591	keeps libev from including F<config.h>, and it also defines dummy	3679	keeps libev from including F<config.h>, and it also defines dummy
2592	implementations for some libevent functions (such as logging, which is not	3680	implementations for some libevent functions (such as logging, which is not
2593	supported). It will also not define any of the structs usually found in	3681	supported). It will also not define any of the structs usually found in
2594	F<event.h> that are not directly supported by the libev core alone.	3682	F<event.h> that are not directly supported by the libev core alone.
2595		3683
		3684	In standalone mode, libev will still try to automatically deduce the
		3685	configuration, but has to be more conservative.
		3686
2596	=item EV_USE_MONOTONIC	3687	=item EV_USE_MONOTONIC
2597		3688
2598	If defined to be C<1>, libev will try to detect the availability of the	3689	If defined to be C<1>, libev will try to detect the availability of the
2599	monotonic clock option at both compiletime and runtime. Otherwise no use	3690	monotonic clock option at both compile time and runtime. Otherwise no
2600	of the monotonic clock option will be attempted. If you enable this, you	3691	use of the monotonic clock option will be attempted. If you enable this,
2601	usually have to link against librt or something similar. Enabling it when	3692	you usually have to link against librt or something similar. Enabling it
2602	the functionality isn't available is safe, though, although you have	3693	when the functionality isn't available is safe, though, although you have
2603	to make sure you link against any libraries where the C<clock_gettime>	3694	to make sure you link against any libraries where the C<clock_gettime>
2604	function is hiding in (often F<-lrt>).	3695	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2605		3696
2606	=item EV_USE_REALTIME	3697	=item EV_USE_REALTIME
2607		3698
2608	If defined to be C<1>, libev will try to detect the availability of the	3699	If defined to be C<1>, libev will try to detect the availability of the
2609	realtime clock option at compiletime (and assume its availability at	3700	real-time clock option at compile time (and assume its availability
2610	runtime if successful). Otherwise no use of the realtime clock option will	3701	at runtime if successful). Otherwise no use of the real-time clock
2611	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3702	option will be attempted. This effectively replaces C<gettimeofday>
2612	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3703	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2613	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3704	correctness. See the note about libraries in the description of
		3705	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3706	C<EV_USE_CLOCK_SYSCALL>.
		3707
		3708	=item EV_USE_CLOCK_SYSCALL
		3709
		3710	If defined to be C<1>, libev will try to use a direct syscall instead
		3711	of calling the system-provided C<clock_gettime> function. This option
		3712	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3713	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3714	programs needlessly. Using a direct syscall is slightly slower (in
		3715	theory), because no optimised vdso implementation can be used, but avoids
		3716	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3717	higher, as it simplifies linking (no need for C<-lrt>).
2614		3718
2615	=item EV_USE_NANOSLEEP	3719	=item EV_USE_NANOSLEEP
2616		3720
2617	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3721	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2618	and will use it for delays. Otherwise it will use C<select ()>.	3722	and will use it for delays. Otherwise it will use C<select ()>.
2619		3723
		3724	=item EV_USE_EVENTFD
		3725
		3726	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3727	available and will probe for kernel support at runtime. This will improve
		3728	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3729	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3730	2.7 or newer, otherwise disabled.
		3731
2620	=item EV_USE_SELECT	3732	=item EV_USE_SELECT
2621		3733
2622	If undefined or defined to be C<1>, libev will compile in support for the	3734	If undefined or defined to be C<1>, libev will compile in support for the
2623	C<select>(2) backend. No attempt at autodetection will be done: if no	3735	C<select>(2) backend. No attempt at auto-detection will be done: if no
2624	other method takes over, select will be it. Otherwise the select backend	3736	other method takes over, select will be it. Otherwise the select backend
2625	will not be compiled in.	3737	will not be compiled in.
2626		3738
2627	=item EV_SELECT_USE_FD_SET	3739	=item EV_SELECT_USE_FD_SET
2628		3740
2629	If defined to C<1>, then the select backend will use the system C<fd_set>	3741	If defined to C<1>, then the select backend will use the system C<fd_set>
2630	structure. This is useful if libev doesn't compile due to a missing	3742	structure. This is useful if libev doesn't compile due to a missing
2631	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3743	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2632	exotic systems. This usually limits the range of file descriptors to some	3744	on exotic systems. This usually limits the range of file descriptors to
2633	low limit such as 1024 or might have other limitations (winsocket only	3745	some low limit such as 1024 or might have other limitations (winsocket
2634	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3746	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2635	influence the size of the C<fd_set> used.	3747	configures the maximum size of the C<fd_set>.
2636		3748
2637	=item EV_SELECT_IS_WINSOCKET	3749	=item EV_SELECT_IS_WINSOCKET
2638		3750
2639	When defined to C<1>, the select backend will assume that	3751	When defined to C<1>, the select backend will assume that
2640	select/socket/connect etc. don't understand file descriptors but	3752	select/socket/connect etc. don't understand file descriptors but
…		…
2642	be used is the winsock select). This means that it will call	3754	be used is the winsock select). This means that it will call
2643	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3755	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2644	it is assumed that all these functions actually work on fds, even	3756	it is assumed that all these functions actually work on fds, even
2645	on win32. Should not be defined on non-win32 platforms.	3757	on win32. Should not be defined on non-win32 platforms.
2646		3758
2647	=item EV_FD_TO_WIN32_HANDLE	3759	=item EV_FD_TO_WIN32_HANDLE(fd)
2648		3760
2649	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3761	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2650	file descriptors to socket handles. When not defining this symbol (the	3762	file descriptors to socket handles. When not defining this symbol (the
2651	default), then libev will call C<_get_osfhandle>, which is usually	3763	default), then libev will call C<_get_osfhandle>, which is usually
2652	correct. In some cases, programs use their own file descriptor management,	3764	correct. In some cases, programs use their own file descriptor management,
2653	in which case they can provide this function to map fds to socket handles.	3765	in which case they can provide this function to map fds to socket handles.
2654		3766
		3767	=item EV_WIN32_HANDLE_TO_FD(handle)
		3768
		3769	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3770	using the standard C<_open_osfhandle> function. For programs implementing
		3771	their own fd to handle mapping, overwriting this function makes it easier
		3772	to do so. This can be done by defining this macro to an appropriate value.
		3773
		3774	=item EV_WIN32_CLOSE_FD(fd)
		3775
		3776	If programs implement their own fd to handle mapping on win32, then this
		3777	macro can be used to override the C<close> function, useful to unregister
		3778	file descriptors again. Note that the replacement function has to close
		3779	the underlying OS handle.
		3780
2655	=item EV_USE_POLL	3781	=item EV_USE_POLL
2656		3782
2657	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3783	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2658	backend. Otherwise it will be enabled on non-win32 platforms. It	3784	backend. Otherwise it will be enabled on non-win32 platforms. It
2659	takes precedence over select.	3785	takes precedence over select.
2660		3786
2661	=item EV_USE_EPOLL	3787	=item EV_USE_EPOLL
2662		3788
2663	If defined to be C<1>, libev will compile in support for the Linux	3789	If defined to be C<1>, libev will compile in support for the Linux
2664	C<epoll>(7) backend. Its availability will be detected at runtime,	3790	C<epoll>(7) backend. Its availability will be detected at runtime,
2665	otherwise another method will be used as fallback. This is the	3791	otherwise another method will be used as fallback. This is the preferred
2666	preferred backend for GNU/Linux systems.	3792	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3793	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2667		3794
2668	=item EV_USE_KQUEUE	3795	=item EV_USE_KQUEUE
2669		3796
2670	If defined to be C<1>, libev will compile in support for the BSD style	3797	If defined to be C<1>, libev will compile in support for the BSD style
2671	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3798	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2684	otherwise another method will be used as fallback. This is the preferred	3811	otherwise another method will be used as fallback. This is the preferred
2685	backend for Solaris 10 systems.	3812	backend for Solaris 10 systems.
2686		3813
2687	=item EV_USE_DEVPOLL	3814	=item EV_USE_DEVPOLL
2688		3815
2689	reserved for future expansion, works like the USE symbols above.	3816	Reserved for future expansion, works like the USE symbols above.
2690		3817
2691	=item EV_USE_INOTIFY	3818	=item EV_USE_INOTIFY
2692		3819
2693	If defined to be C<1>, libev will compile in support for the Linux inotify	3820	If defined to be C<1>, libev will compile in support for the Linux inotify
2694	interface to speed up C<ev_stat> watchers. Its actual availability will	3821	interface to speed up C<ev_stat> watchers. Its actual availability will
2695	be detected at runtime.	3822	be detected at runtime. If undefined, it will be enabled if the headers
		3823	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2696		3824
2697	=item EV_ATOMIC_T	3825	=item EV_ATOMIC_T
2698		3826
2699	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3827	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2700	access is atomic with respect to other threads or signal contexts. No such type	3828	access is atomic with respect to other threads or signal contexts. No such
2701	is easily found using, so you cna provide your own type that you know is safe.	3829	type is easily found in the C language, so you can provide your own type
		3830	that you know is safe for your purposes. It is used both for signal handler "locking"
		3831	as well as for signal and thread safety in C<ev_async> watchers.
2702		3832
2703	In the absense of this define, libev will use C<sig_atomic_t volatile>	3833	In the absence of this define, libev will use C<sig_atomic_t volatile>
2704	from F<signal.h>, which is usually good enough on most platforms.	3834	(from F<signal.h>), which is usually good enough on most platforms.
2705		3835
2706	=item EV_H	3836	=item EV_H (h)
2707		3837
2708	The name of the F<ev.h> header file used to include it. The default if	3838	The name of the F<ev.h> header file used to include it. The default if
2709	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3839	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2710	used to virtually rename the F<ev.h> header file in case of conflicts.	3840	used to virtually rename the F<ev.h> header file in case of conflicts.
2711		3841
2712	=item EV_CONFIG_H	3842	=item EV_CONFIG_H (h)
2713		3843
2714	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3844	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2715	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3845	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2716	C<EV_H>, above.	3846	C<EV_H>, above.
2717		3847
2718	=item EV_EVENT_H	3848	=item EV_EVENT_H (h)
2719		3849
2720	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3850	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2721	of how the F<event.h> header can be found, the default is C<"event.h">.	3851	of how the F<event.h> header can be found, the default is C<"event.h">.
2722		3852
2723	=item EV_PROTOTYPES	3853	=item EV_PROTOTYPES (h)
2724		3854
2725	If defined to be C<0>, then F<ev.h> will not define any function	3855	If defined to be C<0>, then F<ev.h> will not define any function
2726	prototypes, but still define all the structs and other symbols. This is	3856	prototypes, but still define all the structs and other symbols. This is
2727	occasionally useful if you want to provide your own wrapper functions	3857	occasionally useful if you want to provide your own wrapper functions
2728	around libev functions.	3858	around libev functions.
…		…
2747	When doing priority-based operations, libev usually has to linearly search	3877	When doing priority-based operations, libev usually has to linearly search
2748	all the priorities, so having many of them (hundreds) uses a lot of space	3878	all the priorities, so having many of them (hundreds) uses a lot of space
2749	and time, so using the defaults of five priorities (-2 .. +2) is usually	3879	and time, so using the defaults of five priorities (-2 .. +2) is usually
2750	fine.	3880	fine.
2751		3881
2752	If your embedding app does not need any priorities, defining these both to	3882	If your embedding application does not need any priorities, defining these
2753	C<0> will save some memory and cpu.	3883	both to C<0> will save some memory and CPU.
2754		3884
2755	=item EV_PERIODIC_ENABLE	3885	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3886	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3887	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2756		3888
2757	If undefined or defined to be C<1>, then periodic timers are supported. If	3889	If undefined or defined to be C<1> (and the platform supports it), then
2758	defined to be C<0>, then they are not. Disabling them saves a few kB of	3890	the respective watcher type is supported. If defined to be C<0>, then it
2759	code.	3891	is not. Disabling watcher types mainly saves codesize.
2760		3892
2761	=item EV_IDLE_ENABLE	3893	=item EV_FEATURES
2762
2763	If undefined or defined to be C<1>, then idle watchers are supported. If
2764	defined to be C<0>, then they are not. Disabling them saves a few kB of
2765	code.
2766
2767	=item EV_EMBED_ENABLE
2768
2769	If undefined or defined to be C<1>, then embed watchers are supported. If
2770	defined to be C<0>, then they are not.
2771
2772	=item EV_STAT_ENABLE
2773
2774	If undefined or defined to be C<1>, then stat watchers are supported. If
2775	defined to be C<0>, then they are not.
2776
2777	=item EV_FORK_ENABLE
2778
2779	If undefined or defined to be C<1>, then fork watchers are supported. If
2780	defined to be C<0>, then they are not.
2781
2782	=item EV_ASYNC_ENABLE
2783
2784	If undefined or defined to be C<1>, then async watchers are supported. If
2785	defined to be C<0>, then they are not.
2786
2787	=item EV_MINIMAL
2788		3894
2789	If you need to shave off some kilobytes of code at the expense of some	3895	If you need to shave off some kilobytes of code at the expense of some
2790	speed, define this symbol to C<1>. Currently only used for gcc to override	3896	speed (but with the full API), you can define this symbol to request
2791	some inlining decisions, saves roughly 30% codesize of amd64.	3897	certain subsets of functionality. The default is to enable all features
		3898	that can be enabled on the platform.
		3899
		3900	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3901	with some broad features you want) and then selectively re-enable
		3902	additional parts you want, for example if you want everything minimal,
		3903	but multiple event loop support, async and child watchers and the poll
		3904	backend, use this:
		3905
		3906	#define EV_FEATURES 0
		3907	#define EV_MULTIPLICITY 1
		3908	#define EV_USE_POLL 1
		3909	#define EV_CHILD_ENABLE 1
		3910	#define EV_ASYNC_ENABLE 1
		3911
		3912	The actual value is a bitset, it can be a combination of the following
		3913	values:
		3914
		3915	=over 4
		3916
		3917	=item C<1> - faster/larger code
		3918
		3919	Use larger code to speed up some operations.
		3920
		3921	Currently this is used to override some inlining decisions (enlarging the roughly
		3922	30% code size on amd64.
		3923
		3924	When optimising for size, use of compiler flags such as C<-Os> with
		3925	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3926	assertions.
		3927
		3928	=item C<2> - faster/larger data structures
		3929
		3930	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3931	hash table sizes and so on. This will usually further increase codesize
		3932	and can additionally have an effect on the size of data structures at
		3933	runtime.
		3934
		3935	=item C<4> - full API configuration
		3936
		3937	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3938	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3939
		3940	=item C<8> - full API
		3941
		3942	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3943	details on which parts of the API are still available without this
		3944	feature, and do not complain if this subset changes over time.
		3945
		3946	=item C<16> - enable all optional watcher types
		3947
		3948	Enables all optional watcher types. If you want to selectively enable
		3949	only some watcher types other than I/O and timers (e.g. prepare,
		3950	embed, async, child...) you can enable them manually by defining
		3951	C<EV_watchertype_ENABLE> to C<1> instead.
		3952
		3953	=item C<32> - enable all backends
		3954
		3955	This enables all backends - without this feature, you need to enable at
		3956	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3957
		3958	=item C<64> - enable OS-specific "helper" APIs
		3959
		3960	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3961	default.
		3962
		3963	=back
		3964
		3965	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3966	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3967	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3968	watchers, timers and monotonic clock support.
		3969
		3970	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3971	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3972	your program might be left out as well - a binary starting a timer and an
		3973	I/O watcher then might come out at only 5Kb.
		3974
		3975	=item EV_AVOID_STDIO
		3976
		3977	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3978	functions (printf, scanf, perror etc.). This will increase the codesize
		3979	somewhat, but if your program doesn't otherwise depend on stdio and your
		3980	libc allows it, this avoids linking in the stdio library which is quite
		3981	big.
		3982
		3983	Note that error messages might become less precise when this option is
		3984	enabled.
		3985
		3986	=item EV_NSIG
		3987
		3988	The highest supported signal number, +1 (or, the number of
		3989	signals): Normally, libev tries to deduce the maximum number of signals
		3990	automatically, but sometimes this fails, in which case it can be
		3991	specified. Also, using a lower number than detected (C<32> should be
		3992	good for about any system in existance) can save some memory, as libev
		3993	statically allocates some 12-24 bytes per signal number.
2792		3994
2793	=item EV_PID_HASHSIZE	3995	=item EV_PID_HASHSIZE
2794		3996
2795	C<ev_child> watchers use a small hash table to distribute workload by	3997	C<ev_child> watchers use a small hash table to distribute workload by
2796	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3998	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
2797	than enough. If you need to manage thousands of children you might want to	3999	usually more than enough. If you need to manage thousands of children you
2798	increase this value (I<must> be a power of two).	4000	might want to increase this value (I<must> be a power of two).
2799		4001
2800	=item EV_INOTIFY_HASHSIZE	4002	=item EV_INOTIFY_HASHSIZE
2801		4003
2802	C<ev_stat> watchers use a small hash table to distribute workload by	4004	C<ev_stat> watchers use a small hash table to distribute workload by
2803	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4005	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
2804	usually more than enough. If you need to manage thousands of C<ev_stat>	4006	disabled), usually more than enough. If you need to manage thousands of
2805	watchers you might want to increase this value (I<must> be a power of	4007	C<ev_stat> watchers you might want to increase this value (I<must> be a
2806	two).	4008	power of two).
		4009
		4010	=item EV_USE_4HEAP
		4011
		4012	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		4013	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		4014	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		4015	faster performance with many (thousands) of watchers.
		4016
		4017	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4018	will be C<0>.
		4019
		4020	=item EV_HEAP_CACHE_AT
		4021
		4022	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		4023	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		4024	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		4025	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		4026	but avoids random read accesses on heap changes. This improves performance
		4027	noticeably with many (hundreds) of watchers.
		4028
		4029	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4030	will be C<0>.
		4031
		4032	=item EV_VERIFY
		4033
		4034	Controls how much internal verification (see C<ev_loop_verify ()>) will
		4035	be done: If set to C<0>, no internal verification code will be compiled
		4036	in. If set to C<1>, then verification code will be compiled in, but not
		4037	called. If set to C<2>, then the internal verification code will be
		4038	called once per loop, which can slow down libev. If set to C<3>, then the
		4039	verification code will be called very frequently, which will slow down
		4040	libev considerably.
		4041
		4042	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4043	will be C<0>.
2807		4044
2808	=item EV_COMMON	4045	=item EV_COMMON
2809		4046
2810	By default, all watchers have a C<void *data> member. By redefining	4047	By default, all watchers have a C<void *data> member. By redefining
2811	this macro to a something else you can include more and other types of	4048	this macro to a something else you can include more and other types of
2812	members. You have to define it each time you include one of the files,	4049	members. You have to define it each time you include one of the files,
2813	though, and it must be identical each time.	4050	though, and it must be identical each time.
2814		4051
2815	For example, the perl EV module uses something like this:	4052	For example, the perl EV module uses something like this:
2816		4053
2817	#define EV_COMMON \	4054	#define EV_COMMON \
2818	SV *self; /* contains this struct */ \	4055	SV *self; /* contains this struct */ \
2819	SV *cb_sv, *fh /* note no trailing ";" */	4056	SV *cb_sv, *fh /* note no trailing ";" */
2820		4057
2821	=item EV_CB_DECLARE (type)	4058	=item EV_CB_DECLARE (type)
2822		4059
2823	=item EV_CB_INVOKE (watcher, revents)	4060	=item EV_CB_INVOKE (watcher, revents)
2824		4061
…		…
2829	definition and a statement, respectively. See the F<ev.h> header file for	4066	definition and a statement, respectively. See the F<ev.h> header file for
2830	their default definitions. One possible use for overriding these is to	4067	their default definitions. One possible use for overriding these is to
2831	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4068	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2832	method calls instead of plain function calls in C++.	4069	method calls instead of plain function calls in C++.
2833		4070
		4071	=back
		4072
2834	=head2 EXPORTED API SYMBOLS	4073	=head2 EXPORTED API SYMBOLS
2835		4074
2836	If you need to re-export the API (e.g. via a dll) and you need a list of	4075	If you need to re-export the API (e.g. via a DLL) and you need a list of
2837	exported symbols, you can use the provided F<Symbol.*> files which list	4076	exported symbols, you can use the provided F<Symbol.*> files which list
2838	all public symbols, one per line:	4077	all public symbols, one per line:
2839		4078
2840	Symbols.ev for libev proper	4079	Symbols.ev for libev proper
2841	Symbols.event for the libevent emulation	4080	Symbols.event for the libevent emulation
2842		4081
2843	This can also be used to rename all public symbols to avoid clashes with	4082	This can also be used to rename all public symbols to avoid clashes with
2844	multiple versions of libev linked together (which is obviously bad in	4083	multiple versions of libev linked together (which is obviously bad in
2845	itself, but sometimes it is inconvinient to avoid this).	4084	itself, but sometimes it is inconvenient to avoid this).
2846		4085
2847	A sed command like this will create wrapper C<#define>'s that you need to	4086	A sed command like this will create wrapper C<#define>'s that you need to
2848	include before including F<ev.h>:	4087	include before including F<ev.h>:
2849		4088
2850	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4089	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2867	file.	4106	file.
2868		4107
2869	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4108	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2870	that everybody includes and which overrides some configure choices:	4109	that everybody includes and which overrides some configure choices:
2871		4110
2872	#define EV_MINIMAL 1	4111	#define EV_FEATURES 8
2873	#define EV_USE_POLL 0	4112	#define EV_USE_SELECT 1
2874	#define EV_MULTIPLICITY 0
2875	#define EV_PERIODIC_ENABLE 0	4113	#define EV_PREPARE_ENABLE 1
		4114	#define EV_IDLE_ENABLE 1
2876	#define EV_STAT_ENABLE 0	4115	#define EV_SIGNAL_ENABLE 1
2877	#define EV_FORK_ENABLE 0	4116	#define EV_CHILD_ENABLE 1
		4117	#define EV_USE_STDEXCEPT 0
2878	#define EV_CONFIG_H <config.h>	4118	#define EV_CONFIG_H <config.h>
2879	#define EV_MINPRI 0
2880	#define EV_MAXPRI 0
2881		4119
2882	#include "ev++.h"	4120	#include "ev++.h"
2883		4121
2884	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4122	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2885		4123
2886	#include "ev_cpp.h"	4124	#include "ev_cpp.h"
2887	#include "ev.c"	4125	#include "ev.c"
2888		4126
		4127	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2889		4128
2890	=head1 COMPLEXITIES	4129	=head2 THREADS AND COROUTINES
2891		4130
2892	In this section the complexities of (many of) the algorithms used inside	4131	=head3 THREADS
2893	libev will be explained. For complexity discussions about backends see the
2894	documentation for C<ev_default_init>.
2895		4132
2896	All of the following are about amortised time: If an array needs to be	4133	All libev functions are reentrant and thread-safe unless explicitly
2897	extended, libev needs to realloc and move the whole array, but this	4134	documented otherwise, but libev implements no locking itself. This means
2898	happens asymptotically never with higher number of elements, so O(1) might	4135	that you can use as many loops as you want in parallel, as long as there
2899	mean it might do a lengthy realloc operation in rare cases, but on average	4136	are no concurrent calls into any libev function with the same loop
2900	it is much faster and asymptotically approaches constant time.	4137	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4138	of course): libev guarantees that different event loops share no data
		4139	structures that need any locking.
		4140
		4141	Or to put it differently: calls with different loop parameters can be done
		4142	concurrently from multiple threads, calls with the same loop parameter
		4143	must be done serially (but can be done from different threads, as long as
		4144	only one thread ever is inside a call at any point in time, e.g. by using
		4145	a mutex per loop).
		4146
		4147	Specifically to support threads (and signal handlers), libev implements
		4148	so-called C<ev_async> watchers, which allow some limited form of
		4149	concurrency on the same event loop, namely waking it up "from the
		4150	outside".
		4151
		4152	If you want to know which design (one loop, locking, or multiple loops
		4153	without or something else still) is best for your problem, then I cannot
		4154	help you, but here is some generic advice:
2901		4155
2902	=over 4	4156	=over 4
2903		4157
2904	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4158	=item * most applications have a main thread: use the default libev loop
		4159	in that thread, or create a separate thread running only the default loop.
2905		4160
2906	This means that, when you have a watcher that triggers in one hour and	4161	This helps integrating other libraries or software modules that use libev
2907	there are 100 watchers that would trigger before that then inserting will	4162	themselves and don't care/know about threading.
2908	have to skip roughly seven (C<ld 100>) of these watchers.
2909		4163
2910	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4164	=item * one loop per thread is usually a good model.
2911		4165
2912	That means that changing a timer costs less than removing/adding them	4166	Doing this is almost never wrong, sometimes a better-performance model
2913	as only the relative motion in the event queue has to be paid for.	4167	exists, but it is always a good start.
2914		4168
2915	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	4169	=item * other models exist, such as the leader/follower pattern, where one
		4170	loop is handed through multiple threads in a kind of round-robin fashion.
2916		4171
2917	These just add the watcher into an array or at the head of a list.	4172	Choosing a model is hard - look around, learn, know that usually you can do
		4173	better than you currently do :-)
2918		4174
2919	=item Stopping check/prepare/idle watchers: O(1)	4175	=item * often you need to talk to some other thread which blocks in the
		4176	event loop.
2920		4177
2921	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4178	C<ev_async> watchers can be used to wake them up from other threads safely
		4179	(or from signal contexts...).
2922		4180
2923	These watchers are stored in lists then need to be walked to find the	4181	An example use would be to communicate signals or other events that only
2924	correct watcher to remove. The lists are usually short (you don't usually	4182	work in the default loop by registering the signal watcher with the
2925	have many watchers waiting for the same fd or signal).	4183	default loop and triggering an C<ev_async> watcher from the default loop
2926		4184	watcher callback into the event loop interested in the signal.
2927	=item Finding the next timer in each loop iteration: O(1)
2928
2929	By virtue of using a binary heap, the next timer is always found at the
2930	beginning of the storage array.
2931
2932	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2933
2934	A change means an I/O watcher gets started or stopped, which requires
2935	libev to recalculate its status (and possibly tell the kernel, depending
2936	on backend and wether C<ev_io_set> was used).
2937
2938	=item Activating one watcher (putting it into the pending state): O(1)
2939
2940	=item Priority handling: O(number_of_priorities)
2941
2942	Priorities are implemented by allocating some space for each
2943	priority. When doing priority-based operations, libev usually has to
2944	linearly search all the priorities, but starting/stopping and activating
2945	watchers becomes O(1) w.r.t. prioritiy handling.
2946		4185
2947	=back	4186	=back
2948		4187
		4188	=head4 THREAD LOCKING EXAMPLE
2949		4189
2950	=head1 Win32 platform limitations and workarounds	4190	Here is a fictitious example of how to run an event loop in a different
		4191	thread than where callbacks are being invoked and watchers are
		4192	created/added/removed.
		4193
		4194	For a real-world example, see the C<EV::Loop::Async> perl module,
		4195	which uses exactly this technique (which is suited for many high-level
		4196	languages).
		4197
		4198	The example uses a pthread mutex to protect the loop data, a condition
		4199	variable to wait for callback invocations, an async watcher to notify the
		4200	event loop thread and an unspecified mechanism to wake up the main thread.
		4201
		4202	First, you need to associate some data with the event loop:
		4203
		4204	typedef struct {
		4205	mutex_t lock; /* global loop lock */
		4206	ev_async async_w;
		4207	thread_t tid;
		4208	cond_t invoke_cv;
		4209	} userdata;
		4210
		4211	void prepare_loop (EV_P)
		4212	{
		4213	// for simplicity, we use a static userdata struct.
		4214	static userdata u;
		4215
		4216	ev_async_init (&u->async_w, async_cb);
		4217	ev_async_start (EV_A_ &u->async_w);
		4218
		4219	pthread_mutex_init (&u->lock, 0);
		4220	pthread_cond_init (&u->invoke_cv, 0);
		4221
		4222	// now associate this with the loop
		4223	ev_set_userdata (EV_A_ u);
		4224	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4225	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4226
		4227	// then create the thread running ev_loop
		4228	pthread_create (&u->tid, 0, l_run, EV_A);
		4229	}
		4230
		4231	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4232	solely to wake up the event loop so it takes notice of any new watchers
		4233	that might have been added:
		4234
		4235	static void
		4236	async_cb (EV_P_ ev_async *w, int revents)
		4237	{
		4238	// just used for the side effects
		4239	}
		4240
		4241	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4242	protecting the loop data, respectively.
		4243
		4244	static void
		4245	l_release (EV_P)
		4246	{
		4247	userdata *u = ev_userdata (EV_A);
		4248	pthread_mutex_unlock (&u->lock);
		4249	}
		4250
		4251	static void
		4252	l_acquire (EV_P)
		4253	{
		4254	userdata *u = ev_userdata (EV_A);
		4255	pthread_mutex_lock (&u->lock);
		4256	}
		4257
		4258	The event loop thread first acquires the mutex, and then jumps straight
		4259	into C<ev_loop>:
		4260
		4261	void *
		4262	l_run (void *thr_arg)
		4263	{
		4264	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4265
		4266	l_acquire (EV_A);
		4267	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4268	ev_loop (EV_A_ 0);
		4269	l_release (EV_A);
		4270
		4271	return 0;
		4272	}
		4273
		4274	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4275	signal the main thread via some unspecified mechanism (signals? pipe
		4276	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4277	have been called (in a while loop because a) spurious wakeups are possible
		4278	and b) skipping inter-thread-communication when there are no pending
		4279	watchers is very beneficial):
		4280
		4281	static void
		4282	l_invoke (EV_P)
		4283	{
		4284	userdata *u = ev_userdata (EV_A);
		4285
		4286	while (ev_pending_count (EV_A))
		4287	{
		4288	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4289	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4290	}
		4291	}
		4292
		4293	Now, whenever the main thread gets told to invoke pending watchers, it
		4294	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4295	thread to continue:
		4296
		4297	static void
		4298	real_invoke_pending (EV_P)
		4299	{
		4300	userdata *u = ev_userdata (EV_A);
		4301
		4302	pthread_mutex_lock (&u->lock);
		4303	ev_invoke_pending (EV_A);
		4304	pthread_cond_signal (&u->invoke_cv);
		4305	pthread_mutex_unlock (&u->lock);
		4306	}
		4307
		4308	Whenever you want to start/stop a watcher or do other modifications to an
		4309	event loop, you will now have to lock:
		4310
		4311	ev_timer timeout_watcher;
		4312	userdata *u = ev_userdata (EV_A);
		4313
		4314	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4315
		4316	pthread_mutex_lock (&u->lock);
		4317	ev_timer_start (EV_A_ &timeout_watcher);
		4318	ev_async_send (EV_A_ &u->async_w);
		4319	pthread_mutex_unlock (&u->lock);
		4320
		4321	Note that sending the C<ev_async> watcher is required because otherwise
		4322	an event loop currently blocking in the kernel will have no knowledge
		4323	about the newly added timer. By waking up the loop it will pick up any new
		4324	watchers in the next event loop iteration.
		4325
		4326	=head3 COROUTINES
		4327
		4328	Libev is very accommodating to coroutines ("cooperative threads"):
		4329	libev fully supports nesting calls to its functions from different
		4330	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		4331	different coroutines, and switch freely between both coroutines running
		4332	the loop, as long as you don't confuse yourself). The only exception is
		4333	that you must not do this from C<ev_periodic> reschedule callbacks.
		4334
		4335	Care has been taken to ensure that libev does not keep local state inside
		4336	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		4337	they do not call any callbacks.
		4338
		4339	=head2 COMPILER WARNINGS
		4340
		4341	Depending on your compiler and compiler settings, you might get no or a
		4342	lot of warnings when compiling libev code. Some people are apparently
		4343	scared by this.
		4344
		4345	However, these are unavoidable for many reasons. For one, each compiler
		4346	has different warnings, and each user has different tastes regarding
		4347	warning options. "Warn-free" code therefore cannot be a goal except when
		4348	targeting a specific compiler and compiler-version.
		4349
		4350	Another reason is that some compiler warnings require elaborate
		4351	workarounds, or other changes to the code that make it less clear and less
		4352	maintainable.
		4353
		4354	And of course, some compiler warnings are just plain stupid, or simply
		4355	wrong (because they don't actually warn about the condition their message
		4356	seems to warn about). For example, certain older gcc versions had some
		4357	warnings that resulted an extreme number of false positives. These have
		4358	been fixed, but some people still insist on making code warn-free with
		4359	such buggy versions.
		4360
		4361	While libev is written to generate as few warnings as possible,
		4362	"warn-free" code is not a goal, and it is recommended not to build libev
		4363	with any compiler warnings enabled unless you are prepared to cope with
		4364	them (e.g. by ignoring them). Remember that warnings are just that:
		4365	warnings, not errors, or proof of bugs.
		4366
		4367
		4368	=head2 VALGRIND
		4369
		4370	Valgrind has a special section here because it is a popular tool that is
		4371	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		4372
		4373	If you think you found a bug (memory leak, uninitialised data access etc.)
		4374	in libev, then check twice: If valgrind reports something like:
		4375
		4376	==2274== definitely lost: 0 bytes in 0 blocks.
		4377	==2274== possibly lost: 0 bytes in 0 blocks.
		4378	==2274== still reachable: 256 bytes in 1 blocks.
		4379
		4380	Then there is no memory leak, just as memory accounted to global variables
		4381	is not a memleak - the memory is still being referenced, and didn't leak.
		4382
		4383	Similarly, under some circumstances, valgrind might report kernel bugs
		4384	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4385	although an acceptable workaround has been found here), or it might be
		4386	confused.
		4387
		4388	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		4389	make it into some kind of religion.
		4390
		4391	If you are unsure about something, feel free to contact the mailing list
		4392	with the full valgrind report and an explanation on why you think this
		4393	is a bug in libev (best check the archives, too :). However, don't be
		4394	annoyed when you get a brisk "this is no bug" answer and take the chance
		4395	of learning how to interpret valgrind properly.
		4396
		4397	If you need, for some reason, empty reports from valgrind for your project
		4398	I suggest using suppression lists.
		4399
		4400
		4401	=head1 PORTABILITY NOTES
		4402
		4403	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
2951		4404
2952	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4405	Win32 doesn't support any of the standards (e.g. POSIX) that libev
2953	requires, and its I/O model is fundamentally incompatible with the POSIX	4406	requires, and its I/O model is fundamentally incompatible with the POSIX
2954	model. Libev still offers limited functionality on this platform in	4407	model. Libev still offers limited functionality on this platform in
2955	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4408	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2956	descriptors. This only applies when using Win32 natively, not when using	4409	descriptors. This only applies when using Win32 natively, not when using
2957	e.g. cygwin.	4410	e.g. cygwin.
2958		4411
		4412	Lifting these limitations would basically require the full
		4413	re-implementation of the I/O system. If you are into these kinds of
		4414	things, then note that glib does exactly that for you in a very portable
		4415	way (note also that glib is the slowest event library known to man).
		4416
2959	There is no supported compilation method available on windows except	4417	There is no supported compilation method available on windows except
2960	embedding it into other applications.	4418	embedding it into other applications.
2961		4419
		4420	Sensible signal handling is officially unsupported by Microsoft - libev
		4421	tries its best, but under most conditions, signals will simply not work.
		4422
		4423	Not a libev limitation but worth mentioning: windows apparently doesn't
		4424	accept large writes: instead of resulting in a partial write, windows will
		4425	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4426	so make sure you only write small amounts into your sockets (less than a
		4427	megabyte seems safe, but this apparently depends on the amount of memory
		4428	available).
		4429
2962	Due to the many, low, and arbitrary limits on the win32 platform and the	4430	Due to the many, low, and arbitrary limits on the win32 platform and
2963	abysmal performance of winsockets, using a large number of sockets is not	4431	the abysmal performance of winsockets, using a large number of sockets
2964	recommended (and not reasonable). If your program needs to use more than	4432	is not recommended (and not reasonable). If your program needs to use
2965	a hundred or so sockets, then likely it needs to use a totally different	4433	more than a hundred or so sockets, then likely it needs to use a totally
2966	implementation for windows, as libev offers the POSIX model, which cannot	4434	different implementation for windows, as libev offers the POSIX readiness
2967	be implemented efficiently on windows (microsoft monopoly games).	4435	notification model, which cannot be implemented efficiently on windows
		4436	(due to Microsoft monopoly games).
		4437
		4438	A typical way to use libev under windows is to embed it (see the embedding
		4439	section for details) and use the following F<evwrap.h> header file instead
		4440	of F<ev.h>:
		4441
		4442	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4443	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4444
		4445	#include "ev.h"
		4446
		4447	And compile the following F<evwrap.c> file into your project (make sure
		4448	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4449
		4450	#include "evwrap.h"
		4451	#include "ev.c"
2968		4452
2969	=over 4	4453	=over 4
2970		4454
2971	=item The winsocket select function	4455	=item The winsocket select function
2972		4456
2973	The winsocket C<select> function doesn't follow POSIX in that it requires	4457	The winsocket C<select> function doesn't follow POSIX in that it
2974	socket I<handles> and not socket I<file descriptors>. This makes select	4458	requires socket I<handles> and not socket I<file descriptors> (it is
2975	very inefficient, and also requires a mapping from file descriptors	4459	also extremely buggy). This makes select very inefficient, and also
2976	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4460	requires a mapping from file descriptors to socket handles (the Microsoft
2977	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4461	C runtime provides the function C<_open_osfhandle> for this). See the
2978	symbols for more info.	4462	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4463	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2979		4464
2980	The configuration for a "naked" win32 using the microsoft runtime	4465	The configuration for a "naked" win32 using the Microsoft runtime
2981	libraries and raw winsocket select is:	4466	libraries and raw winsocket select is:
2982		4467
2983	#define EV_USE_SELECT 1	4468	#define EV_USE_SELECT 1
2984	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4469	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2985		4470
2986	Note that winsockets handling of fd sets is O(n), so you can easily get a	4471	Note that winsockets handling of fd sets is O(n), so you can easily get a
2987	complexity in the O(n²) range when using win32.	4472	complexity in the O(n²) range when using win32.
2988		4473
2989	=item Limited number of file descriptors	4474	=item Limited number of file descriptors
2990		4475
2991	Windows has numerous arbitrary (and low) limits on things. Early versions	4476	Windows has numerous arbitrary (and low) limits on things.
2992	of winsocket's select only supported waiting for a max. of C<64> handles	4477
		4478	Early versions of winsocket's select only supported waiting for a maximum
2993	(probably owning to the fact that all windows kernels can only wait for	4479	of C<64> handles (probably owning to the fact that all windows kernels
2994	C<64> things at the same time internally; microsoft recommends spawning a	4480	can only wait for C<64> things at the same time internally; Microsoft
2995	chain of threads and wait for 63 handles and the previous thread in each).	4481	recommends spawning a chain of threads and wait for 63 handles and the
		4482	previous thread in each. Sounds great!).
2996		4483
2997	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4484	Newer versions support more handles, but you need to define C<FD_SETSIZE>
2998	to some high number (e.g. C<2048>) before compiling the winsocket select	4485	to some high number (e.g. C<2048>) before compiling the winsocket select
2999	call (which might be in libev or elsewhere, for example, perl does its own	4486	call (which might be in libev or elsewhere, for example, perl and many
3000	select emulation on windows).	4487	other interpreters do their own select emulation on windows).
3001		4488
3002	Another limit is the number of file descriptors in the microsoft runtime	4489	Another limit is the number of file descriptors in the Microsoft runtime
3003	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4490	libraries, which by default is C<64> (there must be a hidden I<64>
3004	or something like this inside microsoft). You can increase this by calling	4491	fetish or something like this inside Microsoft). You can increase this
3005	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4492	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3006	arbitrary limit), but is broken in many versions of the microsoft runtime	4493	(another arbitrary limit), but is broken in many versions of the Microsoft
3007	libraries.
3008
3009	This might get you to about C<512> or C<2048> sockets (depending on	4494	runtime libraries. This might get you to about C<512> or C<2048> sockets
3010	windows version and/or the phase of the moon). To get more, you need to	4495	(depending on windows version and/or the phase of the moon). To get more,
3011	wrap all I/O functions and provide your own fd management, but the cost of	4496	you need to wrap all I/O functions and provide your own fd management, but
3012	calling select (O(n²)) will likely make this unworkable.	4497	the cost of calling select (O(n²)) will likely make this unworkable.
3013		4498
3014	=back	4499	=back
3015		4500
		4501	=head2 PORTABILITY REQUIREMENTS
		4502
		4503	In addition to a working ISO-C implementation and of course the
		4504	backend-specific APIs, libev relies on a few additional extensions:
		4505
		4506	=over 4
		4507
		4508	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4509	calling conventions regardless of C<ev_watcher_type *>.
		4510
		4511	Libev assumes not only that all watcher pointers have the same internal
		4512	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4513	assumes that the same (machine) code can be used to call any watcher
		4514	callback: The watcher callbacks have different type signatures, but libev
		4515	calls them using an C<ev_watcher *> internally.
		4516
		4517	=item C<sig_atomic_t volatile> must be thread-atomic as well
		4518
		4519	The type C<sig_atomic_t volatile> (or whatever is defined as
		4520	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		4521	threads. This is not part of the specification for C<sig_atomic_t>, but is
		4522	believed to be sufficiently portable.
		4523
		4524	=item C<sigprocmask> must work in a threaded environment
		4525
		4526	Libev uses C<sigprocmask> to temporarily block signals. This is not
		4527	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		4528	pthread implementations will either allow C<sigprocmask> in the "main
		4529	thread" or will block signals process-wide, both behaviours would
		4530	be compatible with libev. Interaction between C<sigprocmask> and
		4531	C<pthread_sigmask> could complicate things, however.
		4532
		4533	The most portable way to handle signals is to block signals in all threads
		4534	except the initial one, and run the default loop in the initial thread as
		4535	well.
		4536
		4537	=item C<long> must be large enough for common memory allocation sizes
		4538
		4539	To improve portability and simplify its API, libev uses C<long> internally
		4540	instead of C<size_t> when allocating its data structures. On non-POSIX
		4541	systems (Microsoft...) this might be unexpectedly low, but is still at
		4542	least 31 bits everywhere, which is enough for hundreds of millions of
		4543	watchers.
		4544
		4545	=item C<double> must hold a time value in seconds with enough accuracy
		4546
		4547	The type C<double> is used to represent timestamps. It is required to
		4548	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4549	enough for at least into the year 4000. This requirement is fulfilled by
		4550	implementations implementing IEEE 754, which is basically all existing
		4551	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4552	2200.
		4553
		4554	=back
		4555
		4556	If you know of other additional requirements drop me a note.
		4557
		4558
		4559	=head1 ALGORITHMIC COMPLEXITIES
		4560
		4561	In this section the complexities of (many of) the algorithms used inside
		4562	libev will be documented. For complexity discussions about backends see
		4563	the documentation for C<ev_default_init>.
		4564
		4565	All of the following are about amortised time: If an array needs to be
		4566	extended, libev needs to realloc and move the whole array, but this
		4567	happens asymptotically rarer with higher number of elements, so O(1) might
		4568	mean that libev does a lengthy realloc operation in rare cases, but on
		4569	average it is much faster and asymptotically approaches constant time.
		4570
		4571	=over 4
		4572
		4573	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4574
		4575	This means that, when you have a watcher that triggers in one hour and
		4576	there are 100 watchers that would trigger before that, then inserting will
		4577	have to skip roughly seven (C<ld 100>) of these watchers.
		4578
		4579	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4580
		4581	That means that changing a timer costs less than removing/adding them,
		4582	as only the relative motion in the event queue has to be paid for.
		4583
		4584	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4585
		4586	These just add the watcher into an array or at the head of a list.
		4587
		4588	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4589
		4590	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4591
		4592	These watchers are stored in lists, so they need to be walked to find the
		4593	correct watcher to remove. The lists are usually short (you don't usually
		4594	have many watchers waiting for the same fd or signal: one is typical, two
		4595	is rare).
		4596
		4597	=item Finding the next timer in each loop iteration: O(1)
		4598
		4599	By virtue of using a binary or 4-heap, the next timer is always found at a
		4600	fixed position in the storage array.
		4601
		4602	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4603
		4604	A change means an I/O watcher gets started or stopped, which requires
		4605	libev to recalculate its status (and possibly tell the kernel, depending
		4606	on backend and whether C<ev_io_set> was used).
		4607
		4608	=item Activating one watcher (putting it into the pending state): O(1)
		4609
		4610	=item Priority handling: O(number_of_priorities)
		4611
		4612	Priorities are implemented by allocating some space for each
		4613	priority. When doing priority-based operations, libev usually has to
		4614	linearly search all the priorities, but starting/stopping and activating
		4615	watchers becomes O(1) with respect to priority handling.
		4616
		4617	=item Sending an ev_async: O(1)
		4618
		4619	=item Processing ev_async_send: O(number_of_async_watchers)
		4620
		4621	=item Processing signals: O(max_signal_number)
		4622
		4623	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4624	calls in the current loop iteration. Checking for async and signal events
		4625	involves iterating over all running async watchers or all signal numbers.
		4626
		4627	=back
		4628
		4629
		4630	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4631
		4632	The major version 4 introduced some minor incompatible changes to the API.
		4633
		4634	At the moment, the C<ev.h> header file tries to implement superficial
		4635	compatibility, so most programs should still compile. Those might be
		4636	removed in later versions of libev, so better update early than late.
		4637
		4638	=over 4
		4639
		4640	=item C<ev_loop_count> renamed to C<ev_iteration>
		4641
		4642	=item C<ev_loop_depth> renamed to C<ev_depth>
		4643
		4644	=item C<ev_loop_verify> renamed to C<ev_verify>
		4645
		4646	Most functions working on C<struct ev_loop> objects don't have an
		4647	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
		4648	still called C<ev_loop_fork> because it would otherwise clash with the
		4649	C<ev_fork> typedef.
		4650
		4651	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
		4652
		4653	This is a simple rename - all other watcher types use their name
		4654	as revents flag, and now C<ev_timer> does, too.
		4655
		4656	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4657	and continue to be present for the forseeable future, so this is mostly a
		4658	documentation change.
		4659
		4660	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4661
		4662	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4663	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4664	and work, but the library code will of course be larger.
		4665
		4666	=back
		4667
		4668
		4669	=head1 GLOSSARY
		4670
		4671	=over 4
		4672
		4673	=item active
		4674
		4675	A watcher is active as long as it has been started (has been attached to
		4676	an event loop) but not yet stopped (disassociated from the event loop).
		4677
		4678	=item application
		4679
		4680	In this document, an application is whatever is using libev.
		4681
		4682	=item callback
		4683
		4684	The address of a function that is called when some event has been
		4685	detected. Callbacks are being passed the event loop, the watcher that
		4686	received the event, and the actual event bitset.
		4687
		4688	=item callback invocation
		4689
		4690	The act of calling the callback associated with a watcher.
		4691
		4692	=item event
		4693
		4694	A change of state of some external event, such as data now being available
		4695	for reading on a file descriptor, time having passed or simply not having
		4696	any other events happening anymore.
		4697
		4698	In libev, events are represented as single bits (such as C<EV_READ> or
		4699	C<EV_TIMER>).
		4700
		4701	=item event library
		4702
		4703	A software package implementing an event model and loop.
		4704
		4705	=item event loop
		4706
		4707	An entity that handles and processes external events and converts them
		4708	into callback invocations.
		4709
		4710	=item event model
		4711
		4712	The model used to describe how an event loop handles and processes
		4713	watchers and events.
		4714
		4715	=item pending
		4716
		4717	A watcher is pending as soon as the corresponding event has been detected,
		4718	and stops being pending as soon as the watcher will be invoked or its
		4719	pending status is explicitly cleared by the application.
		4720
		4721	A watcher can be pending, but not active. Stopping a watcher also clears
		4722	its pending status.
		4723
		4724	=item real time
		4725
		4726	The physical time that is observed. It is apparently strictly monotonic :)
		4727
		4728	=item wall-clock time
		4729
		4730	The time and date as shown on clocks. Unlike real time, it can actually
		4731	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4732	clock.
		4733
		4734	=item watcher
		4735
		4736	A data structure that describes interest in certain events. Watchers need
		4737	to be started (attached to an event loop) before they can receive events.
		4738
		4739	=item watcher invocation
		4740
		4741	The act of calling the callback associated with a watcher.
		4742
		4743	=back
3016		4744
3017	=head1 AUTHOR	4745	=head1 AUTHOR
3018		4746
3019	Marc Lehmann <libev@schmorp.de>.	4747	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3020		4748

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