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Revision 1.281 by root, Tue Mar 9 08:46:17 2010 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	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
116	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
117	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
118	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
119	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
120	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
121		157
122	=head1 GLOBAL FUNCTIONS	158	=head1 GLOBAL FUNCTIONS
123		159
124	These functions can be called anytime, even before initialising the	160	These functions can be called anytime, even before initialising the
125	library in any way.	161	library in any way.
…		…
134		170
135	=item ev_sleep (ev_tstamp interval)	171	=item ev_sleep (ev_tstamp interval)
136		172
137	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
138	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
139	this is a subsecond-resolution C<sleep ()>.	175	this is a sub-second-resolution C<sleep ()>.
140		176
141	=item int ev_version_major ()	177	=item int ev_version_major ()
142		178
143	=item int ev_version_minor ()	179	=item int ev_version_minor ()
144		180
…		…
157	not a problem.	193	not a problem.
158		194
159	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
160	version.	196	version.
161		197
162	assert (("libev version mismatch",	198	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	199	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	200	&& ev_version_minor () >= EV_VERSION_MINOR));
165		201
166	=item unsigned int ev_supported_backends ()	202	=item unsigned int ev_supported_backends ()
167		203
168	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_*>
169	value) compiled into this binary of libev (independent of their	205	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	207	a description of the set values.
172		208
173	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
174	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
175		211
176	assert (("sorry, no epoll, no sex",	212	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	213	ev_supported_backends () & EVBACKEND_EPOLL));
178		214
179	=item unsigned int ev_recommended_backends ()	215	=item unsigned int ev_recommended_backends ()
180		216
181	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
182	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
183	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
184	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
185	(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
186	libev will probe for if you specify no backends explicitly.	222	libev will probe for if you specify no backends explicitly.
187		223
188	=item unsigned int ev_embeddable_backends ()	224	=item unsigned int ev_embeddable_backends ()
189		225
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	230	recommended ones.
195		231
196	See the description of C<ev_embed> watchers for more info.	232	See the description of C<ev_embed> watchers for more info.
197		233
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		235
200	Sets the allocation function to use (the prototype is similar - the	236	Sets the allocation function to use (the prototype is similar - the
201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	238	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	239	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	265	}
230		266
231	...	267	...
232	ev_set_allocator (persistent_realloc);	268	ev_set_allocator (persistent_realloc);
233		269
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		271
236	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
237	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
238	indicating the system call or subsystem causing the problem. If this	274	indicating the system call or subsystem causing the problem. If this
239	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
240	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
241	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
242	(such as abort).	278	(such as abort).
243		279
244	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.
…		…
255		291
256	=back	292	=back
257		293
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		295
260	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>
261	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>
262	events, and dynamically created loops which do not.	298	I<function>).
		299
		300	The library knows two types of such loops, the I<default> loop, which
		301	supports signals and child events, and dynamically created loops which do
		302	not.
263		303
264	=over 4	304	=over 4
265		305
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		307
…		…
273	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
274	function.	314	function.
275		315
276	Note that this function is I<not> thread-safe, so if you want to use it	316	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	317	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
279		319
280	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
281	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
282	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
283	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
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	325	C<ev_default_init>.
286		326
287	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
…		…
296	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
297	thing, believe me).	337	thing, believe me).
298		338
299	=item C<EVFLAG_NOENV>	339	=item C<EVFLAG_NOENV>
300		340
301	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
302	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
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	343	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	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
305	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
306	around bugs.	346	around bugs.
…		…
313		353
314	This works by calling C<getpid ()> on every iteration of the loop,	354	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	355	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	356	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	358	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	359	C<pthread_atfork> which is even faster).
320		360
321	The big advantage of this flag is that you can forget about fork (and	361	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	362	forget about forgetting to tell libev about forking) when you use this
323	flag.	363	flag.
324		364
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	366	environment variable.
		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
327		387
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		389
330	This is your standard select(2) backend. Not I<completely> standard, as	390	This is your standard select(2) backend. Not I<completely> standard, as
331	libev tries to roll its own fd_set with no limits on the number of fds,	391	libev tries to roll its own fd_set with no limits on the number of fds,
332	but if that fails, expect a fairly low limit on the number of fds when	392	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	393	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	394	usually the fastest backend for a low number of (low-numbered :) fds.
335		395
336	To get good performance out of this backend you need a high amount of	396	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	397	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	398	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	399	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	400	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness notifications you get per iteration.	401	readiness notifications you get per iteration.
		402
		403	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		404	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		405	C<exceptfds> set on that platform).
342		406
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	407	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		408
345	And this is your standard poll(2) backend. It's more complicated	409	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	410	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	411	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	412	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	413	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	414	performance tips.
351		415
		416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		418
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
353		423
354	For few fds, this backend is a bit little slower than poll and select,	424	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	425	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	426	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	427	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	428
359	cases and requiring a syscall per fd change, no fork support and bad	429	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	430	of the more advanced event mechanisms: mere annoyances include silently
		431	dropping file descriptors, requiring a system call per change per file
		432	descriptor (and unnecessary guessing of parameters), problems with dup and
		433	so on. The biggest issue is fork races, however - if a program forks then
		434	I<both> parent and child process have to recreate the epoll set, which can
		435	take considerable time (one syscall per file descriptor) and is of course
		436	hard to detect.
		437
		438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		439	of course I<doesn't>, and epoll just loves to report events for totally
		440	I<different> file descriptors (even already closed ones, so one cannot
		441	even remove them from the set) than registered in the set (especially
		442	on SMP systems). Libev tries to counter these spurious notifications by
		443	employing an additional generation counter and comparing that against the
		444	events to filter out spurious ones, recreating the set when required.
361		445
362	While stopping, setting and starting an I/O watcher in the same iteration	446	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	447	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	448	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	450	file descriptors might not work very well if you register events for both
367		451	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		452
372	Best performance from this backend is achieved by not unregistering all	453	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	454	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	455	i.e. keep at least one watcher active per fd at all times. Stopping and
		456	starting a watcher (without re-setting it) also usually doesn't cause
		457	extra overhead. A fork can both result in spurious notifications as well
		458	as in libev having to destroy and recreate the epoll object, which can
		459	take considerable time and thus should be avoided.
375		460
		461	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		462	faster than epoll for maybe up to a hundred file descriptors, depending on
		463	the usage. So sad.
		464
376	While nominally embeddeble in other event loops, this feature is broken in	465	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	466	all kernel versions tested so far.
		467
		468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		469	C<EVBACKEND_POLL>.
378		470
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		472
381	Kqueue deserves special mention, as at the time of this writing, it	473	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	474	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	475	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	476	it's completely useless). Unlike epoll, however, whose brokenness
		477	is by design, these kqueue bugs can (and eventually will) be fixed
		478	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	479	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	480	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	481	system like NetBSD.
388		482
389	You still can embed kqueue into a normal poll or select backend and use it	483	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	484	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	485	the target platform). See C<ev_embed> watchers for more info.
392		486
393	It scales in the same way as the epoll backend, but the interface to the	487	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	488	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	489	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	491	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		493	cases
399		494
400	This backend usually performs well under most conditions.	495	This backend usually performs well under most conditions.
401		496
402	While nominally embeddable in other event loops, this doesn't work	497	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	498	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	499	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	500	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	501	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	502	also broken on OS X)) and, did I mention it, using it only for sockets.
		503
		504	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		505	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		506	C<NOTE_EOF>.
408		507
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	508	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		509
411	This is not implemented yet (and might never be, unless you send me an	510	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	511	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		516
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	518	it's really slow, but it still scales very well (O(active_fds)).
420		519
421	Please note that solaris event ports can deliver a lot of spurious	520	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	521	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	522	blocking when no data (or space) is available.
424		523
425	While this backend scales well, it requires one system call per active	524	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	525	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	527	might perform better.
429		528
430	On the positive side, ignoring the spurious readiness notifications, this	529	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	530	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	531	in all tests and is fully embeddable, which is a rare feat among the
		532	OS-specific backends (I vastly prefer correctness over speed hacks).
		533
		534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		535	C<EVBACKEND_POLL>.
433		536
434	=item C<EVBACKEND_ALL>	537	=item C<EVBACKEND_ALL>
435		538
436	Try all backends (even potentially broken ones that wouldn't be tried	539	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		542
440	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
441		544
442	=back	545	=back
443		546
444	If one or more of these are ored into the flags value, then only these	547	If one or more of the backend flags are or'ed into the flags value,
445	backends will be tried (in the reverse order as listed here). If none are	548	then only these backends will be tried (in the reverse order as listed
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
447		551
448	The most typical usage is like this:	552	Example: This is the most typical usage.
449		553
450	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		556
453	Restrict libev to the select and poll backends, and do not allow	557	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	558	environment settings to be taken into account:
455		559
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		561
458	Use whatever libev has to offer, but make sure that kqueue is used if	562	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	563	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	564	private event loop and only if you know the OS supports your types of
		565	fds):
461		566
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		568
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	569	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		570
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	571	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	572	always distinct from the default loop. Unlike the default loop, it cannot
…		…
472	libev with threads is indeed to create one loop per thread, and using the	577	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	578	default loop in the "main" or "initial" thread.
474		579
475	Example: Try to create a event loop that uses epoll and nothing else.	580	Example: Try to create a event loop that uses epoll and nothing else.
476		581
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	583	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	584	fatal ("no epoll found here, maybe it hides under your chair");
480		585
481	=item ev_default_destroy ()	586	=item ev_default_destroy ()
482		587
483	Destroys the default loop again (frees all memory and kernel state	588	Destroys the default loop again (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	589	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	590	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	591	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	592	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	593	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	594	for example).
490		595
491	Note that certain global state, such as signal state, will not be freed by	596	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	597	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	598	as signal and child watchers) would need to be stopped manually.
494		599
495	In general it is not advisable to call this function except in the	600	In general it is not advisable to call this function except in the
496	rare occasion where you really need to free e.g. the signal handling	601	rare occasion where you really need to free e.g. the signal handling
497	pipe fds. If you need dynamically allocated loops it is better to use	602	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	603	C<ev_loop_new> and C<ev_loop_destroy>.
499		604
500	=item ev_loop_destroy (loop)	605	=item ev_loop_destroy (loop)
501		606
502	Like C<ev_default_destroy>, but destroys an event loop created by an	607	Like C<ev_default_destroy>, but destroys an event loop created by an
503	earlier call to C<ev_loop_new>.	608	earlier call to C<ev_loop_new>.
…		…
523		628
524	=item ev_loop_fork (loop)	629	=item ev_loop_fork (loop)
525		630
526	Like C<ev_default_fork>, but acts on an event loop created by	631	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	632	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.	633	after fork that you want to re-use in the child, and how you do this is
		634	entirely your own problem.
529		635
530	=item int ev_is_default_loop (loop)	636	=item int ev_is_default_loop (loop)
531		637
532	Returns true when the given loop actually is the default loop, false otherwise.	638	Returns true when the given loop is, in fact, the default loop, and false
		639	otherwise.
533		640
534	=item unsigned int ev_loop_count (loop)	641	=item unsigned int ev_loop_count (loop)
535		642
536	Returns the count of loop iterations for the loop, which is identical to	643	Returns the count of loop iterations for the loop, which is identical to
537	the number of times libev did poll for new events. It starts at C<0> and	644	the number of times libev did poll for new events. It starts at C<0> and
538	happily wraps around with enough iterations.	645	happily wraps around with enough iterations.
539		646
540	This value can sometimes be useful as a generation counter of sorts (it	647	This value can sometimes be useful as a generation counter of sorts (it
541	"ticks" the number of loop iterations), as it roughly corresponds with	648	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	649	C<ev_prepare> and C<ev_check> calls.
		650
		651	=item unsigned int ev_loop_depth (loop)
		652
		653	Returns the number of times C<ev_loop> was entered minus the number of
		654	times C<ev_loop> was exited, in other words, the recursion depth.
		655
		656	Outside C<ev_loop>, this number is zero. In a callback, this number is
		657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		658	in which case it is higher.
		659
		660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		661	etc.), doesn't count as exit.
543		662
544	=item unsigned int ev_backend (loop)	663	=item unsigned int ev_backend (loop)
545		664
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	666	use.
…		…
552	received events and started processing them. This timestamp does not	671	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	672	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	673	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	674	event occurring (or more correctly, libev finding out about it).
556		675
		676	=item ev_now_update (loop)
		677
		678	Establishes the current time by querying the kernel, updating the time
		679	returned by C<ev_now ()> in the progress. This is a costly operation and
		680	is usually done automatically within C<ev_loop ()>.
		681
		682	This function is rarely useful, but when some event callback runs for a
		683	very long time without entering the event loop, updating libev's idea of
		684	the current time is a good idea.
		685
		686	See also L<The special problem of time updates> in the C<ev_timer> section.
		687
		688	=item ev_suspend (loop)
		689
		690	=item ev_resume (loop)
		691
		692	These two functions suspend and resume a loop, for use when the loop is
		693	not used for a while and timeouts should not be processed.
		694
		695	A typical use case would be an interactive program such as a game: When
		696	the user presses C<^Z> to suspend the game and resumes it an hour later it
		697	would be best to handle timeouts as if no time had actually passed while
		698	the program was suspended. This can be achieved by calling C<ev_suspend>
		699	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		700	C<ev_resume> directly afterwards to resume timer processing.
		701
		702	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		703	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		704	will be rescheduled (that is, they will lose any events that would have
		705	occured while suspended).
		706
		707	After calling C<ev_suspend> you B<must not> call I<any> function on the
		708	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		709	without a previous call to C<ev_suspend>.
		710
		711	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		712	event loop time (see C<ev_now_update>).
		713
557	=item ev_loop (loop, int flags)	714	=item ev_loop (loop, int flags)
558		715
559	Finally, this is it, the event handler. This function usually is called	716	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	717	after you have initialised all your watchers and you want to start
561	events.	718	handling events.
562		719
563	If the flags argument is specified as C<0>, it will not return until	720	If the flags argument is specified as C<0>, it will not return until
564	either no event watchers are active anymore or C<ev_unloop> was called.	721	either no event watchers are active anymore or C<ev_unloop> was called.
565		722
566	Please note that an explicit C<ev_unloop> is usually better than	723	Please note that an explicit C<ev_unloop> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	724	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	725	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	726	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	727	of relying on its watchers stopping correctly, that is truly a thing of
		728	beauty.
571		729
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	730	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	731	those events and any already outstanding ones, but will not block your
574	case there are no events and will return after one iteration of the loop.	732	process in case there are no events and will return after one iteration of
		733	the loop.
575		734
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	735	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	736	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	737	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	738	be an event internal to libev itself, so there is no guarantee that a
580	external event in conjunction with something not expressible using other	739	user-registered callback will be called), and will return after one
		740	iteration of the loop.
		741
		742	This is useful if you are waiting for some external event in conjunction
		743	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	744	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	745	usually a better approach for this kind of thing.
583		746
584	Here are the gory details of what C<ev_loop> does:	747	Here are the gory details of what C<ev_loop> does:
585		748
586	- Before the first iteration, call any pending watchers.	749	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	750	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	751	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	752	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	753	- If we have been forked, detach and recreate the kernel state
		754	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	755	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	756	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	757	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	758	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	759	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	760	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	761	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	762	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	763	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	764	- Queue all expired timers.
601	- Queue all outstanding periodics.	765	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	766	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	767	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	768	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	769	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	770	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	771	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	776	anymore.
613		777
614	... queue jobs here, make sure they register event watchers as long	778	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	779	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	780	ev_loop (my_loop, 0);
617	... jobs done. yeah!	781	... jobs done or somebody called unloop. yeah!
618		782
619	=item ev_unloop (loop, how)	783	=item ev_unloop (loop, how)
620		784
621	Can be used to make a call to C<ev_loop> return early (but only after it	785	Can be used to make a call to C<ev_loop> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	786	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	787	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	788	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		789
626	This "unloop state" will be cleared when entering C<ev_loop> again.	790	This "unloop state" will be cleared when entering C<ev_loop> again.
627		791
		792	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		793
628	=item ev_ref (loop)	794	=item ev_ref (loop)
629		795
630	=item ev_unref (loop)	796	=item ev_unref (loop)
631		797
632	Ref/unref can be used to add or remove a reference count on the event	798	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	799	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	800	count is nonzero, C<ev_loop> will not return on its own.
635	a watcher you never unregister that should not keep C<ev_loop> from	801
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	802	This is useful when you have a watcher that you never intend to
		803	unregister, but that nevertheless should not keep C<ev_loop> from
		804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		805	before stopping it.
		806
637	example, libev itself uses this for its internal signal pipe: It is not	807	As an example, libev itself uses this for its internal signal pipe: It
638	visible to the libev user and should not keep C<ev_loop> from exiting if	808	is not visible to the libev user and should not keep C<ev_loop> from
639	no event watchers registered by it are active. It is also an excellent	809	exiting if no event watchers registered by it are active. It is also an
640	way to do this for generic recurring timers or from within third-party	810	excellent way to do this for generic recurring timers or from within
641	libraries. Just remember to I<unref after start> and I<ref before stop>	811	third-party libraries. Just remember to I<unref after start> and I<ref
642	(but only if the watcher wasn't active before, or was active before,	812	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	813	before, respectively. Note also that libev might stop watchers itself
		814	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		815	in the callback).
644		816
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	817	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	818	running when nothing else is active.
647		819
648	struct ev_signal exitsig;	820	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	821	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	822	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	823	evf_unref (loop);
652		824
653	Example: For some weird reason, unregister the above signal handler again.	825	Example: For some weird reason, unregister the above signal handler again.
654		826
655	ev_ref (loop);	827	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	828	ev_signal_stop (loop, &exitsig);
657		829
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	830	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		831
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	832	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		833
662	These advanced functions influence the time that libev will spend waiting	834	These advanced functions influence the time that libev will spend waiting
663	for events. Both are by default C<0>, meaning that libev will try to	835	for events. Both time intervals are by default C<0>, meaning that libev
664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	836	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		837	latency.
665		838
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	839	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
667	allows libev to delay invocation of I/O and timer/periodic callbacks to	840	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	841	to increase efficiency of loop iterations (or to increase power-saving
		842	opportunities).
669		843
670	The background is that sometimes your program runs just fast enough to	844	The idea is that sometimes your program runs just fast enough to handle
671	handle one (or very few) event(s) per loop iteration. While this makes	845	one (or very few) event(s) per loop iteration. While this makes the
672	the program responsive, it also wastes a lot of CPU time to poll for new	846	program responsive, it also wastes a lot of CPU time to poll for new
673	events, especially with backends like C<select ()> which have a high	847	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	848	overhead for the actual polling but can deliver many events at once.
675		849
676	By setting a higher I<io collect interval> you allow libev to spend more	850	By setting a higher I<io collect interval> you allow libev to spend more
677	time collecting I/O events, so you can handle more events per iteration,	851	time collecting I/O events, so you can handle more events per iteration,
678	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	852	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	853	C<ev_timer>) will be not affected. Setting this to a non-null value will
680	introduce an additional C<ev_sleep ()> call into most loop iterations.	854	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		855	sleep time ensures that libev will not poll for I/O events more often then
		856	once per this interval, on average.
681		857
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	858	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	859	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	860	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	861	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	862	value will not introduce any overhead in libev.
687		863
688	Many (busy) programs can usually benefit by setting the io collect	864	Many (busy) programs can usually benefit by setting the I/O collect
689	interval to a value near C<0.1> or so, which is often enough for	865	interval to a value near C<0.1> or so, which is often enough for
690	interactive servers (of course not for games), likewise for timeouts. It	866	interactive servers (of course not for games), likewise for timeouts. It
691	usually doesn't make much sense to set it to a lower value than C<0.01>,	867	usually doesn't make much sense to set it to a lower value than C<0.01>,
692	as this approsaches the timing granularity of most systems.	868	as this approaches the timing granularity of most systems. Note that if
		869	you do transactions with the outside world and you can't increase the
		870	parallelity, then this setting will limit your transaction rate (if you
		871	need to poll once per transaction and the I/O collect interval is 0.01,
		872	then you can't do more than 100 transations per second).
		873
		874	Setting the I<timeout collect interval> can improve the opportunity for
		875	saving power, as the program will "bundle" timer callback invocations that
		876	are "near" in time together, by delaying some, thus reducing the number of
		877	times the process sleeps and wakes up again. Another useful technique to
		878	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		879	they fire on, say, one-second boundaries only.
		880
		881	Example: we only need 0.1s timeout granularity, and we wish not to poll
		882	more often than 100 times per second:
		883
		884	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		886
		887	=item ev_invoke_pending (loop)
		888
		889	This call will simply invoke all pending watchers while resetting their
		890	pending state. Normally, C<ev_loop> does this automatically when required,
		891	but when overriding the invoke callback this call comes handy.
		892
		893	=item int ev_pending_count (loop)
		894
		895	Returns the number of pending watchers - zero indicates that no watchers
		896	are pending.
		897
		898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		899
		900	This overrides the invoke pending functionality of the loop: Instead of
		901	invoking all pending watchers when there are any, C<ev_loop> will call
		902	this callback instead. This is useful, for example, when you want to
		903	invoke the actual watchers inside another context (another thread etc.).
		904
		905	If you want to reset the callback, use C<ev_invoke_pending> as new
		906	callback.
		907
		908	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		909
		910	Sometimes you want to share the same loop between multiple threads. This
		911	can be done relatively simply by putting mutex_lock/unlock calls around
		912	each call to a libev function.
		913
		914	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		915	wait for it to return. One way around this is to wake up the loop via
		916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		917	and I<acquire> callbacks on the loop.
		918
		919	When set, then C<release> will be called just before the thread is
		920	suspended waiting for new events, and C<acquire> is called just
		921	afterwards.
		922
		923	Ideally, C<release> will just call your mutex_unlock function, and
		924	C<acquire> will just call the mutex_lock function again.
		925
		926	While event loop modifications are allowed between invocations of
		927	C<release> and C<acquire> (that's their only purpose after all), no
		928	modifications done will affect the event loop, i.e. adding watchers will
		929	have no effect on the set of file descriptors being watched, or the time
		930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		931	to take note of any changes you made.
		932
		933	In theory, threads executing C<ev_loop> will be async-cancel safe between
		934	invocations of C<release> and C<acquire>.
		935
		936	See also the locking example in the C<THREADS> section later in this
		937	document.
		938
		939	=item ev_set_userdata (loop, void *data)
		940
		941	=item ev_userdata (loop)
		942
		943	Set and retrieve a single C<void *> associated with a loop. When
		944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		945	C<0.>
		946
		947	These two functions can be used to associate arbitrary data with a loop,
		948	and are intended solely for the C<invoke_pending_cb>, C<release> and
		949	C<acquire> callbacks described above, but of course can be (ab-)used for
		950	any other purpose as well.
		951
		952	=item ev_loop_verify (loop)
		953
		954	This function only does something when C<EV_VERIFY> support has been
		955	compiled in, which is the default for non-minimal builds. It tries to go
		956	through all internal structures and checks them for validity. If anything
		957	is found to be inconsistent, it will print an error message to standard
		958	error and call C<abort ()>.
		959
		960	This can be used to catch bugs inside libev itself: under normal
		961	circumstances, this function will never abort as of course libev keeps its
		962	data structures consistent.
693		963
694	=back	964	=back
695		965
696		966
697	=head1 ANATOMY OF A WATCHER	967	=head1 ANATOMY OF A WATCHER
		968
		969	In the following description, uppercase C<TYPE> in names stands for the
		970	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		971	watchers and C<ev_io_start> for I/O watchers.
698		972
699	A watcher is a structure that you create and register to record your	973	A watcher is a structure that you create and register to record your
700	interest in some event. For instance, if you want to wait for STDIN to	974	interest in some event. For instance, if you want to wait for STDIN to
701	become readable, you would create an C<ev_io> watcher for that:	975	become readable, you would create an C<ev_io> watcher for that:
702		976
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	977	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	978	{
705	ev_io_stop (w);	979	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	980	ev_unloop (loop, EVUNLOOP_ALL);
707	}	981	}
708		982
709	struct ev_loop *loop = ev_default_loop (0);	983	struct ev_loop *loop = ev_default_loop (0);
		984
710	struct ev_io stdin_watcher;	985	ev_io stdin_watcher;
		986
711	ev_init (&stdin_watcher, my_cb);	987	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	989	ev_io_start (loop, &stdin_watcher);
		990
714	ev_loop (loop, 0);	991	ev_loop (loop, 0);
715		992
716	As you can see, you are responsible for allocating the memory for your	993	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	994	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	995	stack).
		996
		997	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		998	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		999
720	Each watcher structure must be initialised by a call to C<ev_init	1000	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	1001	(watcher *, callback)>, which expects a callback to be provided. This
722	callback gets invoked each time the event occurs (or, in the case of io	1002	callback gets invoked each time the event occurs (or, in the case of I/O
723	watchers, each time the event loop detects that the file descriptor given	1003	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	1004	is readable and/or writable).
725		1005
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1006	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
727	with arguments specific to this watcher type. There is also a macro	1007	macro to configure it, with arguments specific to the watcher type. There
728	to combine initialisation and setting in one call: C<< ev_<type>_init	1008	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	1009	ev_TYPE_init (watcher *, callback, ...) >>.
730		1010
731	To make the watcher actually watch out for events, you have to start it	1011	To make the watcher actually watch out for events, you have to start it
732	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1012	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
733	*) >>), and you can stop watching for events at any time by calling the	1013	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1014	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		1015
736	As long as your watcher is active (has been started but not stopped) you	1016	As long as your watcher is active (has been started but not stopped) you
737	must not touch the values stored in it. Most specifically you must never	1017	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	1018	reinitialise it or call its C<ev_TYPE_set> macro.
739		1019
740	Each and every callback receives the event loop pointer as first, the	1020	Each and every callback receives the event loop pointer as first, the
741	registered watcher structure as second, and a bitset of received events as	1021	registered watcher structure as second, and a bitset of received events as
742	third argument.	1022	third argument.
743		1023
…		…
801		1081
802	=item C<EV_ASYNC>	1082	=item C<EV_ASYNC>
803		1083
804	The given async watcher has been asynchronously notified (see C<ev_async>).	1084	The given async watcher has been asynchronously notified (see C<ev_async>).
805		1085
		1086	=item C<EV_CUSTOM>
		1087
		1088	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1089	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1090
806	=item C<EV_ERROR>	1091	=item C<EV_ERROR>
807		1092
808	An unspecified error has occured, the watcher has been stopped. This might	1093	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	1094	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	1095	ran out of memory, a file descriptor was found to be closed or any other
		1096	problem. Libev considers these application bugs.
		1097
811	problem. You best act on it by reporting the problem and somehow coping	1098	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	1099	watcher being stopped. Note that well-written programs should not receive
		1100	an error ever, so when your watcher receives it, this usually indicates a
		1101	bug in your program.
813		1102
814	Libev will usually signal a few "dummy" events together with an error,	1103	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	1104	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	1105	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	1106	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	1107	programs, though, as the fd could already be closed and reused for another
		1108	thing, so beware.
819		1109
820	=back	1110	=back
821		1111
822	=head2 GENERIC WATCHER FUNCTIONS	1112	=head2 GENERIC WATCHER FUNCTIONS
823
824	In the following description, C<TYPE> stands for the watcher type,
825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
826		1113
827	=over 4	1114	=over 4
828		1115
829	=item C<ev_init> (ev_TYPE *watcher, callback)	1116	=item C<ev_init> (ev_TYPE *watcher, callback)
830		1117
…		…
836	which rolls both calls into one.	1123	which rolls both calls into one.
837		1124
838	You can reinitialise a watcher at any time as long as it has been stopped	1125	You can reinitialise a watcher at any time as long as it has been stopped
839	(or never started) and there are no pending events outstanding.	1126	(or never started) and there are no pending events outstanding.
840		1127
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1128	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	1129	int revents)>.
843		1130
		1131	Example: Initialise an C<ev_io> watcher in two steps.
		1132
		1133	ev_io w;
		1134	ev_init (&w, my_cb);
		1135	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1136
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1137	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
845		1138
846	This macro initialises the type-specific parts of a watcher. You need to	1139	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	1140	call C<ev_init> at least once before you call this macro, but you can
848	call C<ev_TYPE_set> any number of times. You must not, however, call this	1141	call C<ev_TYPE_set> any number of times. You must not, however, call this
849	macro on a watcher that is active (it can be pending, however, which is a	1142	macro on a watcher that is active (it can be pending, however, which is a
850	difference to the C<ev_init> macro).	1143	difference to the C<ev_init> macro).
851		1144
852	Although some watcher types do not have type-specific arguments	1145	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1146	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		1147
		1148	See C<ev_init>, above, for an example.
		1149
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1150	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		1151
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1152	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	1153	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	1154	a watcher. The same limitations apply, of course.
860		1155
		1156	Example: Initialise and set an C<ev_io> watcher in one step.
		1157
		1158	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1159
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1160	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
862		1161
863	Starts (activates) the given watcher. Only active watchers will receive	1162	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1163	events. If the watcher is already active nothing will happen.
865		1164
		1165	Example: Start the C<ev_io> watcher that is being abused as example in this
		1166	whole section.
		1167
		1168	ev_io_start (EV_DEFAULT_UC, &w);
		1169
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1170	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
867		1171
868	Stops the given watcher again (if active) and clears the pending	1172	Stops the given watcher if active, and clears the pending status (whether
		1173	the watcher was active or not).
		1174
869	status. It is possible that stopped watchers are pending (for example,	1175	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1176	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1177	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	1178	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	1179	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1180
875	=item bool ev_is_active (ev_TYPE *watcher)	1181	=item bool ev_is_active (ev_TYPE *watcher)
876		1182
877	Returns a true value iff the watcher is active (i.e. it has been started	1183	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	1184	and not yet been stopped). As long as a watcher is active you must not modify
…		…
894	=item ev_cb_set (ev_TYPE *watcher, callback)	1200	=item ev_cb_set (ev_TYPE *watcher, callback)
895		1201
896	Change the callback. You can change the callback at virtually any time	1202	Change the callback. You can change the callback at virtually any time
897	(modulo threads).	1203	(modulo threads).
898		1204
899	=item ev_set_priority (ev_TYPE *watcher, priority)	1205	=item ev_set_priority (ev_TYPE *watcher, int priority)
900		1206
901	=item int ev_priority (ev_TYPE *watcher)	1207	=item int ev_priority (ev_TYPE *watcher)
902		1208
903	Set and query the priority of the watcher. The priority is a small	1209	Set and query the priority of the watcher. The priority is a small
904	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1210	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
905	(default: C<-2>). Pending watchers with higher priority will be invoked	1211	(default: C<-2>). Pending watchers with higher priority will be invoked
906	before watchers with lower priority, but priority will not keep watchers	1212	before watchers with lower priority, but priority will not keep watchers
907	from being executed (except for C<ev_idle> watchers).	1213	from being executed (except for C<ev_idle> watchers).
908		1214
909	This means that priorities are I<only> used for ordering callback
910	invocation after new events have been received. This is useful, for
911	example, to reduce latency after idling, or more often, to bind two
912	watchers on the same event and make sure one is called first.
913
914	If you need to suppress invocation when higher priority events are pending	1215	If you need to suppress invocation when higher priority events are pending
915	you need to look at C<ev_idle> watchers, which provide this functionality.	1216	you need to look at C<ev_idle> watchers, which provide this functionality.
916		1217
917	You I<must not> change the priority of a watcher as long as it is active or	1218	You I<must not> change the priority of a watcher as long as it is active or
918	pending.	1219	pending.
919		1220
		1221	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1222	fine, as long as you do not mind that the priority value you query might
		1223	or might not have been clamped to the valid range.
		1224
920	The default priority used by watchers when no priority has been set is	1225	The default priority used by watchers when no priority has been set is
921	always C<0>, which is supposed to not be too high and not be too low :).	1226	always C<0>, which is supposed to not be too high and not be too low :).
922		1227
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1228	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
924	fine, as long as you do not mind that the priority value you query might	1229	priorities.
925	or might not have been adjusted to be within valid range.
926		1230
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1231	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1232
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1233	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1234	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1235	can deal with that fact, as both are simply passed through to the
		1236	callback.
932		1237
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1238	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1239
935	If the watcher is pending, this function returns clears its pending status	1240	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1241	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1242	watcher isn't pending it does nothing and returns C<0>.
938		1243
		1244	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1245	callback to be invoked, which can be accomplished with this function.
		1246
		1247	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1248
		1249	Feeds the given event set into the event loop, as if the specified event
		1250	had happened for the specified watcher (which must be a pointer to an
		1251	initialised but not necessarily started event watcher). Obviously you must
		1252	not free the watcher as long as it has pending events.
		1253
		1254	Stopping the watcher, letting libev invoke it, or calling
		1255	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1256	not started in the first place.
		1257
		1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1259	functions that do not need a watcher.
		1260
939	=back	1261	=back
940		1262
941		1263
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1265
944	Each watcher has, by default, a member C<void *data> that you can change	1266	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1267	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1268	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1269	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1270	member, you can also "subclass" the watcher type and provide your own
949	data:	1271	data:
950		1272
951	struct my_io	1273	struct my_io
952	{	1274	{
953	struct ev_io io;	1275	ev_io io;
954	int otherfd;	1276	int otherfd;
955	void *somedata;	1277	void *somedata;
956	struct whatever *mostinteresting;	1278	struct whatever *mostinteresting;
957	}	1279	};
		1280
		1281	...
		1282	struct my_io w;
		1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1284
959	And since your callback will be called with a pointer to the watcher, you	1285	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1286	can cast it back to your own type:
961		1287
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1288	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1289	{
964	struct my_io *w = (struct my_io *)w_;	1290	struct my_io *w = (struct my_io *)w_;
965	...	1291	...
966	}	1292	}
967		1293
968	More interesting and less C-conformant ways of casting your callback type	1294	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1295	instead have been omitted.
970		1296
971	Another common scenario is having some data structure with multiple	1297	Another common scenario is to use some data structure with multiple
972	watchers:	1298	embedded watchers:
973		1299
974	struct my_biggy	1300	struct my_biggy
975	{	1301	{
976	int some_data;	1302	int some_data;
977	ev_timer t1;	1303	ev_timer t1;
978	ev_timer t2;	1304	ev_timer t2;
979	}	1305	}
980		1306
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1307	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1308	complicated: Either you store the address of your C<my_biggy> struct
		1309	in the C<data> member of the watcher (for woozies), or you need to use
		1310	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1311	programmers):
983		1312
984	#include <stddef.h>	1313	#include <stddef.h>
985		1314
986	static void	1315	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1316	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1317	{
989	struct my_biggy big = (struct my_biggy *	1318	struct my_biggy big = (struct my_biggy *)
990	(((char *)w) - offsetof (struct my_biggy, t1));	1319	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1320	}
992		1321
993	static void	1322	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1323	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1324	{
996	struct my_biggy big = (struct my_biggy *	1325	struct my_biggy big = (struct my_biggy *)
997	(((char *)w) - offsetof (struct my_biggy, t2));	1326	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1327	}
		1328
		1329	=head2 WATCHER PRIORITY MODELS
		1330
		1331	Many event loops support I<watcher priorities>, which are usually small
		1332	integers that influence the ordering of event callback invocation
		1333	between watchers in some way, all else being equal.
		1334
		1335	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1336	description for the more technical details such as the actual priority
		1337	range.
		1338
		1339	There are two common ways how these these priorities are being interpreted
		1340	by event loops:
		1341
		1342	In the more common lock-out model, higher priorities "lock out" invocation
		1343	of lower priority watchers, which means as long as higher priority
		1344	watchers receive events, lower priority watchers are not being invoked.
		1345
		1346	The less common only-for-ordering model uses priorities solely to order
		1347	callback invocation within a single event loop iteration: Higher priority
		1348	watchers are invoked before lower priority ones, but they all get invoked
		1349	before polling for new events.
		1350
		1351	Libev uses the second (only-for-ordering) model for all its watchers
		1352	except for idle watchers (which use the lock-out model).
		1353
		1354	The rationale behind this is that implementing the lock-out model for
		1355	watchers is not well supported by most kernel interfaces, and most event
		1356	libraries will just poll for the same events again and again as long as
		1357	their callbacks have not been executed, which is very inefficient in the
		1358	common case of one high-priority watcher locking out a mass of lower
		1359	priority ones.
		1360
		1361	Static (ordering) priorities are most useful when you have two or more
		1362	watchers handling the same resource: a typical usage example is having an
		1363	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1364	timeouts. Under load, data might be received while the program handles
		1365	other jobs, but since timers normally get invoked first, the timeout
		1366	handler will be executed before checking for data. In that case, giving
		1367	the timer a lower priority than the I/O watcher ensures that I/O will be
		1368	handled first even under adverse conditions (which is usually, but not
		1369	always, what you want).
		1370
		1371	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1372	will only be executed when no same or higher priority watchers have
		1373	received events, they can be used to implement the "lock-out" model when
		1374	required.
		1375
		1376	For example, to emulate how many other event libraries handle priorities,
		1377	you can associate an C<ev_idle> watcher to each such watcher, and in
		1378	the normal watcher callback, you just start the idle watcher. The real
		1379	processing is done in the idle watcher callback. This causes libev to
		1380	continously poll and process kernel event data for the watcher, but when
		1381	the lock-out case is known to be rare (which in turn is rare :), this is
		1382	workable.
		1383
		1384	Usually, however, the lock-out model implemented that way will perform
		1385	miserably under the type of load it was designed to handle. In that case,
		1386	it might be preferable to stop the real watcher before starting the
		1387	idle watcher, so the kernel will not have to process the event in case
		1388	the actual processing will be delayed for considerable time.
		1389
		1390	Here is an example of an I/O watcher that should run at a strictly lower
		1391	priority than the default, and which should only process data when no
		1392	other events are pending:
		1393
		1394	ev_idle idle; // actual processing watcher
		1395	ev_io io; // actual event watcher
		1396
		1397	static void
		1398	io_cb (EV_P_ ev_io *w, int revents)
		1399	{
		1400	// stop the I/O watcher, we received the event, but
		1401	// are not yet ready to handle it.
		1402	ev_io_stop (EV_A_ w);
		1403
		1404	// start the idle watcher to ahndle the actual event.
		1405	// it will not be executed as long as other watchers
		1406	// with the default priority are receiving events.
		1407	ev_idle_start (EV_A_ &idle);
		1408	}
		1409
		1410	static void
		1411	idle_cb (EV_P_ ev_idle *w, int revents)
		1412	{
		1413	// actual processing
		1414	read (STDIN_FILENO, ...);
		1415
		1416	// have to start the I/O watcher again, as
		1417	// we have handled the event
		1418	ev_io_start (EV_P_ &io);
		1419	}
		1420
		1421	// initialisation
		1422	ev_idle_init (&idle, idle_cb);
		1423	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1424	ev_io_start (EV_DEFAULT_ &io);
		1425
		1426	In the "real" world, it might also be beneficial to start a timer, so that
		1427	low-priority connections can not be locked out forever under load. This
		1428	enables your program to keep a lower latency for important connections
		1429	during short periods of high load, while not completely locking out less
		1430	important ones.
999		1431
1000		1432
1001	=head1 WATCHER TYPES	1433	=head1 WATCHER TYPES
1002		1434
1003	This section describes each watcher in detail, but will not repeat	1435	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1459	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1460	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1461	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1462	required if you know what you are doing).
1031		1463
1032	If you must do this, then force the use of a known-to-be-good backend	1464	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1465	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1467	descriptors for which non-blocking operation makes no sense (such as
		1468	files) - libev doesn't guarentee any specific behaviour in that case.
1035		1469
1036	Another thing you have to watch out for is that it is quite easy to	1470	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readiness notifications, that is your callback might	1471	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1473	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1474	lot of those (for example Solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1475	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1476	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1477	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1478
1045	If you cannot run the fd in non-blocking mode (for example you should not	1479	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1480	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1481	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1482	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1483	does this on its own, so its quite safe to use). Some people additionally
		1484	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1485	indefinitely.
		1486
		1487	But really, best use non-blocking mode.
1050		1488
1051	=head3 The special problem of disappearing file descriptors	1489	=head3 The special problem of disappearing file descriptors
1052		1490
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1491	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1492	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1493	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1494	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1495	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1496	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1497	fact, a different file descriptor.
1060		1498
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1529	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1530	C<EVBACKEND_POLL>.
1093		1531
1094	=head3 The special problem of SIGPIPE	1532	=head3 The special problem of SIGPIPE
1095		1533
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1534	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1535	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1536	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1537	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1538
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1539	So when you encounter spurious, unexplained daemon exits, make sure you
1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1540	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104	somewhere, as that would have given you a big clue).	1541	somewhere, as that would have given you a big clue).
1105		1542
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1548	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1549
1113	=item ev_io_set (ev_io *, int fd, int events)	1550	=item ev_io_set (ev_io *, int fd, int events)
1114		1551
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1552	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1553	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1554	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1555
1119	=item int fd [read-only]	1556	=item int fd [read-only]
1120		1557
1121	The file descriptor being watched.	1558	The file descriptor being watched.
1122		1559
…		…
1130		1567
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1568	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1569	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1570	attempt to read a whole line in the callback.
1134		1571
1135	static void	1572	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1573	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1574	{
1138	ev_io_stop (loop, w);	1575	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1576	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1577	}
1141		1578
1142	...	1579	...
1143	struct ev_loop *loop = ev_default_init (0);	1580	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1581	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1582	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1583	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1584	ev_loop (loop, 0);
1148		1585
1149		1586
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1587	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1588
1152	Timer watchers are simple relative timers that generate an event after a	1589	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1590	given time, and optionally repeating in regular intervals after that.
1154		1591
1155	The timers are based on real time, that is, if you register an event that	1592	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to january last	1593	times out after an hour and you reset your system clock to January last
1157	year, it will still time out after (roughly) and hour. "Roughly" because	1594	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1595	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1596	monotonic clock option helps a lot here).
		1597
		1598	The callback is guaranteed to be invoked only I<after> its timeout has
		1599	passed (not I<at>, so on systems with very low-resolution clocks this
		1600	might introduce a small delay). If multiple timers become ready during the
		1601	same loop iteration then the ones with earlier time-out values are invoked
		1602	before ones of the same priority with later time-out values (but this is
		1603	no longer true when a callback calls C<ev_loop> recursively).
		1604
		1605	=head3 Be smart about timeouts
		1606
		1607	Many real-world problems involve some kind of timeout, usually for error
		1608	recovery. A typical example is an HTTP request - if the other side hangs,
		1609	you want to raise some error after a while.
		1610
		1611	What follows are some ways to handle this problem, from obvious and
		1612	inefficient to smart and efficient.
		1613
		1614	In the following, a 60 second activity timeout is assumed - a timeout that
		1615	gets reset to 60 seconds each time there is activity (e.g. each time some
		1616	data or other life sign was received).
		1617
		1618	=over 4
		1619
		1620	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1621
		1622	This is the most obvious, but not the most simple way: In the beginning,
		1623	start the watcher:
		1624
		1625	ev_timer_init (timer, callback, 60., 0.);
		1626	ev_timer_start (loop, timer);
		1627
		1628	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1629	and start it again:
		1630
		1631	ev_timer_stop (loop, timer);
		1632	ev_timer_set (timer, 60., 0.);
		1633	ev_timer_start (loop, timer);
		1634
		1635	This is relatively simple to implement, but means that each time there is
		1636	some activity, libev will first have to remove the timer from its internal
		1637	data structure and then add it again. Libev tries to be fast, but it's
		1638	still not a constant-time operation.
		1639
		1640	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1641
		1642	This is the easiest way, and involves using C<ev_timer_again> instead of
		1643	C<ev_timer_start>.
		1644
		1645	To implement this, configure an C<ev_timer> with a C<repeat> value
		1646	of C<60> and then call C<ev_timer_again> at start and each time you
		1647	successfully read or write some data. If you go into an idle state where
		1648	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1649	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1650
		1651	That means you can ignore both the C<ev_timer_start> function and the
		1652	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1653	member and C<ev_timer_again>.
		1654
		1655	At start:
		1656
		1657	ev_init (timer, callback);
		1658	timer->repeat = 60.;
		1659	ev_timer_again (loop, timer);
		1660
		1661	Each time there is some activity:
		1662
		1663	ev_timer_again (loop, timer);
		1664
		1665	It is even possible to change the time-out on the fly, regardless of
		1666	whether the watcher is active or not:
		1667
		1668	timer->repeat = 30.;
		1669	ev_timer_again (loop, timer);
		1670
		1671	This is slightly more efficient then stopping/starting the timer each time
		1672	you want to modify its timeout value, as libev does not have to completely
		1673	remove and re-insert the timer from/into its internal data structure.
		1674
		1675	It is, however, even simpler than the "obvious" way to do it.
		1676
		1677	=item 3. Let the timer time out, but then re-arm it as required.
		1678
		1679	This method is more tricky, but usually most efficient: Most timeouts are
		1680	relatively long compared to the intervals between other activity - in
		1681	our example, within 60 seconds, there are usually many I/O events with
		1682	associated activity resets.
		1683
		1684	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1685	but remember the time of last activity, and check for a real timeout only
		1686	within the callback:
		1687
		1688	ev_tstamp last_activity; // time of last activity
		1689
		1690	static void
		1691	callback (EV_P_ ev_timer *w, int revents)
		1692	{
		1693	ev_tstamp now = ev_now (EV_A);
		1694	ev_tstamp timeout = last_activity + 60.;
		1695
		1696	// if last_activity + 60. is older than now, we did time out
		1697	if (timeout < now)
		1698	{
		1699	// timeout occured, take action
		1700	}
		1701	else
		1702	{
		1703	// callback was invoked, but there was some activity, re-arm
		1704	// the watcher to fire in last_activity + 60, which is
		1705	// guaranteed to be in the future, so "again" is positive:
		1706	w->repeat = timeout - now;
		1707	ev_timer_again (EV_A_ w);
		1708	}
		1709	}
		1710
		1711	To summarise the callback: first calculate the real timeout (defined
		1712	as "60 seconds after the last activity"), then check if that time has
		1713	been reached, which means something I<did>, in fact, time out. Otherwise
		1714	the callback was invoked too early (C<timeout> is in the future), so
		1715	re-schedule the timer to fire at that future time, to see if maybe we have
		1716	a timeout then.
		1717
		1718	Note how C<ev_timer_again> is used, taking advantage of the
		1719	C<ev_timer_again> optimisation when the timer is already running.
		1720
		1721	This scheme causes more callback invocations (about one every 60 seconds
		1722	minus half the average time between activity), but virtually no calls to
		1723	libev to change the timeout.
		1724
		1725	To start the timer, simply initialise the watcher and set C<last_activity>
		1726	to the current time (meaning we just have some activity :), then call the
		1727	callback, which will "do the right thing" and start the timer:
		1728
		1729	ev_init (timer, callback);
		1730	last_activity = ev_now (loop);
		1731	callback (loop, timer, EV_TIMEOUT);
		1732
		1733	And when there is some activity, simply store the current time in
		1734	C<last_activity>, no libev calls at all:
		1735
		1736	last_actiivty = ev_now (loop);
		1737
		1738	This technique is slightly more complex, but in most cases where the
		1739	time-out is unlikely to be triggered, much more efficient.
		1740
		1741	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1742	callback :) - just change the timeout and invoke the callback, which will
		1743	fix things for you.
		1744
		1745	=item 4. Wee, just use a double-linked list for your timeouts.
		1746
		1747	If there is not one request, but many thousands (millions...), all
		1748	employing some kind of timeout with the same timeout value, then one can
		1749	do even better:
		1750
		1751	When starting the timeout, calculate the timeout value and put the timeout
		1752	at the I<end> of the list.
		1753
		1754	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1755	the list is expected to fire (for example, using the technique #3).
		1756
		1757	When there is some activity, remove the timer from the list, recalculate
		1758	the timeout, append it to the end of the list again, and make sure to
		1759	update the C<ev_timer> if it was taken from the beginning of the list.
		1760
		1761	This way, one can manage an unlimited number of timeouts in O(1) time for
		1762	starting, stopping and updating the timers, at the expense of a major
		1763	complication, and having to use a constant timeout. The constant timeout
		1764	ensures that the list stays sorted.
		1765
		1766	=back
		1767
		1768	So which method the best?
		1769
		1770	Method #2 is a simple no-brain-required solution that is adequate in most
		1771	situations. Method #3 requires a bit more thinking, but handles many cases
		1772	better, and isn't very complicated either. In most case, choosing either
		1773	one is fine, with #3 being better in typical situations.
		1774
		1775	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1776	rather complicated, but extremely efficient, something that really pays
		1777	off after the first million or so of active timers, i.e. it's usually
		1778	overkill :)
		1779
		1780	=head3 The special problem of time updates
		1781
		1782	Establishing the current time is a costly operation (it usually takes at
		1783	least two system calls): EV therefore updates its idea of the current
		1784	time only before and after C<ev_loop> collects new events, which causes a
		1785	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1786	lots of events in one iteration.
1160		1787
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1788	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1789	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1790	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1791	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1792	timeout on the current time, use something like this to adjust for this:
1166		1793
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1794	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1795
1169	The callback is guarenteed to be invoked only after its timeout has passed,	1796	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1797	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1798	()>.
		1799
		1800	=head3 The special problems of suspended animation
		1801
		1802	When you leave the server world it is quite customary to hit machines that
		1803	can suspend/hibernate - what happens to the clocks during such a suspend?
		1804
		1805	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1806	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1807	to run until the system is suspended, but they will not advance while the
		1808	system is suspended. That means, on resume, it will be as if the program
		1809	was frozen for a few seconds, but the suspend time will not be counted
		1810	towards C<ev_timer> when a monotonic clock source is used. The real time
		1811	clock advanced as expected, but if it is used as sole clocksource, then a
		1812	long suspend would be detected as a time jump by libev, and timers would
		1813	be adjusted accordingly.
		1814
		1815	I would not be surprised to see different behaviour in different between
		1816	operating systems, OS versions or even different hardware.
		1817
		1818	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1819	time jump in the monotonic clocks and the realtime clock. If the program
		1820	is suspended for a very long time, and monotonic clock sources are in use,
		1821	then you can expect C<ev_timer>s to expire as the full suspension time
		1822	will be counted towards the timers. When no monotonic clock source is in
		1823	use, then libev will again assume a timejump and adjust accordingly.
		1824
		1825	It might be beneficial for this latter case to call C<ev_suspend>
		1826	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1827	deterministic behaviour in this case (you can do nothing against
		1828	C<SIGSTOP>).
1172		1829
1173	=head3 Watcher-Specific Functions and Data Members	1830	=head3 Watcher-Specific Functions and Data Members
1174		1831
1175	=over 4	1832	=over 4
1176		1833
…		…
1195	This will act as if the timer timed out and restart it again if it is	1852	This will act as if the timer timed out and restart it again if it is
1196	repeating. The exact semantics are:	1853	repeating. The exact semantics are:
1197		1854
1198	If the timer is pending, its pending status is cleared.	1855	If the timer is pending, its pending status is cleared.
1199		1856
1200	If the timer is started but nonrepeating, stop it (as if it timed out).	1857	If the timer is started but non-repeating, stop it (as if it timed out).
1201		1858
1202	If the timer is repeating, either start it if necessary (with the	1859	If the timer is repeating, either start it if necessary (with the
1203	C<repeat> value), or reset the running timer to the C<repeat> value.	1860	C<repeat> value), or reset the running timer to the C<repeat> value.
1204		1861
1205	This sounds a bit complicated, but here is a useful and typical	1862	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1206	example: Imagine you have a tcp connection and you want a so-called idle	1863	usage example.
1207	timeout, that is, you want to be called when there have been, say, 60
1208	seconds of inactivity on the socket. The easiest way to do this is to
1209	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1210	C<ev_timer_again> each time you successfully read or write some data. If
1211	you go into an idle state where you do not expect data to travel on the
1212	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1213	automatically restart it if need be.
1214		1864
1215	That means you can ignore the C<after> value and C<ev_timer_start>	1865	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1216	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1217		1866
1218	ev_timer_init (timer, callback, 0., 5.);	1867	Returns the remaining time until a timer fires. If the timer is active,
1219	ev_timer_again (loop, timer);	1868	then this time is relative to the current event loop time, otherwise it's
1220	...	1869	the timeout value currently configured.
1221	timer->again = 17.;
1222	ev_timer_again (loop, timer);
1223	...
1224	timer->again = 10.;
1225	ev_timer_again (loop, timer);
1226		1870
1227	This is more slightly efficient then stopping/starting the timer each time	1871	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1228	you want to modify its timeout value.	1872	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1873	will return C<4>. When the timer expires and is restarted, it will return
		1874	roughly C<7> (likely slightly less as callback invocation takes some time,
		1875	too), and so on.
1229		1876
1230	=item ev_tstamp repeat [read-write]	1877	=item ev_tstamp repeat [read-write]
1231		1878
1232	The current C<repeat> value. Will be used each time the watcher times out	1879	The current C<repeat> value. Will be used each time the watcher times out
1233	or C<ev_timer_again> is called and determines the next timeout (if any),	1880	or C<ev_timer_again> is called, and determines the next timeout (if any),
1234	which is also when any modifications are taken into account.	1881	which is also when any modifications are taken into account.
1235		1882
1236	=back	1883	=back
1237		1884
1238	=head3 Examples	1885	=head3 Examples
1239		1886
1240	Example: Create a timer that fires after 60 seconds.	1887	Example: Create a timer that fires after 60 seconds.
1241		1888
1242	static void	1889	static void
1243	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1890	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1244	{	1891	{
1245	.. one minute over, w is actually stopped right here	1892	.. one minute over, w is actually stopped right here
1246	}	1893	}
1247		1894
1248	struct ev_timer mytimer;	1895	ev_timer mytimer;
1249	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1896	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1250	ev_timer_start (loop, &mytimer);	1897	ev_timer_start (loop, &mytimer);
1251		1898
1252	Example: Create a timeout timer that times out after 10 seconds of	1899	Example: Create a timeout timer that times out after 10 seconds of
1253	inactivity.	1900	inactivity.
1254		1901
1255	static void	1902	static void
1256	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1903	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1257	{	1904	{
1258	.. ten seconds without any activity	1905	.. ten seconds without any activity
1259	}	1906	}
1260		1907
1261	struct ev_timer mytimer;	1908	ev_timer mytimer;
1262	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1909	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1263	ev_timer_again (&mytimer); /* start timer */	1910	ev_timer_again (&mytimer); /* start timer */
1264	ev_loop (loop, 0);	1911	ev_loop (loop, 0);
1265		1912
1266	// and in some piece of code that gets executed on any "activity":	1913	// and in some piece of code that gets executed on any "activity":
1267	// reset the timeout to start ticking again at 10 seconds	1914	// reset the timeout to start ticking again at 10 seconds
1268	ev_timer_again (&mytimer);	1915	ev_timer_again (&mytimer);
1269		1916
1270		1917
1271	=head2 C<ev_periodic> - to cron or not to cron?	1918	=head2 C<ev_periodic> - to cron or not to cron?
1272		1919
1273	Periodic watchers are also timers of a kind, but they are very versatile	1920	Periodic watchers are also timers of a kind, but they are very versatile
1274	(and unfortunately a bit complex).	1921	(and unfortunately a bit complex).
1275		1922
1276	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1923	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1277	but on wallclock time (absolute time). You can tell a periodic watcher	1924	relative time, the physical time that passes) but on wall clock time
1278	to trigger after some specific point in time. For example, if you tell a	1925	(absolute time, the thing you can read on your calender or clock). The
1279	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1926	difference is that wall clock time can run faster or slower than real
1280	+ 10.>, that is, an absolute time not a delay) and then reset your system	1927	time, and time jumps are not uncommon (e.g. when you adjust your
1281	clock to january of the previous year, then it will take more than year	1928	wrist-watch).
1282	to trigger the event (unlike an C<ev_timer>, which would still trigger
1283	roughly 10 seconds later as it uses a relative timeout).
1284		1929
		1930	You can tell a periodic watcher to trigger after some specific point
		1931	in time: for example, if you tell a periodic watcher to trigger "in 10
		1932	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1933	not a delay) and then reset your system clock to January of the previous
		1934	year, then it will take a year or more to trigger the event (unlike an
		1935	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1936	it, as it uses a relative timeout).
		1937
1285	C<ev_periodic>s can also be used to implement vastly more complex timers,	1938	C<ev_periodic> watchers can also be used to implement vastly more complex
1286	such as triggering an event on each "midnight, local time", or other	1939	timers, such as triggering an event on each "midnight, local time", or
1287	complicated, rules.	1940	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1941	those cannot react to time jumps.
1288		1942
1289	As with timers, the callback is guarenteed to be invoked only when the	1943	As with timers, the callback is guaranteed to be invoked only when the
1290	time (C<at>) has passed, but if multiple periodic timers become ready	1944	point in time where it is supposed to trigger has passed. If multiple
1291	during the same loop iteration then order of execution is undefined.	1945	timers become ready during the same loop iteration then the ones with
		1946	earlier time-out values are invoked before ones with later time-out values
		1947	(but this is no longer true when a callback calls C<ev_loop> recursively).
1292		1948
1293	=head3 Watcher-Specific Functions and Data Members	1949	=head3 Watcher-Specific Functions and Data Members
1294		1950
1295	=over 4	1951	=over 4
1296		1952
1297	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1953	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		1954
1299	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1955	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1300		1956
1301	Lots of arguments, lets sort it out... There are basically three modes of	1957	Lots of arguments, let's sort it out... There are basically three modes of
1302	operation, and we will explain them from simplest to complex:	1958	operation, and we will explain them from simplest to most complex:
1303		1959
1304	=over 4	1960	=over 4
1305		1961
1306	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1962	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1307		1963
1308	In this configuration the watcher triggers an event after the wallclock	1964	In this configuration the watcher triggers an event after the wall clock
1309	time C<at> has passed and doesn't repeat. It will not adjust when a time	1965	time C<offset> has passed. It will not repeat and will not adjust when a
1310	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1966	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1311	run when the system time reaches or surpasses this time.	1967	will be stopped and invoked when the system clock reaches or surpasses
		1968	this point in time.
1312		1969
1313	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1970	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1314		1971
1315	In this mode the watcher will always be scheduled to time out at the next	1972	In this mode the watcher will always be scheduled to time out at the next
1316	C<at + N * interval> time (for some integer N, which can also be negative)	1973	C<offset + N * interval> time (for some integer N, which can also be
1317	and then repeat, regardless of any time jumps.	1974	negative) and then repeat, regardless of any time jumps. The C<offset>
		1975	argument is merely an offset into the C<interval> periods.
1318		1976
1319	This can be used to create timers that do not drift with respect to system	1977	This can be used to create timers that do not drift with respect to the
1320	time, for example, here is a C<ev_periodic> that triggers each hour, on	1978	system clock, for example, here is an C<ev_periodic> that triggers each
1321	the hour:	1979	hour, on the hour (with respect to UTC):
1322		1980
1323	ev_periodic_set (&periodic, 0., 3600., 0);	1981	ev_periodic_set (&periodic, 0., 3600., 0);
1324		1982
1325	This doesn't mean there will always be 3600 seconds in between triggers,	1983	This doesn't mean there will always be 3600 seconds in between triggers,
1326	but only that the the callback will be called when the system time shows a	1984	but only that the callback will be called when the system time shows a
1327	full hour (UTC), or more correctly, when the system time is evenly divisible	1985	full hour (UTC), or more correctly, when the system time is evenly divisible
1328	by 3600.	1986	by 3600.
1329		1987
1330	Another way to think about it (for the mathematically inclined) is that	1988	Another way to think about it (for the mathematically inclined) is that
1331	C<ev_periodic> will try to run the callback in this mode at the next possible	1989	C<ev_periodic> will try to run the callback in this mode at the next possible
1332	time where C<time = at (mod interval)>, regardless of any time jumps.	1990	time where C<time = offset (mod interval)>, regardless of any time jumps.
1333		1991
1334	For numerical stability it is preferable that the C<at> value is near	1992	For numerical stability it is preferable that the C<offset> value is near
1335	C<ev_now ()> (the current time), but there is no range requirement for	1993	C<ev_now ()> (the current time), but there is no range requirement for
1336	this value, and in fact is often specified as zero.	1994	this value, and in fact is often specified as zero.
1337		1995
1338	Note also that there is an upper limit to how often a timer can fire (cpu	1996	Note also that there is an upper limit to how often a timer can fire (CPU
1339	speed for example), so if C<interval> is very small then timing stability	1997	speed for example), so if C<interval> is very small then timing stability
1340	will of course detoriate. Libev itself tries to be exact to be about one	1998	will of course deteriorate. Libev itself tries to be exact to be about one
1341	millisecond (if the OS supports it and the machine is fast enough).	1999	millisecond (if the OS supports it and the machine is fast enough).
1342		2000
1343	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2001	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1344		2002
1345	In this mode the values for C<interval> and C<at> are both being	2003	In this mode the values for C<interval> and C<offset> are both being
1346	ignored. Instead, each time the periodic watcher gets scheduled, the	2004	ignored. Instead, each time the periodic watcher gets scheduled, the
1347	reschedule callback will be called with the watcher as first, and the	2005	reschedule callback will be called with the watcher as first, and the
1348	current time as second argument.	2006	current time as second argument.
1349		2007
1350	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2008	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1351	ever, or make ANY event loop modifications whatsoever>.	2009	or make ANY other event loop modifications whatsoever, unless explicitly
		2010	allowed by documentation here>.
1352		2011
1353	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2012	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1354	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2013	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1355	only event loop modification you are allowed to do).	2014	only event loop modification you are allowed to do).
1356		2015
1357	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2016	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1358	*w, ev_tstamp now)>, e.g.:	2017	*w, ev_tstamp now)>, e.g.:
1359		2018
		2019	static ev_tstamp
1360	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2020	my_rescheduler (ev_periodic *w, ev_tstamp now)
1361	{	2021	{
1362	return now + 60.;	2022	return now + 60.;
1363	}	2023	}
1364		2024
1365	It must return the next time to trigger, based on the passed time value	2025	It must return the next time to trigger, based on the passed time value
…		…
1385	a different time than the last time it was called (e.g. in a crond like	2045	a different time than the last time it was called (e.g. in a crond like
1386	program when the crontabs have changed).	2046	program when the crontabs have changed).
1387		2047
1388	=item ev_tstamp ev_periodic_at (ev_periodic *)	2048	=item ev_tstamp ev_periodic_at (ev_periodic *)
1389		2049
1390	When active, returns the absolute time that the watcher is supposed to	2050	When active, returns the absolute time that the watcher is supposed
1391	trigger next.	2051	to trigger next. This is not the same as the C<offset> argument to
		2052	C<ev_periodic_set>, but indeed works even in interval and manual
		2053	rescheduling modes.
1392		2054
1393	=item ev_tstamp offset [read-write]	2055	=item ev_tstamp offset [read-write]
1394		2056
1395	When repeating, this contains the offset value, otherwise this is the	2057	When repeating, this contains the offset value, otherwise this is the
1396	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2058	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2059	although libev might modify this value for better numerical stability).
1397		2060
1398	Can be modified any time, but changes only take effect when the periodic	2061	Can be modified any time, but changes only take effect when the periodic
1399	timer fires or C<ev_periodic_again> is being called.	2062	timer fires or C<ev_periodic_again> is being called.
1400		2063
1401	=item ev_tstamp interval [read-write]	2064	=item ev_tstamp interval [read-write]
1402		2065
1403	The current interval value. Can be modified any time, but changes only	2066	The current interval value. Can be modified any time, but changes only
1404	take effect when the periodic timer fires or C<ev_periodic_again> is being	2067	take effect when the periodic timer fires or C<ev_periodic_again> is being
1405	called.	2068	called.
1406		2069
1407	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2070	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1408		2071
1409	The current reschedule callback, or C<0>, if this functionality is	2072	The current reschedule callback, or C<0>, if this functionality is
1410	switched off. Can be changed any time, but changes only take effect when	2073	switched off. Can be changed any time, but changes only take effect when
1411	the periodic timer fires or C<ev_periodic_again> is being called.	2074	the periodic timer fires or C<ev_periodic_again> is being called.
1412		2075
1413	=back	2076	=back
1414		2077
1415	=head3 Examples	2078	=head3 Examples
1416		2079
1417	Example: Call a callback every hour, or, more precisely, whenever the	2080	Example: Call a callback every hour, or, more precisely, whenever the
1418	system clock is divisible by 3600. The callback invocation times have	2081	system time is divisible by 3600. The callback invocation times have
1419	potentially a lot of jittering, but good long-term stability.	2082	potentially a lot of jitter, but good long-term stability.
1420		2083
1421	static void	2084	static void
1422	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2085	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1423	{	2086	{
1424	... its now a full hour (UTC, or TAI or whatever your clock follows)	2087	... its now a full hour (UTC, or TAI or whatever your clock follows)
1425	}	2088	}
1426		2089
1427	struct ev_periodic hourly_tick;	2090	ev_periodic hourly_tick;
1428	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2091	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1429	ev_periodic_start (loop, &hourly_tick);	2092	ev_periodic_start (loop, &hourly_tick);
1430		2093
1431	Example: The same as above, but use a reschedule callback to do it:	2094	Example: The same as above, but use a reschedule callback to do it:
1432		2095
1433	#include <math.h>	2096	#include <math.h>
1434		2097
1435	static ev_tstamp	2098	static ev_tstamp
1436	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2099	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1437	{	2100	{
1438	return fmod (now, 3600.) + 3600.;	2101	return now + (3600. - fmod (now, 3600.));
1439	}	2102	}
1440		2103
1441	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2104	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1442		2105
1443	Example: Call a callback every hour, starting now:	2106	Example: Call a callback every hour, starting now:
1444		2107
1445	struct ev_periodic hourly_tick;	2108	ev_periodic hourly_tick;
1446	ev_periodic_init (&hourly_tick, clock_cb,	2109	ev_periodic_init (&hourly_tick, clock_cb,
1447	fmod (ev_now (loop), 3600.), 3600., 0);	2110	fmod (ev_now (loop), 3600.), 3600., 0);
1448	ev_periodic_start (loop, &hourly_tick);	2111	ev_periodic_start (loop, &hourly_tick);
1449		2112
1450		2113
1451	=head2 C<ev_signal> - signal me when a signal gets signalled!	2114	=head2 C<ev_signal> - signal me when a signal gets signalled!
1452		2115
1453	Signal watchers will trigger an event when the process receives a specific	2116	Signal watchers will trigger an event when the process receives a specific
1454	signal one or more times. Even though signals are very asynchronous, libev	2117	signal one or more times. Even though signals are very asynchronous, libev
1455	will try it's best to deliver signals synchronously, i.e. as part of the	2118	will try it's best to deliver signals synchronously, i.e. as part of the
1456	normal event processing, like any other event.	2119	normal event processing, like any other event.
1457		2120
		2121	If you want signals to be delivered truly asynchronously, just use
		2122	C<sigaction> as you would do without libev and forget about sharing
		2123	the signal. You can even use C<ev_async> from a signal handler to
		2124	synchronously wake up an event loop.
		2125
1458	You can configure as many watchers as you like per signal. Only when the	2126	You can configure as many watchers as you like for the same signal, but
		2127	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2128	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2129	C<SIGINT> in both the default loop and another loop at the same time. At
		2130	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2131
1459	first watcher gets started will libev actually register a signal watcher	2132	When the first watcher gets started will libev actually register something
1460	with the kernel (thus it coexists with your own signal handlers as long	2133	with the kernel (thus it coexists with your own signal handlers as long as
1461	as you don't register any with libev). Similarly, when the last signal	2134	you don't register any with libev for the same signal).
1462	watcher for a signal is stopped libev will reset the signal handler to
1463	SIG_DFL (regardless of what it was set to before).
1464		2135
1465	If possible and supported, libev will install its handlers with	2136	If possible and supported, libev will install its handlers with
1466	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2137	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1467	interrupted. If you have a problem with syscalls getting interrupted by	2138	not be unduly interrupted. If you have a problem with system calls getting
1468	signals you can block all signals in an C<ev_check> watcher and unblock	2139	interrupted by signals you can block all signals in an C<ev_check> watcher
1469	them in an C<ev_prepare> watcher.	2140	and unblock them in an C<ev_prepare> watcher.
		2141
		2142	=head3 The special problem of inheritance over fork/execve/pthread_create
		2143
		2144	Both the signal mask (C<sigprocmask>) and the signal disposition
		2145	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2146	stopping it again), that is, libev might or might not block the signal,
		2147	and might or might not set or restore the installed signal handler.
		2148
		2149	While this does not matter for the signal disposition (libev never
		2150	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2151	C<execve>), this matters for the signal mask: many programs do not expect
		2152	certain signals to be blocked.
		2153
		2154	This means that before calling C<exec> (from the child) you should reset
		2155	the signal mask to whatever "default" you expect (all clear is a good
		2156	choice usually).
		2157
		2158	The simplest way to ensure that the signal mask is reset in the child is
		2159	to install a fork handler with C<pthread_atfork> that resets it. That will
		2160	catch fork calls done by libraries (such as the libc) as well.
		2161
		2162	In current versions of libev, the signal will not be blocked indefinitely
		2163	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2164	the window of opportunity for problems, it will not go away, as libev
		2165	I<has> to modify the signal mask, at least temporarily.
		2166
		2167	So I can't stress this enough: I<If you do not reset your signal mask when
		2168	you expect it to be empty, you have a race condition in your code>. This
		2169	is not a libev-specific thing, this is true for most event libraries.
1470		2170
1471	=head3 Watcher-Specific Functions and Data Members	2171	=head3 Watcher-Specific Functions and Data Members
1472		2172
1473	=over 4	2173	=over 4
1474		2174
…		…
1485		2185
1486	=back	2186	=back
1487		2187
1488	=head3 Examples	2188	=head3 Examples
1489		2189
1490	Example: Try to exit cleanly on SIGINT and SIGTERM.	2190	Example: Try to exit cleanly on SIGINT.
1491		2191
1492	static void	2192	static void
1493	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2193	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1494	{	2194	{
1495	ev_unloop (loop, EVUNLOOP_ALL);	2195	ev_unloop (loop, EVUNLOOP_ALL);
1496	}	2196	}
1497		2197
1498	struct ev_signal signal_watcher;	2198	ev_signal signal_watcher;
1499	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2199	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1500	ev_signal_start (loop, &sigint_cb);	2200	ev_signal_start (loop, &signal_watcher);
1501		2201
1502		2202
1503	=head2 C<ev_child> - watch out for process status changes	2203	=head2 C<ev_child> - watch out for process status changes
1504		2204
1505	Child watchers trigger when your process receives a SIGCHLD in response to	2205	Child watchers trigger when your process receives a SIGCHLD in response to
1506	some child status changes (most typically when a child of yours dies). It	2206	some child status changes (most typically when a child of yours dies or
1507	is permissible to install a child watcher I<after> the child has been	2207	exits). It is permissible to install a child watcher I<after> the child
1508	forked (which implies it might have already exited), as long as the event	2208	has been forked (which implies it might have already exited), as long
1509	loop isn't entered (or is continued from a watcher).	2209	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2210	forking and then immediately registering a watcher for the child is fine,
		2211	but forking and registering a watcher a few event loop iterations later or
		2212	in the next callback invocation is not.
1510		2213
1511	Only the default event loop is capable of handling signals, and therefore	2214	Only the default event loop is capable of handling signals, and therefore
1512	you can only rgeister child watchers in the default event loop.	2215	you can only register child watchers in the default event loop.
		2216
		2217	Due to some design glitches inside libev, child watchers will always be
		2218	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2219	libev)
1513		2220
1514	=head3 Process Interaction	2221	=head3 Process Interaction
1515		2222
1516	Libev grabs C<SIGCHLD> as soon as the default event loop is	2223	Libev grabs C<SIGCHLD> as soon as the default event loop is
1517	initialised. This is necessary to guarantee proper behaviour even if	2224	initialised. This is necessary to guarantee proper behaviour even if the
1518	the first child watcher is started after the child exits. The occurance	2225	first child watcher is started after the child exits. The occurrence
1519	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2226	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1520	synchronously as part of the event loop processing. Libev always reaps all	2227	synchronously as part of the event loop processing. Libev always reaps all
1521	children, even ones not watched.	2228	children, even ones not watched.
1522		2229
1523	=head3 Overriding the Built-In Processing	2230	=head3 Overriding the Built-In Processing
…		…
1527	handler, you can override it easily by installing your own handler for	2234	handler, you can override it easily by installing your own handler for
1528	C<SIGCHLD> after initialising the default loop, and making sure the	2235	C<SIGCHLD> after initialising the default loop, and making sure the
1529	default loop never gets destroyed. You are encouraged, however, to use an	2236	default loop never gets destroyed. You are encouraged, however, to use an
1530	event-based approach to child reaping and thus use libev's support for	2237	event-based approach to child reaping and thus use libev's support for
1531	that, so other libev users can use C<ev_child> watchers freely.	2238	that, so other libev users can use C<ev_child> watchers freely.
		2239
		2240	=head3 Stopping the Child Watcher
		2241
		2242	Currently, the child watcher never gets stopped, even when the
		2243	child terminates, so normally one needs to stop the watcher in the
		2244	callback. Future versions of libev might stop the watcher automatically
		2245	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2246	problem).
1532		2247
1533	=head3 Watcher-Specific Functions and Data Members	2248	=head3 Watcher-Specific Functions and Data Members
1534		2249
1535	=over 4	2250	=over 4
1536		2251
…		…
1565	=head3 Examples	2280	=head3 Examples
1566		2281
1567	Example: C<fork()> a new process and install a child handler to wait for	2282	Example: C<fork()> a new process and install a child handler to wait for
1568	its completion.	2283	its completion.
1569		2284
1570	ev_child cw;	2285	ev_child cw;
1571		2286
1572	static void	2287	static void
1573	child_cb (EV_P_ struct ev_child *w, int revents)	2288	child_cb (EV_P_ ev_child *w, int revents)
1574	{	2289	{
1575	ev_child_stop (EV_A_ w);	2290	ev_child_stop (EV_A_ w);
1576	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2291	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1577	}	2292	}
1578		2293
1579	pid_t pid = fork ();	2294	pid_t pid = fork ();
1580		2295
1581	if (pid < 0)	2296	if (pid < 0)
1582	// error	2297	// error
1583	else if (pid == 0)	2298	else if (pid == 0)
1584	{	2299	{
1585	// the forked child executes here	2300	// the forked child executes here
1586	exit (1);	2301	exit (1);
1587	}	2302	}
1588	else	2303	else
1589	{	2304	{
1590	ev_child_init (&cw, child_cb, pid, 0);	2305	ev_child_init (&cw, child_cb, pid, 0);
1591	ev_child_start (EV_DEFAULT_ &cw);	2306	ev_child_start (EV_DEFAULT_ &cw);
1592	}	2307	}
1593		2308
1594		2309
1595	=head2 C<ev_stat> - did the file attributes just change?	2310	=head2 C<ev_stat> - did the file attributes just change?
1596		2311
1597	This watches a filesystem path for attribute changes. That is, it calls	2312	This watches a file system path for attribute changes. That is, it calls
1598	C<stat> regularly (or when the OS says it changed) and sees if it changed	2313	C<stat> on that path in regular intervals (or when the OS says it changed)
1599	compared to the last time, invoking the callback if it did.	2314	and sees if it changed compared to the last time, invoking the callback if
		2315	it did.
1600		2316
1601	The path does not need to exist: changing from "path exists" to "path does	2317	The path does not need to exist: changing from "path exists" to "path does
1602	not exist" is a status change like any other. The condition "path does	2318	not exist" is a status change like any other. The condition "path does not
1603	not exist" is signified by the C<st_nlink> field being zero (which is	2319	exist" (or more correctly "path cannot be stat'ed") is signified by the
1604	otherwise always forced to be at least one) and all the other fields of	2320	C<st_nlink> field being zero (which is otherwise always forced to be at
1605	the stat buffer having unspecified contents.	2321	least one) and all the other fields of the stat buffer having unspecified
		2322	contents.
1606		2323
1607	The path I<should> be absolute and I<must not> end in a slash. If it is	2324	The path I<must not> end in a slash or contain special components such as
		2325	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1608	relative and your working directory changes, the behaviour is undefined.	2326	your working directory changes, then the behaviour is undefined.
1609		2327
1610	Since there is no standard to do this, the portable implementation simply	2328	Since there is no portable change notification interface available, the
1611	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2329	portable implementation simply calls C<stat(2)> regularly on the path
1612	can specify a recommended polling interval for this case. If you specify	2330	to see if it changed somehow. You can specify a recommended polling
1613	a polling interval of C<0> (highly recommended!) then a I<suitable,	2331	interval for this case. If you specify a polling interval of C<0> (highly
1614	unspecified default> value will be used (which you can expect to be around	2332	recommended!) then a I<suitable, unspecified default> value will be used
1615	five seconds, although this might change dynamically). Libev will also	2333	(which you can expect to be around five seconds, although this might
1616	impose a minimum interval which is currently around C<0.1>, but thats	2334	change dynamically). Libev will also impose a minimum interval which is
1617	usually overkill.	2335	currently around C<0.1>, but that's usually overkill.
1618		2336
1619	This watcher type is not meant for massive numbers of stat watchers,	2337	This watcher type is not meant for massive numbers of stat watchers,
1620	as even with OS-supported change notifications, this can be	2338	as even with OS-supported change notifications, this can be
1621	resource-intensive.	2339	resource-intensive.
1622		2340
1623	At the time of this writing, only the Linux inotify interface is	2341	At the time of this writing, the only OS-specific interface implemented
1624	implemented (implementing kqueue support is left as an exercise for the	2342	is the Linux inotify interface (implementing kqueue support is left as an
1625	reader, note, however, that the author sees no way of implementing ev_stat	2343	exercise for the reader. Note, however, that the author sees no way of
1626	semantics with kqueue). Inotify will be used to give hints only and should	2344	implementing C<ev_stat> semantics with kqueue, except as a hint).
1627	not change the semantics of C<ev_stat> watchers, which means that libev
1628	sometimes needs to fall back to regular polling again even with inotify,
1629	but changes are usually detected immediately, and if the file exists there
1630	will be no polling.
1631		2345
1632	=head3 ABI Issues (Largefile Support)	2346	=head3 ABI Issues (Largefile Support)
1633		2347
1634	Libev by default (unless the user overrides this) uses the default	2348	Libev by default (unless the user overrides this) uses the default
1635	compilation environment, which means that on systems with optionally	2349	compilation environment, which means that on systems with large file
1636	disabled large file support, you get the 32 bit version of the stat	2350	support disabled by default, you get the 32 bit version of the stat
1637	structure. When using the library from programs that change the ABI to	2351	structure. When using the library from programs that change the ABI to
1638	use 64 bit file offsets the programs will fail. In that case you have to	2352	use 64 bit file offsets the programs will fail. In that case you have to
1639	compile libev with the same flags to get binary compatibility. This is	2353	compile libev with the same flags to get binary compatibility. This is
1640	obviously the case with any flags that change the ABI, but the problem is	2354	obviously the case with any flags that change the ABI, but the problem is
1641	most noticably with ev_stat and largefile support.	2355	most noticeably displayed with ev_stat and large file support.
1642		2356
1643	=head3 Inotify	2357	The solution for this is to lobby your distribution maker to make large
		2358	file interfaces available by default (as e.g. FreeBSD does) and not
		2359	optional. Libev cannot simply switch on large file support because it has
		2360	to exchange stat structures with application programs compiled using the
		2361	default compilation environment.
1644		2362
		2363	=head3 Inotify and Kqueue
		2364
1645	When C<inotify (7)> support has been compiled into libev (generally only	2365	When C<inotify (7)> support has been compiled into libev and present at
1646	available on Linux) and present at runtime, it will be used to speed up	2366	runtime, it will be used to speed up change detection where possible. The
1647	change detection where possible. The inotify descriptor will be created lazily	2367	inotify descriptor will be created lazily when the first C<ev_stat>
1648	when the first C<ev_stat> watcher is being started.	2368	watcher is being started.
1649		2369
1650	Inotify presence does not change the semantics of C<ev_stat> watchers	2370	Inotify presence does not change the semantics of C<ev_stat> watchers
1651	except that changes might be detected earlier, and in some cases, to avoid	2371	except that changes might be detected earlier, and in some cases, to avoid
1652	making regular C<stat> calls. Even in the presence of inotify support	2372	making regular C<stat> calls. Even in the presence of inotify support
1653	there are many cases where libev has to resort to regular C<stat> polling.	2373	there are many cases where libev has to resort to regular C<stat> polling,
		2374	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2375	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2376	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2377	xfs are fully working) libev usually gets away without polling.
1654		2378
1655	(There is no support for kqueue, as apparently it cannot be used to	2379	There is no support for kqueue, as apparently it cannot be used to
1656	implement this functionality, due to the requirement of having a file	2380	implement this functionality, due to the requirement of having a file
1657	descriptor open on the object at all times).	2381	descriptor open on the object at all times, and detecting renames, unlinks
		2382	etc. is difficult.
		2383
		2384	=head3 C<stat ()> is a synchronous operation
		2385
		2386	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2387	the process. The exception are C<ev_stat> watchers - those call C<stat
		2388	()>, which is a synchronous operation.
		2389
		2390	For local paths, this usually doesn't matter: unless the system is very
		2391	busy or the intervals between stat's are large, a stat call will be fast,
		2392	as the path data is usually in memory already (except when starting the
		2393	watcher).
		2394
		2395	For networked file systems, calling C<stat ()> can block an indefinite
		2396	time due to network issues, and even under good conditions, a stat call
		2397	often takes multiple milliseconds.
		2398
		2399	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2400	paths, although this is fully supported by libev.
1658		2401
1659	=head3 The special problem of stat time resolution	2402	=head3 The special problem of stat time resolution
1660		2403
1661	The C<stat ()> syscall only supports full-second resolution portably, and	2404	The C<stat ()> system call only supports full-second resolution portably,
1662	even on systems where the resolution is higher, many filesystems still	2405	and even on systems where the resolution is higher, most file systems
1663	only support whole seconds.	2406	still only support whole seconds.
1664		2407
1665	That means that, if the time is the only thing that changes, you can	2408	That means that, if the time is the only thing that changes, you can
1666	easily miss updates: on the first update, C<ev_stat> detects a change and	2409	easily miss updates: on the first update, C<ev_stat> detects a change and
1667	calls your callback, which does something. When there is another update	2410	calls your callback, which does something. When there is another update
1668	within the same second, C<ev_stat> will be unable to detect it as the stat	2411	within the same second, C<ev_stat> will be unable to detect unless the
1669	data does not change.	2412	stat data does change in other ways (e.g. file size).
1670		2413
1671	The solution to this is to delay acting on a change for slightly more	2414	The solution to this is to delay acting on a change for slightly more
1672	than a second (or till slightly after the next full second boundary), using	2415	than a second (or till slightly after the next full second boundary), using
1673	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2416	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1674	ev_timer_again (loop, w)>).	2417	ev_timer_again (loop, w)>).
…		…
1694	C<path>. The C<interval> is a hint on how quickly a change is expected to	2437	C<path>. The C<interval> is a hint on how quickly a change is expected to
1695	be detected and should normally be specified as C<0> to let libev choose	2438	be detected and should normally be specified as C<0> to let libev choose
1696	a suitable value. The memory pointed to by C<path> must point to the same	2439	a suitable value. The memory pointed to by C<path> must point to the same
1697	path for as long as the watcher is active.	2440	path for as long as the watcher is active.
1698		2441
1699	The callback will receive C<EV_STAT> when a change was detected, relative	2442	The callback will receive an C<EV_STAT> event when a change was detected,
1700	to the attributes at the time the watcher was started (or the last change	2443	relative to the attributes at the time the watcher was started (or the
1701	was detected).	2444	last change was detected).
1702		2445
1703	=item ev_stat_stat (loop, ev_stat *)	2446	=item ev_stat_stat (loop, ev_stat *)
1704		2447
1705	Updates the stat buffer immediately with new values. If you change the	2448	Updates the stat buffer immediately with new values. If you change the
1706	watched path in your callback, you could call this function to avoid	2449	watched path in your callback, you could call this function to avoid
…		…
1727		2470
1728	The specified interval.	2471	The specified interval.
1729		2472
1730	=item const char *path [read-only]	2473	=item const char *path [read-only]
1731		2474
1732	The filesystem path that is being watched.	2475	The file system path that is being watched.
1733		2476
1734	=back	2477	=back
1735		2478
1736	=head3 Examples	2479	=head3 Examples
1737		2480
1738	Example: Watch C</etc/passwd> for attribute changes.	2481	Example: Watch C</etc/passwd> for attribute changes.
1739		2482
1740	static void	2483	static void
1741	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2484	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1742	{	2485	{
1743	/* /etc/passwd changed in some way */	2486	/* /etc/passwd changed in some way */
1744	if (w->attr.st_nlink)	2487	if (w->attr.st_nlink)
1745	{	2488	{
1746	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2489	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1747	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2490	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1748	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2491	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1749	}	2492	}
1750	else	2493	else
1751	/* you shalt not abuse printf for puts */	2494	/* you shalt not abuse printf for puts */
1752	puts ("wow, /etc/passwd is not there, expect problems. "	2495	puts ("wow, /etc/passwd is not there, expect problems. "
1753	"if this is windows, they already arrived\n");	2496	"if this is windows, they already arrived\n");
1754	}	2497	}
1755		2498
1756	...	2499	...
1757	ev_stat passwd;	2500	ev_stat passwd;
1758		2501
1759	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2502	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1760	ev_stat_start (loop, &passwd);	2503	ev_stat_start (loop, &passwd);
1761		2504
1762	Example: Like above, but additionally use a one-second delay so we do not	2505	Example: Like above, but additionally use a one-second delay so we do not
1763	miss updates (however, frequent updates will delay processing, too, so	2506	miss updates (however, frequent updates will delay processing, too, so
1764	one might do the work both on C<ev_stat> callback invocation I<and> on	2507	one might do the work both on C<ev_stat> callback invocation I<and> on
1765	C<ev_timer> callback invocation).	2508	C<ev_timer> callback invocation).
1766		2509
1767	static ev_stat passwd;	2510	static ev_stat passwd;
1768	static ev_timer timer;	2511	static ev_timer timer;
1769		2512
1770	static void	2513	static void
1771	timer_cb (EV_P_ ev_timer *w, int revents)	2514	timer_cb (EV_P_ ev_timer *w, int revents)
1772	{	2515	{
1773	ev_timer_stop (EV_A_ w);	2516	ev_timer_stop (EV_A_ w);
1774		2517
1775	/* now it's one second after the most recent passwd change */	2518	/* now it's one second after the most recent passwd change */
1776	}	2519	}
1777		2520
1778	static void	2521	static void
1779	stat_cb (EV_P_ ev_stat *w, int revents)	2522	stat_cb (EV_P_ ev_stat *w, int revents)
1780	{	2523	{
1781	/* reset the one-second timer */	2524	/* reset the one-second timer */
1782	ev_timer_again (EV_A_ &timer);	2525	ev_timer_again (EV_A_ &timer);
1783	}	2526	}
1784		2527
1785	...	2528	...
1786	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2529	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1787	ev_stat_start (loop, &passwd);	2530	ev_stat_start (loop, &passwd);
1788	ev_timer_init (&timer, timer_cb, 0., 1.02);	2531	ev_timer_init (&timer, timer_cb, 0., 1.02);
1789		2532
1790		2533
1791	=head2 C<ev_idle> - when you've got nothing better to do...	2534	=head2 C<ev_idle> - when you've got nothing better to do...
1792		2535
1793	Idle watchers trigger events when no other events of the same or higher	2536	Idle watchers trigger events when no other events of the same or higher
1794	priority are pending (prepare, check and other idle watchers do not	2537	priority are pending (prepare, check and other idle watchers do not count
1795	count).	2538	as receiving "events").
1796		2539
1797	That is, as long as your process is busy handling sockets or timeouts	2540	That is, as long as your process is busy handling sockets or timeouts
1798	(or even signals, imagine) of the same or higher priority it will not be	2541	(or even signals, imagine) of the same or higher priority it will not be
1799	triggered. But when your process is idle (or only lower-priority watchers	2542	triggered. But when your process is idle (or only lower-priority watchers
1800	are pending), the idle watchers are being called once per event loop	2543	are pending), the idle watchers are being called once per event loop
…		…
1811		2554
1812	=head3 Watcher-Specific Functions and Data Members	2555	=head3 Watcher-Specific Functions and Data Members
1813		2556
1814	=over 4	2557	=over 4
1815		2558
1816	=item ev_idle_init (ev_signal *, callback)	2559	=item ev_idle_init (ev_idle *, callback)
1817		2560
1818	Initialises and configures the idle watcher - it has no parameters of any	2561	Initialises and configures the idle watcher - it has no parameters of any
1819	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2562	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1820	believe me.	2563	believe me.
1821		2564
…		…
1824	=head3 Examples	2567	=head3 Examples
1825		2568
1826	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2569	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1827	callback, free it. Also, use no error checking, as usual.	2570	callback, free it. Also, use no error checking, as usual.
1828		2571
1829	static void	2572	static void
1830	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2573	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1831	{	2574	{
1832	free (w);	2575	free (w);
1833	// now do something you wanted to do when the program has	2576	// now do something you wanted to do when the program has
1834	// no longer anything immediate to do.	2577	// no longer anything immediate to do.
1835	}	2578	}
1836		2579
1837	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2580	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1838	ev_idle_init (idle_watcher, idle_cb);	2581	ev_idle_init (idle_watcher, idle_cb);
1839	ev_idle_start (loop, idle_cb);	2582	ev_idle_start (loop, idle_watcher);
1840		2583
1841		2584
1842	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2585	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1843		2586
1844	Prepare and check watchers are usually (but not always) used in tandem:	2587	Prepare and check watchers are usually (but not always) used in pairs:
1845	prepare watchers get invoked before the process blocks and check watchers	2588	prepare watchers get invoked before the process blocks and check watchers
1846	afterwards.	2589	afterwards.
1847		2590
1848	You I<must not> call C<ev_loop> or similar functions that enter	2591	You I<must not> call C<ev_loop> or similar functions that enter
1849	the current event loop from either C<ev_prepare> or C<ev_check>	2592	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1852	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2595	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1853	C<ev_check> so if you have one watcher of each kind they will always be	2596	C<ev_check> so if you have one watcher of each kind they will always be
1854	called in pairs bracketing the blocking call.	2597	called in pairs bracketing the blocking call.
1855		2598
1856	Their main purpose is to integrate other event mechanisms into libev and	2599	Their main purpose is to integrate other event mechanisms into libev and
1857	their use is somewhat advanced. This could be used, for example, to track	2600	their use is somewhat advanced. They could be used, for example, to track
1858	variable changes, implement your own watchers, integrate net-snmp or a	2601	variable changes, implement your own watchers, integrate net-snmp or a
1859	coroutine library and lots more. They are also occasionally useful if	2602	coroutine library and lots more. They are also occasionally useful if
1860	you cache some data and want to flush it before blocking (for example,	2603	you cache some data and want to flush it before blocking (for example,
1861	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2604	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1862	watcher).	2605	watcher).
1863		2606
1864	This is done by examining in each prepare call which file descriptors need	2607	This is done by examining in each prepare call which file descriptors
1865	to be watched by the other library, registering C<ev_io> watchers for	2608	need to be watched by the other library, registering C<ev_io> watchers
1866	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2609	for them and starting an C<ev_timer> watcher for any timeouts (many
1867	provide just this functionality). Then, in the check watcher you check for	2610	libraries provide exactly this functionality). Then, in the check watcher,
1868	any events that occured (by checking the pending status of all watchers	2611	you check for any events that occurred (by checking the pending status
1869	and stopping them) and call back into the library. The I/O and timer	2612	of all watchers and stopping them) and call back into the library. The
1870	callbacks will never actually be called (but must be valid nevertheless,	2613	I/O and timer callbacks will never actually be called (but must be valid
1871	because you never know, you know?).	2614	nevertheless, because you never know, you know?).
1872		2615
1873	As another example, the Perl Coro module uses these hooks to integrate	2616	As another example, the Perl Coro module uses these hooks to integrate
1874	coroutines into libev programs, by yielding to other active coroutines	2617	coroutines into libev programs, by yielding to other active coroutines
1875	during each prepare and only letting the process block if no coroutines	2618	during each prepare and only letting the process block if no coroutines
1876	are ready to run (it's actually more complicated: it only runs coroutines	2619	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1879	loop from blocking if lower-priority coroutines are active, thus mapping	2622	loop from blocking if lower-priority coroutines are active, thus mapping
1880	low-priority coroutines to idle/background tasks).	2623	low-priority coroutines to idle/background tasks).
1881		2624
1882	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2625	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1883	priority, to ensure that they are being run before any other watchers	2626	priority, to ensure that they are being run before any other watchers
		2627	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2628
1884	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2629	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1885	too) should not activate ("feed") events into libev. While libev fully	2630	activate ("feed") events into libev. While libev fully supports this, they
1886	supports this, they might get executed before other C<ev_check> watchers	2631	might get executed before other C<ev_check> watchers did their job. As
1887	did their job. As C<ev_check> watchers are often used to embed other	2632	C<ev_check> watchers are often used to embed other (non-libev) event
1888	(non-libev) event loops those other event loops might be in an unusable	2633	loops those other event loops might be in an unusable state until their
1889	state until their C<ev_check> watcher ran (always remind yourself to	2634	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1890	coexist peacefully with others).	2635	others).
1891		2636
1892	=head3 Watcher-Specific Functions and Data Members	2637	=head3 Watcher-Specific Functions and Data Members
1893		2638
1894	=over 4	2639	=over 4
1895		2640
…		…
1897		2642
1898	=item ev_check_init (ev_check *, callback)	2643	=item ev_check_init (ev_check *, callback)
1899		2644
1900	Initialises and configures the prepare or check watcher - they have no	2645	Initialises and configures the prepare or check watcher - they have no
1901	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2646	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1902	macros, but using them is utterly, utterly and completely pointless.	2647	macros, but using them is utterly, utterly, utterly and completely
		2648	pointless.
1903		2649
1904	=back	2650	=back
1905		2651
1906	=head3 Examples	2652	=head3 Examples
1907		2653
…		…
1916	and in a check watcher, destroy them and call into libadns. What follows	2662	and in a check watcher, destroy them and call into libadns. What follows
1917	is pseudo-code only of course. This requires you to either use a low	2663	is pseudo-code only of course. This requires you to either use a low
1918	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2664	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1919	the callbacks for the IO/timeout watchers might not have been called yet.	2665	the callbacks for the IO/timeout watchers might not have been called yet.
1920		2666
1921	static ev_io iow [nfd];	2667	static ev_io iow [nfd];
1922	static ev_timer tw;	2668	static ev_timer tw;
1923		2669
1924	static void	2670	static void
1925	io_cb (ev_loop *loop, ev_io *w, int revents)	2671	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1926	{	2672	{
1927	}	2673	}
1928		2674
1929	// create io watchers for each fd and a timer before blocking	2675	// create io watchers for each fd and a timer before blocking
1930	static void	2676	static void
1931	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2677	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1932	{	2678	{
1933	int timeout = 3600000;	2679	int timeout = 3600000;
1934	struct pollfd fds [nfd];	2680	struct pollfd fds [nfd];
1935	// actual code will need to loop here and realloc etc.	2681	// actual code will need to loop here and realloc etc.
1936	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2682	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1937		2683
1938	/* the callback is illegal, but won't be called as we stop during check */	2684	/* the callback is illegal, but won't be called as we stop during check */
1939	ev_timer_init (&tw, 0, timeout * 1e-3);	2685	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1940	ev_timer_start (loop, &tw);	2686	ev_timer_start (loop, &tw);
1941		2687
1942	// create one ev_io per pollfd	2688	// create one ev_io per pollfd
1943	for (int i = 0; i < nfd; ++i)	2689	for (int i = 0; i < nfd; ++i)
1944	{	2690	{
1945	ev_io_init (iow + i, io_cb, fds [i].fd,	2691	ev_io_init (iow + i, io_cb, fds [i].fd,
1946	((fds [i].events & POLLIN ? EV_READ : 0)	2692	((fds [i].events & POLLIN ? EV_READ : 0)
1947	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2693	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1948		2694
1949	fds [i].revents = 0;	2695	fds [i].revents = 0;
1950	ev_io_start (loop, iow + i);	2696	ev_io_start (loop, iow + i);
1951	}	2697	}
1952	}	2698	}
1953		2699
1954	// stop all watchers after blocking	2700	// stop all watchers after blocking
1955	static void	2701	static void
1956	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2702	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1957	{	2703	{
1958	ev_timer_stop (loop, &tw);	2704	ev_timer_stop (loop, &tw);
1959		2705
1960	for (int i = 0; i < nfd; ++i)	2706	for (int i = 0; i < nfd; ++i)
1961	{	2707	{
1962	// set the relevant poll flags	2708	// set the relevant poll flags
1963	// could also call adns_processreadable etc. here	2709	// could also call adns_processreadable etc. here
1964	struct pollfd *fd = fds + i;	2710	struct pollfd *fd = fds + i;
1965	int revents = ev_clear_pending (iow + i);	2711	int revents = ev_clear_pending (iow + i);
1966	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2712	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1967	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2713	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1968		2714
1969	// now stop the watcher	2715	// now stop the watcher
1970	ev_io_stop (loop, iow + i);	2716	ev_io_stop (loop, iow + i);
1971	}	2717	}
1972		2718
1973	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2719	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1974	}	2720	}
1975		2721
1976	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2722	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1977	in the prepare watcher and would dispose of the check watcher.	2723	in the prepare watcher and would dispose of the check watcher.
1978		2724
1979	Method 3: If the module to be embedded supports explicit event	2725	Method 3: If the module to be embedded supports explicit event
1980	notification (adns does), you can also make use of the actual watcher	2726	notification (libadns does), you can also make use of the actual watcher
1981	callbacks, and only destroy/create the watchers in the prepare watcher.	2727	callbacks, and only destroy/create the watchers in the prepare watcher.
1982		2728
1983	static void	2729	static void
1984	timer_cb (EV_P_ ev_timer *w, int revents)	2730	timer_cb (EV_P_ ev_timer *w, int revents)
1985	{	2731	{
1986	adns_state ads = (adns_state)w->data;	2732	adns_state ads = (adns_state)w->data;
1987	update_now (EV_A);	2733	update_now (EV_A);
1988		2734
1989	adns_processtimeouts (ads, &tv_now);	2735	adns_processtimeouts (ads, &tv_now);
1990	}	2736	}
1991		2737
1992	static void	2738	static void
1993	io_cb (EV_P_ ev_io *w, int revents)	2739	io_cb (EV_P_ ev_io *w, int revents)
1994	{	2740	{
1995	adns_state ads = (adns_state)w->data;	2741	adns_state ads = (adns_state)w->data;
1996	update_now (EV_A);	2742	update_now (EV_A);
1997		2743
1998	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2744	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1999	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2745	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2000	}	2746	}
2001		2747
2002	// do not ever call adns_afterpoll	2748	// do not ever call adns_afterpoll
2003		2749
2004	Method 4: Do not use a prepare or check watcher because the module you	2750	Method 4: Do not use a prepare or check watcher because the module you
2005	want to embed is too inflexible to support it. Instead, youc na override	2751	want to embed is not flexible enough to support it. Instead, you can
2006	their poll function. The drawback with this solution is that the main	2752	override their poll function. The drawback with this solution is that the
2007	loop is now no longer controllable by EV. The C<Glib::EV> module does	2753	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2008	this.	2754	this approach, effectively embedding EV as a client into the horrible
		2755	libglib event loop.
2009		2756
2010	static gint	2757	static gint
2011	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2758	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2012	{	2759	{
2013	int got_events = 0;	2760	int got_events = 0;
2014		2761
2015	for (n = 0; n < nfds; ++n)	2762	for (n = 0; n < nfds; ++n)
2016	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2763	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2017		2764
2018	if (timeout >= 0)	2765	if (timeout >= 0)
2019	// create/start timer	2766	// create/start timer
2020		2767
2021	// poll	2768	// poll
2022	ev_loop (EV_A_ 0);	2769	ev_loop (EV_A_ 0);
2023		2770
2024	// stop timer again	2771	// stop timer again
2025	if (timeout >= 0)	2772	if (timeout >= 0)
2026	ev_timer_stop (EV_A_ &to);	2773	ev_timer_stop (EV_A_ &to);
2027		2774
2028	// stop io watchers again - their callbacks should have set	2775	// stop io watchers again - their callbacks should have set
2029	for (n = 0; n < nfds; ++n)	2776	for (n = 0; n < nfds; ++n)
2030	ev_io_stop (EV_A_ iow [n]);	2777	ev_io_stop (EV_A_ iow [n]);
2031		2778
2032	return got_events;	2779	return got_events;
2033	}	2780	}
2034		2781
2035		2782
2036	=head2 C<ev_embed> - when one backend isn't enough...	2783	=head2 C<ev_embed> - when one backend isn't enough...
2037		2784
2038	This is a rather advanced watcher type that lets you embed one event loop	2785	This is a rather advanced watcher type that lets you embed one event loop
…		…
2044	prioritise I/O.	2791	prioritise I/O.
2045		2792
2046	As an example for a bug workaround, the kqueue backend might only support	2793	As an example for a bug workaround, the kqueue backend might only support
2047	sockets on some platform, so it is unusable as generic backend, but you	2794	sockets on some platform, so it is unusable as generic backend, but you
2048	still want to make use of it because you have many sockets and it scales	2795	still want to make use of it because you have many sockets and it scales
2049	so nicely. In this case, you would create a kqueue-based loop and embed it	2796	so nicely. In this case, you would create a kqueue-based loop and embed
2050	into your default loop (which might use e.g. poll). Overall operation will	2797	it into your default loop (which might use e.g. poll). Overall operation
2051	be a bit slower because first libev has to poll and then call kevent, but	2798	will be a bit slower because first libev has to call C<poll> and then
2052	at least you can use both at what they are best.	2799	C<kevent>, but at least you can use both mechanisms for what they are
		2800	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2053		2801
2054	As for prioritising I/O: rarely you have the case where some fds have	2802	As for prioritising I/O: under rare circumstances you have the case where
2055	to be watched and handled very quickly (with low latency), and even	2803	some fds have to be watched and handled very quickly (with low latency),
2056	priorities and idle watchers might have too much overhead. In this case	2804	and even priorities and idle watchers might have too much overhead. In
2057	you would put all the high priority stuff in one loop and all the rest in	2805	this case you would put all the high priority stuff in one loop and all
2058	a second one, and embed the second one in the first.	2806	the rest in a second one, and embed the second one in the first.
2059		2807
2060	As long as the watcher is active, the callback will be invoked every time	2808	As long as the watcher is active, the callback will be invoked every
2061	there might be events pending in the embedded loop. The callback must then	2809	time there might be events pending in the embedded loop. The callback
2062	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2810	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2063	their callbacks (you could also start an idle watcher to give the embedded	2811	sweep and invoke their callbacks (the callback doesn't need to invoke the
2064	loop strictly lower priority for example). You can also set the callback	2812	C<ev_embed_sweep> function directly, it could also start an idle watcher
2065	to C<0>, in which case the embed watcher will automatically execute the	2813	to give the embedded loop strictly lower priority for example).
2066	embedded loop sweep.
2067		2814
2068	As long as the watcher is started it will automatically handle events. The	2815	You can also set the callback to C<0>, in which case the embed watcher
2069	callback will be invoked whenever some events have been handled. You can	2816	will automatically execute the embedded loop sweep whenever necessary.
2070	set the callback to C<0> to avoid having to specify one if you are not
2071	interested in that.
2072		2817
2073	Also, there have not currently been made special provisions for forking:	2818	Fork detection will be handled transparently while the C<ev_embed> watcher
2074	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2819	is active, i.e., the embedded loop will automatically be forked when the
2075	but you will also have to stop and restart any C<ev_embed> watchers	2820	embedding loop forks. In other cases, the user is responsible for calling
2076	yourself.	2821	C<ev_loop_fork> on the embedded loop.
2077		2822
2078	Unfortunately, not all backends are embeddable, only the ones returned by	2823	Unfortunately, not all backends are embeddable: only the ones returned by
2079	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2824	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2080	portable one.	2825	portable one.
2081		2826
2082	So when you want to use this feature you will always have to be prepared	2827	So when you want to use this feature you will always have to be prepared
2083	that you cannot get an embeddable loop. The recommended way to get around	2828	that you cannot get an embeddable loop. The recommended way to get around
2084	this is to have a separate variables for your embeddable loop, try to	2829	this is to have a separate variables for your embeddable loop, try to
2085	create it, and if that fails, use the normal loop for everything.	2830	create it, and if that fails, use the normal loop for everything.
2086		2831
		2832	=head3 C<ev_embed> and fork
		2833
		2834	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2835	automatically be applied to the embedded loop as well, so no special
		2836	fork handling is required in that case. When the watcher is not running,
		2837	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2838	as applicable.
		2839
2087	=head3 Watcher-Specific Functions and Data Members	2840	=head3 Watcher-Specific Functions and Data Members
2088		2841
2089	=over 4	2842	=over 4
2090		2843
2091	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2844	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2094		2847
2095	Configures the watcher to embed the given loop, which must be	2848	Configures the watcher to embed the given loop, which must be
2096	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2849	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2097	invoked automatically, otherwise it is the responsibility of the callback	2850	invoked automatically, otherwise it is the responsibility of the callback
2098	to invoke it (it will continue to be called until the sweep has been done,	2851	to invoke it (it will continue to be called until the sweep has been done,
2099	if you do not want thta, you need to temporarily stop the embed watcher).	2852	if you do not want that, you need to temporarily stop the embed watcher).
2100		2853
2101	=item ev_embed_sweep (loop, ev_embed *)	2854	=item ev_embed_sweep (loop, ev_embed *)
2102		2855
2103	Make a single, non-blocking sweep over the embedded loop. This works	2856	Make a single, non-blocking sweep over the embedded loop. This works
2104	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2857	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2105	apropriate way for embedded loops.	2858	appropriate way for embedded loops.
2106		2859
2107	=item struct ev_loop *other [read-only]	2860	=item struct ev_loop *other [read-only]
2108		2861
2109	The embedded event loop.	2862	The embedded event loop.
2110		2863
…		…
2112		2865
2113	=head3 Examples	2866	=head3 Examples
2114		2867
2115	Example: Try to get an embeddable event loop and embed it into the default	2868	Example: Try to get an embeddable event loop and embed it into the default
2116	event loop. If that is not possible, use the default loop. The default	2869	event loop. If that is not possible, use the default loop. The default
2117	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2870	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2118	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2871	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2119	used).	2872	used).
2120		2873
2121	struct ev_loop *loop_hi = ev_default_init (0);	2874	struct ev_loop *loop_hi = ev_default_init (0);
2122	struct ev_loop *loop_lo = 0;	2875	struct ev_loop *loop_lo = 0;
2123	struct ev_embed embed;	2876	ev_embed embed;
2124		2877
2125	// see if there is a chance of getting one that works	2878	// see if there is a chance of getting one that works
2126	// (remember that a flags value of 0 means autodetection)	2879	// (remember that a flags value of 0 means autodetection)
2127	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2880	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2128	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2881	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2129	: 0;	2882	: 0;
2130		2883
2131	// if we got one, then embed it, otherwise default to loop_hi	2884	// if we got one, then embed it, otherwise default to loop_hi
2132	if (loop_lo)	2885	if (loop_lo)
2133	{	2886	{
2134	ev_embed_init (&embed, 0, loop_lo);	2887	ev_embed_init (&embed, 0, loop_lo);
2135	ev_embed_start (loop_hi, &embed);	2888	ev_embed_start (loop_hi, &embed);
2136	}	2889	}
2137	else	2890	else
2138	loop_lo = loop_hi;	2891	loop_lo = loop_hi;
2139		2892
2140	Example: Check if kqueue is available but not recommended and create	2893	Example: Check if kqueue is available but not recommended and create
2141	a kqueue backend for use with sockets (which usually work with any	2894	a kqueue backend for use with sockets (which usually work with any
2142	kqueue implementation). Store the kqueue/socket-only event loop in	2895	kqueue implementation). Store the kqueue/socket-only event loop in
2143	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2896	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2144		2897
2145	struct ev_loop *loop = ev_default_init (0);	2898	struct ev_loop *loop = ev_default_init (0);
2146	struct ev_loop *loop_socket = 0;	2899	struct ev_loop *loop_socket = 0;
2147	struct ev_embed embed;	2900	ev_embed embed;
2148		2901
2149	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2902	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2150	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2903	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2151	{	2904	{
2152	ev_embed_init (&embed, 0, loop_socket);	2905	ev_embed_init (&embed, 0, loop_socket);
2153	ev_embed_start (loop, &embed);	2906	ev_embed_start (loop, &embed);
2154	}	2907	}
2155		2908
2156	if (!loop_socket)	2909	if (!loop_socket)
2157	loop_socket = loop;	2910	loop_socket = loop;
2158		2911
2159	// now use loop_socket for all sockets, and loop for everything else	2912	// now use loop_socket for all sockets, and loop for everything else
2160		2913
2161		2914
2162	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2915	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2163		2916
2164	Fork watchers are called when a C<fork ()> was detected (usually because	2917	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2167	event loop blocks next and before C<ev_check> watchers are being called,	2920	event loop blocks next and before C<ev_check> watchers are being called,
2168	and only in the child after the fork. If whoever good citizen calling	2921	and only in the child after the fork. If whoever good citizen calling
2169	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2922	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2170	handlers will be invoked, too, of course.	2923	handlers will be invoked, too, of course.
2171		2924
		2925	=head3 The special problem of life after fork - how is it possible?
		2926
		2927	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2928	up/change the process environment, followed by a call to C<exec()>. This
		2929	sequence should be handled by libev without any problems.
		2930
		2931	This changes when the application actually wants to do event handling
		2932	in the child, or both parent in child, in effect "continuing" after the
		2933	fork.
		2934
		2935	The default mode of operation (for libev, with application help to detect
		2936	forks) is to duplicate all the state in the child, as would be expected
		2937	when I<either> the parent I<or> the child process continues.
		2938
		2939	When both processes want to continue using libev, then this is usually the
		2940	wrong result. In that case, usually one process (typically the parent) is
		2941	supposed to continue with all watchers in place as before, while the other
		2942	process typically wants to start fresh, i.e. without any active watchers.
		2943
		2944	The cleanest and most efficient way to achieve that with libev is to
		2945	simply create a new event loop, which of course will be "empty", and
		2946	use that for new watchers. This has the advantage of not touching more
		2947	memory than necessary, and thus avoiding the copy-on-write, and the
		2948	disadvantage of having to use multiple event loops (which do not support
		2949	signal watchers).
		2950
		2951	When this is not possible, or you want to use the default loop for
		2952	other reasons, then in the process that wants to start "fresh", call
		2953	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2954	the default loop will "orphan" (not stop) all registered watchers, so you
		2955	have to be careful not to execute code that modifies those watchers. Note
		2956	also that in that case, you have to re-register any signal watchers.
		2957
2172	=head3 Watcher-Specific Functions and Data Members	2958	=head3 Watcher-Specific Functions and Data Members
2173		2959
2174	=over 4	2960	=over 4
2175		2961
2176	=item ev_fork_init (ev_signal *, callback)	2962	=item ev_fork_init (ev_signal *, callback)
…		…
2205	=head3 Queueing	2991	=head3 Queueing
2206		2992
2207	C<ev_async> does not support queueing of data in any way. The reason	2993	C<ev_async> does not support queueing of data in any way. The reason
2208	is that the author does not know of a simple (or any) algorithm for a	2994	is that the author does not know of a simple (or any) algorithm for a
2209	multiple-writer-single-reader queue that works in all cases and doesn't	2995	multiple-writer-single-reader queue that works in all cases and doesn't
2210	need elaborate support such as pthreads.	2996	need elaborate support such as pthreads or unportable memory access
		2997	semantics.
2211		2998
2212	That means that if you want to queue data, you have to provide your own	2999	That means that if you want to queue data, you have to provide your own
2213	queue. But at least I can tell you would implement locking around your	3000	queue. But at least I can tell you how to implement locking around your
2214	queue:	3001	queue:
2215		3002
2216	=over 4	3003	=over 4
2217		3004
2218	=item queueing from a signal handler context	3005	=item queueing from a signal handler context
2219		3006
2220	To implement race-free queueing, you simply add to the queue in the signal	3007	To implement race-free queueing, you simply add to the queue in the signal
2221	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3008	handler but you block the signal handler in the watcher callback. Here is
2222	some fictitiuous SIGUSR1 handler:	3009	an example that does that for some fictitious SIGUSR1 handler:
2223		3010
2224	static ev_async mysig;	3011	static ev_async mysig;
2225		3012
2226	static void	3013	static void
2227	sigusr1_handler (void)	3014	sigusr1_handler (void)
…		…
2293	=over 4	3080	=over 4
2294		3081
2295	=item ev_async_init (ev_async *, callback)	3082	=item ev_async_init (ev_async *, callback)
2296		3083
2297	Initialises and configures the async watcher - it has no parameters of any	3084	Initialises and configures the async watcher - it has no parameters of any
2298	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3085	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2299	believe me.	3086	trust me.
2300		3087
2301	=item ev_async_send (loop, ev_async *)	3088	=item ev_async_send (loop, ev_async *)
2302		3089
2303	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3090	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2304	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3091	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2305	C<ev_feed_event>, this call is safe to do in other threads, signal or	3092	C<ev_feed_event>, this call is safe to do from other threads, signal or
2306	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3093	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2307	section below on what exactly this means).	3094	section below on what exactly this means).
2308		3095
		3096	Note that, as with other watchers in libev, multiple events might get
		3097	compressed into a single callback invocation (another way to look at this
		3098	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3099	reset when the event loop detects that).
		3100
2309	This call incurs the overhead of a syscall only once per loop iteration,	3101	This call incurs the overhead of a system call only once per event loop
2310	so while the overhead might be noticable, it doesn't apply to repeated	3102	iteration, so while the overhead might be noticeable, it doesn't apply to
2311	calls to C<ev_async_send>.	3103	repeated calls to C<ev_async_send> for the same event loop.
2312		3104
2313	=item bool = ev_async_pending (ev_async *)	3105	=item bool = ev_async_pending (ev_async *)
2314		3106
2315	Returns a non-zero value when C<ev_async_send> has been called on the	3107	Returns a non-zero value when C<ev_async_send> has been called on the
2316	watcher but the event has not yet been processed (or even noted) by the	3108	watcher but the event has not yet been processed (or even noted) by the
2317	event loop.	3109	event loop.
2318		3110
2319	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3111	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2320	the loop iterates next and checks for the watcher to have become active,	3112	the loop iterates next and checks for the watcher to have become active,
2321	it will reset the flag again. C<ev_async_pending> can be used to very	3113	it will reset the flag again. C<ev_async_pending> can be used to very
2322	quickly check wether invoking the loop might be a good idea.	3114	quickly check whether invoking the loop might be a good idea.
2323		3115
2324	Not that this does I<not> check wether the watcher itself is pending, only	3116	Not that this does I<not> check whether the watcher itself is pending,
2325	wether it has been requested to make this watcher pending.	3117	only whether it has been requested to make this watcher pending: there
		3118	is a time window between the event loop checking and resetting the async
		3119	notification, and the callback being invoked.
2326		3120
2327	=back	3121	=back
2328		3122
2329		3123
2330	=head1 OTHER FUNCTIONS	3124	=head1 OTHER FUNCTIONS
…		…
2334	=over 4	3128	=over 4
2335		3129
2336	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3130	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2337		3131
2338	This function combines a simple timer and an I/O watcher, calls your	3132	This function combines a simple timer and an I/O watcher, calls your
2339	callback on whichever event happens first and automatically stop both	3133	callback on whichever event happens first and automatically stops both
2340	watchers. This is useful if you want to wait for a single event on an fd	3134	watchers. This is useful if you want to wait for a single event on an fd
2341	or timeout without having to allocate/configure/start/stop/free one or	3135	or timeout without having to allocate/configure/start/stop/free one or
2342	more watchers yourself.	3136	more watchers yourself.
2343		3137
2344	If C<fd> is less than 0, then no I/O watcher will be started and events	3138	If C<fd> is less than 0, then no I/O watcher will be started and the
2345	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3139	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2346	C<events> set will be craeted and started.	3140	the given C<fd> and C<events> set will be created and started.
2347		3141
2348	If C<timeout> is less than 0, then no timeout watcher will be	3142	If C<timeout> is less than 0, then no timeout watcher will be
2349	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3143	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2350	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3144	repeat = 0) will be started. C<0> is a valid timeout.
2351	dubious value.
2352		3145
2353	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3146	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2354	passed an C<revents> set like normal event callbacks (a combination of	3147	passed an C<revents> set like normal event callbacks (a combination of
2355	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3148	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2356	value passed to C<ev_once>:	3149	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3150	a timeout and an io event at the same time - you probably should give io
		3151	events precedence.
2357		3152
		3153	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3154
2358	static void stdin_ready (int revents, void *arg)	3155	static void stdin_ready (int revents, void *arg)
2359	{	3156	{
2360	if (revents & EV_TIMEOUT)
2361	/* doh, nothing entered */;
2362	else if (revents & EV_READ)	3157	if (revents & EV_READ)
2363	/* stdin might have data for us, joy! */;	3158	/* stdin might have data for us, joy! */;
		3159	else if (revents & EV_TIMEOUT)
		3160	/* doh, nothing entered */;
2364	}	3161	}
2365		3162
2366	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3163	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2367		3164
2368	=item ev_feed_event (ev_loop *, watcher *, int revents)
2369
2370	Feeds the given event set into the event loop, as if the specified event
2371	had happened for the specified watcher (which must be a pointer to an
2372	initialised but not necessarily started event watcher).
2373
2374	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3165	=item ev_feed_fd_event (loop, int fd, int revents)
2375		3166
2376	Feed an event on the given fd, as if a file descriptor backend detected	3167	Feed an event on the given fd, as if a file descriptor backend detected
2377	the given events it.	3168	the given events it.
2378		3169
2379	=item ev_feed_signal_event (ev_loop *loop, int signum)	3170	=item ev_feed_signal_event (loop, int signum)
2380		3171
2381	Feed an event as if the given signal occured (C<loop> must be the default	3172	Feed an event as if the given signal occurred (C<loop> must be the default
2382	loop!).	3173	loop!).
2383		3174
2384	=back	3175	=back
2385		3176
2386		3177
…		…
2415	=back	3206	=back
2416		3207
2417	=head1 C++ SUPPORT	3208	=head1 C++ SUPPORT
2418		3209
2419	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3210	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2420	you to use some convinience methods to start/stop watchers and also change	3211	you to use some convenience methods to start/stop watchers and also change
2421	the callback model to a model using method callbacks on objects.	3212	the callback model to a model using method callbacks on objects.
2422		3213
2423	To use it,	3214	To use it,
2424		3215
2425	#include <ev++.h>	3216	#include <ev++.h>
2426		3217
2427	This automatically includes F<ev.h> and puts all of its definitions (many	3218	This automatically includes F<ev.h> and puts all of its definitions (many
2428	of them macros) into the global namespace. All C++ specific things are	3219	of them macros) into the global namespace. All C++ specific things are
2429	put into the C<ev> namespace. It should support all the same embedding	3220	put into the C<ev> namespace. It should support all the same embedding
2430	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3221	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2464		3255
2465	=over 4	3256	=over 4
2466		3257
2467	=item ev::TYPE::TYPE ()	3258	=item ev::TYPE::TYPE ()
2468		3259
2469	=item ev::TYPE::TYPE (struct ev_loop *)	3260	=item ev::TYPE::TYPE (loop)
2470		3261
2471	=item ev::TYPE::~TYPE	3262	=item ev::TYPE::~TYPE
2472		3263
2473	The constructor (optionally) takes an event loop to associate the watcher	3264	The constructor (optionally) takes an event loop to associate the watcher
2474	with. If it is omitted, it will use C<EV_DEFAULT>.	3265	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2497	your compiler is good :), then the method will be fully inlined into the	3288	your compiler is good :), then the method will be fully inlined into the
2498	thunking function, making it as fast as a direct C callback.	3289	thunking function, making it as fast as a direct C callback.
2499		3290
2500	Example: simple class declaration and watcher initialisation	3291	Example: simple class declaration and watcher initialisation
2501		3292
2502	struct myclass	3293	struct myclass
2503	{	3294	{
2504	void io_cb (ev::io &w, int revents) { }	3295	void io_cb (ev::io &w, int revents) { }
2505	}	3296	}
2506		3297
2507	myclass obj;	3298	myclass obj;
2508	ev::io iow;	3299	ev::io iow;
2509	iow.set <myclass, &myclass::io_cb> (&obj);	3300	iow.set <myclass, &myclass::io_cb> (&obj);
		3301
		3302	=item w->set (object *)
		3303
		3304	This is an B<experimental> feature that might go away in a future version.
		3305
		3306	This is a variation of a method callback - leaving out the method to call
		3307	will default the method to C<operator ()>, which makes it possible to use
		3308	functor objects without having to manually specify the C<operator ()> all
		3309	the time. Incidentally, you can then also leave out the template argument
		3310	list.
		3311
		3312	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3313	int revents)>.
		3314
		3315	See the method-C<set> above for more details.
		3316
		3317	Example: use a functor object as callback.
		3318
		3319	struct myfunctor
		3320	{
		3321	void operator() (ev::io &w, int revents)
		3322	{
		3323	...
		3324	}
		3325	}
		3326
		3327	myfunctor f;
		3328
		3329	ev::io w;
		3330	w.set (&f);
2510		3331
2511	=item w->set<function> (void *data = 0)	3332	=item w->set<function> (void *data = 0)
2512		3333
2513	Also sets a callback, but uses a static method or plain function as	3334	Also sets a callback, but uses a static method or plain function as
2514	callback. The optional C<data> argument will be stored in the watcher's	3335	callback. The optional C<data> argument will be stored in the watcher's
…		…
2516		3337
2517	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3338	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2518		3339
2519	See the method-C<set> above for more details.	3340	See the method-C<set> above for more details.
2520		3341
2521	Example:	3342	Example: Use a plain function as callback.
2522		3343
2523	static void io_cb (ev::io &w, int revents) { }	3344	static void io_cb (ev::io &w, int revents) { }
2524	iow.set <io_cb> ();	3345	iow.set <io_cb> ();
2525		3346
2526	=item w->set (struct ev_loop *)	3347	=item w->set (loop)
2527		3348
2528	Associates a different C<struct ev_loop> with this watcher. You can only	3349	Associates a different C<struct ev_loop> with this watcher. You can only
2529	do this when the watcher is inactive (and not pending either).	3350	do this when the watcher is inactive (and not pending either).
2530		3351
2531	=item w->set ([args])	3352	=item w->set ([arguments])
2532		3353
2533	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3354	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2534	called at least once. Unlike the C counterpart, an active watcher gets	3355	called at least once. Unlike the C counterpart, an active watcher gets
2535	automatically stopped and restarted when reconfiguring it with this	3356	automatically stopped and restarted when reconfiguring it with this
2536	method.	3357	method.
2537		3358
2538	=item w->start ()	3359	=item w->start ()
…		…
2562	=back	3383	=back
2563		3384
2564	Example: Define a class with an IO and idle watcher, start one of them in	3385	Example: Define a class with an IO and idle watcher, start one of them in
2565	the constructor.	3386	the constructor.
2566		3387
2567	class myclass	3388	class myclass
2568	{	3389	{
2569	ev::io io; void io_cb (ev::io &w, int revents);	3390	ev::io io ; void io_cb (ev::io &w, int revents);
2570	ev:idle idle void idle_cb (ev::idle &w, int revents);	3391	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2571		3392
2572	myclass (int fd)	3393	myclass (int fd)
2573	{	3394	{
2574	io .set <myclass, &myclass::io_cb > (this);	3395	io .set <myclass, &myclass::io_cb > (this);
2575	idle.set <myclass, &myclass::idle_cb> (this);	3396	idle.set <myclass, &myclass::idle_cb> (this);
2576		3397
2577	io.start (fd, ev::READ);	3398	io.start (fd, ev::READ);
2578	}	3399	}
2579	};	3400	};
2580		3401
2581		3402
2582	=head1 OTHER LANGUAGE BINDINGS	3403	=head1 OTHER LANGUAGE BINDINGS
2583		3404
2584	Libev does not offer other language bindings itself, but bindings for a	3405	Libev does not offer other language bindings itself, but bindings for a
2585	numbe rof languages exist in the form of third-party packages. If you know	3406	number of languages exist in the form of third-party packages. If you know
2586	any interesting language binding in addition to the ones listed here, drop	3407	any interesting language binding in addition to the ones listed here, drop
2587	me a note.	3408	me a note.
2588		3409
2589	=over 4	3410	=over 4
2590		3411
2591	=item Perl	3412	=item Perl
2592		3413
2593	The EV module implements the full libev API and is actually used to test	3414	The EV module implements the full libev API and is actually used to test
2594	libev. EV is developed together with libev. Apart from the EV core module,	3415	libev. EV is developed together with libev. Apart from the EV core module,
2595	there are additional modules that implement libev-compatible interfaces	3416	there are additional modules that implement libev-compatible interfaces
2596	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3417	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2597	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3418	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3419	and C<EV::Glib>).
2598		3420
2599	It can be found and installed via CPAN, its homepage is found at	3421	It can be found and installed via CPAN, its homepage is at
2600	L<http://software.schmorp.de/pkg/EV>.	3422	L<http://software.schmorp.de/pkg/EV>.
2601		3423
		3424	=item Python
		3425
		3426	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3427	seems to be quite complete and well-documented.
		3428
2602	=item Ruby	3429	=item Ruby
2603		3430
2604	Tony Arcieri has written a ruby extension that offers access to a subset	3431	Tony Arcieri has written a ruby extension that offers access to a subset
2605	of the libev API and adds filehandle abstractions, asynchronous DNS and	3432	of the libev API and adds file handle abstractions, asynchronous DNS and
2606	more on top of it. It can be found via gem servers. Its homepage is at	3433	more on top of it. It can be found via gem servers. Its homepage is at
2607	L<http://rev.rubyforge.org/>.	3434	L<http://rev.rubyforge.org/>.
2608		3435
		3436	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3437	makes rev work even on mingw.
		3438
		3439	=item Haskell
		3440
		3441	A haskell binding to libev is available at
		3442	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3443
2609	=item D	3444	=item D
2610		3445
2611	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3446	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2612	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3447	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3448
		3449	=item Ocaml
		3450
		3451	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3452	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3453
		3454	=item Lua
		3455
		3456	Brian Maher has written a partial interface to libev for lua (at the
		3457	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3458	L<http://github.com/brimworks/lua-ev>.
2613		3459
2614	=back	3460	=back
2615		3461
2616		3462
2617	=head1 MACRO MAGIC	3463	=head1 MACRO MAGIC
2618		3464
2619	Libev can be compiled with a variety of options, the most fundamantal	3465	Libev can be compiled with a variety of options, the most fundamental
2620	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3466	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2621	functions and callbacks have an initial C<struct ev_loop *> argument.	3467	functions and callbacks have an initial C<struct ev_loop *> argument.
2622		3468
2623	To make it easier to write programs that cope with either variant, the	3469	To make it easier to write programs that cope with either variant, the
2624	following macros are defined:	3470	following macros are defined:
…		…
2629		3475
2630	This provides the loop I<argument> for functions, if one is required ("ev	3476	This provides the loop I<argument> for functions, if one is required ("ev
2631	loop argument"). The C<EV_A> form is used when this is the sole argument,	3477	loop argument"). The C<EV_A> form is used when this is the sole argument,
2632	C<EV_A_> is used when other arguments are following. Example:	3478	C<EV_A_> is used when other arguments are following. Example:
2633		3479
2634	ev_unref (EV_A);	3480	ev_unref (EV_A);
2635	ev_timer_add (EV_A_ watcher);	3481	ev_timer_add (EV_A_ watcher);
2636	ev_loop (EV_A_ 0);	3482	ev_loop (EV_A_ 0);
2637		3483
2638	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3484	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2639	which is often provided by the following macro.	3485	which is often provided by the following macro.
2640		3486
2641	=item C<EV_P>, C<EV_P_>	3487	=item C<EV_P>, C<EV_P_>
2642		3488
2643	This provides the loop I<parameter> for functions, if one is required ("ev	3489	This provides the loop I<parameter> for functions, if one is required ("ev
2644	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3490	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2645	C<EV_P_> is used when other parameters are following. Example:	3491	C<EV_P_> is used when other parameters are following. Example:
2646		3492
2647	// this is how ev_unref is being declared	3493	// this is how ev_unref is being declared
2648	static void ev_unref (EV_P);	3494	static void ev_unref (EV_P);
2649		3495
2650	// this is how you can declare your typical callback	3496	// this is how you can declare your typical callback
2651	static void cb (EV_P_ ev_timer *w, int revents)	3497	static void cb (EV_P_ ev_timer *w, int revents)
2652		3498
2653	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3499	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2654	suitable for use with C<EV_A>.	3500	suitable for use with C<EV_A>.
2655		3501
2656	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3502	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2672		3518
2673	Example: Declare and initialise a check watcher, utilising the above	3519	Example: Declare and initialise a check watcher, utilising the above
2674	macros so it will work regardless of whether multiple loops are supported	3520	macros so it will work regardless of whether multiple loops are supported
2675	or not.	3521	or not.
2676		3522
2677	static void	3523	static void
2678	check_cb (EV_P_ ev_timer *w, int revents)	3524	check_cb (EV_P_ ev_timer *w, int revents)
2679	{	3525	{
2680	ev_check_stop (EV_A_ w);	3526	ev_check_stop (EV_A_ w);
2681	}	3527	}
2682		3528
2683	ev_check check;	3529	ev_check check;
2684	ev_check_init (&check, check_cb);	3530	ev_check_init (&check, check_cb);
2685	ev_check_start (EV_DEFAULT_ &check);	3531	ev_check_start (EV_DEFAULT_ &check);
2686	ev_loop (EV_DEFAULT_ 0);	3532	ev_loop (EV_DEFAULT_ 0);
2687		3533
2688	=head1 EMBEDDING	3534	=head1 EMBEDDING
2689		3535
2690	Libev can (and often is) directly embedded into host	3536	Libev can (and often is) directly embedded into host
2691	applications. Examples of applications that embed it include the Deliantra	3537	applications. Examples of applications that embed it include the Deliantra
…		…
2698	libev somewhere in your source tree).	3544	libev somewhere in your source tree).
2699		3545
2700	=head2 FILESETS	3546	=head2 FILESETS
2701		3547
2702	Depending on what features you need you need to include one or more sets of files	3548	Depending on what features you need you need to include one or more sets of files
2703	in your app.	3549	in your application.
2704		3550
2705	=head3 CORE EVENT LOOP	3551	=head3 CORE EVENT LOOP
2706		3552
2707	To include only the libev core (all the C<ev_*> functions), with manual	3553	To include only the libev core (all the C<ev_*> functions), with manual
2708	configuration (no autoconf):	3554	configuration (no autoconf):
2709		3555
2710	#define EV_STANDALONE 1	3556	#define EV_STANDALONE 1
2711	#include "ev.c"	3557	#include "ev.c"
2712		3558
2713	This will automatically include F<ev.h>, too, and should be done in a	3559	This will automatically include F<ev.h>, too, and should be done in a
2714	single C source file only to provide the function implementations. To use	3560	single C source file only to provide the function implementations. To use
2715	it, do the same for F<ev.h> in all files wishing to use this API (best	3561	it, do the same for F<ev.h> in all files wishing to use this API (best
2716	done by writing a wrapper around F<ev.h> that you can include instead and	3562	done by writing a wrapper around F<ev.h> that you can include instead and
2717	where you can put other configuration options):	3563	where you can put other configuration options):
2718		3564
2719	#define EV_STANDALONE 1	3565	#define EV_STANDALONE 1
2720	#include "ev.h"	3566	#include "ev.h"
2721		3567
2722	Both header files and implementation files can be compiled with a C++	3568	Both header files and implementation files can be compiled with a C++
2723	compiler (at least, thats a stated goal, and breakage will be treated	3569	compiler (at least, that's a stated goal, and breakage will be treated
2724	as a bug).	3570	as a bug).
2725		3571
2726	You need the following files in your source tree, or in a directory	3572	You need the following files in your source tree, or in a directory
2727	in your include path (e.g. in libev/ when using -Ilibev):	3573	in your include path (e.g. in libev/ when using -Ilibev):
2728		3574
2729	ev.h	3575	ev.h
2730	ev.c	3576	ev.c
2731	ev_vars.h	3577	ev_vars.h
2732	ev_wrap.h	3578	ev_wrap.h
2733		3579
2734	ev_win32.c required on win32 platforms only	3580	ev_win32.c required on win32 platforms only
2735		3581
2736	ev_select.c only when select backend is enabled (which is enabled by default)	3582	ev_select.c only when select backend is enabled (which is enabled by default)
2737	ev_poll.c only when poll backend is enabled (disabled by default)	3583	ev_poll.c only when poll backend is enabled (disabled by default)
2738	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3584	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2739	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3585	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2740	ev_port.c only when the solaris port backend is enabled (disabled by default)	3586	ev_port.c only when the solaris port backend is enabled (disabled by default)
2741		3587
2742	F<ev.c> includes the backend files directly when enabled, so you only need	3588	F<ev.c> includes the backend files directly when enabled, so you only need
2743	to compile this single file.	3589	to compile this single file.
2744		3590
2745	=head3 LIBEVENT COMPATIBILITY API	3591	=head3 LIBEVENT COMPATIBILITY API
2746		3592
2747	To include the libevent compatibility API, also include:	3593	To include the libevent compatibility API, also include:
2748		3594
2749	#include "event.c"	3595	#include "event.c"
2750		3596
2751	in the file including F<ev.c>, and:	3597	in the file including F<ev.c>, and:
2752		3598
2753	#include "event.h"	3599	#include "event.h"
2754		3600
2755	in the files that want to use the libevent API. This also includes F<ev.h>.	3601	in the files that want to use the libevent API. This also includes F<ev.h>.
2756		3602
2757	You need the following additional files for this:	3603	You need the following additional files for this:
2758		3604
2759	event.h	3605	event.h
2760	event.c	3606	event.c
2761		3607
2762	=head3 AUTOCONF SUPPORT	3608	=head3 AUTOCONF SUPPORT
2763		3609
2764	Instead of using C<EV_STANDALONE=1> and providing your config in	3610	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2765	whatever way you want, you can also C<m4_include([libev.m4])> in your	3611	whatever way you want, you can also C<m4_include([libev.m4])> in your
2766	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3612	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2767	include F<config.h> and configure itself accordingly.	3613	include F<config.h> and configure itself accordingly.
2768		3614
2769	For this of course you need the m4 file:	3615	For this of course you need the m4 file:
2770		3616
2771	libev.m4	3617	libev.m4
2772		3618
2773	=head2 PREPROCESSOR SYMBOLS/MACROS	3619	=head2 PREPROCESSOR SYMBOLS/MACROS
2774		3620
2775	Libev can be configured via a variety of preprocessor symbols you have to	3621	Libev can be configured via a variety of preprocessor symbols you have to
2776	define before including any of its files. The default in the absense of	3622	define before including (or compiling) any of its files. The default in
2777	autoconf is noted for every option.	3623	the absence of autoconf is documented for every option.
		3624
		3625	Symbols marked with "(h)" do not change the ABI, and can have different
		3626	values when compiling libev vs. including F<ev.h>, so it is permissible
		3627	to redefine them before including F<ev.h> without breakign compatibility
		3628	to a compiled library. All other symbols change the ABI, which means all
		3629	users of libev and the libev code itself must be compiled with compatible
		3630	settings.
2778		3631
2779	=over 4	3632	=over 4
2780		3633
2781	=item EV_STANDALONE	3634	=item EV_STANDALONE (h)
2782		3635
2783	Must always be C<1> if you do not use autoconf configuration, which	3636	Must always be C<1> if you do not use autoconf configuration, which
2784	keeps libev from including F<config.h>, and it also defines dummy	3637	keeps libev from including F<config.h>, and it also defines dummy
2785	implementations for some libevent functions (such as logging, which is not	3638	implementations for some libevent functions (such as logging, which is not
2786	supported). It will also not define any of the structs usually found in	3639	supported). It will also not define any of the structs usually found in
2787	F<event.h> that are not directly supported by the libev core alone.	3640	F<event.h> that are not directly supported by the libev core alone.
2788		3641
		3642	In standalone mode, libev will still try to automatically deduce the
		3643	configuration, but has to be more conservative.
		3644
2789	=item EV_USE_MONOTONIC	3645	=item EV_USE_MONOTONIC
2790		3646
2791	If defined to be C<1>, libev will try to detect the availability of the	3647	If defined to be C<1>, libev will try to detect the availability of the
2792	monotonic clock option at both compiletime and runtime. Otherwise no use	3648	monotonic clock option at both compile time and runtime. Otherwise no
2793	of the monotonic clock option will be attempted. If you enable this, you	3649	use of the monotonic clock option will be attempted. If you enable this,
2794	usually have to link against librt or something similar. Enabling it when	3650	you usually have to link against librt or something similar. Enabling it
2795	the functionality isn't available is safe, though, although you have	3651	when the functionality isn't available is safe, though, although you have
2796	to make sure you link against any libraries where the C<clock_gettime>	3652	to make sure you link against any libraries where the C<clock_gettime>
2797	function is hiding in (often F<-lrt>).	3653	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2798		3654
2799	=item EV_USE_REALTIME	3655	=item EV_USE_REALTIME
2800		3656
2801	If defined to be C<1>, libev will try to detect the availability of the	3657	If defined to be C<1>, libev will try to detect the availability of the
2802	realtime clock option at compiletime (and assume its availability at	3658	real-time clock option at compile time (and assume its availability
2803	runtime if successful). Otherwise no use of the realtime clock option will	3659	at runtime if successful). Otherwise no use of the real-time clock
2804	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3660	option will be attempted. This effectively replaces C<gettimeofday>
2805	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3661	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2806	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3662	correctness. See the note about libraries in the description of
		3663	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3664	C<EV_USE_CLOCK_SYSCALL>.
		3665
		3666	=item EV_USE_CLOCK_SYSCALL
		3667
		3668	If defined to be C<1>, libev will try to use a direct syscall instead
		3669	of calling the system-provided C<clock_gettime> function. This option
		3670	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3671	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3672	programs needlessly. Using a direct syscall is slightly slower (in
		3673	theory), because no optimised vdso implementation can be used, but avoids
		3674	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3675	higher, as it simplifies linking (no need for C<-lrt>).
2807		3676
2808	=item EV_USE_NANOSLEEP	3677	=item EV_USE_NANOSLEEP
2809		3678
2810	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3679	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2811	and will use it for delays. Otherwise it will use C<select ()>.	3680	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2819	2.7 or newer, otherwise disabled.	3688	2.7 or newer, otherwise disabled.
2820		3689
2821	=item EV_USE_SELECT	3690	=item EV_USE_SELECT
2822		3691
2823	If undefined or defined to be C<1>, libev will compile in support for the	3692	If undefined or defined to be C<1>, libev will compile in support for the
2824	C<select>(2) backend. No attempt at autodetection will be done: if no	3693	C<select>(2) backend. No attempt at auto-detection will be done: if no
2825	other method takes over, select will be it. Otherwise the select backend	3694	other method takes over, select will be it. Otherwise the select backend
2826	will not be compiled in.	3695	will not be compiled in.
2827		3696
2828	=item EV_SELECT_USE_FD_SET	3697	=item EV_SELECT_USE_FD_SET
2829		3698
2830	If defined to C<1>, then the select backend will use the system C<fd_set>	3699	If defined to C<1>, then the select backend will use the system C<fd_set>
2831	structure. This is useful if libev doesn't compile due to a missing	3700	structure. This is useful if libev doesn't compile due to a missing
2832	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3701	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2833	exotic systems. This usually limits the range of file descriptors to some	3702	on exotic systems. This usually limits the range of file descriptors to
2834	low limit such as 1024 or might have other limitations (winsocket only	3703	some low limit such as 1024 or might have other limitations (winsocket
2835	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3704	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2836	influence the size of the C<fd_set> used.	3705	configures the maximum size of the C<fd_set>.
2837		3706
2838	=item EV_SELECT_IS_WINSOCKET	3707	=item EV_SELECT_IS_WINSOCKET
2839		3708
2840	When defined to C<1>, the select backend will assume that	3709	When defined to C<1>, the select backend will assume that
2841	select/socket/connect etc. don't understand file descriptors but	3710	select/socket/connect etc. don't understand file descriptors but
…		…
2843	be used is the winsock select). This means that it will call	3712	be used is the winsock select). This means that it will call
2844	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3713	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2845	it is assumed that all these functions actually work on fds, even	3714	it is assumed that all these functions actually work on fds, even
2846	on win32. Should not be defined on non-win32 platforms.	3715	on win32. Should not be defined on non-win32 platforms.
2847		3716
2848	=item EV_FD_TO_WIN32_HANDLE	3717	=item EV_FD_TO_WIN32_HANDLE(fd)
2849		3718
2850	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3719	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2851	file descriptors to socket handles. When not defining this symbol (the	3720	file descriptors to socket handles. When not defining this symbol (the
2852	default), then libev will call C<_get_osfhandle>, which is usually	3721	default), then libev will call C<_get_osfhandle>, which is usually
2853	correct. In some cases, programs use their own file descriptor management,	3722	correct. In some cases, programs use their own file descriptor management,
2854	in which case they can provide this function to map fds to socket handles.	3723	in which case they can provide this function to map fds to socket handles.
		3724
		3725	=item EV_WIN32_HANDLE_TO_FD(handle)
		3726
		3727	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3728	using the standard C<_open_osfhandle> function. For programs implementing
		3729	their own fd to handle mapping, overwriting this function makes it easier
		3730	to do so. This can be done by defining this macro to an appropriate value.
		3731
		3732	=item EV_WIN32_CLOSE_FD(fd)
		3733
		3734	If programs implement their own fd to handle mapping on win32, then this
		3735	macro can be used to override the C<close> function, useful to unregister
		3736	file descriptors again. Note that the replacement function has to close
		3737	the underlying OS handle.
2855		3738
2856	=item EV_USE_POLL	3739	=item EV_USE_POLL
2857		3740
2858	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3741	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2859	backend. Otherwise it will be enabled on non-win32 platforms. It	3742	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2886	otherwise another method will be used as fallback. This is the preferred	3769	otherwise another method will be used as fallback. This is the preferred
2887	backend for Solaris 10 systems.	3770	backend for Solaris 10 systems.
2888		3771
2889	=item EV_USE_DEVPOLL	3772	=item EV_USE_DEVPOLL
2890		3773
2891	reserved for future expansion, works like the USE symbols above.	3774	Reserved for future expansion, works like the USE symbols above.
2892		3775
2893	=item EV_USE_INOTIFY	3776	=item EV_USE_INOTIFY
2894		3777
2895	If defined to be C<1>, libev will compile in support for the Linux inotify	3778	If defined to be C<1>, libev will compile in support for the Linux inotify
2896	interface to speed up C<ev_stat> watchers. Its actual availability will	3779	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2903	access is atomic with respect to other threads or signal contexts. No such	3786	access is atomic with respect to other threads or signal contexts. No such
2904	type is easily found in the C language, so you can provide your own type	3787	type is easily found in the C language, so you can provide your own type
2905	that you know is safe for your purposes. It is used both for signal handler "locking"	3788	that you know is safe for your purposes. It is used both for signal handler "locking"
2906	as well as for signal and thread safety in C<ev_async> watchers.	3789	as well as for signal and thread safety in C<ev_async> watchers.
2907		3790
2908	In the absense of this define, libev will use C<sig_atomic_t volatile>	3791	In the absence of this define, libev will use C<sig_atomic_t volatile>
2909	(from F<signal.h>), which is usually good enough on most platforms.	3792	(from F<signal.h>), which is usually good enough on most platforms.
2910		3793
2911	=item EV_H	3794	=item EV_H (h)
2912		3795
2913	The name of the F<ev.h> header file used to include it. The default if	3796	The name of the F<ev.h> header file used to include it. The default if
2914	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3797	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2915	used to virtually rename the F<ev.h> header file in case of conflicts.	3798	used to virtually rename the F<ev.h> header file in case of conflicts.
2916		3799
2917	=item EV_CONFIG_H	3800	=item EV_CONFIG_H (h)
2918		3801
2919	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3802	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2920	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3803	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2921	C<EV_H>, above.	3804	C<EV_H>, above.
2922		3805
2923	=item EV_EVENT_H	3806	=item EV_EVENT_H (h)
2924		3807
2925	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3808	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2926	of how the F<event.h> header can be found, the default is C<"event.h">.	3809	of how the F<event.h> header can be found, the default is C<"event.h">.
2927		3810
2928	=item EV_PROTOTYPES	3811	=item EV_PROTOTYPES (h)
2929		3812
2930	If defined to be C<0>, then F<ev.h> will not define any function	3813	If defined to be C<0>, then F<ev.h> will not define any function
2931	prototypes, but still define all the structs and other symbols. This is	3814	prototypes, but still define all the structs and other symbols. This is
2932	occasionally useful if you want to provide your own wrapper functions	3815	occasionally useful if you want to provide your own wrapper functions
2933	around libev functions.	3816	around libev functions.
…		…
2952	When doing priority-based operations, libev usually has to linearly search	3835	When doing priority-based operations, libev usually has to linearly search
2953	all the priorities, so having many of them (hundreds) uses a lot of space	3836	all the priorities, so having many of them (hundreds) uses a lot of space
2954	and time, so using the defaults of five priorities (-2 .. +2) is usually	3837	and time, so using the defaults of five priorities (-2 .. +2) is usually
2955	fine.	3838	fine.
2956		3839
2957	If your embedding app does not need any priorities, defining these both to	3840	If your embedding application does not need any priorities, defining these
2958	C<0> will save some memory and cpu.	3841	both to C<0> will save some memory and CPU.
2959		3842
2960	=item EV_PERIODIC_ENABLE	3843	=item EV_PERIODIC_ENABLE
2961		3844
2962	If undefined or defined to be C<1>, then periodic timers are supported. If	3845	If undefined or defined to be C<1>, then periodic timers are supported. If
2963	defined to be C<0>, then they are not. Disabling them saves a few kB of	3846	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2970	code.	3853	code.
2971		3854
2972	=item EV_EMBED_ENABLE	3855	=item EV_EMBED_ENABLE
2973		3856
2974	If undefined or defined to be C<1>, then embed watchers are supported. If	3857	If undefined or defined to be C<1>, then embed watchers are supported. If
2975	defined to be C<0>, then they are not.	3858	defined to be C<0>, then they are not. Embed watchers rely on most other
		3859	watcher types, which therefore must not be disabled.
2976		3860
2977	=item EV_STAT_ENABLE	3861	=item EV_STAT_ENABLE
2978		3862
2979	If undefined or defined to be C<1>, then stat watchers are supported. If	3863	If undefined or defined to be C<1>, then stat watchers are supported. If
2980	defined to be C<0>, then they are not.	3864	defined to be C<0>, then they are not.
…		…
2990	defined to be C<0>, then they are not.	3874	defined to be C<0>, then they are not.
2991		3875
2992	=item EV_MINIMAL	3876	=item EV_MINIMAL
2993		3877
2994	If you need to shave off some kilobytes of code at the expense of some	3878	If you need to shave off some kilobytes of code at the expense of some
2995	speed, define this symbol to C<1>. Currently this is used to override some	3879	speed (but with the full API), define this symbol to C<1>. Currently this
2996	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3880	is used to override some inlining decisions, saves roughly 30% code size
2997	much smaller 2-heap for timer management over the default 4-heap.	3881	on amd64. It also selects a much smaller 2-heap for timer management over
		3882	the default 4-heap.
		3883
		3884	You can save even more by disabling watcher types you do not need
		3885	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3886	(C<-DNDEBUG>) will usually reduce code size a lot.
		3887
		3888	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3889	provide a bare-bones event library. See C<ev.h> for details on what parts
		3890	of the API are still available, and do not complain if this subset changes
		3891	over time.
		3892
		3893	=item EV_AVOID_STDIO
		3894
		3895	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3896	functions (printf, scanf, perror etc.). This will increase the codesize
		3897	somewhat, but if your program doesn't otherwise depend on stdio and your
		3898	libc allows it, this avoids linking in the stdio library which is quite
		3899	big.
		3900
		3901	Note that error messages might become less precise when this option is
		3902	enabled.
		3903
		3904	=item EV_NSIG
		3905
		3906	The highest supported signal number, +1 (or, the number of
		3907	signals): Normally, libev tries to deduce the maximum number of signals
		3908	automatically, but sometimes this fails, in which case it can be
		3909	specified. Also, using a lower number than detected (C<32> should be
		3910	good for about any system in existance) can save some memory, as libev
		3911	statically allocates some 12-24 bytes per signal number.
2998		3912
2999	=item EV_PID_HASHSIZE	3913	=item EV_PID_HASHSIZE
3000		3914
3001	C<ev_child> watchers use a small hash table to distribute workload by	3915	C<ev_child> watchers use a small hash table to distribute workload by
3002	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3916	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3012	two).	3926	two).
3013		3927
3014	=item EV_USE_4HEAP	3928	=item EV_USE_4HEAP
3015		3929
3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3930	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3017	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3931	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3018	to C<1>. The 4-heap uses more complicated (longer) code but has	3932	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3019	noticably faster performance with many (thousands) of watchers.	3933	faster performance with many (thousands) of watchers.
3020		3934
3021	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3935	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3022	(disabled).	3936	(disabled).
3023		3937
3024	=item EV_HEAP_CACHE_AT	3938	=item EV_HEAP_CACHE_AT
3025		3939
3026	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3940	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3027	timer and periodics heap, libev can cache the timestamp (I<at>) within	3941	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3028	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3942	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3029	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3943	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3030	but avoids random read accesses on heap changes. This improves performance	3944	but avoids random read accesses on heap changes. This improves performance
3031	noticably with with many (hundreds) of watchers.	3945	noticeably with many (hundreds) of watchers.
3032		3946
3033	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3947	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3034	(disabled).	3948	(disabled).
		3949
		3950	=item EV_VERIFY
		3951
		3952	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3953	be done: If set to C<0>, no internal verification code will be compiled
		3954	in. If set to C<1>, then verification code will be compiled in, but not
		3955	called. If set to C<2>, then the internal verification code will be
		3956	called once per loop, which can slow down libev. If set to C<3>, then the
		3957	verification code will be called very frequently, which will slow down
		3958	libev considerably.
		3959
		3960	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3961	C<0>.
3035		3962
3036	=item EV_COMMON	3963	=item EV_COMMON
3037		3964
3038	By default, all watchers have a C<void *data> member. By redefining	3965	By default, all watchers have a C<void *data> member. By redefining
3039	this macro to a something else you can include more and other types of	3966	this macro to a something else you can include more and other types of
3040	members. You have to define it each time you include one of the files,	3967	members. You have to define it each time you include one of the files,
3041	though, and it must be identical each time.	3968	though, and it must be identical each time.
3042		3969
3043	For example, the perl EV module uses something like this:	3970	For example, the perl EV module uses something like this:
3044		3971
3045	#define EV_COMMON \	3972	#define EV_COMMON \
3046	SV *self; /* contains this struct */ \	3973	SV *self; /* contains this struct */ \
3047	SV *cb_sv, *fh /* note no trailing ";" */	3974	SV *cb_sv, *fh /* note no trailing ";" */
3048		3975
3049	=item EV_CB_DECLARE (type)	3976	=item EV_CB_DECLARE (type)
3050		3977
3051	=item EV_CB_INVOKE (watcher, revents)	3978	=item EV_CB_INVOKE (watcher, revents)
3052		3979
…		…
3057	definition and a statement, respectively. See the F<ev.h> header file for	3984	definition and a statement, respectively. See the F<ev.h> header file for
3058	their default definitions. One possible use for overriding these is to	3985	their default definitions. One possible use for overriding these is to
3059	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3986	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3060	method calls instead of plain function calls in C++.	3987	method calls instead of plain function calls in C++.
3061		3988
		3989	=back
		3990
3062	=head2 EXPORTED API SYMBOLS	3991	=head2 EXPORTED API SYMBOLS
3063		3992
3064	If you need to re-export the API (e.g. via a dll) and you need a list of	3993	If you need to re-export the API (e.g. via a DLL) and you need a list of
3065	exported symbols, you can use the provided F<Symbol.*> files which list	3994	exported symbols, you can use the provided F<Symbol.*> files which list
3066	all public symbols, one per line:	3995	all public symbols, one per line:
3067		3996
3068	Symbols.ev for libev proper	3997	Symbols.ev for libev proper
3069	Symbols.event for the libevent emulation	3998	Symbols.event for the libevent emulation
3070		3999
3071	This can also be used to rename all public symbols to avoid clashes with	4000	This can also be used to rename all public symbols to avoid clashes with
3072	multiple versions of libev linked together (which is obviously bad in	4001	multiple versions of libev linked together (which is obviously bad in
3073	itself, but sometimes it is inconvinient to avoid this).	4002	itself, but sometimes it is inconvenient to avoid this).
3074		4003
3075	A sed command like this will create wrapper C<#define>'s that you need to	4004	A sed command like this will create wrapper C<#define>'s that you need to
3076	include before including F<ev.h>:	4005	include before including F<ev.h>:
3077		4006
3078	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4007	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3095	file.	4024	file.
3096		4025
3097	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4026	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3098	that everybody includes and which overrides some configure choices:	4027	that everybody includes and which overrides some configure choices:
3099		4028
3100	#define EV_MINIMAL 1	4029	#define EV_MINIMAL 1
3101	#define EV_USE_POLL 0	4030	#define EV_USE_POLL 0
3102	#define EV_MULTIPLICITY 0	4031	#define EV_MULTIPLICITY 0
3103	#define EV_PERIODIC_ENABLE 0	4032	#define EV_PERIODIC_ENABLE 0
3104	#define EV_STAT_ENABLE 0	4033	#define EV_STAT_ENABLE 0
3105	#define EV_FORK_ENABLE 0	4034	#define EV_FORK_ENABLE 0
3106	#define EV_CONFIG_H <config.h>	4035	#define EV_CONFIG_H <config.h>
3107	#define EV_MINPRI 0	4036	#define EV_MINPRI 0
3108	#define EV_MAXPRI 0	4037	#define EV_MAXPRI 0
3109		4038
3110	#include "ev++.h"	4039	#include "ev++.h"
3111		4040
3112	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4041	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3113		4042
3114	#include "ev_cpp.h"	4043	#include "ev_cpp.h"
3115	#include "ev.c"	4044	#include "ev.c"
3116		4045
		4046	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3117		4047
3118	=head1 THREADS AND COROUTINES	4048	=head2 THREADS AND COROUTINES
3119		4049
3120	=head2 THREADS	4050	=head3 THREADS
3121		4051
3122	Libev itself is completely threadsafe, but it uses no locking. This	4052	All libev functions are reentrant and thread-safe unless explicitly
		4053	documented otherwise, but libev implements no locking itself. This means
3123	means that you can use as many loops as you want in parallel, as long as	4054	that you can use as many loops as you want in parallel, as long as there
3124	only one thread ever calls into one libev function with the same loop	4055	are no concurrent calls into any libev function with the same loop
3125	parameter.	4056	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4057	of course): libev guarantees that different event loops share no data
		4058	structures that need any locking.
3126		4059
3127	Or put differently: calls with different loop parameters can be done in	4060	Or to put it differently: calls with different loop parameters can be done
3128	parallel from multiple threads, calls with the same loop parameter must be	4061	concurrently from multiple threads, calls with the same loop parameter
3129	done serially (but can be done from different threads, as long as only one	4062	must be done serially (but can be done from different threads, as long as
3130	thread ever is inside a call at any point in time, e.g. by using a mutex	4063	only one thread ever is inside a call at any point in time, e.g. by using
3131	per loop).	4064	a mutex per loop).
3132		4065
3133	If you want to know which design is best for your problem, then I cannot	4066	Specifically to support threads (and signal handlers), libev implements
		4067	so-called C<ev_async> watchers, which allow some limited form of
		4068	concurrency on the same event loop, namely waking it up "from the
		4069	outside".
		4070
		4071	If you want to know which design (one loop, locking, or multiple loops
		4072	without or something else still) is best for your problem, then I cannot
3134	help you but by giving some generic advice:	4073	help you, but here is some generic advice:
3135		4074
3136	=over 4	4075	=over 4
3137		4076
3138	=item * most applications have a main thread: use the default libev loop	4077	=item * most applications have a main thread: use the default libev loop
3139	in that thread, or create a seperate thread running only the default loop.	4078	in that thread, or create a separate thread running only the default loop.
3140		4079
3141	This helps integrating other libraries or software modules that use libev	4080	This helps integrating other libraries or software modules that use libev
3142	themselves and don't care/know about threading.	4081	themselves and don't care/know about threading.
3143		4082
3144	=item * one loop per thread is usually a good model.	4083	=item * one loop per thread is usually a good model.
3145		4084
3146	Doing this is almost never wrong, sometimes a better-performance model	4085	Doing this is almost never wrong, sometimes a better-performance model
3147	exists, but it is always a good start.	4086	exists, but it is always a good start.
3148		4087
3149	=item * other models exist, such as the leader/follower pattern, where one	4088	=item * other models exist, such as the leader/follower pattern, where one
3150	loop is handed through multiple threads in a kind of round-robbin fashion.	4089	loop is handed through multiple threads in a kind of round-robin fashion.
3151		4090
3152	Chosing a model is hard - look around, learn, know that usually you cna do	4091	Choosing a model is hard - look around, learn, know that usually you can do
3153	better than you currently do :-)	4092	better than you currently do :-)
3154		4093
3155	=item * often you need to talk to some other thread which blocks in the	4094	=item * often you need to talk to some other thread which blocks in the
		4095	event loop.
		4096
3156	event loop - C<ev_async> watchers can be used to wake them up from other	4097	C<ev_async> watchers can be used to wake them up from other threads safely
3157	threads safely (or from signal contexts...).	4098	(or from signal contexts...).
		4099
		4100	An example use would be to communicate signals or other events that only
		4101	work in the default loop by registering the signal watcher with the
		4102	default loop and triggering an C<ev_async> watcher from the default loop
		4103	watcher callback into the event loop interested in the signal.
3158		4104
3159	=back	4105	=back
3160		4106
		4107	=head4 THREAD LOCKING EXAMPLE
		4108
		4109	Here is a fictitious example of how to run an event loop in a different
		4110	thread than where callbacks are being invoked and watchers are
		4111	created/added/removed.
		4112
		4113	For a real-world example, see the C<EV::Loop::Async> perl module,
		4114	which uses exactly this technique (which is suited for many high-level
		4115	languages).
		4116
		4117	The example uses a pthread mutex to protect the loop data, a condition
		4118	variable to wait for callback invocations, an async watcher to notify the
		4119	event loop thread and an unspecified mechanism to wake up the main thread.
		4120
		4121	First, you need to associate some data with the event loop:
		4122
		4123	typedef struct {
		4124	mutex_t lock; /* global loop lock */
		4125	ev_async async_w;
		4126	thread_t tid;
		4127	cond_t invoke_cv;
		4128	} userdata;
		4129
		4130	void prepare_loop (EV_P)
		4131	{
		4132	// for simplicity, we use a static userdata struct.
		4133	static userdata u;
		4134
		4135	ev_async_init (&u->async_w, async_cb);
		4136	ev_async_start (EV_A_ &u->async_w);
		4137
		4138	pthread_mutex_init (&u->lock, 0);
		4139	pthread_cond_init (&u->invoke_cv, 0);
		4140
		4141	// now associate this with the loop
		4142	ev_set_userdata (EV_A_ u);
		4143	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4144	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4145
		4146	// then create the thread running ev_loop
		4147	pthread_create (&u->tid, 0, l_run, EV_A);
		4148	}
		4149
		4150	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4151	solely to wake up the event loop so it takes notice of any new watchers
		4152	that might have been added:
		4153
		4154	static void
		4155	async_cb (EV_P_ ev_async *w, int revents)
		4156	{
		4157	// just used for the side effects
		4158	}
		4159
		4160	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4161	protecting the loop data, respectively.
		4162
		4163	static void
		4164	l_release (EV_P)
		4165	{
		4166	userdata *u = ev_userdata (EV_A);
		4167	pthread_mutex_unlock (&u->lock);
		4168	}
		4169
		4170	static void
		4171	l_acquire (EV_P)
		4172	{
		4173	userdata *u = ev_userdata (EV_A);
		4174	pthread_mutex_lock (&u->lock);
		4175	}
		4176
		4177	The event loop thread first acquires the mutex, and then jumps straight
		4178	into C<ev_loop>:
		4179
		4180	void *
		4181	l_run (void *thr_arg)
		4182	{
		4183	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4184
		4185	l_acquire (EV_A);
		4186	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4187	ev_loop (EV_A_ 0);
		4188	l_release (EV_A);
		4189
		4190	return 0;
		4191	}
		4192
		4193	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4194	signal the main thread via some unspecified mechanism (signals? pipe
		4195	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4196	have been called (in a while loop because a) spurious wakeups are possible
		4197	and b) skipping inter-thread-communication when there are no pending
		4198	watchers is very beneficial):
		4199
		4200	static void
		4201	l_invoke (EV_P)
		4202	{
		4203	userdata *u = ev_userdata (EV_A);
		4204
		4205	while (ev_pending_count (EV_A))
		4206	{
		4207	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4208	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4209	}
		4210	}
		4211
		4212	Now, whenever the main thread gets told to invoke pending watchers, it
		4213	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4214	thread to continue:
		4215
		4216	static void
		4217	real_invoke_pending (EV_P)
		4218	{
		4219	userdata *u = ev_userdata (EV_A);
		4220
		4221	pthread_mutex_lock (&u->lock);
		4222	ev_invoke_pending (EV_A);
		4223	pthread_cond_signal (&u->invoke_cv);
		4224	pthread_mutex_unlock (&u->lock);
		4225	}
		4226
		4227	Whenever you want to start/stop a watcher or do other modifications to an
		4228	event loop, you will now have to lock:
		4229
		4230	ev_timer timeout_watcher;
		4231	userdata *u = ev_userdata (EV_A);
		4232
		4233	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4234
		4235	pthread_mutex_lock (&u->lock);
		4236	ev_timer_start (EV_A_ &timeout_watcher);
		4237	ev_async_send (EV_A_ &u->async_w);
		4238	pthread_mutex_unlock (&u->lock);
		4239
		4240	Note that sending the C<ev_async> watcher is required because otherwise
		4241	an event loop currently blocking in the kernel will have no knowledge
		4242	about the newly added timer. By waking up the loop it will pick up any new
		4243	watchers in the next event loop iteration.
		4244
3161	=head2 COROUTINES	4245	=head3 COROUTINES
3162		4246
3163	Libev is much more accomodating to coroutines ("cooperative threads"):	4247	Libev is very accommodating to coroutines ("cooperative threads"):
3164	libev fully supports nesting calls to it's functions from different	4248	libev fully supports nesting calls to its functions from different
3165	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4249	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3166	different coroutines and switch freely between both coroutines running the	4250	different coroutines, and switch freely between both coroutines running
3167	loop, as long as you don't confuse yourself). The only exception is that	4251	the loop, as long as you don't confuse yourself). The only exception is
3168	you must not do this from C<ev_periodic> reschedule callbacks.	4252	that you must not do this from C<ev_periodic> reschedule callbacks.
3169		4253
3170	Care has been invested into making sure that libev does not keep local	4254	Care has been taken to ensure that libev does not keep local state inside
3171	state inside C<ev_loop>, and other calls do not usually allow coroutine	4255	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3172	switches.	4256	they do not call any callbacks.
3173		4257
		4258	=head2 COMPILER WARNINGS
3174		4259
3175	=head1 COMPLEXITIES	4260	Depending on your compiler and compiler settings, you might get no or a
		4261	lot of warnings when compiling libev code. Some people are apparently
		4262	scared by this.
3176		4263
3177	In this section the complexities of (many of) the algorithms used inside	4264	However, these are unavoidable for many reasons. For one, each compiler
3178	libev will be explained. For complexity discussions about backends see the	4265	has different warnings, and each user has different tastes regarding
3179	documentation for C<ev_default_init>.	4266	warning options. "Warn-free" code therefore cannot be a goal except when
		4267	targeting a specific compiler and compiler-version.
3180		4268
3181	All of the following are about amortised time: If an array needs to be	4269	Another reason is that some compiler warnings require elaborate
3182	extended, libev needs to realloc and move the whole array, but this	4270	workarounds, or other changes to the code that make it less clear and less
3183	happens asymptotically never with higher number of elements, so O(1) might	4271	maintainable.
3184	mean it might do a lengthy realloc operation in rare cases, but on average
3185	it is much faster and asymptotically approaches constant time.
3186		4272
3187	=over 4	4273	And of course, some compiler warnings are just plain stupid, or simply
		4274	wrong (because they don't actually warn about the condition their message
		4275	seems to warn about). For example, certain older gcc versions had some
		4276	warnings that resulted an extreme number of false positives. These have
		4277	been fixed, but some people still insist on making code warn-free with
		4278	such buggy versions.
3188		4279
3189	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4280	While libev is written to generate as few warnings as possible,
		4281	"warn-free" code is not a goal, and it is recommended not to build libev
		4282	with any compiler warnings enabled unless you are prepared to cope with
		4283	them (e.g. by ignoring them). Remember that warnings are just that:
		4284	warnings, not errors, or proof of bugs.
3190		4285
3191	This means that, when you have a watcher that triggers in one hour and
3192	there are 100 watchers that would trigger before that then inserting will
3193	have to skip roughly seven (C<ld 100>) of these watchers.
3194		4286
3195	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4287	=head2 VALGRIND
3196		4288
3197	That means that changing a timer costs less than removing/adding them	4289	Valgrind has a special section here because it is a popular tool that is
3198	as only the relative motion in the event queue has to be paid for.	4290	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3199		4291
3200	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4292	If you think you found a bug (memory leak, uninitialised data access etc.)
		4293	in libev, then check twice: If valgrind reports something like:
3201		4294
3202	These just add the watcher into an array or at the head of a list.	4295	==2274== definitely lost: 0 bytes in 0 blocks.
		4296	==2274== possibly lost: 0 bytes in 0 blocks.
		4297	==2274== still reachable: 256 bytes in 1 blocks.
3203		4298
3204	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4299	Then there is no memory leak, just as memory accounted to global variables
		4300	is not a memleak - the memory is still being referenced, and didn't leak.
3205		4301
3206	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4302	Similarly, under some circumstances, valgrind might report kernel bugs
		4303	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4304	although an acceptable workaround has been found here), or it might be
		4305	confused.
3207		4306
3208	These watchers are stored in lists then need to be walked to find the	4307	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3209	correct watcher to remove. The lists are usually short (you don't usually	4308	make it into some kind of religion.
3210	have many watchers waiting for the same fd or signal).
3211		4309
3212	=item Finding the next timer in each loop iteration: O(1)	4310	If you are unsure about something, feel free to contact the mailing list
		4311	with the full valgrind report and an explanation on why you think this
		4312	is a bug in libev (best check the archives, too :). However, don't be
		4313	annoyed when you get a brisk "this is no bug" answer and take the chance
		4314	of learning how to interpret valgrind properly.
3213		4315
3214	By virtue of using a binary or 4-heap, the next timer is always found at a	4316	If you need, for some reason, empty reports from valgrind for your project
3215	fixed position in the storage array.	4317	I suggest using suppression lists.
3216		4318
3217	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3218		4319
3219	A change means an I/O watcher gets started or stopped, which requires	4320	=head1 PORTABILITY NOTES
3220	libev to recalculate its status (and possibly tell the kernel, depending
3221	on backend and wether C<ev_io_set> was used).
3222		4321
3223	=item Activating one watcher (putting it into the pending state): O(1)	4322	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3224
3225	=item Priority handling: O(number_of_priorities)
3226
3227	Priorities are implemented by allocating some space for each
3228	priority. When doing priority-based operations, libev usually has to
3229	linearly search all the priorities, but starting/stopping and activating
3230	watchers becomes O(1) w.r.t. priority handling.
3231
3232	=item Sending an ev_async: O(1)
3233
3234	=item Processing ev_async_send: O(number_of_async_watchers)
3235
3236	=item Processing signals: O(max_signal_number)
3237
3238	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3239	calls in the current loop iteration. Checking for async and signal events
3240	involves iterating over all running async watchers or all signal numbers.
3241
3242	=back
3243
3244
3245	=head1 Win32 platform limitations and workarounds
3246		4323
3247	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4324	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3248	requires, and its I/O model is fundamentally incompatible with the POSIX	4325	requires, and its I/O model is fundamentally incompatible with the POSIX
3249	model. Libev still offers limited functionality on this platform in	4326	model. Libev still offers limited functionality on this platform in
3250	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4327	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3257	way (note also that glib is the slowest event library known to man).	4334	way (note also that glib is the slowest event library known to man).
3258		4335
3259	There is no supported compilation method available on windows except	4336	There is no supported compilation method available on windows except
3260	embedding it into other applications.	4337	embedding it into other applications.
3261		4338
		4339	Sensible signal handling is officially unsupported by Microsoft - libev
		4340	tries its best, but under most conditions, signals will simply not work.
		4341
		4342	Not a libev limitation but worth mentioning: windows apparently doesn't
		4343	accept large writes: instead of resulting in a partial write, windows will
		4344	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4345	so make sure you only write small amounts into your sockets (less than a
		4346	megabyte seems safe, but this apparently depends on the amount of memory
		4347	available).
		4348
3262	Due to the many, low, and arbitrary limits on the win32 platform and	4349	Due to the many, low, and arbitrary limits on the win32 platform and
3263	the abysmal performance of winsockets, using a large number of sockets	4350	the abysmal performance of winsockets, using a large number of sockets
3264	is not recommended (and not reasonable). If your program needs to use	4351	is not recommended (and not reasonable). If your program needs to use
3265	more than a hundred or so sockets, then likely it needs to use a totally	4352	more than a hundred or so sockets, then likely it needs to use a totally
3266	different implementation for windows, as libev offers the POSIX readiness	4353	different implementation for windows, as libev offers the POSIX readiness
3267	notification model, which cannot be implemented efficiently on windows	4354	notification model, which cannot be implemented efficiently on windows
3268	(microsoft monopoly games).	4355	(due to Microsoft monopoly games).
		4356
		4357	A typical way to use libev under windows is to embed it (see the embedding
		4358	section for details) and use the following F<evwrap.h> header file instead
		4359	of F<ev.h>:
		4360
		4361	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4362	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4363
		4364	#include "ev.h"
		4365
		4366	And compile the following F<evwrap.c> file into your project (make sure
		4367	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4368
		4369	#include "evwrap.h"
		4370	#include "ev.c"
3269		4371
3270	=over 4	4372	=over 4
3271		4373
3272	=item The winsocket select function	4374	=item The winsocket select function
3273		4375
3274	The winsocket C<select> function doesn't follow POSIX in that it requires	4376	The winsocket C<select> function doesn't follow POSIX in that it
3275	socket I<handles> and not socket I<file descriptors>. This makes select	4377	requires socket I<handles> and not socket I<file descriptors> (it is
3276	very inefficient, and also requires a mapping from file descriptors	4378	also extremely buggy). This makes select very inefficient, and also
3277	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4379	requires a mapping from file descriptors to socket handles (the Microsoft
3278	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4380	C runtime provides the function C<_open_osfhandle> for this). See the
3279	symbols for more info.	4381	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4382	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3280		4383
3281	The configuration for a "naked" win32 using the microsoft runtime	4384	The configuration for a "naked" win32 using the Microsoft runtime
3282	libraries and raw winsocket select is:	4385	libraries and raw winsocket select is:
3283		4386
3284	#define EV_USE_SELECT 1	4387	#define EV_USE_SELECT 1
3285	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4388	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3286		4389
3287	Note that winsockets handling of fd sets is O(n), so you can easily get a	4390	Note that winsockets handling of fd sets is O(n), so you can easily get a
3288	complexity in the O(n²) range when using win32.	4391	complexity in the O(n²) range when using win32.
3289		4392
3290	=item Limited number of file descriptors	4393	=item Limited number of file descriptors
3291		4394
3292	Windows has numerous arbitrary (and low) limits on things.	4395	Windows has numerous arbitrary (and low) limits on things.
3293		4396
3294	Early versions of winsocket's select only supported waiting for a maximum	4397	Early versions of winsocket's select only supported waiting for a maximum
3295	of C<64> handles (probably owning to the fact that all windows kernels	4398	of C<64> handles (probably owning to the fact that all windows kernels
3296	can only wait for C<64> things at the same time internally; microsoft	4399	can only wait for C<64> things at the same time internally; Microsoft
3297	recommends spawning a chain of threads and wait for 63 handles and the	4400	recommends spawning a chain of threads and wait for 63 handles and the
3298	previous thread in each. Great).	4401	previous thread in each. Sounds great!).
3299		4402
3300	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4403	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3301	to some high number (e.g. C<2048>) before compiling the winsocket select	4404	to some high number (e.g. C<2048>) before compiling the winsocket select
3302	call (which might be in libev or elsewhere, for example, perl does its own	4405	call (which might be in libev or elsewhere, for example, perl and many
3303	select emulation on windows).	4406	other interpreters do their own select emulation on windows).
3304		4407
3305	Another limit is the number of file descriptors in the microsoft runtime	4408	Another limit is the number of file descriptors in the Microsoft runtime
3306	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4409	libraries, which by default is C<64> (there must be a hidden I<64>
3307	or something like this inside microsoft). You can increase this by calling	4410	fetish or something like this inside Microsoft). You can increase this
3308	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4411	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3309	arbitrary limit), but is broken in many versions of the microsoft runtime	4412	(another arbitrary limit), but is broken in many versions of the Microsoft
3310	libraries.
3311
3312	This might get you to about C<512> or C<2048> sockets (depending on	4413	runtime libraries. This might get you to about C<512> or C<2048> sockets
3313	windows version and/or the phase of the moon). To get more, you need to	4414	(depending on windows version and/or the phase of the moon). To get more,
3314	wrap all I/O functions and provide your own fd management, but the cost of	4415	you need to wrap all I/O functions and provide your own fd management, but
3315	calling select (O(n²)) will likely make this unworkable.	4416	the cost of calling select (O(n²)) will likely make this unworkable.
3316		4417
3317	=back	4418	=back
3318		4419
3319
3320	=head1 PORTABILITY REQUIREMENTS	4420	=head2 PORTABILITY REQUIREMENTS
3321		4421
3322	In addition to a working ISO-C implementation, libev relies on a few	4422	In addition to a working ISO-C implementation and of course the
3323	additional extensions:	4423	backend-specific APIs, libev relies on a few additional extensions:
3324		4424
3325	=over 4	4425	=over 4
3326		4426
		4427	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4428	calling conventions regardless of C<ev_watcher_type *>.
		4429
		4430	Libev assumes not only that all watcher pointers have the same internal
		4431	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4432	assumes that the same (machine) code can be used to call any watcher
		4433	callback: The watcher callbacks have different type signatures, but libev
		4434	calls them using an C<ev_watcher *> internally.
		4435
3327	=item C<sig_atomic_t volatile> must be thread-atomic as well	4436	=item C<sig_atomic_t volatile> must be thread-atomic as well
3328		4437
3329	The type C<sig_atomic_t volatile> (or whatever is defined as	4438	The type C<sig_atomic_t volatile> (or whatever is defined as
3330	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4439	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3331	threads. This is not part of the specification for C<sig_atomic_t>, but is	4440	threads. This is not part of the specification for C<sig_atomic_t>, but is
3332	believed to be sufficiently portable.	4441	believed to be sufficiently portable.
3333		4442
3334	=item C<sigprocmask> must work in a threaded environment	4443	=item C<sigprocmask> must work in a threaded environment
3335		4444
…		…
3344	except the initial one, and run the default loop in the initial thread as	4453	except the initial one, and run the default loop in the initial thread as
3345	well.	4454	well.
3346		4455
3347	=item C<long> must be large enough for common memory allocation sizes	4456	=item C<long> must be large enough for common memory allocation sizes
3348		4457
3349	To improve portability and simplify using libev, libev uses C<long>	4458	To improve portability and simplify its API, libev uses C<long> internally
3350	internally instead of C<size_t> when allocating its data structures. On	4459	instead of C<size_t> when allocating its data structures. On non-POSIX
3351	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4460	systems (Microsoft...) this might be unexpectedly low, but is still at
3352	is still at least 31 bits everywhere, which is enough for hundreds of	4461	least 31 bits everywhere, which is enough for hundreds of millions of
3353	millions of watchers.	4462	watchers.
3354		4463
3355	=item C<double> must hold a time value in seconds with enough accuracy	4464	=item C<double> must hold a time value in seconds with enough accuracy
3356		4465
3357	The type C<double> is used to represent timestamps. It is required to	4466	The type C<double> is used to represent timestamps. It is required to
3358	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4467	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3359	enough for at least into the year 4000. This requirement is fulfilled by	4468	enough for at least into the year 4000. This requirement is fulfilled by
3360	implementations implementing IEEE 754 (basically all existing ones).	4469	implementations implementing IEEE 754, which is basically all existing
		4470	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4471	2200.
3361		4472
3362	=back	4473	=back
3363		4474
3364	If you know of other additional requirements drop me a note.	4475	If you know of other additional requirements drop me a note.
3365		4476
3366		4477
3367	=head1 VALGRIND	4478	=head1 ALGORITHMIC COMPLEXITIES
3368		4479
3369	Valgrind has a special section here because it is a popular tool that is	4480	In this section the complexities of (many of) the algorithms used inside
3370	highly useful, but valgrind reports are very hard to interpret.	4481	libev will be documented. For complexity discussions about backends see
		4482	the documentation for C<ev_default_init>.
3371		4483
3372	If you think you found a bug (memory leak, uninitialised data access etc.)	4484	All of the following are about amortised time: If an array needs to be
3373	in libev, then check twice: If valgrind reports something like:	4485	extended, libev needs to realloc and move the whole array, but this
		4486	happens asymptotically rarer with higher number of elements, so O(1) might
		4487	mean that libev does a lengthy realloc operation in rare cases, but on
		4488	average it is much faster and asymptotically approaches constant time.
3374		4489
3375	==2274== definitely lost: 0 bytes in 0 blocks.	4490	=over 4
3376	==2274== possibly lost: 0 bytes in 0 blocks.
3377	==2274== still reachable: 256 bytes in 1 blocks.
3378		4491
3379	then there is no memory leak. Similarly, under some circumstances,	4492	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3380	valgrind might report kernel bugs as if it were a bug in libev, or it
3381	might be confused (it is a very good tool, but only a tool).
3382		4493
3383	If you are unsure about something, feel free to contact the mailing list	4494	This means that, when you have a watcher that triggers in one hour and
3384	with the full valgrind report and an explanation on why you think this is	4495	there are 100 watchers that would trigger before that, then inserting will
3385	a bug in libev. However, don't be annoyed when you get a brisk "this is	4496	have to skip roughly seven (C<ld 100>) of these watchers.
3386	no bug" answer and take the chance of learning how to interpret valgrind
3387	properly.
3388		4497
3389	If you need, for some reason, empty reports from valgrind for your project	4498	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3390	I suggest using suppression lists.
3391		4499
		4500	That means that changing a timer costs less than removing/adding them,
		4501	as only the relative motion in the event queue has to be paid for.
		4502
		4503	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4504
		4505	These just add the watcher into an array or at the head of a list.
		4506
		4507	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4508
		4509	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4510
		4511	These watchers are stored in lists, so they need to be walked to find the
		4512	correct watcher to remove. The lists are usually short (you don't usually
		4513	have many watchers waiting for the same fd or signal: one is typical, two
		4514	is rare).
		4515
		4516	=item Finding the next timer in each loop iteration: O(1)
		4517
		4518	By virtue of using a binary or 4-heap, the next timer is always found at a
		4519	fixed position in the storage array.
		4520
		4521	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4522
		4523	A change means an I/O watcher gets started or stopped, which requires
		4524	libev to recalculate its status (and possibly tell the kernel, depending
		4525	on backend and whether C<ev_io_set> was used).
		4526
		4527	=item Activating one watcher (putting it into the pending state): O(1)
		4528
		4529	=item Priority handling: O(number_of_priorities)
		4530
		4531	Priorities are implemented by allocating some space for each
		4532	priority. When doing priority-based operations, libev usually has to
		4533	linearly search all the priorities, but starting/stopping and activating
		4534	watchers becomes O(1) with respect to priority handling.
		4535
		4536	=item Sending an ev_async: O(1)
		4537
		4538	=item Processing ev_async_send: O(number_of_async_watchers)
		4539
		4540	=item Processing signals: O(max_signal_number)
		4541
		4542	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4543	calls in the current loop iteration. Checking for async and signal events
		4544	involves iterating over all running async watchers or all signal numbers.
		4545
		4546	=back
		4547
		4548
		4549	=head1 GLOSSARY
		4550
		4551	=over 4
		4552
		4553	=item active
		4554
		4555	A watcher is active as long as it has been started (has been attached to
		4556	an event loop) but not yet stopped (disassociated from the event loop).
		4557
		4558	=item application
		4559
		4560	In this document, an application is whatever is using libev.
		4561
		4562	=item callback
		4563
		4564	The address of a function that is called when some event has been
		4565	detected. Callbacks are being passed the event loop, the watcher that
		4566	received the event, and the actual event bitset.
		4567
		4568	=item callback invocation
		4569
		4570	The act of calling the callback associated with a watcher.
		4571
		4572	=item event
		4573
		4574	A change of state of some external event, such as data now being available
		4575	for reading on a file descriptor, time having passed or simply not having
		4576	any other events happening anymore.
		4577
		4578	In libev, events are represented as single bits (such as C<EV_READ> or
		4579	C<EV_TIMEOUT>).
		4580
		4581	=item event library
		4582
		4583	A software package implementing an event model and loop.
		4584
		4585	=item event loop
		4586
		4587	An entity that handles and processes external events and converts them
		4588	into callback invocations.
		4589
		4590	=item event model
		4591
		4592	The model used to describe how an event loop handles and processes
		4593	watchers and events.
		4594
		4595	=item pending
		4596
		4597	A watcher is pending as soon as the corresponding event has been detected,
		4598	and stops being pending as soon as the watcher will be invoked or its
		4599	pending status is explicitly cleared by the application.
		4600
		4601	A watcher can be pending, but not active. Stopping a watcher also clears
		4602	its pending status.
		4603
		4604	=item real time
		4605
		4606	The physical time that is observed. It is apparently strictly monotonic :)
		4607
		4608	=item wall-clock time
		4609
		4610	The time and date as shown on clocks. Unlike real time, it can actually
		4611	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4612	clock.
		4613
		4614	=item watcher
		4615
		4616	A data structure that describes interest in certain events. Watchers need
		4617	to be started (attached to an event loop) before they can receive events.
		4618
		4619	=item watcher invocation
		4620
		4621	The act of calling the callback associated with a watcher.
		4622
		4623	=back
3392		4624
3393	=head1 AUTHOR	4625	=head1 AUTHOR
3394		4626
3395	Marc Lehmann <libev@schmorp.de>.	4627	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3396		4628

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