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Revision 1.154 by root, Sun May 11 11:47:27 2008 UTC vs.
Revision 1.276 by root, Tue Dec 29 13:11:00 2009 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_NOSIGFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
327		382
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		384
330	This is your standard select(2) backend. Not I<completely> standard, as	385	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,	386	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	387	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	388	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.	389	usually the fastest backend for a low number of (low-numbered :) fds.
335		390
336	To get good performance out of this backend you need a high amount of	391	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	392	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	393	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	394	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	395	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	396	readiness notifications you get per iteration.
		397
		398	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		399	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		400	C<exceptfds> set on that platform).
342		401
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	402	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		403
345	And this is your standard poll(2) backend. It's more complicated	404	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	405	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	406	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,	407	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	408	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	409	performance tips.
351		410
		411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		413
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		415
		416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		417	kernels).
353		418
354	For few fds, this backend is a bit little slower than poll and select,	419	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	420	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),	421	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	422	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	423
359	cases and requiring a syscall per fd change, no fork support and bad	424	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	425	of the more advanced event mechanisms: mere annoyances include silently
		426	dropping file descriptors, requiring a system call per change per file
		427	descriptor (and unnecessary guessing of parameters), problems with dup and
		428	so on. The biggest issue is fork races, however - if a program forks then
		429	I<both> parent and child process have to recreate the epoll set, which can
		430	take considerable time (one syscall per file descriptor) and is of course
		431	hard to detect.
		432
		433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		434	of course I<doesn't>, and epoll just loves to report events for totally
		435	I<different> file descriptors (even already closed ones, so one cannot
		436	even remove them from the set) than registered in the set (especially
		437	on SMP systems). Libev tries to counter these spurious notifications by
		438	employing an additional generation counter and comparing that against the
		439	events to filter out spurious ones, recreating the set when required.
361		440
362	While stopping, setting and starting an I/O watcher in the same iteration	441	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	442	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	443	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	444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	445	file descriptors might not work very well if you register events for both
367		446	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		447
372	Best performance from this backend is achieved by not unregistering all	448	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.	449	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	450	i.e. keep at least one watcher active per fd at all times. Stopping and
		451	starting a watcher (without re-setting it) also usually doesn't cause
		452	extra overhead. A fork can both result in spurious notifications as well
		453	as in libev having to destroy and recreate the epoll object, which can
		454	take considerable time and thus should be avoided.
375		455
		456	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		457	faster than epoll for maybe up to a hundred file descriptors, depending on
		458	the usage. So sad.
		459
376	While nominally embeddeble in other event loops, this feature is broken in	460	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	461	all kernel versions tested so far.
		462
		463	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		464	C<EVBACKEND_POLL>.
378		465
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	466	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		467
381	Kqueue deserves special mention, as at the time of this writing, it	468	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	469	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	470	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"	471	it's completely useless). Unlike epoll, however, whose brokenness
		472	is by design, these kqueue bugs can (and eventually will) be fixed
		473	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	474	"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)	475	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	476	system like NetBSD.
388		477
389	You still can embed kqueue into a normal poll or select backend and use it	478	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	479	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.	480	the target platform). See C<ev_embed> watchers for more info.
392		481
393	It scales in the same way as the epoll backend, but the interface to the	482	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	483	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	484	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	485	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	486	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	487	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		488	cases
399		489
400	This backend usually performs well under most conditions.	490	This backend usually performs well under most conditions.
401		491
402	While nominally embeddable in other event loops, this doesn't work	492	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	493	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	494	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	495	(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	496	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	497	also broken on OS X)) and, did I mention it, using it only for sockets.
		498
		499	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		500	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		501	C<NOTE_EOF>.
408		502
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	503	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		504
411	This is not implemented yet (and might never be, unless you send me an	505	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	506	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	510	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		511
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	512	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)).	513	it's really slow, but it still scales very well (O(active_fds)).
420		514
421	Please note that solaris event ports can deliver a lot of spurious	515	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	516	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	517	blocking when no data (or space) is available.
424		518
425	While this backend scales well, it requires one system call per active	519	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	520	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	521	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	522	might perform better.
429		523
430	On the positive side, ignoring the spurious readyness notifications, this	524	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	525	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	526	in all tests and is fully embeddable, which is a rare feat among the
		527	OS-specific backends (I vastly prefer correctness over speed hacks).
		528
		529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		530	C<EVBACKEND_POLL>.
433		531
434	=item C<EVBACKEND_ALL>	532	=item C<EVBACKEND_ALL>
435		533
436	Try all backends (even potentially broken ones that wouldn't be tried	534	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	535	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		537
440	It is definitely not recommended to use this flag.	538	It is definitely not recommended to use this flag.
441		539
442	=back	540	=back
443		541
444	If one or more of these are ored into the flags value, then only these	542	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	543	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.	544	here). If none are specified, all backends in C<ev_recommended_backends
		545	()> will be tried.
447		546
448	The most typical usage is like this:	547	Example: This is the most typical usage.
449		548
450	if (!ev_default_loop (0))	549	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		551
453	Restrict libev to the select and poll backends, and do not allow	552	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	553	environment settings to be taken into account:
455		554
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	555	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		556
458	Use whatever libev has to offer, but make sure that kqueue is used if	557	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	558	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):	559	private event loop and only if you know the OS supports your types of
		560	fds):
461		561
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	562	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		563
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	564	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		565
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	566	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	567	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	572	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	573	default loop in the "main" or "initial" thread.
474		574
475	Example: Try to create a event loop that uses epoll and nothing else.	575	Example: Try to create a event loop that uses epoll and nothing else.
476		576
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	577	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	578	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	579	fatal ("no epoll found here, maybe it hides under your chair");
480		580
481	=item ev_default_destroy ()	581	=item ev_default_destroy ()
482		582
483	Destroys the default loop again (frees all memory and kernel state	583	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	584	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	585	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>	586	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	587	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	588	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	589	for example).
490		590
491	Note that certain global state, such as signal state, will not be freed by	591	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	592	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	593	as signal and child watchers) would need to be stopped manually.
494		594
495	In general it is not advisable to call this function except in the	595	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	596	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	597	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	598	C<ev_loop_new> and C<ev_loop_destroy>.
499		599
500	=item ev_loop_destroy (loop)	600	=item ev_loop_destroy (loop)
501		601
502	Like C<ev_default_destroy>, but destroys an event loop created by an	602	Like C<ev_default_destroy>, but destroys an event loop created by an
503	earlier call to C<ev_loop_new>.	603	earlier call to C<ev_loop_new>.
…		…
523		623
524	=item ev_loop_fork (loop)	624	=item ev_loop_fork (loop)
525		625
526	Like C<ev_default_fork>, but acts on an event loop created by	626	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	627	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.	628	after fork that you want to re-use in the child, and how you do this is
		629	entirely your own problem.
529		630
530	=item int ev_is_default_loop (loop)	631	=item int ev_is_default_loop (loop)
531		632
532	Returns true when the given loop actually is the default loop, false otherwise.	633	Returns true when the given loop is, in fact, the default loop, and false
		634	otherwise.
533		635
534	=item unsigned int ev_loop_count (loop)	636	=item unsigned int ev_loop_count (loop)
535		637
536	Returns the count of loop iterations for the loop, which is identical to	638	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	639	the number of times libev did poll for new events. It starts at C<0> and
538	happily wraps around with enough iterations.	640	happily wraps around with enough iterations.
539		641
540	This value can sometimes be useful as a generation counter of sorts (it	642	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	643	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	644	C<ev_prepare> and C<ev_check> calls.
		645
		646	=item unsigned int ev_loop_depth (loop)
		647
		648	Returns the number of times C<ev_loop> was entered minus the number of
		649	times C<ev_loop> was exited, in other words, the recursion depth.
		650
		651	Outside C<ev_loop>, this number is zero. In a callback, this number is
		652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		653	in which case it is higher.
		654
		655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		656	etc.), doesn't count as exit.
543		657
544	=item unsigned int ev_backend (loop)	658	=item unsigned int ev_backend (loop)
545		659
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	661	use.
…		…
552	received events and started processing them. This timestamp does not	666	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	667	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	668	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).	669	event occurring (or more correctly, libev finding out about it).
556		670
		671	=item ev_now_update (loop)
		672
		673	Establishes the current time by querying the kernel, updating the time
		674	returned by C<ev_now ()> in the progress. This is a costly operation and
		675	is usually done automatically within C<ev_loop ()>.
		676
		677	This function is rarely useful, but when some event callback runs for a
		678	very long time without entering the event loop, updating libev's idea of
		679	the current time is a good idea.
		680
		681	See also L<The special problem of time updates> in the C<ev_timer> section.
		682
		683	=item ev_suspend (loop)
		684
		685	=item ev_resume (loop)
		686
		687	These two functions suspend and resume a loop, for use when the loop is
		688	not used for a while and timeouts should not be processed.
		689
		690	A typical use case would be an interactive program such as a game: When
		691	the user presses C<^Z> to suspend the game and resumes it an hour later it
		692	would be best to handle timeouts as if no time had actually passed while
		693	the program was suspended. This can be achieved by calling C<ev_suspend>
		694	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		695	C<ev_resume> directly afterwards to resume timer processing.
		696
		697	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		699	will be rescheduled (that is, they will lose any events that would have
		700	occured while suspended).
		701
		702	After calling C<ev_suspend> you B<must not> call I<any> function on the
		703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		704	without a previous call to C<ev_suspend>.
		705
		706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		707	event loop time (see C<ev_now_update>).
		708
557	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
558		710
559	Finally, this is it, the event handler. This function usually is called	711	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	712	after you have initialised all your watchers and you want to start
561	events.	713	handling events.
562		714
563	If the flags argument is specified as C<0>, it will not return until	715	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.	716	either no event watchers are active anymore or C<ev_unloop> was called.
565		717
566	Please note that an explicit C<ev_unloop> is usually better than	718	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	719	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	720	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	721	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.	722	of relying on its watchers stopping correctly, that is truly a thing of
		723	beauty.
571		724
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	725	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	726	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.	727	process in case there are no events and will return after one iteration of
		728	the loop.
575		729
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	730	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	731	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	732	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	733	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	734	user-registered callback will be called), and will return after one
		735	iteration of the loop.
		736
		737	This is useful if you are waiting for some external event in conjunction
		738	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	739	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.	740	usually a better approach for this kind of thing.
583		741
584	Here are the gory details of what C<ev_loop> does:	742	Here are the gory details of what C<ev_loop> does:
585		743
586	- Before the first iteration, call any pending watchers.	744	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	745	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	746	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	747	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	748	- If we have been forked, detach and recreate the kernel state
		749	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	750	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	751	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	752	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	753	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	754	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	755	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	756	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	757	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	758	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	759	- Queue all expired timers.
601	- Queue all outstanding periodics.	760	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	761	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	762	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	763	- 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	764	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	765	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	766	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	771	anymore.
613		772
614	... queue jobs here, make sure they register event watchers as long	773	... 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..)	774	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	775	ev_loop (my_loop, 0);
617	... jobs done. yeah!	776	... jobs done or somebody called unloop. yeah!
618		777
619	=item ev_unloop (loop, how)	778	=item ev_unloop (loop, how)
620		779
621	Can be used to make a call to C<ev_loop> return early (but only after it	780	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	781	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	782	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.	783	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		784
626	This "unloop state" will be cleared when entering C<ev_loop> again.	785	This "unloop state" will be cleared when entering C<ev_loop> again.
627		786
		787	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		788
628	=item ev_ref (loop)	789	=item ev_ref (loop)
629		790
630	=item ev_unref (loop)	791	=item ev_unref (loop)
631		792
632	Ref/unref can be used to add or remove a reference count on the event	793	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	794	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	795	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	796
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	797	This is useful when you have a watcher that you never intend to
		798	unregister, but that nevertheless should not keep C<ev_loop> from
		799	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		800	before stopping it.
		801
637	example, libev itself uses this for its internal signal pipe: It is not	802	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	803	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	804	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	805	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>	806	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,	807	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	808	before, respectively. Note also that libev might stop watchers itself
		809	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		810	in the callback).
644		811
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	812	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	813	running when nothing else is active.
647		814
648	struct ev_signal exitsig;	815	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	816	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	817	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	818	evf_unref (loop);
652		819
653	Example: For some weird reason, unregister the above signal handler again.	820	Example: For some weird reason, unregister the above signal handler again.
654		821
655	ev_ref (loop);	822	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	823	ev_signal_stop (loop, &exitsig);
657		824
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	825	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		826
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	827	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		828
662	These advanced functions influence the time that libev will spend waiting	829	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	830	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.	831	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		832	latency.
665		833
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	834	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	835	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	836	to increase efficiency of loop iterations (or to increase power-saving
		837	opportunities).
669		838
670	The background is that sometimes your program runs just fast enough to	839	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	840	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	841	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	842	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	843	overhead for the actual polling but can deliver many events at once.
675		844
676	By setting a higher I<io collect interval> you allow libev to spend more	845	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,	846	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	847	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	848	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.	849	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		850	sleep time ensures that libev will not poll for I/O events more often then
		851	once per this interval, on average.
681		852
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	853	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	854	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	855	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	856	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	857	value will not introduce any overhead in libev.
687		858
688	Many (busy) programs can usually benefit by setting the io collect	859	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	860	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	861	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>,	862	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.	863	as this approaches the timing granularity of most systems. Note that if
		864	you do transactions with the outside world and you can't increase the
		865	parallelity, then this setting will limit your transaction rate (if you
		866	need to poll once per transaction and the I/O collect interval is 0.01,
		867	then you can't do more than 100 transations per second).
		868
		869	Setting the I<timeout collect interval> can improve the opportunity for
		870	saving power, as the program will "bundle" timer callback invocations that
		871	are "near" in time together, by delaying some, thus reducing the number of
		872	times the process sleeps and wakes up again. Another useful technique to
		873	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		874	they fire on, say, one-second boundaries only.
		875
		876	Example: we only need 0.1s timeout granularity, and we wish not to poll
		877	more often than 100 times per second:
		878
		879	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		880	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		881
		882	=item ev_invoke_pending (loop)
		883
		884	This call will simply invoke all pending watchers while resetting their
		885	pending state. Normally, C<ev_loop> does this automatically when required,
		886	but when overriding the invoke callback this call comes handy.
		887
		888	=item int ev_pending_count (loop)
		889
		890	Returns the number of pending watchers - zero indicates that no watchers
		891	are pending.
		892
		893	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		894
		895	This overrides the invoke pending functionality of the loop: Instead of
		896	invoking all pending watchers when there are any, C<ev_loop> will call
		897	this callback instead. This is useful, for example, when you want to
		898	invoke the actual watchers inside another context (another thread etc.).
		899
		900	If you want to reset the callback, use C<ev_invoke_pending> as new
		901	callback.
		902
		903	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		904
		905	Sometimes you want to share the same loop between multiple threads. This
		906	can be done relatively simply by putting mutex_lock/unlock calls around
		907	each call to a libev function.
		908
		909	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		910	wait for it to return. One way around this is to wake up the loop via
		911	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		912	and I<acquire> callbacks on the loop.
		913
		914	When set, then C<release> will be called just before the thread is
		915	suspended waiting for new events, and C<acquire> is called just
		916	afterwards.
		917
		918	Ideally, C<release> will just call your mutex_unlock function, and
		919	C<acquire> will just call the mutex_lock function again.
		920
		921	While event loop modifications are allowed between invocations of
		922	C<release> and C<acquire> (that's their only purpose after all), no
		923	modifications done will affect the event loop, i.e. adding watchers will
		924	have no effect on the set of file descriptors being watched, or the time
		925	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		926	to take note of any changes you made.
		927
		928	In theory, threads executing C<ev_loop> will be async-cancel safe between
		929	invocations of C<release> and C<acquire>.
		930
		931	See also the locking example in the C<THREADS> section later in this
		932	document.
		933
		934	=item ev_set_userdata (loop, void *data)
		935
		936	=item ev_userdata (loop)
		937
		938	Set and retrieve a single C<void *> associated with a loop. When
		939	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		940	C<0.>
		941
		942	These two functions can be used to associate arbitrary data with a loop,
		943	and are intended solely for the C<invoke_pending_cb>, C<release> and
		944	C<acquire> callbacks described above, but of course can be (ab-)used for
		945	any other purpose as well.
		946
		947	=item ev_loop_verify (loop)
		948
		949	This function only does something when C<EV_VERIFY> support has been
		950	compiled in, which is the default for non-minimal builds. It tries to go
		951	through all internal structures and checks them for validity. If anything
		952	is found to be inconsistent, it will print an error message to standard
		953	error and call C<abort ()>.
		954
		955	This can be used to catch bugs inside libev itself: under normal
		956	circumstances, this function will never abort as of course libev keeps its
		957	data structures consistent.
693		958
694	=back	959	=back
695		960
696		961
697	=head1 ANATOMY OF A WATCHER	962	=head1 ANATOMY OF A WATCHER
		963
		964	In the following description, uppercase C<TYPE> in names stands for the
		965	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		966	watchers and C<ev_io_start> for I/O watchers.
698		967
699	A watcher is a structure that you create and register to record your	968	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	969	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:	970	become readable, you would create an C<ev_io> watcher for that:
702		971
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	972	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	973	{
705	ev_io_stop (w);	974	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	975	ev_unloop (loop, EVUNLOOP_ALL);
707	}	976	}
708		977
709	struct ev_loop *loop = ev_default_loop (0);	978	struct ev_loop *loop = ev_default_loop (0);
		979
710	struct ev_io stdin_watcher;	980	ev_io stdin_watcher;
		981
711	ev_init (&stdin_watcher, my_cb);	982	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	983	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	984	ev_io_start (loop, &stdin_watcher);
		985
714	ev_loop (loop, 0);	986	ev_loop (loop, 0);
715		987
716	As you can see, you are responsible for allocating the memory for your	988	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,	989	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	990	stack).
		991
		992	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		993	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		994
720	Each watcher structure must be initialised by a call to C<ev_init	995	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	996	(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	997	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	998	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	999	is readable and/or writable).
725		1000
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1001	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	1002	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	1003	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	1004	ev_TYPE_init (watcher *, callback, ...) >>.
730		1005
731	To make the watcher actually watch out for events, you have to start it	1006	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	1007	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	1008	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1009	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		1010
736	As long as your watcher is active (has been started but not stopped) you	1011	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	1012	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	1013	reinitialise it or call its C<ev_TYPE_set> macro.
739		1014
740	Each and every callback receives the event loop pointer as first, the	1015	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	1016	registered watcher structure as second, and a bitset of received events as
742	third argument.	1017	third argument.
743		1018
…		…
801		1076
802	=item C<EV_ASYNC>	1077	=item C<EV_ASYNC>
803		1078
804	The given async watcher has been asynchronously notified (see C<ev_async>).	1079	The given async watcher has been asynchronously notified (see C<ev_async>).
805		1080
		1081	=item C<EV_CUSTOM>
		1082
		1083	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1084	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1085
806	=item C<EV_ERROR>	1086	=item C<EV_ERROR>
807		1087
808	An unspecified error has occured, the watcher has been stopped. This might	1088	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	1089	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	1090	ran out of memory, a file descriptor was found to be closed or any other
		1091	problem. Libev considers these application bugs.
		1092
811	problem. You best act on it by reporting the problem and somehow coping	1093	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	1094	watcher being stopped. Note that well-written programs should not receive
		1095	an error ever, so when your watcher receives it, this usually indicates a
		1096	bug in your program.
813		1097
814	Libev will usually signal a few "dummy" events together with an error,	1098	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	1099	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	1100	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	1101	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	1102	programs, though, as the fd could already be closed and reused for another
		1103	thing, so beware.
819		1104
820	=back	1105	=back
821		1106
822	=head2 GENERIC WATCHER FUNCTIONS	1107	=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		1108
827	=over 4	1109	=over 4
828		1110
829	=item C<ev_init> (ev_TYPE *watcher, callback)	1111	=item C<ev_init> (ev_TYPE *watcher, callback)
830		1112
…		…
836	which rolls both calls into one.	1118	which rolls both calls into one.
837		1119
838	You can reinitialise a watcher at any time as long as it has been stopped	1120	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.	1121	(or never started) and there are no pending events outstanding.
840		1122
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1123	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	1124	int revents)>.
843		1125
		1126	Example: Initialise an C<ev_io> watcher in two steps.
		1127
		1128	ev_io w;
		1129	ev_init (&w, my_cb);
		1130	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1131
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1132	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
845		1133
846	This macro initialises the type-specific parts of a watcher. You need to	1134	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	1135	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	1136	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	1137	macro on a watcher that is active (it can be pending, however, which is a
850	difference to the C<ev_init> macro).	1138	difference to the C<ev_init> macro).
851		1139
852	Although some watcher types do not have type-specific arguments	1140	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.	1141	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		1142
		1143	See C<ev_init>, above, for an example.
		1144
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1145	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		1146
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1147	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	1148	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	1149	a watcher. The same limitations apply, of course.
860		1150
		1151	Example: Initialise and set an C<ev_io> watcher in one step.
		1152
		1153	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1154
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1155	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
862		1156
863	Starts (activates) the given watcher. Only active watchers will receive	1157	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1158	events. If the watcher is already active nothing will happen.
865		1159
		1160	Example: Start the C<ev_io> watcher that is being abused as example in this
		1161	whole section.
		1162
		1163	ev_io_start (EV_DEFAULT_UC, &w);
		1164
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1165	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
867		1166
868	Stops the given watcher again (if active) and clears the pending	1167	Stops the given watcher if active, and clears the pending status (whether
		1168	the watcher was active or not).
		1169
869	status. It is possible that stopped watchers are pending (for example,	1170	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1171	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	1172	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	1173	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.	1174	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1175
875	=item bool ev_is_active (ev_TYPE *watcher)	1176	=item bool ev_is_active (ev_TYPE *watcher)
876		1177
877	Returns a true value iff the watcher is active (i.e. it has been started	1178	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	1179	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)	1195	=item ev_cb_set (ev_TYPE *watcher, callback)
895		1196
896	Change the callback. You can change the callback at virtually any time	1197	Change the callback. You can change the callback at virtually any time
897	(modulo threads).	1198	(modulo threads).
898		1199
899	=item ev_set_priority (ev_TYPE *watcher, priority)	1200	=item ev_set_priority (ev_TYPE *watcher, int priority)
900		1201
901	=item int ev_priority (ev_TYPE *watcher)	1202	=item int ev_priority (ev_TYPE *watcher)
902		1203
903	Set and query the priority of the watcher. The priority is a small	1204	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>	1205	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
905	(default: C<-2>). Pending watchers with higher priority will be invoked	1206	(default: C<-2>). Pending watchers with higher priority will be invoked
906	before watchers with lower priority, but priority will not keep watchers	1207	before watchers with lower priority, but priority will not keep watchers
907	from being executed (except for C<ev_idle> watchers).	1208	from being executed (except for C<ev_idle> watchers).
908		1209
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	1210	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.	1211	you need to look at C<ev_idle> watchers, which provide this functionality.
916		1212
917	You I<must not> change the priority of a watcher as long as it is active or	1213	You I<must not> change the priority of a watcher as long as it is active or
918	pending.	1214	pending.
919		1215
		1216	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1217	fine, as long as you do not mind that the priority value you query might
		1218	or might not have been clamped to the valid range.
		1219
920	The default priority used by watchers when no priority has been set is	1220	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 :).	1221	always C<0>, which is supposed to not be too high and not be too low :).
922		1222
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1223	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	1224	priorities.
925	or might not have been adjusted to be within valid range.
926		1225
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1226	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1227
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1228	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	1229	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1230	can deal with that fact, as both are simply passed through to the
		1231	callback.
932		1232
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1233	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1234
935	If the watcher is pending, this function returns clears its pending status	1235	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	1236	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>.	1237	watcher isn't pending it does nothing and returns C<0>.
938		1238
		1239	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1240	callback to be invoked, which can be accomplished with this function.
		1241
		1242	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1243
		1244	Feeds the given event set into the event loop, as if the specified event
		1245	had happened for the specified watcher (which must be a pointer to an
		1246	initialised but not necessarily started event watcher). Obviously you must
		1247	not free the watcher as long as it has pending events.
		1248
		1249	Stopping the watcher, letting libev invoke it, or calling
		1250	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1251	not started in the first place.
		1252
		1253	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1254	functions that do not need a watcher.
		1255
939	=back	1256	=back
940		1257
941		1258
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1259	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1260
944	Each watcher has, by default, a member C<void *data> that you can change	1261	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	1262	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	1263	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	1264	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	1265	member, you can also "subclass" the watcher type and provide your own
949	data:	1266	data:
950		1267
951	struct my_io	1268	struct my_io
952	{	1269	{
953	struct ev_io io;	1270	ev_io io;
954	int otherfd;	1271	int otherfd;
955	void *somedata;	1272	void *somedata;
956	struct whatever *mostinteresting;	1273	struct whatever *mostinteresting;
957	}	1274	};
		1275
		1276	...
		1277	struct my_io w;
		1278	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1279
959	And since your callback will be called with a pointer to the watcher, you	1280	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1281	can cast it back to your own type:
961		1282
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1283	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1284	{
964	struct my_io *w = (struct my_io *)w_;	1285	struct my_io *w = (struct my_io *)w_;
965	...	1286	...
966	}	1287	}
967		1288
968	More interesting and less C-conformant ways of casting your callback type	1289	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1290	instead have been omitted.
970		1291
971	Another common scenario is having some data structure with multiple	1292	Another common scenario is to use some data structure with multiple
972	watchers:	1293	embedded watchers:
973		1294
974	struct my_biggy	1295	struct my_biggy
975	{	1296	{
976	int some_data;	1297	int some_data;
977	ev_timer t1;	1298	ev_timer t1;
978	ev_timer t2;	1299	ev_timer t2;
979	}	1300	}
980		1301
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1302	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1303	complicated: Either you store the address of your C<my_biggy> struct
		1304	in the C<data> member of the watcher (for woozies), or you need to use
		1305	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1306	programmers):
983		1307
984	#include <stddef.h>	1308	#include <stddef.h>
985		1309
986	static void	1310	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1311	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1312	{
989	struct my_biggy big = (struct my_biggy *	1313	struct my_biggy big = (struct my_biggy *)
990	(((char *)w) - offsetof (struct my_biggy, t1));	1314	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1315	}
992		1316
993	static void	1317	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1318	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1319	{
996	struct my_biggy big = (struct my_biggy *	1320	struct my_biggy big = (struct my_biggy *)
997	(((char *)w) - offsetof (struct my_biggy, t2));	1321	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1322	}
		1323
		1324	=head2 WATCHER PRIORITY MODELS
		1325
		1326	Many event loops support I<watcher priorities>, which are usually small
		1327	integers that influence the ordering of event callback invocation
		1328	between watchers in some way, all else being equal.
		1329
		1330	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1331	description for the more technical details such as the actual priority
		1332	range.
		1333
		1334	There are two common ways how these these priorities are being interpreted
		1335	by event loops:
		1336
		1337	In the more common lock-out model, higher priorities "lock out" invocation
		1338	of lower priority watchers, which means as long as higher priority
		1339	watchers receive events, lower priority watchers are not being invoked.
		1340
		1341	The less common only-for-ordering model uses priorities solely to order
		1342	callback invocation within a single event loop iteration: Higher priority
		1343	watchers are invoked before lower priority ones, but they all get invoked
		1344	before polling for new events.
		1345
		1346	Libev uses the second (only-for-ordering) model for all its watchers
		1347	except for idle watchers (which use the lock-out model).
		1348
		1349	The rationale behind this is that implementing the lock-out model for
		1350	watchers is not well supported by most kernel interfaces, and most event
		1351	libraries will just poll for the same events again and again as long as
		1352	their callbacks have not been executed, which is very inefficient in the
		1353	common case of one high-priority watcher locking out a mass of lower
		1354	priority ones.
		1355
		1356	Static (ordering) priorities are most useful when you have two or more
		1357	watchers handling the same resource: a typical usage example is having an
		1358	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1359	timeouts. Under load, data might be received while the program handles
		1360	other jobs, but since timers normally get invoked first, the timeout
		1361	handler will be executed before checking for data. In that case, giving
		1362	the timer a lower priority than the I/O watcher ensures that I/O will be
		1363	handled first even under adverse conditions (which is usually, but not
		1364	always, what you want).
		1365
		1366	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1367	will only be executed when no same or higher priority watchers have
		1368	received events, they can be used to implement the "lock-out" model when
		1369	required.
		1370
		1371	For example, to emulate how many other event libraries handle priorities,
		1372	you can associate an C<ev_idle> watcher to each such watcher, and in
		1373	the normal watcher callback, you just start the idle watcher. The real
		1374	processing is done in the idle watcher callback. This causes libev to
		1375	continously poll and process kernel event data for the watcher, but when
		1376	the lock-out case is known to be rare (which in turn is rare :), this is
		1377	workable.
		1378
		1379	Usually, however, the lock-out model implemented that way will perform
		1380	miserably under the type of load it was designed to handle. In that case,
		1381	it might be preferable to stop the real watcher before starting the
		1382	idle watcher, so the kernel will not have to process the event in case
		1383	the actual processing will be delayed for considerable time.
		1384
		1385	Here is an example of an I/O watcher that should run at a strictly lower
		1386	priority than the default, and which should only process data when no
		1387	other events are pending:
		1388
		1389	ev_idle idle; // actual processing watcher
		1390	ev_io io; // actual event watcher
		1391
		1392	static void
		1393	io_cb (EV_P_ ev_io *w, int revents)
		1394	{
		1395	// stop the I/O watcher, we received the event, but
		1396	// are not yet ready to handle it.
		1397	ev_io_stop (EV_A_ w);
		1398
		1399	// start the idle watcher to ahndle the actual event.
		1400	// it will not be executed as long as other watchers
		1401	// with the default priority are receiving events.
		1402	ev_idle_start (EV_A_ &idle);
		1403	}
		1404
		1405	static void
		1406	idle_cb (EV_P_ ev_idle *w, int revents)
		1407	{
		1408	// actual processing
		1409	read (STDIN_FILENO, ...);
		1410
		1411	// have to start the I/O watcher again, as
		1412	// we have handled the event
		1413	ev_io_start (EV_P_ &io);
		1414	}
		1415
		1416	// initialisation
		1417	ev_idle_init (&idle, idle_cb);
		1418	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1419	ev_io_start (EV_DEFAULT_ &io);
		1420
		1421	In the "real" world, it might also be beneficial to start a timer, so that
		1422	low-priority connections can not be locked out forever under load. This
		1423	enables your program to keep a lower latency for important connections
		1424	during short periods of high load, while not completely locking out less
		1425	important ones.
999		1426
1000		1427
1001	=head1 WATCHER TYPES	1428	=head1 WATCHER TYPES
1002		1429
1003	This section describes each watcher in detail, but will not repeat	1430	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	1454	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	1455	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	1456	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1457	required if you know what you are doing).
1031		1458
1032	If you must do this, then force the use of a known-to-be-good backend	1459	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	1460	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1461	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1462	descriptors for which non-blocking operation makes no sense (such as
		1463	files) - libev doesn't guarentee any specific behaviour in that case.
1035		1464
1036	Another thing you have to watch out for is that it is quite easy to	1465	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1466	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	1467	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	1468	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	1469	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	1470	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	1471	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.	1472	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1473
1045	If you cannot run the fd in non-blocking mode (for example you should not	1474	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	1475	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	1476	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	1477	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1478	does this on its own, so its quite safe to use). Some people additionally
		1479	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1480	indefinitely.
		1481
		1482	But really, best use non-blocking mode.
1050		1483
1051	=head3 The special problem of disappearing file descriptors	1484	=head3 The special problem of disappearing file descriptors
1052		1485
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1486	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,	1487	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	1488	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	1489	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	1490	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	1491	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1492	fact, a different file descriptor.
1060		1493
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1524	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1525	C<EVBACKEND_POLL>.
1093		1526
1094	=head3 The special problem of SIGPIPE	1527	=head3 The special problem of SIGPIPE
1095		1528
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1529	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	1530	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	1531	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1532	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1533
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1534	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	1535	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).	1536	somewhere, as that would have given you a big clue).
1105		1537
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1543	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1544
1113	=item ev_io_set (ev_io *, int fd, int events)	1545	=item ev_io_set (ev_io *, int fd, int events)
1114		1546
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1547	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	1548	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.	1549	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1550
1119	=item int fd [read-only]	1551	=item int fd [read-only]
1120		1552
1121	The file descriptor being watched.	1553	The file descriptor being watched.
1122		1554
…		…
1130		1562
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1563	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	1564	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1565	attempt to read a whole line in the callback.
1134		1566
1135	static void	1567	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1568	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1569	{
1138	ev_io_stop (loop, w);	1570	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1571	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1572	}
1141		1573
1142	...	1574	...
1143	struct ev_loop *loop = ev_default_init (0);	1575	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1576	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1577	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1578	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1579	ev_loop (loop, 0);
1148		1580
1149		1581
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1582	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1583
1152	Timer watchers are simple relative timers that generate an event after a	1584	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1585	given time, and optionally repeating in regular intervals after that.
1154		1586
1155	The timers are based on real time, that is, if you register an event that	1587	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 last years	1588	times out after an hour and you reset your system clock to January last
1157	time, it will still time out after (roughly) and hour. "Roughly" because	1589	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1590	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1591	monotonic clock option helps a lot here).
		1592
		1593	The callback is guaranteed to be invoked only I<after> its timeout has
		1594	passed (not I<at>, so on systems with very low-resolution clocks this
		1595	might introduce a small delay). If multiple timers become ready during the
		1596	same loop iteration then the ones with earlier time-out values are invoked
		1597	before ones of the same priority with later time-out values (but this is
		1598	no longer true when a callback calls C<ev_loop> recursively).
		1599
		1600	=head3 Be smart about timeouts
		1601
		1602	Many real-world problems involve some kind of timeout, usually for error
		1603	recovery. A typical example is an HTTP request - if the other side hangs,
		1604	you want to raise some error after a while.
		1605
		1606	What follows are some ways to handle this problem, from obvious and
		1607	inefficient to smart and efficient.
		1608
		1609	In the following, a 60 second activity timeout is assumed - a timeout that
		1610	gets reset to 60 seconds each time there is activity (e.g. each time some
		1611	data or other life sign was received).
		1612
		1613	=over 4
		1614
		1615	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1616
		1617	This is the most obvious, but not the most simple way: In the beginning,
		1618	start the watcher:
		1619
		1620	ev_timer_init (timer, callback, 60., 0.);
		1621	ev_timer_start (loop, timer);
		1622
		1623	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1624	and start it again:
		1625
		1626	ev_timer_stop (loop, timer);
		1627	ev_timer_set (timer, 60., 0.);
		1628	ev_timer_start (loop, timer);
		1629
		1630	This is relatively simple to implement, but means that each time there is
		1631	some activity, libev will first have to remove the timer from its internal
		1632	data structure and then add it again. Libev tries to be fast, but it's
		1633	still not a constant-time operation.
		1634
		1635	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1636
		1637	This is the easiest way, and involves using C<ev_timer_again> instead of
		1638	C<ev_timer_start>.
		1639
		1640	To implement this, configure an C<ev_timer> with a C<repeat> value
		1641	of C<60> and then call C<ev_timer_again> at start and each time you
		1642	successfully read or write some data. If you go into an idle state where
		1643	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1644	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1645
		1646	That means you can ignore both the C<ev_timer_start> function and the
		1647	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1648	member and C<ev_timer_again>.
		1649
		1650	At start:
		1651
		1652	ev_init (timer, callback);
		1653	timer->repeat = 60.;
		1654	ev_timer_again (loop, timer);
		1655
		1656	Each time there is some activity:
		1657
		1658	ev_timer_again (loop, timer);
		1659
		1660	It is even possible to change the time-out on the fly, regardless of
		1661	whether the watcher is active or not:
		1662
		1663	timer->repeat = 30.;
		1664	ev_timer_again (loop, timer);
		1665
		1666	This is slightly more efficient then stopping/starting the timer each time
		1667	you want to modify its timeout value, as libev does not have to completely
		1668	remove and re-insert the timer from/into its internal data structure.
		1669
		1670	It is, however, even simpler than the "obvious" way to do it.
		1671
		1672	=item 3. Let the timer time out, but then re-arm it as required.
		1673
		1674	This method is more tricky, but usually most efficient: Most timeouts are
		1675	relatively long compared to the intervals between other activity - in
		1676	our example, within 60 seconds, there are usually many I/O events with
		1677	associated activity resets.
		1678
		1679	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1680	but remember the time of last activity, and check for a real timeout only
		1681	within the callback:
		1682
		1683	ev_tstamp last_activity; // time of last activity
		1684
		1685	static void
		1686	callback (EV_P_ ev_timer *w, int revents)
		1687	{
		1688	ev_tstamp now = ev_now (EV_A);
		1689	ev_tstamp timeout = last_activity + 60.;
		1690
		1691	// if last_activity + 60. is older than now, we did time out
		1692	if (timeout < now)
		1693	{
		1694	// timeout occured, take action
		1695	}
		1696	else
		1697	{
		1698	// callback was invoked, but there was some activity, re-arm
		1699	// the watcher to fire in last_activity + 60, which is
		1700	// guaranteed to be in the future, so "again" is positive:
		1701	w->repeat = timeout - now;
		1702	ev_timer_again (EV_A_ w);
		1703	}
		1704	}
		1705
		1706	To summarise the callback: first calculate the real timeout (defined
		1707	as "60 seconds after the last activity"), then check if that time has
		1708	been reached, which means something I<did>, in fact, time out. Otherwise
		1709	the callback was invoked too early (C<timeout> is in the future), so
		1710	re-schedule the timer to fire at that future time, to see if maybe we have
		1711	a timeout then.
		1712
		1713	Note how C<ev_timer_again> is used, taking advantage of the
		1714	C<ev_timer_again> optimisation when the timer is already running.
		1715
		1716	This scheme causes more callback invocations (about one every 60 seconds
		1717	minus half the average time between activity), but virtually no calls to
		1718	libev to change the timeout.
		1719
		1720	To start the timer, simply initialise the watcher and set C<last_activity>
		1721	to the current time (meaning we just have some activity :), then call the
		1722	callback, which will "do the right thing" and start the timer:
		1723
		1724	ev_init (timer, callback);
		1725	last_activity = ev_now (loop);
		1726	callback (loop, timer, EV_TIMEOUT);
		1727
		1728	And when there is some activity, simply store the current time in
		1729	C<last_activity>, no libev calls at all:
		1730
		1731	last_actiivty = ev_now (loop);
		1732
		1733	This technique is slightly more complex, but in most cases where the
		1734	time-out is unlikely to be triggered, much more efficient.
		1735
		1736	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1737	callback :) - just change the timeout and invoke the callback, which will
		1738	fix things for you.
		1739
		1740	=item 4. Wee, just use a double-linked list for your timeouts.
		1741
		1742	If there is not one request, but many thousands (millions...), all
		1743	employing some kind of timeout with the same timeout value, then one can
		1744	do even better:
		1745
		1746	When starting the timeout, calculate the timeout value and put the timeout
		1747	at the I<end> of the list.
		1748
		1749	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1750	the list is expected to fire (for example, using the technique #3).
		1751
		1752	When there is some activity, remove the timer from the list, recalculate
		1753	the timeout, append it to the end of the list again, and make sure to
		1754	update the C<ev_timer> if it was taken from the beginning of the list.
		1755
		1756	This way, one can manage an unlimited number of timeouts in O(1) time for
		1757	starting, stopping and updating the timers, at the expense of a major
		1758	complication, and having to use a constant timeout. The constant timeout
		1759	ensures that the list stays sorted.
		1760
		1761	=back
		1762
		1763	So which method the best?
		1764
		1765	Method #2 is a simple no-brain-required solution that is adequate in most
		1766	situations. Method #3 requires a bit more thinking, but handles many cases
		1767	better, and isn't very complicated either. In most case, choosing either
		1768	one is fine, with #3 being better in typical situations.
		1769
		1770	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1771	rather complicated, but extremely efficient, something that really pays
		1772	off after the first million or so of active timers, i.e. it's usually
		1773	overkill :)
		1774
		1775	=head3 The special problem of time updates
		1776
		1777	Establishing the current time is a costly operation (it usually takes at
		1778	least two system calls): EV therefore updates its idea of the current
		1779	time only before and after C<ev_loop> collects new events, which causes a
		1780	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1781	lots of events in one iteration.
1160		1782
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1783	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	1784	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	1785	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	1786	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:	1787	timeout on the current time, use something like this to adjust for this:
1166		1788
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1789	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1790
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1791	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	1792	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1793	()>.
		1794
		1795	=head3 The special problems of suspended animation
		1796
		1797	When you leave the server world it is quite customary to hit machines that
		1798	can suspend/hibernate - what happens to the clocks during such a suspend?
		1799
		1800	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1801	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1802	to run until the system is suspended, but they will not advance while the
		1803	system is suspended. That means, on resume, it will be as if the program
		1804	was frozen for a few seconds, but the suspend time will not be counted
		1805	towards C<ev_timer> when a monotonic clock source is used. The real time
		1806	clock advanced as expected, but if it is used as sole clocksource, then a
		1807	long suspend would be detected as a time jump by libev, and timers would
		1808	be adjusted accordingly.
		1809
		1810	I would not be surprised to see different behaviour in different between
		1811	operating systems, OS versions or even different hardware.
		1812
		1813	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1814	time jump in the monotonic clocks and the realtime clock. If the program
		1815	is suspended for a very long time, and monotonic clock sources are in use,
		1816	then you can expect C<ev_timer>s to expire as the full suspension time
		1817	will be counted towards the timers. When no monotonic clock source is in
		1818	use, then libev will again assume a timejump and adjust accordingly.
		1819
		1820	It might be beneficial for this latter case to call C<ev_suspend>
		1821	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1822	deterministic behaviour in this case (you can do nothing against
		1823	C<SIGSTOP>).
1172		1824
1173	=head3 Watcher-Specific Functions and Data Members	1825	=head3 Watcher-Specific Functions and Data Members
1174		1826
1175	=over 4	1827	=over 4
1176		1828
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1829	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1830
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1831	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1832
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1833	Configure the timer to trigger after C<after> seconds. If C<repeat>
1182	C<0.>, then it will automatically be stopped. If it is positive, then the	1834	is C<0.>, then it will automatically be stopped once the timeout is
1183	timer will automatically be configured to trigger again C<repeat> seconds	1835	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1836	configured to trigger again C<repeat> seconds later, again, and again,
		1837	until stopped manually.
1185		1838
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1839	The timer itself will do a best-effort at avoiding drift, that is, if
1187	configure a timer to trigger every 10 seconds, then it will trigger at	1840	you configure a timer to trigger every 10 seconds, then it will normally
1188	exactly 10 second intervals. If, however, your program cannot keep up with	1841	trigger at exactly 10 second intervals. If, however, your program cannot
1189	the timer (because it takes longer than those 10 seconds to do stuff) the	1842	keep up with the timer (because it takes longer than those 10 seconds to
1190	timer will not fire more than once per event loop iteration.	1843	do stuff) the timer will not fire more than once per event loop iteration.
1191		1844
1192	=item ev_timer_again (loop, ev_timer *)	1845	=item ev_timer_again (loop, ev_timer *)
1193		1846
1194	This will act as if the timer timed out and restart it again if it is	1847	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1848	repeating. The exact semantics are:
1196		1849
1197	If the timer is pending, its pending status is cleared.	1850	If the timer is pending, its pending status is cleared.
1198		1851
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1852	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1853
1201	If the timer is repeating, either start it if necessary (with the	1854	If the timer is repeating, either start it if necessary (with the
1202	C<repeat> value), or reset the running timer to the C<repeat> value.	1855	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1856
1204	This sounds a bit complicated, but here is a useful and typical	1857	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1205	example: Imagine you have a tcp connection and you want a so-called idle	1858	usage example.
1206	timeout, that is, you want to be called when there have been, say, 60
1207	seconds of inactivity on the socket. The easiest way to do this is to
1208	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1209	C<ev_timer_again> each time you successfully read or write some data. If
1210	you go into an idle state where you do not expect data to travel on the
1211	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1212	automatically restart it if need be.
1213		1859
1214	That means you can ignore the C<after> value and C<ev_timer_start>	1860	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1215	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1216		1861
1217	ev_timer_init (timer, callback, 0., 5.);	1862	Returns the remaining time until a timer fires. If the timer is active,
1218	ev_timer_again (loop, timer);	1863	then this time is relative to the current event loop time, otherwise it's
1219	...	1864	the timeout value currently configured.
1220	timer->again = 17.;
1221	ev_timer_again (loop, timer);
1222	...
1223	timer->again = 10.;
1224	ev_timer_again (loop, timer);
1225		1865
1226	This is more slightly efficient then stopping/starting the timer each time	1866	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1227	you want to modify its timeout value.	1867	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1868	will return C<4>. When the timer expires and is restarted, it will return
		1869	roughly C<7> (likely slightly less as callback invocation takes some time,
		1870	too), and so on.
1228		1871
1229	=item ev_tstamp repeat [read-write]	1872	=item ev_tstamp repeat [read-write]
1230		1873
1231	The current C<repeat> value. Will be used each time the watcher times out	1874	The current C<repeat> value. Will be used each time the watcher times out
1232	or C<ev_timer_again> is called and determines the next timeout (if any),	1875	or C<ev_timer_again> is called, and determines the next timeout (if any),
1233	which is also when any modifications are taken into account.	1876	which is also when any modifications are taken into account.
1234		1877
1235	=back	1878	=back
1236		1879
1237	=head3 Examples	1880	=head3 Examples
1238		1881
1239	Example: Create a timer that fires after 60 seconds.	1882	Example: Create a timer that fires after 60 seconds.
1240		1883
1241	static void	1884	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1885	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1243	{	1886	{
1244	.. one minute over, w is actually stopped right here	1887	.. one minute over, w is actually stopped right here
1245	}	1888	}
1246		1889
1247	struct ev_timer mytimer;	1890	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1891	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1892	ev_timer_start (loop, &mytimer);
1250		1893
1251	Example: Create a timeout timer that times out after 10 seconds of	1894	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1895	inactivity.
1253		1896
1254	static void	1897	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1898	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1256	{	1899	{
1257	.. ten seconds without any activity	1900	.. ten seconds without any activity
1258	}	1901	}
1259		1902
1260	struct ev_timer mytimer;	1903	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1904	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1905	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1906	ev_loop (loop, 0);
1264		1907
1265	// and in some piece of code that gets executed on any "activity":	1908	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1909	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1910	ev_timer_again (&mytimer);
1268		1911
1269		1912
1270	=head2 C<ev_periodic> - to cron or not to cron?	1913	=head2 C<ev_periodic> - to cron or not to cron?
1271		1914
1272	Periodic watchers are also timers of a kind, but they are very versatile	1915	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1916	(and unfortunately a bit complex).
1274		1917
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1918	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1276	but on wallclock time (absolute time). You can tell a periodic watcher	1919	relative time, the physical time that passes) but on wall clock time
1277	to trigger "at" some specific point in time. For example, if you tell a	1920	(absolute time, the thing you can read on your calender or clock). The
1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1921	difference is that wall clock time can run faster or slower than real
1279	+ 10.>) and then reset your system clock to the last year, then it will	1922	time, and time jumps are not uncommon (e.g. when you adjust your
1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1923	wrist-watch).
1281	roughly 10 seconds later).
1282		1924
1283	They can also be used to implement vastly more complex timers, such as	1925	You can tell a periodic watcher to trigger after some specific point
1284	triggering an event on each midnight, local time or other, complicated,	1926	in time: for example, if you tell a periodic watcher to trigger "in 10
1285	rules.	1927	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1928	not a delay) and then reset your system clock to January of the previous
		1929	year, then it will take a year or more to trigger the event (unlike an
		1930	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1931	it, as it uses a relative timeout).
1286		1932
		1933	C<ev_periodic> watchers can also be used to implement vastly more complex
		1934	timers, such as triggering an event on each "midnight, local time", or
		1935	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1936	those cannot react to time jumps.
		1937
1287	As with timers, the callback is guarenteed to be invoked only when the	1938	As with timers, the callback is guaranteed to be invoked only when the
1288	time (C<at>) has been passed, but if multiple periodic timers become ready	1939	point in time where it is supposed to trigger has passed. If multiple
1289	during the same loop iteration then order of execution is undefined.	1940	timers become ready during the same loop iteration then the ones with
		1941	earlier time-out values are invoked before ones with later time-out values
		1942	(but this is no longer true when a callback calls C<ev_loop> recursively).
1290		1943
1291	=head3 Watcher-Specific Functions and Data Members	1944	=head3 Watcher-Specific Functions and Data Members
1292		1945
1293	=over 4	1946	=over 4
1294		1947
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1948	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1296		1949
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1950	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		1951
1299	Lots of arguments, lets sort it out... There are basically three modes of	1952	Lots of arguments, let's sort it out... There are basically three modes of
1300	operation, and we will explain them from simplest to complex:	1953	operation, and we will explain them from simplest to most complex:
1301		1954
1302	=over 4	1955	=over 4
1303		1956
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1957	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1305		1958
1306	In this configuration the watcher triggers an event at the wallclock time	1959	In this configuration the watcher triggers an event after the wall clock
1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1960	time C<offset> has passed. It will not repeat and will not adjust when a
1308	that is, if it is to be run at January 1st 2011 then it will run when the	1961	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1309	system time reaches or surpasses this time.	1962	will be stopped and invoked when the system clock reaches or surpasses
		1963	this point in time.
1310		1964
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1965	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1312		1966
1313	In this mode the watcher will always be scheduled to time out at the next	1967	In this mode the watcher will always be scheduled to time out at the next
1314	C<at + N * interval> time (for some integer N, which can also be negative)	1968	C<offset + N * interval> time (for some integer N, which can also be
1315	and then repeat, regardless of any time jumps.	1969	negative) and then repeat, regardless of any time jumps. The C<offset>
		1970	argument is merely an offset into the C<interval> periods.
1316		1971
1317	This can be used to create timers that do not drift with respect to system	1972	This can be used to create timers that do not drift with respect to the
1318	time:	1973	system clock, for example, here is an C<ev_periodic> that triggers each
		1974	hour, on the hour (with respect to UTC):
1319		1975
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1976	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1977
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1978	This doesn't mean there will always be 3600 seconds in between triggers,
1323	but only that the the callback will be called when the system time shows a	1979	but only that the callback will be called when the system time shows a
1324	full hour (UTC), or more correctly, when the system time is evenly divisible	1980	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1981	by 3600.
1326		1982
1327	Another way to think about it (for the mathematically inclined) is that	1983	Another way to think about it (for the mathematically inclined) is that
1328	C<ev_periodic> will try to run the callback in this mode at the next possible	1984	C<ev_periodic> will try to run the callback in this mode at the next possible
1329	time where C<time = at (mod interval)>, regardless of any time jumps.	1985	time where C<time = offset (mod interval)>, regardless of any time jumps.
1330		1986
1331	For numerical stability it is preferable that the C<at> value is near	1987	For numerical stability it is preferable that the C<offset> value is near
1332	C<ev_now ()> (the current time), but there is no range requirement for	1988	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1989	this value, and in fact is often specified as zero.
1334		1990
		1991	Note also that there is an upper limit to how often a timer can fire (CPU
		1992	speed for example), so if C<interval> is very small then timing stability
		1993	will of course deteriorate. Libev itself tries to be exact to be about one
		1994	millisecond (if the OS supports it and the machine is fast enough).
		1995
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1996	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1336		1997
1337	In this mode the values for C<interval> and C<at> are both being	1998	In this mode the values for C<interval> and C<offset> are both being
1338	ignored. Instead, each time the periodic watcher gets scheduled, the	1999	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	2000	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	2001	current time as second argument.
1341		2002
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2003	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1343	ever, or make any event loop modifications>. If you need to stop it,	2004	or make ANY other event loop modifications whatsoever, unless explicitly
1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	2005	allowed by documentation here>.
1345	starting an C<ev_prepare> watcher, which is legal).
1346		2006
		2007	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		2008	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		2009	only event loop modification you are allowed to do).
		2010
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	2011	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	2012	*w, ev_tstamp now)>, e.g.:
1349		2013
		2014	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2015	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	2016	{
1352	return now + 60.;	2017	return now + 60.;
1353	}	2018	}
1354		2019
1355	It must return the next time to trigger, based on the passed time value	2020	It must return the next time to trigger, based on the passed time value
1356	(that is, the lowest time value larger than to the second argument). It	2021	(that is, the lowest time value larger than to the second argument). It
1357	will usually be called just before the callback will be triggered, but	2022	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	2023	might be called at other times, too.
1359		2024
1360	NOTE: I<< This callback must always return a time that is later than the	2025	NOTE: I<< This callback must always return a time that is higher than or
1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	2026	equal to the passed C<now> value >>.
1362		2027
1363	This can be used to create very complex timers, such as a timer that	2028	This can be used to create very complex timers, such as a timer that
1364	triggers on each midnight, local time. To do this, you would calculate the	2029	triggers on "next midnight, local time". To do this, you would calculate the
1365	next midnight after C<now> and return the timestamp value for this. How	2030	next midnight after C<now> and return the timestamp value for this. How
1366	you do this is, again, up to you (but it is not trivial, which is the main	2031	you do this is, again, up to you (but it is not trivial, which is the main
1367	reason I omitted it as an example).	2032	reason I omitted it as an example).
1368		2033
1369	=back	2034	=back
…		…
1375	a different time than the last time it was called (e.g. in a crond like	2040	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	2041	program when the crontabs have changed).
1377		2042
1378	=item ev_tstamp ev_periodic_at (ev_periodic *)	2043	=item ev_tstamp ev_periodic_at (ev_periodic *)
1379		2044
1380	When active, returns the absolute time that the watcher is supposed to	2045	When active, returns the absolute time that the watcher is supposed
1381	trigger next.	2046	to trigger next. This is not the same as the C<offset> argument to
		2047	C<ev_periodic_set>, but indeed works even in interval and manual
		2048	rescheduling modes.
1382		2049
1383	=item ev_tstamp offset [read-write]	2050	=item ev_tstamp offset [read-write]
1384		2051
1385	When repeating, this contains the offset value, otherwise this is the	2052	When repeating, this contains the offset value, otherwise this is the
1386	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2053	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2054	although libev might modify this value for better numerical stability).
1387		2055
1388	Can be modified any time, but changes only take effect when the periodic	2056	Can be modified any time, but changes only take effect when the periodic
1389	timer fires or C<ev_periodic_again> is being called.	2057	timer fires or C<ev_periodic_again> is being called.
1390		2058
1391	=item ev_tstamp interval [read-write]	2059	=item ev_tstamp interval [read-write]
1392		2060
1393	The current interval value. Can be modified any time, but changes only	2061	The current interval value. Can be modified any time, but changes only
1394	take effect when the periodic timer fires or C<ev_periodic_again> is being	2062	take effect when the periodic timer fires or C<ev_periodic_again> is being
1395	called.	2063	called.
1396		2064
1397	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2065	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1398		2066
1399	The current reschedule callback, or C<0>, if this functionality is	2067	The current reschedule callback, or C<0>, if this functionality is
1400	switched off. Can be changed any time, but changes only take effect when	2068	switched off. Can be changed any time, but changes only take effect when
1401	the periodic timer fires or C<ev_periodic_again> is being called.	2069	the periodic timer fires or C<ev_periodic_again> is being called.
1402		2070
1403	=back	2071	=back
1404		2072
1405	=head3 Examples	2073	=head3 Examples
1406		2074
1407	Example: Call a callback every hour, or, more precisely, whenever the	2075	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	2076	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	2077	potentially a lot of jitter, but good long-term stability.
1410		2078
1411	static void	2079	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2080	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1413	{	2081	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	2082	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	2083	}
1416		2084
1417	struct ev_periodic hourly_tick;	2085	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2086	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	2087	ev_periodic_start (loop, &hourly_tick);
1420		2088
1421	Example: The same as above, but use a reschedule callback to do it:	2089	Example: The same as above, but use a reschedule callback to do it:
1422		2090
1423	#include <math.h>	2091	#include <math.h>
1424		2092
1425	static ev_tstamp	2093	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2094	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	2095	{
1428	return fmod (now, 3600.) + 3600.;	2096	return now + (3600. - fmod (now, 3600.));
1429	}	2097	}
1430		2098
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2099	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		2100
1433	Example: Call a callback every hour, starting now:	2101	Example: Call a callback every hour, starting now:
1434		2102
1435	struct ev_periodic hourly_tick;	2103	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	2104	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	2105	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	2106	ev_periodic_start (loop, &hourly_tick);
1439		2107
1440		2108
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	2109	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		2110
1443	Signal watchers will trigger an event when the process receives a specific	2111	Signal watchers will trigger an event when the process receives a specific
1444	signal one or more times. Even though signals are very asynchronous, libev	2112	signal one or more times. Even though signals are very asynchronous, libev
1445	will try it's best to deliver signals synchronously, i.e. as part of the	2113	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	2114	normal event processing, like any other event.
1447		2115
		2116	If you want signals to be delivered truly asynchronously, just use
		2117	C<sigaction> as you would do without libev and forget about sharing
		2118	the signal. You can even use C<ev_async> from a signal handler to
		2119	synchronously wake up an event loop.
		2120
1448	You can configure as many watchers as you like per signal. Only when the	2121	You can configure as many watchers as you like for the same signal, but
		2122	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2123	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2124	C<SIGINT> in both the default loop and another loop at the same time. At
		2125	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2126
1449	first watcher gets started will libev actually register a signal watcher	2127	When the first watcher gets started will libev actually register something
1450	with the kernel (thus it coexists with your own signal handlers as long	2128	with the kernel (thus it coexists with your own signal handlers as long as
1451	as you don't register any with libev). Similarly, when the last signal	2129	you don't register any with libev for the same signal).
1452	watcher for a signal is stopped libev will reset the signal handler to
1453	SIG_DFL (regardless of what it was set to before).
1454		2130
1455	If possible and supported, libev will install its handlers with	2131	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2132	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1457	interrupted. If you have a problem with syscalls getting interrupted by	2133	not be unduly interrupted. If you have a problem with system calls getting
1458	signals you can block all signals in an C<ev_check> watcher and unblock	2134	interrupted by signals you can block all signals in an C<ev_check> watcher
1459	them in an C<ev_prepare> watcher.	2135	and unblock them in an C<ev_prepare> watcher.
		2136
		2137	=head3 The special problem of inheritance over execve
		2138
		2139	Both the signal mask (C<sigprocmask>) and the signal disposition
		2140	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2141	stopping it again), that is, libev might or might not block the signal,
		2142	and might or might not set or restore the installed signal handler.
		2143
		2144	While this does not matter for the signal disposition (libev never
		2145	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2146	C<execve>), this matters for the signal mask: many programs do not expect
		2147	certain signals to be blocked.
		2148
		2149	This means that before calling C<exec> (from the child) you should reset
		2150	the signal mask to whatever "default" you expect (all clear is a good
		2151	choice usually).
		2152
		2153	The simplest way to ensure that the signal mask is reset in the child is
		2154	to install a fork handler with C<pthread_atfork> that resets it. That will
		2155	catch fork calls done by libraries (such as the libc) as well.
		2156
		2157	In current versions of libev, you can also ensure that the signal mask is
		2158	not blocking any signals (except temporarily, so thread users watch out)
		2159	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2160	is not guaranteed for future versions, however.
1460		2161
1461	=head3 Watcher-Specific Functions and Data Members	2162	=head3 Watcher-Specific Functions and Data Members
1462		2163
1463	=over 4	2164	=over 4
1464		2165
…		…
1475		2176
1476	=back	2177	=back
1477		2178
1478	=head3 Examples	2179	=head3 Examples
1479		2180
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	2181	Example: Try to exit cleanly on SIGINT.
1481		2182
1482	static void	2183	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2184	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1484	{	2185	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	2186	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	2187	}
1487		2188
1488	struct ev_signal signal_watcher;	2189	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2190	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	2191	ev_signal_start (loop, &signal_watcher);
1491		2192
1492		2193
1493	=head2 C<ev_child> - watch out for process status changes	2194	=head2 C<ev_child> - watch out for process status changes
1494		2195
1495	Child watchers trigger when your process receives a SIGCHLD in response to	2196	Child watchers trigger when your process receives a SIGCHLD in response to
1496	some child status changes (most typically when a child of yours dies). It	2197	some child status changes (most typically when a child of yours dies or
1497	is permissible to install a child watcher I<after> the child has been	2198	exits). It is permissible to install a child watcher I<after> the child
1498	forked (which implies it might have already exited), as long as the event	2199	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	2200	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2201	forking and then immediately registering a watcher for the child is fine,
		2202	but forking and registering a watcher a few event loop iterations later or
		2203	in the next callback invocation is not.
1500		2204
1501	Only the default event loop is capable of handling signals, and therefore	2205	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	2206	you can only register child watchers in the default event loop.
		2207
		2208	Due to some design glitches inside libev, child watchers will always be
		2209	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2210	libev)
1503		2211
1504	=head3 Process Interaction	2212	=head3 Process Interaction
1505		2213
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	2214	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	2215	initialised. This is necessary to guarantee proper behaviour even if the
1508	the first child watcher is started after the child exits. The occurance	2216	first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2217	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	2218	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	2219	children, even ones not watched.
1512		2220
1513	=head3 Overriding the Built-In Processing	2221	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	2225	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	2226	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	2227	default loop never gets destroyed. You are encouraged, however, to use an
1520	event-based approach to child reaping and thus use libev's support for	2228	event-based approach to child reaping and thus use libev's support for
1521	that, so other libev users can use C<ev_child> watchers freely.	2229	that, so other libev users can use C<ev_child> watchers freely.
		2230
		2231	=head3 Stopping the Child Watcher
		2232
		2233	Currently, the child watcher never gets stopped, even when the
		2234	child terminates, so normally one needs to stop the watcher in the
		2235	callback. Future versions of libev might stop the watcher automatically
		2236	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2237	problem).
1522		2238
1523	=head3 Watcher-Specific Functions and Data Members	2239	=head3 Watcher-Specific Functions and Data Members
1524		2240
1525	=over 4	2241	=over 4
1526		2242
…		…
1555	=head3 Examples	2271	=head3 Examples
1556		2272
1557	Example: C<fork()> a new process and install a child handler to wait for	2273	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	2274	its completion.
1559		2275
1560	ev_child cw;	2276	ev_child cw;
1561		2277
1562	static void	2278	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	2279	child_cb (EV_P_ ev_child *w, int revents)
1564	{	2280	{
1565	ev_child_stop (EV_A_ w);	2281	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2282	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	2283	}
1568		2284
1569	pid_t pid = fork ();	2285	pid_t pid = fork ();
1570		2286
1571	if (pid < 0)	2287	if (pid < 0)
1572	// error	2288	// error
1573	else if (pid == 0)	2289	else if (pid == 0)
1574	{	2290	{
1575	// the forked child executes here	2291	// the forked child executes here
1576	exit (1);	2292	exit (1);
1577	}	2293	}
1578	else	2294	else
1579	{	2295	{
1580	ev_child_init (&cw, child_cb, pid, 0);	2296	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	2297	ev_child_start (EV_DEFAULT_ &cw);
1582	}	2298	}
1583		2299
1584		2300
1585	=head2 C<ev_stat> - did the file attributes just change?	2301	=head2 C<ev_stat> - did the file attributes just change?
1586		2302
1587	This watches a filesystem path for attribute changes. That is, it calls	2303	This watches a file system path for attribute changes. That is, it calls
1588	C<stat> regularly (or when the OS says it changed) and sees if it changed	2304	C<stat> on that path in regular intervals (or when the OS says it changed)
1589	compared to the last time, invoking the callback if it did.	2305	and sees if it changed compared to the last time, invoking the callback if
		2306	it did.
1590		2307
1591	The path does not need to exist: changing from "path exists" to "path does	2308	The path does not need to exist: changing from "path exists" to "path does
1592	not exist" is a status change like any other. The condition "path does	2309	not exist" is a status change like any other. The condition "path does not
1593	not exist" is signified by the C<st_nlink> field being zero (which is	2310	exist" (or more correctly "path cannot be stat'ed") is signified by the
1594	otherwise always forced to be at least one) and all the other fields of	2311	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	2312	least one) and all the other fields of the stat buffer having unspecified
		2313	contents.
1596		2314
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	2315	The path I<must not> end in a slash or contain special components such as
		2316	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1598	relative and your working directory changes, the behaviour is undefined.	2317	your working directory changes, then the behaviour is undefined.
1599		2318
1600	Since there is no standard to do this, the portable implementation simply	2319	Since there is no portable change notification interface available, the
1601	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2320	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	2321	to see if it changed somehow. You can specify a recommended polling
1603	a polling interval of C<0> (highly recommended!) then a I<suitable,	2322	interval for this case. If you specify a polling interval of C<0> (highly
1604	unspecified default> value will be used (which you can expect to be around	2323	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	2324	(which you can expect to be around five seconds, although this might
1606	impose a minimum interval which is currently around C<0.1>, but thats	2325	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	2326	currently around C<0.1>, but that's usually overkill.
1608		2327
1609	This watcher type is not meant for massive numbers of stat watchers,	2328	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	2329	as even with OS-supported change notifications, this can be
1611	resource-intensive.	2330	resource-intensive.
1612		2331
1613	At the time of this writing, only the Linux inotify interface is	2332	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	2333	is the Linux inotify interface (implementing kqueue support is left as an
1615	reader, note, however, that the author sees no way of implementing ev_stat	2334	exercise for the reader. Note, however, that the author sees no way of
1616	semantics with kqueue). Inotify will be used to give hints only and should	2335	implementing C<ev_stat> semantics with kqueue, except as a hint).
1617	not change the semantics of C<ev_stat> watchers, which means that libev
1618	sometimes needs to fall back to regular polling again even with inotify,
1619	but changes are usually detected immediately, and if the file exists there
1620	will be no polling.
1621		2336
1622	=head3 ABI Issues (Largefile Support)	2337	=head3 ABI Issues (Largefile Support)
1623		2338
1624	Libev by default (unless the user overrides this) uses the default	2339	Libev by default (unless the user overrides this) uses the default
1625	compilation environment, which means that on systems with optionally	2340	compilation environment, which means that on systems with large file
1626	disabled large file support, you get the 32 bit version of the stat	2341	support disabled by default, you get the 32 bit version of the stat
1627	structure. When using the library from programs that change the ABI to	2342	structure. When using the library from programs that change the ABI to
1628	use 64 bit file offsets the programs will fail. In that case you have to	2343	use 64 bit file offsets the programs will fail. In that case you have to
1629	compile libev with the same flags to get binary compatibility. This is	2344	compile libev with the same flags to get binary compatibility. This is
1630	obviously the case with any flags that change the ABI, but the problem is	2345	obviously the case with any flags that change the ABI, but the problem is
1631	most noticably with ev_stat and largefile support.	2346	most noticeably displayed with ev_stat and large file support.
1632		2347
1633	=head3 Inotify	2348	The solution for this is to lobby your distribution maker to make large
		2349	file interfaces available by default (as e.g. FreeBSD does) and not
		2350	optional. Libev cannot simply switch on large file support because it has
		2351	to exchange stat structures with application programs compiled using the
		2352	default compilation environment.
1634		2353
		2354	=head3 Inotify and Kqueue
		2355
1635	When C<inotify (7)> support has been compiled into libev (generally only	2356	When C<inotify (7)> support has been compiled into libev and present at
1636	available on Linux) and present at runtime, it will be used to speed up	2357	runtime, it will be used to speed up change detection where possible. The
1637	change detection where possible. The inotify descriptor will be created lazily	2358	inotify descriptor will be created lazily when the first C<ev_stat>
1638	when the first C<ev_stat> watcher is being started.	2359	watcher is being started.
1639		2360
1640	Inotify presence does not change the semantics of C<ev_stat> watchers	2361	Inotify presence does not change the semantics of C<ev_stat> watchers
1641	except that changes might be detected earlier, and in some cases, to avoid	2362	except that changes might be detected earlier, and in some cases, to avoid
1642	making regular C<stat> calls. Even in the presence of inotify support	2363	making regular C<stat> calls. Even in the presence of inotify support
1643	there are many cases where libev has to resort to regular C<stat> polling.	2364	there are many cases where libev has to resort to regular C<stat> polling,
		2365	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2366	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2367	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2368	xfs are fully working) libev usually gets away without polling.
1644		2369
1645	(There is no support for kqueue, as apparently it cannot be used to	2370	There is no support for kqueue, as apparently it cannot be used to
1646	implement this functionality, due to the requirement of having a file	2371	implement this functionality, due to the requirement of having a file
1647	descriptor open on the object at all times).	2372	descriptor open on the object at all times, and detecting renames, unlinks
		2373	etc. is difficult.
		2374
		2375	=head3 C<stat ()> is a synchronous operation
		2376
		2377	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2378	the process. The exception are C<ev_stat> watchers - those call C<stat
		2379	()>, which is a synchronous operation.
		2380
		2381	For local paths, this usually doesn't matter: unless the system is very
		2382	busy or the intervals between stat's are large, a stat call will be fast,
		2383	as the path data is usually in memory already (except when starting the
		2384	watcher).
		2385
		2386	For networked file systems, calling C<stat ()> can block an indefinite
		2387	time due to network issues, and even under good conditions, a stat call
		2388	often takes multiple milliseconds.
		2389
		2390	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2391	paths, although this is fully supported by libev.
1648		2392
1649	=head3 The special problem of stat time resolution	2393	=head3 The special problem of stat time resolution
1650		2394
1651	The C<stat ()> syscall only supports full-second resolution portably, and	2395	The C<stat ()> system call only supports full-second resolution portably,
1652	even on systems where the resolution is higher, many filesystems still	2396	and even on systems where the resolution is higher, most file systems
1653	only support whole seconds.	2397	still only support whole seconds.
1654		2398
1655	That means that, if the time is the only thing that changes, you can	2399	That means that, if the time is the only thing that changes, you can
1656	easily miss updates: on the first update, C<ev_stat> detects a change and	2400	easily miss updates: on the first update, C<ev_stat> detects a change and
1657	calls your callback, which does something. When there is another update	2401	calls your callback, which does something. When there is another update
1658	within the same second, C<ev_stat> will be unable to detect it as the stat	2402	within the same second, C<ev_stat> will be unable to detect unless the
1659	data does not change.	2403	stat data does change in other ways (e.g. file size).
1660		2404
1661	The solution to this is to delay acting on a change for slightly more	2405	The solution to this is to delay acting on a change for slightly more
1662	than second (or till slightly after the next full second boundary), using	2406	than a second (or till slightly after the next full second boundary), using
1663	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2407	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1664	ev_timer_again (loop, w)>).	2408	ev_timer_again (loop, w)>).
1665		2409
1666	The C<.02> offset is added to work around small timing inconsistencies	2410	The C<.02> offset is added to work around small timing inconsistencies
1667	of some operating systems (where the second counter of the current time	2411	of some operating systems (where the second counter of the current time
…		…
1684	C<path>. The C<interval> is a hint on how quickly a change is expected to	2428	C<path>. The C<interval> is a hint on how quickly a change is expected to
1685	be detected and should normally be specified as C<0> to let libev choose	2429	be detected and should normally be specified as C<0> to let libev choose
1686	a suitable value. The memory pointed to by C<path> must point to the same	2430	a suitable value. The memory pointed to by C<path> must point to the same
1687	path for as long as the watcher is active.	2431	path for as long as the watcher is active.
1688		2432
1689	The callback will receive C<EV_STAT> when a change was detected, relative	2433	The callback will receive an C<EV_STAT> event when a change was detected,
1690	to the attributes at the time the watcher was started (or the last change	2434	relative to the attributes at the time the watcher was started (or the
1691	was detected).	2435	last change was detected).
1692		2436
1693	=item ev_stat_stat (loop, ev_stat *)	2437	=item ev_stat_stat (loop, ev_stat *)
1694		2438
1695	Updates the stat buffer immediately with new values. If you change the	2439	Updates the stat buffer immediately with new values. If you change the
1696	watched path in your callback, you could call this function to avoid	2440	watched path in your callback, you could call this function to avoid
…		…
1717		2461
1718	The specified interval.	2462	The specified interval.
1719		2463
1720	=item const char *path [read-only]	2464	=item const char *path [read-only]
1721		2465
1722	The filesystem path that is being watched.	2466	The file system path that is being watched.
1723		2467
1724	=back	2468	=back
1725		2469
1726	=head3 Examples	2470	=head3 Examples
1727		2471
1728	Example: Watch C</etc/passwd> for attribute changes.	2472	Example: Watch C</etc/passwd> for attribute changes.
1729		2473
1730	static void	2474	static void
1731	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2475	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1732	{	2476	{
1733	/* /etc/passwd changed in some way */	2477	/* /etc/passwd changed in some way */
1734	if (w->attr.st_nlink)	2478	if (w->attr.st_nlink)
1735	{	2479	{
1736	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2480	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1737	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2481	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1738	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2482	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1739	}	2483	}
1740	else	2484	else
1741	/* you shalt not abuse printf for puts */	2485	/* you shalt not abuse printf for puts */
1742	puts ("wow, /etc/passwd is not there, expect problems. "	2486	puts ("wow, /etc/passwd is not there, expect problems. "
1743	"if this is windows, they already arrived\n");	2487	"if this is windows, they already arrived\n");
1744	}	2488	}
1745		2489
1746	...	2490	...
1747	ev_stat passwd;	2491	ev_stat passwd;
1748		2492
1749	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2493	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1750	ev_stat_start (loop, &passwd);	2494	ev_stat_start (loop, &passwd);
1751		2495
1752	Example: Like above, but additionally use a one-second delay so we do not	2496	Example: Like above, but additionally use a one-second delay so we do not
1753	miss updates (however, frequent updates will delay processing, too, so	2497	miss updates (however, frequent updates will delay processing, too, so
1754	one might do the work both on C<ev_stat> callback invocation I<and> on	2498	one might do the work both on C<ev_stat> callback invocation I<and> on
1755	C<ev_timer> callback invocation).	2499	C<ev_timer> callback invocation).
1756		2500
1757	static ev_stat passwd;	2501	static ev_stat passwd;
1758	static ev_timer timer;	2502	static ev_timer timer;
1759		2503
1760	static void	2504	static void
1761	timer_cb (EV_P_ ev_timer *w, int revents)	2505	timer_cb (EV_P_ ev_timer *w, int revents)
1762	{	2506	{
1763	ev_timer_stop (EV_A_ w);	2507	ev_timer_stop (EV_A_ w);
1764		2508
1765	/* now it's one second after the most recent passwd change */	2509	/* now it's one second after the most recent passwd change */
1766	}	2510	}
1767		2511
1768	static void	2512	static void
1769	stat_cb (EV_P_ ev_stat *w, int revents)	2513	stat_cb (EV_P_ ev_stat *w, int revents)
1770	{	2514	{
1771	/* reset the one-second timer */	2515	/* reset the one-second timer */
1772	ev_timer_again (EV_A_ &timer);	2516	ev_timer_again (EV_A_ &timer);
1773	}	2517	}
1774		2518
1775	...	2519	...
1776	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2520	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1777	ev_stat_start (loop, &passwd);	2521	ev_stat_start (loop, &passwd);
1778	ev_timer_init (&timer, timer_cb, 0., 1.02);	2522	ev_timer_init (&timer, timer_cb, 0., 1.02);
1779		2523
1780		2524
1781	=head2 C<ev_idle> - when you've got nothing better to do...	2525	=head2 C<ev_idle> - when you've got nothing better to do...
1782		2526
1783	Idle watchers trigger events when no other events of the same or higher	2527	Idle watchers trigger events when no other events of the same or higher
1784	priority are pending (prepare, check and other idle watchers do not	2528	priority are pending (prepare, check and other idle watchers do not count
1785	count).	2529	as receiving "events").
1786		2530
1787	That is, as long as your process is busy handling sockets or timeouts	2531	That is, as long as your process is busy handling sockets or timeouts
1788	(or even signals, imagine) of the same or higher priority it will not be	2532	(or even signals, imagine) of the same or higher priority it will not be
1789	triggered. But when your process is idle (or only lower-priority watchers	2533	triggered. But when your process is idle (or only lower-priority watchers
1790	are pending), the idle watchers are being called once per event loop	2534	are pending), the idle watchers are being called once per event loop
…		…
1801		2545
1802	=head3 Watcher-Specific Functions and Data Members	2546	=head3 Watcher-Specific Functions and Data Members
1803		2547
1804	=over 4	2548	=over 4
1805		2549
1806	=item ev_idle_init (ev_signal *, callback)	2550	=item ev_idle_init (ev_idle *, callback)
1807		2551
1808	Initialises and configures the idle watcher - it has no parameters of any	2552	Initialises and configures the idle watcher - it has no parameters of any
1809	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2553	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1810	believe me.	2554	believe me.
1811		2555
…		…
1814	=head3 Examples	2558	=head3 Examples
1815		2559
1816	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2560	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1817	callback, free it. Also, use no error checking, as usual.	2561	callback, free it. Also, use no error checking, as usual.
1818		2562
1819	static void	2563	static void
1820	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2564	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1821	{	2565	{
1822	free (w);	2566	free (w);
1823	// now do something you wanted to do when the program has	2567	// now do something you wanted to do when the program has
1824	// no longer anything immediate to do.	2568	// no longer anything immediate to do.
1825	}	2569	}
1826		2570
1827	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2571	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1828	ev_idle_init (idle_watcher, idle_cb);	2572	ev_idle_init (idle_watcher, idle_cb);
1829	ev_idle_start (loop, idle_cb);	2573	ev_idle_start (loop, idle_watcher);
1830		2574
1831		2575
1832	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2576	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1833		2577
1834	Prepare and check watchers are usually (but not always) used in tandem:	2578	Prepare and check watchers are usually (but not always) used in pairs:
1835	prepare watchers get invoked before the process blocks and check watchers	2579	prepare watchers get invoked before the process blocks and check watchers
1836	afterwards.	2580	afterwards.
1837		2581
1838	You I<must not> call C<ev_loop> or similar functions that enter	2582	You I<must not> call C<ev_loop> or similar functions that enter
1839	the current event loop from either C<ev_prepare> or C<ev_check>	2583	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1842	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2586	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1843	C<ev_check> so if you have one watcher of each kind they will always be	2587	C<ev_check> so if you have one watcher of each kind they will always be
1844	called in pairs bracketing the blocking call.	2588	called in pairs bracketing the blocking call.
1845		2589
1846	Their main purpose is to integrate other event mechanisms into libev and	2590	Their main purpose is to integrate other event mechanisms into libev and
1847	their use is somewhat advanced. This could be used, for example, to track	2591	their use is somewhat advanced. They could be used, for example, to track
1848	variable changes, implement your own watchers, integrate net-snmp or a	2592	variable changes, implement your own watchers, integrate net-snmp or a
1849	coroutine library and lots more. They are also occasionally useful if	2593	coroutine library and lots more. They are also occasionally useful if
1850	you cache some data and want to flush it before blocking (for example,	2594	you cache some data and want to flush it before blocking (for example,
1851	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2595	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1852	watcher).	2596	watcher).
1853		2597
1854	This is done by examining in each prepare call which file descriptors need	2598	This is done by examining in each prepare call which file descriptors
1855	to be watched by the other library, registering C<ev_io> watchers for	2599	need to be watched by the other library, registering C<ev_io> watchers
1856	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2600	for them and starting an C<ev_timer> watcher for any timeouts (many
1857	provide just this functionality). Then, in the check watcher you check for	2601	libraries provide exactly this functionality). Then, in the check watcher,
1858	any events that occured (by checking the pending status of all watchers	2602	you check for any events that occurred (by checking the pending status
1859	and stopping them) and call back into the library. The I/O and timer	2603	of all watchers and stopping them) and call back into the library. The
1860	callbacks will never actually be called (but must be valid nevertheless,	2604	I/O and timer callbacks will never actually be called (but must be valid
1861	because you never know, you know?).	2605	nevertheless, because you never know, you know?).
1862		2606
1863	As another example, the Perl Coro module uses these hooks to integrate	2607	As another example, the Perl Coro module uses these hooks to integrate
1864	coroutines into libev programs, by yielding to other active coroutines	2608	coroutines into libev programs, by yielding to other active coroutines
1865	during each prepare and only letting the process block if no coroutines	2609	during each prepare and only letting the process block if no coroutines
1866	are ready to run (it's actually more complicated: it only runs coroutines	2610	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1869	loop from blocking if lower-priority coroutines are active, thus mapping	2613	loop from blocking if lower-priority coroutines are active, thus mapping
1870	low-priority coroutines to idle/background tasks).	2614	low-priority coroutines to idle/background tasks).
1871		2615
1872	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2616	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1873	priority, to ensure that they are being run before any other watchers	2617	priority, to ensure that they are being run before any other watchers
		2618	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2619
1874	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2620	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1875	too) should not activate ("feed") events into libev. While libev fully	2621	activate ("feed") events into libev. While libev fully supports this, they
1876	supports this, they might get executed before other C<ev_check> watchers	2622	might get executed before other C<ev_check> watchers did their job. As
1877	did their job. As C<ev_check> watchers are often used to embed other	2623	C<ev_check> watchers are often used to embed other (non-libev) event
1878	(non-libev) event loops those other event loops might be in an unusable	2624	loops those other event loops might be in an unusable state until their
1879	state until their C<ev_check> watcher ran (always remind yourself to	2625	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1880	coexist peacefully with others).	2626	others).
1881		2627
1882	=head3 Watcher-Specific Functions and Data Members	2628	=head3 Watcher-Specific Functions and Data Members
1883		2629
1884	=over 4	2630	=over 4
1885		2631
…		…
1887		2633
1888	=item ev_check_init (ev_check *, callback)	2634	=item ev_check_init (ev_check *, callback)
1889		2635
1890	Initialises and configures the prepare or check watcher - they have no	2636	Initialises and configures the prepare or check watcher - they have no
1891	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2637	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1892	macros, but using them is utterly, utterly and completely pointless.	2638	macros, but using them is utterly, utterly, utterly and completely
		2639	pointless.
1893		2640
1894	=back	2641	=back
1895		2642
1896	=head3 Examples	2643	=head3 Examples
1897		2644
…		…
1906	and in a check watcher, destroy them and call into libadns. What follows	2653	and in a check watcher, destroy them and call into libadns. What follows
1907	is pseudo-code only of course. This requires you to either use a low	2654	is pseudo-code only of course. This requires you to either use a low
1908	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2655	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1909	the callbacks for the IO/timeout watchers might not have been called yet.	2656	the callbacks for the IO/timeout watchers might not have been called yet.
1910		2657
1911	static ev_io iow [nfd];	2658	static ev_io iow [nfd];
1912	static ev_timer tw;	2659	static ev_timer tw;
1913		2660
1914	static void	2661	static void
1915	io_cb (ev_loop *loop, ev_io *w, int revents)	2662	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1916	{	2663	{
1917	}	2664	}
1918		2665
1919	// create io watchers for each fd and a timer before blocking	2666	// create io watchers for each fd and a timer before blocking
1920	static void	2667	static void
1921	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2668	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1922	{	2669	{
1923	int timeout = 3600000;	2670	int timeout = 3600000;
1924	struct pollfd fds [nfd];	2671	struct pollfd fds [nfd];
1925	// actual code will need to loop here and realloc etc.	2672	// actual code will need to loop here and realloc etc.
1926	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2673	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1927		2674
1928	/* the callback is illegal, but won't be called as we stop during check */	2675	/* the callback is illegal, but won't be called as we stop during check */
1929	ev_timer_init (&tw, 0, timeout * 1e-3);	2676	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1930	ev_timer_start (loop, &tw);	2677	ev_timer_start (loop, &tw);
1931		2678
1932	// create one ev_io per pollfd	2679	// create one ev_io per pollfd
1933	for (int i = 0; i < nfd; ++i)	2680	for (int i = 0; i < nfd; ++i)
1934	{	2681	{
1935	ev_io_init (iow + i, io_cb, fds [i].fd,	2682	ev_io_init (iow + i, io_cb, fds [i].fd,
1936	((fds [i].events & POLLIN ? EV_READ : 0)	2683	((fds [i].events & POLLIN ? EV_READ : 0)
1937	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2684	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1938		2685
1939	fds [i].revents = 0;	2686	fds [i].revents = 0;
1940	ev_io_start (loop, iow + i);	2687	ev_io_start (loop, iow + i);
1941	}	2688	}
1942	}	2689	}
1943		2690
1944	// stop all watchers after blocking	2691	// stop all watchers after blocking
1945	static void	2692	static void
1946	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2693	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1947	{	2694	{
1948	ev_timer_stop (loop, &tw);	2695	ev_timer_stop (loop, &tw);
1949		2696
1950	for (int i = 0; i < nfd; ++i)	2697	for (int i = 0; i < nfd; ++i)
1951	{	2698	{
1952	// set the relevant poll flags	2699	// set the relevant poll flags
1953	// could also call adns_processreadable etc. here	2700	// could also call adns_processreadable etc. here
1954	struct pollfd *fd = fds + i;	2701	struct pollfd *fd = fds + i;
1955	int revents = ev_clear_pending (iow + i);	2702	int revents = ev_clear_pending (iow + i);
1956	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2703	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1957	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2704	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1958		2705
1959	// now stop the watcher	2706	// now stop the watcher
1960	ev_io_stop (loop, iow + i);	2707	ev_io_stop (loop, iow + i);
1961	}	2708	}
1962		2709
1963	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2710	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1964	}	2711	}
1965		2712
1966	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2713	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1967	in the prepare watcher and would dispose of the check watcher.	2714	in the prepare watcher and would dispose of the check watcher.
1968		2715
1969	Method 3: If the module to be embedded supports explicit event	2716	Method 3: If the module to be embedded supports explicit event
1970	notification (adns does), you can also make use of the actual watcher	2717	notification (libadns does), you can also make use of the actual watcher
1971	callbacks, and only destroy/create the watchers in the prepare watcher.	2718	callbacks, and only destroy/create the watchers in the prepare watcher.
1972		2719
1973	static void	2720	static void
1974	timer_cb (EV_P_ ev_timer *w, int revents)	2721	timer_cb (EV_P_ ev_timer *w, int revents)
1975	{	2722	{
1976	adns_state ads = (adns_state)w->data;	2723	adns_state ads = (adns_state)w->data;
1977	update_now (EV_A);	2724	update_now (EV_A);
1978		2725
1979	adns_processtimeouts (ads, &tv_now);	2726	adns_processtimeouts (ads, &tv_now);
1980	}	2727	}
1981		2728
1982	static void	2729	static void
1983	io_cb (EV_P_ ev_io *w, int revents)	2730	io_cb (EV_P_ ev_io *w, int revents)
1984	{	2731	{
1985	adns_state ads = (adns_state)w->data;	2732	adns_state ads = (adns_state)w->data;
1986	update_now (EV_A);	2733	update_now (EV_A);
1987		2734
1988	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2735	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1989	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2736	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1990	}	2737	}
1991		2738
1992	// do not ever call adns_afterpoll	2739	// do not ever call adns_afterpoll
1993		2740
1994	Method 4: Do not use a prepare or check watcher because the module you	2741	Method 4: Do not use a prepare or check watcher because the module you
1995	want to embed is too inflexible to support it. Instead, youc na override	2742	want to embed is not flexible enough to support it. Instead, you can
1996	their poll function. The drawback with this solution is that the main	2743	override their poll function. The drawback with this solution is that the
1997	loop is now no longer controllable by EV. The C<Glib::EV> module does	2744	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1998	this.	2745	this approach, effectively embedding EV as a client into the horrible
		2746	libglib event loop.
1999		2747
2000	static gint	2748	static gint
2001	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2749	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2002	{	2750	{
2003	int got_events = 0;	2751	int got_events = 0;
2004		2752
2005	for (n = 0; n < nfds; ++n)	2753	for (n = 0; n < nfds; ++n)
2006	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2754	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2007		2755
2008	if (timeout >= 0)	2756	if (timeout >= 0)
2009	// create/start timer	2757	// create/start timer
2010		2758
2011	// poll	2759	// poll
2012	ev_loop (EV_A_ 0);	2760	ev_loop (EV_A_ 0);
2013		2761
2014	// stop timer again	2762	// stop timer again
2015	if (timeout >= 0)	2763	if (timeout >= 0)
2016	ev_timer_stop (EV_A_ &to);	2764	ev_timer_stop (EV_A_ &to);
2017		2765
2018	// stop io watchers again - their callbacks should have set	2766	// stop io watchers again - their callbacks should have set
2019	for (n = 0; n < nfds; ++n)	2767	for (n = 0; n < nfds; ++n)
2020	ev_io_stop (EV_A_ iow [n]);	2768	ev_io_stop (EV_A_ iow [n]);
2021		2769
2022	return got_events;	2770	return got_events;
2023	}	2771	}
2024		2772
2025		2773
2026	=head2 C<ev_embed> - when one backend isn't enough...	2774	=head2 C<ev_embed> - when one backend isn't enough...
2027		2775
2028	This is a rather advanced watcher type that lets you embed one event loop	2776	This is a rather advanced watcher type that lets you embed one event loop
…		…
2034	prioritise I/O.	2782	prioritise I/O.
2035		2783
2036	As an example for a bug workaround, the kqueue backend might only support	2784	As an example for a bug workaround, the kqueue backend might only support
2037	sockets on some platform, so it is unusable as generic backend, but you	2785	sockets on some platform, so it is unusable as generic backend, but you
2038	still want to make use of it because you have many sockets and it scales	2786	still want to make use of it because you have many sockets and it scales
2039	so nicely. In this case, you would create a kqueue-based loop and embed it	2787	so nicely. In this case, you would create a kqueue-based loop and embed
2040	into your default loop (which might use e.g. poll). Overall operation will	2788	it into your default loop (which might use e.g. poll). Overall operation
2041	be a bit slower because first libev has to poll and then call kevent, but	2789	will be a bit slower because first libev has to call C<poll> and then
2042	at least you can use both at what they are best.	2790	C<kevent>, but at least you can use both mechanisms for what they are
		2791	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2043		2792
2044	As for prioritising I/O: rarely you have the case where some fds have	2793	As for prioritising I/O: under rare circumstances you have the case where
2045	to be watched and handled very quickly (with low latency), and even	2794	some fds have to be watched and handled very quickly (with low latency),
2046	priorities and idle watchers might have too much overhead. In this case	2795	and even priorities and idle watchers might have too much overhead. In
2047	you would put all the high priority stuff in one loop and all the rest in	2796	this case you would put all the high priority stuff in one loop and all
2048	a second one, and embed the second one in the first.	2797	the rest in a second one, and embed the second one in the first.
2049		2798
2050	As long as the watcher is active, the callback will be invoked every time	2799	As long as the watcher is active, the callback will be invoked every
2051	there might be events pending in the embedded loop. The callback must then	2800	time there might be events pending in the embedded loop. The callback
2052	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2801	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2053	their callbacks (you could also start an idle watcher to give the embedded	2802	sweep and invoke their callbacks (the callback doesn't need to invoke the
2054	loop strictly lower priority for example). You can also set the callback	2803	C<ev_embed_sweep> function directly, it could also start an idle watcher
2055	to C<0>, in which case the embed watcher will automatically execute the	2804	to give the embedded loop strictly lower priority for example).
2056	embedded loop sweep.
2057		2805
2058	As long as the watcher is started it will automatically handle events. The	2806	You can also set the callback to C<0>, in which case the embed watcher
2059	callback will be invoked whenever some events have been handled. You can	2807	will automatically execute the embedded loop sweep whenever necessary.
2060	set the callback to C<0> to avoid having to specify one if you are not
2061	interested in that.
2062		2808
2063	Also, there have not currently been made special provisions for forking:	2809	Fork detection will be handled transparently while the C<ev_embed> watcher
2064	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2810	is active, i.e., the embedded loop will automatically be forked when the
2065	but you will also have to stop and restart any C<ev_embed> watchers	2811	embedding loop forks. In other cases, the user is responsible for calling
2066	yourself.	2812	C<ev_loop_fork> on the embedded loop.
2067		2813
2068	Unfortunately, not all backends are embeddable, only the ones returned by	2814	Unfortunately, not all backends are embeddable: only the ones returned by
2069	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2815	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2070	portable one.	2816	portable one.
2071		2817
2072	So when you want to use this feature you will always have to be prepared	2818	So when you want to use this feature you will always have to be prepared
2073	that you cannot get an embeddable loop. The recommended way to get around	2819	that you cannot get an embeddable loop. The recommended way to get around
2074	this is to have a separate variables for your embeddable loop, try to	2820	this is to have a separate variables for your embeddable loop, try to
2075	create it, and if that fails, use the normal loop for everything.	2821	create it, and if that fails, use the normal loop for everything.
2076		2822
		2823	=head3 C<ev_embed> and fork
		2824
		2825	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2826	automatically be applied to the embedded loop as well, so no special
		2827	fork handling is required in that case. When the watcher is not running,
		2828	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2829	as applicable.
		2830
2077	=head3 Watcher-Specific Functions and Data Members	2831	=head3 Watcher-Specific Functions and Data Members
2078		2832
2079	=over 4	2833	=over 4
2080		2834
2081	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2835	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2084		2838
2085	Configures the watcher to embed the given loop, which must be	2839	Configures the watcher to embed the given loop, which must be
2086	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2840	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2087	invoked automatically, otherwise it is the responsibility of the callback	2841	invoked automatically, otherwise it is the responsibility of the callback
2088	to invoke it (it will continue to be called until the sweep has been done,	2842	to invoke it (it will continue to be called until the sweep has been done,
2089	if you do not want thta, you need to temporarily stop the embed watcher).	2843	if you do not want that, you need to temporarily stop the embed watcher).
2090		2844
2091	=item ev_embed_sweep (loop, ev_embed *)	2845	=item ev_embed_sweep (loop, ev_embed *)
2092		2846
2093	Make a single, non-blocking sweep over the embedded loop. This works	2847	Make a single, non-blocking sweep over the embedded loop. This works
2094	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2848	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2095	apropriate way for embedded loops.	2849	appropriate way for embedded loops.
2096		2850
2097	=item struct ev_loop *other [read-only]	2851	=item struct ev_loop *other [read-only]
2098		2852
2099	The embedded event loop.	2853	The embedded event loop.
2100		2854
…		…
2102		2856
2103	=head3 Examples	2857	=head3 Examples
2104		2858
2105	Example: Try to get an embeddable event loop and embed it into the default	2859	Example: Try to get an embeddable event loop and embed it into the default
2106	event loop. If that is not possible, use the default loop. The default	2860	event loop. If that is not possible, use the default loop. The default
2107	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2861	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2108	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2862	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2109	used).	2863	used).
2110		2864
2111	struct ev_loop *loop_hi = ev_default_init (0);	2865	struct ev_loop *loop_hi = ev_default_init (0);
2112	struct ev_loop *loop_lo = 0;	2866	struct ev_loop *loop_lo = 0;
2113	struct ev_embed embed;	2867	ev_embed embed;
2114		2868
2115	// see if there is a chance of getting one that works	2869	// see if there is a chance of getting one that works
2116	// (remember that a flags value of 0 means autodetection)	2870	// (remember that a flags value of 0 means autodetection)
2117	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2871	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2118	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2872	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2119	: 0;	2873	: 0;
2120		2874
2121	// if we got one, then embed it, otherwise default to loop_hi	2875	// if we got one, then embed it, otherwise default to loop_hi
2122	if (loop_lo)	2876	if (loop_lo)
2123	{	2877	{
2124	ev_embed_init (&embed, 0, loop_lo);	2878	ev_embed_init (&embed, 0, loop_lo);
2125	ev_embed_start (loop_hi, &embed);	2879	ev_embed_start (loop_hi, &embed);
2126	}	2880	}
2127	else	2881	else
2128	loop_lo = loop_hi;	2882	loop_lo = loop_hi;
2129		2883
2130	Example: Check if kqueue is available but not recommended and create	2884	Example: Check if kqueue is available but not recommended and create
2131	a kqueue backend for use with sockets (which usually work with any	2885	a kqueue backend for use with sockets (which usually work with any
2132	kqueue implementation). Store the kqueue/socket-only event loop in	2886	kqueue implementation). Store the kqueue/socket-only event loop in
2133	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2887	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2134		2888
2135	struct ev_loop *loop = ev_default_init (0);	2889	struct ev_loop *loop = ev_default_init (0);
2136	struct ev_loop *loop_socket = 0;	2890	struct ev_loop *loop_socket = 0;
2137	struct ev_embed embed;	2891	ev_embed embed;
2138		2892
2139	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2893	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2140	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2894	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2141	{	2895	{
2142	ev_embed_init (&embed, 0, loop_socket);	2896	ev_embed_init (&embed, 0, loop_socket);
2143	ev_embed_start (loop, &embed);	2897	ev_embed_start (loop, &embed);
2144	}	2898	}
2145		2899
2146	if (!loop_socket)	2900	if (!loop_socket)
2147	loop_socket = loop;	2901	loop_socket = loop;
2148		2902
2149	// now use loop_socket for all sockets, and loop for everything else	2903	// now use loop_socket for all sockets, and loop for everything else
2150		2904
2151		2905
2152	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2906	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2153		2907
2154	Fork watchers are called when a C<fork ()> was detected (usually because	2908	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2157	event loop blocks next and before C<ev_check> watchers are being called,	2911	event loop blocks next and before C<ev_check> watchers are being called,
2158	and only in the child after the fork. If whoever good citizen calling	2912	and only in the child after the fork. If whoever good citizen calling
2159	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2913	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2160	handlers will be invoked, too, of course.	2914	handlers will be invoked, too, of course.
2161		2915
		2916	=head3 The special problem of life after fork - how is it possible?
		2917
		2918	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2919	up/change the process environment, followed by a call to C<exec()>. This
		2920	sequence should be handled by libev without any problems.
		2921
		2922	This changes when the application actually wants to do event handling
		2923	in the child, or both parent in child, in effect "continuing" after the
		2924	fork.
		2925
		2926	The default mode of operation (for libev, with application help to detect
		2927	forks) is to duplicate all the state in the child, as would be expected
		2928	when I<either> the parent I<or> the child process continues.
		2929
		2930	When both processes want to continue using libev, then this is usually the
		2931	wrong result. In that case, usually one process (typically the parent) is
		2932	supposed to continue with all watchers in place as before, while the other
		2933	process typically wants to start fresh, i.e. without any active watchers.
		2934
		2935	The cleanest and most efficient way to achieve that with libev is to
		2936	simply create a new event loop, which of course will be "empty", and
		2937	use that for new watchers. This has the advantage of not touching more
		2938	memory than necessary, and thus avoiding the copy-on-write, and the
		2939	disadvantage of having to use multiple event loops (which do not support
		2940	signal watchers).
		2941
		2942	When this is not possible, or you want to use the default loop for
		2943	other reasons, then in the process that wants to start "fresh", call
		2944	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2945	the default loop will "orphan" (not stop) all registered watchers, so you
		2946	have to be careful not to execute code that modifies those watchers. Note
		2947	also that in that case, you have to re-register any signal watchers.
		2948
2162	=head3 Watcher-Specific Functions and Data Members	2949	=head3 Watcher-Specific Functions and Data Members
2163		2950
2164	=over 4	2951	=over 4
2165		2952
2166	=item ev_fork_init (ev_signal *, callback)	2953	=item ev_fork_init (ev_signal *, callback)
…		…
2195	=head3 Queueing	2982	=head3 Queueing
2196		2983
2197	C<ev_async> does not support queueing of data in any way. The reason	2984	C<ev_async> does not support queueing of data in any way. The reason
2198	is that the author does not know of a simple (or any) algorithm for a	2985	is that the author does not know of a simple (or any) algorithm for a
2199	multiple-writer-single-reader queue that works in all cases and doesn't	2986	multiple-writer-single-reader queue that works in all cases and doesn't
2200	need elaborate support such as pthreads.	2987	need elaborate support such as pthreads or unportable memory access
		2988	semantics.
2201		2989
2202	That means that if you want to queue data, you have to provide your own	2990	That means that if you want to queue data, you have to provide your own
2203	queue. But at least I can tell you would implement locking around your	2991	queue. But at least I can tell you how to implement locking around your
2204	queue:	2992	queue:
2205		2993
2206	=over 4	2994	=over 4
2207		2995
2208	=item queueing from a signal handler context	2996	=item queueing from a signal handler context
2209		2997
2210	To implement race-free queueing, you simply add to the queue in the signal	2998	To implement race-free queueing, you simply add to the queue in the signal
2211	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2999	handler but you block the signal handler in the watcher callback. Here is
2212	some fictitiuous SIGUSR1 handler:	3000	an example that does that for some fictitious SIGUSR1 handler:
2213		3001
2214	static ev_async mysig;	3002	static ev_async mysig;
2215		3003
2216	static void	3004	static void
2217	sigusr1_handler (void)	3005	sigusr1_handler (void)
…		…
2283	=over 4	3071	=over 4
2284		3072
2285	=item ev_async_init (ev_async *, callback)	3073	=item ev_async_init (ev_async *, callback)
2286		3074
2287	Initialises and configures the async watcher - it has no parameters of any	3075	Initialises and configures the async watcher - it has no parameters of any
2288	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3076	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2289	believe me.	3077	trust me.
2290		3078
2291	=item ev_async_send (loop, ev_async *)	3079	=item ev_async_send (loop, ev_async *)
2292		3080
2293	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3081	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2294	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3082	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2295	C<ev_feed_event>, this call is safe to do in other threads, signal or	3083	C<ev_feed_event>, this call is safe to do from other threads, signal or
2296	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3084	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2297	section below on what exactly this means).	3085	section below on what exactly this means).
2298		3086
		3087	Note that, as with other watchers in libev, multiple events might get
		3088	compressed into a single callback invocation (another way to look at this
		3089	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3090	reset when the event loop detects that).
		3091
2299	This call incurs the overhead of a syscall only once per loop iteration,	3092	This call incurs the overhead of a system call only once per event loop
2300	so while the overhead might be noticable, it doesn't apply to repeated	3093	iteration, so while the overhead might be noticeable, it doesn't apply to
2301	calls to C<ev_async_send>.	3094	repeated calls to C<ev_async_send> for the same event loop.
2302		3095
2303	=item bool = ev_async_pending (ev_async *)	3096	=item bool = ev_async_pending (ev_async *)
2304		3097
2305	Returns a non-zero value when C<ev_async_send> has been called on the	3098	Returns a non-zero value when C<ev_async_send> has been called on the
2306	watcher but the event has not yet been processed (or even noted) by the	3099	watcher but the event has not yet been processed (or even noted) by the
2307	event loop.	3100	event loop.
2308		3101
2309	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3102	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2310	the loop iterates next and checks for the watcher to have become active,	3103	the loop iterates next and checks for the watcher to have become active,
2311	it will reset the flag again. C<ev_async_pending> can be used to very	3104	it will reset the flag again. C<ev_async_pending> can be used to very
2312	quickly check wether invoking the loop might be a good idea.	3105	quickly check whether invoking the loop might be a good idea.
2313		3106
2314	Not that this does I<not> check wether the watcher itself is pending, only	3107	Not that this does I<not> check whether the watcher itself is pending,
2315	wether it has been requested to make this watcher pending.	3108	only whether it has been requested to make this watcher pending: there
		3109	is a time window between the event loop checking and resetting the async
		3110	notification, and the callback being invoked.
2316		3111
2317	=back	3112	=back
2318		3113
2319		3114
2320	=head1 OTHER FUNCTIONS	3115	=head1 OTHER FUNCTIONS
…		…
2324	=over 4	3119	=over 4
2325		3120
2326	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3121	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2327		3122
2328	This function combines a simple timer and an I/O watcher, calls your	3123	This function combines a simple timer and an I/O watcher, calls your
2329	callback on whichever event happens first and automatically stop both	3124	callback on whichever event happens first and automatically stops both
2330	watchers. This is useful if you want to wait for a single event on an fd	3125	watchers. This is useful if you want to wait for a single event on an fd
2331	or timeout without having to allocate/configure/start/stop/free one or	3126	or timeout without having to allocate/configure/start/stop/free one or
2332	more watchers yourself.	3127	more watchers yourself.
2333		3128
2334	If C<fd> is less than 0, then no I/O watcher will be started and events	3129	If C<fd> is less than 0, then no I/O watcher will be started and the
2335	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3130	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2336	C<events> set will be craeted and started.	3131	the given C<fd> and C<events> set will be created and started.
2337		3132
2338	If C<timeout> is less than 0, then no timeout watcher will be	3133	If C<timeout> is less than 0, then no timeout watcher will be
2339	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3134	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2340	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3135	repeat = 0) will be started. C<0> is a valid timeout.
2341	dubious value.
2342		3136
2343	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3137	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2344	passed an C<revents> set like normal event callbacks (a combination of	3138	passed an C<revents> set like normal event callbacks (a combination of
2345	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3139	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2346	value passed to C<ev_once>:	3140	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3141	a timeout and an io event at the same time - you probably should give io
		3142	events precedence.
2347		3143
		3144	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3145
2348	static void stdin_ready (int revents, void *arg)	3146	static void stdin_ready (int revents, void *arg)
2349	{	3147	{
2350	if (revents & EV_TIMEOUT)
2351	/* doh, nothing entered */;
2352	else if (revents & EV_READ)	3148	if (revents & EV_READ)
2353	/* stdin might have data for us, joy! */;	3149	/* stdin might have data for us, joy! */;
		3150	else if (revents & EV_TIMEOUT)
		3151	/* doh, nothing entered */;
2354	}	3152	}
2355		3153
2356	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3154	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2357		3155
2358	=item ev_feed_event (ev_loop *, watcher *, int revents)
2359
2360	Feeds the given event set into the event loop, as if the specified event
2361	had happened for the specified watcher (which must be a pointer to an
2362	initialised but not necessarily started event watcher).
2363
2364	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3156	=item ev_feed_fd_event (loop, int fd, int revents)
2365		3157
2366	Feed an event on the given fd, as if a file descriptor backend detected	3158	Feed an event on the given fd, as if a file descriptor backend detected
2367	the given events it.	3159	the given events it.
2368		3160
2369	=item ev_feed_signal_event (ev_loop *loop, int signum)	3161	=item ev_feed_signal_event (loop, int signum)
2370		3162
2371	Feed an event as if the given signal occured (C<loop> must be the default	3163	Feed an event as if the given signal occurred (C<loop> must be the default
2372	loop!).	3164	loop!).
2373		3165
2374	=back	3166	=back
2375		3167
2376		3168
…		…
2405	=back	3197	=back
2406		3198
2407	=head1 C++ SUPPORT	3199	=head1 C++ SUPPORT
2408		3200
2409	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3201	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2410	you to use some convinience methods to start/stop watchers and also change	3202	you to use some convenience methods to start/stop watchers and also change
2411	the callback model to a model using method callbacks on objects.	3203	the callback model to a model using method callbacks on objects.
2412		3204
2413	To use it,	3205	To use it,
2414		3206
2415	#include <ev++.h>	3207	#include <ev++.h>
2416		3208
2417	This automatically includes F<ev.h> and puts all of its definitions (many	3209	This automatically includes F<ev.h> and puts all of its definitions (many
2418	of them macros) into the global namespace. All C++ specific things are	3210	of them macros) into the global namespace. All C++ specific things are
2419	put into the C<ev> namespace. It should support all the same embedding	3211	put into the C<ev> namespace. It should support all the same embedding
2420	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3212	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2454		3246
2455	=over 4	3247	=over 4
2456		3248
2457	=item ev::TYPE::TYPE ()	3249	=item ev::TYPE::TYPE ()
2458		3250
2459	=item ev::TYPE::TYPE (struct ev_loop *)	3251	=item ev::TYPE::TYPE (loop)
2460		3252
2461	=item ev::TYPE::~TYPE	3253	=item ev::TYPE::~TYPE
2462		3254
2463	The constructor (optionally) takes an event loop to associate the watcher	3255	The constructor (optionally) takes an event loop to associate the watcher
2464	with. If it is omitted, it will use C<EV_DEFAULT>.	3256	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2487	your compiler is good :), then the method will be fully inlined into the	3279	your compiler is good :), then the method will be fully inlined into the
2488	thunking function, making it as fast as a direct C callback.	3280	thunking function, making it as fast as a direct C callback.
2489		3281
2490	Example: simple class declaration and watcher initialisation	3282	Example: simple class declaration and watcher initialisation
2491		3283
2492	struct myclass	3284	struct myclass
2493	{	3285	{
2494	void io_cb (ev::io &w, int revents) { }	3286	void io_cb (ev::io &w, int revents) { }
2495	}	3287	}
2496		3288
2497	myclass obj;	3289	myclass obj;
2498	ev::io iow;	3290	ev::io iow;
2499	iow.set <myclass, &myclass::io_cb> (&obj);	3291	iow.set <myclass, &myclass::io_cb> (&obj);
		3292
		3293	=item w->set (object *)
		3294
		3295	This is an B<experimental> feature that might go away in a future version.
		3296
		3297	This is a variation of a method callback - leaving out the method to call
		3298	will default the method to C<operator ()>, which makes it possible to use
		3299	functor objects without having to manually specify the C<operator ()> all
		3300	the time. Incidentally, you can then also leave out the template argument
		3301	list.
		3302
		3303	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3304	int revents)>.
		3305
		3306	See the method-C<set> above for more details.
		3307
		3308	Example: use a functor object as callback.
		3309
		3310	struct myfunctor
		3311	{
		3312	void operator() (ev::io &w, int revents)
		3313	{
		3314	...
		3315	}
		3316	}
		3317
		3318	myfunctor f;
		3319
		3320	ev::io w;
		3321	w.set (&f);
2500		3322
2501	=item w->set<function> (void *data = 0)	3323	=item w->set<function> (void *data = 0)
2502		3324
2503	Also sets a callback, but uses a static method or plain function as	3325	Also sets a callback, but uses a static method or plain function as
2504	callback. The optional C<data> argument will be stored in the watcher's	3326	callback. The optional C<data> argument will be stored in the watcher's
…		…
2506		3328
2507	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3329	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2508		3330
2509	See the method-C<set> above for more details.	3331	See the method-C<set> above for more details.
2510		3332
2511	Example:	3333	Example: Use a plain function as callback.
2512		3334
2513	static void io_cb (ev::io &w, int revents) { }	3335	static void io_cb (ev::io &w, int revents) { }
2514	iow.set <io_cb> ();	3336	iow.set <io_cb> ();
2515		3337
2516	=item w->set (struct ev_loop *)	3338	=item w->set (loop)
2517		3339
2518	Associates a different C<struct ev_loop> with this watcher. You can only	3340	Associates a different C<struct ev_loop> with this watcher. You can only
2519	do this when the watcher is inactive (and not pending either).	3341	do this when the watcher is inactive (and not pending either).
2520		3342
2521	=item w->set ([args])	3343	=item w->set ([arguments])
2522		3344
2523	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3345	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2524	called at least once. Unlike the C counterpart, an active watcher gets	3346	called at least once. Unlike the C counterpart, an active watcher gets
2525	automatically stopped and restarted when reconfiguring it with this	3347	automatically stopped and restarted when reconfiguring it with this
2526	method.	3348	method.
2527		3349
2528	=item w->start ()	3350	=item w->start ()
…		…
2552	=back	3374	=back
2553		3375
2554	Example: Define a class with an IO and idle watcher, start one of them in	3376	Example: Define a class with an IO and idle watcher, start one of them in
2555	the constructor.	3377	the constructor.
2556		3378
2557	class myclass	3379	class myclass
2558	{	3380	{
2559	ev::io io; void io_cb (ev::io &w, int revents);	3381	ev::io io ; void io_cb (ev::io &w, int revents);
2560	ev:idle idle void idle_cb (ev::idle &w, int revents);	3382	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2561		3383
2562	myclass (int fd)	3384	myclass (int fd)
2563	{	3385	{
2564	io .set <myclass, &myclass::io_cb > (this);	3386	io .set <myclass, &myclass::io_cb > (this);
2565	idle.set <myclass, &myclass::idle_cb> (this);	3387	idle.set <myclass, &myclass::idle_cb> (this);
2566		3388
2567	io.start (fd, ev::READ);	3389	io.start (fd, ev::READ);
2568	}	3390	}
2569	};	3391	};
2570		3392
2571		3393
2572	=head1 OTHER LANGUAGE BINDINGS	3394	=head1 OTHER LANGUAGE BINDINGS
2573		3395
2574	Libev does not offer other language bindings itself, but bindings for a	3396	Libev does not offer other language bindings itself, but bindings for a
2575	numbe rof languages exist in the form of third-party packages. If you know	3397	number of languages exist in the form of third-party packages. If you know
2576	any interesting language binding in addition to the ones listed here, drop	3398	any interesting language binding in addition to the ones listed here, drop
2577	me a note.	3399	me a note.
2578		3400
2579	=over 4	3401	=over 4
2580		3402
2581	=item Perl	3403	=item Perl
2582		3404
2583	The EV module implements the full libev API and is actually used to test	3405	The EV module implements the full libev API and is actually used to test
2584	libev. EV is developed together with libev. Apart from the EV core module,	3406	libev. EV is developed together with libev. Apart from the EV core module,
2585	there are additional modules that implement libev-compatible interfaces	3407	there are additional modules that implement libev-compatible interfaces
2586	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3408	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2587	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3409	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3410	and C<EV::Glib>).
2588		3411
2589	It can be found and installed via CPAN, its homepage is found at	3412	It can be found and installed via CPAN, its homepage is at
2590	L<http://software.schmorp.de/pkg/EV>.	3413	L<http://software.schmorp.de/pkg/EV>.
2591		3414
		3415	=item Python
		3416
		3417	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3418	seems to be quite complete and well-documented.
		3419
2592	=item Ruby	3420	=item Ruby
2593		3421
2594	Tony Arcieri has written a ruby extension that offers access to a subset	3422	Tony Arcieri has written a ruby extension that offers access to a subset
2595	of the libev API and adds filehandle abstractions, asynchronous DNS and	3423	of the libev API and adds file handle abstractions, asynchronous DNS and
2596	more on top of it. It can be found via gem servers. Its homepage is at	3424	more on top of it. It can be found via gem servers. Its homepage is at
2597	L<http://rev.rubyforge.org/>.	3425	L<http://rev.rubyforge.org/>.
2598		3426
		3427	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3428	makes rev work even on mingw.
		3429
		3430	=item Haskell
		3431
		3432	A haskell binding to libev is available at
		3433	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3434
2599	=item D	3435	=item D
2600		3436
2601	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3437	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2602	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3438	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3439
		3440	=item Ocaml
		3441
		3442	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3443	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3444
		3445	=item Lua
		3446
		3447	Brian Maher has written a partial interface to libev
		3448	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3449	L<http://github.com/brimworks/lua-ev>.
2603		3450
2604	=back	3451	=back
2605		3452
2606		3453
2607	=head1 MACRO MAGIC	3454	=head1 MACRO MAGIC
2608		3455
2609	Libev can be compiled with a variety of options, the most fundamantal	3456	Libev can be compiled with a variety of options, the most fundamental
2610	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3457	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2611	functions and callbacks have an initial C<struct ev_loop *> argument.	3458	functions and callbacks have an initial C<struct ev_loop *> argument.
2612		3459
2613	To make it easier to write programs that cope with either variant, the	3460	To make it easier to write programs that cope with either variant, the
2614	following macros are defined:	3461	following macros are defined:
…		…
2619		3466
2620	This provides the loop I<argument> for functions, if one is required ("ev	3467	This provides the loop I<argument> for functions, if one is required ("ev
2621	loop argument"). The C<EV_A> form is used when this is the sole argument,	3468	loop argument"). The C<EV_A> form is used when this is the sole argument,
2622	C<EV_A_> is used when other arguments are following. Example:	3469	C<EV_A_> is used when other arguments are following. Example:
2623		3470
2624	ev_unref (EV_A);	3471	ev_unref (EV_A);
2625	ev_timer_add (EV_A_ watcher);	3472	ev_timer_add (EV_A_ watcher);
2626	ev_loop (EV_A_ 0);	3473	ev_loop (EV_A_ 0);
2627		3474
2628	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3475	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2629	which is often provided by the following macro.	3476	which is often provided by the following macro.
2630		3477
2631	=item C<EV_P>, C<EV_P_>	3478	=item C<EV_P>, C<EV_P_>
2632		3479
2633	This provides the loop I<parameter> for functions, if one is required ("ev	3480	This provides the loop I<parameter> for functions, if one is required ("ev
2634	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3481	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2635	C<EV_P_> is used when other parameters are following. Example:	3482	C<EV_P_> is used when other parameters are following. Example:
2636		3483
2637	// this is how ev_unref is being declared	3484	// this is how ev_unref is being declared
2638	static void ev_unref (EV_P);	3485	static void ev_unref (EV_P);
2639		3486
2640	// this is how you can declare your typical callback	3487	// this is how you can declare your typical callback
2641	static void cb (EV_P_ ev_timer *w, int revents)	3488	static void cb (EV_P_ ev_timer *w, int revents)
2642		3489
2643	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3490	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2644	suitable for use with C<EV_A>.	3491	suitable for use with C<EV_A>.
2645		3492
2646	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3493	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2662		3509
2663	Example: Declare and initialise a check watcher, utilising the above	3510	Example: Declare and initialise a check watcher, utilising the above
2664	macros so it will work regardless of whether multiple loops are supported	3511	macros so it will work regardless of whether multiple loops are supported
2665	or not.	3512	or not.
2666		3513
2667	static void	3514	static void
2668	check_cb (EV_P_ ev_timer *w, int revents)	3515	check_cb (EV_P_ ev_timer *w, int revents)
2669	{	3516	{
2670	ev_check_stop (EV_A_ w);	3517	ev_check_stop (EV_A_ w);
2671	}	3518	}
2672		3519
2673	ev_check check;	3520	ev_check check;
2674	ev_check_init (&check, check_cb);	3521	ev_check_init (&check, check_cb);
2675	ev_check_start (EV_DEFAULT_ &check);	3522	ev_check_start (EV_DEFAULT_ &check);
2676	ev_loop (EV_DEFAULT_ 0);	3523	ev_loop (EV_DEFAULT_ 0);
2677		3524
2678	=head1 EMBEDDING	3525	=head1 EMBEDDING
2679		3526
2680	Libev can (and often is) directly embedded into host	3527	Libev can (and often is) directly embedded into host
2681	applications. Examples of applications that embed it include the Deliantra	3528	applications. Examples of applications that embed it include the Deliantra
…		…
2688	libev somewhere in your source tree).	3535	libev somewhere in your source tree).
2689		3536
2690	=head2 FILESETS	3537	=head2 FILESETS
2691		3538
2692	Depending on what features you need you need to include one or more sets of files	3539	Depending on what features you need you need to include one or more sets of files
2693	in your app.	3540	in your application.
2694		3541
2695	=head3 CORE EVENT LOOP	3542	=head3 CORE EVENT LOOP
2696		3543
2697	To include only the libev core (all the C<ev_*> functions), with manual	3544	To include only the libev core (all the C<ev_*> functions), with manual
2698	configuration (no autoconf):	3545	configuration (no autoconf):
2699		3546
2700	#define EV_STANDALONE 1	3547	#define EV_STANDALONE 1
2701	#include "ev.c"	3548	#include "ev.c"
2702		3549
2703	This will automatically include F<ev.h>, too, and should be done in a	3550	This will automatically include F<ev.h>, too, and should be done in a
2704	single C source file only to provide the function implementations. To use	3551	single C source file only to provide the function implementations. To use
2705	it, do the same for F<ev.h> in all files wishing to use this API (best	3552	it, do the same for F<ev.h> in all files wishing to use this API (best
2706	done by writing a wrapper around F<ev.h> that you can include instead and	3553	done by writing a wrapper around F<ev.h> that you can include instead and
2707	where you can put other configuration options):	3554	where you can put other configuration options):
2708		3555
2709	#define EV_STANDALONE 1	3556	#define EV_STANDALONE 1
2710	#include "ev.h"	3557	#include "ev.h"
2711		3558
2712	Both header files and implementation files can be compiled with a C++	3559	Both header files and implementation files can be compiled with a C++
2713	compiler (at least, thats a stated goal, and breakage will be treated	3560	compiler (at least, that's a stated goal, and breakage will be treated
2714	as a bug).	3561	as a bug).
2715		3562
2716	You need the following files in your source tree, or in a directory	3563	You need the following files in your source tree, or in a directory
2717	in your include path (e.g. in libev/ when using -Ilibev):	3564	in your include path (e.g. in libev/ when using -Ilibev):
2718		3565
2719	ev.h	3566	ev.h
2720	ev.c	3567	ev.c
2721	ev_vars.h	3568	ev_vars.h
2722	ev_wrap.h	3569	ev_wrap.h
2723		3570
2724	ev_win32.c required on win32 platforms only	3571	ev_win32.c required on win32 platforms only
2725		3572
2726	ev_select.c only when select backend is enabled (which is enabled by default)	3573	ev_select.c only when select backend is enabled (which is enabled by default)
2727	ev_poll.c only when poll backend is enabled (disabled by default)	3574	ev_poll.c only when poll backend is enabled (disabled by default)
2728	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3575	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2729	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3576	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2730	ev_port.c only when the solaris port backend is enabled (disabled by default)	3577	ev_port.c only when the solaris port backend is enabled (disabled by default)
2731		3578
2732	F<ev.c> includes the backend files directly when enabled, so you only need	3579	F<ev.c> includes the backend files directly when enabled, so you only need
2733	to compile this single file.	3580	to compile this single file.
2734		3581
2735	=head3 LIBEVENT COMPATIBILITY API	3582	=head3 LIBEVENT COMPATIBILITY API
2736		3583
2737	To include the libevent compatibility API, also include:	3584	To include the libevent compatibility API, also include:
2738		3585
2739	#include "event.c"	3586	#include "event.c"
2740		3587
2741	in the file including F<ev.c>, and:	3588	in the file including F<ev.c>, and:
2742		3589
2743	#include "event.h"	3590	#include "event.h"
2744		3591
2745	in the files that want to use the libevent API. This also includes F<ev.h>.	3592	in the files that want to use the libevent API. This also includes F<ev.h>.
2746		3593
2747	You need the following additional files for this:	3594	You need the following additional files for this:
2748		3595
2749	event.h	3596	event.h
2750	event.c	3597	event.c
2751		3598
2752	=head3 AUTOCONF SUPPORT	3599	=head3 AUTOCONF SUPPORT
2753		3600
2754	Instead of using C<EV_STANDALONE=1> and providing your config in	3601	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2755	whatever way you want, you can also C<m4_include([libev.m4])> in your	3602	whatever way you want, you can also C<m4_include([libev.m4])> in your
2756	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3603	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2757	include F<config.h> and configure itself accordingly.	3604	include F<config.h> and configure itself accordingly.
2758		3605
2759	For this of course you need the m4 file:	3606	For this of course you need the m4 file:
2760		3607
2761	libev.m4	3608	libev.m4
2762		3609
2763	=head2 PREPROCESSOR SYMBOLS/MACROS	3610	=head2 PREPROCESSOR SYMBOLS/MACROS
2764		3611
2765	Libev can be configured via a variety of preprocessor symbols you have to	3612	Libev can be configured via a variety of preprocessor symbols you have to
2766	define before including any of its files. The default in the absense of	3613	define before including any of its files. The default in the absence of
2767	autoconf is noted for every option.	3614	autoconf is documented for every option.
2768		3615
2769	=over 4	3616	=over 4
2770		3617
2771	=item EV_STANDALONE	3618	=item EV_STANDALONE
2772		3619
…		…
2774	keeps libev from including F<config.h>, and it also defines dummy	3621	keeps libev from including F<config.h>, and it also defines dummy
2775	implementations for some libevent functions (such as logging, which is not	3622	implementations for some libevent functions (such as logging, which is not
2776	supported). It will also not define any of the structs usually found in	3623	supported). It will also not define any of the structs usually found in
2777	F<event.h> that are not directly supported by the libev core alone.	3624	F<event.h> that are not directly supported by the libev core alone.
2778		3625
		3626	In standalone mode, libev will still try to automatically deduce the
		3627	configuration, but has to be more conservative.
		3628
2779	=item EV_USE_MONOTONIC	3629	=item EV_USE_MONOTONIC
2780		3630
2781	If defined to be C<1>, libev will try to detect the availability of the	3631	If defined to be C<1>, libev will try to detect the availability of the
2782	monotonic clock option at both compiletime and runtime. Otherwise no use	3632	monotonic clock option at both compile time and runtime. Otherwise no
2783	of the monotonic clock option will be attempted. If you enable this, you	3633	use of the monotonic clock option will be attempted. If you enable this,
2784	usually have to link against librt or something similar. Enabling it when	3634	you usually have to link against librt or something similar. Enabling it
2785	the functionality isn't available is safe, though, although you have	3635	when the functionality isn't available is safe, though, although you have
2786	to make sure you link against any libraries where the C<clock_gettime>	3636	to make sure you link against any libraries where the C<clock_gettime>
2787	function is hiding in (often F<-lrt>).	3637	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2788		3638
2789	=item EV_USE_REALTIME	3639	=item EV_USE_REALTIME
2790		3640
2791	If defined to be C<1>, libev will try to detect the availability of the	3641	If defined to be C<1>, libev will try to detect the availability of the
2792	realtime clock option at compiletime (and assume its availability at	3642	real-time clock option at compile time (and assume its availability
2793	runtime if successful). Otherwise no use of the realtime clock option will	3643	at runtime if successful). Otherwise no use of the real-time clock
2794	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3644	option will be attempted. This effectively replaces C<gettimeofday>
2795	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3645	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2796	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3646	correctness. See the note about libraries in the description of
		3647	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3648	C<EV_USE_CLOCK_SYSCALL>.
		3649
		3650	=item EV_USE_CLOCK_SYSCALL
		3651
		3652	If defined to be C<1>, libev will try to use a direct syscall instead
		3653	of calling the system-provided C<clock_gettime> function. This option
		3654	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3655	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3656	programs needlessly. Using a direct syscall is slightly slower (in
		3657	theory), because no optimised vdso implementation can be used, but avoids
		3658	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3659	higher, as it simplifies linking (no need for C<-lrt>).
2797		3660
2798	=item EV_USE_NANOSLEEP	3661	=item EV_USE_NANOSLEEP
2799		3662
2800	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3663	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2801	and will use it for delays. Otherwise it will use C<select ()>.	3664	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2809	2.7 or newer, otherwise disabled.	3672	2.7 or newer, otherwise disabled.
2810		3673
2811	=item EV_USE_SELECT	3674	=item EV_USE_SELECT
2812		3675
2813	If undefined or defined to be C<1>, libev will compile in support for the	3676	If undefined or defined to be C<1>, libev will compile in support for the
2814	C<select>(2) backend. No attempt at autodetection will be done: if no	3677	C<select>(2) backend. No attempt at auto-detection will be done: if no
2815	other method takes over, select will be it. Otherwise the select backend	3678	other method takes over, select will be it. Otherwise the select backend
2816	will not be compiled in.	3679	will not be compiled in.
2817		3680
2818	=item EV_SELECT_USE_FD_SET	3681	=item EV_SELECT_USE_FD_SET
2819		3682
2820	If defined to C<1>, then the select backend will use the system C<fd_set>	3683	If defined to C<1>, then the select backend will use the system C<fd_set>
2821	structure. This is useful if libev doesn't compile due to a missing	3684	structure. This is useful if libev doesn't compile due to a missing
2822	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3685	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2823	exotic systems. This usually limits the range of file descriptors to some	3686	on exotic systems. This usually limits the range of file descriptors to
2824	low limit such as 1024 or might have other limitations (winsocket only	3687	some low limit such as 1024 or might have other limitations (winsocket
2825	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3688	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2826	influence the size of the C<fd_set> used.	3689	configures the maximum size of the C<fd_set>.
2827		3690
2828	=item EV_SELECT_IS_WINSOCKET	3691	=item EV_SELECT_IS_WINSOCKET
2829		3692
2830	When defined to C<1>, the select backend will assume that	3693	When defined to C<1>, the select backend will assume that
2831	select/socket/connect etc. don't understand file descriptors but	3694	select/socket/connect etc. don't understand file descriptors but
…		…
2833	be used is the winsock select). This means that it will call	3696	be used is the winsock select). This means that it will call
2834	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3697	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2835	it is assumed that all these functions actually work on fds, even	3698	it is assumed that all these functions actually work on fds, even
2836	on win32. Should not be defined on non-win32 platforms.	3699	on win32. Should not be defined on non-win32 platforms.
2837		3700
2838	=item EV_FD_TO_WIN32_HANDLE	3701	=item EV_FD_TO_WIN32_HANDLE(fd)
2839		3702
2840	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3703	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2841	file descriptors to socket handles. When not defining this symbol (the	3704	file descriptors to socket handles. When not defining this symbol (the
2842	default), then libev will call C<_get_osfhandle>, which is usually	3705	default), then libev will call C<_get_osfhandle>, which is usually
2843	correct. In some cases, programs use their own file descriptor management,	3706	correct. In some cases, programs use their own file descriptor management,
2844	in which case they can provide this function to map fds to socket handles.	3707	in which case they can provide this function to map fds to socket handles.
		3708
		3709	=item EV_WIN32_HANDLE_TO_FD(handle)
		3710
		3711	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3712	using the standard C<_open_osfhandle> function. For programs implementing
		3713	their own fd to handle mapping, overwriting this function makes it easier
		3714	to do so. This can be done by defining this macro to an appropriate value.
		3715
		3716	=item EV_WIN32_CLOSE_FD(fd)
		3717
		3718	If programs implement their own fd to handle mapping on win32, then this
		3719	macro can be used to override the C<close> function, useful to unregister
		3720	file descriptors again. Note that the replacement function has to close
		3721	the underlying OS handle.
2845		3722
2846	=item EV_USE_POLL	3723	=item EV_USE_POLL
2847		3724
2848	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3725	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2849	backend. Otherwise it will be enabled on non-win32 platforms. It	3726	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2876	otherwise another method will be used as fallback. This is the preferred	3753	otherwise another method will be used as fallback. This is the preferred
2877	backend for Solaris 10 systems.	3754	backend for Solaris 10 systems.
2878		3755
2879	=item EV_USE_DEVPOLL	3756	=item EV_USE_DEVPOLL
2880		3757
2881	reserved for future expansion, works like the USE symbols above.	3758	Reserved for future expansion, works like the USE symbols above.
2882		3759
2883	=item EV_USE_INOTIFY	3760	=item EV_USE_INOTIFY
2884		3761
2885	If defined to be C<1>, libev will compile in support for the Linux inotify	3762	If defined to be C<1>, libev will compile in support for the Linux inotify
2886	interface to speed up C<ev_stat> watchers. Its actual availability will	3763	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2893	access is atomic with respect to other threads or signal contexts. No such	3770	access is atomic with respect to other threads or signal contexts. No such
2894	type is easily found in the C language, so you can provide your own type	3771	type is easily found in the C language, so you can provide your own type
2895	that you know is safe for your purposes. It is used both for signal handler "locking"	3772	that you know is safe for your purposes. It is used both for signal handler "locking"
2896	as well as for signal and thread safety in C<ev_async> watchers.	3773	as well as for signal and thread safety in C<ev_async> watchers.
2897		3774
2898	In the absense of this define, libev will use C<sig_atomic_t volatile>	3775	In the absence of this define, libev will use C<sig_atomic_t volatile>
2899	(from F<signal.h>), which is usually good enough on most platforms.	3776	(from F<signal.h>), which is usually good enough on most platforms.
2900		3777
2901	=item EV_H	3778	=item EV_H
2902		3779
2903	The name of the F<ev.h> header file used to include it. The default if	3780	The name of the F<ev.h> header file used to include it. The default if
…		…
2942	When doing priority-based operations, libev usually has to linearly search	3819	When doing priority-based operations, libev usually has to linearly search
2943	all the priorities, so having many of them (hundreds) uses a lot of space	3820	all the priorities, so having many of them (hundreds) uses a lot of space
2944	and time, so using the defaults of five priorities (-2 .. +2) is usually	3821	and time, so using the defaults of five priorities (-2 .. +2) is usually
2945	fine.	3822	fine.
2946		3823
2947	If your embedding app does not need any priorities, defining these both to	3824	If your embedding application does not need any priorities, defining these
2948	C<0> will save some memory and cpu.	3825	both to C<0> will save some memory and CPU.
2949		3826
2950	=item EV_PERIODIC_ENABLE	3827	=item EV_PERIODIC_ENABLE
2951		3828
2952	If undefined or defined to be C<1>, then periodic timers are supported. If	3829	If undefined or defined to be C<1>, then periodic timers are supported. If
2953	defined to be C<0>, then they are not. Disabling them saves a few kB of	3830	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2960	code.	3837	code.
2961		3838
2962	=item EV_EMBED_ENABLE	3839	=item EV_EMBED_ENABLE
2963		3840
2964	If undefined or defined to be C<1>, then embed watchers are supported. If	3841	If undefined or defined to be C<1>, then embed watchers are supported. If
2965	defined to be C<0>, then they are not.	3842	defined to be C<0>, then they are not. Embed watchers rely on most other
		3843	watcher types, which therefore must not be disabled.
2966		3844
2967	=item EV_STAT_ENABLE	3845	=item EV_STAT_ENABLE
2968		3846
2969	If undefined or defined to be C<1>, then stat watchers are supported. If	3847	If undefined or defined to be C<1>, then stat watchers are supported. If
2970	defined to be C<0>, then they are not.	3848	defined to be C<0>, then they are not.
…		…
2980	defined to be C<0>, then they are not.	3858	defined to be C<0>, then they are not.
2981		3859
2982	=item EV_MINIMAL	3860	=item EV_MINIMAL
2983		3861
2984	If you need to shave off some kilobytes of code at the expense of some	3862	If you need to shave off some kilobytes of code at the expense of some
2985	speed, define this symbol to C<1>. Currently this is used to override some	3863	speed (but with the full API), define this symbol to C<1>. Currently this
2986	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3864	is used to override some inlining decisions, saves roughly 30% code size
2987	much smaller 2-heap for timer management over the default 4-heap.	3865	on amd64. It also selects a much smaller 2-heap for timer management over
		3866	the default 4-heap.
		3867
		3868	You can save even more by disabling watcher types you do not need
		3869	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3870	(C<-DNDEBUG>) will usually reduce code size a lot.
		3871
		3872	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3873	provide a bare-bones event library. See C<ev.h> for details on what parts
		3874	of the API are still available, and do not complain if this subset changes
		3875	over time.
		3876
		3877	=item EV_NSIG
		3878
		3879	The highest supported signal number, +1 (or, the number of
		3880	signals): Normally, libev tries to deduce the maximum number of signals
		3881	automatically, but sometimes this fails, in which case it can be
		3882	specified. Also, using a lower number than detected (C<32> should be
		3883	good for about any system in existance) can save some memory, as libev
		3884	statically allocates some 12-24 bytes per signal number.
2988		3885
2989	=item EV_PID_HASHSIZE	3886	=item EV_PID_HASHSIZE
2990		3887
2991	C<ev_child> watchers use a small hash table to distribute workload by	3888	C<ev_child> watchers use a small hash table to distribute workload by
2992	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3889	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3002	two).	3899	two).
3003		3900
3004	=item EV_USE_4HEAP	3901	=item EV_USE_4HEAP
3005		3902
3006	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3903	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3007	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3904	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3008	to C<1>. The 4-heap uses more complicated (longer) code but has a	3905	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3009	noticable after performance with many (thousands) of watchers.	3906	faster performance with many (thousands) of watchers.
3010		3907
3011	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3908	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3012	(disabled).	3909	(disabled).
3013		3910
3014	=item EV_HEAP_CACHE_AT	3911	=item EV_HEAP_CACHE_AT
3015		3912
3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3913	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3017	timer and periodics heap, libev can cache the timestamp (I<at>) within	3914	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3018	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3915	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3019	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3916	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3020	but avoids random read accesses on heap changes. This noticably improves	3917	but avoids random read accesses on heap changes. This improves performance
3021	performance noticably with with many (hundreds) of watchers.	3918	noticeably with many (hundreds) of watchers.
3022		3919
3023	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3920	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3024	(disabled).	3921	(disabled).
		3922
		3923	=item EV_VERIFY
		3924
		3925	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3926	be done: If set to C<0>, no internal verification code will be compiled
		3927	in. If set to C<1>, then verification code will be compiled in, but not
		3928	called. If set to C<2>, then the internal verification code will be
		3929	called once per loop, which can slow down libev. If set to C<3>, then the
		3930	verification code will be called very frequently, which will slow down
		3931	libev considerably.
		3932
		3933	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3934	C<0>.
3025		3935
3026	=item EV_COMMON	3936	=item EV_COMMON
3027		3937
3028	By default, all watchers have a C<void *data> member. By redefining	3938	By default, all watchers have a C<void *data> member. By redefining
3029	this macro to a something else you can include more and other types of	3939	this macro to a something else you can include more and other types of
3030	members. You have to define it each time you include one of the files,	3940	members. You have to define it each time you include one of the files,
3031	though, and it must be identical each time.	3941	though, and it must be identical each time.
3032		3942
3033	For example, the perl EV module uses something like this:	3943	For example, the perl EV module uses something like this:
3034		3944
3035	#define EV_COMMON \	3945	#define EV_COMMON \
3036	SV *self; /* contains this struct */ \	3946	SV *self; /* contains this struct */ \
3037	SV *cb_sv, *fh /* note no trailing ";" */	3947	SV *cb_sv, *fh /* note no trailing ";" */
3038		3948
3039	=item EV_CB_DECLARE (type)	3949	=item EV_CB_DECLARE (type)
3040		3950
3041	=item EV_CB_INVOKE (watcher, revents)	3951	=item EV_CB_INVOKE (watcher, revents)
3042		3952
…		…
3047	definition and a statement, respectively. See the F<ev.h> header file for	3957	definition and a statement, respectively. See the F<ev.h> header file for
3048	their default definitions. One possible use for overriding these is to	3958	their default definitions. One possible use for overriding these is to
3049	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3959	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3050	method calls instead of plain function calls in C++.	3960	method calls instead of plain function calls in C++.
3051		3961
		3962	=back
		3963
3052	=head2 EXPORTED API SYMBOLS	3964	=head2 EXPORTED API SYMBOLS
3053		3965
3054	If you need to re-export the API (e.g. via a dll) and you need a list of	3966	If you need to re-export the API (e.g. via a DLL) and you need a list of
3055	exported symbols, you can use the provided F<Symbol.*> files which list	3967	exported symbols, you can use the provided F<Symbol.*> files which list
3056	all public symbols, one per line:	3968	all public symbols, one per line:
3057		3969
3058	Symbols.ev for libev proper	3970	Symbols.ev for libev proper
3059	Symbols.event for the libevent emulation	3971	Symbols.event for the libevent emulation
3060		3972
3061	This can also be used to rename all public symbols to avoid clashes with	3973	This can also be used to rename all public symbols to avoid clashes with
3062	multiple versions of libev linked together (which is obviously bad in	3974	multiple versions of libev linked together (which is obviously bad in
3063	itself, but sometimes it is inconvinient to avoid this).	3975	itself, but sometimes it is inconvenient to avoid this).
3064		3976
3065	A sed command like this will create wrapper C<#define>'s that you need to	3977	A sed command like this will create wrapper C<#define>'s that you need to
3066	include before including F<ev.h>:	3978	include before including F<ev.h>:
3067		3979
3068	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3980	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3085	file.	3997	file.
3086		3998
3087	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3999	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3088	that everybody includes and which overrides some configure choices:	4000	that everybody includes and which overrides some configure choices:
3089		4001
3090	#define EV_MINIMAL 1	4002	#define EV_MINIMAL 1
3091	#define EV_USE_POLL 0	4003	#define EV_USE_POLL 0
3092	#define EV_MULTIPLICITY 0	4004	#define EV_MULTIPLICITY 0
3093	#define EV_PERIODIC_ENABLE 0	4005	#define EV_PERIODIC_ENABLE 0
3094	#define EV_STAT_ENABLE 0	4006	#define EV_STAT_ENABLE 0
3095	#define EV_FORK_ENABLE 0	4007	#define EV_FORK_ENABLE 0
3096	#define EV_CONFIG_H <config.h>	4008	#define EV_CONFIG_H <config.h>
3097	#define EV_MINPRI 0	4009	#define EV_MINPRI 0
3098	#define EV_MAXPRI 0	4010	#define EV_MAXPRI 0
3099		4011
3100	#include "ev++.h"	4012	#include "ev++.h"
3101		4013
3102	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4014	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3103		4015
3104	#include "ev_cpp.h"	4016	#include "ev_cpp.h"
3105	#include "ev.c"	4017	#include "ev.c"
3106		4018
		4019	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3107		4020
3108	=head1 THREADS AND COROUTINES	4021	=head2 THREADS AND COROUTINES
3109		4022
3110	=head2 THREADS	4023	=head3 THREADS
3111		4024
3112	Libev itself is completely threadsafe, but it uses no locking. This	4025	All libev functions are reentrant and thread-safe unless explicitly
		4026	documented otherwise, but libev implements no locking itself. This means
3113	means that you can use as many loops as you want in parallel, as long as	4027	that you can use as many loops as you want in parallel, as long as there
3114	only one thread ever calls into one libev function with the same loop	4028	are no concurrent calls into any libev function with the same loop
3115	parameter.	4029	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4030	of course): libev guarantees that different event loops share no data
		4031	structures that need any locking.
3116		4032
3117	Or put differently: calls with different loop parameters can be done in	4033	Or to put it differently: calls with different loop parameters can be done
3118	parallel from multiple threads, calls with the same loop parameter must be	4034	concurrently from multiple threads, calls with the same loop parameter
3119	done serially (but can be done from different threads, as long as only one	4035	must be done serially (but can be done from different threads, as long as
3120	thread ever is inside a call at any point in time, e.g. by using a mutex	4036	only one thread ever is inside a call at any point in time, e.g. by using
3121	per loop).	4037	a mutex per loop).
3122		4038
3123	If you want to know which design is best for your problem, then I cannot	4039	Specifically to support threads (and signal handlers), libev implements
		4040	so-called C<ev_async> watchers, which allow some limited form of
		4041	concurrency on the same event loop, namely waking it up "from the
		4042	outside".
		4043
		4044	If you want to know which design (one loop, locking, or multiple loops
		4045	without or something else still) is best for your problem, then I cannot
3124	help you but by giving some generic advice:	4046	help you, but here is some generic advice:
3125		4047
3126	=over 4	4048	=over 4
3127		4049
3128	=item * most applications have a main thread: use the default libev loop	4050	=item * most applications have a main thread: use the default libev loop
3129	in that thread, or create a seperate thread running only the default loop.	4051	in that thread, or create a separate thread running only the default loop.
3130		4052
3131	This helps integrating other libraries or software modules that use libev	4053	This helps integrating other libraries or software modules that use libev
3132	themselves and don't care/know about threading.	4054	themselves and don't care/know about threading.
3133		4055
3134	=item * one loop per thread is usually a good model.	4056	=item * one loop per thread is usually a good model.
3135		4057
3136	Doing this is almost never wrong, sometimes a better-performance model	4058	Doing this is almost never wrong, sometimes a better-performance model
3137	exists, but it is always a good start.	4059	exists, but it is always a good start.
3138		4060
3139	=item * other models exist, such as the leader/follower pattern, where one	4061	=item * other models exist, such as the leader/follower pattern, where one
3140	loop is handed through multiple threads in a kind of round-robbin fashion.	4062	loop is handed through multiple threads in a kind of round-robin fashion.
3141		4063
3142	Chosing a model is hard - look around, learn, know that usually you cna do	4064	Choosing a model is hard - look around, learn, know that usually you can do
3143	better than you currently do :-)	4065	better than you currently do :-)
3144		4066
3145	=item * often you need to talk to some other thread which blocks in the	4067	=item * often you need to talk to some other thread which blocks in the
		4068	event loop.
		4069
3146	event loop - C<ev_async> watchers can be used to wake them up from other	4070	C<ev_async> watchers can be used to wake them up from other threads safely
3147	threads safely (or from signal contexts...).	4071	(or from signal contexts...).
		4072
		4073	An example use would be to communicate signals or other events that only
		4074	work in the default loop by registering the signal watcher with the
		4075	default loop and triggering an C<ev_async> watcher from the default loop
		4076	watcher callback into the event loop interested in the signal.
3148		4077
3149	=back	4078	=back
3150		4079
		4080	=head4 THREAD LOCKING EXAMPLE
		4081
		4082	Here is a fictitious example of how to run an event loop in a different
		4083	thread than where callbacks are being invoked and watchers are
		4084	created/added/removed.
		4085
		4086	For a real-world example, see the C<EV::Loop::Async> perl module,
		4087	which uses exactly this technique (which is suited for many high-level
		4088	languages).
		4089
		4090	The example uses a pthread mutex to protect the loop data, a condition
		4091	variable to wait for callback invocations, an async watcher to notify the
		4092	event loop thread and an unspecified mechanism to wake up the main thread.
		4093
		4094	First, you need to associate some data with the event loop:
		4095
		4096	typedef struct {
		4097	mutex_t lock; /* global loop lock */
		4098	ev_async async_w;
		4099	thread_t tid;
		4100	cond_t invoke_cv;
		4101	} userdata;
		4102
		4103	void prepare_loop (EV_P)
		4104	{
		4105	// for simplicity, we use a static userdata struct.
		4106	static userdata u;
		4107
		4108	ev_async_init (&u->async_w, async_cb);
		4109	ev_async_start (EV_A_ &u->async_w);
		4110
		4111	pthread_mutex_init (&u->lock, 0);
		4112	pthread_cond_init (&u->invoke_cv, 0);
		4113
		4114	// now associate this with the loop
		4115	ev_set_userdata (EV_A_ u);
		4116	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4117	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4118
		4119	// then create the thread running ev_loop
		4120	pthread_create (&u->tid, 0, l_run, EV_A);
		4121	}
		4122
		4123	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4124	solely to wake up the event loop so it takes notice of any new watchers
		4125	that might have been added:
		4126
		4127	static void
		4128	async_cb (EV_P_ ev_async *w, int revents)
		4129	{
		4130	// just used for the side effects
		4131	}
		4132
		4133	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4134	protecting the loop data, respectively.
		4135
		4136	static void
		4137	l_release (EV_P)
		4138	{
		4139	userdata *u = ev_userdata (EV_A);
		4140	pthread_mutex_unlock (&u->lock);
		4141	}
		4142
		4143	static void
		4144	l_acquire (EV_P)
		4145	{
		4146	userdata *u = ev_userdata (EV_A);
		4147	pthread_mutex_lock (&u->lock);
		4148	}
		4149
		4150	The event loop thread first acquires the mutex, and then jumps straight
		4151	into C<ev_loop>:
		4152
		4153	void *
		4154	l_run (void *thr_arg)
		4155	{
		4156	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4157
		4158	l_acquire (EV_A);
		4159	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4160	ev_loop (EV_A_ 0);
		4161	l_release (EV_A);
		4162
		4163	return 0;
		4164	}
		4165
		4166	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4167	signal the main thread via some unspecified mechanism (signals? pipe
		4168	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4169	have been called (in a while loop because a) spurious wakeups are possible
		4170	and b) skipping inter-thread-communication when there are no pending
		4171	watchers is very beneficial):
		4172
		4173	static void
		4174	l_invoke (EV_P)
		4175	{
		4176	userdata *u = ev_userdata (EV_A);
		4177
		4178	while (ev_pending_count (EV_A))
		4179	{
		4180	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4181	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4182	}
		4183	}
		4184
		4185	Now, whenever the main thread gets told to invoke pending watchers, it
		4186	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4187	thread to continue:
		4188
		4189	static void
		4190	real_invoke_pending (EV_P)
		4191	{
		4192	userdata *u = ev_userdata (EV_A);
		4193
		4194	pthread_mutex_lock (&u->lock);
		4195	ev_invoke_pending (EV_A);
		4196	pthread_cond_signal (&u->invoke_cv);
		4197	pthread_mutex_unlock (&u->lock);
		4198	}
		4199
		4200	Whenever you want to start/stop a watcher or do other modifications to an
		4201	event loop, you will now have to lock:
		4202
		4203	ev_timer timeout_watcher;
		4204	userdata *u = ev_userdata (EV_A);
		4205
		4206	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4207
		4208	pthread_mutex_lock (&u->lock);
		4209	ev_timer_start (EV_A_ &timeout_watcher);
		4210	ev_async_send (EV_A_ &u->async_w);
		4211	pthread_mutex_unlock (&u->lock);
		4212
		4213	Note that sending the C<ev_async> watcher is required because otherwise
		4214	an event loop currently blocking in the kernel will have no knowledge
		4215	about the newly added timer. By waking up the loop it will pick up any new
		4216	watchers in the next event loop iteration.
		4217
3151	=head2 COROUTINES	4218	=head3 COROUTINES
3152		4219
3153	Libev is much more accomodating to coroutines ("cooperative threads"):	4220	Libev is very accommodating to coroutines ("cooperative threads"):
3154	libev fully supports nesting calls to it's functions from different	4221	libev fully supports nesting calls to its functions from different
3155	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4222	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3156	different coroutines and switch freely between both coroutines running the	4223	different coroutines, and switch freely between both coroutines running
3157	loop, as long as you don't confuse yourself). The only exception is that	4224	the loop, as long as you don't confuse yourself). The only exception is
3158	you must not do this from C<ev_periodic> reschedule callbacks.	4225	that you must not do this from C<ev_periodic> reschedule callbacks.
3159		4226
3160	Care has been invested into making sure that libev does not keep local	4227	Care has been taken to ensure that libev does not keep local state inside
3161	state inside C<ev_loop>, and other calls do not usually allow coroutine	4228	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3162	switches.	4229	they do not call any callbacks.
3163		4230
		4231	=head2 COMPILER WARNINGS
3164		4232
3165	=head1 COMPLEXITIES	4233	Depending on your compiler and compiler settings, you might get no or a
		4234	lot of warnings when compiling libev code. Some people are apparently
		4235	scared by this.
3166		4236
3167	In this section the complexities of (many of) the algorithms used inside	4237	However, these are unavoidable for many reasons. For one, each compiler
3168	libev will be explained. For complexity discussions about backends see the	4238	has different warnings, and each user has different tastes regarding
3169	documentation for C<ev_default_init>.	4239	warning options. "Warn-free" code therefore cannot be a goal except when
		4240	targeting a specific compiler and compiler-version.
3170		4241
3171	All of the following are about amortised time: If an array needs to be	4242	Another reason is that some compiler warnings require elaborate
3172	extended, libev needs to realloc and move the whole array, but this	4243	workarounds, or other changes to the code that make it less clear and less
3173	happens asymptotically never with higher number of elements, so O(1) might	4244	maintainable.
3174	mean it might do a lengthy realloc operation in rare cases, but on average
3175	it is much faster and asymptotically approaches constant time.
3176		4245
3177	=over 4	4246	And of course, some compiler warnings are just plain stupid, or simply
		4247	wrong (because they don't actually warn about the condition their message
		4248	seems to warn about). For example, certain older gcc versions had some
		4249	warnings that resulted an extreme number of false positives. These have
		4250	been fixed, but some people still insist on making code warn-free with
		4251	such buggy versions.
3178		4252
3179	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4253	While libev is written to generate as few warnings as possible,
		4254	"warn-free" code is not a goal, and it is recommended not to build libev
		4255	with any compiler warnings enabled unless you are prepared to cope with
		4256	them (e.g. by ignoring them). Remember that warnings are just that:
		4257	warnings, not errors, or proof of bugs.
3180		4258
3181	This means that, when you have a watcher that triggers in one hour and
3182	there are 100 watchers that would trigger before that then inserting will
3183	have to skip roughly seven (C<ld 100>) of these watchers.
3184		4259
3185	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4260	=head2 VALGRIND
3186		4261
3187	That means that changing a timer costs less than removing/adding them	4262	Valgrind has a special section here because it is a popular tool that is
3188	as only the relative motion in the event queue has to be paid for.	4263	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3189		4264
3190	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4265	If you think you found a bug (memory leak, uninitialised data access etc.)
		4266	in libev, then check twice: If valgrind reports something like:
3191		4267
3192	These just add the watcher into an array or at the head of a list.	4268	==2274== definitely lost: 0 bytes in 0 blocks.
		4269	==2274== possibly lost: 0 bytes in 0 blocks.
		4270	==2274== still reachable: 256 bytes in 1 blocks.
3193		4271
3194	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4272	Then there is no memory leak, just as memory accounted to global variables
		4273	is not a memleak - the memory is still being referenced, and didn't leak.
3195		4274
3196	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4275	Similarly, under some circumstances, valgrind might report kernel bugs
		4276	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4277	although an acceptable workaround has been found here), or it might be
		4278	confused.
3197		4279
3198	These watchers are stored in lists then need to be walked to find the	4280	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3199	correct watcher to remove. The lists are usually short (you don't usually	4281	make it into some kind of religion.
3200	have many watchers waiting for the same fd or signal).
3201		4282
3202	=item Finding the next timer in each loop iteration: O(1)	4283	If you are unsure about something, feel free to contact the mailing list
		4284	with the full valgrind report and an explanation on why you think this
		4285	is a bug in libev (best check the archives, too :). However, don't be
		4286	annoyed when you get a brisk "this is no bug" answer and take the chance
		4287	of learning how to interpret valgrind properly.
3203		4288
3204	By virtue of using a binary or 4-heap, the next timer is always found at a	4289	If you need, for some reason, empty reports from valgrind for your project
3205	fixed position in the storage array.	4290	I suggest using suppression lists.
3206		4291
3207	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3208		4292
3209	A change means an I/O watcher gets started or stopped, which requires	4293	=head1 PORTABILITY NOTES
3210	libev to recalculate its status (and possibly tell the kernel, depending
3211	on backend and wether C<ev_io_set> was used).
3212		4294
3213	=item Activating one watcher (putting it into the pending state): O(1)	4295	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3214
3215	=item Priority handling: O(number_of_priorities)
3216
3217	Priorities are implemented by allocating some space for each
3218	priority. When doing priority-based operations, libev usually has to
3219	linearly search all the priorities, but starting/stopping and activating
3220	watchers becomes O(1) w.r.t. priority handling.
3221
3222	=item Sending an ev_async: O(1)
3223
3224	=item Processing ev_async_send: O(number_of_async_watchers)
3225
3226	=item Processing signals: O(max_signal_number)
3227
3228	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3229	calls in the current loop iteration. Checking for async and signal events
3230	involves iterating over all running async watchers or all signal numbers.
3231
3232	=back
3233
3234
3235	=head1 Win32 platform limitations and workarounds
3236		4296
3237	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4297	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3238	requires, and its I/O model is fundamentally incompatible with the POSIX	4298	requires, and its I/O model is fundamentally incompatible with the POSIX
3239	model. Libev still offers limited functionality on this platform in	4299	model. Libev still offers limited functionality on this platform in
3240	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4300	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3247	way (note also that glib is the slowest event library known to man).	4307	way (note also that glib is the slowest event library known to man).
3248		4308
3249	There is no supported compilation method available on windows except	4309	There is no supported compilation method available on windows except
3250	embedding it into other applications.	4310	embedding it into other applications.
3251		4311
		4312	Sensible signal handling is officially unsupported by Microsoft - libev
		4313	tries its best, but under most conditions, signals will simply not work.
		4314
		4315	Not a libev limitation but worth mentioning: windows apparently doesn't
		4316	accept large writes: instead of resulting in a partial write, windows will
		4317	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4318	so make sure you only write small amounts into your sockets (less than a
		4319	megabyte seems safe, but this apparently depends on the amount of memory
		4320	available).
		4321
3252	Due to the many, low, and arbitrary limits on the win32 platform and	4322	Due to the many, low, and arbitrary limits on the win32 platform and
3253	the abysmal performance of winsockets, using a large number of sockets	4323	the abysmal performance of winsockets, using a large number of sockets
3254	is not recommended (and not reasonable). If your program needs to use	4324	is not recommended (and not reasonable). If your program needs to use
3255	more than a hundred or so sockets, then likely it needs to use a totally	4325	more than a hundred or so sockets, then likely it needs to use a totally
3256	different implementation for windows, as libev offers the POSIX readyness	4326	different implementation for windows, as libev offers the POSIX readiness
3257	notification model, which cannot be implemented efficiently on windows	4327	notification model, which cannot be implemented efficiently on windows
3258	(microsoft monopoly games).	4328	(due to Microsoft monopoly games).
		4329
		4330	A typical way to use libev under windows is to embed it (see the embedding
		4331	section for details) and use the following F<evwrap.h> header file instead
		4332	of F<ev.h>:
		4333
		4334	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4335	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4336
		4337	#include "ev.h"
		4338
		4339	And compile the following F<evwrap.c> file into your project (make sure
		4340	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4341
		4342	#include "evwrap.h"
		4343	#include "ev.c"
3259		4344
3260	=over 4	4345	=over 4
3261		4346
3262	=item The winsocket select function	4347	=item The winsocket select function
3263		4348
3264	The winsocket C<select> function doesn't follow POSIX in that it requires	4349	The winsocket C<select> function doesn't follow POSIX in that it
3265	socket I<handles> and not socket I<file descriptors>. This makes select	4350	requires socket I<handles> and not socket I<file descriptors> (it is
3266	very inefficient, and also requires a mapping from file descriptors	4351	also extremely buggy). This makes select very inefficient, and also
3267	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4352	requires a mapping from file descriptors to socket handles (the Microsoft
3268	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4353	C runtime provides the function C<_open_osfhandle> for this). See the
3269	symbols for more info.	4354	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4355	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3270		4356
3271	The configuration for a "naked" win32 using the microsoft runtime	4357	The configuration for a "naked" win32 using the Microsoft runtime
3272	libraries and raw winsocket select is:	4358	libraries and raw winsocket select is:
3273		4359
3274	#define EV_USE_SELECT 1	4360	#define EV_USE_SELECT 1
3275	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4361	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3276		4362
3277	Note that winsockets handling of fd sets is O(n), so you can easily get a	4363	Note that winsockets handling of fd sets is O(n), so you can easily get a
3278	complexity in the O(n²) range when using win32.	4364	complexity in the O(n²) range when using win32.
3279		4365
3280	=item Limited number of file descriptors	4366	=item Limited number of file descriptors
3281		4367
3282	Windows has numerous arbitrary (and low) limits on things.	4368	Windows has numerous arbitrary (and low) limits on things.
3283		4369
3284	Early versions of winsocket's select only supported waiting for a maximum	4370	Early versions of winsocket's select only supported waiting for a maximum
3285	of C<64> handles (probably owning to the fact that all windows kernels	4371	of C<64> handles (probably owning to the fact that all windows kernels
3286	can only wait for C<64> things at the same time internally; microsoft	4372	can only wait for C<64> things at the same time internally; Microsoft
3287	recommends spawning a chain of threads and wait for 63 handles and the	4373	recommends spawning a chain of threads and wait for 63 handles and the
3288	previous thread in each. Great).	4374	previous thread in each. Sounds great!).
3289		4375
3290	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4376	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3291	to some high number (e.g. C<2048>) before compiling the winsocket select	4377	to some high number (e.g. C<2048>) before compiling the winsocket select
3292	call (which might be in libev or elsewhere, for example, perl does its own	4378	call (which might be in libev or elsewhere, for example, perl and many
3293	select emulation on windows).	4379	other interpreters do their own select emulation on windows).
3294		4380
3295	Another limit is the number of file descriptors in the microsoft runtime	4381	Another limit is the number of file descriptors in the Microsoft runtime
3296	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4382	libraries, which by default is C<64> (there must be a hidden I<64>
3297	or something like this inside microsoft). You can increase this by calling	4383	fetish or something like this inside Microsoft). You can increase this
3298	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4384	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3299	arbitrary limit), but is broken in many versions of the microsoft runtime	4385	(another arbitrary limit), but is broken in many versions of the Microsoft
3300	libraries.
3301
3302	This might get you to about C<512> or C<2048> sockets (depending on	4386	runtime libraries. This might get you to about C<512> or C<2048> sockets
3303	windows version and/or the phase of the moon). To get more, you need to	4387	(depending on windows version and/or the phase of the moon). To get more,
3304	wrap all I/O functions and provide your own fd management, but the cost of	4388	you need to wrap all I/O functions and provide your own fd management, but
3305	calling select (O(n²)) will likely make this unworkable.	4389	the cost of calling select (O(n²)) will likely make this unworkable.
3306		4390
3307	=back	4391	=back
3308		4392
3309
3310	=head1 PORTABILITY REQUIREMENTS	4393	=head2 PORTABILITY REQUIREMENTS
3311		4394
3312	In addition to a working ISO-C implementation, libev relies on a few	4395	In addition to a working ISO-C implementation and of course the
3313	additional extensions:	4396	backend-specific APIs, libev relies on a few additional extensions:
3314		4397
3315	=over 4	4398	=over 4
3316		4399
		4400	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4401	calling conventions regardless of C<ev_watcher_type *>.
		4402
		4403	Libev assumes not only that all watcher pointers have the same internal
		4404	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4405	assumes that the same (machine) code can be used to call any watcher
		4406	callback: The watcher callbacks have different type signatures, but libev
		4407	calls them using an C<ev_watcher *> internally.
		4408
3317	=item C<sig_atomic_t volatile> must be thread-atomic as well	4409	=item C<sig_atomic_t volatile> must be thread-atomic as well
3318		4410
3319	The type C<sig_atomic_t volatile> (or whatever is defined as	4411	The type C<sig_atomic_t volatile> (or whatever is defined as
3320	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4412	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3321	threads. This is not part of the specification for C<sig_atomic_t>, but is	4413	threads. This is not part of the specification for C<sig_atomic_t>, but is
3322	believed to be sufficiently portable.	4414	believed to be sufficiently portable.
3323		4415
3324	=item C<sigprocmask> must work in a threaded environment	4416	=item C<sigprocmask> must work in a threaded environment
3325		4417
…		…
3334	except the initial one, and run the default loop in the initial thread as	4426	except the initial one, and run the default loop in the initial thread as
3335	well.	4427	well.
3336		4428
3337	=item C<long> must be large enough for common memory allocation sizes	4429	=item C<long> must be large enough for common memory allocation sizes
3338		4430
3339	To improve portability and simplify using libev, libev uses C<long>	4431	To improve portability and simplify its API, libev uses C<long> internally
3340	internally instead of C<size_t> when allocating its data structures. On	4432	instead of C<size_t> when allocating its data structures. On non-POSIX
3341	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4433	systems (Microsoft...) this might be unexpectedly low, but is still at
3342	is still at least 31 bits everywhere, which is enough for hundreds of	4434	least 31 bits everywhere, which is enough for hundreds of millions of
3343	millions of watchers.	4435	watchers.
3344		4436
3345	=item C<double> must hold a time value in seconds with enough accuracy	4437	=item C<double> must hold a time value in seconds with enough accuracy
3346		4438
3347	The type C<double> is used to represent timestamps. It is required to	4439	The type C<double> is used to represent timestamps. It is required to
3348	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4440	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3349	enough for at least into the year 4000. This requirement is fulfilled by	4441	enough for at least into the year 4000. This requirement is fulfilled by
3350	implementations implementing IEEE 754 (basically all existing ones).	4442	implementations implementing IEEE 754, which is basically all existing
		4443	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4444	2200.
3351		4445
3352	=back	4446	=back
3353		4447
3354	If you know of other additional requirements drop me a note.	4448	If you know of other additional requirements drop me a note.
3355		4449
3356		4450
		4451	=head1 ALGORITHMIC COMPLEXITIES
		4452
		4453	In this section the complexities of (many of) the algorithms used inside
		4454	libev will be documented. For complexity discussions about backends see
		4455	the documentation for C<ev_default_init>.
		4456
		4457	All of the following are about amortised time: If an array needs to be
		4458	extended, libev needs to realloc and move the whole array, but this
		4459	happens asymptotically rarer with higher number of elements, so O(1) might
		4460	mean that libev does a lengthy realloc operation in rare cases, but on
		4461	average it is much faster and asymptotically approaches constant time.
		4462
		4463	=over 4
		4464
		4465	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4466
		4467	This means that, when you have a watcher that triggers in one hour and
		4468	there are 100 watchers that would trigger before that, then inserting will
		4469	have to skip roughly seven (C<ld 100>) of these watchers.
		4470
		4471	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4472
		4473	That means that changing a timer costs less than removing/adding them,
		4474	as only the relative motion in the event queue has to be paid for.
		4475
		4476	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4477
		4478	These just add the watcher into an array or at the head of a list.
		4479
		4480	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4481
		4482	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4483
		4484	These watchers are stored in lists, so they need to be walked to find the
		4485	correct watcher to remove. The lists are usually short (you don't usually
		4486	have many watchers waiting for the same fd or signal: one is typical, two
		4487	is rare).
		4488
		4489	=item Finding the next timer in each loop iteration: O(1)
		4490
		4491	By virtue of using a binary or 4-heap, the next timer is always found at a
		4492	fixed position in the storage array.
		4493
		4494	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4495
		4496	A change means an I/O watcher gets started or stopped, which requires
		4497	libev to recalculate its status (and possibly tell the kernel, depending
		4498	on backend and whether C<ev_io_set> was used).
		4499
		4500	=item Activating one watcher (putting it into the pending state): O(1)
		4501
		4502	=item Priority handling: O(number_of_priorities)
		4503
		4504	Priorities are implemented by allocating some space for each
		4505	priority. When doing priority-based operations, libev usually has to
		4506	linearly search all the priorities, but starting/stopping and activating
		4507	watchers becomes O(1) with respect to priority handling.
		4508
		4509	=item Sending an ev_async: O(1)
		4510
		4511	=item Processing ev_async_send: O(number_of_async_watchers)
		4512
		4513	=item Processing signals: O(max_signal_number)
		4514
		4515	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4516	calls in the current loop iteration. Checking for async and signal events
		4517	involves iterating over all running async watchers or all signal numbers.
		4518
		4519	=back
		4520
		4521
		4522	=head1 GLOSSARY
		4523
		4524	=over 4
		4525
		4526	=item active
		4527
		4528	A watcher is active as long as it has been started (has been attached to
		4529	an event loop) but not yet stopped (disassociated from the event loop).
		4530
		4531	=item application
		4532
		4533	In this document, an application is whatever is using libev.
		4534
		4535	=item callback
		4536
		4537	The address of a function that is called when some event has been
		4538	detected. Callbacks are being passed the event loop, the watcher that
		4539	received the event, and the actual event bitset.
		4540
		4541	=item callback invocation
		4542
		4543	The act of calling the callback associated with a watcher.
		4544
		4545	=item event
		4546
		4547	A change of state of some external event, such as data now being available
		4548	for reading on a file descriptor, time having passed or simply not having
		4549	any other events happening anymore.
		4550
		4551	In libev, events are represented as single bits (such as C<EV_READ> or
		4552	C<EV_TIMEOUT>).
		4553
		4554	=item event library
		4555
		4556	A software package implementing an event model and loop.
		4557
		4558	=item event loop
		4559
		4560	An entity that handles and processes external events and converts them
		4561	into callback invocations.
		4562
		4563	=item event model
		4564
		4565	The model used to describe how an event loop handles and processes
		4566	watchers and events.
		4567
		4568	=item pending
		4569
		4570	A watcher is pending as soon as the corresponding event has been detected,
		4571	and stops being pending as soon as the watcher will be invoked or its
		4572	pending status is explicitly cleared by the application.
		4573
		4574	A watcher can be pending, but not active. Stopping a watcher also clears
		4575	its pending status.
		4576
		4577	=item real time
		4578
		4579	The physical time that is observed. It is apparently strictly monotonic :)
		4580
		4581	=item wall-clock time
		4582
		4583	The time and date as shown on clocks. Unlike real time, it can actually
		4584	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4585	clock.
		4586
		4587	=item watcher
		4588
		4589	A data structure that describes interest in certain events. Watchers need
		4590	to be started (attached to an event loop) before they can receive events.
		4591
		4592	=item watcher invocation
		4593
		4594	The act of calling the callback associated with a watcher.
		4595
		4596	=back
		4597
3357	=head1 AUTHOR	4598	=head1 AUTHOR
3358		4599
3359	Marc Lehmann <libev@schmorp.de>.	4600	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3360		4601

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