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Revision 1.263 by root, Mon Jul 27 01:10:17 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://cvs.schmorp.de/libev/ev.html>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
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
…		…
103	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
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<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_NOSIGNALFD>
		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)
353		415
354	For few fds, this backend is a bit little slower than poll and select,	416	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	417	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),	418	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	419	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	420
359	cases and requiring a syscall per fd change, no fork support and bad	421	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	422	of the more advanced event mechanisms: mere annoyances include silently
		423	dropping file descriptors, requiring a system call per change per file
		424	descriptor (and unnecessary guessing of parameters), problems with dup and
		425	so on. The biggest issue is fork races, however - if a program forks then
		426	I<both> parent and child process have to recreate the epoll set, which can
		427	take considerable time (one syscall per file descriptor) and is of course
		428	hard to detect.
		429
		430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		431	of course I<doesn't>, and epoll just loves to report events for totally
		432	I<different> file descriptors (even already closed ones, so one cannot
		433	even remove them from the set) than registered in the set (especially
		434	on SMP systems). Libev tries to counter these spurious notifications by
		435	employing an additional generation counter and comparing that against the
		436	events to filter out spurious ones, recreating the set when required.
361		437
362	While stopping, setting and starting an I/O watcher in the same iteration	438	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	439	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	440	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	441	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	442	file descriptors might not work very well if you register events for both
367		443	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		444
372	Best performance from this backend is achieved by not unregistering all	445	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.	446	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	447	i.e. keep at least one watcher active per fd at all times. Stopping and
		448	starting a watcher (without re-setting it) also usually doesn't cause
		449	extra overhead. A fork can both result in spurious notifications as well
		450	as in libev having to destroy and recreate the epoll object, which can
		451	take considerable time and thus should be avoided.
375		452
		453	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		454	faster than epoll for maybe up to a hundred file descriptors, depending on
		455	the usage. So sad.
		456
376	While nominally embeddeble in other event loops, this feature is broken in	457	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	458	all kernel versions tested so far.
		459
		460	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		461	C<EVBACKEND_POLL>.
378		462
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	463	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		464
381	Kqueue deserves special mention, as at the time of this writing, it	465	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	466	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	467	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"	468	it's completely useless). Unlike epoll, however, whose brokenness
		469	is by design, these kqueue bugs can (and eventually will) be fixed
		470	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	471	"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)	472	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	473	system like NetBSD.
388		474
389	You still can embed kqueue into a normal poll or select backend and use it	475	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	476	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.	477	the target platform). See C<ev_embed> watchers for more info.
392		478
393	It scales in the same way as the epoll backend, but the interface to the	479	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	480	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	481	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	482	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	483	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	484	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		485	cases
399		486
400	This backend usually performs well under most conditions.	487	This backend usually performs well under most conditions.
401		488
402	While nominally embeddable in other event loops, this doesn't work	489	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	490	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	491	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	492	(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	493	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	494	also broken on OS X)) and, did I mention it, using it only for sockets.
		495
		496	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		497	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		498	C<NOTE_EOF>.
408		499
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	500	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		501
411	This is not implemented yet (and might never be, unless you send me an	502	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	503	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	507	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		508
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	509	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)).	510	it's really slow, but it still scales very well (O(active_fds)).
420		511
421	Please note that solaris event ports can deliver a lot of spurious	512	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	513	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	514	blocking when no data (or space) is available.
424		515
425	While this backend scales well, it requires one system call per active	516	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	517	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	518	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	519	might perform better.
429		520
430	On the positive side, ignoring the spurious readyness notifications, this	521	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	522	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	523	in all tests and is fully embeddable, which is a rare feat among the
		524	OS-specific backends (I vastly prefer correctness over speed hacks).
		525
		526	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		527	C<EVBACKEND_POLL>.
433		528
434	=item C<EVBACKEND_ALL>	529	=item C<EVBACKEND_ALL>
435		530
436	Try all backends (even potentially broken ones that wouldn't be tried	531	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	532	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		534
440	It is definitely not recommended to use this flag.	535	It is definitely not recommended to use this flag.
441		536
442	=back	537	=back
443		538
444	If one or more of these are ored into the flags value, then only these	539	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	540	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.	541	here). If none are specified, all backends in C<ev_recommended_backends
		542	()> will be tried.
447		543
448	The most typical usage is like this:	544	Example: This is the most typical usage.
449		545
450	if (!ev_default_loop (0))	546	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		548
453	Restrict libev to the select and poll backends, and do not allow	549	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	550	environment settings to be taken into account:
455		551
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	552	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		553
458	Use whatever libev has to offer, but make sure that kqueue is used if	554	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	555	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):	556	private event loop and only if you know the OS supports your types of
		557	fds):
461		558
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	559	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		560
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	561	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		562
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	563	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	564	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	569	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	570	default loop in the "main" or "initial" thread.
474		571
475	Example: Try to create a event loop that uses epoll and nothing else.	572	Example: Try to create a event loop that uses epoll and nothing else.
476		573
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	574	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	575	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	576	fatal ("no epoll found here, maybe it hides under your chair");
480		577
481	=item ev_default_destroy ()	578	=item ev_default_destroy ()
482		579
483	Destroys the default loop again (frees all memory and kernel state	580	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	581	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	582	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>	583	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	584	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	585	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	586	for example).
490		587
491	Note that certain global state, such as signal state, will not be freed by	588	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	589	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	590	as signal and child watchers) would need to be stopped manually.
494		591
495	In general it is not advisable to call this function except in the	592	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	593	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	594	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	595	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		620
524	=item ev_loop_fork (loop)	621	=item ev_loop_fork (loop)
525		622
526	Like C<ev_default_fork>, but acts on an event loop created by	623	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	624	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.	625	after fork that you want to re-use in the child, and how you do this is
		626	entirely your own problem.
529		627
530	=item int ev_is_default_loop (loop)	628	=item int ev_is_default_loop (loop)
531		629
532	Returns true when the given loop actually is the default loop, false otherwise.	630	Returns true when the given loop is, in fact, the default loop, and false
		631	otherwise.
533		632
534	=item unsigned int ev_loop_count (loop)	633	=item unsigned int ev_loop_count (loop)
535		634
536	Returns the count of loop iterations for the loop, which is identical to	635	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	636	the number of times libev did poll for new events. It starts at C<0> and
538	happily wraps around with enough iterations.	637	happily wraps around with enough iterations.
539		638
540	This value can sometimes be useful as a generation counter of sorts (it	639	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	640	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	641	C<ev_prepare> and C<ev_check> calls.
		642
		643	=item unsigned int ev_loop_depth (loop)
		644
		645	Returns the number of times C<ev_loop> was entered minus the number of
		646	times C<ev_loop> was exited, in other words, the recursion depth.
		647
		648	Outside C<ev_loop>, this number is zero. In a callback, this number is
		649	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		650	in which case it is higher.
		651
		652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		653	etc.), doesn't count as exit.
543		654
544	=item unsigned int ev_backend (loop)	655	=item unsigned int ev_backend (loop)
545		656
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	657	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	658	use.
…		…
552	received events and started processing them. This timestamp does not	663	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	664	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	665	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).	666	event occurring (or more correctly, libev finding out about it).
556		667
		668	=item ev_now_update (loop)
		669
		670	Establishes the current time by querying the kernel, updating the time
		671	returned by C<ev_now ()> in the progress. This is a costly operation and
		672	is usually done automatically within C<ev_loop ()>.
		673
		674	This function is rarely useful, but when some event callback runs for a
		675	very long time without entering the event loop, updating libev's idea of
		676	the current time is a good idea.
		677
		678	See also L<The special problem of time updates> in the C<ev_timer> section.
		679
		680	=item ev_suspend (loop)
		681
		682	=item ev_resume (loop)
		683
		684	These two functions suspend and resume a loop, for use when the loop is
		685	not used for a while and timeouts should not be processed.
		686
		687	A typical use case would be an interactive program such as a game: When
		688	the user presses C<^Z> to suspend the game and resumes it an hour later it
		689	would be best to handle timeouts as if no time had actually passed while
		690	the program was suspended. This can be achieved by calling C<ev_suspend>
		691	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		692	C<ev_resume> directly afterwards to resume timer processing.
		693
		694	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		695	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		696	will be rescheduled (that is, they will lose any events that would have
		697	occured while suspended).
		698
		699	After calling C<ev_suspend> you B<must not> call I<any> function on the
		700	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		701	without a previous call to C<ev_suspend>.
		702
		703	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		704	event loop time (see C<ev_now_update>).
		705
557	=item ev_loop (loop, int flags)	706	=item ev_loop (loop, int flags)
558		707
559	Finally, this is it, the event handler. This function usually is called	708	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	709	after you initialised all your watchers and you want to start handling
561	events.	710	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	712	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.	713	either no event watchers are active anymore or C<ev_unloop> was called.
565		714
566	Please note that an explicit C<ev_unloop> is usually better than	715	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	716	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	717	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	718	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.	719	of relying on its watchers stopping correctly, that is truly a thing of
		720	beauty.
571		721
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	722	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	723	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.	724	process in case there are no events and will return after one iteration of
		725	the loop.
575		726
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	727	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	728	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	729	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	730	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	731	user-registered callback will be called), and will return after one
		732	iteration of the loop.
		733
		734	This is useful if you are waiting for some external event in conjunction
		735	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	736	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.	737	usually a better approach for this kind of thing.
583		738
584	Here are the gory details of what C<ev_loop> does:	739	Here are the gory details of what C<ev_loop> does:
585		740
586	- Before the first iteration, call any pending watchers.	741	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	742	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	743	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	744	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	745	- If we have been forked, detach and recreate the kernel state
		746	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	747	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	748	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	749	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	750	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	751	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	752	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	753	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	754	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	755	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	756	- Queue all expired timers.
601	- Queue all outstanding periodics.	757	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	758	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	759	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	760	- 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	761	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	762	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	763	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	768	anymore.
613		769
614	... queue jobs here, make sure they register event watchers as long	770	... 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..)	771	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	772	ev_loop (my_loop, 0);
617	... jobs done. yeah!	773	... jobs done or somebody called unloop. yeah!
618		774
619	=item ev_unloop (loop, how)	775	=item ev_unloop (loop, how)
620		776
621	Can be used to make a call to C<ev_loop> return early (but only after it	777	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	778	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	779	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.	780	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		781
626	This "unloop state" will be cleared when entering C<ev_loop> again.	782	This "unloop state" will be cleared when entering C<ev_loop> again.
627		783
		784	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		785
628	=item ev_ref (loop)	786	=item ev_ref (loop)
629		787
630	=item ev_unref (loop)	788	=item ev_unref (loop)
631		789
632	Ref/unref can be used to add or remove a reference count on the event	790	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	791	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	792	count is nonzero, C<ev_loop> will not return on its own.
		793
635	a watcher you never unregister that should not keep C<ev_loop> from	794	If you have a watcher you never unregister that should not keep C<ev_loop>
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	795	from returning, call ev_unref() after starting, and ev_ref() before
		796	stopping it.
		797
637	example, libev itself uses this for its internal signal pipe: It is not	798	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	799	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	800	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	801	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>	802	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,	803	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	804	before, respectively. Note also that libev might stop watchers itself
		805	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		806	in the callback).
644		807
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	808	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	809	running when nothing else is active.
647		810
648	struct ev_signal exitsig;	811	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	812	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	813	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	814	evf_unref (loop);
652		815
653	Example: For some weird reason, unregister the above signal handler again.	816	Example: For some weird reason, unregister the above signal handler again.
654		817
655	ev_ref (loop);	818	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	819	ev_signal_stop (loop, &exitsig);
657		820
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	821	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		822
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	823	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		824
662	These advanced functions influence the time that libev will spend waiting	825	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	826	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.	827	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		828	latency.
665		829
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	830	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	831	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	832	to increase efficiency of loop iterations (or to increase power-saving
		833	opportunities).
669		834
670	The background is that sometimes your program runs just fast enough to	835	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	836	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	837	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	838	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	839	overhead for the actual polling but can deliver many events at once.
675		840
676	By setting a higher I<io collect interval> you allow libev to spend more	841	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,	842	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	843	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	844	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.	845	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		846	sleep time ensures that libev will not poll for I/O events more often then
		847	once per this interval, on average.
681		848
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	849	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	850	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	851	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	852	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	853	value will not introduce any overhead in libev.
687		854
688	Many (busy) programs can usually benefit by setting the io collect	855	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	856	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	857	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>,	858	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.	859	as this approaches the timing granularity of most systems. Note that if
		860	you do transactions with the outside world and you can't increase the
		861	parallelity, then this setting will limit your transaction rate (if you
		862	need to poll once per transaction and the I/O collect interval is 0.01,
		863	then you can't do more than 100 transations per second).
		864
		865	Setting the I<timeout collect interval> can improve the opportunity for
		866	saving power, as the program will "bundle" timer callback invocations that
		867	are "near" in time together, by delaying some, thus reducing the number of
		868	times the process sleeps and wakes up again. Another useful technique to
		869	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		870	they fire on, say, one-second boundaries only.
		871
		872	Example: we only need 0.1s timeout granularity, and we wish not to poll
		873	more often than 100 times per second:
		874
		875	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		877
		878	=item ev_invoke_pending (loop)
		879
		880	This call will simply invoke all pending watchers while resetting their
		881	pending state. Normally, C<ev_loop> does this automatically when required,
		882	but when overriding the invoke callback this call comes handy.
		883
		884	=item int ev_pending_count (loop)
		885
		886	Returns the number of pending watchers - zero indicates that no watchers
		887	are pending.
		888
		889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		890
		891	This overrides the invoke pending functionality of the loop: Instead of
		892	invoking all pending watchers when there are any, C<ev_loop> will call
		893	this callback instead. This is useful, for example, when you want to
		894	invoke the actual watchers inside another context (another thread etc.).
		895
		896	If you want to reset the callback, use C<ev_invoke_pending> as new
		897	callback.
		898
		899	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		900
		901	Sometimes you want to share the same loop between multiple threads. This
		902	can be done relatively simply by putting mutex_lock/unlock calls around
		903	each call to a libev function.
		904
		905	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		906	wait for it to return. One way around this is to wake up the loop via
		907	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		908	and I<acquire> callbacks on the loop.
		909
		910	When set, then C<release> will be called just before the thread is
		911	suspended waiting for new events, and C<acquire> is called just
		912	afterwards.
		913
		914	Ideally, C<release> will just call your mutex_unlock function, and
		915	C<acquire> will just call the mutex_lock function again.
		916
		917	While event loop modifications are allowed between invocations of
		918	C<release> and C<acquire> (that's their only purpose after all), no
		919	modifications done will affect the event loop, i.e. adding watchers will
		920	have no effect on the set of file descriptors being watched, or the time
		921	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		922	to take note of any changes you made.
		923
		924	In theory, threads executing C<ev_loop> will be async-cancel safe between
		925	invocations of C<release> and C<acquire>.
		926
		927	See also the locking example in the C<THREADS> section later in this
		928	document.
		929
		930	=item ev_set_userdata (loop, void *data)
		931
		932	=item ev_userdata (loop)
		933
		934	Set and retrieve a single C<void *> associated with a loop. When
		935	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		936	C<0.>
		937
		938	These two functions can be used to associate arbitrary data with a loop,
		939	and are intended solely for the C<invoke_pending_cb>, C<release> and
		940	C<acquire> callbacks described above, but of course can be (ab-)used for
		941	any other purpose as well.
		942
		943	=item ev_loop_verify (loop)
		944
		945	This function only does something when C<EV_VERIFY> support has been
		946	compiled in, which is the default for non-minimal builds. It tries to go
		947	through all internal structures and checks them for validity. If anything
		948	is found to be inconsistent, it will print an error message to standard
		949	error and call C<abort ()>.
		950
		951	This can be used to catch bugs inside libev itself: under normal
		952	circumstances, this function will never abort as of course libev keeps its
		953	data structures consistent.
693		954
694	=back	955	=back
695		956
696		957
697	=head1 ANATOMY OF A WATCHER	958	=head1 ANATOMY OF A WATCHER
		959
		960	In the following description, uppercase C<TYPE> in names stands for the
		961	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		962	watchers and C<ev_io_start> for I/O watchers.
698		963
699	A watcher is a structure that you create and register to record your	964	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	965	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:	966	become readable, you would create an C<ev_io> watcher for that:
702		967
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	968	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	969	{
705	ev_io_stop (w);	970	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	971	ev_unloop (loop, EVUNLOOP_ALL);
707	}	972	}
708		973
709	struct ev_loop *loop = ev_default_loop (0);	974	struct ev_loop *loop = ev_default_loop (0);
		975
710	struct ev_io stdin_watcher;	976	ev_io stdin_watcher;
		977
711	ev_init (&stdin_watcher, my_cb);	978	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	980	ev_io_start (loop, &stdin_watcher);
		981
714	ev_loop (loop, 0);	982	ev_loop (loop, 0);
715		983
716	As you can see, you are responsible for allocating the memory for your	984	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,	985	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	986	stack).
		987
		988	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		989	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		990
720	Each watcher structure must be initialised by a call to C<ev_init	991	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	992	(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	993	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	994	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	995	is readable and/or writable).
725		996
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	997	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	998	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	999	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	1000	ev_TYPE_init (watcher *, callback, ...) >>.
730		1001
731	To make the watcher actually watch out for events, you have to start it	1002	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	1003	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	1004	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1005	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		1006
736	As long as your watcher is active (has been started but not stopped) you	1007	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	1008	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	1009	reinitialise it or call its C<ev_TYPE_set> macro.
739		1010
740	Each and every callback receives the event loop pointer as first, the	1011	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	1012	registered watcher structure as second, and a bitset of received events as
742	third argument.	1013	third argument.
743		1014
…		…
801		1072
802	=item C<EV_ASYNC>	1073	=item C<EV_ASYNC>
803		1074
804	The given async watcher has been asynchronously notified (see C<ev_async>).	1075	The given async watcher has been asynchronously notified (see C<ev_async>).
805		1076
		1077	=item C<EV_CUSTOM>
		1078
		1079	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1080	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1081
806	=item C<EV_ERROR>	1082	=item C<EV_ERROR>
807		1083
808	An unspecified error has occured, the watcher has been stopped. This might	1084	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	1085	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	1086	ran out of memory, a file descriptor was found to be closed or any other
		1087	problem. Libev considers these application bugs.
		1088
811	problem. You best act on it by reporting the problem and somehow coping	1089	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	1090	watcher being stopped. Note that well-written programs should not receive
		1091	an error ever, so when your watcher receives it, this usually indicates a
		1092	bug in your program.
813		1093
814	Libev will usually signal a few "dummy" events together with an error,	1094	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	1095	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	1096	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	1097	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	1098	programs, though, as the fd could already be closed and reused for another
		1099	thing, so beware.
819		1100
820	=back	1101	=back
821		1102
822	=head2 GENERIC WATCHER FUNCTIONS	1103	=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		1104
827	=over 4	1105	=over 4
828		1106
829	=item C<ev_init> (ev_TYPE *watcher, callback)	1107	=item C<ev_init> (ev_TYPE *watcher, callback)
830		1108
…		…
836	which rolls both calls into one.	1114	which rolls both calls into one.
837		1115
838	You can reinitialise a watcher at any time as long as it has been stopped	1116	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.	1117	(or never started) and there are no pending events outstanding.
840		1118
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1119	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	1120	int revents)>.
		1121
		1122	Example: Initialise an C<ev_io> watcher in two steps.
		1123
		1124	ev_io w;
		1125	ev_init (&w, my_cb);
		1126	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		1127
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		1129
846	This macro initialises the type-specific parts of a watcher. You need to	1130	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	1131	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	1134	difference to the C<ev_init> macro).
851		1135
852	Although some watcher types do not have type-specific arguments	1136	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.	1137	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		1138
		1139	See C<ev_init>, above, for an example.
		1140
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1141	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		1142
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1143	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	1144	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	1145	a watcher. The same limitations apply, of course.
		1146
		1147	Example: Initialise and set an C<ev_io> watcher in one step.
		1148
		1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		1150
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		1152
863	Starts (activates) the given watcher. Only active watchers will receive	1153	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1154	events. If the watcher is already active nothing will happen.
865		1155
		1156	Example: Start the C<ev_io> watcher that is being abused as example in this
		1157	whole section.
		1158
		1159	ev_io_start (EV_DEFAULT_UC, &w);
		1160
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		1162
868	Stops the given watcher again (if active) and clears the pending	1163	Stops the given watcher if active, and clears the pending status (whether
		1164	the watcher was active or not).
		1165
869	status. It is possible that stopped watchers are pending (for example,	1166	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1167	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	1168	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	1169	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.	1170	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1171
875	=item bool ev_is_active (ev_TYPE *watcher)	1172	=item bool ev_is_active (ev_TYPE *watcher)
876		1173
877	Returns a true value iff the watcher is active (i.e. it has been started	1174	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	1175	and not yet been stopped). As long as a watcher is active you must not modify
…		…
904	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1201	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
905	(default: C<-2>). Pending watchers with higher priority will be invoked	1202	(default: C<-2>). Pending watchers with higher priority will be invoked
906	before watchers with lower priority, but priority will not keep watchers	1203	before watchers with lower priority, but priority will not keep watchers
907	from being executed (except for C<ev_idle> watchers).	1204	from being executed (except for C<ev_idle> watchers).
908		1205
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	1206	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.	1207	you need to look at C<ev_idle> watchers, which provide this functionality.
916		1208
917	You I<must not> change the priority of a watcher as long as it is active or	1209	You I<must not> change the priority of a watcher as long as it is active or
918	pending.	1210	pending.
919		1211
		1212	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1213	fine, as long as you do not mind that the priority value you query might
		1214	or might not have been clamped to the valid range.
		1215
920	The default priority used by watchers when no priority has been set is	1216	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 :).	1217	always C<0>, which is supposed to not be too high and not be too low :).
922		1218
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1219	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	1220	priorities.
925	or might not have been adjusted to be within valid range.
926		1221
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1223
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1224	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	1225	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1226	can deal with that fact, as both are simply passed through to the
		1227	callback.
932		1228
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1229	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1230
935	If the watcher is pending, this function returns clears its pending status	1231	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	1232	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>.	1233	watcher isn't pending it does nothing and returns C<0>.
938		1234
		1235	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1236	callback to be invoked, which can be accomplished with this function.
		1237
939	=back	1238	=back
940		1239
941		1240
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1242
944	Each watcher has, by default, a member C<void *data> that you can change	1243	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	1244	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	1245	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	1246	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	1247	member, you can also "subclass" the watcher type and provide your own
949	data:	1248	data:
950		1249
951	struct my_io	1250	struct my_io
952	{	1251	{
953	struct ev_io io;	1252	ev_io io;
954	int otherfd;	1253	int otherfd;
955	void *somedata;	1254	void *somedata;
956	struct whatever *mostinteresting;	1255	struct whatever *mostinteresting;
957	}	1256	};
		1257
		1258	...
		1259	struct my_io w;
		1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1261
959	And since your callback will be called with a pointer to the watcher, you	1262	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1263	can cast it back to your own type:
961		1264
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1265	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1266	{
964	struct my_io *w = (struct my_io *)w_;	1267	struct my_io *w = (struct my_io *)w_;
965	...	1268	...
966	}	1269	}
967		1270
968	More interesting and less C-conformant ways of casting your callback type	1271	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1272	instead have been omitted.
970		1273
971	Another common scenario is having some data structure with multiple	1274	Another common scenario is to use some data structure with multiple
972	watchers:	1275	embedded watchers:
973		1276
974	struct my_biggy	1277	struct my_biggy
975	{	1278	{
976	int some_data;	1279	int some_data;
977	ev_timer t1;	1280	ev_timer t1;
978	ev_timer t2;	1281	ev_timer t2;
979	}	1282	}
980		1283
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1284	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1285	complicated: Either you store the address of your C<my_biggy> struct
		1286	in the C<data> member of the watcher (for woozies), or you need to use
		1287	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1288	programmers):
983		1289
984	#include <stddef.h>	1290	#include <stddef.h>
985		1291
986	static void	1292	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1293	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1294	{
989	struct my_biggy big = (struct my_biggy *	1295	struct my_biggy big = (struct my_biggy *)
990	(((char *)w) - offsetof (struct my_biggy, t1));	1296	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1297	}
992		1298
993	static void	1299	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1300	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1301	{
996	struct my_biggy big = (struct my_biggy *	1302	struct my_biggy big = (struct my_biggy *)
997	(((char *)w) - offsetof (struct my_biggy, t2));	1303	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1304	}
		1305
		1306	=head2 WATCHER PRIORITY MODELS
		1307
		1308	Many event loops support I<watcher priorities>, which are usually small
		1309	integers that influence the ordering of event callback invocation
		1310	between watchers in some way, all else being equal.
		1311
		1312	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1313	description for the more technical details such as the actual priority
		1314	range.
		1315
		1316	There are two common ways how these these priorities are being interpreted
		1317	by event loops:
		1318
		1319	In the more common lock-out model, higher priorities "lock out" invocation
		1320	of lower priority watchers, which means as long as higher priority
		1321	watchers receive events, lower priority watchers are not being invoked.
		1322
		1323	The less common only-for-ordering model uses priorities solely to order
		1324	callback invocation within a single event loop iteration: Higher priority
		1325	watchers are invoked before lower priority ones, but they all get invoked
		1326	before polling for new events.
		1327
		1328	Libev uses the second (only-for-ordering) model for all its watchers
		1329	except for idle watchers (which use the lock-out model).
		1330
		1331	The rationale behind this is that implementing the lock-out model for
		1332	watchers is not well supported by most kernel interfaces, and most event
		1333	libraries will just poll for the same events again and again as long as
		1334	their callbacks have not been executed, which is very inefficient in the
		1335	common case of one high-priority watcher locking out a mass of lower
		1336	priority ones.
		1337
		1338	Static (ordering) priorities are most useful when you have two or more
		1339	watchers handling the same resource: a typical usage example is having an
		1340	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1341	timeouts. Under load, data might be received while the program handles
		1342	other jobs, but since timers normally get invoked first, the timeout
		1343	handler will be executed before checking for data. In that case, giving
		1344	the timer a lower priority than the I/O watcher ensures that I/O will be
		1345	handled first even under adverse conditions (which is usually, but not
		1346	always, what you want).
		1347
		1348	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1349	will only be executed when no same or higher priority watchers have
		1350	received events, they can be used to implement the "lock-out" model when
		1351	required.
		1352
		1353	For example, to emulate how many other event libraries handle priorities,
		1354	you can associate an C<ev_idle> watcher to each such watcher, and in
		1355	the normal watcher callback, you just start the idle watcher. The real
		1356	processing is done in the idle watcher callback. This causes libev to
		1357	continously poll and process kernel event data for the watcher, but when
		1358	the lock-out case is known to be rare (which in turn is rare :), this is
		1359	workable.
		1360
		1361	Usually, however, the lock-out model implemented that way will perform
		1362	miserably under the type of load it was designed to handle. In that case,
		1363	it might be preferable to stop the real watcher before starting the
		1364	idle watcher, so the kernel will not have to process the event in case
		1365	the actual processing will be delayed for considerable time.
		1366
		1367	Here is an example of an I/O watcher that should run at a strictly lower
		1368	priority than the default, and which should only process data when no
		1369	other events are pending:
		1370
		1371	ev_idle idle; // actual processing watcher
		1372	ev_io io; // actual event watcher
		1373
		1374	static void
		1375	io_cb (EV_P_ ev_io *w, int revents)
		1376	{
		1377	// stop the I/O watcher, we received the event, but
		1378	// are not yet ready to handle it.
		1379	ev_io_stop (EV_A_ w);
		1380
		1381	// start the idle watcher to ahndle the actual event.
		1382	// it will not be executed as long as other watchers
		1383	// with the default priority are receiving events.
		1384	ev_idle_start (EV_A_ &idle);
		1385	}
		1386
		1387	static void
		1388	idle_cb (EV_P_ ev_idle *w, int revents)
		1389	{
		1390	// actual processing
		1391	read (STDIN_FILENO, ...);
		1392
		1393	// have to start the I/O watcher again, as
		1394	// we have handled the event
		1395	ev_io_start (EV_P_ &io);
		1396	}
		1397
		1398	// initialisation
		1399	ev_idle_init (&idle, idle_cb);
		1400	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1401	ev_io_start (EV_DEFAULT_ &io);
		1402
		1403	In the "real" world, it might also be beneficial to start a timer, so that
		1404	low-priority connections can not be locked out forever under load. This
		1405	enables your program to keep a lower latency for important connections
		1406	during short periods of high load, while not completely locking out less
		1407	important ones.
999		1408
1000		1409
1001	=head1 WATCHER TYPES	1410	=head1 WATCHER TYPES
1002		1411
1003	This section describes each watcher in detail, but will not repeat	1412	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	1436	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	1437	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	1438	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1439	required if you know what you are doing).
1031		1440
1032	If you must do this, then force the use of a known-to-be-good backend	1441	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	1442	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1443	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1444	descriptors for which non-blocking operation makes no sense (such as
		1445	files) - libev doesn't guarentee any specific behaviour in that case.
1035		1446
1036	Another thing you have to watch out for is that it is quite easy to	1447	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	1448	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	1449	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	1450	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	1451	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	1452	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	1453	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.	1454	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1455
1045	If you cannot run the fd in non-blocking mode (for example you should not	1456	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	1457	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	1458	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	1459	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1460	does this on its own, so its quite safe to use). Some people additionally
		1461	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1462	indefinitely.
		1463
		1464	But really, best use non-blocking mode.
1050		1465
1051	=head3 The special problem of disappearing file descriptors	1466	=head3 The special problem of disappearing file descriptors
1052		1467
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1468	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,	1469	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	1470	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	1471	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	1472	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	1473	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1474	fact, a different file descriptor.
1060		1475
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1506	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1507	C<EVBACKEND_POLL>.
1093		1508
1094	=head3 The special problem of SIGPIPE	1509	=head3 The special problem of SIGPIPE
1095		1510
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1511	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	1512	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	1513	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1514	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1515
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1516	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	1517	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).	1518	somewhere, as that would have given you a big clue).
1105		1519
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1525	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1526
1113	=item ev_io_set (ev_io *, int fd, int events)	1527	=item ev_io_set (ev_io *, int fd, int events)
1114		1528
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1529	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	1530	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.	1531	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1532
1119	=item int fd [read-only]	1533	=item int fd [read-only]
1120		1534
1121	The file descriptor being watched.	1535	The file descriptor being watched.
1122		1536
…		…
1130		1544
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1545	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	1546	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1547	attempt to read a whole line in the callback.
1134		1548
1135	static void	1549	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1550	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1551	{
1138	ev_io_stop (loop, w);	1552	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1553	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1554	}
1141		1555
1142	...	1556	...
1143	struct ev_loop *loop = ev_default_init (0);	1557	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1558	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1559	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1560	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1561	ev_loop (loop, 0);
1148		1562
1149		1563
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1564	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1565
1152	Timer watchers are simple relative timers that generate an event after a	1566	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1567	given time, and optionally repeating in regular intervals after that.
1154		1568
1155	The timers are based on real time, that is, if you register an event that	1569	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	1570	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	1571	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1573	monotonic clock option helps a lot here).
		1574
		1575	The callback is guaranteed to be invoked only I<after> its timeout has
		1576	passed (not I<at>, so on systems with very low-resolution clocks this
		1577	might introduce a small delay). If multiple timers become ready during the
		1578	same loop iteration then the ones with earlier time-out values are invoked
		1579	before ones of the same priority with later time-out values (but this is
		1580	no longer true when a callback calls C<ev_loop> recursively).
		1581
		1582	=head3 Be smart about timeouts
		1583
		1584	Many real-world problems involve some kind of timeout, usually for error
		1585	recovery. A typical example is an HTTP request - if the other side hangs,
		1586	you want to raise some error after a while.
		1587
		1588	What follows are some ways to handle this problem, from obvious and
		1589	inefficient to smart and efficient.
		1590
		1591	In the following, a 60 second activity timeout is assumed - a timeout that
		1592	gets reset to 60 seconds each time there is activity (e.g. each time some
		1593	data or other life sign was received).
		1594
		1595	=over 4
		1596
		1597	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1598
		1599	This is the most obvious, but not the most simple way: In the beginning,
		1600	start the watcher:
		1601
		1602	ev_timer_init (timer, callback, 60., 0.);
		1603	ev_timer_start (loop, timer);
		1604
		1605	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1606	and start it again:
		1607
		1608	ev_timer_stop (loop, timer);
		1609	ev_timer_set (timer, 60., 0.);
		1610	ev_timer_start (loop, timer);
		1611
		1612	This is relatively simple to implement, but means that each time there is
		1613	some activity, libev will first have to remove the timer from its internal
		1614	data structure and then add it again. Libev tries to be fast, but it's
		1615	still not a constant-time operation.
		1616
		1617	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1618
		1619	This is the easiest way, and involves using C<ev_timer_again> instead of
		1620	C<ev_timer_start>.
		1621
		1622	To implement this, configure an C<ev_timer> with a C<repeat> value
		1623	of C<60> and then call C<ev_timer_again> at start and each time you
		1624	successfully read or write some data. If you go into an idle state where
		1625	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1626	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1627
		1628	That means you can ignore both the C<ev_timer_start> function and the
		1629	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1630	member and C<ev_timer_again>.
		1631
		1632	At start:
		1633
		1634	ev_init (timer, callback);
		1635	timer->repeat = 60.;
		1636	ev_timer_again (loop, timer);
		1637
		1638	Each time there is some activity:
		1639
		1640	ev_timer_again (loop, timer);
		1641
		1642	It is even possible to change the time-out on the fly, regardless of
		1643	whether the watcher is active or not:
		1644
		1645	timer->repeat = 30.;
		1646	ev_timer_again (loop, timer);
		1647
		1648	This is slightly more efficient then stopping/starting the timer each time
		1649	you want to modify its timeout value, as libev does not have to completely
		1650	remove and re-insert the timer from/into its internal data structure.
		1651
		1652	It is, however, even simpler than the "obvious" way to do it.
		1653
		1654	=item 3. Let the timer time out, but then re-arm it as required.
		1655
		1656	This method is more tricky, but usually most efficient: Most timeouts are
		1657	relatively long compared to the intervals between other activity - in
		1658	our example, within 60 seconds, there are usually many I/O events with
		1659	associated activity resets.
		1660
		1661	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1662	but remember the time of last activity, and check for a real timeout only
		1663	within the callback:
		1664
		1665	ev_tstamp last_activity; // time of last activity
		1666
		1667	static void
		1668	callback (EV_P_ ev_timer *w, int revents)
		1669	{
		1670	ev_tstamp now = ev_now (EV_A);
		1671	ev_tstamp timeout = last_activity + 60.;
		1672
		1673	// if last_activity + 60. is older than now, we did time out
		1674	if (timeout < now)
		1675	{
		1676	// timeout occured, take action
		1677	}
		1678	else
		1679	{
		1680	// callback was invoked, but there was some activity, re-arm
		1681	// the watcher to fire in last_activity + 60, which is
		1682	// guaranteed to be in the future, so "again" is positive:
		1683	w->repeat = timeout - now;
		1684	ev_timer_again (EV_A_ w);
		1685	}
		1686	}
		1687
		1688	To summarise the callback: first calculate the real timeout (defined
		1689	as "60 seconds after the last activity"), then check if that time has
		1690	been reached, which means something I<did>, in fact, time out. Otherwise
		1691	the callback was invoked too early (C<timeout> is in the future), so
		1692	re-schedule the timer to fire at that future time, to see if maybe we have
		1693	a timeout then.
		1694
		1695	Note how C<ev_timer_again> is used, taking advantage of the
		1696	C<ev_timer_again> optimisation when the timer is already running.
		1697
		1698	This scheme causes more callback invocations (about one every 60 seconds
		1699	minus half the average time between activity), but virtually no calls to
		1700	libev to change the timeout.
		1701
		1702	To start the timer, simply initialise the watcher and set C<last_activity>
		1703	to the current time (meaning we just have some activity :), then call the
		1704	callback, which will "do the right thing" and start the timer:
		1705
		1706	ev_init (timer, callback);
		1707	last_activity = ev_now (loop);
		1708	callback (loop, timer, EV_TIMEOUT);
		1709
		1710	And when there is some activity, simply store the current time in
		1711	C<last_activity>, no libev calls at all:
		1712
		1713	last_actiivty = ev_now (loop);
		1714
		1715	This technique is slightly more complex, but in most cases where the
		1716	time-out is unlikely to be triggered, much more efficient.
		1717
		1718	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1719	callback :) - just change the timeout and invoke the callback, which will
		1720	fix things for you.
		1721
		1722	=item 4. Wee, just use a double-linked list for your timeouts.
		1723
		1724	If there is not one request, but many thousands (millions...), all
		1725	employing some kind of timeout with the same timeout value, then one can
		1726	do even better:
		1727
		1728	When starting the timeout, calculate the timeout value and put the timeout
		1729	at the I<end> of the list.
		1730
		1731	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1732	the list is expected to fire (for example, using the technique #3).
		1733
		1734	When there is some activity, remove the timer from the list, recalculate
		1735	the timeout, append it to the end of the list again, and make sure to
		1736	update the C<ev_timer> if it was taken from the beginning of the list.
		1737
		1738	This way, one can manage an unlimited number of timeouts in O(1) time for
		1739	starting, stopping and updating the timers, at the expense of a major
		1740	complication, and having to use a constant timeout. The constant timeout
		1741	ensures that the list stays sorted.
		1742
		1743	=back
		1744
		1745	So which method the best?
		1746
		1747	Method #2 is a simple no-brain-required solution that is adequate in most
		1748	situations. Method #3 requires a bit more thinking, but handles many cases
		1749	better, and isn't very complicated either. In most case, choosing either
		1750	one is fine, with #3 being better in typical situations.
		1751
		1752	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1753	rather complicated, but extremely efficient, something that really pays
		1754	off after the first million or so of active timers, i.e. it's usually
		1755	overkill :)
		1756
		1757	=head3 The special problem of time updates
		1758
		1759	Establishing the current time is a costly operation (it usually takes at
		1760	least two system calls): EV therefore updates its idea of the current
		1761	time only before and after C<ev_loop> collects new events, which causes a
		1762	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1763	lots of events in one iteration.
1160		1764
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1765	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	1766	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	1767	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	1768	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:	1769	timeout on the current time, use something like this to adjust for this:
1166		1770
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1772
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1773	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	1774	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1775	()>.
		1776
		1777	=head3 The special problems of suspended animation
		1778
		1779	When you leave the server world it is quite customary to hit machines that
		1780	can suspend/hibernate - what happens to the clocks during such a suspend?
		1781
		1782	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1783	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1784	to run until the system is suspended, but they will not advance while the
		1785	system is suspended. That means, on resume, it will be as if the program
		1786	was frozen for a few seconds, but the suspend time will not be counted
		1787	towards C<ev_timer> when a monotonic clock source is used. The real time
		1788	clock advanced as expected, but if it is used as sole clocksource, then a
		1789	long suspend would be detected as a time jump by libev, and timers would
		1790	be adjusted accordingly.
		1791
		1792	I would not be surprised to see different behaviour in different between
		1793	operating systems, OS versions or even different hardware.
		1794
		1795	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1796	time jump in the monotonic clocks and the realtime clock. If the program
		1797	is suspended for a very long time, and monotonic clock sources are in use,
		1798	then you can expect C<ev_timer>s to expire as the full suspension time
		1799	will be counted towards the timers. When no monotonic clock source is in
		1800	use, then libev will again assume a timejump and adjust accordingly.
		1801
		1802	It might be beneficial for this latter case to call C<ev_suspend>
		1803	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1804	deterministic behaviour in this case (you can do nothing against
		1805	C<SIGSTOP>).
1172		1806
1173	=head3 Watcher-Specific Functions and Data Members	1807	=head3 Watcher-Specific Functions and Data Members
1174		1808
1175	=over 4	1809	=over 4
1176		1810
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1811	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1812
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1813	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1814
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1815	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	1816	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	1817	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1818	configured to trigger again C<repeat> seconds later, again, and again,
		1819	until stopped manually.
1185		1820
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1821	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	1822	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	1823	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	1824	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.	1825	do stuff) the timer will not fire more than once per event loop iteration.
1191		1826
1192	=item ev_timer_again (loop, ev_timer *)	1827	=item ev_timer_again (loop, ev_timer *)
1193		1828
1194	This will act as if the timer timed out and restart it again if it is	1829	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1830	repeating. The exact semantics are:
1196		1831
1197	If the timer is pending, its pending status is cleared.	1832	If the timer is pending, its pending status is cleared.
1198		1833
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1834	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1835
1201	If the timer is repeating, either start it if necessary (with the	1836	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.	1837	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1838
1204	This sounds a bit complicated, but here is a useful and typical	1839	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	1840	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		1841
1214	That means you can ignore the C<after> value and C<ev_timer_start>	1842	=item ev_timer_remaining (loop, ev_timer *)
1215	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1216		1843
1217	ev_timer_init (timer, callback, 0., 5.);	1844	Returns the remaining time until a timer fires. If the timer is active,
1218	ev_timer_again (loop, timer);	1845	then this time is relative to the current event loop time, otherwise it's
1219	...	1846	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		1847
1226	This is more slightly efficient then stopping/starting the timer each time	1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1227	you want to modify its timeout value.	1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1850	will return C<4>. When the timer expires and is restarted, it will return
		1851	roughly C<7> (likely slightly less as callback invocation takes some time,
		1852	too), and so on.
1228		1853
1229	=item ev_tstamp repeat [read-write]	1854	=item ev_tstamp repeat [read-write]
1230		1855
1231	The current C<repeat> value. Will be used each time the watcher times out	1856	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),	1857	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.	1858	which is also when any modifications are taken into account.
1234		1859
1235	=back	1860	=back
1236		1861
1237	=head3 Examples	1862	=head3 Examples
1238		1863
1239	Example: Create a timer that fires after 60 seconds.	1864	Example: Create a timer that fires after 60 seconds.
1240		1865
1241	static void	1866	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1867	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1243	{	1868	{
1244	.. one minute over, w is actually stopped right here	1869	.. one minute over, w is actually stopped right here
1245	}	1870	}
1246		1871
1247	struct ev_timer mytimer;	1872	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1873	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1874	ev_timer_start (loop, &mytimer);
1250		1875
1251	Example: Create a timeout timer that times out after 10 seconds of	1876	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1877	inactivity.
1253		1878
1254	static void	1879	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1880	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1256	{	1881	{
1257	.. ten seconds without any activity	1882	.. ten seconds without any activity
1258	}	1883	}
1259		1884
1260	struct ev_timer mytimer;	1885	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1886	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1887	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1888	ev_loop (loop, 0);
1264		1889
1265	// and in some piece of code that gets executed on any "activity":	1890	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1891	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1892	ev_timer_again (&mytimer);
1268		1893
1269		1894
1270	=head2 C<ev_periodic> - to cron or not to cron?	1895	=head2 C<ev_periodic> - to cron or not to cron?
1271		1896
1272	Periodic watchers are also timers of a kind, but they are very versatile	1897	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1898	(and unfortunately a bit complex).
1274		1899
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1900	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	1901	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	1902	(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 ()	1903	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	1904	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	1905	wrist-watch).
1281	roughly 10 seconds later).
1282		1906
1283	They can also be used to implement vastly more complex timers, such as	1907	You can tell a periodic watcher to trigger after some specific point
1284	triggering an event on each midnight, local time or other, complicated,	1908	in time: for example, if you tell a periodic watcher to trigger "in 10
1285	rules.	1909	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1910	not a delay) and then reset your system clock to January of the previous
		1911	year, then it will take a year or more to trigger the event (unlike an
		1912	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1913	it, as it uses a relative timeout).
1286		1914
		1915	C<ev_periodic> watchers can also be used to implement vastly more complex
		1916	timers, such as triggering an event on each "midnight, local time", or
		1917	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1918	those cannot react to time jumps.
		1919
1287	As with timers, the callback is guarenteed to be invoked only when the	1920	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	1921	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.	1922	timers become ready during the same loop iteration then the ones with
		1923	earlier time-out values are invoked before ones with later time-out values
		1924	(but this is no longer true when a callback calls C<ev_loop> recursively).
1290		1925
1291	=head3 Watcher-Specific Functions and Data Members	1926	=head3 Watcher-Specific Functions and Data Members
1292		1927
1293	=over 4	1928	=over 4
1294		1929
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1930	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1296		1931
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1932	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		1933
1299	Lots of arguments, lets sort it out... There are basically three modes of	1934	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:	1935	operation, and we will explain them from simplest to most complex:
1301		1936
1302	=over 4	1937	=over 4
1303		1938
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1939	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1305		1940
1306	In this configuration the watcher triggers an event at the wallclock time	1941	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,	1942	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	1943	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.	1944	will be stopped and invoked when the system clock reaches or surpasses
		1945	this point in time.
1310		1946
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1947	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1312		1948
1313	In this mode the watcher will always be scheduled to time out at the next	1949	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)	1950	C<offset + N * interval> time (for some integer N, which can also be
1315	and then repeat, regardless of any time jumps.	1951	negative) and then repeat, regardless of any time jumps. The C<offset>
		1952	argument is merely an offset into the C<interval> periods.
1316		1953
1317	This can be used to create timers that do not drift with respect to system	1954	This can be used to create timers that do not drift with respect to the
1318	time:	1955	system clock, for example, here is an C<ev_periodic> that triggers each
		1956	hour, on the hour (with respect to UTC):
1319		1957
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1958	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1959
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1960	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	1961	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	1962	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1963	by 3600.
1326		1964
1327	Another way to think about it (for the mathematically inclined) is that	1965	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	1966	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.	1967	time where C<time = offset (mod interval)>, regardless of any time jumps.
1330		1968
1331	For numerical stability it is preferable that the C<at> value is near	1969	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	1970	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1971	this value, and in fact is often specified as zero.
1334		1972
		1973	Note also that there is an upper limit to how often a timer can fire (CPU
		1974	speed for example), so if C<interval> is very small then timing stability
		1975	will of course deteriorate. Libev itself tries to be exact to be about one
		1976	millisecond (if the OS supports it and the machine is fast enough).
		1977
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1978	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1336		1979
1337	In this mode the values for C<interval> and C<at> are both being	1980	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	1981	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1982	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1983	current time as second argument.
1341		1984
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1985	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,	1986	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	1987	allowed by documentation here>.
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1988
		1989	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1990	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1991	only event loop modification you are allowed to do).
		1992
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1993	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	1994	*w, ev_tstamp now)>, e.g.:
1349		1995
		1996	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1997	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	1998	{
1352	return now + 60.;	1999	return now + 60.;
1353	}	2000	}
1354		2001
1355	It must return the next time to trigger, based on the passed time value	2002	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	2003	(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	2004	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	2005	might be called at other times, too.
1359		2006
1360	NOTE: I<< This callback must always return a time that is later than the	2007	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.	2008	equal to the passed C<now> value >>.
1362		2009
1363	This can be used to create very complex timers, such as a timer that	2010	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	2011	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	2012	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	2013	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).	2014	reason I omitted it as an example).
1368		2015
1369	=back	2016	=back
…		…
1373	Simply stops and restarts the periodic watcher again. This is only useful	2020	Simply stops and restarts the periodic watcher again. This is only useful
1374	when you changed some parameters or the reschedule callback would return	2021	when you changed some parameters or the reschedule callback would return
1375	a different time than the last time it was called (e.g. in a crond like	2022	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	2023	program when the crontabs have changed).
1377		2024
		2025	=item ev_tstamp ev_periodic_at (ev_periodic *)
		2026
		2027	When active, returns the absolute time that the watcher is supposed
		2028	to trigger next. This is not the same as the C<offset> argument to
		2029	C<ev_periodic_set>, but indeed works even in interval and manual
		2030	rescheduling modes.
		2031
1378	=item ev_tstamp offset [read-write]	2032	=item ev_tstamp offset [read-write]
1379		2033
1380	When repeating, this contains the offset value, otherwise this is the	2034	When repeating, this contains the offset value, otherwise this is the
1381	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2035	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2036	although libev might modify this value for better numerical stability).
1382		2037
1383	Can be modified any time, but changes only take effect when the periodic	2038	Can be modified any time, but changes only take effect when the periodic
1384	timer fires or C<ev_periodic_again> is being called.	2039	timer fires or C<ev_periodic_again> is being called.
1385		2040
1386	=item ev_tstamp interval [read-write]	2041	=item ev_tstamp interval [read-write]
1387		2042
1388	The current interval value. Can be modified any time, but changes only	2043	The current interval value. Can be modified any time, but changes only
1389	take effect when the periodic timer fires or C<ev_periodic_again> is being	2044	take effect when the periodic timer fires or C<ev_periodic_again> is being
1390	called.	2045	called.
1391		2046
1392	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2047	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1393		2048
1394	The current reschedule callback, or C<0>, if this functionality is	2049	The current reschedule callback, or C<0>, if this functionality is
1395	switched off. Can be changed any time, but changes only take effect when	2050	switched off. Can be changed any time, but changes only take effect when
1396	the periodic timer fires or C<ev_periodic_again> is being called.	2051	the periodic timer fires or C<ev_periodic_again> is being called.
1397		2052
1398	=item ev_tstamp at [read-only]
1399
1400	When active, contains the absolute time that the watcher is supposed to
1401	trigger next.
1402
1403	=back	2053	=back
1404		2054
1405	=head3 Examples	2055	=head3 Examples
1406		2056
1407	Example: Call a callback every hour, or, more precisely, whenever the	2057	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	2058	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	2059	potentially a lot of jitter, but good long-term stability.
1410		2060
1411	static void	2061	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1413	{	2063	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	2064	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	2065	}
1416		2066
1417	struct ev_periodic hourly_tick;	2067	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2068	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	2069	ev_periodic_start (loop, &hourly_tick);
1420		2070
1421	Example: The same as above, but use a reschedule callback to do it:	2071	Example: The same as above, but use a reschedule callback to do it:
1422		2072
1423	#include <math.h>	2073	#include <math.h>
1424		2074
1425	static ev_tstamp	2075	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2076	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	2077	{
1428	return fmod (now, 3600.) + 3600.;	2078	return now + (3600. - fmod (now, 3600.));
1429	}	2079	}
1430		2080
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2081	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		2082
1433	Example: Call a callback every hour, starting now:	2083	Example: Call a callback every hour, starting now:
1434		2084
1435	struct ev_periodic hourly_tick;	2085	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	2086	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	2087	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	2088	ev_periodic_start (loop, &hourly_tick);
1439		2089
1440		2090
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	2091	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		2092
1443	Signal watchers will trigger an event when the process receives a specific	2093	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	2094	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	2095	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	2096	normal event processing, like any other event.
1447		2097
		2098	If you want signals to be delivered truly asynchronously, just use
		2099	C<sigaction> as you would do without libev and forget about sharing
		2100	the signal. You can even use C<ev_async> from a signal handler to
		2101	synchronously wake up an event loop.
		2102
1448	You can configure as many watchers as you like per signal. Only when the	2103	You can configure as many watchers as you like for the same signal, but
		2104	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2105	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2106	C<SIGINT> in both the default loop and another loop at the same time. At
		2107	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2108
1449	first watcher gets started will libev actually register a signal watcher	2109	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	2110	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	2111	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	2112
1453	SIG_DFL (regardless of what it was set to before).	2113	Both the signal mask state (C<sigprocmask>) and the signal handler state
		2114	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2115	sotpping it again), that is, libev might or might not block the signal,
		2116	and might or might not set or restore the installed signal handler.
1454		2117
1455	If possible and supported, libev will install its handlers with	2118	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2119	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1457	interrupted. If you have a problem with syscalls getting interrupted by	2120	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	2121	interrupted by signals you can block all signals in an C<ev_check> watcher
1459	them in an C<ev_prepare> watcher.	2122	and unblock them in an C<ev_prepare> watcher.
1460		2123
1461	=head3 Watcher-Specific Functions and Data Members	2124	=head3 Watcher-Specific Functions and Data Members
1462		2125
1463	=over 4	2126	=over 4
1464		2127
…		…
1475		2138
1476	=back	2139	=back
1477		2140
1478	=head3 Examples	2141	=head3 Examples
1479		2142
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	2143	Example: Try to exit cleanly on SIGINT.
1481		2144
1482	static void	2145	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2146	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1484	{	2147	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	2148	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	2149	}
1487		2150
1488	struct ev_signal signal_watcher;	2151	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2152	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	2153	ev_signal_start (loop, &signal_watcher);
1491		2154
1492		2155
1493	=head2 C<ev_child> - watch out for process status changes	2156	=head2 C<ev_child> - watch out for process status changes
1494		2157
1495	Child watchers trigger when your process receives a SIGCHLD in response to	2158	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	2159	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	2160	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	2161	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	2162	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2163	forking and then immediately registering a watcher for the child is fine,
		2164	but forking and registering a watcher a few event loop iterations later or
		2165	in the next callback invocation is not.
1500		2166
1501	Only the default event loop is capable of handling signals, and therefore	2167	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	2168	you can only register child watchers in the default event loop.
		2169
		2170	Due to some design glitches inside libev, child watchers will always be
		2171	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2172	libev)
1503		2173
1504	=head3 Process Interaction	2174	=head3 Process Interaction
1505		2175
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	2176	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	2177	initialised. This is necessary to guarantee proper behaviour even if the
1508	the first child watcher is started after the child exits. The occurance	2178	first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2179	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	2180	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	2181	children, even ones not watched.
1512		2182
1513	=head3 Overriding the Built-In Processing	2183	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	2187	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	2188	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	2189	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	2190	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.	2191	that, so other libev users can use C<ev_child> watchers freely.
		2192
		2193	=head3 Stopping the Child Watcher
		2194
		2195	Currently, the child watcher never gets stopped, even when the
		2196	child terminates, so normally one needs to stop the watcher in the
		2197	callback. Future versions of libev might stop the watcher automatically
		2198	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2199	problem).
1522		2200
1523	=head3 Watcher-Specific Functions and Data Members	2201	=head3 Watcher-Specific Functions and Data Members
1524		2202
1525	=over 4	2203	=over 4
1526		2204
…		…
1555	=head3 Examples	2233	=head3 Examples
1556		2234
1557	Example: C<fork()> a new process and install a child handler to wait for	2235	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	2236	its completion.
1559		2237
1560	ev_child cw;	2238	ev_child cw;
1561		2239
1562	static void	2240	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	2241	child_cb (EV_P_ ev_child *w, int revents)
1564	{	2242	{
1565	ev_child_stop (EV_A_ w);	2243	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2244	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	2245	}
1568		2246
1569	pid_t pid = fork ();	2247	pid_t pid = fork ();
1570		2248
1571	if (pid < 0)	2249	if (pid < 0)
1572	// error	2250	// error
1573	else if (pid == 0)	2251	else if (pid == 0)
1574	{	2252	{
1575	// the forked child executes here	2253	// the forked child executes here
1576	exit (1);	2254	exit (1);
1577	}	2255	}
1578	else	2256	else
1579	{	2257	{
1580	ev_child_init (&cw, child_cb, pid, 0);	2258	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	2259	ev_child_start (EV_DEFAULT_ &cw);
1582	}	2260	}
1583		2261
1584		2262
1585	=head2 C<ev_stat> - did the file attributes just change?	2263	=head2 C<ev_stat> - did the file attributes just change?
1586		2264
1587	This watches a filesystem path for attribute changes. That is, it calls	2265	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	2266	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.	2267	and sees if it changed compared to the last time, invoking the callback if
		2268	it did.
1590		2269
1591	The path does not need to exist: changing from "path exists" to "path does	2270	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	2271	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	2272	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	2273	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	2274	least one) and all the other fields of the stat buffer having unspecified
		2275	contents.
1596		2276
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	2277	The path I<must not> end in a slash or contain special components such as
		2278	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.	2279	your working directory changes, then the behaviour is undefined.
1599		2280
1600	Since there is no standard to do this, the portable implementation simply	2281	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	2282	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	2283	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,	2284	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	2285	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	2286	(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	2287	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	2288	currently around C<0.1>, but that's usually overkill.
1608		2289
1609	This watcher type is not meant for massive numbers of stat watchers,	2290	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	2291	as even with OS-supported change notifications, this can be
1611	resource-intensive.	2292	resource-intensive.
1612		2293
1613	At the time of this writing, only the Linux inotify interface is	2294	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	2295	is the Linux inotify interface (implementing kqueue support is left as an
1615	reader). Inotify will be used to give hints only and should not change the	2296	exercise for the reader. Note, however, that the author sees no way of
1616	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2297	implementing C<ev_stat> semantics with kqueue, except as a hint).
1617	to fall back to regular polling again even with inotify, but changes are
1618	usually detected immediately, and if the file exists there will be no
1619	polling.
1620		2298
1621	=head3 ABI Issues (Largefile Support)	2299	=head3 ABI Issues (Largefile Support)
1622		2300
1623	Libev by default (unless the user overrides this) uses the default	2301	Libev by default (unless the user overrides this) uses the default
1624	compilation environment, which means that on systems with optionally	2302	compilation environment, which means that on systems with large file
1625	disabled large file support, you get the 32 bit version of the stat	2303	support disabled by default, you get the 32 bit version of the stat
1626	structure. When using the library from programs that change the ABI to	2304	structure. When using the library from programs that change the ABI to
1627	use 64 bit file offsets the programs will fail. In that case you have to	2305	use 64 bit file offsets the programs will fail. In that case you have to
1628	compile libev with the same flags to get binary compatibility. This is	2306	compile libev with the same flags to get binary compatibility. This is
1629	obviously the case with any flags that change the ABI, but the problem is	2307	obviously the case with any flags that change the ABI, but the problem is
1630	most noticably with ev_stat and largefile support.	2308	most noticeably displayed with ev_stat and large file support.
1631		2309
1632	=head3 Inotify	2310	The solution for this is to lobby your distribution maker to make large
		2311	file interfaces available by default (as e.g. FreeBSD does) and not
		2312	optional. Libev cannot simply switch on large file support because it has
		2313	to exchange stat structures with application programs compiled using the
		2314	default compilation environment.
1633		2315
		2316	=head3 Inotify and Kqueue
		2317
1634	When C<inotify (7)> support has been compiled into libev (generally only	2318	When C<inotify (7)> support has been compiled into libev and present at
1635	available on Linux) and present at runtime, it will be used to speed up	2319	runtime, it will be used to speed up change detection where possible. The
1636	change detection where possible. The inotify descriptor will be created lazily	2320	inotify descriptor will be created lazily when the first C<ev_stat>
1637	when the first C<ev_stat> watcher is being started.	2321	watcher is being started.
1638		2322
1639	Inotify presence does not change the semantics of C<ev_stat> watchers	2323	Inotify presence does not change the semantics of C<ev_stat> watchers
1640	except that changes might be detected earlier, and in some cases, to avoid	2324	except that changes might be detected earlier, and in some cases, to avoid
1641	making regular C<stat> calls. Even in the presence of inotify support	2325	making regular C<stat> calls. Even in the presence of inotify support
1642	there are many cases where libev has to resort to regular C<stat> polling.	2326	there are many cases where libev has to resort to regular C<stat> polling,
		2327	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2328	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2329	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2330	xfs are fully working) libev usually gets away without polling.
1643		2331
1644	(There is no support for kqueue, as apparently it cannot be used to	2332	There is no support for kqueue, as apparently it cannot be used to
1645	implement this functionality, due to the requirement of having a file	2333	implement this functionality, due to the requirement of having a file
1646	descriptor open on the object at all times).	2334	descriptor open on the object at all times, and detecting renames, unlinks
		2335	etc. is difficult.
		2336
		2337	=head3 C<stat ()> is a synchronous operation
		2338
		2339	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2340	the process. The exception are C<ev_stat> watchers - those call C<stat
		2341	()>, which is a synchronous operation.
		2342
		2343	For local paths, this usually doesn't matter: unless the system is very
		2344	busy or the intervals between stat's are large, a stat call will be fast,
		2345	as the path data is usually in memory already (except when starting the
		2346	watcher).
		2347
		2348	For networked file systems, calling C<stat ()> can block an indefinite
		2349	time due to network issues, and even under good conditions, a stat call
		2350	often takes multiple milliseconds.
		2351
		2352	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2353	paths, although this is fully supported by libev.
1647		2354
1648	=head3 The special problem of stat time resolution	2355	=head3 The special problem of stat time resolution
1649		2356
1650	The C<stat ()> syscall only supports full-second resolution portably, and	2357	The C<stat ()> system call only supports full-second resolution portably,
1651	even on systems where the resolution is higher, many filesystems still	2358	and even on systems where the resolution is higher, most file systems
1652	only support whole seconds.	2359	still only support whole seconds.
1653		2360
1654	That means that, if the time is the only thing that changes, you might	2361	That means that, if the time is the only thing that changes, you can
1655	miss updates: on the first update, C<ev_stat> detects a change and calls	2362	easily miss updates: on the first update, C<ev_stat> detects a change and
1656	your callback, which does something. When there is another update within	2363	calls your callback, which does something. When there is another update
1657	the same second, C<ev_stat> will be unable to detect it.	2364	within the same second, C<ev_stat> will be unable to detect unless the
		2365	stat data does change in other ways (e.g. file size).
1658		2366
1659	The solution to this is to delay acting on a change for a second (or till	2367	The solution to this is to delay acting on a change for slightly more
1660	the next second boundary), using a roughly one-second delay C<ev_timer>	2368	than a second (or till slightly after the next full second boundary), using
1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2369	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1662	is added to work around small timing inconsistencies of some operating	2370	ev_timer_again (loop, w)>).
1663	systems.	2371
		2372	The C<.02> offset is added to work around small timing inconsistencies
		2373	of some operating systems (where the second counter of the current time
		2374	might be be delayed. One such system is the Linux kernel, where a call to
		2375	C<gettimeofday> might return a timestamp with a full second later than
		2376	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2377	update file times then there will be a small window where the kernel uses
		2378	the previous second to update file times but libev might already execute
		2379	the timer callback).
1664		2380
1665	=head3 Watcher-Specific Functions and Data Members	2381	=head3 Watcher-Specific Functions and Data Members
1666		2382
1667	=over 4	2383	=over 4
1668		2384
…		…
1674	C<path>. The C<interval> is a hint on how quickly a change is expected to	2390	C<path>. The C<interval> is a hint on how quickly a change is expected to
1675	be detected and should normally be specified as C<0> to let libev choose	2391	be detected and should normally be specified as C<0> to let libev choose
1676	a suitable value. The memory pointed to by C<path> must point to the same	2392	a suitable value. The memory pointed to by C<path> must point to the same
1677	path for as long as the watcher is active.	2393	path for as long as the watcher is active.
1678		2394
1679	The callback will be receive C<EV_STAT> when a change was detected,	2395	The callback will receive an C<EV_STAT> event when a change was detected,
1680	relative to the attributes at the time the watcher was started (or the	2396	relative to the attributes at the time the watcher was started (or the
1681	last change was detected).	2397	last change was detected).
1682		2398
1683	=item ev_stat_stat (loop, ev_stat *)	2399	=item ev_stat_stat (loop, ev_stat *)
1684		2400
1685	Updates the stat buffer immediately with new values. If you change the	2401	Updates the stat buffer immediately with new values. If you change the
1686	watched path in your callback, you could call this fucntion to avoid	2402	watched path in your callback, you could call this function to avoid
1687	detecting this change (while introducing a race condition). Can also be	2403	detecting this change (while introducing a race condition if you are not
1688	useful simply to find out the new values.	2404	the only one changing the path). Can also be useful simply to find out the
		2405	new values.
1689		2406
1690	=item ev_statdata attr [read-only]	2407	=item ev_statdata attr [read-only]
1691		2408
1692	The most-recently detected attributes of the file. Although the type is of	2409	The most-recently detected attributes of the file. Although the type is
1693	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2410	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1694	suitable for your system. If the C<st_nlink> member is C<0>, then there	2411	suitable for your system, but you can only rely on the POSIX-standardised
		2412	members to be present. If the C<st_nlink> member is C<0>, then there was
1695	was some error while C<stat>ing the file.	2413	some error while C<stat>ing the file.
1696		2414
1697	=item ev_statdata prev [read-only]	2415	=item ev_statdata prev [read-only]
1698		2416
1699	The previous attributes of the file. The callback gets invoked whenever	2417	The previous attributes of the file. The callback gets invoked whenever
1700	C<prev> != C<attr>.	2418	C<prev> != C<attr>, or, more precisely, one or more of these members
		2419	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2420	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1701		2421
1702	=item ev_tstamp interval [read-only]	2422	=item ev_tstamp interval [read-only]
1703		2423
1704	The specified interval.	2424	The specified interval.
1705		2425
1706	=item const char *path [read-only]	2426	=item const char *path [read-only]
1707		2427
1708	The filesystem path that is being watched.	2428	The file system path that is being watched.
1709		2429
1710	=back	2430	=back
1711		2431
1712	=head3 Examples	2432	=head3 Examples
1713		2433
1714	Example: Watch C</etc/passwd> for attribute changes.	2434	Example: Watch C</etc/passwd> for attribute changes.
1715		2435
1716	static void	2436	static void
1717	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2437	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1718	{	2438	{
1719	/* /etc/passwd changed in some way */	2439	/* /etc/passwd changed in some way */
1720	if (w->attr.st_nlink)	2440	if (w->attr.st_nlink)
1721	{	2441	{
1722	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2442	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1723	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2443	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1724	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2444	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1725	}	2445	}
1726	else	2446	else
1727	/* you shalt not abuse printf for puts */	2447	/* you shalt not abuse printf for puts */
1728	puts ("wow, /etc/passwd is not there, expect problems. "	2448	puts ("wow, /etc/passwd is not there, expect problems. "
1729	"if this is windows, they already arrived\n");	2449	"if this is windows, they already arrived\n");
1730	}	2450	}
1731		2451
1732	...	2452	...
1733	ev_stat passwd;	2453	ev_stat passwd;
1734		2454
1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2455	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	2456	ev_stat_start (loop, &passwd);
1737		2457
1738	Example: Like above, but additionally use a one-second delay so we do not	2458	Example: Like above, but additionally use a one-second delay so we do not
1739	miss updates (however, frequent updates will delay processing, too, so	2459	miss updates (however, frequent updates will delay processing, too, so
1740	one might do the work both on C<ev_stat> callback invocation I<and> on	2460	one might do the work both on C<ev_stat> callback invocation I<and> on
1741	C<ev_timer> callback invocation).	2461	C<ev_timer> callback invocation).
1742		2462
1743	static ev_stat passwd;	2463	static ev_stat passwd;
1744	static ev_timer timer;	2464	static ev_timer timer;
1745		2465
1746	static void	2466	static void
1747	timer_cb (EV_P_ ev_timer *w, int revents)	2467	timer_cb (EV_P_ ev_timer *w, int revents)
1748	{	2468	{
1749	ev_timer_stop (EV_A_ w);	2469	ev_timer_stop (EV_A_ w);
1750		2470
1751	/* now it's one second after the most recent passwd change */	2471	/* now it's one second after the most recent passwd change */
1752	}	2472	}
1753		2473
1754	static void	2474	static void
1755	stat_cb (EV_P_ ev_stat *w, int revents)	2475	stat_cb (EV_P_ ev_stat *w, int revents)
1756	{	2476	{
1757	/* reset the one-second timer */	2477	/* reset the one-second timer */
1758	ev_timer_again (EV_A_ &timer);	2478	ev_timer_again (EV_A_ &timer);
1759	}	2479	}
1760		2480
1761	...	2481	...
1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2482	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1763	ev_stat_start (loop, &passwd);	2483	ev_stat_start (loop, &passwd);
1764	ev_timer_init (&timer, timer_cb, 0., 1.01);	2484	ev_timer_init (&timer, timer_cb, 0., 1.02);
1765		2485
1766		2486
1767	=head2 C<ev_idle> - when you've got nothing better to do...	2487	=head2 C<ev_idle> - when you've got nothing better to do...
1768		2488
1769	Idle watchers trigger events when no other events of the same or higher	2489	Idle watchers trigger events when no other events of the same or higher
1770	priority are pending (prepare, check and other idle watchers do not	2490	priority are pending (prepare, check and other idle watchers do not count
1771	count).	2491	as receiving "events").
1772		2492
1773	That is, as long as your process is busy handling sockets or timeouts	2493	That is, as long as your process is busy handling sockets or timeouts
1774	(or even signals, imagine) of the same or higher priority it will not be	2494	(or even signals, imagine) of the same or higher priority it will not be
1775	triggered. But when your process is idle (or only lower-priority watchers	2495	triggered. But when your process is idle (or only lower-priority watchers
1776	are pending), the idle watchers are being called once per event loop	2496	are pending), the idle watchers are being called once per event loop
…		…
1787		2507
1788	=head3 Watcher-Specific Functions and Data Members	2508	=head3 Watcher-Specific Functions and Data Members
1789		2509
1790	=over 4	2510	=over 4
1791		2511
1792	=item ev_idle_init (ev_signal *, callback)	2512	=item ev_idle_init (ev_idle *, callback)
1793		2513
1794	Initialises and configures the idle watcher - it has no parameters of any	2514	Initialises and configures the idle watcher - it has no parameters of any
1795	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2515	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1796	believe me.	2516	believe me.
1797		2517
…		…
1800	=head3 Examples	2520	=head3 Examples
1801		2521
1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2522	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1803	callback, free it. Also, use no error checking, as usual.	2523	callback, free it. Also, use no error checking, as usual.
1804		2524
1805	static void	2525	static void
1806	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2526	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1807	{	2527	{
1808	free (w);	2528	free (w);
1809	// now do something you wanted to do when the program has	2529	// now do something you wanted to do when the program has
1810	// no longer anything immediate to do.	2530	// no longer anything immediate to do.
1811	}	2531	}
1812		2532
1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2533	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1814	ev_idle_init (idle_watcher, idle_cb);	2534	ev_idle_init (idle_watcher, idle_cb);
1815	ev_idle_start (loop, idle_cb);	2535	ev_idle_start (loop, idle_watcher);
1816		2536
1817		2537
1818	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2538	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1819		2539
1820	Prepare and check watchers are usually (but not always) used in tandem:	2540	Prepare and check watchers are usually (but not always) used in pairs:
1821	prepare watchers get invoked before the process blocks and check watchers	2541	prepare watchers get invoked before the process blocks and check watchers
1822	afterwards.	2542	afterwards.
1823		2543
1824	You I<must not> call C<ev_loop> or similar functions that enter	2544	You I<must not> call C<ev_loop> or similar functions that enter
1825	the current event loop from either C<ev_prepare> or C<ev_check>	2545	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1828	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2548	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1829	C<ev_check> so if you have one watcher of each kind they will always be	2549	C<ev_check> so if you have one watcher of each kind they will always be
1830	called in pairs bracketing the blocking call.	2550	called in pairs bracketing the blocking call.
1831		2551
1832	Their main purpose is to integrate other event mechanisms into libev and	2552	Their main purpose is to integrate other event mechanisms into libev and
1833	their use is somewhat advanced. This could be used, for example, to track	2553	their use is somewhat advanced. They could be used, for example, to track
1834	variable changes, implement your own watchers, integrate net-snmp or a	2554	variable changes, implement your own watchers, integrate net-snmp or a
1835	coroutine library and lots more. They are also occasionally useful if	2555	coroutine library and lots more. They are also occasionally useful if
1836	you cache some data and want to flush it before blocking (for example,	2556	you cache some data and want to flush it before blocking (for example,
1837	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2557	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1838	watcher).	2558	watcher).
1839		2559
1840	This is done by examining in each prepare call which file descriptors need	2560	This is done by examining in each prepare call which file descriptors
1841	to be watched by the other library, registering C<ev_io> watchers for	2561	need to be watched by the other library, registering C<ev_io> watchers
1842	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2562	for them and starting an C<ev_timer> watcher for any timeouts (many
1843	provide just this functionality). Then, in the check watcher you check for	2563	libraries provide exactly this functionality). Then, in the check watcher,
1844	any events that occured (by checking the pending status of all watchers	2564	you check for any events that occurred (by checking the pending status
1845	and stopping them) and call back into the library. The I/O and timer	2565	of all watchers and stopping them) and call back into the library. The
1846	callbacks will never actually be called (but must be valid nevertheless,	2566	I/O and timer callbacks will never actually be called (but must be valid
1847	because you never know, you know?).	2567	nevertheless, because you never know, you know?).
1848		2568
1849	As another example, the Perl Coro module uses these hooks to integrate	2569	As another example, the Perl Coro module uses these hooks to integrate
1850	coroutines into libev programs, by yielding to other active coroutines	2570	coroutines into libev programs, by yielding to other active coroutines
1851	during each prepare and only letting the process block if no coroutines	2571	during each prepare and only letting the process block if no coroutines
1852	are ready to run (it's actually more complicated: it only runs coroutines	2572	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1855	loop from blocking if lower-priority coroutines are active, thus mapping	2575	loop from blocking if lower-priority coroutines are active, thus mapping
1856	low-priority coroutines to idle/background tasks).	2576	low-priority coroutines to idle/background tasks).
1857		2577
1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2578	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1859	priority, to ensure that they are being run before any other watchers	2579	priority, to ensure that they are being run before any other watchers
		2580	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2581
1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2582	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1861	too) should not activate ("feed") events into libev. While libev fully	2583	activate ("feed") events into libev. While libev fully supports this, they
1862	supports this, they will be called before other C<ev_check> watchers	2584	might get executed before other C<ev_check> watchers did their job. As
1863	did their job. As C<ev_check> watchers are often used to embed other	2585	C<ev_check> watchers are often used to embed other (non-libev) event
1864	(non-libev) event loops those other event loops might be in an unusable	2586	loops those other event loops might be in an unusable state until their
1865	state until their C<ev_check> watcher ran (always remind yourself to	2587	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1866	coexist peacefully with others).	2588	others).
1867		2589
1868	=head3 Watcher-Specific Functions and Data Members	2590	=head3 Watcher-Specific Functions and Data Members
1869		2591
1870	=over 4	2592	=over 4
1871		2593
…		…
1873		2595
1874	=item ev_check_init (ev_check *, callback)	2596	=item ev_check_init (ev_check *, callback)
1875		2597
1876	Initialises and configures the prepare or check watcher - they have no	2598	Initialises and configures the prepare or check watcher - they have no
1877	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2599	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1878	macros, but using them is utterly, utterly and completely pointless.	2600	macros, but using them is utterly, utterly, utterly and completely
		2601	pointless.
1879		2602
1880	=back	2603	=back
1881		2604
1882	=head3 Examples	2605	=head3 Examples
1883		2606
1884	There are a number of principal ways to embed other event loops or modules	2607	There are a number of principal ways to embed other event loops or modules
1885	into libev. Here are some ideas on how to include libadns into libev	2608	into libev. Here are some ideas on how to include libadns into libev
1886	(there is a Perl module named C<EV::ADNS> that does this, which you could	2609	(there is a Perl module named C<EV::ADNS> that does this, which you could
1887	use for an actually working example. Another Perl module named C<EV::Glib>	2610	use as a working example. Another Perl module named C<EV::Glib> embeds a
1888	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2611	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1889	into the Glib event loop).	2612	Glib event loop).
1890		2613
1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2614	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1892	and in a check watcher, destroy them and call into libadns. What follows	2615	and in a check watcher, destroy them and call into libadns. What follows
1893	is pseudo-code only of course. This requires you to either use a low	2616	is pseudo-code only of course. This requires you to either use a low
1894	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2617	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1895	the callbacks for the IO/timeout watchers might not have been called yet.	2618	the callbacks for the IO/timeout watchers might not have been called yet.
1896		2619
1897	static ev_io iow [nfd];	2620	static ev_io iow [nfd];
1898	static ev_timer tw;	2621	static ev_timer tw;
1899		2622
1900	static void	2623	static void
1901	io_cb (ev_loop *loop, ev_io *w, int revents)	2624	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1902	{	2625	{
1903	}	2626	}
1904		2627
1905	// create io watchers for each fd and a timer before blocking	2628	// create io watchers for each fd and a timer before blocking
1906	static void	2629	static void
1907	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2630	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1908	{	2631	{
1909	int timeout = 3600000;	2632	int timeout = 3600000;
1910	struct pollfd fds [nfd];	2633	struct pollfd fds [nfd];
1911	// actual code will need to loop here and realloc etc.	2634	// actual code will need to loop here and realloc etc.
1912	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2635	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1913		2636
1914	/* the callback is illegal, but won't be called as we stop during check */	2637	/* the callback is illegal, but won't be called as we stop during check */
1915	ev_timer_init (&tw, 0, timeout * 1e-3);	2638	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1916	ev_timer_start (loop, &tw);	2639	ev_timer_start (loop, &tw);
1917		2640
1918	// create one ev_io per pollfd	2641	// create one ev_io per pollfd
1919	for (int i = 0; i < nfd; ++i)	2642	for (int i = 0; i < nfd; ++i)
1920	{	2643	{
1921	ev_io_init (iow + i, io_cb, fds [i].fd,	2644	ev_io_init (iow + i, io_cb, fds [i].fd,
1922	((fds [i].events & POLLIN ? EV_READ : 0)	2645	((fds [i].events & POLLIN ? EV_READ : 0)
1923	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2646	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1924		2647
1925	fds [i].revents = 0;	2648	fds [i].revents = 0;
1926	ev_io_start (loop, iow + i);	2649	ev_io_start (loop, iow + i);
1927	}	2650	}
1928	}	2651	}
1929		2652
1930	// stop all watchers after blocking	2653	// stop all watchers after blocking
1931	static void	2654	static void
1932	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2655	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1933	{	2656	{
1934	ev_timer_stop (loop, &tw);	2657	ev_timer_stop (loop, &tw);
1935		2658
1936	for (int i = 0; i < nfd; ++i)	2659	for (int i = 0; i < nfd; ++i)
1937	{	2660	{
1938	// set the relevant poll flags	2661	// set the relevant poll flags
1939	// could also call adns_processreadable etc. here	2662	// could also call adns_processreadable etc. here
1940	struct pollfd *fd = fds + i;	2663	struct pollfd *fd = fds + i;
1941	int revents = ev_clear_pending (iow + i);	2664	int revents = ev_clear_pending (iow + i);
1942	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2665	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1943	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2666	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1944		2667
1945	// now stop the watcher	2668	// now stop the watcher
1946	ev_io_stop (loop, iow + i);	2669	ev_io_stop (loop, iow + i);
1947	}	2670	}
1948		2671
1949	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2672	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1950	}	2673	}
1951		2674
1952	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2675	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1953	in the prepare watcher and would dispose of the check watcher.	2676	in the prepare watcher and would dispose of the check watcher.
1954		2677
1955	Method 3: If the module to be embedded supports explicit event	2678	Method 3: If the module to be embedded supports explicit event
1956	notification (adns does), you can also make use of the actual watcher	2679	notification (libadns does), you can also make use of the actual watcher
1957	callbacks, and only destroy/create the watchers in the prepare watcher.	2680	callbacks, and only destroy/create the watchers in the prepare watcher.
1958		2681
1959	static void	2682	static void
1960	timer_cb (EV_P_ ev_timer *w, int revents)	2683	timer_cb (EV_P_ ev_timer *w, int revents)
1961	{	2684	{
1962	adns_state ads = (adns_state)w->data;	2685	adns_state ads = (adns_state)w->data;
1963	update_now (EV_A);	2686	update_now (EV_A);
1964		2687
1965	adns_processtimeouts (ads, &tv_now);	2688	adns_processtimeouts (ads, &tv_now);
1966	}	2689	}
1967		2690
1968	static void	2691	static void
1969	io_cb (EV_P_ ev_io *w, int revents)	2692	io_cb (EV_P_ ev_io *w, int revents)
1970	{	2693	{
1971	adns_state ads = (adns_state)w->data;	2694	adns_state ads = (adns_state)w->data;
1972	update_now (EV_A);	2695	update_now (EV_A);
1973		2696
1974	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2697	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1975	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2698	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1976	}	2699	}
1977		2700
1978	// do not ever call adns_afterpoll	2701	// do not ever call adns_afterpoll
1979		2702
1980	Method 4: Do not use a prepare or check watcher because the module you	2703	Method 4: Do not use a prepare or check watcher because the module you
1981	want to embed is too inflexible to support it. Instead, youc na override	2704	want to embed is not flexible enough to support it. Instead, you can
1982	their poll function. The drawback with this solution is that the main	2705	override their poll function. The drawback with this solution is that the
1983	loop is now no longer controllable by EV. The C<Glib::EV> module does	2706	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1984	this.	2707	this approach, effectively embedding EV as a client into the horrible
		2708	libglib event loop.
1985		2709
1986	static gint	2710	static gint
1987	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2711	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1988	{	2712	{
1989	int got_events = 0;	2713	int got_events = 0;
1990		2714
1991	for (n = 0; n < nfds; ++n)	2715	for (n = 0; n < nfds; ++n)
1992	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2716	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1993		2717
1994	if (timeout >= 0)	2718	if (timeout >= 0)
1995	// create/start timer	2719	// create/start timer
1996		2720
1997	// poll	2721	// poll
1998	ev_loop (EV_A_ 0);	2722	ev_loop (EV_A_ 0);
1999		2723
2000	// stop timer again	2724	// stop timer again
2001	if (timeout >= 0)	2725	if (timeout >= 0)
2002	ev_timer_stop (EV_A_ &to);	2726	ev_timer_stop (EV_A_ &to);
2003		2727
2004	// stop io watchers again - their callbacks should have set	2728	// stop io watchers again - their callbacks should have set
2005	for (n = 0; n < nfds; ++n)	2729	for (n = 0; n < nfds; ++n)
2006	ev_io_stop (EV_A_ iow [n]);	2730	ev_io_stop (EV_A_ iow [n]);
2007		2731
2008	return got_events;	2732	return got_events;
2009	}	2733	}
2010		2734
2011		2735
2012	=head2 C<ev_embed> - when one backend isn't enough...	2736	=head2 C<ev_embed> - when one backend isn't enough...
2013		2737
2014	This is a rather advanced watcher type that lets you embed one event loop	2738	This is a rather advanced watcher type that lets you embed one event loop
…		…
2020	prioritise I/O.	2744	prioritise I/O.
2021		2745
2022	As an example for a bug workaround, the kqueue backend might only support	2746	As an example for a bug workaround, the kqueue backend might only support
2023	sockets on some platform, so it is unusable as generic backend, but you	2747	sockets on some platform, so it is unusable as generic backend, but you
2024	still want to make use of it because you have many sockets and it scales	2748	still want to make use of it because you have many sockets and it scales
2025	so nicely. In this case, you would create a kqueue-based loop and embed it	2749	so nicely. In this case, you would create a kqueue-based loop and embed
2026	into your default loop (which might use e.g. poll). Overall operation will	2750	it into your default loop (which might use e.g. poll). Overall operation
2027	be a bit slower because first libev has to poll and then call kevent, but	2751	will be a bit slower because first libev has to call C<poll> and then
2028	at least you can use both at what they are best.	2752	C<kevent>, but at least you can use both mechanisms for what they are
		2753	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2029		2754
2030	As for prioritising I/O: rarely you have the case where some fds have	2755	As for prioritising I/O: under rare circumstances you have the case where
2031	to be watched and handled very quickly (with low latency), and even	2756	some fds have to be watched and handled very quickly (with low latency),
2032	priorities and idle watchers might have too much overhead. In this case	2757	and even priorities and idle watchers might have too much overhead. In
2033	you would put all the high priority stuff in one loop and all the rest in	2758	this case you would put all the high priority stuff in one loop and all
2034	a second one, and embed the second one in the first.	2759	the rest in a second one, and embed the second one in the first.
2035		2760
2036	As long as the watcher is active, the callback will be invoked every time	2761	As long as the watcher is active, the callback will be invoked every
2037	there might be events pending in the embedded loop. The callback must then	2762	time there might be events pending in the embedded loop. The callback
2038	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2763	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2039	their callbacks (you could also start an idle watcher to give the embedded	2764	sweep and invoke their callbacks (the callback doesn't need to invoke the
2040	loop strictly lower priority for example). You can also set the callback	2765	C<ev_embed_sweep> function directly, it could also start an idle watcher
2041	to C<0>, in which case the embed watcher will automatically execute the	2766	to give the embedded loop strictly lower priority for example).
2042	embedded loop sweep.
2043		2767
2044	As long as the watcher is started it will automatically handle events. The	2768	You can also set the callback to C<0>, in which case the embed watcher
2045	callback will be invoked whenever some events have been handled. You can	2769	will automatically execute the embedded loop sweep whenever necessary.
2046	set the callback to C<0> to avoid having to specify one if you are not
2047	interested in that.
2048		2770
2049	Also, there have not currently been made special provisions for forking:	2771	Fork detection will be handled transparently while the C<ev_embed> watcher
2050	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2772	is active, i.e., the embedded loop will automatically be forked when the
2051	but you will also have to stop and restart any C<ev_embed> watchers	2773	embedding loop forks. In other cases, the user is responsible for calling
2052	yourself.	2774	C<ev_loop_fork> on the embedded loop.
2053		2775
2054	Unfortunately, not all backends are embeddable, only the ones returned by	2776	Unfortunately, not all backends are embeddable: only the ones returned by
2055	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2777	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2056	portable one.	2778	portable one.
2057		2779
2058	So when you want to use this feature you will always have to be prepared	2780	So when you want to use this feature you will always have to be prepared
2059	that you cannot get an embeddable loop. The recommended way to get around	2781	that you cannot get an embeddable loop. The recommended way to get around
2060	this is to have a separate variables for your embeddable loop, try to	2782	this is to have a separate variables for your embeddable loop, try to
2061	create it, and if that fails, use the normal loop for everything.	2783	create it, and if that fails, use the normal loop for everything.
2062		2784
		2785	=head3 C<ev_embed> and fork
		2786
		2787	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2788	automatically be applied to the embedded loop as well, so no special
		2789	fork handling is required in that case. When the watcher is not running,
		2790	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2791	as applicable.
		2792
2063	=head3 Watcher-Specific Functions and Data Members	2793	=head3 Watcher-Specific Functions and Data Members
2064		2794
2065	=over 4	2795	=over 4
2066		2796
2067	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2797	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2070		2800
2071	Configures the watcher to embed the given loop, which must be	2801	Configures the watcher to embed the given loop, which must be
2072	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2802	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2073	invoked automatically, otherwise it is the responsibility of the callback	2803	invoked automatically, otherwise it is the responsibility of the callback
2074	to invoke it (it will continue to be called until the sweep has been done,	2804	to invoke it (it will continue to be called until the sweep has been done,
2075	if you do not want thta, you need to temporarily stop the embed watcher).	2805	if you do not want that, you need to temporarily stop the embed watcher).
2076		2806
2077	=item ev_embed_sweep (loop, ev_embed *)	2807	=item ev_embed_sweep (loop, ev_embed *)
2078		2808
2079	Make a single, non-blocking sweep over the embedded loop. This works	2809	Make a single, non-blocking sweep over the embedded loop. This works
2080	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2810	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2081	apropriate way for embedded loops.	2811	appropriate way for embedded loops.
2082		2812
2083	=item struct ev_loop *other [read-only]	2813	=item struct ev_loop *other [read-only]
2084		2814
2085	The embedded event loop.	2815	The embedded event loop.
2086		2816
…		…
2088		2818
2089	=head3 Examples	2819	=head3 Examples
2090		2820
2091	Example: Try to get an embeddable event loop and embed it into the default	2821	Example: Try to get an embeddable event loop and embed it into the default
2092	event loop. If that is not possible, use the default loop. The default	2822	event loop. If that is not possible, use the default loop. The default
2093	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2823	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2094	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2824	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2095	used).	2825	used).
2096		2826
2097	struct ev_loop *loop_hi = ev_default_init (0);	2827	struct ev_loop *loop_hi = ev_default_init (0);
2098	struct ev_loop *loop_lo = 0;	2828	struct ev_loop *loop_lo = 0;
2099	struct ev_embed embed;	2829	ev_embed embed;
2100		2830
2101	// see if there is a chance of getting one that works	2831	// see if there is a chance of getting one that works
2102	// (remember that a flags value of 0 means autodetection)	2832	// (remember that a flags value of 0 means autodetection)
2103	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2833	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2104	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2834	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2105	: 0;	2835	: 0;
2106		2836
2107	// if we got one, then embed it, otherwise default to loop_hi	2837	// if we got one, then embed it, otherwise default to loop_hi
2108	if (loop_lo)	2838	if (loop_lo)
2109	{	2839	{
2110	ev_embed_init (&embed, 0, loop_lo);	2840	ev_embed_init (&embed, 0, loop_lo);
2111	ev_embed_start (loop_hi, &embed);	2841	ev_embed_start (loop_hi, &embed);
2112	}	2842	}
2113	else	2843	else
2114	loop_lo = loop_hi;	2844	loop_lo = loop_hi;
2115		2845
2116	Example: Check if kqueue is available but not recommended and create	2846	Example: Check if kqueue is available but not recommended and create
2117	a kqueue backend for use with sockets (which usually work with any	2847	a kqueue backend for use with sockets (which usually work with any
2118	kqueue implementation). Store the kqueue/socket-only event loop in	2848	kqueue implementation). Store the kqueue/socket-only event loop in
2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2849	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2120		2850
2121	struct ev_loop *loop = ev_default_init (0);	2851	struct ev_loop *loop = ev_default_init (0);
2122	struct ev_loop *loop_socket = 0;	2852	struct ev_loop *loop_socket = 0;
2123	struct ev_embed embed;	2853	ev_embed embed;
2124		2854
2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2855	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2856	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2127	{	2857	{
2128	ev_embed_init (&embed, 0, loop_socket);	2858	ev_embed_init (&embed, 0, loop_socket);
2129	ev_embed_start (loop, &embed);	2859	ev_embed_start (loop, &embed);
2130	}	2860	}
2131		2861
2132	if (!loop_socket)	2862	if (!loop_socket)
2133	loop_socket = loop;	2863	loop_socket = loop;
2134		2864
2135	// now use loop_socket for all sockets, and loop for everything else	2865	// now use loop_socket for all sockets, and loop for everything else
2136		2866
2137		2867
2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2868	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2139		2869
2140	Fork watchers are called when a C<fork ()> was detected (usually because	2870	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2143	event loop blocks next and before C<ev_check> watchers are being called,	2873	event loop blocks next and before C<ev_check> watchers are being called,
2144	and only in the child after the fork. If whoever good citizen calling	2874	and only in the child after the fork. If whoever good citizen calling
2145	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2875	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2146	handlers will be invoked, too, of course.	2876	handlers will be invoked, too, of course.
2147		2877
		2878	=head3 The special problem of life after fork - how is it possible?
		2879
		2880	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2881	up/change the process environment, followed by a call to C<exec()>. This
		2882	sequence should be handled by libev without any problems.
		2883
		2884	This changes when the application actually wants to do event handling
		2885	in the child, or both parent in child, in effect "continuing" after the
		2886	fork.
		2887
		2888	The default mode of operation (for libev, with application help to detect
		2889	forks) is to duplicate all the state in the child, as would be expected
		2890	when I<either> the parent I<or> the child process continues.
		2891
		2892	When both processes want to continue using libev, then this is usually the
		2893	wrong result. In that case, usually one process (typically the parent) is
		2894	supposed to continue with all watchers in place as before, while the other
		2895	process typically wants to start fresh, i.e. without any active watchers.
		2896
		2897	The cleanest and most efficient way to achieve that with libev is to
		2898	simply create a new event loop, which of course will be "empty", and
		2899	use that for new watchers. This has the advantage of not touching more
		2900	memory than necessary, and thus avoiding the copy-on-write, and the
		2901	disadvantage of having to use multiple event loops (which do not support
		2902	signal watchers).
		2903
		2904	When this is not possible, or you want to use the default loop for
		2905	other reasons, then in the process that wants to start "fresh", call
		2906	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2907	the default loop will "orphan" (not stop) all registered watchers, so you
		2908	have to be careful not to execute code that modifies those watchers. Note
		2909	also that in that case, you have to re-register any signal watchers.
		2910
2148	=head3 Watcher-Specific Functions and Data Members	2911	=head3 Watcher-Specific Functions and Data Members
2149		2912
2150	=over 4	2913	=over 4
2151		2914
2152	=item ev_fork_init (ev_signal *, callback)	2915	=item ev_fork_init (ev_signal *, callback)
…		…
2184	is that the author does not know of a simple (or any) algorithm for a	2947	is that the author does not know of a simple (or any) algorithm for a
2185	multiple-writer-single-reader queue that works in all cases and doesn't	2948	multiple-writer-single-reader queue that works in all cases and doesn't
2186	need elaborate support such as pthreads.	2949	need elaborate support such as pthreads.
2187		2950
2188	That means that if you want to queue data, you have to provide your own	2951	That means that if you want to queue data, you have to provide your own
2189	queue. But at least I can tell you would implement locking around your	2952	queue. But at least I can tell you how to implement locking around your
2190	queue:	2953	queue:
2191		2954
2192	=over 4	2955	=over 4
2193		2956
2194	=item queueing from a signal handler context	2957	=item queueing from a signal handler context
2195		2958
2196	To implement race-free queueing, you simply add to the queue in the signal	2959	To implement race-free queueing, you simply add to the queue in the signal
2197	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2960	handler but you block the signal handler in the watcher callback. Here is
2198	some fictitiuous SIGUSR1 handler:	2961	an example that does that for some fictitious SIGUSR1 handler:
2199		2962
2200	static ev_async mysig;	2963	static ev_async mysig;
2201		2964
2202	static void	2965	static void
2203	sigusr1_handler (void)	2966	sigusr1_handler (void)
…		…
2269	=over 4	3032	=over 4
2270		3033
2271	=item ev_async_init (ev_async *, callback)	3034	=item ev_async_init (ev_async *, callback)
2272		3035
2273	Initialises and configures the async watcher - it has no parameters of any	3036	Initialises and configures the async watcher - it has no parameters of any
2274	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3037	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2275	believe me.	3038	trust me.
2276		3039
2277	=item ev_async_send (loop, ev_async *)	3040	=item ev_async_send (loop, ev_async *)
2278		3041
2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3042	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2280	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3043	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2281	C<ev_feed_event>, this call is safe to do in other threads, signal or	3044	C<ev_feed_event>, this call is safe to do from other threads, signal or
2282	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3045	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2283	section below on what exactly this means).	3046	section below on what exactly this means).
2284		3047
		3048	Note that, as with other watchers in libev, multiple events might get
		3049	compressed into a single callback invocation (another way to look at this
		3050	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3051	reset when the event loop detects that).
		3052
2285	This call incurs the overhead of a syscall only once per loop iteration,	3053	This call incurs the overhead of a system call only once per event loop
2286	so while the overhead might be noticable, it doesn't apply to repeated	3054	iteration, so while the overhead might be noticeable, it doesn't apply to
2287	calls to C<ev_async_send>.	3055	repeated calls to C<ev_async_send> for the same event loop.
2288		3056
2289	=item bool = ev_async_pending (ev_async *)	3057	=item bool = ev_async_pending (ev_async *)
2290		3058
2291	Returns a non-zero value when C<ev_async_send> has been called on the	3059	Returns a non-zero value when C<ev_async_send> has been called on the
2292	watcher but the event has not yet been processed (or even noted) by the	3060	watcher but the event has not yet been processed (or even noted) by the
2293	event loop.	3061	event loop.
2294		3062
2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3063	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2296	the loop iterates next and checks for the watcher to have become active,	3064	the loop iterates next and checks for the watcher to have become active,
2297	it will reset the flag again. C<ev_async_pending> can be used to very	3065	it will reset the flag again. C<ev_async_pending> can be used to very
2298	quickly check wether invoking the loop might be a good idea.	3066	quickly check whether invoking the loop might be a good idea.
2299		3067
2300	Not that this does I<not> check wether the watcher itself is pending, only	3068	Not that this does I<not> check whether the watcher itself is pending,
2301	wether it has been requested to make this watcher pending.	3069	only whether it has been requested to make this watcher pending: there
		3070	is a time window between the event loop checking and resetting the async
		3071	notification, and the callback being invoked.
2302		3072
2303	=back	3073	=back
2304		3074
2305		3075
2306	=head1 OTHER FUNCTIONS	3076	=head1 OTHER FUNCTIONS
…		…
2310	=over 4	3080	=over 4
2311		3081
2312	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3082	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2313		3083
2314	This function combines a simple timer and an I/O watcher, calls your	3084	This function combines a simple timer and an I/O watcher, calls your
2315	callback on whichever event happens first and automatically stop both	3085	callback on whichever event happens first and automatically stops both
2316	watchers. This is useful if you want to wait for a single event on an fd	3086	watchers. This is useful if you want to wait for a single event on an fd
2317	or timeout without having to allocate/configure/start/stop/free one or	3087	or timeout without having to allocate/configure/start/stop/free one or
2318	more watchers yourself.	3088	more watchers yourself.
2319		3089
2320	If C<fd> is less than 0, then no I/O watcher will be started and events	3090	If C<fd> is less than 0, then no I/O watcher will be started and the
2321	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3091	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2322	C<events> set will be craeted and started.	3092	the given C<fd> and C<events> set will be created and started.
2323		3093
2324	If C<timeout> is less than 0, then no timeout watcher will be	3094	If C<timeout> is less than 0, then no timeout watcher will be
2325	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3095	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2326	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3096	repeat = 0) will be started. C<0> is a valid timeout.
2327	dubious value.
2328		3097
2329	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3098	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2330	passed an C<revents> set like normal event callbacks (a combination of	3099	passed an C<revents> set like normal event callbacks (a combination of
2331	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3100	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2332	value passed to C<ev_once>:	3101	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3102	a timeout and an io event at the same time - you probably should give io
		3103	events precedence.
2333		3104
		3105	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3106
2334	static void stdin_ready (int revents, void *arg)	3107	static void stdin_ready (int revents, void *arg)
2335	{	3108	{
2336	if (revents & EV_TIMEOUT)
2337	/* doh, nothing entered */;
2338	else if (revents & EV_READ)	3109	if (revents & EV_READ)
2339	/* stdin might have data for us, joy! */;	3110	/* stdin might have data for us, joy! */;
		3111	else if (revents & EV_TIMEOUT)
		3112	/* doh, nothing entered */;
2340	}	3113	}
2341		3114
2342	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3115	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2343		3116
2344	=item ev_feed_event (ev_loop *, watcher *, int revents)	3117	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2345		3118
2346	Feeds the given event set into the event loop, as if the specified event	3119	Feeds the given event set into the event loop, as if the specified event
2347	had happened for the specified watcher (which must be a pointer to an	3120	had happened for the specified watcher (which must be a pointer to an
2348	initialised but not necessarily started event watcher).	3121	initialised but not necessarily started event watcher).
2349		3122
2350	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3123	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2351		3124
2352	Feed an event on the given fd, as if a file descriptor backend detected	3125	Feed an event on the given fd, as if a file descriptor backend detected
2353	the given events it.	3126	the given events it.
2354		3127
2355	=item ev_feed_signal_event (ev_loop *loop, int signum)	3128	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2356		3129
2357	Feed an event as if the given signal occured (C<loop> must be the default	3130	Feed an event as if the given signal occurred (C<loop> must be the default
2358	loop!).	3131	loop!).
2359		3132
2360	=back	3133	=back
2361		3134
2362		3135
…		…
2391	=back	3164	=back
2392		3165
2393	=head1 C++ SUPPORT	3166	=head1 C++ SUPPORT
2394		3167
2395	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3168	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2396	you to use some convinience methods to start/stop watchers and also change	3169	you to use some convenience methods to start/stop watchers and also change
2397	the callback model to a model using method callbacks on objects.	3170	the callback model to a model using method callbacks on objects.
2398		3171
2399	To use it,	3172	To use it,
2400		3173
2401	#include <ev++.h>	3174	#include <ev++.h>
2402		3175
2403	This automatically includes F<ev.h> and puts all of its definitions (many	3176	This automatically includes F<ev.h> and puts all of its definitions (many
2404	of them macros) into the global namespace. All C++ specific things are	3177	of them macros) into the global namespace. All C++ specific things are
2405	put into the C<ev> namespace. It should support all the same embedding	3178	put into the C<ev> namespace. It should support all the same embedding
2406	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3179	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2473	your compiler is good :), then the method will be fully inlined into the	3246	your compiler is good :), then the method will be fully inlined into the
2474	thunking function, making it as fast as a direct C callback.	3247	thunking function, making it as fast as a direct C callback.
2475		3248
2476	Example: simple class declaration and watcher initialisation	3249	Example: simple class declaration and watcher initialisation
2477		3250
2478	struct myclass	3251	struct myclass
2479	{	3252	{
2480	void io_cb (ev::io &w, int revents) { }	3253	void io_cb (ev::io &w, int revents) { }
2481	}	3254	}
2482		3255
2483	myclass obj;	3256	myclass obj;
2484	ev::io iow;	3257	ev::io iow;
2485	iow.set <myclass, &myclass::io_cb> (&obj);	3258	iow.set <myclass, &myclass::io_cb> (&obj);
		3259
		3260	=item w->set (object *)
		3261
		3262	This is an B<experimental> feature that might go away in a future version.
		3263
		3264	This is a variation of a method callback - leaving out the method to call
		3265	will default the method to C<operator ()>, which makes it possible to use
		3266	functor objects without having to manually specify the C<operator ()> all
		3267	the time. Incidentally, you can then also leave out the template argument
		3268	list.
		3269
		3270	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3271	int revents)>.
		3272
		3273	See the method-C<set> above for more details.
		3274
		3275	Example: use a functor object as callback.
		3276
		3277	struct myfunctor
		3278	{
		3279	void operator() (ev::io &w, int revents)
		3280	{
		3281	...
		3282	}
		3283	}
		3284
		3285	myfunctor f;
		3286
		3287	ev::io w;
		3288	w.set (&f);
2486		3289
2487	=item w->set<function> (void *data = 0)	3290	=item w->set<function> (void *data = 0)
2488		3291
2489	Also sets a callback, but uses a static method or plain function as	3292	Also sets a callback, but uses a static method or plain function as
2490	callback. The optional C<data> argument will be stored in the watcher's	3293	callback. The optional C<data> argument will be stored in the watcher's
…		…
2492		3295
2493	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3296	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2494		3297
2495	See the method-C<set> above for more details.	3298	See the method-C<set> above for more details.
2496		3299
2497	Example:	3300	Example: Use a plain function as callback.
2498		3301
2499	static void io_cb (ev::io &w, int revents) { }	3302	static void io_cb (ev::io &w, int revents) { }
2500	iow.set <io_cb> ();	3303	iow.set <io_cb> ();
2501		3304
2502	=item w->set (struct ev_loop *)	3305	=item w->set (struct ev_loop *)
2503		3306
2504	Associates a different C<struct ev_loop> with this watcher. You can only	3307	Associates a different C<struct ev_loop> with this watcher. You can only
2505	do this when the watcher is inactive (and not pending either).	3308	do this when the watcher is inactive (and not pending either).
2506		3309
2507	=item w->set ([args])	3310	=item w->set ([arguments])
2508		3311
2509	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3312	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2510	called at least once. Unlike the C counterpart, an active watcher gets	3313	called at least once. Unlike the C counterpart, an active watcher gets
2511	automatically stopped and restarted when reconfiguring it with this	3314	automatically stopped and restarted when reconfiguring it with this
2512	method.	3315	method.
2513		3316
2514	=item w->start ()	3317	=item w->start ()
…		…
2538	=back	3341	=back
2539		3342
2540	Example: Define a class with an IO and idle watcher, start one of them in	3343	Example: Define a class with an IO and idle watcher, start one of them in
2541	the constructor.	3344	the constructor.
2542		3345
2543	class myclass	3346	class myclass
2544	{	3347	{
2545	ev::io io; void io_cb (ev::io &w, int revents);	3348	ev::io io ; void io_cb (ev::io &w, int revents);
2546	ev:idle idle void idle_cb (ev::idle &w, int revents);	3349	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2547		3350
2548	myclass (int fd)	3351	myclass (int fd)
2549	{	3352	{
2550	io .set <myclass, &myclass::io_cb > (this);	3353	io .set <myclass, &myclass::io_cb > (this);
2551	idle.set <myclass, &myclass::idle_cb> (this);	3354	idle.set <myclass, &myclass::idle_cb> (this);
2552		3355
2553	io.start (fd, ev::READ);	3356	io.start (fd, ev::READ);
2554	}	3357	}
2555	};	3358	};
2556		3359
2557		3360
2558	=head1 OTHER LANGUAGE BINDINGS	3361	=head1 OTHER LANGUAGE BINDINGS
2559		3362
2560	Libev does not offer other language bindings itself, but bindings for a	3363	Libev does not offer other language bindings itself, but bindings for a
2561	numbe rof languages exist in the form of third-party packages. If you know	3364	number of languages exist in the form of third-party packages. If you know
2562	any interesting language binding in addition to the ones listed here, drop	3365	any interesting language binding in addition to the ones listed here, drop
2563	me a note.	3366	me a note.
2564		3367
2565	=over 4	3368	=over 4
2566		3369
2567	=item Perl	3370	=item Perl
2568		3371
2569	The EV module implements the full libev API and is actually used to test	3372	The EV module implements the full libev API and is actually used to test
2570	libev. EV is developed together with libev. Apart from the EV core module,	3373	libev. EV is developed together with libev. Apart from the EV core module,
2571	there are additional modules that implement libev-compatible interfaces	3374	there are additional modules that implement libev-compatible interfaces
2572	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3375	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2573	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3376	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3377	and C<EV::Glib>).
2574		3378
2575	It can be found and installed via CPAN, its homepage is found at	3379	It can be found and installed via CPAN, its homepage is at
2576	L<http://software.schmorp.de/pkg/EV>.	3380	L<http://software.schmorp.de/pkg/EV>.
2577		3381
		3382	=item Python
		3383
		3384	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3385	seems to be quite complete and well-documented.
		3386
2578	=item Ruby	3387	=item Ruby
2579		3388
2580	Tony Arcieri has written a ruby extension that offers access to a subset	3389	Tony Arcieri has written a ruby extension that offers access to a subset
2581	of the libev API and adds filehandle abstractions, asynchronous DNS and	3390	of the libev API and adds file handle abstractions, asynchronous DNS and
2582	more on top of it. It can be found via gem servers. Its homepage is at	3391	more on top of it. It can be found via gem servers. Its homepage is at
2583	L<http://rev.rubyforge.org/>.	3392	L<http://rev.rubyforge.org/>.
2584		3393
		3394	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3395	makes rev work even on mingw.
		3396
		3397	=item Haskell
		3398
		3399	A haskell binding to libev is available at
		3400	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3401
2585	=item D	3402	=item D
2586		3403
2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3404	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2588	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3405	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3406
		3407	=item Ocaml
		3408
		3409	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3410	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3411
		3412	=item Lua
		3413
		3414	Brian Maher has written a partial interface to libev
		3415	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3416	L<http://github.com/brimworks/lua-ev>.
2589		3417
2590	=back	3418	=back
2591		3419
2592		3420
2593	=head1 MACRO MAGIC	3421	=head1 MACRO MAGIC
2594		3422
2595	Libev can be compiled with a variety of options, the most fundamantal	3423	Libev can be compiled with a variety of options, the most fundamental
2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3424	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2597	functions and callbacks have an initial C<struct ev_loop *> argument.	3425	functions and callbacks have an initial C<struct ev_loop *> argument.
2598		3426
2599	To make it easier to write programs that cope with either variant, the	3427	To make it easier to write programs that cope with either variant, the
2600	following macros are defined:	3428	following macros are defined:
…		…
2605		3433
2606	This provides the loop I<argument> for functions, if one is required ("ev	3434	This provides the loop I<argument> for functions, if one is required ("ev
2607	loop argument"). The C<EV_A> form is used when this is the sole argument,	3435	loop argument"). The C<EV_A> form is used when this is the sole argument,
2608	C<EV_A_> is used when other arguments are following. Example:	3436	C<EV_A_> is used when other arguments are following. Example:
2609		3437
2610	ev_unref (EV_A);	3438	ev_unref (EV_A);
2611	ev_timer_add (EV_A_ watcher);	3439	ev_timer_add (EV_A_ watcher);
2612	ev_loop (EV_A_ 0);	3440	ev_loop (EV_A_ 0);
2613		3441
2614	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3442	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2615	which is often provided by the following macro.	3443	which is often provided by the following macro.
2616		3444
2617	=item C<EV_P>, C<EV_P_>	3445	=item C<EV_P>, C<EV_P_>
2618		3446
2619	This provides the loop I<parameter> for functions, if one is required ("ev	3447	This provides the loop I<parameter> for functions, if one is required ("ev
2620	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3448	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2621	C<EV_P_> is used when other parameters are following. Example:	3449	C<EV_P_> is used when other parameters are following. Example:
2622		3450
2623	// this is how ev_unref is being declared	3451	// this is how ev_unref is being declared
2624	static void ev_unref (EV_P);	3452	static void ev_unref (EV_P);
2625		3453
2626	// this is how you can declare your typical callback	3454	// this is how you can declare your typical callback
2627	static void cb (EV_P_ ev_timer *w, int revents)	3455	static void cb (EV_P_ ev_timer *w, int revents)
2628		3456
2629	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3457	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2630	suitable for use with C<EV_A>.	3458	suitable for use with C<EV_A>.
2631		3459
2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3460	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2648		3476
2649	Example: Declare and initialise a check watcher, utilising the above	3477	Example: Declare and initialise a check watcher, utilising the above
2650	macros so it will work regardless of whether multiple loops are supported	3478	macros so it will work regardless of whether multiple loops are supported
2651	or not.	3479	or not.
2652		3480
2653	static void	3481	static void
2654	check_cb (EV_P_ ev_timer *w, int revents)	3482	check_cb (EV_P_ ev_timer *w, int revents)
2655	{	3483	{
2656	ev_check_stop (EV_A_ w);	3484	ev_check_stop (EV_A_ w);
2657	}	3485	}
2658		3486
2659	ev_check check;	3487	ev_check check;
2660	ev_check_init (&check, check_cb);	3488	ev_check_init (&check, check_cb);
2661	ev_check_start (EV_DEFAULT_ &check);	3489	ev_check_start (EV_DEFAULT_ &check);
2662	ev_loop (EV_DEFAULT_ 0);	3490	ev_loop (EV_DEFAULT_ 0);
2663		3491
2664	=head1 EMBEDDING	3492	=head1 EMBEDDING
2665		3493
2666	Libev can (and often is) directly embedded into host	3494	Libev can (and often is) directly embedded into host
2667	applications. Examples of applications that embed it include the Deliantra	3495	applications. Examples of applications that embed it include the Deliantra
…		…
2674	libev somewhere in your source tree).	3502	libev somewhere in your source tree).
2675		3503
2676	=head2 FILESETS	3504	=head2 FILESETS
2677		3505
2678	Depending on what features you need you need to include one or more sets of files	3506	Depending on what features you need you need to include one or more sets of files
2679	in your app.	3507	in your application.
2680		3508
2681	=head3 CORE EVENT LOOP	3509	=head3 CORE EVENT LOOP
2682		3510
2683	To include only the libev core (all the C<ev_*> functions), with manual	3511	To include only the libev core (all the C<ev_*> functions), with manual
2684	configuration (no autoconf):	3512	configuration (no autoconf):
2685		3513
2686	#define EV_STANDALONE 1	3514	#define EV_STANDALONE 1
2687	#include "ev.c"	3515	#include "ev.c"
2688		3516
2689	This will automatically include F<ev.h>, too, and should be done in a	3517	This will automatically include F<ev.h>, too, and should be done in a
2690	single C source file only to provide the function implementations. To use	3518	single C source file only to provide the function implementations. To use
2691	it, do the same for F<ev.h> in all files wishing to use this API (best	3519	it, do the same for F<ev.h> in all files wishing to use this API (best
2692	done by writing a wrapper around F<ev.h> that you can include instead and	3520	done by writing a wrapper around F<ev.h> that you can include instead and
2693	where you can put other configuration options):	3521	where you can put other configuration options):
2694		3522
2695	#define EV_STANDALONE 1	3523	#define EV_STANDALONE 1
2696	#include "ev.h"	3524	#include "ev.h"
2697		3525
2698	Both header files and implementation files can be compiled with a C++	3526	Both header files and implementation files can be compiled with a C++
2699	compiler (at least, thats a stated goal, and breakage will be treated	3527	compiler (at least, that's a stated goal, and breakage will be treated
2700	as a bug).	3528	as a bug).
2701		3529
2702	You need the following files in your source tree, or in a directory	3530	You need the following files in your source tree, or in a directory
2703	in your include path (e.g. in libev/ when using -Ilibev):	3531	in your include path (e.g. in libev/ when using -Ilibev):
2704		3532
2705	ev.h	3533	ev.h
2706	ev.c	3534	ev.c
2707	ev_vars.h	3535	ev_vars.h
2708	ev_wrap.h	3536	ev_wrap.h
2709		3537
2710	ev_win32.c required on win32 platforms only	3538	ev_win32.c required on win32 platforms only
2711		3539
2712	ev_select.c only when select backend is enabled (which is enabled by default)	3540	ev_select.c only when select backend is enabled (which is enabled by default)
2713	ev_poll.c only when poll backend is enabled (disabled by default)	3541	ev_poll.c only when poll backend is enabled (disabled by default)
2714	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3542	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2715	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3543	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2716	ev_port.c only when the solaris port backend is enabled (disabled by default)	3544	ev_port.c only when the solaris port backend is enabled (disabled by default)
2717		3545
2718	F<ev.c> includes the backend files directly when enabled, so you only need	3546	F<ev.c> includes the backend files directly when enabled, so you only need
2719	to compile this single file.	3547	to compile this single file.
2720		3548
2721	=head3 LIBEVENT COMPATIBILITY API	3549	=head3 LIBEVENT COMPATIBILITY API
2722		3550
2723	To include the libevent compatibility API, also include:	3551	To include the libevent compatibility API, also include:
2724		3552
2725	#include "event.c"	3553	#include "event.c"
2726		3554
2727	in the file including F<ev.c>, and:	3555	in the file including F<ev.c>, and:
2728		3556
2729	#include "event.h"	3557	#include "event.h"
2730		3558
2731	in the files that want to use the libevent API. This also includes F<ev.h>.	3559	in the files that want to use the libevent API. This also includes F<ev.h>.
2732		3560
2733	You need the following additional files for this:	3561	You need the following additional files for this:
2734		3562
2735	event.h	3563	event.h
2736	event.c	3564	event.c
2737		3565
2738	=head3 AUTOCONF SUPPORT	3566	=head3 AUTOCONF SUPPORT
2739		3567
2740	Instead of using C<EV_STANDALONE=1> and providing your config in	3568	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2741	whatever way you want, you can also C<m4_include([libev.m4])> in your	3569	whatever way you want, you can also C<m4_include([libev.m4])> in your
2742	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3570	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2743	include F<config.h> and configure itself accordingly.	3571	include F<config.h> and configure itself accordingly.
2744		3572
2745	For this of course you need the m4 file:	3573	For this of course you need the m4 file:
2746		3574
2747	libev.m4	3575	libev.m4
2748		3576
2749	=head2 PREPROCESSOR SYMBOLS/MACROS	3577	=head2 PREPROCESSOR SYMBOLS/MACROS
2750		3578
2751	Libev can be configured via a variety of preprocessor symbols you have to	3579	Libev can be configured via a variety of preprocessor symbols you have to
2752	define before including any of its files. The default in the absense of	3580	define before including any of its files. The default in the absence of
2753	autoconf is noted for every option.	3581	autoconf is documented for every option.
2754		3582
2755	=over 4	3583	=over 4
2756		3584
2757	=item EV_STANDALONE	3585	=item EV_STANDALONE
2758		3586
…		…
2760	keeps libev from including F<config.h>, and it also defines dummy	3588	keeps libev from including F<config.h>, and it also defines dummy
2761	implementations for some libevent functions (such as logging, which is not	3589	implementations for some libevent functions (such as logging, which is not
2762	supported). It will also not define any of the structs usually found in	3590	supported). It will also not define any of the structs usually found in
2763	F<event.h> that are not directly supported by the libev core alone.	3591	F<event.h> that are not directly supported by the libev core alone.
2764		3592
		3593	In standalone mode, libev will still try to automatically deduce the
		3594	configuration, but has to be more conservative.
		3595
2765	=item EV_USE_MONOTONIC	3596	=item EV_USE_MONOTONIC
2766		3597
2767	If defined to be C<1>, libev will try to detect the availability of the	3598	If defined to be C<1>, libev will try to detect the availability of the
2768	monotonic clock option at both compiletime and runtime. Otherwise no use	3599	monotonic clock option at both compile time and runtime. Otherwise no
2769	of the monotonic clock option will be attempted. If you enable this, you	3600	use of the monotonic clock option will be attempted. If you enable this,
2770	usually have to link against librt or something similar. Enabling it when	3601	you usually have to link against librt or something similar. Enabling it
2771	the functionality isn't available is safe, though, although you have	3602	when the functionality isn't available is safe, though, although you have
2772	to make sure you link against any libraries where the C<clock_gettime>	3603	to make sure you link against any libraries where the C<clock_gettime>
2773	function is hiding in (often F<-lrt>).	3604	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2774		3605
2775	=item EV_USE_REALTIME	3606	=item EV_USE_REALTIME
2776		3607
2777	If defined to be C<1>, libev will try to detect the availability of the	3608	If defined to be C<1>, libev will try to detect the availability of the
2778	realtime clock option at compiletime (and assume its availability at	3609	real-time clock option at compile time (and assume its availability
2779	runtime if successful). Otherwise no use of the realtime clock option will	3610	at runtime if successful). Otherwise no use of the real-time clock
2780	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3611	option will be attempted. This effectively replaces C<gettimeofday>
2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3612	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3613	correctness. See the note about libraries in the description of
		3614	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3615	C<EV_USE_CLOCK_SYSCALL>.
		3616
		3617	=item EV_USE_CLOCK_SYSCALL
		3618
		3619	If defined to be C<1>, libev will try to use a direct syscall instead
		3620	of calling the system-provided C<clock_gettime> function. This option
		3621	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3622	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3623	programs needlessly. Using a direct syscall is slightly slower (in
		3624	theory), because no optimised vdso implementation can be used, but avoids
		3625	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3626	higher, as it simplifies linking (no need for C<-lrt>).
2783		3627
2784	=item EV_USE_NANOSLEEP	3628	=item EV_USE_NANOSLEEP
2785		3629
2786	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3630	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2787	and will use it for delays. Otherwise it will use C<select ()>.	3631	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2795	2.7 or newer, otherwise disabled.	3639	2.7 or newer, otherwise disabled.
2796		3640
2797	=item EV_USE_SELECT	3641	=item EV_USE_SELECT
2798		3642
2799	If undefined or defined to be C<1>, libev will compile in support for the	3643	If undefined or defined to be C<1>, libev will compile in support for the
2800	C<select>(2) backend. No attempt at autodetection will be done: if no	3644	C<select>(2) backend. No attempt at auto-detection will be done: if no
2801	other method takes over, select will be it. Otherwise the select backend	3645	other method takes over, select will be it. Otherwise the select backend
2802	will not be compiled in.	3646	will not be compiled in.
2803		3647
2804	=item EV_SELECT_USE_FD_SET	3648	=item EV_SELECT_USE_FD_SET
2805		3649
2806	If defined to C<1>, then the select backend will use the system C<fd_set>	3650	If defined to C<1>, then the select backend will use the system C<fd_set>
2807	structure. This is useful if libev doesn't compile due to a missing	3651	structure. This is useful if libev doesn't compile due to a missing
2808	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3652	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2809	exotic systems. This usually limits the range of file descriptors to some	3653	on exotic systems. This usually limits the range of file descriptors to
2810	low limit such as 1024 or might have other limitations (winsocket only	3654	some low limit such as 1024 or might have other limitations (winsocket
2811	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3655	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2812	influence the size of the C<fd_set> used.	3656	configures the maximum size of the C<fd_set>.
2813		3657
2814	=item EV_SELECT_IS_WINSOCKET	3658	=item EV_SELECT_IS_WINSOCKET
2815		3659
2816	When defined to C<1>, the select backend will assume that	3660	When defined to C<1>, the select backend will assume that
2817	select/socket/connect etc. don't understand file descriptors but	3661	select/socket/connect etc. don't understand file descriptors but
…		…
2862	otherwise another method will be used as fallback. This is the preferred	3706	otherwise another method will be used as fallback. This is the preferred
2863	backend for Solaris 10 systems.	3707	backend for Solaris 10 systems.
2864		3708
2865	=item EV_USE_DEVPOLL	3709	=item EV_USE_DEVPOLL
2866		3710
2867	reserved for future expansion, works like the USE symbols above.	3711	Reserved for future expansion, works like the USE symbols above.
2868		3712
2869	=item EV_USE_INOTIFY	3713	=item EV_USE_INOTIFY
2870		3714
2871	If defined to be C<1>, libev will compile in support for the Linux inotify	3715	If defined to be C<1>, libev will compile in support for the Linux inotify
2872	interface to speed up C<ev_stat> watchers. Its actual availability will	3716	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2879	access is atomic with respect to other threads or signal contexts. No such	3723	access is atomic with respect to other threads or signal contexts. No such
2880	type is easily found in the C language, so you can provide your own type	3724	type is easily found in the C language, so you can provide your own type
2881	that you know is safe for your purposes. It is used both for signal handler "locking"	3725	that you know is safe for your purposes. It is used both for signal handler "locking"
2882	as well as for signal and thread safety in C<ev_async> watchers.	3726	as well as for signal and thread safety in C<ev_async> watchers.
2883		3727
2884	In the absense of this define, libev will use C<sig_atomic_t volatile>	3728	In the absence of this define, libev will use C<sig_atomic_t volatile>
2885	(from F<signal.h>), which is usually good enough on most platforms.	3729	(from F<signal.h>), which is usually good enough on most platforms.
2886		3730
2887	=item EV_H	3731	=item EV_H
2888		3732
2889	The name of the F<ev.h> header file used to include it. The default if	3733	The name of the F<ev.h> header file used to include it. The default if
…		…
2928	When doing priority-based operations, libev usually has to linearly search	3772	When doing priority-based operations, libev usually has to linearly search
2929	all the priorities, so having many of them (hundreds) uses a lot of space	3773	all the priorities, so having many of them (hundreds) uses a lot of space
2930	and time, so using the defaults of five priorities (-2 .. +2) is usually	3774	and time, so using the defaults of five priorities (-2 .. +2) is usually
2931	fine.	3775	fine.
2932		3776
2933	If your embedding app does not need any priorities, defining these both to	3777	If your embedding application does not need any priorities, defining these
2934	C<0> will save some memory and cpu.	3778	both to C<0> will save some memory and CPU.
2935		3779
2936	=item EV_PERIODIC_ENABLE	3780	=item EV_PERIODIC_ENABLE
2937		3781
2938	If undefined or defined to be C<1>, then periodic timers are supported. If	3782	If undefined or defined to be C<1>, then periodic timers are supported. If
2939	defined to be C<0>, then they are not. Disabling them saves a few kB of	3783	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2946	code.	3790	code.
2947		3791
2948	=item EV_EMBED_ENABLE	3792	=item EV_EMBED_ENABLE
2949		3793
2950	If undefined or defined to be C<1>, then embed watchers are supported. If	3794	If undefined or defined to be C<1>, then embed watchers are supported. If
2951	defined to be C<0>, then they are not.	3795	defined to be C<0>, then they are not. Embed watchers rely on most other
		3796	watcher types, which therefore must not be disabled.
2952		3797
2953	=item EV_STAT_ENABLE	3798	=item EV_STAT_ENABLE
2954		3799
2955	If undefined or defined to be C<1>, then stat watchers are supported. If	3800	If undefined or defined to be C<1>, then stat watchers are supported. If
2956	defined to be C<0>, then they are not.	3801	defined to be C<0>, then they are not.
…		…
2966	defined to be C<0>, then they are not.	3811	defined to be C<0>, then they are not.
2967		3812
2968	=item EV_MINIMAL	3813	=item EV_MINIMAL
2969		3814
2970	If you need to shave off some kilobytes of code at the expense of some	3815	If you need to shave off some kilobytes of code at the expense of some
2971	speed, define this symbol to C<1>. Currently only used for gcc to override	3816	speed (but with the full API), define this symbol to C<1>. Currently this
2972	some inlining decisions, saves roughly 30% codesize of amd64.	3817	is used to override some inlining decisions, saves roughly 30% code size
		3818	on amd64. It also selects a much smaller 2-heap for timer management over
		3819	the default 4-heap.
		3820
		3821	You can save even more by disabling watcher types you do not need
		3822	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3823	(C<-DNDEBUG>) will usually reduce code size a lot.
		3824
		3825	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3826	provide a bare-bones event library. See C<ev.h> for details on what parts
		3827	of the API are still available, and do not complain if this subset changes
		3828	over time.
		3829
		3830	=item EV_NSIG
		3831
		3832	The highest supported signal number, +1 (or, the number of
		3833	signals): Normally, libev tries to deduce the maximum number of signals
		3834	automatically, but sometimes this fails, in which case it can be
		3835	specified. Also, using a lower number than detected (C<32> should be
		3836	good for about any system in existance) can save some memory, as libev
		3837	statically allocates some 12-24 bytes per signal number.
2973		3838
2974	=item EV_PID_HASHSIZE	3839	=item EV_PID_HASHSIZE
2975		3840
2976	C<ev_child> watchers use a small hash table to distribute workload by	3841	C<ev_child> watchers use a small hash table to distribute workload by
2977	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3842	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3849	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2985	usually more than enough. If you need to manage thousands of C<ev_stat>	3850	usually more than enough. If you need to manage thousands of C<ev_stat>
2986	watchers you might want to increase this value (I<must> be a power of	3851	watchers you might want to increase this value (I<must> be a power of
2987	two).	3852	two).
2988		3853
		3854	=item EV_USE_4HEAP
		3855
		3856	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3857	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3858	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3859	faster performance with many (thousands) of watchers.
		3860
		3861	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3862	(disabled).
		3863
		3864	=item EV_HEAP_CACHE_AT
		3865
		3866	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3867	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3868	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3869	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3870	but avoids random read accesses on heap changes. This improves performance
		3871	noticeably with many (hundreds) of watchers.
		3872
		3873	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3874	(disabled).
		3875
		3876	=item EV_VERIFY
		3877
		3878	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3879	be done: If set to C<0>, no internal verification code will be compiled
		3880	in. If set to C<1>, then verification code will be compiled in, but not
		3881	called. If set to C<2>, then the internal verification code will be
		3882	called once per loop, which can slow down libev. If set to C<3>, then the
		3883	verification code will be called very frequently, which will slow down
		3884	libev considerably.
		3885
		3886	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3887	C<0>.
		3888
2989	=item EV_COMMON	3889	=item EV_COMMON
2990		3890
2991	By default, all watchers have a C<void *data> member. By redefining	3891	By default, all watchers have a C<void *data> member. By redefining
2992	this macro to a something else you can include more and other types of	3892	this macro to a something else you can include more and other types of
2993	members. You have to define it each time you include one of the files,	3893	members. You have to define it each time you include one of the files,
2994	though, and it must be identical each time.	3894	though, and it must be identical each time.
2995		3895
2996	For example, the perl EV module uses something like this:	3896	For example, the perl EV module uses something like this:
2997		3897
2998	#define EV_COMMON \	3898	#define EV_COMMON \
2999	SV *self; /* contains this struct */ \	3899	SV *self; /* contains this struct */ \
3000	SV *cb_sv, *fh /* note no trailing ";" */	3900	SV *cb_sv, *fh /* note no trailing ";" */
3001		3901
3002	=item EV_CB_DECLARE (type)	3902	=item EV_CB_DECLARE (type)
3003		3903
3004	=item EV_CB_INVOKE (watcher, revents)	3904	=item EV_CB_INVOKE (watcher, revents)
3005		3905
…		…
3010	definition and a statement, respectively. See the F<ev.h> header file for	3910	definition and a statement, respectively. See the F<ev.h> header file for
3011	their default definitions. One possible use for overriding these is to	3911	their default definitions. One possible use for overriding these is to
3012	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3912	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3013	method calls instead of plain function calls in C++.	3913	method calls instead of plain function calls in C++.
3014		3914
		3915	=back
		3916
3015	=head2 EXPORTED API SYMBOLS	3917	=head2 EXPORTED API SYMBOLS
3016		3918
3017	If you need to re-export the API (e.g. via a dll) and you need a list of	3919	If you need to re-export the API (e.g. via a DLL) and you need a list of
3018	exported symbols, you can use the provided F<Symbol.*> files which list	3920	exported symbols, you can use the provided F<Symbol.*> files which list
3019	all public symbols, one per line:	3921	all public symbols, one per line:
3020		3922
3021	Symbols.ev for libev proper	3923	Symbols.ev for libev proper
3022	Symbols.event for the libevent emulation	3924	Symbols.event for the libevent emulation
3023		3925
3024	This can also be used to rename all public symbols to avoid clashes with	3926	This can also be used to rename all public symbols to avoid clashes with
3025	multiple versions of libev linked together (which is obviously bad in	3927	multiple versions of libev linked together (which is obviously bad in
3026	itself, but sometimes it is inconvinient to avoid this).	3928	itself, but sometimes it is inconvenient to avoid this).
3027		3929
3028	A sed command like this will create wrapper C<#define>'s that you need to	3930	A sed command like this will create wrapper C<#define>'s that you need to
3029	include before including F<ev.h>:	3931	include before including F<ev.h>:
3030		3932
3031	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3933	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3048	file.	3950	file.
3049		3951
3050	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3952	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3051	that everybody includes and which overrides some configure choices:	3953	that everybody includes and which overrides some configure choices:
3052		3954
3053	#define EV_MINIMAL 1	3955	#define EV_MINIMAL 1
3054	#define EV_USE_POLL 0	3956	#define EV_USE_POLL 0
3055	#define EV_MULTIPLICITY 0	3957	#define EV_MULTIPLICITY 0
3056	#define EV_PERIODIC_ENABLE 0	3958	#define EV_PERIODIC_ENABLE 0
3057	#define EV_STAT_ENABLE 0	3959	#define EV_STAT_ENABLE 0
3058	#define EV_FORK_ENABLE 0	3960	#define EV_FORK_ENABLE 0
3059	#define EV_CONFIG_H <config.h>	3961	#define EV_CONFIG_H <config.h>
3060	#define EV_MINPRI 0	3962	#define EV_MINPRI 0
3061	#define EV_MAXPRI 0	3963	#define EV_MAXPRI 0
3062		3964
3063	#include "ev++.h"	3965	#include "ev++.h"
3064		3966
3065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3967	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3066		3968
3067	#include "ev_cpp.h"	3969	#include "ev_cpp.h"
3068	#include "ev.c"	3970	#include "ev.c"
3069		3971
		3972	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3070		3973
3071	=head1 THREADS AND COROUTINES	3974	=head2 THREADS AND COROUTINES
3072		3975
3073	=head2 THREADS	3976	=head3 THREADS
3074		3977
3075	Libev itself is completely threadsafe, but it uses no locking. This	3978	All libev functions are reentrant and thread-safe unless explicitly
		3979	documented otherwise, but libev implements no locking itself. This means
3076	means that you can use as many loops as you want in parallel, as long as	3980	that you can use as many loops as you want in parallel, as long as there
3077	only one thread ever calls into one libev function with the same loop	3981	are no concurrent calls into any libev function with the same loop
3078	parameter.	3982	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3983	of course): libev guarantees that different event loops share no data
		3984	structures that need any locking.
3079		3985
3080	Or put differently: calls with different loop parameters can be done in	3986	Or to put it differently: calls with different loop parameters can be done
3081	parallel from multiple threads, calls with the same loop parameter must be	3987	concurrently from multiple threads, calls with the same loop parameter
3082	done serially (but can be done from different threads, as long as only one	3988	must be done serially (but can be done from different threads, as long as
3083	thread ever is inside a call at any point in time, e.g. by using a mutex	3989	only one thread ever is inside a call at any point in time, e.g. by using
3084	per loop).	3990	a mutex per loop).
3085		3991
3086	If you want to know which design is best for your problem, then I cannot	3992	Specifically to support threads (and signal handlers), libev implements
		3993	so-called C<ev_async> watchers, which allow some limited form of
		3994	concurrency on the same event loop, namely waking it up "from the
		3995	outside".
		3996
		3997	If you want to know which design (one loop, locking, or multiple loops
		3998	without or something else still) is best for your problem, then I cannot
3087	help you but by giving some generic advice:	3999	help you, but here is some generic advice:
3088		4000
3089	=over 4	4001	=over 4
3090		4002
3091	=item * most applications have a main thread: use the default libev loop	4003	=item * most applications have a main thread: use the default libev loop
3092	in that thread, or create a seperate thread running only the default loop.	4004	in that thread, or create a separate thread running only the default loop.
3093		4005
3094	This helps integrating other libraries or software modules that use libev	4006	This helps integrating other libraries or software modules that use libev
3095	themselves and don't care/know about threading.	4007	themselves and don't care/know about threading.
3096		4008
3097	=item * one loop per thread is usually a good model.	4009	=item * one loop per thread is usually a good model.
3098		4010
3099	Doing this is almost never wrong, sometimes a better-performance model	4011	Doing this is almost never wrong, sometimes a better-performance model
3100	exists, but it is always a good start.	4012	exists, but it is always a good start.
3101		4013
3102	=item * other models exist, such as the leader/follower pattern, where one	4014	=item * other models exist, such as the leader/follower pattern, where one
3103	loop is handed through multiple threads in a kind of round-robbin fashion.	4015	loop is handed through multiple threads in a kind of round-robin fashion.
3104		4016
3105	Chosing a model is hard - look around, learn, know that usually you cna do	4017	Choosing a model is hard - look around, learn, know that usually you can do
3106	better than you currently do :-)	4018	better than you currently do :-)
3107		4019
3108	=item * often you need to talk to some other thread which blocks in the	4020	=item * often you need to talk to some other thread which blocks in the
		4021	event loop.
		4022
3109	event loop - C<ev_async> watchers can be used to wake them up from other	4023	C<ev_async> watchers can be used to wake them up from other threads safely
3110	threads safely (or from signal contexts...).	4024	(or from signal contexts...).
		4025
		4026	An example use would be to communicate signals or other events that only
		4027	work in the default loop by registering the signal watcher with the
		4028	default loop and triggering an C<ev_async> watcher from the default loop
		4029	watcher callback into the event loop interested in the signal.
3111		4030
3112	=back	4031	=back
3113		4032
		4033	=head4 THREAD LOCKING EXAMPLE
		4034
		4035	Here is a fictitious example of how to run an event loop in a different
		4036	thread than where callbacks are being invoked and watchers are
		4037	created/added/removed.
		4038
		4039	For a real-world example, see the C<EV::Loop::Async> perl module,
		4040	which uses exactly this technique (which is suited for many high-level
		4041	languages).
		4042
		4043	The example uses a pthread mutex to protect the loop data, a condition
		4044	variable to wait for callback invocations, an async watcher to notify the
		4045	event loop thread and an unspecified mechanism to wake up the main thread.
		4046
		4047	First, you need to associate some data with the event loop:
		4048
		4049	typedef struct {
		4050	mutex_t lock; /* global loop lock */
		4051	ev_async async_w;
		4052	thread_t tid;
		4053	cond_t invoke_cv;
		4054	} userdata;
		4055
		4056	void prepare_loop (EV_P)
		4057	{
		4058	// for simplicity, we use a static userdata struct.
		4059	static userdata u;
		4060
		4061	ev_async_init (&u->async_w, async_cb);
		4062	ev_async_start (EV_A_ &u->async_w);
		4063
		4064	pthread_mutex_init (&u->lock, 0);
		4065	pthread_cond_init (&u->invoke_cv, 0);
		4066
		4067	// now associate this with the loop
		4068	ev_set_userdata (EV_A_ u);
		4069	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4070	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4071
		4072	// then create the thread running ev_loop
		4073	pthread_create (&u->tid, 0, l_run, EV_A);
		4074	}
		4075
		4076	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4077	solely to wake up the event loop so it takes notice of any new watchers
		4078	that might have been added:
		4079
		4080	static void
		4081	async_cb (EV_P_ ev_async *w, int revents)
		4082	{
		4083	// just used for the side effects
		4084	}
		4085
		4086	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4087	protecting the loop data, respectively.
		4088
		4089	static void
		4090	l_release (EV_P)
		4091	{
		4092	userdata *u = ev_userdata (EV_A);
		4093	pthread_mutex_unlock (&u->lock);
		4094	}
		4095
		4096	static void
		4097	l_acquire (EV_P)
		4098	{
		4099	userdata *u = ev_userdata (EV_A);
		4100	pthread_mutex_lock (&u->lock);
		4101	}
		4102
		4103	The event loop thread first acquires the mutex, and then jumps straight
		4104	into C<ev_loop>:
		4105
		4106	void *
		4107	l_run (void *thr_arg)
		4108	{
		4109	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4110
		4111	l_acquire (EV_A);
		4112	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4113	ev_loop (EV_A_ 0);
		4114	l_release (EV_A);
		4115
		4116	return 0;
		4117	}
		4118
		4119	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4120	signal the main thread via some unspecified mechanism (signals? pipe
		4121	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4122	have been called (in a while loop because a) spurious wakeups are possible
		4123	and b) skipping inter-thread-communication when there are no pending
		4124	watchers is very beneficial):
		4125
		4126	static void
		4127	l_invoke (EV_P)
		4128	{
		4129	userdata *u = ev_userdata (EV_A);
		4130
		4131	while (ev_pending_count (EV_A))
		4132	{
		4133	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4134	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4135	}
		4136	}
		4137
		4138	Now, whenever the main thread gets told to invoke pending watchers, it
		4139	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4140	thread to continue:
		4141
		4142	static void
		4143	real_invoke_pending (EV_P)
		4144	{
		4145	userdata *u = ev_userdata (EV_A);
		4146
		4147	pthread_mutex_lock (&u->lock);
		4148	ev_invoke_pending (EV_A);
		4149	pthread_cond_signal (&u->invoke_cv);
		4150	pthread_mutex_unlock (&u->lock);
		4151	}
		4152
		4153	Whenever you want to start/stop a watcher or do other modifications to an
		4154	event loop, you will now have to lock:
		4155
		4156	ev_timer timeout_watcher;
		4157	userdata *u = ev_userdata (EV_A);
		4158
		4159	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4160
		4161	pthread_mutex_lock (&u->lock);
		4162	ev_timer_start (EV_A_ &timeout_watcher);
		4163	ev_async_send (EV_A_ &u->async_w);
		4164	pthread_mutex_unlock (&u->lock);
		4165
		4166	Note that sending the C<ev_async> watcher is required because otherwise
		4167	an event loop currently blocking in the kernel will have no knowledge
		4168	about the newly added timer. By waking up the loop it will pick up any new
		4169	watchers in the next event loop iteration.
		4170
3114	=head2 COROUTINES	4171	=head3 COROUTINES
3115		4172
3116	Libev is much more accomodating to coroutines ("cooperative threads"):	4173	Libev is very accommodating to coroutines ("cooperative threads"):
3117	libev fully supports nesting calls to it's functions from different	4174	libev fully supports nesting calls to its functions from different
3118	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4175	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3119	different coroutines and switch freely between both coroutines running the	4176	different coroutines, and switch freely between both coroutines running
3120	loop, as long as you don't confuse yourself). The only exception is that	4177	the loop, as long as you don't confuse yourself). The only exception is
3121	you must not do this from C<ev_periodic> reschedule callbacks.	4178	that you must not do this from C<ev_periodic> reschedule callbacks.
3122		4179
3123	Care has been invested into making sure that libev does not keep local	4180	Care has been taken to ensure that libev does not keep local state inside
3124	state inside C<ev_loop>, and other calls do not usually allow coroutine	4181	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3125	switches.	4182	they do not call any callbacks.
3126		4183
		4184	=head2 COMPILER WARNINGS
3127		4185
3128	=head1 COMPLEXITIES	4186	Depending on your compiler and compiler settings, you might get no or a
		4187	lot of warnings when compiling libev code. Some people are apparently
		4188	scared by this.
3129		4189
3130	In this section the complexities of (many of) the algorithms used inside	4190	However, these are unavoidable for many reasons. For one, each compiler
3131	libev will be explained. For complexity discussions about backends see the	4191	has different warnings, and each user has different tastes regarding
3132	documentation for C<ev_default_init>.	4192	warning options. "Warn-free" code therefore cannot be a goal except when
		4193	targeting a specific compiler and compiler-version.
3133		4194
3134	All of the following are about amortised time: If an array needs to be	4195	Another reason is that some compiler warnings require elaborate
3135	extended, libev needs to realloc and move the whole array, but this	4196	workarounds, or other changes to the code that make it less clear and less
3136	happens asymptotically never with higher number of elements, so O(1) might	4197	maintainable.
3137	mean it might do a lengthy realloc operation in rare cases, but on average
3138	it is much faster and asymptotically approaches constant time.
3139		4198
3140	=over 4	4199	And of course, some compiler warnings are just plain stupid, or simply
		4200	wrong (because they don't actually warn about the condition their message
		4201	seems to warn about). For example, certain older gcc versions had some
		4202	warnings that resulted an extreme number of false positives. These have
		4203	been fixed, but some people still insist on making code warn-free with
		4204	such buggy versions.
3141		4205
3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4206	While libev is written to generate as few warnings as possible,
		4207	"warn-free" code is not a goal, and it is recommended not to build libev
		4208	with any compiler warnings enabled unless you are prepared to cope with
		4209	them (e.g. by ignoring them). Remember that warnings are just that:
		4210	warnings, not errors, or proof of bugs.
3143		4211
3144	This means that, when you have a watcher that triggers in one hour and
3145	there are 100 watchers that would trigger before that then inserting will
3146	have to skip roughly seven (C<ld 100>) of these watchers.
3147		4212
3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4213	=head2 VALGRIND
3149		4214
3150	That means that changing a timer costs less than removing/adding them	4215	Valgrind has a special section here because it is a popular tool that is
3151	as only the relative motion in the event queue has to be paid for.	4216	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3152		4217
3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4218	If you think you found a bug (memory leak, uninitialised data access etc.)
		4219	in libev, then check twice: If valgrind reports something like:
3154		4220
3155	These just add the watcher into an array or at the head of a list.	4221	==2274== definitely lost: 0 bytes in 0 blocks.
		4222	==2274== possibly lost: 0 bytes in 0 blocks.
		4223	==2274== still reachable: 256 bytes in 1 blocks.
3156		4224
3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4225	Then there is no memory leak, just as memory accounted to global variables
		4226	is not a memleak - the memory is still being referenced, and didn't leak.
3158		4227
3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4228	Similarly, under some circumstances, valgrind might report kernel bugs
		4229	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4230	although an acceptable workaround has been found here), or it might be
		4231	confused.
3160		4232
3161	These watchers are stored in lists then need to be walked to find the	4233	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3162	correct watcher to remove. The lists are usually short (you don't usually	4234	make it into some kind of religion.
3163	have many watchers waiting for the same fd or signal).
3164		4235
3165	=item Finding the next timer in each loop iteration: O(1)	4236	If you are unsure about something, feel free to contact the mailing list
		4237	with the full valgrind report and an explanation on why you think this
		4238	is a bug in libev (best check the archives, too :). However, don't be
		4239	annoyed when you get a brisk "this is no bug" answer and take the chance
		4240	of learning how to interpret valgrind properly.
3166		4241
3167	By virtue of using a binary heap, the next timer is always found at the	4242	If you need, for some reason, empty reports from valgrind for your project
3168	beginning of the storage array.	4243	I suggest using suppression lists.
3169		4244
3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3171		4245
3172	A change means an I/O watcher gets started or stopped, which requires	4246	=head1 PORTABILITY NOTES
3173	libev to recalculate its status (and possibly tell the kernel, depending
3174	on backend and wether C<ev_io_set> was used).
3175		4247
3176	=item Activating one watcher (putting it into the pending state): O(1)	4248	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3177
3178	=item Priority handling: O(number_of_priorities)
3179
3180	Priorities are implemented by allocating some space for each
3181	priority. When doing priority-based operations, libev usually has to
3182	linearly search all the priorities, but starting/stopping and activating
3183	watchers becomes O(1) w.r.t. priority handling.
3184
3185	=item Sending an ev_async: O(1)
3186
3187	=item Processing ev_async_send: O(number_of_async_watchers)
3188
3189	=item Processing signals: O(max_signal_number)
3190
3191	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3192	calls in the current loop iteration. Checking for async and signal events
3193	involves iterating over all running async watchers or all signal numbers.
3194
3195	=back
3196
3197
3198	=head1 Win32 platform limitations and workarounds
3199		4249
3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4250	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3201	requires, and its I/O model is fundamentally incompatible with the POSIX	4251	requires, and its I/O model is fundamentally incompatible with the POSIX
3202	model. Libev still offers limited functionality on this platform in	4252	model. Libev still offers limited functionality on this platform in
3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4253	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3204	descriptors. This only applies when using Win32 natively, not when using	4254	descriptors. This only applies when using Win32 natively, not when using
3205	e.g. cygwin.	4255	e.g. cygwin.
3206		4256
		4257	Lifting these limitations would basically require the full
		4258	re-implementation of the I/O system. If you are into these kinds of
		4259	things, then note that glib does exactly that for you in a very portable
		4260	way (note also that glib is the slowest event library known to man).
		4261
3207	There is no supported compilation method available on windows except	4262	There is no supported compilation method available on windows except
3208	embedding it into other applications.	4263	embedding it into other applications.
3209		4264
		4265	Sensible signal handling is officially unsupported by Microsoft - libev
		4266	tries its best, but under most conditions, signals will simply not work.
		4267
		4268	Not a libev limitation but worth mentioning: windows apparently doesn't
		4269	accept large writes: instead of resulting in a partial write, windows will
		4270	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4271	so make sure you only write small amounts into your sockets (less than a
		4272	megabyte seems safe, but this apparently depends on the amount of memory
		4273	available).
		4274
3210	Due to the many, low, and arbitrary limits on the win32 platform and the	4275	Due to the many, low, and arbitrary limits on the win32 platform and
3211	abysmal performance of winsockets, using a large number of sockets is not	4276	the abysmal performance of winsockets, using a large number of sockets
3212	recommended (and not reasonable). If your program needs to use more than	4277	is not recommended (and not reasonable). If your program needs to use
3213	a hundred or so sockets, then likely it needs to use a totally different	4278	more than a hundred or so sockets, then likely it needs to use a totally
3214	implementation for windows, as libev offers the POSIX model, which cannot	4279	different implementation for windows, as libev offers the POSIX readiness
3215	be implemented efficiently on windows (microsoft monopoly games).	4280	notification model, which cannot be implemented efficiently on windows
		4281	(due to Microsoft monopoly games).
		4282
		4283	A typical way to use libev under windows is to embed it (see the embedding
		4284	section for details) and use the following F<evwrap.h> header file instead
		4285	of F<ev.h>:
		4286
		4287	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4288	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4289
		4290	#include "ev.h"
		4291
		4292	And compile the following F<evwrap.c> file into your project (make sure
		4293	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4294
		4295	#include "evwrap.h"
		4296	#include "ev.c"
3216		4297
3217	=over 4	4298	=over 4
3218		4299
3219	=item The winsocket select function	4300	=item The winsocket select function
3220		4301
3221	The winsocket C<select> function doesn't follow POSIX in that it requires	4302	The winsocket C<select> function doesn't follow POSIX in that it
3222	socket I<handles> and not socket I<file descriptors>. This makes select	4303	requires socket I<handles> and not socket I<file descriptors> (it is
3223	very inefficient, and also requires a mapping from file descriptors	4304	also extremely buggy). This makes select very inefficient, and also
3224	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4305	requires a mapping from file descriptors to socket handles (the Microsoft
3225	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4306	C runtime provides the function C<_open_osfhandle> for this). See the
3226	symbols for more info.	4307	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4308	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3227		4309
3228	The configuration for a "naked" win32 using the microsoft runtime	4310	The configuration for a "naked" win32 using the Microsoft runtime
3229	libraries and raw winsocket select is:	4311	libraries and raw winsocket select is:
3230		4312
3231	#define EV_USE_SELECT 1	4313	#define EV_USE_SELECT 1
3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4314	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3233		4315
3234	Note that winsockets handling of fd sets is O(n), so you can easily get a	4316	Note that winsockets handling of fd sets is O(n), so you can easily get a
3235	complexity in the O(n²) range when using win32.	4317	complexity in the O(n²) range when using win32.
3236		4318
3237	=item Limited number of file descriptors	4319	=item Limited number of file descriptors
3238		4320
3239	Windows has numerous arbitrary (and low) limits on things. Early versions	4321	Windows has numerous arbitrary (and low) limits on things.
3240	of winsocket's select only supported waiting for a max. of C<64> handles	4322
		4323	Early versions of winsocket's select only supported waiting for a maximum
3241	(probably owning to the fact that all windows kernels can only wait for	4324	of C<64> handles (probably owning to the fact that all windows kernels
3242	C<64> things at the same time internally; microsoft recommends spawning a	4325	can only wait for C<64> things at the same time internally; Microsoft
3243	chain of threads and wait for 63 handles and the previous thread in each).	4326	recommends spawning a chain of threads and wait for 63 handles and the
		4327	previous thread in each. Sounds great!).
3244		4328
3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4329	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3246	to some high number (e.g. C<2048>) before compiling the winsocket select	4330	to some high number (e.g. C<2048>) before compiling the winsocket select
3247	call (which might be in libev or elsewhere, for example, perl does its own	4331	call (which might be in libev or elsewhere, for example, perl and many
3248	select emulation on windows).	4332	other interpreters do their own select emulation on windows).
3249		4333
3250	Another limit is the number of file descriptors in the microsoft runtime	4334	Another limit is the number of file descriptors in the Microsoft runtime
3251	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4335	libraries, which by default is C<64> (there must be a hidden I<64>
3252	or something like this inside microsoft). You can increase this by calling	4336	fetish or something like this inside Microsoft). You can increase this
3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4337	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3254	arbitrary limit), but is broken in many versions of the microsoft runtime	4338	(another arbitrary limit), but is broken in many versions of the Microsoft
3255	libraries.
3256
3257	This might get you to about C<512> or C<2048> sockets (depending on	4339	runtime libraries. This might get you to about C<512> or C<2048> sockets
3258	windows version and/or the phase of the moon). To get more, you need to	4340	(depending on windows version and/or the phase of the moon). To get more,
3259	wrap all I/O functions and provide your own fd management, but the cost of	4341	you need to wrap all I/O functions and provide your own fd management, but
3260	calling select (O(n²)) will likely make this unworkable.	4342	the cost of calling select (O(n²)) will likely make this unworkable.
3261		4343
3262	=back	4344	=back
3263		4345
3264
3265	=head1 PORTABILITY REQUIREMENTS	4346	=head2 PORTABILITY REQUIREMENTS
3266		4347
3267	In addition to a working ISO-C implementation, libev relies on a few	4348	In addition to a working ISO-C implementation and of course the
3268	additional extensions:	4349	backend-specific APIs, libev relies on a few additional extensions:
3269		4350
3270	=over 4	4351	=over 4
3271		4352
		4353	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4354	calling conventions regardless of C<ev_watcher_type *>.
		4355
		4356	Libev assumes not only that all watcher pointers have the same internal
		4357	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4358	assumes that the same (machine) code can be used to call any watcher
		4359	callback: The watcher callbacks have different type signatures, but libev
		4360	calls them using an C<ev_watcher *> internally.
		4361
3272	=item C<sig_atomic_t volatile> must be thread-atomic as well	4362	=item C<sig_atomic_t volatile> must be thread-atomic as well
3273		4363
3274	The type C<sig_atomic_t volatile> (or whatever is defined as	4364	The type C<sig_atomic_t volatile> (or whatever is defined as
3275	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4365	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3276	threads. This is not part of the specification for C<sig_atomic_t>, but is	4366	threads. This is not part of the specification for C<sig_atomic_t>, but is
3277	believed to be sufficiently portable.	4367	believed to be sufficiently portable.
3278		4368
3279	=item C<sigprocmask> must work in a threaded environment	4369	=item C<sigprocmask> must work in a threaded environment
3280		4370
…		…
3287		4377
3288	The most portable way to handle signals is to block signals in all threads	4378	The most portable way to handle signals is to block signals in all threads
3289	except the initial one, and run the default loop in the initial thread as	4379	except the initial one, and run the default loop in the initial thread as
3290	well.	4380	well.
3291		4381
		4382	=item C<long> must be large enough for common memory allocation sizes
		4383
		4384	To improve portability and simplify its API, libev uses C<long> internally
		4385	instead of C<size_t> when allocating its data structures. On non-POSIX
		4386	systems (Microsoft...) this might be unexpectedly low, but is still at
		4387	least 31 bits everywhere, which is enough for hundreds of millions of
		4388	watchers.
		4389
		4390	=item C<double> must hold a time value in seconds with enough accuracy
		4391
		4392	The type C<double> is used to represent timestamps. It is required to
		4393	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4394	enough for at least into the year 4000. This requirement is fulfilled by
		4395	implementations implementing IEEE 754, which is basically all existing
		4396	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4397	2200.
		4398
3292	=back	4399	=back
3293		4400
3294	If you know of other additional requirements drop me a note.	4401	If you know of other additional requirements drop me a note.
3295		4402
3296		4403
		4404	=head1 ALGORITHMIC COMPLEXITIES
		4405
		4406	In this section the complexities of (many of) the algorithms used inside
		4407	libev will be documented. For complexity discussions about backends see
		4408	the documentation for C<ev_default_init>.
		4409
		4410	All of the following are about amortised time: If an array needs to be
		4411	extended, libev needs to realloc and move the whole array, but this
		4412	happens asymptotically rarer with higher number of elements, so O(1) might
		4413	mean that libev does a lengthy realloc operation in rare cases, but on
		4414	average it is much faster and asymptotically approaches constant time.
		4415
		4416	=over 4
		4417
		4418	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4419
		4420	This means that, when you have a watcher that triggers in one hour and
		4421	there are 100 watchers that would trigger before that, then inserting will
		4422	have to skip roughly seven (C<ld 100>) of these watchers.
		4423
		4424	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4425
		4426	That means that changing a timer costs less than removing/adding them,
		4427	as only the relative motion in the event queue has to be paid for.
		4428
		4429	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4430
		4431	These just add the watcher into an array or at the head of a list.
		4432
		4433	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4434
		4435	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4436
		4437	These watchers are stored in lists, so they need to be walked to find the
		4438	correct watcher to remove. The lists are usually short (you don't usually
		4439	have many watchers waiting for the same fd or signal: one is typical, two
		4440	is rare).
		4441
		4442	=item Finding the next timer in each loop iteration: O(1)
		4443
		4444	By virtue of using a binary or 4-heap, the next timer is always found at a
		4445	fixed position in the storage array.
		4446
		4447	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4448
		4449	A change means an I/O watcher gets started or stopped, which requires
		4450	libev to recalculate its status (and possibly tell the kernel, depending
		4451	on backend and whether C<ev_io_set> was used).
		4452
		4453	=item Activating one watcher (putting it into the pending state): O(1)
		4454
		4455	=item Priority handling: O(number_of_priorities)
		4456
		4457	Priorities are implemented by allocating some space for each
		4458	priority. When doing priority-based operations, libev usually has to
		4459	linearly search all the priorities, but starting/stopping and activating
		4460	watchers becomes O(1) with respect to priority handling.
		4461
		4462	=item Sending an ev_async: O(1)
		4463
		4464	=item Processing ev_async_send: O(number_of_async_watchers)
		4465
		4466	=item Processing signals: O(max_signal_number)
		4467
		4468	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4469	calls in the current loop iteration. Checking for async and signal events
		4470	involves iterating over all running async watchers or all signal numbers.
		4471
		4472	=back
		4473
		4474
		4475	=head1 GLOSSARY
		4476
		4477	=over 4
		4478
		4479	=item active
		4480
		4481	A watcher is active as long as it has been started (has been attached to
		4482	an event loop) but not yet stopped (disassociated from the event loop).
		4483
		4484	=item application
		4485
		4486	In this document, an application is whatever is using libev.
		4487
		4488	=item callback
		4489
		4490	The address of a function that is called when some event has been
		4491	detected. Callbacks are being passed the event loop, the watcher that
		4492	received the event, and the actual event bitset.
		4493
		4494	=item callback invocation
		4495
		4496	The act of calling the callback associated with a watcher.
		4497
		4498	=item event
		4499
		4500	A change of state of some external event, such as data now being available
		4501	for reading on a file descriptor, time having passed or simply not having
		4502	any other events happening anymore.
		4503
		4504	In libev, events are represented as single bits (such as C<EV_READ> or
		4505	C<EV_TIMEOUT>).
		4506
		4507	=item event library
		4508
		4509	A software package implementing an event model and loop.
		4510
		4511	=item event loop
		4512
		4513	An entity that handles and processes external events and converts them
		4514	into callback invocations.
		4515
		4516	=item event model
		4517
		4518	The model used to describe how an event loop handles and processes
		4519	watchers and events.
		4520
		4521	=item pending
		4522
		4523	A watcher is pending as soon as the corresponding event has been detected,
		4524	and stops being pending as soon as the watcher will be invoked or its
		4525	pending status is explicitly cleared by the application.
		4526
		4527	A watcher can be pending, but not active. Stopping a watcher also clears
		4528	its pending status.
		4529
		4530	=item real time
		4531
		4532	The physical time that is observed. It is apparently strictly monotonic :)
		4533
		4534	=item wall-clock time
		4535
		4536	The time and date as shown on clocks. Unlike real time, it can actually
		4537	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4538	clock.
		4539
		4540	=item watcher
		4541
		4542	A data structure that describes interest in certain events. Watchers need
		4543	to be started (attached to an event loop) before they can receive events.
		4544
		4545	=item watcher invocation
		4546
		4547	The act of calling the callback associated with a watcher.
		4548
		4549	=back
		4550
3297	=head1 AUTHOR	4551	=head1 AUTHOR
3298		4552
3299	Marc Lehmann <libev@schmorp.de>.	4553	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3300		4554

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