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Revision 1.159 by root, Thu May 22 02:44:57 2008 UTC vs.
Revision 1.275 by root, Sat Dec 26 09:21:54 2009 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	132	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floatingpoint value. Unlike the name	133	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
		136
		137	=head1 ERROR HANDLING
		138
		139	Libev knows three classes of errors: operating system errors, usage errors
		140	and internal errors (bugs).
		141
		142	When libev catches an operating system error it cannot handle (for example
		143	a system call indicating a condition libev cannot fix), it calls the callback
		144	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		145	abort. The default is to print a diagnostic message and to call C<abort
		146	()>.
		147
		148	When libev detects a usage error such as a negative timer interval, then
		149	it will print a diagnostic message and abort (via the C<assert> mechanism,
		150	so C<NDEBUG> will disable this checking): these are programming errors in
		151	the libev caller and need to be fixed there.
		152
		153	Libev also has a few internal error-checking C<assert>ions, and also has
		154	extensive consistency checking code. These do not trigger under normal
		155	circumstances, as they indicate either a bug in libev or worse.
		156
121		157
122	=head1 GLOBAL FUNCTIONS	158	=head1 GLOBAL FUNCTIONS
123		159
124	These functions can be called anytime, even before initialising the	160	These functions can be called anytime, even before initialising the
125	library in any way.	161	library in any way.
…		…
134		170
135	=item ev_sleep (ev_tstamp interval)	171	=item ev_sleep (ev_tstamp interval)
136		172
137	Sleep for the given interval: The current thread will be blocked until	173	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	174	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	175	this is a sub-second-resolution C<sleep ()>.
140		176
141	=item int ev_version_major ()	177	=item int ev_version_major ()
142		178
143	=item int ev_version_minor ()	179	=item int ev_version_minor ()
144		180
…		…
157	not a problem.	193	not a problem.
158		194
159	Example: Make sure we haven't accidentally been linked against the wrong	195	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	196	version.
161		197
162	assert (("libev version mismatch",	198	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	199	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	200	&& ev_version_minor () >= EV_VERSION_MINOR));
165		201
166	=item unsigned int ev_supported_backends ()	202	=item unsigned int ev_supported_backends ()
167		203
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	204	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	205	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	207	a description of the set values.
172		208
173	Example: make sure we have the epoll method, because yeah this is cool and	209	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	210	a must have and can we have a torrent of it please!!!11
175		211
176	assert (("sorry, no epoll, no sex",	212	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	213	ev_supported_backends () & EVBACKEND_EPOLL));
178		214
179	=item unsigned int ev_recommended_backends ()	215	=item unsigned int ev_recommended_backends ()
180		216
181	Return the set of all backends compiled into this binary of libev and also	217	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	218	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	219	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	220	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	221	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	222	libev will probe for if you specify no backends explicitly.
187		223
188	=item unsigned int ev_embeddable_backends ()	224	=item unsigned int ev_embeddable_backends ()
189		225
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	230	recommended ones.
195		231
196	See the description of C<ev_embed> watchers for more info.	232	See the description of C<ev_embed> watchers for more info.
197		233
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		235
200	Sets the allocation function to use (the prototype is similar - the	236	Sets the allocation function to use (the prototype is similar - the
201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	238	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	239	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	265	}
230		266
231	...	267	...
232	ev_set_allocator (persistent_realloc);	268	ev_set_allocator (persistent_realloc);
233		269
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		271
236	Set the callback function to call on a retryable syscall error (such	272	Set the callback function to call on a retryable system call error (such
237	as failed select, poll, epoll_wait). The message is a printable string	273	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	274	indicating the system call or subsystem causing the problem. If this
239	callback is set, then libev will expect it to remedy the sitution, no	275	callback is set, then libev will expect it to remedy the situation, no
240	matter what, when it returns. That is, libev will generally retry the	276	matter what, when it returns. That is, libev will generally retry the
241	requested operation, or, if the condition doesn't go away, do bad stuff	277	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	278	(such as abort).
243		279
244	Example: This is basically the same thing that libev does internally, too.	280	Example: This is basically the same thing that libev does internally, too.
…		…
255		291
256	=back	292	=back
257		293
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		295
260	An event loop is described by a C<struct ev_loop *>. The library knows two	296	An event loop is described by a C<struct ev_loop *> (the C<struct>
261	types of such loops, the I<default> loop, which supports signals and child	297	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	298	I<function>).
		299
		300	The library knows two types of such loops, the I<default> loop, which
		301	supports signals and child events, and dynamically created loops which do
		302	not.
263		303
264	=over 4	304	=over 4
265		305
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		307
…		…
273	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
274	function.	314	function.
275		315
276	Note that this function is I<not> thread-safe, so if you want to use it	316	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	317	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
279		319
280	The default loop is the only loop that can handle C<ev_signal> and	320	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	321	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	322	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	325	C<ev_default_init>.
286		326
287	The flags argument can be used to specify special behaviour or specific	327	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	336	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	337	thing, believe me).
298		338
299	=item C<EVFLAG_NOENV>	339	=item C<EVFLAG_NOENV>
300		340
301	If this flag bit is ored into the flag value (or the program runs setuid	341	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	342	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	343	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	344	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	345	useful to try out specific backends to test their performance, or to work
306	around bugs.	346	around bugs.
…		…
313		353
314	This works by calling C<getpid ()> on every iteration of the loop,	354	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	355	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	356	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	358	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	359	C<pthread_atfork> which is even faster).
320		360
321	The big advantage of this flag is that you can forget about fork (and	361	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	362	forget about forgetting to tell libev about forking) when you use this
323	flag.	363	flag.
324		364
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	366	environment variable.
		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_NOSIGFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
327		382
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		384
330	This is your standard select(2) backend. Not I<completely> standard, as	385	This is your standard select(2) backend. Not I<completely> standard, as
331	libev tries to roll its own fd_set with no limits on the number of fds,	386	libev tries to roll its own fd_set with no limits on the number of fds,
332	but if that fails, expect a fairly low limit on the number of fds when	387	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	388	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	389	usually the fastest backend for a low number of (low-numbered :) fds.
335		390
336	To get good performance out of this backend you need a high amount of	391	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	392	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	393	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	394	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	395	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness notifications you get per iteration.	396	readiness notifications you get per iteration.
		397
		398	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		399	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		400	C<exceptfds> set on that platform).
342		401
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	402	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		403
345	And this is your standard poll(2) backend. It's more complicated	404	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	405	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	406	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	407	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	408	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	409	performance tips.
351		410
		411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		413
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		415
		416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		417	kernels).
353		418
354	For few fds, this backend is a bit little slower than poll and select,	419	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	420	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	421	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	422	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	423
359	cases and requiring a syscall per fd change, no fork support and bad	424	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	425	of the more advanced event mechanisms: mere annoyances include silently
		426	dropping file descriptors, requiring a system call per change per file
		427	descriptor (and unnecessary guessing of parameters), problems with dup and
		428	so on. The biggest issue is fork races, however - if a program forks then
		429	I<both> parent and child process have to recreate the epoll set, which can
		430	take considerable time (one syscall per file descriptor) and is of course
		431	hard to detect.
		432
		433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		434	of course I<doesn't>, and epoll just loves to report events for totally
		435	I<different> file descriptors (even already closed ones, so one cannot
		436	even remove them from the set) than registered in the set (especially
		437	on SMP systems). Libev tries to counter these spurious notifications by
		438	employing an additional generation counter and comparing that against the
		439	events to filter out spurious ones, recreating the set when required.
361		440
362	While stopping, setting and starting an I/O watcher in the same iteration	441	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	442	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	443	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	445	file descriptors might not work very well if you register events for both
367		446	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		447
372	Best performance from this backend is achieved by not unregistering all	448	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	449	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	450	i.e. keep at least one watcher active per fd at all times. Stopping and
		451	starting a watcher (without re-setting it) also usually doesn't cause
		452	extra overhead. A fork can both result in spurious notifications as well
		453	as in libev having to destroy and recreate the epoll object, which can
		454	take considerable time and thus should be avoided.
375		455
		456	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		457	faster than epoll for maybe up to a hundred file descriptors, depending on
		458	the usage. So sad.
		459
376	While nominally embeddeble in other event loops, this feature is broken in	460	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	461	all kernel versions tested so far.
		462
		463	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		464	C<EVBACKEND_POLL>.
378		465
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	466	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		467
381	Kqueue deserves special mention, as at the time of this writing, it	468	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	469	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	470	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	471	it's completely useless). Unlike epoll, however, whose brokenness
		472	is by design, these kqueue bugs can (and eventually will) be fixed
		473	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	474	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	475	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	476	system like NetBSD.
388		477
389	You still can embed kqueue into a normal poll or select backend and use it	478	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	479	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	480	the target platform). See C<ev_embed> watchers for more info.
392		481
393	It scales in the same way as the epoll backend, but the interface to the	482	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	483	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	484	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	485	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	486	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	487	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		488	cases
399		489
400	This backend usually performs well under most conditions.	490	This backend usually performs well under most conditions.
401		491
402	While nominally embeddable in other event loops, this doesn't work	492	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	493	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	494	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	495	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	496	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	497	also broken on OS X)) and, did I mention it, using it only for sockets.
		498
		499	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		500	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		501	C<NOTE_EOF>.
408		502
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	503	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		504
411	This is not implemented yet (and might never be, unless you send me an	505	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	506	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	510	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		511
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	512	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	513	it's really slow, but it still scales very well (O(active_fds)).
420		514
421	Please note that solaris event ports can deliver a lot of spurious	515	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	516	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	517	blocking when no data (or space) is available.
424		518
425	While this backend scales well, it requires one system call per active	519	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	520	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	521	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	522	might perform better.
429		523
430	On the positive side, ignoring the spurious readiness notifications, this	524	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	525	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	526	in all tests and is fully embeddable, which is a rare feat among the
		527	OS-specific backends (I vastly prefer correctness over speed hacks).
		528
		529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		530	C<EVBACKEND_POLL>.
433		531
434	=item C<EVBACKEND_ALL>	532	=item C<EVBACKEND_ALL>
435		533
436	Try all backends (even potentially broken ones that wouldn't be tried	534	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	535	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		537
440	It is definitely not recommended to use this flag.	538	It is definitely not recommended to use this flag.
441		539
442	=back	540	=back
443		541
444	If one or more of these are ored into the flags value, then only these	542	If one or more of the backend flags are or'ed into the flags value,
445	backends will be tried (in the reverse order as listed here). If none are	543	then only these backends will be tried (in the reverse order as listed
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	544	here). If none are specified, all backends in C<ev_recommended_backends
		545	()> will be tried.
447		546
448	The most typical usage is like this:	547	Example: This is the most typical usage.
449		548
450	if (!ev_default_loop (0))	549	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		551
453	Restrict libev to the select and poll backends, and do not allow	552	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	553	environment settings to be taken into account:
455		554
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	555	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		556
458	Use whatever libev has to offer, but make sure that kqueue is used if	557	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	558	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	559	private event loop and only if you know the OS supports your types of
		560	fds):
461		561
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	562	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		563
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	564	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		565
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	566	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	567	always distinct from the default loop. Unlike the default loop, it cannot
…		…
472	libev with threads is indeed to create one loop per thread, and using the	572	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	573	default loop in the "main" or "initial" thread.
474		574
475	Example: Try to create a event loop that uses epoll and nothing else.	575	Example: Try to create a event loop that uses epoll and nothing else.
476		576
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	577	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	578	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	579	fatal ("no epoll found here, maybe it hides under your chair");
480		580
481	=item ev_default_destroy ()	581	=item ev_default_destroy ()
482		582
483	Destroys the default loop again (frees all memory and kernel state	583	Destroys the default loop again (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	584	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	585	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	586	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	587	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	588	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	589	for example).
490		590
491	Note that certain global state, such as signal state, will not be freed by	591	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	592	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	593	as signal and child watchers) would need to be stopped manually.
494		594
495	In general it is not advisable to call this function except in the	595	In general it is not advisable to call this function except in the
496	rare occasion where you really need to free e.g. the signal handling	596	rare occasion where you really need to free e.g. the signal handling
497	pipe fds. If you need dynamically allocated loops it is better to use	597	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	598	C<ev_loop_new> and C<ev_loop_destroy>.
499		599
500	=item ev_loop_destroy (loop)	600	=item ev_loop_destroy (loop)
501		601
502	Like C<ev_default_destroy>, but destroys an event loop created by an	602	Like C<ev_default_destroy>, but destroys an event loop created by an
503	earlier call to C<ev_loop_new>.	603	earlier call to C<ev_loop_new>.
…		…
523		623
524	=item ev_loop_fork (loop)	624	=item ev_loop_fork (loop)
525		625
526	Like C<ev_default_fork>, but acts on an event loop created by	626	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	627	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.	628	after fork that you want to re-use in the child, and how you do this is
		629	entirely your own problem.
529		630
530	=item int ev_is_default_loop (loop)	631	=item int ev_is_default_loop (loop)
531		632
532	Returns true when the given loop actually is the default loop, false otherwise.	633	Returns true when the given loop is, in fact, the default loop, and false
		634	otherwise.
533		635
534	=item unsigned int ev_loop_count (loop)	636	=item unsigned int ev_loop_count (loop)
535		637
536	Returns the count of loop iterations for the loop, which is identical to	638	Returns the count of loop iterations for the loop, which is identical to
537	the number of times libev did poll for new events. It starts at C<0> and	639	the number of times libev did poll for new events. It starts at C<0> and
538	happily wraps around with enough iterations.	640	happily wraps around with enough iterations.
539		641
540	This value can sometimes be useful as a generation counter of sorts (it	642	This value can sometimes be useful as a generation counter of sorts (it
541	"ticks" the number of loop iterations), as it roughly corresponds with	643	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	644	C<ev_prepare> and C<ev_check> calls.
		645
		646	=item unsigned int ev_loop_depth (loop)
		647
		648	Returns the number of times C<ev_loop> was entered minus the number of
		649	times C<ev_loop> was exited, in other words, the recursion depth.
		650
		651	Outside C<ev_loop>, this number is zero. In a callback, this number is
		652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		653	in which case it is higher.
		654
		655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		656	etc.), doesn't count as exit.
543		657
544	=item unsigned int ev_backend (loop)	658	=item unsigned int ev_backend (loop)
545		659
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	661	use.
…		…
552	received events and started processing them. This timestamp does not	666	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	667	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	668	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	669	event occurring (or more correctly, libev finding out about it).
556		670
		671	=item ev_now_update (loop)
		672
		673	Establishes the current time by querying the kernel, updating the time
		674	returned by C<ev_now ()> in the progress. This is a costly operation and
		675	is usually done automatically within C<ev_loop ()>.
		676
		677	This function is rarely useful, but when some event callback runs for a
		678	very long time without entering the event loop, updating libev's idea of
		679	the current time is a good idea.
		680
		681	See also L<The special problem of time updates> in the C<ev_timer> section.
		682
		683	=item ev_suspend (loop)
		684
		685	=item ev_resume (loop)
		686
		687	These two functions suspend and resume a loop, for use when the loop is
		688	not used for a while and timeouts should not be processed.
		689
		690	A typical use case would be an interactive program such as a game: When
		691	the user presses C<^Z> to suspend the game and resumes it an hour later it
		692	would be best to handle timeouts as if no time had actually passed while
		693	the program was suspended. This can be achieved by calling C<ev_suspend>
		694	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		695	C<ev_resume> directly afterwards to resume timer processing.
		696
		697	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		699	will be rescheduled (that is, they will lose any events that would have
		700	occured while suspended).
		701
		702	After calling C<ev_suspend> you B<must not> call I<any> function on the
		703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		704	without a previous call to C<ev_suspend>.
		705
		706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		707	event loop time (see C<ev_now_update>).
		708
557	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
558		710
559	Finally, this is it, the event handler. This function usually is called	711	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	712	after you have initialised all your watchers and you want to start
561	events.	713	handling events.
562		714
563	If the flags argument is specified as C<0>, it will not return until	715	If the flags argument is specified as C<0>, it will not return until
564	either no event watchers are active anymore or C<ev_unloop> was called.	716	either no event watchers are active anymore or C<ev_unloop> was called.
565		717
566	Please note that an explicit C<ev_unloop> is usually better than	718	Please note that an explicit C<ev_unloop> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	719	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	720	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	721	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	722	of relying on its watchers stopping correctly, that is truly a thing of
		723	beauty.
571		724
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	725	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	726	those events and any already outstanding ones, but will not block your
574	case there are no events and will return after one iteration of the loop.	727	process in case there are no events and will return after one iteration of
		728	the loop.
575		729
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	730	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	731	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	732	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	733	be an event internal to libev itself, so there is no guarantee that a
580	external event in conjunction with something not expressible using other	734	user-registered callback will be called), and will return after one
		735	iteration of the loop.
		736
		737	This is useful if you are waiting for some external event in conjunction
		738	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	739	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	740	usually a better approach for this kind of thing.
583		741
584	Here are the gory details of what C<ev_loop> does:	742	Here are the gory details of what C<ev_loop> does:
585		743
586	- Before the first iteration, call any pending watchers.	744	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	745	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	746	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	747	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	748	- If we have been forked, detach and recreate the kernel state
		749	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	750	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	751	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	752	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	753	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	754	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	755	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	756	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	757	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	758	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	759	- Queue all expired timers.
601	- Queue all outstanding periodics.	760	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	761	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	762	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	763	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	764	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	765	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	766	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	771	anymore.
613		772
614	... queue jobs here, make sure they register event watchers as long	773	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	774	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	775	ev_loop (my_loop, 0);
617	... jobs done. yeah!	776	... jobs done or somebody called unloop. yeah!
618		777
619	=item ev_unloop (loop, how)	778	=item ev_unloop (loop, how)
620		779
621	Can be used to make a call to C<ev_loop> return early (but only after it	780	Can be used to make a call to C<ev_loop> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	781	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	782	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	783	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		784
626	This "unloop state" will be cleared when entering C<ev_loop> again.	785	This "unloop state" will be cleared when entering C<ev_loop> again.
627		786
		787	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		788
628	=item ev_ref (loop)	789	=item ev_ref (loop)
629		790
630	=item ev_unref (loop)	791	=item ev_unref (loop)
631		792
632	Ref/unref can be used to add or remove a reference count on the event	793	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	794	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	795	count is nonzero, C<ev_loop> will not return on its own.
		796
635	a watcher you never unregister that should not keep C<ev_loop> from	797	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	798	from returning, call ev_unref() after starting, and ev_ref() before
		799	stopping it.
		800
637	example, libev itself uses this for its internal signal pipe: It is not	801	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	802	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	803	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	804	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>	805	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,	806	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	807	before, respectively. Note also that libev might stop watchers itself
		808	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		809	in the callback).
644		810
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	811	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	812	running when nothing else is active.
647		813
648	struct ev_signal exitsig;	814	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	815	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	816	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	817	evf_unref (loop);
652		818
653	Example: For some weird reason, unregister the above signal handler again.	819	Example: For some weird reason, unregister the above signal handler again.
654		820
655	ev_ref (loop);	821	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	822	ev_signal_stop (loop, &exitsig);
657		823
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	824	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		825
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	826	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		827
662	These advanced functions influence the time that libev will spend waiting	828	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	829	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.	830	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		831	latency.
665		832
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	833	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	834	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	835	to increase efficiency of loop iterations (or to increase power-saving
		836	opportunities).
669		837
670	The background is that sometimes your program runs just fast enough to	838	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	839	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	840	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	841	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	842	overhead for the actual polling but can deliver many events at once.
675		843
676	By setting a higher I<io collect interval> you allow libev to spend more	844	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,	845	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	846	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	847	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.	848	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		849	sleep time ensures that libev will not poll for I/O events more often then
		850	once per this interval, on average.
681		851
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	852	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	853	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	854	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	855	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	856	value will not introduce any overhead in libev.
687		857
688	Many (busy) programs can usually benefit by setting the io collect	858	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	859	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	860	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>,	861	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.	862	as this approaches the timing granularity of most systems. Note that if
		863	you do transactions with the outside world and you can't increase the
		864	parallelity, then this setting will limit your transaction rate (if you
		865	need to poll once per transaction and the I/O collect interval is 0.01,
		866	then you can't do more than 100 transations per second).
		867
		868	Setting the I<timeout collect interval> can improve the opportunity for
		869	saving power, as the program will "bundle" timer callback invocations that
		870	are "near" in time together, by delaying some, thus reducing the number of
		871	times the process sleeps and wakes up again. Another useful technique to
		872	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		873	they fire on, say, one-second boundaries only.
		874
		875	Example: we only need 0.1s timeout granularity, and we wish not to poll
		876	more often than 100 times per second:
		877
		878	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		880
		881	=item ev_invoke_pending (loop)
		882
		883	This call will simply invoke all pending watchers while resetting their
		884	pending state. Normally, C<ev_loop> does this automatically when required,
		885	but when overriding the invoke callback this call comes handy.
		886
		887	=item int ev_pending_count (loop)
		888
		889	Returns the number of pending watchers - zero indicates that no watchers
		890	are pending.
		891
		892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		893
		894	This overrides the invoke pending functionality of the loop: Instead of
		895	invoking all pending watchers when there are any, C<ev_loop> will call
		896	this callback instead. This is useful, for example, when you want to
		897	invoke the actual watchers inside another context (another thread etc.).
		898
		899	If you want to reset the callback, use C<ev_invoke_pending> as new
		900	callback.
		901
		902	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		903
		904	Sometimes you want to share the same loop between multiple threads. This
		905	can be done relatively simply by putting mutex_lock/unlock calls around
		906	each call to a libev function.
		907
		908	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		909	wait for it to return. One way around this is to wake up the loop via
		910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		911	and I<acquire> callbacks on the loop.
		912
		913	When set, then C<release> will be called just before the thread is
		914	suspended waiting for new events, and C<acquire> is called just
		915	afterwards.
		916
		917	Ideally, C<release> will just call your mutex_unlock function, and
		918	C<acquire> will just call the mutex_lock function again.
		919
		920	While event loop modifications are allowed between invocations of
		921	C<release> and C<acquire> (that's their only purpose after all), no
		922	modifications done will affect the event loop, i.e. adding watchers will
		923	have no effect on the set of file descriptors being watched, or the time
		924	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		925	to take note of any changes you made.
		926
		927	In theory, threads executing C<ev_loop> will be async-cancel safe between
		928	invocations of C<release> and C<acquire>.
		929
		930	See also the locking example in the C<THREADS> section later in this
		931	document.
		932
		933	=item ev_set_userdata (loop, void *data)
		934
		935	=item ev_userdata (loop)
		936
		937	Set and retrieve a single C<void *> associated with a loop. When
		938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		939	C<0.>
		940
		941	These two functions can be used to associate arbitrary data with a loop,
		942	and are intended solely for the C<invoke_pending_cb>, C<release> and
		943	C<acquire> callbacks described above, but of course can be (ab-)used for
		944	any other purpose as well.
693		945
694	=item ev_loop_verify (loop)	946	=item ev_loop_verify (loop)
695		947
696	This function only does something when C<EV_VERIFY> support has been	948	This function only does something when C<EV_VERIFY> support has been
697	compiled in. It tries to go through all internal structures and checks	949	compiled in, which is the default for non-minimal builds. It tries to go
698	them for validity. If anything is found to be inconsistent, it will print	950	through all internal structures and checks them for validity. If anything
699	an error message to standard error and call C<abort ()>.	951	is found to be inconsistent, it will print an error message to standard
		952	error and call C<abort ()>.
700		953
701	This can be used to catch bugs inside libev itself: under normal	954	This can be used to catch bugs inside libev itself: under normal
702	circumstances, this function will never abort as of course libev keeps its	955	circumstances, this function will never abort as of course libev keeps its
703	data structures consistent.	956	data structures consistent.
704		957
705	=back	958	=back
706		959
707		960
708	=head1 ANATOMY OF A WATCHER	961	=head1 ANATOMY OF A WATCHER
709		962
		963	In the following description, uppercase C<TYPE> in names stands for the
		964	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		965	watchers and C<ev_io_start> for I/O watchers.
		966
710	A watcher is a structure that you create and register to record your	967	A watcher is a structure that you create and register to record your
711	interest in some event. For instance, if you want to wait for STDIN to	968	interest in some event. For instance, if you want to wait for STDIN to
712	become readable, you would create an C<ev_io> watcher for that:	969	become readable, you would create an C<ev_io> watcher for that:
713		970
714	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
715	{	972	{
716	ev_io_stop (w);	973	ev_io_stop (w);
717	ev_unloop (loop, EVUNLOOP_ALL);	974	ev_unloop (loop, EVUNLOOP_ALL);
718	}	975	}
719		976
720	struct ev_loop *loop = ev_default_loop (0);	977	struct ev_loop *loop = ev_default_loop (0);
		978
721	struct ev_io stdin_watcher;	979	ev_io stdin_watcher;
		980
722	ev_init (&stdin_watcher, my_cb);	981	ev_init (&stdin_watcher, my_cb);
723	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
724	ev_io_start (loop, &stdin_watcher);	983	ev_io_start (loop, &stdin_watcher);
		984
725	ev_loop (loop, 0);	985	ev_loop (loop, 0);
726		986
727	As you can see, you are responsible for allocating the memory for your	987	As you can see, you are responsible for allocating the memory for your
728	watcher structures (and it is usually a bad idea to do this on the stack,	988	watcher structures (and it is I<usually> a bad idea to do this on the
729	although this can sometimes be quite valid).	989	stack).
		990
		991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		992	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
730		993
731	Each watcher structure must be initialised by a call to C<ev_init	994	Each watcher structure must be initialised by a call to C<ev_init
732	(watcher *, callback)>, which expects a callback to be provided. This	995	(watcher *, callback)>, which expects a callback to be provided. This
733	callback gets invoked each time the event occurs (or, in the case of io	996	callback gets invoked each time the event occurs (or, in the case of I/O
734	watchers, each time the event loop detects that the file descriptor given	997	watchers, each time the event loop detects that the file descriptor given
735	is readable and/or writable).	998	is readable and/or writable).
736		999
737	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1000	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
738	with arguments specific to this watcher type. There is also a macro	1001	macro to configure it, with arguments specific to the watcher type. There
739	to combine initialisation and setting in one call: C<< ev_<type>_init	1002	is also a macro to combine initialisation and setting in one call: C<<
740	(watcher *, callback, ...) >>.	1003	ev_TYPE_init (watcher *, callback, ...) >>.
741		1004
742	To make the watcher actually watch out for events, you have to start it	1005	To make the watcher actually watch out for events, you have to start it
743	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1006	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
744	*) >>), and you can stop watching for events at any time by calling the	1007	*) >>), and you can stop watching for events at any time by calling the
745	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1008	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
746		1009
747	As long as your watcher is active (has been started but not stopped) you	1010	As long as your watcher is active (has been started but not stopped) you
748	must not touch the values stored in it. Most specifically you must never	1011	must not touch the values stored in it. Most specifically you must never
749	reinitialise it or call its C<set> macro.	1012	reinitialise it or call its C<ev_TYPE_set> macro.
750		1013
751	Each and every callback receives the event loop pointer as first, the	1014	Each and every callback receives the event loop pointer as first, the
752	registered watcher structure as second, and a bitset of received events as	1015	registered watcher structure as second, and a bitset of received events as
753	third argument.	1016	third argument.
754		1017
…		…
812		1075
813	=item C<EV_ASYNC>	1076	=item C<EV_ASYNC>
814		1077
815	The given async watcher has been asynchronously notified (see C<ev_async>).	1078	The given async watcher has been asynchronously notified (see C<ev_async>).
816		1079
		1080	=item C<EV_CUSTOM>
		1081
		1082	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1083	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1084
817	=item C<EV_ERROR>	1085	=item C<EV_ERROR>
818		1086
819	An unspecified error has occured, the watcher has been stopped. This might	1087	An unspecified error has occurred, the watcher has been stopped. This might
820	happen because the watcher could not be properly started because libev	1088	happen because the watcher could not be properly started because libev
821	ran out of memory, a file descriptor was found to be closed or any other	1089	ran out of memory, a file descriptor was found to be closed or any other
		1090	problem. Libev considers these application bugs.
		1091
822	problem. You best act on it by reporting the problem and somehow coping	1092	You best act on it by reporting the problem and somehow coping with the
823	with the watcher being stopped.	1093	watcher being stopped. Note that well-written programs should not receive
		1094	an error ever, so when your watcher receives it, this usually indicates a
		1095	bug in your program.
824		1096
825	Libev will usually signal a few "dummy" events together with an error,	1097	Libev will usually signal a few "dummy" events together with an error, for
826	for example it might indicate that a fd is readable or writable, and if	1098	example it might indicate that a fd is readable or writable, and if your
827	your callbacks is well-written it can just attempt the operation and cope	1099	callbacks is well-written it can just attempt the operation and cope with
828	with the error from read() or write(). This will not work in multithreaded	1100	the error from read() or write(). This will not work in multi-threaded
829	programs, though, so beware.	1101	programs, though, as the fd could already be closed and reused for another
		1102	thing, so beware.
830		1103
831	=back	1104	=back
832		1105
833	=head2 GENERIC WATCHER FUNCTIONS	1106	=head2 GENERIC WATCHER FUNCTIONS
834
835	In the following description, C<TYPE> stands for the watcher type,
836	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
837		1107
838	=over 4	1108	=over 4
839		1109
840	=item C<ev_init> (ev_TYPE *watcher, callback)	1110	=item C<ev_init> (ev_TYPE *watcher, callback)
841		1111
…		…
847	which rolls both calls into one.	1117	which rolls both calls into one.
848		1118
849	You can reinitialise a watcher at any time as long as it has been stopped	1119	You can reinitialise a watcher at any time as long as it has been stopped
850	(or never started) and there are no pending events outstanding.	1120	(or never started) and there are no pending events outstanding.
851		1121
852	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1122	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
853	int revents)>.	1123	int revents)>.
854		1124
		1125	Example: Initialise an C<ev_io> watcher in two steps.
		1126
		1127	ev_io w;
		1128	ev_init (&w, my_cb);
		1129	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1130
855	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1131	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
856		1132
857	This macro initialises the type-specific parts of a watcher. You need to	1133	This macro initialises the type-specific parts of a watcher. You need to
858	call C<ev_init> at least once before you call this macro, but you can	1134	call C<ev_init> at least once before you call this macro, but you can
859	call C<ev_TYPE_set> any number of times. You must not, however, call this	1135	call C<ev_TYPE_set> any number of times. You must not, however, call this
860	macro on a watcher that is active (it can be pending, however, which is a	1136	macro on a watcher that is active (it can be pending, however, which is a
861	difference to the C<ev_init> macro).	1137	difference to the C<ev_init> macro).
862		1138
863	Although some watcher types do not have type-specific arguments	1139	Although some watcher types do not have type-specific arguments
864	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1140	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
865		1141
		1142	See C<ev_init>, above, for an example.
		1143
866	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1144	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
867		1145
868	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1146	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
869	calls into a single call. This is the most convinient method to initialise	1147	calls into a single call. This is the most convenient method to initialise
870	a watcher. The same limitations apply, of course.	1148	a watcher. The same limitations apply, of course.
871		1149
		1150	Example: Initialise and set an C<ev_io> watcher in one step.
		1151
		1152	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1153
872	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1154	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
873		1155
874	Starts (activates) the given watcher. Only active watchers will receive	1156	Starts (activates) the given watcher. Only active watchers will receive
875	events. If the watcher is already active nothing will happen.	1157	events. If the watcher is already active nothing will happen.
876		1158
		1159	Example: Start the C<ev_io> watcher that is being abused as example in this
		1160	whole section.
		1161
		1162	ev_io_start (EV_DEFAULT_UC, &w);
		1163
877	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1164	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
878		1165
879	Stops the given watcher again (if active) and clears the pending	1166	Stops the given watcher if active, and clears the pending status (whether
		1167	the watcher was active or not).
		1168
880	status. It is possible that stopped watchers are pending (for example,	1169	It is possible that stopped watchers are pending - for example,
881	non-repeating timers are being stopped when they become pending), but	1170	non-repeating timers are being stopped when they become pending - but
882	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1171	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
883	you want to free or reuse the memory used by the watcher it is therefore a	1172	pending. If you want to free or reuse the memory used by the watcher it is
884	good idea to always call its C<ev_TYPE_stop> function.	1173	therefore a good idea to always call its C<ev_TYPE_stop> function.
885		1174
886	=item bool ev_is_active (ev_TYPE *watcher)	1175	=item bool ev_is_active (ev_TYPE *watcher)
887		1176
888	Returns a true value iff the watcher is active (i.e. it has been started	1177	Returns a true value iff the watcher is active (i.e. it has been started
889	and not yet been stopped). As long as a watcher is active you must not modify	1178	and not yet been stopped). As long as a watcher is active you must not modify
…		…
905	=item ev_cb_set (ev_TYPE *watcher, callback)	1194	=item ev_cb_set (ev_TYPE *watcher, callback)
906		1195
907	Change the callback. You can change the callback at virtually any time	1196	Change the callback. You can change the callback at virtually any time
908	(modulo threads).	1197	(modulo threads).
909		1198
910	=item ev_set_priority (ev_TYPE *watcher, priority)	1199	=item ev_set_priority (ev_TYPE *watcher, int priority)
911		1200
912	=item int ev_priority (ev_TYPE *watcher)	1201	=item int ev_priority (ev_TYPE *watcher)
913		1202
914	Set and query the priority of the watcher. The priority is a small	1203	Set and query the priority of the watcher. The priority is a small
915	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1204	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
916	(default: C<-2>). Pending watchers with higher priority will be invoked	1205	(default: C<-2>). Pending watchers with higher priority will be invoked
917	before watchers with lower priority, but priority will not keep watchers	1206	before watchers with lower priority, but priority will not keep watchers
918	from being executed (except for C<ev_idle> watchers).	1207	from being executed (except for C<ev_idle> watchers).
919		1208
920	This means that priorities are I<only> used for ordering callback
921	invocation after new events have been received. This is useful, for
922	example, to reduce latency after idling, or more often, to bind two
923	watchers on the same event and make sure one is called first.
924
925	If you need to suppress invocation when higher priority events are pending	1209	If you need to suppress invocation when higher priority events are pending
926	you need to look at C<ev_idle> watchers, which provide this functionality.	1210	you need to look at C<ev_idle> watchers, which provide this functionality.
927		1211
928	You I<must not> change the priority of a watcher as long as it is active or	1212	You I<must not> change the priority of a watcher as long as it is active or
929	pending.	1213	pending.
930		1214
		1215	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1216	fine, as long as you do not mind that the priority value you query might
		1217	or might not have been clamped to the valid range.
		1218
931	The default priority used by watchers when no priority has been set is	1219	The default priority used by watchers when no priority has been set is
932	always C<0>, which is supposed to not be too high and not be too low :).	1220	always C<0>, which is supposed to not be too high and not be too low :).
933		1221
934	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1222	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
935	fine, as long as you do not mind that the priority value you query might	1223	priorities.
936	or might not have been adjusted to be within valid range.
937		1224
938	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1225	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
939		1226
940	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1227	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
941	C<loop> nor C<revents> need to be valid as long as the watcher callback	1228	C<loop> nor C<revents> need to be valid as long as the watcher callback
942	can deal with that fact.	1229	can deal with that fact, as both are simply passed through to the
		1230	callback.
943		1231
944	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1232	=item int ev_clear_pending (loop, ev_TYPE *watcher)
945		1233
946	If the watcher is pending, this function returns clears its pending status	1234	If the watcher is pending, this function clears its pending status and
947	and returns its C<revents> bitset (as if its callback was invoked). If the	1235	returns its C<revents> bitset (as if its callback was invoked). If the
948	watcher isn't pending it does nothing and returns C<0>.	1236	watcher isn't pending it does nothing and returns C<0>.
949		1237
		1238	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1239	callback to be invoked, which can be accomplished with this function.
		1240
		1241	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1242
		1243	Feeds the given event set into the event loop, as if the specified event
		1244	had happened for the specified watcher (which must be a pointer to an
		1245	initialised but not necessarily started event watcher). Obviously you must
		1246	not free the watcher as long as it has pending events.
		1247
		1248	Stopping the watcher, letting libev invoke it, or calling
		1249	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1250	not started in the first place.
		1251
		1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1253	functions that do not need a watcher.
		1254
950	=back	1255	=back
951		1256
952		1257
953	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
954		1259
955	Each watcher has, by default, a member C<void *data> that you can change	1260	Each watcher has, by default, a member C<void *data> that you can change
956	and read at any time, libev will completely ignore it. This can be used	1261	and read at any time: libev will completely ignore it. This can be used
957	to associate arbitrary data with your watcher. If you need more data and	1262	to associate arbitrary data with your watcher. If you need more data and
958	don't want to allocate memory and store a pointer to it in that data	1263	don't want to allocate memory and store a pointer to it in that data
959	member, you can also "subclass" the watcher type and provide your own	1264	member, you can also "subclass" the watcher type and provide your own
960	data:	1265	data:
961		1266
962	struct my_io	1267	struct my_io
963	{	1268	{
964	struct ev_io io;	1269	ev_io io;
965	int otherfd;	1270	int otherfd;
966	void *somedata;	1271	void *somedata;
967	struct whatever *mostinteresting;	1272	struct whatever *mostinteresting;
968	}	1273	};
		1274
		1275	...
		1276	struct my_io w;
		1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
969		1278
970	And since your callback will be called with a pointer to the watcher, you	1279	And since your callback will be called with a pointer to the watcher, you
971	can cast it back to your own type:	1280	can cast it back to your own type:
972		1281
973	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
974	{	1283	{
975	struct my_io *w = (struct my_io *)w_;	1284	struct my_io *w = (struct my_io *)w_;
976	...	1285	...
977	}	1286	}
978		1287
979	More interesting and less C-conformant ways of casting your callback type	1288	More interesting and less C-conformant ways of casting your callback type
980	instead have been omitted.	1289	instead have been omitted.
981		1290
982	Another common scenario is having some data structure with multiple	1291	Another common scenario is to use some data structure with multiple
983	watchers:	1292	embedded watchers:
984		1293
985	struct my_biggy	1294	struct my_biggy
986	{	1295	{
987	int some_data;	1296	int some_data;
988	ev_timer t1;	1297	ev_timer t1;
989	ev_timer t2;	1298	ev_timer t2;
990	}	1299	}
991		1300
992	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1301	In this case getting the pointer to C<my_biggy> is a bit more
993	you need to use C<offsetof>:	1302	complicated: Either you store the address of your C<my_biggy> struct
		1303	in the C<data> member of the watcher (for woozies), or you need to use
		1304	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1305	programmers):
994		1306
995	#include <stddef.h>	1307	#include <stddef.h>
996		1308
997	static void	1309	static void
998	t1_cb (EV_P_ struct ev_timer *w, int revents)	1310	t1_cb (EV_P_ ev_timer *w, int revents)
999	{	1311	{
1000	struct my_biggy big = (struct my_biggy *	1312	struct my_biggy big = (struct my_biggy *)
1001	(((char *)w) - offsetof (struct my_biggy, t1));	1313	(((char *)w) - offsetof (struct my_biggy, t1));
1002	}	1314	}
1003		1315
1004	static void	1316	static void
1005	t2_cb (EV_P_ struct ev_timer *w, int revents)	1317	t2_cb (EV_P_ ev_timer *w, int revents)
1006	{	1318	{
1007	struct my_biggy big = (struct my_biggy *	1319	struct my_biggy big = (struct my_biggy *)
1008	(((char *)w) - offsetof (struct my_biggy, t2));	1320	(((char *)w) - offsetof (struct my_biggy, t2));
1009	}	1321	}
		1322
		1323	=head2 WATCHER PRIORITY MODELS
		1324
		1325	Many event loops support I<watcher priorities>, which are usually small
		1326	integers that influence the ordering of event callback invocation
		1327	between watchers in some way, all else being equal.
		1328
		1329	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1330	description for the more technical details such as the actual priority
		1331	range.
		1332
		1333	There are two common ways how these these priorities are being interpreted
		1334	by event loops:
		1335
		1336	In the more common lock-out model, higher priorities "lock out" invocation
		1337	of lower priority watchers, which means as long as higher priority
		1338	watchers receive events, lower priority watchers are not being invoked.
		1339
		1340	The less common only-for-ordering model uses priorities solely to order
		1341	callback invocation within a single event loop iteration: Higher priority
		1342	watchers are invoked before lower priority ones, but they all get invoked
		1343	before polling for new events.
		1344
		1345	Libev uses the second (only-for-ordering) model for all its watchers
		1346	except for idle watchers (which use the lock-out model).
		1347
		1348	The rationale behind this is that implementing the lock-out model for
		1349	watchers is not well supported by most kernel interfaces, and most event
		1350	libraries will just poll for the same events again and again as long as
		1351	their callbacks have not been executed, which is very inefficient in the
		1352	common case of one high-priority watcher locking out a mass of lower
		1353	priority ones.
		1354
		1355	Static (ordering) priorities are most useful when you have two or more
		1356	watchers handling the same resource: a typical usage example is having an
		1357	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1358	timeouts. Under load, data might be received while the program handles
		1359	other jobs, but since timers normally get invoked first, the timeout
		1360	handler will be executed before checking for data. In that case, giving
		1361	the timer a lower priority than the I/O watcher ensures that I/O will be
		1362	handled first even under adverse conditions (which is usually, but not
		1363	always, what you want).
		1364
		1365	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1366	will only be executed when no same or higher priority watchers have
		1367	received events, they can be used to implement the "lock-out" model when
		1368	required.
		1369
		1370	For example, to emulate how many other event libraries handle priorities,
		1371	you can associate an C<ev_idle> watcher to each such watcher, and in
		1372	the normal watcher callback, you just start the idle watcher. The real
		1373	processing is done in the idle watcher callback. This causes libev to
		1374	continously poll and process kernel event data for the watcher, but when
		1375	the lock-out case is known to be rare (which in turn is rare :), this is
		1376	workable.
		1377
		1378	Usually, however, the lock-out model implemented that way will perform
		1379	miserably under the type of load it was designed to handle. In that case,
		1380	it might be preferable to stop the real watcher before starting the
		1381	idle watcher, so the kernel will not have to process the event in case
		1382	the actual processing will be delayed for considerable time.
		1383
		1384	Here is an example of an I/O watcher that should run at a strictly lower
		1385	priority than the default, and which should only process data when no
		1386	other events are pending:
		1387
		1388	ev_idle idle; // actual processing watcher
		1389	ev_io io; // actual event watcher
		1390
		1391	static void
		1392	io_cb (EV_P_ ev_io *w, int revents)
		1393	{
		1394	// stop the I/O watcher, we received the event, but
		1395	// are not yet ready to handle it.
		1396	ev_io_stop (EV_A_ w);
		1397
		1398	// start the idle watcher to ahndle the actual event.
		1399	// it will not be executed as long as other watchers
		1400	// with the default priority are receiving events.
		1401	ev_idle_start (EV_A_ &idle);
		1402	}
		1403
		1404	static void
		1405	idle_cb (EV_P_ ev_idle *w, int revents)
		1406	{
		1407	// actual processing
		1408	read (STDIN_FILENO, ...);
		1409
		1410	// have to start the I/O watcher again, as
		1411	// we have handled the event
		1412	ev_io_start (EV_P_ &io);
		1413	}
		1414
		1415	// initialisation
		1416	ev_idle_init (&idle, idle_cb);
		1417	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1418	ev_io_start (EV_DEFAULT_ &io);
		1419
		1420	In the "real" world, it might also be beneficial to start a timer, so that
		1421	low-priority connections can not be locked out forever under load. This
		1422	enables your program to keep a lower latency for important connections
		1423	during short periods of high load, while not completely locking out less
		1424	important ones.
1010		1425
1011		1426
1012	=head1 WATCHER TYPES	1427	=head1 WATCHER TYPES
1013		1428
1014	This section describes each watcher in detail, but will not repeat	1429	This section describes each watcher in detail, but will not repeat
…		…
1038	In general you can register as many read and/or write event watchers per	1453	In general you can register as many read and/or write event watchers per
1039	fd as you want (as long as you don't confuse yourself). Setting all file	1454	fd as you want (as long as you don't confuse yourself). Setting all file
1040	descriptors to non-blocking mode is also usually a good idea (but not	1455	descriptors to non-blocking mode is also usually a good idea (but not
1041	required if you know what you are doing).	1456	required if you know what you are doing).
1042		1457
1043	If you must do this, then force the use of a known-to-be-good backend	1458	If you cannot use non-blocking mode, then force the use of a
1044	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1459	known-to-be-good backend (at the time of this writing, this includes only
1045	C<EVBACKEND_POLL>).	1460	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1461	descriptors for which non-blocking operation makes no sense (such as
		1462	files) - libev doesn't guarentee any specific behaviour in that case.
1046		1463
1047	Another thing you have to watch out for is that it is quite easy to	1464	Another thing you have to watch out for is that it is quite easy to
1048	receive "spurious" readiness notifications, that is your callback might	1465	receive "spurious" readiness notifications, that is your callback might
1049	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1466	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1050	because there is no data. Not only are some backends known to create a	1467	because there is no data. Not only are some backends known to create a
1051	lot of those (for example solaris ports), it is very easy to get into	1468	lot of those (for example Solaris ports), it is very easy to get into
1052	this situation even with a relatively standard program structure. Thus	1469	this situation even with a relatively standard program structure. Thus
1053	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1470	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1054	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1471	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1055		1472
1056	If you cannot run the fd in non-blocking mode (for example you should not	1473	If you cannot run the fd in non-blocking mode (for example you should
1057	play around with an Xlib connection), then you have to seperately re-test	1474	not play around with an Xlib connection), then you have to separately
1058	whether a file descriptor is really ready with a known-to-be good interface	1475	re-test whether a file descriptor is really ready with a known-to-be good
1059	such as poll (fortunately in our Xlib example, Xlib already does this on	1476	interface such as poll (fortunately in our Xlib example, Xlib already
1060	its own, so its quite safe to use).	1477	does this on its own, so its quite safe to use). Some people additionally
		1478	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1479	indefinitely.
		1480
		1481	But really, best use non-blocking mode.
1061		1482
1062	=head3 The special problem of disappearing file descriptors	1483	=head3 The special problem of disappearing file descriptors
1063		1484
1064	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1485	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1065	descriptor (either by calling C<close> explicitly or by any other means,	1486	descriptor (either due to calling C<close> explicitly or any other means,
1066	such as C<dup>). The reason is that you register interest in some file	1487	such as C<dup2>). The reason is that you register interest in some file
1067	descriptor, but when it goes away, the operating system will silently drop	1488	descriptor, but when it goes away, the operating system will silently drop
1068	this interest. If another file descriptor with the same number then is	1489	this interest. If another file descriptor with the same number then is
1069	registered with libev, there is no efficient way to see that this is, in	1490	registered with libev, there is no efficient way to see that this is, in
1070	fact, a different file descriptor.	1491	fact, a different file descriptor.
1071		1492
…		…
1102	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1523	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1103	C<EVBACKEND_POLL>.	1524	C<EVBACKEND_POLL>.
1104		1525
1105	=head3 The special problem of SIGPIPE	1526	=head3 The special problem of SIGPIPE
1106		1527
1107	While not really specific to libev, it is easy to forget about SIGPIPE:	1528	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1108	when reading from a pipe whose other end has been closed, your program	1529	when writing to a pipe whose other end has been closed, your program gets
1109	gets send a SIGPIPE, which, by default, aborts your program. For most	1530	sent a SIGPIPE, which, by default, aborts your program. For most programs
1110	programs this is sensible behaviour, for daemons, this is usually	1531	this is sensible behaviour, for daemons, this is usually undesirable.
1111	undesirable.
1112		1532
1113	So when you encounter spurious, unexplained daemon exits, make sure you	1533	So when you encounter spurious, unexplained daemon exits, make sure you
1114	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1534	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1115	somewhere, as that would have given you a big clue).	1535	somewhere, as that would have given you a big clue).
1116		1536
…		…
1122	=item ev_io_init (ev_io *, callback, int fd, int events)	1542	=item ev_io_init (ev_io *, callback, int fd, int events)
1123		1543
1124	=item ev_io_set (ev_io *, int fd, int events)	1544	=item ev_io_set (ev_io *, int fd, int events)
1125		1545
1126	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1546	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1127	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1547	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1128	C<EV_READ | EV_WRITE> to receive the given events.	1548	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1129		1549
1130	=item int fd [read-only]	1550	=item int fd [read-only]
1131		1551
1132	The file descriptor being watched.	1552	The file descriptor being watched.
1133		1553
…		…
1141		1561
1142	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1562	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1143	readable, but only once. Since it is likely line-buffered, you could	1563	readable, but only once. Since it is likely line-buffered, you could
1144	attempt to read a whole line in the callback.	1564	attempt to read a whole line in the callback.
1145		1565
1146	static void	1566	static void
1147	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1567	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1148	{	1568	{
1149	ev_io_stop (loop, w);	1569	ev_io_stop (loop, w);
1150	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1570	.. read from stdin here (or from w->fd) and handle any I/O errors
1151	}	1571	}
1152		1572
1153	...	1573	...
1154	struct ev_loop *loop = ev_default_init (0);	1574	struct ev_loop *loop = ev_default_init (0);
1155	struct ev_io stdin_readable;	1575	ev_io stdin_readable;
1156	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1157	ev_io_start (loop, &stdin_readable);	1577	ev_io_start (loop, &stdin_readable);
1158	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1159		1579
1160		1580
1161	=head2 C<ev_timer> - relative and optionally repeating timeouts	1581	=head2 C<ev_timer> - relative and optionally repeating timeouts
1162		1582
1163	Timer watchers are simple relative timers that generate an event after a	1583	Timer watchers are simple relative timers that generate an event after a
1164	given time, and optionally repeating in regular intervals after that.	1584	given time, and optionally repeating in regular intervals after that.
1165		1585
1166	The timers are based on real time, that is, if you register an event that	1586	The timers are based on real time, that is, if you register an event that
1167	times out after an hour and you reset your system clock to january last	1587	times out after an hour and you reset your system clock to January last
1168	year, it will still time out after (roughly) and hour. "Roughly" because	1588	year, it will still time out after (roughly) one hour. "Roughly" because
1169	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1589	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1170	monotonic clock option helps a lot here).	1590	monotonic clock option helps a lot here).
		1591
		1592	The callback is guaranteed to be invoked only I<after> its timeout has
		1593	passed (not I<at>, so on systems with very low-resolution clocks this
		1594	might introduce a small delay). If multiple timers become ready during the
		1595	same loop iteration then the ones with earlier time-out values are invoked
		1596	before ones of the same priority with later time-out values (but this is
		1597	no longer true when a callback calls C<ev_loop> recursively).
		1598
		1599	=head3 Be smart about timeouts
		1600
		1601	Many real-world problems involve some kind of timeout, usually for error
		1602	recovery. A typical example is an HTTP request - if the other side hangs,
		1603	you want to raise some error after a while.
		1604
		1605	What follows are some ways to handle this problem, from obvious and
		1606	inefficient to smart and efficient.
		1607
		1608	In the following, a 60 second activity timeout is assumed - a timeout that
		1609	gets reset to 60 seconds each time there is activity (e.g. each time some
		1610	data or other life sign was received).
		1611
		1612	=over 4
		1613
		1614	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1615
		1616	This is the most obvious, but not the most simple way: In the beginning,
		1617	start the watcher:
		1618
		1619	ev_timer_init (timer, callback, 60., 0.);
		1620	ev_timer_start (loop, timer);
		1621
		1622	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1623	and start it again:
		1624
		1625	ev_timer_stop (loop, timer);
		1626	ev_timer_set (timer, 60., 0.);
		1627	ev_timer_start (loop, timer);
		1628
		1629	This is relatively simple to implement, but means that each time there is
		1630	some activity, libev will first have to remove the timer from its internal
		1631	data structure and then add it again. Libev tries to be fast, but it's
		1632	still not a constant-time operation.
		1633
		1634	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1635
		1636	This is the easiest way, and involves using C<ev_timer_again> instead of
		1637	C<ev_timer_start>.
		1638
		1639	To implement this, configure an C<ev_timer> with a C<repeat> value
		1640	of C<60> and then call C<ev_timer_again> at start and each time you
		1641	successfully read or write some data. If you go into an idle state where
		1642	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1643	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1644
		1645	That means you can ignore both the C<ev_timer_start> function and the
		1646	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1647	member and C<ev_timer_again>.
		1648
		1649	At start:
		1650
		1651	ev_init (timer, callback);
		1652	timer->repeat = 60.;
		1653	ev_timer_again (loop, timer);
		1654
		1655	Each time there is some activity:
		1656
		1657	ev_timer_again (loop, timer);
		1658
		1659	It is even possible to change the time-out on the fly, regardless of
		1660	whether the watcher is active or not:
		1661
		1662	timer->repeat = 30.;
		1663	ev_timer_again (loop, timer);
		1664
		1665	This is slightly more efficient then stopping/starting the timer each time
		1666	you want to modify its timeout value, as libev does not have to completely
		1667	remove and re-insert the timer from/into its internal data structure.
		1668
		1669	It is, however, even simpler than the "obvious" way to do it.
		1670
		1671	=item 3. Let the timer time out, but then re-arm it as required.
		1672
		1673	This method is more tricky, but usually most efficient: Most timeouts are
		1674	relatively long compared to the intervals between other activity - in
		1675	our example, within 60 seconds, there are usually many I/O events with
		1676	associated activity resets.
		1677
		1678	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1679	but remember the time of last activity, and check for a real timeout only
		1680	within the callback:
		1681
		1682	ev_tstamp last_activity; // time of last activity
		1683
		1684	static void
		1685	callback (EV_P_ ev_timer *w, int revents)
		1686	{
		1687	ev_tstamp now = ev_now (EV_A);
		1688	ev_tstamp timeout = last_activity + 60.;
		1689
		1690	// if last_activity + 60. is older than now, we did time out
		1691	if (timeout < now)
		1692	{
		1693	// timeout occured, take action
		1694	}
		1695	else
		1696	{
		1697	// callback was invoked, but there was some activity, re-arm
		1698	// the watcher to fire in last_activity + 60, which is
		1699	// guaranteed to be in the future, so "again" is positive:
		1700	w->repeat = timeout - now;
		1701	ev_timer_again (EV_A_ w);
		1702	}
		1703	}
		1704
		1705	To summarise the callback: first calculate the real timeout (defined
		1706	as "60 seconds after the last activity"), then check if that time has
		1707	been reached, which means something I<did>, in fact, time out. Otherwise
		1708	the callback was invoked too early (C<timeout> is in the future), so
		1709	re-schedule the timer to fire at that future time, to see if maybe we have
		1710	a timeout then.
		1711
		1712	Note how C<ev_timer_again> is used, taking advantage of the
		1713	C<ev_timer_again> optimisation when the timer is already running.
		1714
		1715	This scheme causes more callback invocations (about one every 60 seconds
		1716	minus half the average time between activity), but virtually no calls to
		1717	libev to change the timeout.
		1718
		1719	To start the timer, simply initialise the watcher and set C<last_activity>
		1720	to the current time (meaning we just have some activity :), then call the
		1721	callback, which will "do the right thing" and start the timer:
		1722
		1723	ev_init (timer, callback);
		1724	last_activity = ev_now (loop);
		1725	callback (loop, timer, EV_TIMEOUT);
		1726
		1727	And when there is some activity, simply store the current time in
		1728	C<last_activity>, no libev calls at all:
		1729
		1730	last_actiivty = ev_now (loop);
		1731
		1732	This technique is slightly more complex, but in most cases where the
		1733	time-out is unlikely to be triggered, much more efficient.
		1734
		1735	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1736	callback :) - just change the timeout and invoke the callback, which will
		1737	fix things for you.
		1738
		1739	=item 4. Wee, just use a double-linked list for your timeouts.
		1740
		1741	If there is not one request, but many thousands (millions...), all
		1742	employing some kind of timeout with the same timeout value, then one can
		1743	do even better:
		1744
		1745	When starting the timeout, calculate the timeout value and put the timeout
		1746	at the I<end> of the list.
		1747
		1748	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1749	the list is expected to fire (for example, using the technique #3).
		1750
		1751	When there is some activity, remove the timer from the list, recalculate
		1752	the timeout, append it to the end of the list again, and make sure to
		1753	update the C<ev_timer> if it was taken from the beginning of the list.
		1754
		1755	This way, one can manage an unlimited number of timeouts in O(1) time for
		1756	starting, stopping and updating the timers, at the expense of a major
		1757	complication, and having to use a constant timeout. The constant timeout
		1758	ensures that the list stays sorted.
		1759
		1760	=back
		1761
		1762	So which method the best?
		1763
		1764	Method #2 is a simple no-brain-required solution that is adequate in most
		1765	situations. Method #3 requires a bit more thinking, but handles many cases
		1766	better, and isn't very complicated either. In most case, choosing either
		1767	one is fine, with #3 being better in typical situations.
		1768
		1769	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1770	rather complicated, but extremely efficient, something that really pays
		1771	off after the first million or so of active timers, i.e. it's usually
		1772	overkill :)
		1773
		1774	=head3 The special problem of time updates
		1775
		1776	Establishing the current time is a costly operation (it usually takes at
		1777	least two system calls): EV therefore updates its idea of the current
		1778	time only before and after C<ev_loop> collects new events, which causes a
		1779	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1780	lots of events in one iteration.
1171		1781
1172	The relative timeouts are calculated relative to the C<ev_now ()>	1782	The relative timeouts are calculated relative to the C<ev_now ()>
1173	time. This is usually the right thing as this timestamp refers to the time	1783	time. This is usually the right thing as this timestamp refers to the time
1174	of the event triggering whatever timeout you are modifying/starting. If	1784	of the event triggering whatever timeout you are modifying/starting. If
1175	you suspect event processing to be delayed and you I<need> to base the timeout	1785	you suspect event processing to be delayed and you I<need> to base the
1176	on the current time, use something like this to adjust for this:	1786	timeout on the current time, use something like this to adjust for this:
1177		1787
1178	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1788	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1179		1789
1180	The callback is guarenteed to be invoked only after its timeout has passed,	1790	If the event loop is suspended for a long time, you can also force an
1181	but if multiple timers become ready during the same loop iteration then	1791	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1182	order of execution is undefined.	1792	()>.
		1793
		1794	=head3 The special problems of suspended animation
		1795
		1796	When you leave the server world it is quite customary to hit machines that
		1797	can suspend/hibernate - what happens to the clocks during such a suspend?
		1798
		1799	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1800	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1801	to run until the system is suspended, but they will not advance while the
		1802	system is suspended. That means, on resume, it will be as if the program
		1803	was frozen for a few seconds, but the suspend time will not be counted
		1804	towards C<ev_timer> when a monotonic clock source is used. The real time
		1805	clock advanced as expected, but if it is used as sole clocksource, then a
		1806	long suspend would be detected as a time jump by libev, and timers would
		1807	be adjusted accordingly.
		1808
		1809	I would not be surprised to see different behaviour in different between
		1810	operating systems, OS versions or even different hardware.
		1811
		1812	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1813	time jump in the monotonic clocks and the realtime clock. If the program
		1814	is suspended for a very long time, and monotonic clock sources are in use,
		1815	then you can expect C<ev_timer>s to expire as the full suspension time
		1816	will be counted towards the timers. When no monotonic clock source is in
		1817	use, then libev will again assume a timejump and adjust accordingly.
		1818
		1819	It might be beneficial for this latter case to call C<ev_suspend>
		1820	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1821	deterministic behaviour in this case (you can do nothing against
		1822	C<SIGSTOP>).
1183		1823
1184	=head3 Watcher-Specific Functions and Data Members	1824	=head3 Watcher-Specific Functions and Data Members
1185		1825
1186	=over 4	1826	=over 4
1187		1827
…		…
1206	This will act as if the timer timed out and restart it again if it is	1846	This will act as if the timer timed out and restart it again if it is
1207	repeating. The exact semantics are:	1847	repeating. The exact semantics are:
1208		1848
1209	If the timer is pending, its pending status is cleared.	1849	If the timer is pending, its pending status is cleared.
1210		1850
1211	If the timer is started but nonrepeating, stop it (as if it timed out).	1851	If the timer is started but non-repeating, stop it (as if it timed out).
1212		1852
1213	If the timer is repeating, either start it if necessary (with the	1853	If the timer is repeating, either start it if necessary (with the
1214	C<repeat> value), or reset the running timer to the C<repeat> value.	1854	C<repeat> value), or reset the running timer to the C<repeat> value.
1215		1855
1216	This sounds a bit complicated, but here is a useful and typical	1856	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1217	example: Imagine you have a tcp connection and you want a so-called idle	1857	usage example.
1218	timeout, that is, you want to be called when there have been, say, 60
1219	seconds of inactivity on the socket. The easiest way to do this is to
1220	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1221	C<ev_timer_again> each time you successfully read or write some data. If
1222	you go into an idle state where you do not expect data to travel on the
1223	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1224	automatically restart it if need be.
1225		1858
1226	That means you can ignore the C<after> value and C<ev_timer_start>	1859	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1227	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1228		1860
1229	ev_timer_init (timer, callback, 0., 5.);	1861	Returns the remaining time until a timer fires. If the timer is active,
1230	ev_timer_again (loop, timer);	1862	then this time is relative to the current event loop time, otherwise it's
1231	...	1863	the timeout value currently configured.
1232	timer->again = 17.;
1233	ev_timer_again (loop, timer);
1234	...
1235	timer->again = 10.;
1236	ev_timer_again (loop, timer);
1237		1864
1238	This is more slightly efficient then stopping/starting the timer each time	1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1239	you want to modify its timeout value.	1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1867	will return C<4>. When the timer expires and is restarted, it will return
		1868	roughly C<7> (likely slightly less as callback invocation takes some time,
		1869	too), and so on.
1240		1870
1241	=item ev_tstamp repeat [read-write]	1871	=item ev_tstamp repeat [read-write]
1242		1872
1243	The current C<repeat> value. Will be used each time the watcher times out	1873	The current C<repeat> value. Will be used each time the watcher times out
1244	or C<ev_timer_again> is called and determines the next timeout (if any),	1874	or C<ev_timer_again> is called, and determines the next timeout (if any),
1245	which is also when any modifications are taken into account.	1875	which is also when any modifications are taken into account.
1246		1876
1247	=back	1877	=back
1248		1878
1249	=head3 Examples	1879	=head3 Examples
1250		1880
1251	Example: Create a timer that fires after 60 seconds.	1881	Example: Create a timer that fires after 60 seconds.
1252		1882
1253	static void	1883	static void
1254	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1884	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1255	{	1885	{
1256	.. one minute over, w is actually stopped right here	1886	.. one minute over, w is actually stopped right here
1257	}	1887	}
1258		1888
1259	struct ev_timer mytimer;	1889	ev_timer mytimer;
1260	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1261	ev_timer_start (loop, &mytimer);	1891	ev_timer_start (loop, &mytimer);
1262		1892
1263	Example: Create a timeout timer that times out after 10 seconds of	1893	Example: Create a timeout timer that times out after 10 seconds of
1264	inactivity.	1894	inactivity.
1265		1895
1266	static void	1896	static void
1267	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1897	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1268	{	1898	{
1269	.. ten seconds without any activity	1899	.. ten seconds without any activity
1270	}	1900	}
1271		1901
1272	struct ev_timer mytimer;	1902	ev_timer mytimer;
1273	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1274	ev_timer_again (&mytimer); /* start timer */	1904	ev_timer_again (&mytimer); /* start timer */
1275	ev_loop (loop, 0);	1905	ev_loop (loop, 0);
1276		1906
1277	// and in some piece of code that gets executed on any "activity":	1907	// and in some piece of code that gets executed on any "activity":
1278	// reset the timeout to start ticking again at 10 seconds	1908	// reset the timeout to start ticking again at 10 seconds
1279	ev_timer_again (&mytimer);	1909	ev_timer_again (&mytimer);
1280		1910
1281		1911
1282	=head2 C<ev_periodic> - to cron or not to cron?	1912	=head2 C<ev_periodic> - to cron or not to cron?
1283		1913
1284	Periodic watchers are also timers of a kind, but they are very versatile	1914	Periodic watchers are also timers of a kind, but they are very versatile
1285	(and unfortunately a bit complex).	1915	(and unfortunately a bit complex).
1286		1916
1287	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1917	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1288	but on wallclock time (absolute time). You can tell a periodic watcher	1918	relative time, the physical time that passes) but on wall clock time
1289	to trigger after some specific point in time. For example, if you tell a	1919	(absolute time, the thing you can read on your calender or clock). The
1290	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1920	difference is that wall clock time can run faster or slower than real
1291	+ 10.>, that is, an absolute time not a delay) and then reset your system	1921	time, and time jumps are not uncommon (e.g. when you adjust your
1292	clock to january of the previous year, then it will take more than year	1922	wrist-watch).
1293	to trigger the event (unlike an C<ev_timer>, which would still trigger
1294	roughly 10 seconds later as it uses a relative timeout).
1295		1923
		1924	You can tell a periodic watcher to trigger after some specific point
		1925	in time: for example, if you tell a periodic watcher to trigger "in 10
		1926	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1927	not a delay) and then reset your system clock to January of the previous
		1928	year, then it will take a year or more to trigger the event (unlike an
		1929	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1930	it, as it uses a relative timeout).
		1931
1296	C<ev_periodic>s can also be used to implement vastly more complex timers,	1932	C<ev_periodic> watchers can also be used to implement vastly more complex
1297	such as triggering an event on each "midnight, local time", or other	1933	timers, such as triggering an event on each "midnight, local time", or
1298	complicated, rules.	1934	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1935	those cannot react to time jumps.
1299		1936
1300	As with timers, the callback is guarenteed to be invoked only when the	1937	As with timers, the callback is guaranteed to be invoked only when the
1301	time (C<at>) has passed, but if multiple periodic timers become ready	1938	point in time where it is supposed to trigger has passed. If multiple
1302	during the same loop iteration then order of execution is undefined.	1939	timers become ready during the same loop iteration then the ones with
		1940	earlier time-out values are invoked before ones with later time-out values
		1941	(but this is no longer true when a callback calls C<ev_loop> recursively).
1303		1942
1304	=head3 Watcher-Specific Functions and Data Members	1943	=head3 Watcher-Specific Functions and Data Members
1305		1944
1306	=over 4	1945	=over 4
1307		1946
1308	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1947	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1309		1948
1310	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1949	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1311		1950
1312	Lots of arguments, lets sort it out... There are basically three modes of	1951	Lots of arguments, let's sort it out... There are basically three modes of
1313	operation, and we will explain them from simplest to complex:	1952	operation, and we will explain them from simplest to most complex:
1314		1953
1315	=over 4	1954	=over 4
1316		1955
1317	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1956	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1318		1957
1319	In this configuration the watcher triggers an event after the wallclock	1958	In this configuration the watcher triggers an event after the wall clock
1320	time C<at> has passed and doesn't repeat. It will not adjust when a time	1959	time C<offset> has passed. It will not repeat and will not adjust when a
1321	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1960	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1322	run when the system time reaches or surpasses this time.	1961	will be stopped and invoked when the system clock reaches or surpasses
		1962	this point in time.
1323		1963
1324	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1964	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1325		1965
1326	In this mode the watcher will always be scheduled to time out at the next	1966	In this mode the watcher will always be scheduled to time out at the next
1327	C<at + N * interval> time (for some integer N, which can also be negative)	1967	C<offset + N * interval> time (for some integer N, which can also be
1328	and then repeat, regardless of any time jumps.	1968	negative) and then repeat, regardless of any time jumps. The C<offset>
		1969	argument is merely an offset into the C<interval> periods.
1329		1970
1330	This can be used to create timers that do not drift with respect to system	1971	This can be used to create timers that do not drift with respect to the
1331	time, for example, here is a C<ev_periodic> that triggers each hour, on	1972	system clock, for example, here is an C<ev_periodic> that triggers each
1332	the hour:	1973	hour, on the hour (with respect to UTC):
1333		1974
1334	ev_periodic_set (&periodic, 0., 3600., 0);	1975	ev_periodic_set (&periodic, 0., 3600., 0);
1335		1976
1336	This doesn't mean there will always be 3600 seconds in between triggers,	1977	This doesn't mean there will always be 3600 seconds in between triggers,
1337	but only that the the callback will be called when the system time shows a	1978	but only that the callback will be called when the system time shows a
1338	full hour (UTC), or more correctly, when the system time is evenly divisible	1979	full hour (UTC), or more correctly, when the system time is evenly divisible
1339	by 3600.	1980	by 3600.
1340		1981
1341	Another way to think about it (for the mathematically inclined) is that	1982	Another way to think about it (for the mathematically inclined) is that
1342	C<ev_periodic> will try to run the callback in this mode at the next possible	1983	C<ev_periodic> will try to run the callback in this mode at the next possible
1343	time where C<time = at (mod interval)>, regardless of any time jumps.	1984	time where C<time = offset (mod interval)>, regardless of any time jumps.
1344		1985
1345	For numerical stability it is preferable that the C<at> value is near	1986	For numerical stability it is preferable that the C<offset> value is near
1346	C<ev_now ()> (the current time), but there is no range requirement for	1987	C<ev_now ()> (the current time), but there is no range requirement for
1347	this value, and in fact is often specified as zero.	1988	this value, and in fact is often specified as zero.
1348		1989
1349	Note also that there is an upper limit to how often a timer can fire (cpu	1990	Note also that there is an upper limit to how often a timer can fire (CPU
1350	speed for example), so if C<interval> is very small then timing stability	1991	speed for example), so if C<interval> is very small then timing stability
1351	will of course detoriate. Libev itself tries to be exact to be about one	1992	will of course deteriorate. Libev itself tries to be exact to be about one
1352	millisecond (if the OS supports it and the machine is fast enough).	1993	millisecond (if the OS supports it and the machine is fast enough).
1353		1994
1354	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1995	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1355		1996
1356	In this mode the values for C<interval> and C<at> are both being	1997	In this mode the values for C<interval> and C<offset> are both being
1357	ignored. Instead, each time the periodic watcher gets scheduled, the	1998	ignored. Instead, each time the periodic watcher gets scheduled, the
1358	reschedule callback will be called with the watcher as first, and the	1999	reschedule callback will be called with the watcher as first, and the
1359	current time as second argument.	2000	current time as second argument.
1360		2001
1361	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2002	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1362	ever, or make ANY event loop modifications whatsoever>.	2003	or make ANY other event loop modifications whatsoever, unless explicitly
		2004	allowed by documentation here>.
1363		2005
1364	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2006	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1365	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2007	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1366	only event loop modification you are allowed to do).	2008	only event loop modification you are allowed to do).
1367		2009
1368	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2010	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1369	*w, ev_tstamp now)>, e.g.:	2011	*w, ev_tstamp now)>, e.g.:
1370		2012
		2013	static ev_tstamp
1371	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2014	my_rescheduler (ev_periodic *w, ev_tstamp now)
1372	{	2015	{
1373	return now + 60.;	2016	return now + 60.;
1374	}	2017	}
1375		2018
1376	It must return the next time to trigger, based on the passed time value	2019	It must return the next time to trigger, based on the passed time value
…		…
1396	a different time than the last time it was called (e.g. in a crond like	2039	a different time than the last time it was called (e.g. in a crond like
1397	program when the crontabs have changed).	2040	program when the crontabs have changed).
1398		2041
1399	=item ev_tstamp ev_periodic_at (ev_periodic *)	2042	=item ev_tstamp ev_periodic_at (ev_periodic *)
1400		2043
1401	When active, returns the absolute time that the watcher is supposed to	2044	When active, returns the absolute time that the watcher is supposed
1402	trigger next.	2045	to trigger next. This is not the same as the C<offset> argument to
		2046	C<ev_periodic_set>, but indeed works even in interval and manual
		2047	rescheduling modes.
1403		2048
1404	=item ev_tstamp offset [read-write]	2049	=item ev_tstamp offset [read-write]
1405		2050
1406	When repeating, this contains the offset value, otherwise this is the	2051	When repeating, this contains the offset value, otherwise this is the
1407	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2052	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2053	although libev might modify this value for better numerical stability).
1408		2054
1409	Can be modified any time, but changes only take effect when the periodic	2055	Can be modified any time, but changes only take effect when the periodic
1410	timer fires or C<ev_periodic_again> is being called.	2056	timer fires or C<ev_periodic_again> is being called.
1411		2057
1412	=item ev_tstamp interval [read-write]	2058	=item ev_tstamp interval [read-write]
1413		2059
1414	The current interval value. Can be modified any time, but changes only	2060	The current interval value. Can be modified any time, but changes only
1415	take effect when the periodic timer fires or C<ev_periodic_again> is being	2061	take effect when the periodic timer fires or C<ev_periodic_again> is being
1416	called.	2062	called.
1417		2063
1418	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2064	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1419		2065
1420	The current reschedule callback, or C<0>, if this functionality is	2066	The current reschedule callback, or C<0>, if this functionality is
1421	switched off. Can be changed any time, but changes only take effect when	2067	switched off. Can be changed any time, but changes only take effect when
1422	the periodic timer fires or C<ev_periodic_again> is being called.	2068	the periodic timer fires or C<ev_periodic_again> is being called.
1423		2069
1424	=back	2070	=back
1425		2071
1426	=head3 Examples	2072	=head3 Examples
1427		2073
1428	Example: Call a callback every hour, or, more precisely, whenever the	2074	Example: Call a callback every hour, or, more precisely, whenever the
1429	system clock is divisible by 3600. The callback invocation times have	2075	system time is divisible by 3600. The callback invocation times have
1430	potentially a lot of jittering, but good long-term stability.	2076	potentially a lot of jitter, but good long-term stability.
1431		2077
1432	static void	2078	static void
1433	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1434	{	2080	{
1435	... its now a full hour (UTC, or TAI or whatever your clock follows)	2081	... its now a full hour (UTC, or TAI or whatever your clock follows)
1436	}	2082	}
1437		2083
1438	struct ev_periodic hourly_tick;	2084	ev_periodic hourly_tick;
1439	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2085	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1440	ev_periodic_start (loop, &hourly_tick);	2086	ev_periodic_start (loop, &hourly_tick);
1441		2087
1442	Example: The same as above, but use a reschedule callback to do it:	2088	Example: The same as above, but use a reschedule callback to do it:
1443		2089
1444	#include <math.h>	2090	#include <math.h>
1445		2091
1446	static ev_tstamp	2092	static ev_tstamp
1447	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2093	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1448	{	2094	{
1449	return fmod (now, 3600.) + 3600.;	2095	return now + (3600. - fmod (now, 3600.));
1450	}	2096	}
1451		2097
1452	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2098	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1453		2099
1454	Example: Call a callback every hour, starting now:	2100	Example: Call a callback every hour, starting now:
1455		2101
1456	struct ev_periodic hourly_tick;	2102	ev_periodic hourly_tick;
1457	ev_periodic_init (&hourly_tick, clock_cb,	2103	ev_periodic_init (&hourly_tick, clock_cb,
1458	fmod (ev_now (loop), 3600.), 3600., 0);	2104	fmod (ev_now (loop), 3600.), 3600., 0);
1459	ev_periodic_start (loop, &hourly_tick);	2105	ev_periodic_start (loop, &hourly_tick);
1460		2106
1461		2107
1462	=head2 C<ev_signal> - signal me when a signal gets signalled!	2108	=head2 C<ev_signal> - signal me when a signal gets signalled!
1463		2109
1464	Signal watchers will trigger an event when the process receives a specific	2110	Signal watchers will trigger an event when the process receives a specific
1465	signal one or more times. Even though signals are very asynchronous, libev	2111	signal one or more times. Even though signals are very asynchronous, libev
1466	will try it's best to deliver signals synchronously, i.e. as part of the	2112	will try it's best to deliver signals synchronously, i.e. as part of the
1467	normal event processing, like any other event.	2113	normal event processing, like any other event.
1468		2114
		2115	If you want signals to be delivered truly asynchronously, just use
		2116	C<sigaction> as you would do without libev and forget about sharing
		2117	the signal. You can even use C<ev_async> from a signal handler to
		2118	synchronously wake up an event loop.
		2119
1469	You can configure as many watchers as you like per signal. Only when the	2120	You can configure as many watchers as you like for the same signal, but
		2121	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2122	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2123	C<SIGINT> in both the default loop and another loop at the same time. At
		2124	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2125
1470	first watcher gets started will libev actually register a signal watcher	2126	When the first watcher gets started will libev actually register something
1471	with the kernel (thus it coexists with your own signal handlers as long	2127	with the kernel (thus it coexists with your own signal handlers as long as
1472	as you don't register any with libev). Similarly, when the last signal	2128	you don't register any with libev for the same signal).
1473	watcher for a signal is stopped libev will reset the signal handler to
1474	SIG_DFL (regardless of what it was set to before).
1475		2129
1476	If possible and supported, libev will install its handlers with	2130	If possible and supported, libev will install its handlers with
1477	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1478	interrupted. If you have a problem with syscalls getting interrupted by	2132	not be unduly interrupted. If you have a problem with system calls getting
1479	signals you can block all signals in an C<ev_check> watcher and unblock	2133	interrupted by signals you can block all signals in an C<ev_check> watcher
1480	them in an C<ev_prepare> watcher.	2134	and unblock them in an C<ev_prepare> watcher.
		2135
		2136	=head3 The special problem of inheritance over execve
		2137
		2138	Both the signal mask (C<sigprocmask>) and the signal disposition
		2139	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2140	stopping it again), that is, libev might or might not block the signal,
		2141	and might or might not set or restore the installed signal handler.
		2142
		2143	While this does not matter for the signal disposition (libev never
		2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2145	C<execve>), this matters for the signal mask: many programs do not expect
		2146	certain signals to be blocked.
		2147
		2148	This means that before calling C<exec> (from the child) you should reset
		2149	the signal mask to whatever "default" you expect (all clear is a good
		2150	choice usually).
		2151
		2152	The simplest way to ensure that the signal mask is reset in the child is
		2153	to install a fork handler with C<pthread_atfork> that resets it. That will
		2154	catch fork calls done by libraries (such as the libc) as well.
		2155
		2156	In current versions of libev, you can also ensure that the signal mask is
		2157	not blocking any signals (except temporarily, so thread users watch out)
		2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2159	is not guaranteed for future versions, however.
1481		2160
1482	=head3 Watcher-Specific Functions and Data Members	2161	=head3 Watcher-Specific Functions and Data Members
1483		2162
1484	=over 4	2163	=over 4
1485		2164
…		…
1496		2175
1497	=back	2176	=back
1498		2177
1499	=head3 Examples	2178	=head3 Examples
1500		2179
1501	Example: Try to exit cleanly on SIGINT and SIGTERM.	2180	Example: Try to exit cleanly on SIGINT.
1502		2181
1503	static void	2182	static void
1504	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1505	{	2184	{
1506	ev_unloop (loop, EVUNLOOP_ALL);	2185	ev_unloop (loop, EVUNLOOP_ALL);
1507	}	2186	}
1508		2187
1509	struct ev_signal signal_watcher;	2188	ev_signal signal_watcher;
1510	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1511	ev_signal_start (loop, &sigint_cb);	2190	ev_signal_start (loop, &signal_watcher);
1512		2191
1513		2192
1514	=head2 C<ev_child> - watch out for process status changes	2193	=head2 C<ev_child> - watch out for process status changes
1515		2194
1516	Child watchers trigger when your process receives a SIGCHLD in response to	2195	Child watchers trigger when your process receives a SIGCHLD in response to
1517	some child status changes (most typically when a child of yours dies). It	2196	some child status changes (most typically when a child of yours dies or
1518	is permissible to install a child watcher I<after> the child has been	2197	exits). It is permissible to install a child watcher I<after> the child
1519	forked (which implies it might have already exited), as long as the event	2198	has been forked (which implies it might have already exited), as long
1520	loop isn't entered (or is continued from a watcher).	2199	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2200	forking and then immediately registering a watcher for the child is fine,
		2201	but forking and registering a watcher a few event loop iterations later or
		2202	in the next callback invocation is not.
1521		2203
1522	Only the default event loop is capable of handling signals, and therefore	2204	Only the default event loop is capable of handling signals, and therefore
1523	you can only rgeister child watchers in the default event loop.	2205	you can only register child watchers in the default event loop.
		2206
		2207	Due to some design glitches inside libev, child watchers will always be
		2208	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2209	libev)
1524		2210
1525	=head3 Process Interaction	2211	=head3 Process Interaction
1526		2212
1527	Libev grabs C<SIGCHLD> as soon as the default event loop is	2213	Libev grabs C<SIGCHLD> as soon as the default event loop is
1528	initialised. This is necessary to guarantee proper behaviour even if	2214	initialised. This is necessary to guarantee proper behaviour even if the
1529	the first child watcher is started after the child exits. The occurance	2215	first child watcher is started after the child exits. The occurrence
1530	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2216	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1531	synchronously as part of the event loop processing. Libev always reaps all	2217	synchronously as part of the event loop processing. Libev always reaps all
1532	children, even ones not watched.	2218	children, even ones not watched.
1533		2219
1534	=head3 Overriding the Built-In Processing	2220	=head3 Overriding the Built-In Processing
…		…
1538	handler, you can override it easily by installing your own handler for	2224	handler, you can override it easily by installing your own handler for
1539	C<SIGCHLD> after initialising the default loop, and making sure the	2225	C<SIGCHLD> after initialising the default loop, and making sure the
1540	default loop never gets destroyed. You are encouraged, however, to use an	2226	default loop never gets destroyed. You are encouraged, however, to use an
1541	event-based approach to child reaping and thus use libev's support for	2227	event-based approach to child reaping and thus use libev's support for
1542	that, so other libev users can use C<ev_child> watchers freely.	2228	that, so other libev users can use C<ev_child> watchers freely.
		2229
		2230	=head3 Stopping the Child Watcher
		2231
		2232	Currently, the child watcher never gets stopped, even when the
		2233	child terminates, so normally one needs to stop the watcher in the
		2234	callback. Future versions of libev might stop the watcher automatically
		2235	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2236	problem).
1543		2237
1544	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1545		2239
1546	=over 4	2240	=over 4
1547		2241
…		…
1576	=head3 Examples	2270	=head3 Examples
1577		2271
1578	Example: C<fork()> a new process and install a child handler to wait for	2272	Example: C<fork()> a new process and install a child handler to wait for
1579	its completion.	2273	its completion.
1580		2274
1581	ev_child cw;	2275	ev_child cw;
1582		2276
1583	static void	2277	static void
1584	child_cb (EV_P_ struct ev_child *w, int revents)	2278	child_cb (EV_P_ ev_child *w, int revents)
1585	{	2279	{
1586	ev_child_stop (EV_A_ w);	2280	ev_child_stop (EV_A_ w);
1587	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2281	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1588	}	2282	}
1589		2283
1590	pid_t pid = fork ();	2284	pid_t pid = fork ();
1591		2285
1592	if (pid < 0)	2286	if (pid < 0)
1593	// error	2287	// error
1594	else if (pid == 0)	2288	else if (pid == 0)
1595	{	2289	{
1596	// the forked child executes here	2290	// the forked child executes here
1597	exit (1);	2291	exit (1);
1598	}	2292	}
1599	else	2293	else
1600	{	2294	{
1601	ev_child_init (&cw, child_cb, pid, 0);	2295	ev_child_init (&cw, child_cb, pid, 0);
1602	ev_child_start (EV_DEFAULT_ &cw);	2296	ev_child_start (EV_DEFAULT_ &cw);
1603	}	2297	}
1604		2298
1605		2299
1606	=head2 C<ev_stat> - did the file attributes just change?	2300	=head2 C<ev_stat> - did the file attributes just change?
1607		2301
1608	This watches a filesystem path for attribute changes. That is, it calls	2302	This watches a file system path for attribute changes. That is, it calls
1609	C<stat> regularly (or when the OS says it changed) and sees if it changed	2303	C<stat> on that path in regular intervals (or when the OS says it changed)
1610	compared to the last time, invoking the callback if it did.	2304	and sees if it changed compared to the last time, invoking the callback if
		2305	it did.
1611		2306
1612	The path does not need to exist: changing from "path exists" to "path does	2307	The path does not need to exist: changing from "path exists" to "path does
1613	not exist" is a status change like any other. The condition "path does	2308	not exist" is a status change like any other. The condition "path does not
1614	not exist" is signified by the C<st_nlink> field being zero (which is	2309	exist" (or more correctly "path cannot be stat'ed") is signified by the
1615	otherwise always forced to be at least one) and all the other fields of	2310	C<st_nlink> field being zero (which is otherwise always forced to be at
1616	the stat buffer having unspecified contents.	2311	least one) and all the other fields of the stat buffer having unspecified
		2312	contents.
1617		2313
1618	The path I<should> be absolute and I<must not> end in a slash. If it is	2314	The path I<must not> end in a slash or contain special components such as
		2315	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1619	relative and your working directory changes, the behaviour is undefined.	2316	your working directory changes, then the behaviour is undefined.
1620		2317
1621	Since there is no standard to do this, the portable implementation simply	2318	Since there is no portable change notification interface available, the
1622	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2319	portable implementation simply calls C<stat(2)> regularly on the path
1623	can specify a recommended polling interval for this case. If you specify	2320	to see if it changed somehow. You can specify a recommended polling
1624	a polling interval of C<0> (highly recommended!) then a I<suitable,	2321	interval for this case. If you specify a polling interval of C<0> (highly
1625	unspecified default> value will be used (which you can expect to be around	2322	recommended!) then a I<suitable, unspecified default> value will be used
1626	five seconds, although this might change dynamically). Libev will also	2323	(which you can expect to be around five seconds, although this might
1627	impose a minimum interval which is currently around C<0.1>, but thats	2324	change dynamically). Libev will also impose a minimum interval which is
1628	usually overkill.	2325	currently around C<0.1>, but that's usually overkill.
1629		2326
1630	This watcher type is not meant for massive numbers of stat watchers,	2327	This watcher type is not meant for massive numbers of stat watchers,
1631	as even with OS-supported change notifications, this can be	2328	as even with OS-supported change notifications, this can be
1632	resource-intensive.	2329	resource-intensive.
1633		2330
1634	At the time of this writing, only the Linux inotify interface is	2331	At the time of this writing, the only OS-specific interface implemented
1635	implemented (implementing kqueue support is left as an exercise for the	2332	is the Linux inotify interface (implementing kqueue support is left as an
1636	reader, note, however, that the author sees no way of implementing ev_stat	2333	exercise for the reader. Note, however, that the author sees no way of
1637	semantics with kqueue). Inotify will be used to give hints only and should	2334	implementing C<ev_stat> semantics with kqueue, except as a hint).
1638	not change the semantics of C<ev_stat> watchers, which means that libev
1639	sometimes needs to fall back to regular polling again even with inotify,
1640	but changes are usually detected immediately, and if the file exists there
1641	will be no polling.
1642		2335
1643	=head3 ABI Issues (Largefile Support)	2336	=head3 ABI Issues (Largefile Support)
1644		2337
1645	Libev by default (unless the user overrides this) uses the default	2338	Libev by default (unless the user overrides this) uses the default
1646	compilation environment, which means that on systems with optionally	2339	compilation environment, which means that on systems with large file
1647	disabled large file support, you get the 32 bit version of the stat	2340	support disabled by default, you get the 32 bit version of the stat
1648	structure. When using the library from programs that change the ABI to	2341	structure. When using the library from programs that change the ABI to
1649	use 64 bit file offsets the programs will fail. In that case you have to	2342	use 64 bit file offsets the programs will fail. In that case you have to
1650	compile libev with the same flags to get binary compatibility. This is	2343	compile libev with the same flags to get binary compatibility. This is
1651	obviously the case with any flags that change the ABI, but the problem is	2344	obviously the case with any flags that change the ABI, but the problem is
1652	most noticably with ev_stat and largefile support.	2345	most noticeably displayed with ev_stat and large file support.
1653		2346
1654	=head3 Inotify	2347	The solution for this is to lobby your distribution maker to make large
		2348	file interfaces available by default (as e.g. FreeBSD does) and not
		2349	optional. Libev cannot simply switch on large file support because it has
		2350	to exchange stat structures with application programs compiled using the
		2351	default compilation environment.
1655		2352
		2353	=head3 Inotify and Kqueue
		2354
1656	When C<inotify (7)> support has been compiled into libev (generally only	2355	When C<inotify (7)> support has been compiled into libev and present at
1657	available on Linux) and present at runtime, it will be used to speed up	2356	runtime, it will be used to speed up change detection where possible. The
1658	change detection where possible. The inotify descriptor will be created lazily	2357	inotify descriptor will be created lazily when the first C<ev_stat>
1659	when the first C<ev_stat> watcher is being started.	2358	watcher is being started.
1660		2359
1661	Inotify presence does not change the semantics of C<ev_stat> watchers	2360	Inotify presence does not change the semantics of C<ev_stat> watchers
1662	except that changes might be detected earlier, and in some cases, to avoid	2361	except that changes might be detected earlier, and in some cases, to avoid
1663	making regular C<stat> calls. Even in the presence of inotify support	2362	making regular C<stat> calls. Even in the presence of inotify support
1664	there are many cases where libev has to resort to regular C<stat> polling.	2363	there are many cases where libev has to resort to regular C<stat> polling,
		2364	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2365	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2366	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2367	xfs are fully working) libev usually gets away without polling.
1665		2368
1666	(There is no support for kqueue, as apparently it cannot be used to	2369	There is no support for kqueue, as apparently it cannot be used to
1667	implement this functionality, due to the requirement of having a file	2370	implement this functionality, due to the requirement of having a file
1668	descriptor open on the object at all times).	2371	descriptor open on the object at all times, and detecting renames, unlinks
		2372	etc. is difficult.
		2373
		2374	=head3 C<stat ()> is a synchronous operation
		2375
		2376	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2377	the process. The exception are C<ev_stat> watchers - those call C<stat
		2378	()>, which is a synchronous operation.
		2379
		2380	For local paths, this usually doesn't matter: unless the system is very
		2381	busy or the intervals between stat's are large, a stat call will be fast,
		2382	as the path data is usually in memory already (except when starting the
		2383	watcher).
		2384
		2385	For networked file systems, calling C<stat ()> can block an indefinite
		2386	time due to network issues, and even under good conditions, a stat call
		2387	often takes multiple milliseconds.
		2388
		2389	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2390	paths, although this is fully supported by libev.
1669		2391
1670	=head3 The special problem of stat time resolution	2392	=head3 The special problem of stat time resolution
1671		2393
1672	The C<stat ()> syscall only supports full-second resolution portably, and	2394	The C<stat ()> system call only supports full-second resolution portably,
1673	even on systems where the resolution is higher, many filesystems still	2395	and even on systems where the resolution is higher, most file systems
1674	only support whole seconds.	2396	still only support whole seconds.
1675		2397
1676	That means that, if the time is the only thing that changes, you can	2398	That means that, if the time is the only thing that changes, you can
1677	easily miss updates: on the first update, C<ev_stat> detects a change and	2399	easily miss updates: on the first update, C<ev_stat> detects a change and
1678	calls your callback, which does something. When there is another update	2400	calls your callback, which does something. When there is another update
1679	within the same second, C<ev_stat> will be unable to detect it as the stat	2401	within the same second, C<ev_stat> will be unable to detect unless the
1680	data does not change.	2402	stat data does change in other ways (e.g. file size).
1681		2403
1682	The solution to this is to delay acting on a change for slightly more	2404	The solution to this is to delay acting on a change for slightly more
1683	than a second (or till slightly after the next full second boundary), using	2405	than a second (or till slightly after the next full second boundary), using
1684	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2406	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1685	ev_timer_again (loop, w)>).	2407	ev_timer_again (loop, w)>).
…		…
1705	C<path>. The C<interval> is a hint on how quickly a change is expected to	2427	C<path>. The C<interval> is a hint on how quickly a change is expected to
1706	be detected and should normally be specified as C<0> to let libev choose	2428	be detected and should normally be specified as C<0> to let libev choose
1707	a suitable value. The memory pointed to by C<path> must point to the same	2429	a suitable value. The memory pointed to by C<path> must point to the same
1708	path for as long as the watcher is active.	2430	path for as long as the watcher is active.
1709		2431
1710	The callback will receive C<EV_STAT> when a change was detected, relative	2432	The callback will receive an C<EV_STAT> event when a change was detected,
1711	to the attributes at the time the watcher was started (or the last change	2433	relative to the attributes at the time the watcher was started (or the
1712	was detected).	2434	last change was detected).
1713		2435
1714	=item ev_stat_stat (loop, ev_stat *)	2436	=item ev_stat_stat (loop, ev_stat *)
1715		2437
1716	Updates the stat buffer immediately with new values. If you change the	2438	Updates the stat buffer immediately with new values. If you change the
1717	watched path in your callback, you could call this function to avoid	2439	watched path in your callback, you could call this function to avoid
…		…
1738		2460
1739	The specified interval.	2461	The specified interval.
1740		2462
1741	=item const char *path [read-only]	2463	=item const char *path [read-only]
1742		2464
1743	The filesystem path that is being watched.	2465	The file system path that is being watched.
1744		2466
1745	=back	2467	=back
1746		2468
1747	=head3 Examples	2469	=head3 Examples
1748		2470
1749	Example: Watch C</etc/passwd> for attribute changes.	2471	Example: Watch C</etc/passwd> for attribute changes.
1750		2472
1751	static void	2473	static void
1752	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2474	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1753	{	2475	{
1754	/* /etc/passwd changed in some way */	2476	/* /etc/passwd changed in some way */
1755	if (w->attr.st_nlink)	2477	if (w->attr.st_nlink)
1756	{	2478	{
1757	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2479	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1758	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2480	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1759	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2481	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1760	}	2482	}
1761	else	2483	else
1762	/* you shalt not abuse printf for puts */	2484	/* you shalt not abuse printf for puts */
1763	puts ("wow, /etc/passwd is not there, expect problems. "	2485	puts ("wow, /etc/passwd is not there, expect problems. "
1764	"if this is windows, they already arrived\n");	2486	"if this is windows, they already arrived\n");
1765	}	2487	}
1766		2488
1767	...	2489	...
1768	ev_stat passwd;	2490	ev_stat passwd;
1769		2491
1770	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2492	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1771	ev_stat_start (loop, &passwd);	2493	ev_stat_start (loop, &passwd);
1772		2494
1773	Example: Like above, but additionally use a one-second delay so we do not	2495	Example: Like above, but additionally use a one-second delay so we do not
1774	miss updates (however, frequent updates will delay processing, too, so	2496	miss updates (however, frequent updates will delay processing, too, so
1775	one might do the work both on C<ev_stat> callback invocation I<and> on	2497	one might do the work both on C<ev_stat> callback invocation I<and> on
1776	C<ev_timer> callback invocation).	2498	C<ev_timer> callback invocation).
1777		2499
1778	static ev_stat passwd;	2500	static ev_stat passwd;
1779	static ev_timer timer;	2501	static ev_timer timer;
1780		2502
1781	static void	2503	static void
1782	timer_cb (EV_P_ ev_timer *w, int revents)	2504	timer_cb (EV_P_ ev_timer *w, int revents)
1783	{	2505	{
1784	ev_timer_stop (EV_A_ w);	2506	ev_timer_stop (EV_A_ w);
1785		2507
1786	/* now it's one second after the most recent passwd change */	2508	/* now it's one second after the most recent passwd change */
1787	}	2509	}
1788		2510
1789	static void	2511	static void
1790	stat_cb (EV_P_ ev_stat *w, int revents)	2512	stat_cb (EV_P_ ev_stat *w, int revents)
1791	{	2513	{
1792	/* reset the one-second timer */	2514	/* reset the one-second timer */
1793	ev_timer_again (EV_A_ &timer);	2515	ev_timer_again (EV_A_ &timer);
1794	}	2516	}
1795		2517
1796	...	2518	...
1797	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2519	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1798	ev_stat_start (loop, &passwd);	2520	ev_stat_start (loop, &passwd);
1799	ev_timer_init (&timer, timer_cb, 0., 1.02);	2521	ev_timer_init (&timer, timer_cb, 0., 1.02);
1800		2522
1801		2523
1802	=head2 C<ev_idle> - when you've got nothing better to do...	2524	=head2 C<ev_idle> - when you've got nothing better to do...
1803		2525
1804	Idle watchers trigger events when no other events of the same or higher	2526	Idle watchers trigger events when no other events of the same or higher
1805	priority are pending (prepare, check and other idle watchers do not	2527	priority are pending (prepare, check and other idle watchers do not count
1806	count).	2528	as receiving "events").
1807		2529
1808	That is, as long as your process is busy handling sockets or timeouts	2530	That is, as long as your process is busy handling sockets or timeouts
1809	(or even signals, imagine) of the same or higher priority it will not be	2531	(or even signals, imagine) of the same or higher priority it will not be
1810	triggered. But when your process is idle (or only lower-priority watchers	2532	triggered. But when your process is idle (or only lower-priority watchers
1811	are pending), the idle watchers are being called once per event loop	2533	are pending), the idle watchers are being called once per event loop
…		…
1822		2544
1823	=head3 Watcher-Specific Functions and Data Members	2545	=head3 Watcher-Specific Functions and Data Members
1824		2546
1825	=over 4	2547	=over 4
1826		2548
1827	=item ev_idle_init (ev_signal *, callback)	2549	=item ev_idle_init (ev_idle *, callback)
1828		2550
1829	Initialises and configures the idle watcher - it has no parameters of any	2551	Initialises and configures the idle watcher - it has no parameters of any
1830	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2552	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1831	believe me.	2553	believe me.
1832		2554
…		…
1835	=head3 Examples	2557	=head3 Examples
1836		2558
1837	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2559	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1838	callback, free it. Also, use no error checking, as usual.	2560	callback, free it. Also, use no error checking, as usual.
1839		2561
1840	static void	2562	static void
1841	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2563	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1842	{	2564	{
1843	free (w);	2565	free (w);
1844	// now do something you wanted to do when the program has	2566	// now do something you wanted to do when the program has
1845	// no longer anything immediate to do.	2567	// no longer anything immediate to do.
1846	}	2568	}
1847		2569
1848	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2570	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1849	ev_idle_init (idle_watcher, idle_cb);	2571	ev_idle_init (idle_watcher, idle_cb);
1850	ev_idle_start (loop, idle_cb);	2572	ev_idle_start (loop, idle_watcher);
1851		2573
1852		2574
1853	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2575	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1854		2576
1855	Prepare and check watchers are usually (but not always) used in tandem:	2577	Prepare and check watchers are usually (but not always) used in pairs:
1856	prepare watchers get invoked before the process blocks and check watchers	2578	prepare watchers get invoked before the process blocks and check watchers
1857	afterwards.	2579	afterwards.
1858		2580
1859	You I<must not> call C<ev_loop> or similar functions that enter	2581	You I<must not> call C<ev_loop> or similar functions that enter
1860	the current event loop from either C<ev_prepare> or C<ev_check>	2582	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1863	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2585	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1864	C<ev_check> so if you have one watcher of each kind they will always be	2586	C<ev_check> so if you have one watcher of each kind they will always be
1865	called in pairs bracketing the blocking call.	2587	called in pairs bracketing the blocking call.
1866		2588
1867	Their main purpose is to integrate other event mechanisms into libev and	2589	Their main purpose is to integrate other event mechanisms into libev and
1868	their use is somewhat advanced. This could be used, for example, to track	2590	their use is somewhat advanced. They could be used, for example, to track
1869	variable changes, implement your own watchers, integrate net-snmp or a	2591	variable changes, implement your own watchers, integrate net-snmp or a
1870	coroutine library and lots more. They are also occasionally useful if	2592	coroutine library and lots more. They are also occasionally useful if
1871	you cache some data and want to flush it before blocking (for example,	2593	you cache some data and want to flush it before blocking (for example,
1872	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2594	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1873	watcher).	2595	watcher).
1874		2596
1875	This is done by examining in each prepare call which file descriptors need	2597	This is done by examining in each prepare call which file descriptors
1876	to be watched by the other library, registering C<ev_io> watchers for	2598	need to be watched by the other library, registering C<ev_io> watchers
1877	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2599	for them and starting an C<ev_timer> watcher for any timeouts (many
1878	provide just this functionality). Then, in the check watcher you check for	2600	libraries provide exactly this functionality). Then, in the check watcher,
1879	any events that occured (by checking the pending status of all watchers	2601	you check for any events that occurred (by checking the pending status
1880	and stopping them) and call back into the library. The I/O and timer	2602	of all watchers and stopping them) and call back into the library. The
1881	callbacks will never actually be called (but must be valid nevertheless,	2603	I/O and timer callbacks will never actually be called (but must be valid
1882	because you never know, you know?).	2604	nevertheless, because you never know, you know?).
1883		2605
1884	As another example, the Perl Coro module uses these hooks to integrate	2606	As another example, the Perl Coro module uses these hooks to integrate
1885	coroutines into libev programs, by yielding to other active coroutines	2607	coroutines into libev programs, by yielding to other active coroutines
1886	during each prepare and only letting the process block if no coroutines	2608	during each prepare and only letting the process block if no coroutines
1887	are ready to run (it's actually more complicated: it only runs coroutines	2609	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1890	loop from blocking if lower-priority coroutines are active, thus mapping	2612	loop from blocking if lower-priority coroutines are active, thus mapping
1891	low-priority coroutines to idle/background tasks).	2613	low-priority coroutines to idle/background tasks).
1892		2614
1893	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2615	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1894	priority, to ensure that they are being run before any other watchers	2616	priority, to ensure that they are being run before any other watchers
		2617	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2618
1895	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2619	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1896	too) should not activate ("feed") events into libev. While libev fully	2620	activate ("feed") events into libev. While libev fully supports this, they
1897	supports this, they might get executed before other C<ev_check> watchers	2621	might get executed before other C<ev_check> watchers did their job. As
1898	did their job. As C<ev_check> watchers are often used to embed other	2622	C<ev_check> watchers are often used to embed other (non-libev) event
1899	(non-libev) event loops those other event loops might be in an unusable	2623	loops those other event loops might be in an unusable state until their
1900	state until their C<ev_check> watcher ran (always remind yourself to	2624	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1901	coexist peacefully with others).	2625	others).
1902		2626
1903	=head3 Watcher-Specific Functions and Data Members	2627	=head3 Watcher-Specific Functions and Data Members
1904		2628
1905	=over 4	2629	=over 4
1906		2630
…		…
1908		2632
1909	=item ev_check_init (ev_check *, callback)	2633	=item ev_check_init (ev_check *, callback)
1910		2634
1911	Initialises and configures the prepare or check watcher - they have no	2635	Initialises and configures the prepare or check watcher - they have no
1912	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2636	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1913	macros, but using them is utterly, utterly and completely pointless.	2637	macros, but using them is utterly, utterly, utterly and completely
		2638	pointless.
1914		2639
1915	=back	2640	=back
1916		2641
1917	=head3 Examples	2642	=head3 Examples
1918		2643
…		…
1927	and in a check watcher, destroy them and call into libadns. What follows	2652	and in a check watcher, destroy them and call into libadns. What follows
1928	is pseudo-code only of course. This requires you to either use a low	2653	is pseudo-code only of course. This requires you to either use a low
1929	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2654	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1930	the callbacks for the IO/timeout watchers might not have been called yet.	2655	the callbacks for the IO/timeout watchers might not have been called yet.
1931		2656
1932	static ev_io iow [nfd];	2657	static ev_io iow [nfd];
1933	static ev_timer tw;	2658	static ev_timer tw;
1934		2659
1935	static void	2660	static void
1936	io_cb (ev_loop *loop, ev_io *w, int revents)	2661	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1937	{	2662	{
1938	}	2663	}
1939		2664
1940	// create io watchers for each fd and a timer before blocking	2665	// create io watchers for each fd and a timer before blocking
1941	static void	2666	static void
1942	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2667	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1943	{	2668	{
1944	int timeout = 3600000;	2669	int timeout = 3600000;
1945	struct pollfd fds [nfd];	2670	struct pollfd fds [nfd];
1946	// actual code will need to loop here and realloc etc.	2671	// actual code will need to loop here and realloc etc.
1947	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2672	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1948		2673
1949	/* the callback is illegal, but won't be called as we stop during check */	2674	/* the callback is illegal, but won't be called as we stop during check */
1950	ev_timer_init (&tw, 0, timeout * 1e-3);	2675	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1951	ev_timer_start (loop, &tw);	2676	ev_timer_start (loop, &tw);
1952		2677
1953	// create one ev_io per pollfd	2678	// create one ev_io per pollfd
1954	for (int i = 0; i < nfd; ++i)	2679	for (int i = 0; i < nfd; ++i)
1955	{	2680	{
1956	ev_io_init (iow + i, io_cb, fds [i].fd,	2681	ev_io_init (iow + i, io_cb, fds [i].fd,
1957	((fds [i].events & POLLIN ? EV_READ : 0)	2682	((fds [i].events & POLLIN ? EV_READ : 0)
1958	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2683	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1959		2684
1960	fds [i].revents = 0;	2685	fds [i].revents = 0;
1961	ev_io_start (loop, iow + i);	2686	ev_io_start (loop, iow + i);
1962	}	2687	}
1963	}	2688	}
1964		2689
1965	// stop all watchers after blocking	2690	// stop all watchers after blocking
1966	static void	2691	static void
1967	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2692	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1968	{	2693	{
1969	ev_timer_stop (loop, &tw);	2694	ev_timer_stop (loop, &tw);
1970		2695
1971	for (int i = 0; i < nfd; ++i)	2696	for (int i = 0; i < nfd; ++i)
1972	{	2697	{
1973	// set the relevant poll flags	2698	// set the relevant poll flags
1974	// could also call adns_processreadable etc. here	2699	// could also call adns_processreadable etc. here
1975	struct pollfd *fd = fds + i;	2700	struct pollfd *fd = fds + i;
1976	int revents = ev_clear_pending (iow + i);	2701	int revents = ev_clear_pending (iow + i);
1977	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2702	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1978	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2703	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1979		2704
1980	// now stop the watcher	2705	// now stop the watcher
1981	ev_io_stop (loop, iow + i);	2706	ev_io_stop (loop, iow + i);
1982	}	2707	}
1983		2708
1984	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2709	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1985	}	2710	}
1986		2711
1987	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2712	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1988	in the prepare watcher and would dispose of the check watcher.	2713	in the prepare watcher and would dispose of the check watcher.
1989		2714
1990	Method 3: If the module to be embedded supports explicit event	2715	Method 3: If the module to be embedded supports explicit event
1991	notification (adns does), you can also make use of the actual watcher	2716	notification (libadns does), you can also make use of the actual watcher
1992	callbacks, and only destroy/create the watchers in the prepare watcher.	2717	callbacks, and only destroy/create the watchers in the prepare watcher.
1993		2718
1994	static void	2719	static void
1995	timer_cb (EV_P_ ev_timer *w, int revents)	2720	timer_cb (EV_P_ ev_timer *w, int revents)
1996	{	2721	{
1997	adns_state ads = (adns_state)w->data;	2722	adns_state ads = (adns_state)w->data;
1998	update_now (EV_A);	2723	update_now (EV_A);
1999		2724
2000	adns_processtimeouts (ads, &tv_now);	2725	adns_processtimeouts (ads, &tv_now);
2001	}	2726	}
2002		2727
2003	static void	2728	static void
2004	io_cb (EV_P_ ev_io *w, int revents)	2729	io_cb (EV_P_ ev_io *w, int revents)
2005	{	2730	{
2006	adns_state ads = (adns_state)w->data;	2731	adns_state ads = (adns_state)w->data;
2007	update_now (EV_A);	2732	update_now (EV_A);
2008		2733
2009	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2734	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2010	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2735	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2011	}	2736	}
2012		2737
2013	// do not ever call adns_afterpoll	2738	// do not ever call adns_afterpoll
2014		2739
2015	Method 4: Do not use a prepare or check watcher because the module you	2740	Method 4: Do not use a prepare or check watcher because the module you
2016	want to embed is too inflexible to support it. Instead, youc na override	2741	want to embed is not flexible enough to support it. Instead, you can
2017	their poll function. The drawback with this solution is that the main	2742	override their poll function. The drawback with this solution is that the
2018	loop is now no longer controllable by EV. The C<Glib::EV> module does	2743	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2019	this.	2744	this approach, effectively embedding EV as a client into the horrible
		2745	libglib event loop.
2020		2746
2021	static gint	2747	static gint
2022	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2748	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2023	{	2749	{
2024	int got_events = 0;	2750	int got_events = 0;
2025		2751
2026	for (n = 0; n < nfds; ++n)	2752	for (n = 0; n < nfds; ++n)
2027	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2753	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2028		2754
2029	if (timeout >= 0)	2755	if (timeout >= 0)
2030	// create/start timer	2756	// create/start timer
2031		2757
2032	// poll	2758	// poll
2033	ev_loop (EV_A_ 0);	2759	ev_loop (EV_A_ 0);
2034		2760
2035	// stop timer again	2761	// stop timer again
2036	if (timeout >= 0)	2762	if (timeout >= 0)
2037	ev_timer_stop (EV_A_ &to);	2763	ev_timer_stop (EV_A_ &to);
2038		2764
2039	// stop io watchers again - their callbacks should have set	2765	// stop io watchers again - their callbacks should have set
2040	for (n = 0; n < nfds; ++n)	2766	for (n = 0; n < nfds; ++n)
2041	ev_io_stop (EV_A_ iow [n]);	2767	ev_io_stop (EV_A_ iow [n]);
2042		2768
2043	return got_events;	2769	return got_events;
2044	}	2770	}
2045		2771
2046		2772
2047	=head2 C<ev_embed> - when one backend isn't enough...	2773	=head2 C<ev_embed> - when one backend isn't enough...
2048		2774
2049	This is a rather advanced watcher type that lets you embed one event loop	2775	This is a rather advanced watcher type that lets you embed one event loop
…		…
2055	prioritise I/O.	2781	prioritise I/O.
2056		2782
2057	As an example for a bug workaround, the kqueue backend might only support	2783	As an example for a bug workaround, the kqueue backend might only support
2058	sockets on some platform, so it is unusable as generic backend, but you	2784	sockets on some platform, so it is unusable as generic backend, but you
2059	still want to make use of it because you have many sockets and it scales	2785	still want to make use of it because you have many sockets and it scales
2060	so nicely. In this case, you would create a kqueue-based loop and embed it	2786	so nicely. In this case, you would create a kqueue-based loop and embed
2061	into your default loop (which might use e.g. poll). Overall operation will	2787	it into your default loop (which might use e.g. poll). Overall operation
2062	be a bit slower because first libev has to poll and then call kevent, but	2788	will be a bit slower because first libev has to call C<poll> and then
2063	at least you can use both at what they are best.	2789	C<kevent>, but at least you can use both mechanisms for what they are
		2790	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2064		2791
2065	As for prioritising I/O: rarely you have the case where some fds have	2792	As for prioritising I/O: under rare circumstances you have the case where
2066	to be watched and handled very quickly (with low latency), and even	2793	some fds have to be watched and handled very quickly (with low latency),
2067	priorities and idle watchers might have too much overhead. In this case	2794	and even priorities and idle watchers might have too much overhead. In
2068	you would put all the high priority stuff in one loop and all the rest in	2795	this case you would put all the high priority stuff in one loop and all
2069	a second one, and embed the second one in the first.	2796	the rest in a second one, and embed the second one in the first.
2070		2797
2071	As long as the watcher is active, the callback will be invoked every time	2798	As long as the watcher is active, the callback will be invoked every
2072	there might be events pending in the embedded loop. The callback must then	2799	time there might be events pending in the embedded loop. The callback
2073	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2800	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2074	their callbacks (you could also start an idle watcher to give the embedded	2801	sweep and invoke their callbacks (the callback doesn't need to invoke the
2075	loop strictly lower priority for example). You can also set the callback	2802	C<ev_embed_sweep> function directly, it could also start an idle watcher
2076	to C<0>, in which case the embed watcher will automatically execute the	2803	to give the embedded loop strictly lower priority for example).
2077	embedded loop sweep.
2078		2804
2079	As long as the watcher is started it will automatically handle events. The	2805	You can also set the callback to C<0>, in which case the embed watcher
2080	callback will be invoked whenever some events have been handled. You can	2806	will automatically execute the embedded loop sweep whenever necessary.
2081	set the callback to C<0> to avoid having to specify one if you are not
2082	interested in that.
2083		2807
2084	Also, there have not currently been made special provisions for forking:	2808	Fork detection will be handled transparently while the C<ev_embed> watcher
2085	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2809	is active, i.e., the embedded loop will automatically be forked when the
2086	but you will also have to stop and restart any C<ev_embed> watchers	2810	embedding loop forks. In other cases, the user is responsible for calling
2087	yourself.	2811	C<ev_loop_fork> on the embedded loop.
2088		2812
2089	Unfortunately, not all backends are embeddable, only the ones returned by	2813	Unfortunately, not all backends are embeddable: only the ones returned by
2090	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2814	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2091	portable one.	2815	portable one.
2092		2816
2093	So when you want to use this feature you will always have to be prepared	2817	So when you want to use this feature you will always have to be prepared
2094	that you cannot get an embeddable loop. The recommended way to get around	2818	that you cannot get an embeddable loop. The recommended way to get around
2095	this is to have a separate variables for your embeddable loop, try to	2819	this is to have a separate variables for your embeddable loop, try to
2096	create it, and if that fails, use the normal loop for everything.	2820	create it, and if that fails, use the normal loop for everything.
2097		2821
		2822	=head3 C<ev_embed> and fork
		2823
		2824	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2825	automatically be applied to the embedded loop as well, so no special
		2826	fork handling is required in that case. When the watcher is not running,
		2827	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2828	as applicable.
		2829
2098	=head3 Watcher-Specific Functions and Data Members	2830	=head3 Watcher-Specific Functions and Data Members
2099		2831
2100	=over 4	2832	=over 4
2101		2833
2102	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2834	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2105		2837
2106	Configures the watcher to embed the given loop, which must be	2838	Configures the watcher to embed the given loop, which must be
2107	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2839	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2108	invoked automatically, otherwise it is the responsibility of the callback	2840	invoked automatically, otherwise it is the responsibility of the callback
2109	to invoke it (it will continue to be called until the sweep has been done,	2841	to invoke it (it will continue to be called until the sweep has been done,
2110	if you do not want thta, you need to temporarily stop the embed watcher).	2842	if you do not want that, you need to temporarily stop the embed watcher).
2111		2843
2112	=item ev_embed_sweep (loop, ev_embed *)	2844	=item ev_embed_sweep (loop, ev_embed *)
2113		2845
2114	Make a single, non-blocking sweep over the embedded loop. This works	2846	Make a single, non-blocking sweep over the embedded loop. This works
2115	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2847	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2116	apropriate way for embedded loops.	2848	appropriate way for embedded loops.
2117		2849
2118	=item struct ev_loop *other [read-only]	2850	=item struct ev_loop *other [read-only]
2119		2851
2120	The embedded event loop.	2852	The embedded event loop.
2121		2853
…		…
2123		2855
2124	=head3 Examples	2856	=head3 Examples
2125		2857
2126	Example: Try to get an embeddable event loop and embed it into the default	2858	Example: Try to get an embeddable event loop and embed it into the default
2127	event loop. If that is not possible, use the default loop. The default	2859	event loop. If that is not possible, use the default loop. The default
2128	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2860	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2129	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2861	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2130	used).	2862	used).
2131		2863
2132	struct ev_loop *loop_hi = ev_default_init (0);	2864	struct ev_loop *loop_hi = ev_default_init (0);
2133	struct ev_loop *loop_lo = 0;	2865	struct ev_loop *loop_lo = 0;
2134	struct ev_embed embed;	2866	ev_embed embed;
2135		2867
2136	// see if there is a chance of getting one that works	2868	// see if there is a chance of getting one that works
2137	// (remember that a flags value of 0 means autodetection)	2869	// (remember that a flags value of 0 means autodetection)
2138	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2870	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2139	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2871	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2140	: 0;	2872	: 0;
2141		2873
2142	// if we got one, then embed it, otherwise default to loop_hi	2874	// if we got one, then embed it, otherwise default to loop_hi
2143	if (loop_lo)	2875	if (loop_lo)
2144	{	2876	{
2145	ev_embed_init (&embed, 0, loop_lo);	2877	ev_embed_init (&embed, 0, loop_lo);
2146	ev_embed_start (loop_hi, &embed);	2878	ev_embed_start (loop_hi, &embed);
2147	}	2879	}
2148	else	2880	else
2149	loop_lo = loop_hi;	2881	loop_lo = loop_hi;
2150		2882
2151	Example: Check if kqueue is available but not recommended and create	2883	Example: Check if kqueue is available but not recommended and create
2152	a kqueue backend for use with sockets (which usually work with any	2884	a kqueue backend for use with sockets (which usually work with any
2153	kqueue implementation). Store the kqueue/socket-only event loop in	2885	kqueue implementation). Store the kqueue/socket-only event loop in
2154	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2886	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2155		2887
2156	struct ev_loop *loop = ev_default_init (0);	2888	struct ev_loop *loop = ev_default_init (0);
2157	struct ev_loop *loop_socket = 0;	2889	struct ev_loop *loop_socket = 0;
2158	struct ev_embed embed;	2890	ev_embed embed;
2159		2891
2160	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2892	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2161	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2893	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2162	{	2894	{
2163	ev_embed_init (&embed, 0, loop_socket);	2895	ev_embed_init (&embed, 0, loop_socket);
2164	ev_embed_start (loop, &embed);	2896	ev_embed_start (loop, &embed);
2165	}	2897	}
2166		2898
2167	if (!loop_socket)	2899	if (!loop_socket)
2168	loop_socket = loop;	2900	loop_socket = loop;
2169		2901
2170	// now use loop_socket for all sockets, and loop for everything else	2902	// now use loop_socket for all sockets, and loop for everything else
2171		2903
2172		2904
2173	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2905	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2174		2906
2175	Fork watchers are called when a C<fork ()> was detected (usually because	2907	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2178	event loop blocks next and before C<ev_check> watchers are being called,	2910	event loop blocks next and before C<ev_check> watchers are being called,
2179	and only in the child after the fork. If whoever good citizen calling	2911	and only in the child after the fork. If whoever good citizen calling
2180	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2181	handlers will be invoked, too, of course.	2913	handlers will be invoked, too, of course.
2182		2914
		2915	=head3 The special problem of life after fork - how is it possible?
		2916
		2917	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2918	up/change the process environment, followed by a call to C<exec()>. This
		2919	sequence should be handled by libev without any problems.
		2920
		2921	This changes when the application actually wants to do event handling
		2922	in the child, or both parent in child, in effect "continuing" after the
		2923	fork.
		2924
		2925	The default mode of operation (for libev, with application help to detect
		2926	forks) is to duplicate all the state in the child, as would be expected
		2927	when I<either> the parent I<or> the child process continues.
		2928
		2929	When both processes want to continue using libev, then this is usually the
		2930	wrong result. In that case, usually one process (typically the parent) is
		2931	supposed to continue with all watchers in place as before, while the other
		2932	process typically wants to start fresh, i.e. without any active watchers.
		2933
		2934	The cleanest and most efficient way to achieve that with libev is to
		2935	simply create a new event loop, which of course will be "empty", and
		2936	use that for new watchers. This has the advantage of not touching more
		2937	memory than necessary, and thus avoiding the copy-on-write, and the
		2938	disadvantage of having to use multiple event loops (which do not support
		2939	signal watchers).
		2940
		2941	When this is not possible, or you want to use the default loop for
		2942	other reasons, then in the process that wants to start "fresh", call
		2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2944	the default loop will "orphan" (not stop) all registered watchers, so you
		2945	have to be careful not to execute code that modifies those watchers. Note
		2946	also that in that case, you have to re-register any signal watchers.
		2947
2183	=head3 Watcher-Specific Functions and Data Members	2948	=head3 Watcher-Specific Functions and Data Members
2184		2949
2185	=over 4	2950	=over 4
2186		2951
2187	=item ev_fork_init (ev_signal *, callback)	2952	=item ev_fork_init (ev_signal *, callback)
…		…
2216	=head3 Queueing	2981	=head3 Queueing
2217		2982
2218	C<ev_async> does not support queueing of data in any way. The reason	2983	C<ev_async> does not support queueing of data in any way. The reason
2219	is that the author does not know of a simple (or any) algorithm for a	2984	is that the author does not know of a simple (or any) algorithm for a
2220	multiple-writer-single-reader queue that works in all cases and doesn't	2985	multiple-writer-single-reader queue that works in all cases and doesn't
2221	need elaborate support such as pthreads.	2986	need elaborate support such as pthreads or unportable memory access
		2987	semantics.
2222		2988
2223	That means that if you want to queue data, you have to provide your own	2989	That means that if you want to queue data, you have to provide your own
2224	queue. But at least I can tell you would implement locking around your	2990	queue. But at least I can tell you how to implement locking around your
2225	queue:	2991	queue:
2226		2992
2227	=over 4	2993	=over 4
2228		2994
2229	=item queueing from a signal handler context	2995	=item queueing from a signal handler context
2230		2996
2231	To implement race-free queueing, you simply add to the queue in the signal	2997	To implement race-free queueing, you simply add to the queue in the signal
2232	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2998	handler but you block the signal handler in the watcher callback. Here is
2233	some fictitiuous SIGUSR1 handler:	2999	an example that does that for some fictitious SIGUSR1 handler:
2234		3000
2235	static ev_async mysig;	3001	static ev_async mysig;
2236		3002
2237	static void	3003	static void
2238	sigusr1_handler (void)	3004	sigusr1_handler (void)
…		…
2304	=over 4	3070	=over 4
2305		3071
2306	=item ev_async_init (ev_async *, callback)	3072	=item ev_async_init (ev_async *, callback)
2307		3073
2308	Initialises and configures the async watcher - it has no parameters of any	3074	Initialises and configures the async watcher - it has no parameters of any
2309	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3075	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2310	believe me.	3076	trust me.
2311		3077
2312	=item ev_async_send (loop, ev_async *)	3078	=item ev_async_send (loop, ev_async *)
2313		3079
2314	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3080	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2315	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3081	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2316	C<ev_feed_event>, this call is safe to do in other threads, signal or	3082	C<ev_feed_event>, this call is safe to do from other threads, signal or
2317	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3083	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2318	section below on what exactly this means).	3084	section below on what exactly this means).
2319		3085
		3086	Note that, as with other watchers in libev, multiple events might get
		3087	compressed into a single callback invocation (another way to look at this
		3088	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3089	reset when the event loop detects that).
		3090
2320	This call incurs the overhead of a syscall only once per loop iteration,	3091	This call incurs the overhead of a system call only once per event loop
2321	so while the overhead might be noticable, it doesn't apply to repeated	3092	iteration, so while the overhead might be noticeable, it doesn't apply to
2322	calls to C<ev_async_send>.	3093	repeated calls to C<ev_async_send> for the same event loop.
2323		3094
2324	=item bool = ev_async_pending (ev_async *)	3095	=item bool = ev_async_pending (ev_async *)
2325		3096
2326	Returns a non-zero value when C<ev_async_send> has been called on the	3097	Returns a non-zero value when C<ev_async_send> has been called on the
2327	watcher but the event has not yet been processed (or even noted) by the	3098	watcher but the event has not yet been processed (or even noted) by the
2328	event loop.	3099	event loop.
2329		3100
2330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3101	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2331	the loop iterates next and checks for the watcher to have become active,	3102	the loop iterates next and checks for the watcher to have become active,
2332	it will reset the flag again. C<ev_async_pending> can be used to very	3103	it will reset the flag again. C<ev_async_pending> can be used to very
2333	quickly check wether invoking the loop might be a good idea.	3104	quickly check whether invoking the loop might be a good idea.
2334		3105
2335	Not that this does I<not> check wether the watcher itself is pending, only	3106	Not that this does I<not> check whether the watcher itself is pending,
2336	wether it has been requested to make this watcher pending.	3107	only whether it has been requested to make this watcher pending: there
		3108	is a time window between the event loop checking and resetting the async
		3109	notification, and the callback being invoked.
2337		3110
2338	=back	3111	=back
2339		3112
2340		3113
2341	=head1 OTHER FUNCTIONS	3114	=head1 OTHER FUNCTIONS
…		…
2345	=over 4	3118	=over 4
2346		3119
2347	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3120	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2348		3121
2349	This function combines a simple timer and an I/O watcher, calls your	3122	This function combines a simple timer and an I/O watcher, calls your
2350	callback on whichever event happens first and automatically stop both	3123	callback on whichever event happens first and automatically stops both
2351	watchers. This is useful if you want to wait for a single event on an fd	3124	watchers. This is useful if you want to wait for a single event on an fd
2352	or timeout without having to allocate/configure/start/stop/free one or	3125	or timeout without having to allocate/configure/start/stop/free one or
2353	more watchers yourself.	3126	more watchers yourself.
2354		3127
2355	If C<fd> is less than 0, then no I/O watcher will be started and events	3128	If C<fd> is less than 0, then no I/O watcher will be started and the
2356	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3129	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2357	C<events> set will be craeted and started.	3130	the given C<fd> and C<events> set will be created and started.
2358		3131
2359	If C<timeout> is less than 0, then no timeout watcher will be	3132	If C<timeout> is less than 0, then no timeout watcher will be
2360	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3133	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2361	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3134	repeat = 0) will be started. C<0> is a valid timeout.
2362	dubious value.
2363		3135
2364	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3136	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2365	passed an C<revents> set like normal event callbacks (a combination of	3137	passed an C<revents> set like normal event callbacks (a combination of
2366	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3138	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2367	value passed to C<ev_once>:	3139	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3140	a timeout and an io event at the same time - you probably should give io
		3141	events precedence.
2368		3142
		3143	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3144
2369	static void stdin_ready (int revents, void *arg)	3145	static void stdin_ready (int revents, void *arg)
2370	{	3146	{
2371	if (revents & EV_TIMEOUT)
2372	/* doh, nothing entered */;
2373	else if (revents & EV_READ)	3147	if (revents & EV_READ)
2374	/* stdin might have data for us, joy! */;	3148	/* stdin might have data for us, joy! */;
		3149	else if (revents & EV_TIMEOUT)
		3150	/* doh, nothing entered */;
2375	}	3151	}
2376		3152
2377	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3153	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2378		3154
2379	=item ev_feed_event (ev_loop *, watcher *, int revents)
2380
2381	Feeds the given event set into the event loop, as if the specified event
2382	had happened for the specified watcher (which must be a pointer to an
2383	initialised but not necessarily started event watcher).
2384
2385	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3155	=item ev_feed_fd_event (loop, int fd, int revents)
2386		3156
2387	Feed an event on the given fd, as if a file descriptor backend detected	3157	Feed an event on the given fd, as if a file descriptor backend detected
2388	the given events it.	3158	the given events it.
2389		3159
2390	=item ev_feed_signal_event (ev_loop *loop, int signum)	3160	=item ev_feed_signal_event (loop, int signum)
2391		3161
2392	Feed an event as if the given signal occured (C<loop> must be the default	3162	Feed an event as if the given signal occurred (C<loop> must be the default
2393	loop!).	3163	loop!).
2394		3164
2395	=back	3165	=back
2396		3166
2397		3167
…		…
2426	=back	3196	=back
2427		3197
2428	=head1 C++ SUPPORT	3198	=head1 C++ SUPPORT
2429		3199
2430	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3200	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2431	you to use some convinience methods to start/stop watchers and also change	3201	you to use some convenience methods to start/stop watchers and also change
2432	the callback model to a model using method callbacks on objects.	3202	the callback model to a model using method callbacks on objects.
2433		3203
2434	To use it,	3204	To use it,
2435		3205
2436	#include <ev++.h>	3206	#include <ev++.h>
2437		3207
2438	This automatically includes F<ev.h> and puts all of its definitions (many	3208	This automatically includes F<ev.h> and puts all of its definitions (many
2439	of them macros) into the global namespace. All C++ specific things are	3209	of them macros) into the global namespace. All C++ specific things are
2440	put into the C<ev> namespace. It should support all the same embedding	3210	put into the C<ev> namespace. It should support all the same embedding
2441	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3211	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2475		3245
2476	=over 4	3246	=over 4
2477		3247
2478	=item ev::TYPE::TYPE ()	3248	=item ev::TYPE::TYPE ()
2479		3249
2480	=item ev::TYPE::TYPE (struct ev_loop *)	3250	=item ev::TYPE::TYPE (loop)
2481		3251
2482	=item ev::TYPE::~TYPE	3252	=item ev::TYPE::~TYPE
2483		3253
2484	The constructor (optionally) takes an event loop to associate the watcher	3254	The constructor (optionally) takes an event loop to associate the watcher
2485	with. If it is omitted, it will use C<EV_DEFAULT>.	3255	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2508	your compiler is good :), then the method will be fully inlined into the	3278	your compiler is good :), then the method will be fully inlined into the
2509	thunking function, making it as fast as a direct C callback.	3279	thunking function, making it as fast as a direct C callback.
2510		3280
2511	Example: simple class declaration and watcher initialisation	3281	Example: simple class declaration and watcher initialisation
2512		3282
2513	struct myclass	3283	struct myclass
2514	{	3284	{
2515	void io_cb (ev::io &w, int revents) { }	3285	void io_cb (ev::io &w, int revents) { }
2516	}	3286	}
2517		3287
2518	myclass obj;	3288	myclass obj;
2519	ev::io iow;	3289	ev::io iow;
2520	iow.set <myclass, &myclass::io_cb> (&obj);	3290	iow.set <myclass, &myclass::io_cb> (&obj);
		3291
		3292	=item w->set (object *)
		3293
		3294	This is an B<experimental> feature that might go away in a future version.
		3295
		3296	This is a variation of a method callback - leaving out the method to call
		3297	will default the method to C<operator ()>, which makes it possible to use
		3298	functor objects without having to manually specify the C<operator ()> all
		3299	the time. Incidentally, you can then also leave out the template argument
		3300	list.
		3301
		3302	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3303	int revents)>.
		3304
		3305	See the method-C<set> above for more details.
		3306
		3307	Example: use a functor object as callback.
		3308
		3309	struct myfunctor
		3310	{
		3311	void operator() (ev::io &w, int revents)
		3312	{
		3313	...
		3314	}
		3315	}
		3316
		3317	myfunctor f;
		3318
		3319	ev::io w;
		3320	w.set (&f);
2521		3321
2522	=item w->set<function> (void *data = 0)	3322	=item w->set<function> (void *data = 0)
2523		3323
2524	Also sets a callback, but uses a static method or plain function as	3324	Also sets a callback, but uses a static method or plain function as
2525	callback. The optional C<data> argument will be stored in the watcher's	3325	callback. The optional C<data> argument will be stored in the watcher's
…		…
2527		3327
2528	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3328	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2529		3329
2530	See the method-C<set> above for more details.	3330	See the method-C<set> above for more details.
2531		3331
2532	Example:	3332	Example: Use a plain function as callback.
2533		3333
2534	static void io_cb (ev::io &w, int revents) { }	3334	static void io_cb (ev::io &w, int revents) { }
2535	iow.set <io_cb> ();	3335	iow.set <io_cb> ();
2536		3336
2537	=item w->set (struct ev_loop *)	3337	=item w->set (loop)
2538		3338
2539	Associates a different C<struct ev_loop> with this watcher. You can only	3339	Associates a different C<struct ev_loop> with this watcher. You can only
2540	do this when the watcher is inactive (and not pending either).	3340	do this when the watcher is inactive (and not pending either).
2541		3341
2542	=item w->set ([args])	3342	=item w->set ([arguments])
2543		3343
2544	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3344	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2545	called at least once. Unlike the C counterpart, an active watcher gets	3345	called at least once. Unlike the C counterpart, an active watcher gets
2546	automatically stopped and restarted when reconfiguring it with this	3346	automatically stopped and restarted when reconfiguring it with this
2547	method.	3347	method.
2548		3348
2549	=item w->start ()	3349	=item w->start ()
…		…
2573	=back	3373	=back
2574		3374
2575	Example: Define a class with an IO and idle watcher, start one of them in	3375	Example: Define a class with an IO and idle watcher, start one of them in
2576	the constructor.	3376	the constructor.
2577		3377
2578	class myclass	3378	class myclass
2579	{	3379	{
2580	ev::io io; void io_cb (ev::io &w, int revents);	3380	ev::io io ; void io_cb (ev::io &w, int revents);
2581	ev:idle idle void idle_cb (ev::idle &w, int revents);	3381	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2582		3382
2583	myclass (int fd)	3383	myclass (int fd)
2584	{	3384	{
2585	io .set <myclass, &myclass::io_cb > (this);	3385	io .set <myclass, &myclass::io_cb > (this);
2586	idle.set <myclass, &myclass::idle_cb> (this);	3386	idle.set <myclass, &myclass::idle_cb> (this);
2587		3387
2588	io.start (fd, ev::READ);	3388	io.start (fd, ev::READ);
2589	}	3389	}
2590	};	3390	};
2591		3391
2592		3392
2593	=head1 OTHER LANGUAGE BINDINGS	3393	=head1 OTHER LANGUAGE BINDINGS
2594		3394
2595	Libev does not offer other language bindings itself, but bindings for a	3395	Libev does not offer other language bindings itself, but bindings for a
2596	numbe rof languages exist in the form of third-party packages. If you know	3396	number of languages exist in the form of third-party packages. If you know
2597	any interesting language binding in addition to the ones listed here, drop	3397	any interesting language binding in addition to the ones listed here, drop
2598	me a note.	3398	me a note.
2599		3399
2600	=over 4	3400	=over 4
2601		3401
2602	=item Perl	3402	=item Perl
2603		3403
2604	The EV module implements the full libev API and is actually used to test	3404	The EV module implements the full libev API and is actually used to test
2605	libev. EV is developed together with libev. Apart from the EV core module,	3405	libev. EV is developed together with libev. Apart from the EV core module,
2606	there are additional modules that implement libev-compatible interfaces	3406	there are additional modules that implement libev-compatible interfaces
2607	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3407	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2608	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3408	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3409	and C<EV::Glib>).
2609		3410
2610	It can be found and installed via CPAN, its homepage is found at	3411	It can be found and installed via CPAN, its homepage is at
2611	L<http://software.schmorp.de/pkg/EV>.	3412	L<http://software.schmorp.de/pkg/EV>.
2612		3413
		3414	=item Python
		3415
		3416	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3417	seems to be quite complete and well-documented.
		3418
2613	=item Ruby	3419	=item Ruby
2614		3420
2615	Tony Arcieri has written a ruby extension that offers access to a subset	3421	Tony Arcieri has written a ruby extension that offers access to a subset
2616	of the libev API and adds filehandle abstractions, asynchronous DNS and	3422	of the libev API and adds file handle abstractions, asynchronous DNS and
2617	more on top of it. It can be found via gem servers. Its homepage is at	3423	more on top of it. It can be found via gem servers. Its homepage is at
2618	L<http://rev.rubyforge.org/>.	3424	L<http://rev.rubyforge.org/>.
2619		3425
		3426	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3427	makes rev work even on mingw.
		3428
		3429	=item Haskell
		3430
		3431	A haskell binding to libev is available at
		3432	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3433
2620	=item D	3434	=item D
2621		3435
2622	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3436	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2623	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3437	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3438
		3439	=item Ocaml
		3440
		3441	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3442	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3443
		3444	=item Lua
		3445
		3446	Brian Maher has written a partial interface to libev
		3447	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3448	L<http://github.com/brimworks/lua-ev>.
2624		3449
2625	=back	3450	=back
2626		3451
2627		3452
2628	=head1 MACRO MAGIC	3453	=head1 MACRO MAGIC
2629		3454
2630	Libev can be compiled with a variety of options, the most fundamantal	3455	Libev can be compiled with a variety of options, the most fundamental
2631	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3456	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2632	functions and callbacks have an initial C<struct ev_loop *> argument.	3457	functions and callbacks have an initial C<struct ev_loop *> argument.
2633		3458
2634	To make it easier to write programs that cope with either variant, the	3459	To make it easier to write programs that cope with either variant, the
2635	following macros are defined:	3460	following macros are defined:
…		…
2640		3465
2641	This provides the loop I<argument> for functions, if one is required ("ev	3466	This provides the loop I<argument> for functions, if one is required ("ev
2642	loop argument"). The C<EV_A> form is used when this is the sole argument,	3467	loop argument"). The C<EV_A> form is used when this is the sole argument,
2643	C<EV_A_> is used when other arguments are following. Example:	3468	C<EV_A_> is used when other arguments are following. Example:
2644		3469
2645	ev_unref (EV_A);	3470	ev_unref (EV_A);
2646	ev_timer_add (EV_A_ watcher);	3471	ev_timer_add (EV_A_ watcher);
2647	ev_loop (EV_A_ 0);	3472	ev_loop (EV_A_ 0);
2648		3473
2649	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3474	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2650	which is often provided by the following macro.	3475	which is often provided by the following macro.
2651		3476
2652	=item C<EV_P>, C<EV_P_>	3477	=item C<EV_P>, C<EV_P_>
2653		3478
2654	This provides the loop I<parameter> for functions, if one is required ("ev	3479	This provides the loop I<parameter> for functions, if one is required ("ev
2655	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3480	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2656	C<EV_P_> is used when other parameters are following. Example:	3481	C<EV_P_> is used when other parameters are following. Example:
2657		3482
2658	// this is how ev_unref is being declared	3483	// this is how ev_unref is being declared
2659	static void ev_unref (EV_P);	3484	static void ev_unref (EV_P);
2660		3485
2661	// this is how you can declare your typical callback	3486	// this is how you can declare your typical callback
2662	static void cb (EV_P_ ev_timer *w, int revents)	3487	static void cb (EV_P_ ev_timer *w, int revents)
2663		3488
2664	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3489	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2665	suitable for use with C<EV_A>.	3490	suitable for use with C<EV_A>.
2666		3491
2667	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3492	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2683		3508
2684	Example: Declare and initialise a check watcher, utilising the above	3509	Example: Declare and initialise a check watcher, utilising the above
2685	macros so it will work regardless of whether multiple loops are supported	3510	macros so it will work regardless of whether multiple loops are supported
2686	or not.	3511	or not.
2687		3512
2688	static void	3513	static void
2689	check_cb (EV_P_ ev_timer *w, int revents)	3514	check_cb (EV_P_ ev_timer *w, int revents)
2690	{	3515	{
2691	ev_check_stop (EV_A_ w);	3516	ev_check_stop (EV_A_ w);
2692	}	3517	}
2693		3518
2694	ev_check check;	3519	ev_check check;
2695	ev_check_init (&check, check_cb);	3520	ev_check_init (&check, check_cb);
2696	ev_check_start (EV_DEFAULT_ &check);	3521	ev_check_start (EV_DEFAULT_ &check);
2697	ev_loop (EV_DEFAULT_ 0);	3522	ev_loop (EV_DEFAULT_ 0);
2698		3523
2699	=head1 EMBEDDING	3524	=head1 EMBEDDING
2700		3525
2701	Libev can (and often is) directly embedded into host	3526	Libev can (and often is) directly embedded into host
2702	applications. Examples of applications that embed it include the Deliantra	3527	applications. Examples of applications that embed it include the Deliantra
…		…
2709	libev somewhere in your source tree).	3534	libev somewhere in your source tree).
2710		3535
2711	=head2 FILESETS	3536	=head2 FILESETS
2712		3537
2713	Depending on what features you need you need to include one or more sets of files	3538	Depending on what features you need you need to include one or more sets of files
2714	in your app.	3539	in your application.
2715		3540
2716	=head3 CORE EVENT LOOP	3541	=head3 CORE EVENT LOOP
2717		3542
2718	To include only the libev core (all the C<ev_*> functions), with manual	3543	To include only the libev core (all the C<ev_*> functions), with manual
2719	configuration (no autoconf):	3544	configuration (no autoconf):
2720		3545
2721	#define EV_STANDALONE 1	3546	#define EV_STANDALONE 1
2722	#include "ev.c"	3547	#include "ev.c"
2723		3548
2724	This will automatically include F<ev.h>, too, and should be done in a	3549	This will automatically include F<ev.h>, too, and should be done in a
2725	single C source file only to provide the function implementations. To use	3550	single C source file only to provide the function implementations. To use
2726	it, do the same for F<ev.h> in all files wishing to use this API (best	3551	it, do the same for F<ev.h> in all files wishing to use this API (best
2727	done by writing a wrapper around F<ev.h> that you can include instead and	3552	done by writing a wrapper around F<ev.h> that you can include instead and
2728	where you can put other configuration options):	3553	where you can put other configuration options):
2729		3554
2730	#define EV_STANDALONE 1	3555	#define EV_STANDALONE 1
2731	#include "ev.h"	3556	#include "ev.h"
2732		3557
2733	Both header files and implementation files can be compiled with a C++	3558	Both header files and implementation files can be compiled with a C++
2734	compiler (at least, thats a stated goal, and breakage will be treated	3559	compiler (at least, that's a stated goal, and breakage will be treated
2735	as a bug).	3560	as a bug).
2736		3561
2737	You need the following files in your source tree, or in a directory	3562	You need the following files in your source tree, or in a directory
2738	in your include path (e.g. in libev/ when using -Ilibev):	3563	in your include path (e.g. in libev/ when using -Ilibev):
2739		3564
2740	ev.h	3565	ev.h
2741	ev.c	3566	ev.c
2742	ev_vars.h	3567	ev_vars.h
2743	ev_wrap.h	3568	ev_wrap.h
2744		3569
2745	ev_win32.c required on win32 platforms only	3570	ev_win32.c required on win32 platforms only
2746		3571
2747	ev_select.c only when select backend is enabled (which is enabled by default)	3572	ev_select.c only when select backend is enabled (which is enabled by default)
2748	ev_poll.c only when poll backend is enabled (disabled by default)	3573	ev_poll.c only when poll backend is enabled (disabled by default)
2749	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3574	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2750	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3575	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2751	ev_port.c only when the solaris port backend is enabled (disabled by default)	3576	ev_port.c only when the solaris port backend is enabled (disabled by default)
2752		3577
2753	F<ev.c> includes the backend files directly when enabled, so you only need	3578	F<ev.c> includes the backend files directly when enabled, so you only need
2754	to compile this single file.	3579	to compile this single file.
2755		3580
2756	=head3 LIBEVENT COMPATIBILITY API	3581	=head3 LIBEVENT COMPATIBILITY API
2757		3582
2758	To include the libevent compatibility API, also include:	3583	To include the libevent compatibility API, also include:
2759		3584
2760	#include "event.c"	3585	#include "event.c"
2761		3586
2762	in the file including F<ev.c>, and:	3587	in the file including F<ev.c>, and:
2763		3588
2764	#include "event.h"	3589	#include "event.h"
2765		3590
2766	in the files that want to use the libevent API. This also includes F<ev.h>.	3591	in the files that want to use the libevent API. This also includes F<ev.h>.
2767		3592
2768	You need the following additional files for this:	3593	You need the following additional files for this:
2769		3594
2770	event.h	3595	event.h
2771	event.c	3596	event.c
2772		3597
2773	=head3 AUTOCONF SUPPORT	3598	=head3 AUTOCONF SUPPORT
2774		3599
2775	Instead of using C<EV_STANDALONE=1> and providing your config in	3600	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2776	whatever way you want, you can also C<m4_include([libev.m4])> in your	3601	whatever way you want, you can also C<m4_include([libev.m4])> in your
2777	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3602	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2778	include F<config.h> and configure itself accordingly.	3603	include F<config.h> and configure itself accordingly.
2779		3604
2780	For this of course you need the m4 file:	3605	For this of course you need the m4 file:
2781		3606
2782	libev.m4	3607	libev.m4
2783		3608
2784	=head2 PREPROCESSOR SYMBOLS/MACROS	3609	=head2 PREPROCESSOR SYMBOLS/MACROS
2785		3610
2786	Libev can be configured via a variety of preprocessor symbols you have to	3611	Libev can be configured via a variety of preprocessor symbols you have to
2787	define before including any of its files. The default in the absense of	3612	define before including any of its files. The default in the absence of
2788	autoconf is noted for every option.	3613	autoconf is documented for every option.
2789		3614
2790	=over 4	3615	=over 4
2791		3616
2792	=item EV_STANDALONE	3617	=item EV_STANDALONE
2793		3618
…		…
2795	keeps libev from including F<config.h>, and it also defines dummy	3620	keeps libev from including F<config.h>, and it also defines dummy
2796	implementations for some libevent functions (such as logging, which is not	3621	implementations for some libevent functions (such as logging, which is not
2797	supported). It will also not define any of the structs usually found in	3622	supported). It will also not define any of the structs usually found in
2798	F<event.h> that are not directly supported by the libev core alone.	3623	F<event.h> that are not directly supported by the libev core alone.
2799		3624
		3625	In standalone mode, libev will still try to automatically deduce the
		3626	configuration, but has to be more conservative.
		3627
2800	=item EV_USE_MONOTONIC	3628	=item EV_USE_MONOTONIC
2801		3629
2802	If defined to be C<1>, libev will try to detect the availability of the	3630	If defined to be C<1>, libev will try to detect the availability of the
2803	monotonic clock option at both compiletime and runtime. Otherwise no use	3631	monotonic clock option at both compile time and runtime. Otherwise no
2804	of the monotonic clock option will be attempted. If you enable this, you	3632	use of the monotonic clock option will be attempted. If you enable this,
2805	usually have to link against librt or something similar. Enabling it when	3633	you usually have to link against librt or something similar. Enabling it
2806	the functionality isn't available is safe, though, although you have	3634	when the functionality isn't available is safe, though, although you have
2807	to make sure you link against any libraries where the C<clock_gettime>	3635	to make sure you link against any libraries where the C<clock_gettime>
2808	function is hiding in (often F<-lrt>).	3636	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2809		3637
2810	=item EV_USE_REALTIME	3638	=item EV_USE_REALTIME
2811		3639
2812	If defined to be C<1>, libev will try to detect the availability of the	3640	If defined to be C<1>, libev will try to detect the availability of the
2813	realtime clock option at compiletime (and assume its availability at	3641	real-time clock option at compile time (and assume its availability
2814	runtime if successful). Otherwise no use of the realtime clock option will	3642	at runtime if successful). Otherwise no use of the real-time clock
2815	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3643	option will be attempted. This effectively replaces C<gettimeofday>
2816	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3644	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2817	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3645	correctness. See the note about libraries in the description of
		3646	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3647	C<EV_USE_CLOCK_SYSCALL>.
		3648
		3649	=item EV_USE_CLOCK_SYSCALL
		3650
		3651	If defined to be C<1>, libev will try to use a direct syscall instead
		3652	of calling the system-provided C<clock_gettime> function. This option
		3653	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3654	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3655	programs needlessly. Using a direct syscall is slightly slower (in
		3656	theory), because no optimised vdso implementation can be used, but avoids
		3657	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3658	higher, as it simplifies linking (no need for C<-lrt>).
2818		3659
2819	=item EV_USE_NANOSLEEP	3660	=item EV_USE_NANOSLEEP
2820		3661
2821	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3662	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2822	and will use it for delays. Otherwise it will use C<select ()>.	3663	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2830	2.7 or newer, otherwise disabled.	3671	2.7 or newer, otherwise disabled.
2831		3672
2832	=item EV_USE_SELECT	3673	=item EV_USE_SELECT
2833		3674
2834	If undefined or defined to be C<1>, libev will compile in support for the	3675	If undefined or defined to be C<1>, libev will compile in support for the
2835	C<select>(2) backend. No attempt at autodetection will be done: if no	3676	C<select>(2) backend. No attempt at auto-detection will be done: if no
2836	other method takes over, select will be it. Otherwise the select backend	3677	other method takes over, select will be it. Otherwise the select backend
2837	will not be compiled in.	3678	will not be compiled in.
2838		3679
2839	=item EV_SELECT_USE_FD_SET	3680	=item EV_SELECT_USE_FD_SET
2840		3681
2841	If defined to C<1>, then the select backend will use the system C<fd_set>	3682	If defined to C<1>, then the select backend will use the system C<fd_set>
2842	structure. This is useful if libev doesn't compile due to a missing	3683	structure. This is useful if libev doesn't compile due to a missing
2843	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3684	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2844	exotic systems. This usually limits the range of file descriptors to some	3685	on exotic systems. This usually limits the range of file descriptors to
2845	low limit such as 1024 or might have other limitations (winsocket only	3686	some low limit such as 1024 or might have other limitations (winsocket
2846	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3687	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2847	influence the size of the C<fd_set> used.	3688	configures the maximum size of the C<fd_set>.
2848		3689
2849	=item EV_SELECT_IS_WINSOCKET	3690	=item EV_SELECT_IS_WINSOCKET
2850		3691
2851	When defined to C<1>, the select backend will assume that	3692	When defined to C<1>, the select backend will assume that
2852	select/socket/connect etc. don't understand file descriptors but	3693	select/socket/connect etc. don't understand file descriptors but
…		…
2854	be used is the winsock select). This means that it will call	3695	be used is the winsock select). This means that it will call
2855	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3696	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2856	it is assumed that all these functions actually work on fds, even	3697	it is assumed that all these functions actually work on fds, even
2857	on win32. Should not be defined on non-win32 platforms.	3698	on win32. Should not be defined on non-win32 platforms.
2858		3699
2859	=item EV_FD_TO_WIN32_HANDLE	3700	=item EV_FD_TO_WIN32_HANDLE(fd)
2860		3701
2861	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3702	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2862	file descriptors to socket handles. When not defining this symbol (the	3703	file descriptors to socket handles. When not defining this symbol (the
2863	default), then libev will call C<_get_osfhandle>, which is usually	3704	default), then libev will call C<_get_osfhandle>, which is usually
2864	correct. In some cases, programs use their own file descriptor management,	3705	correct. In some cases, programs use their own file descriptor management,
2865	in which case they can provide this function to map fds to socket handles.	3706	in which case they can provide this function to map fds to socket handles.
		3707
		3708	=item EV_WIN32_HANDLE_TO_FD(handle)
		3709
		3710	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3711	using the standard C<_open_osfhandle> function. For programs implementing
		3712	their own fd to handle mapping, overwriting this function makes it easier
		3713	to do so. This can be done by defining this macro to an appropriate value.
		3714
		3715	=item EV_WIN32_CLOSE_FD(fd)
		3716
		3717	If programs implement their own fd to handle mapping on win32, then this
		3718	macro can be used to override the C<close> function, useful to unregister
		3719	file descriptors again. Note that the replacement function has to close
		3720	the underlying OS handle.
2866		3721
2867	=item EV_USE_POLL	3722	=item EV_USE_POLL
2868		3723
2869	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3724	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2870	backend. Otherwise it will be enabled on non-win32 platforms. It	3725	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2897	otherwise another method will be used as fallback. This is the preferred	3752	otherwise another method will be used as fallback. This is the preferred
2898	backend for Solaris 10 systems.	3753	backend for Solaris 10 systems.
2899		3754
2900	=item EV_USE_DEVPOLL	3755	=item EV_USE_DEVPOLL
2901		3756
2902	reserved for future expansion, works like the USE symbols above.	3757	Reserved for future expansion, works like the USE symbols above.
2903		3758
2904	=item EV_USE_INOTIFY	3759	=item EV_USE_INOTIFY
2905		3760
2906	If defined to be C<1>, libev will compile in support for the Linux inotify	3761	If defined to be C<1>, libev will compile in support for the Linux inotify
2907	interface to speed up C<ev_stat> watchers. Its actual availability will	3762	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2914	access is atomic with respect to other threads or signal contexts. No such	3769	access is atomic with respect to other threads or signal contexts. No such
2915	type is easily found in the C language, so you can provide your own type	3770	type is easily found in the C language, so you can provide your own type
2916	that you know is safe for your purposes. It is used both for signal handler "locking"	3771	that you know is safe for your purposes. It is used both for signal handler "locking"
2917	as well as for signal and thread safety in C<ev_async> watchers.	3772	as well as for signal and thread safety in C<ev_async> watchers.
2918		3773
2919	In the absense of this define, libev will use C<sig_atomic_t volatile>	3774	In the absence of this define, libev will use C<sig_atomic_t volatile>
2920	(from F<signal.h>), which is usually good enough on most platforms.	3775	(from F<signal.h>), which is usually good enough on most platforms.
2921		3776
2922	=item EV_H	3777	=item EV_H
2923		3778
2924	The name of the F<ev.h> header file used to include it. The default if	3779	The name of the F<ev.h> header file used to include it. The default if
…		…
2963	When doing priority-based operations, libev usually has to linearly search	3818	When doing priority-based operations, libev usually has to linearly search
2964	all the priorities, so having many of them (hundreds) uses a lot of space	3819	all the priorities, so having many of them (hundreds) uses a lot of space
2965	and time, so using the defaults of five priorities (-2 .. +2) is usually	3820	and time, so using the defaults of five priorities (-2 .. +2) is usually
2966	fine.	3821	fine.
2967		3822
2968	If your embedding app does not need any priorities, defining these both to	3823	If your embedding application does not need any priorities, defining these
2969	C<0> will save some memory and cpu.	3824	both to C<0> will save some memory and CPU.
2970		3825
2971	=item EV_PERIODIC_ENABLE	3826	=item EV_PERIODIC_ENABLE
2972		3827
2973	If undefined or defined to be C<1>, then periodic timers are supported. If	3828	If undefined or defined to be C<1>, then periodic timers are supported. If
2974	defined to be C<0>, then they are not. Disabling them saves a few kB of	3829	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2981	code.	3836	code.
2982		3837
2983	=item EV_EMBED_ENABLE	3838	=item EV_EMBED_ENABLE
2984		3839
2985	If undefined or defined to be C<1>, then embed watchers are supported. If	3840	If undefined or defined to be C<1>, then embed watchers are supported. If
2986	defined to be C<0>, then they are not.	3841	defined to be C<0>, then they are not. Embed watchers rely on most other
		3842	watcher types, which therefore must not be disabled.
2987		3843
2988	=item EV_STAT_ENABLE	3844	=item EV_STAT_ENABLE
2989		3845
2990	If undefined or defined to be C<1>, then stat watchers are supported. If	3846	If undefined or defined to be C<1>, then stat watchers are supported. If
2991	defined to be C<0>, then they are not.	3847	defined to be C<0>, then they are not.
…		…
3001	defined to be C<0>, then they are not.	3857	defined to be C<0>, then they are not.
3002		3858
3003	=item EV_MINIMAL	3859	=item EV_MINIMAL
3004		3860
3005	If you need to shave off some kilobytes of code at the expense of some	3861	If you need to shave off some kilobytes of code at the expense of some
3006	speed, define this symbol to C<1>. Currently this is used to override some	3862	speed (but with the full API), define this symbol to C<1>. Currently this
3007	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3863	is used to override some inlining decisions, saves roughly 30% code size
3008	much smaller 2-heap for timer management over the default 4-heap.	3864	on amd64. It also selects a much smaller 2-heap for timer management over
		3865	the default 4-heap.
		3866
		3867	You can save even more by disabling watcher types you do not need
		3868	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3869	(C<-DNDEBUG>) will usually reduce code size a lot.
		3870
		3871	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3872	provide a bare-bones event library. See C<ev.h> for details on what parts
		3873	of the API are still available, and do not complain if this subset changes
		3874	over time.
		3875
		3876	=item EV_NSIG
		3877
		3878	The highest supported signal number, +1 (or, the number of
		3879	signals): Normally, libev tries to deduce the maximum number of signals
		3880	automatically, but sometimes this fails, in which case it can be
		3881	specified. Also, using a lower number than detected (C<32> should be
		3882	good for about any system in existance) can save some memory, as libev
		3883	statically allocates some 12-24 bytes per signal number.
3009		3884
3010	=item EV_PID_HASHSIZE	3885	=item EV_PID_HASHSIZE
3011		3886
3012	C<ev_child> watchers use a small hash table to distribute workload by	3887	C<ev_child> watchers use a small hash table to distribute workload by
3013	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3888	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3023	two).	3898	two).
3024		3899
3025	=item EV_USE_4HEAP	3900	=item EV_USE_4HEAP
3026		3901
3027	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3902	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3028	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3903	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3029	to C<1>. The 4-heap uses more complicated (longer) code but has	3904	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3030	noticably faster performance with many (thousands) of watchers.	3905	faster performance with many (thousands) of watchers.
3031		3906
3032	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3907	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3033	(disabled).	3908	(disabled).
3034		3909
3035	=item EV_HEAP_CACHE_AT	3910	=item EV_HEAP_CACHE_AT
3036		3911
3037	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3912	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3038	timer and periodics heap, libev can cache the timestamp (I<at>) within	3913	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3039	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3914	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3040	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3915	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3041	but avoids random read accesses on heap changes. This improves performance	3916	but avoids random read accesses on heap changes. This improves performance
3042	noticably with with many (hundreds) of watchers.	3917	noticeably with many (hundreds) of watchers.
3043		3918
3044	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3919	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3045	(disabled).	3920	(disabled).
3046		3921
3047	=item EV_VERIFY	3922	=item EV_VERIFY
…		…
3053	called once per loop, which can slow down libev. If set to C<3>, then the	3928	called once per loop, which can slow down libev. If set to C<3>, then the
3054	verification code will be called very frequently, which will slow down	3929	verification code will be called very frequently, which will slow down
3055	libev considerably.	3930	libev considerably.
3056		3931
3057	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3932	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3058	C<0.>	3933	C<0>.
3059		3934
3060	=item EV_COMMON	3935	=item EV_COMMON
3061		3936
3062	By default, all watchers have a C<void *data> member. By redefining	3937	By default, all watchers have a C<void *data> member. By redefining
3063	this macro to a something else you can include more and other types of	3938	this macro to a something else you can include more and other types of
3064	members. You have to define it each time you include one of the files,	3939	members. You have to define it each time you include one of the files,
3065	though, and it must be identical each time.	3940	though, and it must be identical each time.
3066		3941
3067	For example, the perl EV module uses something like this:	3942	For example, the perl EV module uses something like this:
3068		3943
3069	#define EV_COMMON \	3944	#define EV_COMMON \
3070	SV *self; /* contains this struct */ \	3945	SV *self; /* contains this struct */ \
3071	SV *cb_sv, *fh /* note no trailing ";" */	3946	SV *cb_sv, *fh /* note no trailing ";" */
3072		3947
3073	=item EV_CB_DECLARE (type)	3948	=item EV_CB_DECLARE (type)
3074		3949
3075	=item EV_CB_INVOKE (watcher, revents)	3950	=item EV_CB_INVOKE (watcher, revents)
3076		3951
…		…
3081	definition and a statement, respectively. See the F<ev.h> header file for	3956	definition and a statement, respectively. See the F<ev.h> header file for
3082	their default definitions. One possible use for overriding these is to	3957	their default definitions. One possible use for overriding these is to
3083	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3958	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3084	method calls instead of plain function calls in C++.	3959	method calls instead of plain function calls in C++.
3085		3960
		3961	=back
		3962
3086	=head2 EXPORTED API SYMBOLS	3963	=head2 EXPORTED API SYMBOLS
3087		3964
3088	If you need to re-export the API (e.g. via a dll) and you need a list of	3965	If you need to re-export the API (e.g. via a DLL) and you need a list of
3089	exported symbols, you can use the provided F<Symbol.*> files which list	3966	exported symbols, you can use the provided F<Symbol.*> files which list
3090	all public symbols, one per line:	3967	all public symbols, one per line:
3091		3968
3092	Symbols.ev for libev proper	3969	Symbols.ev for libev proper
3093	Symbols.event for the libevent emulation	3970	Symbols.event for the libevent emulation
3094		3971
3095	This can also be used to rename all public symbols to avoid clashes with	3972	This can also be used to rename all public symbols to avoid clashes with
3096	multiple versions of libev linked together (which is obviously bad in	3973	multiple versions of libev linked together (which is obviously bad in
3097	itself, but sometimes it is inconvinient to avoid this).	3974	itself, but sometimes it is inconvenient to avoid this).
3098		3975
3099	A sed command like this will create wrapper C<#define>'s that you need to	3976	A sed command like this will create wrapper C<#define>'s that you need to
3100	include before including F<ev.h>:	3977	include before including F<ev.h>:
3101		3978
3102	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3979	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3119	file.	3996	file.
3120		3997
3121	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3998	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3122	that everybody includes and which overrides some configure choices:	3999	that everybody includes and which overrides some configure choices:
3123		4000
3124	#define EV_MINIMAL 1	4001	#define EV_MINIMAL 1
3125	#define EV_USE_POLL 0	4002	#define EV_USE_POLL 0
3126	#define EV_MULTIPLICITY 0	4003	#define EV_MULTIPLICITY 0
3127	#define EV_PERIODIC_ENABLE 0	4004	#define EV_PERIODIC_ENABLE 0
3128	#define EV_STAT_ENABLE 0	4005	#define EV_STAT_ENABLE 0
3129	#define EV_FORK_ENABLE 0	4006	#define EV_FORK_ENABLE 0
3130	#define EV_CONFIG_H <config.h>	4007	#define EV_CONFIG_H <config.h>
3131	#define EV_MINPRI 0	4008	#define EV_MINPRI 0
3132	#define EV_MAXPRI 0	4009	#define EV_MAXPRI 0
3133		4010
3134	#include "ev++.h"	4011	#include "ev++.h"
3135		4012
3136	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4013	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3137		4014
3138	#include "ev_cpp.h"	4015	#include "ev_cpp.h"
3139	#include "ev.c"	4016	#include "ev.c"
3140		4017
		4018	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3141		4019
3142	=head1 THREADS AND COROUTINES	4020	=head2 THREADS AND COROUTINES
3143		4021
3144	=head2 THREADS	4022	=head3 THREADS
3145		4023
3146	Libev itself is completely threadsafe, but it uses no locking. This	4024	All libev functions are reentrant and thread-safe unless explicitly
		4025	documented otherwise, but libev implements no locking itself. This means
3147	means that you can use as many loops as you want in parallel, as long as	4026	that you can use as many loops as you want in parallel, as long as there
3148	only one thread ever calls into one libev function with the same loop	4027	are no concurrent calls into any libev function with the same loop
3149	parameter.	4028	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4029	of course): libev guarantees that different event loops share no data
		4030	structures that need any locking.
3150		4031
3151	Or put differently: calls with different loop parameters can be done in	4032	Or to put it differently: calls with different loop parameters can be done
3152	parallel from multiple threads, calls with the same loop parameter must be	4033	concurrently from multiple threads, calls with the same loop parameter
3153	done serially (but can be done from different threads, as long as only one	4034	must be done serially (but can be done from different threads, as long as
3154	thread ever is inside a call at any point in time, e.g. by using a mutex	4035	only one thread ever is inside a call at any point in time, e.g. by using
3155	per loop).	4036	a mutex per loop).
3156		4037
3157	If you want to know which design is best for your problem, then I cannot	4038	Specifically to support threads (and signal handlers), libev implements
		4039	so-called C<ev_async> watchers, which allow some limited form of
		4040	concurrency on the same event loop, namely waking it up "from the
		4041	outside".
		4042
		4043	If you want to know which design (one loop, locking, or multiple loops
		4044	without or something else still) is best for your problem, then I cannot
3158	help you but by giving some generic advice:	4045	help you, but here is some generic advice:
3159		4046
3160	=over 4	4047	=over 4
3161		4048
3162	=item * most applications have a main thread: use the default libev loop	4049	=item * most applications have a main thread: use the default libev loop
3163	in that thread, or create a seperate thread running only the default loop.	4050	in that thread, or create a separate thread running only the default loop.
3164		4051
3165	This helps integrating other libraries or software modules that use libev	4052	This helps integrating other libraries or software modules that use libev
3166	themselves and don't care/know about threading.	4053	themselves and don't care/know about threading.
3167		4054
3168	=item * one loop per thread is usually a good model.	4055	=item * one loop per thread is usually a good model.
3169		4056
3170	Doing this is almost never wrong, sometimes a better-performance model	4057	Doing this is almost never wrong, sometimes a better-performance model
3171	exists, but it is always a good start.	4058	exists, but it is always a good start.
3172		4059
3173	=item * other models exist, such as the leader/follower pattern, where one	4060	=item * other models exist, such as the leader/follower pattern, where one
3174	loop is handed through multiple threads in a kind of round-robbin fashion.	4061	loop is handed through multiple threads in a kind of round-robin fashion.
3175		4062
3176	Chosing a model is hard - look around, learn, know that usually you cna do	4063	Choosing a model is hard - look around, learn, know that usually you can do
3177	better than you currently do :-)	4064	better than you currently do :-)
3178		4065
3179	=item * often you need to talk to some other thread which blocks in the	4066	=item * often you need to talk to some other thread which blocks in the
		4067	event loop.
		4068
3180	event loop - C<ev_async> watchers can be used to wake them up from other	4069	C<ev_async> watchers can be used to wake them up from other threads safely
3181	threads safely (or from signal contexts...).	4070	(or from signal contexts...).
		4071
		4072	An example use would be to communicate signals or other events that only
		4073	work in the default loop by registering the signal watcher with the
		4074	default loop and triggering an C<ev_async> watcher from the default loop
		4075	watcher callback into the event loop interested in the signal.
3182		4076
3183	=back	4077	=back
3184		4078
		4079	=head4 THREAD LOCKING EXAMPLE
		4080
		4081	Here is a fictitious example of how to run an event loop in a different
		4082	thread than where callbacks are being invoked and watchers are
		4083	created/added/removed.
		4084
		4085	For a real-world example, see the C<EV::Loop::Async> perl module,
		4086	which uses exactly this technique (which is suited for many high-level
		4087	languages).
		4088
		4089	The example uses a pthread mutex to protect the loop data, a condition
		4090	variable to wait for callback invocations, an async watcher to notify the
		4091	event loop thread and an unspecified mechanism to wake up the main thread.
		4092
		4093	First, you need to associate some data with the event loop:
		4094
		4095	typedef struct {
		4096	mutex_t lock; /* global loop lock */
		4097	ev_async async_w;
		4098	thread_t tid;
		4099	cond_t invoke_cv;
		4100	} userdata;
		4101
		4102	void prepare_loop (EV_P)
		4103	{
		4104	// for simplicity, we use a static userdata struct.
		4105	static userdata u;
		4106
		4107	ev_async_init (&u->async_w, async_cb);
		4108	ev_async_start (EV_A_ &u->async_w);
		4109
		4110	pthread_mutex_init (&u->lock, 0);
		4111	pthread_cond_init (&u->invoke_cv, 0);
		4112
		4113	// now associate this with the loop
		4114	ev_set_userdata (EV_A_ u);
		4115	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4116	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4117
		4118	// then create the thread running ev_loop
		4119	pthread_create (&u->tid, 0, l_run, EV_A);
		4120	}
		4121
		4122	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4123	solely to wake up the event loop so it takes notice of any new watchers
		4124	that might have been added:
		4125
		4126	static void
		4127	async_cb (EV_P_ ev_async *w, int revents)
		4128	{
		4129	// just used for the side effects
		4130	}
		4131
		4132	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4133	protecting the loop data, respectively.
		4134
		4135	static void
		4136	l_release (EV_P)
		4137	{
		4138	userdata *u = ev_userdata (EV_A);
		4139	pthread_mutex_unlock (&u->lock);
		4140	}
		4141
		4142	static void
		4143	l_acquire (EV_P)
		4144	{
		4145	userdata *u = ev_userdata (EV_A);
		4146	pthread_mutex_lock (&u->lock);
		4147	}
		4148
		4149	The event loop thread first acquires the mutex, and then jumps straight
		4150	into C<ev_loop>:
		4151
		4152	void *
		4153	l_run (void *thr_arg)
		4154	{
		4155	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4156
		4157	l_acquire (EV_A);
		4158	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4159	ev_loop (EV_A_ 0);
		4160	l_release (EV_A);
		4161
		4162	return 0;
		4163	}
		4164
		4165	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4166	signal the main thread via some unspecified mechanism (signals? pipe
		4167	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4168	have been called (in a while loop because a) spurious wakeups are possible
		4169	and b) skipping inter-thread-communication when there are no pending
		4170	watchers is very beneficial):
		4171
		4172	static void
		4173	l_invoke (EV_P)
		4174	{
		4175	userdata *u = ev_userdata (EV_A);
		4176
		4177	while (ev_pending_count (EV_A))
		4178	{
		4179	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4180	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4181	}
		4182	}
		4183
		4184	Now, whenever the main thread gets told to invoke pending watchers, it
		4185	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4186	thread to continue:
		4187
		4188	static void
		4189	real_invoke_pending (EV_P)
		4190	{
		4191	userdata *u = ev_userdata (EV_A);
		4192
		4193	pthread_mutex_lock (&u->lock);
		4194	ev_invoke_pending (EV_A);
		4195	pthread_cond_signal (&u->invoke_cv);
		4196	pthread_mutex_unlock (&u->lock);
		4197	}
		4198
		4199	Whenever you want to start/stop a watcher or do other modifications to an
		4200	event loop, you will now have to lock:
		4201
		4202	ev_timer timeout_watcher;
		4203	userdata *u = ev_userdata (EV_A);
		4204
		4205	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4206
		4207	pthread_mutex_lock (&u->lock);
		4208	ev_timer_start (EV_A_ &timeout_watcher);
		4209	ev_async_send (EV_A_ &u->async_w);
		4210	pthread_mutex_unlock (&u->lock);
		4211
		4212	Note that sending the C<ev_async> watcher is required because otherwise
		4213	an event loop currently blocking in the kernel will have no knowledge
		4214	about the newly added timer. By waking up the loop it will pick up any new
		4215	watchers in the next event loop iteration.
		4216
3185	=head2 COROUTINES	4217	=head3 COROUTINES
3186		4218
3187	Libev is much more accomodating to coroutines ("cooperative threads"):	4219	Libev is very accommodating to coroutines ("cooperative threads"):
3188	libev fully supports nesting calls to it's functions from different	4220	libev fully supports nesting calls to its functions from different
3189	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4221	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3190	different coroutines and switch freely between both coroutines running the	4222	different coroutines, and switch freely between both coroutines running
3191	loop, as long as you don't confuse yourself). The only exception is that	4223	the loop, as long as you don't confuse yourself). The only exception is
3192	you must not do this from C<ev_periodic> reschedule callbacks.	4224	that you must not do this from C<ev_periodic> reschedule callbacks.
3193		4225
3194	Care has been invested into making sure that libev does not keep local	4226	Care has been taken to ensure that libev does not keep local state inside
3195	state inside C<ev_loop>, and other calls do not usually allow coroutine	4227	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3196	switches.	4228	they do not call any callbacks.
3197		4229
		4230	=head2 COMPILER WARNINGS
3198		4231
3199	=head1 COMPLEXITIES	4232	Depending on your compiler and compiler settings, you might get no or a
		4233	lot of warnings when compiling libev code. Some people are apparently
		4234	scared by this.
3200		4235
3201	In this section the complexities of (many of) the algorithms used inside	4236	However, these are unavoidable for many reasons. For one, each compiler
3202	libev will be explained. For complexity discussions about backends see the	4237	has different warnings, and each user has different tastes regarding
3203	documentation for C<ev_default_init>.	4238	warning options. "Warn-free" code therefore cannot be a goal except when
		4239	targeting a specific compiler and compiler-version.
3204		4240
3205	All of the following are about amortised time: If an array needs to be	4241	Another reason is that some compiler warnings require elaborate
3206	extended, libev needs to realloc and move the whole array, but this	4242	workarounds, or other changes to the code that make it less clear and less
3207	happens asymptotically never with higher number of elements, so O(1) might	4243	maintainable.
3208	mean it might do a lengthy realloc operation in rare cases, but on average
3209	it is much faster and asymptotically approaches constant time.
3210		4244
3211	=over 4	4245	And of course, some compiler warnings are just plain stupid, or simply
		4246	wrong (because they don't actually warn about the condition their message
		4247	seems to warn about). For example, certain older gcc versions had some
		4248	warnings that resulted an extreme number of false positives. These have
		4249	been fixed, but some people still insist on making code warn-free with
		4250	such buggy versions.
3212		4251
3213	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4252	While libev is written to generate as few warnings as possible,
		4253	"warn-free" code is not a goal, and it is recommended not to build libev
		4254	with any compiler warnings enabled unless you are prepared to cope with
		4255	them (e.g. by ignoring them). Remember that warnings are just that:
		4256	warnings, not errors, or proof of bugs.
3214		4257
3215	This means that, when you have a watcher that triggers in one hour and
3216	there are 100 watchers that would trigger before that then inserting will
3217	have to skip roughly seven (C<ld 100>) of these watchers.
3218		4258
3219	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4259	=head2 VALGRIND
3220		4260
3221	That means that changing a timer costs less than removing/adding them	4261	Valgrind has a special section here because it is a popular tool that is
3222	as only the relative motion in the event queue has to be paid for.	4262	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3223		4263
3224	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4264	If you think you found a bug (memory leak, uninitialised data access etc.)
		4265	in libev, then check twice: If valgrind reports something like:
3225		4266
3226	These just add the watcher into an array or at the head of a list.	4267	==2274== definitely lost: 0 bytes in 0 blocks.
		4268	==2274== possibly lost: 0 bytes in 0 blocks.
		4269	==2274== still reachable: 256 bytes in 1 blocks.
3227		4270
3228	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4271	Then there is no memory leak, just as memory accounted to global variables
		4272	is not a memleak - the memory is still being referenced, and didn't leak.
3229		4273
3230	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4274	Similarly, under some circumstances, valgrind might report kernel bugs
		4275	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4276	although an acceptable workaround has been found here), or it might be
		4277	confused.
3231		4278
3232	These watchers are stored in lists then need to be walked to find the	4279	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3233	correct watcher to remove. The lists are usually short (you don't usually	4280	make it into some kind of religion.
3234	have many watchers waiting for the same fd or signal).
3235		4281
3236	=item Finding the next timer in each loop iteration: O(1)	4282	If you are unsure about something, feel free to contact the mailing list
		4283	with the full valgrind report and an explanation on why you think this
		4284	is a bug in libev (best check the archives, too :). However, don't be
		4285	annoyed when you get a brisk "this is no bug" answer and take the chance
		4286	of learning how to interpret valgrind properly.
3237		4287
3238	By virtue of using a binary or 4-heap, the next timer is always found at a	4288	If you need, for some reason, empty reports from valgrind for your project
3239	fixed position in the storage array.	4289	I suggest using suppression lists.
3240		4290
3241	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3242		4291
3243	A change means an I/O watcher gets started or stopped, which requires	4292	=head1 PORTABILITY NOTES
3244	libev to recalculate its status (and possibly tell the kernel, depending
3245	on backend and wether C<ev_io_set> was used).
3246		4293
3247	=item Activating one watcher (putting it into the pending state): O(1)	4294	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3248
3249	=item Priority handling: O(number_of_priorities)
3250
3251	Priorities are implemented by allocating some space for each
3252	priority. When doing priority-based operations, libev usually has to
3253	linearly search all the priorities, but starting/stopping and activating
3254	watchers becomes O(1) w.r.t. priority handling.
3255
3256	=item Sending an ev_async: O(1)
3257
3258	=item Processing ev_async_send: O(number_of_async_watchers)
3259
3260	=item Processing signals: O(max_signal_number)
3261
3262	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3263	calls in the current loop iteration. Checking for async and signal events
3264	involves iterating over all running async watchers or all signal numbers.
3265
3266	=back
3267
3268
3269	=head1 Win32 platform limitations and workarounds
3270		4295
3271	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4296	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3272	requires, and its I/O model is fundamentally incompatible with the POSIX	4297	requires, and its I/O model is fundamentally incompatible with the POSIX
3273	model. Libev still offers limited functionality on this platform in	4298	model. Libev still offers limited functionality on this platform in
3274	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4299	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3281	way (note also that glib is the slowest event library known to man).	4306	way (note also that glib is the slowest event library known to man).
3282		4307
3283	There is no supported compilation method available on windows except	4308	There is no supported compilation method available on windows except
3284	embedding it into other applications.	4309	embedding it into other applications.
3285		4310
		4311	Sensible signal handling is officially unsupported by Microsoft - libev
		4312	tries its best, but under most conditions, signals will simply not work.
		4313
		4314	Not a libev limitation but worth mentioning: windows apparently doesn't
		4315	accept large writes: instead of resulting in a partial write, windows will
		4316	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4317	so make sure you only write small amounts into your sockets (less than a
		4318	megabyte seems safe, but this apparently depends on the amount of memory
		4319	available).
		4320
3286	Due to the many, low, and arbitrary limits on the win32 platform and	4321	Due to the many, low, and arbitrary limits on the win32 platform and
3287	the abysmal performance of winsockets, using a large number of sockets	4322	the abysmal performance of winsockets, using a large number of sockets
3288	is not recommended (and not reasonable). If your program needs to use	4323	is not recommended (and not reasonable). If your program needs to use
3289	more than a hundred or so sockets, then likely it needs to use a totally	4324	more than a hundred or so sockets, then likely it needs to use a totally
3290	different implementation for windows, as libev offers the POSIX readiness	4325	different implementation for windows, as libev offers the POSIX readiness
3291	notification model, which cannot be implemented efficiently on windows	4326	notification model, which cannot be implemented efficiently on windows
3292	(microsoft monopoly games).	4327	(due to Microsoft monopoly games).
		4328
		4329	A typical way to use libev under windows is to embed it (see the embedding
		4330	section for details) and use the following F<evwrap.h> header file instead
		4331	of F<ev.h>:
		4332
		4333	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4334	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4335
		4336	#include "ev.h"
		4337
		4338	And compile the following F<evwrap.c> file into your project (make sure
		4339	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4340
		4341	#include "evwrap.h"
		4342	#include "ev.c"
3293		4343
3294	=over 4	4344	=over 4
3295		4345
3296	=item The winsocket select function	4346	=item The winsocket select function
3297		4347
3298	The winsocket C<select> function doesn't follow POSIX in that it requires	4348	The winsocket C<select> function doesn't follow POSIX in that it
3299	socket I<handles> and not socket I<file descriptors>. This makes select	4349	requires socket I<handles> and not socket I<file descriptors> (it is
3300	very inefficient, and also requires a mapping from file descriptors	4350	also extremely buggy). This makes select very inefficient, and also
3301	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4351	requires a mapping from file descriptors to socket handles (the Microsoft
3302	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4352	C runtime provides the function C<_open_osfhandle> for this). See the
3303	symbols for more info.	4353	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4354	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3304		4355
3305	The configuration for a "naked" win32 using the microsoft runtime	4356	The configuration for a "naked" win32 using the Microsoft runtime
3306	libraries and raw winsocket select is:	4357	libraries and raw winsocket select is:
3307		4358
3308	#define EV_USE_SELECT 1	4359	#define EV_USE_SELECT 1
3309	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4360	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3310		4361
3311	Note that winsockets handling of fd sets is O(n), so you can easily get a	4362	Note that winsockets handling of fd sets is O(n), so you can easily get a
3312	complexity in the O(n²) range when using win32.	4363	complexity in the O(n²) range when using win32.
3313		4364
3314	=item Limited number of file descriptors	4365	=item Limited number of file descriptors
3315		4366
3316	Windows has numerous arbitrary (and low) limits on things.	4367	Windows has numerous arbitrary (and low) limits on things.
3317		4368
3318	Early versions of winsocket's select only supported waiting for a maximum	4369	Early versions of winsocket's select only supported waiting for a maximum
3319	of C<64> handles (probably owning to the fact that all windows kernels	4370	of C<64> handles (probably owning to the fact that all windows kernels
3320	can only wait for C<64> things at the same time internally; microsoft	4371	can only wait for C<64> things at the same time internally; Microsoft
3321	recommends spawning a chain of threads and wait for 63 handles and the	4372	recommends spawning a chain of threads and wait for 63 handles and the
3322	previous thread in each. Great).	4373	previous thread in each. Sounds great!).
3323		4374
3324	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4375	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3325	to some high number (e.g. C<2048>) before compiling the winsocket select	4376	to some high number (e.g. C<2048>) before compiling the winsocket select
3326	call (which might be in libev or elsewhere, for example, perl does its own	4377	call (which might be in libev or elsewhere, for example, perl and many
3327	select emulation on windows).	4378	other interpreters do their own select emulation on windows).
3328		4379
3329	Another limit is the number of file descriptors in the microsoft runtime	4380	Another limit is the number of file descriptors in the Microsoft runtime
3330	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4381	libraries, which by default is C<64> (there must be a hidden I<64>
3331	or something like this inside microsoft). You can increase this by calling	4382	fetish or something like this inside Microsoft). You can increase this
3332	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4383	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3333	arbitrary limit), but is broken in many versions of the microsoft runtime	4384	(another arbitrary limit), but is broken in many versions of the Microsoft
3334	libraries.
3335
3336	This might get you to about C<512> or C<2048> sockets (depending on	4385	runtime libraries. This might get you to about C<512> or C<2048> sockets
3337	windows version and/or the phase of the moon). To get more, you need to	4386	(depending on windows version and/or the phase of the moon). To get more,
3338	wrap all I/O functions and provide your own fd management, but the cost of	4387	you need to wrap all I/O functions and provide your own fd management, but
3339	calling select (O(n²)) will likely make this unworkable.	4388	the cost of calling select (O(n²)) will likely make this unworkable.
3340		4389
3341	=back	4390	=back
3342		4391
3343
3344	=head1 PORTABILITY REQUIREMENTS	4392	=head2 PORTABILITY REQUIREMENTS
3345		4393
3346	In addition to a working ISO-C implementation, libev relies on a few	4394	In addition to a working ISO-C implementation and of course the
3347	additional extensions:	4395	backend-specific APIs, libev relies on a few additional extensions:
3348		4396
3349	=over 4	4397	=over 4
3350		4398
		4399	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4400	calling conventions regardless of C<ev_watcher_type *>.
		4401
		4402	Libev assumes not only that all watcher pointers have the same internal
		4403	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4404	assumes that the same (machine) code can be used to call any watcher
		4405	callback: The watcher callbacks have different type signatures, but libev
		4406	calls them using an C<ev_watcher *> internally.
		4407
3351	=item C<sig_atomic_t volatile> must be thread-atomic as well	4408	=item C<sig_atomic_t volatile> must be thread-atomic as well
3352		4409
3353	The type C<sig_atomic_t volatile> (or whatever is defined as	4410	The type C<sig_atomic_t volatile> (or whatever is defined as
3354	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4411	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3355	threads. This is not part of the specification for C<sig_atomic_t>, but is	4412	threads. This is not part of the specification for C<sig_atomic_t>, but is
3356	believed to be sufficiently portable.	4413	believed to be sufficiently portable.
3357		4414
3358	=item C<sigprocmask> must work in a threaded environment	4415	=item C<sigprocmask> must work in a threaded environment
3359		4416
…		…
3368	except the initial one, and run the default loop in the initial thread as	4425	except the initial one, and run the default loop in the initial thread as
3369	well.	4426	well.
3370		4427
3371	=item C<long> must be large enough for common memory allocation sizes	4428	=item C<long> must be large enough for common memory allocation sizes
3372		4429
3373	To improve portability and simplify using libev, libev uses C<long>	4430	To improve portability and simplify its API, libev uses C<long> internally
3374	internally instead of C<size_t> when allocating its data structures. On	4431	instead of C<size_t> when allocating its data structures. On non-POSIX
3375	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4432	systems (Microsoft...) this might be unexpectedly low, but is still at
3376	is still at least 31 bits everywhere, which is enough for hundreds of	4433	least 31 bits everywhere, which is enough for hundreds of millions of
3377	millions of watchers.	4434	watchers.
3378		4435
3379	=item C<double> must hold a time value in seconds with enough accuracy	4436	=item C<double> must hold a time value in seconds with enough accuracy
3380		4437
3381	The type C<double> is used to represent timestamps. It is required to	4438	The type C<double> is used to represent timestamps. It is required to
3382	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4439	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3383	enough for at least into the year 4000. This requirement is fulfilled by	4440	enough for at least into the year 4000. This requirement is fulfilled by
3384	implementations implementing IEEE 754 (basically all existing ones).	4441	implementations implementing IEEE 754, which is basically all existing
		4442	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4443	2200.
3385		4444
3386	=back	4445	=back
3387		4446
3388	If you know of other additional requirements drop me a note.	4447	If you know of other additional requirements drop me a note.
3389		4448
3390		4449
3391	=head1 VALGRIND	4450	=head1 ALGORITHMIC COMPLEXITIES
3392		4451
3393	Valgrind has a special section here because it is a popular tool that is	4452	In this section the complexities of (many of) the algorithms used inside
3394	highly useful, but valgrind reports are very hard to interpret.	4453	libev will be documented. For complexity discussions about backends see
		4454	the documentation for C<ev_default_init>.
3395		4455
3396	If you think you found a bug (memory leak, uninitialised data access etc.)	4456	All of the following are about amortised time: If an array needs to be
3397	in libev, then check twice: If valgrind reports something like:	4457	extended, libev needs to realloc and move the whole array, but this
		4458	happens asymptotically rarer with higher number of elements, so O(1) might
		4459	mean that libev does a lengthy realloc operation in rare cases, but on
		4460	average it is much faster and asymptotically approaches constant time.
3398		4461
3399	==2274== definitely lost: 0 bytes in 0 blocks.	4462	=over 4
3400	==2274== possibly lost: 0 bytes in 0 blocks.
3401	==2274== still reachable: 256 bytes in 1 blocks.
3402		4463
3403	then there is no memory leak. Similarly, under some circumstances,	4464	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3404	valgrind might report kernel bugs as if it were a bug in libev, or it
3405	might be confused (it is a very good tool, but only a tool).
3406		4465
3407	If you are unsure about something, feel free to contact the mailing list	4466	This means that, when you have a watcher that triggers in one hour and
3408	with the full valgrind report and an explanation on why you think this is	4467	there are 100 watchers that would trigger before that, then inserting will
3409	a bug in libev. However, don't be annoyed when you get a brisk "this is	4468	have to skip roughly seven (C<ld 100>) of these watchers.
3410	no bug" answer and take the chance of learning how to interpret valgrind
3411	properly.
3412		4469
3413	If you need, for some reason, empty reports from valgrind for your project	4470	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3414	I suggest using suppression lists.
3415		4471
		4472	That means that changing a timer costs less than removing/adding them,
		4473	as only the relative motion in the event queue has to be paid for.
		4474
		4475	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4476
		4477	These just add the watcher into an array or at the head of a list.
		4478
		4479	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4480
		4481	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4482
		4483	These watchers are stored in lists, so they need to be walked to find the
		4484	correct watcher to remove. The lists are usually short (you don't usually
		4485	have many watchers waiting for the same fd or signal: one is typical, two
		4486	is rare).
		4487
		4488	=item Finding the next timer in each loop iteration: O(1)
		4489
		4490	By virtue of using a binary or 4-heap, the next timer is always found at a
		4491	fixed position in the storage array.
		4492
		4493	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4494
		4495	A change means an I/O watcher gets started or stopped, which requires
		4496	libev to recalculate its status (and possibly tell the kernel, depending
		4497	on backend and whether C<ev_io_set> was used).
		4498
		4499	=item Activating one watcher (putting it into the pending state): O(1)
		4500
		4501	=item Priority handling: O(number_of_priorities)
		4502
		4503	Priorities are implemented by allocating some space for each
		4504	priority. When doing priority-based operations, libev usually has to
		4505	linearly search all the priorities, but starting/stopping and activating
		4506	watchers becomes O(1) with respect to priority handling.
		4507
		4508	=item Sending an ev_async: O(1)
		4509
		4510	=item Processing ev_async_send: O(number_of_async_watchers)
		4511
		4512	=item Processing signals: O(max_signal_number)
		4513
		4514	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4515	calls in the current loop iteration. Checking for async and signal events
		4516	involves iterating over all running async watchers or all signal numbers.
		4517
		4518	=back
		4519
		4520
		4521	=head1 GLOSSARY
		4522
		4523	=over 4
		4524
		4525	=item active
		4526
		4527	A watcher is active as long as it has been started (has been attached to
		4528	an event loop) but not yet stopped (disassociated from the event loop).
		4529
		4530	=item application
		4531
		4532	In this document, an application is whatever is using libev.
		4533
		4534	=item callback
		4535
		4536	The address of a function that is called when some event has been
		4537	detected. Callbacks are being passed the event loop, the watcher that
		4538	received the event, and the actual event bitset.
		4539
		4540	=item callback invocation
		4541
		4542	The act of calling the callback associated with a watcher.
		4543
		4544	=item event
		4545
		4546	A change of state of some external event, such as data now being available
		4547	for reading on a file descriptor, time having passed or simply not having
		4548	any other events happening anymore.
		4549
		4550	In libev, events are represented as single bits (such as C<EV_READ> or
		4551	C<EV_TIMEOUT>).
		4552
		4553	=item event library
		4554
		4555	A software package implementing an event model and loop.
		4556
		4557	=item event loop
		4558
		4559	An entity that handles and processes external events and converts them
		4560	into callback invocations.
		4561
		4562	=item event model
		4563
		4564	The model used to describe how an event loop handles and processes
		4565	watchers and events.
		4566
		4567	=item pending
		4568
		4569	A watcher is pending as soon as the corresponding event has been detected,
		4570	and stops being pending as soon as the watcher will be invoked or its
		4571	pending status is explicitly cleared by the application.
		4572
		4573	A watcher can be pending, but not active. Stopping a watcher also clears
		4574	its pending status.
		4575
		4576	=item real time
		4577
		4578	The physical time that is observed. It is apparently strictly monotonic :)
		4579
		4580	=item wall-clock time
		4581
		4582	The time and date as shown on clocks. Unlike real time, it can actually
		4583	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4584	clock.
		4585
		4586	=item watcher
		4587
		4588	A data structure that describes interest in certain events. Watchers need
		4589	to be started (attached to an event loop) before they can receive events.
		4590
		4591	=item watcher invocation
		4592
		4593	The act of calling the callback associated with a watcher.
		4594
		4595	=back
3416		4596
3417	=head1 AUTHOR	4597	=head1 AUTHOR
3418		4598
3419	Marc Lehmann <libev@schmorp.de>.	4599	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3420		4600

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