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Revision 1.293 by root, Wed Mar 24 18:27:13 2010 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (in practise
115	the beginning of 1970, details are complicated, don't ask). This type is	130	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	132	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floatingpoint value. Unlike the name	133	any calculations on it, you should treat it as some floating point value.
		134
119	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	136	time differences (e.g. delays) throughout libev.
		137
		138	=head1 ERROR HANDLING
		139
		140	Libev knows three classes of errors: operating system errors, usage errors
		141	and internal errors (bugs).
		142
		143	When libev catches an operating system error it cannot handle (for example
		144	a system call indicating a condition libev cannot fix), it calls the callback
		145	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		146	abort. The default is to print a diagnostic message and to call C<abort
		147	()>.
		148
		149	When libev detects a usage error such as a negative timer interval, then
		150	it will print a diagnostic message and abort (via the C<assert> mechanism,
		151	so C<NDEBUG> will disable this checking): these are programming errors in
		152	the libev caller and need to be fixed there.
		153
		154	Libev also has a few internal error-checking C<assert>ions, and also has
		155	extensive consistency checking code. These do not trigger under normal
		156	circumstances, as they indicate either a bug in libev or worse.
		157
121		158
122	=head1 GLOBAL FUNCTIONS	159	=head1 GLOBAL FUNCTIONS
123		160
124	These functions can be called anytime, even before initialising the	161	These functions can be called anytime, even before initialising the
125	library in any way.	162	library in any way.
…		…
134		171
135	=item ev_sleep (ev_tstamp interval)	172	=item ev_sleep (ev_tstamp interval)
136		173
137	Sleep for the given interval: The current thread will be blocked until	174	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	175	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	176	this is a sub-second-resolution C<sleep ()>.
140		177
141	=item int ev_version_major ()	178	=item int ev_version_major ()
142		179
143	=item int ev_version_minor ()	180	=item int ev_version_minor ()
144		181
…		…
157	not a problem.	194	not a problem.
158		195
159	Example: Make sure we haven't accidentally been linked against the wrong	196	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	197	version.
161		198
162	assert (("libev version mismatch",	199	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	200	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	201	&& ev_version_minor () >= EV_VERSION_MINOR));
165		202
166	=item unsigned int ev_supported_backends ()	203	=item unsigned int ev_supported_backends ()
167		204
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	205	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	206	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	208	a description of the set values.
172		209
173	Example: make sure we have the epoll method, because yeah this is cool and	210	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	211	a must have and can we have a torrent of it please!!!11
175		212
176	assert (("sorry, no epoll, no sex",	213	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	214	ev_supported_backends () & EVBACKEND_EPOLL));
178		215
179	=item unsigned int ev_recommended_backends ()	216	=item unsigned int ev_recommended_backends ()
180		217
181	Return the set of all backends compiled into this binary of libev and also	218	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	219	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	220	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	221	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	222	(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.	223	libev will probe for if you specify no backends explicitly.
187		224
188	=item unsigned int ev_embeddable_backends ()	225	=item unsigned int ev_embeddable_backends ()
189		226
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	231	recommended ones.
195		232
196	See the description of C<ev_embed> watchers for more info.	233	See the description of C<ev_embed> watchers for more info.
197		234
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		236
200	Sets the allocation function to use (the prototype is similar - the	237	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	238	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	239	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	240	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	266	}
230		267
231	...	268	...
232	ev_set_allocator (persistent_realloc);	269	ev_set_allocator (persistent_realloc);
233		270
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		272
236	Set the callback function to call on a retryable syscall error (such	273	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	274	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	275	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	276	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	277	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	278	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	279	(such as abort).
243		280
244	Example: This is basically the same thing that libev does internally, too.	281	Example: This is basically the same thing that libev does internally, too.
…		…
255		292
256	=back	293	=back
257		294
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		296
260	An event loop is described by a C<struct ev_loop *>. The library knows two	297	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	298	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	299	I<function>).
		300
		301	The library knows two types of such loops, the I<default> loop, which
		302	supports signals and child events, and dynamically created loops which do
		303	not.
263		304
264	=over 4	305	=over 4
265		306
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	307	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		308
…		…
273	If you don't know what event loop to use, use the one returned from this	314	If you don't know what event loop to use, use the one returned from this
274	function.	315	function.
275		316
276	Note that this function is I<not> thread-safe, so if you want to use it	317	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,	318	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	319	as loops cannot be shared easily between threads anyway).
279		320
280	The default loop is the only loop that can handle C<ev_signal> and	321	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	322	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	323	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	324	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	325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	326	C<ev_default_init>.
286		327
287	The flags argument can be used to specify special behaviour or specific	328	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	337	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	338	thing, believe me).
298		339
299	=item C<EVFLAG_NOENV>	340	=item C<EVFLAG_NOENV>
300		341
301	If this flag bit is ored into the flag value (or the program runs setuid	342	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	343	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	344	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	345	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	346	useful to try out specific backends to test their performance, or to work
306	around bugs.	347	around bugs.
307		348
308	=item C<EVFLAG_FORKCHECK>	349	=item C<EVFLAG_FORKCHECK>
309		350
310	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	351	Instead of calling C<ev_loop_fork> manually after a fork, you can also
311	a fork, you can also make libev check for a fork in each iteration by	352	make libev check for a fork in each iteration by enabling this flag.
312	enabling this flag.
313		353
314	This works by calling C<getpid ()> on every iteration of the loop,	354	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	355	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	356	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	358	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	359	C<pthread_atfork> which is even faster).
320		360
321	The big advantage of this flag is that you can forget about fork (and	361	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	362	forget about forgetting to tell libev about forking) when you use this
323	flag.	363	flag.
324		364
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	366	environment variable.
		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
327		387
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		389
330	This is your standard select(2) backend. Not I<completely> standard, as	390	This is your standard select(2) backend. Not I<completely> standard, as
331	libev tries to roll its own fd_set with no limits on the number of fds,	391	libev tries to roll its own fd_set with no limits on the number of fds,
332	but if that fails, expect a fairly low limit on the number of fds when	392	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	393	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	394	usually the fastest backend for a low number of (low-numbered :) fds.
335		395
336	To get good performance out of this backend you need a high amount of	396	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	397	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	398	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	399	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	400	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness notifications you get per iteration.	401	readiness notifications you get per iteration.
		402
		403	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		404	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		405	C<exceptfds> set on that platform).
342		406
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	407	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		408
345	And this is your standard poll(2) backend. It's more complicated	409	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	410	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	411	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	412	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	413	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	414	performance tips.
351		415
		416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		418
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
353		423
354	For few fds, this backend is a bit little slower than poll and select,	424	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	425	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	426	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	427	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	428
359	cases and requiring a syscall per fd change, no fork support and bad	429	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	430	of the more advanced event mechanisms: mere annoyances include silently
		431	dropping file descriptors, requiring a system call per change per file
		432	descriptor (and unnecessary guessing of parameters), problems with dup and
		433	so on. The biggest issue is fork races, however - if a program forks then
		434	I<both> parent and child process have to recreate the epoll set, which can
		435	take considerable time (one syscall per file descriptor) and is of course
		436	hard to detect.
		437
		438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		439	of course I<doesn't>, and epoll just loves to report events for totally
		440	I<different> file descriptors (even already closed ones, so one cannot
		441	even remove them from the set) than registered in the set (especially
		442	on SMP systems). Libev tries to counter these spurious notifications by
		443	employing an additional generation counter and comparing that against the
		444	events to filter out spurious ones, recreating the set when required.
361		445
362	While stopping, setting and starting an I/O watcher in the same iteration	446	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	447	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	448	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	450	file descriptors might not work very well if you register events for both
367		451	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		452
372	Best performance from this backend is achieved by not unregistering all	453	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	454	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	455	i.e. keep at least one watcher active per fd at all times. Stopping and
		456	starting a watcher (without re-setting it) also usually doesn't cause
		457	extra overhead. A fork can both result in spurious notifications as well
		458	as in libev having to destroy and recreate the epoll object, which can
		459	take considerable time and thus should be avoided.
375		460
		461	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		462	faster than epoll for maybe up to a hundred file descriptors, depending on
		463	the usage. So sad.
		464
376	While nominally embeddeble in other event loops, this feature is broken in	465	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	466	all kernel versions tested so far.
		467
		468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		469	C<EVBACKEND_POLL>.
378		470
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		472
381	Kqueue deserves special mention, as at the time of this writing, it	473	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	474	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	475	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	476	it's completely useless). Unlike epoll, however, whose brokenness
		477	is by design, these kqueue bugs can (and eventually will) be fixed
		478	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	479	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	480	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	481	system like NetBSD.
388		482
389	You still can embed kqueue into a normal poll or select backend and use it	483	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	484	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	485	the target platform). See C<ev_embed> watchers for more info.
392		486
393	It scales in the same way as the epoll backend, but the interface to the	487	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	488	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	489	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	491	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		493	cases
399		494
400	This backend usually performs well under most conditions.	495	This backend usually performs well under most conditions.
401		496
402	While nominally embeddable in other event loops, this doesn't work	497	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	498	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	499	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	500	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	501	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	502	also broken on OS X)) and, did I mention it, using it only for sockets.
		503
		504	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		505	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		506	C<NOTE_EOF>.
408		507
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	508	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		509
411	This is not implemented yet (and might never be, unless you send me an	510	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	511	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		516
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	518	it's really slow, but it still scales very well (O(active_fds)).
420		519
421	Please note that solaris event ports can deliver a lot of spurious	520	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	521	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	522	blocking when no data (or space) is available.
424		523
425	While this backend scales well, it requires one system call per active	524	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	525	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	527	might perform better.
429		528
430	On the positive side, ignoring the spurious readiness notifications, this	529	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	530	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	531	in all tests and is fully embeddable, which is a rare feat among the
		532	OS-specific backends (I vastly prefer correctness over speed hacks).
		533
		534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		535	C<EVBACKEND_POLL>.
433		536
434	=item C<EVBACKEND_ALL>	537	=item C<EVBACKEND_ALL>
435		538
436	Try all backends (even potentially broken ones that wouldn't be tried	539	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		542
440	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
441		544
442	=back	545	=back
443		546
444	If one or more of these are ored into the flags value, then only these	547	If one or more of the backend flags are or'ed into the flags value,
445	backends will be tried (in the reverse order as listed here). If none are	548	then only these backends will be tried (in the reverse order as listed
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
447		551
448	The most typical usage is like this:	552	Example: This is the most typical usage.
449		553
450	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		556
453	Restrict libev to the select and poll backends, and do not allow	557	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	558	environment settings to be taken into account:
455		559
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		561
458	Use whatever libev has to offer, but make sure that kqueue is used if	562	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	563	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	564	private event loop and only if you know the OS supports your types of
		565	fds):
461		566
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		568
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	569	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		570
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	571	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	572	always distinct from the default loop.
468	handle signal and child watchers, and attempts to do so will be greeted by
469	undefined behaviour (or a failed assertion if assertions are enabled).
470		573
471	Note that this function I<is> thread-safe, and the recommended way to use	574	Note that this function I<is> thread-safe, and one common way to use
472	libev with threads is indeed to create one loop per thread, and using the	575	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	576	default loop in the "main" or "initial" thread.
474		577
475	Example: Try to create a event loop that uses epoll and nothing else.	578	Example: Try to create a event loop that uses epoll and nothing else.
476		579
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	581	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	582	fatal ("no epoll found here, maybe it hides under your chair");
480		583
481	=item ev_default_destroy ()	584	=item ev_default_destroy ()
482		585
483	Destroys the default loop again (frees all memory and kernel state	586	Destroys the default loop (frees all memory and kernel state etc.). None
484	etc.). None of the active event watchers will be stopped in the normal	587	of the active event watchers will be stopped in the normal sense, so
485	sense, so e.g. C<ev_is_active> might still return true. It is your	588	e.g. C<ev_is_active> might still return true. It is your responsibility to
486	responsibility to either stop all watchers cleanly yoursef I<before>	589	either stop all watchers cleanly yourself I<before> calling this function,
487	calling this function, or cope with the fact afterwards (which is usually	590	or cope with the fact afterwards (which is usually the easiest thing, you
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	591	can just ignore the watchers and/or C<free ()> them for example).
489	for example).
490		592
491	Note that certain global state, such as signal state, will not be freed by	593	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	594	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	595	as signal and child watchers) would need to be stopped manually.
494		596
495	In general it is not advisable to call this function except in the	597	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	598	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	599	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	600	C<ev_loop_new> and C<ev_loop_destroy>.
499		601
500	=item ev_loop_destroy (loop)	602	=item ev_loop_destroy (loop)
501		603
502	Like C<ev_default_destroy>, but destroys an event loop created by an	604	Like C<ev_default_destroy>, but destroys an event loop created by an
503	earlier call to C<ev_loop_new>.	605	earlier call to C<ev_loop_new>.
…		…
509	name, you can call it anytime, but it makes most sense after forking, in	611	name, you can call it anytime, but it makes most sense after forking, in
510	the child process (or both child and parent, but that again makes little	612	the child process (or both child and parent, but that again makes little
511	sense). You I<must> call it in the child before using any of the libev	613	sense). You I<must> call it in the child before using any of the libev
512	functions, and it will only take effect at the next C<ev_loop> iteration.	614	functions, and it will only take effect at the next C<ev_loop> iteration.
513		615
		616	Again, you I<have> to call it on I<any> loop that you want to re-use after
		617	a fork, I<even if you do not plan to use the loop in the parent>. This is
		618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		619	during fork.
		620
514	On the other hand, you only need to call this function in the child	621	On the other hand, you only need to call this function in the child
515	process if and only if you want to use the event library in the child. If	622	process if and only if you want to use the event loop in the child. If you
516	you just fork+exec, you don't have to call it at all.	623	just fork+exec or create a new loop in the child, you don't have to call
		624	it at all.
517		625
518	The function itself is quite fast and it's usually not a problem to call	626	The function itself is quite fast and it's usually not a problem to call
519	it just in case after a fork. To make this easy, the function will fit in	627	it just in case after a fork. To make this easy, the function will fit in
520	quite nicely into a call to C<pthread_atfork>:	628	quite nicely into a call to C<pthread_atfork>:
521		629
…		…
523		631
524	=item ev_loop_fork (loop)	632	=item ev_loop_fork (loop)
525		633
526	Like C<ev_default_fork>, but acts on an event loop created by	634	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	635	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.	636	after fork that you want to re-use in the child, and how you keep track of
		637	them is entirely your own problem.
529		638
530	=item int ev_is_default_loop (loop)	639	=item int ev_is_default_loop (loop)
531		640
532	Returns true when the given loop actually is the default loop, false otherwise.	641	Returns true when the given loop is, in fact, the default loop, and false
		642	otherwise.
533		643
534	=item unsigned int ev_loop_count (loop)	644	=item unsigned int ev_iteration (loop)
535		645
536	Returns the count of loop iterations for the loop, which is identical to	646	Returns the current iteration count for the loop, which is identical to
537	the number of times libev did poll for new events. It starts at C<0> and	647	the number of times libev did poll for new events. It starts at C<0> and
538	happily wraps around with enough iterations.	648	happily wraps around with enough iterations.
539		649
540	This value can sometimes be useful as a generation counter of sorts (it	650	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	651	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	652	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		653	prepare and check phases.
		654
		655	=item unsigned int ev_depth (loop)
		656
		657	Returns the number of times C<ev_loop> was entered minus the number of
		658	times C<ev_loop> was exited, in other words, the recursion depth.
		659
		660	Outside C<ev_loop>, this number is zero. In a callback, this number is
		661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		662	in which case it is higher.
		663
		664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		665	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		666	ungentleman behaviour unless it's really convenient.
543		667
544	=item unsigned int ev_backend (loop)	668	=item unsigned int ev_backend (loop)
545		669
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	671	use.
…		…
552	received events and started processing them. This timestamp does not	676	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	677	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	678	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).	679	event occurring (or more correctly, libev finding out about it).
556		680
		681	=item ev_now_update (loop)
		682
		683	Establishes the current time by querying the kernel, updating the time
		684	returned by C<ev_now ()> in the progress. This is a costly operation and
		685	is usually done automatically within C<ev_loop ()>.
		686
		687	This function is rarely useful, but when some event callback runs for a
		688	very long time without entering the event loop, updating libev's idea of
		689	the current time is a good idea.
		690
		691	See also L<The special problem of time updates> in the C<ev_timer> section.
		692
		693	=item ev_suspend (loop)
		694
		695	=item ev_resume (loop)
		696
		697	These two functions suspend and resume a loop, for use when the loop is
		698	not used for a while and timeouts should not be processed.
		699
		700	A typical use case would be an interactive program such as a game: When
		701	the user presses C<^Z> to suspend the game and resumes it an hour later it
		702	would be best to handle timeouts as if no time had actually passed while
		703	the program was suspended. This can be achieved by calling C<ev_suspend>
		704	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		705	C<ev_resume> directly afterwards to resume timer processing.
		706
		707	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		708	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		709	will be rescheduled (that is, they will lose any events that would have
		710	occured while suspended).
		711
		712	After calling C<ev_suspend> you B<must not> call I<any> function on the
		713	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		714	without a previous call to C<ev_suspend>.
		715
		716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		717	event loop time (see C<ev_now_update>).
		718
557	=item ev_loop (loop, int flags)	719	=item ev_loop (loop, int flags)
558		720
559	Finally, this is it, the event handler. This function usually is called	721	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	722	after you have initialised all your watchers and you want to start
561	events.	723	handling events.
562		724
563	If the flags argument is specified as C<0>, it will not return until	725	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.	726	either no event watchers are active anymore or C<ev_unloop> was called.
565		727
566	Please note that an explicit C<ev_unloop> is usually better than	728	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	729	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	730	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	731	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.	732	of relying on its watchers stopping correctly, that is truly a thing of
		733	beauty.
571		734
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	735	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	736	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.	737	process in case there are no events and will return after one iteration of
		738	the loop.
575		739
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	740	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	741	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	742	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	743	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	744	user-registered callback will be called), and will return after one
		745	iteration of the loop.
		746
		747	This is useful if you are waiting for some external event in conjunction
		748	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	749	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.	750	usually a better approach for this kind of thing.
583		751
584	Here are the gory details of what C<ev_loop> does:	752	Here are the gory details of what C<ev_loop> does:
585		753
586	- Before the first iteration, call any pending watchers.	754	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	755	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	756	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	757	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	758	- If we have been forked, detach and recreate the kernel state
		759	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	760	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	761	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	762	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	763	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	764	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	765	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	766	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	767	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	768	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	769	- Queue all expired timers.
601	- Queue all outstanding periodics.	770	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	771	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	772	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	773	- 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	774	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	775	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	776	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	781	anymore.
613		782
614	... queue jobs here, make sure they register event watchers as long	783	... 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..)	784	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	785	ev_loop (my_loop, 0);
617	... jobs done. yeah!	786	... jobs done or somebody called unloop. yeah!
618		787
619	=item ev_unloop (loop, how)	788	=item ev_unloop (loop, how)
620		789
621	Can be used to make a call to C<ev_loop> return early (but only after it	790	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	791	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	792	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.	793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		794
626	This "unloop state" will be cleared when entering C<ev_loop> again.	795	This "unloop state" will be cleared when entering C<ev_loop> again.
627		796
		797	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		798
628	=item ev_ref (loop)	799	=item ev_ref (loop)
629		800
630	=item ev_unref (loop)	801	=item ev_unref (loop)
631		802
632	Ref/unref can be used to add or remove a reference count on the event	803	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	804	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	805	count is nonzero, C<ev_loop> will not return on its own.
635	a watcher you never unregister that should not keep C<ev_loop> from	806
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	807	This is useful when you have a watcher that you never intend to
		808	unregister, but that nevertheless should not keep C<ev_loop> from
		809	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		810	before stopping it.
		811
637	example, libev itself uses this for its internal signal pipe: It is not	812	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	813	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	814	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	815	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>	816	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,	817	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	818	before, respectively. Note also that libev might stop watchers itself
		819	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		820	in the callback).
644		821
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	823	running when nothing else is active.
647		824
648	struct ev_signal exitsig;	825	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	826	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	827	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	828	evf_unref (loop);
652		829
653	Example: For some weird reason, unregister the above signal handler again.	830	Example: For some weird reason, unregister the above signal handler again.
654		831
655	ev_ref (loop);	832	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	833	ev_signal_stop (loop, &exitsig);
657		834
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	835	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		836
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	837	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		838
662	These advanced functions influence the time that libev will spend waiting	839	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	840	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.	841	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		842	latency.
665		843
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	844	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	845	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	846	to increase efficiency of loop iterations (or to increase power-saving
		847	opportunities).
669		848
670	The background is that sometimes your program runs just fast enough to	849	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	850	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	851	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	852	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	853	overhead for the actual polling but can deliver many events at once.
675		854
676	By setting a higher I<io collect interval> you allow libev to spend more	855	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,	856	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	857	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	858	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.	859	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		860	sleep time ensures that libev will not poll for I/O events more often then
		861	once per this interval, on average.
681		862
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	863	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	864	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	865	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	866	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	867	value will not introduce any overhead in libev.
687		868
688	Many (busy) programs can usually benefit by setting the io collect	869	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	870	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	871	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>,	872	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.	873	as this approaches the timing granularity of most systems. Note that if
		874	you do transactions with the outside world and you can't increase the
		875	parallelity, then this setting will limit your transaction rate (if you
		876	need to poll once per transaction and the I/O collect interval is 0.01,
		877	then you can't do more than 100 transations per second).
		878
		879	Setting the I<timeout collect interval> can improve the opportunity for
		880	saving power, as the program will "bundle" timer callback invocations that
		881	are "near" in time together, by delaying some, thus reducing the number of
		882	times the process sleeps and wakes up again. Another useful technique to
		883	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		884	they fire on, say, one-second boundaries only.
		885
		886	Example: we only need 0.1s timeout granularity, and we wish not to poll
		887	more often than 100 times per second:
		888
		889	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		891
		892	=item ev_invoke_pending (loop)
		893
		894	This call will simply invoke all pending watchers while resetting their
		895	pending state. Normally, C<ev_loop> does this automatically when required,
		896	but when overriding the invoke callback this call comes handy.
		897
		898	=item int ev_pending_count (loop)
		899
		900	Returns the number of pending watchers - zero indicates that no watchers
		901	are pending.
		902
		903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		904
		905	This overrides the invoke pending functionality of the loop: Instead of
		906	invoking all pending watchers when there are any, C<ev_loop> will call
		907	this callback instead. This is useful, for example, when you want to
		908	invoke the actual watchers inside another context (another thread etc.).
		909
		910	If you want to reset the callback, use C<ev_invoke_pending> as new
		911	callback.
		912
		913	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		914
		915	Sometimes you want to share the same loop between multiple threads. This
		916	can be done relatively simply by putting mutex_lock/unlock calls around
		917	each call to a libev function.
		918
		919	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		920	wait for it to return. One way around this is to wake up the loop via
		921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		922	and I<acquire> callbacks on the loop.
		923
		924	When set, then C<release> will be called just before the thread is
		925	suspended waiting for new events, and C<acquire> is called just
		926	afterwards.
		927
		928	Ideally, C<release> will just call your mutex_unlock function, and
		929	C<acquire> will just call the mutex_lock function again.
		930
		931	While event loop modifications are allowed between invocations of
		932	C<release> and C<acquire> (that's their only purpose after all), no
		933	modifications done will affect the event loop, i.e. adding watchers will
		934	have no effect on the set of file descriptors being watched, or the time
		935	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		936	to take note of any changes you made.
		937
		938	In theory, threads executing C<ev_loop> will be async-cancel safe between
		939	invocations of C<release> and C<acquire>.
		940
		941	See also the locking example in the C<THREADS> section later in this
		942	document.
		943
		944	=item ev_set_userdata (loop, void *data)
		945
		946	=item ev_userdata (loop)
		947
		948	Set and retrieve a single C<void *> associated with a loop. When
		949	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		950	C<0.>
		951
		952	These two functions can be used to associate arbitrary data with a loop,
		953	and are intended solely for the C<invoke_pending_cb>, C<release> and
		954	C<acquire> callbacks described above, but of course can be (ab-)used for
		955	any other purpose as well.
693		956
694	=item ev_loop_verify (loop)	957	=item ev_loop_verify (loop)
695		958
696	This function only does something when C<EV_VERIFY> support has been	959	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	960	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	961	through all internal structures and checks them for validity. If anything
699	an error message to standard error and call C<abort ()>.	962	is found to be inconsistent, it will print an error message to standard
		963	error and call C<abort ()>.
700		964
701	This can be used to catch bugs inside libev itself: under normal	965	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	966	circumstances, this function will never abort as of course libev keeps its
703	data structures consistent.	967	data structures consistent.
704		968
705	=back	969	=back
706		970
707		971
708	=head1 ANATOMY OF A WATCHER	972	=head1 ANATOMY OF A WATCHER
709		973
		974	In the following description, uppercase C<TYPE> in names stands for the
		975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		976	watchers and C<ev_io_start> for I/O watchers.
		977
710	A watcher is a structure that you create and register to record your	978	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	979	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:	980	become readable, you would create an C<ev_io> watcher for that:
713		981
714	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
715	{	983	{
716	ev_io_stop (w);	984	ev_io_stop (w);
717	ev_unloop (loop, EVUNLOOP_ALL);	985	ev_unloop (loop, EVUNLOOP_ALL);
718	}	986	}
719		987
720	struct ev_loop *loop = ev_default_loop (0);	988	struct ev_loop *loop = ev_default_loop (0);
		989
721	struct ev_io stdin_watcher;	990	ev_io stdin_watcher;
		991
722	ev_init (&stdin_watcher, my_cb);	992	ev_init (&stdin_watcher, my_cb);
723	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
724	ev_io_start (loop, &stdin_watcher);	994	ev_io_start (loop, &stdin_watcher);
		995
725	ev_loop (loop, 0);	996	ev_loop (loop, 0);
726		997
727	As you can see, you are responsible for allocating the memory for your	998	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,	999	watcher structures (and it is I<usually> a bad idea to do this on the
729	although this can sometimes be quite valid).	1000	stack).
		1001
		1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
730		1004
731	Each watcher structure must be initialised by a call to C<ev_init	1005	Each watcher structure must be initialised by a call to C<ev_init
732	(watcher *, callback)>, which expects a callback to be provided. This	1006	(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	1007	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	1008	watchers, each time the event loop detects that the file descriptor given
735	is readable and/or writable).	1009	is readable and/or writable).
736		1010
737	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1011	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	1012	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	1013	is also a macro to combine initialisation and setting in one call: C<<
740	(watcher *, callback, ...) >>.	1014	ev_TYPE_init (watcher *, callback, ...) >>.
741		1015
742	To make the watcher actually watch out for events, you have to start it	1016	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	1017	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	1018	*) >>), and you can stop watching for events at any time by calling the
745	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1019	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
746		1020
747	As long as your watcher is active (has been started but not stopped) you	1021	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	1022	must not touch the values stored in it. Most specifically you must never
749	reinitialise it or call its C<set> macro.	1023	reinitialise it or call its C<ev_TYPE_set> macro.
750		1024
751	Each and every callback receives the event loop pointer as first, the	1025	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	1026	registered watcher structure as second, and a bitset of received events as
753	third argument.	1027	third argument.
754		1028
…		…
763	=item C<EV_WRITE>	1037	=item C<EV_WRITE>
764		1038
765	The file descriptor in the C<ev_io> watcher has become readable and/or	1039	The file descriptor in the C<ev_io> watcher has become readable and/or
766	writable.	1040	writable.
767		1041
768	=item C<EV_TIMEOUT>	1042	=item C<EV_TIMER>
769		1043
770	The C<ev_timer> watcher has timed out.	1044	The C<ev_timer> watcher has timed out.
771		1045
772	=item C<EV_PERIODIC>	1046	=item C<EV_PERIODIC>
773		1047
…		…
812		1086
813	=item C<EV_ASYNC>	1087	=item C<EV_ASYNC>
814		1088
815	The given async watcher has been asynchronously notified (see C<ev_async>).	1089	The given async watcher has been asynchronously notified (see C<ev_async>).
816		1090
		1091	=item C<EV_CUSTOM>
		1092
		1093	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1094	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1095
817	=item C<EV_ERROR>	1096	=item C<EV_ERROR>
818		1097
819	An unspecified error has occured, the watcher has been stopped. This might	1098	An unspecified error has occurred, the watcher has been stopped. This might
820	happen because the watcher could not be properly started because libev	1099	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	1100	ran out of memory, a file descriptor was found to be closed or any other
		1101	problem. Libev considers these application bugs.
		1102
822	problem. You best act on it by reporting the problem and somehow coping	1103	You best act on it by reporting the problem and somehow coping with the
823	with the watcher being stopped.	1104	watcher being stopped. Note that well-written programs should not receive
		1105	an error ever, so when your watcher receives it, this usually indicates a
		1106	bug in your program.
824		1107
825	Libev will usually signal a few "dummy" events together with an error,	1108	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	1109	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	1110	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	1111	the error from read() or write(). This will not work in multi-threaded
829	programs, though, so beware.	1112	programs, though, as the fd could already be closed and reused for another
		1113	thing, so beware.
830		1114
831	=back	1115	=back
832		1116
833	=head2 GENERIC WATCHER FUNCTIONS	1117	=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		1118
838	=over 4	1119	=over 4
839		1120
840	=item C<ev_init> (ev_TYPE *watcher, callback)	1121	=item C<ev_init> (ev_TYPE *watcher, callback)
841		1122
…		…
847	which rolls both calls into one.	1128	which rolls both calls into one.
848		1129
849	You can reinitialise a watcher at any time as long as it has been stopped	1130	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.	1131	(or never started) and there are no pending events outstanding.
851		1132
852	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1133	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
853	int revents)>.	1134	int revents)>.
854		1135
		1136	Example: Initialise an C<ev_io> watcher in two steps.
		1137
		1138	ev_io w;
		1139	ev_init (&w, my_cb);
		1140	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1141
855	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1142	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
856		1143
857	This macro initialises the type-specific parts of a watcher. You need to	1144	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	1145	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	1146	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	1147	macro on a watcher that is active (it can be pending, however, which is a
861	difference to the C<ev_init> macro).	1148	difference to the C<ev_init> macro).
862		1149
863	Although some watcher types do not have type-specific arguments	1150	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.	1151	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
865		1152
		1153	See C<ev_init>, above, for an example.
		1154
866	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1155	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
867		1156
868	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1157	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	1158	calls into a single call. This is the most convenient method to initialise
870	a watcher. The same limitations apply, of course.	1159	a watcher. The same limitations apply, of course.
871		1160
		1161	Example: Initialise and set an C<ev_io> watcher in one step.
		1162
		1163	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1164
872	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1165	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
873		1166
874	Starts (activates) the given watcher. Only active watchers will receive	1167	Starts (activates) the given watcher. Only active watchers will receive
875	events. If the watcher is already active nothing will happen.	1168	events. If the watcher is already active nothing will happen.
876		1169
		1170	Example: Start the C<ev_io> watcher that is being abused as example in this
		1171	whole section.
		1172
		1173	ev_io_start (EV_DEFAULT_UC, &w);
		1174
877	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1175	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
878		1176
879	Stops the given watcher again (if active) and clears the pending	1177	Stops the given watcher if active, and clears the pending status (whether
		1178	the watcher was active or not).
		1179
880	status. It is possible that stopped watchers are pending (for example,	1180	It is possible that stopped watchers are pending - for example,
881	non-repeating timers are being stopped when they become pending), but	1181	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	1182	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	1183	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.	1184	therefore a good idea to always call its C<ev_TYPE_stop> function.
885		1185
886	=item bool ev_is_active (ev_TYPE *watcher)	1186	=item bool ev_is_active (ev_TYPE *watcher)
887		1187
888	Returns a true value iff the watcher is active (i.e. it has been started	1188	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	1189	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)	1205	=item ev_cb_set (ev_TYPE *watcher, callback)
906		1206
907	Change the callback. You can change the callback at virtually any time	1207	Change the callback. You can change the callback at virtually any time
908	(modulo threads).	1208	(modulo threads).
909		1209
910	=item ev_set_priority (ev_TYPE *watcher, priority)	1210	=item ev_set_priority (ev_TYPE *watcher, int priority)
911		1211
912	=item int ev_priority (ev_TYPE *watcher)	1212	=item int ev_priority (ev_TYPE *watcher)
913		1213
914	Set and query the priority of the watcher. The priority is a small	1214	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>	1215	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
916	(default: C<-2>). Pending watchers with higher priority will be invoked	1216	(default: C<-2>). Pending watchers with higher priority will be invoked
917	before watchers with lower priority, but priority will not keep watchers	1217	before watchers with lower priority, but priority will not keep watchers
918	from being executed (except for C<ev_idle> watchers).	1218	from being executed (except for C<ev_idle> watchers).
919		1219
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	1220	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.	1221	you need to look at C<ev_idle> watchers, which provide this functionality.
927		1222
928	You I<must not> change the priority of a watcher as long as it is active or	1223	You I<must not> change the priority of a watcher as long as it is active or
929	pending.	1224	pending.
930		1225
		1226	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1227	fine, as long as you do not mind that the priority value you query might
		1228	or might not have been clamped to the valid range.
		1229
931	The default priority used by watchers when no priority has been set is	1230	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 :).	1231	always C<0>, which is supposed to not be too high and not be too low :).
933		1232
934	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1233	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	1234	priorities.
936	or might not have been adjusted to be within valid range.
937		1235
938	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1236	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
939		1237
940	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1238	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	1239	C<loop> nor C<revents> need to be valid as long as the watcher callback
942	can deal with that fact.	1240	can deal with that fact, as both are simply passed through to the
		1241	callback.
943		1242
944	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1243	=item int ev_clear_pending (loop, ev_TYPE *watcher)
945		1244
946	If the watcher is pending, this function returns clears its pending status	1245	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	1246	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>.	1247	watcher isn't pending it does nothing and returns C<0>.
949		1248
		1249	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1250	callback to be invoked, which can be accomplished with this function.
		1251
		1252	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1253
		1254	Feeds the given event set into the event loop, as if the specified event
		1255	had happened for the specified watcher (which must be a pointer to an
		1256	initialised but not necessarily started event watcher). Obviously you must
		1257	not free the watcher as long as it has pending events.
		1258
		1259	Stopping the watcher, letting libev invoke it, or calling
		1260	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1261	not started in the first place.
		1262
		1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1264	functions that do not need a watcher.
		1265
950	=back	1266	=back
951		1267
952		1268
953	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
954		1270
955	Each watcher has, by default, a member C<void *data> that you can change	1271	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	1272	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	1273	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	1274	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	1275	member, you can also "subclass" the watcher type and provide your own
960	data:	1276	data:
961		1277
962	struct my_io	1278	struct my_io
963	{	1279	{
964	struct ev_io io;	1280	ev_io io;
965	int otherfd;	1281	int otherfd;
966	void *somedata;	1282	void *somedata;
967	struct whatever *mostinteresting;	1283	struct whatever *mostinteresting;
968	}	1284	};
		1285
		1286	...
		1287	struct my_io w;
		1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
969		1289
970	And since your callback will be called with a pointer to the watcher, you	1290	And since your callback will be called with a pointer to the watcher, you
971	can cast it back to your own type:	1291	can cast it back to your own type:
972		1292
973	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
974	{	1294	{
975	struct my_io *w = (struct my_io *)w_;	1295	struct my_io *w = (struct my_io *)w_;
976	...	1296	...
977	}	1297	}
978		1298
979	More interesting and less C-conformant ways of casting your callback type	1299	More interesting and less C-conformant ways of casting your callback type
980	instead have been omitted.	1300	instead have been omitted.
981		1301
982	Another common scenario is having some data structure with multiple	1302	Another common scenario is to use some data structure with multiple
983	watchers:	1303	embedded watchers:
984		1304
985	struct my_biggy	1305	struct my_biggy
986	{	1306	{
987	int some_data;	1307	int some_data;
988	ev_timer t1;	1308	ev_timer t1;
989	ev_timer t2;	1309	ev_timer t2;
990	}	1310	}
991		1311
992	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1312	In this case getting the pointer to C<my_biggy> is a bit more
993	you need to use C<offsetof>:	1313	complicated: Either you store the address of your C<my_biggy> struct
		1314	in the C<data> member of the watcher (for woozies), or you need to use
		1315	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1316	programmers):
994		1317
995	#include <stddef.h>	1318	#include <stddef.h>
996		1319
997	static void	1320	static void
998	t1_cb (EV_P_ struct ev_timer *w, int revents)	1321	t1_cb (EV_P_ ev_timer *w, int revents)
999	{	1322	{
1000	struct my_biggy big = (struct my_biggy *	1323	struct my_biggy big = (struct my_biggy *)
1001	(((char *)w) - offsetof (struct my_biggy, t1));	1324	(((char *)w) - offsetof (struct my_biggy, t1));
1002	}	1325	}
1003		1326
1004	static void	1327	static void
1005	t2_cb (EV_P_ struct ev_timer *w, int revents)	1328	t2_cb (EV_P_ ev_timer *w, int revents)
1006	{	1329	{
1007	struct my_biggy big = (struct my_biggy *	1330	struct my_biggy big = (struct my_biggy *)
1008	(((char *)w) - offsetof (struct my_biggy, t2));	1331	(((char *)w) - offsetof (struct my_biggy, t2));
1009	}	1332	}
		1333
		1334	=head2 WATCHER PRIORITY MODELS
		1335
		1336	Many event loops support I<watcher priorities>, which are usually small
		1337	integers that influence the ordering of event callback invocation
		1338	between watchers in some way, all else being equal.
		1339
		1340	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1341	description for the more technical details such as the actual priority
		1342	range.
		1343
		1344	There are two common ways how these these priorities are being interpreted
		1345	by event loops:
		1346
		1347	In the more common lock-out model, higher priorities "lock out" invocation
		1348	of lower priority watchers, which means as long as higher priority
		1349	watchers receive events, lower priority watchers are not being invoked.
		1350
		1351	The less common only-for-ordering model uses priorities solely to order
		1352	callback invocation within a single event loop iteration: Higher priority
		1353	watchers are invoked before lower priority ones, but they all get invoked
		1354	before polling for new events.
		1355
		1356	Libev uses the second (only-for-ordering) model for all its watchers
		1357	except for idle watchers (which use the lock-out model).
		1358
		1359	The rationale behind this is that implementing the lock-out model for
		1360	watchers is not well supported by most kernel interfaces, and most event
		1361	libraries will just poll for the same events again and again as long as
		1362	their callbacks have not been executed, which is very inefficient in the
		1363	common case of one high-priority watcher locking out a mass of lower
		1364	priority ones.
		1365
		1366	Static (ordering) priorities are most useful when you have two or more
		1367	watchers handling the same resource: a typical usage example is having an
		1368	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1369	timeouts. Under load, data might be received while the program handles
		1370	other jobs, but since timers normally get invoked first, the timeout
		1371	handler will be executed before checking for data. In that case, giving
		1372	the timer a lower priority than the I/O watcher ensures that I/O will be
		1373	handled first even under adverse conditions (which is usually, but not
		1374	always, what you want).
		1375
		1376	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1377	will only be executed when no same or higher priority watchers have
		1378	received events, they can be used to implement the "lock-out" model when
		1379	required.
		1380
		1381	For example, to emulate how many other event libraries handle priorities,
		1382	you can associate an C<ev_idle> watcher to each such watcher, and in
		1383	the normal watcher callback, you just start the idle watcher. The real
		1384	processing is done in the idle watcher callback. This causes libev to
		1385	continously poll and process kernel event data for the watcher, but when
		1386	the lock-out case is known to be rare (which in turn is rare :), this is
		1387	workable.
		1388
		1389	Usually, however, the lock-out model implemented that way will perform
		1390	miserably under the type of load it was designed to handle. In that case,
		1391	it might be preferable to stop the real watcher before starting the
		1392	idle watcher, so the kernel will not have to process the event in case
		1393	the actual processing will be delayed for considerable time.
		1394
		1395	Here is an example of an I/O watcher that should run at a strictly lower
		1396	priority than the default, and which should only process data when no
		1397	other events are pending:
		1398
		1399	ev_idle idle; // actual processing watcher
		1400	ev_io io; // actual event watcher
		1401
		1402	static void
		1403	io_cb (EV_P_ ev_io *w, int revents)
		1404	{
		1405	// stop the I/O watcher, we received the event, but
		1406	// are not yet ready to handle it.
		1407	ev_io_stop (EV_A_ w);
		1408
		1409	// start the idle watcher to ahndle the actual event.
		1410	// it will not be executed as long as other watchers
		1411	// with the default priority are receiving events.
		1412	ev_idle_start (EV_A_ &idle);
		1413	}
		1414
		1415	static void
		1416	idle_cb (EV_P_ ev_idle *w, int revents)
		1417	{
		1418	// actual processing
		1419	read (STDIN_FILENO, ...);
		1420
		1421	// have to start the I/O watcher again, as
		1422	// we have handled the event
		1423	ev_io_start (EV_P_ &io);
		1424	}
		1425
		1426	// initialisation
		1427	ev_idle_init (&idle, idle_cb);
		1428	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1429	ev_io_start (EV_DEFAULT_ &io);
		1430
		1431	In the "real" world, it might also be beneficial to start a timer, so that
		1432	low-priority connections can not be locked out forever under load. This
		1433	enables your program to keep a lower latency for important connections
		1434	during short periods of high load, while not completely locking out less
		1435	important ones.
1010		1436
1011		1437
1012	=head1 WATCHER TYPES	1438	=head1 WATCHER TYPES
1013		1439
1014	This section describes each watcher in detail, but will not repeat	1440	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	1464	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	1465	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	1466	descriptors to non-blocking mode is also usually a good idea (but not
1041	required if you know what you are doing).	1467	required if you know what you are doing).
1042		1468
1043	If you must do this, then force the use of a known-to-be-good backend	1469	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	1470	known-to-be-good backend (at the time of this writing, this includes only
1045	C<EVBACKEND_POLL>).	1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1472	descriptors for which non-blocking operation makes no sense (such as
		1473	files) - libev doesn't guarentee any specific behaviour in that case.
1046		1474
1047	Another thing you have to watch out for is that it is quite easy to	1475	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	1476	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	1477	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	1478	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	1479	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	1480	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	1481	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.	1482	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1055		1483
1056	If you cannot run the fd in non-blocking mode (for example you should not	1484	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	1485	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	1486	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	1487	interface such as poll (fortunately in our Xlib example, Xlib already
1060	its own, so its quite safe to use).	1488	does this on its own, so its quite safe to use). Some people additionally
		1489	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1490	indefinitely.
		1491
		1492	But really, best use non-blocking mode.
1061		1493
1062	=head3 The special problem of disappearing file descriptors	1494	=head3 The special problem of disappearing file descriptors
1063		1495
1064	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1496	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,	1497	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	1498	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	1499	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	1500	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	1501	registered with libev, there is no efficient way to see that this is, in
1070	fact, a different file descriptor.	1502	fact, a different file descriptor.
1071		1503
…		…
1102	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1534	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1103	C<EVBACKEND_POLL>.	1535	C<EVBACKEND_POLL>.
1104		1536
1105	=head3 The special problem of SIGPIPE	1537	=head3 The special problem of SIGPIPE
1106		1538
1107	While not really specific to libev, it is easy to forget about SIGPIPE:	1539	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	1540	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	1541	sent a SIGPIPE, which, by default, aborts your program. For most programs
1110	programs this is sensible behaviour, for daemons, this is usually	1542	this is sensible behaviour, for daemons, this is usually undesirable.
1111	undesirable.
1112		1543
1113	So when you encounter spurious, unexplained daemon exits, make sure you	1544	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	1545	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).	1546	somewhere, as that would have given you a big clue).
1116		1547
		1548	=head3 The special problem of accept()ing when you can't
		1549
		1550	Many implementations of the POSIX C<accept> function (for example,
		1551	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1552	connection from the pending queue in all error cases.
		1553
		1554	For example, larger servers often run out of file descriptors (because
		1555	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1556	rejecting the connection, leading to libev signalling readiness on
		1557	the next iteration again (the connection still exists after all), and
		1558	typically causing the program to loop at 100% CPU usage.
		1559
		1560	Unfortunately, the set of errors that cause this issue differs between
		1561	operating systems, there is usually little the app can do to remedy the
		1562	situation, and no known thread-safe method of removing the connection to
		1563	cope with overload is known (to me).
		1564
		1565	One of the easiest ways to handle this situation is to just ignore it
		1566	- when the program encounters an overload, it will just loop until the
		1567	situation is over. While this is a form of busy waiting, no OS offers an
		1568	event-based way to handle this situation, so it's the best one can do.
		1569
		1570	A better way to handle the situation is to log any errors other than
		1571	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1572	messages, and continue as usual, which at least gives the user an idea of
		1573	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1574	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1575	usage.
		1576
		1577	If your program is single-threaded, then you could also keep a dummy file
		1578	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1579	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1580	close that fd, and create a new dummy fd. This will gracefully refuse
		1581	clients under typical overload conditions.
		1582
		1583	The last way to handle it is to simply log the error and C<exit>, as
		1584	is often done with C<malloc> failures, but this results in an easy
		1585	opportunity for a DoS attack.
1117		1586
1118	=head3 Watcher-Specific Functions	1587	=head3 Watcher-Specific Functions
1119		1588
1120	=over 4	1589	=over 4
1121		1590
1122	=item ev_io_init (ev_io *, callback, int fd, int events)	1591	=item ev_io_init (ev_io *, callback, int fd, int events)
1123		1592
1124	=item ev_io_set (ev_io *, int fd, int events)	1593	=item ev_io_set (ev_io *, int fd, int events)
1125		1594
1126	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1595	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	1596	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.	1597	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1129		1598
1130	=item int fd [read-only]	1599	=item int fd [read-only]
1131		1600
1132	The file descriptor being watched.	1601	The file descriptor being watched.
1133		1602
…		…
1141		1610
1142	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1611	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	1612	readable, but only once. Since it is likely line-buffered, you could
1144	attempt to read a whole line in the callback.	1613	attempt to read a whole line in the callback.
1145		1614
1146	static void	1615	static void
1147	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1616	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1148	{	1617	{
1149	ev_io_stop (loop, w);	1618	ev_io_stop (loop, w);
1150	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1619	.. read from stdin here (or from w->fd) and handle any I/O errors
1151	}	1620	}
1152		1621
1153	...	1622	...
1154	struct ev_loop *loop = ev_default_init (0);	1623	struct ev_loop *loop = ev_default_init (0);
1155	struct ev_io stdin_readable;	1624	ev_io stdin_readable;
1156	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1157	ev_io_start (loop, &stdin_readable);	1626	ev_io_start (loop, &stdin_readable);
1158	ev_loop (loop, 0);	1627	ev_loop (loop, 0);
1159		1628
1160		1629
1161	=head2 C<ev_timer> - relative and optionally repeating timeouts	1630	=head2 C<ev_timer> - relative and optionally repeating timeouts
1162		1631
1163	Timer watchers are simple relative timers that generate an event after a	1632	Timer watchers are simple relative timers that generate an event after a
1164	given time, and optionally repeating in regular intervals after that.	1633	given time, and optionally repeating in regular intervals after that.
1165		1634
1166	The timers are based on real time, that is, if you register an event that	1635	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	1636	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	1637	year, it will still time out after (roughly) one hour. "Roughly" because
1169	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1170	monotonic clock option helps a lot here).	1639	monotonic clock option helps a lot here).
		1640
		1641	The callback is guaranteed to be invoked only I<after> its timeout has
		1642	passed (not I<at>, so on systems with very low-resolution clocks this
		1643	might introduce a small delay). If multiple timers become ready during the
		1644	same loop iteration then the ones with earlier time-out values are invoked
		1645	before ones of the same priority with later time-out values (but this is
		1646	no longer true when a callback calls C<ev_loop> recursively).
		1647
		1648	=head3 Be smart about timeouts
		1649
		1650	Many real-world problems involve some kind of timeout, usually for error
		1651	recovery. A typical example is an HTTP request - if the other side hangs,
		1652	you want to raise some error after a while.
		1653
		1654	What follows are some ways to handle this problem, from obvious and
		1655	inefficient to smart and efficient.
		1656
		1657	In the following, a 60 second activity timeout is assumed - a timeout that
		1658	gets reset to 60 seconds each time there is activity (e.g. each time some
		1659	data or other life sign was received).
		1660
		1661	=over 4
		1662
		1663	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1664
		1665	This is the most obvious, but not the most simple way: In the beginning,
		1666	start the watcher:
		1667
		1668	ev_timer_init (timer, callback, 60., 0.);
		1669	ev_timer_start (loop, timer);
		1670
		1671	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1672	and start it again:
		1673
		1674	ev_timer_stop (loop, timer);
		1675	ev_timer_set (timer, 60., 0.);
		1676	ev_timer_start (loop, timer);
		1677
		1678	This is relatively simple to implement, but means that each time there is
		1679	some activity, libev will first have to remove the timer from its internal
		1680	data structure and then add it again. Libev tries to be fast, but it's
		1681	still not a constant-time operation.
		1682
		1683	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1684
		1685	This is the easiest way, and involves using C<ev_timer_again> instead of
		1686	C<ev_timer_start>.
		1687
		1688	To implement this, configure an C<ev_timer> with a C<repeat> value
		1689	of C<60> and then call C<ev_timer_again> at start and each time you
		1690	successfully read or write some data. If you go into an idle state where
		1691	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1692	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1693
		1694	That means you can ignore both the C<ev_timer_start> function and the
		1695	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1696	member and C<ev_timer_again>.
		1697
		1698	At start:
		1699
		1700	ev_init (timer, callback);
		1701	timer->repeat = 60.;
		1702	ev_timer_again (loop, timer);
		1703
		1704	Each time there is some activity:
		1705
		1706	ev_timer_again (loop, timer);
		1707
		1708	It is even possible to change the time-out on the fly, regardless of
		1709	whether the watcher is active or not:
		1710
		1711	timer->repeat = 30.;
		1712	ev_timer_again (loop, timer);
		1713
		1714	This is slightly more efficient then stopping/starting the timer each time
		1715	you want to modify its timeout value, as libev does not have to completely
		1716	remove and re-insert the timer from/into its internal data structure.
		1717
		1718	It is, however, even simpler than the "obvious" way to do it.
		1719
		1720	=item 3. Let the timer time out, but then re-arm it as required.
		1721
		1722	This method is more tricky, but usually most efficient: Most timeouts are
		1723	relatively long compared to the intervals between other activity - in
		1724	our example, within 60 seconds, there are usually many I/O events with
		1725	associated activity resets.
		1726
		1727	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1728	but remember the time of last activity, and check for a real timeout only
		1729	within the callback:
		1730
		1731	ev_tstamp last_activity; // time of last activity
		1732
		1733	static void
		1734	callback (EV_P_ ev_timer *w, int revents)
		1735	{
		1736	ev_tstamp now = ev_now (EV_A);
		1737	ev_tstamp timeout = last_activity + 60.;
		1738
		1739	// if last_activity + 60. is older than now, we did time out
		1740	if (timeout < now)
		1741	{
		1742	// timeout occured, take action
		1743	}
		1744	else
		1745	{
		1746	// callback was invoked, but there was some activity, re-arm
		1747	// the watcher to fire in last_activity + 60, which is
		1748	// guaranteed to be in the future, so "again" is positive:
		1749	w->repeat = timeout - now;
		1750	ev_timer_again (EV_A_ w);
		1751	}
		1752	}
		1753
		1754	To summarise the callback: first calculate the real timeout (defined
		1755	as "60 seconds after the last activity"), then check if that time has
		1756	been reached, which means something I<did>, in fact, time out. Otherwise
		1757	the callback was invoked too early (C<timeout> is in the future), so
		1758	re-schedule the timer to fire at that future time, to see if maybe we have
		1759	a timeout then.
		1760
		1761	Note how C<ev_timer_again> is used, taking advantage of the
		1762	C<ev_timer_again> optimisation when the timer is already running.
		1763
		1764	This scheme causes more callback invocations (about one every 60 seconds
		1765	minus half the average time between activity), but virtually no calls to
		1766	libev to change the timeout.
		1767
		1768	To start the timer, simply initialise the watcher and set C<last_activity>
		1769	to the current time (meaning we just have some activity :), then call the
		1770	callback, which will "do the right thing" and start the timer:
		1771
		1772	ev_init (timer, callback);
		1773	last_activity = ev_now (loop);
		1774	callback (loop, timer, EV_TIMER);
		1775
		1776	And when there is some activity, simply store the current time in
		1777	C<last_activity>, no libev calls at all:
		1778
		1779	last_actiivty = ev_now (loop);
		1780
		1781	This technique is slightly more complex, but in most cases where the
		1782	time-out is unlikely to be triggered, much more efficient.
		1783
		1784	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1785	callback :) - just change the timeout and invoke the callback, which will
		1786	fix things for you.
		1787
		1788	=item 4. Wee, just use a double-linked list for your timeouts.
		1789
		1790	If there is not one request, but many thousands (millions...), all
		1791	employing some kind of timeout with the same timeout value, then one can
		1792	do even better:
		1793
		1794	When starting the timeout, calculate the timeout value and put the timeout
		1795	at the I<end> of the list.
		1796
		1797	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1798	the list is expected to fire (for example, using the technique #3).
		1799
		1800	When there is some activity, remove the timer from the list, recalculate
		1801	the timeout, append it to the end of the list again, and make sure to
		1802	update the C<ev_timer> if it was taken from the beginning of the list.
		1803
		1804	This way, one can manage an unlimited number of timeouts in O(1) time for
		1805	starting, stopping and updating the timers, at the expense of a major
		1806	complication, and having to use a constant timeout. The constant timeout
		1807	ensures that the list stays sorted.
		1808
		1809	=back
		1810
		1811	So which method the best?
		1812
		1813	Method #2 is a simple no-brain-required solution that is adequate in most
		1814	situations. Method #3 requires a bit more thinking, but handles many cases
		1815	better, and isn't very complicated either. In most case, choosing either
		1816	one is fine, with #3 being better in typical situations.
		1817
		1818	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1819	rather complicated, but extremely efficient, something that really pays
		1820	off after the first million or so of active timers, i.e. it's usually
		1821	overkill :)
		1822
		1823	=head3 The special problem of time updates
		1824
		1825	Establishing the current time is a costly operation (it usually takes at
		1826	least two system calls): EV therefore updates its idea of the current
		1827	time only before and after C<ev_loop> collects new events, which causes a
		1828	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1829	lots of events in one iteration.
1171		1830
1172	The relative timeouts are calculated relative to the C<ev_now ()>	1831	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	1832	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	1833	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	1834	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:	1835	timeout on the current time, use something like this to adjust for this:
1177		1836
1178	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1837	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1179		1838
1180	The callback is guarenteed to be invoked only after its timeout has passed,	1839	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	1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1182	order of execution is undefined.	1841	()>.
		1842
		1843	=head3 The special problems of suspended animation
		1844
		1845	When you leave the server world it is quite customary to hit machines that
		1846	can suspend/hibernate - what happens to the clocks during such a suspend?
		1847
		1848	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1849	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1850	to run until the system is suspended, but they will not advance while the
		1851	system is suspended. That means, on resume, it will be as if the program
		1852	was frozen for a few seconds, but the suspend time will not be counted
		1853	towards C<ev_timer> when a monotonic clock source is used. The real time
		1854	clock advanced as expected, but if it is used as sole clocksource, then a
		1855	long suspend would be detected as a time jump by libev, and timers would
		1856	be adjusted accordingly.
		1857
		1858	I would not be surprised to see different behaviour in different between
		1859	operating systems, OS versions or even different hardware.
		1860
		1861	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1862	time jump in the monotonic clocks and the realtime clock. If the program
		1863	is suspended for a very long time, and monotonic clock sources are in use,
		1864	then you can expect C<ev_timer>s to expire as the full suspension time
		1865	will be counted towards the timers. When no monotonic clock source is in
		1866	use, then libev will again assume a timejump and adjust accordingly.
		1867
		1868	It might be beneficial for this latter case to call C<ev_suspend>
		1869	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1870	deterministic behaviour in this case (you can do nothing against
		1871	C<SIGSTOP>).
1183		1872
1184	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1185		1874
1186	=over 4	1875	=over 4
1187		1876
…		…
1206	This will act as if the timer timed out and restart it again if it is	1895	This will act as if the timer timed out and restart it again if it is
1207	repeating. The exact semantics are:	1896	repeating. The exact semantics are:
1208		1897
1209	If the timer is pending, its pending status is cleared.	1898	If the timer is pending, its pending status is cleared.
1210		1899
1211	If the timer is started but nonrepeating, stop it (as if it timed out).	1900	If the timer is started but non-repeating, stop it (as if it timed out).
1212		1901
1213	If the timer is repeating, either start it if necessary (with the	1902	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.	1903	C<repeat> value), or reset the running timer to the C<repeat> value.
1215		1904
1216	This sounds a bit complicated, but here is a useful and typical	1905	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	1906	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		1907
1226	That means you can ignore the C<after> value and C<ev_timer_start>	1908	=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		1909
1229	ev_timer_init (timer, callback, 0., 5.);	1910	Returns the remaining time until a timer fires. If the timer is active,
1230	ev_timer_again (loop, timer);	1911	then this time is relative to the current event loop time, otherwise it's
1231	...	1912	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		1913
1238	This is more slightly efficient then stopping/starting the timer each time	1914	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1239	you want to modify its timeout value.	1915	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1916	will return C<4>. When the timer expires and is restarted, it will return
		1917	roughly C<7> (likely slightly less as callback invocation takes some time,
		1918	too), and so on.
1240		1919
1241	=item ev_tstamp repeat [read-write]	1920	=item ev_tstamp repeat [read-write]
1242		1921
1243	The current C<repeat> value. Will be used each time the watcher times out	1922	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),	1923	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.	1924	which is also when any modifications are taken into account.
1246		1925
1247	=back	1926	=back
1248		1927
1249	=head3 Examples	1928	=head3 Examples
1250		1929
1251	Example: Create a timer that fires after 60 seconds.	1930	Example: Create a timer that fires after 60 seconds.
1252		1931
1253	static void	1932	static void
1254	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1933	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1255	{	1934	{
1256	.. one minute over, w is actually stopped right here	1935	.. one minute over, w is actually stopped right here
1257	}	1936	}
1258		1937
1259	struct ev_timer mytimer;	1938	ev_timer mytimer;
1260	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1939	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1261	ev_timer_start (loop, &mytimer);	1940	ev_timer_start (loop, &mytimer);
1262		1941
1263	Example: Create a timeout timer that times out after 10 seconds of	1942	Example: Create a timeout timer that times out after 10 seconds of
1264	inactivity.	1943	inactivity.
1265		1944
1266	static void	1945	static void
1267	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1946	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1268	{	1947	{
1269	.. ten seconds without any activity	1948	.. ten seconds without any activity
1270	}	1949	}
1271		1950
1272	struct ev_timer mytimer;	1951	ev_timer mytimer;
1273	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1274	ev_timer_again (&mytimer); /* start timer */	1953	ev_timer_again (&mytimer); /* start timer */
1275	ev_loop (loop, 0);	1954	ev_loop (loop, 0);
1276		1955
1277	// and in some piece of code that gets executed on any "activity":	1956	// and in some piece of code that gets executed on any "activity":
1278	// reset the timeout to start ticking again at 10 seconds	1957	// reset the timeout to start ticking again at 10 seconds
1279	ev_timer_again (&mytimer);	1958	ev_timer_again (&mytimer);
1280		1959
1281		1960
1282	=head2 C<ev_periodic> - to cron or not to cron?	1961	=head2 C<ev_periodic> - to cron or not to cron?
1283		1962
1284	Periodic watchers are also timers of a kind, but they are very versatile	1963	Periodic watchers are also timers of a kind, but they are very versatile
1285	(and unfortunately a bit complex).	1964	(and unfortunately a bit complex).
1286		1965
1287	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1966	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	1967	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	1968	(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 ()	1969	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	1970	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	1971	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		1972
		1973	You can tell a periodic watcher to trigger after some specific point
		1974	in time: for example, if you tell a periodic watcher to trigger "in 10
		1975	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1976	not a delay) and then reset your system clock to January of the previous
		1977	year, then it will take a year or more to trigger the event (unlike an
		1978	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1979	it, as it uses a relative timeout).
		1980
1296	C<ev_periodic>s can also be used to implement vastly more complex timers,	1981	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	1982	timers, such as triggering an event on each "midnight, local time", or
1298	complicated, rules.	1983	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1984	those cannot react to time jumps.
1299		1985
1300	As with timers, the callback is guarenteed to be invoked only when the	1986	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	1987	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.	1988	timers become ready during the same loop iteration then the ones with
		1989	earlier time-out values are invoked before ones with later time-out values
		1990	(but this is no longer true when a callback calls C<ev_loop> recursively).
1303		1991
1304	=head3 Watcher-Specific Functions and Data Members	1992	=head3 Watcher-Specific Functions and Data Members
1305		1993
1306	=over 4	1994	=over 4
1307		1995
1308	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1996	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1309		1997
1310	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1998	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1311		1999
1312	Lots of arguments, lets sort it out... There are basically three modes of	2000	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:	2001	operation, and we will explain them from simplest to most complex:
1314		2002
1315	=over 4	2003	=over 4
1316		2004
1317	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2005	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1318		2006
1319	In this configuration the watcher triggers an event after the wallclock	2007	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	2008	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	2009	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.	2010	will be stopped and invoked when the system clock reaches or surpasses
		2011	this point in time.
1323		2012
1324	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2013	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1325		2014
1326	In this mode the watcher will always be scheduled to time out at the next	2015	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)	2016	C<offset + N * interval> time (for some integer N, which can also be
1328	and then repeat, regardless of any time jumps.	2017	negative) and then repeat, regardless of any time jumps. The C<offset>
		2018	argument is merely an offset into the C<interval> periods.
1329		2019
1330	This can be used to create timers that do not drift with respect to system	2020	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	2021	system clock, for example, here is an C<ev_periodic> that triggers each
1332	the hour:	2022	hour, on the hour (with respect to UTC):
1333		2023
1334	ev_periodic_set (&periodic, 0., 3600., 0);	2024	ev_periodic_set (&periodic, 0., 3600., 0);
1335		2025
1336	This doesn't mean there will always be 3600 seconds in between triggers,	2026	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	2027	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	2028	full hour (UTC), or more correctly, when the system time is evenly divisible
1339	by 3600.	2029	by 3600.
1340		2030
1341	Another way to think about it (for the mathematically inclined) is that	2031	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	2032	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.	2033	time where C<time = offset (mod interval)>, regardless of any time jumps.
1344		2034
1345	For numerical stability it is preferable that the C<at> value is near	2035	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	2036	C<ev_now ()> (the current time), but there is no range requirement for
1347	this value, and in fact is often specified as zero.	2037	this value, and in fact is often specified as zero.
1348		2038
1349	Note also that there is an upper limit to how often a timer can fire (cpu	2039	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	2040	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	2041	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).	2042	millisecond (if the OS supports it and the machine is fast enough).
1353		2043
1354	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2044	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1355		2045
1356	In this mode the values for C<interval> and C<at> are both being	2046	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	2047	ignored. Instead, each time the periodic watcher gets scheduled, the
1358	reschedule callback will be called with the watcher as first, and the	2048	reschedule callback will be called with the watcher as first, and the
1359	current time as second argument.	2049	current time as second argument.
1360		2050
1361	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2051	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1362	ever, or make ANY event loop modifications whatsoever>.	2052	or make ANY other event loop modifications whatsoever, unless explicitly
		2053	allowed by documentation here>.
1363		2054
1364	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2055	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	2056	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1366	only event loop modification you are allowed to do).	2057	only event loop modification you are allowed to do).
1367		2058
1368	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2059	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1369	*w, ev_tstamp now)>, e.g.:	2060	*w, ev_tstamp now)>, e.g.:
1370		2061
		2062	static ev_tstamp
1371	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2063	my_rescheduler (ev_periodic *w, ev_tstamp now)
1372	{	2064	{
1373	return now + 60.;	2065	return now + 60.;
1374	}	2066	}
1375		2067
1376	It must return the next time to trigger, based on the passed time value	2068	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	2088	a different time than the last time it was called (e.g. in a crond like
1397	program when the crontabs have changed).	2089	program when the crontabs have changed).
1398		2090
1399	=item ev_tstamp ev_periodic_at (ev_periodic *)	2091	=item ev_tstamp ev_periodic_at (ev_periodic *)
1400		2092
1401	When active, returns the absolute time that the watcher is supposed to	2093	When active, returns the absolute time that the watcher is supposed
1402	trigger next.	2094	to trigger next. This is not the same as the C<offset> argument to
		2095	C<ev_periodic_set>, but indeed works even in interval and manual
		2096	rescheduling modes.
1403		2097
1404	=item ev_tstamp offset [read-write]	2098	=item ev_tstamp offset [read-write]
1405		2099
1406	When repeating, this contains the offset value, otherwise this is the	2100	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>).	2101	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2102	although libev might modify this value for better numerical stability).
1408		2103
1409	Can be modified any time, but changes only take effect when the periodic	2104	Can be modified any time, but changes only take effect when the periodic
1410	timer fires or C<ev_periodic_again> is being called.	2105	timer fires or C<ev_periodic_again> is being called.
1411		2106
1412	=item ev_tstamp interval [read-write]	2107	=item ev_tstamp interval [read-write]
1413		2108
1414	The current interval value. Can be modified any time, but changes only	2109	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	2110	take effect when the periodic timer fires or C<ev_periodic_again> is being
1416	called.	2111	called.
1417		2112
1418	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2113	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1419		2114
1420	The current reschedule callback, or C<0>, if this functionality is	2115	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	2116	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.	2117	the periodic timer fires or C<ev_periodic_again> is being called.
1423		2118
1424	=back	2119	=back
1425		2120
1426	=head3 Examples	2121	=head3 Examples
1427		2122
1428	Example: Call a callback every hour, or, more precisely, whenever the	2123	Example: Call a callback every hour, or, more precisely, whenever the
1429	system clock is divisible by 3600. The callback invocation times have	2124	system time is divisible by 3600. The callback invocation times have
1430	potentially a lot of jittering, but good long-term stability.	2125	potentially a lot of jitter, but good long-term stability.
1431		2126
1432	static void	2127	static void
1433	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2128	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1434	{	2129	{
1435	... its now a full hour (UTC, or TAI or whatever your clock follows)	2130	... its now a full hour (UTC, or TAI or whatever your clock follows)
1436	}	2131	}
1437		2132
1438	struct ev_periodic hourly_tick;	2133	ev_periodic hourly_tick;
1439	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2134	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1440	ev_periodic_start (loop, &hourly_tick);	2135	ev_periodic_start (loop, &hourly_tick);
1441		2136
1442	Example: The same as above, but use a reschedule callback to do it:	2137	Example: The same as above, but use a reschedule callback to do it:
1443		2138
1444	#include <math.h>	2139	#include <math.h>
1445		2140
1446	static ev_tstamp	2141	static ev_tstamp
1447	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2142	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1448	{	2143	{
1449	return fmod (now, 3600.) + 3600.;	2144	return now + (3600. - fmod (now, 3600.));
1450	}	2145	}
1451		2146
1452	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2147	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1453		2148
1454	Example: Call a callback every hour, starting now:	2149	Example: Call a callback every hour, starting now:
1455		2150
1456	struct ev_periodic hourly_tick;	2151	ev_periodic hourly_tick;
1457	ev_periodic_init (&hourly_tick, clock_cb,	2152	ev_periodic_init (&hourly_tick, clock_cb,
1458	fmod (ev_now (loop), 3600.), 3600., 0);	2153	fmod (ev_now (loop), 3600.), 3600., 0);
1459	ev_periodic_start (loop, &hourly_tick);	2154	ev_periodic_start (loop, &hourly_tick);
1460		2155
1461		2156
1462	=head2 C<ev_signal> - signal me when a signal gets signalled!	2157	=head2 C<ev_signal> - signal me when a signal gets signalled!
1463		2158
1464	Signal watchers will trigger an event when the process receives a specific	2159	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	2160	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	2161	will try it's best to deliver signals synchronously, i.e. as part of the
1467	normal event processing, like any other event.	2162	normal event processing, like any other event.
1468		2163
		2164	If you want signals to be delivered truly asynchronously, just use
		2165	C<sigaction> as you would do without libev and forget about sharing
		2166	the signal. You can even use C<ev_async> from a signal handler to
		2167	synchronously wake up an event loop.
		2168
1469	You can configure as many watchers as you like per signal. Only when the	2169	You can configure as many watchers as you like for the same signal, but
		2170	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2171	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2172	C<SIGINT> in both the default loop and another loop at the same time. At
		2173	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2174
1470	first watcher gets started will libev actually register a signal watcher	2175	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	2176	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	2177	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		2178
1476	If possible and supported, libev will install its handlers with	2179	If possible and supported, libev will install its handlers with
1477	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2180	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1478	interrupted. If you have a problem with syscalls getting interrupted by	2181	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	2182	interrupted by signals you can block all signals in an C<ev_check> watcher
1480	them in an C<ev_prepare> watcher.	2183	and unblock them in an C<ev_prepare> watcher.
		2184
		2185	=head3 The special problem of inheritance over fork/execve/pthread_create
		2186
		2187	Both the signal mask (C<sigprocmask>) and the signal disposition
		2188	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2189	stopping it again), that is, libev might or might not block the signal,
		2190	and might or might not set or restore the installed signal handler.
		2191
		2192	While this does not matter for the signal disposition (libev never
		2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2194	C<execve>), this matters for the signal mask: many programs do not expect
		2195	certain signals to be blocked.
		2196
		2197	This means that before calling C<exec> (from the child) you should reset
		2198	the signal mask to whatever "default" you expect (all clear is a good
		2199	choice usually).
		2200
		2201	The simplest way to ensure that the signal mask is reset in the child is
		2202	to install a fork handler with C<pthread_atfork> that resets it. That will
		2203	catch fork calls done by libraries (such as the libc) as well.
		2204
		2205	In current versions of libev, the signal will not be blocked indefinitely
		2206	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2207	the window of opportunity for problems, it will not go away, as libev
		2208	I<has> to modify the signal mask, at least temporarily.
		2209
		2210	So I can't stress this enough: I<If you do not reset your signal mask when
		2211	you expect it to be empty, you have a race condition in your code>. This
		2212	is not a libev-specific thing, this is true for most event libraries.
1481		2213
1482	=head3 Watcher-Specific Functions and Data Members	2214	=head3 Watcher-Specific Functions and Data Members
1483		2215
1484	=over 4	2216	=over 4
1485		2217
…		…
1496		2228
1497	=back	2229	=back
1498		2230
1499	=head3 Examples	2231	=head3 Examples
1500		2232
1501	Example: Try to exit cleanly on SIGINT and SIGTERM.	2233	Example: Try to exit cleanly on SIGINT.
1502		2234
1503	static void	2235	static void
1504	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1505	{	2237	{
1506	ev_unloop (loop, EVUNLOOP_ALL);	2238	ev_unloop (loop, EVUNLOOP_ALL);
1507	}	2239	}
1508		2240
1509	struct ev_signal signal_watcher;	2241	ev_signal signal_watcher;
1510	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1511	ev_signal_start (loop, &sigint_cb);	2243	ev_signal_start (loop, &signal_watcher);
1512		2244
1513		2245
1514	=head2 C<ev_child> - watch out for process status changes	2246	=head2 C<ev_child> - watch out for process status changes
1515		2247
1516	Child watchers trigger when your process receives a SIGCHLD in response to	2248	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	2249	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	2250	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	2251	has been forked (which implies it might have already exited), as long
1520	loop isn't entered (or is continued from a watcher).	2252	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2253	forking and then immediately registering a watcher for the child is fine,
		2254	but forking and registering a watcher a few event loop iterations later or
		2255	in the next callback invocation is not.
1521		2256
1522	Only the default event loop is capable of handling signals, and therefore	2257	Only the default event loop is capable of handling signals, and therefore
1523	you can only rgeister child watchers in the default event loop.	2258	you can only register child watchers in the default event loop.
		2259
		2260	Due to some design glitches inside libev, child watchers will always be
		2261	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2262	libev)
1524		2263
1525	=head3 Process Interaction	2264	=head3 Process Interaction
1526		2265
1527	Libev grabs C<SIGCHLD> as soon as the default event loop is	2266	Libev grabs C<SIGCHLD> as soon as the default event loop is
1528	initialised. This is necessary to guarantee proper behaviour even if	2267	initialised. This is necessary to guarantee proper behaviour even if the
1529	the first child watcher is started after the child exits. The occurance	2268	first child watcher is started after the child exits. The occurrence
1530	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2269	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1531	synchronously as part of the event loop processing. Libev always reaps all	2270	synchronously as part of the event loop processing. Libev always reaps all
1532	children, even ones not watched.	2271	children, even ones not watched.
1533		2272
1534	=head3 Overriding the Built-In Processing	2273	=head3 Overriding the Built-In Processing
…		…
1538	handler, you can override it easily by installing your own handler for	2277	handler, you can override it easily by installing your own handler for
1539	C<SIGCHLD> after initialising the default loop, and making sure the	2278	C<SIGCHLD> after initialising the default loop, and making sure the
1540	default loop never gets destroyed. You are encouraged, however, to use an	2279	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	2280	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.	2281	that, so other libev users can use C<ev_child> watchers freely.
		2282
		2283	=head3 Stopping the Child Watcher
		2284
		2285	Currently, the child watcher never gets stopped, even when the
		2286	child terminates, so normally one needs to stop the watcher in the
		2287	callback. Future versions of libev might stop the watcher automatically
		2288	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2289	problem).
1543		2290
1544	=head3 Watcher-Specific Functions and Data Members	2291	=head3 Watcher-Specific Functions and Data Members
1545		2292
1546	=over 4	2293	=over 4
1547		2294
…		…
1576	=head3 Examples	2323	=head3 Examples
1577		2324
1578	Example: C<fork()> a new process and install a child handler to wait for	2325	Example: C<fork()> a new process and install a child handler to wait for
1579	its completion.	2326	its completion.
1580		2327
1581	ev_child cw;	2328	ev_child cw;
1582		2329
1583	static void	2330	static void
1584	child_cb (EV_P_ struct ev_child *w, int revents)	2331	child_cb (EV_P_ ev_child *w, int revents)
1585	{	2332	{
1586	ev_child_stop (EV_A_ w);	2333	ev_child_stop (EV_A_ w);
1587	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2334	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1588	}	2335	}
1589		2336
1590	pid_t pid = fork ();	2337	pid_t pid = fork ();
1591		2338
1592	if (pid < 0)	2339	if (pid < 0)
1593	// error	2340	// error
1594	else if (pid == 0)	2341	else if (pid == 0)
1595	{	2342	{
1596	// the forked child executes here	2343	// the forked child executes here
1597	exit (1);	2344	exit (1);
1598	}	2345	}
1599	else	2346	else
1600	{	2347	{
1601	ev_child_init (&cw, child_cb, pid, 0);	2348	ev_child_init (&cw, child_cb, pid, 0);
1602	ev_child_start (EV_DEFAULT_ &cw);	2349	ev_child_start (EV_DEFAULT_ &cw);
1603	}	2350	}
1604		2351
1605		2352
1606	=head2 C<ev_stat> - did the file attributes just change?	2353	=head2 C<ev_stat> - did the file attributes just change?
1607		2354
1608	This watches a filesystem path for attribute changes. That is, it calls	2355	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	2356	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.	2357	and sees if it changed compared to the last time, invoking the callback if
		2358	it did.
1611		2359
1612	The path does not need to exist: changing from "path exists" to "path does	2360	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	2361	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	2362	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	2363	C<st_nlink> field being zero (which is otherwise always forced to be at
1616	the stat buffer having unspecified contents.	2364	least one) and all the other fields of the stat buffer having unspecified
		2365	contents.
1617		2366
1618	The path I<should> be absolute and I<must not> end in a slash. If it is	2367	The path I<must not> end in a slash or contain special components such as
		2368	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.	2369	your working directory changes, then the behaviour is undefined.
1620		2370
1621	Since there is no standard to do this, the portable implementation simply	2371	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	2372	portable implementation simply calls C<stat(2)> regularly on the path
1623	can specify a recommended polling interval for this case. If you specify	2373	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,	2374	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	2375	recommended!) then a I<suitable, unspecified default> value will be used
1626	five seconds, although this might change dynamically). Libev will also	2376	(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	2377	change dynamically). Libev will also impose a minimum interval which is
1628	usually overkill.	2378	currently around C<0.1>, but that's usually overkill.
1629		2379
1630	This watcher type is not meant for massive numbers of stat watchers,	2380	This watcher type is not meant for massive numbers of stat watchers,
1631	as even with OS-supported change notifications, this can be	2381	as even with OS-supported change notifications, this can be
1632	resource-intensive.	2382	resource-intensive.
1633		2383
1634	At the time of this writing, only the Linux inotify interface is	2384	At the time of this writing, the only OS-specific interface implemented
1635	implemented (implementing kqueue support is left as an exercise for the	2385	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	2386	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	2387	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		2388
1643	=head3 ABI Issues (Largefile Support)	2389	=head3 ABI Issues (Largefile Support)
1644		2390
1645	Libev by default (unless the user overrides this) uses the default	2391	Libev by default (unless the user overrides this) uses the default
1646	compilation environment, which means that on systems with optionally	2392	compilation environment, which means that on systems with large file
1647	disabled large file support, you get the 32 bit version of the stat	2393	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	2394	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	2395	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	2396	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	2397	obviously the case with any flags that change the ABI, but the problem is
1652	most noticably with ev_stat and largefile support.	2398	most noticeably displayed with ev_stat and large file support.
1653		2399
1654	=head3 Inotify	2400	The solution for this is to lobby your distribution maker to make large
		2401	file interfaces available by default (as e.g. FreeBSD does) and not
		2402	optional. Libev cannot simply switch on large file support because it has
		2403	to exchange stat structures with application programs compiled using the
		2404	default compilation environment.
1655		2405
		2406	=head3 Inotify and Kqueue
		2407
1656	When C<inotify (7)> support has been compiled into libev (generally only	2408	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	2409	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	2410	inotify descriptor will be created lazily when the first C<ev_stat>
1659	when the first C<ev_stat> watcher is being started.	2411	watcher is being started.
1660		2412
1661	Inotify presence does not change the semantics of C<ev_stat> watchers	2413	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	2414	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	2415	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.	2416	there are many cases where libev has to resort to regular C<stat> polling,
		2417	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2418	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2419	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2420	xfs are fully working) libev usually gets away without polling.
1665		2421
1666	(There is no support for kqueue, as apparently it cannot be used to	2422	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	2423	implement this functionality, due to the requirement of having a file
1668	descriptor open on the object at all times).	2424	descriptor open on the object at all times, and detecting renames, unlinks
		2425	etc. is difficult.
		2426
		2427	=head3 C<stat ()> is a synchronous operation
		2428
		2429	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2430	the process. The exception are C<ev_stat> watchers - those call C<stat
		2431	()>, which is a synchronous operation.
		2432
		2433	For local paths, this usually doesn't matter: unless the system is very
		2434	busy or the intervals between stat's are large, a stat call will be fast,
		2435	as the path data is usually in memory already (except when starting the
		2436	watcher).
		2437
		2438	For networked file systems, calling C<stat ()> can block an indefinite
		2439	time due to network issues, and even under good conditions, a stat call
		2440	often takes multiple milliseconds.
		2441
		2442	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2443	paths, although this is fully supported by libev.
1669		2444
1670	=head3 The special problem of stat time resolution	2445	=head3 The special problem of stat time resolution
1671		2446
1672	The C<stat ()> syscall only supports full-second resolution portably, and	2447	The C<stat ()> system call only supports full-second resolution portably,
1673	even on systems where the resolution is higher, many filesystems still	2448	and even on systems where the resolution is higher, most file systems
1674	only support whole seconds.	2449	still only support whole seconds.
1675		2450
1676	That means that, if the time is the only thing that changes, you can	2451	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	2452	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	2453	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	2454	within the same second, C<ev_stat> will be unable to detect unless the
1680	data does not change.	2455	stat data does change in other ways (e.g. file size).
1681		2456
1682	The solution to this is to delay acting on a change for slightly more	2457	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	2458	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);	2459	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1685	ev_timer_again (loop, w)>).	2460	ev_timer_again (loop, w)>).
…		…
1705	C<path>. The C<interval> is a hint on how quickly a change is expected to	2480	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	2481	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	2482	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.	2483	path for as long as the watcher is active.
1709		2484
1710	The callback will receive C<EV_STAT> when a change was detected, relative	2485	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	2486	relative to the attributes at the time the watcher was started (or the
1712	was detected).	2487	last change was detected).
1713		2488
1714	=item ev_stat_stat (loop, ev_stat *)	2489	=item ev_stat_stat (loop, ev_stat *)
1715		2490
1716	Updates the stat buffer immediately with new values. If you change the	2491	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	2492	watched path in your callback, you could call this function to avoid
…		…
1738		2513
1739	The specified interval.	2514	The specified interval.
1740		2515
1741	=item const char *path [read-only]	2516	=item const char *path [read-only]
1742		2517
1743	The filesystem path that is being watched.	2518	The file system path that is being watched.
1744		2519
1745	=back	2520	=back
1746		2521
1747	=head3 Examples	2522	=head3 Examples
1748		2523
1749	Example: Watch C</etc/passwd> for attribute changes.	2524	Example: Watch C</etc/passwd> for attribute changes.
1750		2525
1751	static void	2526	static void
1752	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2527	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1753	{	2528	{
1754	/* /etc/passwd changed in some way */	2529	/* /etc/passwd changed in some way */
1755	if (w->attr.st_nlink)	2530	if (w->attr.st_nlink)
1756	{	2531	{
1757	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2532	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1758	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2533	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1759	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2534	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1760	}	2535	}
1761	else	2536	else
1762	/* you shalt not abuse printf for puts */	2537	/* you shalt not abuse printf for puts */
1763	puts ("wow, /etc/passwd is not there, expect problems. "	2538	puts ("wow, /etc/passwd is not there, expect problems. "
1764	"if this is windows, they already arrived\n");	2539	"if this is windows, they already arrived\n");
1765	}	2540	}
1766		2541
1767	...	2542	...
1768	ev_stat passwd;	2543	ev_stat passwd;
1769		2544
1770	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2545	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1771	ev_stat_start (loop, &passwd);	2546	ev_stat_start (loop, &passwd);
1772		2547
1773	Example: Like above, but additionally use a one-second delay so we do not	2548	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	2549	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	2550	one might do the work both on C<ev_stat> callback invocation I<and> on
1776	C<ev_timer> callback invocation).	2551	C<ev_timer> callback invocation).
1777		2552
1778	static ev_stat passwd;	2553	static ev_stat passwd;
1779	static ev_timer timer;	2554	static ev_timer timer;
1780		2555
1781	static void	2556	static void
1782	timer_cb (EV_P_ ev_timer *w, int revents)	2557	timer_cb (EV_P_ ev_timer *w, int revents)
1783	{	2558	{
1784	ev_timer_stop (EV_A_ w);	2559	ev_timer_stop (EV_A_ w);
1785		2560
1786	/* now it's one second after the most recent passwd change */	2561	/* now it's one second after the most recent passwd change */
1787	}	2562	}
1788		2563
1789	static void	2564	static void
1790	stat_cb (EV_P_ ev_stat *w, int revents)	2565	stat_cb (EV_P_ ev_stat *w, int revents)
1791	{	2566	{
1792	/* reset the one-second timer */	2567	/* reset the one-second timer */
1793	ev_timer_again (EV_A_ &timer);	2568	ev_timer_again (EV_A_ &timer);
1794	}	2569	}
1795		2570
1796	...	2571	...
1797	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2572	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1798	ev_stat_start (loop, &passwd);	2573	ev_stat_start (loop, &passwd);
1799	ev_timer_init (&timer, timer_cb, 0., 1.02);	2574	ev_timer_init (&timer, timer_cb, 0., 1.02);
1800		2575
1801		2576
1802	=head2 C<ev_idle> - when you've got nothing better to do...	2577	=head2 C<ev_idle> - when you've got nothing better to do...
1803		2578
1804	Idle watchers trigger events when no other events of the same or higher	2579	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	2580	priority are pending (prepare, check and other idle watchers do not count
1806	count).	2581	as receiving "events").
1807		2582
1808	That is, as long as your process is busy handling sockets or timeouts	2583	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	2584	(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	2585	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	2586	are pending), the idle watchers are being called once per event loop
…		…
1822		2597
1823	=head3 Watcher-Specific Functions and Data Members	2598	=head3 Watcher-Specific Functions and Data Members
1824		2599
1825	=over 4	2600	=over 4
1826		2601
1827	=item ev_idle_init (ev_signal *, callback)	2602	=item ev_idle_init (ev_idle *, callback)
1828		2603
1829	Initialises and configures the idle watcher - it has no parameters of any	2604	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,	2605	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1831	believe me.	2606	believe me.
1832		2607
…		…
1835	=head3 Examples	2610	=head3 Examples
1836		2611
1837	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2612	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1838	callback, free it. Also, use no error checking, as usual.	2613	callback, free it. Also, use no error checking, as usual.
1839		2614
1840	static void	2615	static void
1841	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2616	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1842	{	2617	{
1843	free (w);	2618	free (w);
1844	// now do something you wanted to do when the program has	2619	// now do something you wanted to do when the program has
1845	// no longer anything immediate to do.	2620	// no longer anything immediate to do.
1846	}	2621	}
1847		2622
1848	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2623	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1849	ev_idle_init (idle_watcher, idle_cb);	2624	ev_idle_init (idle_watcher, idle_cb);
1850	ev_idle_start (loop, idle_cb);	2625	ev_idle_start (loop, idle_watcher);
1851		2626
1852		2627
1853	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2628	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1854		2629
1855	Prepare and check watchers are usually (but not always) used in tandem:	2630	Prepare and check watchers are usually (but not always) used in pairs:
1856	prepare watchers get invoked before the process blocks and check watchers	2631	prepare watchers get invoked before the process blocks and check watchers
1857	afterwards.	2632	afterwards.
1858		2633
1859	You I<must not> call C<ev_loop> or similar functions that enter	2634	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>	2635	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,	2638	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	2639	C<ev_check> so if you have one watcher of each kind they will always be
1865	called in pairs bracketing the blocking call.	2640	called in pairs bracketing the blocking call.
1866		2641
1867	Their main purpose is to integrate other event mechanisms into libev and	2642	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	2643	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	2644	variable changes, implement your own watchers, integrate net-snmp or a
1870	coroutine library and lots more. They are also occasionally useful if	2645	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,	2646	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>	2647	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1873	watcher).	2648	watcher).
1874		2649
1875	This is done by examining in each prepare call which file descriptors need	2650	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	2651	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	2652	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	2653	libraries provide exactly this functionality). Then, in the check watcher,
1879	any events that occured (by checking the pending status of all watchers	2654	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	2655	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,	2656	I/O and timer callbacks will never actually be called (but must be valid
1882	because you never know, you know?).	2657	nevertheless, because you never know, you know?).
1883		2658
1884	As another example, the Perl Coro module uses these hooks to integrate	2659	As another example, the Perl Coro module uses these hooks to integrate
1885	coroutines into libev programs, by yielding to other active coroutines	2660	coroutines into libev programs, by yielding to other active coroutines
1886	during each prepare and only letting the process block if no coroutines	2661	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	2662	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	2665	loop from blocking if lower-priority coroutines are active, thus mapping
1891	low-priority coroutines to idle/background tasks).	2666	low-priority coroutines to idle/background tasks).
1892		2667
1893	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2668	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	2669	priority, to ensure that they are being run before any other watchers
		2670	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2671
1895	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2672	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	2673	activate ("feed") events into libev. While libev fully supports this, they
1897	supports this, they might get executed before other C<ev_check> watchers	2674	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	2675	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	2676	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	2677	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1901	coexist peacefully with others).	2678	others).
1902		2679
1903	=head3 Watcher-Specific Functions and Data Members	2680	=head3 Watcher-Specific Functions and Data Members
1904		2681
1905	=over 4	2682	=over 4
1906		2683
…		…
1908		2685
1909	=item ev_check_init (ev_check *, callback)	2686	=item ev_check_init (ev_check *, callback)
1910		2687
1911	Initialises and configures the prepare or check watcher - they have no	2688	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>	2689	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.	2690	macros, but using them is utterly, utterly, utterly and completely
		2691	pointless.
1914		2692
1915	=back	2693	=back
1916		2694
1917	=head3 Examples	2695	=head3 Examples
1918		2696
…		…
1927	and in a check watcher, destroy them and call into libadns. What follows	2705	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	2706	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	2707	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.	2708	the callbacks for the IO/timeout watchers might not have been called yet.
1931		2709
1932	static ev_io iow [nfd];	2710	static ev_io iow [nfd];
1933	static ev_timer tw;	2711	static ev_timer tw;
1934		2712
1935	static void	2713	static void
1936	io_cb (ev_loop *loop, ev_io *w, int revents)	2714	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1937	{	2715	{
1938	}	2716	}
1939		2717
1940	// create io watchers for each fd and a timer before blocking	2718	// create io watchers for each fd and a timer before blocking
1941	static void	2719	static void
1942	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2720	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1943	{	2721	{
1944	int timeout = 3600000;	2722	int timeout = 3600000;
1945	struct pollfd fds [nfd];	2723	struct pollfd fds [nfd];
1946	// actual code will need to loop here and realloc etc.	2724	// actual code will need to loop here and realloc etc.
1947	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2725	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1948		2726
1949	/* the callback is illegal, but won't be called as we stop during check */	2727	/* the callback is illegal, but won't be called as we stop during check */
1950	ev_timer_init (&tw, 0, timeout * 1e-3);	2728	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1951	ev_timer_start (loop, &tw);	2729	ev_timer_start (loop, &tw);
1952		2730
1953	// create one ev_io per pollfd	2731	// create one ev_io per pollfd
1954	for (int i = 0; i < nfd; ++i)	2732	for (int i = 0; i < nfd; ++i)
1955	{	2733	{
1956	ev_io_init (iow + i, io_cb, fds [i].fd,	2734	ev_io_init (iow + i, io_cb, fds [i].fd,
1957	((fds [i].events & POLLIN ? EV_READ : 0)	2735	((fds [i].events & POLLIN ? EV_READ : 0)
1958	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2736	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1959		2737
1960	fds [i].revents = 0;	2738	fds [i].revents = 0;
1961	ev_io_start (loop, iow + i);	2739	ev_io_start (loop, iow + i);
1962	}	2740	}
1963	}	2741	}
1964		2742
1965	// stop all watchers after blocking	2743	// stop all watchers after blocking
1966	static void	2744	static void
1967	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2745	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1968	{	2746	{
1969	ev_timer_stop (loop, &tw);	2747	ev_timer_stop (loop, &tw);
1970		2748
1971	for (int i = 0; i < nfd; ++i)	2749	for (int i = 0; i < nfd; ++i)
1972	{	2750	{
1973	// set the relevant poll flags	2751	// set the relevant poll flags
1974	// could also call adns_processreadable etc. here	2752	// could also call adns_processreadable etc. here
1975	struct pollfd *fd = fds + i;	2753	struct pollfd *fd = fds + i;
1976	int revents = ev_clear_pending (iow + i);	2754	int revents = ev_clear_pending (iow + i);
1977	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2755	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1978	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2756	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1979		2757
1980	// now stop the watcher	2758	// now stop the watcher
1981	ev_io_stop (loop, iow + i);	2759	ev_io_stop (loop, iow + i);
1982	}	2760	}
1983		2761
1984	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2762	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1985	}	2763	}
1986		2764
1987	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2765	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.	2766	in the prepare watcher and would dispose of the check watcher.
1989		2767
1990	Method 3: If the module to be embedded supports explicit event	2768	Method 3: If the module to be embedded supports explicit event
1991	notification (adns does), you can also make use of the actual watcher	2769	notification (libadns does), you can also make use of the actual watcher
1992	callbacks, and only destroy/create the watchers in the prepare watcher.	2770	callbacks, and only destroy/create the watchers in the prepare watcher.
1993		2771
1994	static void	2772	static void
1995	timer_cb (EV_P_ ev_timer *w, int revents)	2773	timer_cb (EV_P_ ev_timer *w, int revents)
1996	{	2774	{
1997	adns_state ads = (adns_state)w->data;	2775	adns_state ads = (adns_state)w->data;
1998	update_now (EV_A);	2776	update_now (EV_A);
1999		2777
2000	adns_processtimeouts (ads, &tv_now);	2778	adns_processtimeouts (ads, &tv_now);
2001	}	2779	}
2002		2780
2003	static void	2781	static void
2004	io_cb (EV_P_ ev_io *w, int revents)	2782	io_cb (EV_P_ ev_io *w, int revents)
2005	{	2783	{
2006	adns_state ads = (adns_state)w->data;	2784	adns_state ads = (adns_state)w->data;
2007	update_now (EV_A);	2785	update_now (EV_A);
2008		2786
2009	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2787	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2010	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2788	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2011	}	2789	}
2012		2790
2013	// do not ever call adns_afterpoll	2791	// do not ever call adns_afterpoll
2014		2792
2015	Method 4: Do not use a prepare or check watcher because the module you	2793	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	2794	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	2795	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	2796	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2019	this.	2797	this approach, effectively embedding EV as a client into the horrible
		2798	libglib event loop.
2020		2799
2021	static gint	2800	static gint
2022	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2801	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2023	{	2802	{
2024	int got_events = 0;	2803	int got_events = 0;
2025		2804
2026	for (n = 0; n < nfds; ++n)	2805	for (n = 0; n < nfds; ++n)
2027	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2806	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2028		2807
2029	if (timeout >= 0)	2808	if (timeout >= 0)
2030	// create/start timer	2809	// create/start timer
2031		2810
2032	// poll	2811	// poll
2033	ev_loop (EV_A_ 0);	2812	ev_loop (EV_A_ 0);
2034		2813
2035	// stop timer again	2814	// stop timer again
2036	if (timeout >= 0)	2815	if (timeout >= 0)
2037	ev_timer_stop (EV_A_ &to);	2816	ev_timer_stop (EV_A_ &to);
2038		2817
2039	// stop io watchers again - their callbacks should have set	2818	// stop io watchers again - their callbacks should have set
2040	for (n = 0; n < nfds; ++n)	2819	for (n = 0; n < nfds; ++n)
2041	ev_io_stop (EV_A_ iow [n]);	2820	ev_io_stop (EV_A_ iow [n]);
2042		2821
2043	return got_events;	2822	return got_events;
2044	}	2823	}
2045		2824
2046		2825
2047	=head2 C<ev_embed> - when one backend isn't enough...	2826	=head2 C<ev_embed> - when one backend isn't enough...
2048		2827
2049	This is a rather advanced watcher type that lets you embed one event loop	2828	This is a rather advanced watcher type that lets you embed one event loop
…		…
2055	prioritise I/O.	2834	prioritise I/O.
2056		2835
2057	As an example for a bug workaround, the kqueue backend might only support	2836	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	2837	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	2838	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	2839	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	2840	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	2841	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.	2842	C<kevent>, but at least you can use both mechanisms for what they are
		2843	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2064		2844
2065	As for prioritising I/O: rarely you have the case where some fds have	2845	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	2846	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	2847	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	2848	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.	2849	the rest in a second one, and embed the second one in the first.
2070		2850
2071	As long as the watcher is active, the callback will be invoked every time	2851	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	2852	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	2853	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	2854	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	2855	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	2856	to give the embedded loop strictly lower priority for example).
2077	embedded loop sweep.
2078		2857
2079	As long as the watcher is started it will automatically handle events. The	2858	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	2859	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		2860
2084	Also, there have not currently been made special provisions for forking:	2861	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,	2862	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	2863	embedding loop forks. In other cases, the user is responsible for calling
2087	yourself.	2864	C<ev_loop_fork> on the embedded loop.
2088		2865
2089	Unfortunately, not all backends are embeddable, only the ones returned by	2866	Unfortunately, not all backends are embeddable: only the ones returned by
2090	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2867	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2091	portable one.	2868	portable one.
2092		2869
2093	So when you want to use this feature you will always have to be prepared	2870	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	2871	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	2872	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.	2873	create it, and if that fails, use the normal loop for everything.
2097		2874
		2875	=head3 C<ev_embed> and fork
		2876
		2877	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2878	automatically be applied to the embedded loop as well, so no special
		2879	fork handling is required in that case. When the watcher is not running,
		2880	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2881	as applicable.
		2882
2098	=head3 Watcher-Specific Functions and Data Members	2883	=head3 Watcher-Specific Functions and Data Members
2099		2884
2100	=over 4	2885	=over 4
2101		2886
2102	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2887	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2105		2890
2106	Configures the watcher to embed the given loop, which must be	2891	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	2892	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	2893	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,	2894	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).	2895	if you do not want that, you need to temporarily stop the embed watcher).
2111		2896
2112	=item ev_embed_sweep (loop, ev_embed *)	2897	=item ev_embed_sweep (loop, ev_embed *)
2113		2898
2114	Make a single, non-blocking sweep over the embedded loop. This works	2899	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	2900	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2116	apropriate way for embedded loops.	2901	appropriate way for embedded loops.
2117		2902
2118	=item struct ev_loop *other [read-only]	2903	=item struct ev_loop *other [read-only]
2119		2904
2120	The embedded event loop.	2905	The embedded event loop.
2121		2906
…		…
2123		2908
2124	=head3 Examples	2909	=head3 Examples
2125		2910
2126	Example: Try to get an embeddable event loop and embed it into the default	2911	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	2912	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	2913	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	2914	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2130	used).	2915	used).
2131		2916
2132	struct ev_loop *loop_hi = ev_default_init (0);	2917	struct ev_loop *loop_hi = ev_default_init (0);
2133	struct ev_loop *loop_lo = 0;	2918	struct ev_loop *loop_lo = 0;
2134	struct ev_embed embed;	2919	ev_embed embed;
2135		2920
2136	// see if there is a chance of getting one that works	2921	// see if there is a chance of getting one that works
2137	// (remember that a flags value of 0 means autodetection)	2922	// (remember that a flags value of 0 means autodetection)
2138	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2923	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2139	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2924	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2140	: 0;	2925	: 0;
2141		2926
2142	// if we got one, then embed it, otherwise default to loop_hi	2927	// if we got one, then embed it, otherwise default to loop_hi
2143	if (loop_lo)	2928	if (loop_lo)
2144	{	2929	{
2145	ev_embed_init (&embed, 0, loop_lo);	2930	ev_embed_init (&embed, 0, loop_lo);
2146	ev_embed_start (loop_hi, &embed);	2931	ev_embed_start (loop_hi, &embed);
2147	}	2932	}
2148	else	2933	else
2149	loop_lo = loop_hi;	2934	loop_lo = loop_hi;
2150		2935
2151	Example: Check if kqueue is available but not recommended and create	2936	Example: Check if kqueue is available but not recommended and create
2152	a kqueue backend for use with sockets (which usually work with any	2937	a kqueue backend for use with sockets (which usually work with any
2153	kqueue implementation). Store the kqueue/socket-only event loop in	2938	kqueue implementation). Store the kqueue/socket-only event loop in
2154	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2939	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2155		2940
2156	struct ev_loop *loop = ev_default_init (0);	2941	struct ev_loop *loop = ev_default_init (0);
2157	struct ev_loop *loop_socket = 0;	2942	struct ev_loop *loop_socket = 0;
2158	struct ev_embed embed;	2943	ev_embed embed;
2159		2944
2160	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2945	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2161	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2946	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2162	{	2947	{
2163	ev_embed_init (&embed, 0, loop_socket);	2948	ev_embed_init (&embed, 0, loop_socket);
2164	ev_embed_start (loop, &embed);	2949	ev_embed_start (loop, &embed);
2165	}	2950	}
2166		2951
2167	if (!loop_socket)	2952	if (!loop_socket)
2168	loop_socket = loop;	2953	loop_socket = loop;
2169		2954
2170	// now use loop_socket for all sockets, and loop for everything else	2955	// now use loop_socket for all sockets, and loop for everything else
2171		2956
2172		2957
2173	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2958	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2174		2959
2175	Fork watchers are called when a C<fork ()> was detected (usually because	2960	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,	2963	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	2964	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	2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2181	handlers will be invoked, too, of course.	2966	handlers will be invoked, too, of course.
2182		2967
		2968	=head3 The special problem of life after fork - how is it possible?
		2969
		2970	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2971	up/change the process environment, followed by a call to C<exec()>. This
		2972	sequence should be handled by libev without any problems.
		2973
		2974	This changes when the application actually wants to do event handling
		2975	in the child, or both parent in child, in effect "continuing" after the
		2976	fork.
		2977
		2978	The default mode of operation (for libev, with application help to detect
		2979	forks) is to duplicate all the state in the child, as would be expected
		2980	when I<either> the parent I<or> the child process continues.
		2981
		2982	When both processes want to continue using libev, then this is usually the
		2983	wrong result. In that case, usually one process (typically the parent) is
		2984	supposed to continue with all watchers in place as before, while the other
		2985	process typically wants to start fresh, i.e. without any active watchers.
		2986
		2987	The cleanest and most efficient way to achieve that with libev is to
		2988	simply create a new event loop, which of course will be "empty", and
		2989	use that for new watchers. This has the advantage of not touching more
		2990	memory than necessary, and thus avoiding the copy-on-write, and the
		2991	disadvantage of having to use multiple event loops (which do not support
		2992	signal watchers).
		2993
		2994	When this is not possible, or you want to use the default loop for
		2995	other reasons, then in the process that wants to start "fresh", call
		2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2997	the default loop will "orphan" (not stop) all registered watchers, so you
		2998	have to be careful not to execute code that modifies those watchers. Note
		2999	also that in that case, you have to re-register any signal watchers.
		3000
2183	=head3 Watcher-Specific Functions and Data Members	3001	=head3 Watcher-Specific Functions and Data Members
2184		3002
2185	=over 4	3003	=over 4
2186		3004
2187	=item ev_fork_init (ev_signal *, callback)	3005	=item ev_fork_init (ev_signal *, callback)
…		…
2216	=head3 Queueing	3034	=head3 Queueing
2217		3035
2218	C<ev_async> does not support queueing of data in any way. The reason	3036	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	3037	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	3038	multiple-writer-single-reader queue that works in all cases and doesn't
2221	need elaborate support such as pthreads.	3039	need elaborate support such as pthreads or unportable memory access
		3040	semantics.
2222		3041
2223	That means that if you want to queue data, you have to provide your own	3042	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	3043	queue. But at least I can tell you how to implement locking around your
2225	queue:	3044	queue:
2226		3045
2227	=over 4	3046	=over 4
2228		3047
2229	=item queueing from a signal handler context	3048	=item queueing from a signal handler context
2230		3049
2231	To implement race-free queueing, you simply add to the queue in the signal	3050	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	3051	handler but you block the signal handler in the watcher callback. Here is
2233	some fictitiuous SIGUSR1 handler:	3052	an example that does that for some fictitious SIGUSR1 handler:
2234		3053
2235	static ev_async mysig;	3054	static ev_async mysig;
2236		3055
2237	static void	3056	static void
2238	sigusr1_handler (void)	3057	sigusr1_handler (void)
…		…
2304	=over 4	3123	=over 4
2305		3124
2306	=item ev_async_init (ev_async *, callback)	3125	=item ev_async_init (ev_async *, callback)
2307		3126
2308	Initialises and configures the async watcher - it has no parameters of any	3127	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,	3128	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2310	believe me.	3129	trust me.
2311		3130
2312	=item ev_async_send (loop, ev_async *)	3131	=item ev_async_send (loop, ev_async *)
2313		3132
2314	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3133	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	3134	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	3135	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	3136	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2318	section below on what exactly this means).	3137	section below on what exactly this means).
2319		3138
		3139	Note that, as with other watchers in libev, multiple events might get
		3140	compressed into a single callback invocation (another way to look at this
		3141	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3142	reset when the event loop detects that).
		3143
2320	This call incurs the overhead of a syscall only once per loop iteration,	3144	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	3145	iteration, so while the overhead might be noticeable, it doesn't apply to
2322	calls to C<ev_async_send>.	3146	repeated calls to C<ev_async_send> for the same event loop.
2323		3147
2324	=item bool = ev_async_pending (ev_async *)	3148	=item bool = ev_async_pending (ev_async *)
2325		3149
2326	Returns a non-zero value when C<ev_async_send> has been called on the	3150	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	3151	watcher but the event has not yet been processed (or even noted) by the
2328	event loop.	3152	event loop.
2329		3153
2330	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3154	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,	3155	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	3156	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.	3157	quickly check whether invoking the loop might be a good idea.
2334		3158
2335	Not that this does I<not> check wether the watcher itself is pending, only	3159	Not that this does I<not> check whether the watcher itself is pending,
2336	wether it has been requested to make this watcher pending.	3160	only whether it has been requested to make this watcher pending: there
		3161	is a time window between the event loop checking and resetting the async
		3162	notification, and the callback being invoked.
2337		3163
2338	=back	3164	=back
2339		3165
2340		3166
2341	=head1 OTHER FUNCTIONS	3167	=head1 OTHER FUNCTIONS
…		…
2345	=over 4	3171	=over 4
2346		3172
2347	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3173	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2348		3174
2349	This function combines a simple timer and an I/O watcher, calls your	3175	This function combines a simple timer and an I/O watcher, calls your
2350	callback on whichever event happens first and automatically stop both	3176	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	3177	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	3178	or timeout without having to allocate/configure/start/stop/free one or
2353	more watchers yourself.	3179	more watchers yourself.
2354		3180
2355	If C<fd> is less than 0, then no I/O watcher will be started and events	3181	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	3182	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2357	C<events> set will be craeted and started.	3183	the given C<fd> and C<events> set will be created and started.
2358		3184
2359	If C<timeout> is less than 0, then no timeout watcher will be	3185	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	3186	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	3187	repeat = 0) will be started. C<0> is a valid timeout.
2362	dubious value.
2363		3188
2364	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3189	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2365	passed an C<revents> set like normal event callbacks (a combination of	3190	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>	3191	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2367	value passed to C<ev_once>:	3192	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3193	a timeout and an io event at the same time - you probably should give io
		3194	events precedence.
2368		3195
		3196	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3197
2369	static void stdin_ready (int revents, void *arg)	3198	static void stdin_ready (int revents, void *arg)
2370	{	3199	{
2371	if (revents & EV_TIMEOUT)
2372	/* doh, nothing entered */;
2373	else if (revents & EV_READ)	3200	if (revents & EV_READ)
2374	/* stdin might have data for us, joy! */;	3201	/* stdin might have data for us, joy! */;
		3202	else if (revents & EV_TIMER)
		3203	/* doh, nothing entered */;
2375	}	3204	}
2376		3205
2377	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3206	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2378		3207
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)	3208	=item ev_feed_fd_event (loop, int fd, int revents)
2386		3209
2387	Feed an event on the given fd, as if a file descriptor backend detected	3210	Feed an event on the given fd, as if a file descriptor backend detected
2388	the given events it.	3211	the given events it.
2389		3212
2390	=item ev_feed_signal_event (ev_loop *loop, int signum)	3213	=item ev_feed_signal_event (loop, int signum)
2391		3214
2392	Feed an event as if the given signal occured (C<loop> must be the default	3215	Feed an event as if the given signal occurred (C<loop> must be the default
2393	loop!).	3216	loop!).
2394		3217
2395	=back	3218	=back
2396		3219
2397		3220
…		…
2426	=back	3249	=back
2427		3250
2428	=head1 C++ SUPPORT	3251	=head1 C++ SUPPORT
2429		3252
2430	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3253	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	3254	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.	3255	the callback model to a model using method callbacks on objects.
2433		3256
2434	To use it,	3257	To use it,
2435		3258
2436	#include <ev++.h>	3259	#include <ev++.h>
2437		3260
2438	This automatically includes F<ev.h> and puts all of its definitions (many	3261	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	3262	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	3263	put into the C<ev> namespace. It should support all the same embedding
2441	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3264	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2475		3298
2476	=over 4	3299	=over 4
2477		3300
2478	=item ev::TYPE::TYPE ()	3301	=item ev::TYPE::TYPE ()
2479		3302
2480	=item ev::TYPE::TYPE (struct ev_loop *)	3303	=item ev::TYPE::TYPE (loop)
2481		3304
2482	=item ev::TYPE::~TYPE	3305	=item ev::TYPE::~TYPE
2483		3306
2484	The constructor (optionally) takes an event loop to associate the watcher	3307	The constructor (optionally) takes an event loop to associate the watcher
2485	with. If it is omitted, it will use C<EV_DEFAULT>.	3308	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	3331	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.	3332	thunking function, making it as fast as a direct C callback.
2510		3333
2511	Example: simple class declaration and watcher initialisation	3334	Example: simple class declaration and watcher initialisation
2512		3335
2513	struct myclass	3336	struct myclass
2514	{	3337	{
2515	void io_cb (ev::io &w, int revents) { }	3338	void io_cb (ev::io &w, int revents) { }
2516	}	3339	}
2517		3340
2518	myclass obj;	3341	myclass obj;
2519	ev::io iow;	3342	ev::io iow;
2520	iow.set <myclass, &myclass::io_cb> (&obj);	3343	iow.set <myclass, &myclass::io_cb> (&obj);
		3344
		3345	=item w->set (object *)
		3346
		3347	This is an B<experimental> feature that might go away in a future version.
		3348
		3349	This is a variation of a method callback - leaving out the method to call
		3350	will default the method to C<operator ()>, which makes it possible to use
		3351	functor objects without having to manually specify the C<operator ()> all
		3352	the time. Incidentally, you can then also leave out the template argument
		3353	list.
		3354
		3355	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3356	int revents)>.
		3357
		3358	See the method-C<set> above for more details.
		3359
		3360	Example: use a functor object as callback.
		3361
		3362	struct myfunctor
		3363	{
		3364	void operator() (ev::io &w, int revents)
		3365	{
		3366	...
		3367	}
		3368	}
		3369
		3370	myfunctor f;
		3371
		3372	ev::io w;
		3373	w.set (&f);
2521		3374
2522	=item w->set<function> (void *data = 0)	3375	=item w->set<function> (void *data = 0)
2523		3376
2524	Also sets a callback, but uses a static method or plain function as	3377	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	3378	callback. The optional C<data> argument will be stored in the watcher's
…		…
2527		3380
2528	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3381	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2529		3382
2530	See the method-C<set> above for more details.	3383	See the method-C<set> above for more details.
2531		3384
2532	Example:	3385	Example: Use a plain function as callback.
2533		3386
2534	static void io_cb (ev::io &w, int revents) { }	3387	static void io_cb (ev::io &w, int revents) { }
2535	iow.set <io_cb> ();	3388	iow.set <io_cb> ();
2536		3389
2537	=item w->set (struct ev_loop *)	3390	=item w->set (loop)
2538		3391
2539	Associates a different C<struct ev_loop> with this watcher. You can only	3392	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).	3393	do this when the watcher is inactive (and not pending either).
2541		3394
2542	=item w->set ([args])	3395	=item w->set ([arguments])
2543		3396
2544	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3397	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	3398	called at least once. Unlike the C counterpart, an active watcher gets
2546	automatically stopped and restarted when reconfiguring it with this	3399	automatically stopped and restarted when reconfiguring it with this
2547	method.	3400	method.
2548		3401
2549	=item w->start ()	3402	=item w->start ()
…		…
2573	=back	3426	=back
2574		3427
2575	Example: Define a class with an IO and idle watcher, start one of them in	3428	Example: Define a class with an IO and idle watcher, start one of them in
2576	the constructor.	3429	the constructor.
2577		3430
2578	class myclass	3431	class myclass
2579	{	3432	{
2580	ev::io io; void io_cb (ev::io &w, int revents);	3433	ev::io io ; void io_cb (ev::io &w, int revents);
2581	ev:idle idle void idle_cb (ev::idle &w, int revents);	3434	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2582		3435
2583	myclass (int fd)	3436	myclass (int fd)
2584	{	3437	{
2585	io .set <myclass, &myclass::io_cb > (this);	3438	io .set <myclass, &myclass::io_cb > (this);
2586	idle.set <myclass, &myclass::idle_cb> (this);	3439	idle.set <myclass, &myclass::idle_cb> (this);
2587		3440
2588	io.start (fd, ev::READ);	3441	io.start (fd, ev::READ);
2589	}	3442	}
2590	};	3443	};
2591		3444
2592		3445
2593	=head1 OTHER LANGUAGE BINDINGS	3446	=head1 OTHER LANGUAGE BINDINGS
2594		3447
2595	Libev does not offer other language bindings itself, but bindings for a	3448	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	3449	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	3450	any interesting language binding in addition to the ones listed here, drop
2598	me a note.	3451	me a note.
2599		3452
2600	=over 4	3453	=over 4
2601		3454
2602	=item Perl	3455	=item Perl
2603		3456
2604	The EV module implements the full libev API and is actually used to test	3457	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,	3458	libev. EV is developed together with libev. Apart from the EV core module,
2606	there are additional modules that implement libev-compatible interfaces	3459	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	3460	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>).	3461	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3462	and C<EV::Glib>).
2609		3463
2610	It can be found and installed via CPAN, its homepage is found at	3464	It can be found and installed via CPAN, its homepage is at
2611	L<http://software.schmorp.de/pkg/EV>.	3465	L<http://software.schmorp.de/pkg/EV>.
2612		3466
		3467	=item Python
		3468
		3469	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3470	seems to be quite complete and well-documented.
		3471
2613	=item Ruby	3472	=item Ruby
2614		3473
2615	Tony Arcieri has written a ruby extension that offers access to a subset	3474	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	3475	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	3476	more on top of it. It can be found via gem servers. Its homepage is at
2618	L<http://rev.rubyforge.org/>.	3477	L<http://rev.rubyforge.org/>.
2619		3478
		3479	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3480	makes rev work even on mingw.
		3481
		3482	=item Haskell
		3483
		3484	A haskell binding to libev is available at
		3485	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3486
2620	=item D	3487	=item D
2621		3488
2622	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3489	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>.	3490	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3491
		3492	=item Ocaml
		3493
		3494	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3495	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3496
		3497	=item Lua
		3498
		3499	Brian Maher has written a partial interface to libev for lua (at the
		3500	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3501	L<http://github.com/brimworks/lua-ev>.
2624		3502
2625	=back	3503	=back
2626		3504
2627		3505
2628	=head1 MACRO MAGIC	3506	=head1 MACRO MAGIC
2629		3507
2630	Libev can be compiled with a variety of options, the most fundamantal	3508	Libev can be compiled with a variety of options, the most fundamental
2631	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3509	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2632	functions and callbacks have an initial C<struct ev_loop *> argument.	3510	functions and callbacks have an initial C<struct ev_loop *> argument.
2633		3511
2634	To make it easier to write programs that cope with either variant, the	3512	To make it easier to write programs that cope with either variant, the
2635	following macros are defined:	3513	following macros are defined:
…		…
2640		3518
2641	This provides the loop I<argument> for functions, if one is required ("ev	3519	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,	3520	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:	3521	C<EV_A_> is used when other arguments are following. Example:
2644		3522
2645	ev_unref (EV_A);	3523	ev_unref (EV_A);
2646	ev_timer_add (EV_A_ watcher);	3524	ev_timer_add (EV_A_ watcher);
2647	ev_loop (EV_A_ 0);	3525	ev_loop (EV_A_ 0);
2648		3526
2649	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3527	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2650	which is often provided by the following macro.	3528	which is often provided by the following macro.
2651		3529
2652	=item C<EV_P>, C<EV_P_>	3530	=item C<EV_P>, C<EV_P_>
2653		3531
2654	This provides the loop I<parameter> for functions, if one is required ("ev	3532	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,	3533	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:	3534	C<EV_P_> is used when other parameters are following. Example:
2657		3535
2658	// this is how ev_unref is being declared	3536	// this is how ev_unref is being declared
2659	static void ev_unref (EV_P);	3537	static void ev_unref (EV_P);
2660		3538
2661	// this is how you can declare your typical callback	3539	// this is how you can declare your typical callback
2662	static void cb (EV_P_ ev_timer *w, int revents)	3540	static void cb (EV_P_ ev_timer *w, int revents)
2663		3541
2664	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3542	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2665	suitable for use with C<EV_A>.	3543	suitable for use with C<EV_A>.
2666		3544
2667	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3545	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2683		3561
2684	Example: Declare and initialise a check watcher, utilising the above	3562	Example: Declare and initialise a check watcher, utilising the above
2685	macros so it will work regardless of whether multiple loops are supported	3563	macros so it will work regardless of whether multiple loops are supported
2686	or not.	3564	or not.
2687		3565
2688	static void	3566	static void
2689	check_cb (EV_P_ ev_timer *w, int revents)	3567	check_cb (EV_P_ ev_timer *w, int revents)
2690	{	3568	{
2691	ev_check_stop (EV_A_ w);	3569	ev_check_stop (EV_A_ w);
2692	}	3570	}
2693		3571
2694	ev_check check;	3572	ev_check check;
2695	ev_check_init (&check, check_cb);	3573	ev_check_init (&check, check_cb);
2696	ev_check_start (EV_DEFAULT_ &check);	3574	ev_check_start (EV_DEFAULT_ &check);
2697	ev_loop (EV_DEFAULT_ 0);	3575	ev_loop (EV_DEFAULT_ 0);
2698		3576
2699	=head1 EMBEDDING	3577	=head1 EMBEDDING
2700		3578
2701	Libev can (and often is) directly embedded into host	3579	Libev can (and often is) directly embedded into host
2702	applications. Examples of applications that embed it include the Deliantra	3580	applications. Examples of applications that embed it include the Deliantra
…		…
2709	libev somewhere in your source tree).	3587	libev somewhere in your source tree).
2710		3588
2711	=head2 FILESETS	3589	=head2 FILESETS
2712		3590
2713	Depending on what features you need you need to include one or more sets of files	3591	Depending on what features you need you need to include one or more sets of files
2714	in your app.	3592	in your application.
2715		3593
2716	=head3 CORE EVENT LOOP	3594	=head3 CORE EVENT LOOP
2717		3595
2718	To include only the libev core (all the C<ev_*> functions), with manual	3596	To include only the libev core (all the C<ev_*> functions), with manual
2719	configuration (no autoconf):	3597	configuration (no autoconf):
2720		3598
2721	#define EV_STANDALONE 1	3599	#define EV_STANDALONE 1
2722	#include "ev.c"	3600	#include "ev.c"
2723		3601
2724	This will automatically include F<ev.h>, too, and should be done in a	3602	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	3603	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	3604	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	3605	done by writing a wrapper around F<ev.h> that you can include instead and
2728	where you can put other configuration options):	3606	where you can put other configuration options):
2729		3607
2730	#define EV_STANDALONE 1	3608	#define EV_STANDALONE 1
2731	#include "ev.h"	3609	#include "ev.h"
2732		3610
2733	Both header files and implementation files can be compiled with a C++	3611	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	3612	compiler (at least, that's a stated goal, and breakage will be treated
2735	as a bug).	3613	as a bug).
2736		3614
2737	You need the following files in your source tree, or in a directory	3615	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):	3616	in your include path (e.g. in libev/ when using -Ilibev):
2739		3617
2740	ev.h	3618	ev.h
2741	ev.c	3619	ev.c
2742	ev_vars.h	3620	ev_vars.h
2743	ev_wrap.h	3621	ev_wrap.h
2744		3622
2745	ev_win32.c required on win32 platforms only	3623	ev_win32.c required on win32 platforms only
2746		3624
2747	ev_select.c only when select backend is enabled (which is enabled by default)	3625	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)	3626	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)	3627	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)	3628	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)	3629	ev_port.c only when the solaris port backend is enabled (disabled by default)
2752		3630
2753	F<ev.c> includes the backend files directly when enabled, so you only need	3631	F<ev.c> includes the backend files directly when enabled, so you only need
2754	to compile this single file.	3632	to compile this single file.
2755		3633
2756	=head3 LIBEVENT COMPATIBILITY API	3634	=head3 LIBEVENT COMPATIBILITY API
2757		3635
2758	To include the libevent compatibility API, also include:	3636	To include the libevent compatibility API, also include:
2759		3637
2760	#include "event.c"	3638	#include "event.c"
2761		3639
2762	in the file including F<ev.c>, and:	3640	in the file including F<ev.c>, and:
2763		3641
2764	#include "event.h"	3642	#include "event.h"
2765		3643
2766	in the files that want to use the libevent API. This also includes F<ev.h>.	3644	in the files that want to use the libevent API. This also includes F<ev.h>.
2767		3645
2768	You need the following additional files for this:	3646	You need the following additional files for this:
2769		3647
2770	event.h	3648	event.h
2771	event.c	3649	event.c
2772		3650
2773	=head3 AUTOCONF SUPPORT	3651	=head3 AUTOCONF SUPPORT
2774		3652
2775	Instead of using C<EV_STANDALONE=1> and providing your config in	3653	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	3654	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	3655	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2778	include F<config.h> and configure itself accordingly.	3656	include F<config.h> and configure itself accordingly.
2779		3657
2780	For this of course you need the m4 file:	3658	For this of course you need the m4 file:
2781		3659
2782	libev.m4	3660	libev.m4
2783		3661
2784	=head2 PREPROCESSOR SYMBOLS/MACROS	3662	=head2 PREPROCESSOR SYMBOLS/MACROS
2785		3663
2786	Libev can be configured via a variety of preprocessor symbols you have to	3664	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	3665	define before including (or compiling) any of its files. The default in
2788	autoconf is noted for every option.	3666	the absence of autoconf is documented for every option.
		3667
		3668	Symbols marked with "(h)" do not change the ABI, and can have different
		3669	values when compiling libev vs. including F<ev.h>, so it is permissible
		3670	to redefine them before including F<ev.h> without breaking compatibility
		3671	to a compiled library. All other symbols change the ABI, which means all
		3672	users of libev and the libev code itself must be compiled with compatible
		3673	settings.
2789		3674
2790	=over 4	3675	=over 4
2791		3676
2792	=item EV_STANDALONE	3677	=item EV_STANDALONE (h)
2793		3678
2794	Must always be C<1> if you do not use autoconf configuration, which	3679	Must always be C<1> if you do not use autoconf configuration, which
2795	keeps libev from including F<config.h>, and it also defines dummy	3680	keeps libev from including F<config.h>, and it also defines dummy
2796	implementations for some libevent functions (such as logging, which is not	3681	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	3682	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.	3683	F<event.h> that are not directly supported by the libev core alone.
2799		3684
		3685	In standalone mode, libev will still try to automatically deduce the
		3686	configuration, but has to be more conservative.
		3687
2800	=item EV_USE_MONOTONIC	3688	=item EV_USE_MONOTONIC
2801		3689
2802	If defined to be C<1>, libev will try to detect the availability of the	3690	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	3691	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	3692	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	3693	you usually have to link against librt or something similar. Enabling it
2806	the functionality isn't available is safe, though, although you have	3694	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>	3695	to make sure you link against any libraries where the C<clock_gettime>
2808	function is hiding in (often F<-lrt>).	3696	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2809		3697
2810	=item EV_USE_REALTIME	3698	=item EV_USE_REALTIME
2811		3699
2812	If defined to be C<1>, libev will try to detect the availability of the	3700	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	3701	real-time clock option at compile time (and assume its availability
2814	runtime if successful). Otherwise no use of the realtime clock option will	3702	at runtime if successful). Otherwise no use of the real-time clock
2815	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3703	option will be attempted. This effectively replaces C<gettimeofday>
2816	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3704	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2817	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3705	correctness. See the note about libraries in the description of
		3706	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3707	C<EV_USE_CLOCK_SYSCALL>.
		3708
		3709	=item EV_USE_CLOCK_SYSCALL
		3710
		3711	If defined to be C<1>, libev will try to use a direct syscall instead
		3712	of calling the system-provided C<clock_gettime> function. This option
		3713	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3714	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3715	programs needlessly. Using a direct syscall is slightly slower (in
		3716	theory), because no optimised vdso implementation can be used, but avoids
		3717	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3718	higher, as it simplifies linking (no need for C<-lrt>).
2818		3719
2819	=item EV_USE_NANOSLEEP	3720	=item EV_USE_NANOSLEEP
2820		3721
2821	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3722	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 ()>.	3723	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2830	2.7 or newer, otherwise disabled.	3731	2.7 or newer, otherwise disabled.
2831		3732
2832	=item EV_USE_SELECT	3733	=item EV_USE_SELECT
2833		3734
2834	If undefined or defined to be C<1>, libev will compile in support for the	3735	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	3736	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	3737	other method takes over, select will be it. Otherwise the select backend
2837	will not be compiled in.	3738	will not be compiled in.
2838		3739
2839	=item EV_SELECT_USE_FD_SET	3740	=item EV_SELECT_USE_FD_SET
2840		3741
2841	If defined to C<1>, then the select backend will use the system C<fd_set>	3742	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	3743	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	3744	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	3745	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	3746	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	3747	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2847	influence the size of the C<fd_set> used.	3748	configures the maximum size of the C<fd_set>.
2848		3749
2849	=item EV_SELECT_IS_WINSOCKET	3750	=item EV_SELECT_IS_WINSOCKET
2850		3751
2851	When defined to C<1>, the select backend will assume that	3752	When defined to C<1>, the select backend will assume that
2852	select/socket/connect etc. don't understand file descriptors but	3753	select/socket/connect etc. don't understand file descriptors but
…		…
2854	be used is the winsock select). This means that it will call	3755	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,	3756	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	3757	it is assumed that all these functions actually work on fds, even
2857	on win32. Should not be defined on non-win32 platforms.	3758	on win32. Should not be defined on non-win32 platforms.
2858		3759
2859	=item EV_FD_TO_WIN32_HANDLE	3760	=item EV_FD_TO_WIN32_HANDLE(fd)
2860		3761
2861	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3762	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	3763	file descriptors to socket handles. When not defining this symbol (the
2863	default), then libev will call C<_get_osfhandle>, which is usually	3764	default), then libev will call C<_get_osfhandle>, which is usually
2864	correct. In some cases, programs use their own file descriptor management,	3765	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.	3766	in which case they can provide this function to map fds to socket handles.
		3767
		3768	=item EV_WIN32_HANDLE_TO_FD(handle)
		3769
		3770	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3771	using the standard C<_open_osfhandle> function. For programs implementing
		3772	their own fd to handle mapping, overwriting this function makes it easier
		3773	to do so. This can be done by defining this macro to an appropriate value.
		3774
		3775	=item EV_WIN32_CLOSE_FD(fd)
		3776
		3777	If programs implement their own fd to handle mapping on win32, then this
		3778	macro can be used to override the C<close> function, useful to unregister
		3779	file descriptors again. Note that the replacement function has to close
		3780	the underlying OS handle.
2866		3781
2867	=item EV_USE_POLL	3782	=item EV_USE_POLL
2868		3783
2869	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3784	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	3785	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2897	otherwise another method will be used as fallback. This is the preferred	3812	otherwise another method will be used as fallback. This is the preferred
2898	backend for Solaris 10 systems.	3813	backend for Solaris 10 systems.
2899		3814
2900	=item EV_USE_DEVPOLL	3815	=item EV_USE_DEVPOLL
2901		3816
2902	reserved for future expansion, works like the USE symbols above.	3817	Reserved for future expansion, works like the USE symbols above.
2903		3818
2904	=item EV_USE_INOTIFY	3819	=item EV_USE_INOTIFY
2905		3820
2906	If defined to be C<1>, libev will compile in support for the Linux inotify	3821	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	3822	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	3829	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	3830	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"	3831	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.	3832	as well as for signal and thread safety in C<ev_async> watchers.
2918		3833
2919	In the absense of this define, libev will use C<sig_atomic_t volatile>	3834	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.	3835	(from F<signal.h>), which is usually good enough on most platforms.
2921		3836
2922	=item EV_H	3837	=item EV_H (h)
2923		3838
2924	The name of the F<ev.h> header file used to include it. The default if	3839	The name of the F<ev.h> header file used to include it. The default if
2925	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3840	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2926	used to virtually rename the F<ev.h> header file in case of conflicts.	3841	used to virtually rename the F<ev.h> header file in case of conflicts.
2927		3842
2928	=item EV_CONFIG_H	3843	=item EV_CONFIG_H (h)
2929		3844
2930	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3845	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2931	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3846	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2932	C<EV_H>, above.	3847	C<EV_H>, above.
2933		3848
2934	=item EV_EVENT_H	3849	=item EV_EVENT_H (h)
2935		3850
2936	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3851	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2937	of how the F<event.h> header can be found, the default is C<"event.h">.	3852	of how the F<event.h> header can be found, the default is C<"event.h">.
2938		3853
2939	=item EV_PROTOTYPES	3854	=item EV_PROTOTYPES (h)
2940		3855
2941	If defined to be C<0>, then F<ev.h> will not define any function	3856	If defined to be C<0>, then F<ev.h> will not define any function
2942	prototypes, but still define all the structs and other symbols. This is	3857	prototypes, but still define all the structs and other symbols. This is
2943	occasionally useful if you want to provide your own wrapper functions	3858	occasionally useful if you want to provide your own wrapper functions
2944	around libev functions.	3859	around libev functions.
…		…
2963	When doing priority-based operations, libev usually has to linearly search	3878	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	3879	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	3880	and time, so using the defaults of five priorities (-2 .. +2) is usually
2966	fine.	3881	fine.
2967		3882
2968	If your embedding app does not need any priorities, defining these both to	3883	If your embedding application does not need any priorities, defining these
2969	C<0> will save some memory and cpu.	3884	both to C<0> will save some memory and CPU.
2970		3885
2971	=item EV_PERIODIC_ENABLE	3886	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3887	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3888	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2972		3889
2973	If undefined or defined to be C<1>, then periodic timers are supported. If	3890	If undefined or defined to be C<1> (and the platform supports it), then
2974	defined to be C<0>, then they are not. Disabling them saves a few kB of	3891	the respective watcher type is supported. If defined to be C<0>, then it
2975	code.	3892	is not. Disabling watcher types mainly saves codesize.
2976		3893
2977	=item EV_IDLE_ENABLE	3894	=item EV_FEATURES
2978
2979	If undefined or defined to be C<1>, then idle watchers are supported. If
2980	defined to be C<0>, then they are not. Disabling them saves a few kB of
2981	code.
2982
2983	=item EV_EMBED_ENABLE
2984
2985	If undefined or defined to be C<1>, then embed watchers are supported. If
2986	defined to be C<0>, then they are not.
2987
2988	=item EV_STAT_ENABLE
2989
2990	If undefined or defined to be C<1>, then stat watchers are supported. If
2991	defined to be C<0>, then they are not.
2992
2993	=item EV_FORK_ENABLE
2994
2995	If undefined or defined to be C<1>, then fork watchers are supported. If
2996	defined to be C<0>, then they are not.
2997
2998	=item EV_ASYNC_ENABLE
2999
3000	If undefined or defined to be C<1>, then async watchers are supported. If
3001	defined to be C<0>, then they are not.
3002
3003	=item EV_MINIMAL
3004		3895
3005	If you need to shave off some kilobytes of code at the expense of some	3896	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	3897	speed (but with the full API), you can define this symbol to request
3007	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3898	certain subsets of functionality. The default is to enable all features
3008	much smaller 2-heap for timer management over the default 4-heap.	3899	that can be enabled on the platform.
		3900
		3901	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3902	with some broad features you want) and then selectively re-enable
		3903	additional parts you want, for example if you want everything minimal,
		3904	but multiple event loop support, async and child watchers and the poll
		3905	backend, use this:
		3906
		3907	#define EV_FEATURES 0
		3908	#define EV_MULTIPLICITY 1
		3909	#define EV_USE_POLL 1
		3910	#define EV_CHILD_ENABLE 1
		3911	#define EV_ASYNC_ENABLE 1
		3912
		3913	The actual value is a bitset, it can be a combination of the following
		3914	values:
		3915
		3916	=over 4
		3917
		3918	=item C<1> - faster/larger code
		3919
		3920	Use larger code to speed up some operations.
		3921
		3922	Currently this is used to override some inlining decisions (enlarging the roughly
		3923	30% code size on amd64.
		3924
		3925	When optimising for size, use of compiler flags such as C<-Os> with
		3926	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3927	assertions.
		3928
		3929	=item C<2> - faster/larger data structures
		3930
		3931	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3932	hash table sizes and so on. This will usually further increase codesize
		3933	and can additionally have an effect on the size of data structures at
		3934	runtime.
		3935
		3936	=item C<4> - full API configuration
		3937
		3938	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3939	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3940
		3941	=item C<8> - full API
		3942
		3943	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3944	details on which parts of the API are still available without this
		3945	feature, and do not complain if this subset changes over time.
		3946
		3947	=item C<16> - enable all optional watcher types
		3948
		3949	Enables all optional watcher types. If you want to selectively enable
		3950	only some watcher types other than I/O and timers (e.g. prepare,
		3951	embed, async, child...) you can enable them manually by defining
		3952	C<EV_watchertype_ENABLE> to C<1> instead.
		3953
		3954	=item C<32> - enable all backends
		3955
		3956	This enables all backends - without this feature, you need to enable at
		3957	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3958
		3959	=item C<64> - enable OS-specific "helper" APIs
		3960
		3961	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3962	default.
		3963
		3964	=back
		3965
		3966	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3967	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3968	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3969	watchers, timers and monotonic clock support.
		3970
		3971	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3972	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3973	your program might be left out as well - a binary starting a timer and an
		3974	I/O watcher then might come out at only 5Kb.
		3975
		3976	=item EV_AVOID_STDIO
		3977
		3978	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3979	functions (printf, scanf, perror etc.). This will increase the codesize
		3980	somewhat, but if your program doesn't otherwise depend on stdio and your
		3981	libc allows it, this avoids linking in the stdio library which is quite
		3982	big.
		3983
		3984	Note that error messages might become less precise when this option is
		3985	enabled.
		3986
		3987	=item EV_NSIG
		3988
		3989	The highest supported signal number, +1 (or, the number of
		3990	signals): Normally, libev tries to deduce the maximum number of signals
		3991	automatically, but sometimes this fails, in which case it can be
		3992	specified. Also, using a lower number than detected (C<32> should be
		3993	good for about any system in existance) can save some memory, as libev
		3994	statically allocates some 12-24 bytes per signal number.
3009		3995
3010	=item EV_PID_HASHSIZE	3996	=item EV_PID_HASHSIZE
3011		3997
3012	C<ev_child> watchers use a small hash table to distribute workload by	3998	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	3999	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3014	than enough. If you need to manage thousands of children you might want to	4000	usually more than enough. If you need to manage thousands of children you
3015	increase this value (I<must> be a power of two).	4001	might want to increase this value (I<must> be a power of two).
3016		4002
3017	=item EV_INOTIFY_HASHSIZE	4003	=item EV_INOTIFY_HASHSIZE
3018		4004
3019	C<ev_stat> watchers use a small hash table to distribute workload by	4005	C<ev_stat> watchers use a small hash table to distribute workload by
3020	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4006	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3021	usually more than enough. If you need to manage thousands of C<ev_stat>	4007	disabled), usually more than enough. If you need to manage thousands of
3022	watchers you might want to increase this value (I<must> be a power of	4008	C<ev_stat> watchers you might want to increase this value (I<must> be a
3023	two).	4009	power of two).
3024		4010
3025	=item EV_USE_4HEAP	4011	=item EV_USE_4HEAP
3026		4012
3027	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4013	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	4014	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	4015	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3030	noticably faster performance with many (thousands) of watchers.	4016	faster performance with many (thousands) of watchers.
3031		4017
3032	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4018	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3033	(disabled).	4019	will be C<0>.
3034		4020
3035	=item EV_HEAP_CACHE_AT	4021	=item EV_HEAP_CACHE_AT
3036		4022
3037	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4023	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	4024	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>),	4025	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,	4026	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	4027	but avoids random read accesses on heap changes. This improves performance
3042	noticably with with many (hundreds) of watchers.	4028	noticeably with many (hundreds) of watchers.
3043		4029
3044	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4030	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3045	(disabled).	4031	will be C<0>.
3046		4032
3047	=item EV_VERIFY	4033	=item EV_VERIFY
3048		4034
3049	Controls how much internal verification (see C<ev_loop_verify ()>) will	4035	Controls how much internal verification (see C<ev_loop_verify ()>) will
3050	be done: If set to C<0>, no internal verification code will be compiled	4036	be done: If set to C<0>, no internal verification code will be compiled
…		…
3052	called. If set to C<2>, then the internal verification code will be	4038	called. If set to C<2>, then the internal verification code will be
3053	called once per loop, which can slow down libev. If set to C<3>, then the	4039	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	4040	verification code will be called very frequently, which will slow down
3055	libev considerably.	4041	libev considerably.
3056		4042
3057	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4043	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3058	C<0.>	4044	will be C<0>.
3059		4045
3060	=item EV_COMMON	4046	=item EV_COMMON
3061		4047
3062	By default, all watchers have a C<void *data> member. By redefining	4048	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	4049	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,	4050	members. You have to define it each time you include one of the files,
3065	though, and it must be identical each time.	4051	though, and it must be identical each time.
3066		4052
3067	For example, the perl EV module uses something like this:	4053	For example, the perl EV module uses something like this:
3068		4054
3069	#define EV_COMMON \	4055	#define EV_COMMON \
3070	SV *self; /* contains this struct */ \	4056	SV *self; /* contains this struct */ \
3071	SV *cb_sv, *fh /* note no trailing ";" */	4057	SV *cb_sv, *fh /* note no trailing ";" */
3072		4058
3073	=item EV_CB_DECLARE (type)	4059	=item EV_CB_DECLARE (type)
3074		4060
3075	=item EV_CB_INVOKE (watcher, revents)	4061	=item EV_CB_INVOKE (watcher, revents)
3076		4062
…		…
3081	definition and a statement, respectively. See the F<ev.h> header file for	4067	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	4068	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	4069	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++.	4070	method calls instead of plain function calls in C++.
3085		4071
		4072	=back
		4073
3086	=head2 EXPORTED API SYMBOLS	4074	=head2 EXPORTED API SYMBOLS
3087		4075
3088	If you need to re-export the API (e.g. via a dll) and you need a list of	4076	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	4077	exported symbols, you can use the provided F<Symbol.*> files which list
3090	all public symbols, one per line:	4078	all public symbols, one per line:
3091		4079
3092	Symbols.ev for libev proper	4080	Symbols.ev for libev proper
3093	Symbols.event for the libevent emulation	4081	Symbols.event for the libevent emulation
3094		4082
3095	This can also be used to rename all public symbols to avoid clashes with	4083	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	4084	multiple versions of libev linked together (which is obviously bad in
3097	itself, but sometimes it is inconvinient to avoid this).	4085	itself, but sometimes it is inconvenient to avoid this).
3098		4086
3099	A sed command like this will create wrapper C<#define>'s that you need to	4087	A sed command like this will create wrapper C<#define>'s that you need to
3100	include before including F<ev.h>:	4088	include before including F<ev.h>:
3101		4089
3102	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4090	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3119	file.	4107	file.
3120		4108
3121	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4109	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:	4110	that everybody includes and which overrides some configure choices:
3123		4111
3124	#define EV_MINIMAL 1	4112	#define EV_FEATURES 8
3125	#define EV_USE_POLL 0	4113	#define EV_USE_SELECT 1
3126	#define EV_MULTIPLICITY 0
3127	#define EV_PERIODIC_ENABLE 0	4114	#define EV_PREPARE_ENABLE 1
		4115	#define EV_IDLE_ENABLE 1
3128	#define EV_STAT_ENABLE 0	4116	#define EV_SIGNAL_ENABLE 1
3129	#define EV_FORK_ENABLE 0	4117	#define EV_CHILD_ENABLE 1
		4118	#define EV_USE_STDEXCEPT 0
3130	#define EV_CONFIG_H <config.h>	4119	#define EV_CONFIG_H <config.h>
3131	#define EV_MINPRI 0
3132	#define EV_MAXPRI 0
3133		4120
3134	#include "ev++.h"	4121	#include "ev++.h"
3135		4122
3136	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4123	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3137		4124
3138	#include "ev_cpp.h"	4125	#include "ev_cpp.h"
3139	#include "ev.c"	4126	#include "ev.c"
3140		4127
		4128	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3141		4129
3142	=head1 THREADS AND COROUTINES	4130	=head2 THREADS AND COROUTINES
3143		4131
3144	=head2 THREADS	4132	=head3 THREADS
3145		4133
3146	Libev itself is completely threadsafe, but it uses no locking. This	4134	All libev functions are reentrant and thread-safe unless explicitly
		4135	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	4136	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	4137	are no concurrent calls into any libev function with the same loop
3149	parameter.	4138	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4139	of course): libev guarantees that different event loops share no data
		4140	structures that need any locking.
3150		4141
3151	Or put differently: calls with different loop parameters can be done in	4142	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	4143	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	4144	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	4145	only one thread ever is inside a call at any point in time, e.g. by using
3155	per loop).	4146	a mutex per loop).
3156		4147
3157	If you want to know which design is best for your problem, then I cannot	4148	Specifically to support threads (and signal handlers), libev implements
		4149	so-called C<ev_async> watchers, which allow some limited form of
		4150	concurrency on the same event loop, namely waking it up "from the
		4151	outside".
		4152
		4153	If you want to know which design (one loop, locking, or multiple loops
		4154	without or something else still) is best for your problem, then I cannot
3158	help you but by giving some generic advice:	4155	help you, but here is some generic advice:
3159		4156
3160	=over 4	4157	=over 4
3161		4158
3162	=item * most applications have a main thread: use the default libev loop	4159	=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.	4160	in that thread, or create a separate thread running only the default loop.
3164		4161
3165	This helps integrating other libraries or software modules that use libev	4162	This helps integrating other libraries or software modules that use libev
3166	themselves and don't care/know about threading.	4163	themselves and don't care/know about threading.
3167		4164
3168	=item * one loop per thread is usually a good model.	4165	=item * one loop per thread is usually a good model.
3169		4166
3170	Doing this is almost never wrong, sometimes a better-performance model	4167	Doing this is almost never wrong, sometimes a better-performance model
3171	exists, but it is always a good start.	4168	exists, but it is always a good start.
3172		4169
3173	=item * other models exist, such as the leader/follower pattern, where one	4170	=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.	4171	loop is handed through multiple threads in a kind of round-robin fashion.
3175		4172
3176	Chosing a model is hard - look around, learn, know that usually you cna do	4173	Choosing a model is hard - look around, learn, know that usually you can do
3177	better than you currently do :-)	4174	better than you currently do :-)
3178		4175
3179	=item * often you need to talk to some other thread which blocks in the	4176	=item * often you need to talk to some other thread which blocks in the
		4177	event loop.
		4178
3180	event loop - C<ev_async> watchers can be used to wake them up from other	4179	C<ev_async> watchers can be used to wake them up from other threads safely
3181	threads safely (or from signal contexts...).	4180	(or from signal contexts...).
		4181
		4182	An example use would be to communicate signals or other events that only
		4183	work in the default loop by registering the signal watcher with the
		4184	default loop and triggering an C<ev_async> watcher from the default loop
		4185	watcher callback into the event loop interested in the signal.
3182		4186
3183	=back	4187	=back
3184		4188
		4189	=head4 THREAD LOCKING EXAMPLE
		4190
		4191	Here is a fictitious example of how to run an event loop in a different
		4192	thread than where callbacks are being invoked and watchers are
		4193	created/added/removed.
		4194
		4195	For a real-world example, see the C<EV::Loop::Async> perl module,
		4196	which uses exactly this technique (which is suited for many high-level
		4197	languages).
		4198
		4199	The example uses a pthread mutex to protect the loop data, a condition
		4200	variable to wait for callback invocations, an async watcher to notify the
		4201	event loop thread and an unspecified mechanism to wake up the main thread.
		4202
		4203	First, you need to associate some data with the event loop:
		4204
		4205	typedef struct {
		4206	mutex_t lock; /* global loop lock */
		4207	ev_async async_w;
		4208	thread_t tid;
		4209	cond_t invoke_cv;
		4210	} userdata;
		4211
		4212	void prepare_loop (EV_P)
		4213	{
		4214	// for simplicity, we use a static userdata struct.
		4215	static userdata u;
		4216
		4217	ev_async_init (&u->async_w, async_cb);
		4218	ev_async_start (EV_A_ &u->async_w);
		4219
		4220	pthread_mutex_init (&u->lock, 0);
		4221	pthread_cond_init (&u->invoke_cv, 0);
		4222
		4223	// now associate this with the loop
		4224	ev_set_userdata (EV_A_ u);
		4225	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4226	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4227
		4228	// then create the thread running ev_loop
		4229	pthread_create (&u->tid, 0, l_run, EV_A);
		4230	}
		4231
		4232	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4233	solely to wake up the event loop so it takes notice of any new watchers
		4234	that might have been added:
		4235
		4236	static void
		4237	async_cb (EV_P_ ev_async *w, int revents)
		4238	{
		4239	// just used for the side effects
		4240	}
		4241
		4242	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4243	protecting the loop data, respectively.
		4244
		4245	static void
		4246	l_release (EV_P)
		4247	{
		4248	userdata *u = ev_userdata (EV_A);
		4249	pthread_mutex_unlock (&u->lock);
		4250	}
		4251
		4252	static void
		4253	l_acquire (EV_P)
		4254	{
		4255	userdata *u = ev_userdata (EV_A);
		4256	pthread_mutex_lock (&u->lock);
		4257	}
		4258
		4259	The event loop thread first acquires the mutex, and then jumps straight
		4260	into C<ev_loop>:
		4261
		4262	void *
		4263	l_run (void *thr_arg)
		4264	{
		4265	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4266
		4267	l_acquire (EV_A);
		4268	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4269	ev_loop (EV_A_ 0);
		4270	l_release (EV_A);
		4271
		4272	return 0;
		4273	}
		4274
		4275	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4276	signal the main thread via some unspecified mechanism (signals? pipe
		4277	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4278	have been called (in a while loop because a) spurious wakeups are possible
		4279	and b) skipping inter-thread-communication when there are no pending
		4280	watchers is very beneficial):
		4281
		4282	static void
		4283	l_invoke (EV_P)
		4284	{
		4285	userdata *u = ev_userdata (EV_A);
		4286
		4287	while (ev_pending_count (EV_A))
		4288	{
		4289	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4290	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4291	}
		4292	}
		4293
		4294	Now, whenever the main thread gets told to invoke pending watchers, it
		4295	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4296	thread to continue:
		4297
		4298	static void
		4299	real_invoke_pending (EV_P)
		4300	{
		4301	userdata *u = ev_userdata (EV_A);
		4302
		4303	pthread_mutex_lock (&u->lock);
		4304	ev_invoke_pending (EV_A);
		4305	pthread_cond_signal (&u->invoke_cv);
		4306	pthread_mutex_unlock (&u->lock);
		4307	}
		4308
		4309	Whenever you want to start/stop a watcher or do other modifications to an
		4310	event loop, you will now have to lock:
		4311
		4312	ev_timer timeout_watcher;
		4313	userdata *u = ev_userdata (EV_A);
		4314
		4315	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4316
		4317	pthread_mutex_lock (&u->lock);
		4318	ev_timer_start (EV_A_ &timeout_watcher);
		4319	ev_async_send (EV_A_ &u->async_w);
		4320	pthread_mutex_unlock (&u->lock);
		4321
		4322	Note that sending the C<ev_async> watcher is required because otherwise
		4323	an event loop currently blocking in the kernel will have no knowledge
		4324	about the newly added timer. By waking up the loop it will pick up any new
		4325	watchers in the next event loop iteration.
		4326
3185	=head2 COROUTINES	4327	=head3 COROUTINES
3186		4328
3187	Libev is much more accomodating to coroutines ("cooperative threads"):	4329	Libev is very accommodating to coroutines ("cooperative threads"):
3188	libev fully supports nesting calls to it's functions from different	4330	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	4331	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	4332	different coroutines, and switch freely between both coroutines running
3191	loop, as long as you don't confuse yourself). The only exception is that	4333	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.	4334	that you must not do this from C<ev_periodic> reschedule callbacks.
3193		4335
3194	Care has been invested into making sure that libev does not keep local	4336	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	4337	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3196	switches.	4338	they do not call any callbacks.
3197		4339
		4340	=head2 COMPILER WARNINGS
3198		4341
3199	=head1 COMPLEXITIES	4342	Depending on your compiler and compiler settings, you might get no or a
		4343	lot of warnings when compiling libev code. Some people are apparently
		4344	scared by this.
3200		4345
3201	In this section the complexities of (many of) the algorithms used inside	4346	However, these are unavoidable for many reasons. For one, each compiler
3202	libev will be explained. For complexity discussions about backends see the	4347	has different warnings, and each user has different tastes regarding
3203	documentation for C<ev_default_init>.	4348	warning options. "Warn-free" code therefore cannot be a goal except when
		4349	targeting a specific compiler and compiler-version.
3204		4350
3205	All of the following are about amortised time: If an array needs to be	4351	Another reason is that some compiler warnings require elaborate
3206	extended, libev needs to realloc and move the whole array, but this	4352	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	4353	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		4354
3211	=over 4	4355	And of course, some compiler warnings are just plain stupid, or simply
		4356	wrong (because they don't actually warn about the condition their message
		4357	seems to warn about). For example, certain older gcc versions had some
		4358	warnings that resulted an extreme number of false positives. These have
		4359	been fixed, but some people still insist on making code warn-free with
		4360	such buggy versions.
3212		4361
3213	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4362	While libev is written to generate as few warnings as possible,
		4363	"warn-free" code is not a goal, and it is recommended not to build libev
		4364	with any compiler warnings enabled unless you are prepared to cope with
		4365	them (e.g. by ignoring them). Remember that warnings are just that:
		4366	warnings, not errors, or proof of bugs.
3214		4367
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		4368
3219	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4369	=head2 VALGRIND
3220		4370
3221	That means that changing a timer costs less than removing/adding them	4371	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.	4372	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3223		4373
3224	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4374	If you think you found a bug (memory leak, uninitialised data access etc.)
		4375	in libev, then check twice: If valgrind reports something like:
3225		4376
3226	These just add the watcher into an array or at the head of a list.	4377	==2274== definitely lost: 0 bytes in 0 blocks.
		4378	==2274== possibly lost: 0 bytes in 0 blocks.
		4379	==2274== still reachable: 256 bytes in 1 blocks.
3227		4380
3228	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4381	Then there is no memory leak, just as memory accounted to global variables
		4382	is not a memleak - the memory is still being referenced, and didn't leak.
3229		4383
3230	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4384	Similarly, under some circumstances, valgrind might report kernel bugs
		4385	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4386	although an acceptable workaround has been found here), or it might be
		4387	confused.
3231		4388
3232	These watchers are stored in lists then need to be walked to find the	4389	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	4390	make it into some kind of religion.
3234	have many watchers waiting for the same fd or signal).
3235		4391
3236	=item Finding the next timer in each loop iteration: O(1)	4392	If you are unsure about something, feel free to contact the mailing list
		4393	with the full valgrind report and an explanation on why you think this
		4394	is a bug in libev (best check the archives, too :). However, don't be
		4395	annoyed when you get a brisk "this is no bug" answer and take the chance
		4396	of learning how to interpret valgrind properly.
3237		4397
3238	By virtue of using a binary or 4-heap, the next timer is always found at a	4398	If you need, for some reason, empty reports from valgrind for your project
3239	fixed position in the storage array.	4399	I suggest using suppression lists.
3240		4400
3241	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3242		4401
3243	A change means an I/O watcher gets started or stopped, which requires	4402	=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		4403
3247	=item Activating one watcher (putting it into the pending state): O(1)	4404	=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		4405
3271	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4406	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	4407	requires, and its I/O model is fundamentally incompatible with the POSIX
3273	model. Libev still offers limited functionality on this platform in	4408	model. Libev still offers limited functionality on this platform in
3274	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4409	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).	4416	way (note also that glib is the slowest event library known to man).
3282		4417
3283	There is no supported compilation method available on windows except	4418	There is no supported compilation method available on windows except
3284	embedding it into other applications.	4419	embedding it into other applications.
3285		4420
		4421	Sensible signal handling is officially unsupported by Microsoft - libev
		4422	tries its best, but under most conditions, signals will simply not work.
		4423
		4424	Not a libev limitation but worth mentioning: windows apparently doesn't
		4425	accept large writes: instead of resulting in a partial write, windows will
		4426	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4427	so make sure you only write small amounts into your sockets (less than a
		4428	megabyte seems safe, but this apparently depends on the amount of memory
		4429	available).
		4430
3286	Due to the many, low, and arbitrary limits on the win32 platform and	4431	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	4432	the abysmal performance of winsockets, using a large number of sockets
3288	is not recommended (and not reasonable). If your program needs to use	4433	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	4434	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	4435	different implementation for windows, as libev offers the POSIX readiness
3291	notification model, which cannot be implemented efficiently on windows	4436	notification model, which cannot be implemented efficiently on windows
3292	(microsoft monopoly games).	4437	(due to Microsoft monopoly games).
		4438
		4439	A typical way to use libev under windows is to embed it (see the embedding
		4440	section for details) and use the following F<evwrap.h> header file instead
		4441	of F<ev.h>:
		4442
		4443	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4444	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4445
		4446	#include "ev.h"
		4447
		4448	And compile the following F<evwrap.c> file into your project (make sure
		4449	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4450
		4451	#include "evwrap.h"
		4452	#include "ev.c"
3293		4453
3294	=over 4	4454	=over 4
3295		4455
3296	=item The winsocket select function	4456	=item The winsocket select function
3297		4457
3298	The winsocket C<select> function doesn't follow POSIX in that it requires	4458	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	4459	requires socket I<handles> and not socket I<file descriptors> (it is
3300	very inefficient, and also requires a mapping from file descriptors	4460	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>,	4461	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	4462	C runtime provides the function C<_open_osfhandle> for this). See the
3303	symbols for more info.	4463	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4464	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3304		4465
3305	The configuration for a "naked" win32 using the microsoft runtime	4466	The configuration for a "naked" win32 using the Microsoft runtime
3306	libraries and raw winsocket select is:	4467	libraries and raw winsocket select is:
3307		4468
3308	#define EV_USE_SELECT 1	4469	#define EV_USE_SELECT 1
3309	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4470	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3310		4471
3311	Note that winsockets handling of fd sets is O(n), so you can easily get a	4472	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.	4473	complexity in the O(n²) range when using win32.
3313		4474
3314	=item Limited number of file descriptors	4475	=item Limited number of file descriptors
3315		4476
3316	Windows has numerous arbitrary (and low) limits on things.	4477	Windows has numerous arbitrary (and low) limits on things.
3317		4478
3318	Early versions of winsocket's select only supported waiting for a maximum	4479	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	4480	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	4481	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	4482	recommends spawning a chain of threads and wait for 63 handles and the
3322	previous thread in each. Great).	4483	previous thread in each. Sounds great!).
3323		4484
3324	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4485	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	4486	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	4487	call (which might be in libev or elsewhere, for example, perl and many
3327	select emulation on windows).	4488	other interpreters do their own select emulation on windows).
3328		4489
3329	Another limit is the number of file descriptors in the microsoft runtime	4490	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	4491	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	4492	fetish or something like this inside Microsoft). You can increase this
3332	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4493	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	4494	(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	4495	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	4496	(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	4497	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.	4498	the cost of calling select (O(n²)) will likely make this unworkable.
3340		4499
3341	=back	4500	=back
3342		4501
3343
3344	=head1 PORTABILITY REQUIREMENTS	4502	=head2 PORTABILITY REQUIREMENTS
3345		4503
3346	In addition to a working ISO-C implementation, libev relies on a few	4504	In addition to a working ISO-C implementation and of course the
3347	additional extensions:	4505	backend-specific APIs, libev relies on a few additional extensions:
3348		4506
3349	=over 4	4507	=over 4
3350		4508
		4509	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4510	calling conventions regardless of C<ev_watcher_type *>.
		4511
		4512	Libev assumes not only that all watcher pointers have the same internal
		4513	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4514	assumes that the same (machine) code can be used to call any watcher
		4515	callback: The watcher callbacks have different type signatures, but libev
		4516	calls them using an C<ev_watcher *> internally.
		4517
3351	=item C<sig_atomic_t volatile> must be thread-atomic as well	4518	=item C<sig_atomic_t volatile> must be thread-atomic as well
3352		4519
3353	The type C<sig_atomic_t volatile> (or whatever is defined as	4520	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	4521	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	4522	threads. This is not part of the specification for C<sig_atomic_t>, but is
3356	believed to be sufficiently portable.	4523	believed to be sufficiently portable.
3357		4524
3358	=item C<sigprocmask> must work in a threaded environment	4525	=item C<sigprocmask> must work in a threaded environment
3359		4526
…		…
3368	except the initial one, and run the default loop in the initial thread as	4535	except the initial one, and run the default loop in the initial thread as
3369	well.	4536	well.
3370		4537
3371	=item C<long> must be large enough for common memory allocation sizes	4538	=item C<long> must be large enough for common memory allocation sizes
3372		4539
3373	To improve portability and simplify using libev, libev uses C<long>	4540	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	4541	instead of C<size_t> when allocating its data structures. On non-POSIX
3375	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4542	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	4543	least 31 bits everywhere, which is enough for hundreds of millions of
3377	millions of watchers.	4544	watchers.
3378		4545
3379	=item C<double> must hold a time value in seconds with enough accuracy	4546	=item C<double> must hold a time value in seconds with enough accuracy
3380		4547
3381	The type C<double> is used to represent timestamps. It is required to	4548	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	4549	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	4550	enough for at least into the year 4000. This requirement is fulfilled by
3384	implementations implementing IEEE 754 (basically all existing ones).	4551	implementations implementing IEEE 754, which is basically all existing
		4552	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4553	2200.
3385		4554
3386	=back	4555	=back
3387		4556
3388	If you know of other additional requirements drop me a note.	4557	If you know of other additional requirements drop me a note.
3389		4558
3390		4559
3391	=head1 VALGRIND	4560	=head1 ALGORITHMIC COMPLEXITIES
3392		4561
3393	Valgrind has a special section here because it is a popular tool that is	4562	In this section the complexities of (many of) the algorithms used inside
3394	highly useful, but valgrind reports are very hard to interpret.	4563	libev will be documented. For complexity discussions about backends see
		4564	the documentation for C<ev_default_init>.
3395		4565
3396	If you think you found a bug (memory leak, uninitialised data access etc.)	4566	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:	4567	extended, libev needs to realloc and move the whole array, but this
		4568	happens asymptotically rarer with higher number of elements, so O(1) might
		4569	mean that libev does a lengthy realloc operation in rare cases, but on
		4570	average it is much faster and asymptotically approaches constant time.
3398		4571
3399	==2274== definitely lost: 0 bytes in 0 blocks.	4572	=over 4
3400	==2274== possibly lost: 0 bytes in 0 blocks.
3401	==2274== still reachable: 256 bytes in 1 blocks.
3402		4573
3403	then there is no memory leak. Similarly, under some circumstances,	4574	=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		4575
3407	If you are unsure about something, feel free to contact the mailing list	4576	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	4577	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	4578	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		4579
3413	If you need, for some reason, empty reports from valgrind for your project	4580	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3414	I suggest using suppression lists.
3415		4581
		4582	That means that changing a timer costs less than removing/adding them,
		4583	as only the relative motion in the event queue has to be paid for.
		4584
		4585	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4586
		4587	These just add the watcher into an array or at the head of a list.
		4588
		4589	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4590
		4591	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4592
		4593	These watchers are stored in lists, so they need to be walked to find the
		4594	correct watcher to remove. The lists are usually short (you don't usually
		4595	have many watchers waiting for the same fd or signal: one is typical, two
		4596	is rare).
		4597
		4598	=item Finding the next timer in each loop iteration: O(1)
		4599
		4600	By virtue of using a binary or 4-heap, the next timer is always found at a
		4601	fixed position in the storage array.
		4602
		4603	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4604
		4605	A change means an I/O watcher gets started or stopped, which requires
		4606	libev to recalculate its status (and possibly tell the kernel, depending
		4607	on backend and whether C<ev_io_set> was used).
		4608
		4609	=item Activating one watcher (putting it into the pending state): O(1)
		4610
		4611	=item Priority handling: O(number_of_priorities)
		4612
		4613	Priorities are implemented by allocating some space for each
		4614	priority. When doing priority-based operations, libev usually has to
		4615	linearly search all the priorities, but starting/stopping and activating
		4616	watchers becomes O(1) with respect to priority handling.
		4617
		4618	=item Sending an ev_async: O(1)
		4619
		4620	=item Processing ev_async_send: O(number_of_async_watchers)
		4621
		4622	=item Processing signals: O(max_signal_number)
		4623
		4624	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4625	calls in the current loop iteration. Checking for async and signal events
		4626	involves iterating over all running async watchers or all signal numbers.
		4627
		4628	=back
		4629
		4630
		4631	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4632
		4633	The major version 4 introduced some minor incompatible changes to the API.
		4634
		4635	At the moment, the C<ev.h> header file tries to implement superficial
		4636	compatibility, so most programs should still compile. Those might be
		4637	removed in later versions of libev, so better update early than late.
		4638
		4639	=over 4
		4640
		4641	=item C<ev_loop_count> renamed to C<ev_iteration>
		4642
		4643	=item C<ev_loop_depth> renamed to C<ev_depth>
		4644
		4645	=item C<ev_loop_verify> renamed to C<ev_verify>
		4646
		4647	Most functions working on C<struct ev_loop> objects don't have an
		4648	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
		4649	still called C<ev_loop_fork> because it would otherwise clash with the
		4650	C<ev_fork> typedef.
		4651
		4652	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
		4653
		4654	This is a simple rename - all other watcher types use their name
		4655	as revents flag, and now C<ev_timer> does, too.
		4656
		4657	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4658	and continue to be present for the forseeable future, so this is mostly a
		4659	documentation change.
		4660
		4661	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4662
		4663	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4664	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4665	and work, but the library code will of course be larger.
		4666
		4667	=back
		4668
		4669
		4670	=head1 GLOSSARY
		4671
		4672	=over 4
		4673
		4674	=item active
		4675
		4676	A watcher is active as long as it has been started (has been attached to
		4677	an event loop) but not yet stopped (disassociated from the event loop).
		4678
		4679	=item application
		4680
		4681	In this document, an application is whatever is using libev.
		4682
		4683	=item callback
		4684
		4685	The address of a function that is called when some event has been
		4686	detected. Callbacks are being passed the event loop, the watcher that
		4687	received the event, and the actual event bitset.
		4688
		4689	=item callback invocation
		4690
		4691	The act of calling the callback associated with a watcher.
		4692
		4693	=item event
		4694
		4695	A change of state of some external event, such as data now being available
		4696	for reading on a file descriptor, time having passed or simply not having
		4697	any other events happening anymore.
		4698
		4699	In libev, events are represented as single bits (such as C<EV_READ> or
		4700	C<EV_TIMER>).
		4701
		4702	=item event library
		4703
		4704	A software package implementing an event model and loop.
		4705
		4706	=item event loop
		4707
		4708	An entity that handles and processes external events and converts them
		4709	into callback invocations.
		4710
		4711	=item event model
		4712
		4713	The model used to describe how an event loop handles and processes
		4714	watchers and events.
		4715
		4716	=item pending
		4717
		4718	A watcher is pending as soon as the corresponding event has been detected,
		4719	and stops being pending as soon as the watcher will be invoked or its
		4720	pending status is explicitly cleared by the application.
		4721
		4722	A watcher can be pending, but not active. Stopping a watcher also clears
		4723	its pending status.
		4724
		4725	=item real time
		4726
		4727	The physical time that is observed. It is apparently strictly monotonic :)
		4728
		4729	=item wall-clock time
		4730
		4731	The time and date as shown on clocks. Unlike real time, it can actually
		4732	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4733	clock.
		4734
		4735	=item watcher
		4736
		4737	A data structure that describes interest in certain events. Watchers need
		4738	to be started (attached to an event loop) before they can receive events.
		4739
		4740	=item watcher invocation
		4741
		4742	The act of calling the callback associated with a watcher.
		4743
		4744	=back
3416		4745
3417	=head1 AUTHOR	4746	=head1 AUTHOR
3418		4747
3419	Marc Lehmann <libev@schmorp.de>.	4748	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3420		4749

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