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Revision 1.157 by root, Tue May 20 23:49:41 2008 UTC vs.
Revision 1.307 by root, Thu Oct 21 02:33:08 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	Familiarity 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
…		…
155	as this indicates an incompatible change. Minor versions are usually	192	as this indicates an incompatible change. Minor versions are usually
156	compatible to older versions, so a larger minor version alone is usually	193	compatible to older versions, so a larger minor version alone is usually
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 (note, however, that this will not detect ABI mismatches :).
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. Last
		445	not least, it also refuses to work with some file descriptors which work
		446	perfectly fine with C<select> (files, many character devices...).
361		447
362	While stopping, setting and starting an I/O watcher in the same iteration	448	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	449	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	450	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	451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	452	file descriptors might not work very well if you register events for both
367		453	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		454
372	Best performance from this backend is achieved by not unregistering all	455	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.	456	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	457	i.e. keep at least one watcher active per fd at all times. Stopping and
		458	starting a watcher (without re-setting it) also usually doesn't cause
		459	extra overhead. A fork can both result in spurious notifications as well
		460	as in libev having to destroy and recreate the epoll object, which can
		461	take considerable time and thus should be avoided.
375		462
		463	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		464	faster than epoll for maybe up to a hundred file descriptors, depending on
		465	the usage. So sad.
		466
376	While nominally embeddeble in other event loops, this feature is broken in	467	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	468	all kernel versions tested so far.
		469
		470	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		471	C<EVBACKEND_POLL>.
378		472
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	473	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		474
381	Kqueue deserves special mention, as at the time of this writing, it	475	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	476	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	477	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"	478	it's completely useless). Unlike epoll, however, whose brokenness
		479	is by design, these kqueue bugs can (and eventually will) be fixed
		480	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	481	"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)	482	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	483	system like NetBSD.
388		484
389	You still can embed kqueue into a normal poll or select backend and use it	485	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	486	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.	487	the target platform). See C<ev_embed> watchers for more info.
392		488
393	It scales in the same way as the epoll backend, but the interface to the	489	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	490	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	491	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	492	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	493	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	494	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		495	cases
399		496
400	This backend usually performs well under most conditions.	497	This backend usually performs well under most conditions.
401		498
402	While nominally embeddable in other event loops, this doesn't work	499	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	500	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	501	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	502	(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	503	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	504	also broken on OS X)) and, did I mention it, using it only for sockets.
		505
		506	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		507	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		508	C<NOTE_EOF>.
408		509
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	510	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		511
411	This is not implemented yet (and might never be, unless you send me an	512	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	513	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		518
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	519	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)).	520	it's really slow, but it still scales very well (O(active_fds)).
420		521
421	Please note that solaris event ports can deliver a lot of spurious	522	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	523	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	524	blocking when no data (or space) is available.
424		525
425	While this backend scales well, it requires one system call per active	526	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	527	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	529	might perform better.
429		530
430	On the positive side, ignoring the spurious readiness notifications, this	531	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	532	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	533	in all tests and is fully embeddable, which is a rare feat among the
		534	OS-specific backends (I vastly prefer correctness over speed hacks).
		535
		536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		537	C<EVBACKEND_POLL>.
433		538
434	=item C<EVBACKEND_ALL>	539	=item C<EVBACKEND_ALL>
435		540
436	Try all backends (even potentially broken ones that wouldn't be tried	541	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	542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		544
440	It is definitely not recommended to use this flag.	545	It is definitely not recommended to use this flag.
441		546
442	=back	547	=back
443		548
444	If one or more of these are ored into the flags value, then only these	549	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	550	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.	551	here). If none are specified, all backends in C<ev_recommended_backends
		552	()> will be tried.
447		553
448	The most typical usage is like this:	554	Example: This is the most typical usage.
449		555
450	if (!ev_default_loop (0))	556	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		558
453	Restrict libev to the select and poll backends, and do not allow	559	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	560	environment settings to be taken into account:
455		561
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	562	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		563
458	Use whatever libev has to offer, but make sure that kqueue is used if	564	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	565	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):	566	private event loop and only if you know the OS supports your types of
		567	fds):
461		568
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	569	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		570
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	571	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		572
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	573	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	574	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		575
471	Note that this function I<is> thread-safe, and the recommended way to use	576	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	577	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	578	default loop in the "main" or "initial" thread.
474		579
475	Example: Try to create a event loop that uses epoll and nothing else.	580	Example: Try to create a event loop that uses epoll and nothing else.
476		581
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	583	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	584	fatal ("no epoll found here, maybe it hides under your chair");
480		585
481	=item ev_default_destroy ()	586	=item ev_default_destroy ()
482		587
483	Destroys the default loop again (frees all memory and kernel state	588	Destroys the default loop (frees all memory and kernel state etc.). None
484	etc.). None of the active event watchers will be stopped in the normal	589	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	590	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>	591	either stop all watchers cleanly yourself I<before> calling this function,
487	calling this function, or cope with the fact afterwards (which is usually	592	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	593	can just ignore the watchers and/or C<free ()> them for example).
489	for example).
490		594
491	Note that certain global state, such as signal state, will not be freed by	595	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	596	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	597	as signal and child watchers) would need to be stopped manually.
494		598
495	In general it is not advisable to call this function except in the	599	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	600	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	601	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	602	C<ev_loop_new> and C<ev_loop_destroy>.
499		603
500	=item ev_loop_destroy (loop)	604	=item ev_loop_destroy (loop)
501		605
502	Like C<ev_default_destroy>, but destroys an event loop created by an	606	Like C<ev_default_destroy>, but destroys an event loop created by an
503	earlier call to C<ev_loop_new>.	607	earlier call to C<ev_loop_new>.
…		…
509	name, you can call it anytime, but it makes most sense after forking, in	613	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	614	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	615	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.	616	functions, and it will only take effect at the next C<ev_loop> iteration.
513		617
		618	Again, you I<have> to call it on I<any> loop that you want to re-use after
		619	a fork, I<even if you do not plan to use the loop in the parent>. This is
		620	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		621	during fork.
		622
514	On the other hand, you only need to call this function in the child	623	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	624	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.	625	just fork+exec or create a new loop in the child, you don't have to call
		626	it at all.
517		627
518	The function itself is quite fast and it's usually not a problem to call	628	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	629	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>:	630	quite nicely into a call to C<pthread_atfork>:
521		631
…		…
523		633
524	=item ev_loop_fork (loop)	634	=item ev_loop_fork (loop)
525		635
526	Like C<ev_default_fork>, but acts on an event loop created by	636	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	637	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.	638	after fork that you want to re-use in the child, and how you keep track of
		639	them is entirely your own problem.
529		640
530	=item int ev_is_default_loop (loop)	641	=item int ev_is_default_loop (loop)
531		642
532	Returns true when the given loop actually is the default loop, false otherwise.	643	Returns true when the given loop is, in fact, the default loop, and false
		644	otherwise.
533		645
534	=item unsigned int ev_loop_count (loop)	646	=item unsigned int ev_iteration (loop)
535		647
536	Returns the count of loop iterations for the loop, which is identical to	648	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	649	the number of times libev did poll for new events. It starts at C<0> and
538	happily wraps around with enough iterations.	650	happily wraps around with enough iterations.
539		651
540	This value can sometimes be useful as a generation counter of sorts (it	652	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	653	"ticks" the number of loop iterations), as it roughly corresponds with
542	C<ev_prepare> and C<ev_check> calls.	654	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		655	prepare and check phases.
		656
		657	=item unsigned int ev_depth (loop)
		658
		659	Returns the number of times C<ev_loop> was entered minus the number of
		660	times C<ev_loop> was exited, in other words, the recursion depth.
		661
		662	Outside C<ev_loop>, this number is zero. In a callback, this number is
		663	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		664	in which case it is higher.
		665
		666	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		667	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		668	ungentleman behaviour unless it's really convenient.
543		669
544	=item unsigned int ev_backend (loop)	670	=item unsigned int ev_backend (loop)
545		671
546	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	672	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
547	use.	673	use.
…		…
552	received events and started processing them. This timestamp does not	678	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	679	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	680	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).	681	event occurring (or more correctly, libev finding out about it).
556		682
		683	=item ev_now_update (loop)
		684
		685	Establishes the current time by querying the kernel, updating the time
		686	returned by C<ev_now ()> in the progress. This is a costly operation and
		687	is usually done automatically within C<ev_loop ()>.
		688
		689	This function is rarely useful, but when some event callback runs for a
		690	very long time without entering the event loop, updating libev's idea of
		691	the current time is a good idea.
		692
		693	See also L<The special problem of time updates> in the C<ev_timer> section.
		694
		695	=item ev_suspend (loop)
		696
		697	=item ev_resume (loop)
		698
		699	These two functions suspend and resume a loop, for use when the loop is
		700	not used for a while and timeouts should not be processed.
		701
		702	A typical use case would be an interactive program such as a game: When
		703	the user presses C<^Z> to suspend the game and resumes it an hour later it
		704	would be best to handle timeouts as if no time had actually passed while
		705	the program was suspended. This can be achieved by calling C<ev_suspend>
		706	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		707	C<ev_resume> directly afterwards to resume timer processing.
		708
		709	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		710	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		711	will be rescheduled (that is, they will lose any events that would have
		712	occurred while suspended).
		713
		714	After calling C<ev_suspend> you B<must not> call I<any> function on the
		715	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		716	without a previous call to C<ev_suspend>.
		717
		718	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		719	event loop time (see C<ev_now_update>).
		720
557	=item ev_loop (loop, int flags)	721	=item ev_loop (loop, int flags)
558		722
559	Finally, this is it, the event handler. This function usually is called	723	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	724	after you have initialised all your watchers and you want to start
561	events.	725	handling events.
562		726
563	If the flags argument is specified as C<0>, it will not return until	727	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.	728	either no event watchers are active anymore or C<ev_unloop> was called.
565		729
566	Please note that an explicit C<ev_unloop> is usually better than	730	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	731	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	732	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	733	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.	734	of relying on its watchers stopping correctly, that is truly a thing of
		735	beauty.
571		736
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	737	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	738	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.	739	process in case there are no events and will return after one iteration of
		740	the loop.
575		741
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	742	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	743	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	744	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	745	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	746	user-registered callback will be called), and will return after one
		747	iteration of the loop.
		748
		749	This is useful if you are waiting for some external event in conjunction
		750	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	751	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.	752	usually a better approach for this kind of thing.
583		753
584	Here are the gory details of what C<ev_loop> does:	754	Here are the gory details of what C<ev_loop> does:
585		755
586	- Before the first iteration, call any pending watchers.	756	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	757	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	758	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	759	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	760	- If we have been forked, detach and recreate the kernel state
		761	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	762	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	763	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	764	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	765	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	766	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	767	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	768	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	769	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	770	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	771	- Queue all expired timers.
601	- Queue all outstanding periodics.	772	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	773	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	774	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	775	- 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	776	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	777	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	778	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	783	anymore.
613		784
614	... queue jobs here, make sure they register event watchers as long	785	... 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..)	786	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	787	ev_loop (my_loop, 0);
617	... jobs done. yeah!	788	... jobs done or somebody called unloop. yeah!
618		789
619	=item ev_unloop (loop, how)	790	=item ev_unloop (loop, how)
620		791
621	Can be used to make a call to C<ev_loop> return early (but only after it	792	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	793	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	794	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.	795	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		796
626	This "unloop state" will be cleared when entering C<ev_loop> again.	797	This "unloop state" will be cleared when entering C<ev_loop> again.
627		798
		799	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.
		800
628	=item ev_ref (loop)	801	=item ev_ref (loop)
629		802
630	=item ev_unref (loop)	803	=item ev_unref (loop)
631		804
632	Ref/unref can be used to add or remove a reference count on the event	805	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	806	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	807	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	808
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	809	This is useful when you have a watcher that you never intend to
		810	unregister, but that nevertheless should not keep C<ev_loop> from
		811	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		812	before stopping it.
		813
637	example, libev itself uses this for its internal signal pipe: It is not	814	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	815	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	816	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	817	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>	818	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,	819	before stop> (but only if the watcher wasn't active before, or was active
643	respectively).	820	before, respectively. Note also that libev might stop watchers itself
		821	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		822	in the callback).
644		823
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	824	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	825	running when nothing else is active.
647		826
648	struct ev_signal exitsig;	827	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	828	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	829	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	830	evf_unref (loop);
652		831
653	Example: For some weird reason, unregister the above signal handler again.	832	Example: For some weird reason, unregister the above signal handler again.
654		833
655	ev_ref (loop);	834	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	835	ev_signal_stop (loop, &exitsig);
657		836
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	837	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		838
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	839	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		840
662	These advanced functions influence the time that libev will spend waiting	841	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	842	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.	843	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		844	latency.
665		845
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	846	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	847	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	848	to increase efficiency of loop iterations (or to increase power-saving
		849	opportunities).
669		850
670	The background is that sometimes your program runs just fast enough to	851	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	852	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	853	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	854	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	855	overhead for the actual polling but can deliver many events at once.
675		856
676	By setting a higher I<io collect interval> you allow libev to spend more	857	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,	858	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	859	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	860	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.	861	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		862	sleep time ensures that libev will not poll for I/O events more often then
		863	once per this interval, on average.
681		864
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	865	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	866	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	867	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	868	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	869	value will not introduce any overhead in libev.
687		870
688	Many (busy) programs can usually benefit by setting the io collect	871	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	872	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	873	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>,	874	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.	875	as this approaches the timing granularity of most systems. Note that if
		876	you do transactions with the outside world and you can't increase the
		877	parallelity, then this setting will limit your transaction rate (if you
		878	need to poll once per transaction and the I/O collect interval is 0.01,
		879	then you can't do more than 100 transactions per second).
		880
		881	Setting the I<timeout collect interval> can improve the opportunity for
		882	saving power, as the program will "bundle" timer callback invocations that
		883	are "near" in time together, by delaying some, thus reducing the number of
		884	times the process sleeps and wakes up again. Another useful technique to
		885	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		886	they fire on, say, one-second boundaries only.
		887
		888	Example: we only need 0.1s timeout granularity, and we wish not to poll
		889	more often than 100 times per second:
		890
		891	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		892	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		893
		894	=item ev_invoke_pending (loop)
		895
		896	This call will simply invoke all pending watchers while resetting their
		897	pending state. Normally, C<ev_loop> does this automatically when required,
		898	but when overriding the invoke callback this call comes handy.
		899
		900	=item int ev_pending_count (loop)
		901
		902	Returns the number of pending watchers - zero indicates that no watchers
		903	are pending.
		904
		905	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		906
		907	This overrides the invoke pending functionality of the loop: Instead of
		908	invoking all pending watchers when there are any, C<ev_loop> will call
		909	this callback instead. This is useful, for example, when you want to
		910	invoke the actual watchers inside another context (another thread etc.).
		911
		912	If you want to reset the callback, use C<ev_invoke_pending> as new
		913	callback.
		914
		915	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		916
		917	Sometimes you want to share the same loop between multiple threads. This
		918	can be done relatively simply by putting mutex_lock/unlock calls around
		919	each call to a libev function.
		920
		921	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		922	wait for it to return. One way around this is to wake up the loop via
		923	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		924	and I<acquire> callbacks on the loop.
		925
		926	When set, then C<release> will be called just before the thread is
		927	suspended waiting for new events, and C<acquire> is called just
		928	afterwards.
		929
		930	Ideally, C<release> will just call your mutex_unlock function, and
		931	C<acquire> will just call the mutex_lock function again.
		932
		933	While event loop modifications are allowed between invocations of
		934	C<release> and C<acquire> (that's their only purpose after all), no
		935	modifications done will affect the event loop, i.e. adding watchers will
		936	have no effect on the set of file descriptors being watched, or the time
		937	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		938	to take note of any changes you made.
		939
		940	In theory, threads executing C<ev_loop> will be async-cancel safe between
		941	invocations of C<release> and C<acquire>.
		942
		943	See also the locking example in the C<THREADS> section later in this
		944	document.
		945
		946	=item ev_set_userdata (loop, void *data)
		947
		948	=item ev_userdata (loop)
		949
		950	Set and retrieve a single C<void *> associated with a loop. When
		951	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		952	C<0.>
		953
		954	These two functions can be used to associate arbitrary data with a loop,
		955	and are intended solely for the C<invoke_pending_cb>, C<release> and
		956	C<acquire> callbacks described above, but of course can be (ab-)used for
		957	any other purpose as well.
		958
		959	=item ev_loop_verify (loop)
		960
		961	This function only does something when C<EV_VERIFY> support has been
		962	compiled in, which is the default for non-minimal builds. It tries to go
		963	through all internal structures and checks them for validity. If anything
		964	is found to be inconsistent, it will print an error message to standard
		965	error and call C<abort ()>.
		966
		967	This can be used to catch bugs inside libev itself: under normal
		968	circumstances, this function will never abort as of course libev keeps its
		969	data structures consistent.
693		970
694	=back	971	=back
695		972
696		973
697	=head1 ANATOMY OF A WATCHER	974	=head1 ANATOMY OF A WATCHER
		975
		976	In the following description, uppercase C<TYPE> in names stands for the
		977	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		978	watchers and C<ev_io_start> for I/O watchers.
698		979
699	A watcher is a structure that you create and register to record your	980	A watcher is a structure that you create and register to record your
700	interest in some event. For instance, if you want to wait for STDIN to	981	interest in some event. For instance, if you want to wait for STDIN to
701	become readable, you would create an C<ev_io> watcher for that:	982	become readable, you would create an C<ev_io> watcher for that:
702		983
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	984	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	985	{
705	ev_io_stop (w);	986	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	987	ev_unloop (loop, EVUNLOOP_ALL);
707	}	988	}
708		989
709	struct ev_loop *loop = ev_default_loop (0);	990	struct ev_loop *loop = ev_default_loop (0);
		991
710	struct ev_io stdin_watcher;	992	ev_io stdin_watcher;
		993
711	ev_init (&stdin_watcher, my_cb);	994	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	995	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	996	ev_io_start (loop, &stdin_watcher);
		997
714	ev_loop (loop, 0);	998	ev_loop (loop, 0);
715		999
716	As you can see, you are responsible for allocating the memory for your	1000	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	1001	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	1002	stack).
		1003
		1004	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1005	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		1006
720	Each watcher structure must be initialised by a call to C<ev_init	1007	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	1008	(watcher *, callback)>, which expects a callback to be provided. This
722	callback gets invoked each time the event occurs (or, in the case of io	1009	callback gets invoked each time the event occurs (or, in the case of I/O
723	watchers, each time the event loop detects that the file descriptor given	1010	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	1011	is readable and/or writable).
725		1012
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1013	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
727	with arguments specific to this watcher type. There is also a macro	1014	macro to configure it, with arguments specific to the watcher type. There
728	to combine initialisation and setting in one call: C<< ev_<type>_init	1015	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	1016	ev_TYPE_init (watcher *, callback, ...) >>.
730		1017
731	To make the watcher actually watch out for events, you have to start it	1018	To make the watcher actually watch out for events, you have to start it
732	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1019	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
733	*) >>), and you can stop watching for events at any time by calling the	1020	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1021	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		1022
736	As long as your watcher is active (has been started but not stopped) you	1023	As long as your watcher is active (has been started but not stopped) you
737	must not touch the values stored in it. Most specifically you must never	1024	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	1025	reinitialise it or call its C<ev_TYPE_set> macro.
739		1026
740	Each and every callback receives the event loop pointer as first, the	1027	Each and every callback receives the event loop pointer as first, the
741	registered watcher structure as second, and a bitset of received events as	1028	registered watcher structure as second, and a bitset of received events as
742	third argument.	1029	third argument.
743		1030
…		…
752	=item C<EV_WRITE>	1039	=item C<EV_WRITE>
753		1040
754	The file descriptor in the C<ev_io> watcher has become readable and/or	1041	The file descriptor in the C<ev_io> watcher has become readable and/or
755	writable.	1042	writable.
756		1043
757	=item C<EV_TIMEOUT>	1044	=item C<EV_TIMER>
758		1045
759	The C<ev_timer> watcher has timed out.	1046	The C<ev_timer> watcher has timed out.
760		1047
761	=item C<EV_PERIODIC>	1048	=item C<EV_PERIODIC>
762		1049
…		…
801		1088
802	=item C<EV_ASYNC>	1089	=item C<EV_ASYNC>
803		1090
804	The given async watcher has been asynchronously notified (see C<ev_async>).	1091	The given async watcher has been asynchronously notified (see C<ev_async>).
805		1092
		1093	=item C<EV_CUSTOM>
		1094
		1095	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1096	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1097
806	=item C<EV_ERROR>	1098	=item C<EV_ERROR>
807		1099
808	An unspecified error has occured, the watcher has been stopped. This might	1100	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	1101	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	1102	ran out of memory, a file descriptor was found to be closed or any other
		1103	problem. Libev considers these application bugs.
		1104
811	problem. You best act on it by reporting the problem and somehow coping	1105	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	1106	watcher being stopped. Note that well-written programs should not receive
		1107	an error ever, so when your watcher receives it, this usually indicates a
		1108	bug in your program.
813		1109
814	Libev will usually signal a few "dummy" events together with an error,	1110	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	1111	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	1112	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	1113	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	1114	programs, though, as the fd could already be closed and reused for another
		1115	thing, so beware.
819		1116
820	=back	1117	=back
821		1118
822	=head2 GENERIC WATCHER FUNCTIONS	1119	=head2 GENERIC WATCHER FUNCTIONS
823
824	In the following description, C<TYPE> stands for the watcher type,
825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
826		1120
827	=over 4	1121	=over 4
828		1122
829	=item C<ev_init> (ev_TYPE *watcher, callback)	1123	=item C<ev_init> (ev_TYPE *watcher, callback)
830		1124
…		…
836	which rolls both calls into one.	1130	which rolls both calls into one.
837		1131
838	You can reinitialise a watcher at any time as long as it has been stopped	1132	You can reinitialise a watcher at any time as long as it has been stopped
839	(or never started) and there are no pending events outstanding.	1133	(or never started) and there are no pending events outstanding.
840		1134
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1135	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	1136	int revents)>.
843		1137
		1138	Example: Initialise an C<ev_io> watcher in two steps.
		1139
		1140	ev_io w;
		1141	ev_init (&w, my_cb);
		1142	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1143
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1144	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
845		1145
846	This macro initialises the type-specific parts of a watcher. You need to	1146	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	1147	call C<ev_init> at least once before you call this macro, but you can
848	call C<ev_TYPE_set> any number of times. You must not, however, call this	1148	call C<ev_TYPE_set> any number of times. You must not, however, call this
849	macro on a watcher that is active (it can be pending, however, which is a	1149	macro on a watcher that is active (it can be pending, however, which is a
850	difference to the C<ev_init> macro).	1150	difference to the C<ev_init> macro).
851		1151
852	Although some watcher types do not have type-specific arguments	1152	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1153	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		1154
		1155	See C<ev_init>, above, for an example.
		1156
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1157	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		1158
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1159	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	1160	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	1161	a watcher. The same limitations apply, of course.
860		1162
		1163	Example: Initialise and set an C<ev_io> watcher in one step.
		1164
		1165	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1166
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1167	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
862		1168
863	Starts (activates) the given watcher. Only active watchers will receive	1169	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1170	events. If the watcher is already active nothing will happen.
865		1171
		1172	Example: Start the C<ev_io> watcher that is being abused as example in this
		1173	whole section.
		1174
		1175	ev_io_start (EV_DEFAULT_UC, &w);
		1176
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1177	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
867		1178
868	Stops the given watcher again (if active) and clears the pending	1179	Stops the given watcher if active, and clears the pending status (whether
		1180	the watcher was active or not).
		1181
869	status. It is possible that stopped watchers are pending (for example,	1182	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1183	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1184	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	1185	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	1186	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1187
875	=item bool ev_is_active (ev_TYPE *watcher)	1188	=item bool ev_is_active (ev_TYPE *watcher)
876		1189
877	Returns a true value iff the watcher is active (i.e. it has been started	1190	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	1191	and not yet been stopped). As long as a watcher is active you must not modify
…		…
894	=item ev_cb_set (ev_TYPE *watcher, callback)	1207	=item ev_cb_set (ev_TYPE *watcher, callback)
895		1208
896	Change the callback. You can change the callback at virtually any time	1209	Change the callback. You can change the callback at virtually any time
897	(modulo threads).	1210	(modulo threads).
898		1211
899	=item ev_set_priority (ev_TYPE *watcher, priority)	1212	=item ev_set_priority (ev_TYPE *watcher, int priority)
900		1213
901	=item int ev_priority (ev_TYPE *watcher)	1214	=item int ev_priority (ev_TYPE *watcher)
902		1215
903	Set and query the priority of the watcher. The priority is a small	1216	Set and query the priority of the watcher. The priority is a small
904	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1217	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
905	(default: C<-2>). Pending watchers with higher priority will be invoked	1218	(default: C<-2>). Pending watchers with higher priority will be invoked
906	before watchers with lower priority, but priority will not keep watchers	1219	before watchers with lower priority, but priority will not keep watchers
907	from being executed (except for C<ev_idle> watchers).	1220	from being executed (except for C<ev_idle> watchers).
908		1221
909	This means that priorities are I<only> used for ordering callback
910	invocation after new events have been received. This is useful, for
911	example, to reduce latency after idling, or more often, to bind two
912	watchers on the same event and make sure one is called first.
913
914	If you need to suppress invocation when higher priority events are pending	1222	If you need to suppress invocation when higher priority events are pending
915	you need to look at C<ev_idle> watchers, which provide this functionality.	1223	you need to look at C<ev_idle> watchers, which provide this functionality.
916		1224
917	You I<must not> change the priority of a watcher as long as it is active or	1225	You I<must not> change the priority of a watcher as long as it is active or
918	pending.	1226	pending.
919		1227
		1228	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1229	fine, as long as you do not mind that the priority value you query might
		1230	or might not have been clamped to the valid range.
		1231
920	The default priority used by watchers when no priority has been set is	1232	The default priority used by watchers when no priority has been set is
921	always C<0>, which is supposed to not be too high and not be too low :).	1233	always C<0>, which is supposed to not be too high and not be too low :).
922		1234
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1235	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
924	fine, as long as you do not mind that the priority value you query might	1236	priorities.
925	or might not have been adjusted to be within valid range.
926		1237
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1238	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1239
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1240	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1241	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1242	can deal with that fact, as both are simply passed through to the
		1243	callback.
932		1244
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1245	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1246
935	If the watcher is pending, this function returns clears its pending status	1247	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1248	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1249	watcher isn't pending it does nothing and returns C<0>.
938		1250
		1251	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1252	callback to be invoked, which can be accomplished with this function.
		1253
		1254	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1255
		1256	Feeds the given event set into the event loop, as if the specified event
		1257	had happened for the specified watcher (which must be a pointer to an
		1258	initialised but not necessarily started event watcher). Obviously you must
		1259	not free the watcher as long as it has pending events.
		1260
		1261	Stopping the watcher, letting libev invoke it, or calling
		1262	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1263	not started in the first place.
		1264
		1265	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1266	functions that do not need a watcher.
		1267
939	=back	1268	=back
940		1269
941		1270
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1271	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1272
944	Each watcher has, by default, a member C<void *data> that you can change	1273	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1274	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1275	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1276	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1277	member, you can also "subclass" the watcher type and provide your own
949	data:	1278	data:
950		1279
951	struct my_io	1280	struct my_io
952	{	1281	{
953	struct ev_io io;	1282	ev_io io;
954	int otherfd;	1283	int otherfd;
955	void *somedata;	1284	void *somedata;
956	struct whatever *mostinteresting;	1285	struct whatever *mostinteresting;
957	}	1286	};
		1287
		1288	...
		1289	struct my_io w;
		1290	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1291
959	And since your callback will be called with a pointer to the watcher, you	1292	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1293	can cast it back to your own type:
961		1294
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1295	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1296	{
964	struct my_io *w = (struct my_io *)w_;	1297	struct my_io *w = (struct my_io *)w_;
965	...	1298	...
966	}	1299	}
967		1300
968	More interesting and less C-conformant ways of casting your callback type	1301	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1302	instead have been omitted.
970		1303
971	Another common scenario is having some data structure with multiple	1304	Another common scenario is to use some data structure with multiple
972	watchers:	1305	embedded watchers:
973		1306
974	struct my_biggy	1307	struct my_biggy
975	{	1308	{
976	int some_data;	1309	int some_data;
977	ev_timer t1;	1310	ev_timer t1;
978	ev_timer t2;	1311	ev_timer t2;
979	}	1312	}
980		1313
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1314	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1315	complicated: Either you store the address of your C<my_biggy> struct
		1316	in the C<data> member of the watcher (for woozies), or you need to use
		1317	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1318	programmers):
983		1319
984	#include <stddef.h>	1320	#include <stddef.h>
985		1321
986	static void	1322	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1323	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1324	{
989	struct my_biggy big = (struct my_biggy *	1325	struct my_biggy big = (struct my_biggy *)
990	(((char *)w) - offsetof (struct my_biggy, t1));	1326	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1327	}
992		1328
993	static void	1329	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1330	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1331	{
996	struct my_biggy big = (struct my_biggy *	1332	struct my_biggy big = (struct my_biggy *)
997	(((char *)w) - offsetof (struct my_biggy, t2));	1333	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1334	}
		1335
		1336	=head2 WATCHER PRIORITY MODELS
		1337
		1338	Many event loops support I<watcher priorities>, which are usually small
		1339	integers that influence the ordering of event callback invocation
		1340	between watchers in some way, all else being equal.
		1341
		1342	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1343	description for the more technical details such as the actual priority
		1344	range.
		1345
		1346	There are two common ways how these these priorities are being interpreted
		1347	by event loops:
		1348
		1349	In the more common lock-out model, higher priorities "lock out" invocation
		1350	of lower priority watchers, which means as long as higher priority
		1351	watchers receive events, lower priority watchers are not being invoked.
		1352
		1353	The less common only-for-ordering model uses priorities solely to order
		1354	callback invocation within a single event loop iteration: Higher priority
		1355	watchers are invoked before lower priority ones, but they all get invoked
		1356	before polling for new events.
		1357
		1358	Libev uses the second (only-for-ordering) model for all its watchers
		1359	except for idle watchers (which use the lock-out model).
		1360
		1361	The rationale behind this is that implementing the lock-out model for
		1362	watchers is not well supported by most kernel interfaces, and most event
		1363	libraries will just poll for the same events again and again as long as
		1364	their callbacks have not been executed, which is very inefficient in the
		1365	common case of one high-priority watcher locking out a mass of lower
		1366	priority ones.
		1367
		1368	Static (ordering) priorities are most useful when you have two or more
		1369	watchers handling the same resource: a typical usage example is having an
		1370	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1371	timeouts. Under load, data might be received while the program handles
		1372	other jobs, but since timers normally get invoked first, the timeout
		1373	handler will be executed before checking for data. In that case, giving
		1374	the timer a lower priority than the I/O watcher ensures that I/O will be
		1375	handled first even under adverse conditions (which is usually, but not
		1376	always, what you want).
		1377
		1378	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1379	will only be executed when no same or higher priority watchers have
		1380	received events, they can be used to implement the "lock-out" model when
		1381	required.
		1382
		1383	For example, to emulate how many other event libraries handle priorities,
		1384	you can associate an C<ev_idle> watcher to each such watcher, and in
		1385	the normal watcher callback, you just start the idle watcher. The real
		1386	processing is done in the idle watcher callback. This causes libev to
		1387	continuously poll and process kernel event data for the watcher, but when
		1388	the lock-out case is known to be rare (which in turn is rare :), this is
		1389	workable.
		1390
		1391	Usually, however, the lock-out model implemented that way will perform
		1392	miserably under the type of load it was designed to handle. In that case,
		1393	it might be preferable to stop the real watcher before starting the
		1394	idle watcher, so the kernel will not have to process the event in case
		1395	the actual processing will be delayed for considerable time.
		1396
		1397	Here is an example of an I/O watcher that should run at a strictly lower
		1398	priority than the default, and which should only process data when no
		1399	other events are pending:
		1400
		1401	ev_idle idle; // actual processing watcher
		1402	ev_io io; // actual event watcher
		1403
		1404	static void
		1405	io_cb (EV_P_ ev_io *w, int revents)
		1406	{
		1407	// stop the I/O watcher, we received the event, but
		1408	// are not yet ready to handle it.
		1409	ev_io_stop (EV_A_ w);
		1410
		1411	// start the idle watcher to handle the actual event.
		1412	// it will not be executed as long as other watchers
		1413	// with the default priority are receiving events.
		1414	ev_idle_start (EV_A_ &idle);
		1415	}
		1416
		1417	static void
		1418	idle_cb (EV_P_ ev_idle *w, int revents)
		1419	{
		1420	// actual processing
		1421	read (STDIN_FILENO, ...);
		1422
		1423	// have to start the I/O watcher again, as
		1424	// we have handled the event
		1425	ev_io_start (EV_P_ &io);
		1426	}
		1427
		1428	// initialisation
		1429	ev_idle_init (&idle, idle_cb);
		1430	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1431	ev_io_start (EV_DEFAULT_ &io);
		1432
		1433	In the "real" world, it might also be beneficial to start a timer, so that
		1434	low-priority connections can not be locked out forever under load. This
		1435	enables your program to keep a lower latency for important connections
		1436	during short periods of high load, while not completely locking out less
		1437	important ones.
999		1438
1000		1439
1001	=head1 WATCHER TYPES	1440	=head1 WATCHER TYPES
1002		1441
1003	This section describes each watcher in detail, but will not repeat	1442	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1466	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1467	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1468	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1469	required if you know what you are doing).
1031		1470
1032	If you must do this, then force the use of a known-to-be-good backend	1471	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1472	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1473	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1474	descriptors for which non-blocking operation makes no sense (such as
		1475	files) - libev doesn't guarantee any specific behaviour in that case.
1035		1476
1036	Another thing you have to watch out for is that it is quite easy to	1477	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readiness notifications, that is your callback might	1478	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1479	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1480	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1481	lot of those (for example Solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1482	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1483	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1484	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1485
1045	If you cannot run the fd in non-blocking mode (for example you should not	1486	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1487	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1488	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1489	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1490	does this on its own, so its quite safe to use). Some people additionally
		1491	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1492	indefinitely.
		1493
		1494	But really, best use non-blocking mode.
1050		1495
1051	=head3 The special problem of disappearing file descriptors	1496	=head3 The special problem of disappearing file descriptors
1052		1497
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1498	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1499	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1500	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1501	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1502	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1503	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1504	fact, a different file descriptor.
1060		1505
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1536	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1537	C<EVBACKEND_POLL>.
1093		1538
1094	=head3 The special problem of SIGPIPE	1539	=head3 The special problem of SIGPIPE
1095		1540
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1541	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1542	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1543	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1544	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1545
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1546	So when you encounter spurious, unexplained daemon exits, make sure you
1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1547	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104	somewhere, as that would have given you a big clue).	1548	somewhere, as that would have given you a big clue).
1105		1549
		1550	=head3 The special problem of accept()ing when you can't
		1551
		1552	Many implementations of the POSIX C<accept> function (for example,
		1553	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1554	connection from the pending queue in all error cases.
		1555
		1556	For example, larger servers often run out of file descriptors (because
		1557	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1558	rejecting the connection, leading to libev signalling readiness on
		1559	the next iteration again (the connection still exists after all), and
		1560	typically causing the program to loop at 100% CPU usage.
		1561
		1562	Unfortunately, the set of errors that cause this issue differs between
		1563	operating systems, there is usually little the app can do to remedy the
		1564	situation, and no known thread-safe method of removing the connection to
		1565	cope with overload is known (to me).
		1566
		1567	One of the easiest ways to handle this situation is to just ignore it
		1568	- when the program encounters an overload, it will just loop until the
		1569	situation is over. While this is a form of busy waiting, no OS offers an
		1570	event-based way to handle this situation, so it's the best one can do.
		1571
		1572	A better way to handle the situation is to log any errors other than
		1573	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1574	messages, and continue as usual, which at least gives the user an idea of
		1575	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1576	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1577	usage.
		1578
		1579	If your program is single-threaded, then you could also keep a dummy file
		1580	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1581	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1582	close that fd, and create a new dummy fd. This will gracefully refuse
		1583	clients under typical overload conditions.
		1584
		1585	The last way to handle it is to simply log the error and C<exit>, as
		1586	is often done with C<malloc> failures, but this results in an easy
		1587	opportunity for a DoS attack.
1106		1588
1107	=head3 Watcher-Specific Functions	1589	=head3 Watcher-Specific Functions
1108		1590
1109	=over 4	1591	=over 4
1110		1592
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1593	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1594
1113	=item ev_io_set (ev_io *, int fd, int events)	1595	=item ev_io_set (ev_io *, int fd, int events)
1114		1596
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1597	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1598	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1599	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1600
1119	=item int fd [read-only]	1601	=item int fd [read-only]
1120		1602
1121	The file descriptor being watched.	1603	The file descriptor being watched.
1122		1604
…		…
1130		1612
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1613	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1614	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1615	attempt to read a whole line in the callback.
1134		1616
1135	static void	1617	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1618	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1619	{
1138	ev_io_stop (loop, w);	1620	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1621	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1622	}
1141		1623
1142	...	1624	...
1143	struct ev_loop *loop = ev_default_init (0);	1625	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1626	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1627	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1628	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1629	ev_loop (loop, 0);
1148		1630
1149		1631
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1632	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1633
1152	Timer watchers are simple relative timers that generate an event after a	1634	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1635	given time, and optionally repeating in regular intervals after that.
1154		1636
1155	The timers are based on real time, that is, if you register an event that	1637	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to january last	1638	times out after an hour and you reset your system clock to January last
1157	year, it will still time out after (roughly) and hour. "Roughly" because	1639	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1640	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1641	monotonic clock option helps a lot here).
		1642
		1643	The callback is guaranteed to be invoked only I<after> its timeout has
		1644	passed (not I<at>, so on systems with very low-resolution clocks this
		1645	might introduce a small delay). If multiple timers become ready during the
		1646	same loop iteration then the ones with earlier time-out values are invoked
		1647	before ones of the same priority with later time-out values (but this is
		1648	no longer true when a callback calls C<ev_loop> recursively).
		1649
		1650	=head3 Be smart about timeouts
		1651
		1652	Many real-world problems involve some kind of timeout, usually for error
		1653	recovery. A typical example is an HTTP request - if the other side hangs,
		1654	you want to raise some error after a while.
		1655
		1656	What follows are some ways to handle this problem, from obvious and
		1657	inefficient to smart and efficient.
		1658
		1659	In the following, a 60 second activity timeout is assumed - a timeout that
		1660	gets reset to 60 seconds each time there is activity (e.g. each time some
		1661	data or other life sign was received).
		1662
		1663	=over 4
		1664
		1665	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1666
		1667	This is the most obvious, but not the most simple way: In the beginning,
		1668	start the watcher:
		1669
		1670	ev_timer_init (timer, callback, 60., 0.);
		1671	ev_timer_start (loop, timer);
		1672
		1673	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1674	and start it again:
		1675
		1676	ev_timer_stop (loop, timer);
		1677	ev_timer_set (timer, 60., 0.);
		1678	ev_timer_start (loop, timer);
		1679
		1680	This is relatively simple to implement, but means that each time there is
		1681	some activity, libev will first have to remove the timer from its internal
		1682	data structure and then add it again. Libev tries to be fast, but it's
		1683	still not a constant-time operation.
		1684
		1685	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1686
		1687	This is the easiest way, and involves using C<ev_timer_again> instead of
		1688	C<ev_timer_start>.
		1689
		1690	To implement this, configure an C<ev_timer> with a C<repeat> value
		1691	of C<60> and then call C<ev_timer_again> at start and each time you
		1692	successfully read or write some data. If you go into an idle state where
		1693	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1694	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1695
		1696	That means you can ignore both the C<ev_timer_start> function and the
		1697	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1698	member and C<ev_timer_again>.
		1699
		1700	At start:
		1701
		1702	ev_init (timer, callback);
		1703	timer->repeat = 60.;
		1704	ev_timer_again (loop, timer);
		1705
		1706	Each time there is some activity:
		1707
		1708	ev_timer_again (loop, timer);
		1709
		1710	It is even possible to change the time-out on the fly, regardless of
		1711	whether the watcher is active or not:
		1712
		1713	timer->repeat = 30.;
		1714	ev_timer_again (loop, timer);
		1715
		1716	This is slightly more efficient then stopping/starting the timer each time
		1717	you want to modify its timeout value, as libev does not have to completely
		1718	remove and re-insert the timer from/into its internal data structure.
		1719
		1720	It is, however, even simpler than the "obvious" way to do it.
		1721
		1722	=item 3. Let the timer time out, but then re-arm it as required.
		1723
		1724	This method is more tricky, but usually most efficient: Most timeouts are
		1725	relatively long compared to the intervals between other activity - in
		1726	our example, within 60 seconds, there are usually many I/O events with
		1727	associated activity resets.
		1728
		1729	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1730	but remember the time of last activity, and check for a real timeout only
		1731	within the callback:
		1732
		1733	ev_tstamp last_activity; // time of last activity
		1734
		1735	static void
		1736	callback (EV_P_ ev_timer *w, int revents)
		1737	{
		1738	ev_tstamp now = ev_now (EV_A);
		1739	ev_tstamp timeout = last_activity + 60.;
		1740
		1741	// if last_activity + 60. is older than now, we did time out
		1742	if (timeout < now)
		1743	{
		1744	// timeout occurred, take action
		1745	}
		1746	else
		1747	{
		1748	// callback was invoked, but there was some activity, re-arm
		1749	// the watcher to fire in last_activity + 60, which is
		1750	// guaranteed to be in the future, so "again" is positive:
		1751	w->repeat = timeout - now;
		1752	ev_timer_again (EV_A_ w);
		1753	}
		1754	}
		1755
		1756	To summarise the callback: first calculate the real timeout (defined
		1757	as "60 seconds after the last activity"), then check if that time has
		1758	been reached, which means something I<did>, in fact, time out. Otherwise
		1759	the callback was invoked too early (C<timeout> is in the future), so
		1760	re-schedule the timer to fire at that future time, to see if maybe we have
		1761	a timeout then.
		1762
		1763	Note how C<ev_timer_again> is used, taking advantage of the
		1764	C<ev_timer_again> optimisation when the timer is already running.
		1765
		1766	This scheme causes more callback invocations (about one every 60 seconds
		1767	minus half the average time between activity), but virtually no calls to
		1768	libev to change the timeout.
		1769
		1770	To start the timer, simply initialise the watcher and set C<last_activity>
		1771	to the current time (meaning we just have some activity :), then call the
		1772	callback, which will "do the right thing" and start the timer:
		1773
		1774	ev_init (timer, callback);
		1775	last_activity = ev_now (loop);
		1776	callback (loop, timer, EV_TIMER);
		1777
		1778	And when there is some activity, simply store the current time in
		1779	C<last_activity>, no libev calls at all:
		1780
		1781	last_activity = ev_now (loop);
		1782
		1783	This technique is slightly more complex, but in most cases where the
		1784	time-out is unlikely to be triggered, much more efficient.
		1785
		1786	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1787	callback :) - just change the timeout and invoke the callback, which will
		1788	fix things for you.
		1789
		1790	=item 4. Wee, just use a double-linked list for your timeouts.
		1791
		1792	If there is not one request, but many thousands (millions...), all
		1793	employing some kind of timeout with the same timeout value, then one can
		1794	do even better:
		1795
		1796	When starting the timeout, calculate the timeout value and put the timeout
		1797	at the I<end> of the list.
		1798
		1799	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1800	the list is expected to fire (for example, using the technique #3).
		1801
		1802	When there is some activity, remove the timer from the list, recalculate
		1803	the timeout, append it to the end of the list again, and make sure to
		1804	update the C<ev_timer> if it was taken from the beginning of the list.
		1805
		1806	This way, one can manage an unlimited number of timeouts in O(1) time for
		1807	starting, stopping and updating the timers, at the expense of a major
		1808	complication, and having to use a constant timeout. The constant timeout
		1809	ensures that the list stays sorted.
		1810
		1811	=back
		1812
		1813	So which method the best?
		1814
		1815	Method #2 is a simple no-brain-required solution that is adequate in most
		1816	situations. Method #3 requires a bit more thinking, but handles many cases
		1817	better, and isn't very complicated either. In most case, choosing either
		1818	one is fine, with #3 being better in typical situations.
		1819
		1820	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1821	rather complicated, but extremely efficient, something that really pays
		1822	off after the first million or so of active timers, i.e. it's usually
		1823	overkill :)
		1824
		1825	=head3 The special problem of time updates
		1826
		1827	Establishing the current time is a costly operation (it usually takes at
		1828	least two system calls): EV therefore updates its idea of the current
		1829	time only before and after C<ev_loop> collects new events, which causes a
		1830	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1831	lots of events in one iteration.
1160		1832
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1833	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1834	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1835	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1836	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1837	timeout on the current time, use something like this to adjust for this:
1166		1838
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1839	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1840
1169	The callback is guarenteed to be invoked only after its timeout has passed,	1841	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1842	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1843	()>.
		1844
		1845	=head3 The special problems of suspended animation
		1846
		1847	When you leave the server world it is quite customary to hit machines that
		1848	can suspend/hibernate - what happens to the clocks during such a suspend?
		1849
		1850	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1851	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1852	to run until the system is suspended, but they will not advance while the
		1853	system is suspended. That means, on resume, it will be as if the program
		1854	was frozen for a few seconds, but the suspend time will not be counted
		1855	towards C<ev_timer> when a monotonic clock source is used. The real time
		1856	clock advanced as expected, but if it is used as sole clocksource, then a
		1857	long suspend would be detected as a time jump by libev, and timers would
		1858	be adjusted accordingly.
		1859
		1860	I would not be surprised to see different behaviour in different between
		1861	operating systems, OS versions or even different hardware.
		1862
		1863	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1864	time jump in the monotonic clocks and the realtime clock. If the program
		1865	is suspended for a very long time, and monotonic clock sources are in use,
		1866	then you can expect C<ev_timer>s to expire as the full suspension time
		1867	will be counted towards the timers. When no monotonic clock source is in
		1868	use, then libev will again assume a timejump and adjust accordingly.
		1869
		1870	It might be beneficial for this latter case to call C<ev_suspend>
		1871	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1872	deterministic behaviour in this case (you can do nothing against
		1873	C<SIGSTOP>).
1172		1874
1173	=head3 Watcher-Specific Functions and Data Members	1875	=head3 Watcher-Specific Functions and Data Members
1174		1876
1175	=over 4	1877	=over 4
1176		1878
…		…
1195	This will act as if the timer timed out and restart it again if it is	1897	This will act as if the timer timed out and restart it again if it is
1196	repeating. The exact semantics are:	1898	repeating. The exact semantics are:
1197		1899
1198	If the timer is pending, its pending status is cleared.	1900	If the timer is pending, its pending status is cleared.
1199		1901
1200	If the timer is started but nonrepeating, stop it (as if it timed out).	1902	If the timer is started but non-repeating, stop it (as if it timed out).
1201		1903
1202	If the timer is repeating, either start it if necessary (with the	1904	If the timer is repeating, either start it if necessary (with the
1203	C<repeat> value), or reset the running timer to the C<repeat> value.	1905	C<repeat> value), or reset the running timer to the C<repeat> value.
1204		1906
1205	This sounds a bit complicated, but here is a useful and typical	1907	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1206	example: Imagine you have a tcp connection and you want a so-called idle	1908	usage example.
1207	timeout, that is, you want to be called when there have been, say, 60
1208	seconds of inactivity on the socket. The easiest way to do this is to
1209	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1210	C<ev_timer_again> each time you successfully read or write some data. If
1211	you go into an idle state where you do not expect data to travel on the
1212	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1213	automatically restart it if need be.
1214		1909
1215	That means you can ignore the C<after> value and C<ev_timer_start>	1910	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1216	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1217		1911
1218	ev_timer_init (timer, callback, 0., 5.);	1912	Returns the remaining time until a timer fires. If the timer is active,
1219	ev_timer_again (loop, timer);	1913	then this time is relative to the current event loop time, otherwise it's
1220	...	1914	the timeout value currently configured.
1221	timer->again = 17.;
1222	ev_timer_again (loop, timer);
1223	...
1224	timer->again = 10.;
1225	ev_timer_again (loop, timer);
1226		1915
1227	This is more slightly efficient then stopping/starting the timer each time	1916	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1228	you want to modify its timeout value.	1917	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1918	will return C<4>. When the timer expires and is restarted, it will return
		1919	roughly C<7> (likely slightly less as callback invocation takes some time,
		1920	too), and so on.
1229		1921
1230	=item ev_tstamp repeat [read-write]	1922	=item ev_tstamp repeat [read-write]
1231		1923
1232	The current C<repeat> value. Will be used each time the watcher times out	1924	The current C<repeat> value. Will be used each time the watcher times out
1233	or C<ev_timer_again> is called and determines the next timeout (if any),	1925	or C<ev_timer_again> is called, and determines the next timeout (if any),
1234	which is also when any modifications are taken into account.	1926	which is also when any modifications are taken into account.
1235		1927
1236	=back	1928	=back
1237		1929
1238	=head3 Examples	1930	=head3 Examples
1239		1931
1240	Example: Create a timer that fires after 60 seconds.	1932	Example: Create a timer that fires after 60 seconds.
1241		1933
1242	static void	1934	static void
1243	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1935	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1244	{	1936	{
1245	.. one minute over, w is actually stopped right here	1937	.. one minute over, w is actually stopped right here
1246	}	1938	}
1247		1939
1248	struct ev_timer mytimer;	1940	ev_timer mytimer;
1249	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1941	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1250	ev_timer_start (loop, &mytimer);	1942	ev_timer_start (loop, &mytimer);
1251		1943
1252	Example: Create a timeout timer that times out after 10 seconds of	1944	Example: Create a timeout timer that times out after 10 seconds of
1253	inactivity.	1945	inactivity.
1254		1946
1255	static void	1947	static void
1256	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1948	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1257	{	1949	{
1258	.. ten seconds without any activity	1950	.. ten seconds without any activity
1259	}	1951	}
1260		1952
1261	struct ev_timer mytimer;	1953	ev_timer mytimer;
1262	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1954	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1263	ev_timer_again (&mytimer); /* start timer */	1955	ev_timer_again (&mytimer); /* start timer */
1264	ev_loop (loop, 0);	1956	ev_loop (loop, 0);
1265		1957
1266	// and in some piece of code that gets executed on any "activity":	1958	// and in some piece of code that gets executed on any "activity":
1267	// reset the timeout to start ticking again at 10 seconds	1959	// reset the timeout to start ticking again at 10 seconds
1268	ev_timer_again (&mytimer);	1960	ev_timer_again (&mytimer);
1269		1961
1270		1962
1271	=head2 C<ev_periodic> - to cron or not to cron?	1963	=head2 C<ev_periodic> - to cron or not to cron?
1272		1964
1273	Periodic watchers are also timers of a kind, but they are very versatile	1965	Periodic watchers are also timers of a kind, but they are very versatile
1274	(and unfortunately a bit complex).	1966	(and unfortunately a bit complex).
1275		1967
1276	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1968	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1277	but on wallclock time (absolute time). You can tell a periodic watcher	1969	relative time, the physical time that passes) but on wall clock time
1278	to trigger after some specific point in time. For example, if you tell a	1970	(absolute time, the thing you can read on your calender or clock). The
1279	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1971	difference is that wall clock time can run faster or slower than real
1280	+ 10.>, that is, an absolute time not a delay) and then reset your system	1972	time, and time jumps are not uncommon (e.g. when you adjust your
1281	clock to january of the previous year, then it will take more than year	1973	wrist-watch).
1282	to trigger the event (unlike an C<ev_timer>, which would still trigger
1283	roughly 10 seconds later as it uses a relative timeout).
1284		1974
		1975	You can tell a periodic watcher to trigger after some specific point
		1976	in time: for example, if you tell a periodic watcher to trigger "in 10
		1977	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1978	not a delay) and then reset your system clock to January of the previous
		1979	year, then it will take a year or more to trigger the event (unlike an
		1980	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1981	it, as it uses a relative timeout).
		1982
1285	C<ev_periodic>s can also be used to implement vastly more complex timers,	1983	C<ev_periodic> watchers can also be used to implement vastly more complex
1286	such as triggering an event on each "midnight, local time", or other	1984	timers, such as triggering an event on each "midnight, local time", or
1287	complicated, rules.	1985	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1986	those cannot react to time jumps.
1288		1987
1289	As with timers, the callback is guarenteed to be invoked only when the	1988	As with timers, the callback is guaranteed to be invoked only when the
1290	time (C<at>) has passed, but if multiple periodic timers become ready	1989	point in time where it is supposed to trigger has passed. If multiple
1291	during the same loop iteration then order of execution is undefined.	1990	timers become ready during the same loop iteration then the ones with
		1991	earlier time-out values are invoked before ones with later time-out values
		1992	(but this is no longer true when a callback calls C<ev_loop> recursively).
1292		1993
1293	=head3 Watcher-Specific Functions and Data Members	1994	=head3 Watcher-Specific Functions and Data Members
1294		1995
1295	=over 4	1996	=over 4
1296		1997
1297	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1998	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1298		1999
1299	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2000	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1300		2001
1301	Lots of arguments, lets sort it out... There are basically three modes of	2002	Lots of arguments, let's sort it out... There are basically three modes of
1302	operation, and we will explain them from simplest to complex:	2003	operation, and we will explain them from simplest to most complex:
1303		2004
1304	=over 4	2005	=over 4
1305		2006
1306	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2007	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1307		2008
1308	In this configuration the watcher triggers an event after the wallclock	2009	In this configuration the watcher triggers an event after the wall clock
1309	time C<at> has passed and doesn't repeat. It will not adjust when a time	2010	time C<offset> has passed. It will not repeat and will not adjust when a
1310	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2011	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1311	run when the system time reaches or surpasses this time.	2012	will be stopped and invoked when the system clock reaches or surpasses
		2013	this point in time.
1312		2014
1313	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2015	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1314		2016
1315	In this mode the watcher will always be scheduled to time out at the next	2017	In this mode the watcher will always be scheduled to time out at the next
1316	C<at + N * interval> time (for some integer N, which can also be negative)	2018	C<offset + N * interval> time (for some integer N, which can also be
1317	and then repeat, regardless of any time jumps.	2019	negative) and then repeat, regardless of any time jumps. The C<offset>
		2020	argument is merely an offset into the C<interval> periods.
1318		2021
1319	This can be used to create timers that do not drift with respect to system	2022	This can be used to create timers that do not drift with respect to the
1320	time, for example, here is a C<ev_periodic> that triggers each hour, on	2023	system clock, for example, here is an C<ev_periodic> that triggers each
1321	the hour:	2024	hour, on the hour (with respect to UTC):
1322		2025
1323	ev_periodic_set (&periodic, 0., 3600., 0);	2026	ev_periodic_set (&periodic, 0., 3600., 0);
1324		2027
1325	This doesn't mean there will always be 3600 seconds in between triggers,	2028	This doesn't mean there will always be 3600 seconds in between triggers,
1326	but only that the the callback will be called when the system time shows a	2029	but only that the callback will be called when the system time shows a
1327	full hour (UTC), or more correctly, when the system time is evenly divisible	2030	full hour (UTC), or more correctly, when the system time is evenly divisible
1328	by 3600.	2031	by 3600.
1329		2032
1330	Another way to think about it (for the mathematically inclined) is that	2033	Another way to think about it (for the mathematically inclined) is that
1331	C<ev_periodic> will try to run the callback in this mode at the next possible	2034	C<ev_periodic> will try to run the callback in this mode at the next possible
1332	time where C<time = at (mod interval)>, regardless of any time jumps.	2035	time where C<time = offset (mod interval)>, regardless of any time jumps.
1333		2036
1334	For numerical stability it is preferable that the C<at> value is near	2037	For numerical stability it is preferable that the C<offset> value is near
1335	C<ev_now ()> (the current time), but there is no range requirement for	2038	C<ev_now ()> (the current time), but there is no range requirement for
1336	this value, and in fact is often specified as zero.	2039	this value, and in fact is often specified as zero.
1337		2040
		2041	Note also that there is an upper limit to how often a timer can fire (CPU
		2042	speed for example), so if C<interval> is very small then timing stability
		2043	will of course deteriorate. Libev itself tries to be exact to be about one
		2044	millisecond (if the OS supports it and the machine is fast enough).
		2045
1338	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2046	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1339		2047
1340	In this mode the values for C<interval> and C<at> are both being	2048	In this mode the values for C<interval> and C<offset> are both being
1341	ignored. Instead, each time the periodic watcher gets scheduled, the	2049	ignored. Instead, each time the periodic watcher gets scheduled, the
1342	reschedule callback will be called with the watcher as first, and the	2050	reschedule callback will be called with the watcher as first, and the
1343	current time as second argument.	2051	current time as second argument.
1344		2052
1345	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2053	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1346	ever, or make ANY event loop modifications whatsoever>.	2054	or make ANY other event loop modifications whatsoever, unless explicitly
		2055	allowed by documentation here>.
1347		2056
1348	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2057	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1349	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2058	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1350	only event loop modification you are allowed to do).	2059	only event loop modification you are allowed to do).
1351		2060
1352	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2061	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1353	*w, ev_tstamp now)>, e.g.:	2062	*w, ev_tstamp now)>, e.g.:
1354		2063
		2064	static ev_tstamp
1355	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2065	my_rescheduler (ev_periodic *w, ev_tstamp now)
1356	{	2066	{
1357	return now + 60.;	2067	return now + 60.;
1358	}	2068	}
1359		2069
1360	It must return the next time to trigger, based on the passed time value	2070	It must return the next time to trigger, based on the passed time value
…		…
1380	a different time than the last time it was called (e.g. in a crond like	2090	a different time than the last time it was called (e.g. in a crond like
1381	program when the crontabs have changed).	2091	program when the crontabs have changed).
1382		2092
1383	=item ev_tstamp ev_periodic_at (ev_periodic *)	2093	=item ev_tstamp ev_periodic_at (ev_periodic *)
1384		2094
1385	When active, returns the absolute time that the watcher is supposed to	2095	When active, returns the absolute time that the watcher is supposed
1386	trigger next.	2096	to trigger next. This is not the same as the C<offset> argument to
		2097	C<ev_periodic_set>, but indeed works even in interval and manual
		2098	rescheduling modes.
1387		2099
1388	=item ev_tstamp offset [read-write]	2100	=item ev_tstamp offset [read-write]
1389		2101
1390	When repeating, this contains the offset value, otherwise this is the	2102	When repeating, this contains the offset value, otherwise this is the
1391	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2103	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2104	although libev might modify this value for better numerical stability).
1392		2105
1393	Can be modified any time, but changes only take effect when the periodic	2106	Can be modified any time, but changes only take effect when the periodic
1394	timer fires or C<ev_periodic_again> is being called.	2107	timer fires or C<ev_periodic_again> is being called.
1395		2108
1396	=item ev_tstamp interval [read-write]	2109	=item ev_tstamp interval [read-write]
1397		2110
1398	The current interval value. Can be modified any time, but changes only	2111	The current interval value. Can be modified any time, but changes only
1399	take effect when the periodic timer fires or C<ev_periodic_again> is being	2112	take effect when the periodic timer fires or C<ev_periodic_again> is being
1400	called.	2113	called.
1401		2114
1402	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2115	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1403		2116
1404	The current reschedule callback, or C<0>, if this functionality is	2117	The current reschedule callback, or C<0>, if this functionality is
1405	switched off. Can be changed any time, but changes only take effect when	2118	switched off. Can be changed any time, but changes only take effect when
1406	the periodic timer fires or C<ev_periodic_again> is being called.	2119	the periodic timer fires or C<ev_periodic_again> is being called.
1407		2120
1408	=back	2121	=back
1409		2122
1410	=head3 Examples	2123	=head3 Examples
1411		2124
1412	Example: Call a callback every hour, or, more precisely, whenever the	2125	Example: Call a callback every hour, or, more precisely, whenever the
1413	system clock is divisible by 3600. The callback invocation times have	2126	system time is divisible by 3600. The callback invocation times have
1414	potentially a lot of jittering, but good long-term stability.	2127	potentially a lot of jitter, but good long-term stability.
1415		2128
1416	static void	2129	static void
1417	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2130	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1418	{	2131	{
1419	... its now a full hour (UTC, or TAI or whatever your clock follows)	2132	... its now a full hour (UTC, or TAI or whatever your clock follows)
1420	}	2133	}
1421		2134
1422	struct ev_periodic hourly_tick;	2135	ev_periodic hourly_tick;
1423	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2136	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1424	ev_periodic_start (loop, &hourly_tick);	2137	ev_periodic_start (loop, &hourly_tick);
1425		2138
1426	Example: The same as above, but use a reschedule callback to do it:	2139	Example: The same as above, but use a reschedule callback to do it:
1427		2140
1428	#include <math.h>	2141	#include <math.h>
1429		2142
1430	static ev_tstamp	2143	static ev_tstamp
1431	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2144	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1432	{	2145	{
1433	return fmod (now, 3600.) + 3600.;	2146	return now + (3600. - fmod (now, 3600.));
1434	}	2147	}
1435		2148
1436	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2149	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1437		2150
1438	Example: Call a callback every hour, starting now:	2151	Example: Call a callback every hour, starting now:
1439		2152
1440	struct ev_periodic hourly_tick;	2153	ev_periodic hourly_tick;
1441	ev_periodic_init (&hourly_tick, clock_cb,	2154	ev_periodic_init (&hourly_tick, clock_cb,
1442	fmod (ev_now (loop), 3600.), 3600., 0);	2155	fmod (ev_now (loop), 3600.), 3600., 0);
1443	ev_periodic_start (loop, &hourly_tick);	2156	ev_periodic_start (loop, &hourly_tick);
1444		2157
1445		2158
1446	=head2 C<ev_signal> - signal me when a signal gets signalled!	2159	=head2 C<ev_signal> - signal me when a signal gets signalled!
1447		2160
1448	Signal watchers will trigger an event when the process receives a specific	2161	Signal watchers will trigger an event when the process receives a specific
1449	signal one or more times. Even though signals are very asynchronous, libev	2162	signal one or more times. Even though signals are very asynchronous, libev
1450	will try it's best to deliver signals synchronously, i.e. as part of the	2163	will try it's best to deliver signals synchronously, i.e. as part of the
1451	normal event processing, like any other event.	2164	normal event processing, like any other event.
1452		2165
		2166	If you want signals to be delivered truly asynchronously, just use
		2167	C<sigaction> as you would do without libev and forget about sharing
		2168	the signal. You can even use C<ev_async> from a signal handler to
		2169	synchronously wake up an event loop.
		2170
1453	You can configure as many watchers as you like per signal. Only when the	2171	You can configure as many watchers as you like for the same signal, but
		2172	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2173	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2174	C<SIGINT> in both the default loop and another loop at the same time. At
		2175	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2176
1454	first watcher gets started will libev actually register a signal watcher	2177	When the first watcher gets started will libev actually register something
1455	with the kernel (thus it coexists with your own signal handlers as long	2178	with the kernel (thus it coexists with your own signal handlers as long as
1456	as you don't register any with libev). Similarly, when the last signal	2179	you don't register any with libev for the same signal).
1457	watcher for a signal is stopped libev will reset the signal handler to
1458	SIG_DFL (regardless of what it was set to before).
1459		2180
1460	If possible and supported, libev will install its handlers with	2181	If possible and supported, libev will install its handlers with
1461	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2182	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1462	interrupted. If you have a problem with syscalls getting interrupted by	2183	not be unduly interrupted. If you have a problem with system calls getting
1463	signals you can block all signals in an C<ev_check> watcher and unblock	2184	interrupted by signals you can block all signals in an C<ev_check> watcher
1464	them in an C<ev_prepare> watcher.	2185	and unblock them in an C<ev_prepare> watcher.
		2186
		2187	=head3 The special problem of inheritance over fork/execve/pthread_create
		2188
		2189	Both the signal mask (C<sigprocmask>) and the signal disposition
		2190	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2191	stopping it again), that is, libev might or might not block the signal,
		2192	and might or might not set or restore the installed signal handler.
		2193
		2194	While this does not matter for the signal disposition (libev never
		2195	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2196	C<execve>), this matters for the signal mask: many programs do not expect
		2197	certain signals to be blocked.
		2198
		2199	This means that before calling C<exec> (from the child) you should reset
		2200	the signal mask to whatever "default" you expect (all clear is a good
		2201	choice usually).
		2202
		2203	The simplest way to ensure that the signal mask is reset in the child is
		2204	to install a fork handler with C<pthread_atfork> that resets it. That will
		2205	catch fork calls done by libraries (such as the libc) as well.
		2206
		2207	In current versions of libev, the signal will not be blocked indefinitely
		2208	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2209	the window of opportunity for problems, it will not go away, as libev
		2210	I<has> to modify the signal mask, at least temporarily.
		2211
		2212	So I can't stress this enough: I<If you do not reset your signal mask when
		2213	you expect it to be empty, you have a race condition in your code>. This
		2214	is not a libev-specific thing, this is true for most event libraries.
1465		2215
1466	=head3 Watcher-Specific Functions and Data Members	2216	=head3 Watcher-Specific Functions and Data Members
1467		2217
1468	=over 4	2218	=over 4
1469		2219
…		…
1480		2230
1481	=back	2231	=back
1482		2232
1483	=head3 Examples	2233	=head3 Examples
1484		2234
1485	Example: Try to exit cleanly on SIGINT and SIGTERM.	2235	Example: Try to exit cleanly on SIGINT.
1486		2236
1487	static void	2237	static void
1488	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2238	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1489	{	2239	{
1490	ev_unloop (loop, EVUNLOOP_ALL);	2240	ev_unloop (loop, EVUNLOOP_ALL);
1491	}	2241	}
1492		2242
1493	struct ev_signal signal_watcher;	2243	ev_signal signal_watcher;
1494	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2244	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1495	ev_signal_start (loop, &sigint_cb);	2245	ev_signal_start (loop, &signal_watcher);
1496		2246
1497		2247
1498	=head2 C<ev_child> - watch out for process status changes	2248	=head2 C<ev_child> - watch out for process status changes
1499		2249
1500	Child watchers trigger when your process receives a SIGCHLD in response to	2250	Child watchers trigger when your process receives a SIGCHLD in response to
1501	some child status changes (most typically when a child of yours dies). It	2251	some child status changes (most typically when a child of yours dies or
1502	is permissible to install a child watcher I<after> the child has been	2252	exits). It is permissible to install a child watcher I<after> the child
1503	forked (which implies it might have already exited), as long as the event	2253	has been forked (which implies it might have already exited), as long
1504	loop isn't entered (or is continued from a watcher).	2254	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2255	forking and then immediately registering a watcher for the child is fine,
		2256	but forking and registering a watcher a few event loop iterations later or
		2257	in the next callback invocation is not.
1505		2258
1506	Only the default event loop is capable of handling signals, and therefore	2259	Only the default event loop is capable of handling signals, and therefore
1507	you can only rgeister child watchers in the default event loop.	2260	you can only register child watchers in the default event loop.
		2261
		2262	Due to some design glitches inside libev, child watchers will always be
		2263	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2264	libev)
1508		2265
1509	=head3 Process Interaction	2266	=head3 Process Interaction
1510		2267
1511	Libev grabs C<SIGCHLD> as soon as the default event loop is	2268	Libev grabs C<SIGCHLD> as soon as the default event loop is
1512	initialised. This is necessary to guarantee proper behaviour even if	2269	initialised. This is necessary to guarantee proper behaviour even if the
1513	the first child watcher is started after the child exits. The occurance	2270	first child watcher is started after the child exits. The occurrence
1514	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2271	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1515	synchronously as part of the event loop processing. Libev always reaps all	2272	synchronously as part of the event loop processing. Libev always reaps all
1516	children, even ones not watched.	2273	children, even ones not watched.
1517		2274
1518	=head3 Overriding the Built-In Processing	2275	=head3 Overriding the Built-In Processing
…		…
1522	handler, you can override it easily by installing your own handler for	2279	handler, you can override it easily by installing your own handler for
1523	C<SIGCHLD> after initialising the default loop, and making sure the	2280	C<SIGCHLD> after initialising the default loop, and making sure the
1524	default loop never gets destroyed. You are encouraged, however, to use an	2281	default loop never gets destroyed. You are encouraged, however, to use an
1525	event-based approach to child reaping and thus use libev's support for	2282	event-based approach to child reaping and thus use libev's support for
1526	that, so other libev users can use C<ev_child> watchers freely.	2283	that, so other libev users can use C<ev_child> watchers freely.
		2284
		2285	=head3 Stopping the Child Watcher
		2286
		2287	Currently, the child watcher never gets stopped, even when the
		2288	child terminates, so normally one needs to stop the watcher in the
		2289	callback. Future versions of libev might stop the watcher automatically
		2290	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2291	problem).
1527		2292
1528	=head3 Watcher-Specific Functions and Data Members	2293	=head3 Watcher-Specific Functions and Data Members
1529		2294
1530	=over 4	2295	=over 4
1531		2296
…		…
1560	=head3 Examples	2325	=head3 Examples
1561		2326
1562	Example: C<fork()> a new process and install a child handler to wait for	2327	Example: C<fork()> a new process and install a child handler to wait for
1563	its completion.	2328	its completion.
1564		2329
1565	ev_child cw;	2330	ev_child cw;
1566		2331
1567	static void	2332	static void
1568	child_cb (EV_P_ struct ev_child *w, int revents)	2333	child_cb (EV_P_ ev_child *w, int revents)
1569	{	2334	{
1570	ev_child_stop (EV_A_ w);	2335	ev_child_stop (EV_A_ w);
1571	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2336	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1572	}	2337	}
1573		2338
1574	pid_t pid = fork ();	2339	pid_t pid = fork ();
1575		2340
1576	if (pid < 0)	2341	if (pid < 0)
1577	// error	2342	// error
1578	else if (pid == 0)	2343	else if (pid == 0)
1579	{	2344	{
1580	// the forked child executes here	2345	// the forked child executes here
1581	exit (1);	2346	exit (1);
1582	}	2347	}
1583	else	2348	else
1584	{	2349	{
1585	ev_child_init (&cw, child_cb, pid, 0);	2350	ev_child_init (&cw, child_cb, pid, 0);
1586	ev_child_start (EV_DEFAULT_ &cw);	2351	ev_child_start (EV_DEFAULT_ &cw);
1587	}	2352	}
1588		2353
1589		2354
1590	=head2 C<ev_stat> - did the file attributes just change?	2355	=head2 C<ev_stat> - did the file attributes just change?
1591		2356
1592	This watches a filesystem path for attribute changes. That is, it calls	2357	This watches a file system path for attribute changes. That is, it calls
1593	C<stat> regularly (or when the OS says it changed) and sees if it changed	2358	C<stat> on that path in regular intervals (or when the OS says it changed)
1594	compared to the last time, invoking the callback if it did.	2359	and sees if it changed compared to the last time, invoking the callback if
		2360	it did.
1595		2361
1596	The path does not need to exist: changing from "path exists" to "path does	2362	The path does not need to exist: changing from "path exists" to "path does
1597	not exist" is a status change like any other. The condition "path does	2363	not exist" is a status change like any other. The condition "path does not
1598	not exist" is signified by the C<st_nlink> field being zero (which is	2364	exist" (or more correctly "path cannot be stat'ed") is signified by the
1599	otherwise always forced to be at least one) and all the other fields of	2365	C<st_nlink> field being zero (which is otherwise always forced to be at
1600	the stat buffer having unspecified contents.	2366	least one) and all the other fields of the stat buffer having unspecified
		2367	contents.
1601		2368
1602	The path I<should> be absolute and I<must not> end in a slash. If it is	2369	The path I<must not> end in a slash or contain special components such as
		2370	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1603	relative and your working directory changes, the behaviour is undefined.	2371	your working directory changes, then the behaviour is undefined.
1604		2372
1605	Since there is no standard to do this, the portable implementation simply	2373	Since there is no portable change notification interface available, the
1606	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2374	portable implementation simply calls C<stat(2)> regularly on the path
1607	can specify a recommended polling interval for this case. If you specify	2375	to see if it changed somehow. You can specify a recommended polling
1608	a polling interval of C<0> (highly recommended!) then a I<suitable,	2376	interval for this case. If you specify a polling interval of C<0> (highly
1609	unspecified default> value will be used (which you can expect to be around	2377	recommended!) then a I<suitable, unspecified default> value will be used
1610	five seconds, although this might change dynamically). Libev will also	2378	(which you can expect to be around five seconds, although this might
1611	impose a minimum interval which is currently around C<0.1>, but thats	2379	change dynamically). Libev will also impose a minimum interval which is
1612	usually overkill.	2380	currently around C<0.1>, but that's usually overkill.
1613		2381
1614	This watcher type is not meant for massive numbers of stat watchers,	2382	This watcher type is not meant for massive numbers of stat watchers,
1615	as even with OS-supported change notifications, this can be	2383	as even with OS-supported change notifications, this can be
1616	resource-intensive.	2384	resource-intensive.
1617		2385
1618	At the time of this writing, only the Linux inotify interface is	2386	At the time of this writing, the only OS-specific interface implemented
1619	implemented (implementing kqueue support is left as an exercise for the	2387	is the Linux inotify interface (implementing kqueue support is left as an
1620	reader, note, however, that the author sees no way of implementing ev_stat	2388	exercise for the reader. Note, however, that the author sees no way of
1621	semantics with kqueue). Inotify will be used to give hints only and should	2389	implementing C<ev_stat> semantics with kqueue, except as a hint).
1622	not change the semantics of C<ev_stat> watchers, which means that libev
1623	sometimes needs to fall back to regular polling again even with inotify,
1624	but changes are usually detected immediately, and if the file exists there
1625	will be no polling.
1626		2390
1627	=head3 ABI Issues (Largefile Support)	2391	=head3 ABI Issues (Largefile Support)
1628		2392
1629	Libev by default (unless the user overrides this) uses the default	2393	Libev by default (unless the user overrides this) uses the default
1630	compilation environment, which means that on systems with optionally	2394	compilation environment, which means that on systems with large file
1631	disabled large file support, you get the 32 bit version of the stat	2395	support disabled by default, you get the 32 bit version of the stat
1632	structure. When using the library from programs that change the ABI to	2396	structure. When using the library from programs that change the ABI to
1633	use 64 bit file offsets the programs will fail. In that case you have to	2397	use 64 bit file offsets the programs will fail. In that case you have to
1634	compile libev with the same flags to get binary compatibility. This is	2398	compile libev with the same flags to get binary compatibility. This is
1635	obviously the case with any flags that change the ABI, but the problem is	2399	obviously the case with any flags that change the ABI, but the problem is
1636	most noticably with ev_stat and largefile support.	2400	most noticeably displayed with ev_stat and large file support.
1637		2401
1638	=head3 Inotify	2402	The solution for this is to lobby your distribution maker to make large
		2403	file interfaces available by default (as e.g. FreeBSD does) and not
		2404	optional. Libev cannot simply switch on large file support because it has
		2405	to exchange stat structures with application programs compiled using the
		2406	default compilation environment.
1639		2407
		2408	=head3 Inotify and Kqueue
		2409
1640	When C<inotify (7)> support has been compiled into libev (generally only	2410	When C<inotify (7)> support has been compiled into libev and present at
1641	available on Linux) and present at runtime, it will be used to speed up	2411	runtime, it will be used to speed up change detection where possible. The
1642	change detection where possible. The inotify descriptor will be created lazily	2412	inotify descriptor will be created lazily when the first C<ev_stat>
1643	when the first C<ev_stat> watcher is being started.	2413	watcher is being started.
1644		2414
1645	Inotify presence does not change the semantics of C<ev_stat> watchers	2415	Inotify presence does not change the semantics of C<ev_stat> watchers
1646	except that changes might be detected earlier, and in some cases, to avoid	2416	except that changes might be detected earlier, and in some cases, to avoid
1647	making regular C<stat> calls. Even in the presence of inotify support	2417	making regular C<stat> calls. Even in the presence of inotify support
1648	there are many cases where libev has to resort to regular C<stat> polling.	2418	there are many cases where libev has to resort to regular C<stat> polling,
		2419	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2420	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2421	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2422	xfs are fully working) libev usually gets away without polling.
1649		2423
1650	(There is no support for kqueue, as apparently it cannot be used to	2424	There is no support for kqueue, as apparently it cannot be used to
1651	implement this functionality, due to the requirement of having a file	2425	implement this functionality, due to the requirement of having a file
1652	descriptor open on the object at all times).	2426	descriptor open on the object at all times, and detecting renames, unlinks
		2427	etc. is difficult.
		2428
		2429	=head3 C<stat ()> is a synchronous operation
		2430
		2431	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2432	the process. The exception are C<ev_stat> watchers - those call C<stat
		2433	()>, which is a synchronous operation.
		2434
		2435	For local paths, this usually doesn't matter: unless the system is very
		2436	busy or the intervals between stat's are large, a stat call will be fast,
		2437	as the path data is usually in memory already (except when starting the
		2438	watcher).
		2439
		2440	For networked file systems, calling C<stat ()> can block an indefinite
		2441	time due to network issues, and even under good conditions, a stat call
		2442	often takes multiple milliseconds.
		2443
		2444	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2445	paths, although this is fully supported by libev.
1653		2446
1654	=head3 The special problem of stat time resolution	2447	=head3 The special problem of stat time resolution
1655		2448
1656	The C<stat ()> syscall only supports full-second resolution portably, and	2449	The C<stat ()> system call only supports full-second resolution portably,
1657	even on systems where the resolution is higher, many filesystems still	2450	and even on systems where the resolution is higher, most file systems
1658	only support whole seconds.	2451	still only support whole seconds.
1659		2452
1660	That means that, if the time is the only thing that changes, you can	2453	That means that, if the time is the only thing that changes, you can
1661	easily miss updates: on the first update, C<ev_stat> detects a change and	2454	easily miss updates: on the first update, C<ev_stat> detects a change and
1662	calls your callback, which does something. When there is another update	2455	calls your callback, which does something. When there is another update
1663	within the same second, C<ev_stat> will be unable to detect it as the stat	2456	within the same second, C<ev_stat> will be unable to detect unless the
1664	data does not change.	2457	stat data does change in other ways (e.g. file size).
1665		2458
1666	The solution to this is to delay acting on a change for slightly more	2459	The solution to this is to delay acting on a change for slightly more
1667	than a second (or till slightly after the next full second boundary), using	2460	than a second (or till slightly after the next full second boundary), using
1668	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2461	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1669	ev_timer_again (loop, w)>).	2462	ev_timer_again (loop, w)>).
…		…
1689	C<path>. The C<interval> is a hint on how quickly a change is expected to	2482	C<path>. The C<interval> is a hint on how quickly a change is expected to
1690	be detected and should normally be specified as C<0> to let libev choose	2483	be detected and should normally be specified as C<0> to let libev choose
1691	a suitable value. The memory pointed to by C<path> must point to the same	2484	a suitable value. The memory pointed to by C<path> must point to the same
1692	path for as long as the watcher is active.	2485	path for as long as the watcher is active.
1693		2486
1694	The callback will receive C<EV_STAT> when a change was detected, relative	2487	The callback will receive an C<EV_STAT> event when a change was detected,
1695	to the attributes at the time the watcher was started (or the last change	2488	relative to the attributes at the time the watcher was started (or the
1696	was detected).	2489	last change was detected).
1697		2490
1698	=item ev_stat_stat (loop, ev_stat *)	2491	=item ev_stat_stat (loop, ev_stat *)
1699		2492
1700	Updates the stat buffer immediately with new values. If you change the	2493	Updates the stat buffer immediately with new values. If you change the
1701	watched path in your callback, you could call this function to avoid	2494	watched path in your callback, you could call this function to avoid
…		…
1722		2515
1723	The specified interval.	2516	The specified interval.
1724		2517
1725	=item const char *path [read-only]	2518	=item const char *path [read-only]
1726		2519
1727	The filesystem path that is being watched.	2520	The file system path that is being watched.
1728		2521
1729	=back	2522	=back
1730		2523
1731	=head3 Examples	2524	=head3 Examples
1732		2525
1733	Example: Watch C</etc/passwd> for attribute changes.	2526	Example: Watch C</etc/passwd> for attribute changes.
1734		2527
1735	static void	2528	static void
1736	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2529	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1737	{	2530	{
1738	/* /etc/passwd changed in some way */	2531	/* /etc/passwd changed in some way */
1739	if (w->attr.st_nlink)	2532	if (w->attr.st_nlink)
1740	{	2533	{
1741	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2534	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1742	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2535	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1743	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2536	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1744	}	2537	}
1745	else	2538	else
1746	/* you shalt not abuse printf for puts */	2539	/* you shalt not abuse printf for puts */
1747	puts ("wow, /etc/passwd is not there, expect problems. "	2540	puts ("wow, /etc/passwd is not there, expect problems. "
1748	"if this is windows, they already arrived\n");	2541	"if this is windows, they already arrived\n");
1749	}	2542	}
1750		2543
1751	...	2544	...
1752	ev_stat passwd;	2545	ev_stat passwd;
1753		2546
1754	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2547	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1755	ev_stat_start (loop, &passwd);	2548	ev_stat_start (loop, &passwd);
1756		2549
1757	Example: Like above, but additionally use a one-second delay so we do not	2550	Example: Like above, but additionally use a one-second delay so we do not
1758	miss updates (however, frequent updates will delay processing, too, so	2551	miss updates (however, frequent updates will delay processing, too, so
1759	one might do the work both on C<ev_stat> callback invocation I<and> on	2552	one might do the work both on C<ev_stat> callback invocation I<and> on
1760	C<ev_timer> callback invocation).	2553	C<ev_timer> callback invocation).
1761		2554
1762	static ev_stat passwd;	2555	static ev_stat passwd;
1763	static ev_timer timer;	2556	static ev_timer timer;
1764		2557
1765	static void	2558	static void
1766	timer_cb (EV_P_ ev_timer *w, int revents)	2559	timer_cb (EV_P_ ev_timer *w, int revents)
1767	{	2560	{
1768	ev_timer_stop (EV_A_ w);	2561	ev_timer_stop (EV_A_ w);
1769		2562
1770	/* now it's one second after the most recent passwd change */	2563	/* now it's one second after the most recent passwd change */
1771	}	2564	}
1772		2565
1773	static void	2566	static void
1774	stat_cb (EV_P_ ev_stat *w, int revents)	2567	stat_cb (EV_P_ ev_stat *w, int revents)
1775	{	2568	{
1776	/* reset the one-second timer */	2569	/* reset the one-second timer */
1777	ev_timer_again (EV_A_ &timer);	2570	ev_timer_again (EV_A_ &timer);
1778	}	2571	}
1779		2572
1780	...	2573	...
1781	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2574	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1782	ev_stat_start (loop, &passwd);	2575	ev_stat_start (loop, &passwd);
1783	ev_timer_init (&timer, timer_cb, 0., 1.02);	2576	ev_timer_init (&timer, timer_cb, 0., 1.02);
1784		2577
1785		2578
1786	=head2 C<ev_idle> - when you've got nothing better to do...	2579	=head2 C<ev_idle> - when you've got nothing better to do...
1787		2580
1788	Idle watchers trigger events when no other events of the same or higher	2581	Idle watchers trigger events when no other events of the same or higher
1789	priority are pending (prepare, check and other idle watchers do not	2582	priority are pending (prepare, check and other idle watchers do not count
1790	count).	2583	as receiving "events").
1791		2584
1792	That is, as long as your process is busy handling sockets or timeouts	2585	That is, as long as your process is busy handling sockets or timeouts
1793	(or even signals, imagine) of the same or higher priority it will not be	2586	(or even signals, imagine) of the same or higher priority it will not be
1794	triggered. But when your process is idle (or only lower-priority watchers	2587	triggered. But when your process is idle (or only lower-priority watchers
1795	are pending), the idle watchers are being called once per event loop	2588	are pending), the idle watchers are being called once per event loop
…		…
1806		2599
1807	=head3 Watcher-Specific Functions and Data Members	2600	=head3 Watcher-Specific Functions and Data Members
1808		2601
1809	=over 4	2602	=over 4
1810		2603
1811	=item ev_idle_init (ev_signal *, callback)	2604	=item ev_idle_init (ev_idle *, callback)
1812		2605
1813	Initialises and configures the idle watcher - it has no parameters of any	2606	Initialises and configures the idle watcher - it has no parameters of any
1814	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2607	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1815	believe me.	2608	believe me.
1816		2609
…		…
1819	=head3 Examples	2612	=head3 Examples
1820		2613
1821	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2614	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1822	callback, free it. Also, use no error checking, as usual.	2615	callback, free it. Also, use no error checking, as usual.
1823		2616
1824	static void	2617	static void
1825	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2618	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1826	{	2619	{
1827	free (w);	2620	free (w);
1828	// now do something you wanted to do when the program has	2621	// now do something you wanted to do when the program has
1829	// no longer anything immediate to do.	2622	// no longer anything immediate to do.
1830	}	2623	}
1831		2624
1832	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2625	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1833	ev_idle_init (idle_watcher, idle_cb);	2626	ev_idle_init (idle_watcher, idle_cb);
1834	ev_idle_start (loop, idle_cb);	2627	ev_idle_start (loop, idle_watcher);
1835		2628
1836		2629
1837	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2630	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1838		2631
1839	Prepare and check watchers are usually (but not always) used in tandem:	2632	Prepare and check watchers are usually (but not always) used in pairs:
1840	prepare watchers get invoked before the process blocks and check watchers	2633	prepare watchers get invoked before the process blocks and check watchers
1841	afterwards.	2634	afterwards.
1842		2635
1843	You I<must not> call C<ev_loop> or similar functions that enter	2636	You I<must not> call C<ev_loop> or similar functions that enter
1844	the current event loop from either C<ev_prepare> or C<ev_check>	2637	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1847	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2640	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1848	C<ev_check> so if you have one watcher of each kind they will always be	2641	C<ev_check> so if you have one watcher of each kind they will always be
1849	called in pairs bracketing the blocking call.	2642	called in pairs bracketing the blocking call.
1850		2643
1851	Their main purpose is to integrate other event mechanisms into libev and	2644	Their main purpose is to integrate other event mechanisms into libev and
1852	their use is somewhat advanced. This could be used, for example, to track	2645	their use is somewhat advanced. They could be used, for example, to track
1853	variable changes, implement your own watchers, integrate net-snmp or a	2646	variable changes, implement your own watchers, integrate net-snmp or a
1854	coroutine library and lots more. They are also occasionally useful if	2647	coroutine library and lots more. They are also occasionally useful if
1855	you cache some data and want to flush it before blocking (for example,	2648	you cache some data and want to flush it before blocking (for example,
1856	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2649	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1857	watcher).	2650	watcher).
1858		2651
1859	This is done by examining in each prepare call which file descriptors need	2652	This is done by examining in each prepare call which file descriptors
1860	to be watched by the other library, registering C<ev_io> watchers for	2653	need to be watched by the other library, registering C<ev_io> watchers
1861	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2654	for them and starting an C<ev_timer> watcher for any timeouts (many
1862	provide just this functionality). Then, in the check watcher you check for	2655	libraries provide exactly this functionality). Then, in the check watcher,
1863	any events that occured (by checking the pending status of all watchers	2656	you check for any events that occurred (by checking the pending status
1864	and stopping them) and call back into the library. The I/O and timer	2657	of all watchers and stopping them) and call back into the library. The
1865	callbacks will never actually be called (but must be valid nevertheless,	2658	I/O and timer callbacks will never actually be called (but must be valid
1866	because you never know, you know?).	2659	nevertheless, because you never know, you know?).
1867		2660
1868	As another example, the Perl Coro module uses these hooks to integrate	2661	As another example, the Perl Coro module uses these hooks to integrate
1869	coroutines into libev programs, by yielding to other active coroutines	2662	coroutines into libev programs, by yielding to other active coroutines
1870	during each prepare and only letting the process block if no coroutines	2663	during each prepare and only letting the process block if no coroutines
1871	are ready to run (it's actually more complicated: it only runs coroutines	2664	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1874	loop from blocking if lower-priority coroutines are active, thus mapping	2667	loop from blocking if lower-priority coroutines are active, thus mapping
1875	low-priority coroutines to idle/background tasks).	2668	low-priority coroutines to idle/background tasks).
1876		2669
1877	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2670	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1878	priority, to ensure that they are being run before any other watchers	2671	priority, to ensure that they are being run before any other watchers
		2672	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2673
1879	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2674	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1880	too) should not activate ("feed") events into libev. While libev fully	2675	activate ("feed") events into libev. While libev fully supports this, they
1881	supports this, they might get executed before other C<ev_check> watchers	2676	might get executed before other C<ev_check> watchers did their job. As
1882	did their job. As C<ev_check> watchers are often used to embed other	2677	C<ev_check> watchers are often used to embed other (non-libev) event
1883	(non-libev) event loops those other event loops might be in an unusable	2678	loops those other event loops might be in an unusable state until their
1884	state until their C<ev_check> watcher ran (always remind yourself to	2679	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1885	coexist peacefully with others).	2680	others).
1886		2681
1887	=head3 Watcher-Specific Functions and Data Members	2682	=head3 Watcher-Specific Functions and Data Members
1888		2683
1889	=over 4	2684	=over 4
1890		2685
…		…
1892		2687
1893	=item ev_check_init (ev_check *, callback)	2688	=item ev_check_init (ev_check *, callback)
1894		2689
1895	Initialises and configures the prepare or check watcher - they have no	2690	Initialises and configures the prepare or check watcher - they have no
1896	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2691	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1897	macros, but using them is utterly, utterly and completely pointless.	2692	macros, but using them is utterly, utterly, utterly and completely
		2693	pointless.
1898		2694
1899	=back	2695	=back
1900		2696
1901	=head3 Examples	2697	=head3 Examples
1902		2698
…		…
1911	and in a check watcher, destroy them and call into libadns. What follows	2707	and in a check watcher, destroy them and call into libadns. What follows
1912	is pseudo-code only of course. This requires you to either use a low	2708	is pseudo-code only of course. This requires you to either use a low
1913	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2709	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1914	the callbacks for the IO/timeout watchers might not have been called yet.	2710	the callbacks for the IO/timeout watchers might not have been called yet.
1915		2711
1916	static ev_io iow [nfd];	2712	static ev_io iow [nfd];
1917	static ev_timer tw;	2713	static ev_timer tw;
1918		2714
1919	static void	2715	static void
1920	io_cb (ev_loop *loop, ev_io *w, int revents)	2716	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1921	{	2717	{
1922	}	2718	}
1923		2719
1924	// create io watchers for each fd and a timer before blocking	2720	// create io watchers for each fd and a timer before blocking
1925	static void	2721	static void
1926	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2722	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1927	{	2723	{
1928	int timeout = 3600000;	2724	int timeout = 3600000;
1929	struct pollfd fds [nfd];	2725	struct pollfd fds [nfd];
1930	// actual code will need to loop here and realloc etc.	2726	// actual code will need to loop here and realloc etc.
1931	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2727	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1932		2728
1933	/* the callback is illegal, but won't be called as we stop during check */	2729	/* the callback is illegal, but won't be called as we stop during check */
1934	ev_timer_init (&tw, 0, timeout * 1e-3);	2730	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1935	ev_timer_start (loop, &tw);	2731	ev_timer_start (loop, &tw);
1936		2732
1937	// create one ev_io per pollfd	2733	// create one ev_io per pollfd
1938	for (int i = 0; i < nfd; ++i)	2734	for (int i = 0; i < nfd; ++i)
1939	{	2735	{
1940	ev_io_init (iow + i, io_cb, fds [i].fd,	2736	ev_io_init (iow + i, io_cb, fds [i].fd,
1941	((fds [i].events & POLLIN ? EV_READ : 0)	2737	((fds [i].events & POLLIN ? EV_READ : 0)
1942	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2738	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1943		2739
1944	fds [i].revents = 0;	2740	fds [i].revents = 0;
1945	ev_io_start (loop, iow + i);	2741	ev_io_start (loop, iow + i);
1946	}	2742	}
1947	}	2743	}
1948		2744
1949	// stop all watchers after blocking	2745	// stop all watchers after blocking
1950	static void	2746	static void
1951	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2747	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1952	{	2748	{
1953	ev_timer_stop (loop, &tw);	2749	ev_timer_stop (loop, &tw);
1954		2750
1955	for (int i = 0; i < nfd; ++i)	2751	for (int i = 0; i < nfd; ++i)
1956	{	2752	{
1957	// set the relevant poll flags	2753	// set the relevant poll flags
1958	// could also call adns_processreadable etc. here	2754	// could also call adns_processreadable etc. here
1959	struct pollfd *fd = fds + i;	2755	struct pollfd *fd = fds + i;
1960	int revents = ev_clear_pending (iow + i);	2756	int revents = ev_clear_pending (iow + i);
1961	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2757	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1962	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2758	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1963		2759
1964	// now stop the watcher	2760	// now stop the watcher
1965	ev_io_stop (loop, iow + i);	2761	ev_io_stop (loop, iow + i);
1966	}	2762	}
1967		2763
1968	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2764	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1969	}	2765	}
1970		2766
1971	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2767	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1972	in the prepare watcher and would dispose of the check watcher.	2768	in the prepare watcher and would dispose of the check watcher.
1973		2769
1974	Method 3: If the module to be embedded supports explicit event	2770	Method 3: If the module to be embedded supports explicit event
1975	notification (adns does), you can also make use of the actual watcher	2771	notification (libadns does), you can also make use of the actual watcher
1976	callbacks, and only destroy/create the watchers in the prepare watcher.	2772	callbacks, and only destroy/create the watchers in the prepare watcher.
1977		2773
1978	static void	2774	static void
1979	timer_cb (EV_P_ ev_timer *w, int revents)	2775	timer_cb (EV_P_ ev_timer *w, int revents)
1980	{	2776	{
1981	adns_state ads = (adns_state)w->data;	2777	adns_state ads = (adns_state)w->data;
1982	update_now (EV_A);	2778	update_now (EV_A);
1983		2779
1984	adns_processtimeouts (ads, &tv_now);	2780	adns_processtimeouts (ads, &tv_now);
1985	}	2781	}
1986		2782
1987	static void	2783	static void
1988	io_cb (EV_P_ ev_io *w, int revents)	2784	io_cb (EV_P_ ev_io *w, int revents)
1989	{	2785	{
1990	adns_state ads = (adns_state)w->data;	2786	adns_state ads = (adns_state)w->data;
1991	update_now (EV_A);	2787	update_now (EV_A);
1992		2788
1993	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2789	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1994	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2790	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1995	}	2791	}
1996		2792
1997	// do not ever call adns_afterpoll	2793	// do not ever call adns_afterpoll
1998		2794
1999	Method 4: Do not use a prepare or check watcher because the module you	2795	Method 4: Do not use a prepare or check watcher because the module you
2000	want to embed is too inflexible to support it. Instead, youc na override	2796	want to embed is not flexible enough to support it. Instead, you can
2001	their poll function. The drawback with this solution is that the main	2797	override their poll function. The drawback with this solution is that the
2002	loop is now no longer controllable by EV. The C<Glib::EV> module does	2798	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2003	this.	2799	this approach, effectively embedding EV as a client into the horrible
		2800	libglib event loop.
2004		2801
2005	static gint	2802	static gint
2006	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2803	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2007	{	2804	{
2008	int got_events = 0;	2805	int got_events = 0;
2009		2806
2010	for (n = 0; n < nfds; ++n)	2807	for (n = 0; n < nfds; ++n)
2011	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2808	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2012		2809
2013	if (timeout >= 0)	2810	if (timeout >= 0)
2014	// create/start timer	2811	// create/start timer
2015		2812
2016	// poll	2813	// poll
2017	ev_loop (EV_A_ 0);	2814	ev_loop (EV_A_ 0);
2018		2815
2019	// stop timer again	2816	// stop timer again
2020	if (timeout >= 0)	2817	if (timeout >= 0)
2021	ev_timer_stop (EV_A_ &to);	2818	ev_timer_stop (EV_A_ &to);
2022		2819
2023	// stop io watchers again - their callbacks should have set	2820	// stop io watchers again - their callbacks should have set
2024	for (n = 0; n < nfds; ++n)	2821	for (n = 0; n < nfds; ++n)
2025	ev_io_stop (EV_A_ iow [n]);	2822	ev_io_stop (EV_A_ iow [n]);
2026		2823
2027	return got_events;	2824	return got_events;
2028	}	2825	}
2029		2826
2030		2827
2031	=head2 C<ev_embed> - when one backend isn't enough...	2828	=head2 C<ev_embed> - when one backend isn't enough...
2032		2829
2033	This is a rather advanced watcher type that lets you embed one event loop	2830	This is a rather advanced watcher type that lets you embed one event loop
…		…
2039	prioritise I/O.	2836	prioritise I/O.
2040		2837
2041	As an example for a bug workaround, the kqueue backend might only support	2838	As an example for a bug workaround, the kqueue backend might only support
2042	sockets on some platform, so it is unusable as generic backend, but you	2839	sockets on some platform, so it is unusable as generic backend, but you
2043	still want to make use of it because you have many sockets and it scales	2840	still want to make use of it because you have many sockets and it scales
2044	so nicely. In this case, you would create a kqueue-based loop and embed it	2841	so nicely. In this case, you would create a kqueue-based loop and embed
2045	into your default loop (which might use e.g. poll). Overall operation will	2842	it into your default loop (which might use e.g. poll). Overall operation
2046	be a bit slower because first libev has to poll and then call kevent, but	2843	will be a bit slower because first libev has to call C<poll> and then
2047	at least you can use both at what they are best.	2844	C<kevent>, but at least you can use both mechanisms for what they are
		2845	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2048		2846
2049	As for prioritising I/O: rarely you have the case where some fds have	2847	As for prioritising I/O: under rare circumstances you have the case where
2050	to be watched and handled very quickly (with low latency), and even	2848	some fds have to be watched and handled very quickly (with low latency),
2051	priorities and idle watchers might have too much overhead. In this case	2849	and even priorities and idle watchers might have too much overhead. In
2052	you would put all the high priority stuff in one loop and all the rest in	2850	this case you would put all the high priority stuff in one loop and all
2053	a second one, and embed the second one in the first.	2851	the rest in a second one, and embed the second one in the first.
2054		2852
2055	As long as the watcher is active, the callback will be invoked every time	2853	As long as the watcher is active, the callback will be invoked every
2056	there might be events pending in the embedded loop. The callback must then	2854	time there might be events pending in the embedded loop. The callback
2057	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2855	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2058	their callbacks (you could also start an idle watcher to give the embedded	2856	sweep and invoke their callbacks (the callback doesn't need to invoke the
2059	loop strictly lower priority for example). You can also set the callback	2857	C<ev_embed_sweep> function directly, it could also start an idle watcher
2060	to C<0>, in which case the embed watcher will automatically execute the	2858	to give the embedded loop strictly lower priority for example).
2061	embedded loop sweep.
2062		2859
2063	As long as the watcher is started it will automatically handle events. The	2860	You can also set the callback to C<0>, in which case the embed watcher
2064	callback will be invoked whenever some events have been handled. You can	2861	will automatically execute the embedded loop sweep whenever necessary.
2065	set the callback to C<0> to avoid having to specify one if you are not
2066	interested in that.
2067		2862
2068	Also, there have not currently been made special provisions for forking:	2863	Fork detection will be handled transparently while the C<ev_embed> watcher
2069	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2864	is active, i.e., the embedded loop will automatically be forked when the
2070	but you will also have to stop and restart any C<ev_embed> watchers	2865	embedding loop forks. In other cases, the user is responsible for calling
2071	yourself.	2866	C<ev_loop_fork> on the embedded loop.
2072		2867
2073	Unfortunately, not all backends are embeddable, only the ones returned by	2868	Unfortunately, not all backends are embeddable: only the ones returned by
2074	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2869	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2075	portable one.	2870	portable one.
2076		2871
2077	So when you want to use this feature you will always have to be prepared	2872	So when you want to use this feature you will always have to be prepared
2078	that you cannot get an embeddable loop. The recommended way to get around	2873	that you cannot get an embeddable loop. The recommended way to get around
2079	this is to have a separate variables for your embeddable loop, try to	2874	this is to have a separate variables for your embeddable loop, try to
2080	create it, and if that fails, use the normal loop for everything.	2875	create it, and if that fails, use the normal loop for everything.
2081		2876
		2877	=head3 C<ev_embed> and fork
		2878
		2879	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2880	automatically be applied to the embedded loop as well, so no special
		2881	fork handling is required in that case. When the watcher is not running,
		2882	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2883	as applicable.
		2884
2082	=head3 Watcher-Specific Functions and Data Members	2885	=head3 Watcher-Specific Functions and Data Members
2083		2886
2084	=over 4	2887	=over 4
2085		2888
2086	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2889	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2089		2892
2090	Configures the watcher to embed the given loop, which must be	2893	Configures the watcher to embed the given loop, which must be
2091	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2894	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2092	invoked automatically, otherwise it is the responsibility of the callback	2895	invoked automatically, otherwise it is the responsibility of the callback
2093	to invoke it (it will continue to be called until the sweep has been done,	2896	to invoke it (it will continue to be called until the sweep has been done,
2094	if you do not want thta, you need to temporarily stop the embed watcher).	2897	if you do not want that, you need to temporarily stop the embed watcher).
2095		2898
2096	=item ev_embed_sweep (loop, ev_embed *)	2899	=item ev_embed_sweep (loop, ev_embed *)
2097		2900
2098	Make a single, non-blocking sweep over the embedded loop. This works	2901	Make a single, non-blocking sweep over the embedded loop. This works
2099	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2902	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2100	apropriate way for embedded loops.	2903	appropriate way for embedded loops.
2101		2904
2102	=item struct ev_loop *other [read-only]	2905	=item struct ev_loop *other [read-only]
2103		2906
2104	The embedded event loop.	2907	The embedded event loop.
2105		2908
…		…
2107		2910
2108	=head3 Examples	2911	=head3 Examples
2109		2912
2110	Example: Try to get an embeddable event loop and embed it into the default	2913	Example: Try to get an embeddable event loop and embed it into the default
2111	event loop. If that is not possible, use the default loop. The default	2914	event loop. If that is not possible, use the default loop. The default
2112	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2915	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2113	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2916	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2114	used).	2917	used).
2115		2918
2116	struct ev_loop *loop_hi = ev_default_init (0);	2919	struct ev_loop *loop_hi = ev_default_init (0);
2117	struct ev_loop *loop_lo = 0;	2920	struct ev_loop *loop_lo = 0;
2118	struct ev_embed embed;	2921	ev_embed embed;
2119		2922
2120	// see if there is a chance of getting one that works	2923	// see if there is a chance of getting one that works
2121	// (remember that a flags value of 0 means autodetection)	2924	// (remember that a flags value of 0 means autodetection)
2122	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2925	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2123	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2926	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2124	: 0;	2927	: 0;
2125		2928
2126	// if we got one, then embed it, otherwise default to loop_hi	2929	// if we got one, then embed it, otherwise default to loop_hi
2127	if (loop_lo)	2930	if (loop_lo)
2128	{	2931	{
2129	ev_embed_init (&embed, 0, loop_lo);	2932	ev_embed_init (&embed, 0, loop_lo);
2130	ev_embed_start (loop_hi, &embed);	2933	ev_embed_start (loop_hi, &embed);
2131	}	2934	}
2132	else	2935	else
2133	loop_lo = loop_hi;	2936	loop_lo = loop_hi;
2134		2937
2135	Example: Check if kqueue is available but not recommended and create	2938	Example: Check if kqueue is available but not recommended and create
2136	a kqueue backend for use with sockets (which usually work with any	2939	a kqueue backend for use with sockets (which usually work with any
2137	kqueue implementation). Store the kqueue/socket-only event loop in	2940	kqueue implementation). Store the kqueue/socket-only event loop in
2138	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2941	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2139		2942
2140	struct ev_loop *loop = ev_default_init (0);	2943	struct ev_loop *loop = ev_default_init (0);
2141	struct ev_loop *loop_socket = 0;	2944	struct ev_loop *loop_socket = 0;
2142	struct ev_embed embed;	2945	ev_embed embed;
2143		2946
2144	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2947	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2145	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2948	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2146	{	2949	{
2147	ev_embed_init (&embed, 0, loop_socket);	2950	ev_embed_init (&embed, 0, loop_socket);
2148	ev_embed_start (loop, &embed);	2951	ev_embed_start (loop, &embed);
2149	}	2952	}
2150		2953
2151	if (!loop_socket)	2954	if (!loop_socket)
2152	loop_socket = loop;	2955	loop_socket = loop;
2153		2956
2154	// now use loop_socket for all sockets, and loop for everything else	2957	// now use loop_socket for all sockets, and loop for everything else
2155		2958
2156		2959
2157	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2960	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2158		2961
2159	Fork watchers are called when a C<fork ()> was detected (usually because	2962	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2162	event loop blocks next and before C<ev_check> watchers are being called,	2965	event loop blocks next and before C<ev_check> watchers are being called,
2163	and only in the child after the fork. If whoever good citizen calling	2966	and only in the child after the fork. If whoever good citizen calling
2164	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2967	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2165	handlers will be invoked, too, of course.	2968	handlers will be invoked, too, of course.
2166		2969
		2970	=head3 The special problem of life after fork - how is it possible?
		2971
		2972	Most uses of C<fork()> consist of forking, then some simple calls to set
		2973	up/change the process environment, followed by a call to C<exec()>. This
		2974	sequence should be handled by libev without any problems.
		2975
		2976	This changes when the application actually wants to do event handling
		2977	in the child, or both parent in child, in effect "continuing" after the
		2978	fork.
		2979
		2980	The default mode of operation (for libev, with application help to detect
		2981	forks) is to duplicate all the state in the child, as would be expected
		2982	when I<either> the parent I<or> the child process continues.
		2983
		2984	When both processes want to continue using libev, then this is usually the
		2985	wrong result. In that case, usually one process (typically the parent) is
		2986	supposed to continue with all watchers in place as before, while the other
		2987	process typically wants to start fresh, i.e. without any active watchers.
		2988
		2989	The cleanest and most efficient way to achieve that with libev is to
		2990	simply create a new event loop, which of course will be "empty", and
		2991	use that for new watchers. This has the advantage of not touching more
		2992	memory than necessary, and thus avoiding the copy-on-write, and the
		2993	disadvantage of having to use multiple event loops (which do not support
		2994	signal watchers).
		2995
		2996	When this is not possible, or you want to use the default loop for
		2997	other reasons, then in the process that wants to start "fresh", call
		2998	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2999	the default loop will "orphan" (not stop) all registered watchers, so you
		3000	have to be careful not to execute code that modifies those watchers. Note
		3001	also that in that case, you have to re-register any signal watchers.
		3002
2167	=head3 Watcher-Specific Functions and Data Members	3003	=head3 Watcher-Specific Functions and Data Members
2168		3004
2169	=over 4	3005	=over 4
2170		3006
2171	=item ev_fork_init (ev_signal *, callback)	3007	=item ev_fork_init (ev_signal *, callback)
…		…
2175	believe me.	3011	believe me.
2176		3012
2177	=back	3013	=back
2178		3014
2179		3015
2180	=head2 C<ev_async> - how to wake up another event loop	3016	=head2 C<ev_async> - how to wake up an event loop
2181		3017
2182	In general, you cannot use an C<ev_loop> from multiple threads or other	3018	In general, you cannot use an C<ev_loop> from multiple threads or other
2183	asynchronous sources such as signal handlers (as opposed to multiple event	3019	asynchronous sources such as signal handlers (as opposed to multiple event
2184	loops - those are of course safe to use in different threads).	3020	loops - those are of course safe to use in different threads).
2185		3021
2186	Sometimes, however, you need to wake up another event loop you do not	3022	Sometimes, however, you need to wake up an event loop you do not control,
2187	control, for example because it belongs to another thread. This is what	3023	for example because it belongs to another thread. This is what C<ev_async>
2188	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3024	watchers do: as long as the C<ev_async> watcher is active, you can signal
2189	can signal it by calling C<ev_async_send>, which is thread- and signal	3025	it by calling C<ev_async_send>, which is thread- and signal safe.
2190	safe.
2191		3026
2192	This functionality is very similar to C<ev_signal> watchers, as signals,	3027	This functionality is very similar to C<ev_signal> watchers, as signals,
2193	too, are asynchronous in nature, and signals, too, will be compressed	3028	too, are asynchronous in nature, and signals, too, will be compressed
2194	(i.e. the number of callback invocations may be less than the number of	3029	(i.e. the number of callback invocations may be less than the number of
2195	C<ev_async_sent> calls).	3030	C<ev_async_sent> calls).
…		…
2200	=head3 Queueing	3035	=head3 Queueing
2201		3036
2202	C<ev_async> does not support queueing of data in any way. The reason	3037	C<ev_async> does not support queueing of data in any way. The reason
2203	is that the author does not know of a simple (or any) algorithm for a	3038	is that the author does not know of a simple (or any) algorithm for a
2204	multiple-writer-single-reader queue that works in all cases and doesn't	3039	multiple-writer-single-reader queue that works in all cases and doesn't
2205	need elaborate support such as pthreads.	3040	need elaborate support such as pthreads or unportable memory access
		3041	semantics.
2206		3042
2207	That means that if you want to queue data, you have to provide your own	3043	That means that if you want to queue data, you have to provide your own
2208	queue. But at least I can tell you would implement locking around your	3044	queue. But at least I can tell you how to implement locking around your
2209	queue:	3045	queue:
2210		3046
2211	=over 4	3047	=over 4
2212		3048
2213	=item queueing from a signal handler context	3049	=item queueing from a signal handler context
2214		3050
2215	To implement race-free queueing, you simply add to the queue in the signal	3051	To implement race-free queueing, you simply add to the queue in the signal
2216	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3052	handler but you block the signal handler in the watcher callback. Here is
2217	some fictitiuous SIGUSR1 handler:	3053	an example that does that for some fictitious SIGUSR1 handler:
2218		3054
2219	static ev_async mysig;	3055	static ev_async mysig;
2220		3056
2221	static void	3057	static void
2222	sigusr1_handler (void)	3058	sigusr1_handler (void)
…		…
2288	=over 4	3124	=over 4
2289		3125
2290	=item ev_async_init (ev_async *, callback)	3126	=item ev_async_init (ev_async *, callback)
2291		3127
2292	Initialises and configures the async watcher - it has no parameters of any	3128	Initialises and configures the async watcher - it has no parameters of any
2293	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3129	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2294	believe me.	3130	trust me.
2295		3131
2296	=item ev_async_send (loop, ev_async *)	3132	=item ev_async_send (loop, ev_async *)
2297		3133
2298	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3134	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2299	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3135	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2300	C<ev_feed_event>, this call is safe to do in other threads, signal or	3136	C<ev_feed_event>, this call is safe to do from other threads, signal or
2301	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3137	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2302	section below on what exactly this means).	3138	section below on what exactly this means).
2303		3139
		3140	Note that, as with other watchers in libev, multiple events might get
		3141	compressed into a single callback invocation (another way to look at this
		3142	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3143	reset when the event loop detects that).
		3144
2304	This call incurs the overhead of a syscall only once per loop iteration,	3145	This call incurs the overhead of a system call only once per event loop
2305	so while the overhead might be noticable, it doesn't apply to repeated	3146	iteration, so while the overhead might be noticeable, it doesn't apply to
2306	calls to C<ev_async_send>.	3147	repeated calls to C<ev_async_send> for the same event loop.
2307		3148
2308	=item bool = ev_async_pending (ev_async *)	3149	=item bool = ev_async_pending (ev_async *)
2309		3150
2310	Returns a non-zero value when C<ev_async_send> has been called on the	3151	Returns a non-zero value when C<ev_async_send> has been called on the
2311	watcher but the event has not yet been processed (or even noted) by the	3152	watcher but the event has not yet been processed (or even noted) by the
2312	event loop.	3153	event loop.
2313		3154
2314	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3155	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2315	the loop iterates next and checks for the watcher to have become active,	3156	the loop iterates next and checks for the watcher to have become active,
2316	it will reset the flag again. C<ev_async_pending> can be used to very	3157	it will reset the flag again. C<ev_async_pending> can be used to very
2317	quickly check wether invoking the loop might be a good idea.	3158	quickly check whether invoking the loop might be a good idea.
2318		3159
2319	Not that this does I<not> check wether the watcher itself is pending, only	3160	Not that this does I<not> check whether the watcher itself is pending,
2320	wether it has been requested to make this watcher pending.	3161	only whether it has been requested to make this watcher pending: there
		3162	is a time window between the event loop checking and resetting the async
		3163	notification, and the callback being invoked.
2321		3164
2322	=back	3165	=back
2323		3166
2324		3167
2325	=head1 OTHER FUNCTIONS	3168	=head1 OTHER FUNCTIONS
…		…
2329	=over 4	3172	=over 4
2330		3173
2331	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3174	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2332		3175
2333	This function combines a simple timer and an I/O watcher, calls your	3176	This function combines a simple timer and an I/O watcher, calls your
2334	callback on whichever event happens first and automatically stop both	3177	callback on whichever event happens first and automatically stops both
2335	watchers. This is useful if you want to wait for a single event on an fd	3178	watchers. This is useful if you want to wait for a single event on an fd
2336	or timeout without having to allocate/configure/start/stop/free one or	3179	or timeout without having to allocate/configure/start/stop/free one or
2337	more watchers yourself.	3180	more watchers yourself.
2338		3181
2339	If C<fd> is less than 0, then no I/O watcher will be started and events	3182	If C<fd> is less than 0, then no I/O watcher will be started and the
2340	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3183	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2341	C<events> set will be craeted and started.	3184	the given C<fd> and C<events> set will be created and started.
2342		3185
2343	If C<timeout> is less than 0, then no timeout watcher will be	3186	If C<timeout> is less than 0, then no timeout watcher will be
2344	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3187	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2345	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3188	repeat = 0) will be started. C<0> is a valid timeout.
2346	dubious value.
2347		3189
2348	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3190	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2349	passed an C<revents> set like normal event callbacks (a combination of	3191	passed an C<revents> set like normal event callbacks (a combination of
2350	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3192	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2351	value passed to C<ev_once>:	3193	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3194	a timeout and an io event at the same time - you probably should give io
		3195	events precedence.
2352		3196
		3197	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3198
2353	static void stdin_ready (int revents, void *arg)	3199	static void stdin_ready (int revents, void *arg)
2354	{	3200	{
2355	if (revents & EV_TIMEOUT)
2356	/* doh, nothing entered */;
2357	else if (revents & EV_READ)	3201	if (revents & EV_READ)
2358	/* stdin might have data for us, joy! */;	3202	/* stdin might have data for us, joy! */;
		3203	else if (revents & EV_TIMER)
		3204	/* doh, nothing entered */;
2359	}	3205	}
2360		3206
2361	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3207	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2362		3208
2363	=item ev_feed_event (ev_loop *, watcher *, int revents)
2364
2365	Feeds the given event set into the event loop, as if the specified event
2366	had happened for the specified watcher (which must be a pointer to an
2367	initialised but not necessarily started event watcher).
2368
2369	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3209	=item ev_feed_fd_event (loop, int fd, int revents)
2370		3210
2371	Feed an event on the given fd, as if a file descriptor backend detected	3211	Feed an event on the given fd, as if a file descriptor backend detected
2372	the given events it.	3212	the given events it.
2373		3213
2374	=item ev_feed_signal_event (ev_loop *loop, int signum)	3214	=item ev_feed_signal_event (loop, int signum)
2375		3215
2376	Feed an event as if the given signal occured (C<loop> must be the default	3216	Feed an event as if the given signal occurred (C<loop> must be the default
2377	loop!).	3217	loop!).
2378		3218
2379	=back	3219	=back
2380		3220
2381		3221
…		…
2410	=back	3250	=back
2411		3251
2412	=head1 C++ SUPPORT	3252	=head1 C++ SUPPORT
2413		3253
2414	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3254	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2415	you to use some convinience methods to start/stop watchers and also change	3255	you to use some convenience methods to start/stop watchers and also change
2416	the callback model to a model using method callbacks on objects.	3256	the callback model to a model using method callbacks on objects.
2417		3257
2418	To use it,	3258	To use it,
2419		3259
2420	#include <ev++.h>	3260	#include <ev++.h>
2421		3261
2422	This automatically includes F<ev.h> and puts all of its definitions (many	3262	This automatically includes F<ev.h> and puts all of its definitions (many
2423	of them macros) into the global namespace. All C++ specific things are	3263	of them macros) into the global namespace. All C++ specific things are
2424	put into the C<ev> namespace. It should support all the same embedding	3264	put into the C<ev> namespace. It should support all the same embedding
2425	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3265	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2459		3299
2460	=over 4	3300	=over 4
2461		3301
2462	=item ev::TYPE::TYPE ()	3302	=item ev::TYPE::TYPE ()
2463		3303
2464	=item ev::TYPE::TYPE (struct ev_loop *)	3304	=item ev::TYPE::TYPE (loop)
2465		3305
2466	=item ev::TYPE::~TYPE	3306	=item ev::TYPE::~TYPE
2467		3307
2468	The constructor (optionally) takes an event loop to associate the watcher	3308	The constructor (optionally) takes an event loop to associate the watcher
2469	with. If it is omitted, it will use C<EV_DEFAULT>.	3309	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2492	your compiler is good :), then the method will be fully inlined into the	3332	your compiler is good :), then the method will be fully inlined into the
2493	thunking function, making it as fast as a direct C callback.	3333	thunking function, making it as fast as a direct C callback.
2494		3334
2495	Example: simple class declaration and watcher initialisation	3335	Example: simple class declaration and watcher initialisation
2496		3336
2497	struct myclass	3337	struct myclass
2498	{	3338	{
2499	void io_cb (ev::io &w, int revents) { }	3339	void io_cb (ev::io &w, int revents) { }
2500	}	3340	}
2501		3341
2502	myclass obj;	3342	myclass obj;
2503	ev::io iow;	3343	ev::io iow;
2504	iow.set <myclass, &myclass::io_cb> (&obj);	3344	iow.set <myclass, &myclass::io_cb> (&obj);
		3345
		3346	=item w->set (object *)
		3347
		3348	This is a variation of a method callback - leaving out the method to call
		3349	will default the method to C<operator ()>, which makes it possible to use
		3350	functor objects without having to manually specify the C<operator ()> all
		3351	the time. Incidentally, you can then also leave out the template argument
		3352	list.
		3353
		3354	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3355	int revents)>.
		3356
		3357	See the method-C<set> above for more details.
		3358
		3359	Example: use a functor object as callback.
		3360
		3361	struct myfunctor
		3362	{
		3363	void operator() (ev::io &w, int revents)
		3364	{
		3365	...
		3366	}
		3367	}
		3368
		3369	myfunctor f;
		3370
		3371	ev::io w;
		3372	w.set (&f);
2505		3373
2506	=item w->set<function> (void *data = 0)	3374	=item w->set<function> (void *data = 0)
2507		3375
2508	Also sets a callback, but uses a static method or plain function as	3376	Also sets a callback, but uses a static method or plain function as
2509	callback. The optional C<data> argument will be stored in the watcher's	3377	callback. The optional C<data> argument will be stored in the watcher's
…		…
2511		3379
2512	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3380	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2513		3381
2514	See the method-C<set> above for more details.	3382	See the method-C<set> above for more details.
2515		3383
2516	Example:	3384	Example: Use a plain function as callback.
2517		3385
2518	static void io_cb (ev::io &w, int revents) { }	3386	static void io_cb (ev::io &w, int revents) { }
2519	iow.set <io_cb> ();	3387	iow.set <io_cb> ();
2520		3388
2521	=item w->set (struct ev_loop *)	3389	=item w->set (loop)
2522		3390
2523	Associates a different C<struct ev_loop> with this watcher. You can only	3391	Associates a different C<struct ev_loop> with this watcher. You can only
2524	do this when the watcher is inactive (and not pending either).	3392	do this when the watcher is inactive (and not pending either).
2525		3393
2526	=item w->set ([args])	3394	=item w->set ([arguments])
2527		3395
2528	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3396	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2529	called at least once. Unlike the C counterpart, an active watcher gets	3397	method or a suitable start method must be called at least once. Unlike the
2530	automatically stopped and restarted when reconfiguring it with this	3398	C counterpart, an active watcher gets automatically stopped and restarted
2531	method.	3399	when reconfiguring it with this method.
2532		3400
2533	=item w->start ()	3401	=item w->start ()
2534		3402
2535	Starts the watcher. Note that there is no C<loop> argument, as the	3403	Starts the watcher. Note that there is no C<loop> argument, as the
2536	constructor already stores the event loop.	3404	constructor already stores the event loop.
2537		3405
		3406	=item w->start ([arguments])
		3407
		3408	Instead of calling C<set> and C<start> methods separately, it is often
		3409	convenient to wrap them in one call. Uses the same type of arguments as
		3410	the configure C<set> method of the watcher.
		3411
2538	=item w->stop ()	3412	=item w->stop ()
2539		3413
2540	Stops the watcher if it is active. Again, no C<loop> argument.	3414	Stops the watcher if it is active. Again, no C<loop> argument.
2541		3415
2542	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3416	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2554		3428
2555	=back	3429	=back
2556		3430
2557	=back	3431	=back
2558		3432
2559	Example: Define a class with an IO and idle watcher, start one of them in	3433	Example: Define a class with two I/O and idle watchers, start the I/O
2560	the constructor.	3434	watchers in the constructor.
2561		3435
2562	class myclass	3436	class myclass
2563	{	3437	{
2564	ev::io io; void io_cb (ev::io &w, int revents);	3438	ev::io io ; void io_cb (ev::io &w, int revents);
		3439	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2565	ev:idle idle void idle_cb (ev::idle &w, int revents);	3440	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2566		3441
2567	myclass (int fd)	3442	myclass (int fd)
2568	{	3443	{
2569	io .set <myclass, &myclass::io_cb > (this);	3444	io .set <myclass, &myclass::io_cb > (this);
		3445	io2 .set <myclass, &myclass::io2_cb > (this);
2570	idle.set <myclass, &myclass::idle_cb> (this);	3446	idle.set <myclass, &myclass::idle_cb> (this);
2571		3447
2572	io.start (fd, ev::READ);	3448	io.set (fd, ev::WRITE); // configure the watcher
		3449	io.start (); // start it whenever convenient
		3450
		3451	io2.start (fd, ev::READ); // set + start in one call
2573	}	3452	}
2574	};	3453	};
2575		3454
2576		3455
2577	=head1 OTHER LANGUAGE BINDINGS	3456	=head1 OTHER LANGUAGE BINDINGS
2578		3457
2579	Libev does not offer other language bindings itself, but bindings for a	3458	Libev does not offer other language bindings itself, but bindings for a
2580	numbe rof languages exist in the form of third-party packages. If you know	3459	number of languages exist in the form of third-party packages. If you know
2581	any interesting language binding in addition to the ones listed here, drop	3460	any interesting language binding in addition to the ones listed here, drop
2582	me a note.	3461	me a note.
2583		3462
2584	=over 4	3463	=over 4
2585		3464
2586	=item Perl	3465	=item Perl
2587		3466
2588	The EV module implements the full libev API and is actually used to test	3467	The EV module implements the full libev API and is actually used to test
2589	libev. EV is developed together with libev. Apart from the EV core module,	3468	libev. EV is developed together with libev. Apart from the EV core module,
2590	there are additional modules that implement libev-compatible interfaces	3469	there are additional modules that implement libev-compatible interfaces
2591	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3470	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2592	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3471	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3472	and C<EV::Glib>).
2593		3473
2594	It can be found and installed via CPAN, its homepage is found at	3474	It can be found and installed via CPAN, its homepage is at
2595	L<http://software.schmorp.de/pkg/EV>.	3475	L<http://software.schmorp.de/pkg/EV>.
2596		3476
		3477	=item Python
		3478
		3479	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3480	seems to be quite complete and well-documented.
		3481
2597	=item Ruby	3482	=item Ruby
2598		3483
2599	Tony Arcieri has written a ruby extension that offers access to a subset	3484	Tony Arcieri has written a ruby extension that offers access to a subset
2600	of the libev API and adds filehandle abstractions, asynchronous DNS and	3485	of the libev API and adds file handle abstractions, asynchronous DNS and
2601	more on top of it. It can be found via gem servers. Its homepage is at	3486	more on top of it. It can be found via gem servers. Its homepage is at
2602	L<http://rev.rubyforge.org/>.	3487	L<http://rev.rubyforge.org/>.
2603		3488
		3489	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3490	makes rev work even on mingw.
		3491
		3492	=item Haskell
		3493
		3494	A haskell binding to libev is available at
		3495	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3496
2604	=item D	3497	=item D
2605		3498
2606	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3499	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2607	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3500	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3501
		3502	=item Ocaml
		3503
		3504	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3505	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3506
		3507	=item Lua
		3508
		3509	Brian Maher has written a partial interface to libev for lua (at the
		3510	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3511	L<http://github.com/brimworks/lua-ev>.
2608		3512
2609	=back	3513	=back
2610		3514
2611		3515
2612	=head1 MACRO MAGIC	3516	=head1 MACRO MAGIC
2613		3517
2614	Libev can be compiled with a variety of options, the most fundamantal	3518	Libev can be compiled with a variety of options, the most fundamental
2615	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3519	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2616	functions and callbacks have an initial C<struct ev_loop *> argument.	3520	functions and callbacks have an initial C<struct ev_loop *> argument.
2617		3521
2618	To make it easier to write programs that cope with either variant, the	3522	To make it easier to write programs that cope with either variant, the
2619	following macros are defined:	3523	following macros are defined:
…		…
2624		3528
2625	This provides the loop I<argument> for functions, if one is required ("ev	3529	This provides the loop I<argument> for functions, if one is required ("ev
2626	loop argument"). The C<EV_A> form is used when this is the sole argument,	3530	loop argument"). The C<EV_A> form is used when this is the sole argument,
2627	C<EV_A_> is used when other arguments are following. Example:	3531	C<EV_A_> is used when other arguments are following. Example:
2628		3532
2629	ev_unref (EV_A);	3533	ev_unref (EV_A);
2630	ev_timer_add (EV_A_ watcher);	3534	ev_timer_add (EV_A_ watcher);
2631	ev_loop (EV_A_ 0);	3535	ev_loop (EV_A_ 0);
2632		3536
2633	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3537	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2634	which is often provided by the following macro.	3538	which is often provided by the following macro.
2635		3539
2636	=item C<EV_P>, C<EV_P_>	3540	=item C<EV_P>, C<EV_P_>
2637		3541
2638	This provides the loop I<parameter> for functions, if one is required ("ev	3542	This provides the loop I<parameter> for functions, if one is required ("ev
2639	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3543	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2640	C<EV_P_> is used when other parameters are following. Example:	3544	C<EV_P_> is used when other parameters are following. Example:
2641		3545
2642	// this is how ev_unref is being declared	3546	// this is how ev_unref is being declared
2643	static void ev_unref (EV_P);	3547	static void ev_unref (EV_P);
2644		3548
2645	// this is how you can declare your typical callback	3549	// this is how you can declare your typical callback
2646	static void cb (EV_P_ ev_timer *w, int revents)	3550	static void cb (EV_P_ ev_timer *w, int revents)
2647		3551
2648	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3552	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2649	suitable for use with C<EV_A>.	3553	suitable for use with C<EV_A>.
2650		3554
2651	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3555	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2667		3571
2668	Example: Declare and initialise a check watcher, utilising the above	3572	Example: Declare and initialise a check watcher, utilising the above
2669	macros so it will work regardless of whether multiple loops are supported	3573	macros so it will work regardless of whether multiple loops are supported
2670	or not.	3574	or not.
2671		3575
2672	static void	3576	static void
2673	check_cb (EV_P_ ev_timer *w, int revents)	3577	check_cb (EV_P_ ev_timer *w, int revents)
2674	{	3578	{
2675	ev_check_stop (EV_A_ w);	3579	ev_check_stop (EV_A_ w);
2676	}	3580	}
2677		3581
2678	ev_check check;	3582	ev_check check;
2679	ev_check_init (&check, check_cb);	3583	ev_check_init (&check, check_cb);
2680	ev_check_start (EV_DEFAULT_ &check);	3584	ev_check_start (EV_DEFAULT_ &check);
2681	ev_loop (EV_DEFAULT_ 0);	3585	ev_loop (EV_DEFAULT_ 0);
2682		3586
2683	=head1 EMBEDDING	3587	=head1 EMBEDDING
2684		3588
2685	Libev can (and often is) directly embedded into host	3589	Libev can (and often is) directly embedded into host
2686	applications. Examples of applications that embed it include the Deliantra	3590	applications. Examples of applications that embed it include the Deliantra
…		…
2693	libev somewhere in your source tree).	3597	libev somewhere in your source tree).
2694		3598
2695	=head2 FILESETS	3599	=head2 FILESETS
2696		3600
2697	Depending on what features you need you need to include one or more sets of files	3601	Depending on what features you need you need to include one or more sets of files
2698	in your app.	3602	in your application.
2699		3603
2700	=head3 CORE EVENT LOOP	3604	=head3 CORE EVENT LOOP
2701		3605
2702	To include only the libev core (all the C<ev_*> functions), with manual	3606	To include only the libev core (all the C<ev_*> functions), with manual
2703	configuration (no autoconf):	3607	configuration (no autoconf):
2704		3608
2705	#define EV_STANDALONE 1	3609	#define EV_STANDALONE 1
2706	#include "ev.c"	3610	#include "ev.c"
2707		3611
2708	This will automatically include F<ev.h>, too, and should be done in a	3612	This will automatically include F<ev.h>, too, and should be done in a
2709	single C source file only to provide the function implementations. To use	3613	single C source file only to provide the function implementations. To use
2710	it, do the same for F<ev.h> in all files wishing to use this API (best	3614	it, do the same for F<ev.h> in all files wishing to use this API (best
2711	done by writing a wrapper around F<ev.h> that you can include instead and	3615	done by writing a wrapper around F<ev.h> that you can include instead and
2712	where you can put other configuration options):	3616	where you can put other configuration options):
2713		3617
2714	#define EV_STANDALONE 1	3618	#define EV_STANDALONE 1
2715	#include "ev.h"	3619	#include "ev.h"
2716		3620
2717	Both header files and implementation files can be compiled with a C++	3621	Both header files and implementation files can be compiled with a C++
2718	compiler (at least, thats a stated goal, and breakage will be treated	3622	compiler (at least, that's a stated goal, and breakage will be treated
2719	as a bug).	3623	as a bug).
2720		3624
2721	You need the following files in your source tree, or in a directory	3625	You need the following files in your source tree, or in a directory
2722	in your include path (e.g. in libev/ when using -Ilibev):	3626	in your include path (e.g. in libev/ when using -Ilibev):
2723		3627
2724	ev.h	3628	ev.h
2725	ev.c	3629	ev.c
2726	ev_vars.h	3630	ev_vars.h
2727	ev_wrap.h	3631	ev_wrap.h
2728		3632
2729	ev_win32.c required on win32 platforms only	3633	ev_win32.c required on win32 platforms only
2730		3634
2731	ev_select.c only when select backend is enabled (which is enabled by default)	3635	ev_select.c only when select backend is enabled (which is enabled by default)
2732	ev_poll.c only when poll backend is enabled (disabled by default)	3636	ev_poll.c only when poll backend is enabled (disabled by default)
2733	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3637	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2734	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3638	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2735	ev_port.c only when the solaris port backend is enabled (disabled by default)	3639	ev_port.c only when the solaris port backend is enabled (disabled by default)
2736		3640
2737	F<ev.c> includes the backend files directly when enabled, so you only need	3641	F<ev.c> includes the backend files directly when enabled, so you only need
2738	to compile this single file.	3642	to compile this single file.
2739		3643
2740	=head3 LIBEVENT COMPATIBILITY API	3644	=head3 LIBEVENT COMPATIBILITY API
2741		3645
2742	To include the libevent compatibility API, also include:	3646	To include the libevent compatibility API, also include:
2743		3647
2744	#include "event.c"	3648	#include "event.c"
2745		3649
2746	in the file including F<ev.c>, and:	3650	in the file including F<ev.c>, and:
2747		3651
2748	#include "event.h"	3652	#include "event.h"
2749		3653
2750	in the files that want to use the libevent API. This also includes F<ev.h>.	3654	in the files that want to use the libevent API. This also includes F<ev.h>.
2751		3655
2752	You need the following additional files for this:	3656	You need the following additional files for this:
2753		3657
2754	event.h	3658	event.h
2755	event.c	3659	event.c
2756		3660
2757	=head3 AUTOCONF SUPPORT	3661	=head3 AUTOCONF SUPPORT
2758		3662
2759	Instead of using C<EV_STANDALONE=1> and providing your config in	3663	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2760	whatever way you want, you can also C<m4_include([libev.m4])> in your	3664	whatever way you want, you can also C<m4_include([libev.m4])> in your
2761	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3665	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2762	include F<config.h> and configure itself accordingly.	3666	include F<config.h> and configure itself accordingly.
2763		3667
2764	For this of course you need the m4 file:	3668	For this of course you need the m4 file:
2765		3669
2766	libev.m4	3670	libev.m4
2767		3671
2768	=head2 PREPROCESSOR SYMBOLS/MACROS	3672	=head2 PREPROCESSOR SYMBOLS/MACROS
2769		3673
2770	Libev can be configured via a variety of preprocessor symbols you have to	3674	Libev can be configured via a variety of preprocessor symbols you have to
2771	define before including any of its files. The default in the absense of	3675	define before including (or compiling) any of its files. The default in
2772	autoconf is noted for every option.	3676	the absence of autoconf is documented for every option.
		3677
		3678	Symbols marked with "(h)" do not change the ABI, and can have different
		3679	values when compiling libev vs. including F<ev.h>, so it is permissible
		3680	to redefine them before including F<ev.h> without breaking compatibility
		3681	to a compiled library. All other symbols change the ABI, which means all
		3682	users of libev and the libev code itself must be compiled with compatible
		3683	settings.
2773		3684
2774	=over 4	3685	=over 4
2775		3686
2776	=item EV_STANDALONE	3687	=item EV_STANDALONE (h)
2777		3688
2778	Must always be C<1> if you do not use autoconf configuration, which	3689	Must always be C<1> if you do not use autoconf configuration, which
2779	keeps libev from including F<config.h>, and it also defines dummy	3690	keeps libev from including F<config.h>, and it also defines dummy
2780	implementations for some libevent functions (such as logging, which is not	3691	implementations for some libevent functions (such as logging, which is not
2781	supported). It will also not define any of the structs usually found in	3692	supported). It will also not define any of the structs usually found in
2782	F<event.h> that are not directly supported by the libev core alone.	3693	F<event.h> that are not directly supported by the libev core alone.
2783		3694
		3695	In standalone mode, libev will still try to automatically deduce the
		3696	configuration, but has to be more conservative.
		3697
2784	=item EV_USE_MONOTONIC	3698	=item EV_USE_MONOTONIC
2785		3699
2786	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
2787	monotonic clock option at both compiletime and runtime. Otherwise no use	3701	monotonic clock option at both compile time and runtime. Otherwise no
2788	of the monotonic clock option will be attempted. If you enable this, you	3702	use of the monotonic clock option will be attempted. If you enable this,
2789	usually have to link against librt or something similar. Enabling it when	3703	you usually have to link against librt or something similar. Enabling it
2790	the functionality isn't available is safe, though, although you have	3704	when the functionality isn't available is safe, though, although you have
2791	to make sure you link against any libraries where the C<clock_gettime>	3705	to make sure you link against any libraries where the C<clock_gettime>
2792	function is hiding in (often F<-lrt>).	3706	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2793		3707
2794	=item EV_USE_REALTIME	3708	=item EV_USE_REALTIME
2795		3709
2796	If defined to be C<1>, libev will try to detect the availability of the	3710	If defined to be C<1>, libev will try to detect the availability of the
2797	realtime clock option at compiletime (and assume its availability at	3711	real-time clock option at compile time (and assume its availability
2798	runtime if successful). Otherwise no use of the realtime clock option will	3712	at runtime if successful). Otherwise no use of the real-time clock
2799	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3713	option will be attempted. This effectively replaces C<gettimeofday>
2800	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3714	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2801	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3715	correctness. See the note about libraries in the description of
		3716	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3717	C<EV_USE_CLOCK_SYSCALL>.
		3718
		3719	=item EV_USE_CLOCK_SYSCALL
		3720
		3721	If defined to be C<1>, libev will try to use a direct syscall instead
		3722	of calling the system-provided C<clock_gettime> function. This option
		3723	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3724	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3725	programs needlessly. Using a direct syscall is slightly slower (in
		3726	theory), because no optimised vdso implementation can be used, but avoids
		3727	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3728	higher, as it simplifies linking (no need for C<-lrt>).
2802		3729
2803	=item EV_USE_NANOSLEEP	3730	=item EV_USE_NANOSLEEP
2804		3731
2805	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3732	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2806	and will use it for delays. Otherwise it will use C<select ()>.	3733	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2814	2.7 or newer, otherwise disabled.	3741	2.7 or newer, otherwise disabled.
2815		3742
2816	=item EV_USE_SELECT	3743	=item EV_USE_SELECT
2817		3744
2818	If undefined or defined to be C<1>, libev will compile in support for the	3745	If undefined or defined to be C<1>, libev will compile in support for the
2819	C<select>(2) backend. No attempt at autodetection will be done: if no	3746	C<select>(2) backend. No attempt at auto-detection will be done: if no
2820	other method takes over, select will be it. Otherwise the select backend	3747	other method takes over, select will be it. Otherwise the select backend
2821	will not be compiled in.	3748	will not be compiled in.
2822		3749
2823	=item EV_SELECT_USE_FD_SET	3750	=item EV_SELECT_USE_FD_SET
2824		3751
2825	If defined to C<1>, then the select backend will use the system C<fd_set>	3752	If defined to C<1>, then the select backend will use the system C<fd_set>
2826	structure. This is useful if libev doesn't compile due to a missing	3753	structure. This is useful if libev doesn't compile due to a missing
2827	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3754	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2828	exotic systems. This usually limits the range of file descriptors to some	3755	on exotic systems. This usually limits the range of file descriptors to
2829	low limit such as 1024 or might have other limitations (winsocket only	3756	some low limit such as 1024 or might have other limitations (winsocket
2830	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3757	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2831	influence the size of the C<fd_set> used.	3758	configures the maximum size of the C<fd_set>.
2832		3759
2833	=item EV_SELECT_IS_WINSOCKET	3760	=item EV_SELECT_IS_WINSOCKET
2834		3761
2835	When defined to C<1>, the select backend will assume that	3762	When defined to C<1>, the select backend will assume that
2836	select/socket/connect etc. don't understand file descriptors but	3763	select/socket/connect etc. don't understand file descriptors but
…		…
2838	be used is the winsock select). This means that it will call	3765	be used is the winsock select). This means that it will call
2839	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3766	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2840	it is assumed that all these functions actually work on fds, even	3767	it is assumed that all these functions actually work on fds, even
2841	on win32. Should not be defined on non-win32 platforms.	3768	on win32. Should not be defined on non-win32 platforms.
2842		3769
2843	=item EV_FD_TO_WIN32_HANDLE	3770	=item EV_FD_TO_WIN32_HANDLE(fd)
2844		3771
2845	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3772	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2846	file descriptors to socket handles. When not defining this symbol (the	3773	file descriptors to socket handles. When not defining this symbol (the
2847	default), then libev will call C<_get_osfhandle>, which is usually	3774	default), then libev will call C<_get_osfhandle>, which is usually
2848	correct. In some cases, programs use their own file descriptor management,	3775	correct. In some cases, programs use their own file descriptor management,
2849	in which case they can provide this function to map fds to socket handles.	3776	in which case they can provide this function to map fds to socket handles.
		3777
		3778	=item EV_WIN32_HANDLE_TO_FD(handle)
		3779
		3780	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3781	using the standard C<_open_osfhandle> function. For programs implementing
		3782	their own fd to handle mapping, overwriting this function makes it easier
		3783	to do so. This can be done by defining this macro to an appropriate value.
		3784
		3785	=item EV_WIN32_CLOSE_FD(fd)
		3786
		3787	If programs implement their own fd to handle mapping on win32, then this
		3788	macro can be used to override the C<close> function, useful to unregister
		3789	file descriptors again. Note that the replacement function has to close
		3790	the underlying OS handle.
2850		3791
2851	=item EV_USE_POLL	3792	=item EV_USE_POLL
2852		3793
2853	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3794	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2854	backend. Otherwise it will be enabled on non-win32 platforms. It	3795	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2881	otherwise another method will be used as fallback. This is the preferred	3822	otherwise another method will be used as fallback. This is the preferred
2882	backend for Solaris 10 systems.	3823	backend for Solaris 10 systems.
2883		3824
2884	=item EV_USE_DEVPOLL	3825	=item EV_USE_DEVPOLL
2885		3826
2886	reserved for future expansion, works like the USE symbols above.	3827	Reserved for future expansion, works like the USE symbols above.
2887		3828
2888	=item EV_USE_INOTIFY	3829	=item EV_USE_INOTIFY
2889		3830
2890	If defined to be C<1>, libev will compile in support for the Linux inotify	3831	If defined to be C<1>, libev will compile in support for the Linux inotify
2891	interface to speed up C<ev_stat> watchers. Its actual availability will	3832	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2898	access is atomic with respect to other threads or signal contexts. No such	3839	access is atomic with respect to other threads or signal contexts. No such
2899	type is easily found in the C language, so you can provide your own type	3840	type is easily found in the C language, so you can provide your own type
2900	that you know is safe for your purposes. It is used both for signal handler "locking"	3841	that you know is safe for your purposes. It is used both for signal handler "locking"
2901	as well as for signal and thread safety in C<ev_async> watchers.	3842	as well as for signal and thread safety in C<ev_async> watchers.
2902		3843
2903	In the absense of this define, libev will use C<sig_atomic_t volatile>	3844	In the absence of this define, libev will use C<sig_atomic_t volatile>
2904	(from F<signal.h>), which is usually good enough on most platforms.	3845	(from F<signal.h>), which is usually good enough on most platforms.
2905		3846
2906	=item EV_H	3847	=item EV_H (h)
2907		3848
2908	The name of the F<ev.h> header file used to include it. The default if	3849	The name of the F<ev.h> header file used to include it. The default if
2909	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3850	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2910	used to virtually rename the F<ev.h> header file in case of conflicts.	3851	used to virtually rename the F<ev.h> header file in case of conflicts.
2911		3852
2912	=item EV_CONFIG_H	3853	=item EV_CONFIG_H (h)
2913		3854
2914	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3855	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2915	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3856	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2916	C<EV_H>, above.	3857	C<EV_H>, above.
2917		3858
2918	=item EV_EVENT_H	3859	=item EV_EVENT_H (h)
2919		3860
2920	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3861	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2921	of how the F<event.h> header can be found, the default is C<"event.h">.	3862	of how the F<event.h> header can be found, the default is C<"event.h">.
2922		3863
2923	=item EV_PROTOTYPES	3864	=item EV_PROTOTYPES (h)
2924		3865
2925	If defined to be C<0>, then F<ev.h> will not define any function	3866	If defined to be C<0>, then F<ev.h> will not define any function
2926	prototypes, but still define all the structs and other symbols. This is	3867	prototypes, but still define all the structs and other symbols. This is
2927	occasionally useful if you want to provide your own wrapper functions	3868	occasionally useful if you want to provide your own wrapper functions
2928	around libev functions.	3869	around libev functions.
…		…
2947	When doing priority-based operations, libev usually has to linearly search	3888	When doing priority-based operations, libev usually has to linearly search
2948	all the priorities, so having many of them (hundreds) uses a lot of space	3889	all the priorities, so having many of them (hundreds) uses a lot of space
2949	and time, so using the defaults of five priorities (-2 .. +2) is usually	3890	and time, so using the defaults of five priorities (-2 .. +2) is usually
2950	fine.	3891	fine.
2951		3892
2952	If your embedding app does not need any priorities, defining these both to	3893	If your embedding application does not need any priorities, defining these
2953	C<0> will save some memory and cpu.	3894	both to C<0> will save some memory and CPU.
2954		3895
2955	=item EV_PERIODIC_ENABLE	3896	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3897	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3898	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2956		3899
2957	If undefined or defined to be C<1>, then periodic timers are supported. If	3900	If undefined or defined to be C<1> (and the platform supports it), then
2958	defined to be C<0>, then they are not. Disabling them saves a few kB of	3901	the respective watcher type is supported. If defined to be C<0>, then it
2959	code.	3902	is not. Disabling watcher types mainly saves code size.
2960		3903
2961	=item EV_IDLE_ENABLE	3904	=item EV_FEATURES
2962
2963	If undefined or defined to be C<1>, then idle watchers are supported. If
2964	defined to be C<0>, then they are not. Disabling them saves a few kB of
2965	code.
2966
2967	=item EV_EMBED_ENABLE
2968
2969	If undefined or defined to be C<1>, then embed watchers are supported. If
2970	defined to be C<0>, then they are not.
2971
2972	=item EV_STAT_ENABLE
2973
2974	If undefined or defined to be C<1>, then stat watchers are supported. If
2975	defined to be C<0>, then they are not.
2976
2977	=item EV_FORK_ENABLE
2978
2979	If undefined or defined to be C<1>, then fork watchers are supported. If
2980	defined to be C<0>, then they are not.
2981
2982	=item EV_ASYNC_ENABLE
2983
2984	If undefined or defined to be C<1>, then async watchers are supported. If
2985	defined to be C<0>, then they are not.
2986
2987	=item EV_MINIMAL
2988		3905
2989	If you need to shave off some kilobytes of code at the expense of some	3906	If you need to shave off some kilobytes of code at the expense of some
2990	speed, define this symbol to C<1>. Currently this is used to override some	3907	speed (but with the full API), you can define this symbol to request
2991	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3908	certain subsets of functionality. The default is to enable all features
2992	much smaller 2-heap for timer management over the default 4-heap.	3909	that can be enabled on the platform.
		3910
		3911	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3912	with some broad features you want) and then selectively re-enable
		3913	additional parts you want, for example if you want everything minimal,
		3914	but multiple event loop support, async and child watchers and the poll
		3915	backend, use this:
		3916
		3917	#define EV_FEATURES 0
		3918	#define EV_MULTIPLICITY 1
		3919	#define EV_USE_POLL 1
		3920	#define EV_CHILD_ENABLE 1
		3921	#define EV_ASYNC_ENABLE 1
		3922
		3923	The actual value is a bitset, it can be a combination of the following
		3924	values:
		3925
		3926	=over 4
		3927
		3928	=item C<1> - faster/larger code
		3929
		3930	Use larger code to speed up some operations.
		3931
		3932	Currently this is used to override some inlining decisions (enlarging the
		3933	code size by roughly 30% on amd64).
		3934
		3935	When optimising for size, use of compiler flags such as C<-Os> with
		3936	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3937	assertions.
		3938
		3939	=item C<2> - faster/larger data structures
		3940
		3941	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3942	hash table sizes and so on. This will usually further increase code size
		3943	and can additionally have an effect on the size of data structures at
		3944	runtime.
		3945
		3946	=item C<4> - full API configuration
		3947
		3948	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3949	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3950
		3951	=item C<8> - full API
		3952
		3953	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3954	details on which parts of the API are still available without this
		3955	feature, and do not complain if this subset changes over time.
		3956
		3957	=item C<16> - enable all optional watcher types
		3958
		3959	Enables all optional watcher types. If you want to selectively enable
		3960	only some watcher types other than I/O and timers (e.g. prepare,
		3961	embed, async, child...) you can enable them manually by defining
		3962	C<EV_watchertype_ENABLE> to C<1> instead.
		3963
		3964	=item C<32> - enable all backends
		3965
		3966	This enables all backends - without this feature, you need to enable at
		3967	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3968
		3969	=item C<64> - enable OS-specific "helper" APIs
		3970
		3971	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3972	default.
		3973
		3974	=back
		3975
		3976	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3977	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3978	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3979	watchers, timers and monotonic clock support.
		3980
		3981	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3982	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3983	your program might be left out as well - a binary starting a timer and an
		3984	I/O watcher then might come out at only 5Kb.
		3985
		3986	=item EV_AVOID_STDIO
		3987
		3988	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3989	functions (printf, scanf, perror etc.). This will increase the code size
		3990	somewhat, but if your program doesn't otherwise depend on stdio and your
		3991	libc allows it, this avoids linking in the stdio library which is quite
		3992	big.
		3993
		3994	Note that error messages might become less precise when this option is
		3995	enabled.
		3996
		3997	=item EV_NSIG
		3998
		3999	The highest supported signal number, +1 (or, the number of
		4000	signals): Normally, libev tries to deduce the maximum number of signals
		4001	automatically, but sometimes this fails, in which case it can be
		4002	specified. Also, using a lower number than detected (C<32> should be
		4003	good for about any system in existence) can save some memory, as libev
		4004	statically allocates some 12-24 bytes per signal number.
2993		4005
2994	=item EV_PID_HASHSIZE	4006	=item EV_PID_HASHSIZE
2995		4007
2996	C<ev_child> watchers use a small hash table to distribute workload by	4008	C<ev_child> watchers use a small hash table to distribute workload by
2997	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4009	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
2998	than enough. If you need to manage thousands of children you might want to	4010	usually more than enough. If you need to manage thousands of children you
2999	increase this value (I<must> be a power of two).	4011	might want to increase this value (I<must> be a power of two).
3000		4012
3001	=item EV_INOTIFY_HASHSIZE	4013	=item EV_INOTIFY_HASHSIZE
3002		4014
3003	C<ev_stat> watchers use a small hash table to distribute workload by	4015	C<ev_stat> watchers use a small hash table to distribute workload by
3004	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4016	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3005	usually more than enough. If you need to manage thousands of C<ev_stat>	4017	disabled), usually more than enough. If you need to manage thousands of
3006	watchers you might want to increase this value (I<must> be a power of	4018	C<ev_stat> watchers you might want to increase this value (I<must> be a
3007	two).	4019	power of two).
3008		4020
3009	=item EV_USE_4HEAP	4021	=item EV_USE_4HEAP
3010		4022
3011	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
3012	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4024	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3013	to C<1>. The 4-heap uses more complicated (longer) code but has	4025	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3014	noticably faster performance with many (thousands) of watchers.	4026	faster performance with many (thousands) of watchers.
3015		4027
3016	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4028	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3017	(disabled).	4029	will be C<0>.
3018		4030
3019	=item EV_HEAP_CACHE_AT	4031	=item EV_HEAP_CACHE_AT
3020		4032
3021	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4033	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3022	timer and periodics heap, libev can cache the timestamp (I<at>) within	4034	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3023	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4035	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3024	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4036	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3025	but avoids random read accesses on heap changes. This improves performance	4037	but avoids random read accesses on heap changes. This improves performance
3026	noticably with with many (hundreds) of watchers.	4038	noticeably with many (hundreds) of watchers.
3027		4039
3028	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4040	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3029	(disabled).	4041	will be C<0>.
		4042
		4043	=item EV_VERIFY
		4044
		4045	Controls how much internal verification (see C<ev_loop_verify ()>) will
		4046	be done: If set to C<0>, no internal verification code will be compiled
		4047	in. If set to C<1>, then verification code will be compiled in, but not
		4048	called. If set to C<2>, then the internal verification code will be
		4049	called once per loop, which can slow down libev. If set to C<3>, then the
		4050	verification code will be called very frequently, which will slow down
		4051	libev considerably.
		4052
		4053	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
		4054	will be C<0>.
3030		4055
3031	=item EV_COMMON	4056	=item EV_COMMON
3032		4057
3033	By default, all watchers have a C<void *data> member. By redefining	4058	By default, all watchers have a C<void *data> member. By redefining
3034	this macro to a something else you can include more and other types of	4059	this macro to something else you can include more and other types of
3035	members. You have to define it each time you include one of the files,	4060	members. You have to define it each time you include one of the files,
3036	though, and it must be identical each time.	4061	though, and it must be identical each time.
3037		4062
3038	For example, the perl EV module uses something like this:	4063	For example, the perl EV module uses something like this:
3039		4064
3040	#define EV_COMMON \	4065	#define EV_COMMON \
3041	SV *self; /* contains this struct */ \	4066	SV *self; /* contains this struct */ \
3042	SV *cb_sv, *fh /* note no trailing ";" */	4067	SV *cb_sv, *fh /* note no trailing ";" */
3043		4068
3044	=item EV_CB_DECLARE (type)	4069	=item EV_CB_DECLARE (type)
3045		4070
3046	=item EV_CB_INVOKE (watcher, revents)	4071	=item EV_CB_INVOKE (watcher, revents)
3047		4072
…		…
3052	definition and a statement, respectively. See the F<ev.h> header file for	4077	definition and a statement, respectively. See the F<ev.h> header file for
3053	their default definitions. One possible use for overriding these is to	4078	their default definitions. One possible use for overriding these is to
3054	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4079	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3055	method calls instead of plain function calls in C++.	4080	method calls instead of plain function calls in C++.
3056		4081
		4082	=back
		4083
3057	=head2 EXPORTED API SYMBOLS	4084	=head2 EXPORTED API SYMBOLS
3058		4085
3059	If you need to re-export the API (e.g. via a dll) and you need a list of	4086	If you need to re-export the API (e.g. via a DLL) and you need a list of
3060	exported symbols, you can use the provided F<Symbol.*> files which list	4087	exported symbols, you can use the provided F<Symbol.*> files which list
3061	all public symbols, one per line:	4088	all public symbols, one per line:
3062		4089
3063	Symbols.ev for libev proper	4090	Symbols.ev for libev proper
3064	Symbols.event for the libevent emulation	4091	Symbols.event for the libevent emulation
3065		4092
3066	This can also be used to rename all public symbols to avoid clashes with	4093	This can also be used to rename all public symbols to avoid clashes with
3067	multiple versions of libev linked together (which is obviously bad in	4094	multiple versions of libev linked together (which is obviously bad in
3068	itself, but sometimes it is inconvinient to avoid this).	4095	itself, but sometimes it is inconvenient to avoid this).
3069		4096
3070	A sed command like this will create wrapper C<#define>'s that you need to	4097	A sed command like this will create wrapper C<#define>'s that you need to
3071	include before including F<ev.h>:	4098	include before including F<ev.h>:
3072		4099
3073	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	4100	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3090	file.	4117	file.
3091		4118
3092	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4119	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3093	that everybody includes and which overrides some configure choices:	4120	that everybody includes and which overrides some configure choices:
3094		4121
3095	#define EV_MINIMAL 1	4122	#define EV_FEATURES 8
3096	#define EV_USE_POLL 0	4123	#define EV_USE_SELECT 1
3097	#define EV_MULTIPLICITY 0
3098	#define EV_PERIODIC_ENABLE 0	4124	#define EV_PREPARE_ENABLE 1
		4125	#define EV_IDLE_ENABLE 1
3099	#define EV_STAT_ENABLE 0	4126	#define EV_SIGNAL_ENABLE 1
3100	#define EV_FORK_ENABLE 0	4127	#define EV_CHILD_ENABLE 1
		4128	#define EV_USE_STDEXCEPT 0
3101	#define EV_CONFIG_H <config.h>	4129	#define EV_CONFIG_H <config.h>
3102	#define EV_MINPRI 0
3103	#define EV_MAXPRI 0
3104		4130
3105	#include "ev++.h"	4131	#include "ev++.h"
3106		4132
3107	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4133	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3108		4134
3109	#include "ev_cpp.h"	4135	#include "ev_cpp.h"
3110	#include "ev.c"	4136	#include "ev.c"
3111		4137
		4138	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3112		4139
3113	=head1 THREADS AND COROUTINES	4140	=head2 THREADS AND COROUTINES
3114		4141
3115	=head2 THREADS	4142	=head3 THREADS
3116		4143
3117	Libev itself is completely threadsafe, but it uses no locking. This	4144	All libev functions are reentrant and thread-safe unless explicitly
		4145	documented otherwise, but libev implements no locking itself. This means
3118	means that you can use as many loops as you want in parallel, as long as	4146	that you can use as many loops as you want in parallel, as long as there
3119	only one thread ever calls into one libev function with the same loop	4147	are no concurrent calls into any libev function with the same loop
3120	parameter.	4148	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4149	of course): libev guarantees that different event loops share no data
		4150	structures that need any locking.
3121		4151
3122	Or put differently: calls with different loop parameters can be done in	4152	Or to put it differently: calls with different loop parameters can be done
3123	parallel from multiple threads, calls with the same loop parameter must be	4153	concurrently from multiple threads, calls with the same loop parameter
3124	done serially (but can be done from different threads, as long as only one	4154	must be done serially (but can be done from different threads, as long as
3125	thread ever is inside a call at any point in time, e.g. by using a mutex	4155	only one thread ever is inside a call at any point in time, e.g. by using
3126	per loop).	4156	a mutex per loop).
3127		4157
3128	If you want to know which design is best for your problem, then I cannot	4158	Specifically to support threads (and signal handlers), libev implements
		4159	so-called C<ev_async> watchers, which allow some limited form of
		4160	concurrency on the same event loop, namely waking it up "from the
		4161	outside".
		4162
		4163	If you want to know which design (one loop, locking, or multiple loops
		4164	without or something else still) is best for your problem, then I cannot
3129	help you but by giving some generic advice:	4165	help you, but here is some generic advice:
3130		4166
3131	=over 4	4167	=over 4
3132		4168
3133	=item * most applications have a main thread: use the default libev loop	4169	=item * most applications have a main thread: use the default libev loop
3134	in that thread, or create a seperate thread running only the default loop.	4170	in that thread, or create a separate thread running only the default loop.
3135		4171
3136	This helps integrating other libraries or software modules that use libev	4172	This helps integrating other libraries or software modules that use libev
3137	themselves and don't care/know about threading.	4173	themselves and don't care/know about threading.
3138		4174
3139	=item * one loop per thread is usually a good model.	4175	=item * one loop per thread is usually a good model.
3140		4176
3141	Doing this is almost never wrong, sometimes a better-performance model	4177	Doing this is almost never wrong, sometimes a better-performance model
3142	exists, but it is always a good start.	4178	exists, but it is always a good start.
3143		4179
3144	=item * other models exist, such as the leader/follower pattern, where one	4180	=item * other models exist, such as the leader/follower pattern, where one
3145	loop is handed through multiple threads in a kind of round-robbin fashion.	4181	loop is handed through multiple threads in a kind of round-robin fashion.
3146		4182
3147	Chosing a model is hard - look around, learn, know that usually you cna do	4183	Choosing a model is hard - look around, learn, know that usually you can do
3148	better than you currently do :-)	4184	better than you currently do :-)
3149		4185
3150	=item * often you need to talk to some other thread which blocks in the	4186	=item * often you need to talk to some other thread which blocks in the
		4187	event loop.
		4188
3151	event loop - C<ev_async> watchers can be used to wake them up from other	4189	C<ev_async> watchers can be used to wake them up from other threads safely
3152	threads safely (or from signal contexts...).	4190	(or from signal contexts...).
		4191
		4192	An example use would be to communicate signals or other events that only
		4193	work in the default loop by registering the signal watcher with the
		4194	default loop and triggering an C<ev_async> watcher from the default loop
		4195	watcher callback into the event loop interested in the signal.
3153		4196
3154	=back	4197	=back
3155		4198
		4199	=head4 THREAD LOCKING EXAMPLE
		4200
		4201	Here is a fictitious example of how to run an event loop in a different
		4202	thread than where callbacks are being invoked and watchers are
		4203	created/added/removed.
		4204
		4205	For a real-world example, see the C<EV::Loop::Async> perl module,
		4206	which uses exactly this technique (which is suited for many high-level
		4207	languages).
		4208
		4209	The example uses a pthread mutex to protect the loop data, a condition
		4210	variable to wait for callback invocations, an async watcher to notify the
		4211	event loop thread and an unspecified mechanism to wake up the main thread.
		4212
		4213	First, you need to associate some data with the event loop:
		4214
		4215	typedef struct {
		4216	mutex_t lock; /* global loop lock */
		4217	ev_async async_w;
		4218	thread_t tid;
		4219	cond_t invoke_cv;
		4220	} userdata;
		4221
		4222	void prepare_loop (EV_P)
		4223	{
		4224	// for simplicity, we use a static userdata struct.
		4225	static userdata u;
		4226
		4227	ev_async_init (&u->async_w, async_cb);
		4228	ev_async_start (EV_A_ &u->async_w);
		4229
		4230	pthread_mutex_init (&u->lock, 0);
		4231	pthread_cond_init (&u->invoke_cv, 0);
		4232
		4233	// now associate this with the loop
		4234	ev_set_userdata (EV_A_ u);
		4235	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4236	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4237
		4238	// then create the thread running ev_loop
		4239	pthread_create (&u->tid, 0, l_run, EV_A);
		4240	}
		4241
		4242	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4243	solely to wake up the event loop so it takes notice of any new watchers
		4244	that might have been added:
		4245
		4246	static void
		4247	async_cb (EV_P_ ev_async *w, int revents)
		4248	{
		4249	// just used for the side effects
		4250	}
		4251
		4252	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4253	protecting the loop data, respectively.
		4254
		4255	static void
		4256	l_release (EV_P)
		4257	{
		4258	userdata *u = ev_userdata (EV_A);
		4259	pthread_mutex_unlock (&u->lock);
		4260	}
		4261
		4262	static void
		4263	l_acquire (EV_P)
		4264	{
		4265	userdata *u = ev_userdata (EV_A);
		4266	pthread_mutex_lock (&u->lock);
		4267	}
		4268
		4269	The event loop thread first acquires the mutex, and then jumps straight
		4270	into C<ev_loop>:
		4271
		4272	void *
		4273	l_run (void *thr_arg)
		4274	{
		4275	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4276
		4277	l_acquire (EV_A);
		4278	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4279	ev_loop (EV_A_ 0);
		4280	l_release (EV_A);
		4281
		4282	return 0;
		4283	}
		4284
		4285	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4286	signal the main thread via some unspecified mechanism (signals? pipe
		4287	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4288	have been called (in a while loop because a) spurious wakeups are possible
		4289	and b) skipping inter-thread-communication when there are no pending
		4290	watchers is very beneficial):
		4291
		4292	static void
		4293	l_invoke (EV_P)
		4294	{
		4295	userdata *u = ev_userdata (EV_A);
		4296
		4297	while (ev_pending_count (EV_A))
		4298	{
		4299	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4300	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4301	}
		4302	}
		4303
		4304	Now, whenever the main thread gets told to invoke pending watchers, it
		4305	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4306	thread to continue:
		4307
		4308	static void
		4309	real_invoke_pending (EV_P)
		4310	{
		4311	userdata *u = ev_userdata (EV_A);
		4312
		4313	pthread_mutex_lock (&u->lock);
		4314	ev_invoke_pending (EV_A);
		4315	pthread_cond_signal (&u->invoke_cv);
		4316	pthread_mutex_unlock (&u->lock);
		4317	}
		4318
		4319	Whenever you want to start/stop a watcher or do other modifications to an
		4320	event loop, you will now have to lock:
		4321
		4322	ev_timer timeout_watcher;
		4323	userdata *u = ev_userdata (EV_A);
		4324
		4325	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4326
		4327	pthread_mutex_lock (&u->lock);
		4328	ev_timer_start (EV_A_ &timeout_watcher);
		4329	ev_async_send (EV_A_ &u->async_w);
		4330	pthread_mutex_unlock (&u->lock);
		4331
		4332	Note that sending the C<ev_async> watcher is required because otherwise
		4333	an event loop currently blocking in the kernel will have no knowledge
		4334	about the newly added timer. By waking up the loop it will pick up any new
		4335	watchers in the next event loop iteration.
		4336
3156	=head2 COROUTINES	4337	=head3 COROUTINES
3157		4338
3158	Libev is much more accomodating to coroutines ("cooperative threads"):	4339	Libev is very accommodating to coroutines ("cooperative threads"):
3159	libev fully supports nesting calls to it's functions from different	4340	libev fully supports nesting calls to its functions from different
3160	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4341	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3161	different coroutines and switch freely between both coroutines running the	4342	different coroutines, and switch freely between both coroutines running
3162	loop, as long as you don't confuse yourself). The only exception is that	4343	the loop, as long as you don't confuse yourself). The only exception is
3163	you must not do this from C<ev_periodic> reschedule callbacks.	4344	that you must not do this from C<ev_periodic> reschedule callbacks.
3164		4345
3165	Care has been invested into making sure that libev does not keep local	4346	Care has been taken to ensure that libev does not keep local state inside
3166	state inside C<ev_loop>, and other calls do not usually allow coroutine	4347	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3167	switches.	4348	they do not call any callbacks.
3168		4349
		4350	=head2 COMPILER WARNINGS
3169		4351
3170	=head1 COMPLEXITIES	4352	Depending on your compiler and compiler settings, you might get no or a
		4353	lot of warnings when compiling libev code. Some people are apparently
		4354	scared by this.
3171		4355
3172	In this section the complexities of (many of) the algorithms used inside	4356	However, these are unavoidable for many reasons. For one, each compiler
3173	libev will be explained. For complexity discussions about backends see the	4357	has different warnings, and each user has different tastes regarding
3174	documentation for C<ev_default_init>.	4358	warning options. "Warn-free" code therefore cannot be a goal except when
		4359	targeting a specific compiler and compiler-version.
3175		4360
3176	All of the following are about amortised time: If an array needs to be	4361	Another reason is that some compiler warnings require elaborate
3177	extended, libev needs to realloc and move the whole array, but this	4362	workarounds, or other changes to the code that make it less clear and less
3178	happens asymptotically never with higher number of elements, so O(1) might	4363	maintainable.
3179	mean it might do a lengthy realloc operation in rare cases, but on average
3180	it is much faster and asymptotically approaches constant time.
3181		4364
3182	=over 4	4365	And of course, some compiler warnings are just plain stupid, or simply
		4366	wrong (because they don't actually warn about the condition their message
		4367	seems to warn about). For example, certain older gcc versions had some
		4368	warnings that resulted in an extreme number of false positives. These have
		4369	been fixed, but some people still insist on making code warn-free with
		4370	such buggy versions.
3183		4371
3184	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4372	While libev is written to generate as few warnings as possible,
		4373	"warn-free" code is not a goal, and it is recommended not to build libev
		4374	with any compiler warnings enabled unless you are prepared to cope with
		4375	them (e.g. by ignoring them). Remember that warnings are just that:
		4376	warnings, not errors, or proof of bugs.
3185		4377
3186	This means that, when you have a watcher that triggers in one hour and
3187	there are 100 watchers that would trigger before that then inserting will
3188	have to skip roughly seven (C<ld 100>) of these watchers.
3189		4378
3190	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4379	=head2 VALGRIND
3191		4380
3192	That means that changing a timer costs less than removing/adding them	4381	Valgrind has a special section here because it is a popular tool that is
3193	as only the relative motion in the event queue has to be paid for.	4382	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3194		4383
3195	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4384	If you think you found a bug (memory leak, uninitialised data access etc.)
		4385	in libev, then check twice: If valgrind reports something like:
3196		4386
3197	These just add the watcher into an array or at the head of a list.	4387	==2274== definitely lost: 0 bytes in 0 blocks.
		4388	==2274== possibly lost: 0 bytes in 0 blocks.
		4389	==2274== still reachable: 256 bytes in 1 blocks.
3198		4390
3199	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4391	Then there is no memory leak, just as memory accounted to global variables
		4392	is not a memleak - the memory is still being referenced, and didn't leak.
3200		4393
3201	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4394	Similarly, under some circumstances, valgrind might report kernel bugs
		4395	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4396	although an acceptable workaround has been found here), or it might be
		4397	confused.
3202		4398
3203	These watchers are stored in lists then need to be walked to find the	4399	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3204	correct watcher to remove. The lists are usually short (you don't usually	4400	make it into some kind of religion.
3205	have many watchers waiting for the same fd or signal).
3206		4401
3207	=item Finding the next timer in each loop iteration: O(1)	4402	If you are unsure about something, feel free to contact the mailing list
		4403	with the full valgrind report and an explanation on why you think this
		4404	is a bug in libev (best check the archives, too :). However, don't be
		4405	annoyed when you get a brisk "this is no bug" answer and take the chance
		4406	of learning how to interpret valgrind properly.
3208		4407
3209	By virtue of using a binary or 4-heap, the next timer is always found at a	4408	If you need, for some reason, empty reports from valgrind for your project
3210	fixed position in the storage array.	4409	I suggest using suppression lists.
3211		4410
3212	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3213		4411
3214	A change means an I/O watcher gets started or stopped, which requires	4412	=head1 PORTABILITY NOTES
3215	libev to recalculate its status (and possibly tell the kernel, depending
3216	on backend and wether C<ev_io_set> was used).
3217		4413
3218	=item Activating one watcher (putting it into the pending state): O(1)	4414	=head2 GNU/LINUX 32 BIT LIMITATIONS
3219		4415
3220	=item Priority handling: O(number_of_priorities)	4416	GNU/Linux is the only common platform that supports 64 bit file/large file
		4417	interfaces but I<disables> them by default.
3221		4418
3222	Priorities are implemented by allocating some space for each	4419	That means that libev compiled in the default environment doesn't support
3223	priority. When doing priority-based operations, libev usually has to	4420	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3224	linearly search all the priorities, but starting/stopping and activating
3225	watchers becomes O(1) w.r.t. priority handling.
3226		4421
3227	=item Sending an ev_async: O(1)	4422	Unfortunately, many programs try to work around this GNU/Linux issue
		4423	by enabling the large file API, which makes them incompatible with the
		4424	standard libev compiled for their system.
3228		4425
3229	=item Processing ev_async_send: O(number_of_async_watchers)	4426	Likewise, libev cannot enable the large file API itself as this would
		4427	suddenly make it incompatible to the default compile time environment,
		4428	i.e. all programs not using special compile switches.
3230		4429
3231	=item Processing signals: O(max_signal_number)	4430	=head2 OS/X AND DARWIN BUGS
3232		4431
3233	Sending involves a syscall I<iff> there were no other C<ev_async_send>	4432	The whole thing is a bug if you ask me - basically any system interface
3234	calls in the current loop iteration. Checking for async and signal events	4433	you touch is broken, whether it is locales, poll, kqueue or even the
3235	involves iterating over all running async watchers or all signal numbers.	4434	OpenGL drivers.
3236		4435
3237	=back	4436	=head3 C<kqueue> is buggy
3238		4437
		4438	The kqueue syscall is broken in all known versions - most versions support
		4439	only sockets, many support pipes.
3239		4440
3240	=head1 Win32 platform limitations and workarounds	4441	Libev tries to work around this by not using C<kqueue> by default on
		4442	this rotten platform, but of course you can still ask for it when creating
		4443	a loop.
		4444
		4445	=head3 C<poll> is buggy
		4446
		4447	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4448	implementation by something calling C<kqueue> internally around the 10.5.6
		4449	release, so now C<kqueue> I<and> C<poll> are broken.
		4450
		4451	Libev tries to work around this by not using C<poll> by default on
		4452	this rotten platform, but of course you can still ask for it when creating
		4453	a loop.
		4454
		4455	=head3 C<select> is buggy
		4456
		4457	All that's left is C<select>, and of course Apple found a way to fuck this
		4458	one up as well: On OS/X, C<select> actively limits the number of file
		4459	descriptors you can pass in to 1024 - your program suddenly crashes when
		4460	you use more.
		4461
		4462	There is an undocumented "workaround" for this - defining
		4463	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4464	work on OS/X.
		4465
		4466	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4467
		4468	=head3 C<errno> reentrancy
		4469
		4470	The default compile environment on Solaris is unfortunately so
		4471	thread-unsafe that you can't even use components/libraries compiled
		4472	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,
		4473	isn't defined by default.
		4474
		4475	If you want to use libev in threaded environments you have to make sure
		4476	it's compiled with C<_REENTRANT> defined.
		4477
		4478	=head3 Event port backend
		4479
		4480	The scalable event interface for Solaris is called "event ports". Unfortunately,
		4481	this mechanism is very buggy. If you run into high CPU usage, your program
		4482	freezes or you get a large number of spurious wakeups, make sure you have
		4483	all the relevant and latest kernel patches applied. No, I don't know which
		4484	ones, but there are multiple ones.
		4485
		4486	If you can't get it to work, you can try running the program by setting
		4487	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4488	C<select> backends.
		4489
		4490	=head2 AIX POLL BUG
		4491
		4492	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4493	this by trying to avoid the poll backend altogether (i.e. it's not even
		4494	compiled in), which normally isn't a big problem as C<select> works fine
		4495	with large bitsets, and AIX is dead anyway.
		4496
		4497	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4498
		4499	=head3 General issues
3241		4500
3242	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4501	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3243	requires, and its I/O model is fundamentally incompatible with the POSIX	4502	requires, and its I/O model is fundamentally incompatible with the POSIX
3244	model. Libev still offers limited functionality on this platform in	4503	model. Libev still offers limited functionality on this platform in
3245	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4504	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3246	descriptors. This only applies when using Win32 natively, not when using	4505	descriptors. This only applies when using Win32 natively, not when using
3247	e.g. cygwin.	4506	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4507	as every compielr comes with a slightly differently broken/incompatible
		4508	environment.
3248		4509
3249	Lifting these limitations would basically require the full	4510	Lifting these limitations would basically require the full
3250	re-implementation of the I/O system. If you are into these kinds of	4511	re-implementation of the I/O system. If you are into this kind of thing,
3251	things, then note that glib does exactly that for you in a very portable	4512	then note that glib does exactly that for you in a very portable way (note
3252	way (note also that glib is the slowest event library known to man).	4513	also that glib is the slowest event library known to man).
3253		4514
3254	There is no supported compilation method available on windows except	4515	There is no supported compilation method available on windows except
3255	embedding it into other applications.	4516	embedding it into other applications.
		4517
		4518	Sensible signal handling is officially unsupported by Microsoft - libev
		4519	tries its best, but under most conditions, signals will simply not work.
		4520
		4521	Not a libev limitation but worth mentioning: windows apparently doesn't
		4522	accept large writes: instead of resulting in a partial write, windows will
		4523	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4524	so make sure you only write small amounts into your sockets (less than a
		4525	megabyte seems safe, but this apparently depends on the amount of memory
		4526	available).
3256		4527
3257	Due to the many, low, and arbitrary limits on the win32 platform and	4528	Due to the many, low, and arbitrary limits on the win32 platform and
3258	the abysmal performance of winsockets, using a large number of sockets	4529	the abysmal performance of winsockets, using a large number of sockets
3259	is not recommended (and not reasonable). If your program needs to use	4530	is not recommended (and not reasonable). If your program needs to use
3260	more than a hundred or so sockets, then likely it needs to use a totally	4531	more than a hundred or so sockets, then likely it needs to use a totally
3261	different implementation for windows, as libev offers the POSIX readiness	4532	different implementation for windows, as libev offers the POSIX readiness
3262	notification model, which cannot be implemented efficiently on windows	4533	notification model, which cannot be implemented efficiently on windows
3263	(microsoft monopoly games).	4534	(due to Microsoft monopoly games).
3264		4535
3265	=over 4	4536	A typical way to use libev under windows is to embed it (see the embedding
		4537	section for details) and use the following F<evwrap.h> header file instead
		4538	of F<ev.h>:
3266		4539
		4540	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4541	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4542
		4543	#include "ev.h"
		4544
		4545	And compile the following F<evwrap.c> file into your project (make sure
		4546	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4547
		4548	#include "evwrap.h"
		4549	#include "ev.c"
		4550
3267	=item The winsocket select function	4551	=head3 The winsocket C<select> function
3268		4552
3269	The winsocket C<select> function doesn't follow POSIX in that it requires	4553	The winsocket C<select> function doesn't follow POSIX in that it
3270	socket I<handles> and not socket I<file descriptors>. This makes select	4554	requires socket I<handles> and not socket I<file descriptors> (it is
3271	very inefficient, and also requires a mapping from file descriptors	4555	also extremely buggy). This makes select very inefficient, and also
3272	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4556	requires a mapping from file descriptors to socket handles (the Microsoft
3273	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4557	C runtime provides the function C<_open_osfhandle> for this). See the
3274	symbols for more info.	4558	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4559	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3275		4560
3276	The configuration for a "naked" win32 using the microsoft runtime	4561	The configuration for a "naked" win32 using the Microsoft runtime
3277	libraries and raw winsocket select is:	4562	libraries and raw winsocket select is:
3278		4563
3279	#define EV_USE_SELECT 1	4564	#define EV_USE_SELECT 1
3280	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4565	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3281		4566
3282	Note that winsockets handling of fd sets is O(n), so you can easily get a	4567	Note that winsockets handling of fd sets is O(n), so you can easily get a
3283	complexity in the O(n²) range when using win32.	4568	complexity in the O(n²) range when using win32.
3284		4569
3285	=item Limited number of file descriptors	4570	=head3 Limited number of file descriptors
3286		4571
3287	Windows has numerous arbitrary (and low) limits on things.	4572	Windows has numerous arbitrary (and low) limits on things.
3288		4573
3289	Early versions of winsocket's select only supported waiting for a maximum	4574	Early versions of winsocket's select only supported waiting for a maximum
3290	of C<64> handles (probably owning to the fact that all windows kernels	4575	of C<64> handles (probably owning to the fact that all windows kernels
3291	can only wait for C<64> things at the same time internally; microsoft	4576	can only wait for C<64> things at the same time internally; Microsoft
3292	recommends spawning a chain of threads and wait for 63 handles and the	4577	recommends spawning a chain of threads and wait for 63 handles and the
3293	previous thread in each. Great).	4578	previous thread in each. Sounds great!).
3294		4579
3295	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4580	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3296	to some high number (e.g. C<2048>) before compiling the winsocket select	4581	to some high number (e.g. C<2048>) before compiling the winsocket select
3297	call (which might be in libev or elsewhere, for example, perl does its own	4582	call (which might be in libev or elsewhere, for example, perl and many
3298	select emulation on windows).	4583	other interpreters do their own select emulation on windows).
3299		4584
3300	Another limit is the number of file descriptors in the microsoft runtime	4585	Another limit is the number of file descriptors in the Microsoft runtime
3301	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4586	libraries, which by default is C<64> (there must be a hidden I<64>
3302	or something like this inside microsoft). You can increase this by calling	4587	fetish or something like this inside Microsoft). You can increase this
3303	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4588	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3304	arbitrary limit), but is broken in many versions of the microsoft runtime	4589	(another arbitrary limit), but is broken in many versions of the Microsoft
3305	libraries.
3306
3307	This might get you to about C<512> or C<2048> sockets (depending on	4590	runtime libraries. This might get you to about C<512> or C<2048> sockets
3308	windows version and/or the phase of the moon). To get more, you need to	4591	(depending on windows version and/or the phase of the moon). To get more,
3309	wrap all I/O functions and provide your own fd management, but the cost of	4592	you need to wrap all I/O functions and provide your own fd management, but
3310	calling select (O(n²)) will likely make this unworkable.	4593	the cost of calling select (O(n²)) will likely make this unworkable.
3311		4594
3312	=back
3313
3314
3315	=head1 PORTABILITY REQUIREMENTS	4595	=head2 PORTABILITY REQUIREMENTS
3316		4596
3317	In addition to a working ISO-C implementation, libev relies on a few	4597	In addition to a working ISO-C implementation and of course the
3318	additional extensions:	4598	backend-specific APIs, libev relies on a few additional extensions:
3319		4599
3320	=over 4	4600	=over 4
3321		4601
		4602	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4603	calling conventions regardless of C<ev_watcher_type *>.
		4604
		4605	Libev assumes not only that all watcher pointers have the same internal
		4606	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4607	assumes that the same (machine) code can be used to call any watcher
		4608	callback: The watcher callbacks have different type signatures, but libev
		4609	calls them using an C<ev_watcher *> internally.
		4610
3322	=item C<sig_atomic_t volatile> must be thread-atomic as well	4611	=item C<sig_atomic_t volatile> must be thread-atomic as well
3323		4612
3324	The type C<sig_atomic_t volatile> (or whatever is defined as	4613	The type C<sig_atomic_t volatile> (or whatever is defined as
3325	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4614	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3326	threads. This is not part of the specification for C<sig_atomic_t>, but is	4615	threads. This is not part of the specification for C<sig_atomic_t>, but is
3327	believed to be sufficiently portable.	4616	believed to be sufficiently portable.
3328		4617
3329	=item C<sigprocmask> must work in a threaded environment	4618	=item C<sigprocmask> must work in a threaded environment
3330		4619
…		…
3339	except the initial one, and run the default loop in the initial thread as	4628	except the initial one, and run the default loop in the initial thread as
3340	well.	4629	well.
3341		4630
3342	=item C<long> must be large enough for common memory allocation sizes	4631	=item C<long> must be large enough for common memory allocation sizes
3343		4632
3344	To improve portability and simplify using libev, libev uses C<long>	4633	To improve portability and simplify its API, libev uses C<long> internally
3345	internally instead of C<size_t> when allocating its data structures. On	4634	instead of C<size_t> when allocating its data structures. On non-POSIX
3346	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4635	systems (Microsoft...) this might be unexpectedly low, but is still at
3347	is still at least 31 bits everywhere, which is enough for hundreds of	4636	least 31 bits everywhere, which is enough for hundreds of millions of
3348	millions of watchers.	4637	watchers.
3349		4638
3350	=item C<double> must hold a time value in seconds with enough accuracy	4639	=item C<double> must hold a time value in seconds with enough accuracy
3351		4640
3352	The type C<double> is used to represent timestamps. It is required to	4641	The type C<double> is used to represent timestamps. It is required to
3353	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4642	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3354	enough for at least into the year 4000. This requirement is fulfilled by	4643	enough for at least into the year 4000. This requirement is fulfilled by
3355	implementations implementing IEEE 754 (basically all existing ones).	4644	implementations implementing IEEE 754, which is basically all existing
		4645	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4646	2200.
3356		4647
3357	=back	4648	=back
3358		4649
3359	If you know of other additional requirements drop me a note.	4650	If you know of other additional requirements drop me a note.
3360		4651
3361		4652
3362	=head1 VALGRIND	4653	=head1 ALGORITHMIC COMPLEXITIES
3363		4654
3364	Valgrind has a special section here because it is a popular tool that is	4655	In this section the complexities of (many of) the algorithms used inside
3365	highly useful, but valgrind reports are very hard to interpret.	4656	libev will be documented. For complexity discussions about backends see
		4657	the documentation for C<ev_default_init>.
3366		4658
3367	If you think you found a bug (memory leak, uninitialised data access etc.)	4659	All of the following are about amortised time: If an array needs to be
3368	in libev, then check twice: If valgrind reports something like:	4660	extended, libev needs to realloc and move the whole array, but this
		4661	happens asymptotically rarer with higher number of elements, so O(1) might
		4662	mean that libev does a lengthy realloc operation in rare cases, but on
		4663	average it is much faster and asymptotically approaches constant time.
3369		4664
3370	==2274== definitely lost: 0 bytes in 0 blocks.	4665	=over 4
3371	==2274== possibly lost: 0 bytes in 0 blocks.
3372	==2274== still reachable: 256 bytes in 1 blocks.
3373		4666
3374	then there is no memory leak. Similarly, under some circumstances,	4667	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3375	valgrind might report kernel bugs as if it were a bug in libev, or it
3376	might be confused (it is a very good tool, but only a tool).
3377		4668
3378	If you are unsure about something, feel free to contact the mailing list	4669	This means that, when you have a watcher that triggers in one hour and
3379	with the full valgrind report and an explanation on why you think this is	4670	there are 100 watchers that would trigger before that, then inserting will
3380	a bug in libev. However, don't be annoyed when you get a brisk "this is	4671	have to skip roughly seven (C<ld 100>) of these watchers.
3381	no bug" answer and take the chance of learning how to interpret valgrind
3382	properly.
3383		4672
3384	If you need, for some reason, empty reports from valgrind for your project	4673	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3385	I suggest using suppression lists.
3386		4674
		4675	That means that changing a timer costs less than removing/adding them,
		4676	as only the relative motion in the event queue has to be paid for.
		4677
		4678	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4679
		4680	These just add the watcher into an array or at the head of a list.
		4681
		4682	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4683
		4684	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4685
		4686	These watchers are stored in lists, so they need to be walked to find the
		4687	correct watcher to remove. The lists are usually short (you don't usually
		4688	have many watchers waiting for the same fd or signal: one is typical, two
		4689	is rare).
		4690
		4691	=item Finding the next timer in each loop iteration: O(1)
		4692
		4693	By virtue of using a binary or 4-heap, the next timer is always found at a
		4694	fixed position in the storage array.
		4695
		4696	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4697
		4698	A change means an I/O watcher gets started or stopped, which requires
		4699	libev to recalculate its status (and possibly tell the kernel, depending
		4700	on backend and whether C<ev_io_set> was used).
		4701
		4702	=item Activating one watcher (putting it into the pending state): O(1)
		4703
		4704	=item Priority handling: O(number_of_priorities)
		4705
		4706	Priorities are implemented by allocating some space for each
		4707	priority. When doing priority-based operations, libev usually has to
		4708	linearly search all the priorities, but starting/stopping and activating
		4709	watchers becomes O(1) with respect to priority handling.
		4710
		4711	=item Sending an ev_async: O(1)
		4712
		4713	=item Processing ev_async_send: O(number_of_async_watchers)
		4714
		4715	=item Processing signals: O(max_signal_number)
		4716
		4717	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4718	calls in the current loop iteration. Checking for async and signal events
		4719	involves iterating over all running async watchers or all signal numbers.
		4720
		4721	=back
		4722
		4723
		4724	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4725
		4726	The major version 4 introduced some minor incompatible changes to the API.
		4727
		4728	At the moment, the C<ev.h> header file tries to implement superficial
		4729	compatibility, so most programs should still compile. Those might be
		4730	removed in later versions of libev, so better update early than late.
		4731
		4732	=over 4
		4733
		4734	=item C<ev_loop_count> renamed to C<ev_iteration>
		4735
		4736	=item C<ev_loop_depth> renamed to C<ev_depth>
		4737
		4738	=item C<ev_loop_verify> renamed to C<ev_verify>
		4739
		4740	Most functions working on C<struct ev_loop> objects don't have an
		4741	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
		4742	still called C<ev_loop_fork> because it would otherwise clash with the
		4743	C<ev_fork> typedef.
		4744
		4745	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
		4746
		4747	This is a simple rename - all other watcher types use their name
		4748	as revents flag, and now C<ev_timer> does, too.
		4749
		4750	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4751	and continue to be present for the foreseeable future, so this is mostly a
		4752	documentation change.
		4753
		4754	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4755
		4756	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4757	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4758	and work, but the library code will of course be larger.
		4759
		4760	=back
		4761
		4762
		4763	=head1 GLOSSARY
		4764
		4765	=over 4
		4766
		4767	=item active
		4768
		4769	A watcher is active as long as it has been started (has been attached to
		4770	an event loop) but not yet stopped (disassociated from the event loop).
		4771
		4772	=item application
		4773
		4774	In this document, an application is whatever is using libev.
		4775
		4776	=item callback
		4777
		4778	The address of a function that is called when some event has been
		4779	detected. Callbacks are being passed the event loop, the watcher that
		4780	received the event, and the actual event bitset.
		4781
		4782	=item callback invocation
		4783
		4784	The act of calling the callback associated with a watcher.
		4785
		4786	=item event
		4787
		4788	A change of state of some external event, such as data now being available
		4789	for reading on a file descriptor, time having passed or simply not having
		4790	any other events happening anymore.
		4791
		4792	In libev, events are represented as single bits (such as C<EV_READ> or
		4793	C<EV_TIMER>).
		4794
		4795	=item event library
		4796
		4797	A software package implementing an event model and loop.
		4798
		4799	=item event loop
		4800
		4801	An entity that handles and processes external events and converts them
		4802	into callback invocations.
		4803
		4804	=item event model
		4805
		4806	The model used to describe how an event loop handles and processes
		4807	watchers and events.
		4808
		4809	=item pending
		4810
		4811	A watcher is pending as soon as the corresponding event has been detected,
		4812	and stops being pending as soon as the watcher will be invoked or its
		4813	pending status is explicitly cleared by the application.
		4814
		4815	A watcher can be pending, but not active. Stopping a watcher also clears
		4816	its pending status.
		4817
		4818	=item real time
		4819
		4820	The physical time that is observed. It is apparently strictly monotonic :)
		4821
		4822	=item wall-clock time
		4823
		4824	The time and date as shown on clocks. Unlike real time, it can actually
		4825	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4826	clock.
		4827
		4828	=item watcher
		4829
		4830	A data structure that describes interest in certain events. Watchers need
		4831	to be started (attached to an event loop) before they can receive events.
		4832
		4833	=item watcher invocation
		4834
		4835	The act of calling the callback associated with a watcher.
		4836
		4837	=back
3387		4838
3388	=head1 AUTHOR	4839	=head1 AUTHOR
3389		4840
3390	Marc Lehmann <libev@schmorp.de>.	4841	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3391		4842

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