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Revision 1.99 by root, Sat Dec 22 06:16:36 2007 UTC vs.
Revision 1.226 by root, Wed Mar 4 12:51:37 2009 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	#include <stdio.h> // for puts
		15
		16	// every watcher type has its own typedef'd struct
		17	// with the name ev_TYPE
13	ev_io stdin_watcher;	18	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
15		20
16	/* called when data readable on stdin */	21	// all watcher callbacks have a similar signature
		22	// this callback is called when data is readable on stdin
17	static void	23	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	25	{
20	/* puts ("stdin ready"); */	26	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	27	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	28	// with its corresponding stop function.
		29	ev_io_stop (EV_A_ w);
		30
		31	// this causes all nested ev_loop's to stop iterating
		32	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	33	}
24		34
		35	// another callback, this time for a time-out
25	static void	36	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	38	{
28	/* puts ("timeout"); */	39	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	40	// this causes the innermost ev_loop to stop iterating
		41	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	42	}
31		43
32	int	44	int
33	main (void)	45	main (void)
34	{	46	{
		47	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
36		49
37	/* initialise an io watcher, then start it */	50	// initialise an io watcher, then start it
		51	// this one will watch for stdin to become readable
38	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);
39	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
40		54
		55	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	56	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
44		59
45	/* loop till timeout or data ready */	60	// now wait for events to arrive
46	ev_loop (loop, 0);	61	ev_loop (loop, 0);
47		62
		63	// unloop was called, so exit
48	return 0;	64	return 0;
49	}	65	}
50		66
51	=head1 DESCRIPTION	67	=head1 DESCRIPTION
52		68
53	The newest version of this document is also available as a html-formatted	69	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	70	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		72
57	Libev is an event loop: you register interest in certain events (such as a	73	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	74	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	75	these event sources and provide your program with events.
60		76
…		…
65	You register interest in certain events by registering so-called I<event	81	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	82	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	83	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	84	watcher.
69		85
70	=head1 FEATURES	86	=head2 FEATURES
71		87
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	88	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		98
83	It also is quite fast (see this	99	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	100	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	101	for example).
86		102
87	=head1 CONVENTIONS	103	=head2 CONVENTIONS
88		104
89	Libev is very configurable. In this manual the default configuration will	105	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	106	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	107	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	108	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	109	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	110	name C<loop> (which is always of type C<ev_loop *>) will not have
		111	this argument.
95		112
96	=head1 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
97		114
98	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	116	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	117	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	118	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	119	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as some floatingpoint value. Unlike the name	120	it, you should treat it as some floating point value. Unlike the name
104	component C<stamp> might indicate, it is also used for time differences	121	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	122	throughout libev.
		123
		124	=head1 ERROR HANDLING
		125
		126	Libev knows three classes of errors: operating system errors, usage errors
		127	and internal errors (bugs).
		128
		129	When libev catches an operating system error it cannot handle (for example
		130	a system call indicating a condition libev cannot fix), it calls the callback
		131	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		132	abort. The default is to print a diagnostic message and to call C<abort
		133	()>.
		134
		135	When libev detects a usage error such as a negative timer interval, then
		136	it will print a diagnostic message and abort (via the C<assert> mechanism,
		137	so C<NDEBUG> will disable this checking): these are programming errors in
		138	the libev caller and need to be fixed there.
		139
		140	Libev also has a few internal error-checking C<assert>ions, and also has
		141	extensive consistency checking code. These do not trigger under normal
		142	circumstances, as they indicate either a bug in libev or worse.
		143
106		144
107	=head1 GLOBAL FUNCTIONS	145	=head1 GLOBAL FUNCTIONS
108		146
109	These functions can be called anytime, even before initialising the	147	These functions can be called anytime, even before initialising the
110	library in any way.	148	library in any way.
…		…
119		157
120	=item ev_sleep (ev_tstamp interval)	158	=item ev_sleep (ev_tstamp interval)
121		159
122	Sleep for the given interval: The current thread will be blocked until	160	Sleep for the given interval: The current thread will be blocked until
123	either it is interrupted or the given time interval has passed. Basically	161	either it is interrupted or the given time interval has passed. Basically
124	this is a subsecond-resolution C<sleep ()>.	162	this is a sub-second-resolution C<sleep ()>.
125		163
126	=item int ev_version_major ()	164	=item int ev_version_major ()
127		165
128	=item int ev_version_minor ()	166	=item int ev_version_minor ()
129		167
…		…
142	not a problem.	180	not a problem.
143		181
144	Example: Make sure we haven't accidentally been linked against the wrong	182	Example: Make sure we haven't accidentally been linked against the wrong
145	version.	183	version.
146		184
147	assert (("libev version mismatch",	185	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	186	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	187	&& ev_version_minor () >= EV_VERSION_MINOR));
150		188
151	=item unsigned int ev_supported_backends ()	189	=item unsigned int ev_supported_backends ()
152		190
153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	191	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
154	value) compiled into this binary of libev (independent of their	192	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	194	a description of the set values.
157		195
158	Example: make sure we have the epoll method, because yeah this is cool and	196	Example: make sure we have the epoll method, because yeah this is cool and
159	a must have and can we have a torrent of it please!!!11	197	a must have and can we have a torrent of it please!!!11
160		198
161	assert (("sorry, no epoll, no sex",	199	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	200	ev_supported_backends () & EVBACKEND_EPOLL));
163		201
164	=item unsigned int ev_recommended_backends ()	202	=item unsigned int ev_recommended_backends ()
165		203
166	Return the set of all backends compiled into this binary of libev and also	204	Return the set of all backends compiled into this binary of libev and also
167	recommended for this platform. This set is often smaller than the one	205	recommended for this platform. This set is often smaller than the one
168	returned by C<ev_supported_backends>, as for example kqueue is broken on	206	returned by C<ev_supported_backends>, as for example kqueue is broken on
169	most BSDs and will not be autodetected unless you explicitly request it	207	most BSDs and will not be auto-detected unless you explicitly request it
170	(assuming you know what you are doing). This is the set of backends that	208	(assuming you know what you are doing). This is the set of backends that
171	libev will probe for if you specify no backends explicitly.	209	libev will probe for if you specify no backends explicitly.
172		210
173	=item unsigned int ev_embeddable_backends ()	211	=item unsigned int ev_embeddable_backends ()
174		212
…		…
178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
179	recommended ones.	217	recommended ones.
180		218
181	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
182		220
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
184		222
185	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
187	allocate and free memory (no surprises here). If it returns zero when	225	used to allocate and free memory (no surprises here). If it returns zero
188	memory needs to be allocated, the library might abort or take some	226	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	227	or take some potentially destructive action.
190	function.	228
		229	Since some systems (at least OpenBSD and Darwin) fail to implement
		230	correct C<realloc> semantics, libev will use a wrapper around the system
		231	C<realloc> and C<free> functions by default.
191		232
192	You could override this function in high-availability programs to, say,	233	You could override this function in high-availability programs to, say,
193	free some memory if it cannot allocate memory, to use a special allocator,	234	free some memory if it cannot allocate memory, to use a special allocator,
194	or even to sleep a while and retry until some memory is available.	235	or even to sleep a while and retry until some memory is available.
195		236
196	Example: Replace the libev allocator with one that waits a bit and then	237	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	238	retries (example requires a standards-compliant C<realloc>).
198		239
199	static void *	240	static void *
200	persistent_realloc (void *ptr, size_t size)	241	persistent_realloc (void *ptr, size_t size)
201	{	242	{
202	for (;;)	243	for (;;)
…		…
211	}	252	}
212		253
213	...	254	...
214	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
215		256
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
217		258
218	Set the callback function to call on a retryable syscall error (such	259	Set the callback function to call on a retryable system call error (such
219	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
220	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
221	callback is set, then libev will expect it to remedy the sitution, no	262	callback is set, then libev will expect it to remedy the situation, no
222	matter what, when it returns. That is, libev will generally retry the	263	matter what, when it returns. That is, libev will generally retry the
223	requested operation, or, if the condition doesn't go away, do bad stuff	264	requested operation, or, if the condition doesn't go away, do bad stuff
224	(such as abort).	265	(such as abort).
225		266
226	Example: This is basically the same thing that libev does internally, too.	267	Example: This is basically the same thing that libev does internally, too.
…		…
237		278
238	=back	279	=back
239		280
240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
241		282
242	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
243	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
244	events, and dynamically created loops which do not.	285	I<function>).
245		286
246	If you use threads, a common model is to run the default event loop	287	The library knows two types of such loops, the I<default> loop, which
247	in your main thread (or in a separate thread) and for each thread you	288	supports signals and child events, and dynamically created loops which do
248	create, you also create another event loop. Libev itself does no locking	289	not.
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252		290
253	=over 4	291	=over 4
254		292
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		294
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	298	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		299
262	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
263	function.	301	function.
264		302
		303	Note that this function is I<not> thread-safe, so if you want to use it
		304	from multiple threads, you have to lock (note also that this is unlikely,
		305	as loops cannot be shared easily between threads anyway).
		306
		307	The default loop is the only loop that can handle C<ev_signal> and
		308	C<ev_child> watchers, and to do this, it always registers a handler
		309	for C<SIGCHLD>. If this is a problem for your application you can either
		310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		312	C<ev_default_init>.
		313
265	The flags argument can be used to specify special behaviour or specific	314	The flags argument can be used to specify special behaviour or specific
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	315	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		316
268	The following flags are supported:	317	The following flags are supported:
269		318
…		…
274	The default flags value. Use this if you have no clue (it's the right	323	The default flags value. Use this if you have no clue (it's the right
275	thing, believe me).	324	thing, believe me).
276		325
277	=item C<EVFLAG_NOENV>	326	=item C<EVFLAG_NOENV>
278		327
279	If this flag bit is ored into the flag value (or the program runs setuid	328	If this flag bit is or'ed into the flag value (or the program runs setuid
280	or setgid) then libev will I<not> look at the environment variable	329	or setgid) then libev will I<not> look at the environment variable
281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
282	override the flags completely if it is found in the environment. This is	331	override the flags completely if it is found in the environment. This is
283	useful to try out specific backends to test their performance, or to work	332	useful to try out specific backends to test their performance, or to work
284	around bugs.	333	around bugs.
…		…
290	enabling this flag.	339	enabling this flag.
291		340
292	This works by calling C<getpid ()> on every iteration of the loop,	341	This works by calling C<getpid ()> on every iteration of the loop,
293	and thus this might slow down your event loop if you do a lot of loop	342	and thus this might slow down your event loop if you do a lot of loop
294	iterations and little real work, but is usually not noticeable (on my	343	iterations and little real work, but is usually not noticeable (on my
295	Linux system for example, C<getpid> is actually a simple 5-insn sequence	344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
296	without a syscall and thus I<very> fast, but my Linux system also has	345	without a system call and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	346	C<pthread_atfork> which is even faster).
298		347
299	The big advantage of this flag is that you can forget about fork (and	348	The big advantage of this flag is that you can forget about fork (and
300	forget about forgetting to tell libev about forking) when you use this	349	forget about forgetting to tell libev about forking) when you use this
301	flag.	350	flag.
302		351
303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
304	environment variable.	353	environment variable.
305		354
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		356
308	This is your standard select(2) backend. Not I<completely> standard, as	357	This is your standard select(2) backend. Not I<completely> standard, as
309	libev tries to roll its own fd_set with no limits on the number of fds,	358	libev tries to roll its own fd_set with no limits on the number of fds,
310	but if that fails, expect a fairly low limit on the number of fds when	359	but if that fails, expect a fairly low limit on the number of fds when
311	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	360	using this backend. It doesn't scale too well (O(highest_fd)), but its
312	the fastest backend for a low number of fds.	361	usually the fastest backend for a low number of (low-numbered :) fds.
		362
		363	To get good performance out of this backend you need a high amount of
		364	parallelism (most of the file descriptors should be busy). If you are
		365	writing a server, you should C<accept ()> in a loop to accept as many
		366	connections as possible during one iteration. You might also want to have
		367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		368	readiness notifications you get per iteration.
		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
313		373
314	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
315		375
316	And this is your standard poll(2) backend. It's more complicated than	376	And this is your standard poll(2) backend. It's more complicated
317	select, but handles sparse fds better and has no artificial limit on the	377	than select, but handles sparse fds better and has no artificial
318	number of fds you can use (except it will slow down considerably with a	378	limit on the number of fds you can use (except it will slow down
319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	379	considerably with a lot of inactive fds). It scales similarly to select,
		380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		381	performance tips.
		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
320		385
321	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
322		387
323	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
324	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
325	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
326	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
327	of shortcomings, such as silently dropping events in some hard-to-detect	392
328	cases and rewiring a syscall per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
329	support for dup:	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
330		409
331	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
332	will result in some caching, there is still a syscall per such incident	411	will result in some caching, there is still a system call per such
333	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
334	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
335	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
		415	file descriptors.
336		416
337	Please note that epoll sometimes generates spurious notifications, so you	417	Best performance from this backend is achieved by not unregistering all
338	need to use non-blocking I/O or other means to avoid blocking when no data	418	watchers for a file descriptor until it has been closed, if possible,
339	(or space) is available.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
		428
		429	While nominally embeddable in other event loops, this feature is broken in
		430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
340		434
341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
342		436
343	Kqueue deserves special mention, as at the time of this writing, it	437	Kqueue deserves special mention, as at the time of this writing, it
344	was broken on I<all> BSDs (usually it doesn't work with anything but	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
345	sockets and pipes, except on Darwin, where of course it's completely	439	with anything but sockets and pipes, except on Darwin, where of course
346	useless. On NetBSD, it seems to work for all the FD types I tested, so it	440	it's completely useless). Unlike epoll, however, whose brokenness
347	is used by default there). For this reason it's not being "autodetected"	441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	without API changes to existing programs. For this reason it's not being
348	unless you explicitly specify it explicitly in the flags (i.e. using	443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
349	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
350	system like NetBSD.	445	system like NetBSD.
351		446
		447	You still can embed kqueue into a normal poll or select backend and use it
		448	only for sockets (after having made sure that sockets work with kqueue on
		449	the target platform). See C<ev_embed> watchers for more info.
		450
352	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
353	kernel is more efficient (which says nothing about its actual speed,	452	kernel is more efficient (which says nothing about its actual speed, of
354	of course). While stopping, setting and starting an I/O watcher does	453	course). While stopping, setting and starting an I/O watcher does never
355	never cause an extra syscall as with epoll, it still adds up to two event	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
356	changes per incident, support for C<fork ()> is very bad and it drops fds	455	two event changes per incident. Support for C<fork ()> is very bad (but
357	silently in similarly hard-to-detetc cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
		458
		459	This backend usually performs well under most conditions.
		460
		461	While nominally embeddable in other event loops, this doesn't work
		462	everywhere, so you might need to test for this. And since it is broken
		463	almost everywhere, you should only use it when you have a lot of sockets
		464	(for which it usually works), by embedding it into another event loop
		465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
		466	also broken on OS X)) and, did I mention it, using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
358		471
359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
360		473
361	This is not implemented yet (and might never be).	474	This is not implemented yet (and might never be, unless you send me an
		475	implementation). According to reports, C</dev/poll> only supports sockets
		476	and is not embeddable, which would limit the usefulness of this backend
		477	immensely.
362		478
363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
364		480
365	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
366	it's really slow, but it still scales very well (O(active_fds)).	482	it's really slow, but it still scales very well (O(active_fds)).
367		483
368	Please note that solaris event ports can deliver a lot of spurious	484	Please note that Solaris event ports can deliver a lot of spurious
369	notifications, so you need to use non-blocking I/O or other means to avoid	485	notifications, so you need to use non-blocking I/O or other means to avoid
370	blocking when no data (or space) is available.	486	blocking when no data (or space) is available.
		487
		488	While this backend scales well, it requires one system call per active
		489	file descriptor per loop iteration. For small and medium numbers of file
		490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		491	might perform better.
		492
		493	On the positive side, with the exception of the spurious readiness
		494	notifications, this backend actually performed fully to specification
		495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
371		500
372	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
373		502
374	Try all backends (even potentially broken ones that wouldn't be tried	503	Try all backends (even potentially broken ones that wouldn't be tried
375	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
376	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
377		506
		507	It is definitely not recommended to use this flag.
		508
378	=back	509	=back
379		510
380	If one or more of these are ored into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
381	backends will be tried (in the reverse order as given here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
382	specified, most compiled-in backend will be tried, usually in reverse	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
383	order of their flag values :)
384		514
385	The most typical usage is like this:	515	Example: This is the most typical usage.
386		516
387	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
388	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
389		519
390	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
391	environment settings to be taken into account:	521	environment settings to be taken into account:
392		522
393	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
394		524
395	Use whatever libev has to offer, but make sure that kqueue is used if	525	Example: Use whatever libev has to offer, but make sure that kqueue is
396	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
397	event loop and only if you know the OS supports your types of fds):	527	private event loop and only if you know the OS supports your types of
		528	fds):
398		529
399	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
400		531
401	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
402		533
403	Similar to C<ev_default_loop>, but always creates a new event loop that is	534	Similar to C<ev_default_loop>, but always creates a new event loop that is
404	always distinct from the default loop. Unlike the default loop, it cannot	535	always distinct from the default loop. Unlike the default loop, it cannot
405	handle signal and child watchers, and attempts to do so will be greeted by	536	handle signal and child watchers, and attempts to do so will be greeted by
406	undefined behaviour (or a failed assertion if assertions are enabled).	537	undefined behaviour (or a failed assertion if assertions are enabled).
407		538
		539	Note that this function I<is> thread-safe, and the recommended way to use
		540	libev with threads is indeed to create one loop per thread, and using the
		541	default loop in the "main" or "initial" thread.
		542
408	Example: Try to create a event loop that uses epoll and nothing else.	543	Example: Try to create a event loop that uses epoll and nothing else.
409		544
410	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
411	if (!epoller)	546	if (!epoller)
412	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
413		548
414	=item ev_default_destroy ()	549	=item ev_default_destroy ()
415		550
416	Destroys the default loop again (frees all memory and kernel state	551	Destroys the default loop again (frees all memory and kernel state
417	etc.). None of the active event watchers will be stopped in the normal	552	etc.). None of the active event watchers will be stopped in the normal
418	sense, so e.g. C<ev_is_active> might still return true. It is your	553	sense, so e.g. C<ev_is_active> might still return true. It is your
419	responsibility to either stop all watchers cleanly yoursef I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
420	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
421	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
422	for example).	557	for example).
423		558
424	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
425	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
426	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
427		562
428	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
429	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
430	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
431	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
435	Like C<ev_default_destroy>, but destroys an event loop created by an	570	Like C<ev_default_destroy>, but destroys an event loop created by an
436	earlier call to C<ev_loop_new>.	571	earlier call to C<ev_loop_new>.
437		572
438	=item ev_default_fork ()	573	=item ev_default_fork ()
439		574
		575	This function sets a flag that causes subsequent C<ev_loop> iterations
440	This function reinitialises the kernel state for backends that have	576	to reinitialise the kernel state for backends that have one. Despite the
441	one. Despite the name, you can call it anytime, but it makes most sense	577	name, you can call it anytime, but it makes most sense after forking, in
442	after forking, in either the parent or child process (or both, but that	578	the child process (or both child and parent, but that again makes little
443	again makes little sense).	579	sense). You I<must> call it in the child before using any of the libev
		580	functions, and it will only take effect at the next C<ev_loop> iteration.
444		581
445	You I<must> call this function in the child process after forking if and	582	On the other hand, you only need to call this function in the child
446	only if you want to use the event library in both processes. If you just	583	process if and only if you want to use the event library in the child. If
447	fork+exec, you don't have to call it.	584	you just fork+exec, you don't have to call it at all.
448		585
449	The function itself is quite fast and it's usually not a problem to call	586	The function itself is quite fast and it's usually not a problem to call
450	it just in case after a fork. To make this easy, the function will fit in	587	it just in case after a fork. To make this easy, the function will fit in
451	quite nicely into a call to C<pthread_atfork>:	588	quite nicely into a call to C<pthread_atfork>:
452		589
453	pthread_atfork (0, 0, ev_default_fork);	590	pthread_atfork (0, 0, ev_default_fork);
454		591
455	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
456	without calling this function, so if you force one of those backends you
457	do not need to care.
458
459	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
460		593
461	Like C<ev_default_fork>, but acts on an event loop created by	594	Like C<ev_default_fork>, but acts on an event loop created by
462	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
463	after fork, and how you do this is entirely your own problem.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
		598
		599	=item int ev_is_default_loop (loop)
		600
		601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
464		603
465	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
466		605
467	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
468	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
483	received events and started processing them. This timestamp does not	622	received events and started processing them. This timestamp does not
484	change as long as callbacks are being processed, and this is also the base	623	change as long as callbacks are being processed, and this is also the base
485	time used for relative timers. You can treat it as the timestamp of the	624	time used for relative timers. You can treat it as the timestamp of the
486	event occurring (or more correctly, libev finding out about it).	625	event occurring (or more correctly, libev finding out about it).
487		626
		627	=item ev_now_update (loop)
		628
		629	Establishes the current time by querying the kernel, updating the time
		630	returned by C<ev_now ()> in the progress. This is a costly operation and
		631	is usually done automatically within C<ev_loop ()>.
		632
		633	This function is rarely useful, but when some event callback runs for a
		634	very long time without entering the event loop, updating libev's idea of
		635	the current time is a good idea.
		636
		637	See also "The special problem of time updates" in the C<ev_timer> section.
		638
488	=item ev_loop (loop, int flags)	639	=item ev_loop (loop, int flags)
489		640
490	Finally, this is it, the event handler. This function usually is called	641	Finally, this is it, the event handler. This function usually is called
491	after you initialised all your watchers and you want to start handling	642	after you initialised all your watchers and you want to start handling
492	events.	643	events.
…		…
494	If the flags argument is specified as C<0>, it will not return until	645	If the flags argument is specified as C<0>, it will not return until
495	either no event watchers are active anymore or C<ev_unloop> was called.	646	either no event watchers are active anymore or C<ev_unloop> was called.
496		647
497	Please note that an explicit C<ev_unloop> is usually better than	648	Please note that an explicit C<ev_unloop> is usually better than
498	relying on all watchers to be stopped when deciding when a program has	649	relying on all watchers to be stopped when deciding when a program has
499	finished (especially in interactive programs), but having a program that	650	finished (especially in interactive programs), but having a program
500	automatically loops as long as it has to and no longer by virtue of	651	that automatically loops as long as it has to and no longer by virtue
501	relying on its watchers stopping correctly is a thing of beauty.	652	of relying on its watchers stopping correctly, that is truly a thing of
		653	beauty.
502		654
503	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
504	those events and any outstanding ones, but will not block your process in	656	those events and any already outstanding ones, but will not block your
505	case there are no events and will return after one iteration of the loop.	657	process in case there are no events and will return after one iteration of
		658	the loop.
506		659
507	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
508	neccessary) and will handle those and any outstanding ones. It will block	661	necessary) and will handle those and any already outstanding ones. It
509	your process until at least one new event arrives, and will return after	662	will block your process until at least one new event arrives (which could
510	one iteration of the loop. This is useful if you are waiting for some	663	be an event internal to libev itself, so there is no guarantee that a
511	external event in conjunction with something not expressible using other	664	user-registered callback will be called), and will return after one
		665	iteration of the loop.
		666
		667	This is useful if you are waiting for some external event in conjunction
		668	with something not expressible using other libev watchers (i.e. "roll your
512	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
513	usually a better approach for this kind of thing.	670	usually a better approach for this kind of thing.
514		671
515	Here are the gory details of what C<ev_loop> does:	672	Here are the gory details of what C<ev_loop> does:
516		673
517	- Before the first iteration, call any pending watchers.	674	- Before the first iteration, call any pending watchers.
518	* If there are no active watchers (reference count is zero), return.	675	* If EVFLAG_FORKCHECK was used, check for a fork.
519	- Queue all prepare watchers and then call all outstanding watchers.	676	- If a fork was detected (by any means), queue and call all fork watchers.
		677	- Queue and call all prepare watchers.
520	- If we have been forked, recreate the kernel state.	678	- If we have been forked, detach and recreate the kernel state
		679	as to not disturb the other process.
521	- Update the kernel state with all outstanding changes.	680	- Update the kernel state with all outstanding changes.
522	- Update the "event loop time".	681	- Update the "event loop time" (ev_now ()).
523	- Calculate for how long to block.	682	- Calculate for how long to sleep or block, if at all
		683	(active idle watchers, EVLOOP_NONBLOCK or not having
		684	any active watchers at all will result in not sleeping).
		685	- Sleep if the I/O and timer collect interval say so.
524	- Block the process, waiting for any events.	686	- Block the process, waiting for any events.
525	- Queue all outstanding I/O (fd) events.	687	- Queue all outstanding I/O (fd) events.
526	- Update the "event loop time" and do time jump handling.	688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
527	- Queue all outstanding timers.	689	- Queue all expired timers.
528	- Queue all outstanding periodics.	690	- Queue all expired periodics.
529	- If no events are pending now, queue all idle watchers.	691	- Unless any events are pending now, queue all idle watchers.
530	- Queue all check watchers.	692	- Queue all check watchers.
531	- Call all queued watchers in reverse order (i.e. check watchers first).	693	- Call all queued watchers in reverse order (i.e. check watchers first).
532	Signals and child watchers are implemented as I/O watchers, and will	694	Signals and child watchers are implemented as I/O watchers, and will
533	be handled here by queueing them when their watcher gets executed.	695	be handled here by queueing them when their watcher gets executed.
534	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
535	were used, return, otherwise continue with step *.	697	were used, or there are no active watchers, return, otherwise
		698	continue with step *.
536		699
537	Example: Queue some jobs and then loop until no events are outsanding	700	Example: Queue some jobs and then loop until no events are outstanding
538	anymore.	701	anymore.
539		702
540	... queue jobs here, make sure they register event watchers as long	703	... queue jobs here, make sure they register event watchers as long
541	... as they still have work to do (even an idle watcher will do..)	704	... as they still have work to do (even an idle watcher will do..)
542	ev_loop (my_loop, 0);	705	ev_loop (my_loop, 0);
543	... jobs done. yeah!	706	... jobs done or somebody called unloop. yeah!
544		707
545	=item ev_unloop (loop, how)	708	=item ev_unloop (loop, how)
546		709
547	Can be used to make a call to C<ev_loop> return early (but only after it	710	Can be used to make a call to C<ev_loop> return early (but only after it
548	has processed all outstanding events). The C<how> argument must be either	711	has processed all outstanding events). The C<how> argument must be either
549	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
550	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
551		714
		715	This "unloop state" will be cleared when entering C<ev_loop> again.
		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
552	=item ev_ref (loop)	719	=item ev_ref (loop)
553		720
554	=item ev_unref (loop)	721	=item ev_unref (loop)
555		722
556	Ref/unref can be used to add or remove a reference count on the event	723	Ref/unref can be used to add or remove a reference count on the event
557	loop: Every watcher keeps one reference, and as long as the reference	724	loop: Every watcher keeps one reference, and as long as the reference
558	count is nonzero, C<ev_loop> will not return on its own. If you have	725	count is nonzero, C<ev_loop> will not return on its own.
		726
559	a watcher you never unregister that should not keep C<ev_loop> from	727	If you have a watcher you never unregister that should not keep C<ev_loop>
560	returning, ev_unref() after starting, and ev_ref() before stopping it. For	728	from returning, call ev_unref() after starting, and ev_ref() before
		729	stopping it.
		730
561	example, libev itself uses this for its internal signal pipe: It is not	731	As an example, libev itself uses this for its internal signal pipe: It is
562	visible to the libev user and should not keep C<ev_loop> from exiting if	732	not visible to the libev user and should not keep C<ev_loop> from exiting
563	no event watchers registered by it are active. It is also an excellent	733	if no event watchers registered by it are active. It is also an excellent
564	way to do this for generic recurring timers or from within third-party	734	way to do this for generic recurring timers or from within third-party
565	libraries. Just remember to I<unref after start> and I<ref before stop>.	735	libraries. Just remember to I<unref after start> and I<ref before stop>
		736	(but only if the watcher wasn't active before, or was active before,
		737	respectively).
566		738
567	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
568	running when nothing else is active.	740	running when nothing else is active.
569		741
570	struct ev_signal exitsig;	742	ev_signal exitsig;
571	ev_signal_init (&exitsig, sig_cb, SIGINT);	743	ev_signal_init (&exitsig, sig_cb, SIGINT);
572	ev_signal_start (loop, &exitsig);	744	ev_signal_start (loop, &exitsig);
573	evf_unref (loop);	745	evf_unref (loop);
574		746
575	Example: For some weird reason, unregister the above signal handler again.	747	Example: For some weird reason, unregister the above signal handler again.
576		748
577	ev_ref (loop);	749	ev_ref (loop);
578	ev_signal_stop (loop, &exitsig);	750	ev_signal_stop (loop, &exitsig);
579		751
580	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	752	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
581		753
582	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	754	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
583		755
584	These advanced functions influence the time that libev will spend waiting	756	These advanced functions influence the time that libev will spend waiting
585	for events. Both are by default C<0>, meaning that libev will try to	757	for events. Both time intervals are by default C<0>, meaning that libev
586	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	758	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		759	latency.
587		760
588	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	761	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
589	allows libev to delay invocation of I/O and timer/periodic callbacks to	762	allows libev to delay invocation of I/O and timer/periodic callbacks
590	increase efficiency of loop iterations.	763	to increase efficiency of loop iterations (or to increase power-saving
		764	opportunities).
591		765
592	The background is that sometimes your program runs just fast enough to	766	The idea is that sometimes your program runs just fast enough to handle
593	handle one (or very few) event(s) per loop iteration. While this makes	767	one (or very few) event(s) per loop iteration. While this makes the
594	the program responsive, it also wastes a lot of CPU time to poll for new	768	program responsive, it also wastes a lot of CPU time to poll for new
595	events, especially with backends like C<select ()> which have a high	769	events, especially with backends like C<select ()> which have a high
596	overhead for the actual polling but can deliver many events at once.	770	overhead for the actual polling but can deliver many events at once.
597		771
598	By setting a higher I<io collect interval> you allow libev to spend more	772	By setting a higher I<io collect interval> you allow libev to spend more
599	time collecting I/O events, so you can handle more events per iteration,	773	time collecting I/O events, so you can handle more events per iteration,
600	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	774	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
601	C<ev_timer>) will be not affected. Setting this to a non-null bvalue will	775	C<ev_timer>) will be not affected. Setting this to a non-null value will
602	introduce an additional C<ev_sleep ()> call into most loop iterations.	776	introduce an additional C<ev_sleep ()> call into most loop iterations.
603		777
604	Likewise, by setting a higher I<timeout collect interval> you allow libev	778	Likewise, by setting a higher I<timeout collect interval> you allow libev
605	to spend more time collecting timeouts, at the expense of increased	779	to spend more time collecting timeouts, at the expense of increased
606	latency (the watcher callback will be called later). C<ev_io> watchers	780	latency/jitter/inexactness (the watcher callback will be called
607	will not be affected. Setting this to a non-null value will not introduce	781	later). C<ev_io> watchers will not be affected. Setting this to a non-null
608	any overhead in libev.	782	value will not introduce any overhead in libev.
609		783
610	Many (busy) programs can usually benefit by setting the io collect	784	Many (busy) programs can usually benefit by setting the I/O collect
611	interval to a value near C<0.1> or so, which is often enough for	785	interval to a value near C<0.1> or so, which is often enough for
612	interactive servers (of course not for games), likewise for timeouts. It	786	interactive servers (of course not for games), likewise for timeouts. It
613	usually doesn't make much sense to set it to a lower value than C<0.01>,	787	usually doesn't make much sense to set it to a lower value than C<0.01>,
614	as this approsaches the timing granularity of most systems.	788	as this approaches the timing granularity of most systems.
		789
		790	Setting the I<timeout collect interval> can improve the opportunity for
		791	saving power, as the program will "bundle" timer callback invocations that
		792	are "near" in time together, by delaying some, thus reducing the number of
		793	times the process sleeps and wakes up again. Another useful technique to
		794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		795	they fire on, say, one-second boundaries only.
		796
		797	=item ev_loop_verify (loop)
		798
		799	This function only does something when C<EV_VERIFY> support has been
		800	compiled in, which is the default for non-minimal builds. It tries to go
		801	through all internal structures and checks them for validity. If anything
		802	is found to be inconsistent, it will print an error message to standard
		803	error and call C<abort ()>.
		804
		805	This can be used to catch bugs inside libev itself: under normal
		806	circumstances, this function will never abort as of course libev keeps its
		807	data structures consistent.
615		808
616	=back	809	=back
617		810
618		811
619	=head1 ANATOMY OF A WATCHER	812	=head1 ANATOMY OF A WATCHER
		813
		814	In the following description, uppercase C<TYPE> in names stands for the
		815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		816	watchers and C<ev_io_start> for I/O watchers.
620		817
621	A watcher is a structure that you create and register to record your	818	A watcher is a structure that you create and register to record your
622	interest in some event. For instance, if you want to wait for STDIN to	819	interest in some event. For instance, if you want to wait for STDIN to
623	become readable, you would create an C<ev_io> watcher for that:	820	become readable, you would create an C<ev_io> watcher for that:
624		821
625	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
626	{	823	{
627	ev_io_stop (w);	824	ev_io_stop (w);
628	ev_unloop (loop, EVUNLOOP_ALL);	825	ev_unloop (loop, EVUNLOOP_ALL);
629	}	826	}
630		827
631	struct ev_loop *loop = ev_default_loop (0);	828	struct ev_loop *loop = ev_default_loop (0);
		829
632	struct ev_io stdin_watcher;	830	ev_io stdin_watcher;
		831
633	ev_init (&stdin_watcher, my_cb);	832	ev_init (&stdin_watcher, my_cb);
634	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
635	ev_io_start (loop, &stdin_watcher);	834	ev_io_start (loop, &stdin_watcher);
		835
636	ev_loop (loop, 0);	836	ev_loop (loop, 0);
637		837
638	As you can see, you are responsible for allocating the memory for your	838	As you can see, you are responsible for allocating the memory for your
639	watcher structures (and it is usually a bad idea to do this on the stack,	839	watcher structures (and it is I<usually> a bad idea to do this on the
640	although this can sometimes be quite valid).	840	stack).
		841
		842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
641		844
642	Each watcher structure must be initialised by a call to C<ev_init	845	Each watcher structure must be initialised by a call to C<ev_init
643	(watcher *, callback)>, which expects a callback to be provided. This	846	(watcher *, callback)>, which expects a callback to be provided. This
644	callback gets invoked each time the event occurs (or, in the case of io	847	callback gets invoked each time the event occurs (or, in the case of I/O
645	watchers, each time the event loop detects that the file descriptor given	848	watchers, each time the event loop detects that the file descriptor given
646	is readable and/or writable).	849	is readable and/or writable).
647		850
648	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
649	with arguments specific to this watcher type. There is also a macro	852	macro to configure it, with arguments specific to the watcher type. There
650	to combine initialisation and setting in one call: C<< ev_<type>_init	853	is also a macro to combine initialisation and setting in one call: C<<
651	(watcher *, callback, ...) >>.	854	ev_TYPE_init (watcher *, callback, ...) >>.
652		855
653	To make the watcher actually watch out for events, you have to start it	856	To make the watcher actually watch out for events, you have to start it
654	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	857	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
655	*) >>), and you can stop watching for events at any time by calling the	858	*) >>), and you can stop watching for events at any time by calling the
656	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
657		860
658	As long as your watcher is active (has been started but not stopped) you	861	As long as your watcher is active (has been started but not stopped) you
659	must not touch the values stored in it. Most specifically you must never	862	must not touch the values stored in it. Most specifically you must never
660	reinitialise it or call its C<set> macro.	863	reinitialise it or call its C<ev_TYPE_set> macro.
661		864
662	Each and every callback receives the event loop pointer as first, the	865	Each and every callback receives the event loop pointer as first, the
663	registered watcher structure as second, and a bitset of received events as	866	registered watcher structure as second, and a bitset of received events as
664	third argument.	867	third argument.
665		868
…		…
719	=item C<EV_FORK>	922	=item C<EV_FORK>
720		923
721	The event loop has been resumed in the child process after fork (see	924	The event loop has been resumed in the child process after fork (see
722	C<ev_fork>).	925	C<ev_fork>).
723		926
		927	=item C<EV_ASYNC>
		928
		929	The given async watcher has been asynchronously notified (see C<ev_async>).
		930
724	=item C<EV_ERROR>	931	=item C<EV_ERROR>
725		932
726	An unspecified error has occured, the watcher has been stopped. This might	933	An unspecified error has occurred, the watcher has been stopped. This might
727	happen because the watcher could not be properly started because libev	934	happen because the watcher could not be properly started because libev
728	ran out of memory, a file descriptor was found to be closed or any other	935	ran out of memory, a file descriptor was found to be closed or any other
		936	problem. Libev considers these application bugs.
		937
729	problem. You best act on it by reporting the problem and somehow coping	938	You best act on it by reporting the problem and somehow coping with the
730	with the watcher being stopped.	939	watcher being stopped. Note that well-written programs should not receive
		940	an error ever, so when your watcher receives it, this usually indicates a
		941	bug in your program.
731		942
732	Libev will usually signal a few "dummy" events together with an error,	943	Libev will usually signal a few "dummy" events together with an error, for
733	for example it might indicate that a fd is readable or writable, and if	944	example it might indicate that a fd is readable or writable, and if your
734	your callbacks is well-written it can just attempt the operation and cope	945	callbacks is well-written it can just attempt the operation and cope with
735	with the error from read() or write(). This will not work in multithreaded	946	the error from read() or write(). This will not work in multi-threaded
736	programs, though, so beware.	947	programs, though, as the fd could already be closed and reused for another
		948	thing, so beware.
737		949
738	=back	950	=back
739		951
740	=head2 GENERIC WATCHER FUNCTIONS	952	=head2 GENERIC WATCHER FUNCTIONS
741
742	In the following description, C<TYPE> stands for the watcher type,
743	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
744		953
745	=over 4	954	=over 4
746		955
747	=item C<ev_init> (ev_TYPE *watcher, callback)	956	=item C<ev_init> (ev_TYPE *watcher, callback)
748		957
…		…
754	which rolls both calls into one.	963	which rolls both calls into one.
755		964
756	You can reinitialise a watcher at any time as long as it has been stopped	965	You can reinitialise a watcher at any time as long as it has been stopped
757	(or never started) and there are no pending events outstanding.	966	(or never started) and there are no pending events outstanding.
758		967
759	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	968	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
760	int revents)>.	969	int revents)>.
		970
		971	Example: Initialise an C<ev_io> watcher in two steps.
		972
		973	ev_io w;
		974	ev_init (&w, my_cb);
		975	ev_io_set (&w, STDIN_FILENO, EV_READ);
761		976
762	=item C<ev_TYPE_set> (ev_TYPE *, [args])	977	=item C<ev_TYPE_set> (ev_TYPE *, [args])
763		978
764	This macro initialises the type-specific parts of a watcher. You need to	979	This macro initialises the type-specific parts of a watcher. You need to
765	call C<ev_init> at least once before you call this macro, but you can	980	call C<ev_init> at least once before you call this macro, but you can
…		…
768	difference to the C<ev_init> macro).	983	difference to the C<ev_init> macro).
769		984
770	Although some watcher types do not have type-specific arguments	985	Although some watcher types do not have type-specific arguments
771	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	986	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
772		987
		988	See C<ev_init>, above, for an example.
		989
773	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	990	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
774		991
775	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	992	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
776	calls into a single call. This is the most convinient method to initialise	993	calls into a single call. This is the most convenient method to initialise
777	a watcher. The same limitations apply, of course.	994	a watcher. The same limitations apply, of course.
		995
		996	Example: Initialise and set an C<ev_io> watcher in one step.
		997
		998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
778		999
779	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
780		1001
781	Starts (activates) the given watcher. Only active watchers will receive	1002	Starts (activates) the given watcher. Only active watchers will receive
782	events. If the watcher is already active nothing will happen.	1003	events. If the watcher is already active nothing will happen.
783		1004
		1005	Example: Start the C<ev_io> watcher that is being abused as example in this
		1006	whole section.
		1007
		1008	ev_io_start (EV_DEFAULT_UC, &w);
		1009
784	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
785		1011
786	Stops the given watcher again (if active) and clears the pending	1012	Stops the given watcher if active, and clears the pending status (whether
		1013	the watcher was active or not).
		1014
787	status. It is possible that stopped watchers are pending (for example,	1015	It is possible that stopped watchers are pending - for example,
788	non-repeating timers are being stopped when they become pending), but	1016	non-repeating timers are being stopped when they become pending - but
789	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1017	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
790	you want to free or reuse the memory used by the watcher it is therefore a	1018	pending. If you want to free or reuse the memory used by the watcher it is
791	good idea to always call its C<ev_TYPE_stop> function.	1019	therefore a good idea to always call its C<ev_TYPE_stop> function.
792		1020
793	=item bool ev_is_active (ev_TYPE *watcher)	1021	=item bool ev_is_active (ev_TYPE *watcher)
794		1022
795	Returns a true value iff the watcher is active (i.e. it has been started	1023	Returns a true value iff the watcher is active (i.e. it has been started
796	and not yet been stopped). As long as a watcher is active you must not modify	1024	and not yet been stopped). As long as a watcher is active you must not modify
…		…
838	The default priority used by watchers when no priority has been set is	1066	The default priority used by watchers when no priority has been set is
839	always C<0>, which is supposed to not be too high and not be too low :).	1067	always C<0>, which is supposed to not be too high and not be too low :).
840		1068
841	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
842	fine, as long as you do not mind that the priority value you query might	1070	fine, as long as you do not mind that the priority value you query might
843	or might not have been adjusted to be within valid range.	1071	or might not have been clamped to the valid range.
844		1072
845	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
846		1074
847	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
848	C<loop> nor C<revents> need to be valid as long as the watcher callback	1076	C<loop> nor C<revents> need to be valid as long as the watcher callback
849	can deal with that fact.	1077	can deal with that fact, as both are simply passed through to the
		1078	callback.
850		1079
851	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1080	=item int ev_clear_pending (loop, ev_TYPE *watcher)
852		1081
853	If the watcher is pending, this function returns clears its pending status	1082	If the watcher is pending, this function clears its pending status and
854	and returns its C<revents> bitset (as if its callback was invoked). If the	1083	returns its C<revents> bitset (as if its callback was invoked). If the
855	watcher isn't pending it does nothing and returns C<0>.	1084	watcher isn't pending it does nothing and returns C<0>.
856		1085
		1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1087	callback to be invoked, which can be accomplished with this function.
		1088
857	=back	1089	=back
858		1090
859		1091
860	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
861		1093
862	Each watcher has, by default, a member C<void *data> that you can change	1094	Each watcher has, by default, a member C<void *data> that you can change
863	and read at any time, libev will completely ignore it. This can be used	1095	and read at any time: libev will completely ignore it. This can be used
864	to associate arbitrary data with your watcher. If you need more data and	1096	to associate arbitrary data with your watcher. If you need more data and
865	don't want to allocate memory and store a pointer to it in that data	1097	don't want to allocate memory and store a pointer to it in that data
866	member, you can also "subclass" the watcher type and provide your own	1098	member, you can also "subclass" the watcher type and provide your own
867	data:	1099	data:
868		1100
869	struct my_io	1101	struct my_io
870	{	1102	{
871	struct ev_io io;	1103	ev_io io;
872	int otherfd;	1104	int otherfd;
873	void *somedata;	1105	void *somedata;
874	struct whatever *mostinteresting;	1106	struct whatever *mostinteresting;
875	}	1107	};
		1108
		1109	...
		1110	struct my_io w;
		1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
876		1112
877	And since your callback will be called with a pointer to the watcher, you	1113	And since your callback will be called with a pointer to the watcher, you
878	can cast it back to your own type:	1114	can cast it back to your own type:
879		1115
880	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
881	{	1117	{
882	struct my_io *w = (struct my_io *)w_;	1118	struct my_io *w = (struct my_io *)w_;
883	...	1119	...
884	}	1120	}
885		1121
886	More interesting and less C-conformant ways of casting your callback type	1122	More interesting and less C-conformant ways of casting your callback type
887	instead have been omitted.	1123	instead have been omitted.
888		1124
889	Another common scenario is having some data structure with multiple	1125	Another common scenario is to use some data structure with multiple
890	watchers:	1126	embedded watchers:
891		1127
892	struct my_biggy	1128	struct my_biggy
893	{	1129	{
894	int some_data;	1130	int some_data;
895	ev_timer t1;	1131	ev_timer t1;
896	ev_timer t2;	1132	ev_timer t2;
897	}	1133	}
898		1134
899	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1135	In this case getting the pointer to C<my_biggy> is a bit more
900	you need to use C<offsetof>:	1136	complicated: Either you store the address of your C<my_biggy> struct
		1137	in the C<data> member of the watcher (for woozies), or you need to use
		1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1139	programmers):
901		1140
902	#include <stddef.h>	1141	#include <stddef.h>
903		1142
904	static void	1143	static void
905	t1_cb (EV_P_ struct ev_timer *w, int revents)	1144	t1_cb (EV_P_ ev_timer *w, int revents)
906	{	1145	{
907	struct my_biggy big = (struct my_biggy *	1146	struct my_biggy big = (struct my_biggy *
908	(((char *)w) - offsetof (struct my_biggy, t1));	1147	(((char *)w) - offsetof (struct my_biggy, t1));
909	}	1148	}
910		1149
911	static void	1150	static void
912	t2_cb (EV_P_ struct ev_timer *w, int revents)	1151	t2_cb (EV_P_ ev_timer *w, int revents)
913	{	1152	{
914	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
915	(((char *)w) - offsetof (struct my_biggy, t2));	1154	(((char *)w) - offsetof (struct my_biggy, t2));
916	}	1155	}
917		1156
918		1157
919	=head1 WATCHER TYPES	1158	=head1 WATCHER TYPES
920		1159
921	This section describes each watcher in detail, but will not repeat	1160	This section describes each watcher in detail, but will not repeat
…		…
945	In general you can register as many read and/or write event watchers per	1184	In general you can register as many read and/or write event watchers per
946	fd as you want (as long as you don't confuse yourself). Setting all file	1185	fd as you want (as long as you don't confuse yourself). Setting all file
947	descriptors to non-blocking mode is also usually a good idea (but not	1186	descriptors to non-blocking mode is also usually a good idea (but not
948	required if you know what you are doing).	1187	required if you know what you are doing).
949		1188
950	You have to be careful with dup'ed file descriptors, though. Some backends	1189	If you cannot use non-blocking mode, then force the use of a
951	(the linux epoll backend is a notable example) cannot handle dup'ed file	1190	known-to-be-good backend (at the time of this writing, this includes only
952	descriptors correctly if you register interest in two or more fds pointing	1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
953	to the same underlying file/socket/etc. description (that is, they share
954	the same underlying "file open").
955
956	If you must do this, then force the use of a known-to-be-good backend
957	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
958	C<EVBACKEND_POLL>).
959		1192
960	Another thing you have to watch out for is that it is quite easy to	1193	Another thing you have to watch out for is that it is quite easy to
961	receive "spurious" readyness notifications, that is your callback might	1194	receive "spurious" readiness notifications, that is your callback might
962	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
963	because there is no data. Not only are some backends known to create a	1196	because there is no data. Not only are some backends known to create a
964	lot of those (for example solaris ports), it is very easy to get into	1197	lot of those (for example Solaris ports), it is very easy to get into
965	this situation even with a relatively standard program structure. Thus	1198	this situation even with a relatively standard program structure. Thus
966	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
967	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.
968		1201
969	If you cannot run the fd in non-blocking mode (for example you should not	1202	If you cannot run the fd in non-blocking mode (for example you should
970	play around with an Xlib connection), then you have to seperately re-test	1203	not play around with an Xlib connection), then you have to separately
971	whether a file descriptor is really ready with a known-to-be good interface	1204	re-test whether a file descriptor is really ready with a known-to-be good
972	such as poll (fortunately in our Xlib example, Xlib already does this on	1205	interface such as poll (fortunately in our Xlib example, Xlib already
973	its own, so its quite safe to use).	1206	does this on its own, so its quite safe to use). Some people additionally
		1207	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1208	indefinitely.
		1209
		1210	But really, best use non-blocking mode.
974		1211
975	=head3 The special problem of disappearing file descriptors	1212	=head3 The special problem of disappearing file descriptors
976		1213
977	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1214	Some backends (e.g. kqueue, epoll) need to be told about closing a file
978	descriptor (either by calling C<close> explicitly or by any other means,	1215	descriptor (either due to calling C<close> explicitly or any other means,
979	such as C<dup>). The reason is that you register interest in some file	1216	such as C<dup2>). The reason is that you register interest in some file
980	descriptor, but when it goes away, the operating system will silently drop	1217	descriptor, but when it goes away, the operating system will silently drop
981	this interest. If another file descriptor with the same number then is	1218	this interest. If another file descriptor with the same number then is
982	registered with libev, there is no efficient way to see that this is, in	1219	registered with libev, there is no efficient way to see that this is, in
983	fact, a different file descriptor.	1220	fact, a different file descriptor.
984		1221
…		…
994	optimisations to libev.	1231	optimisations to libev.
995		1232
996	=head3 The special problem of dup'ed file descriptors	1233	=head3 The special problem of dup'ed file descriptors
997		1234
998	Some backends (e.g. epoll), cannot register events for file descriptors,	1235	Some backends (e.g. epoll), cannot register events for file descriptors,
999	but only events for the underlying file descriptions. That menas when you	1236	but only events for the underlying file descriptions. That means when you
1000	have C<dup ()>'ed file descriptors and register events for them, only one	1237	have C<dup ()>'ed file descriptors or weirder constellations, and register
1001	file descriptor might actually receive events.	1238	events for them, only one file descriptor might actually receive events.
1002		1239
1003	There is no workaorund possible except not registering events	1240	There is no workaround possible except not registering events
1004	for potentially C<dup ()>'ed file descriptors or to resort to	1241	for potentially C<dup ()>'ed file descriptors, or to resort to
1005	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1242	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1006		1243
1007	=head3 The special problem of fork	1244	=head3 The special problem of fork
1008		1245
1009	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1246	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
1013	To support fork in your programs, you either have to call	1250	To support fork in your programs, you either have to call
1014	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1251	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1015	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1016	C<EVBACKEND_POLL>.	1253	C<EVBACKEND_POLL>.
1017		1254
		1255	=head3 The special problem of SIGPIPE
		1256
		1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1258	when writing to a pipe whose other end has been closed, your program gets
		1259	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1260	this is sensible behaviour, for daemons, this is usually undesirable.
		1261
		1262	So when you encounter spurious, unexplained daemon exits, make sure you
		1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1264	somewhere, as that would have given you a big clue).
		1265
1018		1266
1019	=head3 Watcher-Specific Functions	1267	=head3 Watcher-Specific Functions
1020		1268
1021	=over 4	1269	=over 4
1022		1270
1023	=item ev_io_init (ev_io *, callback, int fd, int events)	1271	=item ev_io_init (ev_io *, callback, int fd, int events)
1024		1272
1025	=item ev_io_set (ev_io *, int fd, int events)	1273	=item ev_io_set (ev_io *, int fd, int events)
1026		1274
1027	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1275	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1028	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1276	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1029	C<EV_READ | EV_WRITE> to receive the given events.	1277	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1030		1278
1031	=item int fd [read-only]	1279	=item int fd [read-only]
1032		1280
1033	The file descriptor being watched.	1281	The file descriptor being watched.
1034		1282
1035	=item int events [read-only]	1283	=item int events [read-only]
1036		1284
1037	The events being watched.	1285	The events being watched.
1038		1286
1039	=back	1287	=back
		1288
		1289	=head3 Examples
1040		1290
1041	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1291	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1042	readable, but only once. Since it is likely line-buffered, you could	1292	readable, but only once. Since it is likely line-buffered, you could
1043	attempt to read a whole line in the callback.	1293	attempt to read a whole line in the callback.
1044		1294
1045	static void	1295	static void
1046	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1296	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1047	{	1297	{
1048	ev_io_stop (loop, w);	1298	ev_io_stop (loop, w);
1049	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1299	.. read from stdin here (or from w->fd) and handle any I/O errors
1050	}	1300	}
1051		1301
1052	...	1302	...
1053	struct ev_loop *loop = ev_default_init (0);	1303	struct ev_loop *loop = ev_default_init (0);
1054	struct ev_io stdin_readable;	1304	ev_io stdin_readable;
1055	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1056	ev_io_start (loop, &stdin_readable);	1306	ev_io_start (loop, &stdin_readable);
1057	ev_loop (loop, 0);	1307	ev_loop (loop, 0);
1058		1308
1059		1309
1060	=head2 C<ev_timer> - relative and optionally repeating timeouts	1310	=head2 C<ev_timer> - relative and optionally repeating timeouts
1061		1311
1062	Timer watchers are simple relative timers that generate an event after a	1312	Timer watchers are simple relative timers that generate an event after a
1063	given time, and optionally repeating in regular intervals after that.	1313	given time, and optionally repeating in regular intervals after that.
1064		1314
1065	The timers are based on real time, that is, if you register an event that	1315	The timers are based on real time, that is, if you register an event that
1066	times out after an hour and you reset your system clock to last years	1316	times out after an hour and you reset your system clock to January last
1067	time, it will still time out after (roughly) and hour. "Roughly" because	1317	year, it will still time out after (roughly) one hour. "Roughly" because
1068	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1069	monotonic clock option helps a lot here).	1319	monotonic clock option helps a lot here).
		1320
		1321	The callback is guaranteed to be invoked only I<after> its timeout has
		1322	passed, but if multiple timers become ready during the same loop iteration
		1323	then order of execution is undefined.
		1324
		1325	=head3 Be smart about timeouts
		1326
		1327	Many real-world problems involve some kind of timeout, usually for error
		1328	recovery. A typical example is an HTTP request - if the other side hangs,
		1329	you want to raise some error after a while.
		1330
		1331	What follows are some ways to handle this problem, from obvious and
		1332	inefficient to smart and efficient.
		1333
		1334	In the following, a 60 second activity timeout is assumed - a timeout that
		1335	gets reset to 60 seconds each time there is activity (e.g. each time some
		1336	data or other life sign was received).
		1337
		1338	=over 4
		1339
		1340	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1341
		1342	This is the most obvious, but not the most simple way: In the beginning,
		1343	start the watcher:
		1344
		1345	ev_timer_init (timer, callback, 60., 0.);
		1346	ev_timer_start (loop, timer);
		1347
		1348	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1349	and start it again:
		1350
		1351	ev_timer_stop (loop, timer);
		1352	ev_timer_set (timer, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	This is relatively simple to implement, but means that each time there is
		1356	some activity, libev will first have to remove the timer from its internal
		1357	data structure and then add it again. Libev tries to be fast, but it's
		1358	still not a constant-time operation.
		1359
		1360	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1361
		1362	This is the easiest way, and involves using C<ev_timer_again> instead of
		1363	C<ev_timer_start>.
		1364
		1365	To implement this, configure an C<ev_timer> with a C<repeat> value
		1366	of C<60> and then call C<ev_timer_again> at start and each time you
		1367	successfully read or write some data. If you go into an idle state where
		1368	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1369	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1370
		1371	That means you can ignore both the C<ev_timer_start> function and the
		1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1373	member and C<ev_timer_again>.
		1374
		1375	At start:
		1376
		1377	ev_timer_init (timer, callback);
		1378	timer->repeat = 60.;
		1379	ev_timer_again (loop, timer);
		1380
		1381	Each time there is some activity:
		1382
		1383	ev_timer_again (loop, timer);
		1384
		1385	It is even possible to change the time-out on the fly, regardless of
		1386	whether the watcher is active or not:
		1387
		1388	timer->repeat = 30.;
		1389	ev_timer_again (loop, timer);
		1390
		1391	This is slightly more efficient then stopping/starting the timer each time
		1392	you want to modify its timeout value, as libev does not have to completely
		1393	remove and re-insert the timer from/into its internal data structure.
		1394
		1395	It is, however, even simpler than the "obvious" way to do it.
		1396
		1397	=item 3. Let the timer time out, but then re-arm it as required.
		1398
		1399	This method is more tricky, but usually most efficient: Most timeouts are
		1400	relatively long compared to the intervals between other activity - in
		1401	our example, within 60 seconds, there are usually many I/O events with
		1402	associated activity resets.
		1403
		1404	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1405	but remember the time of last activity, and check for a real timeout only
		1406	within the callback:
		1407
		1408	ev_tstamp last_activity; // time of last activity
		1409
		1410	static void
		1411	callback (EV_P_ ev_timer *w, int revents)
		1412	{
		1413	ev_tstamp now = ev_now (EV_A);
		1414	ev_tstamp timeout = last_activity + 60.;
		1415
		1416	// if last_activity + 60. is older than now, we did time out
		1417	if (timeout < now)
		1418	{
		1419	// timeout occured, take action
		1420	}
		1421	else
		1422	{
		1423	// callback was invoked, but there was some activity, re-arm
		1424	// the watcher to fire in last_activity + 60, which is
		1425	// guaranteed to be in the future, so "again" is positive:
		1426	w->repeat = timeout - now;
		1427	ev_timer_again (EV_A_ w);
		1428	}
		1429	}
		1430
		1431	To summarise the callback: first calculate the real timeout (defined
		1432	as "60 seconds after the last activity"), then check if that time has
		1433	been reached, which means something I<did>, in fact, time out. Otherwise
		1434	the callback was invoked too early (C<timeout> is in the future), so
		1435	re-schedule the timer to fire at that future time, to see if maybe we have
		1436	a timeout then.
		1437
		1438	Note how C<ev_timer_again> is used, taking advantage of the
		1439	C<ev_timer_again> optimisation when the timer is already running.
		1440
		1441	This scheme causes more callback invocations (about one every 60 seconds
		1442	minus half the average time between activity), but virtually no calls to
		1443	libev to change the timeout.
		1444
		1445	To start the timer, simply initialise the watcher and set C<last_activity>
		1446	to the current time (meaning we just have some activity :), then call the
		1447	callback, which will "do the right thing" and start the timer:
		1448
		1449	ev_timer_init (timer, callback);
		1450	last_activity = ev_now (loop);
		1451	callback (loop, timer, EV_TIMEOUT);
		1452
		1453	And when there is some activity, simply store the current time in
		1454	C<last_activity>, no libev calls at all:
		1455
		1456	last_actiivty = ev_now (loop);
		1457
		1458	This technique is slightly more complex, but in most cases where the
		1459	time-out is unlikely to be triggered, much more efficient.
		1460
		1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1462	callback :) - just change the timeout and invoke the callback, which will
		1463	fix things for you.
		1464
		1465	=item 4. Wee, just use a double-linked list for your timeouts.
		1466
		1467	If there is not one request, but many thousands (millions...), all
		1468	employing some kind of timeout with the same timeout value, then one can
		1469	do even better:
		1470
		1471	When starting the timeout, calculate the timeout value and put the timeout
		1472	at the I<end> of the list.
		1473
		1474	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1475	the list is expected to fire (for example, using the technique #3).
		1476
		1477	When there is some activity, remove the timer from the list, recalculate
		1478	the timeout, append it to the end of the list again, and make sure to
		1479	update the C<ev_timer> if it was taken from the beginning of the list.
		1480
		1481	This way, one can manage an unlimited number of timeouts in O(1) time for
		1482	starting, stopping and updating the timers, at the expense of a major
		1483	complication, and having to use a constant timeout. The constant timeout
		1484	ensures that the list stays sorted.
		1485
		1486	=back
		1487
		1488	So which method the best?
		1489
		1490	Method #2 is a simple no-brain-required solution that is adequate in most
		1491	situations. Method #3 requires a bit more thinking, but handles many cases
		1492	better, and isn't very complicated either. In most case, choosing either
		1493	one is fine, with #3 being better in typical situations.
		1494
		1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1496	rather complicated, but extremely efficient, something that really pays
		1497	off after the first million or so of active timers, i.e. it's usually
		1498	overkill :)
		1499
		1500	=head3 The special problem of time updates
		1501
		1502	Establishing the current time is a costly operation (it usually takes at
		1503	least two system calls): EV therefore updates its idea of the current
		1504	time only before and after C<ev_loop> collects new events, which causes a
		1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1506	lots of events in one iteration.
1070		1507
1071	The relative timeouts are calculated relative to the C<ev_now ()>	1508	The relative timeouts are calculated relative to the C<ev_now ()>
1072	time. This is usually the right thing as this timestamp refers to the time	1509	time. This is usually the right thing as this timestamp refers to the time
1073	of the event triggering whatever timeout you are modifying/starting. If	1510	of the event triggering whatever timeout you are modifying/starting. If
1074	you suspect event processing to be delayed and you I<need> to base the timeout	1511	you suspect event processing to be delayed and you I<need> to base the
1075	on the current time, use something like this to adjust for this:	1512	timeout on the current time, use something like this to adjust for this:
1076		1513
1077	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1078		1515
1079	The callback is guarenteed to be invoked only when its timeout has passed,	1516	If the event loop is suspended for a long time, you can also force an
1080	but if multiple timers become ready during the same loop iteration then	1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1081	order of execution is undefined.	1518	()>.
1082		1519
1083	=head3 Watcher-Specific Functions and Data Members	1520	=head3 Watcher-Specific Functions and Data Members
1084		1521
1085	=over 4	1522	=over 4
1086		1523
1087	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1088		1525
1089	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1526	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1090		1527
1091	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1528	Configure the timer to trigger after C<after> seconds. If C<repeat>
1092	C<0.>, then it will automatically be stopped. If it is positive, then the	1529	is C<0.>, then it will automatically be stopped once the timeout is
1093	timer will automatically be configured to trigger again C<repeat> seconds	1530	reached. If it is positive, then the timer will automatically be
1094	later, again, and again, until stopped manually.	1531	configured to trigger again C<repeat> seconds later, again, and again,
		1532	until stopped manually.
1095		1533
1096	The timer itself will do a best-effort at avoiding drift, that is, if you	1534	The timer itself will do a best-effort at avoiding drift, that is, if
1097	configure a timer to trigger every 10 seconds, then it will trigger at	1535	you configure a timer to trigger every 10 seconds, then it will normally
1098	exactly 10 second intervals. If, however, your program cannot keep up with	1536	trigger at exactly 10 second intervals. If, however, your program cannot
1099	the timer (because it takes longer than those 10 seconds to do stuff) the	1537	keep up with the timer (because it takes longer than those 10 seconds to
1100	timer will not fire more than once per event loop iteration.	1538	do stuff) the timer will not fire more than once per event loop iteration.
1101		1539
1102	=item ev_timer_again (loop)	1540	=item ev_timer_again (loop, ev_timer *)
1103		1541
1104	This will act as if the timer timed out and restart it again if it is	1542	This will act as if the timer timed out and restart it again if it is
1105	repeating. The exact semantics are:	1543	repeating. The exact semantics are:
1106		1544
1107	If the timer is pending, its pending status is cleared.	1545	If the timer is pending, its pending status is cleared.
1108		1546
1109	If the timer is started but nonrepeating, stop it (as if it timed out).	1547	If the timer is started but non-repeating, stop it (as if it timed out).
1110		1548
1111	If the timer is repeating, either start it if necessary (with the	1549	If the timer is repeating, either start it if necessary (with the
1112	C<repeat> value), or reset the running timer to the C<repeat> value.	1550	C<repeat> value), or reset the running timer to the C<repeat> value.
1113		1551
1114	This sounds a bit complicated, but here is a useful and typical	1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1115	example: Imagine you have a tcp connection and you want a so-called idle	1553	usage example.
1116	timeout, that is, you want to be called when there have been, say, 60
1117	seconds of inactivity on the socket. The easiest way to do this is to
1118	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1119	C<ev_timer_again> each time you successfully read or write some data. If
1120	you go into an idle state where you do not expect data to travel on the
1121	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1122	automatically restart it if need be.
1123
1124	That means you can ignore the C<after> value and C<ev_timer_start>
1125	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1126
1127	ev_timer_init (timer, callback, 0., 5.);
1128	ev_timer_again (loop, timer);
1129	...
1130	timer->again = 17.;
1131	ev_timer_again (loop, timer);
1132	...
1133	timer->again = 10.;
1134	ev_timer_again (loop, timer);
1135
1136	This is more slightly efficient then stopping/starting the timer each time
1137	you want to modify its timeout value.
1138		1554
1139	=item ev_tstamp repeat [read-write]	1555	=item ev_tstamp repeat [read-write]
1140		1556
1141	The current C<repeat> value. Will be used each time the watcher times out	1557	The current C<repeat> value. Will be used each time the watcher times out
1142	or C<ev_timer_again> is called and determines the next timeout (if any),	1558	or C<ev_timer_again> is called, and determines the next timeout (if any),
1143	which is also when any modifications are taken into account.	1559	which is also when any modifications are taken into account.
1144		1560
1145	=back	1561	=back
1146		1562
		1563	=head3 Examples
		1564
1147	Example: Create a timer that fires after 60 seconds.	1565	Example: Create a timer that fires after 60 seconds.
1148		1566
1149	static void	1567	static void
1150	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1568	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1151	{	1569	{
1152	.. one minute over, w is actually stopped right here	1570	.. one minute over, w is actually stopped right here
1153	}	1571	}
1154		1572
1155	struct ev_timer mytimer;	1573	ev_timer mytimer;
1156	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1574	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1157	ev_timer_start (loop, &mytimer);	1575	ev_timer_start (loop, &mytimer);
1158		1576
1159	Example: Create a timeout timer that times out after 10 seconds of	1577	Example: Create a timeout timer that times out after 10 seconds of
1160	inactivity.	1578	inactivity.
1161		1579
1162	static void	1580	static void
1163	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1581	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1164	{	1582	{
1165	.. ten seconds without any activity	1583	.. ten seconds without any activity
1166	}	1584	}
1167		1585
1168	struct ev_timer mytimer;	1586	ev_timer mytimer;
1169	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1170	ev_timer_again (&mytimer); /* start timer */	1588	ev_timer_again (&mytimer); /* start timer */
1171	ev_loop (loop, 0);	1589	ev_loop (loop, 0);
1172		1590
1173	// and in some piece of code that gets executed on any "activity":	1591	// and in some piece of code that gets executed on any "activity":
1174	// reset the timeout to start ticking again at 10 seconds	1592	// reset the timeout to start ticking again at 10 seconds
1175	ev_timer_again (&mytimer);	1593	ev_timer_again (&mytimer);
1176		1594
1177		1595
1178	=head2 C<ev_periodic> - to cron or not to cron?	1596	=head2 C<ev_periodic> - to cron or not to cron?
1179		1597
1180	Periodic watchers are also timers of a kind, but they are very versatile	1598	Periodic watchers are also timers of a kind, but they are very versatile
1181	(and unfortunately a bit complex).	1599	(and unfortunately a bit complex).
1182		1600
1183	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1184	but on wallclock time (absolute time). You can tell a periodic watcher	1602	but on wall clock time (absolute time). You can tell a periodic watcher
1185	to trigger "at" some specific point in time. For example, if you tell a	1603	to trigger after some specific point in time. For example, if you tell a
1186	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1187	+ 10.>) and then reset your system clock to the last year, then it will	1605	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1606	clock to January of the previous year, then it will take more than year
1188	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1189	roughly 10 seconds later).	1608	roughly 10 seconds later as it uses a relative timeout).
1190		1609
1191	They can also be used to implement vastly more complex timers, such as	1610	C<ev_periodic>s can also be used to implement vastly more complex timers,
1192	triggering an event on each midnight, local time or other, complicated,	1611	such as triggering an event on each "midnight, local time", or other
1193	rules.	1612	complicated rules.
1194		1613
1195	As with timers, the callback is guarenteed to be invoked only when the	1614	As with timers, the callback is guaranteed to be invoked only when the
1196	time (C<at>) has been passed, but if multiple periodic timers become ready	1615	time (C<at>) has passed, but if multiple periodic timers become ready
1197	during the same loop iteration then order of execution is undefined.	1616	during the same loop iteration, then order of execution is undefined.
1198		1617
1199	=head3 Watcher-Specific Functions and Data Members	1618	=head3 Watcher-Specific Functions and Data Members
1200		1619
1201	=over 4	1620	=over 4
1202		1621
1203	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1204		1623
1205	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1624	=item ev_periodic_set (ev_periodic *, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1206		1625
1207	Lots of arguments, lets sort it out... There are basically three modes of	1626	Lots of arguments, lets sort it out... There are basically three modes of
1208	operation, and we will explain them from simplest to complex:	1627	operation, and we will explain them from simplest to most complex:
1209		1628
1210	=over 4	1629	=over 4
1211		1630
1212	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1213		1632
1214	In this configuration the watcher triggers an event at the wallclock time	1633	In this configuration the watcher triggers an event after the wall clock
1215	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1634	time C<at> has passed. It will not repeat and will not adjust when a time
1216	that is, if it is to be run at January 1st 2011 then it will run when the	1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1217	system time reaches or surpasses this time.	1636	only run when the system clock reaches or surpasses this time.
1218		1637
1219	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1220		1639
1221	In this mode the watcher will always be scheduled to time out at the next	1640	In this mode the watcher will always be scheduled to time out at the next
1222	C<at + N * interval> time (for some integer N, which can also be negative)	1641	C<at + N * interval> time (for some integer N, which can also be negative)
1223	and then repeat, regardless of any time jumps.	1642	and then repeat, regardless of any time jumps.
1224		1643
1225	This can be used to create timers that do not drift with respect to system	1644	This can be used to create timers that do not drift with respect to the
1226	time:	1645	system clock, for example, here is a C<ev_periodic> that triggers each
		1646	hour, on the hour:
1227		1647
1228	ev_periodic_set (&periodic, 0., 3600., 0);	1648	ev_periodic_set (&periodic, 0., 3600., 0);
1229		1649
1230	This doesn't mean there will always be 3600 seconds in between triggers,	1650	This doesn't mean there will always be 3600 seconds in between triggers,
1231	but only that the the callback will be called when the system time shows a	1651	but only that the callback will be called when the system time shows a
1232	full hour (UTC), or more correctly, when the system time is evenly divisible	1652	full hour (UTC), or more correctly, when the system time is evenly divisible
1233	by 3600.	1653	by 3600.
1234		1654
1235	Another way to think about it (for the mathematically inclined) is that	1655	Another way to think about it (for the mathematically inclined) is that
1236	C<ev_periodic> will try to run the callback in this mode at the next possible	1656	C<ev_periodic> will try to run the callback in this mode at the next possible
1237	time where C<time = at (mod interval)>, regardless of any time jumps.	1657	time where C<time = at (mod interval)>, regardless of any time jumps.
1238		1658
1239	For numerical stability it is preferable that the C<at> value is near	1659	For numerical stability it is preferable that the C<at> value is near
1240	C<ev_now ()> (the current time), but there is no range requirement for	1660	C<ev_now ()> (the current time), but there is no range requirement for
1241	this value.	1661	this value, and in fact is often specified as zero.
		1662
		1663	Note also that there is an upper limit to how often a timer can fire (CPU
		1664	speed for example), so if C<interval> is very small then timing stability
		1665	will of course deteriorate. Libev itself tries to be exact to be about one
		1666	millisecond (if the OS supports it and the machine is fast enough).
1242		1667
1243	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1244		1669
1245	In this mode the values for C<interval> and C<at> are both being	1670	In this mode the values for C<interval> and C<at> are both being
1246	ignored. Instead, each time the periodic watcher gets scheduled, the	1671	ignored. Instead, each time the periodic watcher gets scheduled, the
1247	reschedule callback will be called with the watcher as first, and the	1672	reschedule callback will be called with the watcher as first, and the
1248	current time as second argument.	1673	current time as second argument.
1249		1674
1250	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1251	ever, or make any event loop modifications>. If you need to stop it,	1676	ever, or make ANY other event loop modifications whatsoever>.
1252	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1253	starting an C<ev_prepare> watcher, which is legal).
1254		1677
		1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1680	only event loop modification you are allowed to do).
		1681
1255	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1682	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1256	ev_tstamp now)>, e.g.:	1683	*w, ev_tstamp now)>, e.g.:
1257		1684
		1685	static ev_tstamp
1258	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1686	my_rescheduler (ev_periodic *w, ev_tstamp now)
1259	{	1687	{
1260	return now + 60.;	1688	return now + 60.;
1261	}	1689	}
1262		1690
1263	It must return the next time to trigger, based on the passed time value	1691	It must return the next time to trigger, based on the passed time value
1264	(that is, the lowest time value larger than to the second argument). It	1692	(that is, the lowest time value larger than to the second argument). It
1265	will usually be called just before the callback will be triggered, but	1693	will usually be called just before the callback will be triggered, but
1266	might be called at other times, too.	1694	might be called at other times, too.
1267		1695
1268	NOTE: I<< This callback must always return a time that is later than the	1696	NOTE: I<< This callback must always return a time that is higher than or
1269	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1697	equal to the passed C<now> value >>.
1270		1698
1271	This can be used to create very complex timers, such as a timer that	1699	This can be used to create very complex timers, such as a timer that
1272	triggers on each midnight, local time. To do this, you would calculate the	1700	triggers on "next midnight, local time". To do this, you would calculate the
1273	next midnight after C<now> and return the timestamp value for this. How	1701	next midnight after C<now> and return the timestamp value for this. How
1274	you do this is, again, up to you (but it is not trivial, which is the main	1702	you do this is, again, up to you (but it is not trivial, which is the main
1275	reason I omitted it as an example).	1703	reason I omitted it as an example).
1276		1704
1277	=back	1705	=back
…		…
1281	Simply stops and restarts the periodic watcher again. This is only useful	1709	Simply stops and restarts the periodic watcher again. This is only useful
1282	when you changed some parameters or the reschedule callback would return	1710	when you changed some parameters or the reschedule callback would return
1283	a different time than the last time it was called (e.g. in a crond like	1711	a different time than the last time it was called (e.g. in a crond like
1284	program when the crontabs have changed).	1712	program when the crontabs have changed).
1285		1713
		1714	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1715
		1716	When active, returns the absolute time that the watcher is supposed to
		1717	trigger next.
		1718
1286	=item ev_tstamp offset [read-write]	1719	=item ev_tstamp offset [read-write]
1287		1720
1288	When repeating, this contains the offset value, otherwise this is the	1721	When repeating, this contains the offset value, otherwise this is the
1289	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1290		1723
…		…
1295		1728
1296	The current interval value. Can be modified any time, but changes only	1729	The current interval value. Can be modified any time, but changes only
1297	take effect when the periodic timer fires or C<ev_periodic_again> is being	1730	take effect when the periodic timer fires or C<ev_periodic_again> is being
1298	called.	1731	called.
1299		1732
1300	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1733	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1301		1734
1302	The current reschedule callback, or C<0>, if this functionality is	1735	The current reschedule callback, or C<0>, if this functionality is
1303	switched off. Can be changed any time, but changes only take effect when	1736	switched off. Can be changed any time, but changes only take effect when
1304	the periodic timer fires or C<ev_periodic_again> is being called.	1737	the periodic timer fires or C<ev_periodic_again> is being called.
1305		1738
1306	=item ev_tstamp at [read-only]
1307
1308	When active, contains the absolute time that the watcher is supposed to
1309	trigger next.
1310
1311	=back	1739	=back
1312		1740
		1741	=head3 Examples
		1742
1313	Example: Call a callback every hour, or, more precisely, whenever the	1743	Example: Call a callback every hour, or, more precisely, whenever the
1314	system clock is divisible by 3600. The callback invocation times have	1744	system time is divisible by 3600. The callback invocation times have
1315	potentially a lot of jittering, but good long-term stability.	1745	potentially a lot of jitter, but good long-term stability.
1316		1746
1317	static void	1747	static void
1318	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1319	{	1749	{
1320	... its now a full hour (UTC, or TAI or whatever your clock follows)	1750	... its now a full hour (UTC, or TAI or whatever your clock follows)
1321	}	1751	}
1322		1752
1323	struct ev_periodic hourly_tick;	1753	ev_periodic hourly_tick;
1324	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1754	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1325	ev_periodic_start (loop, &hourly_tick);	1755	ev_periodic_start (loop, &hourly_tick);
1326		1756
1327	Example: The same as above, but use a reschedule callback to do it:	1757	Example: The same as above, but use a reschedule callback to do it:
1328		1758
1329	#include <math.h>	1759	#include <math.h>
1330		1760
1331	static ev_tstamp	1761	static ev_tstamp
1332	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1762	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1333	{	1763	{
1334	return fmod (now, 3600.) + 3600.;	1764	return now + (3600. - fmod (now, 3600.));
1335	}	1765	}
1336		1766
1337	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1767	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1338		1768
1339	Example: Call a callback every hour, starting now:	1769	Example: Call a callback every hour, starting now:
1340		1770
1341	struct ev_periodic hourly_tick;	1771	ev_periodic hourly_tick;
1342	ev_periodic_init (&hourly_tick, clock_cb,	1772	ev_periodic_init (&hourly_tick, clock_cb,
1343	fmod (ev_now (loop), 3600.), 3600., 0);	1773	fmod (ev_now (loop), 3600.), 3600., 0);
1344	ev_periodic_start (loop, &hourly_tick);	1774	ev_periodic_start (loop, &hourly_tick);
1345		1775
1346		1776
1347	=head2 C<ev_signal> - signal me when a signal gets signalled!	1777	=head2 C<ev_signal> - signal me when a signal gets signalled!
1348		1778
1349	Signal watchers will trigger an event when the process receives a specific	1779	Signal watchers will trigger an event when the process receives a specific
1350	signal one or more times. Even though signals are very asynchronous, libev	1780	signal one or more times. Even though signals are very asynchronous, libev
1351	will try it's best to deliver signals synchronously, i.e. as part of the	1781	will try it's best to deliver signals synchronously, i.e. as part of the
1352	normal event processing, like any other event.	1782	normal event processing, like any other event.
1353		1783
		1784	If you want signals asynchronously, just use C<sigaction> as you would
		1785	do without libev and forget about sharing the signal. You can even use
		1786	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1787
1354	You can configure as many watchers as you like per signal. Only when the	1788	You can configure as many watchers as you like per signal. Only when the
1355	first watcher gets started will libev actually register a signal watcher	1789	first watcher gets started will libev actually register a signal handler
1356	with the kernel (thus it coexists with your own signal handlers as long	1790	with the kernel (thus it coexists with your own signal handlers as long as
1357	as you don't register any with libev). Similarly, when the last signal	1791	you don't register any with libev for the same signal). Similarly, when
1358	watcher for a signal is stopped libev will reset the signal handler to	1792	the last signal watcher for a signal is stopped, libev will reset the
1359	SIG_DFL (regardless of what it was set to before).	1793	signal handler to SIG_DFL (regardless of what it was set to before).
		1794
		1795	If possible and supported, libev will install its handlers with
		1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1797	interrupted. If you have a problem with system calls getting interrupted by
		1798	signals you can block all signals in an C<ev_check> watcher and unblock
		1799	them in an C<ev_prepare> watcher.
1360		1800
1361	=head3 Watcher-Specific Functions and Data Members	1801	=head3 Watcher-Specific Functions and Data Members
1362		1802
1363	=over 4	1803	=over 4
1364		1804
…		…
1373		1813
1374	The signal the watcher watches out for.	1814	The signal the watcher watches out for.
1375		1815
1376	=back	1816	=back
1377		1817
		1818	=head3 Examples
		1819
		1820	Example: Try to exit cleanly on SIGINT.
		1821
		1822	static void
		1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1824	{
		1825	ev_unloop (loop, EVUNLOOP_ALL);
		1826	}
		1827
		1828	ev_signal signal_watcher;
		1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1830	ev_signal_start (loop, &signal_watcher);
		1831
1378		1832
1379	=head2 C<ev_child> - watch out for process status changes	1833	=head2 C<ev_child> - watch out for process status changes
1380		1834
1381	Child watchers trigger when your process receives a SIGCHLD in response to	1835	Child watchers trigger when your process receives a SIGCHLD in response to
1382	some child status changes (most typically when a child of yours dies).	1836	some child status changes (most typically when a child of yours dies or
		1837	exits). It is permissible to install a child watcher I<after> the child
		1838	has been forked (which implies it might have already exited), as long
		1839	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1840	forking and then immediately registering a watcher for the child is fine,
		1841	but forking and registering a watcher a few event loop iterations later is
		1842	not.
		1843
		1844	Only the default event loop is capable of handling signals, and therefore
		1845	you can only register child watchers in the default event loop.
		1846
		1847	=head3 Process Interaction
		1848
		1849	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1850	initialised. This is necessary to guarantee proper behaviour even if
		1851	the first child watcher is started after the child exits. The occurrence
		1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1853	synchronously as part of the event loop processing. Libev always reaps all
		1854	children, even ones not watched.
		1855
		1856	=head3 Overriding the Built-In Processing
		1857
		1858	Libev offers no special support for overriding the built-in child
		1859	processing, but if your application collides with libev's default child
		1860	handler, you can override it easily by installing your own handler for
		1861	C<SIGCHLD> after initialising the default loop, and making sure the
		1862	default loop never gets destroyed. You are encouraged, however, to use an
		1863	event-based approach to child reaping and thus use libev's support for
		1864	that, so other libev users can use C<ev_child> watchers freely.
		1865
		1866	=head3 Stopping the Child Watcher
		1867
		1868	Currently, the child watcher never gets stopped, even when the
		1869	child terminates, so normally one needs to stop the watcher in the
		1870	callback. Future versions of libev might stop the watcher automatically
		1871	when a child exit is detected.
1383		1872
1384	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1385		1874
1386	=over 4	1875	=over 4
1387		1876
1388	=item ev_child_init (ev_child *, callback, int pid)	1877	=item ev_child_init (ev_child *, callback, int pid, int trace)
1389		1878
1390	=item ev_child_set (ev_child *, int pid)	1879	=item ev_child_set (ev_child *, int pid, int trace)
1391		1880
1392	Configures the watcher to wait for status changes of process C<pid> (or	1881	Configures the watcher to wait for status changes of process C<pid> (or
1393	I<any> process if C<pid> is specified as C<0>). The callback can look	1882	I<any> process if C<pid> is specified as C<0>). The callback can look
1394	at the C<rstatus> member of the C<ev_child> watcher structure to see	1883	at the C<rstatus> member of the C<ev_child> watcher structure to see
1395	the status word (use the macros from C<sys/wait.h> and see your systems	1884	the status word (use the macros from C<sys/wait.h> and see your systems
1396	C<waitpid> documentation). The C<rpid> member contains the pid of the	1885	C<waitpid> documentation). The C<rpid> member contains the pid of the
1397	process causing the status change.	1886	process causing the status change. C<trace> must be either C<0> (only
		1887	activate the watcher when the process terminates) or C<1> (additionally
		1888	activate the watcher when the process is stopped or continued).
1398		1889
1399	=item int pid [read-only]	1890	=item int pid [read-only]
1400		1891
1401	The process id this watcher watches out for, or C<0>, meaning any process id.	1892	The process id this watcher watches out for, or C<0>, meaning any process id.
1402		1893
…		…
1409	The process exit/trace status caused by C<rpid> (see your systems	1900	The process exit/trace status caused by C<rpid> (see your systems
1410	C<waitpid> and C<sys/wait.h> documentation for details).	1901	C<waitpid> and C<sys/wait.h> documentation for details).
1411		1902
1412	=back	1903	=back
1413		1904
1414	Example: Try to exit cleanly on SIGINT and SIGTERM.	1905	=head3 Examples
1415		1906
		1907	Example: C<fork()> a new process and install a child handler to wait for
		1908	its completion.
		1909
		1910	ev_child cw;
		1911
1416	static void	1912	static void
1417	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1913	child_cb (EV_P_ ev_child *w, int revents)
1418	{	1914	{
1419	ev_unloop (loop, EVUNLOOP_ALL);	1915	ev_child_stop (EV_A_ w);
		1916	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1420	}	1917	}
1421		1918
1422	struct ev_signal signal_watcher;	1919	pid_t pid = fork ();
1423	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1920
1424	ev_signal_start (loop, &sigint_cb);	1921	if (pid < 0)
		1922	// error
		1923	else if (pid == 0)
		1924	{
		1925	// the forked child executes here
		1926	exit (1);
		1927	}
		1928	else
		1929	{
		1930	ev_child_init (&cw, child_cb, pid, 0);
		1931	ev_child_start (EV_DEFAULT_ &cw);
		1932	}
1425		1933
1426		1934
1427	=head2 C<ev_stat> - did the file attributes just change?	1935	=head2 C<ev_stat> - did the file attributes just change?
1428		1936
1429	This watches a filesystem path for attribute changes. That is, it calls	1937	This watches a file system path for attribute changes. That is, it calls
1430	C<stat> regularly (or when the OS says it changed) and sees if it changed	1938	C<stat> on that path in regular intervals (or when the OS says it changed)
1431	compared to the last time, invoking the callback if it did.	1939	and sees if it changed compared to the last time, invoking the callback if
		1940	it did.
1432		1941
1433	The path does not need to exist: changing from "path exists" to "path does	1942	The path does not need to exist: changing from "path exists" to "path does
1434	not exist" is a status change like any other. The condition "path does	1943	not exist" is a status change like any other. The condition "path does not
1435	not exist" is signified by the C<st_nlink> field being zero (which is	1944	exist" (or more correctly "path cannot be stat'ed") is signified by the
1436	otherwise always forced to be at least one) and all the other fields of	1945	C<st_nlink> field being zero (which is otherwise always forced to be at
1437	the stat buffer having unspecified contents.	1946	least one) and all the other fields of the stat buffer having unspecified
		1947	contents.
1438		1948
1439	The path I<should> be absolute and I<must not> end in a slash. If it is	1949	The path I<must not> end in a slash or contain special components such as
		1950	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1440	relative and your working directory changes, the behaviour is undefined.	1951	your working directory changes, then the behaviour is undefined.
1441		1952
1442	Since there is no standard to do this, the portable implementation simply	1953	Since there is no portable change notification interface available, the
1443	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1954	portable implementation simply calls C<stat(2)> regularly on the path
1444	can specify a recommended polling interval for this case. If you specify	1955	to see if it changed somehow. You can specify a recommended polling
1445	a polling interval of C<0> (highly recommended!) then a I<suitable,	1956	interval for this case. If you specify a polling interval of C<0> (highly
1446	unspecified default> value will be used (which you can expect to be around	1957	recommended!) then a I<suitable, unspecified default> value will be used
1447	five seconds, although this might change dynamically). Libev will also	1958	(which you can expect to be around five seconds, although this might
1448	impose a minimum interval which is currently around C<0.1>, but thats	1959	change dynamically). Libev will also impose a minimum interval which is
1449	usually overkill.	1960	currently around C<0.1>, but that's usually overkill.
1450		1961
1451	This watcher type is not meant for massive numbers of stat watchers,	1962	This watcher type is not meant for massive numbers of stat watchers,
1452	as even with OS-supported change notifications, this can be	1963	as even with OS-supported change notifications, this can be
1453	resource-intensive.	1964	resource-intensive.
1454		1965
1455	At the time of this writing, only the Linux inotify interface is	1966	At the time of this writing, the only OS-specific interface implemented
1456	implemented (implementing kqueue support is left as an exercise for the	1967	is the Linux inotify interface (implementing kqueue support is left as an
1457	reader). Inotify will be used to give hints only and should not change the	1968	exercise for the reader. Note, however, that the author sees no way of
1458	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1969	implementing C<ev_stat> semantics with kqueue, except as a hint).
1459	to fall back to regular polling again even with inotify, but changes are	1970
1460	usually detected immediately, and if the file exists there will be no	1971	=head3 ABI Issues (Largefile Support)
1461	polling.	1972
		1973	Libev by default (unless the user overrides this) uses the default
		1974	compilation environment, which means that on systems with large file
		1975	support disabled by default, you get the 32 bit version of the stat
		1976	structure. When using the library from programs that change the ABI to
		1977	use 64 bit file offsets the programs will fail. In that case you have to
		1978	compile libev with the same flags to get binary compatibility. This is
		1979	obviously the case with any flags that change the ABI, but the problem is
		1980	most noticeably displayed with ev_stat and large file support.
		1981
		1982	The solution for this is to lobby your distribution maker to make large
		1983	file interfaces available by default (as e.g. FreeBSD does) and not
		1984	optional. Libev cannot simply switch on large file support because it has
		1985	to exchange stat structures with application programs compiled using the
		1986	default compilation environment.
		1987
		1988	=head3 Inotify and Kqueue
		1989
		1990	When C<inotify (7)> support has been compiled into libev and present at
		1991	runtime, it will be used to speed up change detection where possible. The
		1992	inotify descriptor will be created lazily when the first C<ev_stat>
		1993	watcher is being started.
		1994
		1995	Inotify presence does not change the semantics of C<ev_stat> watchers
		1996	except that changes might be detected earlier, and in some cases, to avoid
		1997	making regular C<stat> calls. Even in the presence of inotify support
		1998	there are many cases where libev has to resort to regular C<stat> polling,
		1999	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2000	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2001	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2002	xfs are fully working) libev usually gets away without polling.
		2003
		2004	There is no support for kqueue, as apparently it cannot be used to
		2005	implement this functionality, due to the requirement of having a file
		2006	descriptor open on the object at all times, and detecting renames, unlinks
		2007	etc. is difficult.
		2008
		2009	=head3 C<stat ()> is a synchronous operation
		2010
		2011	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2012	the process. The exception are C<ev_stat> watchers - those call C<stat
		2013	()>, which is a synchronous operation.
		2014
		2015	For local paths, this usually doesn't matter: unless the system is very
		2016	busy or the intervals between stat's are large, a stat call will be fast,
		2017	as the path data is usually in memory already (except when starting the
		2018	watcher).
		2019
		2020	For networked file systems, calling C<stat ()> can block an indefinite
		2021	time due to network issues, and even under good conditions, a stat call
		2022	often takes multiple milliseconds.
		2023
		2024	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2025	paths, although this is fully supported by libev.
		2026
		2027	=head3 The special problem of stat time resolution
		2028
		2029	The C<stat ()> system call only supports full-second resolution portably,
		2030	and even on systems where the resolution is higher, most file systems
		2031	still only support whole seconds.
		2032
		2033	That means that, if the time is the only thing that changes, you can
		2034	easily miss updates: on the first update, C<ev_stat> detects a change and
		2035	calls your callback, which does something. When there is another update
		2036	within the same second, C<ev_stat> will be unable to detect unless the
		2037	stat data does change in other ways (e.g. file size).
		2038
		2039	The solution to this is to delay acting on a change for slightly more
		2040	than a second (or till slightly after the next full second boundary), using
		2041	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		2042	ev_timer_again (loop, w)>).
		2043
		2044	The C<.02> offset is added to work around small timing inconsistencies
		2045	of some operating systems (where the second counter of the current time
		2046	might be be delayed. One such system is the Linux kernel, where a call to
		2047	C<gettimeofday> might return a timestamp with a full second later than
		2048	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2049	update file times then there will be a small window where the kernel uses
		2050	the previous second to update file times but libev might already execute
		2051	the timer callback).
1462		2052
1463	=head3 Watcher-Specific Functions and Data Members	2053	=head3 Watcher-Specific Functions and Data Members
1464		2054
1465	=over 4	2055	=over 4
1466		2056
…		…
1472	C<path>. The C<interval> is a hint on how quickly a change is expected to	2062	C<path>. The C<interval> is a hint on how quickly a change is expected to
1473	be detected and should normally be specified as C<0> to let libev choose	2063	be detected and should normally be specified as C<0> to let libev choose
1474	a suitable value. The memory pointed to by C<path> must point to the same	2064	a suitable value. The memory pointed to by C<path> must point to the same
1475	path for as long as the watcher is active.	2065	path for as long as the watcher is active.
1476		2066
1477	The callback will be receive C<EV_STAT> when a change was detected,	2067	The callback will receive an C<EV_STAT> event when a change was detected,
1478	relative to the attributes at the time the watcher was started (or the	2068	relative to the attributes at the time the watcher was started (or the
1479	last change was detected).	2069	last change was detected).
1480		2070
1481	=item ev_stat_stat (ev_stat *)	2071	=item ev_stat_stat (loop, ev_stat *)
1482		2072
1483	Updates the stat buffer immediately with new values. If you change the	2073	Updates the stat buffer immediately with new values. If you change the
1484	watched path in your callback, you could call this fucntion to avoid	2074	watched path in your callback, you could call this function to avoid
1485	detecting this change (while introducing a race condition). Can also be	2075	detecting this change (while introducing a race condition if you are not
1486	useful simply to find out the new values.	2076	the only one changing the path). Can also be useful simply to find out the
		2077	new values.
1487		2078
1488	=item ev_statdata attr [read-only]	2079	=item ev_statdata attr [read-only]
1489		2080
1490	The most-recently detected attributes of the file. Although the type is of	2081	The most-recently detected attributes of the file. Although the type is
1491	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2082	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1492	suitable for your system. If the C<st_nlink> member is C<0>, then there	2083	suitable for your system, but you can only rely on the POSIX-standardised
		2084	members to be present. If the C<st_nlink> member is C<0>, then there was
1493	was some error while C<stat>ing the file.	2085	some error while C<stat>ing the file.
1494		2086
1495	=item ev_statdata prev [read-only]	2087	=item ev_statdata prev [read-only]
1496		2088
1497	The previous attributes of the file. The callback gets invoked whenever	2089	The previous attributes of the file. The callback gets invoked whenever
1498	C<prev> != C<attr>.	2090	C<prev> != C<attr>, or, more precisely, one or more of these members
		2091	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2092	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1499		2093
1500	=item ev_tstamp interval [read-only]	2094	=item ev_tstamp interval [read-only]
1501		2095
1502	The specified interval.	2096	The specified interval.
1503		2097
1504	=item const char *path [read-only]	2098	=item const char *path [read-only]
1505		2099
1506	The filesystem path that is being watched.	2100	The file system path that is being watched.
1507		2101
1508	=back	2102	=back
1509		2103
		2104	=head3 Examples
		2105
1510	Example: Watch C</etc/passwd> for attribute changes.	2106	Example: Watch C</etc/passwd> for attribute changes.
1511		2107
1512	static void	2108	static void
1513	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2109	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1514	{	2110	{
1515	/* /etc/passwd changed in some way */	2111	/* /etc/passwd changed in some way */
1516	if (w->attr.st_nlink)	2112	if (w->attr.st_nlink)
1517	{	2113	{
1518	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2114	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1519	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2115	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1520	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2116	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1521	}	2117	}
1522	else	2118	else
1523	/* you shalt not abuse printf for puts */	2119	/* you shalt not abuse printf for puts */
1524	puts ("wow, /etc/passwd is not there, expect problems. "	2120	puts ("wow, /etc/passwd is not there, expect problems. "
1525	"if this is windows, they already arrived\n");	2121	"if this is windows, they already arrived\n");
1526	}	2122	}
1527		2123
1528	...	2124	...
1529	ev_stat passwd;	2125	ev_stat passwd;
1530		2126
1531	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2127	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1532	ev_stat_start (loop, &passwd);	2128	ev_stat_start (loop, &passwd);
		2129
		2130	Example: Like above, but additionally use a one-second delay so we do not
		2131	miss updates (however, frequent updates will delay processing, too, so
		2132	one might do the work both on C<ev_stat> callback invocation I<and> on
		2133	C<ev_timer> callback invocation).
		2134
		2135	static ev_stat passwd;
		2136	static ev_timer timer;
		2137
		2138	static void
		2139	timer_cb (EV_P_ ev_timer *w, int revents)
		2140	{
		2141	ev_timer_stop (EV_A_ w);
		2142
		2143	/* now it's one second after the most recent passwd change */
		2144	}
		2145
		2146	static void
		2147	stat_cb (EV_P_ ev_stat *w, int revents)
		2148	{
		2149	/* reset the one-second timer */
		2150	ev_timer_again (EV_A_ &timer);
		2151	}
		2152
		2153	...
		2154	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		2155	ev_stat_start (loop, &passwd);
		2156	ev_timer_init (&timer, timer_cb, 0., 1.02);
1533		2157
1534		2158
1535	=head2 C<ev_idle> - when you've got nothing better to do...	2159	=head2 C<ev_idle> - when you've got nothing better to do...
1536		2160
1537	Idle watchers trigger events when no other events of the same or higher	2161	Idle watchers trigger events when no other events of the same or higher
1538	priority are pending (prepare, check and other idle watchers do not	2162	priority are pending (prepare, check and other idle watchers do not count
1539	count).	2163	as receiving "events").
1540		2164
1541	That is, as long as your process is busy handling sockets or timeouts	2165	That is, as long as your process is busy handling sockets or timeouts
1542	(or even signals, imagine) of the same or higher priority it will not be	2166	(or even signals, imagine) of the same or higher priority it will not be
1543	triggered. But when your process is idle (or only lower-priority watchers	2167	triggered. But when your process is idle (or only lower-priority watchers
1544	are pending), the idle watchers are being called once per event loop	2168	are pending), the idle watchers are being called once per event loop
…		…
1555		2179
1556	=head3 Watcher-Specific Functions and Data Members	2180	=head3 Watcher-Specific Functions and Data Members
1557		2181
1558	=over 4	2182	=over 4
1559		2183
1560	=item ev_idle_init (ev_signal *, callback)	2184	=item ev_idle_init (ev_idle *, callback)
1561		2185
1562	Initialises and configures the idle watcher - it has no parameters of any	2186	Initialises and configures the idle watcher - it has no parameters of any
1563	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2187	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1564	believe me.	2188	believe me.
1565		2189
1566	=back	2190	=back
1567		2191
		2192	=head3 Examples
		2193
1568	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2194	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1569	callback, free it. Also, use no error checking, as usual.	2195	callback, free it. Also, use no error checking, as usual.
1570		2196
1571	static void	2197	static void
1572	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1573	{	2199	{
1574	free (w);	2200	free (w);
1575	// now do something you wanted to do when the program has	2201	// now do something you wanted to do when the program has
1576	// no longer asnything immediate to do.	2202	// no longer anything immediate to do.
1577	}	2203	}
1578		2204
1579	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1580	ev_idle_init (idle_watcher, idle_cb);	2206	ev_idle_init (idle_watcher, idle_cb);
1581	ev_idle_start (loop, idle_cb);	2207	ev_idle_start (loop, idle_cb);
1582		2208
1583		2209
1584	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1585		2211
1586	Prepare and check watchers are usually (but not always) used in tandem:	2212	Prepare and check watchers are usually (but not always) used in pairs:
1587	prepare watchers get invoked before the process blocks and check watchers	2213	prepare watchers get invoked before the process blocks and check watchers
1588	afterwards.	2214	afterwards.
1589		2215
1590	You I<must not> call C<ev_loop> or similar functions that enter	2216	You I<must not> call C<ev_loop> or similar functions that enter
1591	the current event loop from either C<ev_prepare> or C<ev_check>	2217	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1594	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1595	C<ev_check> so if you have one watcher of each kind they will always be	2221	C<ev_check> so if you have one watcher of each kind they will always be
1596	called in pairs bracketing the blocking call.	2222	called in pairs bracketing the blocking call.
1597		2223
1598	Their main purpose is to integrate other event mechanisms into libev and	2224	Their main purpose is to integrate other event mechanisms into libev and
1599	their use is somewhat advanced. This could be used, for example, to track	2225	their use is somewhat advanced. They could be used, for example, to track
1600	variable changes, implement your own watchers, integrate net-snmp or a	2226	variable changes, implement your own watchers, integrate net-snmp or a
1601	coroutine library and lots more. They are also occasionally useful if	2227	coroutine library and lots more. They are also occasionally useful if
1602	you cache some data and want to flush it before blocking (for example,	2228	you cache some data and want to flush it before blocking (for example,
1603	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2229	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1604	watcher).	2230	watcher).
1605		2231
1606	This is done by examining in each prepare call which file descriptors need	2232	This is done by examining in each prepare call which file descriptors
1607	to be watched by the other library, registering C<ev_io> watchers for	2233	need to be watched by the other library, registering C<ev_io> watchers
1608	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2234	for them and starting an C<ev_timer> watcher for any timeouts (many
1609	provide just this functionality). Then, in the check watcher you check for	2235	libraries provide exactly this functionality). Then, in the check watcher,
1610	any events that occured (by checking the pending status of all watchers	2236	you check for any events that occurred (by checking the pending status
1611	and stopping them) and call back into the library. The I/O and timer	2237	of all watchers and stopping them) and call back into the library. The
1612	callbacks will never actually be called (but must be valid nevertheless,	2238	I/O and timer callbacks will never actually be called (but must be valid
1613	because you never know, you know?).	2239	nevertheless, because you never know, you know?).
1614		2240
1615	As another example, the Perl Coro module uses these hooks to integrate	2241	As another example, the Perl Coro module uses these hooks to integrate
1616	coroutines into libev programs, by yielding to other active coroutines	2242	coroutines into libev programs, by yielding to other active coroutines
1617	during each prepare and only letting the process block if no coroutines	2243	during each prepare and only letting the process block if no coroutines
1618	are ready to run (it's actually more complicated: it only runs coroutines	2244	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1621	loop from blocking if lower-priority coroutines are active, thus mapping	2247	loop from blocking if lower-priority coroutines are active, thus mapping
1622	low-priority coroutines to idle/background tasks).	2248	low-priority coroutines to idle/background tasks).
1623		2249
1624	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1625	priority, to ensure that they are being run before any other watchers	2251	priority, to ensure that they are being run before any other watchers
		2252	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2253
1626	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1627	too) should not activate ("feed") events into libev. While libev fully	2255	activate ("feed") events into libev. While libev fully supports this, they
1628	supports this, they will be called before other C<ev_check> watchers did	2256	might get executed before other C<ev_check> watchers did their job. As
1629	their job. As C<ev_check> watchers are often used to embed other event	2257	C<ev_check> watchers are often used to embed other (non-libev) event
1630	loops those other event loops might be in an unusable state until their	2258	loops those other event loops might be in an unusable state until their
1631	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2259	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1632	others).	2260	others).
1633		2261
1634	=head3 Watcher-Specific Functions and Data Members	2262	=head3 Watcher-Specific Functions and Data Members
…		…
1639		2267
1640	=item ev_check_init (ev_check *, callback)	2268	=item ev_check_init (ev_check *, callback)
1641		2269
1642	Initialises and configures the prepare or check watcher - they have no	2270	Initialises and configures the prepare or check watcher - they have no
1643	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2271	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1644	macros, but using them is utterly, utterly and completely pointless.	2272	macros, but using them is utterly, utterly, utterly and completely
		2273	pointless.
1645		2274
1646	=back	2275	=back
		2276
		2277	=head3 Examples
1647		2278
1648	There are a number of principal ways to embed other event loops or modules	2279	There are a number of principal ways to embed other event loops or modules
1649	into libev. Here are some ideas on how to include libadns into libev	2280	into libev. Here are some ideas on how to include libadns into libev
1650	(there is a Perl module named C<EV::ADNS> that does this, which you could	2281	(there is a Perl module named C<EV::ADNS> that does this, which you could
1651	use for an actually working example. Another Perl module named C<EV::Glib>	2282	use as a working example. Another Perl module named C<EV::Glib> embeds a
1652	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2283	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1653	into the Glib event loop).	2284	Glib event loop).
1654		2285
1655	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2286	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1656	and in a check watcher, destroy them and call into libadns. What follows	2287	and in a check watcher, destroy them and call into libadns. What follows
1657	is pseudo-code only of course. This requires you to either use a low	2288	is pseudo-code only of course. This requires you to either use a low
1658	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2289	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1659	the callbacks for the IO/timeout watchers might not have been called yet.	2290	the callbacks for the IO/timeout watchers might not have been called yet.
1660		2291
1661	static ev_io iow [nfd];	2292	static ev_io iow [nfd];
1662	static ev_timer tw;	2293	static ev_timer tw;
1663		2294
1664	static void	2295	static void
1665	io_cb (ev_loop *loop, ev_io *w, int revents)	2296	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1666	{	2297	{
1667	}	2298	}
1668		2299
1669	// create io watchers for each fd and a timer before blocking	2300	// create io watchers for each fd and a timer before blocking
1670	static void	2301	static void
1671	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2302	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1672	{	2303	{
1673	int timeout = 3600000;	2304	int timeout = 3600000;
1674	struct pollfd fds [nfd];	2305	struct pollfd fds [nfd];
1675	// actual code will need to loop here and realloc etc.	2306	// actual code will need to loop here and realloc etc.
1676	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1677		2308
1678	/* the callback is illegal, but won't be called as we stop during check */	2309	/* the callback is illegal, but won't be called as we stop during check */
1679	ev_timer_init (&tw, 0, timeout * 1e-3);	2310	ev_timer_init (&tw, 0, timeout * 1e-3);
1680	ev_timer_start (loop, &tw);	2311	ev_timer_start (loop, &tw);
1681		2312
1682	// create one ev_io per pollfd	2313	// create one ev_io per pollfd
1683	for (int i = 0; i < nfd; ++i)	2314	for (int i = 0; i < nfd; ++i)
1684	{	2315	{
1685	ev_io_init (iow + i, io_cb, fds [i].fd,	2316	ev_io_init (iow + i, io_cb, fds [i].fd,
1686	((fds [i].events & POLLIN ? EV_READ : 0)	2317	((fds [i].events & POLLIN ? EV_READ : 0)
1687	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2318	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1688		2319
1689	fds [i].revents = 0;	2320	fds [i].revents = 0;
1690	ev_io_start (loop, iow + i);	2321	ev_io_start (loop, iow + i);
1691	}	2322	}
1692	}	2323	}
1693		2324
1694	// stop all watchers after blocking	2325	// stop all watchers after blocking
1695	static void	2326	static void
1696	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2327	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1697	{	2328	{
1698	ev_timer_stop (loop, &tw);	2329	ev_timer_stop (loop, &tw);
1699		2330
1700	for (int i = 0; i < nfd; ++i)	2331	for (int i = 0; i < nfd; ++i)
1701	{	2332	{
1702	// set the relevant poll flags	2333	// set the relevant poll flags
1703	// could also call adns_processreadable etc. here	2334	// could also call adns_processreadable etc. here
1704	struct pollfd *fd = fds + i;	2335	struct pollfd *fd = fds + i;
1705	int revents = ev_clear_pending (iow + i);	2336	int revents = ev_clear_pending (iow + i);
1706	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2337	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1707	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2338	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1708		2339
1709	// now stop the watcher	2340	// now stop the watcher
1710	ev_io_stop (loop, iow + i);	2341	ev_io_stop (loop, iow + i);
1711	}	2342	}
1712		2343
1713	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2344	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1714	}	2345	}
1715		2346
1716	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2347	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1717	in the prepare watcher and would dispose of the check watcher.	2348	in the prepare watcher and would dispose of the check watcher.
1718		2349
1719	Method 3: If the module to be embedded supports explicit event	2350	Method 3: If the module to be embedded supports explicit event
1720	notification (adns does), you can also make use of the actual watcher	2351	notification (libadns does), you can also make use of the actual watcher
1721	callbacks, and only destroy/create the watchers in the prepare watcher.	2352	callbacks, and only destroy/create the watchers in the prepare watcher.
1722		2353
1723	static void	2354	static void
1724	timer_cb (EV_P_ ev_timer *w, int revents)	2355	timer_cb (EV_P_ ev_timer *w, int revents)
1725	{	2356	{
1726	adns_state ads = (adns_state)w->data;	2357	adns_state ads = (adns_state)w->data;
1727	update_now (EV_A);	2358	update_now (EV_A);
1728		2359
1729	adns_processtimeouts (ads, &tv_now);	2360	adns_processtimeouts (ads, &tv_now);
1730	}	2361	}
1731		2362
1732	static void	2363	static void
1733	io_cb (EV_P_ ev_io *w, int revents)	2364	io_cb (EV_P_ ev_io *w, int revents)
1734	{	2365	{
1735	adns_state ads = (adns_state)w->data;	2366	adns_state ads = (adns_state)w->data;
1736	update_now (EV_A);	2367	update_now (EV_A);
1737		2368
1738	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2369	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1739	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2370	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1740	}	2371	}
1741		2372
1742	// do not ever call adns_afterpoll	2373	// do not ever call adns_afterpoll
1743		2374
1744	Method 4: Do not use a prepare or check watcher because the module you	2375	Method 4: Do not use a prepare or check watcher because the module you
1745	want to embed is too inflexible to support it. Instead, youc na override	2376	want to embed is not flexible enough to support it. Instead, you can
1746	their poll function. The drawback with this solution is that the main	2377	override their poll function. The drawback with this solution is that the
1747	loop is now no longer controllable by EV. The C<Glib::EV> module does	2378	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1748	this.	2379	this approach, effectively embedding EV as a client into the horrible
		2380	libglib event loop.
1749		2381
1750	static gint	2382	static gint
1751	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2383	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1752	{	2384	{
1753	int got_events = 0;	2385	int got_events = 0;
1754		2386
1755	for (n = 0; n < nfds; ++n)	2387	for (n = 0; n < nfds; ++n)
1756	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2388	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1757		2389
1758	if (timeout >= 0)	2390	if (timeout >= 0)
1759	// create/start timer	2391	// create/start timer
1760		2392
1761	// poll	2393	// poll
1762	ev_loop (EV_A_ 0);	2394	ev_loop (EV_A_ 0);
1763		2395
1764	// stop timer again	2396	// stop timer again
1765	if (timeout >= 0)	2397	if (timeout >= 0)
1766	ev_timer_stop (EV_A_ &to);	2398	ev_timer_stop (EV_A_ &to);
1767		2399
1768	// stop io watchers again - their callbacks should have set	2400	// stop io watchers again - their callbacks should have set
1769	for (n = 0; n < nfds; ++n)	2401	for (n = 0; n < nfds; ++n)
1770	ev_io_stop (EV_A_ iow [n]);	2402	ev_io_stop (EV_A_ iow [n]);
1771		2403
1772	return got_events;	2404	return got_events;
1773	}	2405	}
1774		2406
1775		2407
1776	=head2 C<ev_embed> - when one backend isn't enough...	2408	=head2 C<ev_embed> - when one backend isn't enough...
1777		2409
1778	This is a rather advanced watcher type that lets you embed one event loop	2410	This is a rather advanced watcher type that lets you embed one event loop
1779	into another (currently only C<ev_io> events are supported in the embedded	2411	into another (currently only C<ev_io> events are supported in the embedded
1780	loop, other types of watchers might be handled in a delayed or incorrect	2412	loop, other types of watchers might be handled in a delayed or incorrect
1781	fashion and must not be used). (See portability notes, below).	2413	fashion and must not be used).
1782		2414
1783	There are primarily two reasons you would want that: work around bugs and	2415	There are primarily two reasons you would want that: work around bugs and
1784	prioritise I/O.	2416	prioritise I/O.
1785		2417
1786	As an example for a bug workaround, the kqueue backend might only support	2418	As an example for a bug workaround, the kqueue backend might only support
1787	sockets on some platform, so it is unusable as generic backend, but you	2419	sockets on some platform, so it is unusable as generic backend, but you
1788	still want to make use of it because you have many sockets and it scales	2420	still want to make use of it because you have many sockets and it scales
1789	so nicely. In this case, you would create a kqueue-based loop and embed it	2421	so nicely. In this case, you would create a kqueue-based loop and embed
1790	into your default loop (which might use e.g. poll). Overall operation will	2422	it into your default loop (which might use e.g. poll). Overall operation
1791	be a bit slower because first libev has to poll and then call kevent, but	2423	will be a bit slower because first libev has to call C<poll> and then
1792	at least you can use both at what they are best.	2424	C<kevent>, but at least you can use both mechanisms for what they are
		2425	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1793		2426
1794	As for prioritising I/O: rarely you have the case where some fds have	2427	As for prioritising I/O: under rare circumstances you have the case where
1795	to be watched and handled very quickly (with low latency), and even	2428	some fds have to be watched and handled very quickly (with low latency),
1796	priorities and idle watchers might have too much overhead. In this case	2429	and even priorities and idle watchers might have too much overhead. In
1797	you would put all the high priority stuff in one loop and all the rest in	2430	this case you would put all the high priority stuff in one loop and all
1798	a second one, and embed the second one in the first.	2431	the rest in a second one, and embed the second one in the first.
1799		2432
1800	As long as the watcher is active, the callback will be invoked every time	2433	As long as the watcher is active, the callback will be invoked every
1801	there might be events pending in the embedded loop. The callback must then	2434	time there might be events pending in the embedded loop. The callback
1802	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2435	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
1803	their callbacks (you could also start an idle watcher to give the embedded	2436	sweep and invoke their callbacks (the callback doesn't need to invoke the
1804	loop strictly lower priority for example). You can also set the callback	2437	C<ev_embed_sweep> function directly, it could also start an idle watcher
1805	to C<0>, in which case the embed watcher will automatically execute the	2438	to give the embedded loop strictly lower priority for example).
1806	embedded loop sweep.
1807		2439
1808	As long as the watcher is started it will automatically handle events. The	2440	You can also set the callback to C<0>, in which case the embed watcher
1809	callback will be invoked whenever some events have been handled. You can	2441	will automatically execute the embedded loop sweep whenever necessary.
1810	set the callback to C<0> to avoid having to specify one if you are not
1811	interested in that.
1812		2442
1813	Also, there have not currently been made special provisions for forking:	2443	Fork detection will be handled transparently while the C<ev_embed> watcher
1814	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2444	is active, i.e., the embedded loop will automatically be forked when the
1815	but you will also have to stop and restart any C<ev_embed> watchers	2445	embedding loop forks. In other cases, the user is responsible for calling
1816	yourself.	2446	C<ev_loop_fork> on the embedded loop.
1817		2447
1818	Unfortunately, not all backends are embeddable, only the ones returned by	2448	Unfortunately, not all backends are embeddable: only the ones returned by
1819	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2449	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1820	portable one.	2450	portable one.
1821		2451
1822	So when you want to use this feature you will always have to be prepared	2452	So when you want to use this feature you will always have to be prepared
1823	that you cannot get an embeddable loop. The recommended way to get around	2453	that you cannot get an embeddable loop. The recommended way to get around
1824	this is to have a separate variables for your embeddable loop, try to	2454	this is to have a separate variables for your embeddable loop, try to
1825	create it, and if that fails, use the normal loop for everything:	2455	create it, and if that fails, use the normal loop for everything.
1826		2456
1827	struct ev_loop *loop_hi = ev_default_init (0);	2457	=head3 C<ev_embed> and fork
1828	struct ev_loop *loop_lo = 0;
1829	struct ev_embed embed;
1830
1831	// see if there is a chance of getting one that works
1832	// (remember that a flags value of 0 means autodetection)
1833	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1834	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1835	: 0;
1836		2458
1837	// if we got one, then embed it, otherwise default to loop_hi	2459	While the C<ev_embed> watcher is running, forks in the embedding loop will
1838	if (loop_lo)	2460	automatically be applied to the embedded loop as well, so no special
1839	{	2461	fork handling is required in that case. When the watcher is not running,
1840	ev_embed_init (&embed, 0, loop_lo);	2462	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1841	ev_embed_start (loop_hi, &embed);	2463	as applicable.
1842	}
1843	else
1844	loop_lo = loop_hi;
1845
1846	=head2 Portability notes
1847
1848	Kqueue is nominally embeddable, but this is broken on all BSDs that I
1849	tried, in various ways. Usually the embedded event loop will simply never
1850	receive events, sometimes it will only trigger a few times, sometimes in a
1851	loop. Epoll is also nominally embeddable, but many Linux kernel versions
1852	will always eport the epoll fd as ready, even when no events are pending.
1853
1854	While libev allows embedding these backends (they are contained in
1855	C<ev_embeddable_backends ()>), take extreme care that it will actually
1856	work.
1857
1858	When in doubt, create a dynamic event loop forced to use sockets (this
1859	usually works) and possibly another thread and a pipe or so to report to
1860	your main event loop.
1861		2464
1862	=head3 Watcher-Specific Functions and Data Members	2465	=head3 Watcher-Specific Functions and Data Members
1863		2466
1864	=over 4	2467	=over 4
1865		2468
…		…
1869		2472
1870	Configures the watcher to embed the given loop, which must be	2473	Configures the watcher to embed the given loop, which must be
1871	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2474	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1872	invoked automatically, otherwise it is the responsibility of the callback	2475	invoked automatically, otherwise it is the responsibility of the callback
1873	to invoke it (it will continue to be called until the sweep has been done,	2476	to invoke it (it will continue to be called until the sweep has been done,
1874	if you do not want thta, you need to temporarily stop the embed watcher).	2477	if you do not want that, you need to temporarily stop the embed watcher).
1875		2478
1876	=item ev_embed_sweep (loop, ev_embed *)	2479	=item ev_embed_sweep (loop, ev_embed *)
1877		2480
1878	Make a single, non-blocking sweep over the embedded loop. This works	2481	Make a single, non-blocking sweep over the embedded loop. This works
1879	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1880	apropriate way for embedded loops.	2483	appropriate way for embedded loops.
1881		2484
1882	=item struct ev_loop *other [read-only]	2485	=item struct ev_loop *other [read-only]
1883		2486
1884	The embedded event loop.	2487	The embedded event loop.
1885		2488
1886	=back	2489	=back
		2490
		2491	=head3 Examples
		2492
		2493	Example: Try to get an embeddable event loop and embed it into the default
		2494	event loop. If that is not possible, use the default loop. The default
		2495	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2496	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2497	used).
		2498
		2499	struct ev_loop *loop_hi = ev_default_init (0);
		2500	struct ev_loop *loop_lo = 0;
		2501	ev_embed embed;
		2502
		2503	// see if there is a chance of getting one that works
		2504	// (remember that a flags value of 0 means autodetection)
		2505	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2506	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2507	: 0;
		2508
		2509	// if we got one, then embed it, otherwise default to loop_hi
		2510	if (loop_lo)
		2511	{
		2512	ev_embed_init (&embed, 0, loop_lo);
		2513	ev_embed_start (loop_hi, &embed);
		2514	}
		2515	else
		2516	loop_lo = loop_hi;
		2517
		2518	Example: Check if kqueue is available but not recommended and create
		2519	a kqueue backend for use with sockets (which usually work with any
		2520	kqueue implementation). Store the kqueue/socket-only event loop in
		2521	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2522
		2523	struct ev_loop *loop = ev_default_init (0);
		2524	struct ev_loop *loop_socket = 0;
		2525	ev_embed embed;
		2526
		2527	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2528	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2529	{
		2530	ev_embed_init (&embed, 0, loop_socket);
		2531	ev_embed_start (loop, &embed);
		2532	}
		2533
		2534	if (!loop_socket)
		2535	loop_socket = loop;
		2536
		2537	// now use loop_socket for all sockets, and loop for everything else
1887		2538
1888		2539
1889	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2540	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1890		2541
1891	Fork watchers are called when a C<fork ()> was detected (usually because	2542	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1907	believe me.	2558	believe me.
1908		2559
1909	=back	2560	=back
1910		2561
1911		2562
		2563	=head2 C<ev_async> - how to wake up another event loop
		2564
		2565	In general, you cannot use an C<ev_loop> from multiple threads or other
		2566	asynchronous sources such as signal handlers (as opposed to multiple event
		2567	loops - those are of course safe to use in different threads).
		2568
		2569	Sometimes, however, you need to wake up another event loop you do not
		2570	control, for example because it belongs to another thread. This is what
		2571	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2572	can signal it by calling C<ev_async_send>, which is thread- and signal
		2573	safe.
		2574
		2575	This functionality is very similar to C<ev_signal> watchers, as signals,
		2576	too, are asynchronous in nature, and signals, too, will be compressed
		2577	(i.e. the number of callback invocations may be less than the number of
		2578	C<ev_async_sent> calls).
		2579
		2580	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2581	just the default loop.
		2582
		2583	=head3 Queueing
		2584
		2585	C<ev_async> does not support queueing of data in any way. The reason
		2586	is that the author does not know of a simple (or any) algorithm for a
		2587	multiple-writer-single-reader queue that works in all cases and doesn't
		2588	need elaborate support such as pthreads.
		2589
		2590	That means that if you want to queue data, you have to provide your own
		2591	queue. But at least I can tell you how to implement locking around your
		2592	queue:
		2593
		2594	=over 4
		2595
		2596	=item queueing from a signal handler context
		2597
		2598	To implement race-free queueing, you simply add to the queue in the signal
		2599	handler but you block the signal handler in the watcher callback. Here is
		2600	an example that does that for some fictitious SIGUSR1 handler:
		2601
		2602	static ev_async mysig;
		2603
		2604	static void
		2605	sigusr1_handler (void)
		2606	{
		2607	sometype data;
		2608
		2609	// no locking etc.
		2610	queue_put (data);
		2611	ev_async_send (EV_DEFAULT_ &mysig);
		2612	}
		2613
		2614	static void
		2615	mysig_cb (EV_P_ ev_async *w, int revents)
		2616	{
		2617	sometype data;
		2618	sigset_t block, prev;
		2619
		2620	sigemptyset (&block);
		2621	sigaddset (&block, SIGUSR1);
		2622	sigprocmask (SIG_BLOCK, &block, &prev);
		2623
		2624	while (queue_get (&data))
		2625	process (data);
		2626
		2627	if (sigismember (&prev, SIGUSR1)
		2628	sigprocmask (SIG_UNBLOCK, &block, 0);
		2629	}
		2630
		2631	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2632	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2633	either...).
		2634
		2635	=item queueing from a thread context
		2636
		2637	The strategy for threads is different, as you cannot (easily) block
		2638	threads but you can easily preempt them, so to queue safely you need to
		2639	employ a traditional mutex lock, such as in this pthread example:
		2640
		2641	static ev_async mysig;
		2642	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2643
		2644	static void
		2645	otherthread (void)
		2646	{
		2647	// only need to lock the actual queueing operation
		2648	pthread_mutex_lock (&mymutex);
		2649	queue_put (data);
		2650	pthread_mutex_unlock (&mymutex);
		2651
		2652	ev_async_send (EV_DEFAULT_ &mysig);
		2653	}
		2654
		2655	static void
		2656	mysig_cb (EV_P_ ev_async *w, int revents)
		2657	{
		2658	pthread_mutex_lock (&mymutex);
		2659
		2660	while (queue_get (&data))
		2661	process (data);
		2662
		2663	pthread_mutex_unlock (&mymutex);
		2664	}
		2665
		2666	=back
		2667
		2668
		2669	=head3 Watcher-Specific Functions and Data Members
		2670
		2671	=over 4
		2672
		2673	=item ev_async_init (ev_async *, callback)
		2674
		2675	Initialises and configures the async watcher - it has no parameters of any
		2676	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
		2677	trust me.
		2678
		2679	=item ev_async_send (loop, ev_async *)
		2680
		2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2683	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2685	section below on what exactly this means).
		2686
		2687	This call incurs the overhead of a system call only once per loop iteration,
		2688	so while the overhead might be noticeable, it doesn't apply to repeated
		2689	calls to C<ev_async_send>.
		2690
		2691	=item bool = ev_async_pending (ev_async *)
		2692
		2693	Returns a non-zero value when C<ev_async_send> has been called on the
		2694	watcher but the event has not yet been processed (or even noted) by the
		2695	event loop.
		2696
		2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2698	the loop iterates next and checks for the watcher to have become active,
		2699	it will reset the flag again. C<ev_async_pending> can be used to very
		2700	quickly check whether invoking the loop might be a good idea.
		2701
		2702	Not that this does I<not> check whether the watcher itself is pending, only
		2703	whether it has been requested to make this watcher pending.
		2704
		2705	=back
		2706
		2707
1912	=head1 OTHER FUNCTIONS	2708	=head1 OTHER FUNCTIONS
1913		2709
1914	There are some other functions of possible interest. Described. Here. Now.	2710	There are some other functions of possible interest. Described. Here. Now.
1915		2711
1916	=over 4	2712	=over 4
1917		2713
1918	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2714	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1919		2715
1920	This function combines a simple timer and an I/O watcher, calls your	2716	This function combines a simple timer and an I/O watcher, calls your
1921	callback on whichever event happens first and automatically stop both	2717	callback on whichever event happens first and automatically stops both
1922	watchers. This is useful if you want to wait for a single event on an fd	2718	watchers. This is useful if you want to wait for a single event on an fd
1923	or timeout without having to allocate/configure/start/stop/free one or	2719	or timeout without having to allocate/configure/start/stop/free one or
1924	more watchers yourself.	2720	more watchers yourself.
1925		2721
1926	If C<fd> is less than 0, then no I/O watcher will be started and events	2722	If C<fd> is less than 0, then no I/O watcher will be started and the
1927	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2723	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1928	C<events> set will be craeted and started.	2724	the given C<fd> and C<events> set will be created and started.
1929		2725
1930	If C<timeout> is less than 0, then no timeout watcher will be	2726	If C<timeout> is less than 0, then no timeout watcher will be
1931	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1932	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2728	repeat = 0) will be started. C<0> is a valid timeout.
1933	dubious value.
1934		2729
1935	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1936	passed an C<revents> set like normal event callbacks (a combination of	2731	passed an C<revents> set like normal event callbacks (a combination of
1937	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1938	value passed to C<ev_once>:	2733	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2734	a timeout and an io event at the same time - you probably should give io
		2735	events precedence.
1939		2736
		2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2738
1940	static void stdin_ready (int revents, void *arg)	2739	static void stdin_ready (int revents, void *arg)
1941	{	2740	{
1942	if (revents & EV_TIMEOUT)
1943	/* doh, nothing entered */;
1944	else if (revents & EV_READ)	2741	if (revents & EV_READ)
1945	/* stdin might have data for us, joy! */;	2742	/* stdin might have data for us, joy! */;
		2743	else if (revents & EV_TIMEOUT)
		2744	/* doh, nothing entered */;
1946	}	2745	}
1947		2746
1948	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1949		2748
1950	=item ev_feed_event (ev_loop *, watcher *, int revents)	2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1951		2750
1952	Feeds the given event set into the event loop, as if the specified event	2751	Feeds the given event set into the event loop, as if the specified event
1953	had happened for the specified watcher (which must be a pointer to an	2752	had happened for the specified watcher (which must be a pointer to an
1954	initialised but not necessarily started event watcher).	2753	initialised but not necessarily started event watcher).
1955		2754
1956	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1957		2756
1958	Feed an event on the given fd, as if a file descriptor backend detected	2757	Feed an event on the given fd, as if a file descriptor backend detected
1959	the given events it.	2758	the given events it.
1960		2759
1961	=item ev_feed_signal_event (ev_loop *loop, int signum)	2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1962		2761
1963	Feed an event as if the given signal occured (C<loop> must be the default	2762	Feed an event as if the given signal occurred (C<loop> must be the default
1964	loop!).	2763	loop!).
1965		2764
1966	=back	2765	=back
1967		2766
1968		2767
…		…
1984		2783
1985	=item * Priorities are not currently supported. Initialising priorities	2784	=item * Priorities are not currently supported. Initialising priorities
1986	will fail and all watchers will have the same priority, even though there	2785	will fail and all watchers will have the same priority, even though there
1987	is an ev_pri field.	2786	is an ev_pri field.
1988		2787
		2788	=item * In libevent, the last base created gets the signals, in libev, the
		2789	first base created (== the default loop) gets the signals.
		2790
1989	=item * Other members are not supported.	2791	=item * Other members are not supported.
1990		2792
1991	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1992	to use the libev header file and library.	2794	to use the libev header file and library.
1993		2795
1994	=back	2796	=back
1995		2797
1996	=head1 C++ SUPPORT	2798	=head1 C++ SUPPORT
1997		2799
1998	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2800	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1999	you to use some convinience methods to start/stop watchers and also change	2801	you to use some convenience methods to start/stop watchers and also change
2000	the callback model to a model using method callbacks on objects.	2802	the callback model to a model using method callbacks on objects.
2001		2803
2002	To use it,	2804	To use it,
2003		2805
2004	#include <ev++.h>	2806	#include <ev++.h>
2005		2807
2006	This automatically includes F<ev.h> and puts all of its definitions (many	2808	This automatically includes F<ev.h> and puts all of its definitions (many
2007	of them macros) into the global namespace. All C++ specific things are	2809	of them macros) into the global namespace. All C++ specific things are
2008	put into the C<ev> namespace. It should support all the same embedding	2810	put into the C<ev> namespace. It should support all the same embedding
2009	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2811	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2076	your compiler is good :), then the method will be fully inlined into the	2878	your compiler is good :), then the method will be fully inlined into the
2077	thunking function, making it as fast as a direct C callback.	2879	thunking function, making it as fast as a direct C callback.
2078		2880
2079	Example: simple class declaration and watcher initialisation	2881	Example: simple class declaration and watcher initialisation
2080		2882
2081	struct myclass	2883	struct myclass
2082	{	2884	{
2083	void io_cb (ev::io &w, int revents) { }	2885	void io_cb (ev::io &w, int revents) { }
2084	}	2886	}
2085		2887
2086	myclass obj;	2888	myclass obj;
2087	ev::io iow;	2889	ev::io iow;
2088	iow.set <myclass, &myclass::io_cb> (&obj);	2890	iow.set <myclass, &myclass::io_cb> (&obj);
		2891
		2892	=item w->set (object *)
		2893
		2894	This is an B<experimental> feature that might go away in a future version.
		2895
		2896	This is a variation of a method callback - leaving out the method to call
		2897	will default the method to C<operator ()>, which makes it possible to use
		2898	functor objects without having to manually specify the C<operator ()> all
		2899	the time. Incidentally, you can then also leave out the template argument
		2900	list.
		2901
		2902	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2903	int revents)>.
		2904
		2905	See the method-C<set> above for more details.
		2906
		2907	Example: use a functor object as callback.
		2908
		2909	struct myfunctor
		2910	{
		2911	void operator() (ev::io &w, int revents)
		2912	{
		2913	...
		2914	}
		2915	}
		2916
		2917	myfunctor f;
		2918
		2919	ev::io w;
		2920	w.set (&f);
2089		2921
2090	=item w->set<function> (void *data = 0)	2922	=item w->set<function> (void *data = 0)
2091		2923
2092	Also sets a callback, but uses a static method or plain function as	2924	Also sets a callback, but uses a static method or plain function as
2093	callback. The optional C<data> argument will be stored in the watcher's	2925	callback. The optional C<data> argument will be stored in the watcher's
…		…
2095		2927
2096	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2928	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2097		2929
2098	See the method-C<set> above for more details.	2930	See the method-C<set> above for more details.
2099		2931
2100	Example:	2932	Example: Use a plain function as callback.
2101		2933
2102	static void io_cb (ev::io &w, int revents) { }	2934	static void io_cb (ev::io &w, int revents) { }
2103	iow.set <io_cb> ();	2935	iow.set <io_cb> ();
2104		2936
2105	=item w->set (struct ev_loop *)	2937	=item w->set (struct ev_loop *)
2106		2938
2107	Associates a different C<struct ev_loop> with this watcher. You can only	2939	Associates a different C<struct ev_loop> with this watcher. You can only
2108	do this when the watcher is inactive (and not pending either).	2940	do this when the watcher is inactive (and not pending either).
2109		2941
2110	=item w->set ([args])	2942	=item w->set ([arguments])
2111		2943
2112	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2113	called at least once. Unlike the C counterpart, an active watcher gets	2945	called at least once. Unlike the C counterpart, an active watcher gets
2114	automatically stopped and restarted when reconfiguring it with this	2946	automatically stopped and restarted when reconfiguring it with this
2115	method.	2947	method.
2116		2948
2117	=item w->start ()	2949	=item w->start ()
…		…
2141	=back	2973	=back
2142		2974
2143	Example: Define a class with an IO and idle watcher, start one of them in	2975	Example: Define a class with an IO and idle watcher, start one of them in
2144	the constructor.	2976	the constructor.
2145		2977
2146	class myclass	2978	class myclass
2147	{	2979	{
2148	ev_io io; void io_cb (ev::io &w, int revents);	2980	ev::io io ; void io_cb (ev::io &w, int revents);
2149	ev_idle idle void idle_cb (ev::idle &w, int revents);	2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2150		2982
2151	myclass ();	2983	myclass (int fd)
2152	}	2984	{
2153
2154	myclass::myclass (int fd)
2155	{
2156	io .set <myclass, &myclass::io_cb > (this);	2985	io .set <myclass, &myclass::io_cb > (this);
2157	idle.set <myclass, &myclass::idle_cb> (this);	2986	idle.set <myclass, &myclass::idle_cb> (this);
2158		2987
2159	io.start (fd, ev::READ);	2988	io.start (fd, ev::READ);
		2989	}
2160	}	2990	};
		2991
		2992
		2993	=head1 OTHER LANGUAGE BINDINGS
		2994
		2995	Libev does not offer other language bindings itself, but bindings for a
		2996	number of languages exist in the form of third-party packages. If you know
		2997	any interesting language binding in addition to the ones listed here, drop
		2998	me a note.
		2999
		3000	=over 4
		3001
		3002	=item Perl
		3003
		3004	The EV module implements the full libev API and is actually used to test
		3005	libev. EV is developed together with libev. Apart from the EV core module,
		3006	there are additional modules that implement libev-compatible interfaces
		3007	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		3008	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3009	and C<EV::Glib>).
		3010
		3011	It can be found and installed via CPAN, its homepage is at
		3012	L<http://software.schmorp.de/pkg/EV>.
		3013
		3014	=item Python
		3015
		3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3017	seems to be quite complete and well-documented. Note, however, that the
		3018	patch they require for libev is outright dangerous as it breaks the ABI
		3019	for everybody else, and therefore, should never be applied in an installed
		3020	libev (if python requires an incompatible ABI then it needs to embed
		3021	libev).
		3022
		3023	=item Ruby
		3024
		3025	Tony Arcieri has written a ruby extension that offers access to a subset
		3026	of the libev API and adds file handle abstractions, asynchronous DNS and
		3027	more on top of it. It can be found via gem servers. Its homepage is at
		3028	L<http://rev.rubyforge.org/>.
		3029
		3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3031	makes rev work even on mingw.
		3032
		3033	=item D
		3034
		3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3037
		3038	=item Ocaml
		3039
		3040	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3042
		3043	=back
2161		3044
2162		3045
2163	=head1 MACRO MAGIC	3046	=head1 MACRO MAGIC
2164		3047
2165	Libev can be compiled with a variety of options, the most fundamantal	3048	Libev can be compiled with a variety of options, the most fundamental
2166	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3049	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2167	functions and callbacks have an initial C<struct ev_loop *> argument.	3050	functions and callbacks have an initial C<struct ev_loop *> argument.
2168		3051
2169	To make it easier to write programs that cope with either variant, the	3052	To make it easier to write programs that cope with either variant, the
2170	following macros are defined:	3053	following macros are defined:
…		…
2175		3058
2176	This provides the loop I<argument> for functions, if one is required ("ev	3059	This provides the loop I<argument> for functions, if one is required ("ev
2177	loop argument"). The C<EV_A> form is used when this is the sole argument,	3060	loop argument"). The C<EV_A> form is used when this is the sole argument,
2178	C<EV_A_> is used when other arguments are following. Example:	3061	C<EV_A_> is used when other arguments are following. Example:
2179		3062
2180	ev_unref (EV_A);	3063	ev_unref (EV_A);
2181	ev_timer_add (EV_A_ watcher);	3064	ev_timer_add (EV_A_ watcher);
2182	ev_loop (EV_A_ 0);	3065	ev_loop (EV_A_ 0);
2183		3066
2184	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2185	which is often provided by the following macro.	3068	which is often provided by the following macro.
2186		3069
2187	=item C<EV_P>, C<EV_P_>	3070	=item C<EV_P>, C<EV_P_>
2188		3071
2189	This provides the loop I<parameter> for functions, if one is required ("ev	3072	This provides the loop I<parameter> for functions, if one is required ("ev
2190	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3073	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2191	C<EV_P_> is used when other parameters are following. Example:	3074	C<EV_P_> is used when other parameters are following. Example:
2192		3075
2193	// this is how ev_unref is being declared	3076	// this is how ev_unref is being declared
2194	static void ev_unref (EV_P);	3077	static void ev_unref (EV_P);
2195		3078
2196	// this is how you can declare your typical callback	3079	// this is how you can declare your typical callback
2197	static void cb (EV_P_ ev_timer *w, int revents)	3080	static void cb (EV_P_ ev_timer *w, int revents)
2198		3081
2199	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3082	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2200	suitable for use with C<EV_A>.	3083	suitable for use with C<EV_A>.
2201		3084
2202	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3085	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2203		3086
2204	Similar to the other two macros, this gives you the value of the default	3087	Similar to the other two macros, this gives you the value of the default
2205	loop, if multiple loops are supported ("ev loop default").	3088	loop, if multiple loops are supported ("ev loop default").
		3089
		3090	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3091
		3092	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3093	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3094	is undefined when the default loop has not been initialised by a previous
		3095	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3096
		3097	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3098	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2206		3099
2207	=back	3100	=back
2208		3101
2209	Example: Declare and initialise a check watcher, utilising the above	3102	Example: Declare and initialise a check watcher, utilising the above
2210	macros so it will work regardless of whether multiple loops are supported	3103	macros so it will work regardless of whether multiple loops are supported
2211	or not.	3104	or not.
2212		3105
2213	static void	3106	static void
2214	check_cb (EV_P_ ev_timer *w, int revents)	3107	check_cb (EV_P_ ev_timer *w, int revents)
2215	{	3108	{
2216	ev_check_stop (EV_A_ w);	3109	ev_check_stop (EV_A_ w);
2217	}	3110	}
2218		3111
2219	ev_check check;	3112	ev_check check;
2220	ev_check_init (&check, check_cb);	3113	ev_check_init (&check, check_cb);
2221	ev_check_start (EV_DEFAULT_ &check);	3114	ev_check_start (EV_DEFAULT_ &check);
2222	ev_loop (EV_DEFAULT_ 0);	3115	ev_loop (EV_DEFAULT_ 0);
2223		3116
2224	=head1 EMBEDDING	3117	=head1 EMBEDDING
2225		3118
2226	Libev can (and often is) directly embedded into host	3119	Libev can (and often is) directly embedded into host
2227	applications. Examples of applications that embed it include the Deliantra	3120	applications. Examples of applications that embed it include the Deliantra
…		…
2234	libev somewhere in your source tree).	3127	libev somewhere in your source tree).
2235		3128
2236	=head2 FILESETS	3129	=head2 FILESETS
2237		3130
2238	Depending on what features you need you need to include one or more sets of files	3131	Depending on what features you need you need to include one or more sets of files
2239	in your app.	3132	in your application.
2240		3133
2241	=head3 CORE EVENT LOOP	3134	=head3 CORE EVENT LOOP
2242		3135
2243	To include only the libev core (all the C<ev_*> functions), with manual	3136	To include only the libev core (all the C<ev_*> functions), with manual
2244	configuration (no autoconf):	3137	configuration (no autoconf):
2245		3138
2246	#define EV_STANDALONE 1	3139	#define EV_STANDALONE 1
2247	#include "ev.c"	3140	#include "ev.c"
2248		3141
2249	This will automatically include F<ev.h>, too, and should be done in a	3142	This will automatically include F<ev.h>, too, and should be done in a
2250	single C source file only to provide the function implementations. To use	3143	single C source file only to provide the function implementations. To use
2251	it, do the same for F<ev.h> in all files wishing to use this API (best	3144	it, do the same for F<ev.h> in all files wishing to use this API (best
2252	done by writing a wrapper around F<ev.h> that you can include instead and	3145	done by writing a wrapper around F<ev.h> that you can include instead and
2253	where you can put other configuration options):	3146	where you can put other configuration options):
2254		3147
2255	#define EV_STANDALONE 1	3148	#define EV_STANDALONE 1
2256	#include "ev.h"	3149	#include "ev.h"
2257		3150
2258	Both header files and implementation files can be compiled with a C++	3151	Both header files and implementation files can be compiled with a C++
2259	compiler (at least, thats a stated goal, and breakage will be treated	3152	compiler (at least, that's a stated goal, and breakage will be treated
2260	as a bug).	3153	as a bug).
2261		3154
2262	You need the following files in your source tree, or in a directory	3155	You need the following files in your source tree, or in a directory
2263	in your include path (e.g. in libev/ when using -Ilibev):	3156	in your include path (e.g. in libev/ when using -Ilibev):
2264		3157
2265	ev.h	3158	ev.h
2266	ev.c	3159	ev.c
2267	ev_vars.h	3160	ev_vars.h
2268	ev_wrap.h	3161	ev_wrap.h
2269		3162
2270	ev_win32.c required on win32 platforms only	3163	ev_win32.c required on win32 platforms only
2271		3164
2272	ev_select.c only when select backend is enabled (which is enabled by default)	3165	ev_select.c only when select backend is enabled (which is enabled by default)
2273	ev_poll.c only when poll backend is enabled (disabled by default)	3166	ev_poll.c only when poll backend is enabled (disabled by default)
2274	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3167	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2275	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3168	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2276	ev_port.c only when the solaris port backend is enabled (disabled by default)	3169	ev_port.c only when the solaris port backend is enabled (disabled by default)
2277		3170
2278	F<ev.c> includes the backend files directly when enabled, so you only need	3171	F<ev.c> includes the backend files directly when enabled, so you only need
2279	to compile this single file.	3172	to compile this single file.
2280		3173
2281	=head3 LIBEVENT COMPATIBILITY API	3174	=head3 LIBEVENT COMPATIBILITY API
2282		3175
2283	To include the libevent compatibility API, also include:	3176	To include the libevent compatibility API, also include:
2284		3177
2285	#include "event.c"	3178	#include "event.c"
2286		3179
2287	in the file including F<ev.c>, and:	3180	in the file including F<ev.c>, and:
2288		3181
2289	#include "event.h"	3182	#include "event.h"
2290		3183
2291	in the files that want to use the libevent API. This also includes F<ev.h>.	3184	in the files that want to use the libevent API. This also includes F<ev.h>.
2292		3185
2293	You need the following additional files for this:	3186	You need the following additional files for this:
2294		3187
2295	event.h	3188	event.h
2296	event.c	3189	event.c
2297		3190
2298	=head3 AUTOCONF SUPPORT	3191	=head3 AUTOCONF SUPPORT
2299		3192
2300	Instead of using C<EV_STANDALONE=1> and providing your config in	3193	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2301	whatever way you want, you can also C<m4_include([libev.m4])> in your	3194	whatever way you want, you can also C<m4_include([libev.m4])> in your
2302	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3195	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2303	include F<config.h> and configure itself accordingly.	3196	include F<config.h> and configure itself accordingly.
2304		3197
2305	For this of course you need the m4 file:	3198	For this of course you need the m4 file:
2306		3199
2307	libev.m4	3200	libev.m4
2308		3201
2309	=head2 PREPROCESSOR SYMBOLS/MACROS	3202	=head2 PREPROCESSOR SYMBOLS/MACROS
2310		3203
2311	Libev can be configured via a variety of preprocessor symbols you have to define	3204	Libev can be configured via a variety of preprocessor symbols you have to
2312	before including any of its files. The default is not to build for multiplicity	3205	define before including any of its files. The default in the absence of
2313	and only include the select backend.	3206	autoconf is documented for every option.
2314		3207
2315	=over 4	3208	=over 4
2316		3209
2317	=item EV_STANDALONE	3210	=item EV_STANDALONE
2318		3211
…		…
2320	keeps libev from including F<config.h>, and it also defines dummy	3213	keeps libev from including F<config.h>, and it also defines dummy
2321	implementations for some libevent functions (such as logging, which is not	3214	implementations for some libevent functions (such as logging, which is not
2322	supported). It will also not define any of the structs usually found in	3215	supported). It will also not define any of the structs usually found in
2323	F<event.h> that are not directly supported by the libev core alone.	3216	F<event.h> that are not directly supported by the libev core alone.
2324		3217
		3218	In stanbdalone mode, libev will still try to automatically deduce the
		3219	configuration, but has to be more conservative.
		3220
2325	=item EV_USE_MONOTONIC	3221	=item EV_USE_MONOTONIC
2326		3222
2327	If defined to be C<1>, libev will try to detect the availability of the	3223	If defined to be C<1>, libev will try to detect the availability of the
2328	monotonic clock option at both compiletime and runtime. Otherwise no use	3224	monotonic clock option at both compile time and runtime. Otherwise no
2329	of the monotonic clock option will be attempted. If you enable this, you	3225	use of the monotonic clock option will be attempted. If you enable this,
2330	usually have to link against librt or something similar. Enabling it when	3226	you usually have to link against librt or something similar. Enabling it
2331	the functionality isn't available is safe, though, although you have	3227	when the functionality isn't available is safe, though, although you have
2332	to make sure you link against any libraries where the C<clock_gettime>	3228	to make sure you link against any libraries where the C<clock_gettime>
2333	function is hiding in (often F<-lrt>).	3229	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2334		3230
2335	=item EV_USE_REALTIME	3231	=item EV_USE_REALTIME
2336		3232
2337	If defined to be C<1>, libev will try to detect the availability of the	3233	If defined to be C<1>, libev will try to detect the availability of the
2338	realtime clock option at compiletime (and assume its availability at	3234	real-time clock option at compile time (and assume its availability
2339	runtime if successful). Otherwise no use of the realtime clock option will	3235	at runtime if successful). Otherwise no use of the real-time clock
2340	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3236	option will be attempted. This effectively replaces C<gettimeofday>
2341	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3237	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2342	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3238	correctness. See the note about libraries in the description of
		3239	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3240	C<EV_USE_CLOCK_SYSCALL>.
		3241
		3242	=item EV_USE_CLOCK_SYSCALL
		3243
		3244	If defined to be C<1>, libev will try to use a direct syscall instead
		3245	of calling the system-provided C<clock_gettime> function. This option
		3246	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3247	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3248	programs needlessly. Using a direct syscall is slightly slower (in
		3249	theory), because no optimised vdso implementation can be used, but avoids
		3250	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3251	higher, as it simplifies linking (no need for C<-lrt>).
2343		3252
2344	=item EV_USE_NANOSLEEP	3253	=item EV_USE_NANOSLEEP
2345		3254
2346	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3255	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2347	and will use it for delays. Otherwise it will use C<select ()>.	3256	and will use it for delays. Otherwise it will use C<select ()>.
2348		3257
		3258	=item EV_USE_EVENTFD
		3259
		3260	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3261	available and will probe for kernel support at runtime. This will improve
		3262	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3263	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3264	2.7 or newer, otherwise disabled.
		3265
2349	=item EV_USE_SELECT	3266	=item EV_USE_SELECT
2350		3267
2351	If undefined or defined to be C<1>, libev will compile in support for the	3268	If undefined or defined to be C<1>, libev will compile in support for the
2352	C<select>(2) backend. No attempt at autodetection will be done: if no	3269	C<select>(2) backend. No attempt at auto-detection will be done: if no
2353	other method takes over, select will be it. Otherwise the select backend	3270	other method takes over, select will be it. Otherwise the select backend
2354	will not be compiled in.	3271	will not be compiled in.
2355		3272
2356	=item EV_SELECT_USE_FD_SET	3273	=item EV_SELECT_USE_FD_SET
2357		3274
2358	If defined to C<1>, then the select backend will use the system C<fd_set>	3275	If defined to C<1>, then the select backend will use the system C<fd_set>
2359	structure. This is useful if libev doesn't compile due to a missing	3276	structure. This is useful if libev doesn't compile due to a missing
2360	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3277	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2361	exotic systems. This usually limits the range of file descriptors to some	3278	on exotic systems. This usually limits the range of file descriptors to
2362	low limit such as 1024 or might have other limitations (winsocket only	3279	some low limit such as 1024 or might have other limitations (winsocket
2363	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3280	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2364	influence the size of the C<fd_set> used.	3281	configures the maximum size of the C<fd_set>.
2365		3282
2366	=item EV_SELECT_IS_WINSOCKET	3283	=item EV_SELECT_IS_WINSOCKET
2367		3284
2368	When defined to C<1>, the select backend will assume that	3285	When defined to C<1>, the select backend will assume that
2369	select/socket/connect etc. don't understand file descriptors but	3286	select/socket/connect etc. don't understand file descriptors but
…		…
2371	be used is the winsock select). This means that it will call	3288	be used is the winsock select). This means that it will call
2372	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3289	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2373	it is assumed that all these functions actually work on fds, even	3290	it is assumed that all these functions actually work on fds, even
2374	on win32. Should not be defined on non-win32 platforms.	3291	on win32. Should not be defined on non-win32 platforms.
2375		3292
		3293	=item EV_FD_TO_WIN32_HANDLE
		3294
		3295	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3296	file descriptors to socket handles. When not defining this symbol (the
		3297	default), then libev will call C<_get_osfhandle>, which is usually
		3298	correct. In some cases, programs use their own file descriptor management,
		3299	in which case they can provide this function to map fds to socket handles.
		3300
2376	=item EV_USE_POLL	3301	=item EV_USE_POLL
2377		3302
2378	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3303	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2379	backend. Otherwise it will be enabled on non-win32 platforms. It	3304	backend. Otherwise it will be enabled on non-win32 platforms. It
2380	takes precedence over select.	3305	takes precedence over select.
2381		3306
2382	=item EV_USE_EPOLL	3307	=item EV_USE_EPOLL
2383		3308
2384	If defined to be C<1>, libev will compile in support for the Linux	3309	If defined to be C<1>, libev will compile in support for the Linux
2385	C<epoll>(7) backend. Its availability will be detected at runtime,	3310	C<epoll>(7) backend. Its availability will be detected at runtime,
2386	otherwise another method will be used as fallback. This is the	3311	otherwise another method will be used as fallback. This is the preferred
2387	preferred backend for GNU/Linux systems.	3312	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3313	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2388		3314
2389	=item EV_USE_KQUEUE	3315	=item EV_USE_KQUEUE
2390		3316
2391	If defined to be C<1>, libev will compile in support for the BSD style	3317	If defined to be C<1>, libev will compile in support for the BSD style
2392	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3318	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2405	otherwise another method will be used as fallback. This is the preferred	3331	otherwise another method will be used as fallback. This is the preferred
2406	backend for Solaris 10 systems.	3332	backend for Solaris 10 systems.
2407		3333
2408	=item EV_USE_DEVPOLL	3334	=item EV_USE_DEVPOLL
2409		3335
2410	reserved for future expansion, works like the USE symbols above.	3336	Reserved for future expansion, works like the USE symbols above.
2411		3337
2412	=item EV_USE_INOTIFY	3338	=item EV_USE_INOTIFY
2413		3339
2414	If defined to be C<1>, libev will compile in support for the Linux inotify	3340	If defined to be C<1>, libev will compile in support for the Linux inotify
2415	interface to speed up C<ev_stat> watchers. Its actual availability will	3341	interface to speed up C<ev_stat> watchers. Its actual availability will
2416	be detected at runtime.	3342	be detected at runtime. If undefined, it will be enabled if the headers
		3343	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3344
		3345	=item EV_ATOMIC_T
		3346
		3347	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3348	access is atomic with respect to other threads or signal contexts. No such
		3349	type is easily found in the C language, so you can provide your own type
		3350	that you know is safe for your purposes. It is used both for signal handler "locking"
		3351	as well as for signal and thread safety in C<ev_async> watchers.
		3352
		3353	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3354	(from F<signal.h>), which is usually good enough on most platforms.
2417		3355
2418	=item EV_H	3356	=item EV_H
2419		3357
2420	The name of the F<ev.h> header file used to include it. The default if	3358	The name of the F<ev.h> header file used to include it. The default if
2421	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3359	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2422	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3360	used to virtually rename the F<ev.h> header file in case of conflicts.
2423		3361
2424	=item EV_CONFIG_H	3362	=item EV_CONFIG_H
2425		3363
2426	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3364	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2427	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2428	C<EV_H>, above.	3366	C<EV_H>, above.
2429		3367
2430	=item EV_EVENT_H	3368	=item EV_EVENT_H
2431		3369
2432	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3370	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2433	of how the F<event.h> header can be found.	3371	of how the F<event.h> header can be found, the default is C<"event.h">.
2434		3372
2435	=item EV_PROTOTYPES	3373	=item EV_PROTOTYPES
2436		3374
2437	If defined to be C<0>, then F<ev.h> will not define any function	3375	If defined to be C<0>, then F<ev.h> will not define any function
2438	prototypes, but still define all the structs and other symbols. This is	3376	prototypes, but still define all the structs and other symbols. This is
…		…
2459	When doing priority-based operations, libev usually has to linearly search	3397	When doing priority-based operations, libev usually has to linearly search
2460	all the priorities, so having many of them (hundreds) uses a lot of space	3398	all the priorities, so having many of them (hundreds) uses a lot of space
2461	and time, so using the defaults of five priorities (-2 .. +2) is usually	3399	and time, so using the defaults of five priorities (-2 .. +2) is usually
2462	fine.	3400	fine.
2463		3401
2464	If your embedding app does not need any priorities, defining these both to	3402	If your embedding application does not need any priorities, defining these
2465	C<0> will save some memory and cpu.	3403	both to C<0> will save some memory and CPU.
2466		3404
2467	=item EV_PERIODIC_ENABLE	3405	=item EV_PERIODIC_ENABLE
2468		3406
2469	If undefined or defined to be C<1>, then periodic timers are supported. If	3407	If undefined or defined to be C<1>, then periodic timers are supported. If
2470	defined to be C<0>, then they are not. Disabling them saves a few kB of	3408	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2477	code.	3415	code.
2478		3416
2479	=item EV_EMBED_ENABLE	3417	=item EV_EMBED_ENABLE
2480		3418
2481	If undefined or defined to be C<1>, then embed watchers are supported. If	3419	If undefined or defined to be C<1>, then embed watchers are supported. If
2482	defined to be C<0>, then they are not.	3420	defined to be C<0>, then they are not. Embed watchers rely on most other
		3421	watcher types, which therefore must not be disabled.
2483		3422
2484	=item EV_STAT_ENABLE	3423	=item EV_STAT_ENABLE
2485		3424
2486	If undefined or defined to be C<1>, then stat watchers are supported. If	3425	If undefined or defined to be C<1>, then stat watchers are supported. If
2487	defined to be C<0>, then they are not.	3426	defined to be C<0>, then they are not.
…		…
2489	=item EV_FORK_ENABLE	3428	=item EV_FORK_ENABLE
2490		3429
2491	If undefined or defined to be C<1>, then fork watchers are supported. If	3430	If undefined or defined to be C<1>, then fork watchers are supported. If
2492	defined to be C<0>, then they are not.	3431	defined to be C<0>, then they are not.
2493		3432
		3433	=item EV_ASYNC_ENABLE
		3434
		3435	If undefined or defined to be C<1>, then async watchers are supported. If
		3436	defined to be C<0>, then they are not.
		3437
2494	=item EV_MINIMAL	3438	=item EV_MINIMAL
2495		3439
2496	If you need to shave off some kilobytes of code at the expense of some	3440	If you need to shave off some kilobytes of code at the expense of some
2497	speed, define this symbol to C<1>. Currently only used for gcc to override	3441	speed, define this symbol to C<1>. Currently this is used to override some
2498	some inlining decisions, saves roughly 30% codesize of amd64.	3442	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3443	much smaller 2-heap for timer management over the default 4-heap.
2499		3444
2500	=item EV_PID_HASHSIZE	3445	=item EV_PID_HASHSIZE
2501		3446
2502	C<ev_child> watchers use a small hash table to distribute workload by	3447	C<ev_child> watchers use a small hash table to distribute workload by
2503	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3448	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2504	than enough. If you need to manage thousands of children you might want to	3449	than enough. If you need to manage thousands of children you might want to
2505	increase this value (I<must> be a power of two).	3450	increase this value (I<must> be a power of two).
2506		3451
2507	=item EV_INOTIFY_HASHSIZE	3452	=item EV_INOTIFY_HASHSIZE
2508		3453
2509	C<ev_staz> watchers use a small hash table to distribute workload by	3454	C<ev_stat> watchers use a small hash table to distribute workload by
2510	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3455	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2511	usually more than enough. If you need to manage thousands of C<ev_stat>	3456	usually more than enough. If you need to manage thousands of C<ev_stat>
2512	watchers you might want to increase this value (I<must> be a power of	3457	watchers you might want to increase this value (I<must> be a power of
2513	two).	3458	two).
2514		3459
		3460	=item EV_USE_4HEAP
		3461
		3462	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3463	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3464	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3465	faster performance with many (thousands) of watchers.
		3466
		3467	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3468	(disabled).
		3469
		3470	=item EV_HEAP_CACHE_AT
		3471
		3472	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3473	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3474	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3475	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3476	but avoids random read accesses on heap changes. This improves performance
		3477	noticeably with many (hundreds) of watchers.
		3478
		3479	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3480	(disabled).
		3481
		3482	=item EV_VERIFY
		3483
		3484	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3485	be done: If set to C<0>, no internal verification code will be compiled
		3486	in. If set to C<1>, then verification code will be compiled in, but not
		3487	called. If set to C<2>, then the internal verification code will be
		3488	called once per loop, which can slow down libev. If set to C<3>, then the
		3489	verification code will be called very frequently, which will slow down
		3490	libev considerably.
		3491
		3492	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3493	C<0>.
		3494
2515	=item EV_COMMON	3495	=item EV_COMMON
2516		3496
2517	By default, all watchers have a C<void *data> member. By redefining	3497	By default, all watchers have a C<void *data> member. By redefining
2518	this macro to a something else you can include more and other types of	3498	this macro to a something else you can include more and other types of
2519	members. You have to define it each time you include one of the files,	3499	members. You have to define it each time you include one of the files,
2520	though, and it must be identical each time.	3500	though, and it must be identical each time.
2521		3501
2522	For example, the perl EV module uses something like this:	3502	For example, the perl EV module uses something like this:
2523		3503
2524	#define EV_COMMON \	3504	#define EV_COMMON \
2525	SV *self; /* contains this struct */ \	3505	SV *self; /* contains this struct */ \
2526	SV *cb_sv, *fh /* note no trailing ";" */	3506	SV *cb_sv, *fh /* note no trailing ";" */
2527		3507
2528	=item EV_CB_DECLARE (type)	3508	=item EV_CB_DECLARE (type)
2529		3509
2530	=item EV_CB_INVOKE (watcher, revents)	3510	=item EV_CB_INVOKE (watcher, revents)
2531		3511
…		…
2536	definition and a statement, respectively. See the F<ev.h> header file for	3516	definition and a statement, respectively. See the F<ev.h> header file for
2537	their default definitions. One possible use for overriding these is to	3517	their default definitions. One possible use for overriding these is to
2538	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3518	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2539	method calls instead of plain function calls in C++.	3519	method calls instead of plain function calls in C++.
2540		3520
		3521	=back
		3522
2541	=head2 EXPORTED API SYMBOLS	3523	=head2 EXPORTED API SYMBOLS
2542		3524
2543	If you need to re-export the API (e.g. via a dll) and you need a list of	3525	If you need to re-export the API (e.g. via a DLL) and you need a list of
2544	exported symbols, you can use the provided F<Symbol.*> files which list	3526	exported symbols, you can use the provided F<Symbol.*> files which list
2545	all public symbols, one per line:	3527	all public symbols, one per line:
2546		3528
2547	Symbols.ev for libev proper	3529	Symbols.ev for libev proper
2548	Symbols.event for the libevent emulation	3530	Symbols.event for the libevent emulation
2549		3531
2550	This can also be used to rename all public symbols to avoid clashes with	3532	This can also be used to rename all public symbols to avoid clashes with
2551	multiple versions of libev linked together (which is obviously bad in	3533	multiple versions of libev linked together (which is obviously bad in
2552	itself, but sometimes it is inconvinient to avoid this).	3534	itself, but sometimes it is inconvenient to avoid this).
2553		3535
2554	A sed command like this will create wrapper C<#define>'s that you need to	3536	A sed command like this will create wrapper C<#define>'s that you need to
2555	include before including F<ev.h>:	3537	include before including F<ev.h>:
2556		3538
2557	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3539	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2574	file.	3556	file.
2575		3557
2576	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3558	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2577	that everybody includes and which overrides some configure choices:	3559	that everybody includes and which overrides some configure choices:
2578		3560
2579	#define EV_MINIMAL 1	3561	#define EV_MINIMAL 1
2580	#define EV_USE_POLL 0	3562	#define EV_USE_POLL 0
2581	#define EV_MULTIPLICITY 0	3563	#define EV_MULTIPLICITY 0
2582	#define EV_PERIODIC_ENABLE 0	3564	#define EV_PERIODIC_ENABLE 0
2583	#define EV_STAT_ENABLE 0	3565	#define EV_STAT_ENABLE 0
2584	#define EV_FORK_ENABLE 0	3566	#define EV_FORK_ENABLE 0
2585	#define EV_CONFIG_H <config.h>	3567	#define EV_CONFIG_H <config.h>
2586	#define EV_MINPRI 0	3568	#define EV_MINPRI 0
2587	#define EV_MAXPRI 0	3569	#define EV_MAXPRI 0
2588		3570
2589	#include "ev++.h"	3571	#include "ev++.h"
2590		3572
2591	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2592		3574
2593	#include "ev_cpp.h"	3575	#include "ev_cpp.h"
2594	#include "ev.c"	3576	#include "ev.c"
2595		3577
		3578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2596		3579
		3580	=head2 THREADS AND COROUTINES
		3581
		3582	=head3 THREADS
		3583
		3584	All libev functions are reentrant and thread-safe unless explicitly
		3585	documented otherwise, but libev implements no locking itself. This means
		3586	that you can use as many loops as you want in parallel, as long as there
		3587	are no concurrent calls into any libev function with the same loop
		3588	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3589	of course): libev guarantees that different event loops share no data
		3590	structures that need any locking.
		3591
		3592	Or to put it differently: calls with different loop parameters can be done
		3593	concurrently from multiple threads, calls with the same loop parameter
		3594	must be done serially (but can be done from different threads, as long as
		3595	only one thread ever is inside a call at any point in time, e.g. by using
		3596	a mutex per loop).
		3597
		3598	Specifically to support threads (and signal handlers), libev implements
		3599	so-called C<ev_async> watchers, which allow some limited form of
		3600	concurrency on the same event loop, namely waking it up "from the
		3601	outside".
		3602
		3603	If you want to know which design (one loop, locking, or multiple loops
		3604	without or something else still) is best for your problem, then I cannot
		3605	help you, but here is some generic advice:
		3606
		3607	=over 4
		3608
		3609	=item * most applications have a main thread: use the default libev loop
		3610	in that thread, or create a separate thread running only the default loop.
		3611
		3612	This helps integrating other libraries or software modules that use libev
		3613	themselves and don't care/know about threading.
		3614
		3615	=item * one loop per thread is usually a good model.
		3616
		3617	Doing this is almost never wrong, sometimes a better-performance model
		3618	exists, but it is always a good start.
		3619
		3620	=item * other models exist, such as the leader/follower pattern, where one
		3621	loop is handed through multiple threads in a kind of round-robin fashion.
		3622
		3623	Choosing a model is hard - look around, learn, know that usually you can do
		3624	better than you currently do :-)
		3625
		3626	=item * often you need to talk to some other thread which blocks in the
		3627	event loop.
		3628
		3629	C<ev_async> watchers can be used to wake them up from other threads safely
		3630	(or from signal contexts...).
		3631
		3632	An example use would be to communicate signals or other events that only
		3633	work in the default loop by registering the signal watcher with the
		3634	default loop and triggering an C<ev_async> watcher from the default loop
		3635	watcher callback into the event loop interested in the signal.
		3636
		3637	=back
		3638
		3639	=head3 COROUTINES
		3640
		3641	Libev is very accommodating to coroutines ("cooperative threads"):
		3642	libev fully supports nesting calls to its functions from different
		3643	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3644	different coroutines, and switch freely between both coroutines running the
		3645	loop, as long as you don't confuse yourself). The only exception is that
		3646	you must not do this from C<ev_periodic> reschedule callbacks.
		3647
		3648	Care has been taken to ensure that libev does not keep local state inside
		3649	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3650	they do not call any callbacks.
		3651
		3652	=head2 COMPILER WARNINGS
		3653
		3654	Depending on your compiler and compiler settings, you might get no or a
		3655	lot of warnings when compiling libev code. Some people are apparently
		3656	scared by this.
		3657
		3658	However, these are unavoidable for many reasons. For one, each compiler
		3659	has different warnings, and each user has different tastes regarding
		3660	warning options. "Warn-free" code therefore cannot be a goal except when
		3661	targeting a specific compiler and compiler-version.
		3662
		3663	Another reason is that some compiler warnings require elaborate
		3664	workarounds, or other changes to the code that make it less clear and less
		3665	maintainable.
		3666
		3667	And of course, some compiler warnings are just plain stupid, or simply
		3668	wrong (because they don't actually warn about the condition their message
		3669	seems to warn about). For example, certain older gcc versions had some
		3670	warnings that resulted an extreme number of false positives. These have
		3671	been fixed, but some people still insist on making code warn-free with
		3672	such buggy versions.
		3673
		3674	While libev is written to generate as few warnings as possible,
		3675	"warn-free" code is not a goal, and it is recommended not to build libev
		3676	with any compiler warnings enabled unless you are prepared to cope with
		3677	them (e.g. by ignoring them). Remember that warnings are just that:
		3678	warnings, not errors, or proof of bugs.
		3679
		3680
		3681	=head2 VALGRIND
		3682
		3683	Valgrind has a special section here because it is a popular tool that is
		3684	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3685
		3686	If you think you found a bug (memory leak, uninitialised data access etc.)
		3687	in libev, then check twice: If valgrind reports something like:
		3688
		3689	==2274== definitely lost: 0 bytes in 0 blocks.
		3690	==2274== possibly lost: 0 bytes in 0 blocks.
		3691	==2274== still reachable: 256 bytes in 1 blocks.
		3692
		3693	Then there is no memory leak, just as memory accounted to global variables
		3694	is not a memleak - the memory is still being referenced, and didn't leak.
		3695
		3696	Similarly, under some circumstances, valgrind might report kernel bugs
		3697	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3698	although an acceptable workaround has been found here), or it might be
		3699	confused.
		3700
		3701	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3702	make it into some kind of religion.
		3703
		3704	If you are unsure about something, feel free to contact the mailing list
		3705	with the full valgrind report and an explanation on why you think this
		3706	is a bug in libev (best check the archives, too :). However, don't be
		3707	annoyed when you get a brisk "this is no bug" answer and take the chance
		3708	of learning how to interpret valgrind properly.
		3709
		3710	If you need, for some reason, empty reports from valgrind for your project
		3711	I suggest using suppression lists.
		3712
		3713
		3714	=head1 PORTABILITY NOTES
		3715
		3716	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3717
		3718	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3719	requires, and its I/O model is fundamentally incompatible with the POSIX
		3720	model. Libev still offers limited functionality on this platform in
		3721	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3722	descriptors. This only applies when using Win32 natively, not when using
		3723	e.g. cygwin.
		3724
		3725	Lifting these limitations would basically require the full
		3726	re-implementation of the I/O system. If you are into these kinds of
		3727	things, then note that glib does exactly that for you in a very portable
		3728	way (note also that glib is the slowest event library known to man).
		3729
		3730	There is no supported compilation method available on windows except
		3731	embedding it into other applications.
		3732
		3733	Not a libev limitation but worth mentioning: windows apparently doesn't
		3734	accept large writes: instead of resulting in a partial write, windows will
		3735	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3736	so make sure you only write small amounts into your sockets (less than a
		3737	megabyte seems safe, but this apparently depends on the amount of memory
		3738	available).
		3739
		3740	Due to the many, low, and arbitrary limits on the win32 platform and
		3741	the abysmal performance of winsockets, using a large number of sockets
		3742	is not recommended (and not reasonable). If your program needs to use
		3743	more than a hundred or so sockets, then likely it needs to use a totally
		3744	different implementation for windows, as libev offers the POSIX readiness
		3745	notification model, which cannot be implemented efficiently on windows
		3746	(Microsoft monopoly games).
		3747
		3748	A typical way to use libev under windows is to embed it (see the embedding
		3749	section for details) and use the following F<evwrap.h> header file instead
		3750	of F<ev.h>:
		3751
		3752	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3753	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3754
		3755	#include "ev.h"
		3756
		3757	And compile the following F<evwrap.c> file into your project (make sure
		3758	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3759
		3760	#include "evwrap.h"
		3761	#include "ev.c"
		3762
		3763	=over 4
		3764
		3765	=item The winsocket select function
		3766
		3767	The winsocket C<select> function doesn't follow POSIX in that it
		3768	requires socket I<handles> and not socket I<file descriptors> (it is
		3769	also extremely buggy). This makes select very inefficient, and also
		3770	requires a mapping from file descriptors to socket handles (the Microsoft
		3771	C runtime provides the function C<_open_osfhandle> for this). See the
		3772	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3773	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3774
		3775	The configuration for a "naked" win32 using the Microsoft runtime
		3776	libraries and raw winsocket select is:
		3777
		3778	#define EV_USE_SELECT 1
		3779	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3780
		3781	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3782	complexity in the O(n²) range when using win32.
		3783
		3784	=item Limited number of file descriptors
		3785
		3786	Windows has numerous arbitrary (and low) limits on things.
		3787
		3788	Early versions of winsocket's select only supported waiting for a maximum
		3789	of C<64> handles (probably owning to the fact that all windows kernels
		3790	can only wait for C<64> things at the same time internally; Microsoft
		3791	recommends spawning a chain of threads and wait for 63 handles and the
		3792	previous thread in each. Great).
		3793
		3794	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3795	to some high number (e.g. C<2048>) before compiling the winsocket select
		3796	call (which might be in libev or elsewhere, for example, perl does its own
		3797	select emulation on windows).
		3798
		3799	Another limit is the number of file descriptors in the Microsoft runtime
		3800	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3801	or something like this inside Microsoft). You can increase this by calling
		3802	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3803	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3804	libraries.
		3805
		3806	This might get you to about C<512> or C<2048> sockets (depending on
		3807	windows version and/or the phase of the moon). To get more, you need to
		3808	wrap all I/O functions and provide your own fd management, but the cost of
		3809	calling select (O(n²)) will likely make this unworkable.
		3810
		3811	=back
		3812
		3813	=head2 PORTABILITY REQUIREMENTS
		3814
		3815	In addition to a working ISO-C implementation and of course the
		3816	backend-specific APIs, libev relies on a few additional extensions:
		3817
		3818	=over 4
		3819
		3820	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3821	calling conventions regardless of C<ev_watcher_type *>.
		3822
		3823	Libev assumes not only that all watcher pointers have the same internal
		3824	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3825	assumes that the same (machine) code can be used to call any watcher
		3826	callback: The watcher callbacks have different type signatures, but libev
		3827	calls them using an C<ev_watcher *> internally.
		3828
		3829	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3830
		3831	The type C<sig_atomic_t volatile> (or whatever is defined as
		3832	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3833	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3834	believed to be sufficiently portable.
		3835
		3836	=item C<sigprocmask> must work in a threaded environment
		3837
		3838	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3839	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3840	pthread implementations will either allow C<sigprocmask> in the "main
		3841	thread" or will block signals process-wide, both behaviours would
		3842	be compatible with libev. Interaction between C<sigprocmask> and
		3843	C<pthread_sigmask> could complicate things, however.
		3844
		3845	The most portable way to handle signals is to block signals in all threads
		3846	except the initial one, and run the default loop in the initial thread as
		3847	well.
		3848
		3849	=item C<long> must be large enough for common memory allocation sizes
		3850
		3851	To improve portability and simplify its API, libev uses C<long> internally
		3852	instead of C<size_t> when allocating its data structures. On non-POSIX
		3853	systems (Microsoft...) this might be unexpectedly low, but is still at
		3854	least 31 bits everywhere, which is enough for hundreds of millions of
		3855	watchers.
		3856
		3857	=item C<double> must hold a time value in seconds with enough accuracy
		3858
		3859	The type C<double> is used to represent timestamps. It is required to
		3860	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3861	enough for at least into the year 4000. This requirement is fulfilled by
		3862	implementations implementing IEEE 754 (basically all existing ones).
		3863
		3864	=back
		3865
		3866	If you know of other additional requirements drop me a note.
		3867
		3868
2597	=head1 COMPLEXITIES	3869	=head1 ALGORITHMIC COMPLEXITIES
2598		3870
2599	In this section the complexities of (many of) the algorithms used inside	3871	In this section the complexities of (many of) the algorithms used inside
2600	libev will be explained. For complexity discussions about backends see the	3872	libev will be documented. For complexity discussions about backends see
2601	documentation for C<ev_default_init>.	3873	the documentation for C<ev_default_init>.
2602		3874
2603	All of the following are about amortised time: If an array needs to be	3875	All of the following are about amortised time: If an array needs to be
2604	extended, libev needs to realloc and move the whole array, but this	3876	extended, libev needs to realloc and move the whole array, but this
2605	happens asymptotically never with higher number of elements, so O(1) might	3877	happens asymptotically rarer with higher number of elements, so O(1) might
2606	mean it might do a lengthy realloc operation in rare cases, but on average	3878	mean that libev does a lengthy realloc operation in rare cases, but on
2607	it is much faster and asymptotically approaches constant time.	3879	average it is much faster and asymptotically approaches constant time.
2608		3880
2609	=over 4	3881	=over 4
2610		3882
2611	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3883	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2612		3884
2613	This means that, when you have a watcher that triggers in one hour and	3885	This means that, when you have a watcher that triggers in one hour and
2614	there are 100 watchers that would trigger before that then inserting will	3886	there are 100 watchers that would trigger before that, then inserting will
2615	have to skip those 100 watchers.	3887	have to skip roughly seven (C<ld 100>) of these watchers.
2616		3888
2617	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3889	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2618		3890
2619	That means that for changing a timer costs less than removing/adding them	3891	That means that changing a timer costs less than removing/adding them,
2620	as only the relative motion in the event queue has to be paid for.	3892	as only the relative motion in the event queue has to be paid for.
2621		3893
2622	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3894	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2623		3895
2624	These just add the watcher into an array or at the head of a list.	3896	These just add the watcher into an array or at the head of a list.
		3897
2625	=item Stopping check/prepare/idle watchers: O(1)	3898	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2626		3899
2627	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3900	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2628		3901
2629	These watchers are stored in lists then need to be walked to find the	3902	These watchers are stored in lists, so they need to be walked to find the
2630	correct watcher to remove. The lists are usually short (you don't usually	3903	correct watcher to remove. The lists are usually short (you don't usually
2631	have many watchers waiting for the same fd or signal).	3904	have many watchers waiting for the same fd or signal: one is typical, two
		3905	is rare).
2632		3906
2633	=item Finding the next timer per loop iteration: O(1)	3907	=item Finding the next timer in each loop iteration: O(1)
		3908
		3909	By virtue of using a binary or 4-heap, the next timer is always found at a
		3910	fixed position in the storage array.
2634		3911
2635	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3912	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2636		3913
2637	A change means an I/O watcher gets started or stopped, which requires	3914	A change means an I/O watcher gets started or stopped, which requires
2638	libev to recalculate its status (and possibly tell the kernel).	3915	libev to recalculate its status (and possibly tell the kernel, depending
		3916	on backend and whether C<ev_io_set> was used).
2639		3917
2640	=item Activating one watcher: O(1)	3918	=item Activating one watcher (putting it into the pending state): O(1)
2641		3919
2642	=item Priority handling: O(number_of_priorities)	3920	=item Priority handling: O(number_of_priorities)
2643		3921
2644	Priorities are implemented by allocating some space for each	3922	Priorities are implemented by allocating some space for each
2645	priority. When doing priority-based operations, libev usually has to	3923	priority. When doing priority-based operations, libev usually has to
2646	linearly search all the priorities.	3924	linearly search all the priorities, but starting/stopping and activating
		3925	watchers becomes O(1) with respect to priority handling.
		3926
		3927	=item Sending an ev_async: O(1)
		3928
		3929	=item Processing ev_async_send: O(number_of_async_watchers)
		3930
		3931	=item Processing signals: O(max_signal_number)
		3932
		3933	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3934	calls in the current loop iteration. Checking for async and signal events
		3935	involves iterating over all running async watchers or all signal numbers.
2647		3936
2648	=back	3937	=back
2649		3938
2650		3939
2651	=head1 AUTHOR	3940	=head1 AUTHOR
2652		3941
2653	Marc Lehmann <libev@schmorp.de>.	3942	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
2654		3943

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