ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.91 by root, Thu Dec 20 07:12:57 2007 UTC vs.
Revision 1.223 by root, Sun Dec 14 21:58:08 2008 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 occuring), 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
61	To do this, it must take more or less complete control over your process	77	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	78	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	79	communicate events via a callback mechanism.
…		…
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.
…		…
114	=item ev_tstamp ev_time ()	152	=item ev_tstamp ev_time ()
115		153
116	Returns the current time as libev would use it. Please note that the	154	Returns the current time as libev would use it. Please note that the
117	C<ev_now> function is usually faster and also often returns the timestamp	155	C<ev_now> function is usually faster and also often returns the timestamp
118	you actually want to know.	156	you actually want to know.
		157
		158	=item ev_sleep (ev_tstamp interval)
		159
		160	Sleep for the given interval: The current thread will be blocked until
		161	either it is interrupted or the given time interval has passed. Basically
		162	this is a sub-second-resolution C<sleep ()>.
119		163
120	=item int ev_version_major ()	164	=item int ev_version_major ()
121		165
122	=item int ev_version_minor ()	166	=item int ev_version_minor ()
123		167
…		…
136	not a problem.	180	not a problem.
137		181
138	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
139	version.	183	version.
140		184
141	assert (("libev version mismatch",	185	assert (("libev version mismatch",
142	ev_version_major () == EV_VERSION_MAJOR	186	ev_version_major () == EV_VERSION_MAJOR
143	&& ev_version_minor () >= EV_VERSION_MINOR));	187	&& ev_version_minor () >= EV_VERSION_MINOR));
144		188
145	=item unsigned int ev_supported_backends ()	189	=item unsigned int ev_supported_backends ()
146		190
147	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_*>
148	value) compiled into this binary of libev (independent of their	192	value) compiled into this binary of libev (independent of their
…		…
150	a description of the set values.	194	a description of the set values.
151		195
152	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
153	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
154		198
155	assert (("sorry, no epoll, no sex",	199	assert (("sorry, no epoll, no sex",
156	ev_supported_backends () & EVBACKEND_EPOLL));	200	ev_supported_backends () & EVBACKEND_EPOLL));
157		201
158	=item unsigned int ev_recommended_backends ()	202	=item unsigned int ev_recommended_backends ()
159		203
160	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
161	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
162	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
163	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
164	(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
165	libev will probe for if you specify no backends explicitly.	209	libev will probe for if you specify no backends explicitly.
166		210
167	=item unsigned int ev_embeddable_backends ()	211	=item unsigned int ev_embeddable_backends ()
168		212
…		…
172	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
173	recommended ones.	217	recommended ones.
174		218
175	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
176		220
177	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
178		222
179	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
180	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
181	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
182	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
183	potentially destructive action. The default is your system realloc	227	or take some potentially destructive action.
184	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.
185		232
186	You could override this function in high-availability programs to, say,	233	You could override this function in high-availability programs to, say,
187	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,
188	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.
189		236
190	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
191	retries).	238	retries (example requires a standards-compliant C<realloc>).
192		239
193	static void *	240	static void *
194	persistent_realloc (void *ptr, size_t size)	241	persistent_realloc (void *ptr, size_t size)
195	{	242	{
196	for (;;)	243	for (;;)
…		…
205	}	252	}
206		253
207	...	254	...
208	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
209		256
210	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
211		258
212	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
213	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
214	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
215	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
216	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
217	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
218	(such as abort).	265	(such as abort).
219		266
220	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.
…		…
231		278
232	=back	279	=back
233		280
234	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
235		282
236	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>
237	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>
238	events, and dynamically created loops which do not.	285	I<function>).
239		286
240	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
241	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
242	create, you also create another event loop. Libev itself does no locking	289	not.
243	whatsoever, so if you mix calls to the same event loop in different
244	threads, make sure you lock (this is usually a bad idea, though, even if
245	done correctly, because it's hideous and inefficient).
246		290
247	=over 4	291	=over 4
248		292
249	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
250		294
…		…
254	flags. If that is troubling you, check C<ev_backend ()> afterwards).	298	flags. If that is troubling you, check C<ev_backend ()> afterwards).
255		299
256	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
257	function.	301	function.
258		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
259	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
260	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>).
261		316
262	The following flags are supported:	317	The following flags are supported:
263		318
…		…
268	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
269	thing, believe me).	324	thing, believe me).
270		325
271	=item C<EVFLAG_NOENV>	326	=item C<EVFLAG_NOENV>
272		327
273	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
274	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
275	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
276	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
277	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
278	around bugs.	333	around bugs.
…		…
284	enabling this flag.	339	enabling this flag.
285		340
286	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,
287	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
288	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
289	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
290	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
291	C<pthread_atfork> which is even faster).	346	C<pthread_atfork> which is even faster).
292		347
293	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
294	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
295	flag.	350	flag.
296		351
297	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>
298	environment variable.	353	environment variable.
299		354
300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301		356
302	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
303	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,
304	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
305	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
306	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).
307		373
308	=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)
309		375
310	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
311	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
312	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
313	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>.
314		385
315	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
316		387
317	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,
318	but it scales phenomenally better. While poll and select usually scale like	389	but it scales phenomenally better. While poll and select usually scale
319	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	390	like O(total_fds) where n is the total number of fds (or the highest fd),
320	either O(1) or O(active_fds).	391	epoll scales either O(1) or O(active_fds).
321		392
		393	The epoll mechanism deserves honorable mention as the most misdesigned
		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.
		409
322	While stopping and starting an I/O watcher in the same iteration will	410	While stopping, setting and starting an I/O watcher in the same iteration
323	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
324	(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
325	best to avoid that. Also, dup()ed file descriptors might not work very	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
326	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.
327		416
328	Please note that epoll sometimes generates spurious notifications, so you	417	Best performance from this backend is achieved by not unregistering all
329	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,
330	(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>.
331		434
332	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
333		436
334	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
335	was broken on all BSDs except NetBSD (usually it doesn't work with	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
336	anything but sockets and pipes, except on Darwin, where of course it's	439	with anything but sockets and pipes, except on Darwin, where of course
337	completely useless). For this reason it's not being "autodetected"	440	it's completely useless). Unlike epoll, however, whose brokenness
		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
338	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
339	C<EVBACKEND_KQUEUE>).	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		445	system like NetBSD.
		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.
340		450
341	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
342	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
343	course). While starting and stopping an I/O watcher does not cause an	453	course). While stopping, setting and starting an I/O watcher does never
344	extra syscall as with epoll, it still adds up to four event changes per	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
345	incident, so its best to avoid that.	455	two event changes per incident. Support for C<fork ()> is very bad (but
		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>.
346		471
347	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
348		473
349	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.
350		478
351	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
352		480
353	This uses the Solaris 10 port mechanism. As with everything on Solaris,	481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
354	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)).
355		483
356	Please note that solaris ports can result in a lot of spurious	484	Please note that Solaris event ports can deliver a lot of spurious
357	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
358	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>.
359		500
360	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
361		502
362	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
363	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
364	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
365		506
		507	It is definitely not recommended to use this flag.
		508
366	=back	509	=back
367		510
368	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
369	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
370	specified, most compiled-in backend will be tried, usually in reverse	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
371	order of their flag values :)
372		514
373	The most typical usage is like this:	515	Example: This is the most typical usage.
374		516
375	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
376	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
377		519
378	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
379	environment settings to be taken into account:	521	environment settings to be taken into account:
380		522
381	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
382		524
383	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
384	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
385	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):
386		529
387	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
388		531
389	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
390		533
391	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
392	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
393	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
394	undefined behaviour (or a failed assertion if assertions are enabled).	537	undefined behaviour (or a failed assertion if assertions are enabled).
395		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
396	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.
397		544
398	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
399	if (!epoller)	546	if (!epoller)
400	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
401		548
402	=item ev_default_destroy ()	549	=item ev_default_destroy ()
403		550
404	Destroys the default loop again (frees all memory and kernel state	551	Destroys the default loop again (frees all memory and kernel state
405	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
406	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
407	responsibility to either stop all watchers cleanly yoursef I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
408	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
409	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
410	for example).	557	for example).
411		558
412	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
413	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
414	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
415		562
416	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
417	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
418	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
419	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
423	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
424	earlier call to C<ev_loop_new>.	571	earlier call to C<ev_loop_new>.
425		572
426	=item ev_default_fork ()	573	=item ev_default_fork ()
427		574
		575	This function sets a flag that causes subsequent C<ev_loop> iterations
428	This function reinitialises the kernel state for backends that have	576	to reinitialise the kernel state for backends that have one. Despite the
429	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
430	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
431	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.
432		581
433	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
434	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
435	fork+exec, you don't have to call it.	584	you just fork+exec, you don't have to call it at all.
436		585
437	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
438	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
439	quite nicely into a call to C<pthread_atfork>:	588	quite nicely into a call to C<pthread_atfork>:
440		589
441	pthread_atfork (0, 0, ev_default_fork);	590	pthread_atfork (0, 0, ev_default_fork);
442		591
443	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
444	without calling this function, so if you force one of those backends you
445	do not need to care.
446
447	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
448		593
449	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
450	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
451	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.
452		603
453	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
454		605
455	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
456	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
…		…
469		620
470	Returns the current "event loop time", which is the time the event loop	621	Returns the current "event loop time", which is the time the event loop
471	received events and started processing them. This timestamp does not	622	received events and started processing them. This timestamp does not
472	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
473	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
474	event occuring (or more correctly, libev finding out about it).	625	event occurring (or more correctly, libev finding out about it).
		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.
475		638
476	=item ev_loop (loop, int flags)	639	=item ev_loop (loop, int flags)
477		640
478	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
479	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
…		…
482	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
483	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.
484		647
485	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
486	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
487	finished (especially in interactive programs), but having a program that	650	finished (especially in interactive programs), but having a program
488	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
489	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.
490		654
491	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
492	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
493	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.
494		659
495	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
496	neccessary) and will handle those and any outstanding ones. It will block	661	necessary) and will handle those and any already outstanding ones. It
497	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
498	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
499	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
500	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
501	usually a better approach for this kind of thing.	670	usually a better approach for this kind of thing.
502		671
503	Here are the gory details of what C<ev_loop> does:	672	Here are the gory details of what C<ev_loop> does:
504		673
505	- Before the first iteration, call any pending watchers.	674	- Before the first iteration, call any pending watchers.
506	* If there are no active watchers (reference count is zero), return.	675	* If EVFLAG_FORKCHECK was used, check for a fork.
507	- 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.
508	- 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.
509	- Update the kernel state with all outstanding changes.	680	- Update the kernel state with all outstanding changes.
510	- Update the "event loop time".	681	- Update the "event loop time" (ev_now ()).
511	- 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.
512	- Block the process, waiting for any events.	686	- Block the process, waiting for any events.
513	- Queue all outstanding I/O (fd) events.	687	- Queue all outstanding I/O (fd) events.
514	- Update the "event loop time" and do time jump handling.	688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
515	- Queue all outstanding timers.	689	- Queue all expired timers.
516	- Queue all outstanding periodics.	690	- Queue all expired periodics.
517	- If no events are pending now, queue all idle watchers.	691	- Unless any events are pending now, queue all idle watchers.
518	- Queue all check watchers.	692	- Queue all check watchers.
519	- 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).
520	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
521	be handled here by queueing them when their watcher gets executed.	695	be handled here by queueing them when their watcher gets executed.
522	- 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
523	were used, return, otherwise continue with step *.	697	were used, or there are no active watchers, return, otherwise
		698	continue with step *.
524		699
525	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
526	anymore.	701	anymore.
527		702
528	... queue jobs here, make sure they register event watchers as long	703	... queue jobs here, make sure they register event watchers as long
529	... 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..)
530	ev_loop (my_loop, 0);	705	ev_loop (my_loop, 0);
531	... jobs done. yeah!	706	... jobs done or somebody called unloop. yeah!
532		707
533	=item ev_unloop (loop, how)	708	=item ev_unloop (loop, how)
534		709
535	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
536	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
537	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
538	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.
539		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
540	=item ev_ref (loop)	719	=item ev_ref (loop)
541		720
542	=item ev_unref (loop)	721	=item ev_unref (loop)
543		722
544	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
545	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
546	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
547	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>
548	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
549	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
550	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
551	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
552	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
553	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).
554		738
555	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>
556	running when nothing else is active.	740	running when nothing else is active.
557		741
558	struct ev_signal exitsig;	742	ev_signal exitsig;
559	ev_signal_init (&exitsig, sig_cb, SIGINT);	743	ev_signal_init (&exitsig, sig_cb, SIGINT);
560	ev_signal_start (loop, &exitsig);	744	ev_signal_start (loop, &exitsig);
561	evf_unref (loop);	745	evf_unref (loop);
562		746
563	Example: For some weird reason, unregister the above signal handler again.	747	Example: For some weird reason, unregister the above signal handler again.
564		748
565	ev_ref (loop);	749	ev_ref (loop);
566	ev_signal_stop (loop, &exitsig);	750	ev_signal_stop (loop, &exitsig);
		751
		752	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		753
		754	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		755
		756	These advanced functions influence the time that libev will spend waiting
		757	for events. Both time intervals are by default C<0>, meaning that libev
		758	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		759	latency.
		760
		761	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		762	allows libev to delay invocation of I/O and timer/periodic callbacks
		763	to increase efficiency of loop iterations (or to increase power-saving
		764	opportunities).
		765
		766	The idea is that sometimes your program runs just fast enough to handle
		767	one (or very few) event(s) per loop iteration. While this makes the
		768	program responsive, it also wastes a lot of CPU time to poll for new
		769	events, especially with backends like C<select ()> which have a high
		770	overhead for the actual polling but can deliver many events at once.
		771
		772	By setting a higher I<io collect interval> you allow libev to spend more
		773	time collecting I/O events, so you can handle more events per iteration,
		774	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		775	C<ev_timer>) will be not affected. Setting this to a non-null value will
		776	introduce an additional C<ev_sleep ()> call into most loop iterations.
		777
		778	Likewise, by setting a higher I<timeout collect interval> you allow libev
		779	to spend more time collecting timeouts, at the expense of increased
		780	latency/jitter/inexactness (the watcher callback will be called
		781	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		782	value will not introduce any overhead in libev.
		783
		784	Many (busy) programs can usually benefit by setting the I/O collect
		785	interval to a value near C<0.1> or so, which is often enough for
		786	interactive servers (of course not for games), likewise for timeouts. It
		787	usually doesn't make much sense to set it to a lower value than C<0.01>,
		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.
567		808
568	=back	809	=back
569		810
570		811
571	=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.
572		817
573	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
574	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
575	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:
576		821
577	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)
578	{	823	{
579	ev_io_stop (w);	824	ev_io_stop (w);
580	ev_unloop (loop, EVUNLOOP_ALL);	825	ev_unloop (loop, EVUNLOOP_ALL);
581	}	826	}
582		827
583	struct ev_loop *loop = ev_default_loop (0);	828	struct ev_loop *loop = ev_default_loop (0);
		829
584	struct ev_io stdin_watcher;	830	ev_io stdin_watcher;
		831
585	ev_init (&stdin_watcher, my_cb);	832	ev_init (&stdin_watcher, my_cb);
586	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
587	ev_io_start (loop, &stdin_watcher);	834	ev_io_start (loop, &stdin_watcher);
		835
588	ev_loop (loop, 0);	836	ev_loop (loop, 0);
589		837
590	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
591	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
592	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).
593		844
594	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
595	(watcher *, callback)>, which expects a callback to be provided. This	846	(watcher *, callback)>, which expects a callback to be provided. This
596	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
597	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
598	is readable and/or writable).	849	is readable and/or writable).
599		850
600	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 *, ...) >>
601	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
602	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<<
603	(watcher *, callback, ...) >>.	854	ev_TYPE_init (watcher *, callback, ...) >>.
604		855
605	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
606	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
607	*) >>), 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
608	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
609		860
610	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
611	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
612	reinitialise it or call its C<set> macro.	863	reinitialise it or call its C<ev_TYPE_set> macro.
613		864
614	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
615	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
616	third argument.	867	third argument.
617		868
…		…
671	=item C<EV_FORK>	922	=item C<EV_FORK>
672		923
673	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
674	C<ev_fork>).	925	C<ev_fork>).
675		926
		927	=item C<EV_ASYNC>
		928
		929	The given async watcher has been asynchronously notified (see C<ev_async>).
		930
676	=item C<EV_ERROR>	931	=item C<EV_ERROR>
677		932
678	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
679	happen because the watcher could not be properly started because libev	934	happen because the watcher could not be properly started because libev
680	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
681	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
682	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.
683		942
684	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
685	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
686	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
687	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
688	programs, though, so beware.	947	programs, though, as the fd could already be closed and reused for another
		948	thing, so beware.
689		949
690	=back	950	=back
691		951
692	=head2 GENERIC WATCHER FUNCTIONS	952	=head2 GENERIC WATCHER FUNCTIONS
693
694	In the following description, C<TYPE> stands for the watcher type,
695	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
696		953
697	=over 4	954	=over 4
698		955
699	=item C<ev_init> (ev_TYPE *watcher, callback)	956	=item C<ev_init> (ev_TYPE *watcher, callback)
700		957
…		…
706	which rolls both calls into one.	963	which rolls both calls into one.
707		964
708	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
709	(or never started) and there are no pending events outstanding.	966	(or never started) and there are no pending events outstanding.
710		967
711	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,
712	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);
713		976
714	=item C<ev_TYPE_set> (ev_TYPE *, [args])	977	=item C<ev_TYPE_set> (ev_TYPE *, [args])
715		978
716	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
717	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
…		…
720	difference to the C<ev_init> macro).	983	difference to the C<ev_init> macro).
721		984
722	Although some watcher types do not have type-specific arguments	985	Although some watcher types do not have type-specific arguments
723	(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.
724		987
		988	See C<ev_init>, above, for an example.
		989
725	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	990	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
726		991
727	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
728	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
729	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);
730		999
731	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
732		1001
733	Starts (activates) the given watcher. Only active watchers will receive	1002	Starts (activates) the given watcher. Only active watchers will receive
734	events. If the watcher is already active nothing will happen.	1003	events. If the watcher is already active nothing will happen.
735		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
736	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
737		1011
738	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
739	status. It is possible that stopped watchers are pending (for example,	1015	It is possible that stopped watchers are pending - for example,
740	non-repeating timers are being stopped when they become pending), but	1016	non-repeating timers are being stopped when they become pending - but
741	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
742	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
743	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.
744		1020
745	=item bool ev_is_active (ev_TYPE *watcher)	1021	=item bool ev_is_active (ev_TYPE *watcher)
746		1022
747	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
748	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
…		…
790	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
791	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 :).
792		1068
793	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
794	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
795	or might not have been adjusted to be within valid range.	1071	or might not have been clamped to the valid range.
796		1072
797	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
798		1074
799	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
800	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
801	can deal with that fact.	1077	can deal with that fact, as both are simply passed through to the
		1078	callback.
802		1079
803	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1080	=item int ev_clear_pending (loop, ev_TYPE *watcher)
804		1081
805	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
806	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
807	watcher isn't pending it does nothing and returns C<0>.	1084	watcher isn't pending it does nothing and returns C<0>.
808		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
809	=back	1089	=back
810		1090
811		1091
812	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
813		1093
814	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
815	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
816	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
817	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
818	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
819	data:	1099	data:
820		1100
821	struct my_io	1101	struct my_io
822	{	1102	{
823	struct ev_io io;	1103	ev_io io;
824	int otherfd;	1104	int otherfd;
825	void *somedata;	1105	void *somedata;
826	struct whatever *mostinteresting;	1106	struct whatever *mostinteresting;
827	}	1107	};
		1108
		1109	...
		1110	struct my_io w;
		1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
828		1112
829	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
830	can cast it back to your own type:	1114	can cast it back to your own type:
831		1115
832	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)
833	{	1117	{
834	struct my_io *w = (struct my_io *)w_;	1118	struct my_io *w = (struct my_io *)w_;
835	...	1119	...
836	}	1120	}
837		1121
838	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
839	instead have been omitted.	1123	instead have been omitted.
840		1124
841	Another common scenario is having some data structure with multiple	1125	Another common scenario is to use some data structure with multiple
842	watchers:	1126	embedded watchers:
843		1127
844	struct my_biggy	1128	struct my_biggy
845	{	1129	{
846	int some_data;	1130	int some_data;
847	ev_timer t1;	1131	ev_timer t1;
848	ev_timer t2;	1132	ev_timer t2;
849	}	1133	}
850		1134
851	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
852	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):
853		1140
854	#include <stddef.h>	1141	#include <stddef.h>
855		1142
856	static void	1143	static void
857	t1_cb (EV_P_ struct ev_timer *w, int revents)	1144	t1_cb (EV_P_ ev_timer *w, int revents)
858	{	1145	{
859	struct my_biggy big = (struct my_biggy *	1146	struct my_biggy big = (struct my_biggy *
860	(((char *)w) - offsetof (struct my_biggy, t1));	1147	(((char *)w) - offsetof (struct my_biggy, t1));
861	}	1148	}
862		1149
863	static void	1150	static void
864	t2_cb (EV_P_ struct ev_timer *w, int revents)	1151	t2_cb (EV_P_ ev_timer *w, int revents)
865	{	1152	{
866	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
867	(((char *)w) - offsetof (struct my_biggy, t2));	1154	(((char *)w) - offsetof (struct my_biggy, t2));
868	}	1155	}
869		1156
870		1157
871	=head1 WATCHER TYPES	1158	=head1 WATCHER TYPES
872		1159
873	This section describes each watcher in detail, but will not repeat	1160	This section describes each watcher in detail, but will not repeat
…		…
897	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
898	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
899	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
900	required if you know what you are doing).	1187	required if you know what you are doing).
901		1188
902	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
903	(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
904	descriptors correctly if you register interest in two or more fds pointing	1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
905	to the same underlying file/socket/etc. description (that is, they share
906	the same underlying "file open").
907
908	If you must do this, then force the use of a known-to-be-good backend
909	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
910	C<EVBACKEND_POLL>).
911		1192
912	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
913	receive "spurious" readyness notifications, that is your callback might	1194	receive "spurious" readiness notifications, that is your callback might
914	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
915	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
916	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
917	this situation even with a relatively standard program structure. Thus	1198	this situation even with a relatively standard program structure. Thus
918	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
919	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.
920		1201
921	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
922	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
923	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
924	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
925	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.
926		1211
927	=head3 The special problem of disappearing file descriptors	1212	=head3 The special problem of disappearing file descriptors
928		1213
929	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
930	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,
931	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
932	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
933	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
934	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
935	fact, a different file descriptor.	1220	fact, a different file descriptor.
936		1221
…		…
943		1228
944	This is how one would do it normally anyway, the important point is that	1229	This is how one would do it normally anyway, the important point is that
945	the libev application should not optimise around libev but should leave	1230	the libev application should not optimise around libev but should leave
946	optimisations to libev.	1231	optimisations to libev.
947		1232
		1233	=head3 The special problem of dup'ed file descriptors
		1234
		1235	Some backends (e.g. epoll), cannot register events for file descriptors,
		1236	but only events for the underlying file descriptions. That means when you
		1237	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1238	events for them, only one file descriptor might actually receive events.
		1239
		1240	There is no workaround possible except not registering events
		1241	for potentially C<dup ()>'ed file descriptors, or to resort to
		1242	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1243
		1244	=head3 The special problem of fork
		1245
		1246	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1247	useless behaviour. Libev fully supports fork, but needs to be told about
		1248	it in the child.
		1249
		1250	To support fork in your programs, you either have to call
		1251	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1253	C<EVBACKEND_POLL>.
		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
948		1266
949	=head3 Watcher-Specific Functions	1267	=head3 Watcher-Specific Functions
950		1268
951	=over 4	1269	=over 4
952		1270
953	=item ev_io_init (ev_io *, callback, int fd, int events)	1271	=item ev_io_init (ev_io *, callback, int fd, int events)
954		1272
955	=item ev_io_set (ev_io *, int fd, int events)	1273	=item ev_io_set (ev_io *, int fd, int events)
956		1274
957	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
958	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
959	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.
960		1278
961	=item int fd [read-only]	1279	=item int fd [read-only]
962		1280
963	The file descriptor being watched.	1281	The file descriptor being watched.
964		1282
965	=item int events [read-only]	1283	=item int events [read-only]
966		1284
967	The events being watched.	1285	The events being watched.
968		1286
969	=back	1287	=back
		1288
		1289	=head3 Examples
970		1290
971	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
972	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
973	attempt to read a whole line in the callback.	1293	attempt to read a whole line in the callback.
974		1294
975	static void	1295	static void
976	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)
977	{	1297	{
978	ev_io_stop (loop, w);	1298	ev_io_stop (loop, w);
979	.. 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
980	}	1300	}
981		1301
982	...	1302	...
983	struct ev_loop *loop = ev_default_init (0);	1303	struct ev_loop *loop = ev_default_init (0);
984	struct ev_io stdin_readable;	1304	ev_io stdin_readable;
985	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);
986	ev_io_start (loop, &stdin_readable);	1306	ev_io_start (loop, &stdin_readable);
987	ev_loop (loop, 0);	1307	ev_loop (loop, 0);
988		1308
989		1309
990	=head2 C<ev_timer> - relative and optionally repeating timeouts	1310	=head2 C<ev_timer> - relative and optionally repeating timeouts
991		1311
992	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
993	given time, and optionally repeating in regular intervals after that.	1313	given time, and optionally repeating in regular intervals after that.
994		1314
995	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
996	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
997	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
998	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the
999	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.
1000		1507
1001	The relative timeouts are calculated relative to the C<ev_now ()>	1508	The relative timeouts are calculated relative to the C<ev_now ()>
1002	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
1003	of the event triggering whatever timeout you are modifying/starting. If	1510	of the event triggering whatever timeout you are modifying/starting. If
1004	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
1005	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:
1006		1513
1007	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1008		1515
1009	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
1010	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
1011	order of execution is undefined.	1518	()>.
1012		1519
1013	=head3 Watcher-Specific Functions and Data Members	1520	=head3 Watcher-Specific Functions and Data Members
1014		1521
1015	=over 4	1522	=over 4
1016		1523
1017	=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)
1018		1525
1019	=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)
1020		1527
1021	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>
1022	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
1023	timer will automatically be configured to trigger again C<repeat> seconds	1530	reached. If it is positive, then the timer will automatically be
1024	later, again, and again, until stopped manually.	1531	configured to trigger again C<repeat> seconds later, again, and again,
		1532	until stopped manually.
1025		1533
1026	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
1027	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
1028	exactly 10 second intervals. If, however, your program cannot keep up with	1536	trigger at exactly 10 second intervals. If, however, your program cannot
1029	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
1030	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.
1031		1539
1032	=item ev_timer_again (loop)	1540	=item ev_timer_again (loop, ev_timer *)
1033		1541
1034	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
1035	repeating. The exact semantics are:	1543	repeating. The exact semantics are:
1036		1544
1037	If the timer is pending, its pending status is cleared.	1545	If the timer is pending, its pending status is cleared.
1038		1546
1039	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).
1040		1548
1041	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
1042	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.
1043		1551
1044	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
1045	example: Imagine you have a tcp connection and you want a so-called idle	1553	usage example.
1046	timeout, that is, you want to be called when there have been, say, 60
1047	seconds of inactivity on the socket. The easiest way to do this is to
1048	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1049	C<ev_timer_again> each time you successfully read or write some data. If
1050	you go into an idle state where you do not expect data to travel on the
1051	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1052	automatically restart it if need be.
1053
1054	That means you can ignore the C<after> value and C<ev_timer_start>
1055	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1056
1057	ev_timer_init (timer, callback, 0., 5.);
1058	ev_timer_again (loop, timer);
1059	...
1060	timer->again = 17.;
1061	ev_timer_again (loop, timer);
1062	...
1063	timer->again = 10.;
1064	ev_timer_again (loop, timer);
1065
1066	This is more slightly efficient then stopping/starting the timer each time
1067	you want to modify its timeout value.
1068		1554
1069	=item ev_tstamp repeat [read-write]	1555	=item ev_tstamp repeat [read-write]
1070		1556
1071	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
1072	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),
1073	which is also when any modifications are taken into account.	1559	which is also when any modifications are taken into account.
1074		1560
1075	=back	1561	=back
1076		1562
		1563	=head3 Examples
		1564
1077	Example: Create a timer that fires after 60 seconds.	1565	Example: Create a timer that fires after 60 seconds.
1078		1566
1079	static void	1567	static void
1080	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)
1081	{	1569	{
1082	.. one minute over, w is actually stopped right here	1570	.. one minute over, w is actually stopped right here
1083	}	1571	}
1084		1572
1085	struct ev_timer mytimer;	1573	ev_timer mytimer;
1086	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1574	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1087	ev_timer_start (loop, &mytimer);	1575	ev_timer_start (loop, &mytimer);
1088		1576
1089	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
1090	inactivity.	1578	inactivity.
1091		1579
1092	static void	1580	static void
1093	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1581	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1094	{	1582	{
1095	.. ten seconds without any activity	1583	.. ten seconds without any activity
1096	}	1584	}
1097		1585
1098	struct ev_timer mytimer;	1586	ev_timer mytimer;
1099	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 */
1100	ev_timer_again (&mytimer); /* start timer */	1588	ev_timer_again (&mytimer); /* start timer */
1101	ev_loop (loop, 0);	1589	ev_loop (loop, 0);
1102		1590
1103	// 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":
1104	// reset the timeout to start ticking again at 10 seconds	1592	// reset the timeout to start ticking again at 10 seconds
1105	ev_timer_again (&mytimer);	1593	ev_timer_again (&mytimer);
1106		1594
1107		1595
1108	=head2 C<ev_periodic> - to cron or not to cron?	1596	=head2 C<ev_periodic> - to cron or not to cron?
1109		1597
1110	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
1111	(and unfortunately a bit complex).	1599	(and unfortunately a bit complex).
1112		1600
1113	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)
1114	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
1115	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
1116	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 ()
1117	+ 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
1118	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
1119	roughly 10 seconds later).	1608	roughly 10 seconds later as it uses a relative timeout).
1120		1609
1121	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,
1122	triggering an event on each midnight, local time or other, complicated,	1611	such as triggering an event on each "midnight, local time", or other
1123	rules.	1612	complicated rules.
1124		1613
1125	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
1126	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
1127	during the same loop iteration then order of execution is undefined.	1616	during the same loop iteration, then order of execution is undefined.
1128		1617
1129	=head3 Watcher-Specific Functions and Data Members	1618	=head3 Watcher-Specific Functions and Data Members
1130		1619
1131	=over 4	1620	=over 4
1132		1621
1133	=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)
1134		1623
1135	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1136		1625
1137	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
1138	operation, and we will explain them from simplest to complex:	1627	operation, and we will explain them from simplest to most complex:
1139		1628
1140	=over 4	1629	=over 4
1141		1630
1142	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1143		1632
1144	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
1145	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
1146	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
1147	system time reaches or surpasses this time.	1636	only run when the system clock reaches or surpasses this time.
1148		1637
1149	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1150		1639
1151	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
1152	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)
1153	and then repeat, regardless of any time jumps.	1642	and then repeat, regardless of any time jumps.
1154		1643
1155	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
1156	time:	1645	system clock, for example, here is a C<ev_periodic> that triggers each
		1646	hour, on the hour:
1157		1647
1158	ev_periodic_set (&periodic, 0., 3600., 0);	1648	ev_periodic_set (&periodic, 0., 3600., 0);
1159		1649
1160	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,
1161	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
1162	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
1163	by 3600.	1653	by 3600.
1164		1654
1165	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
1166	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
1167	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.
1168		1658
1169	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
1170	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
1171	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).
1172		1667
1173	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1174		1669
1175	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
1176	ignored. Instead, each time the periodic watcher gets scheduled, the	1671	ignored. Instead, each time the periodic watcher gets scheduled, the
1177	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
1178	current time as second argument.	1673	current time as second argument.
1179		1674
1180	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,
1181	ever, or make any event loop modifications>. If you need to stop it,	1676	ever, or make ANY event loop modifications whatsoever>.
1182	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1183	starting an C<ev_prepare> watcher, which is legal).
1184		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
1185	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1682	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1186	ev_tstamp now)>, e.g.:	1683	*w, ev_tstamp now)>, e.g.:
1187		1684
		1685	static ev_tstamp
1188	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1686	my_rescheduler (ev_periodic *w, ev_tstamp now)
1189	{	1687	{
1190	return now + 60.;	1688	return now + 60.;
1191	}	1689	}
1192		1690
1193	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
1194	(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
1195	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
1196	might be called at other times, too.	1694	might be called at other times, too.
1197		1695
1198	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
1199	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1697	equal to the passed C<now> value >>.
1200		1698
1201	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
1202	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
1203	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
1204	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
1205	reason I omitted it as an example).	1703	reason I omitted it as an example).
1206		1704
1207	=back	1705	=back
…		…
1211	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
1212	when you changed some parameters or the reschedule callback would return	1710	when you changed some parameters or the reschedule callback would return
1213	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
1214	program when the crontabs have changed).	1712	program when the crontabs have changed).
1215		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
1216	=item ev_tstamp offset [read-write]	1719	=item ev_tstamp offset [read-write]
1217		1720
1218	When repeating, this contains the offset value, otherwise this is the	1721	When repeating, this contains the offset value, otherwise this is the
1219	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>).
1220		1723
…		…
1225		1728
1226	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
1227	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
1228	called.	1731	called.
1229		1732
1230	=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]
1231		1734
1232	The current reschedule callback, or C<0>, if this functionality is	1735	The current reschedule callback, or C<0>, if this functionality is
1233	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
1234	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.
1235		1738
1236	=item ev_tstamp at [read-only]
1237
1238	When active, contains the absolute time that the watcher is supposed to
1239	trigger next.
1240
1241	=back	1739	=back
1242		1740
		1741	=head3 Examples
		1742
1243	Example: Call a callback every hour, or, more precisely, whenever the	1743	Example: Call a callback every hour, or, more precisely, whenever the
1244	system clock is divisible by 3600. The callback invocation times have	1744	system time is divisible by 3600. The callback invocation times have
1245	potentially a lot of jittering, but good long-term stability.	1745	potentially a lot of jitter, but good long-term stability.
1246		1746
1247	static void	1747	static void
1248	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1249	{	1749	{
1250	... 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)
1251	}	1751	}
1252		1752
1253	struct ev_periodic hourly_tick;	1753	ev_periodic hourly_tick;
1254	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1754	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1255	ev_periodic_start (loop, &hourly_tick);	1755	ev_periodic_start (loop, &hourly_tick);
1256		1756
1257	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:
1258		1758
1259	#include <math.h>	1759	#include <math.h>
1260		1760
1261	static ev_tstamp	1761	static ev_tstamp
1262	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1762	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1263	{	1763	{
1264	return fmod (now, 3600.) + 3600.;	1764	return now + (3600. - fmod (now, 3600.));
1265	}	1765	}
1266		1766
1267	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);
1268		1768
1269	Example: Call a callback every hour, starting now:	1769	Example: Call a callback every hour, starting now:
1270		1770
1271	struct ev_periodic hourly_tick;	1771	ev_periodic hourly_tick;
1272	ev_periodic_init (&hourly_tick, clock_cb,	1772	ev_periodic_init (&hourly_tick, clock_cb,
1273	fmod (ev_now (loop), 3600.), 3600., 0);	1773	fmod (ev_now (loop), 3600.), 3600., 0);
1274	ev_periodic_start (loop, &hourly_tick);	1774	ev_periodic_start (loop, &hourly_tick);
1275		1775
1276		1776
1277	=head2 C<ev_signal> - signal me when a signal gets signalled!	1777	=head2 C<ev_signal> - signal me when a signal gets signalled!
1278		1778
1279	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
1280	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
1281	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
1282	normal event processing, like any other event.	1782	normal event processing, like any other event.
1283		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
1284	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
1285	first watcher gets started will libev actually register a signal watcher	1789	first watcher gets started will libev actually register a signal handler
1286	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
1287	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
1288	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
1289	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.
1290		1800
1291	=head3 Watcher-Specific Functions and Data Members	1801	=head3 Watcher-Specific Functions and Data Members
1292		1802
1293	=over 4	1803	=over 4
1294		1804
…		…
1303		1813
1304	The signal the watcher watches out for.	1814	The signal the watcher watches out for.
1305		1815
1306	=back	1816	=back
1307		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
1308		1832
1309	=head2 C<ev_child> - watch out for process status changes	1833	=head2 C<ev_child> - watch out for process status changes
1310		1834
1311	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
1312	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.
1313		1872
1314	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1315		1874
1316	=over 4	1875	=over 4
1317		1876
1318	=item ev_child_init (ev_child *, callback, int pid)	1877	=item ev_child_init (ev_child *, callback, int pid, int trace)
1319		1878
1320	=item ev_child_set (ev_child *, int pid)	1879	=item ev_child_set (ev_child *, int pid, int trace)
1321		1880
1322	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
1323	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
1324	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
1325	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
1326	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
1327	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).
1328		1889
1329	=item int pid [read-only]	1890	=item int pid [read-only]
1330		1891
1331	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.
1332		1893
…		…
1339	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
1340	C<waitpid> and C<sys/wait.h> documentation for details).	1901	C<waitpid> and C<sys/wait.h> documentation for details).
1341		1902
1342	=back	1903	=back
1343		1904
1344	Example: Try to exit cleanly on SIGINT and SIGTERM.	1905	=head3 Examples
1345		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
1346	static void	1912	static void
1347	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1913	child_cb (EV_P_ ev_child *w, int revents)
1348	{	1914	{
1349	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);
1350	}	1917	}
1351		1918
1352	struct ev_signal signal_watcher;	1919	pid_t pid = fork ();
1353	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1920
1354	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	}
1355		1933
1356		1934
1357	=head2 C<ev_stat> - did the file attributes just change?	1935	=head2 C<ev_stat> - did the file attributes just change?
1358		1936
1359	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
1360	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)
1361	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.
1362		1941
1363	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
1364	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
1365	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
1366	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
1367	the stat buffer having unspecified contents.	1946	least one) and all the other fields of the stat buffer having unspecified
		1947	contents.
1368		1948
1369	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
1370	relative and your working directory changes, the behaviour is undefined.	1951	your working directory changes, then the behaviour is undefined.
1371		1952
1372	Since there is no standard to do this, the portable implementation simply	1953	Since there is no portable change notification interface available, the
1373	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
1374	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
1375	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
1376	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
1377	five seconds, although this might change dynamically). Libev will also	1958	(which you can expect to be around five seconds, although this might
1378	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
1379	usually overkill.	1960	currently around C<0.1>, but that's usually overkill.
1380		1961
1381	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,
1382	as even with OS-supported change notifications, this can be	1963	as even with OS-supported change notifications, this can be
1383	resource-intensive.	1964	resource-intensive.
1384		1965
1385	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
1386	implemented (implementing kqueue support is left as an exercise for the	1967	is the Linux inotify interface (implementing kqueue support is left as an
1387	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
1388	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1969	implementing C<ev_stat> semantics with kqueue, except as a hint).
1389	to fall back to regular polling again even with inotify, but changes are	1970
1390	usually detected immediately, and if the file exists there will be no	1971	=head3 ABI Issues (Largefile Support)
1391	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).
1392		2052
1393	=head3 Watcher-Specific Functions and Data Members	2053	=head3 Watcher-Specific Functions and Data Members
1394		2054
1395	=over 4	2055	=over 4
1396		2056
…		…
1402	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
1403	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
1404	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
1405	path for as long as the watcher is active.	2065	path for as long as the watcher is active.
1406		2066
1407	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,
1408	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
1409	last change was detected).	2069	last change was detected).
1410		2070
1411	=item ev_stat_stat (ev_stat *)	2071	=item ev_stat_stat (loop, ev_stat *)
1412		2072
1413	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
1414	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
1415	detecting this change (while introducing a race condition). Can also be	2075	detecting this change (while introducing a race condition if you are not
1416	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.
1417		2078
1418	=item ev_statdata attr [read-only]	2079	=item ev_statdata attr [read-only]
1419		2080
1420	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
1421	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
1422	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
1423	was some error while C<stat>ing the file.	2085	some error while C<stat>ing the file.
1424		2086
1425	=item ev_statdata prev [read-only]	2087	=item ev_statdata prev [read-only]
1426		2088
1427	The previous attributes of the file. The callback gets invoked whenever	2089	The previous attributes of the file. The callback gets invoked whenever
1428	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>.
1429		2093
1430	=item ev_tstamp interval [read-only]	2094	=item ev_tstamp interval [read-only]
1431		2095
1432	The specified interval.	2096	The specified interval.
1433		2097
1434	=item const char *path [read-only]	2098	=item const char *path [read-only]
1435		2099
1436	The filesystem path that is being watched.	2100	The file system path that is being watched.
1437		2101
1438	=back	2102	=back
1439		2103
		2104	=head3 Examples
		2105
1440	Example: Watch C</etc/passwd> for attribute changes.	2106	Example: Watch C</etc/passwd> for attribute changes.
1441		2107
1442	static void	2108	static void
1443	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2109	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1444	{	2110	{
1445	/* /etc/passwd changed in some way */	2111	/* /etc/passwd changed in some way */
1446	if (w->attr.st_nlink)	2112	if (w->attr.st_nlink)
1447	{	2113	{
1448	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2114	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1449	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2115	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1450	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2116	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1451	}	2117	}
1452	else	2118	else
1453	/* you shalt not abuse printf for puts */	2119	/* you shalt not abuse printf for puts */
1454	puts ("wow, /etc/passwd is not there, expect problems. "	2120	puts ("wow, /etc/passwd is not there, expect problems. "
1455	"if this is windows, they already arrived\n");	2121	"if this is windows, they already arrived\n");
1456	}	2122	}
1457		2123
1458	...	2124	...
1459	ev_stat passwd;	2125	ev_stat passwd;
1460		2126
1461	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2127	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1462	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);
1463		2157
1464		2158
1465	=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...
1466		2160
1467	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
1468	priority are pending (prepare, check and other idle watchers do not	2162	priority are pending (prepare, check and other idle watchers do not count
1469	count).	2163	as receiving "events").
1470		2164
1471	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
1472	(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
1473	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
1474	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
…		…
1493	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,
1494	believe me.	2188	believe me.
1495		2189
1496	=back	2190	=back
1497		2191
		2192	=head3 Examples
		2193
1498	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
1499	callback, free it. Also, use no error checking, as usual.	2195	callback, free it. Also, use no error checking, as usual.
1500		2196
1501	static void	2197	static void
1502	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1503	{	2199	{
1504	free (w);	2200	free (w);
1505	// now do something you wanted to do when the program has	2201	// now do something you wanted to do when the program has
1506	// no longer asnything immediate to do.	2202	// no longer anything immediate to do.
1507	}	2203	}
1508		2204
1509	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1510	ev_idle_init (idle_watcher, idle_cb);	2206	ev_idle_init (idle_watcher, idle_cb);
1511	ev_idle_start (loop, idle_cb);	2207	ev_idle_start (loop, idle_cb);
1512		2208
1513		2209
1514	=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!
1515		2211
1516	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:
1517	prepare watchers get invoked before the process blocks and check watchers	2213	prepare watchers get invoked before the process blocks and check watchers
1518	afterwards.	2214	afterwards.
1519		2215
1520	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
1521	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>
…		…
1524	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,
1525	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
1526	called in pairs bracketing the blocking call.	2222	called in pairs bracketing the blocking call.
1527		2223
1528	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
1529	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
1530	variable changes, implement your own watchers, integrate net-snmp or a	2226	variable changes, implement your own watchers, integrate net-snmp or a
1531	coroutine library and lots more. They are also occasionally useful if	2227	coroutine library and lots more. They are also occasionally useful if
1532	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,
1533	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>
1534	watcher).	2230	watcher).
1535		2231
1536	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
1537	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
1538	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
1539	provide just this functionality). Then, in the check watcher you check for	2235	libraries provide exactly this functionality). Then, in the check watcher,
1540	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
1541	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
1542	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
1543	because you never know, you know?).	2239	nevertheless, because you never know, you know?).
1544		2240
1545	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
1546	coroutines into libev programs, by yielding to other active coroutines	2242	coroutines into libev programs, by yielding to other active coroutines
1547	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
1548	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
…		…
1551	loop from blocking if lower-priority coroutines are active, thus mapping	2247	loop from blocking if lower-priority coroutines are active, thus mapping
1552	low-priority coroutines to idle/background tasks).	2248	low-priority coroutines to idle/background tasks).
1553		2249
1554	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>)
1555	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
1556	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
1557	too) should not activate ("feed") events into libev. While libev fully	2255	activate ("feed") events into libev. While libev fully supports this, they
1558	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
1559	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
1560	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
1561	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
1562	others).	2260	others).
1563		2261
1564	=head3 Watcher-Specific Functions and Data Members	2262	=head3 Watcher-Specific Functions and Data Members
…		…
1569		2267
1570	=item ev_check_init (ev_check *, callback)	2268	=item ev_check_init (ev_check *, callback)
1571		2269
1572	Initialises and configures the prepare or check watcher - they have no	2270	Initialises and configures the prepare or check watcher - they have no
1573	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>
1574	macros, but using them is utterly, utterly and completely pointless.	2272	macros, but using them is utterly, utterly, utterly and completely
		2273	pointless.
1575		2274
1576	=back	2275	=back
		2276
		2277	=head3 Examples
1577		2278
1578	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
1579	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
1580	(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
1581	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
1582	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
1583	into the Glib event loop).	2284	Glib event loop).
1584		2285
1585	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,
1586	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
1587	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
1588	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
1589	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.
1590		2291
1591	static ev_io iow [nfd];	2292	static ev_io iow [nfd];
1592	static ev_timer tw;	2293	static ev_timer tw;
1593		2294
1594	static void	2295	static void
1595	io_cb (ev_loop *loop, ev_io *w, int revents)	2296	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1596	{	2297	{
1597	}	2298	}
1598		2299
1599	// create io watchers for each fd and a timer before blocking	2300	// create io watchers for each fd and a timer before blocking
1600	static void	2301	static void
1601	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2302	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1602	{	2303	{
1603	int timeout = 3600000;	2304	int timeout = 3600000;
1604	struct pollfd fds [nfd];	2305	struct pollfd fds [nfd];
1605	// actual code will need to loop here and realloc etc.	2306	// actual code will need to loop here and realloc etc.
1606	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1607		2308
1608	/* 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 */
1609	ev_timer_init (&tw, 0, timeout * 1e-3);	2310	ev_timer_init (&tw, 0, timeout * 1e-3);
1610	ev_timer_start (loop, &tw);	2311	ev_timer_start (loop, &tw);
1611		2312
1612	// create one ev_io per pollfd	2313	// create one ev_io per pollfd
1613	for (int i = 0; i < nfd; ++i)	2314	for (int i = 0; i < nfd; ++i)
1614	{	2315	{
1615	ev_io_init (iow + i, io_cb, fds [i].fd,	2316	ev_io_init (iow + i, io_cb, fds [i].fd,
1616	((fds [i].events & POLLIN ? EV_READ : 0)	2317	((fds [i].events & POLLIN ? EV_READ : 0)
1617	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2318	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1618		2319
1619	fds [i].revents = 0;	2320	fds [i].revents = 0;
1620	ev_io_start (loop, iow + i);	2321	ev_io_start (loop, iow + i);
1621	}	2322	}
1622	}	2323	}
1623		2324
1624	// stop all watchers after blocking	2325	// stop all watchers after blocking
1625	static void	2326	static void
1626	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2327	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1627	{	2328	{
1628	ev_timer_stop (loop, &tw);	2329	ev_timer_stop (loop, &tw);
1629		2330
1630	for (int i = 0; i < nfd; ++i)	2331	for (int i = 0; i < nfd; ++i)
1631	{	2332	{
1632	// set the relevant poll flags	2333	// set the relevant poll flags
1633	// could also call adns_processreadable etc. here	2334	// could also call adns_processreadable etc. here
1634	struct pollfd *fd = fds + i;	2335	struct pollfd *fd = fds + i;
1635	int revents = ev_clear_pending (iow + i);	2336	int revents = ev_clear_pending (iow + i);
1636	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2337	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1637	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2338	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1638		2339
1639	// now stop the watcher	2340	// now stop the watcher
1640	ev_io_stop (loop, iow + i);	2341	ev_io_stop (loop, iow + i);
1641	}	2342	}
1642		2343
1643	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2344	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1644	}	2345	}
1645		2346
1646	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>
1647	in the prepare watcher and would dispose of the check watcher.	2348	in the prepare watcher and would dispose of the check watcher.
1648		2349
1649	Method 3: If the module to be embedded supports explicit event	2350	Method 3: If the module to be embedded supports explicit event
1650	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
1651	callbacks, and only destroy/create the watchers in the prepare watcher.	2352	callbacks, and only destroy/create the watchers in the prepare watcher.
1652		2353
1653	static void	2354	static void
1654	timer_cb (EV_P_ ev_timer *w, int revents)	2355	timer_cb (EV_P_ ev_timer *w, int revents)
1655	{	2356	{
1656	adns_state ads = (adns_state)w->data;	2357	adns_state ads = (adns_state)w->data;
1657	update_now (EV_A);	2358	update_now (EV_A);
1658		2359
1659	adns_processtimeouts (ads, &tv_now);	2360	adns_processtimeouts (ads, &tv_now);
1660	}	2361	}
1661		2362
1662	static void	2363	static void
1663	io_cb (EV_P_ ev_io *w, int revents)	2364	io_cb (EV_P_ ev_io *w, int revents)
1664	{	2365	{
1665	adns_state ads = (adns_state)w->data;	2366	adns_state ads = (adns_state)w->data;
1666	update_now (EV_A);	2367	update_now (EV_A);
1667		2368
1668	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2369	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1669	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2370	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1670	}	2371	}
1671		2372
1672	// do not ever call adns_afterpoll	2373	// do not ever call adns_afterpoll
1673		2374
1674	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
1675	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
1676	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
1677	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
1678	this.	2379	this approach, effectively embedding EV as a client into the horrible
		2380	libglib event loop.
1679		2381
1680	static gint	2382	static gint
1681	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2383	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1682	{	2384	{
1683	int got_events = 0;	2385	int got_events = 0;
1684		2386
1685	for (n = 0; n < nfds; ++n)	2387	for (n = 0; n < nfds; ++n)
1686	// 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
1687		2389
1688	if (timeout >= 0)	2390	if (timeout >= 0)
1689	// create/start timer	2391	// create/start timer
1690		2392
1691	// poll	2393	// poll
1692	ev_loop (EV_A_ 0);	2394	ev_loop (EV_A_ 0);
1693		2395
1694	// stop timer again	2396	// stop timer again
1695	if (timeout >= 0)	2397	if (timeout >= 0)
1696	ev_timer_stop (EV_A_ &to);	2398	ev_timer_stop (EV_A_ &to);
1697		2399
1698	// stop io watchers again - their callbacks should have set	2400	// stop io watchers again - their callbacks should have set
1699	for (n = 0; n < nfds; ++n)	2401	for (n = 0; n < nfds; ++n)
1700	ev_io_stop (EV_A_ iow [n]);	2402	ev_io_stop (EV_A_ iow [n]);
1701		2403
1702	return got_events;	2404	return got_events;
1703	}	2405	}
1704		2406
1705		2407
1706	=head2 C<ev_embed> - when one backend isn't enough...	2408	=head2 C<ev_embed> - when one backend isn't enough...
1707		2409
1708	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
…		…
1714	prioritise I/O.	2416	prioritise I/O.
1715		2417
1716	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
1717	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
1718	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
1719	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
1720	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
1721	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
1722	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 :)
1723		2426
1724	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
1725	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),
1726	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
1727	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
1728	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.
1729		2432
1730	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
1731	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
1732	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
1733	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
1734	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
1735	to C<0>, in which case the embed watcher will automatically execute the	2438	to give the embedded loop strictly lower priority for example).
1736	embedded loop sweep.
1737		2439
1738	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
1739	callback will be invoked whenever some events have been handled. You can	2441	will automatically execute the embedded loop sweep whenever necessary.
1740	set the callback to C<0> to avoid having to specify one if you are not
1741	interested in that.
1742		2442
1743	Also, there have not currently been made special provisions for forking:	2443	Fork detection will be handled transparently while the C<ev_embed> watcher
1744	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
1745	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
1746	yourself.	2446	C<ev_loop_fork> on the embedded loop.
1747		2447
1748	Unfortunately, not all backends are embeddable, only the ones returned by	2448	Unfortunately, not all backends are embeddable: only the ones returned by
1749	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2449	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1750	portable one.	2450	portable one.
1751		2451
1752	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
1753	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
1754	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
1755	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.
1756		2456
1757	struct ev_loop *loop_hi = ev_default_init (0);	2457	=head3 C<ev_embed> and fork
1758	struct ev_loop *loop_lo = 0;
1759	struct ev_embed embed;
1760
1761	// see if there is a chance of getting one that works
1762	// (remember that a flags value of 0 means autodetection)
1763	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1764	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1765	: 0;
1766		2458
1767	// 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
1768	if (loop_lo)	2460	automatically be applied to the embedded loop as well, so no special
1769	{	2461	fork handling is required in that case. When the watcher is not running,
1770	ev_embed_init (&embed, 0, loop_lo);	2462	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1771	ev_embed_start (loop_hi, &embed);	2463	as applicable.
1772	}
1773	else
1774	loop_lo = loop_hi;
1775		2464
1776	=head3 Watcher-Specific Functions and Data Members	2465	=head3 Watcher-Specific Functions and Data Members
1777		2466
1778	=over 4	2467	=over 4
1779		2468
…		…
1783		2472
1784	Configures the watcher to embed the given loop, which must be	2473	Configures the watcher to embed the given loop, which must be
1785	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
1786	invoked automatically, otherwise it is the responsibility of the callback	2475	invoked automatically, otherwise it is the responsibility of the callback
1787	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,
1788	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).
1789		2478
1790	=item ev_embed_sweep (loop, ev_embed *)	2479	=item ev_embed_sweep (loop, ev_embed *)
1791		2480
1792	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
1793	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
1794	apropriate way for embedded loops.	2483	appropriate way for embedded loops.
1795		2484
1796	=item struct ev_loop *other [read-only]	2485	=item struct ev_loop *other [read-only]
1797		2486
1798	The embedded event loop.	2487	The embedded event loop.
1799		2488
1800	=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
1801		2538
1802		2539
1803	=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
1804		2541
1805	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
…		…
1821	believe me.	2558	believe me.
1822		2559
1823	=back	2560	=back
1824		2561
1825		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
1826	=head1 OTHER FUNCTIONS	2708	=head1 OTHER FUNCTIONS
1827		2709
1828	There are some other functions of possible interest. Described. Here. Now.	2710	There are some other functions of possible interest. Described. Here. Now.
1829		2711
1830	=over 4	2712	=over 4
1831		2713
1832	=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)
1833		2715
1834	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
1835	callback on whichever event happens first and automatically stop both	2717	callback on whichever event happens first and automatically stops both
1836	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
1837	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
1838	more watchers yourself.	2720	more watchers yourself.
1839		2721
1840	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
1841	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
1842	C<events> set will be craeted and started.	2724	the given C<fd> and C<events> set will be created and started.
1843		2725
1844	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
1845	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
1846	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.
1847	dubious value.
1848		2729
1849	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
1850	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
1851	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>
1852	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.
1853		2736
		2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2738
1854	static void stdin_ready (int revents, void *arg)	2739	static void stdin_ready (int revents, void *arg)
1855	{	2740	{
1856	if (revents & EV_TIMEOUT)
1857	/* doh, nothing entered */;
1858	else if (revents & EV_READ)	2741	if (revents & EV_READ)
1859	/* 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 */;
1860	}	2745	}
1861		2746
1862	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1863		2748
1864	=item ev_feed_event (ev_loop *, watcher *, int revents)	2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1865		2750
1866	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
1867	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
1868	initialised but not necessarily started event watcher).	2753	initialised but not necessarily started event watcher).
1869		2754
1870	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1871		2756
1872	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
1873	the given events it.	2758	the given events it.
1874		2759
1875	=item ev_feed_signal_event (ev_loop *loop, int signum)	2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1876		2761
1877	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
1878	loop!).	2763	loop!).
1879		2764
1880	=back	2765	=back
1881		2766
1882		2767
…		…
1898		2783
1899	=item * Priorities are not currently supported. Initialising priorities	2784	=item * Priorities are not currently supported. Initialising priorities
1900	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
1901	is an ev_pri field.	2786	is an ev_pri field.
1902		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
1903	=item * Other members are not supported.	2791	=item * Other members are not supported.
1904		2792
1905	=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
1906	to use the libev header file and library.	2794	to use the libev header file and library.
1907		2795
1908	=back	2796	=back
1909		2797
1910	=head1 C++ SUPPORT	2798	=head1 C++ SUPPORT
1911		2799
1912	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
1913	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
1914	the callback model to a model using method callbacks on objects.	2802	the callback model to a model using method callbacks on objects.
1915		2803
1916	To use it,	2804	To use it,
1917		2805
1918	#include <ev++.h>	2806	#include <ev++.h>
1919		2807
1920	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
1921	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
1922	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
1923	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2811	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1990	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
1991	thunking function, making it as fast as a direct C callback.	2879	thunking function, making it as fast as a direct C callback.
1992		2880
1993	Example: simple class declaration and watcher initialisation	2881	Example: simple class declaration and watcher initialisation
1994		2882
1995	struct myclass	2883	struct myclass
1996	{	2884	{
1997	void io_cb (ev::io &w, int revents) { }	2885	void io_cb (ev::io &w, int revents) { }
1998	}	2886	}
1999		2887
2000	myclass obj;	2888	myclass obj;
2001	ev::io iow;	2889	ev::io iow;
2002	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);
2003		2921
2004	=item w->set<function> (void *data = 0)	2922	=item w->set<function> (void *data = 0)
2005		2923
2006	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
2007	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
…		…
2009		2927
2010	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)>.
2011		2929
2012	See the method-C<set> above for more details.	2930	See the method-C<set> above for more details.
2013		2931
2014	Example:	2932	Example: Use a plain function as callback.
2015		2933
2016	static void io_cb (ev::io &w, int revents) { }	2934	static void io_cb (ev::io &w, int revents) { }
2017	iow.set <io_cb> ();	2935	iow.set <io_cb> ();
2018		2936
2019	=item w->set (struct ev_loop *)	2937	=item w->set (struct ev_loop *)
2020		2938
2021	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
2022	do this when the watcher is inactive (and not pending either).	2940	do this when the watcher is inactive (and not pending either).
2023		2941
2024	=item w->set ([args])	2942	=item w->set ([arguments])
2025		2943
2026	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
2027	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
2028	automatically stopped and restarted when reconfiguring it with this	2946	automatically stopped and restarted when reconfiguring it with this
2029	method.	2947	method.
2030		2948
2031	=item w->start ()	2949	=item w->start ()
…		…
2055	=back	2973	=back
2056		2974
2057	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
2058	the constructor.	2976	the constructor.
2059		2977
2060	class myclass	2978	class myclass
2061	{	2979	{
2062	ev_io io; void io_cb (ev::io &w, int revents);	2980	ev::io io ; void io_cb (ev::io &w, int revents);
2063	ev_idle idle void idle_cb (ev::idle &w, int revents);	2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2064		2982
2065	myclass ();	2983	myclass (int fd)
2066	}	2984	{
2067
2068	myclass::myclass (int fd)
2069	{
2070	io .set <myclass, &myclass::io_cb > (this);	2985	io .set <myclass, &myclass::io_cb > (this);
2071	idle.set <myclass, &myclass::idle_cb> (this);	2986	idle.set <myclass, &myclass::idle_cb> (this);
2072		2987
2073	io.start (fd, ev::READ);	2988	io.start (fd, ev::READ);
		2989	}
2074	}	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
2075		3044
2076		3045
2077	=head1 MACRO MAGIC	3046	=head1 MACRO MAGIC
2078		3047
2079	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
2080	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3049	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2081	functions and callbacks have an initial C<struct ev_loop *> argument.	3050	functions and callbacks have an initial C<struct ev_loop *> argument.
2082		3051
2083	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
2084	following macros are defined:	3053	following macros are defined:
…		…
2089		3058
2090	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
2091	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,
2092	C<EV_A_> is used when other arguments are following. Example:	3061	C<EV_A_> is used when other arguments are following. Example:
2093		3062
2094	ev_unref (EV_A);	3063	ev_unref (EV_A);
2095	ev_timer_add (EV_A_ watcher);	3064	ev_timer_add (EV_A_ watcher);
2096	ev_loop (EV_A_ 0);	3065	ev_loop (EV_A_ 0);
2097		3066
2098	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,
2099	which is often provided by the following macro.	3068	which is often provided by the following macro.
2100		3069
2101	=item C<EV_P>, C<EV_P_>	3070	=item C<EV_P>, C<EV_P_>
2102		3071
2103	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
2104	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,
2105	C<EV_P_> is used when other parameters are following. Example:	3074	C<EV_P_> is used when other parameters are following. Example:
2106		3075
2107	// this is how ev_unref is being declared	3076	// this is how ev_unref is being declared
2108	static void ev_unref (EV_P);	3077	static void ev_unref (EV_P);
2109		3078
2110	// this is how you can declare your typical callback	3079	// this is how you can declare your typical callback
2111	static void cb (EV_P_ ev_timer *w, int revents)	3080	static void cb (EV_P_ ev_timer *w, int revents)
2112		3081
2113	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
2114	suitable for use with C<EV_A>.	3083	suitable for use with C<EV_A>.
2115		3084
2116	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3085	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2117		3086
2118	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
2119	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.
2120		3099
2121	=back	3100	=back
2122		3101
2123	Example: Declare and initialise a check watcher, utilising the above	3102	Example: Declare and initialise a check watcher, utilising the above
2124	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
2125	or not.	3104	or not.
2126		3105
2127	static void	3106	static void
2128	check_cb (EV_P_ ev_timer *w, int revents)	3107	check_cb (EV_P_ ev_timer *w, int revents)
2129	{	3108	{
2130	ev_check_stop (EV_A_ w);	3109	ev_check_stop (EV_A_ w);
2131	}	3110	}
2132		3111
2133	ev_check check;	3112	ev_check check;
2134	ev_check_init (&check, check_cb);	3113	ev_check_init (&check, check_cb);
2135	ev_check_start (EV_DEFAULT_ &check);	3114	ev_check_start (EV_DEFAULT_ &check);
2136	ev_loop (EV_DEFAULT_ 0);	3115	ev_loop (EV_DEFAULT_ 0);
2137		3116
2138	=head1 EMBEDDING	3117	=head1 EMBEDDING
2139		3118
2140	Libev can (and often is) directly embedded into host	3119	Libev can (and often is) directly embedded into host
2141	applications. Examples of applications that embed it include the Deliantra	3120	applications. Examples of applications that embed it include the Deliantra
…		…
2148	libev somewhere in your source tree).	3127	libev somewhere in your source tree).
2149		3128
2150	=head2 FILESETS	3129	=head2 FILESETS
2151		3130
2152	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
2153	in your app.	3132	in your application.
2154		3133
2155	=head3 CORE EVENT LOOP	3134	=head3 CORE EVENT LOOP
2156		3135
2157	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
2158	configuration (no autoconf):	3137	configuration (no autoconf):
2159		3138
2160	#define EV_STANDALONE 1	3139	#define EV_STANDALONE 1
2161	#include "ev.c"	3140	#include "ev.c"
2162		3141
2163	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
2164	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
2165	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
2166	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
2167	where you can put other configuration options):	3146	where you can put other configuration options):
2168		3147
2169	#define EV_STANDALONE 1	3148	#define EV_STANDALONE 1
2170	#include "ev.h"	3149	#include "ev.h"
2171		3150
2172	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++
2173	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
2174	as a bug).	3153	as a bug).
2175		3154
2176	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
2177	in your include path (e.g. in libev/ when using -Ilibev):	3156	in your include path (e.g. in libev/ when using -Ilibev):
2178		3157
2179	ev.h	3158	ev.h
2180	ev.c	3159	ev.c
2181	ev_vars.h	3160	ev_vars.h
2182	ev_wrap.h	3161	ev_wrap.h
2183		3162
2184	ev_win32.c required on win32 platforms only	3163	ev_win32.c required on win32 platforms only
2185		3164
2186	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)
2187	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)
2188	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)
2189	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)
2190	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)
2191		3170
2192	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
2193	to compile this single file.	3172	to compile this single file.
2194		3173
2195	=head3 LIBEVENT COMPATIBILITY API	3174	=head3 LIBEVENT COMPATIBILITY API
2196		3175
2197	To include the libevent compatibility API, also include:	3176	To include the libevent compatibility API, also include:
2198		3177
2199	#include "event.c"	3178	#include "event.c"
2200		3179
2201	in the file including F<ev.c>, and:	3180	in the file including F<ev.c>, and:
2202		3181
2203	#include "event.h"	3182	#include "event.h"
2204		3183
2205	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>.
2206		3185
2207	You need the following additional files for this:	3186	You need the following additional files for this:
2208		3187
2209	event.h	3188	event.h
2210	event.c	3189	event.c
2211		3190
2212	=head3 AUTOCONF SUPPORT	3191	=head3 AUTOCONF SUPPORT
2213		3192
2214	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
2215	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
2216	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
2217	include F<config.h> and configure itself accordingly.	3196	include F<config.h> and configure itself accordingly.
2218		3197
2219	For this of course you need the m4 file:	3198	For this of course you need the m4 file:
2220		3199
2221	libev.m4	3200	libev.m4
2222		3201
2223	=head2 PREPROCESSOR SYMBOLS/MACROS	3202	=head2 PREPROCESSOR SYMBOLS/MACROS
2224		3203
2225	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
2226	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
2227	and only include the select backend.	3206	autoconf is documented for every option.
2228		3207
2229	=over 4	3208	=over 4
2230		3209
2231	=item EV_STANDALONE	3210	=item EV_STANDALONE
2232		3211
…		…
2234	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
2235	implementations for some libevent functions (such as logging, which is not	3214	implementations for some libevent functions (such as logging, which is not
2236	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
2237	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.
2238		3217
		3218	In stanbdalone mode, libev will still try to automatically deduce the
		3219	configuration, but has to be more conservative.
		3220
2239	=item EV_USE_MONOTONIC	3221	=item EV_USE_MONOTONIC
2240		3222
2241	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
2242	monotonic clock option at both compiletime and runtime. Otherwise no use	3224	monotonic clock option at both compile time and runtime. Otherwise no
2243	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,
2244	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
2245	the functionality isn't available is safe, though, althoguh you have	3227	when the functionality isn't available is safe, though, although you have
2246	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>
2247	function is hiding in (often F<-lrt>).	3229	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2248		3230
2249	=item EV_USE_REALTIME	3231	=item EV_USE_REALTIME
2250		3232
2251	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
2252	realtime clock option at compiletime (and assume its availability at	3234	real-time clock option at compile time (and assume its availability at
2253	runtime if successful). Otherwise no use of the realtime clock option will	3235	runtime if successful). Otherwise no use of the real-time clock option will
2254	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3236	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2255	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3237	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2256	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3238	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2257		3239
		3240	=item EV_USE_CLOCK_SYSCALL
		3241
		3242	If defined to be C<1>, libev will try to use a direct syscall instead
		3243	of calling the system-provided C<clock_gettime> function. This option
		3244	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3245	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3246	programs needlessly. Using a direct syscall is slightly slower (in
		3247	theory), because no optimised vdso implementation can be used, but avoids
		3248	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3249	higher, as it simplifies linking (no need for C<-lrt>).
		3250
		3251	=item EV_USE_NANOSLEEP
		3252
		3253	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3254	and will use it for delays. Otherwise it will use C<select ()>.
		3255
		3256	=item EV_USE_EVENTFD
		3257
		3258	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3259	available and will probe for kernel support at runtime. This will improve
		3260	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3261	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3262	2.7 or newer, otherwise disabled.
		3263
2258	=item EV_USE_SELECT	3264	=item EV_USE_SELECT
2259		3265
2260	If undefined or defined to be C<1>, libev will compile in support for the	3266	If undefined or defined to be C<1>, libev will compile in support for the
2261	C<select>(2) backend. No attempt at autodetection will be done: if no	3267	C<select>(2) backend. No attempt at auto-detection will be done: if no
2262	other method takes over, select will be it. Otherwise the select backend	3268	other method takes over, select will be it. Otherwise the select backend
2263	will not be compiled in.	3269	will not be compiled in.
2264		3270
2265	=item EV_SELECT_USE_FD_SET	3271	=item EV_SELECT_USE_FD_SET
2266		3272
2267	If defined to C<1>, then the select backend will use the system C<fd_set>	3273	If defined to C<1>, then the select backend will use the system C<fd_set>
2268	structure. This is useful if libev doesn't compile due to a missing	3274	structure. This is useful if libev doesn't compile due to a missing
2269	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3275	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2270	exotic systems. This usually limits the range of file descriptors to some	3276	on exotic systems. This usually limits the range of file descriptors to
2271	low limit such as 1024 or might have other limitations (winsocket only	3277	some low limit such as 1024 or might have other limitations (winsocket
2272	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3278	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2273	influence the size of the C<fd_set> used.	3279	configures the maximum size of the C<fd_set>.
2274		3280
2275	=item EV_SELECT_IS_WINSOCKET	3281	=item EV_SELECT_IS_WINSOCKET
2276		3282
2277	When defined to C<1>, the select backend will assume that	3283	When defined to C<1>, the select backend will assume that
2278	select/socket/connect etc. don't understand file descriptors but	3284	select/socket/connect etc. don't understand file descriptors but
…		…
2280	be used is the winsock select). This means that it will call	3286	be used is the winsock select). This means that it will call
2281	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3287	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2282	it is assumed that all these functions actually work on fds, even	3288	it is assumed that all these functions actually work on fds, even
2283	on win32. Should not be defined on non-win32 platforms.	3289	on win32. Should not be defined on non-win32 platforms.
2284		3290
		3291	=item EV_FD_TO_WIN32_HANDLE
		3292
		3293	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3294	file descriptors to socket handles. When not defining this symbol (the
		3295	default), then libev will call C<_get_osfhandle>, which is usually
		3296	correct. In some cases, programs use their own file descriptor management,
		3297	in which case they can provide this function to map fds to socket handles.
		3298
2285	=item EV_USE_POLL	3299	=item EV_USE_POLL
2286		3300
2287	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3301	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2288	backend. Otherwise it will be enabled on non-win32 platforms. It	3302	backend. Otherwise it will be enabled on non-win32 platforms. It
2289	takes precedence over select.	3303	takes precedence over select.
2290		3304
2291	=item EV_USE_EPOLL	3305	=item EV_USE_EPOLL
2292		3306
2293	If defined to be C<1>, libev will compile in support for the Linux	3307	If defined to be C<1>, libev will compile in support for the Linux
2294	C<epoll>(7) backend. Its availability will be detected at runtime,	3308	C<epoll>(7) backend. Its availability will be detected at runtime,
2295	otherwise another method will be used as fallback. This is the	3309	otherwise another method will be used as fallback. This is the preferred
2296	preferred backend for GNU/Linux systems.	3310	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3311	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2297		3312
2298	=item EV_USE_KQUEUE	3313	=item EV_USE_KQUEUE
2299		3314
2300	If defined to be C<1>, libev will compile in support for the BSD style	3315	If defined to be C<1>, libev will compile in support for the BSD style
2301	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3316	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2314	otherwise another method will be used as fallback. This is the preferred	3329	otherwise another method will be used as fallback. This is the preferred
2315	backend for Solaris 10 systems.	3330	backend for Solaris 10 systems.
2316		3331
2317	=item EV_USE_DEVPOLL	3332	=item EV_USE_DEVPOLL
2318		3333
2319	reserved for future expansion, works like the USE symbols above.	3334	Reserved for future expansion, works like the USE symbols above.
2320		3335
2321	=item EV_USE_INOTIFY	3336	=item EV_USE_INOTIFY
2322		3337
2323	If defined to be C<1>, libev will compile in support for the Linux inotify	3338	If defined to be C<1>, libev will compile in support for the Linux inotify
2324	interface to speed up C<ev_stat> watchers. Its actual availability will	3339	interface to speed up C<ev_stat> watchers. Its actual availability will
2325	be detected at runtime.	3340	be detected at runtime. If undefined, it will be enabled if the headers
		3341	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3342
		3343	=item EV_ATOMIC_T
		3344
		3345	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3346	access is atomic with respect to other threads or signal contexts. No such
		3347	type is easily found in the C language, so you can provide your own type
		3348	that you know is safe for your purposes. It is used both for signal handler "locking"
		3349	as well as for signal and thread safety in C<ev_async> watchers.
		3350
		3351	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3352	(from F<signal.h>), which is usually good enough on most platforms.
2326		3353
2327	=item EV_H	3354	=item EV_H
2328		3355
2329	The name of the F<ev.h> header file used to include it. The default if	3356	The name of the F<ev.h> header file used to include it. The default if
2330	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3357	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2331	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3358	used to virtually rename the F<ev.h> header file in case of conflicts.
2332		3359
2333	=item EV_CONFIG_H	3360	=item EV_CONFIG_H
2334		3361
2335	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3362	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2336	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3363	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2337	C<EV_H>, above.	3364	C<EV_H>, above.
2338		3365
2339	=item EV_EVENT_H	3366	=item EV_EVENT_H
2340		3367
2341	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3368	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2342	of how the F<event.h> header can be found.	3369	of how the F<event.h> header can be found, the default is C<"event.h">.
2343		3370
2344	=item EV_PROTOTYPES	3371	=item EV_PROTOTYPES
2345		3372
2346	If defined to be C<0>, then F<ev.h> will not define any function	3373	If defined to be C<0>, then F<ev.h> will not define any function
2347	prototypes, but still define all the structs and other symbols. This is	3374	prototypes, but still define all the structs and other symbols. This is
…		…
2368	When doing priority-based operations, libev usually has to linearly search	3395	When doing priority-based operations, libev usually has to linearly search
2369	all the priorities, so having many of them (hundreds) uses a lot of space	3396	all the priorities, so having many of them (hundreds) uses a lot of space
2370	and time, so using the defaults of five priorities (-2 .. +2) is usually	3397	and time, so using the defaults of five priorities (-2 .. +2) is usually
2371	fine.	3398	fine.
2372		3399
2373	If your embedding app does not need any priorities, defining these both to	3400	If your embedding application does not need any priorities, defining these
2374	C<0> will save some memory and cpu.	3401	both to C<0> will save some memory and CPU.
2375		3402
2376	=item EV_PERIODIC_ENABLE	3403	=item EV_PERIODIC_ENABLE
2377		3404
2378	If undefined or defined to be C<1>, then periodic timers are supported. If	3405	If undefined or defined to be C<1>, then periodic timers are supported. If
2379	defined to be C<0>, then they are not. Disabling them saves a few kB of	3406	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2386	code.	3413	code.
2387		3414
2388	=item EV_EMBED_ENABLE	3415	=item EV_EMBED_ENABLE
2389		3416
2390	If undefined or defined to be C<1>, then embed watchers are supported. If	3417	If undefined or defined to be C<1>, then embed watchers are supported. If
2391	defined to be C<0>, then they are not.	3418	defined to be C<0>, then they are not. Embed watchers rely on most other
		3419	watcher types, which therefore must not be disabled.
2392		3420
2393	=item EV_STAT_ENABLE	3421	=item EV_STAT_ENABLE
2394		3422
2395	If undefined or defined to be C<1>, then stat watchers are supported. If	3423	If undefined or defined to be C<1>, then stat watchers are supported. If
2396	defined to be C<0>, then they are not.	3424	defined to be C<0>, then they are not.
…		…
2398	=item EV_FORK_ENABLE	3426	=item EV_FORK_ENABLE
2399		3427
2400	If undefined or defined to be C<1>, then fork watchers are supported. If	3428	If undefined or defined to be C<1>, then fork watchers are supported. If
2401	defined to be C<0>, then they are not.	3429	defined to be C<0>, then they are not.
2402		3430
		3431	=item EV_ASYNC_ENABLE
		3432
		3433	If undefined or defined to be C<1>, then async watchers are supported. If
		3434	defined to be C<0>, then they are not.
		3435
2403	=item EV_MINIMAL	3436	=item EV_MINIMAL
2404		3437
2405	If you need to shave off some kilobytes of code at the expense of some	3438	If you need to shave off some kilobytes of code at the expense of some
2406	speed, define this symbol to C<1>. Currently only used for gcc to override	3439	speed, define this symbol to C<1>. Currently this is used to override some
2407	some inlining decisions, saves roughly 30% codesize of amd64.	3440	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3441	much smaller 2-heap for timer management over the default 4-heap.
2408		3442
2409	=item EV_PID_HASHSIZE	3443	=item EV_PID_HASHSIZE
2410		3444
2411	C<ev_child> watchers use a small hash table to distribute workload by	3445	C<ev_child> watchers use a small hash table to distribute workload by
2412	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3446	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2413	than enough. If you need to manage thousands of children you might want to	3447	than enough. If you need to manage thousands of children you might want to
2414	increase this value (I<must> be a power of two).	3448	increase this value (I<must> be a power of two).
2415		3449
2416	=item EV_INOTIFY_HASHSIZE	3450	=item EV_INOTIFY_HASHSIZE
2417		3451
2418	C<ev_staz> watchers use a small hash table to distribute workload by	3452	C<ev_stat> watchers use a small hash table to distribute workload by
2419	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3453	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2420	usually more than enough. If you need to manage thousands of C<ev_stat>	3454	usually more than enough. If you need to manage thousands of C<ev_stat>
2421	watchers you might want to increase this value (I<must> be a power of	3455	watchers you might want to increase this value (I<must> be a power of
2422	two).	3456	two).
2423		3457
		3458	=item EV_USE_4HEAP
		3459
		3460	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3461	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3462	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3463	faster performance with many (thousands) of watchers.
		3464
		3465	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3466	(disabled).
		3467
		3468	=item EV_HEAP_CACHE_AT
		3469
		3470	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3471	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3472	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3473	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3474	but avoids random read accesses on heap changes. This improves performance
		3475	noticeably with many (hundreds) of watchers.
		3476
		3477	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3478	(disabled).
		3479
		3480	=item EV_VERIFY
		3481
		3482	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3483	be done: If set to C<0>, no internal verification code will be compiled
		3484	in. If set to C<1>, then verification code will be compiled in, but not
		3485	called. If set to C<2>, then the internal verification code will be
		3486	called once per loop, which can slow down libev. If set to C<3>, then the
		3487	verification code will be called very frequently, which will slow down
		3488	libev considerably.
		3489
		3490	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3491	C<0>.
		3492
2424	=item EV_COMMON	3493	=item EV_COMMON
2425		3494
2426	By default, all watchers have a C<void *data> member. By redefining	3495	By default, all watchers have a C<void *data> member. By redefining
2427	this macro to a something else you can include more and other types of	3496	this macro to a something else you can include more and other types of
2428	members. You have to define it each time you include one of the files,	3497	members. You have to define it each time you include one of the files,
2429	though, and it must be identical each time.	3498	though, and it must be identical each time.
2430		3499
2431	For example, the perl EV module uses something like this:	3500	For example, the perl EV module uses something like this:
2432		3501
2433	#define EV_COMMON \	3502	#define EV_COMMON \
2434	SV *self; /* contains this struct */ \	3503	SV *self; /* contains this struct */ \
2435	SV *cb_sv, *fh /* note no trailing ";" */	3504	SV *cb_sv, *fh /* note no trailing ";" */
2436		3505
2437	=item EV_CB_DECLARE (type)	3506	=item EV_CB_DECLARE (type)
2438		3507
2439	=item EV_CB_INVOKE (watcher, revents)	3508	=item EV_CB_INVOKE (watcher, revents)
2440		3509
2441	=item ev_set_cb (ev, cb)	3510	=item ev_set_cb (ev, cb)
2442		3511
2443	Can be used to change the callback member declaration in each watcher,	3512	Can be used to change the callback member declaration in each watcher,
2444	and the way callbacks are invoked and set. Must expand to a struct member	3513	and the way callbacks are invoked and set. Must expand to a struct member
2445	definition and a statement, respectively. See the F<ev.v> header file for	3514	definition and a statement, respectively. See the F<ev.h> header file for
2446	their default definitions. One possible use for overriding these is to	3515	their default definitions. One possible use for overriding these is to
2447	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3516	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2448	method calls instead of plain function calls in C++.	3517	method calls instead of plain function calls in C++.
2449		3518
		3519	=back
		3520
2450	=head2 EXPORTED API SYMBOLS	3521	=head2 EXPORTED API SYMBOLS
2451		3522
2452	If you need to re-export the API (e.g. via a dll) and you need a list of	3523	If you need to re-export the API (e.g. via a DLL) and you need a list of
2453	exported symbols, you can use the provided F<Symbol.*> files which list	3524	exported symbols, you can use the provided F<Symbol.*> files which list
2454	all public symbols, one per line:	3525	all public symbols, one per line:
2455		3526
2456	Symbols.ev for libev proper	3527	Symbols.ev for libev proper
2457	Symbols.event for the libevent emulation	3528	Symbols.event for the libevent emulation
2458		3529
2459	This can also be used to rename all public symbols to avoid clashes with	3530	This can also be used to rename all public symbols to avoid clashes with
2460	multiple versions of libev linked together (which is obviously bad in	3531	multiple versions of libev linked together (which is obviously bad in
2461	itself, but sometimes it is inconvinient to avoid this).	3532	itself, but sometimes it is inconvenient to avoid this).
2462		3533
2463	A sed comamnd like this will create wrapper C<#define>'s that you need to	3534	A sed command like this will create wrapper C<#define>'s that you need to
2464	include before including F<ev.h>:	3535	include before including F<ev.h>:
2465		3536
2466	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3537	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2467		3538
2468	This would create a file F<wrap.h> which essentially looks like this:	3539	This would create a file F<wrap.h> which essentially looks like this:
…		…
2483	file.	3554	file.
2484		3555
2485	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3556	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2486	that everybody includes and which overrides some configure choices:	3557	that everybody includes and which overrides some configure choices:
2487		3558
2488	#define EV_MINIMAL 1	3559	#define EV_MINIMAL 1
2489	#define EV_USE_POLL 0	3560	#define EV_USE_POLL 0
2490	#define EV_MULTIPLICITY 0	3561	#define EV_MULTIPLICITY 0
2491	#define EV_PERIODIC_ENABLE 0	3562	#define EV_PERIODIC_ENABLE 0
2492	#define EV_STAT_ENABLE 0	3563	#define EV_STAT_ENABLE 0
2493	#define EV_FORK_ENABLE 0	3564	#define EV_FORK_ENABLE 0
2494	#define EV_CONFIG_H <config.h>	3565	#define EV_CONFIG_H <config.h>
2495	#define EV_MINPRI 0	3566	#define EV_MINPRI 0
2496	#define EV_MAXPRI 0	3567	#define EV_MAXPRI 0
2497		3568
2498	#include "ev++.h"	3569	#include "ev++.h"
2499		3570
2500	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3571	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2501		3572
2502	#include "ev_cpp.h"	3573	#include "ev_cpp.h"
2503	#include "ev.c"	3574	#include "ev.c"
2504		3575
		3576	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2505		3577
		3578	=head2 THREADS AND COROUTINES
		3579
		3580	=head3 THREADS
		3581
		3582	All libev functions are reentrant and thread-safe unless explicitly
		3583	documented otherwise, but libev implements no locking itself. This means
		3584	that you can use as many loops as you want in parallel, as long as there
		3585	are no concurrent calls into any libev function with the same loop
		3586	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3587	of course): libev guarantees that different event loops share no data
		3588	structures that need any locking.
		3589
		3590	Or to put it differently: calls with different loop parameters can be done
		3591	concurrently from multiple threads, calls with the same loop parameter
		3592	must be done serially (but can be done from different threads, as long as
		3593	only one thread ever is inside a call at any point in time, e.g. by using
		3594	a mutex per loop).
		3595
		3596	Specifically to support threads (and signal handlers), libev implements
		3597	so-called C<ev_async> watchers, which allow some limited form of
		3598	concurrency on the same event loop, namely waking it up "from the
		3599	outside".
		3600
		3601	If you want to know which design (one loop, locking, or multiple loops
		3602	without or something else still) is best for your problem, then I cannot
		3603	help you, but here is some generic advice:
		3604
		3605	=over 4
		3606
		3607	=item * most applications have a main thread: use the default libev loop
		3608	in that thread, or create a separate thread running only the default loop.
		3609
		3610	This helps integrating other libraries or software modules that use libev
		3611	themselves and don't care/know about threading.
		3612
		3613	=item * one loop per thread is usually a good model.
		3614
		3615	Doing this is almost never wrong, sometimes a better-performance model
		3616	exists, but it is always a good start.
		3617
		3618	=item * other models exist, such as the leader/follower pattern, where one
		3619	loop is handed through multiple threads in a kind of round-robin fashion.
		3620
		3621	Choosing a model is hard - look around, learn, know that usually you can do
		3622	better than you currently do :-)
		3623
		3624	=item * often you need to talk to some other thread which blocks in the
		3625	event loop.
		3626
		3627	C<ev_async> watchers can be used to wake them up from other threads safely
		3628	(or from signal contexts...).
		3629
		3630	An example use would be to communicate signals or other events that only
		3631	work in the default loop by registering the signal watcher with the
		3632	default loop and triggering an C<ev_async> watcher from the default loop
		3633	watcher callback into the event loop interested in the signal.
		3634
		3635	=back
		3636
		3637	=head3 COROUTINES
		3638
		3639	Libev is very accommodating to coroutines ("cooperative threads"):
		3640	libev fully supports nesting calls to its functions from different
		3641	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3642	different coroutines, and switch freely between both coroutines running the
		3643	loop, as long as you don't confuse yourself). The only exception is that
		3644	you must not do this from C<ev_periodic> reschedule callbacks.
		3645
		3646	Care has been taken to ensure that libev does not keep local state inside
		3647	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3648	they do not call any callbacks.
		3649
		3650	=head2 COMPILER WARNINGS
		3651
		3652	Depending on your compiler and compiler settings, you might get no or a
		3653	lot of warnings when compiling libev code. Some people are apparently
		3654	scared by this.
		3655
		3656	However, these are unavoidable for many reasons. For one, each compiler
		3657	has different warnings, and each user has different tastes regarding
		3658	warning options. "Warn-free" code therefore cannot be a goal except when
		3659	targeting a specific compiler and compiler-version.
		3660
		3661	Another reason is that some compiler warnings require elaborate
		3662	workarounds, or other changes to the code that make it less clear and less
		3663	maintainable.
		3664
		3665	And of course, some compiler warnings are just plain stupid, or simply
		3666	wrong (because they don't actually warn about the condition their message
		3667	seems to warn about). For example, certain older gcc versions had some
		3668	warnings that resulted an extreme number of false positives. These have
		3669	been fixed, but some people still insist on making code warn-free with
		3670	such buggy versions.
		3671
		3672	While libev is written to generate as few warnings as possible,
		3673	"warn-free" code is not a goal, and it is recommended not to build libev
		3674	with any compiler warnings enabled unless you are prepared to cope with
		3675	them (e.g. by ignoring them). Remember that warnings are just that:
		3676	warnings, not errors, or proof of bugs.
		3677
		3678
		3679	=head2 VALGRIND
		3680
		3681	Valgrind has a special section here because it is a popular tool that is
		3682	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3683
		3684	If you think you found a bug (memory leak, uninitialised data access etc.)
		3685	in libev, then check twice: If valgrind reports something like:
		3686
		3687	==2274== definitely lost: 0 bytes in 0 blocks.
		3688	==2274== possibly lost: 0 bytes in 0 blocks.
		3689	==2274== still reachable: 256 bytes in 1 blocks.
		3690
		3691	Then there is no memory leak, just as memory accounted to global variables
		3692	is not a memleak - the memory is still being referenced, and didn't leak.
		3693
		3694	Similarly, under some circumstances, valgrind might report kernel bugs
		3695	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3696	although an acceptable workaround has been found here), or it might be
		3697	confused.
		3698
		3699	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3700	make it into some kind of religion.
		3701
		3702	If you are unsure about something, feel free to contact the mailing list
		3703	with the full valgrind report and an explanation on why you think this
		3704	is a bug in libev (best check the archives, too :). However, don't be
		3705	annoyed when you get a brisk "this is no bug" answer and take the chance
		3706	of learning how to interpret valgrind properly.
		3707
		3708	If you need, for some reason, empty reports from valgrind for your project
		3709	I suggest using suppression lists.
		3710
		3711
		3712	=head1 PORTABILITY NOTES
		3713
		3714	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3715
		3716	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3717	requires, and its I/O model is fundamentally incompatible with the POSIX
		3718	model. Libev still offers limited functionality on this platform in
		3719	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3720	descriptors. This only applies when using Win32 natively, not when using
		3721	e.g. cygwin.
		3722
		3723	Lifting these limitations would basically require the full
		3724	re-implementation of the I/O system. If you are into these kinds of
		3725	things, then note that glib does exactly that for you in a very portable
		3726	way (note also that glib is the slowest event library known to man).
		3727
		3728	There is no supported compilation method available on windows except
		3729	embedding it into other applications.
		3730
		3731	Not a libev limitation but worth mentioning: windows apparently doesn't
		3732	accept large writes: instead of resulting in a partial write, windows will
		3733	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3734	so make sure you only write small amounts into your sockets (less than a
		3735	megabyte seems safe, but this apparently depends on the amount of memory
		3736	available).
		3737
		3738	Due to the many, low, and arbitrary limits on the win32 platform and
		3739	the abysmal performance of winsockets, using a large number of sockets
		3740	is not recommended (and not reasonable). If your program needs to use
		3741	more than a hundred or so sockets, then likely it needs to use a totally
		3742	different implementation for windows, as libev offers the POSIX readiness
		3743	notification model, which cannot be implemented efficiently on windows
		3744	(Microsoft monopoly games).
		3745
		3746	A typical way to use libev under windows is to embed it (see the embedding
		3747	section for details) and use the following F<evwrap.h> header file instead
		3748	of F<ev.h>:
		3749
		3750	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3751	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3752
		3753	#include "ev.h"
		3754
		3755	And compile the following F<evwrap.c> file into your project (make sure
		3756	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3757
		3758	#include "evwrap.h"
		3759	#include "ev.c"
		3760
		3761	=over 4
		3762
		3763	=item The winsocket select function
		3764
		3765	The winsocket C<select> function doesn't follow POSIX in that it
		3766	requires socket I<handles> and not socket I<file descriptors> (it is
		3767	also extremely buggy). This makes select very inefficient, and also
		3768	requires a mapping from file descriptors to socket handles (the Microsoft
		3769	C runtime provides the function C<_open_osfhandle> for this). See the
		3770	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3771	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3772
		3773	The configuration for a "naked" win32 using the Microsoft runtime
		3774	libraries and raw winsocket select is:
		3775
		3776	#define EV_USE_SELECT 1
		3777	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3778
		3779	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3780	complexity in the O(n²) range when using win32.
		3781
		3782	=item Limited number of file descriptors
		3783
		3784	Windows has numerous arbitrary (and low) limits on things.
		3785
		3786	Early versions of winsocket's select only supported waiting for a maximum
		3787	of C<64> handles (probably owning to the fact that all windows kernels
		3788	can only wait for C<64> things at the same time internally; Microsoft
		3789	recommends spawning a chain of threads and wait for 63 handles and the
		3790	previous thread in each. Great).
		3791
		3792	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3793	to some high number (e.g. C<2048>) before compiling the winsocket select
		3794	call (which might be in libev or elsewhere, for example, perl does its own
		3795	select emulation on windows).
		3796
		3797	Another limit is the number of file descriptors in the Microsoft runtime
		3798	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3799	or something like this inside Microsoft). You can increase this by calling
		3800	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3801	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3802	libraries.
		3803
		3804	This might get you to about C<512> or C<2048> sockets (depending on
		3805	windows version and/or the phase of the moon). To get more, you need to
		3806	wrap all I/O functions and provide your own fd management, but the cost of
		3807	calling select (O(n²)) will likely make this unworkable.
		3808
		3809	=back
		3810
		3811	=head2 PORTABILITY REQUIREMENTS
		3812
		3813	In addition to a working ISO-C implementation and of course the
		3814	backend-specific APIs, libev relies on a few additional extensions:
		3815
		3816	=over 4
		3817
		3818	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3819	calling conventions regardless of C<ev_watcher_type *>.
		3820
		3821	Libev assumes not only that all watcher pointers have the same internal
		3822	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3823	assumes that the same (machine) code can be used to call any watcher
		3824	callback: The watcher callbacks have different type signatures, but libev
		3825	calls them using an C<ev_watcher *> internally.
		3826
		3827	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3828
		3829	The type C<sig_atomic_t volatile> (or whatever is defined as
		3830	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3831	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3832	believed to be sufficiently portable.
		3833
		3834	=item C<sigprocmask> must work in a threaded environment
		3835
		3836	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3837	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3838	pthread implementations will either allow C<sigprocmask> in the "main
		3839	thread" or will block signals process-wide, both behaviours would
		3840	be compatible with libev. Interaction between C<sigprocmask> and
		3841	C<pthread_sigmask> could complicate things, however.
		3842
		3843	The most portable way to handle signals is to block signals in all threads
		3844	except the initial one, and run the default loop in the initial thread as
		3845	well.
		3846
		3847	=item C<long> must be large enough for common memory allocation sizes
		3848
		3849	To improve portability and simplify its API, libev uses C<long> internally
		3850	instead of C<size_t> when allocating its data structures. On non-POSIX
		3851	systems (Microsoft...) this might be unexpectedly low, but is still at
		3852	least 31 bits everywhere, which is enough for hundreds of millions of
		3853	watchers.
		3854
		3855	=item C<double> must hold a time value in seconds with enough accuracy
		3856
		3857	The type C<double> is used to represent timestamps. It is required to
		3858	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3859	enough for at least into the year 4000. This requirement is fulfilled by
		3860	implementations implementing IEEE 754 (basically all existing ones).
		3861
		3862	=back
		3863
		3864	If you know of other additional requirements drop me a note.
		3865
		3866
2506	=head1 COMPLEXITIES	3867	=head1 ALGORITHMIC COMPLEXITIES
2507		3868
2508	In this section the complexities of (many of) the algorithms used inside	3869	In this section the complexities of (many of) the algorithms used inside
2509	libev will be explained. For complexity discussions about backends see the	3870	libev will be documented. For complexity discussions about backends see
2510	documentation for C<ev_default_init>.	3871	the documentation for C<ev_default_init>.
2511		3872
2512	All of the following are about amortised time: If an array needs to be	3873	All of the following are about amortised time: If an array needs to be
2513	extended, libev needs to realloc and move the whole array, but this	3874	extended, libev needs to realloc and move the whole array, but this
2514	happens asymptotically never with higher number of elements, so O(1) might	3875	happens asymptotically rarer with higher number of elements, so O(1) might
2515	mean it might do a lengthy realloc operation in rare cases, but on average	3876	mean that libev does a lengthy realloc operation in rare cases, but on
2516	it is much faster and asymptotically approaches constant time.	3877	average it is much faster and asymptotically approaches constant time.
2517		3878
2518	=over 4	3879	=over 4
2519		3880
2520	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3881	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2521		3882
2522	This means that, when you have a watcher that triggers in one hour and	3883	This means that, when you have a watcher that triggers in one hour and
2523	there are 100 watchers that would trigger before that then inserting will	3884	there are 100 watchers that would trigger before that, then inserting will
2524	have to skip those 100 watchers.	3885	have to skip roughly seven (C<ld 100>) of these watchers.
2525		3886
2526	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3887	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2527		3888
2528	That means that for changing a timer costs less than removing/adding them	3889	That means that changing a timer costs less than removing/adding them,
2529	as only the relative motion in the event queue has to be paid for.	3890	as only the relative motion in the event queue has to be paid for.
2530		3891
2531	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3892	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2532		3893
2533	These just add the watcher into an array or at the head of a list.	3894	These just add the watcher into an array or at the head of a list.
		3895
2534	=item Stopping check/prepare/idle watchers: O(1)	3896	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2535		3897
2536	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3898	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2537		3899
2538	These watchers are stored in lists then need to be walked to find the	3900	These watchers are stored in lists, so they need to be walked to find the
2539	correct watcher to remove. The lists are usually short (you don't usually	3901	correct watcher to remove. The lists are usually short (you don't usually
2540	have many watchers waiting for the same fd or signal).	3902	have many watchers waiting for the same fd or signal: one is typical, two
		3903	is rare).
2541		3904
2542	=item Finding the next timer per loop iteration: O(1)	3905	=item Finding the next timer in each loop iteration: O(1)
		3906
		3907	By virtue of using a binary or 4-heap, the next timer is always found at a
		3908	fixed position in the storage array.
2543		3909
2544	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3910	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2545		3911
2546	A change means an I/O watcher gets started or stopped, which requires	3912	A change means an I/O watcher gets started or stopped, which requires
2547	libev to recalculate its status (and possibly tell the kernel).	3913	libev to recalculate its status (and possibly tell the kernel, depending
		3914	on backend and whether C<ev_io_set> was used).
2548		3915
2549	=item Activating one watcher: O(1)	3916	=item Activating one watcher (putting it into the pending state): O(1)
2550		3917
2551	=item Priority handling: O(number_of_priorities)	3918	=item Priority handling: O(number_of_priorities)
2552		3919
2553	Priorities are implemented by allocating some space for each	3920	Priorities are implemented by allocating some space for each
2554	priority. When doing priority-based operations, libev usually has to	3921	priority. When doing priority-based operations, libev usually has to
2555	linearly search all the priorities.	3922	linearly search all the priorities, but starting/stopping and activating
		3923	watchers becomes O(1) with respect to priority handling.
		3924
		3925	=item Sending an ev_async: O(1)
		3926
		3927	=item Processing ev_async_send: O(number_of_async_watchers)
		3928
		3929	=item Processing signals: O(max_signal_number)
		3930
		3931	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3932	calls in the current loop iteration. Checking for async and signal events
		3933	involves iterating over all running async watchers or all signal numbers.
2556		3934
2557	=back	3935	=back
2558		3936
2559		3937
2560	=head1 AUTHOR	3938	=head1 AUTHOR
2561		3939
2562	Marc Lehmann <libev@schmorp.de>.	3940	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
2563		3941

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines