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Revision 1.105 by root, Sun Dec 23 03:50:10 2007 UTC vs.
Revision 1.210 by root, Thu Oct 30 08:09:30 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	=head2 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	// every watcher type has its own typedef'd struct
		15	// with the name ev_TYPE
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	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	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head2 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	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>	107	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.	108	name C<loop> (which is always of type C<ev_loop *>) will not have
		109	this argument.
95		110
96	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	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	116	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	117	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	118	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	119	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
106		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
…		…
119		155
120	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
121		157
122	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
123	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
124	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
125		161
126	=item int ev_version_major ()	162	=item int ev_version_major ()
127		163
128	=item int ev_version_minor ()	164	=item int ev_version_minor ()
129		165
…		…
142	not a problem.	178	not a problem.
143		179
144	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
145	version.	181	version.
146		182
147	assert (("libev version mismatch",	183	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
150		186
151	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
152		188
153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
154	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	192	a description of the set values.
157		193
158	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
159	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
160		196
161	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
163		199
164	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
165		201
166	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
167	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
168	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
169	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
170	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
171	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
172		208
173	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
174		210
…		…
178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
179	recommended ones.	215	recommended ones.
180		216
181	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
182		218
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
184		220
185	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
187	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
188	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
190	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
191		230
192	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
193	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
194	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
195		234
196	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	236	retries (example requires a standards-compliant C<realloc>).
198		237
199	static void *	238	static void *
200	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
201	{	240	{
202	for (;;)	241	for (;;)
…		…
211	}	250	}
212		251
213	...	252	...
214	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
215		254
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
217		256
218	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
219	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
220	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
221	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
222	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
223	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
224	(such as abort).	263	(such as abort).
225		264
226	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
237		276
238	=back	277	=back
239		278
240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
241		280
242	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
243	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
244	events, and dynamically created loops which do not.	283	I<function>).
245		284
246	If you use threads, a common model is to run the default event loop	285	The library knows two types of such loops, the I<default> loop, which
247	in your main thread (or in a separate thread) and for each thread you	286	supports signals and child events, and dynamically created loops which do
248	create, you also create another event loop. Libev itself does no locking	287	not.
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252		288
253	=over 4	289	=over 4
254		290
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		292
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	296	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		297
262	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
263	function.	299	function.
264		300
		301	Note that this function is I<not> thread-safe, so if you want to use it
		302	from multiple threads, you have to lock (note also that this is unlikely,
		303	as loops cannot be shared easily between threads anyway).
		304
		305	The default loop is the only loop that can handle C<ev_signal> and
		306	C<ev_child> watchers, and to do this, it always registers a handler
		307	for C<SIGCHLD>. If this is a problem for your application you can either
		308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		310	C<ev_default_init>.
		311
265	The flags argument can be used to specify special behaviour or specific	312	The flags argument can be used to specify special behaviour or specific
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		314
268	The following flags are supported:	315	The following flags are supported:
269		316
…		…
274	The default flags value. Use this if you have no clue (it's the right	321	The default flags value. Use this if you have no clue (it's the right
275	thing, believe me).	322	thing, believe me).
276		323
277	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
278		325
279	If this flag bit is ored into the flag value (or the program runs setuid	326	If this flag bit is or'ed into the flag value (or the program runs setuid
280	or setgid) then libev will I<not> look at the environment variable	327	or setgid) then libev will I<not> look at the environment variable
281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
282	override the flags completely if it is found in the environment. This is	329	override the flags completely if it is found in the environment. This is
283	useful to try out specific backends to test their performance, or to work	330	useful to try out specific backends to test their performance, or to work
284	around bugs.	331	around bugs.
…		…
290	enabling this flag.	337	enabling this flag.
291		338
292	This works by calling C<getpid ()> on every iteration of the loop,	339	This works by calling C<getpid ()> on every iteration of the loop,
293	and thus this might slow down your event loop if you do a lot of loop	340	and thus this might slow down your event loop if you do a lot of loop
294	iterations and little real work, but is usually not noticeable (on my	341	iterations and little real work, but is usually not noticeable (on my
295	Linux system for example, C<getpid> is actually a simple 5-insn sequence	342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
296	without a syscall and thus I<very> fast, but my Linux system also has	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
298		345
299	The big advantage of this flag is that you can forget about fork (and	346	The big advantage of this flag is that you can forget about fork (and
300	forget about forgetting to tell libev about forking) when you use this	347	forget about forgetting to tell libev about forking) when you use this
301	flag.	348	flag.
302		349
303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
304	environment variable.	351	environment variable.
305		352
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		354
308	This is your standard select(2) backend. Not I<completely> standard, as	355	This is your standard select(2) backend. Not I<completely> standard, as
…		…
310	but if that fails, expect a fairly low limit on the number of fds when	357	but if that fails, expect a fairly low limit on the number of fds when
311	using this backend. It doesn't scale too well (O(highest_fd)), but its	358	using this backend. It doesn't scale too well (O(highest_fd)), but its
312	usually the fastest backend for a low number of (low-numbered :) fds.	359	usually the fastest backend for a low number of (low-numbered :) fds.
313		360
314	To get good performance out of this backend you need a high amount of	361	To get good performance out of this backend you need a high amount of
315	parallelity (most of the file descriptors should be busy). If you are	362	parallelism (most of the file descriptors should be busy). If you are
316	writing a server, you should C<accept ()> in a loop to accept as many	363	writing a server, you should C<accept ()> in a loop to accept as many
317	connections as possible during one iteration. You might also want to have	364	connections as possible during one iteration. You might also want to have
318	a look at C<ev_set_io_collect_interval ()> to increase the amount of	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
319	readyness notifications you get per iteration.	366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
320		371
321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
322		373
323	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
324	than select, but handles sparse fds better and has no artificial	375	than select, but handles sparse fds better and has no artificial
325	limit on the number of fds you can use (except it will slow down	376	limit on the number of fds you can use (except it will slow down
326	considerably with a lot of inactive fds). It scales similarly to select,	377	considerably with a lot of inactive fds). It scales similarly to select,
327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
328	performance tips.	379	performance tips.
329		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
330	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
331		385
332	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
333	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
334	like O(total_fds) where n is the total number of fds (or the highest fd),	388	like O(total_fds) where n is the total number of fds (or the highest fd),
335	epoll scales either O(1) or O(active_fds). The epoll design has a number	389	epoll scales either O(1) or O(active_fds).
336	of shortcomings, such as silently dropping events in some hard-to-detect	390
337	cases and rewiring a syscall per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
338	support for dup.	392	of the more advanced event mechanisms: mere annoyances include silently
		393	dropping file descriptors, requiring a system call per change per file
		394	descriptor (and unnecessary guessing of parameters), problems with dup and
		395	so on. The biggest issue is fork races, however - if a program forks then
		396	I<both> parent and child process have to recreate the epoll set, which can
		397	take considerable time (one syscall per file descriptor) and is of course
		398	hard to detect.
		399
		400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		401	of course I<doesn't>, and epoll just loves to report events for totally
		402	I<different> file descriptors (even already closed ones, so one cannot
		403	even remove them from the set) than registered in the set (especially
		404	on SMP systems). Libev tries to counter these spurious notifications by
		405	employing an additional generation counter and comparing that against the
		406	events to filter out spurious ones, recreating the set when required.
339		407
340	While stopping, setting and starting an I/O watcher in the same iteration	408	While stopping, setting and starting an I/O watcher in the same iteration
341	will result in some caching, there is still a syscall per such incident	409	will result in some caching, there is still a system call per such
342	(because the fd could point to a different file description now), so its	410	incident (because the same I<file descriptor> could point to a different
343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
344	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
345		413	file descriptors.
346	Please note that epoll sometimes generates spurious notifications, so you
347	need to use non-blocking I/O or other means to avoid blocking when no data
348	(or space) is available.
349		414
350	Best performance from this backend is achieved by not unregistering all	415	Best performance from this backend is achieved by not unregistering all
351	watchers for a file descriptor until it has been closed, if possible, i.e.	416	watchers for a file descriptor until it has been closed, if possible,
352	keep at least one watcher active per fd at all times.	417	i.e. keep at least one watcher active per fd at all times. Stopping and
		418	starting a watcher (without re-setting it) also usually doesn't cause
		419	extra overhead. A fork can both result in spurious notifications as well
		420	as in libev having to destroy and recreate the epoll object, which can
		421	take considerable time and thus should be avoided.
353		422
354	While nominally embeddeble in other event loops, this feature is broken in	423	While nominally embeddable in other event loops, this feature is broken in
355	all kernel versions tested so far.	424	all kernel versions tested so far.
		425
		426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		427	C<EVBACKEND_POLL>.
356		428
357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
358		430
359	Kqueue deserves special mention, as at the time of this writing, it	431	Kqueue deserves special mention, as at the time of this writing, it
360	was broken on all BSDs except NetBSD (usually it doesn't work reliably	432	was broken on all BSDs except NetBSD (usually it doesn't work reliably
361	with anything but sockets and pipes, except on Darwin, where of course	433	with anything but sockets and pipes, except on Darwin, where of course
362	it's completely useless). For this reason it's not being "autodetected"	434	it's completely useless). Unlike epoll, however, whose brokenness
		435	is by design, these kqueue bugs can (and eventually will) be fixed
		436	without API changes to existing programs. For this reason it's not being
363	unless you explicitly specify it explicitly in the flags (i.e. using	437	"auto-detected" unless you explicitly specify it in the flags (i.e. using
364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
365	system like NetBSD.	439	system like NetBSD.
366		440
367	You still can embed kqueue into a normal poll or select backend and use it	441	You still can embed kqueue into a normal poll or select backend and use it
368	only for sockets (after having made sure that sockets work with kqueue on	442	only for sockets (after having made sure that sockets work with kqueue on
369	the target platform). See C<ev_embed> watchers for more info.	443	the target platform). See C<ev_embed> watchers for more info.
370		444
371	It scales in the same way as the epoll backend, but the interface to the	445	It scales in the same way as the epoll backend, but the interface to the
372	kernel is more efficient (which says nothing about its actual speed, of	446	kernel is more efficient (which says nothing about its actual speed, of
373	course). While stopping, setting and starting an I/O watcher does never	447	course). While stopping, setting and starting an I/O watcher does never
374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	448	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
375	two event changes per incident, support for C<fork ()> is very bad and it	449	two event changes per incident. Support for C<fork ()> is very bad (but
376	drops fds silently in similarly hard-to-detect cases.	450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		451	cases
377		452
378	This backend usually performs well under most conditions.	453	This backend usually performs well under most conditions.
379		454
380	While nominally embeddable in other event loops, this doesn't work	455	While nominally embeddable in other event loops, this doesn't work
381	everywhere, so you might need to test for this. And since it is broken	456	everywhere, so you might need to test for this. And since it is broken
382	almost everywhere, you should only use it when you have a lot of sockets	457	almost everywhere, you should only use it when you have a lot of sockets
383	(for which it usually works), by embedding it into another event loop	458	(for which it usually works), by embedding it into another event loop
384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	459	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
385	sockets.	460	using it only for sockets.
		461
		462	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		463	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		464	C<NOTE_EOF>.
386		465
387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	466	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
388		467
389	This is not implemented yet (and might never be, unless you send me an	468	This is not implemented yet (and might never be, unless you send me an
390	implementation). According to reports, C</dev/poll> only supports sockets	469	implementation). According to reports, C</dev/poll> only supports sockets
…		…
394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	473	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
395		474
396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	475	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
397	it's really slow, but it still scales very well (O(active_fds)).	476	it's really slow, but it still scales very well (O(active_fds)).
398		477
399	Please note that solaris event ports can deliver a lot of spurious	478	Please note that Solaris event ports can deliver a lot of spurious
400	notifications, so you need to use non-blocking I/O or other means to avoid	479	notifications, so you need to use non-blocking I/O or other means to avoid
401	blocking when no data (or space) is available.	480	blocking when no data (or space) is available.
402		481
403	While this backend scales well, it requires one system call per active	482	While this backend scales well, it requires one system call per active
404	file descriptor per loop iteration. For small and medium numbers of file	483	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	484	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	485	might perform better.
407		486
		487	On the positive side, with the exception of the spurious readiness
		488	notifications, this backend actually performed fully to specification
		489	in all tests and is fully embeddable, which is a rare feat among the
		490	OS-specific backends (I vastly prefer correctness over speed hacks).
		491
		492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		493	C<EVBACKEND_POLL>.
		494
408	=item C<EVBACKEND_ALL>	495	=item C<EVBACKEND_ALL>
409		496
410	Try all backends (even potentially broken ones that wouldn't be tried	497	Try all backends (even potentially broken ones that wouldn't be tried
411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	498	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	499	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413		500
414	It is definitely not recommended to use this flag.	501	It is definitely not recommended to use this flag.
415		502
416	=back	503	=back
417		504
418	If one or more of these are ored into the flags value, then only these	505	If one or more of these are or'ed into the flags value, then only these
419	backends will be tried (in the reverse order as given here). If none are	506	backends will be tried (in the reverse order as listed here). If none are
420	specified, most compiled-in backend will be tried, usually in reverse	507	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		508
423	The most typical usage is like this:	509	Example: This is the most typical usage.
424		510
425	if (!ev_default_loop (0))	511	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
427		513
428	Restrict libev to the select and poll backends, and do not allow	514	Example: Restrict libev to the select and poll backends, and do not allow
429	environment settings to be taken into account:	515	environment settings to be taken into account:
430		516
431	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
432		518
433	Use whatever libev has to offer, but make sure that kqueue is used if	519	Example: Use whatever libev has to offer, but make sure that kqueue is
434	available (warning, breaks stuff, best use only with your own private	520	used if available (warning, breaks stuff, best use only with your own
435	event loop and only if you know the OS supports your types of fds):	521	private event loop and only if you know the OS supports your types of
		522	fds):
436		523
437	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
438		525
439	=item struct ev_loop *ev_loop_new (unsigned int flags)	526	=item struct ev_loop *ev_loop_new (unsigned int flags)
440		527
441	Similar to C<ev_default_loop>, but always creates a new event loop that is	528	Similar to C<ev_default_loop>, but always creates a new event loop that is
442	always distinct from the default loop. Unlike the default loop, it cannot	529	always distinct from the default loop. Unlike the default loop, it cannot
443	handle signal and child watchers, and attempts to do so will be greeted by	530	handle signal and child watchers, and attempts to do so will be greeted by
444	undefined behaviour (or a failed assertion if assertions are enabled).	531	undefined behaviour (or a failed assertion if assertions are enabled).
445		532
		533	Note that this function I<is> thread-safe, and the recommended way to use
		534	libev with threads is indeed to create one loop per thread, and using the
		535	default loop in the "main" or "initial" thread.
		536
446	Example: Try to create a event loop that uses epoll and nothing else.	537	Example: Try to create a event loop that uses epoll and nothing else.
447		538
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	539	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	540	if (!epoller)
450	fatal ("no epoll found here, maybe it hides under your chair");	541	fatal ("no epoll found here, maybe it hides under your chair");
451		542
452	=item ev_default_destroy ()	543	=item ev_default_destroy ()
453		544
454	Destroys the default loop again (frees all memory and kernel state	545	Destroys the default loop again (frees all memory and kernel state
455	etc.). None of the active event watchers will be stopped in the normal	546	etc.). None of the active event watchers will be stopped in the normal
456	sense, so e.g. C<ev_is_active> might still return true. It is your	547	sense, so e.g. C<ev_is_active> might still return true. It is your
457	responsibility to either stop all watchers cleanly yoursef I<before>	548	responsibility to either stop all watchers cleanly yourself I<before>
458	calling this function, or cope with the fact afterwards (which is usually	549	calling this function, or cope with the fact afterwards (which is usually
459	the easiest thing, you can just ignore the watchers and/or C<free ()> them	550	the easiest thing, you can just ignore the watchers and/or C<free ()> them
460	for example).	551	for example).
461		552
462	Note that certain global state, such as signal state, will not be freed by	553	Note that certain global state, such as signal state (and installed signal
463	this function, and related watchers (such as signal and child watchers)	554	handlers), will not be freed by this function, and related watchers (such
464	would need to be stopped manually.	555	as signal and child watchers) would need to be stopped manually.
465		556
466	In general it is not advisable to call this function except in the	557	In general it is not advisable to call this function except in the
467	rare occasion where you really need to free e.g. the signal handling	558	rare occasion where you really need to free e.g. the signal handling
468	pipe fds. If you need dynamically allocated loops it is better to use	559	pipe fds. If you need dynamically allocated loops it is better to use
469	C<ev_loop_new> and C<ev_loop_destroy>).	560	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	564	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	565	earlier call to C<ev_loop_new>.
475		566
476	=item ev_default_fork ()	567	=item ev_default_fork ()
477		568
		569	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	570	to reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	571	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	572	the child process (or both child and parent, but that again makes little
481	again makes little sense).	573	sense). You I<must> call it in the child before using any of the libev
		574	functions, and it will only take effect at the next C<ev_loop> iteration.
482		575
483	You I<must> call this function in the child process after forking if and	576	On the other hand, you only need to call this function in the child
484	only if you want to use the event library in both processes. If you just	577	process if and only if you want to use the event library in the child. If
485	fork+exec, you don't have to call it.	578	you just fork+exec, you don't have to call it at all.
486		579
487	The function itself is quite fast and it's usually not a problem to call	580	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	581	it just in case after a fork. To make this easy, the function will fit in
489	quite nicely into a call to C<pthread_atfork>:	582	quite nicely into a call to C<pthread_atfork>:
490		583
491	pthread_atfork (0, 0, ev_default_fork);	584	pthread_atfork (0, 0, ev_default_fork);
492		585
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496
497	=item ev_loop_fork (loop)	586	=item ev_loop_fork (loop)
498		587
499	Like C<ev_default_fork>, but acts on an event loop created by	588	Like C<ev_default_fork>, but acts on an event loop created by
500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	589	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
501	after fork, and how you do this is entirely your own problem.	590	after fork that you want to re-use in the child, and how you do this is
		591	entirely your own problem.
		592
		593	=item int ev_is_default_loop (loop)
		594
		595	Returns true when the given loop is, in fact, the default loop, and false
		596	otherwise.
502		597
503	=item unsigned int ev_loop_count (loop)	598	=item unsigned int ev_loop_count (loop)
504		599
505	Returns the count of loop iterations for the loop, which is identical to	600	Returns the count of loop iterations for the loop, which is identical to
506	the number of times libev did poll for new events. It starts at C<0> and	601	the number of times libev did poll for new events. It starts at C<0> and
…		…
521	received events and started processing them. This timestamp does not	616	received events and started processing them. This timestamp does not
522	change as long as callbacks are being processed, and this is also the base	617	change as long as callbacks are being processed, and this is also the base
523	time used for relative timers. You can treat it as the timestamp of the	618	time used for relative timers. You can treat it as the timestamp of the
524	event occurring (or more correctly, libev finding out about it).	619	event occurring (or more correctly, libev finding out about it).
525		620
		621	=item ev_now_update (loop)
		622
		623	Establishes the current time by querying the kernel, updating the time
		624	returned by C<ev_now ()> in the progress. This is a costly operation and
		625	is usually done automatically within C<ev_loop ()>.
		626
		627	This function is rarely useful, but when some event callback runs for a
		628	very long time without entering the event loop, updating libev's idea of
		629	the current time is a good idea.
		630
		631	See also "The special problem of time updates" in the C<ev_timer> section.
		632
526	=item ev_loop (loop, int flags)	633	=item ev_loop (loop, int flags)
527		634
528	Finally, this is it, the event handler. This function usually is called	635	Finally, this is it, the event handler. This function usually is called
529	after you initialised all your watchers and you want to start handling	636	after you initialised all your watchers and you want to start handling
530	events.	637	events.
…		…
532	If the flags argument is specified as C<0>, it will not return until	639	If the flags argument is specified as C<0>, it will not return until
533	either no event watchers are active anymore or C<ev_unloop> was called.	640	either no event watchers are active anymore or C<ev_unloop> was called.
534		641
535	Please note that an explicit C<ev_unloop> is usually better than	642	Please note that an explicit C<ev_unloop> is usually better than
536	relying on all watchers to be stopped when deciding when a program has	643	relying on all watchers to be stopped when deciding when a program has
537	finished (especially in interactive programs), but having a program that	644	finished (especially in interactive programs), but having a program
538	automatically loops as long as it has to and no longer by virtue of	645	that automatically loops as long as it has to and no longer by virtue
539	relying on its watchers stopping correctly is a thing of beauty.	646	of relying on its watchers stopping correctly, that is truly a thing of
		647	beauty.
540		648
541	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	649	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
542	those events and any outstanding ones, but will not block your process in	650	those events and any already outstanding ones, but will not block your
543	case there are no events and will return after one iteration of the loop.	651	process in case there are no events and will return after one iteration of
		652	the loop.
544		653
545	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	654	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
546	neccessary) and will handle those and any outstanding ones. It will block	655	necessary) and will handle those and any already outstanding ones. It
547	your process until at least one new event arrives, and will return after	656	will block your process until at least one new event arrives (which could
548	one iteration of the loop. This is useful if you are waiting for some	657	be an event internal to libev itself, so there is no guarantee that a
549	external event in conjunction with something not expressible using other	658	user-registered callback will be called), and will return after one
		659	iteration of the loop.
		660
		661	This is useful if you are waiting for some external event in conjunction
		662	with something not expressible using other libev watchers (i.e. "roll your
550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	663	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
551	usually a better approach for this kind of thing.	664	usually a better approach for this kind of thing.
552		665
553	Here are the gory details of what C<ev_loop> does:	666	Here are the gory details of what C<ev_loop> does:
554		667
555	- Before the first iteration, call any pending watchers.	668	- Before the first iteration, call any pending watchers.
556	* If there are no active watchers (reference count is zero), return.	669	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- Queue all prepare watchers and then call all outstanding watchers.	670	- If a fork was detected (by any means), queue and call all fork watchers.
		671	- Queue and call all prepare watchers.
558	- If we have been forked, recreate the kernel state.	672	- If we have been forked, detach and recreate the kernel state
		673	as to not disturb the other process.
559	- Update the kernel state with all outstanding changes.	674	- Update the kernel state with all outstanding changes.
560	- Update the "event loop time".	675	- Update the "event loop time" (ev_now ()).
561	- Calculate for how long to block.	676	- Calculate for how long to sleep or block, if at all
		677	(active idle watchers, EVLOOP_NONBLOCK or not having
		678	any active watchers at all will result in not sleeping).
		679	- Sleep if the I/O and timer collect interval say so.
562	- Block the process, waiting for any events.	680	- Block the process, waiting for any events.
563	- Queue all outstanding I/O (fd) events.	681	- Queue all outstanding I/O (fd) events.
564	- Update the "event loop time" and do time jump handling.	682	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
565	- Queue all outstanding timers.	683	- Queue all expired timers.
566	- Queue all outstanding periodics.	684	- Queue all expired periodics.
567	- If no events are pending now, queue all idle watchers.	685	- Unless any events are pending now, queue all idle watchers.
568	- Queue all check watchers.	686	- Queue all check watchers.
569	- Call all queued watchers in reverse order (i.e. check watchers first).	687	- Call all queued watchers in reverse order (i.e. check watchers first).
570	Signals and child watchers are implemented as I/O watchers, and will	688	Signals and child watchers are implemented as I/O watchers, and will
571	be handled here by queueing them when their watcher gets executed.	689	be handled here by queueing them when their watcher gets executed.
572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	690	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573	were used, return, otherwise continue with step *.	691	were used, or there are no active watchers, return, otherwise
		692	continue with step *.
574		693
575	Example: Queue some jobs and then loop until no events are outsanding	694	Example: Queue some jobs and then loop until no events are outstanding
576	anymore.	695	anymore.
577		696
578	... queue jobs here, make sure they register event watchers as long	697	... queue jobs here, make sure they register event watchers as long
579	... as they still have work to do (even an idle watcher will do..)	698	... as they still have work to do (even an idle watcher will do..)
580	ev_loop (my_loop, 0);	699	ev_loop (my_loop, 0);
581	... jobs done. yeah!	700	... jobs done or somebody called unloop. yeah!
582		701
583	=item ev_unloop (loop, how)	702	=item ev_unloop (loop, how)
584		703
585	Can be used to make a call to C<ev_loop> return early (but only after it	704	Can be used to make a call to C<ev_loop> return early (but only after it
586	has processed all outstanding events). The C<how> argument must be either	705	has processed all outstanding events). The C<how> argument must be either
587	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	706	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
588	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
589		708
		709	This "unloop state" will be cleared when entering C<ev_loop> again.
		710
		711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		712
590	=item ev_ref (loop)	713	=item ev_ref (loop)
591		714
592	=item ev_unref (loop)	715	=item ev_unref (loop)
593		716
594	Ref/unref can be used to add or remove a reference count on the event	717	Ref/unref can be used to add or remove a reference count on the event
595	loop: Every watcher keeps one reference, and as long as the reference	718	loop: Every watcher keeps one reference, and as long as the reference
596	count is nonzero, C<ev_loop> will not return on its own. If you have	719	count is nonzero, C<ev_loop> will not return on its own.
		720
597	a watcher you never unregister that should not keep C<ev_loop> from	721	If you have a watcher you never unregister that should not keep C<ev_loop>
598	returning, ev_unref() after starting, and ev_ref() before stopping it. For	722	from returning, call ev_unref() after starting, and ev_ref() before
		723	stopping it.
		724
599	example, libev itself uses this for its internal signal pipe: It is not	725	As an example, libev itself uses this for its internal signal pipe: It is
600	visible to the libev user and should not keep C<ev_loop> from exiting if	726	not visible to the libev user and should not keep C<ev_loop> from exiting
601	no event watchers registered by it are active. It is also an excellent	727	if no event watchers registered by it are active. It is also an excellent
602	way to do this for generic recurring timers or from within third-party	728	way to do this for generic recurring timers or from within third-party
603	libraries. Just remember to I<unref after start> and I<ref before stop>.	729	libraries. Just remember to I<unref after start> and I<ref before stop>
		730	(but only if the watcher wasn't active before, or was active before,
		731	respectively).
604		732
605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606	running when nothing else is active.	734	running when nothing else is active.
607		735
608	struct ev_signal exitsig;	736	ev_signal exitsig;
609	ev_signal_init (&exitsig, sig_cb, SIGINT);	737	ev_signal_init (&exitsig, sig_cb, SIGINT);
610	ev_signal_start (loop, &exitsig);	738	ev_signal_start (loop, &exitsig);
611	evf_unref (loop);	739	evf_unref (loop);
612		740
613	Example: For some weird reason, unregister the above signal handler again.	741	Example: For some weird reason, unregister the above signal handler again.
614		742
615	ev_ref (loop);	743	ev_ref (loop);
616	ev_signal_stop (loop, &exitsig);	744	ev_signal_stop (loop, &exitsig);
617		745
618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	746	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
619		747
620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	748	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
621		749
622	These advanced functions influence the time that libev will spend waiting	750	These advanced functions influence the time that libev will spend waiting
623	for events. Both are by default C<0>, meaning that libev will try to	751	for events. Both time intervals are by default C<0>, meaning that libev
624	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	752	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		753	latency.
625		754
626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	755	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
627	allows libev to delay invocation of I/O and timer/periodic callbacks to	756	allows libev to delay invocation of I/O and timer/periodic callbacks
628	increase efficiency of loop iterations.	757	to increase efficiency of loop iterations (or to increase power-saving
		758	opportunities).
629		759
630	The background is that sometimes your program runs just fast enough to	760	The idea is that sometimes your program runs just fast enough to handle
631	handle one (or very few) event(s) per loop iteration. While this makes	761	one (or very few) event(s) per loop iteration. While this makes the
632	the program responsive, it also wastes a lot of CPU time to poll for new	762	program responsive, it also wastes a lot of CPU time to poll for new
633	events, especially with backends like C<select ()> which have a high	763	events, especially with backends like C<select ()> which have a high
634	overhead for the actual polling but can deliver many events at once.	764	overhead for the actual polling but can deliver many events at once.
635		765
636	By setting a higher I<io collect interval> you allow libev to spend more	766	By setting a higher I<io collect interval> you allow libev to spend more
637	time collecting I/O events, so you can handle more events per iteration,	767	time collecting I/O events, so you can handle more events per iteration,
…		…
639	C<ev_timer>) will be not affected. Setting this to a non-null value will	769	C<ev_timer>) will be not affected. Setting this to a non-null value will
640	introduce an additional C<ev_sleep ()> call into most loop iterations.	770	introduce an additional C<ev_sleep ()> call into most loop iterations.
641		771
642	Likewise, by setting a higher I<timeout collect interval> you allow libev	772	Likewise, by setting a higher I<timeout collect interval> you allow libev
643	to spend more time collecting timeouts, at the expense of increased	773	to spend more time collecting timeouts, at the expense of increased
644	latency (the watcher callback will be called later). C<ev_io> watchers	774	latency/jitter/inexactness (the watcher callback will be called
645	will not be affected. Setting this to a non-null value will not introduce	775	later). C<ev_io> watchers will not be affected. Setting this to a non-null
646	any overhead in libev.	776	value will not introduce any overhead in libev.
647		777
648	Many (busy) programs can usually benefit by setting the io collect	778	Many (busy) programs can usually benefit by setting the I/O collect
649	interval to a value near C<0.1> or so, which is often enough for	779	interval to a value near C<0.1> or so, which is often enough for
650	interactive servers (of course not for games), likewise for timeouts. It	780	interactive servers (of course not for games), likewise for timeouts. It
651	usually doesn't make much sense to set it to a lower value than C<0.01>,	781	usually doesn't make much sense to set it to a lower value than C<0.01>,
652	as this approsaches the timing granularity of most systems.	782	as this approaches the timing granularity of most systems.
		783
		784	Setting the I<timeout collect interval> can improve the opportunity for
		785	saving power, as the program will "bundle" timer callback invocations that
		786	are "near" in time together, by delaying some, thus reducing the number of
		787	times the process sleeps and wakes up again. Another useful technique to
		788	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		789	they fire on, say, one-second boundaries only.
		790
		791	=item ev_loop_verify (loop)
		792
		793	This function only does something when C<EV_VERIFY> support has been
		794	compiled in, which is the default for non-minimal builds. It tries to go
		795	through all internal structures and checks them for validity. If anything
		796	is found to be inconsistent, it will print an error message to standard
		797	error and call C<abort ()>.
		798
		799	This can be used to catch bugs inside libev itself: under normal
		800	circumstances, this function will never abort as of course libev keeps its
		801	data structures consistent.
653		802
654	=back	803	=back
655		804
656		805
657	=head1 ANATOMY OF A WATCHER	806	=head1 ANATOMY OF A WATCHER
		807
		808	In the following description, uppercase C<TYPE> in names stands for the
		809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		810	watchers and C<ev_io_start> for I/O watchers.
658		811
659	A watcher is a structure that you create and register to record your	812	A watcher is a structure that you create and register to record your
660	interest in some event. For instance, if you want to wait for STDIN to	813	interest in some event. For instance, if you want to wait for STDIN to
661	become readable, you would create an C<ev_io> watcher for that:	814	become readable, you would create an C<ev_io> watcher for that:
662		815
663	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
664	{	817	{
665	ev_io_stop (w);	818	ev_io_stop (w);
666	ev_unloop (loop, EVUNLOOP_ALL);	819	ev_unloop (loop, EVUNLOOP_ALL);
667	}	820	}
668		821
669	struct ev_loop *loop = ev_default_loop (0);	822	struct ev_loop *loop = ev_default_loop (0);
		823
670	struct ev_io stdin_watcher;	824	ev_io stdin_watcher;
		825
671	ev_init (&stdin_watcher, my_cb);	826	ev_init (&stdin_watcher, my_cb);
672	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
673	ev_io_start (loop, &stdin_watcher);	828	ev_io_start (loop, &stdin_watcher);
		829
674	ev_loop (loop, 0);	830	ev_loop (loop, 0);
675		831
676	As you can see, you are responsible for allocating the memory for your	832	As you can see, you are responsible for allocating the memory for your
677	watcher structures (and it is usually a bad idea to do this on the stack,	833	watcher structures (and it is I<usually> a bad idea to do this on the
678	although this can sometimes be quite valid).	834	stack).
		835
		836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
679		838
680	Each watcher structure must be initialised by a call to C<ev_init	839	Each watcher structure must be initialised by a call to C<ev_init
681	(watcher *, callback)>, which expects a callback to be provided. This	840	(watcher *, callback)>, which expects a callback to be provided. This
682	callback gets invoked each time the event occurs (or, in the case of io	841	callback gets invoked each time the event occurs (or, in the case of I/O
683	watchers, each time the event loop detects that the file descriptor given	842	watchers, each time the event loop detects that the file descriptor given
684	is readable and/or writable).	843	is readable and/or writable).
685		844
686	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	845	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
687	with arguments specific to this watcher type. There is also a macro	846	macro to configure it, with arguments specific to the watcher type. There
688	to combine initialisation and setting in one call: C<< ev_<type>_init	847	is also a macro to combine initialisation and setting in one call: C<<
689	(watcher *, callback, ...) >>.	848	ev_TYPE_init (watcher *, callback, ...) >>.
690		849
691	To make the watcher actually watch out for events, you have to start it	850	To make the watcher actually watch out for events, you have to start it
692	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	851	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
693	*) >>), and you can stop watching for events at any time by calling the	852	*) >>), and you can stop watching for events at any time by calling the
694	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	853	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
695		854
696	As long as your watcher is active (has been started but not stopped) you	855	As long as your watcher is active (has been started but not stopped) you
697	must not touch the values stored in it. Most specifically you must never	856	must not touch the values stored in it. Most specifically you must never
698	reinitialise it or call its C<set> macro.	857	reinitialise it or call its C<ev_TYPE_set> macro.
699		858
700	Each and every callback receives the event loop pointer as first, the	859	Each and every callback receives the event loop pointer as first, the
701	registered watcher structure as second, and a bitset of received events as	860	registered watcher structure as second, and a bitset of received events as
702	third argument.	861	third argument.
703		862
…		…
757	=item C<EV_FORK>	916	=item C<EV_FORK>
758		917
759	The event loop has been resumed in the child process after fork (see	918	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	919	C<ev_fork>).
761		920
		921	=item C<EV_ASYNC>
		922
		923	The given async watcher has been asynchronously notified (see C<ev_async>).
		924
762	=item C<EV_ERROR>	925	=item C<EV_ERROR>
763		926
764	An unspecified error has occured, the watcher has been stopped. This might	927	An unspecified error has occurred, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	928	happen because the watcher could not be properly started because libev
766	ran out of memory, a file descriptor was found to be closed or any other	929	ran out of memory, a file descriptor was found to be closed or any other
		930	problem. Libev considers these application bugs.
		931
767	problem. You best act on it by reporting the problem and somehow coping	932	You best act on it by reporting the problem and somehow coping with the
768	with the watcher being stopped.	933	watcher being stopped. Note that well-written programs should not receive
		934	an error ever, so when your watcher receives it, this usually indicates a
		935	bug in your program.
769		936
770	Libev will usually signal a few "dummy" events together with an error,	937	Libev will usually signal a few "dummy" events together with an error, for
771	for example it might indicate that a fd is readable or writable, and if	938	example it might indicate that a fd is readable or writable, and if your
772	your callbacks is well-written it can just attempt the operation and cope	939	callbacks is well-written it can just attempt the operation and cope with
773	with the error from read() or write(). This will not work in multithreaded	940	the error from read() or write(). This will not work in multi-threaded
774	programs, though, so beware.	941	programs, though, as the fd could already be closed and reused for another
		942	thing, so beware.
775		943
776	=back	944	=back
777		945
778	=head2 GENERIC WATCHER FUNCTIONS	946	=head2 GENERIC WATCHER FUNCTIONS
779
780	In the following description, C<TYPE> stands for the watcher type,
781	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
782		947
783	=over 4	948	=over 4
784		949
785	=item C<ev_init> (ev_TYPE *watcher, callback)	950	=item C<ev_init> (ev_TYPE *watcher, callback)
786		951
…		…
792	which rolls both calls into one.	957	which rolls both calls into one.
793		958
794	You can reinitialise a watcher at any time as long as it has been stopped	959	You can reinitialise a watcher at any time as long as it has been stopped
795	(or never started) and there are no pending events outstanding.	960	(or never started) and there are no pending events outstanding.
796		961
797	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	962	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
798	int revents)>.	963	int revents)>.
		964
		965	Example: Initialise an C<ev_io> watcher in two steps.
		966
		967	ev_io w;
		968	ev_init (&w, my_cb);
		969	ev_io_set (&w, STDIN_FILENO, EV_READ);
799		970
800	=item C<ev_TYPE_set> (ev_TYPE *, [args])	971	=item C<ev_TYPE_set> (ev_TYPE *, [args])
801		972
802	This macro initialises the type-specific parts of a watcher. You need to	973	This macro initialises the type-specific parts of a watcher. You need to
803	call C<ev_init> at least once before you call this macro, but you can	974	call C<ev_init> at least once before you call this macro, but you can
…		…
806	difference to the C<ev_init> macro).	977	difference to the C<ev_init> macro).
807		978
808	Although some watcher types do not have type-specific arguments	979	Although some watcher types do not have type-specific arguments
809	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	980	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
810		981
		982	See C<ev_init>, above, for an example.
		983
811	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	984	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
812		985
813	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	986	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
814	calls into a single call. This is the most convinient method to initialise	987	calls into a single call. This is the most convenient method to initialise
815	a watcher. The same limitations apply, of course.	988	a watcher. The same limitations apply, of course.
		989
		990	Example: Initialise and set an C<ev_io> watcher in one step.
		991
		992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
816		993
817	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
818		995
819	Starts (activates) the given watcher. Only active watchers will receive	996	Starts (activates) the given watcher. Only active watchers will receive
820	events. If the watcher is already active nothing will happen.	997	events. If the watcher is already active nothing will happen.
821		998
		999	Example: Start the C<ev_io> watcher that is being abused as example in this
		1000	whole section.
		1001
		1002	ev_io_start (EV_DEFAULT_UC, &w);
		1003
822	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
823		1005
824	Stops the given watcher again (if active) and clears the pending	1006	Stops the given watcher if active, and clears the pending status (whether
		1007	the watcher was active or not).
		1008
825	status. It is possible that stopped watchers are pending (for example,	1009	It is possible that stopped watchers are pending - for example,
826	non-repeating timers are being stopped when they become pending), but	1010	non-repeating timers are being stopped when they become pending - but
827	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1011	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
828	you want to free or reuse the memory used by the watcher it is therefore a	1012	pending. If you want to free or reuse the memory used by the watcher it is
829	good idea to always call its C<ev_TYPE_stop> function.	1013	therefore a good idea to always call its C<ev_TYPE_stop> function.
830		1014
831	=item bool ev_is_active (ev_TYPE *watcher)	1015	=item bool ev_is_active (ev_TYPE *watcher)
832		1016
833	Returns a true value iff the watcher is active (i.e. it has been started	1017	Returns a true value iff the watcher is active (i.e. it has been started
834	and not yet been stopped). As long as a watcher is active you must not modify	1018	and not yet been stopped). As long as a watcher is active you must not modify
…		…
876	The default priority used by watchers when no priority has been set is	1060	The default priority used by watchers when no priority has been set is
877	always C<0>, which is supposed to not be too high and not be too low :).	1061	always C<0>, which is supposed to not be too high and not be too low :).
878		1062
879	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1063	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
880	fine, as long as you do not mind that the priority value you query might	1064	fine, as long as you do not mind that the priority value you query might
881	or might not have been adjusted to be within valid range.	1065	or might not have been clamped to the valid range.
882		1066
883	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
884		1068
885	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1069	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
886	C<loop> nor C<revents> need to be valid as long as the watcher callback	1070	C<loop> nor C<revents> need to be valid as long as the watcher callback
887	can deal with that fact.	1071	can deal with that fact, as both are simply passed through to the
		1072	callback.
888		1073
889	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1074	=item int ev_clear_pending (loop, ev_TYPE *watcher)
890		1075
891	If the watcher is pending, this function returns clears its pending status	1076	If the watcher is pending, this function clears its pending status and
892	and returns its C<revents> bitset (as if its callback was invoked). If the	1077	returns its C<revents> bitset (as if its callback was invoked). If the
893	watcher isn't pending it does nothing and returns C<0>.	1078	watcher isn't pending it does nothing and returns C<0>.
894		1079
		1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1081	callback to be invoked, which can be accomplished with this function.
		1082
895	=back	1083	=back
896		1084
897		1085
898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
899		1087
900	Each watcher has, by default, a member C<void *data> that you can change	1088	Each watcher has, by default, a member C<void *data> that you can change
901	and read at any time, libev will completely ignore it. This can be used	1089	and read at any time: libev will completely ignore it. This can be used
902	to associate arbitrary data with your watcher. If you need more data and	1090	to associate arbitrary data with your watcher. If you need more data and
903	don't want to allocate memory and store a pointer to it in that data	1091	don't want to allocate memory and store a pointer to it in that data
904	member, you can also "subclass" the watcher type and provide your own	1092	member, you can also "subclass" the watcher type and provide your own
905	data:	1093	data:
906		1094
907	struct my_io	1095	struct my_io
908	{	1096	{
909	struct ev_io io;	1097	ev_io io;
910	int otherfd;	1098	int otherfd;
911	void *somedata;	1099	void *somedata;
912	struct whatever *mostinteresting;	1100	struct whatever *mostinteresting;
913	}	1101	};
		1102
		1103	...
		1104	struct my_io w;
		1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
914		1106
915	And since your callback will be called with a pointer to the watcher, you	1107	And since your callback will be called with a pointer to the watcher, you
916	can cast it back to your own type:	1108	can cast it back to your own type:
917		1109
918	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
919	{	1111	{
920	struct my_io *w = (struct my_io *)w_;	1112	struct my_io *w = (struct my_io *)w_;
921	...	1113	...
922	}	1114	}
923		1115
924	More interesting and less C-conformant ways of casting your callback type	1116	More interesting and less C-conformant ways of casting your callback type
925	instead have been omitted.	1117	instead have been omitted.
926		1118
927	Another common scenario is having some data structure with multiple	1119	Another common scenario is to use some data structure with multiple
928	watchers:	1120	embedded watchers:
929		1121
930	struct my_biggy	1122	struct my_biggy
931	{	1123	{
932	int some_data;	1124	int some_data;
933	ev_timer t1;	1125	ev_timer t1;
934	ev_timer t2;	1126	ev_timer t2;
935	}	1127	}
936		1128
937	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1129	In this case getting the pointer to C<my_biggy> is a bit more
938	you need to use C<offsetof>:	1130	complicated: Either you store the address of your C<my_biggy> struct
		1131	in the C<data> member of the watcher (for woozies), or you need to use
		1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1133	programmers):
939		1134
940	#include <stddef.h>	1135	#include <stddef.h>
941		1136
942	static void	1137	static void
943	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
944	{	1139	{
945	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
946	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
947	}	1142	}
948		1143
949	static void	1144	static void
950	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
951	{	1146	{
952	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
953	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
954	}	1149	}
955		1150
956		1151
957	=head1 WATCHER TYPES	1152	=head1 WATCHER TYPES
958		1153
959	This section describes each watcher in detail, but will not repeat	1154	This section describes each watcher in detail, but will not repeat
…		…
983	In general you can register as many read and/or write event watchers per	1178	In general you can register as many read and/or write event watchers per
984	fd as you want (as long as you don't confuse yourself). Setting all file	1179	fd as you want (as long as you don't confuse yourself). Setting all file
985	descriptors to non-blocking mode is also usually a good idea (but not	1180	descriptors to non-blocking mode is also usually a good idea (but not
986	required if you know what you are doing).	1181	required if you know what you are doing).
987		1182
988	You have to be careful with dup'ed file descriptors, though. Some backends	1183	If you cannot use non-blocking mode, then force the use of a
989	(the linux epoll backend is a notable example) cannot handle dup'ed file	1184	known-to-be-good backend (at the time of this writing, this includes only
990	descriptors correctly if you register interest in two or more fds pointing	1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
991	to the same underlying file/socket/etc. description (that is, they share
992	the same underlying "file open").
993
994	If you must do this, then force the use of a known-to-be-good backend
995	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
996	C<EVBACKEND_POLL>).
997		1186
998	Another thing you have to watch out for is that it is quite easy to	1187	Another thing you have to watch out for is that it is quite easy to
999	receive "spurious" readyness notifications, that is your callback might	1188	receive "spurious" readiness notifications, that is your callback might
1000	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1189	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1001	because there is no data. Not only are some backends known to create a	1190	because there is no data. Not only are some backends known to create a
1002	lot of those (for example solaris ports), it is very easy to get into	1191	lot of those (for example Solaris ports), it is very easy to get into
1003	this situation even with a relatively standard program structure. Thus	1192	this situation even with a relatively standard program structure. Thus
1004	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1193	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1005	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1194	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1006		1195
1007	If you cannot run the fd in non-blocking mode (for example you should not	1196	If you cannot run the fd in non-blocking mode (for example you should
1008	play around with an Xlib connection), then you have to seperately re-test	1197	not play around with an Xlib connection), then you have to separately
1009	whether a file descriptor is really ready with a known-to-be good interface	1198	re-test whether a file descriptor is really ready with a known-to-be good
1010	such as poll (fortunately in our Xlib example, Xlib already does this on	1199	interface such as poll (fortunately in our Xlib example, Xlib already
1011	its own, so its quite safe to use).	1200	does this on its own, so its quite safe to use). Some people additionally
		1201	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1202	indefinitely.
		1203
		1204	But really, best use non-blocking mode.
1012		1205
1013	=head3 The special problem of disappearing file descriptors	1206	=head3 The special problem of disappearing file descriptors
1014		1207
1015	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1208	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1016	descriptor (either by calling C<close> explicitly or by any other means,	1209	descriptor (either due to calling C<close> explicitly or any other means,
1017	such as C<dup>). The reason is that you register interest in some file	1210	such as C<dup2>). The reason is that you register interest in some file
1018	descriptor, but when it goes away, the operating system will silently drop	1211	descriptor, but when it goes away, the operating system will silently drop
1019	this interest. If another file descriptor with the same number then is	1212	this interest. If another file descriptor with the same number then is
1020	registered with libev, there is no efficient way to see that this is, in	1213	registered with libev, there is no efficient way to see that this is, in
1021	fact, a different file descriptor.	1214	fact, a different file descriptor.
1022		1215
…		…
1033		1226
1034	=head3 The special problem of dup'ed file descriptors	1227	=head3 The special problem of dup'ed file descriptors
1035		1228
1036	Some backends (e.g. epoll), cannot register events for file descriptors,	1229	Some backends (e.g. epoll), cannot register events for file descriptors,
1037	but only events for the underlying file descriptions. That means when you	1230	but only events for the underlying file descriptions. That means when you
1038	have C<dup ()>'ed file descriptors and register events for them, only one	1231	have C<dup ()>'ed file descriptors or weirder constellations, and register
1039	file descriptor might actually receive events.	1232	events for them, only one file descriptor might actually receive events.
1040		1233
1041	There is no workaround possible except not registering events	1234	There is no workaround possible except not registering events
1042	for potentially C<dup ()>'ed file descriptors, or to resort to	1235	for potentially C<dup ()>'ed file descriptors, or to resort to
1043	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1236	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1044		1237
…		…
1051	To support fork in your programs, you either have to call	1244	To support fork in your programs, you either have to call
1052	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1245	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1053	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1054	C<EVBACKEND_POLL>.	1247	C<EVBACKEND_POLL>.
1055		1248
		1249	=head3 The special problem of SIGPIPE
		1250
		1251	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1252	when writing to a pipe whose other end has been closed, your program gets
		1253	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1254	this is sensible behaviour, for daemons, this is usually undesirable.
		1255
		1256	So when you encounter spurious, unexplained daemon exits, make sure you
		1257	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1258	somewhere, as that would have given you a big clue).
		1259
1056		1260
1057	=head3 Watcher-Specific Functions	1261	=head3 Watcher-Specific Functions
1058		1262
1059	=over 4	1263	=over 4
1060		1264
1061	=item ev_io_init (ev_io *, callback, int fd, int events)	1265	=item ev_io_init (ev_io *, callback, int fd, int events)
1062		1266
1063	=item ev_io_set (ev_io *, int fd, int events)	1267	=item ev_io_set (ev_io *, int fd, int events)
1064		1268
1065	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1269	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1066	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1270	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1067	C<EV_READ | EV_WRITE> to receive the given events.	1271	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1068		1272
1069	=item int fd [read-only]	1273	=item int fd [read-only]
1070		1274
1071	The file descriptor being watched.	1275	The file descriptor being watched.
1072		1276
1073	=item int events [read-only]	1277	=item int events [read-only]
1074		1278
1075	The events being watched.	1279	The events being watched.
1076		1280
1077	=back	1281	=back
		1282
		1283	=head3 Examples
1078		1284
1079	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1285	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1080	readable, but only once. Since it is likely line-buffered, you could	1286	readable, but only once. Since it is likely line-buffered, you could
1081	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1082		1288
1083	static void	1289	static void
1084	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1290	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1085	{	1291	{
1086	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1087	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1293	.. read from stdin here (or from w->fd) and handle any I/O errors
1088	}	1294	}
1089		1295
1090	...	1296	...
1091	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1092	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1093	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1094	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1095	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1096		1302
1097		1303
1098	=head2 C<ev_timer> - relative and optionally repeating timeouts	1304	=head2 C<ev_timer> - relative and optionally repeating timeouts
1099		1305
1100	Timer watchers are simple relative timers that generate an event after a	1306	Timer watchers are simple relative timers that generate an event after a
1101	given time, and optionally repeating in regular intervals after that.	1307	given time, and optionally repeating in regular intervals after that.
1102		1308
1103	The timers are based on real time, that is, if you register an event that	1309	The timers are based on real time, that is, if you register an event that
1104	times out after an hour and you reset your system clock to last years	1310	times out after an hour and you reset your system clock to January last
1105	time, it will still time out after (roughly) and hour. "Roughly" because	1311	year, it will still time out after (roughly) one hour. "Roughly" because
1106	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1107	monotonic clock option helps a lot here).	1313	monotonic clock option helps a lot here).
		1314
		1315	The callback is guaranteed to be invoked only I<after> its timeout has
		1316	passed, but if multiple timers become ready during the same loop iteration
		1317	then order of execution is undefined.
		1318
		1319	=head3 Be smart about timeouts
		1320
		1321	Many real-world problems involve some kind of timeout, usually for error
		1322	recovery. A typical example is an HTTP request - if the other side hangs,
		1323	you want to raise some error after a while.
		1324
		1325	What follows are some ways to handle this problem, from obvious and
		1326	inefficient to smart and efficient.
		1327
		1328	In the following, a 60 second activity timeout is assumed - a timeout that
		1329	gets reset to 60 seconds each time there is activity (e.g. each time some
		1330	data or other life sign was received).
		1331
		1332	=over 4
		1333
		1334	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1335
		1336	This is the most obvious, but not the most simple way: In the beginning,
		1337	start the watcher:
		1338
		1339	ev_timer_init (timer, callback, 60., 0.);
		1340	ev_timer_start (loop, timer);
		1341
		1342	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1343	and start it again:
		1344
		1345	ev_timer_stop (loop, timer);
		1346	ev_timer_set (timer, 60., 0.);
		1347	ev_timer_start (loop, timer);
		1348
		1349	This is relatively simple to implement, but means that each time there is
		1350	some activity, libev will first have to remove the timer from its internal
		1351	data structure and then add it again. Libev tries to be fast, but it's
		1352	still not a constant-time operation.
		1353
		1354	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1355
		1356	This is the easiest way, and involves using C<ev_timer_again> instead of
		1357	C<ev_timer_start>.
		1358
		1359	To implement this, configure an C<ev_timer> with a C<repeat> value
		1360	of C<60> and then call C<ev_timer_again> at start and each time you
		1361	successfully read or write some data. If you go into an idle state where
		1362	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1363	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1364
		1365	That means you can ignore both the C<ev_timer_start> function and the
		1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1367	member and C<ev_timer_again>.
		1368
		1369	At start:
		1370
		1371	ev_timer_init (timer, callback);
		1372	timer->repeat = 60.;
		1373	ev_timer_again (loop, timer);
		1374
		1375	Each time there is some activity:
		1376
		1377	ev_timer_again (loop, timer);
		1378
		1379	It is even possible to change the time-out on the fly, regardless of
		1380	whether the watcher is active or not:
		1381
		1382	timer->repeat = 30.;
		1383	ev_timer_again (loop, timer);
		1384
		1385	This is slightly more efficient then stopping/starting the timer each time
		1386	you want to modify its timeout value, as libev does not have to completely
		1387	remove and re-insert the timer from/into its internal data structure.
		1388
		1389	It is, however, even simpler than the "obvious" way to do it.
		1390
		1391	=item 3. Let the timer time out, but then re-arm it as required.
		1392
		1393	This method is more tricky, but usually most efficient: Most timeouts are
		1394	relatively long compared to the intervals between other activity - in
		1395	our example, within 60 seconds, there are usually many I/O events with
		1396	associated activity resets.
		1397
		1398	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1399	but remember the time of last activity, and check for a real timeout only
		1400	within the callback:
		1401
		1402	ev_tstamp last_activity; // time of last activity
		1403
		1404	static void
		1405	callback (EV_P_ ev_timer *w, int revents)
		1406	{
		1407	ev_tstamp now = ev_now (EV_A);
		1408	ev_tstamp timeout = last_activity + 60.;
		1409
		1410	// if last_activity + 60. is older than now, we did time out
		1411	if (timeout < now)
		1412	{
		1413	// timeout occured, take action
		1414	}
		1415	else
		1416	{
		1417	// callback was invoked, but there was some activity, re-arm
		1418	// the watcher to fire in last_activity + 60, which is
		1419	// guaranteed to be in the future, so "again" is positive:
		1420	w->again = timeout - now;
		1421	ev_timer_again (EV_A_ w);
		1422	}
		1423	}
		1424
		1425	To summarise the callback: first calculate the real timeout (defined
		1426	as "60 seconds after the last activity"), then check if that time has
		1427	been reached, which means something I<did>, in fact, time out. Otherwise
		1428	the callback was invoked too early (C<timeout> is in the future), so
		1429	re-schedule the timer to fire at that future time, to see if maybe we have
		1430	a timeout then.
		1431
		1432	Note how C<ev_timer_again> is used, taking advantage of the
		1433	C<ev_timer_again> optimisation when the timer is already running.
		1434
		1435	This scheme causes more callback invocations (about one every 60 seconds
		1436	minus half the average time between activity), but virtually no calls to
		1437	libev to change the timeout.
		1438
		1439	To start the timer, simply initialise the watcher and set C<last_activity>
		1440	to the current time (meaning we just have some activity :), then call the
		1441	callback, which will "do the right thing" and start the timer:
		1442
		1443	ev_timer_init (timer, callback);
		1444	last_activity = ev_now (loop);
		1445	callback (loop, timer, EV_TIMEOUT);
		1446
		1447	And when there is some activity, simply store the current time in
		1448	C<last_activity>, no libev calls at all:
		1449
		1450	last_actiivty = ev_now (loop);
		1451
		1452	This technique is slightly more complex, but in most cases where the
		1453	time-out is unlikely to be triggered, much more efficient.
		1454
		1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1456	callback :) - just change the timeout and invoke the callback, which will
		1457	fix things for you.
		1458
		1459	=item 4. Wee, just use a double-linked list for your timeouts.
		1460
		1461	If there is not one request, but many thousands (millions...), all
		1462	employing some kind of timeout with the same timeout value, then one can
		1463	do even better:
		1464
		1465	When starting the timeout, calculate the timeout value and put the timeout
		1466	at the I<end> of the list.
		1467
		1468	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1469	the list is expected to fire (for example, using the technique #3).
		1470
		1471	When there is some activity, remove the timer from the list, recalculate
		1472	the timeout, append it to the end of the list again, and make sure to
		1473	update the C<ev_timer> if it was taken from the beginning of the list.
		1474
		1475	This way, one can manage an unlimited number of timeouts in O(1) time for
		1476	starting, stopping and updating the timers, at the expense of a major
		1477	complication, and having to use a constant timeout. The constant timeout
		1478	ensures that the list stays sorted.
		1479
		1480	=back
		1481
		1482	So which method the best?
		1483
		1484	Method #2 is a simple no-brain-required solution that is adequate in most
		1485	situations. Method #3 requires a bit more thinking, but handles many cases
		1486	better, and isn't very complicated either. In most case, choosing either
		1487	one is fine, with #3 being better in typical situations.
		1488
		1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1490	rather complicated, but extremely efficient, something that really pays
		1491	off after the first million or so of active timers, i.e. it's usually
		1492	overkill :)
		1493
		1494	=head3 The special problem of time updates
		1495
		1496	Establishing the current time is a costly operation (it usually takes at
		1497	least two system calls): EV therefore updates its idea of the current
		1498	time only before and after C<ev_loop> collects new events, which causes a
		1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1500	lots of events in one iteration.
1108		1501
1109	The relative timeouts are calculated relative to the C<ev_now ()>	1502	The relative timeouts are calculated relative to the C<ev_now ()>
1110	time. This is usually the right thing as this timestamp refers to the time	1503	time. This is usually the right thing as this timestamp refers to the time
1111	of the event triggering whatever timeout you are modifying/starting. If	1504	of the event triggering whatever timeout you are modifying/starting. If
1112	you suspect event processing to be delayed and you I<need> to base the timeout	1505	you suspect event processing to be delayed and you I<need> to base the
1113	on the current time, use something like this to adjust for this:	1506	timeout on the current time, use something like this to adjust for this:
1114		1507
1115	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1508	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1116		1509
1117	The callback is guarenteed to be invoked only when its timeout has passed,	1510	If the event loop is suspended for a long time, you can also force an
1118	but if multiple timers become ready during the same loop iteration then	1511	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1119	order of execution is undefined.	1512	()>.
1120		1513
1121	=head3 Watcher-Specific Functions and Data Members	1514	=head3 Watcher-Specific Functions and Data Members
1122		1515
1123	=over 4	1516	=over 4
1124		1517
1125	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1518	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1126		1519
1127	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1520	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1128		1521
1129	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1522	Configure the timer to trigger after C<after> seconds. If C<repeat>
1130	C<0.>, then it will automatically be stopped. If it is positive, then the	1523	is C<0.>, then it will automatically be stopped once the timeout is
1131	timer will automatically be configured to trigger again C<repeat> seconds	1524	reached. If it is positive, then the timer will automatically be
1132	later, again, and again, until stopped manually.	1525	configured to trigger again C<repeat> seconds later, again, and again,
		1526	until stopped manually.
1133		1527
1134	The timer itself will do a best-effort at avoiding drift, that is, if you	1528	The timer itself will do a best-effort at avoiding drift, that is, if
1135	configure a timer to trigger every 10 seconds, then it will trigger at	1529	you configure a timer to trigger every 10 seconds, then it will normally
1136	exactly 10 second intervals. If, however, your program cannot keep up with	1530	trigger at exactly 10 second intervals. If, however, your program cannot
1137	the timer (because it takes longer than those 10 seconds to do stuff) the	1531	keep up with the timer (because it takes longer than those 10 seconds to
1138	timer will not fire more than once per event loop iteration.	1532	do stuff) the timer will not fire more than once per event loop iteration.
1139		1533
1140	=item ev_timer_again (loop)	1534	=item ev_timer_again (loop, ev_timer *)
1141		1535
1142	This will act as if the timer timed out and restart it again if it is	1536	This will act as if the timer timed out and restart it again if it is
1143	repeating. The exact semantics are:	1537	repeating. The exact semantics are:
1144		1538
1145	If the timer is pending, its pending status is cleared.	1539	If the timer is pending, its pending status is cleared.
1146		1540
1147	If the timer is started but nonrepeating, stop it (as if it timed out).	1541	If the timer is started but non-repeating, stop it (as if it timed out).
1148		1542
1149	If the timer is repeating, either start it if necessary (with the	1543	If the timer is repeating, either start it if necessary (with the
1150	C<repeat> value), or reset the running timer to the C<repeat> value.	1544	C<repeat> value), or reset the running timer to the C<repeat> value.
1151		1545
1152	This sounds a bit complicated, but here is a useful and typical	1546	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1153	example: Imagine you have a tcp connection and you want a so-called idle	1547	usage example.
1154	timeout, that is, you want to be called when there have been, say, 60
1155	seconds of inactivity on the socket. The easiest way to do this is to
1156	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1157	C<ev_timer_again> each time you successfully read or write some data. If
1158	you go into an idle state where you do not expect data to travel on the
1159	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1160	automatically restart it if need be.
1161
1162	That means you can ignore the C<after> value and C<ev_timer_start>
1163	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1164
1165	ev_timer_init (timer, callback, 0., 5.);
1166	ev_timer_again (loop, timer);
1167	...
1168	timer->again = 17.;
1169	ev_timer_again (loop, timer);
1170	...
1171	timer->again = 10.;
1172	ev_timer_again (loop, timer);
1173
1174	This is more slightly efficient then stopping/starting the timer each time
1175	you want to modify its timeout value.
1176		1548
1177	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1178		1550
1179	The current C<repeat> value. Will be used each time the watcher times out	1551	The current C<repeat> value. Will be used each time the watcher times out
1180	or C<ev_timer_again> is called and determines the next timeout (if any),	1552	or C<ev_timer_again> is called, and determines the next timeout (if any),
1181	which is also when any modifications are taken into account.	1553	which is also when any modifications are taken into account.
1182		1554
1183	=back	1555	=back
1184		1556
		1557	=head3 Examples
		1558
1185	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1186		1560
1187	static void	1561	static void
1188	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1562	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1189	{	1563	{
1190	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1191	}	1565	}
1192		1566
1193	struct ev_timer mytimer;	1567	ev_timer mytimer;
1194	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1195	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1196		1570
1197	Example: Create a timeout timer that times out after 10 seconds of	1571	Example: Create a timeout timer that times out after 10 seconds of
1198	inactivity.	1572	inactivity.
1199		1573
1200	static void	1574	static void
1201	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1202	{	1576	{
1203	.. ten seconds without any activity	1577	.. ten seconds without any activity
1204	}	1578	}
1205		1579
1206	struct ev_timer mytimer;	1580	ev_timer mytimer;
1207	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1208	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1209	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1210		1584
1211	// and in some piece of code that gets executed on any "activity":	1585	// and in some piece of code that gets executed on any "activity":
1212	// reset the timeout to start ticking again at 10 seconds	1586	// reset the timeout to start ticking again at 10 seconds
1213	ev_timer_again (&mytimer);	1587	ev_timer_again (&mytimer);
1214		1588
1215		1589
1216	=head2 C<ev_periodic> - to cron or not to cron?	1590	=head2 C<ev_periodic> - to cron or not to cron?
1217		1591
1218	Periodic watchers are also timers of a kind, but they are very versatile	1592	Periodic watchers are also timers of a kind, but they are very versatile
1219	(and unfortunately a bit complex).	1593	(and unfortunately a bit complex).
1220		1594
1221	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1595	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1222	but on wallclock time (absolute time). You can tell a periodic watcher	1596	but on wall clock time (absolute time). You can tell a periodic watcher
1223	to trigger "at" some specific point in time. For example, if you tell a	1597	to trigger after some specific point in time. For example, if you tell a
1224	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1598	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1225	+ 10.>) and then reset your system clock to the last year, then it will	1599	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1600	clock to January of the previous year, then it will take more than year
1226	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1227	roughly 10 seconds later).	1602	roughly 10 seconds later as it uses a relative timeout).
1228		1603
1229	They can also be used to implement vastly more complex timers, such as	1604	C<ev_periodic>s can also be used to implement vastly more complex timers,
1230	triggering an event on each midnight, local time or other, complicated,	1605	such as triggering an event on each "midnight, local time", or other
1231	rules.	1606	complicated rules.
1232		1607
1233	As with timers, the callback is guarenteed to be invoked only when the	1608	As with timers, the callback is guaranteed to be invoked only when the
1234	time (C<at>) has been passed, but if multiple periodic timers become ready	1609	time (C<at>) has passed, but if multiple periodic timers become ready
1235	during the same loop iteration then order of execution is undefined.	1610	during the same loop iteration, then order of execution is undefined.
1236		1611
1237	=head3 Watcher-Specific Functions and Data Members	1612	=head3 Watcher-Specific Functions and Data Members
1238		1613
1239	=over 4	1614	=over 4
1240		1615
1241	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1242		1617
1243	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1244		1619
1245	Lots of arguments, lets sort it out... There are basically three modes of	1620	Lots of arguments, lets sort it out... There are basically three modes of
1246	operation, and we will explain them from simplest to complex:	1621	operation, and we will explain them from simplest to most complex:
1247		1622
1248	=over 4	1623	=over 4
1249		1624
1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1251		1626
1252	In this configuration the watcher triggers an event at the wallclock time	1627	In this configuration the watcher triggers an event after the wall clock
1253	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1628	time C<at> has passed. It will not repeat and will not adjust when a time
1254	that is, if it is to be run at January 1st 2011 then it will run when the	1629	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1255	system time reaches or surpasses this time.	1630	only run when the system clock reaches or surpasses this time.
1256		1631
1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1258		1633
1259	In this mode the watcher will always be scheduled to time out at the next	1634	In this mode the watcher will always be scheduled to time out at the next
1260	C<at + N * interval> time (for some integer N, which can also be negative)	1635	C<at + N * interval> time (for some integer N, which can also be negative)
1261	and then repeat, regardless of any time jumps.	1636	and then repeat, regardless of any time jumps.
1262		1637
1263	This can be used to create timers that do not drift with respect to system	1638	This can be used to create timers that do not drift with respect to the
1264	time:	1639	system clock, for example, here is a C<ev_periodic> that triggers each
		1640	hour, on the hour:
1265		1641
1266	ev_periodic_set (&periodic, 0., 3600., 0);	1642	ev_periodic_set (&periodic, 0., 3600., 0);
1267		1643
1268	This doesn't mean there will always be 3600 seconds in between triggers,	1644	This doesn't mean there will always be 3600 seconds in between triggers,
1269	but only that the the callback will be called when the system time shows a	1645	but only that the callback will be called when the system time shows a
1270	full hour (UTC), or more correctly, when the system time is evenly divisible	1646	full hour (UTC), or more correctly, when the system time is evenly divisible
1271	by 3600.	1647	by 3600.
1272		1648
1273	Another way to think about it (for the mathematically inclined) is that	1649	Another way to think about it (for the mathematically inclined) is that
1274	C<ev_periodic> will try to run the callback in this mode at the next possible	1650	C<ev_periodic> will try to run the callback in this mode at the next possible
1275	time where C<time = at (mod interval)>, regardless of any time jumps.	1651	time where C<time = at (mod interval)>, regardless of any time jumps.
1276		1652
1277	For numerical stability it is preferable that the C<at> value is near	1653	For numerical stability it is preferable that the C<at> value is near
1278	C<ev_now ()> (the current time), but there is no range requirement for	1654	C<ev_now ()> (the current time), but there is no range requirement for
1279	this value.	1655	this value, and in fact is often specified as zero.
		1656
		1657	Note also that there is an upper limit to how often a timer can fire (CPU
		1658	speed for example), so if C<interval> is very small then timing stability
		1659	will of course deteriorate. Libev itself tries to be exact to be about one
		1660	millisecond (if the OS supports it and the machine is fast enough).
1280		1661
1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1662	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1282		1663
1283	In this mode the values for C<interval> and C<at> are both being	1664	In this mode the values for C<interval> and C<at> are both being
1284	ignored. Instead, each time the periodic watcher gets scheduled, the	1665	ignored. Instead, each time the periodic watcher gets scheduled, the
1285	reschedule callback will be called with the watcher as first, and the	1666	reschedule callback will be called with the watcher as first, and the
1286	current time as second argument.	1667	current time as second argument.
1287		1668
1288	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1669	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1289	ever, or make any event loop modifications>. If you need to stop it,	1670	ever, or make ANY event loop modifications whatsoever>.
1290	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1291	starting an C<ev_prepare> watcher, which is legal).
1292		1671
		1672	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1674	only event loop modification you are allowed to do).
		1675
1293	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1294	ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1295		1678
		1679	static ev_tstamp
1296	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1297	{	1681	{
1298	return now + 60.;	1682	return now + 60.;
1299	}	1683	}
1300		1684
1301	It must return the next time to trigger, based on the passed time value	1685	It must return the next time to trigger, based on the passed time value
1302	(that is, the lowest time value larger than to the second argument). It	1686	(that is, the lowest time value larger than to the second argument). It
1303	will usually be called just before the callback will be triggered, but	1687	will usually be called just before the callback will be triggered, but
1304	might be called at other times, too.	1688	might be called at other times, too.
1305		1689
1306	NOTE: I<< This callback must always return a time that is later than the	1690	NOTE: I<< This callback must always return a time that is higher than or
1307	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1691	equal to the passed C<now> value >>.
1308		1692
1309	This can be used to create very complex timers, such as a timer that	1693	This can be used to create very complex timers, such as a timer that
1310	triggers on each midnight, local time. To do this, you would calculate the	1694	triggers on "next midnight, local time". To do this, you would calculate the
1311	next midnight after C<now> and return the timestamp value for this. How	1695	next midnight after C<now> and return the timestamp value for this. How
1312	you do this is, again, up to you (but it is not trivial, which is the main	1696	you do this is, again, up to you (but it is not trivial, which is the main
1313	reason I omitted it as an example).	1697	reason I omitted it as an example).
1314		1698
1315	=back	1699	=back
…		…
1319	Simply stops and restarts the periodic watcher again. This is only useful	1703	Simply stops and restarts the periodic watcher again. This is only useful
1320	when you changed some parameters or the reschedule callback would return	1704	when you changed some parameters or the reschedule callback would return
1321	a different time than the last time it was called (e.g. in a crond like	1705	a different time than the last time it was called (e.g. in a crond like
1322	program when the crontabs have changed).	1706	program when the crontabs have changed).
1323		1707
		1708	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1709
		1710	When active, returns the absolute time that the watcher is supposed to
		1711	trigger next.
		1712
1324	=item ev_tstamp offset [read-write]	1713	=item ev_tstamp offset [read-write]
1325		1714
1326	When repeating, this contains the offset value, otherwise this is the	1715	When repeating, this contains the offset value, otherwise this is the
1327	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1716	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1328		1717
…		…
1333		1722
1334	The current interval value. Can be modified any time, but changes only	1723	The current interval value. Can be modified any time, but changes only
1335	take effect when the periodic timer fires or C<ev_periodic_again> is being	1724	take effect when the periodic timer fires or C<ev_periodic_again> is being
1336	called.	1725	called.
1337		1726
1338	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1727	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1339		1728
1340	The current reschedule callback, or C<0>, if this functionality is	1729	The current reschedule callback, or C<0>, if this functionality is
1341	switched off. Can be changed any time, but changes only take effect when	1730	switched off. Can be changed any time, but changes only take effect when
1342	the periodic timer fires or C<ev_periodic_again> is being called.	1731	the periodic timer fires or C<ev_periodic_again> is being called.
1343		1732
1344	=item ev_tstamp at [read-only]
1345
1346	When active, contains the absolute time that the watcher is supposed to
1347	trigger next.
1348
1349	=back	1733	=back
1350		1734
		1735	=head3 Examples
		1736
1351	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1352	system clock is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1353	potentially a lot of jittering, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1354		1740
1355	static void	1741	static void
1356	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1357	{	1743	{
1358	... its now a full hour (UTC, or TAI or whatever your clock follows)	1744	... its now a full hour (UTC, or TAI or whatever your clock follows)
1359	}	1745	}
1360		1746
1361	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1362	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1363	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1364		1750
1365	Example: The same as above, but use a reschedule callback to do it:	1751	Example: The same as above, but use a reschedule callback to do it:
1366		1752
1367	#include <math.h>	1753	#include <math.h>
1368		1754
1369	static ev_tstamp	1755	static ev_tstamp
1370	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1371	{	1757	{
1372	return fmod (now, 3600.) + 3600.;	1758	return now + (3600. - fmod (now, 3600.));
1373	}	1759	}
1374		1760
1375	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1761	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1376		1762
1377	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1378		1764
1379	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1380	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1381	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1382	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1383		1769
1384		1770
1385	=head2 C<ev_signal> - signal me when a signal gets signalled!	1771	=head2 C<ev_signal> - signal me when a signal gets signalled!
1386		1772
1387	Signal watchers will trigger an event when the process receives a specific	1773	Signal watchers will trigger an event when the process receives a specific
1388	signal one or more times. Even though signals are very asynchronous, libev	1774	signal one or more times. Even though signals are very asynchronous, libev
1389	will try it's best to deliver signals synchronously, i.e. as part of the	1775	will try it's best to deliver signals synchronously, i.e. as part of the
1390	normal event processing, like any other event.	1776	normal event processing, like any other event.
1391		1777
		1778	If you want signals asynchronously, just use C<sigaction> as you would
		1779	do without libev and forget about sharing the signal. You can even use
		1780	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1781
1392	You can configure as many watchers as you like per signal. Only when the	1782	You can configure as many watchers as you like per signal. Only when the
1393	first watcher gets started will libev actually register a signal watcher	1783	first watcher gets started will libev actually register a signal handler
1394	with the kernel (thus it coexists with your own signal handlers as long	1784	with the kernel (thus it coexists with your own signal handlers as long as
1395	as you don't register any with libev). Similarly, when the last signal	1785	you don't register any with libev for the same signal). Similarly, when
1396	watcher for a signal is stopped libev will reset the signal handler to	1786	the last signal watcher for a signal is stopped, libev will reset the
1397	SIG_DFL (regardless of what it was set to before).	1787	signal handler to SIG_DFL (regardless of what it was set to before).
		1788
		1789	If possible and supported, libev will install its handlers with
		1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1791	interrupted. If you have a problem with system calls getting interrupted by
		1792	signals you can block all signals in an C<ev_check> watcher and unblock
		1793	them in an C<ev_prepare> watcher.
1398		1794
1399	=head3 Watcher-Specific Functions and Data Members	1795	=head3 Watcher-Specific Functions and Data Members
1400		1796
1401	=over 4	1797	=over 4
1402		1798
…		…
1411		1807
1412	The signal the watcher watches out for.	1808	The signal the watcher watches out for.
1413		1809
1414	=back	1810	=back
1415		1811
		1812	=head3 Examples
		1813
		1814	Example: Try to exit cleanly on SIGINT.
		1815
		1816	static void
		1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1818	{
		1819	ev_unloop (loop, EVUNLOOP_ALL);
		1820	}
		1821
		1822	ev_signal signal_watcher;
		1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1824	ev_signal_start (loop, &signal_watcher);
		1825
1416		1826
1417	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
1418		1828
1419	Child watchers trigger when your process receives a SIGCHLD in response to	1829	Child watchers trigger when your process receives a SIGCHLD in response to
1420	some child status changes (most typically when a child of yours dies).	1830	some child status changes (most typically when a child of yours dies or
		1831	exits). It is permissible to install a child watcher I<after> the child
		1832	has been forked (which implies it might have already exited), as long
		1833	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1834	forking and then immediately registering a watcher for the child is fine,
		1835	but forking and registering a watcher a few event loop iterations later is
		1836	not.
		1837
		1838	Only the default event loop is capable of handling signals, and therefore
		1839	you can only register child watchers in the default event loop.
		1840
		1841	=head3 Process Interaction
		1842
		1843	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1844	initialised. This is necessary to guarantee proper behaviour even if
		1845	the first child watcher is started after the child exits. The occurrence
		1846	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1847	synchronously as part of the event loop processing. Libev always reaps all
		1848	children, even ones not watched.
		1849
		1850	=head3 Overriding the Built-In Processing
		1851
		1852	Libev offers no special support for overriding the built-in child
		1853	processing, but if your application collides with libev's default child
		1854	handler, you can override it easily by installing your own handler for
		1855	C<SIGCHLD> after initialising the default loop, and making sure the
		1856	default loop never gets destroyed. You are encouraged, however, to use an
		1857	event-based approach to child reaping and thus use libev's support for
		1858	that, so other libev users can use C<ev_child> watchers freely.
		1859
		1860	=head3 Stopping the Child Watcher
		1861
		1862	Currently, the child watcher never gets stopped, even when the
		1863	child terminates, so normally one needs to stop the watcher in the
		1864	callback. Future versions of libev might stop the watcher automatically
		1865	when a child exit is detected.
1421		1866
1422	=head3 Watcher-Specific Functions and Data Members	1867	=head3 Watcher-Specific Functions and Data Members
1423		1868
1424	=over 4	1869	=over 4
1425		1870
1426	=item ev_child_init (ev_child *, callback, int pid)	1871	=item ev_child_init (ev_child *, callback, int pid, int trace)
1427		1872
1428	=item ev_child_set (ev_child *, int pid)	1873	=item ev_child_set (ev_child *, int pid, int trace)
1429		1874
1430	Configures the watcher to wait for status changes of process C<pid> (or	1875	Configures the watcher to wait for status changes of process C<pid> (or
1431	I<any> process if C<pid> is specified as C<0>). The callback can look	1876	I<any> process if C<pid> is specified as C<0>). The callback can look
1432	at the C<rstatus> member of the C<ev_child> watcher structure to see	1877	at the C<rstatus> member of the C<ev_child> watcher structure to see
1433	the status word (use the macros from C<sys/wait.h> and see your systems	1878	the status word (use the macros from C<sys/wait.h> and see your systems
1434	C<waitpid> documentation). The C<rpid> member contains the pid of the	1879	C<waitpid> documentation). The C<rpid> member contains the pid of the
1435	process causing the status change.	1880	process causing the status change. C<trace> must be either C<0> (only
		1881	activate the watcher when the process terminates) or C<1> (additionally
		1882	activate the watcher when the process is stopped or continued).
1436		1883
1437	=item int pid [read-only]	1884	=item int pid [read-only]
1438		1885
1439	The process id this watcher watches out for, or C<0>, meaning any process id.	1886	The process id this watcher watches out for, or C<0>, meaning any process id.
1440		1887
…		…
1447	The process exit/trace status caused by C<rpid> (see your systems	1894	The process exit/trace status caused by C<rpid> (see your systems
1448	C<waitpid> and C<sys/wait.h> documentation for details).	1895	C<waitpid> and C<sys/wait.h> documentation for details).
1449		1896
1450	=back	1897	=back
1451		1898
1452	Example: Try to exit cleanly on SIGINT and SIGTERM.	1899	=head3 Examples
1453		1900
		1901	Example: C<fork()> a new process and install a child handler to wait for
		1902	its completion.
		1903
		1904	ev_child cw;
		1905
1454	static void	1906	static void
1455	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1456	{	1908	{
1457	ev_unloop (loop, EVUNLOOP_ALL);	1909	ev_child_stop (EV_A_ w);
		1910	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1458	}	1911	}
1459		1912
1460	struct ev_signal signal_watcher;	1913	pid_t pid = fork ();
1461	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1914
1462	ev_signal_start (loop, &sigint_cb);	1915	if (pid < 0)
		1916	// error
		1917	else if (pid == 0)
		1918	{
		1919	// the forked child executes here
		1920	exit (1);
		1921	}
		1922	else
		1923	{
		1924	ev_child_init (&cw, child_cb, pid, 0);
		1925	ev_child_start (EV_DEFAULT_ &cw);
		1926	}
1463		1927
1464		1928
1465	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1466		1930
1467	This watches a filesystem path for attribute changes. That is, it calls	1931	This watches a file system path for attribute changes. That is, it calls
1468	C<stat> regularly (or when the OS says it changed) and sees if it changed	1932	C<stat> on that path in regular intervals (or when the OS says it changed)
1469	compared to the last time, invoking the callback if it did.	1933	and sees if it changed compared to the last time, invoking the callback if
		1934	it did.
1470		1935
1471	The path does not need to exist: changing from "path exists" to "path does	1936	The path does not need to exist: changing from "path exists" to "path does
1472	not exist" is a status change like any other. The condition "path does	1937	not exist" is a status change like any other. The condition "path does
1473	not exist" is signified by the C<st_nlink> field being zero (which is	1938	not exist" is signified by the C<st_nlink> field being zero (which is
1474	otherwise always forced to be at least one) and all the other fields of	1939	otherwise always forced to be at least one) and all the other fields of
1475	the stat buffer having unspecified contents.	1940	the stat buffer having unspecified contents.
1476		1941
1477	The path I<should> be absolute and I<must not> end in a slash. If it is	1942	The path I<must not> end in a slash or contain special components such as
		1943	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1478	relative and your working directory changes, the behaviour is undefined.	1944	your working directory changes, then the behaviour is undefined.
1479		1945
1480	Since there is no standard to do this, the portable implementation simply	1946	Since there is no portable change notification interface available, the
1481	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1947	portable implementation simply calls C<stat(2)> regularly on the path
1482	can specify a recommended polling interval for this case. If you specify	1948	to see if it changed somehow. You can specify a recommended polling
1483	a polling interval of C<0> (highly recommended!) then a I<suitable,	1949	interval for this case. If you specify a polling interval of C<0> (highly
1484	unspecified default> value will be used (which you can expect to be around	1950	recommended!) then a I<suitable, unspecified default> value will be used
1485	five seconds, although this might change dynamically). Libev will also	1951	(which you can expect to be around five seconds, although this might
1486	impose a minimum interval which is currently around C<0.1>, but thats	1952	change dynamically). Libev will also impose a minimum interval which is
1487	usually overkill.	1953	currently around C<0.1>, but that's usually overkill.
1488		1954
1489	This watcher type is not meant for massive numbers of stat watchers,	1955	This watcher type is not meant for massive numbers of stat watchers,
1490	as even with OS-supported change notifications, this can be	1956	as even with OS-supported change notifications, this can be
1491	resource-intensive.	1957	resource-intensive.
1492		1958
1493	At the time of this writing, only the Linux inotify interface is	1959	At the time of this writing, the only OS-specific interface implemented
1494	implemented (implementing kqueue support is left as an exercise for the	1960	is the Linux inotify interface (implementing kqueue support is left as
1495	reader). Inotify will be used to give hints only and should not change the	1961	an exercise for the reader. Note, however, that the author sees no way
1496	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1962	of implementing C<ev_stat> semantics with kqueue).
1497	to fall back to regular polling again even with inotify, but changes are	1963
1498	usually detected immediately, and if the file exists there will be no	1964	=head3 ABI Issues (Largefile Support)
1499	polling.	1965
		1966	Libev by default (unless the user overrides this) uses the default
		1967	compilation environment, which means that on systems with large file
		1968	support disabled by default, you get the 32 bit version of the stat
		1969	structure. When using the library from programs that change the ABI to
		1970	use 64 bit file offsets the programs will fail. In that case you have to
		1971	compile libev with the same flags to get binary compatibility. This is
		1972	obviously the case with any flags that change the ABI, but the problem is
		1973	most noticeably displayed with ev_stat and large file support.
		1974
		1975	The solution for this is to lobby your distribution maker to make large
		1976	file interfaces available by default (as e.g. FreeBSD does) and not
		1977	optional. Libev cannot simply switch on large file support because it has
		1978	to exchange stat structures with application programs compiled using the
		1979	default compilation environment.
		1980
		1981	=head3 Inotify and Kqueue
		1982
		1983	When C<inotify (7)> support has been compiled into libev (generally
		1984	only available with Linux 2.6.25 or above due to bugs in earlier
		1985	implementations) and present at runtime, it will be used to speed up
		1986	change detection where possible. The inotify descriptor will be created
		1987	lazily when the first C<ev_stat> watcher is being started.
		1988
		1989	Inotify presence does not change the semantics of C<ev_stat> watchers
		1990	except that changes might be detected earlier, and in some cases, to avoid
		1991	making regular C<stat> calls. Even in the presence of inotify support
		1992	there are many cases where libev has to resort to regular C<stat> polling,
		1993	but as long as the path exists, libev usually gets away without polling.
		1994
		1995	There is no support for kqueue, as apparently it cannot be used to
		1996	implement this functionality, due to the requirement of having a file
		1997	descriptor open on the object at all times, and detecting renames, unlinks
		1998	etc. is difficult.
		1999
		2000	=head3 The special problem of stat time resolution
		2001
		2002	The C<stat ()> system call only supports full-second resolution portably,
		2003	and even on systems where the resolution is higher, most file systems
		2004	still only support whole seconds.
		2005
		2006	That means that, if the time is the only thing that changes, you can
		2007	easily miss updates: on the first update, C<ev_stat> detects a change and
		2008	calls your callback, which does something. When there is another update
		2009	within the same second, C<ev_stat> will be unable to detect unless the
		2010	stat data does change in other ways (e.g. file size).
		2011
		2012	The solution to this is to delay acting on a change for slightly more
		2013	than a second (or till slightly after the next full second boundary), using
		2014	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		2015	ev_timer_again (loop, w)>).
		2016
		2017	The C<.02> offset is added to work around small timing inconsistencies
		2018	of some operating systems (where the second counter of the current time
		2019	might be be delayed. One such system is the Linux kernel, where a call to
		2020	C<gettimeofday> might return a timestamp with a full second later than
		2021	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2022	update file times then there will be a small window where the kernel uses
		2023	the previous second to update file times but libev might already execute
		2024	the timer callback).
1500		2025
1501	=head3 Watcher-Specific Functions and Data Members	2026	=head3 Watcher-Specific Functions and Data Members
1502		2027
1503	=over 4	2028	=over 4
1504		2029
…		…
1510	C<path>. The C<interval> is a hint on how quickly a change is expected to	2035	C<path>. The C<interval> is a hint on how quickly a change is expected to
1511	be detected and should normally be specified as C<0> to let libev choose	2036	be detected and should normally be specified as C<0> to let libev choose
1512	a suitable value. The memory pointed to by C<path> must point to the same	2037	a suitable value. The memory pointed to by C<path> must point to the same
1513	path for as long as the watcher is active.	2038	path for as long as the watcher is active.
1514		2039
1515	The callback will be receive C<EV_STAT> when a change was detected,	2040	The callback will receive an C<EV_STAT> event when a change was detected,
1516	relative to the attributes at the time the watcher was started (or the	2041	relative to the attributes at the time the watcher was started (or the
1517	last change was detected).	2042	last change was detected).
1518		2043
1519	=item ev_stat_stat (ev_stat *)	2044	=item ev_stat_stat (loop, ev_stat *)
1520		2045
1521	Updates the stat buffer immediately with new values. If you change the	2046	Updates the stat buffer immediately with new values. If you change the
1522	watched path in your callback, you could call this fucntion to avoid	2047	watched path in your callback, you could call this function to avoid
1523	detecting this change (while introducing a race condition). Can also be	2048	detecting this change (while introducing a race condition if you are not
1524	useful simply to find out the new values.	2049	the only one changing the path). Can also be useful simply to find out the
		2050	new values.
1525		2051
1526	=item ev_statdata attr [read-only]	2052	=item ev_statdata attr [read-only]
1527		2053
1528	The most-recently detected attributes of the file. Although the type is of	2054	The most-recently detected attributes of the file. Although the type is
1529	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2055	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1530	suitable for your system. If the C<st_nlink> member is C<0>, then there	2056	suitable for your system, but you can only rely on the POSIX-standardised
		2057	members to be present. If the C<st_nlink> member is C<0>, then there was
1531	was some error while C<stat>ing the file.	2058	some error while C<stat>ing the file.
1532		2059
1533	=item ev_statdata prev [read-only]	2060	=item ev_statdata prev [read-only]
1534		2061
1535	The previous attributes of the file. The callback gets invoked whenever	2062	The previous attributes of the file. The callback gets invoked whenever
1536	C<prev> != C<attr>.	2063	C<prev> != C<attr>, or, more precisely, one or more of these members
		2064	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2065	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1537		2066
1538	=item ev_tstamp interval [read-only]	2067	=item ev_tstamp interval [read-only]
1539		2068
1540	The specified interval.	2069	The specified interval.
1541		2070
1542	=item const char *path [read-only]	2071	=item const char *path [read-only]
1543		2072
1544	The filesystem path that is being watched.	2073	The file system path that is being watched.
1545		2074
1546	=back	2075	=back
1547		2076
		2077	=head3 Examples
		2078
1548	Example: Watch C</etc/passwd> for attribute changes.	2079	Example: Watch C</etc/passwd> for attribute changes.
1549		2080
1550	static void	2081	static void
1551	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2082	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1552	{	2083	{
1553	/* /etc/passwd changed in some way */	2084	/* /etc/passwd changed in some way */
1554	if (w->attr.st_nlink)	2085	if (w->attr.st_nlink)
1555	{	2086	{
1556	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2087	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1557	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2088	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1558	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2089	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1559	}	2090	}
1560	else	2091	else
1561	/* you shalt not abuse printf for puts */	2092	/* you shalt not abuse printf for puts */
1562	puts ("wow, /etc/passwd is not there, expect problems. "	2093	puts ("wow, /etc/passwd is not there, expect problems. "
1563	"if this is windows, they already arrived\n");	2094	"if this is windows, they already arrived\n");
1564	}	2095	}
1565		2096
1566	...	2097	...
1567	ev_stat passwd;	2098	ev_stat passwd;
1568		2099
1569	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2100	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1570	ev_stat_start (loop, &passwd);	2101	ev_stat_start (loop, &passwd);
		2102
		2103	Example: Like above, but additionally use a one-second delay so we do not
		2104	miss updates (however, frequent updates will delay processing, too, so
		2105	one might do the work both on C<ev_stat> callback invocation I<and> on
		2106	C<ev_timer> callback invocation).
		2107
		2108	static ev_stat passwd;
		2109	static ev_timer timer;
		2110
		2111	static void
		2112	timer_cb (EV_P_ ev_timer *w, int revents)
		2113	{
		2114	ev_timer_stop (EV_A_ w);
		2115
		2116	/* now it's one second after the most recent passwd change */
		2117	}
		2118
		2119	static void
		2120	stat_cb (EV_P_ ev_stat *w, int revents)
		2121	{
		2122	/* reset the one-second timer */
		2123	ev_timer_again (EV_A_ &timer);
		2124	}
		2125
		2126	...
		2127	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		2128	ev_stat_start (loop, &passwd);
		2129	ev_timer_init (&timer, timer_cb, 0., 1.02);
1571		2130
1572		2131
1573	=head2 C<ev_idle> - when you've got nothing better to do...	2132	=head2 C<ev_idle> - when you've got nothing better to do...
1574		2133
1575	Idle watchers trigger events when no other events of the same or higher	2134	Idle watchers trigger events when no other events of the same or higher
1576	priority are pending (prepare, check and other idle watchers do not	2135	priority are pending (prepare, check and other idle watchers do not count
1577	count).	2136	as receiving "events").
1578		2137
1579	That is, as long as your process is busy handling sockets or timeouts	2138	That is, as long as your process is busy handling sockets or timeouts
1580	(or even signals, imagine) of the same or higher priority it will not be	2139	(or even signals, imagine) of the same or higher priority it will not be
1581	triggered. But when your process is idle (or only lower-priority watchers	2140	triggered. But when your process is idle (or only lower-priority watchers
1582	are pending), the idle watchers are being called once per event loop	2141	are pending), the idle watchers are being called once per event loop
…		…
1601	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2160	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1602	believe me.	2161	believe me.
1603		2162
1604	=back	2163	=back
1605		2164
		2165	=head3 Examples
		2166
1606	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2167	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1607	callback, free it. Also, use no error checking, as usual.	2168	callback, free it. Also, use no error checking, as usual.
1608		2169
1609	static void	2170	static void
1610	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2171	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1611	{	2172	{
1612	free (w);	2173	free (w);
1613	// now do something you wanted to do when the program has	2174	// now do something you wanted to do when the program has
1614	// no longer asnything immediate to do.	2175	// no longer anything immediate to do.
1615	}	2176	}
1616		2177
1617	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2178	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1618	ev_idle_init (idle_watcher, idle_cb);	2179	ev_idle_init (idle_watcher, idle_cb);
1619	ev_idle_start (loop, idle_cb);	2180	ev_idle_start (loop, idle_cb);
1620		2181
1621		2182
1622	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2183	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1623		2184
1624	Prepare and check watchers are usually (but not always) used in tandem:	2185	Prepare and check watchers are usually (but not always) used in pairs:
1625	prepare watchers get invoked before the process blocks and check watchers	2186	prepare watchers get invoked before the process blocks and check watchers
1626	afterwards.	2187	afterwards.
1627		2188
1628	You I<must not> call C<ev_loop> or similar functions that enter	2189	You I<must not> call C<ev_loop> or similar functions that enter
1629	the current event loop from either C<ev_prepare> or C<ev_check>	2190	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1632	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2193	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1633	C<ev_check> so if you have one watcher of each kind they will always be	2194	C<ev_check> so if you have one watcher of each kind they will always be
1634	called in pairs bracketing the blocking call.	2195	called in pairs bracketing the blocking call.
1635		2196
1636	Their main purpose is to integrate other event mechanisms into libev and	2197	Their main purpose is to integrate other event mechanisms into libev and
1637	their use is somewhat advanced. This could be used, for example, to track	2198	their use is somewhat advanced. They could be used, for example, to track
1638	variable changes, implement your own watchers, integrate net-snmp or a	2199	variable changes, implement your own watchers, integrate net-snmp or a
1639	coroutine library and lots more. They are also occasionally useful if	2200	coroutine library and lots more. They are also occasionally useful if
1640	you cache some data and want to flush it before blocking (for example,	2201	you cache some data and want to flush it before blocking (for example,
1641	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2202	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1642	watcher).	2203	watcher).
1643		2204
1644	This is done by examining in each prepare call which file descriptors need	2205	This is done by examining in each prepare call which file descriptors
1645	to be watched by the other library, registering C<ev_io> watchers for	2206	need to be watched by the other library, registering C<ev_io> watchers
1646	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2207	for them and starting an C<ev_timer> watcher for any timeouts (many
1647	provide just this functionality). Then, in the check watcher you check for	2208	libraries provide exactly this functionality). Then, in the check watcher,
1648	any events that occured (by checking the pending status of all watchers	2209	you check for any events that occurred (by checking the pending status
1649	and stopping them) and call back into the library. The I/O and timer	2210	of all watchers and stopping them) and call back into the library. The
1650	callbacks will never actually be called (but must be valid nevertheless,	2211	I/O and timer callbacks will never actually be called (but must be valid
1651	because you never know, you know?).	2212	nevertheless, because you never know, you know?).
1652		2213
1653	As another example, the Perl Coro module uses these hooks to integrate	2214	As another example, the Perl Coro module uses these hooks to integrate
1654	coroutines into libev programs, by yielding to other active coroutines	2215	coroutines into libev programs, by yielding to other active coroutines
1655	during each prepare and only letting the process block if no coroutines	2216	during each prepare and only letting the process block if no coroutines
1656	are ready to run (it's actually more complicated: it only runs coroutines	2217	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1659	loop from blocking if lower-priority coroutines are active, thus mapping	2220	loop from blocking if lower-priority coroutines are active, thus mapping
1660	low-priority coroutines to idle/background tasks).	2221	low-priority coroutines to idle/background tasks).
1661		2222
1662	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2223	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1663	priority, to ensure that they are being run before any other watchers	2224	priority, to ensure that they are being run before any other watchers
		2225	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2226
1664	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2227	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1665	too) should not activate ("feed") events into libev. While libev fully	2228	activate ("feed") events into libev. While libev fully supports this, they
1666	supports this, they will be called before other C<ev_check> watchers	2229	might get executed before other C<ev_check> watchers did their job. As
1667	did their job. As C<ev_check> watchers are often used to embed other	2230	C<ev_check> watchers are often used to embed other (non-libev) event
1668	(non-libev) event loops those other event loops might be in an unusable	2231	loops those other event loops might be in an unusable state until their
1669	state until their C<ev_check> watcher ran (always remind yourself to	2232	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1670	coexist peacefully with others).	2233	others).
1671		2234
1672	=head3 Watcher-Specific Functions and Data Members	2235	=head3 Watcher-Specific Functions and Data Members
1673		2236
1674	=over 4	2237	=over 4
1675		2238
…		…
1677		2240
1678	=item ev_check_init (ev_check *, callback)	2241	=item ev_check_init (ev_check *, callback)
1679		2242
1680	Initialises and configures the prepare or check watcher - they have no	2243	Initialises and configures the prepare or check watcher - they have no
1681	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2244	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1682	macros, but using them is utterly, utterly and completely pointless.	2245	macros, but using them is utterly, utterly, utterly and completely
		2246	pointless.
1683		2247
1684	=back	2248	=back
		2249
		2250	=head3 Examples
1685		2251
1686	There are a number of principal ways to embed other event loops or modules	2252	There are a number of principal ways to embed other event loops or modules
1687	into libev. Here are some ideas on how to include libadns into libev	2253	into libev. Here are some ideas on how to include libadns into libev
1688	(there is a Perl module named C<EV::ADNS> that does this, which you could	2254	(there is a Perl module named C<EV::ADNS> that does this, which you could
1689	use for an actually working example. Another Perl module named C<EV::Glib>	2255	use as a working example. Another Perl module named C<EV::Glib> embeds a
1690	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2256	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1691	into the Glib event loop).	2257	Glib event loop).
1692		2258
1693	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2259	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1694	and in a check watcher, destroy them and call into libadns. What follows	2260	and in a check watcher, destroy them and call into libadns. What follows
1695	is pseudo-code only of course. This requires you to either use a low	2261	is pseudo-code only of course. This requires you to either use a low
1696	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2262	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1697	the callbacks for the IO/timeout watchers might not have been called yet.	2263	the callbacks for the IO/timeout watchers might not have been called yet.
1698		2264
1699	static ev_io iow [nfd];	2265	static ev_io iow [nfd];
1700	static ev_timer tw;	2266	static ev_timer tw;
1701		2267
1702	static void	2268	static void
1703	io_cb (ev_loop *loop, ev_io *w, int revents)	2269	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1704	{	2270	{
1705	}	2271	}
1706		2272
1707	// create io watchers for each fd and a timer before blocking	2273	// create io watchers for each fd and a timer before blocking
1708	static void	2274	static void
1709	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2275	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1710	{	2276	{
1711	int timeout = 3600000;	2277	int timeout = 3600000;
1712	struct pollfd fds [nfd];	2278	struct pollfd fds [nfd];
1713	// actual code will need to loop here and realloc etc.	2279	// actual code will need to loop here and realloc etc.
1714	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2280	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1715		2281
1716	/* the callback is illegal, but won't be called as we stop during check */	2282	/* the callback is illegal, but won't be called as we stop during check */
1717	ev_timer_init (&tw, 0, timeout * 1e-3);	2283	ev_timer_init (&tw, 0, timeout * 1e-3);
1718	ev_timer_start (loop, &tw);	2284	ev_timer_start (loop, &tw);
1719		2285
1720	// create one ev_io per pollfd	2286	// create one ev_io per pollfd
1721	for (int i = 0; i < nfd; ++i)	2287	for (int i = 0; i < nfd; ++i)
1722	{	2288	{
1723	ev_io_init (iow + i, io_cb, fds [i].fd,	2289	ev_io_init (iow + i, io_cb, fds [i].fd,
1724	((fds [i].events & POLLIN ? EV_READ : 0)	2290	((fds [i].events & POLLIN ? EV_READ : 0)
1725	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2291	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1726		2292
1727	fds [i].revents = 0;	2293	fds [i].revents = 0;
1728	ev_io_start (loop, iow + i);	2294	ev_io_start (loop, iow + i);
1729	}	2295	}
1730	}	2296	}
1731		2297
1732	// stop all watchers after blocking	2298	// stop all watchers after blocking
1733	static void	2299	static void
1734	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2300	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1735	{	2301	{
1736	ev_timer_stop (loop, &tw);	2302	ev_timer_stop (loop, &tw);
1737		2303
1738	for (int i = 0; i < nfd; ++i)	2304	for (int i = 0; i < nfd; ++i)
1739	{	2305	{
1740	// set the relevant poll flags	2306	// set the relevant poll flags
1741	// could also call adns_processreadable etc. here	2307	// could also call adns_processreadable etc. here
1742	struct pollfd *fd = fds + i;	2308	struct pollfd *fd = fds + i;
1743	int revents = ev_clear_pending (iow + i);	2309	int revents = ev_clear_pending (iow + i);
1744	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2310	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1745	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2311	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1746		2312
1747	// now stop the watcher	2313	// now stop the watcher
1748	ev_io_stop (loop, iow + i);	2314	ev_io_stop (loop, iow + i);
1749	}	2315	}
1750		2316
1751	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2317	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1752	}	2318	}
1753		2319
1754	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2320	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1755	in the prepare watcher and would dispose of the check watcher.	2321	in the prepare watcher and would dispose of the check watcher.
1756		2322
1757	Method 3: If the module to be embedded supports explicit event	2323	Method 3: If the module to be embedded supports explicit event
1758	notification (adns does), you can also make use of the actual watcher	2324	notification (libadns does), you can also make use of the actual watcher
1759	callbacks, and only destroy/create the watchers in the prepare watcher.	2325	callbacks, and only destroy/create the watchers in the prepare watcher.
1760		2326
1761	static void	2327	static void
1762	timer_cb (EV_P_ ev_timer *w, int revents)	2328	timer_cb (EV_P_ ev_timer *w, int revents)
1763	{	2329	{
1764	adns_state ads = (adns_state)w->data;	2330	adns_state ads = (adns_state)w->data;
1765	update_now (EV_A);	2331	update_now (EV_A);
1766		2332
1767	adns_processtimeouts (ads, &tv_now);	2333	adns_processtimeouts (ads, &tv_now);
1768	}	2334	}
1769		2335
1770	static void	2336	static void
1771	io_cb (EV_P_ ev_io *w, int revents)	2337	io_cb (EV_P_ ev_io *w, int revents)
1772	{	2338	{
1773	adns_state ads = (adns_state)w->data;	2339	adns_state ads = (adns_state)w->data;
1774	update_now (EV_A);	2340	update_now (EV_A);
1775		2341
1776	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2342	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1777	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2343	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1778	}	2344	}
1779		2345
1780	// do not ever call adns_afterpoll	2346	// do not ever call adns_afterpoll
1781		2347
1782	Method 4: Do not use a prepare or check watcher because the module you	2348	Method 4: Do not use a prepare or check watcher because the module you
1783	want to embed is too inflexible to support it. Instead, youc na override	2349	want to embed is not flexible enough to support it. Instead, you can
1784	their poll function. The drawback with this solution is that the main	2350	override their poll function. The drawback with this solution is that the
1785	loop is now no longer controllable by EV. The C<Glib::EV> module does	2351	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1786	this.	2352	this approach, effectively embedding EV as a client into the horrible
		2353	libglib event loop.
1787		2354
1788	static gint	2355	static gint
1789	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2356	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1790	{	2357	{
1791	int got_events = 0;	2358	int got_events = 0;
1792		2359
1793	for (n = 0; n < nfds; ++n)	2360	for (n = 0; n < nfds; ++n)
1794	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2361	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1795		2362
1796	if (timeout >= 0)	2363	if (timeout >= 0)
1797	// create/start timer	2364	// create/start timer
1798		2365
1799	// poll	2366	// poll
1800	ev_loop (EV_A_ 0);	2367	ev_loop (EV_A_ 0);
1801		2368
1802	// stop timer again	2369	// stop timer again
1803	if (timeout >= 0)	2370	if (timeout >= 0)
1804	ev_timer_stop (EV_A_ &to);	2371	ev_timer_stop (EV_A_ &to);
1805		2372
1806	// stop io watchers again - their callbacks should have set	2373	// stop io watchers again - their callbacks should have set
1807	for (n = 0; n < nfds; ++n)	2374	for (n = 0; n < nfds; ++n)
1808	ev_io_stop (EV_A_ iow [n]);	2375	ev_io_stop (EV_A_ iow [n]);
1809		2376
1810	return got_events;	2377	return got_events;
1811	}	2378	}
1812		2379
1813		2380
1814	=head2 C<ev_embed> - when one backend isn't enough...	2381	=head2 C<ev_embed> - when one backend isn't enough...
1815		2382
1816	This is a rather advanced watcher type that lets you embed one event loop	2383	This is a rather advanced watcher type that lets you embed one event loop
…		…
1822	prioritise I/O.	2389	prioritise I/O.
1823		2390
1824	As an example for a bug workaround, the kqueue backend might only support	2391	As an example for a bug workaround, the kqueue backend might only support
1825	sockets on some platform, so it is unusable as generic backend, but you	2392	sockets on some platform, so it is unusable as generic backend, but you
1826	still want to make use of it because you have many sockets and it scales	2393	still want to make use of it because you have many sockets and it scales
1827	so nicely. In this case, you would create a kqueue-based loop and embed it	2394	so nicely. In this case, you would create a kqueue-based loop and embed
1828	into your default loop (which might use e.g. poll). Overall operation will	2395	it into your default loop (which might use e.g. poll). Overall operation
1829	be a bit slower because first libev has to poll and then call kevent, but	2396	will be a bit slower because first libev has to call C<poll> and then
1830	at least you can use both at what they are best.	2397	C<kevent>, but at least you can use both mechanisms for what they are
		2398	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1831		2399
1832	As for prioritising I/O: rarely you have the case where some fds have	2400	As for prioritising I/O: under rare circumstances you have the case where
1833	to be watched and handled very quickly (with low latency), and even	2401	some fds have to be watched and handled very quickly (with low latency),
1834	priorities and idle watchers might have too much overhead. In this case	2402	and even priorities and idle watchers might have too much overhead. In
1835	you would put all the high priority stuff in one loop and all the rest in	2403	this case you would put all the high priority stuff in one loop and all
1836	a second one, and embed the second one in the first.	2404	the rest in a second one, and embed the second one in the first.
1837		2405
1838	As long as the watcher is active, the callback will be invoked every time	2406	As long as the watcher is active, the callback will be invoked every time
1839	there might be events pending in the embedded loop. The callback must then	2407	there might be events pending in the embedded loop. The callback must then
1840	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2408	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1841	their callbacks (you could also start an idle watcher to give the embedded	2409	their callbacks (you could also start an idle watcher to give the embedded
…		…
1849	interested in that.	2417	interested in that.
1850		2418
1851	Also, there have not currently been made special provisions for forking:	2419	Also, there have not currently been made special provisions for forking:
1852	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2420	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1853	but you will also have to stop and restart any C<ev_embed> watchers	2421	but you will also have to stop and restart any C<ev_embed> watchers
1854	yourself.	2422	yourself - but you can use a fork watcher to handle this automatically,
		2423	and future versions of libev might do just that.
1855		2424
1856	Unfortunately, not all backends are embeddable, only the ones returned by	2425	Unfortunately, not all backends are embeddable: only the ones returned by
1857	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2426	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1858	portable one.	2427	portable one.
1859		2428
1860	So when you want to use this feature you will always have to be prepared	2429	So when you want to use this feature you will always have to be prepared
1861	that you cannot get an embeddable loop. The recommended way to get around	2430	that you cannot get an embeddable loop. The recommended way to get around
1862	this is to have a separate variables for your embeddable loop, try to	2431	this is to have a separate variables for your embeddable loop, try to
1863	create it, and if that fails, use the normal loop for everything:	2432	create it, and if that fails, use the normal loop for everything.
1864		2433
1865	struct ev_loop *loop_hi = ev_default_init (0);	2434	=head3 C<ev_embed> and fork
1866	struct ev_loop *loop_lo = 0;
1867	struct ev_embed embed;
1868
1869	// see if there is a chance of getting one that works
1870	// (remember that a flags value of 0 means autodetection)
1871	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1872	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1873	: 0;
1874		2435
1875	// if we got one, then embed it, otherwise default to loop_hi	2436	While the C<ev_embed> watcher is running, forks in the embedding loop will
1876	if (loop_lo)	2437	automatically be applied to the embedded loop as well, so no special
1877	{	2438	fork handling is required in that case. When the watcher is not running,
1878	ev_embed_init (&embed, 0, loop_lo);	2439	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1879	ev_embed_start (loop_hi, &embed);	2440	as applicable.
1880	}
1881	else
1882	loop_lo = loop_hi;
1883		2441
1884	=head3 Watcher-Specific Functions and Data Members	2442	=head3 Watcher-Specific Functions and Data Members
1885		2443
1886	=over 4	2444	=over 4
1887		2445
…		…
1891		2449
1892	Configures the watcher to embed the given loop, which must be	2450	Configures the watcher to embed the given loop, which must be
1893	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2451	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1894	invoked automatically, otherwise it is the responsibility of the callback	2452	invoked automatically, otherwise it is the responsibility of the callback
1895	to invoke it (it will continue to be called until the sweep has been done,	2453	to invoke it (it will continue to be called until the sweep has been done,
1896	if you do not want thta, you need to temporarily stop the embed watcher).	2454	if you do not want that, you need to temporarily stop the embed watcher).
1897		2455
1898	=item ev_embed_sweep (loop, ev_embed *)	2456	=item ev_embed_sweep (loop, ev_embed *)
1899		2457
1900	Make a single, non-blocking sweep over the embedded loop. This works	2458	Make a single, non-blocking sweep over the embedded loop. This works
1901	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2459	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1902	apropriate way for embedded loops.	2460	appropriate way for embedded loops.
1903		2461
1904	=item struct ev_loop *other [read-only]	2462	=item struct ev_loop *other [read-only]
1905		2463
1906	The embedded event loop.	2464	The embedded event loop.
1907		2465
1908	=back	2466	=back
		2467
		2468	=head3 Examples
		2469
		2470	Example: Try to get an embeddable event loop and embed it into the default
		2471	event loop. If that is not possible, use the default loop. The default
		2472	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2473	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2474	used).
		2475
		2476	struct ev_loop *loop_hi = ev_default_init (0);
		2477	struct ev_loop *loop_lo = 0;
		2478	ev_embed embed;
		2479
		2480	// see if there is a chance of getting one that works
		2481	// (remember that a flags value of 0 means autodetection)
		2482	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2483	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2484	: 0;
		2485
		2486	// if we got one, then embed it, otherwise default to loop_hi
		2487	if (loop_lo)
		2488	{
		2489	ev_embed_init (&embed, 0, loop_lo);
		2490	ev_embed_start (loop_hi, &embed);
		2491	}
		2492	else
		2493	loop_lo = loop_hi;
		2494
		2495	Example: Check if kqueue is available but not recommended and create
		2496	a kqueue backend for use with sockets (which usually work with any
		2497	kqueue implementation). Store the kqueue/socket-only event loop in
		2498	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2499
		2500	struct ev_loop *loop = ev_default_init (0);
		2501	struct ev_loop *loop_socket = 0;
		2502	ev_embed embed;
		2503
		2504	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2505	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2506	{
		2507	ev_embed_init (&embed, 0, loop_socket);
		2508	ev_embed_start (loop, &embed);
		2509	}
		2510
		2511	if (!loop_socket)
		2512	loop_socket = loop;
		2513
		2514	// now use loop_socket for all sockets, and loop for everything else
1909		2515
1910		2516
1911	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2517	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1912		2518
1913	Fork watchers are called when a C<fork ()> was detected (usually because	2519	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1929	believe me.	2535	believe me.
1930		2536
1931	=back	2537	=back
1932		2538
1933		2539
		2540	=head2 C<ev_async> - how to wake up another event loop
		2541
		2542	In general, you cannot use an C<ev_loop> from multiple threads or other
		2543	asynchronous sources such as signal handlers (as opposed to multiple event
		2544	loops - those are of course safe to use in different threads).
		2545
		2546	Sometimes, however, you need to wake up another event loop you do not
		2547	control, for example because it belongs to another thread. This is what
		2548	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2549	can signal it by calling C<ev_async_send>, which is thread- and signal
		2550	safe.
		2551
		2552	This functionality is very similar to C<ev_signal> watchers, as signals,
		2553	too, are asynchronous in nature, and signals, too, will be compressed
		2554	(i.e. the number of callback invocations may be less than the number of
		2555	C<ev_async_sent> calls).
		2556
		2557	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2558	just the default loop.
		2559
		2560	=head3 Queueing
		2561
		2562	C<ev_async> does not support queueing of data in any way. The reason
		2563	is that the author does not know of a simple (or any) algorithm for a
		2564	multiple-writer-single-reader queue that works in all cases and doesn't
		2565	need elaborate support such as pthreads.
		2566
		2567	That means that if you want to queue data, you have to provide your own
		2568	queue. But at least I can tell you how to implement locking around your
		2569	queue:
		2570
		2571	=over 4
		2572
		2573	=item queueing from a signal handler context
		2574
		2575	To implement race-free queueing, you simply add to the queue in the signal
		2576	handler but you block the signal handler in the watcher callback. Here is
		2577	an example that does that for some fictitious SIGUSR1 handler:
		2578
		2579	static ev_async mysig;
		2580
		2581	static void
		2582	sigusr1_handler (void)
		2583	{
		2584	sometype data;
		2585
		2586	// no locking etc.
		2587	queue_put (data);
		2588	ev_async_send (EV_DEFAULT_ &mysig);
		2589	}
		2590
		2591	static void
		2592	mysig_cb (EV_P_ ev_async *w, int revents)
		2593	{
		2594	sometype data;
		2595	sigset_t block, prev;
		2596
		2597	sigemptyset (&block);
		2598	sigaddset (&block, SIGUSR1);
		2599	sigprocmask (SIG_BLOCK, &block, &prev);
		2600
		2601	while (queue_get (&data))
		2602	process (data);
		2603
		2604	if (sigismember (&prev, SIGUSR1)
		2605	sigprocmask (SIG_UNBLOCK, &block, 0);
		2606	}
		2607
		2608	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2609	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2610	either...).
		2611
		2612	=item queueing from a thread context
		2613
		2614	The strategy for threads is different, as you cannot (easily) block
		2615	threads but you can easily preempt them, so to queue safely you need to
		2616	employ a traditional mutex lock, such as in this pthread example:
		2617
		2618	static ev_async mysig;
		2619	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2620
		2621	static void
		2622	otherthread (void)
		2623	{
		2624	// only need to lock the actual queueing operation
		2625	pthread_mutex_lock (&mymutex);
		2626	queue_put (data);
		2627	pthread_mutex_unlock (&mymutex);
		2628
		2629	ev_async_send (EV_DEFAULT_ &mysig);
		2630	}
		2631
		2632	static void
		2633	mysig_cb (EV_P_ ev_async *w, int revents)
		2634	{
		2635	pthread_mutex_lock (&mymutex);
		2636
		2637	while (queue_get (&data))
		2638	process (data);
		2639
		2640	pthread_mutex_unlock (&mymutex);
		2641	}
		2642
		2643	=back
		2644
		2645
		2646	=head3 Watcher-Specific Functions and Data Members
		2647
		2648	=over 4
		2649
		2650	=item ev_async_init (ev_async *, callback)
		2651
		2652	Initialises and configures the async watcher - it has no parameters of any
		2653	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
		2654	trust me.
		2655
		2656	=item ev_async_send (loop, ev_async *)
		2657
		2658	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2659	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2660	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2661	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2662	section below on what exactly this means).
		2663
		2664	This call incurs the overhead of a system call only once per loop iteration,
		2665	so while the overhead might be noticeable, it doesn't apply to repeated
		2666	calls to C<ev_async_send>.
		2667
		2668	=item bool = ev_async_pending (ev_async *)
		2669
		2670	Returns a non-zero value when C<ev_async_send> has been called on the
		2671	watcher but the event has not yet been processed (or even noted) by the
		2672	event loop.
		2673
		2674	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2675	the loop iterates next and checks for the watcher to have become active,
		2676	it will reset the flag again. C<ev_async_pending> can be used to very
		2677	quickly check whether invoking the loop might be a good idea.
		2678
		2679	Not that this does I<not> check whether the watcher itself is pending, only
		2680	whether it has been requested to make this watcher pending.
		2681
		2682	=back
		2683
		2684
1934	=head1 OTHER FUNCTIONS	2685	=head1 OTHER FUNCTIONS
1935		2686
1936	There are some other functions of possible interest. Described. Here. Now.	2687	There are some other functions of possible interest. Described. Here. Now.
1937		2688
1938	=over 4	2689	=over 4
1939		2690
1940	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2691	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1941		2692
1942	This function combines a simple timer and an I/O watcher, calls your	2693	This function combines a simple timer and an I/O watcher, calls your
1943	callback on whichever event happens first and automatically stop both	2694	callback on whichever event happens first and automatically stops both
1944	watchers. This is useful if you want to wait for a single event on an fd	2695	watchers. This is useful if you want to wait for a single event on an fd
1945	or timeout without having to allocate/configure/start/stop/free one or	2696	or timeout without having to allocate/configure/start/stop/free one or
1946	more watchers yourself.	2697	more watchers yourself.
1947		2698
1948	If C<fd> is less than 0, then no I/O watcher will be started and events	2699	If C<fd> is less than 0, then no I/O watcher will be started and the
1949	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2700	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1950	C<events> set will be craeted and started.	2701	the given C<fd> and C<events> set will be created and started.
1951		2702
1952	If C<timeout> is less than 0, then no timeout watcher will be	2703	If C<timeout> is less than 0, then no timeout watcher will be
1953	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2704	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1954	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2705	repeat = 0) will be started. C<0> is a valid timeout.
1955	dubious value.
1956		2706
1957	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2707	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1958	passed an C<revents> set like normal event callbacks (a combination of	2708	passed an C<revents> set like normal event callbacks (a combination of
1959	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2709	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1960	value passed to C<ev_once>:	2710	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2711	a timeout and an io event at the same time - you probably should give io
		2712	events precedence.
1961		2713
		2714	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2715
1962	static void stdin_ready (int revents, void *arg)	2716	static void stdin_ready (int revents, void *arg)
1963	{	2717	{
1964	if (revents & EV_TIMEOUT)
1965	/* doh, nothing entered */;
1966	else if (revents & EV_READ)	2718	if (revents & EV_READ)
1967	/* stdin might have data for us, joy! */;	2719	/* stdin might have data for us, joy! */;
		2720	else if (revents & EV_TIMEOUT)
		2721	/* doh, nothing entered */;
1968	}	2722	}
1969		2723
1970	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2724	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1971		2725
1972	=item ev_feed_event (ev_loop *, watcher *, int revents)	2726	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1973		2727
1974	Feeds the given event set into the event loop, as if the specified event	2728	Feeds the given event set into the event loop, as if the specified event
1975	had happened for the specified watcher (which must be a pointer to an	2729	had happened for the specified watcher (which must be a pointer to an
1976	initialised but not necessarily started event watcher).	2730	initialised but not necessarily started event watcher).
1977		2731
1978	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2732	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1979		2733
1980	Feed an event on the given fd, as if a file descriptor backend detected	2734	Feed an event on the given fd, as if a file descriptor backend detected
1981	the given events it.	2735	the given events it.
1982		2736
1983	=item ev_feed_signal_event (ev_loop *loop, int signum)	2737	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1984		2738
1985	Feed an event as if the given signal occured (C<loop> must be the default	2739	Feed an event as if the given signal occurred (C<loop> must be the default
1986	loop!).	2740	loop!).
1987		2741
1988	=back	2742	=back
1989		2743
1990		2744
…		…
2006		2760
2007	=item * Priorities are not currently supported. Initialising priorities	2761	=item * Priorities are not currently supported. Initialising priorities
2008	will fail and all watchers will have the same priority, even though there	2762	will fail and all watchers will have the same priority, even though there
2009	is an ev_pri field.	2763	is an ev_pri field.
2010		2764
		2765	=item * In libevent, the last base created gets the signals, in libev, the
		2766	first base created (== the default loop) gets the signals.
		2767
2011	=item * Other members are not supported.	2768	=item * Other members are not supported.
2012		2769
2013	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2770	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2014	to use the libev header file and library.	2771	to use the libev header file and library.
2015		2772
2016	=back	2773	=back
2017		2774
2018	=head1 C++ SUPPORT	2775	=head1 C++ SUPPORT
2019		2776
2020	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2777	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2021	you to use some convinience methods to start/stop watchers and also change	2778	you to use some convenience methods to start/stop watchers and also change
2022	the callback model to a model using method callbacks on objects.	2779	the callback model to a model using method callbacks on objects.
2023		2780
2024	To use it,	2781	To use it,
2025		2782
2026	#include <ev++.h>	2783	#include <ev++.h>
2027		2784
2028	This automatically includes F<ev.h> and puts all of its definitions (many	2785	This automatically includes F<ev.h> and puts all of its definitions (many
2029	of them macros) into the global namespace. All C++ specific things are	2786	of them macros) into the global namespace. All C++ specific things are
2030	put into the C<ev> namespace. It should support all the same embedding	2787	put into the C<ev> namespace. It should support all the same embedding
2031	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2788	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2098	your compiler is good :), then the method will be fully inlined into the	2855	your compiler is good :), then the method will be fully inlined into the
2099	thunking function, making it as fast as a direct C callback.	2856	thunking function, making it as fast as a direct C callback.
2100		2857
2101	Example: simple class declaration and watcher initialisation	2858	Example: simple class declaration and watcher initialisation
2102		2859
2103	struct myclass	2860	struct myclass
2104	{	2861	{
2105	void io_cb (ev::io &w, int revents) { }	2862	void io_cb (ev::io &w, int revents) { }
2106	}	2863	}
2107		2864
2108	myclass obj;	2865	myclass obj;
2109	ev::io iow;	2866	ev::io iow;
2110	iow.set <myclass, &myclass::io_cb> (&obj);	2867	iow.set <myclass, &myclass::io_cb> (&obj);
2111		2868
2112	=item w->set<function> (void *data = 0)	2869	=item w->set<function> (void *data = 0)
2113		2870
2114	Also sets a callback, but uses a static method or plain function as	2871	Also sets a callback, but uses a static method or plain function as
2115	callback. The optional C<data> argument will be stored in the watcher's	2872	callback. The optional C<data> argument will be stored in the watcher's
…		…
2117		2874
2118	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2875	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2119		2876
2120	See the method-C<set> above for more details.	2877	See the method-C<set> above for more details.
2121		2878
2122	Example:	2879	Example: Use a plain function as callback.
2123		2880
2124	static void io_cb (ev::io &w, int revents) { }	2881	static void io_cb (ev::io &w, int revents) { }
2125	iow.set <io_cb> ();	2882	iow.set <io_cb> ();
2126		2883
2127	=item w->set (struct ev_loop *)	2884	=item w->set (struct ev_loop *)
2128		2885
2129	Associates a different C<struct ev_loop> with this watcher. You can only	2886	Associates a different C<struct ev_loop> with this watcher. You can only
2130	do this when the watcher is inactive (and not pending either).	2887	do this when the watcher is inactive (and not pending either).
2131		2888
2132	=item w->set ([args])	2889	=item w->set ([arguments])
2133		2890
2134	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2891	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2135	called at least once. Unlike the C counterpart, an active watcher gets	2892	called at least once. Unlike the C counterpart, an active watcher gets
2136	automatically stopped and restarted when reconfiguring it with this	2893	automatically stopped and restarted when reconfiguring it with this
2137	method.	2894	method.
2138		2895
2139	=item w->start ()	2896	=item w->start ()
…		…
2163	=back	2920	=back
2164		2921
2165	Example: Define a class with an IO and idle watcher, start one of them in	2922	Example: Define a class with an IO and idle watcher, start one of them in
2166	the constructor.	2923	the constructor.
2167		2924
2168	class myclass	2925	class myclass
2169	{	2926	{
2170	ev_io io; void io_cb (ev::io &w, int revents);	2927	ev::io io ; void io_cb (ev::io &w, int revents);
2171	ev_idle idle void idle_cb (ev::idle &w, int revents);	2928	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2172		2929
2173	myclass ();	2930	myclass (int fd)
2174	}	2931	{
2175
2176	myclass::myclass (int fd)
2177	{
2178	io .set <myclass, &myclass::io_cb > (this);	2932	io .set <myclass, &myclass::io_cb > (this);
2179	idle.set <myclass, &myclass::idle_cb> (this);	2933	idle.set <myclass, &myclass::idle_cb> (this);
2180		2934
2181	io.start (fd, ev::READ);	2935	io.start (fd, ev::READ);
		2936	}
2182	}	2937	};
		2938
		2939
		2940	=head1 OTHER LANGUAGE BINDINGS
		2941
		2942	Libev does not offer other language bindings itself, but bindings for a
		2943	number of languages exist in the form of third-party packages. If you know
		2944	any interesting language binding in addition to the ones listed here, drop
		2945	me a note.
		2946
		2947	=over 4
		2948
		2949	=item Perl
		2950
		2951	The EV module implements the full libev API and is actually used to test
		2952	libev. EV is developed together with libev. Apart from the EV core module,
		2953	there are additional modules that implement libev-compatible interfaces
		2954	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2955	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2956	and C<EV::Glib>).
		2957
		2958	It can be found and installed via CPAN, its homepage is at
		2959	L<http://software.schmorp.de/pkg/EV>.
		2960
		2961	=item Python
		2962
		2963	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2964	seems to be quite complete and well-documented. Note, however, that the
		2965	patch they require for libev is outright dangerous as it breaks the ABI
		2966	for everybody else, and therefore, should never be applied in an installed
		2967	libev (if python requires an incompatible ABI then it needs to embed
		2968	libev).
		2969
		2970	=item Ruby
		2971
		2972	Tony Arcieri has written a ruby extension that offers access to a subset
		2973	of the libev API and adds file handle abstractions, asynchronous DNS and
		2974	more on top of it. It can be found via gem servers. Its homepage is at
		2975	L<http://rev.rubyforge.org/>.
		2976
		2977	=item D
		2978
		2979	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2980	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2981
		2982	=item Ocaml
		2983
		2984	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2985	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2986
		2987	=back
2183		2988
2184		2989
2185	=head1 MACRO MAGIC	2990	=head1 MACRO MAGIC
2186		2991
2187	Libev can be compiled with a variety of options, the most fundamantal	2992	Libev can be compiled with a variety of options, the most fundamental
2188	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2993	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2189	functions and callbacks have an initial C<struct ev_loop *> argument.	2994	functions and callbacks have an initial C<struct ev_loop *> argument.
2190		2995
2191	To make it easier to write programs that cope with either variant, the	2996	To make it easier to write programs that cope with either variant, the
2192	following macros are defined:	2997	following macros are defined:
…		…
2197		3002
2198	This provides the loop I<argument> for functions, if one is required ("ev	3003	This provides the loop I<argument> for functions, if one is required ("ev
2199	loop argument"). The C<EV_A> form is used when this is the sole argument,	3004	loop argument"). The C<EV_A> form is used when this is the sole argument,
2200	C<EV_A_> is used when other arguments are following. Example:	3005	C<EV_A_> is used when other arguments are following. Example:
2201		3006
2202	ev_unref (EV_A);	3007	ev_unref (EV_A);
2203	ev_timer_add (EV_A_ watcher);	3008	ev_timer_add (EV_A_ watcher);
2204	ev_loop (EV_A_ 0);	3009	ev_loop (EV_A_ 0);
2205		3010
2206	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3011	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2207	which is often provided by the following macro.	3012	which is often provided by the following macro.
2208		3013
2209	=item C<EV_P>, C<EV_P_>	3014	=item C<EV_P>, C<EV_P_>
2210		3015
2211	This provides the loop I<parameter> for functions, if one is required ("ev	3016	This provides the loop I<parameter> for functions, if one is required ("ev
2212	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3017	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2213	C<EV_P_> is used when other parameters are following. Example:	3018	C<EV_P_> is used when other parameters are following. Example:
2214		3019
2215	// this is how ev_unref is being declared	3020	// this is how ev_unref is being declared
2216	static void ev_unref (EV_P);	3021	static void ev_unref (EV_P);
2217		3022
2218	// this is how you can declare your typical callback	3023	// this is how you can declare your typical callback
2219	static void cb (EV_P_ ev_timer *w, int revents)	3024	static void cb (EV_P_ ev_timer *w, int revents)
2220		3025
2221	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3026	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2222	suitable for use with C<EV_A>.	3027	suitable for use with C<EV_A>.
2223		3028
2224	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3029	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2225		3030
2226	Similar to the other two macros, this gives you the value of the default	3031	Similar to the other two macros, this gives you the value of the default
2227	loop, if multiple loops are supported ("ev loop default").	3032	loop, if multiple loops are supported ("ev loop default").
		3033
		3034	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3035
		3036	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3037	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3038	is undefined when the default loop has not been initialised by a previous
		3039	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3040
		3041	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3042	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2228		3043
2229	=back	3044	=back
2230		3045
2231	Example: Declare and initialise a check watcher, utilising the above	3046	Example: Declare and initialise a check watcher, utilising the above
2232	macros so it will work regardless of whether multiple loops are supported	3047	macros so it will work regardless of whether multiple loops are supported
2233	or not.	3048	or not.
2234		3049
2235	static void	3050	static void
2236	check_cb (EV_P_ ev_timer *w, int revents)	3051	check_cb (EV_P_ ev_timer *w, int revents)
2237	{	3052	{
2238	ev_check_stop (EV_A_ w);	3053	ev_check_stop (EV_A_ w);
2239	}	3054	}
2240		3055
2241	ev_check check;	3056	ev_check check;
2242	ev_check_init (&check, check_cb);	3057	ev_check_init (&check, check_cb);
2243	ev_check_start (EV_DEFAULT_ &check);	3058	ev_check_start (EV_DEFAULT_ &check);
2244	ev_loop (EV_DEFAULT_ 0);	3059	ev_loop (EV_DEFAULT_ 0);
2245		3060
2246	=head1 EMBEDDING	3061	=head1 EMBEDDING
2247		3062
2248	Libev can (and often is) directly embedded into host	3063	Libev can (and often is) directly embedded into host
2249	applications. Examples of applications that embed it include the Deliantra	3064	applications. Examples of applications that embed it include the Deliantra
…		…
2256	libev somewhere in your source tree).	3071	libev somewhere in your source tree).
2257		3072
2258	=head2 FILESETS	3073	=head2 FILESETS
2259		3074
2260	Depending on what features you need you need to include one or more sets of files	3075	Depending on what features you need you need to include one or more sets of files
2261	in your app.	3076	in your application.
2262		3077
2263	=head3 CORE EVENT LOOP	3078	=head3 CORE EVENT LOOP
2264		3079
2265	To include only the libev core (all the C<ev_*> functions), with manual	3080	To include only the libev core (all the C<ev_*> functions), with manual
2266	configuration (no autoconf):	3081	configuration (no autoconf):
2267		3082
2268	#define EV_STANDALONE 1	3083	#define EV_STANDALONE 1
2269	#include "ev.c"	3084	#include "ev.c"
2270		3085
2271	This will automatically include F<ev.h>, too, and should be done in a	3086	This will automatically include F<ev.h>, too, and should be done in a
2272	single C source file only to provide the function implementations. To use	3087	single C source file only to provide the function implementations. To use
2273	it, do the same for F<ev.h> in all files wishing to use this API (best	3088	it, do the same for F<ev.h> in all files wishing to use this API (best
2274	done by writing a wrapper around F<ev.h> that you can include instead and	3089	done by writing a wrapper around F<ev.h> that you can include instead and
2275	where you can put other configuration options):	3090	where you can put other configuration options):
2276		3091
2277	#define EV_STANDALONE 1	3092	#define EV_STANDALONE 1
2278	#include "ev.h"	3093	#include "ev.h"
2279		3094
2280	Both header files and implementation files can be compiled with a C++	3095	Both header files and implementation files can be compiled with a C++
2281	compiler (at least, thats a stated goal, and breakage will be treated	3096	compiler (at least, that's a stated goal, and breakage will be treated
2282	as a bug).	3097	as a bug).
2283		3098
2284	You need the following files in your source tree, or in a directory	3099	You need the following files in your source tree, or in a directory
2285	in your include path (e.g. in libev/ when using -Ilibev):	3100	in your include path (e.g. in libev/ when using -Ilibev):
2286		3101
2287	ev.h	3102	ev.h
2288	ev.c	3103	ev.c
2289	ev_vars.h	3104	ev_vars.h
2290	ev_wrap.h	3105	ev_wrap.h
2291		3106
2292	ev_win32.c required on win32 platforms only	3107	ev_win32.c required on win32 platforms only
2293		3108
2294	ev_select.c only when select backend is enabled (which is enabled by default)	3109	ev_select.c only when select backend is enabled (which is enabled by default)
2295	ev_poll.c only when poll backend is enabled (disabled by default)	3110	ev_poll.c only when poll backend is enabled (disabled by default)
2296	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3111	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2297	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3112	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2298	ev_port.c only when the solaris port backend is enabled (disabled by default)	3113	ev_port.c only when the solaris port backend is enabled (disabled by default)
2299		3114
2300	F<ev.c> includes the backend files directly when enabled, so you only need	3115	F<ev.c> includes the backend files directly when enabled, so you only need
2301	to compile this single file.	3116	to compile this single file.
2302		3117
2303	=head3 LIBEVENT COMPATIBILITY API	3118	=head3 LIBEVENT COMPATIBILITY API
2304		3119
2305	To include the libevent compatibility API, also include:	3120	To include the libevent compatibility API, also include:
2306		3121
2307	#include "event.c"	3122	#include "event.c"
2308		3123
2309	in the file including F<ev.c>, and:	3124	in the file including F<ev.c>, and:
2310		3125
2311	#include "event.h"	3126	#include "event.h"
2312		3127
2313	in the files that want to use the libevent API. This also includes F<ev.h>.	3128	in the files that want to use the libevent API. This also includes F<ev.h>.
2314		3129
2315	You need the following additional files for this:	3130	You need the following additional files for this:
2316		3131
2317	event.h	3132	event.h
2318	event.c	3133	event.c
2319		3134
2320	=head3 AUTOCONF SUPPORT	3135	=head3 AUTOCONF SUPPORT
2321		3136
2322	Instead of using C<EV_STANDALONE=1> and providing your config in	3137	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2323	whatever way you want, you can also C<m4_include([libev.m4])> in your	3138	whatever way you want, you can also C<m4_include([libev.m4])> in your
2324	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3139	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2325	include F<config.h> and configure itself accordingly.	3140	include F<config.h> and configure itself accordingly.
2326		3141
2327	For this of course you need the m4 file:	3142	For this of course you need the m4 file:
2328		3143
2329	libev.m4	3144	libev.m4
2330		3145
2331	=head2 PREPROCESSOR SYMBOLS/MACROS	3146	=head2 PREPROCESSOR SYMBOLS/MACROS
2332		3147
2333	Libev can be configured via a variety of preprocessor symbols you have to define	3148	Libev can be configured via a variety of preprocessor symbols you have to
2334	before including any of its files. The default is not to build for multiplicity	3149	define before including any of its files. The default in the absence of
2335	and only include the select backend.	3150	autoconf is documented for every option.
2336		3151
2337	=over 4	3152	=over 4
2338		3153
2339	=item EV_STANDALONE	3154	=item EV_STANDALONE
2340		3155
…		…
2345	F<event.h> that are not directly supported by the libev core alone.	3160	F<event.h> that are not directly supported by the libev core alone.
2346		3161
2347	=item EV_USE_MONOTONIC	3162	=item EV_USE_MONOTONIC
2348		3163
2349	If defined to be C<1>, libev will try to detect the availability of the	3164	If defined to be C<1>, libev will try to detect the availability of the
2350	monotonic clock option at both compiletime and runtime. Otherwise no use	3165	monotonic clock option at both compile time and runtime. Otherwise no use
2351	of the monotonic clock option will be attempted. If you enable this, you	3166	of the monotonic clock option will be attempted. If you enable this, you
2352	usually have to link against librt or something similar. Enabling it when	3167	usually have to link against librt or something similar. Enabling it when
2353	the functionality isn't available is safe, though, although you have	3168	the functionality isn't available is safe, though, although you have
2354	to make sure you link against any libraries where the C<clock_gettime>	3169	to make sure you link against any libraries where the C<clock_gettime>
2355	function is hiding in (often F<-lrt>).	3170	function is hiding in (often F<-lrt>).
2356		3171
2357	=item EV_USE_REALTIME	3172	=item EV_USE_REALTIME
2358		3173
2359	If defined to be C<1>, libev will try to detect the availability of the	3174	If defined to be C<1>, libev will try to detect the availability of the
2360	realtime clock option at compiletime (and assume its availability at	3175	real-time clock option at compile time (and assume its availability at
2361	runtime if successful). Otherwise no use of the realtime clock option will	3176	runtime if successful). Otherwise no use of the real-time clock option will
2362	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3177	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2363	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3178	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2364	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3179	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2365		3180
2366	=item EV_USE_NANOSLEEP	3181	=item EV_USE_NANOSLEEP
2367		3182
2368	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3183	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2369	and will use it for delays. Otherwise it will use C<select ()>.	3184	and will use it for delays. Otherwise it will use C<select ()>.
2370		3185
		3186	=item EV_USE_EVENTFD
		3187
		3188	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3189	available and will probe for kernel support at runtime. This will improve
		3190	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3191	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3192	2.7 or newer, otherwise disabled.
		3193
2371	=item EV_USE_SELECT	3194	=item EV_USE_SELECT
2372		3195
2373	If undefined or defined to be C<1>, libev will compile in support for the	3196	If undefined or defined to be C<1>, libev will compile in support for the
2374	C<select>(2) backend. No attempt at autodetection will be done: if no	3197	C<select>(2) backend. No attempt at auto-detection will be done: if no
2375	other method takes over, select will be it. Otherwise the select backend	3198	other method takes over, select will be it. Otherwise the select backend
2376	will not be compiled in.	3199	will not be compiled in.
2377		3200
2378	=item EV_SELECT_USE_FD_SET	3201	=item EV_SELECT_USE_FD_SET
2379		3202
2380	If defined to C<1>, then the select backend will use the system C<fd_set>	3203	If defined to C<1>, then the select backend will use the system C<fd_set>
2381	structure. This is useful if libev doesn't compile due to a missing	3204	structure. This is useful if libev doesn't compile due to a missing
2382	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3205	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2383	exotic systems. This usually limits the range of file descriptors to some	3206	exotic systems. This usually limits the range of file descriptors to some
2384	low limit such as 1024 or might have other limitations (winsocket only	3207	low limit such as 1024 or might have other limitations (winsocket only
2385	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3208	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2386	influence the size of the C<fd_set> used.	3209	influence the size of the C<fd_set> used.
2387		3210
…		…
2393	be used is the winsock select). This means that it will call	3216	be used is the winsock select). This means that it will call
2394	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3217	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2395	it is assumed that all these functions actually work on fds, even	3218	it is assumed that all these functions actually work on fds, even
2396	on win32. Should not be defined on non-win32 platforms.	3219	on win32. Should not be defined on non-win32 platforms.
2397		3220
		3221	=item EV_FD_TO_WIN32_HANDLE
		3222
		3223	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3224	file descriptors to socket handles. When not defining this symbol (the
		3225	default), then libev will call C<_get_osfhandle>, which is usually
		3226	correct. In some cases, programs use their own file descriptor management,
		3227	in which case they can provide this function to map fds to socket handles.
		3228
2398	=item EV_USE_POLL	3229	=item EV_USE_POLL
2399		3230
2400	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3231	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2401	backend. Otherwise it will be enabled on non-win32 platforms. It	3232	backend. Otherwise it will be enabled on non-win32 platforms. It
2402	takes precedence over select.	3233	takes precedence over select.
2403		3234
2404	=item EV_USE_EPOLL	3235	=item EV_USE_EPOLL
2405		3236
2406	If defined to be C<1>, libev will compile in support for the Linux	3237	If defined to be C<1>, libev will compile in support for the Linux
2407	C<epoll>(7) backend. Its availability will be detected at runtime,	3238	C<epoll>(7) backend. Its availability will be detected at runtime,
2408	otherwise another method will be used as fallback. This is the	3239	otherwise another method will be used as fallback. This is the preferred
2409	preferred backend for GNU/Linux systems.	3240	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3241	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2410		3242
2411	=item EV_USE_KQUEUE	3243	=item EV_USE_KQUEUE
2412		3244
2413	If defined to be C<1>, libev will compile in support for the BSD style	3245	If defined to be C<1>, libev will compile in support for the BSD style
2414	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3246	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2427	otherwise another method will be used as fallback. This is the preferred	3259	otherwise another method will be used as fallback. This is the preferred
2428	backend for Solaris 10 systems.	3260	backend for Solaris 10 systems.
2429		3261
2430	=item EV_USE_DEVPOLL	3262	=item EV_USE_DEVPOLL
2431		3263
2432	reserved for future expansion, works like the USE symbols above.	3264	Reserved for future expansion, works like the USE symbols above.
2433		3265
2434	=item EV_USE_INOTIFY	3266	=item EV_USE_INOTIFY
2435		3267
2436	If defined to be C<1>, libev will compile in support for the Linux inotify	3268	If defined to be C<1>, libev will compile in support for the Linux inotify
2437	interface to speed up C<ev_stat> watchers. Its actual availability will	3269	interface to speed up C<ev_stat> watchers. Its actual availability will
2438	be detected at runtime.	3270	be detected at runtime. If undefined, it will be enabled if the headers
		3271	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3272
		3273	=item EV_ATOMIC_T
		3274
		3275	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3276	access is atomic with respect to other threads or signal contexts. No such
		3277	type is easily found in the C language, so you can provide your own type
		3278	that you know is safe for your purposes. It is used both for signal handler "locking"
		3279	as well as for signal and thread safety in C<ev_async> watchers.
		3280
		3281	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3282	(from F<signal.h>), which is usually good enough on most platforms.
2439		3283
2440	=item EV_H	3284	=item EV_H
2441		3285
2442	The name of the F<ev.h> header file used to include it. The default if	3286	The name of the F<ev.h> header file used to include it. The default if
2443	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3287	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2444	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3288	used to virtually rename the F<ev.h> header file in case of conflicts.
2445		3289
2446	=item EV_CONFIG_H	3290	=item EV_CONFIG_H
2447		3291
2448	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3292	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2449	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3293	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2450	C<EV_H>, above.	3294	C<EV_H>, above.
2451		3295
2452	=item EV_EVENT_H	3296	=item EV_EVENT_H
2453		3297
2454	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3298	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2455	of how the F<event.h> header can be found.	3299	of how the F<event.h> header can be found, the default is C<"event.h">.
2456		3300
2457	=item EV_PROTOTYPES	3301	=item EV_PROTOTYPES
2458		3302
2459	If defined to be C<0>, then F<ev.h> will not define any function	3303	If defined to be C<0>, then F<ev.h> will not define any function
2460	prototypes, but still define all the structs and other symbols. This is	3304	prototypes, but still define all the structs and other symbols. This is
…		…
2481	When doing priority-based operations, libev usually has to linearly search	3325	When doing priority-based operations, libev usually has to linearly search
2482	all the priorities, so having many of them (hundreds) uses a lot of space	3326	all the priorities, so having many of them (hundreds) uses a lot of space
2483	and time, so using the defaults of five priorities (-2 .. +2) is usually	3327	and time, so using the defaults of five priorities (-2 .. +2) is usually
2484	fine.	3328	fine.
2485		3329
2486	If your embedding app does not need any priorities, defining these both to	3330	If your embedding application does not need any priorities, defining these
2487	C<0> will save some memory and cpu.	3331	both to C<0> will save some memory and CPU.
2488		3332
2489	=item EV_PERIODIC_ENABLE	3333	=item EV_PERIODIC_ENABLE
2490		3334
2491	If undefined or defined to be C<1>, then periodic timers are supported. If	3335	If undefined or defined to be C<1>, then periodic timers are supported. If
2492	defined to be C<0>, then they are not. Disabling them saves a few kB of	3336	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2499	code.	3343	code.
2500		3344
2501	=item EV_EMBED_ENABLE	3345	=item EV_EMBED_ENABLE
2502		3346
2503	If undefined or defined to be C<1>, then embed watchers are supported. If	3347	If undefined or defined to be C<1>, then embed watchers are supported. If
2504	defined to be C<0>, then they are not.	3348	defined to be C<0>, then they are not. Embed watchers rely on most other
		3349	watcher types, which therefore must not be disabled.
2505		3350
2506	=item EV_STAT_ENABLE	3351	=item EV_STAT_ENABLE
2507		3352
2508	If undefined or defined to be C<1>, then stat watchers are supported. If	3353	If undefined or defined to be C<1>, then stat watchers are supported. If
2509	defined to be C<0>, then they are not.	3354	defined to be C<0>, then they are not.
…		…
2511	=item EV_FORK_ENABLE	3356	=item EV_FORK_ENABLE
2512		3357
2513	If undefined or defined to be C<1>, then fork watchers are supported. If	3358	If undefined or defined to be C<1>, then fork watchers are supported. If
2514	defined to be C<0>, then they are not.	3359	defined to be C<0>, then they are not.
2515		3360
		3361	=item EV_ASYNC_ENABLE
		3362
		3363	If undefined or defined to be C<1>, then async watchers are supported. If
		3364	defined to be C<0>, then they are not.
		3365
2516	=item EV_MINIMAL	3366	=item EV_MINIMAL
2517		3367
2518	If you need to shave off some kilobytes of code at the expense of some	3368	If you need to shave off some kilobytes of code at the expense of some
2519	speed, define this symbol to C<1>. Currently only used for gcc to override	3369	speed, define this symbol to C<1>. Currently this is used to override some
2520	some inlining decisions, saves roughly 30% codesize of amd64.	3370	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3371	much smaller 2-heap for timer management over the default 4-heap.
2521		3372
2522	=item EV_PID_HASHSIZE	3373	=item EV_PID_HASHSIZE
2523		3374
2524	C<ev_child> watchers use a small hash table to distribute workload by	3375	C<ev_child> watchers use a small hash table to distribute workload by
2525	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3376	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2532	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3383	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2533	usually more than enough. If you need to manage thousands of C<ev_stat>	3384	usually more than enough. If you need to manage thousands of C<ev_stat>
2534	watchers you might want to increase this value (I<must> be a power of	3385	watchers you might want to increase this value (I<must> be a power of
2535	two).	3386	two).
2536		3387
		3388	=item EV_USE_4HEAP
		3389
		3390	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3391	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3392	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3393	faster performance with many (thousands) of watchers.
		3394
		3395	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3396	(disabled).
		3397
		3398	=item EV_HEAP_CACHE_AT
		3399
		3400	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3401	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3402	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3403	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3404	but avoids random read accesses on heap changes. This improves performance
		3405	noticeably with many (hundreds) of watchers.
		3406
		3407	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3408	(disabled).
		3409
		3410	=item EV_VERIFY
		3411
		3412	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3413	be done: If set to C<0>, no internal verification code will be compiled
		3414	in. If set to C<1>, then verification code will be compiled in, but not
		3415	called. If set to C<2>, then the internal verification code will be
		3416	called once per loop, which can slow down libev. If set to C<3>, then the
		3417	verification code will be called very frequently, which will slow down
		3418	libev considerably.
		3419
		3420	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3421	C<0>.
		3422
2537	=item EV_COMMON	3423	=item EV_COMMON
2538		3424
2539	By default, all watchers have a C<void *data> member. By redefining	3425	By default, all watchers have a C<void *data> member. By redefining
2540	this macro to a something else you can include more and other types of	3426	this macro to a something else you can include more and other types of
2541	members. You have to define it each time you include one of the files,	3427	members. You have to define it each time you include one of the files,
2542	though, and it must be identical each time.	3428	though, and it must be identical each time.
2543		3429
2544	For example, the perl EV module uses something like this:	3430	For example, the perl EV module uses something like this:
2545		3431
2546	#define EV_COMMON \	3432	#define EV_COMMON \
2547	SV *self; /* contains this struct */ \	3433	SV *self; /* contains this struct */ \
2548	SV *cb_sv, *fh /* note no trailing ";" */	3434	SV *cb_sv, *fh /* note no trailing ";" */
2549		3435
2550	=item EV_CB_DECLARE (type)	3436	=item EV_CB_DECLARE (type)
2551		3437
2552	=item EV_CB_INVOKE (watcher, revents)	3438	=item EV_CB_INVOKE (watcher, revents)
2553		3439
…		…
2558	definition and a statement, respectively. See the F<ev.h> header file for	3444	definition and a statement, respectively. See the F<ev.h> header file for
2559	their default definitions. One possible use for overriding these is to	3445	their default definitions. One possible use for overriding these is to
2560	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3446	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2561	method calls instead of plain function calls in C++.	3447	method calls instead of plain function calls in C++.
2562		3448
		3449	=back
		3450
2563	=head2 EXPORTED API SYMBOLS	3451	=head2 EXPORTED API SYMBOLS
2564		3452
2565	If you need to re-export the API (e.g. via a dll) and you need a list of	3453	If you need to re-export the API (e.g. via a DLL) and you need a list of
2566	exported symbols, you can use the provided F<Symbol.*> files which list	3454	exported symbols, you can use the provided F<Symbol.*> files which list
2567	all public symbols, one per line:	3455	all public symbols, one per line:
2568		3456
2569	Symbols.ev for libev proper	3457	Symbols.ev for libev proper
2570	Symbols.event for the libevent emulation	3458	Symbols.event for the libevent emulation
2571		3459
2572	This can also be used to rename all public symbols to avoid clashes with	3460	This can also be used to rename all public symbols to avoid clashes with
2573	multiple versions of libev linked together (which is obviously bad in	3461	multiple versions of libev linked together (which is obviously bad in
2574	itself, but sometimes it is inconvinient to avoid this).	3462	itself, but sometimes it is inconvenient to avoid this).
2575		3463
2576	A sed command like this will create wrapper C<#define>'s that you need to	3464	A sed command like this will create wrapper C<#define>'s that you need to
2577	include before including F<ev.h>:	3465	include before including F<ev.h>:
2578		3466
2579	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3467	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2596	file.	3484	file.
2597		3485
2598	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3486	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2599	that everybody includes and which overrides some configure choices:	3487	that everybody includes and which overrides some configure choices:
2600		3488
2601	#define EV_MINIMAL 1	3489	#define EV_MINIMAL 1
2602	#define EV_USE_POLL 0	3490	#define EV_USE_POLL 0
2603	#define EV_MULTIPLICITY 0	3491	#define EV_MULTIPLICITY 0
2604	#define EV_PERIODIC_ENABLE 0	3492	#define EV_PERIODIC_ENABLE 0
2605	#define EV_STAT_ENABLE 0	3493	#define EV_STAT_ENABLE 0
2606	#define EV_FORK_ENABLE 0	3494	#define EV_FORK_ENABLE 0
2607	#define EV_CONFIG_H <config.h>	3495	#define EV_CONFIG_H <config.h>
2608	#define EV_MINPRI 0	3496	#define EV_MINPRI 0
2609	#define EV_MAXPRI 0	3497	#define EV_MAXPRI 0
2610		3498
2611	#include "ev++.h"	3499	#include "ev++.h"
2612		3500
2613	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3501	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2614		3502
2615	#include "ev_cpp.h"	3503	#include "ev_cpp.h"
2616	#include "ev.c"	3504	#include "ev.c"
2617		3505
		3506	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2618		3507
		3508	=head2 THREADS AND COROUTINES
		3509
		3510	=head3 THREADS
		3511
		3512	All libev functions are reentrant and thread-safe unless explicitly
		3513	documented otherwise, but libev implements no locking itself. This means
		3514	that you can use as many loops as you want in parallel, as long as there
		3515	are no concurrent calls into any libev function with the same loop
		3516	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3517	of course): libev guarantees that different event loops share no data
		3518	structures that need any locking.
		3519
		3520	Or to put it differently: calls with different loop parameters can be done
		3521	concurrently from multiple threads, calls with the same loop parameter
		3522	must be done serially (but can be done from different threads, as long as
		3523	only one thread ever is inside a call at any point in time, e.g. by using
		3524	a mutex per loop).
		3525
		3526	Specifically to support threads (and signal handlers), libev implements
		3527	so-called C<ev_async> watchers, which allow some limited form of
		3528	concurrency on the same event loop, namely waking it up "from the
		3529	outside".
		3530
		3531	If you want to know which design (one loop, locking, or multiple loops
		3532	without or something else still) is best for your problem, then I cannot
		3533	help you, but here is some generic advice:
		3534
		3535	=over 4
		3536
		3537	=item * most applications have a main thread: use the default libev loop
		3538	in that thread, or create a separate thread running only the default loop.
		3539
		3540	This helps integrating other libraries or software modules that use libev
		3541	themselves and don't care/know about threading.
		3542
		3543	=item * one loop per thread is usually a good model.
		3544
		3545	Doing this is almost never wrong, sometimes a better-performance model
		3546	exists, but it is always a good start.
		3547
		3548	=item * other models exist, such as the leader/follower pattern, where one
		3549	loop is handed through multiple threads in a kind of round-robin fashion.
		3550
		3551	Choosing a model is hard - look around, learn, know that usually you can do
		3552	better than you currently do :-)
		3553
		3554	=item * often you need to talk to some other thread which blocks in the
		3555	event loop.
		3556
		3557	C<ev_async> watchers can be used to wake them up from other threads safely
		3558	(or from signal contexts...).
		3559
		3560	An example use would be to communicate signals or other events that only
		3561	work in the default loop by registering the signal watcher with the
		3562	default loop and triggering an C<ev_async> watcher from the default loop
		3563	watcher callback into the event loop interested in the signal.
		3564
		3565	=back
		3566
		3567	=head3 COROUTINES
		3568
		3569	Libev is very accommodating to coroutines ("cooperative threads"):
		3570	libev fully supports nesting calls to its functions from different
		3571	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3572	different coroutines, and switch freely between both coroutines running the
		3573	loop, as long as you don't confuse yourself). The only exception is that
		3574	you must not do this from C<ev_periodic> reschedule callbacks.
		3575
		3576	Care has been taken to ensure that libev does not keep local state inside
		3577	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3578	they do not call any callbacks.
		3579
		3580	=head2 COMPILER WARNINGS
		3581
		3582	Depending on your compiler and compiler settings, you might get no or a
		3583	lot of warnings when compiling libev code. Some people are apparently
		3584	scared by this.
		3585
		3586	However, these are unavoidable for many reasons. For one, each compiler
		3587	has different warnings, and each user has different tastes regarding
		3588	warning options. "Warn-free" code therefore cannot be a goal except when
		3589	targeting a specific compiler and compiler-version.
		3590
		3591	Another reason is that some compiler warnings require elaborate
		3592	workarounds, or other changes to the code that make it less clear and less
		3593	maintainable.
		3594
		3595	And of course, some compiler warnings are just plain stupid, or simply
		3596	wrong (because they don't actually warn about the condition their message
		3597	seems to warn about). For example, certain older gcc versions had some
		3598	warnings that resulted an extreme number of false positives. These have
		3599	been fixed, but some people still insist on making code warn-free with
		3600	such buggy versions.
		3601
		3602	While libev is written to generate as few warnings as possible,
		3603	"warn-free" code is not a goal, and it is recommended not to build libev
		3604	with any compiler warnings enabled unless you are prepared to cope with
		3605	them (e.g. by ignoring them). Remember that warnings are just that:
		3606	warnings, not errors, or proof of bugs.
		3607
		3608
		3609	=head2 VALGRIND
		3610
		3611	Valgrind has a special section here because it is a popular tool that is
		3612	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3613
		3614	If you think you found a bug (memory leak, uninitialised data access etc.)
		3615	in libev, then check twice: If valgrind reports something like:
		3616
		3617	==2274== definitely lost: 0 bytes in 0 blocks.
		3618	==2274== possibly lost: 0 bytes in 0 blocks.
		3619	==2274== still reachable: 256 bytes in 1 blocks.
		3620
		3621	Then there is no memory leak, just as memory accounted to global variables
		3622	is not a memleak - the memory is still being referenced, and didn't leak.
		3623
		3624	Similarly, under some circumstances, valgrind might report kernel bugs
		3625	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3626	although an acceptable workaround has been found here), or it might be
		3627	confused.
		3628
		3629	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3630	make it into some kind of religion.
		3631
		3632	If you are unsure about something, feel free to contact the mailing list
		3633	with the full valgrind report and an explanation on why you think this
		3634	is a bug in libev (best check the archives, too :). However, don't be
		3635	annoyed when you get a brisk "this is no bug" answer and take the chance
		3636	of learning how to interpret valgrind properly.
		3637
		3638	If you need, for some reason, empty reports from valgrind for your project
		3639	I suggest using suppression lists.
		3640
		3641
		3642	=head1 PORTABILITY NOTES
		3643
		3644	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3645
		3646	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3647	requires, and its I/O model is fundamentally incompatible with the POSIX
		3648	model. Libev still offers limited functionality on this platform in
		3649	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3650	descriptors. This only applies when using Win32 natively, not when using
		3651	e.g. cygwin.
		3652
		3653	Lifting these limitations would basically require the full
		3654	re-implementation of the I/O system. If you are into these kinds of
		3655	things, then note that glib does exactly that for you in a very portable
		3656	way (note also that glib is the slowest event library known to man).
		3657
		3658	There is no supported compilation method available on windows except
		3659	embedding it into other applications.
		3660
		3661	Not a libev limitation but worth mentioning: windows apparently doesn't
		3662	accept large writes: instead of resulting in a partial write, windows will
		3663	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3664	so make sure you only write small amounts into your sockets (less than a
		3665	megabyte seems safe, but this apparently depends on the amount of memory
		3666	available).
		3667
		3668	Due to the many, low, and arbitrary limits on the win32 platform and
		3669	the abysmal performance of winsockets, using a large number of sockets
		3670	is not recommended (and not reasonable). If your program needs to use
		3671	more than a hundred or so sockets, then likely it needs to use a totally
		3672	different implementation for windows, as libev offers the POSIX readiness
		3673	notification model, which cannot be implemented efficiently on windows
		3674	(Microsoft monopoly games).
		3675
		3676	A typical way to use libev under windows is to embed it (see the embedding
		3677	section for details) and use the following F<evwrap.h> header file instead
		3678	of F<ev.h>:
		3679
		3680	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3681	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3682
		3683	#include "ev.h"
		3684
		3685	And compile the following F<evwrap.c> file into your project (make sure
		3686	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3687
		3688	#include "evwrap.h"
		3689	#include "ev.c"
		3690
		3691	=over 4
		3692
		3693	=item The winsocket select function
		3694
		3695	The winsocket C<select> function doesn't follow POSIX in that it
		3696	requires socket I<handles> and not socket I<file descriptors> (it is
		3697	also extremely buggy). This makes select very inefficient, and also
		3698	requires a mapping from file descriptors to socket handles (the Microsoft
		3699	C runtime provides the function C<_open_osfhandle> for this). See the
		3700	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3701	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3702
		3703	The configuration for a "naked" win32 using the Microsoft runtime
		3704	libraries and raw winsocket select is:
		3705
		3706	#define EV_USE_SELECT 1
		3707	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3708
		3709	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3710	complexity in the O(n²) range when using win32.
		3711
		3712	=item Limited number of file descriptors
		3713
		3714	Windows has numerous arbitrary (and low) limits on things.
		3715
		3716	Early versions of winsocket's select only supported waiting for a maximum
		3717	of C<64> handles (probably owning to the fact that all windows kernels
		3718	can only wait for C<64> things at the same time internally; Microsoft
		3719	recommends spawning a chain of threads and wait for 63 handles and the
		3720	previous thread in each. Great).
		3721
		3722	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3723	to some high number (e.g. C<2048>) before compiling the winsocket select
		3724	call (which might be in libev or elsewhere, for example, perl does its own
		3725	select emulation on windows).
		3726
		3727	Another limit is the number of file descriptors in the Microsoft runtime
		3728	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3729	or something like this inside Microsoft). You can increase this by calling
		3730	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3731	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3732	libraries.
		3733
		3734	This might get you to about C<512> or C<2048> sockets (depending on
		3735	windows version and/or the phase of the moon). To get more, you need to
		3736	wrap all I/O functions and provide your own fd management, but the cost of
		3737	calling select (O(n²)) will likely make this unworkable.
		3738
		3739	=back
		3740
		3741	=head2 PORTABILITY REQUIREMENTS
		3742
		3743	In addition to a working ISO-C implementation and of course the
		3744	backend-specific APIs, libev relies on a few additional extensions:
		3745
		3746	=over 4
		3747
		3748	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3749	calling conventions regardless of C<ev_watcher_type *>.
		3750
		3751	Libev assumes not only that all watcher pointers have the same internal
		3752	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3753	assumes that the same (machine) code can be used to call any watcher
		3754	callback: The watcher callbacks have different type signatures, but libev
		3755	calls them using an C<ev_watcher *> internally.
		3756
		3757	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3758
		3759	The type C<sig_atomic_t volatile> (or whatever is defined as
		3760	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3761	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3762	believed to be sufficiently portable.
		3763
		3764	=item C<sigprocmask> must work in a threaded environment
		3765
		3766	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3767	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3768	pthread implementations will either allow C<sigprocmask> in the "main
		3769	thread" or will block signals process-wide, both behaviours would
		3770	be compatible with libev. Interaction between C<sigprocmask> and
		3771	C<pthread_sigmask> could complicate things, however.
		3772
		3773	The most portable way to handle signals is to block signals in all threads
		3774	except the initial one, and run the default loop in the initial thread as
		3775	well.
		3776
		3777	=item C<long> must be large enough for common memory allocation sizes
		3778
		3779	To improve portability and simplify its API, libev uses C<long> internally
		3780	instead of C<size_t> when allocating its data structures. On non-POSIX
		3781	systems (Microsoft...) this might be unexpectedly low, but is still at
		3782	least 31 bits everywhere, which is enough for hundreds of millions of
		3783	watchers.
		3784
		3785	=item C<double> must hold a time value in seconds with enough accuracy
		3786
		3787	The type C<double> is used to represent timestamps. It is required to
		3788	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3789	enough for at least into the year 4000. This requirement is fulfilled by
		3790	implementations implementing IEEE 754 (basically all existing ones).
		3791
		3792	=back
		3793
		3794	If you know of other additional requirements drop me a note.
		3795
		3796
2619	=head1 COMPLEXITIES	3797	=head1 ALGORITHMIC COMPLEXITIES
2620		3798
2621	In this section the complexities of (many of) the algorithms used inside	3799	In this section the complexities of (many of) the algorithms used inside
2622	libev will be explained. For complexity discussions about backends see the	3800	libev will be documented. For complexity discussions about backends see
2623	documentation for C<ev_default_init>.	3801	the documentation for C<ev_default_init>.
2624		3802
2625	All of the following are about amortised time: If an array needs to be	3803	All of the following are about amortised time: If an array needs to be
2626	extended, libev needs to realloc and move the whole array, but this	3804	extended, libev needs to realloc and move the whole array, but this
2627	happens asymptotically never with higher number of elements, so O(1) might	3805	happens asymptotically rarer with higher number of elements, so O(1) might
2628	mean it might do a lengthy realloc operation in rare cases, but on average	3806	mean that libev does a lengthy realloc operation in rare cases, but on
2629	it is much faster and asymptotically approaches constant time.	3807	average it is much faster and asymptotically approaches constant time.
2630		3808
2631	=over 4	3809	=over 4
2632		3810
2633	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3811	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2634		3812
2635	This means that, when you have a watcher that triggers in one hour and	3813	This means that, when you have a watcher that triggers in one hour and
2636	there are 100 watchers that would trigger before that then inserting will	3814	there are 100 watchers that would trigger before that, then inserting will
2637	have to skip those 100 watchers.	3815	have to skip roughly seven (C<ld 100>) of these watchers.
2638		3816
2639	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3817	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2640		3818
2641	That means that for changing a timer costs less than removing/adding them	3819	That means that changing a timer costs less than removing/adding them,
2642	as only the relative motion in the event queue has to be paid for.	3820	as only the relative motion in the event queue has to be paid for.
2643		3821
2644	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3822	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2645		3823
2646	These just add the watcher into an array or at the head of a list.	3824	These just add the watcher into an array or at the head of a list.
		3825
2647	=item Stopping check/prepare/idle watchers: O(1)	3826	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2648		3827
2649	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3828	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2650		3829
2651	These watchers are stored in lists then need to be walked to find the	3830	These watchers are stored in lists, so they need to be walked to find the
2652	correct watcher to remove. The lists are usually short (you don't usually	3831	correct watcher to remove. The lists are usually short (you don't usually
2653	have many watchers waiting for the same fd or signal).	3832	have many watchers waiting for the same fd or signal: one is typical, two
		3833	is rare).
2654		3834
2655	=item Finding the next timer per loop iteration: O(1)	3835	=item Finding the next timer in each loop iteration: O(1)
		3836
		3837	By virtue of using a binary or 4-heap, the next timer is always found at a
		3838	fixed position in the storage array.
2656		3839
2657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3840	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2658		3841
2659	A change means an I/O watcher gets started or stopped, which requires	3842	A change means an I/O watcher gets started or stopped, which requires
2660	libev to recalculate its status (and possibly tell the kernel).	3843	libev to recalculate its status (and possibly tell the kernel, depending
		3844	on backend and whether C<ev_io_set> was used).
2661		3845
2662	=item Activating one watcher: O(1)	3846	=item Activating one watcher (putting it into the pending state): O(1)
2663		3847
2664	=item Priority handling: O(number_of_priorities)	3848	=item Priority handling: O(number_of_priorities)
2665		3849
2666	Priorities are implemented by allocating some space for each	3850	Priorities are implemented by allocating some space for each
2667	priority. When doing priority-based operations, libev usually has to	3851	priority. When doing priority-based operations, libev usually has to
2668	linearly search all the priorities.	3852	linearly search all the priorities, but starting/stopping and activating
		3853	watchers becomes O(1) with respect to priority handling.
		3854
		3855	=item Sending an ev_async: O(1)
		3856
		3857	=item Processing ev_async_send: O(number_of_async_watchers)
		3858
		3859	=item Processing signals: O(max_signal_number)
		3860
		3861	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3862	calls in the current loop iteration. Checking for async and signal events
		3863	involves iterating over all running async watchers or all signal numbers.
2669		3864
2670	=back	3865	=back
2671		3866
2672		3867
2673	=head1 AUTHOR	3868	=head1 AUTHOR
2674		3869
2675	Marc Lehmann <libev@schmorp.de>.	3870	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
2676		3871

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