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Revision 1.134 by root, Sat Mar 8 07:04:56 2008 UTC vs.
Revision 1.216 by root, Thu Nov 13 15:55:38 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
265	The default loop is the only loop that can handle C<ev_signal> and	305	The default loop is the only loop that can handle C<ev_signal> and
266	C<ev_child> watchers, and to do this, it always registers a handler	306	C<ev_child> watchers, and to do this, it always registers a handler
267	for C<SIGCHLD>. If this is a problem for your app you can either	307	for C<SIGCHLD>. If this is a problem for your application you can either
268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270	C<ev_default_init>.	310	C<ev_default_init>.
271		311
272	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
…		…
281	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
282	thing, believe me).	322	thing, believe me).
283		323
284	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
285		325
286	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
287	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
288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
289	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
290	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
291	around bugs.	331	around bugs.
…		…
297	enabling this flag.	337	enabling this flag.
298		338
299	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,
300	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
301	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
302	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
303	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
304	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
305		345
306	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
307	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
308	flag.	348	flag.
309		349
310	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>
311	environment variable.	351	environment variable.
312		352
313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
314		354
315	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
…		…
317	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
318	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
319	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.
320		360
321	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
322	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
323	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
324	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
325	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
326	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).
327		371
328	=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)
329		373
330	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
331	than select, but handles sparse fds better and has no artificial	375	than select, but handles sparse fds better and has no artificial
332	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
333	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,
334	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
335	performance tips.	379	performance tips.
336		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
337	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
338		385
339	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,
340	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
341	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),
342	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).
343	of shortcomings, such as silently dropping events in some hard-to-detect	390
344	cases and rewiring a syscall per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
345	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.
346		407
347	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
348	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
349	(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
350	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
351	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
352		413	file descriptors.
353	Please note that epoll sometimes generates spurious notifications, so you
354	need to use non-blocking I/O or other means to avoid blocking when no data
355	(or space) is available.
356		414
357	Best performance from this backend is achieved by not unregistering all	415	Best performance from this backend is achieved by not unregistering all
358	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,
359	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.
360		422
		423	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		424	faster than epoll for maybe up to a hundred file descriptors, depending on
		425	the usage. So sad.
		426
361	While nominally embeddeble in other event loops, this feature is broken in	427	While nominally embeddable in other event loops, this feature is broken in
362	all kernel versions tested so far.	428	all kernel versions tested so far.
		429
		430	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		431	C<EVBACKEND_POLL>.
363		432
364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	433	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
365		434
366	Kqueue deserves special mention, as at the time of this writing, it	435	Kqueue deserves special mention, as at the time of this writing, it
367	was broken on all BSDs except NetBSD (usually it doesn't work reliably	436	was broken on all BSDs except NetBSD (usually it doesn't work reliably
368	with anything but sockets and pipes, except on Darwin, where of course	437	with anything but sockets and pipes, except on Darwin, where of course
369	it's completely useless). For this reason it's not being "autodetected"	438	it's completely useless). Unlike epoll, however, whose brokenness
		439	is by design, these kqueue bugs can (and eventually will) be fixed
		440	without API changes to existing programs. For this reason it's not being
370	unless you explicitly specify it explicitly in the flags (i.e. using	441	"auto-detected" unless you explicitly specify it in the flags (i.e. using
371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	442	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
372	system like NetBSD.	443	system like NetBSD.
373		444
374	You still can embed kqueue into a normal poll or select backend and use it	445	You still can embed kqueue into a normal poll or select backend and use it
375	only for sockets (after having made sure that sockets work with kqueue on	446	only for sockets (after having made sure that sockets work with kqueue on
376	the target platform). See C<ev_embed> watchers for more info.	447	the target platform). See C<ev_embed> watchers for more info.
377		448
378	It scales in the same way as the epoll backend, but the interface to the	449	It scales in the same way as the epoll backend, but the interface to the
379	kernel is more efficient (which says nothing about its actual speed, of	450	kernel is more efficient (which says nothing about its actual speed, of
380	course). While stopping, setting and starting an I/O watcher does never	451	course). While stopping, setting and starting an I/O watcher does never
381	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	452	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
382	two event changes per incident, support for C<fork ()> is very bad and it	453	two event changes per incident. Support for C<fork ()> is very bad (but
383	drops fds silently in similarly hard-to-detect cases.	454	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		455	cases
384		456
385	This backend usually performs well under most conditions.	457	This backend usually performs well under most conditions.
386		458
387	While nominally embeddable in other event loops, this doesn't work	459	While nominally embeddable in other event loops, this doesn't work
388	everywhere, so you might need to test for this. And since it is broken	460	everywhere, so you might need to test for this. And since it is broken
389	almost everywhere, you should only use it when you have a lot of sockets	461	almost everywhere, you should only use it when you have a lot of sockets
390	(for which it usually works), by embedding it into another event loop	462	(for which it usually works), by embedding it into another event loop
391	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	463	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
392	sockets.	464	using it only for sockets.
		465
		466	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		467	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		468	C<NOTE_EOF>.
393		469
394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	470	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
395		471
396	This is not implemented yet (and might never be, unless you send me an	472	This is not implemented yet (and might never be, unless you send me an
397	implementation). According to reports, C</dev/poll> only supports sockets	473	implementation). According to reports, C</dev/poll> only supports sockets
…		…
401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	477	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
402		478
403	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	479	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
404	it's really slow, but it still scales very well (O(active_fds)).	480	it's really slow, but it still scales very well (O(active_fds)).
405		481
406	Please note that solaris event ports can deliver a lot of spurious	482	Please note that Solaris event ports can deliver a lot of spurious
407	notifications, so you need to use non-blocking I/O or other means to avoid	483	notifications, so you need to use non-blocking I/O or other means to avoid
408	blocking when no data (or space) is available.	484	blocking when no data (or space) is available.
409		485
410	While this backend scales well, it requires one system call per active	486	While this backend scales well, it requires one system call per active
411	file descriptor per loop iteration. For small and medium numbers of file	487	file descriptor per loop iteration. For small and medium numbers of file
412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	488	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413	might perform better.	489	might perform better.
414		490
415	On the positive side, ignoring the spurious readyness notifications, this	491	On the positive side, with the exception of the spurious readiness
416	backend actually performed to specification in all tests and is fully	492	notifications, this backend actually performed fully to specification
417	embeddable, which is a rare feat among the OS-specific backends.	493	in all tests and is fully embeddable, which is a rare feat among the
		494	OS-specific backends (I vastly prefer correctness over speed hacks).
		495
		496	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		497	C<EVBACKEND_POLL>.
418		498
419	=item C<EVBACKEND_ALL>	499	=item C<EVBACKEND_ALL>
420		500
421	Try all backends (even potentially broken ones that wouldn't be tried	501	Try all backends (even potentially broken ones that wouldn't be tried
422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	502	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
424		504
425	It is definitely not recommended to use this flag.	505	It is definitely not recommended to use this flag.
426		506
427	=back	507	=back
428		508
429	If one or more of these are ored into the flags value, then only these	509	If one or more of these are or'ed into the flags value, then only these
430	backends will be tried (in the reverse order as listed here). If none are	510	backends will be tried (in the reverse order as listed here). If none are
431	specified, all backends in C<ev_recommended_backends ()> will be tried.	511	specified, all backends in C<ev_recommended_backends ()> will be tried.
432		512
433	The most typical usage is like this:	513	Example: This is the most typical usage.
434		514
435	if (!ev_default_loop (0))	515	if (!ev_default_loop (0))
436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	516	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
437		517
438	Restrict libev to the select and poll backends, and do not allow	518	Example: Restrict libev to the select and poll backends, and do not allow
439	environment settings to be taken into account:	519	environment settings to be taken into account:
440		520
441	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	521	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
442		522
443	Use whatever libev has to offer, but make sure that kqueue is used if	523	Example: Use whatever libev has to offer, but make sure that kqueue is
444	available (warning, breaks stuff, best use only with your own private	524	used if available (warning, breaks stuff, best use only with your own
445	event loop and only if you know the OS supports your types of fds):	525	private event loop and only if you know the OS supports your types of
		526	fds):
446		527
447	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	528	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
448		529
449	=item struct ev_loop *ev_loop_new (unsigned int flags)	530	=item struct ev_loop *ev_loop_new (unsigned int flags)
450		531
451	Similar to C<ev_default_loop>, but always creates a new event loop that is	532	Similar to C<ev_default_loop>, but always creates a new event loop that is
452	always distinct from the default loop. Unlike the default loop, it cannot	533	always distinct from the default loop. Unlike the default loop, it cannot
453	handle signal and child watchers, and attempts to do so will be greeted by	534	handle signal and child watchers, and attempts to do so will be greeted by
454	undefined behaviour (or a failed assertion if assertions are enabled).	535	undefined behaviour (or a failed assertion if assertions are enabled).
455		536
		537	Note that this function I<is> thread-safe, and the recommended way to use
		538	libev with threads is indeed to create one loop per thread, and using the
		539	default loop in the "main" or "initial" thread.
		540
456	Example: Try to create a event loop that uses epoll and nothing else.	541	Example: Try to create a event loop that uses epoll and nothing else.
457		542
458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	543	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
459	if (!epoller)	544	if (!epoller)
460	fatal ("no epoll found here, maybe it hides under your chair");	545	fatal ("no epoll found here, maybe it hides under your chair");
461		546
462	=item ev_default_destroy ()	547	=item ev_default_destroy ()
463		548
464	Destroys the default loop again (frees all memory and kernel state	549	Destroys the default loop again (frees all memory and kernel state
465	etc.). None of the active event watchers will be stopped in the normal	550	etc.). None of the active event watchers will be stopped in the normal
466	sense, so e.g. C<ev_is_active> might still return true. It is your	551	sense, so e.g. C<ev_is_active> might still return true. It is your
467	responsibility to either stop all watchers cleanly yoursef I<before>	552	responsibility to either stop all watchers cleanly yourself I<before>
468	calling this function, or cope with the fact afterwards (which is usually	553	calling this function, or cope with the fact afterwards (which is usually
469	the easiest thing, you can just ignore the watchers and/or C<free ()> them	554	the easiest thing, you can just ignore the watchers and/or C<free ()> them
470	for example).	555	for example).
471		556
472	Note that certain global state, such as signal state, will not be freed by	557	Note that certain global state, such as signal state (and installed signal
473	this function, and related watchers (such as signal and child watchers)	558	handlers), will not be freed by this function, and related watchers (such
474	would need to be stopped manually.	559	as signal and child watchers) would need to be stopped manually.
475		560
476	In general it is not advisable to call this function except in the	561	In general it is not advisable to call this function except in the
477	rare occasion where you really need to free e.g. the signal handling	562	rare occasion where you really need to free e.g. the signal handling
478	pipe fds. If you need dynamically allocated loops it is better to use	563	pipe fds. If you need dynamically allocated loops it is better to use
479	C<ev_loop_new> and C<ev_loop_destroy>).	564	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
504		589
505	=item ev_loop_fork (loop)	590	=item ev_loop_fork (loop)
506		591
507	Like C<ev_default_fork>, but acts on an event loop created by	592	Like C<ev_default_fork>, but acts on an event loop created by
508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	593	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
509	after fork, and how you do this is entirely your own problem.	594	after fork that you want to re-use in the child, and how you do this is
		595	entirely your own problem.
510		596
511	=item int ev_is_default_loop (loop)	597	=item int ev_is_default_loop (loop)
512		598
513	Returns true when the given loop actually is the default loop, false otherwise.	599	Returns true when the given loop is, in fact, the default loop, and false
		600	otherwise.
514		601
515	=item unsigned int ev_loop_count (loop)	602	=item unsigned int ev_loop_count (loop)
516		603
517	Returns the count of loop iterations for the loop, which is identical to	604	Returns the count of loop iterations for the loop, which is identical to
518	the number of times libev did poll for new events. It starts at C<0> and	605	the number of times libev did poll for new events. It starts at C<0> and
…		…
533	received events and started processing them. This timestamp does not	620	received events and started processing them. This timestamp does not
534	change as long as callbacks are being processed, and this is also the base	621	change as long as callbacks are being processed, and this is also the base
535	time used for relative timers. You can treat it as the timestamp of the	622	time used for relative timers. You can treat it as the timestamp of the
536	event occurring (or more correctly, libev finding out about it).	623	event occurring (or more correctly, libev finding out about it).
537		624
		625	=item ev_now_update (loop)
		626
		627	Establishes the current time by querying the kernel, updating the time
		628	returned by C<ev_now ()> in the progress. This is a costly operation and
		629	is usually done automatically within C<ev_loop ()>.
		630
		631	This function is rarely useful, but when some event callback runs for a
		632	very long time without entering the event loop, updating libev's idea of
		633	the current time is a good idea.
		634
		635	See also "The special problem of time updates" in the C<ev_timer> section.
		636
538	=item ev_loop (loop, int flags)	637	=item ev_loop (loop, int flags)
539		638
540	Finally, this is it, the event handler. This function usually is called	639	Finally, this is it, the event handler. This function usually is called
541	after you initialised all your watchers and you want to start handling	640	after you initialised all your watchers and you want to start handling
542	events.	641	events.
…		…
544	If the flags argument is specified as C<0>, it will not return until	643	If the flags argument is specified as C<0>, it will not return until
545	either no event watchers are active anymore or C<ev_unloop> was called.	644	either no event watchers are active anymore or C<ev_unloop> was called.
546		645
547	Please note that an explicit C<ev_unloop> is usually better than	646	Please note that an explicit C<ev_unloop> is usually better than
548	relying on all watchers to be stopped when deciding when a program has	647	relying on all watchers to be stopped when deciding when a program has
549	finished (especially in interactive programs), but having a program that	648	finished (especially in interactive programs), but having a program
550	automatically loops as long as it has to and no longer by virtue of	649	that automatically loops as long as it has to and no longer by virtue
551	relying on its watchers stopping correctly is a thing of beauty.	650	of relying on its watchers stopping correctly, that is truly a thing of
		651	beauty.
552		652
553	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	653	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
554	those events and any outstanding ones, but will not block your process in	654	those events and any already outstanding ones, but will not block your
555	case there are no events and will return after one iteration of the loop.	655	process in case there are no events and will return after one iteration of
		656	the loop.
556		657
557	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	658	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
558	neccessary) and will handle those and any outstanding ones. It will block	659	necessary) and will handle those and any already outstanding ones. It
559	your process until at least one new event arrives, and will return after	660	will block your process until at least one new event arrives (which could
560	one iteration of the loop. This is useful if you are waiting for some	661	be an event internal to libev itself, so there is no guarantee that a
561	external event in conjunction with something not expressible using other	662	user-registered callback will be called), and will return after one
		663	iteration of the loop.
		664
		665	This is useful if you are waiting for some external event in conjunction
		666	with something not expressible using other libev watchers (i.e. "roll your
562	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	667	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
563	usually a better approach for this kind of thing.	668	usually a better approach for this kind of thing.
564		669
565	Here are the gory details of what C<ev_loop> does:	670	Here are the gory details of what C<ev_loop> does:
566		671
567	- Before the first iteration, call any pending watchers.	672	- Before the first iteration, call any pending watchers.
568	* If EVFLAG_FORKCHECK was used, check for a fork.	673	* If EVFLAG_FORKCHECK was used, check for a fork.
569	- If a fork was detected, queue and call all fork watchers.	674	- If a fork was detected (by any means), queue and call all fork watchers.
570	- Queue and call all prepare watchers.	675	- Queue and call all prepare watchers.
571	- If we have been forked, recreate the kernel state.	676	- If we have been forked, detach and recreate the kernel state
		677	as to not disturb the other process.
572	- Update the kernel state with all outstanding changes.	678	- Update the kernel state with all outstanding changes.
573	- Update the "event loop time".	679	- Update the "event loop time" (ev_now ()).
574	- Calculate for how long to sleep or block, if at all	680	- Calculate for how long to sleep or block, if at all
575	(active idle watchers, EVLOOP_NONBLOCK or not having	681	(active idle watchers, EVLOOP_NONBLOCK or not having
576	any active watchers at all will result in not sleeping).	682	any active watchers at all will result in not sleeping).
577	- Sleep if the I/O and timer collect interval say so.	683	- Sleep if the I/O and timer collect interval say so.
578	- Block the process, waiting for any events.	684	- Block the process, waiting for any events.
579	- Queue all outstanding I/O (fd) events.	685	- Queue all outstanding I/O (fd) events.
580	- Update the "event loop time" and do time jump handling.	686	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
581	- Queue all outstanding timers.	687	- Queue all expired timers.
582	- Queue all outstanding periodics.	688	- Queue all expired periodics.
583	- If no events are pending now, queue all idle watchers.	689	- Unless any events are pending now, queue all idle watchers.
584	- Queue all check watchers.	690	- Queue all check watchers.
585	- Call all queued watchers in reverse order (i.e. check watchers first).	691	- Call all queued watchers in reverse order (i.e. check watchers first).
586	Signals and child watchers are implemented as I/O watchers, and will	692	Signals and child watchers are implemented as I/O watchers, and will
587	be handled here by queueing them when their watcher gets executed.	693	be handled here by queueing them when their watcher gets executed.
588	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	694	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
593	anymore.	699	anymore.
594		700
595	... queue jobs here, make sure they register event watchers as long	701	... queue jobs here, make sure they register event watchers as long
596	... as they still have work to do (even an idle watcher will do..)	702	... as they still have work to do (even an idle watcher will do..)
597	ev_loop (my_loop, 0);	703	ev_loop (my_loop, 0);
598	... jobs done. yeah!	704	... jobs done or somebody called unloop. yeah!
599		705
600	=item ev_unloop (loop, how)	706	=item ev_unloop (loop, how)
601		707
602	Can be used to make a call to C<ev_loop> return early (but only after it	708	Can be used to make a call to C<ev_loop> return early (but only after it
603	has processed all outstanding events). The C<how> argument must be either	709	has processed all outstanding events). The C<how> argument must be either
604	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	710	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
605	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	711	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
606		712
607	This "unloop state" will be cleared when entering C<ev_loop> again.	713	This "unloop state" will be cleared when entering C<ev_loop> again.
608		714
		715	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		716
609	=item ev_ref (loop)	717	=item ev_ref (loop)
610		718
611	=item ev_unref (loop)	719	=item ev_unref (loop)
612		720
613	Ref/unref can be used to add or remove a reference count on the event	721	Ref/unref can be used to add or remove a reference count on the event
614	loop: Every watcher keeps one reference, and as long as the reference	722	loop: Every watcher keeps one reference, and as long as the reference
615	count is nonzero, C<ev_loop> will not return on its own. If you have	723	count is nonzero, C<ev_loop> will not return on its own.
		724
616	a watcher you never unregister that should not keep C<ev_loop> from	725	If you have a watcher you never unregister that should not keep C<ev_loop>
617	returning, ev_unref() after starting, and ev_ref() before stopping it. For	726	from returning, call ev_unref() after starting, and ev_ref() before
		727	stopping it.
		728
618	example, libev itself uses this for its internal signal pipe: It is not	729	As an example, libev itself uses this for its internal signal pipe: It is
619	visible to the libev user and should not keep C<ev_loop> from exiting if	730	not visible to the libev user and should not keep C<ev_loop> from exiting
620	no event watchers registered by it are active. It is also an excellent	731	if no event watchers registered by it are active. It is also an excellent
621	way to do this for generic recurring timers or from within third-party	732	way to do this for generic recurring timers or from within third-party
622	libraries. Just remember to I<unref after start> and I<ref before stop>	733	libraries. Just remember to I<unref after start> and I<ref before stop>
623	(but only if the watcher wasn't active before, or was active before,	734	(but only if the watcher wasn't active before, or was active before,
624	respectively).	735	respectively).
625		736
626	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	737	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
627	running when nothing else is active.	738	running when nothing else is active.
628		739
629	struct ev_signal exitsig;	740	ev_signal exitsig;
630	ev_signal_init (&exitsig, sig_cb, SIGINT);	741	ev_signal_init (&exitsig, sig_cb, SIGINT);
631	ev_signal_start (loop, &exitsig);	742	ev_signal_start (loop, &exitsig);
632	evf_unref (loop);	743	evf_unref (loop);
633		744
634	Example: For some weird reason, unregister the above signal handler again.	745	Example: For some weird reason, unregister the above signal handler again.
635		746
636	ev_ref (loop);	747	ev_ref (loop);
637	ev_signal_stop (loop, &exitsig);	748	ev_signal_stop (loop, &exitsig);
638		749
639	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	750	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
640		751
641	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	752	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
642		753
643	These advanced functions influence the time that libev will spend waiting	754	These advanced functions influence the time that libev will spend waiting
644	for events. Both are by default C<0>, meaning that libev will try to	755	for events. Both time intervals are by default C<0>, meaning that libev
645	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	756	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		757	latency.
646		758
647	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	759	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
648	allows libev to delay invocation of I/O and timer/periodic callbacks to	760	allows libev to delay invocation of I/O and timer/periodic callbacks
649	increase efficiency of loop iterations.	761	to increase efficiency of loop iterations (or to increase power-saving
		762	opportunities).
650		763
651	The background is that sometimes your program runs just fast enough to	764	The idea is that sometimes your program runs just fast enough to handle
652	handle one (or very few) event(s) per loop iteration. While this makes	765	one (or very few) event(s) per loop iteration. While this makes the
653	the program responsive, it also wastes a lot of CPU time to poll for new	766	program responsive, it also wastes a lot of CPU time to poll for new
654	events, especially with backends like C<select ()> which have a high	767	events, especially with backends like C<select ()> which have a high
655	overhead for the actual polling but can deliver many events at once.	768	overhead for the actual polling but can deliver many events at once.
656		769
657	By setting a higher I<io collect interval> you allow libev to spend more	770	By setting a higher I<io collect interval> you allow libev to spend more
658	time collecting I/O events, so you can handle more events per iteration,	771	time collecting I/O events, so you can handle more events per iteration,
…		…
660	C<ev_timer>) will be not affected. Setting this to a non-null value will	773	C<ev_timer>) will be not affected. Setting this to a non-null value will
661	introduce an additional C<ev_sleep ()> call into most loop iterations.	774	introduce an additional C<ev_sleep ()> call into most loop iterations.
662		775
663	Likewise, by setting a higher I<timeout collect interval> you allow libev	776	Likewise, by setting a higher I<timeout collect interval> you allow libev
664	to spend more time collecting timeouts, at the expense of increased	777	to spend more time collecting timeouts, at the expense of increased
665	latency (the watcher callback will be called later). C<ev_io> watchers	778	latency/jitter/inexactness (the watcher callback will be called
666	will not be affected. Setting this to a non-null value will not introduce	779	later). C<ev_io> watchers will not be affected. Setting this to a non-null
667	any overhead in libev.	780	value will not introduce any overhead in libev.
668		781
669	Many (busy) programs can usually benefit by setting the io collect	782	Many (busy) programs can usually benefit by setting the I/O collect
670	interval to a value near C<0.1> or so, which is often enough for	783	interval to a value near C<0.1> or so, which is often enough for
671	interactive servers (of course not for games), likewise for timeouts. It	784	interactive servers (of course not for games), likewise for timeouts. It
672	usually doesn't make much sense to set it to a lower value than C<0.01>,	785	usually doesn't make much sense to set it to a lower value than C<0.01>,
673	as this approsaches the timing granularity of most systems.	786	as this approaches the timing granularity of most systems.
		787
		788	Setting the I<timeout collect interval> can improve the opportunity for
		789	saving power, as the program will "bundle" timer callback invocations that
		790	are "near" in time together, by delaying some, thus reducing the number of
		791	times the process sleeps and wakes up again. Another useful technique to
		792	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		793	they fire on, say, one-second boundaries only.
		794
		795	=item ev_loop_verify (loop)
		796
		797	This function only does something when C<EV_VERIFY> support has been
		798	compiled in, which is the default for non-minimal builds. It tries to go
		799	through all internal structures and checks them for validity. If anything
		800	is found to be inconsistent, it will print an error message to standard
		801	error and call C<abort ()>.
		802
		803	This can be used to catch bugs inside libev itself: under normal
		804	circumstances, this function will never abort as of course libev keeps its
		805	data structures consistent.
674		806
675	=back	807	=back
676		808
677		809
678	=head1 ANATOMY OF A WATCHER	810	=head1 ANATOMY OF A WATCHER
		811
		812	In the following description, uppercase C<TYPE> in names stands for the
		813	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		814	watchers and C<ev_io_start> for I/O watchers.
679		815
680	A watcher is a structure that you create and register to record your	816	A watcher is a structure that you create and register to record your
681	interest in some event. For instance, if you want to wait for STDIN to	817	interest in some event. For instance, if you want to wait for STDIN to
682	become readable, you would create an C<ev_io> watcher for that:	818	become readable, you would create an C<ev_io> watcher for that:
683		819
684	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	820	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
685	{	821	{
686	ev_io_stop (w);	822	ev_io_stop (w);
687	ev_unloop (loop, EVUNLOOP_ALL);	823	ev_unloop (loop, EVUNLOOP_ALL);
688	}	824	}
689		825
690	struct ev_loop *loop = ev_default_loop (0);	826	struct ev_loop *loop = ev_default_loop (0);
		827
691	struct ev_io stdin_watcher;	828	ev_io stdin_watcher;
		829
692	ev_init (&stdin_watcher, my_cb);	830	ev_init (&stdin_watcher, my_cb);
693	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	831	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
694	ev_io_start (loop, &stdin_watcher);	832	ev_io_start (loop, &stdin_watcher);
		833
695	ev_loop (loop, 0);	834	ev_loop (loop, 0);
696		835
697	As you can see, you are responsible for allocating the memory for your	836	As you can see, you are responsible for allocating the memory for your
698	watcher structures (and it is usually a bad idea to do this on the stack,	837	watcher structures (and it is I<usually> a bad idea to do this on the
699	although this can sometimes be quite valid).	838	stack).
		839
		840	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		841	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
700		842
701	Each watcher structure must be initialised by a call to C<ev_init	843	Each watcher structure must be initialised by a call to C<ev_init
702	(watcher *, callback)>, which expects a callback to be provided. This	844	(watcher *, callback)>, which expects a callback to be provided. This
703	callback gets invoked each time the event occurs (or, in the case of io	845	callback gets invoked each time the event occurs (or, in the case of I/O
704	watchers, each time the event loop detects that the file descriptor given	846	watchers, each time the event loop detects that the file descriptor given
705	is readable and/or writable).	847	is readable and/or writable).
706		848
707	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	849	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
708	with arguments specific to this watcher type. There is also a macro	850	macro to configure it, with arguments specific to the watcher type. There
709	to combine initialisation and setting in one call: C<< ev_<type>_init	851	is also a macro to combine initialisation and setting in one call: C<<
710	(watcher *, callback, ...) >>.	852	ev_TYPE_init (watcher *, callback, ...) >>.
711		853
712	To make the watcher actually watch out for events, you have to start it	854	To make the watcher actually watch out for events, you have to start it
713	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	855	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
714	*) >>), and you can stop watching for events at any time by calling the	856	*) >>), and you can stop watching for events at any time by calling the
715	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	857	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
716		858
717	As long as your watcher is active (has been started but not stopped) you	859	As long as your watcher is active (has been started but not stopped) you
718	must not touch the values stored in it. Most specifically you must never	860	must not touch the values stored in it. Most specifically you must never
719	reinitialise it or call its C<set> macro.	861	reinitialise it or call its C<ev_TYPE_set> macro.
720		862
721	Each and every callback receives the event loop pointer as first, the	863	Each and every callback receives the event loop pointer as first, the
722	registered watcher structure as second, and a bitset of received events as	864	registered watcher structure as second, and a bitset of received events as
723	third argument.	865	third argument.
724		866
…		…
784		926
785	The given async watcher has been asynchronously notified (see C<ev_async>).	927	The given async watcher has been asynchronously notified (see C<ev_async>).
786		928
787	=item C<EV_ERROR>	929	=item C<EV_ERROR>
788		930
789	An unspecified error has occured, the watcher has been stopped. This might	931	An unspecified error has occurred, the watcher has been stopped. This might
790	happen because the watcher could not be properly started because libev	932	happen because the watcher could not be properly started because libev
791	ran out of memory, a file descriptor was found to be closed or any other	933	ran out of memory, a file descriptor was found to be closed or any other
		934	problem. Libev considers these application bugs.
		935
792	problem. You best act on it by reporting the problem and somehow coping	936	You best act on it by reporting the problem and somehow coping with the
793	with the watcher being stopped.	937	watcher being stopped. Note that well-written programs should not receive
		938	an error ever, so when your watcher receives it, this usually indicates a
		939	bug in your program.
794		940
795	Libev will usually signal a few "dummy" events together with an error,	941	Libev will usually signal a few "dummy" events together with an error, for
796	for example it might indicate that a fd is readable or writable, and if	942	example it might indicate that a fd is readable or writable, and if your
797	your callbacks is well-written it can just attempt the operation and cope	943	callbacks is well-written it can just attempt the operation and cope with
798	with the error from read() or write(). This will not work in multithreaded	944	the error from read() or write(). This will not work in multi-threaded
799	programs, though, so beware.	945	programs, though, as the fd could already be closed and reused for another
		946	thing, so beware.
800		947
801	=back	948	=back
802		949
803	=head2 GENERIC WATCHER FUNCTIONS	950	=head2 GENERIC WATCHER FUNCTIONS
804
805	In the following description, C<TYPE> stands for the watcher type,
806	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
807		951
808	=over 4	952	=over 4
809		953
810	=item C<ev_init> (ev_TYPE *watcher, callback)	954	=item C<ev_init> (ev_TYPE *watcher, callback)
811		955
…		…
817	which rolls both calls into one.	961	which rolls both calls into one.
818		962
819	You can reinitialise a watcher at any time as long as it has been stopped	963	You can reinitialise a watcher at any time as long as it has been stopped
820	(or never started) and there are no pending events outstanding.	964	(or never started) and there are no pending events outstanding.
821		965
822	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	966	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
823	int revents)>.	967	int revents)>.
		968
		969	Example: Initialise an C<ev_io> watcher in two steps.
		970
		971	ev_io w;
		972	ev_init (&w, my_cb);
		973	ev_io_set (&w, STDIN_FILENO, EV_READ);
824		974
825	=item C<ev_TYPE_set> (ev_TYPE *, [args])	975	=item C<ev_TYPE_set> (ev_TYPE *, [args])
826		976
827	This macro initialises the type-specific parts of a watcher. You need to	977	This macro initialises the type-specific parts of a watcher. You need to
828	call C<ev_init> at least once before you call this macro, but you can	978	call C<ev_init> at least once before you call this macro, but you can
…		…
831	difference to the C<ev_init> macro).	981	difference to the C<ev_init> macro).
832		982
833	Although some watcher types do not have type-specific arguments	983	Although some watcher types do not have type-specific arguments
834	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	984	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
835		985
		986	See C<ev_init>, above, for an example.
		987
836	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	988	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
837		989
838	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	990	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
839	calls into a single call. This is the most convinient method to initialise	991	calls into a single call. This is the most convenient method to initialise
840	a watcher. The same limitations apply, of course.	992	a watcher. The same limitations apply, of course.
		993
		994	Example: Initialise and set an C<ev_io> watcher in one step.
		995
		996	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
841		997
842	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	998	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
843		999
844	Starts (activates) the given watcher. Only active watchers will receive	1000	Starts (activates) the given watcher. Only active watchers will receive
845	events. If the watcher is already active nothing will happen.	1001	events. If the watcher is already active nothing will happen.
846		1002
		1003	Example: Start the C<ev_io> watcher that is being abused as example in this
		1004	whole section.
		1005
		1006	ev_io_start (EV_DEFAULT_UC, &w);
		1007
847	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1008	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
848		1009
849	Stops the given watcher again (if active) and clears the pending	1010	Stops the given watcher if active, and clears the pending status (whether
		1011	the watcher was active or not).
		1012
850	status. It is possible that stopped watchers are pending (for example,	1013	It is possible that stopped watchers are pending - for example,
851	non-repeating timers are being stopped when they become pending), but	1014	non-repeating timers are being stopped when they become pending - but
852	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1015	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
853	you want to free or reuse the memory used by the watcher it is therefore a	1016	pending. If you want to free or reuse the memory used by the watcher it is
854	good idea to always call its C<ev_TYPE_stop> function.	1017	therefore a good idea to always call its C<ev_TYPE_stop> function.
855		1018
856	=item bool ev_is_active (ev_TYPE *watcher)	1019	=item bool ev_is_active (ev_TYPE *watcher)
857		1020
858	Returns a true value iff the watcher is active (i.e. it has been started	1021	Returns a true value iff the watcher is active (i.e. it has been started
859	and not yet been stopped). As long as a watcher is active you must not modify	1022	and not yet been stopped). As long as a watcher is active you must not modify
…		…
901	The default priority used by watchers when no priority has been set is	1064	The default priority used by watchers when no priority has been set is
902	always C<0>, which is supposed to not be too high and not be too low :).	1065	always C<0>, which is supposed to not be too high and not be too low :).
903		1066
904	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1067	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
905	fine, as long as you do not mind that the priority value you query might	1068	fine, as long as you do not mind that the priority value you query might
906	or might not have been adjusted to be within valid range.	1069	or might not have been clamped to the valid range.
907		1070
908	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1071	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
909		1072
910	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1073	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
911	C<loop> nor C<revents> need to be valid as long as the watcher callback	1074	C<loop> nor C<revents> need to be valid as long as the watcher callback
912	can deal with that fact.	1075	can deal with that fact, as both are simply passed through to the
		1076	callback.
913		1077
914	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1078	=item int ev_clear_pending (loop, ev_TYPE *watcher)
915		1079
916	If the watcher is pending, this function returns clears its pending status	1080	If the watcher is pending, this function clears its pending status and
917	and returns its C<revents> bitset (as if its callback was invoked). If the	1081	returns its C<revents> bitset (as if its callback was invoked). If the
918	watcher isn't pending it does nothing and returns C<0>.	1082	watcher isn't pending it does nothing and returns C<0>.
919		1083
		1084	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1085	callback to be invoked, which can be accomplished with this function.
		1086
920	=back	1087	=back
921		1088
922		1089
923	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1090	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
924		1091
925	Each watcher has, by default, a member C<void *data> that you can change	1092	Each watcher has, by default, a member C<void *data> that you can change
926	and read at any time, libev will completely ignore it. This can be used	1093	and read at any time: libev will completely ignore it. This can be used
927	to associate arbitrary data with your watcher. If you need more data and	1094	to associate arbitrary data with your watcher. If you need more data and
928	don't want to allocate memory and store a pointer to it in that data	1095	don't want to allocate memory and store a pointer to it in that data
929	member, you can also "subclass" the watcher type and provide your own	1096	member, you can also "subclass" the watcher type and provide your own
930	data:	1097	data:
931		1098
932	struct my_io	1099	struct my_io
933	{	1100	{
934	struct ev_io io;	1101	ev_io io;
935	int otherfd;	1102	int otherfd;
936	void *somedata;	1103	void *somedata;
937	struct whatever *mostinteresting;	1104	struct whatever *mostinteresting;
938	}	1105	};
		1106
		1107	...
		1108	struct my_io w;
		1109	ev_io_init (&w.io, my_cb, fd, EV_READ);
939		1110
940	And since your callback will be called with a pointer to the watcher, you	1111	And since your callback will be called with a pointer to the watcher, you
941	can cast it back to your own type:	1112	can cast it back to your own type:
942		1113
943	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1114	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
944	{	1115	{
945	struct my_io *w = (struct my_io *)w_;	1116	struct my_io *w = (struct my_io *)w_;
946	...	1117	...
947	}	1118	}
948		1119
949	More interesting and less C-conformant ways of casting your callback type	1120	More interesting and less C-conformant ways of casting your callback type
950	instead have been omitted.	1121	instead have been omitted.
951		1122
952	Another common scenario is having some data structure with multiple	1123	Another common scenario is to use some data structure with multiple
953	watchers:	1124	embedded watchers:
954		1125
955	struct my_biggy	1126	struct my_biggy
956	{	1127	{
957	int some_data;	1128	int some_data;
958	ev_timer t1;	1129	ev_timer t1;
959	ev_timer t2;	1130	ev_timer t2;
960	}	1131	}
961		1132
962	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1133	In this case getting the pointer to C<my_biggy> is a bit more
963	you need to use C<offsetof>:	1134	complicated: Either you store the address of your C<my_biggy> struct
		1135	in the C<data> member of the watcher (for woozies), or you need to use
		1136	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1137	programmers):
964		1138
965	#include <stddef.h>	1139	#include <stddef.h>
966		1140
967	static void	1141	static void
968	t1_cb (EV_P_ struct ev_timer *w, int revents)	1142	t1_cb (EV_P_ ev_timer *w, int revents)
969	{	1143	{
970	struct my_biggy big = (struct my_biggy *	1144	struct my_biggy big = (struct my_biggy *
971	(((char *)w) - offsetof (struct my_biggy, t1));	1145	(((char *)w) - offsetof (struct my_biggy, t1));
972	}	1146	}
973		1147
974	static void	1148	static void
975	t2_cb (EV_P_ struct ev_timer *w, int revents)	1149	t2_cb (EV_P_ ev_timer *w, int revents)
976	{	1150	{
977	struct my_biggy big = (struct my_biggy *	1151	struct my_biggy big = (struct my_biggy *
978	(((char *)w) - offsetof (struct my_biggy, t2));	1152	(((char *)w) - offsetof (struct my_biggy, t2));
979	}	1153	}
980		1154
981		1155
982	=head1 WATCHER TYPES	1156	=head1 WATCHER TYPES
983		1157
984	This section describes each watcher in detail, but will not repeat	1158	This section describes each watcher in detail, but will not repeat
…		…
1008	In general you can register as many read and/or write event watchers per	1182	In general you can register as many read and/or write event watchers per
1009	fd as you want (as long as you don't confuse yourself). Setting all file	1183	fd as you want (as long as you don't confuse yourself). Setting all file
1010	descriptors to non-blocking mode is also usually a good idea (but not	1184	descriptors to non-blocking mode is also usually a good idea (but not
1011	required if you know what you are doing).	1185	required if you know what you are doing).
1012		1186
1013	If you must do this, then force the use of a known-to-be-good backend	1187	If you cannot use non-blocking mode, then force the use of a
1014	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1188	known-to-be-good backend (at the time of this writing, this includes only
1015	C<EVBACKEND_POLL>).	1189	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1016		1190
1017	Another thing you have to watch out for is that it is quite easy to	1191	Another thing you have to watch out for is that it is quite easy to
1018	receive "spurious" readyness notifications, that is your callback might	1192	receive "spurious" readiness notifications, that is your callback might
1019	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1193	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1020	because there is no data. Not only are some backends known to create a	1194	because there is no data. Not only are some backends known to create a
1021	lot of those (for example solaris ports), it is very easy to get into	1195	lot of those (for example Solaris ports), it is very easy to get into
1022	this situation even with a relatively standard program structure. Thus	1196	this situation even with a relatively standard program structure. Thus
1023	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1197	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1024	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1198	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1025		1199
1026	If you cannot run the fd in non-blocking mode (for example you should not	1200	If you cannot run the fd in non-blocking mode (for example you should
1027	play around with an Xlib connection), then you have to seperately re-test	1201	not play around with an Xlib connection), then you have to separately
1028	whether a file descriptor is really ready with a known-to-be good interface	1202	re-test whether a file descriptor is really ready with a known-to-be good
1029	such as poll (fortunately in our Xlib example, Xlib already does this on	1203	interface such as poll (fortunately in our Xlib example, Xlib already
1030	its own, so its quite safe to use).	1204	does this on its own, so its quite safe to use). Some people additionally
		1205	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1206	indefinitely.
		1207
		1208	But really, best use non-blocking mode.
1031		1209
1032	=head3 The special problem of disappearing file descriptors	1210	=head3 The special problem of disappearing file descriptors
1033		1211
1034	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1212	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1035	descriptor (either by calling C<close> explicitly or by any other means,	1213	descriptor (either due to calling C<close> explicitly or any other means,
1036	such as C<dup>). The reason is that you register interest in some file	1214	such as C<dup2>). The reason is that you register interest in some file
1037	descriptor, but when it goes away, the operating system will silently drop	1215	descriptor, but when it goes away, the operating system will silently drop
1038	this interest. If another file descriptor with the same number then is	1216	this interest. If another file descriptor with the same number then is
1039	registered with libev, there is no efficient way to see that this is, in	1217	registered with libev, there is no efficient way to see that this is, in
1040	fact, a different file descriptor.	1218	fact, a different file descriptor.
1041		1219
…		…
1070	To support fork in your programs, you either have to call	1248	To support fork in your programs, you either have to call
1071	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1249	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1072	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1250	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1073	C<EVBACKEND_POLL>.	1251	C<EVBACKEND_POLL>.
1074		1252
		1253	=head3 The special problem of SIGPIPE
		1254
		1255	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1256	when writing to a pipe whose other end has been closed, your program gets
		1257	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1258	this is sensible behaviour, for daemons, this is usually undesirable.
		1259
		1260	So when you encounter spurious, unexplained daemon exits, make sure you
		1261	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1262	somewhere, as that would have given you a big clue).
		1263
1075		1264
1076	=head3 Watcher-Specific Functions	1265	=head3 Watcher-Specific Functions
1077		1266
1078	=over 4	1267	=over 4
1079		1268
1080	=item ev_io_init (ev_io *, callback, int fd, int events)	1269	=item ev_io_init (ev_io *, callback, int fd, int events)
1081		1270
1082	=item ev_io_set (ev_io *, int fd, int events)	1271	=item ev_io_set (ev_io *, int fd, int events)
1083		1272
1084	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1273	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1085	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1274	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1086	C<EV_READ | EV_WRITE> to receive the given events.	1275	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1087		1276
1088	=item int fd [read-only]	1277	=item int fd [read-only]
1089		1278
1090	The file descriptor being watched.	1279	The file descriptor being watched.
1091		1280
…		…
1099		1288
1100	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1289	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1101	readable, but only once. Since it is likely line-buffered, you could	1290	readable, but only once. Since it is likely line-buffered, you could
1102	attempt to read a whole line in the callback.	1291	attempt to read a whole line in the callback.
1103		1292
1104	static void	1293	static void
1105	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1294	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1106	{	1295	{
1107	ev_io_stop (loop, w);	1296	ev_io_stop (loop, w);
1108	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1297	.. read from stdin here (or from w->fd) and handle any I/O errors
1109	}	1298	}
1110		1299
1111	...	1300	...
1112	struct ev_loop *loop = ev_default_init (0);	1301	struct ev_loop *loop = ev_default_init (0);
1113	struct ev_io stdin_readable;	1302	ev_io stdin_readable;
1114	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1303	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1115	ev_io_start (loop, &stdin_readable);	1304	ev_io_start (loop, &stdin_readable);
1116	ev_loop (loop, 0);	1305	ev_loop (loop, 0);
1117		1306
1118		1307
1119	=head2 C<ev_timer> - relative and optionally repeating timeouts	1308	=head2 C<ev_timer> - relative and optionally repeating timeouts
1120		1309
1121	Timer watchers are simple relative timers that generate an event after a	1310	Timer watchers are simple relative timers that generate an event after a
1122	given time, and optionally repeating in regular intervals after that.	1311	given time, and optionally repeating in regular intervals after that.
1123		1312
1124	The timers are based on real time, that is, if you register an event that	1313	The timers are based on real time, that is, if you register an event that
1125	times out after an hour and you reset your system clock to last years	1314	times out after an hour and you reset your system clock to January last
1126	time, it will still time out after (roughly) and hour. "Roughly" because	1315	year, it will still time out after (roughly) one hour. "Roughly" because
1127	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1316	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1128	monotonic clock option helps a lot here).	1317	monotonic clock option helps a lot here).
		1318
		1319	The callback is guaranteed to be invoked only I<after> its timeout has
		1320	passed, but if multiple timers become ready during the same loop iteration
		1321	then order of execution is undefined.
		1322
		1323	=head3 Be smart about timeouts
		1324
		1325	Many real-world problems involve some kind of timeout, usually for error
		1326	recovery. A typical example is an HTTP request - if the other side hangs,
		1327	you want to raise some error after a while.
		1328
		1329	What follows are some ways to handle this problem, from obvious and
		1330	inefficient to smart and efficient.
		1331
		1332	In the following, a 60 second activity timeout is assumed - a timeout that
		1333	gets reset to 60 seconds each time there is activity (e.g. each time some
		1334	data or other life sign was received).
		1335
		1336	=over 4
		1337
		1338	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1339
		1340	This is the most obvious, but not the most simple way: In the beginning,
		1341	start the watcher:
		1342
		1343	ev_timer_init (timer, callback, 60., 0.);
		1344	ev_timer_start (loop, timer);
		1345
		1346	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1347	and start it again:
		1348
		1349	ev_timer_stop (loop, timer);
		1350	ev_timer_set (timer, 60., 0.);
		1351	ev_timer_start (loop, timer);
		1352
		1353	This is relatively simple to implement, but means that each time there is
		1354	some activity, libev will first have to remove the timer from its internal
		1355	data structure and then add it again. Libev tries to be fast, but it's
		1356	still not a constant-time operation.
		1357
		1358	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1359
		1360	This is the easiest way, and involves using C<ev_timer_again> instead of
		1361	C<ev_timer_start>.
		1362
		1363	To implement this, configure an C<ev_timer> with a C<repeat> value
		1364	of C<60> and then call C<ev_timer_again> at start and each time you
		1365	successfully read or write some data. If you go into an idle state where
		1366	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1367	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1368
		1369	That means you can ignore both the C<ev_timer_start> function and the
		1370	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1371	member and C<ev_timer_again>.
		1372
		1373	At start:
		1374
		1375	ev_timer_init (timer, callback);
		1376	timer->repeat = 60.;
		1377	ev_timer_again (loop, timer);
		1378
		1379	Each time there is some activity:
		1380
		1381	ev_timer_again (loop, timer);
		1382
		1383	It is even possible to change the time-out on the fly, regardless of
		1384	whether the watcher is active or not:
		1385
		1386	timer->repeat = 30.;
		1387	ev_timer_again (loop, timer);
		1388
		1389	This is slightly more efficient then stopping/starting the timer each time
		1390	you want to modify its timeout value, as libev does not have to completely
		1391	remove and re-insert the timer from/into its internal data structure.
		1392
		1393	It is, however, even simpler than the "obvious" way to do it.
		1394
		1395	=item 3. Let the timer time out, but then re-arm it as required.
		1396
		1397	This method is more tricky, but usually most efficient: Most timeouts are
		1398	relatively long compared to the intervals between other activity - in
		1399	our example, within 60 seconds, there are usually many I/O events with
		1400	associated activity resets.
		1401
		1402	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1403	but remember the time of last activity, and check for a real timeout only
		1404	within the callback:
		1405
		1406	ev_tstamp last_activity; // time of last activity
		1407
		1408	static void
		1409	callback (EV_P_ ev_timer *w, int revents)
		1410	{
		1411	ev_tstamp now = ev_now (EV_A);
		1412	ev_tstamp timeout = last_activity + 60.;
		1413
		1414	// if last_activity + 60. is older than now, we did time out
		1415	if (timeout < now)
		1416	{
		1417	// timeout occured, take action
		1418	}
		1419	else
		1420	{
		1421	// callback was invoked, but there was some activity, re-arm
		1422	// the watcher to fire in last_activity + 60, which is
		1423	// guaranteed to be in the future, so "again" is positive:
		1424	w->repeat = timeout - now;
		1425	ev_timer_again (EV_A_ w);
		1426	}
		1427	}
		1428
		1429	To summarise the callback: first calculate the real timeout (defined
		1430	as "60 seconds after the last activity"), then check if that time has
		1431	been reached, which means something I<did>, in fact, time out. Otherwise
		1432	the callback was invoked too early (C<timeout> is in the future), so
		1433	re-schedule the timer to fire at that future time, to see if maybe we have
		1434	a timeout then.
		1435
		1436	Note how C<ev_timer_again> is used, taking advantage of the
		1437	C<ev_timer_again> optimisation when the timer is already running.
		1438
		1439	This scheme causes more callback invocations (about one every 60 seconds
		1440	minus half the average time between activity), but virtually no calls to
		1441	libev to change the timeout.
		1442
		1443	To start the timer, simply initialise the watcher and set C<last_activity>
		1444	to the current time (meaning we just have some activity :), then call the
		1445	callback, which will "do the right thing" and start the timer:
		1446
		1447	ev_timer_init (timer, callback);
		1448	last_activity = ev_now (loop);
		1449	callback (loop, timer, EV_TIMEOUT);
		1450
		1451	And when there is some activity, simply store the current time in
		1452	C<last_activity>, no libev calls at all:
		1453
		1454	last_actiivty = ev_now (loop);
		1455
		1456	This technique is slightly more complex, but in most cases where the
		1457	time-out is unlikely to be triggered, much more efficient.
		1458
		1459	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1460	callback :) - just change the timeout and invoke the callback, which will
		1461	fix things for you.
		1462
		1463	=item 4. Wee, just use a double-linked list for your timeouts.
		1464
		1465	If there is not one request, but many thousands (millions...), all
		1466	employing some kind of timeout with the same timeout value, then one can
		1467	do even better:
		1468
		1469	When starting the timeout, calculate the timeout value and put the timeout
		1470	at the I<end> of the list.
		1471
		1472	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1473	the list is expected to fire (for example, using the technique #3).
		1474
		1475	When there is some activity, remove the timer from the list, recalculate
		1476	the timeout, append it to the end of the list again, and make sure to
		1477	update the C<ev_timer> if it was taken from the beginning of the list.
		1478
		1479	This way, one can manage an unlimited number of timeouts in O(1) time for
		1480	starting, stopping and updating the timers, at the expense of a major
		1481	complication, and having to use a constant timeout. The constant timeout
		1482	ensures that the list stays sorted.
		1483
		1484	=back
		1485
		1486	So which method the best?
		1487
		1488	Method #2 is a simple no-brain-required solution that is adequate in most
		1489	situations. Method #3 requires a bit more thinking, but handles many cases
		1490	better, and isn't very complicated either. In most case, choosing either
		1491	one is fine, with #3 being better in typical situations.
		1492
		1493	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1494	rather complicated, but extremely efficient, something that really pays
		1495	off after the first million or so of active timers, i.e. it's usually
		1496	overkill :)
		1497
		1498	=head3 The special problem of time updates
		1499
		1500	Establishing the current time is a costly operation (it usually takes at
		1501	least two system calls): EV therefore updates its idea of the current
		1502	time only before and after C<ev_loop> collects new events, which causes a
		1503	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1504	lots of events in one iteration.
1129		1505
1130	The relative timeouts are calculated relative to the C<ev_now ()>	1506	The relative timeouts are calculated relative to the C<ev_now ()>
1131	time. This is usually the right thing as this timestamp refers to the time	1507	time. This is usually the right thing as this timestamp refers to the time
1132	of the event triggering whatever timeout you are modifying/starting. If	1508	of the event triggering whatever timeout you are modifying/starting. If
1133	you suspect event processing to be delayed and you I<need> to base the timeout	1509	you suspect event processing to be delayed and you I<need> to base the
1134	on the current time, use something like this to adjust for this:	1510	timeout on the current time, use something like this to adjust for this:
1135		1511
1136	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1512	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1137		1513
1138	The callback is guarenteed to be invoked only when its timeout has passed,	1514	If the event loop is suspended for a long time, you can also force an
1139	but if multiple timers become ready during the same loop iteration then	1515	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1140	order of execution is undefined.	1516	()>.
1141		1517
1142	=head3 Watcher-Specific Functions and Data Members	1518	=head3 Watcher-Specific Functions and Data Members
1143		1519
1144	=over 4	1520	=over 4
1145		1521
1146	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1522	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1147		1523
1148	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1524	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1149		1525
1150	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1526	Configure the timer to trigger after C<after> seconds. If C<repeat>
1151	C<0.>, then it will automatically be stopped. If it is positive, then the	1527	is C<0.>, then it will automatically be stopped once the timeout is
1152	timer will automatically be configured to trigger again C<repeat> seconds	1528	reached. If it is positive, then the timer will automatically be
1153	later, again, and again, until stopped manually.	1529	configured to trigger again C<repeat> seconds later, again, and again,
		1530	until stopped manually.
1154		1531
1155	The timer itself will do a best-effort at avoiding drift, that is, if you	1532	The timer itself will do a best-effort at avoiding drift, that is, if
1156	configure a timer to trigger every 10 seconds, then it will trigger at	1533	you configure a timer to trigger every 10 seconds, then it will normally
1157	exactly 10 second intervals. If, however, your program cannot keep up with	1534	trigger at exactly 10 second intervals. If, however, your program cannot
1158	the timer (because it takes longer than those 10 seconds to do stuff) the	1535	keep up with the timer (because it takes longer than those 10 seconds to
1159	timer will not fire more than once per event loop iteration.	1536	do stuff) the timer will not fire more than once per event loop iteration.
1160		1537
1161	=item ev_timer_again (loop, ev_timer *)	1538	=item ev_timer_again (loop, ev_timer *)
1162		1539
1163	This will act as if the timer timed out and restart it again if it is	1540	This will act as if the timer timed out and restart it again if it is
1164	repeating. The exact semantics are:	1541	repeating. The exact semantics are:
1165		1542
1166	If the timer is pending, its pending status is cleared.	1543	If the timer is pending, its pending status is cleared.
1167		1544
1168	If the timer is started but nonrepeating, stop it (as if it timed out).	1545	If the timer is started but non-repeating, stop it (as if it timed out).
1169		1546
1170	If the timer is repeating, either start it if necessary (with the	1547	If the timer is repeating, either start it if necessary (with the
1171	C<repeat> value), or reset the running timer to the C<repeat> value.	1548	C<repeat> value), or reset the running timer to the C<repeat> value.
1172		1549
1173	This sounds a bit complicated, but here is a useful and typical	1550	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1174	example: Imagine you have a tcp connection and you want a so-called idle	1551	usage example.
1175	timeout, that is, you want to be called when there have been, say, 60
1176	seconds of inactivity on the socket. The easiest way to do this is to
1177	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1178	C<ev_timer_again> each time you successfully read or write some data. If
1179	you go into an idle state where you do not expect data to travel on the
1180	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1181	automatically restart it if need be.
1182
1183	That means you can ignore the C<after> value and C<ev_timer_start>
1184	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1185
1186	ev_timer_init (timer, callback, 0., 5.);
1187	ev_timer_again (loop, timer);
1188	...
1189	timer->again = 17.;
1190	ev_timer_again (loop, timer);
1191	...
1192	timer->again = 10.;
1193	ev_timer_again (loop, timer);
1194
1195	This is more slightly efficient then stopping/starting the timer each time
1196	you want to modify its timeout value.
1197		1552
1198	=item ev_tstamp repeat [read-write]	1553	=item ev_tstamp repeat [read-write]
1199		1554
1200	The current C<repeat> value. Will be used each time the watcher times out	1555	The current C<repeat> value. Will be used each time the watcher times out
1201	or C<ev_timer_again> is called and determines the next timeout (if any),	1556	or C<ev_timer_again> is called, and determines the next timeout (if any),
1202	which is also when any modifications are taken into account.	1557	which is also when any modifications are taken into account.
1203		1558
1204	=back	1559	=back
1205		1560
1206	=head3 Examples	1561	=head3 Examples
1207		1562
1208	Example: Create a timer that fires after 60 seconds.	1563	Example: Create a timer that fires after 60 seconds.
1209		1564
1210	static void	1565	static void
1211	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1566	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1212	{	1567	{
1213	.. one minute over, w is actually stopped right here	1568	.. one minute over, w is actually stopped right here
1214	}	1569	}
1215		1570
1216	struct ev_timer mytimer;	1571	ev_timer mytimer;
1217	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1572	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1218	ev_timer_start (loop, &mytimer);	1573	ev_timer_start (loop, &mytimer);
1219		1574
1220	Example: Create a timeout timer that times out after 10 seconds of	1575	Example: Create a timeout timer that times out after 10 seconds of
1221	inactivity.	1576	inactivity.
1222		1577
1223	static void	1578	static void
1224	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1579	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1225	{	1580	{
1226	.. ten seconds without any activity	1581	.. ten seconds without any activity
1227	}	1582	}
1228		1583
1229	struct ev_timer mytimer;	1584	ev_timer mytimer;
1230	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1585	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1231	ev_timer_again (&mytimer); /* start timer */	1586	ev_timer_again (&mytimer); /* start timer */
1232	ev_loop (loop, 0);	1587	ev_loop (loop, 0);
1233		1588
1234	// and in some piece of code that gets executed on any "activity":	1589	// and in some piece of code that gets executed on any "activity":
1235	// reset the timeout to start ticking again at 10 seconds	1590	// reset the timeout to start ticking again at 10 seconds
1236	ev_timer_again (&mytimer);	1591	ev_timer_again (&mytimer);
1237		1592
1238		1593
1239	=head2 C<ev_periodic> - to cron or not to cron?	1594	=head2 C<ev_periodic> - to cron or not to cron?
1240		1595
1241	Periodic watchers are also timers of a kind, but they are very versatile	1596	Periodic watchers are also timers of a kind, but they are very versatile
1242	(and unfortunately a bit complex).	1597	(and unfortunately a bit complex).
1243		1598
1244	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1599	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1245	but on wallclock time (absolute time). You can tell a periodic watcher	1600	but on wall clock time (absolute time). You can tell a periodic watcher
1246	to trigger "at" some specific point in time. For example, if you tell a	1601	to trigger after some specific point in time. For example, if you tell a
1247	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1602	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1248	+ 10.>) and then reset your system clock to the last year, then it will	1603	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1604	clock to January of the previous year, then it will take more than year
1249	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1605	to trigger the event (unlike an C<ev_timer>, which would still trigger
1250	roughly 10 seconds later).	1606	roughly 10 seconds later as it uses a relative timeout).
1251		1607
1252	They can also be used to implement vastly more complex timers, such as	1608	C<ev_periodic>s can also be used to implement vastly more complex timers,
1253	triggering an event on each midnight, local time or other, complicated,	1609	such as triggering an event on each "midnight, local time", or other
1254	rules.	1610	complicated rules.
1255		1611
1256	As with timers, the callback is guarenteed to be invoked only when the	1612	As with timers, the callback is guaranteed to be invoked only when the
1257	time (C<at>) has been passed, but if multiple periodic timers become ready	1613	time (C<at>) has passed, but if multiple periodic timers become ready
1258	during the same loop iteration then order of execution is undefined.	1614	during the same loop iteration, then order of execution is undefined.
1259		1615
1260	=head3 Watcher-Specific Functions and Data Members	1616	=head3 Watcher-Specific Functions and Data Members
1261		1617
1262	=over 4	1618	=over 4
1263		1619
1264	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1620	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1265		1621
1266	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1622	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1267		1623
1268	Lots of arguments, lets sort it out... There are basically three modes of	1624	Lots of arguments, lets sort it out... There are basically three modes of
1269	operation, and we will explain them from simplest to complex:	1625	operation, and we will explain them from simplest to most complex:
1270		1626
1271	=over 4	1627	=over 4
1272		1628
1273	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1629	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1274		1630
1275	In this configuration the watcher triggers an event at the wallclock time	1631	In this configuration the watcher triggers an event after the wall clock
1276	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1632	time C<at> has passed. It will not repeat and will not adjust when a time
1277	that is, if it is to be run at January 1st 2011 then it will run when the	1633	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1278	system time reaches or surpasses this time.	1634	only run when the system clock reaches or surpasses this time.
1279		1635
1280	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1636	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1281		1637
1282	In this mode the watcher will always be scheduled to time out at the next	1638	In this mode the watcher will always be scheduled to time out at the next
1283	C<at + N * interval> time (for some integer N, which can also be negative)	1639	C<at + N * interval> time (for some integer N, which can also be negative)
1284	and then repeat, regardless of any time jumps.	1640	and then repeat, regardless of any time jumps.
1285		1641
1286	This can be used to create timers that do not drift with respect to system	1642	This can be used to create timers that do not drift with respect to the
1287	time:	1643	system clock, for example, here is a C<ev_periodic> that triggers each
		1644	hour, on the hour:
1288		1645
1289	ev_periodic_set (&periodic, 0., 3600., 0);	1646	ev_periodic_set (&periodic, 0., 3600., 0);
1290		1647
1291	This doesn't mean there will always be 3600 seconds in between triggers,	1648	This doesn't mean there will always be 3600 seconds in between triggers,
1292	but only that the the callback will be called when the system time shows a	1649	but only that the callback will be called when the system time shows a
1293	full hour (UTC), or more correctly, when the system time is evenly divisible	1650	full hour (UTC), or more correctly, when the system time is evenly divisible
1294	by 3600.	1651	by 3600.
1295		1652
1296	Another way to think about it (for the mathematically inclined) is that	1653	Another way to think about it (for the mathematically inclined) is that
1297	C<ev_periodic> will try to run the callback in this mode at the next possible	1654	C<ev_periodic> will try to run the callback in this mode at the next possible
1298	time where C<time = at (mod interval)>, regardless of any time jumps.	1655	time where C<time = at (mod interval)>, regardless of any time jumps.
1299		1656
1300	For numerical stability it is preferable that the C<at> value is near	1657	For numerical stability it is preferable that the C<at> value is near
1301	C<ev_now ()> (the current time), but there is no range requirement for	1658	C<ev_now ()> (the current time), but there is no range requirement for
1302	this value.	1659	this value, and in fact is often specified as zero.
		1660
		1661	Note also that there is an upper limit to how often a timer can fire (CPU
		1662	speed for example), so if C<interval> is very small then timing stability
		1663	will of course deteriorate. Libev itself tries to be exact to be about one
		1664	millisecond (if the OS supports it and the machine is fast enough).
1303		1665
1304	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1666	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1305		1667
1306	In this mode the values for C<interval> and C<at> are both being	1668	In this mode the values for C<interval> and C<at> are both being
1307	ignored. Instead, each time the periodic watcher gets scheduled, the	1669	ignored. Instead, each time the periodic watcher gets scheduled, the
1308	reschedule callback will be called with the watcher as first, and the	1670	reschedule callback will be called with the watcher as first, and the
1309	current time as second argument.	1671	current time as second argument.
1310		1672
1311	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1673	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1312	ever, or make any event loop modifications>. If you need to stop it,	1674	ever, or make ANY event loop modifications whatsoever>.
1313	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1314	starting an C<ev_prepare> watcher, which is legal).
1315		1675
		1676	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1677	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1678	only event loop modification you are allowed to do).
		1679
1316	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1680	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1317	ev_tstamp now)>, e.g.:	1681	*w, ev_tstamp now)>, e.g.:
1318		1682
		1683	static ev_tstamp
1319	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1684	my_rescheduler (ev_periodic *w, ev_tstamp now)
1320	{	1685	{
1321	return now + 60.;	1686	return now + 60.;
1322	}	1687	}
1323		1688
1324	It must return the next time to trigger, based on the passed time value	1689	It must return the next time to trigger, based on the passed time value
1325	(that is, the lowest time value larger than to the second argument). It	1690	(that is, the lowest time value larger than to the second argument). It
1326	will usually be called just before the callback will be triggered, but	1691	will usually be called just before the callback will be triggered, but
1327	might be called at other times, too.	1692	might be called at other times, too.
1328		1693
1329	NOTE: I<< This callback must always return a time that is later than the	1694	NOTE: I<< This callback must always return a time that is higher than or
1330	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1695	equal to the passed C<now> value >>.
1331		1696
1332	This can be used to create very complex timers, such as a timer that	1697	This can be used to create very complex timers, such as a timer that
1333	triggers on each midnight, local time. To do this, you would calculate the	1698	triggers on "next midnight, local time". To do this, you would calculate the
1334	next midnight after C<now> and return the timestamp value for this. How	1699	next midnight after C<now> and return the timestamp value for this. How
1335	you do this is, again, up to you (but it is not trivial, which is the main	1700	you do this is, again, up to you (but it is not trivial, which is the main
1336	reason I omitted it as an example).	1701	reason I omitted it as an example).
1337		1702
1338	=back	1703	=back
…		…
1342	Simply stops and restarts the periodic watcher again. This is only useful	1707	Simply stops and restarts the periodic watcher again. This is only useful
1343	when you changed some parameters or the reschedule callback would return	1708	when you changed some parameters or the reschedule callback would return
1344	a different time than the last time it was called (e.g. in a crond like	1709	a different time than the last time it was called (e.g. in a crond like
1345	program when the crontabs have changed).	1710	program when the crontabs have changed).
1346		1711
		1712	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1713
		1714	When active, returns the absolute time that the watcher is supposed to
		1715	trigger next.
		1716
1347	=item ev_tstamp offset [read-write]	1717	=item ev_tstamp offset [read-write]
1348		1718
1349	When repeating, this contains the offset value, otherwise this is the	1719	When repeating, this contains the offset value, otherwise this is the
1350	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1720	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1351		1721
…		…
1356		1726
1357	The current interval value. Can be modified any time, but changes only	1727	The current interval value. Can be modified any time, but changes only
1358	take effect when the periodic timer fires or C<ev_periodic_again> is being	1728	take effect when the periodic timer fires or C<ev_periodic_again> is being
1359	called.	1729	called.
1360		1730
1361	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1731	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1362		1732
1363	The current reschedule callback, or C<0>, if this functionality is	1733	The current reschedule callback, or C<0>, if this functionality is
1364	switched off. Can be changed any time, but changes only take effect when	1734	switched off. Can be changed any time, but changes only take effect when
1365	the periodic timer fires or C<ev_periodic_again> is being called.	1735	the periodic timer fires or C<ev_periodic_again> is being called.
1366		1736
1367	=item ev_tstamp at [read-only]
1368
1369	When active, contains the absolute time that the watcher is supposed to
1370	trigger next.
1371
1372	=back	1737	=back
1373		1738
1374	=head3 Examples	1739	=head3 Examples
1375		1740
1376	Example: Call a callback every hour, or, more precisely, whenever the	1741	Example: Call a callback every hour, or, more precisely, whenever the
1377	system clock is divisible by 3600. The callback invocation times have	1742	system time is divisible by 3600. The callback invocation times have
1378	potentially a lot of jittering, but good long-term stability.	1743	potentially a lot of jitter, but good long-term stability.
1379		1744
1380	static void	1745	static void
1381	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1746	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1382	{	1747	{
1383	... its now a full hour (UTC, or TAI or whatever your clock follows)	1748	... its now a full hour (UTC, or TAI or whatever your clock follows)
1384	}	1749	}
1385		1750
1386	struct ev_periodic hourly_tick;	1751	ev_periodic hourly_tick;
1387	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1752	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1388	ev_periodic_start (loop, &hourly_tick);	1753	ev_periodic_start (loop, &hourly_tick);
1389		1754
1390	Example: The same as above, but use a reschedule callback to do it:	1755	Example: The same as above, but use a reschedule callback to do it:
1391		1756
1392	#include <math.h>	1757	#include <math.h>
1393		1758
1394	static ev_tstamp	1759	static ev_tstamp
1395	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1760	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1396	{	1761	{
1397	return fmod (now, 3600.) + 3600.;	1762	return now + (3600. - fmod (now, 3600.));
1398	}	1763	}
1399		1764
1400	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1765	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1401		1766
1402	Example: Call a callback every hour, starting now:	1767	Example: Call a callback every hour, starting now:
1403		1768
1404	struct ev_periodic hourly_tick;	1769	ev_periodic hourly_tick;
1405	ev_periodic_init (&hourly_tick, clock_cb,	1770	ev_periodic_init (&hourly_tick, clock_cb,
1406	fmod (ev_now (loop), 3600.), 3600., 0);	1771	fmod (ev_now (loop), 3600.), 3600., 0);
1407	ev_periodic_start (loop, &hourly_tick);	1772	ev_periodic_start (loop, &hourly_tick);
1408		1773
1409		1774
1410	=head2 C<ev_signal> - signal me when a signal gets signalled!	1775	=head2 C<ev_signal> - signal me when a signal gets signalled!
1411		1776
1412	Signal watchers will trigger an event when the process receives a specific	1777	Signal watchers will trigger an event when the process receives a specific
1413	signal one or more times. Even though signals are very asynchronous, libev	1778	signal one or more times. Even though signals are very asynchronous, libev
1414	will try it's best to deliver signals synchronously, i.e. as part of the	1779	will try it's best to deliver signals synchronously, i.e. as part of the
1415	normal event processing, like any other event.	1780	normal event processing, like any other event.
1416		1781
		1782	If you want signals asynchronously, just use C<sigaction> as you would
		1783	do without libev and forget about sharing the signal. You can even use
		1784	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1785
1417	You can configure as many watchers as you like per signal. Only when the	1786	You can configure as many watchers as you like per signal. Only when the
1418	first watcher gets started will libev actually register a signal watcher	1787	first watcher gets started will libev actually register a signal handler
1419	with the kernel (thus it coexists with your own signal handlers as long	1788	with the kernel (thus it coexists with your own signal handlers as long as
1420	as you don't register any with libev). Similarly, when the last signal	1789	you don't register any with libev for the same signal). Similarly, when
1421	watcher for a signal is stopped libev will reset the signal handler to	1790	the last signal watcher for a signal is stopped, libev will reset the
1422	SIG_DFL (regardless of what it was set to before).	1791	signal handler to SIG_DFL (regardless of what it was set to before).
		1792
		1793	If possible and supported, libev will install its handlers with
		1794	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1795	interrupted. If you have a problem with system calls getting interrupted by
		1796	signals you can block all signals in an C<ev_check> watcher and unblock
		1797	them in an C<ev_prepare> watcher.
1423		1798
1424	=head3 Watcher-Specific Functions and Data Members	1799	=head3 Watcher-Specific Functions and Data Members
1425		1800
1426	=over 4	1801	=over 4
1427		1802
…		…
1438		1813
1439	=back	1814	=back
1440		1815
1441	=head3 Examples	1816	=head3 Examples
1442		1817
1443	Example: Try to exit cleanly on SIGINT and SIGTERM.	1818	Example: Try to exit cleanly on SIGINT.
1444		1819
1445	static void	1820	static void
1446	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1821	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1447	{	1822	{
1448	ev_unloop (loop, EVUNLOOP_ALL);	1823	ev_unloop (loop, EVUNLOOP_ALL);
1449	}	1824	}
1450		1825
1451	struct ev_signal signal_watcher;	1826	ev_signal signal_watcher;
1452	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1827	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1453	ev_signal_start (loop, &sigint_cb);	1828	ev_signal_start (loop, &signal_watcher);
1454		1829
1455		1830
1456	=head2 C<ev_child> - watch out for process status changes	1831	=head2 C<ev_child> - watch out for process status changes
1457		1832
1458	Child watchers trigger when your process receives a SIGCHLD in response to	1833	Child watchers trigger when your process receives a SIGCHLD in response to
1459	some child status changes (most typically when a child of yours dies). It	1834	some child status changes (most typically when a child of yours dies or
1460	is permissible to install a child watcher I<after> the child has been	1835	exits). It is permissible to install a child watcher I<after> the child
1461	forked (which implies it might have already exited), as long as the event	1836	has been forked (which implies it might have already exited), as long
1462	loop isn't entered (or is continued from a watcher).	1837	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1838	forking and then immediately registering a watcher for the child is fine,
		1839	but forking and registering a watcher a few event loop iterations later is
		1840	not.
1463		1841
1464	Only the default event loop is capable of handling signals, and therefore	1842	Only the default event loop is capable of handling signals, and therefore
1465	you can only rgeister child watchers in the default event loop.	1843	you can only register child watchers in the default event loop.
1466		1844
1467	=head3 Process Interaction	1845	=head3 Process Interaction
1468		1846
1469	Libev grabs C<SIGCHLD> as soon as the default event loop is	1847	Libev grabs C<SIGCHLD> as soon as the default event loop is
1470	initialised. This is necessary to guarantee proper behaviour even if	1848	initialised. This is necessary to guarantee proper behaviour even if
1471	the first child watcher is started after the child exits. The occurance	1849	the first child watcher is started after the child exits. The occurrence
1472	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1850	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1473	synchronously as part of the event loop processing. Libev always reaps all	1851	synchronously as part of the event loop processing. Libev always reaps all
1474	children, even ones not watched.	1852	children, even ones not watched.
1475		1853
1476	=head3 Overriding the Built-In Processing	1854	=head3 Overriding the Built-In Processing
…		…
1480	handler, you can override it easily by installing your own handler for	1858	handler, you can override it easily by installing your own handler for
1481	C<SIGCHLD> after initialising the default loop, and making sure the	1859	C<SIGCHLD> after initialising the default loop, and making sure the
1482	default loop never gets destroyed. You are encouraged, however, to use an	1860	default loop never gets destroyed. You are encouraged, however, to use an
1483	event-based approach to child reaping and thus use libev's support for	1861	event-based approach to child reaping and thus use libev's support for
1484	that, so other libev users can use C<ev_child> watchers freely.	1862	that, so other libev users can use C<ev_child> watchers freely.
		1863
		1864	=head3 Stopping the Child Watcher
		1865
		1866	Currently, the child watcher never gets stopped, even when the
		1867	child terminates, so normally one needs to stop the watcher in the
		1868	callback. Future versions of libev might stop the watcher automatically
		1869	when a child exit is detected.
1485		1870
1486	=head3 Watcher-Specific Functions and Data Members	1871	=head3 Watcher-Specific Functions and Data Members
1487		1872
1488	=over 4	1873	=over 4
1489		1874
…		…
1518	=head3 Examples	1903	=head3 Examples
1519		1904
1520	Example: C<fork()> a new process and install a child handler to wait for	1905	Example: C<fork()> a new process and install a child handler to wait for
1521	its completion.	1906	its completion.
1522		1907
1523	ev_child cw;	1908	ev_child cw;
1524		1909
1525	static void	1910	static void
1526	child_cb (EV_P_ struct ev_child *w, int revents)	1911	child_cb (EV_P_ ev_child *w, int revents)
1527	{	1912	{
1528	ev_child_stop (EV_A_ w);	1913	ev_child_stop (EV_A_ w);
1529	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1914	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1530	}	1915	}
1531		1916
1532	pid_t pid = fork ();	1917	pid_t pid = fork ();
1533		1918
1534	if (pid < 0)	1919	if (pid < 0)
1535	// error	1920	// error
1536	else if (pid == 0)	1921	else if (pid == 0)
1537	{	1922	{
1538	// the forked child executes here	1923	// the forked child executes here
1539	exit (1);	1924	exit (1);
1540	}	1925	}
1541	else	1926	else
1542	{	1927	{
1543	ev_child_init (&cw, child_cb, pid, 0);	1928	ev_child_init (&cw, child_cb, pid, 0);
1544	ev_child_start (EV_DEFAULT_ &cw);	1929	ev_child_start (EV_DEFAULT_ &cw);
1545	}	1930	}
1546		1931
1547		1932
1548	=head2 C<ev_stat> - did the file attributes just change?	1933	=head2 C<ev_stat> - did the file attributes just change?
1549		1934
1550	This watches a filesystem path for attribute changes. That is, it calls	1935	This watches a file system path for attribute changes. That is, it calls
1551	C<stat> regularly (or when the OS says it changed) and sees if it changed	1936	C<stat> on that path in regular intervals (or when the OS says it changed)
1552	compared to the last time, invoking the callback if it did.	1937	and sees if it changed compared to the last time, invoking the callback if
		1938	it did.
1553		1939
1554	The path does not need to exist: changing from "path exists" to "path does	1940	The path does not need to exist: changing from "path exists" to "path does
1555	not exist" is a status change like any other. The condition "path does	1941	not exist" is a status change like any other. The condition "path does not
1556	not exist" is signified by the C<st_nlink> field being zero (which is	1942	exist" (or more correctly "path cannot be stat'ed") is signified by the
1557	otherwise always forced to be at least one) and all the other fields of	1943	C<st_nlink> field being zero (which is otherwise always forced to be at
1558	the stat buffer having unspecified contents.	1944	least one) and all the other fields of the stat buffer having unspecified
		1945	contents.
1559		1946
1560	The path I<should> be absolute and I<must not> end in a slash. If it is	1947	The path I<must not> end in a slash or contain special components such as
		1948	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1561	relative and your working directory changes, the behaviour is undefined.	1949	your working directory changes, then the behaviour is undefined.
1562		1950
1563	Since there is no standard to do this, the portable implementation simply	1951	Since there is no portable change notification interface available, the
1564	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1952	portable implementation simply calls C<stat(2)> regularly on the path
1565	can specify a recommended polling interval for this case. If you specify	1953	to see if it changed somehow. You can specify a recommended polling
1566	a polling interval of C<0> (highly recommended!) then a I<suitable,	1954	interval for this case. If you specify a polling interval of C<0> (highly
1567	unspecified default> value will be used (which you can expect to be around	1955	recommended!) then a I<suitable, unspecified default> value will be used
1568	five seconds, although this might change dynamically). Libev will also	1956	(which you can expect to be around five seconds, although this might
1569	impose a minimum interval which is currently around C<0.1>, but thats	1957	change dynamically). Libev will also impose a minimum interval which is
1570	usually overkill.	1958	currently around C<0.1>, but that's usually overkill.
1571		1959
1572	This watcher type is not meant for massive numbers of stat watchers,	1960	This watcher type is not meant for massive numbers of stat watchers,
1573	as even with OS-supported change notifications, this can be	1961	as even with OS-supported change notifications, this can be
1574	resource-intensive.	1962	resource-intensive.
1575		1963
1576	At the time of this writing, only the Linux inotify interface is	1964	At the time of this writing, the only OS-specific interface implemented
1577	implemented (implementing kqueue support is left as an exercise for the	1965	is the Linux inotify interface (implementing kqueue support is left as an
1578	reader). Inotify will be used to give hints only and should not change the	1966	exercise for the reader. Note, however, that the author sees no way of
1579	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1967	implementing C<ev_stat> semantics with kqueue, except as a hint).
1580	to fall back to regular polling again even with inotify, but changes are
1581	usually detected immediately, and if the file exists there will be no
1582	polling.
1583		1968
1584	=head3 Inotify	1969	=head3 ABI Issues (Largefile Support)
1585		1970
		1971	Libev by default (unless the user overrides this) uses the default
		1972	compilation environment, which means that on systems with large file
		1973	support disabled by default, you get the 32 bit version of the stat
		1974	structure. When using the library from programs that change the ABI to
		1975	use 64 bit file offsets the programs will fail. In that case you have to
		1976	compile libev with the same flags to get binary compatibility. This is
		1977	obviously the case with any flags that change the ABI, but the problem is
		1978	most noticeably displayed with ev_stat and large file support.
		1979
		1980	The solution for this is to lobby your distribution maker to make large
		1981	file interfaces available by default (as e.g. FreeBSD does) and not
		1982	optional. Libev cannot simply switch on large file support because it has
		1983	to exchange stat structures with application programs compiled using the
		1984	default compilation environment.
		1985
		1986	=head3 Inotify and Kqueue
		1987
1586	When C<inotify (7)> support has been compiled into libev (generally only	1988	When C<inotify (7)> support has been compiled into libev and present at
1587	available on Linux) and present at runtime, it will be used to speed up	1989	runtime, it will be used to speed up change detection where possible. The
1588	change detection where possible. The inotify descriptor will be created lazily	1990	inotify descriptor will be created lazily when the first C<ev_stat>
1589	when the first C<ev_stat> watcher is being started.	1991	watcher is being started.
1590		1992
1591	Inotify presense does not change the semantics of C<ev_stat> watchers	1993	Inotify presence does not change the semantics of C<ev_stat> watchers
1592	except that changes might be detected earlier, and in some cases, to avoid	1994	except that changes might be detected earlier, and in some cases, to avoid
1593	making regular C<stat> calls. Even in the presense of inotify support	1995	making regular C<stat> calls. Even in the presence of inotify support
1594	there are many cases where libev has to resort to regular C<stat> polling.	1996	there are many cases where libev has to resort to regular C<stat> polling,
		1997	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1998	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1999	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2000	xfs are fully working) libev usually gets away without polling.
1595		2001
1596	(There is no support for kqueue, as apparently it cannot be used to	2002	There is no support for kqueue, as apparently it cannot be used to
1597	implement this functionality, due to the requirement of having a file	2003	implement this functionality, due to the requirement of having a file
1598	descriptor open on the object at all times).	2004	descriptor open on the object at all times, and detecting renames, unlinks
		2005	etc. is difficult.
		2006
		2007	=head3 C<stat ()> is a synchronous operation
		2008
		2009	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2010	the process. The exception are C<ev_stat> watchers - those call C<stat
		2011	()>, which is a synchronous operation.
		2012
		2013	For local paths, this usually doesn't matter: unless the system is very
		2014	busy or the intervals between stat's are large, a stat call will be fast,
		2015	as the path data is suually in memory already (except when starting the
		2016	watcher).
		2017
		2018	For networked file systems, calling C<stat ()> can block an indefinite
		2019	time due to network issues, and even under good conditions, a stat call
		2020	often takes multiple milliseconds.
		2021
		2022	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2023	paths, although this is fully supported by libev.
1599		2024
1600	=head3 The special problem of stat time resolution	2025	=head3 The special problem of stat time resolution
1601		2026
1602	The C<stat ()> syscall only supports full-second resolution portably, and	2027	The C<stat ()> system call only supports full-second resolution portably,
1603	even on systems where the resolution is higher, many filesystems still	2028	and even on systems where the resolution is higher, most file systems
1604	only support whole seconds.	2029	still only support whole seconds.
1605		2030
1606	That means that, if the time is the only thing that changes, you might	2031	That means that, if the time is the only thing that changes, you can
1607	miss updates: on the first update, C<ev_stat> detects a change and calls	2032	easily miss updates: on the first update, C<ev_stat> detects a change and
1608	your callback, which does something. When there is another update within	2033	calls your callback, which does something. When there is another update
1609	the same second, C<ev_stat> will be unable to detect it.	2034	within the same second, C<ev_stat> will be unable to detect unless the
		2035	stat data does change in other ways (e.g. file size).
1610		2036
1611	The solution to this is to delay acting on a change for a second (or till	2037	The solution to this is to delay acting on a change for slightly more
1612	the next second boundary), using a roughly one-second delay C<ev_timer>	2038	than a second (or till slightly after the next full second boundary), using
1613	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2039	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1614	is added to work around small timing inconsistencies of some operating	2040	ev_timer_again (loop, w)>).
1615	systems.	2041
		2042	The C<.02> offset is added to work around small timing inconsistencies
		2043	of some operating systems (where the second counter of the current time
		2044	might be be delayed. One such system is the Linux kernel, where a call to
		2045	C<gettimeofday> might return a timestamp with a full second later than
		2046	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2047	update file times then there will be a small window where the kernel uses
		2048	the previous second to update file times but libev might already execute
		2049	the timer callback).
1616		2050
1617	=head3 Watcher-Specific Functions and Data Members	2051	=head3 Watcher-Specific Functions and Data Members
1618		2052
1619	=over 4	2053	=over 4
1620		2054
…		…
1626	C<path>. The C<interval> is a hint on how quickly a change is expected to	2060	C<path>. The C<interval> is a hint on how quickly a change is expected to
1627	be detected and should normally be specified as C<0> to let libev choose	2061	be detected and should normally be specified as C<0> to let libev choose
1628	a suitable value. The memory pointed to by C<path> must point to the same	2062	a suitable value. The memory pointed to by C<path> must point to the same
1629	path for as long as the watcher is active.	2063	path for as long as the watcher is active.
1630		2064
1631	The callback will be receive C<EV_STAT> when a change was detected,	2065	The callback will receive an C<EV_STAT> event when a change was detected,
1632	relative to the attributes at the time the watcher was started (or the	2066	relative to the attributes at the time the watcher was started (or the
1633	last change was detected).	2067	last change was detected).
1634		2068
1635	=item ev_stat_stat (loop, ev_stat *)	2069	=item ev_stat_stat (loop, ev_stat *)
1636		2070
1637	Updates the stat buffer immediately with new values. If you change the	2071	Updates the stat buffer immediately with new values. If you change the
1638	watched path in your callback, you could call this fucntion to avoid	2072	watched path in your callback, you could call this function to avoid
1639	detecting this change (while introducing a race condition). Can also be	2073	detecting this change (while introducing a race condition if you are not
1640	useful simply to find out the new values.	2074	the only one changing the path). Can also be useful simply to find out the
		2075	new values.
1641		2076
1642	=item ev_statdata attr [read-only]	2077	=item ev_statdata attr [read-only]
1643		2078
1644	The most-recently detected attributes of the file. Although the type is of	2079	The most-recently detected attributes of the file. Although the type is
1645	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2080	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1646	suitable for your system. If the C<st_nlink> member is C<0>, then there	2081	suitable for your system, but you can only rely on the POSIX-standardised
		2082	members to be present. If the C<st_nlink> member is C<0>, then there was
1647	was some error while C<stat>ing the file.	2083	some error while C<stat>ing the file.
1648		2084
1649	=item ev_statdata prev [read-only]	2085	=item ev_statdata prev [read-only]
1650		2086
1651	The previous attributes of the file. The callback gets invoked whenever	2087	The previous attributes of the file. The callback gets invoked whenever
1652	C<prev> != C<attr>.	2088	C<prev> != C<attr>, or, more precisely, one or more of these members
		2089	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2090	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1653		2091
1654	=item ev_tstamp interval [read-only]	2092	=item ev_tstamp interval [read-only]
1655		2093
1656	The specified interval.	2094	The specified interval.
1657		2095
1658	=item const char *path [read-only]	2096	=item const char *path [read-only]
1659		2097
1660	The filesystem path that is being watched.	2098	The file system path that is being watched.
1661		2099
1662	=back	2100	=back
1663		2101
1664	=head3 Examples	2102	=head3 Examples
1665		2103
1666	Example: Watch C</etc/passwd> for attribute changes.	2104	Example: Watch C</etc/passwd> for attribute changes.
1667		2105
1668	static void	2106	static void
1669	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2107	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1670	{	2108	{
1671	/* /etc/passwd changed in some way */	2109	/* /etc/passwd changed in some way */
1672	if (w->attr.st_nlink)	2110	if (w->attr.st_nlink)
1673	{	2111	{
1674	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2112	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1675	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2113	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1676	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2114	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1677	}	2115	}
1678	else	2116	else
1679	/* you shalt not abuse printf for puts */	2117	/* you shalt not abuse printf for puts */
1680	puts ("wow, /etc/passwd is not there, expect problems. "	2118	puts ("wow, /etc/passwd is not there, expect problems. "
1681	"if this is windows, they already arrived\n");	2119	"if this is windows, they already arrived\n");
1682	}	2120	}
1683		2121
1684	...	2122	...
1685	ev_stat passwd;	2123	ev_stat passwd;
1686		2124
1687	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2125	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1688	ev_stat_start (loop, &passwd);	2126	ev_stat_start (loop, &passwd);
1689		2127
1690	Example: Like above, but additionally use a one-second delay so we do not	2128	Example: Like above, but additionally use a one-second delay so we do not
1691	miss updates (however, frequent updates will delay processing, too, so	2129	miss updates (however, frequent updates will delay processing, too, so
1692	one might do the work both on C<ev_stat> callback invocation I<and> on	2130	one might do the work both on C<ev_stat> callback invocation I<and> on
1693	C<ev_timer> callback invocation).	2131	C<ev_timer> callback invocation).
1694		2132
1695	static ev_stat passwd;	2133	static ev_stat passwd;
1696	static ev_timer timer;	2134	static ev_timer timer;
1697		2135
1698	static void	2136	static void
1699	timer_cb (EV_P_ ev_timer *w, int revents)	2137	timer_cb (EV_P_ ev_timer *w, int revents)
1700	{	2138	{
1701	ev_timer_stop (EV_A_ w);	2139	ev_timer_stop (EV_A_ w);
1702		2140
1703	/* now it's one second after the most recent passwd change */	2141	/* now it's one second after the most recent passwd change */
1704	}	2142	}
1705		2143
1706	static void	2144	static void
1707	stat_cb (EV_P_ ev_stat *w, int revents)	2145	stat_cb (EV_P_ ev_stat *w, int revents)
1708	{	2146	{
1709	/* reset the one-second timer */	2147	/* reset the one-second timer */
1710	ev_timer_again (EV_A_ &timer);	2148	ev_timer_again (EV_A_ &timer);
1711	}	2149	}
1712		2150
1713	...	2151	...
1714	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2152	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1715	ev_stat_start (loop, &passwd);	2153	ev_stat_start (loop, &passwd);
1716	ev_timer_init (&timer, timer_cb, 0., 1.01);	2154	ev_timer_init (&timer, timer_cb, 0., 1.02);
1717		2155
1718		2156
1719	=head2 C<ev_idle> - when you've got nothing better to do...	2157	=head2 C<ev_idle> - when you've got nothing better to do...
1720		2158
1721	Idle watchers trigger events when no other events of the same or higher	2159	Idle watchers trigger events when no other events of the same or higher
1722	priority are pending (prepare, check and other idle watchers do not	2160	priority are pending (prepare, check and other idle watchers do not count
1723	count).	2161	as receiving "events").
1724		2162
1725	That is, as long as your process is busy handling sockets or timeouts	2163	That is, as long as your process is busy handling sockets or timeouts
1726	(or even signals, imagine) of the same or higher priority it will not be	2164	(or even signals, imagine) of the same or higher priority it will not be
1727	triggered. But when your process is idle (or only lower-priority watchers	2165	triggered. But when your process is idle (or only lower-priority watchers
1728	are pending), the idle watchers are being called once per event loop	2166	are pending), the idle watchers are being called once per event loop
…		…
1752	=head3 Examples	2190	=head3 Examples
1753		2191
1754	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2192	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1755	callback, free it. Also, use no error checking, as usual.	2193	callback, free it. Also, use no error checking, as usual.
1756		2194
1757	static void	2195	static void
1758	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2196	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1759	{	2197	{
1760	free (w);	2198	free (w);
1761	// now do something you wanted to do when the program has	2199	// now do something you wanted to do when the program has
1762	// no longer anything immediate to do.	2200	// no longer anything immediate to do.
1763	}	2201	}
1764		2202
1765	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2203	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1766	ev_idle_init (idle_watcher, idle_cb);	2204	ev_idle_init (idle_watcher, idle_cb);
1767	ev_idle_start (loop, idle_cb);	2205	ev_idle_start (loop, idle_cb);
1768		2206
1769		2207
1770	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2208	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1771		2209
1772	Prepare and check watchers are usually (but not always) used in tandem:	2210	Prepare and check watchers are usually (but not always) used in pairs:
1773	prepare watchers get invoked before the process blocks and check watchers	2211	prepare watchers get invoked before the process blocks and check watchers
1774	afterwards.	2212	afterwards.
1775		2213
1776	You I<must not> call C<ev_loop> or similar functions that enter	2214	You I<must not> call C<ev_loop> or similar functions that enter
1777	the current event loop from either C<ev_prepare> or C<ev_check>	2215	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1780	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2218	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1781	C<ev_check> so if you have one watcher of each kind they will always be	2219	C<ev_check> so if you have one watcher of each kind they will always be
1782	called in pairs bracketing the blocking call.	2220	called in pairs bracketing the blocking call.
1783		2221
1784	Their main purpose is to integrate other event mechanisms into libev and	2222	Their main purpose is to integrate other event mechanisms into libev and
1785	their use is somewhat advanced. This could be used, for example, to track	2223	their use is somewhat advanced. They could be used, for example, to track
1786	variable changes, implement your own watchers, integrate net-snmp or a	2224	variable changes, implement your own watchers, integrate net-snmp or a
1787	coroutine library and lots more. They are also occasionally useful if	2225	coroutine library and lots more. They are also occasionally useful if
1788	you cache some data and want to flush it before blocking (for example,	2226	you cache some data and want to flush it before blocking (for example,
1789	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2227	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1790	watcher).	2228	watcher).
1791		2229
1792	This is done by examining in each prepare call which file descriptors need	2230	This is done by examining in each prepare call which file descriptors
1793	to be watched by the other library, registering C<ev_io> watchers for	2231	need to be watched by the other library, registering C<ev_io> watchers
1794	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2232	for them and starting an C<ev_timer> watcher for any timeouts (many
1795	provide just this functionality). Then, in the check watcher you check for	2233	libraries provide exactly this functionality). Then, in the check watcher,
1796	any events that occured (by checking the pending status of all watchers	2234	you check for any events that occurred (by checking the pending status
1797	and stopping them) and call back into the library. The I/O and timer	2235	of all watchers and stopping them) and call back into the library. The
1798	callbacks will never actually be called (but must be valid nevertheless,	2236	I/O and timer callbacks will never actually be called (but must be valid
1799	because you never know, you know?).	2237	nevertheless, because you never know, you know?).
1800		2238
1801	As another example, the Perl Coro module uses these hooks to integrate	2239	As another example, the Perl Coro module uses these hooks to integrate
1802	coroutines into libev programs, by yielding to other active coroutines	2240	coroutines into libev programs, by yielding to other active coroutines
1803	during each prepare and only letting the process block if no coroutines	2241	during each prepare and only letting the process block if no coroutines
1804	are ready to run (it's actually more complicated: it only runs coroutines	2242	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1807	loop from blocking if lower-priority coroutines are active, thus mapping	2245	loop from blocking if lower-priority coroutines are active, thus mapping
1808	low-priority coroutines to idle/background tasks).	2246	low-priority coroutines to idle/background tasks).
1809		2247
1810	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2248	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1811	priority, to ensure that they are being run before any other watchers	2249	priority, to ensure that they are being run before any other watchers
		2250	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2251
1812	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2252	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1813	too) should not activate ("feed") events into libev. While libev fully	2253	activate ("feed") events into libev. While libev fully supports this, they
1814	supports this, they will be called before other C<ev_check> watchers	2254	might get executed before other C<ev_check> watchers did their job. As
1815	did their job. As C<ev_check> watchers are often used to embed other	2255	C<ev_check> watchers are often used to embed other (non-libev) event
1816	(non-libev) event loops those other event loops might be in an unusable	2256	loops those other event loops might be in an unusable state until their
1817	state until their C<ev_check> watcher ran (always remind yourself to	2257	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1818	coexist peacefully with others).	2258	others).
1819		2259
1820	=head3 Watcher-Specific Functions and Data Members	2260	=head3 Watcher-Specific Functions and Data Members
1821		2261
1822	=over 4	2262	=over 4
1823		2263
…		…
1825		2265
1826	=item ev_check_init (ev_check *, callback)	2266	=item ev_check_init (ev_check *, callback)
1827		2267
1828	Initialises and configures the prepare or check watcher - they have no	2268	Initialises and configures the prepare or check watcher - they have no
1829	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2269	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1830	macros, but using them is utterly, utterly and completely pointless.	2270	macros, but using them is utterly, utterly, utterly and completely
		2271	pointless.
1831		2272
1832	=back	2273	=back
1833		2274
1834	=head3 Examples	2275	=head3 Examples
1835		2276
1836	There are a number of principal ways to embed other event loops or modules	2277	There are a number of principal ways to embed other event loops or modules
1837	into libev. Here are some ideas on how to include libadns into libev	2278	into libev. Here are some ideas on how to include libadns into libev
1838	(there is a Perl module named C<EV::ADNS> that does this, which you could	2279	(there is a Perl module named C<EV::ADNS> that does this, which you could
1839	use for an actually working example. Another Perl module named C<EV::Glib>	2280	use as a working example. Another Perl module named C<EV::Glib> embeds a
1840	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2281	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1841	into the Glib event loop).	2282	Glib event loop).
1842		2283
1843	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2284	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1844	and in a check watcher, destroy them and call into libadns. What follows	2285	and in a check watcher, destroy them and call into libadns. What follows
1845	is pseudo-code only of course. This requires you to either use a low	2286	is pseudo-code only of course. This requires you to either use a low
1846	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2287	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1847	the callbacks for the IO/timeout watchers might not have been called yet.	2288	the callbacks for the IO/timeout watchers might not have been called yet.
1848		2289
1849	static ev_io iow [nfd];	2290	static ev_io iow [nfd];
1850	static ev_timer tw;	2291	static ev_timer tw;
1851		2292
1852	static void	2293	static void
1853	io_cb (ev_loop *loop, ev_io *w, int revents)	2294	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1854	{	2295	{
1855	}	2296	}
1856		2297
1857	// create io watchers for each fd and a timer before blocking	2298	// create io watchers for each fd and a timer before blocking
1858	static void	2299	static void
1859	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2300	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1860	{	2301	{
1861	int timeout = 3600000;	2302	int timeout = 3600000;
1862	struct pollfd fds [nfd];	2303	struct pollfd fds [nfd];
1863	// actual code will need to loop here and realloc etc.	2304	// actual code will need to loop here and realloc etc.
1864	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2305	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1865		2306
1866	/* the callback is illegal, but won't be called as we stop during check */	2307	/* the callback is illegal, but won't be called as we stop during check */
1867	ev_timer_init (&tw, 0, timeout * 1e-3);	2308	ev_timer_init (&tw, 0, timeout * 1e-3);
1868	ev_timer_start (loop, &tw);	2309	ev_timer_start (loop, &tw);
1869		2310
1870	// create one ev_io per pollfd	2311	// create one ev_io per pollfd
1871	for (int i = 0; i < nfd; ++i)	2312	for (int i = 0; i < nfd; ++i)
1872	{	2313	{
1873	ev_io_init (iow + i, io_cb, fds [i].fd,	2314	ev_io_init (iow + i, io_cb, fds [i].fd,
1874	((fds [i].events & POLLIN ? EV_READ : 0)	2315	((fds [i].events & POLLIN ? EV_READ : 0)
1875	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2316	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1876		2317
1877	fds [i].revents = 0;	2318	fds [i].revents = 0;
1878	ev_io_start (loop, iow + i);	2319	ev_io_start (loop, iow + i);
1879	}	2320	}
1880	}	2321	}
1881		2322
1882	// stop all watchers after blocking	2323	// stop all watchers after blocking
1883	static void	2324	static void
1884	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2325	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1885	{	2326	{
1886	ev_timer_stop (loop, &tw);	2327	ev_timer_stop (loop, &tw);
1887		2328
1888	for (int i = 0; i < nfd; ++i)	2329	for (int i = 0; i < nfd; ++i)
1889	{	2330	{
1890	// set the relevant poll flags	2331	// set the relevant poll flags
1891	// could also call adns_processreadable etc. here	2332	// could also call adns_processreadable etc. here
1892	struct pollfd *fd = fds + i;	2333	struct pollfd *fd = fds + i;
1893	int revents = ev_clear_pending (iow + i);	2334	int revents = ev_clear_pending (iow + i);
1894	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2335	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1895	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2336	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1896		2337
1897	// now stop the watcher	2338	// now stop the watcher
1898	ev_io_stop (loop, iow + i);	2339	ev_io_stop (loop, iow + i);
1899	}	2340	}
1900		2341
1901	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2342	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1902	}	2343	}
1903		2344
1904	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2345	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1905	in the prepare watcher and would dispose of the check watcher.	2346	in the prepare watcher and would dispose of the check watcher.
1906		2347
1907	Method 3: If the module to be embedded supports explicit event	2348	Method 3: If the module to be embedded supports explicit event
1908	notification (adns does), you can also make use of the actual watcher	2349	notification (libadns does), you can also make use of the actual watcher
1909	callbacks, and only destroy/create the watchers in the prepare watcher.	2350	callbacks, and only destroy/create the watchers in the prepare watcher.
1910		2351
1911	static void	2352	static void
1912	timer_cb (EV_P_ ev_timer *w, int revents)	2353	timer_cb (EV_P_ ev_timer *w, int revents)
1913	{	2354	{
1914	adns_state ads = (adns_state)w->data;	2355	adns_state ads = (adns_state)w->data;
1915	update_now (EV_A);	2356	update_now (EV_A);
1916		2357
1917	adns_processtimeouts (ads, &tv_now);	2358	adns_processtimeouts (ads, &tv_now);
1918	}	2359	}
1919		2360
1920	static void	2361	static void
1921	io_cb (EV_P_ ev_io *w, int revents)	2362	io_cb (EV_P_ ev_io *w, int revents)
1922	{	2363	{
1923	adns_state ads = (adns_state)w->data;	2364	adns_state ads = (adns_state)w->data;
1924	update_now (EV_A);	2365	update_now (EV_A);
1925		2366
1926	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2367	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1927	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2368	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1928	}	2369	}
1929		2370
1930	// do not ever call adns_afterpoll	2371	// do not ever call adns_afterpoll
1931		2372
1932	Method 4: Do not use a prepare or check watcher because the module you	2373	Method 4: Do not use a prepare or check watcher because the module you
1933	want to embed is too inflexible to support it. Instead, youc na override	2374	want to embed is not flexible enough to support it. Instead, you can
1934	their poll function. The drawback with this solution is that the main	2375	override their poll function. The drawback with this solution is that the
1935	loop is now no longer controllable by EV. The C<Glib::EV> module does	2376	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1936	this.	2377	this approach, effectively embedding EV as a client into the horrible
		2378	libglib event loop.
1937		2379
1938	static gint	2380	static gint
1939	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2381	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1940	{	2382	{
1941	int got_events = 0;	2383	int got_events = 0;
1942		2384
1943	for (n = 0; n < nfds; ++n)	2385	for (n = 0; n < nfds; ++n)
1944	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2386	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1945		2387
1946	if (timeout >= 0)	2388	if (timeout >= 0)
1947	// create/start timer	2389	// create/start timer
1948		2390
1949	// poll	2391	// poll
1950	ev_loop (EV_A_ 0);	2392	ev_loop (EV_A_ 0);
1951		2393
1952	// stop timer again	2394	// stop timer again
1953	if (timeout >= 0)	2395	if (timeout >= 0)
1954	ev_timer_stop (EV_A_ &to);	2396	ev_timer_stop (EV_A_ &to);
1955		2397
1956	// stop io watchers again - their callbacks should have set	2398	// stop io watchers again - their callbacks should have set
1957	for (n = 0; n < nfds; ++n)	2399	for (n = 0; n < nfds; ++n)
1958	ev_io_stop (EV_A_ iow [n]);	2400	ev_io_stop (EV_A_ iow [n]);
1959		2401
1960	return got_events;	2402	return got_events;
1961	}	2403	}
1962		2404
1963		2405
1964	=head2 C<ev_embed> - when one backend isn't enough...	2406	=head2 C<ev_embed> - when one backend isn't enough...
1965		2407
1966	This is a rather advanced watcher type that lets you embed one event loop	2408	This is a rather advanced watcher type that lets you embed one event loop
…		…
1972	prioritise I/O.	2414	prioritise I/O.
1973		2415
1974	As an example for a bug workaround, the kqueue backend might only support	2416	As an example for a bug workaround, the kqueue backend might only support
1975	sockets on some platform, so it is unusable as generic backend, but you	2417	sockets on some platform, so it is unusable as generic backend, but you
1976	still want to make use of it because you have many sockets and it scales	2418	still want to make use of it because you have many sockets and it scales
1977	so nicely. In this case, you would create a kqueue-based loop and embed it	2419	so nicely. In this case, you would create a kqueue-based loop and embed
1978	into your default loop (which might use e.g. poll). Overall operation will	2420	it into your default loop (which might use e.g. poll). Overall operation
1979	be a bit slower because first libev has to poll and then call kevent, but	2421	will be a bit slower because first libev has to call C<poll> and then
1980	at least you can use both at what they are best.	2422	C<kevent>, but at least you can use both mechanisms for what they are
		2423	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1981		2424
1982	As for prioritising I/O: rarely you have the case where some fds have	2425	As for prioritising I/O: under rare circumstances you have the case where
1983	to be watched and handled very quickly (with low latency), and even	2426	some fds have to be watched and handled very quickly (with low latency),
1984	priorities and idle watchers might have too much overhead. In this case	2427	and even priorities and idle watchers might have too much overhead. In
1985	you would put all the high priority stuff in one loop and all the rest in	2428	this case you would put all the high priority stuff in one loop and all
1986	a second one, and embed the second one in the first.	2429	the rest in a second one, and embed the second one in the first.
1987		2430
1988	As long as the watcher is active, the callback will be invoked every time	2431	As long as the watcher is active, the callback will be invoked every time
1989	there might be events pending in the embedded loop. The callback must then	2432	there might be events pending in the embedded loop. The callback must then
1990	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2433	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1991	their callbacks (you could also start an idle watcher to give the embedded	2434	their callbacks (you could also start an idle watcher to give the embedded
…		…
1999	interested in that.	2442	interested in that.
2000		2443
2001	Also, there have not currently been made special provisions for forking:	2444	Also, there have not currently been made special provisions for forking:
2002	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2445	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2003	but you will also have to stop and restart any C<ev_embed> watchers	2446	but you will also have to stop and restart any C<ev_embed> watchers
2004	yourself.	2447	yourself - but you can use a fork watcher to handle this automatically,
		2448	and future versions of libev might do just that.
2005		2449
2006	Unfortunately, not all backends are embeddable, only the ones returned by	2450	Unfortunately, not all backends are embeddable: only the ones returned by
2007	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2451	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2008	portable one.	2452	portable one.
2009		2453
2010	So when you want to use this feature you will always have to be prepared	2454	So when you want to use this feature you will always have to be prepared
2011	that you cannot get an embeddable loop. The recommended way to get around	2455	that you cannot get an embeddable loop. The recommended way to get around
2012	this is to have a separate variables for your embeddable loop, try to	2456	this is to have a separate variables for your embeddable loop, try to
2013	create it, and if that fails, use the normal loop for everything.	2457	create it, and if that fails, use the normal loop for everything.
2014		2458
		2459	=head3 C<ev_embed> and fork
		2460
		2461	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2462	automatically be applied to the embedded loop as well, so no special
		2463	fork handling is required in that case. When the watcher is not running,
		2464	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2465	as applicable.
		2466
2015	=head3 Watcher-Specific Functions and Data Members	2467	=head3 Watcher-Specific Functions and Data Members
2016		2468
2017	=over 4	2469	=over 4
2018		2470
2019	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2471	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2022		2474
2023	Configures the watcher to embed the given loop, which must be	2475	Configures the watcher to embed the given loop, which must be
2024	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2476	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2025	invoked automatically, otherwise it is the responsibility of the callback	2477	invoked automatically, otherwise it is the responsibility of the callback
2026	to invoke it (it will continue to be called until the sweep has been done,	2478	to invoke it (it will continue to be called until the sweep has been done,
2027	if you do not want thta, you need to temporarily stop the embed watcher).	2479	if you do not want that, you need to temporarily stop the embed watcher).
2028		2480
2029	=item ev_embed_sweep (loop, ev_embed *)	2481	=item ev_embed_sweep (loop, ev_embed *)
2030		2482
2031	Make a single, non-blocking sweep over the embedded loop. This works	2483	Make a single, non-blocking sweep over the embedded loop. This works
2032	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2484	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2033	apropriate way for embedded loops.	2485	appropriate way for embedded loops.
2034		2486
2035	=item struct ev_loop *other [read-only]	2487	=item struct ev_loop *other [read-only]
2036		2488
2037	The embedded event loop.	2489	The embedded event loop.
2038		2490
…		…
2040		2492
2041	=head3 Examples	2493	=head3 Examples
2042		2494
2043	Example: Try to get an embeddable event loop and embed it into the default	2495	Example: Try to get an embeddable event loop and embed it into the default
2044	event loop. If that is not possible, use the default loop. The default	2496	event loop. If that is not possible, use the default loop. The default
2045	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2497	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2046	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2498	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2047	used).	2499	used).
2048		2500
2049	struct ev_loop *loop_hi = ev_default_init (0);	2501	struct ev_loop *loop_hi = ev_default_init (0);
2050	struct ev_loop *loop_lo = 0;	2502	struct ev_loop *loop_lo = 0;
2051	struct ev_embed embed;	2503	ev_embed embed;
2052		2504
2053	// see if there is a chance of getting one that works	2505	// see if there is a chance of getting one that works
2054	// (remember that a flags value of 0 means autodetection)	2506	// (remember that a flags value of 0 means autodetection)
2055	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2507	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2056	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2508	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2057	: 0;	2509	: 0;
2058		2510
2059	// if we got one, then embed it, otherwise default to loop_hi	2511	// if we got one, then embed it, otherwise default to loop_hi
2060	if (loop_lo)	2512	if (loop_lo)
2061	{	2513	{
2062	ev_embed_init (&embed, 0, loop_lo);	2514	ev_embed_init (&embed, 0, loop_lo);
2063	ev_embed_start (loop_hi, &embed);	2515	ev_embed_start (loop_hi, &embed);
2064	}	2516	}
2065	else	2517	else
2066	loop_lo = loop_hi;	2518	loop_lo = loop_hi;
2067		2519
2068	Example: Check if kqueue is available but not recommended and create	2520	Example: Check if kqueue is available but not recommended and create
2069	a kqueue backend for use with sockets (which usually work with any	2521	a kqueue backend for use with sockets (which usually work with any
2070	kqueue implementation). Store the kqueue/socket-only event loop in	2522	kqueue implementation). Store the kqueue/socket-only event loop in
2071	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2523	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2072		2524
2073	struct ev_loop *loop = ev_default_init (0);	2525	struct ev_loop *loop = ev_default_init (0);
2074	struct ev_loop *loop_socket = 0;	2526	struct ev_loop *loop_socket = 0;
2075	struct ev_embed embed;	2527	ev_embed embed;
2076		2528
2077	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2529	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2078	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2530	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2079	{	2531	{
2080	ev_embed_init (&embed, 0, loop_socket);	2532	ev_embed_init (&embed, 0, loop_socket);
2081	ev_embed_start (loop, &embed);	2533	ev_embed_start (loop, &embed);
2082	}	2534	}
2083		2535
2084	if (!loop_socket)	2536	if (!loop_socket)
2085	loop_socket = loop;	2537	loop_socket = loop;
2086		2538
2087	// now use loop_socket for all sockets, and loop for everything else	2539	// now use loop_socket for all sockets, and loop for everything else
2088		2540
2089		2541
2090	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2542	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2091		2543
2092	Fork watchers are called when a C<fork ()> was detected (usually because	2544	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2136	is that the author does not know of a simple (or any) algorithm for a	2588	is that the author does not know of a simple (or any) algorithm for a
2137	multiple-writer-single-reader queue that works in all cases and doesn't	2589	multiple-writer-single-reader queue that works in all cases and doesn't
2138	need elaborate support such as pthreads.	2590	need elaborate support such as pthreads.
2139		2591
2140	That means that if you want to queue data, you have to provide your own	2592	That means that if you want to queue data, you have to provide your own
2141	queue. But at least I can tell you would implement locking around your	2593	queue. But at least I can tell you how to implement locking around your
2142	queue:	2594	queue:
2143		2595
2144	=over 4	2596	=over 4
2145		2597
2146	=item queueing from a signal handler context	2598	=item queueing from a signal handler context
2147		2599
2148	To implement race-free queueing, you simply add to the queue in the signal	2600	To implement race-free queueing, you simply add to the queue in the signal
2149	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2601	handler but you block the signal handler in the watcher callback. Here is
2150	some fictitiuous SIGUSR1 handler:	2602	an example that does that for some fictitious SIGUSR1 handler:
2151		2603
2152	static ev_async mysig;	2604	static ev_async mysig;
2153		2605
2154	static void	2606	static void
2155	sigusr1_handler (void)	2607	sigusr1_handler (void)
…		…
2221	=over 4	2673	=over 4
2222		2674
2223	=item ev_async_init (ev_async *, callback)	2675	=item ev_async_init (ev_async *, callback)
2224		2676
2225	Initialises and configures the async watcher - it has no parameters of any	2677	Initialises and configures the async watcher - it has no parameters of any
2226	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2678	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2227	believe me.	2679	trust me.
2228		2680
2229	=item ev_async_send (loop, ev_async *)	2681	=item ev_async_send (loop, ev_async *)
2230		2682
2231	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2683	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2232	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2684	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2233	C<ev_feed_event>, this call is safe to do in other threads, signal or	2685	C<ev_feed_event>, this call is safe to do from other threads, signal or
2234	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2686	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2235	section below on what exactly this means).	2687	section below on what exactly this means).
2236		2688
2237	This call incurs the overhead of a syscall only once per loop iteration,	2689	This call incurs the overhead of a system call only once per loop iteration,
2238	so while the overhead might be noticable, it doesn't apply to repeated	2690	so while the overhead might be noticeable, it doesn't apply to repeated
2239	calls to C<ev_async_send>.	2691	calls to C<ev_async_send>.
2240		2692
		2693	=item bool = ev_async_pending (ev_async *)
		2694
		2695	Returns a non-zero value when C<ev_async_send> has been called on the
		2696	watcher but the event has not yet been processed (or even noted) by the
		2697	event loop.
		2698
		2699	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2700	the loop iterates next and checks for the watcher to have become active,
		2701	it will reset the flag again. C<ev_async_pending> can be used to very
		2702	quickly check whether invoking the loop might be a good idea.
		2703
		2704	Not that this does I<not> check whether the watcher itself is pending, only
		2705	whether it has been requested to make this watcher pending.
		2706
2241	=back	2707	=back
2242		2708
2243		2709
2244	=head1 OTHER FUNCTIONS	2710	=head1 OTHER FUNCTIONS
2245		2711
…		…
2248	=over 4	2714	=over 4
2249		2715
2250	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2716	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2251		2717
2252	This function combines a simple timer and an I/O watcher, calls your	2718	This function combines a simple timer and an I/O watcher, calls your
2253	callback on whichever event happens first and automatically stop both	2719	callback on whichever event happens first and automatically stops both
2254	watchers. This is useful if you want to wait for a single event on an fd	2720	watchers. This is useful if you want to wait for a single event on an fd
2255	or timeout without having to allocate/configure/start/stop/free one or	2721	or timeout without having to allocate/configure/start/stop/free one or
2256	more watchers yourself.	2722	more watchers yourself.
2257		2723
2258	If C<fd> is less than 0, then no I/O watcher will be started and events	2724	If C<fd> is less than 0, then no I/O watcher will be started and the
2259	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2725	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2260	C<events> set will be craeted and started.	2726	the given C<fd> and C<events> set will be created and started.
2261		2727
2262	If C<timeout> is less than 0, then no timeout watcher will be	2728	If C<timeout> is less than 0, then no timeout watcher will be
2263	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2729	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2264	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2730	repeat = 0) will be started. C<0> is a valid timeout.
2265	dubious value.
2266		2731
2267	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2732	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2268	passed an C<revents> set like normal event callbacks (a combination of	2733	passed an C<revents> set like normal event callbacks (a combination of
2269	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2734	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2270	value passed to C<ev_once>:	2735	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2736	a timeout and an io event at the same time - you probably should give io
		2737	events precedence.
2271		2738
		2739	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2740
2272	static void stdin_ready (int revents, void *arg)	2741	static void stdin_ready (int revents, void *arg)
2273	{	2742	{
2274	if (revents & EV_TIMEOUT)
2275	/* doh, nothing entered */;
2276	else if (revents & EV_READ)	2743	if (revents & EV_READ)
2277	/* stdin might have data for us, joy! */;	2744	/* stdin might have data for us, joy! */;
		2745	else if (revents & EV_TIMEOUT)
		2746	/* doh, nothing entered */;
2278	}	2747	}
2279		2748
2280	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2749	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2281		2750
2282	=item ev_feed_event (ev_loop *, watcher *, int revents)	2751	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2283		2752
2284	Feeds the given event set into the event loop, as if the specified event	2753	Feeds the given event set into the event loop, as if the specified event
2285	had happened for the specified watcher (which must be a pointer to an	2754	had happened for the specified watcher (which must be a pointer to an
2286	initialised but not necessarily started event watcher).	2755	initialised but not necessarily started event watcher).
2287		2756
2288	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2757	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2289		2758
2290	Feed an event on the given fd, as if a file descriptor backend detected	2759	Feed an event on the given fd, as if a file descriptor backend detected
2291	the given events it.	2760	the given events it.
2292		2761
2293	=item ev_feed_signal_event (ev_loop *loop, int signum)	2762	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2294		2763
2295	Feed an event as if the given signal occured (C<loop> must be the default	2764	Feed an event as if the given signal occurred (C<loop> must be the default
2296	loop!).	2765	loop!).
2297		2766
2298	=back	2767	=back
2299		2768
2300		2769
…		…
2316		2785
2317	=item * Priorities are not currently supported. Initialising priorities	2786	=item * Priorities are not currently supported. Initialising priorities
2318	will fail and all watchers will have the same priority, even though there	2787	will fail and all watchers will have the same priority, even though there
2319	is an ev_pri field.	2788	is an ev_pri field.
2320		2789
		2790	=item * In libevent, the last base created gets the signals, in libev, the
		2791	first base created (== the default loop) gets the signals.
		2792
2321	=item * Other members are not supported.	2793	=item * Other members are not supported.
2322		2794
2323	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2795	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2324	to use the libev header file and library.	2796	to use the libev header file and library.
2325		2797
2326	=back	2798	=back
2327		2799
2328	=head1 C++ SUPPORT	2800	=head1 C++ SUPPORT
2329		2801
2330	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2802	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2331	you to use some convinience methods to start/stop watchers and also change	2803	you to use some convenience methods to start/stop watchers and also change
2332	the callback model to a model using method callbacks on objects.	2804	the callback model to a model using method callbacks on objects.
2333		2805
2334	To use it,	2806	To use it,
2335		2807
2336	#include <ev++.h>	2808	#include <ev++.h>
2337		2809
2338	This automatically includes F<ev.h> and puts all of its definitions (many	2810	This automatically includes F<ev.h> and puts all of its definitions (many
2339	of them macros) into the global namespace. All C++ specific things are	2811	of them macros) into the global namespace. All C++ specific things are
2340	put into the C<ev> namespace. It should support all the same embedding	2812	put into the C<ev> namespace. It should support all the same embedding
2341	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2813	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2408	your compiler is good :), then the method will be fully inlined into the	2880	your compiler is good :), then the method will be fully inlined into the
2409	thunking function, making it as fast as a direct C callback.	2881	thunking function, making it as fast as a direct C callback.
2410		2882
2411	Example: simple class declaration and watcher initialisation	2883	Example: simple class declaration and watcher initialisation
2412		2884
2413	struct myclass	2885	struct myclass
2414	{	2886	{
2415	void io_cb (ev::io &w, int revents) { }	2887	void io_cb (ev::io &w, int revents) { }
2416	}	2888	}
2417		2889
2418	myclass obj;	2890	myclass obj;
2419	ev::io iow;	2891	ev::io iow;
2420	iow.set <myclass, &myclass::io_cb> (&obj);	2892	iow.set <myclass, &myclass::io_cb> (&obj);
2421		2893
2422	=item w->set<function> (void *data = 0)	2894	=item w->set<function> (void *data = 0)
2423		2895
2424	Also sets a callback, but uses a static method or plain function as	2896	Also sets a callback, but uses a static method or plain function as
2425	callback. The optional C<data> argument will be stored in the watcher's	2897	callback. The optional C<data> argument will be stored in the watcher's
…		…
2427		2899
2428	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2900	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2429		2901
2430	See the method-C<set> above for more details.	2902	See the method-C<set> above for more details.
2431		2903
2432	Example:	2904	Example: Use a plain function as callback.
2433		2905
2434	static void io_cb (ev::io &w, int revents) { }	2906	static void io_cb (ev::io &w, int revents) { }
2435	iow.set <io_cb> ();	2907	iow.set <io_cb> ();
2436		2908
2437	=item w->set (struct ev_loop *)	2909	=item w->set (struct ev_loop *)
2438		2910
2439	Associates a different C<struct ev_loop> with this watcher. You can only	2911	Associates a different C<struct ev_loop> with this watcher. You can only
2440	do this when the watcher is inactive (and not pending either).	2912	do this when the watcher is inactive (and not pending either).
2441		2913
2442	=item w->set ([args])	2914	=item w->set ([arguments])
2443		2915
2444	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2916	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2445	called at least once. Unlike the C counterpart, an active watcher gets	2917	called at least once. Unlike the C counterpart, an active watcher gets
2446	automatically stopped and restarted when reconfiguring it with this	2918	automatically stopped and restarted when reconfiguring it with this
2447	method.	2919	method.
2448		2920
2449	=item w->start ()	2921	=item w->start ()
…		…
2473	=back	2945	=back
2474		2946
2475	Example: Define a class with an IO and idle watcher, start one of them in	2947	Example: Define a class with an IO and idle watcher, start one of them in
2476	the constructor.	2948	the constructor.
2477		2949
2478	class myclass	2950	class myclass
2479	{	2951	{
2480	ev::io io; void io_cb (ev::io &w, int revents);	2952	ev::io io ; void io_cb (ev::io &w, int revents);
2481	ev:idle idle void idle_cb (ev::idle &w, int revents);	2953	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2482		2954
2483	myclass (int fd)	2955	myclass (int fd)
2484	{	2956	{
2485	io .set <myclass, &myclass::io_cb > (this);	2957	io .set <myclass, &myclass::io_cb > (this);
2486	idle.set <myclass, &myclass::idle_cb> (this);	2958	idle.set <myclass, &myclass::idle_cb> (this);
2487		2959
2488	io.start (fd, ev::READ);	2960	io.start (fd, ev::READ);
2489	}	2961	}
2490	};	2962	};
		2963
		2964
		2965	=head1 OTHER LANGUAGE BINDINGS
		2966
		2967	Libev does not offer other language bindings itself, but bindings for a
		2968	number of languages exist in the form of third-party packages. If you know
		2969	any interesting language binding in addition to the ones listed here, drop
		2970	me a note.
		2971
		2972	=over 4
		2973
		2974	=item Perl
		2975
		2976	The EV module implements the full libev API and is actually used to test
		2977	libev. EV is developed together with libev. Apart from the EV core module,
		2978	there are additional modules that implement libev-compatible interfaces
		2979	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2980	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2981	and C<EV::Glib>).
		2982
		2983	It can be found and installed via CPAN, its homepage is at
		2984	L<http://software.schmorp.de/pkg/EV>.
		2985
		2986	=item Python
		2987
		2988	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2989	seems to be quite complete and well-documented. Note, however, that the
		2990	patch they require for libev is outright dangerous as it breaks the ABI
		2991	for everybody else, and therefore, should never be applied in an installed
		2992	libev (if python requires an incompatible ABI then it needs to embed
		2993	libev).
		2994
		2995	=item Ruby
		2996
		2997	Tony Arcieri has written a ruby extension that offers access to a subset
		2998	of the libev API and adds file handle abstractions, asynchronous DNS and
		2999	more on top of it. It can be found via gem servers. Its homepage is at
		3000	L<http://rev.rubyforge.org/>.
		3001
		3002	=item D
		3003
		3004	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		3005	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3006
		3007	=item Ocaml
		3008
		3009	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3010	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3011
		3012	=back
2491		3013
2492		3014
2493	=head1 MACRO MAGIC	3015	=head1 MACRO MAGIC
2494		3016
2495	Libev can be compiled with a variety of options, the most fundamantal	3017	Libev can be compiled with a variety of options, the most fundamental
2496	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3018	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2497	functions and callbacks have an initial C<struct ev_loop *> argument.	3019	functions and callbacks have an initial C<struct ev_loop *> argument.
2498		3020
2499	To make it easier to write programs that cope with either variant, the	3021	To make it easier to write programs that cope with either variant, the
2500	following macros are defined:	3022	following macros are defined:
…		…
2505		3027
2506	This provides the loop I<argument> for functions, if one is required ("ev	3028	This provides the loop I<argument> for functions, if one is required ("ev
2507	loop argument"). The C<EV_A> form is used when this is the sole argument,	3029	loop argument"). The C<EV_A> form is used when this is the sole argument,
2508	C<EV_A_> is used when other arguments are following. Example:	3030	C<EV_A_> is used when other arguments are following. Example:
2509		3031
2510	ev_unref (EV_A);	3032	ev_unref (EV_A);
2511	ev_timer_add (EV_A_ watcher);	3033	ev_timer_add (EV_A_ watcher);
2512	ev_loop (EV_A_ 0);	3034	ev_loop (EV_A_ 0);
2513		3035
2514	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3036	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2515	which is often provided by the following macro.	3037	which is often provided by the following macro.
2516		3038
2517	=item C<EV_P>, C<EV_P_>	3039	=item C<EV_P>, C<EV_P_>
2518		3040
2519	This provides the loop I<parameter> for functions, if one is required ("ev	3041	This provides the loop I<parameter> for functions, if one is required ("ev
2520	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3042	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2521	C<EV_P_> is used when other parameters are following. Example:	3043	C<EV_P_> is used when other parameters are following. Example:
2522		3044
2523	// this is how ev_unref is being declared	3045	// this is how ev_unref is being declared
2524	static void ev_unref (EV_P);	3046	static void ev_unref (EV_P);
2525		3047
2526	// this is how you can declare your typical callback	3048	// this is how you can declare your typical callback
2527	static void cb (EV_P_ ev_timer *w, int revents)	3049	static void cb (EV_P_ ev_timer *w, int revents)
2528		3050
2529	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3051	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2530	suitable for use with C<EV_A>.	3052	suitable for use with C<EV_A>.
2531		3053
2532	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3054	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2533		3055
2534	Similar to the other two macros, this gives you the value of the default	3056	Similar to the other two macros, this gives you the value of the default
2535	loop, if multiple loops are supported ("ev loop default").	3057	loop, if multiple loops are supported ("ev loop default").
		3058
		3059	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3060
		3061	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3062	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3063	is undefined when the default loop has not been initialised by a previous
		3064	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3065
		3066	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3067	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2536		3068
2537	=back	3069	=back
2538		3070
2539	Example: Declare and initialise a check watcher, utilising the above	3071	Example: Declare and initialise a check watcher, utilising the above
2540	macros so it will work regardless of whether multiple loops are supported	3072	macros so it will work regardless of whether multiple loops are supported
2541	or not.	3073	or not.
2542		3074
2543	static void	3075	static void
2544	check_cb (EV_P_ ev_timer *w, int revents)	3076	check_cb (EV_P_ ev_timer *w, int revents)
2545	{	3077	{
2546	ev_check_stop (EV_A_ w);	3078	ev_check_stop (EV_A_ w);
2547	}	3079	}
2548		3080
2549	ev_check check;	3081	ev_check check;
2550	ev_check_init (&check, check_cb);	3082	ev_check_init (&check, check_cb);
2551	ev_check_start (EV_DEFAULT_ &check);	3083	ev_check_start (EV_DEFAULT_ &check);
2552	ev_loop (EV_DEFAULT_ 0);	3084	ev_loop (EV_DEFAULT_ 0);
2553		3085
2554	=head1 EMBEDDING	3086	=head1 EMBEDDING
2555		3087
2556	Libev can (and often is) directly embedded into host	3088	Libev can (and often is) directly embedded into host
2557	applications. Examples of applications that embed it include the Deliantra	3089	applications. Examples of applications that embed it include the Deliantra
…		…
2564	libev somewhere in your source tree).	3096	libev somewhere in your source tree).
2565		3097
2566	=head2 FILESETS	3098	=head2 FILESETS
2567		3099
2568	Depending on what features you need you need to include one or more sets of files	3100	Depending on what features you need you need to include one or more sets of files
2569	in your app.	3101	in your application.
2570		3102
2571	=head3 CORE EVENT LOOP	3103	=head3 CORE EVENT LOOP
2572		3104
2573	To include only the libev core (all the C<ev_*> functions), with manual	3105	To include only the libev core (all the C<ev_*> functions), with manual
2574	configuration (no autoconf):	3106	configuration (no autoconf):
2575		3107
2576	#define EV_STANDALONE 1	3108	#define EV_STANDALONE 1
2577	#include "ev.c"	3109	#include "ev.c"
2578		3110
2579	This will automatically include F<ev.h>, too, and should be done in a	3111	This will automatically include F<ev.h>, too, and should be done in a
2580	single C source file only to provide the function implementations. To use	3112	single C source file only to provide the function implementations. To use
2581	it, do the same for F<ev.h> in all files wishing to use this API (best	3113	it, do the same for F<ev.h> in all files wishing to use this API (best
2582	done by writing a wrapper around F<ev.h> that you can include instead and	3114	done by writing a wrapper around F<ev.h> that you can include instead and
2583	where you can put other configuration options):	3115	where you can put other configuration options):
2584		3116
2585	#define EV_STANDALONE 1	3117	#define EV_STANDALONE 1
2586	#include "ev.h"	3118	#include "ev.h"
2587		3119
2588	Both header files and implementation files can be compiled with a C++	3120	Both header files and implementation files can be compiled with a C++
2589	compiler (at least, thats a stated goal, and breakage will be treated	3121	compiler (at least, that's a stated goal, and breakage will be treated
2590	as a bug).	3122	as a bug).
2591		3123
2592	You need the following files in your source tree, or in a directory	3124	You need the following files in your source tree, or in a directory
2593	in your include path (e.g. in libev/ when using -Ilibev):	3125	in your include path (e.g. in libev/ when using -Ilibev):
2594		3126
2595	ev.h	3127	ev.h
2596	ev.c	3128	ev.c
2597	ev_vars.h	3129	ev_vars.h
2598	ev_wrap.h	3130	ev_wrap.h
2599		3131
2600	ev_win32.c required on win32 platforms only	3132	ev_win32.c required on win32 platforms only
2601		3133
2602	ev_select.c only when select backend is enabled (which is enabled by default)	3134	ev_select.c only when select backend is enabled (which is enabled by default)
2603	ev_poll.c only when poll backend is enabled (disabled by default)	3135	ev_poll.c only when poll backend is enabled (disabled by default)
2604	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3136	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2605	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3137	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2606	ev_port.c only when the solaris port backend is enabled (disabled by default)	3138	ev_port.c only when the solaris port backend is enabled (disabled by default)
2607		3139
2608	F<ev.c> includes the backend files directly when enabled, so you only need	3140	F<ev.c> includes the backend files directly when enabled, so you only need
2609	to compile this single file.	3141	to compile this single file.
2610		3142
2611	=head3 LIBEVENT COMPATIBILITY API	3143	=head3 LIBEVENT COMPATIBILITY API
2612		3144
2613	To include the libevent compatibility API, also include:	3145	To include the libevent compatibility API, also include:
2614		3146
2615	#include "event.c"	3147	#include "event.c"
2616		3148
2617	in the file including F<ev.c>, and:	3149	in the file including F<ev.c>, and:
2618		3150
2619	#include "event.h"	3151	#include "event.h"
2620		3152
2621	in the files that want to use the libevent API. This also includes F<ev.h>.	3153	in the files that want to use the libevent API. This also includes F<ev.h>.
2622		3154
2623	You need the following additional files for this:	3155	You need the following additional files for this:
2624		3156
2625	event.h	3157	event.h
2626	event.c	3158	event.c
2627		3159
2628	=head3 AUTOCONF SUPPORT	3160	=head3 AUTOCONF SUPPORT
2629		3161
2630	Instead of using C<EV_STANDALONE=1> and providing your config in	3162	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2631	whatever way you want, you can also C<m4_include([libev.m4])> in your	3163	whatever way you want, you can also C<m4_include([libev.m4])> in your
2632	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3164	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2633	include F<config.h> and configure itself accordingly.	3165	include F<config.h> and configure itself accordingly.
2634		3166
2635	For this of course you need the m4 file:	3167	For this of course you need the m4 file:
2636		3168
2637	libev.m4	3169	libev.m4
2638		3170
2639	=head2 PREPROCESSOR SYMBOLS/MACROS	3171	=head2 PREPROCESSOR SYMBOLS/MACROS
2640		3172
2641	Libev can be configured via a variety of preprocessor symbols you have to define	3173	Libev can be configured via a variety of preprocessor symbols you have to
2642	before including any of its files. The default is not to build for multiplicity	3174	define before including any of its files. The default in the absence of
2643	and only include the select backend.	3175	autoconf is documented for every option.
2644		3176
2645	=over 4	3177	=over 4
2646		3178
2647	=item EV_STANDALONE	3179	=item EV_STANDALONE
2648		3180
…		…
2653	F<event.h> that are not directly supported by the libev core alone.	3185	F<event.h> that are not directly supported by the libev core alone.
2654		3186
2655	=item EV_USE_MONOTONIC	3187	=item EV_USE_MONOTONIC
2656		3188
2657	If defined to be C<1>, libev will try to detect the availability of the	3189	If defined to be C<1>, libev will try to detect the availability of the
2658	monotonic clock option at both compiletime and runtime. Otherwise no use	3190	monotonic clock option at both compile time and runtime. Otherwise no use
2659	of the monotonic clock option will be attempted. If you enable this, you	3191	of the monotonic clock option will be attempted. If you enable this, you
2660	usually have to link against librt or something similar. Enabling it when	3192	usually have to link against librt or something similar. Enabling it when
2661	the functionality isn't available is safe, though, although you have	3193	the functionality isn't available is safe, though, although you have
2662	to make sure you link against any libraries where the C<clock_gettime>	3194	to make sure you link against any libraries where the C<clock_gettime>
2663	function is hiding in (often F<-lrt>).	3195	function is hiding in (often F<-lrt>).
2664		3196
2665	=item EV_USE_REALTIME	3197	=item EV_USE_REALTIME
2666		3198
2667	If defined to be C<1>, libev will try to detect the availability of the	3199	If defined to be C<1>, libev will try to detect the availability of the
2668	realtime clock option at compiletime (and assume its availability at	3200	real-time clock option at compile time (and assume its availability at
2669	runtime if successful). Otherwise no use of the realtime clock option will	3201	runtime if successful). Otherwise no use of the real-time clock option will
2670	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3202	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2671	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3203	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2672	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3204	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2673		3205
2674	=item EV_USE_NANOSLEEP	3206	=item EV_USE_NANOSLEEP
2675		3207
2676	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3208	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2677	and will use it for delays. Otherwise it will use C<select ()>.	3209	and will use it for delays. Otherwise it will use C<select ()>.
2678		3210
		3211	=item EV_USE_EVENTFD
		3212
		3213	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3214	available and will probe for kernel support at runtime. This will improve
		3215	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3216	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3217	2.7 or newer, otherwise disabled.
		3218
2679	=item EV_USE_SELECT	3219	=item EV_USE_SELECT
2680		3220
2681	If undefined or defined to be C<1>, libev will compile in support for the	3221	If undefined or defined to be C<1>, libev will compile in support for the
2682	C<select>(2) backend. No attempt at autodetection will be done: if no	3222	C<select>(2) backend. No attempt at auto-detection will be done: if no
2683	other method takes over, select will be it. Otherwise the select backend	3223	other method takes over, select will be it. Otherwise the select backend
2684	will not be compiled in.	3224	will not be compiled in.
2685		3225
2686	=item EV_SELECT_USE_FD_SET	3226	=item EV_SELECT_USE_FD_SET
2687		3227
2688	If defined to C<1>, then the select backend will use the system C<fd_set>	3228	If defined to C<1>, then the select backend will use the system C<fd_set>
2689	structure. This is useful if libev doesn't compile due to a missing	3229	structure. This is useful if libev doesn't compile due to a missing
2690	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3230	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2691	exotic systems. This usually limits the range of file descriptors to some	3231	exotic systems. This usually limits the range of file descriptors to some
2692	low limit such as 1024 or might have other limitations (winsocket only	3232	low limit such as 1024 or might have other limitations (winsocket only
2693	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3233	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2694	influence the size of the C<fd_set> used.	3234	influence the size of the C<fd_set> used.
2695		3235
…		…
2719		3259
2720	=item EV_USE_EPOLL	3260	=item EV_USE_EPOLL
2721		3261
2722	If defined to be C<1>, libev will compile in support for the Linux	3262	If defined to be C<1>, libev will compile in support for the Linux
2723	C<epoll>(7) backend. Its availability will be detected at runtime,	3263	C<epoll>(7) backend. Its availability will be detected at runtime,
2724	otherwise another method will be used as fallback. This is the	3264	otherwise another method will be used as fallback. This is the preferred
2725	preferred backend for GNU/Linux systems.	3265	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3266	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2726		3267
2727	=item EV_USE_KQUEUE	3268	=item EV_USE_KQUEUE
2728		3269
2729	If defined to be C<1>, libev will compile in support for the BSD style	3270	If defined to be C<1>, libev will compile in support for the BSD style
2730	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3271	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2743	otherwise another method will be used as fallback. This is the preferred	3284	otherwise another method will be used as fallback. This is the preferred
2744	backend for Solaris 10 systems.	3285	backend for Solaris 10 systems.
2745		3286
2746	=item EV_USE_DEVPOLL	3287	=item EV_USE_DEVPOLL
2747		3288
2748	reserved for future expansion, works like the USE symbols above.	3289	Reserved for future expansion, works like the USE symbols above.
2749		3290
2750	=item EV_USE_INOTIFY	3291	=item EV_USE_INOTIFY
2751		3292
2752	If defined to be C<1>, libev will compile in support for the Linux inotify	3293	If defined to be C<1>, libev will compile in support for the Linux inotify
2753	interface to speed up C<ev_stat> watchers. Its actual availability will	3294	interface to speed up C<ev_stat> watchers. Its actual availability will
2754	be detected at runtime.	3295	be detected at runtime. If undefined, it will be enabled if the headers
		3296	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2755		3297
2756	=item EV_ATOMIC_T	3298	=item EV_ATOMIC_T
2757		3299
2758	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3300	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2759	access is atomic with respect to other threads or signal contexts. No such	3301	access is atomic with respect to other threads or signal contexts. No such
2760	type is easily found in the C language, so you can provide your own type	3302	type is easily found in the C language, so you can provide your own type
2761	that you know is safe for your purposes. It is used both for signal handler "locking"	3303	that you know is safe for your purposes. It is used both for signal handler "locking"
2762	as well as for signal and thread safety in C<ev_async> watchers.	3304	as well as for signal and thread safety in C<ev_async> watchers.
2763		3305
2764	In the absense of this define, libev will use C<sig_atomic_t volatile>	3306	In the absence of this define, libev will use C<sig_atomic_t volatile>
2765	(from F<signal.h>), which is usually good enough on most platforms.	3307	(from F<signal.h>), which is usually good enough on most platforms.
2766		3308
2767	=item EV_H	3309	=item EV_H
2768		3310
2769	The name of the F<ev.h> header file used to include it. The default if	3311	The name of the F<ev.h> header file used to include it. The default if
…		…
2808	When doing priority-based operations, libev usually has to linearly search	3350	When doing priority-based operations, libev usually has to linearly search
2809	all the priorities, so having many of them (hundreds) uses a lot of space	3351	all the priorities, so having many of them (hundreds) uses a lot of space
2810	and time, so using the defaults of five priorities (-2 .. +2) is usually	3352	and time, so using the defaults of five priorities (-2 .. +2) is usually
2811	fine.	3353	fine.
2812		3354
2813	If your embedding app does not need any priorities, defining these both to	3355	If your embedding application does not need any priorities, defining these
2814	C<0> will save some memory and cpu.	3356	both to C<0> will save some memory and CPU.
2815		3357
2816	=item EV_PERIODIC_ENABLE	3358	=item EV_PERIODIC_ENABLE
2817		3359
2818	If undefined or defined to be C<1>, then periodic timers are supported. If	3360	If undefined or defined to be C<1>, then periodic timers are supported. If
2819	defined to be C<0>, then they are not. Disabling them saves a few kB of	3361	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2826	code.	3368	code.
2827		3369
2828	=item EV_EMBED_ENABLE	3370	=item EV_EMBED_ENABLE
2829		3371
2830	If undefined or defined to be C<1>, then embed watchers are supported. If	3372	If undefined or defined to be C<1>, then embed watchers are supported. If
2831	defined to be C<0>, then they are not.	3373	defined to be C<0>, then they are not. Embed watchers rely on most other
		3374	watcher types, which therefore must not be disabled.
2832		3375
2833	=item EV_STAT_ENABLE	3376	=item EV_STAT_ENABLE
2834		3377
2835	If undefined or defined to be C<1>, then stat watchers are supported. If	3378	If undefined or defined to be C<1>, then stat watchers are supported. If
2836	defined to be C<0>, then they are not.	3379	defined to be C<0>, then they are not.
…		…
2846	defined to be C<0>, then they are not.	3389	defined to be C<0>, then they are not.
2847		3390
2848	=item EV_MINIMAL	3391	=item EV_MINIMAL
2849		3392
2850	If you need to shave off some kilobytes of code at the expense of some	3393	If you need to shave off some kilobytes of code at the expense of some
2851	speed, define this symbol to C<1>. Currently only used for gcc to override	3394	speed, define this symbol to C<1>. Currently this is used to override some
2852	some inlining decisions, saves roughly 30% codesize of amd64.	3395	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3396	much smaller 2-heap for timer management over the default 4-heap.
2853		3397
2854	=item EV_PID_HASHSIZE	3398	=item EV_PID_HASHSIZE
2855		3399
2856	C<ev_child> watchers use a small hash table to distribute workload by	3400	C<ev_child> watchers use a small hash table to distribute workload by
2857	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3401	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2864	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3408	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2865	usually more than enough. If you need to manage thousands of C<ev_stat>	3409	usually more than enough. If you need to manage thousands of C<ev_stat>
2866	watchers you might want to increase this value (I<must> be a power of	3410	watchers you might want to increase this value (I<must> be a power of
2867	two).	3411	two).
2868		3412
		3413	=item EV_USE_4HEAP
		3414
		3415	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3416	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3417	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3418	faster performance with many (thousands) of watchers.
		3419
		3420	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3421	(disabled).
		3422
		3423	=item EV_HEAP_CACHE_AT
		3424
		3425	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3426	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3427	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3428	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3429	but avoids random read accesses on heap changes. This improves performance
		3430	noticeably with many (hundreds) of watchers.
		3431
		3432	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3433	(disabled).
		3434
		3435	=item EV_VERIFY
		3436
		3437	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3438	be done: If set to C<0>, no internal verification code will be compiled
		3439	in. If set to C<1>, then verification code will be compiled in, but not
		3440	called. If set to C<2>, then the internal verification code will be
		3441	called once per loop, which can slow down libev. If set to C<3>, then the
		3442	verification code will be called very frequently, which will slow down
		3443	libev considerably.
		3444
		3445	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3446	C<0>.
		3447
2869	=item EV_COMMON	3448	=item EV_COMMON
2870		3449
2871	By default, all watchers have a C<void *data> member. By redefining	3450	By default, all watchers have a C<void *data> member. By redefining
2872	this macro to a something else you can include more and other types of	3451	this macro to a something else you can include more and other types of
2873	members. You have to define it each time you include one of the files,	3452	members. You have to define it each time you include one of the files,
2874	though, and it must be identical each time.	3453	though, and it must be identical each time.
2875		3454
2876	For example, the perl EV module uses something like this:	3455	For example, the perl EV module uses something like this:
2877		3456
2878	#define EV_COMMON \	3457	#define EV_COMMON \
2879	SV *self; /* contains this struct */ \	3458	SV *self; /* contains this struct */ \
2880	SV *cb_sv, *fh /* note no trailing ";" */	3459	SV *cb_sv, *fh /* note no trailing ";" */
2881		3460
2882	=item EV_CB_DECLARE (type)	3461	=item EV_CB_DECLARE (type)
2883		3462
2884	=item EV_CB_INVOKE (watcher, revents)	3463	=item EV_CB_INVOKE (watcher, revents)
2885		3464
…		…
2890	definition and a statement, respectively. See the F<ev.h> header file for	3469	definition and a statement, respectively. See the F<ev.h> header file for
2891	their default definitions. One possible use for overriding these is to	3470	their default definitions. One possible use for overriding these is to
2892	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3471	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2893	method calls instead of plain function calls in C++.	3472	method calls instead of plain function calls in C++.
2894		3473
		3474	=back
		3475
2895	=head2 EXPORTED API SYMBOLS	3476	=head2 EXPORTED API SYMBOLS
2896		3477
2897	If you need to re-export the API (e.g. via a dll) and you need a list of	3478	If you need to re-export the API (e.g. via a DLL) and you need a list of
2898	exported symbols, you can use the provided F<Symbol.*> files which list	3479	exported symbols, you can use the provided F<Symbol.*> files which list
2899	all public symbols, one per line:	3480	all public symbols, one per line:
2900		3481
2901	Symbols.ev for libev proper	3482	Symbols.ev for libev proper
2902	Symbols.event for the libevent emulation	3483	Symbols.event for the libevent emulation
2903		3484
2904	This can also be used to rename all public symbols to avoid clashes with	3485	This can also be used to rename all public symbols to avoid clashes with
2905	multiple versions of libev linked together (which is obviously bad in	3486	multiple versions of libev linked together (which is obviously bad in
2906	itself, but sometimes it is inconvinient to avoid this).	3487	itself, but sometimes it is inconvenient to avoid this).
2907		3488
2908	A sed command like this will create wrapper C<#define>'s that you need to	3489	A sed command like this will create wrapper C<#define>'s that you need to
2909	include before including F<ev.h>:	3490	include before including F<ev.h>:
2910		3491
2911	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3492	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2928	file.	3509	file.
2929		3510
2930	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3511	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2931	that everybody includes and which overrides some configure choices:	3512	that everybody includes and which overrides some configure choices:
2932		3513
2933	#define EV_MINIMAL 1	3514	#define EV_MINIMAL 1
2934	#define EV_USE_POLL 0	3515	#define EV_USE_POLL 0
2935	#define EV_MULTIPLICITY 0	3516	#define EV_MULTIPLICITY 0
2936	#define EV_PERIODIC_ENABLE 0	3517	#define EV_PERIODIC_ENABLE 0
2937	#define EV_STAT_ENABLE 0	3518	#define EV_STAT_ENABLE 0
2938	#define EV_FORK_ENABLE 0	3519	#define EV_FORK_ENABLE 0
2939	#define EV_CONFIG_H <config.h>	3520	#define EV_CONFIG_H <config.h>
2940	#define EV_MINPRI 0	3521	#define EV_MINPRI 0
2941	#define EV_MAXPRI 0	3522	#define EV_MAXPRI 0
2942		3523
2943	#include "ev++.h"	3524	#include "ev++.h"
2944		3525
2945	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3526	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2946		3527
2947	#include "ev_cpp.h"	3528	#include "ev_cpp.h"
2948	#include "ev.c"	3529	#include "ev.c"
2949		3530
		3531	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2950		3532
2951	=head1 COMPLEXITIES	3533	=head2 THREADS AND COROUTINES
2952		3534
2953	In this section the complexities of (many of) the algorithms used inside	3535	=head3 THREADS
2954	libev will be explained. For complexity discussions about backends see the
2955	documentation for C<ev_default_init>.
2956		3536
2957	All of the following are about amortised time: If an array needs to be	3537	All libev functions are reentrant and thread-safe unless explicitly
2958	extended, libev needs to realloc and move the whole array, but this	3538	documented otherwise, but libev implements no locking itself. This means
2959	happens asymptotically never with higher number of elements, so O(1) might	3539	that you can use as many loops as you want in parallel, as long as there
2960	mean it might do a lengthy realloc operation in rare cases, but on average	3540	are no concurrent calls into any libev function with the same loop
2961	it is much faster and asymptotically approaches constant time.	3541	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3542	of course): libev guarantees that different event loops share no data
		3543	structures that need any locking.
		3544
		3545	Or to put it differently: calls with different loop parameters can be done
		3546	concurrently from multiple threads, calls with the same loop parameter
		3547	must be done serially (but can be done from different threads, as long as
		3548	only one thread ever is inside a call at any point in time, e.g. by using
		3549	a mutex per loop).
		3550
		3551	Specifically to support threads (and signal handlers), libev implements
		3552	so-called C<ev_async> watchers, which allow some limited form of
		3553	concurrency on the same event loop, namely waking it up "from the
		3554	outside".
		3555
		3556	If you want to know which design (one loop, locking, or multiple loops
		3557	without or something else still) is best for your problem, then I cannot
		3558	help you, but here is some generic advice:
2962		3559
2963	=over 4	3560	=over 4
2964		3561
2965	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3562	=item * most applications have a main thread: use the default libev loop
		3563	in that thread, or create a separate thread running only the default loop.
2966		3564
2967	This means that, when you have a watcher that triggers in one hour and	3565	This helps integrating other libraries or software modules that use libev
2968	there are 100 watchers that would trigger before that then inserting will	3566	themselves and don't care/know about threading.
2969	have to skip roughly seven (C<ld 100>) of these watchers.
2970		3567
2971	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3568	=item * one loop per thread is usually a good model.
2972		3569
2973	That means that changing a timer costs less than removing/adding them	3570	Doing this is almost never wrong, sometimes a better-performance model
2974	as only the relative motion in the event queue has to be paid for.	3571	exists, but it is always a good start.
2975		3572
2976	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3573	=item * other models exist, such as the leader/follower pattern, where one
		3574	loop is handed through multiple threads in a kind of round-robin fashion.
2977		3575
2978	These just add the watcher into an array or at the head of a list.	3576	Choosing a model is hard - look around, learn, know that usually you can do
		3577	better than you currently do :-)
2979		3578
2980	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3579	=item * often you need to talk to some other thread which blocks in the
		3580	event loop.
2981		3581
2982	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3582	C<ev_async> watchers can be used to wake them up from other threads safely
		3583	(or from signal contexts...).
2983		3584
2984	These watchers are stored in lists then need to be walked to find the	3585	An example use would be to communicate signals or other events that only
2985	correct watcher to remove. The lists are usually short (you don't usually	3586	work in the default loop by registering the signal watcher with the
2986	have many watchers waiting for the same fd or signal).	3587	default loop and triggering an C<ev_async> watcher from the default loop
2987		3588	watcher callback into the event loop interested in the signal.
2988	=item Finding the next timer in each loop iteration: O(1)
2989
2990	By virtue of using a binary heap, the next timer is always found at the
2991	beginning of the storage array.
2992
2993	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2994
2995	A change means an I/O watcher gets started or stopped, which requires
2996	libev to recalculate its status (and possibly tell the kernel, depending
2997	on backend and wether C<ev_io_set> was used).
2998
2999	=item Activating one watcher (putting it into the pending state): O(1)
3000
3001	=item Priority handling: O(number_of_priorities)
3002
3003	Priorities are implemented by allocating some space for each
3004	priority. When doing priority-based operations, libev usually has to
3005	linearly search all the priorities, but starting/stopping and activating
3006	watchers becomes O(1) w.r.t. priority handling.
3007
3008	=item Sending an ev_async: O(1)
3009
3010	=item Processing ev_async_send: O(number_of_async_watchers)
3011
3012	=item Processing signals: O(max_signal_number)
3013
3014	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3015	calls in the current loop iteration. Checking for async and signal events
3016	involves iterating over all running async watchers or all signal numbers.
3017		3589
3018	=back	3590	=back
3019		3591
		3592	=head3 COROUTINES
3020		3593
3021	=head1 Win32 platform limitations and workarounds	3594	Libev is very accommodating to coroutines ("cooperative threads"):
		3595	libev fully supports nesting calls to its functions from different
		3596	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3597	different coroutines, and switch freely between both coroutines running the
		3598	loop, as long as you don't confuse yourself). The only exception is that
		3599	you must not do this from C<ev_periodic> reschedule callbacks.
		3600
		3601	Care has been taken to ensure that libev does not keep local state inside
		3602	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3603	they do not call any callbacks.
		3604
		3605	=head2 COMPILER WARNINGS
		3606
		3607	Depending on your compiler and compiler settings, you might get no or a
		3608	lot of warnings when compiling libev code. Some people are apparently
		3609	scared by this.
		3610
		3611	However, these are unavoidable for many reasons. For one, each compiler
		3612	has different warnings, and each user has different tastes regarding
		3613	warning options. "Warn-free" code therefore cannot be a goal except when
		3614	targeting a specific compiler and compiler-version.
		3615
		3616	Another reason is that some compiler warnings require elaborate
		3617	workarounds, or other changes to the code that make it less clear and less
		3618	maintainable.
		3619
		3620	And of course, some compiler warnings are just plain stupid, or simply
		3621	wrong (because they don't actually warn about the condition their message
		3622	seems to warn about). For example, certain older gcc versions had some
		3623	warnings that resulted an extreme number of false positives. These have
		3624	been fixed, but some people still insist on making code warn-free with
		3625	such buggy versions.
		3626
		3627	While libev is written to generate as few warnings as possible,
		3628	"warn-free" code is not a goal, and it is recommended not to build libev
		3629	with any compiler warnings enabled unless you are prepared to cope with
		3630	them (e.g. by ignoring them). Remember that warnings are just that:
		3631	warnings, not errors, or proof of bugs.
		3632
		3633
		3634	=head2 VALGRIND
		3635
		3636	Valgrind has a special section here because it is a popular tool that is
		3637	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3638
		3639	If you think you found a bug (memory leak, uninitialised data access etc.)
		3640	in libev, then check twice: If valgrind reports something like:
		3641
		3642	==2274== definitely lost: 0 bytes in 0 blocks.
		3643	==2274== possibly lost: 0 bytes in 0 blocks.
		3644	==2274== still reachable: 256 bytes in 1 blocks.
		3645
		3646	Then there is no memory leak, just as memory accounted to global variables
		3647	is not a memleak - the memory is still being referenced, and didn't leak.
		3648
		3649	Similarly, under some circumstances, valgrind might report kernel bugs
		3650	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3651	although an acceptable workaround has been found here), or it might be
		3652	confused.
		3653
		3654	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3655	make it into some kind of religion.
		3656
		3657	If you are unsure about something, feel free to contact the mailing list
		3658	with the full valgrind report and an explanation on why you think this
		3659	is a bug in libev (best check the archives, too :). However, don't be
		3660	annoyed when you get a brisk "this is no bug" answer and take the chance
		3661	of learning how to interpret valgrind properly.
		3662
		3663	If you need, for some reason, empty reports from valgrind for your project
		3664	I suggest using suppression lists.
		3665
		3666
		3667	=head1 PORTABILITY NOTES
		3668
		3669	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3022		3670
3023	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3671	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3024	requires, and its I/O model is fundamentally incompatible with the POSIX	3672	requires, and its I/O model is fundamentally incompatible with the POSIX
3025	model. Libev still offers limited functionality on this platform in	3673	model. Libev still offers limited functionality on this platform in
3026	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3674	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3027	descriptors. This only applies when using Win32 natively, not when using	3675	descriptors. This only applies when using Win32 natively, not when using
3028	e.g. cygwin.	3676	e.g. cygwin.
3029		3677
		3678	Lifting these limitations would basically require the full
		3679	re-implementation of the I/O system. If you are into these kinds of
		3680	things, then note that glib does exactly that for you in a very portable
		3681	way (note also that glib is the slowest event library known to man).
		3682
3030	There is no supported compilation method available on windows except	3683	There is no supported compilation method available on windows except
3031	embedding it into other applications.	3684	embedding it into other applications.
3032		3685
		3686	Not a libev limitation but worth mentioning: windows apparently doesn't
		3687	accept large writes: instead of resulting in a partial write, windows will
		3688	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3689	so make sure you only write small amounts into your sockets (less than a
		3690	megabyte seems safe, but this apparently depends on the amount of memory
		3691	available).
		3692
3033	Due to the many, low, and arbitrary limits on the win32 platform and the	3693	Due to the many, low, and arbitrary limits on the win32 platform and
3034	abysmal performance of winsockets, using a large number of sockets is not	3694	the abysmal performance of winsockets, using a large number of sockets
3035	recommended (and not reasonable). If your program needs to use more than	3695	is not recommended (and not reasonable). If your program needs to use
3036	a hundred or so sockets, then likely it needs to use a totally different	3696	more than a hundred or so sockets, then likely it needs to use a totally
3037	implementation for windows, as libev offers the POSIX model, which cannot	3697	different implementation for windows, as libev offers the POSIX readiness
3038	be implemented efficiently on windows (microsoft monopoly games).	3698	notification model, which cannot be implemented efficiently on windows
		3699	(Microsoft monopoly games).
		3700
		3701	A typical way to use libev under windows is to embed it (see the embedding
		3702	section for details) and use the following F<evwrap.h> header file instead
		3703	of F<ev.h>:
		3704
		3705	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3706	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3707
		3708	#include "ev.h"
		3709
		3710	And compile the following F<evwrap.c> file into your project (make sure
		3711	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3712
		3713	#include "evwrap.h"
		3714	#include "ev.c"
3039		3715
3040	=over 4	3716	=over 4
3041		3717
3042	=item The winsocket select function	3718	=item The winsocket select function
3043		3719
3044	The winsocket C<select> function doesn't follow POSIX in that it requires	3720	The winsocket C<select> function doesn't follow POSIX in that it
3045	socket I<handles> and not socket I<file descriptors>. This makes select	3721	requires socket I<handles> and not socket I<file descriptors> (it is
3046	very inefficient, and also requires a mapping from file descriptors	3722	also extremely buggy). This makes select very inefficient, and also
3047	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3723	requires a mapping from file descriptors to socket handles (the Microsoft
3048	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3724	C runtime provides the function C<_open_osfhandle> for this). See the
3049	symbols for more info.	3725	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3726	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3050		3727
3051	The configuration for a "naked" win32 using the microsoft runtime	3728	The configuration for a "naked" win32 using the Microsoft runtime
3052	libraries and raw winsocket select is:	3729	libraries and raw winsocket select is:
3053		3730
3054	#define EV_USE_SELECT 1	3731	#define EV_USE_SELECT 1
3055	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3732	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3056		3733
3057	Note that winsockets handling of fd sets is O(n), so you can easily get a	3734	Note that winsockets handling of fd sets is O(n), so you can easily get a
3058	complexity in the O(n²) range when using win32.	3735	complexity in the O(n²) range when using win32.
3059		3736
3060	=item Limited number of file descriptors	3737	=item Limited number of file descriptors
3061		3738
3062	Windows has numerous arbitrary (and low) limits on things. Early versions	3739	Windows has numerous arbitrary (and low) limits on things.
3063	of winsocket's select only supported waiting for a max. of C<64> handles	3740
		3741	Early versions of winsocket's select only supported waiting for a maximum
3064	(probably owning to the fact that all windows kernels can only wait for	3742	of C<64> handles (probably owning to the fact that all windows kernels
3065	C<64> things at the same time internally; microsoft recommends spawning a	3743	can only wait for C<64> things at the same time internally; Microsoft
3066	chain of threads and wait for 63 handles and the previous thread in each).	3744	recommends spawning a chain of threads and wait for 63 handles and the
		3745	previous thread in each. Great).
3067		3746
3068	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3747	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3069	to some high number (e.g. C<2048>) before compiling the winsocket select	3748	to some high number (e.g. C<2048>) before compiling the winsocket select
3070	call (which might be in libev or elsewhere, for example, perl does its own	3749	call (which might be in libev or elsewhere, for example, perl does its own
3071	select emulation on windows).	3750	select emulation on windows).
3072		3751
3073	Another limit is the number of file descriptors in the microsoft runtime	3752	Another limit is the number of file descriptors in the Microsoft runtime
3074	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3753	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3075	or something like this inside microsoft). You can increase this by calling	3754	or something like this inside Microsoft). You can increase this by calling
3076	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3755	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3077	arbitrary limit), but is broken in many versions of the microsoft runtime	3756	arbitrary limit), but is broken in many versions of the Microsoft runtime
3078	libraries.	3757	libraries.
3079		3758
3080	This might get you to about C<512> or C<2048> sockets (depending on	3759	This might get you to about C<512> or C<2048> sockets (depending on
3081	windows version and/or the phase of the moon). To get more, you need to	3760	windows version and/or the phase of the moon). To get more, you need to
3082	wrap all I/O functions and provide your own fd management, but the cost of	3761	wrap all I/O functions and provide your own fd management, but the cost of
3083	calling select (O(n²)) will likely make this unworkable.	3762	calling select (O(n²)) will likely make this unworkable.
3084		3763
3085	=back	3764	=back
3086		3765
		3766	=head2 PORTABILITY REQUIREMENTS
		3767
		3768	In addition to a working ISO-C implementation and of course the
		3769	backend-specific APIs, libev relies on a few additional extensions:
		3770
		3771	=over 4
		3772
		3773	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3774	calling conventions regardless of C<ev_watcher_type *>.
		3775
		3776	Libev assumes not only that all watcher pointers have the same internal
		3777	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3778	assumes that the same (machine) code can be used to call any watcher
		3779	callback: The watcher callbacks have different type signatures, but libev
		3780	calls them using an C<ev_watcher *> internally.
		3781
		3782	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3783
		3784	The type C<sig_atomic_t volatile> (or whatever is defined as
		3785	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3786	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3787	believed to be sufficiently portable.
		3788
		3789	=item C<sigprocmask> must work in a threaded environment
		3790
		3791	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3792	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3793	pthread implementations will either allow C<sigprocmask> in the "main
		3794	thread" or will block signals process-wide, both behaviours would
		3795	be compatible with libev. Interaction between C<sigprocmask> and
		3796	C<pthread_sigmask> could complicate things, however.
		3797
		3798	The most portable way to handle signals is to block signals in all threads
		3799	except the initial one, and run the default loop in the initial thread as
		3800	well.
		3801
		3802	=item C<long> must be large enough for common memory allocation sizes
		3803
		3804	To improve portability and simplify its API, libev uses C<long> internally
		3805	instead of C<size_t> when allocating its data structures. On non-POSIX
		3806	systems (Microsoft...) this might be unexpectedly low, but is still at
		3807	least 31 bits everywhere, which is enough for hundreds of millions of
		3808	watchers.
		3809
		3810	=item C<double> must hold a time value in seconds with enough accuracy
		3811
		3812	The type C<double> is used to represent timestamps. It is required to
		3813	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3814	enough for at least into the year 4000. This requirement is fulfilled by
		3815	implementations implementing IEEE 754 (basically all existing ones).
		3816
		3817	=back
		3818
		3819	If you know of other additional requirements drop me a note.
		3820
		3821
		3822	=head1 ALGORITHMIC COMPLEXITIES
		3823
		3824	In this section the complexities of (many of) the algorithms used inside
		3825	libev will be documented. For complexity discussions about backends see
		3826	the documentation for C<ev_default_init>.
		3827
		3828	All of the following are about amortised time: If an array needs to be
		3829	extended, libev needs to realloc and move the whole array, but this
		3830	happens asymptotically rarer with higher number of elements, so O(1) might
		3831	mean that libev does a lengthy realloc operation in rare cases, but on
		3832	average it is much faster and asymptotically approaches constant time.
		3833
		3834	=over 4
		3835
		3836	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3837
		3838	This means that, when you have a watcher that triggers in one hour and
		3839	there are 100 watchers that would trigger before that, then inserting will
		3840	have to skip roughly seven (C<ld 100>) of these watchers.
		3841
		3842	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3843
		3844	That means that changing a timer costs less than removing/adding them,
		3845	as only the relative motion in the event queue has to be paid for.
		3846
		3847	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3848
		3849	These just add the watcher into an array or at the head of a list.
		3850
		3851	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3852
		3853	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3854
		3855	These watchers are stored in lists, so they need to be walked to find the
		3856	correct watcher to remove. The lists are usually short (you don't usually
		3857	have many watchers waiting for the same fd or signal: one is typical, two
		3858	is rare).
		3859
		3860	=item Finding the next timer in each loop iteration: O(1)
		3861
		3862	By virtue of using a binary or 4-heap, the next timer is always found at a
		3863	fixed position in the storage array.
		3864
		3865	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3866
		3867	A change means an I/O watcher gets started or stopped, which requires
		3868	libev to recalculate its status (and possibly tell the kernel, depending
		3869	on backend and whether C<ev_io_set> was used).
		3870
		3871	=item Activating one watcher (putting it into the pending state): O(1)
		3872
		3873	=item Priority handling: O(number_of_priorities)
		3874
		3875	Priorities are implemented by allocating some space for each
		3876	priority. When doing priority-based operations, libev usually has to
		3877	linearly search all the priorities, but starting/stopping and activating
		3878	watchers becomes O(1) with respect to priority handling.
		3879
		3880	=item Sending an ev_async: O(1)
		3881
		3882	=item Processing ev_async_send: O(number_of_async_watchers)
		3883
		3884	=item Processing signals: O(max_signal_number)
		3885
		3886	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3887	calls in the current loop iteration. Checking for async and signal events
		3888	involves iterating over all running async watchers or all signal numbers.
		3889
		3890	=back
		3891
3087		3892
3088	=head1 AUTHOR	3893	=head1 AUTHOR
3089		3894
3090	Marc Lehmann <libev@schmorp.de>.	3895	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3091		3896

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