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Revision 1.130 by root, Wed Feb 6 18:34:24 2008 UTC vs.
Revision 1.212 by root, Mon Nov 3 15:13:53 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
361	While nominally embeddeble in other event loops, this feature is broken in	423	While nominally embeddable in other event loops, this feature is broken in
362	all kernel versions tested so far.	424	all kernel versions tested so far.
		425
		426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		427	C<EVBACKEND_POLL>.
363		428
364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
365		430
366	Kqueue deserves special mention, as at the time of this writing, it	431	Kqueue deserves special mention, as at the time of this writing, it
367	was broken on all BSDs except NetBSD (usually it doesn't work reliably	432	was broken on all BSDs except NetBSD (usually it doesn't work reliably
368	with anything but sockets and pipes, except on Darwin, where of course	433	with anything but sockets and pipes, except on Darwin, where of course
369	it's completely useless). For this reason it's not being "autodetected"	434	it's completely useless). Unlike epoll, however, whose brokenness
		435	is by design, these kqueue bugs can (and eventually will) be fixed
		436	without API changes to existing programs. For this reason it's not being
370	unless you explicitly specify it explicitly in the flags (i.e. using	437	"auto-detected" unless you explicitly specify it in the flags (i.e. using
371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
372	system like NetBSD.	439	system like NetBSD.
373		440
374	You still can embed kqueue into a normal poll or select backend and use it	441	You still can embed kqueue into a normal poll or select backend and use it
375	only for sockets (after having made sure that sockets work with kqueue on	442	only for sockets (after having made sure that sockets work with kqueue on
376	the target platform). See C<ev_embed> watchers for more info.	443	the target platform). See C<ev_embed> watchers for more info.
377		444
378	It scales in the same way as the epoll backend, but the interface to the	445	It scales in the same way as the epoll backend, but the interface to the
379	kernel is more efficient (which says nothing about its actual speed, of	446	kernel is more efficient (which says nothing about its actual speed, of
380	course). While stopping, setting and starting an I/O watcher does never	447	course). While stopping, setting and starting an I/O watcher does never
381	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	448	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
382	two event changes per incident, support for C<fork ()> is very bad and it	449	two event changes per incident. Support for C<fork ()> is very bad (but
383	drops fds silently in similarly hard-to-detect cases.	450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		451	cases
384		452
385	This backend usually performs well under most conditions.	453	This backend usually performs well under most conditions.
386		454
387	While nominally embeddable in other event loops, this doesn't work	455	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	456	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	457	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	458	(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	459	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
392	sockets.	460	using it only for sockets.
		461
		462	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		463	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		464	C<NOTE_EOF>.
393		465
394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	466	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
395		467
396	This is not implemented yet (and might never be, unless you send me an	468	This is not implemented yet (and might never be, unless you send me an
397	implementation). According to reports, C</dev/poll> only supports sockets	469	implementation). According to reports, C</dev/poll> only supports sockets
…		…
401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	473	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
402		474
403	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	475	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
404	it's really slow, but it still scales very well (O(active_fds)).	476	it's really slow, but it still scales very well (O(active_fds)).
405		477
406	Please note that solaris event ports can deliver a lot of spurious	478	Please note that Solaris event ports can deliver a lot of spurious
407	notifications, so you need to use non-blocking I/O or other means to avoid	479	notifications, so you need to use non-blocking I/O or other means to avoid
408	blocking when no data (or space) is available.	480	blocking when no data (or space) is available.
409		481
410	While this backend scales well, it requires one system call per active	482	While this backend scales well, it requires one system call per active
411	file descriptor per loop iteration. For small and medium numbers of file	483	file descriptor per loop iteration. For small and medium numbers of file
412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	484	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413	might perform better.	485	might perform better.
414		486
415	On the positive side, ignoring the spurious readyness notifications, this	487	On the positive side, with the exception of the spurious readiness
416	backend actually performed to specification in all tests and is fully	488	notifications, this backend actually performed fully to specification
417	embeddable, which is a rare feat among the OS-specific backends.	489	in all tests and is fully embeddable, which is a rare feat among the
		490	OS-specific backends (I vastly prefer correctness over speed hacks).
		491
		492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		493	C<EVBACKEND_POLL>.
418		494
419	=item C<EVBACKEND_ALL>	495	=item C<EVBACKEND_ALL>
420		496
421	Try all backends (even potentially broken ones that wouldn't be tried	497	Try all backends (even potentially broken ones that wouldn't be tried
422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	498	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
424		500
425	It is definitely not recommended to use this flag.	501	It is definitely not recommended to use this flag.
426		502
427	=back	503	=back
428		504
429	If one or more of these are ored into the flags value, then only these	505	If one or more of these are or'ed into the flags value, then only these
430	backends will be tried (in the reverse order as listed here). If none are	506	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.	507	specified, all backends in C<ev_recommended_backends ()> will be tried.
432		508
433	The most typical usage is like this:	509	Example: This is the most typical usage.
434		510
435	if (!ev_default_loop (0))	511	if (!ev_default_loop (0))
436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
437		513
438	Restrict libev to the select and poll backends, and do not allow	514	Example: Restrict libev to the select and poll backends, and do not allow
439	environment settings to be taken into account:	515	environment settings to be taken into account:
440		516
441	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
442		518
443	Use whatever libev has to offer, but make sure that kqueue is used if	519	Example: Use whatever libev has to offer, but make sure that kqueue is
444	available (warning, breaks stuff, best use only with your own private	520	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):	521	private event loop and only if you know the OS supports your types of
		522	fds):
446		523
447	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
448		525
449	=item struct ev_loop *ev_loop_new (unsigned int flags)	526	=item struct ev_loop *ev_loop_new (unsigned int flags)
450		527
451	Similar to C<ev_default_loop>, but always creates a new event loop that is	528	Similar to C<ev_default_loop>, but always creates a new event loop that is
452	always distinct from the default loop. Unlike the default loop, it cannot	529	always distinct from the default loop. Unlike the default loop, it cannot
453	handle signal and child watchers, and attempts to do so will be greeted by	530	handle signal and child watchers, and attempts to do so will be greeted by
454	undefined behaviour (or a failed assertion if assertions are enabled).	531	undefined behaviour (or a failed assertion if assertions are enabled).
455		532
		533	Note that this function I<is> thread-safe, and the recommended way to use
		534	libev with threads is indeed to create one loop per thread, and using the
		535	default loop in the "main" or "initial" thread.
		536
456	Example: Try to create a event loop that uses epoll and nothing else.	537	Example: Try to create a event loop that uses epoll and nothing else.
457		538
458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	539	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
459	if (!epoller)	540	if (!epoller)
460	fatal ("no epoll found here, maybe it hides under your chair");	541	fatal ("no epoll found here, maybe it hides under your chair");
461		542
462	=item ev_default_destroy ()	543	=item ev_default_destroy ()
463		544
464	Destroys the default loop again (frees all memory and kernel state	545	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	546	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	547	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>	548	responsibility to either stop all watchers cleanly yourself I<before>
468	calling this function, or cope with the fact afterwards (which is usually	549	calling this function, or cope with the fact afterwards (which is usually
469	the easiest thing, you can just ignore the watchers and/or C<free ()> them	550	the easiest thing, you can just ignore the watchers and/or C<free ()> them
470	for example).	551	for example).
471		552
472	Note that certain global state, such as signal state, will not be freed by	553	Note that certain global state, such as signal state (and installed signal
473	this function, and related watchers (such as signal and child watchers)	554	handlers), will not be freed by this function, and related watchers (such
474	would need to be stopped manually.	555	as signal and child watchers) would need to be stopped manually.
475		556
476	In general it is not advisable to call this function except in the	557	In general it is not advisable to call this function except in the
477	rare occasion where you really need to free e.g. the signal handling	558	rare occasion where you really need to free e.g. the signal handling
478	pipe fds. If you need dynamically allocated loops it is better to use	559	pipe fds. If you need dynamically allocated loops it is better to use
479	C<ev_loop_new> and C<ev_loop_destroy>).	560	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
504		585
505	=item ev_loop_fork (loop)	586	=item ev_loop_fork (loop)
506		587
507	Like C<ev_default_fork>, but acts on an event loop created by	588	Like C<ev_default_fork>, but acts on an event loop created by
508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	589	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
509	after fork, and how you do this is entirely your own problem.	590	after fork that you want to re-use in the child, and how you do this is
		591	entirely your own problem.
		592
		593	=item int ev_is_default_loop (loop)
		594
		595	Returns true when the given loop is, in fact, the default loop, and false
		596	otherwise.
510		597
511	=item unsigned int ev_loop_count (loop)	598	=item unsigned int ev_loop_count (loop)
512		599
513	Returns the count of loop iterations for the loop, which is identical to	600	Returns the count of loop iterations for the loop, which is identical to
514	the number of times libev did poll for new events. It starts at C<0> and	601	the number of times libev did poll for new events. It starts at C<0> and
…		…
529	received events and started processing them. This timestamp does not	616	received events and started processing them. This timestamp does not
530	change as long as callbacks are being processed, and this is also the base	617	change as long as callbacks are being processed, and this is also the base
531	time used for relative timers. You can treat it as the timestamp of the	618	time used for relative timers. You can treat it as the timestamp of the
532	event occurring (or more correctly, libev finding out about it).	619	event occurring (or more correctly, libev finding out about it).
533		620
		621	=item ev_now_update (loop)
		622
		623	Establishes the current time by querying the kernel, updating the time
		624	returned by C<ev_now ()> in the progress. This is a costly operation and
		625	is usually done automatically within C<ev_loop ()>.
		626
		627	This function is rarely useful, but when some event callback runs for a
		628	very long time without entering the event loop, updating libev's idea of
		629	the current time is a good idea.
		630
		631	See also "The special problem of time updates" in the C<ev_timer> section.
		632
534	=item ev_loop (loop, int flags)	633	=item ev_loop (loop, int flags)
535		634
536	Finally, this is it, the event handler. This function usually is called	635	Finally, this is it, the event handler. This function usually is called
537	after you initialised all your watchers and you want to start handling	636	after you initialised all your watchers and you want to start handling
538	events.	637	events.
…		…
540	If the flags argument is specified as C<0>, it will not return until	639	If the flags argument is specified as C<0>, it will not return until
541	either no event watchers are active anymore or C<ev_unloop> was called.	640	either no event watchers are active anymore or C<ev_unloop> was called.
542		641
543	Please note that an explicit C<ev_unloop> is usually better than	642	Please note that an explicit C<ev_unloop> is usually better than
544	relying on all watchers to be stopped when deciding when a program has	643	relying on all watchers to be stopped when deciding when a program has
545	finished (especially in interactive programs), but having a program that	644	finished (especially in interactive programs), but having a program
546	automatically loops as long as it has to and no longer by virtue of	645	that automatically loops as long as it has to and no longer by virtue
547	relying on its watchers stopping correctly is a thing of beauty.	646	of relying on its watchers stopping correctly, that is truly a thing of
		647	beauty.
548		648
549	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	649	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
550	those events and any outstanding ones, but will not block your process in	650	those events and any already outstanding ones, but will not block your
551	case there are no events and will return after one iteration of the loop.	651	process in case there are no events and will return after one iteration of
		652	the loop.
552		653
553	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	654	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
554	neccessary) and will handle those and any outstanding ones. It will block	655	necessary) and will handle those and any already outstanding ones. It
555	your process until at least one new event arrives, and will return after	656	will block your process until at least one new event arrives (which could
556	one iteration of the loop. This is useful if you are waiting for some	657	be an event internal to libev itself, so there is no guarantee that a
557	external event in conjunction with something not expressible using other	658	user-registered callback will be called), and will return after one
		659	iteration of the loop.
		660
		661	This is useful if you are waiting for some external event in conjunction
		662	with something not expressible using other libev watchers (i.e. "roll your
558	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	663	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
559	usually a better approach for this kind of thing.	664	usually a better approach for this kind of thing.
560		665
561	Here are the gory details of what C<ev_loop> does:	666	Here are the gory details of what C<ev_loop> does:
562		667
563	- Before the first iteration, call any pending watchers.	668	- Before the first iteration, call any pending watchers.
564	* If EVFLAG_FORKCHECK was used, check for a fork.	669	* If EVFLAG_FORKCHECK was used, check for a fork.
565	- If a fork was detected, queue and call all fork watchers.	670	- If a fork was detected (by any means), queue and call all fork watchers.
566	- Queue and call all prepare watchers.	671	- Queue and call all prepare watchers.
567	- If we have been forked, recreate the kernel state.	672	- If we have been forked, detach and recreate the kernel state
		673	as to not disturb the other process.
568	- Update the kernel state with all outstanding changes.	674	- Update the kernel state with all outstanding changes.
569	- Update the "event loop time".	675	- Update the "event loop time" (ev_now ()).
570	- Calculate for how long to sleep or block, if at all	676	- Calculate for how long to sleep or block, if at all
571	(active idle watchers, EVLOOP_NONBLOCK or not having	677	(active idle watchers, EVLOOP_NONBLOCK or not having
572	any active watchers at all will result in not sleeping).	678	any active watchers at all will result in not sleeping).
573	- Sleep if the I/O and timer collect interval say so.	679	- Sleep if the I/O and timer collect interval say so.
574	- Block the process, waiting for any events.	680	- Block the process, waiting for any events.
575	- Queue all outstanding I/O (fd) events.	681	- Queue all outstanding I/O (fd) events.
576	- Update the "event loop time" and do time jump handling.	682	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
577	- Queue all outstanding timers.	683	- Queue all expired timers.
578	- Queue all outstanding periodics.	684	- Queue all expired periodics.
579	- If no events are pending now, queue all idle watchers.	685	- Unless any events are pending now, queue all idle watchers.
580	- Queue all check watchers.	686	- Queue all check watchers.
581	- Call all queued watchers in reverse order (i.e. check watchers first).	687	- Call all queued watchers in reverse order (i.e. check watchers first).
582	Signals and child watchers are implemented as I/O watchers, and will	688	Signals and child watchers are implemented as I/O watchers, and will
583	be handled here by queueing them when their watcher gets executed.	689	be handled here by queueing them when their watcher gets executed.
584	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	690	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
589	anymore.	695	anymore.
590		696
591	... queue jobs here, make sure they register event watchers as long	697	... queue jobs here, make sure they register event watchers as long
592	... as they still have work to do (even an idle watcher will do..)	698	... as they still have work to do (even an idle watcher will do..)
593	ev_loop (my_loop, 0);	699	ev_loop (my_loop, 0);
594	... jobs done. yeah!	700	... jobs done or somebody called unloop. yeah!
595		701
596	=item ev_unloop (loop, how)	702	=item ev_unloop (loop, how)
597		703
598	Can be used to make a call to C<ev_loop> return early (but only after it	704	Can be used to make a call to C<ev_loop> return early (but only after it
599	has processed all outstanding events). The C<how> argument must be either	705	has processed all outstanding events). The C<how> argument must be either
600	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	706	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
601	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
602		708
603	This "unloop state" will be cleared when entering C<ev_loop> again.	709	This "unloop state" will be cleared when entering C<ev_loop> again.
604		710
		711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		712
605	=item ev_ref (loop)	713	=item ev_ref (loop)
606		714
607	=item ev_unref (loop)	715	=item ev_unref (loop)
608		716
609	Ref/unref can be used to add or remove a reference count on the event	717	Ref/unref can be used to add or remove a reference count on the event
610	loop: Every watcher keeps one reference, and as long as the reference	718	loop: Every watcher keeps one reference, and as long as the reference
611	count is nonzero, C<ev_loop> will not return on its own. If you have	719	count is nonzero, C<ev_loop> will not return on its own.
		720
612	a watcher you never unregister that should not keep C<ev_loop> from	721	If you have a watcher you never unregister that should not keep C<ev_loop>
613	returning, ev_unref() after starting, and ev_ref() before stopping it. For	722	from returning, call ev_unref() after starting, and ev_ref() before
		723	stopping it.
		724
614	example, libev itself uses this for its internal signal pipe: It is not	725	As an example, libev itself uses this for its internal signal pipe: It is
615	visible to the libev user and should not keep C<ev_loop> from exiting if	726	not visible to the libev user and should not keep C<ev_loop> from exiting
616	no event watchers registered by it are active. It is also an excellent	727	if no event watchers registered by it are active. It is also an excellent
617	way to do this for generic recurring timers or from within third-party	728	way to do this for generic recurring timers or from within third-party
618	libraries. Just remember to I<unref after start> and I<ref before stop>	729	libraries. Just remember to I<unref after start> and I<ref before stop>
619	(but only if the watcher wasn't active before, or was active before,	730	(but only if the watcher wasn't active before, or was active before,
620	respectively).	731	respectively).
621		732
622	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
623	running when nothing else is active.	734	running when nothing else is active.
624		735
625	struct ev_signal exitsig;	736	ev_signal exitsig;
626	ev_signal_init (&exitsig, sig_cb, SIGINT);	737	ev_signal_init (&exitsig, sig_cb, SIGINT);
627	ev_signal_start (loop, &exitsig);	738	ev_signal_start (loop, &exitsig);
628	evf_unref (loop);	739	evf_unref (loop);
629		740
630	Example: For some weird reason, unregister the above signal handler again.	741	Example: For some weird reason, unregister the above signal handler again.
631		742
632	ev_ref (loop);	743	ev_ref (loop);
633	ev_signal_stop (loop, &exitsig);	744	ev_signal_stop (loop, &exitsig);
634		745
635	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	746	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
636		747
637	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	748	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
638		749
639	These advanced functions influence the time that libev will spend waiting	750	These advanced functions influence the time that libev will spend waiting
640	for events. Both are by default C<0>, meaning that libev will try to	751	for events. Both time intervals are by default C<0>, meaning that libev
641	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	752	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		753	latency.
642		754
643	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	755	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
644	allows libev to delay invocation of I/O and timer/periodic callbacks to	756	allows libev to delay invocation of I/O and timer/periodic callbacks
645	increase efficiency of loop iterations.	757	to increase efficiency of loop iterations (or to increase power-saving
		758	opportunities).
646		759
647	The background is that sometimes your program runs just fast enough to	760	The idea is that sometimes your program runs just fast enough to handle
648	handle one (or very few) event(s) per loop iteration. While this makes	761	one (or very few) event(s) per loop iteration. While this makes the
649	the program responsive, it also wastes a lot of CPU time to poll for new	762	program responsive, it also wastes a lot of CPU time to poll for new
650	events, especially with backends like C<select ()> which have a high	763	events, especially with backends like C<select ()> which have a high
651	overhead for the actual polling but can deliver many events at once.	764	overhead for the actual polling but can deliver many events at once.
652		765
653	By setting a higher I<io collect interval> you allow libev to spend more	766	By setting a higher I<io collect interval> you allow libev to spend more
654	time collecting I/O events, so you can handle more events per iteration,	767	time collecting I/O events, so you can handle more events per iteration,
…		…
656	C<ev_timer>) will be not affected. Setting this to a non-null value will	769	C<ev_timer>) will be not affected. Setting this to a non-null value will
657	introduce an additional C<ev_sleep ()> call into most loop iterations.	770	introduce an additional C<ev_sleep ()> call into most loop iterations.
658		771
659	Likewise, by setting a higher I<timeout collect interval> you allow libev	772	Likewise, by setting a higher I<timeout collect interval> you allow libev
660	to spend more time collecting timeouts, at the expense of increased	773	to spend more time collecting timeouts, at the expense of increased
661	latency (the watcher callback will be called later). C<ev_io> watchers	774	latency/jitter/inexactness (the watcher callback will be called
662	will not be affected. Setting this to a non-null value will not introduce	775	later). C<ev_io> watchers will not be affected. Setting this to a non-null
663	any overhead in libev.	776	value will not introduce any overhead in libev.
664		777
665	Many (busy) programs can usually benefit by setting the io collect	778	Many (busy) programs can usually benefit by setting the I/O collect
666	interval to a value near C<0.1> or so, which is often enough for	779	interval to a value near C<0.1> or so, which is often enough for
667	interactive servers (of course not for games), likewise for timeouts. It	780	interactive servers (of course not for games), likewise for timeouts. It
668	usually doesn't make much sense to set it to a lower value than C<0.01>,	781	usually doesn't make much sense to set it to a lower value than C<0.01>,
669	as this approsaches the timing granularity of most systems.	782	as this approaches the timing granularity of most systems.
		783
		784	Setting the I<timeout collect interval> can improve the opportunity for
		785	saving power, as the program will "bundle" timer callback invocations that
		786	are "near" in time together, by delaying some, thus reducing the number of
		787	times the process sleeps and wakes up again. Another useful technique to
		788	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		789	they fire on, say, one-second boundaries only.
		790
		791	=item ev_loop_verify (loop)
		792
		793	This function only does something when C<EV_VERIFY> support has been
		794	compiled in, which is the default for non-minimal builds. It tries to go
		795	through all internal structures and checks them for validity. If anything
		796	is found to be inconsistent, it will print an error message to standard
		797	error and call C<abort ()>.
		798
		799	This can be used to catch bugs inside libev itself: under normal
		800	circumstances, this function will never abort as of course libev keeps its
		801	data structures consistent.
670		802
671	=back	803	=back
672		804
673		805
674	=head1 ANATOMY OF A WATCHER	806	=head1 ANATOMY OF A WATCHER
		807
		808	In the following description, uppercase C<TYPE> in names stands for the
		809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		810	watchers and C<ev_io_start> for I/O watchers.
675		811
676	A watcher is a structure that you create and register to record your	812	A watcher is a structure that you create and register to record your
677	interest in some event. For instance, if you want to wait for STDIN to	813	interest in some event. For instance, if you want to wait for STDIN to
678	become readable, you would create an C<ev_io> watcher for that:	814	become readable, you would create an C<ev_io> watcher for that:
679		815
680	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
681	{	817	{
682	ev_io_stop (w);	818	ev_io_stop (w);
683	ev_unloop (loop, EVUNLOOP_ALL);	819	ev_unloop (loop, EVUNLOOP_ALL);
684	}	820	}
685		821
686	struct ev_loop *loop = ev_default_loop (0);	822	struct ev_loop *loop = ev_default_loop (0);
		823
687	struct ev_io stdin_watcher;	824	ev_io stdin_watcher;
		825
688	ev_init (&stdin_watcher, my_cb);	826	ev_init (&stdin_watcher, my_cb);
689	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
690	ev_io_start (loop, &stdin_watcher);	828	ev_io_start (loop, &stdin_watcher);
		829
691	ev_loop (loop, 0);	830	ev_loop (loop, 0);
692		831
693	As you can see, you are responsible for allocating the memory for your	832	As you can see, you are responsible for allocating the memory for your
694	watcher structures (and it is usually a bad idea to do this on the stack,	833	watcher structures (and it is I<usually> a bad idea to do this on the
695	although this can sometimes be quite valid).	834	stack).
		835
		836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
696		838
697	Each watcher structure must be initialised by a call to C<ev_init	839	Each watcher structure must be initialised by a call to C<ev_init
698	(watcher *, callback)>, which expects a callback to be provided. This	840	(watcher *, callback)>, which expects a callback to be provided. This
699	callback gets invoked each time the event occurs (or, in the case of io	841	callback gets invoked each time the event occurs (or, in the case of I/O
700	watchers, each time the event loop detects that the file descriptor given	842	watchers, each time the event loop detects that the file descriptor given
701	is readable and/or writable).	843	is readable and/or writable).
702		844
703	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	845	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
704	with arguments specific to this watcher type. There is also a macro	846	macro to configure it, with arguments specific to the watcher type. There
705	to combine initialisation and setting in one call: C<< ev_<type>_init	847	is also a macro to combine initialisation and setting in one call: C<<
706	(watcher *, callback, ...) >>.	848	ev_TYPE_init (watcher *, callback, ...) >>.
707		849
708	To make the watcher actually watch out for events, you have to start it	850	To make the watcher actually watch out for events, you have to start it
709	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	851	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
710	*) >>), and you can stop watching for events at any time by calling the	852	*) >>), and you can stop watching for events at any time by calling the
711	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	853	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
712		854
713	As long as your watcher is active (has been started but not stopped) you	855	As long as your watcher is active (has been started but not stopped) you
714	must not touch the values stored in it. Most specifically you must never	856	must not touch the values stored in it. Most specifically you must never
715	reinitialise it or call its C<set> macro.	857	reinitialise it or call its C<ev_TYPE_set> macro.
716		858
717	Each and every callback receives the event loop pointer as first, the	859	Each and every callback receives the event loop pointer as first, the
718	registered watcher structure as second, and a bitset of received events as	860	registered watcher structure as second, and a bitset of received events as
719	third argument.	861	third argument.
720		862
…		…
780		922
781	The given async watcher has been asynchronously notified (see C<ev_async>).	923	The given async watcher has been asynchronously notified (see C<ev_async>).
782		924
783	=item C<EV_ERROR>	925	=item C<EV_ERROR>
784		926
785	An unspecified error has occured, the watcher has been stopped. This might	927	An unspecified error has occurred, the watcher has been stopped. This might
786	happen because the watcher could not be properly started because libev	928	happen because the watcher could not be properly started because libev
787	ran out of memory, a file descriptor was found to be closed or any other	929	ran out of memory, a file descriptor was found to be closed or any other
		930	problem. Libev considers these application bugs.
		931
788	problem. You best act on it by reporting the problem and somehow coping	932	You best act on it by reporting the problem and somehow coping with the
789	with the watcher being stopped.	933	watcher being stopped. Note that well-written programs should not receive
		934	an error ever, so when your watcher receives it, this usually indicates a
		935	bug in your program.
790		936
791	Libev will usually signal a few "dummy" events together with an error,	937	Libev will usually signal a few "dummy" events together with an error, for
792	for example it might indicate that a fd is readable or writable, and if	938	example it might indicate that a fd is readable or writable, and if your
793	your callbacks is well-written it can just attempt the operation and cope	939	callbacks is well-written it can just attempt the operation and cope with
794	with the error from read() or write(). This will not work in multithreaded	940	the error from read() or write(). This will not work in multi-threaded
795	programs, though, so beware.	941	programs, though, as the fd could already be closed and reused for another
		942	thing, so beware.
796		943
797	=back	944	=back
798		945
799	=head2 GENERIC WATCHER FUNCTIONS	946	=head2 GENERIC WATCHER FUNCTIONS
800
801	In the following description, C<TYPE> stands for the watcher type,
802	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
803		947
804	=over 4	948	=over 4
805		949
806	=item C<ev_init> (ev_TYPE *watcher, callback)	950	=item C<ev_init> (ev_TYPE *watcher, callback)
807		951
…		…
813	which rolls both calls into one.	957	which rolls both calls into one.
814		958
815	You can reinitialise a watcher at any time as long as it has been stopped	959	You can reinitialise a watcher at any time as long as it has been stopped
816	(or never started) and there are no pending events outstanding.	960	(or never started) and there are no pending events outstanding.
817		961
818	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	962	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
819	int revents)>.	963	int revents)>.
		964
		965	Example: Initialise an C<ev_io> watcher in two steps.
		966
		967	ev_io w;
		968	ev_init (&w, my_cb);
		969	ev_io_set (&w, STDIN_FILENO, EV_READ);
820		970
821	=item C<ev_TYPE_set> (ev_TYPE *, [args])	971	=item C<ev_TYPE_set> (ev_TYPE *, [args])
822		972
823	This macro initialises the type-specific parts of a watcher. You need to	973	This macro initialises the type-specific parts of a watcher. You need to
824	call C<ev_init> at least once before you call this macro, but you can	974	call C<ev_init> at least once before you call this macro, but you can
…		…
827	difference to the C<ev_init> macro).	977	difference to the C<ev_init> macro).
828		978
829	Although some watcher types do not have type-specific arguments	979	Although some watcher types do not have type-specific arguments
830	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	980	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
831		981
		982	See C<ev_init>, above, for an example.
		983
832	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	984	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
833		985
834	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	986	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
835	calls into a single call. This is the most convinient method to initialise	987	calls into a single call. This is the most convenient method to initialise
836	a watcher. The same limitations apply, of course.	988	a watcher. The same limitations apply, of course.
		989
		990	Example: Initialise and set an C<ev_io> watcher in one step.
		991
		992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
837		993
838	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
839		995
840	Starts (activates) the given watcher. Only active watchers will receive	996	Starts (activates) the given watcher. Only active watchers will receive
841	events. If the watcher is already active nothing will happen.	997	events. If the watcher is already active nothing will happen.
842		998
		999	Example: Start the C<ev_io> watcher that is being abused as example in this
		1000	whole section.
		1001
		1002	ev_io_start (EV_DEFAULT_UC, &w);
		1003
843	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
844		1005
845	Stops the given watcher again (if active) and clears the pending	1006	Stops the given watcher if active, and clears the pending status (whether
		1007	the watcher was active or not).
		1008
846	status. It is possible that stopped watchers are pending (for example,	1009	It is possible that stopped watchers are pending - for example,
847	non-repeating timers are being stopped when they become pending), but	1010	non-repeating timers are being stopped when they become pending - but
848	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1011	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
849	you want to free or reuse the memory used by the watcher it is therefore a	1012	pending. If you want to free or reuse the memory used by the watcher it is
850	good idea to always call its C<ev_TYPE_stop> function.	1013	therefore a good idea to always call its C<ev_TYPE_stop> function.
851		1014
852	=item bool ev_is_active (ev_TYPE *watcher)	1015	=item bool ev_is_active (ev_TYPE *watcher)
853		1016
854	Returns a true value iff the watcher is active (i.e. it has been started	1017	Returns a true value iff the watcher is active (i.e. it has been started
855	and not yet been stopped). As long as a watcher is active you must not modify	1018	and not yet been stopped). As long as a watcher is active you must not modify
…		…
897	The default priority used by watchers when no priority has been set is	1060	The default priority used by watchers when no priority has been set is
898	always C<0>, which is supposed to not be too high and not be too low :).	1061	always C<0>, which is supposed to not be too high and not be too low :).
899		1062
900	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1063	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
901	fine, as long as you do not mind that the priority value you query might	1064	fine, as long as you do not mind that the priority value you query might
902	or might not have been adjusted to be within valid range.	1065	or might not have been clamped to the valid range.
903		1066
904	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
905		1068
906	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1069	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
907	C<loop> nor C<revents> need to be valid as long as the watcher callback	1070	C<loop> nor C<revents> need to be valid as long as the watcher callback
908	can deal with that fact.	1071	can deal with that fact, as both are simply passed through to the
		1072	callback.
909		1073
910	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1074	=item int ev_clear_pending (loop, ev_TYPE *watcher)
911		1075
912	If the watcher is pending, this function returns clears its pending status	1076	If the watcher is pending, this function clears its pending status and
913	and returns its C<revents> bitset (as if its callback was invoked). If the	1077	returns its C<revents> bitset (as if its callback was invoked). If the
914	watcher isn't pending it does nothing and returns C<0>.	1078	watcher isn't pending it does nothing and returns C<0>.
915		1079
		1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1081	callback to be invoked, which can be accomplished with this function.
		1082
916	=back	1083	=back
917		1084
918		1085
919	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
920		1087
921	Each watcher has, by default, a member C<void *data> that you can change	1088	Each watcher has, by default, a member C<void *data> that you can change
922	and read at any time, libev will completely ignore it. This can be used	1089	and read at any time: libev will completely ignore it. This can be used
923	to associate arbitrary data with your watcher. If you need more data and	1090	to associate arbitrary data with your watcher. If you need more data and
924	don't want to allocate memory and store a pointer to it in that data	1091	don't want to allocate memory and store a pointer to it in that data
925	member, you can also "subclass" the watcher type and provide your own	1092	member, you can also "subclass" the watcher type and provide your own
926	data:	1093	data:
927		1094
928	struct my_io	1095	struct my_io
929	{	1096	{
930	struct ev_io io;	1097	ev_io io;
931	int otherfd;	1098	int otherfd;
932	void *somedata;	1099	void *somedata;
933	struct whatever *mostinteresting;	1100	struct whatever *mostinteresting;
934	}	1101	};
		1102
		1103	...
		1104	struct my_io w;
		1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
935		1106
936	And since your callback will be called with a pointer to the watcher, you	1107	And since your callback will be called with a pointer to the watcher, you
937	can cast it back to your own type:	1108	can cast it back to your own type:
938		1109
939	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
940	{	1111	{
941	struct my_io *w = (struct my_io *)w_;	1112	struct my_io *w = (struct my_io *)w_;
942	...	1113	...
943	}	1114	}
944		1115
945	More interesting and less C-conformant ways of casting your callback type	1116	More interesting and less C-conformant ways of casting your callback type
946	instead have been omitted.	1117	instead have been omitted.
947		1118
948	Another common scenario is having some data structure with multiple	1119	Another common scenario is to use some data structure with multiple
949	watchers:	1120	embedded watchers:
950		1121
951	struct my_biggy	1122	struct my_biggy
952	{	1123	{
953	int some_data;	1124	int some_data;
954	ev_timer t1;	1125	ev_timer t1;
955	ev_timer t2;	1126	ev_timer t2;
956	}	1127	}
957		1128
958	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1129	In this case getting the pointer to C<my_biggy> is a bit more
959	you need to use C<offsetof>:	1130	complicated: Either you store the address of your C<my_biggy> struct
		1131	in the C<data> member of the watcher (for woozies), or you need to use
		1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1133	programmers):
960		1134
961	#include <stddef.h>	1135	#include <stddef.h>
962		1136
963	static void	1137	static void
964	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
965	{	1139	{
966	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
967	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
968	}	1142	}
969		1143
970	static void	1144	static void
971	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
972	{	1146	{
973	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
974	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
975	}	1149	}
976		1150
977		1151
978	=head1 WATCHER TYPES	1152	=head1 WATCHER TYPES
979		1153
980	This section describes each watcher in detail, but will not repeat	1154	This section describes each watcher in detail, but will not repeat
…		…
1004	In general you can register as many read and/or write event watchers per	1178	In general you can register as many read and/or write event watchers per
1005	fd as you want (as long as you don't confuse yourself). Setting all file	1179	fd as you want (as long as you don't confuse yourself). Setting all file
1006	descriptors to non-blocking mode is also usually a good idea (but not	1180	descriptors to non-blocking mode is also usually a good idea (but not
1007	required if you know what you are doing).	1181	required if you know what you are doing).
1008		1182
1009	If you must do this, then force the use of a known-to-be-good backend	1183	If you cannot use non-blocking mode, then force the use of a
1010	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1184	known-to-be-good backend (at the time of this writing, this includes only
1011	C<EVBACKEND_POLL>).	1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1012		1186
1013	Another thing you have to watch out for is that it is quite easy to	1187	Another thing you have to watch out for is that it is quite easy to
1014	receive "spurious" readyness notifications, that is your callback might	1188	receive "spurious" readiness notifications, that is your callback might
1015	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1189	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1016	because there is no data. Not only are some backends known to create a	1190	because there is no data. Not only are some backends known to create a
1017	lot of those (for example solaris ports), it is very easy to get into	1191	lot of those (for example Solaris ports), it is very easy to get into
1018	this situation even with a relatively standard program structure. Thus	1192	this situation even with a relatively standard program structure. Thus
1019	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1193	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1020	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1194	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1021		1195
1022	If you cannot run the fd in non-blocking mode (for example you should not	1196	If you cannot run the fd in non-blocking mode (for example you should
1023	play around with an Xlib connection), then you have to seperately re-test	1197	not play around with an Xlib connection), then you have to separately
1024	whether a file descriptor is really ready with a known-to-be good interface	1198	re-test whether a file descriptor is really ready with a known-to-be good
1025	such as poll (fortunately in our Xlib example, Xlib already does this on	1199	interface such as poll (fortunately in our Xlib example, Xlib already
1026	its own, so its quite safe to use).	1200	does this on its own, so its quite safe to use). Some people additionally
		1201	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1202	indefinitely.
		1203
		1204	But really, best use non-blocking mode.
1027		1205
1028	=head3 The special problem of disappearing file descriptors	1206	=head3 The special problem of disappearing file descriptors
1029		1207
1030	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1208	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1031	descriptor (either by calling C<close> explicitly or by any other means,	1209	descriptor (either due to calling C<close> explicitly or any other means,
1032	such as C<dup>). The reason is that you register interest in some file	1210	such as C<dup2>). The reason is that you register interest in some file
1033	descriptor, but when it goes away, the operating system will silently drop	1211	descriptor, but when it goes away, the operating system will silently drop
1034	this interest. If another file descriptor with the same number then is	1212	this interest. If another file descriptor with the same number then is
1035	registered with libev, there is no efficient way to see that this is, in	1213	registered with libev, there is no efficient way to see that this is, in
1036	fact, a different file descriptor.	1214	fact, a different file descriptor.
1037		1215
…		…
1066	To support fork in your programs, you either have to call	1244	To support fork in your programs, you either have to call
1067	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1245	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1068	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1069	C<EVBACKEND_POLL>.	1247	C<EVBACKEND_POLL>.
1070		1248
		1249	=head3 The special problem of SIGPIPE
		1250
		1251	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1252	when writing to a pipe whose other end has been closed, your program gets
		1253	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1254	this is sensible behaviour, for daemons, this is usually undesirable.
		1255
		1256	So when you encounter spurious, unexplained daemon exits, make sure you
		1257	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1258	somewhere, as that would have given you a big clue).
		1259
1071		1260
1072	=head3 Watcher-Specific Functions	1261	=head3 Watcher-Specific Functions
1073		1262
1074	=over 4	1263	=over 4
1075		1264
1076	=item ev_io_init (ev_io *, callback, int fd, int events)	1265	=item ev_io_init (ev_io *, callback, int fd, int events)
1077		1266
1078	=item ev_io_set (ev_io *, int fd, int events)	1267	=item ev_io_set (ev_io *, int fd, int events)
1079		1268
1080	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1269	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1081	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1270	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1082	C<EV_READ | EV_WRITE> to receive the given events.	1271	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1083		1272
1084	=item int fd [read-only]	1273	=item int fd [read-only]
1085		1274
1086	The file descriptor being watched.	1275	The file descriptor being watched.
1087		1276
…		…
1095		1284
1096	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1285	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1097	readable, but only once. Since it is likely line-buffered, you could	1286	readable, but only once. Since it is likely line-buffered, you could
1098	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1099		1288
1100	static void	1289	static void
1101	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1290	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1102	{	1291	{
1103	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1104	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1293	.. read from stdin here (or from w->fd) and handle any I/O errors
1105	}	1294	}
1106		1295
1107	...	1296	...
1108	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1109	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1110	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1111	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1112	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1113		1302
1114		1303
1115	=head2 C<ev_timer> - relative and optionally repeating timeouts	1304	=head2 C<ev_timer> - relative and optionally repeating timeouts
1116		1305
1117	Timer watchers are simple relative timers that generate an event after a	1306	Timer watchers are simple relative timers that generate an event after a
1118	given time, and optionally repeating in regular intervals after that.	1307	given time, and optionally repeating in regular intervals after that.
1119		1308
1120	The timers are based on real time, that is, if you register an event that	1309	The timers are based on real time, that is, if you register an event that
1121	times out after an hour and you reset your system clock to last years	1310	times out after an hour and you reset your system clock to January last
1122	time, it will still time out after (roughly) and hour. "Roughly" because	1311	year, it will still time out after (roughly) one hour. "Roughly" because
1123	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1124	monotonic clock option helps a lot here).	1313	monotonic clock option helps a lot here).
		1314
		1315	The callback is guaranteed to be invoked only I<after> its timeout has
		1316	passed, but if multiple timers become ready during the same loop iteration
		1317	then order of execution is undefined.
		1318
		1319	=head3 Be smart about timeouts
		1320
		1321	Many real-world problems involve some kind of timeout, usually for error
		1322	recovery. A typical example is an HTTP request - if the other side hangs,
		1323	you want to raise some error after a while.
		1324
		1325	What follows are some ways to handle this problem, from obvious and
		1326	inefficient to smart and efficient.
		1327
		1328	In the following, a 60 second activity timeout is assumed - a timeout that
		1329	gets reset to 60 seconds each time there is activity (e.g. each time some
		1330	data or other life sign was received).
		1331
		1332	=over 4
		1333
		1334	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1335
		1336	This is the most obvious, but not the most simple way: In the beginning,
		1337	start the watcher:
		1338
		1339	ev_timer_init (timer, callback, 60., 0.);
		1340	ev_timer_start (loop, timer);
		1341
		1342	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1343	and start it again:
		1344
		1345	ev_timer_stop (loop, timer);
		1346	ev_timer_set (timer, 60., 0.);
		1347	ev_timer_start (loop, timer);
		1348
		1349	This is relatively simple to implement, but means that each time there is
		1350	some activity, libev will first have to remove the timer from its internal
		1351	data structure and then add it again. Libev tries to be fast, but it's
		1352	still not a constant-time operation.
		1353
		1354	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1355
		1356	This is the easiest way, and involves using C<ev_timer_again> instead of
		1357	C<ev_timer_start>.
		1358
		1359	To implement this, configure an C<ev_timer> with a C<repeat> value
		1360	of C<60> and then call C<ev_timer_again> at start and each time you
		1361	successfully read or write some data. If you go into an idle state where
		1362	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1363	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1364
		1365	That means you can ignore both the C<ev_timer_start> function and the
		1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1367	member and C<ev_timer_again>.
		1368
		1369	At start:
		1370
		1371	ev_timer_init (timer, callback);
		1372	timer->repeat = 60.;
		1373	ev_timer_again (loop, timer);
		1374
		1375	Each time there is some activity:
		1376
		1377	ev_timer_again (loop, timer);
		1378
		1379	It is even possible to change the time-out on the fly, regardless of
		1380	whether the watcher is active or not:
		1381
		1382	timer->repeat = 30.;
		1383	ev_timer_again (loop, timer);
		1384
		1385	This is slightly more efficient then stopping/starting the timer each time
		1386	you want to modify its timeout value, as libev does not have to completely
		1387	remove and re-insert the timer from/into its internal data structure.
		1388
		1389	It is, however, even simpler than the "obvious" way to do it.
		1390
		1391	=item 3. Let the timer time out, but then re-arm it as required.
		1392
		1393	This method is more tricky, but usually most efficient: Most timeouts are
		1394	relatively long compared to the intervals between other activity - in
		1395	our example, within 60 seconds, there are usually many I/O events with
		1396	associated activity resets.
		1397
		1398	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1399	but remember the time of last activity, and check for a real timeout only
		1400	within the callback:
		1401
		1402	ev_tstamp last_activity; // time of last activity
		1403
		1404	static void
		1405	callback (EV_P_ ev_timer *w, int revents)
		1406	{
		1407	ev_tstamp now = ev_now (EV_A);
		1408	ev_tstamp timeout = last_activity + 60.;
		1409
		1410	// if last_activity + 60. is older than now, we did time out
		1411	if (timeout < now)
		1412	{
		1413	// timeout occured, take action
		1414	}
		1415	else
		1416	{
		1417	// callback was invoked, but there was some activity, re-arm
		1418	// the watcher to fire in last_activity + 60, which is
		1419	// guaranteed to be in the future, so "again" is positive:
		1420	w->again = timeout - now;
		1421	ev_timer_again (EV_A_ w);
		1422	}
		1423	}
		1424
		1425	To summarise the callback: first calculate the real timeout (defined
		1426	as "60 seconds after the last activity"), then check if that time has
		1427	been reached, which means something I<did>, in fact, time out. Otherwise
		1428	the callback was invoked too early (C<timeout> is in the future), so
		1429	re-schedule the timer to fire at that future time, to see if maybe we have
		1430	a timeout then.
		1431
		1432	Note how C<ev_timer_again> is used, taking advantage of the
		1433	C<ev_timer_again> optimisation when the timer is already running.
		1434
		1435	This scheme causes more callback invocations (about one every 60 seconds
		1436	minus half the average time between activity), but virtually no calls to
		1437	libev to change the timeout.
		1438
		1439	To start the timer, simply initialise the watcher and set C<last_activity>
		1440	to the current time (meaning we just have some activity :), then call the
		1441	callback, which will "do the right thing" and start the timer:
		1442
		1443	ev_timer_init (timer, callback);
		1444	last_activity = ev_now (loop);
		1445	callback (loop, timer, EV_TIMEOUT);
		1446
		1447	And when there is some activity, simply store the current time in
		1448	C<last_activity>, no libev calls at all:
		1449
		1450	last_actiivty = ev_now (loop);
		1451
		1452	This technique is slightly more complex, but in most cases where the
		1453	time-out is unlikely to be triggered, much more efficient.
		1454
		1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1456	callback :) - just change the timeout and invoke the callback, which will
		1457	fix things for you.
		1458
		1459	=item 4. Wee, just use a double-linked list for your timeouts.
		1460
		1461	If there is not one request, but many thousands (millions...), all
		1462	employing some kind of timeout with the same timeout value, then one can
		1463	do even better:
		1464
		1465	When starting the timeout, calculate the timeout value and put the timeout
		1466	at the I<end> of the list.
		1467
		1468	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1469	the list is expected to fire (for example, using the technique #3).
		1470
		1471	When there is some activity, remove the timer from the list, recalculate
		1472	the timeout, append it to the end of the list again, and make sure to
		1473	update the C<ev_timer> if it was taken from the beginning of the list.
		1474
		1475	This way, one can manage an unlimited number of timeouts in O(1) time for
		1476	starting, stopping and updating the timers, at the expense of a major
		1477	complication, and having to use a constant timeout. The constant timeout
		1478	ensures that the list stays sorted.
		1479
		1480	=back
		1481
		1482	So which method the best?
		1483
		1484	Method #2 is a simple no-brain-required solution that is adequate in most
		1485	situations. Method #3 requires a bit more thinking, but handles many cases
		1486	better, and isn't very complicated either. In most case, choosing either
		1487	one is fine, with #3 being better in typical situations.
		1488
		1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1490	rather complicated, but extremely efficient, something that really pays
		1491	off after the first million or so of active timers, i.e. it's usually
		1492	overkill :)
		1493
		1494	=head3 The special problem of time updates
		1495
		1496	Establishing the current time is a costly operation (it usually takes at
		1497	least two system calls): EV therefore updates its idea of the current
		1498	time only before and after C<ev_loop> collects new events, which causes a
		1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1500	lots of events in one iteration.
1125		1501
1126	The relative timeouts are calculated relative to the C<ev_now ()>	1502	The relative timeouts are calculated relative to the C<ev_now ()>
1127	time. This is usually the right thing as this timestamp refers to the time	1503	time. This is usually the right thing as this timestamp refers to the time
1128	of the event triggering whatever timeout you are modifying/starting. If	1504	of the event triggering whatever timeout you are modifying/starting. If
1129	you suspect event processing to be delayed and you I<need> to base the timeout	1505	you suspect event processing to be delayed and you I<need> to base the
1130	on the current time, use something like this to adjust for this:	1506	timeout on the current time, use something like this to adjust for this:
1131		1507
1132	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1508	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1133		1509
1134	The callback is guarenteed to be invoked only when its timeout has passed,	1510	If the event loop is suspended for a long time, you can also force an
1135	but if multiple timers become ready during the same loop iteration then	1511	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1136	order of execution is undefined.	1512	()>.
1137		1513
1138	=head3 Watcher-Specific Functions and Data Members	1514	=head3 Watcher-Specific Functions and Data Members
1139		1515
1140	=over 4	1516	=over 4
1141		1517
1142	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1518	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1143		1519
1144	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1520	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1145		1521
1146	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1522	Configure the timer to trigger after C<after> seconds. If C<repeat>
1147	C<0.>, then it will automatically be stopped. If it is positive, then the	1523	is C<0.>, then it will automatically be stopped once the timeout is
1148	timer will automatically be configured to trigger again C<repeat> seconds	1524	reached. If it is positive, then the timer will automatically be
1149	later, again, and again, until stopped manually.	1525	configured to trigger again C<repeat> seconds later, again, and again,
		1526	until stopped manually.
1150		1527
1151	The timer itself will do a best-effort at avoiding drift, that is, if you	1528	The timer itself will do a best-effort at avoiding drift, that is, if
1152	configure a timer to trigger every 10 seconds, then it will trigger at	1529	you configure a timer to trigger every 10 seconds, then it will normally
1153	exactly 10 second intervals. If, however, your program cannot keep up with	1530	trigger at exactly 10 second intervals. If, however, your program cannot
1154	the timer (because it takes longer than those 10 seconds to do stuff) the	1531	keep up with the timer (because it takes longer than those 10 seconds to
1155	timer will not fire more than once per event loop iteration.	1532	do stuff) the timer will not fire more than once per event loop iteration.
1156		1533
1157	=item ev_timer_again (loop)	1534	=item ev_timer_again (loop, ev_timer *)
1158		1535
1159	This will act as if the timer timed out and restart it again if it is	1536	This will act as if the timer timed out and restart it again if it is
1160	repeating. The exact semantics are:	1537	repeating. The exact semantics are:
1161		1538
1162	If the timer is pending, its pending status is cleared.	1539	If the timer is pending, its pending status is cleared.
1163		1540
1164	If the timer is started but nonrepeating, stop it (as if it timed out).	1541	If the timer is started but non-repeating, stop it (as if it timed out).
1165		1542
1166	If the timer is repeating, either start it if necessary (with the	1543	If the timer is repeating, either start it if necessary (with the
1167	C<repeat> value), or reset the running timer to the C<repeat> value.	1544	C<repeat> value), or reset the running timer to the C<repeat> value.
1168		1545
1169	This sounds a bit complicated, but here is a useful and typical	1546	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1170	example: Imagine you have a tcp connection and you want a so-called idle	1547	usage example.
1171	timeout, that is, you want to be called when there have been, say, 60
1172	seconds of inactivity on the socket. The easiest way to do this is to
1173	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1174	C<ev_timer_again> each time you successfully read or write some data. If
1175	you go into an idle state where you do not expect data to travel on the
1176	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1177	automatically restart it if need be.
1178
1179	That means you can ignore the C<after> value and C<ev_timer_start>
1180	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1181
1182	ev_timer_init (timer, callback, 0., 5.);
1183	ev_timer_again (loop, timer);
1184	...
1185	timer->again = 17.;
1186	ev_timer_again (loop, timer);
1187	...
1188	timer->again = 10.;
1189	ev_timer_again (loop, timer);
1190
1191	This is more slightly efficient then stopping/starting the timer each time
1192	you want to modify its timeout value.
1193		1548
1194	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1195		1550
1196	The current C<repeat> value. Will be used each time the watcher times out	1551	The current C<repeat> value. Will be used each time the watcher times out
1197	or C<ev_timer_again> is called and determines the next timeout (if any),	1552	or C<ev_timer_again> is called, and determines the next timeout (if any),
1198	which is also when any modifications are taken into account.	1553	which is also when any modifications are taken into account.
1199		1554
1200	=back	1555	=back
1201		1556
1202	=head3 Examples	1557	=head3 Examples
1203		1558
1204	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1205		1560
1206	static void	1561	static void
1207	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1562	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1208	{	1563	{
1209	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1210	}	1565	}
1211		1566
1212	struct ev_timer mytimer;	1567	ev_timer mytimer;
1213	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1214	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1215		1570
1216	Example: Create a timeout timer that times out after 10 seconds of	1571	Example: Create a timeout timer that times out after 10 seconds of
1217	inactivity.	1572	inactivity.
1218		1573
1219	static void	1574	static void
1220	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1221	{	1576	{
1222	.. ten seconds without any activity	1577	.. ten seconds without any activity
1223	}	1578	}
1224		1579
1225	struct ev_timer mytimer;	1580	ev_timer mytimer;
1226	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1227	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1228	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1229		1584
1230	// and in some piece of code that gets executed on any "activity":	1585	// and in some piece of code that gets executed on any "activity":
1231	// reset the timeout to start ticking again at 10 seconds	1586	// reset the timeout to start ticking again at 10 seconds
1232	ev_timer_again (&mytimer);	1587	ev_timer_again (&mytimer);
1233		1588
1234		1589
1235	=head2 C<ev_periodic> - to cron or not to cron?	1590	=head2 C<ev_periodic> - to cron or not to cron?
1236		1591
1237	Periodic watchers are also timers of a kind, but they are very versatile	1592	Periodic watchers are also timers of a kind, but they are very versatile
1238	(and unfortunately a bit complex).	1593	(and unfortunately a bit complex).
1239		1594
1240	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1595	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1241	but on wallclock time (absolute time). You can tell a periodic watcher	1596	but on wall clock time (absolute time). You can tell a periodic watcher
1242	to trigger "at" some specific point in time. For example, if you tell a	1597	to trigger after some specific point in time. For example, if you tell a
1243	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1598	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1244	+ 10.>) and then reset your system clock to the last year, then it will	1599	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1600	clock to January of the previous year, then it will take more than year
1245	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1246	roughly 10 seconds later).	1602	roughly 10 seconds later as it uses a relative timeout).
1247		1603
1248	They can also be used to implement vastly more complex timers, such as	1604	C<ev_periodic>s can also be used to implement vastly more complex timers,
1249	triggering an event on each midnight, local time or other, complicated,	1605	such as triggering an event on each "midnight, local time", or other
1250	rules.	1606	complicated rules.
1251		1607
1252	As with timers, the callback is guarenteed to be invoked only when the	1608	As with timers, the callback is guaranteed to be invoked only when the
1253	time (C<at>) has been passed, but if multiple periodic timers become ready	1609	time (C<at>) has passed, but if multiple periodic timers become ready
1254	during the same loop iteration then order of execution is undefined.	1610	during the same loop iteration, then order of execution is undefined.
1255		1611
1256	=head3 Watcher-Specific Functions and Data Members	1612	=head3 Watcher-Specific Functions and Data Members
1257		1613
1258	=over 4	1614	=over 4
1259		1615
1260	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1261		1617
1262	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1263		1619
1264	Lots of arguments, lets sort it out... There are basically three modes of	1620	Lots of arguments, lets sort it out... There are basically three modes of
1265	operation, and we will explain them from simplest to complex:	1621	operation, and we will explain them from simplest to most complex:
1266		1622
1267	=over 4	1623	=over 4
1268		1624
1269	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1270		1626
1271	In this configuration the watcher triggers an event at the wallclock time	1627	In this configuration the watcher triggers an event after the wall clock
1272	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1628	time C<at> has passed. It will not repeat and will not adjust when a time
1273	that is, if it is to be run at January 1st 2011 then it will run when the	1629	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1274	system time reaches or surpasses this time.	1630	only run when the system clock reaches or surpasses this time.
1275		1631
1276	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1277		1633
1278	In this mode the watcher will always be scheduled to time out at the next	1634	In this mode the watcher will always be scheduled to time out at the next
1279	C<at + N * interval> time (for some integer N, which can also be negative)	1635	C<at + N * interval> time (for some integer N, which can also be negative)
1280	and then repeat, regardless of any time jumps.	1636	and then repeat, regardless of any time jumps.
1281		1637
1282	This can be used to create timers that do not drift with respect to system	1638	This can be used to create timers that do not drift with respect to the
1283	time:	1639	system clock, for example, here is a C<ev_periodic> that triggers each
		1640	hour, on the hour:
1284		1641
1285	ev_periodic_set (&periodic, 0., 3600., 0);	1642	ev_periodic_set (&periodic, 0., 3600., 0);
1286		1643
1287	This doesn't mean there will always be 3600 seconds in between triggers,	1644	This doesn't mean there will always be 3600 seconds in between triggers,
1288	but only that the the callback will be called when the system time shows a	1645	but only that the callback will be called when the system time shows a
1289	full hour (UTC), or more correctly, when the system time is evenly divisible	1646	full hour (UTC), or more correctly, when the system time is evenly divisible
1290	by 3600.	1647	by 3600.
1291		1648
1292	Another way to think about it (for the mathematically inclined) is that	1649	Another way to think about it (for the mathematically inclined) is that
1293	C<ev_periodic> will try to run the callback in this mode at the next possible	1650	C<ev_periodic> will try to run the callback in this mode at the next possible
1294	time where C<time = at (mod interval)>, regardless of any time jumps.	1651	time where C<time = at (mod interval)>, regardless of any time jumps.
1295		1652
1296	For numerical stability it is preferable that the C<at> value is near	1653	For numerical stability it is preferable that the C<at> value is near
1297	C<ev_now ()> (the current time), but there is no range requirement for	1654	C<ev_now ()> (the current time), but there is no range requirement for
1298	this value.	1655	this value, and in fact is often specified as zero.
		1656
		1657	Note also that there is an upper limit to how often a timer can fire (CPU
		1658	speed for example), so if C<interval> is very small then timing stability
		1659	will of course deteriorate. Libev itself tries to be exact to be about one
		1660	millisecond (if the OS supports it and the machine is fast enough).
1299		1661
1300	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1662	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1301		1663
1302	In this mode the values for C<interval> and C<at> are both being	1664	In this mode the values for C<interval> and C<at> are both being
1303	ignored. Instead, each time the periodic watcher gets scheduled, the	1665	ignored. Instead, each time the periodic watcher gets scheduled, the
1304	reschedule callback will be called with the watcher as first, and the	1666	reschedule callback will be called with the watcher as first, and the
1305	current time as second argument.	1667	current time as second argument.
1306		1668
1307	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1669	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1308	ever, or make any event loop modifications>. If you need to stop it,	1670	ever, or make ANY event loop modifications whatsoever>.
1309	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1310	starting an C<ev_prepare> watcher, which is legal).
1311		1671
		1672	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1674	only event loop modification you are allowed to do).
		1675
1312	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1313	ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1314		1678
		1679	static ev_tstamp
1315	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1316	{	1681	{
1317	return now + 60.;	1682	return now + 60.;
1318	}	1683	}
1319		1684
1320	It must return the next time to trigger, based on the passed time value	1685	It must return the next time to trigger, based on the passed time value
1321	(that is, the lowest time value larger than to the second argument). It	1686	(that is, the lowest time value larger than to the second argument). It
1322	will usually be called just before the callback will be triggered, but	1687	will usually be called just before the callback will be triggered, but
1323	might be called at other times, too.	1688	might be called at other times, too.
1324		1689
1325	NOTE: I<< This callback must always return a time that is later than the	1690	NOTE: I<< This callback must always return a time that is higher than or
1326	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1691	equal to the passed C<now> value >>.
1327		1692
1328	This can be used to create very complex timers, such as a timer that	1693	This can be used to create very complex timers, such as a timer that
1329	triggers on each midnight, local time. To do this, you would calculate the	1694	triggers on "next midnight, local time". To do this, you would calculate the
1330	next midnight after C<now> and return the timestamp value for this. How	1695	next midnight after C<now> and return the timestamp value for this. How
1331	you do this is, again, up to you (but it is not trivial, which is the main	1696	you do this is, again, up to you (but it is not trivial, which is the main
1332	reason I omitted it as an example).	1697	reason I omitted it as an example).
1333		1698
1334	=back	1699	=back
…		…
1338	Simply stops and restarts the periodic watcher again. This is only useful	1703	Simply stops and restarts the periodic watcher again. This is only useful
1339	when you changed some parameters or the reschedule callback would return	1704	when you changed some parameters or the reschedule callback would return
1340	a different time than the last time it was called (e.g. in a crond like	1705	a different time than the last time it was called (e.g. in a crond like
1341	program when the crontabs have changed).	1706	program when the crontabs have changed).
1342		1707
		1708	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1709
		1710	When active, returns the absolute time that the watcher is supposed to
		1711	trigger next.
		1712
1343	=item ev_tstamp offset [read-write]	1713	=item ev_tstamp offset [read-write]
1344		1714
1345	When repeating, this contains the offset value, otherwise this is the	1715	When repeating, this contains the offset value, otherwise this is the
1346	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1716	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1347		1717
…		…
1352		1722
1353	The current interval value. Can be modified any time, but changes only	1723	The current interval value. Can be modified any time, but changes only
1354	take effect when the periodic timer fires or C<ev_periodic_again> is being	1724	take effect when the periodic timer fires or C<ev_periodic_again> is being
1355	called.	1725	called.
1356		1726
1357	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1727	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1358		1728
1359	The current reschedule callback, or C<0>, if this functionality is	1729	The current reschedule callback, or C<0>, if this functionality is
1360	switched off. Can be changed any time, but changes only take effect when	1730	switched off. Can be changed any time, but changes only take effect when
1361	the periodic timer fires or C<ev_periodic_again> is being called.	1731	the periodic timer fires or C<ev_periodic_again> is being called.
1362		1732
1363	=item ev_tstamp at [read-only]
1364
1365	When active, contains the absolute time that the watcher is supposed to
1366	trigger next.
1367
1368	=back	1733	=back
1369		1734
1370	=head3 Examples	1735	=head3 Examples
1371		1736
1372	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1373	system clock is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1374	potentially a lot of jittering, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1375		1740
1376	static void	1741	static void
1377	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1378	{	1743	{
1379	... its now a full hour (UTC, or TAI or whatever your clock follows)	1744	... its now a full hour (UTC, or TAI or whatever your clock follows)
1380	}	1745	}
1381		1746
1382	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1383	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1384	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1385		1750
1386	Example: The same as above, but use a reschedule callback to do it:	1751	Example: The same as above, but use a reschedule callback to do it:
1387		1752
1388	#include <math.h>	1753	#include <math.h>
1389		1754
1390	static ev_tstamp	1755	static ev_tstamp
1391	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1392	{	1757	{
1393	return fmod (now, 3600.) + 3600.;	1758	return now + (3600. - fmod (now, 3600.));
1394	}	1759	}
1395		1760
1396	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1761	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1397		1762
1398	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1399		1764
1400	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1401	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1402	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1403	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1404		1769
1405		1770
1406	=head2 C<ev_signal> - signal me when a signal gets signalled!	1771	=head2 C<ev_signal> - signal me when a signal gets signalled!
1407		1772
1408	Signal watchers will trigger an event when the process receives a specific	1773	Signal watchers will trigger an event when the process receives a specific
1409	signal one or more times. Even though signals are very asynchronous, libev	1774	signal one or more times. Even though signals are very asynchronous, libev
1410	will try it's best to deliver signals synchronously, i.e. as part of the	1775	will try it's best to deliver signals synchronously, i.e. as part of the
1411	normal event processing, like any other event.	1776	normal event processing, like any other event.
1412		1777
		1778	If you want signals asynchronously, just use C<sigaction> as you would
		1779	do without libev and forget about sharing the signal. You can even use
		1780	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1781
1413	You can configure as many watchers as you like per signal. Only when the	1782	You can configure as many watchers as you like per signal. Only when the
1414	first watcher gets started will libev actually register a signal watcher	1783	first watcher gets started will libev actually register a signal handler
1415	with the kernel (thus it coexists with your own signal handlers as long	1784	with the kernel (thus it coexists with your own signal handlers as long as
1416	as you don't register any with libev). Similarly, when the last signal	1785	you don't register any with libev for the same signal). Similarly, when
1417	watcher for a signal is stopped libev will reset the signal handler to	1786	the last signal watcher for a signal is stopped, libev will reset the
1418	SIG_DFL (regardless of what it was set to before).	1787	signal handler to SIG_DFL (regardless of what it was set to before).
		1788
		1789	If possible and supported, libev will install its handlers with
		1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1791	interrupted. If you have a problem with system calls getting interrupted by
		1792	signals you can block all signals in an C<ev_check> watcher and unblock
		1793	them in an C<ev_prepare> watcher.
1419		1794
1420	=head3 Watcher-Specific Functions and Data Members	1795	=head3 Watcher-Specific Functions and Data Members
1421		1796
1422	=over 4	1797	=over 4
1423		1798
…		…
1432		1807
1433	The signal the watcher watches out for.	1808	The signal the watcher watches out for.
1434		1809
1435	=back	1810	=back
1436		1811
		1812	=head3 Examples
		1813
		1814	Example: Try to exit cleanly on SIGINT.
		1815
		1816	static void
		1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1818	{
		1819	ev_unloop (loop, EVUNLOOP_ALL);
		1820	}
		1821
		1822	ev_signal signal_watcher;
		1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1824	ev_signal_start (loop, &signal_watcher);
		1825
1437		1826
1438	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
1439		1828
1440	Child watchers trigger when your process receives a SIGCHLD in response to	1829	Child watchers trigger when your process receives a SIGCHLD in response to
1441	some child status changes (most typically when a child of yours dies).	1830	some child status changes (most typically when a child of yours dies or
		1831	exits). It is permissible to install a child watcher I<after> the child
		1832	has been forked (which implies it might have already exited), as long
		1833	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1834	forking and then immediately registering a watcher for the child is fine,
		1835	but forking and registering a watcher a few event loop iterations later is
		1836	not.
		1837
		1838	Only the default event loop is capable of handling signals, and therefore
		1839	you can only register child watchers in the default event loop.
		1840
		1841	=head3 Process Interaction
		1842
		1843	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1844	initialised. This is necessary to guarantee proper behaviour even if
		1845	the first child watcher is started after the child exits. The occurrence
		1846	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1847	synchronously as part of the event loop processing. Libev always reaps all
		1848	children, even ones not watched.
		1849
		1850	=head3 Overriding the Built-In Processing
		1851
		1852	Libev offers no special support for overriding the built-in child
		1853	processing, but if your application collides with libev's default child
		1854	handler, you can override it easily by installing your own handler for
		1855	C<SIGCHLD> after initialising the default loop, and making sure the
		1856	default loop never gets destroyed. You are encouraged, however, to use an
		1857	event-based approach to child reaping and thus use libev's support for
		1858	that, so other libev users can use C<ev_child> watchers freely.
		1859
		1860	=head3 Stopping the Child Watcher
		1861
		1862	Currently, the child watcher never gets stopped, even when the
		1863	child terminates, so normally one needs to stop the watcher in the
		1864	callback. Future versions of libev might stop the watcher automatically
		1865	when a child exit is detected.
1442		1866
1443	=head3 Watcher-Specific Functions and Data Members	1867	=head3 Watcher-Specific Functions and Data Members
1444		1868
1445	=over 4	1869	=over 4
1446		1870
…		…
1472		1896
1473	=back	1897	=back
1474		1898
1475	=head3 Examples	1899	=head3 Examples
1476		1900
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	1901	Example: C<fork()> a new process and install a child handler to wait for
		1902	its completion.
1478		1903
		1904	ev_child cw;
		1905
1479	static void	1906	static void
1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1481	{	1908	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	1909	ev_child_stop (EV_A_ w);
		1910	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1483	}	1911	}
1484		1912
1485	struct ev_signal signal_watcher;	1913	pid_t pid = fork ();
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1914
1487	ev_signal_start (loop, &sigint_cb);	1915	if (pid < 0)
		1916	// error
		1917	else if (pid == 0)
		1918	{
		1919	// the forked child executes here
		1920	exit (1);
		1921	}
		1922	else
		1923	{
		1924	ev_child_init (&cw, child_cb, pid, 0);
		1925	ev_child_start (EV_DEFAULT_ &cw);
		1926	}
1488		1927
1489		1928
1490	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1491		1930
1492	This watches a filesystem path for attribute changes. That is, it calls	1931	This watches a file system path for attribute changes. That is, it calls
1493	C<stat> regularly (or when the OS says it changed) and sees if it changed	1932	C<stat> on that path in regular intervals (or when the OS says it changed)
1494	compared to the last time, invoking the callback if it did.	1933	and sees if it changed compared to the last time, invoking the callback if
		1934	it did.
1495		1935
1496	The path does not need to exist: changing from "path exists" to "path does	1936	The path does not need to exist: changing from "path exists" to "path does
1497	not exist" is a status change like any other. The condition "path does	1937	not exist" is a status change like any other. The condition "path does not
1498	not exist" is signified by the C<st_nlink> field being zero (which is	1938	exist" (or more correctly "path cannot be stat'ed") is signified by the
1499	otherwise always forced to be at least one) and all the other fields of	1939	C<st_nlink> field being zero (which is otherwise always forced to be at
1500	the stat buffer having unspecified contents.	1940	least one) and all the other fields of the stat buffer having unspecified
		1941	contents.
1501		1942
1502	The path I<should> be absolute and I<must not> end in a slash. If it is	1943	The path I<must not> end in a slash or contain special components such as
		1944	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1503	relative and your working directory changes, the behaviour is undefined.	1945	your working directory changes, then the behaviour is undefined.
1504		1946
1505	Since there is no standard to do this, the portable implementation simply	1947	Since there is no portable change notification interface available, the
1506	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1948	portable implementation simply calls C<stat(2)> regularly on the path
1507	can specify a recommended polling interval for this case. If you specify	1949	to see if it changed somehow. You can specify a recommended polling
1508	a polling interval of C<0> (highly recommended!) then a I<suitable,	1950	interval for this case. If you specify a polling interval of C<0> (highly
1509	unspecified default> value will be used (which you can expect to be around	1951	recommended!) then a I<suitable, unspecified default> value will be used
1510	five seconds, although this might change dynamically). Libev will also	1952	(which you can expect to be around five seconds, although this might
1511	impose a minimum interval which is currently around C<0.1>, but thats	1953	change dynamically). Libev will also impose a minimum interval which is
1512	usually overkill.	1954	currently around C<0.1>, but that's usually overkill.
1513		1955
1514	This watcher type is not meant for massive numbers of stat watchers,	1956	This watcher type is not meant for massive numbers of stat watchers,
1515	as even with OS-supported change notifications, this can be	1957	as even with OS-supported change notifications, this can be
1516	resource-intensive.	1958	resource-intensive.
1517		1959
1518	At the time of this writing, only the Linux inotify interface is	1960	At the time of this writing, the only OS-specific interface implemented
1519	implemented (implementing kqueue support is left as an exercise for the	1961	is the Linux inotify interface (implementing kqueue support is left as an
1520	reader). Inotify will be used to give hints only and should not change the	1962	exercise for the reader. Note, however, that the author sees no way of
1521	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1963	implementing C<ev_stat> semantics with kqueue, except as a hint).
1522	to fall back to regular polling again even with inotify, but changes are
1523	usually detected immediately, and if the file exists there will be no
1524	polling.
1525		1964
1526	=head3 Inotify	1965	=head3 ABI Issues (Largefile Support)
1527		1966
		1967	Libev by default (unless the user overrides this) uses the default
		1968	compilation environment, which means that on systems with large file
		1969	support disabled by default, you get the 32 bit version of the stat
		1970	structure. When using the library from programs that change the ABI to
		1971	use 64 bit file offsets the programs will fail. In that case you have to
		1972	compile libev with the same flags to get binary compatibility. This is
		1973	obviously the case with any flags that change the ABI, but the problem is
		1974	most noticeably displayed with ev_stat and large file support.
		1975
		1976	The solution for this is to lobby your distribution maker to make large
		1977	file interfaces available by default (as e.g. FreeBSD does) and not
		1978	optional. Libev cannot simply switch on large file support because it has
		1979	to exchange stat structures with application programs compiled using the
		1980	default compilation environment.
		1981
		1982	=head3 Inotify and Kqueue
		1983
1528	When C<inotify (7)> support has been compiled into libev (generally only	1984	When C<inotify (7)> support has been compiled into libev and present at
1529	available on Linux) and present at runtime, it will be used to speed up	1985	runtime, it will be used to speed up change detection where possible. The
1530	change detection where possible. The inotify descriptor will be created lazily	1986	inotify descriptor will be created lazily when the first C<ev_stat>
1531	when the first C<ev_stat> watcher is being started.	1987	watcher is being started.
1532		1988
1533	Inotify presense does not change the semantics of C<ev_stat> watchers	1989	Inotify presence does not change the semantics of C<ev_stat> watchers
1534	except that changes might be detected earlier, and in some cases, to avoid	1990	except that changes might be detected earlier, and in some cases, to avoid
1535	making regular C<stat> calls. Even in the presense of inotify support	1991	making regular C<stat> calls. Even in the presence of inotify support
1536	there are many cases where libev has to resort to regular C<stat> polling.	1992	there are many cases where libev has to resort to regular C<stat> polling,
		1993	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1994	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1995	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		1996	xfs are fully working) libev usually gets away without polling.
1537		1997
1538	(There is no support for kqueue, as apparently it cannot be used to	1998	There is no support for kqueue, as apparently it cannot be used to
1539	implement this functionality, due to the requirement of having a file	1999	implement this functionality, due to the requirement of having a file
1540	descriptor open on the object at all times).	2000	descriptor open on the object at all times, and detecting renames, unlinks
		2001	etc. is difficult.
		2002
		2003	=head3 C<stat ()> is a synchronous operation
		2004
		2005	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2006	the process. The exception are C<ev_stat> watchers - those call C<stat
		2007	()>, which is a synchronous operation.
		2008
		2009	For local paths, this usually doesn't matter: unless the system is very
		2010	busy or the intervals between stat's are large, a stat call will be fast,
		2011	as the path data is suually in memory already (except when starting the
		2012	watcher).
		2013
		2014	For networked file systems, calling C<stat ()> can block an indefinite
		2015	time due to network issues, and even under good conditions, a stat call
		2016	often takes multiple milliseconds.
		2017
		2018	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2019	paths, although this is fully supported by libev.
1541		2020
1542	=head3 The special problem of stat time resolution	2021	=head3 The special problem of stat time resolution
1543		2022
1544	The C<stat ()> syscall only supports full-second resolution portably, and	2023	The C<stat ()> system call only supports full-second resolution portably,
1545	even on systems where the resolution is higher, many filesystems still	2024	and even on systems where the resolution is higher, most file systems
1546	only support whole seconds.	2025	still only support whole seconds.
1547		2026
1548	That means that, if the time is the only thing that changes, you might	2027	That means that, if the time is the only thing that changes, you can
1549	miss updates: on the first update, C<ev_stat> detects a change and calls	2028	easily miss updates: on the first update, C<ev_stat> detects a change and
1550	your callback, which does something. When there is another update within	2029	calls your callback, which does something. When there is another update
1551	the same second, C<ev_stat> will be unable to detect it.	2030	within the same second, C<ev_stat> will be unable to detect unless the
		2031	stat data does change in other ways (e.g. file size).
1552		2032
1553	The solution to this is to delay acting on a change for a second (or till	2033	The solution to this is to delay acting on a change for slightly more
1554	the next second boundary), using a roughly one-second delay C<ev_timer>	2034	than a second (or till slightly after the next full second boundary), using
1555	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2035	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1556	is added to work around small timing inconsistencies of some operating	2036	ev_timer_again (loop, w)>).
1557	systems.	2037
		2038	The C<.02> offset is added to work around small timing inconsistencies
		2039	of some operating systems (where the second counter of the current time
		2040	might be be delayed. One such system is the Linux kernel, where a call to
		2041	C<gettimeofday> might return a timestamp with a full second later than
		2042	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2043	update file times then there will be a small window where the kernel uses
		2044	the previous second to update file times but libev might already execute
		2045	the timer callback).
1558		2046
1559	=head3 Watcher-Specific Functions and Data Members	2047	=head3 Watcher-Specific Functions and Data Members
1560		2048
1561	=over 4	2049	=over 4
1562		2050
…		…
1568	C<path>. The C<interval> is a hint on how quickly a change is expected to	2056	C<path>. The C<interval> is a hint on how quickly a change is expected to
1569	be detected and should normally be specified as C<0> to let libev choose	2057	be detected and should normally be specified as C<0> to let libev choose
1570	a suitable value. The memory pointed to by C<path> must point to the same	2058	a suitable value. The memory pointed to by C<path> must point to the same
1571	path for as long as the watcher is active.	2059	path for as long as the watcher is active.
1572		2060
1573	The callback will be receive C<EV_STAT> when a change was detected,	2061	The callback will receive an C<EV_STAT> event when a change was detected,
1574	relative to the attributes at the time the watcher was started (or the	2062	relative to the attributes at the time the watcher was started (or the
1575	last change was detected).	2063	last change was detected).
1576		2064
1577	=item ev_stat_stat (ev_stat *)	2065	=item ev_stat_stat (loop, ev_stat *)
1578		2066
1579	Updates the stat buffer immediately with new values. If you change the	2067	Updates the stat buffer immediately with new values. If you change the
1580	watched path in your callback, you could call this fucntion to avoid	2068	watched path in your callback, you could call this function to avoid
1581	detecting this change (while introducing a race condition). Can also be	2069	detecting this change (while introducing a race condition if you are not
1582	useful simply to find out the new values.	2070	the only one changing the path). Can also be useful simply to find out the
		2071	new values.
1583		2072
1584	=item ev_statdata attr [read-only]	2073	=item ev_statdata attr [read-only]
1585		2074
1586	The most-recently detected attributes of the file. Although the type is of	2075	The most-recently detected attributes of the file. Although the type is
1587	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2076	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1588	suitable for your system. If the C<st_nlink> member is C<0>, then there	2077	suitable for your system, but you can only rely on the POSIX-standardised
		2078	members to be present. If the C<st_nlink> member is C<0>, then there was
1589	was some error while C<stat>ing the file.	2079	some error while C<stat>ing the file.
1590		2080
1591	=item ev_statdata prev [read-only]	2081	=item ev_statdata prev [read-only]
1592		2082
1593	The previous attributes of the file. The callback gets invoked whenever	2083	The previous attributes of the file. The callback gets invoked whenever
1594	C<prev> != C<attr>.	2084	C<prev> != C<attr>, or, more precisely, one or more of these members
		2085	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2086	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1595		2087
1596	=item ev_tstamp interval [read-only]	2088	=item ev_tstamp interval [read-only]
1597		2089
1598	The specified interval.	2090	The specified interval.
1599		2091
1600	=item const char *path [read-only]	2092	=item const char *path [read-only]
1601		2093
1602	The filesystem path that is being watched.	2094	The file system path that is being watched.
1603		2095
1604	=back	2096	=back
1605		2097
1606	=head3 Examples	2098	=head3 Examples
1607		2099
1608	Example: Watch C</etc/passwd> for attribute changes.	2100	Example: Watch C</etc/passwd> for attribute changes.
1609		2101
1610	static void	2102	static void
1611	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2103	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1612	{	2104	{
1613	/* /etc/passwd changed in some way */	2105	/* /etc/passwd changed in some way */
1614	if (w->attr.st_nlink)	2106	if (w->attr.st_nlink)
1615	{	2107	{
1616	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2108	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1617	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2109	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1618	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2110	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1619	}	2111	}
1620	else	2112	else
1621	/* you shalt not abuse printf for puts */	2113	/* you shalt not abuse printf for puts */
1622	puts ("wow, /etc/passwd is not there, expect problems. "	2114	puts ("wow, /etc/passwd is not there, expect problems. "
1623	"if this is windows, they already arrived\n");	2115	"if this is windows, they already arrived\n");
1624	}	2116	}
1625		2117
1626	...	2118	...
1627	ev_stat passwd;	2119	ev_stat passwd;
1628		2120
1629	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2121	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1630	ev_stat_start (loop, &passwd);	2122	ev_stat_start (loop, &passwd);
1631		2123
1632	Example: Like above, but additionally use a one-second delay so we do not	2124	Example: Like above, but additionally use a one-second delay so we do not
1633	miss updates (however, frequent updates will delay processing, too, so	2125	miss updates (however, frequent updates will delay processing, too, so
1634	one might do the work both on C<ev_stat> callback invocation I<and> on	2126	one might do the work both on C<ev_stat> callback invocation I<and> on
1635	C<ev_timer> callback invocation).	2127	C<ev_timer> callback invocation).
1636		2128
1637	static ev_stat passwd;	2129	static ev_stat passwd;
1638	static ev_timer timer;	2130	static ev_timer timer;
1639		2131
1640	static void	2132	static void
1641	timer_cb (EV_P_ ev_timer *w, int revents)	2133	timer_cb (EV_P_ ev_timer *w, int revents)
1642	{	2134	{
1643	ev_timer_stop (EV_A_ w);	2135	ev_timer_stop (EV_A_ w);
1644		2136
1645	/* now it's one second after the most recent passwd change */	2137	/* now it's one second after the most recent passwd change */
1646	}	2138	}
1647		2139
1648	static void	2140	static void
1649	stat_cb (EV_P_ ev_stat *w, int revents)	2141	stat_cb (EV_P_ ev_stat *w, int revents)
1650	{	2142	{
1651	/* reset the one-second timer */	2143	/* reset the one-second timer */
1652	ev_timer_again (EV_A_ &timer);	2144	ev_timer_again (EV_A_ &timer);
1653	}	2145	}
1654		2146
1655	...	2147	...
1656	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2148	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1657	ev_stat_start (loop, &passwd);	2149	ev_stat_start (loop, &passwd);
1658	ev_timer_init (&timer, timer_cb, 0., 1.01);	2150	ev_timer_init (&timer, timer_cb, 0., 1.02);
1659		2151
1660		2152
1661	=head2 C<ev_idle> - when you've got nothing better to do...	2153	=head2 C<ev_idle> - when you've got nothing better to do...
1662		2154
1663	Idle watchers trigger events when no other events of the same or higher	2155	Idle watchers trigger events when no other events of the same or higher
1664	priority are pending (prepare, check and other idle watchers do not	2156	priority are pending (prepare, check and other idle watchers do not count
1665	count).	2157	as receiving "events").
1666		2158
1667	That is, as long as your process is busy handling sockets or timeouts	2159	That is, as long as your process is busy handling sockets or timeouts
1668	(or even signals, imagine) of the same or higher priority it will not be	2160	(or even signals, imagine) of the same or higher priority it will not be
1669	triggered. But when your process is idle (or only lower-priority watchers	2161	triggered. But when your process is idle (or only lower-priority watchers
1670	are pending), the idle watchers are being called once per event loop	2162	are pending), the idle watchers are being called once per event loop
…		…
1694	=head3 Examples	2186	=head3 Examples
1695		2187
1696	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2188	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1697	callback, free it. Also, use no error checking, as usual.	2189	callback, free it. Also, use no error checking, as usual.
1698		2190
1699	static void	2191	static void
1700	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2192	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1701	{	2193	{
1702	free (w);	2194	free (w);
1703	// now do something you wanted to do when the program has	2195	// now do something you wanted to do when the program has
1704	// no longer anything immediate to do.	2196	// no longer anything immediate to do.
1705	}	2197	}
1706		2198
1707	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2199	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1708	ev_idle_init (idle_watcher, idle_cb);	2200	ev_idle_init (idle_watcher, idle_cb);
1709	ev_idle_start (loop, idle_cb);	2201	ev_idle_start (loop, idle_cb);
1710		2202
1711		2203
1712	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2204	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1713		2205
1714	Prepare and check watchers are usually (but not always) used in tandem:	2206	Prepare and check watchers are usually (but not always) used in pairs:
1715	prepare watchers get invoked before the process blocks and check watchers	2207	prepare watchers get invoked before the process blocks and check watchers
1716	afterwards.	2208	afterwards.
1717		2209
1718	You I<must not> call C<ev_loop> or similar functions that enter	2210	You I<must not> call C<ev_loop> or similar functions that enter
1719	the current event loop from either C<ev_prepare> or C<ev_check>	2211	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1722	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2214	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1723	C<ev_check> so if you have one watcher of each kind they will always be	2215	C<ev_check> so if you have one watcher of each kind they will always be
1724	called in pairs bracketing the blocking call.	2216	called in pairs bracketing the blocking call.
1725		2217
1726	Their main purpose is to integrate other event mechanisms into libev and	2218	Their main purpose is to integrate other event mechanisms into libev and
1727	their use is somewhat advanced. This could be used, for example, to track	2219	their use is somewhat advanced. They could be used, for example, to track
1728	variable changes, implement your own watchers, integrate net-snmp or a	2220	variable changes, implement your own watchers, integrate net-snmp or a
1729	coroutine library and lots more. They are also occasionally useful if	2221	coroutine library and lots more. They are also occasionally useful if
1730	you cache some data and want to flush it before blocking (for example,	2222	you cache some data and want to flush it before blocking (for example,
1731	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2223	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1732	watcher).	2224	watcher).
1733		2225
1734	This is done by examining in each prepare call which file descriptors need	2226	This is done by examining in each prepare call which file descriptors
1735	to be watched by the other library, registering C<ev_io> watchers for	2227	need to be watched by the other library, registering C<ev_io> watchers
1736	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2228	for them and starting an C<ev_timer> watcher for any timeouts (many
1737	provide just this functionality). Then, in the check watcher you check for	2229	libraries provide exactly this functionality). Then, in the check watcher,
1738	any events that occured (by checking the pending status of all watchers	2230	you check for any events that occurred (by checking the pending status
1739	and stopping them) and call back into the library. The I/O and timer	2231	of all watchers and stopping them) and call back into the library. The
1740	callbacks will never actually be called (but must be valid nevertheless,	2232	I/O and timer callbacks will never actually be called (but must be valid
1741	because you never know, you know?).	2233	nevertheless, because you never know, you know?).
1742		2234
1743	As another example, the Perl Coro module uses these hooks to integrate	2235	As another example, the Perl Coro module uses these hooks to integrate
1744	coroutines into libev programs, by yielding to other active coroutines	2236	coroutines into libev programs, by yielding to other active coroutines
1745	during each prepare and only letting the process block if no coroutines	2237	during each prepare and only letting the process block if no coroutines
1746	are ready to run (it's actually more complicated: it only runs coroutines	2238	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1749	loop from blocking if lower-priority coroutines are active, thus mapping	2241	loop from blocking if lower-priority coroutines are active, thus mapping
1750	low-priority coroutines to idle/background tasks).	2242	low-priority coroutines to idle/background tasks).
1751		2243
1752	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2244	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1753	priority, to ensure that they are being run before any other watchers	2245	priority, to ensure that they are being run before any other watchers
		2246	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2247
1754	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2248	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1755	too) should not activate ("feed") events into libev. While libev fully	2249	activate ("feed") events into libev. While libev fully supports this, they
1756	supports this, they will be called before other C<ev_check> watchers	2250	might get executed before other C<ev_check> watchers did their job. As
1757	did their job. As C<ev_check> watchers are often used to embed other	2251	C<ev_check> watchers are often used to embed other (non-libev) event
1758	(non-libev) event loops those other event loops might be in an unusable	2252	loops those other event loops might be in an unusable state until their
1759	state until their C<ev_check> watcher ran (always remind yourself to	2253	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1760	coexist peacefully with others).	2254	others).
1761		2255
1762	=head3 Watcher-Specific Functions and Data Members	2256	=head3 Watcher-Specific Functions and Data Members
1763		2257
1764	=over 4	2258	=over 4
1765		2259
…		…
1767		2261
1768	=item ev_check_init (ev_check *, callback)	2262	=item ev_check_init (ev_check *, callback)
1769		2263
1770	Initialises and configures the prepare or check watcher - they have no	2264	Initialises and configures the prepare or check watcher - they have no
1771	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2265	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1772	macros, but using them is utterly, utterly and completely pointless.	2266	macros, but using them is utterly, utterly, utterly and completely
		2267	pointless.
1773		2268
1774	=back	2269	=back
1775		2270
1776	=head3 Examples	2271	=head3 Examples
1777		2272
1778	There are a number of principal ways to embed other event loops or modules	2273	There are a number of principal ways to embed other event loops or modules
1779	into libev. Here are some ideas on how to include libadns into libev	2274	into libev. Here are some ideas on how to include libadns into libev
1780	(there is a Perl module named C<EV::ADNS> that does this, which you could	2275	(there is a Perl module named C<EV::ADNS> that does this, which you could
1781	use for an actually working example. Another Perl module named C<EV::Glib>	2276	use as a working example. Another Perl module named C<EV::Glib> embeds a
1782	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2277	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1783	into the Glib event loop).	2278	Glib event loop).
1784		2279
1785	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2280	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1786	and in a check watcher, destroy them and call into libadns. What follows	2281	and in a check watcher, destroy them and call into libadns. What follows
1787	is pseudo-code only of course. This requires you to either use a low	2282	is pseudo-code only of course. This requires you to either use a low
1788	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2283	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1789	the callbacks for the IO/timeout watchers might not have been called yet.	2284	the callbacks for the IO/timeout watchers might not have been called yet.
1790		2285
1791	static ev_io iow [nfd];	2286	static ev_io iow [nfd];
1792	static ev_timer tw;	2287	static ev_timer tw;
1793		2288
1794	static void	2289	static void
1795	io_cb (ev_loop *loop, ev_io *w, int revents)	2290	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1796	{	2291	{
1797	}	2292	}
1798		2293
1799	// create io watchers for each fd and a timer before blocking	2294	// create io watchers for each fd and a timer before blocking
1800	static void	2295	static void
1801	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2296	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1802	{	2297	{
1803	int timeout = 3600000;	2298	int timeout = 3600000;
1804	struct pollfd fds [nfd];	2299	struct pollfd fds [nfd];
1805	// actual code will need to loop here and realloc etc.	2300	// actual code will need to loop here and realloc etc.
1806	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2301	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1807		2302
1808	/* the callback is illegal, but won't be called as we stop during check */	2303	/* the callback is illegal, but won't be called as we stop during check */
1809	ev_timer_init (&tw, 0, timeout * 1e-3);	2304	ev_timer_init (&tw, 0, timeout * 1e-3);
1810	ev_timer_start (loop, &tw);	2305	ev_timer_start (loop, &tw);
1811		2306
1812	// create one ev_io per pollfd	2307	// create one ev_io per pollfd
1813	for (int i = 0; i < nfd; ++i)	2308	for (int i = 0; i < nfd; ++i)
1814	{	2309	{
1815	ev_io_init (iow + i, io_cb, fds [i].fd,	2310	ev_io_init (iow + i, io_cb, fds [i].fd,
1816	((fds [i].events & POLLIN ? EV_READ : 0)	2311	((fds [i].events & POLLIN ? EV_READ : 0)
1817	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2312	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1818		2313
1819	fds [i].revents = 0;	2314	fds [i].revents = 0;
1820	ev_io_start (loop, iow + i);	2315	ev_io_start (loop, iow + i);
1821	}	2316	}
1822	}	2317	}
1823		2318
1824	// stop all watchers after blocking	2319	// stop all watchers after blocking
1825	static void	2320	static void
1826	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2321	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1827	{	2322	{
1828	ev_timer_stop (loop, &tw);	2323	ev_timer_stop (loop, &tw);
1829		2324
1830	for (int i = 0; i < nfd; ++i)	2325	for (int i = 0; i < nfd; ++i)
1831	{	2326	{
1832	// set the relevant poll flags	2327	// set the relevant poll flags
1833	// could also call adns_processreadable etc. here	2328	// could also call adns_processreadable etc. here
1834	struct pollfd *fd = fds + i;	2329	struct pollfd *fd = fds + i;
1835	int revents = ev_clear_pending (iow + i);	2330	int revents = ev_clear_pending (iow + i);
1836	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2331	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1837	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2332	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1838		2333
1839	// now stop the watcher	2334	// now stop the watcher
1840	ev_io_stop (loop, iow + i);	2335	ev_io_stop (loop, iow + i);
1841	}	2336	}
1842		2337
1843	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2338	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1844	}	2339	}
1845		2340
1846	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2341	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1847	in the prepare watcher and would dispose of the check watcher.	2342	in the prepare watcher and would dispose of the check watcher.
1848		2343
1849	Method 3: If the module to be embedded supports explicit event	2344	Method 3: If the module to be embedded supports explicit event
1850	notification (adns does), you can also make use of the actual watcher	2345	notification (libadns does), you can also make use of the actual watcher
1851	callbacks, and only destroy/create the watchers in the prepare watcher.	2346	callbacks, and only destroy/create the watchers in the prepare watcher.
1852		2347
1853	static void	2348	static void
1854	timer_cb (EV_P_ ev_timer *w, int revents)	2349	timer_cb (EV_P_ ev_timer *w, int revents)
1855	{	2350	{
1856	adns_state ads = (adns_state)w->data;	2351	adns_state ads = (adns_state)w->data;
1857	update_now (EV_A);	2352	update_now (EV_A);
1858		2353
1859	adns_processtimeouts (ads, &tv_now);	2354	adns_processtimeouts (ads, &tv_now);
1860	}	2355	}
1861		2356
1862	static void	2357	static void
1863	io_cb (EV_P_ ev_io *w, int revents)	2358	io_cb (EV_P_ ev_io *w, int revents)
1864	{	2359	{
1865	adns_state ads = (adns_state)w->data;	2360	adns_state ads = (adns_state)w->data;
1866	update_now (EV_A);	2361	update_now (EV_A);
1867		2362
1868	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2363	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1869	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2364	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1870	}	2365	}
1871		2366
1872	// do not ever call adns_afterpoll	2367	// do not ever call adns_afterpoll
1873		2368
1874	Method 4: Do not use a prepare or check watcher because the module you	2369	Method 4: Do not use a prepare or check watcher because the module you
1875	want to embed is too inflexible to support it. Instead, youc na override	2370	want to embed is not flexible enough to support it. Instead, you can
1876	their poll function. The drawback with this solution is that the main	2371	override their poll function. The drawback with this solution is that the
1877	loop is now no longer controllable by EV. The C<Glib::EV> module does	2372	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1878	this.	2373	this approach, effectively embedding EV as a client into the horrible
		2374	libglib event loop.
1879		2375
1880	static gint	2376	static gint
1881	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2377	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1882	{	2378	{
1883	int got_events = 0;	2379	int got_events = 0;
1884		2380
1885	for (n = 0; n < nfds; ++n)	2381	for (n = 0; n < nfds; ++n)
1886	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2382	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1887		2383
1888	if (timeout >= 0)	2384	if (timeout >= 0)
1889	// create/start timer	2385	// create/start timer
1890		2386
1891	// poll	2387	// poll
1892	ev_loop (EV_A_ 0);	2388	ev_loop (EV_A_ 0);
1893		2389
1894	// stop timer again	2390	// stop timer again
1895	if (timeout >= 0)	2391	if (timeout >= 0)
1896	ev_timer_stop (EV_A_ &to);	2392	ev_timer_stop (EV_A_ &to);
1897		2393
1898	// stop io watchers again - their callbacks should have set	2394	// stop io watchers again - their callbacks should have set
1899	for (n = 0; n < nfds; ++n)	2395	for (n = 0; n < nfds; ++n)
1900	ev_io_stop (EV_A_ iow [n]);	2396	ev_io_stop (EV_A_ iow [n]);
1901		2397
1902	return got_events;	2398	return got_events;
1903	}	2399	}
1904		2400
1905		2401
1906	=head2 C<ev_embed> - when one backend isn't enough...	2402	=head2 C<ev_embed> - when one backend isn't enough...
1907		2403
1908	This is a rather advanced watcher type that lets you embed one event loop	2404	This is a rather advanced watcher type that lets you embed one event loop
…		…
1914	prioritise I/O.	2410	prioritise I/O.
1915		2411
1916	As an example for a bug workaround, the kqueue backend might only support	2412	As an example for a bug workaround, the kqueue backend might only support
1917	sockets on some platform, so it is unusable as generic backend, but you	2413	sockets on some platform, so it is unusable as generic backend, but you
1918	still want to make use of it because you have many sockets and it scales	2414	still want to make use of it because you have many sockets and it scales
1919	so nicely. In this case, you would create a kqueue-based loop and embed it	2415	so nicely. In this case, you would create a kqueue-based loop and embed
1920	into your default loop (which might use e.g. poll). Overall operation will	2416	it into your default loop (which might use e.g. poll). Overall operation
1921	be a bit slower because first libev has to poll and then call kevent, but	2417	will be a bit slower because first libev has to call C<poll> and then
1922	at least you can use both at what they are best.	2418	C<kevent>, but at least you can use both mechanisms for what they are
		2419	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1923		2420
1924	As for prioritising I/O: rarely you have the case where some fds have	2421	As for prioritising I/O: under rare circumstances you have the case where
1925	to be watched and handled very quickly (with low latency), and even	2422	some fds have to be watched and handled very quickly (with low latency),
1926	priorities and idle watchers might have too much overhead. In this case	2423	and even priorities and idle watchers might have too much overhead. In
1927	you would put all the high priority stuff in one loop and all the rest in	2424	this case you would put all the high priority stuff in one loop and all
1928	a second one, and embed the second one in the first.	2425	the rest in a second one, and embed the second one in the first.
1929		2426
1930	As long as the watcher is active, the callback will be invoked every time	2427	As long as the watcher is active, the callback will be invoked every time
1931	there might be events pending in the embedded loop. The callback must then	2428	there might be events pending in the embedded loop. The callback must then
1932	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2429	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1933	their callbacks (you could also start an idle watcher to give the embedded	2430	their callbacks (you could also start an idle watcher to give the embedded
…		…
1941	interested in that.	2438	interested in that.
1942		2439
1943	Also, there have not currently been made special provisions for forking:	2440	Also, there have not currently been made special provisions for forking:
1944	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2441	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1945	but you will also have to stop and restart any C<ev_embed> watchers	2442	but you will also have to stop and restart any C<ev_embed> watchers
1946	yourself.	2443	yourself - but you can use a fork watcher to handle this automatically,
		2444	and future versions of libev might do just that.
1947		2445
1948	Unfortunately, not all backends are embeddable, only the ones returned by	2446	Unfortunately, not all backends are embeddable: only the ones returned by
1949	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2447	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1950	portable one.	2448	portable one.
1951		2449
1952	So when you want to use this feature you will always have to be prepared	2450	So when you want to use this feature you will always have to be prepared
1953	that you cannot get an embeddable loop. The recommended way to get around	2451	that you cannot get an embeddable loop. The recommended way to get around
1954	this is to have a separate variables for your embeddable loop, try to	2452	this is to have a separate variables for your embeddable loop, try to
1955	create it, and if that fails, use the normal loop for everything.	2453	create it, and if that fails, use the normal loop for everything.
1956		2454
		2455	=head3 C<ev_embed> and fork
		2456
		2457	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2458	automatically be applied to the embedded loop as well, so no special
		2459	fork handling is required in that case. When the watcher is not running,
		2460	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2461	as applicable.
		2462
1957	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
1958		2464
1959	=over 4	2465	=over 4
1960		2466
1961	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2467	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1964		2470
1965	Configures the watcher to embed the given loop, which must be	2471	Configures the watcher to embed the given loop, which must be
1966	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2472	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1967	invoked automatically, otherwise it is the responsibility of the callback	2473	invoked automatically, otherwise it is the responsibility of the callback
1968	to invoke it (it will continue to be called until the sweep has been done,	2474	to invoke it (it will continue to be called until the sweep has been done,
1969	if you do not want thta, you need to temporarily stop the embed watcher).	2475	if you do not want that, you need to temporarily stop the embed watcher).
1970		2476
1971	=item ev_embed_sweep (loop, ev_embed *)	2477	=item ev_embed_sweep (loop, ev_embed *)
1972		2478
1973	Make a single, non-blocking sweep over the embedded loop. This works	2479	Make a single, non-blocking sweep over the embedded loop. This works
1974	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2480	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1975	apropriate way for embedded loops.	2481	appropriate way for embedded loops.
1976		2482
1977	=item struct ev_loop *other [read-only]	2483	=item struct ev_loop *other [read-only]
1978		2484
1979	The embedded event loop.	2485	The embedded event loop.
1980		2486
…		…
1982		2488
1983	=head3 Examples	2489	=head3 Examples
1984		2490
1985	Example: Try to get an embeddable event loop and embed it into the default	2491	Example: Try to get an embeddable event loop and embed it into the default
1986	event loop. If that is not possible, use the default loop. The default	2492	event loop. If that is not possible, use the default loop. The default
1987	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2493	loop is stored in C<loop_hi>, while the embeddable loop is stored in
1988	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2494	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
1989	used).	2495	used).
1990		2496
1991	struct ev_loop *loop_hi = ev_default_init (0);	2497	struct ev_loop *loop_hi = ev_default_init (0);
1992	struct ev_loop *loop_lo = 0;	2498	struct ev_loop *loop_lo = 0;
1993	struct ev_embed embed;	2499	ev_embed embed;
1994		2500
1995	// see if there is a chance of getting one that works	2501	// see if there is a chance of getting one that works
1996	// (remember that a flags value of 0 means autodetection)	2502	// (remember that a flags value of 0 means autodetection)
1997	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2503	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1998	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2504	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1999	: 0;	2505	: 0;
2000		2506
2001	// if we got one, then embed it, otherwise default to loop_hi	2507	// if we got one, then embed it, otherwise default to loop_hi
2002	if (loop_lo)	2508	if (loop_lo)
2003	{	2509	{
2004	ev_embed_init (&embed, 0, loop_lo);	2510	ev_embed_init (&embed, 0, loop_lo);
2005	ev_embed_start (loop_hi, &embed);	2511	ev_embed_start (loop_hi, &embed);
2006	}	2512	}
2007	else	2513	else
2008	loop_lo = loop_hi;	2514	loop_lo = loop_hi;
2009		2515
2010	Example: Check if kqueue is available but not recommended and create	2516	Example: Check if kqueue is available but not recommended and create
2011	a kqueue backend for use with sockets (which usually work with any	2517	a kqueue backend for use with sockets (which usually work with any
2012	kqueue implementation). Store the kqueue/socket-only event loop in	2518	kqueue implementation). Store the kqueue/socket-only event loop in
2013	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2519	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2014		2520
2015	struct ev_loop *loop = ev_default_init (0);	2521	struct ev_loop *loop = ev_default_init (0);
2016	struct ev_loop *loop_socket = 0;	2522	struct ev_loop *loop_socket = 0;
2017	struct ev_embed embed;	2523	ev_embed embed;
2018		2524
2019	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2525	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2020	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2526	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2021	{	2527	{
2022	ev_embed_init (&embed, 0, loop_socket);	2528	ev_embed_init (&embed, 0, loop_socket);
2023	ev_embed_start (loop, &embed);	2529	ev_embed_start (loop, &embed);
2024	}	2530	}
2025		2531
2026	if (!loop_socket)	2532	if (!loop_socket)
2027	loop_socket = loop;	2533	loop_socket = loop;
2028		2534
2029	// now use loop_socket for all sockets, and loop for everything else	2535	// now use loop_socket for all sockets, and loop for everything else
2030		2536
2031		2537
2032	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2538	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2033		2539
2034	Fork watchers are called when a C<fork ()> was detected (usually because	2540	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2078	is that the author does not know of a simple (or any) algorithm for a	2584	is that the author does not know of a simple (or any) algorithm for a
2079	multiple-writer-single-reader queue that works in all cases and doesn't	2585	multiple-writer-single-reader queue that works in all cases and doesn't
2080	need elaborate support such as pthreads.	2586	need elaborate support such as pthreads.
2081		2587
2082	That means that if you want to queue data, you have to provide your own	2588	That means that if you want to queue data, you have to provide your own
2083	queue. But at least I can tell you would implement locking around your	2589	queue. But at least I can tell you how to implement locking around your
2084	queue:	2590	queue:
2085		2591
2086	=over 4	2592	=over 4
2087		2593
2088	=item queueing from a signal handler context	2594	=item queueing from a signal handler context
2089		2595
2090	To implement race-free queueing, you simply add to the queue in the signal	2596	To implement race-free queueing, you simply add to the queue in the signal
2091	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2597	handler but you block the signal handler in the watcher callback. Here is
2092	some fictitiuous SIGUSR1 handler:	2598	an example that does that for some fictitious SIGUSR1 handler:
2093		2599
2094	static ev_async mysig;	2600	static ev_async mysig;
2095		2601
2096	static void	2602	static void
2097	sigusr1_handler (void)	2603	sigusr1_handler (void)
2098	{	2604	{
2099	sometype data;	2605	sometype data;
2100		2606
2101	// no locking etc.	2607	// no locking etc.
2102	queue_put (data);	2608	queue_put (data);
2103	ev_async_send (DEFAULT_ &mysig);	2609	ev_async_send (EV_DEFAULT_ &mysig);
2104	}	2610	}
2105		2611
2106	static void	2612	static void
2107	mysig_cb (EV_P_ ev_async *w, int revents)	2613	mysig_cb (EV_P_ ev_async *w, int revents)
2108	{	2614	{
…		…
2139	// only need to lock the actual queueing operation	2645	// only need to lock the actual queueing operation
2140	pthread_mutex_lock (&mymutex);	2646	pthread_mutex_lock (&mymutex);
2141	queue_put (data);	2647	queue_put (data);
2142	pthread_mutex_unlock (&mymutex);	2648	pthread_mutex_unlock (&mymutex);
2143		2649
2144	ev_async_send (DEFAULT_ &mysig);	2650	ev_async_send (EV_DEFAULT_ &mysig);
2145	}	2651	}
2146		2652
2147	static void	2653	static void
2148	mysig_cb (EV_P_ ev_async *w, int revents)	2654	mysig_cb (EV_P_ ev_async *w, int revents)
2149	{	2655	{
…		…
2163	=over 4	2669	=over 4
2164		2670
2165	=item ev_async_init (ev_async *, callback)	2671	=item ev_async_init (ev_async *, callback)
2166		2672
2167	Initialises and configures the async watcher - it has no parameters of any	2673	Initialises and configures the async watcher - it has no parameters of any
2168	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2674	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2169	believe me.	2675	trust me.
2170		2676
2171	=item ev_async_send (loop, ev_async *)	2677	=item ev_async_send (loop, ev_async *)
2172		2678
2173	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2679	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2174	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2680	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2175	C<ev_feed_event>, this call is safe to do in other threads, signal or	2681	C<ev_feed_event>, this call is safe to do from other threads, signal or
2176	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2682	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2177	section below on what exactly this means).	2683	section below on what exactly this means).
2178		2684
2179	This call incurs the overhead of a syscall only once per loop iteration,	2685	This call incurs the overhead of a system call only once per loop iteration,
2180	so while the overhead might be noticable, it doesn't apply to repeated	2686	so while the overhead might be noticeable, it doesn't apply to repeated
2181	calls to C<ev_async_send>.	2687	calls to C<ev_async_send>.
2182		2688
		2689	=item bool = ev_async_pending (ev_async *)
		2690
		2691	Returns a non-zero value when C<ev_async_send> has been called on the
		2692	watcher but the event has not yet been processed (or even noted) by the
		2693	event loop.
		2694
		2695	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2696	the loop iterates next and checks for the watcher to have become active,
		2697	it will reset the flag again. C<ev_async_pending> can be used to very
		2698	quickly check whether invoking the loop might be a good idea.
		2699
		2700	Not that this does I<not> check whether the watcher itself is pending, only
		2701	whether it has been requested to make this watcher pending.
		2702
2183	=back	2703	=back
2184		2704
2185		2705
2186	=head1 OTHER FUNCTIONS	2706	=head1 OTHER FUNCTIONS
2187		2707
…		…
2190	=over 4	2710	=over 4
2191		2711
2192	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2712	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2193		2713
2194	This function combines a simple timer and an I/O watcher, calls your	2714	This function combines a simple timer and an I/O watcher, calls your
2195	callback on whichever event happens first and automatically stop both	2715	callback on whichever event happens first and automatically stops both
2196	watchers. This is useful if you want to wait for a single event on an fd	2716	watchers. This is useful if you want to wait for a single event on an fd
2197	or timeout without having to allocate/configure/start/stop/free one or	2717	or timeout without having to allocate/configure/start/stop/free one or
2198	more watchers yourself.	2718	more watchers yourself.
2199		2719
2200	If C<fd> is less than 0, then no I/O watcher will be started and events	2720	If C<fd> is less than 0, then no I/O watcher will be started and the
2201	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2721	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2202	C<events> set will be craeted and started.	2722	the given C<fd> and C<events> set will be created and started.
2203		2723
2204	If C<timeout> is less than 0, then no timeout watcher will be	2724	If C<timeout> is less than 0, then no timeout watcher will be
2205	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2725	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2206	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2726	repeat = 0) will be started. C<0> is a valid timeout.
2207	dubious value.
2208		2727
2209	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2728	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2210	passed an C<revents> set like normal event callbacks (a combination of	2729	passed an C<revents> set like normal event callbacks (a combination of
2211	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2730	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2212	value passed to C<ev_once>:	2731	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2732	a timeout and an io event at the same time - you probably should give io
		2733	events precedence.
2213		2734
		2735	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2736
2214	static void stdin_ready (int revents, void *arg)	2737	static void stdin_ready (int revents, void *arg)
2215	{	2738	{
2216	if (revents & EV_TIMEOUT)
2217	/* doh, nothing entered */;
2218	else if (revents & EV_READ)	2739	if (revents & EV_READ)
2219	/* stdin might have data for us, joy! */;	2740	/* stdin might have data for us, joy! */;
		2741	else if (revents & EV_TIMEOUT)
		2742	/* doh, nothing entered */;
2220	}	2743	}
2221		2744
2222	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2745	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2223		2746
2224	=item ev_feed_event (ev_loop *, watcher *, int revents)	2747	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2225		2748
2226	Feeds the given event set into the event loop, as if the specified event	2749	Feeds the given event set into the event loop, as if the specified event
2227	had happened for the specified watcher (which must be a pointer to an	2750	had happened for the specified watcher (which must be a pointer to an
2228	initialised but not necessarily started event watcher).	2751	initialised but not necessarily started event watcher).
2229		2752
2230	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2753	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2231		2754
2232	Feed an event on the given fd, as if a file descriptor backend detected	2755	Feed an event on the given fd, as if a file descriptor backend detected
2233	the given events it.	2756	the given events it.
2234		2757
2235	=item ev_feed_signal_event (ev_loop *loop, int signum)	2758	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2236		2759
2237	Feed an event as if the given signal occured (C<loop> must be the default	2760	Feed an event as if the given signal occurred (C<loop> must be the default
2238	loop!).	2761	loop!).
2239		2762
2240	=back	2763	=back
2241		2764
2242		2765
…		…
2258		2781
2259	=item * Priorities are not currently supported. Initialising priorities	2782	=item * Priorities are not currently supported. Initialising priorities
2260	will fail and all watchers will have the same priority, even though there	2783	will fail and all watchers will have the same priority, even though there
2261	is an ev_pri field.	2784	is an ev_pri field.
2262		2785
		2786	=item * In libevent, the last base created gets the signals, in libev, the
		2787	first base created (== the default loop) gets the signals.
		2788
2263	=item * Other members are not supported.	2789	=item * Other members are not supported.
2264		2790
2265	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2791	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2266	to use the libev header file and library.	2792	to use the libev header file and library.
2267		2793
2268	=back	2794	=back
2269		2795
2270	=head1 C++ SUPPORT	2796	=head1 C++ SUPPORT
2271		2797
2272	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2798	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2273	you to use some convinience methods to start/stop watchers and also change	2799	you to use some convenience methods to start/stop watchers and also change
2274	the callback model to a model using method callbacks on objects.	2800	the callback model to a model using method callbacks on objects.
2275		2801
2276	To use it,	2802	To use it,
2277		2803
2278	#include <ev++.h>	2804	#include <ev++.h>
2279		2805
2280	This automatically includes F<ev.h> and puts all of its definitions (many	2806	This automatically includes F<ev.h> and puts all of its definitions (many
2281	of them macros) into the global namespace. All C++ specific things are	2807	of them macros) into the global namespace. All C++ specific things are
2282	put into the C<ev> namespace. It should support all the same embedding	2808	put into the C<ev> namespace. It should support all the same embedding
2283	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2809	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2350	your compiler is good :), then the method will be fully inlined into the	2876	your compiler is good :), then the method will be fully inlined into the
2351	thunking function, making it as fast as a direct C callback.	2877	thunking function, making it as fast as a direct C callback.
2352		2878
2353	Example: simple class declaration and watcher initialisation	2879	Example: simple class declaration and watcher initialisation
2354		2880
2355	struct myclass	2881	struct myclass
2356	{	2882	{
2357	void io_cb (ev::io &w, int revents) { }	2883	void io_cb (ev::io &w, int revents) { }
2358	}	2884	}
2359		2885
2360	myclass obj;	2886	myclass obj;
2361	ev::io iow;	2887	ev::io iow;
2362	iow.set <myclass, &myclass::io_cb> (&obj);	2888	iow.set <myclass, &myclass::io_cb> (&obj);
2363		2889
2364	=item w->set<function> (void *data = 0)	2890	=item w->set<function> (void *data = 0)
2365		2891
2366	Also sets a callback, but uses a static method or plain function as	2892	Also sets a callback, but uses a static method or plain function as
2367	callback. The optional C<data> argument will be stored in the watcher's	2893	callback. The optional C<data> argument will be stored in the watcher's
…		…
2369		2895
2370	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2896	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2371		2897
2372	See the method-C<set> above for more details.	2898	See the method-C<set> above for more details.
2373		2899
2374	Example:	2900	Example: Use a plain function as callback.
2375		2901
2376	static void io_cb (ev::io &w, int revents) { }	2902	static void io_cb (ev::io &w, int revents) { }
2377	iow.set <io_cb> ();	2903	iow.set <io_cb> ();
2378		2904
2379	=item w->set (struct ev_loop *)	2905	=item w->set (struct ev_loop *)
2380		2906
2381	Associates a different C<struct ev_loop> with this watcher. You can only	2907	Associates a different C<struct ev_loop> with this watcher. You can only
2382	do this when the watcher is inactive (and not pending either).	2908	do this when the watcher is inactive (and not pending either).
2383		2909
2384	=item w->set ([args])	2910	=item w->set ([arguments])
2385		2911
2386	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2912	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2387	called at least once. Unlike the C counterpart, an active watcher gets	2913	called at least once. Unlike the C counterpart, an active watcher gets
2388	automatically stopped and restarted when reconfiguring it with this	2914	automatically stopped and restarted when reconfiguring it with this
2389	method.	2915	method.
2390		2916
2391	=item w->start ()	2917	=item w->start ()
…		…
2415	=back	2941	=back
2416		2942
2417	Example: Define a class with an IO and idle watcher, start one of them in	2943	Example: Define a class with an IO and idle watcher, start one of them in
2418	the constructor.	2944	the constructor.
2419		2945
2420	class myclass	2946	class myclass
2421	{	2947	{
2422	ev::io io; void io_cb (ev::io &w, int revents);	2948	ev::io io ; void io_cb (ev::io &w, int revents);
2423	ev:idle idle void idle_cb (ev::idle &w, int revents);	2949	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2424		2950
2425	myclass (int fd)	2951	myclass (int fd)
2426	{	2952	{
2427	io .set <myclass, &myclass::io_cb > (this);	2953	io .set <myclass, &myclass::io_cb > (this);
2428	idle.set <myclass, &myclass::idle_cb> (this);	2954	idle.set <myclass, &myclass::idle_cb> (this);
2429		2955
2430	io.start (fd, ev::READ);	2956	io.start (fd, ev::READ);
2431	}	2957	}
2432	};	2958	};
		2959
		2960
		2961	=head1 OTHER LANGUAGE BINDINGS
		2962
		2963	Libev does not offer other language bindings itself, but bindings for a
		2964	number of languages exist in the form of third-party packages. If you know
		2965	any interesting language binding in addition to the ones listed here, drop
		2966	me a note.
		2967
		2968	=over 4
		2969
		2970	=item Perl
		2971
		2972	The EV module implements the full libev API and is actually used to test
		2973	libev. EV is developed together with libev. Apart from the EV core module,
		2974	there are additional modules that implement libev-compatible interfaces
		2975	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2976	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2977	and C<EV::Glib>).
		2978
		2979	It can be found and installed via CPAN, its homepage is at
		2980	L<http://software.schmorp.de/pkg/EV>.
		2981
		2982	=item Python
		2983
		2984	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2985	seems to be quite complete and well-documented. Note, however, that the
		2986	patch they require for libev is outright dangerous as it breaks the ABI
		2987	for everybody else, and therefore, should never be applied in an installed
		2988	libev (if python requires an incompatible ABI then it needs to embed
		2989	libev).
		2990
		2991	=item Ruby
		2992
		2993	Tony Arcieri has written a ruby extension that offers access to a subset
		2994	of the libev API and adds file handle abstractions, asynchronous DNS and
		2995	more on top of it. It can be found via gem servers. Its homepage is at
		2996	L<http://rev.rubyforge.org/>.
		2997
		2998	=item D
		2999
		3000	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		3001	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3002
		3003	=item Ocaml
		3004
		3005	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3006	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3007
		3008	=back
2433		3009
2434		3010
2435	=head1 MACRO MAGIC	3011	=head1 MACRO MAGIC
2436		3012
2437	Libev can be compiled with a variety of options, the most fundamantal	3013	Libev can be compiled with a variety of options, the most fundamental
2438	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3014	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2439	functions and callbacks have an initial C<struct ev_loop *> argument.	3015	functions and callbacks have an initial C<struct ev_loop *> argument.
2440		3016
2441	To make it easier to write programs that cope with either variant, the	3017	To make it easier to write programs that cope with either variant, the
2442	following macros are defined:	3018	following macros are defined:
…		…
2447		3023
2448	This provides the loop I<argument> for functions, if one is required ("ev	3024	This provides the loop I<argument> for functions, if one is required ("ev
2449	loop argument"). The C<EV_A> form is used when this is the sole argument,	3025	loop argument"). The C<EV_A> form is used when this is the sole argument,
2450	C<EV_A_> is used when other arguments are following. Example:	3026	C<EV_A_> is used when other arguments are following. Example:
2451		3027
2452	ev_unref (EV_A);	3028	ev_unref (EV_A);
2453	ev_timer_add (EV_A_ watcher);	3029	ev_timer_add (EV_A_ watcher);
2454	ev_loop (EV_A_ 0);	3030	ev_loop (EV_A_ 0);
2455		3031
2456	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3032	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2457	which is often provided by the following macro.	3033	which is often provided by the following macro.
2458		3034
2459	=item C<EV_P>, C<EV_P_>	3035	=item C<EV_P>, C<EV_P_>
2460		3036
2461	This provides the loop I<parameter> for functions, if one is required ("ev	3037	This provides the loop I<parameter> for functions, if one is required ("ev
2462	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3038	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2463	C<EV_P_> is used when other parameters are following. Example:	3039	C<EV_P_> is used when other parameters are following. Example:
2464		3040
2465	// this is how ev_unref is being declared	3041	// this is how ev_unref is being declared
2466	static void ev_unref (EV_P);	3042	static void ev_unref (EV_P);
2467		3043
2468	// this is how you can declare your typical callback	3044	// this is how you can declare your typical callback
2469	static void cb (EV_P_ ev_timer *w, int revents)	3045	static void cb (EV_P_ ev_timer *w, int revents)
2470		3046
2471	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3047	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2472	suitable for use with C<EV_A>.	3048	suitable for use with C<EV_A>.
2473		3049
2474	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3050	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2475		3051
2476	Similar to the other two macros, this gives you the value of the default	3052	Similar to the other two macros, this gives you the value of the default
2477	loop, if multiple loops are supported ("ev loop default").	3053	loop, if multiple loops are supported ("ev loop default").
		3054
		3055	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3056
		3057	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3058	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3059	is undefined when the default loop has not been initialised by a previous
		3060	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3061
		3062	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3063	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2478		3064
2479	=back	3065	=back
2480		3066
2481	Example: Declare and initialise a check watcher, utilising the above	3067	Example: Declare and initialise a check watcher, utilising the above
2482	macros so it will work regardless of whether multiple loops are supported	3068	macros so it will work regardless of whether multiple loops are supported
2483	or not.	3069	or not.
2484		3070
2485	static void	3071	static void
2486	check_cb (EV_P_ ev_timer *w, int revents)	3072	check_cb (EV_P_ ev_timer *w, int revents)
2487	{	3073	{
2488	ev_check_stop (EV_A_ w);	3074	ev_check_stop (EV_A_ w);
2489	}	3075	}
2490		3076
2491	ev_check check;	3077	ev_check check;
2492	ev_check_init (&check, check_cb);	3078	ev_check_init (&check, check_cb);
2493	ev_check_start (EV_DEFAULT_ &check);	3079	ev_check_start (EV_DEFAULT_ &check);
2494	ev_loop (EV_DEFAULT_ 0);	3080	ev_loop (EV_DEFAULT_ 0);
2495		3081
2496	=head1 EMBEDDING	3082	=head1 EMBEDDING
2497		3083
2498	Libev can (and often is) directly embedded into host	3084	Libev can (and often is) directly embedded into host
2499	applications. Examples of applications that embed it include the Deliantra	3085	applications. Examples of applications that embed it include the Deliantra
…		…
2506	libev somewhere in your source tree).	3092	libev somewhere in your source tree).
2507		3093
2508	=head2 FILESETS	3094	=head2 FILESETS
2509		3095
2510	Depending on what features you need you need to include one or more sets of files	3096	Depending on what features you need you need to include one or more sets of files
2511	in your app.	3097	in your application.
2512		3098
2513	=head3 CORE EVENT LOOP	3099	=head3 CORE EVENT LOOP
2514		3100
2515	To include only the libev core (all the C<ev_*> functions), with manual	3101	To include only the libev core (all the C<ev_*> functions), with manual
2516	configuration (no autoconf):	3102	configuration (no autoconf):
2517		3103
2518	#define EV_STANDALONE 1	3104	#define EV_STANDALONE 1
2519	#include "ev.c"	3105	#include "ev.c"
2520		3106
2521	This will automatically include F<ev.h>, too, and should be done in a	3107	This will automatically include F<ev.h>, too, and should be done in a
2522	single C source file only to provide the function implementations. To use	3108	single C source file only to provide the function implementations. To use
2523	it, do the same for F<ev.h> in all files wishing to use this API (best	3109	it, do the same for F<ev.h> in all files wishing to use this API (best
2524	done by writing a wrapper around F<ev.h> that you can include instead and	3110	done by writing a wrapper around F<ev.h> that you can include instead and
2525	where you can put other configuration options):	3111	where you can put other configuration options):
2526		3112
2527	#define EV_STANDALONE 1	3113	#define EV_STANDALONE 1
2528	#include "ev.h"	3114	#include "ev.h"
2529		3115
2530	Both header files and implementation files can be compiled with a C++	3116	Both header files and implementation files can be compiled with a C++
2531	compiler (at least, thats a stated goal, and breakage will be treated	3117	compiler (at least, that's a stated goal, and breakage will be treated
2532	as a bug).	3118	as a bug).
2533		3119
2534	You need the following files in your source tree, or in a directory	3120	You need the following files in your source tree, or in a directory
2535	in your include path (e.g. in libev/ when using -Ilibev):	3121	in your include path (e.g. in libev/ when using -Ilibev):
2536		3122
2537	ev.h	3123	ev.h
2538	ev.c	3124	ev.c
2539	ev_vars.h	3125	ev_vars.h
2540	ev_wrap.h	3126	ev_wrap.h
2541		3127
2542	ev_win32.c required on win32 platforms only	3128	ev_win32.c required on win32 platforms only
2543		3129
2544	ev_select.c only when select backend is enabled (which is enabled by default)	3130	ev_select.c only when select backend is enabled (which is enabled by default)
2545	ev_poll.c only when poll backend is enabled (disabled by default)	3131	ev_poll.c only when poll backend is enabled (disabled by default)
2546	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3132	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2547	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3133	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2548	ev_port.c only when the solaris port backend is enabled (disabled by default)	3134	ev_port.c only when the solaris port backend is enabled (disabled by default)
2549		3135
2550	F<ev.c> includes the backend files directly when enabled, so you only need	3136	F<ev.c> includes the backend files directly when enabled, so you only need
2551	to compile this single file.	3137	to compile this single file.
2552		3138
2553	=head3 LIBEVENT COMPATIBILITY API	3139	=head3 LIBEVENT COMPATIBILITY API
2554		3140
2555	To include the libevent compatibility API, also include:	3141	To include the libevent compatibility API, also include:
2556		3142
2557	#include "event.c"	3143	#include "event.c"
2558		3144
2559	in the file including F<ev.c>, and:	3145	in the file including F<ev.c>, and:
2560		3146
2561	#include "event.h"	3147	#include "event.h"
2562		3148
2563	in the files that want to use the libevent API. This also includes F<ev.h>.	3149	in the files that want to use the libevent API. This also includes F<ev.h>.
2564		3150
2565	You need the following additional files for this:	3151	You need the following additional files for this:
2566		3152
2567	event.h	3153	event.h
2568	event.c	3154	event.c
2569		3155
2570	=head3 AUTOCONF SUPPORT	3156	=head3 AUTOCONF SUPPORT
2571		3157
2572	Instead of using C<EV_STANDALONE=1> and providing your config in	3158	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2573	whatever way you want, you can also C<m4_include([libev.m4])> in your	3159	whatever way you want, you can also C<m4_include([libev.m4])> in your
2574	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3160	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2575	include F<config.h> and configure itself accordingly.	3161	include F<config.h> and configure itself accordingly.
2576		3162
2577	For this of course you need the m4 file:	3163	For this of course you need the m4 file:
2578		3164
2579	libev.m4	3165	libev.m4
2580		3166
2581	=head2 PREPROCESSOR SYMBOLS/MACROS	3167	=head2 PREPROCESSOR SYMBOLS/MACROS
2582		3168
2583	Libev can be configured via a variety of preprocessor symbols you have to define	3169	Libev can be configured via a variety of preprocessor symbols you have to
2584	before including any of its files. The default is not to build for multiplicity	3170	define before including any of its files. The default in the absence of
2585	and only include the select backend.	3171	autoconf is documented for every option.
2586		3172
2587	=over 4	3173	=over 4
2588		3174
2589	=item EV_STANDALONE	3175	=item EV_STANDALONE
2590		3176
…		…
2595	F<event.h> that are not directly supported by the libev core alone.	3181	F<event.h> that are not directly supported by the libev core alone.
2596		3182
2597	=item EV_USE_MONOTONIC	3183	=item EV_USE_MONOTONIC
2598		3184
2599	If defined to be C<1>, libev will try to detect the availability of the	3185	If defined to be C<1>, libev will try to detect the availability of the
2600	monotonic clock option at both compiletime and runtime. Otherwise no use	3186	monotonic clock option at both compile time and runtime. Otherwise no use
2601	of the monotonic clock option will be attempted. If you enable this, you	3187	of the monotonic clock option will be attempted. If you enable this, you
2602	usually have to link against librt or something similar. Enabling it when	3188	usually have to link against librt or something similar. Enabling it when
2603	the functionality isn't available is safe, though, although you have	3189	the functionality isn't available is safe, though, although you have
2604	to make sure you link against any libraries where the C<clock_gettime>	3190	to make sure you link against any libraries where the C<clock_gettime>
2605	function is hiding in (often F<-lrt>).	3191	function is hiding in (often F<-lrt>).
2606		3192
2607	=item EV_USE_REALTIME	3193	=item EV_USE_REALTIME
2608		3194
2609	If defined to be C<1>, libev will try to detect the availability of the	3195	If defined to be C<1>, libev will try to detect the availability of the
2610	realtime clock option at compiletime (and assume its availability at	3196	real-time clock option at compile time (and assume its availability at
2611	runtime if successful). Otherwise no use of the realtime clock option will	3197	runtime if successful). Otherwise no use of the real-time clock option will
2612	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3198	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2613	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3199	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2614	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3200	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2615		3201
2616	=item EV_USE_NANOSLEEP	3202	=item EV_USE_NANOSLEEP
2617		3203
2618	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3204	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2619	and will use it for delays. Otherwise it will use C<select ()>.	3205	and will use it for delays. Otherwise it will use C<select ()>.
2620		3206
		3207	=item EV_USE_EVENTFD
		3208
		3209	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3210	available and will probe for kernel support at runtime. This will improve
		3211	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3212	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3213	2.7 or newer, otherwise disabled.
		3214
2621	=item EV_USE_SELECT	3215	=item EV_USE_SELECT
2622		3216
2623	If undefined or defined to be C<1>, libev will compile in support for the	3217	If undefined or defined to be C<1>, libev will compile in support for the
2624	C<select>(2) backend. No attempt at autodetection will be done: if no	3218	C<select>(2) backend. No attempt at auto-detection will be done: if no
2625	other method takes over, select will be it. Otherwise the select backend	3219	other method takes over, select will be it. Otherwise the select backend
2626	will not be compiled in.	3220	will not be compiled in.
2627		3221
2628	=item EV_SELECT_USE_FD_SET	3222	=item EV_SELECT_USE_FD_SET
2629		3223
2630	If defined to C<1>, then the select backend will use the system C<fd_set>	3224	If defined to C<1>, then the select backend will use the system C<fd_set>
2631	structure. This is useful if libev doesn't compile due to a missing	3225	structure. This is useful if libev doesn't compile due to a missing
2632	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3226	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2633	exotic systems. This usually limits the range of file descriptors to some	3227	exotic systems. This usually limits the range of file descriptors to some
2634	low limit such as 1024 or might have other limitations (winsocket only	3228	low limit such as 1024 or might have other limitations (winsocket only
2635	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3229	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2636	influence the size of the C<fd_set> used.	3230	influence the size of the C<fd_set> used.
2637		3231
…		…
2661		3255
2662	=item EV_USE_EPOLL	3256	=item EV_USE_EPOLL
2663		3257
2664	If defined to be C<1>, libev will compile in support for the Linux	3258	If defined to be C<1>, libev will compile in support for the Linux
2665	C<epoll>(7) backend. Its availability will be detected at runtime,	3259	C<epoll>(7) backend. Its availability will be detected at runtime,
2666	otherwise another method will be used as fallback. This is the	3260	otherwise another method will be used as fallback. This is the preferred
2667	preferred backend for GNU/Linux systems.	3261	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3262	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2668		3263
2669	=item EV_USE_KQUEUE	3264	=item EV_USE_KQUEUE
2670		3265
2671	If defined to be C<1>, libev will compile in support for the BSD style	3266	If defined to be C<1>, libev will compile in support for the BSD style
2672	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3267	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2685	otherwise another method will be used as fallback. This is the preferred	3280	otherwise another method will be used as fallback. This is the preferred
2686	backend for Solaris 10 systems.	3281	backend for Solaris 10 systems.
2687		3282
2688	=item EV_USE_DEVPOLL	3283	=item EV_USE_DEVPOLL
2689		3284
2690	reserved for future expansion, works like the USE symbols above.	3285	Reserved for future expansion, works like the USE symbols above.
2691		3286
2692	=item EV_USE_INOTIFY	3287	=item EV_USE_INOTIFY
2693		3288
2694	If defined to be C<1>, libev will compile in support for the Linux inotify	3289	If defined to be C<1>, libev will compile in support for the Linux inotify
2695	interface to speed up C<ev_stat> watchers. Its actual availability will	3290	interface to speed up C<ev_stat> watchers. Its actual availability will
2696	be detected at runtime.	3291	be detected at runtime. If undefined, it will be enabled if the headers
		3292	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2697		3293
2698	=item EV_ATOMIC_T	3294	=item EV_ATOMIC_T
2699		3295
2700	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3296	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2701	access is atomic with respect to other threads or signal contexts. No such	3297	access is atomic with respect to other threads or signal contexts. No such
2702	type is easily found in the C language, so you can provide your own type	3298	type is easily found in the C language, so you can provide your own type
2703	that you know is safe for your purposes. It is used both for signal handler "locking"	3299	that you know is safe for your purposes. It is used both for signal handler "locking"
2704	as well as for signal and thread safety in C<ev_async> watchers.	3300	as well as for signal and thread safety in C<ev_async> watchers.
2705		3301
2706	In the absense of this define, libev will use C<sig_atomic_t volatile>	3302	In the absence of this define, libev will use C<sig_atomic_t volatile>
2707	(from F<signal.h>), which is usually good enough on most platforms.	3303	(from F<signal.h>), which is usually good enough on most platforms.
2708		3304
2709	=item EV_H	3305	=item EV_H
2710		3306
2711	The name of the F<ev.h> header file used to include it. The default if	3307	The name of the F<ev.h> header file used to include it. The default if
…		…
2750	When doing priority-based operations, libev usually has to linearly search	3346	When doing priority-based operations, libev usually has to linearly search
2751	all the priorities, so having many of them (hundreds) uses a lot of space	3347	all the priorities, so having many of them (hundreds) uses a lot of space
2752	and time, so using the defaults of five priorities (-2 .. +2) is usually	3348	and time, so using the defaults of five priorities (-2 .. +2) is usually
2753	fine.	3349	fine.
2754		3350
2755	If your embedding app does not need any priorities, defining these both to	3351	If your embedding application does not need any priorities, defining these
2756	C<0> will save some memory and cpu.	3352	both to C<0> will save some memory and CPU.
2757		3353
2758	=item EV_PERIODIC_ENABLE	3354	=item EV_PERIODIC_ENABLE
2759		3355
2760	If undefined or defined to be C<1>, then periodic timers are supported. If	3356	If undefined or defined to be C<1>, then periodic timers are supported. If
2761	defined to be C<0>, then they are not. Disabling them saves a few kB of	3357	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2768	code.	3364	code.
2769		3365
2770	=item EV_EMBED_ENABLE	3366	=item EV_EMBED_ENABLE
2771		3367
2772	If undefined or defined to be C<1>, then embed watchers are supported. If	3368	If undefined or defined to be C<1>, then embed watchers are supported. If
2773	defined to be C<0>, then they are not.	3369	defined to be C<0>, then they are not. Embed watchers rely on most other
		3370	watcher types, which therefore must not be disabled.
2774		3371
2775	=item EV_STAT_ENABLE	3372	=item EV_STAT_ENABLE
2776		3373
2777	If undefined or defined to be C<1>, then stat watchers are supported. If	3374	If undefined or defined to be C<1>, then stat watchers are supported. If
2778	defined to be C<0>, then they are not.	3375	defined to be C<0>, then they are not.
…		…
2788	defined to be C<0>, then they are not.	3385	defined to be C<0>, then they are not.
2789		3386
2790	=item EV_MINIMAL	3387	=item EV_MINIMAL
2791		3388
2792	If you need to shave off some kilobytes of code at the expense of some	3389	If you need to shave off some kilobytes of code at the expense of some
2793	speed, define this symbol to C<1>. Currently only used for gcc to override	3390	speed, define this symbol to C<1>. Currently this is used to override some
2794	some inlining decisions, saves roughly 30% codesize of amd64.	3391	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3392	much smaller 2-heap for timer management over the default 4-heap.
2795		3393
2796	=item EV_PID_HASHSIZE	3394	=item EV_PID_HASHSIZE
2797		3395
2798	C<ev_child> watchers use a small hash table to distribute workload by	3396	C<ev_child> watchers use a small hash table to distribute workload by
2799	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3397	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2806	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3404	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2807	usually more than enough. If you need to manage thousands of C<ev_stat>	3405	usually more than enough. If you need to manage thousands of C<ev_stat>
2808	watchers you might want to increase this value (I<must> be a power of	3406	watchers you might want to increase this value (I<must> be a power of
2809	two).	3407	two).
2810		3408
		3409	=item EV_USE_4HEAP
		3410
		3411	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3412	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3413	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3414	faster performance with many (thousands) of watchers.
		3415
		3416	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3417	(disabled).
		3418
		3419	=item EV_HEAP_CACHE_AT
		3420
		3421	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3422	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3423	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3424	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3425	but avoids random read accesses on heap changes. This improves performance
		3426	noticeably with many (hundreds) of watchers.
		3427
		3428	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3429	(disabled).
		3430
		3431	=item EV_VERIFY
		3432
		3433	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3434	be done: If set to C<0>, no internal verification code will be compiled
		3435	in. If set to C<1>, then verification code will be compiled in, but not
		3436	called. If set to C<2>, then the internal verification code will be
		3437	called once per loop, which can slow down libev. If set to C<3>, then the
		3438	verification code will be called very frequently, which will slow down
		3439	libev considerably.
		3440
		3441	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3442	C<0>.
		3443
2811	=item EV_COMMON	3444	=item EV_COMMON
2812		3445
2813	By default, all watchers have a C<void *data> member. By redefining	3446	By default, all watchers have a C<void *data> member. By redefining
2814	this macro to a something else you can include more and other types of	3447	this macro to a something else you can include more and other types of
2815	members. You have to define it each time you include one of the files,	3448	members. You have to define it each time you include one of the files,
2816	though, and it must be identical each time.	3449	though, and it must be identical each time.
2817		3450
2818	For example, the perl EV module uses something like this:	3451	For example, the perl EV module uses something like this:
2819		3452
2820	#define EV_COMMON \	3453	#define EV_COMMON \
2821	SV *self; /* contains this struct */ \	3454	SV *self; /* contains this struct */ \
2822	SV *cb_sv, *fh /* note no trailing ";" */	3455	SV *cb_sv, *fh /* note no trailing ";" */
2823		3456
2824	=item EV_CB_DECLARE (type)	3457	=item EV_CB_DECLARE (type)
2825		3458
2826	=item EV_CB_INVOKE (watcher, revents)	3459	=item EV_CB_INVOKE (watcher, revents)
2827		3460
…		…
2832	definition and a statement, respectively. See the F<ev.h> header file for	3465	definition and a statement, respectively. See the F<ev.h> header file for
2833	their default definitions. One possible use for overriding these is to	3466	their default definitions. One possible use for overriding these is to
2834	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3467	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2835	method calls instead of plain function calls in C++.	3468	method calls instead of plain function calls in C++.
2836		3469
		3470	=back
		3471
2837	=head2 EXPORTED API SYMBOLS	3472	=head2 EXPORTED API SYMBOLS
2838		3473
2839	If you need to re-export the API (e.g. via a dll) and you need a list of	3474	If you need to re-export the API (e.g. via a DLL) and you need a list of
2840	exported symbols, you can use the provided F<Symbol.*> files which list	3475	exported symbols, you can use the provided F<Symbol.*> files which list
2841	all public symbols, one per line:	3476	all public symbols, one per line:
2842		3477
2843	Symbols.ev for libev proper	3478	Symbols.ev for libev proper
2844	Symbols.event for the libevent emulation	3479	Symbols.event for the libevent emulation
2845		3480
2846	This can also be used to rename all public symbols to avoid clashes with	3481	This can also be used to rename all public symbols to avoid clashes with
2847	multiple versions of libev linked together (which is obviously bad in	3482	multiple versions of libev linked together (which is obviously bad in
2848	itself, but sometimes it is inconvinient to avoid this).	3483	itself, but sometimes it is inconvenient to avoid this).
2849		3484
2850	A sed command like this will create wrapper C<#define>'s that you need to	3485	A sed command like this will create wrapper C<#define>'s that you need to
2851	include before including F<ev.h>:	3486	include before including F<ev.h>:
2852		3487
2853	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3488	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2870	file.	3505	file.
2871		3506
2872	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3507	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2873	that everybody includes and which overrides some configure choices:	3508	that everybody includes and which overrides some configure choices:
2874		3509
2875	#define EV_MINIMAL 1	3510	#define EV_MINIMAL 1
2876	#define EV_USE_POLL 0	3511	#define EV_USE_POLL 0
2877	#define EV_MULTIPLICITY 0	3512	#define EV_MULTIPLICITY 0
2878	#define EV_PERIODIC_ENABLE 0	3513	#define EV_PERIODIC_ENABLE 0
2879	#define EV_STAT_ENABLE 0	3514	#define EV_STAT_ENABLE 0
2880	#define EV_FORK_ENABLE 0	3515	#define EV_FORK_ENABLE 0
2881	#define EV_CONFIG_H <config.h>	3516	#define EV_CONFIG_H <config.h>
2882	#define EV_MINPRI 0	3517	#define EV_MINPRI 0
2883	#define EV_MAXPRI 0	3518	#define EV_MAXPRI 0
2884		3519
2885	#include "ev++.h"	3520	#include "ev++.h"
2886		3521
2887	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3522	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2888		3523
2889	#include "ev_cpp.h"	3524	#include "ev_cpp.h"
2890	#include "ev.c"	3525	#include "ev.c"
2891		3526
		3527	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2892		3528
2893	=head1 COMPLEXITIES	3529	=head2 THREADS AND COROUTINES
2894		3530
2895	In this section the complexities of (many of) the algorithms used inside	3531	=head3 THREADS
2896	libev will be explained. For complexity discussions about backends see the
2897	documentation for C<ev_default_init>.
2898		3532
2899	All of the following are about amortised time: If an array needs to be	3533	All libev functions are reentrant and thread-safe unless explicitly
2900	extended, libev needs to realloc and move the whole array, but this	3534	documented otherwise, but libev implements no locking itself. This means
2901	happens asymptotically never with higher number of elements, so O(1) might	3535	that you can use as many loops as you want in parallel, as long as there
2902	mean it might do a lengthy realloc operation in rare cases, but on average	3536	are no concurrent calls into any libev function with the same loop
2903	it is much faster and asymptotically approaches constant time.	3537	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3538	of course): libev guarantees that different event loops share no data
		3539	structures that need any locking.
		3540
		3541	Or to put it differently: calls with different loop parameters can be done
		3542	concurrently from multiple threads, calls with the same loop parameter
		3543	must be done serially (but can be done from different threads, as long as
		3544	only one thread ever is inside a call at any point in time, e.g. by using
		3545	a mutex per loop).
		3546
		3547	Specifically to support threads (and signal handlers), libev implements
		3548	so-called C<ev_async> watchers, which allow some limited form of
		3549	concurrency on the same event loop, namely waking it up "from the
		3550	outside".
		3551
		3552	If you want to know which design (one loop, locking, or multiple loops
		3553	without or something else still) is best for your problem, then I cannot
		3554	help you, but here is some generic advice:
2904		3555
2905	=over 4	3556	=over 4
2906		3557
2907	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3558	=item * most applications have a main thread: use the default libev loop
		3559	in that thread, or create a separate thread running only the default loop.
2908		3560
2909	This means that, when you have a watcher that triggers in one hour and	3561	This helps integrating other libraries or software modules that use libev
2910	there are 100 watchers that would trigger before that then inserting will	3562	themselves and don't care/know about threading.
2911	have to skip roughly seven (C<ld 100>) of these watchers.
2912		3563
2913	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3564	=item * one loop per thread is usually a good model.
2914		3565
2915	That means that changing a timer costs less than removing/adding them	3566	Doing this is almost never wrong, sometimes a better-performance model
2916	as only the relative motion in the event queue has to be paid for.	3567	exists, but it is always a good start.
2917		3568
2918	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3569	=item * other models exist, such as the leader/follower pattern, where one
		3570	loop is handed through multiple threads in a kind of round-robin fashion.
2919		3571
2920	These just add the watcher into an array or at the head of a list.	3572	Choosing a model is hard - look around, learn, know that usually you can do
		3573	better than you currently do :-)
2921		3574
2922	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3575	=item * often you need to talk to some other thread which blocks in the
		3576	event loop.
2923		3577
2924	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3578	C<ev_async> watchers can be used to wake them up from other threads safely
		3579	(or from signal contexts...).
2925		3580
2926	These watchers are stored in lists then need to be walked to find the	3581	An example use would be to communicate signals or other events that only
2927	correct watcher to remove. The lists are usually short (you don't usually	3582	work in the default loop by registering the signal watcher with the
2928	have many watchers waiting for the same fd or signal).	3583	default loop and triggering an C<ev_async> watcher from the default loop
2929		3584	watcher callback into the event loop interested in the signal.
2930	=item Finding the next timer in each loop iteration: O(1)
2931
2932	By virtue of using a binary heap, the next timer is always found at the
2933	beginning of the storage array.
2934
2935	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2936
2937	A change means an I/O watcher gets started or stopped, which requires
2938	libev to recalculate its status (and possibly tell the kernel, depending
2939	on backend and wether C<ev_io_set> was used).
2940
2941	=item Activating one watcher (putting it into the pending state): O(1)
2942
2943	=item Priority handling: O(number_of_priorities)
2944
2945	Priorities are implemented by allocating some space for each
2946	priority. When doing priority-based operations, libev usually has to
2947	linearly search all the priorities, but starting/stopping and activating
2948	watchers becomes O(1) w.r.t. priority handling.
2949
2950	=item Sending an ev_async: O(1)
2951
2952	=item Processing ev_async_send: O(number_of_async_watchers)
2953
2954	=item Processing signals: O(max_signal_number)
2955
2956	Sending involves a syscall I<iff> there were no other C<ev_async_send>
2957	calls in the current loop iteration. Checking for async and signal events
2958	involves iterating over all running async watchers or all signal numbers.
2959		3585
2960	=back	3586	=back
2961		3587
		3588	=head3 COROUTINES
2962		3589
2963	=head1 Win32 platform limitations and workarounds	3590	Libev is very accommodating to coroutines ("cooperative threads"):
		3591	libev fully supports nesting calls to its functions from different
		3592	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3593	different coroutines, and switch freely between both coroutines running the
		3594	loop, as long as you don't confuse yourself). The only exception is that
		3595	you must not do this from C<ev_periodic> reschedule callbacks.
		3596
		3597	Care has been taken to ensure that libev does not keep local state inside
		3598	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3599	they do not call any callbacks.
		3600
		3601	=head2 COMPILER WARNINGS
		3602
		3603	Depending on your compiler and compiler settings, you might get no or a
		3604	lot of warnings when compiling libev code. Some people are apparently
		3605	scared by this.
		3606
		3607	However, these are unavoidable for many reasons. For one, each compiler
		3608	has different warnings, and each user has different tastes regarding
		3609	warning options. "Warn-free" code therefore cannot be a goal except when
		3610	targeting a specific compiler and compiler-version.
		3611
		3612	Another reason is that some compiler warnings require elaborate
		3613	workarounds, or other changes to the code that make it less clear and less
		3614	maintainable.
		3615
		3616	And of course, some compiler warnings are just plain stupid, or simply
		3617	wrong (because they don't actually warn about the condition their message
		3618	seems to warn about). For example, certain older gcc versions had some
		3619	warnings that resulted an extreme number of false positives. These have
		3620	been fixed, but some people still insist on making code warn-free with
		3621	such buggy versions.
		3622
		3623	While libev is written to generate as few warnings as possible,
		3624	"warn-free" code is not a goal, and it is recommended not to build libev
		3625	with any compiler warnings enabled unless you are prepared to cope with
		3626	them (e.g. by ignoring them). Remember that warnings are just that:
		3627	warnings, not errors, or proof of bugs.
		3628
		3629
		3630	=head2 VALGRIND
		3631
		3632	Valgrind has a special section here because it is a popular tool that is
		3633	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3634
		3635	If you think you found a bug (memory leak, uninitialised data access etc.)
		3636	in libev, then check twice: If valgrind reports something like:
		3637
		3638	==2274== definitely lost: 0 bytes in 0 blocks.
		3639	==2274== possibly lost: 0 bytes in 0 blocks.
		3640	==2274== still reachable: 256 bytes in 1 blocks.
		3641
		3642	Then there is no memory leak, just as memory accounted to global variables
		3643	is not a memleak - the memory is still being referenced, and didn't leak.
		3644
		3645	Similarly, under some circumstances, valgrind might report kernel bugs
		3646	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3647	although an acceptable workaround has been found here), or it might be
		3648	confused.
		3649
		3650	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3651	make it into some kind of religion.
		3652
		3653	If you are unsure about something, feel free to contact the mailing list
		3654	with the full valgrind report and an explanation on why you think this
		3655	is a bug in libev (best check the archives, too :). However, don't be
		3656	annoyed when you get a brisk "this is no bug" answer and take the chance
		3657	of learning how to interpret valgrind properly.
		3658
		3659	If you need, for some reason, empty reports from valgrind for your project
		3660	I suggest using suppression lists.
		3661
		3662
		3663	=head1 PORTABILITY NOTES
		3664
		3665	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
2964		3666
2965	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3667	Win32 doesn't support any of the standards (e.g. POSIX) that libev
2966	requires, and its I/O model is fundamentally incompatible with the POSIX	3668	requires, and its I/O model is fundamentally incompatible with the POSIX
2967	model. Libev still offers limited functionality on this platform in	3669	model. Libev still offers limited functionality on this platform in
2968	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3670	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2969	descriptors. This only applies when using Win32 natively, not when using	3671	descriptors. This only applies when using Win32 natively, not when using
2970	e.g. cygwin.	3672	e.g. cygwin.
2971		3673
		3674	Lifting these limitations would basically require the full
		3675	re-implementation of the I/O system. If you are into these kinds of
		3676	things, then note that glib does exactly that for you in a very portable
		3677	way (note also that glib is the slowest event library known to man).
		3678
2972	There is no supported compilation method available on windows except	3679	There is no supported compilation method available on windows except
2973	embedding it into other applications.	3680	embedding it into other applications.
2974		3681
		3682	Not a libev limitation but worth mentioning: windows apparently doesn't
		3683	accept large writes: instead of resulting in a partial write, windows will
		3684	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3685	so make sure you only write small amounts into your sockets (less than a
		3686	megabyte seems safe, but this apparently depends on the amount of memory
		3687	available).
		3688
2975	Due to the many, low, and arbitrary limits on the win32 platform and the	3689	Due to the many, low, and arbitrary limits on the win32 platform and
2976	abysmal performance of winsockets, using a large number of sockets is not	3690	the abysmal performance of winsockets, using a large number of sockets
2977	recommended (and not reasonable). If your program needs to use more than	3691	is not recommended (and not reasonable). If your program needs to use
2978	a hundred or so sockets, then likely it needs to use a totally different	3692	more than a hundred or so sockets, then likely it needs to use a totally
2979	implementation for windows, as libev offers the POSIX model, which cannot	3693	different implementation for windows, as libev offers the POSIX readiness
2980	be implemented efficiently on windows (microsoft monopoly games).	3694	notification model, which cannot be implemented efficiently on windows
		3695	(Microsoft monopoly games).
		3696
		3697	A typical way to use libev under windows is to embed it (see the embedding
		3698	section for details) and use the following F<evwrap.h> header file instead
		3699	of F<ev.h>:
		3700
		3701	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3702	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3703
		3704	#include "ev.h"
		3705
		3706	And compile the following F<evwrap.c> file into your project (make sure
		3707	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3708
		3709	#include "evwrap.h"
		3710	#include "ev.c"
2981		3711
2982	=over 4	3712	=over 4
2983		3713
2984	=item The winsocket select function	3714	=item The winsocket select function
2985		3715
2986	The winsocket C<select> function doesn't follow POSIX in that it requires	3716	The winsocket C<select> function doesn't follow POSIX in that it
2987	socket I<handles> and not socket I<file descriptors>. This makes select	3717	requires socket I<handles> and not socket I<file descriptors> (it is
2988	very inefficient, and also requires a mapping from file descriptors	3718	also extremely buggy). This makes select very inefficient, and also
2989	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3719	requires a mapping from file descriptors to socket handles (the Microsoft
2990	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3720	C runtime provides the function C<_open_osfhandle> for this). See the
2991	symbols for more info.	3721	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3722	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
2992		3723
2993	The configuration for a "naked" win32 using the microsoft runtime	3724	The configuration for a "naked" win32 using the Microsoft runtime
2994	libraries and raw winsocket select is:	3725	libraries and raw winsocket select is:
2995		3726
2996	#define EV_USE_SELECT 1	3727	#define EV_USE_SELECT 1
2997	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3728	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2998		3729
2999	Note that winsockets handling of fd sets is O(n), so you can easily get a	3730	Note that winsockets handling of fd sets is O(n), so you can easily get a
3000	complexity in the O(n²) range when using win32.	3731	complexity in the O(n²) range when using win32.
3001		3732
3002	=item Limited number of file descriptors	3733	=item Limited number of file descriptors
3003		3734
3004	Windows has numerous arbitrary (and low) limits on things. Early versions	3735	Windows has numerous arbitrary (and low) limits on things.
3005	of winsocket's select only supported waiting for a max. of C<64> handles	3736
		3737	Early versions of winsocket's select only supported waiting for a maximum
3006	(probably owning to the fact that all windows kernels can only wait for	3738	of C<64> handles (probably owning to the fact that all windows kernels
3007	C<64> things at the same time internally; microsoft recommends spawning a	3739	can only wait for C<64> things at the same time internally; Microsoft
3008	chain of threads and wait for 63 handles and the previous thread in each).	3740	recommends spawning a chain of threads and wait for 63 handles and the
		3741	previous thread in each. Great).
3009		3742
3010	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3743	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3011	to some high number (e.g. C<2048>) before compiling the winsocket select	3744	to some high number (e.g. C<2048>) before compiling the winsocket select
3012	call (which might be in libev or elsewhere, for example, perl does its own	3745	call (which might be in libev or elsewhere, for example, perl does its own
3013	select emulation on windows).	3746	select emulation on windows).
3014		3747
3015	Another limit is the number of file descriptors in the microsoft runtime	3748	Another limit is the number of file descriptors in the Microsoft runtime
3016	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3749	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3017	or something like this inside microsoft). You can increase this by calling	3750	or something like this inside Microsoft). You can increase this by calling
3018	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3751	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3019	arbitrary limit), but is broken in many versions of the microsoft runtime	3752	arbitrary limit), but is broken in many versions of the Microsoft runtime
3020	libraries.	3753	libraries.
3021		3754
3022	This might get you to about C<512> or C<2048> sockets (depending on	3755	This might get you to about C<512> or C<2048> sockets (depending on
3023	windows version and/or the phase of the moon). To get more, you need to	3756	windows version and/or the phase of the moon). To get more, you need to
3024	wrap all I/O functions and provide your own fd management, but the cost of	3757	wrap all I/O functions and provide your own fd management, but the cost of
3025	calling select (O(n²)) will likely make this unworkable.	3758	calling select (O(n²)) will likely make this unworkable.
3026		3759
3027	=back	3760	=back
3028		3761
		3762	=head2 PORTABILITY REQUIREMENTS
		3763
		3764	In addition to a working ISO-C implementation and of course the
		3765	backend-specific APIs, libev relies on a few additional extensions:
		3766
		3767	=over 4
		3768
		3769	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3770	calling conventions regardless of C<ev_watcher_type *>.
		3771
		3772	Libev assumes not only that all watcher pointers have the same internal
		3773	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3774	assumes that the same (machine) code can be used to call any watcher
		3775	callback: The watcher callbacks have different type signatures, but libev
		3776	calls them using an C<ev_watcher *> internally.
		3777
		3778	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3779
		3780	The type C<sig_atomic_t volatile> (or whatever is defined as
		3781	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3782	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3783	believed to be sufficiently portable.
		3784
		3785	=item C<sigprocmask> must work in a threaded environment
		3786
		3787	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3788	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3789	pthread implementations will either allow C<sigprocmask> in the "main
		3790	thread" or will block signals process-wide, both behaviours would
		3791	be compatible with libev. Interaction between C<sigprocmask> and
		3792	C<pthread_sigmask> could complicate things, however.
		3793
		3794	The most portable way to handle signals is to block signals in all threads
		3795	except the initial one, and run the default loop in the initial thread as
		3796	well.
		3797
		3798	=item C<long> must be large enough for common memory allocation sizes
		3799
		3800	To improve portability and simplify its API, libev uses C<long> internally
		3801	instead of C<size_t> when allocating its data structures. On non-POSIX
		3802	systems (Microsoft...) this might be unexpectedly low, but is still at
		3803	least 31 bits everywhere, which is enough for hundreds of millions of
		3804	watchers.
		3805
		3806	=item C<double> must hold a time value in seconds with enough accuracy
		3807
		3808	The type C<double> is used to represent timestamps. It is required to
		3809	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3810	enough for at least into the year 4000. This requirement is fulfilled by
		3811	implementations implementing IEEE 754 (basically all existing ones).
		3812
		3813	=back
		3814
		3815	If you know of other additional requirements drop me a note.
		3816
		3817
		3818	=head1 ALGORITHMIC COMPLEXITIES
		3819
		3820	In this section the complexities of (many of) the algorithms used inside
		3821	libev will be documented. For complexity discussions about backends see
		3822	the documentation for C<ev_default_init>.
		3823
		3824	All of the following are about amortised time: If an array needs to be
		3825	extended, libev needs to realloc and move the whole array, but this
		3826	happens asymptotically rarer with higher number of elements, so O(1) might
		3827	mean that libev does a lengthy realloc operation in rare cases, but on
		3828	average it is much faster and asymptotically approaches constant time.
		3829
		3830	=over 4
		3831
		3832	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3833
		3834	This means that, when you have a watcher that triggers in one hour and
		3835	there are 100 watchers that would trigger before that, then inserting will
		3836	have to skip roughly seven (C<ld 100>) of these watchers.
		3837
		3838	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3839
		3840	That means that changing a timer costs less than removing/adding them,
		3841	as only the relative motion in the event queue has to be paid for.
		3842
		3843	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3844
		3845	These just add the watcher into an array or at the head of a list.
		3846
		3847	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3848
		3849	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3850
		3851	These watchers are stored in lists, so they need to be walked to find the
		3852	correct watcher to remove. The lists are usually short (you don't usually
		3853	have many watchers waiting for the same fd or signal: one is typical, two
		3854	is rare).
		3855
		3856	=item Finding the next timer in each loop iteration: O(1)
		3857
		3858	By virtue of using a binary or 4-heap, the next timer is always found at a
		3859	fixed position in the storage array.
		3860
		3861	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3862
		3863	A change means an I/O watcher gets started or stopped, which requires
		3864	libev to recalculate its status (and possibly tell the kernel, depending
		3865	on backend and whether C<ev_io_set> was used).
		3866
		3867	=item Activating one watcher (putting it into the pending state): O(1)
		3868
		3869	=item Priority handling: O(number_of_priorities)
		3870
		3871	Priorities are implemented by allocating some space for each
		3872	priority. When doing priority-based operations, libev usually has to
		3873	linearly search all the priorities, but starting/stopping and activating
		3874	watchers becomes O(1) with respect to priority handling.
		3875
		3876	=item Sending an ev_async: O(1)
		3877
		3878	=item Processing ev_async_send: O(number_of_async_watchers)
		3879
		3880	=item Processing signals: O(max_signal_number)
		3881
		3882	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3883	calls in the current loop iteration. Checking for async and signal events
		3884	involves iterating over all running async watchers or all signal numbers.
		3885
		3886	=back
		3887
3029		3888
3030	=head1 AUTHOR	3889	=head1 AUTHOR
3031		3890
3032	Marc Lehmann <libev@schmorp.de>.	3891	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3033		3892

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