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Revision 1.144 by root, Mon Apr 7 12:33:29 2008 UTC vs.
Revision 1.213 by root, Wed Nov 5 02:48:45 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	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// 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	49	// this one will watch for stdin to become readable
50	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);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	The newest version of this document is also available as an html-formatted
68	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
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		70
71	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
72	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
73	these event sources and provide your program with events.	73	these event sources and provide your program with events.
74		74
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	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
116	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
117	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
118	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
119	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
120	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
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	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
138	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
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
157	not a problem.	178	not a problem.
158		179
159	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
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	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_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	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
174	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
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	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
182	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
183	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
184	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
185	(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
186	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	215	recommended ones.
195		216
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	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
202	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
203	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
204	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
205	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.
206		230
207	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
208	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,
209	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.
210		234
211	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
212	retries).	236	retries (example requires a standards-compliant C<realloc>).
213		237
214	static void *	238	static void *
215	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
216	{	240	{
217	for (;;)	241	for (;;)
…		…
226	}	250	}
227		251
228	...	252	...
229	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
230		254
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		256
233	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
234	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
235	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
236	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
237	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
238	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
239	(such as abort).	263	(such as abort).
240		264
241	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.
…		…
252		276
253	=back	277	=back
254		278
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		280
257	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>
258	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>
259	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
260		288
261	=over 4	289	=over 4
262		290
263	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
264		292
…		…
270	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
271	function.	299	function.
272		300
273	Note that this function is I<not> thread-safe, so if you want to use it	301	Note that this function is I<not> thread-safe, so if you want to use it
274	from multiple threads, you have to lock (note also that this is unlikely,	302	from multiple threads, you have to lock (note also that this is unlikely,
275	as loops cannot bes hared easily between threads anyway).	303	as loops cannot be shared easily between threads anyway).
276		304
277	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
278	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
279	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
280	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
281	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
282	C<ev_default_init>.	310	C<ev_default_init>.
283		311
284	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
…		…
293	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
294	thing, believe me).	322	thing, believe me).
295		323
296	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
297		325
298	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
299	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
300	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
301	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
302	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
303	around bugs.	331	around bugs.
…		…
310		338
311	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,
312	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
313	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
314	GNU/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
315	without a syscall and thus I<very> fast, but my GNU/Linux system also has	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
316	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
317		345
318	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
319	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
320	flag.	348	flag.
321		349
322	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>
323	environment variable.	351	environment variable.
324		352
325	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
326		354
327	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
…		…
329	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
330	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
331	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.
332		360
333	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
334	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
335	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
336	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
337	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
338	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).
339		371
340	=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)
341		373
342	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
343	than select, but handles sparse fds better and has no artificial	375	than select, but handles sparse fds better and has no artificial
344	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
345	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,
346	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
347	performance tips.	379	performance tips.
348		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
349	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
350		385
351	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,
352	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
353	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),
354	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).
355	of shortcomings, such as silently dropping events in some hard-to-detect	390
356	cases and requiring a syscall per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
357	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.
358		407
359	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
360	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
361	(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
362	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
363	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
364		413	file descriptors.
365	Please note that epoll sometimes generates spurious notifications, so you
366	need to use non-blocking I/O or other means to avoid blocking when no data
367	(or space) is available.
368		414
369	Best performance from this backend is achieved by not unregistering all	415	Best performance from this backend is achieved by not unregistering all
370	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,
371	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.
372		422
		423	All this means that, in practise, C<EVBACKEND_SELECT> is as fast or faster
		424	then epoll for maybe up to a hundred file descriptors. So sad.
		425
373	While nominally embeddeble in other event loops, this feature is broken in	426	While nominally embeddable in other event loops, this feature is broken in
374	all kernel versions tested so far.	427	all kernel versions tested so far.
		428
		429	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		430	C<EVBACKEND_POLL>.
375		431
376	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	432	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
377		433
378	Kqueue deserves special mention, as at the time of this writing, it	434	Kqueue deserves special mention, as at the time of this writing, it
379	was broken on all BSDs except NetBSD (usually it doesn't work reliably	435	was broken on all BSDs except NetBSD (usually it doesn't work reliably
380	with anything but sockets and pipes, except on Darwin, where of course	436	with anything but sockets and pipes, except on Darwin, where of course
381	it's completely useless). For this reason it's not being "autodetected"	437	it's completely useless). Unlike epoll, however, whose brokenness
		438	is by design, these kqueue bugs can (and eventually will) be fixed
		439	without API changes to existing programs. For this reason it's not being
382	unless you explicitly specify it explicitly in the flags (i.e. using	440	"auto-detected" unless you explicitly specify it in the flags (i.e. using
383	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	441	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
384	system like NetBSD.	442	system like NetBSD.
385		443
386	You still can embed kqueue into a normal poll or select backend and use it	444	You still can embed kqueue into a normal poll or select backend and use it
387	only for sockets (after having made sure that sockets work with kqueue on	445	only for sockets (after having made sure that sockets work with kqueue on
388	the target platform). See C<ev_embed> watchers for more info.	446	the target platform). See C<ev_embed> watchers for more info.
389		447
390	It scales in the same way as the epoll backend, but the interface to the	448	It scales in the same way as the epoll backend, but the interface to the
391	kernel is more efficient (which says nothing about its actual speed, of	449	kernel is more efficient (which says nothing about its actual speed, of
392	course). While stopping, setting and starting an I/O watcher does never	450	course). While stopping, setting and starting an I/O watcher does never
393	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	451	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
394	two event changes per incident, support for C<fork ()> is very bad and it	452	two event changes per incident. Support for C<fork ()> is very bad (but
395	drops fds silently in similarly hard-to-detect cases.	453	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		454	cases
396		455
397	This backend usually performs well under most conditions.	456	This backend usually performs well under most conditions.
398		457
399	While nominally embeddable in other event loops, this doesn't work	458	While nominally embeddable in other event loops, this doesn't work
400	everywhere, so you might need to test for this. And since it is broken	459	everywhere, so you might need to test for this. And since it is broken
401	almost everywhere, you should only use it when you have a lot of sockets	460	almost everywhere, you should only use it when you have a lot of sockets
402	(for which it usually works), by embedding it into another event loop	461	(for which it usually works), by embedding it into another event loop
403	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	462	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
404	sockets.	463	using it only for sockets.
		464
		465	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		466	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		467	C<NOTE_EOF>.
405		468
406	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	469	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
407		470
408	This is not implemented yet (and might never be, unless you send me an	471	This is not implemented yet (and might never be, unless you send me an
409	implementation). According to reports, C</dev/poll> only supports sockets	472	implementation). According to reports, C</dev/poll> only supports sockets
…		…
413	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	476	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
414		477
415	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	478	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
416	it's really slow, but it still scales very well (O(active_fds)).	479	it's really slow, but it still scales very well (O(active_fds)).
417		480
418	Please note that solaris event ports can deliver a lot of spurious	481	Please note that Solaris event ports can deliver a lot of spurious
419	notifications, so you need to use non-blocking I/O or other means to avoid	482	notifications, so you need to use non-blocking I/O or other means to avoid
420	blocking when no data (or space) is available.	483	blocking when no data (or space) is available.
421		484
422	While this backend scales well, it requires one system call per active	485	While this backend scales well, it requires one system call per active
423	file descriptor per loop iteration. For small and medium numbers of file	486	file descriptor per loop iteration. For small and medium numbers of file
424	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	487	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
425	might perform better.	488	might perform better.
426		489
427	On the positive side, ignoring the spurious readyness notifications, this	490	On the positive side, with the exception of the spurious readiness
428	backend actually performed to specification in all tests and is fully	491	notifications, this backend actually performed fully to specification
429	embeddable, which is a rare feat among the OS-specific backends.	492	in all tests and is fully embeddable, which is a rare feat among the
		493	OS-specific backends (I vastly prefer correctness over speed hacks).
		494
		495	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		496	C<EVBACKEND_POLL>.
430		497
431	=item C<EVBACKEND_ALL>	498	=item C<EVBACKEND_ALL>
432		499
433	Try all backends (even potentially broken ones that wouldn't be tried	500	Try all backends (even potentially broken ones that wouldn't be tried
434	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	501	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
436		503
437	It is definitely not recommended to use this flag.	504	It is definitely not recommended to use this flag.
438		505
439	=back	506	=back
440		507
441	If one or more of these are ored into the flags value, then only these	508	If one or more of these are or'ed into the flags value, then only these
442	backends will be tried (in the reverse order as listed here). If none are	509	backends will be tried (in the reverse order as listed here). If none are
443	specified, all backends in C<ev_recommended_backends ()> will be tried.	510	specified, all backends in C<ev_recommended_backends ()> will be tried.
444		511
445	The most typical usage is like this:	512	Example: This is the most typical usage.
446		513
447	if (!ev_default_loop (0))	514	if (!ev_default_loop (0))
448	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	515	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
449		516
450	Restrict libev to the select and poll backends, and do not allow	517	Example: Restrict libev to the select and poll backends, and do not allow
451	environment settings to be taken into account:	518	environment settings to be taken into account:
452		519
453	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	520	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
454		521
455	Use whatever libev has to offer, but make sure that kqueue is used if	522	Example: Use whatever libev has to offer, but make sure that kqueue is
456	available (warning, breaks stuff, best use only with your own private	523	used if available (warning, breaks stuff, best use only with your own
457	event loop and only if you know the OS supports your types of fds):	524	private event loop and only if you know the OS supports your types of
		525	fds):
458		526
459	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	527	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
460		528
461	=item struct ev_loop *ev_loop_new (unsigned int flags)	529	=item struct ev_loop *ev_loop_new (unsigned int flags)
462		530
463	Similar to C<ev_default_loop>, but always creates a new event loop that is	531	Similar to C<ev_default_loop>, but always creates a new event loop that is
464	always distinct from the default loop. Unlike the default loop, it cannot	532	always distinct from the default loop. Unlike the default loop, it cannot
…		…
469	libev with threads is indeed to create one loop per thread, and using the	537	libev with threads is indeed to create one loop per thread, and using the
470	default loop in the "main" or "initial" thread.	538	default loop in the "main" or "initial" thread.
471		539
472	Example: Try to create a event loop that uses epoll and nothing else.	540	Example: Try to create a event loop that uses epoll and nothing else.
473		541
474	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	542	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
475	if (!epoller)	543	if (!epoller)
476	fatal ("no epoll found here, maybe it hides under your chair");	544	fatal ("no epoll found here, maybe it hides under your chair");
477		545
478	=item ev_default_destroy ()	546	=item ev_default_destroy ()
479		547
480	Destroys the default loop again (frees all memory and kernel state	548	Destroys the default loop again (frees all memory and kernel state
481	etc.). None of the active event watchers will be stopped in the normal	549	etc.). None of the active event watchers will be stopped in the normal
482	sense, so e.g. C<ev_is_active> might still return true. It is your	550	sense, so e.g. C<ev_is_active> might still return true. It is your
483	responsibility to either stop all watchers cleanly yoursef I<before>	551	responsibility to either stop all watchers cleanly yourself I<before>
484	calling this function, or cope with the fact afterwards (which is usually	552	calling this function, or cope with the fact afterwards (which is usually
485	the easiest thing, you can just ignore the watchers and/or C<free ()> them	553	the easiest thing, you can just ignore the watchers and/or C<free ()> them
486	for example).	554	for example).
487		555
488	Note that certain global state, such as signal state, will not be freed by	556	Note that certain global state, such as signal state (and installed signal
489	this function, and related watchers (such as signal and child watchers)	557	handlers), will not be freed by this function, and related watchers (such
490	would need to be stopped manually.	558	as signal and child watchers) would need to be stopped manually.
491		559
492	In general it is not advisable to call this function except in the	560	In general it is not advisable to call this function except in the
493	rare occasion where you really need to free e.g. the signal handling	561	rare occasion where you really need to free e.g. the signal handling
494	pipe fds. If you need dynamically allocated loops it is better to use	562	pipe fds. If you need dynamically allocated loops it is better to use
495	C<ev_loop_new> and C<ev_loop_destroy>).	563	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
520		588
521	=item ev_loop_fork (loop)	589	=item ev_loop_fork (loop)
522		590
523	Like C<ev_default_fork>, but acts on an event loop created by	591	Like C<ev_default_fork>, but acts on an event loop created by
524	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	592	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
525	after fork, and how you do this is entirely your own problem.	593	after fork that you want to re-use in the child, and how you do this is
		594	entirely your own problem.
526		595
527	=item int ev_is_default_loop (loop)	596	=item int ev_is_default_loop (loop)
528		597
529	Returns true when the given loop actually is the default loop, false otherwise.	598	Returns true when the given loop is, in fact, the default loop, and false
		599	otherwise.
530		600
531	=item unsigned int ev_loop_count (loop)	601	=item unsigned int ev_loop_count (loop)
532		602
533	Returns the count of loop iterations for the loop, which is identical to	603	Returns the count of loop iterations for the loop, which is identical to
534	the number of times libev did poll for new events. It starts at C<0> and	604	the number of times libev did poll for new events. It starts at C<0> and
…		…
549	received events and started processing them. This timestamp does not	619	received events and started processing them. This timestamp does not
550	change as long as callbacks are being processed, and this is also the base	620	change as long as callbacks are being processed, and this is also the base
551	time used for relative timers. You can treat it as the timestamp of the	621	time used for relative timers. You can treat it as the timestamp of the
552	event occurring (or more correctly, libev finding out about it).	622	event occurring (or more correctly, libev finding out about it).
553		623
		624	=item ev_now_update (loop)
		625
		626	Establishes the current time by querying the kernel, updating the time
		627	returned by C<ev_now ()> in the progress. This is a costly operation and
		628	is usually done automatically within C<ev_loop ()>.
		629
		630	This function is rarely useful, but when some event callback runs for a
		631	very long time without entering the event loop, updating libev's idea of
		632	the current time is a good idea.
		633
		634	See also "The special problem of time updates" in the C<ev_timer> section.
		635
554	=item ev_loop (loop, int flags)	636	=item ev_loop (loop, int flags)
555		637
556	Finally, this is it, the event handler. This function usually is called	638	Finally, this is it, the event handler. This function usually is called
557	after you initialised all your watchers and you want to start handling	639	after you initialised all your watchers and you want to start handling
558	events.	640	events.
…		…
560	If the flags argument is specified as C<0>, it will not return until	642	If the flags argument is specified as C<0>, it will not return until
561	either no event watchers are active anymore or C<ev_unloop> was called.	643	either no event watchers are active anymore or C<ev_unloop> was called.
562		644
563	Please note that an explicit C<ev_unloop> is usually better than	645	Please note that an explicit C<ev_unloop> is usually better than
564	relying on all watchers to be stopped when deciding when a program has	646	relying on all watchers to be stopped when deciding when a program has
565	finished (especially in interactive programs), but having a program that	647	finished (especially in interactive programs), but having a program
566	automatically loops as long as it has to and no longer by virtue of	648	that automatically loops as long as it has to and no longer by virtue
567	relying on its watchers stopping correctly is a thing of beauty.	649	of relying on its watchers stopping correctly, that is truly a thing of
		650	beauty.
568		651
569	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	652	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
570	those events and any outstanding ones, but will not block your process in	653	those events and any already outstanding ones, but will not block your
571	case there are no events and will return after one iteration of the loop.	654	process in case there are no events and will return after one iteration of
		655	the loop.
572		656
573	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	657	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
574	neccessary) and will handle those and any outstanding ones. It will block	658	necessary) and will handle those and any already outstanding ones. It
575	your process until at least one new event arrives, and will return after	659	will block your process until at least one new event arrives (which could
576	one iteration of the loop. This is useful if you are waiting for some	660	be an event internal to libev itself, so there is no guarantee that a
577	external event in conjunction with something not expressible using other	661	user-registered callback will be called), and will return after one
		662	iteration of the loop.
		663
		664	This is useful if you are waiting for some external event in conjunction
		665	with something not expressible using other libev watchers (i.e. "roll your
578	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	666	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
579	usually a better approach for this kind of thing.	667	usually a better approach for this kind of thing.
580		668
581	Here are the gory details of what C<ev_loop> does:	669	Here are the gory details of what C<ev_loop> does:
582		670
583	- Before the first iteration, call any pending watchers.	671	- Before the first iteration, call any pending watchers.
584	* If EVFLAG_FORKCHECK was used, check for a fork.	672	* If EVFLAG_FORKCHECK was used, check for a fork.
585	- If a fork was detected, queue and call all fork watchers.	673	- If a fork was detected (by any means), queue and call all fork watchers.
586	- Queue and call all prepare watchers.	674	- Queue and call all prepare watchers.
587	- If we have been forked, recreate the kernel state.	675	- If we have been forked, detach and recreate the kernel state
		676	as to not disturb the other process.
588	- Update the kernel state with all outstanding changes.	677	- Update the kernel state with all outstanding changes.
589	- Update the "event loop time".	678	- Update the "event loop time" (ev_now ()).
590	- Calculate for how long to sleep or block, if at all	679	- Calculate for how long to sleep or block, if at all
591	(active idle watchers, EVLOOP_NONBLOCK or not having	680	(active idle watchers, EVLOOP_NONBLOCK or not having
592	any active watchers at all will result in not sleeping).	681	any active watchers at all will result in not sleeping).
593	- Sleep if the I/O and timer collect interval say so.	682	- Sleep if the I/O and timer collect interval say so.
594	- Block the process, waiting for any events.	683	- Block the process, waiting for any events.
595	- Queue all outstanding I/O (fd) events.	684	- Queue all outstanding I/O (fd) events.
596	- Update the "event loop time" and do time jump handling.	685	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
597	- Queue all outstanding timers.	686	- Queue all expired timers.
598	- Queue all outstanding periodics.	687	- Queue all expired periodics.
599	- If no events are pending now, queue all idle watchers.	688	- Unless any events are pending now, queue all idle watchers.
600	- Queue all check watchers.	689	- Queue all check watchers.
601	- Call all queued watchers in reverse order (i.e. check watchers first).	690	- Call all queued watchers in reverse order (i.e. check watchers first).
602	Signals and child watchers are implemented as I/O watchers, and will	691	Signals and child watchers are implemented as I/O watchers, and will
603	be handled here by queueing them when their watcher gets executed.	692	be handled here by queueing them when their watcher gets executed.
604	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	693	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
609	anymore.	698	anymore.
610		699
611	... queue jobs here, make sure they register event watchers as long	700	... queue jobs here, make sure they register event watchers as long
612	... as they still have work to do (even an idle watcher will do..)	701	... as they still have work to do (even an idle watcher will do..)
613	ev_loop (my_loop, 0);	702	ev_loop (my_loop, 0);
614	... jobs done. yeah!	703	... jobs done or somebody called unloop. yeah!
615		704
616	=item ev_unloop (loop, how)	705	=item ev_unloop (loop, how)
617		706
618	Can be used to make a call to C<ev_loop> return early (but only after it	707	Can be used to make a call to C<ev_loop> return early (but only after it
619	has processed all outstanding events). The C<how> argument must be either	708	has processed all outstanding events). The C<how> argument must be either
620	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	709	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
621	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	710	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
622		711
623	This "unloop state" will be cleared when entering C<ev_loop> again.	712	This "unloop state" will be cleared when entering C<ev_loop> again.
624		713
		714	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		715
625	=item ev_ref (loop)	716	=item ev_ref (loop)
626		717
627	=item ev_unref (loop)	718	=item ev_unref (loop)
628		719
629	Ref/unref can be used to add or remove a reference count on the event	720	Ref/unref can be used to add or remove a reference count on the event
630	loop: Every watcher keeps one reference, and as long as the reference	721	loop: Every watcher keeps one reference, and as long as the reference
631	count is nonzero, C<ev_loop> will not return on its own. If you have	722	count is nonzero, C<ev_loop> will not return on its own.
		723
632	a watcher you never unregister that should not keep C<ev_loop> from	724	If you have a watcher you never unregister that should not keep C<ev_loop>
633	returning, ev_unref() after starting, and ev_ref() before stopping it. For	725	from returning, call ev_unref() after starting, and ev_ref() before
		726	stopping it.
		727
634	example, libev itself uses this for its internal signal pipe: It is not	728	As an example, libev itself uses this for its internal signal pipe: It is
635	visible to the libev user and should not keep C<ev_loop> from exiting if	729	not visible to the libev user and should not keep C<ev_loop> from exiting
636	no event watchers registered by it are active. It is also an excellent	730	if no event watchers registered by it are active. It is also an excellent
637	way to do this for generic recurring timers or from within third-party	731	way to do this for generic recurring timers or from within third-party
638	libraries. Just remember to I<unref after start> and I<ref before stop>	732	libraries. Just remember to I<unref after start> and I<ref before stop>
639	(but only if the watcher wasn't active before, or was active before,	733	(but only if the watcher wasn't active before, or was active before,
640	respectively).	734	respectively).
641		735
642	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	736	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
643	running when nothing else is active.	737	running when nothing else is active.
644		738
645	struct ev_signal exitsig;	739	ev_signal exitsig;
646	ev_signal_init (&exitsig, sig_cb, SIGINT);	740	ev_signal_init (&exitsig, sig_cb, SIGINT);
647	ev_signal_start (loop, &exitsig);	741	ev_signal_start (loop, &exitsig);
648	evf_unref (loop);	742	evf_unref (loop);
649		743
650	Example: For some weird reason, unregister the above signal handler again.	744	Example: For some weird reason, unregister the above signal handler again.
651		745
652	ev_ref (loop);	746	ev_ref (loop);
653	ev_signal_stop (loop, &exitsig);	747	ev_signal_stop (loop, &exitsig);
654		748
655	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	749	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
656		750
657	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	751	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
658		752
659	These advanced functions influence the time that libev will spend waiting	753	These advanced functions influence the time that libev will spend waiting
660	for events. Both are by default C<0>, meaning that libev will try to	754	for events. Both time intervals are by default C<0>, meaning that libev
661	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	755	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		756	latency.
662		757
663	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	758	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
664	allows libev to delay invocation of I/O and timer/periodic callbacks to	759	allows libev to delay invocation of I/O and timer/periodic callbacks
665	increase efficiency of loop iterations.	760	to increase efficiency of loop iterations (or to increase power-saving
		761	opportunities).
666		762
667	The background is that sometimes your program runs just fast enough to	763	The idea is that sometimes your program runs just fast enough to handle
668	handle one (or very few) event(s) per loop iteration. While this makes	764	one (or very few) event(s) per loop iteration. While this makes the
669	the program responsive, it also wastes a lot of CPU time to poll for new	765	program responsive, it also wastes a lot of CPU time to poll for new
670	events, especially with backends like C<select ()> which have a high	766	events, especially with backends like C<select ()> which have a high
671	overhead for the actual polling but can deliver many events at once.	767	overhead for the actual polling but can deliver many events at once.
672		768
673	By setting a higher I<io collect interval> you allow libev to spend more	769	By setting a higher I<io collect interval> you allow libev to spend more
674	time collecting I/O events, so you can handle more events per iteration,	770	time collecting I/O events, so you can handle more events per iteration,
…		…
676	C<ev_timer>) will be not affected. Setting this to a non-null value will	772	C<ev_timer>) will be not affected. Setting this to a non-null value will
677	introduce an additional C<ev_sleep ()> call into most loop iterations.	773	introduce an additional C<ev_sleep ()> call into most loop iterations.
678		774
679	Likewise, by setting a higher I<timeout collect interval> you allow libev	775	Likewise, by setting a higher I<timeout collect interval> you allow libev
680	to spend more time collecting timeouts, at the expense of increased	776	to spend more time collecting timeouts, at the expense of increased
681	latency (the watcher callback will be called later). C<ev_io> watchers	777	latency/jitter/inexactness (the watcher callback will be called
682	will not be affected. Setting this to a non-null value will not introduce	778	later). C<ev_io> watchers will not be affected. Setting this to a non-null
683	any overhead in libev.	779	value will not introduce any overhead in libev.
684		780
685	Many (busy) programs can usually benefit by setting the io collect	781	Many (busy) programs can usually benefit by setting the I/O collect
686	interval to a value near C<0.1> or so, which is often enough for	782	interval to a value near C<0.1> or so, which is often enough for
687	interactive servers (of course not for games), likewise for timeouts. It	783	interactive servers (of course not for games), likewise for timeouts. It
688	usually doesn't make much sense to set it to a lower value than C<0.01>,	784	usually doesn't make much sense to set it to a lower value than C<0.01>,
689	as this approsaches the timing granularity of most systems.	785	as this approaches the timing granularity of most systems.
		786
		787	Setting the I<timeout collect interval> can improve the opportunity for
		788	saving power, as the program will "bundle" timer callback invocations that
		789	are "near" in time together, by delaying some, thus reducing the number of
		790	times the process sleeps and wakes up again. Another useful technique to
		791	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		792	they fire on, say, one-second boundaries only.
		793
		794	=item ev_loop_verify (loop)
		795
		796	This function only does something when C<EV_VERIFY> support has been
		797	compiled in, which is the default for non-minimal builds. It tries to go
		798	through all internal structures and checks them for validity. If anything
		799	is found to be inconsistent, it will print an error message to standard
		800	error and call C<abort ()>.
		801
		802	This can be used to catch bugs inside libev itself: under normal
		803	circumstances, this function will never abort as of course libev keeps its
		804	data structures consistent.
690		805
691	=back	806	=back
692		807
693		808
694	=head1 ANATOMY OF A WATCHER	809	=head1 ANATOMY OF A WATCHER
		810
		811	In the following description, uppercase C<TYPE> in names stands for the
		812	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		813	watchers and C<ev_io_start> for I/O watchers.
695		814
696	A watcher is a structure that you create and register to record your	815	A watcher is a structure that you create and register to record your
697	interest in some event. For instance, if you want to wait for STDIN to	816	interest in some event. For instance, if you want to wait for STDIN to
698	become readable, you would create an C<ev_io> watcher for that:	817	become readable, you would create an C<ev_io> watcher for that:
699		818
700	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	819	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
701	{	820	{
702	ev_io_stop (w);	821	ev_io_stop (w);
703	ev_unloop (loop, EVUNLOOP_ALL);	822	ev_unloop (loop, EVUNLOOP_ALL);
704	}	823	}
705		824
706	struct ev_loop *loop = ev_default_loop (0);	825	struct ev_loop *loop = ev_default_loop (0);
		826
707	struct ev_io stdin_watcher;	827	ev_io stdin_watcher;
		828
708	ev_init (&stdin_watcher, my_cb);	829	ev_init (&stdin_watcher, my_cb);
709	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	830	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
710	ev_io_start (loop, &stdin_watcher);	831	ev_io_start (loop, &stdin_watcher);
		832
711	ev_loop (loop, 0);	833	ev_loop (loop, 0);
712		834
713	As you can see, you are responsible for allocating the memory for your	835	As you can see, you are responsible for allocating the memory for your
714	watcher structures (and it is usually a bad idea to do this on the stack,	836	watcher structures (and it is I<usually> a bad idea to do this on the
715	although this can sometimes be quite valid).	837	stack).
		838
		839	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		840	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
716		841
717	Each watcher structure must be initialised by a call to C<ev_init	842	Each watcher structure must be initialised by a call to C<ev_init
718	(watcher *, callback)>, which expects a callback to be provided. This	843	(watcher *, callback)>, which expects a callback to be provided. This
719	callback gets invoked each time the event occurs (or, in the case of io	844	callback gets invoked each time the event occurs (or, in the case of I/O
720	watchers, each time the event loop detects that the file descriptor given	845	watchers, each time the event loop detects that the file descriptor given
721	is readable and/or writable).	846	is readable and/or writable).
722		847
723	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	848	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
724	with arguments specific to this watcher type. There is also a macro	849	macro to configure it, with arguments specific to the watcher type. There
725	to combine initialisation and setting in one call: C<< ev_<type>_init	850	is also a macro to combine initialisation and setting in one call: C<<
726	(watcher *, callback, ...) >>.	851	ev_TYPE_init (watcher *, callback, ...) >>.
727		852
728	To make the watcher actually watch out for events, you have to start it	853	To make the watcher actually watch out for events, you have to start it
729	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	854	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
730	*) >>), and you can stop watching for events at any time by calling the	855	*) >>), and you can stop watching for events at any time by calling the
731	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	856	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
732		857
733	As long as your watcher is active (has been started but not stopped) you	858	As long as your watcher is active (has been started but not stopped) you
734	must not touch the values stored in it. Most specifically you must never	859	must not touch the values stored in it. Most specifically you must never
735	reinitialise it or call its C<set> macro.	860	reinitialise it or call its C<ev_TYPE_set> macro.
736		861
737	Each and every callback receives the event loop pointer as first, the	862	Each and every callback receives the event loop pointer as first, the
738	registered watcher structure as second, and a bitset of received events as	863	registered watcher structure as second, and a bitset of received events as
739	third argument.	864	third argument.
740		865
…		…
800		925
801	The given async watcher has been asynchronously notified (see C<ev_async>).	926	The given async watcher has been asynchronously notified (see C<ev_async>).
802		927
803	=item C<EV_ERROR>	928	=item C<EV_ERROR>
804		929
805	An unspecified error has occured, the watcher has been stopped. This might	930	An unspecified error has occurred, the watcher has been stopped. This might
806	happen because the watcher could not be properly started because libev	931	happen because the watcher could not be properly started because libev
807	ran out of memory, a file descriptor was found to be closed or any other	932	ran out of memory, a file descriptor was found to be closed or any other
		933	problem. Libev considers these application bugs.
		934
808	problem. You best act on it by reporting the problem and somehow coping	935	You best act on it by reporting the problem and somehow coping with the
809	with the watcher being stopped.	936	watcher being stopped. Note that well-written programs should not receive
		937	an error ever, so when your watcher receives it, this usually indicates a
		938	bug in your program.
810		939
811	Libev will usually signal a few "dummy" events together with an error,	940	Libev will usually signal a few "dummy" events together with an error, for
812	for example it might indicate that a fd is readable or writable, and if	941	example it might indicate that a fd is readable or writable, and if your
813	your callbacks is well-written it can just attempt the operation and cope	942	callbacks is well-written it can just attempt the operation and cope with
814	with the error from read() or write(). This will not work in multithreaded	943	the error from read() or write(). This will not work in multi-threaded
815	programs, though, so beware.	944	programs, though, as the fd could already be closed and reused for another
		945	thing, so beware.
816		946
817	=back	947	=back
818		948
819	=head2 GENERIC WATCHER FUNCTIONS	949	=head2 GENERIC WATCHER FUNCTIONS
820
821	In the following description, C<TYPE> stands for the watcher type,
822	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
823		950
824	=over 4	951	=over 4
825		952
826	=item C<ev_init> (ev_TYPE *watcher, callback)	953	=item C<ev_init> (ev_TYPE *watcher, callback)
827		954
…		…
833	which rolls both calls into one.	960	which rolls both calls into one.
834		961
835	You can reinitialise a watcher at any time as long as it has been stopped	962	You can reinitialise a watcher at any time as long as it has been stopped
836	(or never started) and there are no pending events outstanding.	963	(or never started) and there are no pending events outstanding.
837		964
838	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	965	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
839	int revents)>.	966	int revents)>.
		967
		968	Example: Initialise an C<ev_io> watcher in two steps.
		969
		970	ev_io w;
		971	ev_init (&w, my_cb);
		972	ev_io_set (&w, STDIN_FILENO, EV_READ);
840		973
841	=item C<ev_TYPE_set> (ev_TYPE *, [args])	974	=item C<ev_TYPE_set> (ev_TYPE *, [args])
842		975
843	This macro initialises the type-specific parts of a watcher. You need to	976	This macro initialises the type-specific parts of a watcher. You need to
844	call C<ev_init> at least once before you call this macro, but you can	977	call C<ev_init> at least once before you call this macro, but you can
…		…
847	difference to the C<ev_init> macro).	980	difference to the C<ev_init> macro).
848		981
849	Although some watcher types do not have type-specific arguments	982	Although some watcher types do not have type-specific arguments
850	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	983	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
851		984
		985	See C<ev_init>, above, for an example.
		986
852	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	987	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
853		988
854	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	989	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
855	calls into a single call. This is the most convinient method to initialise	990	calls into a single call. This is the most convenient method to initialise
856	a watcher. The same limitations apply, of course.	991	a watcher. The same limitations apply, of course.
		992
		993	Example: Initialise and set an C<ev_io> watcher in one step.
		994
		995	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
857		996
858	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	997	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
859		998
860	Starts (activates) the given watcher. Only active watchers will receive	999	Starts (activates) the given watcher. Only active watchers will receive
861	events. If the watcher is already active nothing will happen.	1000	events. If the watcher is already active nothing will happen.
862		1001
		1002	Example: Start the C<ev_io> watcher that is being abused as example in this
		1003	whole section.
		1004
		1005	ev_io_start (EV_DEFAULT_UC, &w);
		1006
863	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1007	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
864		1008
865	Stops the given watcher again (if active) and clears the pending	1009	Stops the given watcher if active, and clears the pending status (whether
		1010	the watcher was active or not).
		1011
866	status. It is possible that stopped watchers are pending (for example,	1012	It is possible that stopped watchers are pending - for example,
867	non-repeating timers are being stopped when they become pending), but	1013	non-repeating timers are being stopped when they become pending - but
868	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1014	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
869	you want to free or reuse the memory used by the watcher it is therefore a	1015	pending. If you want to free or reuse the memory used by the watcher it is
870	good idea to always call its C<ev_TYPE_stop> function.	1016	therefore a good idea to always call its C<ev_TYPE_stop> function.
871		1017
872	=item bool ev_is_active (ev_TYPE *watcher)	1018	=item bool ev_is_active (ev_TYPE *watcher)
873		1019
874	Returns a true value iff the watcher is active (i.e. it has been started	1020	Returns a true value iff the watcher is active (i.e. it has been started
875	and not yet been stopped). As long as a watcher is active you must not modify	1021	and not yet been stopped). As long as a watcher is active you must not modify
…		…
917	The default priority used by watchers when no priority has been set is	1063	The default priority used by watchers when no priority has been set is
918	always C<0>, which is supposed to not be too high and not be too low :).	1064	always C<0>, which is supposed to not be too high and not be too low :).
919		1065
920	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1066	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
921	fine, as long as you do not mind that the priority value you query might	1067	fine, as long as you do not mind that the priority value you query might
922	or might not have been adjusted to be within valid range.	1068	or might not have been clamped to the valid range.
923		1069
924	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1070	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
925		1071
926	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1072	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
927	C<loop> nor C<revents> need to be valid as long as the watcher callback	1073	C<loop> nor C<revents> need to be valid as long as the watcher callback
928	can deal with that fact.	1074	can deal with that fact, as both are simply passed through to the
		1075	callback.
929		1076
930	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1077	=item int ev_clear_pending (loop, ev_TYPE *watcher)
931		1078
932	If the watcher is pending, this function returns clears its pending status	1079	If the watcher is pending, this function clears its pending status and
933	and returns its C<revents> bitset (as if its callback was invoked). If the	1080	returns its C<revents> bitset (as if its callback was invoked). If the
934	watcher isn't pending it does nothing and returns C<0>.	1081	watcher isn't pending it does nothing and returns C<0>.
935		1082
		1083	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1084	callback to be invoked, which can be accomplished with this function.
		1085
936	=back	1086	=back
937		1087
938		1088
939	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1089	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
940		1090
941	Each watcher has, by default, a member C<void *data> that you can change	1091	Each watcher has, by default, a member C<void *data> that you can change
942	and read at any time, libev will completely ignore it. This can be used	1092	and read at any time: libev will completely ignore it. This can be used
943	to associate arbitrary data with your watcher. If you need more data and	1093	to associate arbitrary data with your watcher. If you need more data and
944	don't want to allocate memory and store a pointer to it in that data	1094	don't want to allocate memory and store a pointer to it in that data
945	member, you can also "subclass" the watcher type and provide your own	1095	member, you can also "subclass" the watcher type and provide your own
946	data:	1096	data:
947		1097
948	struct my_io	1098	struct my_io
949	{	1099	{
950	struct ev_io io;	1100	ev_io io;
951	int otherfd;	1101	int otherfd;
952	void *somedata;	1102	void *somedata;
953	struct whatever *mostinteresting;	1103	struct whatever *mostinteresting;
954	}	1104	};
		1105
		1106	...
		1107	struct my_io w;
		1108	ev_io_init (&w.io, my_cb, fd, EV_READ);
955		1109
956	And since your callback will be called with a pointer to the watcher, you	1110	And since your callback will be called with a pointer to the watcher, you
957	can cast it back to your own type:	1111	can cast it back to your own type:
958		1112
959	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1113	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
960	{	1114	{
961	struct my_io *w = (struct my_io *)w_;	1115	struct my_io *w = (struct my_io *)w_;
962	...	1116	...
963	}	1117	}
964		1118
965	More interesting and less C-conformant ways of casting your callback type	1119	More interesting and less C-conformant ways of casting your callback type
966	instead have been omitted.	1120	instead have been omitted.
967		1121
968	Another common scenario is having some data structure with multiple	1122	Another common scenario is to use some data structure with multiple
969	watchers:	1123	embedded watchers:
970		1124
971	struct my_biggy	1125	struct my_biggy
972	{	1126	{
973	int some_data;	1127	int some_data;
974	ev_timer t1;	1128	ev_timer t1;
975	ev_timer t2;	1129	ev_timer t2;
976	}	1130	}
977		1131
978	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1132	In this case getting the pointer to C<my_biggy> is a bit more
979	you need to use C<offsetof>:	1133	complicated: Either you store the address of your C<my_biggy> struct
		1134	in the C<data> member of the watcher (for woozies), or you need to use
		1135	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1136	programmers):
980		1137
981	#include <stddef.h>	1138	#include <stddef.h>
982		1139
983	static void	1140	static void
984	t1_cb (EV_P_ struct ev_timer *w, int revents)	1141	t1_cb (EV_P_ ev_timer *w, int revents)
985	{	1142	{
986	struct my_biggy big = (struct my_biggy *	1143	struct my_biggy big = (struct my_biggy *
987	(((char *)w) - offsetof (struct my_biggy, t1));	1144	(((char *)w) - offsetof (struct my_biggy, t1));
988	}	1145	}
989		1146
990	static void	1147	static void
991	t2_cb (EV_P_ struct ev_timer *w, int revents)	1148	t2_cb (EV_P_ ev_timer *w, int revents)
992	{	1149	{
993	struct my_biggy big = (struct my_biggy *	1150	struct my_biggy big = (struct my_biggy *
994	(((char *)w) - offsetof (struct my_biggy, t2));	1151	(((char *)w) - offsetof (struct my_biggy, t2));
995	}	1152	}
996		1153
997		1154
998	=head1 WATCHER TYPES	1155	=head1 WATCHER TYPES
999		1156
1000	This section describes each watcher in detail, but will not repeat	1157	This section describes each watcher in detail, but will not repeat
…		…
1024	In general you can register as many read and/or write event watchers per	1181	In general you can register as many read and/or write event watchers per
1025	fd as you want (as long as you don't confuse yourself). Setting all file	1182	fd as you want (as long as you don't confuse yourself). Setting all file
1026	descriptors to non-blocking mode is also usually a good idea (but not	1183	descriptors to non-blocking mode is also usually a good idea (but not
1027	required if you know what you are doing).	1184	required if you know what you are doing).
1028		1185
1029	If you must do this, then force the use of a known-to-be-good backend	1186	If you cannot use non-blocking mode, then force the use of a
1030	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1187	known-to-be-good backend (at the time of this writing, this includes only
1031	C<EVBACKEND_POLL>).	1188	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1032		1189
1033	Another thing you have to watch out for is that it is quite easy to	1190	Another thing you have to watch out for is that it is quite easy to
1034	receive "spurious" readyness notifications, that is your callback might	1191	receive "spurious" readiness notifications, that is your callback might
1035	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1192	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1036	because there is no data. Not only are some backends known to create a	1193	because there is no data. Not only are some backends known to create a
1037	lot of those (for example solaris ports), it is very easy to get into	1194	lot of those (for example Solaris ports), it is very easy to get into
1038	this situation even with a relatively standard program structure. Thus	1195	this situation even with a relatively standard program structure. Thus
1039	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1196	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1040	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1197	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1041		1198
1042	If you cannot run the fd in non-blocking mode (for example you should not	1199	If you cannot run the fd in non-blocking mode (for example you should
1043	play around with an Xlib connection), then you have to seperately re-test	1200	not play around with an Xlib connection), then you have to separately
1044	whether a file descriptor is really ready with a known-to-be good interface	1201	re-test whether a file descriptor is really ready with a known-to-be good
1045	such as poll (fortunately in our Xlib example, Xlib already does this on	1202	interface such as poll (fortunately in our Xlib example, Xlib already
1046	its own, so its quite safe to use).	1203	does this on its own, so its quite safe to use). Some people additionally
		1204	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1205	indefinitely.
		1206
		1207	But really, best use non-blocking mode.
1047		1208
1048	=head3 The special problem of disappearing file descriptors	1209	=head3 The special problem of disappearing file descriptors
1049		1210
1050	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1211	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1051	descriptor (either by calling C<close> explicitly or by any other means,	1212	descriptor (either due to calling C<close> explicitly or any other means,
1052	such as C<dup>). The reason is that you register interest in some file	1213	such as C<dup2>). The reason is that you register interest in some file
1053	descriptor, but when it goes away, the operating system will silently drop	1214	descriptor, but when it goes away, the operating system will silently drop
1054	this interest. If another file descriptor with the same number then is	1215	this interest. If another file descriptor with the same number then is
1055	registered with libev, there is no efficient way to see that this is, in	1216	registered with libev, there is no efficient way to see that this is, in
1056	fact, a different file descriptor.	1217	fact, a different file descriptor.
1057		1218
…		…
1088	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1249	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1089	C<EVBACKEND_POLL>.	1250	C<EVBACKEND_POLL>.
1090		1251
1091	=head3 The special problem of SIGPIPE	1252	=head3 The special problem of SIGPIPE
1092		1253
1093	While not really specific to libev, it is easy to forget about SIGPIPE:	1254	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1094	when reading from a pipe whose other end has been closed, your program	1255	when writing to a pipe whose other end has been closed, your program gets
1095	gets send a SIGPIPE, which, by default, aborts your program. For most	1256	sent a SIGPIPE, which, by default, aborts your program. For most programs
1096	programs this is sensible behaviour, for daemons, this is usually	1257	this is sensible behaviour, for daemons, this is usually undesirable.
1097	undesirable.
1098		1258
1099	So when you encounter spurious, unexplained daemon exits, make sure you	1259	So when you encounter spurious, unexplained daemon exits, make sure you
1100	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1260	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1101	somewhere, as that would have given you a big clue).	1261	somewhere, as that would have given you a big clue).
1102		1262
…		…
1108	=item ev_io_init (ev_io *, callback, int fd, int events)	1268	=item ev_io_init (ev_io *, callback, int fd, int events)
1109		1269
1110	=item ev_io_set (ev_io *, int fd, int events)	1270	=item ev_io_set (ev_io *, int fd, int events)
1111		1271
1112	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1272	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1113	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1273	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1114	C<EV_READ | EV_WRITE> to receive the given events.	1274	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1115		1275
1116	=item int fd [read-only]	1276	=item int fd [read-only]
1117		1277
1118	The file descriptor being watched.	1278	The file descriptor being watched.
1119		1279
…		…
1127		1287
1128	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1288	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1129	readable, but only once. Since it is likely line-buffered, you could	1289	readable, but only once. Since it is likely line-buffered, you could
1130	attempt to read a whole line in the callback.	1290	attempt to read a whole line in the callback.
1131		1291
1132	static void	1292	static void
1133	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1293	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1134	{	1294	{
1135	ev_io_stop (loop, w);	1295	ev_io_stop (loop, w);
1136	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1296	.. read from stdin here (or from w->fd) and handle any I/O errors
1137	}	1297	}
1138		1298
1139	...	1299	...
1140	struct ev_loop *loop = ev_default_init (0);	1300	struct ev_loop *loop = ev_default_init (0);
1141	struct ev_io stdin_readable;	1301	ev_io stdin_readable;
1142	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1302	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1143	ev_io_start (loop, &stdin_readable);	1303	ev_io_start (loop, &stdin_readable);
1144	ev_loop (loop, 0);	1304	ev_loop (loop, 0);
1145		1305
1146		1306
1147	=head2 C<ev_timer> - relative and optionally repeating timeouts	1307	=head2 C<ev_timer> - relative and optionally repeating timeouts
1148		1308
1149	Timer watchers are simple relative timers that generate an event after a	1309	Timer watchers are simple relative timers that generate an event after a
1150	given time, and optionally repeating in regular intervals after that.	1310	given time, and optionally repeating in regular intervals after that.
1151		1311
1152	The timers are based on real time, that is, if you register an event that	1312	The timers are based on real time, that is, if you register an event that
1153	times out after an hour and you reset your system clock to last years	1313	times out after an hour and you reset your system clock to January last
1154	time, it will still time out after (roughly) and hour. "Roughly" because	1314	year, it will still time out after (roughly) one hour. "Roughly" because
1155	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1315	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1156	monotonic clock option helps a lot here).	1316	monotonic clock option helps a lot here).
		1317
		1318	The callback is guaranteed to be invoked only I<after> its timeout has
		1319	passed, but if multiple timers become ready during the same loop iteration
		1320	then order of execution is undefined.
		1321
		1322	=head3 Be smart about timeouts
		1323
		1324	Many real-world problems involve some kind of timeout, usually for error
		1325	recovery. A typical example is an HTTP request - if the other side hangs,
		1326	you want to raise some error after a while.
		1327
		1328	What follows are some ways to handle this problem, from obvious and
		1329	inefficient to smart and efficient.
		1330
		1331	In the following, a 60 second activity timeout is assumed - a timeout that
		1332	gets reset to 60 seconds each time there is activity (e.g. each time some
		1333	data or other life sign was received).
		1334
		1335	=over 4
		1336
		1337	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1338
		1339	This is the most obvious, but not the most simple way: In the beginning,
		1340	start the watcher:
		1341
		1342	ev_timer_init (timer, callback, 60., 0.);
		1343	ev_timer_start (loop, timer);
		1344
		1345	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1346	and start it again:
		1347
		1348	ev_timer_stop (loop, timer);
		1349	ev_timer_set (timer, 60., 0.);
		1350	ev_timer_start (loop, timer);
		1351
		1352	This is relatively simple to implement, but means that each time there is
		1353	some activity, libev will first have to remove the timer from its internal
		1354	data structure and then add it again. Libev tries to be fast, but it's
		1355	still not a constant-time operation.
		1356
		1357	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1358
		1359	This is the easiest way, and involves using C<ev_timer_again> instead of
		1360	C<ev_timer_start>.
		1361
		1362	To implement this, configure an C<ev_timer> with a C<repeat> value
		1363	of C<60> and then call C<ev_timer_again> at start and each time you
		1364	successfully read or write some data. If you go into an idle state where
		1365	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1366	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1367
		1368	That means you can ignore both the C<ev_timer_start> function and the
		1369	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1370	member and C<ev_timer_again>.
		1371
		1372	At start:
		1373
		1374	ev_timer_init (timer, callback);
		1375	timer->repeat = 60.;
		1376	ev_timer_again (loop, timer);
		1377
		1378	Each time there is some activity:
		1379
		1380	ev_timer_again (loop, timer);
		1381
		1382	It is even possible to change the time-out on the fly, regardless of
		1383	whether the watcher is active or not:
		1384
		1385	timer->repeat = 30.;
		1386	ev_timer_again (loop, timer);
		1387
		1388	This is slightly more efficient then stopping/starting the timer each time
		1389	you want to modify its timeout value, as libev does not have to completely
		1390	remove and re-insert the timer from/into its internal data structure.
		1391
		1392	It is, however, even simpler than the "obvious" way to do it.
		1393
		1394	=item 3. Let the timer time out, but then re-arm it as required.
		1395
		1396	This method is more tricky, but usually most efficient: Most timeouts are
		1397	relatively long compared to the intervals between other activity - in
		1398	our example, within 60 seconds, there are usually many I/O events with
		1399	associated activity resets.
		1400
		1401	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1402	but remember the time of last activity, and check for a real timeout only
		1403	within the callback:
		1404
		1405	ev_tstamp last_activity; // time of last activity
		1406
		1407	static void
		1408	callback (EV_P_ ev_timer *w, int revents)
		1409	{
		1410	ev_tstamp now = ev_now (EV_A);
		1411	ev_tstamp timeout = last_activity + 60.;
		1412
		1413	// if last_activity + 60. is older than now, we did time out
		1414	if (timeout < now)
		1415	{
		1416	// timeout occured, take action
		1417	}
		1418	else
		1419	{
		1420	// callback was invoked, but there was some activity, re-arm
		1421	// the watcher to fire in last_activity + 60, which is
		1422	// guaranteed to be in the future, so "again" is positive:
		1423	w->again = timeout - now;
		1424	ev_timer_again (EV_A_ w);
		1425	}
		1426	}
		1427
		1428	To summarise the callback: first calculate the real timeout (defined
		1429	as "60 seconds after the last activity"), then check if that time has
		1430	been reached, which means something I<did>, in fact, time out. Otherwise
		1431	the callback was invoked too early (C<timeout> is in the future), so
		1432	re-schedule the timer to fire at that future time, to see if maybe we have
		1433	a timeout then.
		1434
		1435	Note how C<ev_timer_again> is used, taking advantage of the
		1436	C<ev_timer_again> optimisation when the timer is already running.
		1437
		1438	This scheme causes more callback invocations (about one every 60 seconds
		1439	minus half the average time between activity), but virtually no calls to
		1440	libev to change the timeout.
		1441
		1442	To start the timer, simply initialise the watcher and set C<last_activity>
		1443	to the current time (meaning we just have some activity :), then call the
		1444	callback, which will "do the right thing" and start the timer:
		1445
		1446	ev_timer_init (timer, callback);
		1447	last_activity = ev_now (loop);
		1448	callback (loop, timer, EV_TIMEOUT);
		1449
		1450	And when there is some activity, simply store the current time in
		1451	C<last_activity>, no libev calls at all:
		1452
		1453	last_actiivty = ev_now (loop);
		1454
		1455	This technique is slightly more complex, but in most cases where the
		1456	time-out is unlikely to be triggered, much more efficient.
		1457
		1458	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1459	callback :) - just change the timeout and invoke the callback, which will
		1460	fix things for you.
		1461
		1462	=item 4. Wee, just use a double-linked list for your timeouts.
		1463
		1464	If there is not one request, but many thousands (millions...), all
		1465	employing some kind of timeout with the same timeout value, then one can
		1466	do even better:
		1467
		1468	When starting the timeout, calculate the timeout value and put the timeout
		1469	at the I<end> of the list.
		1470
		1471	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1472	the list is expected to fire (for example, using the technique #3).
		1473
		1474	When there is some activity, remove the timer from the list, recalculate
		1475	the timeout, append it to the end of the list again, and make sure to
		1476	update the C<ev_timer> if it was taken from the beginning of the list.
		1477
		1478	This way, one can manage an unlimited number of timeouts in O(1) time for
		1479	starting, stopping and updating the timers, at the expense of a major
		1480	complication, and having to use a constant timeout. The constant timeout
		1481	ensures that the list stays sorted.
		1482
		1483	=back
		1484
		1485	So which method the best?
		1486
		1487	Method #2 is a simple no-brain-required solution that is adequate in most
		1488	situations. Method #3 requires a bit more thinking, but handles many cases
		1489	better, and isn't very complicated either. In most case, choosing either
		1490	one is fine, with #3 being better in typical situations.
		1491
		1492	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1493	rather complicated, but extremely efficient, something that really pays
		1494	off after the first million or so of active timers, i.e. it's usually
		1495	overkill :)
		1496
		1497	=head3 The special problem of time updates
		1498
		1499	Establishing the current time is a costly operation (it usually takes at
		1500	least two system calls): EV therefore updates its idea of the current
		1501	time only before and after C<ev_loop> collects new events, which causes a
		1502	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1503	lots of events in one iteration.
1157		1504
1158	The relative timeouts are calculated relative to the C<ev_now ()>	1505	The relative timeouts are calculated relative to the C<ev_now ()>
1159	time. This is usually the right thing as this timestamp refers to the time	1506	time. This is usually the right thing as this timestamp refers to the time
1160	of the event triggering whatever timeout you are modifying/starting. If	1507	of the event triggering whatever timeout you are modifying/starting. If
1161	you suspect event processing to be delayed and you I<need> to base the timeout	1508	you suspect event processing to be delayed and you I<need> to base the
1162	on the current time, use something like this to adjust for this:	1509	timeout on the current time, use something like this to adjust for this:
1163		1510
1164	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1511	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1165		1512
1166	The callback is guarenteed to be invoked only when its timeout has passed,	1513	If the event loop is suspended for a long time, you can also force an
1167	but if multiple timers become ready during the same loop iteration then	1514	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1168	order of execution is undefined.	1515	()>.
1169		1516
1170	=head3 Watcher-Specific Functions and Data Members	1517	=head3 Watcher-Specific Functions and Data Members
1171		1518
1172	=over 4	1519	=over 4
1173		1520
1174	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1521	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1175		1522
1176	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1523	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1177		1524
1178	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1525	Configure the timer to trigger after C<after> seconds. If C<repeat>
1179	C<0.>, then it will automatically be stopped. If it is positive, then the	1526	is C<0.>, then it will automatically be stopped once the timeout is
1180	timer will automatically be configured to trigger again C<repeat> seconds	1527	reached. If it is positive, then the timer will automatically be
1181	later, again, and again, until stopped manually.	1528	configured to trigger again C<repeat> seconds later, again, and again,
		1529	until stopped manually.
1182		1530
1183	The timer itself will do a best-effort at avoiding drift, that is, if you	1531	The timer itself will do a best-effort at avoiding drift, that is, if
1184	configure a timer to trigger every 10 seconds, then it will trigger at	1532	you configure a timer to trigger every 10 seconds, then it will normally
1185	exactly 10 second intervals. If, however, your program cannot keep up with	1533	trigger at exactly 10 second intervals. If, however, your program cannot
1186	the timer (because it takes longer than those 10 seconds to do stuff) the	1534	keep up with the timer (because it takes longer than those 10 seconds to
1187	timer will not fire more than once per event loop iteration.	1535	do stuff) the timer will not fire more than once per event loop iteration.
1188		1536
1189	=item ev_timer_again (loop, ev_timer *)	1537	=item ev_timer_again (loop, ev_timer *)
1190		1538
1191	This will act as if the timer timed out and restart it again if it is	1539	This will act as if the timer timed out and restart it again if it is
1192	repeating. The exact semantics are:	1540	repeating. The exact semantics are:
1193		1541
1194	If the timer is pending, its pending status is cleared.	1542	If the timer is pending, its pending status is cleared.
1195		1543
1196	If the timer is started but nonrepeating, stop it (as if it timed out).	1544	If the timer is started but non-repeating, stop it (as if it timed out).
1197		1545
1198	If the timer is repeating, either start it if necessary (with the	1546	If the timer is repeating, either start it if necessary (with the
1199	C<repeat> value), or reset the running timer to the C<repeat> value.	1547	C<repeat> value), or reset the running timer to the C<repeat> value.
1200		1548
1201	This sounds a bit complicated, but here is a useful and typical	1549	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1202	example: Imagine you have a tcp connection and you want a so-called idle	1550	usage example.
1203	timeout, that is, you want to be called when there have been, say, 60
1204	seconds of inactivity on the socket. The easiest way to do this is to
1205	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1206	C<ev_timer_again> each time you successfully read or write some data. If
1207	you go into an idle state where you do not expect data to travel on the
1208	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1209	automatically restart it if need be.
1210
1211	That means you can ignore the C<after> value and C<ev_timer_start>
1212	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1213
1214	ev_timer_init (timer, callback, 0., 5.);
1215	ev_timer_again (loop, timer);
1216	...
1217	timer->again = 17.;
1218	ev_timer_again (loop, timer);
1219	...
1220	timer->again = 10.;
1221	ev_timer_again (loop, timer);
1222
1223	This is more slightly efficient then stopping/starting the timer each time
1224	you want to modify its timeout value.
1225		1551
1226	=item ev_tstamp repeat [read-write]	1552	=item ev_tstamp repeat [read-write]
1227		1553
1228	The current C<repeat> value. Will be used each time the watcher times out	1554	The current C<repeat> value. Will be used each time the watcher times out
1229	or C<ev_timer_again> is called and determines the next timeout (if any),	1555	or C<ev_timer_again> is called, and determines the next timeout (if any),
1230	which is also when any modifications are taken into account.	1556	which is also when any modifications are taken into account.
1231		1557
1232	=back	1558	=back
1233		1559
1234	=head3 Examples	1560	=head3 Examples
1235		1561
1236	Example: Create a timer that fires after 60 seconds.	1562	Example: Create a timer that fires after 60 seconds.
1237		1563
1238	static void	1564	static void
1239	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1565	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1240	{	1566	{
1241	.. one minute over, w is actually stopped right here	1567	.. one minute over, w is actually stopped right here
1242	}	1568	}
1243		1569
1244	struct ev_timer mytimer;	1570	ev_timer mytimer;
1245	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1571	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1246	ev_timer_start (loop, &mytimer);	1572	ev_timer_start (loop, &mytimer);
1247		1573
1248	Example: Create a timeout timer that times out after 10 seconds of	1574	Example: Create a timeout timer that times out after 10 seconds of
1249	inactivity.	1575	inactivity.
1250		1576
1251	static void	1577	static void
1252	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1578	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1253	{	1579	{
1254	.. ten seconds without any activity	1580	.. ten seconds without any activity
1255	}	1581	}
1256		1582
1257	struct ev_timer mytimer;	1583	ev_timer mytimer;
1258	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1584	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1259	ev_timer_again (&mytimer); /* start timer */	1585	ev_timer_again (&mytimer); /* start timer */
1260	ev_loop (loop, 0);	1586	ev_loop (loop, 0);
1261		1587
1262	// and in some piece of code that gets executed on any "activity":	1588	// and in some piece of code that gets executed on any "activity":
1263	// reset the timeout to start ticking again at 10 seconds	1589	// reset the timeout to start ticking again at 10 seconds
1264	ev_timer_again (&mytimer);	1590	ev_timer_again (&mytimer);
1265		1591
1266		1592
1267	=head2 C<ev_periodic> - to cron or not to cron?	1593	=head2 C<ev_periodic> - to cron or not to cron?
1268		1594
1269	Periodic watchers are also timers of a kind, but they are very versatile	1595	Periodic watchers are also timers of a kind, but they are very versatile
1270	(and unfortunately a bit complex).	1596	(and unfortunately a bit complex).
1271		1597
1272	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1598	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1273	but on wallclock time (absolute time). You can tell a periodic watcher	1599	but on wall clock time (absolute time). You can tell a periodic watcher
1274	to trigger "at" some specific point in time. For example, if you tell a	1600	to trigger after some specific point in time. For example, if you tell a
1275	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1601	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1276	+ 10.>) and then reset your system clock to the last year, then it will	1602	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1603	clock to January of the previous year, then it will take more than year
1277	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1604	to trigger the event (unlike an C<ev_timer>, which would still trigger
1278	roughly 10 seconds later).	1605	roughly 10 seconds later as it uses a relative timeout).
1279		1606
1280	They can also be used to implement vastly more complex timers, such as	1607	C<ev_periodic>s can also be used to implement vastly more complex timers,
1281	triggering an event on each midnight, local time or other, complicated,	1608	such as triggering an event on each "midnight, local time", or other
1282	rules.	1609	complicated rules.
1283		1610
1284	As with timers, the callback is guarenteed to be invoked only when the	1611	As with timers, the callback is guaranteed to be invoked only when the
1285	time (C<at>) has been passed, but if multiple periodic timers become ready	1612	time (C<at>) has passed, but if multiple periodic timers become ready
1286	during the same loop iteration then order of execution is undefined.	1613	during the same loop iteration, then order of execution is undefined.
1287		1614
1288	=head3 Watcher-Specific Functions and Data Members	1615	=head3 Watcher-Specific Functions and Data Members
1289		1616
1290	=over 4	1617	=over 4
1291		1618
1292	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1619	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1293		1620
1294	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1621	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1295		1622
1296	Lots of arguments, lets sort it out... There are basically three modes of	1623	Lots of arguments, lets sort it out... There are basically three modes of
1297	operation, and we will explain them from simplest to complex:	1624	operation, and we will explain them from simplest to most complex:
1298		1625
1299	=over 4	1626	=over 4
1300		1627
1301	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1628	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1302		1629
1303	In this configuration the watcher triggers an event at the wallclock time	1630	In this configuration the watcher triggers an event after the wall clock
1304	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1631	time C<at> has passed. It will not repeat and will not adjust when a time
1305	that is, if it is to be run at January 1st 2011 then it will run when the	1632	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1306	system time reaches or surpasses this time.	1633	only run when the system clock reaches or surpasses this time.
1307		1634
1308	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1635	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1309		1636
1310	In this mode the watcher will always be scheduled to time out at the next	1637	In this mode the watcher will always be scheduled to time out at the next
1311	C<at + N * interval> time (for some integer N, which can also be negative)	1638	C<at + N * interval> time (for some integer N, which can also be negative)
1312	and then repeat, regardless of any time jumps.	1639	and then repeat, regardless of any time jumps.
1313		1640
1314	This can be used to create timers that do not drift with respect to system	1641	This can be used to create timers that do not drift with respect to the
1315	time:	1642	system clock, for example, here is a C<ev_periodic> that triggers each
		1643	hour, on the hour:
1316		1644
1317	ev_periodic_set (&periodic, 0., 3600., 0);	1645	ev_periodic_set (&periodic, 0., 3600., 0);
1318		1646
1319	This doesn't mean there will always be 3600 seconds in between triggers,	1647	This doesn't mean there will always be 3600 seconds in between triggers,
1320	but only that the the callback will be called when the system time shows a	1648	but only that the callback will be called when the system time shows a
1321	full hour (UTC), or more correctly, when the system time is evenly divisible	1649	full hour (UTC), or more correctly, when the system time is evenly divisible
1322	by 3600.	1650	by 3600.
1323		1651
1324	Another way to think about it (for the mathematically inclined) is that	1652	Another way to think about it (for the mathematically inclined) is that
1325	C<ev_periodic> will try to run the callback in this mode at the next possible	1653	C<ev_periodic> will try to run the callback in this mode at the next possible
1326	time where C<time = at (mod interval)>, regardless of any time jumps.	1654	time where C<time = at (mod interval)>, regardless of any time jumps.
1327		1655
1328	For numerical stability it is preferable that the C<at> value is near	1656	For numerical stability it is preferable that the C<at> value is near
1329	C<ev_now ()> (the current time), but there is no range requirement for	1657	C<ev_now ()> (the current time), but there is no range requirement for
1330	this value.	1658	this value, and in fact is often specified as zero.
		1659
		1660	Note also that there is an upper limit to how often a timer can fire (CPU
		1661	speed for example), so if C<interval> is very small then timing stability
		1662	will of course deteriorate. Libev itself tries to be exact to be about one
		1663	millisecond (if the OS supports it and the machine is fast enough).
1331		1664
1332	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1665	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1333		1666
1334	In this mode the values for C<interval> and C<at> are both being	1667	In this mode the values for C<interval> and C<at> are both being
1335	ignored. Instead, each time the periodic watcher gets scheduled, the	1668	ignored. Instead, each time the periodic watcher gets scheduled, the
1336	reschedule callback will be called with the watcher as first, and the	1669	reschedule callback will be called with the watcher as first, and the
1337	current time as second argument.	1670	current time as second argument.
1338		1671
1339	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1672	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1340	ever, or make any event loop modifications>. If you need to stop it,	1673	ever, or make ANY event loop modifications whatsoever>.
1341	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1342	starting an C<ev_prepare> watcher, which is legal).
1343		1674
		1675	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1676	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1677	only event loop modification you are allowed to do).
		1678
1344	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1679	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1345	ev_tstamp now)>, e.g.:	1680	*w, ev_tstamp now)>, e.g.:
1346		1681
		1682	static ev_tstamp
1347	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1683	my_rescheduler (ev_periodic *w, ev_tstamp now)
1348	{	1684	{
1349	return now + 60.;	1685	return now + 60.;
1350	}	1686	}
1351		1687
1352	It must return the next time to trigger, based on the passed time value	1688	It must return the next time to trigger, based on the passed time value
1353	(that is, the lowest time value larger than to the second argument). It	1689	(that is, the lowest time value larger than to the second argument). It
1354	will usually be called just before the callback will be triggered, but	1690	will usually be called just before the callback will be triggered, but
1355	might be called at other times, too.	1691	might be called at other times, too.
1356		1692
1357	NOTE: I<< This callback must always return a time that is later than the	1693	NOTE: I<< This callback must always return a time that is higher than or
1358	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1694	equal to the passed C<now> value >>.
1359		1695
1360	This can be used to create very complex timers, such as a timer that	1696	This can be used to create very complex timers, such as a timer that
1361	triggers on each midnight, local time. To do this, you would calculate the	1697	triggers on "next midnight, local time". To do this, you would calculate the
1362	next midnight after C<now> and return the timestamp value for this. How	1698	next midnight after C<now> and return the timestamp value for this. How
1363	you do this is, again, up to you (but it is not trivial, which is the main	1699	you do this is, again, up to you (but it is not trivial, which is the main
1364	reason I omitted it as an example).	1700	reason I omitted it as an example).
1365		1701
1366	=back	1702	=back
…		…
1370	Simply stops and restarts the periodic watcher again. This is only useful	1706	Simply stops and restarts the periodic watcher again. This is only useful
1371	when you changed some parameters or the reschedule callback would return	1707	when you changed some parameters or the reschedule callback would return
1372	a different time than the last time it was called (e.g. in a crond like	1708	a different time than the last time it was called (e.g. in a crond like
1373	program when the crontabs have changed).	1709	program when the crontabs have changed).
1374		1710
		1711	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1712
		1713	When active, returns the absolute time that the watcher is supposed to
		1714	trigger next.
		1715
1375	=item ev_tstamp offset [read-write]	1716	=item ev_tstamp offset [read-write]
1376		1717
1377	When repeating, this contains the offset value, otherwise this is the	1718	When repeating, this contains the offset value, otherwise this is the
1378	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1719	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1379		1720
…		…
1384		1725
1385	The current interval value. Can be modified any time, but changes only	1726	The current interval value. Can be modified any time, but changes only
1386	take effect when the periodic timer fires or C<ev_periodic_again> is being	1727	take effect when the periodic timer fires or C<ev_periodic_again> is being
1387	called.	1728	called.
1388		1729
1389	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1730	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1390		1731
1391	The current reschedule callback, or C<0>, if this functionality is	1732	The current reschedule callback, or C<0>, if this functionality is
1392	switched off. Can be changed any time, but changes only take effect when	1733	switched off. Can be changed any time, but changes only take effect when
1393	the periodic timer fires or C<ev_periodic_again> is being called.	1734	the periodic timer fires or C<ev_periodic_again> is being called.
1394		1735
1395	=item ev_tstamp at [read-only]
1396
1397	When active, contains the absolute time that the watcher is supposed to
1398	trigger next.
1399
1400	=back	1736	=back
1401		1737
1402	=head3 Examples	1738	=head3 Examples
1403		1739
1404	Example: Call a callback every hour, or, more precisely, whenever the	1740	Example: Call a callback every hour, or, more precisely, whenever the
1405	system clock is divisible by 3600. The callback invocation times have	1741	system time is divisible by 3600. The callback invocation times have
1406	potentially a lot of jittering, but good long-term stability.	1742	potentially a lot of jitter, but good long-term stability.
1407		1743
1408	static void	1744	static void
1409	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1745	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1410	{	1746	{
1411	... its now a full hour (UTC, or TAI or whatever your clock follows)	1747	... its now a full hour (UTC, or TAI or whatever your clock follows)
1412	}	1748	}
1413		1749
1414	struct ev_periodic hourly_tick;	1750	ev_periodic hourly_tick;
1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1751	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1416	ev_periodic_start (loop, &hourly_tick);	1752	ev_periodic_start (loop, &hourly_tick);
1417		1753
1418	Example: The same as above, but use a reschedule callback to do it:	1754	Example: The same as above, but use a reschedule callback to do it:
1419		1755
1420	#include <math.h>	1756	#include <math.h>
1421		1757
1422	static ev_tstamp	1758	static ev_tstamp
1423	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1759	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1424	{	1760	{
1425	return fmod (now, 3600.) + 3600.;	1761	return now + (3600. - fmod (now, 3600.));
1426	}	1762	}
1427		1763
1428	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1764	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1429		1765
1430	Example: Call a callback every hour, starting now:	1766	Example: Call a callback every hour, starting now:
1431		1767
1432	struct ev_periodic hourly_tick;	1768	ev_periodic hourly_tick;
1433	ev_periodic_init (&hourly_tick, clock_cb,	1769	ev_periodic_init (&hourly_tick, clock_cb,
1434	fmod (ev_now (loop), 3600.), 3600., 0);	1770	fmod (ev_now (loop), 3600.), 3600., 0);
1435	ev_periodic_start (loop, &hourly_tick);	1771	ev_periodic_start (loop, &hourly_tick);
1436		1772
1437		1773
1438	=head2 C<ev_signal> - signal me when a signal gets signalled!	1774	=head2 C<ev_signal> - signal me when a signal gets signalled!
1439		1775
1440	Signal watchers will trigger an event when the process receives a specific	1776	Signal watchers will trigger an event when the process receives a specific
1441	signal one or more times. Even though signals are very asynchronous, libev	1777	signal one or more times. Even though signals are very asynchronous, libev
1442	will try it's best to deliver signals synchronously, i.e. as part of the	1778	will try it's best to deliver signals synchronously, i.e. as part of the
1443	normal event processing, like any other event.	1779	normal event processing, like any other event.
1444		1780
		1781	If you want signals asynchronously, just use C<sigaction> as you would
		1782	do without libev and forget about sharing the signal. You can even use
		1783	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1784
1445	You can configure as many watchers as you like per signal. Only when the	1785	You can configure as many watchers as you like per signal. Only when the
1446	first watcher gets started will libev actually register a signal watcher	1786	first watcher gets started will libev actually register a signal handler
1447	with the kernel (thus it coexists with your own signal handlers as long	1787	with the kernel (thus it coexists with your own signal handlers as long as
1448	as you don't register any with libev). Similarly, when the last signal	1788	you don't register any with libev for the same signal). Similarly, when
1449	watcher for a signal is stopped libev will reset the signal handler to	1789	the last signal watcher for a signal is stopped, libev will reset the
1450	SIG_DFL (regardless of what it was set to before).	1790	signal handler to SIG_DFL (regardless of what it was set to before).
1451		1791
1452	If possible and supported, libev will install its handlers with	1792	If possible and supported, libev will install its handlers with
1453	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1793	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1454	interrupted. If you have a problem with syscalls getting interrupted by	1794	interrupted. If you have a problem with system calls getting interrupted by
1455	signals you can block all signals in an C<ev_check> watcher and unblock	1795	signals you can block all signals in an C<ev_check> watcher and unblock
1456	them in an C<ev_prepare> watcher.	1796	them in an C<ev_prepare> watcher.
1457		1797
1458	=head3 Watcher-Specific Functions and Data Members	1798	=head3 Watcher-Specific Functions and Data Members
1459		1799
…		…
1472		1812
1473	=back	1813	=back
1474		1814
1475	=head3 Examples	1815	=head3 Examples
1476		1816
1477	Example: Try to exit cleanly on SIGINT and SIGTERM.	1817	Example: Try to exit cleanly on SIGINT.
1478		1818
1479	static void	1819	static void
1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1820	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1481	{	1821	{
1482	ev_unloop (loop, EVUNLOOP_ALL);	1822	ev_unloop (loop, EVUNLOOP_ALL);
1483	}	1823	}
1484		1824
1485	struct ev_signal signal_watcher;	1825	ev_signal signal_watcher;
1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1826	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1487	ev_signal_start (loop, &sigint_cb);	1827	ev_signal_start (loop, &signal_watcher);
1488		1828
1489		1829
1490	=head2 C<ev_child> - watch out for process status changes	1830	=head2 C<ev_child> - watch out for process status changes
1491		1831
1492	Child watchers trigger when your process receives a SIGCHLD in response to	1832	Child watchers trigger when your process receives a SIGCHLD in response to
1493	some child status changes (most typically when a child of yours dies). It	1833	some child status changes (most typically when a child of yours dies or
1494	is permissible to install a child watcher I<after> the child has been	1834	exits). It is permissible to install a child watcher I<after> the child
1495	forked (which implies it might have already exited), as long as the event	1835	has been forked (which implies it might have already exited), as long
1496	loop isn't entered (or is continued from a watcher).	1836	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1837	forking and then immediately registering a watcher for the child is fine,
		1838	but forking and registering a watcher a few event loop iterations later is
		1839	not.
1497		1840
1498	Only the default event loop is capable of handling signals, and therefore	1841	Only the default event loop is capable of handling signals, and therefore
1499	you can only rgeister child watchers in the default event loop.	1842	you can only register child watchers in the default event loop.
1500		1843
1501	=head3 Process Interaction	1844	=head3 Process Interaction
1502		1845
1503	Libev grabs C<SIGCHLD> as soon as the default event loop is	1846	Libev grabs C<SIGCHLD> as soon as the default event loop is
1504	initialised. This is necessary to guarantee proper behaviour even if	1847	initialised. This is necessary to guarantee proper behaviour even if
1505	the first child watcher is started after the child exits. The occurance	1848	the first child watcher is started after the child exits. The occurrence
1506	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1849	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1507	synchronously as part of the event loop processing. Libev always reaps all	1850	synchronously as part of the event loop processing. Libev always reaps all
1508	children, even ones not watched.	1851	children, even ones not watched.
1509		1852
1510	=head3 Overriding the Built-In Processing	1853	=head3 Overriding the Built-In Processing
…		…
1514	handler, you can override it easily by installing your own handler for	1857	handler, you can override it easily by installing your own handler for
1515	C<SIGCHLD> after initialising the default loop, and making sure the	1858	C<SIGCHLD> after initialising the default loop, and making sure the
1516	default loop never gets destroyed. You are encouraged, however, to use an	1859	default loop never gets destroyed. You are encouraged, however, to use an
1517	event-based approach to child reaping and thus use libev's support for	1860	event-based approach to child reaping and thus use libev's support for
1518	that, so other libev users can use C<ev_child> watchers freely.	1861	that, so other libev users can use C<ev_child> watchers freely.
		1862
		1863	=head3 Stopping the Child Watcher
		1864
		1865	Currently, the child watcher never gets stopped, even when the
		1866	child terminates, so normally one needs to stop the watcher in the
		1867	callback. Future versions of libev might stop the watcher automatically
		1868	when a child exit is detected.
1519		1869
1520	=head3 Watcher-Specific Functions and Data Members	1870	=head3 Watcher-Specific Functions and Data Members
1521		1871
1522	=over 4	1872	=over 4
1523		1873
…		…
1552	=head3 Examples	1902	=head3 Examples
1553		1903
1554	Example: C<fork()> a new process and install a child handler to wait for	1904	Example: C<fork()> a new process and install a child handler to wait for
1555	its completion.	1905	its completion.
1556		1906
1557	ev_child cw;	1907	ev_child cw;
1558		1908
1559	static void	1909	static void
1560	child_cb (EV_P_ struct ev_child *w, int revents)	1910	child_cb (EV_P_ ev_child *w, int revents)
1561	{	1911	{
1562	ev_child_stop (EV_A_ w);	1912	ev_child_stop (EV_A_ w);
1563	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1913	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1564	}	1914	}
1565		1915
1566	pid_t pid = fork ();	1916	pid_t pid = fork ();
1567		1917
1568	if (pid < 0)	1918	if (pid < 0)
1569	// error	1919	// error
1570	else if (pid == 0)	1920	else if (pid == 0)
1571	{	1921	{
1572	// the forked child executes here	1922	// the forked child executes here
1573	exit (1);	1923	exit (1);
1574	}	1924	}
1575	else	1925	else
1576	{	1926	{
1577	ev_child_init (&cw, child_cb, pid, 0);	1927	ev_child_init (&cw, child_cb, pid, 0);
1578	ev_child_start (EV_DEFAULT_ &cw);	1928	ev_child_start (EV_DEFAULT_ &cw);
1579	}	1929	}
1580		1930
1581		1931
1582	=head2 C<ev_stat> - did the file attributes just change?	1932	=head2 C<ev_stat> - did the file attributes just change?
1583		1933
1584	This watches a filesystem path for attribute changes. That is, it calls	1934	This watches a file system path for attribute changes. That is, it calls
1585	C<stat> regularly (or when the OS says it changed) and sees if it changed	1935	C<stat> on that path in regular intervals (or when the OS says it changed)
1586	compared to the last time, invoking the callback if it did.	1936	and sees if it changed compared to the last time, invoking the callback if
		1937	it did.
1587		1938
1588	The path does not need to exist: changing from "path exists" to "path does	1939	The path does not need to exist: changing from "path exists" to "path does
1589	not exist" is a status change like any other. The condition "path does	1940	not exist" is a status change like any other. The condition "path does not
1590	not exist" is signified by the C<st_nlink> field being zero (which is	1941	exist" (or more correctly "path cannot be stat'ed") is signified by the
1591	otherwise always forced to be at least one) and all the other fields of	1942	C<st_nlink> field being zero (which is otherwise always forced to be at
1592	the stat buffer having unspecified contents.	1943	least one) and all the other fields of the stat buffer having unspecified
		1944	contents.
1593		1945
1594	The path I<should> be absolute and I<must not> end in a slash. If it is	1946	The path I<must not> end in a slash or contain special components such as
		1947	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1595	relative and your working directory changes, the behaviour is undefined.	1948	your working directory changes, then the behaviour is undefined.
1596		1949
1597	Since there is no standard to do this, the portable implementation simply	1950	Since there is no portable change notification interface available, the
1598	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1951	portable implementation simply calls C<stat(2)> regularly on the path
1599	can specify a recommended polling interval for this case. If you specify	1952	to see if it changed somehow. You can specify a recommended polling
1600	a polling interval of C<0> (highly recommended!) then a I<suitable,	1953	interval for this case. If you specify a polling interval of C<0> (highly
1601	unspecified default> value will be used (which you can expect to be around	1954	recommended!) then a I<suitable, unspecified default> value will be used
1602	five seconds, although this might change dynamically). Libev will also	1955	(which you can expect to be around five seconds, although this might
1603	impose a minimum interval which is currently around C<0.1>, but thats	1956	change dynamically). Libev will also impose a minimum interval which is
1604	usually overkill.	1957	currently around C<0.1>, but that's usually overkill.
1605		1958
1606	This watcher type is not meant for massive numbers of stat watchers,	1959	This watcher type is not meant for massive numbers of stat watchers,
1607	as even with OS-supported change notifications, this can be	1960	as even with OS-supported change notifications, this can be
1608	resource-intensive.	1961	resource-intensive.
1609		1962
1610	At the time of this writing, only the Linux inotify interface is	1963	At the time of this writing, the only OS-specific interface implemented
1611	implemented (implementing kqueue support is left as an exercise for the	1964	is the Linux inotify interface (implementing kqueue support is left as an
1612	reader). Inotify will be used to give hints only and should not change the	1965	exercise for the reader. Note, however, that the author sees no way of
1613	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1966	implementing C<ev_stat> semantics with kqueue, except as a hint).
1614	to fall back to regular polling again even with inotify, but changes are
1615	usually detected immediately, and if the file exists there will be no
1616	polling.
1617		1967
1618	=head3 ABI Issues (Largefile Support)	1968	=head3 ABI Issues (Largefile Support)
1619		1969
1620	Libev by default (unless the user overrides this) uses the default	1970	Libev by default (unless the user overrides this) uses the default
1621	compilation environment, which means that on systems with optionally	1971	compilation environment, which means that on systems with large file
1622	disabled large file support, you get the 32 bit version of the stat	1972	support disabled by default, you get the 32 bit version of the stat
1623	structure. When using the library from programs that change the ABI to	1973	structure. When using the library from programs that change the ABI to
1624	use 64 bit file offsets the programs will fail. In that case you have to	1974	use 64 bit file offsets the programs will fail. In that case you have to
1625	compile libev with the same flags to get binary compatibility. This is	1975	compile libev with the same flags to get binary compatibility. This is
1626	obviously the case with any flags that change the ABI, but the problem is	1976	obviously the case with any flags that change the ABI, but the problem is
1627	most noticably with ev_stat and largefile support.	1977	most noticeably displayed with ev_stat and large file support.
1628		1978
1629	=head3 Inotify	1979	The solution for this is to lobby your distribution maker to make large
		1980	file interfaces available by default (as e.g. FreeBSD does) and not
		1981	optional. Libev cannot simply switch on large file support because it has
		1982	to exchange stat structures with application programs compiled using the
		1983	default compilation environment.
1630		1984
		1985	=head3 Inotify and Kqueue
		1986
1631	When C<inotify (7)> support has been compiled into libev (generally only	1987	When C<inotify (7)> support has been compiled into libev and present at
1632	available on Linux) and present at runtime, it will be used to speed up	1988	runtime, it will be used to speed up change detection where possible. The
1633	change detection where possible. The inotify descriptor will be created lazily	1989	inotify descriptor will be created lazily when the first C<ev_stat>
1634	when the first C<ev_stat> watcher is being started.	1990	watcher is being started.
1635		1991
1636	Inotify presense does not change the semantics of C<ev_stat> watchers	1992	Inotify presence does not change the semantics of C<ev_stat> watchers
1637	except that changes might be detected earlier, and in some cases, to avoid	1993	except that changes might be detected earlier, and in some cases, to avoid
1638	making regular C<stat> calls. Even in the presense of inotify support	1994	making regular C<stat> calls. Even in the presence of inotify support
1639	there are many cases where libev has to resort to regular C<stat> polling.	1995	there are many cases where libev has to resort to regular C<stat> polling,
		1996	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1997	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1998	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		1999	xfs are fully working) libev usually gets away without polling.
1640		2000
1641	(There is no support for kqueue, as apparently it cannot be used to	2001	There is no support for kqueue, as apparently it cannot be used to
1642	implement this functionality, due to the requirement of having a file	2002	implement this functionality, due to the requirement of having a file
1643	descriptor open on the object at all times).	2003	descriptor open on the object at all times, and detecting renames, unlinks
		2004	etc. is difficult.
		2005
		2006	=head3 C<stat ()> is a synchronous operation
		2007
		2008	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2009	the process. The exception are C<ev_stat> watchers - those call C<stat
		2010	()>, which is a synchronous operation.
		2011
		2012	For local paths, this usually doesn't matter: unless the system is very
		2013	busy or the intervals between stat's are large, a stat call will be fast,
		2014	as the path data is suually in memory already (except when starting the
		2015	watcher).
		2016
		2017	For networked file systems, calling C<stat ()> can block an indefinite
		2018	time due to network issues, and even under good conditions, a stat call
		2019	often takes multiple milliseconds.
		2020
		2021	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2022	paths, although this is fully supported by libev.
1644		2023
1645	=head3 The special problem of stat time resolution	2024	=head3 The special problem of stat time resolution
1646		2025
1647	The C<stat ()> syscall only supports full-second resolution portably, and	2026	The C<stat ()> system call only supports full-second resolution portably,
1648	even on systems where the resolution is higher, many filesystems still	2027	and even on systems where the resolution is higher, most file systems
1649	only support whole seconds.	2028	still only support whole seconds.
1650		2029
1651	That means that, if the time is the only thing that changes, you might	2030	That means that, if the time is the only thing that changes, you can
1652	miss updates: on the first update, C<ev_stat> detects a change and calls	2031	easily miss updates: on the first update, C<ev_stat> detects a change and
1653	your callback, which does something. When there is another update within	2032	calls your callback, which does something. When there is another update
1654	the same second, C<ev_stat> will be unable to detect it.	2033	within the same second, C<ev_stat> will be unable to detect unless the
		2034	stat data does change in other ways (e.g. file size).
1655		2035
1656	The solution to this is to delay acting on a change for a second (or till	2036	The solution to this is to delay acting on a change for slightly more
1657	the next second boundary), using a roughly one-second delay C<ev_timer>	2037	than a second (or till slightly after the next full second boundary), using
1658	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2038	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1659	is added to work around small timing inconsistencies of some operating	2039	ev_timer_again (loop, w)>).
1660	systems.	2040
		2041	The C<.02> offset is added to work around small timing inconsistencies
		2042	of some operating systems (where the second counter of the current time
		2043	might be be delayed. One such system is the Linux kernel, where a call to
		2044	C<gettimeofday> might return a timestamp with a full second later than
		2045	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2046	update file times then there will be a small window where the kernel uses
		2047	the previous second to update file times but libev might already execute
		2048	the timer callback).
1661		2049
1662	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1663		2051
1664	=over 4	2052	=over 4
1665		2053
…		…
1671	C<path>. The C<interval> is a hint on how quickly a change is expected to	2059	C<path>. The C<interval> is a hint on how quickly a change is expected to
1672	be detected and should normally be specified as C<0> to let libev choose	2060	be detected and should normally be specified as C<0> to let libev choose
1673	a suitable value. The memory pointed to by C<path> must point to the same	2061	a suitable value. The memory pointed to by C<path> must point to the same
1674	path for as long as the watcher is active.	2062	path for as long as the watcher is active.
1675		2063
1676	The callback will be receive C<EV_STAT> when a change was detected,	2064	The callback will receive an C<EV_STAT> event when a change was detected,
1677	relative to the attributes at the time the watcher was started (or the	2065	relative to the attributes at the time the watcher was started (or the
1678	last change was detected).	2066	last change was detected).
1679		2067
1680	=item ev_stat_stat (loop, ev_stat *)	2068	=item ev_stat_stat (loop, ev_stat *)
1681		2069
1682	Updates the stat buffer immediately with new values. If you change the	2070	Updates the stat buffer immediately with new values. If you change the
1683	watched path in your callback, you could call this fucntion to avoid	2071	watched path in your callback, you could call this function to avoid
1684	detecting this change (while introducing a race condition). Can also be	2072	detecting this change (while introducing a race condition if you are not
1685	useful simply to find out the new values.	2073	the only one changing the path). Can also be useful simply to find out the
		2074	new values.
1686		2075
1687	=item ev_statdata attr [read-only]	2076	=item ev_statdata attr [read-only]
1688		2077
1689	The most-recently detected attributes of the file. Although the type is of	2078	The most-recently detected attributes of the file. Although the type is
1690	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2079	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1691	suitable for your system. If the C<st_nlink> member is C<0>, then there	2080	suitable for your system, but you can only rely on the POSIX-standardised
		2081	members to be present. If the C<st_nlink> member is C<0>, then there was
1692	was some error while C<stat>ing the file.	2082	some error while C<stat>ing the file.
1693		2083
1694	=item ev_statdata prev [read-only]	2084	=item ev_statdata prev [read-only]
1695		2085
1696	The previous attributes of the file. The callback gets invoked whenever	2086	The previous attributes of the file. The callback gets invoked whenever
1697	C<prev> != C<attr>.	2087	C<prev> != C<attr>, or, more precisely, one or more of these members
		2088	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2089	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1698		2090
1699	=item ev_tstamp interval [read-only]	2091	=item ev_tstamp interval [read-only]
1700		2092
1701	The specified interval.	2093	The specified interval.
1702		2094
1703	=item const char *path [read-only]	2095	=item const char *path [read-only]
1704		2096
1705	The filesystem path that is being watched.	2097	The file system path that is being watched.
1706		2098
1707	=back	2099	=back
1708		2100
1709	=head3 Examples	2101	=head3 Examples
1710		2102
1711	Example: Watch C</etc/passwd> for attribute changes.	2103	Example: Watch C</etc/passwd> for attribute changes.
1712		2104
1713	static void	2105	static void
1714	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2106	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1715	{	2107	{
1716	/* /etc/passwd changed in some way */	2108	/* /etc/passwd changed in some way */
1717	if (w->attr.st_nlink)	2109	if (w->attr.st_nlink)
1718	{	2110	{
1719	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2111	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1720	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2112	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1721	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2113	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1722	}	2114	}
1723	else	2115	else
1724	/* you shalt not abuse printf for puts */	2116	/* you shalt not abuse printf for puts */
1725	puts ("wow, /etc/passwd is not there, expect problems. "	2117	puts ("wow, /etc/passwd is not there, expect problems. "
1726	"if this is windows, they already arrived\n");	2118	"if this is windows, they already arrived\n");
1727	}	2119	}
1728		2120
1729	...	2121	...
1730	ev_stat passwd;	2122	ev_stat passwd;
1731		2123
1732	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2124	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1733	ev_stat_start (loop, &passwd);	2125	ev_stat_start (loop, &passwd);
1734		2126
1735	Example: Like above, but additionally use a one-second delay so we do not	2127	Example: Like above, but additionally use a one-second delay so we do not
1736	miss updates (however, frequent updates will delay processing, too, so	2128	miss updates (however, frequent updates will delay processing, too, so
1737	one might do the work both on C<ev_stat> callback invocation I<and> on	2129	one might do the work both on C<ev_stat> callback invocation I<and> on
1738	C<ev_timer> callback invocation).	2130	C<ev_timer> callback invocation).
1739		2131
1740	static ev_stat passwd;	2132	static ev_stat passwd;
1741	static ev_timer timer;	2133	static ev_timer timer;
1742		2134
1743	static void	2135	static void
1744	timer_cb (EV_P_ ev_timer *w, int revents)	2136	timer_cb (EV_P_ ev_timer *w, int revents)
1745	{	2137	{
1746	ev_timer_stop (EV_A_ w);	2138	ev_timer_stop (EV_A_ w);
1747		2139
1748	/* now it's one second after the most recent passwd change */	2140	/* now it's one second after the most recent passwd change */
1749	}	2141	}
1750		2142
1751	static void	2143	static void
1752	stat_cb (EV_P_ ev_stat *w, int revents)	2144	stat_cb (EV_P_ ev_stat *w, int revents)
1753	{	2145	{
1754	/* reset the one-second timer */	2146	/* reset the one-second timer */
1755	ev_timer_again (EV_A_ &timer);	2147	ev_timer_again (EV_A_ &timer);
1756	}	2148	}
1757		2149
1758	...	2150	...
1759	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2151	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1760	ev_stat_start (loop, &passwd);	2152	ev_stat_start (loop, &passwd);
1761	ev_timer_init (&timer, timer_cb, 0., 1.01);	2153	ev_timer_init (&timer, timer_cb, 0., 1.02);
1762		2154
1763		2155
1764	=head2 C<ev_idle> - when you've got nothing better to do...	2156	=head2 C<ev_idle> - when you've got nothing better to do...
1765		2157
1766	Idle watchers trigger events when no other events of the same or higher	2158	Idle watchers trigger events when no other events of the same or higher
1767	priority are pending (prepare, check and other idle watchers do not	2159	priority are pending (prepare, check and other idle watchers do not count
1768	count).	2160	as receiving "events").
1769		2161
1770	That is, as long as your process is busy handling sockets or timeouts	2162	That is, as long as your process is busy handling sockets or timeouts
1771	(or even signals, imagine) of the same or higher priority it will not be	2163	(or even signals, imagine) of the same or higher priority it will not be
1772	triggered. But when your process is idle (or only lower-priority watchers	2164	triggered. But when your process is idle (or only lower-priority watchers
1773	are pending), the idle watchers are being called once per event loop	2165	are pending), the idle watchers are being called once per event loop
…		…
1797	=head3 Examples	2189	=head3 Examples
1798		2190
1799	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2191	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1800	callback, free it. Also, use no error checking, as usual.	2192	callback, free it. Also, use no error checking, as usual.
1801		2193
1802	static void	2194	static void
1803	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2195	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1804	{	2196	{
1805	free (w);	2197	free (w);
1806	// now do something you wanted to do when the program has	2198	// now do something you wanted to do when the program has
1807	// no longer anything immediate to do.	2199	// no longer anything immediate to do.
1808	}	2200	}
1809		2201
1810	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2202	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1811	ev_idle_init (idle_watcher, idle_cb);	2203	ev_idle_init (idle_watcher, idle_cb);
1812	ev_idle_start (loop, idle_cb);	2204	ev_idle_start (loop, idle_cb);
1813		2205
1814		2206
1815	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2207	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1816		2208
1817	Prepare and check watchers are usually (but not always) used in tandem:	2209	Prepare and check watchers are usually (but not always) used in pairs:
1818	prepare watchers get invoked before the process blocks and check watchers	2210	prepare watchers get invoked before the process blocks and check watchers
1819	afterwards.	2211	afterwards.
1820		2212
1821	You I<must not> call C<ev_loop> or similar functions that enter	2213	You I<must not> call C<ev_loop> or similar functions that enter
1822	the current event loop from either C<ev_prepare> or C<ev_check>	2214	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1825	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2217	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1826	C<ev_check> so if you have one watcher of each kind they will always be	2218	C<ev_check> so if you have one watcher of each kind they will always be
1827	called in pairs bracketing the blocking call.	2219	called in pairs bracketing the blocking call.
1828		2220
1829	Their main purpose is to integrate other event mechanisms into libev and	2221	Their main purpose is to integrate other event mechanisms into libev and
1830	their use is somewhat advanced. This could be used, for example, to track	2222	their use is somewhat advanced. They could be used, for example, to track
1831	variable changes, implement your own watchers, integrate net-snmp or a	2223	variable changes, implement your own watchers, integrate net-snmp or a
1832	coroutine library and lots more. They are also occasionally useful if	2224	coroutine library and lots more. They are also occasionally useful if
1833	you cache some data and want to flush it before blocking (for example,	2225	you cache some data and want to flush it before blocking (for example,
1834	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2226	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1835	watcher).	2227	watcher).
1836		2228
1837	This is done by examining in each prepare call which file descriptors need	2229	This is done by examining in each prepare call which file descriptors
1838	to be watched by the other library, registering C<ev_io> watchers for	2230	need to be watched by the other library, registering C<ev_io> watchers
1839	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2231	for them and starting an C<ev_timer> watcher for any timeouts (many
1840	provide just this functionality). Then, in the check watcher you check for	2232	libraries provide exactly this functionality). Then, in the check watcher,
1841	any events that occured (by checking the pending status of all watchers	2233	you check for any events that occurred (by checking the pending status
1842	and stopping them) and call back into the library. The I/O and timer	2234	of all watchers and stopping them) and call back into the library. The
1843	callbacks will never actually be called (but must be valid nevertheless,	2235	I/O and timer callbacks will never actually be called (but must be valid
1844	because you never know, you know?).	2236	nevertheless, because you never know, you know?).
1845		2237
1846	As another example, the Perl Coro module uses these hooks to integrate	2238	As another example, the Perl Coro module uses these hooks to integrate
1847	coroutines into libev programs, by yielding to other active coroutines	2239	coroutines into libev programs, by yielding to other active coroutines
1848	during each prepare and only letting the process block if no coroutines	2240	during each prepare and only letting the process block if no coroutines
1849	are ready to run (it's actually more complicated: it only runs coroutines	2241	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1852	loop from blocking if lower-priority coroutines are active, thus mapping	2244	loop from blocking if lower-priority coroutines are active, thus mapping
1853	low-priority coroutines to idle/background tasks).	2245	low-priority coroutines to idle/background tasks).
1854		2246
1855	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2247	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1856	priority, to ensure that they are being run before any other watchers	2248	priority, to ensure that they are being run before any other watchers
		2249	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2250
1857	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2251	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1858	too) should not activate ("feed") events into libev. While libev fully	2252	activate ("feed") events into libev. While libev fully supports this, they
1859	supports this, they will be called before other C<ev_check> watchers	2253	might get executed before other C<ev_check> watchers did their job. As
1860	did their job. As C<ev_check> watchers are often used to embed other	2254	C<ev_check> watchers are often used to embed other (non-libev) event
1861	(non-libev) event loops those other event loops might be in an unusable	2255	loops those other event loops might be in an unusable state until their
1862	state until their C<ev_check> watcher ran (always remind yourself to	2256	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1863	coexist peacefully with others).	2257	others).
1864		2258
1865	=head3 Watcher-Specific Functions and Data Members	2259	=head3 Watcher-Specific Functions and Data Members
1866		2260
1867	=over 4	2261	=over 4
1868		2262
…		…
1870		2264
1871	=item ev_check_init (ev_check *, callback)	2265	=item ev_check_init (ev_check *, callback)
1872		2266
1873	Initialises and configures the prepare or check watcher - they have no	2267	Initialises and configures the prepare or check watcher - they have no
1874	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2268	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1875	macros, but using them is utterly, utterly and completely pointless.	2269	macros, but using them is utterly, utterly, utterly and completely
		2270	pointless.
1876		2271
1877	=back	2272	=back
1878		2273
1879	=head3 Examples	2274	=head3 Examples
1880		2275
1881	There are a number of principal ways to embed other event loops or modules	2276	There are a number of principal ways to embed other event loops or modules
1882	into libev. Here are some ideas on how to include libadns into libev	2277	into libev. Here are some ideas on how to include libadns into libev
1883	(there is a Perl module named C<EV::ADNS> that does this, which you could	2278	(there is a Perl module named C<EV::ADNS> that does this, which you could
1884	use for an actually working example. Another Perl module named C<EV::Glib>	2279	use as a working example. Another Perl module named C<EV::Glib> embeds a
1885	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2280	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1886	into the Glib event loop).	2281	Glib event loop).
1887		2282
1888	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2283	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1889	and in a check watcher, destroy them and call into libadns. What follows	2284	and in a check watcher, destroy them and call into libadns. What follows
1890	is pseudo-code only of course. This requires you to either use a low	2285	is pseudo-code only of course. This requires you to either use a low
1891	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2286	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1892	the callbacks for the IO/timeout watchers might not have been called yet.	2287	the callbacks for the IO/timeout watchers might not have been called yet.
1893		2288
1894	static ev_io iow [nfd];	2289	static ev_io iow [nfd];
1895	static ev_timer tw;	2290	static ev_timer tw;
1896		2291
1897	static void	2292	static void
1898	io_cb (ev_loop *loop, ev_io *w, int revents)	2293	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1899	{	2294	{
1900	}	2295	}
1901		2296
1902	// create io watchers for each fd and a timer before blocking	2297	// create io watchers for each fd and a timer before blocking
1903	static void	2298	static void
1904	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2299	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1905	{	2300	{
1906	int timeout = 3600000;	2301	int timeout = 3600000;
1907	struct pollfd fds [nfd];	2302	struct pollfd fds [nfd];
1908	// actual code will need to loop here and realloc etc.	2303	// actual code will need to loop here and realloc etc.
1909	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2304	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1910		2305
1911	/* the callback is illegal, but won't be called as we stop during check */	2306	/* the callback is illegal, but won't be called as we stop during check */
1912	ev_timer_init (&tw, 0, timeout * 1e-3);	2307	ev_timer_init (&tw, 0, timeout * 1e-3);
1913	ev_timer_start (loop, &tw);	2308	ev_timer_start (loop, &tw);
1914		2309
1915	// create one ev_io per pollfd	2310	// create one ev_io per pollfd
1916	for (int i = 0; i < nfd; ++i)	2311	for (int i = 0; i < nfd; ++i)
1917	{	2312	{
1918	ev_io_init (iow + i, io_cb, fds [i].fd,	2313	ev_io_init (iow + i, io_cb, fds [i].fd,
1919	((fds [i].events & POLLIN ? EV_READ : 0)	2314	((fds [i].events & POLLIN ? EV_READ : 0)
1920	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2315	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1921		2316
1922	fds [i].revents = 0;	2317	fds [i].revents = 0;
1923	ev_io_start (loop, iow + i);	2318	ev_io_start (loop, iow + i);
1924	}	2319	}
1925	}	2320	}
1926		2321
1927	// stop all watchers after blocking	2322	// stop all watchers after blocking
1928	static void	2323	static void
1929	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2324	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1930	{	2325	{
1931	ev_timer_stop (loop, &tw);	2326	ev_timer_stop (loop, &tw);
1932		2327
1933	for (int i = 0; i < nfd; ++i)	2328	for (int i = 0; i < nfd; ++i)
1934	{	2329	{
1935	// set the relevant poll flags	2330	// set the relevant poll flags
1936	// could also call adns_processreadable etc. here	2331	// could also call adns_processreadable etc. here
1937	struct pollfd *fd = fds + i;	2332	struct pollfd *fd = fds + i;
1938	int revents = ev_clear_pending (iow + i);	2333	int revents = ev_clear_pending (iow + i);
1939	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2334	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1940	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2335	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1941		2336
1942	// now stop the watcher	2337	// now stop the watcher
1943	ev_io_stop (loop, iow + i);	2338	ev_io_stop (loop, iow + i);
1944	}	2339	}
1945		2340
1946	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2341	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1947	}	2342	}
1948		2343
1949	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2344	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1950	in the prepare watcher and would dispose of the check watcher.	2345	in the prepare watcher and would dispose of the check watcher.
1951		2346
1952	Method 3: If the module to be embedded supports explicit event	2347	Method 3: If the module to be embedded supports explicit event
1953	notification (adns does), you can also make use of the actual watcher	2348	notification (libadns does), you can also make use of the actual watcher
1954	callbacks, and only destroy/create the watchers in the prepare watcher.	2349	callbacks, and only destroy/create the watchers in the prepare watcher.
1955		2350
1956	static void	2351	static void
1957	timer_cb (EV_P_ ev_timer *w, int revents)	2352	timer_cb (EV_P_ ev_timer *w, int revents)
1958	{	2353	{
1959	adns_state ads = (adns_state)w->data;	2354	adns_state ads = (adns_state)w->data;
1960	update_now (EV_A);	2355	update_now (EV_A);
1961		2356
1962	adns_processtimeouts (ads, &tv_now);	2357	adns_processtimeouts (ads, &tv_now);
1963	}	2358	}
1964		2359
1965	static void	2360	static void
1966	io_cb (EV_P_ ev_io *w, int revents)	2361	io_cb (EV_P_ ev_io *w, int revents)
1967	{	2362	{
1968	adns_state ads = (adns_state)w->data;	2363	adns_state ads = (adns_state)w->data;
1969	update_now (EV_A);	2364	update_now (EV_A);
1970		2365
1971	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2366	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1972	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2367	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1973	}	2368	}
1974		2369
1975	// do not ever call adns_afterpoll	2370	// do not ever call adns_afterpoll
1976		2371
1977	Method 4: Do not use a prepare or check watcher because the module you	2372	Method 4: Do not use a prepare or check watcher because the module you
1978	want to embed is too inflexible to support it. Instead, youc na override	2373	want to embed is not flexible enough to support it. Instead, you can
1979	their poll function. The drawback with this solution is that the main	2374	override their poll function. The drawback with this solution is that the
1980	loop is now no longer controllable by EV. The C<Glib::EV> module does	2375	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1981	this.	2376	this approach, effectively embedding EV as a client into the horrible
		2377	libglib event loop.
1982		2378
1983	static gint	2379	static gint
1984	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2380	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1985	{	2381	{
1986	int got_events = 0;	2382	int got_events = 0;
1987		2383
1988	for (n = 0; n < nfds; ++n)	2384	for (n = 0; n < nfds; ++n)
1989	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2385	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1990		2386
1991	if (timeout >= 0)	2387	if (timeout >= 0)
1992	// create/start timer	2388	// create/start timer
1993		2389
1994	// poll	2390	// poll
1995	ev_loop (EV_A_ 0);	2391	ev_loop (EV_A_ 0);
1996		2392
1997	// stop timer again	2393	// stop timer again
1998	if (timeout >= 0)	2394	if (timeout >= 0)
1999	ev_timer_stop (EV_A_ &to);	2395	ev_timer_stop (EV_A_ &to);
2000		2396
2001	// stop io watchers again - their callbacks should have set	2397	// stop io watchers again - their callbacks should have set
2002	for (n = 0; n < nfds; ++n)	2398	for (n = 0; n < nfds; ++n)
2003	ev_io_stop (EV_A_ iow [n]);	2399	ev_io_stop (EV_A_ iow [n]);
2004		2400
2005	return got_events;	2401	return got_events;
2006	}	2402	}
2007		2403
2008		2404
2009	=head2 C<ev_embed> - when one backend isn't enough...	2405	=head2 C<ev_embed> - when one backend isn't enough...
2010		2406
2011	This is a rather advanced watcher type that lets you embed one event loop	2407	This is a rather advanced watcher type that lets you embed one event loop
…		…
2017	prioritise I/O.	2413	prioritise I/O.
2018		2414
2019	As an example for a bug workaround, the kqueue backend might only support	2415	As an example for a bug workaround, the kqueue backend might only support
2020	sockets on some platform, so it is unusable as generic backend, but you	2416	sockets on some platform, so it is unusable as generic backend, but you
2021	still want to make use of it because you have many sockets and it scales	2417	still want to make use of it because you have many sockets and it scales
2022	so nicely. In this case, you would create a kqueue-based loop and embed it	2418	so nicely. In this case, you would create a kqueue-based loop and embed
2023	into your default loop (which might use e.g. poll). Overall operation will	2419	it into your default loop (which might use e.g. poll). Overall operation
2024	be a bit slower because first libev has to poll and then call kevent, but	2420	will be a bit slower because first libev has to call C<poll> and then
2025	at least you can use both at what they are best.	2421	C<kevent>, but at least you can use both mechanisms for what they are
		2422	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2026		2423
2027	As for prioritising I/O: rarely you have the case where some fds have	2424	As for prioritising I/O: under rare circumstances you have the case where
2028	to be watched and handled very quickly (with low latency), and even	2425	some fds have to be watched and handled very quickly (with low latency),
2029	priorities and idle watchers might have too much overhead. In this case	2426	and even priorities and idle watchers might have too much overhead. In
2030	you would put all the high priority stuff in one loop and all the rest in	2427	this case you would put all the high priority stuff in one loop and all
2031	a second one, and embed the second one in the first.	2428	the rest in a second one, and embed the second one in the first.
2032		2429
2033	As long as the watcher is active, the callback will be invoked every time	2430	As long as the watcher is active, the callback will be invoked every time
2034	there might be events pending in the embedded loop. The callback must then	2431	there might be events pending in the embedded loop. The callback must then
2035	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2432	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2036	their callbacks (you could also start an idle watcher to give the embedded	2433	their callbacks (you could also start an idle watcher to give the embedded
…		…
2044	interested in that.	2441	interested in that.
2045		2442
2046	Also, there have not currently been made special provisions for forking:	2443	Also, there have not currently been made special provisions for forking:
2047	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2444	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2048	but you will also have to stop and restart any C<ev_embed> watchers	2445	but you will also have to stop and restart any C<ev_embed> watchers
2049	yourself.	2446	yourself - but you can use a fork watcher to handle this automatically,
		2447	and future versions of libev might do just that.
2050		2448
2051	Unfortunately, not all backends are embeddable, only the ones returned by	2449	Unfortunately, not all backends are embeddable: only the ones returned by
2052	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2450	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2053	portable one.	2451	portable one.
2054		2452
2055	So when you want to use this feature you will always have to be prepared	2453	So when you want to use this feature you will always have to be prepared
2056	that you cannot get an embeddable loop. The recommended way to get around	2454	that you cannot get an embeddable loop. The recommended way to get around
2057	this is to have a separate variables for your embeddable loop, try to	2455	this is to have a separate variables for your embeddable loop, try to
2058	create it, and if that fails, use the normal loop for everything.	2456	create it, and if that fails, use the normal loop for everything.
2059		2457
		2458	=head3 C<ev_embed> and fork
		2459
		2460	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2461	automatically be applied to the embedded loop as well, so no special
		2462	fork handling is required in that case. When the watcher is not running,
		2463	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2464	as applicable.
		2465
2060	=head3 Watcher-Specific Functions and Data Members	2466	=head3 Watcher-Specific Functions and Data Members
2061		2467
2062	=over 4	2468	=over 4
2063		2469
2064	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2470	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2067		2473
2068	Configures the watcher to embed the given loop, which must be	2474	Configures the watcher to embed the given loop, which must be
2069	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2475	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2070	invoked automatically, otherwise it is the responsibility of the callback	2476	invoked automatically, otherwise it is the responsibility of the callback
2071	to invoke it (it will continue to be called until the sweep has been done,	2477	to invoke it (it will continue to be called until the sweep has been done,
2072	if you do not want thta, you need to temporarily stop the embed watcher).	2478	if you do not want that, you need to temporarily stop the embed watcher).
2073		2479
2074	=item ev_embed_sweep (loop, ev_embed *)	2480	=item ev_embed_sweep (loop, ev_embed *)
2075		2481
2076	Make a single, non-blocking sweep over the embedded loop. This works	2482	Make a single, non-blocking sweep over the embedded loop. This works
2077	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2483	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2078	apropriate way for embedded loops.	2484	appropriate way for embedded loops.
2079		2485
2080	=item struct ev_loop *other [read-only]	2486	=item struct ev_loop *other [read-only]
2081		2487
2082	The embedded event loop.	2488	The embedded event loop.
2083		2489
…		…
2085		2491
2086	=head3 Examples	2492	=head3 Examples
2087		2493
2088	Example: Try to get an embeddable event loop and embed it into the default	2494	Example: Try to get an embeddable event loop and embed it into the default
2089	event loop. If that is not possible, use the default loop. The default	2495	event loop. If that is not possible, use the default loop. The default
2090	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2496	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2091	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2497	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2092	used).	2498	used).
2093		2499
2094	struct ev_loop *loop_hi = ev_default_init (0);	2500	struct ev_loop *loop_hi = ev_default_init (0);
2095	struct ev_loop *loop_lo = 0;	2501	struct ev_loop *loop_lo = 0;
2096	struct ev_embed embed;	2502	ev_embed embed;
2097		2503
2098	// see if there is a chance of getting one that works	2504	// see if there is a chance of getting one that works
2099	// (remember that a flags value of 0 means autodetection)	2505	// (remember that a flags value of 0 means autodetection)
2100	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2506	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2101	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2507	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2102	: 0;	2508	: 0;
2103		2509
2104	// if we got one, then embed it, otherwise default to loop_hi	2510	// if we got one, then embed it, otherwise default to loop_hi
2105	if (loop_lo)	2511	if (loop_lo)
2106	{	2512	{
2107	ev_embed_init (&embed, 0, loop_lo);	2513	ev_embed_init (&embed, 0, loop_lo);
2108	ev_embed_start (loop_hi, &embed);	2514	ev_embed_start (loop_hi, &embed);
2109	}	2515	}
2110	else	2516	else
2111	loop_lo = loop_hi;	2517	loop_lo = loop_hi;
2112		2518
2113	Example: Check if kqueue is available but not recommended and create	2519	Example: Check if kqueue is available but not recommended and create
2114	a kqueue backend for use with sockets (which usually work with any	2520	a kqueue backend for use with sockets (which usually work with any
2115	kqueue implementation). Store the kqueue/socket-only event loop in	2521	kqueue implementation). Store the kqueue/socket-only event loop in
2116	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2522	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2117		2523
2118	struct ev_loop *loop = ev_default_init (0);	2524	struct ev_loop *loop = ev_default_init (0);
2119	struct ev_loop *loop_socket = 0;	2525	struct ev_loop *loop_socket = 0;
2120	struct ev_embed embed;	2526	ev_embed embed;
2121		2527
2122	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2528	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2123	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2529	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2124	{	2530	{
2125	ev_embed_init (&embed, 0, loop_socket);	2531	ev_embed_init (&embed, 0, loop_socket);
2126	ev_embed_start (loop, &embed);	2532	ev_embed_start (loop, &embed);
2127	}	2533	}
2128		2534
2129	if (!loop_socket)	2535	if (!loop_socket)
2130	loop_socket = loop;	2536	loop_socket = loop;
2131		2537
2132	// now use loop_socket for all sockets, and loop for everything else	2538	// now use loop_socket for all sockets, and loop for everything else
2133		2539
2134		2540
2135	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2541	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2136		2542
2137	Fork watchers are called when a C<fork ()> was detected (usually because	2543	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2181	is that the author does not know of a simple (or any) algorithm for a	2587	is that the author does not know of a simple (or any) algorithm for a
2182	multiple-writer-single-reader queue that works in all cases and doesn't	2588	multiple-writer-single-reader queue that works in all cases and doesn't
2183	need elaborate support such as pthreads.	2589	need elaborate support such as pthreads.
2184		2590
2185	That means that if you want to queue data, you have to provide your own	2591	That means that if you want to queue data, you have to provide your own
2186	queue. But at least I can tell you would implement locking around your	2592	queue. But at least I can tell you how to implement locking around your
2187	queue:	2593	queue:
2188		2594
2189	=over 4	2595	=over 4
2190		2596
2191	=item queueing from a signal handler context	2597	=item queueing from a signal handler context
2192		2598
2193	To implement race-free queueing, you simply add to the queue in the signal	2599	To implement race-free queueing, you simply add to the queue in the signal
2194	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2600	handler but you block the signal handler in the watcher callback. Here is
2195	some fictitiuous SIGUSR1 handler:	2601	an example that does that for some fictitious SIGUSR1 handler:
2196		2602
2197	static ev_async mysig;	2603	static ev_async mysig;
2198		2604
2199	static void	2605	static void
2200	sigusr1_handler (void)	2606	sigusr1_handler (void)
…		…
2266	=over 4	2672	=over 4
2267		2673
2268	=item ev_async_init (ev_async *, callback)	2674	=item ev_async_init (ev_async *, callback)
2269		2675
2270	Initialises and configures the async watcher - it has no parameters of any	2676	Initialises and configures the async watcher - it has no parameters of any
2271	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2677	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2272	believe me.	2678	trust me.
2273		2679
2274	=item ev_async_send (loop, ev_async *)	2680	=item ev_async_send (loop, ev_async *)
2275		2681
2276	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2682	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2277	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2683	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2278	C<ev_feed_event>, this call is safe to do in other threads, signal or	2684	C<ev_feed_event>, this call is safe to do from other threads, signal or
2279	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2685	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2280	section below on what exactly this means).	2686	section below on what exactly this means).
2281		2687
2282	This call incurs the overhead of a syscall only once per loop iteration,	2688	This call incurs the overhead of a system call only once per loop iteration,
2283	so while the overhead might be noticable, it doesn't apply to repeated	2689	so while the overhead might be noticeable, it doesn't apply to repeated
2284	calls to C<ev_async_send>.	2690	calls to C<ev_async_send>.
2285		2691
2286	=item bool = ev_async_pending (ev_async *)	2692	=item bool = ev_async_pending (ev_async *)
2287		2693
2288	Returns a non-zero value when C<ev_async_send> has been called on the	2694	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2290	event loop.	2696	event loop.
2291		2697
2292	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2698	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2293	the loop iterates next and checks for the watcher to have become active,	2699	the loop iterates next and checks for the watcher to have become active,
2294	it will reset the flag again. C<ev_async_pending> can be used to very	2700	it will reset the flag again. C<ev_async_pending> can be used to very
2295	quickly check wether invoking the loop might be a good idea.	2701	quickly check whether invoking the loop might be a good idea.
2296		2702
2297	Not that this does I<not> check wether the watcher itself is pending, only	2703	Not that this does I<not> check whether the watcher itself is pending, only
2298	wether it has been requested to make this watcher pending.	2704	whether it has been requested to make this watcher pending.
2299		2705
2300	=back	2706	=back
2301		2707
2302		2708
2303	=head1 OTHER FUNCTIONS	2709	=head1 OTHER FUNCTIONS
…		…
2307	=over 4	2713	=over 4
2308		2714
2309	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2715	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2310		2716
2311	This function combines a simple timer and an I/O watcher, calls your	2717	This function combines a simple timer and an I/O watcher, calls your
2312	callback on whichever event happens first and automatically stop both	2718	callback on whichever event happens first and automatically stops both
2313	watchers. This is useful if you want to wait for a single event on an fd	2719	watchers. This is useful if you want to wait for a single event on an fd
2314	or timeout without having to allocate/configure/start/stop/free one or	2720	or timeout without having to allocate/configure/start/stop/free one or
2315	more watchers yourself.	2721	more watchers yourself.
2316		2722
2317	If C<fd> is less than 0, then no I/O watcher will be started and events	2723	If C<fd> is less than 0, then no I/O watcher will be started and the
2318	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2724	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2319	C<events> set will be craeted and started.	2725	the given C<fd> and C<events> set will be created and started.
2320		2726
2321	If C<timeout> is less than 0, then no timeout watcher will be	2727	If C<timeout> is less than 0, then no timeout watcher will be
2322	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2728	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2323	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2729	repeat = 0) will be started. C<0> is a valid timeout.
2324	dubious value.
2325		2730
2326	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2731	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2327	passed an C<revents> set like normal event callbacks (a combination of	2732	passed an C<revents> set like normal event callbacks (a combination of
2328	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2733	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2329	value passed to C<ev_once>:	2734	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2735	a timeout and an io event at the same time - you probably should give io
		2736	events precedence.
2330		2737
		2738	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2739
2331	static void stdin_ready (int revents, void *arg)	2740	static void stdin_ready (int revents, void *arg)
2332	{	2741	{
2333	if (revents & EV_TIMEOUT)
2334	/* doh, nothing entered */;
2335	else if (revents & EV_READ)	2742	if (revents & EV_READ)
2336	/* stdin might have data for us, joy! */;	2743	/* stdin might have data for us, joy! */;
		2744	else if (revents & EV_TIMEOUT)
		2745	/* doh, nothing entered */;
2337	}	2746	}
2338		2747
2339	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2748	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2340		2749
2341	=item ev_feed_event (ev_loop *, watcher *, int revents)	2750	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2342		2751
2343	Feeds the given event set into the event loop, as if the specified event	2752	Feeds the given event set into the event loop, as if the specified event
2344	had happened for the specified watcher (which must be a pointer to an	2753	had happened for the specified watcher (which must be a pointer to an
2345	initialised but not necessarily started event watcher).	2754	initialised but not necessarily started event watcher).
2346		2755
2347	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2756	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2348		2757
2349	Feed an event on the given fd, as if a file descriptor backend detected	2758	Feed an event on the given fd, as if a file descriptor backend detected
2350	the given events it.	2759	the given events it.
2351		2760
2352	=item ev_feed_signal_event (ev_loop *loop, int signum)	2761	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2353		2762
2354	Feed an event as if the given signal occured (C<loop> must be the default	2763	Feed an event as if the given signal occurred (C<loop> must be the default
2355	loop!).	2764	loop!).
2356		2765
2357	=back	2766	=back
2358		2767
2359		2768
…		…
2375		2784
2376	=item * Priorities are not currently supported. Initialising priorities	2785	=item * Priorities are not currently supported. Initialising priorities
2377	will fail and all watchers will have the same priority, even though there	2786	will fail and all watchers will have the same priority, even though there
2378	is an ev_pri field.	2787	is an ev_pri field.
2379		2788
		2789	=item * In libevent, the last base created gets the signals, in libev, the
		2790	first base created (== the default loop) gets the signals.
		2791
2380	=item * Other members are not supported.	2792	=item * Other members are not supported.
2381		2793
2382	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2794	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2383	to use the libev header file and library.	2795	to use the libev header file and library.
2384		2796
2385	=back	2797	=back
2386		2798
2387	=head1 C++ SUPPORT	2799	=head1 C++ SUPPORT
2388		2800
2389	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2801	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2390	you to use some convinience methods to start/stop watchers and also change	2802	you to use some convenience methods to start/stop watchers and also change
2391	the callback model to a model using method callbacks on objects.	2803	the callback model to a model using method callbacks on objects.
2392		2804
2393	To use it,	2805	To use it,
2394		2806
2395	#include <ev++.h>	2807	#include <ev++.h>
2396		2808
2397	This automatically includes F<ev.h> and puts all of its definitions (many	2809	This automatically includes F<ev.h> and puts all of its definitions (many
2398	of them macros) into the global namespace. All C++ specific things are	2810	of them macros) into the global namespace. All C++ specific things are
2399	put into the C<ev> namespace. It should support all the same embedding	2811	put into the C<ev> namespace. It should support all the same embedding
2400	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2812	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2467	your compiler is good :), then the method will be fully inlined into the	2879	your compiler is good :), then the method will be fully inlined into the
2468	thunking function, making it as fast as a direct C callback.	2880	thunking function, making it as fast as a direct C callback.
2469		2881
2470	Example: simple class declaration and watcher initialisation	2882	Example: simple class declaration and watcher initialisation
2471		2883
2472	struct myclass	2884	struct myclass
2473	{	2885	{
2474	void io_cb (ev::io &w, int revents) { }	2886	void io_cb (ev::io &w, int revents) { }
2475	}	2887	}
2476		2888
2477	myclass obj;	2889	myclass obj;
2478	ev::io iow;	2890	ev::io iow;
2479	iow.set <myclass, &myclass::io_cb> (&obj);	2891	iow.set <myclass, &myclass::io_cb> (&obj);
2480		2892
2481	=item w->set<function> (void *data = 0)	2893	=item w->set<function> (void *data = 0)
2482		2894
2483	Also sets a callback, but uses a static method or plain function as	2895	Also sets a callback, but uses a static method or plain function as
2484	callback. The optional C<data> argument will be stored in the watcher's	2896	callback. The optional C<data> argument will be stored in the watcher's
…		…
2486		2898
2487	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2899	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2488		2900
2489	See the method-C<set> above for more details.	2901	See the method-C<set> above for more details.
2490		2902
2491	Example:	2903	Example: Use a plain function as callback.
2492		2904
2493	static void io_cb (ev::io &w, int revents) { }	2905	static void io_cb (ev::io &w, int revents) { }
2494	iow.set <io_cb> ();	2906	iow.set <io_cb> ();
2495		2907
2496	=item w->set (struct ev_loop *)	2908	=item w->set (struct ev_loop *)
2497		2909
2498	Associates a different C<struct ev_loop> with this watcher. You can only	2910	Associates a different C<struct ev_loop> with this watcher. You can only
2499	do this when the watcher is inactive (and not pending either).	2911	do this when the watcher is inactive (and not pending either).
2500		2912
2501	=item w->set ([args])	2913	=item w->set ([arguments])
2502		2914
2503	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2915	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2504	called at least once. Unlike the C counterpart, an active watcher gets	2916	called at least once. Unlike the C counterpart, an active watcher gets
2505	automatically stopped and restarted when reconfiguring it with this	2917	automatically stopped and restarted when reconfiguring it with this
2506	method.	2918	method.
2507		2919
2508	=item w->start ()	2920	=item w->start ()
…		…
2532	=back	2944	=back
2533		2945
2534	Example: Define a class with an IO and idle watcher, start one of them in	2946	Example: Define a class with an IO and idle watcher, start one of them in
2535	the constructor.	2947	the constructor.
2536		2948
2537	class myclass	2949	class myclass
2538	{	2950	{
2539	ev::io io; void io_cb (ev::io &w, int revents);	2951	ev::io io ; void io_cb (ev::io &w, int revents);
2540	ev:idle idle void idle_cb (ev::idle &w, int revents);	2952	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2541		2953
2542	myclass (int fd)	2954	myclass (int fd)
2543	{	2955	{
2544	io .set <myclass, &myclass::io_cb > (this);	2956	io .set <myclass, &myclass::io_cb > (this);
2545	idle.set <myclass, &myclass::idle_cb> (this);	2957	idle.set <myclass, &myclass::idle_cb> (this);
2546		2958
2547	io.start (fd, ev::READ);	2959	io.start (fd, ev::READ);
2548	}	2960	}
2549	};	2961	};
2550		2962
2551		2963
2552	=head1 OTHER LANGUAGE BINDINGS	2964	=head1 OTHER LANGUAGE BINDINGS
2553		2965
2554	Libev does not offer other language bindings itself, but bindings for a	2966	Libev does not offer other language bindings itself, but bindings for a
2555	numbe rof languages exist in the form of third-party packages. If you know	2967	number of languages exist in the form of third-party packages. If you know
2556	any interesting language binding in addition to the ones listed here, drop	2968	any interesting language binding in addition to the ones listed here, drop
2557	me a note.	2969	me a note.
2558		2970
2559	=over 4	2971	=over 4
2560		2972
2561	=item Perl	2973	=item Perl
2562		2974
2563	The EV module implements the full libev API and is actually used to test	2975	The EV module implements the full libev API and is actually used to test
2564	libev. EV is developed together with libev. Apart from the EV core module,	2976	libev. EV is developed together with libev. Apart from the EV core module,
2565	there are additional modules that implement libev-compatible interfaces	2977	there are additional modules that implement libev-compatible interfaces
2566	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2978	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2567	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2979	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2980	and C<EV::Glib>).
2568		2981
2569	It can be found and installed via CPAN, its homepage is found at	2982	It can be found and installed via CPAN, its homepage is at
2570	L<http://software.schmorp.de/pkg/EV>.	2983	L<http://software.schmorp.de/pkg/EV>.
2571		2984
		2985	=item Python
		2986
		2987	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2988	seems to be quite complete and well-documented. Note, however, that the
		2989	patch they require for libev is outright dangerous as it breaks the ABI
		2990	for everybody else, and therefore, should never be applied in an installed
		2991	libev (if python requires an incompatible ABI then it needs to embed
		2992	libev).
		2993
2572	=item Ruby	2994	=item Ruby
2573		2995
2574	Tony Arcieri has written a ruby extension that offers access to a subset	2996	Tony Arcieri has written a ruby extension that offers access to a subset
2575	of the libev API and adds filehandle abstractions, asynchronous DNS and	2997	of the libev API and adds file handle abstractions, asynchronous DNS and
2576	more on top of it. It can be found via gem servers. Its homepage is at	2998	more on top of it. It can be found via gem servers. Its homepage is at
2577	L<http://rev.rubyforge.org/>.	2999	L<http://rev.rubyforge.org/>.
2578		3000
2579	=item D	3001	=item D
2580		3002
2581	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3003	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2582	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3004	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3005
		3006	=item Ocaml
		3007
		3008	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3009	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2583		3010
2584	=back	3011	=back
2585		3012
2586		3013
2587	=head1 MACRO MAGIC	3014	=head1 MACRO MAGIC
2588		3015
2589	Libev can be compiled with a variety of options, the most fundamantal	3016	Libev can be compiled with a variety of options, the most fundamental
2590	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3017	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2591	functions and callbacks have an initial C<struct ev_loop *> argument.	3018	functions and callbacks have an initial C<struct ev_loop *> argument.
2592		3019
2593	To make it easier to write programs that cope with either variant, the	3020	To make it easier to write programs that cope with either variant, the
2594	following macros are defined:	3021	following macros are defined:
…		…
2599		3026
2600	This provides the loop I<argument> for functions, if one is required ("ev	3027	This provides the loop I<argument> for functions, if one is required ("ev
2601	loop argument"). The C<EV_A> form is used when this is the sole argument,	3028	loop argument"). The C<EV_A> form is used when this is the sole argument,
2602	C<EV_A_> is used when other arguments are following. Example:	3029	C<EV_A_> is used when other arguments are following. Example:
2603		3030
2604	ev_unref (EV_A);	3031	ev_unref (EV_A);
2605	ev_timer_add (EV_A_ watcher);	3032	ev_timer_add (EV_A_ watcher);
2606	ev_loop (EV_A_ 0);	3033	ev_loop (EV_A_ 0);
2607		3034
2608	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3035	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2609	which is often provided by the following macro.	3036	which is often provided by the following macro.
2610		3037
2611	=item C<EV_P>, C<EV_P_>	3038	=item C<EV_P>, C<EV_P_>
2612		3039
2613	This provides the loop I<parameter> for functions, if one is required ("ev	3040	This provides the loop I<parameter> for functions, if one is required ("ev
2614	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3041	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2615	C<EV_P_> is used when other parameters are following. Example:	3042	C<EV_P_> is used when other parameters are following. Example:
2616		3043
2617	// this is how ev_unref is being declared	3044	// this is how ev_unref is being declared
2618	static void ev_unref (EV_P);	3045	static void ev_unref (EV_P);
2619		3046
2620	// this is how you can declare your typical callback	3047	// this is how you can declare your typical callback
2621	static void cb (EV_P_ ev_timer *w, int revents)	3048	static void cb (EV_P_ ev_timer *w, int revents)
2622		3049
2623	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3050	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2624	suitable for use with C<EV_A>.	3051	suitable for use with C<EV_A>.
2625		3052
2626	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3053	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2642		3069
2643	Example: Declare and initialise a check watcher, utilising the above	3070	Example: Declare and initialise a check watcher, utilising the above
2644	macros so it will work regardless of whether multiple loops are supported	3071	macros so it will work regardless of whether multiple loops are supported
2645	or not.	3072	or not.
2646		3073
2647	static void	3074	static void
2648	check_cb (EV_P_ ev_timer *w, int revents)	3075	check_cb (EV_P_ ev_timer *w, int revents)
2649	{	3076	{
2650	ev_check_stop (EV_A_ w);	3077	ev_check_stop (EV_A_ w);
2651	}	3078	}
2652		3079
2653	ev_check check;	3080	ev_check check;
2654	ev_check_init (&check, check_cb);	3081	ev_check_init (&check, check_cb);
2655	ev_check_start (EV_DEFAULT_ &check);	3082	ev_check_start (EV_DEFAULT_ &check);
2656	ev_loop (EV_DEFAULT_ 0);	3083	ev_loop (EV_DEFAULT_ 0);
2657		3084
2658	=head1 EMBEDDING	3085	=head1 EMBEDDING
2659		3086
2660	Libev can (and often is) directly embedded into host	3087	Libev can (and often is) directly embedded into host
2661	applications. Examples of applications that embed it include the Deliantra	3088	applications. Examples of applications that embed it include the Deliantra
…		…
2668	libev somewhere in your source tree).	3095	libev somewhere in your source tree).
2669		3096
2670	=head2 FILESETS	3097	=head2 FILESETS
2671		3098
2672	Depending on what features you need you need to include one or more sets of files	3099	Depending on what features you need you need to include one or more sets of files
2673	in your app.	3100	in your application.
2674		3101
2675	=head3 CORE EVENT LOOP	3102	=head3 CORE EVENT LOOP
2676		3103
2677	To include only the libev core (all the C<ev_*> functions), with manual	3104	To include only the libev core (all the C<ev_*> functions), with manual
2678	configuration (no autoconf):	3105	configuration (no autoconf):
2679		3106
2680	#define EV_STANDALONE 1	3107	#define EV_STANDALONE 1
2681	#include "ev.c"	3108	#include "ev.c"
2682		3109
2683	This will automatically include F<ev.h>, too, and should be done in a	3110	This will automatically include F<ev.h>, too, and should be done in a
2684	single C source file only to provide the function implementations. To use	3111	single C source file only to provide the function implementations. To use
2685	it, do the same for F<ev.h> in all files wishing to use this API (best	3112	it, do the same for F<ev.h> in all files wishing to use this API (best
2686	done by writing a wrapper around F<ev.h> that you can include instead and	3113	done by writing a wrapper around F<ev.h> that you can include instead and
2687	where you can put other configuration options):	3114	where you can put other configuration options):
2688		3115
2689	#define EV_STANDALONE 1	3116	#define EV_STANDALONE 1
2690	#include "ev.h"	3117	#include "ev.h"
2691		3118
2692	Both header files and implementation files can be compiled with a C++	3119	Both header files and implementation files can be compiled with a C++
2693	compiler (at least, thats a stated goal, and breakage will be treated	3120	compiler (at least, that's a stated goal, and breakage will be treated
2694	as a bug).	3121	as a bug).
2695		3122
2696	You need the following files in your source tree, or in a directory	3123	You need the following files in your source tree, or in a directory
2697	in your include path (e.g. in libev/ when using -Ilibev):	3124	in your include path (e.g. in libev/ when using -Ilibev):
2698		3125
2699	ev.h	3126	ev.h
2700	ev.c	3127	ev.c
2701	ev_vars.h	3128	ev_vars.h
2702	ev_wrap.h	3129	ev_wrap.h
2703		3130
2704	ev_win32.c required on win32 platforms only	3131	ev_win32.c required on win32 platforms only
2705		3132
2706	ev_select.c only when select backend is enabled (which is enabled by default)	3133	ev_select.c only when select backend is enabled (which is enabled by default)
2707	ev_poll.c only when poll backend is enabled (disabled by default)	3134	ev_poll.c only when poll backend is enabled (disabled by default)
2708	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3135	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2709	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3136	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2710	ev_port.c only when the solaris port backend is enabled (disabled by default)	3137	ev_port.c only when the solaris port backend is enabled (disabled by default)
2711		3138
2712	F<ev.c> includes the backend files directly when enabled, so you only need	3139	F<ev.c> includes the backend files directly when enabled, so you only need
2713	to compile this single file.	3140	to compile this single file.
2714		3141
2715	=head3 LIBEVENT COMPATIBILITY API	3142	=head3 LIBEVENT COMPATIBILITY API
2716		3143
2717	To include the libevent compatibility API, also include:	3144	To include the libevent compatibility API, also include:
2718		3145
2719	#include "event.c"	3146	#include "event.c"
2720		3147
2721	in the file including F<ev.c>, and:	3148	in the file including F<ev.c>, and:
2722		3149
2723	#include "event.h"	3150	#include "event.h"
2724		3151
2725	in the files that want to use the libevent API. This also includes F<ev.h>.	3152	in the files that want to use the libevent API. This also includes F<ev.h>.
2726		3153
2727	You need the following additional files for this:	3154	You need the following additional files for this:
2728		3155
2729	event.h	3156	event.h
2730	event.c	3157	event.c
2731		3158
2732	=head3 AUTOCONF SUPPORT	3159	=head3 AUTOCONF SUPPORT
2733		3160
2734	Instead of using C<EV_STANDALONE=1> and providing your config in	3161	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2735	whatever way you want, you can also C<m4_include([libev.m4])> in your	3162	whatever way you want, you can also C<m4_include([libev.m4])> in your
2736	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3163	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2737	include F<config.h> and configure itself accordingly.	3164	include F<config.h> and configure itself accordingly.
2738		3165
2739	For this of course you need the m4 file:	3166	For this of course you need the m4 file:
2740		3167
2741	libev.m4	3168	libev.m4
2742		3169
2743	=head2 PREPROCESSOR SYMBOLS/MACROS	3170	=head2 PREPROCESSOR SYMBOLS/MACROS
2744		3171
2745	Libev can be configured via a variety of preprocessor symbols you have to	3172	Libev can be configured via a variety of preprocessor symbols you have to
2746	define before including any of its files. The default in the absense of	3173	define before including any of its files. The default in the absence of
2747	autoconf is noted for every option.	3174	autoconf is documented for every option.
2748		3175
2749	=over 4	3176	=over 4
2750		3177
2751	=item EV_STANDALONE	3178	=item EV_STANDALONE
2752		3179
…		…
2757	F<event.h> that are not directly supported by the libev core alone.	3184	F<event.h> that are not directly supported by the libev core alone.
2758		3185
2759	=item EV_USE_MONOTONIC	3186	=item EV_USE_MONOTONIC
2760		3187
2761	If defined to be C<1>, libev will try to detect the availability of the	3188	If defined to be C<1>, libev will try to detect the availability of the
2762	monotonic clock option at both compiletime and runtime. Otherwise no use	3189	monotonic clock option at both compile time and runtime. Otherwise no use
2763	of the monotonic clock option will be attempted. If you enable this, you	3190	of the monotonic clock option will be attempted. If you enable this, you
2764	usually have to link against librt or something similar. Enabling it when	3191	usually have to link against librt or something similar. Enabling it when
2765	the functionality isn't available is safe, though, although you have	3192	the functionality isn't available is safe, though, although you have
2766	to make sure you link against any libraries where the C<clock_gettime>	3193	to make sure you link against any libraries where the C<clock_gettime>
2767	function is hiding in (often F<-lrt>).	3194	function is hiding in (often F<-lrt>).
2768		3195
2769	=item EV_USE_REALTIME	3196	=item EV_USE_REALTIME
2770		3197
2771	If defined to be C<1>, libev will try to detect the availability of the	3198	If defined to be C<1>, libev will try to detect the availability of the
2772	realtime clock option at compiletime (and assume its availability at	3199	real-time clock option at compile time (and assume its availability at
2773	runtime if successful). Otherwise no use of the realtime clock option will	3200	runtime if successful). Otherwise no use of the real-time clock option will
2774	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3201	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2775	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3202	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2776	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3203	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2777		3204
2778	=item EV_USE_NANOSLEEP	3205	=item EV_USE_NANOSLEEP
…		…
2789	2.7 or newer, otherwise disabled.	3216	2.7 or newer, otherwise disabled.
2790		3217
2791	=item EV_USE_SELECT	3218	=item EV_USE_SELECT
2792		3219
2793	If undefined or defined to be C<1>, libev will compile in support for the	3220	If undefined or defined to be C<1>, libev will compile in support for the
2794	C<select>(2) backend. No attempt at autodetection will be done: if no	3221	C<select>(2) backend. No attempt at auto-detection will be done: if no
2795	other method takes over, select will be it. Otherwise the select backend	3222	other method takes over, select will be it. Otherwise the select backend
2796	will not be compiled in.	3223	will not be compiled in.
2797		3224
2798	=item EV_SELECT_USE_FD_SET	3225	=item EV_SELECT_USE_FD_SET
2799		3226
2800	If defined to C<1>, then the select backend will use the system C<fd_set>	3227	If defined to C<1>, then the select backend will use the system C<fd_set>
2801	structure. This is useful if libev doesn't compile due to a missing	3228	structure. This is useful if libev doesn't compile due to a missing
2802	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3229	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2803	exotic systems. This usually limits the range of file descriptors to some	3230	exotic systems. This usually limits the range of file descriptors to some
2804	low limit such as 1024 or might have other limitations (winsocket only	3231	low limit such as 1024 or might have other limitations (winsocket only
2805	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3232	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2806	influence the size of the C<fd_set> used.	3233	influence the size of the C<fd_set> used.
2807		3234
…		…
2856	otherwise another method will be used as fallback. This is the preferred	3283	otherwise another method will be used as fallback. This is the preferred
2857	backend for Solaris 10 systems.	3284	backend for Solaris 10 systems.
2858		3285
2859	=item EV_USE_DEVPOLL	3286	=item EV_USE_DEVPOLL
2860		3287
2861	reserved for future expansion, works like the USE symbols above.	3288	Reserved for future expansion, works like the USE symbols above.
2862		3289
2863	=item EV_USE_INOTIFY	3290	=item EV_USE_INOTIFY
2864		3291
2865	If defined to be C<1>, libev will compile in support for the Linux inotify	3292	If defined to be C<1>, libev will compile in support for the Linux inotify
2866	interface to speed up C<ev_stat> watchers. Its actual availability will	3293	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2873	access is atomic with respect to other threads or signal contexts. No such	3300	access is atomic with respect to other threads or signal contexts. No such
2874	type is easily found in the C language, so you can provide your own type	3301	type is easily found in the C language, so you can provide your own type
2875	that you know is safe for your purposes. It is used both for signal handler "locking"	3302	that you know is safe for your purposes. It is used both for signal handler "locking"
2876	as well as for signal and thread safety in C<ev_async> watchers.	3303	as well as for signal and thread safety in C<ev_async> watchers.
2877		3304
2878	In the absense of this define, libev will use C<sig_atomic_t volatile>	3305	In the absence of this define, libev will use C<sig_atomic_t volatile>
2879	(from F<signal.h>), which is usually good enough on most platforms.	3306	(from F<signal.h>), which is usually good enough on most platforms.
2880		3307
2881	=item EV_H	3308	=item EV_H
2882		3309
2883	The name of the F<ev.h> header file used to include it. The default if	3310	The name of the F<ev.h> header file used to include it. The default if
…		…
2922	When doing priority-based operations, libev usually has to linearly search	3349	When doing priority-based operations, libev usually has to linearly search
2923	all the priorities, so having many of them (hundreds) uses a lot of space	3350	all the priorities, so having many of them (hundreds) uses a lot of space
2924	and time, so using the defaults of five priorities (-2 .. +2) is usually	3351	and time, so using the defaults of five priorities (-2 .. +2) is usually
2925	fine.	3352	fine.
2926		3353
2927	If your embedding app does not need any priorities, defining these both to	3354	If your embedding application does not need any priorities, defining these
2928	C<0> will save some memory and cpu.	3355	both to C<0> will save some memory and CPU.
2929		3356
2930	=item EV_PERIODIC_ENABLE	3357	=item EV_PERIODIC_ENABLE
2931		3358
2932	If undefined or defined to be C<1>, then periodic timers are supported. If	3359	If undefined or defined to be C<1>, then periodic timers are supported. If
2933	defined to be C<0>, then they are not. Disabling them saves a few kB of	3360	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2940	code.	3367	code.
2941		3368
2942	=item EV_EMBED_ENABLE	3369	=item EV_EMBED_ENABLE
2943		3370
2944	If undefined or defined to be C<1>, then embed watchers are supported. If	3371	If undefined or defined to be C<1>, then embed watchers are supported. If
2945	defined to be C<0>, then they are not.	3372	defined to be C<0>, then they are not. Embed watchers rely on most other
		3373	watcher types, which therefore must not be disabled.
2946		3374
2947	=item EV_STAT_ENABLE	3375	=item EV_STAT_ENABLE
2948		3376
2949	If undefined or defined to be C<1>, then stat watchers are supported. If	3377	If undefined or defined to be C<1>, then stat watchers are supported. If
2950	defined to be C<0>, then they are not.	3378	defined to be C<0>, then they are not.
…		…
2960	defined to be C<0>, then they are not.	3388	defined to be C<0>, then they are not.
2961		3389
2962	=item EV_MINIMAL	3390	=item EV_MINIMAL
2963		3391
2964	If you need to shave off some kilobytes of code at the expense of some	3392	If you need to shave off some kilobytes of code at the expense of some
2965	speed, define this symbol to C<1>. Currently only used for gcc to override	3393	speed, define this symbol to C<1>. Currently this is used to override some
2966	some inlining decisions, saves roughly 30% codesize of amd64.	3394	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3395	much smaller 2-heap for timer management over the default 4-heap.
2967		3396
2968	=item EV_PID_HASHSIZE	3397	=item EV_PID_HASHSIZE
2969		3398
2970	C<ev_child> watchers use a small hash table to distribute workload by	3399	C<ev_child> watchers use a small hash table to distribute workload by
2971	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3400	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2978	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3407	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2979	usually more than enough. If you need to manage thousands of C<ev_stat>	3408	usually more than enough. If you need to manage thousands of C<ev_stat>
2980	watchers you might want to increase this value (I<must> be a power of	3409	watchers you might want to increase this value (I<must> be a power of
2981	two).	3410	two).
2982		3411
		3412	=item EV_USE_4HEAP
		3413
		3414	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3415	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3416	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3417	faster performance with many (thousands) of watchers.
		3418
		3419	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3420	(disabled).
		3421
		3422	=item EV_HEAP_CACHE_AT
		3423
		3424	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3425	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3426	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3427	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3428	but avoids random read accesses on heap changes. This improves performance
		3429	noticeably with many (hundreds) of watchers.
		3430
		3431	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3432	(disabled).
		3433
		3434	=item EV_VERIFY
		3435
		3436	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3437	be done: If set to C<0>, no internal verification code will be compiled
		3438	in. If set to C<1>, then verification code will be compiled in, but not
		3439	called. If set to C<2>, then the internal verification code will be
		3440	called once per loop, which can slow down libev. If set to C<3>, then the
		3441	verification code will be called very frequently, which will slow down
		3442	libev considerably.
		3443
		3444	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3445	C<0>.
		3446
2983	=item EV_COMMON	3447	=item EV_COMMON
2984		3448
2985	By default, all watchers have a C<void *data> member. By redefining	3449	By default, all watchers have a C<void *data> member. By redefining
2986	this macro to a something else you can include more and other types of	3450	this macro to a something else you can include more and other types of
2987	members. You have to define it each time you include one of the files,	3451	members. You have to define it each time you include one of the files,
2988	though, and it must be identical each time.	3452	though, and it must be identical each time.
2989		3453
2990	For example, the perl EV module uses something like this:	3454	For example, the perl EV module uses something like this:
2991		3455
2992	#define EV_COMMON \	3456	#define EV_COMMON \
2993	SV *self; /* contains this struct */ \	3457	SV *self; /* contains this struct */ \
2994	SV *cb_sv, *fh /* note no trailing ";" */	3458	SV *cb_sv, *fh /* note no trailing ";" */
2995		3459
2996	=item EV_CB_DECLARE (type)	3460	=item EV_CB_DECLARE (type)
2997		3461
2998	=item EV_CB_INVOKE (watcher, revents)	3462	=item EV_CB_INVOKE (watcher, revents)
2999		3463
…		…
3004	definition and a statement, respectively. See the F<ev.h> header file for	3468	definition and a statement, respectively. See the F<ev.h> header file for
3005	their default definitions. One possible use for overriding these is to	3469	their default definitions. One possible use for overriding these is to
3006	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3470	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3007	method calls instead of plain function calls in C++.	3471	method calls instead of plain function calls in C++.
3008		3472
		3473	=back
		3474
3009	=head2 EXPORTED API SYMBOLS	3475	=head2 EXPORTED API SYMBOLS
3010		3476
3011	If you need to re-export the API (e.g. via a dll) and you need a list of	3477	If you need to re-export the API (e.g. via a DLL) and you need a list of
3012	exported symbols, you can use the provided F<Symbol.*> files which list	3478	exported symbols, you can use the provided F<Symbol.*> files which list
3013	all public symbols, one per line:	3479	all public symbols, one per line:
3014		3480
3015	Symbols.ev for libev proper	3481	Symbols.ev for libev proper
3016	Symbols.event for the libevent emulation	3482	Symbols.event for the libevent emulation
3017		3483
3018	This can also be used to rename all public symbols to avoid clashes with	3484	This can also be used to rename all public symbols to avoid clashes with
3019	multiple versions of libev linked together (which is obviously bad in	3485	multiple versions of libev linked together (which is obviously bad in
3020	itself, but sometimes it is inconvinient to avoid this).	3486	itself, but sometimes it is inconvenient to avoid this).
3021		3487
3022	A sed command like this will create wrapper C<#define>'s that you need to	3488	A sed command like this will create wrapper C<#define>'s that you need to
3023	include before including F<ev.h>:	3489	include before including F<ev.h>:
3024		3490
3025	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3491	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3042	file.	3508	file.
3043		3509
3044	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3510	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3045	that everybody includes and which overrides some configure choices:	3511	that everybody includes and which overrides some configure choices:
3046		3512
3047	#define EV_MINIMAL 1	3513	#define EV_MINIMAL 1
3048	#define EV_USE_POLL 0	3514	#define EV_USE_POLL 0
3049	#define EV_MULTIPLICITY 0	3515	#define EV_MULTIPLICITY 0
3050	#define EV_PERIODIC_ENABLE 0	3516	#define EV_PERIODIC_ENABLE 0
3051	#define EV_STAT_ENABLE 0	3517	#define EV_STAT_ENABLE 0
3052	#define EV_FORK_ENABLE 0	3518	#define EV_FORK_ENABLE 0
3053	#define EV_CONFIG_H <config.h>	3519	#define EV_CONFIG_H <config.h>
3054	#define EV_MINPRI 0	3520	#define EV_MINPRI 0
3055	#define EV_MAXPRI 0	3521	#define EV_MAXPRI 0
3056		3522
3057	#include "ev++.h"	3523	#include "ev++.h"
3058		3524
3059	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3525	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3060		3526
3061	#include "ev_cpp.h"	3527	#include "ev_cpp.h"
3062	#include "ev.c"	3528	#include "ev.c"
3063		3529
		3530	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3064		3531
3065	=head1 THREADS AND COROUTINES	3532	=head2 THREADS AND COROUTINES
3066		3533
3067	=head2 THREADS	3534	=head3 THREADS
3068		3535
3069	Libev itself is completely threadsafe, but it uses no locking. This	3536	All libev functions are reentrant and thread-safe unless explicitly
		3537	documented otherwise, but libev implements no locking itself. This means
3070	means that you can use as many loops as you want in parallel, as long as	3538	that you can use as many loops as you want in parallel, as long as there
3071	only one thread ever calls into one libev function with the same loop	3539	are no concurrent calls into any libev function with the same loop
3072	parameter.	3540	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3541	of course): libev guarantees that different event loops share no data
		3542	structures that need any locking.
3073		3543
3074	Or put differently: calls with different loop parameters can be done in	3544	Or to put it differently: calls with different loop parameters can be done
3075	parallel from multiple threads, calls with the same loop parameter must be	3545	concurrently from multiple threads, calls with the same loop parameter
3076	done serially (but can be done from different threads, as long as only one	3546	must be done serially (but can be done from different threads, as long as
3077	thread ever is inside a call at any point in time, e.g. by using a mutex	3547	only one thread ever is inside a call at any point in time, e.g. by using
3078	per loop).	3548	a mutex per loop).
3079		3549
3080	If you want to know which design is best for your problem, then I cannot	3550	Specifically to support threads (and signal handlers), libev implements
		3551	so-called C<ev_async> watchers, which allow some limited form of
		3552	concurrency on the same event loop, namely waking it up "from the
		3553	outside".
		3554
		3555	If you want to know which design (one loop, locking, or multiple loops
		3556	without or something else still) is best for your problem, then I cannot
3081	help you but by giving some generic advice:	3557	help you, but here is some generic advice:
3082		3558
3083	=over 4	3559	=over 4
3084		3560
3085	=item * most applications have a main thread: use the default libev loop	3561	=item * most applications have a main thread: use the default libev loop
3086	in that thread, or create a seperate thread running only the default loop.	3562	in that thread, or create a separate thread running only the default loop.
3087		3563
3088	This helps integrating other libraries or software modules that use libev	3564	This helps integrating other libraries or software modules that use libev
3089	themselves and don't care/know about threading.	3565	themselves and don't care/know about threading.
3090		3566
3091	=item * one loop per thread is usually a good model.	3567	=item * one loop per thread is usually a good model.
3092		3568
3093	Doing this is almost never wrong, sometimes a better-performance model	3569	Doing this is almost never wrong, sometimes a better-performance model
3094	exists, but it is always a good start.	3570	exists, but it is always a good start.
3095		3571
3096	=item * other models exist, such as the leader/follower pattern, where one	3572	=item * other models exist, such as the leader/follower pattern, where one
3097	loop is handed through multiple threads in a kind of round-robbin fashion.	3573	loop is handed through multiple threads in a kind of round-robin fashion.
3098		3574
3099	Chosing a model is hard - look around, learn, know that usually you cna do	3575	Choosing a model is hard - look around, learn, know that usually you can do
3100	better than you currently do :-)	3576	better than you currently do :-)
3101		3577
3102	=item * often you need to talk to some other thread which blocks in the	3578	=item * often you need to talk to some other thread which blocks in the
		3579	event loop.
		3580
3103	event loop - C<ev_async> watchers can be used to wake them up from other	3581	C<ev_async> watchers can be used to wake them up from other threads safely
3104	threads safely (or from signal contexts...).	3582	(or from signal contexts...).
		3583
		3584	An example use would be to communicate signals or other events that only
		3585	work in the default loop by registering the signal watcher with the
		3586	default loop and triggering an C<ev_async> watcher from the default loop
		3587	watcher callback into the event loop interested in the signal.
3105		3588
3106	=back	3589	=back
3107		3590
3108	=head2 COROUTINES	3591	=head3 COROUTINES
3109		3592
3110	Libev is much more accomodating to coroutines ("cooperative threads"):	3593	Libev is very accommodating to coroutines ("cooperative threads"):
3111	libev fully supports nesting calls to it's functions from different	3594	libev fully supports nesting calls to its functions from different
3112	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3595	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3113	different coroutines and switch freely between both coroutines running the	3596	different coroutines, and switch freely between both coroutines running the
3114	loop, as long as you don't confuse yourself). The only exception is that	3597	loop, as long as you don't confuse yourself). The only exception is that
3115	you must not do this from C<ev_periodic> reschedule callbacks.	3598	you must not do this from C<ev_periodic> reschedule callbacks.
3116		3599
3117	Care has been invested into making sure that libev does not keep local	3600	Care has been taken to ensure that libev does not keep local state inside
3118	state inside C<ev_loop>, and other calls do not usually allow coroutine	3601	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3119	switches.	3602	they do not call any callbacks.
3120		3603
		3604	=head2 COMPILER WARNINGS
3121		3605
3122	=head1 COMPLEXITIES	3606	Depending on your compiler and compiler settings, you might get no or a
		3607	lot of warnings when compiling libev code. Some people are apparently
		3608	scared by this.
3123		3609
3124	In this section the complexities of (many of) the algorithms used inside	3610	However, these are unavoidable for many reasons. For one, each compiler
3125	libev will be explained. For complexity discussions about backends see the	3611	has different warnings, and each user has different tastes regarding
3126	documentation for C<ev_default_init>.	3612	warning options. "Warn-free" code therefore cannot be a goal except when
		3613	targeting a specific compiler and compiler-version.
3127		3614
3128	All of the following are about amortised time: If an array needs to be	3615	Another reason is that some compiler warnings require elaborate
3129	extended, libev needs to realloc and move the whole array, but this	3616	workarounds, or other changes to the code that make it less clear and less
3130	happens asymptotically never with higher number of elements, so O(1) might	3617	maintainable.
3131	mean it might do a lengthy realloc operation in rare cases, but on average
3132	it is much faster and asymptotically approaches constant time.
3133		3618
3134	=over 4	3619	And of course, some compiler warnings are just plain stupid, or simply
		3620	wrong (because they don't actually warn about the condition their message
		3621	seems to warn about). For example, certain older gcc versions had some
		3622	warnings that resulted an extreme number of false positives. These have
		3623	been fixed, but some people still insist on making code warn-free with
		3624	such buggy versions.
3135		3625
3136	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3626	While libev is written to generate as few warnings as possible,
		3627	"warn-free" code is not a goal, and it is recommended not to build libev
		3628	with any compiler warnings enabled unless you are prepared to cope with
		3629	them (e.g. by ignoring them). Remember that warnings are just that:
		3630	warnings, not errors, or proof of bugs.
3137		3631
3138	This means that, when you have a watcher that triggers in one hour and
3139	there are 100 watchers that would trigger before that then inserting will
3140	have to skip roughly seven (C<ld 100>) of these watchers.
3141		3632
3142	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3633	=head2 VALGRIND
3143		3634
3144	That means that changing a timer costs less than removing/adding them	3635	Valgrind has a special section here because it is a popular tool that is
3145	as only the relative motion in the event queue has to be paid for.	3636	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3146		3637
3147	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3638	If you think you found a bug (memory leak, uninitialised data access etc.)
		3639	in libev, then check twice: If valgrind reports something like:
3148		3640
3149	These just add the watcher into an array or at the head of a list.	3641	==2274== definitely lost: 0 bytes in 0 blocks.
		3642	==2274== possibly lost: 0 bytes in 0 blocks.
		3643	==2274== still reachable: 256 bytes in 1 blocks.
3150		3644
3151	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3645	Then there is no memory leak, just as memory accounted to global variables
		3646	is not a memleak - the memory is still being referenced, and didn't leak.
3152		3647
3153	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3648	Similarly, under some circumstances, valgrind might report kernel bugs
		3649	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3650	although an acceptable workaround has been found here), or it might be
		3651	confused.
3154		3652
3155	These watchers are stored in lists then need to be walked to find the	3653	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3156	correct watcher to remove. The lists are usually short (you don't usually	3654	make it into some kind of religion.
3157	have many watchers waiting for the same fd or signal).
3158		3655
3159	=item Finding the next timer in each loop iteration: O(1)	3656	If you are unsure about something, feel free to contact the mailing list
		3657	with the full valgrind report and an explanation on why you think this
		3658	is a bug in libev (best check the archives, too :). However, don't be
		3659	annoyed when you get a brisk "this is no bug" answer and take the chance
		3660	of learning how to interpret valgrind properly.
3160		3661
3161	By virtue of using a binary heap, the next timer is always found at the	3662	If you need, for some reason, empty reports from valgrind for your project
3162	beginning of the storage array.	3663	I suggest using suppression lists.
3163		3664
3164	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3165		3665
3166	A change means an I/O watcher gets started or stopped, which requires	3666	=head1 PORTABILITY NOTES
3167	libev to recalculate its status (and possibly tell the kernel, depending
3168	on backend and wether C<ev_io_set> was used).
3169		3667
3170	=item Activating one watcher (putting it into the pending state): O(1)	3668	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3171
3172	=item Priority handling: O(number_of_priorities)
3173
3174	Priorities are implemented by allocating some space for each
3175	priority. When doing priority-based operations, libev usually has to
3176	linearly search all the priorities, but starting/stopping and activating
3177	watchers becomes O(1) w.r.t. priority handling.
3178
3179	=item Sending an ev_async: O(1)
3180
3181	=item Processing ev_async_send: O(number_of_async_watchers)
3182
3183	=item Processing signals: O(max_signal_number)
3184
3185	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3186	calls in the current loop iteration. Checking for async and signal events
3187	involves iterating over all running async watchers or all signal numbers.
3188
3189	=back
3190
3191
3192	=head1 Win32 platform limitations and workarounds
3193		3669
3194	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3670	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3195	requires, and its I/O model is fundamentally incompatible with the POSIX	3671	requires, and its I/O model is fundamentally incompatible with the POSIX
3196	model. Libev still offers limited functionality on this platform in	3672	model. Libev still offers limited functionality on this platform in
3197	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3673	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3198	descriptors. This only applies when using Win32 natively, not when using	3674	descriptors. This only applies when using Win32 natively, not when using
3199	e.g. cygwin.	3675	e.g. cygwin.
3200		3676
		3677	Lifting these limitations would basically require the full
		3678	re-implementation of the I/O system. If you are into these kinds of
		3679	things, then note that glib does exactly that for you in a very portable
		3680	way (note also that glib is the slowest event library known to man).
		3681
3201	There is no supported compilation method available on windows except	3682	There is no supported compilation method available on windows except
3202	embedding it into other applications.	3683	embedding it into other applications.
3203		3684
		3685	Not a libev limitation but worth mentioning: windows apparently doesn't
		3686	accept large writes: instead of resulting in a partial write, windows will
		3687	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3688	so make sure you only write small amounts into your sockets (less than a
		3689	megabyte seems safe, but this apparently depends on the amount of memory
		3690	available).
		3691
3204	Due to the many, low, and arbitrary limits on the win32 platform and the	3692	Due to the many, low, and arbitrary limits on the win32 platform and
3205	abysmal performance of winsockets, using a large number of sockets is not	3693	the abysmal performance of winsockets, using a large number of sockets
3206	recommended (and not reasonable). If your program needs to use more than	3694	is not recommended (and not reasonable). If your program needs to use
3207	a hundred or so sockets, then likely it needs to use a totally different	3695	more than a hundred or so sockets, then likely it needs to use a totally
3208	implementation for windows, as libev offers the POSIX model, which cannot	3696	different implementation for windows, as libev offers the POSIX readiness
3209	be implemented efficiently on windows (microsoft monopoly games).	3697	notification model, which cannot be implemented efficiently on windows
		3698	(Microsoft monopoly games).
		3699
		3700	A typical way to use libev under windows is to embed it (see the embedding
		3701	section for details) and use the following F<evwrap.h> header file instead
		3702	of F<ev.h>:
		3703
		3704	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3705	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3706
		3707	#include "ev.h"
		3708
		3709	And compile the following F<evwrap.c> file into your project (make sure
		3710	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3711
		3712	#include "evwrap.h"
		3713	#include "ev.c"
3210		3714
3211	=over 4	3715	=over 4
3212		3716
3213	=item The winsocket select function	3717	=item The winsocket select function
3214		3718
3215	The winsocket C<select> function doesn't follow POSIX in that it requires	3719	The winsocket C<select> function doesn't follow POSIX in that it
3216	socket I<handles> and not socket I<file descriptors>. This makes select	3720	requires socket I<handles> and not socket I<file descriptors> (it is
3217	very inefficient, and also requires a mapping from file descriptors	3721	also extremely buggy). This makes select very inefficient, and also
3218	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3722	requires a mapping from file descriptors to socket handles (the Microsoft
3219	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3723	C runtime provides the function C<_open_osfhandle> for this). See the
3220	symbols for more info.	3724	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3725	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3221		3726
3222	The configuration for a "naked" win32 using the microsoft runtime	3727	The configuration for a "naked" win32 using the Microsoft runtime
3223	libraries and raw winsocket select is:	3728	libraries and raw winsocket select is:
3224		3729
3225	#define EV_USE_SELECT 1	3730	#define EV_USE_SELECT 1
3226	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3731	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3227		3732
3228	Note that winsockets handling of fd sets is O(n), so you can easily get a	3733	Note that winsockets handling of fd sets is O(n), so you can easily get a
3229	complexity in the O(n²) range when using win32.	3734	complexity in the O(n²) range when using win32.
3230		3735
3231	=item Limited number of file descriptors	3736	=item Limited number of file descriptors
3232		3737
3233	Windows has numerous arbitrary (and low) limits on things. Early versions	3738	Windows has numerous arbitrary (and low) limits on things.
3234	of winsocket's select only supported waiting for a max. of C<64> handles	3739
		3740	Early versions of winsocket's select only supported waiting for a maximum
3235	(probably owning to the fact that all windows kernels can only wait for	3741	of C<64> handles (probably owning to the fact that all windows kernels
3236	C<64> things at the same time internally; microsoft recommends spawning a	3742	can only wait for C<64> things at the same time internally; Microsoft
3237	chain of threads and wait for 63 handles and the previous thread in each).	3743	recommends spawning a chain of threads and wait for 63 handles and the
		3744	previous thread in each. Great).
3238		3745
3239	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3746	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3240	to some high number (e.g. C<2048>) before compiling the winsocket select	3747	to some high number (e.g. C<2048>) before compiling the winsocket select
3241	call (which might be in libev or elsewhere, for example, perl does its own	3748	call (which might be in libev or elsewhere, for example, perl does its own
3242	select emulation on windows).	3749	select emulation on windows).
3243		3750
3244	Another limit is the number of file descriptors in the microsoft runtime	3751	Another limit is the number of file descriptors in the Microsoft runtime
3245	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3752	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3246	or something like this inside microsoft). You can increase this by calling	3753	or something like this inside Microsoft). You can increase this by calling
3247	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3754	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3248	arbitrary limit), but is broken in many versions of the microsoft runtime	3755	arbitrary limit), but is broken in many versions of the Microsoft runtime
3249	libraries.	3756	libraries.
3250		3757
3251	This might get you to about C<512> or C<2048> sockets (depending on	3758	This might get you to about C<512> or C<2048> sockets (depending on
3252	windows version and/or the phase of the moon). To get more, you need to	3759	windows version and/or the phase of the moon). To get more, you need to
3253	wrap all I/O functions and provide your own fd management, but the cost of	3760	wrap all I/O functions and provide your own fd management, but the cost of
3254	calling select (O(n²)) will likely make this unworkable.	3761	calling select (O(n²)) will likely make this unworkable.
3255		3762
3256	=back	3763	=back
3257		3764
		3765	=head2 PORTABILITY REQUIREMENTS
		3766
		3767	In addition to a working ISO-C implementation and of course the
		3768	backend-specific APIs, libev relies on a few additional extensions:
		3769
		3770	=over 4
		3771
		3772	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3773	calling conventions regardless of C<ev_watcher_type *>.
		3774
		3775	Libev assumes not only that all watcher pointers have the same internal
		3776	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3777	assumes that the same (machine) code can be used to call any watcher
		3778	callback: The watcher callbacks have different type signatures, but libev
		3779	calls them using an C<ev_watcher *> internally.
		3780
		3781	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3782
		3783	The type C<sig_atomic_t volatile> (or whatever is defined as
		3784	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3785	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3786	believed to be sufficiently portable.
		3787
		3788	=item C<sigprocmask> must work in a threaded environment
		3789
		3790	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3791	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3792	pthread implementations will either allow C<sigprocmask> in the "main
		3793	thread" or will block signals process-wide, both behaviours would
		3794	be compatible with libev. Interaction between C<sigprocmask> and
		3795	C<pthread_sigmask> could complicate things, however.
		3796
		3797	The most portable way to handle signals is to block signals in all threads
		3798	except the initial one, and run the default loop in the initial thread as
		3799	well.
		3800
		3801	=item C<long> must be large enough for common memory allocation sizes
		3802
		3803	To improve portability and simplify its API, libev uses C<long> internally
		3804	instead of C<size_t> when allocating its data structures. On non-POSIX
		3805	systems (Microsoft...) this might be unexpectedly low, but is still at
		3806	least 31 bits everywhere, which is enough for hundreds of millions of
		3807	watchers.
		3808
		3809	=item C<double> must hold a time value in seconds with enough accuracy
		3810
		3811	The type C<double> is used to represent timestamps. It is required to
		3812	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3813	enough for at least into the year 4000. This requirement is fulfilled by
		3814	implementations implementing IEEE 754 (basically all existing ones).
		3815
		3816	=back
		3817
		3818	If you know of other additional requirements drop me a note.
		3819
		3820
		3821	=head1 ALGORITHMIC COMPLEXITIES
		3822
		3823	In this section the complexities of (many of) the algorithms used inside
		3824	libev will be documented. For complexity discussions about backends see
		3825	the documentation for C<ev_default_init>.
		3826
		3827	All of the following are about amortised time: If an array needs to be
		3828	extended, libev needs to realloc and move the whole array, but this
		3829	happens asymptotically rarer with higher number of elements, so O(1) might
		3830	mean that libev does a lengthy realloc operation in rare cases, but on
		3831	average it is much faster and asymptotically approaches constant time.
		3832
		3833	=over 4
		3834
		3835	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3836
		3837	This means that, when you have a watcher that triggers in one hour and
		3838	there are 100 watchers that would trigger before that, then inserting will
		3839	have to skip roughly seven (C<ld 100>) of these watchers.
		3840
		3841	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3842
		3843	That means that changing a timer costs less than removing/adding them,
		3844	as only the relative motion in the event queue has to be paid for.
		3845
		3846	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3847
		3848	These just add the watcher into an array or at the head of a list.
		3849
		3850	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3851
		3852	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3853
		3854	These watchers are stored in lists, so they need to be walked to find the
		3855	correct watcher to remove. The lists are usually short (you don't usually
		3856	have many watchers waiting for the same fd or signal: one is typical, two
		3857	is rare).
		3858
		3859	=item Finding the next timer in each loop iteration: O(1)
		3860
		3861	By virtue of using a binary or 4-heap, the next timer is always found at a
		3862	fixed position in the storage array.
		3863
		3864	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3865
		3866	A change means an I/O watcher gets started or stopped, which requires
		3867	libev to recalculate its status (and possibly tell the kernel, depending
		3868	on backend and whether C<ev_io_set> was used).
		3869
		3870	=item Activating one watcher (putting it into the pending state): O(1)
		3871
		3872	=item Priority handling: O(number_of_priorities)
		3873
		3874	Priorities are implemented by allocating some space for each
		3875	priority. When doing priority-based operations, libev usually has to
		3876	linearly search all the priorities, but starting/stopping and activating
		3877	watchers becomes O(1) with respect to priority handling.
		3878
		3879	=item Sending an ev_async: O(1)
		3880
		3881	=item Processing ev_async_send: O(number_of_async_watchers)
		3882
		3883	=item Processing signals: O(max_signal_number)
		3884
		3885	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3886	calls in the current loop iteration. Checking for async and signal events
		3887	involves iterating over all running async watchers or all signal numbers.
		3888
		3889	=back
		3890
3258		3891
3259	=head1 AUTHOR	3892	=head1 AUTHOR
3260		3893
3261	Marc Lehmann <libev@schmorp.de>.	3894	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3262		3895

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