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Revision 1.147 by root, Wed Apr 23 08:21:02 2008 UTC vs.
Revision 1.224 by root, Fri Feb 6 20:17:43 2009 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	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 DESCRIPTION
66		68
67	The newest version of this document is also available as an html-formatted	69	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	70	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		72
71	Libev is an event loop: you register interest in certain events (such as a	73	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	74	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	75	these event sources and provide your program with events.
74		76
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	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	109	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	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	116	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	117	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	118	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	119	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	120	it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	121	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	122	throughout libev.
		123
		124	=head1 ERROR HANDLING
		125
		126	Libev knows three classes of errors: operating system errors, usage errors
		127	and internal errors (bugs).
		128
		129	When libev catches an operating system error it cannot handle (for example
		130	a system call indicating a condition libev cannot fix), it calls the callback
		131	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		132	abort. The default is to print a diagnostic message and to call C<abort
		133	()>.
		134
		135	When libev detects a usage error such as a negative timer interval, then
		136	it will print a diagnostic message and abort (via the C<assert> mechanism,
		137	so C<NDEBUG> will disable this checking): these are programming errors in
		138	the libev caller and need to be fixed there.
		139
		140	Libev also has a few internal error-checking C<assert>ions, and also has
		141	extensive consistency checking code. These do not trigger under normal
		142	circumstances, as they indicate either a bug in libev or worse.
		143
121		144
122	=head1 GLOBAL FUNCTIONS	145	=head1 GLOBAL FUNCTIONS
123		146
124	These functions can be called anytime, even before initialising the	147	These functions can be called anytime, even before initialising the
125	library in any way.	148	library in any way.
…		…
134		157
135	=item ev_sleep (ev_tstamp interval)	158	=item ev_sleep (ev_tstamp interval)
136		159
137	Sleep for the given interval: The current thread will be blocked until	160	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	161	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	162	this is a sub-second-resolution C<sleep ()>.
140		163
141	=item int ev_version_major ()	164	=item int ev_version_major ()
142		165
143	=item int ev_version_minor ()	166	=item int ev_version_minor ()
144		167
…		…
157	not a problem.	180	not a problem.
158		181
159	Example: Make sure we haven't accidentally been linked against the wrong	182	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	183	version.
161		184
162	assert (("libev version mismatch",	185	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	186	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	187	&& ev_version_minor () >= EV_VERSION_MINOR));
165		188
166	=item unsigned int ev_supported_backends ()	189	=item unsigned int ev_supported_backends ()
167		190
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	191	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	192	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	194	a description of the set values.
172		195
173	Example: make sure we have the epoll method, because yeah this is cool and	196	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	197	a must have and can we have a torrent of it please!!!11
175		198
176	assert (("sorry, no epoll, no sex",	199	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	200	ev_supported_backends () & EVBACKEND_EPOLL));
178		201
179	=item unsigned int ev_recommended_backends ()	202	=item unsigned int ev_recommended_backends ()
180		203
181	Return the set of all backends compiled into this binary of libev and also	204	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	205	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	206	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	207	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	208	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	209	libev will probe for if you specify no backends explicitly.
187		210
188	=item unsigned int ev_embeddable_backends ()	211	=item unsigned int ev_embeddable_backends ()
189		212
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	217	recommended ones.
195		218
196	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
197		220
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		222
200	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
201	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	225	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	226	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	252	}
230		253
231	...	254	...
232	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
233		256
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		258
236	Set the callback function to call on a retryable syscall error (such	259	Set the callback function to call on a retryable system call error (such
237	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
238	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
239	callback is set, then libev will expect it to remedy the sitution, no	262	callback is set, then libev will expect it to remedy the situation, no
240	matter what, when it returns. That is, libev will generally retry the	263	matter what, when it returns. That is, libev will generally retry the
241	requested operation, or, if the condition doesn't go away, do bad stuff	264	requested operation, or, if the condition doesn't go away, do bad stuff
242	(such as abort).	265	(such as abort).
243		266
244	Example: This is basically the same thing that libev does internally, too.	267	Example: This is basically the same thing that libev does internally, too.
…		…
255		278
256	=back	279	=back
257		280
258	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
259		282
260	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
261	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
262	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
263		290
264	=over 4	291	=over 4
265		292
266	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
267		294
…		…
273	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
274	function.	301	function.
275		302
276	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
277	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
279		306
280	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	312	C<ev_default_init>.
286		313
287	The flags argument can be used to specify special behaviour or specific	314	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	323	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	324	thing, believe me).
298		325
299	=item C<EVFLAG_NOENV>	326	=item C<EVFLAG_NOENV>
300		327
301	If this flag bit is ored into the flag value (or the program runs setuid	328	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	329	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	331	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	332	useful to try out specific backends to test their performance, or to work
306	around bugs.	333	around bugs.
…		…
313		340
314	This works by calling C<getpid ()> on every iteration of the loop,	341	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	342	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	343	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	345	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	346	C<pthread_atfork> which is even faster).
320		347
321	The big advantage of this flag is that you can forget about fork (and	348	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	349	forget about forgetting to tell libev about forking) when you use this
323	flag.	350	flag.
324		351
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	353	environment variable.
327		354
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		356
330	This is your standard select(2) backend. Not I<completely> standard, as	357	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	359	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	360	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	361	usually the fastest backend for a low number of (low-numbered :) fds.
335		362
336	To get good performance out of this backend you need a high amount of	363	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	364	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	365	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	366	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	368	readiness notifications you get per iteration.
		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
342		373
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		375
345	And this is your standard poll(2) backend. It's more complicated	376	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	377	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	378	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	379	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	381	performance tips.
351		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		385
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		387
354	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	392
359	cases and requiring a syscall per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
361		409
362	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	411	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
367		415	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		416
372	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	418	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
375		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
		428
376	While nominally embeddeble in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
378		434
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		436
381	Kqueue deserves special mention, as at the time of this writing, it	437	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	439	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	445	system like NetBSD.
388		446
389	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	449	the target platform). See C<ev_embed> watchers for more info.
392		450
393	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
399		458
400	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
401		460
402	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
408		471
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		473
411	This is not implemented yet (and might never be, unless you send me an	474	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	475	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		480
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	482	it's really slow, but it still scales very well (O(active_fds)).
420		483
421	Please note that solaris event ports can deliver a lot of spurious	484	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	485	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	486	blocking when no data (or space) is available.
424		487
425	While this backend scales well, it requires one system call per active	488	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	489	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	491	might perform better.
429		492
430	On the positive side, ignoring the spurious readyness notifications, this	493	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
433		500
434	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
435		502
436	Try all backends (even potentially broken ones that wouldn't be tried	503	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		506
440	It is definitely not recommended to use this flag.	507	It is definitely not recommended to use this flag.
441		508
442	=back	509	=back
443		510
444	If one or more of these are ored into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		514
448	The most typical usage is like this:	515	Example: This is the most typical usage.
449		516
450	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		519
453	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	521	environment settings to be taken into account:
455		522
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		524
458	Use whatever libev has to offer, but make sure that kqueue is used if	525	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	527	private event loop and only if you know the OS supports your types of
		528	fds):
461		529
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		531
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		533
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	534	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	535	always distinct from the default loop. Unlike the default loop, it cannot
…		…
472	libev with threads is indeed to create one loop per thread, and using the	540	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	541	default loop in the "main" or "initial" thread.
474		542
475	Example: Try to create a event loop that uses epoll and nothing else.	543	Example: Try to create a event loop that uses epoll and nothing else.
476		544
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	546	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
480		548
481	=item ev_default_destroy ()	549	=item ev_default_destroy ()
482		550
483	Destroys the default loop again (frees all memory and kernel state	551	Destroys the default loop again (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	552	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	553	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	557	for example).
490		558
491	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
492	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
493	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
494		562
495	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
496	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
497	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
498	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
523		591
524	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
525		593
526	Like C<ev_default_fork>, but acts on an event loop created by	594	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
529		598
530	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
531		600
532	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
533		603
534	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
535		605
536	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
537	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
552	received events and started processing them. This timestamp does not	622	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	623	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	624	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	625	event occurring (or more correctly, libev finding out about it).
556		626
		627	=item ev_now_update (loop)
		628
		629	Establishes the current time by querying the kernel, updating the time
		630	returned by C<ev_now ()> in the progress. This is a costly operation and
		631	is usually done automatically within C<ev_loop ()>.
		632
		633	This function is rarely useful, but when some event callback runs for a
		634	very long time without entering the event loop, updating libev's idea of
		635	the current time is a good idea.
		636
		637	See also "The special problem of time updates" in the C<ev_timer> section.
		638
557	=item ev_loop (loop, int flags)	639	=item ev_loop (loop, int flags)
558		640
559	Finally, this is it, the event handler. This function usually is called	641	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	642	after you initialised all your watchers and you want to start handling
561	events.	643	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	645	If the flags argument is specified as C<0>, it will not return until
564	either no event watchers are active anymore or C<ev_unloop> was called.	646	either no event watchers are active anymore or C<ev_unloop> was called.
565		647
566	Please note that an explicit C<ev_unloop> is usually better than	648	Please note that an explicit C<ev_unloop> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	649	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	650	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	651	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	652	of relying on its watchers stopping correctly, that is truly a thing of
		653	beauty.
571		654
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	656	those events and any already outstanding ones, but will not block your
574	case there are no events and will return after one iteration of the loop.	657	process in case there are no events and will return after one iteration of
		658	the loop.
575		659
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	661	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	662	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	663	be an event internal to libev itself, so there is no guarantee that a
580	external event in conjunction with something not expressible using other	664	user-registered callback will be called), and will return after one
		665	iteration of the loop.
		666
		667	This is useful if you are waiting for some external event in conjunction
		668	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	670	usually a better approach for this kind of thing.
583		671
584	Here are the gory details of what C<ev_loop> does:	672	Here are the gory details of what C<ev_loop> does:
585		673
586	- Before the first iteration, call any pending watchers.	674	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	675	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	676	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	677	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	678	- If we have been forked, detach and recreate the kernel state
		679	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	680	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	681	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	682	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	683	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	684	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	685	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	686	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	687	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	689	- Queue all expired timers.
601	- Queue all outstanding periodics.	690	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	691	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	692	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	693	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	694	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	695	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	701	anymore.
613		702
614	... queue jobs here, make sure they register event watchers as long	703	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	704	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	705	ev_loop (my_loop, 0);
617	... jobs done. yeah!	706	... jobs done or somebody called unloop. yeah!
618		707
619	=item ev_unloop (loop, how)	708	=item ev_unloop (loop, how)
620		709
621	Can be used to make a call to C<ev_loop> return early (but only after it	710	Can be used to make a call to C<ev_loop> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	711	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		714
626	This "unloop state" will be cleared when entering C<ev_loop> again.	715	This "unloop state" will be cleared when entering C<ev_loop> again.
627		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
628	=item ev_ref (loop)	719	=item ev_ref (loop)
629		720
630	=item ev_unref (loop)	721	=item ev_unref (loop)
631		722
632	Ref/unref can be used to add or remove a reference count on the event	723	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	724	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	725	count is nonzero, C<ev_loop> will not return on its own.
		726
635	a watcher you never unregister that should not keep C<ev_loop> from	727	If you have a watcher you never unregister that should not keep C<ev_loop>
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	728	from returning, call ev_unref() after starting, and ev_ref() before
		729	stopping it.
		730
637	example, libev itself uses this for its internal signal pipe: It is not	731	As an example, libev itself uses this for its internal signal pipe: It is
638	visible to the libev user and should not keep C<ev_loop> from exiting if	732	not visible to the libev user and should not keep C<ev_loop> from exiting
639	no event watchers registered by it are active. It is also an excellent	733	if no event watchers registered by it are active. It is also an excellent
640	way to do this for generic recurring timers or from within third-party	734	way to do this for generic recurring timers or from within third-party
641	libraries. Just remember to I<unref after start> and I<ref before stop>	735	libraries. Just remember to I<unref after start> and I<ref before stop>
642	(but only if the watcher wasn't active before, or was active before,	736	(but only if the watcher wasn't active before, or was active before,
643	respectively).	737	respectively).
644		738
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	740	running when nothing else is active.
647		741
648	struct ev_signal exitsig;	742	ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	743	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	744	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	745	evf_unref (loop);
652		746
653	Example: For some weird reason, unregister the above signal handler again.	747	Example: For some weird reason, unregister the above signal handler again.
654		748
655	ev_ref (loop);	749	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	750	ev_signal_stop (loop, &exitsig);
657		751
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	752	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		753
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	754	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		755
662	These advanced functions influence the time that libev will spend waiting	756	These advanced functions influence the time that libev will spend waiting
663	for events. Both are by default C<0>, meaning that libev will try to	757	for events. Both time intervals are by default C<0>, meaning that libev
664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	758	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		759	latency.
665		760
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	761	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
667	allows libev to delay invocation of I/O and timer/periodic callbacks to	762	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	763	to increase efficiency of loop iterations (or to increase power-saving
		764	opportunities).
669		765
670	The background is that sometimes your program runs just fast enough to	766	The idea is that sometimes your program runs just fast enough to handle
671	handle one (or very few) event(s) per loop iteration. While this makes	767	one (or very few) event(s) per loop iteration. While this makes the
672	the program responsive, it also wastes a lot of CPU time to poll for new	768	program responsive, it also wastes a lot of CPU time to poll for new
673	events, especially with backends like C<select ()> which have a high	769	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	770	overhead for the actual polling but can deliver many events at once.
675		771
676	By setting a higher I<io collect interval> you allow libev to spend more	772	By setting a higher I<io collect interval> you allow libev to spend more
677	time collecting I/O events, so you can handle more events per iteration,	773	time collecting I/O events, so you can handle more events per iteration,
…		…
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	775	C<ev_timer>) will be not affected. Setting this to a non-null value will
680	introduce an additional C<ev_sleep ()> call into most loop iterations.	776	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		777
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	778	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	779	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	780	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	781	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	782	value will not introduce any overhead in libev.
687		783
688	Many (busy) programs can usually benefit by setting the io collect	784	Many (busy) programs can usually benefit by setting the I/O collect
689	interval to a value near C<0.1> or so, which is often enough for	785	interval to a value near C<0.1> or so, which is often enough for
690	interactive servers (of course not for games), likewise for timeouts. It	786	interactive servers (of course not for games), likewise for timeouts. It
691	usually doesn't make much sense to set it to a lower value than C<0.01>,	787	usually doesn't make much sense to set it to a lower value than C<0.01>,
692	as this approsaches the timing granularity of most systems.	788	as this approaches the timing granularity of most systems.
		789
		790	Setting the I<timeout collect interval> can improve the opportunity for
		791	saving power, as the program will "bundle" timer callback invocations that
		792	are "near" in time together, by delaying some, thus reducing the number of
		793	times the process sleeps and wakes up again. Another useful technique to
		794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		795	they fire on, say, one-second boundaries only.
		796
		797	=item ev_loop_verify (loop)
		798
		799	This function only does something when C<EV_VERIFY> support has been
		800	compiled in, which is the default for non-minimal builds. It tries to go
		801	through all internal structures and checks them for validity. If anything
		802	is found to be inconsistent, it will print an error message to standard
		803	error and call C<abort ()>.
		804
		805	This can be used to catch bugs inside libev itself: under normal
		806	circumstances, this function will never abort as of course libev keeps its
		807	data structures consistent.
693		808
694	=back	809	=back
695		810
696		811
697	=head1 ANATOMY OF A WATCHER	812	=head1 ANATOMY OF A WATCHER
		813
		814	In the following description, uppercase C<TYPE> in names stands for the
		815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		816	watchers and C<ev_io_start> for I/O watchers.
698		817
699	A watcher is a structure that you create and register to record your	818	A watcher is a structure that you create and register to record your
700	interest in some event. For instance, if you want to wait for STDIN to	819	interest in some event. For instance, if you want to wait for STDIN to
701	become readable, you would create an C<ev_io> watcher for that:	820	become readable, you would create an C<ev_io> watcher for that:
702		821
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
704	{	823	{
705	ev_io_stop (w);	824	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	825	ev_unloop (loop, EVUNLOOP_ALL);
707	}	826	}
708		827
709	struct ev_loop *loop = ev_default_loop (0);	828	struct ev_loop *loop = ev_default_loop (0);
		829
710	struct ev_io stdin_watcher;	830	ev_io stdin_watcher;
		831
711	ev_init (&stdin_watcher, my_cb);	832	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	834	ev_io_start (loop, &stdin_watcher);
		835
714	ev_loop (loop, 0);	836	ev_loop (loop, 0);
715		837
716	As you can see, you are responsible for allocating the memory for your	838	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	839	watcher structures (and it is I<usually> a bad idea to do this on the
718	although this can sometimes be quite valid).	840	stack).
		841
		842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
719		844
720	Each watcher structure must be initialised by a call to C<ev_init	845	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	846	(watcher *, callback)>, which expects a callback to be provided. This
722	callback gets invoked each time the event occurs (or, in the case of io	847	callback gets invoked each time the event occurs (or, in the case of I/O
723	watchers, each time the event loop detects that the file descriptor given	848	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	849	is readable and/or writable).
725		850
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
727	with arguments specific to this watcher type. There is also a macro	852	macro to configure it, with arguments specific to the watcher type. There
728	to combine initialisation and setting in one call: C<< ev_<type>_init	853	is also a macro to combine initialisation and setting in one call: C<<
729	(watcher *, callback, ...) >>.	854	ev_TYPE_init (watcher *, callback, ...) >>.
730		855
731	To make the watcher actually watch out for events, you have to start it	856	To make the watcher actually watch out for events, you have to start it
732	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	857	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
733	*) >>), and you can stop watching for events at any time by calling the	858	*) >>), and you can stop watching for events at any time by calling the
734	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
735		860
736	As long as your watcher is active (has been started but not stopped) you	861	As long as your watcher is active (has been started but not stopped) you
737	must not touch the values stored in it. Most specifically you must never	862	must not touch the values stored in it. Most specifically you must never
738	reinitialise it or call its C<set> macro.	863	reinitialise it or call its C<ev_TYPE_set> macro.
739		864
740	Each and every callback receives the event loop pointer as first, the	865	Each and every callback receives the event loop pointer as first, the
741	registered watcher structure as second, and a bitset of received events as	866	registered watcher structure as second, and a bitset of received events as
742	third argument.	867	third argument.
743		868
…		…
803		928
804	The given async watcher has been asynchronously notified (see C<ev_async>).	929	The given async watcher has been asynchronously notified (see C<ev_async>).
805		930
806	=item C<EV_ERROR>	931	=item C<EV_ERROR>
807		932
808	An unspecified error has occured, the watcher has been stopped. This might	933	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	934	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	935	ran out of memory, a file descriptor was found to be closed or any other
		936	problem. Libev considers these application bugs.
		937
811	problem. You best act on it by reporting the problem and somehow coping	938	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	939	watcher being stopped. Note that well-written programs should not receive
		940	an error ever, so when your watcher receives it, this usually indicates a
		941	bug in your program.
813		942
814	Libev will usually signal a few "dummy" events together with an error,	943	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	944	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	945	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	946	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	947	programs, though, as the fd could already be closed and reused for another
		948	thing, so beware.
819		949
820	=back	950	=back
821		951
822	=head2 GENERIC WATCHER FUNCTIONS	952	=head2 GENERIC WATCHER FUNCTIONS
823
824	In the following description, C<TYPE> stands for the watcher type,
825	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
826		953
827	=over 4	954	=over 4
828		955
829	=item C<ev_init> (ev_TYPE *watcher, callback)	956	=item C<ev_init> (ev_TYPE *watcher, callback)
830		957
…		…
836	which rolls both calls into one.	963	which rolls both calls into one.
837		964
838	You can reinitialise a watcher at any time as long as it has been stopped	965	You can reinitialise a watcher at any time as long as it has been stopped
839	(or never started) and there are no pending events outstanding.	966	(or never started) and there are no pending events outstanding.
840		967
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	968	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	969	int revents)>.
		970
		971	Example: Initialise an C<ev_io> watcher in two steps.
		972
		973	ev_io w;
		974	ev_init (&w, my_cb);
		975	ev_io_set (&w, STDIN_FILENO, EV_READ);
843		976
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	977	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		978
846	This macro initialises the type-specific parts of a watcher. You need to	979	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	980	call C<ev_init> at least once before you call this macro, but you can
…		…
850	difference to the C<ev_init> macro).	983	difference to the C<ev_init> macro).
851		984
852	Although some watcher types do not have type-specific arguments	985	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	986	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		987
		988	See C<ev_init>, above, for an example.
		989
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	990	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		991
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	992	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	993	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	994	a watcher. The same limitations apply, of course.
		995
		996	Example: Initialise and set an C<ev_io> watcher in one step.
		997
		998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		999
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		1001
863	Starts (activates) the given watcher. Only active watchers will receive	1002	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	1003	events. If the watcher is already active nothing will happen.
865		1004
		1005	Example: Start the C<ev_io> watcher that is being abused as example in this
		1006	whole section.
		1007
		1008	ev_io_start (EV_DEFAULT_UC, &w);
		1009
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		1011
868	Stops the given watcher again (if active) and clears the pending	1012	Stops the given watcher if active, and clears the pending status (whether
		1013	the watcher was active or not).
		1014
869	status. It is possible that stopped watchers are pending (for example,	1015	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	1016	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1017	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	1018	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	1019	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		1020
875	=item bool ev_is_active (ev_TYPE *watcher)	1021	=item bool ev_is_active (ev_TYPE *watcher)
876		1022
877	Returns a true value iff the watcher is active (i.e. it has been started	1023	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	1024	and not yet been stopped). As long as a watcher is active you must not modify
…		…
920	The default priority used by watchers when no priority has been set is	1066	The default priority used by watchers when no priority has been set is
921	always C<0>, which is supposed to not be too high and not be too low :).	1067	always C<0>, which is supposed to not be too high and not be too low :).
922		1068
923	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
924	fine, as long as you do not mind that the priority value you query might	1070	fine, as long as you do not mind that the priority value you query might
925	or might not have been adjusted to be within valid range.	1071	or might not have been clamped to the valid range.
926		1072
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1074
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1076	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1077	can deal with that fact, as both are simply passed through to the
		1078	callback.
932		1079
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1080	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1081
935	If the watcher is pending, this function returns clears its pending status	1082	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1083	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1084	watcher isn't pending it does nothing and returns C<0>.
938		1085
		1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1087	callback to be invoked, which can be accomplished with this function.
		1088
939	=back	1089	=back
940		1090
941		1091
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1093
944	Each watcher has, by default, a member C<void *data> that you can change	1094	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1095	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1096	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1097	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1098	member, you can also "subclass" the watcher type and provide your own
949	data:	1099	data:
950		1100
951	struct my_io	1101	struct my_io
952	{	1102	{
953	struct ev_io io;	1103	ev_io io;
954	int otherfd;	1104	int otherfd;
955	void *somedata;	1105	void *somedata;
956	struct whatever *mostinteresting;	1106	struct whatever *mostinteresting;
957	}	1107	};
		1108
		1109	...
		1110	struct my_io w;
		1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1112
959	And since your callback will be called with a pointer to the watcher, you	1113	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1114	can cast it back to your own type:
961		1115
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
963	{	1117	{
964	struct my_io *w = (struct my_io *)w_;	1118	struct my_io *w = (struct my_io *)w_;
965	...	1119	...
966	}	1120	}
967		1121
968	More interesting and less C-conformant ways of casting your callback type	1122	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1123	instead have been omitted.
970		1124
971	Another common scenario is having some data structure with multiple	1125	Another common scenario is to use some data structure with multiple
972	watchers:	1126	embedded watchers:
973		1127
974	struct my_biggy	1128	struct my_biggy
975	{	1129	{
976	int some_data;	1130	int some_data;
977	ev_timer t1;	1131	ev_timer t1;
978	ev_timer t2;	1132	ev_timer t2;
979	}	1133	}
980		1134
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1135	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1136	complicated: Either you store the address of your C<my_biggy> struct
		1137	in the C<data> member of the watcher (for woozies), or you need to use
		1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1139	programmers):
983		1140
984	#include <stddef.h>	1141	#include <stddef.h>
985		1142
986	static void	1143	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1144	t1_cb (EV_P_ ev_timer *w, int revents)
988	{	1145	{
989	struct my_biggy big = (struct my_biggy *	1146	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1147	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1148	}
992		1149
993	static void	1150	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1151	t2_cb (EV_P_ ev_timer *w, int revents)
995	{	1152	{
996	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1154	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1155	}
999		1156
1000		1157
1001	=head1 WATCHER TYPES	1158	=head1 WATCHER TYPES
1002		1159
1003	This section describes each watcher in detail, but will not repeat	1160	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1184	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1185	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1186	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1187	required if you know what you are doing).
1031		1188
1032	If you must do this, then force the use of a known-to-be-good backend	1189	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1190	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1192
1036	Another thing you have to watch out for is that it is quite easy to	1193	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readyness notifications, that is your callback might	1194	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1196	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1197	lot of those (for example Solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1198	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1201
1045	If you cannot run the fd in non-blocking mode (for example you should not	1202	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1203	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1204	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1205	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1206	does this on its own, so its quite safe to use). Some people additionally
		1207	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1208	indefinitely.
		1209
		1210	But really, best use non-blocking mode.
1050		1211
1051	=head3 The special problem of disappearing file descriptors	1212	=head3 The special problem of disappearing file descriptors
1052		1213
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1214	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1215	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1216	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1217	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1218	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1219	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1220	fact, a different file descriptor.
1060		1221
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1253	C<EVBACKEND_POLL>.
1093		1254
1094	=head3 The special problem of SIGPIPE	1255	=head3 The special problem of SIGPIPE
1095		1256
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1258	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1259	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1260	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1261
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1262	So when you encounter spurious, unexplained daemon exits, make sure you
1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104	somewhere, as that would have given you a big clue).	1264	somewhere, as that would have given you a big clue).
1105		1265
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1271	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1272
1113	=item ev_io_set (ev_io *, int fd, int events)	1273	=item ev_io_set (ev_io *, int fd, int events)
1114		1274
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1275	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1276	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1277	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1278
1119	=item int fd [read-only]	1279	=item int fd [read-only]
1120		1280
1121	The file descriptor being watched.	1281	The file descriptor being watched.
1122		1282
…		…
1130		1290
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1291	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1292	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1293	attempt to read a whole line in the callback.
1134		1294
1135	static void	1295	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1296	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1137	{	1297	{
1138	ev_io_stop (loop, w);	1298	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1299	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1300	}
1141		1301
1142	...	1302	...
1143	struct ev_loop *loop = ev_default_init (0);	1303	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1304	ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1306	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1307	ev_loop (loop, 0);
1148		1308
1149		1309
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1310	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1311
1152	Timer watchers are simple relative timers that generate an event after a	1312	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1313	given time, and optionally repeating in regular intervals after that.
1154		1314
1155	The timers are based on real time, that is, if you register an event that	1315	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to last years	1316	times out after an hour and you reset your system clock to January last
1157	time, it will still time out after (roughly) and hour. "Roughly" because	1317	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1319	monotonic clock option helps a lot here).
		1320
		1321	The callback is guaranteed to be invoked only I<after> its timeout has
		1322	passed, but if multiple timers become ready during the same loop iteration
		1323	then order of execution is undefined.
		1324
		1325	=head3 Be smart about timeouts
		1326
		1327	Many real-world problems involve some kind of timeout, usually for error
		1328	recovery. A typical example is an HTTP request - if the other side hangs,
		1329	you want to raise some error after a while.
		1330
		1331	What follows are some ways to handle this problem, from obvious and
		1332	inefficient to smart and efficient.
		1333
		1334	In the following, a 60 second activity timeout is assumed - a timeout that
		1335	gets reset to 60 seconds each time there is activity (e.g. each time some
		1336	data or other life sign was received).
		1337
		1338	=over 4
		1339
		1340	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1341
		1342	This is the most obvious, but not the most simple way: In the beginning,
		1343	start the watcher:
		1344
		1345	ev_timer_init (timer, callback, 60., 0.);
		1346	ev_timer_start (loop, timer);
		1347
		1348	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1349	and start it again:
		1350
		1351	ev_timer_stop (loop, timer);
		1352	ev_timer_set (timer, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	This is relatively simple to implement, but means that each time there is
		1356	some activity, libev will first have to remove the timer from its internal
		1357	data structure and then add it again. Libev tries to be fast, but it's
		1358	still not a constant-time operation.
		1359
		1360	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1361
		1362	This is the easiest way, and involves using C<ev_timer_again> instead of
		1363	C<ev_timer_start>.
		1364
		1365	To implement this, configure an C<ev_timer> with a C<repeat> value
		1366	of C<60> and then call C<ev_timer_again> at start and each time you
		1367	successfully read or write some data. If you go into an idle state where
		1368	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1369	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1370
		1371	That means you can ignore both the C<ev_timer_start> function and the
		1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1373	member and C<ev_timer_again>.
		1374
		1375	At start:
		1376
		1377	ev_timer_init (timer, callback);
		1378	timer->repeat = 60.;
		1379	ev_timer_again (loop, timer);
		1380
		1381	Each time there is some activity:
		1382
		1383	ev_timer_again (loop, timer);
		1384
		1385	It is even possible to change the time-out on the fly, regardless of
		1386	whether the watcher is active or not:
		1387
		1388	timer->repeat = 30.;
		1389	ev_timer_again (loop, timer);
		1390
		1391	This is slightly more efficient then stopping/starting the timer each time
		1392	you want to modify its timeout value, as libev does not have to completely
		1393	remove and re-insert the timer from/into its internal data structure.
		1394
		1395	It is, however, even simpler than the "obvious" way to do it.
		1396
		1397	=item 3. Let the timer time out, but then re-arm it as required.
		1398
		1399	This method is more tricky, but usually most efficient: Most timeouts are
		1400	relatively long compared to the intervals between other activity - in
		1401	our example, within 60 seconds, there are usually many I/O events with
		1402	associated activity resets.
		1403
		1404	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1405	but remember the time of last activity, and check for a real timeout only
		1406	within the callback:
		1407
		1408	ev_tstamp last_activity; // time of last activity
		1409
		1410	static void
		1411	callback (EV_P_ ev_timer *w, int revents)
		1412	{
		1413	ev_tstamp now = ev_now (EV_A);
		1414	ev_tstamp timeout = last_activity + 60.;
		1415
		1416	// if last_activity + 60. is older than now, we did time out
		1417	if (timeout < now)
		1418	{
		1419	// timeout occured, take action
		1420	}
		1421	else
		1422	{
		1423	// callback was invoked, but there was some activity, re-arm
		1424	// the watcher to fire in last_activity + 60, which is
		1425	// guaranteed to be in the future, so "again" is positive:
		1426	w->repeat = timeout - now;
		1427	ev_timer_again (EV_A_ w);
		1428	}
		1429	}
		1430
		1431	To summarise the callback: first calculate the real timeout (defined
		1432	as "60 seconds after the last activity"), then check if that time has
		1433	been reached, which means something I<did>, in fact, time out. Otherwise
		1434	the callback was invoked too early (C<timeout> is in the future), so
		1435	re-schedule the timer to fire at that future time, to see if maybe we have
		1436	a timeout then.
		1437
		1438	Note how C<ev_timer_again> is used, taking advantage of the
		1439	C<ev_timer_again> optimisation when the timer is already running.
		1440
		1441	This scheme causes more callback invocations (about one every 60 seconds
		1442	minus half the average time between activity), but virtually no calls to
		1443	libev to change the timeout.
		1444
		1445	To start the timer, simply initialise the watcher and set C<last_activity>
		1446	to the current time (meaning we just have some activity :), then call the
		1447	callback, which will "do the right thing" and start the timer:
		1448
		1449	ev_timer_init (timer, callback);
		1450	last_activity = ev_now (loop);
		1451	callback (loop, timer, EV_TIMEOUT);
		1452
		1453	And when there is some activity, simply store the current time in
		1454	C<last_activity>, no libev calls at all:
		1455
		1456	last_actiivty = ev_now (loop);
		1457
		1458	This technique is slightly more complex, but in most cases where the
		1459	time-out is unlikely to be triggered, much more efficient.
		1460
		1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1462	callback :) - just change the timeout and invoke the callback, which will
		1463	fix things for you.
		1464
		1465	=item 4. Wee, just use a double-linked list for your timeouts.
		1466
		1467	If there is not one request, but many thousands (millions...), all
		1468	employing some kind of timeout with the same timeout value, then one can
		1469	do even better:
		1470
		1471	When starting the timeout, calculate the timeout value and put the timeout
		1472	at the I<end> of the list.
		1473
		1474	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1475	the list is expected to fire (for example, using the technique #3).
		1476
		1477	When there is some activity, remove the timer from the list, recalculate
		1478	the timeout, append it to the end of the list again, and make sure to
		1479	update the C<ev_timer> if it was taken from the beginning of the list.
		1480
		1481	This way, one can manage an unlimited number of timeouts in O(1) time for
		1482	starting, stopping and updating the timers, at the expense of a major
		1483	complication, and having to use a constant timeout. The constant timeout
		1484	ensures that the list stays sorted.
		1485
		1486	=back
		1487
		1488	So which method the best?
		1489
		1490	Method #2 is a simple no-brain-required solution that is adequate in most
		1491	situations. Method #3 requires a bit more thinking, but handles many cases
		1492	better, and isn't very complicated either. In most case, choosing either
		1493	one is fine, with #3 being better in typical situations.
		1494
		1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1496	rather complicated, but extremely efficient, something that really pays
		1497	off after the first million or so of active timers, i.e. it's usually
		1498	overkill :)
		1499
		1500	=head3 The special problem of time updates
		1501
		1502	Establishing the current time is a costly operation (it usually takes at
		1503	least two system calls): EV therefore updates its idea of the current
		1504	time only before and after C<ev_loop> collects new events, which causes a
		1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1506	lots of events in one iteration.
1160		1507
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1508	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1509	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1510	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1511	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1512	timeout on the current time, use something like this to adjust for this:
1166		1513
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1515
1169	The callback is guarenteed to be invoked only when its timeout has passed,	1516	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1518	()>.
1172		1519
1173	=head3 Watcher-Specific Functions and Data Members	1520	=head3 Watcher-Specific Functions and Data Members
1174		1521
1175	=over 4	1522	=over 4
1176		1523
1177	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1178		1525
1179	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1526	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1180		1527
1181	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1528	Configure the timer to trigger after C<after> seconds. If C<repeat>
1182	C<0.>, then it will automatically be stopped. If it is positive, then the	1529	is C<0.>, then it will automatically be stopped once the timeout is
1183	timer will automatically be configured to trigger again C<repeat> seconds	1530	reached. If it is positive, then the timer will automatically be
1184	later, again, and again, until stopped manually.	1531	configured to trigger again C<repeat> seconds later, again, and again,
		1532	until stopped manually.
1185		1533
1186	The timer itself will do a best-effort at avoiding drift, that is, if you	1534	The timer itself will do a best-effort at avoiding drift, that is, if
1187	configure a timer to trigger every 10 seconds, then it will trigger at	1535	you configure a timer to trigger every 10 seconds, then it will normally
1188	exactly 10 second intervals. If, however, your program cannot keep up with	1536	trigger at exactly 10 second intervals. If, however, your program cannot
1189	the timer (because it takes longer than those 10 seconds to do stuff) the	1537	keep up with the timer (because it takes longer than those 10 seconds to
1190	timer will not fire more than once per event loop iteration.	1538	do stuff) the timer will not fire more than once per event loop iteration.
1191		1539
1192	=item ev_timer_again (loop, ev_timer *)	1540	=item ev_timer_again (loop, ev_timer *)
1193		1541
1194	This will act as if the timer timed out and restart it again if it is	1542	This will act as if the timer timed out and restart it again if it is
1195	repeating. The exact semantics are:	1543	repeating. The exact semantics are:
1196		1544
1197	If the timer is pending, its pending status is cleared.	1545	If the timer is pending, its pending status is cleared.
1198		1546
1199	If the timer is started but nonrepeating, stop it (as if it timed out).	1547	If the timer is started but non-repeating, stop it (as if it timed out).
1200		1548
1201	If the timer is repeating, either start it if necessary (with the	1549	If the timer is repeating, either start it if necessary (with the
1202	C<repeat> value), or reset the running timer to the C<repeat> value.	1550	C<repeat> value), or reset the running timer to the C<repeat> value.
1203		1551
1204	This sounds a bit complicated, but here is a useful and typical	1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1205	example: Imagine you have a tcp connection and you want a so-called idle	1553	usage example.
1206	timeout, that is, you want to be called when there have been, say, 60
1207	seconds of inactivity on the socket. The easiest way to do this is to
1208	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1209	C<ev_timer_again> each time you successfully read or write some data. If
1210	you go into an idle state where you do not expect data to travel on the
1211	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1212	automatically restart it if need be.
1213
1214	That means you can ignore the C<after> value and C<ev_timer_start>
1215	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1216
1217	ev_timer_init (timer, callback, 0., 5.);
1218	ev_timer_again (loop, timer);
1219	...
1220	timer->again = 17.;
1221	ev_timer_again (loop, timer);
1222	...
1223	timer->again = 10.;
1224	ev_timer_again (loop, timer);
1225
1226	This is more slightly efficient then stopping/starting the timer each time
1227	you want to modify its timeout value.
1228		1554
1229	=item ev_tstamp repeat [read-write]	1555	=item ev_tstamp repeat [read-write]
1230		1556
1231	The current C<repeat> value. Will be used each time the watcher times out	1557	The current C<repeat> value. Will be used each time the watcher times out
1232	or C<ev_timer_again> is called and determines the next timeout (if any),	1558	or C<ev_timer_again> is called, and determines the next timeout (if any),
1233	which is also when any modifications are taken into account.	1559	which is also when any modifications are taken into account.
1234		1560
1235	=back	1561	=back
1236		1562
1237	=head3 Examples	1563	=head3 Examples
1238		1564
1239	Example: Create a timer that fires after 60 seconds.	1565	Example: Create a timer that fires after 60 seconds.
1240		1566
1241	static void	1567	static void
1242	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1568	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1243	{	1569	{
1244	.. one minute over, w is actually stopped right here	1570	.. one minute over, w is actually stopped right here
1245	}	1571	}
1246		1572
1247	struct ev_timer mytimer;	1573	ev_timer mytimer;
1248	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1574	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1249	ev_timer_start (loop, &mytimer);	1575	ev_timer_start (loop, &mytimer);
1250		1576
1251	Example: Create a timeout timer that times out after 10 seconds of	1577	Example: Create a timeout timer that times out after 10 seconds of
1252	inactivity.	1578	inactivity.
1253		1579
1254	static void	1580	static void
1255	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1581	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1256	{	1582	{
1257	.. ten seconds without any activity	1583	.. ten seconds without any activity
1258	}	1584	}
1259		1585
1260	struct ev_timer mytimer;	1586	ev_timer mytimer;
1261	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1262	ev_timer_again (&mytimer); /* start timer */	1588	ev_timer_again (&mytimer); /* start timer */
1263	ev_loop (loop, 0);	1589	ev_loop (loop, 0);
1264		1590
1265	// and in some piece of code that gets executed on any "activity":	1591	// and in some piece of code that gets executed on any "activity":
1266	// reset the timeout to start ticking again at 10 seconds	1592	// reset the timeout to start ticking again at 10 seconds
1267	ev_timer_again (&mytimer);	1593	ev_timer_again (&mytimer);
1268		1594
1269		1595
1270	=head2 C<ev_periodic> - to cron or not to cron?	1596	=head2 C<ev_periodic> - to cron or not to cron?
1271		1597
1272	Periodic watchers are also timers of a kind, but they are very versatile	1598	Periodic watchers are also timers of a kind, but they are very versatile
1273	(and unfortunately a bit complex).	1599	(and unfortunately a bit complex).
1274		1600
1275	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1276	but on wallclock time (absolute time). You can tell a periodic watcher	1602	but on wall clock time (absolute time). You can tell a periodic watcher
1277	to trigger "at" some specific point in time. For example, if you tell a	1603	to trigger after some specific point in time. For example, if you tell a
1278	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1279	+ 10.>) and then reset your system clock to the last year, then it will	1605	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1606	clock to January of the previous year, then it will take more than year
1280	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1281	roughly 10 seconds later).	1608	roughly 10 seconds later as it uses a relative timeout).
1282		1609
1283	They can also be used to implement vastly more complex timers, such as	1610	C<ev_periodic>s can also be used to implement vastly more complex timers,
1284	triggering an event on each midnight, local time or other, complicated,	1611	such as triggering an event on each "midnight, local time", or other
1285	rules.	1612	complicated rules.
1286		1613
1287	As with timers, the callback is guarenteed to be invoked only when the	1614	As with timers, the callback is guaranteed to be invoked only when the
1288	time (C<at>) has been passed, but if multiple periodic timers become ready	1615	time (C<at>) has passed, but if multiple periodic timers become ready
1289	during the same loop iteration then order of execution is undefined.	1616	during the same loop iteration, then order of execution is undefined.
1290		1617
1291	=head3 Watcher-Specific Functions and Data Members	1618	=head3 Watcher-Specific Functions and Data Members
1292		1619
1293	=over 4	1620	=over 4
1294		1621
1295	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1296		1623
1297	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1298		1625
1299	Lots of arguments, lets sort it out... There are basically three modes of	1626	Lots of arguments, lets sort it out... There are basically three modes of
1300	operation, and we will explain them from simplest to complex:	1627	operation, and we will explain them from simplest to most complex:
1301		1628
1302	=over 4	1629	=over 4
1303		1630
1304	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1305		1632
1306	In this configuration the watcher triggers an event at the wallclock time	1633	In this configuration the watcher triggers an event after the wall clock
1307	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1634	time C<at> has passed. It will not repeat and will not adjust when a time
1308	that is, if it is to be run at January 1st 2011 then it will run when the	1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1309	system time reaches or surpasses this time.	1636	only run when the system clock reaches or surpasses this time.
1310		1637
1311	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1312		1639
1313	In this mode the watcher will always be scheduled to time out at the next	1640	In this mode the watcher will always be scheduled to time out at the next
1314	C<at + N * interval> time (for some integer N, which can also be negative)	1641	C<at + N * interval> time (for some integer N, which can also be negative)
1315	and then repeat, regardless of any time jumps.	1642	and then repeat, regardless of any time jumps.
1316		1643
1317	This can be used to create timers that do not drift with respect to system	1644	This can be used to create timers that do not drift with respect to the
1318	time:	1645	system clock, for example, here is a C<ev_periodic> that triggers each
		1646	hour, on the hour:
1319		1647
1320	ev_periodic_set (&periodic, 0., 3600., 0);	1648	ev_periodic_set (&periodic, 0., 3600., 0);
1321		1649
1322	This doesn't mean there will always be 3600 seconds in between triggers,	1650	This doesn't mean there will always be 3600 seconds in between triggers,
1323	but only that the the callback will be called when the system time shows a	1651	but only that the callback will be called when the system time shows a
1324	full hour (UTC), or more correctly, when the system time is evenly divisible	1652	full hour (UTC), or more correctly, when the system time is evenly divisible
1325	by 3600.	1653	by 3600.
1326		1654
1327	Another way to think about it (for the mathematically inclined) is that	1655	Another way to think about it (for the mathematically inclined) is that
1328	C<ev_periodic> will try to run the callback in this mode at the next possible	1656	C<ev_periodic> will try to run the callback in this mode at the next possible
1329	time where C<time = at (mod interval)>, regardless of any time jumps.	1657	time where C<time = at (mod interval)>, regardless of any time jumps.
1330		1658
1331	For numerical stability it is preferable that the C<at> value is near	1659	For numerical stability it is preferable that the C<at> value is near
1332	C<ev_now ()> (the current time), but there is no range requirement for	1660	C<ev_now ()> (the current time), but there is no range requirement for
1333	this value.	1661	this value, and in fact is often specified as zero.
		1662
		1663	Note also that there is an upper limit to how often a timer can fire (CPU
		1664	speed for example), so if C<interval> is very small then timing stability
		1665	will of course deteriorate. Libev itself tries to be exact to be about one
		1666	millisecond (if the OS supports it and the machine is fast enough).
1334		1667
1335	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1336		1669
1337	In this mode the values for C<interval> and C<at> are both being	1670	In this mode the values for C<interval> and C<at> are both being
1338	ignored. Instead, each time the periodic watcher gets scheduled, the	1671	ignored. Instead, each time the periodic watcher gets scheduled, the
1339	reschedule callback will be called with the watcher as first, and the	1672	reschedule callback will be called with the watcher as first, and the
1340	current time as second argument.	1673	current time as second argument.
1341		1674
1342	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1343	ever, or make any event loop modifications>. If you need to stop it,	1676	ever, or make ANY event loop modifications whatsoever>.
1344	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1345	starting an C<ev_prepare> watcher, which is legal).
1346		1677
		1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1680	only event loop modification you are allowed to do).
		1681
1347	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1682	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1348	ev_tstamp now)>, e.g.:	1683	*w, ev_tstamp now)>, e.g.:
1349		1684
		1685	static ev_tstamp
1350	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1686	my_rescheduler (ev_periodic *w, ev_tstamp now)
1351	{	1687	{
1352	return now + 60.;	1688	return now + 60.;
1353	}	1689	}
1354		1690
1355	It must return the next time to trigger, based on the passed time value	1691	It must return the next time to trigger, based on the passed time value
1356	(that is, the lowest time value larger than to the second argument). It	1692	(that is, the lowest time value larger than to the second argument). It
1357	will usually be called just before the callback will be triggered, but	1693	will usually be called just before the callback will be triggered, but
1358	might be called at other times, too.	1694	might be called at other times, too.
1359		1695
1360	NOTE: I<< This callback must always return a time that is later than the	1696	NOTE: I<< This callback must always return a time that is higher than or
1361	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1697	equal to the passed C<now> value >>.
1362		1698
1363	This can be used to create very complex timers, such as a timer that	1699	This can be used to create very complex timers, such as a timer that
1364	triggers on each midnight, local time. To do this, you would calculate the	1700	triggers on "next midnight, local time". To do this, you would calculate the
1365	next midnight after C<now> and return the timestamp value for this. How	1701	next midnight after C<now> and return the timestamp value for this. How
1366	you do this is, again, up to you (but it is not trivial, which is the main	1702	you do this is, again, up to you (but it is not trivial, which is the main
1367	reason I omitted it as an example).	1703	reason I omitted it as an example).
1368		1704
1369	=back	1705	=back
…		…
1373	Simply stops and restarts the periodic watcher again. This is only useful	1709	Simply stops and restarts the periodic watcher again. This is only useful
1374	when you changed some parameters or the reschedule callback would return	1710	when you changed some parameters or the reschedule callback would return
1375	a different time than the last time it was called (e.g. in a crond like	1711	a different time than the last time it was called (e.g. in a crond like
1376	program when the crontabs have changed).	1712	program when the crontabs have changed).
1377		1713
		1714	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1715
		1716	When active, returns the absolute time that the watcher is supposed to
		1717	trigger next.
		1718
1378	=item ev_tstamp offset [read-write]	1719	=item ev_tstamp offset [read-write]
1379		1720
1380	When repeating, this contains the offset value, otherwise this is the	1721	When repeating, this contains the offset value, otherwise this is the
1381	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1382		1723
…		…
1387		1728
1388	The current interval value. Can be modified any time, but changes only	1729	The current interval value. Can be modified any time, but changes only
1389	take effect when the periodic timer fires or C<ev_periodic_again> is being	1730	take effect when the periodic timer fires or C<ev_periodic_again> is being
1390	called.	1731	called.
1391		1732
1392	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1733	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1393		1734
1394	The current reschedule callback, or C<0>, if this functionality is	1735	The current reschedule callback, or C<0>, if this functionality is
1395	switched off. Can be changed any time, but changes only take effect when	1736	switched off. Can be changed any time, but changes only take effect when
1396	the periodic timer fires or C<ev_periodic_again> is being called.	1737	the periodic timer fires or C<ev_periodic_again> is being called.
1397		1738
1398	=item ev_tstamp at [read-only]
1399
1400	When active, contains the absolute time that the watcher is supposed to
1401	trigger next.
1402
1403	=back	1739	=back
1404		1740
1405	=head3 Examples	1741	=head3 Examples
1406		1742
1407	Example: Call a callback every hour, or, more precisely, whenever the	1743	Example: Call a callback every hour, or, more precisely, whenever the
1408	system clock is divisible by 3600. The callback invocation times have	1744	system time is divisible by 3600. The callback invocation times have
1409	potentially a lot of jittering, but good long-term stability.	1745	potentially a lot of jitter, but good long-term stability.
1410		1746
1411	static void	1747	static void
1412	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1413	{	1749	{
1414	... its now a full hour (UTC, or TAI or whatever your clock follows)	1750	... its now a full hour (UTC, or TAI or whatever your clock follows)
1415	}	1751	}
1416		1752
1417	struct ev_periodic hourly_tick;	1753	ev_periodic hourly_tick;
1418	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1754	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1419	ev_periodic_start (loop, &hourly_tick);	1755	ev_periodic_start (loop, &hourly_tick);
1420		1756
1421	Example: The same as above, but use a reschedule callback to do it:	1757	Example: The same as above, but use a reschedule callback to do it:
1422		1758
1423	#include <math.h>	1759	#include <math.h>
1424		1760
1425	static ev_tstamp	1761	static ev_tstamp
1426	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1762	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1427	{	1763	{
1428	return fmod (now, 3600.) + 3600.;	1764	return now + (3600. - fmod (now, 3600.));
1429	}	1765	}
1430		1766
1431	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1767	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1432		1768
1433	Example: Call a callback every hour, starting now:	1769	Example: Call a callback every hour, starting now:
1434		1770
1435	struct ev_periodic hourly_tick;	1771	ev_periodic hourly_tick;
1436	ev_periodic_init (&hourly_tick, clock_cb,	1772	ev_periodic_init (&hourly_tick, clock_cb,
1437	fmod (ev_now (loop), 3600.), 3600., 0);	1773	fmod (ev_now (loop), 3600.), 3600., 0);
1438	ev_periodic_start (loop, &hourly_tick);	1774	ev_periodic_start (loop, &hourly_tick);
1439		1775
1440		1776
1441	=head2 C<ev_signal> - signal me when a signal gets signalled!	1777	=head2 C<ev_signal> - signal me when a signal gets signalled!
1442		1778
1443	Signal watchers will trigger an event when the process receives a specific	1779	Signal watchers will trigger an event when the process receives a specific
1444	signal one or more times. Even though signals are very asynchronous, libev	1780	signal one or more times. Even though signals are very asynchronous, libev
1445	will try it's best to deliver signals synchronously, i.e. as part of the	1781	will try it's best to deliver signals synchronously, i.e. as part of the
1446	normal event processing, like any other event.	1782	normal event processing, like any other event.
1447		1783
		1784	If you want signals asynchronously, just use C<sigaction> as you would
		1785	do without libev and forget about sharing the signal. You can even use
		1786	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1787
1448	You can configure as many watchers as you like per signal. Only when the	1788	You can configure as many watchers as you like per signal. Only when the
1449	first watcher gets started will libev actually register a signal watcher	1789	first watcher gets started will libev actually register a signal handler
1450	with the kernel (thus it coexists with your own signal handlers as long	1790	with the kernel (thus it coexists with your own signal handlers as long as
1451	as you don't register any with libev). Similarly, when the last signal	1791	you don't register any with libev for the same signal). Similarly, when
1452	watcher for a signal is stopped libev will reset the signal handler to	1792	the last signal watcher for a signal is stopped, libev will reset the
1453	SIG_DFL (regardless of what it was set to before).	1793	signal handler to SIG_DFL (regardless of what it was set to before).
1454		1794
1455	If possible and supported, libev will install its handlers with	1795	If possible and supported, libev will install its handlers with
1456	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1457	interrupted. If you have a problem with syscalls getting interrupted by	1797	interrupted. If you have a problem with system calls getting interrupted by
1458	signals you can block all signals in an C<ev_check> watcher and unblock	1798	signals you can block all signals in an C<ev_check> watcher and unblock
1459	them in an C<ev_prepare> watcher.	1799	them in an C<ev_prepare> watcher.
1460		1800
1461	=head3 Watcher-Specific Functions and Data Members	1801	=head3 Watcher-Specific Functions and Data Members
1462		1802
…		…
1475		1815
1476	=back	1816	=back
1477		1817
1478	=head3 Examples	1818	=head3 Examples
1479		1819
1480	Example: Try to exit cleanly on SIGINT and SIGTERM.	1820	Example: Try to exit cleanly on SIGINT.
1481		1821
1482	static void	1822	static void
1483	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1484	{	1824	{
1485	ev_unloop (loop, EVUNLOOP_ALL);	1825	ev_unloop (loop, EVUNLOOP_ALL);
1486	}	1826	}
1487		1827
1488	struct ev_signal signal_watcher;	1828	ev_signal signal_watcher;
1489	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1490	ev_signal_start (loop, &sigint_cb);	1830	ev_signal_start (loop, &signal_watcher);
1491		1831
1492		1832
1493	=head2 C<ev_child> - watch out for process status changes	1833	=head2 C<ev_child> - watch out for process status changes
1494		1834
1495	Child watchers trigger when your process receives a SIGCHLD in response to	1835	Child watchers trigger when your process receives a SIGCHLD in response to
1496	some child status changes (most typically when a child of yours dies). It	1836	some child status changes (most typically when a child of yours dies or
1497	is permissible to install a child watcher I<after> the child has been	1837	exits). It is permissible to install a child watcher I<after> the child
1498	forked (which implies it might have already exited), as long as the event	1838	has been forked (which implies it might have already exited), as long
1499	loop isn't entered (or is continued from a watcher).	1839	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1840	forking and then immediately registering a watcher for the child is fine,
		1841	but forking and registering a watcher a few event loop iterations later is
		1842	not.
1500		1843
1501	Only the default event loop is capable of handling signals, and therefore	1844	Only the default event loop is capable of handling signals, and therefore
1502	you can only rgeister child watchers in the default event loop.	1845	you can only register child watchers in the default event loop.
1503		1846
1504	=head3 Process Interaction	1847	=head3 Process Interaction
1505		1848
1506	Libev grabs C<SIGCHLD> as soon as the default event loop is	1849	Libev grabs C<SIGCHLD> as soon as the default event loop is
1507	initialised. This is necessary to guarantee proper behaviour even if	1850	initialised. This is necessary to guarantee proper behaviour even if
1508	the first child watcher is started after the child exits. The occurance	1851	the first child watcher is started after the child exits. The occurrence
1509	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1510	synchronously as part of the event loop processing. Libev always reaps all	1853	synchronously as part of the event loop processing. Libev always reaps all
1511	children, even ones not watched.	1854	children, even ones not watched.
1512		1855
1513	=head3 Overriding the Built-In Processing	1856	=head3 Overriding the Built-In Processing
…		…
1517	handler, you can override it easily by installing your own handler for	1860	handler, you can override it easily by installing your own handler for
1518	C<SIGCHLD> after initialising the default loop, and making sure the	1861	C<SIGCHLD> after initialising the default loop, and making sure the
1519	default loop never gets destroyed. You are encouraged, however, to use an	1862	default loop never gets destroyed. You are encouraged, however, to use an
1520	event-based approach to child reaping and thus use libev's support for	1863	event-based approach to child reaping and thus use libev's support for
1521	that, so other libev users can use C<ev_child> watchers freely.	1864	that, so other libev users can use C<ev_child> watchers freely.
		1865
		1866	=head3 Stopping the Child Watcher
		1867
		1868	Currently, the child watcher never gets stopped, even when the
		1869	child terminates, so normally one needs to stop the watcher in the
		1870	callback. Future versions of libev might stop the watcher automatically
		1871	when a child exit is detected.
1522		1872
1523	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1524		1874
1525	=over 4	1875	=over 4
1526		1876
…		…
1555	=head3 Examples	1905	=head3 Examples
1556		1906
1557	Example: C<fork()> a new process and install a child handler to wait for	1907	Example: C<fork()> a new process and install a child handler to wait for
1558	its completion.	1908	its completion.
1559		1909
1560	ev_child cw;	1910	ev_child cw;
1561		1911
1562	static void	1912	static void
1563	child_cb (EV_P_ struct ev_child *w, int revents)	1913	child_cb (EV_P_ ev_child *w, int revents)
1564	{	1914	{
1565	ev_child_stop (EV_A_ w);	1915	ev_child_stop (EV_A_ w);
1566	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1916	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1567	}	1917	}
1568		1918
1569	pid_t pid = fork ();	1919	pid_t pid = fork ();
1570		1920
1571	if (pid < 0)	1921	if (pid < 0)
1572	// error	1922	// error
1573	else if (pid == 0)	1923	else if (pid == 0)
1574	{	1924	{
1575	// the forked child executes here	1925	// the forked child executes here
1576	exit (1);	1926	exit (1);
1577	}	1927	}
1578	else	1928	else
1579	{	1929	{
1580	ev_child_init (&cw, child_cb, pid, 0);	1930	ev_child_init (&cw, child_cb, pid, 0);
1581	ev_child_start (EV_DEFAULT_ &cw);	1931	ev_child_start (EV_DEFAULT_ &cw);
1582	}	1932	}
1583		1933
1584		1934
1585	=head2 C<ev_stat> - did the file attributes just change?	1935	=head2 C<ev_stat> - did the file attributes just change?
1586		1936
1587	This watches a filesystem path for attribute changes. That is, it calls	1937	This watches a file system path for attribute changes. That is, it calls
1588	C<stat> regularly (or when the OS says it changed) and sees if it changed	1938	C<stat> on that path in regular intervals (or when the OS says it changed)
1589	compared to the last time, invoking the callback if it did.	1939	and sees if it changed compared to the last time, invoking the callback if
		1940	it did.
1590		1941
1591	The path does not need to exist: changing from "path exists" to "path does	1942	The path does not need to exist: changing from "path exists" to "path does
1592	not exist" is a status change like any other. The condition "path does	1943	not exist" is a status change like any other. The condition "path does not
1593	not exist" is signified by the C<st_nlink> field being zero (which is	1944	exist" (or more correctly "path cannot be stat'ed") is signified by the
1594	otherwise always forced to be at least one) and all the other fields of	1945	C<st_nlink> field being zero (which is otherwise always forced to be at
1595	the stat buffer having unspecified contents.	1946	least one) and all the other fields of the stat buffer having unspecified
		1947	contents.
1596		1948
1597	The path I<should> be absolute and I<must not> end in a slash. If it is	1949	The path I<must not> end in a slash or contain special components such as
		1950	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1598	relative and your working directory changes, the behaviour is undefined.	1951	your working directory changes, then the behaviour is undefined.
1599		1952
1600	Since there is no standard to do this, the portable implementation simply	1953	Since there is no portable change notification interface available, the
1601	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1954	portable implementation simply calls C<stat(2)> regularly on the path
1602	can specify a recommended polling interval for this case. If you specify	1955	to see if it changed somehow. You can specify a recommended polling
1603	a polling interval of C<0> (highly recommended!) then a I<suitable,	1956	interval for this case. If you specify a polling interval of C<0> (highly
1604	unspecified default> value will be used (which you can expect to be around	1957	recommended!) then a I<suitable, unspecified default> value will be used
1605	five seconds, although this might change dynamically). Libev will also	1958	(which you can expect to be around five seconds, although this might
1606	impose a minimum interval which is currently around C<0.1>, but thats	1959	change dynamically). Libev will also impose a minimum interval which is
1607	usually overkill.	1960	currently around C<0.1>, but that's usually overkill.
1608		1961
1609	This watcher type is not meant for massive numbers of stat watchers,	1962	This watcher type is not meant for massive numbers of stat watchers,
1610	as even with OS-supported change notifications, this can be	1963	as even with OS-supported change notifications, this can be
1611	resource-intensive.	1964	resource-intensive.
1612		1965
1613	At the time of this writing, only the Linux inotify interface is	1966	At the time of this writing, the only OS-specific interface implemented
1614	implemented (implementing kqueue support is left as an exercise for the	1967	is the Linux inotify interface (implementing kqueue support is left as an
1615	reader). Inotify will be used to give hints only and should not change the	1968	exercise for the reader. Note, however, that the author sees no way of
1616	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1969	implementing C<ev_stat> semantics with kqueue, except as a hint).
1617	to fall back to regular polling again even with inotify, but changes are
1618	usually detected immediately, and if the file exists there will be no
1619	polling.
1620		1970
1621	=head3 ABI Issues (Largefile Support)	1971	=head3 ABI Issues (Largefile Support)
1622		1972
1623	Libev by default (unless the user overrides this) uses the default	1973	Libev by default (unless the user overrides this) uses the default
1624	compilation environment, which means that on systems with optionally	1974	compilation environment, which means that on systems with large file
1625	disabled large file support, you get the 32 bit version of the stat	1975	support disabled by default, you get the 32 bit version of the stat
1626	structure. When using the library from programs that change the ABI to	1976	structure. When using the library from programs that change the ABI to
1627	use 64 bit file offsets the programs will fail. In that case you have to	1977	use 64 bit file offsets the programs will fail. In that case you have to
1628	compile libev with the same flags to get binary compatibility. This is	1978	compile libev with the same flags to get binary compatibility. This is
1629	obviously the case with any flags that change the ABI, but the problem is	1979	obviously the case with any flags that change the ABI, but the problem is
1630	most noticably with ev_stat and largefile support.	1980	most noticeably displayed with ev_stat and large file support.
1631		1981
1632	=head3 Inotify	1982	The solution for this is to lobby your distribution maker to make large
		1983	file interfaces available by default (as e.g. FreeBSD does) and not
		1984	optional. Libev cannot simply switch on large file support because it has
		1985	to exchange stat structures with application programs compiled using the
		1986	default compilation environment.
1633		1987
		1988	=head3 Inotify and Kqueue
		1989
1634	When C<inotify (7)> support has been compiled into libev (generally only	1990	When C<inotify (7)> support has been compiled into libev and present at
1635	available on Linux) and present at runtime, it will be used to speed up	1991	runtime, it will be used to speed up change detection where possible. The
1636	change detection where possible. The inotify descriptor will be created lazily	1992	inotify descriptor will be created lazily when the first C<ev_stat>
1637	when the first C<ev_stat> watcher is being started.	1993	watcher is being started.
1638		1994
1639	Inotify presence does not change the semantics of C<ev_stat> watchers	1995	Inotify presence does not change the semantics of C<ev_stat> watchers
1640	except that changes might be detected earlier, and in some cases, to avoid	1996	except that changes might be detected earlier, and in some cases, to avoid
1641	making regular C<stat> calls. Even in the presence of inotify support	1997	making regular C<stat> calls. Even in the presence of inotify support
1642	there are many cases where libev has to resort to regular C<stat> polling.	1998	there are many cases where libev has to resort to regular C<stat> polling,
		1999	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2000	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2001	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2002	xfs are fully working) libev usually gets away without polling.
1643		2003
1644	(There is no support for kqueue, as apparently it cannot be used to	2004	There is no support for kqueue, as apparently it cannot be used to
1645	implement this functionality, due to the requirement of having a file	2005	implement this functionality, due to the requirement of having a file
1646	descriptor open on the object at all times).	2006	descriptor open on the object at all times, and detecting renames, unlinks
		2007	etc. is difficult.
		2008
		2009	=head3 C<stat ()> is a synchronous operation
		2010
		2011	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2012	the process. The exception are C<ev_stat> watchers - those call C<stat
		2013	()>, which is a synchronous operation.
		2014
		2015	For local paths, this usually doesn't matter: unless the system is very
		2016	busy or the intervals between stat's are large, a stat call will be fast,
		2017	as the path data is usually in memory already (except when starting the
		2018	watcher).
		2019
		2020	For networked file systems, calling C<stat ()> can block an indefinite
		2021	time due to network issues, and even under good conditions, a stat call
		2022	often takes multiple milliseconds.
		2023
		2024	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2025	paths, although this is fully supported by libev.
1647		2026
1648	=head3 The special problem of stat time resolution	2027	=head3 The special problem of stat time resolution
1649		2028
1650	The C<stat ()> syscall only supports full-second resolution portably, and	2029	The C<stat ()> system call only supports full-second resolution portably,
1651	even on systems where the resolution is higher, many filesystems still	2030	and even on systems where the resolution is higher, most file systems
1652	only support whole seconds.	2031	still only support whole seconds.
1653		2032
1654	That means that, if the time is the only thing that changes, you might	2033	That means that, if the time is the only thing that changes, you can
1655	miss updates: on the first update, C<ev_stat> detects a change and calls	2034	easily miss updates: on the first update, C<ev_stat> detects a change and
1656	your callback, which does something. When there is another update within	2035	calls your callback, which does something. When there is another update
1657	the same second, C<ev_stat> will be unable to detect it.	2036	within the same second, C<ev_stat> will be unable to detect unless the
		2037	stat data does change in other ways (e.g. file size).
1658		2038
1659	The solution to this is to delay acting on a change for a second (or till	2039	The solution to this is to delay acting on a change for slightly more
1660	the next second boundary), using a roughly one-second delay C<ev_timer>	2040	than a second (or till slightly after the next full second boundary), using
1661	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2041	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1662	is added to work around small timing inconsistencies of some operating	2042	ev_timer_again (loop, w)>).
1663	systems.	2043
		2044	The C<.02> offset is added to work around small timing inconsistencies
		2045	of some operating systems (where the second counter of the current time
		2046	might be be delayed. One such system is the Linux kernel, where a call to
		2047	C<gettimeofday> might return a timestamp with a full second later than
		2048	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2049	update file times then there will be a small window where the kernel uses
		2050	the previous second to update file times but libev might already execute
		2051	the timer callback).
1664		2052
1665	=head3 Watcher-Specific Functions and Data Members	2053	=head3 Watcher-Specific Functions and Data Members
1666		2054
1667	=over 4	2055	=over 4
1668		2056
…		…
1674	C<path>. The C<interval> is a hint on how quickly a change is expected to	2062	C<path>. The C<interval> is a hint on how quickly a change is expected to
1675	be detected and should normally be specified as C<0> to let libev choose	2063	be detected and should normally be specified as C<0> to let libev choose
1676	a suitable value. The memory pointed to by C<path> must point to the same	2064	a suitable value. The memory pointed to by C<path> must point to the same
1677	path for as long as the watcher is active.	2065	path for as long as the watcher is active.
1678		2066
1679	The callback will be receive C<EV_STAT> when a change was detected,	2067	The callback will receive an C<EV_STAT> event when a change was detected,
1680	relative to the attributes at the time the watcher was started (or the	2068	relative to the attributes at the time the watcher was started (or the
1681	last change was detected).	2069	last change was detected).
1682		2070
1683	=item ev_stat_stat (loop, ev_stat *)	2071	=item ev_stat_stat (loop, ev_stat *)
1684		2072
1685	Updates the stat buffer immediately with new values. If you change the	2073	Updates the stat buffer immediately with new values. If you change the
1686	watched path in your callback, you could call this fucntion to avoid	2074	watched path in your callback, you could call this function to avoid
1687	detecting this change (while introducing a race condition). Can also be	2075	detecting this change (while introducing a race condition if you are not
1688	useful simply to find out the new values.	2076	the only one changing the path). Can also be useful simply to find out the
		2077	new values.
1689		2078
1690	=item ev_statdata attr [read-only]	2079	=item ev_statdata attr [read-only]
1691		2080
1692	The most-recently detected attributes of the file. Although the type is of	2081	The most-recently detected attributes of the file. Although the type is
1693	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2082	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1694	suitable for your system. If the C<st_nlink> member is C<0>, then there	2083	suitable for your system, but you can only rely on the POSIX-standardised
		2084	members to be present. If the C<st_nlink> member is C<0>, then there was
1695	was some error while C<stat>ing the file.	2085	some error while C<stat>ing the file.
1696		2086
1697	=item ev_statdata prev [read-only]	2087	=item ev_statdata prev [read-only]
1698		2088
1699	The previous attributes of the file. The callback gets invoked whenever	2089	The previous attributes of the file. The callback gets invoked whenever
1700	C<prev> != C<attr>.	2090	C<prev> != C<attr>, or, more precisely, one or more of these members
		2091	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2092	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1701		2093
1702	=item ev_tstamp interval [read-only]	2094	=item ev_tstamp interval [read-only]
1703		2095
1704	The specified interval.	2096	The specified interval.
1705		2097
1706	=item const char *path [read-only]	2098	=item const char *path [read-only]
1707		2099
1708	The filesystem path that is being watched.	2100	The file system path that is being watched.
1709		2101
1710	=back	2102	=back
1711		2103
1712	=head3 Examples	2104	=head3 Examples
1713		2105
1714	Example: Watch C</etc/passwd> for attribute changes.	2106	Example: Watch C</etc/passwd> for attribute changes.
1715		2107
1716	static void	2108	static void
1717	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2109	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1718	{	2110	{
1719	/* /etc/passwd changed in some way */	2111	/* /etc/passwd changed in some way */
1720	if (w->attr.st_nlink)	2112	if (w->attr.st_nlink)
1721	{	2113	{
1722	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2114	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1723	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2115	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1724	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2116	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1725	}	2117	}
1726	else	2118	else
1727	/* you shalt not abuse printf for puts */	2119	/* you shalt not abuse printf for puts */
1728	puts ("wow, /etc/passwd is not there, expect problems. "	2120	puts ("wow, /etc/passwd is not there, expect problems. "
1729	"if this is windows, they already arrived\n");	2121	"if this is windows, they already arrived\n");
1730	}	2122	}
1731		2123
1732	...	2124	...
1733	ev_stat passwd;	2125	ev_stat passwd;
1734		2126
1735	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2127	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	2128	ev_stat_start (loop, &passwd);
1737		2129
1738	Example: Like above, but additionally use a one-second delay so we do not	2130	Example: Like above, but additionally use a one-second delay so we do not
1739	miss updates (however, frequent updates will delay processing, too, so	2131	miss updates (however, frequent updates will delay processing, too, so
1740	one might do the work both on C<ev_stat> callback invocation I<and> on	2132	one might do the work both on C<ev_stat> callback invocation I<and> on
1741	C<ev_timer> callback invocation).	2133	C<ev_timer> callback invocation).
1742		2134
1743	static ev_stat passwd;	2135	static ev_stat passwd;
1744	static ev_timer timer;	2136	static ev_timer timer;
1745		2137
1746	static void	2138	static void
1747	timer_cb (EV_P_ ev_timer *w, int revents)	2139	timer_cb (EV_P_ ev_timer *w, int revents)
1748	{	2140	{
1749	ev_timer_stop (EV_A_ w);	2141	ev_timer_stop (EV_A_ w);
1750		2142
1751	/* now it's one second after the most recent passwd change */	2143	/* now it's one second after the most recent passwd change */
1752	}	2144	}
1753		2145
1754	static void	2146	static void
1755	stat_cb (EV_P_ ev_stat *w, int revents)	2147	stat_cb (EV_P_ ev_stat *w, int revents)
1756	{	2148	{
1757	/* reset the one-second timer */	2149	/* reset the one-second timer */
1758	ev_timer_again (EV_A_ &timer);	2150	ev_timer_again (EV_A_ &timer);
1759	}	2151	}
1760		2152
1761	...	2153	...
1762	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2154	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1763	ev_stat_start (loop, &passwd);	2155	ev_stat_start (loop, &passwd);
1764	ev_timer_init (&timer, timer_cb, 0., 1.01);	2156	ev_timer_init (&timer, timer_cb, 0., 1.02);
1765		2157
1766		2158
1767	=head2 C<ev_idle> - when you've got nothing better to do...	2159	=head2 C<ev_idle> - when you've got nothing better to do...
1768		2160
1769	Idle watchers trigger events when no other events of the same or higher	2161	Idle watchers trigger events when no other events of the same or higher
1770	priority are pending (prepare, check and other idle watchers do not	2162	priority are pending (prepare, check and other idle watchers do not count
1771	count).	2163	as receiving "events").
1772		2164
1773	That is, as long as your process is busy handling sockets or timeouts	2165	That is, as long as your process is busy handling sockets or timeouts
1774	(or even signals, imagine) of the same or higher priority it will not be	2166	(or even signals, imagine) of the same or higher priority it will not be
1775	triggered. But when your process is idle (or only lower-priority watchers	2167	triggered. But when your process is idle (or only lower-priority watchers
1776	are pending), the idle watchers are being called once per event loop	2168	are pending), the idle watchers are being called once per event loop
…		…
1800	=head3 Examples	2192	=head3 Examples
1801		2193
1802	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2194	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1803	callback, free it. Also, use no error checking, as usual.	2195	callback, free it. Also, use no error checking, as usual.
1804		2196
1805	static void	2197	static void
1806	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1807	{	2199	{
1808	free (w);	2200	free (w);
1809	// now do something you wanted to do when the program has	2201	// now do something you wanted to do when the program has
1810	// no longer anything immediate to do.	2202	// no longer anything immediate to do.
1811	}	2203	}
1812		2204
1813	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1814	ev_idle_init (idle_watcher, idle_cb);	2206	ev_idle_init (idle_watcher, idle_cb);
1815	ev_idle_start (loop, idle_cb);	2207	ev_idle_start (loop, idle_cb);
1816		2208
1817		2209
1818	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1819		2211
1820	Prepare and check watchers are usually (but not always) used in tandem:	2212	Prepare and check watchers are usually (but not always) used in pairs:
1821	prepare watchers get invoked before the process blocks and check watchers	2213	prepare watchers get invoked before the process blocks and check watchers
1822	afterwards.	2214	afterwards.
1823		2215
1824	You I<must not> call C<ev_loop> or similar functions that enter	2216	You I<must not> call C<ev_loop> or similar functions that enter
1825	the current event loop from either C<ev_prepare> or C<ev_check>	2217	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1828	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1829	C<ev_check> so if you have one watcher of each kind they will always be	2221	C<ev_check> so if you have one watcher of each kind they will always be
1830	called in pairs bracketing the blocking call.	2222	called in pairs bracketing the blocking call.
1831		2223
1832	Their main purpose is to integrate other event mechanisms into libev and	2224	Their main purpose is to integrate other event mechanisms into libev and
1833	their use is somewhat advanced. This could be used, for example, to track	2225	their use is somewhat advanced. They could be used, for example, to track
1834	variable changes, implement your own watchers, integrate net-snmp or a	2226	variable changes, implement your own watchers, integrate net-snmp or a
1835	coroutine library and lots more. They are also occasionally useful if	2227	coroutine library and lots more. They are also occasionally useful if
1836	you cache some data and want to flush it before blocking (for example,	2228	you cache some data and want to flush it before blocking (for example,
1837	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2229	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1838	watcher).	2230	watcher).
1839		2231
1840	This is done by examining in each prepare call which file descriptors need	2232	This is done by examining in each prepare call which file descriptors
1841	to be watched by the other library, registering C<ev_io> watchers for	2233	need to be watched by the other library, registering C<ev_io> watchers
1842	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2234	for them and starting an C<ev_timer> watcher for any timeouts (many
1843	provide just this functionality). Then, in the check watcher you check for	2235	libraries provide exactly this functionality). Then, in the check watcher,
1844	any events that occured (by checking the pending status of all watchers	2236	you check for any events that occurred (by checking the pending status
1845	and stopping them) and call back into the library. The I/O and timer	2237	of all watchers and stopping them) and call back into the library. The
1846	callbacks will never actually be called (but must be valid nevertheless,	2238	I/O and timer callbacks will never actually be called (but must be valid
1847	because you never know, you know?).	2239	nevertheless, because you never know, you know?).
1848		2240
1849	As another example, the Perl Coro module uses these hooks to integrate	2241	As another example, the Perl Coro module uses these hooks to integrate
1850	coroutines into libev programs, by yielding to other active coroutines	2242	coroutines into libev programs, by yielding to other active coroutines
1851	during each prepare and only letting the process block if no coroutines	2243	during each prepare and only letting the process block if no coroutines
1852	are ready to run (it's actually more complicated: it only runs coroutines	2244	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1855	loop from blocking if lower-priority coroutines are active, thus mapping	2247	loop from blocking if lower-priority coroutines are active, thus mapping
1856	low-priority coroutines to idle/background tasks).	2248	low-priority coroutines to idle/background tasks).
1857		2249
1858	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1859	priority, to ensure that they are being run before any other watchers	2251	priority, to ensure that they are being run before any other watchers
		2252	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2253
1860	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1861	too) should not activate ("feed") events into libev. While libev fully	2255	activate ("feed") events into libev. While libev fully supports this, they
1862	supports this, they will be called before other C<ev_check> watchers	2256	might get executed before other C<ev_check> watchers did their job. As
1863	did their job. As C<ev_check> watchers are often used to embed other	2257	C<ev_check> watchers are often used to embed other (non-libev) event
1864	(non-libev) event loops those other event loops might be in an unusable	2258	loops those other event loops might be in an unusable state until their
1865	state until their C<ev_check> watcher ran (always remind yourself to	2259	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1866	coexist peacefully with others).	2260	others).
1867		2261
1868	=head3 Watcher-Specific Functions and Data Members	2262	=head3 Watcher-Specific Functions and Data Members
1869		2263
1870	=over 4	2264	=over 4
1871		2265
…		…
1873		2267
1874	=item ev_check_init (ev_check *, callback)	2268	=item ev_check_init (ev_check *, callback)
1875		2269
1876	Initialises and configures the prepare or check watcher - they have no	2270	Initialises and configures the prepare or check watcher - they have no
1877	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2271	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1878	macros, but using them is utterly, utterly and completely pointless.	2272	macros, but using them is utterly, utterly, utterly and completely
		2273	pointless.
1879		2274
1880	=back	2275	=back
1881		2276
1882	=head3 Examples	2277	=head3 Examples
1883		2278
1884	There are a number of principal ways to embed other event loops or modules	2279	There are a number of principal ways to embed other event loops or modules
1885	into libev. Here are some ideas on how to include libadns into libev	2280	into libev. Here are some ideas on how to include libadns into libev
1886	(there is a Perl module named C<EV::ADNS> that does this, which you could	2281	(there is a Perl module named C<EV::ADNS> that does this, which you could
1887	use for an actually working example. Another Perl module named C<EV::Glib>	2282	use as a working example. Another Perl module named C<EV::Glib> embeds a
1888	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2283	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1889	into the Glib event loop).	2284	Glib event loop).
1890		2285
1891	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2286	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1892	and in a check watcher, destroy them and call into libadns. What follows	2287	and in a check watcher, destroy them and call into libadns. What follows
1893	is pseudo-code only of course. This requires you to either use a low	2288	is pseudo-code only of course. This requires you to either use a low
1894	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2289	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1895	the callbacks for the IO/timeout watchers might not have been called yet.	2290	the callbacks for the IO/timeout watchers might not have been called yet.
1896		2291
1897	static ev_io iow [nfd];	2292	static ev_io iow [nfd];
1898	static ev_timer tw;	2293	static ev_timer tw;
1899		2294
1900	static void	2295	static void
1901	io_cb (ev_loop *loop, ev_io *w, int revents)	2296	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1902	{	2297	{
1903	}	2298	}
1904		2299
1905	// create io watchers for each fd and a timer before blocking	2300	// create io watchers for each fd and a timer before blocking
1906	static void	2301	static void
1907	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2302	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1908	{	2303	{
1909	int timeout = 3600000;	2304	int timeout = 3600000;
1910	struct pollfd fds [nfd];	2305	struct pollfd fds [nfd];
1911	// actual code will need to loop here and realloc etc.	2306	// actual code will need to loop here and realloc etc.
1912	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1913		2308
1914	/* the callback is illegal, but won't be called as we stop during check */	2309	/* the callback is illegal, but won't be called as we stop during check */
1915	ev_timer_init (&tw, 0, timeout * 1e-3);	2310	ev_timer_init (&tw, 0, timeout * 1e-3);
1916	ev_timer_start (loop, &tw);	2311	ev_timer_start (loop, &tw);
1917		2312
1918	// create one ev_io per pollfd	2313	// create one ev_io per pollfd
1919	for (int i = 0; i < nfd; ++i)	2314	for (int i = 0; i < nfd; ++i)
1920	{	2315	{
1921	ev_io_init (iow + i, io_cb, fds [i].fd,	2316	ev_io_init (iow + i, io_cb, fds [i].fd,
1922	((fds [i].events & POLLIN ? EV_READ : 0)	2317	((fds [i].events & POLLIN ? EV_READ : 0)
1923	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2318	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1924		2319
1925	fds [i].revents = 0;	2320	fds [i].revents = 0;
1926	ev_io_start (loop, iow + i);	2321	ev_io_start (loop, iow + i);
1927	}	2322	}
1928	}	2323	}
1929		2324
1930	// stop all watchers after blocking	2325	// stop all watchers after blocking
1931	static void	2326	static void
1932	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2327	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1933	{	2328	{
1934	ev_timer_stop (loop, &tw);	2329	ev_timer_stop (loop, &tw);
1935		2330
1936	for (int i = 0; i < nfd; ++i)	2331	for (int i = 0; i < nfd; ++i)
1937	{	2332	{
1938	// set the relevant poll flags	2333	// set the relevant poll flags
1939	// could also call adns_processreadable etc. here	2334	// could also call adns_processreadable etc. here
1940	struct pollfd *fd = fds + i;	2335	struct pollfd *fd = fds + i;
1941	int revents = ev_clear_pending (iow + i);	2336	int revents = ev_clear_pending (iow + i);
1942	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2337	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1943	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2338	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1944		2339
1945	// now stop the watcher	2340	// now stop the watcher
1946	ev_io_stop (loop, iow + i);	2341	ev_io_stop (loop, iow + i);
1947	}	2342	}
1948		2343
1949	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2344	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1950	}	2345	}
1951		2346
1952	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2347	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1953	in the prepare watcher and would dispose of the check watcher.	2348	in the prepare watcher and would dispose of the check watcher.
1954		2349
1955	Method 3: If the module to be embedded supports explicit event	2350	Method 3: If the module to be embedded supports explicit event
1956	notification (adns does), you can also make use of the actual watcher	2351	notification (libadns does), you can also make use of the actual watcher
1957	callbacks, and only destroy/create the watchers in the prepare watcher.	2352	callbacks, and only destroy/create the watchers in the prepare watcher.
1958		2353
1959	static void	2354	static void
1960	timer_cb (EV_P_ ev_timer *w, int revents)	2355	timer_cb (EV_P_ ev_timer *w, int revents)
1961	{	2356	{
1962	adns_state ads = (adns_state)w->data;	2357	adns_state ads = (adns_state)w->data;
1963	update_now (EV_A);	2358	update_now (EV_A);
1964		2359
1965	adns_processtimeouts (ads, &tv_now);	2360	adns_processtimeouts (ads, &tv_now);
1966	}	2361	}
1967		2362
1968	static void	2363	static void
1969	io_cb (EV_P_ ev_io *w, int revents)	2364	io_cb (EV_P_ ev_io *w, int revents)
1970	{	2365	{
1971	adns_state ads = (adns_state)w->data;	2366	adns_state ads = (adns_state)w->data;
1972	update_now (EV_A);	2367	update_now (EV_A);
1973		2368
1974	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2369	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1975	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2370	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1976	}	2371	}
1977		2372
1978	// do not ever call adns_afterpoll	2373	// do not ever call adns_afterpoll
1979		2374
1980	Method 4: Do not use a prepare or check watcher because the module you	2375	Method 4: Do not use a prepare or check watcher because the module you
1981	want to embed is too inflexible to support it. Instead, youc na override	2376	want to embed is not flexible enough to support it. Instead, you can
1982	their poll function. The drawback with this solution is that the main	2377	override their poll function. The drawback with this solution is that the
1983	loop is now no longer controllable by EV. The C<Glib::EV> module does	2378	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1984	this.	2379	this approach, effectively embedding EV as a client into the horrible
		2380	libglib event loop.
1985		2381
1986	static gint	2382	static gint
1987	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2383	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1988	{	2384	{
1989	int got_events = 0;	2385	int got_events = 0;
1990		2386
1991	for (n = 0; n < nfds; ++n)	2387	for (n = 0; n < nfds; ++n)
1992	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2388	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1993		2389
1994	if (timeout >= 0)	2390	if (timeout >= 0)
1995	// create/start timer	2391	// create/start timer
1996		2392
1997	// poll	2393	// poll
1998	ev_loop (EV_A_ 0);	2394	ev_loop (EV_A_ 0);
1999		2395
2000	// stop timer again	2396	// stop timer again
2001	if (timeout >= 0)	2397	if (timeout >= 0)
2002	ev_timer_stop (EV_A_ &to);	2398	ev_timer_stop (EV_A_ &to);
2003		2399
2004	// stop io watchers again - their callbacks should have set	2400	// stop io watchers again - their callbacks should have set
2005	for (n = 0; n < nfds; ++n)	2401	for (n = 0; n < nfds; ++n)
2006	ev_io_stop (EV_A_ iow [n]);	2402	ev_io_stop (EV_A_ iow [n]);
2007		2403
2008	return got_events;	2404	return got_events;
2009	}	2405	}
2010		2406
2011		2407
2012	=head2 C<ev_embed> - when one backend isn't enough...	2408	=head2 C<ev_embed> - when one backend isn't enough...
2013		2409
2014	This is a rather advanced watcher type that lets you embed one event loop	2410	This is a rather advanced watcher type that lets you embed one event loop
…		…
2020	prioritise I/O.	2416	prioritise I/O.
2021		2417
2022	As an example for a bug workaround, the kqueue backend might only support	2418	As an example for a bug workaround, the kqueue backend might only support
2023	sockets on some platform, so it is unusable as generic backend, but you	2419	sockets on some platform, so it is unusable as generic backend, but you
2024	still want to make use of it because you have many sockets and it scales	2420	still want to make use of it because you have many sockets and it scales
2025	so nicely. In this case, you would create a kqueue-based loop and embed it	2421	so nicely. In this case, you would create a kqueue-based loop and embed
2026	into your default loop (which might use e.g. poll). Overall operation will	2422	it into your default loop (which might use e.g. poll). Overall operation
2027	be a bit slower because first libev has to poll and then call kevent, but	2423	will be a bit slower because first libev has to call C<poll> and then
2028	at least you can use both at what they are best.	2424	C<kevent>, but at least you can use both mechanisms for what they are
		2425	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2029		2426
2030	As for prioritising I/O: rarely you have the case where some fds have	2427	As for prioritising I/O: under rare circumstances you have the case where
2031	to be watched and handled very quickly (with low latency), and even	2428	some fds have to be watched and handled very quickly (with low latency),
2032	priorities and idle watchers might have too much overhead. In this case	2429	and even priorities and idle watchers might have too much overhead. In
2033	you would put all the high priority stuff in one loop and all the rest in	2430	this case you would put all the high priority stuff in one loop and all
2034	a second one, and embed the second one in the first.	2431	the rest in a second one, and embed the second one in the first.
2035		2432
2036	As long as the watcher is active, the callback will be invoked every time	2433	As long as the watcher is active, the callback will be invoked every
2037	there might be events pending in the embedded loop. The callback must then	2434	time there might be events pending in the embedded loop. The callback
2038	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2435	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2039	their callbacks (you could also start an idle watcher to give the embedded	2436	sweep and invoke their callbacks (the callback doesn't need to invoke the
2040	loop strictly lower priority for example). You can also set the callback	2437	C<ev_embed_sweep> function directly, it could also start an idle watcher
2041	to C<0>, in which case the embed watcher will automatically execute the	2438	to give the embedded loop strictly lower priority for example).
2042	embedded loop sweep.
2043		2439
2044	As long as the watcher is started it will automatically handle events. The	2440	You can also set the callback to C<0>, in which case the embed watcher
2045	callback will be invoked whenever some events have been handled. You can	2441	will automatically execute the embedded loop sweep whenever necessary.
2046	set the callback to C<0> to avoid having to specify one if you are not
2047	interested in that.
2048		2442
2049	Also, there have not currently been made special provisions for forking:	2443	Fork detection will be handled transparently while the C<ev_embed> watcher
2050	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2444	is active, i.e., the embedded loop will automatically be forked when the
2051	but you will also have to stop and restart any C<ev_embed> watchers	2445	embedding loop forks. In other cases, the user is responsible for calling
2052	yourself.	2446	C<ev_loop_fork> on the embedded loop.
2053		2447
2054	Unfortunately, not all backends are embeddable, only the ones returned by	2448	Unfortunately, not all backends are embeddable: only the ones returned by
2055	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2449	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2056	portable one.	2450	portable one.
2057		2451
2058	So when you want to use this feature you will always have to be prepared	2452	So when you want to use this feature you will always have to be prepared
2059	that you cannot get an embeddable loop. The recommended way to get around	2453	that you cannot get an embeddable loop. The recommended way to get around
2060	this is to have a separate variables for your embeddable loop, try to	2454	this is to have a separate variables for your embeddable loop, try to
2061	create it, and if that fails, use the normal loop for everything.	2455	create it, and if that fails, use the normal loop for everything.
2062		2456
		2457	=head3 C<ev_embed> and fork
		2458
		2459	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2460	automatically be applied to the embedded loop as well, so no special
		2461	fork handling is required in that case. When the watcher is not running,
		2462	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2463	as applicable.
		2464
2063	=head3 Watcher-Specific Functions and Data Members	2465	=head3 Watcher-Specific Functions and Data Members
2064		2466
2065	=over 4	2467	=over 4
2066		2468
2067	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2469	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2070		2472
2071	Configures the watcher to embed the given loop, which must be	2473	Configures the watcher to embed the given loop, which must be
2072	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2474	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2073	invoked automatically, otherwise it is the responsibility of the callback	2475	invoked automatically, otherwise it is the responsibility of the callback
2074	to invoke it (it will continue to be called until the sweep has been done,	2476	to invoke it (it will continue to be called until the sweep has been done,
2075	if you do not want thta, you need to temporarily stop the embed watcher).	2477	if you do not want that, you need to temporarily stop the embed watcher).
2076		2478
2077	=item ev_embed_sweep (loop, ev_embed *)	2479	=item ev_embed_sweep (loop, ev_embed *)
2078		2480
2079	Make a single, non-blocking sweep over the embedded loop. This works	2481	Make a single, non-blocking sweep over the embedded loop. This works
2080	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2081	apropriate way for embedded loops.	2483	appropriate way for embedded loops.
2082		2484
2083	=item struct ev_loop *other [read-only]	2485	=item struct ev_loop *other [read-only]
2084		2486
2085	The embedded event loop.	2487	The embedded event loop.
2086		2488
…		…
2088		2490
2089	=head3 Examples	2491	=head3 Examples
2090		2492
2091	Example: Try to get an embeddable event loop and embed it into the default	2493	Example: Try to get an embeddable event loop and embed it into the default
2092	event loop. If that is not possible, use the default loop. The default	2494	event loop. If that is not possible, use the default loop. The default
2093	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2495	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2094	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2496	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2095	used).	2497	used).
2096		2498
2097	struct ev_loop *loop_hi = ev_default_init (0);	2499	struct ev_loop *loop_hi = ev_default_init (0);
2098	struct ev_loop *loop_lo = 0;	2500	struct ev_loop *loop_lo = 0;
2099	struct ev_embed embed;	2501	ev_embed embed;
2100		2502
2101	// see if there is a chance of getting one that works	2503	// see if there is a chance of getting one that works
2102	// (remember that a flags value of 0 means autodetection)	2504	// (remember that a flags value of 0 means autodetection)
2103	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2505	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2104	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2506	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2105	: 0;	2507	: 0;
2106		2508
2107	// if we got one, then embed it, otherwise default to loop_hi	2509	// if we got one, then embed it, otherwise default to loop_hi
2108	if (loop_lo)	2510	if (loop_lo)
2109	{	2511	{
2110	ev_embed_init (&embed, 0, loop_lo);	2512	ev_embed_init (&embed, 0, loop_lo);
2111	ev_embed_start (loop_hi, &embed);	2513	ev_embed_start (loop_hi, &embed);
2112	}	2514	}
2113	else	2515	else
2114	loop_lo = loop_hi;	2516	loop_lo = loop_hi;
2115		2517
2116	Example: Check if kqueue is available but not recommended and create	2518	Example: Check if kqueue is available but not recommended and create
2117	a kqueue backend for use with sockets (which usually work with any	2519	a kqueue backend for use with sockets (which usually work with any
2118	kqueue implementation). Store the kqueue/socket-only event loop in	2520	kqueue implementation). Store the kqueue/socket-only event loop in
2119	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2521	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2120		2522
2121	struct ev_loop *loop = ev_default_init (0);	2523	struct ev_loop *loop = ev_default_init (0);
2122	struct ev_loop *loop_socket = 0;	2524	struct ev_loop *loop_socket = 0;
2123	struct ev_embed embed;	2525	ev_embed embed;
2124		2526
2125	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2527	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2126	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2528	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2127	{	2529	{
2128	ev_embed_init (&embed, 0, loop_socket);	2530	ev_embed_init (&embed, 0, loop_socket);
2129	ev_embed_start (loop, &embed);	2531	ev_embed_start (loop, &embed);
2130	}	2532	}
2131		2533
2132	if (!loop_socket)	2534	if (!loop_socket)
2133	loop_socket = loop;	2535	loop_socket = loop;
2134		2536
2135	// now use loop_socket for all sockets, and loop for everything else	2537	// now use loop_socket for all sockets, and loop for everything else
2136		2538
2137		2539
2138	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2540	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2139		2541
2140	Fork watchers are called when a C<fork ()> was detected (usually because	2542	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2184	is that the author does not know of a simple (or any) algorithm for a	2586	is that the author does not know of a simple (or any) algorithm for a
2185	multiple-writer-single-reader queue that works in all cases and doesn't	2587	multiple-writer-single-reader queue that works in all cases and doesn't
2186	need elaborate support such as pthreads.	2588	need elaborate support such as pthreads.
2187		2589
2188	That means that if you want to queue data, you have to provide your own	2590	That means that if you want to queue data, you have to provide your own
2189	queue. But at least I can tell you would implement locking around your	2591	queue. But at least I can tell you how to implement locking around your
2190	queue:	2592	queue:
2191		2593
2192	=over 4	2594	=over 4
2193		2595
2194	=item queueing from a signal handler context	2596	=item queueing from a signal handler context
2195		2597
2196	To implement race-free queueing, you simply add to the queue in the signal	2598	To implement race-free queueing, you simply add to the queue in the signal
2197	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2599	handler but you block the signal handler in the watcher callback. Here is
2198	some fictitiuous SIGUSR1 handler:	2600	an example that does that for some fictitious SIGUSR1 handler:
2199		2601
2200	static ev_async mysig;	2602	static ev_async mysig;
2201		2603
2202	static void	2604	static void
2203	sigusr1_handler (void)	2605	sigusr1_handler (void)
…		…
2269	=over 4	2671	=over 4
2270		2672
2271	=item ev_async_init (ev_async *, callback)	2673	=item ev_async_init (ev_async *, callback)
2272		2674
2273	Initialises and configures the async watcher - it has no parameters of any	2675	Initialises and configures the async watcher - it has no parameters of any
2274	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2676	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2275	believe me.	2677	trust me.
2276		2678
2277	=item ev_async_send (loop, ev_async *)	2679	=item ev_async_send (loop, ev_async *)
2278		2680
2279	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2280	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2281	C<ev_feed_event>, this call is safe to do in other threads, signal or	2683	C<ev_feed_event>, this call is safe to do from other threads, signal or
2282	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2283	section below on what exactly this means).	2685	section below on what exactly this means).
2284		2686
2285	This call incurs the overhead of a syscall only once per loop iteration,	2687	This call incurs the overhead of a system call only once per loop iteration,
2286	so while the overhead might be noticable, it doesn't apply to repeated	2688	so while the overhead might be noticeable, it doesn't apply to repeated
2287	calls to C<ev_async_send>.	2689	calls to C<ev_async_send>.
2288		2690
2289	=item bool = ev_async_pending (ev_async *)	2691	=item bool = ev_async_pending (ev_async *)
2290		2692
2291	Returns a non-zero value when C<ev_async_send> has been called on the	2693	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2293	event loop.	2695	event loop.
2294		2696
2295	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2296	the loop iterates next and checks for the watcher to have become active,	2698	the loop iterates next and checks for the watcher to have become active,
2297	it will reset the flag again. C<ev_async_pending> can be used to very	2699	it will reset the flag again. C<ev_async_pending> can be used to very
2298	quickly check wether invoking the loop might be a good idea.	2700	quickly check whether invoking the loop might be a good idea.
2299		2701
2300	Not that this does I<not> check wether the watcher itself is pending, only	2702	Not that this does I<not> check whether the watcher itself is pending, only
2301	wether it has been requested to make this watcher pending.	2703	whether it has been requested to make this watcher pending.
2302		2704
2303	=back	2705	=back
2304		2706
2305		2707
2306	=head1 OTHER FUNCTIONS	2708	=head1 OTHER FUNCTIONS
…		…
2310	=over 4	2712	=over 4
2311		2713
2312	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2714	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2313		2715
2314	This function combines a simple timer and an I/O watcher, calls your	2716	This function combines a simple timer and an I/O watcher, calls your
2315	callback on whichever event happens first and automatically stop both	2717	callback on whichever event happens first and automatically stops both
2316	watchers. This is useful if you want to wait for a single event on an fd	2718	watchers. This is useful if you want to wait for a single event on an fd
2317	or timeout without having to allocate/configure/start/stop/free one or	2719	or timeout without having to allocate/configure/start/stop/free one or
2318	more watchers yourself.	2720	more watchers yourself.
2319		2721
2320	If C<fd> is less than 0, then no I/O watcher will be started and events	2722	If C<fd> is less than 0, then no I/O watcher will be started and the
2321	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2723	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2322	C<events> set will be craeted and started.	2724	the given C<fd> and C<events> set will be created and started.
2323		2725
2324	If C<timeout> is less than 0, then no timeout watcher will be	2726	If C<timeout> is less than 0, then no timeout watcher will be
2325	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2326	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2728	repeat = 0) will be started. C<0> is a valid timeout.
2327	dubious value.
2328		2729
2329	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2330	passed an C<revents> set like normal event callbacks (a combination of	2731	passed an C<revents> set like normal event callbacks (a combination of
2331	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2332	value passed to C<ev_once>:	2733	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2734	a timeout and an io event at the same time - you probably should give io
		2735	events precedence.
2333		2736
		2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2738
2334	static void stdin_ready (int revents, void *arg)	2739	static void stdin_ready (int revents, void *arg)
2335	{	2740	{
2336	if (revents & EV_TIMEOUT)
2337	/* doh, nothing entered */;
2338	else if (revents & EV_READ)	2741	if (revents & EV_READ)
2339	/* stdin might have data for us, joy! */;	2742	/* stdin might have data for us, joy! */;
		2743	else if (revents & EV_TIMEOUT)
		2744	/* doh, nothing entered */;
2340	}	2745	}
2341		2746
2342	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2343		2748
2344	=item ev_feed_event (ev_loop *, watcher *, int revents)	2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2345		2750
2346	Feeds the given event set into the event loop, as if the specified event	2751	Feeds the given event set into the event loop, as if the specified event
2347	had happened for the specified watcher (which must be a pointer to an	2752	had happened for the specified watcher (which must be a pointer to an
2348	initialised but not necessarily started event watcher).	2753	initialised but not necessarily started event watcher).
2349		2754
2350	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2351		2756
2352	Feed an event on the given fd, as if a file descriptor backend detected	2757	Feed an event on the given fd, as if a file descriptor backend detected
2353	the given events it.	2758	the given events it.
2354		2759
2355	=item ev_feed_signal_event (ev_loop *loop, int signum)	2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2356		2761
2357	Feed an event as if the given signal occured (C<loop> must be the default	2762	Feed an event as if the given signal occurred (C<loop> must be the default
2358	loop!).	2763	loop!).
2359		2764
2360	=back	2765	=back
2361		2766
2362		2767
…		…
2391	=back	2796	=back
2392		2797
2393	=head1 C++ SUPPORT	2798	=head1 C++ SUPPORT
2394		2799
2395	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2800	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2396	you to use some convinience methods to start/stop watchers and also change	2801	you to use some convenience methods to start/stop watchers and also change
2397	the callback model to a model using method callbacks on objects.	2802	the callback model to a model using method callbacks on objects.
2398		2803
2399	To use it,	2804	To use it,
2400		2805
2401	#include <ev++.h>	2806	#include <ev++.h>
2402		2807
2403	This automatically includes F<ev.h> and puts all of its definitions (many	2808	This automatically includes F<ev.h> and puts all of its definitions (many
2404	of them macros) into the global namespace. All C++ specific things are	2809	of them macros) into the global namespace. All C++ specific things are
2405	put into the C<ev> namespace. It should support all the same embedding	2810	put into the C<ev> namespace. It should support all the same embedding
2406	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2811	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2473	your compiler is good :), then the method will be fully inlined into the	2878	your compiler is good :), then the method will be fully inlined into the
2474	thunking function, making it as fast as a direct C callback.	2879	thunking function, making it as fast as a direct C callback.
2475		2880
2476	Example: simple class declaration and watcher initialisation	2881	Example: simple class declaration and watcher initialisation
2477		2882
2478	struct myclass	2883	struct myclass
2479	{	2884	{
2480	void io_cb (ev::io &w, int revents) { }	2885	void io_cb (ev::io &w, int revents) { }
2481	}	2886	}
2482		2887
2483	myclass obj;	2888	myclass obj;
2484	ev::io iow;	2889	ev::io iow;
2485	iow.set <myclass, &myclass::io_cb> (&obj);	2890	iow.set <myclass, &myclass::io_cb> (&obj);
		2891
		2892	=item w->set (object *)
		2893
		2894	This is an B<experimental> feature that might go away in a future version.
		2895
		2896	This is a variation of a method callback - leaving out the method to call
		2897	will default the method to C<operator ()>, which makes it possible to use
		2898	functor objects without having to manually specify the C<operator ()> all
		2899	the time. Incidentally, you can then also leave out the template argument
		2900	list.
		2901
		2902	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2903	int revents)>.
		2904
		2905	See the method-C<set> above for more details.
		2906
		2907	Example: use a functor object as callback.
		2908
		2909	struct myfunctor
		2910	{
		2911	void operator() (ev::io &w, int revents)
		2912	{
		2913	...
		2914	}
		2915	}
		2916
		2917	myfunctor f;
		2918
		2919	ev::io w;
		2920	w.set (&f);
2486		2921
2487	=item w->set<function> (void *data = 0)	2922	=item w->set<function> (void *data = 0)
2488		2923
2489	Also sets a callback, but uses a static method or plain function as	2924	Also sets a callback, but uses a static method or plain function as
2490	callback. The optional C<data> argument will be stored in the watcher's	2925	callback. The optional C<data> argument will be stored in the watcher's
…		…
2492		2927
2493	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2928	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2494		2929
2495	See the method-C<set> above for more details.	2930	See the method-C<set> above for more details.
2496		2931
2497	Example:	2932	Example: Use a plain function as callback.
2498		2933
2499	static void io_cb (ev::io &w, int revents) { }	2934	static void io_cb (ev::io &w, int revents) { }
2500	iow.set <io_cb> ();	2935	iow.set <io_cb> ();
2501		2936
2502	=item w->set (struct ev_loop *)	2937	=item w->set (struct ev_loop *)
2503		2938
2504	Associates a different C<struct ev_loop> with this watcher. You can only	2939	Associates a different C<struct ev_loop> with this watcher. You can only
2505	do this when the watcher is inactive (and not pending either).	2940	do this when the watcher is inactive (and not pending either).
2506		2941
2507	=item w->set ([args])	2942	=item w->set ([arguments])
2508		2943
2509	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2510	called at least once. Unlike the C counterpart, an active watcher gets	2945	called at least once. Unlike the C counterpart, an active watcher gets
2511	automatically stopped and restarted when reconfiguring it with this	2946	automatically stopped and restarted when reconfiguring it with this
2512	method.	2947	method.
2513		2948
2514	=item w->start ()	2949	=item w->start ()
…		…
2538	=back	2973	=back
2539		2974
2540	Example: Define a class with an IO and idle watcher, start one of them in	2975	Example: Define a class with an IO and idle watcher, start one of them in
2541	the constructor.	2976	the constructor.
2542		2977
2543	class myclass	2978	class myclass
2544	{	2979	{
2545	ev::io io; void io_cb (ev::io &w, int revents);	2980	ev::io io ; void io_cb (ev::io &w, int revents);
2546	ev:idle idle void idle_cb (ev::idle &w, int revents);	2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2547		2982
2548	myclass (int fd)	2983	myclass (int fd)
2549	{	2984	{
2550	io .set <myclass, &myclass::io_cb > (this);	2985	io .set <myclass, &myclass::io_cb > (this);
2551	idle.set <myclass, &myclass::idle_cb> (this);	2986	idle.set <myclass, &myclass::idle_cb> (this);
2552		2987
2553	io.start (fd, ev::READ);	2988	io.start (fd, ev::READ);
2554	}	2989	}
2555	};	2990	};
2556		2991
2557		2992
2558	=head1 OTHER LANGUAGE BINDINGS	2993	=head1 OTHER LANGUAGE BINDINGS
2559		2994
2560	Libev does not offer other language bindings itself, but bindings for a	2995	Libev does not offer other language bindings itself, but bindings for a
2561	numbe rof languages exist in the form of third-party packages. If you know	2996	number of languages exist in the form of third-party packages. If you know
2562	any interesting language binding in addition to the ones listed here, drop	2997	any interesting language binding in addition to the ones listed here, drop
2563	me a note.	2998	me a note.
2564		2999
2565	=over 4	3000	=over 4
2566		3001
2567	=item Perl	3002	=item Perl
2568		3003
2569	The EV module implements the full libev API and is actually used to test	3004	The EV module implements the full libev API and is actually used to test
2570	libev. EV is developed together with libev. Apart from the EV core module,	3005	libev. EV is developed together with libev. Apart from the EV core module,
2571	there are additional modules that implement libev-compatible interfaces	3006	there are additional modules that implement libev-compatible interfaces
2572	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3007	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2573	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3008	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3009	and C<EV::Glib>).
2574		3010
2575	It can be found and installed via CPAN, its homepage is found at	3011	It can be found and installed via CPAN, its homepage is at
2576	L<http://software.schmorp.de/pkg/EV>.	3012	L<http://software.schmorp.de/pkg/EV>.
2577		3013
		3014	=item Python
		3015
		3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3017	seems to be quite complete and well-documented. Note, however, that the
		3018	patch they require for libev is outright dangerous as it breaks the ABI
		3019	for everybody else, and therefore, should never be applied in an installed
		3020	libev (if python requires an incompatible ABI then it needs to embed
		3021	libev).
		3022
2578	=item Ruby	3023	=item Ruby
2579		3024
2580	Tony Arcieri has written a ruby extension that offers access to a subset	3025	Tony Arcieri has written a ruby extension that offers access to a subset
2581	of the libev API and adds filehandle abstractions, asynchronous DNS and	3026	of the libev API and adds file handle abstractions, asynchronous DNS and
2582	more on top of it. It can be found via gem servers. Its homepage is at	3027	more on top of it. It can be found via gem servers. Its homepage is at
2583	L<http://rev.rubyforge.org/>.	3028	L<http://rev.rubyforge.org/>.
2584		3029
		3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3031	makes rev work even on mingw.
		3032
2585	=item D	3033	=item D
2586		3034
2587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2588	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3037
		3038	=item Ocaml
		3039
		3040	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2589		3042
2590	=back	3043	=back
2591		3044
2592		3045
2593	=head1 MACRO MAGIC	3046	=head1 MACRO MAGIC
2594		3047
2595	Libev can be compiled with a variety of options, the most fundamantal	3048	Libev can be compiled with a variety of options, the most fundamental
2596	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3049	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2597	functions and callbacks have an initial C<struct ev_loop *> argument.	3050	functions and callbacks have an initial C<struct ev_loop *> argument.
2598		3051
2599	To make it easier to write programs that cope with either variant, the	3052	To make it easier to write programs that cope with either variant, the
2600	following macros are defined:	3053	following macros are defined:
…		…
2605		3058
2606	This provides the loop I<argument> for functions, if one is required ("ev	3059	This provides the loop I<argument> for functions, if one is required ("ev
2607	loop argument"). The C<EV_A> form is used when this is the sole argument,	3060	loop argument"). The C<EV_A> form is used when this is the sole argument,
2608	C<EV_A_> is used when other arguments are following. Example:	3061	C<EV_A_> is used when other arguments are following. Example:
2609		3062
2610	ev_unref (EV_A);	3063	ev_unref (EV_A);
2611	ev_timer_add (EV_A_ watcher);	3064	ev_timer_add (EV_A_ watcher);
2612	ev_loop (EV_A_ 0);	3065	ev_loop (EV_A_ 0);
2613		3066
2614	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2615	which is often provided by the following macro.	3068	which is often provided by the following macro.
2616		3069
2617	=item C<EV_P>, C<EV_P_>	3070	=item C<EV_P>, C<EV_P_>
2618		3071
2619	This provides the loop I<parameter> for functions, if one is required ("ev	3072	This provides the loop I<parameter> for functions, if one is required ("ev
2620	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3073	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2621	C<EV_P_> is used when other parameters are following. Example:	3074	C<EV_P_> is used when other parameters are following. Example:
2622		3075
2623	// this is how ev_unref is being declared	3076	// this is how ev_unref is being declared
2624	static void ev_unref (EV_P);	3077	static void ev_unref (EV_P);
2625		3078
2626	// this is how you can declare your typical callback	3079	// this is how you can declare your typical callback
2627	static void cb (EV_P_ ev_timer *w, int revents)	3080	static void cb (EV_P_ ev_timer *w, int revents)
2628		3081
2629	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3082	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2630	suitable for use with C<EV_A>.	3083	suitable for use with C<EV_A>.
2631		3084
2632	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3085	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2648		3101
2649	Example: Declare and initialise a check watcher, utilising the above	3102	Example: Declare and initialise a check watcher, utilising the above
2650	macros so it will work regardless of whether multiple loops are supported	3103	macros so it will work regardless of whether multiple loops are supported
2651	or not.	3104	or not.
2652		3105
2653	static void	3106	static void
2654	check_cb (EV_P_ ev_timer *w, int revents)	3107	check_cb (EV_P_ ev_timer *w, int revents)
2655	{	3108	{
2656	ev_check_stop (EV_A_ w);	3109	ev_check_stop (EV_A_ w);
2657	}	3110	}
2658		3111
2659	ev_check check;	3112	ev_check check;
2660	ev_check_init (&check, check_cb);	3113	ev_check_init (&check, check_cb);
2661	ev_check_start (EV_DEFAULT_ &check);	3114	ev_check_start (EV_DEFAULT_ &check);
2662	ev_loop (EV_DEFAULT_ 0);	3115	ev_loop (EV_DEFAULT_ 0);
2663		3116
2664	=head1 EMBEDDING	3117	=head1 EMBEDDING
2665		3118
2666	Libev can (and often is) directly embedded into host	3119	Libev can (and often is) directly embedded into host
2667	applications. Examples of applications that embed it include the Deliantra	3120	applications. Examples of applications that embed it include the Deliantra
…		…
2674	libev somewhere in your source tree).	3127	libev somewhere in your source tree).
2675		3128
2676	=head2 FILESETS	3129	=head2 FILESETS
2677		3130
2678	Depending on what features you need you need to include one or more sets of files	3131	Depending on what features you need you need to include one or more sets of files
2679	in your app.	3132	in your application.
2680		3133
2681	=head3 CORE EVENT LOOP	3134	=head3 CORE EVENT LOOP
2682		3135
2683	To include only the libev core (all the C<ev_*> functions), with manual	3136	To include only the libev core (all the C<ev_*> functions), with manual
2684	configuration (no autoconf):	3137	configuration (no autoconf):
2685		3138
2686	#define EV_STANDALONE 1	3139	#define EV_STANDALONE 1
2687	#include "ev.c"	3140	#include "ev.c"
2688		3141
2689	This will automatically include F<ev.h>, too, and should be done in a	3142	This will automatically include F<ev.h>, too, and should be done in a
2690	single C source file only to provide the function implementations. To use	3143	single C source file only to provide the function implementations. To use
2691	it, do the same for F<ev.h> in all files wishing to use this API (best	3144	it, do the same for F<ev.h> in all files wishing to use this API (best
2692	done by writing a wrapper around F<ev.h> that you can include instead and	3145	done by writing a wrapper around F<ev.h> that you can include instead and
2693	where you can put other configuration options):	3146	where you can put other configuration options):
2694		3147
2695	#define EV_STANDALONE 1	3148	#define EV_STANDALONE 1
2696	#include "ev.h"	3149	#include "ev.h"
2697		3150
2698	Both header files and implementation files can be compiled with a C++	3151	Both header files and implementation files can be compiled with a C++
2699	compiler (at least, thats a stated goal, and breakage will be treated	3152	compiler (at least, that's a stated goal, and breakage will be treated
2700	as a bug).	3153	as a bug).
2701		3154
2702	You need the following files in your source tree, or in a directory	3155	You need the following files in your source tree, or in a directory
2703	in your include path (e.g. in libev/ when using -Ilibev):	3156	in your include path (e.g. in libev/ when using -Ilibev):
2704		3157
2705	ev.h	3158	ev.h
2706	ev.c	3159	ev.c
2707	ev_vars.h	3160	ev_vars.h
2708	ev_wrap.h	3161	ev_wrap.h
2709		3162
2710	ev_win32.c required on win32 platforms only	3163	ev_win32.c required on win32 platforms only
2711		3164
2712	ev_select.c only when select backend is enabled (which is enabled by default)	3165	ev_select.c only when select backend is enabled (which is enabled by default)
2713	ev_poll.c only when poll backend is enabled (disabled by default)	3166	ev_poll.c only when poll backend is enabled (disabled by default)
2714	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3167	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2715	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3168	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2716	ev_port.c only when the solaris port backend is enabled (disabled by default)	3169	ev_port.c only when the solaris port backend is enabled (disabled by default)
2717		3170
2718	F<ev.c> includes the backend files directly when enabled, so you only need	3171	F<ev.c> includes the backend files directly when enabled, so you only need
2719	to compile this single file.	3172	to compile this single file.
2720		3173
2721	=head3 LIBEVENT COMPATIBILITY API	3174	=head3 LIBEVENT COMPATIBILITY API
2722		3175
2723	To include the libevent compatibility API, also include:	3176	To include the libevent compatibility API, also include:
2724		3177
2725	#include "event.c"	3178	#include "event.c"
2726		3179
2727	in the file including F<ev.c>, and:	3180	in the file including F<ev.c>, and:
2728		3181
2729	#include "event.h"	3182	#include "event.h"
2730		3183
2731	in the files that want to use the libevent API. This also includes F<ev.h>.	3184	in the files that want to use the libevent API. This also includes F<ev.h>.
2732		3185
2733	You need the following additional files for this:	3186	You need the following additional files for this:
2734		3187
2735	event.h	3188	event.h
2736	event.c	3189	event.c
2737		3190
2738	=head3 AUTOCONF SUPPORT	3191	=head3 AUTOCONF SUPPORT
2739		3192
2740	Instead of using C<EV_STANDALONE=1> and providing your config in	3193	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2741	whatever way you want, you can also C<m4_include([libev.m4])> in your	3194	whatever way you want, you can also C<m4_include([libev.m4])> in your
2742	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3195	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2743	include F<config.h> and configure itself accordingly.	3196	include F<config.h> and configure itself accordingly.
2744		3197
2745	For this of course you need the m4 file:	3198	For this of course you need the m4 file:
2746		3199
2747	libev.m4	3200	libev.m4
2748		3201
2749	=head2 PREPROCESSOR SYMBOLS/MACROS	3202	=head2 PREPROCESSOR SYMBOLS/MACROS
2750		3203
2751	Libev can be configured via a variety of preprocessor symbols you have to	3204	Libev can be configured via a variety of preprocessor symbols you have to
2752	define before including any of its files. The default in the absense of	3205	define before including any of its files. The default in the absence of
2753	autoconf is noted for every option.	3206	autoconf is documented for every option.
2754		3207
2755	=over 4	3208	=over 4
2756		3209
2757	=item EV_STANDALONE	3210	=item EV_STANDALONE
2758		3211
…		…
2760	keeps libev from including F<config.h>, and it also defines dummy	3213	keeps libev from including F<config.h>, and it also defines dummy
2761	implementations for some libevent functions (such as logging, which is not	3214	implementations for some libevent functions (such as logging, which is not
2762	supported). It will also not define any of the structs usually found in	3215	supported). It will also not define any of the structs usually found in
2763	F<event.h> that are not directly supported by the libev core alone.	3216	F<event.h> that are not directly supported by the libev core alone.
2764		3217
		3218	In stanbdalone mode, libev will still try to automatically deduce the
		3219	configuration, but has to be more conservative.
		3220
2765	=item EV_USE_MONOTONIC	3221	=item EV_USE_MONOTONIC
2766		3222
2767	If defined to be C<1>, libev will try to detect the availability of the	3223	If defined to be C<1>, libev will try to detect the availability of the
2768	monotonic clock option at both compiletime and runtime. Otherwise no use	3224	monotonic clock option at both compile time and runtime. Otherwise no
2769	of the monotonic clock option will be attempted. If you enable this, you	3225	use of the monotonic clock option will be attempted. If you enable this,
2770	usually have to link against librt or something similar. Enabling it when	3226	you usually have to link against librt or something similar. Enabling it
2771	the functionality isn't available is safe, though, although you have	3227	when the functionality isn't available is safe, though, although you have
2772	to make sure you link against any libraries where the C<clock_gettime>	3228	to make sure you link against any libraries where the C<clock_gettime>
2773	function is hiding in (often F<-lrt>).	3229	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2774		3230
2775	=item EV_USE_REALTIME	3231	=item EV_USE_REALTIME
2776		3232
2777	If defined to be C<1>, libev will try to detect the availability of the	3233	If defined to be C<1>, libev will try to detect the availability of the
2778	realtime clock option at compiletime (and assume its availability at	3234	real-time clock option at compile time (and assume its availability
2779	runtime if successful). Otherwise no use of the realtime clock option will	3235	at runtime if successful). Otherwise no use of the real-time clock
2780	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3236	option will be attempted. This effectively replaces C<gettimeofday>
2781	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3237	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2782	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3238	correctness. See the note about libraries in the description of
		3239	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3240	C<EV_USE_CLOCK_SYSCALL>.
		3241
		3242	=item EV_USE_CLOCK_SYSCALL
		3243
		3244	If defined to be C<1>, libev will try to use a direct syscall instead
		3245	of calling the system-provided C<clock_gettime> function. This option
		3246	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3247	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3248	programs needlessly. Using a direct syscall is slightly slower (in
		3249	theory), because no optimised vdso implementation can be used, but avoids
		3250	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3251	higher, as it simplifies linking (no need for C<-lrt>).
2783		3252
2784	=item EV_USE_NANOSLEEP	3253	=item EV_USE_NANOSLEEP
2785		3254
2786	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3255	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2787	and will use it for delays. Otherwise it will use C<select ()>.	3256	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2795	2.7 or newer, otherwise disabled.	3264	2.7 or newer, otherwise disabled.
2796		3265
2797	=item EV_USE_SELECT	3266	=item EV_USE_SELECT
2798		3267
2799	If undefined or defined to be C<1>, libev will compile in support for the	3268	If undefined or defined to be C<1>, libev will compile in support for the
2800	C<select>(2) backend. No attempt at autodetection will be done: if no	3269	C<select>(2) backend. No attempt at auto-detection will be done: if no
2801	other method takes over, select will be it. Otherwise the select backend	3270	other method takes over, select will be it. Otherwise the select backend
2802	will not be compiled in.	3271	will not be compiled in.
2803		3272
2804	=item EV_SELECT_USE_FD_SET	3273	=item EV_SELECT_USE_FD_SET
2805		3274
2806	If defined to C<1>, then the select backend will use the system C<fd_set>	3275	If defined to C<1>, then the select backend will use the system C<fd_set>
2807	structure. This is useful if libev doesn't compile due to a missing	3276	structure. This is useful if libev doesn't compile due to a missing
2808	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3277	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2809	exotic systems. This usually limits the range of file descriptors to some	3278	on exotic systems. This usually limits the range of file descriptors to
2810	low limit such as 1024 or might have other limitations (winsocket only	3279	some low limit such as 1024 or might have other limitations (winsocket
2811	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3280	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2812	influence the size of the C<fd_set> used.	3281	configures the maximum size of the C<fd_set>.
2813		3282
2814	=item EV_SELECT_IS_WINSOCKET	3283	=item EV_SELECT_IS_WINSOCKET
2815		3284
2816	When defined to C<1>, the select backend will assume that	3285	When defined to C<1>, the select backend will assume that
2817	select/socket/connect etc. don't understand file descriptors but	3286	select/socket/connect etc. don't understand file descriptors but
…		…
2862	otherwise another method will be used as fallback. This is the preferred	3331	otherwise another method will be used as fallback. This is the preferred
2863	backend for Solaris 10 systems.	3332	backend for Solaris 10 systems.
2864		3333
2865	=item EV_USE_DEVPOLL	3334	=item EV_USE_DEVPOLL
2866		3335
2867	reserved for future expansion, works like the USE symbols above.	3336	Reserved for future expansion, works like the USE symbols above.
2868		3337
2869	=item EV_USE_INOTIFY	3338	=item EV_USE_INOTIFY
2870		3339
2871	If defined to be C<1>, libev will compile in support for the Linux inotify	3340	If defined to be C<1>, libev will compile in support for the Linux inotify
2872	interface to speed up C<ev_stat> watchers. Its actual availability will	3341	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2879	access is atomic with respect to other threads or signal contexts. No such	3348	access is atomic with respect to other threads or signal contexts. No such
2880	type is easily found in the C language, so you can provide your own type	3349	type is easily found in the C language, so you can provide your own type
2881	that you know is safe for your purposes. It is used both for signal handler "locking"	3350	that you know is safe for your purposes. It is used both for signal handler "locking"
2882	as well as for signal and thread safety in C<ev_async> watchers.	3351	as well as for signal and thread safety in C<ev_async> watchers.
2883		3352
2884	In the absense of this define, libev will use C<sig_atomic_t volatile>	3353	In the absence of this define, libev will use C<sig_atomic_t volatile>
2885	(from F<signal.h>), which is usually good enough on most platforms.	3354	(from F<signal.h>), which is usually good enough on most platforms.
2886		3355
2887	=item EV_H	3356	=item EV_H
2888		3357
2889	The name of the F<ev.h> header file used to include it. The default if	3358	The name of the F<ev.h> header file used to include it. The default if
…		…
2928	When doing priority-based operations, libev usually has to linearly search	3397	When doing priority-based operations, libev usually has to linearly search
2929	all the priorities, so having many of them (hundreds) uses a lot of space	3398	all the priorities, so having many of them (hundreds) uses a lot of space
2930	and time, so using the defaults of five priorities (-2 .. +2) is usually	3399	and time, so using the defaults of five priorities (-2 .. +2) is usually
2931	fine.	3400	fine.
2932		3401
2933	If your embedding app does not need any priorities, defining these both to	3402	If your embedding application does not need any priorities, defining these
2934	C<0> will save some memory and cpu.	3403	both to C<0> will save some memory and CPU.
2935		3404
2936	=item EV_PERIODIC_ENABLE	3405	=item EV_PERIODIC_ENABLE
2937		3406
2938	If undefined or defined to be C<1>, then periodic timers are supported. If	3407	If undefined or defined to be C<1>, then periodic timers are supported. If
2939	defined to be C<0>, then they are not. Disabling them saves a few kB of	3408	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2946	code.	3415	code.
2947		3416
2948	=item EV_EMBED_ENABLE	3417	=item EV_EMBED_ENABLE
2949		3418
2950	If undefined or defined to be C<1>, then embed watchers are supported. If	3419	If undefined or defined to be C<1>, then embed watchers are supported. If
2951	defined to be C<0>, then they are not.	3420	defined to be C<0>, then they are not. Embed watchers rely on most other
		3421	watcher types, which therefore must not be disabled.
2952		3422
2953	=item EV_STAT_ENABLE	3423	=item EV_STAT_ENABLE
2954		3424
2955	If undefined or defined to be C<1>, then stat watchers are supported. If	3425	If undefined or defined to be C<1>, then stat watchers are supported. If
2956	defined to be C<0>, then they are not.	3426	defined to be C<0>, then they are not.
…		…
2966	defined to be C<0>, then they are not.	3436	defined to be C<0>, then they are not.
2967		3437
2968	=item EV_MINIMAL	3438	=item EV_MINIMAL
2969		3439
2970	If you need to shave off some kilobytes of code at the expense of some	3440	If you need to shave off some kilobytes of code at the expense of some
2971	speed, define this symbol to C<1>. Currently only used for gcc to override	3441	speed, define this symbol to C<1>. Currently this is used to override some
2972	some inlining decisions, saves roughly 30% codesize of amd64.	3442	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3443	much smaller 2-heap for timer management over the default 4-heap.
2973		3444
2974	=item EV_PID_HASHSIZE	3445	=item EV_PID_HASHSIZE
2975		3446
2976	C<ev_child> watchers use a small hash table to distribute workload by	3447	C<ev_child> watchers use a small hash table to distribute workload by
2977	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3448	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2984	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3455	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2985	usually more than enough. If you need to manage thousands of C<ev_stat>	3456	usually more than enough. If you need to manage thousands of C<ev_stat>
2986	watchers you might want to increase this value (I<must> be a power of	3457	watchers you might want to increase this value (I<must> be a power of
2987	two).	3458	two).
2988		3459
		3460	=item EV_USE_4HEAP
		3461
		3462	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3463	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3464	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3465	faster performance with many (thousands) of watchers.
		3466
		3467	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3468	(disabled).
		3469
		3470	=item EV_HEAP_CACHE_AT
		3471
		3472	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3473	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3474	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3475	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3476	but avoids random read accesses on heap changes. This improves performance
		3477	noticeably with many (hundreds) of watchers.
		3478
		3479	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3480	(disabled).
		3481
		3482	=item EV_VERIFY
		3483
		3484	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3485	be done: If set to C<0>, no internal verification code will be compiled
		3486	in. If set to C<1>, then verification code will be compiled in, but not
		3487	called. If set to C<2>, then the internal verification code will be
		3488	called once per loop, which can slow down libev. If set to C<3>, then the
		3489	verification code will be called very frequently, which will slow down
		3490	libev considerably.
		3491
		3492	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3493	C<0>.
		3494
2989	=item EV_COMMON	3495	=item EV_COMMON
2990		3496
2991	By default, all watchers have a C<void *data> member. By redefining	3497	By default, all watchers have a C<void *data> member. By redefining
2992	this macro to a something else you can include more and other types of	3498	this macro to a something else you can include more and other types of
2993	members. You have to define it each time you include one of the files,	3499	members. You have to define it each time you include one of the files,
2994	though, and it must be identical each time.	3500	though, and it must be identical each time.
2995		3501
2996	For example, the perl EV module uses something like this:	3502	For example, the perl EV module uses something like this:
2997		3503
2998	#define EV_COMMON \	3504	#define EV_COMMON \
2999	SV *self; /* contains this struct */ \	3505	SV *self; /* contains this struct */ \
3000	SV *cb_sv, *fh /* note no trailing ";" */	3506	SV *cb_sv, *fh /* note no trailing ";" */
3001		3507
3002	=item EV_CB_DECLARE (type)	3508	=item EV_CB_DECLARE (type)
3003		3509
3004	=item EV_CB_INVOKE (watcher, revents)	3510	=item EV_CB_INVOKE (watcher, revents)
3005		3511
…		…
3010	definition and a statement, respectively. See the F<ev.h> header file for	3516	definition and a statement, respectively. See the F<ev.h> header file for
3011	their default definitions. One possible use for overriding these is to	3517	their default definitions. One possible use for overriding these is to
3012	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3518	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3013	method calls instead of plain function calls in C++.	3519	method calls instead of plain function calls in C++.
3014		3520
		3521	=back
		3522
3015	=head2 EXPORTED API SYMBOLS	3523	=head2 EXPORTED API SYMBOLS
3016		3524
3017	If you need to re-export the API (e.g. via a dll) and you need a list of	3525	If you need to re-export the API (e.g. via a DLL) and you need a list of
3018	exported symbols, you can use the provided F<Symbol.*> files which list	3526	exported symbols, you can use the provided F<Symbol.*> files which list
3019	all public symbols, one per line:	3527	all public symbols, one per line:
3020		3528
3021	Symbols.ev for libev proper	3529	Symbols.ev for libev proper
3022	Symbols.event for the libevent emulation	3530	Symbols.event for the libevent emulation
3023		3531
3024	This can also be used to rename all public symbols to avoid clashes with	3532	This can also be used to rename all public symbols to avoid clashes with
3025	multiple versions of libev linked together (which is obviously bad in	3533	multiple versions of libev linked together (which is obviously bad in
3026	itself, but sometimes it is inconvinient to avoid this).	3534	itself, but sometimes it is inconvenient to avoid this).
3027		3535
3028	A sed command like this will create wrapper C<#define>'s that you need to	3536	A sed command like this will create wrapper C<#define>'s that you need to
3029	include before including F<ev.h>:	3537	include before including F<ev.h>:
3030		3538
3031	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3539	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3048	file.	3556	file.
3049		3557
3050	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3558	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3051	that everybody includes and which overrides some configure choices:	3559	that everybody includes and which overrides some configure choices:
3052		3560
3053	#define EV_MINIMAL 1	3561	#define EV_MINIMAL 1
3054	#define EV_USE_POLL 0	3562	#define EV_USE_POLL 0
3055	#define EV_MULTIPLICITY 0	3563	#define EV_MULTIPLICITY 0
3056	#define EV_PERIODIC_ENABLE 0	3564	#define EV_PERIODIC_ENABLE 0
3057	#define EV_STAT_ENABLE 0	3565	#define EV_STAT_ENABLE 0
3058	#define EV_FORK_ENABLE 0	3566	#define EV_FORK_ENABLE 0
3059	#define EV_CONFIG_H <config.h>	3567	#define EV_CONFIG_H <config.h>
3060	#define EV_MINPRI 0	3568	#define EV_MINPRI 0
3061	#define EV_MAXPRI 0	3569	#define EV_MAXPRI 0
3062		3570
3063	#include "ev++.h"	3571	#include "ev++.h"
3064		3572
3065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3066		3574
3067	#include "ev_cpp.h"	3575	#include "ev_cpp.h"
3068	#include "ev.c"	3576	#include "ev.c"
3069		3577
		3578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3070		3579
3071	=head1 THREADS AND COROUTINES	3580	=head2 THREADS AND COROUTINES
3072		3581
3073	=head2 THREADS	3582	=head3 THREADS
3074		3583
3075	Libev itself is completely threadsafe, but it uses no locking. This	3584	All libev functions are reentrant and thread-safe unless explicitly
		3585	documented otherwise, but libev implements no locking itself. This means
3076	means that you can use as many loops as you want in parallel, as long as	3586	that you can use as many loops as you want in parallel, as long as there
3077	only one thread ever calls into one libev function with the same loop	3587	are no concurrent calls into any libev function with the same loop
3078	parameter.	3588	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3589	of course): libev guarantees that different event loops share no data
		3590	structures that need any locking.
3079		3591
3080	Or put differently: calls with different loop parameters can be done in	3592	Or to put it differently: calls with different loop parameters can be done
3081	parallel from multiple threads, calls with the same loop parameter must be	3593	concurrently from multiple threads, calls with the same loop parameter
3082	done serially (but can be done from different threads, as long as only one	3594	must be done serially (but can be done from different threads, as long as
3083	thread ever is inside a call at any point in time, e.g. by using a mutex	3595	only one thread ever is inside a call at any point in time, e.g. by using
3084	per loop).	3596	a mutex per loop).
3085		3597
3086	If you want to know which design is best for your problem, then I cannot	3598	Specifically to support threads (and signal handlers), libev implements
		3599	so-called C<ev_async> watchers, which allow some limited form of
		3600	concurrency on the same event loop, namely waking it up "from the
		3601	outside".
		3602
		3603	If you want to know which design (one loop, locking, or multiple loops
		3604	without or something else still) is best for your problem, then I cannot
3087	help you but by giving some generic advice:	3605	help you, but here is some generic advice:
3088		3606
3089	=over 4	3607	=over 4
3090		3608
3091	=item * most applications have a main thread: use the default libev loop	3609	=item * most applications have a main thread: use the default libev loop
3092	in that thread, or create a seperate thread running only the default loop.	3610	in that thread, or create a separate thread running only the default loop.
3093		3611
3094	This helps integrating other libraries or software modules that use libev	3612	This helps integrating other libraries or software modules that use libev
3095	themselves and don't care/know about threading.	3613	themselves and don't care/know about threading.
3096		3614
3097	=item * one loop per thread is usually a good model.	3615	=item * one loop per thread is usually a good model.
3098		3616
3099	Doing this is almost never wrong, sometimes a better-performance model	3617	Doing this is almost never wrong, sometimes a better-performance model
3100	exists, but it is always a good start.	3618	exists, but it is always a good start.
3101		3619
3102	=item * other models exist, such as the leader/follower pattern, where one	3620	=item * other models exist, such as the leader/follower pattern, where one
3103	loop is handed through multiple threads in a kind of round-robbin fashion.	3621	loop is handed through multiple threads in a kind of round-robin fashion.
3104		3622
3105	Chosing a model is hard - look around, learn, know that usually you cna do	3623	Choosing a model is hard - look around, learn, know that usually you can do
3106	better than you currently do :-)	3624	better than you currently do :-)
3107		3625
3108	=item * often you need to talk to some other thread which blocks in the	3626	=item * often you need to talk to some other thread which blocks in the
		3627	event loop.
		3628
3109	event loop - C<ev_async> watchers can be used to wake them up from other	3629	C<ev_async> watchers can be used to wake them up from other threads safely
3110	threads safely (or from signal contexts...).	3630	(or from signal contexts...).
		3631
		3632	An example use would be to communicate signals or other events that only
		3633	work in the default loop by registering the signal watcher with the
		3634	default loop and triggering an C<ev_async> watcher from the default loop
		3635	watcher callback into the event loop interested in the signal.
3111		3636
3112	=back	3637	=back
3113		3638
3114	=head2 COROUTINES	3639	=head3 COROUTINES
3115		3640
3116	Libev is much more accomodating to coroutines ("cooperative threads"):	3641	Libev is very accommodating to coroutines ("cooperative threads"):
3117	libev fully supports nesting calls to it's functions from different	3642	libev fully supports nesting calls to its functions from different
3118	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3643	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3119	different coroutines and switch freely between both coroutines running the	3644	different coroutines, and switch freely between both coroutines running the
3120	loop, as long as you don't confuse yourself). The only exception is that	3645	loop, as long as you don't confuse yourself). The only exception is that
3121	you must not do this from C<ev_periodic> reschedule callbacks.	3646	you must not do this from C<ev_periodic> reschedule callbacks.
3122		3647
3123	Care has been invested into making sure that libev does not keep local	3648	Care has been taken to ensure that libev does not keep local state inside
3124	state inside C<ev_loop>, and other calls do not usually allow coroutine	3649	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3125	switches.	3650	they do not call any callbacks.
3126		3651
		3652	=head2 COMPILER WARNINGS
3127		3653
3128	=head1 COMPLEXITIES	3654	Depending on your compiler and compiler settings, you might get no or a
		3655	lot of warnings when compiling libev code. Some people are apparently
		3656	scared by this.
3129		3657
3130	In this section the complexities of (many of) the algorithms used inside	3658	However, these are unavoidable for many reasons. For one, each compiler
3131	libev will be explained. For complexity discussions about backends see the	3659	has different warnings, and each user has different tastes regarding
3132	documentation for C<ev_default_init>.	3660	warning options. "Warn-free" code therefore cannot be a goal except when
		3661	targeting a specific compiler and compiler-version.
3133		3662
3134	All of the following are about amortised time: If an array needs to be	3663	Another reason is that some compiler warnings require elaborate
3135	extended, libev needs to realloc and move the whole array, but this	3664	workarounds, or other changes to the code that make it less clear and less
3136	happens asymptotically never with higher number of elements, so O(1) might	3665	maintainable.
3137	mean it might do a lengthy realloc operation in rare cases, but on average
3138	it is much faster and asymptotically approaches constant time.
3139		3666
3140	=over 4	3667	And of course, some compiler warnings are just plain stupid, or simply
		3668	wrong (because they don't actually warn about the condition their message
		3669	seems to warn about). For example, certain older gcc versions had some
		3670	warnings that resulted an extreme number of false positives. These have
		3671	been fixed, but some people still insist on making code warn-free with
		3672	such buggy versions.
3141		3673
3142	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3674	While libev is written to generate as few warnings as possible,
		3675	"warn-free" code is not a goal, and it is recommended not to build libev
		3676	with any compiler warnings enabled unless you are prepared to cope with
		3677	them (e.g. by ignoring them). Remember that warnings are just that:
		3678	warnings, not errors, or proof of bugs.
3143		3679
3144	This means that, when you have a watcher that triggers in one hour and
3145	there are 100 watchers that would trigger before that then inserting will
3146	have to skip roughly seven (C<ld 100>) of these watchers.
3147		3680
3148	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3681	=head2 VALGRIND
3149		3682
3150	That means that changing a timer costs less than removing/adding them	3683	Valgrind has a special section here because it is a popular tool that is
3151	as only the relative motion in the event queue has to be paid for.	3684	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3152		3685
3153	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3686	If you think you found a bug (memory leak, uninitialised data access etc.)
		3687	in libev, then check twice: If valgrind reports something like:
3154		3688
3155	These just add the watcher into an array or at the head of a list.	3689	==2274== definitely lost: 0 bytes in 0 blocks.
		3690	==2274== possibly lost: 0 bytes in 0 blocks.
		3691	==2274== still reachable: 256 bytes in 1 blocks.
3156		3692
3157	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3693	Then there is no memory leak, just as memory accounted to global variables
		3694	is not a memleak - the memory is still being referenced, and didn't leak.
3158		3695
3159	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3696	Similarly, under some circumstances, valgrind might report kernel bugs
		3697	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3698	although an acceptable workaround has been found here), or it might be
		3699	confused.
3160		3700
3161	These watchers are stored in lists then need to be walked to find the	3701	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3162	correct watcher to remove. The lists are usually short (you don't usually	3702	make it into some kind of religion.
3163	have many watchers waiting for the same fd or signal).
3164		3703
3165	=item Finding the next timer in each loop iteration: O(1)	3704	If you are unsure about something, feel free to contact the mailing list
		3705	with the full valgrind report and an explanation on why you think this
		3706	is a bug in libev (best check the archives, too :). However, don't be
		3707	annoyed when you get a brisk "this is no bug" answer and take the chance
		3708	of learning how to interpret valgrind properly.
3166		3709
3167	By virtue of using a binary heap, the next timer is always found at the	3710	If you need, for some reason, empty reports from valgrind for your project
3168	beginning of the storage array.	3711	I suggest using suppression lists.
3169		3712
3170	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3171		3713
3172	A change means an I/O watcher gets started or stopped, which requires	3714	=head1 PORTABILITY NOTES
3173	libev to recalculate its status (and possibly tell the kernel, depending
3174	on backend and wether C<ev_io_set> was used).
3175		3715
3176	=item Activating one watcher (putting it into the pending state): O(1)	3716	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3177
3178	=item Priority handling: O(number_of_priorities)
3179
3180	Priorities are implemented by allocating some space for each
3181	priority. When doing priority-based operations, libev usually has to
3182	linearly search all the priorities, but starting/stopping and activating
3183	watchers becomes O(1) w.r.t. priority handling.
3184
3185	=item Sending an ev_async: O(1)
3186
3187	=item Processing ev_async_send: O(number_of_async_watchers)
3188
3189	=item Processing signals: O(max_signal_number)
3190
3191	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3192	calls in the current loop iteration. Checking for async and signal events
3193	involves iterating over all running async watchers or all signal numbers.
3194
3195	=back
3196
3197
3198	=head1 Win32 platform limitations and workarounds
3199		3717
3200	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3718	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3201	requires, and its I/O model is fundamentally incompatible with the POSIX	3719	requires, and its I/O model is fundamentally incompatible with the POSIX
3202	model. Libev still offers limited functionality on this platform in	3720	model. Libev still offers limited functionality on this platform in
3203	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3721	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3204	descriptors. This only applies when using Win32 natively, not when using	3722	descriptors. This only applies when using Win32 natively, not when using
3205	e.g. cygwin.	3723	e.g. cygwin.
3206		3724
		3725	Lifting these limitations would basically require the full
		3726	re-implementation of the I/O system. If you are into these kinds of
		3727	things, then note that glib does exactly that for you in a very portable
		3728	way (note also that glib is the slowest event library known to man).
		3729
3207	There is no supported compilation method available on windows except	3730	There is no supported compilation method available on windows except
3208	embedding it into other applications.	3731	embedding it into other applications.
3209		3732
		3733	Not a libev limitation but worth mentioning: windows apparently doesn't
		3734	accept large writes: instead of resulting in a partial write, windows will
		3735	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3736	so make sure you only write small amounts into your sockets (less than a
		3737	megabyte seems safe, but this apparently depends on the amount of memory
		3738	available).
		3739
3210	Due to the many, low, and arbitrary limits on the win32 platform and the	3740	Due to the many, low, and arbitrary limits on the win32 platform and
3211	abysmal performance of winsockets, using a large number of sockets is not	3741	the abysmal performance of winsockets, using a large number of sockets
3212	recommended (and not reasonable). If your program needs to use more than	3742	is not recommended (and not reasonable). If your program needs to use
3213	a hundred or so sockets, then likely it needs to use a totally different	3743	more than a hundred or so sockets, then likely it needs to use a totally
3214	implementation for windows, as libev offers the POSIX model, which cannot	3744	different implementation for windows, as libev offers the POSIX readiness
3215	be implemented efficiently on windows (microsoft monopoly games).	3745	notification model, which cannot be implemented efficiently on windows
		3746	(Microsoft monopoly games).
		3747
		3748	A typical way to use libev under windows is to embed it (see the embedding
		3749	section for details) and use the following F<evwrap.h> header file instead
		3750	of F<ev.h>:
		3751
		3752	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3753	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3754
		3755	#include "ev.h"
		3756
		3757	And compile the following F<evwrap.c> file into your project (make sure
		3758	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3759
		3760	#include "evwrap.h"
		3761	#include "ev.c"
3216		3762
3217	=over 4	3763	=over 4
3218		3764
3219	=item The winsocket select function	3765	=item The winsocket select function
3220		3766
3221	The winsocket C<select> function doesn't follow POSIX in that it requires	3767	The winsocket C<select> function doesn't follow POSIX in that it
3222	socket I<handles> and not socket I<file descriptors>. This makes select	3768	requires socket I<handles> and not socket I<file descriptors> (it is
3223	very inefficient, and also requires a mapping from file descriptors	3769	also extremely buggy). This makes select very inefficient, and also
3224	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3770	requires a mapping from file descriptors to socket handles (the Microsoft
3225	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3771	C runtime provides the function C<_open_osfhandle> for this). See the
3226	symbols for more info.	3772	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3773	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3227		3774
3228	The configuration for a "naked" win32 using the microsoft runtime	3775	The configuration for a "naked" win32 using the Microsoft runtime
3229	libraries and raw winsocket select is:	3776	libraries and raw winsocket select is:
3230		3777
3231	#define EV_USE_SELECT 1	3778	#define EV_USE_SELECT 1
3232	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3779	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3233		3780
3234	Note that winsockets handling of fd sets is O(n), so you can easily get a	3781	Note that winsockets handling of fd sets is O(n), so you can easily get a
3235	complexity in the O(n²) range when using win32.	3782	complexity in the O(n²) range when using win32.
3236		3783
3237	=item Limited number of file descriptors	3784	=item Limited number of file descriptors
3238		3785
3239	Windows has numerous arbitrary (and low) limits on things. Early versions	3786	Windows has numerous arbitrary (and low) limits on things.
3240	of winsocket's select only supported waiting for a max. of C<64> handles	3787
		3788	Early versions of winsocket's select only supported waiting for a maximum
3241	(probably owning to the fact that all windows kernels can only wait for	3789	of C<64> handles (probably owning to the fact that all windows kernels
3242	C<64> things at the same time internally; microsoft recommends spawning a	3790	can only wait for C<64> things at the same time internally; Microsoft
3243	chain of threads and wait for 63 handles and the previous thread in each).	3791	recommends spawning a chain of threads and wait for 63 handles and the
		3792	previous thread in each. Great).
3244		3793
3245	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3794	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3246	to some high number (e.g. C<2048>) before compiling the winsocket select	3795	to some high number (e.g. C<2048>) before compiling the winsocket select
3247	call (which might be in libev or elsewhere, for example, perl does its own	3796	call (which might be in libev or elsewhere, for example, perl does its own
3248	select emulation on windows).	3797	select emulation on windows).
3249		3798
3250	Another limit is the number of file descriptors in the microsoft runtime	3799	Another limit is the number of file descriptors in the Microsoft runtime
3251	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3800	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3252	or something like this inside microsoft). You can increase this by calling	3801	or something like this inside Microsoft). You can increase this by calling
3253	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3802	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3254	arbitrary limit), but is broken in many versions of the microsoft runtime	3803	arbitrary limit), but is broken in many versions of the Microsoft runtime
3255	libraries.	3804	libraries.
3256		3805
3257	This might get you to about C<512> or C<2048> sockets (depending on	3806	This might get you to about C<512> or C<2048> sockets (depending on
3258	windows version and/or the phase of the moon). To get more, you need to	3807	windows version and/or the phase of the moon). To get more, you need to
3259	wrap all I/O functions and provide your own fd management, but the cost of	3808	wrap all I/O functions and provide your own fd management, but the cost of
3260	calling select (O(n²)) will likely make this unworkable.	3809	calling select (O(n²)) will likely make this unworkable.
3261		3810
3262	=back	3811	=back
3263		3812
		3813	=head2 PORTABILITY REQUIREMENTS
		3814
		3815	In addition to a working ISO-C implementation and of course the
		3816	backend-specific APIs, libev relies on a few additional extensions:
		3817
		3818	=over 4
		3819
		3820	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3821	calling conventions regardless of C<ev_watcher_type *>.
		3822
		3823	Libev assumes not only that all watcher pointers have the same internal
		3824	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3825	assumes that the same (machine) code can be used to call any watcher
		3826	callback: The watcher callbacks have different type signatures, but libev
		3827	calls them using an C<ev_watcher *> internally.
		3828
		3829	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3830
		3831	The type C<sig_atomic_t volatile> (or whatever is defined as
		3832	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3833	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3834	believed to be sufficiently portable.
		3835
		3836	=item C<sigprocmask> must work in a threaded environment
		3837
		3838	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3839	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3840	pthread implementations will either allow C<sigprocmask> in the "main
		3841	thread" or will block signals process-wide, both behaviours would
		3842	be compatible with libev. Interaction between C<sigprocmask> and
		3843	C<pthread_sigmask> could complicate things, however.
		3844
		3845	The most portable way to handle signals is to block signals in all threads
		3846	except the initial one, and run the default loop in the initial thread as
		3847	well.
		3848
		3849	=item C<long> must be large enough for common memory allocation sizes
		3850
		3851	To improve portability and simplify its API, libev uses C<long> internally
		3852	instead of C<size_t> when allocating its data structures. On non-POSIX
		3853	systems (Microsoft...) this might be unexpectedly low, but is still at
		3854	least 31 bits everywhere, which is enough for hundreds of millions of
		3855	watchers.
		3856
		3857	=item C<double> must hold a time value in seconds with enough accuracy
		3858
		3859	The type C<double> is used to represent timestamps. It is required to
		3860	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3861	enough for at least into the year 4000. This requirement is fulfilled by
		3862	implementations implementing IEEE 754 (basically all existing ones).
		3863
		3864	=back
		3865
		3866	If you know of other additional requirements drop me a note.
		3867
		3868
		3869	=head1 ALGORITHMIC COMPLEXITIES
		3870
		3871	In this section the complexities of (many of) the algorithms used inside
		3872	libev will be documented. For complexity discussions about backends see
		3873	the documentation for C<ev_default_init>.
		3874
		3875	All of the following are about amortised time: If an array needs to be
		3876	extended, libev needs to realloc and move the whole array, but this
		3877	happens asymptotically rarer with higher number of elements, so O(1) might
		3878	mean that libev does a lengthy realloc operation in rare cases, but on
		3879	average it is much faster and asymptotically approaches constant time.
		3880
		3881	=over 4
		3882
		3883	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3884
		3885	This means that, when you have a watcher that triggers in one hour and
		3886	there are 100 watchers that would trigger before that, then inserting will
		3887	have to skip roughly seven (C<ld 100>) of these watchers.
		3888
		3889	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3890
		3891	That means that changing a timer costs less than removing/adding them,
		3892	as only the relative motion in the event queue has to be paid for.
		3893
		3894	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3895
		3896	These just add the watcher into an array or at the head of a list.
		3897
		3898	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3899
		3900	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3901
		3902	These watchers are stored in lists, so they need to be walked to find the
		3903	correct watcher to remove. The lists are usually short (you don't usually
		3904	have many watchers waiting for the same fd or signal: one is typical, two
		3905	is rare).
		3906
		3907	=item Finding the next timer in each loop iteration: O(1)
		3908
		3909	By virtue of using a binary or 4-heap, the next timer is always found at a
		3910	fixed position in the storage array.
		3911
		3912	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3913
		3914	A change means an I/O watcher gets started or stopped, which requires
		3915	libev to recalculate its status (and possibly tell the kernel, depending
		3916	on backend and whether C<ev_io_set> was used).
		3917
		3918	=item Activating one watcher (putting it into the pending state): O(1)
		3919
		3920	=item Priority handling: O(number_of_priorities)
		3921
		3922	Priorities are implemented by allocating some space for each
		3923	priority. When doing priority-based operations, libev usually has to
		3924	linearly search all the priorities, but starting/stopping and activating
		3925	watchers becomes O(1) with respect to priority handling.
		3926
		3927	=item Sending an ev_async: O(1)
		3928
		3929	=item Processing ev_async_send: O(number_of_async_watchers)
		3930
		3931	=item Processing signals: O(max_signal_number)
		3932
		3933	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3934	calls in the current loop iteration. Checking for async and signal events
		3935	involves iterating over all running async watchers or all signal numbers.
		3936
		3937	=back
		3938
3264		3939
3265	=head1 AUTHOR	3940	=head1 AUTHOR
3266		3941
3267	Marc Lehmann <libev@schmorp.de>.	3942	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3268		3943

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