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Revision 1.83 by root, Wed Dec 12 17:55:31 2007 UTC vs.
Revision 1.177 by root, Mon Sep 8 17:27:42 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
104		142
105	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
106		144
107	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
108	library in any way.	146	library in any way.
…		…
112	=item ev_tstamp ev_time ()	150	=item ev_tstamp ev_time ()
113		151
114	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	154	you actually want to know.
		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	Sleep for the given interval: The current thread will be blocked until
		159	either it is interrupted or the given time interval has passed. Basically
		160	this is a sub-second-resolution C<sleep ()>.
117		161
118	=item int ev_version_major ()	162	=item int ev_version_major ()
119		163
120	=item int ev_version_minor ()	164	=item int ev_version_minor ()
121		165
…		…
134	not a problem.	178	not a problem.
135		179
136	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
137	version.	181	version.
138		182
139	assert (("libev version mismatch",	183	assert (("libev version mismatch",
140	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
141	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
142		186
143	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
144		188
145	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
146	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
148	a description of the set values.	192	a description of the set values.
149		193
150	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
151	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
152		196
153	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
154	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
155		199
156	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
157		201
158	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
159	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
160	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
161	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
162	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
163	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
164		208
165	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
166		210
…		…
173	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
174		218
175	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
176		220
177	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
178	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
179	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
180	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
181	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
182	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
183		230
184	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
185	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
186	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
187		234
188	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
189	retries).	236	retries (example requires a standards-compliant C<realloc>).
190		237
191	static void *	238	static void *
192	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
193	{	240	{
194	for (;;)	241	for (;;)
…		…
205	...	252	...
206	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
207		254
208	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
209		256
210	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
211	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
212	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
213	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
214	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
215	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
216	(such as abort).	263	(such as abort).
217		264
218	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
232	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
233		280
234	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
235	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
236	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
237
238	If you use threads, a common model is to run the default event loop
239	in your main thread (or in a separate thread) and for each thread you
240	create, you also create another event loop. Libev itself does no locking
241	whatsoever, so if you mix calls to the same event loop in different
242	threads, make sure you lock (this is usually a bad idea, though, even if
243	done correctly, because it's hideous and inefficient).
244		284
245	=over 4	285	=over 4
246		286
247	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
248		288
…		…
252	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
253		293
254	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
255	function.	295	function.
256		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
257	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
258	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
259		310
260	The following flags are supported:	311	The following flags are supported:
261		312
…		…
266	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
267	thing, believe me).	318	thing, believe me).
268		319
269	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
270		321
271	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
272	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
274	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
275	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
276	around bugs.	327	around bugs.
…		…
282	enabling this flag.	333	enabling this flag.
283		334
284	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
285	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
286	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
287	Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
288	without a syscall and thus I<very> fast, but my Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
289	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
290		341
291	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
292	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
293	flag.	344	flag.
294		345
295	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
296	environment variable.	347	environment variable.
297		348
298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
299		350
300	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
301	libev tries to roll its own fd_set with no limits on the number of fds,	352	libev tries to roll its own fd_set with no limits on the number of fds,
302	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
303	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
304	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
305		363
306	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
307		365
308	And this is your standard poll(2) backend. It's more complicated than	366	And this is your standard poll(2) backend. It's more complicated
309	select, but handles sparse fds better and has no artificial limit on the	367	than select, but handles sparse fds better and has no artificial
310	number of fds you can use (except it will slow down considerably with a	368	limit on the number of fds you can use (except it will slow down
311	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	369	considerably with a lot of inactive fds). It scales similarly to select,
		370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		371	performance tips.
312		372
313	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
314		374
315	For few fds, this backend is a bit little slower than poll and select,	375	For few fds, this backend is a bit little slower than poll and select,
316	but it scales phenomenally better. While poll and select usually scale like	376	but it scales phenomenally better. While poll and select usually scale
317	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	377	like O(total_fds) where n is the total number of fds (or the highest fd),
318	either O(1) or O(active_fds).	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
		379	of shortcomings, such as silently dropping events in some hard-to-detect
		380	cases and requiring a system call per fd change, no fork support and bad
		381	support for dup.
319		382
320	While stopping and starting an I/O watcher in the same iteration will	383	While stopping, setting and starting an I/O watcher in the same iteration
321	result in some caching, there is still a syscall per such incident	384	will result in some caching, there is still a system call per such incident
322	(because the fd could point to a different file description now), so its	385	(because the fd could point to a different file description now), so its
323	best to avoid that. Also, dup()ed file descriptors might not work very	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
324	well if you register events for both fds.	387	very well if you register events for both fds.
325		388
326	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
327	need to use non-blocking I/O or other means to avoid blocking when no data	390	need to use non-blocking I/O or other means to avoid blocking when no data
328	(or space) is available.	391	(or space) is available.
329		392
		393	Best performance from this backend is achieved by not unregistering all
		394	watchers for a file descriptor until it has been closed, if possible, i.e.
		395	keep at least one watcher active per fd at all times.
		396
		397	While nominally embeddable in other event loops, this feature is broken in
		398	all kernel versions tested so far.
		399
330	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
331		401
332	Kqueue deserves special mention, as at the time of this writing, it	402	Kqueue deserves special mention, as at the time of this writing, it
333	was broken on all BSDs except NetBSD (usually it doesn't work with	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
334	anything but sockets and pipes, except on Darwin, where of course its	404	with anything but sockets and pipes, except on Darwin, where of course
335	completely useless). For this reason its not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
336	unless you explicitly specify it explicitly in the flags (i.e. using	406	unless you explicitly specify it explicitly in the flags (i.e. using
337	C<EVBACKEND_KQUEUE>).	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		408	system like NetBSD.
		409
		410	You still can embed kqueue into a normal poll or select backend and use it
		411	only for sockets (after having made sure that sockets work with kqueue on
		412	the target platform). See C<ev_embed> watchers for more info.
338		413
339	It scales in the same way as the epoll backend, but the interface to the	414	It scales in the same way as the epoll backend, but the interface to the
340	kernel is more efficient (which says nothing about its actual speed, of	415	kernel is more efficient (which says nothing about its actual speed, of
341	course). While starting and stopping an I/O watcher does not cause an	416	course). While stopping, setting and starting an I/O watcher does never
342	extra syscall as with epoll, it still adds up to four event changes per	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
343	incident, so its best to avoid that.	418	two event changes per incident, support for C<fork ()> is very bad and it
		419	drops fds silently in similarly hard-to-detect cases.
		420
		421	This backend usually performs well under most conditions.
		422
		423	While nominally embeddable in other event loops, this doesn't work
		424	everywhere, so you might need to test for this. And since it is broken
		425	almost everywhere, you should only use it when you have a lot of sockets
		426	(for which it usually works), by embedding it into another event loop
		427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		428	sockets.
344		429
345	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
346		431
347	This is not implemented yet (and might never be).	432	This is not implemented yet (and might never be, unless you send me an
		433	implementation). According to reports, C</dev/poll> only supports sockets
		434	and is not embeddable, which would limit the usefulness of this backend
		435	immensely.
348		436
349	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
350		438
351	This uses the Solaris 10 port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
352	it's really slow, but it still scales very well (O(active_fds)).	440	it's really slow, but it still scales very well (O(active_fds)).
353		441
354	Please note that solaris ports can result in a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
355	notifications, so you need to use non-blocking I/O or other means to avoid	443	notifications, so you need to use non-blocking I/O or other means to avoid
356	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
		445
		446	While this backend scales well, it requires one system call per active
		447	file descriptor per loop iteration. For small and medium numbers of file
		448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		449	might perform better.
		450
		451	On the positive side, ignoring the spurious readiness notifications, this
		452	backend actually performed to specification in all tests and is fully
		453	embeddable, which is a rare feat among the OS-specific backends.
357		454
358	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
359		456
360	Try all backends (even potentially broken ones that wouldn't be tried	457	Try all backends (even potentially broken ones that wouldn't be tried
361	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
362	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
363		460
		461	It is definitely not recommended to use this flag.
		462
364	=back	463	=back
365		464
366	If one or more of these are ored into the flags value, then only these	465	If one or more of these are or'ed into the flags value, then only these
367	backends will be tried (in the reverse order as given here). If none are	466	backends will be tried (in the reverse order as listed here). If none are
368	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
369	order of their flag values :)
370		468
371	The most typical usage is like this:	469	The most typical usage is like this:
372		470
373	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
374	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
375		473
376	Restrict libev to the select and poll backends, and do not allow	474	Restrict libev to the select and poll backends, and do not allow
377	environment settings to be taken into account:	475	environment settings to be taken into account:
378		476
379	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
380		478
381	Use whatever libev has to offer, but make sure that kqueue is used if	479	Use whatever libev has to offer, but make sure that kqueue is used if
382	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
383	event loop and only if you know the OS supports your types of fds):	481	event loop and only if you know the OS supports your types of fds):
384		482
385	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
386		484
387	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
388		486
389	Similar to C<ev_default_loop>, but always creates a new event loop that is	487	Similar to C<ev_default_loop>, but always creates a new event loop that is
390	always distinct from the default loop. Unlike the default loop, it cannot	488	always distinct from the default loop. Unlike the default loop, it cannot
391	handle signal and child watchers, and attempts to do so will be greeted by	489	handle signal and child watchers, and attempts to do so will be greeted by
392	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
393		491
		492	Note that this function I<is> thread-safe, and the recommended way to use
		493	libev with threads is indeed to create one loop per thread, and using the
		494	default loop in the "main" or "initial" thread.
		495
394	Example: Try to create a event loop that uses epoll and nothing else.	496	Example: Try to create a event loop that uses epoll and nothing else.
395		497
396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
397	if (!epoller)	499	if (!epoller)
398	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
399		501
400	=item ev_default_destroy ()	502	=item ev_default_destroy ()
401		503
402	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
403	etc.). None of the active event watchers will be stopped in the normal	505	etc.). None of the active event watchers will be stopped in the normal
404	sense, so e.g. C<ev_is_active> might still return true. It is your	506	sense, so e.g. C<ev_is_active> might still return true. It is your
405	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
406	calling this function, or cope with the fact afterwards (which is usually	508	calling this function, or cope with the fact afterwards (which is usually
407	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
408	for example).	510	for example).
		511
		512	Note that certain global state, such as signal state, will not be freed by
		513	this function, and related watchers (such as signal and child watchers)
		514	would need to be stopped manually.
		515
		516	In general it is not advisable to call this function except in the
		517	rare occasion where you really need to free e.g. the signal handling
		518	pipe fds. If you need dynamically allocated loops it is better to use
		519	C<ev_loop_new> and C<ev_loop_destroy>).
409		520
410	=item ev_loop_destroy (loop)	521	=item ev_loop_destroy (loop)
411		522
412	Like C<ev_default_destroy>, but destroys an event loop created by an	523	Like C<ev_default_destroy>, but destroys an event loop created by an
413	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
414		525
415	=item ev_default_fork ()	526	=item ev_default_fork ()
416		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
417	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
418	one. Despite the name, you can call it anytime, but it makes most sense	530	name, you can call it anytime, but it makes most sense after forking, in
419	after forking, in either the parent or child process (or both, but that	531	the child process (or both child and parent, but that again makes little
420	again makes little sense).	532	sense). You I<must> call it in the child before using any of the libev
		533	functions, and it will only take effect at the next C<ev_loop> iteration.
421		534
422	You I<must> call this function in the child process after forking if and	535	On the other hand, you only need to call this function in the child
423	only if you want to use the event library in both processes. If you just	536	process if and only if you want to use the event library in the child. If
424	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
425		538
426	The function itself is quite fast and it's usually not a problem to call	539	The function itself is quite fast and it's usually not a problem to call
427	it just in case after a fork. To make this easy, the function will fit in	540	it just in case after a fork. To make this easy, the function will fit in
428	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
429		542
430	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
431		544
432	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
433	without calling this function, so if you force one of those backends you
434	do not need to care.
435
436	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
437		546
438	Like C<ev_default_fork>, but acts on an event loop created by	547	Like C<ev_default_fork>, but acts on an event loop created by
439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
440	after fork, and how you do this is entirely your own problem.	549	after fork, and how you do this is entirely your own problem.
		550
		551	=item int ev_is_default_loop (loop)
		552
		553	Returns true when the given loop actually is the default loop, false otherwise.
441		554
442	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
443		556
444	Returns the count of loop iterations for the loop, which is identical to	557	Returns the count of loop iterations for the loop, which is identical to
445	the number of times libev did poll for new events. It starts at C<0> and	558	the number of times libev did poll for new events. It starts at C<0> and
…		…
458		571
459	Returns the current "event loop time", which is the time the event loop	572	Returns the current "event loop time", which is the time the event loop
460	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
461	change as long as callbacks are being processed, and this is also the base	574	change as long as callbacks are being processed, and this is also the base
462	time used for relative timers. You can treat it as the timestamp of the	575	time used for relative timers. You can treat it as the timestamp of the
463	event occuring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
		577
		578	=item ev_now_update (loop)
		579
		580	Establishes the current time by querying the kernel, updating the time
		581	returned by C<ev_now ()> in the progress. This is a costly operation and
		582	is usually done automatically within C<ev_loop ()>.
		583
		584	This function is rarely useful, but when some event callback runs for a
		585	very long time without entering the event loop, updating libev's idea of
		586	the current time is a good idea.
		587
		588	See also "The special problem of time updates" in the C<ev_timer> section.
464		589
465	=item ev_loop (loop, int flags)	590	=item ev_loop (loop, int flags)
466		591
467	Finally, this is it, the event handler. This function usually is called	592	Finally, this is it, the event handler. This function usually is called
468	after you initialised all your watchers and you want to start handling	593	after you initialised all your watchers and you want to start handling
…		…
480	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
481	those events and any outstanding ones, but will not block your process in	606	those events and any outstanding ones, but will not block your process in
482	case there are no events and will return after one iteration of the loop.	607	case there are no events and will return after one iteration of the loop.
483		608
484	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
485	neccessary) and will handle those and any outstanding ones. It will block	610	necessary) and will handle those and any outstanding ones. It will block
486	your process until at least one new event arrives, and will return after	611	your process until at least one new event arrives, and will return after
487	one iteration of the loop. This is useful if you are waiting for some	612	one iteration of the loop. This is useful if you are waiting for some
488	external event in conjunction with something not expressible using other	613	external event in conjunction with something not expressible using other
489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	614	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
490	usually a better approach for this kind of thing.	615	usually a better approach for this kind of thing.
491		616
492	Here are the gory details of what C<ev_loop> does:	617	Here are the gory details of what C<ev_loop> does:
493		618
494	- Before the first iteration, call any pending watchers.	619	- Before the first iteration, call any pending watchers.
495	* If there are no active watchers (reference count is zero), return.	620	* If EVFLAG_FORKCHECK was used, check for a fork.
496	- Queue all prepare watchers and then call all outstanding watchers.	621	- If a fork was detected (by any means), queue and call all fork watchers.
		622	- Queue and call all prepare watchers.
497	- If we have been forked, recreate the kernel state.	623	- If we have been forked, detach and recreate the kernel state
		624	as to not disturb the other process.
498	- Update the kernel state with all outstanding changes.	625	- Update the kernel state with all outstanding changes.
499	- Update the "event loop time".	626	- Update the "event loop time" (ev_now ()).
500	- Calculate for how long to block.	627	- Calculate for how long to sleep or block, if at all
		628	(active idle watchers, EVLOOP_NONBLOCK or not having
		629	any active watchers at all will result in not sleeping).
		630	- Sleep if the I/O and timer collect interval say so.
501	- Block the process, waiting for any events.	631	- Block the process, waiting for any events.
502	- Queue all outstanding I/O (fd) events.	632	- Queue all outstanding I/O (fd) events.
503	- Update the "event loop time" and do time jump handling.	633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
504	- Queue all outstanding timers.	634	- Queue all outstanding timers.
505	- Queue all outstanding periodics.	635	- Queue all outstanding periodics.
506	- If no events are pending now, queue all idle watchers.	636	- Unless any events are pending now, queue all idle watchers.
507	- Queue all check watchers.	637	- Queue all check watchers.
508	- Call all queued watchers in reverse order (i.e. check watchers first).	638	- Call all queued watchers in reverse order (i.e. check watchers first).
509	Signals and child watchers are implemented as I/O watchers, and will	639	Signals and child watchers are implemented as I/O watchers, and will
510	be handled here by queueing them when their watcher gets executed.	640	be handled here by queueing them when their watcher gets executed.
511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	641	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
512	were used, return, otherwise continue with step *.	642	were used, or there are no active watchers, return, otherwise
		643	continue with step *.
513		644
514	Example: Queue some jobs and then loop until no events are outsanding	645	Example: Queue some jobs and then loop until no events are outstanding
515	anymore.	646	anymore.
516		647
517	... queue jobs here, make sure they register event watchers as long	648	... queue jobs here, make sure they register event watchers as long
518	... as they still have work to do (even an idle watcher will do..)	649	... as they still have work to do (even an idle watcher will do..)
519	ev_loop (my_loop, 0);	650	ev_loop (my_loop, 0);
520	... jobs done. yeah!	651	... jobs done or somebody called unloop. yeah!
521		652
522	=item ev_unloop (loop, how)	653	=item ev_unloop (loop, how)
523		654
524	Can be used to make a call to C<ev_loop> return early (but only after it	655	Can be used to make a call to C<ev_loop> return early (but only after it
525	has processed all outstanding events). The C<how> argument must be either	656	has processed all outstanding events). The C<how> argument must be either
526	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	657	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
527	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	658	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		659
		660	This "unloop state" will be cleared when entering C<ev_loop> again.
528		661
529	=item ev_ref (loop)	662	=item ev_ref (loop)
530		663
531	=item ev_unref (loop)	664	=item ev_unref (loop)
532		665
…		…
537	returning, ev_unref() after starting, and ev_ref() before stopping it. For	670	returning, ev_unref() after starting, and ev_ref() before stopping it. For
538	example, libev itself uses this for its internal signal pipe: It is not	671	example, libev itself uses this for its internal signal pipe: It is not
539	visible to the libev user and should not keep C<ev_loop> from exiting if	672	visible to the libev user and should not keep C<ev_loop> from exiting if
540	no event watchers registered by it are active. It is also an excellent	673	no event watchers registered by it are active. It is also an excellent
541	way to do this for generic recurring timers or from within third-party	674	way to do this for generic recurring timers or from within third-party
542	libraries. Just remember to I<unref after start> and I<ref before stop>.	675	libraries. Just remember to I<unref after start> and I<ref before stop>
		676	(but only if the watcher wasn't active before, or was active before,
		677	respectively).
543		678
544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
545	running when nothing else is active.	680	running when nothing else is active.
546		681
547	struct ev_signal exitsig;	682	struct ev_signal exitsig;
548	ev_signal_init (&exitsig, sig_cb, SIGINT);	683	ev_signal_init (&exitsig, sig_cb, SIGINT);
549	ev_signal_start (loop, &exitsig);	684	ev_signal_start (loop, &exitsig);
550	evf_unref (loop);	685	evf_unref (loop);
551		686
552	Example: For some weird reason, unregister the above signal handler again.	687	Example: For some weird reason, unregister the above signal handler again.
553		688
554	ev_ref (loop);	689	ev_ref (loop);
555	ev_signal_stop (loop, &exitsig);	690	ev_signal_stop (loop, &exitsig);
		691
		692	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		693
		694	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		695
		696	These advanced functions influence the time that libev will spend waiting
		697	for events. Both time intervals are by default C<0>, meaning that libev
		698	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		699	latency.
		700
		701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		702	allows libev to delay invocation of I/O and timer/periodic callbacks
		703	to increase efficiency of loop iterations (or to increase power-saving
		704	opportunities).
		705
		706	The background is that sometimes your program runs just fast enough to
		707	handle one (or very few) event(s) per loop iteration. While this makes
		708	the program responsive, it also wastes a lot of CPU time to poll for new
		709	events, especially with backends like C<select ()> which have a high
		710	overhead for the actual polling but can deliver many events at once.
		711
		712	By setting a higher I<io collect interval> you allow libev to spend more
		713	time collecting I/O events, so you can handle more events per iteration,
		714	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		715	C<ev_timer>) will be not affected. Setting this to a non-null value will
		716	introduce an additional C<ev_sleep ()> call into most loop iterations.
		717
		718	Likewise, by setting a higher I<timeout collect interval> you allow libev
		719	to spend more time collecting timeouts, at the expense of increased
		720	latency (the watcher callback will be called later). C<ev_io> watchers
		721	will not be affected. Setting this to a non-null value will not introduce
		722	any overhead in libev.
		723
		724	Many (busy) programs can usually benefit by setting the I/O collect
		725	interval to a value near C<0.1> or so, which is often enough for
		726	interactive servers (of course not for games), likewise for timeouts. It
		727	usually doesn't make much sense to set it to a lower value than C<0.01>,
		728	as this approaches the timing granularity of most systems.
		729
		730	Setting the I<timeout collect interval> can improve the opportunity for
		731	saving power, as the program will "bundle" timer callback invocations that
		732	are "near" in time together, by delaying some, thus reducing the number of
		733	times the process sleeps and wakes up again. Another useful technique to
		734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		735	they fire on, say, one-second boundaries only.
		736
		737	=item ev_loop_verify (loop)
		738
		739	This function only does something when C<EV_VERIFY> support has been
		740	compiled in. It tries to go through all internal structures and checks
		741	them for validity. If anything is found to be inconsistent, it will print
		742	an error message to standard error and call C<abort ()>.
		743
		744	This can be used to catch bugs inside libev itself: under normal
		745	circumstances, this function will never abort as of course libev keeps its
		746	data structures consistent.
556		747
557	=back	748	=back
558		749
559		750
560	=head1 ANATOMY OF A WATCHER	751	=head1 ANATOMY OF A WATCHER
561		752
562	A watcher is a structure that you create and register to record your	753	A watcher is a structure that you create and register to record your
563	interest in some event. For instance, if you want to wait for STDIN to	754	interest in some event. For instance, if you want to wait for STDIN to
564	become readable, you would create an C<ev_io> watcher for that:	755	become readable, you would create an C<ev_io> watcher for that:
565		756
566	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
567	{	758	{
568	ev_io_stop (w);	759	ev_io_stop (w);
569	ev_unloop (loop, EVUNLOOP_ALL);	760	ev_unloop (loop, EVUNLOOP_ALL);
570	}	761	}
571		762
572	struct ev_loop *loop = ev_default_loop (0);	763	struct ev_loop *loop = ev_default_loop (0);
573	struct ev_io stdin_watcher;	764	struct ev_io stdin_watcher;
574	ev_init (&stdin_watcher, my_cb);	765	ev_init (&stdin_watcher, my_cb);
575	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
576	ev_io_start (loop, &stdin_watcher);	767	ev_io_start (loop, &stdin_watcher);
577	ev_loop (loop, 0);	768	ev_loop (loop, 0);
578		769
579	As you can see, you are responsible for allocating the memory for your	770	As you can see, you are responsible for allocating the memory for your
580	watcher structures (and it is usually a bad idea to do this on the stack,	771	watcher structures (and it is usually a bad idea to do this on the stack,
581	although this can sometimes be quite valid).	772	although this can sometimes be quite valid).
582		773
583	Each watcher structure must be initialised by a call to C<ev_init	774	Each watcher structure must be initialised by a call to C<ev_init
584	(watcher *, callback)>, which expects a callback to be provided. This	775	(watcher *, callback)>, which expects a callback to be provided. This
585	callback gets invoked each time the event occurs (or, in the case of io	776	callback gets invoked each time the event occurs (or, in the case of I/O
586	watchers, each time the event loop detects that the file descriptor given	777	watchers, each time the event loop detects that the file descriptor given
587	is readable and/or writable).	778	is readable and/or writable).
588		779
589	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
590	with arguments specific to this watcher type. There is also a macro	781	with arguments specific to this watcher type. There is also a macro
…		…
660	=item C<EV_FORK>	851	=item C<EV_FORK>
661		852
662	The event loop has been resumed in the child process after fork (see	853	The event loop has been resumed in the child process after fork (see
663	C<ev_fork>).	854	C<ev_fork>).
664		855
		856	=item C<EV_ASYNC>
		857
		858	The given async watcher has been asynchronously notified (see C<ev_async>).
		859
665	=item C<EV_ERROR>	860	=item C<EV_ERROR>
666		861
667	An unspecified error has occured, the watcher has been stopped. This might	862	An unspecified error has occurred, the watcher has been stopped. This might
668	happen because the watcher could not be properly started because libev	863	happen because the watcher could not be properly started because libev
669	ran out of memory, a file descriptor was found to be closed or any other	864	ran out of memory, a file descriptor was found to be closed or any other
670	problem. You best act on it by reporting the problem and somehow coping	865	problem. You best act on it by reporting the problem and somehow coping
671	with the watcher being stopped.	866	with the watcher being stopped.
672		867
673	Libev will usually signal a few "dummy" events together with an error,	868	Libev will usually signal a few "dummy" events together with an error,
674	for example it might indicate that a fd is readable or writable, and if	869	for example it might indicate that a fd is readable or writable, and if
675	your callbacks is well-written it can just attempt the operation and cope	870	your callbacks is well-written it can just attempt the operation and cope
676	with the error from read() or write(). This will not work in multithreaded	871	with the error from read() or write(). This will not work in multi-threaded
677	programs, though, so beware.	872	programs, though, so beware.
678		873
679	=back	874	=back
680		875
681	=head2 GENERIC WATCHER FUNCTIONS	876	=head2 GENERIC WATCHER FUNCTIONS
…		…
711	Although some watcher types do not have type-specific arguments	906	Although some watcher types do not have type-specific arguments
712	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
713		908
714	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
715		910
716	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
717	calls into a single call. This is the most convinient method to initialise	912	calls into a single call. This is the most convenient method to initialise
718	a watcher. The same limitations apply, of course.	913	a watcher. The same limitations apply, of course.
719		914
720	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
721		916
722	Starts (activates) the given watcher. Only active watchers will receive	917	Starts (activates) the given watcher. Only active watchers will receive
…		…
805	to associate arbitrary data with your watcher. If you need more data and	1000	to associate arbitrary data with your watcher. If you need more data and
806	don't want to allocate memory and store a pointer to it in that data	1001	don't want to allocate memory and store a pointer to it in that data
807	member, you can also "subclass" the watcher type and provide your own	1002	member, you can also "subclass" the watcher type and provide your own
808	data:	1003	data:
809		1004
810	struct my_io	1005	struct my_io
811	{	1006	{
812	struct ev_io io;	1007	struct ev_io io;
813	int otherfd;	1008	int otherfd;
814	void *somedata;	1009	void *somedata;
815	struct whatever *mostinteresting;	1010	struct whatever *mostinteresting;
816	}	1011	}
817		1012
818	And since your callback will be called with a pointer to the watcher, you	1013	And since your callback will be called with a pointer to the watcher, you
819	can cast it back to your own type:	1014	can cast it back to your own type:
820		1015
821	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1016	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
822	{	1017	{
823	struct my_io *w = (struct my_io *)w_;	1018	struct my_io *w = (struct my_io *)w_;
824	...	1019	...
825	}	1020	}
826		1021
827	More interesting and less C-conformant ways of casting your callback type	1022	More interesting and less C-conformant ways of casting your callback type
828	instead have been omitted.	1023	instead have been omitted.
829		1024
830	Another common scenario is having some data structure with multiple	1025	Another common scenario is having some data structure with multiple
831	watchers:	1026	watchers:
832		1027
833	struct my_biggy	1028	struct my_biggy
834	{	1029	{
835	int some_data;	1030	int some_data;
836	ev_timer t1;	1031	ev_timer t1;
837	ev_timer t2;	1032	ev_timer t2;
838	}	1033	}
839		1034
840	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1035	In this case getting the pointer to C<my_biggy> is a bit more complicated,
841	you need to use C<offsetof>:	1036	you need to use C<offsetof>:
842		1037
843	#include <stddef.h>	1038	#include <stddef.h>
844		1039
845	static void	1040	static void
846	t1_cb (EV_P_ struct ev_timer *w, int revents)	1041	t1_cb (EV_P_ struct ev_timer *w, int revents)
847	{	1042	{
848	struct my_biggy big = (struct my_biggy *	1043	struct my_biggy big = (struct my_biggy *
849	(((char *)w) - offsetof (struct my_biggy, t1));	1044	(((char *)w) - offsetof (struct my_biggy, t1));
850	}	1045	}
851		1046
852	static void	1047	static void
853	t2_cb (EV_P_ struct ev_timer *w, int revents)	1048	t2_cb (EV_P_ struct ev_timer *w, int revents)
854	{	1049	{
855	struct my_biggy big = (struct my_biggy *	1050	struct my_biggy big = (struct my_biggy *
856	(((char *)w) - offsetof (struct my_biggy, t2));	1051	(((char *)w) - offsetof (struct my_biggy, t2));
857	}	1052	}
858		1053
859		1054
860	=head1 WATCHER TYPES	1055	=head1 WATCHER TYPES
861		1056
862	This section describes each watcher in detail, but will not repeat	1057	This section describes each watcher in detail, but will not repeat
…		…
886	In general you can register as many read and/or write event watchers per	1081	In general you can register as many read and/or write event watchers per
887	fd as you want (as long as you don't confuse yourself). Setting all file	1082	fd as you want (as long as you don't confuse yourself). Setting all file
888	descriptors to non-blocking mode is also usually a good idea (but not	1083	descriptors to non-blocking mode is also usually a good idea (but not
889	required if you know what you are doing).	1084	required if you know what you are doing).
890		1085
891	You have to be careful with dup'ed file descriptors, though. Some backends
892	(the linux epoll backend is a notable example) cannot handle dup'ed file
893	descriptors correctly if you register interest in two or more fds pointing
894	to the same underlying file/socket/etc. description (that is, they share
895	the same underlying "file open").
896
897	If you must do this, then force the use of a known-to-be-good backend	1086	If you must do this, then force the use of a known-to-be-good backend
898	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1087	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
899	C<EVBACKEND_POLL>).	1088	C<EVBACKEND_POLL>).
900		1089
901	Another thing you have to watch out for is that it is quite easy to	1090	Another thing you have to watch out for is that it is quite easy to
902	receive "spurious" readyness notifications, that is your callback might	1091	receive "spurious" readiness notifications, that is your callback might
903	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1092	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
904	because there is no data. Not only are some backends known to create a	1093	because there is no data. Not only are some backends known to create a
905	lot of those (for example solaris ports), it is very easy to get into	1094	lot of those (for example Solaris ports), it is very easy to get into
906	this situation even with a relatively standard program structure. Thus	1095	this situation even with a relatively standard program structure. Thus
907	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1096	it is best to always use non-blocking I/O: An extra C<read>(2) returning
908	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1097	C<EAGAIN> is far preferable to a program hanging until some data arrives.
909		1098
910	If you cannot run the fd in non-blocking mode (for example you should not	1099	If you cannot run the fd in non-blocking mode (for example you should not
911	play around with an Xlib connection), then you have to seperately re-test	1100	play around with an Xlib connection), then you have to separately re-test
912	whether a file descriptor is really ready with a known-to-be good interface	1101	whether a file descriptor is really ready with a known-to-be good interface
913	such as poll (fortunately in our Xlib example, Xlib already does this on	1102	such as poll (fortunately in our Xlib example, Xlib already does this on
914	its own, so its quite safe to use).	1103	its own, so its quite safe to use).
915		1104
916	=head3 The special problem of disappearing file descriptors	1105	=head3 The special problem of disappearing file descriptors
917		1106
918	Some backends (e.g kqueue, epoll) need to be told about closing a file	1107	Some backends (e.g. kqueue, epoll) need to be told about closing a file
919	descriptor (either by calling C<close> explicitly or by any other means,	1108	descriptor (either by calling C<close> explicitly or by any other means,
920	such as C<dup>). The reason is that you register interest in some file	1109	such as C<dup>). The reason is that you register interest in some file
921	descriptor, but when it goes away, the operating system will silently drop	1110	descriptor, but when it goes away, the operating system will silently drop
922	this interest. If another file descriptor with the same number then is	1111	this interest. If another file descriptor with the same number then is
923	registered with libev, there is no efficient way to see that this is, in	1112	registered with libev, there is no efficient way to see that this is, in
…		…
932		1121
933	This is how one would do it normally anyway, the important point is that	1122	This is how one would do it normally anyway, the important point is that
934	the libev application should not optimise around libev but should leave	1123	the libev application should not optimise around libev but should leave
935	optimisations to libev.	1124	optimisations to libev.
936		1125
		1126	=head3 The special problem of dup'ed file descriptors
		1127
		1128	Some backends (e.g. epoll), cannot register events for file descriptors,
		1129	but only events for the underlying file descriptions. That means when you
		1130	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1131	events for them, only one file descriptor might actually receive events.
		1132
		1133	There is no workaround possible except not registering events
		1134	for potentially C<dup ()>'ed file descriptors, or to resort to
		1135	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1136
		1137	=head3 The special problem of fork
		1138
		1139	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1140	useless behaviour. Libev fully supports fork, but needs to be told about
		1141	it in the child.
		1142
		1143	To support fork in your programs, you either have to call
		1144	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1146	C<EVBACKEND_POLL>.
		1147
		1148	=head3 The special problem of SIGPIPE
		1149
		1150	While not really specific to libev, it is easy to forget about SIGPIPE:
		1151	when writing to a pipe whose other end has been closed, your program gets
		1152	send a SIGPIPE, which, by default, aborts your program. For most programs
		1153	this is sensible behaviour, for daemons, this is usually undesirable.
		1154
		1155	So when you encounter spurious, unexplained daemon exits, make sure you
		1156	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1157	somewhere, as that would have given you a big clue).
		1158
937		1159
938	=head3 Watcher-Specific Functions	1160	=head3 Watcher-Specific Functions
939		1161
940	=over 4	1162	=over 4
941		1163
942	=item ev_io_init (ev_io *, callback, int fd, int events)	1164	=item ev_io_init (ev_io *, callback, int fd, int events)
943		1165
944	=item ev_io_set (ev_io *, int fd, int events)	1166	=item ev_io_set (ev_io *, int fd, int events)
945		1167
946	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1168	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
947	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1169	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
948	C<EV_READ | EV_WRITE> to receive the given events.	1170	C<EV_READ | EV_WRITE> to receive the given events.
949		1171
950	=item int fd [read-only]	1172	=item int fd [read-only]
951		1173
952	The file descriptor being watched.	1174	The file descriptor being watched.
…		…
954	=item int events [read-only]	1176	=item int events [read-only]
955		1177
956	The events being watched.	1178	The events being watched.
957		1179
958	=back	1180	=back
		1181
		1182	=head3 Examples
959		1183
960	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1184	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
961	readable, but only once. Since it is likely line-buffered, you could	1185	readable, but only once. Since it is likely line-buffered, you could
962	attempt to read a whole line in the callback.	1186	attempt to read a whole line in the callback.
963		1187
964	static void	1188	static void
965	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1189	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
966	{	1190	{
967	ev_io_stop (loop, w);	1191	ev_io_stop (loop, w);
968	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1192	.. read from stdin here (or from w->fd) and haqndle any I/O errors
969	}	1193	}
970		1194
971	...	1195	...
972	struct ev_loop *loop = ev_default_init (0);	1196	struct ev_loop *loop = ev_default_init (0);
973	struct ev_io stdin_readable;	1197	struct ev_io stdin_readable;
974	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1198	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
975	ev_io_start (loop, &stdin_readable);	1199	ev_io_start (loop, &stdin_readable);
976	ev_loop (loop, 0);	1200	ev_loop (loop, 0);
977		1201
978		1202
979	=head2 C<ev_timer> - relative and optionally repeating timeouts	1203	=head2 C<ev_timer> - relative and optionally repeating timeouts
980		1204
981	Timer watchers are simple relative timers that generate an event after a	1205	Timer watchers are simple relative timers that generate an event after a
982	given time, and optionally repeating in regular intervals after that.	1206	given time, and optionally repeating in regular intervals after that.
983		1207
984	The timers are based on real time, that is, if you register an event that	1208	The timers are based on real time, that is, if you register an event that
985	times out after an hour and you reset your system clock to last years	1209	times out after an hour and you reset your system clock to January last
986	time, it will still time out after (roughly) and hour. "Roughly" because	1210	year, it will still time out after (roughly) and hour. "Roughly" because
987	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the
988	monotonic clock option helps a lot here).	1212	monotonic clock option helps a lot here).
		1213
		1214	The callback is guaranteed to be invoked only after its timeout has passed,
		1215	but if multiple timers become ready during the same loop iteration then
		1216	order of execution is undefined.
		1217
		1218	=head3 The special problem of time updates
		1219
		1220	Establishing the current time is a costly operation (it usually takes at
		1221	least two system calls): EV therefore updates its idea of the current
		1222	time only before and after C<ev_loop> polls for new events, which causes
		1223	a growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1224	lots of events.
989		1225
990	The relative timeouts are calculated relative to the C<ev_now ()>	1226	The relative timeouts are calculated relative to the C<ev_now ()>
991	time. This is usually the right thing as this timestamp refers to the time	1227	time. This is usually the right thing as this timestamp refers to the time
992	of the event triggering whatever timeout you are modifying/starting. If	1228	of the event triggering whatever timeout you are modifying/starting. If
993	you suspect event processing to be delayed and you I<need> to base the timeout	1229	you suspect event processing to be delayed and you I<need> to base the
994	on the current time, use something like this to adjust for this:	1230	timeout on the current time, use something like this to adjust for this:
995		1231
996	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1232	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
997		1233
998	The callback is guarenteed to be invoked only when its timeout has passed,	1234	If the event loop is suspended for a long time, you can also force an
999	but if multiple timers become ready during the same loop iteration then	1235	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1000	order of execution is undefined.	1236	()>.
1001		1237
1002	=head3 Watcher-Specific Functions and Data Members	1238	=head3 Watcher-Specific Functions and Data Members
1003		1239
1004	=over 4	1240	=over 4
1005		1241
1006	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1242	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1007		1243
1008	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1244	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1009		1245
1010	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1246	Configure the timer to trigger after C<after> seconds. If C<repeat>
1011	C<0.>, then it will automatically be stopped. If it is positive, then the	1247	is C<0.>, then it will automatically be stopped once the timeout is
1012	timer will automatically be configured to trigger again C<repeat> seconds	1248	reached. If it is positive, then the timer will automatically be
1013	later, again, and again, until stopped manually.	1249	configured to trigger again C<repeat> seconds later, again, and again,
		1250	until stopped manually.
1014		1251
1015	The timer itself will do a best-effort at avoiding drift, that is, if you	1252	The timer itself will do a best-effort at avoiding drift, that is, if
1016	configure a timer to trigger every 10 seconds, then it will trigger at	1253	you configure a timer to trigger every 10 seconds, then it will normally
1017	exactly 10 second intervals. If, however, your program cannot keep up with	1254	trigger at exactly 10 second intervals. If, however, your program cannot
1018	the timer (because it takes longer than those 10 seconds to do stuff) the	1255	keep up with the timer (because it takes longer than those 10 seconds to
1019	timer will not fire more than once per event loop iteration.	1256	do stuff) the timer will not fire more than once per event loop iteration.
1020		1257
1021	=item ev_timer_again (loop)	1258	=item ev_timer_again (loop, ev_timer *)
1022		1259
1023	This will act as if the timer timed out and restart it again if it is	1260	This will act as if the timer timed out and restart it again if it is
1024	repeating. The exact semantics are:	1261	repeating. The exact semantics are:
1025		1262
1026	If the timer is pending, its pending status is cleared.	1263	If the timer is pending, its pending status is cleared.
1027		1264
1028	If the timer is started but nonrepeating, stop it (as if it timed out).	1265	If the timer is started but non-repeating, stop it (as if it timed out).
1029		1266
1030	If the timer is repeating, either start it if necessary (with the	1267	If the timer is repeating, either start it if necessary (with the
1031	C<repeat> value), or reset the running timer to the C<repeat> value.	1268	C<repeat> value), or reset the running timer to the C<repeat> value.
1032		1269
1033	This sounds a bit complicated, but here is a useful and typical	1270	This sounds a bit complicated, but here is a useful and typical
1034	example: Imagine you have a tcp connection and you want a so-called idle	1271	example: Imagine you have a TCP connection and you want a so-called idle
1035	timeout, that is, you want to be called when there have been, say, 60	1272	timeout, that is, you want to be called when there have been, say, 60
1036	seconds of inactivity on the socket. The easiest way to do this is to	1273	seconds of inactivity on the socket. The easiest way to do this is to
1037	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1274	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1038	C<ev_timer_again> each time you successfully read or write some data. If	1275	C<ev_timer_again> each time you successfully read or write some data. If
1039	you go into an idle state where you do not expect data to travel on the	1276	you go into an idle state where you do not expect data to travel on the
…		…
1061	or C<ev_timer_again> is called and determines the next timeout (if any),	1298	or C<ev_timer_again> is called and determines the next timeout (if any),
1062	which is also when any modifications are taken into account.	1299	which is also when any modifications are taken into account.
1063		1300
1064	=back	1301	=back
1065		1302
		1303	=head3 Examples
		1304
1066	Example: Create a timer that fires after 60 seconds.	1305	Example: Create a timer that fires after 60 seconds.
1067		1306
1068	static void	1307	static void
1069	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1308	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1070	{	1309	{
1071	.. one minute over, w is actually stopped right here	1310	.. one minute over, w is actually stopped right here
1072	}	1311	}
1073		1312
1074	struct ev_timer mytimer;	1313	struct ev_timer mytimer;
1075	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1076	ev_timer_start (loop, &mytimer);	1315	ev_timer_start (loop, &mytimer);
1077		1316
1078	Example: Create a timeout timer that times out after 10 seconds of	1317	Example: Create a timeout timer that times out after 10 seconds of
1079	inactivity.	1318	inactivity.
1080		1319
1081	static void	1320	static void
1082	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1083	{	1322	{
1084	.. ten seconds without any activity	1323	.. ten seconds without any activity
1085	}	1324	}
1086		1325
1087	struct ev_timer mytimer;	1326	struct ev_timer mytimer;
1088	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1327	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1089	ev_timer_again (&mytimer); /* start timer */	1328	ev_timer_again (&mytimer); /* start timer */
1090	ev_loop (loop, 0);	1329	ev_loop (loop, 0);
1091		1330
1092	// and in some piece of code that gets executed on any "activity":	1331	// and in some piece of code that gets executed on any "activity":
1093	// reset the timeout to start ticking again at 10 seconds	1332	// reset the timeout to start ticking again at 10 seconds
1094	ev_timer_again (&mytimer);	1333	ev_timer_again (&mytimer);
1095		1334
1096		1335
1097	=head2 C<ev_periodic> - to cron or not to cron?	1336	=head2 C<ev_periodic> - to cron or not to cron?
1098		1337
1099	Periodic watchers are also timers of a kind, but they are very versatile	1338	Periodic watchers are also timers of a kind, but they are very versatile
1100	(and unfortunately a bit complex).	1339	(and unfortunately a bit complex).
1101		1340
1102	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1341	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1103	but on wallclock time (absolute time). You can tell a periodic watcher	1342	but on wall clock time (absolute time). You can tell a periodic watcher
1104	to trigger "at" some specific point in time. For example, if you tell a	1343	to trigger after some specific point in time. For example, if you tell a
1105	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1344	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1106	+ 10.>) and then reset your system clock to the last year, then it will	1345	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1346	clock to January of the previous year, then it will take more than year
1107	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1347	to trigger the event (unlike an C<ev_timer>, which would still trigger
1108	roughly 10 seconds later).	1348	roughly 10 seconds later as it uses a relative timeout).
1109		1349
1110	They can also be used to implement vastly more complex timers, such as	1350	C<ev_periodic>s can also be used to implement vastly more complex timers,
1111	triggering an event on each midnight, local time or other, complicated,	1351	such as triggering an event on each "midnight, local time", or other
1112	rules.	1352	complicated, rules.
1113		1353
1114	As with timers, the callback is guarenteed to be invoked only when the	1354	As with timers, the callback is guaranteed to be invoked only when the
1115	time (C<at>) has been passed, but if multiple periodic timers become ready	1355	time (C<at>) has passed, but if multiple periodic timers become ready
1116	during the same loop iteration then order of execution is undefined.	1356	during the same loop iteration then order of execution is undefined.
1117		1357
1118	=head3 Watcher-Specific Functions and Data Members	1358	=head3 Watcher-Specific Functions and Data Members
1119		1359
1120	=over 4	1360	=over 4
…		…
1128		1368
1129	=over 4	1369	=over 4
1130		1370
1131	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1132		1372
1133	In this configuration the watcher triggers an event at the wallclock time	1373	In this configuration the watcher triggers an event after the wall clock
1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1374	time C<at> has passed and doesn't repeat. It will not adjust when a time
1135	that is, if it is to be run at January 1st 2011 then it will run when the	1375	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1136	system time reaches or surpasses this time.	1376	run when the system time reaches or surpasses this time.
1137		1377
1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1139		1379
1140	In this mode the watcher will always be scheduled to time out at the next	1380	In this mode the watcher will always be scheduled to time out at the next
1141	C<at + N * interval> time (for some integer N, which can also be negative)	1381	C<at + N * interval> time (for some integer N, which can also be negative)
1142	and then repeat, regardless of any time jumps.	1382	and then repeat, regardless of any time jumps.
1143		1383
1144	This can be used to create timers that do not drift with respect to system	1384	This can be used to create timers that do not drift with respect to system
1145	time:	1385	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1386	the hour:
1146		1387
1147	ev_periodic_set (&periodic, 0., 3600., 0);	1388	ev_periodic_set (&periodic, 0., 3600., 0);
1148		1389
1149	This doesn't mean there will always be 3600 seconds in between triggers,	1390	This doesn't mean there will always be 3600 seconds in between triggers,
1150	but only that the the callback will be called when the system time shows a	1391	but only that the callback will be called when the system time shows a
1151	full hour (UTC), or more correctly, when the system time is evenly divisible	1392	full hour (UTC), or more correctly, when the system time is evenly divisible
1152	by 3600.	1393	by 3600.
1153		1394
1154	Another way to think about it (for the mathematically inclined) is that	1395	Another way to think about it (for the mathematically inclined) is that
1155	C<ev_periodic> will try to run the callback in this mode at the next possible	1396	C<ev_periodic> will try to run the callback in this mode at the next possible
1156	time where C<time = at (mod interval)>, regardless of any time jumps.	1397	time where C<time = at (mod interval)>, regardless of any time jumps.
1157		1398
1158	For numerical stability it is preferable that the C<at> value is near	1399	For numerical stability it is preferable that the C<at> value is near
1159	C<ev_now ()> (the current time), but there is no range requirement for	1400	C<ev_now ()> (the current time), but there is no range requirement for
1160	this value.	1401	this value, and in fact is often specified as zero.
		1402
		1403	Note also that there is an upper limit to how often a timer can fire (CPU
		1404	speed for example), so if C<interval> is very small then timing stability
		1405	will of course deteriorate. Libev itself tries to be exact to be about one
		1406	millisecond (if the OS supports it and the machine is fast enough).
1161		1407
1162	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1408	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1163		1409
1164	In this mode the values for C<interval> and C<at> are both being	1410	In this mode the values for C<interval> and C<at> are both being
1165	ignored. Instead, each time the periodic watcher gets scheduled, the	1411	ignored. Instead, each time the periodic watcher gets scheduled, the
1166	reschedule callback will be called with the watcher as first, and the	1412	reschedule callback will be called with the watcher as first, and the
1167	current time as second argument.	1413	current time as second argument.
1168		1414
1169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1415	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1170	ever, or make any event loop modifications>. If you need to stop it,	1416	ever, or make ANY event loop modifications whatsoever>.
1171	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1172	starting an C<ev_prepare> watcher, which is legal).
1173		1417
		1418	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1419	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1420	only event loop modification you are allowed to do).
		1421
1174	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1175	ev_tstamp now)>, e.g.:	1423	*w, ev_tstamp now)>, e.g.:
1176		1424
1177	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1178	{	1426	{
1179	return now + 60.;	1427	return now + 60.;
1180	}	1428	}
…		…
1182	It must return the next time to trigger, based on the passed time value	1430	It must return the next time to trigger, based on the passed time value
1183	(that is, the lowest time value larger than to the second argument). It	1431	(that is, the lowest time value larger than to the second argument). It
1184	will usually be called just before the callback will be triggered, but	1432	will usually be called just before the callback will be triggered, but
1185	might be called at other times, too.	1433	might be called at other times, too.
1186		1434
1187	NOTE: I<< This callback must always return a time that is later than the	1435	NOTE: I<< This callback must always return a time that is higher than or
1188	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1436	equal to the passed C<now> value >>.
1189		1437
1190	This can be used to create very complex timers, such as a timer that	1438	This can be used to create very complex timers, such as a timer that
1191	triggers on each midnight, local time. To do this, you would calculate the	1439	triggers on "next midnight, local time". To do this, you would calculate the
1192	next midnight after C<now> and return the timestamp value for this. How	1440	next midnight after C<now> and return the timestamp value for this. How
1193	you do this is, again, up to you (but it is not trivial, which is the main	1441	you do this is, again, up to you (but it is not trivial, which is the main
1194	reason I omitted it as an example).	1442	reason I omitted it as an example).
1195		1443
1196	=back	1444	=back
…		…
1200	Simply stops and restarts the periodic watcher again. This is only useful	1448	Simply stops and restarts the periodic watcher again. This is only useful
1201	when you changed some parameters or the reschedule callback would return	1449	when you changed some parameters or the reschedule callback would return
1202	a different time than the last time it was called (e.g. in a crond like	1450	a different time than the last time it was called (e.g. in a crond like
1203	program when the crontabs have changed).	1451	program when the crontabs have changed).
1204		1452
		1453	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1454
		1455	When active, returns the absolute time that the watcher is supposed to
		1456	trigger next.
		1457
1205	=item ev_tstamp offset [read-write]	1458	=item ev_tstamp offset [read-write]
1206		1459
1207	When repeating, this contains the offset value, otherwise this is the	1460	When repeating, this contains the offset value, otherwise this is the
1208	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1461	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1209		1462
…		…
1222	switched off. Can be changed any time, but changes only take effect when	1475	switched off. Can be changed any time, but changes only take effect when
1223	the periodic timer fires or C<ev_periodic_again> is being called.	1476	the periodic timer fires or C<ev_periodic_again> is being called.
1224		1477
1225	=back	1478	=back
1226		1479
		1480	=head3 Examples
		1481
1227	Example: Call a callback every hour, or, more precisely, whenever the	1482	Example: Call a callback every hour, or, more precisely, whenever the
1228	system clock is divisible by 3600. The callback invocation times have	1483	system clock is divisible by 3600. The callback invocation times have
1229	potentially a lot of jittering, but good long-term stability.	1484	potentially a lot of jitter, but good long-term stability.
1230		1485
1231	static void	1486	static void
1232	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1233	{	1488	{
1234	... its now a full hour (UTC, or TAI or whatever your clock follows)	1489	... its now a full hour (UTC, or TAI or whatever your clock follows)
1235	}	1490	}
1236		1491
1237	struct ev_periodic hourly_tick;	1492	struct ev_periodic hourly_tick;
1238	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1239	ev_periodic_start (loop, &hourly_tick);	1494	ev_periodic_start (loop, &hourly_tick);
1240		1495
1241	Example: The same as above, but use a reschedule callback to do it:	1496	Example: The same as above, but use a reschedule callback to do it:
1242		1497
1243	#include <math.h>	1498	#include <math.h>
1244		1499
1245	static ev_tstamp	1500	static ev_tstamp
1246	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1247	{	1502	{
1248	return fmod (now, 3600.) + 3600.;	1503	return fmod (now, 3600.) + 3600.;
1249	}	1504	}
1250		1505
1251	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1506	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1252		1507
1253	Example: Call a callback every hour, starting now:	1508	Example: Call a callback every hour, starting now:
1254		1509
1255	struct ev_periodic hourly_tick;	1510	struct ev_periodic hourly_tick;
1256	ev_periodic_init (&hourly_tick, clock_cb,	1511	ev_periodic_init (&hourly_tick, clock_cb,
1257	fmod (ev_now (loop), 3600.), 3600., 0);	1512	fmod (ev_now (loop), 3600.), 3600., 0);
1258	ev_periodic_start (loop, &hourly_tick);	1513	ev_periodic_start (loop, &hourly_tick);
1259		1514
1260		1515
1261	=head2 C<ev_signal> - signal me when a signal gets signalled!	1516	=head2 C<ev_signal> - signal me when a signal gets signalled!
1262		1517
1263	Signal watchers will trigger an event when the process receives a specific	1518	Signal watchers will trigger an event when the process receives a specific
…		…
1270	with the kernel (thus it coexists with your own signal handlers as long	1525	with the kernel (thus it coexists with your own signal handlers as long
1271	as you don't register any with libev). Similarly, when the last signal	1526	as you don't register any with libev). Similarly, when the last signal
1272	watcher for a signal is stopped libev will reset the signal handler to	1527	watcher for a signal is stopped libev will reset the signal handler to
1273	SIG_DFL (regardless of what it was set to before).	1528	SIG_DFL (regardless of what it was set to before).
1274		1529
		1530	If possible and supported, libev will install its handlers with
		1531	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1532	interrupted. If you have a problem with system calls getting interrupted by
		1533	signals you can block all signals in an C<ev_check> watcher and unblock
		1534	them in an C<ev_prepare> watcher.
		1535
1275	=head3 Watcher-Specific Functions and Data Members	1536	=head3 Watcher-Specific Functions and Data Members
1276		1537
1277	=over 4	1538	=over 4
1278		1539
1279	=item ev_signal_init (ev_signal *, callback, int signum)	1540	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1287		1548
1288	The signal the watcher watches out for.	1549	The signal the watcher watches out for.
1289		1550
1290	=back	1551	=back
1291		1552
		1553	=head3 Examples
		1554
		1555	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1556
		1557	static void
		1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1559	{
		1560	ev_unloop (loop, EVUNLOOP_ALL);
		1561	}
		1562
		1563	struct ev_signal signal_watcher;
		1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1565	ev_signal_start (loop, &sigint_cb);
		1566
1292		1567
1293	=head2 C<ev_child> - watch out for process status changes	1568	=head2 C<ev_child> - watch out for process status changes
1294		1569
1295	Child watchers trigger when your process receives a SIGCHLD in response to	1570	Child watchers trigger when your process receives a SIGCHLD in response to
1296	some child status changes (most typically when a child of yours dies).	1571	some child status changes (most typically when a child of yours dies). It
		1572	is permissible to install a child watcher I<after> the child has been
		1573	forked (which implies it might have already exited), as long as the event
		1574	loop isn't entered (or is continued from a watcher).
		1575
		1576	Only the default event loop is capable of handling signals, and therefore
		1577	you can only register child watchers in the default event loop.
		1578
		1579	=head3 Process Interaction
		1580
		1581	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1582	initialised. This is necessary to guarantee proper behaviour even if
		1583	the first child watcher is started after the child exits. The occurrence
		1584	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1585	synchronously as part of the event loop processing. Libev always reaps all
		1586	children, even ones not watched.
		1587
		1588	=head3 Overriding the Built-In Processing
		1589
		1590	Libev offers no special support for overriding the built-in child
		1591	processing, but if your application collides with libev's default child
		1592	handler, you can override it easily by installing your own handler for
		1593	C<SIGCHLD> after initialising the default loop, and making sure the
		1594	default loop never gets destroyed. You are encouraged, however, to use an
		1595	event-based approach to child reaping and thus use libev's support for
		1596	that, so other libev users can use C<ev_child> watchers freely.
		1597
		1598	=head3 Stopping the Child Watcher
		1599
		1600	Currently, the child watcher never gets stopped, even when the
		1601	child terminates, so normally one needs to stop the watcher in the
		1602	callback. Future versions of libev might stop the watcher automatically
		1603	when a child exit is detected.
1297		1604
1298	=head3 Watcher-Specific Functions and Data Members	1605	=head3 Watcher-Specific Functions and Data Members
1299		1606
1300	=over 4	1607	=over 4
1301		1608
1302	=item ev_child_init (ev_child *, callback, int pid)	1609	=item ev_child_init (ev_child *, callback, int pid, int trace)
1303		1610
1304	=item ev_child_set (ev_child *, int pid)	1611	=item ev_child_set (ev_child *, int pid, int trace)
1305		1612
1306	Configures the watcher to wait for status changes of process C<pid> (or	1613	Configures the watcher to wait for status changes of process C<pid> (or
1307	I<any> process if C<pid> is specified as C<0>). The callback can look	1614	I<any> process if C<pid> is specified as C<0>). The callback can look
1308	at the C<rstatus> member of the C<ev_child> watcher structure to see	1615	at the C<rstatus> member of the C<ev_child> watcher structure to see
1309	the status word (use the macros from C<sys/wait.h> and see your systems	1616	the status word (use the macros from C<sys/wait.h> and see your systems
1310	C<waitpid> documentation). The C<rpid> member contains the pid of the	1617	C<waitpid> documentation). The C<rpid> member contains the pid of the
1311	process causing the status change.	1618	process causing the status change. C<trace> must be either C<0> (only
		1619	activate the watcher when the process terminates) or C<1> (additionally
		1620	activate the watcher when the process is stopped or continued).
1312		1621
1313	=item int pid [read-only]	1622	=item int pid [read-only]
1314		1623
1315	The process id this watcher watches out for, or C<0>, meaning any process id.	1624	The process id this watcher watches out for, or C<0>, meaning any process id.
1316		1625
…		…
1323	The process exit/trace status caused by C<rpid> (see your systems	1632	The process exit/trace status caused by C<rpid> (see your systems
1324	C<waitpid> and C<sys/wait.h> documentation for details).	1633	C<waitpid> and C<sys/wait.h> documentation for details).
1325		1634
1326	=back	1635	=back
1327		1636
1328	Example: Try to exit cleanly on SIGINT and SIGTERM.	1637	=head3 Examples
1329		1638
		1639	Example: C<fork()> a new process and install a child handler to wait for
		1640	its completion.
		1641
		1642	ev_child cw;
		1643
1330	static void	1644	static void
1331	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1645	child_cb (EV_P_ struct ev_child *w, int revents)
1332	{	1646	{
1333	ev_unloop (loop, EVUNLOOP_ALL);	1647	ev_child_stop (EV_A_ w);
		1648	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1334	}	1649	}
1335		1650
1336	struct ev_signal signal_watcher;	1651	pid_t pid = fork ();
1337	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1652
1338	ev_signal_start (loop, &sigint_cb);	1653	if (pid < 0)
		1654	// error
		1655	else if (pid == 0)
		1656	{
		1657	// the forked child executes here
		1658	exit (1);
		1659	}
		1660	else
		1661	{
		1662	ev_child_init (&cw, child_cb, pid, 0);
		1663	ev_child_start (EV_DEFAULT_ &cw);
		1664	}
1339		1665
1340		1666
1341	=head2 C<ev_stat> - did the file attributes just change?	1667	=head2 C<ev_stat> - did the file attributes just change?
1342		1668
1343	This watches a filesystem path for attribute changes. That is, it calls	1669	This watches a file system path for attribute changes. That is, it calls
1344	C<stat> regularly (or when the OS says it changed) and sees if it changed	1670	C<stat> regularly (or when the OS says it changed) and sees if it changed
1345	compared to the last time, invoking the callback if it did.	1671	compared to the last time, invoking the callback if it did.
1346		1672
1347	The path does not need to exist: changing from "path exists" to "path does	1673	The path does not need to exist: changing from "path exists" to "path does
1348	not exist" is a status change like any other. The condition "path does	1674	not exist" is a status change like any other. The condition "path does
…		…
1366	as even with OS-supported change notifications, this can be	1692	as even with OS-supported change notifications, this can be
1367	resource-intensive.	1693	resource-intensive.
1368		1694
1369	At the time of this writing, only the Linux inotify interface is	1695	At the time of this writing, only the Linux inotify interface is
1370	implemented (implementing kqueue support is left as an exercise for the	1696	implemented (implementing kqueue support is left as an exercise for the
		1697	reader, note, however, that the author sees no way of implementing ev_stat
1371	reader). Inotify will be used to give hints only and should not change the	1698	semantics with kqueue). Inotify will be used to give hints only and should
1372	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1699	not change the semantics of C<ev_stat> watchers, which means that libev
1373	to fall back to regular polling again even with inotify, but changes are	1700	sometimes needs to fall back to regular polling again even with inotify,
1374	usually detected immediately, and if the file exists there will be no	1701	but changes are usually detected immediately, and if the file exists there
1375	polling.	1702	will be no polling.
		1703
		1704	=head3 ABI Issues (Largefile Support)
		1705
		1706	Libev by default (unless the user overrides this) uses the default
		1707	compilation environment, which means that on systems with large file
		1708	support disabled by default, you get the 32 bit version of the stat
		1709	structure. When using the library from programs that change the ABI to
		1710	use 64 bit file offsets the programs will fail. In that case you have to
		1711	compile libev with the same flags to get binary compatibility. This is
		1712	obviously the case with any flags that change the ABI, but the problem is
		1713	most noticeably disabled with ev_stat and large file support.
		1714
		1715	The solution for this is to lobby your distribution maker to make large
		1716	file interfaces available by default (as e.g. FreeBSD does) and not
		1717	optional. Libev cannot simply switch on large file support because it has
		1718	to exchange stat structures with application programs compiled using the
		1719	default compilation environment.
		1720
		1721	=head3 Inotify
		1722
		1723	When C<inotify (7)> support has been compiled into libev (generally only
		1724	available on Linux) and present at runtime, it will be used to speed up
		1725	change detection where possible. The inotify descriptor will be created lazily
		1726	when the first C<ev_stat> watcher is being started.
		1727
		1728	Inotify presence does not change the semantics of C<ev_stat> watchers
		1729	except that changes might be detected earlier, and in some cases, to avoid
		1730	making regular C<stat> calls. Even in the presence of inotify support
		1731	there are many cases where libev has to resort to regular C<stat> polling.
		1732
		1733	(There is no support for kqueue, as apparently it cannot be used to
		1734	implement this functionality, due to the requirement of having a file
		1735	descriptor open on the object at all times).
		1736
		1737	=head3 The special problem of stat time resolution
		1738
		1739	The C<stat ()> system call only supports full-second resolution portably, and
		1740	even on systems where the resolution is higher, many file systems still
		1741	only support whole seconds.
		1742
		1743	That means that, if the time is the only thing that changes, you can
		1744	easily miss updates: on the first update, C<ev_stat> detects a change and
		1745	calls your callback, which does something. When there is another update
		1746	within the same second, C<ev_stat> will be unable to detect it as the stat
		1747	data does not change.
		1748
		1749	The solution to this is to delay acting on a change for slightly more
		1750	than a second (or till slightly after the next full second boundary), using
		1751	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1752	ev_timer_again (loop, w)>).
		1753
		1754	The C<.02> offset is added to work around small timing inconsistencies
		1755	of some operating systems (where the second counter of the current time
		1756	might be be delayed. One such system is the Linux kernel, where a call to
		1757	C<gettimeofday> might return a timestamp with a full second later than
		1758	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1759	update file times then there will be a small window where the kernel uses
		1760	the previous second to update file times but libev might already execute
		1761	the timer callback).
1376		1762
1377	=head3 Watcher-Specific Functions and Data Members	1763	=head3 Watcher-Specific Functions and Data Members
1378		1764
1379	=over 4	1765	=over 4
1380		1766
…		…
1386	C<path>. The C<interval> is a hint on how quickly a change is expected to	1772	C<path>. The C<interval> is a hint on how quickly a change is expected to
1387	be detected and should normally be specified as C<0> to let libev choose	1773	be detected and should normally be specified as C<0> to let libev choose
1388	a suitable value. The memory pointed to by C<path> must point to the same	1774	a suitable value. The memory pointed to by C<path> must point to the same
1389	path for as long as the watcher is active.	1775	path for as long as the watcher is active.
1390		1776
1391	The callback will be receive C<EV_STAT> when a change was detected,	1777	The callback will receive C<EV_STAT> when a change was detected, relative
1392	relative to the attributes at the time the watcher was started (or the	1778	to the attributes at the time the watcher was started (or the last change
1393	last change was detected).	1779	was detected).
1394		1780
1395	=item ev_stat_stat (ev_stat *)	1781	=item ev_stat_stat (loop, ev_stat *)
1396		1782
1397	Updates the stat buffer immediately with new values. If you change the	1783	Updates the stat buffer immediately with new values. If you change the
1398	watched path in your callback, you could call this fucntion to avoid	1784	watched path in your callback, you could call this function to avoid
1399	detecting this change (while introducing a race condition). Can also be	1785	detecting this change (while introducing a race condition if you are not
1400	useful simply to find out the new values.	1786	the only one changing the path). Can also be useful simply to find out the
		1787	new values.
1401		1788
1402	=item ev_statdata attr [read-only]	1789	=item ev_statdata attr [read-only]
1403		1790
1404	The most-recently detected attributes of the file. Although the type is of	1791	The most-recently detected attributes of the file. Although the type is
1405	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1792	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1406	suitable for your system. If the C<st_nlink> member is C<0>, then there	1793	suitable for your system, but you can only rely on the POSIX-standardised
		1794	members to be present. If the C<st_nlink> member is C<0>, then there was
1407	was some error while C<stat>ing the file.	1795	some error while C<stat>ing the file.
1408		1796
1409	=item ev_statdata prev [read-only]	1797	=item ev_statdata prev [read-only]
1410		1798
1411	The previous attributes of the file. The callback gets invoked whenever	1799	The previous attributes of the file. The callback gets invoked whenever
1412	C<prev> != C<attr>.	1800	C<prev> != C<attr>, or, more precisely, one or more of these members
		1801	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1802	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1413		1803
1414	=item ev_tstamp interval [read-only]	1804	=item ev_tstamp interval [read-only]
1415		1805
1416	The specified interval.	1806	The specified interval.
1417		1807
1418	=item const char *path [read-only]	1808	=item const char *path [read-only]
1419		1809
1420	The filesystem path that is being watched.	1810	The file system path that is being watched.
1421		1811
1422	=back	1812	=back
1423		1813
		1814	=head3 Examples
		1815
1424	Example: Watch C</etc/passwd> for attribute changes.	1816	Example: Watch C</etc/passwd> for attribute changes.
1425		1817
1426	static void	1818	static void
1427	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1819	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1428	{	1820	{
1429	/* /etc/passwd changed in some way */	1821	/* /etc/passwd changed in some way */
1430	if (w->attr.st_nlink)	1822	if (w->attr.st_nlink)
1431	{	1823	{
1432	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1824	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1433	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1825	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1434	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1826	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1435	}	1827	}
1436	else	1828	else
1437	/* you shalt not abuse printf for puts */	1829	/* you shalt not abuse printf for puts */
1438	puts ("wow, /etc/passwd is not there, expect problems. "	1830	puts ("wow, /etc/passwd is not there, expect problems. "
1439	"if this is windows, they already arrived\n");	1831	"if this is windows, they already arrived\n");
1440	}	1832	}
1441		1833
1442	...	1834	...
1443	ev_stat passwd;	1835	ev_stat passwd;
1444		1836
1445	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1837	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1446	ev_stat_start (loop, &passwd);	1838	ev_stat_start (loop, &passwd);
		1839
		1840	Example: Like above, but additionally use a one-second delay so we do not
		1841	miss updates (however, frequent updates will delay processing, too, so
		1842	one might do the work both on C<ev_stat> callback invocation I<and> on
		1843	C<ev_timer> callback invocation).
		1844
		1845	static ev_stat passwd;
		1846	static ev_timer timer;
		1847
		1848	static void
		1849	timer_cb (EV_P_ ev_timer *w, int revents)
		1850	{
		1851	ev_timer_stop (EV_A_ w);
		1852
		1853	/* now it's one second after the most recent passwd change */
		1854	}
		1855
		1856	static void
		1857	stat_cb (EV_P_ ev_stat *w, int revents)
		1858	{
		1859	/* reset the one-second timer */
		1860	ev_timer_again (EV_A_ &timer);
		1861	}
		1862
		1863	...
		1864	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1865	ev_stat_start (loop, &passwd);
		1866	ev_timer_init (&timer, timer_cb, 0., 1.02);
1447		1867
1448		1868
1449	=head2 C<ev_idle> - when you've got nothing better to do...	1869	=head2 C<ev_idle> - when you've got nothing better to do...
1450		1870
1451	Idle watchers trigger events when no other events of the same or higher	1871	Idle watchers trigger events when no other events of the same or higher
…		…
1477	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1897	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1478	believe me.	1898	believe me.
1479		1899
1480	=back	1900	=back
1481		1901
		1902	=head3 Examples
		1903
1482	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1904	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1483	callback, free it. Also, use no error checking, as usual.	1905	callback, free it. Also, use no error checking, as usual.
1484		1906
1485	static void	1907	static void
1486	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1487	{	1909	{
1488	free (w);	1910	free (w);
1489	// now do something you wanted to do when the program has	1911	// now do something you wanted to do when the program has
1490	// no longer asnything immediate to do.	1912	// no longer anything immediate to do.
1491	}	1913	}
1492		1914
1493	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1494	ev_idle_init (idle_watcher, idle_cb);	1916	ev_idle_init (idle_watcher, idle_cb);
1495	ev_idle_start (loop, idle_cb);	1917	ev_idle_start (loop, idle_cb);
1496		1918
1497		1919
1498	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1920	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1499		1921
1500	Prepare and check watchers are usually (but not always) used in tandem:	1922	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1519		1941
1520	This is done by examining in each prepare call which file descriptors need	1942	This is done by examining in each prepare call which file descriptors need
1521	to be watched by the other library, registering C<ev_io> watchers for	1943	to be watched by the other library, registering C<ev_io> watchers for
1522	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1944	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1523	provide just this functionality). Then, in the check watcher you check for	1945	provide just this functionality). Then, in the check watcher you check for
1524	any events that occured (by checking the pending status of all watchers	1946	any events that occurred (by checking the pending status of all watchers
1525	and stopping them) and call back into the library. The I/O and timer	1947	and stopping them) and call back into the library. The I/O and timer
1526	callbacks will never actually be called (but must be valid nevertheless,	1948	callbacks will never actually be called (but must be valid nevertheless,
1527	because you never know, you know?).	1949	because you never know, you know?).
1528		1950
1529	As another example, the Perl Coro module uses these hooks to integrate	1951	As another example, the Perl Coro module uses these hooks to integrate
…		…
1537		1959
1538	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1960	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1539	priority, to ensure that they are being run before any other watchers	1961	priority, to ensure that they are being run before any other watchers
1540	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1962	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1541	too) should not activate ("feed") events into libev. While libev fully	1963	too) should not activate ("feed") events into libev. While libev fully
1542	supports this, they will be called before other C<ev_check> watchers did	1964	supports this, they might get executed before other C<ev_check> watchers
1543	their job. As C<ev_check> watchers are often used to embed other event	1965	did their job. As C<ev_check> watchers are often used to embed other
1544	loops those other event loops might be in an unusable state until their	1966	(non-libev) event loops those other event loops might be in an unusable
1545	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1967	state until their C<ev_check> watcher ran (always remind yourself to
1546	others).	1968	coexist peacefully with others).
1547		1969
1548	=head3 Watcher-Specific Functions and Data Members	1970	=head3 Watcher-Specific Functions and Data Members
1549		1971
1550	=over 4	1972	=over 4
1551		1973
…		…
1557	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1979	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1558	macros, but using them is utterly, utterly and completely pointless.	1980	macros, but using them is utterly, utterly and completely pointless.
1559		1981
1560	=back	1982	=back
1561		1983
		1984	=head3 Examples
		1985
1562	There are a number of principal ways to embed other event loops or modules	1986	There are a number of principal ways to embed other event loops or modules
1563	into libev. Here are some ideas on how to include libadns into libev	1987	into libev. Here are some ideas on how to include libadns into libev
1564	(there is a Perl module named C<EV::ADNS> that does this, which you could	1988	(there is a Perl module named C<EV::ADNS> that does this, which you could
1565	use for an actually working example. Another Perl module named C<EV::Glib>	1989	use as a working example. Another Perl module named C<EV::Glib> embeds a
1566	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1990	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1567	into the Glib event loop).	1991	Glib event loop).
1568		1992
1569	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1993	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1570	and in a check watcher, destroy them and call into libadns. What follows	1994	and in a check watcher, destroy them and call into libadns. What follows
1571	is pseudo-code only of course. This requires you to either use a low	1995	is pseudo-code only of course. This requires you to either use a low
1572	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1996	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1573	the callbacks for the IO/timeout watchers might not have been called yet.	1997	the callbacks for the IO/timeout watchers might not have been called yet.
1574		1998
1575	static ev_io iow [nfd];	1999	static ev_io iow [nfd];
1576	static ev_timer tw;	2000	static ev_timer tw;
1577		2001
1578	static void	2002	static void
1579	io_cb (ev_loop *loop, ev_io *w, int revents)	2003	io_cb (ev_loop *loop, ev_io *w, int revents)
1580	{	2004	{
1581	}	2005	}
1582		2006
1583	// create io watchers for each fd and a timer before blocking	2007	// create io watchers for each fd and a timer before blocking
1584	static void	2008	static void
1585	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1586	{	2010	{
1587	int timeout = 3600000;	2011	int timeout = 3600000;
1588	struct pollfd fds [nfd];	2012	struct pollfd fds [nfd];
1589	// actual code will need to loop here and realloc etc.	2013	// actual code will need to loop here and realloc etc.
1590	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1591		2015
1592	/* the callback is illegal, but won't be called as we stop during check */	2016	/* the callback is illegal, but won't be called as we stop during check */
1593	ev_timer_init (&tw, 0, timeout * 1e-3);	2017	ev_timer_init (&tw, 0, timeout * 1e-3);
1594	ev_timer_start (loop, &tw);	2018	ev_timer_start (loop, &tw);
1595		2019
1596	// create one ev_io per pollfd	2020	// create one ev_io per pollfd
1597	for (int i = 0; i < nfd; ++i)	2021	for (int i = 0; i < nfd; ++i)
1598	{	2022	{
1599	ev_io_init (iow + i, io_cb, fds [i].fd,	2023	ev_io_init (iow + i, io_cb, fds [i].fd,
1600	((fds [i].events & POLLIN ? EV_READ : 0)	2024	((fds [i].events & POLLIN ? EV_READ : 0)
1601	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2025	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1602		2026
1603	fds [i].revents = 0;	2027	fds [i].revents = 0;
1604	ev_io_start (loop, iow + i);	2028	ev_io_start (loop, iow + i);
1605	}	2029	}
1606	}	2030	}
1607		2031
1608	// stop all watchers after blocking	2032	// stop all watchers after blocking
1609	static void	2033	static void
1610	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1611	{	2035	{
1612	ev_timer_stop (loop, &tw);	2036	ev_timer_stop (loop, &tw);
1613		2037
1614	for (int i = 0; i < nfd; ++i)	2038	for (int i = 0; i < nfd; ++i)
1615	{	2039	{
1616	// set the relevant poll flags	2040	// set the relevant poll flags
1617	// could also call adns_processreadable etc. here	2041	// could also call adns_processreadable etc. here
1618	struct pollfd *fd = fds + i;	2042	struct pollfd *fd = fds + i;
1619	int revents = ev_clear_pending (iow + i);	2043	int revents = ev_clear_pending (iow + i);
1620	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2044	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1621	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2045	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1622		2046
1623	// now stop the watcher	2047	// now stop the watcher
1624	ev_io_stop (loop, iow + i);	2048	ev_io_stop (loop, iow + i);
1625	}	2049	}
1626		2050
1627	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2051	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1628	}	2052	}
1629		2053
1630	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2054	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1631	in the prepare watcher and would dispose of the check watcher.	2055	in the prepare watcher and would dispose of the check watcher.
1632		2056
1633	Method 3: If the module to be embedded supports explicit event	2057	Method 3: If the module to be embedded supports explicit event
1634	notification (adns does), you can also make use of the actual watcher	2058	notification (libadns does), you can also make use of the actual watcher
1635	callbacks, and only destroy/create the watchers in the prepare watcher.	2059	callbacks, and only destroy/create the watchers in the prepare watcher.
1636		2060
1637	static void	2061	static void
1638	timer_cb (EV_P_ ev_timer *w, int revents)	2062	timer_cb (EV_P_ ev_timer *w, int revents)
1639	{	2063	{
1640	adns_state ads = (adns_state)w->data;	2064	adns_state ads = (adns_state)w->data;
1641	update_now (EV_A);	2065	update_now (EV_A);
1642		2066
1643	adns_processtimeouts (ads, &tv_now);	2067	adns_processtimeouts (ads, &tv_now);
1644	}	2068	}
1645		2069
1646	static void	2070	static void
1647	io_cb (EV_P_ ev_io *w, int revents)	2071	io_cb (EV_P_ ev_io *w, int revents)
1648	{	2072	{
1649	adns_state ads = (adns_state)w->data;	2073	adns_state ads = (adns_state)w->data;
1650	update_now (EV_A);	2074	update_now (EV_A);
1651		2075
1652	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2076	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1653	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2077	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1654	}	2078	}
1655		2079
1656	// do not ever call adns_afterpoll	2080	// do not ever call adns_afterpoll
1657		2081
1658	Method 4: Do not use a prepare or check watcher because the module you	2082	Method 4: Do not use a prepare or check watcher because the module you
1659	want to embed is too inflexible to support it. Instead, youc na override	2083	want to embed is too inflexible to support it. Instead, you can override
1660	their poll function. The drawback with this solution is that the main	2084	their poll function. The drawback with this solution is that the main
1661	loop is now no longer controllable by EV. The C<Glib::EV> module does	2085	loop is now no longer controllable by EV. The C<Glib::EV> module does
1662	this.	2086	this.
1663		2087
1664	static gint	2088	static gint
1665	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1666	{	2090	{
1667	int got_events = 0;	2091	int got_events = 0;
1668		2092
1669	for (n = 0; n < nfds; ++n)	2093	for (n = 0; n < nfds; ++n)
1670	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2094	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1671		2095
1672	if (timeout >= 0)	2096	if (timeout >= 0)
1673	// create/start timer	2097	// create/start timer
1674		2098
1675	// poll	2099	// poll
1676	ev_loop (EV_A_ 0);	2100	ev_loop (EV_A_ 0);
1677		2101
1678	// stop timer again	2102	// stop timer again
1679	if (timeout >= 0)	2103	if (timeout >= 0)
1680	ev_timer_stop (EV_A_ &to);	2104	ev_timer_stop (EV_A_ &to);
1681		2105
1682	// stop io watchers again - their callbacks should have set	2106	// stop io watchers again - their callbacks should have set
1683	for (n = 0; n < nfds; ++n)	2107	for (n = 0; n < nfds; ++n)
1684	ev_io_stop (EV_A_ iow [n]);	2108	ev_io_stop (EV_A_ iow [n]);
1685		2109
1686	return got_events;	2110	return got_events;
1687	}	2111	}
1688		2112
1689		2113
1690	=head2 C<ev_embed> - when one backend isn't enough...	2114	=head2 C<ev_embed> - when one backend isn't enough...
1691		2115
1692	This is a rather advanced watcher type that lets you embed one event loop	2116	This is a rather advanced watcher type that lets you embed one event loop
…		…
1734	portable one.	2158	portable one.
1735		2159
1736	So when you want to use this feature you will always have to be prepared	2160	So when you want to use this feature you will always have to be prepared
1737	that you cannot get an embeddable loop. The recommended way to get around	2161	that you cannot get an embeddable loop. The recommended way to get around
1738	this is to have a separate variables for your embeddable loop, try to	2162	this is to have a separate variables for your embeddable loop, try to
1739	create it, and if that fails, use the normal loop for everything:	2163	create it, and if that fails, use the normal loop for everything.
1740
1741	struct ev_loop *loop_hi = ev_default_init (0);
1742	struct ev_loop *loop_lo = 0;
1743	struct ev_embed embed;
1744
1745	// see if there is a chance of getting one that works
1746	// (remember that a flags value of 0 means autodetection)
1747	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1748	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1749	: 0;
1750
1751	// if we got one, then embed it, otherwise default to loop_hi
1752	if (loop_lo)
1753	{
1754	ev_embed_init (&embed, 0, loop_lo);
1755	ev_embed_start (loop_hi, &embed);
1756	}
1757	else
1758	loop_lo = loop_hi;
1759		2164
1760	=head3 Watcher-Specific Functions and Data Members	2165	=head3 Watcher-Specific Functions and Data Members
1761		2166
1762	=over 4	2167	=over 4
1763		2168
…		…
1767		2172
1768	Configures the watcher to embed the given loop, which must be	2173	Configures the watcher to embed the given loop, which must be
1769	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2174	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1770	invoked automatically, otherwise it is the responsibility of the callback	2175	invoked automatically, otherwise it is the responsibility of the callback
1771	to invoke it (it will continue to be called until the sweep has been done,	2176	to invoke it (it will continue to be called until the sweep has been done,
1772	if you do not want thta, you need to temporarily stop the embed watcher).	2177	if you do not want that, you need to temporarily stop the embed watcher).
1773		2178
1774	=item ev_embed_sweep (loop, ev_embed *)	2179	=item ev_embed_sweep (loop, ev_embed *)
1775		2180
1776	Make a single, non-blocking sweep over the embedded loop. This works	2181	Make a single, non-blocking sweep over the embedded loop. This works
1777	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2182	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1778	apropriate way for embedded loops.	2183	appropriate way for embedded loops.
1779		2184
1780	=item struct ev_loop *loop [read-only]	2185	=item struct ev_loop *other [read-only]
1781		2186
1782	The embedded event loop.	2187	The embedded event loop.
1783		2188
1784	=back	2189	=back
		2190
		2191	=head3 Examples
		2192
		2193	Example: Try to get an embeddable event loop and embed it into the default
		2194	event loop. If that is not possible, use the default loop. The default
		2195	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2196	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2197	used).
		2198
		2199	struct ev_loop *loop_hi = ev_default_init (0);
		2200	struct ev_loop *loop_lo = 0;
		2201	struct ev_embed embed;
		2202
		2203	// see if there is a chance of getting one that works
		2204	// (remember that a flags value of 0 means autodetection)
		2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2207	: 0;
		2208
		2209	// if we got one, then embed it, otherwise default to loop_hi
		2210	if (loop_lo)
		2211	{
		2212	ev_embed_init (&embed, 0, loop_lo);
		2213	ev_embed_start (loop_hi, &embed);
		2214	}
		2215	else
		2216	loop_lo = loop_hi;
		2217
		2218	Example: Check if kqueue is available but not recommended and create
		2219	a kqueue backend for use with sockets (which usually work with any
		2220	kqueue implementation). Store the kqueue/socket-only event loop in
		2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2222
		2223	struct ev_loop *loop = ev_default_init (0);
		2224	struct ev_loop *loop_socket = 0;
		2225	struct ev_embed embed;
		2226
		2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2229	{
		2230	ev_embed_init (&embed, 0, loop_socket);
		2231	ev_embed_start (loop, &embed);
		2232	}
		2233
		2234	if (!loop_socket)
		2235	loop_socket = loop;
		2236
		2237	// now use loop_socket for all sockets, and loop for everything else
1785		2238
1786		2239
1787	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2240	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1788		2241
1789	Fork watchers are called when a C<fork ()> was detected (usually because	2242	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1805	believe me.	2258	believe me.
1806		2259
1807	=back	2260	=back
1808		2261
1809		2262
		2263	=head2 C<ev_async> - how to wake up another event loop
		2264
		2265	In general, you cannot use an C<ev_loop> from multiple threads or other
		2266	asynchronous sources such as signal handlers (as opposed to multiple event
		2267	loops - those are of course safe to use in different threads).
		2268
		2269	Sometimes, however, you need to wake up another event loop you do not
		2270	control, for example because it belongs to another thread. This is what
		2271	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2272	can signal it by calling C<ev_async_send>, which is thread- and signal
		2273	safe.
		2274
		2275	This functionality is very similar to C<ev_signal> watchers, as signals,
		2276	too, are asynchronous in nature, and signals, too, will be compressed
		2277	(i.e. the number of callback invocations may be less than the number of
		2278	C<ev_async_sent> calls).
		2279
		2280	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2281	just the default loop.
		2282
		2283	=head3 Queueing
		2284
		2285	C<ev_async> does not support queueing of data in any way. The reason
		2286	is that the author does not know of a simple (or any) algorithm for a
		2287	multiple-writer-single-reader queue that works in all cases and doesn't
		2288	need elaborate support such as pthreads.
		2289
		2290	That means that if you want to queue data, you have to provide your own
		2291	queue. But at least I can tell you would implement locking around your
		2292	queue:
		2293
		2294	=over 4
		2295
		2296	=item queueing from a signal handler context
		2297
		2298	To implement race-free queueing, you simply add to the queue in the signal
		2299	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2300	some fictitious SIGUSR1 handler:
		2301
		2302	static ev_async mysig;
		2303
		2304	static void
		2305	sigusr1_handler (void)
		2306	{
		2307	sometype data;
		2308
		2309	// no locking etc.
		2310	queue_put (data);
		2311	ev_async_send (EV_DEFAULT_ &mysig);
		2312	}
		2313
		2314	static void
		2315	mysig_cb (EV_P_ ev_async *w, int revents)
		2316	{
		2317	sometype data;
		2318	sigset_t block, prev;
		2319
		2320	sigemptyset (&block);
		2321	sigaddset (&block, SIGUSR1);
		2322	sigprocmask (SIG_BLOCK, &block, &prev);
		2323
		2324	while (queue_get (&data))
		2325	process (data);
		2326
		2327	if (sigismember (&prev, SIGUSR1)
		2328	sigprocmask (SIG_UNBLOCK, &block, 0);
		2329	}
		2330
		2331	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2332	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2333	either...).
		2334
		2335	=item queueing from a thread context
		2336
		2337	The strategy for threads is different, as you cannot (easily) block
		2338	threads but you can easily preempt them, so to queue safely you need to
		2339	employ a traditional mutex lock, such as in this pthread example:
		2340
		2341	static ev_async mysig;
		2342	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2343
		2344	static void
		2345	otherthread (void)
		2346	{
		2347	// only need to lock the actual queueing operation
		2348	pthread_mutex_lock (&mymutex);
		2349	queue_put (data);
		2350	pthread_mutex_unlock (&mymutex);
		2351
		2352	ev_async_send (EV_DEFAULT_ &mysig);
		2353	}
		2354
		2355	static void
		2356	mysig_cb (EV_P_ ev_async *w, int revents)
		2357	{
		2358	pthread_mutex_lock (&mymutex);
		2359
		2360	while (queue_get (&data))
		2361	process (data);
		2362
		2363	pthread_mutex_unlock (&mymutex);
		2364	}
		2365
		2366	=back
		2367
		2368
		2369	=head3 Watcher-Specific Functions and Data Members
		2370
		2371	=over 4
		2372
		2373	=item ev_async_init (ev_async *, callback)
		2374
		2375	Initialises and configures the async watcher - it has no parameters of any
		2376	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2377	believe me.
		2378
		2379	=item ev_async_send (loop, ev_async *)
		2380
		2381	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2382	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2383	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2384	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2385	section below on what exactly this means).
		2386
		2387	This call incurs the overhead of a system call only once per loop iteration,
		2388	so while the overhead might be noticeable, it doesn't apply to repeated
		2389	calls to C<ev_async_send>.
		2390
		2391	=item bool = ev_async_pending (ev_async *)
		2392
		2393	Returns a non-zero value when C<ev_async_send> has been called on the
		2394	watcher but the event has not yet been processed (or even noted) by the
		2395	event loop.
		2396
		2397	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2398	the loop iterates next and checks for the watcher to have become active,
		2399	it will reset the flag again. C<ev_async_pending> can be used to very
		2400	quickly check whether invoking the loop might be a good idea.
		2401
		2402	Not that this does I<not> check whether the watcher itself is pending, only
		2403	whether it has been requested to make this watcher pending.
		2404
		2405	=back
		2406
		2407
1810	=head1 OTHER FUNCTIONS	2408	=head1 OTHER FUNCTIONS
1811		2409
1812	There are some other functions of possible interest. Described. Here. Now.	2410	There are some other functions of possible interest. Described. Here. Now.
1813		2411
1814	=over 4	2412	=over 4
…		…
1821	or timeout without having to allocate/configure/start/stop/free one or	2419	or timeout without having to allocate/configure/start/stop/free one or
1822	more watchers yourself.	2420	more watchers yourself.
1823		2421
1824	If C<fd> is less than 0, then no I/O watcher will be started and events	2422	If C<fd> is less than 0, then no I/O watcher will be started and events
1825	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2423	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1826	C<events> set will be craeted and started.	2424	C<events> set will be created and started.
1827		2425
1828	If C<timeout> is less than 0, then no timeout watcher will be	2426	If C<timeout> is less than 0, then no timeout watcher will be
1829	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2427	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1830	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2428	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1831	dubious value.	2429	dubious value.
…		…
1833	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2431	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1834	passed an C<revents> set like normal event callbacks (a combination of	2432	passed an C<revents> set like normal event callbacks (a combination of
1835	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2433	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1836	value passed to C<ev_once>:	2434	value passed to C<ev_once>:
1837		2435
1838	static void stdin_ready (int revents, void *arg)	2436	static void stdin_ready (int revents, void *arg)
1839	{	2437	{
1840	if (revents & EV_TIMEOUT)	2438	if (revents & EV_TIMEOUT)
1841	/* doh, nothing entered */;	2439	/* doh, nothing entered */;
1842	else if (revents & EV_READ)	2440	else if (revents & EV_READ)
1843	/* stdin might have data for us, joy! */;	2441	/* stdin might have data for us, joy! */;
1844	}	2442	}
1845		2443
1846	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1847		2445
1848	=item ev_feed_event (ev_loop *, watcher *, int revents)	2446	=item ev_feed_event (ev_loop *, watcher *, int revents)
1849		2447
1850	Feeds the given event set into the event loop, as if the specified event	2448	Feeds the given event set into the event loop, as if the specified event
1851	had happened for the specified watcher (which must be a pointer to an	2449	had happened for the specified watcher (which must be a pointer to an
…		…
1856	Feed an event on the given fd, as if a file descriptor backend detected	2454	Feed an event on the given fd, as if a file descriptor backend detected
1857	the given events it.	2455	the given events it.
1858		2456
1859	=item ev_feed_signal_event (ev_loop *loop, int signum)	2457	=item ev_feed_signal_event (ev_loop *loop, int signum)
1860		2458
1861	Feed an event as if the given signal occured (C<loop> must be the default	2459	Feed an event as if the given signal occurred (C<loop> must be the default
1862	loop!).	2460	loop!).
1863		2461
1864	=back	2462	=back
1865		2463
1866		2464
…		…
1882		2480
1883	=item * Priorities are not currently supported. Initialising priorities	2481	=item * Priorities are not currently supported. Initialising priorities
1884	will fail and all watchers will have the same priority, even though there	2482	will fail and all watchers will have the same priority, even though there
1885	is an ev_pri field.	2483	is an ev_pri field.
1886		2484
		2485	=item * In libevent, the last base created gets the signals, in libev, the
		2486	first base created (== the default loop) gets the signals.
		2487
1887	=item * Other members are not supported.	2488	=item * Other members are not supported.
1888		2489
1889	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2490	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1890	to use the libev header file and library.	2491	to use the libev header file and library.
1891		2492
1892	=back	2493	=back
1893		2494
1894	=head1 C++ SUPPORT	2495	=head1 C++ SUPPORT
1895		2496
1896	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2497	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1897	you to use some convinience methods to start/stop watchers and also change	2498	you to use some convenience methods to start/stop watchers and also change
1898	the callback model to a model using method callbacks on objects.	2499	the callback model to a model using method callbacks on objects.
1899		2500
1900	To use it,	2501	To use it,
1901		2502
1902	#include <ev++.h>	2503	#include <ev++.h>
1903		2504
1904	This automatically includes F<ev.h> and puts all of its definitions (many	2505	This automatically includes F<ev.h> and puts all of its definitions (many
1905	of them macros) into the global namespace. All C++ specific things are	2506	of them macros) into the global namespace. All C++ specific things are
1906	put into the C<ev> namespace. It should support all the same embedding	2507	put into the C<ev> namespace. It should support all the same embedding
1907	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2508	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1974	your compiler is good :), then the method will be fully inlined into the	2575	your compiler is good :), then the method will be fully inlined into the
1975	thunking function, making it as fast as a direct C callback.	2576	thunking function, making it as fast as a direct C callback.
1976		2577
1977	Example: simple class declaration and watcher initialisation	2578	Example: simple class declaration and watcher initialisation
1978		2579
1979	struct myclass	2580	struct myclass
1980	{	2581	{
1981	void io_cb (ev::io &w, int revents) { }	2582	void io_cb (ev::io &w, int revents) { }
1982	}	2583	}
1983		2584
1984	myclass obj;	2585	myclass obj;
1985	ev::io iow;	2586	ev::io iow;
1986	iow.set <myclass, &myclass::io_cb> (&obj);	2587	iow.set <myclass, &myclass::io_cb> (&obj);
1987		2588
1988	=item w->set<function> (void *data = 0)	2589	=item w->set<function> (void *data = 0)
1989		2590
1990	Also sets a callback, but uses a static method or plain function as	2591	Also sets a callback, but uses a static method or plain function as
1991	callback. The optional C<data> argument will be stored in the watcher's	2592	callback. The optional C<data> argument will be stored in the watcher's
…		…
1995		2596
1996	See the method-C<set> above for more details.	2597	See the method-C<set> above for more details.
1997		2598
1998	Example:	2599	Example:
1999		2600
2000	static void io_cb (ev::io &w, int revents) { }	2601	static void io_cb (ev::io &w, int revents) { }
2001	iow.set <io_cb> ();	2602	iow.set <io_cb> ();
2002		2603
2003	=item w->set (struct ev_loop *)	2604	=item w->set (struct ev_loop *)
2004		2605
2005	Associates a different C<struct ev_loop> with this watcher. You can only	2606	Associates a different C<struct ev_loop> with this watcher. You can only
2006	do this when the watcher is inactive (and not pending either).	2607	do this when the watcher is inactive (and not pending either).
2007		2608
2008	=item w->set ([args])	2609	=item w->set ([arguments])
2009		2610
2010	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2611	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2011	called at least once. Unlike the C counterpart, an active watcher gets	2612	called at least once. Unlike the C counterpart, an active watcher gets
2012	automatically stopped and restarted when reconfiguring it with this	2613	automatically stopped and restarted when reconfiguring it with this
2013	method.	2614	method.
2014		2615
2015	=item w->start ()	2616	=item w->start ()
…		…
2019		2620
2020	=item w->stop ()	2621	=item w->stop ()
2021		2622
2022	Stops the watcher if it is active. Again, no C<loop> argument.	2623	Stops the watcher if it is active. Again, no C<loop> argument.
2023		2624
2024	=item w->again () C<ev::timer>, C<ev::periodic> only	2625	=item w->again () (C<ev::timer>, C<ev::periodic> only)
2025		2626
2026	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2627	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
2027	C<ev_TYPE_again> function.	2628	C<ev_TYPE_again> function.
2028		2629
2029	=item w->sweep () C<ev::embed> only	2630	=item w->sweep () (C<ev::embed> only)
2030		2631
2031	Invokes C<ev_embed_sweep>.	2632	Invokes C<ev_embed_sweep>.
2032		2633
2033	=item w->update () C<ev::stat> only	2634	=item w->update () (C<ev::stat> only)
2034		2635
2035	Invokes C<ev_stat_stat>.	2636	Invokes C<ev_stat_stat>.
2036		2637
2037	=back	2638	=back
2038		2639
2039	=back	2640	=back
2040		2641
2041	Example: Define a class with an IO and idle watcher, start one of them in	2642	Example: Define a class with an IO and idle watcher, start one of them in
2042	the constructor.	2643	the constructor.
2043		2644
2044	class myclass	2645	class myclass
2045	{	2646	{
2046	ev_io io; void io_cb (ev::io &w, int revents);	2647	ev::io io; void io_cb (ev::io &w, int revents);
2047	ev_idle idle void idle_cb (ev::idle &w, int revents);	2648	ev:idle idle void idle_cb (ev::idle &w, int revents);
2048		2649
2049	myclass ();	2650	myclass (int fd)
2050	}	2651	{
2051
2052	myclass::myclass (int fd)
2053	{
2054	io .set <myclass, &myclass::io_cb > (this);	2652	io .set <myclass, &myclass::io_cb > (this);
2055	idle.set <myclass, &myclass::idle_cb> (this);	2653	idle.set <myclass, &myclass::idle_cb> (this);
2056		2654
2057	io.start (fd, ev::READ);	2655	io.start (fd, ev::READ);
		2656	}
2058	}	2657	};
		2658
		2659
		2660	=head1 OTHER LANGUAGE BINDINGS
		2661
		2662	Libev does not offer other language bindings itself, but bindings for a
		2663	number of languages exist in the form of third-party packages. If you know
		2664	any interesting language binding in addition to the ones listed here, drop
		2665	me a note.
		2666
		2667	=over 4
		2668
		2669	=item Perl
		2670
		2671	The EV module implements the full libev API and is actually used to test
		2672	libev. EV is developed together with libev. Apart from the EV core module,
		2673	there are additional modules that implement libev-compatible interfaces
		2674	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2675	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2676
		2677	It can be found and installed via CPAN, its homepage is at
		2678	L<http://software.schmorp.de/pkg/EV>.
		2679
		2680	=item Python
		2681
		2682	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2683	seems to be quite complete and well-documented. Note, however, that the
		2684	patch they require for libev is outright dangerous as it breaks the ABI
		2685	for everybody else, and therefore, should never be applied in an installed
		2686	libev (if python requires an incompatible ABI then it needs to embed
		2687	libev).
		2688
		2689	=item Ruby
		2690
		2691	Tony Arcieri has written a ruby extension that offers access to a subset
		2692	of the libev API and adds file handle abstractions, asynchronous DNS and
		2693	more on top of it. It can be found via gem servers. Its homepage is at
		2694	L<http://rev.rubyforge.org/>.
		2695
		2696	=item D
		2697
		2698	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2699	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2700
		2701	=back
2059		2702
2060		2703
2061	=head1 MACRO MAGIC	2704	=head1 MACRO MAGIC
2062		2705
2063	Libev can be compiled with a variety of options, the most fundemantal is	2706	Libev can be compiled with a variety of options, the most fundamental
2064	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2707	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2065	callbacks have an initial C<struct ev_loop *> argument.	2708	functions and callbacks have an initial C<struct ev_loop *> argument.
2066		2709
2067	To make it easier to write programs that cope with either variant, the	2710	To make it easier to write programs that cope with either variant, the
2068	following macros are defined:	2711	following macros are defined:
2069		2712
2070	=over 4	2713	=over 4
…		…
2073		2716
2074	This provides the loop I<argument> for functions, if one is required ("ev	2717	This provides the loop I<argument> for functions, if one is required ("ev
2075	loop argument"). The C<EV_A> form is used when this is the sole argument,	2718	loop argument"). The C<EV_A> form is used when this is the sole argument,
2076	C<EV_A_> is used when other arguments are following. Example:	2719	C<EV_A_> is used when other arguments are following. Example:
2077		2720
2078	ev_unref (EV_A);	2721	ev_unref (EV_A);
2079	ev_timer_add (EV_A_ watcher);	2722	ev_timer_add (EV_A_ watcher);
2080	ev_loop (EV_A_ 0);	2723	ev_loop (EV_A_ 0);
2081		2724
2082	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2725	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2083	which is often provided by the following macro.	2726	which is often provided by the following macro.
2084		2727
2085	=item C<EV_P>, C<EV_P_>	2728	=item C<EV_P>, C<EV_P_>
2086		2729
2087	This provides the loop I<parameter> for functions, if one is required ("ev	2730	This provides the loop I<parameter> for functions, if one is required ("ev
2088	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2731	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2089	C<EV_P_> is used when other parameters are following. Example:	2732	C<EV_P_> is used when other parameters are following. Example:
2090		2733
2091	// this is how ev_unref is being declared	2734	// this is how ev_unref is being declared
2092	static void ev_unref (EV_P);	2735	static void ev_unref (EV_P);
2093		2736
2094	// this is how you can declare your typical callback	2737	// this is how you can declare your typical callback
2095	static void cb (EV_P_ ev_timer *w, int revents)	2738	static void cb (EV_P_ ev_timer *w, int revents)
2096		2739
2097	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2740	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2098	suitable for use with C<EV_A>.	2741	suitable for use with C<EV_A>.
2099		2742
2100	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2743	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2101		2744
2102	Similar to the other two macros, this gives you the value of the default	2745	Similar to the other two macros, this gives you the value of the default
2103	loop, if multiple loops are supported ("ev loop default").	2746	loop, if multiple loops are supported ("ev loop default").
		2747
		2748	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2749
		2750	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2751	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2752	is undefined when the default loop has not been initialised by a previous
		2753	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2754
		2755	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2756	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2104		2757
2105	=back	2758	=back
2106		2759
2107	Example: Declare and initialise a check watcher, utilising the above	2760	Example: Declare and initialise a check watcher, utilising the above
2108	macros so it will work regardless of whether multiple loops are supported	2761	macros so it will work regardless of whether multiple loops are supported
2109	or not.	2762	or not.
2110		2763
2111	static void	2764	static void
2112	check_cb (EV_P_ ev_timer *w, int revents)	2765	check_cb (EV_P_ ev_timer *w, int revents)
2113	{	2766	{
2114	ev_check_stop (EV_A_ w);	2767	ev_check_stop (EV_A_ w);
2115	}	2768	}
2116		2769
2117	ev_check check;	2770	ev_check check;
2118	ev_check_init (&check, check_cb);	2771	ev_check_init (&check, check_cb);
2119	ev_check_start (EV_DEFAULT_ &check);	2772	ev_check_start (EV_DEFAULT_ &check);
2120	ev_loop (EV_DEFAULT_ 0);	2773	ev_loop (EV_DEFAULT_ 0);
2121		2774
2122	=head1 EMBEDDING	2775	=head1 EMBEDDING
2123		2776
2124	Libev can (and often is) directly embedded into host	2777	Libev can (and often is) directly embedded into host
2125	applications. Examples of applications that embed it include the Deliantra	2778	applications. Examples of applications that embed it include the Deliantra
2126	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2779	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2127	and rxvt-unicode.	2780	and rxvt-unicode.
2128		2781
2129	The goal is to enable you to just copy the neecssary files into your	2782	The goal is to enable you to just copy the necessary files into your
2130	source directory without having to change even a single line in them, so	2783	source directory without having to change even a single line in them, so
2131	you can easily upgrade by simply copying (or having a checked-out copy of	2784	you can easily upgrade by simply copying (or having a checked-out copy of
2132	libev somewhere in your source tree).	2785	libev somewhere in your source tree).
2133		2786
2134	=head2 FILESETS	2787	=head2 FILESETS
2135		2788
2136	Depending on what features you need you need to include one or more sets of files	2789	Depending on what features you need you need to include one or more sets of files
2137	in your app.	2790	in your application.
2138		2791
2139	=head3 CORE EVENT LOOP	2792	=head3 CORE EVENT LOOP
2140		2793
2141	To include only the libev core (all the C<ev_*> functions), with manual	2794	To include only the libev core (all the C<ev_*> functions), with manual
2142	configuration (no autoconf):	2795	configuration (no autoconf):
2143		2796
2144	#define EV_STANDALONE 1	2797	#define EV_STANDALONE 1
2145	#include "ev.c"	2798	#include "ev.c"
2146		2799
2147	This will automatically include F<ev.h>, too, and should be done in a	2800	This will automatically include F<ev.h>, too, and should be done in a
2148	single C source file only to provide the function implementations. To use	2801	single C source file only to provide the function implementations. To use
2149	it, do the same for F<ev.h> in all files wishing to use this API (best	2802	it, do the same for F<ev.h> in all files wishing to use this API (best
2150	done by writing a wrapper around F<ev.h> that you can include instead and	2803	done by writing a wrapper around F<ev.h> that you can include instead and
2151	where you can put other configuration options):	2804	where you can put other configuration options):
2152		2805
2153	#define EV_STANDALONE 1	2806	#define EV_STANDALONE 1
2154	#include "ev.h"	2807	#include "ev.h"
2155		2808
2156	Both header files and implementation files can be compiled with a C++	2809	Both header files and implementation files can be compiled with a C++
2157	compiler (at least, thats a stated goal, and breakage will be treated	2810	compiler (at least, thats a stated goal, and breakage will be treated
2158	as a bug).	2811	as a bug).
2159		2812
2160	You need the following files in your source tree, or in a directory	2813	You need the following files in your source tree, or in a directory
2161	in your include path (e.g. in libev/ when using -Ilibev):	2814	in your include path (e.g. in libev/ when using -Ilibev):
2162		2815
2163	ev.h	2816	ev.h
2164	ev.c	2817	ev.c
2165	ev_vars.h	2818	ev_vars.h
2166	ev_wrap.h	2819	ev_wrap.h
2167		2820
2168	ev_win32.c required on win32 platforms only	2821	ev_win32.c required on win32 platforms only
2169		2822
2170	ev_select.c only when select backend is enabled (which is enabled by default)	2823	ev_select.c only when select backend is enabled (which is enabled by default)
2171	ev_poll.c only when poll backend is enabled (disabled by default)	2824	ev_poll.c only when poll backend is enabled (disabled by default)
2172	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2825	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2173	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2826	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2174	ev_port.c only when the solaris port backend is enabled (disabled by default)	2827	ev_port.c only when the solaris port backend is enabled (disabled by default)
2175		2828
2176	F<ev.c> includes the backend files directly when enabled, so you only need	2829	F<ev.c> includes the backend files directly when enabled, so you only need
2177	to compile this single file.	2830	to compile this single file.
2178		2831
2179	=head3 LIBEVENT COMPATIBILITY API	2832	=head3 LIBEVENT COMPATIBILITY API
2180		2833
2181	To include the libevent compatibility API, also include:	2834	To include the libevent compatibility API, also include:
2182		2835
2183	#include "event.c"	2836	#include "event.c"
2184		2837
2185	in the file including F<ev.c>, and:	2838	in the file including F<ev.c>, and:
2186		2839
2187	#include "event.h"	2840	#include "event.h"
2188		2841
2189	in the files that want to use the libevent API. This also includes F<ev.h>.	2842	in the files that want to use the libevent API. This also includes F<ev.h>.
2190		2843
2191	You need the following additional files for this:	2844	You need the following additional files for this:
2192		2845
2193	event.h	2846	event.h
2194	event.c	2847	event.c
2195		2848
2196	=head3 AUTOCONF SUPPORT	2849	=head3 AUTOCONF SUPPORT
2197		2850
2198	Instead of using C<EV_STANDALONE=1> and providing your config in	2851	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2199	whatever way you want, you can also C<m4_include([libev.m4])> in your	2852	whatever way you want, you can also C<m4_include([libev.m4])> in your
2200	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2853	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2201	include F<config.h> and configure itself accordingly.	2854	include F<config.h> and configure itself accordingly.
2202		2855
2203	For this of course you need the m4 file:	2856	For this of course you need the m4 file:
2204		2857
2205	libev.m4	2858	libev.m4
2206		2859
2207	=head2 PREPROCESSOR SYMBOLS/MACROS	2860	=head2 PREPROCESSOR SYMBOLS/MACROS
2208		2861
2209	Libev can be configured via a variety of preprocessor symbols you have to define	2862	Libev can be configured via a variety of preprocessor symbols you have to
2210	before including any of its files. The default is not to build for multiplicity	2863	define before including any of its files. The default in the absence of
2211	and only include the select backend.	2864	autoconf is noted for every option.
2212		2865
2213	=over 4	2866	=over 4
2214		2867
2215	=item EV_STANDALONE	2868	=item EV_STANDALONE
2216		2869
…		…
2221	F<event.h> that are not directly supported by the libev core alone.	2874	F<event.h> that are not directly supported by the libev core alone.
2222		2875
2223	=item EV_USE_MONOTONIC	2876	=item EV_USE_MONOTONIC
2224		2877
2225	If defined to be C<1>, libev will try to detect the availability of the	2878	If defined to be C<1>, libev will try to detect the availability of the
2226	monotonic clock option at both compiletime and runtime. Otherwise no use	2879	monotonic clock option at both compile time and runtime. Otherwise no use
2227	of the monotonic clock option will be attempted. If you enable this, you	2880	of the monotonic clock option will be attempted. If you enable this, you
2228	usually have to link against librt or something similar. Enabling it when	2881	usually have to link against librt or something similar. Enabling it when
2229	the functionality isn't available is safe, though, althoguh you have	2882	the functionality isn't available is safe, though, although you have
2230	to make sure you link against any libraries where the C<clock_gettime>	2883	to make sure you link against any libraries where the C<clock_gettime>
2231	function is hiding in (often F<-lrt>).	2884	function is hiding in (often F<-lrt>).
2232		2885
2233	=item EV_USE_REALTIME	2886	=item EV_USE_REALTIME
2234		2887
2235	If defined to be C<1>, libev will try to detect the availability of the	2888	If defined to be C<1>, libev will try to detect the availability of the
2236	realtime clock option at compiletime (and assume its availability at	2889	real-time clock option at compile time (and assume its availability at
2237	runtime if successful). Otherwise no use of the realtime clock option will	2890	runtime if successful). Otherwise no use of the real-time clock option will
2238	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2891	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2239	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2892	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2240	in the description of C<EV_USE_MONOTONIC>, though.	2893	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2894
		2895	=item EV_USE_NANOSLEEP
		2896
		2897	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2898	and will use it for delays. Otherwise it will use C<select ()>.
		2899
		2900	=item EV_USE_EVENTFD
		2901
		2902	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2903	available and will probe for kernel support at runtime. This will improve
		2904	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2905	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2906	2.7 or newer, otherwise disabled.
2241		2907
2242	=item EV_USE_SELECT	2908	=item EV_USE_SELECT
2243		2909
2244	If undefined or defined to be C<1>, libev will compile in support for the	2910	If undefined or defined to be C<1>, libev will compile in support for the
2245	C<select>(2) backend. No attempt at autodetection will be done: if no	2911	C<select>(2) backend. No attempt at auto-detection will be done: if no
2246	other method takes over, select will be it. Otherwise the select backend	2912	other method takes over, select will be it. Otherwise the select backend
2247	will not be compiled in.	2913	will not be compiled in.
2248		2914
2249	=item EV_SELECT_USE_FD_SET	2915	=item EV_SELECT_USE_FD_SET
2250		2916
2251	If defined to C<1>, then the select backend will use the system C<fd_set>	2917	If defined to C<1>, then the select backend will use the system C<fd_set>
2252	structure. This is useful if libev doesn't compile due to a missing	2918	structure. This is useful if libev doesn't compile due to a missing
2253	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2919	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2254	exotic systems. This usually limits the range of file descriptors to some	2920	exotic systems. This usually limits the range of file descriptors to some
2255	low limit such as 1024 or might have other limitations (winsocket only	2921	low limit such as 1024 or might have other limitations (winsocket only
2256	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2922	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2257	influence the size of the C<fd_set> used.	2923	influence the size of the C<fd_set> used.
2258		2924
…		…
2264	be used is the winsock select). This means that it will call	2930	be used is the winsock select). This means that it will call
2265	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2931	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2266	it is assumed that all these functions actually work on fds, even	2932	it is assumed that all these functions actually work on fds, even
2267	on win32. Should not be defined on non-win32 platforms.	2933	on win32. Should not be defined on non-win32 platforms.
2268		2934
		2935	=item EV_FD_TO_WIN32_HANDLE
		2936
		2937	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2938	file descriptors to socket handles. When not defining this symbol (the
		2939	default), then libev will call C<_get_osfhandle>, which is usually
		2940	correct. In some cases, programs use their own file descriptor management,
		2941	in which case they can provide this function to map fds to socket handles.
		2942
2269	=item EV_USE_POLL	2943	=item EV_USE_POLL
2270		2944
2271	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2945	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2272	backend. Otherwise it will be enabled on non-win32 platforms. It	2946	backend. Otherwise it will be enabled on non-win32 platforms. It
2273	takes precedence over select.	2947	takes precedence over select.
2274		2948
2275	=item EV_USE_EPOLL	2949	=item EV_USE_EPOLL
2276		2950
2277	If defined to be C<1>, libev will compile in support for the Linux	2951	If defined to be C<1>, libev will compile in support for the Linux
2278	C<epoll>(7) backend. Its availability will be detected at runtime,	2952	C<epoll>(7) backend. Its availability will be detected at runtime,
2279	otherwise another method will be used as fallback. This is the	2953	otherwise another method will be used as fallback. This is the preferred
2280	preferred backend for GNU/Linux systems.	2954	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2955	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2281		2956
2282	=item EV_USE_KQUEUE	2957	=item EV_USE_KQUEUE
2283		2958
2284	If defined to be C<1>, libev will compile in support for the BSD style	2959	If defined to be C<1>, libev will compile in support for the BSD style
2285	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2960	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2298	otherwise another method will be used as fallback. This is the preferred	2973	otherwise another method will be used as fallback. This is the preferred
2299	backend for Solaris 10 systems.	2974	backend for Solaris 10 systems.
2300		2975
2301	=item EV_USE_DEVPOLL	2976	=item EV_USE_DEVPOLL
2302		2977
2303	reserved for future expansion, works like the USE symbols above.	2978	Reserved for future expansion, works like the USE symbols above.
2304		2979
2305	=item EV_USE_INOTIFY	2980	=item EV_USE_INOTIFY
2306		2981
2307	If defined to be C<1>, libev will compile in support for the Linux inotify	2982	If defined to be C<1>, libev will compile in support for the Linux inotify
2308	interface to speed up C<ev_stat> watchers. Its actual availability will	2983	interface to speed up C<ev_stat> watchers. Its actual availability will
2309	be detected at runtime.	2984	be detected at runtime. If undefined, it will be enabled if the headers
		2985	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2986
		2987	=item EV_ATOMIC_T
		2988
		2989	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2990	access is atomic with respect to other threads or signal contexts. No such
		2991	type is easily found in the C language, so you can provide your own type
		2992	that you know is safe for your purposes. It is used both for signal handler "locking"
		2993	as well as for signal and thread safety in C<ev_async> watchers.
		2994
		2995	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2996	(from F<signal.h>), which is usually good enough on most platforms.
2310		2997
2311	=item EV_H	2998	=item EV_H
2312		2999
2313	The name of the F<ev.h> header file used to include it. The default if	3000	The name of the F<ev.h> header file used to include it. The default if
2314	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3001	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2315	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3002	used to virtually rename the F<ev.h> header file in case of conflicts.
2316		3003
2317	=item EV_CONFIG_H	3004	=item EV_CONFIG_H
2318		3005
2319	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3006	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2320	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3007	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2321	C<EV_H>, above.	3008	C<EV_H>, above.
2322		3009
2323	=item EV_EVENT_H	3010	=item EV_EVENT_H
2324		3011
2325	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3012	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2326	of how the F<event.h> header can be found.	3013	of how the F<event.h> header can be found, the default is C<"event.h">.
2327		3014
2328	=item EV_PROTOTYPES	3015	=item EV_PROTOTYPES
2329		3016
2330	If defined to be C<0>, then F<ev.h> will not define any function	3017	If defined to be C<0>, then F<ev.h> will not define any function
2331	prototypes, but still define all the structs and other symbols. This is	3018	prototypes, but still define all the structs and other symbols. This is
…		…
2352	When doing priority-based operations, libev usually has to linearly search	3039	When doing priority-based operations, libev usually has to linearly search
2353	all the priorities, so having many of them (hundreds) uses a lot of space	3040	all the priorities, so having many of them (hundreds) uses a lot of space
2354	and time, so using the defaults of five priorities (-2 .. +2) is usually	3041	and time, so using the defaults of five priorities (-2 .. +2) is usually
2355	fine.	3042	fine.
2356		3043
2357	If your embedding app does not need any priorities, defining these both to	3044	If your embedding application does not need any priorities, defining these both to
2358	C<0> will save some memory and cpu.	3045	C<0> will save some memory and CPU.
2359		3046
2360	=item EV_PERIODIC_ENABLE	3047	=item EV_PERIODIC_ENABLE
2361		3048
2362	If undefined or defined to be C<1>, then periodic timers are supported. If	3049	If undefined or defined to be C<1>, then periodic timers are supported. If
2363	defined to be C<0>, then they are not. Disabling them saves a few kB of	3050	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2382	=item EV_FORK_ENABLE	3069	=item EV_FORK_ENABLE
2383		3070
2384	If undefined or defined to be C<1>, then fork watchers are supported. If	3071	If undefined or defined to be C<1>, then fork watchers are supported. If
2385	defined to be C<0>, then they are not.	3072	defined to be C<0>, then they are not.
2386		3073
		3074	=item EV_ASYNC_ENABLE
		3075
		3076	If undefined or defined to be C<1>, then async watchers are supported. If
		3077	defined to be C<0>, then they are not.
		3078
2387	=item EV_MINIMAL	3079	=item EV_MINIMAL
2388		3080
2389	If you need to shave off some kilobytes of code at the expense of some	3081	If you need to shave off some kilobytes of code at the expense of some
2390	speed, define this symbol to C<1>. Currently only used for gcc to override	3082	speed, define this symbol to C<1>. Currently this is used to override some
2391	some inlining decisions, saves roughly 30% codesize of amd64.	3083	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3084	much smaller 2-heap for timer management over the default 4-heap.
2392		3085
2393	=item EV_PID_HASHSIZE	3086	=item EV_PID_HASHSIZE
2394		3087
2395	C<ev_child> watchers use a small hash table to distribute workload by	3088	C<ev_child> watchers use a small hash table to distribute workload by
2396	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3089	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2397	than enough. If you need to manage thousands of children you might want to	3090	than enough. If you need to manage thousands of children you might want to
2398	increase this value (I<must> be a power of two).	3091	increase this value (I<must> be a power of two).
2399		3092
2400	=item EV_INOTIFY_HASHSIZE	3093	=item EV_INOTIFY_HASHSIZE
2401		3094
2402	C<ev_staz> watchers use a small hash table to distribute workload by	3095	C<ev_stat> watchers use a small hash table to distribute workload by
2403	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3096	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2404	usually more than enough. If you need to manage thousands of C<ev_stat>	3097	usually more than enough. If you need to manage thousands of C<ev_stat>
2405	watchers you might want to increase this value (I<must> be a power of	3098	watchers you might want to increase this value (I<must> be a power of
2406	two).	3099	two).
2407		3100
		3101	=item EV_USE_4HEAP
		3102
		3103	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3104	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3105	to C<1>. The 4-heap uses more complicated (longer) code but has
		3106	noticeably faster performance with many (thousands) of watchers.
		3107
		3108	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3109	(disabled).
		3110
		3111	=item EV_HEAP_CACHE_AT
		3112
		3113	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3114	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3115	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3116	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3117	but avoids random read accesses on heap changes. This improves performance
		3118	noticeably with with many (hundreds) of watchers.
		3119
		3120	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3121	(disabled).
		3122
		3123	=item EV_VERIFY
		3124
		3125	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3126	be done: If set to C<0>, no internal verification code will be compiled
		3127	in. If set to C<1>, then verification code will be compiled in, but not
		3128	called. If set to C<2>, then the internal verification code will be
		3129	called once per loop, which can slow down libev. If set to C<3>, then the
		3130	verification code will be called very frequently, which will slow down
		3131	libev considerably.
		3132
		3133	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3134	C<0.>
		3135
2408	=item EV_COMMON	3136	=item EV_COMMON
2409		3137
2410	By default, all watchers have a C<void *data> member. By redefining	3138	By default, all watchers have a C<void *data> member. By redefining
2411	this macro to a something else you can include more and other types of	3139	this macro to a something else you can include more and other types of
2412	members. You have to define it each time you include one of the files,	3140	members. You have to define it each time you include one of the files,
2413	though, and it must be identical each time.	3141	though, and it must be identical each time.
2414		3142
2415	For example, the perl EV module uses something like this:	3143	For example, the perl EV module uses something like this:
2416		3144
2417	#define EV_COMMON \	3145	#define EV_COMMON \
2418	SV *self; /* contains this struct */ \	3146	SV *self; /* contains this struct */ \
2419	SV *cb_sv, *fh /* note no trailing ";" */	3147	SV *cb_sv, *fh /* note no trailing ";" */
2420		3148
2421	=item EV_CB_DECLARE (type)	3149	=item EV_CB_DECLARE (type)
2422		3150
2423	=item EV_CB_INVOKE (watcher, revents)	3151	=item EV_CB_INVOKE (watcher, revents)
2424		3152
2425	=item ev_set_cb (ev, cb)	3153	=item ev_set_cb (ev, cb)
2426		3154
2427	Can be used to change the callback member declaration in each watcher,	3155	Can be used to change the callback member declaration in each watcher,
2428	and the way callbacks are invoked and set. Must expand to a struct member	3156	and the way callbacks are invoked and set. Must expand to a struct member
2429	definition and a statement, respectively. See the F<ev.v> header file for	3157	definition and a statement, respectively. See the F<ev.h> header file for
2430	their default definitions. One possible use for overriding these is to	3158	their default definitions. One possible use for overriding these is to
2431	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3159	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2432	method calls instead of plain function calls in C++.	3160	method calls instead of plain function calls in C++.
		3161
		3162	=head2 EXPORTED API SYMBOLS
		3163
		3164	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3165	exported symbols, you can use the provided F<Symbol.*> files which list
		3166	all public symbols, one per line:
		3167
		3168	Symbols.ev for libev proper
		3169	Symbols.event for the libevent emulation
		3170
		3171	This can also be used to rename all public symbols to avoid clashes with
		3172	multiple versions of libev linked together (which is obviously bad in
		3173	itself, but sometimes it is inconvenient to avoid this).
		3174
		3175	A sed command like this will create wrapper C<#define>'s that you need to
		3176	include before including F<ev.h>:
		3177
		3178	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3179
		3180	This would create a file F<wrap.h> which essentially looks like this:
		3181
		3182	#define ev_backend myprefix_ev_backend
		3183	#define ev_check_start myprefix_ev_check_start
		3184	#define ev_check_stop myprefix_ev_check_stop
		3185	...
2433		3186
2434	=head2 EXAMPLES	3187	=head2 EXAMPLES
2435		3188
2436	For a real-world example of a program the includes libev	3189	For a real-world example of a program the includes libev
2437	verbatim, you can have a look at the EV perl module	3190	verbatim, you can have a look at the EV perl module
…		…
2442	file.	3195	file.
2443		3196
2444	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3197	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2445	that everybody includes and which overrides some configure choices:	3198	that everybody includes and which overrides some configure choices:
2446		3199
2447	#define EV_MINIMAL 1	3200	#define EV_MINIMAL 1
2448	#define EV_USE_POLL 0	3201	#define EV_USE_POLL 0
2449	#define EV_MULTIPLICITY 0	3202	#define EV_MULTIPLICITY 0
2450	#define EV_PERIODIC_ENABLE 0	3203	#define EV_PERIODIC_ENABLE 0
2451	#define EV_STAT_ENABLE 0	3204	#define EV_STAT_ENABLE 0
2452	#define EV_FORK_ENABLE 0	3205	#define EV_FORK_ENABLE 0
2453	#define EV_CONFIG_H <config.h>	3206	#define EV_CONFIG_H <config.h>
2454	#define EV_MINPRI 0	3207	#define EV_MINPRI 0
2455	#define EV_MAXPRI 0	3208	#define EV_MAXPRI 0
2456		3209
2457	#include "ev++.h"	3210	#include "ev++.h"
2458		3211
2459	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3212	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2460		3213
2461	#include "ev_cpp.h"	3214	#include "ev_cpp.h"
2462	#include "ev.c"	3215	#include "ev.c"
		3216
		3217
		3218	=head1 THREADS AND COROUTINES
		3219
		3220	=head2 THREADS
		3221
		3222	Libev itself is completely thread-safe, but it uses no locking. This
		3223	means that you can use as many loops as you want in parallel, as long as
		3224	only one thread ever calls into one libev function with the same loop
		3225	parameter.
		3226
		3227	Or put differently: calls with different loop parameters can be done in
		3228	parallel from multiple threads, calls with the same loop parameter must be
		3229	done serially (but can be done from different threads, as long as only one
		3230	thread ever is inside a call at any point in time, e.g. by using a mutex
		3231	per loop).
		3232
		3233	If you want to know which design (one loop, locking, or multiple loops
		3234	without or something else still) is best for your problem, then I cannot
		3235	help you. I can give some generic advice however:
		3236
		3237	=over 4
		3238
		3239	=item * most applications have a main thread: use the default libev loop
		3240	in that thread, or create a separate thread running only the default loop.
		3241
		3242	This helps integrating other libraries or software modules that use libev
		3243	themselves and don't care/know about threading.
		3244
		3245	=item * one loop per thread is usually a good model.
		3246
		3247	Doing this is almost never wrong, sometimes a better-performance model
		3248	exists, but it is always a good start.
		3249
		3250	=item * other models exist, such as the leader/follower pattern, where one
		3251	loop is handed through multiple threads in a kind of round-robin fashion.
		3252
		3253	Choosing a model is hard - look around, learn, know that usually you can do
		3254	better than you currently do :-)
		3255
		3256	=item * often you need to talk to some other thread which blocks in the
		3257	event loop - C<ev_async> watchers can be used to wake them up from other
		3258	threads safely (or from signal contexts...).
		3259
		3260	=back
		3261
		3262	=head2 COROUTINES
		3263
		3264	Libev is much more accommodating to coroutines ("cooperative threads"):
		3265	libev fully supports nesting calls to it's functions from different
		3266	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3267	different coroutines and switch freely between both coroutines running the
		3268	loop, as long as you don't confuse yourself). The only exception is that
		3269	you must not do this from C<ev_periodic> reschedule callbacks.
		3270
		3271	Care has been invested into making sure that libev does not keep local
		3272	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3273	switches.
2463		3274
2464		3275
2465	=head1 COMPLEXITIES	3276	=head1 COMPLEXITIES
2466		3277
2467	In this section the complexities of (many of) the algorithms used inside	3278	In this section the complexities of (many of) the algorithms used inside
…		…
2478		3289
2479	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3290	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2480		3291
2481	This means that, when you have a watcher that triggers in one hour and	3292	This means that, when you have a watcher that triggers in one hour and
2482	there are 100 watchers that would trigger before that then inserting will	3293	there are 100 watchers that would trigger before that then inserting will
2483	have to skip those 100 watchers.	3294	have to skip roughly seven (C<ld 100>) of these watchers.
2484		3295
2485	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2486		3297
2487	That means that for changing a timer costs less than removing/adding them	3298	That means that changing a timer costs less than removing/adding them
2488	as only the relative motion in the event queue has to be paid for.	3299	as only the relative motion in the event queue has to be paid for.
2489		3300
2490	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3301	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2491		3302
2492	These just add the watcher into an array or at the head of a list.	3303	These just add the watcher into an array or at the head of a list.
		3304
2493	=item Stopping check/prepare/idle watchers: O(1)	3305	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2494		3306
2495	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3307	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2496		3308
2497	These watchers are stored in lists then need to be walked to find the	3309	These watchers are stored in lists then need to be walked to find the
2498	correct watcher to remove. The lists are usually short (you don't usually	3310	correct watcher to remove. The lists are usually short (you don't usually
2499	have many watchers waiting for the same fd or signal).	3311	have many watchers waiting for the same fd or signal).
2500		3312
2501	=item Finding the next timer per loop iteration: O(1)	3313	=item Finding the next timer in each loop iteration: O(1)
		3314
		3315	By virtue of using a binary or 4-heap, the next timer is always found at a
		3316	fixed position in the storage array.
2502		3317
2503	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2504		3319
2505	A change means an I/O watcher gets started or stopped, which requires	3320	A change means an I/O watcher gets started or stopped, which requires
2506	libev to recalculate its status (and possibly tell the kernel).	3321	libev to recalculate its status (and possibly tell the kernel, depending
		3322	on backend and whether C<ev_io_set> was used).
2507		3323
2508	=item Activating one watcher: O(1)	3324	=item Activating one watcher (putting it into the pending state): O(1)
2509		3325
2510	=item Priority handling: O(number_of_priorities)	3326	=item Priority handling: O(number_of_priorities)
2511		3327
2512	Priorities are implemented by allocating some space for each	3328	Priorities are implemented by allocating some space for each
2513	priority. When doing priority-based operations, libev usually has to	3329	priority. When doing priority-based operations, libev usually has to
2514	linearly search all the priorities.	3330	linearly search all the priorities, but starting/stopping and activating
		3331	watchers becomes O(1) w.r.t. priority handling.
		3332
		3333	=item Sending an ev_async: O(1)
		3334
		3335	=item Processing ev_async_send: O(number_of_async_watchers)
		3336
		3337	=item Processing signals: O(max_signal_number)
		3338
		3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3340	calls in the current loop iteration. Checking for async and signal events
		3341	involves iterating over all running async watchers or all signal numbers.
2515		3342
2516	=back	3343	=back
2517		3344
2518		3345
		3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3347
		3348	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3349	requires, and its I/O model is fundamentally incompatible with the POSIX
		3350	model. Libev still offers limited functionality on this platform in
		3351	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3352	descriptors. This only applies when using Win32 natively, not when using
		3353	e.g. cygwin.
		3354
		3355	Lifting these limitations would basically require the full
		3356	re-implementation of the I/O system. If you are into these kinds of
		3357	things, then note that glib does exactly that for you in a very portable
		3358	way (note also that glib is the slowest event library known to man).
		3359
		3360	There is no supported compilation method available on windows except
		3361	embedding it into other applications.
		3362
		3363	Not a libev limitation but worth mentioning: windows apparently doesn't
		3364	accept large writes: instead of resulting in a partial write, windows will
		3365	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3366	so make sure you only write small amounts into your sockets (less than a
		3367	megabyte seems safe, but thsi apparently depends on the amount of memory
		3368	available).
		3369
		3370	Due to the many, low, and arbitrary limits on the win32 platform and
		3371	the abysmal performance of winsockets, using a large number of sockets
		3372	is not recommended (and not reasonable). If your program needs to use
		3373	more than a hundred or so sockets, then likely it needs to use a totally
		3374	different implementation for windows, as libev offers the POSIX readiness
		3375	notification model, which cannot be implemented efficiently on windows
		3376	(Microsoft monopoly games).
		3377
		3378	A typical way to use libev under windows is to embed it (see the embedding
		3379	section for details) and use the following F<evwrap.h> header file instead
		3380	of F<ev.h>:
		3381
		3382	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3384
		3385	#include "ev.h"
		3386
		3387	And compile the following F<evwrap.c> file into your project (make sure
		3388	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3389
		3390	#include "evwrap.h"
		3391	#include "ev.c"
		3392
		3393	=over 4
		3394
		3395	=item The winsocket select function
		3396
		3397	The winsocket C<select> function doesn't follow POSIX in that it
		3398	requires socket I<handles> and not socket I<file descriptors> (it is
		3399	also extremely buggy). This makes select very inefficient, and also
		3400	requires a mapping from file descriptors to socket handles (the Microsoft
		3401	C runtime provides the function C<_open_osfhandle> for this). See the
		3402	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3403	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3404
		3405	The configuration for a "naked" win32 using the Microsoft runtime
		3406	libraries and raw winsocket select is:
		3407
		3408	#define EV_USE_SELECT 1
		3409	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3410
		3411	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3412	complexity in the O(n²) range when using win32.
		3413
		3414	=item Limited number of file descriptors
		3415
		3416	Windows has numerous arbitrary (and low) limits on things.
		3417
		3418	Early versions of winsocket's select only supported waiting for a maximum
		3419	of C<64> handles (probably owning to the fact that all windows kernels
		3420	can only wait for C<64> things at the same time internally; Microsoft
		3421	recommends spawning a chain of threads and wait for 63 handles and the
		3422	previous thread in each. Great).
		3423
		3424	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3425	to some high number (e.g. C<2048>) before compiling the winsocket select
		3426	call (which might be in libev or elsewhere, for example, perl does its own
		3427	select emulation on windows).
		3428
		3429	Another limit is the number of file descriptors in the Microsoft runtime
		3430	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3431	or something like this inside Microsoft). You can increase this by calling
		3432	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3433	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3434	libraries.
		3435
		3436	This might get you to about C<512> or C<2048> sockets (depending on
		3437	windows version and/or the phase of the moon). To get more, you need to
		3438	wrap all I/O functions and provide your own fd management, but the cost of
		3439	calling select (O(n²)) will likely make this unworkable.
		3440
		3441	=back
		3442
		3443
		3444	=head1 PORTABILITY REQUIREMENTS
		3445
		3446	In addition to a working ISO-C implementation, libev relies on a few
		3447	additional extensions:
		3448
		3449	=over 4
		3450
		3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3452	calling conventions regardless of C<ev_watcher_type *>.
		3453
		3454	Libev assumes not only that all watcher pointers have the same internal
		3455	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3456	assumes that the same (machine) code can be used to call any watcher
		3457	callback: The watcher callbacks have different type signatures, but libev
		3458	calls them using an C<ev_watcher *> internally.
		3459
		3460	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3461
		3462	The type C<sig_atomic_t volatile> (or whatever is defined as
		3463	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3464	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3465	believed to be sufficiently portable.
		3466
		3467	=item C<sigprocmask> must work in a threaded environment
		3468
		3469	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3470	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3471	pthread implementations will either allow C<sigprocmask> in the "main
		3472	thread" or will block signals process-wide, both behaviours would
		3473	be compatible with libev. Interaction between C<sigprocmask> and
		3474	C<pthread_sigmask> could complicate things, however.
		3475
		3476	The most portable way to handle signals is to block signals in all threads
		3477	except the initial one, and run the default loop in the initial thread as
		3478	well.
		3479
		3480	=item C<long> must be large enough for common memory allocation sizes
		3481
		3482	To improve portability and simplify using libev, libev uses C<long>
		3483	internally instead of C<size_t> when allocating its data structures. On
		3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3485	is still at least 31 bits everywhere, which is enough for hundreds of
		3486	millions of watchers.
		3487
		3488	=item C<double> must hold a time value in seconds with enough accuracy
		3489
		3490	The type C<double> is used to represent timestamps. It is required to
		3491	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3492	enough for at least into the year 4000. This requirement is fulfilled by
		3493	implementations implementing IEEE 754 (basically all existing ones).
		3494
		3495	=back
		3496
		3497	If you know of other additional requirements drop me a note.
		3498
		3499
		3500	=head1 COMPILER WARNINGS
		3501
		3502	Depending on your compiler and compiler settings, you might get no or a
		3503	lot of warnings when compiling libev code. Some people are apparently
		3504	scared by this.
		3505
		3506	However, these are unavoidable for many reasons. For one, each compiler
		3507	has different warnings, and each user has different tastes regarding
		3508	warning options. "Warn-free" code therefore cannot be a goal except when
		3509	targeting a specific compiler and compiler-version.
		3510
		3511	Another reason is that some compiler warnings require elaborate
		3512	workarounds, or other changes to the code that make it less clear and less
		3513	maintainable.
		3514
		3515	And of course, some compiler warnings are just plain stupid, or simply
		3516	wrong (because they don't actually warn about the condition their message
		3517	seems to warn about).
		3518
		3519	While libev is written to generate as few warnings as possible,
		3520	"warn-free" code is not a goal, and it is recommended not to build libev
		3521	with any compiler warnings enabled unless you are prepared to cope with
		3522	them (e.g. by ignoring them). Remember that warnings are just that:
		3523	warnings, not errors, or proof of bugs.
		3524
		3525
		3526	=head1 VALGRIND
		3527
		3528	Valgrind has a special section here because it is a popular tool that is
		3529	highly useful, but valgrind reports are very hard to interpret.
		3530
		3531	If you think you found a bug (memory leak, uninitialised data access etc.)
		3532	in libev, then check twice: If valgrind reports something like:
		3533
		3534	==2274== definitely lost: 0 bytes in 0 blocks.
		3535	==2274== possibly lost: 0 bytes in 0 blocks.
		3536	==2274== still reachable: 256 bytes in 1 blocks.
		3537
		3538	Then there is no memory leak. Similarly, under some circumstances,
		3539	valgrind might report kernel bugs as if it were a bug in libev, or it
		3540	might be confused (it is a very good tool, but only a tool).
		3541
		3542	If you are unsure about something, feel free to contact the mailing list
		3543	with the full valgrind report and an explanation on why you think this is
		3544	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3545	no bug" answer and take the chance of learning how to interpret valgrind
		3546	properly.
		3547
		3548	If you need, for some reason, empty reports from valgrind for your project
		3549	I suggest using suppression lists.
		3550
		3551
2519	=head1 AUTHOR	3552	=head1 AUTHOR
2520		3553
2521	Marc Lehmann <libev@schmorp.de>.	3554	Marc Lehmann <libev@schmorp.de>.
2522		3555

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