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Revision 1.96 by ayin, Fri Dec 21 10:06:50 2007 UTC vs.
Revision 1.169 by root, Fri Jun 20 23:31:19 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 occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
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 some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
104	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
106		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
…		…
114	=item ev_tstamp ev_time ()	150	=item ev_tstamp ev_time ()
115		151
116	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
117	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
118	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 ()>.
119		161
120	=item int ev_version_major ()	162	=item int ev_version_major ()
121		163
122	=item int ev_version_minor ()	164	=item int ev_version_minor ()
123		165
…		…
136	not a problem.	178	not a problem.
137		179
138	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
139	version.	181	version.
140		182
141	assert (("libev version mismatch",	183	assert (("libev version mismatch",
142	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
143	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
144		186
145	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
146		188
147	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_*>
148	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
150	a description of the set values.	192	a description of the set values.
151		193
152	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
153	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
154		196
155	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
156	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
157		199
158	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
159		201
160	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
161	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
162	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
163	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
164	(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
165	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
166		208
167	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
168		210
…		…
175	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
176		218
177	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
178		220
179	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
180	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
181	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
182	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
183	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
184	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.
185		230
186	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
187	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,
188	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.
189		234
190	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
191	retries).	236	retries (example requires a standards-compliant C<realloc>).
192		237
193	static void *	238	static void *
194	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
195	{	240	{
196	for (;;)	241	for (;;)
…		…
207	...	252	...
208	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
209		254
210	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
211		256
212	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
213	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
214	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
215	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
216	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
217	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
218	(such as abort).	263	(such as abort).
219		264
220	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.
…		…
234	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
235		280
236	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
237	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
238	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
239
240	If you use threads, a common model is to run the default event loop
241	in your main thread (or in a separate thread) and for each thread you
242	create, you also create another event loop. Libev itself does no locking
243	whatsoever, so if you mix calls to the same event loop in different
244	threads, make sure you lock (this is usually a bad idea, though, even if
245	done correctly, because it's hideous and inefficient).
246		284
247	=over 4	285	=over 4
248		286
249	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
250		288
…		…
254	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
255		293
256	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
257	function.	295	function.
258		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
259	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
260	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>).
261		310
262	The following flags are supported:	311	The following flags are supported:
263		312
…		…
268	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
269	thing, believe me).	318	thing, believe me).
270		319
271	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
272		321
273	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
274	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
275	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
276	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
277	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
278	around bugs.	327	around bugs.
…		…
284	enabling this flag.	333	enabling this flag.
285		334
286	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,
287	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
288	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
289	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
290	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
291	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
292		341
293	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
294	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
295	flag.	344	flag.
296		345
297	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>
298	environment variable.	347	environment variable.
299		348
300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301		350
302	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
303	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,
304	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
305	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
306	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.
307		363
308	=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)
309		365
310	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
311	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
312	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
313	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.
314		372
315	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
316		374
317	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,
318	but it scales phenomenally better. While poll and select usually scale	376	but it scales phenomenally better. While poll and select usually scale
319	like O(total_fds) where n is the total number of fds (or the highest fd),	377	like O(total_fds) where n is the total number of fds (or the highest fd),
320	epoll scales either O(1) or O(active_fds). The epoll design has a number	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
321	of shortcomings, such as silently dropping events in some hard-to-detect	379	of shortcomings, such as silently dropping events in some hard-to-detect
322	cases and rewiring a syscall per fd change, no fork support and bad	380	cases and requiring a system call per fd change, no fork support and bad
323	support for dup:	381	support for dup.
324		382
325	While stopping, setting and starting an I/O watcher in the same iteration	383	While stopping, setting and starting an I/O watcher in the same iteration
326	will 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
327	(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
328	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
329	very well if you register events for both fds.	387	very well if you register events for both fds.
330		388
331	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
332	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
333	(or space) is available.	391	(or space) is available.
334		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
335	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
336		401
337	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
338	was broken on I<all> BSDs (usually it doesn't work with anything but	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
339	sockets and pipes, except on Darwin, where of course it's completely	404	with anything but sockets and pipes, except on Darwin, where of course
340	useless. On NetBSD, it seems to work for all the FD types I tested, so it
341	is used by default there). For this reason it's not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
342	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
343	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
344	system like NetBSD.	408	system like NetBSD.
345		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.
		413
346	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
347	kernel is more efficient (which says nothing about its actual speed,	415	kernel is more efficient (which says nothing about its actual speed, of
348	of course). While stopping, setting and starting an I/O watcher does	416	course). While stopping, setting and starting an I/O watcher does never
349	never cause an extra syscall as with epoll, it still adds up to two event	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
350	changes per incident, support for C<fork ()> is very bad and it drops fds	418	two event changes per incident, support for C<fork ()> is very bad and it
351	silently in similarly hard-to-detetc cases.	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.
352		429
353	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
354		431
355	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.
356		436
357	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
358		438
359	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
360	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)).
361		441
362	Please note that solaris event ports can deliver a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
363	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
364	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.
365		454
366	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
367		456
368	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
369	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
370	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
371		460
		461	It is definitely not recommended to use this flag.
		462
372	=back	463	=back
373		464
374	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
375	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
376	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
377	order of their flag values :)
378		468
379	The most typical usage is like this:	469	The most typical usage is like this:
380		470
381	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
382	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
383		473
384	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
385	environment settings to be taken into account:	475	environment settings to be taken into account:
386		476
387	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
388		478
389	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
390	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
391	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):
392		482
393	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
394		484
395	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
396		486
397	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
398	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
399	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
400	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
401		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
402	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.
403		497
404	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
405	if (!epoller)	499	if (!epoller)
406	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
407		501
408	=item ev_default_destroy ()	502	=item ev_default_destroy ()
409		503
410	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
411	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
412	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
413	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
414	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
415	the easiest thing, you can just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
416	for example).	510	for example).
417		511
418	Note that certain global state, such as signal state, will not be freed by	512	Note that certain global state, such as signal state, will not be freed by
…		…
429	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
430	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
431		525
432	=item ev_default_fork ()	526	=item ev_default_fork ()
433		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
434	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
435	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
436	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
437	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.
438		534
439	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
440	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
441	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
442		538
443	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
444	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
445	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
446		542
447	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
448		544
449	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
450	without calling this function, so if you force one of those backends you
451	do not need to care.
452
453	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
454		546
455	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
456	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
457	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.
458		554
459	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
460		556
461	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
462	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
…		…
497	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
498	those events and any outstanding ones, but will not block your process in	594	those events and any outstanding ones, but will not block your process in
499	case there are no events and will return after one iteration of the loop.	595	case there are no events and will return after one iteration of the loop.
500		596
501	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
502	neccessary) and will handle those and any outstanding ones. It will block	598	necessary) and will handle those and any outstanding ones. It will block
503	your process until at least one new event arrives, and will return after	599	your process until at least one new event arrives, and will return after
504	one iteration of the loop. This is useful if you are waiting for some	600	one iteration of the loop. This is useful if you are waiting for some
505	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
506	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
507	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
508		604
509	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
510		606
511	- Before the first iteration, call any pending watchers.	607	- Before the first iteration, call any pending watchers.
512	* If there are no active watchers (reference count is zero), return.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
513	- Queue all prepare watchers and then call all outstanding watchers.	609	- If a fork was detected, queue and call all fork watchers.
		610	- Queue and call all prepare watchers.
514	- If we have been forked, recreate the kernel state.	611	- If we have been forked, recreate the kernel state.
515	- Update the kernel state with all outstanding changes.	612	- Update the kernel state with all outstanding changes.
516	- Update the "event loop time".	613	- Update the "event loop time".
517	- Calculate for how long to block.	614	- Calculate for how long to sleep or block, if at all
		615	(active idle watchers, EVLOOP_NONBLOCK or not having
		616	any active watchers at all will result in not sleeping).
		617	- Sleep if the I/O and timer collect interval say so.
518	- Block the process, waiting for any events.	618	- Block the process, waiting for any events.
519	- Queue all outstanding I/O (fd) events.	619	- Queue all outstanding I/O (fd) events.
520	- Update the "event loop time" and do time jump handling.	620	- Update the "event loop time" and do time jump handling.
521	- Queue all outstanding timers.	621	- Queue all outstanding timers.
522	- Queue all outstanding periodics.	622	- Queue all outstanding periodics.
523	- If no events are pending now, queue all idle watchers.	623	- If no events are pending now, queue all idle watchers.
524	- Queue all check watchers.	624	- Queue all check watchers.
525	- Call all queued watchers in reverse order (i.e. check watchers first).	625	- Call all queued watchers in reverse order (i.e. check watchers first).
526	Signals and child watchers are implemented as I/O watchers, and will	626	Signals and child watchers are implemented as I/O watchers, and will
527	be handled here by queueing them when their watcher gets executed.	627	be handled here by queueing them when their watcher gets executed.
528	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
529	were used, return, otherwise continue with step *.	629	were used, or there are no active watchers, return, otherwise
		630	continue with step *.
530		631
531	Example: Queue some jobs and then loop until no events are outsanding	632	Example: Queue some jobs and then loop until no events are outstanding
532	anymore.	633	anymore.
533		634
534	... queue jobs here, make sure they register event watchers as long	635	... queue jobs here, make sure they register event watchers as long
535	... as they still have work to do (even an idle watcher will do..)	636	... as they still have work to do (even an idle watcher will do..)
536	ev_loop (my_loop, 0);	637	ev_loop (my_loop, 0);
…		…
540		641
541	Can be used to make a call to C<ev_loop> return early (but only after it	642	Can be used to make a call to C<ev_loop> return early (but only after it
542	has processed all outstanding events). The C<how> argument must be either	643	has processed all outstanding events). The C<how> argument must be either
543	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
544	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		646
		647	This "unloop state" will be cleared when entering C<ev_loop> again.
545		648
546	=item ev_ref (loop)	649	=item ev_ref (loop)
547		650
548	=item ev_unref (loop)	651	=item ev_unref (loop)
549		652
…		…
554	returning, ev_unref() after starting, and ev_ref() before stopping it. For	657	returning, ev_unref() after starting, and ev_ref() before stopping it. For
555	example, libev itself uses this for its internal signal pipe: It is not	658	example, libev itself uses this for its internal signal pipe: It is not
556	visible to the libev user and should not keep C<ev_loop> from exiting if	659	visible to the libev user and should not keep C<ev_loop> from exiting if
557	no event watchers registered by it are active. It is also an excellent	660	no event watchers registered by it are active. It is also an excellent
558	way to do this for generic recurring timers or from within third-party	661	way to do this for generic recurring timers or from within third-party
559	libraries. Just remember to I<unref after start> and I<ref before stop>.	662	libraries. Just remember to I<unref after start> and I<ref before stop>
		663	(but only if the watcher wasn't active before, or was active before,
		664	respectively).
560		665
561	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
562	running when nothing else is active.	667	running when nothing else is active.
563		668
564	struct ev_signal exitsig;	669	struct ev_signal exitsig;
565	ev_signal_init (&exitsig, sig_cb, SIGINT);	670	ev_signal_init (&exitsig, sig_cb, SIGINT);
566	ev_signal_start (loop, &exitsig);	671	ev_signal_start (loop, &exitsig);
567	evf_unref (loop);	672	evf_unref (loop);
568		673
569	Example: For some weird reason, unregister the above signal handler again.	674	Example: For some weird reason, unregister the above signal handler again.
570		675
571	ev_ref (loop);	676	ev_ref (loop);
572	ev_signal_stop (loop, &exitsig);	677	ev_signal_stop (loop, &exitsig);
		678
		679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		680
		681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		682
		683	These advanced functions influence the time that libev will spend waiting
		684	for events. Both are by default C<0>, meaning that libev will try to
		685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		686
		687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		688	allows libev to delay invocation of I/O and timer/periodic callbacks to
		689	increase efficiency of loop iterations.
		690
		691	The background is that sometimes your program runs just fast enough to
		692	handle one (or very few) event(s) per loop iteration. While this makes
		693	the program responsive, it also wastes a lot of CPU time to poll for new
		694	events, especially with backends like C<select ()> which have a high
		695	overhead for the actual polling but can deliver many events at once.
		696
		697	By setting a higher I<io collect interval> you allow libev to spend more
		698	time collecting I/O events, so you can handle more events per iteration,
		699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		700	C<ev_timer>) will be not affected. Setting this to a non-null value will
		701	introduce an additional C<ev_sleep ()> call into most loop iterations.
		702
		703	Likewise, by setting a higher I<timeout collect interval> you allow libev
		704	to spend more time collecting timeouts, at the expense of increased
		705	latency (the watcher callback will be called later). C<ev_io> watchers
		706	will not be affected. Setting this to a non-null value will not introduce
		707	any overhead in libev.
		708
		709	Many (busy) programs can usually benefit by setting the I/O collect
		710	interval to a value near C<0.1> or so, which is often enough for
		711	interactive servers (of course not for games), likewise for timeouts. It
		712	usually doesn't make much sense to set it to a lower value than C<0.01>,
		713	as this approaches the timing granularity of most systems.
		714
		715	=item ev_loop_verify (loop)
		716
		717	This function only does something when C<EV_VERIFY> support has been
		718	compiled in. It tries to go through all internal structures and checks
		719	them for validity. If anything is found to be inconsistent, it will print
		720	an error message to standard error and call C<abort ()>.
		721
		722	This can be used to catch bugs inside libev itself: under normal
		723	circumstances, this function will never abort as of course libev keeps its
		724	data structures consistent.
573		725
574	=back	726	=back
575		727
576		728
577	=head1 ANATOMY OF A WATCHER	729	=head1 ANATOMY OF A WATCHER
578		730
579	A watcher is a structure that you create and register to record your	731	A watcher is a structure that you create and register to record your
580	interest in some event. For instance, if you want to wait for STDIN to	732	interest in some event. For instance, if you want to wait for STDIN to
581	become readable, you would create an C<ev_io> watcher for that:	733	become readable, you would create an C<ev_io> watcher for that:
582		734
583	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
584	{	736	{
585	ev_io_stop (w);	737	ev_io_stop (w);
586	ev_unloop (loop, EVUNLOOP_ALL);	738	ev_unloop (loop, EVUNLOOP_ALL);
587	}	739	}
588		740
589	struct ev_loop *loop = ev_default_loop (0);	741	struct ev_loop *loop = ev_default_loop (0);
590	struct ev_io stdin_watcher;	742	struct ev_io stdin_watcher;
591	ev_init (&stdin_watcher, my_cb);	743	ev_init (&stdin_watcher, my_cb);
592	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
593	ev_io_start (loop, &stdin_watcher);	745	ev_io_start (loop, &stdin_watcher);
594	ev_loop (loop, 0);	746	ev_loop (loop, 0);
595		747
596	As you can see, you are responsible for allocating the memory for your	748	As you can see, you are responsible for allocating the memory for your
597	watcher structures (and it is usually a bad idea to do this on the stack,	749	watcher structures (and it is usually a bad idea to do this on the stack,
598	although this can sometimes be quite valid).	750	although this can sometimes be quite valid).
599		751
600	Each watcher structure must be initialised by a call to C<ev_init	752	Each watcher structure must be initialised by a call to C<ev_init
601	(watcher *, callback)>, which expects a callback to be provided. This	753	(watcher *, callback)>, which expects a callback to be provided. This
602	callback gets invoked each time the event occurs (or, in the case of io	754	callback gets invoked each time the event occurs (or, in the case of I/O
603	watchers, each time the event loop detects that the file descriptor given	755	watchers, each time the event loop detects that the file descriptor given
604	is readable and/or writable).	756	is readable and/or writable).
605		757
606	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
607	with arguments specific to this watcher type. There is also a macro	759	with arguments specific to this watcher type. There is also a macro
…		…
677	=item C<EV_FORK>	829	=item C<EV_FORK>
678		830
679	The event loop has been resumed in the child process after fork (see	831	The event loop has been resumed in the child process after fork (see
680	C<ev_fork>).	832	C<ev_fork>).
681		833
		834	=item C<EV_ASYNC>
		835
		836	The given async watcher has been asynchronously notified (see C<ev_async>).
		837
682	=item C<EV_ERROR>	838	=item C<EV_ERROR>
683		839
684	An unspecified error has occured, the watcher has been stopped. This might	840	An unspecified error has occurred, the watcher has been stopped. This might
685	happen because the watcher could not be properly started because libev	841	happen because the watcher could not be properly started because libev
686	ran out of memory, a file descriptor was found to be closed or any other	842	ran out of memory, a file descriptor was found to be closed or any other
687	problem. You best act on it by reporting the problem and somehow coping	843	problem. You best act on it by reporting the problem and somehow coping
688	with the watcher being stopped.	844	with the watcher being stopped.
689		845
690	Libev will usually signal a few "dummy" events together with an error,	846	Libev will usually signal a few "dummy" events together with an error,
691	for example it might indicate that a fd is readable or writable, and if	847	for example it might indicate that a fd is readable or writable, and if
692	your callbacks is well-written it can just attempt the operation and cope	848	your callbacks is well-written it can just attempt the operation and cope
693	with the error from read() or write(). This will not work in multithreaded	849	with the error from read() or write(). This will not work in multi-threaded
694	programs, though, so beware.	850	programs, though, so beware.
695		851
696	=back	852	=back
697		853
698	=head2 GENERIC WATCHER FUNCTIONS	854	=head2 GENERIC WATCHER FUNCTIONS
…		…
728	Although some watcher types do not have type-specific arguments	884	Although some watcher types do not have type-specific arguments
729	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
730		886
731	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
732		888
733	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
734	calls into a single call. This is the most convinient method to initialise	890	calls into a single call. This is the most convenient method to initialise
735	a watcher. The same limitations apply, of course.	891	a watcher. The same limitations apply, of course.
736		892
737	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
738		894
739	Starts (activates) the given watcher. Only active watchers will receive	895	Starts (activates) the given watcher. Only active watchers will receive
…		…
822	to associate arbitrary data with your watcher. If you need more data and	978	to associate arbitrary data with your watcher. If you need more data and
823	don't want to allocate memory and store a pointer to it in that data	979	don't want to allocate memory and store a pointer to it in that data
824	member, you can also "subclass" the watcher type and provide your own	980	member, you can also "subclass" the watcher type and provide your own
825	data:	981	data:
826		982
827	struct my_io	983	struct my_io
828	{	984	{
829	struct ev_io io;	985	struct ev_io io;
830	int otherfd;	986	int otherfd;
831	void *somedata;	987	void *somedata;
832	struct whatever *mostinteresting;	988	struct whatever *mostinteresting;
833	}	989	}
834		990
835	And since your callback will be called with a pointer to the watcher, you	991	And since your callback will be called with a pointer to the watcher, you
836	can cast it back to your own type:	992	can cast it back to your own type:
837		993
838	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
839	{	995	{
840	struct my_io *w = (struct my_io *)w_;	996	struct my_io *w = (struct my_io *)w_;
841	...	997	...
842	}	998	}
843		999
844	More interesting and less C-conformant ways of casting your callback type	1000	More interesting and less C-conformant ways of casting your callback type
845	instead have been omitted.	1001	instead have been omitted.
846		1002
847	Another common scenario is having some data structure with multiple	1003	Another common scenario is having some data structure with multiple
848	watchers:	1004	watchers:
849		1005
850	struct my_biggy	1006	struct my_biggy
851	{	1007	{
852	int some_data;	1008	int some_data;
853	ev_timer t1;	1009	ev_timer t1;
854	ev_timer t2;	1010	ev_timer t2;
855	}	1011	}
856		1012
857	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,
858	you need to use C<offsetof>:	1014	you need to use C<offsetof>:
859		1015
860	#include <stddef.h>	1016	#include <stddef.h>
861		1017
862	static void	1018	static void
863	t1_cb (EV_P_ struct ev_timer *w, int revents)	1019	t1_cb (EV_P_ struct ev_timer *w, int revents)
864	{	1020	{
865	struct my_biggy big = (struct my_biggy *	1021	struct my_biggy big = (struct my_biggy *
866	(((char *)w) - offsetof (struct my_biggy, t1));	1022	(((char *)w) - offsetof (struct my_biggy, t1));
867	}	1023	}
868		1024
869	static void	1025	static void
870	t2_cb (EV_P_ struct ev_timer *w, int revents)	1026	t2_cb (EV_P_ struct ev_timer *w, int revents)
871	{	1027	{
872	struct my_biggy big = (struct my_biggy *	1028	struct my_biggy big = (struct my_biggy *
873	(((char *)w) - offsetof (struct my_biggy, t2));	1029	(((char *)w) - offsetof (struct my_biggy, t2));
874	}	1030	}
875		1031
876		1032
877	=head1 WATCHER TYPES	1033	=head1 WATCHER TYPES
878		1034
879	This section describes each watcher in detail, but will not repeat	1035	This section describes each watcher in detail, but will not repeat
…		…
903	In general you can register as many read and/or write event watchers per	1059	In general you can register as many read and/or write event watchers per
904	fd as you want (as long as you don't confuse yourself). Setting all file	1060	fd as you want (as long as you don't confuse yourself). Setting all file
905	descriptors to non-blocking mode is also usually a good idea (but not	1061	descriptors to non-blocking mode is also usually a good idea (but not
906	required if you know what you are doing).	1062	required if you know what you are doing).
907		1063
908	You have to be careful with dup'ed file descriptors, though. Some backends
909	(the linux epoll backend is a notable example) cannot handle dup'ed file
910	descriptors correctly if you register interest in two or more fds pointing
911	to the same underlying file/socket/etc. description (that is, they share
912	the same underlying "file open").
913
914	If you must do this, then force the use of a known-to-be-good backend	1064	If you must do this, then force the use of a known-to-be-good backend
915	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
916	C<EVBACKEND_POLL>).	1066	C<EVBACKEND_POLL>).
917		1067
918	Another thing you have to watch out for is that it is quite easy to	1068	Another thing you have to watch out for is that it is quite easy to
919	receive "spurious" readyness notifications, that is your callback might	1069	receive "spurious" readiness notifications, that is your callback might
920	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
921	because there is no data. Not only are some backends known to create a	1071	because there is no data. Not only are some backends known to create a
922	lot of those (for example solaris ports), it is very easy to get into	1072	lot of those (for example Solaris ports), it is very easy to get into
923	this situation even with a relatively standard program structure. Thus	1073	this situation even with a relatively standard program structure. Thus
924	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning
925	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.
926		1076
927	If you cannot run the fd in non-blocking mode (for example you should not	1077	If you cannot run the fd in non-blocking mode (for example you should not
928	play around with an Xlib connection), then you have to seperately re-test	1078	play around with an Xlib connection), then you have to separately re-test
929	whether a file descriptor is really ready with a known-to-be good interface	1079	whether a file descriptor is really ready with a known-to-be good interface
930	such as poll (fortunately in our Xlib example, Xlib already does this on	1080	such as poll (fortunately in our Xlib example, Xlib already does this on
931	its own, so its quite safe to use).	1081	its own, so its quite safe to use).
932		1082
933	=head3 The special problem of disappearing file descriptors	1083	=head3 The special problem of disappearing file descriptors
…		…
952	optimisations to libev.	1102	optimisations to libev.
953		1103
954	=head3 The special problem of dup'ed file descriptors	1104	=head3 The special problem of dup'ed file descriptors
955		1105
956	Some backends (e.g. epoll), cannot register events for file descriptors,	1106	Some backends (e.g. epoll), cannot register events for file descriptors,
957	but only events for the underlying file descriptions. That menas when you	1107	but only events for the underlying file descriptions. That means when you
958	have C<dup ()>'ed file descriptors and register events for them, only one	1108	have C<dup ()>'ed file descriptors or weirder constellations, and register
959	file descriptor might actually receive events.	1109	events for them, only one file descriptor might actually receive events.
960		1110
961	There is no workaorund possible except not registering events	1111	There is no workaround possible except not registering events
962	for potentially C<dup ()>'ed file descriptors or to resort to	1112	for potentially C<dup ()>'ed file descriptors, or to resort to
963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1113	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
964		1114
965	=head3 The special problem of fork	1115	=head3 The special problem of fork
966		1116
967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1117	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
971	To support fork in your programs, you either have to call	1121	To support fork in your programs, you either have to call
972	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1122	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
973	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
974	C<EVBACKEND_POLL>.	1124	C<EVBACKEND_POLL>.
975		1125
		1126	=head3 The special problem of SIGPIPE
		1127
		1128	While not really specific to libev, it is easy to forget about SIGPIPE:
		1129	when reading from a pipe whose other end has been closed, your program
		1130	gets send a SIGPIPE, which, by default, aborts your program. For most
		1131	programs this is sensible behaviour, for daemons, this is usually
		1132	undesirable.
		1133
		1134	So when you encounter spurious, unexplained daemon exits, make sure you
		1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1136	somewhere, as that would have given you a big clue).
		1137
976		1138
977	=head3 Watcher-Specific Functions	1139	=head3 Watcher-Specific Functions
978		1140
979	=over 4	1141	=over 4
980		1142
981	=item ev_io_init (ev_io *, callback, int fd, int events)	1143	=item ev_io_init (ev_io *, callback, int fd, int events)
982		1144
983	=item ev_io_set (ev_io *, int fd, int events)	1145	=item ev_io_set (ev_io *, int fd, int events)
984		1146
985	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
986	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
987	C<EV_READ | EV_WRITE> to receive the given events.	1149	C<EV_READ | EV_WRITE> to receive the given events.
988		1150
989	=item int fd [read-only]	1151	=item int fd [read-only]
990		1152
991	The file descriptor being watched.	1153	The file descriptor being watched.
…		…
993	=item int events [read-only]	1155	=item int events [read-only]
994		1156
995	The events being watched.	1157	The events being watched.
996		1158
997	=back	1159	=back
		1160
		1161	=head3 Examples
998		1162
999	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1000	readable, but only once. Since it is likely line-buffered, you could	1164	readable, but only once. Since it is likely line-buffered, you could
1001	attempt to read a whole line in the callback.	1165	attempt to read a whole line in the callback.
1002		1166
1003	static void	1167	static void
1004	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1005	{	1169	{
1006	ev_io_stop (loop, w);	1170	ev_io_stop (loop, w);
1007	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1008	}	1172	}
1009		1173
1010	...	1174	...
1011	struct ev_loop *loop = ev_default_init (0);	1175	struct ev_loop *loop = ev_default_init (0);
1012	struct ev_io stdin_readable;	1176	struct ev_io stdin_readable;
1013	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1014	ev_io_start (loop, &stdin_readable);	1178	ev_io_start (loop, &stdin_readable);
1015	ev_loop (loop, 0);	1179	ev_loop (loop, 0);
1016		1180
1017		1181
1018	=head2 C<ev_timer> - relative and optionally repeating timeouts	1182	=head2 C<ev_timer> - relative and optionally repeating timeouts
1019		1183
1020	Timer watchers are simple relative timers that generate an event after a	1184	Timer watchers are simple relative timers that generate an event after a
1021	given time, and optionally repeating in regular intervals after that.	1185	given time, and optionally repeating in regular intervals after that.
1022		1186
1023	The timers are based on real time, that is, if you register an event that	1187	The timers are based on real time, that is, if you register an event that
1024	times out after an hour and you reset your system clock to last years	1188	times out after an hour and you reset your system clock to January last
1025	time, it will still time out after (roughly) and hour. "Roughly" because	1189	year, it will still time out after (roughly) and hour. "Roughly" because
1026	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1027	monotonic clock option helps a lot here).	1191	monotonic clock option helps a lot here).
1028		1192
1029	The relative timeouts are calculated relative to the C<ev_now ()>	1193	The relative timeouts are calculated relative to the C<ev_now ()>
1030	time. This is usually the right thing as this timestamp refers to the time	1194	time. This is usually the right thing as this timestamp refers to the time
…		…
1032	you suspect event processing to be delayed and you I<need> to base the timeout	1196	you suspect event processing to be delayed and you I<need> to base the timeout
1033	on the current time, use something like this to adjust for this:	1197	on the current time, use something like this to adjust for this:
1034		1198
1035	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1036		1200
1037	The callback is guarenteed to be invoked only when its timeout has passed,	1201	The callback is guaranteed to be invoked only after its timeout has passed,
1038	but if multiple timers become ready during the same loop iteration then	1202	but if multiple timers become ready during the same loop iteration then
1039	order of execution is undefined.	1203	order of execution is undefined.
1040		1204
1041	=head3 Watcher-Specific Functions and Data Members	1205	=head3 Watcher-Specific Functions and Data Members
1042		1206
…		…
1044		1208
1045	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1209	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1046		1210
1047	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1211	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1048		1212
1049	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1213	Configure the timer to trigger after C<after> seconds. If C<repeat>
1050	C<0.>, then it will automatically be stopped. If it is positive, then the	1214	is C<0.>, then it will automatically be stopped once the timeout is
1051	timer will automatically be configured to trigger again C<repeat> seconds	1215	reached. If it is positive, then the timer will automatically be
1052	later, again, and again, until stopped manually.	1216	configured to trigger again C<repeat> seconds later, again, and again,
		1217	until stopped manually.
1053		1218
1054	The timer itself will do a best-effort at avoiding drift, that is, if you	1219	The timer itself will do a best-effort at avoiding drift, that is, if
1055	configure a timer to trigger every 10 seconds, then it will trigger at	1220	you configure a timer to trigger every 10 seconds, then it will normally
1056	exactly 10 second intervals. If, however, your program cannot keep up with	1221	trigger at exactly 10 second intervals. If, however, your program cannot
1057	the timer (because it takes longer than those 10 seconds to do stuff) the	1222	keep up with the timer (because it takes longer than those 10 seconds to
1058	timer will not fire more than once per event loop iteration.	1223	do stuff) the timer will not fire more than once per event loop iteration.
1059		1224
1060	=item ev_timer_again (loop)	1225	=item ev_timer_again (loop, ev_timer *)
1061		1226
1062	This will act as if the timer timed out and restart it again if it is	1227	This will act as if the timer timed out and restart it again if it is
1063	repeating. The exact semantics are:	1228	repeating. The exact semantics are:
1064		1229
1065	If the timer is pending, its pending status is cleared.	1230	If the timer is pending, its pending status is cleared.
1066		1231
1067	If the timer is started but nonrepeating, stop it (as if it timed out).	1232	If the timer is started but non-repeating, stop it (as if it timed out).
1068		1233
1069	If the timer is repeating, either start it if necessary (with the	1234	If the timer is repeating, either start it if necessary (with the
1070	C<repeat> value), or reset the running timer to the C<repeat> value.	1235	C<repeat> value), or reset the running timer to the C<repeat> value.
1071		1236
1072	This sounds a bit complicated, but here is a useful and typical	1237	This sounds a bit complicated, but here is a useful and typical
1073	example: Imagine you have a tcp connection and you want a so-called idle	1238	example: Imagine you have a TCP connection and you want a so-called idle
1074	timeout, that is, you want to be called when there have been, say, 60	1239	timeout, that is, you want to be called when there have been, say, 60
1075	seconds of inactivity on the socket. The easiest way to do this is to	1240	seconds of inactivity on the socket. The easiest way to do this is to
1076	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1077	C<ev_timer_again> each time you successfully read or write some data. If	1242	C<ev_timer_again> each time you successfully read or write some data. If
1078	you go into an idle state where you do not expect data to travel on the	1243	you go into an idle state where you do not expect data to travel on the
…		…
1100	or C<ev_timer_again> is called and determines the next timeout (if any),	1265	or C<ev_timer_again> is called and determines the next timeout (if any),
1101	which is also when any modifications are taken into account.	1266	which is also when any modifications are taken into account.
1102		1267
1103	=back	1268	=back
1104		1269
		1270	=head3 Examples
		1271
1105	Example: Create a timer that fires after 60 seconds.	1272	Example: Create a timer that fires after 60 seconds.
1106		1273
1107	static void	1274	static void
1108	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1109	{	1276	{
1110	.. one minute over, w is actually stopped right here	1277	.. one minute over, w is actually stopped right here
1111	}	1278	}
1112		1279
1113	struct ev_timer mytimer;	1280	struct ev_timer mytimer;
1114	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1115	ev_timer_start (loop, &mytimer);	1282	ev_timer_start (loop, &mytimer);
1116		1283
1117	Example: Create a timeout timer that times out after 10 seconds of	1284	Example: Create a timeout timer that times out after 10 seconds of
1118	inactivity.	1285	inactivity.
1119		1286
1120	static void	1287	static void
1121	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1122	{	1289	{
1123	.. ten seconds without any activity	1290	.. ten seconds without any activity
1124	}	1291	}
1125		1292
1126	struct ev_timer mytimer;	1293	struct ev_timer mytimer;
1127	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1128	ev_timer_again (&mytimer); /* start timer */	1295	ev_timer_again (&mytimer); /* start timer */
1129	ev_loop (loop, 0);	1296	ev_loop (loop, 0);
1130		1297
1131	// and in some piece of code that gets executed on any "activity":	1298	// and in some piece of code that gets executed on any "activity":
1132	// reset the timeout to start ticking again at 10 seconds	1299	// reset the timeout to start ticking again at 10 seconds
1133	ev_timer_again (&mytimer);	1300	ev_timer_again (&mytimer);
1134		1301
1135		1302
1136	=head2 C<ev_periodic> - to cron or not to cron?	1303	=head2 C<ev_periodic> - to cron or not to cron?
1137		1304
1138	Periodic watchers are also timers of a kind, but they are very versatile	1305	Periodic watchers are also timers of a kind, but they are very versatile
1139	(and unfortunately a bit complex).	1306	(and unfortunately a bit complex).
1140		1307
1141	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1142	but on wallclock time (absolute time). You can tell a periodic watcher	1309	but on wall clock time (absolute time). You can tell a periodic watcher
1143	to trigger "at" some specific point in time. For example, if you tell a	1310	to trigger after some specific point in time. For example, if you tell a
1144	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1145	+ 10.>) and then reset your system clock to the last year, then it will	1312	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1313	clock to January of the previous year, then it will take more than year
1146	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1147	roughly 10 seconds later).	1315	roughly 10 seconds later as it uses a relative timeout).
1148		1316
1149	They can also be used to implement vastly more complex timers, such as	1317	C<ev_periodic>s can also be used to implement vastly more complex timers,
1150	triggering an event on each midnight, local time or other, complicated,	1318	such as triggering an event on each "midnight, local time", or other
1151	rules.	1319	complicated, rules.
1152		1320
1153	As with timers, the callback is guarenteed to be invoked only when the	1321	As with timers, the callback is guaranteed to be invoked only when the
1154	time (C<at>) has been passed, but if multiple periodic timers become ready	1322	time (C<at>) has passed, but if multiple periodic timers become ready
1155	during the same loop iteration then order of execution is undefined.	1323	during the same loop iteration then order of execution is undefined.
1156		1324
1157	=head3 Watcher-Specific Functions and Data Members	1325	=head3 Watcher-Specific Functions and Data Members
1158		1326
1159	=over 4	1327	=over 4
…		…
1167		1335
1168	=over 4	1336	=over 4
1169		1337
1170	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1171		1339
1172	In this configuration the watcher triggers an event at the wallclock time	1340	In this configuration the watcher triggers an event after the wall clock
1173	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1341	time C<at> has passed and doesn't repeat. It will not adjust when a time
1174	that is, if it is to be run at January 1st 2011 then it will run when the	1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1175	system time reaches or surpasses this time.	1343	run when the system time reaches or surpasses this time.
1176		1344
1177	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1178		1346
1179	In this mode the watcher will always be scheduled to time out at the next	1347	In this mode the watcher will always be scheduled to time out at the next
1180	C<at + N * interval> time (for some integer N, which can also be negative)	1348	C<at + N * interval> time (for some integer N, which can also be negative)
1181	and then repeat, regardless of any time jumps.	1349	and then repeat, regardless of any time jumps.
1182		1350
1183	This can be used to create timers that do not drift with respect to system	1351	This can be used to create timers that do not drift with respect to system
1184	time:	1352	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1353	the hour:
1185		1354
1186	ev_periodic_set (&periodic, 0., 3600., 0);	1355	ev_periodic_set (&periodic, 0., 3600., 0);
1187		1356
1188	This doesn't mean there will always be 3600 seconds in between triggers,	1357	This doesn't mean there will always be 3600 seconds in between triggers,
1189	but only that the the callback will be called when the system time shows a	1358	but only that the callback will be called when the system time shows a
1190	full hour (UTC), or more correctly, when the system time is evenly divisible	1359	full hour (UTC), or more correctly, when the system time is evenly divisible
1191	by 3600.	1360	by 3600.
1192		1361
1193	Another way to think about it (for the mathematically inclined) is that	1362	Another way to think about it (for the mathematically inclined) is that
1194	C<ev_periodic> will try to run the callback in this mode at the next possible	1363	C<ev_periodic> will try to run the callback in this mode at the next possible
1195	time where C<time = at (mod interval)>, regardless of any time jumps.	1364	time where C<time = at (mod interval)>, regardless of any time jumps.
1196		1365
1197	For numerical stability it is preferable that the C<at> value is near	1366	For numerical stability it is preferable that the C<at> value is near
1198	C<ev_now ()> (the current time), but there is no range requirement for	1367	C<ev_now ()> (the current time), but there is no range requirement for
1199	this value.	1368	this value, and in fact is often specified as zero.
		1369
		1370	Note also that there is an upper limit to how often a timer can fire (CPU
		1371	speed for example), so if C<interval> is very small then timing stability
		1372	will of course deteriorate. Libev itself tries to be exact to be about one
		1373	millisecond (if the OS supports it and the machine is fast enough).
1200		1374
1201	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1202		1376
1203	In this mode the values for C<interval> and C<at> are both being	1377	In this mode the values for C<interval> and C<at> are both being
1204	ignored. Instead, each time the periodic watcher gets scheduled, the	1378	ignored. Instead, each time the periodic watcher gets scheduled, the
1205	reschedule callback will be called with the watcher as first, and the	1379	reschedule callback will be called with the watcher as first, and the
1206	current time as second argument.	1380	current time as second argument.
1207		1381
1208	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1209	ever, or make any event loop modifications>. If you need to stop it,	1383	ever, or make ANY event loop modifications whatsoever>.
1210	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1211	starting an C<ev_prepare> watcher, which is legal).
1212		1384
		1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1387	only event loop modification you are allowed to do).
		1388
1213	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1214	ev_tstamp now)>, e.g.:	1390	*w, ev_tstamp now)>, e.g.:
1215		1391
1216	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1217	{	1393	{
1218	return now + 60.;	1394	return now + 60.;
1219	}	1395	}
…		…
1221	It must return the next time to trigger, based on the passed time value	1397	It must return the next time to trigger, based on the passed time value
1222	(that is, the lowest time value larger than to the second argument). It	1398	(that is, the lowest time value larger than to the second argument). It
1223	will usually be called just before the callback will be triggered, but	1399	will usually be called just before the callback will be triggered, but
1224	might be called at other times, too.	1400	might be called at other times, too.
1225		1401
1226	NOTE: I<< This callback must always return a time that is later than the	1402	NOTE: I<< This callback must always return a time that is higher than or
1227	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1403	equal to the passed C<now> value >>.
1228		1404
1229	This can be used to create very complex timers, such as a timer that	1405	This can be used to create very complex timers, such as a timer that
1230	triggers on each midnight, local time. To do this, you would calculate the	1406	triggers on "next midnight, local time". To do this, you would calculate the
1231	next midnight after C<now> and return the timestamp value for this. How	1407	next midnight after C<now> and return the timestamp value for this. How
1232	you do this is, again, up to you (but it is not trivial, which is the main	1408	you do this is, again, up to you (but it is not trivial, which is the main
1233	reason I omitted it as an example).	1409	reason I omitted it as an example).
1234		1410
1235	=back	1411	=back
…		…
1239	Simply stops and restarts the periodic watcher again. This is only useful	1415	Simply stops and restarts the periodic watcher again. This is only useful
1240	when you changed some parameters or the reschedule callback would return	1416	when you changed some parameters or the reschedule callback would return
1241	a different time than the last time it was called (e.g. in a crond like	1417	a different time than the last time it was called (e.g. in a crond like
1242	program when the crontabs have changed).	1418	program when the crontabs have changed).
1243		1419
		1420	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1421
		1422	When active, returns the absolute time that the watcher is supposed to
		1423	trigger next.
		1424
1244	=item ev_tstamp offset [read-write]	1425	=item ev_tstamp offset [read-write]
1245		1426
1246	When repeating, this contains the offset value, otherwise this is the	1427	When repeating, this contains the offset value, otherwise this is the
1247	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1248		1429
…		…
1259		1440
1260	The current reschedule callback, or C<0>, if this functionality is	1441	The current reschedule callback, or C<0>, if this functionality is
1261	switched off. Can be changed any time, but changes only take effect when	1442	switched off. Can be changed any time, but changes only take effect when
1262	the periodic timer fires or C<ev_periodic_again> is being called.	1443	the periodic timer fires or C<ev_periodic_again> is being called.
1263		1444
1264	=item ev_tstamp at [read-only]
1265
1266	When active, contains the absolute time that the watcher is supposed to
1267	trigger next.
1268
1269	=back	1445	=back
		1446
		1447	=head3 Examples
1270		1448
1271	Example: Call a callback every hour, or, more precisely, whenever the	1449	Example: Call a callback every hour, or, more precisely, whenever the
1272	system clock is divisible by 3600. The callback invocation times have	1450	system clock is divisible by 3600. The callback invocation times have
1273	potentially a lot of jittering, but good long-term stability.	1451	potentially a lot of jitter, but good long-term stability.
1274		1452
1275	static void	1453	static void
1276	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1277	{	1455	{
1278	... its now a full hour (UTC, or TAI or whatever your clock follows)	1456	... its now a full hour (UTC, or TAI or whatever your clock follows)
1279	}	1457	}
1280		1458
1281	struct ev_periodic hourly_tick;	1459	struct ev_periodic hourly_tick;
1282	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1283	ev_periodic_start (loop, &hourly_tick);	1461	ev_periodic_start (loop, &hourly_tick);
1284		1462
1285	Example: The same as above, but use a reschedule callback to do it:	1463	Example: The same as above, but use a reschedule callback to do it:
1286		1464
1287	#include <math.h>	1465	#include <math.h>
1288		1466
1289	static ev_tstamp	1467	static ev_tstamp
1290	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1291	{	1469	{
1292	return fmod (now, 3600.) + 3600.;	1470	return fmod (now, 3600.) + 3600.;
1293	}	1471	}
1294		1472
1295	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1296		1474
1297	Example: Call a callback every hour, starting now:	1475	Example: Call a callback every hour, starting now:
1298		1476
1299	struct ev_periodic hourly_tick;	1477	struct ev_periodic hourly_tick;
1300	ev_periodic_init (&hourly_tick, clock_cb,	1478	ev_periodic_init (&hourly_tick, clock_cb,
1301	fmod (ev_now (loop), 3600.), 3600., 0);	1479	fmod (ev_now (loop), 3600.), 3600., 0);
1302	ev_periodic_start (loop, &hourly_tick);	1480	ev_periodic_start (loop, &hourly_tick);
1303		1481
1304		1482
1305	=head2 C<ev_signal> - signal me when a signal gets signalled!	1483	=head2 C<ev_signal> - signal me when a signal gets signalled!
1306		1484
1307	Signal watchers will trigger an event when the process receives a specific	1485	Signal watchers will trigger an event when the process receives a specific
…		…
1314	with the kernel (thus it coexists with your own signal handlers as long	1492	with the kernel (thus it coexists with your own signal handlers as long
1315	as you don't register any with libev). Similarly, when the last signal	1493	as you don't register any with libev). Similarly, when the last signal
1316	watcher for a signal is stopped libev will reset the signal handler to	1494	watcher for a signal is stopped libev will reset the signal handler to
1317	SIG_DFL (regardless of what it was set to before).	1495	SIG_DFL (regardless of what it was set to before).
1318		1496
		1497	If possible and supported, libev will install its handlers with
		1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1499	interrupted. If you have a problem with system calls getting interrupted by
		1500	signals you can block all signals in an C<ev_check> watcher and unblock
		1501	them in an C<ev_prepare> watcher.
		1502
1319	=head3 Watcher-Specific Functions and Data Members	1503	=head3 Watcher-Specific Functions and Data Members
1320		1504
1321	=over 4	1505	=over 4
1322		1506
1323	=item ev_signal_init (ev_signal *, callback, int signum)	1507	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1331		1515
1332	The signal the watcher watches out for.	1516	The signal the watcher watches out for.
1333		1517
1334	=back	1518	=back
1335		1519
		1520	=head3 Examples
		1521
		1522	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1523
		1524	static void
		1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1526	{
		1527	ev_unloop (loop, EVUNLOOP_ALL);
		1528	}
		1529
		1530	struct ev_signal signal_watcher;
		1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1532	ev_signal_start (loop, &sigint_cb);
		1533
1336		1534
1337	=head2 C<ev_child> - watch out for process status changes	1535	=head2 C<ev_child> - watch out for process status changes
1338		1536
1339	Child watchers trigger when your process receives a SIGCHLD in response to	1537	Child watchers trigger when your process receives a SIGCHLD in response to
1340	some child status changes (most typically when a child of yours dies).	1538	some child status changes (most typically when a child of yours dies). It
		1539	is permissible to install a child watcher I<after> the child has been
		1540	forked (which implies it might have already exited), as long as the event
		1541	loop isn't entered (or is continued from a watcher).
		1542
		1543	Only the default event loop is capable of handling signals, and therefore
		1544	you can only register child watchers in the default event loop.
		1545
		1546	=head3 Process Interaction
		1547
		1548	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1549	initialised. This is necessary to guarantee proper behaviour even if
		1550	the first child watcher is started after the child exits. The occurrence
		1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1552	synchronously as part of the event loop processing. Libev always reaps all
		1553	children, even ones not watched.
		1554
		1555	=head3 Overriding the Built-In Processing
		1556
		1557	Libev offers no special support for overriding the built-in child
		1558	processing, but if your application collides with libev's default child
		1559	handler, you can override it easily by installing your own handler for
		1560	C<SIGCHLD> after initialising the default loop, and making sure the
		1561	default loop never gets destroyed. You are encouraged, however, to use an
		1562	event-based approach to child reaping and thus use libev's support for
		1563	that, so other libev users can use C<ev_child> watchers freely.
1341		1564
1342	=head3 Watcher-Specific Functions and Data Members	1565	=head3 Watcher-Specific Functions and Data Members
1343		1566
1344	=over 4	1567	=over 4
1345		1568
1346	=item ev_child_init (ev_child *, callback, int pid)	1569	=item ev_child_init (ev_child *, callback, int pid, int trace)
1347		1570
1348	=item ev_child_set (ev_child *, int pid)	1571	=item ev_child_set (ev_child *, int pid, int trace)
1349		1572
1350	Configures the watcher to wait for status changes of process C<pid> (or	1573	Configures the watcher to wait for status changes of process C<pid> (or
1351	I<any> process if C<pid> is specified as C<0>). The callback can look	1574	I<any> process if C<pid> is specified as C<0>). The callback can look
1352	at the C<rstatus> member of the C<ev_child> watcher structure to see	1575	at the C<rstatus> member of the C<ev_child> watcher structure to see
1353	the status word (use the macros from C<sys/wait.h> and see your systems	1576	the status word (use the macros from C<sys/wait.h> and see your systems
1354	C<waitpid> documentation). The C<rpid> member contains the pid of the	1577	C<waitpid> documentation). The C<rpid> member contains the pid of the
1355	process causing the status change.	1578	process causing the status change. C<trace> must be either C<0> (only
		1579	activate the watcher when the process terminates) or C<1> (additionally
		1580	activate the watcher when the process is stopped or continued).
1356		1581
1357	=item int pid [read-only]	1582	=item int pid [read-only]
1358		1583
1359	The process id this watcher watches out for, or C<0>, meaning any process id.	1584	The process id this watcher watches out for, or C<0>, meaning any process id.
1360		1585
…		…
1367	The process exit/trace status caused by C<rpid> (see your systems	1592	The process exit/trace status caused by C<rpid> (see your systems
1368	C<waitpid> and C<sys/wait.h> documentation for details).	1593	C<waitpid> and C<sys/wait.h> documentation for details).
1369		1594
1370	=back	1595	=back
1371		1596
1372	Example: Try to exit cleanly on SIGINT and SIGTERM.	1597	=head3 Examples
1373		1598
		1599	Example: C<fork()> a new process and install a child handler to wait for
		1600	its completion.
		1601
		1602	ev_child cw;
		1603
1374	static void	1604	static void
1375	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1605	child_cb (EV_P_ struct ev_child *w, int revents)
1376	{	1606	{
1377	ev_unloop (loop, EVUNLOOP_ALL);	1607	ev_child_stop (EV_A_ w);
		1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1378	}	1609	}
1379		1610
1380	struct ev_signal signal_watcher;	1611	pid_t pid = fork ();
1381	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1612
1382	ev_signal_start (loop, &sigint_cb);	1613	if (pid < 0)
		1614	// error
		1615	else if (pid == 0)
		1616	{
		1617	// the forked child executes here
		1618	exit (1);
		1619	}
		1620	else
		1621	{
		1622	ev_child_init (&cw, child_cb, pid, 0);
		1623	ev_child_start (EV_DEFAULT_ &cw);
		1624	}
1383		1625
1384		1626
1385	=head2 C<ev_stat> - did the file attributes just change?	1627	=head2 C<ev_stat> - did the file attributes just change?
1386		1628
1387	This watches a filesystem path for attribute changes. That is, it calls	1629	This watches a file system path for attribute changes. That is, it calls
1388	C<stat> regularly (or when the OS says it changed) and sees if it changed	1630	C<stat> regularly (or when the OS says it changed) and sees if it changed
1389	compared to the last time, invoking the callback if it did.	1631	compared to the last time, invoking the callback if it did.
1390		1632
1391	The path does not need to exist: changing from "path exists" to "path does	1633	The path does not need to exist: changing from "path exists" to "path does
1392	not exist" is a status change like any other. The condition "path does	1634	not exist" is a status change like any other. The condition "path does
…		…
1410	as even with OS-supported change notifications, this can be	1652	as even with OS-supported change notifications, this can be
1411	resource-intensive.	1653	resource-intensive.
1412		1654
1413	At the time of this writing, only the Linux inotify interface is	1655	At the time of this writing, only the Linux inotify interface is
1414	implemented (implementing kqueue support is left as an exercise for the	1656	implemented (implementing kqueue support is left as an exercise for the
		1657	reader, note, however, that the author sees no way of implementing ev_stat
1415	reader). Inotify will be used to give hints only and should not change the	1658	semantics with kqueue). Inotify will be used to give hints only and should
1416	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1659	not change the semantics of C<ev_stat> watchers, which means that libev
1417	to fall back to regular polling again even with inotify, but changes are	1660	sometimes needs to fall back to regular polling again even with inotify,
1418	usually detected immediately, and if the file exists there will be no	1661	but changes are usually detected immediately, and if the file exists there
1419	polling.	1662	will be no polling.
		1663
		1664	=head3 ABI Issues (Largefile Support)
		1665
		1666	Libev by default (unless the user overrides this) uses the default
		1667	compilation environment, which means that on systems with large file
		1668	support disabled by default, you get the 32 bit version of the stat
		1669	structure. When using the library from programs that change the ABI to
		1670	use 64 bit file offsets the programs will fail. In that case you have to
		1671	compile libev with the same flags to get binary compatibility. This is
		1672	obviously the case with any flags that change the ABI, but the problem is
		1673	most noticeably disabled with ev_stat and large file support.
		1674
		1675	The solution for this is to lobby your distribution maker to make large
		1676	file interfaces available by default (as e.g. FreeBSD does) and not
		1677	optional. Libev cannot simply switch on large file support because it has
		1678	to exchange stat structures with application programs compiled using the
		1679	default compilation environment.
		1680
		1681	=head3 Inotify
		1682
		1683	When C<inotify (7)> support has been compiled into libev (generally only
		1684	available on Linux) and present at runtime, it will be used to speed up
		1685	change detection where possible. The inotify descriptor will be created lazily
		1686	when the first C<ev_stat> watcher is being started.
		1687
		1688	Inotify presence does not change the semantics of C<ev_stat> watchers
		1689	except that changes might be detected earlier, and in some cases, to avoid
		1690	making regular C<stat> calls. Even in the presence of inotify support
		1691	there are many cases where libev has to resort to regular C<stat> polling.
		1692
		1693	(There is no support for kqueue, as apparently it cannot be used to
		1694	implement this functionality, due to the requirement of having a file
		1695	descriptor open on the object at all times).
		1696
		1697	=head3 The special problem of stat time resolution
		1698
		1699	The C<stat ()> system call only supports full-second resolution portably, and
		1700	even on systems where the resolution is higher, many file systems still
		1701	only support whole seconds.
		1702
		1703	That means that, if the time is the only thing that changes, you can
		1704	easily miss updates: on the first update, C<ev_stat> detects a change and
		1705	calls your callback, which does something. When there is another update
		1706	within the same second, C<ev_stat> will be unable to detect it as the stat
		1707	data does not change.
		1708
		1709	The solution to this is to delay acting on a change for slightly more
		1710	than a second (or till slightly after the next full second boundary), using
		1711	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1712	ev_timer_again (loop, w)>).
		1713
		1714	The C<.02> offset is added to work around small timing inconsistencies
		1715	of some operating systems (where the second counter of the current time
		1716	might be be delayed. One such system is the Linux kernel, where a call to
		1717	C<gettimeofday> might return a timestamp with a full second later than
		1718	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1719	update file times then there will be a small window where the kernel uses
		1720	the previous second to update file times but libev might already execute
		1721	the timer callback).
1420		1722
1421	=head3 Watcher-Specific Functions and Data Members	1723	=head3 Watcher-Specific Functions and Data Members
1422		1724
1423	=over 4	1725	=over 4
1424		1726
…		…
1430	C<path>. The C<interval> is a hint on how quickly a change is expected to	1732	C<path>. The C<interval> is a hint on how quickly a change is expected to
1431	be detected and should normally be specified as C<0> to let libev choose	1733	be detected and should normally be specified as C<0> to let libev choose
1432	a suitable value. The memory pointed to by C<path> must point to the same	1734	a suitable value. The memory pointed to by C<path> must point to the same
1433	path for as long as the watcher is active.	1735	path for as long as the watcher is active.
1434		1736
1435	The callback will be receive C<EV_STAT> when a change was detected,	1737	The callback will receive C<EV_STAT> when a change was detected, relative
1436	relative to the attributes at the time the watcher was started (or the	1738	to the attributes at the time the watcher was started (or the last change
1437	last change was detected).	1739	was detected).
1438		1740
1439	=item ev_stat_stat (ev_stat *)	1741	=item ev_stat_stat (loop, ev_stat *)
1440		1742
1441	Updates the stat buffer immediately with new values. If you change the	1743	Updates the stat buffer immediately with new values. If you change the
1442	watched path in your callback, you could call this fucntion to avoid	1744	watched path in your callback, you could call this function to avoid
1443	detecting this change (while introducing a race condition). Can also be	1745	detecting this change (while introducing a race condition if you are not
1444	useful simply to find out the new values.	1746	the only one changing the path). Can also be useful simply to find out the
		1747	new values.
1445		1748
1446	=item ev_statdata attr [read-only]	1749	=item ev_statdata attr [read-only]
1447		1750
1448	The most-recently detected attributes of the file. Although the type is of	1751	The most-recently detected attributes of the file. Although the type is
1449	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1752	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1450	suitable for your system. If the C<st_nlink> member is C<0>, then there	1753	suitable for your system, but you can only rely on the POSIX-standardised
		1754	members to be present. If the C<st_nlink> member is C<0>, then there was
1451	was some error while C<stat>ing the file.	1755	some error while C<stat>ing the file.
1452		1756
1453	=item ev_statdata prev [read-only]	1757	=item ev_statdata prev [read-only]
1454		1758
1455	The previous attributes of the file. The callback gets invoked whenever	1759	The previous attributes of the file. The callback gets invoked whenever
1456	C<prev> != C<attr>.	1760	C<prev> != C<attr>, or, more precisely, one or more of these members
		1761	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1762	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1457		1763
1458	=item ev_tstamp interval [read-only]	1764	=item ev_tstamp interval [read-only]
1459		1765
1460	The specified interval.	1766	The specified interval.
1461		1767
1462	=item const char *path [read-only]	1768	=item const char *path [read-only]
1463		1769
1464	The filesystem path that is being watched.	1770	The file system path that is being watched.
1465		1771
1466	=back	1772	=back
1467		1773
		1774	=head3 Examples
		1775
1468	Example: Watch C</etc/passwd> for attribute changes.	1776	Example: Watch C</etc/passwd> for attribute changes.
1469		1777
1470	static void	1778	static void
1471	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1779	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1472	{	1780	{
1473	/* /etc/passwd changed in some way */	1781	/* /etc/passwd changed in some way */
1474	if (w->attr.st_nlink)	1782	if (w->attr.st_nlink)
1475	{	1783	{
1476	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1784	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1477	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1785	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1478	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1786	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1479	}	1787	}
1480	else	1788	else
1481	/* you shalt not abuse printf for puts */	1789	/* you shalt not abuse printf for puts */
1482	puts ("wow, /etc/passwd is not there, expect problems. "	1790	puts ("wow, /etc/passwd is not there, expect problems. "
1483	"if this is windows, they already arrived\n");	1791	"if this is windows, they already arrived\n");
1484	}	1792	}
1485		1793
1486	...	1794	...
1487	ev_stat passwd;	1795	ev_stat passwd;
1488		1796
1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1797	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1490	ev_stat_start (loop, &passwd);	1798	ev_stat_start (loop, &passwd);
		1799
		1800	Example: Like above, but additionally use a one-second delay so we do not
		1801	miss updates (however, frequent updates will delay processing, too, so
		1802	one might do the work both on C<ev_stat> callback invocation I<and> on
		1803	C<ev_timer> callback invocation).
		1804
		1805	static ev_stat passwd;
		1806	static ev_timer timer;
		1807
		1808	static void
		1809	timer_cb (EV_P_ ev_timer *w, int revents)
		1810	{
		1811	ev_timer_stop (EV_A_ w);
		1812
		1813	/* now it's one second after the most recent passwd change */
		1814	}
		1815
		1816	static void
		1817	stat_cb (EV_P_ ev_stat *w, int revents)
		1818	{
		1819	/* reset the one-second timer */
		1820	ev_timer_again (EV_A_ &timer);
		1821	}
		1822
		1823	...
		1824	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1825	ev_stat_start (loop, &passwd);
		1826	ev_timer_init (&timer, timer_cb, 0., 1.02);
1491		1827
1492		1828
1493	=head2 C<ev_idle> - when you've got nothing better to do...	1829	=head2 C<ev_idle> - when you've got nothing better to do...
1494		1830
1495	Idle watchers trigger events when no other events of the same or higher	1831	Idle watchers trigger events when no other events of the same or higher
…		…
1521	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1857	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1522	believe me.	1858	believe me.
1523		1859
1524	=back	1860	=back
1525		1861
		1862	=head3 Examples
		1863
1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1864	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1527	callback, free it. Also, use no error checking, as usual.	1865	callback, free it. Also, use no error checking, as usual.
1528		1866
1529	static void	1867	static void
1530	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1868	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1531	{	1869	{
1532	free (w);	1870	free (w);
1533	// now do something you wanted to do when the program has	1871	// now do something you wanted to do when the program has
1534	// no longer asnything immediate to do.	1872	// no longer anything immediate to do.
1535	}	1873	}
1536		1874
1537	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1875	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1538	ev_idle_init (idle_watcher, idle_cb);	1876	ev_idle_init (idle_watcher, idle_cb);
1539	ev_idle_start (loop, idle_cb);	1877	ev_idle_start (loop, idle_cb);
1540		1878
1541		1879
1542	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1880	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1543		1881
1544	Prepare and check watchers are usually (but not always) used in tandem:	1882	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1563		1901
1564	This is done by examining in each prepare call which file descriptors need	1902	This is done by examining in each prepare call which file descriptors need
1565	to be watched by the other library, registering C<ev_io> watchers for	1903	to be watched by the other library, registering C<ev_io> watchers for
1566	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1904	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1567	provide just this functionality). Then, in the check watcher you check for	1905	provide just this functionality). Then, in the check watcher you check for
1568	any events that occured (by checking the pending status of all watchers	1906	any events that occurred (by checking the pending status of all watchers
1569	and stopping them) and call back into the library. The I/O and timer	1907	and stopping them) and call back into the library. The I/O and timer
1570	callbacks will never actually be called (but must be valid nevertheless,	1908	callbacks will never actually be called (but must be valid nevertheless,
1571	because you never know, you know?).	1909	because you never know, you know?).
1572		1910
1573	As another example, the Perl Coro module uses these hooks to integrate	1911	As another example, the Perl Coro module uses these hooks to integrate
…		…
1581		1919
1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1920	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1583	priority, to ensure that they are being run before any other watchers	1921	priority, to ensure that they are being run before any other watchers
1584	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1922	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1585	too) should not activate ("feed") events into libev. While libev fully	1923	too) should not activate ("feed") events into libev. While libev fully
1586	supports this, they will be called before other C<ev_check> watchers did	1924	supports this, they might get executed before other C<ev_check> watchers
1587	their job. As C<ev_check> watchers are often used to embed other event	1925	did their job. As C<ev_check> watchers are often used to embed other
1588	loops those other event loops might be in an unusable state until their	1926	(non-libev) event loops those other event loops might be in an unusable
1589	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1927	state until their C<ev_check> watcher ran (always remind yourself to
1590	others).	1928	coexist peacefully with others).
1591		1929
1592	=head3 Watcher-Specific Functions and Data Members	1930	=head3 Watcher-Specific Functions and Data Members
1593		1931
1594	=over 4	1932	=over 4
1595		1933
…		…
1601	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1939	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1602	macros, but using them is utterly, utterly and completely pointless.	1940	macros, but using them is utterly, utterly and completely pointless.
1603		1941
1604	=back	1942	=back
1605		1943
		1944	=head3 Examples
		1945
1606	There are a number of principal ways to embed other event loops or modules	1946	There are a number of principal ways to embed other event loops or modules
1607	into libev. Here are some ideas on how to include libadns into libev	1947	into libev. Here are some ideas on how to include libadns into libev
1608	(there is a Perl module named C<EV::ADNS> that does this, which you could	1948	(there is a Perl module named C<EV::ADNS> that does this, which you could
1609	use for an actually working example. Another Perl module named C<EV::Glib>	1949	use as a working example. Another Perl module named C<EV::Glib> embeds a
1610	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1950	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1611	into the Glib event loop).	1951	Glib event loop).
1612		1952
1613	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1953	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1614	and in a check watcher, destroy them and call into libadns. What follows	1954	and in a check watcher, destroy them and call into libadns. What follows
1615	is pseudo-code only of course. This requires you to either use a low	1955	is pseudo-code only of course. This requires you to either use a low
1616	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1956	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1617	the callbacks for the IO/timeout watchers might not have been called yet.	1957	the callbacks for the IO/timeout watchers might not have been called yet.
1618		1958
1619	static ev_io iow [nfd];	1959	static ev_io iow [nfd];
1620	static ev_timer tw;	1960	static ev_timer tw;
1621		1961
1622	static void	1962	static void
1623	io_cb (ev_loop *loop, ev_io *w, int revents)	1963	io_cb (ev_loop *loop, ev_io *w, int revents)
1624	{	1964	{
1625	}	1965	}
1626		1966
1627	// create io watchers for each fd and a timer before blocking	1967	// create io watchers for each fd and a timer before blocking
1628	static void	1968	static void
1629	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1969	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1630	{	1970	{
1631	int timeout = 3600000;	1971	int timeout = 3600000;
1632	struct pollfd fds [nfd];	1972	struct pollfd fds [nfd];
1633	// actual code will need to loop here and realloc etc.	1973	// actual code will need to loop here and realloc etc.
1634	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1974	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1635		1975
1636	/* the callback is illegal, but won't be called as we stop during check */	1976	/* the callback is illegal, but won't be called as we stop during check */
1637	ev_timer_init (&tw, 0, timeout * 1e-3);	1977	ev_timer_init (&tw, 0, timeout * 1e-3);
1638	ev_timer_start (loop, &tw);	1978	ev_timer_start (loop, &tw);
1639		1979
1640	// create one ev_io per pollfd	1980	// create one ev_io per pollfd
1641	for (int i = 0; i < nfd; ++i)	1981	for (int i = 0; i < nfd; ++i)
1642	{	1982	{
1643	ev_io_init (iow + i, io_cb, fds [i].fd,	1983	ev_io_init (iow + i, io_cb, fds [i].fd,
1644	((fds [i].events & POLLIN ? EV_READ : 0)	1984	((fds [i].events & POLLIN ? EV_READ : 0)
1645	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1985	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1646		1986
1647	fds [i].revents = 0;	1987	fds [i].revents = 0;
1648	ev_io_start (loop, iow + i);	1988	ev_io_start (loop, iow + i);
1649	}	1989	}
1650	}	1990	}
1651		1991
1652	// stop all watchers after blocking	1992	// stop all watchers after blocking
1653	static void	1993	static void
1654	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1994	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1655	{	1995	{
1656	ev_timer_stop (loop, &tw);	1996	ev_timer_stop (loop, &tw);
1657		1997
1658	for (int i = 0; i < nfd; ++i)	1998	for (int i = 0; i < nfd; ++i)
1659	{	1999	{
1660	// set the relevant poll flags	2000	// set the relevant poll flags
1661	// could also call adns_processreadable etc. here	2001	// could also call adns_processreadable etc. here
1662	struct pollfd *fd = fds + i;	2002	struct pollfd *fd = fds + i;
1663	int revents = ev_clear_pending (iow + i);	2003	int revents = ev_clear_pending (iow + i);
1664	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2004	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1665	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2005	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1666		2006
1667	// now stop the watcher	2007	// now stop the watcher
1668	ev_io_stop (loop, iow + i);	2008	ev_io_stop (loop, iow + i);
1669	}	2009	}
1670		2010
1671	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2011	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1672	}	2012	}
1673		2013
1674	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2014	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1675	in the prepare watcher and would dispose of the check watcher.	2015	in the prepare watcher and would dispose of the check watcher.
1676		2016
1677	Method 3: If the module to be embedded supports explicit event	2017	Method 3: If the module to be embedded supports explicit event
1678	notification (adns does), you can also make use of the actual watcher	2018	notification (libadns does), you can also make use of the actual watcher
1679	callbacks, and only destroy/create the watchers in the prepare watcher.	2019	callbacks, and only destroy/create the watchers in the prepare watcher.
1680		2020
1681	static void	2021	static void
1682	timer_cb (EV_P_ ev_timer *w, int revents)	2022	timer_cb (EV_P_ ev_timer *w, int revents)
1683	{	2023	{
1684	adns_state ads = (adns_state)w->data;	2024	adns_state ads = (adns_state)w->data;
1685	update_now (EV_A);	2025	update_now (EV_A);
1686		2026
1687	adns_processtimeouts (ads, &tv_now);	2027	adns_processtimeouts (ads, &tv_now);
1688	}	2028	}
1689		2029
1690	static void	2030	static void
1691	io_cb (EV_P_ ev_io *w, int revents)	2031	io_cb (EV_P_ ev_io *w, int revents)
1692	{	2032	{
1693	adns_state ads = (adns_state)w->data;	2033	adns_state ads = (adns_state)w->data;
1694	update_now (EV_A);	2034	update_now (EV_A);
1695		2035
1696	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2036	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1697	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2037	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1698	}	2038	}
1699		2039
1700	// do not ever call adns_afterpoll	2040	// do not ever call adns_afterpoll
1701		2041
1702	Method 4: Do not use a prepare or check watcher because the module you	2042	Method 4: Do not use a prepare or check watcher because the module you
1703	want to embed is too inflexible to support it. Instead, youc na override	2043	want to embed is too inflexible to support it. Instead, you can override
1704	their poll function. The drawback with this solution is that the main	2044	their poll function. The drawback with this solution is that the main
1705	loop is now no longer controllable by EV. The C<Glib::EV> module does	2045	loop is now no longer controllable by EV. The C<Glib::EV> module does
1706	this.	2046	this.
1707		2047
1708	static gint	2048	static gint
1709	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2049	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1710	{	2050	{
1711	int got_events = 0;	2051	int got_events = 0;
1712		2052
1713	for (n = 0; n < nfds; ++n)	2053	for (n = 0; n < nfds; ++n)
1714	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2054	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1715		2055
1716	if (timeout >= 0)	2056	if (timeout >= 0)
1717	// create/start timer	2057	// create/start timer
1718		2058
1719	// poll	2059	// poll
1720	ev_loop (EV_A_ 0);	2060	ev_loop (EV_A_ 0);
1721		2061
1722	// stop timer again	2062	// stop timer again
1723	if (timeout >= 0)	2063	if (timeout >= 0)
1724	ev_timer_stop (EV_A_ &to);	2064	ev_timer_stop (EV_A_ &to);
1725		2065
1726	// stop io watchers again - their callbacks should have set	2066	// stop io watchers again - their callbacks should have set
1727	for (n = 0; n < nfds; ++n)	2067	for (n = 0; n < nfds; ++n)
1728	ev_io_stop (EV_A_ iow [n]);	2068	ev_io_stop (EV_A_ iow [n]);
1729		2069
1730	return got_events;	2070	return got_events;
1731	}	2071	}
1732		2072
1733		2073
1734	=head2 C<ev_embed> - when one backend isn't enough...	2074	=head2 C<ev_embed> - when one backend isn't enough...
1735		2075
1736	This is a rather advanced watcher type that lets you embed one event loop	2076	This is a rather advanced watcher type that lets you embed one event loop
1737	into another (currently only C<ev_io> events are supported in the embedded	2077	into another (currently only C<ev_io> events are supported in the embedded
1738	loop, other types of watchers might be handled in a delayed or incorrect	2078	loop, other types of watchers might be handled in a delayed or incorrect
1739	fashion and must not be used). (See portability notes, below).	2079	fashion and must not be used).
1740		2080
1741	There are primarily two reasons you would want that: work around bugs and	2081	There are primarily two reasons you would want that: work around bugs and
1742	prioritise I/O.	2082	prioritise I/O.
1743		2083
1744	As an example for a bug workaround, the kqueue backend might only support	2084	As an example for a bug workaround, the kqueue backend might only support
…		…
1778	portable one.	2118	portable one.
1779		2119
1780	So when you want to use this feature you will always have to be prepared	2120	So when you want to use this feature you will always have to be prepared
1781	that you cannot get an embeddable loop. The recommended way to get around	2121	that you cannot get an embeddable loop. The recommended way to get around
1782	this is to have a separate variables for your embeddable loop, try to	2122	this is to have a separate variables for your embeddable loop, try to
1783	create it, and if that fails, use the normal loop for everything:	2123	create it, and if that fails, use the normal loop for everything.
1784
1785	struct ev_loop *loop_hi = ev_default_init (0);
1786	struct ev_loop *loop_lo = 0;
1787	struct ev_embed embed;
1788
1789	// see if there is a chance of getting one that works
1790	// (remember that a flags value of 0 means autodetection)
1791	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1792	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1793	: 0;
1794
1795	// if we got one, then embed it, otherwise default to loop_hi
1796	if (loop_lo)
1797	{
1798	ev_embed_init (&embed, 0, loop_lo);
1799	ev_embed_start (loop_hi, &embed);
1800	}
1801	else
1802	loop_lo = loop_hi;
1803
1804	=head2 Portability notes
1805
1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I
1807	tried, in various ways. Usually the embedded event loop will simply never
1808	receive events, sometimes it will only trigger a few times, sometimes in a
1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions
1810	will always eport the epoll fd as ready, even when no events are pending.
1811
1812	While libev allows embedding these backends (they are contained in
1813	C<ev_embeddable_backends ()>), take extreme care that it will actually
1814	work.
1815
1816	When in doubt, create a dynamic event loop forced to use sockets (this
1817	usually works) and possibly another thread and a pipe or so to report to
1818	your main event loop.
1819		2124
1820	=head3 Watcher-Specific Functions and Data Members	2125	=head3 Watcher-Specific Functions and Data Members
1821		2126
1822	=over 4	2127	=over 4
1823		2128
…		…
1827		2132
1828	Configures the watcher to embed the given loop, which must be	2133	Configures the watcher to embed the given loop, which must be
1829	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2134	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1830	invoked automatically, otherwise it is the responsibility of the callback	2135	invoked automatically, otherwise it is the responsibility of the callback
1831	to invoke it (it will continue to be called until the sweep has been done,	2136	to invoke it (it will continue to be called until the sweep has been done,
1832	if you do not want thta, you need to temporarily stop the embed watcher).	2137	if you do not want that, you need to temporarily stop the embed watcher).
1833		2138
1834	=item ev_embed_sweep (loop, ev_embed *)	2139	=item ev_embed_sweep (loop, ev_embed *)
1835		2140
1836	Make a single, non-blocking sweep over the embedded loop. This works	2141	Make a single, non-blocking sweep over the embedded loop. This works
1837	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2142	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1838	apropriate way for embedded loops.	2143	appropriate way for embedded loops.
1839		2144
1840	=item struct ev_loop *other [read-only]	2145	=item struct ev_loop *other [read-only]
1841		2146
1842	The embedded event loop.	2147	The embedded event loop.
1843		2148
1844	=back	2149	=back
		2150
		2151	=head3 Examples
		2152
		2153	Example: Try to get an embeddable event loop and embed it into the default
		2154	event loop. If that is not possible, use the default loop. The default
		2155	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2156	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2157	used).
		2158
		2159	struct ev_loop *loop_hi = ev_default_init (0);
		2160	struct ev_loop *loop_lo = 0;
		2161	struct ev_embed embed;
		2162
		2163	// see if there is a chance of getting one that works
		2164	// (remember that a flags value of 0 means autodetection)
		2165	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2166	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2167	: 0;
		2168
		2169	// if we got one, then embed it, otherwise default to loop_hi
		2170	if (loop_lo)
		2171	{
		2172	ev_embed_init (&embed, 0, loop_lo);
		2173	ev_embed_start (loop_hi, &embed);
		2174	}
		2175	else
		2176	loop_lo = loop_hi;
		2177
		2178	Example: Check if kqueue is available but not recommended and create
		2179	a kqueue backend for use with sockets (which usually work with any
		2180	kqueue implementation). Store the kqueue/socket-only event loop in
		2181	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2182
		2183	struct ev_loop *loop = ev_default_init (0);
		2184	struct ev_loop *loop_socket = 0;
		2185	struct ev_embed embed;
		2186
		2187	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2188	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2189	{
		2190	ev_embed_init (&embed, 0, loop_socket);
		2191	ev_embed_start (loop, &embed);
		2192	}
		2193
		2194	if (!loop_socket)
		2195	loop_socket = loop;
		2196
		2197	// now use loop_socket for all sockets, and loop for everything else
1845		2198
1846		2199
1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2200	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1848		2201
1849	Fork watchers are called when a C<fork ()> was detected (usually because	2202	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1865	believe me.	2218	believe me.
1866		2219
1867	=back	2220	=back
1868		2221
1869		2222
		2223	=head2 C<ev_async> - how to wake up another event loop
		2224
		2225	In general, you cannot use an C<ev_loop> from multiple threads or other
		2226	asynchronous sources such as signal handlers (as opposed to multiple event
		2227	loops - those are of course safe to use in different threads).
		2228
		2229	Sometimes, however, you need to wake up another event loop you do not
		2230	control, for example because it belongs to another thread. This is what
		2231	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2232	can signal it by calling C<ev_async_send>, which is thread- and signal
		2233	safe.
		2234
		2235	This functionality is very similar to C<ev_signal> watchers, as signals,
		2236	too, are asynchronous in nature, and signals, too, will be compressed
		2237	(i.e. the number of callback invocations may be less than the number of
		2238	C<ev_async_sent> calls).
		2239
		2240	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2241	just the default loop.
		2242
		2243	=head3 Queueing
		2244
		2245	C<ev_async> does not support queueing of data in any way. The reason
		2246	is that the author does not know of a simple (or any) algorithm for a
		2247	multiple-writer-single-reader queue that works in all cases and doesn't
		2248	need elaborate support such as pthreads.
		2249
		2250	That means that if you want to queue data, you have to provide your own
		2251	queue. But at least I can tell you would implement locking around your
		2252	queue:
		2253
		2254	=over 4
		2255
		2256	=item queueing from a signal handler context
		2257
		2258	To implement race-free queueing, you simply add to the queue in the signal
		2259	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2260	some fictitious SIGUSR1 handler:
		2261
		2262	static ev_async mysig;
		2263
		2264	static void
		2265	sigusr1_handler (void)
		2266	{
		2267	sometype data;
		2268
		2269	// no locking etc.
		2270	queue_put (data);
		2271	ev_async_send (EV_DEFAULT_ &mysig);
		2272	}
		2273
		2274	static void
		2275	mysig_cb (EV_P_ ev_async *w, int revents)
		2276	{
		2277	sometype data;
		2278	sigset_t block, prev;
		2279
		2280	sigemptyset (&block);
		2281	sigaddset (&block, SIGUSR1);
		2282	sigprocmask (SIG_BLOCK, &block, &prev);
		2283
		2284	while (queue_get (&data))
		2285	process (data);
		2286
		2287	if (sigismember (&prev, SIGUSR1)
		2288	sigprocmask (SIG_UNBLOCK, &block, 0);
		2289	}
		2290
		2291	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2292	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2293	either...).
		2294
		2295	=item queueing from a thread context
		2296
		2297	The strategy for threads is different, as you cannot (easily) block
		2298	threads but you can easily preempt them, so to queue safely you need to
		2299	employ a traditional mutex lock, such as in this pthread example:
		2300
		2301	static ev_async mysig;
		2302	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2303
		2304	static void
		2305	otherthread (void)
		2306	{
		2307	// only need to lock the actual queueing operation
		2308	pthread_mutex_lock (&mymutex);
		2309	queue_put (data);
		2310	pthread_mutex_unlock (&mymutex);
		2311
		2312	ev_async_send (EV_DEFAULT_ &mysig);
		2313	}
		2314
		2315	static void
		2316	mysig_cb (EV_P_ ev_async *w, int revents)
		2317	{
		2318	pthread_mutex_lock (&mymutex);
		2319
		2320	while (queue_get (&data))
		2321	process (data);
		2322
		2323	pthread_mutex_unlock (&mymutex);
		2324	}
		2325
		2326	=back
		2327
		2328
		2329	=head3 Watcher-Specific Functions and Data Members
		2330
		2331	=over 4
		2332
		2333	=item ev_async_init (ev_async *, callback)
		2334
		2335	Initialises and configures the async watcher - it has no parameters of any
		2336	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2337	believe me.
		2338
		2339	=item ev_async_send (loop, ev_async *)
		2340
		2341	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2342	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2343	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2344	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2345	section below on what exactly this means).
		2346
		2347	This call incurs the overhead of a system call only once per loop iteration,
		2348	so while the overhead might be noticeable, it doesn't apply to repeated
		2349	calls to C<ev_async_send>.
		2350
		2351	=item bool = ev_async_pending (ev_async *)
		2352
		2353	Returns a non-zero value when C<ev_async_send> has been called on the
		2354	watcher but the event has not yet been processed (or even noted) by the
		2355	event loop.
		2356
		2357	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2358	the loop iterates next and checks for the watcher to have become active,
		2359	it will reset the flag again. C<ev_async_pending> can be used to very
		2360	quickly check whether invoking the loop might be a good idea.
		2361
		2362	Not that this does I<not> check whether the watcher itself is pending, only
		2363	whether it has been requested to make this watcher pending.
		2364
		2365	=back
		2366
		2367
1870	=head1 OTHER FUNCTIONS	2368	=head1 OTHER FUNCTIONS
1871		2369
1872	There are some other functions of possible interest. Described. Here. Now.	2370	There are some other functions of possible interest. Described. Here. Now.
1873		2371
1874	=over 4	2372	=over 4
…		…
1881	or timeout without having to allocate/configure/start/stop/free one or	2379	or timeout without having to allocate/configure/start/stop/free one or
1882	more watchers yourself.	2380	more watchers yourself.
1883		2381
1884	If C<fd> is less than 0, then no I/O watcher will be started and events	2382	If C<fd> is less than 0, then no I/O watcher will be started and events
1885	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2383	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1886	C<events> set will be craeted and started.	2384	C<events> set will be created and started.
1887		2385
1888	If C<timeout> is less than 0, then no timeout watcher will be	2386	If C<timeout> is less than 0, then no timeout watcher will be
1889	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2387	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1890	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2388	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1891	dubious value.	2389	dubious value.
…		…
1893	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2391	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1894	passed an C<revents> set like normal event callbacks (a combination of	2392	passed an C<revents> set like normal event callbacks (a combination of
1895	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2393	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1896	value passed to C<ev_once>:	2394	value passed to C<ev_once>:
1897		2395
1898	static void stdin_ready (int revents, void *arg)	2396	static void stdin_ready (int revents, void *arg)
1899	{	2397	{
1900	if (revents & EV_TIMEOUT)	2398	if (revents & EV_TIMEOUT)
1901	/* doh, nothing entered */;	2399	/* doh, nothing entered */;
1902	else if (revents & EV_READ)	2400	else if (revents & EV_READ)
1903	/* stdin might have data for us, joy! */;	2401	/* stdin might have data for us, joy! */;
1904	}	2402	}
1905		2403
1906	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2404	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1907		2405
1908	=item ev_feed_event (ev_loop *, watcher *, int revents)	2406	=item ev_feed_event (ev_loop *, watcher *, int revents)
1909		2407
1910	Feeds the given event set into the event loop, as if the specified event	2408	Feeds the given event set into the event loop, as if the specified event
1911	had happened for the specified watcher (which must be a pointer to an	2409	had happened for the specified watcher (which must be a pointer to an
…		…
1916	Feed an event on the given fd, as if a file descriptor backend detected	2414	Feed an event on the given fd, as if a file descriptor backend detected
1917	the given events it.	2415	the given events it.
1918		2416
1919	=item ev_feed_signal_event (ev_loop *loop, int signum)	2417	=item ev_feed_signal_event (ev_loop *loop, int signum)
1920		2418
1921	Feed an event as if the given signal occured (C<loop> must be the default	2419	Feed an event as if the given signal occurred (C<loop> must be the default
1922	loop!).	2420	loop!).
1923		2421
1924	=back	2422	=back
1925		2423
1926		2424
…		…
1942		2440
1943	=item * Priorities are not currently supported. Initialising priorities	2441	=item * Priorities are not currently supported. Initialising priorities
1944	will fail and all watchers will have the same priority, even though there	2442	will fail and all watchers will have the same priority, even though there
1945	is an ev_pri field.	2443	is an ev_pri field.
1946		2444
		2445	=item * In libevent, the last base created gets the signals, in libev, the
		2446	first base created (== the default loop) gets the signals.
		2447
1947	=item * Other members are not supported.	2448	=item * Other members are not supported.
1948		2449
1949	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2450	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1950	to use the libev header file and library.	2451	to use the libev header file and library.
1951		2452
1952	=back	2453	=back
1953		2454
1954	=head1 C++ SUPPORT	2455	=head1 C++ SUPPORT
1955		2456
1956	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2457	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1957	you to use some convinience methods to start/stop watchers and also change	2458	you to use some convenience methods to start/stop watchers and also change
1958	the callback model to a model using method callbacks on objects.	2459	the callback model to a model using method callbacks on objects.
1959		2460
1960	To use it,	2461	To use it,
1961		2462
1962	#include <ev++.h>	2463	#include <ev++.h>
1963		2464
1964	This automatically includes F<ev.h> and puts all of its definitions (many	2465	This automatically includes F<ev.h> and puts all of its definitions (many
1965	of them macros) into the global namespace. All C++ specific things are	2466	of them macros) into the global namespace. All C++ specific things are
1966	put into the C<ev> namespace. It should support all the same embedding	2467	put into the C<ev> namespace. It should support all the same embedding
1967	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2468	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2034	your compiler is good :), then the method will be fully inlined into the	2535	your compiler is good :), then the method will be fully inlined into the
2035	thunking function, making it as fast as a direct C callback.	2536	thunking function, making it as fast as a direct C callback.
2036		2537
2037	Example: simple class declaration and watcher initialisation	2538	Example: simple class declaration and watcher initialisation
2038		2539
2039	struct myclass	2540	struct myclass
2040	{	2541	{
2041	void io_cb (ev::io &w, int revents) { }	2542	void io_cb (ev::io &w, int revents) { }
2042	}	2543	}
2043		2544
2044	myclass obj;	2545	myclass obj;
2045	ev::io iow;	2546	ev::io iow;
2046	iow.set <myclass, &myclass::io_cb> (&obj);	2547	iow.set <myclass, &myclass::io_cb> (&obj);
2047		2548
2048	=item w->set<function> (void *data = 0)	2549	=item w->set<function> (void *data = 0)
2049		2550
2050	Also sets a callback, but uses a static method or plain function as	2551	Also sets a callback, but uses a static method or plain function as
2051	callback. The optional C<data> argument will be stored in the watcher's	2552	callback. The optional C<data> argument will be stored in the watcher's
…		…
2055		2556
2056	See the method-C<set> above for more details.	2557	See the method-C<set> above for more details.
2057		2558
2058	Example:	2559	Example:
2059		2560
2060	static void io_cb (ev::io &w, int revents) { }	2561	static void io_cb (ev::io &w, int revents) { }
2061	iow.set <io_cb> ();	2562	iow.set <io_cb> ();
2062		2563
2063	=item w->set (struct ev_loop *)	2564	=item w->set (struct ev_loop *)
2064		2565
2065	Associates a different C<struct ev_loop> with this watcher. You can only	2566	Associates a different C<struct ev_loop> with this watcher. You can only
2066	do this when the watcher is inactive (and not pending either).	2567	do this when the watcher is inactive (and not pending either).
2067		2568
2068	=item w->set ([args])	2569	=item w->set ([arguments])
2069		2570
2070	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2571	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2071	called at least once. Unlike the C counterpart, an active watcher gets	2572	called at least once. Unlike the C counterpart, an active watcher gets
2072	automatically stopped and restarted when reconfiguring it with this	2573	automatically stopped and restarted when reconfiguring it with this
2073	method.	2574	method.
2074		2575
2075	=item w->start ()	2576	=item w->start ()
…		…
2099	=back	2600	=back
2100		2601
2101	Example: Define a class with an IO and idle watcher, start one of them in	2602	Example: Define a class with an IO and idle watcher, start one of them in
2102	the constructor.	2603	the constructor.
2103		2604
2104	class myclass	2605	class myclass
2105	{	2606	{
2106	ev_io io; void io_cb (ev::io &w, int revents);	2607	ev::io io; void io_cb (ev::io &w, int revents);
2107	ev_idle idle void idle_cb (ev::idle &w, int revents);	2608	ev:idle idle void idle_cb (ev::idle &w, int revents);
2108		2609
2109	myclass ();	2610	myclass (int fd)
2110	}	2611	{
2111
2112	myclass::myclass (int fd)
2113	{
2114	io .set <myclass, &myclass::io_cb > (this);	2612	io .set <myclass, &myclass::io_cb > (this);
2115	idle.set <myclass, &myclass::idle_cb> (this);	2613	idle.set <myclass, &myclass::idle_cb> (this);
2116		2614
2117	io.start (fd, ev::READ);	2615	io.start (fd, ev::READ);
		2616	}
2118	}	2617	};
		2618
		2619
		2620	=head1 OTHER LANGUAGE BINDINGS
		2621
		2622	Libev does not offer other language bindings itself, but bindings for a
		2623	number of languages exist in the form of third-party packages. If you know
		2624	any interesting language binding in addition to the ones listed here, drop
		2625	me a note.
		2626
		2627	=over 4
		2628
		2629	=item Perl
		2630
		2631	The EV module implements the full libev API and is actually used to test
		2632	libev. EV is developed together with libev. Apart from the EV core module,
		2633	there are additional modules that implement libev-compatible interfaces
		2634	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2635	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2636
		2637	It can be found and installed via CPAN, its homepage is at
		2638	L<http://software.schmorp.de/pkg/EV>.
		2639
		2640	=item Python
		2641
		2642	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2643	seems to be quite complete and well-documented. Note, however, that the
		2644	patch they require for libev is outright dangerous as it breaks the ABI
		2645	for everybody else, and therefore, should never be applied in an installed
		2646	libev (if python requires an incompatible ABI then it needs to embed
		2647	libev).
		2648
		2649	=item Ruby
		2650
		2651	Tony Arcieri has written a ruby extension that offers access to a subset
		2652	of the libev API and adds file handle abstractions, asynchronous DNS and
		2653	more on top of it. It can be found via gem servers. Its homepage is at
		2654	L<http://rev.rubyforge.org/>.
		2655
		2656	=item D
		2657
		2658	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2659	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2660
		2661	=back
2119		2662
2120		2663
2121	=head1 MACRO MAGIC	2664	=head1 MACRO MAGIC
2122		2665
2123	Libev can be compiled with a variety of options, the most fundamantal	2666	Libev can be compiled with a variety of options, the most fundamental
2124	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2667	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2125	functions and callbacks have an initial C<struct ev_loop *> argument.	2668	functions and callbacks have an initial C<struct ev_loop *> argument.
2126		2669
2127	To make it easier to write programs that cope with either variant, the	2670	To make it easier to write programs that cope with either variant, the
2128	following macros are defined:	2671	following macros are defined:
…		…
2133		2676
2134	This provides the loop I<argument> for functions, if one is required ("ev	2677	This provides the loop I<argument> for functions, if one is required ("ev
2135	loop argument"). The C<EV_A> form is used when this is the sole argument,	2678	loop argument"). The C<EV_A> form is used when this is the sole argument,
2136	C<EV_A_> is used when other arguments are following. Example:	2679	C<EV_A_> is used when other arguments are following. Example:
2137		2680
2138	ev_unref (EV_A);	2681	ev_unref (EV_A);
2139	ev_timer_add (EV_A_ watcher);	2682	ev_timer_add (EV_A_ watcher);
2140	ev_loop (EV_A_ 0);	2683	ev_loop (EV_A_ 0);
2141		2684
2142	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2685	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2143	which is often provided by the following macro.	2686	which is often provided by the following macro.
2144		2687
2145	=item C<EV_P>, C<EV_P_>	2688	=item C<EV_P>, C<EV_P_>
2146		2689
2147	This provides the loop I<parameter> for functions, if one is required ("ev	2690	This provides the loop I<parameter> for functions, if one is required ("ev
2148	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2691	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2149	C<EV_P_> is used when other parameters are following. Example:	2692	C<EV_P_> is used when other parameters are following. Example:
2150		2693
2151	// this is how ev_unref is being declared	2694	// this is how ev_unref is being declared
2152	static void ev_unref (EV_P);	2695	static void ev_unref (EV_P);
2153		2696
2154	// this is how you can declare your typical callback	2697	// this is how you can declare your typical callback
2155	static void cb (EV_P_ ev_timer *w, int revents)	2698	static void cb (EV_P_ ev_timer *w, int revents)
2156		2699
2157	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2700	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2158	suitable for use with C<EV_A>.	2701	suitable for use with C<EV_A>.
2159		2702
2160	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2703	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2161		2704
2162	Similar to the other two macros, this gives you the value of the default	2705	Similar to the other two macros, this gives you the value of the default
2163	loop, if multiple loops are supported ("ev loop default").	2706	loop, if multiple loops are supported ("ev loop default").
		2707
		2708	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2709
		2710	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2711	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2712	is undefined when the default loop has not been initialised by a previous
		2713	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2714
		2715	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2716	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2164		2717
2165	=back	2718	=back
2166		2719
2167	Example: Declare and initialise a check watcher, utilising the above	2720	Example: Declare and initialise a check watcher, utilising the above
2168	macros so it will work regardless of whether multiple loops are supported	2721	macros so it will work regardless of whether multiple loops are supported
2169	or not.	2722	or not.
2170		2723
2171	static void	2724	static void
2172	check_cb (EV_P_ ev_timer *w, int revents)	2725	check_cb (EV_P_ ev_timer *w, int revents)
2173	{	2726	{
2174	ev_check_stop (EV_A_ w);	2727	ev_check_stop (EV_A_ w);
2175	}	2728	}
2176		2729
2177	ev_check check;	2730	ev_check check;
2178	ev_check_init (&check, check_cb);	2731	ev_check_init (&check, check_cb);
2179	ev_check_start (EV_DEFAULT_ &check);	2732	ev_check_start (EV_DEFAULT_ &check);
2180	ev_loop (EV_DEFAULT_ 0);	2733	ev_loop (EV_DEFAULT_ 0);
2181		2734
2182	=head1 EMBEDDING	2735	=head1 EMBEDDING
2183		2736
2184	Libev can (and often is) directly embedded into host	2737	Libev can (and often is) directly embedded into host
2185	applications. Examples of applications that embed it include the Deliantra	2738	applications. Examples of applications that embed it include the Deliantra
…		…
2192	libev somewhere in your source tree).	2745	libev somewhere in your source tree).
2193		2746
2194	=head2 FILESETS	2747	=head2 FILESETS
2195		2748
2196	Depending on what features you need you need to include one or more sets of files	2749	Depending on what features you need you need to include one or more sets of files
2197	in your app.	2750	in your application.
2198		2751
2199	=head3 CORE EVENT LOOP	2752	=head3 CORE EVENT LOOP
2200		2753
2201	To include only the libev core (all the C<ev_*> functions), with manual	2754	To include only the libev core (all the C<ev_*> functions), with manual
2202	configuration (no autoconf):	2755	configuration (no autoconf):
2203		2756
2204	#define EV_STANDALONE 1	2757	#define EV_STANDALONE 1
2205	#include "ev.c"	2758	#include "ev.c"
2206		2759
2207	This will automatically include F<ev.h>, too, and should be done in a	2760	This will automatically include F<ev.h>, too, and should be done in a
2208	single C source file only to provide the function implementations. To use	2761	single C source file only to provide the function implementations. To use
2209	it, do the same for F<ev.h> in all files wishing to use this API (best	2762	it, do the same for F<ev.h> in all files wishing to use this API (best
2210	done by writing a wrapper around F<ev.h> that you can include instead and	2763	done by writing a wrapper around F<ev.h> that you can include instead and
2211	where you can put other configuration options):	2764	where you can put other configuration options):
2212		2765
2213	#define EV_STANDALONE 1	2766	#define EV_STANDALONE 1
2214	#include "ev.h"	2767	#include "ev.h"
2215		2768
2216	Both header files and implementation files can be compiled with a C++	2769	Both header files and implementation files can be compiled with a C++
2217	compiler (at least, thats a stated goal, and breakage will be treated	2770	compiler (at least, thats a stated goal, and breakage will be treated
2218	as a bug).	2771	as a bug).
2219		2772
2220	You need the following files in your source tree, or in a directory	2773	You need the following files in your source tree, or in a directory
2221	in your include path (e.g. in libev/ when using -Ilibev):	2774	in your include path (e.g. in libev/ when using -Ilibev):
2222		2775
2223	ev.h	2776	ev.h
2224	ev.c	2777	ev.c
2225	ev_vars.h	2778	ev_vars.h
2226	ev_wrap.h	2779	ev_wrap.h
2227		2780
2228	ev_win32.c required on win32 platforms only	2781	ev_win32.c required on win32 platforms only
2229		2782
2230	ev_select.c only when select backend is enabled (which is enabled by default)	2783	ev_select.c only when select backend is enabled (which is enabled by default)
2231	ev_poll.c only when poll backend is enabled (disabled by default)	2784	ev_poll.c only when poll backend is enabled (disabled by default)
2232	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2785	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2233	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2786	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2234	ev_port.c only when the solaris port backend is enabled (disabled by default)	2787	ev_port.c only when the solaris port backend is enabled (disabled by default)
2235		2788
2236	F<ev.c> includes the backend files directly when enabled, so you only need	2789	F<ev.c> includes the backend files directly when enabled, so you only need
2237	to compile this single file.	2790	to compile this single file.
2238		2791
2239	=head3 LIBEVENT COMPATIBILITY API	2792	=head3 LIBEVENT COMPATIBILITY API
2240		2793
2241	To include the libevent compatibility API, also include:	2794	To include the libevent compatibility API, also include:
2242		2795
2243	#include "event.c"	2796	#include "event.c"
2244		2797
2245	in the file including F<ev.c>, and:	2798	in the file including F<ev.c>, and:
2246		2799
2247	#include "event.h"	2800	#include "event.h"
2248		2801
2249	in the files that want to use the libevent API. This also includes F<ev.h>.	2802	in the files that want to use the libevent API. This also includes F<ev.h>.
2250		2803
2251	You need the following additional files for this:	2804	You need the following additional files for this:
2252		2805
2253	event.h	2806	event.h
2254	event.c	2807	event.c
2255		2808
2256	=head3 AUTOCONF SUPPORT	2809	=head3 AUTOCONF SUPPORT
2257		2810
2258	Instead of using C<EV_STANDALONE=1> and providing your config in	2811	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2259	whatever way you want, you can also C<m4_include([libev.m4])> in your	2812	whatever way you want, you can also C<m4_include([libev.m4])> in your
2260	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2813	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2261	include F<config.h> and configure itself accordingly.	2814	include F<config.h> and configure itself accordingly.
2262		2815
2263	For this of course you need the m4 file:	2816	For this of course you need the m4 file:
2264		2817
2265	libev.m4	2818	libev.m4
2266		2819
2267	=head2 PREPROCESSOR SYMBOLS/MACROS	2820	=head2 PREPROCESSOR SYMBOLS/MACROS
2268		2821
2269	Libev can be configured via a variety of preprocessor symbols you have to define	2822	Libev can be configured via a variety of preprocessor symbols you have to
2270	before including any of its files. The default is not to build for multiplicity	2823	define before including any of its files. The default in the absence of
2271	and only include the select backend.	2824	autoconf is noted for every option.
2272		2825
2273	=over 4	2826	=over 4
2274		2827
2275	=item EV_STANDALONE	2828	=item EV_STANDALONE
2276		2829
…		…
2281	F<event.h> that are not directly supported by the libev core alone.	2834	F<event.h> that are not directly supported by the libev core alone.
2282		2835
2283	=item EV_USE_MONOTONIC	2836	=item EV_USE_MONOTONIC
2284		2837
2285	If defined to be C<1>, libev will try to detect the availability of the	2838	If defined to be C<1>, libev will try to detect the availability of the
2286	monotonic clock option at both compiletime and runtime. Otherwise no use	2839	monotonic clock option at both compile time and runtime. Otherwise no use
2287	of the monotonic clock option will be attempted. If you enable this, you	2840	of the monotonic clock option will be attempted. If you enable this, you
2288	usually have to link against librt or something similar. Enabling it when	2841	usually have to link against librt or something similar. Enabling it when
2289	the functionality isn't available is safe, though, although you have	2842	the functionality isn't available is safe, though, although you have
2290	to make sure you link against any libraries where the C<clock_gettime>	2843	to make sure you link against any libraries where the C<clock_gettime>
2291	function is hiding in (often F<-lrt>).	2844	function is hiding in (often F<-lrt>).
2292		2845
2293	=item EV_USE_REALTIME	2846	=item EV_USE_REALTIME
2294		2847
2295	If defined to be C<1>, libev will try to detect the availability of the	2848	If defined to be C<1>, libev will try to detect the availability of the
2296	realtime clock option at compiletime (and assume its availability at	2849	real-time clock option at compile time (and assume its availability at
2297	runtime if successful). Otherwise no use of the realtime clock option will	2850	runtime if successful). Otherwise no use of the real-time clock option will
2298	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2851	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2852	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2853	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2301		2854
		2855	=item EV_USE_NANOSLEEP
		2856
		2857	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2858	and will use it for delays. Otherwise it will use C<select ()>.
		2859
		2860	=item EV_USE_EVENTFD
		2861
		2862	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2863	available and will probe for kernel support at runtime. This will improve
		2864	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2865	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2866	2.7 or newer, otherwise disabled.
		2867
2302	=item EV_USE_SELECT	2868	=item EV_USE_SELECT
2303		2869
2304	If undefined or defined to be C<1>, libev will compile in support for the	2870	If undefined or defined to be C<1>, libev will compile in support for the
2305	C<select>(2) backend. No attempt at autodetection will be done: if no	2871	C<select>(2) backend. No attempt at auto-detection will be done: if no
2306	other method takes over, select will be it. Otherwise the select backend	2872	other method takes over, select will be it. Otherwise the select backend
2307	will not be compiled in.	2873	will not be compiled in.
2308		2874
2309	=item EV_SELECT_USE_FD_SET	2875	=item EV_SELECT_USE_FD_SET
2310		2876
2311	If defined to C<1>, then the select backend will use the system C<fd_set>	2877	If defined to C<1>, then the select backend will use the system C<fd_set>
2312	structure. This is useful if libev doesn't compile due to a missing	2878	structure. This is useful if libev doesn't compile due to a missing
2313	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2879	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2314	exotic systems. This usually limits the range of file descriptors to some	2880	exotic systems. This usually limits the range of file descriptors to some
2315	low limit such as 1024 or might have other limitations (winsocket only	2881	low limit such as 1024 or might have other limitations (winsocket only
2316	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2882	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2317	influence the size of the C<fd_set> used.	2883	influence the size of the C<fd_set> used.
2318		2884
…		…
2324	be used is the winsock select). This means that it will call	2890	be used is the winsock select). This means that it will call
2325	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2891	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2326	it is assumed that all these functions actually work on fds, even	2892	it is assumed that all these functions actually work on fds, even
2327	on win32. Should not be defined on non-win32 platforms.	2893	on win32. Should not be defined on non-win32 platforms.
2328		2894
		2895	=item EV_FD_TO_WIN32_HANDLE
		2896
		2897	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2898	file descriptors to socket handles. When not defining this symbol (the
		2899	default), then libev will call C<_get_osfhandle>, which is usually
		2900	correct. In some cases, programs use their own file descriptor management,
		2901	in which case they can provide this function to map fds to socket handles.
		2902
2329	=item EV_USE_POLL	2903	=item EV_USE_POLL
2330		2904
2331	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2905	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2332	backend. Otherwise it will be enabled on non-win32 platforms. It	2906	backend. Otherwise it will be enabled on non-win32 platforms. It
2333	takes precedence over select.	2907	takes precedence over select.
2334		2908
2335	=item EV_USE_EPOLL	2909	=item EV_USE_EPOLL
2336		2910
2337	If defined to be C<1>, libev will compile in support for the Linux	2911	If defined to be C<1>, libev will compile in support for the Linux
2338	C<epoll>(7) backend. Its availability will be detected at runtime,	2912	C<epoll>(7) backend. Its availability will be detected at runtime,
2339	otherwise another method will be used as fallback. This is the	2913	otherwise another method will be used as fallback. This is the preferred
2340	preferred backend for GNU/Linux systems.	2914	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2915	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2341		2916
2342	=item EV_USE_KQUEUE	2917	=item EV_USE_KQUEUE
2343		2918
2344	If defined to be C<1>, libev will compile in support for the BSD style	2919	If defined to be C<1>, libev will compile in support for the BSD style
2345	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2920	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2358	otherwise another method will be used as fallback. This is the preferred	2933	otherwise another method will be used as fallback. This is the preferred
2359	backend for Solaris 10 systems.	2934	backend for Solaris 10 systems.
2360		2935
2361	=item EV_USE_DEVPOLL	2936	=item EV_USE_DEVPOLL
2362		2937
2363	reserved for future expansion, works like the USE symbols above.	2938	Reserved for future expansion, works like the USE symbols above.
2364		2939
2365	=item EV_USE_INOTIFY	2940	=item EV_USE_INOTIFY
2366		2941
2367	If defined to be C<1>, libev will compile in support for the Linux inotify	2942	If defined to be C<1>, libev will compile in support for the Linux inotify
2368	interface to speed up C<ev_stat> watchers. Its actual availability will	2943	interface to speed up C<ev_stat> watchers. Its actual availability will
2369	be detected at runtime.	2944	be detected at runtime. If undefined, it will be enabled if the headers
		2945	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2946
		2947	=item EV_ATOMIC_T
		2948
		2949	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2950	access is atomic with respect to other threads or signal contexts. No such
		2951	type is easily found in the C language, so you can provide your own type
		2952	that you know is safe for your purposes. It is used both for signal handler "locking"
		2953	as well as for signal and thread safety in C<ev_async> watchers.
		2954
		2955	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2956	(from F<signal.h>), which is usually good enough on most platforms.
2370		2957
2371	=item EV_H	2958	=item EV_H
2372		2959
2373	The name of the F<ev.h> header file used to include it. The default if	2960	The name of the F<ev.h> header file used to include it. The default if
2374	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2961	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2375	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2962	used to virtually rename the F<ev.h> header file in case of conflicts.
2376		2963
2377	=item EV_CONFIG_H	2964	=item EV_CONFIG_H
2378		2965
2379	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2966	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2380	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2967	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2381	C<EV_H>, above.	2968	C<EV_H>, above.
2382		2969
2383	=item EV_EVENT_H	2970	=item EV_EVENT_H
2384		2971
2385	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2972	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2386	of how the F<event.h> header can be found.	2973	of how the F<event.h> header can be found, the default is C<"event.h">.
2387		2974
2388	=item EV_PROTOTYPES	2975	=item EV_PROTOTYPES
2389		2976
2390	If defined to be C<0>, then F<ev.h> will not define any function	2977	If defined to be C<0>, then F<ev.h> will not define any function
2391	prototypes, but still define all the structs and other symbols. This is	2978	prototypes, but still define all the structs and other symbols. This is
…		…
2412	When doing priority-based operations, libev usually has to linearly search	2999	When doing priority-based operations, libev usually has to linearly search
2413	all the priorities, so having many of them (hundreds) uses a lot of space	3000	all the priorities, so having many of them (hundreds) uses a lot of space
2414	and time, so using the defaults of five priorities (-2 .. +2) is usually	3001	and time, so using the defaults of five priorities (-2 .. +2) is usually
2415	fine.	3002	fine.
2416		3003
2417	If your embedding app does not need any priorities, defining these both to	3004	If your embedding application does not need any priorities, defining these both to
2418	C<0> will save some memory and cpu.	3005	C<0> will save some memory and CPU.
2419		3006
2420	=item EV_PERIODIC_ENABLE	3007	=item EV_PERIODIC_ENABLE
2421		3008
2422	If undefined or defined to be C<1>, then periodic timers are supported. If	3009	If undefined or defined to be C<1>, then periodic timers are supported. If
2423	defined to be C<0>, then they are not. Disabling them saves a few kB of	3010	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2442	=item EV_FORK_ENABLE	3029	=item EV_FORK_ENABLE
2443		3030
2444	If undefined or defined to be C<1>, then fork watchers are supported. If	3031	If undefined or defined to be C<1>, then fork watchers are supported. If
2445	defined to be C<0>, then they are not.	3032	defined to be C<0>, then they are not.
2446		3033
		3034	=item EV_ASYNC_ENABLE
		3035
		3036	If undefined or defined to be C<1>, then async watchers are supported. If
		3037	defined to be C<0>, then they are not.
		3038
2447	=item EV_MINIMAL	3039	=item EV_MINIMAL
2448		3040
2449	If you need to shave off some kilobytes of code at the expense of some	3041	If you need to shave off some kilobytes of code at the expense of some
2450	speed, define this symbol to C<1>. Currently only used for gcc to override	3042	speed, define this symbol to C<1>. Currently this is used to override some
2451	some inlining decisions, saves roughly 30% codesize of amd64.	3043	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3044	much smaller 2-heap for timer management over the default 4-heap.
2452		3045
2453	=item EV_PID_HASHSIZE	3046	=item EV_PID_HASHSIZE
2454		3047
2455	C<ev_child> watchers use a small hash table to distribute workload by	3048	C<ev_child> watchers use a small hash table to distribute workload by
2456	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3049	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2457	than enough. If you need to manage thousands of children you might want to	3050	than enough. If you need to manage thousands of children you might want to
2458	increase this value (I<must> be a power of two).	3051	increase this value (I<must> be a power of two).
2459		3052
2460	=item EV_INOTIFY_HASHSIZE	3053	=item EV_INOTIFY_HASHSIZE
2461		3054
2462	C<ev_staz> watchers use a small hash table to distribute workload by	3055	C<ev_stat> watchers use a small hash table to distribute workload by
2463	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3056	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2464	usually more than enough. If you need to manage thousands of C<ev_stat>	3057	usually more than enough. If you need to manage thousands of C<ev_stat>
2465	watchers you might want to increase this value (I<must> be a power of	3058	watchers you might want to increase this value (I<must> be a power of
2466	two).	3059	two).
2467		3060
		3061	=item EV_USE_4HEAP
		3062
		3063	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3064	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3065	to C<1>. The 4-heap uses more complicated (longer) code but has
		3066	noticeably faster performance with many (thousands) of watchers.
		3067
		3068	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3069	(disabled).
		3070
		3071	=item EV_HEAP_CACHE_AT
		3072
		3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3074	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3075	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3076	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3077	but avoids random read accesses on heap changes. This improves performance
		3078	noticeably with with many (hundreds) of watchers.
		3079
		3080	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3081	(disabled).
		3082
		3083	=item EV_VERIFY
		3084
		3085	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3086	be done: If set to C<0>, no internal verification code will be compiled
		3087	in. If set to C<1>, then verification code will be compiled in, but not
		3088	called. If set to C<2>, then the internal verification code will be
		3089	called once per loop, which can slow down libev. If set to C<3>, then the
		3090	verification code will be called very frequently, which will slow down
		3091	libev considerably.
		3092
		3093	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3094	C<0.>
		3095
2468	=item EV_COMMON	3096	=item EV_COMMON
2469		3097
2470	By default, all watchers have a C<void *data> member. By redefining	3098	By default, all watchers have a C<void *data> member. By redefining
2471	this macro to a something else you can include more and other types of	3099	this macro to a something else you can include more and other types of
2472	members. You have to define it each time you include one of the files,	3100	members. You have to define it each time you include one of the files,
2473	though, and it must be identical each time.	3101	though, and it must be identical each time.
2474		3102
2475	For example, the perl EV module uses something like this:	3103	For example, the perl EV module uses something like this:
2476		3104
2477	#define EV_COMMON \	3105	#define EV_COMMON \
2478	SV *self; /* contains this struct */ \	3106	SV *self; /* contains this struct */ \
2479	SV *cb_sv, *fh /* note no trailing ";" */	3107	SV *cb_sv, *fh /* note no trailing ";" */
2480		3108
2481	=item EV_CB_DECLARE (type)	3109	=item EV_CB_DECLARE (type)
2482		3110
2483	=item EV_CB_INVOKE (watcher, revents)	3111	=item EV_CB_INVOKE (watcher, revents)
2484		3112
…		…
2491	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3119	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2492	method calls instead of plain function calls in C++.	3120	method calls instead of plain function calls in C++.
2493		3121
2494	=head2 EXPORTED API SYMBOLS	3122	=head2 EXPORTED API SYMBOLS
2495		3123
2496	If you need to re-export the API (e.g. via a dll) and you need a list of	3124	If you need to re-export the API (e.g. via a DLL) and you need a list of
2497	exported symbols, you can use the provided F<Symbol.*> files which list	3125	exported symbols, you can use the provided F<Symbol.*> files which list
2498	all public symbols, one per line:	3126	all public symbols, one per line:
2499		3127
2500	Symbols.ev for libev proper	3128	Symbols.ev for libev proper
2501	Symbols.event for the libevent emulation	3129	Symbols.event for the libevent emulation
2502		3130
2503	This can also be used to rename all public symbols to avoid clashes with	3131	This can also be used to rename all public symbols to avoid clashes with
2504	multiple versions of libev linked together (which is obviously bad in	3132	multiple versions of libev linked together (which is obviously bad in
2505	itself, but sometimes it is inconvinient to avoid this).	3133	itself, but sometimes it is inconvenient to avoid this).
2506		3134
2507	A sed command like this will create wrapper C<#define>'s that you need to	3135	A sed command like this will create wrapper C<#define>'s that you need to
2508	include before including F<ev.h>:	3136	include before including F<ev.h>:
2509		3137
2510	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3138	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2527	file.	3155	file.
2528		3156
2529	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3157	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2530	that everybody includes and which overrides some configure choices:	3158	that everybody includes and which overrides some configure choices:
2531		3159
2532	#define EV_MINIMAL 1	3160	#define EV_MINIMAL 1
2533	#define EV_USE_POLL 0	3161	#define EV_USE_POLL 0
2534	#define EV_MULTIPLICITY 0	3162	#define EV_MULTIPLICITY 0
2535	#define EV_PERIODIC_ENABLE 0	3163	#define EV_PERIODIC_ENABLE 0
2536	#define EV_STAT_ENABLE 0	3164	#define EV_STAT_ENABLE 0
2537	#define EV_FORK_ENABLE 0	3165	#define EV_FORK_ENABLE 0
2538	#define EV_CONFIG_H <config.h>	3166	#define EV_CONFIG_H <config.h>
2539	#define EV_MINPRI 0	3167	#define EV_MINPRI 0
2540	#define EV_MAXPRI 0	3168	#define EV_MAXPRI 0
2541		3169
2542	#include "ev++.h"	3170	#include "ev++.h"
2543		3171
2544	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3172	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2545		3173
2546	#include "ev_cpp.h"	3174	#include "ev_cpp.h"
2547	#include "ev.c"	3175	#include "ev.c"
		3176
		3177
		3178	=head1 THREADS AND COROUTINES
		3179
		3180	=head2 THREADS
		3181
		3182	Libev itself is completely thread-safe, but it uses no locking. This
		3183	means that you can use as many loops as you want in parallel, as long as
		3184	only one thread ever calls into one libev function with the same loop
		3185	parameter.
		3186
		3187	Or put differently: calls with different loop parameters can be done in
		3188	parallel from multiple threads, calls with the same loop parameter must be
		3189	done serially (but can be done from different threads, as long as only one
		3190	thread ever is inside a call at any point in time, e.g. by using a mutex
		3191	per loop).
		3192
		3193	If you want to know which design is best for your problem, then I cannot
		3194	help you but by giving some generic advice:
		3195
		3196	=over 4
		3197
		3198	=item * most applications have a main thread: use the default libev loop
		3199	in that thread, or create a separate thread running only the default loop.
		3200
		3201	This helps integrating other libraries or software modules that use libev
		3202	themselves and don't care/know about threading.
		3203
		3204	=item * one loop per thread is usually a good model.
		3205
		3206	Doing this is almost never wrong, sometimes a better-performance model
		3207	exists, but it is always a good start.
		3208
		3209	=item * other models exist, such as the leader/follower pattern, where one
		3210	loop is handed through multiple threads in a kind of round-robin fashion.
		3211
		3212	Choosing a model is hard - look around, learn, know that usually you can do
		3213	better than you currently do :-)
		3214
		3215	=item * often you need to talk to some other thread which blocks in the
		3216	event loop - C<ev_async> watchers can be used to wake them up from other
		3217	threads safely (or from signal contexts...).
		3218
		3219	=back
		3220
		3221	=head2 COROUTINES
		3222
		3223	Libev is much more accommodating to coroutines ("cooperative threads"):
		3224	libev fully supports nesting calls to it's functions from different
		3225	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3226	different coroutines and switch freely between both coroutines running the
		3227	loop, as long as you don't confuse yourself). The only exception is that
		3228	you must not do this from C<ev_periodic> reschedule callbacks.
		3229
		3230	Care has been invested into making sure that libev does not keep local
		3231	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3232	switches.
2548		3233
2549		3234
2550	=head1 COMPLEXITIES	3235	=head1 COMPLEXITIES
2551		3236
2552	In this section the complexities of (many of) the algorithms used inside	3237	In this section the complexities of (many of) the algorithms used inside
…		…
2563		3248
2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3249	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2565		3250
2566	This means that, when you have a watcher that triggers in one hour and	3251	This means that, when you have a watcher that triggers in one hour and
2567	there are 100 watchers that would trigger before that then inserting will	3252	there are 100 watchers that would trigger before that then inserting will
2568	have to skip those 100 watchers.	3253	have to skip roughly seven (C<ld 100>) of these watchers.
2569		3254
2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3255	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2571		3256
2572	That means that for changing a timer costs less than removing/adding them	3257	That means that changing a timer costs less than removing/adding them
2573	as only the relative motion in the event queue has to be paid for.	3258	as only the relative motion in the event queue has to be paid for.
2574		3259
2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3260	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2576		3261
2577	These just add the watcher into an array or at the head of a list.	3262	These just add the watcher into an array or at the head of a list.
		3263
2578	=item Stopping check/prepare/idle watchers: O(1)	3264	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2579		3265
2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3266	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2581		3267
2582	These watchers are stored in lists then need to be walked to find the	3268	These watchers are stored in lists then need to be walked to find the
2583	correct watcher to remove. The lists are usually short (you don't usually	3269	correct watcher to remove. The lists are usually short (you don't usually
2584	have many watchers waiting for the same fd or signal).	3270	have many watchers waiting for the same fd or signal).
2585		3271
2586	=item Finding the next timer per loop iteration: O(1)	3272	=item Finding the next timer in each loop iteration: O(1)
		3273
		3274	By virtue of using a binary or 4-heap, the next timer is always found at a
		3275	fixed position in the storage array.
2587		3276
2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3277	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2589		3278
2590	A change means an I/O watcher gets started or stopped, which requires	3279	A change means an I/O watcher gets started or stopped, which requires
2591	libev to recalculate its status (and possibly tell the kernel).	3280	libev to recalculate its status (and possibly tell the kernel, depending
		3281	on backend and whether C<ev_io_set> was used).
2592		3282
2593	=item Activating one watcher: O(1)	3283	=item Activating one watcher (putting it into the pending state): O(1)
2594		3284
2595	=item Priority handling: O(number_of_priorities)	3285	=item Priority handling: O(number_of_priorities)
2596		3286
2597	Priorities are implemented by allocating some space for each	3287	Priorities are implemented by allocating some space for each
2598	priority. When doing priority-based operations, libev usually has to	3288	priority. When doing priority-based operations, libev usually has to
2599	linearly search all the priorities.	3289	linearly search all the priorities, but starting/stopping and activating
		3290	watchers becomes O(1) w.r.t. priority handling.
		3291
		3292	=item Sending an ev_async: O(1)
		3293
		3294	=item Processing ev_async_send: O(number_of_async_watchers)
		3295
		3296	=item Processing signals: O(max_signal_number)
		3297
		3298	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3299	calls in the current loop iteration. Checking for async and signal events
		3300	involves iterating over all running async watchers or all signal numbers.
2600		3301
2601	=back	3302	=back
2602		3303
2603		3304
		3305	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3306
		3307	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3308	requires, and its I/O model is fundamentally incompatible with the POSIX
		3309	model. Libev still offers limited functionality on this platform in
		3310	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3311	descriptors. This only applies when using Win32 natively, not when using
		3312	e.g. cygwin.
		3313
		3314	Lifting these limitations would basically require the full
		3315	re-implementation of the I/O system. If you are into these kinds of
		3316	things, then note that glib does exactly that for you in a very portable
		3317	way (note also that glib is the slowest event library known to man).
		3318
		3319	There is no supported compilation method available on windows except
		3320	embedding it into other applications.
		3321
		3322	Not a libev limitation but worth mentioning: windows apparently doesn't
		3323	accept large writes: instead of resulting in a partial write, windows will
		3324	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3325	so make sure you only write small amounts into your sockets (less than a
		3326	megabyte seems safe, but thsi apparently depends on the amount of memory
		3327	available).
		3328
		3329	Due to the many, low, and arbitrary limits on the win32 platform and
		3330	the abysmal performance of winsockets, using a large number of sockets
		3331	is not recommended (and not reasonable). If your program needs to use
		3332	more than a hundred or so sockets, then likely it needs to use a totally
		3333	different implementation for windows, as libev offers the POSIX readiness
		3334	notification model, which cannot be implemented efficiently on windows
		3335	(Microsoft monopoly games).
		3336
		3337	A typical way to use libev under windows is to embed it (see the embedding
		3338	section for details) and use the following F<evwrap.h> header file instead
		3339	of F<ev.h>:
		3340
		3341	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3342	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3343
		3344	#include "ev.h"
		3345
		3346	And compile the following F<evwrap.c> file into your project (make sure
		3347	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3348
		3349	#include "evwrap.h"
		3350	#include "ev.c"
		3351
		3352	=over 4
		3353
		3354	=item The winsocket select function
		3355
		3356	The winsocket C<select> function doesn't follow POSIX in that it
		3357	requires socket I<handles> and not socket I<file descriptors> (it is
		3358	also extremely buggy). This makes select very inefficient, and also
		3359	requires a mapping from file descriptors to socket handles (the Microsoft
		3360	C runtime provides the function C<_open_osfhandle> for this). See the
		3361	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3362	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3363
		3364	The configuration for a "naked" win32 using the Microsoft runtime
		3365	libraries and raw winsocket select is:
		3366
		3367	#define EV_USE_SELECT 1
		3368	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3369
		3370	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3371	complexity in the O(n²) range when using win32.
		3372
		3373	=item Limited number of file descriptors
		3374
		3375	Windows has numerous arbitrary (and low) limits on things.
		3376
		3377	Early versions of winsocket's select only supported waiting for a maximum
		3378	of C<64> handles (probably owning to the fact that all windows kernels
		3379	can only wait for C<64> things at the same time internally; Microsoft
		3380	recommends spawning a chain of threads and wait for 63 handles and the
		3381	previous thread in each. Great).
		3382
		3383	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3384	to some high number (e.g. C<2048>) before compiling the winsocket select
		3385	call (which might be in libev or elsewhere, for example, perl does its own
		3386	select emulation on windows).
		3387
		3388	Another limit is the number of file descriptors in the Microsoft runtime
		3389	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3390	or something like this inside Microsoft). You can increase this by calling
		3391	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3392	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3393	libraries.
		3394
		3395	This might get you to about C<512> or C<2048> sockets (depending on
		3396	windows version and/or the phase of the moon). To get more, you need to
		3397	wrap all I/O functions and provide your own fd management, but the cost of
		3398	calling select (O(n²)) will likely make this unworkable.
		3399
		3400	=back
		3401
		3402
		3403	=head1 PORTABILITY REQUIREMENTS
		3404
		3405	In addition to a working ISO-C implementation, libev relies on a few
		3406	additional extensions:
		3407
		3408	=over 4
		3409
		3410	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3411	calling conventions regardless of C<ev_watcher_type *>.
		3412
		3413	Libev assumes not only that all watcher pointers have the same internal
		3414	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3415	assumes that the same (machine) code can be used to call any watcher
		3416	callback: The watcher callbacks have different type signatures, but libev
		3417	calls them using an C<ev_watcher *> internally.
		3418
		3419	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3420
		3421	The type C<sig_atomic_t volatile> (or whatever is defined as
		3422	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3423	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3424	believed to be sufficiently portable.
		3425
		3426	=item C<sigprocmask> must work in a threaded environment
		3427
		3428	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3429	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3430	pthread implementations will either allow C<sigprocmask> in the "main
		3431	thread" or will block signals process-wide, both behaviours would
		3432	be compatible with libev. Interaction between C<sigprocmask> and
		3433	C<pthread_sigmask> could complicate things, however.
		3434
		3435	The most portable way to handle signals is to block signals in all threads
		3436	except the initial one, and run the default loop in the initial thread as
		3437	well.
		3438
		3439	=item C<long> must be large enough for common memory allocation sizes
		3440
		3441	To improve portability and simplify using libev, libev uses C<long>
		3442	internally instead of C<size_t> when allocating its data structures. On
		3443	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3444	is still at least 31 bits everywhere, which is enough for hundreds of
		3445	millions of watchers.
		3446
		3447	=item C<double> must hold a time value in seconds with enough accuracy
		3448
		3449	The type C<double> is used to represent timestamps. It is required to
		3450	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3451	enough for at least into the year 4000. This requirement is fulfilled by
		3452	implementations implementing IEEE 754 (basically all existing ones).
		3453
		3454	=back
		3455
		3456	If you know of other additional requirements drop me a note.
		3457
		3458
		3459	=head1 COMPILER WARNINGS
		3460
		3461	Depending on your compiler and compiler settings, you might get no or a
		3462	lot of warnings when compiling libev code. Some people are apparently
		3463	scared by this.
		3464
		3465	However, these are unavoidable for many reasons. For one, each compiler
		3466	has different warnings, and each user has different tastes regarding
		3467	warning options. "Warn-free" code therefore cannot be a goal except when
		3468	targeting a specific compiler and compiler-version.
		3469
		3470	Another reason is that some compiler warnings require elaborate
		3471	workarounds, or other changes to the code that make it less clear and less
		3472	maintainable.
		3473
		3474	And of course, some compiler warnings are just plain stupid, or simply
		3475	wrong (because they don't actually warn about the condition their message
		3476	seems to warn about).
		3477
		3478	While libev is written to generate as few warnings as possible,
		3479	"warn-free" code is not a goal, and it is recommended not to build libev
		3480	with any compiler warnings enabled unless you are prepared to cope with
		3481	them (e.g. by ignoring them). Remember that warnings are just that:
		3482	warnings, not errors, or proof of bugs.
		3483
		3484
		3485	=head1 VALGRIND
		3486
		3487	Valgrind has a special section here because it is a popular tool that is
		3488	highly useful, but valgrind reports are very hard to interpret.
		3489
		3490	If you think you found a bug (memory leak, uninitialised data access etc.)
		3491	in libev, then check twice: If valgrind reports something like:
		3492
		3493	==2274== definitely lost: 0 bytes in 0 blocks.
		3494	==2274== possibly lost: 0 bytes in 0 blocks.
		3495	==2274== still reachable: 256 bytes in 1 blocks.
		3496
		3497	Then there is no memory leak. Similarly, under some circumstances,
		3498	valgrind might report kernel bugs as if it were a bug in libev, or it
		3499	might be confused (it is a very good tool, but only a tool).
		3500
		3501	If you are unsure about something, feel free to contact the mailing list
		3502	with the full valgrind report and an explanation on why you think this is
		3503	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3504	no bug" answer and take the chance of learning how to interpret valgrind
		3505	properly.
		3506
		3507	If you need, for some reason, empty reports from valgrind for your project
		3508	I suggest using suppression lists.
		3509
		3510
2604	=head1 AUTHOR	3511	=head1 AUTHOR
2605		3512
2606	Marc Lehmann <libev@schmorp.de>.	3513	Marc Lehmann <libev@schmorp.de>.
2607		3514

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