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Revision 1.98 by root, Sat Dec 22 06:10:25 2007 UTC vs.
Revision 1.177 by root, Mon Sep 8 17:27:42 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout 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.
…		…
119		155
120	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
121		157
122	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
123	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
124	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
125		161
126	=item int ev_version_major ()	162	=item int ev_version_major ()
127		163
128	=item int ev_version_minor ()	164	=item int ev_version_minor ()
129		165
…		…
142	not a problem.	178	not a problem.
143		179
144	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
145	version.	181	version.
146		182
147	assert (("libev version mismatch",	183	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
150		186
151	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
152		188
153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
154	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	192	a description of the set values.
157		193
158	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
159	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
160		196
161	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
163		199
164	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
165		201
166	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
167	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
168	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
169	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
170	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
171	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
172		208
173	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
174		210
…		…
181	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
182		218
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
184		220
185	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
187	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
188	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
190	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
191		230
192	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
193	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
194	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
195		234
196	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	236	retries (example requires a standards-compliant C<realloc>).
198		237
199	static void *	238	static void *
200	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
201	{	240	{
202	for (;;)	241	for (;;)
…		…
213	...	252	...
214	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
215		254
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
217		256
218	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
219	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
220	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
221	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
222	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
223	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
224	(such as abort).	263	(such as abort).
225		264
226	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
241		280
242	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
243	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
244	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
245
246	If you use threads, a common model is to run the default event loop
247	in your main thread (or in a separate thread) and for each thread you
248	create, you also create another event loop. Libev itself does no locking
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252		284
253	=over 4	285	=over 4
254		286
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		288
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		293
262	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
263	function.	295	function.
264		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
265	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
266	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>).
267		310
268	The following flags are supported:	311	The following flags are supported:
269		312
…		…
274	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
275	thing, believe me).	318	thing, believe me).
276		319
277	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
278		321
279	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
280	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
281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
282	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
283	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
284	around bugs.	327	around bugs.
…		…
290	enabling this flag.	333	enabling this flag.
291		334
292	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,
293	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
294	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
295	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
296	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
297	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
298		341
299	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
300	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
301	flag.	344	flag.
302		345
303	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>
304	environment variable.	347	environment variable.
305		348
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		350
308	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
309	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,
310	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
311	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
312	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.
313		363
314	=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)
315		365
316	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
317	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
318	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
319	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.
320		372
321	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
322		374
323	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,
324	but it scales phenomenally better. While poll and select usually scale	376	but it scales phenomenally better. While poll and select usually scale
325	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),
326	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
327	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
328	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
329	support for dup:	381	support for dup.
330		382
331	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
332	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
333	(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
334	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
335	very well if you register events for both fds.	387	very well if you register events for both fds.
336		388
337	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
338	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
339	(or space) is available.	391	(or space) is available.
340		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
341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
342		401
343	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
344	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
345	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
346	useless. On NetBSD, it seems to work for all the FD types I tested, so it
347	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"
348	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
349	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)
350	system like NetBSD.	408	system like NetBSD.
351		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
352	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
353	kernel is more efficient (which says nothing about its actual speed,	415	kernel is more efficient (which says nothing about its actual speed, of
354	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
355	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
356	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
357	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.
358		429
359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
360		431
361	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.
362		436
363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
364		438
365	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,
366	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)).
367		441
368	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
369	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
370	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.
371		454
372	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
373		456
374	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
375	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
376	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
377		460
		461	It is definitely not recommended to use this flag.
		462
378	=back	463	=back
379		464
380	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
381	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
382	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
383	order of their flag values :)
384		468
385	The most typical usage is like this:	469	The most typical usage is like this:
386		470
387	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
388	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
389		473
390	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
391	environment settings to be taken into account:	475	environment settings to be taken into account:
392		476
393	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
394		478
395	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
396	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
397	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):
398		482
399	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
400		484
401	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
402		486
403	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
404	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
405	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
406	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
407		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
408	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.
409		497
410	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
411	if (!epoller)	499	if (!epoller)
412	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
413		501
414	=item ev_default_destroy ()	502	=item ev_default_destroy ()
415		503
416	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
417	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
418	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
419	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
420	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
421	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
422	for example).	510	for example).
423		511
424	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
…		…
435	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
436	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
437		525
438	=item ev_default_fork ()	526	=item ev_default_fork ()
439		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
440	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
441	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
442	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
443	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.
444		534
445	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
446	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
447	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
448		538
449	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
450	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
451	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
452		542
453	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
454		544
455	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
456	without calling this function, so if you force one of those backends you
457	do not need to care.
458
459	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
460		546
461	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
462	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
463	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.
464		554
465	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
466		556
467	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
468	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
…		…
483	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
484	change as long as callbacks are being processed, and this is also the base	574	change as long as callbacks are being processed, and this is also the base
485	time used for relative timers. You can treat it as the timestamp of the	575	time used for relative timers. You can treat it as the timestamp of the
486	event occurring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
487		577
		578	=item ev_now_update (loop)
		579
		580	Establishes the current time by querying the kernel, updating the time
		581	returned by C<ev_now ()> in the progress. This is a costly operation and
		582	is usually done automatically within C<ev_loop ()>.
		583
		584	This function is rarely useful, but when some event callback runs for a
		585	very long time without entering the event loop, updating libev's idea of
		586	the current time is a good idea.
		587
		588	See also "The special problem of time updates" in the C<ev_timer> section.
		589
488	=item ev_loop (loop, int flags)	590	=item ev_loop (loop, int flags)
489		591
490	Finally, this is it, the event handler. This function usually is called	592	Finally, this is it, the event handler. This function usually is called
491	after you initialised all your watchers and you want to start handling	593	after you initialised all your watchers and you want to start handling
492	events.	594	events.
…		…
503	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
504	those events and any outstanding ones, but will not block your process in	606	those events and any outstanding ones, but will not block your process in
505	case there are no events and will return after one iteration of the loop.	607	case there are no events and will return after one iteration of the loop.
506		608
507	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
508	neccessary) and will handle those and any outstanding ones. It will block	610	necessary) and will handle those and any outstanding ones. It will block
509	your process until at least one new event arrives, and will return after	611	your process until at least one new event arrives, and will return after
510	one iteration of the loop. This is useful if you are waiting for some	612	one iteration of the loop. This is useful if you are waiting for some
511	external event in conjunction with something not expressible using other	613	external event in conjunction with something not expressible using other
512	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	614	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
513	usually a better approach for this kind of thing.	615	usually a better approach for this kind of thing.
514		616
515	Here are the gory details of what C<ev_loop> does:	617	Here are the gory details of what C<ev_loop> does:
516		618
517	- Before the first iteration, call any pending watchers.	619	- Before the first iteration, call any pending watchers.
518	* If there are no active watchers (reference count is zero), return.	620	* If EVFLAG_FORKCHECK was used, check for a fork.
519	- Queue all prepare watchers and then call all outstanding watchers.	621	- If a fork was detected (by any means), queue and call all fork watchers.
		622	- Queue and call all prepare watchers.
520	- If we have been forked, recreate the kernel state.	623	- If we have been forked, detach and recreate the kernel state
		624	as to not disturb the other process.
521	- Update the kernel state with all outstanding changes.	625	- Update the kernel state with all outstanding changes.
522	- Update the "event loop time".	626	- Update the "event loop time" (ev_now ()).
523	- Calculate for how long to block.	627	- Calculate for how long to sleep or block, if at all
		628	(active idle watchers, EVLOOP_NONBLOCK or not having
		629	any active watchers at all will result in not sleeping).
		630	- Sleep if the I/O and timer collect interval say so.
524	- Block the process, waiting for any events.	631	- Block the process, waiting for any events.
525	- Queue all outstanding I/O (fd) events.	632	- Queue all outstanding I/O (fd) events.
526	- Update the "event loop time" and do time jump handling.	633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
527	- Queue all outstanding timers.	634	- Queue all outstanding timers.
528	- Queue all outstanding periodics.	635	- Queue all outstanding periodics.
529	- If no events are pending now, queue all idle watchers.	636	- Unless any events are pending now, queue all idle watchers.
530	- Queue all check watchers.	637	- Queue all check watchers.
531	- Call all queued watchers in reverse order (i.e. check watchers first).	638	- Call all queued watchers in reverse order (i.e. check watchers first).
532	Signals and child watchers are implemented as I/O watchers, and will	639	Signals and child watchers are implemented as I/O watchers, and will
533	be handled here by queueing them when their watcher gets executed.	640	be handled here by queueing them when their watcher gets executed.
534	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	641	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
535	were used, return, otherwise continue with step *.	642	were used, or there are no active watchers, return, otherwise
		643	continue with step *.
536		644
537	Example: Queue some jobs and then loop until no events are outsanding	645	Example: Queue some jobs and then loop until no events are outstanding
538	anymore.	646	anymore.
539		647
540	... queue jobs here, make sure they register event watchers as long	648	... queue jobs here, make sure they register event watchers as long
541	... as they still have work to do (even an idle watcher will do..)	649	... as they still have work to do (even an idle watcher will do..)
542	ev_loop (my_loop, 0);	650	ev_loop (my_loop, 0);
543	... jobs done. yeah!	651	... jobs done or somebody called unloop. yeah!
544		652
545	=item ev_unloop (loop, how)	653	=item ev_unloop (loop, how)
546		654
547	Can be used to make a call to C<ev_loop> return early (but only after it	655	Can be used to make a call to C<ev_loop> return early (but only after it
548	has processed all outstanding events). The C<how> argument must be either	656	has processed all outstanding events). The C<how> argument must be either
549	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	657	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
550	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	658	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		659
		660	This "unloop state" will be cleared when entering C<ev_loop> again.
551		661
552	=item ev_ref (loop)	662	=item ev_ref (loop)
553		663
554	=item ev_unref (loop)	664	=item ev_unref (loop)
555		665
…		…
560	returning, ev_unref() after starting, and ev_ref() before stopping it. For	670	returning, ev_unref() after starting, and ev_ref() before stopping it. For
561	example, libev itself uses this for its internal signal pipe: It is not	671	example, libev itself uses this for its internal signal pipe: It is not
562	visible to the libev user and should not keep C<ev_loop> from exiting if	672	visible to the libev user and should not keep C<ev_loop> from exiting if
563	no event watchers registered by it are active. It is also an excellent	673	no event watchers registered by it are active. It is also an excellent
564	way to do this for generic recurring timers or from within third-party	674	way to do this for generic recurring timers or from within third-party
565	libraries. Just remember to I<unref after start> and I<ref before stop>.	675	libraries. Just remember to I<unref after start> and I<ref before stop>
		676	(but only if the watcher wasn't active before, or was active before,
		677	respectively).
566		678
567	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
568	running when nothing else is active.	680	running when nothing else is active.
569		681
570	struct ev_signal exitsig;	682	struct ev_signal exitsig;
571	ev_signal_init (&exitsig, sig_cb, SIGINT);	683	ev_signal_init (&exitsig, sig_cb, SIGINT);
572	ev_signal_start (loop, &exitsig);	684	ev_signal_start (loop, &exitsig);
573	evf_unref (loop);	685	evf_unref (loop);
574		686
575	Example: For some weird reason, unregister the above signal handler again.	687	Example: For some weird reason, unregister the above signal handler again.
576		688
577	ev_ref (loop);	689	ev_ref (loop);
578	ev_signal_stop (loop, &exitsig);	690	ev_signal_stop (loop, &exitsig);
579		691
580	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	692	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
581		693
582	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	694	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
583		695
584	These advanced functions influence the time that libev will spend waiting	696	These advanced functions influence the time that libev will spend waiting
585	for events. Both are by default C<0>, meaning that libev will try to	697	for events. Both time intervals are by default C<0>, meaning that libev
586	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	698	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		699	latency.
587		700
588	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
589	allows libev to delay invocation of I/O and timer/periodic callbacks to	702	allows libev to delay invocation of I/O and timer/periodic callbacks
590	increase efficiency of loop iterations.	703	to increase efficiency of loop iterations (or to increase power-saving
		704	opportunities).
591		705
592	The background is that sometimes your program runs just fast enough to	706	The background is that sometimes your program runs just fast enough to
593	handle one (or very few) event(s) per loop iteration. While this makes	707	handle one (or very few) event(s) per loop iteration. While this makes
594	the program responsive, it also wastes a lot of CPU time to poll for new	708	the program responsive, it also wastes a lot of CPU time to poll for new
595	events, especially with backends like C<select ()> which have a high	709	events, especially with backends like C<select ()> which have a high
596	overhead for the actual polling but can deliver many events at once.	710	overhead for the actual polling but can deliver many events at once.
597		711
598	By setting a higher I<io collect interval> you allow libev to spend more	712	By setting a higher I<io collect interval> you allow libev to spend more
599	time collecting I/O events, so you can handle more events per iteration,	713	time collecting I/O events, so you can handle more events per iteration,
600	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	714	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
601	C<ev_timer>) will be not affected.	715	C<ev_timer>) will be not affected. Setting this to a non-null value will
		716	introduce an additional C<ev_sleep ()> call into most loop iterations.
602		717
603	Likewise, by setting a higher I<timeout collect interval> you allow libev	718	Likewise, by setting a higher I<timeout collect interval> you allow libev
604	to spend more time collecting timeouts, at the expense of increased	719	to spend more time collecting timeouts, at the expense of increased
605	latency (the watcher callback will be called later). C<ev_io> watchers	720	latency (the watcher callback will be called later). C<ev_io> watchers
606	will not be affected.	721	will not be affected. Setting this to a non-null value will not introduce
		722	any overhead in libev.
607		723
608	Many (busy) programs can usually benefit by setting the io collect	724	Many (busy) programs can usually benefit by setting the I/O collect
609	interval to a value near C<0.1> or so, which is often enough for	725	interval to a value near C<0.1> or so, which is often enough for
610	interactive servers (of course not for games), likewise for timeouts. It	726	interactive servers (of course not for games), likewise for timeouts. It
611	usually doesn't make much sense to set it to a lower value than C<0.01>,	727	usually doesn't make much sense to set it to a lower value than C<0.01>,
612	as this approsaches the timing granularity of most systems.	728	as this approaches the timing granularity of most systems.
		729
		730	Setting the I<timeout collect interval> can improve the opportunity for
		731	saving power, as the program will "bundle" timer callback invocations that
		732	are "near" in time together, by delaying some, thus reducing the number of
		733	times the process sleeps and wakes up again. Another useful technique to
		734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		735	they fire on, say, one-second boundaries only.
		736
		737	=item ev_loop_verify (loop)
		738
		739	This function only does something when C<EV_VERIFY> support has been
		740	compiled in. It tries to go through all internal structures and checks
		741	them for validity. If anything is found to be inconsistent, it will print
		742	an error message to standard error and call C<abort ()>.
		743
		744	This can be used to catch bugs inside libev itself: under normal
		745	circumstances, this function will never abort as of course libev keeps its
		746	data structures consistent.
613		747
614	=back	748	=back
615		749
616		750
617	=head1 ANATOMY OF A WATCHER	751	=head1 ANATOMY OF A WATCHER
618		752
619	A watcher is a structure that you create and register to record your	753	A watcher is a structure that you create and register to record your
620	interest in some event. For instance, if you want to wait for STDIN to	754	interest in some event. For instance, if you want to wait for STDIN to
621	become readable, you would create an C<ev_io> watcher for that:	755	become readable, you would create an C<ev_io> watcher for that:
622		756
623	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
624	{	758	{
625	ev_io_stop (w);	759	ev_io_stop (w);
626	ev_unloop (loop, EVUNLOOP_ALL);	760	ev_unloop (loop, EVUNLOOP_ALL);
627	}	761	}
628		762
629	struct ev_loop *loop = ev_default_loop (0);	763	struct ev_loop *loop = ev_default_loop (0);
630	struct ev_io stdin_watcher;	764	struct ev_io stdin_watcher;
631	ev_init (&stdin_watcher, my_cb);	765	ev_init (&stdin_watcher, my_cb);
632	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
633	ev_io_start (loop, &stdin_watcher);	767	ev_io_start (loop, &stdin_watcher);
634	ev_loop (loop, 0);	768	ev_loop (loop, 0);
635		769
636	As you can see, you are responsible for allocating the memory for your	770	As you can see, you are responsible for allocating the memory for your
637	watcher structures (and it is usually a bad idea to do this on the stack,	771	watcher structures (and it is usually a bad idea to do this on the stack,
638	although this can sometimes be quite valid).	772	although this can sometimes be quite valid).
639		773
640	Each watcher structure must be initialised by a call to C<ev_init	774	Each watcher structure must be initialised by a call to C<ev_init
641	(watcher *, callback)>, which expects a callback to be provided. This	775	(watcher *, callback)>, which expects a callback to be provided. This
642	callback gets invoked each time the event occurs (or, in the case of io	776	callback gets invoked each time the event occurs (or, in the case of I/O
643	watchers, each time the event loop detects that the file descriptor given	777	watchers, each time the event loop detects that the file descriptor given
644	is readable and/or writable).	778	is readable and/or writable).
645		779
646	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
647	with arguments specific to this watcher type. There is also a macro	781	with arguments specific to this watcher type. There is also a macro
…		…
717	=item C<EV_FORK>	851	=item C<EV_FORK>
718		852
719	The event loop has been resumed in the child process after fork (see	853	The event loop has been resumed in the child process after fork (see
720	C<ev_fork>).	854	C<ev_fork>).
721		855
		856	=item C<EV_ASYNC>
		857
		858	The given async watcher has been asynchronously notified (see C<ev_async>).
		859
722	=item C<EV_ERROR>	860	=item C<EV_ERROR>
723		861
724	An unspecified error has occured, the watcher has been stopped. This might	862	An unspecified error has occurred, the watcher has been stopped. This might
725	happen because the watcher could not be properly started because libev	863	happen because the watcher could not be properly started because libev
726	ran out of memory, a file descriptor was found to be closed or any other	864	ran out of memory, a file descriptor was found to be closed or any other
727	problem. You best act on it by reporting the problem and somehow coping	865	problem. You best act on it by reporting the problem and somehow coping
728	with the watcher being stopped.	866	with the watcher being stopped.
729		867
730	Libev will usually signal a few "dummy" events together with an error,	868	Libev will usually signal a few "dummy" events together with an error,
731	for example it might indicate that a fd is readable or writable, and if	869	for example it might indicate that a fd is readable or writable, and if
732	your callbacks is well-written it can just attempt the operation and cope	870	your callbacks is well-written it can just attempt the operation and cope
733	with the error from read() or write(). This will not work in multithreaded	871	with the error from read() or write(). This will not work in multi-threaded
734	programs, though, so beware.	872	programs, though, so beware.
735		873
736	=back	874	=back
737		875
738	=head2 GENERIC WATCHER FUNCTIONS	876	=head2 GENERIC WATCHER FUNCTIONS
…		…
768	Although some watcher types do not have type-specific arguments	906	Although some watcher types do not have type-specific arguments
769	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
770		908
771	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
772		910
773	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
774	calls into a single call. This is the most convinient method to initialise	912	calls into a single call. This is the most convenient method to initialise
775	a watcher. The same limitations apply, of course.	913	a watcher. The same limitations apply, of course.
776		914
777	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
778		916
779	Starts (activates) the given watcher. Only active watchers will receive	917	Starts (activates) the given watcher. Only active watchers will receive
…		…
862	to associate arbitrary data with your watcher. If you need more data and	1000	to associate arbitrary data with your watcher. If you need more data and
863	don't want to allocate memory and store a pointer to it in that data	1001	don't want to allocate memory and store a pointer to it in that data
864	member, you can also "subclass" the watcher type and provide your own	1002	member, you can also "subclass" the watcher type and provide your own
865	data:	1003	data:
866		1004
867	struct my_io	1005	struct my_io
868	{	1006	{
869	struct ev_io io;	1007	struct ev_io io;
870	int otherfd;	1008	int otherfd;
871	void *somedata;	1009	void *somedata;
872	struct whatever *mostinteresting;	1010	struct whatever *mostinteresting;
873	}	1011	}
874		1012
875	And since your callback will be called with a pointer to the watcher, you	1013	And since your callback will be called with a pointer to the watcher, you
876	can cast it back to your own type:	1014	can cast it back to your own type:
877		1015
878	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1016	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
879	{	1017	{
880	struct my_io *w = (struct my_io *)w_;	1018	struct my_io *w = (struct my_io *)w_;
881	...	1019	...
882	}	1020	}
883		1021
884	More interesting and less C-conformant ways of casting your callback type	1022	More interesting and less C-conformant ways of casting your callback type
885	instead have been omitted.	1023	instead have been omitted.
886		1024
887	Another common scenario is having some data structure with multiple	1025	Another common scenario is having some data structure with multiple
888	watchers:	1026	watchers:
889		1027
890	struct my_biggy	1028	struct my_biggy
891	{	1029	{
892	int some_data;	1030	int some_data;
893	ev_timer t1;	1031	ev_timer t1;
894	ev_timer t2;	1032	ev_timer t2;
895	}	1033	}
896		1034
897	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1035	In this case getting the pointer to C<my_biggy> is a bit more complicated,
898	you need to use C<offsetof>:	1036	you need to use C<offsetof>:
899		1037
900	#include <stddef.h>	1038	#include <stddef.h>
901		1039
902	static void	1040	static void
903	t1_cb (EV_P_ struct ev_timer *w, int revents)	1041	t1_cb (EV_P_ struct ev_timer *w, int revents)
904	{	1042	{
905	struct my_biggy big = (struct my_biggy *	1043	struct my_biggy big = (struct my_biggy *
906	(((char *)w) - offsetof (struct my_biggy, t1));	1044	(((char *)w) - offsetof (struct my_biggy, t1));
907	}	1045	}
908		1046
909	static void	1047	static void
910	t2_cb (EV_P_ struct ev_timer *w, int revents)	1048	t2_cb (EV_P_ struct ev_timer *w, int revents)
911	{	1049	{
912	struct my_biggy big = (struct my_biggy *	1050	struct my_biggy big = (struct my_biggy *
913	(((char *)w) - offsetof (struct my_biggy, t2));	1051	(((char *)w) - offsetof (struct my_biggy, t2));
914	}	1052	}
915		1053
916		1054
917	=head1 WATCHER TYPES	1055	=head1 WATCHER TYPES
918		1056
919	This section describes each watcher in detail, but will not repeat	1057	This section describes each watcher in detail, but will not repeat
…		…
943	In general you can register as many read and/or write event watchers per	1081	In general you can register as many read and/or write event watchers per
944	fd as you want (as long as you don't confuse yourself). Setting all file	1082	fd as you want (as long as you don't confuse yourself). Setting all file
945	descriptors to non-blocking mode is also usually a good idea (but not	1083	descriptors to non-blocking mode is also usually a good idea (but not
946	required if you know what you are doing).	1084	required if you know what you are doing).
947		1085
948	You have to be careful with dup'ed file descriptors, though. Some backends
949	(the linux epoll backend is a notable example) cannot handle dup'ed file
950	descriptors correctly if you register interest in two or more fds pointing
951	to the same underlying file/socket/etc. description (that is, they share
952	the same underlying "file open").
953
954	If you must do this, then force the use of a known-to-be-good backend	1086	If you must do this, then force the use of a known-to-be-good backend
955	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1087	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
956	C<EVBACKEND_POLL>).	1088	C<EVBACKEND_POLL>).
957		1089
958	Another thing you have to watch out for is that it is quite easy to	1090	Another thing you have to watch out for is that it is quite easy to
959	receive "spurious" readyness notifications, that is your callback might	1091	receive "spurious" readiness notifications, that is your callback might
960	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1092	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
961	because there is no data. Not only are some backends known to create a	1093	because there is no data. Not only are some backends known to create a
962	lot of those (for example solaris ports), it is very easy to get into	1094	lot of those (for example Solaris ports), it is very easy to get into
963	this situation even with a relatively standard program structure. Thus	1095	this situation even with a relatively standard program structure. Thus
964	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1096	it is best to always use non-blocking I/O: An extra C<read>(2) returning
965	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1097	C<EAGAIN> is far preferable to a program hanging until some data arrives.
966		1098
967	If you cannot run the fd in non-blocking mode (for example you should not	1099	If you cannot run the fd in non-blocking mode (for example you should not
968	play around with an Xlib connection), then you have to seperately re-test	1100	play around with an Xlib connection), then you have to separately re-test
969	whether a file descriptor is really ready with a known-to-be good interface	1101	whether a file descriptor is really ready with a known-to-be good interface
970	such as poll (fortunately in our Xlib example, Xlib already does this on	1102	such as poll (fortunately in our Xlib example, Xlib already does this on
971	its own, so its quite safe to use).	1103	its own, so its quite safe to use).
972		1104
973	=head3 The special problem of disappearing file descriptors	1105	=head3 The special problem of disappearing file descriptors
…		…
992	optimisations to libev.	1124	optimisations to libev.
993		1125
994	=head3 The special problem of dup'ed file descriptors	1126	=head3 The special problem of dup'ed file descriptors
995		1127
996	Some backends (e.g. epoll), cannot register events for file descriptors,	1128	Some backends (e.g. epoll), cannot register events for file descriptors,
997	but only events for the underlying file descriptions. That menas when you	1129	but only events for the underlying file descriptions. That means when you
998	have C<dup ()>'ed file descriptors and register events for them, only one	1130	have C<dup ()>'ed file descriptors or weirder constellations, and register
999	file descriptor might actually receive events.	1131	events for them, only one file descriptor might actually receive events.
1000		1132
1001	There is no workaorund possible except not registering events	1133	There is no workaround possible except not registering events
1002	for potentially C<dup ()>'ed file descriptors or to resort to	1134	for potentially C<dup ()>'ed file descriptors, or to resort to
1003	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1135	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1004		1136
1005	=head3 The special problem of fork	1137	=head3 The special problem of fork
1006		1138
1007	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1139	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
1011	To support fork in your programs, you either have to call	1143	To support fork in your programs, you either have to call
1012	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1144	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1013	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1145	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1014	C<EVBACKEND_POLL>.	1146	C<EVBACKEND_POLL>.
1015		1147
		1148	=head3 The special problem of SIGPIPE
		1149
		1150	While not really specific to libev, it is easy to forget about SIGPIPE:
		1151	when writing to a pipe whose other end has been closed, your program gets
		1152	send a SIGPIPE, which, by default, aborts your program. For most programs
		1153	this is sensible behaviour, for daemons, this is usually undesirable.
		1154
		1155	So when you encounter spurious, unexplained daemon exits, make sure you
		1156	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1157	somewhere, as that would have given you a big clue).
		1158
1016		1159
1017	=head3 Watcher-Specific Functions	1160	=head3 Watcher-Specific Functions
1018		1161
1019	=over 4	1162	=over 4
1020		1163
1021	=item ev_io_init (ev_io *, callback, int fd, int events)	1164	=item ev_io_init (ev_io *, callback, int fd, int events)
1022		1165
1023	=item ev_io_set (ev_io *, int fd, int events)	1166	=item ev_io_set (ev_io *, int fd, int events)
1024		1167
1025	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1168	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1026	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1169	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1027	C<EV_READ | EV_WRITE> to receive the given events.	1170	C<EV_READ | EV_WRITE> to receive the given events.
1028		1171
1029	=item int fd [read-only]	1172	=item int fd [read-only]
1030		1173
1031	The file descriptor being watched.	1174	The file descriptor being watched.
…		…
1033	=item int events [read-only]	1176	=item int events [read-only]
1034		1177
1035	The events being watched.	1178	The events being watched.
1036		1179
1037	=back	1180	=back
		1181
		1182	=head3 Examples
1038		1183
1039	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1184	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1040	readable, but only once. Since it is likely line-buffered, you could	1185	readable, but only once. Since it is likely line-buffered, you could
1041	attempt to read a whole line in the callback.	1186	attempt to read a whole line in the callback.
1042		1187
1043	static void	1188	static void
1044	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1189	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1045	{	1190	{
1046	ev_io_stop (loop, w);	1191	ev_io_stop (loop, w);
1047	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1192	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1048	}	1193	}
1049		1194
1050	...	1195	...
1051	struct ev_loop *loop = ev_default_init (0);	1196	struct ev_loop *loop = ev_default_init (0);
1052	struct ev_io stdin_readable;	1197	struct ev_io stdin_readable;
1053	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1198	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1054	ev_io_start (loop, &stdin_readable);	1199	ev_io_start (loop, &stdin_readable);
1055	ev_loop (loop, 0);	1200	ev_loop (loop, 0);
1056		1201
1057		1202
1058	=head2 C<ev_timer> - relative and optionally repeating timeouts	1203	=head2 C<ev_timer> - relative and optionally repeating timeouts
1059		1204
1060	Timer watchers are simple relative timers that generate an event after a	1205	Timer watchers are simple relative timers that generate an event after a
1061	given time, and optionally repeating in regular intervals after that.	1206	given time, and optionally repeating in regular intervals after that.
1062		1207
1063	The timers are based on real time, that is, if you register an event that	1208	The timers are based on real time, that is, if you register an event that
1064	times out after an hour and you reset your system clock to last years	1209	times out after an hour and you reset your system clock to January last
1065	time, it will still time out after (roughly) and hour. "Roughly" because	1210	year, it will still time out after (roughly) and hour. "Roughly" because
1066	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1211	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1067	monotonic clock option helps a lot here).	1212	monotonic clock option helps a lot here).
		1213
		1214	The callback is guaranteed to be invoked only after its timeout has passed,
		1215	but if multiple timers become ready during the same loop iteration then
		1216	order of execution is undefined.
		1217
		1218	=head3 The special problem of time updates
		1219
		1220	Establishing the current time is a costly operation (it usually takes at
		1221	least two system calls): EV therefore updates its idea of the current
		1222	time only before and after C<ev_loop> polls for new events, which causes
		1223	a growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1224	lots of events.
1068		1225
1069	The relative timeouts are calculated relative to the C<ev_now ()>	1226	The relative timeouts are calculated relative to the C<ev_now ()>
1070	time. This is usually the right thing as this timestamp refers to the time	1227	time. This is usually the right thing as this timestamp refers to the time
1071	of the event triggering whatever timeout you are modifying/starting. If	1228	of the event triggering whatever timeout you are modifying/starting. If
1072	you suspect event processing to be delayed and you I<need> to base the timeout	1229	you suspect event processing to be delayed and you I<need> to base the
1073	on the current time, use something like this to adjust for this:	1230	timeout on the current time, use something like this to adjust for this:
1074		1231
1075	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1232	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1076		1233
1077	The callback is guarenteed to be invoked only when its timeout has passed,	1234	If the event loop is suspended for a long time, you can also force an
1078	but if multiple timers become ready during the same loop iteration then	1235	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1079	order of execution is undefined.	1236	()>.
1080		1237
1081	=head3 Watcher-Specific Functions and Data Members	1238	=head3 Watcher-Specific Functions and Data Members
1082		1239
1083	=over 4	1240	=over 4
1084		1241
1085	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1242	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1086		1243
1087	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1244	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1088		1245
1089	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1246	Configure the timer to trigger after C<after> seconds. If C<repeat>
1090	C<0.>, then it will automatically be stopped. If it is positive, then the	1247	is C<0.>, then it will automatically be stopped once the timeout is
1091	timer will automatically be configured to trigger again C<repeat> seconds	1248	reached. If it is positive, then the timer will automatically be
1092	later, again, and again, until stopped manually.	1249	configured to trigger again C<repeat> seconds later, again, and again,
		1250	until stopped manually.
1093		1251
1094	The timer itself will do a best-effort at avoiding drift, that is, if you	1252	The timer itself will do a best-effort at avoiding drift, that is, if
1095	configure a timer to trigger every 10 seconds, then it will trigger at	1253	you configure a timer to trigger every 10 seconds, then it will normally
1096	exactly 10 second intervals. If, however, your program cannot keep up with	1254	trigger at exactly 10 second intervals. If, however, your program cannot
1097	the timer (because it takes longer than those 10 seconds to do stuff) the	1255	keep up with the timer (because it takes longer than those 10 seconds to
1098	timer will not fire more than once per event loop iteration.	1256	do stuff) the timer will not fire more than once per event loop iteration.
1099		1257
1100	=item ev_timer_again (loop)	1258	=item ev_timer_again (loop, ev_timer *)
1101		1259
1102	This will act as if the timer timed out and restart it again if it is	1260	This will act as if the timer timed out and restart it again if it is
1103	repeating. The exact semantics are:	1261	repeating. The exact semantics are:
1104		1262
1105	If the timer is pending, its pending status is cleared.	1263	If the timer is pending, its pending status is cleared.
1106		1264
1107	If the timer is started but nonrepeating, stop it (as if it timed out).	1265	If the timer is started but non-repeating, stop it (as if it timed out).
1108		1266
1109	If the timer is repeating, either start it if necessary (with the	1267	If the timer is repeating, either start it if necessary (with the
1110	C<repeat> value), or reset the running timer to the C<repeat> value.	1268	C<repeat> value), or reset the running timer to the C<repeat> value.
1111		1269
1112	This sounds a bit complicated, but here is a useful and typical	1270	This sounds a bit complicated, but here is a useful and typical
1113	example: Imagine you have a tcp connection and you want a so-called idle	1271	example: Imagine you have a TCP connection and you want a so-called idle
1114	timeout, that is, you want to be called when there have been, say, 60	1272	timeout, that is, you want to be called when there have been, say, 60
1115	seconds of inactivity on the socket. The easiest way to do this is to	1273	seconds of inactivity on the socket. The easiest way to do this is to
1116	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1274	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1117	C<ev_timer_again> each time you successfully read or write some data. If	1275	C<ev_timer_again> each time you successfully read or write some data. If
1118	you go into an idle state where you do not expect data to travel on the	1276	you go into an idle state where you do not expect data to travel on the
…		…
1140	or C<ev_timer_again> is called and determines the next timeout (if any),	1298	or C<ev_timer_again> is called and determines the next timeout (if any),
1141	which is also when any modifications are taken into account.	1299	which is also when any modifications are taken into account.
1142		1300
1143	=back	1301	=back
1144		1302
		1303	=head3 Examples
		1304
1145	Example: Create a timer that fires after 60 seconds.	1305	Example: Create a timer that fires after 60 seconds.
1146		1306
1147	static void	1307	static void
1148	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1308	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1149	{	1309	{
1150	.. one minute over, w is actually stopped right here	1310	.. one minute over, w is actually stopped right here
1151	}	1311	}
1152		1312
1153	struct ev_timer mytimer;	1313	struct ev_timer mytimer;
1154	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1314	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1155	ev_timer_start (loop, &mytimer);	1315	ev_timer_start (loop, &mytimer);
1156		1316
1157	Example: Create a timeout timer that times out after 10 seconds of	1317	Example: Create a timeout timer that times out after 10 seconds of
1158	inactivity.	1318	inactivity.
1159		1319
1160	static void	1320	static void
1161	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1321	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1162	{	1322	{
1163	.. ten seconds without any activity	1323	.. ten seconds without any activity
1164	}	1324	}
1165		1325
1166	struct ev_timer mytimer;	1326	struct ev_timer mytimer;
1167	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1327	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1168	ev_timer_again (&mytimer); /* start timer */	1328	ev_timer_again (&mytimer); /* start timer */
1169	ev_loop (loop, 0);	1329	ev_loop (loop, 0);
1170		1330
1171	// and in some piece of code that gets executed on any "activity":	1331	// and in some piece of code that gets executed on any "activity":
1172	// reset the timeout to start ticking again at 10 seconds	1332	// reset the timeout to start ticking again at 10 seconds
1173	ev_timer_again (&mytimer);	1333	ev_timer_again (&mytimer);
1174		1334
1175		1335
1176	=head2 C<ev_periodic> - to cron or not to cron?	1336	=head2 C<ev_periodic> - to cron or not to cron?
1177		1337
1178	Periodic watchers are also timers of a kind, but they are very versatile	1338	Periodic watchers are also timers of a kind, but they are very versatile
1179	(and unfortunately a bit complex).	1339	(and unfortunately a bit complex).
1180		1340
1181	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1341	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1182	but on wallclock time (absolute time). You can tell a periodic watcher	1342	but on wall clock time (absolute time). You can tell a periodic watcher
1183	to trigger "at" some specific point in time. For example, if you tell a	1343	to trigger after some specific point in time. For example, if you tell a
1184	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1344	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1185	+ 10.>) and then reset your system clock to the last year, then it will	1345	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1346	clock to January of the previous year, then it will take more than year
1186	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1347	to trigger the event (unlike an C<ev_timer>, which would still trigger
1187	roughly 10 seconds later).	1348	roughly 10 seconds later as it uses a relative timeout).
1188		1349
1189	They can also be used to implement vastly more complex timers, such as	1350	C<ev_periodic>s can also be used to implement vastly more complex timers,
1190	triggering an event on each midnight, local time or other, complicated,	1351	such as triggering an event on each "midnight, local time", or other
1191	rules.	1352	complicated, rules.
1192		1353
1193	As with timers, the callback is guarenteed to be invoked only when the	1354	As with timers, the callback is guaranteed to be invoked only when the
1194	time (C<at>) has been passed, but if multiple periodic timers become ready	1355	time (C<at>) has passed, but if multiple periodic timers become ready
1195	during the same loop iteration then order of execution is undefined.	1356	during the same loop iteration then order of execution is undefined.
1196		1357
1197	=head3 Watcher-Specific Functions and Data Members	1358	=head3 Watcher-Specific Functions and Data Members
1198		1359
1199	=over 4	1360	=over 4
…		…
1207		1368
1208	=over 4	1369	=over 4
1209		1370
1210	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1371	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1211		1372
1212	In this configuration the watcher triggers an event at the wallclock time	1373	In this configuration the watcher triggers an event after the wall clock
1213	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1374	time C<at> has passed and doesn't repeat. It will not adjust when a time
1214	that is, if it is to be run at January 1st 2011 then it will run when the	1375	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1215	system time reaches or surpasses this time.	1376	run when the system time reaches or surpasses this time.
1216		1377
1217	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1378	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1218		1379
1219	In this mode the watcher will always be scheduled to time out at the next	1380	In this mode the watcher will always be scheduled to time out at the next
1220	C<at + N * interval> time (for some integer N, which can also be negative)	1381	C<at + N * interval> time (for some integer N, which can also be negative)
1221	and then repeat, regardless of any time jumps.	1382	and then repeat, regardless of any time jumps.
1222		1383
1223	This can be used to create timers that do not drift with respect to system	1384	This can be used to create timers that do not drift with respect to system
1224	time:	1385	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1386	the hour:
1225		1387
1226	ev_periodic_set (&periodic, 0., 3600., 0);	1388	ev_periodic_set (&periodic, 0., 3600., 0);
1227		1389
1228	This doesn't mean there will always be 3600 seconds in between triggers,	1390	This doesn't mean there will always be 3600 seconds in between triggers,
1229	but only that the the callback will be called when the system time shows a	1391	but only that the callback will be called when the system time shows a
1230	full hour (UTC), or more correctly, when the system time is evenly divisible	1392	full hour (UTC), or more correctly, when the system time is evenly divisible
1231	by 3600.	1393	by 3600.
1232		1394
1233	Another way to think about it (for the mathematically inclined) is that	1395	Another way to think about it (for the mathematically inclined) is that
1234	C<ev_periodic> will try to run the callback in this mode at the next possible	1396	C<ev_periodic> will try to run the callback in this mode at the next possible
1235	time where C<time = at (mod interval)>, regardless of any time jumps.	1397	time where C<time = at (mod interval)>, regardless of any time jumps.
1236		1398
1237	For numerical stability it is preferable that the C<at> value is near	1399	For numerical stability it is preferable that the C<at> value is near
1238	C<ev_now ()> (the current time), but there is no range requirement for	1400	C<ev_now ()> (the current time), but there is no range requirement for
1239	this value.	1401	this value, and in fact is often specified as zero.
		1402
		1403	Note also that there is an upper limit to how often a timer can fire (CPU
		1404	speed for example), so if C<interval> is very small then timing stability
		1405	will of course deteriorate. Libev itself tries to be exact to be about one
		1406	millisecond (if the OS supports it and the machine is fast enough).
1240		1407
1241	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1408	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1242		1409
1243	In this mode the values for C<interval> and C<at> are both being	1410	In this mode the values for C<interval> and C<at> are both being
1244	ignored. Instead, each time the periodic watcher gets scheduled, the	1411	ignored. Instead, each time the periodic watcher gets scheduled, the
1245	reschedule callback will be called with the watcher as first, and the	1412	reschedule callback will be called with the watcher as first, and the
1246	current time as second argument.	1413	current time as second argument.
1247		1414
1248	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1415	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1249	ever, or make any event loop modifications>. If you need to stop it,	1416	ever, or make ANY event loop modifications whatsoever>.
1250	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1251	starting an C<ev_prepare> watcher, which is legal).
1252		1417
		1418	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1419	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1420	only event loop modification you are allowed to do).
		1421
1253	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1422	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1254	ev_tstamp now)>, e.g.:	1423	*w, ev_tstamp now)>, e.g.:
1255		1424
1256	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1425	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1257	{	1426	{
1258	return now + 60.;	1427	return now + 60.;
1259	}	1428	}
…		…
1261	It must return the next time to trigger, based on the passed time value	1430	It must return the next time to trigger, based on the passed time value
1262	(that is, the lowest time value larger than to the second argument). It	1431	(that is, the lowest time value larger than to the second argument). It
1263	will usually be called just before the callback will be triggered, but	1432	will usually be called just before the callback will be triggered, but
1264	might be called at other times, too.	1433	might be called at other times, too.
1265		1434
1266	NOTE: I<< This callback must always return a time that is later than the	1435	NOTE: I<< This callback must always return a time that is higher than or
1267	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1436	equal to the passed C<now> value >>.
1268		1437
1269	This can be used to create very complex timers, such as a timer that	1438	This can be used to create very complex timers, such as a timer that
1270	triggers on each midnight, local time. To do this, you would calculate the	1439	triggers on "next midnight, local time". To do this, you would calculate the
1271	next midnight after C<now> and return the timestamp value for this. How	1440	next midnight after C<now> and return the timestamp value for this. How
1272	you do this is, again, up to you (but it is not trivial, which is the main	1441	you do this is, again, up to you (but it is not trivial, which is the main
1273	reason I omitted it as an example).	1442	reason I omitted it as an example).
1274		1443
1275	=back	1444	=back
…		…
1279	Simply stops and restarts the periodic watcher again. This is only useful	1448	Simply stops and restarts the periodic watcher again. This is only useful
1280	when you changed some parameters or the reschedule callback would return	1449	when you changed some parameters or the reschedule callback would return
1281	a different time than the last time it was called (e.g. in a crond like	1450	a different time than the last time it was called (e.g. in a crond like
1282	program when the crontabs have changed).	1451	program when the crontabs have changed).
1283		1452
		1453	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1454
		1455	When active, returns the absolute time that the watcher is supposed to
		1456	trigger next.
		1457
1284	=item ev_tstamp offset [read-write]	1458	=item ev_tstamp offset [read-write]
1285		1459
1286	When repeating, this contains the offset value, otherwise this is the	1460	When repeating, this contains the offset value, otherwise this is the
1287	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1461	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1288		1462
…		…
1299		1473
1300	The current reschedule callback, or C<0>, if this functionality is	1474	The current reschedule callback, or C<0>, if this functionality is
1301	switched off. Can be changed any time, but changes only take effect when	1475	switched off. Can be changed any time, but changes only take effect when
1302	the periodic timer fires or C<ev_periodic_again> is being called.	1476	the periodic timer fires or C<ev_periodic_again> is being called.
1303		1477
1304	=item ev_tstamp at [read-only]
1305
1306	When active, contains the absolute time that the watcher is supposed to
1307	trigger next.
1308
1309	=back	1478	=back
		1479
		1480	=head3 Examples
1310		1481
1311	Example: Call a callback every hour, or, more precisely, whenever the	1482	Example: Call a callback every hour, or, more precisely, whenever the
1312	system clock is divisible by 3600. The callback invocation times have	1483	system clock is divisible by 3600. The callback invocation times have
1313	potentially a lot of jittering, but good long-term stability.	1484	potentially a lot of jitter, but good long-term stability.
1314		1485
1315	static void	1486	static void
1316	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1487	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1317	{	1488	{
1318	... its now a full hour (UTC, or TAI or whatever your clock follows)	1489	... its now a full hour (UTC, or TAI or whatever your clock follows)
1319	}	1490	}
1320		1491
1321	struct ev_periodic hourly_tick;	1492	struct ev_periodic hourly_tick;
1322	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1493	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1323	ev_periodic_start (loop, &hourly_tick);	1494	ev_periodic_start (loop, &hourly_tick);
1324		1495
1325	Example: The same as above, but use a reschedule callback to do it:	1496	Example: The same as above, but use a reschedule callback to do it:
1326		1497
1327	#include <math.h>	1498	#include <math.h>
1328		1499
1329	static ev_tstamp	1500	static ev_tstamp
1330	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1501	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1331	{	1502	{
1332	return fmod (now, 3600.) + 3600.;	1503	return fmod (now, 3600.) + 3600.;
1333	}	1504	}
1334		1505
1335	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1506	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1336		1507
1337	Example: Call a callback every hour, starting now:	1508	Example: Call a callback every hour, starting now:
1338		1509
1339	struct ev_periodic hourly_tick;	1510	struct ev_periodic hourly_tick;
1340	ev_periodic_init (&hourly_tick, clock_cb,	1511	ev_periodic_init (&hourly_tick, clock_cb,
1341	fmod (ev_now (loop), 3600.), 3600., 0);	1512	fmod (ev_now (loop), 3600.), 3600., 0);
1342	ev_periodic_start (loop, &hourly_tick);	1513	ev_periodic_start (loop, &hourly_tick);
1343		1514
1344		1515
1345	=head2 C<ev_signal> - signal me when a signal gets signalled!	1516	=head2 C<ev_signal> - signal me when a signal gets signalled!
1346		1517
1347	Signal watchers will trigger an event when the process receives a specific	1518	Signal watchers will trigger an event when the process receives a specific
…		…
1354	with the kernel (thus it coexists with your own signal handlers as long	1525	with the kernel (thus it coexists with your own signal handlers as long
1355	as you don't register any with libev). Similarly, when the last signal	1526	as you don't register any with libev). Similarly, when the last signal
1356	watcher for a signal is stopped libev will reset the signal handler to	1527	watcher for a signal is stopped libev will reset the signal handler to
1357	SIG_DFL (regardless of what it was set to before).	1528	SIG_DFL (regardless of what it was set to before).
1358		1529
		1530	If possible and supported, libev will install its handlers with
		1531	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1532	interrupted. If you have a problem with system calls getting interrupted by
		1533	signals you can block all signals in an C<ev_check> watcher and unblock
		1534	them in an C<ev_prepare> watcher.
		1535
1359	=head3 Watcher-Specific Functions and Data Members	1536	=head3 Watcher-Specific Functions and Data Members
1360		1537
1361	=over 4	1538	=over 4
1362		1539
1363	=item ev_signal_init (ev_signal *, callback, int signum)	1540	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1371		1548
1372	The signal the watcher watches out for.	1549	The signal the watcher watches out for.
1373		1550
1374	=back	1551	=back
1375		1552
		1553	=head3 Examples
		1554
		1555	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1556
		1557	static void
		1558	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1559	{
		1560	ev_unloop (loop, EVUNLOOP_ALL);
		1561	}
		1562
		1563	struct ev_signal signal_watcher;
		1564	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1565	ev_signal_start (loop, &sigint_cb);
		1566
1376		1567
1377	=head2 C<ev_child> - watch out for process status changes	1568	=head2 C<ev_child> - watch out for process status changes
1378		1569
1379	Child watchers trigger when your process receives a SIGCHLD in response to	1570	Child watchers trigger when your process receives a SIGCHLD in response to
1380	some child status changes (most typically when a child of yours dies).	1571	some child status changes (most typically when a child of yours dies). It
		1572	is permissible to install a child watcher I<after> the child has been
		1573	forked (which implies it might have already exited), as long as the event
		1574	loop isn't entered (or is continued from a watcher).
		1575
		1576	Only the default event loop is capable of handling signals, and therefore
		1577	you can only register child watchers in the default event loop.
		1578
		1579	=head3 Process Interaction
		1580
		1581	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1582	initialised. This is necessary to guarantee proper behaviour even if
		1583	the first child watcher is started after the child exits. The occurrence
		1584	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1585	synchronously as part of the event loop processing. Libev always reaps all
		1586	children, even ones not watched.
		1587
		1588	=head3 Overriding the Built-In Processing
		1589
		1590	Libev offers no special support for overriding the built-in child
		1591	processing, but if your application collides with libev's default child
		1592	handler, you can override it easily by installing your own handler for
		1593	C<SIGCHLD> after initialising the default loop, and making sure the
		1594	default loop never gets destroyed. You are encouraged, however, to use an
		1595	event-based approach to child reaping and thus use libev's support for
		1596	that, so other libev users can use C<ev_child> watchers freely.
		1597
		1598	=head3 Stopping the Child Watcher
		1599
		1600	Currently, the child watcher never gets stopped, even when the
		1601	child terminates, so normally one needs to stop the watcher in the
		1602	callback. Future versions of libev might stop the watcher automatically
		1603	when a child exit is detected.
1381		1604
1382	=head3 Watcher-Specific Functions and Data Members	1605	=head3 Watcher-Specific Functions and Data Members
1383		1606
1384	=over 4	1607	=over 4
1385		1608
1386	=item ev_child_init (ev_child *, callback, int pid)	1609	=item ev_child_init (ev_child *, callback, int pid, int trace)
1387		1610
1388	=item ev_child_set (ev_child *, int pid)	1611	=item ev_child_set (ev_child *, int pid, int trace)
1389		1612
1390	Configures the watcher to wait for status changes of process C<pid> (or	1613	Configures the watcher to wait for status changes of process C<pid> (or
1391	I<any> process if C<pid> is specified as C<0>). The callback can look	1614	I<any> process if C<pid> is specified as C<0>). The callback can look
1392	at the C<rstatus> member of the C<ev_child> watcher structure to see	1615	at the C<rstatus> member of the C<ev_child> watcher structure to see
1393	the status word (use the macros from C<sys/wait.h> and see your systems	1616	the status word (use the macros from C<sys/wait.h> and see your systems
1394	C<waitpid> documentation). The C<rpid> member contains the pid of the	1617	C<waitpid> documentation). The C<rpid> member contains the pid of the
1395	process causing the status change.	1618	process causing the status change. C<trace> must be either C<0> (only
		1619	activate the watcher when the process terminates) or C<1> (additionally
		1620	activate the watcher when the process is stopped or continued).
1396		1621
1397	=item int pid [read-only]	1622	=item int pid [read-only]
1398		1623
1399	The process id this watcher watches out for, or C<0>, meaning any process id.	1624	The process id this watcher watches out for, or C<0>, meaning any process id.
1400		1625
…		…
1407	The process exit/trace status caused by C<rpid> (see your systems	1632	The process exit/trace status caused by C<rpid> (see your systems
1408	C<waitpid> and C<sys/wait.h> documentation for details).	1633	C<waitpid> and C<sys/wait.h> documentation for details).
1409		1634
1410	=back	1635	=back
1411		1636
1412	Example: Try to exit cleanly on SIGINT and SIGTERM.	1637	=head3 Examples
1413		1638
		1639	Example: C<fork()> a new process and install a child handler to wait for
		1640	its completion.
		1641
		1642	ev_child cw;
		1643
1414	static void	1644	static void
1415	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1645	child_cb (EV_P_ struct ev_child *w, int revents)
1416	{	1646	{
1417	ev_unloop (loop, EVUNLOOP_ALL);	1647	ev_child_stop (EV_A_ w);
		1648	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1418	}	1649	}
1419		1650
1420	struct ev_signal signal_watcher;	1651	pid_t pid = fork ();
1421	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1652
1422	ev_signal_start (loop, &sigint_cb);	1653	if (pid < 0)
		1654	// error
		1655	else if (pid == 0)
		1656	{
		1657	// the forked child executes here
		1658	exit (1);
		1659	}
		1660	else
		1661	{
		1662	ev_child_init (&cw, child_cb, pid, 0);
		1663	ev_child_start (EV_DEFAULT_ &cw);
		1664	}
1423		1665
1424		1666
1425	=head2 C<ev_stat> - did the file attributes just change?	1667	=head2 C<ev_stat> - did the file attributes just change?
1426		1668
1427	This watches a filesystem path for attribute changes. That is, it calls	1669	This watches a file system path for attribute changes. That is, it calls
1428	C<stat> regularly (or when the OS says it changed) and sees if it changed	1670	C<stat> regularly (or when the OS says it changed) and sees if it changed
1429	compared to the last time, invoking the callback if it did.	1671	compared to the last time, invoking the callback if it did.
1430		1672
1431	The path does not need to exist: changing from "path exists" to "path does	1673	The path does not need to exist: changing from "path exists" to "path does
1432	not exist" is a status change like any other. The condition "path does	1674	not exist" is a status change like any other. The condition "path does
…		…
1450	as even with OS-supported change notifications, this can be	1692	as even with OS-supported change notifications, this can be
1451	resource-intensive.	1693	resource-intensive.
1452		1694
1453	At the time of this writing, only the Linux inotify interface is	1695	At the time of this writing, only the Linux inotify interface is
1454	implemented (implementing kqueue support is left as an exercise for the	1696	implemented (implementing kqueue support is left as an exercise for the
		1697	reader, note, however, that the author sees no way of implementing ev_stat
1455	reader). Inotify will be used to give hints only and should not change the	1698	semantics with kqueue). Inotify will be used to give hints only and should
1456	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1699	not change the semantics of C<ev_stat> watchers, which means that libev
1457	to fall back to regular polling again even with inotify, but changes are	1700	sometimes needs to fall back to regular polling again even with inotify,
1458	usually detected immediately, and if the file exists there will be no	1701	but changes are usually detected immediately, and if the file exists there
1459	polling.	1702	will be no polling.
		1703
		1704	=head3 ABI Issues (Largefile Support)
		1705
		1706	Libev by default (unless the user overrides this) uses the default
		1707	compilation environment, which means that on systems with large file
		1708	support disabled by default, you get the 32 bit version of the stat
		1709	structure. When using the library from programs that change the ABI to
		1710	use 64 bit file offsets the programs will fail. In that case you have to
		1711	compile libev with the same flags to get binary compatibility. This is
		1712	obviously the case with any flags that change the ABI, but the problem is
		1713	most noticeably disabled with ev_stat and large file support.
		1714
		1715	The solution for this is to lobby your distribution maker to make large
		1716	file interfaces available by default (as e.g. FreeBSD does) and not
		1717	optional. Libev cannot simply switch on large file support because it has
		1718	to exchange stat structures with application programs compiled using the
		1719	default compilation environment.
		1720
		1721	=head3 Inotify
		1722
		1723	When C<inotify (7)> support has been compiled into libev (generally only
		1724	available on Linux) and present at runtime, it will be used to speed up
		1725	change detection where possible. The inotify descriptor will be created lazily
		1726	when the first C<ev_stat> watcher is being started.
		1727
		1728	Inotify presence does not change the semantics of C<ev_stat> watchers
		1729	except that changes might be detected earlier, and in some cases, to avoid
		1730	making regular C<stat> calls. Even in the presence of inotify support
		1731	there are many cases where libev has to resort to regular C<stat> polling.
		1732
		1733	(There is no support for kqueue, as apparently it cannot be used to
		1734	implement this functionality, due to the requirement of having a file
		1735	descriptor open on the object at all times).
		1736
		1737	=head3 The special problem of stat time resolution
		1738
		1739	The C<stat ()> system call only supports full-second resolution portably, and
		1740	even on systems where the resolution is higher, many file systems still
		1741	only support whole seconds.
		1742
		1743	That means that, if the time is the only thing that changes, you can
		1744	easily miss updates: on the first update, C<ev_stat> detects a change and
		1745	calls your callback, which does something. When there is another update
		1746	within the same second, C<ev_stat> will be unable to detect it as the stat
		1747	data does not change.
		1748
		1749	The solution to this is to delay acting on a change for slightly more
		1750	than a second (or till slightly after the next full second boundary), using
		1751	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1752	ev_timer_again (loop, w)>).
		1753
		1754	The C<.02> offset is added to work around small timing inconsistencies
		1755	of some operating systems (where the second counter of the current time
		1756	might be be delayed. One such system is the Linux kernel, where a call to
		1757	C<gettimeofday> might return a timestamp with a full second later than
		1758	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1759	update file times then there will be a small window where the kernel uses
		1760	the previous second to update file times but libev might already execute
		1761	the timer callback).
1460		1762
1461	=head3 Watcher-Specific Functions and Data Members	1763	=head3 Watcher-Specific Functions and Data Members
1462		1764
1463	=over 4	1765	=over 4
1464		1766
…		…
1470	C<path>. The C<interval> is a hint on how quickly a change is expected to	1772	C<path>. The C<interval> is a hint on how quickly a change is expected to
1471	be detected and should normally be specified as C<0> to let libev choose	1773	be detected and should normally be specified as C<0> to let libev choose
1472	a suitable value. The memory pointed to by C<path> must point to the same	1774	a suitable value. The memory pointed to by C<path> must point to the same
1473	path for as long as the watcher is active.	1775	path for as long as the watcher is active.
1474		1776
1475	The callback will be receive C<EV_STAT> when a change was detected,	1777	The callback will receive C<EV_STAT> when a change was detected, relative
1476	relative to the attributes at the time the watcher was started (or the	1778	to the attributes at the time the watcher was started (or the last change
1477	last change was detected).	1779	was detected).
1478		1780
1479	=item ev_stat_stat (ev_stat *)	1781	=item ev_stat_stat (loop, ev_stat *)
1480		1782
1481	Updates the stat buffer immediately with new values. If you change the	1783	Updates the stat buffer immediately with new values. If you change the
1482	watched path in your callback, you could call this fucntion to avoid	1784	watched path in your callback, you could call this function to avoid
1483	detecting this change (while introducing a race condition). Can also be	1785	detecting this change (while introducing a race condition if you are not
1484	useful simply to find out the new values.	1786	the only one changing the path). Can also be useful simply to find out the
		1787	new values.
1485		1788
1486	=item ev_statdata attr [read-only]	1789	=item ev_statdata attr [read-only]
1487		1790
1488	The most-recently detected attributes of the file. Although the type is of	1791	The most-recently detected attributes of the file. Although the type is
1489	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1792	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1490	suitable for your system. If the C<st_nlink> member is C<0>, then there	1793	suitable for your system, but you can only rely on the POSIX-standardised
		1794	members to be present. If the C<st_nlink> member is C<0>, then there was
1491	was some error while C<stat>ing the file.	1795	some error while C<stat>ing the file.
1492		1796
1493	=item ev_statdata prev [read-only]	1797	=item ev_statdata prev [read-only]
1494		1798
1495	The previous attributes of the file. The callback gets invoked whenever	1799	The previous attributes of the file. The callback gets invoked whenever
1496	C<prev> != C<attr>.	1800	C<prev> != C<attr>, or, more precisely, one or more of these members
		1801	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1802	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1497		1803
1498	=item ev_tstamp interval [read-only]	1804	=item ev_tstamp interval [read-only]
1499		1805
1500	The specified interval.	1806	The specified interval.
1501		1807
1502	=item const char *path [read-only]	1808	=item const char *path [read-only]
1503		1809
1504	The filesystem path that is being watched.	1810	The file system path that is being watched.
1505		1811
1506	=back	1812	=back
1507		1813
		1814	=head3 Examples
		1815
1508	Example: Watch C</etc/passwd> for attribute changes.	1816	Example: Watch C</etc/passwd> for attribute changes.
1509		1817
1510	static void	1818	static void
1511	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1819	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1512	{	1820	{
1513	/* /etc/passwd changed in some way */	1821	/* /etc/passwd changed in some way */
1514	if (w->attr.st_nlink)	1822	if (w->attr.st_nlink)
1515	{	1823	{
1516	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1824	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1517	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1825	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1518	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1826	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1519	}	1827	}
1520	else	1828	else
1521	/* you shalt not abuse printf for puts */	1829	/* you shalt not abuse printf for puts */
1522	puts ("wow, /etc/passwd is not there, expect problems. "	1830	puts ("wow, /etc/passwd is not there, expect problems. "
1523	"if this is windows, they already arrived\n");	1831	"if this is windows, they already arrived\n");
1524	}	1832	}
1525		1833
1526	...	1834	...
1527	ev_stat passwd;	1835	ev_stat passwd;
1528		1836
1529	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1837	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1530	ev_stat_start (loop, &passwd);	1838	ev_stat_start (loop, &passwd);
		1839
		1840	Example: Like above, but additionally use a one-second delay so we do not
		1841	miss updates (however, frequent updates will delay processing, too, so
		1842	one might do the work both on C<ev_stat> callback invocation I<and> on
		1843	C<ev_timer> callback invocation).
		1844
		1845	static ev_stat passwd;
		1846	static ev_timer timer;
		1847
		1848	static void
		1849	timer_cb (EV_P_ ev_timer *w, int revents)
		1850	{
		1851	ev_timer_stop (EV_A_ w);
		1852
		1853	/* now it's one second after the most recent passwd change */
		1854	}
		1855
		1856	static void
		1857	stat_cb (EV_P_ ev_stat *w, int revents)
		1858	{
		1859	/* reset the one-second timer */
		1860	ev_timer_again (EV_A_ &timer);
		1861	}
		1862
		1863	...
		1864	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1865	ev_stat_start (loop, &passwd);
		1866	ev_timer_init (&timer, timer_cb, 0., 1.02);
1531		1867
1532		1868
1533	=head2 C<ev_idle> - when you've got nothing better to do...	1869	=head2 C<ev_idle> - when you've got nothing better to do...
1534		1870
1535	Idle watchers trigger events when no other events of the same or higher	1871	Idle watchers trigger events when no other events of the same or higher
…		…
1561	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1897	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1562	believe me.	1898	believe me.
1563		1899
1564	=back	1900	=back
1565		1901
		1902	=head3 Examples
		1903
1566	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1904	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1567	callback, free it. Also, use no error checking, as usual.	1905	callback, free it. Also, use no error checking, as usual.
1568		1906
1569	static void	1907	static void
1570	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1908	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1571	{	1909	{
1572	free (w);	1910	free (w);
1573	// now do something you wanted to do when the program has	1911	// now do something you wanted to do when the program has
1574	// no longer asnything immediate to do.	1912	// no longer anything immediate to do.
1575	}	1913	}
1576		1914
1577	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1915	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1578	ev_idle_init (idle_watcher, idle_cb);	1916	ev_idle_init (idle_watcher, idle_cb);
1579	ev_idle_start (loop, idle_cb);	1917	ev_idle_start (loop, idle_cb);
1580		1918
1581		1919
1582	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1920	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1583		1921
1584	Prepare and check watchers are usually (but not always) used in tandem:	1922	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1603		1941
1604	This is done by examining in each prepare call which file descriptors need	1942	This is done by examining in each prepare call which file descriptors need
1605	to be watched by the other library, registering C<ev_io> watchers for	1943	to be watched by the other library, registering C<ev_io> watchers for
1606	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1944	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1607	provide just this functionality). Then, in the check watcher you check for	1945	provide just this functionality). Then, in the check watcher you check for
1608	any events that occured (by checking the pending status of all watchers	1946	any events that occurred (by checking the pending status of all watchers
1609	and stopping them) and call back into the library. The I/O and timer	1947	and stopping them) and call back into the library. The I/O and timer
1610	callbacks will never actually be called (but must be valid nevertheless,	1948	callbacks will never actually be called (but must be valid nevertheless,
1611	because you never know, you know?).	1949	because you never know, you know?).
1612		1950
1613	As another example, the Perl Coro module uses these hooks to integrate	1951	As another example, the Perl Coro module uses these hooks to integrate
…		…
1621		1959
1622	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1960	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1623	priority, to ensure that they are being run before any other watchers	1961	priority, to ensure that they are being run before any other watchers
1624	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1962	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1625	too) should not activate ("feed") events into libev. While libev fully	1963	too) should not activate ("feed") events into libev. While libev fully
1626	supports this, they will be called before other C<ev_check> watchers did	1964	supports this, they might get executed before other C<ev_check> watchers
1627	their job. As C<ev_check> watchers are often used to embed other event	1965	did their job. As C<ev_check> watchers are often used to embed other
1628	loops those other event loops might be in an unusable state until their	1966	(non-libev) event loops those other event loops might be in an unusable
1629	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1967	state until their C<ev_check> watcher ran (always remind yourself to
1630	others).	1968	coexist peacefully with others).
1631		1969
1632	=head3 Watcher-Specific Functions and Data Members	1970	=head3 Watcher-Specific Functions and Data Members
1633		1971
1634	=over 4	1972	=over 4
1635		1973
…		…
1641	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1979	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1642	macros, but using them is utterly, utterly and completely pointless.	1980	macros, but using them is utterly, utterly and completely pointless.
1643		1981
1644	=back	1982	=back
1645		1983
		1984	=head3 Examples
		1985
1646	There are a number of principal ways to embed other event loops or modules	1986	There are a number of principal ways to embed other event loops or modules
1647	into libev. Here are some ideas on how to include libadns into libev	1987	into libev. Here are some ideas on how to include libadns into libev
1648	(there is a Perl module named C<EV::ADNS> that does this, which you could	1988	(there is a Perl module named C<EV::ADNS> that does this, which you could
1649	use for an actually working example. Another Perl module named C<EV::Glib>	1989	use as a working example. Another Perl module named C<EV::Glib> embeds a
1650	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1990	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1651	into the Glib event loop).	1991	Glib event loop).
1652		1992
1653	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1993	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1654	and in a check watcher, destroy them and call into libadns. What follows	1994	and in a check watcher, destroy them and call into libadns. What follows
1655	is pseudo-code only of course. This requires you to either use a low	1995	is pseudo-code only of course. This requires you to either use a low
1656	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1996	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1657	the callbacks for the IO/timeout watchers might not have been called yet.	1997	the callbacks for the IO/timeout watchers might not have been called yet.
1658		1998
1659	static ev_io iow [nfd];	1999	static ev_io iow [nfd];
1660	static ev_timer tw;	2000	static ev_timer tw;
1661		2001
1662	static void	2002	static void
1663	io_cb (ev_loop *loop, ev_io *w, int revents)	2003	io_cb (ev_loop *loop, ev_io *w, int revents)
1664	{	2004	{
1665	}	2005	}
1666		2006
1667	// create io watchers for each fd and a timer before blocking	2007	// create io watchers for each fd and a timer before blocking
1668	static void	2008	static void
1669	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2009	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1670	{	2010	{
1671	int timeout = 3600000;	2011	int timeout = 3600000;
1672	struct pollfd fds [nfd];	2012	struct pollfd fds [nfd];
1673	// actual code will need to loop here and realloc etc.	2013	// actual code will need to loop here and realloc etc.
1674	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2014	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1675		2015
1676	/* the callback is illegal, but won't be called as we stop during check */	2016	/* the callback is illegal, but won't be called as we stop during check */
1677	ev_timer_init (&tw, 0, timeout * 1e-3);	2017	ev_timer_init (&tw, 0, timeout * 1e-3);
1678	ev_timer_start (loop, &tw);	2018	ev_timer_start (loop, &tw);
1679		2019
1680	// create one ev_io per pollfd	2020	// create one ev_io per pollfd
1681	for (int i = 0; i < nfd; ++i)	2021	for (int i = 0; i < nfd; ++i)
1682	{	2022	{
1683	ev_io_init (iow + i, io_cb, fds [i].fd,	2023	ev_io_init (iow + i, io_cb, fds [i].fd,
1684	((fds [i].events & POLLIN ? EV_READ : 0)	2024	((fds [i].events & POLLIN ? EV_READ : 0)
1685	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2025	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1686		2026
1687	fds [i].revents = 0;	2027	fds [i].revents = 0;
1688	ev_io_start (loop, iow + i);	2028	ev_io_start (loop, iow + i);
1689	}	2029	}
1690	}	2030	}
1691		2031
1692	// stop all watchers after blocking	2032	// stop all watchers after blocking
1693	static void	2033	static void
1694	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2034	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1695	{	2035	{
1696	ev_timer_stop (loop, &tw);	2036	ev_timer_stop (loop, &tw);
1697		2037
1698	for (int i = 0; i < nfd; ++i)	2038	for (int i = 0; i < nfd; ++i)
1699	{	2039	{
1700	// set the relevant poll flags	2040	// set the relevant poll flags
1701	// could also call adns_processreadable etc. here	2041	// could also call adns_processreadable etc. here
1702	struct pollfd *fd = fds + i;	2042	struct pollfd *fd = fds + i;
1703	int revents = ev_clear_pending (iow + i);	2043	int revents = ev_clear_pending (iow + i);
1704	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2044	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1705	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2045	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1706		2046
1707	// now stop the watcher	2047	// now stop the watcher
1708	ev_io_stop (loop, iow + i);	2048	ev_io_stop (loop, iow + i);
1709	}	2049	}
1710		2050
1711	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2051	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1712	}	2052	}
1713		2053
1714	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2054	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1715	in the prepare watcher and would dispose of the check watcher.	2055	in the prepare watcher and would dispose of the check watcher.
1716		2056
1717	Method 3: If the module to be embedded supports explicit event	2057	Method 3: If the module to be embedded supports explicit event
1718	notification (adns does), you can also make use of the actual watcher	2058	notification (libadns does), you can also make use of the actual watcher
1719	callbacks, and only destroy/create the watchers in the prepare watcher.	2059	callbacks, and only destroy/create the watchers in the prepare watcher.
1720		2060
1721	static void	2061	static void
1722	timer_cb (EV_P_ ev_timer *w, int revents)	2062	timer_cb (EV_P_ ev_timer *w, int revents)
1723	{	2063	{
1724	adns_state ads = (adns_state)w->data;	2064	adns_state ads = (adns_state)w->data;
1725	update_now (EV_A);	2065	update_now (EV_A);
1726		2066
1727	adns_processtimeouts (ads, &tv_now);	2067	adns_processtimeouts (ads, &tv_now);
1728	}	2068	}
1729		2069
1730	static void	2070	static void
1731	io_cb (EV_P_ ev_io *w, int revents)	2071	io_cb (EV_P_ ev_io *w, int revents)
1732	{	2072	{
1733	adns_state ads = (adns_state)w->data;	2073	adns_state ads = (adns_state)w->data;
1734	update_now (EV_A);	2074	update_now (EV_A);
1735		2075
1736	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2076	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1737	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2077	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1738	}	2078	}
1739		2079
1740	// do not ever call adns_afterpoll	2080	// do not ever call adns_afterpoll
1741		2081
1742	Method 4: Do not use a prepare or check watcher because the module you	2082	Method 4: Do not use a prepare or check watcher because the module you
1743	want to embed is too inflexible to support it. Instead, youc na override	2083	want to embed is too inflexible to support it. Instead, you can override
1744	their poll function. The drawback with this solution is that the main	2084	their poll function. The drawback with this solution is that the main
1745	loop is now no longer controllable by EV. The C<Glib::EV> module does	2085	loop is now no longer controllable by EV. The C<Glib::EV> module does
1746	this.	2086	this.
1747		2087
1748	static gint	2088	static gint
1749	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2089	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1750	{	2090	{
1751	int got_events = 0;	2091	int got_events = 0;
1752		2092
1753	for (n = 0; n < nfds; ++n)	2093	for (n = 0; n < nfds; ++n)
1754	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2094	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1755		2095
1756	if (timeout >= 0)	2096	if (timeout >= 0)
1757	// create/start timer	2097	// create/start timer
1758		2098
1759	// poll	2099	// poll
1760	ev_loop (EV_A_ 0);	2100	ev_loop (EV_A_ 0);
1761		2101
1762	// stop timer again	2102	// stop timer again
1763	if (timeout >= 0)	2103	if (timeout >= 0)
1764	ev_timer_stop (EV_A_ &to);	2104	ev_timer_stop (EV_A_ &to);
1765		2105
1766	// stop io watchers again - their callbacks should have set	2106	// stop io watchers again - their callbacks should have set
1767	for (n = 0; n < nfds; ++n)	2107	for (n = 0; n < nfds; ++n)
1768	ev_io_stop (EV_A_ iow [n]);	2108	ev_io_stop (EV_A_ iow [n]);
1769		2109
1770	return got_events;	2110	return got_events;
1771	}	2111	}
1772		2112
1773		2113
1774	=head2 C<ev_embed> - when one backend isn't enough...	2114	=head2 C<ev_embed> - when one backend isn't enough...
1775		2115
1776	This is a rather advanced watcher type that lets you embed one event loop	2116	This is a rather advanced watcher type that lets you embed one event loop
1777	into another (currently only C<ev_io> events are supported in the embedded	2117	into another (currently only C<ev_io> events are supported in the embedded
1778	loop, other types of watchers might be handled in a delayed or incorrect	2118	loop, other types of watchers might be handled in a delayed or incorrect
1779	fashion and must not be used). (See portability notes, below).	2119	fashion and must not be used).
1780		2120
1781	There are primarily two reasons you would want that: work around bugs and	2121	There are primarily two reasons you would want that: work around bugs and
1782	prioritise I/O.	2122	prioritise I/O.
1783		2123
1784	As an example for a bug workaround, the kqueue backend might only support	2124	As an example for a bug workaround, the kqueue backend might only support
…		…
1818	portable one.	2158	portable one.
1819		2159
1820	So when you want to use this feature you will always have to be prepared	2160	So when you want to use this feature you will always have to be prepared
1821	that you cannot get an embeddable loop. The recommended way to get around	2161	that you cannot get an embeddable loop. The recommended way to get around
1822	this is to have a separate variables for your embeddable loop, try to	2162	this is to have a separate variables for your embeddable loop, try to
1823	create it, and if that fails, use the normal loop for everything:	2163	create it, and if that fails, use the normal loop for everything.
1824
1825	struct ev_loop *loop_hi = ev_default_init (0);
1826	struct ev_loop *loop_lo = 0;
1827	struct ev_embed embed;
1828
1829	// see if there is a chance of getting one that works
1830	// (remember that a flags value of 0 means autodetection)
1831	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1832	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1833	: 0;
1834
1835	// if we got one, then embed it, otherwise default to loop_hi
1836	if (loop_lo)
1837	{
1838	ev_embed_init (&embed, 0, loop_lo);
1839	ev_embed_start (loop_hi, &embed);
1840	}
1841	else
1842	loop_lo = loop_hi;
1843
1844	=head2 Portability notes
1845
1846	Kqueue is nominally embeddable, but this is broken on all BSDs that I
1847	tried, in various ways. Usually the embedded event loop will simply never
1848	receive events, sometimes it will only trigger a few times, sometimes in a
1849	loop. Epoll is also nominally embeddable, but many Linux kernel versions
1850	will always eport the epoll fd as ready, even when no events are pending.
1851
1852	While libev allows embedding these backends (they are contained in
1853	C<ev_embeddable_backends ()>), take extreme care that it will actually
1854	work.
1855
1856	When in doubt, create a dynamic event loop forced to use sockets (this
1857	usually works) and possibly another thread and a pipe or so to report to
1858	your main event loop.
1859		2164
1860	=head3 Watcher-Specific Functions and Data Members	2165	=head3 Watcher-Specific Functions and Data Members
1861		2166
1862	=over 4	2167	=over 4
1863		2168
…		…
1867		2172
1868	Configures the watcher to embed the given loop, which must be	2173	Configures the watcher to embed the given loop, which must be
1869	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2174	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1870	invoked automatically, otherwise it is the responsibility of the callback	2175	invoked automatically, otherwise it is the responsibility of the callback
1871	to invoke it (it will continue to be called until the sweep has been done,	2176	to invoke it (it will continue to be called until the sweep has been done,
1872	if you do not want thta, you need to temporarily stop the embed watcher).	2177	if you do not want that, you need to temporarily stop the embed watcher).
1873		2178
1874	=item ev_embed_sweep (loop, ev_embed *)	2179	=item ev_embed_sweep (loop, ev_embed *)
1875		2180
1876	Make a single, non-blocking sweep over the embedded loop. This works	2181	Make a single, non-blocking sweep over the embedded loop. This works
1877	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2182	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1878	apropriate way for embedded loops.	2183	appropriate way for embedded loops.
1879		2184
1880	=item struct ev_loop *other [read-only]	2185	=item struct ev_loop *other [read-only]
1881		2186
1882	The embedded event loop.	2187	The embedded event loop.
1883		2188
1884	=back	2189	=back
		2190
		2191	=head3 Examples
		2192
		2193	Example: Try to get an embeddable event loop and embed it into the default
		2194	event loop. If that is not possible, use the default loop. The default
		2195	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2196	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2197	used).
		2198
		2199	struct ev_loop *loop_hi = ev_default_init (0);
		2200	struct ev_loop *loop_lo = 0;
		2201	struct ev_embed embed;
		2202
		2203	// see if there is a chance of getting one that works
		2204	// (remember that a flags value of 0 means autodetection)
		2205	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2206	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2207	: 0;
		2208
		2209	// if we got one, then embed it, otherwise default to loop_hi
		2210	if (loop_lo)
		2211	{
		2212	ev_embed_init (&embed, 0, loop_lo);
		2213	ev_embed_start (loop_hi, &embed);
		2214	}
		2215	else
		2216	loop_lo = loop_hi;
		2217
		2218	Example: Check if kqueue is available but not recommended and create
		2219	a kqueue backend for use with sockets (which usually work with any
		2220	kqueue implementation). Store the kqueue/socket-only event loop in
		2221	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2222
		2223	struct ev_loop *loop = ev_default_init (0);
		2224	struct ev_loop *loop_socket = 0;
		2225	struct ev_embed embed;
		2226
		2227	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2228	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2229	{
		2230	ev_embed_init (&embed, 0, loop_socket);
		2231	ev_embed_start (loop, &embed);
		2232	}
		2233
		2234	if (!loop_socket)
		2235	loop_socket = loop;
		2236
		2237	// now use loop_socket for all sockets, and loop for everything else
1885		2238
1886		2239
1887	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2240	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1888		2241
1889	Fork watchers are called when a C<fork ()> was detected (usually because	2242	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1905	believe me.	2258	believe me.
1906		2259
1907	=back	2260	=back
1908		2261
1909		2262
		2263	=head2 C<ev_async> - how to wake up another event loop
		2264
		2265	In general, you cannot use an C<ev_loop> from multiple threads or other
		2266	asynchronous sources such as signal handlers (as opposed to multiple event
		2267	loops - those are of course safe to use in different threads).
		2268
		2269	Sometimes, however, you need to wake up another event loop you do not
		2270	control, for example because it belongs to another thread. This is what
		2271	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2272	can signal it by calling C<ev_async_send>, which is thread- and signal
		2273	safe.
		2274
		2275	This functionality is very similar to C<ev_signal> watchers, as signals,
		2276	too, are asynchronous in nature, and signals, too, will be compressed
		2277	(i.e. the number of callback invocations may be less than the number of
		2278	C<ev_async_sent> calls).
		2279
		2280	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2281	just the default loop.
		2282
		2283	=head3 Queueing
		2284
		2285	C<ev_async> does not support queueing of data in any way. The reason
		2286	is that the author does not know of a simple (or any) algorithm for a
		2287	multiple-writer-single-reader queue that works in all cases and doesn't
		2288	need elaborate support such as pthreads.
		2289
		2290	That means that if you want to queue data, you have to provide your own
		2291	queue. But at least I can tell you would implement locking around your
		2292	queue:
		2293
		2294	=over 4
		2295
		2296	=item queueing from a signal handler context
		2297
		2298	To implement race-free queueing, you simply add to the queue in the signal
		2299	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2300	some fictitious SIGUSR1 handler:
		2301
		2302	static ev_async mysig;
		2303
		2304	static void
		2305	sigusr1_handler (void)
		2306	{
		2307	sometype data;
		2308
		2309	// no locking etc.
		2310	queue_put (data);
		2311	ev_async_send (EV_DEFAULT_ &mysig);
		2312	}
		2313
		2314	static void
		2315	mysig_cb (EV_P_ ev_async *w, int revents)
		2316	{
		2317	sometype data;
		2318	sigset_t block, prev;
		2319
		2320	sigemptyset (&block);
		2321	sigaddset (&block, SIGUSR1);
		2322	sigprocmask (SIG_BLOCK, &block, &prev);
		2323
		2324	while (queue_get (&data))
		2325	process (data);
		2326
		2327	if (sigismember (&prev, SIGUSR1)
		2328	sigprocmask (SIG_UNBLOCK, &block, 0);
		2329	}
		2330
		2331	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2332	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2333	either...).
		2334
		2335	=item queueing from a thread context
		2336
		2337	The strategy for threads is different, as you cannot (easily) block
		2338	threads but you can easily preempt them, so to queue safely you need to
		2339	employ a traditional mutex lock, such as in this pthread example:
		2340
		2341	static ev_async mysig;
		2342	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2343
		2344	static void
		2345	otherthread (void)
		2346	{
		2347	// only need to lock the actual queueing operation
		2348	pthread_mutex_lock (&mymutex);
		2349	queue_put (data);
		2350	pthread_mutex_unlock (&mymutex);
		2351
		2352	ev_async_send (EV_DEFAULT_ &mysig);
		2353	}
		2354
		2355	static void
		2356	mysig_cb (EV_P_ ev_async *w, int revents)
		2357	{
		2358	pthread_mutex_lock (&mymutex);
		2359
		2360	while (queue_get (&data))
		2361	process (data);
		2362
		2363	pthread_mutex_unlock (&mymutex);
		2364	}
		2365
		2366	=back
		2367
		2368
		2369	=head3 Watcher-Specific Functions and Data Members
		2370
		2371	=over 4
		2372
		2373	=item ev_async_init (ev_async *, callback)
		2374
		2375	Initialises and configures the async watcher - it has no parameters of any
		2376	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2377	believe me.
		2378
		2379	=item ev_async_send (loop, ev_async *)
		2380
		2381	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2382	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2383	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2384	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2385	section below on what exactly this means).
		2386
		2387	This call incurs the overhead of a system call only once per loop iteration,
		2388	so while the overhead might be noticeable, it doesn't apply to repeated
		2389	calls to C<ev_async_send>.
		2390
		2391	=item bool = ev_async_pending (ev_async *)
		2392
		2393	Returns a non-zero value when C<ev_async_send> has been called on the
		2394	watcher but the event has not yet been processed (or even noted) by the
		2395	event loop.
		2396
		2397	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2398	the loop iterates next and checks for the watcher to have become active,
		2399	it will reset the flag again. C<ev_async_pending> can be used to very
		2400	quickly check whether invoking the loop might be a good idea.
		2401
		2402	Not that this does I<not> check whether the watcher itself is pending, only
		2403	whether it has been requested to make this watcher pending.
		2404
		2405	=back
		2406
		2407
1910	=head1 OTHER FUNCTIONS	2408	=head1 OTHER FUNCTIONS
1911		2409
1912	There are some other functions of possible interest. Described. Here. Now.	2410	There are some other functions of possible interest. Described. Here. Now.
1913		2411
1914	=over 4	2412	=over 4
…		…
1921	or timeout without having to allocate/configure/start/stop/free one or	2419	or timeout without having to allocate/configure/start/stop/free one or
1922	more watchers yourself.	2420	more watchers yourself.
1923		2421
1924	If C<fd> is less than 0, then no I/O watcher will be started and events	2422	If C<fd> is less than 0, then no I/O watcher will be started and events
1925	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2423	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1926	C<events> set will be craeted and started.	2424	C<events> set will be created and started.
1927		2425
1928	If C<timeout> is less than 0, then no timeout watcher will be	2426	If C<timeout> is less than 0, then no timeout watcher will be
1929	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2427	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1930	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2428	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1931	dubious value.	2429	dubious value.
…		…
1933	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2431	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1934	passed an C<revents> set like normal event callbacks (a combination of	2432	passed an C<revents> set like normal event callbacks (a combination of
1935	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2433	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1936	value passed to C<ev_once>:	2434	value passed to C<ev_once>:
1937		2435
1938	static void stdin_ready (int revents, void *arg)	2436	static void stdin_ready (int revents, void *arg)
1939	{	2437	{
1940	if (revents & EV_TIMEOUT)	2438	if (revents & EV_TIMEOUT)
1941	/* doh, nothing entered */;	2439	/* doh, nothing entered */;
1942	else if (revents & EV_READ)	2440	else if (revents & EV_READ)
1943	/* stdin might have data for us, joy! */;	2441	/* stdin might have data for us, joy! */;
1944	}	2442	}
1945		2443
1946	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2444	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1947		2445
1948	=item ev_feed_event (ev_loop *, watcher *, int revents)	2446	=item ev_feed_event (ev_loop *, watcher *, int revents)
1949		2447
1950	Feeds the given event set into the event loop, as if the specified event	2448	Feeds the given event set into the event loop, as if the specified event
1951	had happened for the specified watcher (which must be a pointer to an	2449	had happened for the specified watcher (which must be a pointer to an
…		…
1956	Feed an event on the given fd, as if a file descriptor backend detected	2454	Feed an event on the given fd, as if a file descriptor backend detected
1957	the given events it.	2455	the given events it.
1958		2456
1959	=item ev_feed_signal_event (ev_loop *loop, int signum)	2457	=item ev_feed_signal_event (ev_loop *loop, int signum)
1960		2458
1961	Feed an event as if the given signal occured (C<loop> must be the default	2459	Feed an event as if the given signal occurred (C<loop> must be the default
1962	loop!).	2460	loop!).
1963		2461
1964	=back	2462	=back
1965		2463
1966		2464
…		…
1982		2480
1983	=item * Priorities are not currently supported. Initialising priorities	2481	=item * Priorities are not currently supported. Initialising priorities
1984	will fail and all watchers will have the same priority, even though there	2482	will fail and all watchers will have the same priority, even though there
1985	is an ev_pri field.	2483	is an ev_pri field.
1986		2484
		2485	=item * In libevent, the last base created gets the signals, in libev, the
		2486	first base created (== the default loop) gets the signals.
		2487
1987	=item * Other members are not supported.	2488	=item * Other members are not supported.
1988		2489
1989	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2490	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1990	to use the libev header file and library.	2491	to use the libev header file and library.
1991		2492
1992	=back	2493	=back
1993		2494
1994	=head1 C++ SUPPORT	2495	=head1 C++ SUPPORT
1995		2496
1996	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2497	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1997	you to use some convinience methods to start/stop watchers and also change	2498	you to use some convenience methods to start/stop watchers and also change
1998	the callback model to a model using method callbacks on objects.	2499	the callback model to a model using method callbacks on objects.
1999		2500
2000	To use it,	2501	To use it,
2001		2502
2002	#include <ev++.h>	2503	#include <ev++.h>
2003		2504
2004	This automatically includes F<ev.h> and puts all of its definitions (many	2505	This automatically includes F<ev.h> and puts all of its definitions (many
2005	of them macros) into the global namespace. All C++ specific things are	2506	of them macros) into the global namespace. All C++ specific things are
2006	put into the C<ev> namespace. It should support all the same embedding	2507	put into the C<ev> namespace. It should support all the same embedding
2007	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2508	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2074	your compiler is good :), then the method will be fully inlined into the	2575	your compiler is good :), then the method will be fully inlined into the
2075	thunking function, making it as fast as a direct C callback.	2576	thunking function, making it as fast as a direct C callback.
2076		2577
2077	Example: simple class declaration and watcher initialisation	2578	Example: simple class declaration and watcher initialisation
2078		2579
2079	struct myclass	2580	struct myclass
2080	{	2581	{
2081	void io_cb (ev::io &w, int revents) { }	2582	void io_cb (ev::io &w, int revents) { }
2082	}	2583	}
2083		2584
2084	myclass obj;	2585	myclass obj;
2085	ev::io iow;	2586	ev::io iow;
2086	iow.set <myclass, &myclass::io_cb> (&obj);	2587	iow.set <myclass, &myclass::io_cb> (&obj);
2087		2588
2088	=item w->set<function> (void *data = 0)	2589	=item w->set<function> (void *data = 0)
2089		2590
2090	Also sets a callback, but uses a static method or plain function as	2591	Also sets a callback, but uses a static method or plain function as
2091	callback. The optional C<data> argument will be stored in the watcher's	2592	callback. The optional C<data> argument will be stored in the watcher's
…		…
2095		2596
2096	See the method-C<set> above for more details.	2597	See the method-C<set> above for more details.
2097		2598
2098	Example:	2599	Example:
2099		2600
2100	static void io_cb (ev::io &w, int revents) { }	2601	static void io_cb (ev::io &w, int revents) { }
2101	iow.set <io_cb> ();	2602	iow.set <io_cb> ();
2102		2603
2103	=item w->set (struct ev_loop *)	2604	=item w->set (struct ev_loop *)
2104		2605
2105	Associates a different C<struct ev_loop> with this watcher. You can only	2606	Associates a different C<struct ev_loop> with this watcher. You can only
2106	do this when the watcher is inactive (and not pending either).	2607	do this when the watcher is inactive (and not pending either).
2107		2608
2108	=item w->set ([args])	2609	=item w->set ([arguments])
2109		2610
2110	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2611	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2111	called at least once. Unlike the C counterpart, an active watcher gets	2612	called at least once. Unlike the C counterpart, an active watcher gets
2112	automatically stopped and restarted when reconfiguring it with this	2613	automatically stopped and restarted when reconfiguring it with this
2113	method.	2614	method.
2114		2615
2115	=item w->start ()	2616	=item w->start ()
…		…
2139	=back	2640	=back
2140		2641
2141	Example: Define a class with an IO and idle watcher, start one of them in	2642	Example: Define a class with an IO and idle watcher, start one of them in
2142	the constructor.	2643	the constructor.
2143		2644
2144	class myclass	2645	class myclass
2145	{	2646	{
2146	ev_io io; void io_cb (ev::io &w, int revents);	2647	ev::io io; void io_cb (ev::io &w, int revents);
2147	ev_idle idle void idle_cb (ev::idle &w, int revents);	2648	ev:idle idle void idle_cb (ev::idle &w, int revents);
2148		2649
2149	myclass ();	2650	myclass (int fd)
2150	}	2651	{
2151
2152	myclass::myclass (int fd)
2153	{
2154	io .set <myclass, &myclass::io_cb > (this);	2652	io .set <myclass, &myclass::io_cb > (this);
2155	idle.set <myclass, &myclass::idle_cb> (this);	2653	idle.set <myclass, &myclass::idle_cb> (this);
2156		2654
2157	io.start (fd, ev::READ);	2655	io.start (fd, ev::READ);
		2656	}
2158	}	2657	};
		2658
		2659
		2660	=head1 OTHER LANGUAGE BINDINGS
		2661
		2662	Libev does not offer other language bindings itself, but bindings for a
		2663	number of languages exist in the form of third-party packages. If you know
		2664	any interesting language binding in addition to the ones listed here, drop
		2665	me a note.
		2666
		2667	=over 4
		2668
		2669	=item Perl
		2670
		2671	The EV module implements the full libev API and is actually used to test
		2672	libev. EV is developed together with libev. Apart from the EV core module,
		2673	there are additional modules that implement libev-compatible interfaces
		2674	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2675	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2676
		2677	It can be found and installed via CPAN, its homepage is at
		2678	L<http://software.schmorp.de/pkg/EV>.
		2679
		2680	=item Python
		2681
		2682	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2683	seems to be quite complete and well-documented. Note, however, that the
		2684	patch they require for libev is outright dangerous as it breaks the ABI
		2685	for everybody else, and therefore, should never be applied in an installed
		2686	libev (if python requires an incompatible ABI then it needs to embed
		2687	libev).
		2688
		2689	=item Ruby
		2690
		2691	Tony Arcieri has written a ruby extension that offers access to a subset
		2692	of the libev API and adds file handle abstractions, asynchronous DNS and
		2693	more on top of it. It can be found via gem servers. Its homepage is at
		2694	L<http://rev.rubyforge.org/>.
		2695
		2696	=item D
		2697
		2698	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2699	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2700
		2701	=back
2159		2702
2160		2703
2161	=head1 MACRO MAGIC	2704	=head1 MACRO MAGIC
2162		2705
2163	Libev can be compiled with a variety of options, the most fundamantal	2706	Libev can be compiled with a variety of options, the most fundamental
2164	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2707	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2165	functions and callbacks have an initial C<struct ev_loop *> argument.	2708	functions and callbacks have an initial C<struct ev_loop *> argument.
2166		2709
2167	To make it easier to write programs that cope with either variant, the	2710	To make it easier to write programs that cope with either variant, the
2168	following macros are defined:	2711	following macros are defined:
…		…
2173		2716
2174	This provides the loop I<argument> for functions, if one is required ("ev	2717	This provides the loop I<argument> for functions, if one is required ("ev
2175	loop argument"). The C<EV_A> form is used when this is the sole argument,	2718	loop argument"). The C<EV_A> form is used when this is the sole argument,
2176	C<EV_A_> is used when other arguments are following. Example:	2719	C<EV_A_> is used when other arguments are following. Example:
2177		2720
2178	ev_unref (EV_A);	2721	ev_unref (EV_A);
2179	ev_timer_add (EV_A_ watcher);	2722	ev_timer_add (EV_A_ watcher);
2180	ev_loop (EV_A_ 0);	2723	ev_loop (EV_A_ 0);
2181		2724
2182	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2725	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2183	which is often provided by the following macro.	2726	which is often provided by the following macro.
2184		2727
2185	=item C<EV_P>, C<EV_P_>	2728	=item C<EV_P>, C<EV_P_>
2186		2729
2187	This provides the loop I<parameter> for functions, if one is required ("ev	2730	This provides the loop I<parameter> for functions, if one is required ("ev
2188	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2731	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2189	C<EV_P_> is used when other parameters are following. Example:	2732	C<EV_P_> is used when other parameters are following. Example:
2190		2733
2191	// this is how ev_unref is being declared	2734	// this is how ev_unref is being declared
2192	static void ev_unref (EV_P);	2735	static void ev_unref (EV_P);
2193		2736
2194	// this is how you can declare your typical callback	2737	// this is how you can declare your typical callback
2195	static void cb (EV_P_ ev_timer *w, int revents)	2738	static void cb (EV_P_ ev_timer *w, int revents)
2196		2739
2197	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2740	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2198	suitable for use with C<EV_A>.	2741	suitable for use with C<EV_A>.
2199		2742
2200	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2743	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2201		2744
2202	Similar to the other two macros, this gives you the value of the default	2745	Similar to the other two macros, this gives you the value of the default
2203	loop, if multiple loops are supported ("ev loop default").	2746	loop, if multiple loops are supported ("ev loop default").
		2747
		2748	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2749
		2750	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2751	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2752	is undefined when the default loop has not been initialised by a previous
		2753	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2754
		2755	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2756	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2204		2757
2205	=back	2758	=back
2206		2759
2207	Example: Declare and initialise a check watcher, utilising the above	2760	Example: Declare and initialise a check watcher, utilising the above
2208	macros so it will work regardless of whether multiple loops are supported	2761	macros so it will work regardless of whether multiple loops are supported
2209	or not.	2762	or not.
2210		2763
2211	static void	2764	static void
2212	check_cb (EV_P_ ev_timer *w, int revents)	2765	check_cb (EV_P_ ev_timer *w, int revents)
2213	{	2766	{
2214	ev_check_stop (EV_A_ w);	2767	ev_check_stop (EV_A_ w);
2215	}	2768	}
2216		2769
2217	ev_check check;	2770	ev_check check;
2218	ev_check_init (&check, check_cb);	2771	ev_check_init (&check, check_cb);
2219	ev_check_start (EV_DEFAULT_ &check);	2772	ev_check_start (EV_DEFAULT_ &check);
2220	ev_loop (EV_DEFAULT_ 0);	2773	ev_loop (EV_DEFAULT_ 0);
2221		2774
2222	=head1 EMBEDDING	2775	=head1 EMBEDDING
2223		2776
2224	Libev can (and often is) directly embedded into host	2777	Libev can (and often is) directly embedded into host
2225	applications. Examples of applications that embed it include the Deliantra	2778	applications. Examples of applications that embed it include the Deliantra
…		…
2232	libev somewhere in your source tree).	2785	libev somewhere in your source tree).
2233		2786
2234	=head2 FILESETS	2787	=head2 FILESETS
2235		2788
2236	Depending on what features you need you need to include one or more sets of files	2789	Depending on what features you need you need to include one or more sets of files
2237	in your app.	2790	in your application.
2238		2791
2239	=head3 CORE EVENT LOOP	2792	=head3 CORE EVENT LOOP
2240		2793
2241	To include only the libev core (all the C<ev_*> functions), with manual	2794	To include only the libev core (all the C<ev_*> functions), with manual
2242	configuration (no autoconf):	2795	configuration (no autoconf):
2243		2796
2244	#define EV_STANDALONE 1	2797	#define EV_STANDALONE 1
2245	#include "ev.c"	2798	#include "ev.c"
2246		2799
2247	This will automatically include F<ev.h>, too, and should be done in a	2800	This will automatically include F<ev.h>, too, and should be done in a
2248	single C source file only to provide the function implementations. To use	2801	single C source file only to provide the function implementations. To use
2249	it, do the same for F<ev.h> in all files wishing to use this API (best	2802	it, do the same for F<ev.h> in all files wishing to use this API (best
2250	done by writing a wrapper around F<ev.h> that you can include instead and	2803	done by writing a wrapper around F<ev.h> that you can include instead and
2251	where you can put other configuration options):	2804	where you can put other configuration options):
2252		2805
2253	#define EV_STANDALONE 1	2806	#define EV_STANDALONE 1
2254	#include "ev.h"	2807	#include "ev.h"
2255		2808
2256	Both header files and implementation files can be compiled with a C++	2809	Both header files and implementation files can be compiled with a C++
2257	compiler (at least, thats a stated goal, and breakage will be treated	2810	compiler (at least, thats a stated goal, and breakage will be treated
2258	as a bug).	2811	as a bug).
2259		2812
2260	You need the following files in your source tree, or in a directory	2813	You need the following files in your source tree, or in a directory
2261	in your include path (e.g. in libev/ when using -Ilibev):	2814	in your include path (e.g. in libev/ when using -Ilibev):
2262		2815
2263	ev.h	2816	ev.h
2264	ev.c	2817	ev.c
2265	ev_vars.h	2818	ev_vars.h
2266	ev_wrap.h	2819	ev_wrap.h
2267		2820
2268	ev_win32.c required on win32 platforms only	2821	ev_win32.c required on win32 platforms only
2269		2822
2270	ev_select.c only when select backend is enabled (which is enabled by default)	2823	ev_select.c only when select backend is enabled (which is enabled by default)
2271	ev_poll.c only when poll backend is enabled (disabled by default)	2824	ev_poll.c only when poll backend is enabled (disabled by default)
2272	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2825	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2273	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2826	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2274	ev_port.c only when the solaris port backend is enabled (disabled by default)	2827	ev_port.c only when the solaris port backend is enabled (disabled by default)
2275		2828
2276	F<ev.c> includes the backend files directly when enabled, so you only need	2829	F<ev.c> includes the backend files directly when enabled, so you only need
2277	to compile this single file.	2830	to compile this single file.
2278		2831
2279	=head3 LIBEVENT COMPATIBILITY API	2832	=head3 LIBEVENT COMPATIBILITY API
2280		2833
2281	To include the libevent compatibility API, also include:	2834	To include the libevent compatibility API, also include:
2282		2835
2283	#include "event.c"	2836	#include "event.c"
2284		2837
2285	in the file including F<ev.c>, and:	2838	in the file including F<ev.c>, and:
2286		2839
2287	#include "event.h"	2840	#include "event.h"
2288		2841
2289	in the files that want to use the libevent API. This also includes F<ev.h>.	2842	in the files that want to use the libevent API. This also includes F<ev.h>.
2290		2843
2291	You need the following additional files for this:	2844	You need the following additional files for this:
2292		2845
2293	event.h	2846	event.h
2294	event.c	2847	event.c
2295		2848
2296	=head3 AUTOCONF SUPPORT	2849	=head3 AUTOCONF SUPPORT
2297		2850
2298	Instead of using C<EV_STANDALONE=1> and providing your config in	2851	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2299	whatever way you want, you can also C<m4_include([libev.m4])> in your	2852	whatever way you want, you can also C<m4_include([libev.m4])> in your
2300	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2853	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2301	include F<config.h> and configure itself accordingly.	2854	include F<config.h> and configure itself accordingly.
2302		2855
2303	For this of course you need the m4 file:	2856	For this of course you need the m4 file:
2304		2857
2305	libev.m4	2858	libev.m4
2306		2859
2307	=head2 PREPROCESSOR SYMBOLS/MACROS	2860	=head2 PREPROCESSOR SYMBOLS/MACROS
2308		2861
2309	Libev can be configured via a variety of preprocessor symbols you have to define	2862	Libev can be configured via a variety of preprocessor symbols you have to
2310	before including any of its files. The default is not to build for multiplicity	2863	define before including any of its files. The default in the absence of
2311	and only include the select backend.	2864	autoconf is noted for every option.
2312		2865
2313	=over 4	2866	=over 4
2314		2867
2315	=item EV_STANDALONE	2868	=item EV_STANDALONE
2316		2869
…		…
2321	F<event.h> that are not directly supported by the libev core alone.	2874	F<event.h> that are not directly supported by the libev core alone.
2322		2875
2323	=item EV_USE_MONOTONIC	2876	=item EV_USE_MONOTONIC
2324		2877
2325	If defined to be C<1>, libev will try to detect the availability of the	2878	If defined to be C<1>, libev will try to detect the availability of the
2326	monotonic clock option at both compiletime and runtime. Otherwise no use	2879	monotonic clock option at both compile time and runtime. Otherwise no use
2327	of the monotonic clock option will be attempted. If you enable this, you	2880	of the monotonic clock option will be attempted. If you enable this, you
2328	usually have to link against librt or something similar. Enabling it when	2881	usually have to link against librt or something similar. Enabling it when
2329	the functionality isn't available is safe, though, although you have	2882	the functionality isn't available is safe, though, although you have
2330	to make sure you link against any libraries where the C<clock_gettime>	2883	to make sure you link against any libraries where the C<clock_gettime>
2331	function is hiding in (often F<-lrt>).	2884	function is hiding in (often F<-lrt>).
2332		2885
2333	=item EV_USE_REALTIME	2886	=item EV_USE_REALTIME
2334		2887
2335	If defined to be C<1>, libev will try to detect the availability of the	2888	If defined to be C<1>, libev will try to detect the availability of the
2336	realtime clock option at compiletime (and assume its availability at	2889	real-time clock option at compile time (and assume its availability at
2337	runtime if successful). Otherwise no use of the realtime clock option will	2890	runtime if successful). Otherwise no use of the real-time clock option will
2338	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2891	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2339	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2892	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2340	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2893	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2341		2894
2342	=item EV_USE_NANOSLEEP	2895	=item EV_USE_NANOSLEEP
2343		2896
2344	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2897	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2345	and will use it for delays. Otherwise it will use C<select ()>.	2898	and will use it for delays. Otherwise it will use C<select ()>.
2346		2899
		2900	=item EV_USE_EVENTFD
		2901
		2902	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2903	available and will probe for kernel support at runtime. This will improve
		2904	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2905	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2906	2.7 or newer, otherwise disabled.
		2907
2347	=item EV_USE_SELECT	2908	=item EV_USE_SELECT
2348		2909
2349	If undefined or defined to be C<1>, libev will compile in support for the	2910	If undefined or defined to be C<1>, libev will compile in support for the
2350	C<select>(2) backend. No attempt at autodetection will be done: if no	2911	C<select>(2) backend. No attempt at auto-detection will be done: if no
2351	other method takes over, select will be it. Otherwise the select backend	2912	other method takes over, select will be it. Otherwise the select backend
2352	will not be compiled in.	2913	will not be compiled in.
2353		2914
2354	=item EV_SELECT_USE_FD_SET	2915	=item EV_SELECT_USE_FD_SET
2355		2916
2356	If defined to C<1>, then the select backend will use the system C<fd_set>	2917	If defined to C<1>, then the select backend will use the system C<fd_set>
2357	structure. This is useful if libev doesn't compile due to a missing	2918	structure. This is useful if libev doesn't compile due to a missing
2358	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2919	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2359	exotic systems. This usually limits the range of file descriptors to some	2920	exotic systems. This usually limits the range of file descriptors to some
2360	low limit such as 1024 or might have other limitations (winsocket only	2921	low limit such as 1024 or might have other limitations (winsocket only
2361	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2922	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2362	influence the size of the C<fd_set> used.	2923	influence the size of the C<fd_set> used.
2363		2924
…		…
2369	be used is the winsock select). This means that it will call	2930	be used is the winsock select). This means that it will call
2370	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2931	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2371	it is assumed that all these functions actually work on fds, even	2932	it is assumed that all these functions actually work on fds, even
2372	on win32. Should not be defined on non-win32 platforms.	2933	on win32. Should not be defined on non-win32 platforms.
2373		2934
		2935	=item EV_FD_TO_WIN32_HANDLE
		2936
		2937	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2938	file descriptors to socket handles. When not defining this symbol (the
		2939	default), then libev will call C<_get_osfhandle>, which is usually
		2940	correct. In some cases, programs use their own file descriptor management,
		2941	in which case they can provide this function to map fds to socket handles.
		2942
2374	=item EV_USE_POLL	2943	=item EV_USE_POLL
2375		2944
2376	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2945	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2377	backend. Otherwise it will be enabled on non-win32 platforms. It	2946	backend. Otherwise it will be enabled on non-win32 platforms. It
2378	takes precedence over select.	2947	takes precedence over select.
2379		2948
2380	=item EV_USE_EPOLL	2949	=item EV_USE_EPOLL
2381		2950
2382	If defined to be C<1>, libev will compile in support for the Linux	2951	If defined to be C<1>, libev will compile in support for the Linux
2383	C<epoll>(7) backend. Its availability will be detected at runtime,	2952	C<epoll>(7) backend. Its availability will be detected at runtime,
2384	otherwise another method will be used as fallback. This is the	2953	otherwise another method will be used as fallback. This is the preferred
2385	preferred backend for GNU/Linux systems.	2954	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2955	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2386		2956
2387	=item EV_USE_KQUEUE	2957	=item EV_USE_KQUEUE
2388		2958
2389	If defined to be C<1>, libev will compile in support for the BSD style	2959	If defined to be C<1>, libev will compile in support for the BSD style
2390	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2960	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2403	otherwise another method will be used as fallback. This is the preferred	2973	otherwise another method will be used as fallback. This is the preferred
2404	backend for Solaris 10 systems.	2974	backend for Solaris 10 systems.
2405		2975
2406	=item EV_USE_DEVPOLL	2976	=item EV_USE_DEVPOLL
2407		2977
2408	reserved for future expansion, works like the USE symbols above.	2978	Reserved for future expansion, works like the USE symbols above.
2409		2979
2410	=item EV_USE_INOTIFY	2980	=item EV_USE_INOTIFY
2411		2981
2412	If defined to be C<1>, libev will compile in support for the Linux inotify	2982	If defined to be C<1>, libev will compile in support for the Linux inotify
2413	interface to speed up C<ev_stat> watchers. Its actual availability will	2983	interface to speed up C<ev_stat> watchers. Its actual availability will
2414	be detected at runtime.	2984	be detected at runtime. If undefined, it will be enabled if the headers
		2985	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2986
		2987	=item EV_ATOMIC_T
		2988
		2989	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2990	access is atomic with respect to other threads or signal contexts. No such
		2991	type is easily found in the C language, so you can provide your own type
		2992	that you know is safe for your purposes. It is used both for signal handler "locking"
		2993	as well as for signal and thread safety in C<ev_async> watchers.
		2994
		2995	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2996	(from F<signal.h>), which is usually good enough on most platforms.
2415		2997
2416	=item EV_H	2998	=item EV_H
2417		2999
2418	The name of the F<ev.h> header file used to include it. The default if	3000	The name of the F<ev.h> header file used to include it. The default if
2419	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3001	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2420	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3002	used to virtually rename the F<ev.h> header file in case of conflicts.
2421		3003
2422	=item EV_CONFIG_H	3004	=item EV_CONFIG_H
2423		3005
2424	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3006	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2425	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3007	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2426	C<EV_H>, above.	3008	C<EV_H>, above.
2427		3009
2428	=item EV_EVENT_H	3010	=item EV_EVENT_H
2429		3011
2430	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3012	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2431	of how the F<event.h> header can be found.	3013	of how the F<event.h> header can be found, the default is C<"event.h">.
2432		3014
2433	=item EV_PROTOTYPES	3015	=item EV_PROTOTYPES
2434		3016
2435	If defined to be C<0>, then F<ev.h> will not define any function	3017	If defined to be C<0>, then F<ev.h> will not define any function
2436	prototypes, but still define all the structs and other symbols. This is	3018	prototypes, but still define all the structs and other symbols. This is
…		…
2457	When doing priority-based operations, libev usually has to linearly search	3039	When doing priority-based operations, libev usually has to linearly search
2458	all the priorities, so having many of them (hundreds) uses a lot of space	3040	all the priorities, so having many of them (hundreds) uses a lot of space
2459	and time, so using the defaults of five priorities (-2 .. +2) is usually	3041	and time, so using the defaults of five priorities (-2 .. +2) is usually
2460	fine.	3042	fine.
2461		3043
2462	If your embedding app does not need any priorities, defining these both to	3044	If your embedding application does not need any priorities, defining these both to
2463	C<0> will save some memory and cpu.	3045	C<0> will save some memory and CPU.
2464		3046
2465	=item EV_PERIODIC_ENABLE	3047	=item EV_PERIODIC_ENABLE
2466		3048
2467	If undefined or defined to be C<1>, then periodic timers are supported. If	3049	If undefined or defined to be C<1>, then periodic timers are supported. If
2468	defined to be C<0>, then they are not. Disabling them saves a few kB of	3050	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2487	=item EV_FORK_ENABLE	3069	=item EV_FORK_ENABLE
2488		3070
2489	If undefined or defined to be C<1>, then fork watchers are supported. If	3071	If undefined or defined to be C<1>, then fork watchers are supported. If
2490	defined to be C<0>, then they are not.	3072	defined to be C<0>, then they are not.
2491		3073
		3074	=item EV_ASYNC_ENABLE
		3075
		3076	If undefined or defined to be C<1>, then async watchers are supported. If
		3077	defined to be C<0>, then they are not.
		3078
2492	=item EV_MINIMAL	3079	=item EV_MINIMAL
2493		3080
2494	If you need to shave off some kilobytes of code at the expense of some	3081	If you need to shave off some kilobytes of code at the expense of some
2495	speed, define this symbol to C<1>. Currently only used for gcc to override	3082	speed, define this symbol to C<1>. Currently this is used to override some
2496	some inlining decisions, saves roughly 30% codesize of amd64.	3083	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3084	much smaller 2-heap for timer management over the default 4-heap.
2497		3085
2498	=item EV_PID_HASHSIZE	3086	=item EV_PID_HASHSIZE
2499		3087
2500	C<ev_child> watchers use a small hash table to distribute workload by	3088	C<ev_child> watchers use a small hash table to distribute workload by
2501	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3089	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2502	than enough. If you need to manage thousands of children you might want to	3090	than enough. If you need to manage thousands of children you might want to
2503	increase this value (I<must> be a power of two).	3091	increase this value (I<must> be a power of two).
2504		3092
2505	=item EV_INOTIFY_HASHSIZE	3093	=item EV_INOTIFY_HASHSIZE
2506		3094
2507	C<ev_staz> watchers use a small hash table to distribute workload by	3095	C<ev_stat> watchers use a small hash table to distribute workload by
2508	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3096	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2509	usually more than enough. If you need to manage thousands of C<ev_stat>	3097	usually more than enough. If you need to manage thousands of C<ev_stat>
2510	watchers you might want to increase this value (I<must> be a power of	3098	watchers you might want to increase this value (I<must> be a power of
2511	two).	3099	two).
2512		3100
		3101	=item EV_USE_4HEAP
		3102
		3103	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3104	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3105	to C<1>. The 4-heap uses more complicated (longer) code but has
		3106	noticeably faster performance with many (thousands) of watchers.
		3107
		3108	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3109	(disabled).
		3110
		3111	=item EV_HEAP_CACHE_AT
		3112
		3113	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3114	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3115	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3116	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3117	but avoids random read accesses on heap changes. This improves performance
		3118	noticeably with with many (hundreds) of watchers.
		3119
		3120	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3121	(disabled).
		3122
		3123	=item EV_VERIFY
		3124
		3125	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3126	be done: If set to C<0>, no internal verification code will be compiled
		3127	in. If set to C<1>, then verification code will be compiled in, but not
		3128	called. If set to C<2>, then the internal verification code will be
		3129	called once per loop, which can slow down libev. If set to C<3>, then the
		3130	verification code will be called very frequently, which will slow down
		3131	libev considerably.
		3132
		3133	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3134	C<0.>
		3135
2513	=item EV_COMMON	3136	=item EV_COMMON
2514		3137
2515	By default, all watchers have a C<void *data> member. By redefining	3138	By default, all watchers have a C<void *data> member. By redefining
2516	this macro to a something else you can include more and other types of	3139	this macro to a something else you can include more and other types of
2517	members. You have to define it each time you include one of the files,	3140	members. You have to define it each time you include one of the files,
2518	though, and it must be identical each time.	3141	though, and it must be identical each time.
2519		3142
2520	For example, the perl EV module uses something like this:	3143	For example, the perl EV module uses something like this:
2521		3144
2522	#define EV_COMMON \	3145	#define EV_COMMON \
2523	SV *self; /* contains this struct */ \	3146	SV *self; /* contains this struct */ \
2524	SV *cb_sv, *fh /* note no trailing ";" */	3147	SV *cb_sv, *fh /* note no trailing ";" */
2525		3148
2526	=item EV_CB_DECLARE (type)	3149	=item EV_CB_DECLARE (type)
2527		3150
2528	=item EV_CB_INVOKE (watcher, revents)	3151	=item EV_CB_INVOKE (watcher, revents)
2529		3152
…		…
2536	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3159	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2537	method calls instead of plain function calls in C++.	3160	method calls instead of plain function calls in C++.
2538		3161
2539	=head2 EXPORTED API SYMBOLS	3162	=head2 EXPORTED API SYMBOLS
2540		3163
2541	If you need to re-export the API (e.g. via a dll) and you need a list of	3164	If you need to re-export the API (e.g. via a DLL) and you need a list of
2542	exported symbols, you can use the provided F<Symbol.*> files which list	3165	exported symbols, you can use the provided F<Symbol.*> files which list
2543	all public symbols, one per line:	3166	all public symbols, one per line:
2544		3167
2545	Symbols.ev for libev proper	3168	Symbols.ev for libev proper
2546	Symbols.event for the libevent emulation	3169	Symbols.event for the libevent emulation
2547		3170
2548	This can also be used to rename all public symbols to avoid clashes with	3171	This can also be used to rename all public symbols to avoid clashes with
2549	multiple versions of libev linked together (which is obviously bad in	3172	multiple versions of libev linked together (which is obviously bad in
2550	itself, but sometimes it is inconvinient to avoid this).	3173	itself, but sometimes it is inconvenient to avoid this).
2551		3174
2552	A sed command like this will create wrapper C<#define>'s that you need to	3175	A sed command like this will create wrapper C<#define>'s that you need to
2553	include before including F<ev.h>:	3176	include before including F<ev.h>:
2554		3177
2555	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3178	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2572	file.	3195	file.
2573		3196
2574	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3197	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2575	that everybody includes and which overrides some configure choices:	3198	that everybody includes and which overrides some configure choices:
2576		3199
2577	#define EV_MINIMAL 1	3200	#define EV_MINIMAL 1
2578	#define EV_USE_POLL 0	3201	#define EV_USE_POLL 0
2579	#define EV_MULTIPLICITY 0	3202	#define EV_MULTIPLICITY 0
2580	#define EV_PERIODIC_ENABLE 0	3203	#define EV_PERIODIC_ENABLE 0
2581	#define EV_STAT_ENABLE 0	3204	#define EV_STAT_ENABLE 0
2582	#define EV_FORK_ENABLE 0	3205	#define EV_FORK_ENABLE 0
2583	#define EV_CONFIG_H <config.h>	3206	#define EV_CONFIG_H <config.h>
2584	#define EV_MINPRI 0	3207	#define EV_MINPRI 0
2585	#define EV_MAXPRI 0	3208	#define EV_MAXPRI 0
2586		3209
2587	#include "ev++.h"	3210	#include "ev++.h"
2588		3211
2589	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3212	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2590		3213
2591	#include "ev_cpp.h"	3214	#include "ev_cpp.h"
2592	#include "ev.c"	3215	#include "ev.c"
		3216
		3217
		3218	=head1 THREADS AND COROUTINES
		3219
		3220	=head2 THREADS
		3221
		3222	Libev itself is completely thread-safe, but it uses no locking. This
		3223	means that you can use as many loops as you want in parallel, as long as
		3224	only one thread ever calls into one libev function with the same loop
		3225	parameter.
		3226
		3227	Or put differently: calls with different loop parameters can be done in
		3228	parallel from multiple threads, calls with the same loop parameter must be
		3229	done serially (but can be done from different threads, as long as only one
		3230	thread ever is inside a call at any point in time, e.g. by using a mutex
		3231	per loop).
		3232
		3233	If you want to know which design (one loop, locking, or multiple loops
		3234	without or something else still) is best for your problem, then I cannot
		3235	help you. I can give some generic advice however:
		3236
		3237	=over 4
		3238
		3239	=item * most applications have a main thread: use the default libev loop
		3240	in that thread, or create a separate thread running only the default loop.
		3241
		3242	This helps integrating other libraries or software modules that use libev
		3243	themselves and don't care/know about threading.
		3244
		3245	=item * one loop per thread is usually a good model.
		3246
		3247	Doing this is almost never wrong, sometimes a better-performance model
		3248	exists, but it is always a good start.
		3249
		3250	=item * other models exist, such as the leader/follower pattern, where one
		3251	loop is handed through multiple threads in a kind of round-robin fashion.
		3252
		3253	Choosing a model is hard - look around, learn, know that usually you can do
		3254	better than you currently do :-)
		3255
		3256	=item * often you need to talk to some other thread which blocks in the
		3257	event loop - C<ev_async> watchers can be used to wake them up from other
		3258	threads safely (or from signal contexts...).
		3259
		3260	=back
		3261
		3262	=head2 COROUTINES
		3263
		3264	Libev is much more accommodating to coroutines ("cooperative threads"):
		3265	libev fully supports nesting calls to it's functions from different
		3266	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3267	different coroutines and switch freely between both coroutines running the
		3268	loop, as long as you don't confuse yourself). The only exception is that
		3269	you must not do this from C<ev_periodic> reschedule callbacks.
		3270
		3271	Care has been invested into making sure that libev does not keep local
		3272	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3273	switches.
2593		3274
2594		3275
2595	=head1 COMPLEXITIES	3276	=head1 COMPLEXITIES
2596		3277
2597	In this section the complexities of (many of) the algorithms used inside	3278	In this section the complexities of (many of) the algorithms used inside
…		…
2608		3289
2609	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3290	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2610		3291
2611	This means that, when you have a watcher that triggers in one hour and	3292	This means that, when you have a watcher that triggers in one hour and
2612	there are 100 watchers that would trigger before that then inserting will	3293	there are 100 watchers that would trigger before that then inserting will
2613	have to skip those 100 watchers.	3294	have to skip roughly seven (C<ld 100>) of these watchers.
2614		3295
2615	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3296	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2616		3297
2617	That means that for changing a timer costs less than removing/adding them	3298	That means that changing a timer costs less than removing/adding them
2618	as only the relative motion in the event queue has to be paid for.	3299	as only the relative motion in the event queue has to be paid for.
2619		3300
2620	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3301	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2621		3302
2622	These just add the watcher into an array or at the head of a list.	3303	These just add the watcher into an array or at the head of a list.
		3304
2623	=item Stopping check/prepare/idle watchers: O(1)	3305	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2624		3306
2625	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3307	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2626		3308
2627	These watchers are stored in lists then need to be walked to find the	3309	These watchers are stored in lists then need to be walked to find the
2628	correct watcher to remove. The lists are usually short (you don't usually	3310	correct watcher to remove. The lists are usually short (you don't usually
2629	have many watchers waiting for the same fd or signal).	3311	have many watchers waiting for the same fd or signal).
2630		3312
2631	=item Finding the next timer per loop iteration: O(1)	3313	=item Finding the next timer in each loop iteration: O(1)
		3314
		3315	By virtue of using a binary or 4-heap, the next timer is always found at a
		3316	fixed position in the storage array.
2632		3317
2633	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3318	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2634		3319
2635	A change means an I/O watcher gets started or stopped, which requires	3320	A change means an I/O watcher gets started or stopped, which requires
2636	libev to recalculate its status (and possibly tell the kernel).	3321	libev to recalculate its status (and possibly tell the kernel, depending
		3322	on backend and whether C<ev_io_set> was used).
2637		3323
2638	=item Activating one watcher: O(1)	3324	=item Activating one watcher (putting it into the pending state): O(1)
2639		3325
2640	=item Priority handling: O(number_of_priorities)	3326	=item Priority handling: O(number_of_priorities)
2641		3327
2642	Priorities are implemented by allocating some space for each	3328	Priorities are implemented by allocating some space for each
2643	priority. When doing priority-based operations, libev usually has to	3329	priority. When doing priority-based operations, libev usually has to
2644	linearly search all the priorities.	3330	linearly search all the priorities, but starting/stopping and activating
		3331	watchers becomes O(1) w.r.t. priority handling.
		3332
		3333	=item Sending an ev_async: O(1)
		3334
		3335	=item Processing ev_async_send: O(number_of_async_watchers)
		3336
		3337	=item Processing signals: O(max_signal_number)
		3338
		3339	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3340	calls in the current loop iteration. Checking for async and signal events
		3341	involves iterating over all running async watchers or all signal numbers.
2645		3342
2646	=back	3343	=back
2647		3344
2648		3345
		3346	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3347
		3348	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3349	requires, and its I/O model is fundamentally incompatible with the POSIX
		3350	model. Libev still offers limited functionality on this platform in
		3351	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3352	descriptors. This only applies when using Win32 natively, not when using
		3353	e.g. cygwin.
		3354
		3355	Lifting these limitations would basically require the full
		3356	re-implementation of the I/O system. If you are into these kinds of
		3357	things, then note that glib does exactly that for you in a very portable
		3358	way (note also that glib is the slowest event library known to man).
		3359
		3360	There is no supported compilation method available on windows except
		3361	embedding it into other applications.
		3362
		3363	Not a libev limitation but worth mentioning: windows apparently doesn't
		3364	accept large writes: instead of resulting in a partial write, windows will
		3365	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3366	so make sure you only write small amounts into your sockets (less than a
		3367	megabyte seems safe, but thsi apparently depends on the amount of memory
		3368	available).
		3369
		3370	Due to the many, low, and arbitrary limits on the win32 platform and
		3371	the abysmal performance of winsockets, using a large number of sockets
		3372	is not recommended (and not reasonable). If your program needs to use
		3373	more than a hundred or so sockets, then likely it needs to use a totally
		3374	different implementation for windows, as libev offers the POSIX readiness
		3375	notification model, which cannot be implemented efficiently on windows
		3376	(Microsoft monopoly games).
		3377
		3378	A typical way to use libev under windows is to embed it (see the embedding
		3379	section for details) and use the following F<evwrap.h> header file instead
		3380	of F<ev.h>:
		3381
		3382	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3383	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3384
		3385	#include "ev.h"
		3386
		3387	And compile the following F<evwrap.c> file into your project (make sure
		3388	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3389
		3390	#include "evwrap.h"
		3391	#include "ev.c"
		3392
		3393	=over 4
		3394
		3395	=item The winsocket select function
		3396
		3397	The winsocket C<select> function doesn't follow POSIX in that it
		3398	requires socket I<handles> and not socket I<file descriptors> (it is
		3399	also extremely buggy). This makes select very inefficient, and also
		3400	requires a mapping from file descriptors to socket handles (the Microsoft
		3401	C runtime provides the function C<_open_osfhandle> for this). See the
		3402	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3403	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3404
		3405	The configuration for a "naked" win32 using the Microsoft runtime
		3406	libraries and raw winsocket select is:
		3407
		3408	#define EV_USE_SELECT 1
		3409	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3410
		3411	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3412	complexity in the O(n²) range when using win32.
		3413
		3414	=item Limited number of file descriptors
		3415
		3416	Windows has numerous arbitrary (and low) limits on things.
		3417
		3418	Early versions of winsocket's select only supported waiting for a maximum
		3419	of C<64> handles (probably owning to the fact that all windows kernels
		3420	can only wait for C<64> things at the same time internally; Microsoft
		3421	recommends spawning a chain of threads and wait for 63 handles and the
		3422	previous thread in each. Great).
		3423
		3424	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3425	to some high number (e.g. C<2048>) before compiling the winsocket select
		3426	call (which might be in libev or elsewhere, for example, perl does its own
		3427	select emulation on windows).
		3428
		3429	Another limit is the number of file descriptors in the Microsoft runtime
		3430	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3431	or something like this inside Microsoft). You can increase this by calling
		3432	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3433	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3434	libraries.
		3435
		3436	This might get you to about C<512> or C<2048> sockets (depending on
		3437	windows version and/or the phase of the moon). To get more, you need to
		3438	wrap all I/O functions and provide your own fd management, but the cost of
		3439	calling select (O(n²)) will likely make this unworkable.
		3440
		3441	=back
		3442
		3443
		3444	=head1 PORTABILITY REQUIREMENTS
		3445
		3446	In addition to a working ISO-C implementation, libev relies on a few
		3447	additional extensions:
		3448
		3449	=over 4
		3450
		3451	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3452	calling conventions regardless of C<ev_watcher_type *>.
		3453
		3454	Libev assumes not only that all watcher pointers have the same internal
		3455	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3456	assumes that the same (machine) code can be used to call any watcher
		3457	callback: The watcher callbacks have different type signatures, but libev
		3458	calls them using an C<ev_watcher *> internally.
		3459
		3460	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3461
		3462	The type C<sig_atomic_t volatile> (or whatever is defined as
		3463	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3464	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3465	believed to be sufficiently portable.
		3466
		3467	=item C<sigprocmask> must work in a threaded environment
		3468
		3469	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3470	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3471	pthread implementations will either allow C<sigprocmask> in the "main
		3472	thread" or will block signals process-wide, both behaviours would
		3473	be compatible with libev. Interaction between C<sigprocmask> and
		3474	C<pthread_sigmask> could complicate things, however.
		3475
		3476	The most portable way to handle signals is to block signals in all threads
		3477	except the initial one, and run the default loop in the initial thread as
		3478	well.
		3479
		3480	=item C<long> must be large enough for common memory allocation sizes
		3481
		3482	To improve portability and simplify using libev, libev uses C<long>
		3483	internally instead of C<size_t> when allocating its data structures. On
		3484	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3485	is still at least 31 bits everywhere, which is enough for hundreds of
		3486	millions of watchers.
		3487
		3488	=item C<double> must hold a time value in seconds with enough accuracy
		3489
		3490	The type C<double> is used to represent timestamps. It is required to
		3491	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3492	enough for at least into the year 4000. This requirement is fulfilled by
		3493	implementations implementing IEEE 754 (basically all existing ones).
		3494
		3495	=back
		3496
		3497	If you know of other additional requirements drop me a note.
		3498
		3499
		3500	=head1 COMPILER WARNINGS
		3501
		3502	Depending on your compiler and compiler settings, you might get no or a
		3503	lot of warnings when compiling libev code. Some people are apparently
		3504	scared by this.
		3505
		3506	However, these are unavoidable for many reasons. For one, each compiler
		3507	has different warnings, and each user has different tastes regarding
		3508	warning options. "Warn-free" code therefore cannot be a goal except when
		3509	targeting a specific compiler and compiler-version.
		3510
		3511	Another reason is that some compiler warnings require elaborate
		3512	workarounds, or other changes to the code that make it less clear and less
		3513	maintainable.
		3514
		3515	And of course, some compiler warnings are just plain stupid, or simply
		3516	wrong (because they don't actually warn about the condition their message
		3517	seems to warn about).
		3518
		3519	While libev is written to generate as few warnings as possible,
		3520	"warn-free" code is not a goal, and it is recommended not to build libev
		3521	with any compiler warnings enabled unless you are prepared to cope with
		3522	them (e.g. by ignoring them). Remember that warnings are just that:
		3523	warnings, not errors, or proof of bugs.
		3524
		3525
		3526	=head1 VALGRIND
		3527
		3528	Valgrind has a special section here because it is a popular tool that is
		3529	highly useful, but valgrind reports are very hard to interpret.
		3530
		3531	If you think you found a bug (memory leak, uninitialised data access etc.)
		3532	in libev, then check twice: If valgrind reports something like:
		3533
		3534	==2274== definitely lost: 0 bytes in 0 blocks.
		3535	==2274== possibly lost: 0 bytes in 0 blocks.
		3536	==2274== still reachable: 256 bytes in 1 blocks.
		3537
		3538	Then there is no memory leak. Similarly, under some circumstances,
		3539	valgrind might report kernel bugs as if it were a bug in libev, or it
		3540	might be confused (it is a very good tool, but only a tool).
		3541
		3542	If you are unsure about something, feel free to contact the mailing list
		3543	with the full valgrind report and an explanation on why you think this is
		3544	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3545	no bug" answer and take the chance of learning how to interpret valgrind
		3546	properly.
		3547
		3548	If you need, for some reason, empty reports from valgrind for your project
		3549	I suggest using suppression lists.
		3550
		3551
2649	=head1 AUTHOR	3552	=head1 AUTHOR
2650		3553
2651	Marc Lehmann <libev@schmorp.de>.	3554	Marc Lehmann <libev@schmorp.de>.
2652		3555

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