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Revision 1.107 by root, Mon Dec 24 04:34:00 2007 UTC vs.
Revision 1.181 by root, Fri Sep 19 03:47:50 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#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
…		…
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	=head2 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	=head2 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
…		…
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	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
312	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
313		356
314	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
315	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
316	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
317	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
318	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
319	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
320		367
321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
322		369
323	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
324	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
325	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
326	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
328	performance tips.	375	performance tips.
329		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
330	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
331		381
332	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
333	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
334	like O(total_fds) where n is the total number of fds (or the highest fd),	384	like O(total_fds) where n is the total number of fds (or the highest fd),
335	epoll scales either O(1) or O(active_fds). The epoll design has a number	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
336	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
337	cases and rewiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
338	support for dup.	388	support for dup.
339		389
340	While stopping, setting and starting an I/O watcher in the same iteration	390	While stopping, setting and starting an I/O watcher in the same iteration
341	will result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
342	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
344	very well if you register events for both fds.	394	very well if you register events for both fds.
345		395
346	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
…		…
349		399
350	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
351	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible, i.e.
352	keep at least one watcher active per fd at all times.	402	keep at least one watcher active per fd at all times.
353		403
354	While nominally embeddeble in other event loops, this feature is broken in	404	While nominally embeddable in other event loops, this feature is broken in
355	all kernel versions tested so far.	405	all kernel versions tested so far.
		406
		407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		408	C<EVBACKEND_POLL>.
356		409
357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
358		411
359	Kqueue deserves special mention, as at the time of this writing, it	412	Kqueue deserves special mention, as at the time of this writing, it
360	was broken on all BSDs except NetBSD (usually it doesn't work reliably	413	was broken on all BSDs except NetBSD (usually it doesn't work reliably
361	with anything but sockets and pipes, except on Darwin, where of course	414	with anything but sockets and pipes, except on Darwin, where of course
362	it's completely useless). For this reason it's not being "autodetected"	415	it's completely useless). For this reason it's not being "auto-detected"
363	unless you explicitly specify it explicitly in the flags (i.e. using	416	unless you explicitly specify it explicitly in the flags (i.e. using
364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
365	system like NetBSD.	418	system like NetBSD.
366		419
367	You still can embed kqueue into a normal poll or select backend and use it	420	You still can embed kqueue into a normal poll or select backend and use it
…		…
369	the target platform). See C<ev_embed> watchers for more info.	422	the target platform). See C<ev_embed> watchers for more info.
370		423
371	It scales in the same way as the epoll backend, but the interface to the	424	It scales in the same way as the epoll backend, but the interface to the
372	kernel is more efficient (which says nothing about its actual speed, of	425	kernel is more efficient (which says nothing about its actual speed, of
373	course). While stopping, setting and starting an I/O watcher does never	426	course). While stopping, setting and starting an I/O watcher does never
374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
375	two event changes per incident, support for C<fork ()> is very bad and it	428	two event changes per incident, support for C<fork ()> is very bad and it
376	drops fds silently in similarly hard-to-detect cases.	429	drops fds silently in similarly hard-to-detect cases.
377		430
378	This backend usually performs well under most conditions.	431	This backend usually performs well under most conditions.
379		432
…		…
382	almost everywhere, you should only use it when you have a lot of sockets	435	almost everywhere, you should only use it when you have a lot of sockets
383	(for which it usually works), by embedding it into another event loop	436	(for which it usually works), by embedding it into another event loop
384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
385	sockets.	438	sockets.
386		439
		440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		442	C<NOTE_EOF>.
		443
387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	444	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
388		445
389	This is not implemented yet (and might never be, unless you send me an	446	This is not implemented yet (and might never be, unless you send me an
390	implementation). According to reports, C</dev/poll> only supports sockets	447	implementation). According to reports, C</dev/poll> only supports sockets
391	and is not embeddable, which would limit the usefulness of this backend	448	and is not embeddable, which would limit the usefulness of this backend
…		…
394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	451	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
395		452
396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	453	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
397	it's really slow, but it still scales very well (O(active_fds)).	454	it's really slow, but it still scales very well (O(active_fds)).
398		455
399	Please note that solaris event ports can deliver a lot of spurious	456	Please note that Solaris event ports can deliver a lot of spurious
400	notifications, so you need to use non-blocking I/O or other means to avoid	457	notifications, so you need to use non-blocking I/O or other means to avoid
401	blocking when no data (or space) is available.	458	blocking when no data (or space) is available.
402		459
403	While this backend scales well, it requires one system call per active	460	While this backend scales well, it requires one system call per active
404	file descriptor per loop iteration. For small and medium numbers of file	461	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	463	might perform better.
407		464
		465	On the positive side, ignoring the spurious readiness notifications, this
		466	backend actually performed to specification in all tests and is fully
		467	embeddable, which is a rare feat among the OS-specific backends.
		468
		469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		470	C<EVBACKEND_POLL>.
		471
408	=item C<EVBACKEND_ALL>	472	=item C<EVBACKEND_ALL>
409		473
410	Try all backends (even potentially broken ones that wouldn't be tried	474	Try all backends (even potentially broken ones that wouldn't be tried
411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	475	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	476	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413		477
414	It is definitely not recommended to use this flag.	478	It is definitely not recommended to use this flag.
415		479
416	=back	480	=back
417		481
418	If one or more of these are ored into the flags value, then only these	482	If one or more of these are or'ed into the flags value, then only these
419	backends will be tried (in the reverse order as given here). If none are	483	backends will be tried (in the reverse order as listed here). If none are
420	specified, most compiled-in backend will be tried, usually in reverse	484	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		485
423	The most typical usage is like this:	486	The most typical usage is like this:
424		487
425	if (!ev_default_loop (0))	488	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
427		490
428	Restrict libev to the select and poll backends, and do not allow	491	Restrict libev to the select and poll backends, and do not allow
429	environment settings to be taken into account:	492	environment settings to be taken into account:
430		493
431	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
432		495
433	Use whatever libev has to offer, but make sure that kqueue is used if	496	Use whatever libev has to offer, but make sure that kqueue is used if
434	available (warning, breaks stuff, best use only with your own private	497	available (warning, breaks stuff, best use only with your own private
435	event loop and only if you know the OS supports your types of fds):	498	event loop and only if you know the OS supports your types of fds):
436		499
437	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
438		501
439	=item struct ev_loop *ev_loop_new (unsigned int flags)	502	=item struct ev_loop *ev_loop_new (unsigned int flags)
440		503
441	Similar to C<ev_default_loop>, but always creates a new event loop that is	504	Similar to C<ev_default_loop>, but always creates a new event loop that is
442	always distinct from the default loop. Unlike the default loop, it cannot	505	always distinct from the default loop. Unlike the default loop, it cannot
443	handle signal and child watchers, and attempts to do so will be greeted by	506	handle signal and child watchers, and attempts to do so will be greeted by
444	undefined behaviour (or a failed assertion if assertions are enabled).	507	undefined behaviour (or a failed assertion if assertions are enabled).
445		508
		509	Note that this function I<is> thread-safe, and the recommended way to use
		510	libev with threads is indeed to create one loop per thread, and using the
		511	default loop in the "main" or "initial" thread.
		512
446	Example: Try to create a event loop that uses epoll and nothing else.	513	Example: Try to create a event loop that uses epoll and nothing else.
447		514
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	515	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	516	if (!epoller)
450	fatal ("no epoll found here, maybe it hides under your chair");	517	fatal ("no epoll found here, maybe it hides under your chair");
451		518
452	=item ev_default_destroy ()	519	=item ev_default_destroy ()
453		520
454	Destroys the default loop again (frees all memory and kernel state	521	Destroys the default loop again (frees all memory and kernel state
455	etc.). None of the active event watchers will be stopped in the normal	522	etc.). None of the active event watchers will be stopped in the normal
456	sense, so e.g. C<ev_is_active> might still return true. It is your	523	sense, so e.g. C<ev_is_active> might still return true. It is your
457	responsibility to either stop all watchers cleanly yoursef I<before>	524	responsibility to either stop all watchers cleanly yourself I<before>
458	calling this function, or cope with the fact afterwards (which is usually	525	calling this function, or cope with the fact afterwards (which is usually
459	the easiest thing, you can just ignore the watchers and/or C<free ()> them	526	the easiest thing, you can just ignore the watchers and/or C<free ()> them
460	for example).	527	for example).
461		528
462	Note that certain global state, such as signal state, will not be freed by	529	Note that certain global state, such as signal state, will not be freed by
…		…
473	Like C<ev_default_destroy>, but destroys an event loop created by an	540	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	541	earlier call to C<ev_loop_new>.
475		542
476	=item ev_default_fork ()	543	=item ev_default_fork ()
477		544
		545	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	546	to reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	547	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	548	the child process (or both child and parent, but that again makes little
481	again makes little sense).	549	sense). You I<must> call it in the child before using any of the libev
		550	functions, and it will only take effect at the next C<ev_loop> iteration.
482		551
483	You I<must> call this function in the child process after forking if and	552	On the other hand, you only need to call this function in the child
484	only if you want to use the event library in both processes. If you just	553	process if and only if you want to use the event library in the child. If
485	fork+exec, you don't have to call it.	554	you just fork+exec, you don't have to call it at all.
486		555
487	The function itself is quite fast and it's usually not a problem to call	556	The function itself is quite fast and it's usually not a problem to call
488	it just in case after a fork. To make this easy, the function will fit in	557	it just in case after a fork. To make this easy, the function will fit in
489	quite nicely into a call to C<pthread_atfork>:	558	quite nicely into a call to C<pthread_atfork>:
490		559
491	pthread_atfork (0, 0, ev_default_fork);	560	pthread_atfork (0, 0, ev_default_fork);
492		561
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496
497	=item ev_loop_fork (loop)	562	=item ev_loop_fork (loop)
498		563
499	Like C<ev_default_fork>, but acts on an event loop created by	564	Like C<ev_default_fork>, but acts on an event loop created by
500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
501	after fork, and how you do this is entirely your own problem.	566	after fork, and how you do this is entirely your own problem.
		567
		568	=item int ev_is_default_loop (loop)
		569
		570	Returns true when the given loop actually is the default loop, false otherwise.
502		571
503	=item unsigned int ev_loop_count (loop)	572	=item unsigned int ev_loop_count (loop)
504		573
505	Returns the count of loop iterations for the loop, which is identical to	574	Returns the count of loop iterations for the loop, which is identical to
506	the number of times libev did poll for new events. It starts at C<0> and	575	the number of times libev did poll for new events. It starts at C<0> and
…		…
521	received events and started processing them. This timestamp does not	590	received events and started processing them. This timestamp does not
522	change as long as callbacks are being processed, and this is also the base	591	change as long as callbacks are being processed, and this is also the base
523	time used for relative timers. You can treat it as the timestamp of the	592	time used for relative timers. You can treat it as the timestamp of the
524	event occurring (or more correctly, libev finding out about it).	593	event occurring (or more correctly, libev finding out about it).
525		594
		595	=item ev_now_update (loop)
		596
		597	Establishes the current time by querying the kernel, updating the time
		598	returned by C<ev_now ()> in the progress. This is a costly operation and
		599	is usually done automatically within C<ev_loop ()>.
		600
		601	This function is rarely useful, but when some event callback runs for a
		602	very long time without entering the event loop, updating libev's idea of
		603	the current time is a good idea.
		604
		605	See also "The special problem of time updates" in the C<ev_timer> section.
		606
526	=item ev_loop (loop, int flags)	607	=item ev_loop (loop, int flags)
527		608
528	Finally, this is it, the event handler. This function usually is called	609	Finally, this is it, the event handler. This function usually is called
529	after you initialised all your watchers and you want to start handling	610	after you initialised all your watchers and you want to start handling
530	events.	611	events.
…		…
541	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
542	those events and any outstanding ones, but will not block your process in	623	those events and any outstanding ones, but will not block your process in
543	case there are no events and will return after one iteration of the loop.	624	case there are no events and will return after one iteration of the loop.
544		625
545	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
546	neccessary) and will handle those and any outstanding ones. It will block	627	necessary) and will handle those and any outstanding ones. It will block
547	your process until at least one new event arrives, and will return after	628	your process until at least one new event arrives, and will return after
548	one iteration of the loop. This is useful if you are waiting for some	629	one iteration of the loop. This is useful if you are waiting for some
549	external event in conjunction with something not expressible using other	630	external event in conjunction with something not expressible using other
550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
551	usually a better approach for this kind of thing.	632	usually a better approach for this kind of thing.
552		633
553	Here are the gory details of what C<ev_loop> does:	634	Here are the gory details of what C<ev_loop> does:
554		635
555	- Before the first iteration, call any pending watchers.	636	- Before the first iteration, call any pending watchers.
556	* If there are no active watchers (reference count is zero), return.	637	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- Queue all prepare watchers and then call all outstanding watchers.	638	- If a fork was detected (by any means), queue and call all fork watchers.
		639	- Queue and call all prepare watchers.
558	- If we have been forked, recreate the kernel state.	640	- If we have been forked, detach and recreate the kernel state
		641	as to not disturb the other process.
559	- Update the kernel state with all outstanding changes.	642	- Update the kernel state with all outstanding changes.
560	- Update the "event loop time".	643	- Update the "event loop time" (ev_now ()).
561	- Calculate for how long to block.	644	- Calculate for how long to sleep or block, if at all
		645	(active idle watchers, EVLOOP_NONBLOCK or not having
		646	any active watchers at all will result in not sleeping).
		647	- Sleep if the I/O and timer collect interval say so.
562	- Block the process, waiting for any events.	648	- Block the process, waiting for any events.
563	- Queue all outstanding I/O (fd) events.	649	- Queue all outstanding I/O (fd) events.
564	- Update the "event loop time" and do time jump handling.	650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
565	- Queue all outstanding timers.	651	- Queue all outstanding timers.
566	- Queue all outstanding periodics.	652	- Queue all outstanding periodics.
567	- If no events are pending now, queue all idle watchers.	653	- Unless any events are pending now, queue all idle watchers.
568	- Queue all check watchers.	654	- Queue all check watchers.
569	- Call all queued watchers in reverse order (i.e. check watchers first).	655	- Call all queued watchers in reverse order (i.e. check watchers first).
570	Signals and child watchers are implemented as I/O watchers, and will	656	Signals and child watchers are implemented as I/O watchers, and will
571	be handled here by queueing them when their watcher gets executed.	657	be handled here by queueing them when their watcher gets executed.
572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	658	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573	were used, return, otherwise continue with step *.	659	were used, or there are no active watchers, return, otherwise
		660	continue with step *.
574		661
575	Example: Queue some jobs and then loop until no events are outsanding	662	Example: Queue some jobs and then loop until no events are outstanding
576	anymore.	663	anymore.
577		664
578	... queue jobs here, make sure they register event watchers as long	665	... queue jobs here, make sure they register event watchers as long
579	... as they still have work to do (even an idle watcher will do..)	666	... as they still have work to do (even an idle watcher will do..)
580	ev_loop (my_loop, 0);	667	ev_loop (my_loop, 0);
581	... jobs done. yeah!	668	... jobs done or somebody called unloop. yeah!
582		669
583	=item ev_unloop (loop, how)	670	=item ev_unloop (loop, how)
584		671
585	Can be used to make a call to C<ev_loop> return early (but only after it	672	Can be used to make a call to C<ev_loop> return early (but only after it
586	has processed all outstanding events). The C<how> argument must be either	673	has processed all outstanding events). The C<how> argument must be either
587	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	674	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
588	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	675	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		676
		677	This "unloop state" will be cleared when entering C<ev_loop> again.
589		678
590	=item ev_ref (loop)	679	=item ev_ref (loop)
591		680
592	=item ev_unref (loop)	681	=item ev_unref (loop)
593		682
…		…
598	returning, ev_unref() after starting, and ev_ref() before stopping it. For	687	returning, ev_unref() after starting, and ev_ref() before stopping it. For
599	example, libev itself uses this for its internal signal pipe: It is not	688	example, libev itself uses this for its internal signal pipe: It is not
600	visible to the libev user and should not keep C<ev_loop> from exiting if	689	visible to the libev user and should not keep C<ev_loop> from exiting if
601	no event watchers registered by it are active. It is also an excellent	690	no event watchers registered by it are active. It is also an excellent
602	way to do this for generic recurring timers or from within third-party	691	way to do this for generic recurring timers or from within third-party
603	libraries. Just remember to I<unref after start> and I<ref before stop>.	692	libraries. Just remember to I<unref after start> and I<ref before stop>
		693	(but only if the watcher wasn't active before, or was active before,
		694	respectively).
604		695
605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606	running when nothing else is active.	697	running when nothing else is active.
607		698
608	struct ev_signal exitsig;	699	struct ev_signal exitsig;
609	ev_signal_init (&exitsig, sig_cb, SIGINT);	700	ev_signal_init (&exitsig, sig_cb, SIGINT);
610	ev_signal_start (loop, &exitsig);	701	ev_signal_start (loop, &exitsig);
611	evf_unref (loop);	702	evf_unref (loop);
612		703
613	Example: For some weird reason, unregister the above signal handler again.	704	Example: For some weird reason, unregister the above signal handler again.
614		705
615	ev_ref (loop);	706	ev_ref (loop);
616	ev_signal_stop (loop, &exitsig);	707	ev_signal_stop (loop, &exitsig);
617		708
618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	709	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
619		710
620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	711	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
621		712
622	These advanced functions influence the time that libev will spend waiting	713	These advanced functions influence the time that libev will spend waiting
623	for events. Both are by default C<0>, meaning that libev will try to	714	for events. Both time intervals are by default C<0>, meaning that libev
624	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	715	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		716	latency.
625		717
626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
627	allows libev to delay invocation of I/O and timer/periodic callbacks to	719	allows libev to delay invocation of I/O and timer/periodic callbacks
628	increase efficiency of loop iterations.	720	to increase efficiency of loop iterations (or to increase power-saving
		721	opportunities).
629		722
630	The background is that sometimes your program runs just fast enough to	723	The background is that sometimes your program runs just fast enough to
631	handle one (or very few) event(s) per loop iteration. While this makes	724	handle one (or very few) event(s) per loop iteration. While this makes
632	the program responsive, it also wastes a lot of CPU time to poll for new	725	the program responsive, it also wastes a lot of CPU time to poll for new
633	events, especially with backends like C<select ()> which have a high	726	events, especially with backends like C<select ()> which have a high
…		…
643	to spend more time collecting timeouts, at the expense of increased	736	to spend more time collecting timeouts, at the expense of increased
644	latency (the watcher callback will be called later). C<ev_io> watchers	737	latency (the watcher callback will be called later). C<ev_io> watchers
645	will not be affected. Setting this to a non-null value will not introduce	738	will not be affected. Setting this to a non-null value will not introduce
646	any overhead in libev.	739	any overhead in libev.
647		740
648	Many (busy) programs can usually benefit by setting the io collect	741	Many (busy) programs can usually benefit by setting the I/O collect
649	interval to a value near C<0.1> or so, which is often enough for	742	interval to a value near C<0.1> or so, which is often enough for
650	interactive servers (of course not for games), likewise for timeouts. It	743	interactive servers (of course not for games), likewise for timeouts. It
651	usually doesn't make much sense to set it to a lower value than C<0.01>,	744	usually doesn't make much sense to set it to a lower value than C<0.01>,
652	as this approsaches the timing granularity of most systems.	745	as this approaches the timing granularity of most systems.
		746
		747	Setting the I<timeout collect interval> can improve the opportunity for
		748	saving power, as the program will "bundle" timer callback invocations that
		749	are "near" in time together, by delaying some, thus reducing the number of
		750	times the process sleeps and wakes up again. Another useful technique to
		751	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		752	they fire on, say, one-second boundaries only.
		753
		754	=item ev_loop_verify (loop)
		755
		756	This function only does something when C<EV_VERIFY> support has been
		757	compiled in. It tries to go through all internal structures and checks
		758	them for validity. If anything is found to be inconsistent, it will print
		759	an error message to standard error and call C<abort ()>.
		760
		761	This can be used to catch bugs inside libev itself: under normal
		762	circumstances, this function will never abort as of course libev keeps its
		763	data structures consistent.
653		764
654	=back	765	=back
655		766
656		767
657	=head1 ANATOMY OF A WATCHER	768	=head1 ANATOMY OF A WATCHER
658		769
659	A watcher is a structure that you create and register to record your	770	A watcher is a structure that you create and register to record your
660	interest in some event. For instance, if you want to wait for STDIN to	771	interest in some event. For instance, if you want to wait for STDIN to
661	become readable, you would create an C<ev_io> watcher for that:	772	become readable, you would create an C<ev_io> watcher for that:
662		773
663	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
664	{	775	{
665	ev_io_stop (w);	776	ev_io_stop (w);
666	ev_unloop (loop, EVUNLOOP_ALL);	777	ev_unloop (loop, EVUNLOOP_ALL);
667	}	778	}
668		779
669	struct ev_loop *loop = ev_default_loop (0);	780	struct ev_loop *loop = ev_default_loop (0);
670	struct ev_io stdin_watcher;	781	struct ev_io stdin_watcher;
671	ev_init (&stdin_watcher, my_cb);	782	ev_init (&stdin_watcher, my_cb);
672	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
673	ev_io_start (loop, &stdin_watcher);	784	ev_io_start (loop, &stdin_watcher);
674	ev_loop (loop, 0);	785	ev_loop (loop, 0);
675		786
676	As you can see, you are responsible for allocating the memory for your	787	As you can see, you are responsible for allocating the memory for your
677	watcher structures (and it is usually a bad idea to do this on the stack,	788	watcher structures (and it is usually a bad idea to do this on the stack,
678	although this can sometimes be quite valid).	789	although this can sometimes be quite valid).
679		790
680	Each watcher structure must be initialised by a call to C<ev_init	791	Each watcher structure must be initialised by a call to C<ev_init
681	(watcher *, callback)>, which expects a callback to be provided. This	792	(watcher *, callback)>, which expects a callback to be provided. This
682	callback gets invoked each time the event occurs (or, in the case of io	793	callback gets invoked each time the event occurs (or, in the case of I/O
683	watchers, each time the event loop detects that the file descriptor given	794	watchers, each time the event loop detects that the file descriptor given
684	is readable and/or writable).	795	is readable and/or writable).
685		796
686	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
687	with arguments specific to this watcher type. There is also a macro	798	with arguments specific to this watcher type. There is also a macro
…		…
757	=item C<EV_FORK>	868	=item C<EV_FORK>
758		869
759	The event loop has been resumed in the child process after fork (see	870	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	871	C<ev_fork>).
761		872
		873	=item C<EV_ASYNC>
		874
		875	The given async watcher has been asynchronously notified (see C<ev_async>).
		876
762	=item C<EV_ERROR>	877	=item C<EV_ERROR>
763		878
764	An unspecified error has occured, the watcher has been stopped. This might	879	An unspecified error has occurred, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	880	happen because the watcher could not be properly started because libev
766	ran out of memory, a file descriptor was found to be closed or any other	881	ran out of memory, a file descriptor was found to be closed or any other
767	problem. You best act on it by reporting the problem and somehow coping	882	problem. You best act on it by reporting the problem and somehow coping
768	with the watcher being stopped.	883	with the watcher being stopped.
769		884
770	Libev will usually signal a few "dummy" events together with an error,	885	Libev will usually signal a few "dummy" events together with an error,
771	for example it might indicate that a fd is readable or writable, and if	886	for example it might indicate that a fd is readable or writable, and if
772	your callbacks is well-written it can just attempt the operation and cope	887	your callbacks is well-written it can just attempt the operation and cope
773	with the error from read() or write(). This will not work in multithreaded	888	with the error from read() or write(). This will not work in multi-threaded
774	programs, though, so beware.	889	programs, though, so beware.
775		890
776	=back	891	=back
777		892
778	=head2 GENERIC WATCHER FUNCTIONS	893	=head2 GENERIC WATCHER FUNCTIONS
…		…
808	Although some watcher types do not have type-specific arguments	923	Although some watcher types do not have type-specific arguments
809	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
810		925
811	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
812		927
813	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
814	calls into a single call. This is the most convinient method to initialise	929	calls into a single call. This is the most convenient method to initialise
815	a watcher. The same limitations apply, of course.	930	a watcher. The same limitations apply, of course.
816		931
817	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
818		933
819	Starts (activates) the given watcher. Only active watchers will receive	934	Starts (activates) the given watcher. Only active watchers will receive
…		…
902	to associate arbitrary data with your watcher. If you need more data and	1017	to associate arbitrary data with your watcher. If you need more data and
903	don't want to allocate memory and store a pointer to it in that data	1018	don't want to allocate memory and store a pointer to it in that data
904	member, you can also "subclass" the watcher type and provide your own	1019	member, you can also "subclass" the watcher type and provide your own
905	data:	1020	data:
906		1021
907	struct my_io	1022	struct my_io
908	{	1023	{
909	struct ev_io io;	1024	struct ev_io io;
910	int otherfd;	1025	int otherfd;
911	void *somedata;	1026	void *somedata;
912	struct whatever *mostinteresting;	1027	struct whatever *mostinteresting;
913	}	1028	};
		1029
		1030	...
		1031	struct my_io w;
		1032	ev_io_init (&w.io, my_cb, fd, EV_READ);
914		1033
915	And since your callback will be called with a pointer to the watcher, you	1034	And since your callback will be called with a pointer to the watcher, you
916	can cast it back to your own type:	1035	can cast it back to your own type:
917		1036
918	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
919	{	1038	{
920	struct my_io *w = (struct my_io *)w_;	1039	struct my_io *w = (struct my_io *)w_;
921	...	1040	...
922	}	1041	}
923		1042
924	More interesting and less C-conformant ways of casting your callback type	1043	More interesting and less C-conformant ways of casting your callback type
925	instead have been omitted.	1044	instead have been omitted.
926		1045
927	Another common scenario is having some data structure with multiple	1046	Another common scenario is to use some data structure with multiple
928	watchers:	1047	embedded watchers:
929		1048
930	struct my_biggy	1049	struct my_biggy
931	{	1050	{
932	int some_data;	1051	int some_data;
933	ev_timer t1;	1052	ev_timer t1;
934	ev_timer t2;	1053	ev_timer t2;
935	}	1054	}
936		1055
937	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1056	In this case getting the pointer to C<my_biggy> is a bit more
938	you need to use C<offsetof>:	1057	complicated: Either you store the address of your C<my_biggy> struct
		1058	in the C<data> member of the watcher, or you need to use some pointer
		1059	arithmetic using C<offsetof> inside your watchers:
939		1060
940	#include <stddef.h>	1061	#include <stddef.h>
941		1062
942	static void	1063	static void
943	t1_cb (EV_P_ struct ev_timer *w, int revents)	1064	t1_cb (EV_P_ struct ev_timer *w, int revents)
944	{	1065	{
945	struct my_biggy big = (struct my_biggy *	1066	struct my_biggy big = (struct my_biggy *
946	(((char *)w) - offsetof (struct my_biggy, t1));	1067	(((char *)w) - offsetof (struct my_biggy, t1));
947	}	1068	}
948		1069
949	static void	1070	static void
950	t2_cb (EV_P_ struct ev_timer *w, int revents)	1071	t2_cb (EV_P_ struct ev_timer *w, int revents)
951	{	1072	{
952	struct my_biggy big = (struct my_biggy *	1073	struct my_biggy big = (struct my_biggy *
953	(((char *)w) - offsetof (struct my_biggy, t2));	1074	(((char *)w) - offsetof (struct my_biggy, t2));
954	}	1075	}
955		1076
956		1077
957	=head1 WATCHER TYPES	1078	=head1 WATCHER TYPES
958		1079
959	This section describes each watcher in detail, but will not repeat	1080	This section describes each watcher in detail, but will not repeat
…		…
983	In general you can register as many read and/or write event watchers per	1104	In general you can register as many read and/or write event watchers per
984	fd as you want (as long as you don't confuse yourself). Setting all file	1105	fd as you want (as long as you don't confuse yourself). Setting all file
985	descriptors to non-blocking mode is also usually a good idea (but not	1106	descriptors to non-blocking mode is also usually a good idea (but not
986	required if you know what you are doing).	1107	required if you know what you are doing).
987		1108
988	You have to be careful with dup'ed file descriptors, though. Some backends
989	(the linux epoll backend is a notable example) cannot handle dup'ed file
990	descriptors correctly if you register interest in two or more fds pointing
991	to the same underlying file/socket/etc. description (that is, they share
992	the same underlying "file open").
993
994	If you must do this, then force the use of a known-to-be-good backend	1109	If you must do this, then force the use of a known-to-be-good backend
995	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
996	C<EVBACKEND_POLL>).	1111	C<EVBACKEND_POLL>).
997		1112
998	Another thing you have to watch out for is that it is quite easy to	1113	Another thing you have to watch out for is that it is quite easy to
999	receive "spurious" readyness notifications, that is your callback might	1114	receive "spurious" readiness notifications, that is your callback might
1000	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1001	because there is no data. Not only are some backends known to create a	1116	because there is no data. Not only are some backends known to create a
1002	lot of those (for example solaris ports), it is very easy to get into	1117	lot of those (for example Solaris ports), it is very easy to get into
1003	this situation even with a relatively standard program structure. Thus	1118	this situation even with a relatively standard program structure. Thus
1004	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1005	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1006		1121
1007	If you cannot run the fd in non-blocking mode (for example you should not	1122	If you cannot run the fd in non-blocking mode (for example you should not
1008	play around with an Xlib connection), then you have to seperately re-test	1123	play around with an Xlib connection), then you have to separately re-test
1009	whether a file descriptor is really ready with a known-to-be good interface	1124	whether a file descriptor is really ready with a known-to-be good interface
1010	such as poll (fortunately in our Xlib example, Xlib already does this on	1125	such as poll (fortunately in our Xlib example, Xlib already does this on
1011	its own, so its quite safe to use).	1126	its own, so its quite safe to use).
1012		1127
1013	=head3 The special problem of disappearing file descriptors	1128	=head3 The special problem of disappearing file descriptors
…		…
1033		1148
1034	=head3 The special problem of dup'ed file descriptors	1149	=head3 The special problem of dup'ed file descriptors
1035		1150
1036	Some backends (e.g. epoll), cannot register events for file descriptors,	1151	Some backends (e.g. epoll), cannot register events for file descriptors,
1037	but only events for the underlying file descriptions. That means when you	1152	but only events for the underlying file descriptions. That means when you
1038	have C<dup ()>'ed file descriptors and register events for them, only one	1153	have C<dup ()>'ed file descriptors or weirder constellations, and register
1039	file descriptor might actually receive events.	1154	events for them, only one file descriptor might actually receive events.
1040		1155
1041	There is no workaround possible except not registering events	1156	There is no workaround possible except not registering events
1042	for potentially C<dup ()>'ed file descriptors, or to resort to	1157	for potentially C<dup ()>'ed file descriptors, or to resort to
1043	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1158	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1044		1159
…		…
1051	To support fork in your programs, you either have to call	1166	To support fork in your programs, you either have to call
1052	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1167	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1053	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1054	C<EVBACKEND_POLL>.	1169	C<EVBACKEND_POLL>.
1055		1170
		1171	=head3 The special problem of SIGPIPE
		1172
		1173	While not really specific to libev, it is easy to forget about SIGPIPE:
		1174	when writing to a pipe whose other end has been closed, your program gets
		1175	send a SIGPIPE, which, by default, aborts your program. For most programs
		1176	this is sensible behaviour, for daemons, this is usually undesirable.
		1177
		1178	So when you encounter spurious, unexplained daemon exits, make sure you
		1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1180	somewhere, as that would have given you a big clue).
		1181
1056		1182
1057	=head3 Watcher-Specific Functions	1183	=head3 Watcher-Specific Functions
1058		1184
1059	=over 4	1185	=over 4
1060		1186
1061	=item ev_io_init (ev_io *, callback, int fd, int events)	1187	=item ev_io_init (ev_io *, callback, int fd, int events)
1062		1188
1063	=item ev_io_set (ev_io *, int fd, int events)	1189	=item ev_io_set (ev_io *, int fd, int events)
1064		1190
1065	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1066	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1067	C<EV_READ | EV_WRITE> to receive the given events.	1193	C<EV_READ | EV_WRITE> to receive the given events.
1068		1194
1069	=item int fd [read-only]	1195	=item int fd [read-only]
1070		1196
1071	The file descriptor being watched.	1197	The file descriptor being watched.
…		…
1073	=item int events [read-only]	1199	=item int events [read-only]
1074		1200
1075	The events being watched.	1201	The events being watched.
1076		1202
1077	=back	1203	=back
		1204
		1205	=head3 Examples
1078		1206
1079	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1080	readable, but only once. Since it is likely line-buffered, you could	1208	readable, but only once. Since it is likely line-buffered, you could
1081	attempt to read a whole line in the callback.	1209	attempt to read a whole line in the callback.
1082		1210
1083	static void	1211	static void
1084	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1085	{	1213	{
1086	ev_io_stop (loop, w);	1214	ev_io_stop (loop, w);
1087	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1088	}	1216	}
1089		1217
1090	...	1218	...
1091	struct ev_loop *loop = ev_default_init (0);	1219	struct ev_loop *loop = ev_default_init (0);
1092	struct ev_io stdin_readable;	1220	struct ev_io stdin_readable;
1093	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1094	ev_io_start (loop, &stdin_readable);	1222	ev_io_start (loop, &stdin_readable);
1095	ev_loop (loop, 0);	1223	ev_loop (loop, 0);
1096		1224
1097		1225
1098	=head2 C<ev_timer> - relative and optionally repeating timeouts	1226	=head2 C<ev_timer> - relative and optionally repeating timeouts
1099		1227
1100	Timer watchers are simple relative timers that generate an event after a	1228	Timer watchers are simple relative timers that generate an event after a
1101	given time, and optionally repeating in regular intervals after that.	1229	given time, and optionally repeating in regular intervals after that.
1102		1230
1103	The timers are based on real time, that is, if you register an event that	1231	The timers are based on real time, that is, if you register an event that
1104	times out after an hour and you reset your system clock to last years	1232	times out after an hour and you reset your system clock to January last
1105	time, it will still time out after (roughly) and hour. "Roughly" because	1233	year, it will still time out after (roughly) and hour. "Roughly" because
1106	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1107	monotonic clock option helps a lot here).	1235	monotonic clock option helps a lot here).
		1236
		1237	The callback is guaranteed to be invoked only after its timeout has passed,
		1238	but if multiple timers become ready during the same loop iteration then
		1239	order of execution is undefined.
		1240
		1241	=head3 The special problem of time updates
		1242
		1243	Establishing the current time is a costly operation (it usually takes at
		1244	least two system calls): EV therefore updates its idea of the current
		1245	time only before and after C<ev_loop> polls for new events, which causes
		1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1247	lots of events.
1108		1248
1109	The relative timeouts are calculated relative to the C<ev_now ()>	1249	The relative timeouts are calculated relative to the C<ev_now ()>
1110	time. This is usually the right thing as this timestamp refers to the time	1250	time. This is usually the right thing as this timestamp refers to the time
1111	of the event triggering whatever timeout you are modifying/starting. If	1251	of the event triggering whatever timeout you are modifying/starting. If
1112	you suspect event processing to be delayed and you I<need> to base the timeout	1252	you suspect event processing to be delayed and you I<need> to base the
1113	on the current time, use something like this to adjust for this:	1253	timeout on the current time, use something like this to adjust for this:
1114		1254
1115	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1255	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1116		1256
1117	The callback is guarenteed to be invoked only when its timeout has passed,	1257	If the event loop is suspended for a long time, you can also force an
1118	but if multiple timers become ready during the same loop iteration then	1258	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1119	order of execution is undefined.	1259	()>.
1120		1260
1121	=head3 Watcher-Specific Functions and Data Members	1261	=head3 Watcher-Specific Functions and Data Members
1122		1262
1123	=over 4	1263	=over 4
1124		1264
1125	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1265	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1126		1266
1127	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1267	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1128		1268
1129	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1269	Configure the timer to trigger after C<after> seconds. If C<repeat>
1130	C<0.>, then it will automatically be stopped. If it is positive, then the	1270	is C<0.>, then it will automatically be stopped once the timeout is
1131	timer will automatically be configured to trigger again C<repeat> seconds	1271	reached. If it is positive, then the timer will automatically be
1132	later, again, and again, until stopped manually.	1272	configured to trigger again C<repeat> seconds later, again, and again,
		1273	until stopped manually.
1133		1274
1134	The timer itself will do a best-effort at avoiding drift, that is, if you	1275	The timer itself will do a best-effort at avoiding drift, that is, if
1135	configure a timer to trigger every 10 seconds, then it will trigger at	1276	you configure a timer to trigger every 10 seconds, then it will normally
1136	exactly 10 second intervals. If, however, your program cannot keep up with	1277	trigger at exactly 10 second intervals. If, however, your program cannot
1137	the timer (because it takes longer than those 10 seconds to do stuff) the	1278	keep up with the timer (because it takes longer than those 10 seconds to
1138	timer will not fire more than once per event loop iteration.	1279	do stuff) the timer will not fire more than once per event loop iteration.
1139		1280
1140	=item ev_timer_again (loop)	1281	=item ev_timer_again (loop, ev_timer *)
1141		1282
1142	This will act as if the timer timed out and restart it again if it is	1283	This will act as if the timer timed out and restart it again if it is
1143	repeating. The exact semantics are:	1284	repeating. The exact semantics are:
1144		1285
1145	If the timer is pending, its pending status is cleared.	1286	If the timer is pending, its pending status is cleared.
1146		1287
1147	If the timer is started but nonrepeating, stop it (as if it timed out).	1288	If the timer is started but non-repeating, stop it (as if it timed out).
1148		1289
1149	If the timer is repeating, either start it if necessary (with the	1290	If the timer is repeating, either start it if necessary (with the
1150	C<repeat> value), or reset the running timer to the C<repeat> value.	1291	C<repeat> value), or reset the running timer to the C<repeat> value.
1151		1292
1152	This sounds a bit complicated, but here is a useful and typical	1293	This sounds a bit complicated, but here is a useful and typical
1153	example: Imagine you have a tcp connection and you want a so-called idle	1294	example: Imagine you have a TCP connection and you want a so-called idle
1154	timeout, that is, you want to be called when there have been, say, 60	1295	timeout, that is, you want to be called when there have been, say, 60
1155	seconds of inactivity on the socket. The easiest way to do this is to	1296	seconds of inactivity on the socket. The easiest way to do this is to
1156	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1157	C<ev_timer_again> each time you successfully read or write some data. If	1298	C<ev_timer_again> each time you successfully read or write some data. If
1158	you go into an idle state where you do not expect data to travel on the	1299	you go into an idle state where you do not expect data to travel on the
…		…
1180	or C<ev_timer_again> is called and determines the next timeout (if any),	1321	or C<ev_timer_again> is called and determines the next timeout (if any),
1181	which is also when any modifications are taken into account.	1322	which is also when any modifications are taken into account.
1182		1323
1183	=back	1324	=back
1184		1325
		1326	=head3 Examples
		1327
1185	Example: Create a timer that fires after 60 seconds.	1328	Example: Create a timer that fires after 60 seconds.
1186		1329
1187	static void	1330	static void
1188	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1189	{	1332	{
1190	.. one minute over, w is actually stopped right here	1333	.. one minute over, w is actually stopped right here
1191	}	1334	}
1192		1335
1193	struct ev_timer mytimer;	1336	struct ev_timer mytimer;
1194	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1195	ev_timer_start (loop, &mytimer);	1338	ev_timer_start (loop, &mytimer);
1196		1339
1197	Example: Create a timeout timer that times out after 10 seconds of	1340	Example: Create a timeout timer that times out after 10 seconds of
1198	inactivity.	1341	inactivity.
1199		1342
1200	static void	1343	static void
1201	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1202	{	1345	{
1203	.. ten seconds without any activity	1346	.. ten seconds without any activity
1204	}	1347	}
1205		1348
1206	struct ev_timer mytimer;	1349	struct ev_timer mytimer;
1207	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1208	ev_timer_again (&mytimer); /* start timer */	1351	ev_timer_again (&mytimer); /* start timer */
1209	ev_loop (loop, 0);	1352	ev_loop (loop, 0);
1210		1353
1211	// and in some piece of code that gets executed on any "activity":	1354	// and in some piece of code that gets executed on any "activity":
1212	// reset the timeout to start ticking again at 10 seconds	1355	// reset the timeout to start ticking again at 10 seconds
1213	ev_timer_again (&mytimer);	1356	ev_timer_again (&mytimer);
1214		1357
1215		1358
1216	=head2 C<ev_periodic> - to cron or not to cron?	1359	=head2 C<ev_periodic> - to cron or not to cron?
1217		1360
1218	Periodic watchers are also timers of a kind, but they are very versatile	1361	Periodic watchers are also timers of a kind, but they are very versatile
1219	(and unfortunately a bit complex).	1362	(and unfortunately a bit complex).
1220		1363
1221	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1222	but on wallclock time (absolute time). You can tell a periodic watcher	1365	but on wall clock time (absolute time). You can tell a periodic watcher
1223	to trigger "at" some specific point in time. For example, if you tell a	1366	to trigger after some specific point in time. For example, if you tell a
1224	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1225	+ 10.>) and then reset your system clock to the last year, then it will	1368	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1369	clock to January of the previous year, then it will take more than year
1226	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1227	roughly 10 seconds later).	1371	roughly 10 seconds later as it uses a relative timeout).
1228		1372
1229	They can also be used to implement vastly more complex timers, such as	1373	C<ev_periodic>s can also be used to implement vastly more complex timers,
1230	triggering an event on each midnight, local time or other, complicated,	1374	such as triggering an event on each "midnight, local time", or other
1231	rules.	1375	complicated, rules.
1232		1376
1233	As with timers, the callback is guarenteed to be invoked only when the	1377	As with timers, the callback is guaranteed to be invoked only when the
1234	time (C<at>) has been passed, but if multiple periodic timers become ready	1378	time (C<at>) has passed, but if multiple periodic timers become ready
1235	during the same loop iteration then order of execution is undefined.	1379	during the same loop iteration then order of execution is undefined.
1236		1380
1237	=head3 Watcher-Specific Functions and Data Members	1381	=head3 Watcher-Specific Functions and Data Members
1238		1382
1239	=over 4	1383	=over 4
…		…
1247		1391
1248	=over 4	1392	=over 4
1249		1393
1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1251		1395
1252	In this configuration the watcher triggers an event at the wallclock time	1396	In this configuration the watcher triggers an event after the wall clock
1253	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1397	time C<at> has passed and doesn't repeat. It will not adjust when a time
1254	that is, if it is to be run at January 1st 2011 then it will run when the	1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1255	system time reaches or surpasses this time.	1399	run when the system time reaches or surpasses this time.
1256		1400
1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1258		1402
1259	In this mode the watcher will always be scheduled to time out at the next	1403	In this mode the watcher will always be scheduled to time out at the next
1260	C<at + N * interval> time (for some integer N, which can also be negative)	1404	C<at + N * interval> time (for some integer N, which can also be negative)
1261	and then repeat, regardless of any time jumps.	1405	and then repeat, regardless of any time jumps.
1262		1406
1263	This can be used to create timers that do not drift with respect to system	1407	This can be used to create timers that do not drift with respect to system
1264	time:	1408	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1409	the hour:
1265		1410
1266	ev_periodic_set (&periodic, 0., 3600., 0);	1411	ev_periodic_set (&periodic, 0., 3600., 0);
1267		1412
1268	This doesn't mean there will always be 3600 seconds in between triggers,	1413	This doesn't mean there will always be 3600 seconds in between triggers,
1269	but only that the the callback will be called when the system time shows a	1414	but only that the callback will be called when the system time shows a
1270	full hour (UTC), or more correctly, when the system time is evenly divisible	1415	full hour (UTC), or more correctly, when the system time is evenly divisible
1271	by 3600.	1416	by 3600.
1272		1417
1273	Another way to think about it (for the mathematically inclined) is that	1418	Another way to think about it (for the mathematically inclined) is that
1274	C<ev_periodic> will try to run the callback in this mode at the next possible	1419	C<ev_periodic> will try to run the callback in this mode at the next possible
1275	time where C<time = at (mod interval)>, regardless of any time jumps.	1420	time where C<time = at (mod interval)>, regardless of any time jumps.
1276		1421
1277	For numerical stability it is preferable that the C<at> value is near	1422	For numerical stability it is preferable that the C<at> value is near
1278	C<ev_now ()> (the current time), but there is no range requirement for	1423	C<ev_now ()> (the current time), but there is no range requirement for
1279	this value.	1424	this value, and in fact is often specified as zero.
		1425
		1426	Note also that there is an upper limit to how often a timer can fire (CPU
		1427	speed for example), so if C<interval> is very small then timing stability
		1428	will of course deteriorate. Libev itself tries to be exact to be about one
		1429	millisecond (if the OS supports it and the machine is fast enough).
1280		1430
1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1282		1432
1283	In this mode the values for C<interval> and C<at> are both being	1433	In this mode the values for C<interval> and C<at> are both being
1284	ignored. Instead, each time the periodic watcher gets scheduled, the	1434	ignored. Instead, each time the periodic watcher gets scheduled, the
1285	reschedule callback will be called with the watcher as first, and the	1435	reschedule callback will be called with the watcher as first, and the
1286	current time as second argument.	1436	current time as second argument.
1287		1437
1288	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1289	ever, or make any event loop modifications>. If you need to stop it,	1439	ever, or make ANY event loop modifications whatsoever>.
1290	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1291	starting an C<ev_prepare> watcher, which is legal).
1292		1440
		1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1443	only event loop modification you are allowed to do).
		1444
1293	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1294	ev_tstamp now)>, e.g.:	1446	*w, ev_tstamp now)>, e.g.:
1295		1447
1296	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1297	{	1449	{
1298	return now + 60.;	1450	return now + 60.;
1299	}	1451	}
…		…
1301	It must return the next time to trigger, based on the passed time value	1453	It must return the next time to trigger, based on the passed time value
1302	(that is, the lowest time value larger than to the second argument). It	1454	(that is, the lowest time value larger than to the second argument). It
1303	will usually be called just before the callback will be triggered, but	1455	will usually be called just before the callback will be triggered, but
1304	might be called at other times, too.	1456	might be called at other times, too.
1305		1457
1306	NOTE: I<< This callback must always return a time that is later than the	1458	NOTE: I<< This callback must always return a time that is higher than or
1307	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1459	equal to the passed C<now> value >>.
1308		1460
1309	This can be used to create very complex timers, such as a timer that	1461	This can be used to create very complex timers, such as a timer that
1310	triggers on each midnight, local time. To do this, you would calculate the	1462	triggers on "next midnight, local time". To do this, you would calculate the
1311	next midnight after C<now> and return the timestamp value for this. How	1463	next midnight after C<now> and return the timestamp value for this. How
1312	you do this is, again, up to you (but it is not trivial, which is the main	1464	you do this is, again, up to you (but it is not trivial, which is the main
1313	reason I omitted it as an example).	1465	reason I omitted it as an example).
1314		1466
1315	=back	1467	=back
…		…
1319	Simply stops and restarts the periodic watcher again. This is only useful	1471	Simply stops and restarts the periodic watcher again. This is only useful
1320	when you changed some parameters or the reschedule callback would return	1472	when you changed some parameters or the reschedule callback would return
1321	a different time than the last time it was called (e.g. in a crond like	1473	a different time than the last time it was called (e.g. in a crond like
1322	program when the crontabs have changed).	1474	program when the crontabs have changed).
1323		1475
		1476	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1477
		1478	When active, returns the absolute time that the watcher is supposed to
		1479	trigger next.
		1480
1324	=item ev_tstamp offset [read-write]	1481	=item ev_tstamp offset [read-write]
1325		1482
1326	When repeating, this contains the offset value, otherwise this is the	1483	When repeating, this contains the offset value, otherwise this is the
1327	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1328		1485
…		…
1339		1496
1340	The current reschedule callback, or C<0>, if this functionality is	1497	The current reschedule callback, or C<0>, if this functionality is
1341	switched off. Can be changed any time, but changes only take effect when	1498	switched off. Can be changed any time, but changes only take effect when
1342	the periodic timer fires or C<ev_periodic_again> is being called.	1499	the periodic timer fires or C<ev_periodic_again> is being called.
1343		1500
1344	=item ev_tstamp at [read-only]
1345
1346	When active, contains the absolute time that the watcher is supposed to
1347	trigger next.
1348
1349	=back	1501	=back
		1502
		1503	=head3 Examples
1350		1504
1351	Example: Call a callback every hour, or, more precisely, whenever the	1505	Example: Call a callback every hour, or, more precisely, whenever the
1352	system clock is divisible by 3600. The callback invocation times have	1506	system clock is divisible by 3600. The callback invocation times have
1353	potentially a lot of jittering, but good long-term stability.	1507	potentially a lot of jitter, but good long-term stability.
1354		1508
1355	static void	1509	static void
1356	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1357	{	1511	{
1358	... its now a full hour (UTC, or TAI or whatever your clock follows)	1512	... its now a full hour (UTC, or TAI or whatever your clock follows)
1359	}	1513	}
1360		1514
1361	struct ev_periodic hourly_tick;	1515	struct ev_periodic hourly_tick;
1362	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1363	ev_periodic_start (loop, &hourly_tick);	1517	ev_periodic_start (loop, &hourly_tick);
1364		1518
1365	Example: The same as above, but use a reschedule callback to do it:	1519	Example: The same as above, but use a reschedule callback to do it:
1366		1520
1367	#include <math.h>	1521	#include <math.h>
1368		1522
1369	static ev_tstamp	1523	static ev_tstamp
1370	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1371	{	1525	{
1372	return fmod (now, 3600.) + 3600.;	1526	return fmod (now, 3600.) + 3600.;
1373	}	1527	}
1374		1528
1375	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1376		1530
1377	Example: Call a callback every hour, starting now:	1531	Example: Call a callback every hour, starting now:
1378		1532
1379	struct ev_periodic hourly_tick;	1533	struct ev_periodic hourly_tick;
1380	ev_periodic_init (&hourly_tick, clock_cb,	1534	ev_periodic_init (&hourly_tick, clock_cb,
1381	fmod (ev_now (loop), 3600.), 3600., 0);	1535	fmod (ev_now (loop), 3600.), 3600., 0);
1382	ev_periodic_start (loop, &hourly_tick);	1536	ev_periodic_start (loop, &hourly_tick);
1383		1537
1384		1538
1385	=head2 C<ev_signal> - signal me when a signal gets signalled!	1539	=head2 C<ev_signal> - signal me when a signal gets signalled!
1386		1540
1387	Signal watchers will trigger an event when the process receives a specific	1541	Signal watchers will trigger an event when the process receives a specific
…		…
1394	with the kernel (thus it coexists with your own signal handlers as long	1548	with the kernel (thus it coexists with your own signal handlers as long
1395	as you don't register any with libev). Similarly, when the last signal	1549	as you don't register any with libev). Similarly, when the last signal
1396	watcher for a signal is stopped libev will reset the signal handler to	1550	watcher for a signal is stopped libev will reset the signal handler to
1397	SIG_DFL (regardless of what it was set to before).	1551	SIG_DFL (regardless of what it was set to before).
1398		1552
		1553	If possible and supported, libev will install its handlers with
		1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1555	interrupted. If you have a problem with system calls getting interrupted by
		1556	signals you can block all signals in an C<ev_check> watcher and unblock
		1557	them in an C<ev_prepare> watcher.
		1558
1399	=head3 Watcher-Specific Functions and Data Members	1559	=head3 Watcher-Specific Functions and Data Members
1400		1560
1401	=over 4	1561	=over 4
1402		1562
1403	=item ev_signal_init (ev_signal *, callback, int signum)	1563	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1411		1571
1412	The signal the watcher watches out for.	1572	The signal the watcher watches out for.
1413		1573
1414	=back	1574	=back
1415		1575
		1576	=head3 Examples
		1577
		1578	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1579
		1580	static void
		1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1582	{
		1583	ev_unloop (loop, EVUNLOOP_ALL);
		1584	}
		1585
		1586	struct ev_signal signal_watcher;
		1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1588	ev_signal_start (loop, &sigint_cb);
		1589
1416		1590
1417	=head2 C<ev_child> - watch out for process status changes	1591	=head2 C<ev_child> - watch out for process status changes
1418		1592
1419	Child watchers trigger when your process receives a SIGCHLD in response to	1593	Child watchers trigger when your process receives a SIGCHLD in response to
1420	some child status changes (most typically when a child of yours dies).	1594	some child status changes (most typically when a child of yours dies). It
		1595	is permissible to install a child watcher I<after> the child has been
		1596	forked (which implies it might have already exited), as long as the event
		1597	loop isn't entered (or is continued from a watcher).
		1598
		1599	Only the default event loop is capable of handling signals, and therefore
		1600	you can only register child watchers in the default event loop.
		1601
		1602	=head3 Process Interaction
		1603
		1604	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1605	initialised. This is necessary to guarantee proper behaviour even if
		1606	the first child watcher is started after the child exits. The occurrence
		1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1608	synchronously as part of the event loop processing. Libev always reaps all
		1609	children, even ones not watched.
		1610
		1611	=head3 Overriding the Built-In Processing
		1612
		1613	Libev offers no special support for overriding the built-in child
		1614	processing, but if your application collides with libev's default child
		1615	handler, you can override it easily by installing your own handler for
		1616	C<SIGCHLD> after initialising the default loop, and making sure the
		1617	default loop never gets destroyed. You are encouraged, however, to use an
		1618	event-based approach to child reaping and thus use libev's support for
		1619	that, so other libev users can use C<ev_child> watchers freely.
		1620
		1621	=head3 Stopping the Child Watcher
		1622
		1623	Currently, the child watcher never gets stopped, even when the
		1624	child terminates, so normally one needs to stop the watcher in the
		1625	callback. Future versions of libev might stop the watcher automatically
		1626	when a child exit is detected.
1421		1627
1422	=head3 Watcher-Specific Functions and Data Members	1628	=head3 Watcher-Specific Functions and Data Members
1423		1629
1424	=over 4	1630	=over 4
1425		1631
1426	=item ev_child_init (ev_child *, callback, int pid)	1632	=item ev_child_init (ev_child *, callback, int pid, int trace)
1427		1633
1428	=item ev_child_set (ev_child *, int pid)	1634	=item ev_child_set (ev_child *, int pid, int trace)
1429		1635
1430	Configures the watcher to wait for status changes of process C<pid> (or	1636	Configures the watcher to wait for status changes of process C<pid> (or
1431	I<any> process if C<pid> is specified as C<0>). The callback can look	1637	I<any> process if C<pid> is specified as C<0>). The callback can look
1432	at the C<rstatus> member of the C<ev_child> watcher structure to see	1638	at the C<rstatus> member of the C<ev_child> watcher structure to see
1433	the status word (use the macros from C<sys/wait.h> and see your systems	1639	the status word (use the macros from C<sys/wait.h> and see your systems
1434	C<waitpid> documentation). The C<rpid> member contains the pid of the	1640	C<waitpid> documentation). The C<rpid> member contains the pid of the
1435	process causing the status change.	1641	process causing the status change. C<trace> must be either C<0> (only
		1642	activate the watcher when the process terminates) or C<1> (additionally
		1643	activate the watcher when the process is stopped or continued).
1436		1644
1437	=item int pid [read-only]	1645	=item int pid [read-only]
1438		1646
1439	The process id this watcher watches out for, or C<0>, meaning any process id.	1647	The process id this watcher watches out for, or C<0>, meaning any process id.
1440		1648
…		…
1447	The process exit/trace status caused by C<rpid> (see your systems	1655	The process exit/trace status caused by C<rpid> (see your systems
1448	C<waitpid> and C<sys/wait.h> documentation for details).	1656	C<waitpid> and C<sys/wait.h> documentation for details).
1449		1657
1450	=back	1658	=back
1451		1659
1452	Example: Try to exit cleanly on SIGINT and SIGTERM.	1660	=head3 Examples
1453		1661
		1662	Example: C<fork()> a new process and install a child handler to wait for
		1663	its completion.
		1664
		1665	ev_child cw;
		1666
1454	static void	1667	static void
1455	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1668	child_cb (EV_P_ struct ev_child *w, int revents)
1456	{	1669	{
1457	ev_unloop (loop, EVUNLOOP_ALL);	1670	ev_child_stop (EV_A_ w);
		1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1458	}	1672	}
1459		1673
1460	struct ev_signal signal_watcher;	1674	pid_t pid = fork ();
1461	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1675
1462	ev_signal_start (loop, &sigint_cb);	1676	if (pid < 0)
		1677	// error
		1678	else if (pid == 0)
		1679	{
		1680	// the forked child executes here
		1681	exit (1);
		1682	}
		1683	else
		1684	{
		1685	ev_child_init (&cw, child_cb, pid, 0);
		1686	ev_child_start (EV_DEFAULT_ &cw);
		1687	}
1463		1688
1464		1689
1465	=head2 C<ev_stat> - did the file attributes just change?	1690	=head2 C<ev_stat> - did the file attributes just change?
1466		1691
1467	This watches a filesystem path for attribute changes. That is, it calls	1692	This watches a file system path for attribute changes. That is, it calls
1468	C<stat> regularly (or when the OS says it changed) and sees if it changed	1693	C<stat> regularly (or when the OS says it changed) and sees if it changed
1469	compared to the last time, invoking the callback if it did.	1694	compared to the last time, invoking the callback if it did.
1470		1695
1471	The path does not need to exist: changing from "path exists" to "path does	1696	The path does not need to exist: changing from "path exists" to "path does
1472	not exist" is a status change like any other. The condition "path does	1697	not exist" is a status change like any other. The condition "path does
…		…
1490	as even with OS-supported change notifications, this can be	1715	as even with OS-supported change notifications, this can be
1491	resource-intensive.	1716	resource-intensive.
1492		1717
1493	At the time of this writing, only the Linux inotify interface is	1718	At the time of this writing, only the Linux inotify interface is
1494	implemented (implementing kqueue support is left as an exercise for the	1719	implemented (implementing kqueue support is left as an exercise for the
		1720	reader, note, however, that the author sees no way of implementing ev_stat
1495	reader). Inotify will be used to give hints only and should not change the	1721	semantics with kqueue). Inotify will be used to give hints only and should
1496	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1722	not change the semantics of C<ev_stat> watchers, which means that libev
1497	to fall back to regular polling again even with inotify, but changes are	1723	sometimes needs to fall back to regular polling again even with inotify,
1498	usually detected immediately, and if the file exists there will be no	1724	but changes are usually detected immediately, and if the file exists there
1499	polling.	1725	will be no polling.
		1726
		1727	=head3 ABI Issues (Largefile Support)
		1728
		1729	Libev by default (unless the user overrides this) uses the default
		1730	compilation environment, which means that on systems with large file
		1731	support disabled by default, you get the 32 bit version of the stat
		1732	structure. When using the library from programs that change the ABI to
		1733	use 64 bit file offsets the programs will fail. In that case you have to
		1734	compile libev with the same flags to get binary compatibility. This is
		1735	obviously the case with any flags that change the ABI, but the problem is
		1736	most noticeably disabled with ev_stat and large file support.
		1737
		1738	The solution for this is to lobby your distribution maker to make large
		1739	file interfaces available by default (as e.g. FreeBSD does) and not
		1740	optional. Libev cannot simply switch on large file support because it has
		1741	to exchange stat structures with application programs compiled using the
		1742	default compilation environment.
		1743
		1744	=head3 Inotify
		1745
		1746	When C<inotify (7)> support has been compiled into libev (generally only
		1747	available on Linux) and present at runtime, it will be used to speed up
		1748	change detection where possible. The inotify descriptor will be created lazily
		1749	when the first C<ev_stat> watcher is being started.
		1750
		1751	Inotify presence does not change the semantics of C<ev_stat> watchers
		1752	except that changes might be detected earlier, and in some cases, to avoid
		1753	making regular C<stat> calls. Even in the presence of inotify support
		1754	there are many cases where libev has to resort to regular C<stat> polling.
		1755
		1756	(There is no support for kqueue, as apparently it cannot be used to
		1757	implement this functionality, due to the requirement of having a file
		1758	descriptor open on the object at all times).
1500		1759
1501	=head3 The special problem of stat time resolution	1760	=head3 The special problem of stat time resolution
1502		1761
1503	The C<stat ()> syscall only supports full-second resolution portably, and	1762	The C<stat ()> system call only supports full-second resolution portably, and
1504	even on systems where the resolution is higher, many filesystems still	1763	even on systems where the resolution is higher, many file systems still
1505	only support whole seconds.	1764	only support whole seconds.
1506		1765
1507	That means that, if the time is the only thing that changes, you might	1766	That means that, if the time is the only thing that changes, you can
1508	miss updates: on the first update, C<ev_stat> detects a change and calls	1767	easily miss updates: on the first update, C<ev_stat> detects a change and
1509	your callback, which does something. When there is another update within	1768	calls your callback, which does something. When there is another update
1510	the same second, C<ev_stat> will be unable to detect it.	1769	within the same second, C<ev_stat> will be unable to detect it as the stat
		1770	data does not change.
1511		1771
1512	The solution to this is to delay acting on a change for a second (or till	1772	The solution to this is to delay acting on a change for slightly more
1513	the next second boundary), using a roughly one-second delay C<ev_timer>	1773	than a second (or till slightly after the next full second boundary), using
1514	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1515	is added to work around small timing inconsistencies of some operating	1775	ev_timer_again (loop, w)>).
1516	systems.	1776
		1777	The C<.02> offset is added to work around small timing inconsistencies
		1778	of some operating systems (where the second counter of the current time
		1779	might be be delayed. One such system is the Linux kernel, where a call to
		1780	C<gettimeofday> might return a timestamp with a full second later than
		1781	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1782	update file times then there will be a small window where the kernel uses
		1783	the previous second to update file times but libev might already execute
		1784	the timer callback).
1517		1785
1518	=head3 Watcher-Specific Functions and Data Members	1786	=head3 Watcher-Specific Functions and Data Members
1519		1787
1520	=over 4	1788	=over 4
1521		1789
…		…
1527	C<path>. The C<interval> is a hint on how quickly a change is expected to	1795	C<path>. The C<interval> is a hint on how quickly a change is expected to
1528	be detected and should normally be specified as C<0> to let libev choose	1796	be detected and should normally be specified as C<0> to let libev choose
1529	a suitable value. The memory pointed to by C<path> must point to the same	1797	a suitable value. The memory pointed to by C<path> must point to the same
1530	path for as long as the watcher is active.	1798	path for as long as the watcher is active.
1531		1799
1532	The callback will be receive C<EV_STAT> when a change was detected,	1800	The callback will receive C<EV_STAT> when a change was detected, relative
1533	relative to the attributes at the time the watcher was started (or the	1801	to the attributes at the time the watcher was started (or the last change
1534	last change was detected).	1802	was detected).
1535		1803
1536	=item ev_stat_stat (ev_stat *)	1804	=item ev_stat_stat (loop, ev_stat *)
1537		1805
1538	Updates the stat buffer immediately with new values. If you change the	1806	Updates the stat buffer immediately with new values. If you change the
1539	watched path in your callback, you could call this fucntion to avoid	1807	watched path in your callback, you could call this function to avoid
1540	detecting this change (while introducing a race condition). Can also be	1808	detecting this change (while introducing a race condition if you are not
1541	useful simply to find out the new values.	1809	the only one changing the path). Can also be useful simply to find out the
		1810	new values.
1542		1811
1543	=item ev_statdata attr [read-only]	1812	=item ev_statdata attr [read-only]
1544		1813
1545	The most-recently detected attributes of the file. Although the type is of	1814	The most-recently detected attributes of the file. Although the type is
1546	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1815	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1547	suitable for your system. If the C<st_nlink> member is C<0>, then there	1816	suitable for your system, but you can only rely on the POSIX-standardised
		1817	members to be present. If the C<st_nlink> member is C<0>, then there was
1548	was some error while C<stat>ing the file.	1818	some error while C<stat>ing the file.
1549		1819
1550	=item ev_statdata prev [read-only]	1820	=item ev_statdata prev [read-only]
1551		1821
1552	The previous attributes of the file. The callback gets invoked whenever	1822	The previous attributes of the file. The callback gets invoked whenever
1553	C<prev> != C<attr>.	1823	C<prev> != C<attr>, or, more precisely, one or more of these members
		1824	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1825	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1554		1826
1555	=item ev_tstamp interval [read-only]	1827	=item ev_tstamp interval [read-only]
1556		1828
1557	The specified interval.	1829	The specified interval.
1558		1830
1559	=item const char *path [read-only]	1831	=item const char *path [read-only]
1560		1832
1561	The filesystem path that is being watched.	1833	The file system path that is being watched.
1562		1834
1563	=back	1835	=back
1564		1836
		1837	=head3 Examples
		1838
1565	Example: Watch C</etc/passwd> for attribute changes.	1839	Example: Watch C</etc/passwd> for attribute changes.
1566		1840
1567	static void	1841	static void
1568	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1842	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1569	{	1843	{
1570	/* /etc/passwd changed in some way */	1844	/* /etc/passwd changed in some way */
1571	if (w->attr.st_nlink)	1845	if (w->attr.st_nlink)
1572	{	1846	{
1573	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1847	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1574	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1848	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1575	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1849	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1576	}	1850	}
1577	else	1851	else
1578	/* you shalt not abuse printf for puts */	1852	/* you shalt not abuse printf for puts */
1579	puts ("wow, /etc/passwd is not there, expect problems. "	1853	puts ("wow, /etc/passwd is not there, expect problems. "
1580	"if this is windows, they already arrived\n");	1854	"if this is windows, they already arrived\n");
1581	}	1855	}
1582		1856
1583	...	1857	...
1584	ev_stat passwd;	1858	ev_stat passwd;
1585		1859
1586	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1860	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1587	ev_stat_start (loop, &passwd);	1861	ev_stat_start (loop, &passwd);
1588		1862
1589	Example: Like above, but additionally use a one-second delay so we do not	1863	Example: Like above, but additionally use a one-second delay so we do not
1590	miss updates (however, frequent updates will delay processing, too, so	1864	miss updates (however, frequent updates will delay processing, too, so
1591	one might do the work both on C<ev_stat> callback invocation I<and> on	1865	one might do the work both on C<ev_stat> callback invocation I<and> on
1592	C<ev_timer> callback invocation).	1866	C<ev_timer> callback invocation).
1593		1867
1594	static ev_stat passwd;	1868	static ev_stat passwd;
1595	static ev_timer timer;	1869	static ev_timer timer;
1596		1870
1597	static void	1871	static void
1598	timer_cb (EV_P_ ev_timer *w, int revents)	1872	timer_cb (EV_P_ ev_timer *w, int revents)
1599	{	1873	{
1600	ev_timer_stop (EV_A_ w);	1874	ev_timer_stop (EV_A_ w);
1601		1875
1602	/* now it's one second after the most recent passwd change */	1876	/* now it's one second after the most recent passwd change */
1603	}	1877	}
1604		1878
1605	static void	1879	static void
1606	stat_cb (EV_P_ ev_stat *w, int revents)	1880	stat_cb (EV_P_ ev_stat *w, int revents)
1607	{	1881	{
1608	/* reset the one-second timer */	1882	/* reset the one-second timer */
1609	ev_timer_again (EV_A_ &timer);	1883	ev_timer_again (EV_A_ &timer);
1610	}	1884	}
1611		1885
1612	...	1886	...
1613	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1887	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1614	ev_stat_start (loop, &passwd);	1888	ev_stat_start (loop, &passwd);
1615	ev_timer_init (&timer, timer_cb, 0., 1.01);	1889	ev_timer_init (&timer, timer_cb, 0., 1.02);
1616		1890
1617		1891
1618	=head2 C<ev_idle> - when you've got nothing better to do...	1892	=head2 C<ev_idle> - when you've got nothing better to do...
1619		1893
1620	Idle watchers trigger events when no other events of the same or higher	1894	Idle watchers trigger events when no other events of the same or higher
…		…
1646	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1920	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1647	believe me.	1921	believe me.
1648		1922
1649	=back	1923	=back
1650		1924
		1925	=head3 Examples
		1926
1651	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1652	callback, free it. Also, use no error checking, as usual.	1928	callback, free it. Also, use no error checking, as usual.
1653		1929
1654	static void	1930	static void
1655	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1656	{	1932	{
1657	free (w);	1933	free (w);
1658	// now do something you wanted to do when the program has	1934	// now do something you wanted to do when the program has
1659	// no longer asnything immediate to do.	1935	// no longer anything immediate to do.
1660	}	1936	}
1661		1937
1662	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1663	ev_idle_init (idle_watcher, idle_cb);	1939	ev_idle_init (idle_watcher, idle_cb);
1664	ev_idle_start (loop, idle_cb);	1940	ev_idle_start (loop, idle_cb);
1665		1941
1666		1942
1667	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1668		1944
1669	Prepare and check watchers are usually (but not always) used in tandem:	1945	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1688		1964
1689	This is done by examining in each prepare call which file descriptors need	1965	This is done by examining in each prepare call which file descriptors need
1690	to be watched by the other library, registering C<ev_io> watchers for	1966	to be watched by the other library, registering C<ev_io> watchers for
1691	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1692	provide just this functionality). Then, in the check watcher you check for	1968	provide just this functionality). Then, in the check watcher you check for
1693	any events that occured (by checking the pending status of all watchers	1969	any events that occurred (by checking the pending status of all watchers
1694	and stopping them) and call back into the library. The I/O and timer	1970	and stopping them) and call back into the library. The I/O and timer
1695	callbacks will never actually be called (but must be valid nevertheless,	1971	callbacks will never actually be called (but must be valid nevertheless,
1696	because you never know, you know?).	1972	because you never know, you know?).
1697		1973
1698	As another example, the Perl Coro module uses these hooks to integrate	1974	As another example, the Perl Coro module uses these hooks to integrate
…		…
1706		1982
1707	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1708	priority, to ensure that they are being run before any other watchers	1984	priority, to ensure that they are being run before any other watchers
1709	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1710	too) should not activate ("feed") events into libev. While libev fully	1986	too) should not activate ("feed") events into libev. While libev fully
1711	supports this, they will be called before other C<ev_check> watchers	1987	supports this, they might get executed before other C<ev_check> watchers
1712	did their job. As C<ev_check> watchers are often used to embed other	1988	did their job. As C<ev_check> watchers are often used to embed other
1713	(non-libev) event loops those other event loops might be in an unusable	1989	(non-libev) event loops those other event loops might be in an unusable
1714	state until their C<ev_check> watcher ran (always remind yourself to	1990	state until their C<ev_check> watcher ran (always remind yourself to
1715	coexist peacefully with others).	1991	coexist peacefully with others).
1716		1992
…		…
1726	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1727	macros, but using them is utterly, utterly and completely pointless.	2003	macros, but using them is utterly, utterly and completely pointless.
1728		2004
1729	=back	2005	=back
1730		2006
		2007	=head3 Examples
		2008
1731	There are a number of principal ways to embed other event loops or modules	2009	There are a number of principal ways to embed other event loops or modules
1732	into libev. Here are some ideas on how to include libadns into libev	2010	into libev. Here are some ideas on how to include libadns into libev
1733	(there is a Perl module named C<EV::ADNS> that does this, which you could	2011	(there is a Perl module named C<EV::ADNS> that does this, which you could
1734	use for an actually working example. Another Perl module named C<EV::Glib>	2012	use as a working example. Another Perl module named C<EV::Glib> embeds a
1735	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2013	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1736	into the Glib event loop).	2014	Glib event loop).
1737		2015
1738	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2016	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1739	and in a check watcher, destroy them and call into libadns. What follows	2017	and in a check watcher, destroy them and call into libadns. What follows
1740	is pseudo-code only of course. This requires you to either use a low	2018	is pseudo-code only of course. This requires you to either use a low
1741	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2019	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1742	the callbacks for the IO/timeout watchers might not have been called yet.	2020	the callbacks for the IO/timeout watchers might not have been called yet.
1743		2021
1744	static ev_io iow [nfd];	2022	static ev_io iow [nfd];
1745	static ev_timer tw;	2023	static ev_timer tw;
1746		2024
1747	static void	2025	static void
1748	io_cb (ev_loop *loop, ev_io *w, int revents)	2026	io_cb (ev_loop *loop, ev_io *w, int revents)
1749	{	2027	{
1750	}	2028	}
1751		2029
1752	// create io watchers for each fd and a timer before blocking	2030	// create io watchers for each fd and a timer before blocking
1753	static void	2031	static void
1754	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1755	{	2033	{
1756	int timeout = 3600000;	2034	int timeout = 3600000;
1757	struct pollfd fds [nfd];	2035	struct pollfd fds [nfd];
1758	// actual code will need to loop here and realloc etc.	2036	// actual code will need to loop here and realloc etc.
1759	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1760		2038
1761	/* the callback is illegal, but won't be called as we stop during check */	2039	/* the callback is illegal, but won't be called as we stop during check */
1762	ev_timer_init (&tw, 0, timeout * 1e-3);	2040	ev_timer_init (&tw, 0, timeout * 1e-3);
1763	ev_timer_start (loop, &tw);	2041	ev_timer_start (loop, &tw);
1764		2042
1765	// create one ev_io per pollfd	2043	// create one ev_io per pollfd
1766	for (int i = 0; i < nfd; ++i)	2044	for (int i = 0; i < nfd; ++i)
1767	{	2045	{
1768	ev_io_init (iow + i, io_cb, fds [i].fd,	2046	ev_io_init (iow + i, io_cb, fds [i].fd,
1769	((fds [i].events & POLLIN ? EV_READ : 0)	2047	((fds [i].events & POLLIN ? EV_READ : 0)
1770	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2048	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1771		2049
1772	fds [i].revents = 0;	2050	fds [i].revents = 0;
1773	ev_io_start (loop, iow + i);	2051	ev_io_start (loop, iow + i);
1774	}	2052	}
1775	}	2053	}
1776		2054
1777	// stop all watchers after blocking	2055	// stop all watchers after blocking
1778	static void	2056	static void
1779	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1780	{	2058	{
1781	ev_timer_stop (loop, &tw);	2059	ev_timer_stop (loop, &tw);
1782		2060
1783	for (int i = 0; i < nfd; ++i)	2061	for (int i = 0; i < nfd; ++i)
1784	{	2062	{
1785	// set the relevant poll flags	2063	// set the relevant poll flags
1786	// could also call adns_processreadable etc. here	2064	// could also call adns_processreadable etc. here
1787	struct pollfd *fd = fds + i;	2065	struct pollfd *fd = fds + i;
1788	int revents = ev_clear_pending (iow + i);	2066	int revents = ev_clear_pending (iow + i);
1789	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2067	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1790	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2068	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1791		2069
1792	// now stop the watcher	2070	// now stop the watcher
1793	ev_io_stop (loop, iow + i);	2071	ev_io_stop (loop, iow + i);
1794	}	2072	}
1795		2073
1796	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2074	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1797	}	2075	}
1798		2076
1799	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2077	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1800	in the prepare watcher and would dispose of the check watcher.	2078	in the prepare watcher and would dispose of the check watcher.
1801		2079
1802	Method 3: If the module to be embedded supports explicit event	2080	Method 3: If the module to be embedded supports explicit event
1803	notification (adns does), you can also make use of the actual watcher	2081	notification (libadns does), you can also make use of the actual watcher
1804	callbacks, and only destroy/create the watchers in the prepare watcher.	2082	callbacks, and only destroy/create the watchers in the prepare watcher.
1805		2083
1806	static void	2084	static void
1807	timer_cb (EV_P_ ev_timer *w, int revents)	2085	timer_cb (EV_P_ ev_timer *w, int revents)
1808	{	2086	{
1809	adns_state ads = (adns_state)w->data;	2087	adns_state ads = (adns_state)w->data;
1810	update_now (EV_A);	2088	update_now (EV_A);
1811		2089
1812	adns_processtimeouts (ads, &tv_now);	2090	adns_processtimeouts (ads, &tv_now);
1813	}	2091	}
1814		2092
1815	static void	2093	static void
1816	io_cb (EV_P_ ev_io *w, int revents)	2094	io_cb (EV_P_ ev_io *w, int revents)
1817	{	2095	{
1818	adns_state ads = (adns_state)w->data;	2096	adns_state ads = (adns_state)w->data;
1819	update_now (EV_A);	2097	update_now (EV_A);
1820		2098
1821	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2099	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1822	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2100	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1823	}	2101	}
1824		2102
1825	// do not ever call adns_afterpoll	2103	// do not ever call adns_afterpoll
1826		2104
1827	Method 4: Do not use a prepare or check watcher because the module you	2105	Method 4: Do not use a prepare or check watcher because the module you
1828	want to embed is too inflexible to support it. Instead, youc na override	2106	want to embed is too inflexible to support it. Instead, you can override
1829	their poll function. The drawback with this solution is that the main	2107	their poll function. The drawback with this solution is that the main
1830	loop is now no longer controllable by EV. The C<Glib::EV> module does	2108	loop is now no longer controllable by EV. The C<Glib::EV> module does
1831	this.	2109	this.
1832		2110
1833	static gint	2111	static gint
1834	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1835	{	2113	{
1836	int got_events = 0;	2114	int got_events = 0;
1837		2115
1838	for (n = 0; n < nfds; ++n)	2116	for (n = 0; n < nfds; ++n)
1839	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2117	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1840		2118
1841	if (timeout >= 0)	2119	if (timeout >= 0)
1842	// create/start timer	2120	// create/start timer
1843		2121
1844	// poll	2122	// poll
1845	ev_loop (EV_A_ 0);	2123	ev_loop (EV_A_ 0);
1846		2124
1847	// stop timer again	2125	// stop timer again
1848	if (timeout >= 0)	2126	if (timeout >= 0)
1849	ev_timer_stop (EV_A_ &to);	2127	ev_timer_stop (EV_A_ &to);
1850		2128
1851	// stop io watchers again - their callbacks should have set	2129	// stop io watchers again - their callbacks should have set
1852	for (n = 0; n < nfds; ++n)	2130	for (n = 0; n < nfds; ++n)
1853	ev_io_stop (EV_A_ iow [n]);	2131	ev_io_stop (EV_A_ iow [n]);
1854		2132
1855	return got_events;	2133	return got_events;
1856	}	2134	}
1857		2135
1858		2136
1859	=head2 C<ev_embed> - when one backend isn't enough...	2137	=head2 C<ev_embed> - when one backend isn't enough...
1860		2138
1861	This is a rather advanced watcher type that lets you embed one event loop	2139	This is a rather advanced watcher type that lets you embed one event loop
…		…
1903	portable one.	2181	portable one.
1904		2182
1905	So when you want to use this feature you will always have to be prepared	2183	So when you want to use this feature you will always have to be prepared
1906	that you cannot get an embeddable loop. The recommended way to get around	2184	that you cannot get an embeddable loop. The recommended way to get around
1907	this is to have a separate variables for your embeddable loop, try to	2185	this is to have a separate variables for your embeddable loop, try to
1908	create it, and if that fails, use the normal loop for everything:	2186	create it, and if that fails, use the normal loop for everything.
1909
1910	struct ev_loop *loop_hi = ev_default_init (0);
1911	struct ev_loop *loop_lo = 0;
1912	struct ev_embed embed;
1913
1914	// see if there is a chance of getting one that works
1915	// (remember that a flags value of 0 means autodetection)
1916	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1917	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1918	: 0;
1919
1920	// if we got one, then embed it, otherwise default to loop_hi
1921	if (loop_lo)
1922	{
1923	ev_embed_init (&embed, 0, loop_lo);
1924	ev_embed_start (loop_hi, &embed);
1925	}
1926	else
1927	loop_lo = loop_hi;
1928		2187
1929	=head3 Watcher-Specific Functions and Data Members	2188	=head3 Watcher-Specific Functions and Data Members
1930		2189
1931	=over 4	2190	=over 4
1932		2191
…		…
1936		2195
1937	Configures the watcher to embed the given loop, which must be	2196	Configures the watcher to embed the given loop, which must be
1938	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2197	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1939	invoked automatically, otherwise it is the responsibility of the callback	2198	invoked automatically, otherwise it is the responsibility of the callback
1940	to invoke it (it will continue to be called until the sweep has been done,	2199	to invoke it (it will continue to be called until the sweep has been done,
1941	if you do not want thta, you need to temporarily stop the embed watcher).	2200	if you do not want that, you need to temporarily stop the embed watcher).
1942		2201
1943	=item ev_embed_sweep (loop, ev_embed *)	2202	=item ev_embed_sweep (loop, ev_embed *)
1944		2203
1945	Make a single, non-blocking sweep over the embedded loop. This works	2204	Make a single, non-blocking sweep over the embedded loop. This works
1946	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2205	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1947	apropriate way for embedded loops.	2206	appropriate way for embedded loops.
1948		2207
1949	=item struct ev_loop *other [read-only]	2208	=item struct ev_loop *other [read-only]
1950		2209
1951	The embedded event loop.	2210	The embedded event loop.
1952		2211
1953	=back	2212	=back
		2213
		2214	=head3 Examples
		2215
		2216	Example: Try to get an embeddable event loop and embed it into the default
		2217	event loop. If that is not possible, use the default loop. The default
		2218	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2220	used).
		2221
		2222	struct ev_loop *loop_hi = ev_default_init (0);
		2223	struct ev_loop *loop_lo = 0;
		2224	struct ev_embed embed;
		2225
		2226	// see if there is a chance of getting one that works
		2227	// (remember that a flags value of 0 means autodetection)
		2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2230	: 0;
		2231
		2232	// if we got one, then embed it, otherwise default to loop_hi
		2233	if (loop_lo)
		2234	{
		2235	ev_embed_init (&embed, 0, loop_lo);
		2236	ev_embed_start (loop_hi, &embed);
		2237	}
		2238	else
		2239	loop_lo = loop_hi;
		2240
		2241	Example: Check if kqueue is available but not recommended and create
		2242	a kqueue backend for use with sockets (which usually work with any
		2243	kqueue implementation). Store the kqueue/socket-only event loop in
		2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2245
		2246	struct ev_loop *loop = ev_default_init (0);
		2247	struct ev_loop *loop_socket = 0;
		2248	struct ev_embed embed;
		2249
		2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2252	{
		2253	ev_embed_init (&embed, 0, loop_socket);
		2254	ev_embed_start (loop, &embed);
		2255	}
		2256
		2257	if (!loop_socket)
		2258	loop_socket = loop;
		2259
		2260	// now use loop_socket for all sockets, and loop for everything else
1954		2261
1955		2262
1956	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2263	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1957		2264
1958	Fork watchers are called when a C<fork ()> was detected (usually because	2265	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1974	believe me.	2281	believe me.
1975		2282
1976	=back	2283	=back
1977		2284
1978		2285
		2286	=head2 C<ev_async> - how to wake up another event loop
		2287
		2288	In general, you cannot use an C<ev_loop> from multiple threads or other
		2289	asynchronous sources such as signal handlers (as opposed to multiple event
		2290	loops - those are of course safe to use in different threads).
		2291
		2292	Sometimes, however, you need to wake up another event loop you do not
		2293	control, for example because it belongs to another thread. This is what
		2294	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2295	can signal it by calling C<ev_async_send>, which is thread- and signal
		2296	safe.
		2297
		2298	This functionality is very similar to C<ev_signal> watchers, as signals,
		2299	too, are asynchronous in nature, and signals, too, will be compressed
		2300	(i.e. the number of callback invocations may be less than the number of
		2301	C<ev_async_sent> calls).
		2302
		2303	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2304	just the default loop.
		2305
		2306	=head3 Queueing
		2307
		2308	C<ev_async> does not support queueing of data in any way. The reason
		2309	is that the author does not know of a simple (or any) algorithm for a
		2310	multiple-writer-single-reader queue that works in all cases and doesn't
		2311	need elaborate support such as pthreads.
		2312
		2313	That means that if you want to queue data, you have to provide your own
		2314	queue. But at least I can tell you would implement locking around your
		2315	queue:
		2316
		2317	=over 4
		2318
		2319	=item queueing from a signal handler context
		2320
		2321	To implement race-free queueing, you simply add to the queue in the signal
		2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2323	some fictitious SIGUSR1 handler:
		2324
		2325	static ev_async mysig;
		2326
		2327	static void
		2328	sigusr1_handler (void)
		2329	{
		2330	sometype data;
		2331
		2332	// no locking etc.
		2333	queue_put (data);
		2334	ev_async_send (EV_DEFAULT_ &mysig);
		2335	}
		2336
		2337	static void
		2338	mysig_cb (EV_P_ ev_async *w, int revents)
		2339	{
		2340	sometype data;
		2341	sigset_t block, prev;
		2342
		2343	sigemptyset (&block);
		2344	sigaddset (&block, SIGUSR1);
		2345	sigprocmask (SIG_BLOCK, &block, &prev);
		2346
		2347	while (queue_get (&data))
		2348	process (data);
		2349
		2350	if (sigismember (&prev, SIGUSR1)
		2351	sigprocmask (SIG_UNBLOCK, &block, 0);
		2352	}
		2353
		2354	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2355	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2356	either...).
		2357
		2358	=item queueing from a thread context
		2359
		2360	The strategy for threads is different, as you cannot (easily) block
		2361	threads but you can easily preempt them, so to queue safely you need to
		2362	employ a traditional mutex lock, such as in this pthread example:
		2363
		2364	static ev_async mysig;
		2365	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2366
		2367	static void
		2368	otherthread (void)
		2369	{
		2370	// only need to lock the actual queueing operation
		2371	pthread_mutex_lock (&mymutex);
		2372	queue_put (data);
		2373	pthread_mutex_unlock (&mymutex);
		2374
		2375	ev_async_send (EV_DEFAULT_ &mysig);
		2376	}
		2377
		2378	static void
		2379	mysig_cb (EV_P_ ev_async *w, int revents)
		2380	{
		2381	pthread_mutex_lock (&mymutex);
		2382
		2383	while (queue_get (&data))
		2384	process (data);
		2385
		2386	pthread_mutex_unlock (&mymutex);
		2387	}
		2388
		2389	=back
		2390
		2391
		2392	=head3 Watcher-Specific Functions and Data Members
		2393
		2394	=over 4
		2395
		2396	=item ev_async_init (ev_async *, callback)
		2397
		2398	Initialises and configures the async watcher - it has no parameters of any
		2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2400	believe me.
		2401
		2402	=item ev_async_send (loop, ev_async *)
		2403
		2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2406	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2408	section below on what exactly this means).
		2409
		2410	This call incurs the overhead of a system call only once per loop iteration,
		2411	so while the overhead might be noticeable, it doesn't apply to repeated
		2412	calls to C<ev_async_send>.
		2413
		2414	=item bool = ev_async_pending (ev_async *)
		2415
		2416	Returns a non-zero value when C<ev_async_send> has been called on the
		2417	watcher but the event has not yet been processed (or even noted) by the
		2418	event loop.
		2419
		2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2421	the loop iterates next and checks for the watcher to have become active,
		2422	it will reset the flag again. C<ev_async_pending> can be used to very
		2423	quickly check whether invoking the loop might be a good idea.
		2424
		2425	Not that this does I<not> check whether the watcher itself is pending, only
		2426	whether it has been requested to make this watcher pending.
		2427
		2428	=back
		2429
		2430
1979	=head1 OTHER FUNCTIONS	2431	=head1 OTHER FUNCTIONS
1980		2432
1981	There are some other functions of possible interest. Described. Here. Now.	2433	There are some other functions of possible interest. Described. Here. Now.
1982		2434
1983	=over 4	2435	=over 4
…		…
1990	or timeout without having to allocate/configure/start/stop/free one or	2442	or timeout without having to allocate/configure/start/stop/free one or
1991	more watchers yourself.	2443	more watchers yourself.
1992		2444
1993	If C<fd> is less than 0, then no I/O watcher will be started and events	2445	If C<fd> is less than 0, then no I/O watcher will be started and events
1994	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1995	C<events> set will be craeted and started.	2447	C<events> set will be created and started.
1996		2448
1997	If C<timeout> is less than 0, then no timeout watcher will be	2449	If C<timeout> is less than 0, then no timeout watcher will be
1998	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1999	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of
2000	dubious value.	2452	dubious value.
…		…
2002	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2003	passed an C<revents> set like normal event callbacks (a combination of	2455	passed an C<revents> set like normal event callbacks (a combination of
2004	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2005	value passed to C<ev_once>:	2457	value passed to C<ev_once>:
2006		2458
2007	static void stdin_ready (int revents, void *arg)	2459	static void stdin_ready (int revents, void *arg)
2008	{	2460	{
2009	if (revents & EV_TIMEOUT)	2461	if (revents & EV_TIMEOUT)
2010	/* doh, nothing entered */;	2462	/* doh, nothing entered */;
2011	else if (revents & EV_READ)	2463	else if (revents & EV_READ)
2012	/* stdin might have data for us, joy! */;	2464	/* stdin might have data for us, joy! */;
2013	}	2465	}
2014		2466
2015	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2016		2468
2017	=item ev_feed_event (ev_loop *, watcher *, int revents)	2469	=item ev_feed_event (ev_loop *, watcher *, int revents)
2018		2470
2019	Feeds the given event set into the event loop, as if the specified event	2471	Feeds the given event set into the event loop, as if the specified event
2020	had happened for the specified watcher (which must be a pointer to an	2472	had happened for the specified watcher (which must be a pointer to an
…		…
2025	Feed an event on the given fd, as if a file descriptor backend detected	2477	Feed an event on the given fd, as if a file descriptor backend detected
2026	the given events it.	2478	the given events it.
2027		2479
2028	=item ev_feed_signal_event (ev_loop *loop, int signum)	2480	=item ev_feed_signal_event (ev_loop *loop, int signum)
2029		2481
2030	Feed an event as if the given signal occured (C<loop> must be the default	2482	Feed an event as if the given signal occurred (C<loop> must be the default
2031	loop!).	2483	loop!).
2032		2484
2033	=back	2485	=back
2034		2486
2035		2487
…		…
2051		2503
2052	=item * Priorities are not currently supported. Initialising priorities	2504	=item * Priorities are not currently supported. Initialising priorities
2053	will fail and all watchers will have the same priority, even though there	2505	will fail and all watchers will have the same priority, even though there
2054	is an ev_pri field.	2506	is an ev_pri field.
2055		2507
		2508	=item * In libevent, the last base created gets the signals, in libev, the
		2509	first base created (== the default loop) gets the signals.
		2510
2056	=item * Other members are not supported.	2511	=item * Other members are not supported.
2057		2512
2058	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2513	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2059	to use the libev header file and library.	2514	to use the libev header file and library.
2060		2515
2061	=back	2516	=back
2062		2517
2063	=head1 C++ SUPPORT	2518	=head1 C++ SUPPORT
2064		2519
2065	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2520	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2066	you to use some convinience methods to start/stop watchers and also change	2521	you to use some convenience methods to start/stop watchers and also change
2067	the callback model to a model using method callbacks on objects.	2522	the callback model to a model using method callbacks on objects.
2068		2523
2069	To use it,	2524	To use it,
2070		2525
2071	#include <ev++.h>	2526	#include <ev++.h>
2072		2527
2073	This automatically includes F<ev.h> and puts all of its definitions (many	2528	This automatically includes F<ev.h> and puts all of its definitions (many
2074	of them macros) into the global namespace. All C++ specific things are	2529	of them macros) into the global namespace. All C++ specific things are
2075	put into the C<ev> namespace. It should support all the same embedding	2530	put into the C<ev> namespace. It should support all the same embedding
2076	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2531	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2143	your compiler is good :), then the method will be fully inlined into the	2598	your compiler is good :), then the method will be fully inlined into the
2144	thunking function, making it as fast as a direct C callback.	2599	thunking function, making it as fast as a direct C callback.
2145		2600
2146	Example: simple class declaration and watcher initialisation	2601	Example: simple class declaration and watcher initialisation
2147		2602
2148	struct myclass	2603	struct myclass
2149	{	2604	{
2150	void io_cb (ev::io &w, int revents) { }	2605	void io_cb (ev::io &w, int revents) { }
2151	}	2606	}
2152		2607
2153	myclass obj;	2608	myclass obj;
2154	ev::io iow;	2609	ev::io iow;
2155	iow.set <myclass, &myclass::io_cb> (&obj);	2610	iow.set <myclass, &myclass::io_cb> (&obj);
2156		2611
2157	=item w->set<function> (void *data = 0)	2612	=item w->set<function> (void *data = 0)
2158		2613
2159	Also sets a callback, but uses a static method or plain function as	2614	Also sets a callback, but uses a static method or plain function as
2160	callback. The optional C<data> argument will be stored in the watcher's	2615	callback. The optional C<data> argument will be stored in the watcher's
…		…
2164		2619
2165	See the method-C<set> above for more details.	2620	See the method-C<set> above for more details.
2166		2621
2167	Example:	2622	Example:
2168		2623
2169	static void io_cb (ev::io &w, int revents) { }	2624	static void io_cb (ev::io &w, int revents) { }
2170	iow.set <io_cb> ();	2625	iow.set <io_cb> ();
2171		2626
2172	=item w->set (struct ev_loop *)	2627	=item w->set (struct ev_loop *)
2173		2628
2174	Associates a different C<struct ev_loop> with this watcher. You can only	2629	Associates a different C<struct ev_loop> with this watcher. You can only
2175	do this when the watcher is inactive (and not pending either).	2630	do this when the watcher is inactive (and not pending either).
2176		2631
2177	=item w->set ([args])	2632	=item w->set ([arguments])
2178		2633
2179	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2634	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2180	called at least once. Unlike the C counterpart, an active watcher gets	2635	called at least once. Unlike the C counterpart, an active watcher gets
2181	automatically stopped and restarted when reconfiguring it with this	2636	automatically stopped and restarted when reconfiguring it with this
2182	method.	2637	method.
2183		2638
2184	=item w->start ()	2639	=item w->start ()
…		…
2208	=back	2663	=back
2209		2664
2210	Example: Define a class with an IO and idle watcher, start one of them in	2665	Example: Define a class with an IO and idle watcher, start one of them in
2211	the constructor.	2666	the constructor.
2212		2667
2213	class myclass	2668	class myclass
2214	{	2669	{
2215	ev_io io; void io_cb (ev::io &w, int revents);	2670	ev::io io; void io_cb (ev::io &w, int revents);
2216	ev_idle idle void idle_cb (ev::idle &w, int revents);	2671	ev:idle idle void idle_cb (ev::idle &w, int revents);
2217		2672
2218	myclass ();	2673	myclass (int fd)
2219	}	2674	{
2220
2221	myclass::myclass (int fd)
2222	{
2223	io .set <myclass, &myclass::io_cb > (this);	2675	io .set <myclass, &myclass::io_cb > (this);
2224	idle.set <myclass, &myclass::idle_cb> (this);	2676	idle.set <myclass, &myclass::idle_cb> (this);
2225		2677
2226	io.start (fd, ev::READ);	2678	io.start (fd, ev::READ);
		2679	}
2227	}	2680	};
		2681
		2682
		2683	=head1 OTHER LANGUAGE BINDINGS
		2684
		2685	Libev does not offer other language bindings itself, but bindings for a
		2686	number of languages exist in the form of third-party packages. If you know
		2687	any interesting language binding in addition to the ones listed here, drop
		2688	me a note.
		2689
		2690	=over 4
		2691
		2692	=item Perl
		2693
		2694	The EV module implements the full libev API and is actually used to test
		2695	libev. EV is developed together with libev. Apart from the EV core module,
		2696	there are additional modules that implement libev-compatible interfaces
		2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2699
		2700	It can be found and installed via CPAN, its homepage is at
		2701	L<http://software.schmorp.de/pkg/EV>.
		2702
		2703	=item Python
		2704
		2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2706	seems to be quite complete and well-documented. Note, however, that the
		2707	patch they require for libev is outright dangerous as it breaks the ABI
		2708	for everybody else, and therefore, should never be applied in an installed
		2709	libev (if python requires an incompatible ABI then it needs to embed
		2710	libev).
		2711
		2712	=item Ruby
		2713
		2714	Tony Arcieri has written a ruby extension that offers access to a subset
		2715	of the libev API and adds file handle abstractions, asynchronous DNS and
		2716	more on top of it. It can be found via gem servers. Its homepage is at
		2717	L<http://rev.rubyforge.org/>.
		2718
		2719	=item D
		2720
		2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2723
		2724	=back
2228		2725
2229		2726
2230	=head1 MACRO MAGIC	2727	=head1 MACRO MAGIC
2231		2728
2232	Libev can be compiled with a variety of options, the most fundamantal	2729	Libev can be compiled with a variety of options, the most fundamental
2233	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2730	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2234	functions and callbacks have an initial C<struct ev_loop *> argument.	2731	functions and callbacks have an initial C<struct ev_loop *> argument.
2235		2732
2236	To make it easier to write programs that cope with either variant, the	2733	To make it easier to write programs that cope with either variant, the
2237	following macros are defined:	2734	following macros are defined:
…		…
2242		2739
2243	This provides the loop I<argument> for functions, if one is required ("ev	2740	This provides the loop I<argument> for functions, if one is required ("ev
2244	loop argument"). The C<EV_A> form is used when this is the sole argument,	2741	loop argument"). The C<EV_A> form is used when this is the sole argument,
2245	C<EV_A_> is used when other arguments are following. Example:	2742	C<EV_A_> is used when other arguments are following. Example:
2246		2743
2247	ev_unref (EV_A);	2744	ev_unref (EV_A);
2248	ev_timer_add (EV_A_ watcher);	2745	ev_timer_add (EV_A_ watcher);
2249	ev_loop (EV_A_ 0);	2746	ev_loop (EV_A_ 0);
2250		2747
2251	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2748	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2252	which is often provided by the following macro.	2749	which is often provided by the following macro.
2253		2750
2254	=item C<EV_P>, C<EV_P_>	2751	=item C<EV_P>, C<EV_P_>
2255		2752
2256	This provides the loop I<parameter> for functions, if one is required ("ev	2753	This provides the loop I<parameter> for functions, if one is required ("ev
2257	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2754	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2258	C<EV_P_> is used when other parameters are following. Example:	2755	C<EV_P_> is used when other parameters are following. Example:
2259		2756
2260	// this is how ev_unref is being declared	2757	// this is how ev_unref is being declared
2261	static void ev_unref (EV_P);	2758	static void ev_unref (EV_P);
2262		2759
2263	// this is how you can declare your typical callback	2760	// this is how you can declare your typical callback
2264	static void cb (EV_P_ ev_timer *w, int revents)	2761	static void cb (EV_P_ ev_timer *w, int revents)
2265		2762
2266	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2763	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2267	suitable for use with C<EV_A>.	2764	suitable for use with C<EV_A>.
2268		2765
2269	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2766	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2270		2767
2271	Similar to the other two macros, this gives you the value of the default	2768	Similar to the other two macros, this gives you the value of the default
2272	loop, if multiple loops are supported ("ev loop default").	2769	loop, if multiple loops are supported ("ev loop default").
		2770
		2771	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2772
		2773	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2774	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2775	is undefined when the default loop has not been initialised by a previous
		2776	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2777
		2778	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2779	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2273		2780
2274	=back	2781	=back
2275		2782
2276	Example: Declare and initialise a check watcher, utilising the above	2783	Example: Declare and initialise a check watcher, utilising the above
2277	macros so it will work regardless of whether multiple loops are supported	2784	macros so it will work regardless of whether multiple loops are supported
2278	or not.	2785	or not.
2279		2786
2280	static void	2787	static void
2281	check_cb (EV_P_ ev_timer *w, int revents)	2788	check_cb (EV_P_ ev_timer *w, int revents)
2282	{	2789	{
2283	ev_check_stop (EV_A_ w);	2790	ev_check_stop (EV_A_ w);
2284	}	2791	}
2285		2792
2286	ev_check check;	2793	ev_check check;
2287	ev_check_init (&check, check_cb);	2794	ev_check_init (&check, check_cb);
2288	ev_check_start (EV_DEFAULT_ &check);	2795	ev_check_start (EV_DEFAULT_ &check);
2289	ev_loop (EV_DEFAULT_ 0);	2796	ev_loop (EV_DEFAULT_ 0);
2290		2797
2291	=head1 EMBEDDING	2798	=head1 EMBEDDING
2292		2799
2293	Libev can (and often is) directly embedded into host	2800	Libev can (and often is) directly embedded into host
2294	applications. Examples of applications that embed it include the Deliantra	2801	applications. Examples of applications that embed it include the Deliantra
…		…
2301	libev somewhere in your source tree).	2808	libev somewhere in your source tree).
2302		2809
2303	=head2 FILESETS	2810	=head2 FILESETS
2304		2811
2305	Depending on what features you need you need to include one or more sets of files	2812	Depending on what features you need you need to include one or more sets of files
2306	in your app.	2813	in your application.
2307		2814
2308	=head3 CORE EVENT LOOP	2815	=head3 CORE EVENT LOOP
2309		2816
2310	To include only the libev core (all the C<ev_*> functions), with manual	2817	To include only the libev core (all the C<ev_*> functions), with manual
2311	configuration (no autoconf):	2818	configuration (no autoconf):
2312		2819
2313	#define EV_STANDALONE 1	2820	#define EV_STANDALONE 1
2314	#include "ev.c"	2821	#include "ev.c"
2315		2822
2316	This will automatically include F<ev.h>, too, and should be done in a	2823	This will automatically include F<ev.h>, too, and should be done in a
2317	single C source file only to provide the function implementations. To use	2824	single C source file only to provide the function implementations. To use
2318	it, do the same for F<ev.h> in all files wishing to use this API (best	2825	it, do the same for F<ev.h> in all files wishing to use this API (best
2319	done by writing a wrapper around F<ev.h> that you can include instead and	2826	done by writing a wrapper around F<ev.h> that you can include instead and
2320	where you can put other configuration options):	2827	where you can put other configuration options):
2321		2828
2322	#define EV_STANDALONE 1	2829	#define EV_STANDALONE 1
2323	#include "ev.h"	2830	#include "ev.h"
2324		2831
2325	Both header files and implementation files can be compiled with a C++	2832	Both header files and implementation files can be compiled with a C++
2326	compiler (at least, thats a stated goal, and breakage will be treated	2833	compiler (at least, thats a stated goal, and breakage will be treated
2327	as a bug).	2834	as a bug).
2328		2835
2329	You need the following files in your source tree, or in a directory	2836	You need the following files in your source tree, or in a directory
2330	in your include path (e.g. in libev/ when using -Ilibev):	2837	in your include path (e.g. in libev/ when using -Ilibev):
2331		2838
2332	ev.h	2839	ev.h
2333	ev.c	2840	ev.c
2334	ev_vars.h	2841	ev_vars.h
2335	ev_wrap.h	2842	ev_wrap.h
2336		2843
2337	ev_win32.c required on win32 platforms only	2844	ev_win32.c required on win32 platforms only
2338		2845
2339	ev_select.c only when select backend is enabled (which is enabled by default)	2846	ev_select.c only when select backend is enabled (which is enabled by default)
2340	ev_poll.c only when poll backend is enabled (disabled by default)	2847	ev_poll.c only when poll backend is enabled (disabled by default)
2341	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2848	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2342	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2849	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2343	ev_port.c only when the solaris port backend is enabled (disabled by default)	2850	ev_port.c only when the solaris port backend is enabled (disabled by default)
2344		2851
2345	F<ev.c> includes the backend files directly when enabled, so you only need	2852	F<ev.c> includes the backend files directly when enabled, so you only need
2346	to compile this single file.	2853	to compile this single file.
2347		2854
2348	=head3 LIBEVENT COMPATIBILITY API	2855	=head3 LIBEVENT COMPATIBILITY API
2349		2856
2350	To include the libevent compatibility API, also include:	2857	To include the libevent compatibility API, also include:
2351		2858
2352	#include "event.c"	2859	#include "event.c"
2353		2860
2354	in the file including F<ev.c>, and:	2861	in the file including F<ev.c>, and:
2355		2862
2356	#include "event.h"	2863	#include "event.h"
2357		2864
2358	in the files that want to use the libevent API. This also includes F<ev.h>.	2865	in the files that want to use the libevent API. This also includes F<ev.h>.
2359		2866
2360	You need the following additional files for this:	2867	You need the following additional files for this:
2361		2868
2362	event.h	2869	event.h
2363	event.c	2870	event.c
2364		2871
2365	=head3 AUTOCONF SUPPORT	2872	=head3 AUTOCONF SUPPORT
2366		2873
2367	Instead of using C<EV_STANDALONE=1> and providing your config in	2874	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2368	whatever way you want, you can also C<m4_include([libev.m4])> in your	2875	whatever way you want, you can also C<m4_include([libev.m4])> in your
2369	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2876	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2370	include F<config.h> and configure itself accordingly.	2877	include F<config.h> and configure itself accordingly.
2371		2878
2372	For this of course you need the m4 file:	2879	For this of course you need the m4 file:
2373		2880
2374	libev.m4	2881	libev.m4
2375		2882
2376	=head2 PREPROCESSOR SYMBOLS/MACROS	2883	=head2 PREPROCESSOR SYMBOLS/MACROS
2377		2884
2378	Libev can be configured via a variety of preprocessor symbols you have to define	2885	Libev can be configured via a variety of preprocessor symbols you have to
2379	before including any of its files. The default is not to build for multiplicity	2886	define before including any of its files. The default in the absence of
2380	and only include the select backend.	2887	autoconf is noted for every option.
2381		2888
2382	=over 4	2889	=over 4
2383		2890
2384	=item EV_STANDALONE	2891	=item EV_STANDALONE
2385		2892
…		…
2390	F<event.h> that are not directly supported by the libev core alone.	2897	F<event.h> that are not directly supported by the libev core alone.
2391		2898
2392	=item EV_USE_MONOTONIC	2899	=item EV_USE_MONOTONIC
2393		2900
2394	If defined to be C<1>, libev will try to detect the availability of the	2901	If defined to be C<1>, libev will try to detect the availability of the
2395	monotonic clock option at both compiletime and runtime. Otherwise no use	2902	monotonic clock option at both compile time and runtime. Otherwise no use
2396	of the monotonic clock option will be attempted. If you enable this, you	2903	of the monotonic clock option will be attempted. If you enable this, you
2397	usually have to link against librt or something similar. Enabling it when	2904	usually have to link against librt or something similar. Enabling it when
2398	the functionality isn't available is safe, though, although you have	2905	the functionality isn't available is safe, though, although you have
2399	to make sure you link against any libraries where the C<clock_gettime>	2906	to make sure you link against any libraries where the C<clock_gettime>
2400	function is hiding in (often F<-lrt>).	2907	function is hiding in (often F<-lrt>).
2401		2908
2402	=item EV_USE_REALTIME	2909	=item EV_USE_REALTIME
2403		2910
2404	If defined to be C<1>, libev will try to detect the availability of the	2911	If defined to be C<1>, libev will try to detect the availability of the
2405	realtime clock option at compiletime (and assume its availability at	2912	real-time clock option at compile time (and assume its availability at
2406	runtime if successful). Otherwise no use of the realtime clock option will	2913	runtime if successful). Otherwise no use of the real-time clock option will
2407	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2408	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2409	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2410		2917
2411	=item EV_USE_NANOSLEEP	2918	=item EV_USE_NANOSLEEP
2412		2919
2413	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2414	and will use it for delays. Otherwise it will use C<select ()>.	2921	and will use it for delays. Otherwise it will use C<select ()>.
2415		2922
		2923	=item EV_USE_EVENTFD
		2924
		2925	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2926	available and will probe for kernel support at runtime. This will improve
		2927	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2928	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2929	2.7 or newer, otherwise disabled.
		2930
2416	=item EV_USE_SELECT	2931	=item EV_USE_SELECT
2417		2932
2418	If undefined or defined to be C<1>, libev will compile in support for the	2933	If undefined or defined to be C<1>, libev will compile in support for the
2419	C<select>(2) backend. No attempt at autodetection will be done: if no	2934	C<select>(2) backend. No attempt at auto-detection will be done: if no
2420	other method takes over, select will be it. Otherwise the select backend	2935	other method takes over, select will be it. Otherwise the select backend
2421	will not be compiled in.	2936	will not be compiled in.
2422		2937
2423	=item EV_SELECT_USE_FD_SET	2938	=item EV_SELECT_USE_FD_SET
2424		2939
2425	If defined to C<1>, then the select backend will use the system C<fd_set>	2940	If defined to C<1>, then the select backend will use the system C<fd_set>
2426	structure. This is useful if libev doesn't compile due to a missing	2941	structure. This is useful if libev doesn't compile due to a missing
2427	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2428	exotic systems. This usually limits the range of file descriptors to some	2943	exotic systems. This usually limits the range of file descriptors to some
2429	low limit such as 1024 or might have other limitations (winsocket only	2944	low limit such as 1024 or might have other limitations (winsocket only
2430	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2431	influence the size of the C<fd_set> used.	2946	influence the size of the C<fd_set> used.
2432		2947
…		…
2438	be used is the winsock select). This means that it will call	2953	be used is the winsock select). This means that it will call
2439	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2954	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2440	it is assumed that all these functions actually work on fds, even	2955	it is assumed that all these functions actually work on fds, even
2441	on win32. Should not be defined on non-win32 platforms.	2956	on win32. Should not be defined on non-win32 platforms.
2442		2957
		2958	=item EV_FD_TO_WIN32_HANDLE
		2959
		2960	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2961	file descriptors to socket handles. When not defining this symbol (the
		2962	default), then libev will call C<_get_osfhandle>, which is usually
		2963	correct. In some cases, programs use their own file descriptor management,
		2964	in which case they can provide this function to map fds to socket handles.
		2965
2443	=item EV_USE_POLL	2966	=item EV_USE_POLL
2444		2967
2445	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2968	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2446	backend. Otherwise it will be enabled on non-win32 platforms. It	2969	backend. Otherwise it will be enabled on non-win32 platforms. It
2447	takes precedence over select.	2970	takes precedence over select.
2448		2971
2449	=item EV_USE_EPOLL	2972	=item EV_USE_EPOLL
2450		2973
2451	If defined to be C<1>, libev will compile in support for the Linux	2974	If defined to be C<1>, libev will compile in support for the Linux
2452	C<epoll>(7) backend. Its availability will be detected at runtime,	2975	C<epoll>(7) backend. Its availability will be detected at runtime,
2453	otherwise another method will be used as fallback. This is the	2976	otherwise another method will be used as fallback. This is the preferred
2454	preferred backend for GNU/Linux systems.	2977	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2978	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2455		2979
2456	=item EV_USE_KQUEUE	2980	=item EV_USE_KQUEUE
2457		2981
2458	If defined to be C<1>, libev will compile in support for the BSD style	2982	If defined to be C<1>, libev will compile in support for the BSD style
2459	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2983	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2472	otherwise another method will be used as fallback. This is the preferred	2996	otherwise another method will be used as fallback. This is the preferred
2473	backend for Solaris 10 systems.	2997	backend for Solaris 10 systems.
2474		2998
2475	=item EV_USE_DEVPOLL	2999	=item EV_USE_DEVPOLL
2476		3000
2477	reserved for future expansion, works like the USE symbols above.	3001	Reserved for future expansion, works like the USE symbols above.
2478		3002
2479	=item EV_USE_INOTIFY	3003	=item EV_USE_INOTIFY
2480		3004
2481	If defined to be C<1>, libev will compile in support for the Linux inotify	3005	If defined to be C<1>, libev will compile in support for the Linux inotify
2482	interface to speed up C<ev_stat> watchers. Its actual availability will	3006	interface to speed up C<ev_stat> watchers. Its actual availability will
2483	be detected at runtime.	3007	be detected at runtime. If undefined, it will be enabled if the headers
		3008	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3009
		3010	=item EV_ATOMIC_T
		3011
		3012	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3013	access is atomic with respect to other threads or signal contexts. No such
		3014	type is easily found in the C language, so you can provide your own type
		3015	that you know is safe for your purposes. It is used both for signal handler "locking"
		3016	as well as for signal and thread safety in C<ev_async> watchers.
		3017
		3018	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3019	(from F<signal.h>), which is usually good enough on most platforms.
2484		3020
2485	=item EV_H	3021	=item EV_H
2486		3022
2487	The name of the F<ev.h> header file used to include it. The default if	3023	The name of the F<ev.h> header file used to include it. The default if
2488	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3024	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2489	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3025	used to virtually rename the F<ev.h> header file in case of conflicts.
2490		3026
2491	=item EV_CONFIG_H	3027	=item EV_CONFIG_H
2492		3028
2493	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3029	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2494	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3030	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2495	C<EV_H>, above.	3031	C<EV_H>, above.
2496		3032
2497	=item EV_EVENT_H	3033	=item EV_EVENT_H
2498		3034
2499	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3035	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2500	of how the F<event.h> header can be found.	3036	of how the F<event.h> header can be found, the default is C<"event.h">.
2501		3037
2502	=item EV_PROTOTYPES	3038	=item EV_PROTOTYPES
2503		3039
2504	If defined to be C<0>, then F<ev.h> will not define any function	3040	If defined to be C<0>, then F<ev.h> will not define any function
2505	prototypes, but still define all the structs and other symbols. This is	3041	prototypes, but still define all the structs and other symbols. This is
…		…
2526	When doing priority-based operations, libev usually has to linearly search	3062	When doing priority-based operations, libev usually has to linearly search
2527	all the priorities, so having many of them (hundreds) uses a lot of space	3063	all the priorities, so having many of them (hundreds) uses a lot of space
2528	and time, so using the defaults of five priorities (-2 .. +2) is usually	3064	and time, so using the defaults of five priorities (-2 .. +2) is usually
2529	fine.	3065	fine.
2530		3066
2531	If your embedding app does not need any priorities, defining these both to	3067	If your embedding application does not need any priorities, defining these both to
2532	C<0> will save some memory and cpu.	3068	C<0> will save some memory and CPU.
2533		3069
2534	=item EV_PERIODIC_ENABLE	3070	=item EV_PERIODIC_ENABLE
2535		3071
2536	If undefined or defined to be C<1>, then periodic timers are supported. If	3072	If undefined or defined to be C<1>, then periodic timers are supported. If
2537	defined to be C<0>, then they are not. Disabling them saves a few kB of	3073	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2556	=item EV_FORK_ENABLE	3092	=item EV_FORK_ENABLE
2557		3093
2558	If undefined or defined to be C<1>, then fork watchers are supported. If	3094	If undefined or defined to be C<1>, then fork watchers are supported. If
2559	defined to be C<0>, then they are not.	3095	defined to be C<0>, then they are not.
2560		3096
		3097	=item EV_ASYNC_ENABLE
		3098
		3099	If undefined or defined to be C<1>, then async watchers are supported. If
		3100	defined to be C<0>, then they are not.
		3101
2561	=item EV_MINIMAL	3102	=item EV_MINIMAL
2562		3103
2563	If you need to shave off some kilobytes of code at the expense of some	3104	If you need to shave off some kilobytes of code at the expense of some
2564	speed, define this symbol to C<1>. Currently only used for gcc to override	3105	speed, define this symbol to C<1>. Currently this is used to override some
2565	some inlining decisions, saves roughly 30% codesize of amd64.	3106	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3107	much smaller 2-heap for timer management over the default 4-heap.
2566		3108
2567	=item EV_PID_HASHSIZE	3109	=item EV_PID_HASHSIZE
2568		3110
2569	C<ev_child> watchers use a small hash table to distribute workload by	3111	C<ev_child> watchers use a small hash table to distribute workload by
2570	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3112	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2577	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3119	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2578	usually more than enough. If you need to manage thousands of C<ev_stat>	3120	usually more than enough. If you need to manage thousands of C<ev_stat>
2579	watchers you might want to increase this value (I<must> be a power of	3121	watchers you might want to increase this value (I<must> be a power of
2580	two).	3122	two).
2581		3123
		3124	=item EV_USE_4HEAP
		3125
		3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3128	to C<1>. The 4-heap uses more complicated (longer) code but has
		3129	noticeably faster performance with many (thousands) of watchers.
		3130
		3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3132	(disabled).
		3133
		3134	=item EV_HEAP_CACHE_AT
		3135
		3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3137	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3140	but avoids random read accesses on heap changes. This improves performance
		3141	noticeably with with many (hundreds) of watchers.
		3142
		3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3144	(disabled).
		3145
		3146	=item EV_VERIFY
		3147
		3148	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3149	be done: If set to C<0>, no internal verification code will be compiled
		3150	in. If set to C<1>, then verification code will be compiled in, but not
		3151	called. If set to C<2>, then the internal verification code will be
		3152	called once per loop, which can slow down libev. If set to C<3>, then the
		3153	verification code will be called very frequently, which will slow down
		3154	libev considerably.
		3155
		3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3157	C<0.>
		3158
2582	=item EV_COMMON	3159	=item EV_COMMON
2583		3160
2584	By default, all watchers have a C<void *data> member. By redefining	3161	By default, all watchers have a C<void *data> member. By redefining
2585	this macro to a something else you can include more and other types of	3162	this macro to a something else you can include more and other types of
2586	members. You have to define it each time you include one of the files,	3163	members. You have to define it each time you include one of the files,
2587	though, and it must be identical each time.	3164	though, and it must be identical each time.
2588		3165
2589	For example, the perl EV module uses something like this:	3166	For example, the perl EV module uses something like this:
2590		3167
2591	#define EV_COMMON \	3168	#define EV_COMMON \
2592	SV *self; /* contains this struct */ \	3169	SV *self; /* contains this struct */ \
2593	SV *cb_sv, *fh /* note no trailing ";" */	3170	SV *cb_sv, *fh /* note no trailing ";" */
2594		3171
2595	=item EV_CB_DECLARE (type)	3172	=item EV_CB_DECLARE (type)
2596		3173
2597	=item EV_CB_INVOKE (watcher, revents)	3174	=item EV_CB_INVOKE (watcher, revents)
2598		3175
…		…
2605	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2606	method calls instead of plain function calls in C++.	3183	method calls instead of plain function calls in C++.
2607		3184
2608	=head2 EXPORTED API SYMBOLS	3185	=head2 EXPORTED API SYMBOLS
2609		3186
2610	If you need to re-export the API (e.g. via a dll) and you need a list of	3187	If you need to re-export the API (e.g. via a DLL) and you need a list of
2611	exported symbols, you can use the provided F<Symbol.*> files which list	3188	exported symbols, you can use the provided F<Symbol.*> files which list
2612	all public symbols, one per line:	3189	all public symbols, one per line:
2613		3190
2614	Symbols.ev for libev proper	3191	Symbols.ev for libev proper
2615	Symbols.event for the libevent emulation	3192	Symbols.event for the libevent emulation
2616		3193
2617	This can also be used to rename all public symbols to avoid clashes with	3194	This can also be used to rename all public symbols to avoid clashes with
2618	multiple versions of libev linked together (which is obviously bad in	3195	multiple versions of libev linked together (which is obviously bad in
2619	itself, but sometimes it is inconvinient to avoid this).	3196	itself, but sometimes it is inconvenient to avoid this).
2620		3197
2621	A sed command like this will create wrapper C<#define>'s that you need to	3198	A sed command like this will create wrapper C<#define>'s that you need to
2622	include before including F<ev.h>:	3199	include before including F<ev.h>:
2623		3200
2624	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3201	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2641	file.	3218	file.
2642		3219
2643	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3220	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2644	that everybody includes and which overrides some configure choices:	3221	that everybody includes and which overrides some configure choices:
2645		3222
2646	#define EV_MINIMAL 1	3223	#define EV_MINIMAL 1
2647	#define EV_USE_POLL 0	3224	#define EV_USE_POLL 0
2648	#define EV_MULTIPLICITY 0	3225	#define EV_MULTIPLICITY 0
2649	#define EV_PERIODIC_ENABLE 0	3226	#define EV_PERIODIC_ENABLE 0
2650	#define EV_STAT_ENABLE 0	3227	#define EV_STAT_ENABLE 0
2651	#define EV_FORK_ENABLE 0	3228	#define EV_FORK_ENABLE 0
2652	#define EV_CONFIG_H <config.h>	3229	#define EV_CONFIG_H <config.h>
2653	#define EV_MINPRI 0	3230	#define EV_MINPRI 0
2654	#define EV_MAXPRI 0	3231	#define EV_MAXPRI 0
2655		3232
2656	#include "ev++.h"	3233	#include "ev++.h"
2657		3234
2658	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2659		3236
2660	#include "ev_cpp.h"	3237	#include "ev_cpp.h"
2661	#include "ev.c"	3238	#include "ev.c"
		3239
		3240
		3241	=head1 THREADS AND COROUTINES
		3242
		3243	=head2 THREADS
		3244
		3245	Libev itself is thread-safe (unless the opposite is specifically
		3246	documented for a function), but it uses no locking itself. This means that
		3247	you can use as many loops as you want in parallel, as long as only one
		3248	thread ever calls into one libev function with the same loop parameter:
		3249	libev guarentees that different event loops share no data structures that
		3250	need locking.
		3251
		3252	Or to put it differently: calls with different loop parameters can be done
		3253	concurrently from multiple threads, calls with the same loop parameter
		3254	must be done serially (but can be done from different threads, as long as
		3255	only one thread ever is inside a call at any point in time, e.g. by using
		3256	a mutex per loop).
		3257
		3258	Specifically to support threads (and signal handlers), libev implements
		3259	so-called C<ev_async> watchers, which allow some limited form of
		3260	concurrency on the same event loop.
		3261
		3262	If you want to know which design (one loop, locking, or multiple loops
		3263	without or something else still) is best for your problem, then I cannot
		3264	help you. I can give some generic advice however:
		3265
		3266	=over 4
		3267
		3268	=item * most applications have a main thread: use the default libev loop
		3269	in that thread, or create a separate thread running only the default loop.
		3270
		3271	This helps integrating other libraries or software modules that use libev
		3272	themselves and don't care/know about threading.
		3273
		3274	=item * one loop per thread is usually a good model.
		3275
		3276	Doing this is almost never wrong, sometimes a better-performance model
		3277	exists, but it is always a good start.
		3278
		3279	=item * other models exist, such as the leader/follower pattern, where one
		3280	loop is handed through multiple threads in a kind of round-robin fashion.
		3281
		3282	Choosing a model is hard - look around, learn, know that usually you can do
		3283	better than you currently do :-)
		3284
		3285	=item * often you need to talk to some other thread which blocks in the
		3286	event loop - C<ev_async> watchers can be used to wake them up from other
		3287	threads safely (or from signal contexts...).
		3288
		3289	=item * some watcher types are only supported in the default loop - use
		3290	C<ev_async> watchers to tell your other loops about any such events.
		3291
		3292	=back
		3293
		3294	=head2 COROUTINES
		3295
		3296	Libev is much more accommodating to coroutines ("cooperative threads"):
		3297	libev fully supports nesting calls to it's functions from different
		3298	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3299	different coroutines and switch freely between both coroutines running the
		3300	loop, as long as you don't confuse yourself). The only exception is that
		3301	you must not do this from C<ev_periodic> reschedule callbacks.
		3302
		3303	Care has been taken to ensure that libev does not keep local state inside
		3304	C<ev_loop>, and other calls do not usually allow coroutine switches.
2662		3305
2663		3306
2664	=head1 COMPLEXITIES	3307	=head1 COMPLEXITIES
2665		3308
2666	In this section the complexities of (many of) the algorithms used inside	3309	In this section the complexities of (many of) the algorithms used inside
…		…
2684	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3327	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2685		3328
2686	That means that changing a timer costs less than removing/adding them	3329	That means that changing a timer costs less than removing/adding them
2687	as only the relative motion in the event queue has to be paid for.	3330	as only the relative motion in the event queue has to be paid for.
2688		3331
2689	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3332	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2690		3333
2691	These just add the watcher into an array or at the head of a list.	3334	These just add the watcher into an array or at the head of a list.
2692		3335
2693	=item Stopping check/prepare/idle watchers: O(1)	3336	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2694		3337
2695	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3338	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2696		3339
2697	These watchers are stored in lists then need to be walked to find the	3340	These watchers are stored in lists then need to be walked to find the
2698	correct watcher to remove. The lists are usually short (you don't usually	3341	correct watcher to remove. The lists are usually short (you don't usually
2699	have many watchers waiting for the same fd or signal).	3342	have many watchers waiting for the same fd or signal).
2700		3343
2701	=item Finding the next timer in each loop iteration: O(1)	3344	=item Finding the next timer in each loop iteration: O(1)
2702		3345
2703	By virtue of using a binary heap, the next timer is always found at the	3346	By virtue of using a binary or 4-heap, the next timer is always found at a
2704	beginning of the storage array.	3347	fixed position in the storage array.
2705		3348
2706	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3349	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2707		3350
2708	A change means an I/O watcher gets started or stopped, which requires	3351	A change means an I/O watcher gets started or stopped, which requires
2709	libev to recalculate its status (and possibly tell the kernel, depending	3352	libev to recalculate its status (and possibly tell the kernel, depending
2710	on backend and wether C<ev_io_set> was used).	3353	on backend and whether C<ev_io_set> was used).
2711		3354
2712	=item Activating one watcher (putting it into the pending state): O(1)	3355	=item Activating one watcher (putting it into the pending state): O(1)
2713		3356
2714	=item Priority handling: O(number_of_priorities)	3357	=item Priority handling: O(number_of_priorities)
2715		3358
2716	Priorities are implemented by allocating some space for each	3359	Priorities are implemented by allocating some space for each
2717	priority. When doing priority-based operations, libev usually has to	3360	priority. When doing priority-based operations, libev usually has to
2718	linearly search all the priorities, but starting/stopping and activating	3361	linearly search all the priorities, but starting/stopping and activating
2719	watchers becomes O(1) w.r.t. prioritiy handling.	3362	watchers becomes O(1) w.r.t. priority handling.
		3363
		3364	=item Sending an ev_async: O(1)
		3365
		3366	=item Processing ev_async_send: O(number_of_async_watchers)
		3367
		3368	=item Processing signals: O(max_signal_number)
		3369
		3370	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3371	calls in the current loop iteration. Checking for async and signal events
		3372	involves iterating over all running async watchers or all signal numbers.
2720		3373
2721	=back	3374	=back
2722		3375
2723		3376
		3377	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3378
		3379	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3380	requires, and its I/O model is fundamentally incompatible with the POSIX
		3381	model. Libev still offers limited functionality on this platform in
		3382	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3383	descriptors. This only applies when using Win32 natively, not when using
		3384	e.g. cygwin.
		3385
		3386	Lifting these limitations would basically require the full
		3387	re-implementation of the I/O system. If you are into these kinds of
		3388	things, then note that glib does exactly that for you in a very portable
		3389	way (note also that glib is the slowest event library known to man).
		3390
		3391	There is no supported compilation method available on windows except
		3392	embedding it into other applications.
		3393
		3394	Not a libev limitation but worth mentioning: windows apparently doesn't
		3395	accept large writes: instead of resulting in a partial write, windows will
		3396	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3397	so make sure you only write small amounts into your sockets (less than a
		3398	megabyte seems safe, but thsi apparently depends on the amount of memory
		3399	available).
		3400
		3401	Due to the many, low, and arbitrary limits on the win32 platform and
		3402	the abysmal performance of winsockets, using a large number of sockets
		3403	is not recommended (and not reasonable). If your program needs to use
		3404	more than a hundred or so sockets, then likely it needs to use a totally
		3405	different implementation for windows, as libev offers the POSIX readiness
		3406	notification model, which cannot be implemented efficiently on windows
		3407	(Microsoft monopoly games).
		3408
		3409	A typical way to use libev under windows is to embed it (see the embedding
		3410	section for details) and use the following F<evwrap.h> header file instead
		3411	of F<ev.h>:
		3412
		3413	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3414	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3415
		3416	#include "ev.h"
		3417
		3418	And compile the following F<evwrap.c> file into your project (make sure
		3419	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3420
		3421	#include "evwrap.h"
		3422	#include "ev.c"
		3423
		3424	=over 4
		3425
		3426	=item The winsocket select function
		3427
		3428	The winsocket C<select> function doesn't follow POSIX in that it
		3429	requires socket I<handles> and not socket I<file descriptors> (it is
		3430	also extremely buggy). This makes select very inefficient, and also
		3431	requires a mapping from file descriptors to socket handles (the Microsoft
		3432	C runtime provides the function C<_open_osfhandle> for this). See the
		3433	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3434	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3435
		3436	The configuration for a "naked" win32 using the Microsoft runtime
		3437	libraries and raw winsocket select is:
		3438
		3439	#define EV_USE_SELECT 1
		3440	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3441
		3442	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3443	complexity in the O(n²) range when using win32.
		3444
		3445	=item Limited number of file descriptors
		3446
		3447	Windows has numerous arbitrary (and low) limits on things.
		3448
		3449	Early versions of winsocket's select only supported waiting for a maximum
		3450	of C<64> handles (probably owning to the fact that all windows kernels
		3451	can only wait for C<64> things at the same time internally; Microsoft
		3452	recommends spawning a chain of threads and wait for 63 handles and the
		3453	previous thread in each. Great).
		3454
		3455	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3456	to some high number (e.g. C<2048>) before compiling the winsocket select
		3457	call (which might be in libev or elsewhere, for example, perl does its own
		3458	select emulation on windows).
		3459
		3460	Another limit is the number of file descriptors in the Microsoft runtime
		3461	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3462	or something like this inside Microsoft). You can increase this by calling
		3463	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3464	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3465	libraries.
		3466
		3467	This might get you to about C<512> or C<2048> sockets (depending on
		3468	windows version and/or the phase of the moon). To get more, you need to
		3469	wrap all I/O functions and provide your own fd management, but the cost of
		3470	calling select (O(n²)) will likely make this unworkable.
		3471
		3472	=back
		3473
		3474
		3475	=head1 PORTABILITY REQUIREMENTS
		3476
		3477	In addition to a working ISO-C implementation, libev relies on a few
		3478	additional extensions:
		3479
		3480	=over 4
		3481
		3482	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3483	calling conventions regardless of C<ev_watcher_type *>.
		3484
		3485	Libev assumes not only that all watcher pointers have the same internal
		3486	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3487	assumes that the same (machine) code can be used to call any watcher
		3488	callback: The watcher callbacks have different type signatures, but libev
		3489	calls them using an C<ev_watcher *> internally.
		3490
		3491	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3492
		3493	The type C<sig_atomic_t volatile> (or whatever is defined as
		3494	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3495	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3496	believed to be sufficiently portable.
		3497
		3498	=item C<sigprocmask> must work in a threaded environment
		3499
		3500	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3501	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3502	pthread implementations will either allow C<sigprocmask> in the "main
		3503	thread" or will block signals process-wide, both behaviours would
		3504	be compatible with libev. Interaction between C<sigprocmask> and
		3505	C<pthread_sigmask> could complicate things, however.
		3506
		3507	The most portable way to handle signals is to block signals in all threads
		3508	except the initial one, and run the default loop in the initial thread as
		3509	well.
		3510
		3511	=item C<long> must be large enough for common memory allocation sizes
		3512
		3513	To improve portability and simplify using libev, libev uses C<long>
		3514	internally instead of C<size_t> when allocating its data structures. On
		3515	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3516	is still at least 31 bits everywhere, which is enough for hundreds of
		3517	millions of watchers.
		3518
		3519	=item C<double> must hold a time value in seconds with enough accuracy
		3520
		3521	The type C<double> is used to represent timestamps. It is required to
		3522	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3523	enough for at least into the year 4000. This requirement is fulfilled by
		3524	implementations implementing IEEE 754 (basically all existing ones).
		3525
		3526	=back
		3527
		3528	If you know of other additional requirements drop me a note.
		3529
		3530
		3531	=head1 COMPILER WARNINGS
		3532
		3533	Depending on your compiler and compiler settings, you might get no or a
		3534	lot of warnings when compiling libev code. Some people are apparently
		3535	scared by this.
		3536
		3537	However, these are unavoidable for many reasons. For one, each compiler
		3538	has different warnings, and each user has different tastes regarding
		3539	warning options. "Warn-free" code therefore cannot be a goal except when
		3540	targeting a specific compiler and compiler-version.
		3541
		3542	Another reason is that some compiler warnings require elaborate
		3543	workarounds, or other changes to the code that make it less clear and less
		3544	maintainable.
		3545
		3546	And of course, some compiler warnings are just plain stupid, or simply
		3547	wrong (because they don't actually warn about the condition their message
		3548	seems to warn about).
		3549
		3550	While libev is written to generate as few warnings as possible,
		3551	"warn-free" code is not a goal, and it is recommended not to build libev
		3552	with any compiler warnings enabled unless you are prepared to cope with
		3553	them (e.g. by ignoring them). Remember that warnings are just that:
		3554	warnings, not errors, or proof of bugs.
		3555
		3556
		3557	=head1 VALGRIND
		3558
		3559	Valgrind has a special section here because it is a popular tool that is
		3560	highly useful, but valgrind reports are very hard to interpret.
		3561
		3562	If you think you found a bug (memory leak, uninitialised data access etc.)
		3563	in libev, then check twice: If valgrind reports something like:
		3564
		3565	==2274== definitely lost: 0 bytes in 0 blocks.
		3566	==2274== possibly lost: 0 bytes in 0 blocks.
		3567	==2274== still reachable: 256 bytes in 1 blocks.
		3568
		3569	Then there is no memory leak. Similarly, under some circumstances,
		3570	valgrind might report kernel bugs as if it were a bug in libev, or it
		3571	might be confused (it is a very good tool, but only a tool).
		3572
		3573	If you are unsure about something, feel free to contact the mailing list
		3574	with the full valgrind report and an explanation on why you think this is
		3575	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3576	no bug" answer and take the chance of learning how to interpret valgrind
		3577	properly.
		3578
		3579	If you need, for some reason, empty reports from valgrind for your project
		3580	I suggest using suppression lists.
		3581
		3582
2724	=head1 AUTHOR	3583	=head1 AUTHOR
2725		3584
2726	Marc Lehmann <libev@schmorp.de>.	3585	Marc Lehmann <libev@schmorp.de>.
2727		3586

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