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Revision 1.102 by root, Sat Dec 22 16:21:25 2007 UTC vs.
Revision 1.194 by root, Mon Oct 20 16:08:36 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
104	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
106		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
…		…
119		155
120	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
121		157
122	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
123	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
124	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
125		161
126	=item int ev_version_major ()	162	=item int ev_version_major ()
127		163
128	=item int ev_version_minor ()	164	=item int ev_version_minor ()
129		165
…		…
142	not a problem.	178	not a problem.
143		179
144	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
145	version.	181	version.
146		182
147	assert (("libev version mismatch",	183	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
150		186
151	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
152		188
153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
154	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	192	a description of the set values.
157		193
158	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
159	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
160		196
161	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
163		199
164	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
165		201
166	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
167	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
168	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
169	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
170	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
171	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
172		208
173	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
174		210
…		…
178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
179	recommended ones.	215	recommended ones.
180		216
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)) [NOT REENTRANT]
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 (;;)
…		…
211	}	250	}
212		251
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)); [NOT REENTRANT]
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.
…		…
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		284
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
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
257	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
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
347	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
348	(or space) is available.	398	(or space) is available.
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,
352	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
353		405
354	While nominally embeddeble in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
355	all kernel versions tested so far.	407	all kernel versions tested so far.
356		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
358		413
359	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
360	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
361	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
362	it's completely useless). For this reason it's not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
363	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
365	system like NetBSD.
366		420
367	You still can embed kqueue into a normal poll or select backend and use it	421	You still can embed kqueue into a normal poll or select backend and use it
368	only for sockets (after having made sure that sockets work with kqueue on	422	only for sockets (after having made sure that sockets work with kqueue on
369	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
370		424
371	It scales in the same way as the epoll backend, but the interface to the	425	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	426	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	427	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	428	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	429	two event changes per incident. Support for C<fork ()> is very bad and it
376	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
377		431
378	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
379		433
380	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
381	everywhere, so you might need to test for this. And since it is broken	435	everywhere, so you might need to test for this. And since it is broken
382	almost everywhere, you should only use it when you have a lot of sockets	436	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	437	(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	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
385	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
386		444
387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
388		446
389	This is not implemented yet (and might never be, unless you send me an	447	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	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
395		453
396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	454	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)).	455	it's really slow, but it still scales very well (O(active_fds)).
398		456
399	Please note that solaris event ports can deliver a lot of spurious	457	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	458	notifications, so you need to use non-blocking I/O or other means to avoid
401	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
402		460
403	While this backend scales well, it requires one system call per active	461	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	462	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	464	might perform better.
407		465
		466	On the positive side, with the exception of the spurious readiness
		467	notifications, this backend actually performed fully to specification
		468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
		473
408	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
409		475
410	Try all backends (even potentially broken ones that wouldn't be tried	476	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	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413		479
414	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
415		481
416	=back	482	=back
417		483
418	If one or more of these are ored into the flags value, then only these	484	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	485	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	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		487
423	The most typical usage is like this:	488	Example: This is the most typical usage.
424		489
425	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
427		492
428	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
429	environment settings to be taken into account:	494	environment settings to be taken into account:
430		495
431	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
432		497
433	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
434	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
435	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
436		502
437	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
438		504
439	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
440		506
441	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	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	508	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	509	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).	510	undefined behaviour (or a failed assertion if assertions are enabled).
445		511
		512	Note that this function I<is> thread-safe, and the recommended way to use
		513	libev with threads is indeed to create one loop per thread, and using the
		514	default loop in the "main" or "initial" thread.
		515
446	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
447		517
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	519	if (!epoller)
450	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
451		521
452	=item ev_default_destroy ()	522	=item ev_default_destroy ()
453		523
454	Destroys the default loop again (frees all memory and kernel state	524	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	525	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	526	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>	527	responsibility to either stop all watchers cleanly yourself I<before>
458	calling this function, or cope with the fact afterwards (which is usually	528	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	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
460	for example).	530	for example).
461		531
462	Note that certain global state, such as signal state, will not be freed by	532	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	543	Like C<ev_default_destroy>, but destroys an event loop created by an
474	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
475		545
476	=item ev_default_fork ()	546	=item ev_default_fork ()
477		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	549	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	550	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	551	the child process (or both child and parent, but that again makes little
481	again makes little sense).	552	sense). You I<must> call it in the child before using any of the libev
		553	functions, and it will only take effect at the next C<ev_loop> iteration.
482		554
483	You I<must> call this function in the child process after forking if and	555	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	556	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.	557	you just fork+exec, you don't have to call it at all.
486		558
487	The function itself is quite fast and it's usually not a problem to call	559	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	560	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>:	561	quite nicely into a call to C<pthread_atfork>:
490		562
491	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
492		564
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)	565	=item ev_loop_fork (loop)
498		566
499	Like C<ev_default_fork>, but acts on an event loop created by	567	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	568	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.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
		571
		572	=item int ev_is_default_loop (loop)
		573
		574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
502		576
503	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
504		578
505	Returns the count of loop iterations for the loop, which is identical to	579	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	580	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	595	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	596	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	597	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).	598	event occurring (or more correctly, libev finding out about it).
525		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
526	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
527		613
528	Finally, this is it, the event handler. This function usually is called	614	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	615	after you initialised all your watchers and you want to start handling
530	events.	616	events.
…		…
532	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
533	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
534		620
535	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
536	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
537	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
538	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
539	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
540		627
541	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	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	629	those events and any already outstanding ones, but will not block your
543	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
544		632
545	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	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	634	necessary) and will handle those and any already outstanding ones. It
547	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
548	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
549	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
551	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
552		644
553	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
554		646
555	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
556	* If there are no active watchers (reference count is zero), return.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- Queue all prepare watchers and then call all outstanding watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
		650	- Queue and call all prepare watchers.
558	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
559	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
560	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
561	- Calculate for how long to block.	655	- Calculate for how long to sleep or block, if at all
		656	(active idle watchers, EVLOOP_NONBLOCK or not having
		657	any active watchers at all will result in not sleeping).
		658	- Sleep if the I/O and timer collect interval say so.
562	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
563	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
564	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
565	- Queue all outstanding timers.	662	- Queue all expired timers.
566	- Queue all outstanding periodics.	663	- Queue all expired periodics.
567	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
568	- Queue all check watchers.	665	- Queue all check watchers.
569	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- 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	667	Signals and child watchers are implemented as I/O watchers, and will
571	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
574		672
575	Example: Queue some jobs and then loop until no events are outsanding	673	Example: Queue some jobs and then loop until no events are outstanding
576	anymore.	674	anymore.
577		675
578	... queue jobs here, make sure they register event watchers as long	676	... 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..)	677	... as they still have work to do (even an idle watcher will do..)
580	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
581	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
582		680
583	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
584		682
585	Can be used to make a call to C<ev_loop> return early (but only after it	683	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	684	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	685	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.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
589		687
		688	This "unloop state" will be cleared when entering C<ev_loop> again.
		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
590	=item ev_ref (loop)	692	=item ev_ref (loop)
591		693
592	=item ev_unref (loop)	694	=item ev_unref (loop)
593		695
594	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
595	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
596	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
597	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
598	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
599	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
600	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
601	no event watchers registered by it are active. It is also an excellent	706	if 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	707	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>.	708	libraries. Just remember to I<unref after start> and I<ref before stop>
		709	(but only if the watcher wasn't active before, or was active before,
		710	respectively).
604		711
605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606	running when nothing else is active.	713	running when nothing else is active.
607		714
608	struct ev_signal exitsig;	715	struct ev_signal exitsig;
609	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
610	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
611	evf_unref (loop);	718	evf_unref (loop);
612		719
613	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
614		721
615	ev_ref (loop);	722	ev_ref (loop);
616	ev_signal_stop (loop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
617		724
618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
619		726
620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
621		728
622	These advanced functions influence the time that libev will spend waiting	729	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	730	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.	731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
625		733
626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	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	735	allows libev to delay invocation of I/O and timer/periodic callbacks
628	increase efficiency of loop iterations.	736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
629		738
630	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
631	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
632	the program responsive, it also wastes a lot of CPU time to poll for new	741	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	742	events, especially with backends like C<select ()> which have a high
634	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
635		744
636	By setting a higher I<io collect interval> you allow libev to spend more	745	By setting a higher I<io collect interval> you allow libev to spend more
637	time collecting I/O events, so you can handle more events per iteration,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
639	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	C<ev_timer>) will be not affected. Setting this to a non-null value will
640	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
641		750
642	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
643	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
644	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
645	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
646	any overhead in libev.	755	value will not introduce any overhead in libev.
647		756
648	Many (busy) programs can usually benefit by setting the io collect	757	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	758	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	759	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>,	760	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.	761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
653		781
654	=back	782	=back
655		783
656		784
657	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
658		786
659	A watcher is a structure that you create and register to record your	787	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	788	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:	789	become readable, you would create an C<ev_io> watcher for that:
662		790
663	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
664	{	792	{
665	ev_io_stop (w);	793	ev_io_stop (w);
666	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
667	}	795	}
668		796
669	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
670	struct ev_io stdin_watcher;	798	struct ev_io stdin_watcher;
671	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
672	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
673	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
674	ev_loop (loop, 0);	802	ev_loop (loop, 0);
675		803
676	As you can see, you are responsible for allocating the memory for your	804	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,	805	watcher structures (and it is usually a bad idea to do this on the stack,
678	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
679		807
680	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
681	(watcher *, callback)>, which expects a callback to be provided. This	809	(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	810	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	811	watchers, each time the event loop detects that the file descriptor given
684	is readable and/or writable).	812	is readable and/or writable).
685		813
686	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	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	815	with arguments specific to this watcher type. There is also a macro
…		…
757	=item C<EV_FORK>	885	=item C<EV_FORK>
758		886
759	The event loop has been resumed in the child process after fork (see	887	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	888	C<ev_fork>).
761		889
		890	=item C<EV_ASYNC>
		891
		892	The given async watcher has been asynchronously notified (see C<ev_async>).
		893
762	=item C<EV_ERROR>	894	=item C<EV_ERROR>
763		895
764	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	897	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	898	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	899	problem. You best act on it by reporting the problem and somehow coping
768	with the watcher being stopped.	900	with the watcher being stopped.
769		901
770	Libev will usually signal a few "dummy" events together with an error,	902	Libev will usually signal a few "dummy" events together with an error, for
771	for example it might indicate that a fd is readable or writable, and if	903	example it might indicate that a fd is readable or writable, and if your
772	your callbacks is well-written it can just attempt the operation and cope	904	callbacks is well-written it can just attempt the operation and cope with
773	with the error from read() or write(). This will not work in multithreaded	905	the error from read() or write(). This will not work in multi-threaded
774	programs, though, so beware.	906	programs, though, as the fd could already be closed and reused for another
		907	thing, so beware.
775		908
776	=back	909	=back
777		910
778	=head2 GENERIC WATCHER FUNCTIONS	911	=head2 GENERIC WATCHER FUNCTIONS
779		912
…		…
795	(or never started) and there are no pending events outstanding.	928	(or never started) and there are no pending events outstanding.
796		929
797	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
798	int revents)>.	931	int revents)>.
799		932
		933	Example: Initialise an C<ev_io> watcher in two steps.
		934
		935	ev_io w;
		936	ev_init (&w, my_cb);
		937	ev_io_set (&w, STDIN_FILENO, EV_READ);
		938
800	=item C<ev_TYPE_set> (ev_TYPE *, [args])	939	=item C<ev_TYPE_set> (ev_TYPE *, [args])
801		940
802	This macro initialises the type-specific parts of a watcher. You need to	941	This macro initialises the type-specific parts of a watcher. You need to
803	call C<ev_init> at least once before you call this macro, but you can	942	call C<ev_init> at least once before you call this macro, but you can
804	call C<ev_TYPE_set> any number of times. You must not, however, call this	943	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
806	difference to the C<ev_init> macro).	945	difference to the C<ev_init> macro).
807		946
808	Although some watcher types do not have type-specific arguments	947	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.	948	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
810		949
		950	See C<ev_init>, above, for an example.
		951
811	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	952	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
812		953
813	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	954	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	955	calls into a single call. This is the most convenient method to initialise
815	a watcher. The same limitations apply, of course.	956	a watcher. The same limitations apply, of course.
		957
		958	Example: Initialise and set an C<ev_io> watcher in one step.
		959
		960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
816		961
817	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
818		963
819	Starts (activates) the given watcher. Only active watchers will receive	964	Starts (activates) the given watcher. Only active watchers will receive
820	events. If the watcher is already active nothing will happen.	965	events. If the watcher is already active nothing will happen.
		966
		967	Example: Start the C<ev_io> watcher that is being abused as example in this
		968	whole section.
		969
		970	ev_io_start (EV_DEFAULT_UC, &w);
821		971
822	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
823		973
824	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher again (if active) and clears the pending
825	status. It is possible that stopped watchers are pending (for example,	975	status. It is possible that stopped watchers are pending (for example,
…		…
882		1032
883	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
884		1034
885	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
886	C<loop> nor C<revents> need to be valid as long as the watcher callback	1036	C<loop> nor C<revents> need to be valid as long as the watcher callback
887	can deal with that fact.	1037	can deal with that fact, as both are simply passed through to the
		1038	callback.
888		1039
889	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1040	=item int ev_clear_pending (loop, ev_TYPE *watcher)
890		1041
891	If the watcher is pending, this function returns clears its pending status	1042	If the watcher is pending, this function clears its pending status and
892	and returns its C<revents> bitset (as if its callback was invoked). If the	1043	returns its C<revents> bitset (as if its callback was invoked). If the
893	watcher isn't pending it does nothing and returns C<0>.	1044	watcher isn't pending it does nothing and returns C<0>.
894		1045
		1046	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1047	callback to be invoked, which can be accomplished with this function.
		1048
895	=back	1049	=back
896		1050
897		1051
898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1052	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
899		1053
900	Each watcher has, by default, a member C<void *data> that you can change	1054	Each watcher has, by default, a member C<void *data> that you can change
901	and read at any time, libev will completely ignore it. This can be used	1055	and read at any time: libev will completely ignore it. This can be used
902	to associate arbitrary data with your watcher. If you need more data and	1056	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	1057	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	1058	member, you can also "subclass" the watcher type and provide your own
905	data:	1059	data:
906		1060
907	struct my_io	1061	struct my_io
908	{	1062	{
909	struct ev_io io;	1063	struct ev_io io;
910	int otherfd;	1064	int otherfd;
911	void *somedata;	1065	void *somedata;
912	struct whatever *mostinteresting;	1066	struct whatever *mostinteresting;
913	}	1067	};
		1068
		1069	...
		1070	struct my_io w;
		1071	ev_io_init (&w.io, my_cb, fd, EV_READ);
914		1072
915	And since your callback will be called with a pointer to the watcher, you	1073	And since your callback will be called with a pointer to the watcher, you
916	can cast it back to your own type:	1074	can cast it back to your own type:
917		1075
918	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1076	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
919	{	1077	{
920	struct my_io *w = (struct my_io *)w_;	1078	struct my_io *w = (struct my_io *)w_;
921	...	1079	...
922	}	1080	}
923		1081
924	More interesting and less C-conformant ways of casting your callback type	1082	More interesting and less C-conformant ways of casting your callback type
925	instead have been omitted.	1083	instead have been omitted.
926		1084
927	Another common scenario is having some data structure with multiple	1085	Another common scenario is to use some data structure with multiple
928	watchers:	1086	embedded watchers:
929		1087
930	struct my_biggy	1088	struct my_biggy
931	{	1089	{
932	int some_data;	1090	int some_data;
933	ev_timer t1;	1091	ev_timer t1;
934	ev_timer t2;	1092	ev_timer t2;
935	}	1093	}
936		1094
937	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1095	In this case getting the pointer to C<my_biggy> is a bit more
938	you need to use C<offsetof>:	1096	complicated: Either you store the address of your C<my_biggy> struct
		1097	in the C<data> member of the watcher (for woozies), or you need to use
		1098	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1099	programmers):
939		1100
940	#include <stddef.h>	1101	#include <stddef.h>
941		1102
942	static void	1103	static void
943	t1_cb (EV_P_ struct ev_timer *w, int revents)	1104	t1_cb (EV_P_ struct ev_timer *w, int revents)
944	{	1105	{
945	struct my_biggy big = (struct my_biggy *	1106	struct my_biggy big = (struct my_biggy *
946	(((char *)w) - offsetof (struct my_biggy, t1));	1107	(((char *)w) - offsetof (struct my_biggy, t1));
947	}	1108	}
948		1109
949	static void	1110	static void
950	t2_cb (EV_P_ struct ev_timer *w, int revents)	1111	t2_cb (EV_P_ struct ev_timer *w, int revents)
951	{	1112	{
952	struct my_biggy big = (struct my_biggy *	1113	struct my_biggy big = (struct my_biggy *
953	(((char *)w) - offsetof (struct my_biggy, t2));	1114	(((char *)w) - offsetof (struct my_biggy, t2));
954	}	1115	}
955		1116
956		1117
957	=head1 WATCHER TYPES	1118	=head1 WATCHER TYPES
958		1119
959	This section describes each watcher in detail, but will not repeat	1120	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	1144	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	1145	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	1146	descriptors to non-blocking mode is also usually a good idea (but not
986	required if you know what you are doing).	1147	required if you know what you are doing).
987		1148
988	You have to be careful with dup'ed file descriptors, though. Some backends	1149	If you cannot use non-blocking mode, then force the use of a
989	(the linux epoll backend is a notable example) cannot handle dup'ed file	1150	known-to-be-good backend (at the time of this writing, this includes only
990	descriptors correctly if you register interest in two or more fds pointing	1151	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
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
995	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
996	C<EVBACKEND_POLL>).
997		1152
998	Another thing you have to watch out for is that it is quite easy to	1153	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	1154	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	1155	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	1156	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	1157	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	1158	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	1159	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.	1160	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1006		1161
1007	If you cannot run the fd in non-blocking mode (for example you should not	1162	If you cannot run the fd in non-blocking mode (for example you should
1008	play around with an Xlib connection), then you have to seperately re-test	1163	not play around with an Xlib connection), then you have to separately
1009	whether a file descriptor is really ready with a known-to-be good interface	1164	re-test whether a file descriptor is really ready with a known-to-be good
1010	such as poll (fortunately in our Xlib example, Xlib already does this on	1165	interface such as poll (fortunately in our Xlib example, Xlib already
1011	its own, so its quite safe to use).	1166	does this on its own, so its quite safe to use). Some people additionally
		1167	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1168	indefinitely.
		1169
		1170	But really, best use non-blocking mode.
1012		1171
1013	=head3 The special problem of disappearing file descriptors	1172	=head3 The special problem of disappearing file descriptors
1014		1173
1015	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1174	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1016	descriptor (either by calling C<close> explicitly or by any other means,	1175	descriptor (either due to calling C<close> explicitly or any other means,
1017	such as C<dup>). The reason is that you register interest in some file	1176	such as C<dup2>). The reason is that you register interest in some file
1018	descriptor, but when it goes away, the operating system will silently drop	1177	descriptor, but when it goes away, the operating system will silently drop
1019	this interest. If another file descriptor with the same number then is	1178	this interest. If another file descriptor with the same number then is
1020	registered with libev, there is no efficient way to see that this is, in	1179	registered with libev, there is no efficient way to see that this is, in
1021	fact, a different file descriptor.	1180	fact, a different file descriptor.
1022		1181
…		…
1032	optimisations to libev.	1191	optimisations to libev.
1033		1192
1034	=head3 The special problem of dup'ed file descriptors	1193	=head3 The special problem of dup'ed file descriptors
1035		1194
1036	Some backends (e.g. epoll), cannot register events for file descriptors,	1195	Some backends (e.g. epoll), cannot register events for file descriptors,
1037	but only events for the underlying file descriptions. That menas when you	1196	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	1197	have C<dup ()>'ed file descriptors or weirder constellations, and register
1039	file descriptor might actually receive events.	1198	events for them, only one file descriptor might actually receive events.
1040		1199
1041	There is no workaorund possible except not registering events	1200	There is no workaround possible except not registering events
1042	for potentially C<dup ()>'ed file descriptors or to resort to	1201	for potentially C<dup ()>'ed file descriptors, or to resort to
1043	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1202	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1044		1203
1045	=head3 The special problem of fork	1204	=head3 The special problem of fork
1046		1205
1047	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1206	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
1051	To support fork in your programs, you either have to call	1210	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,	1211	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	1212	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1054	C<EVBACKEND_POLL>.	1213	C<EVBACKEND_POLL>.
1055		1214
		1215	=head3 The special problem of SIGPIPE
		1216
		1217	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1218	when writing to a pipe whose other end has been closed, your program gets
		1219	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1220	this is sensible behaviour, for daemons, this is usually undesirable.
		1221
		1222	So when you encounter spurious, unexplained daemon exits, make sure you
		1223	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1224	somewhere, as that would have given you a big clue).
		1225
1056		1226
1057	=head3 Watcher-Specific Functions	1227	=head3 Watcher-Specific Functions
1058		1228
1059	=over 4	1229	=over 4
1060		1230
1061	=item ev_io_init (ev_io *, callback, int fd, int events)	1231	=item ev_io_init (ev_io *, callback, int fd, int events)
1062		1232
1063	=item ev_io_set (ev_io *, int fd, int events)	1233	=item ev_io_set (ev_io *, int fd, int events)
1064		1234
1065	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1235	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	1236	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1067	C<EV_READ | EV_WRITE> to receive the given events.	1237	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1068		1238
1069	=item int fd [read-only]	1239	=item int fd [read-only]
1070		1240
1071	The file descriptor being watched.	1241	The file descriptor being watched.
1072		1242
1073	=item int events [read-only]	1243	=item int events [read-only]
1074		1244
1075	The events being watched.	1245	The events being watched.
1076		1246
1077	=back	1247	=back
		1248
		1249	=head3 Examples
1078		1250
1079	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1251	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	1252	readable, but only once. Since it is likely line-buffered, you could
1081	attempt to read a whole line in the callback.	1253	attempt to read a whole line in the callback.
1082		1254
1083	static void	1255	static void
1084	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1256	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1085	{	1257	{
1086	ev_io_stop (loop, w);	1258	ev_io_stop (loop, w);
1087	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1259	.. read from stdin here (or from w->fd) and handle any I/O errors
1088	}	1260	}
1089		1261
1090	...	1262	...
1091	struct ev_loop *loop = ev_default_init (0);	1263	struct ev_loop *loop = ev_default_init (0);
1092	struct ev_io stdin_readable;	1264	struct ev_io stdin_readable;
1093	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1094	ev_io_start (loop, &stdin_readable);	1266	ev_io_start (loop, &stdin_readable);
1095	ev_loop (loop, 0);	1267	ev_loop (loop, 0);
1096		1268
1097		1269
1098	=head2 C<ev_timer> - relative and optionally repeating timeouts	1270	=head2 C<ev_timer> - relative and optionally repeating timeouts
1099		1271
1100	Timer watchers are simple relative timers that generate an event after a	1272	Timer watchers are simple relative timers that generate an event after a
1101	given time, and optionally repeating in regular intervals after that.	1273	given time, and optionally repeating in regular intervals after that.
1102		1274
1103	The timers are based on real time, that is, if you register an event that	1275	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	1276	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	1277	year, it will still time out after (roughly) one hour. "Roughly" because
1106	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1107	monotonic clock option helps a lot here).	1279	monotonic clock option helps a lot here).
		1280
		1281	The callback is guaranteed to be invoked only I<after> its timeout has
		1282	passed, but if multiple timers become ready during the same loop iteration
		1283	then order of execution is undefined.
		1284
		1285	=head3 The special problem of time updates
		1286
		1287	Establishing the current time is a costly operation (it usually takes at
		1288	least two system calls): EV therefore updates its idea of the current
		1289	time only before and after C<ev_loop> collects new events, which causes a
		1290	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1291	lots of events in one iteration.
1108		1292
1109	The relative timeouts are calculated relative to the C<ev_now ()>	1293	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	1294	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	1295	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	1296	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:	1297	timeout on the current time, use something like this to adjust for this:
1114		1298
1115	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1299	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1116		1300
1117	The callback is guarenteed to be invoked only when its timeout has passed,	1301	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	1302	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1119	order of execution is undefined.	1303	()>.
1120		1304
1121	=head3 Watcher-Specific Functions and Data Members	1305	=head3 Watcher-Specific Functions and Data Members
1122		1306
1123	=over 4	1307	=over 4
1124		1308
1125	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1309	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1126		1310
1127	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1311	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1128		1312
1129	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1313	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	1314	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	1315	reached. If it is positive, then the timer will automatically be
1132	later, again, and again, until stopped manually.	1316	configured to trigger again C<repeat> seconds later, again, and again,
		1317	until stopped manually.
1133		1318
1134	The timer itself will do a best-effort at avoiding drift, that is, if you	1319	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	1320	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	1321	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	1322	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.	1323	do stuff) the timer will not fire more than once per event loop iteration.
1139		1324
1140	=item ev_timer_again (loop)	1325	=item ev_timer_again (loop, ev_timer *)
1141		1326
1142	This will act as if the timer timed out and restart it again if it is	1327	This will act as if the timer timed out and restart it again if it is
1143	repeating. The exact semantics are:	1328	repeating. The exact semantics are:
1144		1329
1145	If the timer is pending, its pending status is cleared.	1330	If the timer is pending, its pending status is cleared.
1146		1331
1147	If the timer is started but nonrepeating, stop it (as if it timed out).	1332	If the timer is started but non-repeating, stop it (as if it timed out).
1148		1333
1149	If the timer is repeating, either start it if necessary (with the	1334	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.	1335	C<repeat> value), or reset the running timer to the C<repeat> value.
1151		1336
1152	This sounds a bit complicated, but here is a useful and typical	1337	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	1338	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	1339	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	1340	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	1341	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	1342	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	1343	you go into an idle state where you do not expect data to travel on the
…		…
1172	ev_timer_again (loop, timer);	1357	ev_timer_again (loop, timer);
1173		1358
1174	This is more slightly efficient then stopping/starting the timer each time	1359	This is more slightly efficient then stopping/starting the timer each time
1175	you want to modify its timeout value.	1360	you want to modify its timeout value.
1176		1361
		1362	Note, however, that it is often even more efficient to remember the
		1363	time of the last activity and let the timer time-out naturally. In the
		1364	callback, you then check whether the time-out is real, or, if there was
		1365	some activity, you reschedule the watcher to time-out in "last_activity +
		1366	timeout - ev_now ()" seconds.
		1367
1177	=item ev_tstamp repeat [read-write]	1368	=item ev_tstamp repeat [read-write]
1178		1369
1179	The current C<repeat> value. Will be used each time the watcher times out	1370	The current C<repeat> value. Will be used each time the watcher times out
1180	or C<ev_timer_again> is called and determines the next timeout (if any),	1371	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.	1372	which is also when any modifications are taken into account.
1182		1373
1183	=back	1374	=back
1184		1375
		1376	=head3 Examples
		1377
1185	Example: Create a timer that fires after 60 seconds.	1378	Example: Create a timer that fires after 60 seconds.
1186		1379
1187	static void	1380	static void
1188	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1381	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1189	{	1382	{
1190	.. one minute over, w is actually stopped right here	1383	.. one minute over, w is actually stopped right here
1191	}	1384	}
1192		1385
1193	struct ev_timer mytimer;	1386	struct ev_timer mytimer;
1194	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1195	ev_timer_start (loop, &mytimer);	1388	ev_timer_start (loop, &mytimer);
1196		1389
1197	Example: Create a timeout timer that times out after 10 seconds of	1390	Example: Create a timeout timer that times out after 10 seconds of
1198	inactivity.	1391	inactivity.
1199		1392
1200	static void	1393	static void
1201	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1394	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1202	{	1395	{
1203	.. ten seconds without any activity	1396	.. ten seconds without any activity
1204	}	1397	}
1205		1398
1206	struct ev_timer mytimer;	1399	struct ev_timer mytimer;
1207	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1208	ev_timer_again (&mytimer); /* start timer */	1401	ev_timer_again (&mytimer); /* start timer */
1209	ev_loop (loop, 0);	1402	ev_loop (loop, 0);
1210		1403
1211	// and in some piece of code that gets executed on any "activity":	1404	// and in some piece of code that gets executed on any "activity":
1212	// reset the timeout to start ticking again at 10 seconds	1405	// reset the timeout to start ticking again at 10 seconds
1213	ev_timer_again (&mytimer);	1406	ev_timer_again (&mytimer);
1214		1407
1215		1408
1216	=head2 C<ev_periodic> - to cron or not to cron?	1409	=head2 C<ev_periodic> - to cron or not to cron?
1217		1410
1218	Periodic watchers are also timers of a kind, but they are very versatile	1411	Periodic watchers are also timers of a kind, but they are very versatile
1219	(and unfortunately a bit complex).	1412	(and unfortunately a bit complex).
1220		1413
1221	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1414	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	1415	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	1416	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 ()	1417	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	1418	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1419	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	1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1227	roughly 10 seconds later).	1421	roughly 10 seconds later as it uses a relative timeout).
1228		1422
1229	They can also be used to implement vastly more complex timers, such as	1423	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,	1424	such as triggering an event on each "midnight, local time", or other
1231	rules.	1425	complicated rules.
1232		1426
1233	As with timers, the callback is guarenteed to be invoked only when the	1427	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	1428	time (C<at>) has passed, but if multiple periodic timers become ready
1235	during the same loop iteration then order of execution is undefined.	1429	during the same loop iteration, then order of execution is undefined.
1236		1430
1237	=head3 Watcher-Specific Functions and Data Members	1431	=head3 Watcher-Specific Functions and Data Members
1238		1432
1239	=over 4	1433	=over 4
1240		1434
1241	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1242		1436
1243	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1244		1438
1245	Lots of arguments, lets sort it out... There are basically three modes of	1439	Lots of arguments, lets sort it out... There are basically three modes of
1246	operation, and we will explain them from simplest to complex:	1440	operation, and we will explain them from simplest to most complex:
1247		1441
1248	=over 4	1442	=over 4
1249		1443
1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1251		1445
1252	In this configuration the watcher triggers an event at the wallclock time	1446	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,	1447	time C<at> has passed. It will not repeat and 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	1448	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.	1449	only run when the system clock reaches or surpasses this time.
1256		1450
1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1258		1452
1259	In this mode the watcher will always be scheduled to time out at the next	1453	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)	1454	C<at + N * interval> time (for some integer N, which can also be negative)
1261	and then repeat, regardless of any time jumps.	1455	and then repeat, regardless of any time jumps.
1262		1456
1263	This can be used to create timers that do not drift with respect to system	1457	This can be used to create timers that do not drift with respect to the
1264	time:	1458	system clock, for example, here is a C<ev_periodic> that triggers each
		1459	hour, on the hour:
1265		1460
1266	ev_periodic_set (&periodic, 0., 3600., 0);	1461	ev_periodic_set (&periodic, 0., 3600., 0);
1267		1462
1268	This doesn't mean there will always be 3600 seconds in between triggers,	1463	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	1464	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	1465	full hour (UTC), or more correctly, when the system time is evenly divisible
1271	by 3600.	1466	by 3600.
1272		1467
1273	Another way to think about it (for the mathematically inclined) is that	1468	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	1469	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.	1470	time where C<time = at (mod interval)>, regardless of any time jumps.
1276		1471
1277	For numerical stability it is preferable that the C<at> value is near	1472	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	1473	C<ev_now ()> (the current time), but there is no range requirement for
1279	this value.	1474	this value, and in fact is often specified as zero.
		1475
		1476	Note also that there is an upper limit to how often a timer can fire (CPU
		1477	speed for example), so if C<interval> is very small then timing stability
		1478	will of course deteriorate. Libev itself tries to be exact to be about one
		1479	millisecond (if the OS supports it and the machine is fast enough).
1280		1480
1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1481	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1282		1482
1283	In this mode the values for C<interval> and C<at> are both being	1483	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	1484	ignored. Instead, each time the periodic watcher gets scheduled, the
1285	reschedule callback will be called with the watcher as first, and the	1485	reschedule callback will be called with the watcher as first, and the
1286	current time as second argument.	1486	current time as second argument.
1287		1487
1288	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1488	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,	1489	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		1490
		1491	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1492	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1493	only event loop modification you are allowed to do).
		1494
1293	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1495	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1294	ev_tstamp now)>, e.g.:	1496	*w, ev_tstamp now)>, e.g.:
1295		1497
1296	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1498	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1297	{	1499	{
1298	return now + 60.;	1500	return now + 60.;
1299	}	1501	}
…		…
1301	It must return the next time to trigger, based on the passed time value	1503	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	1504	(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	1505	will usually be called just before the callback will be triggered, but
1304	might be called at other times, too.	1506	might be called at other times, too.
1305		1507
1306	NOTE: I<< This callback must always return a time that is later than the	1508	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.	1509	equal to the passed C<now> value >>.
1308		1510
1309	This can be used to create very complex timers, such as a timer that	1511	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	1512	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	1513	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	1514	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).	1515	reason I omitted it as an example).
1314		1516
1315	=back	1517	=back
…		…
1319	Simply stops and restarts the periodic watcher again. This is only useful	1521	Simply stops and restarts the periodic watcher again. This is only useful
1320	when you changed some parameters or the reschedule callback would return	1522	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	1523	a different time than the last time it was called (e.g. in a crond like
1322	program when the crontabs have changed).	1524	program when the crontabs have changed).
1323		1525
		1526	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1527
		1528	When active, returns the absolute time that the watcher is supposed to
		1529	trigger next.
		1530
1324	=item ev_tstamp offset [read-write]	1531	=item ev_tstamp offset [read-write]
1325		1532
1326	When repeating, this contains the offset value, otherwise this is the	1533	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>).	1534	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1328		1535
…		…
1339		1546
1340	The current reschedule callback, or C<0>, if this functionality is	1547	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	1548	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.	1549	the periodic timer fires or C<ev_periodic_again> is being called.
1343		1550
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	1551	=back
1350		1552
		1553	=head3 Examples
		1554
1351	Example: Call a callback every hour, or, more precisely, whenever the	1555	Example: Call a callback every hour, or, more precisely, whenever the
1352	system clock is divisible by 3600. The callback invocation times have	1556	system time is divisible by 3600. The callback invocation times have
1353	potentially a lot of jittering, but good long-term stability.	1557	potentially a lot of jitter, but good long-term stability.
1354		1558
1355	static void	1559	static void
1356	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1560	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1357	{	1561	{
1358	... its now a full hour (UTC, or TAI or whatever your clock follows)	1562	... its now a full hour (UTC, or TAI or whatever your clock follows)
1359	}	1563	}
1360		1564
1361	struct ev_periodic hourly_tick;	1565	struct ev_periodic hourly_tick;
1362	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1363	ev_periodic_start (loop, &hourly_tick);	1567	ev_periodic_start (loop, &hourly_tick);
1364		1568
1365	Example: The same as above, but use a reschedule callback to do it:	1569	Example: The same as above, but use a reschedule callback to do it:
1366		1570
1367	#include <math.h>	1571	#include <math.h>
1368		1572
1369	static ev_tstamp	1573	static ev_tstamp
1370	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1371	{	1575	{
1372	return fmod (now, 3600.) + 3600.;	1576	return now + (3600. - fmod (now, 3600.));
1373	}	1577	}
1374		1578
1375	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1376		1580
1377	Example: Call a callback every hour, starting now:	1581	Example: Call a callback every hour, starting now:
1378		1582
1379	struct ev_periodic hourly_tick;	1583	struct ev_periodic hourly_tick;
1380	ev_periodic_init (&hourly_tick, clock_cb,	1584	ev_periodic_init (&hourly_tick, clock_cb,
1381	fmod (ev_now (loop), 3600.), 3600., 0);	1585	fmod (ev_now (loop), 3600.), 3600., 0);
1382	ev_periodic_start (loop, &hourly_tick);	1586	ev_periodic_start (loop, &hourly_tick);
1383		1587
1384		1588
1385	=head2 C<ev_signal> - signal me when a signal gets signalled!	1589	=head2 C<ev_signal> - signal me when a signal gets signalled!
1386		1590
1387	Signal watchers will trigger an event when the process receives a specific	1591	Signal watchers will trigger an event when the process receives a specific
1388	signal one or more times. Even though signals are very asynchronous, libev	1592	signal one or more times. Even though signals are very asynchronous, libev
1389	will try it's best to deliver signals synchronously, i.e. as part of the	1593	will try it's best to deliver signals synchronously, i.e. as part of the
1390	normal event processing, like any other event.	1594	normal event processing, like any other event.
1391		1595
		1596	If you want signals asynchronously, just use C<sigaction> as you would
		1597	do without libev and forget about sharing the signal. You can even use
		1598	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1599
1392	You can configure as many watchers as you like per signal. Only when the	1600	You can configure as many watchers as you like per signal. Only when the
1393	first watcher gets started will libev actually register a signal watcher	1601	first watcher gets started will libev actually register a signal handler
1394	with the kernel (thus it coexists with your own signal handlers as long	1602	with the kernel (thus it coexists with your own signal handlers as long as
1395	as you don't register any with libev). Similarly, when the last signal	1603	you don't register any with libev for the same signal). Similarly, when
1396	watcher for a signal is stopped libev will reset the signal handler to	1604	the last signal watcher for a signal is stopped, libev will reset the
1397	SIG_DFL (regardless of what it was set to before).	1605	signal handler to SIG_DFL (regardless of what it was set to before).
		1606
		1607	If possible and supported, libev will install its handlers with
		1608	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1609	interrupted. If you have a problem with system calls getting interrupted by
		1610	signals you can block all signals in an C<ev_check> watcher and unblock
		1611	them in an C<ev_prepare> watcher.
1398		1612
1399	=head3 Watcher-Specific Functions and Data Members	1613	=head3 Watcher-Specific Functions and Data Members
1400		1614
1401	=over 4	1615	=over 4
1402		1616
…		…
1411		1625
1412	The signal the watcher watches out for.	1626	The signal the watcher watches out for.
1413		1627
1414	=back	1628	=back
1415		1629
		1630	=head3 Examples
		1631
		1632	Example: Try to exit cleanly on SIGINT.
		1633
		1634	static void
		1635	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1636	{
		1637	ev_unloop (loop, EVUNLOOP_ALL);
		1638	}
		1639
		1640	struct ev_signal signal_watcher;
		1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1642	ev_signal_start (loop, &signal_watcher);
		1643
1416		1644
1417	=head2 C<ev_child> - watch out for process status changes	1645	=head2 C<ev_child> - watch out for process status changes
1418		1646
1419	Child watchers trigger when your process receives a SIGCHLD in response to	1647	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).	1648	some child status changes (most typically when a child of yours dies or
		1649	exits). It is permissible to install a child watcher I<after> the child
		1650	has been forked (which implies it might have already exited), as long
		1651	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1652	forking and then immediately registering a watcher for the child is fine,
		1653	but forking and registering a watcher a few event loop iterations later is
		1654	not.
		1655
		1656	Only the default event loop is capable of handling signals, and therefore
		1657	you can only register child watchers in the default event loop.
		1658
		1659	=head3 Process Interaction
		1660
		1661	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1662	initialised. This is necessary to guarantee proper behaviour even if
		1663	the first child watcher is started after the child exits. The occurrence
		1664	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1665	synchronously as part of the event loop processing. Libev always reaps all
		1666	children, even ones not watched.
		1667
		1668	=head3 Overriding the Built-In Processing
		1669
		1670	Libev offers no special support for overriding the built-in child
		1671	processing, but if your application collides with libev's default child
		1672	handler, you can override it easily by installing your own handler for
		1673	C<SIGCHLD> after initialising the default loop, and making sure the
		1674	default loop never gets destroyed. You are encouraged, however, to use an
		1675	event-based approach to child reaping and thus use libev's support for
		1676	that, so other libev users can use C<ev_child> watchers freely.
		1677
		1678	=head3 Stopping the Child Watcher
		1679
		1680	Currently, the child watcher never gets stopped, even when the
		1681	child terminates, so normally one needs to stop the watcher in the
		1682	callback. Future versions of libev might stop the watcher automatically
		1683	when a child exit is detected.
1421		1684
1422	=head3 Watcher-Specific Functions and Data Members	1685	=head3 Watcher-Specific Functions and Data Members
1423		1686
1424	=over 4	1687	=over 4
1425		1688
1426	=item ev_child_init (ev_child *, callback, int pid)	1689	=item ev_child_init (ev_child *, callback, int pid, int trace)
1427		1690
1428	=item ev_child_set (ev_child *, int pid)	1691	=item ev_child_set (ev_child *, int pid, int trace)
1429		1692
1430	Configures the watcher to wait for status changes of process C<pid> (or	1693	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	1694	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	1695	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	1696	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	1697	C<waitpid> documentation). The C<rpid> member contains the pid of the
1435	process causing the status change.	1698	process causing the status change. C<trace> must be either C<0> (only
		1699	activate the watcher when the process terminates) or C<1> (additionally
		1700	activate the watcher when the process is stopped or continued).
1436		1701
1437	=item int pid [read-only]	1702	=item int pid [read-only]
1438		1703
1439	The process id this watcher watches out for, or C<0>, meaning any process id.	1704	The process id this watcher watches out for, or C<0>, meaning any process id.
1440		1705
…		…
1447	The process exit/trace status caused by C<rpid> (see your systems	1712	The process exit/trace status caused by C<rpid> (see your systems
1448	C<waitpid> and C<sys/wait.h> documentation for details).	1713	C<waitpid> and C<sys/wait.h> documentation for details).
1449		1714
1450	=back	1715	=back
1451		1716
1452	Example: Try to exit cleanly on SIGINT and SIGTERM.	1717	=head3 Examples
1453		1718
		1719	Example: C<fork()> a new process and install a child handler to wait for
		1720	its completion.
		1721
		1722	ev_child cw;
		1723
1454	static void	1724	static void
1455	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1725	child_cb (EV_P_ struct ev_child *w, int revents)
1456	{	1726	{
1457	ev_unloop (loop, EVUNLOOP_ALL);	1727	ev_child_stop (EV_A_ w);
		1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1458	}	1729	}
1459		1730
1460	struct ev_signal signal_watcher;	1731	pid_t pid = fork ();
1461	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1732
1462	ev_signal_start (loop, &sigint_cb);	1733	if (pid < 0)
		1734	// error
		1735	else if (pid == 0)
		1736	{
		1737	// the forked child executes here
		1738	exit (1);
		1739	}
		1740	else
		1741	{
		1742	ev_child_init (&cw, child_cb, pid, 0);
		1743	ev_child_start (EV_DEFAULT_ &cw);
		1744	}
1463		1745
1464		1746
1465	=head2 C<ev_stat> - did the file attributes just change?	1747	=head2 C<ev_stat> - did the file attributes just change?
1466		1748
1467	This watches a filesystem path for attribute changes. That is, it calls	1749	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	1750	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.	1751	compared to the last time, invoking the callback if it did.
1470		1752
1471	The path does not need to exist: changing from "path exists" to "path does	1753	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	1754	not exist" is a status change like any other. The condition "path does
…		…
1475	the stat buffer having unspecified contents.	1757	the stat buffer having unspecified contents.
1476		1758
1477	The path I<should> be absolute and I<must not> end in a slash. If it is	1759	The path I<should> be absolute and I<must not> end in a slash. If it is
1478	relative and your working directory changes, the behaviour is undefined.	1760	relative and your working directory changes, the behaviour is undefined.
1479		1761
1480	Since there is no standard to do this, the portable implementation simply	1762	Since there is no standard kernel interface to do this, the portable
1481	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1763	implementation simply calls C<stat (2)> regularly on the path to see if
1482	can specify a recommended polling interval for this case. If you specify	1764	it changed somehow. You can specify a recommended polling interval for
1483	a polling interval of C<0> (highly recommended!) then a I<suitable,	1765	this case. If you specify a polling interval of C<0> (highly recommended!)
1484	unspecified default> value will be used (which you can expect to be around	1766	then a I<suitable, unspecified default> value will be used (which
1485	five seconds, although this might change dynamically). Libev will also	1767	you can expect to be around five seconds, although this might change
1486	impose a minimum interval which is currently around C<0.1>, but thats	1768	dynamically). Libev will also impose a minimum interval which is currently
1487	usually overkill.	1769	around C<0.1>, but thats usually overkill.
1488		1770
1489	This watcher type is not meant for massive numbers of stat watchers,	1771	This watcher type is not meant for massive numbers of stat watchers,
1490	as even with OS-supported change notifications, this can be	1772	as even with OS-supported change notifications, this can be
1491	resource-intensive.	1773	resource-intensive.
1492		1774
1493	At the time of this writing, only the Linux inotify interface is	1775	At the time of this writing, the only OS-specific interface implemented
1494	implemented (implementing kqueue support is left as an exercise for the	1776	is the Linux inotify interface (implementing kqueue support is left as
1495	reader). Inotify will be used to give hints only and should not change the	1777	an exercise for the reader. Note, however, that the author sees no way
1496	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1778	of implementing C<ev_stat> semantics with kqueue).
1497	to fall back to regular polling again even with inotify, but changes are	1779
1498	usually detected immediately, and if the file exists there will be no	1780	=head3 ABI Issues (Largefile Support)
1499	polling.	1781
		1782	Libev by default (unless the user overrides this) uses the default
		1783	compilation environment, which means that on systems with large file
		1784	support disabled by default, you get the 32 bit version of the stat
		1785	structure. When using the library from programs that change the ABI to
		1786	use 64 bit file offsets the programs will fail. In that case you have to
		1787	compile libev with the same flags to get binary compatibility. This is
		1788	obviously the case with any flags that change the ABI, but the problem is
		1789	most noticeably disabled with ev_stat and large file support.
		1790
		1791	The solution for this is to lobby your distribution maker to make large
		1792	file interfaces available by default (as e.g. FreeBSD does) and not
		1793	optional. Libev cannot simply switch on large file support because it has
		1794	to exchange stat structures with application programs compiled using the
		1795	default compilation environment.
		1796
		1797	=head3 Inotify and Kqueue
		1798
		1799	When C<inotify (7)> support has been compiled into libev (generally only
		1800	available with Linux) and present at runtime, it will be used to speed up
		1801	change detection where possible. The inotify descriptor will be created lazily
		1802	when the first C<ev_stat> watcher is being started.
		1803
		1804	Inotify presence does not change the semantics of C<ev_stat> watchers
		1805	except that changes might be detected earlier, and in some cases, to avoid
		1806	making regular C<stat> calls. Even in the presence of inotify support
		1807	there are many cases where libev has to resort to regular C<stat> polling,
		1808	but as long as the path exists, libev usually gets away without polling.
		1809
		1810	There is no support for kqueue, as apparently it cannot be used to
		1811	implement this functionality, due to the requirement of having a file
		1812	descriptor open on the object at all times, and detecting renames, unlinks
		1813	etc. is difficult.
		1814
		1815	=head3 The special problem of stat time resolution
		1816
		1817	The C<stat ()> system call only supports full-second resolution portably, and
		1818	even on systems where the resolution is higher, most file systems still
		1819	only support whole seconds.
		1820
		1821	That means that, if the time is the only thing that changes, you can
		1822	easily miss updates: on the first update, C<ev_stat> detects a change and
		1823	calls your callback, which does something. When there is another update
		1824	within the same second, C<ev_stat> will be unable to detect unless the
		1825	stat data does change in other ways (e.g. file size).
		1826
		1827	The solution to this is to delay acting on a change for slightly more
		1828	than a second (or till slightly after the next full second boundary), using
		1829	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1830	ev_timer_again (loop, w)>).
		1831
		1832	The C<.02> offset is added to work around small timing inconsistencies
		1833	of some operating systems (where the second counter of the current time
		1834	might be be delayed. One such system is the Linux kernel, where a call to
		1835	C<gettimeofday> might return a timestamp with a full second later than
		1836	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1837	update file times then there will be a small window where the kernel uses
		1838	the previous second to update file times but libev might already execute
		1839	the timer callback).
1500		1840
1501	=head3 Watcher-Specific Functions and Data Members	1841	=head3 Watcher-Specific Functions and Data Members
1502		1842
1503	=over 4	1843	=over 4
1504		1844
…		…
1510	C<path>. The C<interval> is a hint on how quickly a change is expected to	1850	C<path>. The C<interval> is a hint on how quickly a change is expected to
1511	be detected and should normally be specified as C<0> to let libev choose	1851	be detected and should normally be specified as C<0> to let libev choose
1512	a suitable value. The memory pointed to by C<path> must point to the same	1852	a suitable value. The memory pointed to by C<path> must point to the same
1513	path for as long as the watcher is active.	1853	path for as long as the watcher is active.
1514		1854
1515	The callback will be receive C<EV_STAT> when a change was detected,	1855	The callback will receive an C<EV_STAT> event when a change was detected,
1516	relative to the attributes at the time the watcher was started (or the	1856	relative to the attributes at the time the watcher was started (or the
1517	last change was detected).	1857	last change was detected).
1518		1858
1519	=item ev_stat_stat (ev_stat *)	1859	=item ev_stat_stat (loop, ev_stat *)
1520		1860
1521	Updates the stat buffer immediately with new values. If you change the	1861	Updates the stat buffer immediately with new values. If you change the
1522	watched path in your callback, you could call this fucntion to avoid	1862	watched path in your callback, you could call this function to avoid
1523	detecting this change (while introducing a race condition). Can also be	1863	detecting this change (while introducing a race condition if you are not
1524	useful simply to find out the new values.	1864	the only one changing the path). Can also be useful simply to find out the
		1865	new values.
1525		1866
1526	=item ev_statdata attr [read-only]	1867	=item ev_statdata attr [read-only]
1527		1868
1528	The most-recently detected attributes of the file. Although the type is of	1869	The most-recently detected attributes of the file. Although the type is
1529	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1870	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1530	suitable for your system. If the C<st_nlink> member is C<0>, then there	1871	suitable for your system, but you can only rely on the POSIX-standardised
		1872	members to be present. If the C<st_nlink> member is C<0>, then there was
1531	was some error while C<stat>ing the file.	1873	some error while C<stat>ing the file.
1532		1874
1533	=item ev_statdata prev [read-only]	1875	=item ev_statdata prev [read-only]
1534		1876
1535	The previous attributes of the file. The callback gets invoked whenever	1877	The previous attributes of the file. The callback gets invoked whenever
1536	C<prev> != C<attr>.	1878	C<prev> != C<attr>, or, more precisely, one or more of these members
		1879	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1880	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1537		1881
1538	=item ev_tstamp interval [read-only]	1882	=item ev_tstamp interval [read-only]
1539		1883
1540	The specified interval.	1884	The specified interval.
1541		1885
1542	=item const char *path [read-only]	1886	=item const char *path [read-only]
1543		1887
1544	The filesystem path that is being watched.	1888	The file system path that is being watched.
1545		1889
1546	=back	1890	=back
1547		1891
		1892	=head3 Examples
		1893
1548	Example: Watch C</etc/passwd> for attribute changes.	1894	Example: Watch C</etc/passwd> for attribute changes.
1549		1895
1550	static void	1896	static void
1551	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1897	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1552	{	1898	{
1553	/* /etc/passwd changed in some way */	1899	/* /etc/passwd changed in some way */
1554	if (w->attr.st_nlink)	1900	if (w->attr.st_nlink)
1555	{	1901	{
1556	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1902	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1557	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1903	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1558	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1904	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1559	}	1905	}
1560	else	1906	else
1561	/* you shalt not abuse printf for puts */	1907	/* you shalt not abuse printf for puts */
1562	puts ("wow, /etc/passwd is not there, expect problems. "	1908	puts ("wow, /etc/passwd is not there, expect problems. "
1563	"if this is windows, they already arrived\n");	1909	"if this is windows, they already arrived\n");
1564	}	1910	}
1565		1911
1566	...	1912	...
1567	ev_stat passwd;	1913	ev_stat passwd;
1568		1914
1569	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1915	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1570	ev_stat_start (loop, &passwd);	1916	ev_stat_start (loop, &passwd);
		1917
		1918	Example: Like above, but additionally use a one-second delay so we do not
		1919	miss updates (however, frequent updates will delay processing, too, so
		1920	one might do the work both on C<ev_stat> callback invocation I<and> on
		1921	C<ev_timer> callback invocation).
		1922
		1923	static ev_stat passwd;
		1924	static ev_timer timer;
		1925
		1926	static void
		1927	timer_cb (EV_P_ ev_timer *w, int revents)
		1928	{
		1929	ev_timer_stop (EV_A_ w);
		1930
		1931	/* now it's one second after the most recent passwd change */
		1932	}
		1933
		1934	static void
		1935	stat_cb (EV_P_ ev_stat *w, int revents)
		1936	{
		1937	/* reset the one-second timer */
		1938	ev_timer_again (EV_A_ &timer);
		1939	}
		1940
		1941	...
		1942	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1943	ev_stat_start (loop, &passwd);
		1944	ev_timer_init (&timer, timer_cb, 0., 1.02);
1571		1945
1572		1946
1573	=head2 C<ev_idle> - when you've got nothing better to do...	1947	=head2 C<ev_idle> - when you've got nothing better to do...
1574		1948
1575	Idle watchers trigger events when no other events of the same or higher	1949	Idle watchers trigger events when no other events of the same or higher
1576	priority are pending (prepare, check and other idle watchers do not	1950	priority are pending (prepare, check and other idle watchers do not count
1577	count).	1951	as receiving "events").
1578		1952
1579	That is, as long as your process is busy handling sockets or timeouts	1953	That is, as long as your process is busy handling sockets or timeouts
1580	(or even signals, imagine) of the same or higher priority it will not be	1954	(or even signals, imagine) of the same or higher priority it will not be
1581	triggered. But when your process is idle (or only lower-priority watchers	1955	triggered. But when your process is idle (or only lower-priority watchers
1582	are pending), the idle watchers are being called once per event loop	1956	are pending), the idle watchers are being called once per event loop
…		…
1601	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1975	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1602	believe me.	1976	believe me.
1603		1977
1604	=back	1978	=back
1605		1979
		1980	=head3 Examples
		1981
1606	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1607	callback, free it. Also, use no error checking, as usual.	1983	callback, free it. Also, use no error checking, as usual.
1608		1984
1609	static void	1985	static void
1610	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1986	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1611	{	1987	{
1612	free (w);	1988	free (w);
1613	// now do something you wanted to do when the program has	1989	// now do something you wanted to do when the program has
1614	// no longer asnything immediate to do.	1990	// no longer anything immediate to do.
1615	}	1991	}
1616		1992
1617	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1618	ev_idle_init (idle_watcher, idle_cb);	1994	ev_idle_init (idle_watcher, idle_cb);
1619	ev_idle_start (loop, idle_cb);	1995	ev_idle_start (loop, idle_cb);
1620		1996
1621		1997
1622	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1623		1999
1624	Prepare and check watchers are usually (but not always) used in tandem:	2000	Prepare and check watchers are usually (but not always) used in pairs:
1625	prepare watchers get invoked before the process blocks and check watchers	2001	prepare watchers get invoked before the process blocks and check watchers
1626	afterwards.	2002	afterwards.
1627		2003
1628	You I<must not> call C<ev_loop> or similar functions that enter	2004	You I<must not> call C<ev_loop> or similar functions that enter
1629	the current event loop from either C<ev_prepare> or C<ev_check>	2005	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1632	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2008	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1633	C<ev_check> so if you have one watcher of each kind they will always be	2009	C<ev_check> so if you have one watcher of each kind they will always be
1634	called in pairs bracketing the blocking call.	2010	called in pairs bracketing the blocking call.
1635		2011
1636	Their main purpose is to integrate other event mechanisms into libev and	2012	Their main purpose is to integrate other event mechanisms into libev and
1637	their use is somewhat advanced. This could be used, for example, to track	2013	their use is somewhat advanced. They could be used, for example, to track
1638	variable changes, implement your own watchers, integrate net-snmp or a	2014	variable changes, implement your own watchers, integrate net-snmp or a
1639	coroutine library and lots more. They are also occasionally useful if	2015	coroutine library and lots more. They are also occasionally useful if
1640	you cache some data and want to flush it before blocking (for example,	2016	you cache some data and want to flush it before blocking (for example,
1641	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2017	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1642	watcher).	2018	watcher).
1643		2019
1644	This is done by examining in each prepare call which file descriptors need	2020	This is done by examining in each prepare call which file descriptors
1645	to be watched by the other library, registering C<ev_io> watchers for	2021	need to be watched by the other library, registering C<ev_io> watchers
1646	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2022	for them and starting an C<ev_timer> watcher for any timeouts (many
1647	provide just this functionality). Then, in the check watcher you check for	2023	libraries provide exactly this functionality). Then, in the check watcher,
1648	any events that occured (by checking the pending status of all watchers	2024	you check for any events that occurred (by checking the pending status
1649	and stopping them) and call back into the library. The I/O and timer	2025	of all watchers and stopping them) and call back into the library. The
1650	callbacks will never actually be called (but must be valid nevertheless,	2026	I/O and timer callbacks will never actually be called (but must be valid
1651	because you never know, you know?).	2027	nevertheless, because you never know, you know?).
1652		2028
1653	As another example, the Perl Coro module uses these hooks to integrate	2029	As another example, the Perl Coro module uses these hooks to integrate
1654	coroutines into libev programs, by yielding to other active coroutines	2030	coroutines into libev programs, by yielding to other active coroutines
1655	during each prepare and only letting the process block if no coroutines	2031	during each prepare and only letting the process block if no coroutines
1656	are ready to run (it's actually more complicated: it only runs coroutines	2032	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1659	loop from blocking if lower-priority coroutines are active, thus mapping	2035	loop from blocking if lower-priority coroutines are active, thus mapping
1660	low-priority coroutines to idle/background tasks).	2036	low-priority coroutines to idle/background tasks).
1661		2037
1662	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2038	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1663	priority, to ensure that they are being run before any other watchers	2039	priority, to ensure that they are being run before any other watchers
		2040	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2041
1664	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2042	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1665	too) should not activate ("feed") events into libev. While libev fully	2043	activate ("feed") events into libev. While libev fully supports this, they
1666	supports this, they will be called before other C<ev_check> watchers	2044	might get executed before other C<ev_check> watchers did their job. As
1667	did their job. As C<ev_check> watchers are often used to embed other	2045	C<ev_check> watchers are often used to embed other (non-libev) event
1668	(non-libev) event loops those other event loops might be in an unusable	2046	loops those other event loops might be in an unusable state until their
1669	state until their C<ev_check> watcher ran (always remind yourself to	2047	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1670	coexist peacefully with others).	2048	others).
1671		2049
1672	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1673		2051
1674	=over 4	2052	=over 4
1675		2053
…		…
1677		2055
1678	=item ev_check_init (ev_check *, callback)	2056	=item ev_check_init (ev_check *, callback)
1679		2057
1680	Initialises and configures the prepare or check watcher - they have no	2058	Initialises and configures the prepare or check watcher - they have no
1681	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2059	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1682	macros, but using them is utterly, utterly and completely pointless.	2060	macros, but using them is utterly, utterly, utterly and completely
		2061	pointless.
1683		2062
1684	=back	2063	=back
		2064
		2065	=head3 Examples
1685		2066
1686	There are a number of principal ways to embed other event loops or modules	2067	There are a number of principal ways to embed other event loops or modules
1687	into libev. Here are some ideas on how to include libadns into libev	2068	into libev. Here are some ideas on how to include libadns into libev
1688	(there is a Perl module named C<EV::ADNS> that does this, which you could	2069	(there is a Perl module named C<EV::ADNS> that does this, which you could
1689	use for an actually working example. Another Perl module named C<EV::Glib>	2070	use as a working example. Another Perl module named C<EV::Glib> embeds a
1690	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2071	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1691	into the Glib event loop).	2072	Glib event loop).
1692		2073
1693	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2074	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1694	and in a check watcher, destroy them and call into libadns. What follows	2075	and in a check watcher, destroy them and call into libadns. What follows
1695	is pseudo-code only of course. This requires you to either use a low	2076	is pseudo-code only of course. This requires you to either use a low
1696	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2077	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1697	the callbacks for the IO/timeout watchers might not have been called yet.	2078	the callbacks for the IO/timeout watchers might not have been called yet.
1698		2079
1699	static ev_io iow [nfd];	2080	static ev_io iow [nfd];
1700	static ev_timer tw;	2081	static ev_timer tw;
1701		2082
1702	static void	2083	static void
1703	io_cb (ev_loop *loop, ev_io *w, int revents)	2084	io_cb (ev_loop *loop, ev_io *w, int revents)
1704	{	2085	{
1705	}	2086	}
1706		2087
1707	// create io watchers for each fd and a timer before blocking	2088	// create io watchers for each fd and a timer before blocking
1708	static void	2089	static void
1709	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2090	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1710	{	2091	{
1711	int timeout = 3600000;	2092	int timeout = 3600000;
1712	struct pollfd fds [nfd];	2093	struct pollfd fds [nfd];
1713	// actual code will need to loop here and realloc etc.	2094	// actual code will need to loop here and realloc etc.
1714	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1715		2096
1716	/* the callback is illegal, but won't be called as we stop during check */	2097	/* the callback is illegal, but won't be called as we stop during check */
1717	ev_timer_init (&tw, 0, timeout * 1e-3);	2098	ev_timer_init (&tw, 0, timeout * 1e-3);
1718	ev_timer_start (loop, &tw);	2099	ev_timer_start (loop, &tw);
1719		2100
1720	// create one ev_io per pollfd	2101	// create one ev_io per pollfd
1721	for (int i = 0; i < nfd; ++i)	2102	for (int i = 0; i < nfd; ++i)
1722	{	2103	{
1723	ev_io_init (iow + i, io_cb, fds [i].fd,	2104	ev_io_init (iow + i, io_cb, fds [i].fd,
1724	((fds [i].events & POLLIN ? EV_READ : 0)	2105	((fds [i].events & POLLIN ? EV_READ : 0)
1725	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2106	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1726		2107
1727	fds [i].revents = 0;	2108	fds [i].revents = 0;
1728	ev_io_start (loop, iow + i);	2109	ev_io_start (loop, iow + i);
1729	}	2110	}
1730	}	2111	}
1731		2112
1732	// stop all watchers after blocking	2113	// stop all watchers after blocking
1733	static void	2114	static void
1734	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2115	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1735	{	2116	{
1736	ev_timer_stop (loop, &tw);	2117	ev_timer_stop (loop, &tw);
1737		2118
1738	for (int i = 0; i < nfd; ++i)	2119	for (int i = 0; i < nfd; ++i)
1739	{	2120	{
1740	// set the relevant poll flags	2121	// set the relevant poll flags
1741	// could also call adns_processreadable etc. here	2122	// could also call adns_processreadable etc. here
1742	struct pollfd *fd = fds + i;	2123	struct pollfd *fd = fds + i;
1743	int revents = ev_clear_pending (iow + i);	2124	int revents = ev_clear_pending (iow + i);
1744	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2125	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1745	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2126	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1746		2127
1747	// now stop the watcher	2128	// now stop the watcher
1748	ev_io_stop (loop, iow + i);	2129	ev_io_stop (loop, iow + i);
1749	}	2130	}
1750		2131
1751	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2132	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1752	}	2133	}
1753		2134
1754	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2135	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1755	in the prepare watcher and would dispose of the check watcher.	2136	in the prepare watcher and would dispose of the check watcher.
1756		2137
1757	Method 3: If the module to be embedded supports explicit event	2138	Method 3: If the module to be embedded supports explicit event
1758	notification (adns does), you can also make use of the actual watcher	2139	notification (libadns does), you can also make use of the actual watcher
1759	callbacks, and only destroy/create the watchers in the prepare watcher.	2140	callbacks, and only destroy/create the watchers in the prepare watcher.
1760		2141
1761	static void	2142	static void
1762	timer_cb (EV_P_ ev_timer *w, int revents)	2143	timer_cb (EV_P_ ev_timer *w, int revents)
1763	{	2144	{
1764	adns_state ads = (adns_state)w->data;	2145	adns_state ads = (adns_state)w->data;
1765	update_now (EV_A);	2146	update_now (EV_A);
1766		2147
1767	adns_processtimeouts (ads, &tv_now);	2148	adns_processtimeouts (ads, &tv_now);
1768	}	2149	}
1769		2150
1770	static void	2151	static void
1771	io_cb (EV_P_ ev_io *w, int revents)	2152	io_cb (EV_P_ ev_io *w, int revents)
1772	{	2153	{
1773	adns_state ads = (adns_state)w->data;	2154	adns_state ads = (adns_state)w->data;
1774	update_now (EV_A);	2155	update_now (EV_A);
1775		2156
1776	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2157	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1777	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2158	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1778	}	2159	}
1779		2160
1780	// do not ever call adns_afterpoll	2161	// do not ever call adns_afterpoll
1781		2162
1782	Method 4: Do not use a prepare or check watcher because the module you	2163	Method 4: Do not use a prepare or check watcher because the module you
1783	want to embed is too inflexible to support it. Instead, youc na override	2164	want to embed is not flexible enough to support it. Instead, you can
1784	their poll function. The drawback with this solution is that the main	2165	override their poll function. The drawback with this solution is that the
1785	loop is now no longer controllable by EV. The C<Glib::EV> module does	2166	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1786	this.	2167	this approach, effectively embedding EV as a client into the horrible
		2168	libglib event loop.
1787		2169
1788	static gint	2170	static gint
1789	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2171	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1790	{	2172	{
1791	int got_events = 0;	2173	int got_events = 0;
1792		2174
1793	for (n = 0; n < nfds; ++n)	2175	for (n = 0; n < nfds; ++n)
1794	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2176	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1795		2177
1796	if (timeout >= 0)	2178	if (timeout >= 0)
1797	// create/start timer	2179	// create/start timer
1798		2180
1799	// poll	2181	// poll
1800	ev_loop (EV_A_ 0);	2182	ev_loop (EV_A_ 0);
1801		2183
1802	// stop timer again	2184	// stop timer again
1803	if (timeout >= 0)	2185	if (timeout >= 0)
1804	ev_timer_stop (EV_A_ &to);	2186	ev_timer_stop (EV_A_ &to);
1805		2187
1806	// stop io watchers again - their callbacks should have set	2188	// stop io watchers again - their callbacks should have set
1807	for (n = 0; n < nfds; ++n)	2189	for (n = 0; n < nfds; ++n)
1808	ev_io_stop (EV_A_ iow [n]);	2190	ev_io_stop (EV_A_ iow [n]);
1809		2191
1810	return got_events;	2192	return got_events;
1811	}	2193	}
1812		2194
1813		2195
1814	=head2 C<ev_embed> - when one backend isn't enough...	2196	=head2 C<ev_embed> - when one backend isn't enough...
1815		2197
1816	This is a rather advanced watcher type that lets you embed one event loop	2198	This is a rather advanced watcher type that lets you embed one event loop
…		…
1822	prioritise I/O.	2204	prioritise I/O.
1823		2205
1824	As an example for a bug workaround, the kqueue backend might only support	2206	As an example for a bug workaround, the kqueue backend might only support
1825	sockets on some platform, so it is unusable as generic backend, but you	2207	sockets on some platform, so it is unusable as generic backend, but you
1826	still want to make use of it because you have many sockets and it scales	2208	still want to make use of it because you have many sockets and it scales
1827	so nicely. In this case, you would create a kqueue-based loop and embed it	2209	so nicely. In this case, you would create a kqueue-based loop and embed
1828	into your default loop (which might use e.g. poll). Overall operation will	2210	it into your default loop (which might use e.g. poll). Overall operation
1829	be a bit slower because first libev has to poll and then call kevent, but	2211	will be a bit slower because first libev has to call C<poll> and then
1830	at least you can use both at what they are best.	2212	C<kevent>, but at least you can use both mechanisms for what they are
		2213	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1831		2214
1832	As for prioritising I/O: rarely you have the case where some fds have	2215	As for prioritising I/O: under rare circumstances you have the case where
1833	to be watched and handled very quickly (with low latency), and even	2216	some fds have to be watched and handled very quickly (with low latency),
1834	priorities and idle watchers might have too much overhead. In this case	2217	and even priorities and idle watchers might have too much overhead. In
1835	you would put all the high priority stuff in one loop and all the rest in	2218	this case you would put all the high priority stuff in one loop and all
1836	a second one, and embed the second one in the first.	2219	the rest in a second one, and embed the second one in the first.
1837		2220
1838	As long as the watcher is active, the callback will be invoked every time	2221	As long as the watcher is active, the callback will be invoked every time
1839	there might be events pending in the embedded loop. The callback must then	2222	there might be events pending in the embedded loop. The callback must then
1840	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1841	their callbacks (you could also start an idle watcher to give the embedded	2224	their callbacks (you could also start an idle watcher to give the embedded
…		…
1849	interested in that.	2232	interested in that.
1850		2233
1851	Also, there have not currently been made special provisions for forking:	2234	Also, there have not currently been made special provisions for forking:
1852	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1853	but you will also have to stop and restart any C<ev_embed> watchers	2236	but you will also have to stop and restart any C<ev_embed> watchers
1854	yourself.	2237	yourself - but you can use a fork watcher to handle this automatically,
		2238	and future versions of libev might do just that.
1855		2239
1856	Unfortunately, not all backends are embeddable, only the ones returned by	2240	Unfortunately, not all backends are embeddable: only the ones returned by
1857	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1858	portable one.	2242	portable one.
1859		2243
1860	So when you want to use this feature you will always have to be prepared	2244	So when you want to use this feature you will always have to be prepared
1861	that you cannot get an embeddable loop. The recommended way to get around	2245	that you cannot get an embeddable loop. The recommended way to get around
1862	this is to have a separate variables for your embeddable loop, try to	2246	this is to have a separate variables for your embeddable loop, try to
1863	create it, and if that fails, use the normal loop for everything:	2247	create it, and if that fails, use the normal loop for everything.
1864		2248
1865	struct ev_loop *loop_hi = ev_default_init (0);	2249	=head3 C<ev_embed> and fork
1866	struct ev_loop *loop_lo = 0;
1867	struct ev_embed embed;
1868
1869	// see if there is a chance of getting one that works
1870	// (remember that a flags value of 0 means autodetection)
1871	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1872	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1873	: 0;
1874		2250
1875	// if we got one, then embed it, otherwise default to loop_hi	2251	While the C<ev_embed> watcher is running, forks in the embedding loop will
1876	if (loop_lo)	2252	automatically be applied to the embedded loop as well, so no special
1877	{	2253	fork handling is required in that case. When the watcher is not running,
1878	ev_embed_init (&embed, 0, loop_lo);	2254	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1879	ev_embed_start (loop_hi, &embed);	2255	as applicable.
1880	}
1881	else
1882	loop_lo = loop_hi;
1883		2256
1884	=head3 Watcher-Specific Functions and Data Members	2257	=head3 Watcher-Specific Functions and Data Members
1885		2258
1886	=over 4	2259	=over 4
1887		2260
…		…
1891		2264
1892	Configures the watcher to embed the given loop, which must be	2265	Configures the watcher to embed the given loop, which must be
1893	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2266	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1894	invoked automatically, otherwise it is the responsibility of the callback	2267	invoked automatically, otherwise it is the responsibility of the callback
1895	to invoke it (it will continue to be called until the sweep has been done,	2268	to invoke it (it will continue to be called until the sweep has been done,
1896	if you do not want thta, you need to temporarily stop the embed watcher).	2269	if you do not want that, you need to temporarily stop the embed watcher).
1897		2270
1898	=item ev_embed_sweep (loop, ev_embed *)	2271	=item ev_embed_sweep (loop, ev_embed *)
1899		2272
1900	Make a single, non-blocking sweep over the embedded loop. This works	2273	Make a single, non-blocking sweep over the embedded loop. This works
1901	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2274	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1902	apropriate way for embedded loops.	2275	appropriate way for embedded loops.
1903		2276
1904	=item struct ev_loop *other [read-only]	2277	=item struct ev_loop *other [read-only]
1905		2278
1906	The embedded event loop.	2279	The embedded event loop.
1907		2280
1908	=back	2281	=back
		2282
		2283	=head3 Examples
		2284
		2285	Example: Try to get an embeddable event loop and embed it into the default
		2286	event loop. If that is not possible, use the default loop. The default
		2287	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2289	used).
		2290
		2291	struct ev_loop *loop_hi = ev_default_init (0);
		2292	struct ev_loop *loop_lo = 0;
		2293	struct ev_embed embed;
		2294
		2295	// see if there is a chance of getting one that works
		2296	// (remember that a flags value of 0 means autodetection)
		2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2299	: 0;
		2300
		2301	// if we got one, then embed it, otherwise default to loop_hi
		2302	if (loop_lo)
		2303	{
		2304	ev_embed_init (&embed, 0, loop_lo);
		2305	ev_embed_start (loop_hi, &embed);
		2306	}
		2307	else
		2308	loop_lo = loop_hi;
		2309
		2310	Example: Check if kqueue is available but not recommended and create
		2311	a kqueue backend for use with sockets (which usually work with any
		2312	kqueue implementation). Store the kqueue/socket-only event loop in
		2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2314
		2315	struct ev_loop *loop = ev_default_init (0);
		2316	struct ev_loop *loop_socket = 0;
		2317	struct ev_embed embed;
		2318
		2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2321	{
		2322	ev_embed_init (&embed, 0, loop_socket);
		2323	ev_embed_start (loop, &embed);
		2324	}
		2325
		2326	if (!loop_socket)
		2327	loop_socket = loop;
		2328
		2329	// now use loop_socket for all sockets, and loop for everything else
1909		2330
1910		2331
1911	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2332	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1912		2333
1913	Fork watchers are called when a C<fork ()> was detected (usually because	2334	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1929	believe me.	2350	believe me.
1930		2351
1931	=back	2352	=back
1932		2353
1933		2354
		2355	=head2 C<ev_async> - how to wake up another event loop
		2356
		2357	In general, you cannot use an C<ev_loop> from multiple threads or other
		2358	asynchronous sources such as signal handlers (as opposed to multiple event
		2359	loops - those are of course safe to use in different threads).
		2360
		2361	Sometimes, however, you need to wake up another event loop you do not
		2362	control, for example because it belongs to another thread. This is what
		2363	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2364	can signal it by calling C<ev_async_send>, which is thread- and signal
		2365	safe.
		2366
		2367	This functionality is very similar to C<ev_signal> watchers, as signals,
		2368	too, are asynchronous in nature, and signals, too, will be compressed
		2369	(i.e. the number of callback invocations may be less than the number of
		2370	C<ev_async_sent> calls).
		2371
		2372	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2373	just the default loop.
		2374
		2375	=head3 Queueing
		2376
		2377	C<ev_async> does not support queueing of data in any way. The reason
		2378	is that the author does not know of a simple (or any) algorithm for a
		2379	multiple-writer-single-reader queue that works in all cases and doesn't
		2380	need elaborate support such as pthreads.
		2381
		2382	That means that if you want to queue data, you have to provide your own
		2383	queue. But at least I can tell you how to implement locking around your
		2384	queue:
		2385
		2386	=over 4
		2387
		2388	=item queueing from a signal handler context
		2389
		2390	To implement race-free queueing, you simply add to the queue in the signal
		2391	handler but you block the signal handler in the watcher callback. Here is
		2392	an example that does that for some fictitious SIGUSR1 handler:
		2393
		2394	static ev_async mysig;
		2395
		2396	static void
		2397	sigusr1_handler (void)
		2398	{
		2399	sometype data;
		2400
		2401	// no locking etc.
		2402	queue_put (data);
		2403	ev_async_send (EV_DEFAULT_ &mysig);
		2404	}
		2405
		2406	static void
		2407	mysig_cb (EV_P_ ev_async *w, int revents)
		2408	{
		2409	sometype data;
		2410	sigset_t block, prev;
		2411
		2412	sigemptyset (&block);
		2413	sigaddset (&block, SIGUSR1);
		2414	sigprocmask (SIG_BLOCK, &block, &prev);
		2415
		2416	while (queue_get (&data))
		2417	process (data);
		2418
		2419	if (sigismember (&prev, SIGUSR1)
		2420	sigprocmask (SIG_UNBLOCK, &block, 0);
		2421	}
		2422
		2423	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2424	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2425	either...).
		2426
		2427	=item queueing from a thread context
		2428
		2429	The strategy for threads is different, as you cannot (easily) block
		2430	threads but you can easily preempt them, so to queue safely you need to
		2431	employ a traditional mutex lock, such as in this pthread example:
		2432
		2433	static ev_async mysig;
		2434	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2435
		2436	static void
		2437	otherthread (void)
		2438	{
		2439	// only need to lock the actual queueing operation
		2440	pthread_mutex_lock (&mymutex);
		2441	queue_put (data);
		2442	pthread_mutex_unlock (&mymutex);
		2443
		2444	ev_async_send (EV_DEFAULT_ &mysig);
		2445	}
		2446
		2447	static void
		2448	mysig_cb (EV_P_ ev_async *w, int revents)
		2449	{
		2450	pthread_mutex_lock (&mymutex);
		2451
		2452	while (queue_get (&data))
		2453	process (data);
		2454
		2455	pthread_mutex_unlock (&mymutex);
		2456	}
		2457
		2458	=back
		2459
		2460
		2461	=head3 Watcher-Specific Functions and Data Members
		2462
		2463	=over 4
		2464
		2465	=item ev_async_init (ev_async *, callback)
		2466
		2467	Initialises and configures the async watcher - it has no parameters of any
		2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2469	trust me.
		2470
		2471	=item ev_async_send (loop, ev_async *)
		2472
		2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2475	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2477	section below on what exactly this means).
		2478
		2479	This call incurs the overhead of a system call only once per loop iteration,
		2480	so while the overhead might be noticeable, it doesn't apply to repeated
		2481	calls to C<ev_async_send>.
		2482
		2483	=item bool = ev_async_pending (ev_async *)
		2484
		2485	Returns a non-zero value when C<ev_async_send> has been called on the
		2486	watcher but the event has not yet been processed (or even noted) by the
		2487	event loop.
		2488
		2489	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2490	the loop iterates next and checks for the watcher to have become active,
		2491	it will reset the flag again. C<ev_async_pending> can be used to very
		2492	quickly check whether invoking the loop might be a good idea.
		2493
		2494	Not that this does I<not> check whether the watcher itself is pending, only
		2495	whether it has been requested to make this watcher pending.
		2496
		2497	=back
		2498
		2499
1934	=head1 OTHER FUNCTIONS	2500	=head1 OTHER FUNCTIONS
1935		2501
1936	There are some other functions of possible interest. Described. Here. Now.	2502	There are some other functions of possible interest. Described. Here. Now.
1937		2503
1938	=over 4	2504	=over 4
1939		2505
1940	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2506	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1941		2507
1942	This function combines a simple timer and an I/O watcher, calls your	2508	This function combines a simple timer and an I/O watcher, calls your
1943	callback on whichever event happens first and automatically stop both	2509	callback on whichever event happens first and automatically stops both
1944	watchers. This is useful if you want to wait for a single event on an fd	2510	watchers. This is useful if you want to wait for a single event on an fd
1945	or timeout without having to allocate/configure/start/stop/free one or	2511	or timeout without having to allocate/configure/start/stop/free one or
1946	more watchers yourself.	2512	more watchers yourself.
1947		2513
1948	If C<fd> is less than 0, then no I/O watcher will be started and events	2514	If C<fd> is less than 0, then no I/O watcher will be started and the
1949	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2515	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1950	C<events> set will be craeted and started.	2516	the given C<fd> and C<events> set will be created and started.
1951		2517
1952	If C<timeout> is less than 0, then no timeout watcher will be	2518	If C<timeout> is less than 0, then no timeout watcher will be
1953	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2519	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1954	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2520	repeat = 0) will be started. C<0> is a valid timeout.
1955	dubious value.
1956		2521
1957	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2522	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1958	passed an C<revents> set like normal event callbacks (a combination of	2523	passed an C<revents> set like normal event callbacks (a combination of
1959	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2524	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1960	value passed to C<ev_once>:	2525	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2526	a timeout and an io event at the same time - you probably should give io
		2527	events precedence.
1961		2528
		2529	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2530
1962	static void stdin_ready (int revents, void *arg)	2531	static void stdin_ready (int revents, void *arg)
1963	{	2532	{
1964	if (revents & EV_TIMEOUT)
1965	/* doh, nothing entered */;
1966	else if (revents & EV_READ)	2533	if (revents & EV_READ)
1967	/* stdin might have data for us, joy! */;	2534	/* stdin might have data for us, joy! */;
		2535	else if (revents & EV_TIMEOUT)
		2536	/* doh, nothing entered */;
1968	}	2537	}
1969		2538
1970	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1971		2540
1972	=item ev_feed_event (ev_loop *, watcher *, int revents)	2541	=item ev_feed_event (ev_loop *, watcher *, int revents)
1973		2542
1974	Feeds the given event set into the event loop, as if the specified event	2543	Feeds the given event set into the event loop, as if the specified event
1975	had happened for the specified watcher (which must be a pointer to an	2544	had happened for the specified watcher (which must be a pointer to an
…		…
1980	Feed an event on the given fd, as if a file descriptor backend detected	2549	Feed an event on the given fd, as if a file descriptor backend detected
1981	the given events it.	2550	the given events it.
1982		2551
1983	=item ev_feed_signal_event (ev_loop *loop, int signum)	2552	=item ev_feed_signal_event (ev_loop *loop, int signum)
1984		2553
1985	Feed an event as if the given signal occured (C<loop> must be the default	2554	Feed an event as if the given signal occurred (C<loop> must be the default
1986	loop!).	2555	loop!).
1987		2556
1988	=back	2557	=back
1989		2558
1990		2559
…		…
2006		2575
2007	=item * Priorities are not currently supported. Initialising priorities	2576	=item * Priorities are not currently supported. Initialising priorities
2008	will fail and all watchers will have the same priority, even though there	2577	will fail and all watchers will have the same priority, even though there
2009	is an ev_pri field.	2578	is an ev_pri field.
2010		2579
		2580	=item * In libevent, the last base created gets the signals, in libev, the
		2581	first base created (== the default loop) gets the signals.
		2582
2011	=item * Other members are not supported.	2583	=item * Other members are not supported.
2012		2584
2013	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2585	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2014	to use the libev header file and library.	2586	to use the libev header file and library.
2015		2587
2016	=back	2588	=back
2017		2589
2018	=head1 C++ SUPPORT	2590	=head1 C++ SUPPORT
2019		2591
2020	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2592	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2021	you to use some convinience methods to start/stop watchers and also change	2593	you to use some convenience methods to start/stop watchers and also change
2022	the callback model to a model using method callbacks on objects.	2594	the callback model to a model using method callbacks on objects.
2023		2595
2024	To use it,	2596	To use it,
2025		2597
2026	#include <ev++.h>	2598	#include <ev++.h>
2027		2599
2028	This automatically includes F<ev.h> and puts all of its definitions (many	2600	This automatically includes F<ev.h> and puts all of its definitions (many
2029	of them macros) into the global namespace. All C++ specific things are	2601	of them macros) into the global namespace. All C++ specific things are
2030	put into the C<ev> namespace. It should support all the same embedding	2602	put into the C<ev> namespace. It should support all the same embedding
2031	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2603	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2098	your compiler is good :), then the method will be fully inlined into the	2670	your compiler is good :), then the method will be fully inlined into the
2099	thunking function, making it as fast as a direct C callback.	2671	thunking function, making it as fast as a direct C callback.
2100		2672
2101	Example: simple class declaration and watcher initialisation	2673	Example: simple class declaration and watcher initialisation
2102		2674
2103	struct myclass	2675	struct myclass
2104	{	2676	{
2105	void io_cb (ev::io &w, int revents) { }	2677	void io_cb (ev::io &w, int revents) { }
2106	}	2678	}
2107		2679
2108	myclass obj;	2680	myclass obj;
2109	ev::io iow;	2681	ev::io iow;
2110	iow.set <myclass, &myclass::io_cb> (&obj);	2682	iow.set <myclass, &myclass::io_cb> (&obj);
2111		2683
2112	=item w->set<function> (void *data = 0)	2684	=item w->set<function> (void *data = 0)
2113		2685
2114	Also sets a callback, but uses a static method or plain function as	2686	Also sets a callback, but uses a static method or plain function as
2115	callback. The optional C<data> argument will be stored in the watcher's	2687	callback. The optional C<data> argument will be stored in the watcher's
…		…
2117		2689
2118	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2690	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2119		2691
2120	See the method-C<set> above for more details.	2692	See the method-C<set> above for more details.
2121		2693
2122	Example:	2694	Example: Use a plain function as callback.
2123		2695
2124	static void io_cb (ev::io &w, int revents) { }	2696	static void io_cb (ev::io &w, int revents) { }
2125	iow.set <io_cb> ();	2697	iow.set <io_cb> ();
2126		2698
2127	=item w->set (struct ev_loop *)	2699	=item w->set (struct ev_loop *)
2128		2700
2129	Associates a different C<struct ev_loop> with this watcher. You can only	2701	Associates a different C<struct ev_loop> with this watcher. You can only
2130	do this when the watcher is inactive (and not pending either).	2702	do this when the watcher is inactive (and not pending either).
2131		2703
2132	=item w->set ([args])	2704	=item w->set ([arguments])
2133		2705
2134	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2706	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2135	called at least once. Unlike the C counterpart, an active watcher gets	2707	called at least once. Unlike the C counterpart, an active watcher gets
2136	automatically stopped and restarted when reconfiguring it with this	2708	automatically stopped and restarted when reconfiguring it with this
2137	method.	2709	method.
2138		2710
2139	=item w->start ()	2711	=item w->start ()
…		…
2163	=back	2735	=back
2164		2736
2165	Example: Define a class with an IO and idle watcher, start one of them in	2737	Example: Define a class with an IO and idle watcher, start one of them in
2166	the constructor.	2738	the constructor.
2167		2739
2168	class myclass	2740	class myclass
2169	{	2741	{
2170	ev_io io; void io_cb (ev::io &w, int revents);	2742	ev::io io ; void io_cb (ev::io &w, int revents);
2171	ev_idle idle void idle_cb (ev::idle &w, int revents);	2743	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2172		2744
2173	myclass ();	2745	myclass (int fd)
2174	}	2746	{
2175
2176	myclass::myclass (int fd)
2177	{
2178	io .set <myclass, &myclass::io_cb > (this);	2747	io .set <myclass, &myclass::io_cb > (this);
2179	idle.set <myclass, &myclass::idle_cb> (this);	2748	idle.set <myclass, &myclass::idle_cb> (this);
2180		2749
2181	io.start (fd, ev::READ);	2750	io.start (fd, ev::READ);
		2751	}
2182	}	2752	};
		2753
		2754
		2755	=head1 OTHER LANGUAGE BINDINGS
		2756
		2757	Libev does not offer other language bindings itself, but bindings for a
		2758	number of languages exist in the form of third-party packages. If you know
		2759	any interesting language binding in addition to the ones listed here, drop
		2760	me a note.
		2761
		2762	=over 4
		2763
		2764	=item Perl
		2765
		2766	The EV module implements the full libev API and is actually used to test
		2767	libev. EV is developed together with libev. Apart from the EV core module,
		2768	there are additional modules that implement libev-compatible interfaces
		2769	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2770	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2771	and C<EV::Glib>).
		2772
		2773	It can be found and installed via CPAN, its homepage is at
		2774	L<http://software.schmorp.de/pkg/EV>.
		2775
		2776	=item Python
		2777
		2778	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2779	seems to be quite complete and well-documented. Note, however, that the
		2780	patch they require for libev is outright dangerous as it breaks the ABI
		2781	for everybody else, and therefore, should never be applied in an installed
		2782	libev (if python requires an incompatible ABI then it needs to embed
		2783	libev).
		2784
		2785	=item Ruby
		2786
		2787	Tony Arcieri has written a ruby extension that offers access to a subset
		2788	of the libev API and adds file handle abstractions, asynchronous DNS and
		2789	more on top of it. It can be found via gem servers. Its homepage is at
		2790	L<http://rev.rubyforge.org/>.
		2791
		2792	=item D
		2793
		2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2795	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2796
		2797	=back
2183		2798
2184		2799
2185	=head1 MACRO MAGIC	2800	=head1 MACRO MAGIC
2186		2801
2187	Libev can be compiled with a variety of options, the most fundamantal	2802	Libev can be compiled with a variety of options, the most fundamental
2188	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2803	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2189	functions and callbacks have an initial C<struct ev_loop *> argument.	2804	functions and callbacks have an initial C<struct ev_loop *> argument.
2190		2805
2191	To make it easier to write programs that cope with either variant, the	2806	To make it easier to write programs that cope with either variant, the
2192	following macros are defined:	2807	following macros are defined:
…		…
2197		2812
2198	This provides the loop I<argument> for functions, if one is required ("ev	2813	This provides the loop I<argument> for functions, if one is required ("ev
2199	loop argument"). The C<EV_A> form is used when this is the sole argument,	2814	loop argument"). The C<EV_A> form is used when this is the sole argument,
2200	C<EV_A_> is used when other arguments are following. Example:	2815	C<EV_A_> is used when other arguments are following. Example:
2201		2816
2202	ev_unref (EV_A);	2817	ev_unref (EV_A);
2203	ev_timer_add (EV_A_ watcher);	2818	ev_timer_add (EV_A_ watcher);
2204	ev_loop (EV_A_ 0);	2819	ev_loop (EV_A_ 0);
2205		2820
2206	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2821	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2207	which is often provided by the following macro.	2822	which is often provided by the following macro.
2208		2823
2209	=item C<EV_P>, C<EV_P_>	2824	=item C<EV_P>, C<EV_P_>
2210		2825
2211	This provides the loop I<parameter> for functions, if one is required ("ev	2826	This provides the loop I<parameter> for functions, if one is required ("ev
2212	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2827	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2213	C<EV_P_> is used when other parameters are following. Example:	2828	C<EV_P_> is used when other parameters are following. Example:
2214		2829
2215	// this is how ev_unref is being declared	2830	// this is how ev_unref is being declared
2216	static void ev_unref (EV_P);	2831	static void ev_unref (EV_P);
2217		2832
2218	// this is how you can declare your typical callback	2833	// this is how you can declare your typical callback
2219	static void cb (EV_P_ ev_timer *w, int revents)	2834	static void cb (EV_P_ ev_timer *w, int revents)
2220		2835
2221	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2836	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2222	suitable for use with C<EV_A>.	2837	suitable for use with C<EV_A>.
2223		2838
2224	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2839	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2225		2840
2226	Similar to the other two macros, this gives you the value of the default	2841	Similar to the other two macros, this gives you the value of the default
2227	loop, if multiple loops are supported ("ev loop default").	2842	loop, if multiple loops are supported ("ev loop default").
		2843
		2844	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2845
		2846	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2847	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2848	is undefined when the default loop has not been initialised by a previous
		2849	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2850
		2851	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2852	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2228		2853
2229	=back	2854	=back
2230		2855
2231	Example: Declare and initialise a check watcher, utilising the above	2856	Example: Declare and initialise a check watcher, utilising the above
2232	macros so it will work regardless of whether multiple loops are supported	2857	macros so it will work regardless of whether multiple loops are supported
2233	or not.	2858	or not.
2234		2859
2235	static void	2860	static void
2236	check_cb (EV_P_ ev_timer *w, int revents)	2861	check_cb (EV_P_ ev_timer *w, int revents)
2237	{	2862	{
2238	ev_check_stop (EV_A_ w);	2863	ev_check_stop (EV_A_ w);
2239	}	2864	}
2240		2865
2241	ev_check check;	2866	ev_check check;
2242	ev_check_init (&check, check_cb);	2867	ev_check_init (&check, check_cb);
2243	ev_check_start (EV_DEFAULT_ &check);	2868	ev_check_start (EV_DEFAULT_ &check);
2244	ev_loop (EV_DEFAULT_ 0);	2869	ev_loop (EV_DEFAULT_ 0);
2245		2870
2246	=head1 EMBEDDING	2871	=head1 EMBEDDING
2247		2872
2248	Libev can (and often is) directly embedded into host	2873	Libev can (and often is) directly embedded into host
2249	applications. Examples of applications that embed it include the Deliantra	2874	applications. Examples of applications that embed it include the Deliantra
…		…
2256	libev somewhere in your source tree).	2881	libev somewhere in your source tree).
2257		2882
2258	=head2 FILESETS	2883	=head2 FILESETS
2259		2884
2260	Depending on what features you need you need to include one or more sets of files	2885	Depending on what features you need you need to include one or more sets of files
2261	in your app.	2886	in your application.
2262		2887
2263	=head3 CORE EVENT LOOP	2888	=head3 CORE EVENT LOOP
2264		2889
2265	To include only the libev core (all the C<ev_*> functions), with manual	2890	To include only the libev core (all the C<ev_*> functions), with manual
2266	configuration (no autoconf):	2891	configuration (no autoconf):
2267		2892
2268	#define EV_STANDALONE 1	2893	#define EV_STANDALONE 1
2269	#include "ev.c"	2894	#include "ev.c"
2270		2895
2271	This will automatically include F<ev.h>, too, and should be done in a	2896	This will automatically include F<ev.h>, too, and should be done in a
2272	single C source file only to provide the function implementations. To use	2897	single C source file only to provide the function implementations. To use
2273	it, do the same for F<ev.h> in all files wishing to use this API (best	2898	it, do the same for F<ev.h> in all files wishing to use this API (best
2274	done by writing a wrapper around F<ev.h> that you can include instead and	2899	done by writing a wrapper around F<ev.h> that you can include instead and
2275	where you can put other configuration options):	2900	where you can put other configuration options):
2276		2901
2277	#define EV_STANDALONE 1	2902	#define EV_STANDALONE 1
2278	#include "ev.h"	2903	#include "ev.h"
2279		2904
2280	Both header files and implementation files can be compiled with a C++	2905	Both header files and implementation files can be compiled with a C++
2281	compiler (at least, thats a stated goal, and breakage will be treated	2906	compiler (at least, thats a stated goal, and breakage will be treated
2282	as a bug).	2907	as a bug).
2283		2908
2284	You need the following files in your source tree, or in a directory	2909	You need the following files in your source tree, or in a directory
2285	in your include path (e.g. in libev/ when using -Ilibev):	2910	in your include path (e.g. in libev/ when using -Ilibev):
2286		2911
2287	ev.h	2912	ev.h
2288	ev.c	2913	ev.c
2289	ev_vars.h	2914	ev_vars.h
2290	ev_wrap.h	2915	ev_wrap.h
2291		2916
2292	ev_win32.c required on win32 platforms only	2917	ev_win32.c required on win32 platforms only
2293		2918
2294	ev_select.c only when select backend is enabled (which is enabled by default)	2919	ev_select.c only when select backend is enabled (which is enabled by default)
2295	ev_poll.c only when poll backend is enabled (disabled by default)	2920	ev_poll.c only when poll backend is enabled (disabled by default)
2296	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2921	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2297	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2922	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2298	ev_port.c only when the solaris port backend is enabled (disabled by default)	2923	ev_port.c only when the solaris port backend is enabled (disabled by default)
2299		2924
2300	F<ev.c> includes the backend files directly when enabled, so you only need	2925	F<ev.c> includes the backend files directly when enabled, so you only need
2301	to compile this single file.	2926	to compile this single file.
2302		2927
2303	=head3 LIBEVENT COMPATIBILITY API	2928	=head3 LIBEVENT COMPATIBILITY API
2304		2929
2305	To include the libevent compatibility API, also include:	2930	To include the libevent compatibility API, also include:
2306		2931
2307	#include "event.c"	2932	#include "event.c"
2308		2933
2309	in the file including F<ev.c>, and:	2934	in the file including F<ev.c>, and:
2310		2935
2311	#include "event.h"	2936	#include "event.h"
2312		2937
2313	in the files that want to use the libevent API. This also includes F<ev.h>.	2938	in the files that want to use the libevent API. This also includes F<ev.h>.
2314		2939
2315	You need the following additional files for this:	2940	You need the following additional files for this:
2316		2941
2317	event.h	2942	event.h
2318	event.c	2943	event.c
2319		2944
2320	=head3 AUTOCONF SUPPORT	2945	=head3 AUTOCONF SUPPORT
2321		2946
2322	Instead of using C<EV_STANDALONE=1> and providing your config in	2947	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2323	whatever way you want, you can also C<m4_include([libev.m4])> in your	2948	whatever way you want, you can also C<m4_include([libev.m4])> in your
2324	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2949	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2325	include F<config.h> and configure itself accordingly.	2950	include F<config.h> and configure itself accordingly.
2326		2951
2327	For this of course you need the m4 file:	2952	For this of course you need the m4 file:
2328		2953
2329	libev.m4	2954	libev.m4
2330		2955
2331	=head2 PREPROCESSOR SYMBOLS/MACROS	2956	=head2 PREPROCESSOR SYMBOLS/MACROS
2332		2957
2333	Libev can be configured via a variety of preprocessor symbols you have to define	2958	Libev can be configured via a variety of preprocessor symbols you have to
2334	before including any of its files. The default is not to build for multiplicity	2959	define before including any of its files. The default in the absence of
2335	and only include the select backend.	2960	autoconf is documented for every option.
2336		2961
2337	=over 4	2962	=over 4
2338		2963
2339	=item EV_STANDALONE	2964	=item EV_STANDALONE
2340		2965
…		…
2345	F<event.h> that are not directly supported by the libev core alone.	2970	F<event.h> that are not directly supported by the libev core alone.
2346		2971
2347	=item EV_USE_MONOTONIC	2972	=item EV_USE_MONOTONIC
2348		2973
2349	If defined to be C<1>, libev will try to detect the availability of the	2974	If defined to be C<1>, libev will try to detect the availability of the
2350	monotonic clock option at both compiletime and runtime. Otherwise no use	2975	monotonic clock option at both compile time and runtime. Otherwise no use
2351	of the monotonic clock option will be attempted. If you enable this, you	2976	of the monotonic clock option will be attempted. If you enable this, you
2352	usually have to link against librt or something similar. Enabling it when	2977	usually have to link against librt or something similar. Enabling it when
2353	the functionality isn't available is safe, though, although you have	2978	the functionality isn't available is safe, though, although you have
2354	to make sure you link against any libraries where the C<clock_gettime>	2979	to make sure you link against any libraries where the C<clock_gettime>
2355	function is hiding in (often F<-lrt>).	2980	function is hiding in (often F<-lrt>).
2356		2981
2357	=item EV_USE_REALTIME	2982	=item EV_USE_REALTIME
2358		2983
2359	If defined to be C<1>, libev will try to detect the availability of the	2984	If defined to be C<1>, libev will try to detect the availability of the
2360	realtime clock option at compiletime (and assume its availability at	2985	real-time clock option at compile time (and assume its availability at
2361	runtime if successful). Otherwise no use of the realtime clock option will	2986	runtime if successful). Otherwise no use of the real-time clock option will
2362	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2987	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2363	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2988	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2364	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2989	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2365		2990
2366	=item EV_USE_NANOSLEEP	2991	=item EV_USE_NANOSLEEP
2367		2992
2368	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2993	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2369	and will use it for delays. Otherwise it will use C<select ()>.	2994	and will use it for delays. Otherwise it will use C<select ()>.
2370		2995
		2996	=item EV_USE_EVENTFD
		2997
		2998	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2999	available and will probe for kernel support at runtime. This will improve
		3000	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3001	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3002	2.7 or newer, otherwise disabled.
		3003
2371	=item EV_USE_SELECT	3004	=item EV_USE_SELECT
2372		3005
2373	If undefined or defined to be C<1>, libev will compile in support for the	3006	If undefined or defined to be C<1>, libev will compile in support for the
2374	C<select>(2) backend. No attempt at autodetection will be done: if no	3007	C<select>(2) backend. No attempt at auto-detection will be done: if no
2375	other method takes over, select will be it. Otherwise the select backend	3008	other method takes over, select will be it. Otherwise the select backend
2376	will not be compiled in.	3009	will not be compiled in.
2377		3010
2378	=item EV_SELECT_USE_FD_SET	3011	=item EV_SELECT_USE_FD_SET
2379		3012
2380	If defined to C<1>, then the select backend will use the system C<fd_set>	3013	If defined to C<1>, then the select backend will use the system C<fd_set>
2381	structure. This is useful if libev doesn't compile due to a missing	3014	structure. This is useful if libev doesn't compile due to a missing
2382	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3015	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2383	exotic systems. This usually limits the range of file descriptors to some	3016	exotic systems. This usually limits the range of file descriptors to some
2384	low limit such as 1024 or might have other limitations (winsocket only	3017	low limit such as 1024 or might have other limitations (winsocket only
2385	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3018	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2386	influence the size of the C<fd_set> used.	3019	influence the size of the C<fd_set> used.
2387		3020
…		…
2393	be used is the winsock select). This means that it will call	3026	be used is the winsock select). This means that it will call
2394	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3027	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2395	it is assumed that all these functions actually work on fds, even	3028	it is assumed that all these functions actually work on fds, even
2396	on win32. Should not be defined on non-win32 platforms.	3029	on win32. Should not be defined on non-win32 platforms.
2397		3030
		3031	=item EV_FD_TO_WIN32_HANDLE
		3032
		3033	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3034	file descriptors to socket handles. When not defining this symbol (the
		3035	default), then libev will call C<_get_osfhandle>, which is usually
		3036	correct. In some cases, programs use their own file descriptor management,
		3037	in which case they can provide this function to map fds to socket handles.
		3038
2398	=item EV_USE_POLL	3039	=item EV_USE_POLL
2399		3040
2400	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3041	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2401	backend. Otherwise it will be enabled on non-win32 platforms. It	3042	backend. Otherwise it will be enabled on non-win32 platforms. It
2402	takes precedence over select.	3043	takes precedence over select.
2403		3044
2404	=item EV_USE_EPOLL	3045	=item EV_USE_EPOLL
2405		3046
2406	If defined to be C<1>, libev will compile in support for the Linux	3047	If defined to be C<1>, libev will compile in support for the Linux
2407	C<epoll>(7) backend. Its availability will be detected at runtime,	3048	C<epoll>(7) backend. Its availability will be detected at runtime,
2408	otherwise another method will be used as fallback. This is the	3049	otherwise another method will be used as fallback. This is the preferred
2409	preferred backend for GNU/Linux systems.	3050	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3051	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2410		3052
2411	=item EV_USE_KQUEUE	3053	=item EV_USE_KQUEUE
2412		3054
2413	If defined to be C<1>, libev will compile in support for the BSD style	3055	If defined to be C<1>, libev will compile in support for the BSD style
2414	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3056	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2427	otherwise another method will be used as fallback. This is the preferred	3069	otherwise another method will be used as fallback. This is the preferred
2428	backend for Solaris 10 systems.	3070	backend for Solaris 10 systems.
2429		3071
2430	=item EV_USE_DEVPOLL	3072	=item EV_USE_DEVPOLL
2431		3073
2432	reserved for future expansion, works like the USE symbols above.	3074	Reserved for future expansion, works like the USE symbols above.
2433		3075
2434	=item EV_USE_INOTIFY	3076	=item EV_USE_INOTIFY
2435		3077
2436	If defined to be C<1>, libev will compile in support for the Linux inotify	3078	If defined to be C<1>, libev will compile in support for the Linux inotify
2437	interface to speed up C<ev_stat> watchers. Its actual availability will	3079	interface to speed up C<ev_stat> watchers. Its actual availability will
2438	be detected at runtime.	3080	be detected at runtime. If undefined, it will be enabled if the headers
		3081	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3082
		3083	=item EV_ATOMIC_T
		3084
		3085	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3086	access is atomic with respect to other threads or signal contexts. No such
		3087	type is easily found in the C language, so you can provide your own type
		3088	that you know is safe for your purposes. It is used both for signal handler "locking"
		3089	as well as for signal and thread safety in C<ev_async> watchers.
		3090
		3091	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3092	(from F<signal.h>), which is usually good enough on most platforms.
2439		3093
2440	=item EV_H	3094	=item EV_H
2441		3095
2442	The name of the F<ev.h> header file used to include it. The default if	3096	The name of the F<ev.h> header file used to include it. The default if
2443	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3097	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2444	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3098	used to virtually rename the F<ev.h> header file in case of conflicts.
2445		3099
2446	=item EV_CONFIG_H	3100	=item EV_CONFIG_H
2447		3101
2448	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3102	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2449	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3103	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2450	C<EV_H>, above.	3104	C<EV_H>, above.
2451		3105
2452	=item EV_EVENT_H	3106	=item EV_EVENT_H
2453		3107
2454	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3108	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2455	of how the F<event.h> header can be found.	3109	of how the F<event.h> header can be found, the default is C<"event.h">.
2456		3110
2457	=item EV_PROTOTYPES	3111	=item EV_PROTOTYPES
2458		3112
2459	If defined to be C<0>, then F<ev.h> will not define any function	3113	If defined to be C<0>, then F<ev.h> will not define any function
2460	prototypes, but still define all the structs and other symbols. This is	3114	prototypes, but still define all the structs and other symbols. This is
…		…
2481	When doing priority-based operations, libev usually has to linearly search	3135	When doing priority-based operations, libev usually has to linearly search
2482	all the priorities, so having many of them (hundreds) uses a lot of space	3136	all the priorities, so having many of them (hundreds) uses a lot of space
2483	and time, so using the defaults of five priorities (-2 .. +2) is usually	3137	and time, so using the defaults of five priorities (-2 .. +2) is usually
2484	fine.	3138	fine.
2485		3139
2486	If your embedding app does not need any priorities, defining these both to	3140	If your embedding application does not need any priorities, defining these
2487	C<0> will save some memory and cpu.	3141	both to C<0> will save some memory and CPU.
2488		3142
2489	=item EV_PERIODIC_ENABLE	3143	=item EV_PERIODIC_ENABLE
2490		3144
2491	If undefined or defined to be C<1>, then periodic timers are supported. If	3145	If undefined or defined to be C<1>, then periodic timers are supported. If
2492	defined to be C<0>, then they are not. Disabling them saves a few kB of	3146	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2499	code.	3153	code.
2500		3154
2501	=item EV_EMBED_ENABLE	3155	=item EV_EMBED_ENABLE
2502		3156
2503	If undefined or defined to be C<1>, then embed watchers are supported. If	3157	If undefined or defined to be C<1>, then embed watchers are supported. If
2504	defined to be C<0>, then they are not.	3158	defined to be C<0>, then they are not. Embed watchers rely on most other
		3159	watcher types, which therefore must not be disabled.
2505		3160
2506	=item EV_STAT_ENABLE	3161	=item EV_STAT_ENABLE
2507		3162
2508	If undefined or defined to be C<1>, then stat watchers are supported. If	3163	If undefined or defined to be C<1>, then stat watchers are supported. If
2509	defined to be C<0>, then they are not.	3164	defined to be C<0>, then they are not.
…		…
2511	=item EV_FORK_ENABLE	3166	=item EV_FORK_ENABLE
2512		3167
2513	If undefined or defined to be C<1>, then fork watchers are supported. If	3168	If undefined or defined to be C<1>, then fork watchers are supported. If
2514	defined to be C<0>, then they are not.	3169	defined to be C<0>, then they are not.
2515		3170
		3171	=item EV_ASYNC_ENABLE
		3172
		3173	If undefined or defined to be C<1>, then async watchers are supported. If
		3174	defined to be C<0>, then they are not.
		3175
2516	=item EV_MINIMAL	3176	=item EV_MINIMAL
2517		3177
2518	If you need to shave off some kilobytes of code at the expense of some	3178	If you need to shave off some kilobytes of code at the expense of some
2519	speed, define this symbol to C<1>. Currently only used for gcc to override	3179	speed, define this symbol to C<1>. Currently this is used to override some
2520	some inlining decisions, saves roughly 30% codesize of amd64.	3180	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3181	much smaller 2-heap for timer management over the default 4-heap.
2521		3182
2522	=item EV_PID_HASHSIZE	3183	=item EV_PID_HASHSIZE
2523		3184
2524	C<ev_child> watchers use a small hash table to distribute workload by	3185	C<ev_child> watchers use a small hash table to distribute workload by
2525	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3186	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2526	than enough. If you need to manage thousands of children you might want to	3187	than enough. If you need to manage thousands of children you might want to
2527	increase this value (I<must> be a power of two).	3188	increase this value (I<must> be a power of two).
2528		3189
2529	=item EV_INOTIFY_HASHSIZE	3190	=item EV_INOTIFY_HASHSIZE
2530		3191
2531	C<ev_staz> watchers use a small hash table to distribute workload by	3192	C<ev_stat> watchers use a small hash table to distribute workload by
2532	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3193	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2533	usually more than enough. If you need to manage thousands of C<ev_stat>	3194	usually more than enough. If you need to manage thousands of C<ev_stat>
2534	watchers you might want to increase this value (I<must> be a power of	3195	watchers you might want to increase this value (I<must> be a power of
2535	two).	3196	two).
2536		3197
		3198	=item EV_USE_4HEAP
		3199
		3200	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3201	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3202	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3203	faster performance with many (thousands) of watchers.
		3204
		3205	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3206	(disabled).
		3207
		3208	=item EV_HEAP_CACHE_AT
		3209
		3210	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3211	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3212	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3213	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3214	but avoids random read accesses on heap changes. This improves performance
		3215	noticeably with many (hundreds) of watchers.
		3216
		3217	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3218	(disabled).
		3219
		3220	=item EV_VERIFY
		3221
		3222	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3223	be done: If set to C<0>, no internal verification code will be compiled
		3224	in. If set to C<1>, then verification code will be compiled in, but not
		3225	called. If set to C<2>, then the internal verification code will be
		3226	called once per loop, which can slow down libev. If set to C<3>, then the
		3227	verification code will be called very frequently, which will slow down
		3228	libev considerably.
		3229
		3230	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3231	C<0>.
		3232
2537	=item EV_COMMON	3233	=item EV_COMMON
2538		3234
2539	By default, all watchers have a C<void *data> member. By redefining	3235	By default, all watchers have a C<void *data> member. By redefining
2540	this macro to a something else you can include more and other types of	3236	this macro to a something else you can include more and other types of
2541	members. You have to define it each time you include one of the files,	3237	members. You have to define it each time you include one of the files,
2542	though, and it must be identical each time.	3238	though, and it must be identical each time.
2543		3239
2544	For example, the perl EV module uses something like this:	3240	For example, the perl EV module uses something like this:
2545		3241
2546	#define EV_COMMON \	3242	#define EV_COMMON \
2547	SV *self; /* contains this struct */ \	3243	SV *self; /* contains this struct */ \
2548	SV *cb_sv, *fh /* note no trailing ";" */	3244	SV *cb_sv, *fh /* note no trailing ";" */
2549		3245
2550	=item EV_CB_DECLARE (type)	3246	=item EV_CB_DECLARE (type)
2551		3247
2552	=item EV_CB_INVOKE (watcher, revents)	3248	=item EV_CB_INVOKE (watcher, revents)
2553		3249
…		…
2558	definition and a statement, respectively. See the F<ev.h> header file for	3254	definition and a statement, respectively. See the F<ev.h> header file for
2559	their default definitions. One possible use for overriding these is to	3255	their default definitions. One possible use for overriding these is to
2560	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3256	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2561	method calls instead of plain function calls in C++.	3257	method calls instead of plain function calls in C++.
2562		3258
		3259	=back
		3260
2563	=head2 EXPORTED API SYMBOLS	3261	=head2 EXPORTED API SYMBOLS
2564		3262
2565	If you need to re-export the API (e.g. via a dll) and you need a list of	3263	If you need to re-export the API (e.g. via a DLL) and you need a list of
2566	exported symbols, you can use the provided F<Symbol.*> files which list	3264	exported symbols, you can use the provided F<Symbol.*> files which list
2567	all public symbols, one per line:	3265	all public symbols, one per line:
2568		3266
2569	Symbols.ev for libev proper	3267	Symbols.ev for libev proper
2570	Symbols.event for the libevent emulation	3268	Symbols.event for the libevent emulation
2571		3269
2572	This can also be used to rename all public symbols to avoid clashes with	3270	This can also be used to rename all public symbols to avoid clashes with
2573	multiple versions of libev linked together (which is obviously bad in	3271	multiple versions of libev linked together (which is obviously bad in
2574	itself, but sometimes it is inconvinient to avoid this).	3272	itself, but sometimes it is inconvenient to avoid this).
2575		3273
2576	A sed command like this will create wrapper C<#define>'s that you need to	3274	A sed command like this will create wrapper C<#define>'s that you need to
2577	include before including F<ev.h>:	3275	include before including F<ev.h>:
2578		3276
2579	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3277	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2596	file.	3294	file.
2597		3295
2598	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3296	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2599	that everybody includes and which overrides some configure choices:	3297	that everybody includes and which overrides some configure choices:
2600		3298
2601	#define EV_MINIMAL 1	3299	#define EV_MINIMAL 1
2602	#define EV_USE_POLL 0	3300	#define EV_USE_POLL 0
2603	#define EV_MULTIPLICITY 0	3301	#define EV_MULTIPLICITY 0
2604	#define EV_PERIODIC_ENABLE 0	3302	#define EV_PERIODIC_ENABLE 0
2605	#define EV_STAT_ENABLE 0	3303	#define EV_STAT_ENABLE 0
2606	#define EV_FORK_ENABLE 0	3304	#define EV_FORK_ENABLE 0
2607	#define EV_CONFIG_H <config.h>	3305	#define EV_CONFIG_H <config.h>
2608	#define EV_MINPRI 0	3306	#define EV_MINPRI 0
2609	#define EV_MAXPRI 0	3307	#define EV_MAXPRI 0
2610		3308
2611	#include "ev++.h"	3309	#include "ev++.h"
2612		3310
2613	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3311	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2614		3312
2615	#include "ev_cpp.h"	3313	#include "ev_cpp.h"
2616	#include "ev.c"	3314	#include "ev.c"
2617		3315
		3316	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2618		3317
		3318	=head2 THREADS AND COROUTINES
		3319
		3320	=head3 THREADS
		3321
		3322	All libev functions are reentrant and thread-safe unless explicitly
		3323	documented otherwise, but libev implements no locking itself. This means
		3324	that you can use as many loops as you want in parallel, as long as there
		3325	are no concurrent calls into any libev function with the same loop
		3326	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3327	of course): libev guarantees that different event loops share no data
		3328	structures that need any locking.
		3329
		3330	Or to put it differently: calls with different loop parameters can be done
		3331	concurrently from multiple threads, calls with the same loop parameter
		3332	must be done serially (but can be done from different threads, as long as
		3333	only one thread ever is inside a call at any point in time, e.g. by using
		3334	a mutex per loop).
		3335
		3336	Specifically to support threads (and signal handlers), libev implements
		3337	so-called C<ev_async> watchers, which allow some limited form of
		3338	concurrency on the same event loop, namely waking it up "from the
		3339	outside".
		3340
		3341	If you want to know which design (one loop, locking, or multiple loops
		3342	without or something else still) is best for your problem, then I cannot
		3343	help you, but here is some generic advice:
		3344
		3345	=over 4
		3346
		3347	=item * most applications have a main thread: use the default libev loop
		3348	in that thread, or create a separate thread running only the default loop.
		3349
		3350	This helps integrating other libraries or software modules that use libev
		3351	themselves and don't care/know about threading.
		3352
		3353	=item * one loop per thread is usually a good model.
		3354
		3355	Doing this is almost never wrong, sometimes a better-performance model
		3356	exists, but it is always a good start.
		3357
		3358	=item * other models exist, such as the leader/follower pattern, where one
		3359	loop is handed through multiple threads in a kind of round-robin fashion.
		3360
		3361	Choosing a model is hard - look around, learn, know that usually you can do
		3362	better than you currently do :-)
		3363
		3364	=item * often you need to talk to some other thread which blocks in the
		3365	event loop.
		3366
		3367	C<ev_async> watchers can be used to wake them up from other threads safely
		3368	(or from signal contexts...).
		3369
		3370	An example use would be to communicate signals or other events that only
		3371	work in the default loop by registering the signal watcher with the
		3372	default loop and triggering an C<ev_async> watcher from the default loop
		3373	watcher callback into the event loop interested in the signal.
		3374
		3375	=back
		3376
		3377	=head3 COROUTINES
		3378
		3379	Libev is very accommodating to coroutines ("cooperative threads"):
		3380	libev fully supports nesting calls to its functions from different
		3381	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3382	different coroutines, and switch freely between both coroutines running the
		3383	loop, as long as you don't confuse yourself). The only exception is that
		3384	you must not do this from C<ev_periodic> reschedule callbacks.
		3385
		3386	Care has been taken to ensure that libev does not keep local state inside
		3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3388	they do not clal any callbacks.
		3389
		3390	=head2 COMPILER WARNINGS
		3391
		3392	Depending on your compiler and compiler settings, you might get no or a
		3393	lot of warnings when compiling libev code. Some people are apparently
		3394	scared by this.
		3395
		3396	However, these are unavoidable for many reasons. For one, each compiler
		3397	has different warnings, and each user has different tastes regarding
		3398	warning options. "Warn-free" code therefore cannot be a goal except when
		3399	targeting a specific compiler and compiler-version.
		3400
		3401	Another reason is that some compiler warnings require elaborate
		3402	workarounds, or other changes to the code that make it less clear and less
		3403	maintainable.
		3404
		3405	And of course, some compiler warnings are just plain stupid, or simply
		3406	wrong (because they don't actually warn about the condition their message
		3407	seems to warn about). For example, certain older gcc versions had some
		3408	warnings that resulted an extreme number of false positives. These have
		3409	been fixed, but some people still insist on making code warn-free with
		3410	such buggy versions.
		3411
		3412	While libev is written to generate as few warnings as possible,
		3413	"warn-free" code is not a goal, and it is recommended not to build libev
		3414	with any compiler warnings enabled unless you are prepared to cope with
		3415	them (e.g. by ignoring them). Remember that warnings are just that:
		3416	warnings, not errors, or proof of bugs.
		3417
		3418
		3419	=head2 VALGRIND
		3420
		3421	Valgrind has a special section here because it is a popular tool that is
		3422	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3423
		3424	If you think you found a bug (memory leak, uninitialised data access etc.)
		3425	in libev, then check twice: If valgrind reports something like:
		3426
		3427	==2274== definitely lost: 0 bytes in 0 blocks.
		3428	==2274== possibly lost: 0 bytes in 0 blocks.
		3429	==2274== still reachable: 256 bytes in 1 blocks.
		3430
		3431	Then there is no memory leak, just as memory accounted to global variables
		3432	is not a memleak - the memory is still being refernced, and didn't leak.
		3433
		3434	Similarly, under some circumstances, valgrind might report kernel bugs
		3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3436	although an acceptable workaround has been found here), or it might be
		3437	confused.
		3438
		3439	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3440	make it into some kind of religion.
		3441
		3442	If you are unsure about something, feel free to contact the mailing list
		3443	with the full valgrind report and an explanation on why you think this
		3444	is a bug in libev (best check the archives, too :). However, don't be
		3445	annoyed when you get a brisk "this is no bug" answer and take the chance
		3446	of learning how to interpret valgrind properly.
		3447
		3448	If you need, for some reason, empty reports from valgrind for your project
		3449	I suggest using suppression lists.
		3450
		3451
		3452	=head1 PORTABILITY NOTES
		3453
		3454	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3455
		3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3457	requires, and its I/O model is fundamentally incompatible with the POSIX
		3458	model. Libev still offers limited functionality on this platform in
		3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3460	descriptors. This only applies when using Win32 natively, not when using
		3461	e.g. cygwin.
		3462
		3463	Lifting these limitations would basically require the full
		3464	re-implementation of the I/O system. If you are into these kinds of
		3465	things, then note that glib does exactly that for you in a very portable
		3466	way (note also that glib is the slowest event library known to man).
		3467
		3468	There is no supported compilation method available on windows except
		3469	embedding it into other applications.
		3470
		3471	Not a libev limitation but worth mentioning: windows apparently doesn't
		3472	accept large writes: instead of resulting in a partial write, windows will
		3473	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3474	so make sure you only write small amounts into your sockets (less than a
		3475	megabyte seems safe, but this apparently depends on the amount of memory
		3476	available).
		3477
		3478	Due to the many, low, and arbitrary limits on the win32 platform and
		3479	the abysmal performance of winsockets, using a large number of sockets
		3480	is not recommended (and not reasonable). If your program needs to use
		3481	more than a hundred or so sockets, then likely it needs to use a totally
		3482	different implementation for windows, as libev offers the POSIX readiness
		3483	notification model, which cannot be implemented efficiently on windows
		3484	(Microsoft monopoly games).
		3485
		3486	A typical way to use libev under windows is to embed it (see the embedding
		3487	section for details) and use the following F<evwrap.h> header file instead
		3488	of F<ev.h>:
		3489
		3490	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3491	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3492
		3493	#include "ev.h"
		3494
		3495	And compile the following F<evwrap.c> file into your project (make sure
		3496	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3497
		3498	#include "evwrap.h"
		3499	#include "ev.c"
		3500
		3501	=over 4
		3502
		3503	=item The winsocket select function
		3504
		3505	The winsocket C<select> function doesn't follow POSIX in that it
		3506	requires socket I<handles> and not socket I<file descriptors> (it is
		3507	also extremely buggy). This makes select very inefficient, and also
		3508	requires a mapping from file descriptors to socket handles (the Microsoft
		3509	C runtime provides the function C<_open_osfhandle> for this). See the
		3510	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3511	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3512
		3513	The configuration for a "naked" win32 using the Microsoft runtime
		3514	libraries and raw winsocket select is:
		3515
		3516	#define EV_USE_SELECT 1
		3517	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3518
		3519	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3520	complexity in the O(n²) range when using win32.
		3521
		3522	=item Limited number of file descriptors
		3523
		3524	Windows has numerous arbitrary (and low) limits on things.
		3525
		3526	Early versions of winsocket's select only supported waiting for a maximum
		3527	of C<64> handles (probably owning to the fact that all windows kernels
		3528	can only wait for C<64> things at the same time internally; Microsoft
		3529	recommends spawning a chain of threads and wait for 63 handles and the
		3530	previous thread in each. Great).
		3531
		3532	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3533	to some high number (e.g. C<2048>) before compiling the winsocket select
		3534	call (which might be in libev or elsewhere, for example, perl does its own
		3535	select emulation on windows).
		3536
		3537	Another limit is the number of file descriptors in the Microsoft runtime
		3538	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3539	or something like this inside Microsoft). You can increase this by calling
		3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3541	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3542	libraries.
		3543
		3544	This might get you to about C<512> or C<2048> sockets (depending on
		3545	windows version and/or the phase of the moon). To get more, you need to
		3546	wrap all I/O functions and provide your own fd management, but the cost of
		3547	calling select (O(n²)) will likely make this unworkable.
		3548
		3549	=back
		3550
		3551	=head2 PORTABILITY REQUIREMENTS
		3552
		3553	In addition to a working ISO-C implementation and of course the
		3554	backend-specific APIs, libev relies on a few additional extensions:
		3555
		3556	=over 4
		3557
		3558	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3559	calling conventions regardless of C<ev_watcher_type *>.
		3560
		3561	Libev assumes not only that all watcher pointers have the same internal
		3562	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3563	assumes that the same (machine) code can be used to call any watcher
		3564	callback: The watcher callbacks have different type signatures, but libev
		3565	calls them using an C<ev_watcher *> internally.
		3566
		3567	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3568
		3569	The type C<sig_atomic_t volatile> (or whatever is defined as
		3570	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3571	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3572	believed to be sufficiently portable.
		3573
		3574	=item C<sigprocmask> must work in a threaded environment
		3575
		3576	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3577	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3578	pthread implementations will either allow C<sigprocmask> in the "main
		3579	thread" or will block signals process-wide, both behaviours would
		3580	be compatible with libev. Interaction between C<sigprocmask> and
		3581	C<pthread_sigmask> could complicate things, however.
		3582
		3583	The most portable way to handle signals is to block signals in all threads
		3584	except the initial one, and run the default loop in the initial thread as
		3585	well.
		3586
		3587	=item C<long> must be large enough for common memory allocation sizes
		3588
		3589	To improve portability and simplify its API, libev uses C<long> internally
		3590	instead of C<size_t> when allocating its data structures. On non-POSIX
		3591	systems (Microsoft...) this might be unexpectedly low, but is still at
		3592	least 31 bits everywhere, which is enough for hundreds of millions of
		3593	watchers.
		3594
		3595	=item C<double> must hold a time value in seconds with enough accuracy
		3596
		3597	The type C<double> is used to represent timestamps. It is required to
		3598	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3599	enough for at least into the year 4000. This requirement is fulfilled by
		3600	implementations implementing IEEE 754 (basically all existing ones).
		3601
		3602	=back
		3603
		3604	If you know of other additional requirements drop me a note.
		3605
		3606
2619	=head1 COMPLEXITIES	3607	=head1 ALGORITHMIC COMPLEXITIES
2620		3608
2621	In this section the complexities of (many of) the algorithms used inside	3609	In this section the complexities of (many of) the algorithms used inside
2622	libev will be explained. For complexity discussions about backends see the	3610	libev will be documented. For complexity discussions about backends see
2623	documentation for C<ev_default_init>.	3611	the documentation for C<ev_default_init>.
2624		3612
2625	All of the following are about amortised time: If an array needs to be	3613	All of the following are about amortised time: If an array needs to be
2626	extended, libev needs to realloc and move the whole array, but this	3614	extended, libev needs to realloc and move the whole array, but this
2627	happens asymptotically never with higher number of elements, so O(1) might	3615	happens asymptotically rarer with higher number of elements, so O(1) might
2628	mean it might do a lengthy realloc operation in rare cases, but on average	3616	mean that libev does a lengthy realloc operation in rare cases, but on
2629	it is much faster and asymptotically approaches constant time.	3617	average it is much faster and asymptotically approaches constant time.
2630		3618
2631	=over 4	3619	=over 4
2632		3620
2633	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3621	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2634		3622
2635	This means that, when you have a watcher that triggers in one hour and	3623	This means that, when you have a watcher that triggers in one hour and
2636	there are 100 watchers that would trigger before that then inserting will	3624	there are 100 watchers that would trigger before that, then inserting will
2637	have to skip those 100 watchers.	3625	have to skip roughly seven (C<ld 100>) of these watchers.
2638		3626
2639	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3627	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2640		3628
2641	That means that for changing a timer costs less than removing/adding them	3629	That means that changing a timer costs less than removing/adding them,
2642	as only the relative motion in the event queue has to be paid for.	3630	as only the relative motion in the event queue has to be paid for.
2643		3631
2644	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3632	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2645		3633
2646	These just add the watcher into an array or at the head of a list.	3634	These just add the watcher into an array or at the head of a list.
		3635
2647	=item Stopping check/prepare/idle watchers: O(1)	3636	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2648		3637
2649	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3638	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2650		3639
2651	These watchers are stored in lists then need to be walked to find the	3640	These watchers are stored in lists, so they need to be walked to find the
2652	correct watcher to remove. The lists are usually short (you don't usually	3641	correct watcher to remove. The lists are usually short (you don't usually
2653	have many watchers waiting for the same fd or signal).	3642	have many watchers waiting for the same fd or signal: one is typical, two
		3643	is rare).
2654		3644
2655	=item Finding the next timer per loop iteration: O(1)	3645	=item Finding the next timer in each loop iteration: O(1)
		3646
		3647	By virtue of using a binary or 4-heap, the next timer is always found at a
		3648	fixed position in the storage array.
2656		3649
2657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3650	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2658		3651
2659	A change means an I/O watcher gets started or stopped, which requires	3652	A change means an I/O watcher gets started or stopped, which requires
2660	libev to recalculate its status (and possibly tell the kernel).	3653	libev to recalculate its status (and possibly tell the kernel, depending
		3654	on backend and whether C<ev_io_set> was used).
2661		3655
2662	=item Activating one watcher: O(1)	3656	=item Activating one watcher (putting it into the pending state): O(1)
2663		3657
2664	=item Priority handling: O(number_of_priorities)	3658	=item Priority handling: O(number_of_priorities)
2665		3659
2666	Priorities are implemented by allocating some space for each	3660	Priorities are implemented by allocating some space for each
2667	priority. When doing priority-based operations, libev usually has to	3661	priority. When doing priority-based operations, libev usually has to
2668	linearly search all the priorities.	3662	linearly search all the priorities, but starting/stopping and activating
		3663	watchers becomes O(1) with respect to priority handling.
		3664
		3665	=item Sending an ev_async: O(1)
		3666
		3667	=item Processing ev_async_send: O(number_of_async_watchers)
		3668
		3669	=item Processing signals: O(max_signal_number)
		3670
		3671	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3672	calls in the current loop iteration. Checking for async and signal events
		3673	involves iterating over all running async watchers or all signal numbers.
2669		3674
2670	=back	3675	=back
2671		3676
2672		3677
2673	=head1 AUTHOR	3678	=head1 AUTHOR

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