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Revision 1.99 by root, Sat Dec 22 06:16:36 2007 UTC vs.
Revision 1.187 by root, Mon Sep 29 03:31:14 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
309	libev tries to roll its own fd_set with no limits on the number of fds,	352	libev tries to roll its own fd_set with no limits on the number of fds,
310	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
311	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
312	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
		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).
313		367
314	=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)
315		369
316	And this is your standard poll(2) backend. It's more complicated than	370	And this is your standard poll(2) backend. It's more complicated
317	select, but handles sparse fds better and has no artificial limit on the	371	than select, but handles sparse fds better and has no artificial
318	number of fds you can use (except it will slow down considerably with a	372	limit on the number of fds you can use (except it will slow down
319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	373	considerably with a lot of inactive fds). It scales similarly to select,
		374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
320		379
321	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
322		381
323	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,
324	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
325	like O(total_fds) where n is the total number of fds (or the highest fd),	384	like O(total_fds) where n is the total number of fds (or the highest fd),
326	epoll scales either O(1) or O(active_fds). The epoll design has a number	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
327	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
328	cases and rewiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
329	support for dup:	388	support for dup.
330		389
331	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
332	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
333	(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
334	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
335	very well if you register events for both fds.	394	very well if you register events for both fds.
336		395
337	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
338	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
339	(or space) is available.	398	(or space) is available.
340		399
		400	Best performance from this backend is achieved by not unregistering all
		401	watchers for a file descriptor until it has been closed, if possible,
		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.
		405
		406	While nominally embeddable in other event loops, this feature is broken in
		407	all kernel versions tested so far.
		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
342		413
343	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
344	was broken on I<all> BSDs (usually it doesn't work with anything but	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
345	sockets and pipes, except on Darwin, where of course it's completely	416	anything but sockets and pipes, except on Darwin, where of course it's
346	useless. On NetBSD, it seems to work for all the FD types I tested, so it	417	completely useless). For this reason it's not being "auto-detected" unless
347	is used by default there). For this reason it's not being "autodetected"	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
348	unless you explicitly specify it explicitly in the flags (i.e. using	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
349	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	420
350	system like NetBSD.	421	You still can embed kqueue into a normal poll or select backend and use it
		422	only for sockets (after having made sure that sockets work with kqueue on
		423	the target platform). See C<ev_embed> watchers for more info.
351		424
352	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
353	kernel is more efficient (which says nothing about its actual speed,	426	kernel is more efficient (which says nothing about its actual speed, of
354	of course). While stopping, setting and starting an I/O watcher does	427	course). While stopping, setting and starting an I/O watcher does never
355	never cause an extra syscall as with epoll, it still adds up to two event	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
356	changes per incident, support for C<fork ()> is very bad and it drops fds	429	two event changes per incident. Support for C<fork ()> is very bad and it
357	silently in similarly hard-to-detetc cases.	430	drops fds silently in similarly hard-to-detect cases.
		431
		432	This backend usually performs well under most conditions.
		433
		434	While nominally embeddable in other event loops, this doesn't work
		435	everywhere, so you might need to test for this. And since it is broken
		436	almost everywhere, you should only use it when you have a lot of sockets
		437	(for which it usually works), by embedding it into another event loop
		438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		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>.
358		444
359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
360		446
361	This is not implemented yet (and might never be).	447	This is not implemented yet (and might never be, unless you send me an
		448	implementation). According to reports, C</dev/poll> only supports sockets
		449	and is not embeddable, which would limit the usefulness of this backend
		450	immensely.
362		451
363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
364		453
365	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,
366	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)).
367		456
368	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
369	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
370	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
		460
		461	While this backend scales well, it requires one system call per active
		462	file descriptor per loop iteration. For small and medium numbers of file
		463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		464	might perform better.
		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>.
371		473
372	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
373		475
374	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
375	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
376	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
377		479
		480	It is definitely not recommended to use this flag.
		481
378	=back	482	=back
379		483
380	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
381	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
382	specified, most compiled-in backend will be tried, usually in reverse	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
383	order of their flag values :)
384		487
385	The most typical usage is like this:	488	Example: This is the most typical usage.
386		489
387	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
388	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
389		492
390	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
391	environment settings to be taken into account:	494	environment settings to be taken into account:
392		495
393	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
394		497
395	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
396	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
397	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):
398		502
399	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
400		504
401	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
402		506
403	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
404	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
405	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
406	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
407		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
408	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.
409		517
410	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
411	if (!epoller)	519	if (!epoller)
412	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
413		521
414	=item ev_default_destroy ()	522	=item ev_default_destroy ()
415		523
416	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
417	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
418	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
419	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
420	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
421	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
422	for example).	530	for example).
423		531
424	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
…		…
435	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
436	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
437		545
438	=item ev_default_fork ()	546	=item ev_default_fork ()
439		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
440	This function reinitialises the kernel state for backends that have	549	to reinitialise the kernel state for backends that have one. Despite the
441	one. Despite the name, you can call it anytime, but it makes most sense	550	name, you can call it anytime, but it makes most sense after forking, in
442	after forking, in either the parent or child process (or both, but that	551	the child process (or both child and parent, but that again makes little
443	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.
444		554
445	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
446	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
447	fork+exec, you don't have to call it.	557	you just fork+exec, you don't have to call it at all.
448		558
449	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
450	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
451	quite nicely into a call to C<pthread_atfork>:	561	quite nicely into a call to C<pthread_atfork>:
452		562
453	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
454		564
455	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
456	without calling this function, so if you force one of those backends you
457	do not need to care.
458
459	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
460		566
461	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
462	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
463	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.
464		576
465	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
466		578
467	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
468	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
…		…
483	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
484	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
485	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
486	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
487		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
488	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
489		613
490	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
491	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
492	events.	616	events.
…		…
494	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
495	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.
496		620
497	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
498	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
499	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
500	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
501	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.
502		627
503	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
504	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
505	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.
506		632
507	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
508	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
509	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
510	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
511	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
512	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
513	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
514		644
515	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
516		646
517	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
518	* If there are no active watchers (reference count is zero), return.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
519	- 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.
520	- 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.
521	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
522	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
523	- 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.
524	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
525	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
526	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
527	- Queue all outstanding timers.	662	- Queue all expired timers.
528	- Queue all outstanding periodics.	663	- Queue all expired periodics.
529	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
530	- Queue all check watchers.	665	- Queue all check watchers.
531	- 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).
532	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
533	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
534	- 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
535	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
536		672
537	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
538	anymore.	674	anymore.
539		675
540	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
541	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
542	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
543	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
544		680
545	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
546		682
547	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
548	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
549	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
550	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.
551		687
		688	This "unloop state" will be cleared when entering C<ev_loop> again.
		689
552	=item ev_ref (loop)	690	=item ev_ref (loop)
553		691
554	=item ev_unref (loop)	692	=item ev_unref (loop)
555		693
556	Ref/unref can be used to add or remove a reference count on the event	694	Ref/unref can be used to add or remove a reference count on the event
557	loop: Every watcher keeps one reference, and as long as the reference	695	loop: Every watcher keeps one reference, and as long as the reference
558	count is nonzero, C<ev_loop> will not return on its own. If you have	696	count is nonzero, C<ev_loop> will not return on its own.
		697
559	a watcher you never unregister that should not keep C<ev_loop> from	698	If you have a watcher you never unregister that should not keep C<ev_loop>
560	returning, ev_unref() after starting, and ev_ref() before stopping it. For	699	from returning, call ev_unref() after starting, and ev_ref() before
		700	stopping it.
		701
561	example, libev itself uses this for its internal signal pipe: It is not	702	As an example, libev itself uses this for its internal signal pipe: It is
562	visible to the libev user and should not keep C<ev_loop> from exiting if	703	not visible to the libev user and should not keep C<ev_loop> from exiting
563	no event watchers registered by it are active. It is also an excellent	704	if no event watchers registered by it are active. It is also an excellent
564	way to do this for generic recurring timers or from within third-party	705	way to do this for generic recurring timers or from within third-party
565	libraries. Just remember to I<unref after start> and I<ref before stop>.	706	libraries. Just remember to I<unref after start> and I<ref before stop>
		707	(but only if the watcher wasn't active before, or was active before,
		708	respectively).
566		709
567	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
568	running when nothing else is active.	711	running when nothing else is active.
569		712
570	struct ev_signal exitsig;	713	struct ev_signal exitsig;
571	ev_signal_init (&exitsig, sig_cb, SIGINT);	714	ev_signal_init (&exitsig, sig_cb, SIGINT);
572	ev_signal_start (loop, &exitsig);	715	ev_signal_start (loop, &exitsig);
573	evf_unref (loop);	716	evf_unref (loop);
574		717
575	Example: For some weird reason, unregister the above signal handler again.	718	Example: For some weird reason, unregister the above signal handler again.
576		719
577	ev_ref (loop);	720	ev_ref (loop);
578	ev_signal_stop (loop, &exitsig);	721	ev_signal_stop (loop, &exitsig);
579		722
580	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	723	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
581		724
582	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
583		726
584	These advanced functions influence the time that libev will spend waiting	727	These advanced functions influence the time that libev will spend waiting
585	for events. Both are by default C<0>, meaning that libev will try to	728	for events. Both time intervals are by default C<0>, meaning that libev
586	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	729	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		730	latency.
587		731
588	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	732	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
589	allows libev to delay invocation of I/O and timer/periodic callbacks to	733	allows libev to delay invocation of I/O and timer/periodic callbacks
590	increase efficiency of loop iterations.	734	to increase efficiency of loop iterations (or to increase power-saving
		735	opportunities).
591		736
592	The background is that sometimes your program runs just fast enough to	737	The idea is that sometimes your program runs just fast enough to handle
593	handle one (or very few) event(s) per loop iteration. While this makes	738	one (or very few) event(s) per loop iteration. While this makes the
594	the program responsive, it also wastes a lot of CPU time to poll for new	739	program responsive, it also wastes a lot of CPU time to poll for new
595	events, especially with backends like C<select ()> which have a high	740	events, especially with backends like C<select ()> which have a high
596	overhead for the actual polling but can deliver many events at once.	741	overhead for the actual polling but can deliver many events at once.
597		742
598	By setting a higher I<io collect interval> you allow libev to spend more	743	By setting a higher I<io collect interval> you allow libev to spend more
599	time collecting I/O events, so you can handle more events per iteration,	744	time collecting I/O events, so you can handle more events per iteration,
600	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	745	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
601	C<ev_timer>) will be not affected. Setting this to a non-null bvalue will	746	C<ev_timer>) will be not affected. Setting this to a non-null value will
602	introduce an additional C<ev_sleep ()> call into most loop iterations.	747	introduce an additional C<ev_sleep ()> call into most loop iterations.
603		748
604	Likewise, by setting a higher I<timeout collect interval> you allow libev	749	Likewise, by setting a higher I<timeout collect interval> you allow libev
605	to spend more time collecting timeouts, at the expense of increased	750	to spend more time collecting timeouts, at the expense of increased
606	latency (the watcher callback will be called later). C<ev_io> watchers	751	latency/jitter/inexactness (the watcher callback will be called
607	will not be affected. Setting this to a non-null value will not introduce	752	later). C<ev_io> watchers will not be affected. Setting this to a non-null
608	any overhead in libev.	753	value will not introduce any overhead in libev.
609		754
610	Many (busy) programs can usually benefit by setting the io collect	755	Many (busy) programs can usually benefit by setting the I/O collect
611	interval to a value near C<0.1> or so, which is often enough for	756	interval to a value near C<0.1> or so, which is often enough for
612	interactive servers (of course not for games), likewise for timeouts. It	757	interactive servers (of course not for games), likewise for timeouts. It
613	usually doesn't make much sense to set it to a lower value than C<0.01>,	758	usually doesn't make much sense to set it to a lower value than C<0.01>,
614	as this approsaches the timing granularity of most systems.	759	as this approaches the timing granularity of most systems.
		760
		761	Setting the I<timeout collect interval> can improve the opportunity for
		762	saving power, as the program will "bundle" timer callback invocations that
		763	are "near" in time together, by delaying some, thus reducing the number of
		764	times the process sleeps and wakes up again. Another useful technique to
		765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		766	they fire on, say, one-second boundaries only.
		767
		768	=item ev_loop_verify (loop)
		769
		770	This function only does something when C<EV_VERIFY> support has been
		771	compiled in. which is the default for non-minimal builds. It tries to go
		772	through all internal structures and checks them for validity. If anything
		773	is found to be inconsistent, it will print an error message to standard
		774	error and call C<abort ()>.
		775
		776	This can be used to catch bugs inside libev itself: under normal
		777	circumstances, this function will never abort as of course libev keeps its
		778	data structures consistent.
615		779
616	=back	780	=back
617		781
618		782
619	=head1 ANATOMY OF A WATCHER	783	=head1 ANATOMY OF A WATCHER
620		784
621	A watcher is a structure that you create and register to record your	785	A watcher is a structure that you create and register to record your
622	interest in some event. For instance, if you want to wait for STDIN to	786	interest in some event. For instance, if you want to wait for STDIN to
623	become readable, you would create an C<ev_io> watcher for that:	787	become readable, you would create an C<ev_io> watcher for that:
624		788
625	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
626	{	790	{
627	ev_io_stop (w);	791	ev_io_stop (w);
628	ev_unloop (loop, EVUNLOOP_ALL);	792	ev_unloop (loop, EVUNLOOP_ALL);
629	}	793	}
630		794
631	struct ev_loop *loop = ev_default_loop (0);	795	struct ev_loop *loop = ev_default_loop (0);
632	struct ev_io stdin_watcher;	796	struct ev_io stdin_watcher;
633	ev_init (&stdin_watcher, my_cb);	797	ev_init (&stdin_watcher, my_cb);
634	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
635	ev_io_start (loop, &stdin_watcher);	799	ev_io_start (loop, &stdin_watcher);
636	ev_loop (loop, 0);	800	ev_loop (loop, 0);
637		801
638	As you can see, you are responsible for allocating the memory for your	802	As you can see, you are responsible for allocating the memory for your
639	watcher structures (and it is usually a bad idea to do this on the stack,	803	watcher structures (and it is usually a bad idea to do this on the stack,
640	although this can sometimes be quite valid).	804	although this can sometimes be quite valid).
641		805
642	Each watcher structure must be initialised by a call to C<ev_init	806	Each watcher structure must be initialised by a call to C<ev_init
643	(watcher *, callback)>, which expects a callback to be provided. This	807	(watcher *, callback)>, which expects a callback to be provided. This
644	callback gets invoked each time the event occurs (or, in the case of io	808	callback gets invoked each time the event occurs (or, in the case of I/O
645	watchers, each time the event loop detects that the file descriptor given	809	watchers, each time the event loop detects that the file descriptor given
646	is readable and/or writable).	810	is readable and/or writable).
647		811
648	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
649	with arguments specific to this watcher type. There is also a macro	813	with arguments specific to this watcher type. There is also a macro
…		…
719	=item C<EV_FORK>	883	=item C<EV_FORK>
720		884
721	The event loop has been resumed in the child process after fork (see	885	The event loop has been resumed in the child process after fork (see
722	C<ev_fork>).	886	C<ev_fork>).
723		887
		888	=item C<EV_ASYNC>
		889
		890	The given async watcher has been asynchronously notified (see C<ev_async>).
		891
724	=item C<EV_ERROR>	892	=item C<EV_ERROR>
725		893
726	An unspecified error has occured, the watcher has been stopped. This might	894	An unspecified error has occurred, the watcher has been stopped. This might
727	happen because the watcher could not be properly started because libev	895	happen because the watcher could not be properly started because libev
728	ran out of memory, a file descriptor was found to be closed or any other	896	ran out of memory, a file descriptor was found to be closed or any other
729	problem. You best act on it by reporting the problem and somehow coping	897	problem. You best act on it by reporting the problem and somehow coping
730	with the watcher being stopped.	898	with the watcher being stopped.
731		899
732	Libev will usually signal a few "dummy" events together with an error,	900	Libev will usually signal a few "dummy" events together with an error, for
733	for example it might indicate that a fd is readable or writable, and if	901	example it might indicate that a fd is readable or writable, and if your
734	your callbacks is well-written it can just attempt the operation and cope	902	callbacks is well-written it can just attempt the operation and cope with
735	with the error from read() or write(). This will not work in multithreaded	903	the error from read() or write(). This will not work in multi-threaded
736	programs, though, so beware.	904	programs, though, as the fd could already be closed and reused for another
		905	thing, so beware.
737		906
738	=back	907	=back
739		908
740	=head2 GENERIC WATCHER FUNCTIONS	909	=head2 GENERIC WATCHER FUNCTIONS
741		910
…		…
757	(or never started) and there are no pending events outstanding.	926	(or never started) and there are no pending events outstanding.
758		927
759	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
760	int revents)>.	929	int revents)>.
761		930
		931	Example: Initialise an C<ev_io> watcher in two steps.
		932
		933	ev_io w;
		934	ev_init (&w, my_cb);
		935	ev_io_set (&w, STDIN_FILENO, EV_READ);
		936
762	=item C<ev_TYPE_set> (ev_TYPE *, [args])	937	=item C<ev_TYPE_set> (ev_TYPE *, [args])
763		938
764	This macro initialises the type-specific parts of a watcher. You need to	939	This macro initialises the type-specific parts of a watcher. You need to
765	call C<ev_init> at least once before you call this macro, but you can	940	call C<ev_init> at least once before you call this macro, but you can
766	call C<ev_TYPE_set> any number of times. You must not, however, call this	941	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
768	difference to the C<ev_init> macro).	943	difference to the C<ev_init> macro).
769		944
770	Although some watcher types do not have type-specific arguments	945	Although some watcher types do not have type-specific arguments
771	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	946	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
772		947
		948	See C<ev_init>, above, for an example.
		949
773	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	950	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
774		951
775	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	952	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
776	calls into a single call. This is the most convinient method to initialise	953	calls into a single call. This is the most convenient method to initialise
777	a watcher. The same limitations apply, of course.	954	a watcher. The same limitations apply, of course.
		955
		956	Example: Initialise and set an C<ev_io> watcher in one step.
		957
		958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
778		959
779	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
780		961
781	Starts (activates) the given watcher. Only active watchers will receive	962	Starts (activates) the given watcher. Only active watchers will receive
782	events. If the watcher is already active nothing will happen.	963	events. If the watcher is already active nothing will happen.
		964
		965	Example: Start the C<ev_io> watcher that is being abused as example in this
		966	whole section.
		967
		968	ev_io_start (EV_DEFAULT_UC, &w);
783		969
784	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
785		971
786	Stops the given watcher again (if active) and clears the pending	972	Stops the given watcher again (if active) and clears the pending
787	status. It is possible that stopped watchers are pending (for example,	973	status. It is possible that stopped watchers are pending (for example,
…		…
844		1030
845	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
846		1032
847	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
848	C<loop> nor C<revents> need to be valid as long as the watcher callback	1034	C<loop> nor C<revents> need to be valid as long as the watcher callback
849	can deal with that fact.	1035	can deal with that fact, as both are simply passed through to the
		1036	callback.
850		1037
851	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1038	=item int ev_clear_pending (loop, ev_TYPE *watcher)
852		1039
853	If the watcher is pending, this function returns clears its pending status	1040	If the watcher is pending, this function clears its pending status and
854	and returns its C<revents> bitset (as if its callback was invoked). If the	1041	returns its C<revents> bitset (as if its callback was invoked). If the
855	watcher isn't pending it does nothing and returns C<0>.	1042	watcher isn't pending it does nothing and returns C<0>.
856		1043
		1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1045	callback to be invoked, which can be accomplished with this function.
		1046
857	=back	1047	=back
858		1048
859		1049
860	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
861		1051
862	Each watcher has, by default, a member C<void *data> that you can change	1052	Each watcher has, by default, a member C<void *data> that you can change
863	and read at any time, libev will completely ignore it. This can be used	1053	and read at any time: libev will completely ignore it. This can be used
864	to associate arbitrary data with your watcher. If you need more data and	1054	to associate arbitrary data with your watcher. If you need more data and
865	don't want to allocate memory and store a pointer to it in that data	1055	don't want to allocate memory and store a pointer to it in that data
866	member, you can also "subclass" the watcher type and provide your own	1056	member, you can also "subclass" the watcher type and provide your own
867	data:	1057	data:
868		1058
869	struct my_io	1059	struct my_io
870	{	1060	{
871	struct ev_io io;	1061	struct ev_io io;
872	int otherfd;	1062	int otherfd;
873	void *somedata;	1063	void *somedata;
874	struct whatever *mostinteresting;	1064	struct whatever *mostinteresting;
875	}	1065	};
		1066
		1067	...
		1068	struct my_io w;
		1069	ev_io_init (&w.io, my_cb, fd, EV_READ);
876		1070
877	And since your callback will be called with a pointer to the watcher, you	1071	And since your callback will be called with a pointer to the watcher, you
878	can cast it back to your own type:	1072	can cast it back to your own type:
879		1073
880	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
881	{	1075	{
882	struct my_io *w = (struct my_io *)w_;	1076	struct my_io *w = (struct my_io *)w_;
883	...	1077	...
884	}	1078	}
885		1079
886	More interesting and less C-conformant ways of casting your callback type	1080	More interesting and less C-conformant ways of casting your callback type
887	instead have been omitted.	1081	instead have been omitted.
888		1082
889	Another common scenario is having some data structure with multiple	1083	Another common scenario is to use some data structure with multiple
890	watchers:	1084	embedded watchers:
891		1085
892	struct my_biggy	1086	struct my_biggy
893	{	1087	{
894	int some_data;	1088	int some_data;
895	ev_timer t1;	1089	ev_timer t1;
896	ev_timer t2;	1090	ev_timer t2;
897	}	1091	}
898		1092
899	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1093	In this case getting the pointer to C<my_biggy> is a bit more
900	you need to use C<offsetof>:	1094	complicated: Either you store the address of your C<my_biggy> struct
		1095	in the C<data> member of the watcher (for woozies), or you need to use
		1096	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1097	programmers):
901		1098
902	#include <stddef.h>	1099	#include <stddef.h>
903		1100
904	static void	1101	static void
905	t1_cb (EV_P_ struct ev_timer *w, int revents)	1102	t1_cb (EV_P_ struct ev_timer *w, int revents)
906	{	1103	{
907	struct my_biggy big = (struct my_biggy *	1104	struct my_biggy big = (struct my_biggy *
908	(((char *)w) - offsetof (struct my_biggy, t1));	1105	(((char *)w) - offsetof (struct my_biggy, t1));
909	}	1106	}
910		1107
911	static void	1108	static void
912	t2_cb (EV_P_ struct ev_timer *w, int revents)	1109	t2_cb (EV_P_ struct ev_timer *w, int revents)
913	{	1110	{
914	struct my_biggy big = (struct my_biggy *	1111	struct my_biggy big = (struct my_biggy *
915	(((char *)w) - offsetof (struct my_biggy, t2));	1112	(((char *)w) - offsetof (struct my_biggy, t2));
916	}	1113	}
917		1114
918		1115
919	=head1 WATCHER TYPES	1116	=head1 WATCHER TYPES
920		1117
921	This section describes each watcher in detail, but will not repeat	1118	This section describes each watcher in detail, but will not repeat
…		…
945	In general you can register as many read and/or write event watchers per	1142	In general you can register as many read and/or write event watchers per
946	fd as you want (as long as you don't confuse yourself). Setting all file	1143	fd as you want (as long as you don't confuse yourself). Setting all file
947	descriptors to non-blocking mode is also usually a good idea (but not	1144	descriptors to non-blocking mode is also usually a good idea (but not
948	required if you know what you are doing).	1145	required if you know what you are doing).
949		1146
950	You have to be careful with dup'ed file descriptors, though. Some backends	1147	If you cannot use non-blocking mode, then force the use of a
951	(the linux epoll backend is a notable example) cannot handle dup'ed file	1148	known-to-be-good backend (at the time of this writing, this includes only
952	descriptors correctly if you register interest in two or more fds pointing	1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
953	to the same underlying file/socket/etc. description (that is, they share
954	the same underlying "file open").
955
956	If you must do this, then force the use of a known-to-be-good backend
957	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
958	C<EVBACKEND_POLL>).
959		1150
960	Another thing you have to watch out for is that it is quite easy to	1151	Another thing you have to watch out for is that it is quite easy to
961	receive "spurious" readyness notifications, that is your callback might	1152	receive "spurious" readiness notifications, that is your callback might
962	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
963	because there is no data. Not only are some backends known to create a	1154	because there is no data. Not only are some backends known to create a
964	lot of those (for example solaris ports), it is very easy to get into	1155	lot of those (for example Solaris ports), it is very easy to get into
965	this situation even with a relatively standard program structure. Thus	1156	this situation even with a relatively standard program structure. Thus
966	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1157	it is best to always use non-blocking I/O: An extra C<read>(2) returning
967	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1158	C<EAGAIN> is far preferable to a program hanging until some data arrives.
968		1159
969	If you cannot run the fd in non-blocking mode (for example you should not	1160	If you cannot run the fd in non-blocking mode (for example you should
970	play around with an Xlib connection), then you have to seperately re-test	1161	not play around with an Xlib connection), then you have to separately
971	whether a file descriptor is really ready with a known-to-be good interface	1162	re-test whether a file descriptor is really ready with a known-to-be good
972	such as poll (fortunately in our Xlib example, Xlib already does this on	1163	interface such as poll (fortunately in our Xlib example, Xlib already
973	its own, so its quite safe to use).	1164	does this on its own, so its quite safe to use). Some people additionally
		1165	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1166	indefinitely.
		1167
		1168	But really, best use non-blocking mode.
974		1169
975	=head3 The special problem of disappearing file descriptors	1170	=head3 The special problem of disappearing file descriptors
976		1171
977	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1172	Some backends (e.g. kqueue, epoll) need to be told about closing a file
978	descriptor (either by calling C<close> explicitly or by any other means,	1173	descriptor (either due to calling C<close> explicitly or any other means,
979	such as C<dup>). The reason is that you register interest in some file	1174	such as C<dup2>). The reason is that you register interest in some file
980	descriptor, but when it goes away, the operating system will silently drop	1175	descriptor, but when it goes away, the operating system will silently drop
981	this interest. If another file descriptor with the same number then is	1176	this interest. If another file descriptor with the same number then is
982	registered with libev, there is no efficient way to see that this is, in	1177	registered with libev, there is no efficient way to see that this is, in
983	fact, a different file descriptor.	1178	fact, a different file descriptor.
984		1179
…		…
994	optimisations to libev.	1189	optimisations to libev.
995		1190
996	=head3 The special problem of dup'ed file descriptors	1191	=head3 The special problem of dup'ed file descriptors
997		1192
998	Some backends (e.g. epoll), cannot register events for file descriptors,	1193	Some backends (e.g. epoll), cannot register events for file descriptors,
999	but only events for the underlying file descriptions. That menas when you	1194	but only events for the underlying file descriptions. That means when you
1000	have C<dup ()>'ed file descriptors and register events for them, only one	1195	have C<dup ()>'ed file descriptors or weirder constellations, and register
1001	file descriptor might actually receive events.	1196	events for them, only one file descriptor might actually receive events.
1002		1197
1003	There is no workaorund possible except not registering events	1198	There is no workaround possible except not registering events
1004	for potentially C<dup ()>'ed file descriptors or to resort to	1199	for potentially C<dup ()>'ed file descriptors, or to resort to
1005	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1200	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1006		1201
1007	=head3 The special problem of fork	1202	=head3 The special problem of fork
1008		1203
1009	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1204	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
1013	To support fork in your programs, you either have to call	1208	To support fork in your programs, you either have to call
1014	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1209	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1015	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1210	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1016	C<EVBACKEND_POLL>.	1211	C<EVBACKEND_POLL>.
1017		1212
		1213	=head3 The special problem of SIGPIPE
		1214
		1215	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1216	when writing to a pipe whose other end has been closed, your program gets
		1217	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1218	this is sensible behaviour, for daemons, this is usually undesirable.
		1219
		1220	So when you encounter spurious, unexplained daemon exits, make sure you
		1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1222	somewhere, as that would have given you a big clue).
		1223
1018		1224
1019	=head3 Watcher-Specific Functions	1225	=head3 Watcher-Specific Functions
1020		1226
1021	=over 4	1227	=over 4
1022		1228
1023	=item ev_io_init (ev_io *, callback, int fd, int events)	1229	=item ev_io_init (ev_io *, callback, int fd, int events)
1024		1230
1025	=item ev_io_set (ev_io *, int fd, int events)	1231	=item ev_io_set (ev_io *, int fd, int events)
1026		1232
1027	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1233	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1028	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1234	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1029	C<EV_READ | EV_WRITE> to receive the given events.	1235	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1030		1236
1031	=item int fd [read-only]	1237	=item int fd [read-only]
1032		1238
1033	The file descriptor being watched.	1239	The file descriptor being watched.
1034		1240
1035	=item int events [read-only]	1241	=item int events [read-only]
1036		1242
1037	The events being watched.	1243	The events being watched.
1038		1244
1039	=back	1245	=back
		1246
		1247	=head3 Examples
1040		1248
1041	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1042	readable, but only once. Since it is likely line-buffered, you could	1250	readable, but only once. Since it is likely line-buffered, you could
1043	attempt to read a whole line in the callback.	1251	attempt to read a whole line in the callback.
1044		1252
1045	static void	1253	static void
1046	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1047	{	1255	{
1048	ev_io_stop (loop, w);	1256	ev_io_stop (loop, w);
1049	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1257	.. read from stdin here (or from w->fd) and handle any I/O errors
1050	}	1258	}
1051		1259
1052	...	1260	...
1053	struct ev_loop *loop = ev_default_init (0);	1261	struct ev_loop *loop = ev_default_init (0);
1054	struct ev_io stdin_readable;	1262	struct ev_io stdin_readable;
1055	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1056	ev_io_start (loop, &stdin_readable);	1264	ev_io_start (loop, &stdin_readable);
1057	ev_loop (loop, 0);	1265	ev_loop (loop, 0);
1058		1266
1059		1267
1060	=head2 C<ev_timer> - relative and optionally repeating timeouts	1268	=head2 C<ev_timer> - relative and optionally repeating timeouts
1061		1269
1062	Timer watchers are simple relative timers that generate an event after a	1270	Timer watchers are simple relative timers that generate an event after a
1063	given time, and optionally repeating in regular intervals after that.	1271	given time, and optionally repeating in regular intervals after that.
1064		1272
1065	The timers are based on real time, that is, if you register an event that	1273	The timers are based on real time, that is, if you register an event that
1066	times out after an hour and you reset your system clock to last years	1274	times out after an hour and you reset your system clock to January last
1067	time, it will still time out after (roughly) and hour. "Roughly" because	1275	year, it will still time out after (roughly) one hour. "Roughly" because
1068	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1069	monotonic clock option helps a lot here).	1277	monotonic clock option helps a lot here).
		1278
		1279	The callback is guaranteed to be invoked only I<after> its timeout has
		1280	passed, but if multiple timers become ready during the same loop iteration
		1281	then order of execution is undefined.
		1282
		1283	=head3 The special problem of time updates
		1284
		1285	Establishing the current time is a costly operation (it usually takes at
		1286	least two system calls): EV therefore updates its idea of the current
		1287	time only before and after C<ev_loop> collects new events, which causes a
		1288	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1289	lots of events in one iteration.
1070		1290
1071	The relative timeouts are calculated relative to the C<ev_now ()>	1291	The relative timeouts are calculated relative to the C<ev_now ()>
1072	time. This is usually the right thing as this timestamp refers to the time	1292	time. This is usually the right thing as this timestamp refers to the time
1073	of the event triggering whatever timeout you are modifying/starting. If	1293	of the event triggering whatever timeout you are modifying/starting. If
1074	you suspect event processing to be delayed and you I<need> to base the timeout	1294	you suspect event processing to be delayed and you I<need> to base the
1075	on the current time, use something like this to adjust for this:	1295	timeout on the current time, use something like this to adjust for this:
1076		1296
1077	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1297	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1078		1298
1079	The callback is guarenteed to be invoked only when its timeout has passed,	1299	If the event loop is suspended for a long time, you can also force an
1080	but if multiple timers become ready during the same loop iteration then	1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1081	order of execution is undefined.	1301	()>.
1082		1302
1083	=head3 Watcher-Specific Functions and Data Members	1303	=head3 Watcher-Specific Functions and Data Members
1084		1304
1085	=over 4	1305	=over 4
1086		1306
1087	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1088		1308
1089	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1309	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1090		1310
1091	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1311	Configure the timer to trigger after C<after> seconds. If C<repeat>
1092	C<0.>, then it will automatically be stopped. If it is positive, then the	1312	is C<0.>, then it will automatically be stopped once the timeout is
1093	timer will automatically be configured to trigger again C<repeat> seconds	1313	reached. If it is positive, then the timer will automatically be
1094	later, again, and again, until stopped manually.	1314	configured to trigger again C<repeat> seconds later, again, and again,
		1315	until stopped manually.
1095		1316
1096	The timer itself will do a best-effort at avoiding drift, that is, if you	1317	The timer itself will do a best-effort at avoiding drift, that is, if
1097	configure a timer to trigger every 10 seconds, then it will trigger at	1318	you configure a timer to trigger every 10 seconds, then it will normally
1098	exactly 10 second intervals. If, however, your program cannot keep up with	1319	trigger at exactly 10 second intervals. If, however, your program cannot
1099	the timer (because it takes longer than those 10 seconds to do stuff) the	1320	keep up with the timer (because it takes longer than those 10 seconds to
1100	timer will not fire more than once per event loop iteration.	1321	do stuff) the timer will not fire more than once per event loop iteration.
1101		1322
1102	=item ev_timer_again (loop)	1323	=item ev_timer_again (loop, ev_timer *)
1103		1324
1104	This will act as if the timer timed out and restart it again if it is	1325	This will act as if the timer timed out and restart it again if it is
1105	repeating. The exact semantics are:	1326	repeating. The exact semantics are:
1106		1327
1107	If the timer is pending, its pending status is cleared.	1328	If the timer is pending, its pending status is cleared.
1108		1329
1109	If the timer is started but nonrepeating, stop it (as if it timed out).	1330	If the timer is started but non-repeating, stop it (as if it timed out).
1110		1331
1111	If the timer is repeating, either start it if necessary (with the	1332	If the timer is repeating, either start it if necessary (with the
1112	C<repeat> value), or reset the running timer to the C<repeat> value.	1333	C<repeat> value), or reset the running timer to the C<repeat> value.
1113		1334
1114	This sounds a bit complicated, but here is a useful and typical	1335	This sounds a bit complicated, but here is a useful and typical
1115	example: Imagine you have a tcp connection and you want a so-called idle	1336	example: Imagine you have a TCP connection and you want a so-called idle
1116	timeout, that is, you want to be called when there have been, say, 60	1337	timeout, that is, you want to be called when there have been, say, 60
1117	seconds of inactivity on the socket. The easiest way to do this is to	1338	seconds of inactivity on the socket. The easiest way to do this is to
1118	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1119	C<ev_timer_again> each time you successfully read or write some data. If	1340	C<ev_timer_again> each time you successfully read or write some data. If
1120	you go into an idle state where you do not expect data to travel on the	1341	you go into an idle state where you do not expect data to travel on the
…		…
1134	ev_timer_again (loop, timer);	1355	ev_timer_again (loop, timer);
1135		1356
1136	This is more slightly efficient then stopping/starting the timer each time	1357	This is more slightly efficient then stopping/starting the timer each time
1137	you want to modify its timeout value.	1358	you want to modify its timeout value.
1138		1359
		1360	Note, however, that it is often even more efficient to remember the
		1361	time of the last activity and let the timer time-out naturally. In the
		1362	callback, you then check whether the time-out is real, or, if there was
		1363	some activity, you reschedule the watcher to time-out in "last_activity +
		1364	timeout - ev_now ()" seconds.
		1365
1139	=item ev_tstamp repeat [read-write]	1366	=item ev_tstamp repeat [read-write]
1140		1367
1141	The current C<repeat> value. Will be used each time the watcher times out	1368	The current C<repeat> value. Will be used each time the watcher times out
1142	or C<ev_timer_again> is called and determines the next timeout (if any),	1369	or C<ev_timer_again> is called, and determines the next timeout (if any),
1143	which is also when any modifications are taken into account.	1370	which is also when any modifications are taken into account.
1144		1371
1145	=back	1372	=back
1146		1373
		1374	=head3 Examples
		1375
1147	Example: Create a timer that fires after 60 seconds.	1376	Example: Create a timer that fires after 60 seconds.
1148		1377
1149	static void	1378	static void
1150	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1151	{	1380	{
1152	.. one minute over, w is actually stopped right here	1381	.. one minute over, w is actually stopped right here
1153	}	1382	}
1154		1383
1155	struct ev_timer mytimer;	1384	struct ev_timer mytimer;
1156	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1157	ev_timer_start (loop, &mytimer);	1386	ev_timer_start (loop, &mytimer);
1158		1387
1159	Example: Create a timeout timer that times out after 10 seconds of	1388	Example: Create a timeout timer that times out after 10 seconds of
1160	inactivity.	1389	inactivity.
1161		1390
1162	static void	1391	static void
1163	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1164	{	1393	{
1165	.. ten seconds without any activity	1394	.. ten seconds without any activity
1166	}	1395	}
1167		1396
1168	struct ev_timer mytimer;	1397	struct ev_timer mytimer;
1169	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1170	ev_timer_again (&mytimer); /* start timer */	1399	ev_timer_again (&mytimer); /* start timer */
1171	ev_loop (loop, 0);	1400	ev_loop (loop, 0);
1172		1401
1173	// and in some piece of code that gets executed on any "activity":	1402	// and in some piece of code that gets executed on any "activity":
1174	// reset the timeout to start ticking again at 10 seconds	1403	// reset the timeout to start ticking again at 10 seconds
1175	ev_timer_again (&mytimer);	1404	ev_timer_again (&mytimer);
1176		1405
1177		1406
1178	=head2 C<ev_periodic> - to cron or not to cron?	1407	=head2 C<ev_periodic> - to cron or not to cron?
1179		1408
1180	Periodic watchers are also timers of a kind, but they are very versatile	1409	Periodic watchers are also timers of a kind, but they are very versatile
1181	(and unfortunately a bit complex).	1410	(and unfortunately a bit complex).
1182		1411
1183	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1184	but on wallclock time (absolute time). You can tell a periodic watcher	1413	but on wall clock time (absolute time). You can tell a periodic watcher
1185	to trigger "at" some specific point in time. For example, if you tell a	1414	to trigger after some specific point in time. For example, if you tell a
1186	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1187	+ 10.>) and then reset your system clock to the last year, then it will	1416	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1417	clock to January of the previous year, then it will take more than year
1188	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1189	roughly 10 seconds later).	1419	roughly 10 seconds later as it uses a relative timeout).
1190		1420
1191	They can also be used to implement vastly more complex timers, such as	1421	C<ev_periodic>s can also be used to implement vastly more complex timers,
1192	triggering an event on each midnight, local time or other, complicated,	1422	such as triggering an event on each "midnight, local time", or other
1193	rules.	1423	complicated rules.
1194		1424
1195	As with timers, the callback is guarenteed to be invoked only when the	1425	As with timers, the callback is guaranteed to be invoked only when the
1196	time (C<at>) has been passed, but if multiple periodic timers become ready	1426	time (C<at>) has passed, but if multiple periodic timers become ready
1197	during the same loop iteration then order of execution is undefined.	1427	during the same loop iteration, then order of execution is undefined.
1198		1428
1199	=head3 Watcher-Specific Functions and Data Members	1429	=head3 Watcher-Specific Functions and Data Members
1200		1430
1201	=over 4	1431	=over 4
1202		1432
1203	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1204		1434
1205	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1206		1436
1207	Lots of arguments, lets sort it out... There are basically three modes of	1437	Lots of arguments, lets sort it out... There are basically three modes of
1208	operation, and we will explain them from simplest to complex:	1438	operation, and we will explain them from simplest to most complex:
1209		1439
1210	=over 4	1440	=over 4
1211		1441
1212	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1213		1443
1214	In this configuration the watcher triggers an event at the wallclock time	1444	In this configuration the watcher triggers an event after the wall clock
1215	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1445	time C<at> has passed. It will not repeat and will not adjust when a time
1216	that is, if it is to be run at January 1st 2011 then it will run when the	1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1217	system time reaches or surpasses this time.	1447	only run when the system clock reaches or surpasses this time.
1218		1448
1219	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1220		1450
1221	In this mode the watcher will always be scheduled to time out at the next	1451	In this mode the watcher will always be scheduled to time out at the next
1222	C<at + N * interval> time (for some integer N, which can also be negative)	1452	C<at + N * interval> time (for some integer N, which can also be negative)
1223	and then repeat, regardless of any time jumps.	1453	and then repeat, regardless of any time jumps.
1224		1454
1225	This can be used to create timers that do not drift with respect to system	1455	This can be used to create timers that do not drift with respect to the
1226	time:	1456	system clock, for example, here is a C<ev_periodic> that triggers each
		1457	hour, on the hour:
1227		1458
1228	ev_periodic_set (&periodic, 0., 3600., 0);	1459	ev_periodic_set (&periodic, 0., 3600., 0);
1229		1460
1230	This doesn't mean there will always be 3600 seconds in between triggers,	1461	This doesn't mean there will always be 3600 seconds in between triggers,
1231	but only that the the callback will be called when the system time shows a	1462	but only that the callback will be called when the system time shows a
1232	full hour (UTC), or more correctly, when the system time is evenly divisible	1463	full hour (UTC), or more correctly, when the system time is evenly divisible
1233	by 3600.	1464	by 3600.
1234		1465
1235	Another way to think about it (for the mathematically inclined) is that	1466	Another way to think about it (for the mathematically inclined) is that
1236	C<ev_periodic> will try to run the callback in this mode at the next possible	1467	C<ev_periodic> will try to run the callback in this mode at the next possible
1237	time where C<time = at (mod interval)>, regardless of any time jumps.	1468	time where C<time = at (mod interval)>, regardless of any time jumps.
1238		1469
1239	For numerical stability it is preferable that the C<at> value is near	1470	For numerical stability it is preferable that the C<at> value is near
1240	C<ev_now ()> (the current time), but there is no range requirement for	1471	C<ev_now ()> (the current time), but there is no range requirement for
1241	this value.	1472	this value, and in fact is often specified as zero.
		1473
		1474	Note also that there is an upper limit to how often a timer can fire (CPU
		1475	speed for example), so if C<interval> is very small then timing stability
		1476	will of course deteriorate. Libev itself tries to be exact to be about one
		1477	millisecond (if the OS supports it and the machine is fast enough).
1242		1478
1243	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1244		1480
1245	In this mode the values for C<interval> and C<at> are both being	1481	In this mode the values for C<interval> and C<at> are both being
1246	ignored. Instead, each time the periodic watcher gets scheduled, the	1482	ignored. Instead, each time the periodic watcher gets scheduled, the
1247	reschedule callback will be called with the watcher as first, and the	1483	reschedule callback will be called with the watcher as first, and the
1248	current time as second argument.	1484	current time as second argument.
1249		1485
1250	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1251	ever, or make any event loop modifications>. If you need to stop it,	1487	ever, or make ANY event loop modifications whatsoever>.
1252	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1253	starting an C<ev_prepare> watcher, which is legal).
1254		1488
		1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1491	only event loop modification you are allowed to do).
		1492
1255	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1256	ev_tstamp now)>, e.g.:	1494	*w, ev_tstamp now)>, e.g.:
1257		1495
1258	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1259	{	1497	{
1260	return now + 60.;	1498	return now + 60.;
1261	}	1499	}
…		…
1263	It must return the next time to trigger, based on the passed time value	1501	It must return the next time to trigger, based on the passed time value
1264	(that is, the lowest time value larger than to the second argument). It	1502	(that is, the lowest time value larger than to the second argument). It
1265	will usually be called just before the callback will be triggered, but	1503	will usually be called just before the callback will be triggered, but
1266	might be called at other times, too.	1504	might be called at other times, too.
1267		1505
1268	NOTE: I<< This callback must always return a time that is later than the	1506	NOTE: I<< This callback must always return a time that is higher than or
1269	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1507	equal to the passed C<now> value >>.
1270		1508
1271	This can be used to create very complex timers, such as a timer that	1509	This can be used to create very complex timers, such as a timer that
1272	triggers on each midnight, local time. To do this, you would calculate the	1510	triggers on "next midnight, local time". To do this, you would calculate the
1273	next midnight after C<now> and return the timestamp value for this. How	1511	next midnight after C<now> and return the timestamp value for this. How
1274	you do this is, again, up to you (but it is not trivial, which is the main	1512	you do this is, again, up to you (but it is not trivial, which is the main
1275	reason I omitted it as an example).	1513	reason I omitted it as an example).
1276		1514
1277	=back	1515	=back
…		…
1281	Simply stops and restarts the periodic watcher again. This is only useful	1519	Simply stops and restarts the periodic watcher again. This is only useful
1282	when you changed some parameters or the reschedule callback would return	1520	when you changed some parameters or the reschedule callback would return
1283	a different time than the last time it was called (e.g. in a crond like	1521	a different time than the last time it was called (e.g. in a crond like
1284	program when the crontabs have changed).	1522	program when the crontabs have changed).
1285		1523
		1524	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1525
		1526	When active, returns the absolute time that the watcher is supposed to
		1527	trigger next.
		1528
1286	=item ev_tstamp offset [read-write]	1529	=item ev_tstamp offset [read-write]
1287		1530
1288	When repeating, this contains the offset value, otherwise this is the	1531	When repeating, this contains the offset value, otherwise this is the
1289	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1290		1533
…		…
1301		1544
1302	The current reschedule callback, or C<0>, if this functionality is	1545	The current reschedule callback, or C<0>, if this functionality is
1303	switched off. Can be changed any time, but changes only take effect when	1546	switched off. Can be changed any time, but changes only take effect when
1304	the periodic timer fires or C<ev_periodic_again> is being called.	1547	the periodic timer fires or C<ev_periodic_again> is being called.
1305		1548
1306	=item ev_tstamp at [read-only]
1307
1308	When active, contains the absolute time that the watcher is supposed to
1309	trigger next.
1310
1311	=back	1549	=back
1312		1550
		1551	=head3 Examples
		1552
1313	Example: Call a callback every hour, or, more precisely, whenever the	1553	Example: Call a callback every hour, or, more precisely, whenever the
1314	system clock is divisible by 3600. The callback invocation times have	1554	system time is divisible by 3600. The callback invocation times have
1315	potentially a lot of jittering, but good long-term stability.	1555	potentially a lot of jitter, but good long-term stability.
1316		1556
1317	static void	1557	static void
1318	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1319	{	1559	{
1320	... its now a full hour (UTC, or TAI or whatever your clock follows)	1560	... its now a full hour (UTC, or TAI or whatever your clock follows)
1321	}	1561	}
1322		1562
1323	struct ev_periodic hourly_tick;	1563	struct ev_periodic hourly_tick;
1324	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1325	ev_periodic_start (loop, &hourly_tick);	1565	ev_periodic_start (loop, &hourly_tick);
1326		1566
1327	Example: The same as above, but use a reschedule callback to do it:	1567	Example: The same as above, but use a reschedule callback to do it:
1328		1568
1329	#include <math.h>	1569	#include <math.h>
1330		1570
1331	static ev_tstamp	1571	static ev_tstamp
1332	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1333	{	1573	{
1334	return fmod (now, 3600.) + 3600.;	1574	return now + (3600. - fmod (now, 3600.));
1335	}	1575	}
1336		1576
1337	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1338		1578
1339	Example: Call a callback every hour, starting now:	1579	Example: Call a callback every hour, starting now:
1340		1580
1341	struct ev_periodic hourly_tick;	1581	struct ev_periodic hourly_tick;
1342	ev_periodic_init (&hourly_tick, clock_cb,	1582	ev_periodic_init (&hourly_tick, clock_cb,
1343	fmod (ev_now (loop), 3600.), 3600., 0);	1583	fmod (ev_now (loop), 3600.), 3600., 0);
1344	ev_periodic_start (loop, &hourly_tick);	1584	ev_periodic_start (loop, &hourly_tick);
1345		1585
1346		1586
1347	=head2 C<ev_signal> - signal me when a signal gets signalled!	1587	=head2 C<ev_signal> - signal me when a signal gets signalled!
1348		1588
1349	Signal watchers will trigger an event when the process receives a specific	1589	Signal watchers will trigger an event when the process receives a specific
1350	signal one or more times. Even though signals are very asynchronous, libev	1590	signal one or more times. Even though signals are very asynchronous, libev
1351	will try it's best to deliver signals synchronously, i.e. as part of the	1591	will try it's best to deliver signals synchronously, i.e. as part of the
1352	normal event processing, like any other event.	1592	normal event processing, like any other event.
1353		1593
		1594	If you want signals asynchronously, just use C<sigaction> as you would
		1595	do without libev and forget about sharing the signal. You can even use
		1596	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1597
1354	You can configure as many watchers as you like per signal. Only when the	1598	You can configure as many watchers as you like per signal. Only when the
1355	first watcher gets started will libev actually register a signal watcher	1599	first watcher gets started will libev actually register a signal handler
1356	with the kernel (thus it coexists with your own signal handlers as long	1600	with the kernel (thus it coexists with your own signal handlers as long as
1357	as you don't register any with libev). Similarly, when the last signal	1601	you don't register any with libev for the same signal). Similarly, when
1358	watcher for a signal is stopped libev will reset the signal handler to	1602	the last signal watcher for a signal is stopped, libev will reset the
1359	SIG_DFL (regardless of what it was set to before).	1603	signal handler to SIG_DFL (regardless of what it was set to before).
		1604
		1605	If possible and supported, libev will install its handlers with
		1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1607	interrupted. If you have a problem with system calls getting interrupted by
		1608	signals you can block all signals in an C<ev_check> watcher and unblock
		1609	them in an C<ev_prepare> watcher.
1360		1610
1361	=head3 Watcher-Specific Functions and Data Members	1611	=head3 Watcher-Specific Functions and Data Members
1362		1612
1363	=over 4	1613	=over 4
1364		1614
…		…
1373		1623
1374	The signal the watcher watches out for.	1624	The signal the watcher watches out for.
1375		1625
1376	=back	1626	=back
1377		1627
		1628	=head3 Examples
		1629
		1630	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1631
		1632	static void
		1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1634	{
		1635	ev_unloop (loop, EVUNLOOP_ALL);
		1636	}
		1637
		1638	struct ev_signal signal_watcher;
		1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1640	ev_signal_start (loop, &sigint_cb);
		1641
1378		1642
1379	=head2 C<ev_child> - watch out for process status changes	1643	=head2 C<ev_child> - watch out for process status changes
1380		1644
1381	Child watchers trigger when your process receives a SIGCHLD in response to	1645	Child watchers trigger when your process receives a SIGCHLD in response to
1382	some child status changes (most typically when a child of yours dies).	1646	some child status changes (most typically when a child of yours dies or
		1647	exits). It is permissible to install a child watcher I<after> the child
		1648	has been forked (which implies it might have already exited), as long
		1649	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1650	forking and then immediately registering a watcher for the child is fine,
		1651	but forking and registering a watcher a few event loop iterations later is
		1652	not.
		1653
		1654	Only the default event loop is capable of handling signals, and therefore
		1655	you can only register child watchers in the default event loop.
		1656
		1657	=head3 Process Interaction
		1658
		1659	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1660	initialised. This is necessary to guarantee proper behaviour even if
		1661	the first child watcher is started after the child exits. The occurrence
		1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1663	synchronously as part of the event loop processing. Libev always reaps all
		1664	children, even ones not watched.
		1665
		1666	=head3 Overriding the Built-In Processing
		1667
		1668	Libev offers no special support for overriding the built-in child
		1669	processing, but if your application collides with libev's default child
		1670	handler, you can override it easily by installing your own handler for
		1671	C<SIGCHLD> after initialising the default loop, and making sure the
		1672	default loop never gets destroyed. You are encouraged, however, to use an
		1673	event-based approach to child reaping and thus use libev's support for
		1674	that, so other libev users can use C<ev_child> watchers freely.
		1675
		1676	=head3 Stopping the Child Watcher
		1677
		1678	Currently, the child watcher never gets stopped, even when the
		1679	child terminates, so normally one needs to stop the watcher in the
		1680	callback. Future versions of libev might stop the watcher automatically
		1681	when a child exit is detected.
1383		1682
1384	=head3 Watcher-Specific Functions and Data Members	1683	=head3 Watcher-Specific Functions and Data Members
1385		1684
1386	=over 4	1685	=over 4
1387		1686
1388	=item ev_child_init (ev_child *, callback, int pid)	1687	=item ev_child_init (ev_child *, callback, int pid, int trace)
1389		1688
1390	=item ev_child_set (ev_child *, int pid)	1689	=item ev_child_set (ev_child *, int pid, int trace)
1391		1690
1392	Configures the watcher to wait for status changes of process C<pid> (or	1691	Configures the watcher to wait for status changes of process C<pid> (or
1393	I<any> process if C<pid> is specified as C<0>). The callback can look	1692	I<any> process if C<pid> is specified as C<0>). The callback can look
1394	at the C<rstatus> member of the C<ev_child> watcher structure to see	1693	at the C<rstatus> member of the C<ev_child> watcher structure to see
1395	the status word (use the macros from C<sys/wait.h> and see your systems	1694	the status word (use the macros from C<sys/wait.h> and see your systems
1396	C<waitpid> documentation). The C<rpid> member contains the pid of the	1695	C<waitpid> documentation). The C<rpid> member contains the pid of the
1397	process causing the status change.	1696	process causing the status change. C<trace> must be either C<0> (only
		1697	activate the watcher when the process terminates) or C<1> (additionally
		1698	activate the watcher when the process is stopped or continued).
1398		1699
1399	=item int pid [read-only]	1700	=item int pid [read-only]
1400		1701
1401	The process id this watcher watches out for, or C<0>, meaning any process id.	1702	The process id this watcher watches out for, or C<0>, meaning any process id.
1402		1703
…		…
1409	The process exit/trace status caused by C<rpid> (see your systems	1710	The process exit/trace status caused by C<rpid> (see your systems
1410	C<waitpid> and C<sys/wait.h> documentation for details).	1711	C<waitpid> and C<sys/wait.h> documentation for details).
1411		1712
1412	=back	1713	=back
1413		1714
1414	Example: Try to exit cleanly on SIGINT and SIGTERM.	1715	=head3 Examples
1415		1716
		1717	Example: C<fork()> a new process and install a child handler to wait for
		1718	its completion.
		1719
		1720	ev_child cw;
		1721
1416	static void	1722	static void
1417	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1723	child_cb (EV_P_ struct ev_child *w, int revents)
1418	{	1724	{
1419	ev_unloop (loop, EVUNLOOP_ALL);	1725	ev_child_stop (EV_A_ w);
		1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1420	}	1727	}
1421		1728
1422	struct ev_signal signal_watcher;	1729	pid_t pid = fork ();
1423	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1730
1424	ev_signal_start (loop, &sigint_cb);	1731	if (pid < 0)
		1732	// error
		1733	else if (pid == 0)
		1734	{
		1735	// the forked child executes here
		1736	exit (1);
		1737	}
		1738	else
		1739	{
		1740	ev_child_init (&cw, child_cb, pid, 0);
		1741	ev_child_start (EV_DEFAULT_ &cw);
		1742	}
1425		1743
1426		1744
1427	=head2 C<ev_stat> - did the file attributes just change?	1745	=head2 C<ev_stat> - did the file attributes just change?
1428		1746
1429	This watches a filesystem path for attribute changes. That is, it calls	1747	This watches a file system path for attribute changes. That is, it calls
1430	C<stat> regularly (or when the OS says it changed) and sees if it changed	1748	C<stat> regularly (or when the OS says it changed) and sees if it changed
1431	compared to the last time, invoking the callback if it did.	1749	compared to the last time, invoking the callback if it did.
1432		1750
1433	The path does not need to exist: changing from "path exists" to "path does	1751	The path does not need to exist: changing from "path exists" to "path does
1434	not exist" is a status change like any other. The condition "path does	1752	not exist" is a status change like any other. The condition "path does
…		…
1437	the stat buffer having unspecified contents.	1755	the stat buffer having unspecified contents.
1438		1756
1439	The path I<should> be absolute and I<must not> end in a slash. If it is	1757	The path I<should> be absolute and I<must not> end in a slash. If it is
1440	relative and your working directory changes, the behaviour is undefined.	1758	relative and your working directory changes, the behaviour is undefined.
1441		1759
1442	Since there is no standard to do this, the portable implementation simply	1760	Since there is no standard kernel interface to do this, the portable
1443	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1761	implementation simply calls C<stat (2)> regularly on the path to see if
1444	can specify a recommended polling interval for this case. If you specify	1762	it changed somehow. You can specify a recommended polling interval for
1445	a polling interval of C<0> (highly recommended!) then a I<suitable,	1763	this case. If you specify a polling interval of C<0> (highly recommended!)
1446	unspecified default> value will be used (which you can expect to be around	1764	then a I<suitable, unspecified default> value will be used (which
1447	five seconds, although this might change dynamically). Libev will also	1765	you can expect to be around five seconds, although this might change
1448	impose a minimum interval which is currently around C<0.1>, but thats	1766	dynamically). Libev will also impose a minimum interval which is currently
1449	usually overkill.	1767	around C<0.1>, but thats usually overkill.
1450		1768
1451	This watcher type is not meant for massive numbers of stat watchers,	1769	This watcher type is not meant for massive numbers of stat watchers,
1452	as even with OS-supported change notifications, this can be	1770	as even with OS-supported change notifications, this can be
1453	resource-intensive.	1771	resource-intensive.
1454		1772
1455	At the time of this writing, only the Linux inotify interface is	1773	At the time of this writing, the only OS-specific interface implemented
1456	implemented (implementing kqueue support is left as an exercise for the	1774	is the Linux inotify interface (implementing kqueue support is left as
1457	reader). Inotify will be used to give hints only and should not change the	1775	an exercise for the reader. Note, however, that the author sees no way
1458	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1776	of implementing C<ev_stat> semantics with kqueue).
1459	to fall back to regular polling again even with inotify, but changes are	1777
1460	usually detected immediately, and if the file exists there will be no	1778	=head3 ABI Issues (Largefile Support)
1461	polling.	1779
		1780	Libev by default (unless the user overrides this) uses the default
		1781	compilation environment, which means that on systems with large file
		1782	support disabled by default, you get the 32 bit version of the stat
		1783	structure. When using the library from programs that change the ABI to
		1784	use 64 bit file offsets the programs will fail. In that case you have to
		1785	compile libev with the same flags to get binary compatibility. This is
		1786	obviously the case with any flags that change the ABI, but the problem is
		1787	most noticeably disabled with ev_stat and large file support.
		1788
		1789	The solution for this is to lobby your distribution maker to make large
		1790	file interfaces available by default (as e.g. FreeBSD does) and not
		1791	optional. Libev cannot simply switch on large file support because it has
		1792	to exchange stat structures with application programs compiled using the
		1793	default compilation environment.
		1794
		1795	=head3 Inotify and Kqueue
		1796
		1797	When C<inotify (7)> support has been compiled into libev (generally only
		1798	available with Linux) and present at runtime, it will be used to speed up
		1799	change detection where possible. The inotify descriptor will be created lazily
		1800	when the first C<ev_stat> watcher is being started.
		1801
		1802	Inotify presence does not change the semantics of C<ev_stat> watchers
		1803	except that changes might be detected earlier, and in some cases, to avoid
		1804	making regular C<stat> calls. Even in the presence of inotify support
		1805	there are many cases where libev has to resort to regular C<stat> polling,
		1806	but as long as the path exists, libev usually gets away without polling.
		1807
		1808	There is no support for kqueue, as apparently it cannot be used to
		1809	implement this functionality, due to the requirement of having a file
		1810	descriptor open on the object at all times, and detecting renames, unlinks
		1811	etc. is difficult.
		1812
		1813	=head3 The special problem of stat time resolution
		1814
		1815	The C<stat ()> system call only supports full-second resolution portably, and
		1816	even on systems where the resolution is higher, most file systems still
		1817	only support whole seconds.
		1818
		1819	That means that, if the time is the only thing that changes, you can
		1820	easily miss updates: on the first update, C<ev_stat> detects a change and
		1821	calls your callback, which does something. When there is another update
		1822	within the same second, C<ev_stat> will be unable to detect unless the
		1823	stat data does change in other ways (e.g. file size).
		1824
		1825	The solution to this is to delay acting on a change for slightly more
		1826	than a second (or till slightly after the next full second boundary), using
		1827	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1828	ev_timer_again (loop, w)>).
		1829
		1830	The C<.02> offset is added to work around small timing inconsistencies
		1831	of some operating systems (where the second counter of the current time
		1832	might be be delayed. One such system is the Linux kernel, where a call to
		1833	C<gettimeofday> might return a timestamp with a full second later than
		1834	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1835	update file times then there will be a small window where the kernel uses
		1836	the previous second to update file times but libev might already execute
		1837	the timer callback).
1462		1838
1463	=head3 Watcher-Specific Functions and Data Members	1839	=head3 Watcher-Specific Functions and Data Members
1464		1840
1465	=over 4	1841	=over 4
1466		1842
…		…
1472	C<path>. The C<interval> is a hint on how quickly a change is expected to	1848	C<path>. The C<interval> is a hint on how quickly a change is expected to
1473	be detected and should normally be specified as C<0> to let libev choose	1849	be detected and should normally be specified as C<0> to let libev choose
1474	a suitable value. The memory pointed to by C<path> must point to the same	1850	a suitable value. The memory pointed to by C<path> must point to the same
1475	path for as long as the watcher is active.	1851	path for as long as the watcher is active.
1476		1852
1477	The callback will be receive C<EV_STAT> when a change was detected,	1853	The callback will receive an C<EV_STAT> event when a change was detected,
1478	relative to the attributes at the time the watcher was started (or the	1854	relative to the attributes at the time the watcher was started (or the
1479	last change was detected).	1855	last change was detected).
1480		1856
1481	=item ev_stat_stat (ev_stat *)	1857	=item ev_stat_stat (loop, ev_stat *)
1482		1858
1483	Updates the stat buffer immediately with new values. If you change the	1859	Updates the stat buffer immediately with new values. If you change the
1484	watched path in your callback, you could call this fucntion to avoid	1860	watched path in your callback, you could call this function to avoid
1485	detecting this change (while introducing a race condition). Can also be	1861	detecting this change (while introducing a race condition if you are not
1486	useful simply to find out the new values.	1862	the only one changing the path). Can also be useful simply to find out the
		1863	new values.
1487		1864
1488	=item ev_statdata attr [read-only]	1865	=item ev_statdata attr [read-only]
1489		1866
1490	The most-recently detected attributes of the file. Although the type is of	1867	The most-recently detected attributes of the file. Although the type is
1491	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1868	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1492	suitable for your system. If the C<st_nlink> member is C<0>, then there	1869	suitable for your system, but you can only rely on the POSIX-standardised
		1870	members to be present. If the C<st_nlink> member is C<0>, then there was
1493	was some error while C<stat>ing the file.	1871	some error while C<stat>ing the file.
1494		1872
1495	=item ev_statdata prev [read-only]	1873	=item ev_statdata prev [read-only]
1496		1874
1497	The previous attributes of the file. The callback gets invoked whenever	1875	The previous attributes of the file. The callback gets invoked whenever
1498	C<prev> != C<attr>.	1876	C<prev> != C<attr>, or, more precisely, one or more of these members
		1877	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1878	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1499		1879
1500	=item ev_tstamp interval [read-only]	1880	=item ev_tstamp interval [read-only]
1501		1881
1502	The specified interval.	1882	The specified interval.
1503		1883
1504	=item const char *path [read-only]	1884	=item const char *path [read-only]
1505		1885
1506	The filesystem path that is being watched.	1886	The file system path that is being watched.
1507		1887
1508	=back	1888	=back
1509		1889
		1890	=head3 Examples
		1891
1510	Example: Watch C</etc/passwd> for attribute changes.	1892	Example: Watch C</etc/passwd> for attribute changes.
1511		1893
1512	static void	1894	static void
1513	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1895	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1514	{	1896	{
1515	/* /etc/passwd changed in some way */	1897	/* /etc/passwd changed in some way */
1516	if (w->attr.st_nlink)	1898	if (w->attr.st_nlink)
1517	{	1899	{
1518	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1900	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1519	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1901	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1520	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1902	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1521	}	1903	}
1522	else	1904	else
1523	/* you shalt not abuse printf for puts */	1905	/* you shalt not abuse printf for puts */
1524	puts ("wow, /etc/passwd is not there, expect problems. "	1906	puts ("wow, /etc/passwd is not there, expect problems. "
1525	"if this is windows, they already arrived\n");	1907	"if this is windows, they already arrived\n");
1526	}	1908	}
1527		1909
1528	...	1910	...
1529	ev_stat passwd;	1911	ev_stat passwd;
1530		1912
1531	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1913	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1532	ev_stat_start (loop, &passwd);	1914	ev_stat_start (loop, &passwd);
		1915
		1916	Example: Like above, but additionally use a one-second delay so we do not
		1917	miss updates (however, frequent updates will delay processing, too, so
		1918	one might do the work both on C<ev_stat> callback invocation I<and> on
		1919	C<ev_timer> callback invocation).
		1920
		1921	static ev_stat passwd;
		1922	static ev_timer timer;
		1923
		1924	static void
		1925	timer_cb (EV_P_ ev_timer *w, int revents)
		1926	{
		1927	ev_timer_stop (EV_A_ w);
		1928
		1929	/* now it's one second after the most recent passwd change */
		1930	}
		1931
		1932	static void
		1933	stat_cb (EV_P_ ev_stat *w, int revents)
		1934	{
		1935	/* reset the one-second timer */
		1936	ev_timer_again (EV_A_ &timer);
		1937	}
		1938
		1939	...
		1940	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1941	ev_stat_start (loop, &passwd);
		1942	ev_timer_init (&timer, timer_cb, 0., 1.02);
1533		1943
1534		1944
1535	=head2 C<ev_idle> - when you've got nothing better to do...	1945	=head2 C<ev_idle> - when you've got nothing better to do...
1536		1946
1537	Idle watchers trigger events when no other events of the same or higher	1947	Idle watchers trigger events when no other events of the same or higher
1538	priority are pending (prepare, check and other idle watchers do not	1948	priority are pending (prepare, check and other idle watchers do not count
1539	count).	1949	as receiving "events").
1540		1950
1541	That is, as long as your process is busy handling sockets or timeouts	1951	That is, as long as your process is busy handling sockets or timeouts
1542	(or even signals, imagine) of the same or higher priority it will not be	1952	(or even signals, imagine) of the same or higher priority it will not be
1543	triggered. But when your process is idle (or only lower-priority watchers	1953	triggered. But when your process is idle (or only lower-priority watchers
1544	are pending), the idle watchers are being called once per event loop	1954	are pending), the idle watchers are being called once per event loop
…		…
1563	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1564	believe me.	1974	believe me.
1565		1975
1566	=back	1976	=back
1567		1977
		1978	=head3 Examples
		1979
1568	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1569	callback, free it. Also, use no error checking, as usual.	1981	callback, free it. Also, use no error checking, as usual.
1570		1982
1571	static void	1983	static void
1572	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1573	{	1985	{
1574	free (w);	1986	free (w);
1575	// now do something you wanted to do when the program has	1987	// now do something you wanted to do when the program has
1576	// no longer asnything immediate to do.	1988	// no longer anything immediate to do.
1577	}	1989	}
1578		1990
1579	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1580	ev_idle_init (idle_watcher, idle_cb);	1992	ev_idle_init (idle_watcher, idle_cb);
1581	ev_idle_start (loop, idle_cb);	1993	ev_idle_start (loop, idle_cb);
1582		1994
1583		1995
1584	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1585		1997
1586	Prepare and check watchers are usually (but not always) used in tandem:	1998	Prepare and check watchers are usually (but not always) used in pairs:
1587	prepare watchers get invoked before the process blocks and check watchers	1999	prepare watchers get invoked before the process blocks and check watchers
1588	afterwards.	2000	afterwards.
1589		2001
1590	You I<must not> call C<ev_loop> or similar functions that enter	2002	You I<must not> call C<ev_loop> or similar functions that enter
1591	the current event loop from either C<ev_prepare> or C<ev_check>	2003	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1594	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2006	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1595	C<ev_check> so if you have one watcher of each kind they will always be	2007	C<ev_check> so if you have one watcher of each kind they will always be
1596	called in pairs bracketing the blocking call.	2008	called in pairs bracketing the blocking call.
1597		2009
1598	Their main purpose is to integrate other event mechanisms into libev and	2010	Their main purpose is to integrate other event mechanisms into libev and
1599	their use is somewhat advanced. This could be used, for example, to track	2011	their use is somewhat advanced. They could be used, for example, to track
1600	variable changes, implement your own watchers, integrate net-snmp or a	2012	variable changes, implement your own watchers, integrate net-snmp or a
1601	coroutine library and lots more. They are also occasionally useful if	2013	coroutine library and lots more. They are also occasionally useful if
1602	you cache some data and want to flush it before blocking (for example,	2014	you cache some data and want to flush it before blocking (for example,
1603	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2015	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1604	watcher).	2016	watcher).
1605		2017
1606	This is done by examining in each prepare call which file descriptors need	2018	This is done by examining in each prepare call which file descriptors
1607	to be watched by the other library, registering C<ev_io> watchers for	2019	need to be watched by the other library, registering C<ev_io> watchers
1608	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2020	for them and starting an C<ev_timer> watcher for any timeouts (many
1609	provide just this functionality). Then, in the check watcher you check for	2021	libraries provide exactly this functionality). Then, in the check watcher,
1610	any events that occured (by checking the pending status of all watchers	2022	you check for any events that occurred (by checking the pending status
1611	and stopping them) and call back into the library. The I/O and timer	2023	of all watchers and stopping them) and call back into the library. The
1612	callbacks will never actually be called (but must be valid nevertheless,	2024	I/O and timer callbacks will never actually be called (but must be valid
1613	because you never know, you know?).	2025	nevertheless, because you never know, you know?).
1614		2026
1615	As another example, the Perl Coro module uses these hooks to integrate	2027	As another example, the Perl Coro module uses these hooks to integrate
1616	coroutines into libev programs, by yielding to other active coroutines	2028	coroutines into libev programs, by yielding to other active coroutines
1617	during each prepare and only letting the process block if no coroutines	2029	during each prepare and only letting the process block if no coroutines
1618	are ready to run (it's actually more complicated: it only runs coroutines	2030	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1621	loop from blocking if lower-priority coroutines are active, thus mapping	2033	loop from blocking if lower-priority coroutines are active, thus mapping
1622	low-priority coroutines to idle/background tasks).	2034	low-priority coroutines to idle/background tasks).
1623		2035
1624	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2036	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1625	priority, to ensure that they are being run before any other watchers	2037	priority, to ensure that they are being run before any other watchers
		2038	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2039
1626	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1627	too) should not activate ("feed") events into libev. While libev fully	2041	activate ("feed") events into libev. While libev fully supports this, they
1628	supports this, they will be called before other C<ev_check> watchers did	2042	might get executed before other C<ev_check> watchers did their job. As
1629	their job. As C<ev_check> watchers are often used to embed other event	2043	C<ev_check> watchers are often used to embed other (non-libev) event
1630	loops those other event loops might be in an unusable state until their	2044	loops those other event loops might be in an unusable state until their
1631	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1632	others).	2046	others).
1633		2047
1634	=head3 Watcher-Specific Functions and Data Members	2048	=head3 Watcher-Specific Functions and Data Members
…		…
1639		2053
1640	=item ev_check_init (ev_check *, callback)	2054	=item ev_check_init (ev_check *, callback)
1641		2055
1642	Initialises and configures the prepare or check watcher - they have no	2056	Initialises and configures the prepare or check watcher - they have no
1643	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2057	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1644	macros, but using them is utterly, utterly and completely pointless.	2058	macros, but using them is utterly, utterly, utterly and completely
		2059	pointless.
1645		2060
1646	=back	2061	=back
		2062
		2063	=head3 Examples
1647		2064
1648	There are a number of principal ways to embed other event loops or modules	2065	There are a number of principal ways to embed other event loops or modules
1649	into libev. Here are some ideas on how to include libadns into libev	2066	into libev. Here are some ideas on how to include libadns into libev
1650	(there is a Perl module named C<EV::ADNS> that does this, which you could	2067	(there is a Perl module named C<EV::ADNS> that does this, which you could
1651	use for an actually working example. Another Perl module named C<EV::Glib>	2068	use as a working example. Another Perl module named C<EV::Glib> embeds a
1652	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2069	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1653	into the Glib event loop).	2070	Glib event loop).
1654		2071
1655	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2072	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1656	and in a check watcher, destroy them and call into libadns. What follows	2073	and in a check watcher, destroy them and call into libadns. What follows
1657	is pseudo-code only of course. This requires you to either use a low	2074	is pseudo-code only of course. This requires you to either use a low
1658	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2075	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1659	the callbacks for the IO/timeout watchers might not have been called yet.	2076	the callbacks for the IO/timeout watchers might not have been called yet.
1660		2077
1661	static ev_io iow [nfd];	2078	static ev_io iow [nfd];
1662	static ev_timer tw;	2079	static ev_timer tw;
1663		2080
1664	static void	2081	static void
1665	io_cb (ev_loop *loop, ev_io *w, int revents)	2082	io_cb (ev_loop *loop, ev_io *w, int revents)
1666	{	2083	{
1667	}	2084	}
1668		2085
1669	// create io watchers for each fd and a timer before blocking	2086	// create io watchers for each fd and a timer before blocking
1670	static void	2087	static void
1671	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1672	{	2089	{
1673	int timeout = 3600000;	2090	int timeout = 3600000;
1674	struct pollfd fds [nfd];	2091	struct pollfd fds [nfd];
1675	// actual code will need to loop here and realloc etc.	2092	// actual code will need to loop here and realloc etc.
1676	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1677		2094
1678	/* the callback is illegal, but won't be called as we stop during check */	2095	/* the callback is illegal, but won't be called as we stop during check */
1679	ev_timer_init (&tw, 0, timeout * 1e-3);	2096	ev_timer_init (&tw, 0, timeout * 1e-3);
1680	ev_timer_start (loop, &tw);	2097	ev_timer_start (loop, &tw);
1681		2098
1682	// create one ev_io per pollfd	2099	// create one ev_io per pollfd
1683	for (int i = 0; i < nfd; ++i)	2100	for (int i = 0; i < nfd; ++i)
1684	{	2101	{
1685	ev_io_init (iow + i, io_cb, fds [i].fd,	2102	ev_io_init (iow + i, io_cb, fds [i].fd,
1686	((fds [i].events & POLLIN ? EV_READ : 0)	2103	((fds [i].events & POLLIN ? EV_READ : 0)
1687	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2104	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1688		2105
1689	fds [i].revents = 0;	2106	fds [i].revents = 0;
1690	ev_io_start (loop, iow + i);	2107	ev_io_start (loop, iow + i);
1691	}	2108	}
1692	}	2109	}
1693		2110
1694	// stop all watchers after blocking	2111	// stop all watchers after blocking
1695	static void	2112	static void
1696	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1697	{	2114	{
1698	ev_timer_stop (loop, &tw);	2115	ev_timer_stop (loop, &tw);
1699		2116
1700	for (int i = 0; i < nfd; ++i)	2117	for (int i = 0; i < nfd; ++i)
1701	{	2118	{
1702	// set the relevant poll flags	2119	// set the relevant poll flags
1703	// could also call adns_processreadable etc. here	2120	// could also call adns_processreadable etc. here
1704	struct pollfd *fd = fds + i;	2121	struct pollfd *fd = fds + i;
1705	int revents = ev_clear_pending (iow + i);	2122	int revents = ev_clear_pending (iow + i);
1706	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2123	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1707	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2124	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1708		2125
1709	// now stop the watcher	2126	// now stop the watcher
1710	ev_io_stop (loop, iow + i);	2127	ev_io_stop (loop, iow + i);
1711	}	2128	}
1712		2129
1713	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2130	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1714	}	2131	}
1715		2132
1716	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2133	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1717	in the prepare watcher and would dispose of the check watcher.	2134	in the prepare watcher and would dispose of the check watcher.
1718		2135
1719	Method 3: If the module to be embedded supports explicit event	2136	Method 3: If the module to be embedded supports explicit event
1720	notification (adns does), you can also make use of the actual watcher	2137	notification (libadns does), you can also make use of the actual watcher
1721	callbacks, and only destroy/create the watchers in the prepare watcher.	2138	callbacks, and only destroy/create the watchers in the prepare watcher.
1722		2139
1723	static void	2140	static void
1724	timer_cb (EV_P_ ev_timer *w, int revents)	2141	timer_cb (EV_P_ ev_timer *w, int revents)
1725	{	2142	{
1726	adns_state ads = (adns_state)w->data;	2143	adns_state ads = (adns_state)w->data;
1727	update_now (EV_A);	2144	update_now (EV_A);
1728		2145
1729	adns_processtimeouts (ads, &tv_now);	2146	adns_processtimeouts (ads, &tv_now);
1730	}	2147	}
1731		2148
1732	static void	2149	static void
1733	io_cb (EV_P_ ev_io *w, int revents)	2150	io_cb (EV_P_ ev_io *w, int revents)
1734	{	2151	{
1735	adns_state ads = (adns_state)w->data;	2152	adns_state ads = (adns_state)w->data;
1736	update_now (EV_A);	2153	update_now (EV_A);
1737		2154
1738	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2155	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1739	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2156	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1740	}	2157	}
1741		2158
1742	// do not ever call adns_afterpoll	2159	// do not ever call adns_afterpoll
1743		2160
1744	Method 4: Do not use a prepare or check watcher because the module you	2161	Method 4: Do not use a prepare or check watcher because the module you
1745	want to embed is too inflexible to support it. Instead, youc na override	2162	want to embed is not flexible enough to support it. Instead, you can
1746	their poll function. The drawback with this solution is that the main	2163	override their poll function. The drawback with this solution is that the
1747	loop is now no longer controllable by EV. The C<Glib::EV> module does	2164	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1748	this.	2165	this approach, effectively embedding EV as a client into the horrible
		2166	libglib event loop.
1749		2167
1750	static gint	2168	static gint
1751	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2169	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1752	{	2170	{
1753	int got_events = 0;	2171	int got_events = 0;
1754		2172
1755	for (n = 0; n < nfds; ++n)	2173	for (n = 0; n < nfds; ++n)
1756	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2174	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1757		2175
1758	if (timeout >= 0)	2176	if (timeout >= 0)
1759	// create/start timer	2177	// create/start timer
1760		2178
1761	// poll	2179	// poll
1762	ev_loop (EV_A_ 0);	2180	ev_loop (EV_A_ 0);
1763		2181
1764	// stop timer again	2182	// stop timer again
1765	if (timeout >= 0)	2183	if (timeout >= 0)
1766	ev_timer_stop (EV_A_ &to);	2184	ev_timer_stop (EV_A_ &to);
1767		2185
1768	// stop io watchers again - their callbacks should have set	2186	// stop io watchers again - their callbacks should have set
1769	for (n = 0; n < nfds; ++n)	2187	for (n = 0; n < nfds; ++n)
1770	ev_io_stop (EV_A_ iow [n]);	2188	ev_io_stop (EV_A_ iow [n]);
1771		2189
1772	return got_events;	2190	return got_events;
1773	}	2191	}
1774		2192
1775		2193
1776	=head2 C<ev_embed> - when one backend isn't enough...	2194	=head2 C<ev_embed> - when one backend isn't enough...
1777		2195
1778	This is a rather advanced watcher type that lets you embed one event loop	2196	This is a rather advanced watcher type that lets you embed one event loop
1779	into another (currently only C<ev_io> events are supported in the embedded	2197	into another (currently only C<ev_io> events are supported in the embedded
1780	loop, other types of watchers might be handled in a delayed or incorrect	2198	loop, other types of watchers might be handled in a delayed or incorrect
1781	fashion and must not be used). (See portability notes, below).	2199	fashion and must not be used).
1782		2200
1783	There are primarily two reasons you would want that: work around bugs and	2201	There are primarily two reasons you would want that: work around bugs and
1784	prioritise I/O.	2202	prioritise I/O.
1785		2203
1786	As an example for a bug workaround, the kqueue backend might only support	2204	As an example for a bug workaround, the kqueue backend might only support
1787	sockets on some platform, so it is unusable as generic backend, but you	2205	sockets on some platform, so it is unusable as generic backend, but you
1788	still want to make use of it because you have many sockets and it scales	2206	still want to make use of it because you have many sockets and it scales
1789	so nicely. In this case, you would create a kqueue-based loop and embed it	2207	so nicely. In this case, you would create a kqueue-based loop and embed
1790	into your default loop (which might use e.g. poll). Overall operation will	2208	it into your default loop (which might use e.g. poll). Overall operation
1791	be a bit slower because first libev has to poll and then call kevent, but	2209	will be a bit slower because first libev has to call C<poll> and then
1792	at least you can use both at what they are best.	2210	C<kevent>, but at least you can use both mechanisms for what they are
		2211	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1793		2212
1794	As for prioritising I/O: rarely you have the case where some fds have	2213	As for prioritising I/O: under rare circumstances you have the case where
1795	to be watched and handled very quickly (with low latency), and even	2214	some fds have to be watched and handled very quickly (with low latency),
1796	priorities and idle watchers might have too much overhead. In this case	2215	and even priorities and idle watchers might have too much overhead. In
1797	you would put all the high priority stuff in one loop and all the rest in	2216	this case you would put all the high priority stuff in one loop and all
1798	a second one, and embed the second one in the first.	2217	the rest in a second one, and embed the second one in the first.
1799		2218
1800	As long as the watcher is active, the callback will be invoked every time	2219	As long as the watcher is active, the callback will be invoked every time
1801	there might be events pending in the embedded loop. The callback must then	2220	there might be events pending in the embedded loop. The callback must then
1802	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1803	their callbacks (you could also start an idle watcher to give the embedded	2222	their callbacks (you could also start an idle watcher to give the embedded
…		…
1811	interested in that.	2230	interested in that.
1812		2231
1813	Also, there have not currently been made special provisions for forking:	2232	Also, there have not currently been made special provisions for forking:
1814	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1815	but you will also have to stop and restart any C<ev_embed> watchers	2234	but you will also have to stop and restart any C<ev_embed> watchers
1816	yourself.	2235	yourself - but you can use a fork watcher to handle this automatically,
		2236	and future versions of libev might do just that.
1817		2237
1818	Unfortunately, not all backends are embeddable, only the ones returned by	2238	Unfortunately, not all backends are embeddable: only the ones returned by
1819	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1820	portable one.	2240	portable one.
1821		2241
1822	So when you want to use this feature you will always have to be prepared	2242	So when you want to use this feature you will always have to be prepared
1823	that you cannot get an embeddable loop. The recommended way to get around	2243	that you cannot get an embeddable loop. The recommended way to get around
1824	this is to have a separate variables for your embeddable loop, try to	2244	this is to have a separate variables for your embeddable loop, try to
1825	create it, and if that fails, use the normal loop for everything:	2245	create it, and if that fails, use the normal loop for everything.
1826		2246
1827	struct ev_loop *loop_hi = ev_default_init (0);	2247	=head3 C<ev_embed> and fork
1828	struct ev_loop *loop_lo = 0;
1829	struct ev_embed embed;
1830
1831	// see if there is a chance of getting one that works
1832	// (remember that a flags value of 0 means autodetection)
1833	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1834	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1835	: 0;
1836		2248
1837	// if we got one, then embed it, otherwise default to loop_hi	2249	While the C<ev_embed> watcher is running, forks in the embedding loop will
1838	if (loop_lo)	2250	automatically be applied to the embedded loop as well, so no special
1839	{	2251	fork handling is required in that case. When the watcher is not running,
1840	ev_embed_init (&embed, 0, loop_lo);	2252	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1841	ev_embed_start (loop_hi, &embed);	2253	as applicable.
1842	}
1843	else
1844	loop_lo = loop_hi;
1845
1846	=head2 Portability notes
1847
1848	Kqueue is nominally embeddable, but this is broken on all BSDs that I
1849	tried, in various ways. Usually the embedded event loop will simply never
1850	receive events, sometimes it will only trigger a few times, sometimes in a
1851	loop. Epoll is also nominally embeddable, but many Linux kernel versions
1852	will always eport the epoll fd as ready, even when no events are pending.
1853
1854	While libev allows embedding these backends (they are contained in
1855	C<ev_embeddable_backends ()>), take extreme care that it will actually
1856	work.
1857
1858	When in doubt, create a dynamic event loop forced to use sockets (this
1859	usually works) and possibly another thread and a pipe or so to report to
1860	your main event loop.
1861		2254
1862	=head3 Watcher-Specific Functions and Data Members	2255	=head3 Watcher-Specific Functions and Data Members
1863		2256
1864	=over 4	2257	=over 4
1865		2258
…		…
1869		2262
1870	Configures the watcher to embed the given loop, which must be	2263	Configures the watcher to embed the given loop, which must be
1871	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2264	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1872	invoked automatically, otherwise it is the responsibility of the callback	2265	invoked automatically, otherwise it is the responsibility of the callback
1873	to invoke it (it will continue to be called until the sweep has been done,	2266	to invoke it (it will continue to be called until the sweep has been done,
1874	if you do not want thta, you need to temporarily stop the embed watcher).	2267	if you do not want that, you need to temporarily stop the embed watcher).
1875		2268
1876	=item ev_embed_sweep (loop, ev_embed *)	2269	=item ev_embed_sweep (loop, ev_embed *)
1877		2270
1878	Make a single, non-blocking sweep over the embedded loop. This works	2271	Make a single, non-blocking sweep over the embedded loop. This works
1879	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2272	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1880	apropriate way for embedded loops.	2273	appropriate way for embedded loops.
1881		2274
1882	=item struct ev_loop *other [read-only]	2275	=item struct ev_loop *other [read-only]
1883		2276
1884	The embedded event loop.	2277	The embedded event loop.
1885		2278
1886	=back	2279	=back
		2280
		2281	=head3 Examples
		2282
		2283	Example: Try to get an embeddable event loop and embed it into the default
		2284	event loop. If that is not possible, use the default loop. The default
		2285	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2287	used).
		2288
		2289	struct ev_loop *loop_hi = ev_default_init (0);
		2290	struct ev_loop *loop_lo = 0;
		2291	struct ev_embed embed;
		2292
		2293	// see if there is a chance of getting one that works
		2294	// (remember that a flags value of 0 means autodetection)
		2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2297	: 0;
		2298
		2299	// if we got one, then embed it, otherwise default to loop_hi
		2300	if (loop_lo)
		2301	{
		2302	ev_embed_init (&embed, 0, loop_lo);
		2303	ev_embed_start (loop_hi, &embed);
		2304	}
		2305	else
		2306	loop_lo = loop_hi;
		2307
		2308	Example: Check if kqueue is available but not recommended and create
		2309	a kqueue backend for use with sockets (which usually work with any
		2310	kqueue implementation). Store the kqueue/socket-only event loop in
		2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2312
		2313	struct ev_loop *loop = ev_default_init (0);
		2314	struct ev_loop *loop_socket = 0;
		2315	struct ev_embed embed;
		2316
		2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2319	{
		2320	ev_embed_init (&embed, 0, loop_socket);
		2321	ev_embed_start (loop, &embed);
		2322	}
		2323
		2324	if (!loop_socket)
		2325	loop_socket = loop;
		2326
		2327	// now use loop_socket for all sockets, and loop for everything else
1887		2328
1888		2329
1889	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2330	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1890		2331
1891	Fork watchers are called when a C<fork ()> was detected (usually because	2332	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1907	believe me.	2348	believe me.
1908		2349
1909	=back	2350	=back
1910		2351
1911		2352
		2353	=head2 C<ev_async> - how to wake up another event loop
		2354
		2355	In general, you cannot use an C<ev_loop> from multiple threads or other
		2356	asynchronous sources such as signal handlers (as opposed to multiple event
		2357	loops - those are of course safe to use in different threads).
		2358
		2359	Sometimes, however, you need to wake up another event loop you do not
		2360	control, for example because it belongs to another thread. This is what
		2361	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2362	can signal it by calling C<ev_async_send>, which is thread- and signal
		2363	safe.
		2364
		2365	This functionality is very similar to C<ev_signal> watchers, as signals,
		2366	too, are asynchronous in nature, and signals, too, will be compressed
		2367	(i.e. the number of callback invocations may be less than the number of
		2368	C<ev_async_sent> calls).
		2369
		2370	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2371	just the default loop.
		2372
		2373	=head3 Queueing
		2374
		2375	C<ev_async> does not support queueing of data in any way. The reason
		2376	is that the author does not know of a simple (or any) algorithm for a
		2377	multiple-writer-single-reader queue that works in all cases and doesn't
		2378	need elaborate support such as pthreads.
		2379
		2380	That means that if you want to queue data, you have to provide your own
		2381	queue. But at least I can tell you how to implement locking around your
		2382	queue:
		2383
		2384	=over 4
		2385
		2386	=item queueing from a signal handler context
		2387
		2388	To implement race-free queueing, you simply add to the queue in the signal
		2389	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2390	some fictitious SIGUSR1 handler:
		2391
		2392	static ev_async mysig;
		2393
		2394	static void
		2395	sigusr1_handler (void)
		2396	{
		2397	sometype data;
		2398
		2399	// no locking etc.
		2400	queue_put (data);
		2401	ev_async_send (EV_DEFAULT_ &mysig);
		2402	}
		2403
		2404	static void
		2405	mysig_cb (EV_P_ ev_async *w, int revents)
		2406	{
		2407	sometype data;
		2408	sigset_t block, prev;
		2409
		2410	sigemptyset (&block);
		2411	sigaddset (&block, SIGUSR1);
		2412	sigprocmask (SIG_BLOCK, &block, &prev);
		2413
		2414	while (queue_get (&data))
		2415	process (data);
		2416
		2417	if (sigismember (&prev, SIGUSR1)
		2418	sigprocmask (SIG_UNBLOCK, &block, 0);
		2419	}
		2420
		2421	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2422	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2423	either...).
		2424
		2425	=item queueing from a thread context
		2426
		2427	The strategy for threads is different, as you cannot (easily) block
		2428	threads but you can easily preempt them, so to queue safely you need to
		2429	employ a traditional mutex lock, such as in this pthread example:
		2430
		2431	static ev_async mysig;
		2432	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2433
		2434	static void
		2435	otherthread (void)
		2436	{
		2437	// only need to lock the actual queueing operation
		2438	pthread_mutex_lock (&mymutex);
		2439	queue_put (data);
		2440	pthread_mutex_unlock (&mymutex);
		2441
		2442	ev_async_send (EV_DEFAULT_ &mysig);
		2443	}
		2444
		2445	static void
		2446	mysig_cb (EV_P_ ev_async *w, int revents)
		2447	{
		2448	pthread_mutex_lock (&mymutex);
		2449
		2450	while (queue_get (&data))
		2451	process (data);
		2452
		2453	pthread_mutex_unlock (&mymutex);
		2454	}
		2455
		2456	=back
		2457
		2458
		2459	=head3 Watcher-Specific Functions and Data Members
		2460
		2461	=over 4
		2462
		2463	=item ev_async_init (ev_async *, callback)
		2464
		2465	Initialises and configures the async watcher - it has no parameters of any
		2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2467	trust me.
		2468
		2469	=item ev_async_send (loop, ev_async *)
		2470
		2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2473	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2475	section below on what exactly this means).
		2476
		2477	This call incurs the overhead of a system call only once per loop iteration,
		2478	so while the overhead might be noticeable, it doesn't apply to repeated
		2479	calls to C<ev_async_send>.
		2480
		2481	=item bool = ev_async_pending (ev_async *)
		2482
		2483	Returns a non-zero value when C<ev_async_send> has been called on the
		2484	watcher but the event has not yet been processed (or even noted) by the
		2485	event loop.
		2486
		2487	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2488	the loop iterates next and checks for the watcher to have become active,
		2489	it will reset the flag again. C<ev_async_pending> can be used to very
		2490	quickly check whether invoking the loop might be a good idea.
		2491
		2492	Not that this does I<not> check whether the watcher itself is pending, only
		2493	whether it has been requested to make this watcher pending.
		2494
		2495	=back
		2496
		2497
1912	=head1 OTHER FUNCTIONS	2498	=head1 OTHER FUNCTIONS
1913		2499
1914	There are some other functions of possible interest. Described. Here. Now.	2500	There are some other functions of possible interest. Described. Here. Now.
1915		2501
1916	=over 4	2502	=over 4
…		…
1923	or timeout without having to allocate/configure/start/stop/free one or	2509	or timeout without having to allocate/configure/start/stop/free one or
1924	more watchers yourself.	2510	more watchers yourself.
1925		2511
1926	If C<fd> is less than 0, then no I/O watcher will be started and events	2512	If C<fd> is less than 0, then no I/O watcher will be started and events
1927	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2513	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1928	C<events> set will be craeted and started.	2514	C<events> set will be created and started.
1929		2515
1930	If C<timeout> is less than 0, then no timeout watcher will be	2516	If C<timeout> is less than 0, then no timeout watcher will be
1931	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1932	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1933	dubious value.	2519	dubious value.
…		…
1935	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2521	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1936	passed an C<revents> set like normal event callbacks (a combination of	2522	passed an C<revents> set like normal event callbacks (a combination of
1937	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1938	value passed to C<ev_once>:	2524	value passed to C<ev_once>:
1939		2525
1940	static void stdin_ready (int revents, void *arg)	2526	static void stdin_ready (int revents, void *arg)
1941	{	2527	{
1942	if (revents & EV_TIMEOUT)	2528	if (revents & EV_TIMEOUT)
1943	/* doh, nothing entered */;	2529	/* doh, nothing entered */;
1944	else if (revents & EV_READ)	2530	else if (revents & EV_READ)
1945	/* stdin might have data for us, joy! */;	2531	/* stdin might have data for us, joy! */;
1946	}	2532	}
1947		2533
1948	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1949		2535
1950	=item ev_feed_event (ev_loop *, watcher *, int revents)	2536	=item ev_feed_event (ev_loop *, watcher *, int revents)
1951		2537
1952	Feeds the given event set into the event loop, as if the specified event	2538	Feeds the given event set into the event loop, as if the specified event
1953	had happened for the specified watcher (which must be a pointer to an	2539	had happened for the specified watcher (which must be a pointer to an
…		…
1958	Feed an event on the given fd, as if a file descriptor backend detected	2544	Feed an event on the given fd, as if a file descriptor backend detected
1959	the given events it.	2545	the given events it.
1960		2546
1961	=item ev_feed_signal_event (ev_loop *loop, int signum)	2547	=item ev_feed_signal_event (ev_loop *loop, int signum)
1962		2548
1963	Feed an event as if the given signal occured (C<loop> must be the default	2549	Feed an event as if the given signal occurred (C<loop> must be the default
1964	loop!).	2550	loop!).
1965		2551
1966	=back	2552	=back
1967		2553
1968		2554
…		…
1984		2570
1985	=item * Priorities are not currently supported. Initialising priorities	2571	=item * Priorities are not currently supported. Initialising priorities
1986	will fail and all watchers will have the same priority, even though there	2572	will fail and all watchers will have the same priority, even though there
1987	is an ev_pri field.	2573	is an ev_pri field.
1988		2574
		2575	=item * In libevent, the last base created gets the signals, in libev, the
		2576	first base created (== the default loop) gets the signals.
		2577
1989	=item * Other members are not supported.	2578	=item * Other members are not supported.
1990		2579
1991	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2580	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1992	to use the libev header file and library.	2581	to use the libev header file and library.
1993		2582
1994	=back	2583	=back
1995		2584
1996	=head1 C++ SUPPORT	2585	=head1 C++ SUPPORT
1997		2586
1998	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2587	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1999	you to use some convinience methods to start/stop watchers and also change	2588	you to use some convenience methods to start/stop watchers and also change
2000	the callback model to a model using method callbacks on objects.	2589	the callback model to a model using method callbacks on objects.
2001		2590
2002	To use it,	2591	To use it,
2003		2592
2004	#include <ev++.h>	2593	#include <ev++.h>
2005		2594
2006	This automatically includes F<ev.h> and puts all of its definitions (many	2595	This automatically includes F<ev.h> and puts all of its definitions (many
2007	of them macros) into the global namespace. All C++ specific things are	2596	of them macros) into the global namespace. All C++ specific things are
2008	put into the C<ev> namespace. It should support all the same embedding	2597	put into the C<ev> namespace. It should support all the same embedding
2009	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2598	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2076	your compiler is good :), then the method will be fully inlined into the	2665	your compiler is good :), then the method will be fully inlined into the
2077	thunking function, making it as fast as a direct C callback.	2666	thunking function, making it as fast as a direct C callback.
2078		2667
2079	Example: simple class declaration and watcher initialisation	2668	Example: simple class declaration and watcher initialisation
2080		2669
2081	struct myclass	2670	struct myclass
2082	{	2671	{
2083	void io_cb (ev::io &w, int revents) { }	2672	void io_cb (ev::io &w, int revents) { }
2084	}	2673	}
2085		2674
2086	myclass obj;	2675	myclass obj;
2087	ev::io iow;	2676	ev::io iow;
2088	iow.set <myclass, &myclass::io_cb> (&obj);	2677	iow.set <myclass, &myclass::io_cb> (&obj);
2089		2678
2090	=item w->set<function> (void *data = 0)	2679	=item w->set<function> (void *data = 0)
2091		2680
2092	Also sets a callback, but uses a static method or plain function as	2681	Also sets a callback, but uses a static method or plain function as
2093	callback. The optional C<data> argument will be stored in the watcher's	2682	callback. The optional C<data> argument will be stored in the watcher's
…		…
2095		2684
2096	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2685	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2097		2686
2098	See the method-C<set> above for more details.	2687	See the method-C<set> above for more details.
2099		2688
2100	Example:	2689	Example: Use a plain function as callback.
2101		2690
2102	static void io_cb (ev::io &w, int revents) { }	2691	static void io_cb (ev::io &w, int revents) { }
2103	iow.set <io_cb> ();	2692	iow.set <io_cb> ();
2104		2693
2105	=item w->set (struct ev_loop *)	2694	=item w->set (struct ev_loop *)
2106		2695
2107	Associates a different C<struct ev_loop> with this watcher. You can only	2696	Associates a different C<struct ev_loop> with this watcher. You can only
2108	do this when the watcher is inactive (and not pending either).	2697	do this when the watcher is inactive (and not pending either).
2109		2698
2110	=item w->set ([args])	2699	=item w->set ([arguments])
2111		2700
2112	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2701	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2113	called at least once. Unlike the C counterpart, an active watcher gets	2702	called at least once. Unlike the C counterpart, an active watcher gets
2114	automatically stopped and restarted when reconfiguring it with this	2703	automatically stopped and restarted when reconfiguring it with this
2115	method.	2704	method.
2116		2705
2117	=item w->start ()	2706	=item w->start ()
…		…
2141	=back	2730	=back
2142		2731
2143	Example: Define a class with an IO and idle watcher, start one of them in	2732	Example: Define a class with an IO and idle watcher, start one of them in
2144	the constructor.	2733	the constructor.
2145		2734
2146	class myclass	2735	class myclass
2147	{	2736	{
2148	ev_io io; void io_cb (ev::io &w, int revents);	2737	ev::io io ; void io_cb (ev::io &w, int revents);
2149	ev_idle idle void idle_cb (ev::idle &w, int revents);	2738	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2150		2739
2151	myclass ();	2740	myclass (int fd)
2152	}	2741	{
2153
2154	myclass::myclass (int fd)
2155	{
2156	io .set <myclass, &myclass::io_cb > (this);	2742	io .set <myclass, &myclass::io_cb > (this);
2157	idle.set <myclass, &myclass::idle_cb> (this);	2743	idle.set <myclass, &myclass::idle_cb> (this);
2158		2744
2159	io.start (fd, ev::READ);	2745	io.start (fd, ev::READ);
		2746	}
2160	}	2747	};
		2748
		2749
		2750	=head1 OTHER LANGUAGE BINDINGS
		2751
		2752	Libev does not offer other language bindings itself, but bindings for a
		2753	number of languages exist in the form of third-party packages. If you know
		2754	any interesting language binding in addition to the ones listed here, drop
		2755	me a note.
		2756
		2757	=over 4
		2758
		2759	=item Perl
		2760
		2761	The EV module implements the full libev API and is actually used to test
		2762	libev. EV is developed together with libev. Apart from the EV core module,
		2763	there are additional modules that implement libev-compatible interfaces
		2764	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2765	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2766	and C<EV::Glib>).
		2767
		2768	It can be found and installed via CPAN, its homepage is at
		2769	L<http://software.schmorp.de/pkg/EV>.
		2770
		2771	=item Python
		2772
		2773	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2774	seems to be quite complete and well-documented. Note, however, that the
		2775	patch they require for libev is outright dangerous as it breaks the ABI
		2776	for everybody else, and therefore, should never be applied in an installed
		2777	libev (if python requires an incompatible ABI then it needs to embed
		2778	libev).
		2779
		2780	=item Ruby
		2781
		2782	Tony Arcieri has written a ruby extension that offers access to a subset
		2783	of the libev API and adds file handle abstractions, asynchronous DNS and
		2784	more on top of it. It can be found via gem servers. Its homepage is at
		2785	L<http://rev.rubyforge.org/>.
		2786
		2787	=item D
		2788
		2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2791
		2792	=back
2161		2793
2162		2794
2163	=head1 MACRO MAGIC	2795	=head1 MACRO MAGIC
2164		2796
2165	Libev can be compiled with a variety of options, the most fundamantal	2797	Libev can be compiled with a variety of options, the most fundamental
2166	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2798	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2167	functions and callbacks have an initial C<struct ev_loop *> argument.	2799	functions and callbacks have an initial C<struct ev_loop *> argument.
2168		2800
2169	To make it easier to write programs that cope with either variant, the	2801	To make it easier to write programs that cope with either variant, the
2170	following macros are defined:	2802	following macros are defined:
…		…
2175		2807
2176	This provides the loop I<argument> for functions, if one is required ("ev	2808	This provides the loop I<argument> for functions, if one is required ("ev
2177	loop argument"). The C<EV_A> form is used when this is the sole argument,	2809	loop argument"). The C<EV_A> form is used when this is the sole argument,
2178	C<EV_A_> is used when other arguments are following. Example:	2810	C<EV_A_> is used when other arguments are following. Example:
2179		2811
2180	ev_unref (EV_A);	2812	ev_unref (EV_A);
2181	ev_timer_add (EV_A_ watcher);	2813	ev_timer_add (EV_A_ watcher);
2182	ev_loop (EV_A_ 0);	2814	ev_loop (EV_A_ 0);
2183		2815
2184	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2816	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2185	which is often provided by the following macro.	2817	which is often provided by the following macro.
2186		2818
2187	=item C<EV_P>, C<EV_P_>	2819	=item C<EV_P>, C<EV_P_>
2188		2820
2189	This provides the loop I<parameter> for functions, if one is required ("ev	2821	This provides the loop I<parameter> for functions, if one is required ("ev
2190	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2822	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2191	C<EV_P_> is used when other parameters are following. Example:	2823	C<EV_P_> is used when other parameters are following. Example:
2192		2824
2193	// this is how ev_unref is being declared	2825	// this is how ev_unref is being declared
2194	static void ev_unref (EV_P);	2826	static void ev_unref (EV_P);
2195		2827
2196	// this is how you can declare your typical callback	2828	// this is how you can declare your typical callback
2197	static void cb (EV_P_ ev_timer *w, int revents)	2829	static void cb (EV_P_ ev_timer *w, int revents)
2198		2830
2199	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2831	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2200	suitable for use with C<EV_A>.	2832	suitable for use with C<EV_A>.
2201		2833
2202	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2834	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2203		2835
2204	Similar to the other two macros, this gives you the value of the default	2836	Similar to the other two macros, this gives you the value of the default
2205	loop, if multiple loops are supported ("ev loop default").	2837	loop, if multiple loops are supported ("ev loop default").
		2838
		2839	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2840
		2841	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2842	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2843	is undefined when the default loop has not been initialised by a previous
		2844	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2845
		2846	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2847	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2206		2848
2207	=back	2849	=back
2208		2850
2209	Example: Declare and initialise a check watcher, utilising the above	2851	Example: Declare and initialise a check watcher, utilising the above
2210	macros so it will work regardless of whether multiple loops are supported	2852	macros so it will work regardless of whether multiple loops are supported
2211	or not.	2853	or not.
2212		2854
2213	static void	2855	static void
2214	check_cb (EV_P_ ev_timer *w, int revents)	2856	check_cb (EV_P_ ev_timer *w, int revents)
2215	{	2857	{
2216	ev_check_stop (EV_A_ w);	2858	ev_check_stop (EV_A_ w);
2217	}	2859	}
2218		2860
2219	ev_check check;	2861	ev_check check;
2220	ev_check_init (&check, check_cb);	2862	ev_check_init (&check, check_cb);
2221	ev_check_start (EV_DEFAULT_ &check);	2863	ev_check_start (EV_DEFAULT_ &check);
2222	ev_loop (EV_DEFAULT_ 0);	2864	ev_loop (EV_DEFAULT_ 0);
2223		2865
2224	=head1 EMBEDDING	2866	=head1 EMBEDDING
2225		2867
2226	Libev can (and often is) directly embedded into host	2868	Libev can (and often is) directly embedded into host
2227	applications. Examples of applications that embed it include the Deliantra	2869	applications. Examples of applications that embed it include the Deliantra
…		…
2234	libev somewhere in your source tree).	2876	libev somewhere in your source tree).
2235		2877
2236	=head2 FILESETS	2878	=head2 FILESETS
2237		2879
2238	Depending on what features you need you need to include one or more sets of files	2880	Depending on what features you need you need to include one or more sets of files
2239	in your app.	2881	in your application.
2240		2882
2241	=head3 CORE EVENT LOOP	2883	=head3 CORE EVENT LOOP
2242		2884
2243	To include only the libev core (all the C<ev_*> functions), with manual	2885	To include only the libev core (all the C<ev_*> functions), with manual
2244	configuration (no autoconf):	2886	configuration (no autoconf):
2245		2887
2246	#define EV_STANDALONE 1	2888	#define EV_STANDALONE 1
2247	#include "ev.c"	2889	#include "ev.c"
2248		2890
2249	This will automatically include F<ev.h>, too, and should be done in a	2891	This will automatically include F<ev.h>, too, and should be done in a
2250	single C source file only to provide the function implementations. To use	2892	single C source file only to provide the function implementations. To use
2251	it, do the same for F<ev.h> in all files wishing to use this API (best	2893	it, do the same for F<ev.h> in all files wishing to use this API (best
2252	done by writing a wrapper around F<ev.h> that you can include instead and	2894	done by writing a wrapper around F<ev.h> that you can include instead and
2253	where you can put other configuration options):	2895	where you can put other configuration options):
2254		2896
2255	#define EV_STANDALONE 1	2897	#define EV_STANDALONE 1
2256	#include "ev.h"	2898	#include "ev.h"
2257		2899
2258	Both header files and implementation files can be compiled with a C++	2900	Both header files and implementation files can be compiled with a C++
2259	compiler (at least, thats a stated goal, and breakage will be treated	2901	compiler (at least, thats a stated goal, and breakage will be treated
2260	as a bug).	2902	as a bug).
2261		2903
2262	You need the following files in your source tree, or in a directory	2904	You need the following files in your source tree, or in a directory
2263	in your include path (e.g. in libev/ when using -Ilibev):	2905	in your include path (e.g. in libev/ when using -Ilibev):
2264		2906
2265	ev.h	2907	ev.h
2266	ev.c	2908	ev.c
2267	ev_vars.h	2909	ev_vars.h
2268	ev_wrap.h	2910	ev_wrap.h
2269		2911
2270	ev_win32.c required on win32 platforms only	2912	ev_win32.c required on win32 platforms only
2271		2913
2272	ev_select.c only when select backend is enabled (which is enabled by default)	2914	ev_select.c only when select backend is enabled (which is enabled by default)
2273	ev_poll.c only when poll backend is enabled (disabled by default)	2915	ev_poll.c only when poll backend is enabled (disabled by default)
2274	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2916	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2275	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2917	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2276	ev_port.c only when the solaris port backend is enabled (disabled by default)	2918	ev_port.c only when the solaris port backend is enabled (disabled by default)
2277		2919
2278	F<ev.c> includes the backend files directly when enabled, so you only need	2920	F<ev.c> includes the backend files directly when enabled, so you only need
2279	to compile this single file.	2921	to compile this single file.
2280		2922
2281	=head3 LIBEVENT COMPATIBILITY API	2923	=head3 LIBEVENT COMPATIBILITY API
2282		2924
2283	To include the libevent compatibility API, also include:	2925	To include the libevent compatibility API, also include:
2284		2926
2285	#include "event.c"	2927	#include "event.c"
2286		2928
2287	in the file including F<ev.c>, and:	2929	in the file including F<ev.c>, and:
2288		2930
2289	#include "event.h"	2931	#include "event.h"
2290		2932
2291	in the files that want to use the libevent API. This also includes F<ev.h>.	2933	in the files that want to use the libevent API. This also includes F<ev.h>.
2292		2934
2293	You need the following additional files for this:	2935	You need the following additional files for this:
2294		2936
2295	event.h	2937	event.h
2296	event.c	2938	event.c
2297		2939
2298	=head3 AUTOCONF SUPPORT	2940	=head3 AUTOCONF SUPPORT
2299		2941
2300	Instead of using C<EV_STANDALONE=1> and providing your config in	2942	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2301	whatever way you want, you can also C<m4_include([libev.m4])> in your	2943	whatever way you want, you can also C<m4_include([libev.m4])> in your
2302	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2944	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2303	include F<config.h> and configure itself accordingly.	2945	include F<config.h> and configure itself accordingly.
2304		2946
2305	For this of course you need the m4 file:	2947	For this of course you need the m4 file:
2306		2948
2307	libev.m4	2949	libev.m4
2308		2950
2309	=head2 PREPROCESSOR SYMBOLS/MACROS	2951	=head2 PREPROCESSOR SYMBOLS/MACROS
2310		2952
2311	Libev can be configured via a variety of preprocessor symbols you have to define	2953	Libev can be configured via a variety of preprocessor symbols you have to
2312	before including any of its files. The default is not to build for multiplicity	2954	define before including any of its files. The default in the absence of
2313	and only include the select backend.	2955	autoconf is documented for every option.
2314		2956
2315	=over 4	2957	=over 4
2316		2958
2317	=item EV_STANDALONE	2959	=item EV_STANDALONE
2318		2960
…		…
2323	F<event.h> that are not directly supported by the libev core alone.	2965	F<event.h> that are not directly supported by the libev core alone.
2324		2966
2325	=item EV_USE_MONOTONIC	2967	=item EV_USE_MONOTONIC
2326		2968
2327	If defined to be C<1>, libev will try to detect the availability of the	2969	If defined to be C<1>, libev will try to detect the availability of the
2328	monotonic clock option at both compiletime and runtime. Otherwise no use	2970	monotonic clock option at both compile time and runtime. Otherwise no use
2329	of the monotonic clock option will be attempted. If you enable this, you	2971	of the monotonic clock option will be attempted. If you enable this, you
2330	usually have to link against librt or something similar. Enabling it when	2972	usually have to link against librt or something similar. Enabling it when
2331	the functionality isn't available is safe, though, although you have	2973	the functionality isn't available is safe, though, although you have
2332	to make sure you link against any libraries where the C<clock_gettime>	2974	to make sure you link against any libraries where the C<clock_gettime>
2333	function is hiding in (often F<-lrt>).	2975	function is hiding in (often F<-lrt>).
2334		2976
2335	=item EV_USE_REALTIME	2977	=item EV_USE_REALTIME
2336		2978
2337	If defined to be C<1>, libev will try to detect the availability of the	2979	If defined to be C<1>, libev will try to detect the availability of the
2338	realtime clock option at compiletime (and assume its availability at	2980	real-time clock option at compile time (and assume its availability at
2339	runtime if successful). Otherwise no use of the realtime clock option will	2981	runtime if successful). Otherwise no use of the real-time clock option will
2340	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2982	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2341	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2983	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2342	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2984	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2343		2985
2344	=item EV_USE_NANOSLEEP	2986	=item EV_USE_NANOSLEEP
2345		2987
2346	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2988	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2347	and will use it for delays. Otherwise it will use C<select ()>.	2989	and will use it for delays. Otherwise it will use C<select ()>.
2348		2990
		2991	=item EV_USE_EVENTFD
		2992
		2993	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2994	available and will probe for kernel support at runtime. This will improve
		2995	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2996	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2997	2.7 or newer, otherwise disabled.
		2998
2349	=item EV_USE_SELECT	2999	=item EV_USE_SELECT
2350		3000
2351	If undefined or defined to be C<1>, libev will compile in support for the	3001	If undefined or defined to be C<1>, libev will compile in support for the
2352	C<select>(2) backend. No attempt at autodetection will be done: if no	3002	C<select>(2) backend. No attempt at auto-detection will be done: if no
2353	other method takes over, select will be it. Otherwise the select backend	3003	other method takes over, select will be it. Otherwise the select backend
2354	will not be compiled in.	3004	will not be compiled in.
2355		3005
2356	=item EV_SELECT_USE_FD_SET	3006	=item EV_SELECT_USE_FD_SET
2357		3007
2358	If defined to C<1>, then the select backend will use the system C<fd_set>	3008	If defined to C<1>, then the select backend will use the system C<fd_set>
2359	structure. This is useful if libev doesn't compile due to a missing	3009	structure. This is useful if libev doesn't compile due to a missing
2360	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3010	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2361	exotic systems. This usually limits the range of file descriptors to some	3011	exotic systems. This usually limits the range of file descriptors to some
2362	low limit such as 1024 or might have other limitations (winsocket only	3012	low limit such as 1024 or might have other limitations (winsocket only
2363	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2364	influence the size of the C<fd_set> used.	3014	influence the size of the C<fd_set> used.
2365		3015
…		…
2371	be used is the winsock select). This means that it will call	3021	be used is the winsock select). This means that it will call
2372	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3022	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2373	it is assumed that all these functions actually work on fds, even	3023	it is assumed that all these functions actually work on fds, even
2374	on win32. Should not be defined on non-win32 platforms.	3024	on win32. Should not be defined on non-win32 platforms.
2375		3025
		3026	=item EV_FD_TO_WIN32_HANDLE
		3027
		3028	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3029	file descriptors to socket handles. When not defining this symbol (the
		3030	default), then libev will call C<_get_osfhandle>, which is usually
		3031	correct. In some cases, programs use their own file descriptor management,
		3032	in which case they can provide this function to map fds to socket handles.
		3033
2376	=item EV_USE_POLL	3034	=item EV_USE_POLL
2377		3035
2378	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3036	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2379	backend. Otherwise it will be enabled on non-win32 platforms. It	3037	backend. Otherwise it will be enabled on non-win32 platforms. It
2380	takes precedence over select.	3038	takes precedence over select.
2381		3039
2382	=item EV_USE_EPOLL	3040	=item EV_USE_EPOLL
2383		3041
2384	If defined to be C<1>, libev will compile in support for the Linux	3042	If defined to be C<1>, libev will compile in support for the Linux
2385	C<epoll>(7) backend. Its availability will be detected at runtime,	3043	C<epoll>(7) backend. Its availability will be detected at runtime,
2386	otherwise another method will be used as fallback. This is the	3044	otherwise another method will be used as fallback. This is the preferred
2387	preferred backend for GNU/Linux systems.	3045	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3046	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2388		3047
2389	=item EV_USE_KQUEUE	3048	=item EV_USE_KQUEUE
2390		3049
2391	If defined to be C<1>, libev will compile in support for the BSD style	3050	If defined to be C<1>, libev will compile in support for the BSD style
2392	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3051	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2405	otherwise another method will be used as fallback. This is the preferred	3064	otherwise another method will be used as fallback. This is the preferred
2406	backend for Solaris 10 systems.	3065	backend for Solaris 10 systems.
2407		3066
2408	=item EV_USE_DEVPOLL	3067	=item EV_USE_DEVPOLL
2409		3068
2410	reserved for future expansion, works like the USE symbols above.	3069	Reserved for future expansion, works like the USE symbols above.
2411		3070
2412	=item EV_USE_INOTIFY	3071	=item EV_USE_INOTIFY
2413		3072
2414	If defined to be C<1>, libev will compile in support for the Linux inotify	3073	If defined to be C<1>, libev will compile in support for the Linux inotify
2415	interface to speed up C<ev_stat> watchers. Its actual availability will	3074	interface to speed up C<ev_stat> watchers. Its actual availability will
2416	be detected at runtime.	3075	be detected at runtime. If undefined, it will be enabled if the headers
		3076	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3077
		3078	=item EV_ATOMIC_T
		3079
		3080	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3081	access is atomic with respect to other threads or signal contexts. No such
		3082	type is easily found in the C language, so you can provide your own type
		3083	that you know is safe for your purposes. It is used both for signal handler "locking"
		3084	as well as for signal and thread safety in C<ev_async> watchers.
		3085
		3086	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3087	(from F<signal.h>), which is usually good enough on most platforms.
2417		3088
2418	=item EV_H	3089	=item EV_H
2419		3090
2420	The name of the F<ev.h> header file used to include it. The default if	3091	The name of the F<ev.h> header file used to include it. The default if
2421	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3092	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2422	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3093	used to virtually rename the F<ev.h> header file in case of conflicts.
2423		3094
2424	=item EV_CONFIG_H	3095	=item EV_CONFIG_H
2425		3096
2426	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3097	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2427	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3098	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2428	C<EV_H>, above.	3099	C<EV_H>, above.
2429		3100
2430	=item EV_EVENT_H	3101	=item EV_EVENT_H
2431		3102
2432	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3103	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2433	of how the F<event.h> header can be found.	3104	of how the F<event.h> header can be found, the default is C<"event.h">.
2434		3105
2435	=item EV_PROTOTYPES	3106	=item EV_PROTOTYPES
2436		3107
2437	If defined to be C<0>, then F<ev.h> will not define any function	3108	If defined to be C<0>, then F<ev.h> will not define any function
2438	prototypes, but still define all the structs and other symbols. This is	3109	prototypes, but still define all the structs and other symbols. This is
…		…
2459	When doing priority-based operations, libev usually has to linearly search	3130	When doing priority-based operations, libev usually has to linearly search
2460	all the priorities, so having many of them (hundreds) uses a lot of space	3131	all the priorities, so having many of them (hundreds) uses a lot of space
2461	and time, so using the defaults of five priorities (-2 .. +2) is usually	3132	and time, so using the defaults of five priorities (-2 .. +2) is usually
2462	fine.	3133	fine.
2463		3134
2464	If your embedding app does not need any priorities, defining these both to	3135	If your embedding application does not need any priorities, defining these
2465	C<0> will save some memory and cpu.	3136	both to C<0> will save some memory and CPU.
2466		3137
2467	=item EV_PERIODIC_ENABLE	3138	=item EV_PERIODIC_ENABLE
2468		3139
2469	If undefined or defined to be C<1>, then periodic timers are supported. If	3140	If undefined or defined to be C<1>, then periodic timers are supported. If
2470	defined to be C<0>, then they are not. Disabling them saves a few kB of	3141	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2477	code.	3148	code.
2478		3149
2479	=item EV_EMBED_ENABLE	3150	=item EV_EMBED_ENABLE
2480		3151
2481	If undefined or defined to be C<1>, then embed watchers are supported. If	3152	If undefined or defined to be C<1>, then embed watchers are supported. If
2482	defined to be C<0>, then they are not.	3153	defined to be C<0>, then they are not. Embed watchers rely on most other
		3154	watcher types, which therefore must not be disabled.
2483		3155
2484	=item EV_STAT_ENABLE	3156	=item EV_STAT_ENABLE
2485		3157
2486	If undefined or defined to be C<1>, then stat watchers are supported. If	3158	If undefined or defined to be C<1>, then stat watchers are supported. If
2487	defined to be C<0>, then they are not.	3159	defined to be C<0>, then they are not.
…		…
2489	=item EV_FORK_ENABLE	3161	=item EV_FORK_ENABLE
2490		3162
2491	If undefined or defined to be C<1>, then fork watchers are supported. If	3163	If undefined or defined to be C<1>, then fork watchers are supported. If
2492	defined to be C<0>, then they are not.	3164	defined to be C<0>, then they are not.
2493		3165
		3166	=item EV_ASYNC_ENABLE
		3167
		3168	If undefined or defined to be C<1>, then async watchers are supported. If
		3169	defined to be C<0>, then they are not.
		3170
2494	=item EV_MINIMAL	3171	=item EV_MINIMAL
2495		3172
2496	If you need to shave off some kilobytes of code at the expense of some	3173	If you need to shave off some kilobytes of code at the expense of some
2497	speed, define this symbol to C<1>. Currently only used for gcc to override	3174	speed, define this symbol to C<1>. Currently this is used to override some
2498	some inlining decisions, saves roughly 30% codesize of amd64.	3175	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3176	much smaller 2-heap for timer management over the default 4-heap.
2499		3177
2500	=item EV_PID_HASHSIZE	3178	=item EV_PID_HASHSIZE
2501		3179
2502	C<ev_child> watchers use a small hash table to distribute workload by	3180	C<ev_child> watchers use a small hash table to distribute workload by
2503	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3181	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2504	than enough. If you need to manage thousands of children you might want to	3182	than enough. If you need to manage thousands of children you might want to
2505	increase this value (I<must> be a power of two).	3183	increase this value (I<must> be a power of two).
2506		3184
2507	=item EV_INOTIFY_HASHSIZE	3185	=item EV_INOTIFY_HASHSIZE
2508		3186
2509	C<ev_staz> watchers use a small hash table to distribute workload by	3187	C<ev_stat> watchers use a small hash table to distribute workload by
2510	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3188	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2511	usually more than enough. If you need to manage thousands of C<ev_stat>	3189	usually more than enough. If you need to manage thousands of C<ev_stat>
2512	watchers you might want to increase this value (I<must> be a power of	3190	watchers you might want to increase this value (I<must> be a power of
2513	two).	3191	two).
2514		3192
		3193	=item EV_USE_4HEAP
		3194
		3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3196	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3197	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3198	faster performance with many (thousands) of watchers.
		3199
		3200	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3201	(disabled).
		3202
		3203	=item EV_HEAP_CACHE_AT
		3204
		3205	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3206	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3207	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3208	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3209	but avoids random read accesses on heap changes. This improves performance
		3210	noticeably with many (hundreds) of watchers.
		3211
		3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3213	(disabled).
		3214
		3215	=item EV_VERIFY
		3216
		3217	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3218	be done: If set to C<0>, no internal verification code will be compiled
		3219	in. If set to C<1>, then verification code will be compiled in, but not
		3220	called. If set to C<2>, then the internal verification code will be
		3221	called once per loop, which can slow down libev. If set to C<3>, then the
		3222	verification code will be called very frequently, which will slow down
		3223	libev considerably.
		3224
		3225	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3226	C<0>.
		3227
2515	=item EV_COMMON	3228	=item EV_COMMON
2516		3229
2517	By default, all watchers have a C<void *data> member. By redefining	3230	By default, all watchers have a C<void *data> member. By redefining
2518	this macro to a something else you can include more and other types of	3231	this macro to a something else you can include more and other types of
2519	members. You have to define it each time you include one of the files,	3232	members. You have to define it each time you include one of the files,
2520	though, and it must be identical each time.	3233	though, and it must be identical each time.
2521		3234
2522	For example, the perl EV module uses something like this:	3235	For example, the perl EV module uses something like this:
2523		3236
2524	#define EV_COMMON \	3237	#define EV_COMMON \
2525	SV *self; /* contains this struct */ \	3238	SV *self; /* contains this struct */ \
2526	SV *cb_sv, *fh /* note no trailing ";" */	3239	SV *cb_sv, *fh /* note no trailing ";" */
2527		3240
2528	=item EV_CB_DECLARE (type)	3241	=item EV_CB_DECLARE (type)
2529		3242
2530	=item EV_CB_INVOKE (watcher, revents)	3243	=item EV_CB_INVOKE (watcher, revents)
2531		3244
…		…
2536	definition and a statement, respectively. See the F<ev.h> header file for	3249	definition and a statement, respectively. See the F<ev.h> header file for
2537	their default definitions. One possible use for overriding these is to	3250	their default definitions. One possible use for overriding these is to
2538	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3251	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2539	method calls instead of plain function calls in C++.	3252	method calls instead of plain function calls in C++.
2540		3253
		3254	=back
		3255
2541	=head2 EXPORTED API SYMBOLS	3256	=head2 EXPORTED API SYMBOLS
2542		3257
2543	If you need to re-export the API (e.g. via a dll) and you need a list of	3258	If you need to re-export the API (e.g. via a DLL) and you need a list of
2544	exported symbols, you can use the provided F<Symbol.*> files which list	3259	exported symbols, you can use the provided F<Symbol.*> files which list
2545	all public symbols, one per line:	3260	all public symbols, one per line:
2546		3261
2547	Symbols.ev for libev proper	3262	Symbols.ev for libev proper
2548	Symbols.event for the libevent emulation	3263	Symbols.event for the libevent emulation
2549		3264
2550	This can also be used to rename all public symbols to avoid clashes with	3265	This can also be used to rename all public symbols to avoid clashes with
2551	multiple versions of libev linked together (which is obviously bad in	3266	multiple versions of libev linked together (which is obviously bad in
2552	itself, but sometimes it is inconvinient to avoid this).	3267	itself, but sometimes it is inconvenient to avoid this).
2553		3268
2554	A sed command like this will create wrapper C<#define>'s that you need to	3269	A sed command like this will create wrapper C<#define>'s that you need to
2555	include before including F<ev.h>:	3270	include before including F<ev.h>:
2556		3271
2557	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3272	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2574	file.	3289	file.
2575		3290
2576	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3291	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2577	that everybody includes and which overrides some configure choices:	3292	that everybody includes and which overrides some configure choices:
2578		3293
2579	#define EV_MINIMAL 1	3294	#define EV_MINIMAL 1
2580	#define EV_USE_POLL 0	3295	#define EV_USE_POLL 0
2581	#define EV_MULTIPLICITY 0	3296	#define EV_MULTIPLICITY 0
2582	#define EV_PERIODIC_ENABLE 0	3297	#define EV_PERIODIC_ENABLE 0
2583	#define EV_STAT_ENABLE 0	3298	#define EV_STAT_ENABLE 0
2584	#define EV_FORK_ENABLE 0	3299	#define EV_FORK_ENABLE 0
2585	#define EV_CONFIG_H <config.h>	3300	#define EV_CONFIG_H <config.h>
2586	#define EV_MINPRI 0	3301	#define EV_MINPRI 0
2587	#define EV_MAXPRI 0	3302	#define EV_MAXPRI 0
2588		3303
2589	#include "ev++.h"	3304	#include "ev++.h"
2590		3305
2591	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3306	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2592		3307
2593	#include "ev_cpp.h"	3308	#include "ev_cpp.h"
2594	#include "ev.c"	3309	#include "ev.c"
		3310
		3311
		3312	=head1 THREADS AND COROUTINES
		3313
		3314	=head2 THREADS
		3315
		3316	All libev functions are reentrant and thread-safe unless explicitly
		3317	documented otherwise, but it uses no locking itself. This means that you
		3318	can use as many loops as you want in parallel, as long as there are no
		3319	concurrent calls into any libev function with the same loop parameter
		3320	(C<ev_default_*> calls have an implicit default loop parameter, of
		3321	course): libev guarantees that different event loops share no data
		3322	structures that need any locking.
		3323
		3324	Or to put it differently: calls with different loop parameters can be done
		3325	concurrently from multiple threads, calls with the same loop parameter
		3326	must be done serially (but can be done from different threads, as long as
		3327	only one thread ever is inside a call at any point in time, e.g. by using
		3328	a mutex per loop).
		3329
		3330	Specifically to support threads (and signal handlers), libev implements
		3331	so-called C<ev_async> watchers, which allow some limited form of
		3332	concurrency on the same event loop, namely waking it up "from the
		3333	outside".
		3334
		3335	If you want to know which design (one loop, locking, or multiple loops
		3336	without or something else still) is best for your problem, then I cannot
		3337	help you, but here is some generic advice:
		3338
		3339	=over 4
		3340
		3341	=item * most applications have a main thread: use the default libev loop
		3342	in that thread, or create a separate thread running only the default loop.
		3343
		3344	This helps integrating other libraries or software modules that use libev
		3345	themselves and don't care/know about threading.
		3346
		3347	=item * one loop per thread is usually a good model.
		3348
		3349	Doing this is almost never wrong, sometimes a better-performance model
		3350	exists, but it is always a good start.
		3351
		3352	=item * other models exist, such as the leader/follower pattern, where one
		3353	loop is handed through multiple threads in a kind of round-robin fashion.
		3354
		3355	Choosing a model is hard - look around, learn, know that usually you can do
		3356	better than you currently do :-)
		3357
		3358	=item * often you need to talk to some other thread which blocks in the
		3359	event loop.
		3360
		3361	C<ev_async> watchers can be used to wake them up from other threads safely
		3362	(or from signal contexts...).
		3363
		3364	An example use would be to communicate signals or other events that only
		3365	work in the default loop by registering the signal watcher with the
		3366	default loop and triggering an C<ev_async> watcher from the default loop
		3367	watcher callback into the event loop interested in the signal.
		3368
		3369	=back
		3370
		3371	=head2 COROUTINES
		3372
		3373	Libev is much more accommodating to coroutines ("cooperative threads"):
		3374	libev fully supports nesting calls to it's functions from different
		3375	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3376	different coroutines and switch freely between both coroutines running the
		3377	loop, as long as you don't confuse yourself). The only exception is that
		3378	you must not do this from C<ev_periodic> reschedule callbacks.
		3379
		3380	Care has been taken to ensure that libev does not keep local state inside
		3381	C<ev_loop>, and other calls do not usually allow coroutine switches.
2595		3382
2596		3383
2597	=head1 COMPLEXITIES	3384	=head1 COMPLEXITIES
2598		3385
2599	In this section the complexities of (many of) the algorithms used inside	3386	In this section the complexities of (many of) the algorithms used inside
…		…
2610		3397
2611	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3398	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2612		3399
2613	This means that, when you have a watcher that triggers in one hour and	3400	This means that, when you have a watcher that triggers in one hour and
2614	there are 100 watchers that would trigger before that then inserting will	3401	there are 100 watchers that would trigger before that then inserting will
2615	have to skip those 100 watchers.	3402	have to skip roughly seven (C<ld 100>) of these watchers.
2616		3403
2617	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3404	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2618		3405
2619	That means that for changing a timer costs less than removing/adding them	3406	That means that changing a timer costs less than removing/adding them
2620	as only the relative motion in the event queue has to be paid for.	3407	as only the relative motion in the event queue has to be paid for.
2621		3408
2622	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3409	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2623		3410
2624	These just add the watcher into an array or at the head of a list.	3411	These just add the watcher into an array or at the head of a list.
		3412
2625	=item Stopping check/prepare/idle watchers: O(1)	3413	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2626		3414
2627	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3415	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2628		3416
2629	These watchers are stored in lists then need to be walked to find the	3417	These watchers are stored in lists then need to be walked to find the
2630	correct watcher to remove. The lists are usually short (you don't usually	3418	correct watcher to remove. The lists are usually short (you don't usually
2631	have many watchers waiting for the same fd or signal).	3419	have many watchers waiting for the same fd or signal).
2632		3420
2633	=item Finding the next timer per loop iteration: O(1)	3421	=item Finding the next timer in each loop iteration: O(1)
		3422
		3423	By virtue of using a binary or 4-heap, the next timer is always found at a
		3424	fixed position in the storage array.
2634		3425
2635	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3426	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2636		3427
2637	A change means an I/O watcher gets started or stopped, which requires	3428	A change means an I/O watcher gets started or stopped, which requires
2638	libev to recalculate its status (and possibly tell the kernel).	3429	libev to recalculate its status (and possibly tell the kernel, depending
		3430	on backend and whether C<ev_io_set> was used).
2639		3431
2640	=item Activating one watcher: O(1)	3432	=item Activating one watcher (putting it into the pending state): O(1)
2641		3433
2642	=item Priority handling: O(number_of_priorities)	3434	=item Priority handling: O(number_of_priorities)
2643		3435
2644	Priorities are implemented by allocating some space for each	3436	Priorities are implemented by allocating some space for each
2645	priority. When doing priority-based operations, libev usually has to	3437	priority. When doing priority-based operations, libev usually has to
2646	linearly search all the priorities.	3438	linearly search all the priorities, but starting/stopping and activating
		3439	watchers becomes O(1) with respect to priority handling.
		3440
		3441	=item Sending an ev_async: O(1)
		3442
		3443	=item Processing ev_async_send: O(number_of_async_watchers)
		3444
		3445	=item Processing signals: O(max_signal_number)
		3446
		3447	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3448	calls in the current loop iteration. Checking for async and signal events
		3449	involves iterating over all running async watchers or all signal numbers.
2647		3450
2648	=back	3451	=back
2649		3452
2650		3453
		3454	=head1 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
		3552	=head1 PORTABILITY REQUIREMENTS
		3553
		3554	In addition to a working ISO-C implementation, libev relies on a few
		3555	additional extensions:
		3556
		3557	=over 4
		3558
		3559	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3560	calling conventions regardless of C<ev_watcher_type *>.
		3561
		3562	Libev assumes not only that all watcher pointers have the same internal
		3563	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3564	assumes that the same (machine) code can be used to call any watcher
		3565	callback: The watcher callbacks have different type signatures, but libev
		3566	calls them using an C<ev_watcher *> internally.
		3567
		3568	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3569
		3570	The type C<sig_atomic_t volatile> (or whatever is defined as
		3571	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3572	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3573	believed to be sufficiently portable.
		3574
		3575	=item C<sigprocmask> must work in a threaded environment
		3576
		3577	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3578	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3579	pthread implementations will either allow C<sigprocmask> in the "main
		3580	thread" or will block signals process-wide, both behaviours would
		3581	be compatible with libev. Interaction between C<sigprocmask> and
		3582	C<pthread_sigmask> could complicate things, however.
		3583
		3584	The most portable way to handle signals is to block signals in all threads
		3585	except the initial one, and run the default loop in the initial thread as
		3586	well.
		3587
		3588	=item C<long> must be large enough for common memory allocation sizes
		3589
		3590	To improve portability and simplify using libev, libev uses C<long>
		3591	internally instead of C<size_t> when allocating its data structures. On
		3592	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3593	is still at least 31 bits everywhere, which is enough for hundreds of
		3594	millions of watchers.
		3595
		3596	=item C<double> must hold a time value in seconds with enough accuracy
		3597
		3598	The type C<double> is used to represent timestamps. It is required to
		3599	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3600	enough for at least into the year 4000. This requirement is fulfilled by
		3601	implementations implementing IEEE 754 (basically all existing ones).
		3602
		3603	=back
		3604
		3605	If you know of other additional requirements drop me a note.
		3606
		3607
		3608	=head1 COMPILER WARNINGS
		3609
		3610	Depending on your compiler and compiler settings, you might get no or a
		3611	lot of warnings when compiling libev code. Some people are apparently
		3612	scared by this.
		3613
		3614	However, these are unavoidable for many reasons. For one, each compiler
		3615	has different warnings, and each user has different tastes regarding
		3616	warning options. "Warn-free" code therefore cannot be a goal except when
		3617	targeting a specific compiler and compiler-version.
		3618
		3619	Another reason is that some compiler warnings require elaborate
		3620	workarounds, or other changes to the code that make it less clear and less
		3621	maintainable.
		3622
		3623	And of course, some compiler warnings are just plain stupid, or simply
		3624	wrong (because they don't actually warn about the condition their message
		3625	seems to warn about).
		3626
		3627	While libev is written to generate as few warnings as possible,
		3628	"warn-free" code is not a goal, and it is recommended not to build libev
		3629	with any compiler warnings enabled unless you are prepared to cope with
		3630	them (e.g. by ignoring them). Remember that warnings are just that:
		3631	warnings, not errors, or proof of bugs.
		3632
		3633
		3634	=head1 VALGRIND
		3635
		3636	Valgrind has a special section here because it is a popular tool that is
		3637	highly useful, but valgrind reports are very hard to interpret.
		3638
		3639	If you think you found a bug (memory leak, uninitialised data access etc.)
		3640	in libev, then check twice: If valgrind reports something like:
		3641
		3642	==2274== definitely lost: 0 bytes in 0 blocks.
		3643	==2274== possibly lost: 0 bytes in 0 blocks.
		3644	==2274== still reachable: 256 bytes in 1 blocks.
		3645
		3646	Then there is no memory leak. Similarly, under some circumstances,
		3647	valgrind might report kernel bugs as if it were a bug in libev, or it
		3648	might be confused (it is a very good tool, but only a tool).
		3649
		3650	If you are unsure about something, feel free to contact the mailing list
		3651	with the full valgrind report and an explanation on why you think this is
		3652	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3653	no bug" answer and take the chance of learning how to interpret valgrind
		3654	properly.
		3655
		3656	If you need, for some reason, empty reports from valgrind for your project
		3657	I suggest using suppression lists.
		3658
		3659
2651	=head1 AUTHOR	3660	=head1 AUTHOR
2652		3661
2653	Marc Lehmann <libev@schmorp.de>.	3662	Marc Lehmann <libev@schmorp.de>.
2654		3663

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