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Revision 1.97 by root, Sat Dec 22 05:48:02 2007 UTC vs.
Revision 1.165 by root, Sun Jun 1 01:13:59 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
104	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
106		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
…		…
119		155
120	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
121		157
122	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
123	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
124	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
125		161
126	=item int ev_version_major ()	162	=item int ev_version_major ()
127		163
128	=item int ev_version_minor ()	164	=item int ev_version_minor ()
129		165
…		…
142	not a problem.	178	not a problem.
143		179
144	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
145	version.	181	version.
146		182
147	assert (("libev version mismatch",	183	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
150		186
151	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
152		188
153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
154	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	192	a description of the set values.
157		193
158	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
159	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
160		196
161	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
163		199
164	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
165		201
166	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
167	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
168	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
169	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
170	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
171	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
172		208
173	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
174		210
…		…
181	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
182		218
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
184		220
185	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
187	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
188	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
190	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
191		230
192	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
193	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
194	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
195		234
196	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	236	retries (example requires a standards-compliant C<realloc>).
198		237
199	static void *	238	static void *
200	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
201	{	240	{
202	for (;;)	241	for (;;)
…		…
213	...	252	...
214	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
215		254
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
217		256
218	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
219	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
220	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
221	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
222	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
223	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
224	(such as abort).	263	(such as abort).
225		264
226	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
241		280
242	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
243	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
244	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
245
246	If you use threads, a common model is to run the default event loop
247	in your main thread (or in a separate thread) and for each thread you
248	create, you also create another event loop. Libev itself does no locking
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252		284
253	=over 4	285	=over 4
254		286
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		288
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		293
262	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
263	function.	295	function.
264		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
265	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		310
268	The following flags are supported:	311	The following flags are supported:
269		312
…		…
274	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
275	thing, believe me).	318	thing, believe me).
276		319
277	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
278		321
279	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
280	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
282	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
283	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
284	around bugs.	327	around bugs.
…		…
290	enabling this flag.	333	enabling this flag.
291		334
292	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
293	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
294	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
295	Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
296	without a syscall and thus I<very> fast, but my Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
298		341
299	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
300	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
301	flag.	344	flag.
302		345
303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
304	environment variable.	347	environment variable.
305		348
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		350
308	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
309	libev tries to roll its own fd_set with no limits on the number of fds,	352	libev tries to roll its own fd_set with no limits on the number of fds,
310	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
311	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
312	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
313		363
314	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
315		365
316	And this is your standard poll(2) backend. It's more complicated than	366	And this is your standard poll(2) backend. It's more complicated
317	select, but handles sparse fds better and has no artificial limit on the	367	than select, but handles sparse fds better and has no artificial
318	number of fds you can use (except it will slow down considerably with a	368	limit on the number of fds you can use (except it will slow down
319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	369	considerably with a lot of inactive fds). It scales similarly to select,
		370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		371	performance tips.
320		372
321	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
322		374
323	For few fds, this backend is a bit little slower than poll and select,	375	For few fds, this backend is a bit little slower than poll and select,
324	but it scales phenomenally better. While poll and select usually scale	376	but it scales phenomenally better. While poll and select usually scale
325	like O(total_fds) where n is the total number of fds (or the highest fd),	377	like O(total_fds) where n is the total number of fds (or the highest fd),
326	epoll scales either O(1) or O(active_fds). The epoll design has a number	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
327	of shortcomings, such as silently dropping events in some hard-to-detect	379	of shortcomings, such as silently dropping events in some hard-to-detect
328	cases and rewiring a syscall per fd change, no fork support and bad	380	cases and requiring a system call per fd change, no fork support and bad
329	support for dup:	381	support for dup.
330		382
331	While stopping, setting and starting an I/O watcher in the same iteration	383	While stopping, setting and starting an I/O watcher in the same iteration
332	will result in some caching, there is still a syscall per such incident	384	will result in some caching, there is still a system call per such incident
333	(because the fd could point to a different file description now), so its	385	(because the fd could point to a different file description now), so its
334	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
335	very well if you register events for both fds.	387	very well if you register events for both fds.
336		388
337	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
338	need to use non-blocking I/O or other means to avoid blocking when no data	390	need to use non-blocking I/O or other means to avoid blocking when no data
339	(or space) is available.	391	(or space) is available.
340		392
		393	Best performance from this backend is achieved by not unregistering all
		394	watchers for a file descriptor until it has been closed, if possible, i.e.
		395	keep at least one watcher active per fd at all times.
		396
		397	While nominally embeddable in other event loops, this feature is broken in
		398	all kernel versions tested so far.
		399
341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
342		401
343	Kqueue deserves special mention, as at the time of this writing, it	402	Kqueue deserves special mention, as at the time of this writing, it
344	was broken on I<all> BSDs (usually it doesn't work with anything but	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
345	sockets and pipes, except on Darwin, where of course it's completely	404	with anything but sockets and pipes, except on Darwin, where of course
346	useless. On NetBSD, it seems to work for all the FD types I tested, so it
347	is used by default there). For this reason it's not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
348	unless you explicitly specify it explicitly in the flags (i.e. using	406	unless you explicitly specify it explicitly in the flags (i.e. using
349	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
350	system like NetBSD.	408	system like NetBSD.
351		409
		410	You still can embed kqueue into a normal poll or select backend and use it
		411	only for sockets (after having made sure that sockets work with kqueue on
		412	the target platform). See C<ev_embed> watchers for more info.
		413
352	It scales in the same way as the epoll backend, but the interface to the	414	It scales in the same way as the epoll backend, but the interface to the
353	kernel is more efficient (which says nothing about its actual speed,	415	kernel is more efficient (which says nothing about its actual speed, of
354	of course). While stopping, setting and starting an I/O watcher does	416	course). While stopping, setting and starting an I/O watcher does never
355	never cause an extra syscall as with epoll, it still adds up to two event	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
356	changes per incident, support for C<fork ()> is very bad and it drops fds	418	two event changes per incident, support for C<fork ()> is very bad and it
357	silently in similarly hard-to-detetc cases.	419	drops fds silently in similarly hard-to-detect cases.
		420
		421	This backend usually performs well under most conditions.
		422
		423	While nominally embeddable in other event loops, this doesn't work
		424	everywhere, so you might need to test for this. And since it is broken
		425	almost everywhere, you should only use it when you have a lot of sockets
		426	(for which it usually works), by embedding it into another event loop
		427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		428	sockets.
358		429
359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
360		431
361	This is not implemented yet (and might never be).	432	This is not implemented yet (and might never be, unless you send me an
		433	implementation). According to reports, C</dev/poll> only supports sockets
		434	and is not embeddable, which would limit the usefulness of this backend
		435	immensely.
362		436
363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
364		438
365	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
366	it's really slow, but it still scales very well (O(active_fds)).	440	it's really slow, but it still scales very well (O(active_fds)).
367		441
368	Please note that solaris event ports can deliver a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
369	notifications, so you need to use non-blocking I/O or other means to avoid	443	notifications, so you need to use non-blocking I/O or other means to avoid
370	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
		445
		446	While this backend scales well, it requires one system call per active
		447	file descriptor per loop iteration. For small and medium numbers of file
		448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		449	might perform better.
		450
		451	On the positive side, ignoring the spurious readiness notifications, this
		452	backend actually performed to specification in all tests and is fully
		453	embeddable, which is a rare feat among the OS-specific backends.
371		454
372	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
373		456
374	Try all backends (even potentially broken ones that wouldn't be tried	457	Try all backends (even potentially broken ones that wouldn't be tried
375	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
376	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
377		460
		461	It is definitely not recommended to use this flag.
		462
378	=back	463	=back
379		464
380	If one or more of these are ored into the flags value, then only these	465	If one or more of these are or'ed into the flags value, then only these
381	backends will be tried (in the reverse order as given here). If none are	466	backends will be tried (in the reverse order as listed here). If none are
382	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
383	order of their flag values :)
384		468
385	The most typical usage is like this:	469	The most typical usage is like this:
386		470
387	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
388	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
389		473
390	Restrict libev to the select and poll backends, and do not allow	474	Restrict libev to the select and poll backends, and do not allow
391	environment settings to be taken into account:	475	environment settings to be taken into account:
392		476
393	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
394		478
395	Use whatever libev has to offer, but make sure that kqueue is used if	479	Use whatever libev has to offer, but make sure that kqueue is used if
396	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
397	event loop and only if you know the OS supports your types of fds):	481	event loop and only if you know the OS supports your types of fds):
398		482
399	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
400		484
401	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
402		486
403	Similar to C<ev_default_loop>, but always creates a new event loop that is	487	Similar to C<ev_default_loop>, but always creates a new event loop that is
404	always distinct from the default loop. Unlike the default loop, it cannot	488	always distinct from the default loop. Unlike the default loop, it cannot
405	handle signal and child watchers, and attempts to do so will be greeted by	489	handle signal and child watchers, and attempts to do so will be greeted by
406	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
407		491
		492	Note that this function I<is> thread-safe, and the recommended way to use
		493	libev with threads is indeed to create one loop per thread, and using the
		494	default loop in the "main" or "initial" thread.
		495
408	Example: Try to create a event loop that uses epoll and nothing else.	496	Example: Try to create a event loop that uses epoll and nothing else.
409		497
410	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
411	if (!epoller)	499	if (!epoller)
412	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
413		501
414	=item ev_default_destroy ()	502	=item ev_default_destroy ()
415		503
416	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
417	etc.). None of the active event watchers will be stopped in the normal	505	etc.). None of the active event watchers will be stopped in the normal
418	sense, so e.g. C<ev_is_active> might still return true. It is your	506	sense, so e.g. C<ev_is_active> might still return true. It is your
419	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
420	calling this function, or cope with the fact afterwards (which is usually	508	calling this function, or cope with the fact afterwards (which is usually
421	the easiest thing, you can just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
422	for example).	510	for example).
423		511
424	Note that certain global state, such as signal state, will not be freed by	512	Note that certain global state, such as signal state, will not be freed by
…		…
435	Like C<ev_default_destroy>, but destroys an event loop created by an	523	Like C<ev_default_destroy>, but destroys an event loop created by an
436	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
437		525
438	=item ev_default_fork ()	526	=item ev_default_fork ()
439		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
440	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
441	one. Despite the name, you can call it anytime, but it makes most sense	530	name, you can call it anytime, but it makes most sense after forking, in
442	after forking, in either the parent or child process (or both, but that	531	the child process (or both child and parent, but that again makes little
443	again makes little sense).	532	sense). You I<must> call it in the child before using any of the libev
		533	functions, and it will only take effect at the next C<ev_loop> iteration.
444		534
445	You I<must> call this function in the child process after forking if and	535	On the other hand, you only need to call this function in the child
446	only if you want to use the event library in both processes. If you just	536	process if and only if you want to use the event library in the child. If
447	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
448		538
449	The function itself is quite fast and it's usually not a problem to call	539	The function itself is quite fast and it's usually not a problem to call
450	it just in case after a fork. To make this easy, the function will fit in	540	it just in case after a fork. To make this easy, the function will fit in
451	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
452		542
453	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
454		544
455	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
456	without calling this function, so if you force one of those backends you
457	do not need to care.
458
459	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
460		546
461	Like C<ev_default_fork>, but acts on an event loop created by	547	Like C<ev_default_fork>, but acts on an event loop created by
462	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
463	after fork, and how you do this is entirely your own problem.	549	after fork, and how you do this is entirely your own problem.
		550
		551	=item int ev_is_default_loop (loop)
		552
		553	Returns true when the given loop actually is the default loop, false otherwise.
464		554
465	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
466		556
467	Returns the count of loop iterations for the loop, which is identical to	557	Returns the count of loop iterations for the loop, which is identical to
468	the number of times libev did poll for new events. It starts at C<0> and	558	the number of times libev did poll for new events. It starts at C<0> and
…		…
503	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
504	those events and any outstanding ones, but will not block your process in	594	those events and any outstanding ones, but will not block your process in
505	case there are no events and will return after one iteration of the loop.	595	case there are no events and will return after one iteration of the loop.
506		596
507	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
508	neccessary) and will handle those and any outstanding ones. It will block	598	necessary) and will handle those and any outstanding ones. It will block
509	your process until at least one new event arrives, and will return after	599	your process until at least one new event arrives, and will return after
510	one iteration of the loop. This is useful if you are waiting for some	600	one iteration of the loop. This is useful if you are waiting for some
511	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
512	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
513	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
514		604
515	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
516		606
517	- Before the first iteration, call any pending watchers.	607	- Before the first iteration, call any pending watchers.
518	* If there are no active watchers (reference count is zero), return.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
519	- Queue all prepare watchers and then call all outstanding watchers.	609	- If a fork was detected, queue and call all fork watchers.
		610	- Queue and call all prepare watchers.
520	- If we have been forked, recreate the kernel state.	611	- If we have been forked, recreate the kernel state.
521	- Update the kernel state with all outstanding changes.	612	- Update the kernel state with all outstanding changes.
522	- Update the "event loop time".	613	- Update the "event loop time".
523	- Calculate for how long to block.	614	- Calculate for how long to sleep or block, if at all
		615	(active idle watchers, EVLOOP_NONBLOCK or not having
		616	any active watchers at all will result in not sleeping).
		617	- Sleep if the I/O and timer collect interval say so.
524	- Block the process, waiting for any events.	618	- Block the process, waiting for any events.
525	- Queue all outstanding I/O (fd) events.	619	- Queue all outstanding I/O (fd) events.
526	- Update the "event loop time" and do time jump handling.	620	- Update the "event loop time" and do time jump handling.
527	- Queue all outstanding timers.	621	- Queue all outstanding timers.
528	- Queue all outstanding periodics.	622	- Queue all outstanding periodics.
529	- If no events are pending now, queue all idle watchers.	623	- If no events are pending now, queue all idle watchers.
530	- Queue all check watchers.	624	- Queue all check watchers.
531	- Call all queued watchers in reverse order (i.e. check watchers first).	625	- Call all queued watchers in reverse order (i.e. check watchers first).
532	Signals and child watchers are implemented as I/O watchers, and will	626	Signals and child watchers are implemented as I/O watchers, and will
533	be handled here by queueing them when their watcher gets executed.	627	be handled here by queueing them when their watcher gets executed.
534	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
535	were used, return, otherwise continue with step *.	629	were used, or there are no active watchers, return, otherwise
		630	continue with step *.
536		631
537	Example: Queue some jobs and then loop until no events are outsanding	632	Example: Queue some jobs and then loop until no events are outstanding
538	anymore.	633	anymore.
539		634
540	... queue jobs here, make sure they register event watchers as long	635	... 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..)	636	... as they still have work to do (even an idle watcher will do..)
542	ev_loop (my_loop, 0);	637	ev_loop (my_loop, 0);
…		…
546		641
547	Can be used to make a call to C<ev_loop> return early (but only after it	642	Can be used to make a call to C<ev_loop> return early (but only after it
548	has processed all outstanding events). The C<how> argument must be either	643	has processed all outstanding events). The C<how> argument must be either
549	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
550	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		646
		647	This "unloop state" will be cleared when entering C<ev_loop> again.
551		648
552	=item ev_ref (loop)	649	=item ev_ref (loop)
553		650
554	=item ev_unref (loop)	651	=item ev_unref (loop)
555		652
…		…
560	returning, ev_unref() after starting, and ev_ref() before stopping it. For	657	returning, ev_unref() after starting, and ev_ref() before stopping it. For
561	example, libev itself uses this for its internal signal pipe: It is not	658	example, libev itself uses this for its internal signal pipe: It is not
562	visible to the libev user and should not keep C<ev_loop> from exiting if	659	visible to the libev user and should not keep C<ev_loop> from exiting if
563	no event watchers registered by it are active. It is also an excellent	660	no event watchers registered by it are active. It is also an excellent
564	way to do this for generic recurring timers or from within third-party	661	way to do this for generic recurring timers or from within third-party
565	libraries. Just remember to I<unref after start> and I<ref before stop>.	662	libraries. Just remember to I<unref after start> and I<ref before stop>
		663	(but only if the watcher wasn't active before, or was active before,
		664	respectively).
566		665
567	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
568	running when nothing else is active.	667	running when nothing else is active.
569		668
570	struct ev_signal exitsig;	669	struct ev_signal exitsig;
571	ev_signal_init (&exitsig, sig_cb, SIGINT);	670	ev_signal_init (&exitsig, sig_cb, SIGINT);
572	ev_signal_start (loop, &exitsig);	671	ev_signal_start (loop, &exitsig);
573	evf_unref (loop);	672	evf_unref (loop);
574		673
575	Example: For some weird reason, unregister the above signal handler again.	674	Example: For some weird reason, unregister the above signal handler again.
576		675
577	ev_ref (loop);	676	ev_ref (loop);
578	ev_signal_stop (loop, &exitsig);	677	ev_signal_stop (loop, &exitsig);
579		678
580	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
581		680
582	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
583		682
…		…
596	overhead for the actual polling but can deliver many events at once.	695	overhead for the actual polling but can deliver many events at once.
597		696
598	By setting a higher I<io collect interval> you allow libev to spend more	697	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,	698	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	699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
601	C<ev_timer>) will be not affected.	700	C<ev_timer>) will be not affected. Setting this to a non-null value will
		701	introduce an additional C<ev_sleep ()> call into most loop iterations.
602		702
603	Likewise, by setting a higher I<timeout collect interval> you allow libev	703	Likewise, by setting a higher I<timeout collect interval> you allow libev
604	to spend more time collecting timeouts, at the expense of increased	704	to spend more time collecting timeouts, at the expense of increased
605	latency (the watcher callback will be called later). C<ev_io> watchers	705	latency (the watcher callback will be called later). C<ev_io> watchers
606	will not be affected.	706	will not be affected. Setting this to a non-null value will not introduce
		707	any overhead in libev.
607		708
608	Many programs can usually benefit by setting the io collect interval to	709	Many (busy) programs can usually benefit by setting the I/O collect
609	a value near C<0.1> or so, which is often enough for interactive servers	710	interval to a value near C<0.1> or so, which is often enough for
610	(of course not for games), likewise for timeouts. It usually doesn't make	711	interactive servers (of course not for games), likewise for timeouts. It
611	much sense to set it to a lower value than C<0.01>, as this approsaches	712	usually doesn't make much sense to set it to a lower value than C<0.01>,
612	the timing granularity of most systems.	713	as this approaches the timing granularity of most systems.
		714
		715	=item ev_loop_verify (loop)
		716
		717	This function only does something when C<EV_VERIFY> support has been
		718	compiled in. It tries to go through all internal structures and checks
		719	them for validity. If anything is found to be inconsistent, it will print
		720	an error message to standard error and call C<abort ()>.
		721
		722	This can be used to catch bugs inside libev itself: under normal
		723	circumstances, this function will never abort as of course libev keeps its
		724	data structures consistent.
613		725
614	=back	726	=back
615		727
616		728
617	=head1 ANATOMY OF A WATCHER	729	=head1 ANATOMY OF A WATCHER
618		730
619	A watcher is a structure that you create and register to record your	731	A watcher is a structure that you create and register to record your
620	interest in some event. For instance, if you want to wait for STDIN to	732	interest in some event. For instance, if you want to wait for STDIN to
621	become readable, you would create an C<ev_io> watcher for that:	733	become readable, you would create an C<ev_io> watcher for that:
622		734
623	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
624	{	736	{
625	ev_io_stop (w);	737	ev_io_stop (w);
626	ev_unloop (loop, EVUNLOOP_ALL);	738	ev_unloop (loop, EVUNLOOP_ALL);
627	}	739	}
628		740
629	struct ev_loop *loop = ev_default_loop (0);	741	struct ev_loop *loop = ev_default_loop (0);
630	struct ev_io stdin_watcher;	742	struct ev_io stdin_watcher;
631	ev_init (&stdin_watcher, my_cb);	743	ev_init (&stdin_watcher, my_cb);
632	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
633	ev_io_start (loop, &stdin_watcher);	745	ev_io_start (loop, &stdin_watcher);
634	ev_loop (loop, 0);	746	ev_loop (loop, 0);
635		747
636	As you can see, you are responsible for allocating the memory for your	748	As you can see, you are responsible for allocating the memory for your
637	watcher structures (and it is usually a bad idea to do this on the stack,	749	watcher structures (and it is usually a bad idea to do this on the stack,
638	although this can sometimes be quite valid).	750	although this can sometimes be quite valid).
639		751
640	Each watcher structure must be initialised by a call to C<ev_init	752	Each watcher structure must be initialised by a call to C<ev_init
641	(watcher *, callback)>, which expects a callback to be provided. This	753	(watcher *, callback)>, which expects a callback to be provided. This
642	callback gets invoked each time the event occurs (or, in the case of io	754	callback gets invoked each time the event occurs (or, in the case of I/O
643	watchers, each time the event loop detects that the file descriptor given	755	watchers, each time the event loop detects that the file descriptor given
644	is readable and/or writable).	756	is readable and/or writable).
645		757
646	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
647	with arguments specific to this watcher type. There is also a macro	759	with arguments specific to this watcher type. There is also a macro
…		…
717	=item C<EV_FORK>	829	=item C<EV_FORK>
718		830
719	The event loop has been resumed in the child process after fork (see	831	The event loop has been resumed in the child process after fork (see
720	C<ev_fork>).	832	C<ev_fork>).
721		833
		834	=item C<EV_ASYNC>
		835
		836	The given async watcher has been asynchronously notified (see C<ev_async>).
		837
722	=item C<EV_ERROR>	838	=item C<EV_ERROR>
723		839
724	An unspecified error has occured, the watcher has been stopped. This might	840	An unspecified error has occurred, the watcher has been stopped. This might
725	happen because the watcher could not be properly started because libev	841	happen because the watcher could not be properly started because libev
726	ran out of memory, a file descriptor was found to be closed or any other	842	ran out of memory, a file descriptor was found to be closed or any other
727	problem. You best act on it by reporting the problem and somehow coping	843	problem. You best act on it by reporting the problem and somehow coping
728	with the watcher being stopped.	844	with the watcher being stopped.
729		845
730	Libev will usually signal a few "dummy" events together with an error,	846	Libev will usually signal a few "dummy" events together with an error,
731	for example it might indicate that a fd is readable or writable, and if	847	for example it might indicate that a fd is readable or writable, and if
732	your callbacks is well-written it can just attempt the operation and cope	848	your callbacks is well-written it can just attempt the operation and cope
733	with the error from read() or write(). This will not work in multithreaded	849	with the error from read() or write(). This will not work in multi-threaded
734	programs, though, so beware.	850	programs, though, so beware.
735		851
736	=back	852	=back
737		853
738	=head2 GENERIC WATCHER FUNCTIONS	854	=head2 GENERIC WATCHER FUNCTIONS
…		…
768	Although some watcher types do not have type-specific arguments	884	Although some watcher types do not have type-specific arguments
769	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
770		886
771	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
772		888
773	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
774	calls into a single call. This is the most convinient method to initialise	890	calls into a single call. This is the most convenient method to initialise
775	a watcher. The same limitations apply, of course.	891	a watcher. The same limitations apply, of course.
776		892
777	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
778		894
779	Starts (activates) the given watcher. Only active watchers will receive	895	Starts (activates) the given watcher. Only active watchers will receive
…		…
862	to associate arbitrary data with your watcher. If you need more data and	978	to associate arbitrary data with your watcher. If you need more data and
863	don't want to allocate memory and store a pointer to it in that data	979	don't want to allocate memory and store a pointer to it in that data
864	member, you can also "subclass" the watcher type and provide your own	980	member, you can also "subclass" the watcher type and provide your own
865	data:	981	data:
866		982
867	struct my_io	983	struct my_io
868	{	984	{
869	struct ev_io io;	985	struct ev_io io;
870	int otherfd;	986	int otherfd;
871	void *somedata;	987	void *somedata;
872	struct whatever *mostinteresting;	988	struct whatever *mostinteresting;
873	}	989	}
874		990
875	And since your callback will be called with a pointer to the watcher, you	991	And since your callback will be called with a pointer to the watcher, you
876	can cast it back to your own type:	992	can cast it back to your own type:
877		993
878	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
879	{	995	{
880	struct my_io *w = (struct my_io *)w_;	996	struct my_io *w = (struct my_io *)w_;
881	...	997	...
882	}	998	}
883		999
884	More interesting and less C-conformant ways of casting your callback type	1000	More interesting and less C-conformant ways of casting your callback type
885	instead have been omitted.	1001	instead have been omitted.
886		1002
887	Another common scenario is having some data structure with multiple	1003	Another common scenario is having some data structure with multiple
888	watchers:	1004	watchers:
889		1005
890	struct my_biggy	1006	struct my_biggy
891	{	1007	{
892	int some_data;	1008	int some_data;
893	ev_timer t1;	1009	ev_timer t1;
894	ev_timer t2;	1010	ev_timer t2;
895	}	1011	}
896		1012
897	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,
898	you need to use C<offsetof>:	1014	you need to use C<offsetof>:
899		1015
900	#include <stddef.h>	1016	#include <stddef.h>
901		1017
902	static void	1018	static void
903	t1_cb (EV_P_ struct ev_timer *w, int revents)	1019	t1_cb (EV_P_ struct ev_timer *w, int revents)
904	{	1020	{
905	struct my_biggy big = (struct my_biggy *	1021	struct my_biggy big = (struct my_biggy *
906	(((char *)w) - offsetof (struct my_biggy, t1));	1022	(((char *)w) - offsetof (struct my_biggy, t1));
907	}	1023	}
908		1024
909	static void	1025	static void
910	t2_cb (EV_P_ struct ev_timer *w, int revents)	1026	t2_cb (EV_P_ struct ev_timer *w, int revents)
911	{	1027	{
912	struct my_biggy big = (struct my_biggy *	1028	struct my_biggy big = (struct my_biggy *
913	(((char *)w) - offsetof (struct my_biggy, t2));	1029	(((char *)w) - offsetof (struct my_biggy, t2));
914	}	1030	}
915		1031
916		1032
917	=head1 WATCHER TYPES	1033	=head1 WATCHER TYPES
918		1034
919	This section describes each watcher in detail, but will not repeat	1035	This section describes each watcher in detail, but will not repeat
…		…
943	In general you can register as many read and/or write event watchers per	1059	In general you can register as many read and/or write event watchers per
944	fd as you want (as long as you don't confuse yourself). Setting all file	1060	fd as you want (as long as you don't confuse yourself). Setting all file
945	descriptors to non-blocking mode is also usually a good idea (but not	1061	descriptors to non-blocking mode is also usually a good idea (but not
946	required if you know what you are doing).	1062	required if you know what you are doing).
947		1063
948	You have to be careful with dup'ed file descriptors, though. Some backends
949	(the linux epoll backend is a notable example) cannot handle dup'ed file
950	descriptors correctly if you register interest in two or more fds pointing
951	to the same underlying file/socket/etc. description (that is, they share
952	the same underlying "file open").
953
954	If you must do this, then force the use of a known-to-be-good backend	1064	If you must do this, then force the use of a known-to-be-good backend
955	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
956	C<EVBACKEND_POLL>).	1066	C<EVBACKEND_POLL>).
957		1067
958	Another thing you have to watch out for is that it is quite easy to	1068	Another thing you have to watch out for is that it is quite easy to
959	receive "spurious" readyness notifications, that is your callback might	1069	receive "spurious" readiness notifications, that is your callback might
960	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
961	because there is no data. Not only are some backends known to create a	1071	because there is no data. Not only are some backends known to create a
962	lot of those (for example solaris ports), it is very easy to get into	1072	lot of those (for example Solaris ports), it is very easy to get into
963	this situation even with a relatively standard program structure. Thus	1073	this situation even with a relatively standard program structure. Thus
964	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning
965	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.
966		1076
967	If you cannot run the fd in non-blocking mode (for example you should not	1077	If you cannot run the fd in non-blocking mode (for example you should not
968	play around with an Xlib connection), then you have to seperately re-test	1078	play around with an Xlib connection), then you have to separately re-test
969	whether a file descriptor is really ready with a known-to-be good interface	1079	whether a file descriptor is really ready with a known-to-be good interface
970	such as poll (fortunately in our Xlib example, Xlib already does this on	1080	such as poll (fortunately in our Xlib example, Xlib already does this on
971	its own, so its quite safe to use).	1081	its own, so its quite safe to use).
972		1082
973	=head3 The special problem of disappearing file descriptors	1083	=head3 The special problem of disappearing file descriptors
…		…
992	optimisations to libev.	1102	optimisations to libev.
993		1103
994	=head3 The special problem of dup'ed file descriptors	1104	=head3 The special problem of dup'ed file descriptors
995		1105
996	Some backends (e.g. epoll), cannot register events for file descriptors,	1106	Some backends (e.g. epoll), cannot register events for file descriptors,
997	but only events for the underlying file descriptions. That menas when you	1107	but only events for the underlying file descriptions. That means when you
998	have C<dup ()>'ed file descriptors and register events for them, only one	1108	have C<dup ()>'ed file descriptors or weirder constellations, and register
999	file descriptor might actually receive events.	1109	events for them, only one file descriptor might actually receive events.
1000		1110
1001	There is no workaorund possible except not registering events	1111	There is no workaround possible except not registering events
1002	for potentially C<dup ()>'ed file descriptors or to resort to	1112	for potentially C<dup ()>'ed file descriptors, or to resort to
1003	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1113	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1004		1114
1005	=head3 The special problem of fork	1115	=head3 The special problem of fork
1006		1116
1007	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1117	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
1011	To support fork in your programs, you either have to call	1121	To support fork in your programs, you either have to call
1012	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1122	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1013	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1014	C<EVBACKEND_POLL>.	1124	C<EVBACKEND_POLL>.
1015		1125
		1126	=head3 The special problem of SIGPIPE
		1127
		1128	While not really specific to libev, it is easy to forget about SIGPIPE:
		1129	when reading from a pipe whose other end has been closed, your program
		1130	gets send a SIGPIPE, which, by default, aborts your program. For most
		1131	programs this is sensible behaviour, for daemons, this is usually
		1132	undesirable.
		1133
		1134	So when you encounter spurious, unexplained daemon exits, make sure you
		1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1136	somewhere, as that would have given you a big clue).
		1137
1016		1138
1017	=head3 Watcher-Specific Functions	1139	=head3 Watcher-Specific Functions
1018		1140
1019	=over 4	1141	=over 4
1020		1142
1021	=item ev_io_init (ev_io *, callback, int fd, int events)	1143	=item ev_io_init (ev_io *, callback, int fd, int events)
1022		1144
1023	=item ev_io_set (ev_io *, int fd, int events)	1145	=item ev_io_set (ev_io *, int fd, int events)
1024		1146
1025	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1026	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1027	C<EV_READ | EV_WRITE> to receive the given events.	1149	C<EV_READ | EV_WRITE> to receive the given events.
1028		1150
1029	=item int fd [read-only]	1151	=item int fd [read-only]
1030		1152
1031	The file descriptor being watched.	1153	The file descriptor being watched.
…		…
1033	=item int events [read-only]	1155	=item int events [read-only]
1034		1156
1035	The events being watched.	1157	The events being watched.
1036		1158
1037	=back	1159	=back
		1160
		1161	=head3 Examples
1038		1162
1039	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1040	readable, but only once. Since it is likely line-buffered, you could	1164	readable, but only once. Since it is likely line-buffered, you could
1041	attempt to read a whole line in the callback.	1165	attempt to read a whole line in the callback.
1042		1166
1043	static void	1167	static void
1044	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1045	{	1169	{
1046	ev_io_stop (loop, w);	1170	ev_io_stop (loop, w);
1047	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1048	}	1172	}
1049		1173
1050	...	1174	...
1051	struct ev_loop *loop = ev_default_init (0);	1175	struct ev_loop *loop = ev_default_init (0);
1052	struct ev_io stdin_readable;	1176	struct ev_io stdin_readable;
1053	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1054	ev_io_start (loop, &stdin_readable);	1178	ev_io_start (loop, &stdin_readable);
1055	ev_loop (loop, 0);	1179	ev_loop (loop, 0);
1056		1180
1057		1181
1058	=head2 C<ev_timer> - relative and optionally repeating timeouts	1182	=head2 C<ev_timer> - relative and optionally repeating timeouts
1059		1183
1060	Timer watchers are simple relative timers that generate an event after a	1184	Timer watchers are simple relative timers that generate an event after a
1061	given time, and optionally repeating in regular intervals after that.	1185	given time, and optionally repeating in regular intervals after that.
1062		1186
1063	The timers are based on real time, that is, if you register an event that	1187	The timers are based on real time, that is, if you register an event that
1064	times out after an hour and you reset your system clock to last years	1188	times out after an hour and you reset your system clock to January last
1065	time, it will still time out after (roughly) and hour. "Roughly" because	1189	year, it will still time out after (roughly) and hour. "Roughly" because
1066	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1067	monotonic clock option helps a lot here).	1191	monotonic clock option helps a lot here).
1068		1192
1069	The relative timeouts are calculated relative to the C<ev_now ()>	1193	The relative timeouts are calculated relative to the C<ev_now ()>
1070	time. This is usually the right thing as this timestamp refers to the time	1194	time. This is usually the right thing as this timestamp refers to the time
…		…
1072	you suspect event processing to be delayed and you I<need> to base the timeout	1196	you suspect event processing to be delayed and you I<need> to base the timeout
1073	on the current time, use something like this to adjust for this:	1197	on the current time, use something like this to adjust for this:
1074		1198
1075	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1076		1200
1077	The callback is guarenteed to be invoked only when its timeout has passed,	1201	The callback is guaranteed to be invoked only after its timeout has passed,
1078	but if multiple timers become ready during the same loop iteration then	1202	but if multiple timers become ready during the same loop iteration then
1079	order of execution is undefined.	1203	order of execution is undefined.
1080		1204
1081	=head3 Watcher-Specific Functions and Data Members	1205	=head3 Watcher-Specific Functions and Data Members
1082		1206
…		…
1084		1208
1085	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1209	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1086		1210
1087	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1211	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1088		1212
1089	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1213	Configure the timer to trigger after C<after> seconds. If C<repeat>
1090	C<0.>, then it will automatically be stopped. If it is positive, then the	1214	is C<0.>, then it will automatically be stopped once the timeout is
1091	timer will automatically be configured to trigger again C<repeat> seconds	1215	reached. If it is positive, then the timer will automatically be
1092	later, again, and again, until stopped manually.	1216	configured to trigger again C<repeat> seconds later, again, and again,
		1217	until stopped manually.
1093		1218
1094	The timer itself will do a best-effort at avoiding drift, that is, if you	1219	The timer itself will do a best-effort at avoiding drift, that is, if
1095	configure a timer to trigger every 10 seconds, then it will trigger at	1220	you configure a timer to trigger every 10 seconds, then it will normally
1096	exactly 10 second intervals. If, however, your program cannot keep up with	1221	trigger at exactly 10 second intervals. If, however, your program cannot
1097	the timer (because it takes longer than those 10 seconds to do stuff) the	1222	keep up with the timer (because it takes longer than those 10 seconds to
1098	timer will not fire more than once per event loop iteration.	1223	do stuff) the timer will not fire more than once per event loop iteration.
1099		1224
1100	=item ev_timer_again (loop)	1225	=item ev_timer_again (loop, ev_timer *)
1101		1226
1102	This will act as if the timer timed out and restart it again if it is	1227	This will act as if the timer timed out and restart it again if it is
1103	repeating. The exact semantics are:	1228	repeating. The exact semantics are:
1104		1229
1105	If the timer is pending, its pending status is cleared.	1230	If the timer is pending, its pending status is cleared.
1106		1231
1107	If the timer is started but nonrepeating, stop it (as if it timed out).	1232	If the timer is started but non-repeating, stop it (as if it timed out).
1108		1233
1109	If the timer is repeating, either start it if necessary (with the	1234	If the timer is repeating, either start it if necessary (with the
1110	C<repeat> value), or reset the running timer to the C<repeat> value.	1235	C<repeat> value), or reset the running timer to the C<repeat> value.
1111		1236
1112	This sounds a bit complicated, but here is a useful and typical	1237	This sounds a bit complicated, but here is a useful and typical
1113	example: Imagine you have a tcp connection and you want a so-called idle	1238	example: Imagine you have a TCP connection and you want a so-called idle
1114	timeout, that is, you want to be called when there have been, say, 60	1239	timeout, that is, you want to be called when there have been, say, 60
1115	seconds of inactivity on the socket. The easiest way to do this is to	1240	seconds of inactivity on the socket. The easiest way to do this is to
1116	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1117	C<ev_timer_again> each time you successfully read or write some data. If	1242	C<ev_timer_again> each time you successfully read or write some data. If
1118	you go into an idle state where you do not expect data to travel on the	1243	you go into an idle state where you do not expect data to travel on the
…		…
1140	or C<ev_timer_again> is called and determines the next timeout (if any),	1265	or C<ev_timer_again> is called and determines the next timeout (if any),
1141	which is also when any modifications are taken into account.	1266	which is also when any modifications are taken into account.
1142		1267
1143	=back	1268	=back
1144		1269
		1270	=head3 Examples
		1271
1145	Example: Create a timer that fires after 60 seconds.	1272	Example: Create a timer that fires after 60 seconds.
1146		1273
1147	static void	1274	static void
1148	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1149	{	1276	{
1150	.. one minute over, w is actually stopped right here	1277	.. one minute over, w is actually stopped right here
1151	}	1278	}
1152		1279
1153	struct ev_timer mytimer;	1280	struct ev_timer mytimer;
1154	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1155	ev_timer_start (loop, &mytimer);	1282	ev_timer_start (loop, &mytimer);
1156		1283
1157	Example: Create a timeout timer that times out after 10 seconds of	1284	Example: Create a timeout timer that times out after 10 seconds of
1158	inactivity.	1285	inactivity.
1159		1286
1160	static void	1287	static void
1161	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1162	{	1289	{
1163	.. ten seconds without any activity	1290	.. ten seconds without any activity
1164	}	1291	}
1165		1292
1166	struct ev_timer mytimer;	1293	struct ev_timer mytimer;
1167	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1168	ev_timer_again (&mytimer); /* start timer */	1295	ev_timer_again (&mytimer); /* start timer */
1169	ev_loop (loop, 0);	1296	ev_loop (loop, 0);
1170		1297
1171	// and in some piece of code that gets executed on any "activity":	1298	// and in some piece of code that gets executed on any "activity":
1172	// reset the timeout to start ticking again at 10 seconds	1299	// reset the timeout to start ticking again at 10 seconds
1173	ev_timer_again (&mytimer);	1300	ev_timer_again (&mytimer);
1174		1301
1175		1302
1176	=head2 C<ev_periodic> - to cron or not to cron?	1303	=head2 C<ev_periodic> - to cron or not to cron?
1177		1304
1178	Periodic watchers are also timers of a kind, but they are very versatile	1305	Periodic watchers are also timers of a kind, but they are very versatile
1179	(and unfortunately a bit complex).	1306	(and unfortunately a bit complex).
1180		1307
1181	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1182	but on wallclock time (absolute time). You can tell a periodic watcher	1309	but on wall clock time (absolute time). You can tell a periodic watcher
1183	to trigger "at" some specific point in time. For example, if you tell a	1310	to trigger after some specific point in time. For example, if you tell a
1184	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1185	+ 10.>) and then reset your system clock to the last year, then it will	1312	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1313	clock to January of the previous year, then it will take more than year
1186	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1187	roughly 10 seconds later).	1315	roughly 10 seconds later as it uses a relative timeout).
1188		1316
1189	They can also be used to implement vastly more complex timers, such as	1317	C<ev_periodic>s can also be used to implement vastly more complex timers,
1190	triggering an event on each midnight, local time or other, complicated,	1318	such as triggering an event on each "midnight, local time", or other
1191	rules.	1319	complicated, rules.
1192		1320
1193	As with timers, the callback is guarenteed to be invoked only when the	1321	As with timers, the callback is guaranteed to be invoked only when the
1194	time (C<at>) has been passed, but if multiple periodic timers become ready	1322	time (C<at>) has passed, but if multiple periodic timers become ready
1195	during the same loop iteration then order of execution is undefined.	1323	during the same loop iteration then order of execution is undefined.
1196		1324
1197	=head3 Watcher-Specific Functions and Data Members	1325	=head3 Watcher-Specific Functions and Data Members
1198		1326
1199	=over 4	1327	=over 4
…		…
1207		1335
1208	=over 4	1336	=over 4
1209		1337
1210	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1211		1339
1212	In this configuration the watcher triggers an event at the wallclock time	1340	In this configuration the watcher triggers an event after the wall clock
1213	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1341	time C<at> has passed and doesn't repeat. It will not adjust when a time
1214	that is, if it is to be run at January 1st 2011 then it will run when the	1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1215	system time reaches or surpasses this time.	1343	run when the system time reaches or surpasses this time.
1216		1344
1217	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1218		1346
1219	In this mode the watcher will always be scheduled to time out at the next	1347	In this mode the watcher will always be scheduled to time out at the next
1220	C<at + N * interval> time (for some integer N, which can also be negative)	1348	C<at + N * interval> time (for some integer N, which can also be negative)
1221	and then repeat, regardless of any time jumps.	1349	and then repeat, regardless of any time jumps.
1222		1350
1223	This can be used to create timers that do not drift with respect to system	1351	This can be used to create timers that do not drift with respect to system
1224	time:	1352	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1353	the hour:
1225		1354
1226	ev_periodic_set (&periodic, 0., 3600., 0);	1355	ev_periodic_set (&periodic, 0., 3600., 0);
1227		1356
1228	This doesn't mean there will always be 3600 seconds in between triggers,	1357	This doesn't mean there will always be 3600 seconds in between triggers,
1229	but only that the the callback will be called when the system time shows a	1358	but only that the callback will be called when the system time shows a
1230	full hour (UTC), or more correctly, when the system time is evenly divisible	1359	full hour (UTC), or more correctly, when the system time is evenly divisible
1231	by 3600.	1360	by 3600.
1232		1361
1233	Another way to think about it (for the mathematically inclined) is that	1362	Another way to think about it (for the mathematically inclined) is that
1234	C<ev_periodic> will try to run the callback in this mode at the next possible	1363	C<ev_periodic> will try to run the callback in this mode at the next possible
1235	time where C<time = at (mod interval)>, regardless of any time jumps.	1364	time where C<time = at (mod interval)>, regardless of any time jumps.
1236		1365
1237	For numerical stability it is preferable that the C<at> value is near	1366	For numerical stability it is preferable that the C<at> value is near
1238	C<ev_now ()> (the current time), but there is no range requirement for	1367	C<ev_now ()> (the current time), but there is no range requirement for
1239	this value.	1368	this value, and in fact is often specified as zero.
		1369
		1370	Note also that there is an upper limit to how often a timer can fire (CPU
		1371	speed for example), so if C<interval> is very small then timing stability
		1372	will of course deteriorate. Libev itself tries to be exact to be about one
		1373	millisecond (if the OS supports it and the machine is fast enough).
1240		1374
1241	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1242		1376
1243	In this mode the values for C<interval> and C<at> are both being	1377	In this mode the values for C<interval> and C<at> are both being
1244	ignored. Instead, each time the periodic watcher gets scheduled, the	1378	ignored. Instead, each time the periodic watcher gets scheduled, the
1245	reschedule callback will be called with the watcher as first, and the	1379	reschedule callback will be called with the watcher as first, and the
1246	current time as second argument.	1380	current time as second argument.
1247		1381
1248	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1249	ever, or make any event loop modifications>. If you need to stop it,	1383	ever, or make ANY event loop modifications whatsoever>.
1250	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1251	starting an C<ev_prepare> watcher, which is legal).
1252		1384
		1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1387	only event loop modification you are allowed to do).
		1388
1253	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1254	ev_tstamp now)>, e.g.:	1390	*w, ev_tstamp now)>, e.g.:
1255		1391
1256	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1257	{	1393	{
1258	return now + 60.;	1394	return now + 60.;
1259	}	1395	}
…		…
1261	It must return the next time to trigger, based on the passed time value	1397	It must return the next time to trigger, based on the passed time value
1262	(that is, the lowest time value larger than to the second argument). It	1398	(that is, the lowest time value larger than to the second argument). It
1263	will usually be called just before the callback will be triggered, but	1399	will usually be called just before the callback will be triggered, but
1264	might be called at other times, too.	1400	might be called at other times, too.
1265		1401
1266	NOTE: I<< This callback must always return a time that is later than the	1402	NOTE: I<< This callback must always return a time that is higher than or
1267	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1403	equal to the passed C<now> value >>.
1268		1404
1269	This can be used to create very complex timers, such as a timer that	1405	This can be used to create very complex timers, such as a timer that
1270	triggers on each midnight, local time. To do this, you would calculate the	1406	triggers on "next midnight, local time". To do this, you would calculate the
1271	next midnight after C<now> and return the timestamp value for this. How	1407	next midnight after C<now> and return the timestamp value for this. How
1272	you do this is, again, up to you (but it is not trivial, which is the main	1408	you do this is, again, up to you (but it is not trivial, which is the main
1273	reason I omitted it as an example).	1409	reason I omitted it as an example).
1274		1410
1275	=back	1411	=back
…		…
1279	Simply stops and restarts the periodic watcher again. This is only useful	1415	Simply stops and restarts the periodic watcher again. This is only useful
1280	when you changed some parameters or the reschedule callback would return	1416	when you changed some parameters or the reschedule callback would return
1281	a different time than the last time it was called (e.g. in a crond like	1417	a different time than the last time it was called (e.g. in a crond like
1282	program when the crontabs have changed).	1418	program when the crontabs have changed).
1283		1419
		1420	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1421
		1422	When active, returns the absolute time that the watcher is supposed to
		1423	trigger next.
		1424
1284	=item ev_tstamp offset [read-write]	1425	=item ev_tstamp offset [read-write]
1285		1426
1286	When repeating, this contains the offset value, otherwise this is the	1427	When repeating, this contains the offset value, otherwise this is the
1287	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1288		1429
…		…
1299		1440
1300	The current reschedule callback, or C<0>, if this functionality is	1441	The current reschedule callback, or C<0>, if this functionality is
1301	switched off. Can be changed any time, but changes only take effect when	1442	switched off. Can be changed any time, but changes only take effect when
1302	the periodic timer fires or C<ev_periodic_again> is being called.	1443	the periodic timer fires or C<ev_periodic_again> is being called.
1303		1444
1304	=item ev_tstamp at [read-only]
1305
1306	When active, contains the absolute time that the watcher is supposed to
1307	trigger next.
1308
1309	=back	1445	=back
		1446
		1447	=head3 Examples
1310		1448
1311	Example: Call a callback every hour, or, more precisely, whenever the	1449	Example: Call a callback every hour, or, more precisely, whenever the
1312	system clock is divisible by 3600. The callback invocation times have	1450	system clock is divisible by 3600. The callback invocation times have
1313	potentially a lot of jittering, but good long-term stability.	1451	potentially a lot of jitter, but good long-term stability.
1314		1452
1315	static void	1453	static void
1316	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1317	{	1455	{
1318	... its now a full hour (UTC, or TAI or whatever your clock follows)	1456	... its now a full hour (UTC, or TAI or whatever your clock follows)
1319	}	1457	}
1320		1458
1321	struct ev_periodic hourly_tick;	1459	struct ev_periodic hourly_tick;
1322	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1323	ev_periodic_start (loop, &hourly_tick);	1461	ev_periodic_start (loop, &hourly_tick);
1324		1462
1325	Example: The same as above, but use a reschedule callback to do it:	1463	Example: The same as above, but use a reschedule callback to do it:
1326		1464
1327	#include <math.h>	1465	#include <math.h>
1328		1466
1329	static ev_tstamp	1467	static ev_tstamp
1330	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1331	{	1469	{
1332	return fmod (now, 3600.) + 3600.;	1470	return fmod (now, 3600.) + 3600.;
1333	}	1471	}
1334		1472
1335	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1336		1474
1337	Example: Call a callback every hour, starting now:	1475	Example: Call a callback every hour, starting now:
1338		1476
1339	struct ev_periodic hourly_tick;	1477	struct ev_periodic hourly_tick;
1340	ev_periodic_init (&hourly_tick, clock_cb,	1478	ev_periodic_init (&hourly_tick, clock_cb,
1341	fmod (ev_now (loop), 3600.), 3600., 0);	1479	fmod (ev_now (loop), 3600.), 3600., 0);
1342	ev_periodic_start (loop, &hourly_tick);	1480	ev_periodic_start (loop, &hourly_tick);
1343		1481
1344		1482
1345	=head2 C<ev_signal> - signal me when a signal gets signalled!	1483	=head2 C<ev_signal> - signal me when a signal gets signalled!
1346		1484
1347	Signal watchers will trigger an event when the process receives a specific	1485	Signal watchers will trigger an event when the process receives a specific
…		…
1354	with the kernel (thus it coexists with your own signal handlers as long	1492	with the kernel (thus it coexists with your own signal handlers as long
1355	as you don't register any with libev). Similarly, when the last signal	1493	as you don't register any with libev). Similarly, when the last signal
1356	watcher for a signal is stopped libev will reset the signal handler to	1494	watcher for a signal is stopped libev will reset the signal handler to
1357	SIG_DFL (regardless of what it was set to before).	1495	SIG_DFL (regardless of what it was set to before).
1358		1496
		1497	If possible and supported, libev will install its handlers with
		1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1499	interrupted. If you have a problem with system calls getting interrupted by
		1500	signals you can block all signals in an C<ev_check> watcher and unblock
		1501	them in an C<ev_prepare> watcher.
		1502
1359	=head3 Watcher-Specific Functions and Data Members	1503	=head3 Watcher-Specific Functions and Data Members
1360		1504
1361	=over 4	1505	=over 4
1362		1506
1363	=item ev_signal_init (ev_signal *, callback, int signum)	1507	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1371		1515
1372	The signal the watcher watches out for.	1516	The signal the watcher watches out for.
1373		1517
1374	=back	1518	=back
1375		1519
		1520	=head3 Examples
		1521
		1522	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1523
		1524	static void
		1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1526	{
		1527	ev_unloop (loop, EVUNLOOP_ALL);
		1528	}
		1529
		1530	struct ev_signal signal_watcher;
		1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1532	ev_signal_start (loop, &sigint_cb);
		1533
1376		1534
1377	=head2 C<ev_child> - watch out for process status changes	1535	=head2 C<ev_child> - watch out for process status changes
1378		1536
1379	Child watchers trigger when your process receives a SIGCHLD in response to	1537	Child watchers trigger when your process receives a SIGCHLD in response to
1380	some child status changes (most typically when a child of yours dies).	1538	some child status changes (most typically when a child of yours dies). It
		1539	is permissible to install a child watcher I<after> the child has been
		1540	forked (which implies it might have already exited), as long as the event
		1541	loop isn't entered (or is continued from a watcher).
		1542
		1543	Only the default event loop is capable of handling signals, and therefore
		1544	you can only register child watchers in the default event loop.
		1545
		1546	=head3 Process Interaction
		1547
		1548	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1549	initialised. This is necessary to guarantee proper behaviour even if
		1550	the first child watcher is started after the child exits. The occurrence
		1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1552	synchronously as part of the event loop processing. Libev always reaps all
		1553	children, even ones not watched.
		1554
		1555	=head3 Overriding the Built-In Processing
		1556
		1557	Libev offers no special support for overriding the built-in child
		1558	processing, but if your application collides with libev's default child
		1559	handler, you can override it easily by installing your own handler for
		1560	C<SIGCHLD> after initialising the default loop, and making sure the
		1561	default loop never gets destroyed. You are encouraged, however, to use an
		1562	event-based approach to child reaping and thus use libev's support for
		1563	that, so other libev users can use C<ev_child> watchers freely.
1381		1564
1382	=head3 Watcher-Specific Functions and Data Members	1565	=head3 Watcher-Specific Functions and Data Members
1383		1566
1384	=over 4	1567	=over 4
1385		1568
1386	=item ev_child_init (ev_child *, callback, int pid)	1569	=item ev_child_init (ev_child *, callback, int pid, int trace)
1387		1570
1388	=item ev_child_set (ev_child *, int pid)	1571	=item ev_child_set (ev_child *, int pid, int trace)
1389		1572
1390	Configures the watcher to wait for status changes of process C<pid> (or	1573	Configures the watcher to wait for status changes of process C<pid> (or
1391	I<any> process if C<pid> is specified as C<0>). The callback can look	1574	I<any> process if C<pid> is specified as C<0>). The callback can look
1392	at the C<rstatus> member of the C<ev_child> watcher structure to see	1575	at the C<rstatus> member of the C<ev_child> watcher structure to see
1393	the status word (use the macros from C<sys/wait.h> and see your systems	1576	the status word (use the macros from C<sys/wait.h> and see your systems
1394	C<waitpid> documentation). The C<rpid> member contains the pid of the	1577	C<waitpid> documentation). The C<rpid> member contains the pid of the
1395	process causing the status change.	1578	process causing the status change. C<trace> must be either C<0> (only
		1579	activate the watcher when the process terminates) or C<1> (additionally
		1580	activate the watcher when the process is stopped or continued).
1396		1581
1397	=item int pid [read-only]	1582	=item int pid [read-only]
1398		1583
1399	The process id this watcher watches out for, or C<0>, meaning any process id.	1584	The process id this watcher watches out for, or C<0>, meaning any process id.
1400		1585
…		…
1407	The process exit/trace status caused by C<rpid> (see your systems	1592	The process exit/trace status caused by C<rpid> (see your systems
1408	C<waitpid> and C<sys/wait.h> documentation for details).	1593	C<waitpid> and C<sys/wait.h> documentation for details).
1409		1594
1410	=back	1595	=back
1411		1596
1412	Example: Try to exit cleanly on SIGINT and SIGTERM.	1597	=head3 Examples
1413		1598
		1599	Example: C<fork()> a new process and install a child handler to wait for
		1600	its completion.
		1601
		1602	ev_child cw;
		1603
1414	static void	1604	static void
1415	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1605	child_cb (EV_P_ struct ev_child *w, int revents)
1416	{	1606	{
1417	ev_unloop (loop, EVUNLOOP_ALL);	1607	ev_child_stop (EV_A_ w);
		1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1418	}	1609	}
1419		1610
1420	struct ev_signal signal_watcher;	1611	pid_t pid = fork ();
1421	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1612
1422	ev_signal_start (loop, &sigint_cb);	1613	if (pid < 0)
		1614	// error
		1615	else if (pid == 0)
		1616	{
		1617	// the forked child executes here
		1618	exit (1);
		1619	}
		1620	else
		1621	{
		1622	ev_child_init (&cw, child_cb, pid, 0);
		1623	ev_child_start (EV_DEFAULT_ &cw);
		1624	}
1423		1625
1424		1626
1425	=head2 C<ev_stat> - did the file attributes just change?	1627	=head2 C<ev_stat> - did the file attributes just change?
1426		1628
1427	This watches a filesystem path for attribute changes. That is, it calls	1629	This watches a file system path for attribute changes. That is, it calls
1428	C<stat> regularly (or when the OS says it changed) and sees if it changed	1630	C<stat> regularly (or when the OS says it changed) and sees if it changed
1429	compared to the last time, invoking the callback if it did.	1631	compared to the last time, invoking the callback if it did.
1430		1632
1431	The path does not need to exist: changing from "path exists" to "path does	1633	The path does not need to exist: changing from "path exists" to "path does
1432	not exist" is a status change like any other. The condition "path does	1634	not exist" is a status change like any other. The condition "path does
…		…
1450	as even with OS-supported change notifications, this can be	1652	as even with OS-supported change notifications, this can be
1451	resource-intensive.	1653	resource-intensive.
1452		1654
1453	At the time of this writing, only the Linux inotify interface is	1655	At the time of this writing, only the Linux inotify interface is
1454	implemented (implementing kqueue support is left as an exercise for the	1656	implemented (implementing kqueue support is left as an exercise for the
		1657	reader, note, however, that the author sees no way of implementing ev_stat
1455	reader). Inotify will be used to give hints only and should not change the	1658	semantics with kqueue). Inotify will be used to give hints only and should
1456	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1659	not change the semantics of C<ev_stat> watchers, which means that libev
1457	to fall back to regular polling again even with inotify, but changes are	1660	sometimes needs to fall back to regular polling again even with inotify,
1458	usually detected immediately, and if the file exists there will be no	1661	but changes are usually detected immediately, and if the file exists there
1459	polling.	1662	will be no polling.
		1663
		1664	=head3 ABI Issues (Largefile Support)
		1665
		1666	Libev by default (unless the user overrides this) uses the default
		1667	compilation environment, which means that on systems with optionally
		1668	disabled large file support, you get the 32 bit version of the stat
		1669	structure. When using the library from programs that change the ABI to
		1670	use 64 bit file offsets the programs will fail. In that case you have to
		1671	compile libev with the same flags to get binary compatibility. This is
		1672	obviously the case with any flags that change the ABI, but the problem is
		1673	most noticeably with ev_stat and large file support.
		1674
		1675	=head3 Inotify
		1676
		1677	When C<inotify (7)> support has been compiled into libev (generally only
		1678	available on Linux) and present at runtime, it will be used to speed up
		1679	change detection where possible. The inotify descriptor will be created lazily
		1680	when the first C<ev_stat> watcher is being started.
		1681
		1682	Inotify presence does not change the semantics of C<ev_stat> watchers
		1683	except that changes might be detected earlier, and in some cases, to avoid
		1684	making regular C<stat> calls. Even in the presence of inotify support
		1685	there are many cases where libev has to resort to regular C<stat> polling.
		1686
		1687	(There is no support for kqueue, as apparently it cannot be used to
		1688	implement this functionality, due to the requirement of having a file
		1689	descriptor open on the object at all times).
		1690
		1691	=head3 The special problem of stat time resolution
		1692
		1693	The C<stat ()> system call only supports full-second resolution portably, and
		1694	even on systems where the resolution is higher, many file systems still
		1695	only support whole seconds.
		1696
		1697	That means that, if the time is the only thing that changes, you can
		1698	easily miss updates: on the first update, C<ev_stat> detects a change and
		1699	calls your callback, which does something. When there is another update
		1700	within the same second, C<ev_stat> will be unable to detect it as the stat
		1701	data does not change.
		1702
		1703	The solution to this is to delay acting on a change for slightly more
		1704	than a second (or till slightly after the next full second boundary), using
		1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1706	ev_timer_again (loop, w)>).
		1707
		1708	The C<.02> offset is added to work around small timing inconsistencies
		1709	of some operating systems (where the second counter of the current time
		1710	might be be delayed. One such system is the Linux kernel, where a call to
		1711	C<gettimeofday> might return a timestamp with a full second later than
		1712	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1713	update file times then there will be a small window where the kernel uses
		1714	the previous second to update file times but libev might already execute
		1715	the timer callback).
1460		1716
1461	=head3 Watcher-Specific Functions and Data Members	1717	=head3 Watcher-Specific Functions and Data Members
1462		1718
1463	=over 4	1719	=over 4
1464		1720
…		…
1470	C<path>. The C<interval> is a hint on how quickly a change is expected to	1726	C<path>. The C<interval> is a hint on how quickly a change is expected to
1471	be detected and should normally be specified as C<0> to let libev choose	1727	be detected and should normally be specified as C<0> to let libev choose
1472	a suitable value. The memory pointed to by C<path> must point to the same	1728	a suitable value. The memory pointed to by C<path> must point to the same
1473	path for as long as the watcher is active.	1729	path for as long as the watcher is active.
1474		1730
1475	The callback will be receive C<EV_STAT> when a change was detected,	1731	The callback will receive C<EV_STAT> when a change was detected, relative
1476	relative to the attributes at the time the watcher was started (or the	1732	to the attributes at the time the watcher was started (or the last change
1477	last change was detected).	1733	was detected).
1478		1734
1479	=item ev_stat_stat (ev_stat *)	1735	=item ev_stat_stat (loop, ev_stat *)
1480		1736
1481	Updates the stat buffer immediately with new values. If you change the	1737	Updates the stat buffer immediately with new values. If you change the
1482	watched path in your callback, you could call this fucntion to avoid	1738	watched path in your callback, you could call this function to avoid
1483	detecting this change (while introducing a race condition). Can also be	1739	detecting this change (while introducing a race condition if you are not
1484	useful simply to find out the new values.	1740	the only one changing the path). Can also be useful simply to find out the
		1741	new values.
1485		1742
1486	=item ev_statdata attr [read-only]	1743	=item ev_statdata attr [read-only]
1487		1744
1488	The most-recently detected attributes of the file. Although the type is of	1745	The most-recently detected attributes of the file. Although the type is
1489	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1746	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1490	suitable for your system. If the C<st_nlink> member is C<0>, then there	1747	suitable for your system, but you can only rely on the POSIX-standardised
		1748	members to be present. If the C<st_nlink> member is C<0>, then there was
1491	was some error while C<stat>ing the file.	1749	some error while C<stat>ing the file.
1492		1750
1493	=item ev_statdata prev [read-only]	1751	=item ev_statdata prev [read-only]
1494		1752
1495	The previous attributes of the file. The callback gets invoked whenever	1753	The previous attributes of the file. The callback gets invoked whenever
1496	C<prev> != C<attr>.	1754	C<prev> != C<attr>, or, more precisely, one or more of these members
		1755	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1756	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1497		1757
1498	=item ev_tstamp interval [read-only]	1758	=item ev_tstamp interval [read-only]
1499		1759
1500	The specified interval.	1760	The specified interval.
1501		1761
1502	=item const char *path [read-only]	1762	=item const char *path [read-only]
1503		1763
1504	The filesystem path that is being watched.	1764	The file system path that is being watched.
1505		1765
1506	=back	1766	=back
1507		1767
		1768	=head3 Examples
		1769
1508	Example: Watch C</etc/passwd> for attribute changes.	1770	Example: Watch C</etc/passwd> for attribute changes.
1509		1771
1510	static void	1772	static void
1511	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1512	{	1774	{
1513	/* /etc/passwd changed in some way */	1775	/* /etc/passwd changed in some way */
1514	if (w->attr.st_nlink)	1776	if (w->attr.st_nlink)
1515	{	1777	{
1516	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1517	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1518	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1519	}	1781	}
1520	else	1782	else
1521	/* you shalt not abuse printf for puts */	1783	/* you shalt not abuse printf for puts */
1522	puts ("wow, /etc/passwd is not there, expect problems. "	1784	puts ("wow, /etc/passwd is not there, expect problems. "
1523	"if this is windows, they already arrived\n");	1785	"if this is windows, they already arrived\n");
1524	}	1786	}
1525		1787
1526	...	1788	...
1527	ev_stat passwd;	1789	ev_stat passwd;
1528		1790
1529	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1530	ev_stat_start (loop, &passwd);	1792	ev_stat_start (loop, &passwd);
		1793
		1794	Example: Like above, but additionally use a one-second delay so we do not
		1795	miss updates (however, frequent updates will delay processing, too, so
		1796	one might do the work both on C<ev_stat> callback invocation I<and> on
		1797	C<ev_timer> callback invocation).
		1798
		1799	static ev_stat passwd;
		1800	static ev_timer timer;
		1801
		1802	static void
		1803	timer_cb (EV_P_ ev_timer *w, int revents)
		1804	{
		1805	ev_timer_stop (EV_A_ w);
		1806
		1807	/* now it's one second after the most recent passwd change */
		1808	}
		1809
		1810	static void
		1811	stat_cb (EV_P_ ev_stat *w, int revents)
		1812	{
		1813	/* reset the one-second timer */
		1814	ev_timer_again (EV_A_ &timer);
		1815	}
		1816
		1817	...
		1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1819	ev_stat_start (loop, &passwd);
		1820	ev_timer_init (&timer, timer_cb, 0., 1.02);
1531		1821
1532		1822
1533	=head2 C<ev_idle> - when you've got nothing better to do...	1823	=head2 C<ev_idle> - when you've got nothing better to do...
1534		1824
1535	Idle watchers trigger events when no other events of the same or higher	1825	Idle watchers trigger events when no other events of the same or higher
…		…
1561	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1562	believe me.	1852	believe me.
1563		1853
1564	=back	1854	=back
1565		1855
		1856	=head3 Examples
		1857
1566	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1567	callback, free it. Also, use no error checking, as usual.	1859	callback, free it. Also, use no error checking, as usual.
1568		1860
1569	static void	1861	static void
1570	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1571	{	1863	{
1572	free (w);	1864	free (w);
1573	// now do something you wanted to do when the program has	1865	// now do something you wanted to do when the program has
1574	// no longer asnything immediate to do.	1866	// no longer anything immediate to do.
1575	}	1867	}
1576		1868
1577	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1578	ev_idle_init (idle_watcher, idle_cb);	1870	ev_idle_init (idle_watcher, idle_cb);
1579	ev_idle_start (loop, idle_cb);	1871	ev_idle_start (loop, idle_cb);
1580		1872
1581		1873
1582	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1583		1875
1584	Prepare and check watchers are usually (but not always) used in tandem:	1876	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1603		1895
1604	This is done by examining in each prepare call which file descriptors need	1896	This is done by examining in each prepare call which file descriptors need
1605	to be watched by the other library, registering C<ev_io> watchers for	1897	to be watched by the other library, registering C<ev_io> watchers for
1606	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1607	provide just this functionality). Then, in the check watcher you check for	1899	provide just this functionality). Then, in the check watcher you check for
1608	any events that occured (by checking the pending status of all watchers	1900	any events that occurred (by checking the pending status of all watchers
1609	and stopping them) and call back into the library. The I/O and timer	1901	and stopping them) and call back into the library. The I/O and timer
1610	callbacks will never actually be called (but must be valid nevertheless,	1902	callbacks will never actually be called (but must be valid nevertheless,
1611	because you never know, you know?).	1903	because you never know, you know?).
1612		1904
1613	As another example, the Perl Coro module uses these hooks to integrate	1905	As another example, the Perl Coro module uses these hooks to integrate
…		…
1621		1913
1622	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1623	priority, to ensure that they are being run before any other watchers	1915	priority, to ensure that they are being run before any other watchers
1624	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1625	too) should not activate ("feed") events into libev. While libev fully	1917	too) should not activate ("feed") events into libev. While libev fully
1626	supports this, they will be called before other C<ev_check> watchers did	1918	supports this, they might get executed before other C<ev_check> watchers
1627	their job. As C<ev_check> watchers are often used to embed other event	1919	did their job. As C<ev_check> watchers are often used to embed other
1628	loops those other event loops might be in an unusable state until their	1920	(non-libev) event loops those other event loops might be in an unusable
1629	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1921	state until their C<ev_check> watcher ran (always remind yourself to
1630	others).	1922	coexist peacefully with others).
1631		1923
1632	=head3 Watcher-Specific Functions and Data Members	1924	=head3 Watcher-Specific Functions and Data Members
1633		1925
1634	=over 4	1926	=over 4
1635		1927
…		…
1641	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1642	macros, but using them is utterly, utterly and completely pointless.	1934	macros, but using them is utterly, utterly and completely pointless.
1643		1935
1644	=back	1936	=back
1645		1937
		1938	=head3 Examples
		1939
1646	There are a number of principal ways to embed other event loops or modules	1940	There are a number of principal ways to embed other event loops or modules
1647	into libev. Here are some ideas on how to include libadns into libev	1941	into libev. Here are some ideas on how to include libadns into libev
1648	(there is a Perl module named C<EV::ADNS> that does this, which you could	1942	(there is a Perl module named C<EV::ADNS> that does this, which you could
1649	use for an actually working example. Another Perl module named C<EV::Glib>	1943	use as a working example. Another Perl module named C<EV::Glib> embeds a
1650	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1944	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1651	into the Glib event loop).	1945	Glib event loop).
1652		1946
1653	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1947	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1654	and in a check watcher, destroy them and call into libadns. What follows	1948	and in a check watcher, destroy them and call into libadns. What follows
1655	is pseudo-code only of course. This requires you to either use a low	1949	is pseudo-code only of course. This requires you to either use a low
1656	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1657	the callbacks for the IO/timeout watchers might not have been called yet.	1951	the callbacks for the IO/timeout watchers might not have been called yet.
1658		1952
1659	static ev_io iow [nfd];	1953	static ev_io iow [nfd];
1660	static ev_timer tw;	1954	static ev_timer tw;
1661		1955
1662	static void	1956	static void
1663	io_cb (ev_loop *loop, ev_io *w, int revents)	1957	io_cb (ev_loop *loop, ev_io *w, int revents)
1664	{	1958	{
1665	}	1959	}
1666		1960
1667	// create io watchers for each fd and a timer before blocking	1961	// create io watchers for each fd and a timer before blocking
1668	static void	1962	static void
1669	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1670	{	1964	{
1671	int timeout = 3600000;	1965	int timeout = 3600000;
1672	struct pollfd fds [nfd];	1966	struct pollfd fds [nfd];
1673	// actual code will need to loop here and realloc etc.	1967	// actual code will need to loop here and realloc etc.
1674	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1675		1969
1676	/* the callback is illegal, but won't be called as we stop during check */	1970	/* the callback is illegal, but won't be called as we stop during check */
1677	ev_timer_init (&tw, 0, timeout * 1e-3);	1971	ev_timer_init (&tw, 0, timeout * 1e-3);
1678	ev_timer_start (loop, &tw);	1972	ev_timer_start (loop, &tw);
1679		1973
1680	// create one ev_io per pollfd	1974	// create one ev_io per pollfd
1681	for (int i = 0; i < nfd; ++i)	1975	for (int i = 0; i < nfd; ++i)
1682	{	1976	{
1683	ev_io_init (iow + i, io_cb, fds [i].fd,	1977	ev_io_init (iow + i, io_cb, fds [i].fd,
1684	((fds [i].events & POLLIN ? EV_READ : 0)	1978	((fds [i].events & POLLIN ? EV_READ : 0)
1685	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1686		1980
1687	fds [i].revents = 0;	1981	fds [i].revents = 0;
1688	ev_io_start (loop, iow + i);	1982	ev_io_start (loop, iow + i);
1689	}	1983	}
1690	}	1984	}
1691		1985
1692	// stop all watchers after blocking	1986	// stop all watchers after blocking
1693	static void	1987	static void
1694	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1695	{	1989	{
1696	ev_timer_stop (loop, &tw);	1990	ev_timer_stop (loop, &tw);
1697		1991
1698	for (int i = 0; i < nfd; ++i)	1992	for (int i = 0; i < nfd; ++i)
1699	{	1993	{
1700	// set the relevant poll flags	1994	// set the relevant poll flags
1701	// could also call adns_processreadable etc. here	1995	// could also call adns_processreadable etc. here
1702	struct pollfd *fd = fds + i;	1996	struct pollfd *fd = fds + i;
1703	int revents = ev_clear_pending (iow + i);	1997	int revents = ev_clear_pending (iow + i);
1704	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1705	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1706		2000
1707	// now stop the watcher	2001	// now stop the watcher
1708	ev_io_stop (loop, iow + i);	2002	ev_io_stop (loop, iow + i);
1709	}	2003	}
1710		2004
1711	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1712	}	2006	}
1713		2007
1714	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1715	in the prepare watcher and would dispose of the check watcher.	2009	in the prepare watcher and would dispose of the check watcher.
1716		2010
1717	Method 3: If the module to be embedded supports explicit event	2011	Method 3: If the module to be embedded supports explicit event
1718	notification (adns does), you can also make use of the actual watcher	2012	notification (libadns does), you can also make use of the actual watcher
1719	callbacks, and only destroy/create the watchers in the prepare watcher.	2013	callbacks, and only destroy/create the watchers in the prepare watcher.
1720		2014
1721	static void	2015	static void
1722	timer_cb (EV_P_ ev_timer *w, int revents)	2016	timer_cb (EV_P_ ev_timer *w, int revents)
1723	{	2017	{
1724	adns_state ads = (adns_state)w->data;	2018	adns_state ads = (adns_state)w->data;
1725	update_now (EV_A);	2019	update_now (EV_A);
1726		2020
1727	adns_processtimeouts (ads, &tv_now);	2021	adns_processtimeouts (ads, &tv_now);
1728	}	2022	}
1729		2023
1730	static void	2024	static void
1731	io_cb (EV_P_ ev_io *w, int revents)	2025	io_cb (EV_P_ ev_io *w, int revents)
1732	{	2026	{
1733	adns_state ads = (adns_state)w->data;	2027	adns_state ads = (adns_state)w->data;
1734	update_now (EV_A);	2028	update_now (EV_A);
1735		2029
1736	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1737	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1738	}	2032	}
1739		2033
1740	// do not ever call adns_afterpoll	2034	// do not ever call adns_afterpoll
1741		2035
1742	Method 4: Do not use a prepare or check watcher because the module you	2036	Method 4: Do not use a prepare or check watcher because the module you
1743	want to embed is too inflexible to support it. Instead, youc na override	2037	want to embed is too inflexible to support it. Instead, you can override
1744	their poll function. The drawback with this solution is that the main	2038	their poll function. The drawback with this solution is that the main
1745	loop is now no longer controllable by EV. The C<Glib::EV> module does	2039	loop is now no longer controllable by EV. The C<Glib::EV> module does
1746	this.	2040	this.
1747		2041
1748	static gint	2042	static gint
1749	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1750	{	2044	{
1751	int got_events = 0;	2045	int got_events = 0;
1752		2046
1753	for (n = 0; n < nfds; ++n)	2047	for (n = 0; n < nfds; ++n)
1754	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1755		2049
1756	if (timeout >= 0)	2050	if (timeout >= 0)
1757	// create/start timer	2051	// create/start timer
1758		2052
1759	// poll	2053	// poll
1760	ev_loop (EV_A_ 0);	2054	ev_loop (EV_A_ 0);
1761		2055
1762	// stop timer again	2056	// stop timer again
1763	if (timeout >= 0)	2057	if (timeout >= 0)
1764	ev_timer_stop (EV_A_ &to);	2058	ev_timer_stop (EV_A_ &to);
1765		2059
1766	// stop io watchers again - their callbacks should have set	2060	// stop io watchers again - their callbacks should have set
1767	for (n = 0; n < nfds; ++n)	2061	for (n = 0; n < nfds; ++n)
1768	ev_io_stop (EV_A_ iow [n]);	2062	ev_io_stop (EV_A_ iow [n]);
1769		2063
1770	return got_events;	2064	return got_events;
1771	}	2065	}
1772		2066
1773		2067
1774	=head2 C<ev_embed> - when one backend isn't enough...	2068	=head2 C<ev_embed> - when one backend isn't enough...
1775		2069
1776	This is a rather advanced watcher type that lets you embed one event loop	2070	This is a rather advanced watcher type that lets you embed one event loop
1777	into another (currently only C<ev_io> events are supported in the embedded	2071	into another (currently only C<ev_io> events are supported in the embedded
1778	loop, other types of watchers might be handled in a delayed or incorrect	2072	loop, other types of watchers might be handled in a delayed or incorrect
1779	fashion and must not be used). (See portability notes, below).	2073	fashion and must not be used).
1780		2074
1781	There are primarily two reasons you would want that: work around bugs and	2075	There are primarily two reasons you would want that: work around bugs and
1782	prioritise I/O.	2076	prioritise I/O.
1783		2077
1784	As an example for a bug workaround, the kqueue backend might only support	2078	As an example for a bug workaround, the kqueue backend might only support
…		…
1818	portable one.	2112	portable one.
1819		2113
1820	So when you want to use this feature you will always have to be prepared	2114	So when you want to use this feature you will always have to be prepared
1821	that you cannot get an embeddable loop. The recommended way to get around	2115	that you cannot get an embeddable loop. The recommended way to get around
1822	this is to have a separate variables for your embeddable loop, try to	2116	this is to have a separate variables for your embeddable loop, try to
1823	create it, and if that fails, use the normal loop for everything:	2117	create it, and if that fails, use the normal loop for everything.
1824
1825	struct ev_loop *loop_hi = ev_default_init (0);
1826	struct ev_loop *loop_lo = 0;
1827	struct ev_embed embed;
1828
1829	// see if there is a chance of getting one that works
1830	// (remember that a flags value of 0 means autodetection)
1831	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1832	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1833	: 0;
1834
1835	// if we got one, then embed it, otherwise default to loop_hi
1836	if (loop_lo)
1837	{
1838	ev_embed_init (&embed, 0, loop_lo);
1839	ev_embed_start (loop_hi, &embed);
1840	}
1841	else
1842	loop_lo = loop_hi;
1843
1844	=head2 Portability notes
1845
1846	Kqueue is nominally embeddable, but this is broken on all BSDs that I
1847	tried, in various ways. Usually the embedded event loop will simply never
1848	receive events, sometimes it will only trigger a few times, sometimes in a
1849	loop. Epoll is also nominally embeddable, but many Linux kernel versions
1850	will always eport the epoll fd as ready, even when no events are pending.
1851
1852	While libev allows embedding these backends (they are contained in
1853	C<ev_embeddable_backends ()>), take extreme care that it will actually
1854	work.
1855
1856	When in doubt, create a dynamic event loop forced to use sockets (this
1857	usually works) and possibly another thread and a pipe or so to report to
1858	your main event loop.
1859		2118
1860	=head3 Watcher-Specific Functions and Data Members	2119	=head3 Watcher-Specific Functions and Data Members
1861		2120
1862	=over 4	2121	=over 4
1863		2122
…		…
1867		2126
1868	Configures the watcher to embed the given loop, which must be	2127	Configures the watcher to embed the given loop, which must be
1869	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2128	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1870	invoked automatically, otherwise it is the responsibility of the callback	2129	invoked automatically, otherwise it is the responsibility of the callback
1871	to invoke it (it will continue to be called until the sweep has been done,	2130	to invoke it (it will continue to be called until the sweep has been done,
1872	if you do not want thta, you need to temporarily stop the embed watcher).	2131	if you do not want that, you need to temporarily stop the embed watcher).
1873		2132
1874	=item ev_embed_sweep (loop, ev_embed *)	2133	=item ev_embed_sweep (loop, ev_embed *)
1875		2134
1876	Make a single, non-blocking sweep over the embedded loop. This works	2135	Make a single, non-blocking sweep over the embedded loop. This works
1877	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2136	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1878	apropriate way for embedded loops.	2137	appropriate way for embedded loops.
1879		2138
1880	=item struct ev_loop *other [read-only]	2139	=item struct ev_loop *other [read-only]
1881		2140
1882	The embedded event loop.	2141	The embedded event loop.
1883		2142
1884	=back	2143	=back
		2144
		2145	=head3 Examples
		2146
		2147	Example: Try to get an embeddable event loop and embed it into the default
		2148	event loop. If that is not possible, use the default loop. The default
		2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2151	used).
		2152
		2153	struct ev_loop *loop_hi = ev_default_init (0);
		2154	struct ev_loop *loop_lo = 0;
		2155	struct ev_embed embed;
		2156
		2157	// see if there is a chance of getting one that works
		2158	// (remember that a flags value of 0 means autodetection)
		2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2161	: 0;
		2162
		2163	// if we got one, then embed it, otherwise default to loop_hi
		2164	if (loop_lo)
		2165	{
		2166	ev_embed_init (&embed, 0, loop_lo);
		2167	ev_embed_start (loop_hi, &embed);
		2168	}
		2169	else
		2170	loop_lo = loop_hi;
		2171
		2172	Example: Check if kqueue is available but not recommended and create
		2173	a kqueue backend for use with sockets (which usually work with any
		2174	kqueue implementation). Store the kqueue/socket-only event loop in
		2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2176
		2177	struct ev_loop *loop = ev_default_init (0);
		2178	struct ev_loop *loop_socket = 0;
		2179	struct ev_embed embed;
		2180
		2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2183	{
		2184	ev_embed_init (&embed, 0, loop_socket);
		2185	ev_embed_start (loop, &embed);
		2186	}
		2187
		2188	if (!loop_socket)
		2189	loop_socket = loop;
		2190
		2191	// now use loop_socket for all sockets, and loop for everything else
1885		2192
1886		2193
1887	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1888		2195
1889	Fork watchers are called when a C<fork ()> was detected (usually because	2196	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1905	believe me.	2212	believe me.
1906		2213
1907	=back	2214	=back
1908		2215
1909		2216
		2217	=head2 C<ev_async> - how to wake up another event loop
		2218
		2219	In general, you cannot use an C<ev_loop> from multiple threads or other
		2220	asynchronous sources such as signal handlers (as opposed to multiple event
		2221	loops - those are of course safe to use in different threads).
		2222
		2223	Sometimes, however, you need to wake up another event loop you do not
		2224	control, for example because it belongs to another thread. This is what
		2225	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2226	can signal it by calling C<ev_async_send>, which is thread- and signal
		2227	safe.
		2228
		2229	This functionality is very similar to C<ev_signal> watchers, as signals,
		2230	too, are asynchronous in nature, and signals, too, will be compressed
		2231	(i.e. the number of callback invocations may be less than the number of
		2232	C<ev_async_sent> calls).
		2233
		2234	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2235	just the default loop.
		2236
		2237	=head3 Queueing
		2238
		2239	C<ev_async> does not support queueing of data in any way. The reason
		2240	is that the author does not know of a simple (or any) algorithm for a
		2241	multiple-writer-single-reader queue that works in all cases and doesn't
		2242	need elaborate support such as pthreads.
		2243
		2244	That means that if you want to queue data, you have to provide your own
		2245	queue. But at least I can tell you would implement locking around your
		2246	queue:
		2247
		2248	=over 4
		2249
		2250	=item queueing from a signal handler context
		2251
		2252	To implement race-free queueing, you simply add to the queue in the signal
		2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2254	some fictitious SIGUSR1 handler:
		2255
		2256	static ev_async mysig;
		2257
		2258	static void
		2259	sigusr1_handler (void)
		2260	{
		2261	sometype data;
		2262
		2263	// no locking etc.
		2264	queue_put (data);
		2265	ev_async_send (EV_DEFAULT_ &mysig);
		2266	}
		2267
		2268	static void
		2269	mysig_cb (EV_P_ ev_async *w, int revents)
		2270	{
		2271	sometype data;
		2272	sigset_t block, prev;
		2273
		2274	sigemptyset (&block);
		2275	sigaddset (&block, SIGUSR1);
		2276	sigprocmask (SIG_BLOCK, &block, &prev);
		2277
		2278	while (queue_get (&data))
		2279	process (data);
		2280
		2281	if (sigismember (&prev, SIGUSR1)
		2282	sigprocmask (SIG_UNBLOCK, &block, 0);
		2283	}
		2284
		2285	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2286	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2287	either...).
		2288
		2289	=item queueing from a thread context
		2290
		2291	The strategy for threads is different, as you cannot (easily) block
		2292	threads but you can easily preempt them, so to queue safely you need to
		2293	employ a traditional mutex lock, such as in this pthread example:
		2294
		2295	static ev_async mysig;
		2296	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2297
		2298	static void
		2299	otherthread (void)
		2300	{
		2301	// only need to lock the actual queueing operation
		2302	pthread_mutex_lock (&mymutex);
		2303	queue_put (data);
		2304	pthread_mutex_unlock (&mymutex);
		2305
		2306	ev_async_send (EV_DEFAULT_ &mysig);
		2307	}
		2308
		2309	static void
		2310	mysig_cb (EV_P_ ev_async *w, int revents)
		2311	{
		2312	pthread_mutex_lock (&mymutex);
		2313
		2314	while (queue_get (&data))
		2315	process (data);
		2316
		2317	pthread_mutex_unlock (&mymutex);
		2318	}
		2319
		2320	=back
		2321
		2322
		2323	=head3 Watcher-Specific Functions and Data Members
		2324
		2325	=over 4
		2326
		2327	=item ev_async_init (ev_async *, callback)
		2328
		2329	Initialises and configures the async watcher - it has no parameters of any
		2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2331	believe me.
		2332
		2333	=item ev_async_send (loop, ev_async *)
		2334
		2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2337	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2339	section below on what exactly this means).
		2340
		2341	This call incurs the overhead of a system call only once per loop iteration,
		2342	so while the overhead might be noticeable, it doesn't apply to repeated
		2343	calls to C<ev_async_send>.
		2344
		2345	=item bool = ev_async_pending (ev_async *)
		2346
		2347	Returns a non-zero value when C<ev_async_send> has been called on the
		2348	watcher but the event has not yet been processed (or even noted) by the
		2349	event loop.
		2350
		2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2352	the loop iterates next and checks for the watcher to have become active,
		2353	it will reset the flag again. C<ev_async_pending> can be used to very
		2354	quickly check whether invoking the loop might be a good idea.
		2355
		2356	Not that this does I<not> check whether the watcher itself is pending, only
		2357	whether it has been requested to make this watcher pending.
		2358
		2359	=back
		2360
		2361
1910	=head1 OTHER FUNCTIONS	2362	=head1 OTHER FUNCTIONS
1911		2363
1912	There are some other functions of possible interest. Described. Here. Now.	2364	There are some other functions of possible interest. Described. Here. Now.
1913		2365
1914	=over 4	2366	=over 4
…		…
1921	or timeout without having to allocate/configure/start/stop/free one or	2373	or timeout without having to allocate/configure/start/stop/free one or
1922	more watchers yourself.	2374	more watchers yourself.
1923		2375
1924	If C<fd> is less than 0, then no I/O watcher will be started and events	2376	If C<fd> is less than 0, then no I/O watcher will be started and events
1925	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1926	C<events> set will be craeted and started.	2378	C<events> set will be created and started.
1927		2379
1928	If C<timeout> is less than 0, then no timeout watcher will be	2380	If C<timeout> is less than 0, then no timeout watcher will be
1929	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1930	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1931	dubious value.	2383	dubious value.
…		…
1933	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1934	passed an C<revents> set like normal event callbacks (a combination of	2386	passed an C<revents> set like normal event callbacks (a combination of
1935	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1936	value passed to C<ev_once>:	2388	value passed to C<ev_once>:
1937		2389
1938	static void stdin_ready (int revents, void *arg)	2390	static void stdin_ready (int revents, void *arg)
1939	{	2391	{
1940	if (revents & EV_TIMEOUT)	2392	if (revents & EV_TIMEOUT)
1941	/* doh, nothing entered */;	2393	/* doh, nothing entered */;
1942	else if (revents & EV_READ)	2394	else if (revents & EV_READ)
1943	/* stdin might have data for us, joy! */;	2395	/* stdin might have data for us, joy! */;
1944	}	2396	}
1945		2397
1946	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1947		2399
1948	=item ev_feed_event (ev_loop *, watcher *, int revents)	2400	=item ev_feed_event (ev_loop *, watcher *, int revents)
1949		2401
1950	Feeds the given event set into the event loop, as if the specified event	2402	Feeds the given event set into the event loop, as if the specified event
1951	had happened for the specified watcher (which must be a pointer to an	2403	had happened for the specified watcher (which must be a pointer to an
…		…
1956	Feed an event on the given fd, as if a file descriptor backend detected	2408	Feed an event on the given fd, as if a file descriptor backend detected
1957	the given events it.	2409	the given events it.
1958		2410
1959	=item ev_feed_signal_event (ev_loop *loop, int signum)	2411	=item ev_feed_signal_event (ev_loop *loop, int signum)
1960		2412
1961	Feed an event as if the given signal occured (C<loop> must be the default	2413	Feed an event as if the given signal occurred (C<loop> must be the default
1962	loop!).	2414	loop!).
1963		2415
1964	=back	2416	=back
1965		2417
1966		2418
…		…
1982		2434
1983	=item * Priorities are not currently supported. Initialising priorities	2435	=item * Priorities are not currently supported. Initialising priorities
1984	will fail and all watchers will have the same priority, even though there	2436	will fail and all watchers will have the same priority, even though there
1985	is an ev_pri field.	2437	is an ev_pri field.
1986		2438
		2439	=item * In libevent, the last base created gets the signals, in libev, the
		2440	first base created (== the default loop) gets the signals.
		2441
1987	=item * Other members are not supported.	2442	=item * Other members are not supported.
1988		2443
1989	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2444	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1990	to use the libev header file and library.	2445	to use the libev header file and library.
1991		2446
1992	=back	2447	=back
1993		2448
1994	=head1 C++ SUPPORT	2449	=head1 C++ SUPPORT
1995		2450
1996	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2451	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1997	you to use some convinience methods to start/stop watchers and also change	2452	you to use some convenience methods to start/stop watchers and also change
1998	the callback model to a model using method callbacks on objects.	2453	the callback model to a model using method callbacks on objects.
1999		2454
2000	To use it,	2455	To use it,
2001		2456
2002	#include <ev++.h>	2457	#include <ev++.h>
2003		2458
2004	This automatically includes F<ev.h> and puts all of its definitions (many	2459	This automatically includes F<ev.h> and puts all of its definitions (many
2005	of them macros) into the global namespace. All C++ specific things are	2460	of them macros) into the global namespace. All C++ specific things are
2006	put into the C<ev> namespace. It should support all the same embedding	2461	put into the C<ev> namespace. It should support all the same embedding
2007	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2074	your compiler is good :), then the method will be fully inlined into the	2529	your compiler is good :), then the method will be fully inlined into the
2075	thunking function, making it as fast as a direct C callback.	2530	thunking function, making it as fast as a direct C callback.
2076		2531
2077	Example: simple class declaration and watcher initialisation	2532	Example: simple class declaration and watcher initialisation
2078		2533
2079	struct myclass	2534	struct myclass
2080	{	2535	{
2081	void io_cb (ev::io &w, int revents) { }	2536	void io_cb (ev::io &w, int revents) { }
2082	}	2537	}
2083		2538
2084	myclass obj;	2539	myclass obj;
2085	ev::io iow;	2540	ev::io iow;
2086	iow.set <myclass, &myclass::io_cb> (&obj);	2541	iow.set <myclass, &myclass::io_cb> (&obj);
2087		2542
2088	=item w->set<function> (void *data = 0)	2543	=item w->set<function> (void *data = 0)
2089		2544
2090	Also sets a callback, but uses a static method or plain function as	2545	Also sets a callback, but uses a static method or plain function as
2091	callback. The optional C<data> argument will be stored in the watcher's	2546	callback. The optional C<data> argument will be stored in the watcher's
…		…
2095		2550
2096	See the method-C<set> above for more details.	2551	See the method-C<set> above for more details.
2097		2552
2098	Example:	2553	Example:
2099		2554
2100	static void io_cb (ev::io &w, int revents) { }	2555	static void io_cb (ev::io &w, int revents) { }
2101	iow.set <io_cb> ();	2556	iow.set <io_cb> ();
2102		2557
2103	=item w->set (struct ev_loop *)	2558	=item w->set (struct ev_loop *)
2104		2559
2105	Associates a different C<struct ev_loop> with this watcher. You can only	2560	Associates a different C<struct ev_loop> with this watcher. You can only
2106	do this when the watcher is inactive (and not pending either).	2561	do this when the watcher is inactive (and not pending either).
2107		2562
2108	=item w->set ([args])	2563	=item w->set ([arguments])
2109		2564
2110	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2565	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2111	called at least once. Unlike the C counterpart, an active watcher gets	2566	called at least once. Unlike the C counterpart, an active watcher gets
2112	automatically stopped and restarted when reconfiguring it with this	2567	automatically stopped and restarted when reconfiguring it with this
2113	method.	2568	method.
2114		2569
2115	=item w->start ()	2570	=item w->start ()
…		…
2139	=back	2594	=back
2140		2595
2141	Example: Define a class with an IO and idle watcher, start one of them in	2596	Example: Define a class with an IO and idle watcher, start one of them in
2142	the constructor.	2597	the constructor.
2143		2598
2144	class myclass	2599	class myclass
2145	{	2600	{
2146	ev_io io; void io_cb (ev::io &w, int revents);	2601	ev::io io; void io_cb (ev::io &w, int revents);
2147	ev_idle idle void idle_cb (ev::idle &w, int revents);	2602	ev:idle idle void idle_cb (ev::idle &w, int revents);
2148		2603
2149	myclass ();	2604	myclass (int fd)
2150	}	2605	{
2151
2152	myclass::myclass (int fd)
2153	{
2154	io .set <myclass, &myclass::io_cb > (this);	2606	io .set <myclass, &myclass::io_cb > (this);
2155	idle.set <myclass, &myclass::idle_cb> (this);	2607	idle.set <myclass, &myclass::idle_cb> (this);
2156		2608
2157	io.start (fd, ev::READ);	2609	io.start (fd, ev::READ);
		2610	}
2158	}	2611	};
		2612
		2613
		2614	=head1 OTHER LANGUAGE BINDINGS
		2615
		2616	Libev does not offer other language bindings itself, but bindings for a
		2617	number of languages exist in the form of third-party packages. If you know
		2618	any interesting language binding in addition to the ones listed here, drop
		2619	me a note.
		2620
		2621	=over 4
		2622
		2623	=item Perl
		2624
		2625	The EV module implements the full libev API and is actually used to test
		2626	libev. EV is developed together with libev. Apart from the EV core module,
		2627	there are additional modules that implement libev-compatible interfaces
		2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2630
		2631	It can be found and installed via CPAN, its homepage is found at
		2632	L<http://software.schmorp.de/pkg/EV>.
		2633
		2634	=item Ruby
		2635
		2636	Tony Arcieri has written a ruby extension that offers access to a subset
		2637	of the libev API and adds file handle abstractions, asynchronous DNS and
		2638	more on top of it. It can be found via gem servers. Its homepage is at
		2639	L<http://rev.rubyforge.org/>.
		2640
		2641	=item D
		2642
		2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2645
		2646	=back
2159		2647
2160		2648
2161	=head1 MACRO MAGIC	2649	=head1 MACRO MAGIC
2162		2650
2163	Libev can be compiled with a variety of options, the most fundamantal	2651	Libev can be compiled with a variety of options, the most fundamental
2164	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2652	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2165	functions and callbacks have an initial C<struct ev_loop *> argument.	2653	functions and callbacks have an initial C<struct ev_loop *> argument.
2166		2654
2167	To make it easier to write programs that cope with either variant, the	2655	To make it easier to write programs that cope with either variant, the
2168	following macros are defined:	2656	following macros are defined:
…		…
2173		2661
2174	This provides the loop I<argument> for functions, if one is required ("ev	2662	This provides the loop I<argument> for functions, if one is required ("ev
2175	loop argument"). The C<EV_A> form is used when this is the sole argument,	2663	loop argument"). The C<EV_A> form is used when this is the sole argument,
2176	C<EV_A_> is used when other arguments are following. Example:	2664	C<EV_A_> is used when other arguments are following. Example:
2177		2665
2178	ev_unref (EV_A);	2666	ev_unref (EV_A);
2179	ev_timer_add (EV_A_ watcher);	2667	ev_timer_add (EV_A_ watcher);
2180	ev_loop (EV_A_ 0);	2668	ev_loop (EV_A_ 0);
2181		2669
2182	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2183	which is often provided by the following macro.	2671	which is often provided by the following macro.
2184		2672
2185	=item C<EV_P>, C<EV_P_>	2673	=item C<EV_P>, C<EV_P_>
2186		2674
2187	This provides the loop I<parameter> for functions, if one is required ("ev	2675	This provides the loop I<parameter> for functions, if one is required ("ev
2188	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2676	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2189	C<EV_P_> is used when other parameters are following. Example:	2677	C<EV_P_> is used when other parameters are following. Example:
2190		2678
2191	// this is how ev_unref is being declared	2679	// this is how ev_unref is being declared
2192	static void ev_unref (EV_P);	2680	static void ev_unref (EV_P);
2193		2681
2194	// this is how you can declare your typical callback	2682	// this is how you can declare your typical callback
2195	static void cb (EV_P_ ev_timer *w, int revents)	2683	static void cb (EV_P_ ev_timer *w, int revents)
2196		2684
2197	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2198	suitable for use with C<EV_A>.	2686	suitable for use with C<EV_A>.
2199		2687
2200	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2201		2689
2202	Similar to the other two macros, this gives you the value of the default	2690	Similar to the other two macros, this gives you the value of the default
2203	loop, if multiple loops are supported ("ev loop default").	2691	loop, if multiple loops are supported ("ev loop default").
		2692
		2693	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2694
		2695	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2696	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2697	is undefined when the default loop has not been initialised by a previous
		2698	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2699
		2700	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2701	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2204		2702
2205	=back	2703	=back
2206		2704
2207	Example: Declare and initialise a check watcher, utilising the above	2705	Example: Declare and initialise a check watcher, utilising the above
2208	macros so it will work regardless of whether multiple loops are supported	2706	macros so it will work regardless of whether multiple loops are supported
2209	or not.	2707	or not.
2210		2708
2211	static void	2709	static void
2212	check_cb (EV_P_ ev_timer *w, int revents)	2710	check_cb (EV_P_ ev_timer *w, int revents)
2213	{	2711	{
2214	ev_check_stop (EV_A_ w);	2712	ev_check_stop (EV_A_ w);
2215	}	2713	}
2216		2714
2217	ev_check check;	2715	ev_check check;
2218	ev_check_init (&check, check_cb);	2716	ev_check_init (&check, check_cb);
2219	ev_check_start (EV_DEFAULT_ &check);	2717	ev_check_start (EV_DEFAULT_ &check);
2220	ev_loop (EV_DEFAULT_ 0);	2718	ev_loop (EV_DEFAULT_ 0);
2221		2719
2222	=head1 EMBEDDING	2720	=head1 EMBEDDING
2223		2721
2224	Libev can (and often is) directly embedded into host	2722	Libev can (and often is) directly embedded into host
2225	applications. Examples of applications that embed it include the Deliantra	2723	applications. Examples of applications that embed it include the Deliantra
…		…
2232	libev somewhere in your source tree).	2730	libev somewhere in your source tree).
2233		2731
2234	=head2 FILESETS	2732	=head2 FILESETS
2235		2733
2236	Depending on what features you need you need to include one or more sets of files	2734	Depending on what features you need you need to include one or more sets of files
2237	in your app.	2735	in your application.
2238		2736
2239	=head3 CORE EVENT LOOP	2737	=head3 CORE EVENT LOOP
2240		2738
2241	To include only the libev core (all the C<ev_*> functions), with manual	2739	To include only the libev core (all the C<ev_*> functions), with manual
2242	configuration (no autoconf):	2740	configuration (no autoconf):
2243		2741
2244	#define EV_STANDALONE 1	2742	#define EV_STANDALONE 1
2245	#include "ev.c"	2743	#include "ev.c"
2246		2744
2247	This will automatically include F<ev.h>, too, and should be done in a	2745	This will automatically include F<ev.h>, too, and should be done in a
2248	single C source file only to provide the function implementations. To use	2746	single C source file only to provide the function implementations. To use
2249	it, do the same for F<ev.h> in all files wishing to use this API (best	2747	it, do the same for F<ev.h> in all files wishing to use this API (best
2250	done by writing a wrapper around F<ev.h> that you can include instead and	2748	done by writing a wrapper around F<ev.h> that you can include instead and
2251	where you can put other configuration options):	2749	where you can put other configuration options):
2252		2750
2253	#define EV_STANDALONE 1	2751	#define EV_STANDALONE 1
2254	#include "ev.h"	2752	#include "ev.h"
2255		2753
2256	Both header files and implementation files can be compiled with a C++	2754	Both header files and implementation files can be compiled with a C++
2257	compiler (at least, thats a stated goal, and breakage will be treated	2755	compiler (at least, thats a stated goal, and breakage will be treated
2258	as a bug).	2756	as a bug).
2259		2757
2260	You need the following files in your source tree, or in a directory	2758	You need the following files in your source tree, or in a directory
2261	in your include path (e.g. in libev/ when using -Ilibev):	2759	in your include path (e.g. in libev/ when using -Ilibev):
2262		2760
2263	ev.h	2761	ev.h
2264	ev.c	2762	ev.c
2265	ev_vars.h	2763	ev_vars.h
2266	ev_wrap.h	2764	ev_wrap.h
2267		2765
2268	ev_win32.c required on win32 platforms only	2766	ev_win32.c required on win32 platforms only
2269		2767
2270	ev_select.c only when select backend is enabled (which is enabled by default)	2768	ev_select.c only when select backend is enabled (which is enabled by default)
2271	ev_poll.c only when poll backend is enabled (disabled by default)	2769	ev_poll.c only when poll backend is enabled (disabled by default)
2272	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2770	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2273	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2771	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2274	ev_port.c only when the solaris port backend is enabled (disabled by default)	2772	ev_port.c only when the solaris port backend is enabled (disabled by default)
2275		2773
2276	F<ev.c> includes the backend files directly when enabled, so you only need	2774	F<ev.c> includes the backend files directly when enabled, so you only need
2277	to compile this single file.	2775	to compile this single file.
2278		2776
2279	=head3 LIBEVENT COMPATIBILITY API	2777	=head3 LIBEVENT COMPATIBILITY API
2280		2778
2281	To include the libevent compatibility API, also include:	2779	To include the libevent compatibility API, also include:
2282		2780
2283	#include "event.c"	2781	#include "event.c"
2284		2782
2285	in the file including F<ev.c>, and:	2783	in the file including F<ev.c>, and:
2286		2784
2287	#include "event.h"	2785	#include "event.h"
2288		2786
2289	in the files that want to use the libevent API. This also includes F<ev.h>.	2787	in the files that want to use the libevent API. This also includes F<ev.h>.
2290		2788
2291	You need the following additional files for this:	2789	You need the following additional files for this:
2292		2790
2293	event.h	2791	event.h
2294	event.c	2792	event.c
2295		2793
2296	=head3 AUTOCONF SUPPORT	2794	=head3 AUTOCONF SUPPORT
2297		2795
2298	Instead of using C<EV_STANDALONE=1> and providing your config in	2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2299	whatever way you want, you can also C<m4_include([libev.m4])> in your	2797	whatever way you want, you can also C<m4_include([libev.m4])> in your
2300	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2301	include F<config.h> and configure itself accordingly.	2799	include F<config.h> and configure itself accordingly.
2302		2800
2303	For this of course you need the m4 file:	2801	For this of course you need the m4 file:
2304		2802
2305	libev.m4	2803	libev.m4
2306		2804
2307	=head2 PREPROCESSOR SYMBOLS/MACROS	2805	=head2 PREPROCESSOR SYMBOLS/MACROS
2308		2806
2309	Libev can be configured via a variety of preprocessor symbols you have to define	2807	Libev can be configured via a variety of preprocessor symbols you have to
2310	before including any of its files. The default is not to build for multiplicity	2808	define before including any of its files. The default in the absence of
2311	and only include the select backend.	2809	autoconf is noted for every option.
2312		2810
2313	=over 4	2811	=over 4
2314		2812
2315	=item EV_STANDALONE	2813	=item EV_STANDALONE
2316		2814
…		…
2321	F<event.h> that are not directly supported by the libev core alone.	2819	F<event.h> that are not directly supported by the libev core alone.
2322		2820
2323	=item EV_USE_MONOTONIC	2821	=item EV_USE_MONOTONIC
2324		2822
2325	If defined to be C<1>, libev will try to detect the availability of the	2823	If defined to be C<1>, libev will try to detect the availability of the
2326	monotonic clock option at both compiletime and runtime. Otherwise no use	2824	monotonic clock option at both compile time and runtime. Otherwise no use
2327	of the monotonic clock option will be attempted. If you enable this, you	2825	of the monotonic clock option will be attempted. If you enable this, you
2328	usually have to link against librt or something similar. Enabling it when	2826	usually have to link against librt or something similar. Enabling it when
2329	the functionality isn't available is safe, though, although you have	2827	the functionality isn't available is safe, though, although you have
2330	to make sure you link against any libraries where the C<clock_gettime>	2828	to make sure you link against any libraries where the C<clock_gettime>
2331	function is hiding in (often F<-lrt>).	2829	function is hiding in (often F<-lrt>).
2332		2830
2333	=item EV_USE_REALTIME	2831	=item EV_USE_REALTIME
2334		2832
2335	If defined to be C<1>, libev will try to detect the availability of the	2833	If defined to be C<1>, libev will try to detect the availability of the
2336	realtime clock option at compiletime (and assume its availability at	2834	real-time clock option at compile time (and assume its availability at
2337	runtime if successful). Otherwise no use of the realtime clock option will	2835	runtime if successful). Otherwise no use of the real-time clock option will
2338	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2339	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2340	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2341		2839
2342	=item EV_USE_NANOSLEEP	2840	=item EV_USE_NANOSLEEP
2343		2841
2344	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2345	and will use it for delays. Otherwise it will use C<select ()>.	2843	and will use it for delays. Otherwise it will use C<select ()>.
2346		2844
		2845	=item EV_USE_EVENTFD
		2846
		2847	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2848	available and will probe for kernel support at runtime. This will improve
		2849	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2850	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2851	2.7 or newer, otherwise disabled.
		2852
2347	=item EV_USE_SELECT	2853	=item EV_USE_SELECT
2348		2854
2349	If undefined or defined to be C<1>, libev will compile in support for the	2855	If undefined or defined to be C<1>, libev will compile in support for the
2350	C<select>(2) backend. No attempt at autodetection will be done: if no	2856	C<select>(2) backend. No attempt at auto-detection will be done: if no
2351	other method takes over, select will be it. Otherwise the select backend	2857	other method takes over, select will be it. Otherwise the select backend
2352	will not be compiled in.	2858	will not be compiled in.
2353		2859
2354	=item EV_SELECT_USE_FD_SET	2860	=item EV_SELECT_USE_FD_SET
2355		2861
2356	If defined to C<1>, then the select backend will use the system C<fd_set>	2862	If defined to C<1>, then the select backend will use the system C<fd_set>
2357	structure. This is useful if libev doesn't compile due to a missing	2863	structure. This is useful if libev doesn't compile due to a missing
2358	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2359	exotic systems. This usually limits the range of file descriptors to some	2865	exotic systems. This usually limits the range of file descriptors to some
2360	low limit such as 1024 or might have other limitations (winsocket only	2866	low limit such as 1024 or might have other limitations (winsocket only
2361	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2362	influence the size of the C<fd_set> used.	2868	influence the size of the C<fd_set> used.
2363		2869
…		…
2369	be used is the winsock select). This means that it will call	2875	be used is the winsock select). This means that it will call
2370	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2876	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2371	it is assumed that all these functions actually work on fds, even	2877	it is assumed that all these functions actually work on fds, even
2372	on win32. Should not be defined on non-win32 platforms.	2878	on win32. Should not be defined on non-win32 platforms.
2373		2879
		2880	=item EV_FD_TO_WIN32_HANDLE
		2881
		2882	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2883	file descriptors to socket handles. When not defining this symbol (the
		2884	default), then libev will call C<_get_osfhandle>, which is usually
		2885	correct. In some cases, programs use their own file descriptor management,
		2886	in which case they can provide this function to map fds to socket handles.
		2887
2374	=item EV_USE_POLL	2888	=item EV_USE_POLL
2375		2889
2376	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2890	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2377	backend. Otherwise it will be enabled on non-win32 platforms. It	2891	backend. Otherwise it will be enabled on non-win32 platforms. It
2378	takes precedence over select.	2892	takes precedence over select.
2379		2893
2380	=item EV_USE_EPOLL	2894	=item EV_USE_EPOLL
2381		2895
2382	If defined to be C<1>, libev will compile in support for the Linux	2896	If defined to be C<1>, libev will compile in support for the Linux
2383	C<epoll>(7) backend. Its availability will be detected at runtime,	2897	C<epoll>(7) backend. Its availability will be detected at runtime,
2384	otherwise another method will be used as fallback. This is the	2898	otherwise another method will be used as fallback. This is the preferred
2385	preferred backend for GNU/Linux systems.	2899	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2900	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2386		2901
2387	=item EV_USE_KQUEUE	2902	=item EV_USE_KQUEUE
2388		2903
2389	If defined to be C<1>, libev will compile in support for the BSD style	2904	If defined to be C<1>, libev will compile in support for the BSD style
2390	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2905	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2403	otherwise another method will be used as fallback. This is the preferred	2918	otherwise another method will be used as fallback. This is the preferred
2404	backend for Solaris 10 systems.	2919	backend for Solaris 10 systems.
2405		2920
2406	=item EV_USE_DEVPOLL	2921	=item EV_USE_DEVPOLL
2407		2922
2408	reserved for future expansion, works like the USE symbols above.	2923	Reserved for future expansion, works like the USE symbols above.
2409		2924
2410	=item EV_USE_INOTIFY	2925	=item EV_USE_INOTIFY
2411		2926
2412	If defined to be C<1>, libev will compile in support for the Linux inotify	2927	If defined to be C<1>, libev will compile in support for the Linux inotify
2413	interface to speed up C<ev_stat> watchers. Its actual availability will	2928	interface to speed up C<ev_stat> watchers. Its actual availability will
2414	be detected at runtime.	2929	be detected at runtime. If undefined, it will be enabled if the headers
		2930	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2931
		2932	=item EV_ATOMIC_T
		2933
		2934	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2935	access is atomic with respect to other threads or signal contexts. No such
		2936	type is easily found in the C language, so you can provide your own type
		2937	that you know is safe for your purposes. It is used both for signal handler "locking"
		2938	as well as for signal and thread safety in C<ev_async> watchers.
		2939
		2940	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2941	(from F<signal.h>), which is usually good enough on most platforms.
2415		2942
2416	=item EV_H	2943	=item EV_H
2417		2944
2418	The name of the F<ev.h> header file used to include it. The default if	2945	The name of the F<ev.h> header file used to include it. The default if
2419	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2946	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2420	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2947	used to virtually rename the F<ev.h> header file in case of conflicts.
2421		2948
2422	=item EV_CONFIG_H	2949	=item EV_CONFIG_H
2423		2950
2424	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2425	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2426	C<EV_H>, above.	2953	C<EV_H>, above.
2427		2954
2428	=item EV_EVENT_H	2955	=item EV_EVENT_H
2429		2956
2430	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2431	of how the F<event.h> header can be found.	2958	of how the F<event.h> header can be found, the default is C<"event.h">.
2432		2959
2433	=item EV_PROTOTYPES	2960	=item EV_PROTOTYPES
2434		2961
2435	If defined to be C<0>, then F<ev.h> will not define any function	2962	If defined to be C<0>, then F<ev.h> will not define any function
2436	prototypes, but still define all the structs and other symbols. This is	2963	prototypes, but still define all the structs and other symbols. This is
…		…
2457	When doing priority-based operations, libev usually has to linearly search	2984	When doing priority-based operations, libev usually has to linearly search
2458	all the priorities, so having many of them (hundreds) uses a lot of space	2985	all the priorities, so having many of them (hundreds) uses a lot of space
2459	and time, so using the defaults of five priorities (-2 .. +2) is usually	2986	and time, so using the defaults of five priorities (-2 .. +2) is usually
2460	fine.	2987	fine.
2461		2988
2462	If your embedding app does not need any priorities, defining these both to	2989	If your embedding application does not need any priorities, defining these both to
2463	C<0> will save some memory and cpu.	2990	C<0> will save some memory and CPU.
2464		2991
2465	=item EV_PERIODIC_ENABLE	2992	=item EV_PERIODIC_ENABLE
2466		2993
2467	If undefined or defined to be C<1>, then periodic timers are supported. If	2994	If undefined or defined to be C<1>, then periodic timers are supported. If
2468	defined to be C<0>, then they are not. Disabling them saves a few kB of	2995	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2487	=item EV_FORK_ENABLE	3014	=item EV_FORK_ENABLE
2488		3015
2489	If undefined or defined to be C<1>, then fork watchers are supported. If	3016	If undefined or defined to be C<1>, then fork watchers are supported. If
2490	defined to be C<0>, then they are not.	3017	defined to be C<0>, then they are not.
2491		3018
		3019	=item EV_ASYNC_ENABLE
		3020
		3021	If undefined or defined to be C<1>, then async watchers are supported. If
		3022	defined to be C<0>, then they are not.
		3023
2492	=item EV_MINIMAL	3024	=item EV_MINIMAL
2493		3025
2494	If you need to shave off some kilobytes of code at the expense of some	3026	If you need to shave off some kilobytes of code at the expense of some
2495	speed, define this symbol to C<1>. Currently only used for gcc to override	3027	speed, define this symbol to C<1>. Currently this is used to override some
2496	some inlining decisions, saves roughly 30% codesize of amd64.	3028	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3029	much smaller 2-heap for timer management over the default 4-heap.
2497		3030
2498	=item EV_PID_HASHSIZE	3031	=item EV_PID_HASHSIZE
2499		3032
2500	C<ev_child> watchers use a small hash table to distribute workload by	3033	C<ev_child> watchers use a small hash table to distribute workload by
2501	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2502	than enough. If you need to manage thousands of children you might want to	3035	than enough. If you need to manage thousands of children you might want to
2503	increase this value (I<must> be a power of two).	3036	increase this value (I<must> be a power of two).
2504		3037
2505	=item EV_INOTIFY_HASHSIZE	3038	=item EV_INOTIFY_HASHSIZE
2506		3039
2507	C<ev_staz> watchers use a small hash table to distribute workload by	3040	C<ev_stat> watchers use a small hash table to distribute workload by
2508	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2509	usually more than enough. If you need to manage thousands of C<ev_stat>	3042	usually more than enough. If you need to manage thousands of C<ev_stat>
2510	watchers you might want to increase this value (I<must> be a power of	3043	watchers you might want to increase this value (I<must> be a power of
2511	two).	3044	two).
2512		3045
		3046	=item EV_USE_4HEAP
		3047
		3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3050	to C<1>. The 4-heap uses more complicated (longer) code but has
		3051	noticeably faster performance with many (thousands) of watchers.
		3052
		3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3054	(disabled).
		3055
		3056	=item EV_HEAP_CACHE_AT
		3057
		3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3059	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3062	but avoids random read accesses on heap changes. This improves performance
		3063	noticeably with with many (hundreds) of watchers.
		3064
		3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3066	(disabled).
		3067
		3068	=item EV_VERIFY
		3069
		3070	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3071	be done: If set to C<0>, no internal verification code will be compiled
		3072	in. If set to C<1>, then verification code will be compiled in, but not
		3073	called. If set to C<2>, then the internal verification code will be
		3074	called once per loop, which can slow down libev. If set to C<3>, then the
		3075	verification code will be called very frequently, which will slow down
		3076	libev considerably.
		3077
		3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3079	C<0.>
		3080
2513	=item EV_COMMON	3081	=item EV_COMMON
2514		3082
2515	By default, all watchers have a C<void *data> member. By redefining	3083	By default, all watchers have a C<void *data> member. By redefining
2516	this macro to a something else you can include more and other types of	3084	this macro to a something else you can include more and other types of
2517	members. You have to define it each time you include one of the files,	3085	members. You have to define it each time you include one of the files,
2518	though, and it must be identical each time.	3086	though, and it must be identical each time.
2519		3087
2520	For example, the perl EV module uses something like this:	3088	For example, the perl EV module uses something like this:
2521		3089
2522	#define EV_COMMON \	3090	#define EV_COMMON \
2523	SV *self; /* contains this struct */ \	3091	SV *self; /* contains this struct */ \
2524	SV *cb_sv, *fh /* note no trailing ";" */	3092	SV *cb_sv, *fh /* note no trailing ";" */
2525		3093
2526	=item EV_CB_DECLARE (type)	3094	=item EV_CB_DECLARE (type)
2527		3095
2528	=item EV_CB_INVOKE (watcher, revents)	3096	=item EV_CB_INVOKE (watcher, revents)
2529		3097
…		…
2536	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2537	method calls instead of plain function calls in C++.	3105	method calls instead of plain function calls in C++.
2538		3106
2539	=head2 EXPORTED API SYMBOLS	3107	=head2 EXPORTED API SYMBOLS
2540		3108
2541	If you need to re-export the API (e.g. via a dll) and you need a list of	3109	If you need to re-export the API (e.g. via a DLL) and you need a list of
2542	exported symbols, you can use the provided F<Symbol.*> files which list	3110	exported symbols, you can use the provided F<Symbol.*> files which list
2543	all public symbols, one per line:	3111	all public symbols, one per line:
2544		3112
2545	Symbols.ev for libev proper	3113	Symbols.ev for libev proper
2546	Symbols.event for the libevent emulation	3114	Symbols.event for the libevent emulation
2547		3115
2548	This can also be used to rename all public symbols to avoid clashes with	3116	This can also be used to rename all public symbols to avoid clashes with
2549	multiple versions of libev linked together (which is obviously bad in	3117	multiple versions of libev linked together (which is obviously bad in
2550	itself, but sometimes it is inconvinient to avoid this).	3118	itself, but sometimes it is inconvenient to avoid this).
2551		3119
2552	A sed command like this will create wrapper C<#define>'s that you need to	3120	A sed command like this will create wrapper C<#define>'s that you need to
2553	include before including F<ev.h>:	3121	include before including F<ev.h>:
2554		3122
2555	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3123	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2572	file.	3140	file.
2573		3141
2574	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2575	that everybody includes and which overrides some configure choices:	3143	that everybody includes and which overrides some configure choices:
2576		3144
2577	#define EV_MINIMAL 1	3145	#define EV_MINIMAL 1
2578	#define EV_USE_POLL 0	3146	#define EV_USE_POLL 0
2579	#define EV_MULTIPLICITY 0	3147	#define EV_MULTIPLICITY 0
2580	#define EV_PERIODIC_ENABLE 0	3148	#define EV_PERIODIC_ENABLE 0
2581	#define EV_STAT_ENABLE 0	3149	#define EV_STAT_ENABLE 0
2582	#define EV_FORK_ENABLE 0	3150	#define EV_FORK_ENABLE 0
2583	#define EV_CONFIG_H <config.h>	3151	#define EV_CONFIG_H <config.h>
2584	#define EV_MINPRI 0	3152	#define EV_MINPRI 0
2585	#define EV_MAXPRI 0	3153	#define EV_MAXPRI 0
2586		3154
2587	#include "ev++.h"	3155	#include "ev++.h"
2588		3156
2589	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2590		3158
2591	#include "ev_cpp.h"	3159	#include "ev_cpp.h"
2592	#include "ev.c"	3160	#include "ev.c"
		3161
		3162
		3163	=head1 THREADS AND COROUTINES
		3164
		3165	=head2 THREADS
		3166
		3167	Libev itself is completely thread-safe, but it uses no locking. This
		3168	means that you can use as many loops as you want in parallel, as long as
		3169	only one thread ever calls into one libev function with the same loop
		3170	parameter.
		3171
		3172	Or put differently: calls with different loop parameters can be done in
		3173	parallel from multiple threads, calls with the same loop parameter must be
		3174	done serially (but can be done from different threads, as long as only one
		3175	thread ever is inside a call at any point in time, e.g. by using a mutex
		3176	per loop).
		3177
		3178	If you want to know which design is best for your problem, then I cannot
		3179	help you but by giving some generic advice:
		3180
		3181	=over 4
		3182
		3183	=item * most applications have a main thread: use the default libev loop
		3184	in that thread, or create a separate thread running only the default loop.
		3185
		3186	This helps integrating other libraries or software modules that use libev
		3187	themselves and don't care/know about threading.
		3188
		3189	=item * one loop per thread is usually a good model.
		3190
		3191	Doing this is almost never wrong, sometimes a better-performance model
		3192	exists, but it is always a good start.
		3193
		3194	=item * other models exist, such as the leader/follower pattern, where one
		3195	loop is handed through multiple threads in a kind of round-robin fashion.
		3196
		3197	Choosing a model is hard - look around, learn, know that usually you can do
		3198	better than you currently do :-)
		3199
		3200	=item * often you need to talk to some other thread which blocks in the
		3201	event loop - C<ev_async> watchers can be used to wake them up from other
		3202	threads safely (or from signal contexts...).
		3203
		3204	=back
		3205
		3206	=head2 COROUTINES
		3207
		3208	Libev is much more accommodating to coroutines ("cooperative threads"):
		3209	libev fully supports nesting calls to it's functions from different
		3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3211	different coroutines and switch freely between both coroutines running the
		3212	loop, as long as you don't confuse yourself). The only exception is that
		3213	you must not do this from C<ev_periodic> reschedule callbacks.
		3214
		3215	Care has been invested into making sure that libev does not keep local
		3216	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3217	switches.
2593		3218
2594		3219
2595	=head1 COMPLEXITIES	3220	=head1 COMPLEXITIES
2596		3221
2597	In this section the complexities of (many of) the algorithms used inside	3222	In this section the complexities of (many of) the algorithms used inside
…		…
2608		3233
2609	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2610		3235
2611	This means that, when you have a watcher that triggers in one hour and	3236	This means that, when you have a watcher that triggers in one hour and
2612	there are 100 watchers that would trigger before that then inserting will	3237	there are 100 watchers that would trigger before that then inserting will
2613	have to skip those 100 watchers.	3238	have to skip roughly seven (C<ld 100>) of these watchers.
2614		3239
2615	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2616		3241
2617	That means that for changing a timer costs less than removing/adding them	3242	That means that changing a timer costs less than removing/adding them
2618	as only the relative motion in the event queue has to be paid for.	3243	as only the relative motion in the event queue has to be paid for.
2619		3244
2620	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2621		3246
2622	These just add the watcher into an array or at the head of a list.	3247	These just add the watcher into an array or at the head of a list.
		3248
2623	=item Stopping check/prepare/idle watchers: O(1)	3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2624		3250
2625	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2626		3252
2627	These watchers are stored in lists then need to be walked to find the	3253	These watchers are stored in lists then need to be walked to find the
2628	correct watcher to remove. The lists are usually short (you don't usually	3254	correct watcher to remove. The lists are usually short (you don't usually
2629	have many watchers waiting for the same fd or signal).	3255	have many watchers waiting for the same fd or signal).
2630		3256
2631	=item Finding the next timer per loop iteration: O(1)	3257	=item Finding the next timer in each loop iteration: O(1)
		3258
		3259	By virtue of using a binary or 4-heap, the next timer is always found at a
		3260	fixed position in the storage array.
2632		3261
2633	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2634		3263
2635	A change means an I/O watcher gets started or stopped, which requires	3264	A change means an I/O watcher gets started or stopped, which requires
2636	libev to recalculate its status (and possibly tell the kernel).	3265	libev to recalculate its status (and possibly tell the kernel, depending
		3266	on backend and whether C<ev_io_set> was used).
2637		3267
2638	=item Activating one watcher: O(1)	3268	=item Activating one watcher (putting it into the pending state): O(1)
2639		3269
2640	=item Priority handling: O(number_of_priorities)	3270	=item Priority handling: O(number_of_priorities)
2641		3271
2642	Priorities are implemented by allocating some space for each	3272	Priorities are implemented by allocating some space for each
2643	priority. When doing priority-based operations, libev usually has to	3273	priority. When doing priority-based operations, libev usually has to
2644	linearly search all the priorities.	3274	linearly search all the priorities, but starting/stopping and activating
		3275	watchers becomes O(1) w.r.t. priority handling.
		3276
		3277	=item Sending an ev_async: O(1)
		3278
		3279	=item Processing ev_async_send: O(number_of_async_watchers)
		3280
		3281	=item Processing signals: O(max_signal_number)
		3282
		3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3284	calls in the current loop iteration. Checking for async and signal events
		3285	involves iterating over all running async watchers or all signal numbers.
2645		3286
2646	=back	3287	=back
2647		3288
2648		3289
		3290	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3291
		3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3293	requires, and its I/O model is fundamentally incompatible with the POSIX
		3294	model. Libev still offers limited functionality on this platform in
		3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3296	descriptors. This only applies when using Win32 natively, not when using
		3297	e.g. cygwin.
		3298
		3299	Lifting these limitations would basically require the full
		3300	re-implementation of the I/O system. If you are into these kinds of
		3301	things, then note that glib does exactly that for you in a very portable
		3302	way (note also that glib is the slowest event library known to man).
		3303
		3304	There is no supported compilation method available on windows except
		3305	embedding it into other applications.
		3306
		3307	Not a libev limitation but worth mentioning: windows apparently doesn't
		3308	accept large writes: instead of resulting in a partial write, windows will
		3309	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3310	so make sure you only write small amounts into your sockets (less than a
		3311	megabyte seems safe, but thsi apparently depends on the amount of memory
		3312	available).
		3313
		3314	Due to the many, low, and arbitrary limits on the win32 platform and
		3315	the abysmal performance of winsockets, using a large number of sockets
		3316	is not recommended (and not reasonable). If your program needs to use
		3317	more than a hundred or so sockets, then likely it needs to use a totally
		3318	different implementation for windows, as libev offers the POSIX readiness
		3319	notification model, which cannot be implemented efficiently on windows
		3320	(Microsoft monopoly games).
		3321
		3322	=over 4
		3323
		3324	=item The winsocket select function
		3325
		3326	The winsocket C<select> function doesn't follow POSIX in that it
		3327	requires socket I<handles> and not socket I<file descriptors> (it is
		3328	also extremely buggy). This makes select very inefficient, and also
		3329	requires a mapping from file descriptors to socket handles. See the
		3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3332
		3333	The configuration for a "naked" win32 using the Microsoft runtime
		3334	libraries and raw winsocket select is:
		3335
		3336	#define EV_USE_SELECT 1
		3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3338
		3339	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3340	complexity in the O(n²) range when using win32.
		3341
		3342	=item Limited number of file descriptors
		3343
		3344	Windows has numerous arbitrary (and low) limits on things.
		3345
		3346	Early versions of winsocket's select only supported waiting for a maximum
		3347	of C<64> handles (probably owning to the fact that all windows kernels
		3348	can only wait for C<64> things at the same time internally; Microsoft
		3349	recommends spawning a chain of threads and wait for 63 handles and the
		3350	previous thread in each. Great).
		3351
		3352	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3353	to some high number (e.g. C<2048>) before compiling the winsocket select
		3354	call (which might be in libev or elsewhere, for example, perl does its own
		3355	select emulation on windows).
		3356
		3357	Another limit is the number of file descriptors in the Microsoft runtime
		3358	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3359	or something like this inside Microsoft). You can increase this by calling
		3360	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3361	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3362	libraries.
		3363
		3364	This might get you to about C<512> or C<2048> sockets (depending on
		3365	windows version and/or the phase of the moon). To get more, you need to
		3366	wrap all I/O functions and provide your own fd management, but the cost of
		3367	calling select (O(n²)) will likely make this unworkable.
		3368
		3369	=back
		3370
		3371
		3372	=head1 PORTABILITY REQUIREMENTS
		3373
		3374	In addition to a working ISO-C implementation, libev relies on a few
		3375	additional extensions:
		3376
		3377	=over 4
		3378
		3379	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3380	calling conventions regardless of C<ev_watcher_type *>.
		3381
		3382	Libev assumes not only that all watcher pointers have the same internal
		3383	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3384	assumes that the same (machine) code can be used to call any watcher
		3385	callback: The watcher callbacks have different type signatures, but libev
		3386	calls them using an C<ev_watcher *> internally.
		3387
		3388	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3389
		3390	The type C<sig_atomic_t volatile> (or whatever is defined as
		3391	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3392	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3393	believed to be sufficiently portable.
		3394
		3395	=item C<sigprocmask> must work in a threaded environment
		3396
		3397	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3398	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3399	pthread implementations will either allow C<sigprocmask> in the "main
		3400	thread" or will block signals process-wide, both behaviours would
		3401	be compatible with libev. Interaction between C<sigprocmask> and
		3402	C<pthread_sigmask> could complicate things, however.
		3403
		3404	The most portable way to handle signals is to block signals in all threads
		3405	except the initial one, and run the default loop in the initial thread as
		3406	well.
		3407
		3408	=item C<long> must be large enough for common memory allocation sizes
		3409
		3410	To improve portability and simplify using libev, libev uses C<long>
		3411	internally instead of C<size_t> when allocating its data structures. On
		3412	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3413	is still at least 31 bits everywhere, which is enough for hundreds of
		3414	millions of watchers.
		3415
		3416	=item C<double> must hold a time value in seconds with enough accuracy
		3417
		3418	The type C<double> is used to represent timestamps. It is required to
		3419	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3420	enough for at least into the year 4000. This requirement is fulfilled by
		3421	implementations implementing IEEE 754 (basically all existing ones).
		3422
		3423	=back
		3424
		3425	If you know of other additional requirements drop me a note.
		3426
		3427
		3428	=head1 COMPILER WARNINGS
		3429
		3430	Depending on your compiler and compiler settings, you might get no or a
		3431	lot of warnings when compiling libev code. Some people are apparently
		3432	scared by this.
		3433
		3434	However, these are unavoidable for many reasons. For one, each compiler
		3435	has different warnings, and each user has different tastes regarding
		3436	warning options. "Warn-free" code therefore cannot be a goal except when
		3437	targeting a specific compiler and compiler-version.
		3438
		3439	Another reason is that some compiler warnings require elaborate
		3440	workarounds, or other changes to the code that make it less clear and less
		3441	maintainable.
		3442
		3443	And of course, some compiler warnings are just plain stupid, or simply
		3444	wrong (because they don't actually warn about the condition their message
		3445	seems to warn about).
		3446
		3447	While libev is written to generate as few warnings as possible,
		3448	"warn-free" code is not a goal, and it is recommended not to build libev
		3449	with any compiler warnings enabled unless you are prepared to cope with
		3450	them (e.g. by ignoring them). Remember that warnings are just that:
		3451	warnings, not errors, or proof of bugs.
		3452
		3453
		3454	=head1 VALGRIND
		3455
		3456	Valgrind has a special section here because it is a popular tool that is
		3457	highly useful, but valgrind reports are very hard to interpret.
		3458
		3459	If you think you found a bug (memory leak, uninitialised data access etc.)
		3460	in libev, then check twice: If valgrind reports something like:
		3461
		3462	==2274== definitely lost: 0 bytes in 0 blocks.
		3463	==2274== possibly lost: 0 bytes in 0 blocks.
		3464	==2274== still reachable: 256 bytes in 1 blocks.
		3465
		3466	Then there is no memory leak. Similarly, under some circumstances,
		3467	valgrind might report kernel bugs as if it were a bug in libev, or it
		3468	might be confused (it is a very good tool, but only a tool).
		3469
		3470	If you are unsure about something, feel free to contact the mailing list
		3471	with the full valgrind report and an explanation on why you think this is
		3472	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3473	no bug" answer and take the chance of learning how to interpret valgrind
		3474	properly.
		3475
		3476	If you need, for some reason, empty reports from valgrind for your project
		3477	I suggest using suppression lists.
		3478
		3479
2649	=head1 AUTHOR	3480	=head1 AUTHOR
2650		3481
2651	Marc Lehmann <libev@schmorp.de>.	3482	Marc Lehmann <libev@schmorp.de>.
2652		3483

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