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Revision 1.86 by root, Tue Dec 18 01:20:33 2007 UTC vs.
Revision 1.166 by root, Tue Jun 3 03:48:10 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 occuring), 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
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
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.
…		…
114	=item ev_tstamp ev_time ()	150	=item ev_tstamp ev_time ()
115		151
116	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
117	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
118	you actually want to know.	154	you actually want to know.
		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	Sleep for the given interval: The current thread will be blocked until
		159	either it is interrupted or the given time interval has passed. Basically
		160	this is a sub-second-resolution C<sleep ()>.
119		161
120	=item int ev_version_major ()	162	=item int ev_version_major ()
121		163
122	=item int ev_version_minor ()	164	=item int ev_version_minor ()
123		165
…		…
136	not a problem.	178	not a problem.
137		179
138	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
139	version.	181	version.
140		182
141	assert (("libev version mismatch",	183	assert (("libev version mismatch",
142	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
143	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
144		186
145	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
146		188
147	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_*>
148	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
150	a description of the set values.	192	a description of the set values.
151		193
152	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
153	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
154		196
155	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
156	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
157		199
158	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
159		201
160	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
161	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
162	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
163	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
164	(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
165	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
166		208
167	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
168		210
…		…
175	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
176		218
177	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
178		220
179	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
180	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
181	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
182	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
183	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
184	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.
185		230
186	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
187	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,
188	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.
189		234
190	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
191	retries).	236	retries (example requires a standards-compliant C<realloc>).
192		237
193	static void *	238	static void *
194	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
195	{	240	{
196	for (;;)	241	for (;;)
…		…
207	...	252	...
208	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
209		254
210	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
211		256
212	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
213	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
214	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
215	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
216	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
217	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
218	(such as abort).	263	(such as abort).
219		264
220	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.
…		…
234	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
235		280
236	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
237	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
238	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
239
240	If you use threads, a common model is to run the default event loop
241	in your main thread (or in a separate thread) and for each thread you
242	create, you also create another event loop. Libev itself does no locking
243	whatsoever, so if you mix calls to the same event loop in different
244	threads, make sure you lock (this is usually a bad idea, though, even if
245	done correctly, because it's hideous and inefficient).
246		284
247	=over 4	285	=over 4
248		286
249	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
250		288
…		…
254	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
255		293
256	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
257	function.	295	function.
258		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
259	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
260	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>).
261		310
262	The following flags are supported:	311	The following flags are supported:
263		312
…		…
268	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
269	thing, believe me).	318	thing, believe me).
270		319
271	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
272		321
273	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
274	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
275	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
276	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
277	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
278	around bugs.	327	around bugs.
…		…
284	enabling this flag.	333	enabling this flag.
285		334
286	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,
287	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
288	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
289	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
290	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
291	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
292		341
293	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
294	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
295	flag.	344	flag.
296		345
297	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>
298	environment variable.	347	environment variable.
299		348
300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301		350
302	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
303	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,
304	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
305	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
306	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.
307		363
308	=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)
309		365
310	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
311	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
312	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
313	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.
314		372
315	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
316		374
317	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,
318	but it scales phenomenally better. While poll and select usually scale like	376	but it scales phenomenally better. While poll and select usually scale
319	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	377	like O(total_fds) where n is the total number of fds (or the highest fd),
320	either O(1) or O(active_fds).	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
		379	of shortcomings, such as silently dropping events in some hard-to-detect
		380	cases and requiring a system call per fd change, no fork support and bad
		381	support for dup.
321		382
322	While stopping and starting an I/O watcher in the same iteration will	383	While stopping, setting and starting an I/O watcher in the same iteration
323	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
324	(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
325	best to avoid that. Also, dup()ed file descriptors might not work very	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
326	well if you register events for both fds.	387	very well if you register events for both fds.
327		388
328	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
329	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
330	(or space) is available.	391	(or space) is available.
331		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
332	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
333		401
334	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
335	was broken on all BSDs except NetBSD (usually it doesn't work with	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
336	anything but sockets and pipes, except on Darwin, where of course its	404	with anything but sockets and pipes, except on Darwin, where of course
337	completely useless). For this reason its not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
338	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
339	C<EVBACKEND_KQUEUE>).	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		408	system like NetBSD.
		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.
340		413
341	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
342	kernel is more efficient (which says nothing about its actual speed, of	415	kernel is more efficient (which says nothing about its actual speed, of
343	course). While starting and stopping an I/O watcher does not cause an	416	course). While stopping, setting and starting an I/O watcher does never
344	extra syscall as with epoll, it still adds up to four event changes per	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
345	incident, so its best to avoid that.	418	two event changes per incident, support for C<fork ()> is very bad and it
		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.
346		429
347	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
348		431
349	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.
350		436
351	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
352		438
353	This uses the Solaris 10 port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
354	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)).
355		441
356	Please note that solaris ports can result in a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
357	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
358	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.
359		454
360	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
361		456
362	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
363	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
364	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
365		460
		461	It is definitely not recommended to use this flag.
		462
366	=back	463	=back
367		464
368	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
369	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
370	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
371	order of their flag values :)
372		468
373	The most typical usage is like this:	469	The most typical usage is like this:
374		470
375	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
376	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
377		473
378	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
379	environment settings to be taken into account:	475	environment settings to be taken into account:
380		476
381	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
382		478
383	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
384	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
385	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):
386		482
387	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
388		484
389	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
390		486
391	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
392	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
393	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
394	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
395		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
396	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.
397		497
398	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
399	if (!epoller)	499	if (!epoller)
400	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
401		501
402	=item ev_default_destroy ()	502	=item ev_default_destroy ()
403		503
404	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
405	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
406	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
407	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
408	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
409	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
410	for example).	510	for example).
		511
		512	Note that certain global state, such as signal state, will not be freed by
		513	this function, and related watchers (such as signal and child watchers)
		514	would need to be stopped manually.
		515
		516	In general it is not advisable to call this function except in the
		517	rare occasion where you really need to free e.g. the signal handling
		518	pipe fds. If you need dynamically allocated loops it is better to use
		519	C<ev_loop_new> and C<ev_loop_destroy>).
411		520
412	=item ev_loop_destroy (loop)	521	=item ev_loop_destroy (loop)
413		522
414	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
415	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
416		525
417	=item ev_default_fork ()	526	=item ev_default_fork ()
418		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
419	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
420	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
421	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
422	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.
423		534
424	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
425	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
426	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
427		538
428	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
429	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
430	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
431		542
432	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
433		544
434	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
435	without calling this function, so if you force one of those backends you
436	do not need to care.
437
438	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
439		546
440	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
441	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
442	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.
443		554
444	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
445		556
446	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
447	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
…		…
460		571
461	Returns the current "event loop time", which is the time the event loop	572	Returns the current "event loop time", which is the time the event loop
462	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
463	change as long as callbacks are being processed, and this is also the base	574	change as long as callbacks are being processed, and this is also the base
464	time used for relative timers. You can treat it as the timestamp of the	575	time used for relative timers. You can treat it as the timestamp of the
465	event occuring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
466		577
467	=item ev_loop (loop, int flags)	578	=item ev_loop (loop, int flags)
468		579
469	Finally, this is it, the event handler. This function usually is called	580	Finally, this is it, the event handler. This function usually is called
470	after you initialised all your watchers and you want to start handling	581	after you initialised all your watchers and you want to start handling
…		…
482	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
483	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
484	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.
485		596
486	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
487	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
488	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
489	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
490	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
491	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
492	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
493		604
494	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
495		606
496	- Before the first iteration, call any pending watchers.	607	- Before the first iteration, call any pending watchers.
497	* If there are no active watchers (reference count is zero), return.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
498	- 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.
499	- If we have been forked, recreate the kernel state.	611	- If we have been forked, recreate the kernel state.
500	- Update the kernel state with all outstanding changes.	612	- Update the kernel state with all outstanding changes.
501	- Update the "event loop time".	613	- Update the "event loop time".
502	- 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.
503	- Block the process, waiting for any events.	618	- Block the process, waiting for any events.
504	- Queue all outstanding I/O (fd) events.	619	- Queue all outstanding I/O (fd) events.
505	- Update the "event loop time" and do time jump handling.	620	- Update the "event loop time" and do time jump handling.
506	- Queue all outstanding timers.	621	- Queue all outstanding timers.
507	- Queue all outstanding periodics.	622	- Queue all outstanding periodics.
508	- If no events are pending now, queue all idle watchers.	623	- If no events are pending now, queue all idle watchers.
509	- Queue all check watchers.	624	- Queue all check watchers.
510	- 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).
511	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
512	be handled here by queueing them when their watcher gets executed.	627	be handled here by queueing them when their watcher gets executed.
513	- 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
514	were used, return, otherwise continue with step *.	629	were used, or there are no active watchers, return, otherwise
		630	continue with step *.
515		631
516	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
517	anymore.	633	anymore.
518		634
519	... queue jobs here, make sure they register event watchers as long	635	... queue jobs here, make sure they register event watchers as long
520	... 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..)
521	ev_loop (my_loop, 0);	637	ev_loop (my_loop, 0);
…		…
525		641
526	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
527	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
528	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
529	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.
530		648
531	=item ev_ref (loop)	649	=item ev_ref (loop)
532		650
533	=item ev_unref (loop)	651	=item ev_unref (loop)
534		652
…		…
539	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
540	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
541	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
542	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
543	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
544	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).
545		665
546	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>
547	running when nothing else is active.	667	running when nothing else is active.
548		668
549	struct ev_signal exitsig;	669	struct ev_signal exitsig;
550	ev_signal_init (&exitsig, sig_cb, SIGINT);	670	ev_signal_init (&exitsig, sig_cb, SIGINT);
551	ev_signal_start (loop, &exitsig);	671	ev_signal_start (loop, &exitsig);
552	evf_unref (loop);	672	evf_unref (loop);
553		673
554	Example: For some weird reason, unregister the above signal handler again.	674	Example: For some weird reason, unregister the above signal handler again.
555		675
556	ev_ref (loop);	676	ev_ref (loop);
557	ev_signal_stop (loop, &exitsig);	677	ev_signal_stop (loop, &exitsig);
		678
		679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		680
		681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		682
		683	These advanced functions influence the time that libev will spend waiting
		684	for events. Both are by default C<0>, meaning that libev will try to
		685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		686
		687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		688	allows libev to delay invocation of I/O and timer/periodic callbacks to
		689	increase efficiency of loop iterations.
		690
		691	The background is that sometimes your program runs just fast enough to
		692	handle one (or very few) event(s) per loop iteration. While this makes
		693	the program responsive, it also wastes a lot of CPU time to poll for new
		694	events, especially with backends like C<select ()> which have a high
		695	overhead for the actual polling but can deliver many events at once.
		696
		697	By setting a higher I<io collect interval> you allow libev to spend more
		698	time collecting I/O events, so you can handle more events per iteration,
		699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		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.
		702
		703	Likewise, by setting a higher I<timeout collect interval> you allow libev
		704	to spend more time collecting timeouts, at the expense of increased
		705	latency (the watcher callback will be called later). C<ev_io> watchers
		706	will not be affected. Setting this to a non-null value will not introduce
		707	any overhead in libev.
		708
		709	Many (busy) programs can usually benefit by setting the I/O collect
		710	interval to a value near C<0.1> or so, which is often enough for
		711	interactive servers (of course not for games), likewise for timeouts. It
		712	usually doesn't make much sense to set it to a lower value than C<0.01>,
		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.
558		725
559	=back	726	=back
560		727
561		728
562	=head1 ANATOMY OF A WATCHER	729	=head1 ANATOMY OF A WATCHER
563		730
564	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
565	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
566	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:
567		734
568	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)
569	{	736	{
570	ev_io_stop (w);	737	ev_io_stop (w);
571	ev_unloop (loop, EVUNLOOP_ALL);	738	ev_unloop (loop, EVUNLOOP_ALL);
572	}	739	}
573		740
574	struct ev_loop *loop = ev_default_loop (0);	741	struct ev_loop *loop = ev_default_loop (0);
575	struct ev_io stdin_watcher;	742	struct ev_io stdin_watcher;
576	ev_init (&stdin_watcher, my_cb);	743	ev_init (&stdin_watcher, my_cb);
577	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
578	ev_io_start (loop, &stdin_watcher);	745	ev_io_start (loop, &stdin_watcher);
579	ev_loop (loop, 0);	746	ev_loop (loop, 0);
580		747
581	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
582	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,
583	although this can sometimes be quite valid).	750	although this can sometimes be quite valid).
584		751
585	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
586	(watcher *, callback)>, which expects a callback to be provided. This	753	(watcher *, callback)>, which expects a callback to be provided. This
587	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
588	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
589	is readable and/or writable).	756	is readable and/or writable).
590		757
591	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
592	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
…		…
662	=item C<EV_FORK>	829	=item C<EV_FORK>
663		830
664	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
665	C<ev_fork>).	832	C<ev_fork>).
666		833
		834	=item C<EV_ASYNC>
		835
		836	The given async watcher has been asynchronously notified (see C<ev_async>).
		837
667	=item C<EV_ERROR>	838	=item C<EV_ERROR>
668		839
669	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
670	happen because the watcher could not be properly started because libev	841	happen because the watcher could not be properly started because libev
671	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
672	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
673	with the watcher being stopped.	844	with the watcher being stopped.
674		845
675	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,
676	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
677	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
678	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
679	programs, though, so beware.	850	programs, though, so beware.
680		851
681	=back	852	=back
682		853
683	=head2 GENERIC WATCHER FUNCTIONS	854	=head2 GENERIC WATCHER FUNCTIONS
…		…
713	Although some watcher types do not have type-specific arguments	884	Although some watcher types do not have type-specific arguments
714	(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.
715		886
716	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
717		888
718	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
719	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
720	a watcher. The same limitations apply, of course.	891	a watcher. The same limitations apply, of course.
721		892
722	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
723		894
724	Starts (activates) the given watcher. Only active watchers will receive	895	Starts (activates) the given watcher. Only active watchers will receive
…		…
807	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
808	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
809	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
810	data:	981	data:
811		982
812	struct my_io	983	struct my_io
813	{	984	{
814	struct ev_io io;	985	struct ev_io io;
815	int otherfd;	986	int otherfd;
816	void *somedata;	987	void *somedata;
817	struct whatever *mostinteresting;	988	struct whatever *mostinteresting;
818	}	989	}
819		990
820	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
821	can cast it back to your own type:	992	can cast it back to your own type:
822		993
823	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)
824	{	995	{
825	struct my_io *w = (struct my_io *)w_;	996	struct my_io *w = (struct my_io *)w_;
826	...	997	...
827	}	998	}
828		999
829	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
830	instead have been omitted.	1001	instead have been omitted.
831		1002
832	Another common scenario is having some data structure with multiple	1003	Another common scenario is having some data structure with multiple
833	watchers:	1004	watchers:
834		1005
835	struct my_biggy	1006	struct my_biggy
836	{	1007	{
837	int some_data;	1008	int some_data;
838	ev_timer t1;	1009	ev_timer t1;
839	ev_timer t2;	1010	ev_timer t2;
840	}	1011	}
841		1012
842	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,
843	you need to use C<offsetof>:	1014	you need to use C<offsetof>:
844		1015
845	#include <stddef.h>	1016	#include <stddef.h>
846		1017
847	static void	1018	static void
848	t1_cb (EV_P_ struct ev_timer *w, int revents)	1019	t1_cb (EV_P_ struct ev_timer *w, int revents)
849	{	1020	{
850	struct my_biggy big = (struct my_biggy *	1021	struct my_biggy big = (struct my_biggy *
851	(((char *)w) - offsetof (struct my_biggy, t1));	1022	(((char *)w) - offsetof (struct my_biggy, t1));
852	}	1023	}
853		1024
854	static void	1025	static void
855	t2_cb (EV_P_ struct ev_timer *w, int revents)	1026	t2_cb (EV_P_ struct ev_timer *w, int revents)
856	{	1027	{
857	struct my_biggy big = (struct my_biggy *	1028	struct my_biggy big = (struct my_biggy *
858	(((char *)w) - offsetof (struct my_biggy, t2));	1029	(((char *)w) - offsetof (struct my_biggy, t2));
859	}	1030	}
860		1031
861		1032
862	=head1 WATCHER TYPES	1033	=head1 WATCHER TYPES
863		1034
864	This section describes each watcher in detail, but will not repeat	1035	This section describes each watcher in detail, but will not repeat
…		…
888	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
889	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
890	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
891	required if you know what you are doing).	1062	required if you know what you are doing).
892		1063
893	You have to be careful with dup'ed file descriptors, though. Some backends
894	(the linux epoll backend is a notable example) cannot handle dup'ed file
895	descriptors correctly if you register interest in two or more fds pointing
896	to the same underlying file/socket/etc. description (that is, they share
897	the same underlying "file open").
898
899	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
900	(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
901	C<EVBACKEND_POLL>).	1066	C<EVBACKEND_POLL>).
902		1067
903	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
904	receive "spurious" readyness notifications, that is your callback might	1069	receive "spurious" readiness notifications, that is your callback might
905	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
906	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
907	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
908	this situation even with a relatively standard program structure. Thus	1073	this situation even with a relatively standard program structure. Thus
909	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
910	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.
911		1076
912	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
913	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
914	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
915	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
916	its own, so its quite safe to use).	1081	its own, so its quite safe to use).
917		1082
918	=head3 The special problem of disappearing file descriptors	1083	=head3 The special problem of disappearing file descriptors
919		1084
920	Some backends (e.g kqueue, epoll) need to be told about closing a file	1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file
921	descriptor (either by calling C<close> explicitly or by any other means,	1086	descriptor (either by calling C<close> explicitly or by any other means,
922	such as C<dup>). The reason is that you register interest in some file	1087	such as C<dup>). The reason is that you register interest in some file
923	descriptor, but when it goes away, the operating system will silently drop	1088	descriptor, but when it goes away, the operating system will silently drop
924	this interest. If another file descriptor with the same number then is	1089	this interest. If another file descriptor with the same number then is
925	registered with libev, there is no efficient way to see that this is, in	1090	registered with libev, there is no efficient way to see that this is, in
…		…
934		1099
935	This is how one would do it normally anyway, the important point is that	1100	This is how one would do it normally anyway, the important point is that
936	the libev application should not optimise around libev but should leave	1101	the libev application should not optimise around libev but should leave
937	optimisations to libev.	1102	optimisations to libev.
938		1103
		1104	=head3 The special problem of dup'ed file descriptors
		1105
		1106	Some backends (e.g. epoll), cannot register events for file descriptors,
		1107	but only events for the underlying file descriptions. That means when you
		1108	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1109	events for them, only one file descriptor might actually receive events.
		1110
		1111	There is no workaround possible except not registering events
		1112	for potentially C<dup ()>'ed file descriptors, or to resort to
		1113	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1114
		1115	=head3 The special problem of fork
		1116
		1117	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1118	useless behaviour. Libev fully supports fork, but needs to be told about
		1119	it in the child.
		1120
		1121	To support fork in your programs, you either have to call
		1122	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1124	C<EVBACKEND_POLL>.
		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
939		1138
940	=head3 Watcher-Specific Functions	1139	=head3 Watcher-Specific Functions
941		1140
942	=over 4	1141	=over 4
943		1142
944	=item ev_io_init (ev_io *, callback, int fd, int events)	1143	=item ev_io_init (ev_io *, callback, int fd, int events)
945		1144
946	=item ev_io_set (ev_io *, int fd, int events)	1145	=item ev_io_set (ev_io *, int fd, int events)
947		1146
948	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
949	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
950	C<EV_READ | EV_WRITE> to receive the given events.	1149	C<EV_READ | EV_WRITE> to receive the given events.
951		1150
952	=item int fd [read-only]	1151	=item int fd [read-only]
953		1152
954	The file descriptor being watched.	1153	The file descriptor being watched.
…		…
956	=item int events [read-only]	1155	=item int events [read-only]
957		1156
958	The events being watched.	1157	The events being watched.
959		1158
960	=back	1159	=back
		1160
		1161	=head3 Examples
961		1162
962	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
963	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
964	attempt to read a whole line in the callback.	1165	attempt to read a whole line in the callback.
965		1166
966	static void	1167	static void
967	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)
968	{	1169	{
969	ev_io_stop (loop, w);	1170	ev_io_stop (loop, w);
970	.. 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
971	}	1172	}
972		1173
973	...	1174	...
974	struct ev_loop *loop = ev_default_init (0);	1175	struct ev_loop *loop = ev_default_init (0);
975	struct ev_io stdin_readable;	1176	struct ev_io stdin_readable;
976	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);
977	ev_io_start (loop, &stdin_readable);	1178	ev_io_start (loop, &stdin_readable);
978	ev_loop (loop, 0);	1179	ev_loop (loop, 0);
979		1180
980		1181
981	=head2 C<ev_timer> - relative and optionally repeating timeouts	1182	=head2 C<ev_timer> - relative and optionally repeating timeouts
982		1183
983	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
984	given time, and optionally repeating in regular intervals after that.	1185	given time, and optionally repeating in regular intervals after that.
985		1186
986	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
987	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
988	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
989	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the
990	monotonic clock option helps a lot here).	1191	monotonic clock option helps a lot here).
991		1192
992	The relative timeouts are calculated relative to the C<ev_now ()>	1193	The relative timeouts are calculated relative to the C<ev_now ()>
993	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
…		…
995	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
996	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:
997		1198
998	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
999		1200
1000	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,
1001	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
1002	order of execution is undefined.	1203	order of execution is undefined.
1003		1204
1004	=head3 Watcher-Specific Functions and Data Members	1205	=head3 Watcher-Specific Functions and Data Members
1005		1206
…		…
1007		1208
1008	=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)
1009		1210
1010	=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)
1011		1212
1012	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>
1013	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
1014	timer will automatically be configured to trigger again C<repeat> seconds	1215	reached. If it is positive, then the timer will automatically be
1015	later, again, and again, until stopped manually.	1216	configured to trigger again C<repeat> seconds later, again, and again,
		1217	until stopped manually.
1016		1218
1017	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
1018	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
1019	exactly 10 second intervals. If, however, your program cannot keep up with	1221	trigger at exactly 10 second intervals. If, however, your program cannot
1020	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
1021	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.
1022		1224
1023	=item ev_timer_again (loop)	1225	=item ev_timer_again (loop, ev_timer *)
1024		1226
1025	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
1026	repeating. The exact semantics are:	1228	repeating. The exact semantics are:
1027		1229
1028	If the timer is pending, its pending status is cleared.	1230	If the timer is pending, its pending status is cleared.
1029		1231
1030	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).
1031		1233
1032	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
1033	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.
1034		1236
1035	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
1036	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
1037	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
1038	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
1039	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
1040	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
1041	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
…		…
1063	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),
1064	which is also when any modifications are taken into account.	1266	which is also when any modifications are taken into account.
1065		1267
1066	=back	1268	=back
1067		1269
		1270	=head3 Examples
		1271
1068	Example: Create a timer that fires after 60 seconds.	1272	Example: Create a timer that fires after 60 seconds.
1069		1273
1070	static void	1274	static void
1071	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)
1072	{	1276	{
1073	.. one minute over, w is actually stopped right here	1277	.. one minute over, w is actually stopped right here
1074	}	1278	}
1075		1279
1076	struct ev_timer mytimer;	1280	struct ev_timer mytimer;
1077	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1078	ev_timer_start (loop, &mytimer);	1282	ev_timer_start (loop, &mytimer);
1079		1283
1080	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
1081	inactivity.	1285	inactivity.
1082		1286
1083	static void	1287	static void
1084	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)
1085	{	1289	{
1086	.. ten seconds without any activity	1290	.. ten seconds without any activity
1087	}	1291	}
1088		1292
1089	struct ev_timer mytimer;	1293	struct ev_timer mytimer;
1090	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 */
1091	ev_timer_again (&mytimer); /* start timer */	1295	ev_timer_again (&mytimer); /* start timer */
1092	ev_loop (loop, 0);	1296	ev_loop (loop, 0);
1093		1297
1094	// 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":
1095	// reset the timeout to start ticking again at 10 seconds	1299	// reset the timeout to start ticking again at 10 seconds
1096	ev_timer_again (&mytimer);	1300	ev_timer_again (&mytimer);
1097		1301
1098		1302
1099	=head2 C<ev_periodic> - to cron or not to cron?	1303	=head2 C<ev_periodic> - to cron or not to cron?
1100		1304
1101	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
1102	(and unfortunately a bit complex).	1306	(and unfortunately a bit complex).
1103		1307
1104	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)
1105	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
1106	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
1107	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 ()
1108	+ 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
1109	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
1110	roughly 10 seconds later).	1315	roughly 10 seconds later as it uses a relative timeout).
1111		1316
1112	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,
1113	triggering an event on each midnight, local time or other, complicated,	1318	such as triggering an event on each "midnight, local time", or other
1114	rules.	1319	complicated, rules.
1115		1320
1116	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
1117	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
1118	during the same loop iteration then order of execution is undefined.	1323	during the same loop iteration then order of execution is undefined.
1119		1324
1120	=head3 Watcher-Specific Functions and Data Members	1325	=head3 Watcher-Specific Functions and Data Members
1121		1326
1122	=over 4	1327	=over 4
…		…
1130		1335
1131	=over 4	1336	=over 4
1132		1337
1133	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1134		1339
1135	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
1136	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
1137	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
1138	system time reaches or surpasses this time.	1343	run when the system time reaches or surpasses this time.
1139		1344
1140	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1141		1346
1142	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
1143	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)
1144	and then repeat, regardless of any time jumps.	1349	and then repeat, regardless of any time jumps.
1145		1350
1146	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
1147	time:	1352	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1353	the hour:
1148		1354
1149	ev_periodic_set (&periodic, 0., 3600., 0);	1355	ev_periodic_set (&periodic, 0., 3600., 0);
1150		1356
1151	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,
1152	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
1153	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
1154	by 3600.	1360	by 3600.
1155		1361
1156	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
1157	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
1158	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.
1159		1365
1160	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
1161	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
1162	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).
1163		1374
1164	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1165		1376
1166	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
1167	ignored. Instead, each time the periodic watcher gets scheduled, the	1378	ignored. Instead, each time the periodic watcher gets scheduled, the
1168	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
1169	current time as second argument.	1380	current time as second argument.
1170		1381
1171	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,
1172	ever, or make any event loop modifications>. If you need to stop it,	1383	ever, or make ANY event loop modifications whatsoever>.
1173	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1174	starting an C<ev_prepare> watcher, which is legal).
1175		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
1176	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
1177	ev_tstamp now)>, e.g.:	1390	*w, ev_tstamp now)>, e.g.:
1178		1391
1179	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)
1180	{	1393	{
1181	return now + 60.;	1394	return now + 60.;
1182	}	1395	}
…		…
1184	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
1185	(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
1186	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
1187	might be called at other times, too.	1400	might be called at other times, too.
1188		1401
1189	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
1190	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1403	equal to the passed C<now> value >>.
1191		1404
1192	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
1193	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
1194	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
1195	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
1196	reason I omitted it as an example).	1409	reason I omitted it as an example).
1197		1410
1198	=back	1411	=back
…		…
1202	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
1203	when you changed some parameters or the reschedule callback would return	1416	when you changed some parameters or the reschedule callback would return
1204	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
1205	program when the crontabs have changed).	1418	program when the crontabs have changed).
1206		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
1207	=item ev_tstamp offset [read-write]	1425	=item ev_tstamp offset [read-write]
1208		1426
1209	When repeating, this contains the offset value, otherwise this is the	1427	When repeating, this contains the offset value, otherwise this is the
1210	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>).
1211		1429
…		…
1222		1440
1223	The current reschedule callback, or C<0>, if this functionality is	1441	The current reschedule callback, or C<0>, if this functionality is
1224	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
1225	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.
1226		1444
1227	=item ev_tstamp at [read-only]
1228
1229	When active, contains the absolute time that the watcher is supposed to
1230	trigger next.
1231
1232	=back	1445	=back
		1446
		1447	=head3 Examples
1233		1448
1234	Example: Call a callback every hour, or, more precisely, whenever the	1449	Example: Call a callback every hour, or, more precisely, whenever the
1235	system clock is divisible by 3600. The callback invocation times have	1450	system clock is divisible by 3600. The callback invocation times have
1236	potentially a lot of jittering, but good long-term stability.	1451	potentially a lot of jitter, but good long-term stability.
1237		1452
1238	static void	1453	static void
1239	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)
1240	{	1455	{
1241	... 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)
1242	}	1457	}
1243		1458
1244	struct ev_periodic hourly_tick;	1459	struct ev_periodic hourly_tick;
1245	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1246	ev_periodic_start (loop, &hourly_tick);	1461	ev_periodic_start (loop, &hourly_tick);
1247		1462
1248	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:
1249		1464
1250	#include <math.h>	1465	#include <math.h>
1251		1466
1252	static ev_tstamp	1467	static ev_tstamp
1253	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1254	{	1469	{
1255	return fmod (now, 3600.) + 3600.;	1470	return fmod (now, 3600.) + 3600.;
1256	}	1471	}
1257		1472
1258	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);
1259		1474
1260	Example: Call a callback every hour, starting now:	1475	Example: Call a callback every hour, starting now:
1261		1476
1262	struct ev_periodic hourly_tick;	1477	struct ev_periodic hourly_tick;
1263	ev_periodic_init (&hourly_tick, clock_cb,	1478	ev_periodic_init (&hourly_tick, clock_cb,
1264	fmod (ev_now (loop), 3600.), 3600., 0);	1479	fmod (ev_now (loop), 3600.), 3600., 0);
1265	ev_periodic_start (loop, &hourly_tick);	1480	ev_periodic_start (loop, &hourly_tick);
1266		1481
1267		1482
1268	=head2 C<ev_signal> - signal me when a signal gets signalled!	1483	=head2 C<ev_signal> - signal me when a signal gets signalled!
1269		1484
1270	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
…		…
1277	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
1278	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
1279	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
1280	SIG_DFL (regardless of what it was set to before).	1495	SIG_DFL (regardless of what it was set to before).
1281		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
1282	=head3 Watcher-Specific Functions and Data Members	1503	=head3 Watcher-Specific Functions and Data Members
1283		1504
1284	=over 4	1505	=over 4
1285		1506
1286	=item ev_signal_init (ev_signal *, callback, int signum)	1507	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1294		1515
1295	The signal the watcher watches out for.	1516	The signal the watcher watches out for.
1296		1517
1297	=back	1518	=back
1298		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
1299		1534
1300	=head2 C<ev_child> - watch out for process status changes	1535	=head2 C<ev_child> - watch out for process status changes
1301		1536
1302	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
1303	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.
1304		1564
1305	=head3 Watcher-Specific Functions and Data Members	1565	=head3 Watcher-Specific Functions and Data Members
1306		1566
1307	=over 4	1567	=over 4
1308		1568
1309	=item ev_child_init (ev_child *, callback, int pid)	1569	=item ev_child_init (ev_child *, callback, int pid, int trace)
1310		1570
1311	=item ev_child_set (ev_child *, int pid)	1571	=item ev_child_set (ev_child *, int pid, int trace)
1312		1572
1313	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
1314	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
1315	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
1316	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
1317	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
1318	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).
1319		1581
1320	=item int pid [read-only]	1582	=item int pid [read-only]
1321		1583
1322	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.
1323		1585
…		…
1330	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
1331	C<waitpid> and C<sys/wait.h> documentation for details).	1593	C<waitpid> and C<sys/wait.h> documentation for details).
1332		1594
1333	=back	1595	=back
1334		1596
1335	Example: Try to exit cleanly on SIGINT and SIGTERM.	1597	=head3 Examples
1336		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
1337	static void	1604	static void
1338	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1605	child_cb (EV_P_ struct ev_child *w, int revents)
1339	{	1606	{
1340	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);
1341	}	1609	}
1342		1610
1343	struct ev_signal signal_watcher;	1611	pid_t pid = fork ();
1344	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1612
1345	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	}
1346		1625
1347		1626
1348	=head2 C<ev_stat> - did the file attributes just change?	1627	=head2 C<ev_stat> - did the file attributes just change?
1349		1628
1350	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
1351	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
1352	compared to the last time, invoking the callback if it did.	1631	compared to the last time, invoking the callback if it did.
1353		1632
1354	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
1355	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
…		…
1373	as even with OS-supported change notifications, this can be	1652	as even with OS-supported change notifications, this can be
1374	resource-intensive.	1653	resource-intensive.
1375		1654
1376	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
1377	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
1378	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
1379	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
1380	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,
1381	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
1382	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).
1383		1716
1384	=head3 Watcher-Specific Functions and Data Members	1717	=head3 Watcher-Specific Functions and Data Members
1385		1718
1386	=over 4	1719	=over 4
1387		1720
…		…
1393	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
1394	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
1395	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
1396	path for as long as the watcher is active.	1729	path for as long as the watcher is active.
1397		1730
1398	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
1399	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
1400	last change was detected).	1733	was detected).
1401		1734
1402	=item ev_stat_stat (ev_stat *)	1735	=item ev_stat_stat (loop, ev_stat *)
1403		1736
1404	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
1405	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
1406	detecting this change (while introducing a race condition). Can also be	1739	detecting this change (while introducing a race condition if you are not
1407	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.
1408		1742
1409	=item ev_statdata attr [read-only]	1743	=item ev_statdata attr [read-only]
1410		1744
1411	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
1412	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
1413	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
1414	was some error while C<stat>ing the file.	1749	some error while C<stat>ing the file.
1415		1750
1416	=item ev_statdata prev [read-only]	1751	=item ev_statdata prev [read-only]
1417		1752
1418	The previous attributes of the file. The callback gets invoked whenever	1753	The previous attributes of the file. The callback gets invoked whenever
1419	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>.
1420		1757
1421	=item ev_tstamp interval [read-only]	1758	=item ev_tstamp interval [read-only]
1422		1759
1423	The specified interval.	1760	The specified interval.
1424		1761
1425	=item const char *path [read-only]	1762	=item const char *path [read-only]
1426		1763
1427	The filesystem path that is being watched.	1764	The file system path that is being watched.
1428		1765
1429	=back	1766	=back
1430		1767
		1768	=head3 Examples
		1769
1431	Example: Watch C</etc/passwd> for attribute changes.	1770	Example: Watch C</etc/passwd> for attribute changes.
1432		1771
1433	static void	1772	static void
1434	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1435	{	1774	{
1436	/* /etc/passwd changed in some way */	1775	/* /etc/passwd changed in some way */
1437	if (w->attr.st_nlink)	1776	if (w->attr.st_nlink)
1438	{	1777	{
1439	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1440	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1441	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1442	}	1781	}
1443	else	1782	else
1444	/* you shalt not abuse printf for puts */	1783	/* you shalt not abuse printf for puts */
1445	puts ("wow, /etc/passwd is not there, expect problems. "	1784	puts ("wow, /etc/passwd is not there, expect problems. "
1446	"if this is windows, they already arrived\n");	1785	"if this is windows, they already arrived\n");
1447	}	1786	}
1448		1787
1449	...	1788	...
1450	ev_stat passwd;	1789	ev_stat passwd;
1451		1790
1452	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1453	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);
1454		1821
1455		1822
1456	=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...
1457		1824
1458	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
…		…
1484	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,
1485	believe me.	1852	believe me.
1486		1853
1487	=back	1854	=back
1488		1855
		1856	=head3 Examples
		1857
1489	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
1490	callback, free it. Also, use no error checking, as usual.	1859	callback, free it. Also, use no error checking, as usual.
1491		1860
1492	static void	1861	static void
1493	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)
1494	{	1863	{
1495	free (w);	1864	free (w);
1496	// now do something you wanted to do when the program has	1865	// now do something you wanted to do when the program has
1497	// no longer asnything immediate to do.	1866	// no longer anything immediate to do.
1498	}	1867	}
1499		1868
1500	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1501	ev_idle_init (idle_watcher, idle_cb);	1870	ev_idle_init (idle_watcher, idle_cb);
1502	ev_idle_start (loop, idle_cb);	1871	ev_idle_start (loop, idle_cb);
1503		1872
1504		1873
1505	=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!
1506		1875
1507	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:
…		…
1526		1895
1527	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
1528	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
1529	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
1530	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
1531	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
1532	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
1533	callbacks will never actually be called (but must be valid nevertheless,	1902	callbacks will never actually be called (but must be valid nevertheless,
1534	because you never know, you know?).	1903	because you never know, you know?).
1535		1904
1536	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
…		…
1544		1913
1545	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>)
1546	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
1547	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,
1548	too) should not activate ("feed") events into libev. While libev fully	1917	too) should not activate ("feed") events into libev. While libev fully
1549	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
1550	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
1551	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
1552	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
1553	others).	1922	coexist peacefully with others).
1554		1923
1555	=head3 Watcher-Specific Functions and Data Members	1924	=head3 Watcher-Specific Functions and Data Members
1556		1925
1557	=over 4	1926	=over 4
1558		1927
…		…
1564	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>
1565	macros, but using them is utterly, utterly and completely pointless.	1934	macros, but using them is utterly, utterly and completely pointless.
1566		1935
1567	=back	1936	=back
1568		1937
		1938	=head3 Examples
		1939
1569	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
1570	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
1571	(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
1572	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
1573	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
1574	into the Glib event loop).	1945	Glib event loop).
1575		1946
1576	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,
1577	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
1578	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
1579	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
1580	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.
1581		1952
1582	static ev_io iow [nfd];	1953	static ev_io iow [nfd];
1583	static ev_timer tw;	1954	static ev_timer tw;
1584		1955
1585	static void	1956	static void
1586	io_cb (ev_loop *loop, ev_io *w, int revents)	1957	io_cb (ev_loop *loop, ev_io *w, int revents)
1587	{	1958	{
1588	}	1959	}
1589		1960
1590	// create io watchers for each fd and a timer before blocking	1961	// create io watchers for each fd and a timer before blocking
1591	static void	1962	static void
1592	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1593	{	1964	{
1594	int timeout = 3600000;	1965	int timeout = 3600000;
1595	struct pollfd fds [nfd];	1966	struct pollfd fds [nfd];
1596	// actual code will need to loop here and realloc etc.	1967	// actual code will need to loop here and realloc etc.
1597	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1598		1969
1599	/* 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 */
1600	ev_timer_init (&tw, 0, timeout * 1e-3);	1971	ev_timer_init (&tw, 0, timeout * 1e-3);
1601	ev_timer_start (loop, &tw);	1972	ev_timer_start (loop, &tw);
1602		1973
1603	// create one ev_io per pollfd	1974	// create one ev_io per pollfd
1604	for (int i = 0; i < nfd; ++i)	1975	for (int i = 0; i < nfd; ++i)
1605	{	1976	{
1606	ev_io_init (iow + i, io_cb, fds [i].fd,	1977	ev_io_init (iow + i, io_cb, fds [i].fd,
1607	((fds [i].events & POLLIN ? EV_READ : 0)	1978	((fds [i].events & POLLIN ? EV_READ : 0)
1608	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1609		1980
1610	fds [i].revents = 0;	1981	fds [i].revents = 0;
1611	ev_io_start (loop, iow + i);	1982	ev_io_start (loop, iow + i);
1612	}	1983	}
1613	}	1984	}
1614		1985
1615	// stop all watchers after blocking	1986	// stop all watchers after blocking
1616	static void	1987	static void
1617	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1618	{	1989	{
1619	ev_timer_stop (loop, &tw);	1990	ev_timer_stop (loop, &tw);
1620		1991
1621	for (int i = 0; i < nfd; ++i)	1992	for (int i = 0; i < nfd; ++i)
1622	{	1993	{
1623	// set the relevant poll flags	1994	// set the relevant poll flags
1624	// could also call adns_processreadable etc. here	1995	// could also call adns_processreadable etc. here
1625	struct pollfd *fd = fds + i;	1996	struct pollfd *fd = fds + i;
1626	int revents = ev_clear_pending (iow + i);	1997	int revents = ev_clear_pending (iow + i);
1627	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1628	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1629		2000
1630	// now stop the watcher	2001	// now stop the watcher
1631	ev_io_stop (loop, iow + i);	2002	ev_io_stop (loop, iow + i);
1632	}	2003	}
1633		2004
1634	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1635	}	2006	}
1636		2007
1637	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>
1638	in the prepare watcher and would dispose of the check watcher.	2009	in the prepare watcher and would dispose of the check watcher.
1639		2010
1640	Method 3: If the module to be embedded supports explicit event	2011	Method 3: If the module to be embedded supports explicit event
1641	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
1642	callbacks, and only destroy/create the watchers in the prepare watcher.	2013	callbacks, and only destroy/create the watchers in the prepare watcher.
1643		2014
1644	static void	2015	static void
1645	timer_cb (EV_P_ ev_timer *w, int revents)	2016	timer_cb (EV_P_ ev_timer *w, int revents)
1646	{	2017	{
1647	adns_state ads = (adns_state)w->data;	2018	adns_state ads = (adns_state)w->data;
1648	update_now (EV_A);	2019	update_now (EV_A);
1649		2020
1650	adns_processtimeouts (ads, &tv_now);	2021	adns_processtimeouts (ads, &tv_now);
1651	}	2022	}
1652		2023
1653	static void	2024	static void
1654	io_cb (EV_P_ ev_io *w, int revents)	2025	io_cb (EV_P_ ev_io *w, int revents)
1655	{	2026	{
1656	adns_state ads = (adns_state)w->data;	2027	adns_state ads = (adns_state)w->data;
1657	update_now (EV_A);	2028	update_now (EV_A);
1658		2029
1659	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1660	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1661	}	2032	}
1662		2033
1663	// do not ever call adns_afterpoll	2034	// do not ever call adns_afterpoll
1664		2035
1665	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
1666	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
1667	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
1668	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
1669	this.	2040	this.
1670		2041
1671	static gint	2042	static gint
1672	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1673	{	2044	{
1674	int got_events = 0;	2045	int got_events = 0;
1675		2046
1676	for (n = 0; n < nfds; ++n)	2047	for (n = 0; n < nfds; ++n)
1677	// 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
1678		2049
1679	if (timeout >= 0)	2050	if (timeout >= 0)
1680	// create/start timer	2051	// create/start timer
1681		2052
1682	// poll	2053	// poll
1683	ev_loop (EV_A_ 0);	2054	ev_loop (EV_A_ 0);
1684		2055
1685	// stop timer again	2056	// stop timer again
1686	if (timeout >= 0)	2057	if (timeout >= 0)
1687	ev_timer_stop (EV_A_ &to);	2058	ev_timer_stop (EV_A_ &to);
1688		2059
1689	// stop io watchers again - their callbacks should have set	2060	// stop io watchers again - their callbacks should have set
1690	for (n = 0; n < nfds; ++n)	2061	for (n = 0; n < nfds; ++n)
1691	ev_io_stop (EV_A_ iow [n]);	2062	ev_io_stop (EV_A_ iow [n]);
1692		2063
1693	return got_events;	2064	return got_events;
1694	}	2065	}
1695		2066
1696		2067
1697	=head2 C<ev_embed> - when one backend isn't enough...	2068	=head2 C<ev_embed> - when one backend isn't enough...
1698		2069
1699	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
…		…
1741	portable one.	2112	portable one.
1742		2113
1743	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
1744	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
1745	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
1746	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.
1747
1748	struct ev_loop *loop_hi = ev_default_init (0);
1749	struct ev_loop *loop_lo = 0;
1750	struct ev_embed embed;
1751
1752	// see if there is a chance of getting one that works
1753	// (remember that a flags value of 0 means autodetection)
1754	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1755	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1756	: 0;
1757
1758	// if we got one, then embed it, otherwise default to loop_hi
1759	if (loop_lo)
1760	{
1761	ev_embed_init (&embed, 0, loop_lo);
1762	ev_embed_start (loop_hi, &embed);
1763	}
1764	else
1765	loop_lo = loop_hi;
1766		2118
1767	=head3 Watcher-Specific Functions and Data Members	2119	=head3 Watcher-Specific Functions and Data Members
1768		2120
1769	=over 4	2121	=over 4
1770		2122
…		…
1774		2126
1775	Configures the watcher to embed the given loop, which must be	2127	Configures the watcher to embed the given loop, which must be
1776	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
1777	invoked automatically, otherwise it is the responsibility of the callback	2129	invoked automatically, otherwise it is the responsibility of the callback
1778	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,
1779	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).
1780		2132
1781	=item ev_embed_sweep (loop, ev_embed *)	2133	=item ev_embed_sweep (loop, ev_embed *)
1782		2134
1783	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
1784	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
1785	apropriate way for embedded loops.	2137	appropriate way for embedded loops.
1786		2138
1787	=item struct ev_loop *loop [read-only]	2139	=item struct ev_loop *other [read-only]
1788		2140
1789	The embedded event loop.	2141	The embedded event loop.
1790		2142
1791	=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
1792		2192
1793		2193
1794	=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
1795		2195
1796	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
…		…
1812	believe me.	2212	believe me.
1813		2213
1814	=back	2214	=back
1815		2215
1816		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
1817	=head1 OTHER FUNCTIONS	2362	=head1 OTHER FUNCTIONS
1818		2363
1819	There are some other functions of possible interest. Described. Here. Now.	2364	There are some other functions of possible interest. Described. Here. Now.
1820		2365
1821	=over 4	2366	=over 4
…		…
1828	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
1829	more watchers yourself.	2374	more watchers yourself.
1830		2375
1831	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
1832	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
1833	C<events> set will be craeted and started.	2378	C<events> set will be created and started.
1834		2379
1835	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
1836	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
1837	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
1838	dubious value.	2383	dubious value.
…		…
1840	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
1841	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
1842	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>
1843	value passed to C<ev_once>:	2388	value passed to C<ev_once>:
1844		2389
1845	static void stdin_ready (int revents, void *arg)	2390	static void stdin_ready (int revents, void *arg)
1846	{	2391	{
1847	if (revents & EV_TIMEOUT)	2392	if (revents & EV_TIMEOUT)
1848	/* doh, nothing entered */;	2393	/* doh, nothing entered */;
1849	else if (revents & EV_READ)	2394	else if (revents & EV_READ)
1850	/* stdin might have data for us, joy! */;	2395	/* stdin might have data for us, joy! */;
1851	}	2396	}
1852		2397
1853	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1854		2399
1855	=item ev_feed_event (ev_loop *, watcher *, int revents)	2400	=item ev_feed_event (ev_loop *, watcher *, int revents)
1856		2401
1857	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
1858	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
…		…
1863	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
1864	the given events it.	2409	the given events it.
1865		2410
1866	=item ev_feed_signal_event (ev_loop *loop, int signum)	2411	=item ev_feed_signal_event (ev_loop *loop, int signum)
1867		2412
1868	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
1869	loop!).	2414	loop!).
1870		2415
1871	=back	2416	=back
1872		2417
1873		2418
…		…
1889		2434
1890	=item * Priorities are not currently supported. Initialising priorities	2435	=item * Priorities are not currently supported. Initialising priorities
1891	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
1892	is an ev_pri field.	2437	is an ev_pri field.
1893		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
1894	=item * Other members are not supported.	2442	=item * Other members are not supported.
1895		2443
1896	=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
1897	to use the libev header file and library.	2445	to use the libev header file and library.
1898		2446
1899	=back	2447	=back
1900		2448
1901	=head1 C++ SUPPORT	2449	=head1 C++ SUPPORT
1902		2450
1903	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
1904	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
1905	the callback model to a model using method callbacks on objects.	2453	the callback model to a model using method callbacks on objects.
1906		2454
1907	To use it,	2455	To use it,
1908		2456
1909	#include <ev++.h>	2457	#include <ev++.h>
1910		2458
1911	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
1912	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
1913	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
1914	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1981	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
1982	thunking function, making it as fast as a direct C callback.	2530	thunking function, making it as fast as a direct C callback.
1983		2531
1984	Example: simple class declaration and watcher initialisation	2532	Example: simple class declaration and watcher initialisation
1985		2533
1986	struct myclass	2534	struct myclass
1987	{	2535	{
1988	void io_cb (ev::io &w, int revents) { }	2536	void io_cb (ev::io &w, int revents) { }
1989	}	2537	}
1990		2538
1991	myclass obj;	2539	myclass obj;
1992	ev::io iow;	2540	ev::io iow;
1993	iow.set <myclass, &myclass::io_cb> (&obj);	2541	iow.set <myclass, &myclass::io_cb> (&obj);
1994		2542
1995	=item w->set<function> (void *data = 0)	2543	=item w->set<function> (void *data = 0)
1996		2544
1997	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
1998	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
…		…
2002		2550
2003	See the method-C<set> above for more details.	2551	See the method-C<set> above for more details.
2004		2552
2005	Example:	2553	Example:
2006		2554
2007	static void io_cb (ev::io &w, int revents) { }	2555	static void io_cb (ev::io &w, int revents) { }
2008	iow.set <io_cb> ();	2556	iow.set <io_cb> ();
2009		2557
2010	=item w->set (struct ev_loop *)	2558	=item w->set (struct ev_loop *)
2011		2559
2012	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
2013	do this when the watcher is inactive (and not pending either).	2561	do this when the watcher is inactive (and not pending either).
2014		2562
2015	=item w->set ([args])	2563	=item w->set ([arguments])
2016		2564
2017	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
2018	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
2019	automatically stopped and restarted when reconfiguring it with this	2567	automatically stopped and restarted when reconfiguring it with this
2020	method.	2568	method.
2021		2569
2022	=item w->start ()	2570	=item w->start ()
…		…
2046	=back	2594	=back
2047		2595
2048	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
2049	the constructor.	2597	the constructor.
2050		2598
2051	class myclass	2599	class myclass
2052	{	2600	{
2053	ev_io io; void io_cb (ev::io &w, int revents);	2601	ev::io io; void io_cb (ev::io &w, int revents);
2054	ev_idle idle void idle_cb (ev::idle &w, int revents);	2602	ev:idle idle void idle_cb (ev::idle &w, int revents);
2055		2603
2056	myclass ();	2604	myclass (int fd)
2057	}	2605	{
2058
2059	myclass::myclass (int fd)
2060	{
2061	io .set <myclass, &myclass::io_cb > (this);	2606	io .set <myclass, &myclass::io_cb > (this);
2062	idle.set <myclass, &myclass::idle_cb> (this);	2607	idle.set <myclass, &myclass::idle_cb> (this);
2063		2608
2064	io.start (fd, ev::READ);	2609	io.start (fd, ev::READ);
		2610	}
2065	}	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 at
		2632	L<http://software.schmorp.de/pkg/EV>.
		2633
		2634	=item Python
		2635
		2636	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2637	seems to be quite complete and well-documented. Note, however, that the
		2638	patch they require for libev is outright dangerous as it breaks the ABI
		2639	for everybody else, and therefore, should never be applied in an installed
		2640	libev (if python requires an incompatible ABI then it needs to embed
		2641	libev).
		2642
		2643	=item Ruby
		2644
		2645	Tony Arcieri has written a ruby extension that offers access to a subset
		2646	of the libev API and adds file handle abstractions, asynchronous DNS and
		2647	more on top of it. It can be found via gem servers. Its homepage is at
		2648	L<http://rev.rubyforge.org/>.
		2649
		2650	=item D
		2651
		2652	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2653	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2654
		2655	=back
2066		2656
2067		2657
2068	=head1 MACRO MAGIC	2658	=head1 MACRO MAGIC
2069		2659
2070	Libev can be compiled with a variety of options, the most fundamantal	2660	Libev can be compiled with a variety of options, the most fundamental
2071	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2661	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2072	functions and callbacks have an initial C<struct ev_loop *> argument.	2662	functions and callbacks have an initial C<struct ev_loop *> argument.
2073		2663
2074	To make it easier to write programs that cope with either variant, the	2664	To make it easier to write programs that cope with either variant, the
2075	following macros are defined:	2665	following macros are defined:
…		…
2080		2670
2081	This provides the loop I<argument> for functions, if one is required ("ev	2671	This provides the loop I<argument> for functions, if one is required ("ev
2082	loop argument"). The C<EV_A> form is used when this is the sole argument,	2672	loop argument"). The C<EV_A> form is used when this is the sole argument,
2083	C<EV_A_> is used when other arguments are following. Example:	2673	C<EV_A_> is used when other arguments are following. Example:
2084		2674
2085	ev_unref (EV_A);	2675	ev_unref (EV_A);
2086	ev_timer_add (EV_A_ watcher);	2676	ev_timer_add (EV_A_ watcher);
2087	ev_loop (EV_A_ 0);	2677	ev_loop (EV_A_ 0);
2088		2678
2089	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2679	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2090	which is often provided by the following macro.	2680	which is often provided by the following macro.
2091		2681
2092	=item C<EV_P>, C<EV_P_>	2682	=item C<EV_P>, C<EV_P_>
2093		2683
2094	This provides the loop I<parameter> for functions, if one is required ("ev	2684	This provides the loop I<parameter> for functions, if one is required ("ev
2095	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2685	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2096	C<EV_P_> is used when other parameters are following. Example:	2686	C<EV_P_> is used when other parameters are following. Example:
2097		2687
2098	// this is how ev_unref is being declared	2688	// this is how ev_unref is being declared
2099	static void ev_unref (EV_P);	2689	static void ev_unref (EV_P);
2100		2690
2101	// this is how you can declare your typical callback	2691	// this is how you can declare your typical callback
2102	static void cb (EV_P_ ev_timer *w, int revents)	2692	static void cb (EV_P_ ev_timer *w, int revents)
2103		2693
2104	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2694	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2105	suitable for use with C<EV_A>.	2695	suitable for use with C<EV_A>.
2106		2696
2107	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2697	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2108		2698
2109	Similar to the other two macros, this gives you the value of the default	2699	Similar to the other two macros, this gives you the value of the default
2110	loop, if multiple loops are supported ("ev loop default").	2700	loop, if multiple loops are supported ("ev loop default").
		2701
		2702	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2703
		2704	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2705	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2706	is undefined when the default loop has not been initialised by a previous
		2707	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2708
		2709	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2710	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2111		2711
2112	=back	2712	=back
2113		2713
2114	Example: Declare and initialise a check watcher, utilising the above	2714	Example: Declare and initialise a check watcher, utilising the above
2115	macros so it will work regardless of whether multiple loops are supported	2715	macros so it will work regardless of whether multiple loops are supported
2116	or not.	2716	or not.
2117		2717
2118	static void	2718	static void
2119	check_cb (EV_P_ ev_timer *w, int revents)	2719	check_cb (EV_P_ ev_timer *w, int revents)
2120	{	2720	{
2121	ev_check_stop (EV_A_ w);	2721	ev_check_stop (EV_A_ w);
2122	}	2722	}
2123		2723
2124	ev_check check;	2724	ev_check check;
2125	ev_check_init (&check, check_cb);	2725	ev_check_init (&check, check_cb);
2126	ev_check_start (EV_DEFAULT_ &check);	2726	ev_check_start (EV_DEFAULT_ &check);
2127	ev_loop (EV_DEFAULT_ 0);	2727	ev_loop (EV_DEFAULT_ 0);
2128		2728
2129	=head1 EMBEDDING	2729	=head1 EMBEDDING
2130		2730
2131	Libev can (and often is) directly embedded into host	2731	Libev can (and often is) directly embedded into host
2132	applications. Examples of applications that embed it include the Deliantra	2732	applications. Examples of applications that embed it include the Deliantra
2133	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2733	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2134	and rxvt-unicode.	2734	and rxvt-unicode.
2135		2735
2136	The goal is to enable you to just copy the neecssary files into your	2736	The goal is to enable you to just copy the necessary files into your
2137	source directory without having to change even a single line in them, so	2737	source directory without having to change even a single line in them, so
2138	you can easily upgrade by simply copying (or having a checked-out copy of	2738	you can easily upgrade by simply copying (or having a checked-out copy of
2139	libev somewhere in your source tree).	2739	libev somewhere in your source tree).
2140		2740
2141	=head2 FILESETS	2741	=head2 FILESETS
2142		2742
2143	Depending on what features you need you need to include one or more sets of files	2743	Depending on what features you need you need to include one or more sets of files
2144	in your app.	2744	in your application.
2145		2745
2146	=head3 CORE EVENT LOOP	2746	=head3 CORE EVENT LOOP
2147		2747
2148	To include only the libev core (all the C<ev_*> functions), with manual	2748	To include only the libev core (all the C<ev_*> functions), with manual
2149	configuration (no autoconf):	2749	configuration (no autoconf):
2150		2750
2151	#define EV_STANDALONE 1	2751	#define EV_STANDALONE 1
2152	#include "ev.c"	2752	#include "ev.c"
2153		2753
2154	This will automatically include F<ev.h>, too, and should be done in a	2754	This will automatically include F<ev.h>, too, and should be done in a
2155	single C source file only to provide the function implementations. To use	2755	single C source file only to provide the function implementations. To use
2156	it, do the same for F<ev.h> in all files wishing to use this API (best	2756	it, do the same for F<ev.h> in all files wishing to use this API (best
2157	done by writing a wrapper around F<ev.h> that you can include instead and	2757	done by writing a wrapper around F<ev.h> that you can include instead and
2158	where you can put other configuration options):	2758	where you can put other configuration options):
2159		2759
2160	#define EV_STANDALONE 1	2760	#define EV_STANDALONE 1
2161	#include "ev.h"	2761	#include "ev.h"
2162		2762
2163	Both header files and implementation files can be compiled with a C++	2763	Both header files and implementation files can be compiled with a C++
2164	compiler (at least, thats a stated goal, and breakage will be treated	2764	compiler (at least, thats a stated goal, and breakage will be treated
2165	as a bug).	2765	as a bug).
2166		2766
2167	You need the following files in your source tree, or in a directory	2767	You need the following files in your source tree, or in a directory
2168	in your include path (e.g. in libev/ when using -Ilibev):	2768	in your include path (e.g. in libev/ when using -Ilibev):
2169		2769
2170	ev.h	2770	ev.h
2171	ev.c	2771	ev.c
2172	ev_vars.h	2772	ev_vars.h
2173	ev_wrap.h	2773	ev_wrap.h
2174		2774
2175	ev_win32.c required on win32 platforms only	2775	ev_win32.c required on win32 platforms only
2176		2776
2177	ev_select.c only when select backend is enabled (which is enabled by default)	2777	ev_select.c only when select backend is enabled (which is enabled by default)
2178	ev_poll.c only when poll backend is enabled (disabled by default)	2778	ev_poll.c only when poll backend is enabled (disabled by default)
2179	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2779	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2180	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2780	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2181	ev_port.c only when the solaris port backend is enabled (disabled by default)	2781	ev_port.c only when the solaris port backend is enabled (disabled by default)
2182		2782
2183	F<ev.c> includes the backend files directly when enabled, so you only need	2783	F<ev.c> includes the backend files directly when enabled, so you only need
2184	to compile this single file.	2784	to compile this single file.
2185		2785
2186	=head3 LIBEVENT COMPATIBILITY API	2786	=head3 LIBEVENT COMPATIBILITY API
2187		2787
2188	To include the libevent compatibility API, also include:	2788	To include the libevent compatibility API, also include:
2189		2789
2190	#include "event.c"	2790	#include "event.c"
2191		2791
2192	in the file including F<ev.c>, and:	2792	in the file including F<ev.c>, and:
2193		2793
2194	#include "event.h"	2794	#include "event.h"
2195		2795
2196	in the files that want to use the libevent API. This also includes F<ev.h>.	2796	in the files that want to use the libevent API. This also includes F<ev.h>.
2197		2797
2198	You need the following additional files for this:	2798	You need the following additional files for this:
2199		2799
2200	event.h	2800	event.h
2201	event.c	2801	event.c
2202		2802
2203	=head3 AUTOCONF SUPPORT	2803	=head3 AUTOCONF SUPPORT
2204		2804
2205	Instead of using C<EV_STANDALONE=1> and providing your config in	2805	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2206	whatever way you want, you can also C<m4_include([libev.m4])> in your	2806	whatever way you want, you can also C<m4_include([libev.m4])> in your
2207	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2807	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2208	include F<config.h> and configure itself accordingly.	2808	include F<config.h> and configure itself accordingly.
2209		2809
2210	For this of course you need the m4 file:	2810	For this of course you need the m4 file:
2211		2811
2212	libev.m4	2812	libev.m4
2213		2813
2214	=head2 PREPROCESSOR SYMBOLS/MACROS	2814	=head2 PREPROCESSOR SYMBOLS/MACROS
2215		2815
2216	Libev can be configured via a variety of preprocessor symbols you have to define	2816	Libev can be configured via a variety of preprocessor symbols you have to
2217	before including any of its files. The default is not to build for multiplicity	2817	define before including any of its files. The default in the absence of
2218	and only include the select backend.	2818	autoconf is noted for every option.
2219		2819
2220	=over 4	2820	=over 4
2221		2821
2222	=item EV_STANDALONE	2822	=item EV_STANDALONE
2223		2823
…		…
2228	F<event.h> that are not directly supported by the libev core alone.	2828	F<event.h> that are not directly supported by the libev core alone.
2229		2829
2230	=item EV_USE_MONOTONIC	2830	=item EV_USE_MONOTONIC
2231		2831
2232	If defined to be C<1>, libev will try to detect the availability of the	2832	If defined to be C<1>, libev will try to detect the availability of the
2233	monotonic clock option at both compiletime and runtime. Otherwise no use	2833	monotonic clock option at both compile time and runtime. Otherwise no use
2234	of the monotonic clock option will be attempted. If you enable this, you	2834	of the monotonic clock option will be attempted. If you enable this, you
2235	usually have to link against librt or something similar. Enabling it when	2835	usually have to link against librt or something similar. Enabling it when
2236	the functionality isn't available is safe, though, althoguh you have	2836	the functionality isn't available is safe, though, although you have
2237	to make sure you link against any libraries where the C<clock_gettime>	2837	to make sure you link against any libraries where the C<clock_gettime>
2238	function is hiding in (often F<-lrt>).	2838	function is hiding in (often F<-lrt>).
2239		2839
2240	=item EV_USE_REALTIME	2840	=item EV_USE_REALTIME
2241		2841
2242	If defined to be C<1>, libev will try to detect the availability of the	2842	If defined to be C<1>, libev will try to detect the availability of the
2243	realtime clock option at compiletime (and assume its availability at	2843	real-time clock option at compile time (and assume its availability at
2244	runtime if successful). Otherwise no use of the realtime clock option will	2844	runtime if successful). Otherwise no use of the real-time clock option will
2245	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2845	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2246	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2846	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2247	in the description of C<EV_USE_MONOTONIC>, though.	2847	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2848
		2849	=item EV_USE_NANOSLEEP
		2850
		2851	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2852	and will use it for delays. Otherwise it will use C<select ()>.
		2853
		2854	=item EV_USE_EVENTFD
		2855
		2856	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2857	available and will probe for kernel support at runtime. This will improve
		2858	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2859	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2860	2.7 or newer, otherwise disabled.
2248		2861
2249	=item EV_USE_SELECT	2862	=item EV_USE_SELECT
2250		2863
2251	If undefined or defined to be C<1>, libev will compile in support for the	2864	If undefined or defined to be C<1>, libev will compile in support for the
2252	C<select>(2) backend. No attempt at autodetection will be done: if no	2865	C<select>(2) backend. No attempt at auto-detection will be done: if no
2253	other method takes over, select will be it. Otherwise the select backend	2866	other method takes over, select will be it. Otherwise the select backend
2254	will not be compiled in.	2867	will not be compiled in.
2255		2868
2256	=item EV_SELECT_USE_FD_SET	2869	=item EV_SELECT_USE_FD_SET
2257		2870
2258	If defined to C<1>, then the select backend will use the system C<fd_set>	2871	If defined to C<1>, then the select backend will use the system C<fd_set>
2259	structure. This is useful if libev doesn't compile due to a missing	2872	structure. This is useful if libev doesn't compile due to a missing
2260	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2873	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2261	exotic systems. This usually limits the range of file descriptors to some	2874	exotic systems. This usually limits the range of file descriptors to some
2262	low limit such as 1024 or might have other limitations (winsocket only	2875	low limit such as 1024 or might have other limitations (winsocket only
2263	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2876	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2264	influence the size of the C<fd_set> used.	2877	influence the size of the C<fd_set> used.
2265		2878
…		…
2271	be used is the winsock select). This means that it will call	2884	be used is the winsock select). This means that it will call
2272	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2885	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2273	it is assumed that all these functions actually work on fds, even	2886	it is assumed that all these functions actually work on fds, even
2274	on win32. Should not be defined on non-win32 platforms.	2887	on win32. Should not be defined on non-win32 platforms.
2275		2888
		2889	=item EV_FD_TO_WIN32_HANDLE
		2890
		2891	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2892	file descriptors to socket handles. When not defining this symbol (the
		2893	default), then libev will call C<_get_osfhandle>, which is usually
		2894	correct. In some cases, programs use their own file descriptor management,
		2895	in which case they can provide this function to map fds to socket handles.
		2896
2276	=item EV_USE_POLL	2897	=item EV_USE_POLL
2277		2898
2278	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2899	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2279	backend. Otherwise it will be enabled on non-win32 platforms. It	2900	backend. Otherwise it will be enabled on non-win32 platforms. It
2280	takes precedence over select.	2901	takes precedence over select.
2281		2902
2282	=item EV_USE_EPOLL	2903	=item EV_USE_EPOLL
2283		2904
2284	If defined to be C<1>, libev will compile in support for the Linux	2905	If defined to be C<1>, libev will compile in support for the Linux
2285	C<epoll>(7) backend. Its availability will be detected at runtime,	2906	C<epoll>(7) backend. Its availability will be detected at runtime,
2286	otherwise another method will be used as fallback. This is the	2907	otherwise another method will be used as fallback. This is the preferred
2287	preferred backend for GNU/Linux systems.	2908	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2909	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2288		2910
2289	=item EV_USE_KQUEUE	2911	=item EV_USE_KQUEUE
2290		2912
2291	If defined to be C<1>, libev will compile in support for the BSD style	2913	If defined to be C<1>, libev will compile in support for the BSD style
2292	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2914	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2305	otherwise another method will be used as fallback. This is the preferred	2927	otherwise another method will be used as fallback. This is the preferred
2306	backend for Solaris 10 systems.	2928	backend for Solaris 10 systems.
2307		2929
2308	=item EV_USE_DEVPOLL	2930	=item EV_USE_DEVPOLL
2309		2931
2310	reserved for future expansion, works like the USE symbols above.	2932	Reserved for future expansion, works like the USE symbols above.
2311		2933
2312	=item EV_USE_INOTIFY	2934	=item EV_USE_INOTIFY
2313		2935
2314	If defined to be C<1>, libev will compile in support for the Linux inotify	2936	If defined to be C<1>, libev will compile in support for the Linux inotify
2315	interface to speed up C<ev_stat> watchers. Its actual availability will	2937	interface to speed up C<ev_stat> watchers. Its actual availability will
2316	be detected at runtime.	2938	be detected at runtime. If undefined, it will be enabled if the headers
		2939	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2940
		2941	=item EV_ATOMIC_T
		2942
		2943	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2944	access is atomic with respect to other threads or signal contexts. No such
		2945	type is easily found in the C language, so you can provide your own type
		2946	that you know is safe for your purposes. It is used both for signal handler "locking"
		2947	as well as for signal and thread safety in C<ev_async> watchers.
		2948
		2949	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2950	(from F<signal.h>), which is usually good enough on most platforms.
2317		2951
2318	=item EV_H	2952	=item EV_H
2319		2953
2320	The name of the F<ev.h> header file used to include it. The default if	2954	The name of the F<ev.h> header file used to include it. The default if
2321	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2955	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2322	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2956	used to virtually rename the F<ev.h> header file in case of conflicts.
2323		2957
2324	=item EV_CONFIG_H	2958	=item EV_CONFIG_H
2325		2959
2326	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2960	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2327	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2961	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2328	C<EV_H>, above.	2962	C<EV_H>, above.
2329		2963
2330	=item EV_EVENT_H	2964	=item EV_EVENT_H
2331		2965
2332	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2966	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2333	of how the F<event.h> header can be found.	2967	of how the F<event.h> header can be found, the default is C<"event.h">.
2334		2968
2335	=item EV_PROTOTYPES	2969	=item EV_PROTOTYPES
2336		2970
2337	If defined to be C<0>, then F<ev.h> will not define any function	2971	If defined to be C<0>, then F<ev.h> will not define any function
2338	prototypes, but still define all the structs and other symbols. This is	2972	prototypes, but still define all the structs and other symbols. This is
…		…
2359	When doing priority-based operations, libev usually has to linearly search	2993	When doing priority-based operations, libev usually has to linearly search
2360	all the priorities, so having many of them (hundreds) uses a lot of space	2994	all the priorities, so having many of them (hundreds) uses a lot of space
2361	and time, so using the defaults of five priorities (-2 .. +2) is usually	2995	and time, so using the defaults of five priorities (-2 .. +2) is usually
2362	fine.	2996	fine.
2363		2997
2364	If your embedding app does not need any priorities, defining these both to	2998	If your embedding application does not need any priorities, defining these both to
2365	C<0> will save some memory and cpu.	2999	C<0> will save some memory and CPU.
2366		3000
2367	=item EV_PERIODIC_ENABLE	3001	=item EV_PERIODIC_ENABLE
2368		3002
2369	If undefined or defined to be C<1>, then periodic timers are supported. If	3003	If undefined or defined to be C<1>, then periodic timers are supported. If
2370	defined to be C<0>, then they are not. Disabling them saves a few kB of	3004	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2389	=item EV_FORK_ENABLE	3023	=item EV_FORK_ENABLE
2390		3024
2391	If undefined or defined to be C<1>, then fork watchers are supported. If	3025	If undefined or defined to be C<1>, then fork watchers are supported. If
2392	defined to be C<0>, then they are not.	3026	defined to be C<0>, then they are not.
2393		3027
		3028	=item EV_ASYNC_ENABLE
		3029
		3030	If undefined or defined to be C<1>, then async watchers are supported. If
		3031	defined to be C<0>, then they are not.
		3032
2394	=item EV_MINIMAL	3033	=item EV_MINIMAL
2395		3034
2396	If you need to shave off some kilobytes of code at the expense of some	3035	If you need to shave off some kilobytes of code at the expense of some
2397	speed, define this symbol to C<1>. Currently only used for gcc to override	3036	speed, define this symbol to C<1>. Currently this is used to override some
2398	some inlining decisions, saves roughly 30% codesize of amd64.	3037	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3038	much smaller 2-heap for timer management over the default 4-heap.
2399		3039
2400	=item EV_PID_HASHSIZE	3040	=item EV_PID_HASHSIZE
2401		3041
2402	C<ev_child> watchers use a small hash table to distribute workload by	3042	C<ev_child> watchers use a small hash table to distribute workload by
2403	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3043	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2404	than enough. If you need to manage thousands of children you might want to	3044	than enough. If you need to manage thousands of children you might want to
2405	increase this value (I<must> be a power of two).	3045	increase this value (I<must> be a power of two).
2406		3046
2407	=item EV_INOTIFY_HASHSIZE	3047	=item EV_INOTIFY_HASHSIZE
2408		3048
2409	C<ev_staz> watchers use a small hash table to distribute workload by	3049	C<ev_stat> watchers use a small hash table to distribute workload by
2410	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3050	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2411	usually more than enough. If you need to manage thousands of C<ev_stat>	3051	usually more than enough. If you need to manage thousands of C<ev_stat>
2412	watchers you might want to increase this value (I<must> be a power of	3052	watchers you might want to increase this value (I<must> be a power of
2413	two).	3053	two).
2414		3054
		3055	=item EV_USE_4HEAP
		3056
		3057	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3058	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3059	to C<1>. The 4-heap uses more complicated (longer) code but has
		3060	noticeably faster performance with many (thousands) of watchers.
		3061
		3062	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3063	(disabled).
		3064
		3065	=item EV_HEAP_CACHE_AT
		3066
		3067	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3068	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3069	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3070	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3071	but avoids random read accesses on heap changes. This improves performance
		3072	noticeably with with many (hundreds) of watchers.
		3073
		3074	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3075	(disabled).
		3076
		3077	=item EV_VERIFY
		3078
		3079	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3080	be done: If set to C<0>, no internal verification code will be compiled
		3081	in. If set to C<1>, then verification code will be compiled in, but not
		3082	called. If set to C<2>, then the internal verification code will be
		3083	called once per loop, which can slow down libev. If set to C<3>, then the
		3084	verification code will be called very frequently, which will slow down
		3085	libev considerably.
		3086
		3087	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3088	C<0.>
		3089
2415	=item EV_COMMON	3090	=item EV_COMMON
2416		3091
2417	By default, all watchers have a C<void *data> member. By redefining	3092	By default, all watchers have a C<void *data> member. By redefining
2418	this macro to a something else you can include more and other types of	3093	this macro to a something else you can include more and other types of
2419	members. You have to define it each time you include one of the files,	3094	members. You have to define it each time you include one of the files,
2420	though, and it must be identical each time.	3095	though, and it must be identical each time.
2421		3096
2422	For example, the perl EV module uses something like this:	3097	For example, the perl EV module uses something like this:
2423		3098
2424	#define EV_COMMON \	3099	#define EV_COMMON \
2425	SV *self; /* contains this struct */ \	3100	SV *self; /* contains this struct */ \
2426	SV *cb_sv, *fh /* note no trailing ";" */	3101	SV *cb_sv, *fh /* note no trailing ";" */
2427		3102
2428	=item EV_CB_DECLARE (type)	3103	=item EV_CB_DECLARE (type)
2429		3104
2430	=item EV_CB_INVOKE (watcher, revents)	3105	=item EV_CB_INVOKE (watcher, revents)
2431		3106
2432	=item ev_set_cb (ev, cb)	3107	=item ev_set_cb (ev, cb)
2433		3108
2434	Can be used to change the callback member declaration in each watcher,	3109	Can be used to change the callback member declaration in each watcher,
2435	and the way callbacks are invoked and set. Must expand to a struct member	3110	and the way callbacks are invoked and set. Must expand to a struct member
2436	definition and a statement, respectively. See the F<ev.v> header file for	3111	definition and a statement, respectively. See the F<ev.h> header file for
2437	their default definitions. One possible use for overriding these is to	3112	their default definitions. One possible use for overriding these is to
2438	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3113	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2439	method calls instead of plain function calls in C++.	3114	method calls instead of plain function calls in C++.
		3115
		3116	=head2 EXPORTED API SYMBOLS
		3117
		3118	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3119	exported symbols, you can use the provided F<Symbol.*> files which list
		3120	all public symbols, one per line:
		3121
		3122	Symbols.ev for libev proper
		3123	Symbols.event for the libevent emulation
		3124
		3125	This can also be used to rename all public symbols to avoid clashes with
		3126	multiple versions of libev linked together (which is obviously bad in
		3127	itself, but sometimes it is inconvenient to avoid this).
		3128
		3129	A sed command like this will create wrapper C<#define>'s that you need to
		3130	include before including F<ev.h>:
		3131
		3132	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3133
		3134	This would create a file F<wrap.h> which essentially looks like this:
		3135
		3136	#define ev_backend myprefix_ev_backend
		3137	#define ev_check_start myprefix_ev_check_start
		3138	#define ev_check_stop myprefix_ev_check_stop
		3139	...
2440		3140
2441	=head2 EXAMPLES	3141	=head2 EXAMPLES
2442		3142
2443	For a real-world example of a program the includes libev	3143	For a real-world example of a program the includes libev
2444	verbatim, you can have a look at the EV perl module	3144	verbatim, you can have a look at the EV perl module
…		…
2449	file.	3149	file.
2450		3150
2451	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3151	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2452	that everybody includes and which overrides some configure choices:	3152	that everybody includes and which overrides some configure choices:
2453		3153
2454	#define EV_MINIMAL 1	3154	#define EV_MINIMAL 1
2455	#define EV_USE_POLL 0	3155	#define EV_USE_POLL 0
2456	#define EV_MULTIPLICITY 0	3156	#define EV_MULTIPLICITY 0
2457	#define EV_PERIODIC_ENABLE 0	3157	#define EV_PERIODIC_ENABLE 0
2458	#define EV_STAT_ENABLE 0	3158	#define EV_STAT_ENABLE 0
2459	#define EV_FORK_ENABLE 0	3159	#define EV_FORK_ENABLE 0
2460	#define EV_CONFIG_H <config.h>	3160	#define EV_CONFIG_H <config.h>
2461	#define EV_MINPRI 0	3161	#define EV_MINPRI 0
2462	#define EV_MAXPRI 0	3162	#define EV_MAXPRI 0
2463		3163
2464	#include "ev++.h"	3164	#include "ev++.h"
2465		3165
2466	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3166	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2467		3167
2468	#include "ev_cpp.h"	3168	#include "ev_cpp.h"
2469	#include "ev.c"	3169	#include "ev.c"
		3170
		3171
		3172	=head1 THREADS AND COROUTINES
		3173
		3174	=head2 THREADS
		3175
		3176	Libev itself is completely thread-safe, but it uses no locking. This
		3177	means that you can use as many loops as you want in parallel, as long as
		3178	only one thread ever calls into one libev function with the same loop
		3179	parameter.
		3180
		3181	Or put differently: calls with different loop parameters can be done in
		3182	parallel from multiple threads, calls with the same loop parameter must be
		3183	done serially (but can be done from different threads, as long as only one
		3184	thread ever is inside a call at any point in time, e.g. by using a mutex
		3185	per loop).
		3186
		3187	If you want to know which design is best for your problem, then I cannot
		3188	help you but by giving some generic advice:
		3189
		3190	=over 4
		3191
		3192	=item * most applications have a main thread: use the default libev loop
		3193	in that thread, or create a separate thread running only the default loop.
		3194
		3195	This helps integrating other libraries or software modules that use libev
		3196	themselves and don't care/know about threading.
		3197
		3198	=item * one loop per thread is usually a good model.
		3199
		3200	Doing this is almost never wrong, sometimes a better-performance model
		3201	exists, but it is always a good start.
		3202
		3203	=item * other models exist, such as the leader/follower pattern, where one
		3204	loop is handed through multiple threads in a kind of round-robin fashion.
		3205
		3206	Choosing a model is hard - look around, learn, know that usually you can do
		3207	better than you currently do :-)
		3208
		3209	=item * often you need to talk to some other thread which blocks in the
		3210	event loop - C<ev_async> watchers can be used to wake them up from other
		3211	threads safely (or from signal contexts...).
		3212
		3213	=back
		3214
		3215	=head2 COROUTINES
		3216
		3217	Libev is much more accommodating to coroutines ("cooperative threads"):
		3218	libev fully supports nesting calls to it's functions from different
		3219	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3220	different coroutines and switch freely between both coroutines running the
		3221	loop, as long as you don't confuse yourself). The only exception is that
		3222	you must not do this from C<ev_periodic> reschedule callbacks.
		3223
		3224	Care has been invested into making sure that libev does not keep local
		3225	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3226	switches.
2470		3227
2471		3228
2472	=head1 COMPLEXITIES	3229	=head1 COMPLEXITIES
2473		3230
2474	In this section the complexities of (many of) the algorithms used inside	3231	In this section the complexities of (many of) the algorithms used inside
…		…
2485		3242
2486	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3243	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2487		3244
2488	This means that, when you have a watcher that triggers in one hour and	3245	This means that, when you have a watcher that triggers in one hour and
2489	there are 100 watchers that would trigger before that then inserting will	3246	there are 100 watchers that would trigger before that then inserting will
2490	have to skip those 100 watchers.	3247	have to skip roughly seven (C<ld 100>) of these watchers.
2491		3248
2492	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3249	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2493		3250
2494	That means that for changing a timer costs less than removing/adding them	3251	That means that changing a timer costs less than removing/adding them
2495	as only the relative motion in the event queue has to be paid for.	3252	as only the relative motion in the event queue has to be paid for.
2496		3253
2497	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3254	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2498		3255
2499	These just add the watcher into an array or at the head of a list.	3256	These just add the watcher into an array or at the head of a list.
		3257
2500	=item Stopping check/prepare/idle watchers: O(1)	3258	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2501		3259
2502	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3260	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2503		3261
2504	These watchers are stored in lists then need to be walked to find the	3262	These watchers are stored in lists then need to be walked to find the
2505	correct watcher to remove. The lists are usually short (you don't usually	3263	correct watcher to remove. The lists are usually short (you don't usually
2506	have many watchers waiting for the same fd or signal).	3264	have many watchers waiting for the same fd or signal).
2507		3265
2508	=item Finding the next timer per loop iteration: O(1)	3266	=item Finding the next timer in each loop iteration: O(1)
		3267
		3268	By virtue of using a binary or 4-heap, the next timer is always found at a
		3269	fixed position in the storage array.
2509		3270
2510	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3271	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2511		3272
2512	A change means an I/O watcher gets started or stopped, which requires	3273	A change means an I/O watcher gets started or stopped, which requires
2513	libev to recalculate its status (and possibly tell the kernel).	3274	libev to recalculate its status (and possibly tell the kernel, depending
		3275	on backend and whether C<ev_io_set> was used).
2514		3276
2515	=item Activating one watcher: O(1)	3277	=item Activating one watcher (putting it into the pending state): O(1)
2516		3278
2517	=item Priority handling: O(number_of_priorities)	3279	=item Priority handling: O(number_of_priorities)
2518		3280
2519	Priorities are implemented by allocating some space for each	3281	Priorities are implemented by allocating some space for each
2520	priority. When doing priority-based operations, libev usually has to	3282	priority. When doing priority-based operations, libev usually has to
2521	linearly search all the priorities.	3283	linearly search all the priorities, but starting/stopping and activating
		3284	watchers becomes O(1) w.r.t. priority handling.
		3285
		3286	=item Sending an ev_async: O(1)
		3287
		3288	=item Processing ev_async_send: O(number_of_async_watchers)
		3289
		3290	=item Processing signals: O(max_signal_number)
		3291
		3292	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3293	calls in the current loop iteration. Checking for async and signal events
		3294	involves iterating over all running async watchers or all signal numbers.
2522		3295
2523	=back	3296	=back
2524		3297
2525		3298
		3299	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3300
		3301	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3302	requires, and its I/O model is fundamentally incompatible with the POSIX
		3303	model. Libev still offers limited functionality on this platform in
		3304	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3305	descriptors. This only applies when using Win32 natively, not when using
		3306	e.g. cygwin.
		3307
		3308	Lifting these limitations would basically require the full
		3309	re-implementation of the I/O system. If you are into these kinds of
		3310	things, then note that glib does exactly that for you in a very portable
		3311	way (note also that glib is the slowest event library known to man).
		3312
		3313	There is no supported compilation method available on windows except
		3314	embedding it into other applications.
		3315
		3316	Not a libev limitation but worth mentioning: windows apparently doesn't
		3317	accept large writes: instead of resulting in a partial write, windows will
		3318	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3319	so make sure you only write small amounts into your sockets (less than a
		3320	megabyte seems safe, but thsi apparently depends on the amount of memory
		3321	available).
		3322
		3323	Due to the many, low, and arbitrary limits on the win32 platform and
		3324	the abysmal performance of winsockets, using a large number of sockets
		3325	is not recommended (and not reasonable). If your program needs to use
		3326	more than a hundred or so sockets, then likely it needs to use a totally
		3327	different implementation for windows, as libev offers the POSIX readiness
		3328	notification model, which cannot be implemented efficiently on windows
		3329	(Microsoft monopoly games).
		3330
		3331	=over 4
		3332
		3333	=item The winsocket select function
		3334
		3335	The winsocket C<select> function doesn't follow POSIX in that it
		3336	requires socket I<handles> and not socket I<file descriptors> (it is
		3337	also extremely buggy). This makes select very inefficient, and also
		3338	requires a mapping from file descriptors to socket handles. See the
		3339	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3340	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3341
		3342	The configuration for a "naked" win32 using the Microsoft runtime
		3343	libraries and raw winsocket select is:
		3344
		3345	#define EV_USE_SELECT 1
		3346	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3347
		3348	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3349	complexity in the O(n²) range when using win32.
		3350
		3351	=item Limited number of file descriptors
		3352
		3353	Windows has numerous arbitrary (and low) limits on things.
		3354
		3355	Early versions of winsocket's select only supported waiting for a maximum
		3356	of C<64> handles (probably owning to the fact that all windows kernels
		3357	can only wait for C<64> things at the same time internally; Microsoft
		3358	recommends spawning a chain of threads and wait for 63 handles and the
		3359	previous thread in each. Great).
		3360
		3361	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3362	to some high number (e.g. C<2048>) before compiling the winsocket select
		3363	call (which might be in libev or elsewhere, for example, perl does its own
		3364	select emulation on windows).
		3365
		3366	Another limit is the number of file descriptors in the Microsoft runtime
		3367	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3368	or something like this inside Microsoft). You can increase this by calling
		3369	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3370	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3371	libraries.
		3372
		3373	This might get you to about C<512> or C<2048> sockets (depending on
		3374	windows version and/or the phase of the moon). To get more, you need to
		3375	wrap all I/O functions and provide your own fd management, but the cost of
		3376	calling select (O(n²)) will likely make this unworkable.
		3377
		3378	=back
		3379
		3380
		3381	=head1 PORTABILITY REQUIREMENTS
		3382
		3383	In addition to a working ISO-C implementation, libev relies on a few
		3384	additional extensions:
		3385
		3386	=over 4
		3387
		3388	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3389	calling conventions regardless of C<ev_watcher_type *>.
		3390
		3391	Libev assumes not only that all watcher pointers have the same internal
		3392	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3393	assumes that the same (machine) code can be used to call any watcher
		3394	callback: The watcher callbacks have different type signatures, but libev
		3395	calls them using an C<ev_watcher *> internally.
		3396
		3397	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3398
		3399	The type C<sig_atomic_t volatile> (or whatever is defined as
		3400	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3401	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3402	believed to be sufficiently portable.
		3403
		3404	=item C<sigprocmask> must work in a threaded environment
		3405
		3406	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3407	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3408	pthread implementations will either allow C<sigprocmask> in the "main
		3409	thread" or will block signals process-wide, both behaviours would
		3410	be compatible with libev. Interaction between C<sigprocmask> and
		3411	C<pthread_sigmask> could complicate things, however.
		3412
		3413	The most portable way to handle signals is to block signals in all threads
		3414	except the initial one, and run the default loop in the initial thread as
		3415	well.
		3416
		3417	=item C<long> must be large enough for common memory allocation sizes
		3418
		3419	To improve portability and simplify using libev, libev uses C<long>
		3420	internally instead of C<size_t> when allocating its data structures. On
		3421	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3422	is still at least 31 bits everywhere, which is enough for hundreds of
		3423	millions of watchers.
		3424
		3425	=item C<double> must hold a time value in seconds with enough accuracy
		3426
		3427	The type C<double> is used to represent timestamps. It is required to
		3428	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3429	enough for at least into the year 4000. This requirement is fulfilled by
		3430	implementations implementing IEEE 754 (basically all existing ones).
		3431
		3432	=back
		3433
		3434	If you know of other additional requirements drop me a note.
		3435
		3436
		3437	=head1 COMPILER WARNINGS
		3438
		3439	Depending on your compiler and compiler settings, you might get no or a
		3440	lot of warnings when compiling libev code. Some people are apparently
		3441	scared by this.
		3442
		3443	However, these are unavoidable for many reasons. For one, each compiler
		3444	has different warnings, and each user has different tastes regarding
		3445	warning options. "Warn-free" code therefore cannot be a goal except when
		3446	targeting a specific compiler and compiler-version.
		3447
		3448	Another reason is that some compiler warnings require elaborate
		3449	workarounds, or other changes to the code that make it less clear and less
		3450	maintainable.
		3451
		3452	And of course, some compiler warnings are just plain stupid, or simply
		3453	wrong (because they don't actually warn about the condition their message
		3454	seems to warn about).
		3455
		3456	While libev is written to generate as few warnings as possible,
		3457	"warn-free" code is not a goal, and it is recommended not to build libev
		3458	with any compiler warnings enabled unless you are prepared to cope with
		3459	them (e.g. by ignoring them). Remember that warnings are just that:
		3460	warnings, not errors, or proof of bugs.
		3461
		3462
		3463	=head1 VALGRIND
		3464
		3465	Valgrind has a special section here because it is a popular tool that is
		3466	highly useful, but valgrind reports are very hard to interpret.
		3467
		3468	If you think you found a bug (memory leak, uninitialised data access etc.)
		3469	in libev, then check twice: If valgrind reports something like:
		3470
		3471	==2274== definitely lost: 0 bytes in 0 blocks.
		3472	==2274== possibly lost: 0 bytes in 0 blocks.
		3473	==2274== still reachable: 256 bytes in 1 blocks.
		3474
		3475	Then there is no memory leak. Similarly, under some circumstances,
		3476	valgrind might report kernel bugs as if it were a bug in libev, or it
		3477	might be confused (it is a very good tool, but only a tool).
		3478
		3479	If you are unsure about something, feel free to contact the mailing list
		3480	with the full valgrind report and an explanation on why you think this is
		3481	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3482	no bug" answer and take the chance of learning how to interpret valgrind
		3483	properly.
		3484
		3485	If you need, for some reason, empty reports from valgrind for your project
		3486	I suggest using suppression lists.
		3487
		3488
2526	=head1 AUTHOR	3489	=head1 AUTHOR
2527		3490
2528	Marc Lehmann <libev@schmorp.de>.	3491	Marc Lehmann <libev@schmorp.de>.
2529		3492

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