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Revision 1.102 by root, Sat Dec 22 16:21:25 2007 UTC vs.
Revision 1.178 by root, Sat Sep 13 18:25:50 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
104	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
105	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
106		142
107	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
108		144
109	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
110	library in any way.	146	library in any way.
…		…
119		155
120	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
121		157
122	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
123	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
124	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
125		161
126	=item int ev_version_major ()	162	=item int ev_version_major ()
127		163
128	=item int ev_version_minor ()	164	=item int ev_version_minor ()
129		165
…		…
142	not a problem.	178	not a problem.
143		179
144	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
145	version.	181	version.
146		182
147	assert (("libev version mismatch",	183	assert (("libev version mismatch",
148	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
149	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
150		186
151	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
152		188
153	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
154	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
156	a description of the set values.	192	a description of the set values.
157		193
158	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
159	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
160		196
161	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
162	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
163		199
164	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
165		201
166	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
167	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
168	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
169	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
170	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
171	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
172		208
173	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
174		210
…		…
181	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
182		218
183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
184		220
185	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
186	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
187	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
188	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
189	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
190	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
191		230
192	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
193	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
194	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
195		234
196	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
197	retries).	236	retries (example requires a standards-compliant C<realloc>).
198		237
199	static void *	238	static void *
200	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
201	{	240	{
202	for (;;)	241	for (;;)
…		…
213	...	252	...
214	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
215		254
216	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
217		256
218	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
219	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
220	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
221	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
222	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
223	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
224	(such as abort).	263	(such as abort).
225		264
226	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
240	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
241		280
242	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *>. The library knows two
243	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
244	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
245
246	If you use threads, a common model is to run the default event loop
247	in your main thread (or in a separate thread) and for each thread you
248	create, you also create another event loop. Libev itself does no locking
249	whatsoever, so if you mix calls to the same event loop in different
250	threads, make sure you lock (this is usually a bad idea, though, even if
251	done correctly, because it's hideous and inefficient).
252		284
253	=over 4	285	=over 4
254		286
255	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
256		288
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		293
262	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
263	function.	295	function.
264		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
265	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		310
268	The following flags are supported:	311	The following flags are supported:
269		312
…		…
274	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
275	thing, believe me).	318	thing, believe me).
276		319
277	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
278		321
279	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
280	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
282	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
283	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
284	around bugs.	327	around bugs.
…		…
290	enabling this flag.	333	enabling this flag.
291		334
292	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
293	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
294	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
295	Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
296	without a syscall and thus I<very> fast, but my Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
298		341
299	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
300	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
301	flag.	344	flag.
302		345
303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
304	environment variable.	347	environment variable.
305		348
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		350
308	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
310	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
311	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
312	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
313		356
314	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
315	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
316	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
317	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
318	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
319	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
320		363
321	=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)
322		365
323	And this is your standard poll(2) backend. It's more complicated	366	And this is your standard poll(2) backend. It's more complicated
324	than select, but handles sparse fds better and has no artificial	367	than select, but handles sparse fds better and has no artificial
…		…
332	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,
333	but it scales phenomenally better. While poll and select usually scale	376	but it scales phenomenally better. While poll and select usually scale
334	like O(total_fds) where n is the total number of fds (or the highest fd),	377	like O(total_fds) where n is the total number of fds (or the highest fd),
335	epoll scales either O(1) or O(active_fds). The epoll design has a number	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
336	of shortcomings, such as silently dropping events in some hard-to-detect	379	of shortcomings, such as silently dropping events in some hard-to-detect
337	cases and rewiring a syscall per fd change, no fork support and bad	380	cases and requiring a system call per fd change, no fork support and bad
338	support for dup.	381	support for dup.
339		382
340	While stopping, setting and starting an I/O watcher in the same iteration	383	While stopping, setting and starting an I/O watcher in the same iteration
341	will result in some caching, there is still a syscall per such incident	384	will result in some caching, there is still a system call per such incident
342	(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
343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
344	very well if you register events for both fds.	387	very well if you register events for both fds.
345		388
346	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
…		…
349		392
350	Best performance from this backend is achieved by not unregistering all	393	Best performance from this backend is achieved by not unregistering all
351	watchers for a file descriptor until it has been closed, if possible, i.e.	394	watchers for a file descriptor until it has been closed, if possible, i.e.
352	keep at least one watcher active per fd at all times.	395	keep at least one watcher active per fd at all times.
353		396
354	While nominally embeddeble in other event loops, this feature is broken in	397	While nominally embeddable in other event loops, this feature is broken in
355	all kernel versions tested so far.	398	all kernel versions tested so far.
356		399
357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
358		401
359	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
360	was broken on all BSDs except NetBSD (usually it doesn't work reliably	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
361	with anything but sockets and pipes, except on Darwin, where of course	404	with anything but sockets and pipes, except on Darwin, where of course
362	it's completely useless). For this reason it's not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
363	unless you explicitly specify it explicitly in the flags (i.e. using	406	unless you explicitly specify it explicitly in the flags (i.e. using
364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
365	system like NetBSD.	408	system like NetBSD.
366		409
367	You still can embed kqueue into a normal poll or select backend and use it	410	You still can embed kqueue into a normal poll or select backend and use it
…		…
369	the target platform). See C<ev_embed> watchers for more info.	412	the target platform). See C<ev_embed> watchers for more info.
370		413
371	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
372	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
373	course). While stopping, setting and starting an I/O watcher does never	416	course). While stopping, setting and starting an I/O watcher does never
374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
375	two event changes per incident, support for C<fork ()> is very bad and it	418	two event changes per incident, support for C<fork ()> is very bad and it
376	drops fds silently in similarly hard-to-detect cases.	419	drops fds silently in similarly hard-to-detect cases.
377		420
378	This backend usually performs well under most conditions.	421	This backend usually performs well under most conditions.
379		422
…		…
394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
395		438
396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
397	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)).
398		441
399	Please note that solaris event ports can deliver a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
400	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
401	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
402		445
403	While this backend scales well, it requires one system call per active	446	While this backend scales well, it requires one system call per active
404	file descriptor per loop iteration. For small and medium numbers of file	447	file descriptor per loop iteration. For small and medium numbers of file
405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406	might perform better.	449	might perform better.
407		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.
		454
408	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
409		456
410	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
411	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
412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413		460
414	It is definitely not recommended to use this flag.	461	It is definitely not recommended to use this flag.
415		462
416	=back	463	=back
417		464
418	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
419	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
420	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
421	order of their flag values :)
422		468
423	The most typical usage is like this:	469	The most typical usage is like this:
424		470
425	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
426	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
427		473
428	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
429	environment settings to be taken into account:	475	environment settings to be taken into account:
430		476
431	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
432		478
433	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
434	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
435	event loop and only if you know the OS supports your types of fds):	481	event loop and only if you know the OS supports your types of fds):
436		482
437	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
438		484
439	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
440		486
441	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
442	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
443	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
444	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
445		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
446	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.
447		497
448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
449	if (!epoller)	499	if (!epoller)
450	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
451		501
452	=item ev_default_destroy ()	502	=item ev_default_destroy ()
453		503
454	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
455	etc.). None of the active event watchers will be stopped in the normal	505	etc.). None of the active event watchers will be stopped in the normal
456	sense, so e.g. C<ev_is_active> might still return true. It is your	506	sense, so e.g. C<ev_is_active> might still return true. It is your
457	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
458	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
459	the easiest thing, you can just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
460	for example).	510	for example).
461		511
462	Note that certain global state, such as signal state, will not be freed by	512	Note that certain global state, such as signal state, will not be freed by
…		…
473	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
474	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
475		525
476	=item ev_default_fork ()	526	=item ev_default_fork ()
477		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
478	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
479	one. Despite the name, you can call it anytime, but it makes most sense	530	name, you can call it anytime, but it makes most sense after forking, in
480	after forking, in either the parent or child process (or both, but that	531	the child process (or both child and parent, but that again makes little
481	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.
482		534
483	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
484	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
485	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
486		538
487	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
488	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
489	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
490		542
491	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
492		544
493	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494	without calling this function, so if you force one of those backends you
495	do not need to care.
496
497	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
498		546
499	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
500	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
501	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.
502		554
503	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
504		556
505	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
506	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
…		…
521	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
522	change as long as callbacks are being processed, and this is also the base	574	change as long as callbacks are being processed, and this is also the base
523	time used for relative timers. You can treat it as the timestamp of the	575	time used for relative timers. You can treat it as the timestamp of the
524	event occurring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
525		577
		578	=item ev_now_update (loop)
		579
		580	Establishes the current time by querying the kernel, updating the time
		581	returned by C<ev_now ()> in the progress. This is a costly operation and
		582	is usually done automatically within C<ev_loop ()>.
		583
		584	This function is rarely useful, but when some event callback runs for a
		585	very long time without entering the event loop, updating libev's idea of
		586	the current time is a good idea.
		587
		588	See also "The special problem of time updates" in the C<ev_timer> section.
		589
526	=item ev_loop (loop, int flags)	590	=item ev_loop (loop, int flags)
527		591
528	Finally, this is it, the event handler. This function usually is called	592	Finally, this is it, the event handler. This function usually is called
529	after you initialised all your watchers and you want to start handling	593	after you initialised all your watchers and you want to start handling
530	events.	594	events.
…		…
541	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	605	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
542	those events and any outstanding ones, but will not block your process in	606	those events and any outstanding ones, but will not block your process in
543	case there are no events and will return after one iteration of the loop.	607	case there are no events and will return after one iteration of the loop.
544		608
545	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	609	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
546	neccessary) and will handle those and any outstanding ones. It will block	610	necessary) and will handle those and any outstanding ones. It will block
547	your process until at least one new event arrives, and will return after	611	your process until at least one new event arrives, and will return after
548	one iteration of the loop. This is useful if you are waiting for some	612	one iteration of the loop. This is useful if you are waiting for some
549	external event in conjunction with something not expressible using other	613	external event in conjunction with something not expressible using other
550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	614	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
551	usually a better approach for this kind of thing.	615	usually a better approach for this kind of thing.
552		616
553	Here are the gory details of what C<ev_loop> does:	617	Here are the gory details of what C<ev_loop> does:
554		618
555	- Before the first iteration, call any pending watchers.	619	- Before the first iteration, call any pending watchers.
556	* If there are no active watchers (reference count is zero), return.	620	* If EVFLAG_FORKCHECK was used, check for a fork.
557	- Queue all prepare watchers and then call all outstanding watchers.	621	- If a fork was detected (by any means), queue and call all fork watchers.
		622	- Queue and call all prepare watchers.
558	- If we have been forked, recreate the kernel state.	623	- If we have been forked, detach and recreate the kernel state
		624	as to not disturb the other process.
559	- Update the kernel state with all outstanding changes.	625	- Update the kernel state with all outstanding changes.
560	- Update the "event loop time".	626	- Update the "event loop time" (ev_now ()).
561	- Calculate for how long to block.	627	- Calculate for how long to sleep or block, if at all
		628	(active idle watchers, EVLOOP_NONBLOCK or not having
		629	any active watchers at all will result in not sleeping).
		630	- Sleep if the I/O and timer collect interval say so.
562	- Block the process, waiting for any events.	631	- Block the process, waiting for any events.
563	- Queue all outstanding I/O (fd) events.	632	- Queue all outstanding I/O (fd) events.
564	- Update the "event loop time" and do time jump handling.	633	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
565	- Queue all outstanding timers.	634	- Queue all outstanding timers.
566	- Queue all outstanding periodics.	635	- Queue all outstanding periodics.
567	- If no events are pending now, queue all idle watchers.	636	- Unless any events are pending now, queue all idle watchers.
568	- Queue all check watchers.	637	- Queue all check watchers.
569	- Call all queued watchers in reverse order (i.e. check watchers first).	638	- Call all queued watchers in reverse order (i.e. check watchers first).
570	Signals and child watchers are implemented as I/O watchers, and will	639	Signals and child watchers are implemented as I/O watchers, and will
571	be handled here by queueing them when their watcher gets executed.	640	be handled here by queueing them when their watcher gets executed.
572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	641	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573	were used, return, otherwise continue with step *.	642	were used, or there are no active watchers, return, otherwise
		643	continue with step *.
574		644
575	Example: Queue some jobs and then loop until no events are outsanding	645	Example: Queue some jobs and then loop until no events are outstanding
576	anymore.	646	anymore.
577		647
578	... queue jobs here, make sure they register event watchers as long	648	... queue jobs here, make sure they register event watchers as long
579	... as they still have work to do (even an idle watcher will do..)	649	... as they still have work to do (even an idle watcher will do..)
580	ev_loop (my_loop, 0);	650	ev_loop (my_loop, 0);
581	... jobs done. yeah!	651	... jobs done or somebody called unloop. yeah!
582		652
583	=item ev_unloop (loop, how)	653	=item ev_unloop (loop, how)
584		654
585	Can be used to make a call to C<ev_loop> return early (but only after it	655	Can be used to make a call to C<ev_loop> return early (but only after it
586	has processed all outstanding events). The C<how> argument must be either	656	has processed all outstanding events). The C<how> argument must be either
587	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	657	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
588	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	658	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		659
		660	This "unloop state" will be cleared when entering C<ev_loop> again.
589		661
590	=item ev_ref (loop)	662	=item ev_ref (loop)
591		663
592	=item ev_unref (loop)	664	=item ev_unref (loop)
593		665
…		…
598	returning, ev_unref() after starting, and ev_ref() before stopping it. For	670	returning, ev_unref() after starting, and ev_ref() before stopping it. For
599	example, libev itself uses this for its internal signal pipe: It is not	671	example, libev itself uses this for its internal signal pipe: It is not
600	visible to the libev user and should not keep C<ev_loop> from exiting if	672	visible to the libev user and should not keep C<ev_loop> from exiting if
601	no event watchers registered by it are active. It is also an excellent	673	no event watchers registered by it are active. It is also an excellent
602	way to do this for generic recurring timers or from within third-party	674	way to do this for generic recurring timers or from within third-party
603	libraries. Just remember to I<unref after start> and I<ref before stop>.	675	libraries. Just remember to I<unref after start> and I<ref before stop>
		676	(but only if the watcher wasn't active before, or was active before,
		677	respectively).
604		678
605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	679	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606	running when nothing else is active.	680	running when nothing else is active.
607		681
608	struct ev_signal exitsig;	682	struct ev_signal exitsig;
609	ev_signal_init (&exitsig, sig_cb, SIGINT);	683	ev_signal_init (&exitsig, sig_cb, SIGINT);
610	ev_signal_start (loop, &exitsig);	684	ev_signal_start (loop, &exitsig);
611	evf_unref (loop);	685	evf_unref (loop);
612		686
613	Example: For some weird reason, unregister the above signal handler again.	687	Example: For some weird reason, unregister the above signal handler again.
614		688
615	ev_ref (loop);	689	ev_ref (loop);
616	ev_signal_stop (loop, &exitsig);	690	ev_signal_stop (loop, &exitsig);
617		691
618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	692	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
619		693
620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	694	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
621		695
622	These advanced functions influence the time that libev will spend waiting	696	These advanced functions influence the time that libev will spend waiting
623	for events. Both are by default C<0>, meaning that libev will try to	697	for events. Both time intervals are by default C<0>, meaning that libev
624	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	698	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		699	latency.
625		700
626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	701	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
627	allows libev to delay invocation of I/O and timer/periodic callbacks to	702	allows libev to delay invocation of I/O and timer/periodic callbacks
628	increase efficiency of loop iterations.	703	to increase efficiency of loop iterations (or to increase power-saving
		704	opportunities).
629		705
630	The background is that sometimes your program runs just fast enough to	706	The background is that sometimes your program runs just fast enough to
631	handle one (or very few) event(s) per loop iteration. While this makes	707	handle one (or very few) event(s) per loop iteration. While this makes
632	the program responsive, it also wastes a lot of CPU time to poll for new	708	the program responsive, it also wastes a lot of CPU time to poll for new
633	events, especially with backends like C<select ()> which have a high	709	events, especially with backends like C<select ()> which have a high
…		…
643	to spend more time collecting timeouts, at the expense of increased	719	to spend more time collecting timeouts, at the expense of increased
644	latency (the watcher callback will be called later). C<ev_io> watchers	720	latency (the watcher callback will be called later). C<ev_io> watchers
645	will not be affected. Setting this to a non-null value will not introduce	721	will not be affected. Setting this to a non-null value will not introduce
646	any overhead in libev.	722	any overhead in libev.
647		723
648	Many (busy) programs can usually benefit by setting the io collect	724	Many (busy) programs can usually benefit by setting the I/O collect
649	interval to a value near C<0.1> or so, which is often enough for	725	interval to a value near C<0.1> or so, which is often enough for
650	interactive servers (of course not for games), likewise for timeouts. It	726	interactive servers (of course not for games), likewise for timeouts. It
651	usually doesn't make much sense to set it to a lower value than C<0.01>,	727	usually doesn't make much sense to set it to a lower value than C<0.01>,
652	as this approsaches the timing granularity of most systems.	728	as this approaches the timing granularity of most systems.
		729
		730	Setting the I<timeout collect interval> can improve the opportunity for
		731	saving power, as the program will "bundle" timer callback invocations that
		732	are "near" in time together, by delaying some, thus reducing the number of
		733	times the process sleeps and wakes up again. Another useful technique to
		734	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		735	they fire on, say, one-second boundaries only.
		736
		737	=item ev_loop_verify (loop)
		738
		739	This function only does something when C<EV_VERIFY> support has been
		740	compiled in. It tries to go through all internal structures and checks
		741	them for validity. If anything is found to be inconsistent, it will print
		742	an error message to standard error and call C<abort ()>.
		743
		744	This can be used to catch bugs inside libev itself: under normal
		745	circumstances, this function will never abort as of course libev keeps its
		746	data structures consistent.
653		747
654	=back	748	=back
655		749
656		750
657	=head1 ANATOMY OF A WATCHER	751	=head1 ANATOMY OF A WATCHER
658		752
659	A watcher is a structure that you create and register to record your	753	A watcher is a structure that you create and register to record your
660	interest in some event. For instance, if you want to wait for STDIN to	754	interest in some event. For instance, if you want to wait for STDIN to
661	become readable, you would create an C<ev_io> watcher for that:	755	become readable, you would create an C<ev_io> watcher for that:
662		756
663	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	757	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
664	{	758	{
665	ev_io_stop (w);	759	ev_io_stop (w);
666	ev_unloop (loop, EVUNLOOP_ALL);	760	ev_unloop (loop, EVUNLOOP_ALL);
667	}	761	}
668		762
669	struct ev_loop *loop = ev_default_loop (0);	763	struct ev_loop *loop = ev_default_loop (0);
670	struct ev_io stdin_watcher;	764	struct ev_io stdin_watcher;
671	ev_init (&stdin_watcher, my_cb);	765	ev_init (&stdin_watcher, my_cb);
672	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	766	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
673	ev_io_start (loop, &stdin_watcher);	767	ev_io_start (loop, &stdin_watcher);
674	ev_loop (loop, 0);	768	ev_loop (loop, 0);
675		769
676	As you can see, you are responsible for allocating the memory for your	770	As you can see, you are responsible for allocating the memory for your
677	watcher structures (and it is usually a bad idea to do this on the stack,	771	watcher structures (and it is usually a bad idea to do this on the stack,
678	although this can sometimes be quite valid).	772	although this can sometimes be quite valid).
679		773
680	Each watcher structure must be initialised by a call to C<ev_init	774	Each watcher structure must be initialised by a call to C<ev_init
681	(watcher *, callback)>, which expects a callback to be provided. This	775	(watcher *, callback)>, which expects a callback to be provided. This
682	callback gets invoked each time the event occurs (or, in the case of io	776	callback gets invoked each time the event occurs (or, in the case of I/O
683	watchers, each time the event loop detects that the file descriptor given	777	watchers, each time the event loop detects that the file descriptor given
684	is readable and/or writable).	778	is readable and/or writable).
685		779
686	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	780	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
687	with arguments specific to this watcher type. There is also a macro	781	with arguments specific to this watcher type. There is also a macro
…		…
757	=item C<EV_FORK>	851	=item C<EV_FORK>
758		852
759	The event loop has been resumed in the child process after fork (see	853	The event loop has been resumed in the child process after fork (see
760	C<ev_fork>).	854	C<ev_fork>).
761		855
		856	=item C<EV_ASYNC>
		857
		858	The given async watcher has been asynchronously notified (see C<ev_async>).
		859
762	=item C<EV_ERROR>	860	=item C<EV_ERROR>
763		861
764	An unspecified error has occured, the watcher has been stopped. This might	862	An unspecified error has occurred, the watcher has been stopped. This might
765	happen because the watcher could not be properly started because libev	863	happen because the watcher could not be properly started because libev
766	ran out of memory, a file descriptor was found to be closed or any other	864	ran out of memory, a file descriptor was found to be closed or any other
767	problem. You best act on it by reporting the problem and somehow coping	865	problem. You best act on it by reporting the problem and somehow coping
768	with the watcher being stopped.	866	with the watcher being stopped.
769		867
770	Libev will usually signal a few "dummy" events together with an error,	868	Libev will usually signal a few "dummy" events together with an error,
771	for example it might indicate that a fd is readable or writable, and if	869	for example it might indicate that a fd is readable or writable, and if
772	your callbacks is well-written it can just attempt the operation and cope	870	your callbacks is well-written it can just attempt the operation and cope
773	with the error from read() or write(). This will not work in multithreaded	871	with the error from read() or write(). This will not work in multi-threaded
774	programs, though, so beware.	872	programs, though, so beware.
775		873
776	=back	874	=back
777		875
778	=head2 GENERIC WATCHER FUNCTIONS	876	=head2 GENERIC WATCHER FUNCTIONS
…		…
808	Although some watcher types do not have type-specific arguments	906	Although some watcher types do not have type-specific arguments
809	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	907	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
810		908
811	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	909	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
812		910
813	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	911	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
814	calls into a single call. This is the most convinient method to initialise	912	calls into a single call. This is the most convenient method to initialise
815	a watcher. The same limitations apply, of course.	913	a watcher. The same limitations apply, of course.
816		914
817	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	915	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
818		916
819	Starts (activates) the given watcher. Only active watchers will receive	917	Starts (activates) the given watcher. Only active watchers will receive
…		…
902	to associate arbitrary data with your watcher. If you need more data and	1000	to associate arbitrary data with your watcher. If you need more data and
903	don't want to allocate memory and store a pointer to it in that data	1001	don't want to allocate memory and store a pointer to it in that data
904	member, you can also "subclass" the watcher type and provide your own	1002	member, you can also "subclass" the watcher type and provide your own
905	data:	1003	data:
906		1004
907	struct my_io	1005	struct my_io
908	{	1006	{
909	struct ev_io io;	1007	struct ev_io io;
910	int otherfd;	1008	int otherfd;
911	void *somedata;	1009	void *somedata;
912	struct whatever *mostinteresting;	1010	struct whatever *mostinteresting;
913	}	1011	};
		1012
		1013	...
		1014	struct my_io w;
		1015	ev_io_init (&w.io, my_cb, fd, EV_READ);
914		1016
915	And since your callback will be called with a pointer to the watcher, you	1017	And since your callback will be called with a pointer to the watcher, you
916	can cast it back to your own type:	1018	can cast it back to your own type:
917		1019
918	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1020	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
919	{	1021	{
920	struct my_io *w = (struct my_io *)w_;	1022	struct my_io *w = (struct my_io *)w_;
921	...	1023	...
922	}	1024	}
923		1025
924	More interesting and less C-conformant ways of casting your callback type	1026	More interesting and less C-conformant ways of casting your callback type
925	instead have been omitted.	1027	instead have been omitted.
926		1028
927	Another common scenario is having some data structure with multiple	1029	Another common scenario is to use some data structure with multiple
928	watchers:	1030	embedded watchers:
929		1031
930	struct my_biggy	1032	struct my_biggy
931	{	1033	{
932	int some_data;	1034	int some_data;
933	ev_timer t1;	1035	ev_timer t1;
934	ev_timer t2;	1036	ev_timer t2;
935	}	1037	}
936		1038
937	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1039	In this case getting the pointer to C<my_biggy> is a bit more
938	you need to use C<offsetof>:	1040	complicated: Either you store the address of your C<my_biggy> struct
		1041	in the C<data> member of the watcher, or you need to use some pointer
		1042	arithmetic using C<offsetof> inside your watchers:
939		1043
940	#include <stddef.h>	1044	#include <stddef.h>
941		1045
942	static void	1046	static void
943	t1_cb (EV_P_ struct ev_timer *w, int revents)	1047	t1_cb (EV_P_ struct ev_timer *w, int revents)
944	{	1048	{
945	struct my_biggy big = (struct my_biggy *	1049	struct my_biggy big = (struct my_biggy *
946	(((char *)w) - offsetof (struct my_biggy, t1));	1050	(((char *)w) - offsetof (struct my_biggy, t1));
947	}	1051	}
948		1052
949	static void	1053	static void
950	t2_cb (EV_P_ struct ev_timer *w, int revents)	1054	t2_cb (EV_P_ struct ev_timer *w, int revents)
951	{	1055	{
952	struct my_biggy big = (struct my_biggy *	1056	struct my_biggy big = (struct my_biggy *
953	(((char *)w) - offsetof (struct my_biggy, t2));	1057	(((char *)w) - offsetof (struct my_biggy, t2));
954	}	1058	}
955		1059
956		1060
957	=head1 WATCHER TYPES	1061	=head1 WATCHER TYPES
958		1062
959	This section describes each watcher in detail, but will not repeat	1063	This section describes each watcher in detail, but will not repeat
…		…
983	In general you can register as many read and/or write event watchers per	1087	In general you can register as many read and/or write event watchers per
984	fd as you want (as long as you don't confuse yourself). Setting all file	1088	fd as you want (as long as you don't confuse yourself). Setting all file
985	descriptors to non-blocking mode is also usually a good idea (but not	1089	descriptors to non-blocking mode is also usually a good idea (but not
986	required if you know what you are doing).	1090	required if you know what you are doing).
987		1091
988	You have to be careful with dup'ed file descriptors, though. Some backends
989	(the linux epoll backend is a notable example) cannot handle dup'ed file
990	descriptors correctly if you register interest in two or more fds pointing
991	to the same underlying file/socket/etc. description (that is, they share
992	the same underlying "file open").
993
994	If you must do this, then force the use of a known-to-be-good backend	1092	If you must do this, then force the use of a known-to-be-good backend
995	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1093	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
996	C<EVBACKEND_POLL>).	1094	C<EVBACKEND_POLL>).
997		1095
998	Another thing you have to watch out for is that it is quite easy to	1096	Another thing you have to watch out for is that it is quite easy to
999	receive "spurious" readyness notifications, that is your callback might	1097	receive "spurious" readiness notifications, that is your callback might
1000	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1098	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1001	because there is no data. Not only are some backends known to create a	1099	because there is no data. Not only are some backends known to create a
1002	lot of those (for example solaris ports), it is very easy to get into	1100	lot of those (for example Solaris ports), it is very easy to get into
1003	this situation even with a relatively standard program structure. Thus	1101	this situation even with a relatively standard program structure. Thus
1004	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1102	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1005	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1103	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1006		1104
1007	If you cannot run the fd in non-blocking mode (for example you should not	1105	If you cannot run the fd in non-blocking mode (for example you should not
1008	play around with an Xlib connection), then you have to seperately re-test	1106	play around with an Xlib connection), then you have to separately re-test
1009	whether a file descriptor is really ready with a known-to-be good interface	1107	whether a file descriptor is really ready with a known-to-be good interface
1010	such as poll (fortunately in our Xlib example, Xlib already does this on	1108	such as poll (fortunately in our Xlib example, Xlib already does this on
1011	its own, so its quite safe to use).	1109	its own, so its quite safe to use).
1012		1110
1013	=head3 The special problem of disappearing file descriptors	1111	=head3 The special problem of disappearing file descriptors
…		…
1032	optimisations to libev.	1130	optimisations to libev.
1033		1131
1034	=head3 The special problem of dup'ed file descriptors	1132	=head3 The special problem of dup'ed file descriptors
1035		1133
1036	Some backends (e.g. epoll), cannot register events for file descriptors,	1134	Some backends (e.g. epoll), cannot register events for file descriptors,
1037	but only events for the underlying file descriptions. That menas when you	1135	but only events for the underlying file descriptions. That means when you
1038	have C<dup ()>'ed file descriptors and register events for them, only one	1136	have C<dup ()>'ed file descriptors or weirder constellations, and register
1039	file descriptor might actually receive events.	1137	events for them, only one file descriptor might actually receive events.
1040		1138
1041	There is no workaorund possible except not registering events	1139	There is no workaround possible except not registering events
1042	for potentially C<dup ()>'ed file descriptors or to resort to	1140	for potentially C<dup ()>'ed file descriptors, or to resort to
1043	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1141	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1044		1142
1045	=head3 The special problem of fork	1143	=head3 The special problem of fork
1046		1144
1047	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1145	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
1051	To support fork in your programs, you either have to call	1149	To support fork in your programs, you either have to call
1052	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1150	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1053	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1151	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1054	C<EVBACKEND_POLL>.	1152	C<EVBACKEND_POLL>.
1055		1153
		1154	=head3 The special problem of SIGPIPE
		1155
		1156	While not really specific to libev, it is easy to forget about SIGPIPE:
		1157	when writing to a pipe whose other end has been closed, your program gets
		1158	send a SIGPIPE, which, by default, aborts your program. For most programs
		1159	this is sensible behaviour, for daemons, this is usually undesirable.
		1160
		1161	So when you encounter spurious, unexplained daemon exits, make sure you
		1162	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1163	somewhere, as that would have given you a big clue).
		1164
1056		1165
1057	=head3 Watcher-Specific Functions	1166	=head3 Watcher-Specific Functions
1058		1167
1059	=over 4	1168	=over 4
1060		1169
1061	=item ev_io_init (ev_io *, callback, int fd, int events)	1170	=item ev_io_init (ev_io *, callback, int fd, int events)
1062		1171
1063	=item ev_io_set (ev_io *, int fd, int events)	1172	=item ev_io_set (ev_io *, int fd, int events)
1064		1173
1065	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1174	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1066	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1175	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
1067	C<EV_READ | EV_WRITE> to receive the given events.	1176	C<EV_READ | EV_WRITE> to receive the given events.
1068		1177
1069	=item int fd [read-only]	1178	=item int fd [read-only]
1070		1179
1071	The file descriptor being watched.	1180	The file descriptor being watched.
…		…
1073	=item int events [read-only]	1182	=item int events [read-only]
1074		1183
1075	The events being watched.	1184	The events being watched.
1076		1185
1077	=back	1186	=back
		1187
		1188	=head3 Examples
1078		1189
1079	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1190	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1080	readable, but only once. Since it is likely line-buffered, you could	1191	readable, but only once. Since it is likely line-buffered, you could
1081	attempt to read a whole line in the callback.	1192	attempt to read a whole line in the callback.
1082		1193
1083	static void	1194	static void
1084	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1195	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1085	{	1196	{
1086	ev_io_stop (loop, w);	1197	ev_io_stop (loop, w);
1087	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1198	.. read from stdin here (or from w->fd) and haqndle any I/O errors
1088	}	1199	}
1089		1200
1090	...	1201	...
1091	struct ev_loop *loop = ev_default_init (0);	1202	struct ev_loop *loop = ev_default_init (0);
1092	struct ev_io stdin_readable;	1203	struct ev_io stdin_readable;
1093	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1204	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1094	ev_io_start (loop, &stdin_readable);	1205	ev_io_start (loop, &stdin_readable);
1095	ev_loop (loop, 0);	1206	ev_loop (loop, 0);
1096		1207
1097		1208
1098	=head2 C<ev_timer> - relative and optionally repeating timeouts	1209	=head2 C<ev_timer> - relative and optionally repeating timeouts
1099		1210
1100	Timer watchers are simple relative timers that generate an event after a	1211	Timer watchers are simple relative timers that generate an event after a
1101	given time, and optionally repeating in regular intervals after that.	1212	given time, and optionally repeating in regular intervals after that.
1102		1213
1103	The timers are based on real time, that is, if you register an event that	1214	The timers are based on real time, that is, if you register an event that
1104	times out after an hour and you reset your system clock to last years	1215	times out after an hour and you reset your system clock to January last
1105	time, it will still time out after (roughly) and hour. "Roughly" because	1216	year, it will still time out after (roughly) and hour. "Roughly" because
1106	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1217	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1107	monotonic clock option helps a lot here).	1218	monotonic clock option helps a lot here).
		1219
		1220	The callback is guaranteed to be invoked only after its timeout has passed,
		1221	but if multiple timers become ready during the same loop iteration then
		1222	order of execution is undefined.
		1223
		1224	=head3 The special problem of time updates
		1225
		1226	Establishing the current time is a costly operation (it usually takes at
		1227	least two system calls): EV therefore updates its idea of the current
		1228	time only before and after C<ev_loop> polls for new events, which causes
		1229	a growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1230	lots of events.
1108		1231
1109	The relative timeouts are calculated relative to the C<ev_now ()>	1232	The relative timeouts are calculated relative to the C<ev_now ()>
1110	time. This is usually the right thing as this timestamp refers to the time	1233	time. This is usually the right thing as this timestamp refers to the time
1111	of the event triggering whatever timeout you are modifying/starting. If	1234	of the event triggering whatever timeout you are modifying/starting. If
1112	you suspect event processing to be delayed and you I<need> to base the timeout	1235	you suspect event processing to be delayed and you I<need> to base the
1113	on the current time, use something like this to adjust for this:	1236	timeout on the current time, use something like this to adjust for this:
1114		1237
1115	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1238	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1116		1239
1117	The callback is guarenteed to be invoked only when its timeout has passed,	1240	If the event loop is suspended for a long time, you can also force an
1118	but if multiple timers become ready during the same loop iteration then	1241	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1119	order of execution is undefined.	1242	()>.
1120		1243
1121	=head3 Watcher-Specific Functions and Data Members	1244	=head3 Watcher-Specific Functions and Data Members
1122		1245
1123	=over 4	1246	=over 4
1124		1247
1125	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1248	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1126		1249
1127	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1250	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1128		1251
1129	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1252	Configure the timer to trigger after C<after> seconds. If C<repeat>
1130	C<0.>, then it will automatically be stopped. If it is positive, then the	1253	is C<0.>, then it will automatically be stopped once the timeout is
1131	timer will automatically be configured to trigger again C<repeat> seconds	1254	reached. If it is positive, then the timer will automatically be
1132	later, again, and again, until stopped manually.	1255	configured to trigger again C<repeat> seconds later, again, and again,
		1256	until stopped manually.
1133		1257
1134	The timer itself will do a best-effort at avoiding drift, that is, if you	1258	The timer itself will do a best-effort at avoiding drift, that is, if
1135	configure a timer to trigger every 10 seconds, then it will trigger at	1259	you configure a timer to trigger every 10 seconds, then it will normally
1136	exactly 10 second intervals. If, however, your program cannot keep up with	1260	trigger at exactly 10 second intervals. If, however, your program cannot
1137	the timer (because it takes longer than those 10 seconds to do stuff) the	1261	keep up with the timer (because it takes longer than those 10 seconds to
1138	timer will not fire more than once per event loop iteration.	1262	do stuff) the timer will not fire more than once per event loop iteration.
1139		1263
1140	=item ev_timer_again (loop)	1264	=item ev_timer_again (loop, ev_timer *)
1141		1265
1142	This will act as if the timer timed out and restart it again if it is	1266	This will act as if the timer timed out and restart it again if it is
1143	repeating. The exact semantics are:	1267	repeating. The exact semantics are:
1144		1268
1145	If the timer is pending, its pending status is cleared.	1269	If the timer is pending, its pending status is cleared.
1146		1270
1147	If the timer is started but nonrepeating, stop it (as if it timed out).	1271	If the timer is started but non-repeating, stop it (as if it timed out).
1148		1272
1149	If the timer is repeating, either start it if necessary (with the	1273	If the timer is repeating, either start it if necessary (with the
1150	C<repeat> value), or reset the running timer to the C<repeat> value.	1274	C<repeat> value), or reset the running timer to the C<repeat> value.
1151		1275
1152	This sounds a bit complicated, but here is a useful and typical	1276	This sounds a bit complicated, but here is a useful and typical
1153	example: Imagine you have a tcp connection and you want a so-called idle	1277	example: Imagine you have a TCP connection and you want a so-called idle
1154	timeout, that is, you want to be called when there have been, say, 60	1278	timeout, that is, you want to be called when there have been, say, 60
1155	seconds of inactivity on the socket. The easiest way to do this is to	1279	seconds of inactivity on the socket. The easiest way to do this is to
1156	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1280	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1157	C<ev_timer_again> each time you successfully read or write some data. If	1281	C<ev_timer_again> each time you successfully read or write some data. If
1158	you go into an idle state where you do not expect data to travel on the	1282	you go into an idle state where you do not expect data to travel on the
…		…
1180	or C<ev_timer_again> is called and determines the next timeout (if any),	1304	or C<ev_timer_again> is called and determines the next timeout (if any),
1181	which is also when any modifications are taken into account.	1305	which is also when any modifications are taken into account.
1182		1306
1183	=back	1307	=back
1184		1308
		1309	=head3 Examples
		1310
1185	Example: Create a timer that fires after 60 seconds.	1311	Example: Create a timer that fires after 60 seconds.
1186		1312
1187	static void	1313	static void
1188	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1314	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1189	{	1315	{
1190	.. one minute over, w is actually stopped right here	1316	.. one minute over, w is actually stopped right here
1191	}	1317	}
1192		1318
1193	struct ev_timer mytimer;	1319	struct ev_timer mytimer;
1194	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1320	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1195	ev_timer_start (loop, &mytimer);	1321	ev_timer_start (loop, &mytimer);
1196		1322
1197	Example: Create a timeout timer that times out after 10 seconds of	1323	Example: Create a timeout timer that times out after 10 seconds of
1198	inactivity.	1324	inactivity.
1199		1325
1200	static void	1326	static void
1201	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1327	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1202	{	1328	{
1203	.. ten seconds without any activity	1329	.. ten seconds without any activity
1204	}	1330	}
1205		1331
1206	struct ev_timer mytimer;	1332	struct ev_timer mytimer;
1207	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1333	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1208	ev_timer_again (&mytimer); /* start timer */	1334	ev_timer_again (&mytimer); /* start timer */
1209	ev_loop (loop, 0);	1335	ev_loop (loop, 0);
1210		1336
1211	// and in some piece of code that gets executed on any "activity":	1337	// and in some piece of code that gets executed on any "activity":
1212	// reset the timeout to start ticking again at 10 seconds	1338	// reset the timeout to start ticking again at 10 seconds
1213	ev_timer_again (&mytimer);	1339	ev_timer_again (&mytimer);
1214		1340
1215		1341
1216	=head2 C<ev_periodic> - to cron or not to cron?	1342	=head2 C<ev_periodic> - to cron or not to cron?
1217		1343
1218	Periodic watchers are also timers of a kind, but they are very versatile	1344	Periodic watchers are also timers of a kind, but they are very versatile
1219	(and unfortunately a bit complex).	1345	(and unfortunately a bit complex).
1220		1346
1221	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1347	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1222	but on wallclock time (absolute time). You can tell a periodic watcher	1348	but on wall clock time (absolute time). You can tell a periodic watcher
1223	to trigger "at" some specific point in time. For example, if you tell a	1349	to trigger after some specific point in time. For example, if you tell a
1224	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1350	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1225	+ 10.>) and then reset your system clock to the last year, then it will	1351	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1352	clock to January of the previous year, then it will take more than year
1226	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1353	to trigger the event (unlike an C<ev_timer>, which would still trigger
1227	roughly 10 seconds later).	1354	roughly 10 seconds later as it uses a relative timeout).
1228		1355
1229	They can also be used to implement vastly more complex timers, such as	1356	C<ev_periodic>s can also be used to implement vastly more complex timers,
1230	triggering an event on each midnight, local time or other, complicated,	1357	such as triggering an event on each "midnight, local time", or other
1231	rules.	1358	complicated, rules.
1232		1359
1233	As with timers, the callback is guarenteed to be invoked only when the	1360	As with timers, the callback is guaranteed to be invoked only when the
1234	time (C<at>) has been passed, but if multiple periodic timers become ready	1361	time (C<at>) has passed, but if multiple periodic timers become ready
1235	during the same loop iteration then order of execution is undefined.	1362	during the same loop iteration then order of execution is undefined.
1236		1363
1237	=head3 Watcher-Specific Functions and Data Members	1364	=head3 Watcher-Specific Functions and Data Members
1238		1365
1239	=over 4	1366	=over 4
…		…
1247		1374
1248	=over 4	1375	=over 4
1249		1376
1250	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1377	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1251		1378
1252	In this configuration the watcher triggers an event at the wallclock time	1379	In this configuration the watcher triggers an event after the wall clock
1253	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1380	time C<at> has passed and doesn't repeat. It will not adjust when a time
1254	that is, if it is to be run at January 1st 2011 then it will run when the	1381	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1255	system time reaches or surpasses this time.	1382	run when the system time reaches or surpasses this time.
1256		1383
1257	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1384	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1258		1385
1259	In this mode the watcher will always be scheduled to time out at the next	1386	In this mode the watcher will always be scheduled to time out at the next
1260	C<at + N * interval> time (for some integer N, which can also be negative)	1387	C<at + N * interval> time (for some integer N, which can also be negative)
1261	and then repeat, regardless of any time jumps.	1388	and then repeat, regardless of any time jumps.
1262		1389
1263	This can be used to create timers that do not drift with respect to system	1390	This can be used to create timers that do not drift with respect to system
1264	time:	1391	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1392	the hour:
1265		1393
1266	ev_periodic_set (&periodic, 0., 3600., 0);	1394	ev_periodic_set (&periodic, 0., 3600., 0);
1267		1395
1268	This doesn't mean there will always be 3600 seconds in between triggers,	1396	This doesn't mean there will always be 3600 seconds in between triggers,
1269	but only that the the callback will be called when the system time shows a	1397	but only that the callback will be called when the system time shows a
1270	full hour (UTC), or more correctly, when the system time is evenly divisible	1398	full hour (UTC), or more correctly, when the system time is evenly divisible
1271	by 3600.	1399	by 3600.
1272		1400
1273	Another way to think about it (for the mathematically inclined) is that	1401	Another way to think about it (for the mathematically inclined) is that
1274	C<ev_periodic> will try to run the callback in this mode at the next possible	1402	C<ev_periodic> will try to run the callback in this mode at the next possible
1275	time where C<time = at (mod interval)>, regardless of any time jumps.	1403	time where C<time = at (mod interval)>, regardless of any time jumps.
1276		1404
1277	For numerical stability it is preferable that the C<at> value is near	1405	For numerical stability it is preferable that the C<at> value is near
1278	C<ev_now ()> (the current time), but there is no range requirement for	1406	C<ev_now ()> (the current time), but there is no range requirement for
1279	this value.	1407	this value, and in fact is often specified as zero.
		1408
		1409	Note also that there is an upper limit to how often a timer can fire (CPU
		1410	speed for example), so if C<interval> is very small then timing stability
		1411	will of course deteriorate. Libev itself tries to be exact to be about one
		1412	millisecond (if the OS supports it and the machine is fast enough).
1280		1413
1281	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1414	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1282		1415
1283	In this mode the values for C<interval> and C<at> are both being	1416	In this mode the values for C<interval> and C<at> are both being
1284	ignored. Instead, each time the periodic watcher gets scheduled, the	1417	ignored. Instead, each time the periodic watcher gets scheduled, the
1285	reschedule callback will be called with the watcher as first, and the	1418	reschedule callback will be called with the watcher as first, and the
1286	current time as second argument.	1419	current time as second argument.
1287		1420
1288	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1421	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1289	ever, or make any event loop modifications>. If you need to stop it,	1422	ever, or make ANY event loop modifications whatsoever>.
1290	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1291	starting an C<ev_prepare> watcher, which is legal).
1292		1423
		1424	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1425	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1426	only event loop modification you are allowed to do).
		1427
1293	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1428	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1294	ev_tstamp now)>, e.g.:	1429	*w, ev_tstamp now)>, e.g.:
1295		1430
1296	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1431	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1297	{	1432	{
1298	return now + 60.;	1433	return now + 60.;
1299	}	1434	}
…		…
1301	It must return the next time to trigger, based on the passed time value	1436	It must return the next time to trigger, based on the passed time value
1302	(that is, the lowest time value larger than to the second argument). It	1437	(that is, the lowest time value larger than to the second argument). It
1303	will usually be called just before the callback will be triggered, but	1438	will usually be called just before the callback will be triggered, but
1304	might be called at other times, too.	1439	might be called at other times, too.
1305		1440
1306	NOTE: I<< This callback must always return a time that is later than the	1441	NOTE: I<< This callback must always return a time that is higher than or
1307	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1442	equal to the passed C<now> value >>.
1308		1443
1309	This can be used to create very complex timers, such as a timer that	1444	This can be used to create very complex timers, such as a timer that
1310	triggers on each midnight, local time. To do this, you would calculate the	1445	triggers on "next midnight, local time". To do this, you would calculate the
1311	next midnight after C<now> and return the timestamp value for this. How	1446	next midnight after C<now> and return the timestamp value for this. How
1312	you do this is, again, up to you (but it is not trivial, which is the main	1447	you do this is, again, up to you (but it is not trivial, which is the main
1313	reason I omitted it as an example).	1448	reason I omitted it as an example).
1314		1449
1315	=back	1450	=back
…		…
1319	Simply stops and restarts the periodic watcher again. This is only useful	1454	Simply stops and restarts the periodic watcher again. This is only useful
1320	when you changed some parameters or the reschedule callback would return	1455	when you changed some parameters or the reschedule callback would return
1321	a different time than the last time it was called (e.g. in a crond like	1456	a different time than the last time it was called (e.g. in a crond like
1322	program when the crontabs have changed).	1457	program when the crontabs have changed).
1323		1458
		1459	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1460
		1461	When active, returns the absolute time that the watcher is supposed to
		1462	trigger next.
		1463
1324	=item ev_tstamp offset [read-write]	1464	=item ev_tstamp offset [read-write]
1325		1465
1326	When repeating, this contains the offset value, otherwise this is the	1466	When repeating, this contains the offset value, otherwise this is the
1327	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1467	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1328		1468
…		…
1339		1479
1340	The current reschedule callback, or C<0>, if this functionality is	1480	The current reschedule callback, or C<0>, if this functionality is
1341	switched off. Can be changed any time, but changes only take effect when	1481	switched off. Can be changed any time, but changes only take effect when
1342	the periodic timer fires or C<ev_periodic_again> is being called.	1482	the periodic timer fires or C<ev_periodic_again> is being called.
1343		1483
1344	=item ev_tstamp at [read-only]
1345
1346	When active, contains the absolute time that the watcher is supposed to
1347	trigger next.
1348
1349	=back	1484	=back
		1485
		1486	=head3 Examples
1350		1487
1351	Example: Call a callback every hour, or, more precisely, whenever the	1488	Example: Call a callback every hour, or, more precisely, whenever the
1352	system clock is divisible by 3600. The callback invocation times have	1489	system clock is divisible by 3600. The callback invocation times have
1353	potentially a lot of jittering, but good long-term stability.	1490	potentially a lot of jitter, but good long-term stability.
1354		1491
1355	static void	1492	static void
1356	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1493	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1357	{	1494	{
1358	... its now a full hour (UTC, or TAI or whatever your clock follows)	1495	... its now a full hour (UTC, or TAI or whatever your clock follows)
1359	}	1496	}
1360		1497
1361	struct ev_periodic hourly_tick;	1498	struct ev_periodic hourly_tick;
1362	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1499	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1363	ev_periodic_start (loop, &hourly_tick);	1500	ev_periodic_start (loop, &hourly_tick);
1364		1501
1365	Example: The same as above, but use a reschedule callback to do it:	1502	Example: The same as above, but use a reschedule callback to do it:
1366		1503
1367	#include <math.h>	1504	#include <math.h>
1368		1505
1369	static ev_tstamp	1506	static ev_tstamp
1370	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1507	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1371	{	1508	{
1372	return fmod (now, 3600.) + 3600.;	1509	return fmod (now, 3600.) + 3600.;
1373	}	1510	}
1374		1511
1375	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1512	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1376		1513
1377	Example: Call a callback every hour, starting now:	1514	Example: Call a callback every hour, starting now:
1378		1515
1379	struct ev_periodic hourly_tick;	1516	struct ev_periodic hourly_tick;
1380	ev_periodic_init (&hourly_tick, clock_cb,	1517	ev_periodic_init (&hourly_tick, clock_cb,
1381	fmod (ev_now (loop), 3600.), 3600., 0);	1518	fmod (ev_now (loop), 3600.), 3600., 0);
1382	ev_periodic_start (loop, &hourly_tick);	1519	ev_periodic_start (loop, &hourly_tick);
1383		1520
1384		1521
1385	=head2 C<ev_signal> - signal me when a signal gets signalled!	1522	=head2 C<ev_signal> - signal me when a signal gets signalled!
1386		1523
1387	Signal watchers will trigger an event when the process receives a specific	1524	Signal watchers will trigger an event when the process receives a specific
…		…
1394	with the kernel (thus it coexists with your own signal handlers as long	1531	with the kernel (thus it coexists with your own signal handlers as long
1395	as you don't register any with libev). Similarly, when the last signal	1532	as you don't register any with libev). Similarly, when the last signal
1396	watcher for a signal is stopped libev will reset the signal handler to	1533	watcher for a signal is stopped libev will reset the signal handler to
1397	SIG_DFL (regardless of what it was set to before).	1534	SIG_DFL (regardless of what it was set to before).
1398		1535
		1536	If possible and supported, libev will install its handlers with
		1537	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1538	interrupted. If you have a problem with system calls getting interrupted by
		1539	signals you can block all signals in an C<ev_check> watcher and unblock
		1540	them in an C<ev_prepare> watcher.
		1541
1399	=head3 Watcher-Specific Functions and Data Members	1542	=head3 Watcher-Specific Functions and Data Members
1400		1543
1401	=over 4	1544	=over 4
1402		1545
1403	=item ev_signal_init (ev_signal *, callback, int signum)	1546	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1411		1554
1412	The signal the watcher watches out for.	1555	The signal the watcher watches out for.
1413		1556
1414	=back	1557	=back
1415		1558
		1559	=head3 Examples
		1560
		1561	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1562
		1563	static void
		1564	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1565	{
		1566	ev_unloop (loop, EVUNLOOP_ALL);
		1567	}
		1568
		1569	struct ev_signal signal_watcher;
		1570	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1571	ev_signal_start (loop, &sigint_cb);
		1572
1416		1573
1417	=head2 C<ev_child> - watch out for process status changes	1574	=head2 C<ev_child> - watch out for process status changes
1418		1575
1419	Child watchers trigger when your process receives a SIGCHLD in response to	1576	Child watchers trigger when your process receives a SIGCHLD in response to
1420	some child status changes (most typically when a child of yours dies).	1577	some child status changes (most typically when a child of yours dies). It
		1578	is permissible to install a child watcher I<after> the child has been
		1579	forked (which implies it might have already exited), as long as the event
		1580	loop isn't entered (or is continued from a watcher).
		1581
		1582	Only the default event loop is capable of handling signals, and therefore
		1583	you can only register child watchers in the default event loop.
		1584
		1585	=head3 Process Interaction
		1586
		1587	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1588	initialised. This is necessary to guarantee proper behaviour even if
		1589	the first child watcher is started after the child exits. The occurrence
		1590	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1591	synchronously as part of the event loop processing. Libev always reaps all
		1592	children, even ones not watched.
		1593
		1594	=head3 Overriding the Built-In Processing
		1595
		1596	Libev offers no special support for overriding the built-in child
		1597	processing, but if your application collides with libev's default child
		1598	handler, you can override it easily by installing your own handler for
		1599	C<SIGCHLD> after initialising the default loop, and making sure the
		1600	default loop never gets destroyed. You are encouraged, however, to use an
		1601	event-based approach to child reaping and thus use libev's support for
		1602	that, so other libev users can use C<ev_child> watchers freely.
		1603
		1604	=head3 Stopping the Child Watcher
		1605
		1606	Currently, the child watcher never gets stopped, even when the
		1607	child terminates, so normally one needs to stop the watcher in the
		1608	callback. Future versions of libev might stop the watcher automatically
		1609	when a child exit is detected.
1421		1610
1422	=head3 Watcher-Specific Functions and Data Members	1611	=head3 Watcher-Specific Functions and Data Members
1423		1612
1424	=over 4	1613	=over 4
1425		1614
1426	=item ev_child_init (ev_child *, callback, int pid)	1615	=item ev_child_init (ev_child *, callback, int pid, int trace)
1427		1616
1428	=item ev_child_set (ev_child *, int pid)	1617	=item ev_child_set (ev_child *, int pid, int trace)
1429		1618
1430	Configures the watcher to wait for status changes of process C<pid> (or	1619	Configures the watcher to wait for status changes of process C<pid> (or
1431	I<any> process if C<pid> is specified as C<0>). The callback can look	1620	I<any> process if C<pid> is specified as C<0>). The callback can look
1432	at the C<rstatus> member of the C<ev_child> watcher structure to see	1621	at the C<rstatus> member of the C<ev_child> watcher structure to see
1433	the status word (use the macros from C<sys/wait.h> and see your systems	1622	the status word (use the macros from C<sys/wait.h> and see your systems
1434	C<waitpid> documentation). The C<rpid> member contains the pid of the	1623	C<waitpid> documentation). The C<rpid> member contains the pid of the
1435	process causing the status change.	1624	process causing the status change. C<trace> must be either C<0> (only
		1625	activate the watcher when the process terminates) or C<1> (additionally
		1626	activate the watcher when the process is stopped or continued).
1436		1627
1437	=item int pid [read-only]	1628	=item int pid [read-only]
1438		1629
1439	The process id this watcher watches out for, or C<0>, meaning any process id.	1630	The process id this watcher watches out for, or C<0>, meaning any process id.
1440		1631
…		…
1447	The process exit/trace status caused by C<rpid> (see your systems	1638	The process exit/trace status caused by C<rpid> (see your systems
1448	C<waitpid> and C<sys/wait.h> documentation for details).	1639	C<waitpid> and C<sys/wait.h> documentation for details).
1449		1640
1450	=back	1641	=back
1451		1642
1452	Example: Try to exit cleanly on SIGINT and SIGTERM.	1643	=head3 Examples
1453		1644
		1645	Example: C<fork()> a new process and install a child handler to wait for
		1646	its completion.
		1647
		1648	ev_child cw;
		1649
1454	static void	1650	static void
1455	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1651	child_cb (EV_P_ struct ev_child *w, int revents)
1456	{	1652	{
1457	ev_unloop (loop, EVUNLOOP_ALL);	1653	ev_child_stop (EV_A_ w);
		1654	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1458	}	1655	}
1459		1656
1460	struct ev_signal signal_watcher;	1657	pid_t pid = fork ();
1461	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1658
1462	ev_signal_start (loop, &sigint_cb);	1659	if (pid < 0)
		1660	// error
		1661	else if (pid == 0)
		1662	{
		1663	// the forked child executes here
		1664	exit (1);
		1665	}
		1666	else
		1667	{
		1668	ev_child_init (&cw, child_cb, pid, 0);
		1669	ev_child_start (EV_DEFAULT_ &cw);
		1670	}
1463		1671
1464		1672
1465	=head2 C<ev_stat> - did the file attributes just change?	1673	=head2 C<ev_stat> - did the file attributes just change?
1466		1674
1467	This watches a filesystem path for attribute changes. That is, it calls	1675	This watches a file system path for attribute changes. That is, it calls
1468	C<stat> regularly (or when the OS says it changed) and sees if it changed	1676	C<stat> regularly (or when the OS says it changed) and sees if it changed
1469	compared to the last time, invoking the callback if it did.	1677	compared to the last time, invoking the callback if it did.
1470		1678
1471	The path does not need to exist: changing from "path exists" to "path does	1679	The path does not need to exist: changing from "path exists" to "path does
1472	not exist" is a status change like any other. The condition "path does	1680	not exist" is a status change like any other. The condition "path does
…		…
1490	as even with OS-supported change notifications, this can be	1698	as even with OS-supported change notifications, this can be
1491	resource-intensive.	1699	resource-intensive.
1492		1700
1493	At the time of this writing, only the Linux inotify interface is	1701	At the time of this writing, only the Linux inotify interface is
1494	implemented (implementing kqueue support is left as an exercise for the	1702	implemented (implementing kqueue support is left as an exercise for the
		1703	reader, note, however, that the author sees no way of implementing ev_stat
1495	reader). Inotify will be used to give hints only and should not change the	1704	semantics with kqueue). Inotify will be used to give hints only and should
1496	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1705	not change the semantics of C<ev_stat> watchers, which means that libev
1497	to fall back to regular polling again even with inotify, but changes are	1706	sometimes needs to fall back to regular polling again even with inotify,
1498	usually detected immediately, and if the file exists there will be no	1707	but changes are usually detected immediately, and if the file exists there
1499	polling.	1708	will be no polling.
		1709
		1710	=head3 ABI Issues (Largefile Support)
		1711
		1712	Libev by default (unless the user overrides this) uses the default
		1713	compilation environment, which means that on systems with large file
		1714	support disabled by default, you get the 32 bit version of the stat
		1715	structure. When using the library from programs that change the ABI to
		1716	use 64 bit file offsets the programs will fail. In that case you have to
		1717	compile libev with the same flags to get binary compatibility. This is
		1718	obviously the case with any flags that change the ABI, but the problem is
		1719	most noticeably disabled with ev_stat and large file support.
		1720
		1721	The solution for this is to lobby your distribution maker to make large
		1722	file interfaces available by default (as e.g. FreeBSD does) and not
		1723	optional. Libev cannot simply switch on large file support because it has
		1724	to exchange stat structures with application programs compiled using the
		1725	default compilation environment.
		1726
		1727	=head3 Inotify
		1728
		1729	When C<inotify (7)> support has been compiled into libev (generally only
		1730	available on Linux) and present at runtime, it will be used to speed up
		1731	change detection where possible. The inotify descriptor will be created lazily
		1732	when the first C<ev_stat> watcher is being started.
		1733
		1734	Inotify presence does not change the semantics of C<ev_stat> watchers
		1735	except that changes might be detected earlier, and in some cases, to avoid
		1736	making regular C<stat> calls. Even in the presence of inotify support
		1737	there are many cases where libev has to resort to regular C<stat> polling.
		1738
		1739	(There is no support for kqueue, as apparently it cannot be used to
		1740	implement this functionality, due to the requirement of having a file
		1741	descriptor open on the object at all times).
		1742
		1743	=head3 The special problem of stat time resolution
		1744
		1745	The C<stat ()> system call only supports full-second resolution portably, and
		1746	even on systems where the resolution is higher, many file systems still
		1747	only support whole seconds.
		1748
		1749	That means that, if the time is the only thing that changes, you can
		1750	easily miss updates: on the first update, C<ev_stat> detects a change and
		1751	calls your callback, which does something. When there is another update
		1752	within the same second, C<ev_stat> will be unable to detect it as the stat
		1753	data does not change.
		1754
		1755	The solution to this is to delay acting on a change for slightly more
		1756	than a second (or till slightly after the next full second boundary), using
		1757	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1758	ev_timer_again (loop, w)>).
		1759
		1760	The C<.02> offset is added to work around small timing inconsistencies
		1761	of some operating systems (where the second counter of the current time
		1762	might be be delayed. One such system is the Linux kernel, where a call to
		1763	C<gettimeofday> might return a timestamp with a full second later than
		1764	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1765	update file times then there will be a small window where the kernel uses
		1766	the previous second to update file times but libev might already execute
		1767	the timer callback).
1500		1768
1501	=head3 Watcher-Specific Functions and Data Members	1769	=head3 Watcher-Specific Functions and Data Members
1502		1770
1503	=over 4	1771	=over 4
1504		1772
…		…
1510	C<path>. The C<interval> is a hint on how quickly a change is expected to	1778	C<path>. The C<interval> is a hint on how quickly a change is expected to
1511	be detected and should normally be specified as C<0> to let libev choose	1779	be detected and should normally be specified as C<0> to let libev choose
1512	a suitable value. The memory pointed to by C<path> must point to the same	1780	a suitable value. The memory pointed to by C<path> must point to the same
1513	path for as long as the watcher is active.	1781	path for as long as the watcher is active.
1514		1782
1515	The callback will be receive C<EV_STAT> when a change was detected,	1783	The callback will receive C<EV_STAT> when a change was detected, relative
1516	relative to the attributes at the time the watcher was started (or the	1784	to the attributes at the time the watcher was started (or the last change
1517	last change was detected).	1785	was detected).
1518		1786
1519	=item ev_stat_stat (ev_stat *)	1787	=item ev_stat_stat (loop, ev_stat *)
1520		1788
1521	Updates the stat buffer immediately with new values. If you change the	1789	Updates the stat buffer immediately with new values. If you change the
1522	watched path in your callback, you could call this fucntion to avoid	1790	watched path in your callback, you could call this function to avoid
1523	detecting this change (while introducing a race condition). Can also be	1791	detecting this change (while introducing a race condition if you are not
1524	useful simply to find out the new values.	1792	the only one changing the path). Can also be useful simply to find out the
		1793	new values.
1525		1794
1526	=item ev_statdata attr [read-only]	1795	=item ev_statdata attr [read-only]
1527		1796
1528	The most-recently detected attributes of the file. Although the type is of	1797	The most-recently detected attributes of the file. Although the type is
1529	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1798	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1530	suitable for your system. If the C<st_nlink> member is C<0>, then there	1799	suitable for your system, but you can only rely on the POSIX-standardised
		1800	members to be present. If the C<st_nlink> member is C<0>, then there was
1531	was some error while C<stat>ing the file.	1801	some error while C<stat>ing the file.
1532		1802
1533	=item ev_statdata prev [read-only]	1803	=item ev_statdata prev [read-only]
1534		1804
1535	The previous attributes of the file. The callback gets invoked whenever	1805	The previous attributes of the file. The callback gets invoked whenever
1536	C<prev> != C<attr>.	1806	C<prev> != C<attr>, or, more precisely, one or more of these members
		1807	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1808	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1537		1809
1538	=item ev_tstamp interval [read-only]	1810	=item ev_tstamp interval [read-only]
1539		1811
1540	The specified interval.	1812	The specified interval.
1541		1813
1542	=item const char *path [read-only]	1814	=item const char *path [read-only]
1543		1815
1544	The filesystem path that is being watched.	1816	The file system path that is being watched.
1545		1817
1546	=back	1818	=back
1547		1819
		1820	=head3 Examples
		1821
1548	Example: Watch C</etc/passwd> for attribute changes.	1822	Example: Watch C</etc/passwd> for attribute changes.
1549		1823
1550	static void	1824	static void
1551	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1825	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1552	{	1826	{
1553	/* /etc/passwd changed in some way */	1827	/* /etc/passwd changed in some way */
1554	if (w->attr.st_nlink)	1828	if (w->attr.st_nlink)
1555	{	1829	{
1556	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1830	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1557	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1831	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1558	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1832	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1559	}	1833	}
1560	else	1834	else
1561	/* you shalt not abuse printf for puts */	1835	/* you shalt not abuse printf for puts */
1562	puts ("wow, /etc/passwd is not there, expect problems. "	1836	puts ("wow, /etc/passwd is not there, expect problems. "
1563	"if this is windows, they already arrived\n");	1837	"if this is windows, they already arrived\n");
1564	}	1838	}
1565		1839
1566	...	1840	...
1567	ev_stat passwd;	1841	ev_stat passwd;
1568		1842
1569	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1843	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1570	ev_stat_start (loop, &passwd);	1844	ev_stat_start (loop, &passwd);
		1845
		1846	Example: Like above, but additionally use a one-second delay so we do not
		1847	miss updates (however, frequent updates will delay processing, too, so
		1848	one might do the work both on C<ev_stat> callback invocation I<and> on
		1849	C<ev_timer> callback invocation).
		1850
		1851	static ev_stat passwd;
		1852	static ev_timer timer;
		1853
		1854	static void
		1855	timer_cb (EV_P_ ev_timer *w, int revents)
		1856	{
		1857	ev_timer_stop (EV_A_ w);
		1858
		1859	/* now it's one second after the most recent passwd change */
		1860	}
		1861
		1862	static void
		1863	stat_cb (EV_P_ ev_stat *w, int revents)
		1864	{
		1865	/* reset the one-second timer */
		1866	ev_timer_again (EV_A_ &timer);
		1867	}
		1868
		1869	...
		1870	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1871	ev_stat_start (loop, &passwd);
		1872	ev_timer_init (&timer, timer_cb, 0., 1.02);
1571		1873
1572		1874
1573	=head2 C<ev_idle> - when you've got nothing better to do...	1875	=head2 C<ev_idle> - when you've got nothing better to do...
1574		1876
1575	Idle watchers trigger events when no other events of the same or higher	1877	Idle watchers trigger events when no other events of the same or higher
…		…
1601	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1903	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1602	believe me.	1904	believe me.
1603		1905
1604	=back	1906	=back
1605		1907
		1908	=head3 Examples
		1909
1606	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1910	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1607	callback, free it. Also, use no error checking, as usual.	1911	callback, free it. Also, use no error checking, as usual.
1608		1912
1609	static void	1913	static void
1610	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1914	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1611	{	1915	{
1612	free (w);	1916	free (w);
1613	// now do something you wanted to do when the program has	1917	// now do something you wanted to do when the program has
1614	// no longer asnything immediate to do.	1918	// no longer anything immediate to do.
1615	}	1919	}
1616		1920
1617	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1921	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1618	ev_idle_init (idle_watcher, idle_cb);	1922	ev_idle_init (idle_watcher, idle_cb);
1619	ev_idle_start (loop, idle_cb);	1923	ev_idle_start (loop, idle_cb);
1620		1924
1621		1925
1622	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1926	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1623		1927
1624	Prepare and check watchers are usually (but not always) used in tandem:	1928	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1643		1947
1644	This is done by examining in each prepare call which file descriptors need	1948	This is done by examining in each prepare call which file descriptors need
1645	to be watched by the other library, registering C<ev_io> watchers for	1949	to be watched by the other library, registering C<ev_io> watchers for
1646	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1950	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1647	provide just this functionality). Then, in the check watcher you check for	1951	provide just this functionality). Then, in the check watcher you check for
1648	any events that occured (by checking the pending status of all watchers	1952	any events that occurred (by checking the pending status of all watchers
1649	and stopping them) and call back into the library. The I/O and timer	1953	and stopping them) and call back into the library. The I/O and timer
1650	callbacks will never actually be called (but must be valid nevertheless,	1954	callbacks will never actually be called (but must be valid nevertheless,
1651	because you never know, you know?).	1955	because you never know, you know?).
1652		1956
1653	As another example, the Perl Coro module uses these hooks to integrate	1957	As another example, the Perl Coro module uses these hooks to integrate
…		…
1661		1965
1662	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1966	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1663	priority, to ensure that they are being run before any other watchers	1967	priority, to ensure that they are being run before any other watchers
1664	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1968	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1665	too) should not activate ("feed") events into libev. While libev fully	1969	too) should not activate ("feed") events into libev. While libev fully
1666	supports this, they will be called before other C<ev_check> watchers	1970	supports this, they might get executed before other C<ev_check> watchers
1667	did their job. As C<ev_check> watchers are often used to embed other	1971	did their job. As C<ev_check> watchers are often used to embed other
1668	(non-libev) event loops those other event loops might be in an unusable	1972	(non-libev) event loops those other event loops might be in an unusable
1669	state until their C<ev_check> watcher ran (always remind yourself to	1973	state until their C<ev_check> watcher ran (always remind yourself to
1670	coexist peacefully with others).	1974	coexist peacefully with others).
1671		1975
…		…
1681	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1985	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1682	macros, but using them is utterly, utterly and completely pointless.	1986	macros, but using them is utterly, utterly and completely pointless.
1683		1987
1684	=back	1988	=back
1685		1989
		1990	=head3 Examples
		1991
1686	There are a number of principal ways to embed other event loops or modules	1992	There are a number of principal ways to embed other event loops or modules
1687	into libev. Here are some ideas on how to include libadns into libev	1993	into libev. Here are some ideas on how to include libadns into libev
1688	(there is a Perl module named C<EV::ADNS> that does this, which you could	1994	(there is a Perl module named C<EV::ADNS> that does this, which you could
1689	use for an actually working example. Another Perl module named C<EV::Glib>	1995	use as a working example. Another Perl module named C<EV::Glib> embeds a
1690	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1996	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1691	into the Glib event loop).	1997	Glib event loop).
1692		1998
1693	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1999	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1694	and in a check watcher, destroy them and call into libadns. What follows	2000	and in a check watcher, destroy them and call into libadns. What follows
1695	is pseudo-code only of course. This requires you to either use a low	2001	is pseudo-code only of course. This requires you to either use a low
1696	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2002	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1697	the callbacks for the IO/timeout watchers might not have been called yet.	2003	the callbacks for the IO/timeout watchers might not have been called yet.
1698		2004
1699	static ev_io iow [nfd];	2005	static ev_io iow [nfd];
1700	static ev_timer tw;	2006	static ev_timer tw;
1701		2007
1702	static void	2008	static void
1703	io_cb (ev_loop *loop, ev_io *w, int revents)	2009	io_cb (ev_loop *loop, ev_io *w, int revents)
1704	{	2010	{
1705	}	2011	}
1706		2012
1707	// create io watchers for each fd and a timer before blocking	2013	// create io watchers for each fd and a timer before blocking
1708	static void	2014	static void
1709	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2015	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1710	{	2016	{
1711	int timeout = 3600000;	2017	int timeout = 3600000;
1712	struct pollfd fds [nfd];	2018	struct pollfd fds [nfd];
1713	// actual code will need to loop here and realloc etc.	2019	// actual code will need to loop here and realloc etc.
1714	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2020	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1715		2021
1716	/* the callback is illegal, but won't be called as we stop during check */	2022	/* the callback is illegal, but won't be called as we stop during check */
1717	ev_timer_init (&tw, 0, timeout * 1e-3);	2023	ev_timer_init (&tw, 0, timeout * 1e-3);
1718	ev_timer_start (loop, &tw);	2024	ev_timer_start (loop, &tw);
1719		2025
1720	// create one ev_io per pollfd	2026	// create one ev_io per pollfd
1721	for (int i = 0; i < nfd; ++i)	2027	for (int i = 0; i < nfd; ++i)
1722	{	2028	{
1723	ev_io_init (iow + i, io_cb, fds [i].fd,	2029	ev_io_init (iow + i, io_cb, fds [i].fd,
1724	((fds [i].events & POLLIN ? EV_READ : 0)	2030	((fds [i].events & POLLIN ? EV_READ : 0)
1725	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2031	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1726		2032
1727	fds [i].revents = 0;	2033	fds [i].revents = 0;
1728	ev_io_start (loop, iow + i);	2034	ev_io_start (loop, iow + i);
1729	}	2035	}
1730	}	2036	}
1731		2037
1732	// stop all watchers after blocking	2038	// stop all watchers after blocking
1733	static void	2039	static void
1734	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2040	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1735	{	2041	{
1736	ev_timer_stop (loop, &tw);	2042	ev_timer_stop (loop, &tw);
1737		2043
1738	for (int i = 0; i < nfd; ++i)	2044	for (int i = 0; i < nfd; ++i)
1739	{	2045	{
1740	// set the relevant poll flags	2046	// set the relevant poll flags
1741	// could also call adns_processreadable etc. here	2047	// could also call adns_processreadable etc. here
1742	struct pollfd *fd = fds + i;	2048	struct pollfd *fd = fds + i;
1743	int revents = ev_clear_pending (iow + i);	2049	int revents = ev_clear_pending (iow + i);
1744	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2050	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1745	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2051	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1746		2052
1747	// now stop the watcher	2053	// now stop the watcher
1748	ev_io_stop (loop, iow + i);	2054	ev_io_stop (loop, iow + i);
1749	}	2055	}
1750		2056
1751	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2057	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1752	}	2058	}
1753		2059
1754	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2060	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1755	in the prepare watcher and would dispose of the check watcher.	2061	in the prepare watcher and would dispose of the check watcher.
1756		2062
1757	Method 3: If the module to be embedded supports explicit event	2063	Method 3: If the module to be embedded supports explicit event
1758	notification (adns does), you can also make use of the actual watcher	2064	notification (libadns does), you can also make use of the actual watcher
1759	callbacks, and only destroy/create the watchers in the prepare watcher.	2065	callbacks, and only destroy/create the watchers in the prepare watcher.
1760		2066
1761	static void	2067	static void
1762	timer_cb (EV_P_ ev_timer *w, int revents)	2068	timer_cb (EV_P_ ev_timer *w, int revents)
1763	{	2069	{
1764	adns_state ads = (adns_state)w->data;	2070	adns_state ads = (adns_state)w->data;
1765	update_now (EV_A);	2071	update_now (EV_A);
1766		2072
1767	adns_processtimeouts (ads, &tv_now);	2073	adns_processtimeouts (ads, &tv_now);
1768	}	2074	}
1769		2075
1770	static void	2076	static void
1771	io_cb (EV_P_ ev_io *w, int revents)	2077	io_cb (EV_P_ ev_io *w, int revents)
1772	{	2078	{
1773	adns_state ads = (adns_state)w->data;	2079	adns_state ads = (adns_state)w->data;
1774	update_now (EV_A);	2080	update_now (EV_A);
1775		2081
1776	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2082	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1777	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2083	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1778	}	2084	}
1779		2085
1780	// do not ever call adns_afterpoll	2086	// do not ever call adns_afterpoll
1781		2087
1782	Method 4: Do not use a prepare or check watcher because the module you	2088	Method 4: Do not use a prepare or check watcher because the module you
1783	want to embed is too inflexible to support it. Instead, youc na override	2089	want to embed is too inflexible to support it. Instead, you can override
1784	their poll function. The drawback with this solution is that the main	2090	their poll function. The drawback with this solution is that the main
1785	loop is now no longer controllable by EV. The C<Glib::EV> module does	2091	loop is now no longer controllable by EV. The C<Glib::EV> module does
1786	this.	2092	this.
1787		2093
1788	static gint	2094	static gint
1789	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2095	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1790	{	2096	{
1791	int got_events = 0;	2097	int got_events = 0;
1792		2098
1793	for (n = 0; n < nfds; ++n)	2099	for (n = 0; n < nfds; ++n)
1794	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2100	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1795		2101
1796	if (timeout >= 0)	2102	if (timeout >= 0)
1797	// create/start timer	2103	// create/start timer
1798		2104
1799	// poll	2105	// poll
1800	ev_loop (EV_A_ 0);	2106	ev_loop (EV_A_ 0);
1801		2107
1802	// stop timer again	2108	// stop timer again
1803	if (timeout >= 0)	2109	if (timeout >= 0)
1804	ev_timer_stop (EV_A_ &to);	2110	ev_timer_stop (EV_A_ &to);
1805		2111
1806	// stop io watchers again - their callbacks should have set	2112	// stop io watchers again - their callbacks should have set
1807	for (n = 0; n < nfds; ++n)	2113	for (n = 0; n < nfds; ++n)
1808	ev_io_stop (EV_A_ iow [n]);	2114	ev_io_stop (EV_A_ iow [n]);
1809		2115
1810	return got_events;	2116	return got_events;
1811	}	2117	}
1812		2118
1813		2119
1814	=head2 C<ev_embed> - when one backend isn't enough...	2120	=head2 C<ev_embed> - when one backend isn't enough...
1815		2121
1816	This is a rather advanced watcher type that lets you embed one event loop	2122	This is a rather advanced watcher type that lets you embed one event loop
…		…
1858	portable one.	2164	portable one.
1859		2165
1860	So when you want to use this feature you will always have to be prepared	2166	So when you want to use this feature you will always have to be prepared
1861	that you cannot get an embeddable loop. The recommended way to get around	2167	that you cannot get an embeddable loop. The recommended way to get around
1862	this is to have a separate variables for your embeddable loop, try to	2168	this is to have a separate variables for your embeddable loop, try to
1863	create it, and if that fails, use the normal loop for everything:	2169	create it, and if that fails, use the normal loop for everything.
1864
1865	struct ev_loop *loop_hi = ev_default_init (0);
1866	struct ev_loop *loop_lo = 0;
1867	struct ev_embed embed;
1868
1869	// see if there is a chance of getting one that works
1870	// (remember that a flags value of 0 means autodetection)
1871	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1872	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1873	: 0;
1874
1875	// if we got one, then embed it, otherwise default to loop_hi
1876	if (loop_lo)
1877	{
1878	ev_embed_init (&embed, 0, loop_lo);
1879	ev_embed_start (loop_hi, &embed);
1880	}
1881	else
1882	loop_lo = loop_hi;
1883		2170
1884	=head3 Watcher-Specific Functions and Data Members	2171	=head3 Watcher-Specific Functions and Data Members
1885		2172
1886	=over 4	2173	=over 4
1887		2174
…		…
1891		2178
1892	Configures the watcher to embed the given loop, which must be	2179	Configures the watcher to embed the given loop, which must be
1893	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2180	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1894	invoked automatically, otherwise it is the responsibility of the callback	2181	invoked automatically, otherwise it is the responsibility of the callback
1895	to invoke it (it will continue to be called until the sweep has been done,	2182	to invoke it (it will continue to be called until the sweep has been done,
1896	if you do not want thta, you need to temporarily stop the embed watcher).	2183	if you do not want that, you need to temporarily stop the embed watcher).
1897		2184
1898	=item ev_embed_sweep (loop, ev_embed *)	2185	=item ev_embed_sweep (loop, ev_embed *)
1899		2186
1900	Make a single, non-blocking sweep over the embedded loop. This works	2187	Make a single, non-blocking sweep over the embedded loop. This works
1901	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2188	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1902	apropriate way for embedded loops.	2189	appropriate way for embedded loops.
1903		2190
1904	=item struct ev_loop *other [read-only]	2191	=item struct ev_loop *other [read-only]
1905		2192
1906	The embedded event loop.	2193	The embedded event loop.
1907		2194
1908	=back	2195	=back
		2196
		2197	=head3 Examples
		2198
		2199	Example: Try to get an embeddable event loop and embed it into the default
		2200	event loop. If that is not possible, use the default loop. The default
		2201	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2202	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2203	used).
		2204
		2205	struct ev_loop *loop_hi = ev_default_init (0);
		2206	struct ev_loop *loop_lo = 0;
		2207	struct ev_embed embed;
		2208
		2209	// see if there is a chance of getting one that works
		2210	// (remember that a flags value of 0 means autodetection)
		2211	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2212	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2213	: 0;
		2214
		2215	// if we got one, then embed it, otherwise default to loop_hi
		2216	if (loop_lo)
		2217	{
		2218	ev_embed_init (&embed, 0, loop_lo);
		2219	ev_embed_start (loop_hi, &embed);
		2220	}
		2221	else
		2222	loop_lo = loop_hi;
		2223
		2224	Example: Check if kqueue is available but not recommended and create
		2225	a kqueue backend for use with sockets (which usually work with any
		2226	kqueue implementation). Store the kqueue/socket-only event loop in
		2227	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2228
		2229	struct ev_loop *loop = ev_default_init (0);
		2230	struct ev_loop *loop_socket = 0;
		2231	struct ev_embed embed;
		2232
		2233	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2234	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2235	{
		2236	ev_embed_init (&embed, 0, loop_socket);
		2237	ev_embed_start (loop, &embed);
		2238	}
		2239
		2240	if (!loop_socket)
		2241	loop_socket = loop;
		2242
		2243	// now use loop_socket for all sockets, and loop for everything else
1909		2244
1910		2245
1911	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2246	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1912		2247
1913	Fork watchers are called when a C<fork ()> was detected (usually because	2248	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1929	believe me.	2264	believe me.
1930		2265
1931	=back	2266	=back
1932		2267
1933		2268
		2269	=head2 C<ev_async> - how to wake up another event loop
		2270
		2271	In general, you cannot use an C<ev_loop> from multiple threads or other
		2272	asynchronous sources such as signal handlers (as opposed to multiple event
		2273	loops - those are of course safe to use in different threads).
		2274
		2275	Sometimes, however, you need to wake up another event loop you do not
		2276	control, for example because it belongs to another thread. This is what
		2277	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2278	can signal it by calling C<ev_async_send>, which is thread- and signal
		2279	safe.
		2280
		2281	This functionality is very similar to C<ev_signal> watchers, as signals,
		2282	too, are asynchronous in nature, and signals, too, will be compressed
		2283	(i.e. the number of callback invocations may be less than the number of
		2284	C<ev_async_sent> calls).
		2285
		2286	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2287	just the default loop.
		2288
		2289	=head3 Queueing
		2290
		2291	C<ev_async> does not support queueing of data in any way. The reason
		2292	is that the author does not know of a simple (or any) algorithm for a
		2293	multiple-writer-single-reader queue that works in all cases and doesn't
		2294	need elaborate support such as pthreads.
		2295
		2296	That means that if you want to queue data, you have to provide your own
		2297	queue. But at least I can tell you would implement locking around your
		2298	queue:
		2299
		2300	=over 4
		2301
		2302	=item queueing from a signal handler context
		2303
		2304	To implement race-free queueing, you simply add to the queue in the signal
		2305	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2306	some fictitious SIGUSR1 handler:
		2307
		2308	static ev_async mysig;
		2309
		2310	static void
		2311	sigusr1_handler (void)
		2312	{
		2313	sometype data;
		2314
		2315	// no locking etc.
		2316	queue_put (data);
		2317	ev_async_send (EV_DEFAULT_ &mysig);
		2318	}
		2319
		2320	static void
		2321	mysig_cb (EV_P_ ev_async *w, int revents)
		2322	{
		2323	sometype data;
		2324	sigset_t block, prev;
		2325
		2326	sigemptyset (&block);
		2327	sigaddset (&block, SIGUSR1);
		2328	sigprocmask (SIG_BLOCK, &block, &prev);
		2329
		2330	while (queue_get (&data))
		2331	process (data);
		2332
		2333	if (sigismember (&prev, SIGUSR1)
		2334	sigprocmask (SIG_UNBLOCK, &block, 0);
		2335	}
		2336
		2337	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2338	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2339	either...).
		2340
		2341	=item queueing from a thread context
		2342
		2343	The strategy for threads is different, as you cannot (easily) block
		2344	threads but you can easily preempt them, so to queue safely you need to
		2345	employ a traditional mutex lock, such as in this pthread example:
		2346
		2347	static ev_async mysig;
		2348	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2349
		2350	static void
		2351	otherthread (void)
		2352	{
		2353	// only need to lock the actual queueing operation
		2354	pthread_mutex_lock (&mymutex);
		2355	queue_put (data);
		2356	pthread_mutex_unlock (&mymutex);
		2357
		2358	ev_async_send (EV_DEFAULT_ &mysig);
		2359	}
		2360
		2361	static void
		2362	mysig_cb (EV_P_ ev_async *w, int revents)
		2363	{
		2364	pthread_mutex_lock (&mymutex);
		2365
		2366	while (queue_get (&data))
		2367	process (data);
		2368
		2369	pthread_mutex_unlock (&mymutex);
		2370	}
		2371
		2372	=back
		2373
		2374
		2375	=head3 Watcher-Specific Functions and Data Members
		2376
		2377	=over 4
		2378
		2379	=item ev_async_init (ev_async *, callback)
		2380
		2381	Initialises and configures the async watcher - it has no parameters of any
		2382	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2383	believe me.
		2384
		2385	=item ev_async_send (loop, ev_async *)
		2386
		2387	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2388	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2389	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2390	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2391	section below on what exactly this means).
		2392
		2393	This call incurs the overhead of a system call only once per loop iteration,
		2394	so while the overhead might be noticeable, it doesn't apply to repeated
		2395	calls to C<ev_async_send>.
		2396
		2397	=item bool = ev_async_pending (ev_async *)
		2398
		2399	Returns a non-zero value when C<ev_async_send> has been called on the
		2400	watcher but the event has not yet been processed (or even noted) by the
		2401	event loop.
		2402
		2403	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2404	the loop iterates next and checks for the watcher to have become active,
		2405	it will reset the flag again. C<ev_async_pending> can be used to very
		2406	quickly check whether invoking the loop might be a good idea.
		2407
		2408	Not that this does I<not> check whether the watcher itself is pending, only
		2409	whether it has been requested to make this watcher pending.
		2410
		2411	=back
		2412
		2413
1934	=head1 OTHER FUNCTIONS	2414	=head1 OTHER FUNCTIONS
1935		2415
1936	There are some other functions of possible interest. Described. Here. Now.	2416	There are some other functions of possible interest. Described. Here. Now.
1937		2417
1938	=over 4	2418	=over 4
…		…
1945	or timeout without having to allocate/configure/start/stop/free one or	2425	or timeout without having to allocate/configure/start/stop/free one or
1946	more watchers yourself.	2426	more watchers yourself.
1947		2427
1948	If C<fd> is less than 0, then no I/O watcher will be started and events	2428	If C<fd> is less than 0, then no I/O watcher will be started and events
1949	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2429	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1950	C<events> set will be craeted and started.	2430	C<events> set will be created and started.
1951		2431
1952	If C<timeout> is less than 0, then no timeout watcher will be	2432	If C<timeout> is less than 0, then no timeout watcher will be
1953	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2433	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1954	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2434	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1955	dubious value.	2435	dubious value.
…		…
1957	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2437	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1958	passed an C<revents> set like normal event callbacks (a combination of	2438	passed an C<revents> set like normal event callbacks (a combination of
1959	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2439	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1960	value passed to C<ev_once>:	2440	value passed to C<ev_once>:
1961		2441
1962	static void stdin_ready (int revents, void *arg)	2442	static void stdin_ready (int revents, void *arg)
1963	{	2443	{
1964	if (revents & EV_TIMEOUT)	2444	if (revents & EV_TIMEOUT)
1965	/* doh, nothing entered */;	2445	/* doh, nothing entered */;
1966	else if (revents & EV_READ)	2446	else if (revents & EV_READ)
1967	/* stdin might have data for us, joy! */;	2447	/* stdin might have data for us, joy! */;
1968	}	2448	}
1969		2449
1970	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2450	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1971		2451
1972	=item ev_feed_event (ev_loop *, watcher *, int revents)	2452	=item ev_feed_event (ev_loop *, watcher *, int revents)
1973		2453
1974	Feeds the given event set into the event loop, as if the specified event	2454	Feeds the given event set into the event loop, as if the specified event
1975	had happened for the specified watcher (which must be a pointer to an	2455	had happened for the specified watcher (which must be a pointer to an
…		…
1980	Feed an event on the given fd, as if a file descriptor backend detected	2460	Feed an event on the given fd, as if a file descriptor backend detected
1981	the given events it.	2461	the given events it.
1982		2462
1983	=item ev_feed_signal_event (ev_loop *loop, int signum)	2463	=item ev_feed_signal_event (ev_loop *loop, int signum)
1984		2464
1985	Feed an event as if the given signal occured (C<loop> must be the default	2465	Feed an event as if the given signal occurred (C<loop> must be the default
1986	loop!).	2466	loop!).
1987		2467
1988	=back	2468	=back
1989		2469
1990		2470
…		…
2006		2486
2007	=item * Priorities are not currently supported. Initialising priorities	2487	=item * Priorities are not currently supported. Initialising priorities
2008	will fail and all watchers will have the same priority, even though there	2488	will fail and all watchers will have the same priority, even though there
2009	is an ev_pri field.	2489	is an ev_pri field.
2010		2490
		2491	=item * In libevent, the last base created gets the signals, in libev, the
		2492	first base created (== the default loop) gets the signals.
		2493
2011	=item * Other members are not supported.	2494	=item * Other members are not supported.
2012		2495
2013	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2496	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2014	to use the libev header file and library.	2497	to use the libev header file and library.
2015		2498
2016	=back	2499	=back
2017		2500
2018	=head1 C++ SUPPORT	2501	=head1 C++ SUPPORT
2019		2502
2020	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2503	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2021	you to use some convinience methods to start/stop watchers and also change	2504	you to use some convenience methods to start/stop watchers and also change
2022	the callback model to a model using method callbacks on objects.	2505	the callback model to a model using method callbacks on objects.
2023		2506
2024	To use it,	2507	To use it,
2025		2508
2026	#include <ev++.h>	2509	#include <ev++.h>
2027		2510
2028	This automatically includes F<ev.h> and puts all of its definitions (many	2511	This automatically includes F<ev.h> and puts all of its definitions (many
2029	of them macros) into the global namespace. All C++ specific things are	2512	of them macros) into the global namespace. All C++ specific things are
2030	put into the C<ev> namespace. It should support all the same embedding	2513	put into the C<ev> namespace. It should support all the same embedding
2031	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2514	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2098	your compiler is good :), then the method will be fully inlined into the	2581	your compiler is good :), then the method will be fully inlined into the
2099	thunking function, making it as fast as a direct C callback.	2582	thunking function, making it as fast as a direct C callback.
2100		2583
2101	Example: simple class declaration and watcher initialisation	2584	Example: simple class declaration and watcher initialisation
2102		2585
2103	struct myclass	2586	struct myclass
2104	{	2587	{
2105	void io_cb (ev::io &w, int revents) { }	2588	void io_cb (ev::io &w, int revents) { }
2106	}	2589	}
2107		2590
2108	myclass obj;	2591	myclass obj;
2109	ev::io iow;	2592	ev::io iow;
2110	iow.set <myclass, &myclass::io_cb> (&obj);	2593	iow.set <myclass, &myclass::io_cb> (&obj);
2111		2594
2112	=item w->set<function> (void *data = 0)	2595	=item w->set<function> (void *data = 0)
2113		2596
2114	Also sets a callback, but uses a static method or plain function as	2597	Also sets a callback, but uses a static method or plain function as
2115	callback. The optional C<data> argument will be stored in the watcher's	2598	callback. The optional C<data> argument will be stored in the watcher's
…		…
2119		2602
2120	See the method-C<set> above for more details.	2603	See the method-C<set> above for more details.
2121		2604
2122	Example:	2605	Example:
2123		2606
2124	static void io_cb (ev::io &w, int revents) { }	2607	static void io_cb (ev::io &w, int revents) { }
2125	iow.set <io_cb> ();	2608	iow.set <io_cb> ();
2126		2609
2127	=item w->set (struct ev_loop *)	2610	=item w->set (struct ev_loop *)
2128		2611
2129	Associates a different C<struct ev_loop> with this watcher. You can only	2612	Associates a different C<struct ev_loop> with this watcher. You can only
2130	do this when the watcher is inactive (and not pending either).	2613	do this when the watcher is inactive (and not pending either).
2131		2614
2132	=item w->set ([args])	2615	=item w->set ([arguments])
2133		2616
2134	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2617	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2135	called at least once. Unlike the C counterpart, an active watcher gets	2618	called at least once. Unlike the C counterpart, an active watcher gets
2136	automatically stopped and restarted when reconfiguring it with this	2619	automatically stopped and restarted when reconfiguring it with this
2137	method.	2620	method.
2138		2621
2139	=item w->start ()	2622	=item w->start ()
…		…
2163	=back	2646	=back
2164		2647
2165	Example: Define a class with an IO and idle watcher, start one of them in	2648	Example: Define a class with an IO and idle watcher, start one of them in
2166	the constructor.	2649	the constructor.
2167		2650
2168	class myclass	2651	class myclass
2169	{	2652	{
2170	ev_io io; void io_cb (ev::io &w, int revents);	2653	ev::io io; void io_cb (ev::io &w, int revents);
2171	ev_idle idle void idle_cb (ev::idle &w, int revents);	2654	ev:idle idle void idle_cb (ev::idle &w, int revents);
2172		2655
2173	myclass ();	2656	myclass (int fd)
2174	}	2657	{
2175
2176	myclass::myclass (int fd)
2177	{
2178	io .set <myclass, &myclass::io_cb > (this);	2658	io .set <myclass, &myclass::io_cb > (this);
2179	idle.set <myclass, &myclass::idle_cb> (this);	2659	idle.set <myclass, &myclass::idle_cb> (this);
2180		2660
2181	io.start (fd, ev::READ);	2661	io.start (fd, ev::READ);
		2662	}
2182	}	2663	};
		2664
		2665
		2666	=head1 OTHER LANGUAGE BINDINGS
		2667
		2668	Libev does not offer other language bindings itself, but bindings for a
		2669	number of languages exist in the form of third-party packages. If you know
		2670	any interesting language binding in addition to the ones listed here, drop
		2671	me a note.
		2672
		2673	=over 4
		2674
		2675	=item Perl
		2676
		2677	The EV module implements the full libev API and is actually used to test
		2678	libev. EV is developed together with libev. Apart from the EV core module,
		2679	there are additional modules that implement libev-compatible interfaces
		2680	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2681	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2682
		2683	It can be found and installed via CPAN, its homepage is at
		2684	L<http://software.schmorp.de/pkg/EV>.
		2685
		2686	=item Python
		2687
		2688	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2689	seems to be quite complete and well-documented. Note, however, that the
		2690	patch they require for libev is outright dangerous as it breaks the ABI
		2691	for everybody else, and therefore, should never be applied in an installed
		2692	libev (if python requires an incompatible ABI then it needs to embed
		2693	libev).
		2694
		2695	=item Ruby
		2696
		2697	Tony Arcieri has written a ruby extension that offers access to a subset
		2698	of the libev API and adds file handle abstractions, asynchronous DNS and
		2699	more on top of it. It can be found via gem servers. Its homepage is at
		2700	L<http://rev.rubyforge.org/>.
		2701
		2702	=item D
		2703
		2704	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2705	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2706
		2707	=back
2183		2708
2184		2709
2185	=head1 MACRO MAGIC	2710	=head1 MACRO MAGIC
2186		2711
2187	Libev can be compiled with a variety of options, the most fundamantal	2712	Libev can be compiled with a variety of options, the most fundamental
2188	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2713	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2189	functions and callbacks have an initial C<struct ev_loop *> argument.	2714	functions and callbacks have an initial C<struct ev_loop *> argument.
2190		2715
2191	To make it easier to write programs that cope with either variant, the	2716	To make it easier to write programs that cope with either variant, the
2192	following macros are defined:	2717	following macros are defined:
…		…
2197		2722
2198	This provides the loop I<argument> for functions, if one is required ("ev	2723	This provides the loop I<argument> for functions, if one is required ("ev
2199	loop argument"). The C<EV_A> form is used when this is the sole argument,	2724	loop argument"). The C<EV_A> form is used when this is the sole argument,
2200	C<EV_A_> is used when other arguments are following. Example:	2725	C<EV_A_> is used when other arguments are following. Example:
2201		2726
2202	ev_unref (EV_A);	2727	ev_unref (EV_A);
2203	ev_timer_add (EV_A_ watcher);	2728	ev_timer_add (EV_A_ watcher);
2204	ev_loop (EV_A_ 0);	2729	ev_loop (EV_A_ 0);
2205		2730
2206	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2731	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2207	which is often provided by the following macro.	2732	which is often provided by the following macro.
2208		2733
2209	=item C<EV_P>, C<EV_P_>	2734	=item C<EV_P>, C<EV_P_>
2210		2735
2211	This provides the loop I<parameter> for functions, if one is required ("ev	2736	This provides the loop I<parameter> for functions, if one is required ("ev
2212	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2737	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2213	C<EV_P_> is used when other parameters are following. Example:	2738	C<EV_P_> is used when other parameters are following. Example:
2214		2739
2215	// this is how ev_unref is being declared	2740	// this is how ev_unref is being declared
2216	static void ev_unref (EV_P);	2741	static void ev_unref (EV_P);
2217		2742
2218	// this is how you can declare your typical callback	2743	// this is how you can declare your typical callback
2219	static void cb (EV_P_ ev_timer *w, int revents)	2744	static void cb (EV_P_ ev_timer *w, int revents)
2220		2745
2221	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2746	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2222	suitable for use with C<EV_A>.	2747	suitable for use with C<EV_A>.
2223		2748
2224	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2749	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2225		2750
2226	Similar to the other two macros, this gives you the value of the default	2751	Similar to the other two macros, this gives you the value of the default
2227	loop, if multiple loops are supported ("ev loop default").	2752	loop, if multiple loops are supported ("ev loop default").
		2753
		2754	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2755
		2756	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2757	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2758	is undefined when the default loop has not been initialised by a previous
		2759	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2760
		2761	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2762	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2228		2763
2229	=back	2764	=back
2230		2765
2231	Example: Declare and initialise a check watcher, utilising the above	2766	Example: Declare and initialise a check watcher, utilising the above
2232	macros so it will work regardless of whether multiple loops are supported	2767	macros so it will work regardless of whether multiple loops are supported
2233	or not.	2768	or not.
2234		2769
2235	static void	2770	static void
2236	check_cb (EV_P_ ev_timer *w, int revents)	2771	check_cb (EV_P_ ev_timer *w, int revents)
2237	{	2772	{
2238	ev_check_stop (EV_A_ w);	2773	ev_check_stop (EV_A_ w);
2239	}	2774	}
2240		2775
2241	ev_check check;	2776	ev_check check;
2242	ev_check_init (&check, check_cb);	2777	ev_check_init (&check, check_cb);
2243	ev_check_start (EV_DEFAULT_ &check);	2778	ev_check_start (EV_DEFAULT_ &check);
2244	ev_loop (EV_DEFAULT_ 0);	2779	ev_loop (EV_DEFAULT_ 0);
2245		2780
2246	=head1 EMBEDDING	2781	=head1 EMBEDDING
2247		2782
2248	Libev can (and often is) directly embedded into host	2783	Libev can (and often is) directly embedded into host
2249	applications. Examples of applications that embed it include the Deliantra	2784	applications. Examples of applications that embed it include the Deliantra
…		…
2256	libev somewhere in your source tree).	2791	libev somewhere in your source tree).
2257		2792
2258	=head2 FILESETS	2793	=head2 FILESETS
2259		2794
2260	Depending on what features you need you need to include one or more sets of files	2795	Depending on what features you need you need to include one or more sets of files
2261	in your app.	2796	in your application.
2262		2797
2263	=head3 CORE EVENT LOOP	2798	=head3 CORE EVENT LOOP
2264		2799
2265	To include only the libev core (all the C<ev_*> functions), with manual	2800	To include only the libev core (all the C<ev_*> functions), with manual
2266	configuration (no autoconf):	2801	configuration (no autoconf):
2267		2802
2268	#define EV_STANDALONE 1	2803	#define EV_STANDALONE 1
2269	#include "ev.c"	2804	#include "ev.c"
2270		2805
2271	This will automatically include F<ev.h>, too, and should be done in a	2806	This will automatically include F<ev.h>, too, and should be done in a
2272	single C source file only to provide the function implementations. To use	2807	single C source file only to provide the function implementations. To use
2273	it, do the same for F<ev.h> in all files wishing to use this API (best	2808	it, do the same for F<ev.h> in all files wishing to use this API (best
2274	done by writing a wrapper around F<ev.h> that you can include instead and	2809	done by writing a wrapper around F<ev.h> that you can include instead and
2275	where you can put other configuration options):	2810	where you can put other configuration options):
2276		2811
2277	#define EV_STANDALONE 1	2812	#define EV_STANDALONE 1
2278	#include "ev.h"	2813	#include "ev.h"
2279		2814
2280	Both header files and implementation files can be compiled with a C++	2815	Both header files and implementation files can be compiled with a C++
2281	compiler (at least, thats a stated goal, and breakage will be treated	2816	compiler (at least, thats a stated goal, and breakage will be treated
2282	as a bug).	2817	as a bug).
2283		2818
2284	You need the following files in your source tree, or in a directory	2819	You need the following files in your source tree, or in a directory
2285	in your include path (e.g. in libev/ when using -Ilibev):	2820	in your include path (e.g. in libev/ when using -Ilibev):
2286		2821
2287	ev.h	2822	ev.h
2288	ev.c	2823	ev.c
2289	ev_vars.h	2824	ev_vars.h
2290	ev_wrap.h	2825	ev_wrap.h
2291		2826
2292	ev_win32.c required on win32 platforms only	2827	ev_win32.c required on win32 platforms only
2293		2828
2294	ev_select.c only when select backend is enabled (which is enabled by default)	2829	ev_select.c only when select backend is enabled (which is enabled by default)
2295	ev_poll.c only when poll backend is enabled (disabled by default)	2830	ev_poll.c only when poll backend is enabled (disabled by default)
2296	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2831	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2297	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2832	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2298	ev_port.c only when the solaris port backend is enabled (disabled by default)	2833	ev_port.c only when the solaris port backend is enabled (disabled by default)
2299		2834
2300	F<ev.c> includes the backend files directly when enabled, so you only need	2835	F<ev.c> includes the backend files directly when enabled, so you only need
2301	to compile this single file.	2836	to compile this single file.
2302		2837
2303	=head3 LIBEVENT COMPATIBILITY API	2838	=head3 LIBEVENT COMPATIBILITY API
2304		2839
2305	To include the libevent compatibility API, also include:	2840	To include the libevent compatibility API, also include:
2306		2841
2307	#include "event.c"	2842	#include "event.c"
2308		2843
2309	in the file including F<ev.c>, and:	2844	in the file including F<ev.c>, and:
2310		2845
2311	#include "event.h"	2846	#include "event.h"
2312		2847
2313	in the files that want to use the libevent API. This also includes F<ev.h>.	2848	in the files that want to use the libevent API. This also includes F<ev.h>.
2314		2849
2315	You need the following additional files for this:	2850	You need the following additional files for this:
2316		2851
2317	event.h	2852	event.h
2318	event.c	2853	event.c
2319		2854
2320	=head3 AUTOCONF SUPPORT	2855	=head3 AUTOCONF SUPPORT
2321		2856
2322	Instead of using C<EV_STANDALONE=1> and providing your config in	2857	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2323	whatever way you want, you can also C<m4_include([libev.m4])> in your	2858	whatever way you want, you can also C<m4_include([libev.m4])> in your
2324	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2859	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2325	include F<config.h> and configure itself accordingly.	2860	include F<config.h> and configure itself accordingly.
2326		2861
2327	For this of course you need the m4 file:	2862	For this of course you need the m4 file:
2328		2863
2329	libev.m4	2864	libev.m4
2330		2865
2331	=head2 PREPROCESSOR SYMBOLS/MACROS	2866	=head2 PREPROCESSOR SYMBOLS/MACROS
2332		2867
2333	Libev can be configured via a variety of preprocessor symbols you have to define	2868	Libev can be configured via a variety of preprocessor symbols you have to
2334	before including any of its files. The default is not to build for multiplicity	2869	define before including any of its files. The default in the absence of
2335	and only include the select backend.	2870	autoconf is noted for every option.
2336		2871
2337	=over 4	2872	=over 4
2338		2873
2339	=item EV_STANDALONE	2874	=item EV_STANDALONE
2340		2875
…		…
2345	F<event.h> that are not directly supported by the libev core alone.	2880	F<event.h> that are not directly supported by the libev core alone.
2346		2881
2347	=item EV_USE_MONOTONIC	2882	=item EV_USE_MONOTONIC
2348		2883
2349	If defined to be C<1>, libev will try to detect the availability of the	2884	If defined to be C<1>, libev will try to detect the availability of the
2350	monotonic clock option at both compiletime and runtime. Otherwise no use	2885	monotonic clock option at both compile time and runtime. Otherwise no use
2351	of the monotonic clock option will be attempted. If you enable this, you	2886	of the monotonic clock option will be attempted. If you enable this, you
2352	usually have to link against librt or something similar. Enabling it when	2887	usually have to link against librt or something similar. Enabling it when
2353	the functionality isn't available is safe, though, although you have	2888	the functionality isn't available is safe, though, although you have
2354	to make sure you link against any libraries where the C<clock_gettime>	2889	to make sure you link against any libraries where the C<clock_gettime>
2355	function is hiding in (often F<-lrt>).	2890	function is hiding in (often F<-lrt>).
2356		2891
2357	=item EV_USE_REALTIME	2892	=item EV_USE_REALTIME
2358		2893
2359	If defined to be C<1>, libev will try to detect the availability of the	2894	If defined to be C<1>, libev will try to detect the availability of the
2360	realtime clock option at compiletime (and assume its availability at	2895	real-time clock option at compile time (and assume its availability at
2361	runtime if successful). Otherwise no use of the realtime clock option will	2896	runtime if successful). Otherwise no use of the real-time clock option will
2362	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2897	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2363	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2898	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2364	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2899	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2365		2900
2366	=item EV_USE_NANOSLEEP	2901	=item EV_USE_NANOSLEEP
2367		2902
2368	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2903	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2369	and will use it for delays. Otherwise it will use C<select ()>.	2904	and will use it for delays. Otherwise it will use C<select ()>.
2370		2905
		2906	=item EV_USE_EVENTFD
		2907
		2908	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2909	available and will probe for kernel support at runtime. This will improve
		2910	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2911	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2912	2.7 or newer, otherwise disabled.
		2913
2371	=item EV_USE_SELECT	2914	=item EV_USE_SELECT
2372		2915
2373	If undefined or defined to be C<1>, libev will compile in support for the	2916	If undefined or defined to be C<1>, libev will compile in support for the
2374	C<select>(2) backend. No attempt at autodetection will be done: if no	2917	C<select>(2) backend. No attempt at auto-detection will be done: if no
2375	other method takes over, select will be it. Otherwise the select backend	2918	other method takes over, select will be it. Otherwise the select backend
2376	will not be compiled in.	2919	will not be compiled in.
2377		2920
2378	=item EV_SELECT_USE_FD_SET	2921	=item EV_SELECT_USE_FD_SET
2379		2922
2380	If defined to C<1>, then the select backend will use the system C<fd_set>	2923	If defined to C<1>, then the select backend will use the system C<fd_set>
2381	structure. This is useful if libev doesn't compile due to a missing	2924	structure. This is useful if libev doesn't compile due to a missing
2382	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2925	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2383	exotic systems. This usually limits the range of file descriptors to some	2926	exotic systems. This usually limits the range of file descriptors to some
2384	low limit such as 1024 or might have other limitations (winsocket only	2927	low limit such as 1024 or might have other limitations (winsocket only
2385	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2928	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2386	influence the size of the C<fd_set> used.	2929	influence the size of the C<fd_set> used.
2387		2930
…		…
2393	be used is the winsock select). This means that it will call	2936	be used is the winsock select). This means that it will call
2394	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2937	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2395	it is assumed that all these functions actually work on fds, even	2938	it is assumed that all these functions actually work on fds, even
2396	on win32. Should not be defined on non-win32 platforms.	2939	on win32. Should not be defined on non-win32 platforms.
2397		2940
		2941	=item EV_FD_TO_WIN32_HANDLE
		2942
		2943	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2944	file descriptors to socket handles. When not defining this symbol (the
		2945	default), then libev will call C<_get_osfhandle>, which is usually
		2946	correct. In some cases, programs use their own file descriptor management,
		2947	in which case they can provide this function to map fds to socket handles.
		2948
2398	=item EV_USE_POLL	2949	=item EV_USE_POLL
2399		2950
2400	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2951	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2401	backend. Otherwise it will be enabled on non-win32 platforms. It	2952	backend. Otherwise it will be enabled on non-win32 platforms. It
2402	takes precedence over select.	2953	takes precedence over select.
2403		2954
2404	=item EV_USE_EPOLL	2955	=item EV_USE_EPOLL
2405		2956
2406	If defined to be C<1>, libev will compile in support for the Linux	2957	If defined to be C<1>, libev will compile in support for the Linux
2407	C<epoll>(7) backend. Its availability will be detected at runtime,	2958	C<epoll>(7) backend. Its availability will be detected at runtime,
2408	otherwise another method will be used as fallback. This is the	2959	otherwise another method will be used as fallback. This is the preferred
2409	preferred backend for GNU/Linux systems.	2960	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2961	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2410		2962
2411	=item EV_USE_KQUEUE	2963	=item EV_USE_KQUEUE
2412		2964
2413	If defined to be C<1>, libev will compile in support for the BSD style	2965	If defined to be C<1>, libev will compile in support for the BSD style
2414	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2966	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2427	otherwise another method will be used as fallback. This is the preferred	2979	otherwise another method will be used as fallback. This is the preferred
2428	backend for Solaris 10 systems.	2980	backend for Solaris 10 systems.
2429		2981
2430	=item EV_USE_DEVPOLL	2982	=item EV_USE_DEVPOLL
2431		2983
2432	reserved for future expansion, works like the USE symbols above.	2984	Reserved for future expansion, works like the USE symbols above.
2433		2985
2434	=item EV_USE_INOTIFY	2986	=item EV_USE_INOTIFY
2435		2987
2436	If defined to be C<1>, libev will compile in support for the Linux inotify	2988	If defined to be C<1>, libev will compile in support for the Linux inotify
2437	interface to speed up C<ev_stat> watchers. Its actual availability will	2989	interface to speed up C<ev_stat> watchers. Its actual availability will
2438	be detected at runtime.	2990	be detected at runtime. If undefined, it will be enabled if the headers
		2991	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2992
		2993	=item EV_ATOMIC_T
		2994
		2995	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2996	access is atomic with respect to other threads or signal contexts. No such
		2997	type is easily found in the C language, so you can provide your own type
		2998	that you know is safe for your purposes. It is used both for signal handler "locking"
		2999	as well as for signal and thread safety in C<ev_async> watchers.
		3000
		3001	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3002	(from F<signal.h>), which is usually good enough on most platforms.
2439		3003
2440	=item EV_H	3004	=item EV_H
2441		3005
2442	The name of the F<ev.h> header file used to include it. The default if	3006	The name of the F<ev.h> header file used to include it. The default if
2443	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3007	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2444	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3008	used to virtually rename the F<ev.h> header file in case of conflicts.
2445		3009
2446	=item EV_CONFIG_H	3010	=item EV_CONFIG_H
2447		3011
2448	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3012	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2449	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3013	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2450	C<EV_H>, above.	3014	C<EV_H>, above.
2451		3015
2452	=item EV_EVENT_H	3016	=item EV_EVENT_H
2453		3017
2454	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3018	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2455	of how the F<event.h> header can be found.	3019	of how the F<event.h> header can be found, the default is C<"event.h">.
2456		3020
2457	=item EV_PROTOTYPES	3021	=item EV_PROTOTYPES
2458		3022
2459	If defined to be C<0>, then F<ev.h> will not define any function	3023	If defined to be C<0>, then F<ev.h> will not define any function
2460	prototypes, but still define all the structs and other symbols. This is	3024	prototypes, but still define all the structs and other symbols. This is
…		…
2481	When doing priority-based operations, libev usually has to linearly search	3045	When doing priority-based operations, libev usually has to linearly search
2482	all the priorities, so having many of them (hundreds) uses a lot of space	3046	all the priorities, so having many of them (hundreds) uses a lot of space
2483	and time, so using the defaults of five priorities (-2 .. +2) is usually	3047	and time, so using the defaults of five priorities (-2 .. +2) is usually
2484	fine.	3048	fine.
2485		3049
2486	If your embedding app does not need any priorities, defining these both to	3050	If your embedding application does not need any priorities, defining these both to
2487	C<0> will save some memory and cpu.	3051	C<0> will save some memory and CPU.
2488		3052
2489	=item EV_PERIODIC_ENABLE	3053	=item EV_PERIODIC_ENABLE
2490		3054
2491	If undefined or defined to be C<1>, then periodic timers are supported. If	3055	If undefined or defined to be C<1>, then periodic timers are supported. If
2492	defined to be C<0>, then they are not. Disabling them saves a few kB of	3056	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2511	=item EV_FORK_ENABLE	3075	=item EV_FORK_ENABLE
2512		3076
2513	If undefined or defined to be C<1>, then fork watchers are supported. If	3077	If undefined or defined to be C<1>, then fork watchers are supported. If
2514	defined to be C<0>, then they are not.	3078	defined to be C<0>, then they are not.
2515		3079
		3080	=item EV_ASYNC_ENABLE
		3081
		3082	If undefined or defined to be C<1>, then async watchers are supported. If
		3083	defined to be C<0>, then they are not.
		3084
2516	=item EV_MINIMAL	3085	=item EV_MINIMAL
2517		3086
2518	If you need to shave off some kilobytes of code at the expense of some	3087	If you need to shave off some kilobytes of code at the expense of some
2519	speed, define this symbol to C<1>. Currently only used for gcc to override	3088	speed, define this symbol to C<1>. Currently this is used to override some
2520	some inlining decisions, saves roughly 30% codesize of amd64.	3089	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3090	much smaller 2-heap for timer management over the default 4-heap.
2521		3091
2522	=item EV_PID_HASHSIZE	3092	=item EV_PID_HASHSIZE
2523		3093
2524	C<ev_child> watchers use a small hash table to distribute workload by	3094	C<ev_child> watchers use a small hash table to distribute workload by
2525	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3095	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2526	than enough. If you need to manage thousands of children you might want to	3096	than enough. If you need to manage thousands of children you might want to
2527	increase this value (I<must> be a power of two).	3097	increase this value (I<must> be a power of two).
2528		3098
2529	=item EV_INOTIFY_HASHSIZE	3099	=item EV_INOTIFY_HASHSIZE
2530		3100
2531	C<ev_staz> watchers use a small hash table to distribute workload by	3101	C<ev_stat> watchers use a small hash table to distribute workload by
2532	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3102	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2533	usually more than enough. If you need to manage thousands of C<ev_stat>	3103	usually more than enough. If you need to manage thousands of C<ev_stat>
2534	watchers you might want to increase this value (I<must> be a power of	3104	watchers you might want to increase this value (I<must> be a power of
2535	two).	3105	two).
2536		3106
		3107	=item EV_USE_4HEAP
		3108
		3109	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3110	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3111	to C<1>. The 4-heap uses more complicated (longer) code but has
		3112	noticeably faster performance with many (thousands) of watchers.
		3113
		3114	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3115	(disabled).
		3116
		3117	=item EV_HEAP_CACHE_AT
		3118
		3119	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3120	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3121	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3122	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3123	but avoids random read accesses on heap changes. This improves performance
		3124	noticeably with with many (hundreds) of watchers.
		3125
		3126	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3127	(disabled).
		3128
		3129	=item EV_VERIFY
		3130
		3131	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3132	be done: If set to C<0>, no internal verification code will be compiled
		3133	in. If set to C<1>, then verification code will be compiled in, but not
		3134	called. If set to C<2>, then the internal verification code will be
		3135	called once per loop, which can slow down libev. If set to C<3>, then the
		3136	verification code will be called very frequently, which will slow down
		3137	libev considerably.
		3138
		3139	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3140	C<0.>
		3141
2537	=item EV_COMMON	3142	=item EV_COMMON
2538		3143
2539	By default, all watchers have a C<void *data> member. By redefining	3144	By default, all watchers have a C<void *data> member. By redefining
2540	this macro to a something else you can include more and other types of	3145	this macro to a something else you can include more and other types of
2541	members. You have to define it each time you include one of the files,	3146	members. You have to define it each time you include one of the files,
2542	though, and it must be identical each time.	3147	though, and it must be identical each time.
2543		3148
2544	For example, the perl EV module uses something like this:	3149	For example, the perl EV module uses something like this:
2545		3150
2546	#define EV_COMMON \	3151	#define EV_COMMON \
2547	SV *self; /* contains this struct */ \	3152	SV *self; /* contains this struct */ \
2548	SV *cb_sv, *fh /* note no trailing ";" */	3153	SV *cb_sv, *fh /* note no trailing ";" */
2549		3154
2550	=item EV_CB_DECLARE (type)	3155	=item EV_CB_DECLARE (type)
2551		3156
2552	=item EV_CB_INVOKE (watcher, revents)	3157	=item EV_CB_INVOKE (watcher, revents)
2553		3158
…		…
2560	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3165	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2561	method calls instead of plain function calls in C++.	3166	method calls instead of plain function calls in C++.
2562		3167
2563	=head2 EXPORTED API SYMBOLS	3168	=head2 EXPORTED API SYMBOLS
2564		3169
2565	If you need to re-export the API (e.g. via a dll) and you need a list of	3170	If you need to re-export the API (e.g. via a DLL) and you need a list of
2566	exported symbols, you can use the provided F<Symbol.*> files which list	3171	exported symbols, you can use the provided F<Symbol.*> files which list
2567	all public symbols, one per line:	3172	all public symbols, one per line:
2568		3173
2569	Symbols.ev for libev proper	3174	Symbols.ev for libev proper
2570	Symbols.event for the libevent emulation	3175	Symbols.event for the libevent emulation
2571		3176
2572	This can also be used to rename all public symbols to avoid clashes with	3177	This can also be used to rename all public symbols to avoid clashes with
2573	multiple versions of libev linked together (which is obviously bad in	3178	multiple versions of libev linked together (which is obviously bad in
2574	itself, but sometimes it is inconvinient to avoid this).	3179	itself, but sometimes it is inconvenient to avoid this).
2575		3180
2576	A sed command like this will create wrapper C<#define>'s that you need to	3181	A sed command like this will create wrapper C<#define>'s that you need to
2577	include before including F<ev.h>:	3182	include before including F<ev.h>:
2578		3183
2579	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3184	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2596	file.	3201	file.
2597		3202
2598	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3203	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2599	that everybody includes and which overrides some configure choices:	3204	that everybody includes and which overrides some configure choices:
2600		3205
2601	#define EV_MINIMAL 1	3206	#define EV_MINIMAL 1
2602	#define EV_USE_POLL 0	3207	#define EV_USE_POLL 0
2603	#define EV_MULTIPLICITY 0	3208	#define EV_MULTIPLICITY 0
2604	#define EV_PERIODIC_ENABLE 0	3209	#define EV_PERIODIC_ENABLE 0
2605	#define EV_STAT_ENABLE 0	3210	#define EV_STAT_ENABLE 0
2606	#define EV_FORK_ENABLE 0	3211	#define EV_FORK_ENABLE 0
2607	#define EV_CONFIG_H <config.h>	3212	#define EV_CONFIG_H <config.h>
2608	#define EV_MINPRI 0	3213	#define EV_MINPRI 0
2609	#define EV_MAXPRI 0	3214	#define EV_MAXPRI 0
2610		3215
2611	#include "ev++.h"	3216	#include "ev++.h"
2612		3217
2613	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3218	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2614		3219
2615	#include "ev_cpp.h"	3220	#include "ev_cpp.h"
2616	#include "ev.c"	3221	#include "ev.c"
		3222
		3223
		3224	=head1 THREADS AND COROUTINES
		3225
		3226	=head2 THREADS
		3227
		3228	Libev itself is completely thread-safe, but it uses no locking. This
		3229	means that you can use as many loops as you want in parallel, as long as
		3230	only one thread ever calls into one libev function with the same loop
		3231	parameter.
		3232
		3233	Or put differently: calls with different loop parameters can be done in
		3234	parallel from multiple threads, calls with the same loop parameter must be
		3235	done serially (but can be done from different threads, as long as only one
		3236	thread ever is inside a call at any point in time, e.g. by using a mutex
		3237	per loop).
		3238
		3239	If you want to know which design (one loop, locking, or multiple loops
		3240	without or something else still) is best for your problem, then I cannot
		3241	help you. I can give some generic advice however:
		3242
		3243	=over 4
		3244
		3245	=item * most applications have a main thread: use the default libev loop
		3246	in that thread, or create a separate thread running only the default loop.
		3247
		3248	This helps integrating other libraries or software modules that use libev
		3249	themselves and don't care/know about threading.
		3250
		3251	=item * one loop per thread is usually a good model.
		3252
		3253	Doing this is almost never wrong, sometimes a better-performance model
		3254	exists, but it is always a good start.
		3255
		3256	=item * other models exist, such as the leader/follower pattern, where one
		3257	loop is handed through multiple threads in a kind of round-robin fashion.
		3258
		3259	Choosing a model is hard - look around, learn, know that usually you can do
		3260	better than you currently do :-)
		3261
		3262	=item * often you need to talk to some other thread which blocks in the
		3263	event loop - C<ev_async> watchers can be used to wake them up from other
		3264	threads safely (or from signal contexts...).
		3265
		3266	=back
		3267
		3268	=head2 COROUTINES
		3269
		3270	Libev is much more accommodating to coroutines ("cooperative threads"):
		3271	libev fully supports nesting calls to it's functions from different
		3272	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3273	different coroutines and switch freely between both coroutines running the
		3274	loop, as long as you don't confuse yourself). The only exception is that
		3275	you must not do this from C<ev_periodic> reschedule callbacks.
		3276
		3277	Care has been invested into making sure that libev does not keep local
		3278	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3279	switches.
2617		3280
2618		3281
2619	=head1 COMPLEXITIES	3282	=head1 COMPLEXITIES
2620		3283
2621	In this section the complexities of (many of) the algorithms used inside	3284	In this section the complexities of (many of) the algorithms used inside
…		…
2632		3295
2633	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3296	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2634		3297
2635	This means that, when you have a watcher that triggers in one hour and	3298	This means that, when you have a watcher that triggers in one hour and
2636	there are 100 watchers that would trigger before that then inserting will	3299	there are 100 watchers that would trigger before that then inserting will
2637	have to skip those 100 watchers.	3300	have to skip roughly seven (C<ld 100>) of these watchers.
2638		3301
2639	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3302	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2640		3303
2641	That means that for changing a timer costs less than removing/adding them	3304	That means that changing a timer costs less than removing/adding them
2642	as only the relative motion in the event queue has to be paid for.	3305	as only the relative motion in the event queue has to be paid for.
2643		3306
2644	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3307	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2645		3308
2646	These just add the watcher into an array or at the head of a list.	3309	These just add the watcher into an array or at the head of a list.
		3310
2647	=item Stopping check/prepare/idle watchers: O(1)	3311	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2648		3312
2649	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3313	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2650		3314
2651	These watchers are stored in lists then need to be walked to find the	3315	These watchers are stored in lists then need to be walked to find the
2652	correct watcher to remove. The lists are usually short (you don't usually	3316	correct watcher to remove. The lists are usually short (you don't usually
2653	have many watchers waiting for the same fd or signal).	3317	have many watchers waiting for the same fd or signal).
2654		3318
2655	=item Finding the next timer per loop iteration: O(1)	3319	=item Finding the next timer in each loop iteration: O(1)
		3320
		3321	By virtue of using a binary or 4-heap, the next timer is always found at a
		3322	fixed position in the storage array.
2656		3323
2657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3324	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2658		3325
2659	A change means an I/O watcher gets started or stopped, which requires	3326	A change means an I/O watcher gets started or stopped, which requires
2660	libev to recalculate its status (and possibly tell the kernel).	3327	libev to recalculate its status (and possibly tell the kernel, depending
		3328	on backend and whether C<ev_io_set> was used).
2661		3329
2662	=item Activating one watcher: O(1)	3330	=item Activating one watcher (putting it into the pending state): O(1)
2663		3331
2664	=item Priority handling: O(number_of_priorities)	3332	=item Priority handling: O(number_of_priorities)
2665		3333
2666	Priorities are implemented by allocating some space for each	3334	Priorities are implemented by allocating some space for each
2667	priority. When doing priority-based operations, libev usually has to	3335	priority. When doing priority-based operations, libev usually has to
2668	linearly search all the priorities.	3336	linearly search all the priorities, but starting/stopping and activating
		3337	watchers becomes O(1) w.r.t. priority handling.
		3338
		3339	=item Sending an ev_async: O(1)
		3340
		3341	=item Processing ev_async_send: O(number_of_async_watchers)
		3342
		3343	=item Processing signals: O(max_signal_number)
		3344
		3345	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3346	calls in the current loop iteration. Checking for async and signal events
		3347	involves iterating over all running async watchers or all signal numbers.
2669		3348
2670	=back	3349	=back
2671		3350
2672		3351
		3352	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3353
		3354	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3355	requires, and its I/O model is fundamentally incompatible with the POSIX
		3356	model. Libev still offers limited functionality on this platform in
		3357	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3358	descriptors. This only applies when using Win32 natively, not when using
		3359	e.g. cygwin.
		3360
		3361	Lifting these limitations would basically require the full
		3362	re-implementation of the I/O system. If you are into these kinds of
		3363	things, then note that glib does exactly that for you in a very portable
		3364	way (note also that glib is the slowest event library known to man).
		3365
		3366	There is no supported compilation method available on windows except
		3367	embedding it into other applications.
		3368
		3369	Not a libev limitation but worth mentioning: windows apparently doesn't
		3370	accept large writes: instead of resulting in a partial write, windows will
		3371	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3372	so make sure you only write small amounts into your sockets (less than a
		3373	megabyte seems safe, but thsi apparently depends on the amount of memory
		3374	available).
		3375
		3376	Due to the many, low, and arbitrary limits on the win32 platform and
		3377	the abysmal performance of winsockets, using a large number of sockets
		3378	is not recommended (and not reasonable). If your program needs to use
		3379	more than a hundred or so sockets, then likely it needs to use a totally
		3380	different implementation for windows, as libev offers the POSIX readiness
		3381	notification model, which cannot be implemented efficiently on windows
		3382	(Microsoft monopoly games).
		3383
		3384	A typical way to use libev under windows is to embed it (see the embedding
		3385	section for details) and use the following F<evwrap.h> header file instead
		3386	of F<ev.h>:
		3387
		3388	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3389	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3390
		3391	#include "ev.h"
		3392
		3393	And compile the following F<evwrap.c> file into your project (make sure
		3394	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3395
		3396	#include "evwrap.h"
		3397	#include "ev.c"
		3398
		3399	=over 4
		3400
		3401	=item The winsocket select function
		3402
		3403	The winsocket C<select> function doesn't follow POSIX in that it
		3404	requires socket I<handles> and not socket I<file descriptors> (it is
		3405	also extremely buggy). This makes select very inefficient, and also
		3406	requires a mapping from file descriptors to socket handles (the Microsoft
		3407	C runtime provides the function C<_open_osfhandle> for this). See the
		3408	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3409	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3410
		3411	The configuration for a "naked" win32 using the Microsoft runtime
		3412	libraries and raw winsocket select is:
		3413
		3414	#define EV_USE_SELECT 1
		3415	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3416
		3417	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3418	complexity in the O(n²) range when using win32.
		3419
		3420	=item Limited number of file descriptors
		3421
		3422	Windows has numerous arbitrary (and low) limits on things.
		3423
		3424	Early versions of winsocket's select only supported waiting for a maximum
		3425	of C<64> handles (probably owning to the fact that all windows kernels
		3426	can only wait for C<64> things at the same time internally; Microsoft
		3427	recommends spawning a chain of threads and wait for 63 handles and the
		3428	previous thread in each. Great).
		3429
		3430	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3431	to some high number (e.g. C<2048>) before compiling the winsocket select
		3432	call (which might be in libev or elsewhere, for example, perl does its own
		3433	select emulation on windows).
		3434
		3435	Another limit is the number of file descriptors in the Microsoft runtime
		3436	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3437	or something like this inside Microsoft). You can increase this by calling
		3438	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3439	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3440	libraries.
		3441
		3442	This might get you to about C<512> or C<2048> sockets (depending on
		3443	windows version and/or the phase of the moon). To get more, you need to
		3444	wrap all I/O functions and provide your own fd management, but the cost of
		3445	calling select (O(n²)) will likely make this unworkable.
		3446
		3447	=back
		3448
		3449
		3450	=head1 PORTABILITY REQUIREMENTS
		3451
		3452	In addition to a working ISO-C implementation, libev relies on a few
		3453	additional extensions:
		3454
		3455	=over 4
		3456
		3457	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3458	calling conventions regardless of C<ev_watcher_type *>.
		3459
		3460	Libev assumes not only that all watcher pointers have the same internal
		3461	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3462	assumes that the same (machine) code can be used to call any watcher
		3463	callback: The watcher callbacks have different type signatures, but libev
		3464	calls them using an C<ev_watcher *> internally.
		3465
		3466	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3467
		3468	The type C<sig_atomic_t volatile> (or whatever is defined as
		3469	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3470	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3471	believed to be sufficiently portable.
		3472
		3473	=item C<sigprocmask> must work in a threaded environment
		3474
		3475	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3476	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3477	pthread implementations will either allow C<sigprocmask> in the "main
		3478	thread" or will block signals process-wide, both behaviours would
		3479	be compatible with libev. Interaction between C<sigprocmask> and
		3480	C<pthread_sigmask> could complicate things, however.
		3481
		3482	The most portable way to handle signals is to block signals in all threads
		3483	except the initial one, and run the default loop in the initial thread as
		3484	well.
		3485
		3486	=item C<long> must be large enough for common memory allocation sizes
		3487
		3488	To improve portability and simplify using libev, libev uses C<long>
		3489	internally instead of C<size_t> when allocating its data structures. On
		3490	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3491	is still at least 31 bits everywhere, which is enough for hundreds of
		3492	millions of watchers.
		3493
		3494	=item C<double> must hold a time value in seconds with enough accuracy
		3495
		3496	The type C<double> is used to represent timestamps. It is required to
		3497	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3498	enough for at least into the year 4000. This requirement is fulfilled by
		3499	implementations implementing IEEE 754 (basically all existing ones).
		3500
		3501	=back
		3502
		3503	If you know of other additional requirements drop me a note.
		3504
		3505
		3506	=head1 COMPILER WARNINGS
		3507
		3508	Depending on your compiler and compiler settings, you might get no or a
		3509	lot of warnings when compiling libev code. Some people are apparently
		3510	scared by this.
		3511
		3512	However, these are unavoidable for many reasons. For one, each compiler
		3513	has different warnings, and each user has different tastes regarding
		3514	warning options. "Warn-free" code therefore cannot be a goal except when
		3515	targeting a specific compiler and compiler-version.
		3516
		3517	Another reason is that some compiler warnings require elaborate
		3518	workarounds, or other changes to the code that make it less clear and less
		3519	maintainable.
		3520
		3521	And of course, some compiler warnings are just plain stupid, or simply
		3522	wrong (because they don't actually warn about the condition their message
		3523	seems to warn about).
		3524
		3525	While libev is written to generate as few warnings as possible,
		3526	"warn-free" code is not a goal, and it is recommended not to build libev
		3527	with any compiler warnings enabled unless you are prepared to cope with
		3528	them (e.g. by ignoring them). Remember that warnings are just that:
		3529	warnings, not errors, or proof of bugs.
		3530
		3531
		3532	=head1 VALGRIND
		3533
		3534	Valgrind has a special section here because it is a popular tool that is
		3535	highly useful, but valgrind reports are very hard to interpret.
		3536
		3537	If you think you found a bug (memory leak, uninitialised data access etc.)
		3538	in libev, then check twice: If valgrind reports something like:
		3539
		3540	==2274== definitely lost: 0 bytes in 0 blocks.
		3541	==2274== possibly lost: 0 bytes in 0 blocks.
		3542	==2274== still reachable: 256 bytes in 1 blocks.
		3543
		3544	Then there is no memory leak. Similarly, under some circumstances,
		3545	valgrind might report kernel bugs as if it were a bug in libev, or it
		3546	might be confused (it is a very good tool, but only a tool).
		3547
		3548	If you are unsure about something, feel free to contact the mailing list
		3549	with the full valgrind report and an explanation on why you think this is
		3550	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3551	no bug" answer and take the chance of learning how to interpret valgrind
		3552	properly.
		3553
		3554	If you need, for some reason, empty reports from valgrind for your project
		3555	I suggest using suppression lists.
		3556
		3557
2673	=head1 AUTHOR	3558	=head1 AUTHOR
2674		3559
2675	Marc Lehmann <libev@schmorp.de>.	3560	Marc Lehmann <libev@schmorp.de>.
2676		3561

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