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Revision 1.83 by root, Wed Dec 12 17:55:31 2007 UTC vs.
Revision 1.171 by root, Tue Jul 8 09:49:15 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		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
104		142
105	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
106		144
107	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
108	library in any way.	146	library in any way.
…		…
112	=item ev_tstamp ev_time ()	150	=item ev_tstamp ev_time ()
113		151
114	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	154	you actually want to know.
		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	Sleep for the given interval: The current thread will be blocked until
		159	either it is interrupted or the given time interval has passed. Basically
		160	this is a sub-second-resolution C<sleep ()>.
117		161
118	=item int ev_version_major ()	162	=item int ev_version_major ()
119		163
120	=item int ev_version_minor ()	164	=item int ev_version_minor ()
121		165
…		…
134	not a problem.	178	not a problem.
135		179
136	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
137	version.	181	version.
138		182
139	assert (("libev version mismatch",	183	assert (("libev version mismatch",
140	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
141	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
142		186
143	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
144		188
145	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_*>
146	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
148	a description of the set values.	192	a description of the set values.
149		193
150	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
151	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
152		196
153	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
154	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
155		199
156	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
157		201
158	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
159	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
160	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
161	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
162	(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
163	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
164		208
165	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
166		210
…		…
173	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
174		218
175	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
176		220
177	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
178	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
179	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
180	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
181	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
182	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.
183		230
184	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
185	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,
186	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.
187		234
188	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
189	retries).	236	retries (example requires a standards-compliant C<realloc>).
190		237
191	static void *	238	static void *
192	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
193	{	240	{
194	for (;;)	241	for (;;)
…		…
205	...	252	...
206	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
207		254
208	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
209		256
210	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
211	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
212	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
213	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
214	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
215	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
216	(such as abort).	263	(such as abort).
217		264
218	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.
…		…
232	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
233		280
234	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
235	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
236	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
237
238	If you use threads, a common model is to run the default event loop
239	in your main thread (or in a separate thread) and for each thread you
240	create, you also create another event loop. Libev itself does no locking
241	whatsoever, so if you mix calls to the same event loop in different
242	threads, make sure you lock (this is usually a bad idea, though, even if
243	done correctly, because it's hideous and inefficient).
244		284
245	=over 4	285	=over 4
246		286
247	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
248		288
…		…
252	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
253		293
254	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
255	function.	295	function.
256		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
257	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
258	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>).
259		310
260	The following flags are supported:	311	The following flags are supported:
261		312
…		…
266	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
267	thing, believe me).	318	thing, believe me).
268		319
269	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
270		321
271	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
272	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
273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
274	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
275	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
276	around bugs.	327	around bugs.
…		…
282	enabling this flag.	333	enabling this flag.
283		334
284	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,
285	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
286	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
287	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
288	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
289	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
290		341
291	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
292	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
293	flag.	344	flag.
294		345
295	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>
296	environment variable.	347	environment variable.
297		348
298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
299		350
300	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
301	libev tries to roll its own fd_set with no limits on the number of fds,	352	libev tries to roll its own fd_set with no limits on the number of fds,
302	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
303	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
304	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
305		363
306	=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)
307		365
308	And this is your standard poll(2) backend. It's more complicated than	366	And this is your standard poll(2) backend. It's more complicated
309	select, but handles sparse fds better and has no artificial limit on the	367	than select, but handles sparse fds better and has no artificial
310	number of fds you can use (except it will slow down considerably with a	368	limit on the number of fds you can use (except it will slow down
311	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	369	considerably with a lot of inactive fds). It scales similarly to select,
		370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		371	performance tips.
312		372
313	=item C<EVBACKEND_EPOLL> (value 4, Linux)	373	=item C<EVBACKEND_EPOLL> (value 4, Linux)
314		374
315	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,
316	but it scales phenomenally better. While poll and select usually scale like	376	but it scales phenomenally better. While poll and select usually scale
317	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	377	like O(total_fds) where n is the total number of fds (or the highest fd),
318	either O(1) or O(active_fds).	378	epoll scales either O(1) or O(active_fds). The epoll design has a number
		379	of shortcomings, such as silently dropping events in some hard-to-detect
		380	cases and requiring a system call per fd change, no fork support and bad
		381	support for dup.
319		382
320	While stopping and starting an I/O watcher in the same iteration will	383	While stopping, setting and starting an I/O watcher in the same iteration
321	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
322	(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
323	best to avoid that. Also, dup()ed file descriptors might not work very	386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
324	well if you register events for both fds.	387	very well if you register events for both fds.
325		388
326	Please note that epoll sometimes generates spurious notifications, so you	389	Please note that epoll sometimes generates spurious notifications, so you
327	need to use non-blocking I/O or other means to avoid blocking when no data	390	need to use non-blocking I/O or other means to avoid blocking when no data
328	(or space) is available.	391	(or space) is available.
329		392
		393	Best performance from this backend is achieved by not unregistering all
		394	watchers for a file descriptor until it has been closed, if possible, i.e.
		395	keep at least one watcher active per fd at all times.
		396
		397	While nominally embeddable in other event loops, this feature is broken in
		398	all kernel versions tested so far.
		399
330	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
331		401
332	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
333	was broken on all BSDs except NetBSD (usually it doesn't work with	403	was broken on all BSDs except NetBSD (usually it doesn't work reliably
334	anything but sockets and pipes, except on Darwin, where of course its	404	with anything but sockets and pipes, except on Darwin, where of course
335	completely useless). For this reason its not being "autodetected"	405	it's completely useless). For this reason it's not being "auto-detected"
336	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
337	C<EVBACKEND_KQUEUE>).	407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		408	system like NetBSD.
		409
		410	You still can embed kqueue into a normal poll or select backend and use it
		411	only for sockets (after having made sure that sockets work with kqueue on
		412	the target platform). See C<ev_embed> watchers for more info.
338		413
339	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
340	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
341	course). While starting and stopping an I/O watcher does not cause an	416	course). While stopping, setting and starting an I/O watcher does never
342	extra syscall as with epoll, it still adds up to four event changes per	417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
343	incident, so its best to avoid that.	418	two event changes per incident, support for C<fork ()> is very bad and it
		419	drops fds silently in similarly hard-to-detect cases.
		420
		421	This backend usually performs well under most conditions.
		422
		423	While nominally embeddable in other event loops, this doesn't work
		424	everywhere, so you might need to test for this. And since it is broken
		425	almost everywhere, you should only use it when you have a lot of sockets
		426	(for which it usually works), by embedding it into another event loop
		427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		428	sockets.
344		429
345	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
346		431
347	This is not implemented yet (and might never be).	432	This is not implemented yet (and might never be, unless you send me an
		433	implementation). According to reports, C</dev/poll> only supports sockets
		434	and is not embeddable, which would limit the usefulness of this backend
		435	immensely.
348		436
349	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	437	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
350		438
351	This uses the Solaris 10 port mechanism. As with everything on Solaris,	439	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
352	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)).
353		441
354	Please note that solaris ports can result in a lot of spurious	442	Please note that Solaris event ports can deliver a lot of spurious
355	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
356	blocking when no data (or space) is available.	444	blocking when no data (or space) is available.
		445
		446	While this backend scales well, it requires one system call per active
		447	file descriptor per loop iteration. For small and medium numbers of file
		448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		449	might perform better.
		450
		451	On the positive side, ignoring the spurious readiness notifications, this
		452	backend actually performed to specification in all tests and is fully
		453	embeddable, which is a rare feat among the OS-specific backends.
357		454
358	=item C<EVBACKEND_ALL>	455	=item C<EVBACKEND_ALL>
359		456
360	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
361	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
362	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	459	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
363		460
		461	It is definitely not recommended to use this flag.
		462
364	=back	463	=back
365		464
366	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
367	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
368	specified, most compiled-in backend will be tried, usually in reverse	467	specified, all backends in C<ev_recommended_backends ()> will be tried.
369	order of their flag values :)
370		468
371	The most typical usage is like this:	469	The most typical usage is like this:
372		470
373	if (!ev_default_loop (0))	471	if (!ev_default_loop (0))
374	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
375		473
376	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
377	environment settings to be taken into account:	475	environment settings to be taken into account:
378		476
379	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
380		478
381	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
382	available (warning, breaks stuff, best use only with your own private	480	available (warning, breaks stuff, best use only with your own private
383	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):
384		482
385	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
386		484
387	=item struct ev_loop *ev_loop_new (unsigned int flags)	485	=item struct ev_loop *ev_loop_new (unsigned int flags)
388		486
389	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
390	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
391	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
392	undefined behaviour (or a failed assertion if assertions are enabled).	490	undefined behaviour (or a failed assertion if assertions are enabled).
393		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
394	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.
395		497
396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
397	if (!epoller)	499	if (!epoller)
398	fatal ("no epoll found here, maybe it hides under your chair");	500	fatal ("no epoll found here, maybe it hides under your chair");
399		501
400	=item ev_default_destroy ()	502	=item ev_default_destroy ()
401		503
402	Destroys the default loop again (frees all memory and kernel state	504	Destroys the default loop again (frees all memory and kernel state
403	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
404	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
405	responsibility to either stop all watchers cleanly yoursef I<before>	507	responsibility to either stop all watchers cleanly yourself I<before>
406	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
407	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	509	the easiest thing, you can just ignore the watchers and/or C<free ()> them
408	for example).	510	for example).
		511
		512	Note that certain global state, such as signal state, will not be freed by
		513	this function, and related watchers (such as signal and child watchers)
		514	would need to be stopped manually.
		515
		516	In general it is not advisable to call this function except in the
		517	rare occasion where you really need to free e.g. the signal handling
		518	pipe fds. If you need dynamically allocated loops it is better to use
		519	C<ev_loop_new> and C<ev_loop_destroy>).
409		520
410	=item ev_loop_destroy (loop)	521	=item ev_loop_destroy (loop)
411		522
412	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
413	earlier call to C<ev_loop_new>.	524	earlier call to C<ev_loop_new>.
414		525
415	=item ev_default_fork ()	526	=item ev_default_fork ()
416		527
		528	This function sets a flag that causes subsequent C<ev_loop> iterations
417	This function reinitialises the kernel state for backends that have	529	to reinitialise the kernel state for backends that have one. Despite the
418	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
419	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
420	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.
421		534
422	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
423	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
424	fork+exec, you don't have to call it.	537	you just fork+exec, you don't have to call it at all.
425		538
426	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
427	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
428	quite nicely into a call to C<pthread_atfork>:	541	quite nicely into a call to C<pthread_atfork>:
429		542
430	pthread_atfork (0, 0, ev_default_fork);	543	pthread_atfork (0, 0, ev_default_fork);
431		544
432	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
433	without calling this function, so if you force one of those backends you
434	do not need to care.
435
436	=item ev_loop_fork (loop)	545	=item ev_loop_fork (loop)
437		546
438	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
439	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
440	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.
441		554
442	=item unsigned int ev_loop_count (loop)	555	=item unsigned int ev_loop_count (loop)
443		556
444	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
445	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
…		…
458		571
459	Returns the current "event loop time", which is the time the event loop	572	Returns the current "event loop time", which is the time the event loop
460	received events and started processing them. This timestamp does not	573	received events and started processing them. This timestamp does not
461	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
462	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
463	event occuring (or more correctly, libev finding out about it).	576	event occurring (or more correctly, libev finding out about it).
464		577
465	=item ev_loop (loop, int flags)	578	=item ev_loop (loop, int flags)
466		579
467	Finally, this is it, the event handler. This function usually is called	580	Finally, this is it, the event handler. This function usually is called
468	after you initialised all your watchers and you want to start handling	581	after you initialised all your watchers and you want to start handling
…		…
480	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
481	those events and any outstanding ones, but will not block your process in	594	those events and any outstanding ones, but will not block your process in
482	case there are no events and will return after one iteration of the loop.	595	case there are no events and will return after one iteration of the loop.
483		596
484	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
485	neccessary) and will handle those and any outstanding ones. It will block	598	necessary) and will handle those and any outstanding ones. It will block
486	your process until at least one new event arrives, and will return after	599	your process until at least one new event arrives, and will return after
487	one iteration of the loop. This is useful if you are waiting for some	600	one iteration of the loop. This is useful if you are waiting for some
488	external event in conjunction with something not expressible using other	601	external event in conjunction with something not expressible using other
489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
490	usually a better approach for this kind of thing.	603	usually a better approach for this kind of thing.
491		604
492	Here are the gory details of what C<ev_loop> does:	605	Here are the gory details of what C<ev_loop> does:
493		606
494	- Before the first iteration, call any pending watchers.	607	- Before the first iteration, call any pending watchers.
495	* If there are no active watchers (reference count is zero), return.	608	* If EVFLAG_FORKCHECK was used, check for a fork.
496	- Queue all prepare watchers and then call all outstanding watchers.	609	- If a fork was detected (by any means), queue and call all fork watchers.
		610	- Queue and call all prepare watchers.
497	- If we have been forked, recreate the kernel state.	611	- If we have been forked, detach and recreate the kernel state
		612	as to not disturb the other process.
498	- Update the kernel state with all outstanding changes.	613	- Update the kernel state with all outstanding changes.
499	- Update the "event loop time".	614	- Update the "event loop time" (ev_now ()).
500	- Calculate for how long to block.	615	- Calculate for how long to sleep or block, if at all
		616	(active idle watchers, EVLOOP_NONBLOCK or not having
		617	any active watchers at all will result in not sleeping).
		618	- Sleep if the I/O and timer collect interval say so.
501	- Block the process, waiting for any events.	619	- Block the process, waiting for any events.
502	- Queue all outstanding I/O (fd) events.	620	- Queue all outstanding I/O (fd) events.
503	- Update the "event loop time" and do time jump handling.	621	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
504	- Queue all outstanding timers.	622	- Queue all outstanding timers.
505	- Queue all outstanding periodics.	623	- Queue all outstanding periodics.
506	- If no events are pending now, queue all idle watchers.	624	- Unless any events are pending now, queue all idle watchers.
507	- Queue all check watchers.	625	- Queue all check watchers.
508	- Call all queued watchers in reverse order (i.e. check watchers first).	626	- Call all queued watchers in reverse order (i.e. check watchers first).
509	Signals and child watchers are implemented as I/O watchers, and will	627	Signals and child watchers are implemented as I/O watchers, and will
510	be handled here by queueing them when their watcher gets executed.	628	be handled here by queueing them when their watcher gets executed.
511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	629	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
512	were used, return, otherwise continue with step *.	630	were used, or there are no active watchers, return, otherwise
		631	continue with step *.
513		632
514	Example: Queue some jobs and then loop until no events are outsanding	633	Example: Queue some jobs and then loop until no events are outstanding
515	anymore.	634	anymore.
516		635
517	... queue jobs here, make sure they register event watchers as long	636	... queue jobs here, make sure they register event watchers as long
518	... as they still have work to do (even an idle watcher will do..)	637	... as they still have work to do (even an idle watcher will do..)
519	ev_loop (my_loop, 0);	638	ev_loop (my_loop, 0);
520	... jobs done. yeah!	639	... jobs done or somebody called unloop. yeah!
521		640
522	=item ev_unloop (loop, how)	641	=item ev_unloop (loop, how)
523		642
524	Can be used to make a call to C<ev_loop> return early (but only after it	643	Can be used to make a call to C<ev_loop> return early (but only after it
525	has processed all outstanding events). The C<how> argument must be either	644	has processed all outstanding events). The C<how> argument must be either
526	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	645	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
527	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	646	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		647
		648	This "unloop state" will be cleared when entering C<ev_loop> again.
528		649
529	=item ev_ref (loop)	650	=item ev_ref (loop)
530		651
531	=item ev_unref (loop)	652	=item ev_unref (loop)
532		653
…		…
537	returning, ev_unref() after starting, and ev_ref() before stopping it. For	658	returning, ev_unref() after starting, and ev_ref() before stopping it. For
538	example, libev itself uses this for its internal signal pipe: It is not	659	example, libev itself uses this for its internal signal pipe: It is not
539	visible to the libev user and should not keep C<ev_loop> from exiting if	660	visible to the libev user and should not keep C<ev_loop> from exiting if
540	no event watchers registered by it are active. It is also an excellent	661	no event watchers registered by it are active. It is also an excellent
541	way to do this for generic recurring timers or from within third-party	662	way to do this for generic recurring timers or from within third-party
542	libraries. Just remember to I<unref after start> and I<ref before stop>.	663	libraries. Just remember to I<unref after start> and I<ref before stop>
		664	(but only if the watcher wasn't active before, or was active before,
		665	respectively).
543		666
544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	667	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
545	running when nothing else is active.	668	running when nothing else is active.
546		669
547	struct ev_signal exitsig;	670	struct ev_signal exitsig;
548	ev_signal_init (&exitsig, sig_cb, SIGINT);	671	ev_signal_init (&exitsig, sig_cb, SIGINT);
549	ev_signal_start (loop, &exitsig);	672	ev_signal_start (loop, &exitsig);
550	evf_unref (loop);	673	evf_unref (loop);
551		674
552	Example: For some weird reason, unregister the above signal handler again.	675	Example: For some weird reason, unregister the above signal handler again.
553		676
554	ev_ref (loop);	677	ev_ref (loop);
555	ev_signal_stop (loop, &exitsig);	678	ev_signal_stop (loop, &exitsig);
		679
		680	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		681
		682	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		683
		684	These advanced functions influence the time that libev will spend waiting
		685	for events. Both time intervals are by default C<0>, meaning that libev
		686	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		687	latency.
		688
		689	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		690	allows libev to delay invocation of I/O and timer/periodic callbacks
		691	to increase efficiency of loop iterations (or to increase power-saving
		692	opportunities).
		693
		694	The background is that sometimes your program runs just fast enough to
		695	handle one (or very few) event(s) per loop iteration. While this makes
		696	the program responsive, it also wastes a lot of CPU time to poll for new
		697	events, especially with backends like C<select ()> which have a high
		698	overhead for the actual polling but can deliver many events at once.
		699
		700	By setting a higher I<io collect interval> you allow libev to spend more
		701	time collecting I/O events, so you can handle more events per iteration,
		702	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		703	C<ev_timer>) will be not affected. Setting this to a non-null value will
		704	introduce an additional C<ev_sleep ()> call into most loop iterations.
		705
		706	Likewise, by setting a higher I<timeout collect interval> you allow libev
		707	to spend more time collecting timeouts, at the expense of increased
		708	latency (the watcher callback will be called later). C<ev_io> watchers
		709	will not be affected. Setting this to a non-null value will not introduce
		710	any overhead in libev.
		711
		712	Many (busy) programs can usually benefit by setting the I/O collect
		713	interval to a value near C<0.1> or so, which is often enough for
		714	interactive servers (of course not for games), likewise for timeouts. It
		715	usually doesn't make much sense to set it to a lower value than C<0.01>,
		716	as this approaches the timing granularity of most systems.
		717
		718	Setting the I<timeout collect interval> can improve the opportunity for
		719	saving power, as the program will "bundle" timer callback invocations that
		720	are "near" in time together, by delaying some, thus reducing the number of
		721	times the process sleeps and wakes up again. Another useful technique to
		722	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		723	they fire on, say, one-second boundaries only.
		724
		725	=item ev_loop_verify (loop)
		726
		727	This function only does something when C<EV_VERIFY> support has been
		728	compiled in. It tries to go through all internal structures and checks
		729	them for validity. If anything is found to be inconsistent, it will print
		730	an error message to standard error and call C<abort ()>.
		731
		732	This can be used to catch bugs inside libev itself: under normal
		733	circumstances, this function will never abort as of course libev keeps its
		734	data structures consistent.
556		735
557	=back	736	=back
558		737
559		738
560	=head1 ANATOMY OF A WATCHER	739	=head1 ANATOMY OF A WATCHER
561		740
562	A watcher is a structure that you create and register to record your	741	A watcher is a structure that you create and register to record your
563	interest in some event. For instance, if you want to wait for STDIN to	742	interest in some event. For instance, if you want to wait for STDIN to
564	become readable, you would create an C<ev_io> watcher for that:	743	become readable, you would create an C<ev_io> watcher for that:
565		744
566	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	745	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
567	{	746	{
568	ev_io_stop (w);	747	ev_io_stop (w);
569	ev_unloop (loop, EVUNLOOP_ALL);	748	ev_unloop (loop, EVUNLOOP_ALL);
570	}	749	}
571		750
572	struct ev_loop *loop = ev_default_loop (0);	751	struct ev_loop *loop = ev_default_loop (0);
573	struct ev_io stdin_watcher;	752	struct ev_io stdin_watcher;
574	ev_init (&stdin_watcher, my_cb);	753	ev_init (&stdin_watcher, my_cb);
575	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	754	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
576	ev_io_start (loop, &stdin_watcher);	755	ev_io_start (loop, &stdin_watcher);
577	ev_loop (loop, 0);	756	ev_loop (loop, 0);
578		757
579	As you can see, you are responsible for allocating the memory for your	758	As you can see, you are responsible for allocating the memory for your
580	watcher structures (and it is usually a bad idea to do this on the stack,	759	watcher structures (and it is usually a bad idea to do this on the stack,
581	although this can sometimes be quite valid).	760	although this can sometimes be quite valid).
582		761
583	Each watcher structure must be initialised by a call to C<ev_init	762	Each watcher structure must be initialised by a call to C<ev_init
584	(watcher *, callback)>, which expects a callback to be provided. This	763	(watcher *, callback)>, which expects a callback to be provided. This
585	callback gets invoked each time the event occurs (or, in the case of io	764	callback gets invoked each time the event occurs (or, in the case of I/O
586	watchers, each time the event loop detects that the file descriptor given	765	watchers, each time the event loop detects that the file descriptor given
587	is readable and/or writable).	766	is readable and/or writable).
588		767
589	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	768	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
590	with arguments specific to this watcher type. There is also a macro	769	with arguments specific to this watcher type. There is also a macro
…		…
660	=item C<EV_FORK>	839	=item C<EV_FORK>
661		840
662	The event loop has been resumed in the child process after fork (see	841	The event loop has been resumed in the child process after fork (see
663	C<ev_fork>).	842	C<ev_fork>).
664		843
		844	=item C<EV_ASYNC>
		845
		846	The given async watcher has been asynchronously notified (see C<ev_async>).
		847
665	=item C<EV_ERROR>	848	=item C<EV_ERROR>
666		849
667	An unspecified error has occured, the watcher has been stopped. This might	850	An unspecified error has occurred, the watcher has been stopped. This might
668	happen because the watcher could not be properly started because libev	851	happen because the watcher could not be properly started because libev
669	ran out of memory, a file descriptor was found to be closed or any other	852	ran out of memory, a file descriptor was found to be closed or any other
670	problem. You best act on it by reporting the problem and somehow coping	853	problem. You best act on it by reporting the problem and somehow coping
671	with the watcher being stopped.	854	with the watcher being stopped.
672		855
673	Libev will usually signal a few "dummy" events together with an error,	856	Libev will usually signal a few "dummy" events together with an error,
674	for example it might indicate that a fd is readable or writable, and if	857	for example it might indicate that a fd is readable or writable, and if
675	your callbacks is well-written it can just attempt the operation and cope	858	your callbacks is well-written it can just attempt the operation and cope
676	with the error from read() or write(). This will not work in multithreaded	859	with the error from read() or write(). This will not work in multi-threaded
677	programs, though, so beware.	860	programs, though, so beware.
678		861
679	=back	862	=back
680		863
681	=head2 GENERIC WATCHER FUNCTIONS	864	=head2 GENERIC WATCHER FUNCTIONS
…		…
711	Although some watcher types do not have type-specific arguments	894	Although some watcher types do not have type-specific arguments
712	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	895	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
713		896
714	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	897	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
715		898
716	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	899	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
717	calls into a single call. This is the most convinient method to initialise	900	calls into a single call. This is the most convenient method to initialise
718	a watcher. The same limitations apply, of course.	901	a watcher. The same limitations apply, of course.
719		902
720	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	903	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
721		904
722	Starts (activates) the given watcher. Only active watchers will receive	905	Starts (activates) the given watcher. Only active watchers will receive
…		…
805	to associate arbitrary data with your watcher. If you need more data and	988	to associate arbitrary data with your watcher. If you need more data and
806	don't want to allocate memory and store a pointer to it in that data	989	don't want to allocate memory and store a pointer to it in that data
807	member, you can also "subclass" the watcher type and provide your own	990	member, you can also "subclass" the watcher type and provide your own
808	data:	991	data:
809		992
810	struct my_io	993	struct my_io
811	{	994	{
812	struct ev_io io;	995	struct ev_io io;
813	int otherfd;	996	int otherfd;
814	void *somedata;	997	void *somedata;
815	struct whatever *mostinteresting;	998	struct whatever *mostinteresting;
816	}	999	}
817		1000
818	And since your callback will be called with a pointer to the watcher, you	1001	And since your callback will be called with a pointer to the watcher, you
819	can cast it back to your own type:	1002	can cast it back to your own type:
820		1003
821	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1004	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
822	{	1005	{
823	struct my_io *w = (struct my_io *)w_;	1006	struct my_io *w = (struct my_io *)w_;
824	...	1007	...
825	}	1008	}
826		1009
827	More interesting and less C-conformant ways of casting your callback type	1010	More interesting and less C-conformant ways of casting your callback type
828	instead have been omitted.	1011	instead have been omitted.
829		1012
830	Another common scenario is having some data structure with multiple	1013	Another common scenario is having some data structure with multiple
831	watchers:	1014	watchers:
832		1015
833	struct my_biggy	1016	struct my_biggy
834	{	1017	{
835	int some_data;	1018	int some_data;
836	ev_timer t1;	1019	ev_timer t1;
837	ev_timer t2;	1020	ev_timer t2;
838	}	1021	}
839		1022
840	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1023	In this case getting the pointer to C<my_biggy> is a bit more complicated,
841	you need to use C<offsetof>:	1024	you need to use C<offsetof>:
842		1025
843	#include <stddef.h>	1026	#include <stddef.h>
844		1027
845	static void	1028	static void
846	t1_cb (EV_P_ struct ev_timer *w, int revents)	1029	t1_cb (EV_P_ struct ev_timer *w, int revents)
847	{	1030	{
848	struct my_biggy big = (struct my_biggy *	1031	struct my_biggy big = (struct my_biggy *
849	(((char *)w) - offsetof (struct my_biggy, t1));	1032	(((char *)w) - offsetof (struct my_biggy, t1));
850	}	1033	}
851		1034
852	static void	1035	static void
853	t2_cb (EV_P_ struct ev_timer *w, int revents)	1036	t2_cb (EV_P_ struct ev_timer *w, int revents)
854	{	1037	{
855	struct my_biggy big = (struct my_biggy *	1038	struct my_biggy big = (struct my_biggy *
856	(((char *)w) - offsetof (struct my_biggy, t2));	1039	(((char *)w) - offsetof (struct my_biggy, t2));
857	}	1040	}
858		1041
859		1042
860	=head1 WATCHER TYPES	1043	=head1 WATCHER TYPES
861		1044
862	This section describes each watcher in detail, but will not repeat	1045	This section describes each watcher in detail, but will not repeat
…		…
886	In general you can register as many read and/or write event watchers per	1069	In general you can register as many read and/or write event watchers per
887	fd as you want (as long as you don't confuse yourself). Setting all file	1070	fd as you want (as long as you don't confuse yourself). Setting all file
888	descriptors to non-blocking mode is also usually a good idea (but not	1071	descriptors to non-blocking mode is also usually a good idea (but not
889	required if you know what you are doing).	1072	required if you know what you are doing).
890		1073
891	You have to be careful with dup'ed file descriptors, though. Some backends
892	(the linux epoll backend is a notable example) cannot handle dup'ed file
893	descriptors correctly if you register interest in two or more fds pointing
894	to the same underlying file/socket/etc. description (that is, they share
895	the same underlying "file open").
896
897	If you must do this, then force the use of a known-to-be-good backend	1074	If you must do this, then force the use of a known-to-be-good backend
898	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1075	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
899	C<EVBACKEND_POLL>).	1076	C<EVBACKEND_POLL>).
900		1077
901	Another thing you have to watch out for is that it is quite easy to	1078	Another thing you have to watch out for is that it is quite easy to
902	receive "spurious" readyness notifications, that is your callback might	1079	receive "spurious" readiness notifications, that is your callback might
903	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1080	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
904	because there is no data. Not only are some backends known to create a	1081	because there is no data. Not only are some backends known to create a
905	lot of those (for example solaris ports), it is very easy to get into	1082	lot of those (for example Solaris ports), it is very easy to get into
906	this situation even with a relatively standard program structure. Thus	1083	this situation even with a relatively standard program structure. Thus
907	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1084	it is best to always use non-blocking I/O: An extra C<read>(2) returning
908	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1085	C<EAGAIN> is far preferable to a program hanging until some data arrives.
909		1086
910	If you cannot run the fd in non-blocking mode (for example you should not	1087	If you cannot run the fd in non-blocking mode (for example you should not
911	play around with an Xlib connection), then you have to seperately re-test	1088	play around with an Xlib connection), then you have to separately re-test
912	whether a file descriptor is really ready with a known-to-be good interface	1089	whether a file descriptor is really ready with a known-to-be good interface
913	such as poll (fortunately in our Xlib example, Xlib already does this on	1090	such as poll (fortunately in our Xlib example, Xlib already does this on
914	its own, so its quite safe to use).	1091	its own, so its quite safe to use).
915		1092
916	=head3 The special problem of disappearing file descriptors	1093	=head3 The special problem of disappearing file descriptors
917		1094
918	Some backends (e.g kqueue, epoll) need to be told about closing a file	1095	Some backends (e.g. kqueue, epoll) need to be told about closing a file
919	descriptor (either by calling C<close> explicitly or by any other means,	1096	descriptor (either by calling C<close> explicitly or by any other means,
920	such as C<dup>). The reason is that you register interest in some file	1097	such as C<dup>). The reason is that you register interest in some file
921	descriptor, but when it goes away, the operating system will silently drop	1098	descriptor, but when it goes away, the operating system will silently drop
922	this interest. If another file descriptor with the same number then is	1099	this interest. If another file descriptor with the same number then is
923	registered with libev, there is no efficient way to see that this is, in	1100	registered with libev, there is no efficient way to see that this is, in
…		…
932		1109
933	This is how one would do it normally anyway, the important point is that	1110	This is how one would do it normally anyway, the important point is that
934	the libev application should not optimise around libev but should leave	1111	the libev application should not optimise around libev but should leave
935	optimisations to libev.	1112	optimisations to libev.
936		1113
		1114	=head3 The special problem of dup'ed file descriptors
		1115
		1116	Some backends (e.g. epoll), cannot register events for file descriptors,
		1117	but only events for the underlying file descriptions. That means when you
		1118	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1119	events for them, only one file descriptor might actually receive events.
		1120
		1121	There is no workaround possible except not registering events
		1122	for potentially C<dup ()>'ed file descriptors, or to resort to
		1123	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1124
		1125	=head3 The special problem of fork
		1126
		1127	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1128	useless behaviour. Libev fully supports fork, but needs to be told about
		1129	it in the child.
		1130
		1131	To support fork in your programs, you either have to call
		1132	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1133	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1134	C<EVBACKEND_POLL>.
		1135
		1136	=head3 The special problem of SIGPIPE
		1137
		1138	While not really specific to libev, it is easy to forget about SIGPIPE:
		1139	when reading from a pipe whose other end has been closed, your program
		1140	gets send a SIGPIPE, which, by default, aborts your program. For most
		1141	programs this is sensible behaviour, for daemons, this is usually
		1142	undesirable.
		1143
		1144	So when you encounter spurious, unexplained daemon exits, make sure you
		1145	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1146	somewhere, as that would have given you a big clue).
		1147
937		1148
938	=head3 Watcher-Specific Functions	1149	=head3 Watcher-Specific Functions
939		1150
940	=over 4	1151	=over 4
941		1152
942	=item ev_io_init (ev_io *, callback, int fd, int events)	1153	=item ev_io_init (ev_io *, callback, int fd, int events)
943		1154
944	=item ev_io_set (ev_io *, int fd, int events)	1155	=item ev_io_set (ev_io *, int fd, int events)
945		1156
946	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1157	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
947	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1158	receive events for and events is either C<EV_READ>, C<EV_WRITE> or
948	C<EV_READ | EV_WRITE> to receive the given events.	1159	C<EV_READ | EV_WRITE> to receive the given events.
949		1160
950	=item int fd [read-only]	1161	=item int fd [read-only]
951		1162
952	The file descriptor being watched.	1163	The file descriptor being watched.
…		…
954	=item int events [read-only]	1165	=item int events [read-only]
955		1166
956	The events being watched.	1167	The events being watched.
957		1168
958	=back	1169	=back
		1170
		1171	=head3 Examples
959		1172
960	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1173	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
961	readable, but only once. Since it is likely line-buffered, you could	1174	readable, but only once. Since it is likely line-buffered, you could
962	attempt to read a whole line in the callback.	1175	attempt to read a whole line in the callback.
963		1176
964	static void	1177	static void
965	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1178	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
966	{	1179	{
967	ev_io_stop (loop, w);	1180	ev_io_stop (loop, w);
968	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1181	.. read from stdin here (or from w->fd) and haqndle any I/O errors
969	}	1182	}
970		1183
971	...	1184	...
972	struct ev_loop *loop = ev_default_init (0);	1185	struct ev_loop *loop = ev_default_init (0);
973	struct ev_io stdin_readable;	1186	struct ev_io stdin_readable;
974	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1187	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
975	ev_io_start (loop, &stdin_readable);	1188	ev_io_start (loop, &stdin_readable);
976	ev_loop (loop, 0);	1189	ev_loop (loop, 0);
977		1190
978		1191
979	=head2 C<ev_timer> - relative and optionally repeating timeouts	1192	=head2 C<ev_timer> - relative and optionally repeating timeouts
980		1193
981	Timer watchers are simple relative timers that generate an event after a	1194	Timer watchers are simple relative timers that generate an event after a
982	given time, and optionally repeating in regular intervals after that.	1195	given time, and optionally repeating in regular intervals after that.
983		1196
984	The timers are based on real time, that is, if you register an event that	1197	The timers are based on real time, that is, if you register an event that
985	times out after an hour and you reset your system clock to last years	1198	times out after an hour and you reset your system clock to January last
986	time, it will still time out after (roughly) and hour. "Roughly" because	1199	year, it will still time out after (roughly) and hour. "Roughly" because
987	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1200	detecting time jumps is hard, and some inaccuracies are unavoidable (the
988	monotonic clock option helps a lot here).	1201	monotonic clock option helps a lot here).
989		1202
990	The relative timeouts are calculated relative to the C<ev_now ()>	1203	The relative timeouts are calculated relative to the C<ev_now ()>
991	time. This is usually the right thing as this timestamp refers to the time	1204	time. This is usually the right thing as this timestamp refers to the time
…		…
993	you suspect event processing to be delayed and you I<need> to base the timeout	1206	you suspect event processing to be delayed and you I<need> to base the timeout
994	on the current time, use something like this to adjust for this:	1207	on the current time, use something like this to adjust for this:
995		1208
996	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1209	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
997		1210
998	The callback is guarenteed to be invoked only when its timeout has passed,	1211	The callback is guaranteed to be invoked only after its timeout has passed,
999	but if multiple timers become ready during the same loop iteration then	1212	but if multiple timers become ready during the same loop iteration then
1000	order of execution is undefined.	1213	order of execution is undefined.
1001		1214
1002	=head3 Watcher-Specific Functions and Data Members	1215	=head3 Watcher-Specific Functions and Data Members
1003		1216
…		…
1005		1218
1006	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1219	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1007		1220
1008	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1221	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1009		1222
1010	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1223	Configure the timer to trigger after C<after> seconds. If C<repeat>
1011	C<0.>, then it will automatically be stopped. If it is positive, then the	1224	is C<0.>, then it will automatically be stopped once the timeout is
1012	timer will automatically be configured to trigger again C<repeat> seconds	1225	reached. If it is positive, then the timer will automatically be
1013	later, again, and again, until stopped manually.	1226	configured to trigger again C<repeat> seconds later, again, and again,
		1227	until stopped manually.
1014		1228
1015	The timer itself will do a best-effort at avoiding drift, that is, if you	1229	The timer itself will do a best-effort at avoiding drift, that is, if
1016	configure a timer to trigger every 10 seconds, then it will trigger at	1230	you configure a timer to trigger every 10 seconds, then it will normally
1017	exactly 10 second intervals. If, however, your program cannot keep up with	1231	trigger at exactly 10 second intervals. If, however, your program cannot
1018	the timer (because it takes longer than those 10 seconds to do stuff) the	1232	keep up with the timer (because it takes longer than those 10 seconds to
1019	timer will not fire more than once per event loop iteration.	1233	do stuff) the timer will not fire more than once per event loop iteration.
1020		1234
1021	=item ev_timer_again (loop)	1235	=item ev_timer_again (loop, ev_timer *)
1022		1236
1023	This will act as if the timer timed out and restart it again if it is	1237	This will act as if the timer timed out and restart it again if it is
1024	repeating. The exact semantics are:	1238	repeating. The exact semantics are:
1025		1239
1026	If the timer is pending, its pending status is cleared.	1240	If the timer is pending, its pending status is cleared.
1027		1241
1028	If the timer is started but nonrepeating, stop it (as if it timed out).	1242	If the timer is started but non-repeating, stop it (as if it timed out).
1029		1243
1030	If the timer is repeating, either start it if necessary (with the	1244	If the timer is repeating, either start it if necessary (with the
1031	C<repeat> value), or reset the running timer to the C<repeat> value.	1245	C<repeat> value), or reset the running timer to the C<repeat> value.
1032		1246
1033	This sounds a bit complicated, but here is a useful and typical	1247	This sounds a bit complicated, but here is a useful and typical
1034	example: Imagine you have a tcp connection and you want a so-called idle	1248	example: Imagine you have a TCP connection and you want a so-called idle
1035	timeout, that is, you want to be called when there have been, say, 60	1249	timeout, that is, you want to be called when there have been, say, 60
1036	seconds of inactivity on the socket. The easiest way to do this is to	1250	seconds of inactivity on the socket. The easiest way to do this is to
1037	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1251	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1038	C<ev_timer_again> each time you successfully read or write some data. If	1252	C<ev_timer_again> each time you successfully read or write some data. If
1039	you go into an idle state where you do not expect data to travel on the	1253	you go into an idle state where you do not expect data to travel on the
…		…
1061	or C<ev_timer_again> is called and determines the next timeout (if any),	1275	or C<ev_timer_again> is called and determines the next timeout (if any),
1062	which is also when any modifications are taken into account.	1276	which is also when any modifications are taken into account.
1063		1277
1064	=back	1278	=back
1065		1279
		1280	=head3 Examples
		1281
1066	Example: Create a timer that fires after 60 seconds.	1282	Example: Create a timer that fires after 60 seconds.
1067		1283
1068	static void	1284	static void
1069	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1285	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1070	{	1286	{
1071	.. one minute over, w is actually stopped right here	1287	.. one minute over, w is actually stopped right here
1072	}	1288	}
1073		1289
1074	struct ev_timer mytimer;	1290	struct ev_timer mytimer;
1075	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1291	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1076	ev_timer_start (loop, &mytimer);	1292	ev_timer_start (loop, &mytimer);
1077		1293
1078	Example: Create a timeout timer that times out after 10 seconds of	1294	Example: Create a timeout timer that times out after 10 seconds of
1079	inactivity.	1295	inactivity.
1080		1296
1081	static void	1297	static void
1082	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1298	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1083	{	1299	{
1084	.. ten seconds without any activity	1300	.. ten seconds without any activity
1085	}	1301	}
1086		1302
1087	struct ev_timer mytimer;	1303	struct ev_timer mytimer;
1088	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1304	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1089	ev_timer_again (&mytimer); /* start timer */	1305	ev_timer_again (&mytimer); /* start timer */
1090	ev_loop (loop, 0);	1306	ev_loop (loop, 0);
1091		1307
1092	// and in some piece of code that gets executed on any "activity":	1308	// and in some piece of code that gets executed on any "activity":
1093	// reset the timeout to start ticking again at 10 seconds	1309	// reset the timeout to start ticking again at 10 seconds
1094	ev_timer_again (&mytimer);	1310	ev_timer_again (&mytimer);
1095		1311
1096		1312
1097	=head2 C<ev_periodic> - to cron or not to cron?	1313	=head2 C<ev_periodic> - to cron or not to cron?
1098		1314
1099	Periodic watchers are also timers of a kind, but they are very versatile	1315	Periodic watchers are also timers of a kind, but they are very versatile
1100	(and unfortunately a bit complex).	1316	(and unfortunately a bit complex).
1101		1317
1102	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1318	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1103	but on wallclock time (absolute time). You can tell a periodic watcher	1319	but on wall clock time (absolute time). You can tell a periodic watcher
1104	to trigger "at" some specific point in time. For example, if you tell a	1320	to trigger after some specific point in time. For example, if you tell a
1105	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1321	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1106	+ 10.>) and then reset your system clock to the last year, then it will	1322	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1323	clock to January of the previous year, then it will take more than year
1107	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1324	to trigger the event (unlike an C<ev_timer>, which would still trigger
1108	roughly 10 seconds later).	1325	roughly 10 seconds later as it uses a relative timeout).
1109		1326
1110	They can also be used to implement vastly more complex timers, such as	1327	C<ev_periodic>s can also be used to implement vastly more complex timers,
1111	triggering an event on each midnight, local time or other, complicated,	1328	such as triggering an event on each "midnight, local time", or other
1112	rules.	1329	complicated, rules.
1113		1330
1114	As with timers, the callback is guarenteed to be invoked only when the	1331	As with timers, the callback is guaranteed to be invoked only when the
1115	time (C<at>) has been passed, but if multiple periodic timers become ready	1332	time (C<at>) has passed, but if multiple periodic timers become ready
1116	during the same loop iteration then order of execution is undefined.	1333	during the same loop iteration then order of execution is undefined.
1117		1334
1118	=head3 Watcher-Specific Functions and Data Members	1335	=head3 Watcher-Specific Functions and Data Members
1119		1336
1120	=over 4	1337	=over 4
…		…
1128		1345
1129	=over 4	1346	=over 4
1130		1347
1131	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1348	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1132		1349
1133	In this configuration the watcher triggers an event at the wallclock time	1350	In this configuration the watcher triggers an event after the wall clock
1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1351	time C<at> has passed and doesn't repeat. It will not adjust when a time
1135	that is, if it is to be run at January 1st 2011 then it will run when the	1352	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1136	system time reaches or surpasses this time.	1353	run when the system time reaches or surpasses this time.
1137		1354
1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1355	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1139		1356
1140	In this mode the watcher will always be scheduled to time out at the next	1357	In this mode the watcher will always be scheduled to time out at the next
1141	C<at + N * interval> time (for some integer N, which can also be negative)	1358	C<at + N * interval> time (for some integer N, which can also be negative)
1142	and then repeat, regardless of any time jumps.	1359	and then repeat, regardless of any time jumps.
1143		1360
1144	This can be used to create timers that do not drift with respect to system	1361	This can be used to create timers that do not drift with respect to system
1145	time:	1362	time, for example, here is a C<ev_periodic> that triggers each hour, on
		1363	the hour:
1146		1364
1147	ev_periodic_set (&periodic, 0., 3600., 0);	1365	ev_periodic_set (&periodic, 0., 3600., 0);
1148		1366
1149	This doesn't mean there will always be 3600 seconds in between triggers,	1367	This doesn't mean there will always be 3600 seconds in between triggers,
1150	but only that the the callback will be called when the system time shows a	1368	but only that the callback will be called when the system time shows a
1151	full hour (UTC), or more correctly, when the system time is evenly divisible	1369	full hour (UTC), or more correctly, when the system time is evenly divisible
1152	by 3600.	1370	by 3600.
1153		1371
1154	Another way to think about it (for the mathematically inclined) is that	1372	Another way to think about it (for the mathematically inclined) is that
1155	C<ev_periodic> will try to run the callback in this mode at the next possible	1373	C<ev_periodic> will try to run the callback in this mode at the next possible
1156	time where C<time = at (mod interval)>, regardless of any time jumps.	1374	time where C<time = at (mod interval)>, regardless of any time jumps.
1157		1375
1158	For numerical stability it is preferable that the C<at> value is near	1376	For numerical stability it is preferable that the C<at> value is near
1159	C<ev_now ()> (the current time), but there is no range requirement for	1377	C<ev_now ()> (the current time), but there is no range requirement for
1160	this value.	1378	this value, and in fact is often specified as zero.
		1379
		1380	Note also that there is an upper limit to how often a timer can fire (CPU
		1381	speed for example), so if C<interval> is very small then timing stability
		1382	will of course deteriorate. Libev itself tries to be exact to be about one
		1383	millisecond (if the OS supports it and the machine is fast enough).
1161		1384
1162	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1385	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1163		1386
1164	In this mode the values for C<interval> and C<at> are both being	1387	In this mode the values for C<interval> and C<at> are both being
1165	ignored. Instead, each time the periodic watcher gets scheduled, the	1388	ignored. Instead, each time the periodic watcher gets scheduled, the
1166	reschedule callback will be called with the watcher as first, and the	1389	reschedule callback will be called with the watcher as first, and the
1167	current time as second argument.	1390	current time as second argument.
1168		1391
1169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1392	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1170	ever, or make any event loop modifications>. If you need to stop it,	1393	ever, or make ANY event loop modifications whatsoever>.
1171	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1172	starting an C<ev_prepare> watcher, which is legal).
1173		1394
		1395	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1396	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1397	only event loop modification you are allowed to do).
		1398
1174	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1399	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1175	ev_tstamp now)>, e.g.:	1400	*w, ev_tstamp now)>, e.g.:
1176		1401
1177	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1402	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1178	{	1403	{
1179	return now + 60.;	1404	return now + 60.;
1180	}	1405	}
…		…
1182	It must return the next time to trigger, based on the passed time value	1407	It must return the next time to trigger, based on the passed time value
1183	(that is, the lowest time value larger than to the second argument). It	1408	(that is, the lowest time value larger than to the second argument). It
1184	will usually be called just before the callback will be triggered, but	1409	will usually be called just before the callback will be triggered, but
1185	might be called at other times, too.	1410	might be called at other times, too.
1186		1411
1187	NOTE: I<< This callback must always return a time that is later than the	1412	NOTE: I<< This callback must always return a time that is higher than or
1188	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1413	equal to the passed C<now> value >>.
1189		1414
1190	This can be used to create very complex timers, such as a timer that	1415	This can be used to create very complex timers, such as a timer that
1191	triggers on each midnight, local time. To do this, you would calculate the	1416	triggers on "next midnight, local time". To do this, you would calculate the
1192	next midnight after C<now> and return the timestamp value for this. How	1417	next midnight after C<now> and return the timestamp value for this. How
1193	you do this is, again, up to you (but it is not trivial, which is the main	1418	you do this is, again, up to you (but it is not trivial, which is the main
1194	reason I omitted it as an example).	1419	reason I omitted it as an example).
1195		1420
1196	=back	1421	=back
…		…
1200	Simply stops and restarts the periodic watcher again. This is only useful	1425	Simply stops and restarts the periodic watcher again. This is only useful
1201	when you changed some parameters or the reschedule callback would return	1426	when you changed some parameters or the reschedule callback would return
1202	a different time than the last time it was called (e.g. in a crond like	1427	a different time than the last time it was called (e.g. in a crond like
1203	program when the crontabs have changed).	1428	program when the crontabs have changed).
1204		1429
		1430	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1431
		1432	When active, returns the absolute time that the watcher is supposed to
		1433	trigger next.
		1434
1205	=item ev_tstamp offset [read-write]	1435	=item ev_tstamp offset [read-write]
1206		1436
1207	When repeating, this contains the offset value, otherwise this is the	1437	When repeating, this contains the offset value, otherwise this is the
1208	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1438	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1209		1439
…		…
1222	switched off. Can be changed any time, but changes only take effect when	1452	switched off. Can be changed any time, but changes only take effect when
1223	the periodic timer fires or C<ev_periodic_again> is being called.	1453	the periodic timer fires or C<ev_periodic_again> is being called.
1224		1454
1225	=back	1455	=back
1226		1456
		1457	=head3 Examples
		1458
1227	Example: Call a callback every hour, or, more precisely, whenever the	1459	Example: Call a callback every hour, or, more precisely, whenever the
1228	system clock is divisible by 3600. The callback invocation times have	1460	system clock is divisible by 3600. The callback invocation times have
1229	potentially a lot of jittering, but good long-term stability.	1461	potentially a lot of jitter, but good long-term stability.
1230		1462
1231	static void	1463	static void
1232	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1464	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1233	{	1465	{
1234	... its now a full hour (UTC, or TAI or whatever your clock follows)	1466	... its now a full hour (UTC, or TAI or whatever your clock follows)
1235	}	1467	}
1236		1468
1237	struct ev_periodic hourly_tick;	1469	struct ev_periodic hourly_tick;
1238	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1470	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1239	ev_periodic_start (loop, &hourly_tick);	1471	ev_periodic_start (loop, &hourly_tick);
1240		1472
1241	Example: The same as above, but use a reschedule callback to do it:	1473	Example: The same as above, but use a reschedule callback to do it:
1242		1474
1243	#include <math.h>	1475	#include <math.h>
1244		1476
1245	static ev_tstamp	1477	static ev_tstamp
1246	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1478	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1247	{	1479	{
1248	return fmod (now, 3600.) + 3600.;	1480	return fmod (now, 3600.) + 3600.;
1249	}	1481	}
1250		1482
1251	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1483	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1252		1484
1253	Example: Call a callback every hour, starting now:	1485	Example: Call a callback every hour, starting now:
1254		1486
1255	struct ev_periodic hourly_tick;	1487	struct ev_periodic hourly_tick;
1256	ev_periodic_init (&hourly_tick, clock_cb,	1488	ev_periodic_init (&hourly_tick, clock_cb,
1257	fmod (ev_now (loop), 3600.), 3600., 0);	1489	fmod (ev_now (loop), 3600.), 3600., 0);
1258	ev_periodic_start (loop, &hourly_tick);	1490	ev_periodic_start (loop, &hourly_tick);
1259		1491
1260		1492
1261	=head2 C<ev_signal> - signal me when a signal gets signalled!	1493	=head2 C<ev_signal> - signal me when a signal gets signalled!
1262		1494
1263	Signal watchers will trigger an event when the process receives a specific	1495	Signal watchers will trigger an event when the process receives a specific
…		…
1270	with the kernel (thus it coexists with your own signal handlers as long	1502	with the kernel (thus it coexists with your own signal handlers as long
1271	as you don't register any with libev). Similarly, when the last signal	1503	as you don't register any with libev). Similarly, when the last signal
1272	watcher for a signal is stopped libev will reset the signal handler to	1504	watcher for a signal is stopped libev will reset the signal handler to
1273	SIG_DFL (regardless of what it was set to before).	1505	SIG_DFL (regardless of what it was set to before).
1274		1506
		1507	If possible and supported, libev will install its handlers with
		1508	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1509	interrupted. If you have a problem with system calls getting interrupted by
		1510	signals you can block all signals in an C<ev_check> watcher and unblock
		1511	them in an C<ev_prepare> watcher.
		1512
1275	=head3 Watcher-Specific Functions and Data Members	1513	=head3 Watcher-Specific Functions and Data Members
1276		1514
1277	=over 4	1515	=over 4
1278		1516
1279	=item ev_signal_init (ev_signal *, callback, int signum)	1517	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1287		1525
1288	The signal the watcher watches out for.	1526	The signal the watcher watches out for.
1289		1527
1290	=back	1528	=back
1291		1529
		1530	=head3 Examples
		1531
		1532	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1533
		1534	static void
		1535	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1536	{
		1537	ev_unloop (loop, EVUNLOOP_ALL);
		1538	}
		1539
		1540	struct ev_signal signal_watcher;
		1541	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1542	ev_signal_start (loop, &sigint_cb);
		1543
1292		1544
1293	=head2 C<ev_child> - watch out for process status changes	1545	=head2 C<ev_child> - watch out for process status changes
1294		1546
1295	Child watchers trigger when your process receives a SIGCHLD in response to	1547	Child watchers trigger when your process receives a SIGCHLD in response to
1296	some child status changes (most typically when a child of yours dies).	1548	some child status changes (most typically when a child of yours dies). It
		1549	is permissible to install a child watcher I<after> the child has been
		1550	forked (which implies it might have already exited), as long as the event
		1551	loop isn't entered (or is continued from a watcher).
		1552
		1553	Only the default event loop is capable of handling signals, and therefore
		1554	you can only register child watchers in the default event loop.
		1555
		1556	=head3 Process Interaction
		1557
		1558	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1559	initialised. This is necessary to guarantee proper behaviour even if
		1560	the first child watcher is started after the child exits. The occurrence
		1561	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1562	synchronously as part of the event loop processing. Libev always reaps all
		1563	children, even ones not watched.
		1564
		1565	=head3 Overriding the Built-In Processing
		1566
		1567	Libev offers no special support for overriding the built-in child
		1568	processing, but if your application collides with libev's default child
		1569	handler, you can override it easily by installing your own handler for
		1570	C<SIGCHLD> after initialising the default loop, and making sure the
		1571	default loop never gets destroyed. You are encouraged, however, to use an
		1572	event-based approach to child reaping and thus use libev's support for
		1573	that, so other libev users can use C<ev_child> watchers freely.
1297		1574
1298	=head3 Watcher-Specific Functions and Data Members	1575	=head3 Watcher-Specific Functions and Data Members
1299		1576
1300	=over 4	1577	=over 4
1301		1578
1302	=item ev_child_init (ev_child *, callback, int pid)	1579	=item ev_child_init (ev_child *, callback, int pid, int trace)
1303		1580
1304	=item ev_child_set (ev_child *, int pid)	1581	=item ev_child_set (ev_child *, int pid, int trace)
1305		1582
1306	Configures the watcher to wait for status changes of process C<pid> (or	1583	Configures the watcher to wait for status changes of process C<pid> (or
1307	I<any> process if C<pid> is specified as C<0>). The callback can look	1584	I<any> process if C<pid> is specified as C<0>). The callback can look
1308	at the C<rstatus> member of the C<ev_child> watcher structure to see	1585	at the C<rstatus> member of the C<ev_child> watcher structure to see
1309	the status word (use the macros from C<sys/wait.h> and see your systems	1586	the status word (use the macros from C<sys/wait.h> and see your systems
1310	C<waitpid> documentation). The C<rpid> member contains the pid of the	1587	C<waitpid> documentation). The C<rpid> member contains the pid of the
1311	process causing the status change.	1588	process causing the status change. C<trace> must be either C<0> (only
		1589	activate the watcher when the process terminates) or C<1> (additionally
		1590	activate the watcher when the process is stopped or continued).
1312		1591
1313	=item int pid [read-only]	1592	=item int pid [read-only]
1314		1593
1315	The process id this watcher watches out for, or C<0>, meaning any process id.	1594	The process id this watcher watches out for, or C<0>, meaning any process id.
1316		1595
…		…
1323	The process exit/trace status caused by C<rpid> (see your systems	1602	The process exit/trace status caused by C<rpid> (see your systems
1324	C<waitpid> and C<sys/wait.h> documentation for details).	1603	C<waitpid> and C<sys/wait.h> documentation for details).
1325		1604
1326	=back	1605	=back
1327		1606
1328	Example: Try to exit cleanly on SIGINT and SIGTERM.	1607	=head3 Examples
1329		1608
		1609	Example: C<fork()> a new process and install a child handler to wait for
		1610	its completion.
		1611
		1612	ev_child cw;
		1613
1330	static void	1614	static void
1331	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1615	child_cb (EV_P_ struct ev_child *w, int revents)
1332	{	1616	{
1333	ev_unloop (loop, EVUNLOOP_ALL);	1617	ev_child_stop (EV_A_ w);
		1618	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1334	}	1619	}
1335		1620
1336	struct ev_signal signal_watcher;	1621	pid_t pid = fork ();
1337	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1622
1338	ev_signal_start (loop, &sigint_cb);	1623	if (pid < 0)
		1624	// error
		1625	else if (pid == 0)
		1626	{
		1627	// the forked child executes here
		1628	exit (1);
		1629	}
		1630	else
		1631	{
		1632	ev_child_init (&cw, child_cb, pid, 0);
		1633	ev_child_start (EV_DEFAULT_ &cw);
		1634	}
1339		1635
1340		1636
1341	=head2 C<ev_stat> - did the file attributes just change?	1637	=head2 C<ev_stat> - did the file attributes just change?
1342		1638
1343	This watches a filesystem path for attribute changes. That is, it calls	1639	This watches a file system path for attribute changes. That is, it calls
1344	C<stat> regularly (or when the OS says it changed) and sees if it changed	1640	C<stat> regularly (or when the OS says it changed) and sees if it changed
1345	compared to the last time, invoking the callback if it did.	1641	compared to the last time, invoking the callback if it did.
1346		1642
1347	The path does not need to exist: changing from "path exists" to "path does	1643	The path does not need to exist: changing from "path exists" to "path does
1348	not exist" is a status change like any other. The condition "path does	1644	not exist" is a status change like any other. The condition "path does
…		…
1366	as even with OS-supported change notifications, this can be	1662	as even with OS-supported change notifications, this can be
1367	resource-intensive.	1663	resource-intensive.
1368		1664
1369	At the time of this writing, only the Linux inotify interface is	1665	At the time of this writing, only the Linux inotify interface is
1370	implemented (implementing kqueue support is left as an exercise for the	1666	implemented (implementing kqueue support is left as an exercise for the
		1667	reader, note, however, that the author sees no way of implementing ev_stat
1371	reader). Inotify will be used to give hints only and should not change the	1668	semantics with kqueue). Inotify will be used to give hints only and should
1372	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1669	not change the semantics of C<ev_stat> watchers, which means that libev
1373	to fall back to regular polling again even with inotify, but changes are	1670	sometimes needs to fall back to regular polling again even with inotify,
1374	usually detected immediately, and if the file exists there will be no	1671	but changes are usually detected immediately, and if the file exists there
1375	polling.	1672	will be no polling.
		1673
		1674	=head3 ABI Issues (Largefile Support)
		1675
		1676	Libev by default (unless the user overrides this) uses the default
		1677	compilation environment, which means that on systems with large file
		1678	support disabled by default, you get the 32 bit version of the stat
		1679	structure. When using the library from programs that change the ABI to
		1680	use 64 bit file offsets the programs will fail. In that case you have to
		1681	compile libev with the same flags to get binary compatibility. This is
		1682	obviously the case with any flags that change the ABI, but the problem is
		1683	most noticeably disabled with ev_stat and large file support.
		1684
		1685	The solution for this is to lobby your distribution maker to make large
		1686	file interfaces available by default (as e.g. FreeBSD does) and not
		1687	optional. Libev cannot simply switch on large file support because it has
		1688	to exchange stat structures with application programs compiled using the
		1689	default compilation environment.
		1690
		1691	=head3 Inotify
		1692
		1693	When C<inotify (7)> support has been compiled into libev (generally only
		1694	available on Linux) and present at runtime, it will be used to speed up
		1695	change detection where possible. The inotify descriptor will be created lazily
		1696	when the first C<ev_stat> watcher is being started.
		1697
		1698	Inotify presence does not change the semantics of C<ev_stat> watchers
		1699	except that changes might be detected earlier, and in some cases, to avoid
		1700	making regular C<stat> calls. Even in the presence of inotify support
		1701	there are many cases where libev has to resort to regular C<stat> polling.
		1702
		1703	(There is no support for kqueue, as apparently it cannot be used to
		1704	implement this functionality, due to the requirement of having a file
		1705	descriptor open on the object at all times).
		1706
		1707	=head3 The special problem of stat time resolution
		1708
		1709	The C<stat ()> system call only supports full-second resolution portably, and
		1710	even on systems where the resolution is higher, many file systems still
		1711	only support whole seconds.
		1712
		1713	That means that, if the time is the only thing that changes, you can
		1714	easily miss updates: on the first update, C<ev_stat> detects a change and
		1715	calls your callback, which does something. When there is another update
		1716	within the same second, C<ev_stat> will be unable to detect it as the stat
		1717	data does not change.
		1718
		1719	The solution to this is to delay acting on a change for slightly more
		1720	than a second (or till slightly after the next full second boundary), using
		1721	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1722	ev_timer_again (loop, w)>).
		1723
		1724	The C<.02> offset is added to work around small timing inconsistencies
		1725	of some operating systems (where the second counter of the current time
		1726	might be be delayed. One such system is the Linux kernel, where a call to
		1727	C<gettimeofday> might return a timestamp with a full second later than
		1728	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1729	update file times then there will be a small window where the kernel uses
		1730	the previous second to update file times but libev might already execute
		1731	the timer callback).
1376		1732
1377	=head3 Watcher-Specific Functions and Data Members	1733	=head3 Watcher-Specific Functions and Data Members
1378		1734
1379	=over 4	1735	=over 4
1380		1736
…		…
1386	C<path>. The C<interval> is a hint on how quickly a change is expected to	1742	C<path>. The C<interval> is a hint on how quickly a change is expected to
1387	be detected and should normally be specified as C<0> to let libev choose	1743	be detected and should normally be specified as C<0> to let libev choose
1388	a suitable value. The memory pointed to by C<path> must point to the same	1744	a suitable value. The memory pointed to by C<path> must point to the same
1389	path for as long as the watcher is active.	1745	path for as long as the watcher is active.
1390		1746
1391	The callback will be receive C<EV_STAT> when a change was detected,	1747	The callback will receive C<EV_STAT> when a change was detected, relative
1392	relative to the attributes at the time the watcher was started (or the	1748	to the attributes at the time the watcher was started (or the last change
1393	last change was detected).	1749	was detected).
1394		1750
1395	=item ev_stat_stat (ev_stat *)	1751	=item ev_stat_stat (loop, ev_stat *)
1396		1752
1397	Updates the stat buffer immediately with new values. If you change the	1753	Updates the stat buffer immediately with new values. If you change the
1398	watched path in your callback, you could call this fucntion to avoid	1754	watched path in your callback, you could call this function to avoid
1399	detecting this change (while introducing a race condition). Can also be	1755	detecting this change (while introducing a race condition if you are not
1400	useful simply to find out the new values.	1756	the only one changing the path). Can also be useful simply to find out the
		1757	new values.
1401		1758
1402	=item ev_statdata attr [read-only]	1759	=item ev_statdata attr [read-only]
1403		1760
1404	The most-recently detected attributes of the file. Although the type is of	1761	The most-recently detected attributes of the file. Although the type is
1405	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1762	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1406	suitable for your system. If the C<st_nlink> member is C<0>, then there	1763	suitable for your system, but you can only rely on the POSIX-standardised
		1764	members to be present. If the C<st_nlink> member is C<0>, then there was
1407	was some error while C<stat>ing the file.	1765	some error while C<stat>ing the file.
1408		1766
1409	=item ev_statdata prev [read-only]	1767	=item ev_statdata prev [read-only]
1410		1768
1411	The previous attributes of the file. The callback gets invoked whenever	1769	The previous attributes of the file. The callback gets invoked whenever
1412	C<prev> != C<attr>.	1770	C<prev> != C<attr>, or, more precisely, one or more of these members
		1771	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1772	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1413		1773
1414	=item ev_tstamp interval [read-only]	1774	=item ev_tstamp interval [read-only]
1415		1775
1416	The specified interval.	1776	The specified interval.
1417		1777
1418	=item const char *path [read-only]	1778	=item const char *path [read-only]
1419		1779
1420	The filesystem path that is being watched.	1780	The file system path that is being watched.
1421		1781
1422	=back	1782	=back
1423		1783
		1784	=head3 Examples
		1785
1424	Example: Watch C</etc/passwd> for attribute changes.	1786	Example: Watch C</etc/passwd> for attribute changes.
1425		1787
1426	static void	1788	static void
1427	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1789	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1428	{	1790	{
1429	/* /etc/passwd changed in some way */	1791	/* /etc/passwd changed in some way */
1430	if (w->attr.st_nlink)	1792	if (w->attr.st_nlink)
1431	{	1793	{
1432	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1794	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1433	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1795	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1434	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1796	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1435	}	1797	}
1436	else	1798	else
1437	/* you shalt not abuse printf for puts */	1799	/* you shalt not abuse printf for puts */
1438	puts ("wow, /etc/passwd is not there, expect problems. "	1800	puts ("wow, /etc/passwd is not there, expect problems. "
1439	"if this is windows, they already arrived\n");	1801	"if this is windows, they already arrived\n");
1440	}	1802	}
1441		1803
1442	...	1804	...
1443	ev_stat passwd;	1805	ev_stat passwd;
1444		1806
1445	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1807	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1446	ev_stat_start (loop, &passwd);	1808	ev_stat_start (loop, &passwd);
		1809
		1810	Example: Like above, but additionally use a one-second delay so we do not
		1811	miss updates (however, frequent updates will delay processing, too, so
		1812	one might do the work both on C<ev_stat> callback invocation I<and> on
		1813	C<ev_timer> callback invocation).
		1814
		1815	static ev_stat passwd;
		1816	static ev_timer timer;
		1817
		1818	static void
		1819	timer_cb (EV_P_ ev_timer *w, int revents)
		1820	{
		1821	ev_timer_stop (EV_A_ w);
		1822
		1823	/* now it's one second after the most recent passwd change */
		1824	}
		1825
		1826	static void
		1827	stat_cb (EV_P_ ev_stat *w, int revents)
		1828	{
		1829	/* reset the one-second timer */
		1830	ev_timer_again (EV_A_ &timer);
		1831	}
		1832
		1833	...
		1834	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1835	ev_stat_start (loop, &passwd);
		1836	ev_timer_init (&timer, timer_cb, 0., 1.02);
1447		1837
1448		1838
1449	=head2 C<ev_idle> - when you've got nothing better to do...	1839	=head2 C<ev_idle> - when you've got nothing better to do...
1450		1840
1451	Idle watchers trigger events when no other events of the same or higher	1841	Idle watchers trigger events when no other events of the same or higher
…		…
1477	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1867	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1478	believe me.	1868	believe me.
1479		1869
1480	=back	1870	=back
1481		1871
		1872	=head3 Examples
		1873
1482	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1874	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1483	callback, free it. Also, use no error checking, as usual.	1875	callback, free it. Also, use no error checking, as usual.
1484		1876
1485	static void	1877	static void
1486	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1878	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1487	{	1879	{
1488	free (w);	1880	free (w);
1489	// now do something you wanted to do when the program has	1881	// now do something you wanted to do when the program has
1490	// no longer asnything immediate to do.	1882	// no longer anything immediate to do.
1491	}	1883	}
1492		1884
1493	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1885	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1494	ev_idle_init (idle_watcher, idle_cb);	1886	ev_idle_init (idle_watcher, idle_cb);
1495	ev_idle_start (loop, idle_cb);	1887	ev_idle_start (loop, idle_cb);
1496		1888
1497		1889
1498	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1890	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1499		1891
1500	Prepare and check watchers are usually (but not always) used in tandem:	1892	Prepare and check watchers are usually (but not always) used in tandem:
…		…
1519		1911
1520	This is done by examining in each prepare call which file descriptors need	1912	This is done by examining in each prepare call which file descriptors need
1521	to be watched by the other library, registering C<ev_io> watchers for	1913	to be watched by the other library, registering C<ev_io> watchers for
1522	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1914	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1523	provide just this functionality). Then, in the check watcher you check for	1915	provide just this functionality). Then, in the check watcher you check for
1524	any events that occured (by checking the pending status of all watchers	1916	any events that occurred (by checking the pending status of all watchers
1525	and stopping them) and call back into the library. The I/O and timer	1917	and stopping them) and call back into the library. The I/O and timer
1526	callbacks will never actually be called (but must be valid nevertheless,	1918	callbacks will never actually be called (but must be valid nevertheless,
1527	because you never know, you know?).	1919	because you never know, you know?).
1528		1920
1529	As another example, the Perl Coro module uses these hooks to integrate	1921	As another example, the Perl Coro module uses these hooks to integrate
…		…
1537		1929
1538	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1930	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1539	priority, to ensure that they are being run before any other watchers	1931	priority, to ensure that they are being run before any other watchers
1540	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1932	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1541	too) should not activate ("feed") events into libev. While libev fully	1933	too) should not activate ("feed") events into libev. While libev fully
1542	supports this, they will be called before other C<ev_check> watchers did	1934	supports this, they might get executed before other C<ev_check> watchers
1543	their job. As C<ev_check> watchers are often used to embed other event	1935	did their job. As C<ev_check> watchers are often used to embed other
1544	loops those other event loops might be in an unusable state until their	1936	(non-libev) event loops those other event loops might be in an unusable
1545	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1937	state until their C<ev_check> watcher ran (always remind yourself to
1546	others).	1938	coexist peacefully with others).
1547		1939
1548	=head3 Watcher-Specific Functions and Data Members	1940	=head3 Watcher-Specific Functions and Data Members
1549		1941
1550	=over 4	1942	=over 4
1551		1943
…		…
1557	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1949	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1558	macros, but using them is utterly, utterly and completely pointless.	1950	macros, but using them is utterly, utterly and completely pointless.
1559		1951
1560	=back	1952	=back
1561		1953
		1954	=head3 Examples
		1955
1562	There are a number of principal ways to embed other event loops or modules	1956	There are a number of principal ways to embed other event loops or modules
1563	into libev. Here are some ideas on how to include libadns into libev	1957	into libev. Here are some ideas on how to include libadns into libev
1564	(there is a Perl module named C<EV::ADNS> that does this, which you could	1958	(there is a Perl module named C<EV::ADNS> that does this, which you could
1565	use for an actually working example. Another Perl module named C<EV::Glib>	1959	use as a working example. Another Perl module named C<EV::Glib> embeds a
1566	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1960	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1567	into the Glib event loop).	1961	Glib event loop).
1568		1962
1569	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	1963	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1570	and in a check watcher, destroy them and call into libadns. What follows	1964	and in a check watcher, destroy them and call into libadns. What follows
1571	is pseudo-code only of course. This requires you to either use a low	1965	is pseudo-code only of course. This requires you to either use a low
1572	priority for the check watcher or use C<ev_clear_pending> explicitly, as	1966	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1573	the callbacks for the IO/timeout watchers might not have been called yet.	1967	the callbacks for the IO/timeout watchers might not have been called yet.
1574		1968
1575	static ev_io iow [nfd];	1969	static ev_io iow [nfd];
1576	static ev_timer tw;	1970	static ev_timer tw;
1577		1971
1578	static void	1972	static void
1579	io_cb (ev_loop *loop, ev_io *w, int revents)	1973	io_cb (ev_loop *loop, ev_io *w, int revents)
1580	{	1974	{
1581	}	1975	}
1582		1976
1583	// create io watchers for each fd and a timer before blocking	1977	// create io watchers for each fd and a timer before blocking
1584	static void	1978	static void
1585	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1979	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1586	{	1980	{
1587	int timeout = 3600000;	1981	int timeout = 3600000;
1588	struct pollfd fds [nfd];	1982	struct pollfd fds [nfd];
1589	// actual code will need to loop here and realloc etc.	1983	// actual code will need to loop here and realloc etc.
1590	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1984	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1591		1985
1592	/* the callback is illegal, but won't be called as we stop during check */	1986	/* the callback is illegal, but won't be called as we stop during check */
1593	ev_timer_init (&tw, 0, timeout * 1e-3);	1987	ev_timer_init (&tw, 0, timeout * 1e-3);
1594	ev_timer_start (loop, &tw);	1988	ev_timer_start (loop, &tw);
1595		1989
1596	// create one ev_io per pollfd	1990	// create one ev_io per pollfd
1597	for (int i = 0; i < nfd; ++i)	1991	for (int i = 0; i < nfd; ++i)
1598	{	1992	{
1599	ev_io_init (iow + i, io_cb, fds [i].fd,	1993	ev_io_init (iow + i, io_cb, fds [i].fd,
1600	((fds [i].events & POLLIN ? EV_READ : 0)	1994	((fds [i].events & POLLIN ? EV_READ : 0)
1601	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1995	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1602		1996
1603	fds [i].revents = 0;	1997	fds [i].revents = 0;
1604	ev_io_start (loop, iow + i);	1998	ev_io_start (loop, iow + i);
1605	}	1999	}
1606	}	2000	}
1607		2001
1608	// stop all watchers after blocking	2002	// stop all watchers after blocking
1609	static void	2003	static void
1610	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2004	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1611	{	2005	{
1612	ev_timer_stop (loop, &tw);	2006	ev_timer_stop (loop, &tw);
1613		2007
1614	for (int i = 0; i < nfd; ++i)	2008	for (int i = 0; i < nfd; ++i)
1615	{	2009	{
1616	// set the relevant poll flags	2010	// set the relevant poll flags
1617	// could also call adns_processreadable etc. here	2011	// could also call adns_processreadable etc. here
1618	struct pollfd *fd = fds + i;	2012	struct pollfd *fd = fds + i;
1619	int revents = ev_clear_pending (iow + i);	2013	int revents = ev_clear_pending (iow + i);
1620	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2014	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1621	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2015	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1622		2016
1623	// now stop the watcher	2017	// now stop the watcher
1624	ev_io_stop (loop, iow + i);	2018	ev_io_stop (loop, iow + i);
1625	}	2019	}
1626		2020
1627	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2021	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1628	}	2022	}
1629		2023
1630	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2024	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1631	in the prepare watcher and would dispose of the check watcher.	2025	in the prepare watcher and would dispose of the check watcher.
1632		2026
1633	Method 3: If the module to be embedded supports explicit event	2027	Method 3: If the module to be embedded supports explicit event
1634	notification (adns does), you can also make use of the actual watcher	2028	notification (libadns does), you can also make use of the actual watcher
1635	callbacks, and only destroy/create the watchers in the prepare watcher.	2029	callbacks, and only destroy/create the watchers in the prepare watcher.
1636		2030
1637	static void	2031	static void
1638	timer_cb (EV_P_ ev_timer *w, int revents)	2032	timer_cb (EV_P_ ev_timer *w, int revents)
1639	{	2033	{
1640	adns_state ads = (adns_state)w->data;	2034	adns_state ads = (adns_state)w->data;
1641	update_now (EV_A);	2035	update_now (EV_A);
1642		2036
1643	adns_processtimeouts (ads, &tv_now);	2037	adns_processtimeouts (ads, &tv_now);
1644	}	2038	}
1645		2039
1646	static void	2040	static void
1647	io_cb (EV_P_ ev_io *w, int revents)	2041	io_cb (EV_P_ ev_io *w, int revents)
1648	{	2042	{
1649	adns_state ads = (adns_state)w->data;	2043	adns_state ads = (adns_state)w->data;
1650	update_now (EV_A);	2044	update_now (EV_A);
1651		2045
1652	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2046	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1653	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2047	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1654	}	2048	}
1655		2049
1656	// do not ever call adns_afterpoll	2050	// do not ever call adns_afterpoll
1657		2051
1658	Method 4: Do not use a prepare or check watcher because the module you	2052	Method 4: Do not use a prepare or check watcher because the module you
1659	want to embed is too inflexible to support it. Instead, youc na override	2053	want to embed is too inflexible to support it. Instead, you can override
1660	their poll function. The drawback with this solution is that the main	2054	their poll function. The drawback with this solution is that the main
1661	loop is now no longer controllable by EV. The C<Glib::EV> module does	2055	loop is now no longer controllable by EV. The C<Glib::EV> module does
1662	this.	2056	this.
1663		2057
1664	static gint	2058	static gint
1665	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2059	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1666	{	2060	{
1667	int got_events = 0;	2061	int got_events = 0;
1668		2062
1669	for (n = 0; n < nfds; ++n)	2063	for (n = 0; n < nfds; ++n)
1670	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2064	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1671		2065
1672	if (timeout >= 0)	2066	if (timeout >= 0)
1673	// create/start timer	2067	// create/start timer
1674		2068
1675	// poll	2069	// poll
1676	ev_loop (EV_A_ 0);	2070	ev_loop (EV_A_ 0);
1677		2071
1678	// stop timer again	2072	// stop timer again
1679	if (timeout >= 0)	2073	if (timeout >= 0)
1680	ev_timer_stop (EV_A_ &to);	2074	ev_timer_stop (EV_A_ &to);
1681		2075
1682	// stop io watchers again - their callbacks should have set	2076	// stop io watchers again - their callbacks should have set
1683	for (n = 0; n < nfds; ++n)	2077	for (n = 0; n < nfds; ++n)
1684	ev_io_stop (EV_A_ iow [n]);	2078	ev_io_stop (EV_A_ iow [n]);
1685		2079
1686	return got_events;	2080	return got_events;
1687	}	2081	}
1688		2082
1689		2083
1690	=head2 C<ev_embed> - when one backend isn't enough...	2084	=head2 C<ev_embed> - when one backend isn't enough...
1691		2085
1692	This is a rather advanced watcher type that lets you embed one event loop	2086	This is a rather advanced watcher type that lets you embed one event loop
…		…
1734	portable one.	2128	portable one.
1735		2129
1736	So when you want to use this feature you will always have to be prepared	2130	So when you want to use this feature you will always have to be prepared
1737	that you cannot get an embeddable loop. The recommended way to get around	2131	that you cannot get an embeddable loop. The recommended way to get around
1738	this is to have a separate variables for your embeddable loop, try to	2132	this is to have a separate variables for your embeddable loop, try to
1739	create it, and if that fails, use the normal loop for everything:	2133	create it, and if that fails, use the normal loop for everything.
1740
1741	struct ev_loop *loop_hi = ev_default_init (0);
1742	struct ev_loop *loop_lo = 0;
1743	struct ev_embed embed;
1744
1745	// see if there is a chance of getting one that works
1746	// (remember that a flags value of 0 means autodetection)
1747	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1748	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1749	: 0;
1750
1751	// if we got one, then embed it, otherwise default to loop_hi
1752	if (loop_lo)
1753	{
1754	ev_embed_init (&embed, 0, loop_lo);
1755	ev_embed_start (loop_hi, &embed);
1756	}
1757	else
1758	loop_lo = loop_hi;
1759		2134
1760	=head3 Watcher-Specific Functions and Data Members	2135	=head3 Watcher-Specific Functions and Data Members
1761		2136
1762	=over 4	2137	=over 4
1763		2138
…		…
1767		2142
1768	Configures the watcher to embed the given loop, which must be	2143	Configures the watcher to embed the given loop, which must be
1769	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2144	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1770	invoked automatically, otherwise it is the responsibility of the callback	2145	invoked automatically, otherwise it is the responsibility of the callback
1771	to invoke it (it will continue to be called until the sweep has been done,	2146	to invoke it (it will continue to be called until the sweep has been done,
1772	if you do not want thta, you need to temporarily stop the embed watcher).	2147	if you do not want that, you need to temporarily stop the embed watcher).
1773		2148
1774	=item ev_embed_sweep (loop, ev_embed *)	2149	=item ev_embed_sweep (loop, ev_embed *)
1775		2150
1776	Make a single, non-blocking sweep over the embedded loop. This works	2151	Make a single, non-blocking sweep over the embedded loop. This works
1777	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2152	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1778	apropriate way for embedded loops.	2153	appropriate way for embedded loops.
1779		2154
1780	=item struct ev_loop *loop [read-only]	2155	=item struct ev_loop *other [read-only]
1781		2156
1782	The embedded event loop.	2157	The embedded event loop.
1783		2158
1784	=back	2159	=back
		2160
		2161	=head3 Examples
		2162
		2163	Example: Try to get an embeddable event loop and embed it into the default
		2164	event loop. If that is not possible, use the default loop. The default
		2165	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2166	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2167	used).
		2168
		2169	struct ev_loop *loop_hi = ev_default_init (0);
		2170	struct ev_loop *loop_lo = 0;
		2171	struct ev_embed embed;
		2172
		2173	// see if there is a chance of getting one that works
		2174	// (remember that a flags value of 0 means autodetection)
		2175	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2176	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2177	: 0;
		2178
		2179	// if we got one, then embed it, otherwise default to loop_hi
		2180	if (loop_lo)
		2181	{
		2182	ev_embed_init (&embed, 0, loop_lo);
		2183	ev_embed_start (loop_hi, &embed);
		2184	}
		2185	else
		2186	loop_lo = loop_hi;
		2187
		2188	Example: Check if kqueue is available but not recommended and create
		2189	a kqueue backend for use with sockets (which usually work with any
		2190	kqueue implementation). Store the kqueue/socket-only event loop in
		2191	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2192
		2193	struct ev_loop *loop = ev_default_init (0);
		2194	struct ev_loop *loop_socket = 0;
		2195	struct ev_embed embed;
		2196
		2197	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2198	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2199	{
		2200	ev_embed_init (&embed, 0, loop_socket);
		2201	ev_embed_start (loop, &embed);
		2202	}
		2203
		2204	if (!loop_socket)
		2205	loop_socket = loop;
		2206
		2207	// now use loop_socket for all sockets, and loop for everything else
1785		2208
1786		2209
1787	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2210	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1788		2211
1789	Fork watchers are called when a C<fork ()> was detected (usually because	2212	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1805	believe me.	2228	believe me.
1806		2229
1807	=back	2230	=back
1808		2231
1809		2232
		2233	=head2 C<ev_async> - how to wake up another event loop
		2234
		2235	In general, you cannot use an C<ev_loop> from multiple threads or other
		2236	asynchronous sources such as signal handlers (as opposed to multiple event
		2237	loops - those are of course safe to use in different threads).
		2238
		2239	Sometimes, however, you need to wake up another event loop you do not
		2240	control, for example because it belongs to another thread. This is what
		2241	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2242	can signal it by calling C<ev_async_send>, which is thread- and signal
		2243	safe.
		2244
		2245	This functionality is very similar to C<ev_signal> watchers, as signals,
		2246	too, are asynchronous in nature, and signals, too, will be compressed
		2247	(i.e. the number of callback invocations may be less than the number of
		2248	C<ev_async_sent> calls).
		2249
		2250	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2251	just the default loop.
		2252
		2253	=head3 Queueing
		2254
		2255	C<ev_async> does not support queueing of data in any way. The reason
		2256	is that the author does not know of a simple (or any) algorithm for a
		2257	multiple-writer-single-reader queue that works in all cases and doesn't
		2258	need elaborate support such as pthreads.
		2259
		2260	That means that if you want to queue data, you have to provide your own
		2261	queue. But at least I can tell you would implement locking around your
		2262	queue:
		2263
		2264	=over 4
		2265
		2266	=item queueing from a signal handler context
		2267
		2268	To implement race-free queueing, you simply add to the queue in the signal
		2269	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2270	some fictitious SIGUSR1 handler:
		2271
		2272	static ev_async mysig;
		2273
		2274	static void
		2275	sigusr1_handler (void)
		2276	{
		2277	sometype data;
		2278
		2279	// no locking etc.
		2280	queue_put (data);
		2281	ev_async_send (EV_DEFAULT_ &mysig);
		2282	}
		2283
		2284	static void
		2285	mysig_cb (EV_P_ ev_async *w, int revents)
		2286	{
		2287	sometype data;
		2288	sigset_t block, prev;
		2289
		2290	sigemptyset (&block);
		2291	sigaddset (&block, SIGUSR1);
		2292	sigprocmask (SIG_BLOCK, &block, &prev);
		2293
		2294	while (queue_get (&data))
		2295	process (data);
		2296
		2297	if (sigismember (&prev, SIGUSR1)
		2298	sigprocmask (SIG_UNBLOCK, &block, 0);
		2299	}
		2300
		2301	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2302	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2303	either...).
		2304
		2305	=item queueing from a thread context
		2306
		2307	The strategy for threads is different, as you cannot (easily) block
		2308	threads but you can easily preempt them, so to queue safely you need to
		2309	employ a traditional mutex lock, such as in this pthread example:
		2310
		2311	static ev_async mysig;
		2312	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2313
		2314	static void
		2315	otherthread (void)
		2316	{
		2317	// only need to lock the actual queueing operation
		2318	pthread_mutex_lock (&mymutex);
		2319	queue_put (data);
		2320	pthread_mutex_unlock (&mymutex);
		2321
		2322	ev_async_send (EV_DEFAULT_ &mysig);
		2323	}
		2324
		2325	static void
		2326	mysig_cb (EV_P_ ev_async *w, int revents)
		2327	{
		2328	pthread_mutex_lock (&mymutex);
		2329
		2330	while (queue_get (&data))
		2331	process (data);
		2332
		2333	pthread_mutex_unlock (&mymutex);
		2334	}
		2335
		2336	=back
		2337
		2338
		2339	=head3 Watcher-Specific Functions and Data Members
		2340
		2341	=over 4
		2342
		2343	=item ev_async_init (ev_async *, callback)
		2344
		2345	Initialises and configures the async watcher - it has no parameters of any
		2346	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2347	believe me.
		2348
		2349	=item ev_async_send (loop, ev_async *)
		2350
		2351	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2352	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2353	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2354	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2355	section below on what exactly this means).
		2356
		2357	This call incurs the overhead of a system call only once per loop iteration,
		2358	so while the overhead might be noticeable, it doesn't apply to repeated
		2359	calls to C<ev_async_send>.
		2360
		2361	=item bool = ev_async_pending (ev_async *)
		2362
		2363	Returns a non-zero value when C<ev_async_send> has been called on the
		2364	watcher but the event has not yet been processed (or even noted) by the
		2365	event loop.
		2366
		2367	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2368	the loop iterates next and checks for the watcher to have become active,
		2369	it will reset the flag again. C<ev_async_pending> can be used to very
		2370	quickly check whether invoking the loop might be a good idea.
		2371
		2372	Not that this does I<not> check whether the watcher itself is pending, only
		2373	whether it has been requested to make this watcher pending.
		2374
		2375	=back
		2376
		2377
1810	=head1 OTHER FUNCTIONS	2378	=head1 OTHER FUNCTIONS
1811		2379
1812	There are some other functions of possible interest. Described. Here. Now.	2380	There are some other functions of possible interest. Described. Here. Now.
1813		2381
1814	=over 4	2382	=over 4
…		…
1821	or timeout without having to allocate/configure/start/stop/free one or	2389	or timeout without having to allocate/configure/start/stop/free one or
1822	more watchers yourself.	2390	more watchers yourself.
1823		2391
1824	If C<fd> is less than 0, then no I/O watcher will be started and events	2392	If C<fd> is less than 0, then no I/O watcher will be started and events
1825	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2393	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1826	C<events> set will be craeted and started.	2394	C<events> set will be created and started.
1827		2395
1828	If C<timeout> is less than 0, then no timeout watcher will be	2396	If C<timeout> is less than 0, then no timeout watcher will be
1829	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2397	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1830	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2398	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1831	dubious value.	2399	dubious value.
…		…
1833	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2401	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1834	passed an C<revents> set like normal event callbacks (a combination of	2402	passed an C<revents> set like normal event callbacks (a combination of
1835	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2403	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1836	value passed to C<ev_once>:	2404	value passed to C<ev_once>:
1837		2405
1838	static void stdin_ready (int revents, void *arg)	2406	static void stdin_ready (int revents, void *arg)
1839	{	2407	{
1840	if (revents & EV_TIMEOUT)	2408	if (revents & EV_TIMEOUT)
1841	/* doh, nothing entered */;	2409	/* doh, nothing entered */;
1842	else if (revents & EV_READ)	2410	else if (revents & EV_READ)
1843	/* stdin might have data for us, joy! */;	2411	/* stdin might have data for us, joy! */;
1844	}	2412	}
1845		2413
1846	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2414	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1847		2415
1848	=item ev_feed_event (ev_loop *, watcher *, int revents)	2416	=item ev_feed_event (ev_loop *, watcher *, int revents)
1849		2417
1850	Feeds the given event set into the event loop, as if the specified event	2418	Feeds the given event set into the event loop, as if the specified event
1851	had happened for the specified watcher (which must be a pointer to an	2419	had happened for the specified watcher (which must be a pointer to an
…		…
1856	Feed an event on the given fd, as if a file descriptor backend detected	2424	Feed an event on the given fd, as if a file descriptor backend detected
1857	the given events it.	2425	the given events it.
1858		2426
1859	=item ev_feed_signal_event (ev_loop *loop, int signum)	2427	=item ev_feed_signal_event (ev_loop *loop, int signum)
1860		2428
1861	Feed an event as if the given signal occured (C<loop> must be the default	2429	Feed an event as if the given signal occurred (C<loop> must be the default
1862	loop!).	2430	loop!).
1863		2431
1864	=back	2432	=back
1865		2433
1866		2434
…		…
1882		2450
1883	=item * Priorities are not currently supported. Initialising priorities	2451	=item * Priorities are not currently supported. Initialising priorities
1884	will fail and all watchers will have the same priority, even though there	2452	will fail and all watchers will have the same priority, even though there
1885	is an ev_pri field.	2453	is an ev_pri field.
1886		2454
		2455	=item * In libevent, the last base created gets the signals, in libev, the
		2456	first base created (== the default loop) gets the signals.
		2457
1887	=item * Other members are not supported.	2458	=item * Other members are not supported.
1888		2459
1889	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2460	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1890	to use the libev header file and library.	2461	to use the libev header file and library.
1891		2462
1892	=back	2463	=back
1893		2464
1894	=head1 C++ SUPPORT	2465	=head1 C++ SUPPORT
1895		2466
1896	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2467	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1897	you to use some convinience methods to start/stop watchers and also change	2468	you to use some convenience methods to start/stop watchers and also change
1898	the callback model to a model using method callbacks on objects.	2469	the callback model to a model using method callbacks on objects.
1899		2470
1900	To use it,	2471	To use it,
1901		2472
1902	#include <ev++.h>	2473	#include <ev++.h>
1903		2474
1904	This automatically includes F<ev.h> and puts all of its definitions (many	2475	This automatically includes F<ev.h> and puts all of its definitions (many
1905	of them macros) into the global namespace. All C++ specific things are	2476	of them macros) into the global namespace. All C++ specific things are
1906	put into the C<ev> namespace. It should support all the same embedding	2477	put into the C<ev> namespace. It should support all the same embedding
1907	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2478	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1974	your compiler is good :), then the method will be fully inlined into the	2545	your compiler is good :), then the method will be fully inlined into the
1975	thunking function, making it as fast as a direct C callback.	2546	thunking function, making it as fast as a direct C callback.
1976		2547
1977	Example: simple class declaration and watcher initialisation	2548	Example: simple class declaration and watcher initialisation
1978		2549
1979	struct myclass	2550	struct myclass
1980	{	2551	{
1981	void io_cb (ev::io &w, int revents) { }	2552	void io_cb (ev::io &w, int revents) { }
1982	}	2553	}
1983		2554
1984	myclass obj;	2555	myclass obj;
1985	ev::io iow;	2556	ev::io iow;
1986	iow.set <myclass, &myclass::io_cb> (&obj);	2557	iow.set <myclass, &myclass::io_cb> (&obj);
1987		2558
1988	=item w->set<function> (void *data = 0)	2559	=item w->set<function> (void *data = 0)
1989		2560
1990	Also sets a callback, but uses a static method or plain function as	2561	Also sets a callback, but uses a static method or plain function as
1991	callback. The optional C<data> argument will be stored in the watcher's	2562	callback. The optional C<data> argument will be stored in the watcher's
…		…
1995		2566
1996	See the method-C<set> above for more details.	2567	See the method-C<set> above for more details.
1997		2568
1998	Example:	2569	Example:
1999		2570
2000	static void io_cb (ev::io &w, int revents) { }	2571	static void io_cb (ev::io &w, int revents) { }
2001	iow.set <io_cb> ();	2572	iow.set <io_cb> ();
2002		2573
2003	=item w->set (struct ev_loop *)	2574	=item w->set (struct ev_loop *)
2004		2575
2005	Associates a different C<struct ev_loop> with this watcher. You can only	2576	Associates a different C<struct ev_loop> with this watcher. You can only
2006	do this when the watcher is inactive (and not pending either).	2577	do this when the watcher is inactive (and not pending either).
2007		2578
2008	=item w->set ([args])	2579	=item w->set ([arguments])
2009		2580
2010	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2581	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2011	called at least once. Unlike the C counterpart, an active watcher gets	2582	called at least once. Unlike the C counterpart, an active watcher gets
2012	automatically stopped and restarted when reconfiguring it with this	2583	automatically stopped and restarted when reconfiguring it with this
2013	method.	2584	method.
2014		2585
2015	=item w->start ()	2586	=item w->start ()
…		…
2019		2590
2020	=item w->stop ()	2591	=item w->stop ()
2021		2592
2022	Stops the watcher if it is active. Again, no C<loop> argument.	2593	Stops the watcher if it is active. Again, no C<loop> argument.
2023		2594
2024	=item w->again () C<ev::timer>, C<ev::periodic> only	2595	=item w->again () (C<ev::timer>, C<ev::periodic> only)
2025		2596
2026	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2597	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
2027	C<ev_TYPE_again> function.	2598	C<ev_TYPE_again> function.
2028		2599
2029	=item w->sweep () C<ev::embed> only	2600	=item w->sweep () (C<ev::embed> only)
2030		2601
2031	Invokes C<ev_embed_sweep>.	2602	Invokes C<ev_embed_sweep>.
2032		2603
2033	=item w->update () C<ev::stat> only	2604	=item w->update () (C<ev::stat> only)
2034		2605
2035	Invokes C<ev_stat_stat>.	2606	Invokes C<ev_stat_stat>.
2036		2607
2037	=back	2608	=back
2038		2609
2039	=back	2610	=back
2040		2611
2041	Example: Define a class with an IO and idle watcher, start one of them in	2612	Example: Define a class with an IO and idle watcher, start one of them in
2042	the constructor.	2613	the constructor.
2043		2614
2044	class myclass	2615	class myclass
2045	{	2616	{
2046	ev_io io; void io_cb (ev::io &w, int revents);	2617	ev::io io; void io_cb (ev::io &w, int revents);
2047	ev_idle idle void idle_cb (ev::idle &w, int revents);	2618	ev:idle idle void idle_cb (ev::idle &w, int revents);
2048		2619
2049	myclass ();	2620	myclass (int fd)
2050	}	2621	{
2051
2052	myclass::myclass (int fd)
2053	{
2054	io .set <myclass, &myclass::io_cb > (this);	2622	io .set <myclass, &myclass::io_cb > (this);
2055	idle.set <myclass, &myclass::idle_cb> (this);	2623	idle.set <myclass, &myclass::idle_cb> (this);
2056		2624
2057	io.start (fd, ev::READ);	2625	io.start (fd, ev::READ);
		2626	}
2058	}	2627	};
		2628
		2629
		2630	=head1 OTHER LANGUAGE BINDINGS
		2631
		2632	Libev does not offer other language bindings itself, but bindings for a
		2633	number of languages exist in the form of third-party packages. If you know
		2634	any interesting language binding in addition to the ones listed here, drop
		2635	me a note.
		2636
		2637	=over 4
		2638
		2639	=item Perl
		2640
		2641	The EV module implements the full libev API and is actually used to test
		2642	libev. EV is developed together with libev. Apart from the EV core module,
		2643	there are additional modules that implement libev-compatible interfaces
		2644	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2645	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2646
		2647	It can be found and installed via CPAN, its homepage is at
		2648	L<http://software.schmorp.de/pkg/EV>.
		2649
		2650	=item Python
		2651
		2652	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2653	seems to be quite complete and well-documented. Note, however, that the
		2654	patch they require for libev is outright dangerous as it breaks the ABI
		2655	for everybody else, and therefore, should never be applied in an installed
		2656	libev (if python requires an incompatible ABI then it needs to embed
		2657	libev).
		2658
		2659	=item Ruby
		2660
		2661	Tony Arcieri has written a ruby extension that offers access to a subset
		2662	of the libev API and adds file handle abstractions, asynchronous DNS and
		2663	more on top of it. It can be found via gem servers. Its homepage is at
		2664	L<http://rev.rubyforge.org/>.
		2665
		2666	=item D
		2667
		2668	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2669	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2670
		2671	=back
2059		2672
2060		2673
2061	=head1 MACRO MAGIC	2674	=head1 MACRO MAGIC
2062		2675
2063	Libev can be compiled with a variety of options, the most fundemantal is	2676	Libev can be compiled with a variety of options, the most fundamental
2064	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2677	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2065	callbacks have an initial C<struct ev_loop *> argument.	2678	functions and callbacks have an initial C<struct ev_loop *> argument.
2066		2679
2067	To make it easier to write programs that cope with either variant, the	2680	To make it easier to write programs that cope with either variant, the
2068	following macros are defined:	2681	following macros are defined:
2069		2682
2070	=over 4	2683	=over 4
…		…
2073		2686
2074	This provides the loop I<argument> for functions, if one is required ("ev	2687	This provides the loop I<argument> for functions, if one is required ("ev
2075	loop argument"). The C<EV_A> form is used when this is the sole argument,	2688	loop argument"). The C<EV_A> form is used when this is the sole argument,
2076	C<EV_A_> is used when other arguments are following. Example:	2689	C<EV_A_> is used when other arguments are following. Example:
2077		2690
2078	ev_unref (EV_A);	2691	ev_unref (EV_A);
2079	ev_timer_add (EV_A_ watcher);	2692	ev_timer_add (EV_A_ watcher);
2080	ev_loop (EV_A_ 0);	2693	ev_loop (EV_A_ 0);
2081		2694
2082	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2695	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2083	which is often provided by the following macro.	2696	which is often provided by the following macro.
2084		2697
2085	=item C<EV_P>, C<EV_P_>	2698	=item C<EV_P>, C<EV_P_>
2086		2699
2087	This provides the loop I<parameter> for functions, if one is required ("ev	2700	This provides the loop I<parameter> for functions, if one is required ("ev
2088	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2701	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2089	C<EV_P_> is used when other parameters are following. Example:	2702	C<EV_P_> is used when other parameters are following. Example:
2090		2703
2091	// this is how ev_unref is being declared	2704	// this is how ev_unref is being declared
2092	static void ev_unref (EV_P);	2705	static void ev_unref (EV_P);
2093		2706
2094	// this is how you can declare your typical callback	2707	// this is how you can declare your typical callback
2095	static void cb (EV_P_ ev_timer *w, int revents)	2708	static void cb (EV_P_ ev_timer *w, int revents)
2096		2709
2097	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2710	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2098	suitable for use with C<EV_A>.	2711	suitable for use with C<EV_A>.
2099		2712
2100	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2713	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2101		2714
2102	Similar to the other two macros, this gives you the value of the default	2715	Similar to the other two macros, this gives you the value of the default
2103	loop, if multiple loops are supported ("ev loop default").	2716	loop, if multiple loops are supported ("ev loop default").
		2717
		2718	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2719
		2720	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2721	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2722	is undefined when the default loop has not been initialised by a previous
		2723	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2724
		2725	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2726	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2104		2727
2105	=back	2728	=back
2106		2729
2107	Example: Declare and initialise a check watcher, utilising the above	2730	Example: Declare and initialise a check watcher, utilising the above
2108	macros so it will work regardless of whether multiple loops are supported	2731	macros so it will work regardless of whether multiple loops are supported
2109	or not.	2732	or not.
2110		2733
2111	static void	2734	static void
2112	check_cb (EV_P_ ev_timer *w, int revents)	2735	check_cb (EV_P_ ev_timer *w, int revents)
2113	{	2736	{
2114	ev_check_stop (EV_A_ w);	2737	ev_check_stop (EV_A_ w);
2115	}	2738	}
2116		2739
2117	ev_check check;	2740	ev_check check;
2118	ev_check_init (&check, check_cb);	2741	ev_check_init (&check, check_cb);
2119	ev_check_start (EV_DEFAULT_ &check);	2742	ev_check_start (EV_DEFAULT_ &check);
2120	ev_loop (EV_DEFAULT_ 0);	2743	ev_loop (EV_DEFAULT_ 0);
2121		2744
2122	=head1 EMBEDDING	2745	=head1 EMBEDDING
2123		2746
2124	Libev can (and often is) directly embedded into host	2747	Libev can (and often is) directly embedded into host
2125	applications. Examples of applications that embed it include the Deliantra	2748	applications. Examples of applications that embed it include the Deliantra
2126	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2749	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2127	and rxvt-unicode.	2750	and rxvt-unicode.
2128		2751
2129	The goal is to enable you to just copy the neecssary files into your	2752	The goal is to enable you to just copy the necessary files into your
2130	source directory without having to change even a single line in them, so	2753	source directory without having to change even a single line in them, so
2131	you can easily upgrade by simply copying (or having a checked-out copy of	2754	you can easily upgrade by simply copying (or having a checked-out copy of
2132	libev somewhere in your source tree).	2755	libev somewhere in your source tree).
2133		2756
2134	=head2 FILESETS	2757	=head2 FILESETS
2135		2758
2136	Depending on what features you need you need to include one or more sets of files	2759	Depending on what features you need you need to include one or more sets of files
2137	in your app.	2760	in your application.
2138		2761
2139	=head3 CORE EVENT LOOP	2762	=head3 CORE EVENT LOOP
2140		2763
2141	To include only the libev core (all the C<ev_*> functions), with manual	2764	To include only the libev core (all the C<ev_*> functions), with manual
2142	configuration (no autoconf):	2765	configuration (no autoconf):
2143		2766
2144	#define EV_STANDALONE 1	2767	#define EV_STANDALONE 1
2145	#include "ev.c"	2768	#include "ev.c"
2146		2769
2147	This will automatically include F<ev.h>, too, and should be done in a	2770	This will automatically include F<ev.h>, too, and should be done in a
2148	single C source file only to provide the function implementations. To use	2771	single C source file only to provide the function implementations. To use
2149	it, do the same for F<ev.h> in all files wishing to use this API (best	2772	it, do the same for F<ev.h> in all files wishing to use this API (best
2150	done by writing a wrapper around F<ev.h> that you can include instead and	2773	done by writing a wrapper around F<ev.h> that you can include instead and
2151	where you can put other configuration options):	2774	where you can put other configuration options):
2152		2775
2153	#define EV_STANDALONE 1	2776	#define EV_STANDALONE 1
2154	#include "ev.h"	2777	#include "ev.h"
2155		2778
2156	Both header files and implementation files can be compiled with a C++	2779	Both header files and implementation files can be compiled with a C++
2157	compiler (at least, thats a stated goal, and breakage will be treated	2780	compiler (at least, thats a stated goal, and breakage will be treated
2158	as a bug).	2781	as a bug).
2159		2782
2160	You need the following files in your source tree, or in a directory	2783	You need the following files in your source tree, or in a directory
2161	in your include path (e.g. in libev/ when using -Ilibev):	2784	in your include path (e.g. in libev/ when using -Ilibev):
2162		2785
2163	ev.h	2786	ev.h
2164	ev.c	2787	ev.c
2165	ev_vars.h	2788	ev_vars.h
2166	ev_wrap.h	2789	ev_wrap.h
2167		2790
2168	ev_win32.c required on win32 platforms only	2791	ev_win32.c required on win32 platforms only
2169		2792
2170	ev_select.c only when select backend is enabled (which is enabled by default)	2793	ev_select.c only when select backend is enabled (which is enabled by default)
2171	ev_poll.c only when poll backend is enabled (disabled by default)	2794	ev_poll.c only when poll backend is enabled (disabled by default)
2172	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2795	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2173	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2796	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2174	ev_port.c only when the solaris port backend is enabled (disabled by default)	2797	ev_port.c only when the solaris port backend is enabled (disabled by default)
2175		2798
2176	F<ev.c> includes the backend files directly when enabled, so you only need	2799	F<ev.c> includes the backend files directly when enabled, so you only need
2177	to compile this single file.	2800	to compile this single file.
2178		2801
2179	=head3 LIBEVENT COMPATIBILITY API	2802	=head3 LIBEVENT COMPATIBILITY API
2180		2803
2181	To include the libevent compatibility API, also include:	2804	To include the libevent compatibility API, also include:
2182		2805
2183	#include "event.c"	2806	#include "event.c"
2184		2807
2185	in the file including F<ev.c>, and:	2808	in the file including F<ev.c>, and:
2186		2809
2187	#include "event.h"	2810	#include "event.h"
2188		2811
2189	in the files that want to use the libevent API. This also includes F<ev.h>.	2812	in the files that want to use the libevent API. This also includes F<ev.h>.
2190		2813
2191	You need the following additional files for this:	2814	You need the following additional files for this:
2192		2815
2193	event.h	2816	event.h
2194	event.c	2817	event.c
2195		2818
2196	=head3 AUTOCONF SUPPORT	2819	=head3 AUTOCONF SUPPORT
2197		2820
2198	Instead of using C<EV_STANDALONE=1> and providing your config in	2821	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2199	whatever way you want, you can also C<m4_include([libev.m4])> in your	2822	whatever way you want, you can also C<m4_include([libev.m4])> in your
2200	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2823	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2201	include F<config.h> and configure itself accordingly.	2824	include F<config.h> and configure itself accordingly.
2202		2825
2203	For this of course you need the m4 file:	2826	For this of course you need the m4 file:
2204		2827
2205	libev.m4	2828	libev.m4
2206		2829
2207	=head2 PREPROCESSOR SYMBOLS/MACROS	2830	=head2 PREPROCESSOR SYMBOLS/MACROS
2208		2831
2209	Libev can be configured via a variety of preprocessor symbols you have to define	2832	Libev can be configured via a variety of preprocessor symbols you have to
2210	before including any of its files. The default is not to build for multiplicity	2833	define before including any of its files. The default in the absence of
2211	and only include the select backend.	2834	autoconf is noted for every option.
2212		2835
2213	=over 4	2836	=over 4
2214		2837
2215	=item EV_STANDALONE	2838	=item EV_STANDALONE
2216		2839
…		…
2221	F<event.h> that are not directly supported by the libev core alone.	2844	F<event.h> that are not directly supported by the libev core alone.
2222		2845
2223	=item EV_USE_MONOTONIC	2846	=item EV_USE_MONOTONIC
2224		2847
2225	If defined to be C<1>, libev will try to detect the availability of the	2848	If defined to be C<1>, libev will try to detect the availability of the
2226	monotonic clock option at both compiletime and runtime. Otherwise no use	2849	monotonic clock option at both compile time and runtime. Otherwise no use
2227	of the monotonic clock option will be attempted. If you enable this, you	2850	of the monotonic clock option will be attempted. If you enable this, you
2228	usually have to link against librt or something similar. Enabling it when	2851	usually have to link against librt or something similar. Enabling it when
2229	the functionality isn't available is safe, though, althoguh you have	2852	the functionality isn't available is safe, though, although you have
2230	to make sure you link against any libraries where the C<clock_gettime>	2853	to make sure you link against any libraries where the C<clock_gettime>
2231	function is hiding in (often F<-lrt>).	2854	function is hiding in (often F<-lrt>).
2232		2855
2233	=item EV_USE_REALTIME	2856	=item EV_USE_REALTIME
2234		2857
2235	If defined to be C<1>, libev will try to detect the availability of the	2858	If defined to be C<1>, libev will try to detect the availability of the
2236	realtime clock option at compiletime (and assume its availability at	2859	real-time clock option at compile time (and assume its availability at
2237	runtime if successful). Otherwise no use of the realtime clock option will	2860	runtime if successful). Otherwise no use of the real-time clock option will
2238	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2861	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2239	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2862	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2240	in the description of C<EV_USE_MONOTONIC>, though.	2863	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2864
		2865	=item EV_USE_NANOSLEEP
		2866
		2867	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2868	and will use it for delays. Otherwise it will use C<select ()>.
		2869
		2870	=item EV_USE_EVENTFD
		2871
		2872	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2873	available and will probe for kernel support at runtime. This will improve
		2874	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2875	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2876	2.7 or newer, otherwise disabled.
2241		2877
2242	=item EV_USE_SELECT	2878	=item EV_USE_SELECT
2243		2879
2244	If undefined or defined to be C<1>, libev will compile in support for the	2880	If undefined or defined to be C<1>, libev will compile in support for the
2245	C<select>(2) backend. No attempt at autodetection will be done: if no	2881	C<select>(2) backend. No attempt at auto-detection will be done: if no
2246	other method takes over, select will be it. Otherwise the select backend	2882	other method takes over, select will be it. Otherwise the select backend
2247	will not be compiled in.	2883	will not be compiled in.
2248		2884
2249	=item EV_SELECT_USE_FD_SET	2885	=item EV_SELECT_USE_FD_SET
2250		2886
2251	If defined to C<1>, then the select backend will use the system C<fd_set>	2887	If defined to C<1>, then the select backend will use the system C<fd_set>
2252	structure. This is useful if libev doesn't compile due to a missing	2888	structure. This is useful if libev doesn't compile due to a missing
2253	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	2889	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2254	exotic systems. This usually limits the range of file descriptors to some	2890	exotic systems. This usually limits the range of file descriptors to some
2255	low limit such as 1024 or might have other limitations (winsocket only	2891	low limit such as 1024 or might have other limitations (winsocket only
2256	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	2892	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2257	influence the size of the C<fd_set> used.	2893	influence the size of the C<fd_set> used.
2258		2894
…		…
2264	be used is the winsock select). This means that it will call	2900	be used is the winsock select). This means that it will call
2265	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2901	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2266	it is assumed that all these functions actually work on fds, even	2902	it is assumed that all these functions actually work on fds, even
2267	on win32. Should not be defined on non-win32 platforms.	2903	on win32. Should not be defined on non-win32 platforms.
2268		2904
		2905	=item EV_FD_TO_WIN32_HANDLE
		2906
		2907	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2908	file descriptors to socket handles. When not defining this symbol (the
		2909	default), then libev will call C<_get_osfhandle>, which is usually
		2910	correct. In some cases, programs use their own file descriptor management,
		2911	in which case they can provide this function to map fds to socket handles.
		2912
2269	=item EV_USE_POLL	2913	=item EV_USE_POLL
2270		2914
2271	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2915	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2272	backend. Otherwise it will be enabled on non-win32 platforms. It	2916	backend. Otherwise it will be enabled on non-win32 platforms. It
2273	takes precedence over select.	2917	takes precedence over select.
2274		2918
2275	=item EV_USE_EPOLL	2919	=item EV_USE_EPOLL
2276		2920
2277	If defined to be C<1>, libev will compile in support for the Linux	2921	If defined to be C<1>, libev will compile in support for the Linux
2278	C<epoll>(7) backend. Its availability will be detected at runtime,	2922	C<epoll>(7) backend. Its availability will be detected at runtime,
2279	otherwise another method will be used as fallback. This is the	2923	otherwise another method will be used as fallback. This is the preferred
2280	preferred backend for GNU/Linux systems.	2924	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2925	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2281		2926
2282	=item EV_USE_KQUEUE	2927	=item EV_USE_KQUEUE
2283		2928
2284	If defined to be C<1>, libev will compile in support for the BSD style	2929	If defined to be C<1>, libev will compile in support for the BSD style
2285	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2930	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2298	otherwise another method will be used as fallback. This is the preferred	2943	otherwise another method will be used as fallback. This is the preferred
2299	backend for Solaris 10 systems.	2944	backend for Solaris 10 systems.
2300		2945
2301	=item EV_USE_DEVPOLL	2946	=item EV_USE_DEVPOLL
2302		2947
2303	reserved for future expansion, works like the USE symbols above.	2948	Reserved for future expansion, works like the USE symbols above.
2304		2949
2305	=item EV_USE_INOTIFY	2950	=item EV_USE_INOTIFY
2306		2951
2307	If defined to be C<1>, libev will compile in support for the Linux inotify	2952	If defined to be C<1>, libev will compile in support for the Linux inotify
2308	interface to speed up C<ev_stat> watchers. Its actual availability will	2953	interface to speed up C<ev_stat> watchers. Its actual availability will
2309	be detected at runtime.	2954	be detected at runtime. If undefined, it will be enabled if the headers
		2955	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2956
		2957	=item EV_ATOMIC_T
		2958
		2959	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2960	access is atomic with respect to other threads or signal contexts. No such
		2961	type is easily found in the C language, so you can provide your own type
		2962	that you know is safe for your purposes. It is used both for signal handler "locking"
		2963	as well as for signal and thread safety in C<ev_async> watchers.
		2964
		2965	In the absence of this define, libev will use C<sig_atomic_t volatile>
		2966	(from F<signal.h>), which is usually good enough on most platforms.
2310		2967
2311	=item EV_H	2968	=item EV_H
2312		2969
2313	The name of the F<ev.h> header file used to include it. The default if	2970	The name of the F<ev.h> header file used to include it. The default if
2314	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2971	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2315	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2972	used to virtually rename the F<ev.h> header file in case of conflicts.
2316		2973
2317	=item EV_CONFIG_H	2974	=item EV_CONFIG_H
2318		2975
2319	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2976	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2320	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2977	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2321	C<EV_H>, above.	2978	C<EV_H>, above.
2322		2979
2323	=item EV_EVENT_H	2980	=item EV_EVENT_H
2324		2981
2325	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2982	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2326	of how the F<event.h> header can be found.	2983	of how the F<event.h> header can be found, the default is C<"event.h">.
2327		2984
2328	=item EV_PROTOTYPES	2985	=item EV_PROTOTYPES
2329		2986
2330	If defined to be C<0>, then F<ev.h> will not define any function	2987	If defined to be C<0>, then F<ev.h> will not define any function
2331	prototypes, but still define all the structs and other symbols. This is	2988	prototypes, but still define all the structs and other symbols. This is
…		…
2352	When doing priority-based operations, libev usually has to linearly search	3009	When doing priority-based operations, libev usually has to linearly search
2353	all the priorities, so having many of them (hundreds) uses a lot of space	3010	all the priorities, so having many of them (hundreds) uses a lot of space
2354	and time, so using the defaults of five priorities (-2 .. +2) is usually	3011	and time, so using the defaults of five priorities (-2 .. +2) is usually
2355	fine.	3012	fine.
2356		3013
2357	If your embedding app does not need any priorities, defining these both to	3014	If your embedding application does not need any priorities, defining these both to
2358	C<0> will save some memory and cpu.	3015	C<0> will save some memory and CPU.
2359		3016
2360	=item EV_PERIODIC_ENABLE	3017	=item EV_PERIODIC_ENABLE
2361		3018
2362	If undefined or defined to be C<1>, then periodic timers are supported. If	3019	If undefined or defined to be C<1>, then periodic timers are supported. If
2363	defined to be C<0>, then they are not. Disabling them saves a few kB of	3020	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2382	=item EV_FORK_ENABLE	3039	=item EV_FORK_ENABLE
2383		3040
2384	If undefined or defined to be C<1>, then fork watchers are supported. If	3041	If undefined or defined to be C<1>, then fork watchers are supported. If
2385	defined to be C<0>, then they are not.	3042	defined to be C<0>, then they are not.
2386		3043
		3044	=item EV_ASYNC_ENABLE
		3045
		3046	If undefined or defined to be C<1>, then async watchers are supported. If
		3047	defined to be C<0>, then they are not.
		3048
2387	=item EV_MINIMAL	3049	=item EV_MINIMAL
2388		3050
2389	If you need to shave off some kilobytes of code at the expense of some	3051	If you need to shave off some kilobytes of code at the expense of some
2390	speed, define this symbol to C<1>. Currently only used for gcc to override	3052	speed, define this symbol to C<1>. Currently this is used to override some
2391	some inlining decisions, saves roughly 30% codesize of amd64.	3053	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3054	much smaller 2-heap for timer management over the default 4-heap.
2392		3055
2393	=item EV_PID_HASHSIZE	3056	=item EV_PID_HASHSIZE
2394		3057
2395	C<ev_child> watchers use a small hash table to distribute workload by	3058	C<ev_child> watchers use a small hash table to distribute workload by
2396	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3059	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2397	than enough. If you need to manage thousands of children you might want to	3060	than enough. If you need to manage thousands of children you might want to
2398	increase this value (I<must> be a power of two).	3061	increase this value (I<must> be a power of two).
2399		3062
2400	=item EV_INOTIFY_HASHSIZE	3063	=item EV_INOTIFY_HASHSIZE
2401		3064
2402	C<ev_staz> watchers use a small hash table to distribute workload by	3065	C<ev_stat> watchers use a small hash table to distribute workload by
2403	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3066	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2404	usually more than enough. If you need to manage thousands of C<ev_stat>	3067	usually more than enough. If you need to manage thousands of C<ev_stat>
2405	watchers you might want to increase this value (I<must> be a power of	3068	watchers you might want to increase this value (I<must> be a power of
2406	two).	3069	two).
2407		3070
		3071	=item EV_USE_4HEAP
		3072
		3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3074	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3075	to C<1>. The 4-heap uses more complicated (longer) code but has
		3076	noticeably faster performance with many (thousands) of watchers.
		3077
		3078	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3079	(disabled).
		3080
		3081	=item EV_HEAP_CACHE_AT
		3082
		3083	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3084	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3085	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3086	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3087	but avoids random read accesses on heap changes. This improves performance
		3088	noticeably with with many (hundreds) of watchers.
		3089
		3090	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3091	(disabled).
		3092
		3093	=item EV_VERIFY
		3094
		3095	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3096	be done: If set to C<0>, no internal verification code will be compiled
		3097	in. If set to C<1>, then verification code will be compiled in, but not
		3098	called. If set to C<2>, then the internal verification code will be
		3099	called once per loop, which can slow down libev. If set to C<3>, then the
		3100	verification code will be called very frequently, which will slow down
		3101	libev considerably.
		3102
		3103	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3104	C<0.>
		3105
2408	=item EV_COMMON	3106	=item EV_COMMON
2409		3107
2410	By default, all watchers have a C<void *data> member. By redefining	3108	By default, all watchers have a C<void *data> member. By redefining
2411	this macro to a something else you can include more and other types of	3109	this macro to a something else you can include more and other types of
2412	members. You have to define it each time you include one of the files,	3110	members. You have to define it each time you include one of the files,
2413	though, and it must be identical each time.	3111	though, and it must be identical each time.
2414		3112
2415	For example, the perl EV module uses something like this:	3113	For example, the perl EV module uses something like this:
2416		3114
2417	#define EV_COMMON \	3115	#define EV_COMMON \
2418	SV *self; /* contains this struct */ \	3116	SV *self; /* contains this struct */ \
2419	SV *cb_sv, *fh /* note no trailing ";" */	3117	SV *cb_sv, *fh /* note no trailing ";" */
2420		3118
2421	=item EV_CB_DECLARE (type)	3119	=item EV_CB_DECLARE (type)
2422		3120
2423	=item EV_CB_INVOKE (watcher, revents)	3121	=item EV_CB_INVOKE (watcher, revents)
2424		3122
2425	=item ev_set_cb (ev, cb)	3123	=item ev_set_cb (ev, cb)
2426		3124
2427	Can be used to change the callback member declaration in each watcher,	3125	Can be used to change the callback member declaration in each watcher,
2428	and the way callbacks are invoked and set. Must expand to a struct member	3126	and the way callbacks are invoked and set. Must expand to a struct member
2429	definition and a statement, respectively. See the F<ev.v> header file for	3127	definition and a statement, respectively. See the F<ev.h> header file for
2430	their default definitions. One possible use for overriding these is to	3128	their default definitions. One possible use for overriding these is to
2431	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3129	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2432	method calls instead of plain function calls in C++.	3130	method calls instead of plain function calls in C++.
		3131
		3132	=head2 EXPORTED API SYMBOLS
		3133
		3134	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3135	exported symbols, you can use the provided F<Symbol.*> files which list
		3136	all public symbols, one per line:
		3137
		3138	Symbols.ev for libev proper
		3139	Symbols.event for the libevent emulation
		3140
		3141	This can also be used to rename all public symbols to avoid clashes with
		3142	multiple versions of libev linked together (which is obviously bad in
		3143	itself, but sometimes it is inconvenient to avoid this).
		3144
		3145	A sed command like this will create wrapper C<#define>'s that you need to
		3146	include before including F<ev.h>:
		3147
		3148	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3149
		3150	This would create a file F<wrap.h> which essentially looks like this:
		3151
		3152	#define ev_backend myprefix_ev_backend
		3153	#define ev_check_start myprefix_ev_check_start
		3154	#define ev_check_stop myprefix_ev_check_stop
		3155	...
2433		3156
2434	=head2 EXAMPLES	3157	=head2 EXAMPLES
2435		3158
2436	For a real-world example of a program the includes libev	3159	For a real-world example of a program the includes libev
2437	verbatim, you can have a look at the EV perl module	3160	verbatim, you can have a look at the EV perl module
…		…
2442	file.	3165	file.
2443		3166
2444	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3167	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2445	that everybody includes and which overrides some configure choices:	3168	that everybody includes and which overrides some configure choices:
2446		3169
2447	#define EV_MINIMAL 1	3170	#define EV_MINIMAL 1
2448	#define EV_USE_POLL 0	3171	#define EV_USE_POLL 0
2449	#define EV_MULTIPLICITY 0	3172	#define EV_MULTIPLICITY 0
2450	#define EV_PERIODIC_ENABLE 0	3173	#define EV_PERIODIC_ENABLE 0
2451	#define EV_STAT_ENABLE 0	3174	#define EV_STAT_ENABLE 0
2452	#define EV_FORK_ENABLE 0	3175	#define EV_FORK_ENABLE 0
2453	#define EV_CONFIG_H <config.h>	3176	#define EV_CONFIG_H <config.h>
2454	#define EV_MINPRI 0	3177	#define EV_MINPRI 0
2455	#define EV_MAXPRI 0	3178	#define EV_MAXPRI 0
2456		3179
2457	#include "ev++.h"	3180	#include "ev++.h"
2458		3181
2459	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3182	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2460		3183
2461	#include "ev_cpp.h"	3184	#include "ev_cpp.h"
2462	#include "ev.c"	3185	#include "ev.c"
		3186
		3187
		3188	=head1 THREADS AND COROUTINES
		3189
		3190	=head2 THREADS
		3191
		3192	Libev itself is completely thread-safe, but it uses no locking. This
		3193	means that you can use as many loops as you want in parallel, as long as
		3194	only one thread ever calls into one libev function with the same loop
		3195	parameter.
		3196
		3197	Or put differently: calls with different loop parameters can be done in
		3198	parallel from multiple threads, calls with the same loop parameter must be
		3199	done serially (but can be done from different threads, as long as only one
		3200	thread ever is inside a call at any point in time, e.g. by using a mutex
		3201	per loop).
		3202
		3203	If you want to know which design (one loop, locking, or multiple loops
		3204	without or something else still) is best for your problem, then I cannot
		3205	help you. I can give some generic advice however:
		3206
		3207	=over 4
		3208
		3209	=item * most applications have a main thread: use the default libev loop
		3210	in that thread, or create a separate thread running only the default loop.
		3211
		3212	This helps integrating other libraries or software modules that use libev
		3213	themselves and don't care/know about threading.
		3214
		3215	=item * one loop per thread is usually a good model.
		3216
		3217	Doing this is almost never wrong, sometimes a better-performance model
		3218	exists, but it is always a good start.
		3219
		3220	=item * other models exist, such as the leader/follower pattern, where one
		3221	loop is handed through multiple threads in a kind of round-robin fashion.
		3222
		3223	Choosing a model is hard - look around, learn, know that usually you can do
		3224	better than you currently do :-)
		3225
		3226	=item * often you need to talk to some other thread which blocks in the
		3227	event loop - C<ev_async> watchers can be used to wake them up from other
		3228	threads safely (or from signal contexts...).
		3229
		3230	=back
		3231
		3232	=head2 COROUTINES
		3233
		3234	Libev is much more accommodating to coroutines ("cooperative threads"):
		3235	libev fully supports nesting calls to it's functions from different
		3236	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3237	different coroutines and switch freely between both coroutines running the
		3238	loop, as long as you don't confuse yourself). The only exception is that
		3239	you must not do this from C<ev_periodic> reschedule callbacks.
		3240
		3241	Care has been invested into making sure that libev does not keep local
		3242	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3243	switches.
2463		3244
2464		3245
2465	=head1 COMPLEXITIES	3246	=head1 COMPLEXITIES
2466		3247
2467	In this section the complexities of (many of) the algorithms used inside	3248	In this section the complexities of (many of) the algorithms used inside
…		…
2478		3259
2479	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3260	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2480		3261
2481	This means that, when you have a watcher that triggers in one hour and	3262	This means that, when you have a watcher that triggers in one hour and
2482	there are 100 watchers that would trigger before that then inserting will	3263	there are 100 watchers that would trigger before that then inserting will
2483	have to skip those 100 watchers.	3264	have to skip roughly seven (C<ld 100>) of these watchers.
2484		3265
2485	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3266	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2486		3267
2487	That means that for changing a timer costs less than removing/adding them	3268	That means that changing a timer costs less than removing/adding them
2488	as only the relative motion in the event queue has to be paid for.	3269	as only the relative motion in the event queue has to be paid for.
2489		3270
2490	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3271	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2491		3272
2492	These just add the watcher into an array or at the head of a list.	3273	These just add the watcher into an array or at the head of a list.
		3274
2493	=item Stopping check/prepare/idle watchers: O(1)	3275	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2494		3276
2495	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3277	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2496		3278
2497	These watchers are stored in lists then need to be walked to find the	3279	These watchers are stored in lists then need to be walked to find the
2498	correct watcher to remove. The lists are usually short (you don't usually	3280	correct watcher to remove. The lists are usually short (you don't usually
2499	have many watchers waiting for the same fd or signal).	3281	have many watchers waiting for the same fd or signal).
2500		3282
2501	=item Finding the next timer per loop iteration: O(1)	3283	=item Finding the next timer in each loop iteration: O(1)
		3284
		3285	By virtue of using a binary or 4-heap, the next timer is always found at a
		3286	fixed position in the storage array.
2502		3287
2503	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3288	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2504		3289
2505	A change means an I/O watcher gets started or stopped, which requires	3290	A change means an I/O watcher gets started or stopped, which requires
2506	libev to recalculate its status (and possibly tell the kernel).	3291	libev to recalculate its status (and possibly tell the kernel, depending
		3292	on backend and whether C<ev_io_set> was used).
2507		3293
2508	=item Activating one watcher: O(1)	3294	=item Activating one watcher (putting it into the pending state): O(1)
2509		3295
2510	=item Priority handling: O(number_of_priorities)	3296	=item Priority handling: O(number_of_priorities)
2511		3297
2512	Priorities are implemented by allocating some space for each	3298	Priorities are implemented by allocating some space for each
2513	priority. When doing priority-based operations, libev usually has to	3299	priority. When doing priority-based operations, libev usually has to
2514	linearly search all the priorities.	3300	linearly search all the priorities, but starting/stopping and activating
		3301	watchers becomes O(1) w.r.t. priority handling.
		3302
		3303	=item Sending an ev_async: O(1)
		3304
		3305	=item Processing ev_async_send: O(number_of_async_watchers)
		3306
		3307	=item Processing signals: O(max_signal_number)
		3308
		3309	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3310	calls in the current loop iteration. Checking for async and signal events
		3311	involves iterating over all running async watchers or all signal numbers.
2515		3312
2516	=back	3313	=back
2517		3314
2518		3315
		3316	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3317
		3318	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3319	requires, and its I/O model is fundamentally incompatible with the POSIX
		3320	model. Libev still offers limited functionality on this platform in
		3321	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3322	descriptors. This only applies when using Win32 natively, not when using
		3323	e.g. cygwin.
		3324
		3325	Lifting these limitations would basically require the full
		3326	re-implementation of the I/O system. If you are into these kinds of
		3327	things, then note that glib does exactly that for you in a very portable
		3328	way (note also that glib is the slowest event library known to man).
		3329
		3330	There is no supported compilation method available on windows except
		3331	embedding it into other applications.
		3332
		3333	Not a libev limitation but worth mentioning: windows apparently doesn't
		3334	accept large writes: instead of resulting in a partial write, windows will
		3335	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3336	so make sure you only write small amounts into your sockets (less than a
		3337	megabyte seems safe, but thsi apparently depends on the amount of memory
		3338	available).
		3339
		3340	Due to the many, low, and arbitrary limits on the win32 platform and
		3341	the abysmal performance of winsockets, using a large number of sockets
		3342	is not recommended (and not reasonable). If your program needs to use
		3343	more than a hundred or so sockets, then likely it needs to use a totally
		3344	different implementation for windows, as libev offers the POSIX readiness
		3345	notification model, which cannot be implemented efficiently on windows
		3346	(Microsoft monopoly games).
		3347
		3348	A typical way to use libev under windows is to embed it (see the embedding
		3349	section for details) and use the following F<evwrap.h> header file instead
		3350	of F<ev.h>:
		3351
		3352	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3353	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3354
		3355	#include "ev.h"
		3356
		3357	And compile the following F<evwrap.c> file into your project (make sure
		3358	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3359
		3360	#include "evwrap.h"
		3361	#include "ev.c"
		3362
		3363	=over 4
		3364
		3365	=item The winsocket select function
		3366
		3367	The winsocket C<select> function doesn't follow POSIX in that it
		3368	requires socket I<handles> and not socket I<file descriptors> (it is
		3369	also extremely buggy). This makes select very inefficient, and also
		3370	requires a mapping from file descriptors to socket handles (the Microsoft
		3371	C runtime provides the function C<_open_osfhandle> for this). See the
		3372	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3373	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3374
		3375	The configuration for a "naked" win32 using the Microsoft runtime
		3376	libraries and raw winsocket select is:
		3377
		3378	#define EV_USE_SELECT 1
		3379	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3380
		3381	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3382	complexity in the O(n²) range when using win32.
		3383
		3384	=item Limited number of file descriptors
		3385
		3386	Windows has numerous arbitrary (and low) limits on things.
		3387
		3388	Early versions of winsocket's select only supported waiting for a maximum
		3389	of C<64> handles (probably owning to the fact that all windows kernels
		3390	can only wait for C<64> things at the same time internally; Microsoft
		3391	recommends spawning a chain of threads and wait for 63 handles and the
		3392	previous thread in each. Great).
		3393
		3394	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3395	to some high number (e.g. C<2048>) before compiling the winsocket select
		3396	call (which might be in libev or elsewhere, for example, perl does its own
		3397	select emulation on windows).
		3398
		3399	Another limit is the number of file descriptors in the Microsoft runtime
		3400	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3401	or something like this inside Microsoft). You can increase this by calling
		3402	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3403	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3404	libraries.
		3405
		3406	This might get you to about C<512> or C<2048> sockets (depending on
		3407	windows version and/or the phase of the moon). To get more, you need to
		3408	wrap all I/O functions and provide your own fd management, but the cost of
		3409	calling select (O(n²)) will likely make this unworkable.
		3410
		3411	=back
		3412
		3413
		3414	=head1 PORTABILITY REQUIREMENTS
		3415
		3416	In addition to a working ISO-C implementation, libev relies on a few
		3417	additional extensions:
		3418
		3419	=over 4
		3420
		3421	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3422	calling conventions regardless of C<ev_watcher_type *>.
		3423
		3424	Libev assumes not only that all watcher pointers have the same internal
		3425	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3426	assumes that the same (machine) code can be used to call any watcher
		3427	callback: The watcher callbacks have different type signatures, but libev
		3428	calls them using an C<ev_watcher *> internally.
		3429
		3430	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3431
		3432	The type C<sig_atomic_t volatile> (or whatever is defined as
		3433	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3434	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3435	believed to be sufficiently portable.
		3436
		3437	=item C<sigprocmask> must work in a threaded environment
		3438
		3439	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3440	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3441	pthread implementations will either allow C<sigprocmask> in the "main
		3442	thread" or will block signals process-wide, both behaviours would
		3443	be compatible with libev. Interaction between C<sigprocmask> and
		3444	C<pthread_sigmask> could complicate things, however.
		3445
		3446	The most portable way to handle signals is to block signals in all threads
		3447	except the initial one, and run the default loop in the initial thread as
		3448	well.
		3449
		3450	=item C<long> must be large enough for common memory allocation sizes
		3451
		3452	To improve portability and simplify using libev, libev uses C<long>
		3453	internally instead of C<size_t> when allocating its data structures. On
		3454	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3455	is still at least 31 bits everywhere, which is enough for hundreds of
		3456	millions of watchers.
		3457
		3458	=item C<double> must hold a time value in seconds with enough accuracy
		3459
		3460	The type C<double> is used to represent timestamps. It is required to
		3461	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3462	enough for at least into the year 4000. This requirement is fulfilled by
		3463	implementations implementing IEEE 754 (basically all existing ones).
		3464
		3465	=back
		3466
		3467	If you know of other additional requirements drop me a note.
		3468
		3469
		3470	=head1 COMPILER WARNINGS
		3471
		3472	Depending on your compiler and compiler settings, you might get no or a
		3473	lot of warnings when compiling libev code. Some people are apparently
		3474	scared by this.
		3475
		3476	However, these are unavoidable for many reasons. For one, each compiler
		3477	has different warnings, and each user has different tastes regarding
		3478	warning options. "Warn-free" code therefore cannot be a goal except when
		3479	targeting a specific compiler and compiler-version.
		3480
		3481	Another reason is that some compiler warnings require elaborate
		3482	workarounds, or other changes to the code that make it less clear and less
		3483	maintainable.
		3484
		3485	And of course, some compiler warnings are just plain stupid, or simply
		3486	wrong (because they don't actually warn about the condition their message
		3487	seems to warn about).
		3488
		3489	While libev is written to generate as few warnings as possible,
		3490	"warn-free" code is not a goal, and it is recommended not to build libev
		3491	with any compiler warnings enabled unless you are prepared to cope with
		3492	them (e.g. by ignoring them). Remember that warnings are just that:
		3493	warnings, not errors, or proof of bugs.
		3494
		3495
		3496	=head1 VALGRIND
		3497
		3498	Valgrind has a special section here because it is a popular tool that is
		3499	highly useful, but valgrind reports are very hard to interpret.
		3500
		3501	If you think you found a bug (memory leak, uninitialised data access etc.)
		3502	in libev, then check twice: If valgrind reports something like:
		3503
		3504	==2274== definitely lost: 0 bytes in 0 blocks.
		3505	==2274== possibly lost: 0 bytes in 0 blocks.
		3506	==2274== still reachable: 256 bytes in 1 blocks.
		3507
		3508	Then there is no memory leak. Similarly, under some circumstances,
		3509	valgrind might report kernel bugs as if it were a bug in libev, or it
		3510	might be confused (it is a very good tool, but only a tool).
		3511
		3512	If you are unsure about something, feel free to contact the mailing list
		3513	with the full valgrind report and an explanation on why you think this is
		3514	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3515	no bug" answer and take the chance of learning how to interpret valgrind
		3516	properly.
		3517
		3518	If you need, for some reason, empty reports from valgrind for your project
		3519	I suggest using suppression lists.
		3520
		3521
2519	=head1 AUTHOR	3522	=head1 AUTHOR
2520		3523
2521	Marc Lehmann <libev@schmorp.de>.	3524	Marc Lehmann <libev@schmorp.de>.
2522		3525

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