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Revision 1.137 by root, Sun Mar 16 16:42:56 2008 UTC vs.
Revision 1.223 by root, Sun Dec 14 21:58:08 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	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 DESCRIPTION
66		68
67	The newest version of this document is also available as an html-formatted	69	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	70	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		72
71	Libev is an event loop: you register interest in certain events (such as a	73	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	74	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	75	these event sources and provide your program with events.
74		76
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	116	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	117	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	118	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	119	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	120	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	121	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	122	throughout libev.
		123
		124	=head1 ERROR HANDLING
		125
		126	Libev knows three classes of errors: operating system errors, usage errors
		127	and internal errors (bugs).
		128
		129	When libev catches an operating system error it cannot handle (for example
		130	a system call indicating a condition libev cannot fix), it calls the callback
		131	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		132	abort. The default is to print a diagnostic message and to call C<abort
		133	()>.
		134
		135	When libev detects a usage error such as a negative timer interval, then
		136	it will print a diagnostic message and abort (via the C<assert> mechanism,
		137	so C<NDEBUG> will disable this checking): these are programming errors in
		138	the libev caller and need to be fixed there.
		139
		140	Libev also has a few internal error-checking C<assert>ions, and also has
		141	extensive consistency checking code. These do not trigger under normal
		142	circumstances, as they indicate either a bug in libev or worse.
		143
121		144
122	=head1 GLOBAL FUNCTIONS	145	=head1 GLOBAL FUNCTIONS
123		146
124	These functions can be called anytime, even before initialising the	147	These functions can be called anytime, even before initialising the
125	library in any way.	148	library in any way.
…		…
134		157
135	=item ev_sleep (ev_tstamp interval)	158	=item ev_sleep (ev_tstamp interval)
136		159
137	Sleep for the given interval: The current thread will be blocked until	160	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	161	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	162	this is a sub-second-resolution C<sleep ()>.
140		163
141	=item int ev_version_major ()	164	=item int ev_version_major ()
142		165
143	=item int ev_version_minor ()	166	=item int ev_version_minor ()
144		167
…		…
157	not a problem.	180	not a problem.
158		181
159	Example: Make sure we haven't accidentally been linked against the wrong	182	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	183	version.
161		184
162	assert (("libev version mismatch",	185	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	186	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	187	&& ev_version_minor () >= EV_VERSION_MINOR));
165		188
166	=item unsigned int ev_supported_backends ()	189	=item unsigned int ev_supported_backends ()
167		190
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	191	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	192	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	194	a description of the set values.
172		195
173	Example: make sure we have the epoll method, because yeah this is cool and	196	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	197	a must have and can we have a torrent of it please!!!11
175		198
176	assert (("sorry, no epoll, no sex",	199	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	200	ev_supported_backends () & EVBACKEND_EPOLL));
178		201
179	=item unsigned int ev_recommended_backends ()	202	=item unsigned int ev_recommended_backends ()
180		203
181	Return the set of all backends compiled into this binary of libev and also	204	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	205	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	206	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	207	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	208	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	209	libev will probe for if you specify no backends explicitly.
187		210
188	=item unsigned int ev_embeddable_backends ()	211	=item unsigned int ev_embeddable_backends ()
189		212
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	217	recommended ones.
195		218
196	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
197		220
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		222
200	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	225	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	226	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	227	or take some potentially destructive action.
205	function.	228
		229	Since some systems (at least OpenBSD and Darwin) fail to implement
		230	correct C<realloc> semantics, libev will use a wrapper around the system
		231	C<realloc> and C<free> functions by default.
206		232
207	You could override this function in high-availability programs to, say,	233	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	234	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	235	or even to sleep a while and retry until some memory is available.
210		236
211	Example: Replace the libev allocator with one that waits a bit and then	237	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	238	retries (example requires a standards-compliant C<realloc>).
213		239
214	static void *	240	static void *
215	persistent_realloc (void *ptr, size_t size)	241	persistent_realloc (void *ptr, size_t size)
216	{	242	{
217	for (;;)	243	for (;;)
…		…
226	}	252	}
227		253
228	...	254	...
229	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
230		256
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		258
233	Set the callback function to call on a retryable syscall error (such	259	Set the callback function to call on a retryable system call error (such
234	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
236	callback is set, then libev will expect it to remedy the sitution, no	262	callback is set, then libev will expect it to remedy the situation, no
237	matter what, when it returns. That is, libev will generally retry the	263	matter what, when it returns. That is, libev will generally retry the
238	requested operation, or, if the condition doesn't go away, do bad stuff	264	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	265	(such as abort).
240		266
241	Example: This is basically the same thing that libev does internally, too.	267	Example: This is basically the same thing that libev does internally, too.
…		…
252		278
253	=back	279	=back
254		280
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		282
257	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
258	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
259	events, and dynamically created loops which do not.	285	I<function>).
260		286
261	If you use threads, a common model is to run the default event loop	287	The library knows two types of such loops, the I<default> loop, which
262	in your main thread (or in a separate thread) and for each thread you	288	supports signals and child events, and dynamically created loops which do
263	create, you also create another event loop. Libev itself does no locking	289	not.
264	whatsoever, so if you mix calls to the same event loop in different
265	threads, make sure you lock (this is usually a bad idea, though, even if
266	done correctly, because it's hideous and inefficient).
267		290
268	=over 4	291	=over 4
269		292
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		294
…		…
275	flags. If that is troubling you, check C<ev_backend ()> afterwards).	298	flags. If that is troubling you, check C<ev_backend ()> afterwards).
276		299
277	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
278	function.	301	function.
279		302
		303	Note that this function is I<not> thread-safe, so if you want to use it
		304	from multiple threads, you have to lock (note also that this is unlikely,
		305	as loops cannot be shared easily between threads anyway).
		306
280	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	312	C<ev_default_init>.
286		313
287	The flags argument can be used to specify special behaviour or specific	314	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	323	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	324	thing, believe me).
298		325
299	=item C<EVFLAG_NOENV>	326	=item C<EVFLAG_NOENV>
300		327
301	If this flag bit is ored into the flag value (or the program runs setuid	328	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	329	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	331	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	332	useful to try out specific backends to test their performance, or to work
306	around bugs.	333	around bugs.
…		…
313		340
314	This works by calling C<getpid ()> on every iteration of the loop,	341	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	342	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	343	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	345	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	346	C<pthread_atfork> which is even faster).
320		347
321	The big advantage of this flag is that you can forget about fork (and	348	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	349	forget about forgetting to tell libev about forking) when you use this
323	flag.	350	flag.
324		351
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	353	environment variable.
327		354
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		356
330	This is your standard select(2) backend. Not I<completely> standard, as	357	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	359	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	360	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	361	usually the fastest backend for a low number of (low-numbered :) fds.
335		362
336	To get good performance out of this backend you need a high amount of	363	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	364	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	365	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	366	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	368	readiness notifications you get per iteration.
		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
342		373
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		375
345	And this is your standard poll(2) backend. It's more complicated	376	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	377	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	378	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	379	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	381	performance tips.
351		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		385
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		387
354	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
358	of shortcomings, such as silently dropping events in some hard-to-detect	392
359	cases and rewiring a syscall per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
360	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
361		409
362	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	411	will result in some caching, there is still a system call per such
364	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
366	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
367		415	file descriptors.
368	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.
371		416
372	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	418	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
375		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
		428
376	While nominally embeddeble in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
378		434
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		436
381	Kqueue deserves special mention, as at the time of this writing, it	437	Kqueue deserves special mention, as at the time of this writing, it
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
383	with anything but sockets and pipes, except on Darwin, where of course	439	with anything but sockets and pipes, except on Darwin, where of course
384	it's completely useless). For this reason it's not being "autodetected"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	without API changes to existing programs. For this reason it's not being
385	unless you explicitly specify it explicitly in the flags (i.e. using	443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
387	system like NetBSD.	445	system like NetBSD.
388		446
389	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	449	the target platform). See C<ev_embed> watchers for more info.
392		450
393	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
398	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
399		458
400	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
401		460
402	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
407	sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
408		471
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		473
411	This is not implemented yet (and might never be, unless you send me an	474	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	475	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		480
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	482	it's really slow, but it still scales very well (O(active_fds)).
420		483
421	Please note that solaris event ports can deliver a lot of spurious	484	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	485	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	486	blocking when no data (or space) is available.
424		487
425	While this backend scales well, it requires one system call per active	488	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	489	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	491	might perform better.
429		492
430	On the positive side, ignoring the spurious readyness notifications, this	493	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
433		500
434	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
435		502
436	Try all backends (even potentially broken ones that wouldn't be tried	503	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		506
440	It is definitely not recommended to use this flag.	507	It is definitely not recommended to use this flag.
441		508
442	=back	509	=back
443		510
444	If one or more of these are ored into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		514
448	The most typical usage is like this:	515	Example: This is the most typical usage.
449		516
450	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		519
453	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	521	environment settings to be taken into account:
455		522
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		524
458	Use whatever libev has to offer, but make sure that kqueue is used if	525	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	527	private event loop and only if you know the OS supports your types of
		528	fds):
461		529
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		531
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		533
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	534	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	535	always distinct from the default loop. Unlike the default loop, it cannot
468	handle signal and child watchers, and attempts to do so will be greeted by	536	handle signal and child watchers, and attempts to do so will be greeted by
469	undefined behaviour (or a failed assertion if assertions are enabled).	537	undefined behaviour (or a failed assertion if assertions are enabled).
470		538
		539	Note that this function I<is> thread-safe, and the recommended way to use
		540	libev with threads is indeed to create one loop per thread, and using the
		541	default loop in the "main" or "initial" thread.
		542
471	Example: Try to create a event loop that uses epoll and nothing else.	543	Example: Try to create a event loop that uses epoll and nothing else.
472		544
473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
474	if (!epoller)	546	if (!epoller)
475	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
476		548
477	=item ev_default_destroy ()	549	=item ev_default_destroy ()
478		550
479	Destroys the default loop again (frees all memory and kernel state	551	Destroys the default loop again (frees all memory and kernel state
480	etc.). None of the active event watchers will be stopped in the normal	552	etc.). None of the active event watchers will be stopped in the normal
481	sense, so e.g. C<ev_is_active> might still return true. It is your	553	sense, so e.g. C<ev_is_active> might still return true. It is your
482	responsibility to either stop all watchers cleanly yoursef I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
483	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
484	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
485	for example).	557	for example).
486		558
487	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
488	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
489	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
490		562
491	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
492	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
493	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
494	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
519		591
520	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
521		593
522	Like C<ev_default_fork>, but acts on an event loop created by	594	Like C<ev_default_fork>, but acts on an event loop created by
523	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
524	after fork, and how you do this is entirely your own problem.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
525		598
526	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
527		600
528	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
529		603
530	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
531		605
532	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
533	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
548	received events and started processing them. This timestamp does not	622	received events and started processing them. This timestamp does not
549	change as long as callbacks are being processed, and this is also the base	623	change as long as callbacks are being processed, and this is also the base
550	time used for relative timers. You can treat it as the timestamp of the	624	time used for relative timers. You can treat it as the timestamp of the
551	event occurring (or more correctly, libev finding out about it).	625	event occurring (or more correctly, libev finding out about it).
552		626
		627	=item ev_now_update (loop)
		628
		629	Establishes the current time by querying the kernel, updating the time
		630	returned by C<ev_now ()> in the progress. This is a costly operation and
		631	is usually done automatically within C<ev_loop ()>.
		632
		633	This function is rarely useful, but when some event callback runs for a
		634	very long time without entering the event loop, updating libev's idea of
		635	the current time is a good idea.
		636
		637	See also "The special problem of time updates" in the C<ev_timer> section.
		638
553	=item ev_loop (loop, int flags)	639	=item ev_loop (loop, int flags)
554		640
555	Finally, this is it, the event handler. This function usually is called	641	Finally, this is it, the event handler. This function usually is called
556	after you initialised all your watchers and you want to start handling	642	after you initialised all your watchers and you want to start handling
557	events.	643	events.
…		…
559	If the flags argument is specified as C<0>, it will not return until	645	If the flags argument is specified as C<0>, it will not return until
560	either no event watchers are active anymore or C<ev_unloop> was called.	646	either no event watchers are active anymore or C<ev_unloop> was called.
561		647
562	Please note that an explicit C<ev_unloop> is usually better than	648	Please note that an explicit C<ev_unloop> is usually better than
563	relying on all watchers to be stopped when deciding when a program has	649	relying on all watchers to be stopped when deciding when a program has
564	finished (especially in interactive programs), but having a program that	650	finished (especially in interactive programs), but having a program
565	automatically loops as long as it has to and no longer by virtue of	651	that automatically loops as long as it has to and no longer by virtue
566	relying on its watchers stopping correctly is a thing of beauty.	652	of relying on its watchers stopping correctly, that is truly a thing of
		653	beauty.
567		654
568	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
569	those events and any outstanding ones, but will not block your process in	656	those events and any already outstanding ones, but will not block your
570	case there are no events and will return after one iteration of the loop.	657	process in case there are no events and will return after one iteration of
		658	the loop.
571		659
572	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
573	neccessary) and will handle those and any outstanding ones. It will block	661	necessary) and will handle those and any already outstanding ones. It
574	your process until at least one new event arrives, and will return after	662	will block your process until at least one new event arrives (which could
575	one iteration of the loop. This is useful if you are waiting for some	663	be an event internal to libev itself, so there is no guarantee that a
576	external event in conjunction with something not expressible using other	664	user-registered callback will be called), and will return after one
		665	iteration of the loop.
		666
		667	This is useful if you are waiting for some external event in conjunction
		668	with something not expressible using other libev watchers (i.e. "roll your
577	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
578	usually a better approach for this kind of thing.	670	usually a better approach for this kind of thing.
579		671
580	Here are the gory details of what C<ev_loop> does:	672	Here are the gory details of what C<ev_loop> does:
581		673
582	- Before the first iteration, call any pending watchers.	674	- Before the first iteration, call any pending watchers.
583	* If EVFLAG_FORKCHECK was used, check for a fork.	675	* If EVFLAG_FORKCHECK was used, check for a fork.
584	- If a fork was detected, queue and call all fork watchers.	676	- If a fork was detected (by any means), queue and call all fork watchers.
585	- Queue and call all prepare watchers.	677	- Queue and call all prepare watchers.
586	- If we have been forked, recreate the kernel state.	678	- If we have been forked, detach and recreate the kernel state
		679	as to not disturb the other process.
587	- Update the kernel state with all outstanding changes.	680	- Update the kernel state with all outstanding changes.
588	- Update the "event loop time".	681	- Update the "event loop time" (ev_now ()).
589	- Calculate for how long to sleep or block, if at all	682	- Calculate for how long to sleep or block, if at all
590	(active idle watchers, EVLOOP_NONBLOCK or not having	683	(active idle watchers, EVLOOP_NONBLOCK or not having
591	any active watchers at all will result in not sleeping).	684	any active watchers at all will result in not sleeping).
592	- Sleep if the I/O and timer collect interval say so.	685	- Sleep if the I/O and timer collect interval say so.
593	- Block the process, waiting for any events.	686	- Block the process, waiting for any events.
594	- Queue all outstanding I/O (fd) events.	687	- Queue all outstanding I/O (fd) events.
595	- Update the "event loop time" and do time jump handling.	688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
596	- Queue all outstanding timers.	689	- Queue all expired timers.
597	- Queue all outstanding periodics.	690	- Queue all expired periodics.
598	- If no events are pending now, queue all idle watchers.	691	- Unless any events are pending now, queue all idle watchers.
599	- Queue all check watchers.	692	- Queue all check watchers.
600	- Call all queued watchers in reverse order (i.e. check watchers first).	693	- Call all queued watchers in reverse order (i.e. check watchers first).
601	Signals and child watchers are implemented as I/O watchers, and will	694	Signals and child watchers are implemented as I/O watchers, and will
602	be handled here by queueing them when their watcher gets executed.	695	be handled here by queueing them when their watcher gets executed.
603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
608	anymore.	701	anymore.
609		702
610	... queue jobs here, make sure they register event watchers as long	703	... queue jobs here, make sure they register event watchers as long
611	... as they still have work to do (even an idle watcher will do..)	704	... as they still have work to do (even an idle watcher will do..)
612	ev_loop (my_loop, 0);	705	ev_loop (my_loop, 0);
613	... jobs done. yeah!	706	... jobs done or somebody called unloop. yeah!
614		707
615	=item ev_unloop (loop, how)	708	=item ev_unloop (loop, how)
616		709
617	Can be used to make a call to C<ev_loop> return early (but only after it	710	Can be used to make a call to C<ev_loop> return early (but only after it
618	has processed all outstanding events). The C<how> argument must be either	711	has processed all outstanding events). The C<how> argument must be either
619	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
620	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
621		714
622	This "unloop state" will be cleared when entering C<ev_loop> again.	715	This "unloop state" will be cleared when entering C<ev_loop> again.
623		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
624	=item ev_ref (loop)	719	=item ev_ref (loop)
625		720
626	=item ev_unref (loop)	721	=item ev_unref (loop)
627		722
628	Ref/unref can be used to add or remove a reference count on the event	723	Ref/unref can be used to add or remove a reference count on the event
629	loop: Every watcher keeps one reference, and as long as the reference	724	loop: Every watcher keeps one reference, and as long as the reference
630	count is nonzero, C<ev_loop> will not return on its own. If you have	725	count is nonzero, C<ev_loop> will not return on its own.
		726
631	a watcher you never unregister that should not keep C<ev_loop> from	727	If you have a watcher you never unregister that should not keep C<ev_loop>
632	returning, ev_unref() after starting, and ev_ref() before stopping it. For	728	from returning, call ev_unref() after starting, and ev_ref() before
		729	stopping it.
		730
633	example, libev itself uses this for its internal signal pipe: It is not	731	As an example, libev itself uses this for its internal signal pipe: It is
634	visible to the libev user and should not keep C<ev_loop> from exiting if	732	not visible to the libev user and should not keep C<ev_loop> from exiting
635	no event watchers registered by it are active. It is also an excellent	733	if no event watchers registered by it are active. It is also an excellent
636	way to do this for generic recurring timers or from within third-party	734	way to do this for generic recurring timers or from within third-party
637	libraries. Just remember to I<unref after start> and I<ref before stop>	735	libraries. Just remember to I<unref after start> and I<ref before stop>
638	(but only if the watcher wasn't active before, or was active before,	736	(but only if the watcher wasn't active before, or was active before,
639	respectively).	737	respectively).
640		738
641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
642	running when nothing else is active.	740	running when nothing else is active.
643		741
644	struct ev_signal exitsig;	742	ev_signal exitsig;
645	ev_signal_init (&exitsig, sig_cb, SIGINT);	743	ev_signal_init (&exitsig, sig_cb, SIGINT);
646	ev_signal_start (loop, &exitsig);	744	ev_signal_start (loop, &exitsig);
647	evf_unref (loop);	745	evf_unref (loop);
648		746
649	Example: For some weird reason, unregister the above signal handler again.	747	Example: For some weird reason, unregister the above signal handler again.
650		748
651	ev_ref (loop);	749	ev_ref (loop);
652	ev_signal_stop (loop, &exitsig);	750	ev_signal_stop (loop, &exitsig);
653		751
654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	752	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
655		753
656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	754	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
657		755
658	These advanced functions influence the time that libev will spend waiting	756	These advanced functions influence the time that libev will spend waiting
659	for events. Both are by default C<0>, meaning that libev will try to	757	for events. Both time intervals are by default C<0>, meaning that libev
660	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	758	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		759	latency.
661		760
662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	761	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
663	allows libev to delay invocation of I/O and timer/periodic callbacks to	762	allows libev to delay invocation of I/O and timer/periodic callbacks
664	increase efficiency of loop iterations.	763	to increase efficiency of loop iterations (or to increase power-saving
		764	opportunities).
665		765
666	The background is that sometimes your program runs just fast enough to	766	The idea is that sometimes your program runs just fast enough to handle
667	handle one (or very few) event(s) per loop iteration. While this makes	767	one (or very few) event(s) per loop iteration. While this makes the
668	the program responsive, it also wastes a lot of CPU time to poll for new	768	program responsive, it also wastes a lot of CPU time to poll for new
669	events, especially with backends like C<select ()> which have a high	769	events, especially with backends like C<select ()> which have a high
670	overhead for the actual polling but can deliver many events at once.	770	overhead for the actual polling but can deliver many events at once.
671		771
672	By setting a higher I<io collect interval> you allow libev to spend more	772	By setting a higher I<io collect interval> you allow libev to spend more
673	time collecting I/O events, so you can handle more events per iteration,	773	time collecting I/O events, so you can handle more events per iteration,
…		…
675	C<ev_timer>) will be not affected. Setting this to a non-null value will	775	C<ev_timer>) will be not affected. Setting this to a non-null value will
676	introduce an additional C<ev_sleep ()> call into most loop iterations.	776	introduce an additional C<ev_sleep ()> call into most loop iterations.
677		777
678	Likewise, by setting a higher I<timeout collect interval> you allow libev	778	Likewise, by setting a higher I<timeout collect interval> you allow libev
679	to spend more time collecting timeouts, at the expense of increased	779	to spend more time collecting timeouts, at the expense of increased
680	latency (the watcher callback will be called later). C<ev_io> watchers	780	latency/jitter/inexactness (the watcher callback will be called
681	will not be affected. Setting this to a non-null value will not introduce	781	later). C<ev_io> watchers will not be affected. Setting this to a non-null
682	any overhead in libev.	782	value will not introduce any overhead in libev.
683		783
684	Many (busy) programs can usually benefit by setting the io collect	784	Many (busy) programs can usually benefit by setting the I/O collect
685	interval to a value near C<0.1> or so, which is often enough for	785	interval to a value near C<0.1> or so, which is often enough for
686	interactive servers (of course not for games), likewise for timeouts. It	786	interactive servers (of course not for games), likewise for timeouts. It
687	usually doesn't make much sense to set it to a lower value than C<0.01>,	787	usually doesn't make much sense to set it to a lower value than C<0.01>,
688	as this approsaches the timing granularity of most systems.	788	as this approaches the timing granularity of most systems.
		789
		790	Setting the I<timeout collect interval> can improve the opportunity for
		791	saving power, as the program will "bundle" timer callback invocations that
		792	are "near" in time together, by delaying some, thus reducing the number of
		793	times the process sleeps and wakes up again. Another useful technique to
		794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		795	they fire on, say, one-second boundaries only.
		796
		797	=item ev_loop_verify (loop)
		798
		799	This function only does something when C<EV_VERIFY> support has been
		800	compiled in, which is the default for non-minimal builds. It tries to go
		801	through all internal structures and checks them for validity. If anything
		802	is found to be inconsistent, it will print an error message to standard
		803	error and call C<abort ()>.
		804
		805	This can be used to catch bugs inside libev itself: under normal
		806	circumstances, this function will never abort as of course libev keeps its
		807	data structures consistent.
689		808
690	=back	809	=back
691		810
692		811
693	=head1 ANATOMY OF A WATCHER	812	=head1 ANATOMY OF A WATCHER
		813
		814	In the following description, uppercase C<TYPE> in names stands for the
		815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		816	watchers and C<ev_io_start> for I/O watchers.
694		817
695	A watcher is a structure that you create and register to record your	818	A watcher is a structure that you create and register to record your
696	interest in some event. For instance, if you want to wait for STDIN to	819	interest in some event. For instance, if you want to wait for STDIN to
697	become readable, you would create an C<ev_io> watcher for that:	820	become readable, you would create an C<ev_io> watcher for that:
698		821
699	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
700	{	823	{
701	ev_io_stop (w);	824	ev_io_stop (w);
702	ev_unloop (loop, EVUNLOOP_ALL);	825	ev_unloop (loop, EVUNLOOP_ALL);
703	}	826	}
704		827
705	struct ev_loop *loop = ev_default_loop (0);	828	struct ev_loop *loop = ev_default_loop (0);
		829
706	struct ev_io stdin_watcher;	830	ev_io stdin_watcher;
		831
707	ev_init (&stdin_watcher, my_cb);	832	ev_init (&stdin_watcher, my_cb);
708	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
709	ev_io_start (loop, &stdin_watcher);	834	ev_io_start (loop, &stdin_watcher);
		835
710	ev_loop (loop, 0);	836	ev_loop (loop, 0);
711		837
712	As you can see, you are responsible for allocating the memory for your	838	As you can see, you are responsible for allocating the memory for your
713	watcher structures (and it is usually a bad idea to do this on the stack,	839	watcher structures (and it is I<usually> a bad idea to do this on the
714	although this can sometimes be quite valid).	840	stack).
		841
		842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
715		844
716	Each watcher structure must be initialised by a call to C<ev_init	845	Each watcher structure must be initialised by a call to C<ev_init
717	(watcher *, callback)>, which expects a callback to be provided. This	846	(watcher *, callback)>, which expects a callback to be provided. This
718	callback gets invoked each time the event occurs (or, in the case of io	847	callback gets invoked each time the event occurs (or, in the case of I/O
719	watchers, each time the event loop detects that the file descriptor given	848	watchers, each time the event loop detects that the file descriptor given
720	is readable and/or writable).	849	is readable and/or writable).
721		850
722	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
723	with arguments specific to this watcher type. There is also a macro	852	macro to configure it, with arguments specific to the watcher type. There
724	to combine initialisation and setting in one call: C<< ev_<type>_init	853	is also a macro to combine initialisation and setting in one call: C<<
725	(watcher *, callback, ...) >>.	854	ev_TYPE_init (watcher *, callback, ...) >>.
726		855
727	To make the watcher actually watch out for events, you have to start it	856	To make the watcher actually watch out for events, you have to start it
728	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	857	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
729	*) >>), and you can stop watching for events at any time by calling the	858	*) >>), and you can stop watching for events at any time by calling the
730	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
731		860
732	As long as your watcher is active (has been started but not stopped) you	861	As long as your watcher is active (has been started but not stopped) you
733	must not touch the values stored in it. Most specifically you must never	862	must not touch the values stored in it. Most specifically you must never
734	reinitialise it or call its C<set> macro.	863	reinitialise it or call its C<ev_TYPE_set> macro.
735		864
736	Each and every callback receives the event loop pointer as first, the	865	Each and every callback receives the event loop pointer as first, the
737	registered watcher structure as second, and a bitset of received events as	866	registered watcher structure as second, and a bitset of received events as
738	third argument.	867	third argument.
739		868
…		…
799		928
800	The given async watcher has been asynchronously notified (see C<ev_async>).	929	The given async watcher has been asynchronously notified (see C<ev_async>).
801		930
802	=item C<EV_ERROR>	931	=item C<EV_ERROR>
803		932
804	An unspecified error has occured, the watcher has been stopped. This might	933	An unspecified error has occurred, the watcher has been stopped. This might
805	happen because the watcher could not be properly started because libev	934	happen because the watcher could not be properly started because libev
806	ran out of memory, a file descriptor was found to be closed or any other	935	ran out of memory, a file descriptor was found to be closed or any other
		936	problem. Libev considers these application bugs.
		937
807	problem. You best act on it by reporting the problem and somehow coping	938	You best act on it by reporting the problem and somehow coping with the
808	with the watcher being stopped.	939	watcher being stopped. Note that well-written programs should not receive
		940	an error ever, so when your watcher receives it, this usually indicates a
		941	bug in your program.
809		942
810	Libev will usually signal a few "dummy" events together with an error,	943	Libev will usually signal a few "dummy" events together with an error, for
811	for example it might indicate that a fd is readable or writable, and if	944	example it might indicate that a fd is readable or writable, and if your
812	your callbacks is well-written it can just attempt the operation and cope	945	callbacks is well-written it can just attempt the operation and cope with
813	with the error from read() or write(). This will not work in multithreaded	946	the error from read() or write(). This will not work in multi-threaded
814	programs, though, so beware.	947	programs, though, as the fd could already be closed and reused for another
		948	thing, so beware.
815		949
816	=back	950	=back
817		951
818	=head2 GENERIC WATCHER FUNCTIONS	952	=head2 GENERIC WATCHER FUNCTIONS
819
820	In the following description, C<TYPE> stands for the watcher type,
821	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
822		953
823	=over 4	954	=over 4
824		955
825	=item C<ev_init> (ev_TYPE *watcher, callback)	956	=item C<ev_init> (ev_TYPE *watcher, callback)
826		957
…		…
832	which rolls both calls into one.	963	which rolls both calls into one.
833		964
834	You can reinitialise a watcher at any time as long as it has been stopped	965	You can reinitialise a watcher at any time as long as it has been stopped
835	(or never started) and there are no pending events outstanding.	966	(or never started) and there are no pending events outstanding.
836		967
837	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	968	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
838	int revents)>.	969	int revents)>.
		970
		971	Example: Initialise an C<ev_io> watcher in two steps.
		972
		973	ev_io w;
		974	ev_init (&w, my_cb);
		975	ev_io_set (&w, STDIN_FILENO, EV_READ);
839		976
840	=item C<ev_TYPE_set> (ev_TYPE *, [args])	977	=item C<ev_TYPE_set> (ev_TYPE *, [args])
841		978
842	This macro initialises the type-specific parts of a watcher. You need to	979	This macro initialises the type-specific parts of a watcher. You need to
843	call C<ev_init> at least once before you call this macro, but you can	980	call C<ev_init> at least once before you call this macro, but you can
…		…
846	difference to the C<ev_init> macro).	983	difference to the C<ev_init> macro).
847		984
848	Although some watcher types do not have type-specific arguments	985	Although some watcher types do not have type-specific arguments
849	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	986	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
850		987
		988	See C<ev_init>, above, for an example.
		989
851	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	990	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
852		991
853	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	992	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
854	calls into a single call. This is the most convinient method to initialise	993	calls into a single call. This is the most convenient method to initialise
855	a watcher. The same limitations apply, of course.	994	a watcher. The same limitations apply, of course.
		995
		996	Example: Initialise and set an C<ev_io> watcher in one step.
		997
		998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
856		999
857	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
858		1001
859	Starts (activates) the given watcher. Only active watchers will receive	1002	Starts (activates) the given watcher. Only active watchers will receive
860	events. If the watcher is already active nothing will happen.	1003	events. If the watcher is already active nothing will happen.
861		1004
		1005	Example: Start the C<ev_io> watcher that is being abused as example in this
		1006	whole section.
		1007
		1008	ev_io_start (EV_DEFAULT_UC, &w);
		1009
862	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
863		1011
864	Stops the given watcher again (if active) and clears the pending	1012	Stops the given watcher if active, and clears the pending status (whether
		1013	the watcher was active or not).
		1014
865	status. It is possible that stopped watchers are pending (for example,	1015	It is possible that stopped watchers are pending - for example,
866	non-repeating timers are being stopped when they become pending), but	1016	non-repeating timers are being stopped when they become pending - but
867	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1017	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
868	you want to free or reuse the memory used by the watcher it is therefore a	1018	pending. If you want to free or reuse the memory used by the watcher it is
869	good idea to always call its C<ev_TYPE_stop> function.	1019	therefore a good idea to always call its C<ev_TYPE_stop> function.
870		1020
871	=item bool ev_is_active (ev_TYPE *watcher)	1021	=item bool ev_is_active (ev_TYPE *watcher)
872		1022
873	Returns a true value iff the watcher is active (i.e. it has been started	1023	Returns a true value iff the watcher is active (i.e. it has been started
874	and not yet been stopped). As long as a watcher is active you must not modify	1024	and not yet been stopped). As long as a watcher is active you must not modify
…		…
916	The default priority used by watchers when no priority has been set is	1066	The default priority used by watchers when no priority has been set is
917	always C<0>, which is supposed to not be too high and not be too low :).	1067	always C<0>, which is supposed to not be too high and not be too low :).
918		1068
919	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
920	fine, as long as you do not mind that the priority value you query might	1070	fine, as long as you do not mind that the priority value you query might
921	or might not have been adjusted to be within valid range.	1071	or might not have been clamped to the valid range.
922		1072
923	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
924		1074
925	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
926	C<loop> nor C<revents> need to be valid as long as the watcher callback	1076	C<loop> nor C<revents> need to be valid as long as the watcher callback
927	can deal with that fact.	1077	can deal with that fact, as both are simply passed through to the
		1078	callback.
928		1079
929	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1080	=item int ev_clear_pending (loop, ev_TYPE *watcher)
930		1081
931	If the watcher is pending, this function returns clears its pending status	1082	If the watcher is pending, this function clears its pending status and
932	and returns its C<revents> bitset (as if its callback was invoked). If the	1083	returns its C<revents> bitset (as if its callback was invoked). If the
933	watcher isn't pending it does nothing and returns C<0>.	1084	watcher isn't pending it does nothing and returns C<0>.
934		1085
		1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1087	callback to be invoked, which can be accomplished with this function.
		1088
935	=back	1089	=back
936		1090
937		1091
938	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
939		1093
940	Each watcher has, by default, a member C<void *data> that you can change	1094	Each watcher has, by default, a member C<void *data> that you can change
941	and read at any time, libev will completely ignore it. This can be used	1095	and read at any time: libev will completely ignore it. This can be used
942	to associate arbitrary data with your watcher. If you need more data and	1096	to associate arbitrary data with your watcher. If you need more data and
943	don't want to allocate memory and store a pointer to it in that data	1097	don't want to allocate memory and store a pointer to it in that data
944	member, you can also "subclass" the watcher type and provide your own	1098	member, you can also "subclass" the watcher type and provide your own
945	data:	1099	data:
946		1100
947	struct my_io	1101	struct my_io
948	{	1102	{
949	struct ev_io io;	1103	ev_io io;
950	int otherfd;	1104	int otherfd;
951	void *somedata;	1105	void *somedata;
952	struct whatever *mostinteresting;	1106	struct whatever *mostinteresting;
953	}	1107	};
		1108
		1109	...
		1110	struct my_io w;
		1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
954		1112
955	And since your callback will be called with a pointer to the watcher, you	1113	And since your callback will be called with a pointer to the watcher, you
956	can cast it back to your own type:	1114	can cast it back to your own type:
957		1115
958	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
959	{	1117	{
960	struct my_io *w = (struct my_io *)w_;	1118	struct my_io *w = (struct my_io *)w_;
961	...	1119	...
962	}	1120	}
963		1121
964	More interesting and less C-conformant ways of casting your callback type	1122	More interesting and less C-conformant ways of casting your callback type
965	instead have been omitted.	1123	instead have been omitted.
966		1124
967	Another common scenario is having some data structure with multiple	1125	Another common scenario is to use some data structure with multiple
968	watchers:	1126	embedded watchers:
969		1127
970	struct my_biggy	1128	struct my_biggy
971	{	1129	{
972	int some_data;	1130	int some_data;
973	ev_timer t1;	1131	ev_timer t1;
974	ev_timer t2;	1132	ev_timer t2;
975	}	1133	}
976		1134
977	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1135	In this case getting the pointer to C<my_biggy> is a bit more
978	you need to use C<offsetof>:	1136	complicated: Either you store the address of your C<my_biggy> struct
		1137	in the C<data> member of the watcher (for woozies), or you need to use
		1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1139	programmers):
979		1140
980	#include <stddef.h>	1141	#include <stddef.h>
981		1142
982	static void	1143	static void
983	t1_cb (EV_P_ struct ev_timer *w, int revents)	1144	t1_cb (EV_P_ ev_timer *w, int revents)
984	{	1145	{
985	struct my_biggy big = (struct my_biggy *	1146	struct my_biggy big = (struct my_biggy *
986	(((char *)w) - offsetof (struct my_biggy, t1));	1147	(((char *)w) - offsetof (struct my_biggy, t1));
987	}	1148	}
988		1149
989	static void	1150	static void
990	t2_cb (EV_P_ struct ev_timer *w, int revents)	1151	t2_cb (EV_P_ ev_timer *w, int revents)
991	{	1152	{
992	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
993	(((char *)w) - offsetof (struct my_biggy, t2));	1154	(((char *)w) - offsetof (struct my_biggy, t2));
994	}	1155	}
995		1156
996		1157
997	=head1 WATCHER TYPES	1158	=head1 WATCHER TYPES
998		1159
999	This section describes each watcher in detail, but will not repeat	1160	This section describes each watcher in detail, but will not repeat
…		…
1023	In general you can register as many read and/or write event watchers per	1184	In general you can register as many read and/or write event watchers per
1024	fd as you want (as long as you don't confuse yourself). Setting all file	1185	fd as you want (as long as you don't confuse yourself). Setting all file
1025	descriptors to non-blocking mode is also usually a good idea (but not	1186	descriptors to non-blocking mode is also usually a good idea (but not
1026	required if you know what you are doing).	1187	required if you know what you are doing).
1027		1188
1028	If you must do this, then force the use of a known-to-be-good backend	1189	If you cannot use non-blocking mode, then force the use of a
1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1190	known-to-be-good backend (at the time of this writing, this includes only
1030	C<EVBACKEND_POLL>).	1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1031		1192
1032	Another thing you have to watch out for is that it is quite easy to	1193	Another thing you have to watch out for is that it is quite easy to
1033	receive "spurious" readyness notifications, that is your callback might	1194	receive "spurious" readiness notifications, that is your callback might
1034	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1035	because there is no data. Not only are some backends known to create a	1196	because there is no data. Not only are some backends known to create a
1036	lot of those (for example solaris ports), it is very easy to get into	1197	lot of those (for example Solaris ports), it is very easy to get into
1037	this situation even with a relatively standard program structure. Thus	1198	this situation even with a relatively standard program structure. Thus
1038	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1039	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1040		1201
1041	If you cannot run the fd in non-blocking mode (for example you should not	1202	If you cannot run the fd in non-blocking mode (for example you should
1042	play around with an Xlib connection), then you have to seperately re-test	1203	not play around with an Xlib connection), then you have to separately
1043	whether a file descriptor is really ready with a known-to-be good interface	1204	re-test whether a file descriptor is really ready with a known-to-be good
1044	such as poll (fortunately in our Xlib example, Xlib already does this on	1205	interface such as poll (fortunately in our Xlib example, Xlib already
1045	its own, so its quite safe to use).	1206	does this on its own, so its quite safe to use). Some people additionally
		1207	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1208	indefinitely.
		1209
		1210	But really, best use non-blocking mode.
1046		1211
1047	=head3 The special problem of disappearing file descriptors	1212	=head3 The special problem of disappearing file descriptors
1048		1213
1049	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1214	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1050	descriptor (either by calling C<close> explicitly or by any other means,	1215	descriptor (either due to calling C<close> explicitly or any other means,
1051	such as C<dup>). The reason is that you register interest in some file	1216	such as C<dup2>). The reason is that you register interest in some file
1052	descriptor, but when it goes away, the operating system will silently drop	1217	descriptor, but when it goes away, the operating system will silently drop
1053	this interest. If another file descriptor with the same number then is	1218	this interest. If another file descriptor with the same number then is
1054	registered with libev, there is no efficient way to see that this is, in	1219	registered with libev, there is no efficient way to see that this is, in
1055	fact, a different file descriptor.	1220	fact, a different file descriptor.
1056		1221
…		…
1085	To support fork in your programs, you either have to call	1250	To support fork in your programs, you either have to call
1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1251	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1088	C<EVBACKEND_POLL>.	1253	C<EVBACKEND_POLL>.
1089		1254
		1255	=head3 The special problem of SIGPIPE
		1256
		1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1258	when writing to a pipe whose other end has been closed, your program gets
		1259	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1260	this is sensible behaviour, for daemons, this is usually undesirable.
		1261
		1262	So when you encounter spurious, unexplained daemon exits, make sure you
		1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1264	somewhere, as that would have given you a big clue).
		1265
1090		1266
1091	=head3 Watcher-Specific Functions	1267	=head3 Watcher-Specific Functions
1092		1268
1093	=over 4	1269	=over 4
1094		1270
1095	=item ev_io_init (ev_io *, callback, int fd, int events)	1271	=item ev_io_init (ev_io *, callback, int fd, int events)
1096		1272
1097	=item ev_io_set (ev_io *, int fd, int events)	1273	=item ev_io_set (ev_io *, int fd, int events)
1098		1274
1099	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1275	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1100	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1276	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1101	C<EV_READ | EV_WRITE> to receive the given events.	1277	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1102		1278
1103	=item int fd [read-only]	1279	=item int fd [read-only]
1104		1280
1105	The file descriptor being watched.	1281	The file descriptor being watched.
1106		1282
…		…
1114		1290
1115	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1291	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1116	readable, but only once. Since it is likely line-buffered, you could	1292	readable, but only once. Since it is likely line-buffered, you could
1117	attempt to read a whole line in the callback.	1293	attempt to read a whole line in the callback.
1118		1294
1119	static void	1295	static void
1120	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1296	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1121	{	1297	{
1122	ev_io_stop (loop, w);	1298	ev_io_stop (loop, w);
1123	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1299	.. read from stdin here (or from w->fd) and handle any I/O errors
1124	}	1300	}
1125		1301
1126	...	1302	...
1127	struct ev_loop *loop = ev_default_init (0);	1303	struct ev_loop *loop = ev_default_init (0);
1128	struct ev_io stdin_readable;	1304	ev_io stdin_readable;
1129	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1130	ev_io_start (loop, &stdin_readable);	1306	ev_io_start (loop, &stdin_readable);
1131	ev_loop (loop, 0);	1307	ev_loop (loop, 0);
1132		1308
1133		1309
1134	=head2 C<ev_timer> - relative and optionally repeating timeouts	1310	=head2 C<ev_timer> - relative and optionally repeating timeouts
1135		1311
1136	Timer watchers are simple relative timers that generate an event after a	1312	Timer watchers are simple relative timers that generate an event after a
1137	given time, and optionally repeating in regular intervals after that.	1313	given time, and optionally repeating in regular intervals after that.
1138		1314
1139	The timers are based on real time, that is, if you register an event that	1315	The timers are based on real time, that is, if you register an event that
1140	times out after an hour and you reset your system clock to last years	1316	times out after an hour and you reset your system clock to January last
1141	time, it will still time out after (roughly) and hour. "Roughly" because	1317	year, it will still time out after (roughly) one hour. "Roughly" because
1142	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1143	monotonic clock option helps a lot here).	1319	monotonic clock option helps a lot here).
		1320
		1321	The callback is guaranteed to be invoked only I<after> its timeout has
		1322	passed, but if multiple timers become ready during the same loop iteration
		1323	then order of execution is undefined.
		1324
		1325	=head3 Be smart about timeouts
		1326
		1327	Many real-world problems involve some kind of timeout, usually for error
		1328	recovery. A typical example is an HTTP request - if the other side hangs,
		1329	you want to raise some error after a while.
		1330
		1331	What follows are some ways to handle this problem, from obvious and
		1332	inefficient to smart and efficient.
		1333
		1334	In the following, a 60 second activity timeout is assumed - a timeout that
		1335	gets reset to 60 seconds each time there is activity (e.g. each time some
		1336	data or other life sign was received).
		1337
		1338	=over 4
		1339
		1340	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1341
		1342	This is the most obvious, but not the most simple way: In the beginning,
		1343	start the watcher:
		1344
		1345	ev_timer_init (timer, callback, 60., 0.);
		1346	ev_timer_start (loop, timer);
		1347
		1348	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1349	and start it again:
		1350
		1351	ev_timer_stop (loop, timer);
		1352	ev_timer_set (timer, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	This is relatively simple to implement, but means that each time there is
		1356	some activity, libev will first have to remove the timer from its internal
		1357	data structure and then add it again. Libev tries to be fast, but it's
		1358	still not a constant-time operation.
		1359
		1360	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1361
		1362	This is the easiest way, and involves using C<ev_timer_again> instead of
		1363	C<ev_timer_start>.
		1364
		1365	To implement this, configure an C<ev_timer> with a C<repeat> value
		1366	of C<60> and then call C<ev_timer_again> at start and each time you
		1367	successfully read or write some data. If you go into an idle state where
		1368	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1369	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1370
		1371	That means you can ignore both the C<ev_timer_start> function and the
		1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1373	member and C<ev_timer_again>.
		1374
		1375	At start:
		1376
		1377	ev_timer_init (timer, callback);
		1378	timer->repeat = 60.;
		1379	ev_timer_again (loop, timer);
		1380
		1381	Each time there is some activity:
		1382
		1383	ev_timer_again (loop, timer);
		1384
		1385	It is even possible to change the time-out on the fly, regardless of
		1386	whether the watcher is active or not:
		1387
		1388	timer->repeat = 30.;
		1389	ev_timer_again (loop, timer);
		1390
		1391	This is slightly more efficient then stopping/starting the timer each time
		1392	you want to modify its timeout value, as libev does not have to completely
		1393	remove and re-insert the timer from/into its internal data structure.
		1394
		1395	It is, however, even simpler than the "obvious" way to do it.
		1396
		1397	=item 3. Let the timer time out, but then re-arm it as required.
		1398
		1399	This method is more tricky, but usually most efficient: Most timeouts are
		1400	relatively long compared to the intervals between other activity - in
		1401	our example, within 60 seconds, there are usually many I/O events with
		1402	associated activity resets.
		1403
		1404	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1405	but remember the time of last activity, and check for a real timeout only
		1406	within the callback:
		1407
		1408	ev_tstamp last_activity; // time of last activity
		1409
		1410	static void
		1411	callback (EV_P_ ev_timer *w, int revents)
		1412	{
		1413	ev_tstamp now = ev_now (EV_A);
		1414	ev_tstamp timeout = last_activity + 60.;
		1415
		1416	// if last_activity + 60. is older than now, we did time out
		1417	if (timeout < now)
		1418	{
		1419	// timeout occured, take action
		1420	}
		1421	else
		1422	{
		1423	// callback was invoked, but there was some activity, re-arm
		1424	// the watcher to fire in last_activity + 60, which is
		1425	// guaranteed to be in the future, so "again" is positive:
		1426	w->repeat = timeout - now;
		1427	ev_timer_again (EV_A_ w);
		1428	}
		1429	}
		1430
		1431	To summarise the callback: first calculate the real timeout (defined
		1432	as "60 seconds after the last activity"), then check if that time has
		1433	been reached, which means something I<did>, in fact, time out. Otherwise
		1434	the callback was invoked too early (C<timeout> is in the future), so
		1435	re-schedule the timer to fire at that future time, to see if maybe we have
		1436	a timeout then.
		1437
		1438	Note how C<ev_timer_again> is used, taking advantage of the
		1439	C<ev_timer_again> optimisation when the timer is already running.
		1440
		1441	This scheme causes more callback invocations (about one every 60 seconds
		1442	minus half the average time between activity), but virtually no calls to
		1443	libev to change the timeout.
		1444
		1445	To start the timer, simply initialise the watcher and set C<last_activity>
		1446	to the current time (meaning we just have some activity :), then call the
		1447	callback, which will "do the right thing" and start the timer:
		1448
		1449	ev_timer_init (timer, callback);
		1450	last_activity = ev_now (loop);
		1451	callback (loop, timer, EV_TIMEOUT);
		1452
		1453	And when there is some activity, simply store the current time in
		1454	C<last_activity>, no libev calls at all:
		1455
		1456	last_actiivty = ev_now (loop);
		1457
		1458	This technique is slightly more complex, but in most cases where the
		1459	time-out is unlikely to be triggered, much more efficient.
		1460
		1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1462	callback :) - just change the timeout and invoke the callback, which will
		1463	fix things for you.
		1464
		1465	=item 4. Wee, just use a double-linked list for your timeouts.
		1466
		1467	If there is not one request, but many thousands (millions...), all
		1468	employing some kind of timeout with the same timeout value, then one can
		1469	do even better:
		1470
		1471	When starting the timeout, calculate the timeout value and put the timeout
		1472	at the I<end> of the list.
		1473
		1474	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1475	the list is expected to fire (for example, using the technique #3).
		1476
		1477	When there is some activity, remove the timer from the list, recalculate
		1478	the timeout, append it to the end of the list again, and make sure to
		1479	update the C<ev_timer> if it was taken from the beginning of the list.
		1480
		1481	This way, one can manage an unlimited number of timeouts in O(1) time for
		1482	starting, stopping and updating the timers, at the expense of a major
		1483	complication, and having to use a constant timeout. The constant timeout
		1484	ensures that the list stays sorted.
		1485
		1486	=back
		1487
		1488	So which method the best?
		1489
		1490	Method #2 is a simple no-brain-required solution that is adequate in most
		1491	situations. Method #3 requires a bit more thinking, but handles many cases
		1492	better, and isn't very complicated either. In most case, choosing either
		1493	one is fine, with #3 being better in typical situations.
		1494
		1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1496	rather complicated, but extremely efficient, something that really pays
		1497	off after the first million or so of active timers, i.e. it's usually
		1498	overkill :)
		1499
		1500	=head3 The special problem of time updates
		1501
		1502	Establishing the current time is a costly operation (it usually takes at
		1503	least two system calls): EV therefore updates its idea of the current
		1504	time only before and after C<ev_loop> collects new events, which causes a
		1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1506	lots of events in one iteration.
1144		1507
1145	The relative timeouts are calculated relative to the C<ev_now ()>	1508	The relative timeouts are calculated relative to the C<ev_now ()>
1146	time. This is usually the right thing as this timestamp refers to the time	1509	time. This is usually the right thing as this timestamp refers to the time
1147	of the event triggering whatever timeout you are modifying/starting. If	1510	of the event triggering whatever timeout you are modifying/starting. If
1148	you suspect event processing to be delayed and you I<need> to base the timeout	1511	you suspect event processing to be delayed and you I<need> to base the
1149	on the current time, use something like this to adjust for this:	1512	timeout on the current time, use something like this to adjust for this:
1150		1513
1151	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1152		1515
1153	The callback is guarenteed to be invoked only when its timeout has passed,	1516	If the event loop is suspended for a long time, you can also force an
1154	but if multiple timers become ready during the same loop iteration then	1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1155	order of execution is undefined.	1518	()>.
1156		1519
1157	=head3 Watcher-Specific Functions and Data Members	1520	=head3 Watcher-Specific Functions and Data Members
1158		1521
1159	=over 4	1522	=over 4
1160		1523
1161	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1162		1525
1163	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1526	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1164		1527
1165	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1528	Configure the timer to trigger after C<after> seconds. If C<repeat>
1166	C<0.>, then it will automatically be stopped. If it is positive, then the	1529	is C<0.>, then it will automatically be stopped once the timeout is
1167	timer will automatically be configured to trigger again C<repeat> seconds	1530	reached. If it is positive, then the timer will automatically be
1168	later, again, and again, until stopped manually.	1531	configured to trigger again C<repeat> seconds later, again, and again,
		1532	until stopped manually.
1169		1533
1170	The timer itself will do a best-effort at avoiding drift, that is, if you	1534	The timer itself will do a best-effort at avoiding drift, that is, if
1171	configure a timer to trigger every 10 seconds, then it will trigger at	1535	you configure a timer to trigger every 10 seconds, then it will normally
1172	exactly 10 second intervals. If, however, your program cannot keep up with	1536	trigger at exactly 10 second intervals. If, however, your program cannot
1173	the timer (because it takes longer than those 10 seconds to do stuff) the	1537	keep up with the timer (because it takes longer than those 10 seconds to
1174	timer will not fire more than once per event loop iteration.	1538	do stuff) the timer will not fire more than once per event loop iteration.
1175		1539
1176	=item ev_timer_again (loop, ev_timer *)	1540	=item ev_timer_again (loop, ev_timer *)
1177		1541
1178	This will act as if the timer timed out and restart it again if it is	1542	This will act as if the timer timed out and restart it again if it is
1179	repeating. The exact semantics are:	1543	repeating. The exact semantics are:
1180		1544
1181	If the timer is pending, its pending status is cleared.	1545	If the timer is pending, its pending status is cleared.
1182		1546
1183	If the timer is started but nonrepeating, stop it (as if it timed out).	1547	If the timer is started but non-repeating, stop it (as if it timed out).
1184		1548
1185	If the timer is repeating, either start it if necessary (with the	1549	If the timer is repeating, either start it if necessary (with the
1186	C<repeat> value), or reset the running timer to the C<repeat> value.	1550	C<repeat> value), or reset the running timer to the C<repeat> value.
1187		1551
1188	This sounds a bit complicated, but here is a useful and typical	1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1189	example: Imagine you have a tcp connection and you want a so-called idle	1553	usage example.
1190	timeout, that is, you want to be called when there have been, say, 60
1191	seconds of inactivity on the socket. The easiest way to do this is to
1192	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1193	C<ev_timer_again> each time you successfully read or write some data. If
1194	you go into an idle state where you do not expect data to travel on the
1195	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1196	automatically restart it if need be.
1197
1198	That means you can ignore the C<after> value and C<ev_timer_start>
1199	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1200
1201	ev_timer_init (timer, callback, 0., 5.);
1202	ev_timer_again (loop, timer);
1203	...
1204	timer->again = 17.;
1205	ev_timer_again (loop, timer);
1206	...
1207	timer->again = 10.;
1208	ev_timer_again (loop, timer);
1209
1210	This is more slightly efficient then stopping/starting the timer each time
1211	you want to modify its timeout value.
1212		1554
1213	=item ev_tstamp repeat [read-write]	1555	=item ev_tstamp repeat [read-write]
1214		1556
1215	The current C<repeat> value. Will be used each time the watcher times out	1557	The current C<repeat> value. Will be used each time the watcher times out
1216	or C<ev_timer_again> is called and determines the next timeout (if any),	1558	or C<ev_timer_again> is called, and determines the next timeout (if any),
1217	which is also when any modifications are taken into account.	1559	which is also when any modifications are taken into account.
1218		1560
1219	=back	1561	=back
1220		1562
1221	=head3 Examples	1563	=head3 Examples
1222		1564
1223	Example: Create a timer that fires after 60 seconds.	1565	Example: Create a timer that fires after 60 seconds.
1224		1566
1225	static void	1567	static void
1226	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1568	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1227	{	1569	{
1228	.. one minute over, w is actually stopped right here	1570	.. one minute over, w is actually stopped right here
1229	}	1571	}
1230		1572
1231	struct ev_timer mytimer;	1573	ev_timer mytimer;
1232	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1574	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1233	ev_timer_start (loop, &mytimer);	1575	ev_timer_start (loop, &mytimer);
1234		1576
1235	Example: Create a timeout timer that times out after 10 seconds of	1577	Example: Create a timeout timer that times out after 10 seconds of
1236	inactivity.	1578	inactivity.
1237		1579
1238	static void	1580	static void
1239	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1581	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1240	{	1582	{
1241	.. ten seconds without any activity	1583	.. ten seconds without any activity
1242	}	1584	}
1243		1585
1244	struct ev_timer mytimer;	1586	ev_timer mytimer;
1245	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1246	ev_timer_again (&mytimer); /* start timer */	1588	ev_timer_again (&mytimer); /* start timer */
1247	ev_loop (loop, 0);	1589	ev_loop (loop, 0);
1248		1590
1249	// and in some piece of code that gets executed on any "activity":	1591	// and in some piece of code that gets executed on any "activity":
1250	// reset the timeout to start ticking again at 10 seconds	1592	// reset the timeout to start ticking again at 10 seconds
1251	ev_timer_again (&mytimer);	1593	ev_timer_again (&mytimer);
1252		1594
1253		1595
1254	=head2 C<ev_periodic> - to cron or not to cron?	1596	=head2 C<ev_periodic> - to cron or not to cron?
1255		1597
1256	Periodic watchers are also timers of a kind, but they are very versatile	1598	Periodic watchers are also timers of a kind, but they are very versatile
1257	(and unfortunately a bit complex).	1599	(and unfortunately a bit complex).
1258		1600
1259	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1260	but on wallclock time (absolute time). You can tell a periodic watcher	1602	but on wall clock time (absolute time). You can tell a periodic watcher
1261	to trigger "at" some specific point in time. For example, if you tell a	1603	to trigger after some specific point in time. For example, if you tell a
1262	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1263	+ 10.>) and then reset your system clock to the last year, then it will	1605	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1606	clock to January of the previous year, then it will take more than year
1264	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1265	roughly 10 seconds later).	1608	roughly 10 seconds later as it uses a relative timeout).
1266		1609
1267	They can also be used to implement vastly more complex timers, such as	1610	C<ev_periodic>s can also be used to implement vastly more complex timers,
1268	triggering an event on each midnight, local time or other, complicated,	1611	such as triggering an event on each "midnight, local time", or other
1269	rules.	1612	complicated rules.
1270		1613
1271	As with timers, the callback is guarenteed to be invoked only when the	1614	As with timers, the callback is guaranteed to be invoked only when the
1272	time (C<at>) has been passed, but if multiple periodic timers become ready	1615	time (C<at>) has passed, but if multiple periodic timers become ready
1273	during the same loop iteration then order of execution is undefined.	1616	during the same loop iteration, then order of execution is undefined.
1274		1617
1275	=head3 Watcher-Specific Functions and Data Members	1618	=head3 Watcher-Specific Functions and Data Members
1276		1619
1277	=over 4	1620	=over 4
1278		1621
1279	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1280		1623
1281	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1282		1625
1283	Lots of arguments, lets sort it out... There are basically three modes of	1626	Lots of arguments, lets sort it out... There are basically three modes of
1284	operation, and we will explain them from simplest to complex:	1627	operation, and we will explain them from simplest to most complex:
1285		1628
1286	=over 4	1629	=over 4
1287		1630
1288	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1289		1632
1290	In this configuration the watcher triggers an event at the wallclock time	1633	In this configuration the watcher triggers an event after the wall clock
1291	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1634	time C<at> has passed. It will not repeat and will not adjust when a time
1292	that is, if it is to be run at January 1st 2011 then it will run when the	1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1293	system time reaches or surpasses this time.	1636	only run when the system clock reaches or surpasses this time.
1294		1637
1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1296		1639
1297	In this mode the watcher will always be scheduled to time out at the next	1640	In this mode the watcher will always be scheduled to time out at the next
1298	C<at + N * interval> time (for some integer N, which can also be negative)	1641	C<at + N * interval> time (for some integer N, which can also be negative)
1299	and then repeat, regardless of any time jumps.	1642	and then repeat, regardless of any time jumps.
1300		1643
1301	This can be used to create timers that do not drift with respect to system	1644	This can be used to create timers that do not drift with respect to the
1302	time:	1645	system clock, for example, here is a C<ev_periodic> that triggers each
		1646	hour, on the hour:
1303		1647
1304	ev_periodic_set (&periodic, 0., 3600., 0);	1648	ev_periodic_set (&periodic, 0., 3600., 0);
1305		1649
1306	This doesn't mean there will always be 3600 seconds in between triggers,	1650	This doesn't mean there will always be 3600 seconds in between triggers,
1307	but only that the the callback will be called when the system time shows a	1651	but only that the callback will be called when the system time shows a
1308	full hour (UTC), or more correctly, when the system time is evenly divisible	1652	full hour (UTC), or more correctly, when the system time is evenly divisible
1309	by 3600.	1653	by 3600.
1310		1654
1311	Another way to think about it (for the mathematically inclined) is that	1655	Another way to think about it (for the mathematically inclined) is that
1312	C<ev_periodic> will try to run the callback in this mode at the next possible	1656	C<ev_periodic> will try to run the callback in this mode at the next possible
1313	time where C<time = at (mod interval)>, regardless of any time jumps.	1657	time where C<time = at (mod interval)>, regardless of any time jumps.
1314		1658
1315	For numerical stability it is preferable that the C<at> value is near	1659	For numerical stability it is preferable that the C<at> value is near
1316	C<ev_now ()> (the current time), but there is no range requirement for	1660	C<ev_now ()> (the current time), but there is no range requirement for
1317	this value.	1661	this value, and in fact is often specified as zero.
		1662
		1663	Note also that there is an upper limit to how often a timer can fire (CPU
		1664	speed for example), so if C<interval> is very small then timing stability
		1665	will of course deteriorate. Libev itself tries to be exact to be about one
		1666	millisecond (if the OS supports it and the machine is fast enough).
1318		1667
1319	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1320		1669
1321	In this mode the values for C<interval> and C<at> are both being	1670	In this mode the values for C<interval> and C<at> are both being
1322	ignored. Instead, each time the periodic watcher gets scheduled, the	1671	ignored. Instead, each time the periodic watcher gets scheduled, the
1323	reschedule callback will be called with the watcher as first, and the	1672	reschedule callback will be called with the watcher as first, and the
1324	current time as second argument.	1673	current time as second argument.
1325		1674
1326	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1327	ever, or make any event loop modifications>. If you need to stop it,	1676	ever, or make ANY event loop modifications whatsoever>.
1328	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1329	starting an C<ev_prepare> watcher, which is legal).
1330		1677
		1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1680	only event loop modification you are allowed to do).
		1681
1331	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1682	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1332	ev_tstamp now)>, e.g.:	1683	*w, ev_tstamp now)>, e.g.:
1333		1684
		1685	static ev_tstamp
1334	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1686	my_rescheduler (ev_periodic *w, ev_tstamp now)
1335	{	1687	{
1336	return now + 60.;	1688	return now + 60.;
1337	}	1689	}
1338		1690
1339	It must return the next time to trigger, based on the passed time value	1691	It must return the next time to trigger, based on the passed time value
1340	(that is, the lowest time value larger than to the second argument). It	1692	(that is, the lowest time value larger than to the second argument). It
1341	will usually be called just before the callback will be triggered, but	1693	will usually be called just before the callback will be triggered, but
1342	might be called at other times, too.	1694	might be called at other times, too.
1343		1695
1344	NOTE: I<< This callback must always return a time that is later than the	1696	NOTE: I<< This callback must always return a time that is higher than or
1345	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1697	equal to the passed C<now> value >>.
1346		1698
1347	This can be used to create very complex timers, such as a timer that	1699	This can be used to create very complex timers, such as a timer that
1348	triggers on each midnight, local time. To do this, you would calculate the	1700	triggers on "next midnight, local time". To do this, you would calculate the
1349	next midnight after C<now> and return the timestamp value for this. How	1701	next midnight after C<now> and return the timestamp value for this. How
1350	you do this is, again, up to you (but it is not trivial, which is the main	1702	you do this is, again, up to you (but it is not trivial, which is the main
1351	reason I omitted it as an example).	1703	reason I omitted it as an example).
1352		1704
1353	=back	1705	=back
…		…
1357	Simply stops and restarts the periodic watcher again. This is only useful	1709	Simply stops and restarts the periodic watcher again. This is only useful
1358	when you changed some parameters or the reschedule callback would return	1710	when you changed some parameters or the reschedule callback would return
1359	a different time than the last time it was called (e.g. in a crond like	1711	a different time than the last time it was called (e.g. in a crond like
1360	program when the crontabs have changed).	1712	program when the crontabs have changed).
1361		1713
		1714	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1715
		1716	When active, returns the absolute time that the watcher is supposed to
		1717	trigger next.
		1718
1362	=item ev_tstamp offset [read-write]	1719	=item ev_tstamp offset [read-write]
1363		1720
1364	When repeating, this contains the offset value, otherwise this is the	1721	When repeating, this contains the offset value, otherwise this is the
1365	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1366		1723
…		…
1371		1728
1372	The current interval value. Can be modified any time, but changes only	1729	The current interval value. Can be modified any time, but changes only
1373	take effect when the periodic timer fires or C<ev_periodic_again> is being	1730	take effect when the periodic timer fires or C<ev_periodic_again> is being
1374	called.	1731	called.
1375		1732
1376	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1733	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1377		1734
1378	The current reschedule callback, or C<0>, if this functionality is	1735	The current reschedule callback, or C<0>, if this functionality is
1379	switched off. Can be changed any time, but changes only take effect when	1736	switched off. Can be changed any time, but changes only take effect when
1380	the periodic timer fires or C<ev_periodic_again> is being called.	1737	the periodic timer fires or C<ev_periodic_again> is being called.
1381		1738
1382	=item ev_tstamp at [read-only]
1383
1384	When active, contains the absolute time that the watcher is supposed to
1385	trigger next.
1386
1387	=back	1739	=back
1388		1740
1389	=head3 Examples	1741	=head3 Examples
1390		1742
1391	Example: Call a callback every hour, or, more precisely, whenever the	1743	Example: Call a callback every hour, or, more precisely, whenever the
1392	system clock is divisible by 3600. The callback invocation times have	1744	system time is divisible by 3600. The callback invocation times have
1393	potentially a lot of jittering, but good long-term stability.	1745	potentially a lot of jitter, but good long-term stability.
1394		1746
1395	static void	1747	static void
1396	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1397	{	1749	{
1398	... its now a full hour (UTC, or TAI or whatever your clock follows)	1750	... its now a full hour (UTC, or TAI or whatever your clock follows)
1399	}	1751	}
1400		1752
1401	struct ev_periodic hourly_tick;	1753	ev_periodic hourly_tick;
1402	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1754	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1403	ev_periodic_start (loop, &hourly_tick);	1755	ev_periodic_start (loop, &hourly_tick);
1404		1756
1405	Example: The same as above, but use a reschedule callback to do it:	1757	Example: The same as above, but use a reschedule callback to do it:
1406		1758
1407	#include <math.h>	1759	#include <math.h>
1408		1760
1409	static ev_tstamp	1761	static ev_tstamp
1410	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1762	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1411	{	1763	{
1412	return fmod (now, 3600.) + 3600.;	1764	return now + (3600. - fmod (now, 3600.));
1413	}	1765	}
1414		1766
1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1767	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1416		1768
1417	Example: Call a callback every hour, starting now:	1769	Example: Call a callback every hour, starting now:
1418		1770
1419	struct ev_periodic hourly_tick;	1771	ev_periodic hourly_tick;
1420	ev_periodic_init (&hourly_tick, clock_cb,	1772	ev_periodic_init (&hourly_tick, clock_cb,
1421	fmod (ev_now (loop), 3600.), 3600., 0);	1773	fmod (ev_now (loop), 3600.), 3600., 0);
1422	ev_periodic_start (loop, &hourly_tick);	1774	ev_periodic_start (loop, &hourly_tick);
1423		1775
1424		1776
1425	=head2 C<ev_signal> - signal me when a signal gets signalled!	1777	=head2 C<ev_signal> - signal me when a signal gets signalled!
1426		1778
1427	Signal watchers will trigger an event when the process receives a specific	1779	Signal watchers will trigger an event when the process receives a specific
1428	signal one or more times. Even though signals are very asynchronous, libev	1780	signal one or more times. Even though signals are very asynchronous, libev
1429	will try it's best to deliver signals synchronously, i.e. as part of the	1781	will try it's best to deliver signals synchronously, i.e. as part of the
1430	normal event processing, like any other event.	1782	normal event processing, like any other event.
1431		1783
		1784	If you want signals asynchronously, just use C<sigaction> as you would
		1785	do without libev and forget about sharing the signal. You can even use
		1786	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1787
1432	You can configure as many watchers as you like per signal. Only when the	1788	You can configure as many watchers as you like per signal. Only when the
1433	first watcher gets started will libev actually register a signal watcher	1789	first watcher gets started will libev actually register a signal handler
1434	with the kernel (thus it coexists with your own signal handlers as long	1790	with the kernel (thus it coexists with your own signal handlers as long as
1435	as you don't register any with libev). Similarly, when the last signal	1791	you don't register any with libev for the same signal). Similarly, when
1436	watcher for a signal is stopped libev will reset the signal handler to	1792	the last signal watcher for a signal is stopped, libev will reset the
1437	SIG_DFL (regardless of what it was set to before).	1793	signal handler to SIG_DFL (regardless of what it was set to before).
1438		1794
1439	If possible and supported, libev will install its handlers with	1795	If possible and supported, libev will install its handlers with
1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1441	interrupted. If you have a problem with syscalls getting interrupted by	1797	interrupted. If you have a problem with system calls getting interrupted by
1442	signals you can block all signals in an C<ev_check> watcher and unblock	1798	signals you can block all signals in an C<ev_check> watcher and unblock
1443	them in an C<ev_prepare> watcher.	1799	them in an C<ev_prepare> watcher.
1444		1800
1445	=head3 Watcher-Specific Functions and Data Members	1801	=head3 Watcher-Specific Functions and Data Members
1446		1802
…		…
1459		1815
1460	=back	1816	=back
1461		1817
1462	=head3 Examples	1818	=head3 Examples
1463		1819
1464	Example: Try to exit cleanly on SIGINT and SIGTERM.	1820	Example: Try to exit cleanly on SIGINT.
1465		1821
1466	static void	1822	static void
1467	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1468	{	1824	{
1469	ev_unloop (loop, EVUNLOOP_ALL);	1825	ev_unloop (loop, EVUNLOOP_ALL);
1470	}	1826	}
1471		1827
1472	struct ev_signal signal_watcher;	1828	ev_signal signal_watcher;
1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1474	ev_signal_start (loop, &sigint_cb);	1830	ev_signal_start (loop, &signal_watcher);
1475		1831
1476		1832
1477	=head2 C<ev_child> - watch out for process status changes	1833	=head2 C<ev_child> - watch out for process status changes
1478		1834
1479	Child watchers trigger when your process receives a SIGCHLD in response to	1835	Child watchers trigger when your process receives a SIGCHLD in response to
1480	some child status changes (most typically when a child of yours dies). It	1836	some child status changes (most typically when a child of yours dies or
1481	is permissible to install a child watcher I<after> the child has been	1837	exits). It is permissible to install a child watcher I<after> the child
1482	forked (which implies it might have already exited), as long as the event	1838	has been forked (which implies it might have already exited), as long
1483	loop isn't entered (or is continued from a watcher).	1839	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1840	forking and then immediately registering a watcher for the child is fine,
		1841	but forking and registering a watcher a few event loop iterations later is
		1842	not.
1484		1843
1485	Only the default event loop is capable of handling signals, and therefore	1844	Only the default event loop is capable of handling signals, and therefore
1486	you can only rgeister child watchers in the default event loop.	1845	you can only register child watchers in the default event loop.
1487		1846
1488	=head3 Process Interaction	1847	=head3 Process Interaction
1489		1848
1490	Libev grabs C<SIGCHLD> as soon as the default event loop is	1849	Libev grabs C<SIGCHLD> as soon as the default event loop is
1491	initialised. This is necessary to guarantee proper behaviour even if	1850	initialised. This is necessary to guarantee proper behaviour even if
1492	the first child watcher is started after the child exits. The occurance	1851	the first child watcher is started after the child exits. The occurrence
1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1494	synchronously as part of the event loop processing. Libev always reaps all	1853	synchronously as part of the event loop processing. Libev always reaps all
1495	children, even ones not watched.	1854	children, even ones not watched.
1496		1855
1497	=head3 Overriding the Built-In Processing	1856	=head3 Overriding the Built-In Processing
…		…
1501	handler, you can override it easily by installing your own handler for	1860	handler, you can override it easily by installing your own handler for
1502	C<SIGCHLD> after initialising the default loop, and making sure the	1861	C<SIGCHLD> after initialising the default loop, and making sure the
1503	default loop never gets destroyed. You are encouraged, however, to use an	1862	default loop never gets destroyed. You are encouraged, however, to use an
1504	event-based approach to child reaping and thus use libev's support for	1863	event-based approach to child reaping and thus use libev's support for
1505	that, so other libev users can use C<ev_child> watchers freely.	1864	that, so other libev users can use C<ev_child> watchers freely.
		1865
		1866	=head3 Stopping the Child Watcher
		1867
		1868	Currently, the child watcher never gets stopped, even when the
		1869	child terminates, so normally one needs to stop the watcher in the
		1870	callback. Future versions of libev might stop the watcher automatically
		1871	when a child exit is detected.
1506		1872
1507	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1508		1874
1509	=over 4	1875	=over 4
1510		1876
…		…
1539	=head3 Examples	1905	=head3 Examples
1540		1906
1541	Example: C<fork()> a new process and install a child handler to wait for	1907	Example: C<fork()> a new process and install a child handler to wait for
1542	its completion.	1908	its completion.
1543		1909
1544	ev_child cw;	1910	ev_child cw;
1545		1911
1546	static void	1912	static void
1547	child_cb (EV_P_ struct ev_child *w, int revents)	1913	child_cb (EV_P_ ev_child *w, int revents)
1548	{	1914	{
1549	ev_child_stop (EV_A_ w);	1915	ev_child_stop (EV_A_ w);
1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1916	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1551	}	1917	}
1552		1918
1553	pid_t pid = fork ();	1919	pid_t pid = fork ();
1554		1920
1555	if (pid < 0)	1921	if (pid < 0)
1556	// error	1922	// error
1557	else if (pid == 0)	1923	else if (pid == 0)
1558	{	1924	{
1559	// the forked child executes here	1925	// the forked child executes here
1560	exit (1);	1926	exit (1);
1561	}	1927	}
1562	else	1928	else
1563	{	1929	{
1564	ev_child_init (&cw, child_cb, pid, 0);	1930	ev_child_init (&cw, child_cb, pid, 0);
1565	ev_child_start (EV_DEFAULT_ &cw);	1931	ev_child_start (EV_DEFAULT_ &cw);
1566	}	1932	}
1567		1933
1568		1934
1569	=head2 C<ev_stat> - did the file attributes just change?	1935	=head2 C<ev_stat> - did the file attributes just change?
1570		1936
1571	This watches a filesystem path for attribute changes. That is, it calls	1937	This watches a file system path for attribute changes. That is, it calls
1572	C<stat> regularly (or when the OS says it changed) and sees if it changed	1938	C<stat> on that path in regular intervals (or when the OS says it changed)
1573	compared to the last time, invoking the callback if it did.	1939	and sees if it changed compared to the last time, invoking the callback if
		1940	it did.
1574		1941
1575	The path does not need to exist: changing from "path exists" to "path does	1942	The path does not need to exist: changing from "path exists" to "path does
1576	not exist" is a status change like any other. The condition "path does	1943	not exist" is a status change like any other. The condition "path does not
1577	not exist" is signified by the C<st_nlink> field being zero (which is	1944	exist" (or more correctly "path cannot be stat'ed") is signified by the
1578	otherwise always forced to be at least one) and all the other fields of	1945	C<st_nlink> field being zero (which is otherwise always forced to be at
1579	the stat buffer having unspecified contents.	1946	least one) and all the other fields of the stat buffer having unspecified
		1947	contents.
1580		1948
1581	The path I<should> be absolute and I<must not> end in a slash. If it is	1949	The path I<must not> end in a slash or contain special components such as
		1950	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1582	relative and your working directory changes, the behaviour is undefined.	1951	your working directory changes, then the behaviour is undefined.
1583		1952
1584	Since there is no standard to do this, the portable implementation simply	1953	Since there is no portable change notification interface available, the
1585	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1954	portable implementation simply calls C<stat(2)> regularly on the path
1586	can specify a recommended polling interval for this case. If you specify	1955	to see if it changed somehow. You can specify a recommended polling
1587	a polling interval of C<0> (highly recommended!) then a I<suitable,	1956	interval for this case. If you specify a polling interval of C<0> (highly
1588	unspecified default> value will be used (which you can expect to be around	1957	recommended!) then a I<suitable, unspecified default> value will be used
1589	five seconds, although this might change dynamically). Libev will also	1958	(which you can expect to be around five seconds, although this might
1590	impose a minimum interval which is currently around C<0.1>, but thats	1959	change dynamically). Libev will also impose a minimum interval which is
1591	usually overkill.	1960	currently around C<0.1>, but that's usually overkill.
1592		1961
1593	This watcher type is not meant for massive numbers of stat watchers,	1962	This watcher type is not meant for massive numbers of stat watchers,
1594	as even with OS-supported change notifications, this can be	1963	as even with OS-supported change notifications, this can be
1595	resource-intensive.	1964	resource-intensive.
1596		1965
1597	At the time of this writing, only the Linux inotify interface is	1966	At the time of this writing, the only OS-specific interface implemented
1598	implemented (implementing kqueue support is left as an exercise for the	1967	is the Linux inotify interface (implementing kqueue support is left as an
1599	reader). Inotify will be used to give hints only and should not change the	1968	exercise for the reader. Note, however, that the author sees no way of
1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1969	implementing C<ev_stat> semantics with kqueue, except as a hint).
1601	to fall back to regular polling again even with inotify, but changes are
1602	usually detected immediately, and if the file exists there will be no
1603	polling.
1604		1970
1605	=head3 ABI Issues (Largefile Support)	1971	=head3 ABI Issues (Largefile Support)
1606		1972
1607	Libev by default (unless the user overrides this) uses the default	1973	Libev by default (unless the user overrides this) uses the default
1608	compilation environment, which means that on systems with optionally	1974	compilation environment, which means that on systems with large file
1609	disabled large file support, you get the 32 bit version of the stat	1975	support disabled by default, you get the 32 bit version of the stat
1610	structure. When using the library from programs that change the ABI to	1976	structure. When using the library from programs that change the ABI to
1611	use 64 bit file offsets the programs will fail. In that case you have to	1977	use 64 bit file offsets the programs will fail. In that case you have to
1612	compile libev with the same flags to get binary compatibility. This is	1978	compile libev with the same flags to get binary compatibility. This is
1613	obviously the case with any flags that change the ABI, but the problem is	1979	obviously the case with any flags that change the ABI, but the problem is
1614	most noticably with ev_stat and largefile support.	1980	most noticeably displayed with ev_stat and large file support.
1615		1981
1616	=head3 Inotify	1982	The solution for this is to lobby your distribution maker to make large
		1983	file interfaces available by default (as e.g. FreeBSD does) and not
		1984	optional. Libev cannot simply switch on large file support because it has
		1985	to exchange stat structures with application programs compiled using the
		1986	default compilation environment.
1617		1987
		1988	=head3 Inotify and Kqueue
		1989
1618	When C<inotify (7)> support has been compiled into libev (generally only	1990	When C<inotify (7)> support has been compiled into libev and present at
1619	available on Linux) and present at runtime, it will be used to speed up	1991	runtime, it will be used to speed up change detection where possible. The
1620	change detection where possible. The inotify descriptor will be created lazily	1992	inotify descriptor will be created lazily when the first C<ev_stat>
1621	when the first C<ev_stat> watcher is being started.	1993	watcher is being started.
1622		1994
1623	Inotify presense does not change the semantics of C<ev_stat> watchers	1995	Inotify presence does not change the semantics of C<ev_stat> watchers
1624	except that changes might be detected earlier, and in some cases, to avoid	1996	except that changes might be detected earlier, and in some cases, to avoid
1625	making regular C<stat> calls. Even in the presense of inotify support	1997	making regular C<stat> calls. Even in the presence of inotify support
1626	there are many cases where libev has to resort to regular C<stat> polling.	1998	there are many cases where libev has to resort to regular C<stat> polling,
		1999	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2000	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2001	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2002	xfs are fully working) libev usually gets away without polling.
1627		2003
1628	(There is no support for kqueue, as apparently it cannot be used to	2004	There is no support for kqueue, as apparently it cannot be used to
1629	implement this functionality, due to the requirement of having a file	2005	implement this functionality, due to the requirement of having a file
1630	descriptor open on the object at all times).	2006	descriptor open on the object at all times, and detecting renames, unlinks
		2007	etc. is difficult.
		2008
		2009	=head3 C<stat ()> is a synchronous operation
		2010
		2011	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2012	the process. The exception are C<ev_stat> watchers - those call C<stat
		2013	()>, which is a synchronous operation.
		2014
		2015	For local paths, this usually doesn't matter: unless the system is very
		2016	busy or the intervals between stat's are large, a stat call will be fast,
		2017	as the path data is usually in memory already (except when starting the
		2018	watcher).
		2019
		2020	For networked file systems, calling C<stat ()> can block an indefinite
		2021	time due to network issues, and even under good conditions, a stat call
		2022	often takes multiple milliseconds.
		2023
		2024	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2025	paths, although this is fully supported by libev.
1631		2026
1632	=head3 The special problem of stat time resolution	2027	=head3 The special problem of stat time resolution
1633		2028
1634	The C<stat ()> syscall only supports full-second resolution portably, and	2029	The C<stat ()> system call only supports full-second resolution portably,
1635	even on systems where the resolution is higher, many filesystems still	2030	and even on systems where the resolution is higher, most file systems
1636	only support whole seconds.	2031	still only support whole seconds.
1637		2032
1638	That means that, if the time is the only thing that changes, you might	2033	That means that, if the time is the only thing that changes, you can
1639	miss updates: on the first update, C<ev_stat> detects a change and calls	2034	easily miss updates: on the first update, C<ev_stat> detects a change and
1640	your callback, which does something. When there is another update within	2035	calls your callback, which does something. When there is another update
1641	the same second, C<ev_stat> will be unable to detect it.	2036	within the same second, C<ev_stat> will be unable to detect unless the
		2037	stat data does change in other ways (e.g. file size).
1642		2038
1643	The solution to this is to delay acting on a change for a second (or till	2039	The solution to this is to delay acting on a change for slightly more
1644	the next second boundary), using a roughly one-second delay C<ev_timer>	2040	than a second (or till slightly after the next full second boundary), using
1645	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2041	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1646	is added to work around small timing inconsistencies of some operating	2042	ev_timer_again (loop, w)>).
1647	systems.	2043
		2044	The C<.02> offset is added to work around small timing inconsistencies
		2045	of some operating systems (where the second counter of the current time
		2046	might be be delayed. One such system is the Linux kernel, where a call to
		2047	C<gettimeofday> might return a timestamp with a full second later than
		2048	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2049	update file times then there will be a small window where the kernel uses
		2050	the previous second to update file times but libev might already execute
		2051	the timer callback).
1648		2052
1649	=head3 Watcher-Specific Functions and Data Members	2053	=head3 Watcher-Specific Functions and Data Members
1650		2054
1651	=over 4	2055	=over 4
1652		2056
…		…
1658	C<path>. The C<interval> is a hint on how quickly a change is expected to	2062	C<path>. The C<interval> is a hint on how quickly a change is expected to
1659	be detected and should normally be specified as C<0> to let libev choose	2063	be detected and should normally be specified as C<0> to let libev choose
1660	a suitable value. The memory pointed to by C<path> must point to the same	2064	a suitable value. The memory pointed to by C<path> must point to the same
1661	path for as long as the watcher is active.	2065	path for as long as the watcher is active.
1662		2066
1663	The callback will be receive C<EV_STAT> when a change was detected,	2067	The callback will receive an C<EV_STAT> event when a change was detected,
1664	relative to the attributes at the time the watcher was started (or the	2068	relative to the attributes at the time the watcher was started (or the
1665	last change was detected).	2069	last change was detected).
1666		2070
1667	=item ev_stat_stat (loop, ev_stat *)	2071	=item ev_stat_stat (loop, ev_stat *)
1668		2072
1669	Updates the stat buffer immediately with new values. If you change the	2073	Updates the stat buffer immediately with new values. If you change the
1670	watched path in your callback, you could call this fucntion to avoid	2074	watched path in your callback, you could call this function to avoid
1671	detecting this change (while introducing a race condition). Can also be	2075	detecting this change (while introducing a race condition if you are not
1672	useful simply to find out the new values.	2076	the only one changing the path). Can also be useful simply to find out the
		2077	new values.
1673		2078
1674	=item ev_statdata attr [read-only]	2079	=item ev_statdata attr [read-only]
1675		2080
1676	The most-recently detected attributes of the file. Although the type is of	2081	The most-recently detected attributes of the file. Although the type is
1677	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2082	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1678	suitable for your system. If the C<st_nlink> member is C<0>, then there	2083	suitable for your system, but you can only rely on the POSIX-standardised
		2084	members to be present. If the C<st_nlink> member is C<0>, then there was
1679	was some error while C<stat>ing the file.	2085	some error while C<stat>ing the file.
1680		2086
1681	=item ev_statdata prev [read-only]	2087	=item ev_statdata prev [read-only]
1682		2088
1683	The previous attributes of the file. The callback gets invoked whenever	2089	The previous attributes of the file. The callback gets invoked whenever
1684	C<prev> != C<attr>.	2090	C<prev> != C<attr>, or, more precisely, one or more of these members
		2091	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2092	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1685		2093
1686	=item ev_tstamp interval [read-only]	2094	=item ev_tstamp interval [read-only]
1687		2095
1688	The specified interval.	2096	The specified interval.
1689		2097
1690	=item const char *path [read-only]	2098	=item const char *path [read-only]
1691		2099
1692	The filesystem path that is being watched.	2100	The file system path that is being watched.
1693		2101
1694	=back	2102	=back
1695		2103
1696	=head3 Examples	2104	=head3 Examples
1697		2105
1698	Example: Watch C</etc/passwd> for attribute changes.	2106	Example: Watch C</etc/passwd> for attribute changes.
1699		2107
1700	static void	2108	static void
1701	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2109	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1702	{	2110	{
1703	/* /etc/passwd changed in some way */	2111	/* /etc/passwd changed in some way */
1704	if (w->attr.st_nlink)	2112	if (w->attr.st_nlink)
1705	{	2113	{
1706	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2114	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1707	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2115	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1708	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2116	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1709	}	2117	}
1710	else	2118	else
1711	/* you shalt not abuse printf for puts */	2119	/* you shalt not abuse printf for puts */
1712	puts ("wow, /etc/passwd is not there, expect problems. "	2120	puts ("wow, /etc/passwd is not there, expect problems. "
1713	"if this is windows, they already arrived\n");	2121	"if this is windows, they already arrived\n");
1714	}	2122	}
1715		2123
1716	...	2124	...
1717	ev_stat passwd;	2125	ev_stat passwd;
1718		2126
1719	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2127	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1720	ev_stat_start (loop, &passwd);	2128	ev_stat_start (loop, &passwd);
1721		2129
1722	Example: Like above, but additionally use a one-second delay so we do not	2130	Example: Like above, but additionally use a one-second delay so we do not
1723	miss updates (however, frequent updates will delay processing, too, so	2131	miss updates (however, frequent updates will delay processing, too, so
1724	one might do the work both on C<ev_stat> callback invocation I<and> on	2132	one might do the work both on C<ev_stat> callback invocation I<and> on
1725	C<ev_timer> callback invocation).	2133	C<ev_timer> callback invocation).
1726		2134
1727	static ev_stat passwd;	2135	static ev_stat passwd;
1728	static ev_timer timer;	2136	static ev_timer timer;
1729		2137
1730	static void	2138	static void
1731	timer_cb (EV_P_ ev_timer *w, int revents)	2139	timer_cb (EV_P_ ev_timer *w, int revents)
1732	{	2140	{
1733	ev_timer_stop (EV_A_ w);	2141	ev_timer_stop (EV_A_ w);
1734		2142
1735	/* now it's one second after the most recent passwd change */	2143	/* now it's one second after the most recent passwd change */
1736	}	2144	}
1737		2145
1738	static void	2146	static void
1739	stat_cb (EV_P_ ev_stat *w, int revents)	2147	stat_cb (EV_P_ ev_stat *w, int revents)
1740	{	2148	{
1741	/* reset the one-second timer */	2149	/* reset the one-second timer */
1742	ev_timer_again (EV_A_ &timer);	2150	ev_timer_again (EV_A_ &timer);
1743	}	2151	}
1744		2152
1745	...	2153	...
1746	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2154	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1747	ev_stat_start (loop, &passwd);	2155	ev_stat_start (loop, &passwd);
1748	ev_timer_init (&timer, timer_cb, 0., 1.01);	2156	ev_timer_init (&timer, timer_cb, 0., 1.02);
1749		2157
1750		2158
1751	=head2 C<ev_idle> - when you've got nothing better to do...	2159	=head2 C<ev_idle> - when you've got nothing better to do...
1752		2160
1753	Idle watchers trigger events when no other events of the same or higher	2161	Idle watchers trigger events when no other events of the same or higher
1754	priority are pending (prepare, check and other idle watchers do not	2162	priority are pending (prepare, check and other idle watchers do not count
1755	count).	2163	as receiving "events").
1756		2164
1757	That is, as long as your process is busy handling sockets or timeouts	2165	That is, as long as your process is busy handling sockets or timeouts
1758	(or even signals, imagine) of the same or higher priority it will not be	2166	(or even signals, imagine) of the same or higher priority it will not be
1759	triggered. But when your process is idle (or only lower-priority watchers	2167	triggered. But when your process is idle (or only lower-priority watchers
1760	are pending), the idle watchers are being called once per event loop	2168	are pending), the idle watchers are being called once per event loop
…		…
1784	=head3 Examples	2192	=head3 Examples
1785		2193
1786	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2194	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1787	callback, free it. Also, use no error checking, as usual.	2195	callback, free it. Also, use no error checking, as usual.
1788		2196
1789	static void	2197	static void
1790	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1791	{	2199	{
1792	free (w);	2200	free (w);
1793	// now do something you wanted to do when the program has	2201	// now do something you wanted to do when the program has
1794	// no longer anything immediate to do.	2202	// no longer anything immediate to do.
1795	}	2203	}
1796		2204
1797	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1798	ev_idle_init (idle_watcher, idle_cb);	2206	ev_idle_init (idle_watcher, idle_cb);
1799	ev_idle_start (loop, idle_cb);	2207	ev_idle_start (loop, idle_cb);
1800		2208
1801		2209
1802	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1803		2211
1804	Prepare and check watchers are usually (but not always) used in tandem:	2212	Prepare and check watchers are usually (but not always) used in pairs:
1805	prepare watchers get invoked before the process blocks and check watchers	2213	prepare watchers get invoked before the process blocks and check watchers
1806	afterwards.	2214	afterwards.
1807		2215
1808	You I<must not> call C<ev_loop> or similar functions that enter	2216	You I<must not> call C<ev_loop> or similar functions that enter
1809	the current event loop from either C<ev_prepare> or C<ev_check>	2217	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1812	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1813	C<ev_check> so if you have one watcher of each kind they will always be	2221	C<ev_check> so if you have one watcher of each kind they will always be
1814	called in pairs bracketing the blocking call.	2222	called in pairs bracketing the blocking call.
1815		2223
1816	Their main purpose is to integrate other event mechanisms into libev and	2224	Their main purpose is to integrate other event mechanisms into libev and
1817	their use is somewhat advanced. This could be used, for example, to track	2225	their use is somewhat advanced. They could be used, for example, to track
1818	variable changes, implement your own watchers, integrate net-snmp or a	2226	variable changes, implement your own watchers, integrate net-snmp or a
1819	coroutine library and lots more. They are also occasionally useful if	2227	coroutine library and lots more. They are also occasionally useful if
1820	you cache some data and want to flush it before blocking (for example,	2228	you cache some data and want to flush it before blocking (for example,
1821	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2229	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1822	watcher).	2230	watcher).
1823		2231
1824	This is done by examining in each prepare call which file descriptors need	2232	This is done by examining in each prepare call which file descriptors
1825	to be watched by the other library, registering C<ev_io> watchers for	2233	need to be watched by the other library, registering C<ev_io> watchers
1826	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2234	for them and starting an C<ev_timer> watcher for any timeouts (many
1827	provide just this functionality). Then, in the check watcher you check for	2235	libraries provide exactly this functionality). Then, in the check watcher,
1828	any events that occured (by checking the pending status of all watchers	2236	you check for any events that occurred (by checking the pending status
1829	and stopping them) and call back into the library. The I/O and timer	2237	of all watchers and stopping them) and call back into the library. The
1830	callbacks will never actually be called (but must be valid nevertheless,	2238	I/O and timer callbacks will never actually be called (but must be valid
1831	because you never know, you know?).	2239	nevertheless, because you never know, you know?).
1832		2240
1833	As another example, the Perl Coro module uses these hooks to integrate	2241	As another example, the Perl Coro module uses these hooks to integrate
1834	coroutines into libev programs, by yielding to other active coroutines	2242	coroutines into libev programs, by yielding to other active coroutines
1835	during each prepare and only letting the process block if no coroutines	2243	during each prepare and only letting the process block if no coroutines
1836	are ready to run (it's actually more complicated: it only runs coroutines	2244	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1839	loop from blocking if lower-priority coroutines are active, thus mapping	2247	loop from blocking if lower-priority coroutines are active, thus mapping
1840	low-priority coroutines to idle/background tasks).	2248	low-priority coroutines to idle/background tasks).
1841		2249
1842	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1843	priority, to ensure that they are being run before any other watchers	2251	priority, to ensure that they are being run before any other watchers
		2252	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2253
1844	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1845	too) should not activate ("feed") events into libev. While libev fully	2255	activate ("feed") events into libev. While libev fully supports this, they
1846	supports this, they will be called before other C<ev_check> watchers	2256	might get executed before other C<ev_check> watchers did their job. As
1847	did their job. As C<ev_check> watchers are often used to embed other	2257	C<ev_check> watchers are often used to embed other (non-libev) event
1848	(non-libev) event loops those other event loops might be in an unusable	2258	loops those other event loops might be in an unusable state until their
1849	state until their C<ev_check> watcher ran (always remind yourself to	2259	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1850	coexist peacefully with others).	2260	others).
1851		2261
1852	=head3 Watcher-Specific Functions and Data Members	2262	=head3 Watcher-Specific Functions and Data Members
1853		2263
1854	=over 4	2264	=over 4
1855		2265
…		…
1857		2267
1858	=item ev_check_init (ev_check *, callback)	2268	=item ev_check_init (ev_check *, callback)
1859		2269
1860	Initialises and configures the prepare or check watcher - they have no	2270	Initialises and configures the prepare or check watcher - they have no
1861	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2271	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1862	macros, but using them is utterly, utterly and completely pointless.	2272	macros, but using them is utterly, utterly, utterly and completely
		2273	pointless.
1863		2274
1864	=back	2275	=back
1865		2276
1866	=head3 Examples	2277	=head3 Examples
1867		2278
1868	There are a number of principal ways to embed other event loops or modules	2279	There are a number of principal ways to embed other event loops or modules
1869	into libev. Here are some ideas on how to include libadns into libev	2280	into libev. Here are some ideas on how to include libadns into libev
1870	(there is a Perl module named C<EV::ADNS> that does this, which you could	2281	(there is a Perl module named C<EV::ADNS> that does this, which you could
1871	use for an actually working example. Another Perl module named C<EV::Glib>	2282	use as a working example. Another Perl module named C<EV::Glib> embeds a
1872	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2283	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1873	into the Glib event loop).	2284	Glib event loop).
1874		2285
1875	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2286	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1876	and in a check watcher, destroy them and call into libadns. What follows	2287	and in a check watcher, destroy them and call into libadns. What follows
1877	is pseudo-code only of course. This requires you to either use a low	2288	is pseudo-code only of course. This requires you to either use a low
1878	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2289	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1879	the callbacks for the IO/timeout watchers might not have been called yet.	2290	the callbacks for the IO/timeout watchers might not have been called yet.
1880		2291
1881	static ev_io iow [nfd];	2292	static ev_io iow [nfd];
1882	static ev_timer tw;	2293	static ev_timer tw;
1883		2294
1884	static void	2295	static void
1885	io_cb (ev_loop *loop, ev_io *w, int revents)	2296	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1886	{	2297	{
1887	}	2298	}
1888		2299
1889	// create io watchers for each fd and a timer before blocking	2300	// create io watchers for each fd and a timer before blocking
1890	static void	2301	static void
1891	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2302	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1892	{	2303	{
1893	int timeout = 3600000;	2304	int timeout = 3600000;
1894	struct pollfd fds [nfd];	2305	struct pollfd fds [nfd];
1895	// actual code will need to loop here and realloc etc.	2306	// actual code will need to loop here and realloc etc.
1896	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1897		2308
1898	/* the callback is illegal, but won't be called as we stop during check */	2309	/* the callback is illegal, but won't be called as we stop during check */
1899	ev_timer_init (&tw, 0, timeout * 1e-3);	2310	ev_timer_init (&tw, 0, timeout * 1e-3);
1900	ev_timer_start (loop, &tw);	2311	ev_timer_start (loop, &tw);
1901		2312
1902	// create one ev_io per pollfd	2313	// create one ev_io per pollfd
1903	for (int i = 0; i < nfd; ++i)	2314	for (int i = 0; i < nfd; ++i)
1904	{	2315	{
1905	ev_io_init (iow + i, io_cb, fds [i].fd,	2316	ev_io_init (iow + i, io_cb, fds [i].fd,
1906	((fds [i].events & POLLIN ? EV_READ : 0)	2317	((fds [i].events & POLLIN ? EV_READ : 0)
1907	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2318	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1908		2319
1909	fds [i].revents = 0;	2320	fds [i].revents = 0;
1910	ev_io_start (loop, iow + i);	2321	ev_io_start (loop, iow + i);
1911	}	2322	}
1912	}	2323	}
1913		2324
1914	// stop all watchers after blocking	2325	// stop all watchers after blocking
1915	static void	2326	static void
1916	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2327	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1917	{	2328	{
1918	ev_timer_stop (loop, &tw);	2329	ev_timer_stop (loop, &tw);
1919		2330
1920	for (int i = 0; i < nfd; ++i)	2331	for (int i = 0; i < nfd; ++i)
1921	{	2332	{
1922	// set the relevant poll flags	2333	// set the relevant poll flags
1923	// could also call adns_processreadable etc. here	2334	// could also call adns_processreadable etc. here
1924	struct pollfd *fd = fds + i;	2335	struct pollfd *fd = fds + i;
1925	int revents = ev_clear_pending (iow + i);	2336	int revents = ev_clear_pending (iow + i);
1926	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2337	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1927	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2338	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1928		2339
1929	// now stop the watcher	2340	// now stop the watcher
1930	ev_io_stop (loop, iow + i);	2341	ev_io_stop (loop, iow + i);
1931	}	2342	}
1932		2343
1933	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2344	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1934	}	2345	}
1935		2346
1936	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2347	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1937	in the prepare watcher and would dispose of the check watcher.	2348	in the prepare watcher and would dispose of the check watcher.
1938		2349
1939	Method 3: If the module to be embedded supports explicit event	2350	Method 3: If the module to be embedded supports explicit event
1940	notification (adns does), you can also make use of the actual watcher	2351	notification (libadns does), you can also make use of the actual watcher
1941	callbacks, and only destroy/create the watchers in the prepare watcher.	2352	callbacks, and only destroy/create the watchers in the prepare watcher.
1942		2353
1943	static void	2354	static void
1944	timer_cb (EV_P_ ev_timer *w, int revents)	2355	timer_cb (EV_P_ ev_timer *w, int revents)
1945	{	2356	{
1946	adns_state ads = (adns_state)w->data;	2357	adns_state ads = (adns_state)w->data;
1947	update_now (EV_A);	2358	update_now (EV_A);
1948		2359
1949	adns_processtimeouts (ads, &tv_now);	2360	adns_processtimeouts (ads, &tv_now);
1950	}	2361	}
1951		2362
1952	static void	2363	static void
1953	io_cb (EV_P_ ev_io *w, int revents)	2364	io_cb (EV_P_ ev_io *w, int revents)
1954	{	2365	{
1955	adns_state ads = (adns_state)w->data;	2366	adns_state ads = (adns_state)w->data;
1956	update_now (EV_A);	2367	update_now (EV_A);
1957		2368
1958	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2369	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1959	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2370	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1960	}	2371	}
1961		2372
1962	// do not ever call adns_afterpoll	2373	// do not ever call adns_afterpoll
1963		2374
1964	Method 4: Do not use a prepare or check watcher because the module you	2375	Method 4: Do not use a prepare or check watcher because the module you
1965	want to embed is too inflexible to support it. Instead, youc na override	2376	want to embed is not flexible enough to support it. Instead, you can
1966	their poll function. The drawback with this solution is that the main	2377	override their poll function. The drawback with this solution is that the
1967	loop is now no longer controllable by EV. The C<Glib::EV> module does	2378	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1968	this.	2379	this approach, effectively embedding EV as a client into the horrible
		2380	libglib event loop.
1969		2381
1970	static gint	2382	static gint
1971	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2383	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1972	{	2384	{
1973	int got_events = 0;	2385	int got_events = 0;
1974		2386
1975	for (n = 0; n < nfds; ++n)	2387	for (n = 0; n < nfds; ++n)
1976	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2388	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1977		2389
1978	if (timeout >= 0)	2390	if (timeout >= 0)
1979	// create/start timer	2391	// create/start timer
1980		2392
1981	// poll	2393	// poll
1982	ev_loop (EV_A_ 0);	2394	ev_loop (EV_A_ 0);
1983		2395
1984	// stop timer again	2396	// stop timer again
1985	if (timeout >= 0)	2397	if (timeout >= 0)
1986	ev_timer_stop (EV_A_ &to);	2398	ev_timer_stop (EV_A_ &to);
1987		2399
1988	// stop io watchers again - their callbacks should have set	2400	// stop io watchers again - their callbacks should have set
1989	for (n = 0; n < nfds; ++n)	2401	for (n = 0; n < nfds; ++n)
1990	ev_io_stop (EV_A_ iow [n]);	2402	ev_io_stop (EV_A_ iow [n]);
1991		2403
1992	return got_events;	2404	return got_events;
1993	}	2405	}
1994		2406
1995		2407
1996	=head2 C<ev_embed> - when one backend isn't enough...	2408	=head2 C<ev_embed> - when one backend isn't enough...
1997		2409
1998	This is a rather advanced watcher type that lets you embed one event loop	2410	This is a rather advanced watcher type that lets you embed one event loop
…		…
2004	prioritise I/O.	2416	prioritise I/O.
2005		2417
2006	As an example for a bug workaround, the kqueue backend might only support	2418	As an example for a bug workaround, the kqueue backend might only support
2007	sockets on some platform, so it is unusable as generic backend, but you	2419	sockets on some platform, so it is unusable as generic backend, but you
2008	still want to make use of it because you have many sockets and it scales	2420	still want to make use of it because you have many sockets and it scales
2009	so nicely. In this case, you would create a kqueue-based loop and embed it	2421	so nicely. In this case, you would create a kqueue-based loop and embed
2010	into your default loop (which might use e.g. poll). Overall operation will	2422	it into your default loop (which might use e.g. poll). Overall operation
2011	be a bit slower because first libev has to poll and then call kevent, but	2423	will be a bit slower because first libev has to call C<poll> and then
2012	at least you can use both at what they are best.	2424	C<kevent>, but at least you can use both mechanisms for what they are
		2425	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2013		2426
2014	As for prioritising I/O: rarely you have the case where some fds have	2427	As for prioritising I/O: under rare circumstances you have the case where
2015	to be watched and handled very quickly (with low latency), and even	2428	some fds have to be watched and handled very quickly (with low latency),
2016	priorities and idle watchers might have too much overhead. In this case	2429	and even priorities and idle watchers might have too much overhead. In
2017	you would put all the high priority stuff in one loop and all the rest in	2430	this case you would put all the high priority stuff in one loop and all
2018	a second one, and embed the second one in the first.	2431	the rest in a second one, and embed the second one in the first.
2019		2432
2020	As long as the watcher is active, the callback will be invoked every time	2433	As long as the watcher is active, the callback will be invoked every
2021	there might be events pending in the embedded loop. The callback must then	2434	time there might be events pending in the embedded loop. The callback
2022	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2435	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2023	their callbacks (you could also start an idle watcher to give the embedded	2436	sweep and invoke their callbacks (the callback doesn't need to invoke the
2024	loop strictly lower priority for example). You can also set the callback	2437	C<ev_embed_sweep> function directly, it could also start an idle watcher
2025	to C<0>, in which case the embed watcher will automatically execute the	2438	to give the embedded loop strictly lower priority for example).
2026	embedded loop sweep.
2027		2439
2028	As long as the watcher is started it will automatically handle events. The	2440	You can also set the callback to C<0>, in which case the embed watcher
2029	callback will be invoked whenever some events have been handled. You can	2441	will automatically execute the embedded loop sweep whenever necessary.
2030	set the callback to C<0> to avoid having to specify one if you are not
2031	interested in that.
2032		2442
2033	Also, there have not currently been made special provisions for forking:	2443	Fork detection will be handled transparently while the C<ev_embed> watcher
2034	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2444	is active, i.e., the embedded loop will automatically be forked when the
2035	but you will also have to stop and restart any C<ev_embed> watchers	2445	embedding loop forks. In other cases, the user is responsible for calling
2036	yourself.	2446	C<ev_loop_fork> on the embedded loop.
2037		2447
2038	Unfortunately, not all backends are embeddable, only the ones returned by	2448	Unfortunately, not all backends are embeddable: only the ones returned by
2039	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2449	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2040	portable one.	2450	portable one.
2041		2451
2042	So when you want to use this feature you will always have to be prepared	2452	So when you want to use this feature you will always have to be prepared
2043	that you cannot get an embeddable loop. The recommended way to get around	2453	that you cannot get an embeddable loop. The recommended way to get around
2044	this is to have a separate variables for your embeddable loop, try to	2454	this is to have a separate variables for your embeddable loop, try to
2045	create it, and if that fails, use the normal loop for everything.	2455	create it, and if that fails, use the normal loop for everything.
2046		2456
		2457	=head3 C<ev_embed> and fork
		2458
		2459	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2460	automatically be applied to the embedded loop as well, so no special
		2461	fork handling is required in that case. When the watcher is not running,
		2462	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2463	as applicable.
		2464
2047	=head3 Watcher-Specific Functions and Data Members	2465	=head3 Watcher-Specific Functions and Data Members
2048		2466
2049	=over 4	2467	=over 4
2050		2468
2051	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2469	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2054		2472
2055	Configures the watcher to embed the given loop, which must be	2473	Configures the watcher to embed the given loop, which must be
2056	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2474	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2057	invoked automatically, otherwise it is the responsibility of the callback	2475	invoked automatically, otherwise it is the responsibility of the callback
2058	to invoke it (it will continue to be called until the sweep has been done,	2476	to invoke it (it will continue to be called until the sweep has been done,
2059	if you do not want thta, you need to temporarily stop the embed watcher).	2477	if you do not want that, you need to temporarily stop the embed watcher).
2060		2478
2061	=item ev_embed_sweep (loop, ev_embed *)	2479	=item ev_embed_sweep (loop, ev_embed *)
2062		2480
2063	Make a single, non-blocking sweep over the embedded loop. This works	2481	Make a single, non-blocking sweep over the embedded loop. This works
2064	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2065	apropriate way for embedded loops.	2483	appropriate way for embedded loops.
2066		2484
2067	=item struct ev_loop *other [read-only]	2485	=item struct ev_loop *other [read-only]
2068		2486
2069	The embedded event loop.	2487	The embedded event loop.
2070		2488
…		…
2072		2490
2073	=head3 Examples	2491	=head3 Examples
2074		2492
2075	Example: Try to get an embeddable event loop and embed it into the default	2493	Example: Try to get an embeddable event loop and embed it into the default
2076	event loop. If that is not possible, use the default loop. The default	2494	event loop. If that is not possible, use the default loop. The default
2077	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2495	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2078	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2496	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2079	used).	2497	used).
2080		2498
2081	struct ev_loop *loop_hi = ev_default_init (0);	2499	struct ev_loop *loop_hi = ev_default_init (0);
2082	struct ev_loop *loop_lo = 0;	2500	struct ev_loop *loop_lo = 0;
2083	struct ev_embed embed;	2501	ev_embed embed;
2084		2502
2085	// see if there is a chance of getting one that works	2503	// see if there is a chance of getting one that works
2086	// (remember that a flags value of 0 means autodetection)	2504	// (remember that a flags value of 0 means autodetection)
2087	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2505	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2088	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2506	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2089	: 0;	2507	: 0;
2090		2508
2091	// if we got one, then embed it, otherwise default to loop_hi	2509	// if we got one, then embed it, otherwise default to loop_hi
2092	if (loop_lo)	2510	if (loop_lo)
2093	{	2511	{
2094	ev_embed_init (&embed, 0, loop_lo);	2512	ev_embed_init (&embed, 0, loop_lo);
2095	ev_embed_start (loop_hi, &embed);	2513	ev_embed_start (loop_hi, &embed);
2096	}	2514	}
2097	else	2515	else
2098	loop_lo = loop_hi;	2516	loop_lo = loop_hi;
2099		2517
2100	Example: Check if kqueue is available but not recommended and create	2518	Example: Check if kqueue is available but not recommended and create
2101	a kqueue backend for use with sockets (which usually work with any	2519	a kqueue backend for use with sockets (which usually work with any
2102	kqueue implementation). Store the kqueue/socket-only event loop in	2520	kqueue implementation). Store the kqueue/socket-only event loop in
2103	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2521	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2104		2522
2105	struct ev_loop *loop = ev_default_init (0);	2523	struct ev_loop *loop = ev_default_init (0);
2106	struct ev_loop *loop_socket = 0;	2524	struct ev_loop *loop_socket = 0;
2107	struct ev_embed embed;	2525	ev_embed embed;
2108		2526
2109	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2527	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2110	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2528	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2111	{	2529	{
2112	ev_embed_init (&embed, 0, loop_socket);	2530	ev_embed_init (&embed, 0, loop_socket);
2113	ev_embed_start (loop, &embed);	2531	ev_embed_start (loop, &embed);
2114	}	2532	}
2115		2533
2116	if (!loop_socket)	2534	if (!loop_socket)
2117	loop_socket = loop;	2535	loop_socket = loop;
2118		2536
2119	// now use loop_socket for all sockets, and loop for everything else	2537	// now use loop_socket for all sockets, and loop for everything else
2120		2538
2121		2539
2122	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2540	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2123		2541
2124	Fork watchers are called when a C<fork ()> was detected (usually because	2542	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2168	is that the author does not know of a simple (or any) algorithm for a	2586	is that the author does not know of a simple (or any) algorithm for a
2169	multiple-writer-single-reader queue that works in all cases and doesn't	2587	multiple-writer-single-reader queue that works in all cases and doesn't
2170	need elaborate support such as pthreads.	2588	need elaborate support such as pthreads.
2171		2589
2172	That means that if you want to queue data, you have to provide your own	2590	That means that if you want to queue data, you have to provide your own
2173	queue. But at least I can tell you would implement locking around your	2591	queue. But at least I can tell you how to implement locking around your
2174	queue:	2592	queue:
2175		2593
2176	=over 4	2594	=over 4
2177		2595
2178	=item queueing from a signal handler context	2596	=item queueing from a signal handler context
2179		2597
2180	To implement race-free queueing, you simply add to the queue in the signal	2598	To implement race-free queueing, you simply add to the queue in the signal
2181	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2599	handler but you block the signal handler in the watcher callback. Here is
2182	some fictitiuous SIGUSR1 handler:	2600	an example that does that for some fictitious SIGUSR1 handler:
2183		2601
2184	static ev_async mysig;	2602	static ev_async mysig;
2185		2603
2186	static void	2604	static void
2187	sigusr1_handler (void)	2605	sigusr1_handler (void)
…		…
2253	=over 4	2671	=over 4
2254		2672
2255	=item ev_async_init (ev_async *, callback)	2673	=item ev_async_init (ev_async *, callback)
2256		2674
2257	Initialises and configures the async watcher - it has no parameters of any	2675	Initialises and configures the async watcher - it has no parameters of any
2258	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2676	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2259	believe me.	2677	trust me.
2260		2678
2261	=item ev_async_send (loop, ev_async *)	2679	=item ev_async_send (loop, ev_async *)
2262		2680
2263	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2264	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2265	C<ev_feed_event>, this call is safe to do in other threads, signal or	2683	C<ev_feed_event>, this call is safe to do from other threads, signal or
2266	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2267	section below on what exactly this means).	2685	section below on what exactly this means).
2268		2686
2269	This call incurs the overhead of a syscall only once per loop iteration,	2687	This call incurs the overhead of a system call only once per loop iteration,
2270	so while the overhead might be noticable, it doesn't apply to repeated	2688	so while the overhead might be noticeable, it doesn't apply to repeated
2271	calls to C<ev_async_send>.	2689	calls to C<ev_async_send>.
2272		2690
		2691	=item bool = ev_async_pending (ev_async *)
		2692
		2693	Returns a non-zero value when C<ev_async_send> has been called on the
		2694	watcher but the event has not yet been processed (or even noted) by the
		2695	event loop.
		2696
		2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2698	the loop iterates next and checks for the watcher to have become active,
		2699	it will reset the flag again. C<ev_async_pending> can be used to very
		2700	quickly check whether invoking the loop might be a good idea.
		2701
		2702	Not that this does I<not> check whether the watcher itself is pending, only
		2703	whether it has been requested to make this watcher pending.
		2704
2273	=back	2705	=back
2274		2706
2275		2707
2276	=head1 OTHER FUNCTIONS	2708	=head1 OTHER FUNCTIONS
2277		2709
…		…
2280	=over 4	2712	=over 4
2281		2713
2282	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2714	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2283		2715
2284	This function combines a simple timer and an I/O watcher, calls your	2716	This function combines a simple timer and an I/O watcher, calls your
2285	callback on whichever event happens first and automatically stop both	2717	callback on whichever event happens first and automatically stops both
2286	watchers. This is useful if you want to wait for a single event on an fd	2718	watchers. This is useful if you want to wait for a single event on an fd
2287	or timeout without having to allocate/configure/start/stop/free one or	2719	or timeout without having to allocate/configure/start/stop/free one or
2288	more watchers yourself.	2720	more watchers yourself.
2289		2721
2290	If C<fd> is less than 0, then no I/O watcher will be started and events	2722	If C<fd> is less than 0, then no I/O watcher will be started and the
2291	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2723	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2292	C<events> set will be craeted and started.	2724	the given C<fd> and C<events> set will be created and started.
2293		2725
2294	If C<timeout> is less than 0, then no timeout watcher will be	2726	If C<timeout> is less than 0, then no timeout watcher will be
2295	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2296	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2728	repeat = 0) will be started. C<0> is a valid timeout.
2297	dubious value.
2298		2729
2299	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2300	passed an C<revents> set like normal event callbacks (a combination of	2731	passed an C<revents> set like normal event callbacks (a combination of
2301	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2302	value passed to C<ev_once>:	2733	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2734	a timeout and an io event at the same time - you probably should give io
		2735	events precedence.
2303		2736
		2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2738
2304	static void stdin_ready (int revents, void *arg)	2739	static void stdin_ready (int revents, void *arg)
2305	{	2740	{
2306	if (revents & EV_TIMEOUT)
2307	/* doh, nothing entered */;
2308	else if (revents & EV_READ)	2741	if (revents & EV_READ)
2309	/* stdin might have data for us, joy! */;	2742	/* stdin might have data for us, joy! */;
		2743	else if (revents & EV_TIMEOUT)
		2744	/* doh, nothing entered */;
2310	}	2745	}
2311		2746
2312	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2313		2748
2314	=item ev_feed_event (ev_loop *, watcher *, int revents)	2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2315		2750
2316	Feeds the given event set into the event loop, as if the specified event	2751	Feeds the given event set into the event loop, as if the specified event
2317	had happened for the specified watcher (which must be a pointer to an	2752	had happened for the specified watcher (which must be a pointer to an
2318	initialised but not necessarily started event watcher).	2753	initialised but not necessarily started event watcher).
2319		2754
2320	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2321		2756
2322	Feed an event on the given fd, as if a file descriptor backend detected	2757	Feed an event on the given fd, as if a file descriptor backend detected
2323	the given events it.	2758	the given events it.
2324		2759
2325	=item ev_feed_signal_event (ev_loop *loop, int signum)	2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2326		2761
2327	Feed an event as if the given signal occured (C<loop> must be the default	2762	Feed an event as if the given signal occurred (C<loop> must be the default
2328	loop!).	2763	loop!).
2329		2764
2330	=back	2765	=back
2331		2766
2332		2767
…		…
2348		2783
2349	=item * Priorities are not currently supported. Initialising priorities	2784	=item * Priorities are not currently supported. Initialising priorities
2350	will fail and all watchers will have the same priority, even though there	2785	will fail and all watchers will have the same priority, even though there
2351	is an ev_pri field.	2786	is an ev_pri field.
2352		2787
		2788	=item * In libevent, the last base created gets the signals, in libev, the
		2789	first base created (== the default loop) gets the signals.
		2790
2353	=item * Other members are not supported.	2791	=item * Other members are not supported.
2354		2792
2355	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2356	to use the libev header file and library.	2794	to use the libev header file and library.
2357		2795
2358	=back	2796	=back
2359		2797
2360	=head1 C++ SUPPORT	2798	=head1 C++ SUPPORT
2361		2799
2362	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2800	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2363	you to use some convinience methods to start/stop watchers and also change	2801	you to use some convenience methods to start/stop watchers and also change
2364	the callback model to a model using method callbacks on objects.	2802	the callback model to a model using method callbacks on objects.
2365		2803
2366	To use it,	2804	To use it,
2367		2805
2368	#include <ev++.h>	2806	#include <ev++.h>
2369		2807
2370	This automatically includes F<ev.h> and puts all of its definitions (many	2808	This automatically includes F<ev.h> and puts all of its definitions (many
2371	of them macros) into the global namespace. All C++ specific things are	2809	of them macros) into the global namespace. All C++ specific things are
2372	put into the C<ev> namespace. It should support all the same embedding	2810	put into the C<ev> namespace. It should support all the same embedding
2373	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2811	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2440	your compiler is good :), then the method will be fully inlined into the	2878	your compiler is good :), then the method will be fully inlined into the
2441	thunking function, making it as fast as a direct C callback.	2879	thunking function, making it as fast as a direct C callback.
2442		2880
2443	Example: simple class declaration and watcher initialisation	2881	Example: simple class declaration and watcher initialisation
2444		2882
2445	struct myclass	2883	struct myclass
2446	{	2884	{
2447	void io_cb (ev::io &w, int revents) { }	2885	void io_cb (ev::io &w, int revents) { }
2448	}	2886	}
2449		2887
2450	myclass obj;	2888	myclass obj;
2451	ev::io iow;	2889	ev::io iow;
2452	iow.set <myclass, &myclass::io_cb> (&obj);	2890	iow.set <myclass, &myclass::io_cb> (&obj);
		2891
		2892	=item w->set (object *)
		2893
		2894	This is an B<experimental> feature that might go away in a future version.
		2895
		2896	This is a variation of a method callback - leaving out the method to call
		2897	will default the method to C<operator ()>, which makes it possible to use
		2898	functor objects without having to manually specify the C<operator ()> all
		2899	the time. Incidentally, you can then also leave out the template argument
		2900	list.
		2901
		2902	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2903	int revents)>.
		2904
		2905	See the method-C<set> above for more details.
		2906
		2907	Example: use a functor object as callback.
		2908
		2909	struct myfunctor
		2910	{
		2911	void operator() (ev::io &w, int revents)
		2912	{
		2913	...
		2914	}
		2915	}
		2916
		2917	myfunctor f;
		2918
		2919	ev::io w;
		2920	w.set (&f);
2453		2921
2454	=item w->set<function> (void *data = 0)	2922	=item w->set<function> (void *data = 0)
2455		2923
2456	Also sets a callback, but uses a static method or plain function as	2924	Also sets a callback, but uses a static method or plain function as
2457	callback. The optional C<data> argument will be stored in the watcher's	2925	callback. The optional C<data> argument will be stored in the watcher's
…		…
2459		2927
2460	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2928	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2461		2929
2462	See the method-C<set> above for more details.	2930	See the method-C<set> above for more details.
2463		2931
2464	Example:	2932	Example: Use a plain function as callback.
2465		2933
2466	static void io_cb (ev::io &w, int revents) { }	2934	static void io_cb (ev::io &w, int revents) { }
2467	iow.set <io_cb> ();	2935	iow.set <io_cb> ();
2468		2936
2469	=item w->set (struct ev_loop *)	2937	=item w->set (struct ev_loop *)
2470		2938
2471	Associates a different C<struct ev_loop> with this watcher. You can only	2939	Associates a different C<struct ev_loop> with this watcher. You can only
2472	do this when the watcher is inactive (and not pending either).	2940	do this when the watcher is inactive (and not pending either).
2473		2941
2474	=item w->set ([args])	2942	=item w->set ([arguments])
2475		2943
2476	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2477	called at least once. Unlike the C counterpart, an active watcher gets	2945	called at least once. Unlike the C counterpart, an active watcher gets
2478	automatically stopped and restarted when reconfiguring it with this	2946	automatically stopped and restarted when reconfiguring it with this
2479	method.	2947	method.
2480		2948
2481	=item w->start ()	2949	=item w->start ()
…		…
2505	=back	2973	=back
2506		2974
2507	Example: Define a class with an IO and idle watcher, start one of them in	2975	Example: Define a class with an IO and idle watcher, start one of them in
2508	the constructor.	2976	the constructor.
2509		2977
2510	class myclass	2978	class myclass
2511	{	2979	{
2512	ev::io io; void io_cb (ev::io &w, int revents);	2980	ev::io io ; void io_cb (ev::io &w, int revents);
2513	ev:idle idle void idle_cb (ev::idle &w, int revents);	2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2514		2982
2515	myclass (int fd)	2983	myclass (int fd)
2516	{	2984	{
2517	io .set <myclass, &myclass::io_cb > (this);	2985	io .set <myclass, &myclass::io_cb > (this);
2518	idle.set <myclass, &myclass::idle_cb> (this);	2986	idle.set <myclass, &myclass::idle_cb> (this);
2519		2987
2520	io.start (fd, ev::READ);	2988	io.start (fd, ev::READ);
2521	}	2989	}
2522	};	2990	};
2523		2991
2524		2992
2525	=head1 OTHER LANGUAGE BINDINGS	2993	=head1 OTHER LANGUAGE BINDINGS
2526		2994
2527	Libev does not offer other language bindings itself, but bindings for a	2995	Libev does not offer other language bindings itself, but bindings for a
2528	numbe rof languages exist in the form of third-party packages. If you know	2996	number of languages exist in the form of third-party packages. If you know
2529	any interesting language binding in addition to the ones listed here, drop	2997	any interesting language binding in addition to the ones listed here, drop
2530	me a note.	2998	me a note.
2531		2999
2532	=over 4	3000	=over 4
2533		3001
2534	=item Perl	3002	=item Perl
2535		3003
2536	The EV module implements the full libev API and is actually used to test	3004	The EV module implements the full libev API and is actually used to test
2537	libev. EV is developed together with libev. Apart from the EV core module,	3005	libev. EV is developed together with libev. Apart from the EV core module,
2538	there are additional modules that implement libev-compatible interfaces	3006	there are additional modules that implement libev-compatible interfaces
2539	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3007	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2540	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3008	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3009	and C<EV::Glib>).
2541		3010
2542	It can be found and installed via CPAN, its homepage is found at	3011	It can be found and installed via CPAN, its homepage is at
2543	L<http://software.schmorp.de/pkg/EV>.	3012	L<http://software.schmorp.de/pkg/EV>.
2544		3013
		3014	=item Python
		3015
		3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3017	seems to be quite complete and well-documented. Note, however, that the
		3018	patch they require for libev is outright dangerous as it breaks the ABI
		3019	for everybody else, and therefore, should never be applied in an installed
		3020	libev (if python requires an incompatible ABI then it needs to embed
		3021	libev).
		3022
2545	=item Ruby	3023	=item Ruby
2546		3024
2547	Tony Arcieri has written a ruby extension that offers access to a subset	3025	Tony Arcieri has written a ruby extension that offers access to a subset
2548	of the libev API and adds filehandle abstractions, asynchronous DNS and	3026	of the libev API and adds file handle abstractions, asynchronous DNS and
2549	more on top of it. It can be found via gem servers. Its homepage is at	3027	more on top of it. It can be found via gem servers. Its homepage is at
2550	L<http://rev.rubyforge.org/>.	3028	L<http://rev.rubyforge.org/>.
2551		3029
		3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3031	makes rev work even on mingw.
		3032
2552	=item D	3033	=item D
2553		3034
2554	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2555	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3037
		3038	=item Ocaml
		3039
		3040	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2556		3042
2557	=back	3043	=back
2558		3044
2559		3045
2560	=head1 MACRO MAGIC	3046	=head1 MACRO MAGIC
2561		3047
2562	Libev can be compiled with a variety of options, the most fundamantal	3048	Libev can be compiled with a variety of options, the most fundamental
2563	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3049	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2564	functions and callbacks have an initial C<struct ev_loop *> argument.	3050	functions and callbacks have an initial C<struct ev_loop *> argument.
2565		3051
2566	To make it easier to write programs that cope with either variant, the	3052	To make it easier to write programs that cope with either variant, the
2567	following macros are defined:	3053	following macros are defined:
…		…
2572		3058
2573	This provides the loop I<argument> for functions, if one is required ("ev	3059	This provides the loop I<argument> for functions, if one is required ("ev
2574	loop argument"). The C<EV_A> form is used when this is the sole argument,	3060	loop argument"). The C<EV_A> form is used when this is the sole argument,
2575	C<EV_A_> is used when other arguments are following. Example:	3061	C<EV_A_> is used when other arguments are following. Example:
2576		3062
2577	ev_unref (EV_A);	3063	ev_unref (EV_A);
2578	ev_timer_add (EV_A_ watcher);	3064	ev_timer_add (EV_A_ watcher);
2579	ev_loop (EV_A_ 0);	3065	ev_loop (EV_A_ 0);
2580		3066
2581	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2582	which is often provided by the following macro.	3068	which is often provided by the following macro.
2583		3069
2584	=item C<EV_P>, C<EV_P_>	3070	=item C<EV_P>, C<EV_P_>
2585		3071
2586	This provides the loop I<parameter> for functions, if one is required ("ev	3072	This provides the loop I<parameter> for functions, if one is required ("ev
2587	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3073	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2588	C<EV_P_> is used when other parameters are following. Example:	3074	C<EV_P_> is used when other parameters are following. Example:
2589		3075
2590	// this is how ev_unref is being declared	3076	// this is how ev_unref is being declared
2591	static void ev_unref (EV_P);	3077	static void ev_unref (EV_P);
2592		3078
2593	// this is how you can declare your typical callback	3079	// this is how you can declare your typical callback
2594	static void cb (EV_P_ ev_timer *w, int revents)	3080	static void cb (EV_P_ ev_timer *w, int revents)
2595		3081
2596	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3082	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2597	suitable for use with C<EV_A>.	3083	suitable for use with C<EV_A>.
2598		3084
2599	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3085	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2600		3086
2601	Similar to the other two macros, this gives you the value of the default	3087	Similar to the other two macros, this gives you the value of the default
2602	loop, if multiple loops are supported ("ev loop default").	3088	loop, if multiple loops are supported ("ev loop default").
		3089
		3090	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3091
		3092	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3093	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3094	is undefined when the default loop has not been initialised by a previous
		3095	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3096
		3097	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3098	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2603		3099
2604	=back	3100	=back
2605		3101
2606	Example: Declare and initialise a check watcher, utilising the above	3102	Example: Declare and initialise a check watcher, utilising the above
2607	macros so it will work regardless of whether multiple loops are supported	3103	macros so it will work regardless of whether multiple loops are supported
2608	or not.	3104	or not.
2609		3105
2610	static void	3106	static void
2611	check_cb (EV_P_ ev_timer *w, int revents)	3107	check_cb (EV_P_ ev_timer *w, int revents)
2612	{	3108	{
2613	ev_check_stop (EV_A_ w);	3109	ev_check_stop (EV_A_ w);
2614	}	3110	}
2615		3111
2616	ev_check check;	3112	ev_check check;
2617	ev_check_init (&check, check_cb);	3113	ev_check_init (&check, check_cb);
2618	ev_check_start (EV_DEFAULT_ &check);	3114	ev_check_start (EV_DEFAULT_ &check);
2619	ev_loop (EV_DEFAULT_ 0);	3115	ev_loop (EV_DEFAULT_ 0);
2620		3116
2621	=head1 EMBEDDING	3117	=head1 EMBEDDING
2622		3118
2623	Libev can (and often is) directly embedded into host	3119	Libev can (and often is) directly embedded into host
2624	applications. Examples of applications that embed it include the Deliantra	3120	applications. Examples of applications that embed it include the Deliantra
…		…
2631	libev somewhere in your source tree).	3127	libev somewhere in your source tree).
2632		3128
2633	=head2 FILESETS	3129	=head2 FILESETS
2634		3130
2635	Depending on what features you need you need to include one or more sets of files	3131	Depending on what features you need you need to include one or more sets of files
2636	in your app.	3132	in your application.
2637		3133
2638	=head3 CORE EVENT LOOP	3134	=head3 CORE EVENT LOOP
2639		3135
2640	To include only the libev core (all the C<ev_*> functions), with manual	3136	To include only the libev core (all the C<ev_*> functions), with manual
2641	configuration (no autoconf):	3137	configuration (no autoconf):
2642		3138
2643	#define EV_STANDALONE 1	3139	#define EV_STANDALONE 1
2644	#include "ev.c"	3140	#include "ev.c"
2645		3141
2646	This will automatically include F<ev.h>, too, and should be done in a	3142	This will automatically include F<ev.h>, too, and should be done in a
2647	single C source file only to provide the function implementations. To use	3143	single C source file only to provide the function implementations. To use
2648	it, do the same for F<ev.h> in all files wishing to use this API (best	3144	it, do the same for F<ev.h> in all files wishing to use this API (best
2649	done by writing a wrapper around F<ev.h> that you can include instead and	3145	done by writing a wrapper around F<ev.h> that you can include instead and
2650	where you can put other configuration options):	3146	where you can put other configuration options):
2651		3147
2652	#define EV_STANDALONE 1	3148	#define EV_STANDALONE 1
2653	#include "ev.h"	3149	#include "ev.h"
2654		3150
2655	Both header files and implementation files can be compiled with a C++	3151	Both header files and implementation files can be compiled with a C++
2656	compiler (at least, thats a stated goal, and breakage will be treated	3152	compiler (at least, that's a stated goal, and breakage will be treated
2657	as a bug).	3153	as a bug).
2658		3154
2659	You need the following files in your source tree, or in a directory	3155	You need the following files in your source tree, or in a directory
2660	in your include path (e.g. in libev/ when using -Ilibev):	3156	in your include path (e.g. in libev/ when using -Ilibev):
2661		3157
2662	ev.h	3158	ev.h
2663	ev.c	3159	ev.c
2664	ev_vars.h	3160	ev_vars.h
2665	ev_wrap.h	3161	ev_wrap.h
2666		3162
2667	ev_win32.c required on win32 platforms only	3163	ev_win32.c required on win32 platforms only
2668		3164
2669	ev_select.c only when select backend is enabled (which is enabled by default)	3165	ev_select.c only when select backend is enabled (which is enabled by default)
2670	ev_poll.c only when poll backend is enabled (disabled by default)	3166	ev_poll.c only when poll backend is enabled (disabled by default)
2671	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3167	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2672	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3168	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2673	ev_port.c only when the solaris port backend is enabled (disabled by default)	3169	ev_port.c only when the solaris port backend is enabled (disabled by default)
2674		3170
2675	F<ev.c> includes the backend files directly when enabled, so you only need	3171	F<ev.c> includes the backend files directly when enabled, so you only need
2676	to compile this single file.	3172	to compile this single file.
2677		3173
2678	=head3 LIBEVENT COMPATIBILITY API	3174	=head3 LIBEVENT COMPATIBILITY API
2679		3175
2680	To include the libevent compatibility API, also include:	3176	To include the libevent compatibility API, also include:
2681		3177
2682	#include "event.c"	3178	#include "event.c"
2683		3179
2684	in the file including F<ev.c>, and:	3180	in the file including F<ev.c>, and:
2685		3181
2686	#include "event.h"	3182	#include "event.h"
2687		3183
2688	in the files that want to use the libevent API. This also includes F<ev.h>.	3184	in the files that want to use the libevent API. This also includes F<ev.h>.
2689		3185
2690	You need the following additional files for this:	3186	You need the following additional files for this:
2691		3187
2692	event.h	3188	event.h
2693	event.c	3189	event.c
2694		3190
2695	=head3 AUTOCONF SUPPORT	3191	=head3 AUTOCONF SUPPORT
2696		3192
2697	Instead of using C<EV_STANDALONE=1> and providing your config in	3193	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2698	whatever way you want, you can also C<m4_include([libev.m4])> in your	3194	whatever way you want, you can also C<m4_include([libev.m4])> in your
2699	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3195	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2700	include F<config.h> and configure itself accordingly.	3196	include F<config.h> and configure itself accordingly.
2701		3197
2702	For this of course you need the m4 file:	3198	For this of course you need the m4 file:
2703		3199
2704	libev.m4	3200	libev.m4
2705		3201
2706	=head2 PREPROCESSOR SYMBOLS/MACROS	3202	=head2 PREPROCESSOR SYMBOLS/MACROS
2707		3203
2708	Libev can be configured via a variety of preprocessor symbols you have to define	3204	Libev can be configured via a variety of preprocessor symbols you have to
2709	before including any of its files. The default is not to build for multiplicity	3205	define before including any of its files. The default in the absence of
2710	and only include the select backend.	3206	autoconf is documented for every option.
2711		3207
2712	=over 4	3208	=over 4
2713		3209
2714	=item EV_STANDALONE	3210	=item EV_STANDALONE
2715		3211
…		…
2717	keeps libev from including F<config.h>, and it also defines dummy	3213	keeps libev from including F<config.h>, and it also defines dummy
2718	implementations for some libevent functions (such as logging, which is not	3214	implementations for some libevent functions (such as logging, which is not
2719	supported). It will also not define any of the structs usually found in	3215	supported). It will also not define any of the structs usually found in
2720	F<event.h> that are not directly supported by the libev core alone.	3216	F<event.h> that are not directly supported by the libev core alone.
2721		3217
		3218	In stanbdalone mode, libev will still try to automatically deduce the
		3219	configuration, but has to be more conservative.
		3220
2722	=item EV_USE_MONOTONIC	3221	=item EV_USE_MONOTONIC
2723		3222
2724	If defined to be C<1>, libev will try to detect the availability of the	3223	If defined to be C<1>, libev will try to detect the availability of the
2725	monotonic clock option at both compiletime and runtime. Otherwise no use	3224	monotonic clock option at both compile time and runtime. Otherwise no
2726	of the monotonic clock option will be attempted. If you enable this, you	3225	use of the monotonic clock option will be attempted. If you enable this,
2727	usually have to link against librt or something similar. Enabling it when	3226	you usually have to link against librt or something similar. Enabling it
2728	the functionality isn't available is safe, though, although you have	3227	when the functionality isn't available is safe, though, although you have
2729	to make sure you link against any libraries where the C<clock_gettime>	3228	to make sure you link against any libraries where the C<clock_gettime>
2730	function is hiding in (often F<-lrt>).	3229	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2731		3230
2732	=item EV_USE_REALTIME	3231	=item EV_USE_REALTIME
2733		3232
2734	If defined to be C<1>, libev will try to detect the availability of the	3233	If defined to be C<1>, libev will try to detect the availability of the
2735	realtime clock option at compiletime (and assume its availability at	3234	real-time clock option at compile time (and assume its availability at
2736	runtime if successful). Otherwise no use of the realtime clock option will	3235	runtime if successful). Otherwise no use of the real-time clock option will
2737	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3236	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2738	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3237	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2739	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3238	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2740		3239
		3240	=item EV_USE_CLOCK_SYSCALL
		3241
		3242	If defined to be C<1>, libev will try to use a direct syscall instead
		3243	of calling the system-provided C<clock_gettime> function. This option
		3244	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3245	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3246	programs needlessly. Using a direct syscall is slightly slower (in
		3247	theory), because no optimised vdso implementation can be used, but avoids
		3248	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3249	higher, as it simplifies linking (no need for C<-lrt>).
		3250
2741	=item EV_USE_NANOSLEEP	3251	=item EV_USE_NANOSLEEP
2742		3252
2743	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3253	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2744	and will use it for delays. Otherwise it will use C<select ()>.	3254	and will use it for delays. Otherwise it will use C<select ()>.
2745		3255
		3256	=item EV_USE_EVENTFD
		3257
		3258	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3259	available and will probe for kernel support at runtime. This will improve
		3260	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3261	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3262	2.7 or newer, otherwise disabled.
		3263
2746	=item EV_USE_SELECT	3264	=item EV_USE_SELECT
2747		3265
2748	If undefined or defined to be C<1>, libev will compile in support for the	3266	If undefined or defined to be C<1>, libev will compile in support for the
2749	C<select>(2) backend. No attempt at autodetection will be done: if no	3267	C<select>(2) backend. No attempt at auto-detection will be done: if no
2750	other method takes over, select will be it. Otherwise the select backend	3268	other method takes over, select will be it. Otherwise the select backend
2751	will not be compiled in.	3269	will not be compiled in.
2752		3270
2753	=item EV_SELECT_USE_FD_SET	3271	=item EV_SELECT_USE_FD_SET
2754		3272
2755	If defined to C<1>, then the select backend will use the system C<fd_set>	3273	If defined to C<1>, then the select backend will use the system C<fd_set>
2756	structure. This is useful if libev doesn't compile due to a missing	3274	structure. This is useful if libev doesn't compile due to a missing
2757	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3275	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2758	exotic systems. This usually limits the range of file descriptors to some	3276	on exotic systems. This usually limits the range of file descriptors to
2759	low limit such as 1024 or might have other limitations (winsocket only	3277	some low limit such as 1024 or might have other limitations (winsocket
2760	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3278	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2761	influence the size of the C<fd_set> used.	3279	configures the maximum size of the C<fd_set>.
2762		3280
2763	=item EV_SELECT_IS_WINSOCKET	3281	=item EV_SELECT_IS_WINSOCKET
2764		3282
2765	When defined to C<1>, the select backend will assume that	3283	When defined to C<1>, the select backend will assume that
2766	select/socket/connect etc. don't understand file descriptors but	3284	select/socket/connect etc. don't understand file descriptors but
…		…
2786		3304
2787	=item EV_USE_EPOLL	3305	=item EV_USE_EPOLL
2788		3306
2789	If defined to be C<1>, libev will compile in support for the Linux	3307	If defined to be C<1>, libev will compile in support for the Linux
2790	C<epoll>(7) backend. Its availability will be detected at runtime,	3308	C<epoll>(7) backend. Its availability will be detected at runtime,
2791	otherwise another method will be used as fallback. This is the	3309	otherwise another method will be used as fallback. This is the preferred
2792	preferred backend for GNU/Linux systems.	3310	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3311	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2793		3312
2794	=item EV_USE_KQUEUE	3313	=item EV_USE_KQUEUE
2795		3314
2796	If defined to be C<1>, libev will compile in support for the BSD style	3315	If defined to be C<1>, libev will compile in support for the BSD style
2797	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3316	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2810	otherwise another method will be used as fallback. This is the preferred	3329	otherwise another method will be used as fallback. This is the preferred
2811	backend for Solaris 10 systems.	3330	backend for Solaris 10 systems.
2812		3331
2813	=item EV_USE_DEVPOLL	3332	=item EV_USE_DEVPOLL
2814		3333
2815	reserved for future expansion, works like the USE symbols above.	3334	Reserved for future expansion, works like the USE symbols above.
2816		3335
2817	=item EV_USE_INOTIFY	3336	=item EV_USE_INOTIFY
2818		3337
2819	If defined to be C<1>, libev will compile in support for the Linux inotify	3338	If defined to be C<1>, libev will compile in support for the Linux inotify
2820	interface to speed up C<ev_stat> watchers. Its actual availability will	3339	interface to speed up C<ev_stat> watchers. Its actual availability will
2821	be detected at runtime.	3340	be detected at runtime. If undefined, it will be enabled if the headers
		3341	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2822		3342
2823	=item EV_ATOMIC_T	3343	=item EV_ATOMIC_T
2824		3344
2825	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3345	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2826	access is atomic with respect to other threads or signal contexts. No such	3346	access is atomic with respect to other threads or signal contexts. No such
2827	type is easily found in the C language, so you can provide your own type	3347	type is easily found in the C language, so you can provide your own type
2828	that you know is safe for your purposes. It is used both for signal handler "locking"	3348	that you know is safe for your purposes. It is used both for signal handler "locking"
2829	as well as for signal and thread safety in C<ev_async> watchers.	3349	as well as for signal and thread safety in C<ev_async> watchers.
2830		3350
2831	In the absense of this define, libev will use C<sig_atomic_t volatile>	3351	In the absence of this define, libev will use C<sig_atomic_t volatile>
2832	(from F<signal.h>), which is usually good enough on most platforms.	3352	(from F<signal.h>), which is usually good enough on most platforms.
2833		3353
2834	=item EV_H	3354	=item EV_H
2835		3355
2836	The name of the F<ev.h> header file used to include it. The default if	3356	The name of the F<ev.h> header file used to include it. The default if
…		…
2875	When doing priority-based operations, libev usually has to linearly search	3395	When doing priority-based operations, libev usually has to linearly search
2876	all the priorities, so having many of them (hundreds) uses a lot of space	3396	all the priorities, so having many of them (hundreds) uses a lot of space
2877	and time, so using the defaults of five priorities (-2 .. +2) is usually	3397	and time, so using the defaults of five priorities (-2 .. +2) is usually
2878	fine.	3398	fine.
2879		3399
2880	If your embedding app does not need any priorities, defining these both to	3400	If your embedding application does not need any priorities, defining these
2881	C<0> will save some memory and cpu.	3401	both to C<0> will save some memory and CPU.
2882		3402
2883	=item EV_PERIODIC_ENABLE	3403	=item EV_PERIODIC_ENABLE
2884		3404
2885	If undefined or defined to be C<1>, then periodic timers are supported. If	3405	If undefined or defined to be C<1>, then periodic timers are supported. If
2886	defined to be C<0>, then they are not. Disabling them saves a few kB of	3406	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2893	code.	3413	code.
2894		3414
2895	=item EV_EMBED_ENABLE	3415	=item EV_EMBED_ENABLE
2896		3416
2897	If undefined or defined to be C<1>, then embed watchers are supported. If	3417	If undefined or defined to be C<1>, then embed watchers are supported. If
2898	defined to be C<0>, then they are not.	3418	defined to be C<0>, then they are not. Embed watchers rely on most other
		3419	watcher types, which therefore must not be disabled.
2899		3420
2900	=item EV_STAT_ENABLE	3421	=item EV_STAT_ENABLE
2901		3422
2902	If undefined or defined to be C<1>, then stat watchers are supported. If	3423	If undefined or defined to be C<1>, then stat watchers are supported. If
2903	defined to be C<0>, then they are not.	3424	defined to be C<0>, then they are not.
…		…
2913	defined to be C<0>, then they are not.	3434	defined to be C<0>, then they are not.
2914		3435
2915	=item EV_MINIMAL	3436	=item EV_MINIMAL
2916		3437
2917	If you need to shave off some kilobytes of code at the expense of some	3438	If you need to shave off some kilobytes of code at the expense of some
2918	speed, define this symbol to C<1>. Currently only used for gcc to override	3439	speed, define this symbol to C<1>. Currently this is used to override some
2919	some inlining decisions, saves roughly 30% codesize of amd64.	3440	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3441	much smaller 2-heap for timer management over the default 4-heap.
2920		3442
2921	=item EV_PID_HASHSIZE	3443	=item EV_PID_HASHSIZE
2922		3444
2923	C<ev_child> watchers use a small hash table to distribute workload by	3445	C<ev_child> watchers use a small hash table to distribute workload by
2924	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3446	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2931	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3453	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2932	usually more than enough. If you need to manage thousands of C<ev_stat>	3454	usually more than enough. If you need to manage thousands of C<ev_stat>
2933	watchers you might want to increase this value (I<must> be a power of	3455	watchers you might want to increase this value (I<must> be a power of
2934	two).	3456	two).
2935		3457
		3458	=item EV_USE_4HEAP
		3459
		3460	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3461	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3462	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3463	faster performance with many (thousands) of watchers.
		3464
		3465	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3466	(disabled).
		3467
		3468	=item EV_HEAP_CACHE_AT
		3469
		3470	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3471	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3472	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3473	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3474	but avoids random read accesses on heap changes. This improves performance
		3475	noticeably with many (hundreds) of watchers.
		3476
		3477	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3478	(disabled).
		3479
		3480	=item EV_VERIFY
		3481
		3482	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3483	be done: If set to C<0>, no internal verification code will be compiled
		3484	in. If set to C<1>, then verification code will be compiled in, but not
		3485	called. If set to C<2>, then the internal verification code will be
		3486	called once per loop, which can slow down libev. If set to C<3>, then the
		3487	verification code will be called very frequently, which will slow down
		3488	libev considerably.
		3489
		3490	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3491	C<0>.
		3492
2936	=item EV_COMMON	3493	=item EV_COMMON
2937		3494
2938	By default, all watchers have a C<void *data> member. By redefining	3495	By default, all watchers have a C<void *data> member. By redefining
2939	this macro to a something else you can include more and other types of	3496	this macro to a something else you can include more and other types of
2940	members. You have to define it each time you include one of the files,	3497	members. You have to define it each time you include one of the files,
2941	though, and it must be identical each time.	3498	though, and it must be identical each time.
2942		3499
2943	For example, the perl EV module uses something like this:	3500	For example, the perl EV module uses something like this:
2944		3501
2945	#define EV_COMMON \	3502	#define EV_COMMON \
2946	SV *self; /* contains this struct */ \	3503	SV *self; /* contains this struct */ \
2947	SV *cb_sv, *fh /* note no trailing ";" */	3504	SV *cb_sv, *fh /* note no trailing ";" */
2948		3505
2949	=item EV_CB_DECLARE (type)	3506	=item EV_CB_DECLARE (type)
2950		3507
2951	=item EV_CB_INVOKE (watcher, revents)	3508	=item EV_CB_INVOKE (watcher, revents)
2952		3509
…		…
2957	definition and a statement, respectively. See the F<ev.h> header file for	3514	definition and a statement, respectively. See the F<ev.h> header file for
2958	their default definitions. One possible use for overriding these is to	3515	their default definitions. One possible use for overriding these is to
2959	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3516	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2960	method calls instead of plain function calls in C++.	3517	method calls instead of plain function calls in C++.
2961		3518
		3519	=back
		3520
2962	=head2 EXPORTED API SYMBOLS	3521	=head2 EXPORTED API SYMBOLS
2963		3522
2964	If you need to re-export the API (e.g. via a dll) and you need a list of	3523	If you need to re-export the API (e.g. via a DLL) and you need a list of
2965	exported symbols, you can use the provided F<Symbol.*> files which list	3524	exported symbols, you can use the provided F<Symbol.*> files which list
2966	all public symbols, one per line:	3525	all public symbols, one per line:
2967		3526
2968	Symbols.ev for libev proper	3527	Symbols.ev for libev proper
2969	Symbols.event for the libevent emulation	3528	Symbols.event for the libevent emulation
2970		3529
2971	This can also be used to rename all public symbols to avoid clashes with	3530	This can also be used to rename all public symbols to avoid clashes with
2972	multiple versions of libev linked together (which is obviously bad in	3531	multiple versions of libev linked together (which is obviously bad in
2973	itself, but sometimes it is inconvinient to avoid this).	3532	itself, but sometimes it is inconvenient to avoid this).
2974		3533
2975	A sed command like this will create wrapper C<#define>'s that you need to	3534	A sed command like this will create wrapper C<#define>'s that you need to
2976	include before including F<ev.h>:	3535	include before including F<ev.h>:
2977		3536
2978	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3537	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2995	file.	3554	file.
2996		3555
2997	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3556	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2998	that everybody includes and which overrides some configure choices:	3557	that everybody includes and which overrides some configure choices:
2999		3558
3000	#define EV_MINIMAL 1	3559	#define EV_MINIMAL 1
3001	#define EV_USE_POLL 0	3560	#define EV_USE_POLL 0
3002	#define EV_MULTIPLICITY 0	3561	#define EV_MULTIPLICITY 0
3003	#define EV_PERIODIC_ENABLE 0	3562	#define EV_PERIODIC_ENABLE 0
3004	#define EV_STAT_ENABLE 0	3563	#define EV_STAT_ENABLE 0
3005	#define EV_FORK_ENABLE 0	3564	#define EV_FORK_ENABLE 0
3006	#define EV_CONFIG_H <config.h>	3565	#define EV_CONFIG_H <config.h>
3007	#define EV_MINPRI 0	3566	#define EV_MINPRI 0
3008	#define EV_MAXPRI 0	3567	#define EV_MAXPRI 0
3009		3568
3010	#include "ev++.h"	3569	#include "ev++.h"
3011		3570
3012	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3571	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3013		3572
3014	#include "ev_cpp.h"	3573	#include "ev_cpp.h"
3015	#include "ev.c"	3574	#include "ev.c"
3016		3575
		3576	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3017		3577
3018	=head1 COMPLEXITIES	3578	=head2 THREADS AND COROUTINES
3019		3579
3020	In this section the complexities of (many of) the algorithms used inside	3580	=head3 THREADS
3021	libev will be explained. For complexity discussions about backends see the
3022	documentation for C<ev_default_init>.
3023		3581
3024	All of the following are about amortised time: If an array needs to be	3582	All libev functions are reentrant and thread-safe unless explicitly
3025	extended, libev needs to realloc and move the whole array, but this	3583	documented otherwise, but libev implements no locking itself. This means
3026	happens asymptotically never with higher number of elements, so O(1) might	3584	that you can use as many loops as you want in parallel, as long as there
3027	mean it might do a lengthy realloc operation in rare cases, but on average	3585	are no concurrent calls into any libev function with the same loop
3028	it is much faster and asymptotically approaches constant time.	3586	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3587	of course): libev guarantees that different event loops share no data
		3588	structures that need any locking.
		3589
		3590	Or to put it differently: calls with different loop parameters can be done
		3591	concurrently from multiple threads, calls with the same loop parameter
		3592	must be done serially (but can be done from different threads, as long as
		3593	only one thread ever is inside a call at any point in time, e.g. by using
		3594	a mutex per loop).
		3595
		3596	Specifically to support threads (and signal handlers), libev implements
		3597	so-called C<ev_async> watchers, which allow some limited form of
		3598	concurrency on the same event loop, namely waking it up "from the
		3599	outside".
		3600
		3601	If you want to know which design (one loop, locking, or multiple loops
		3602	without or something else still) is best for your problem, then I cannot
		3603	help you, but here is some generic advice:
3029		3604
3030	=over 4	3605	=over 4
3031		3606
3032	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3607	=item * most applications have a main thread: use the default libev loop
		3608	in that thread, or create a separate thread running only the default loop.
3033		3609
3034	This means that, when you have a watcher that triggers in one hour and	3610	This helps integrating other libraries or software modules that use libev
3035	there are 100 watchers that would trigger before that then inserting will	3611	themselves and don't care/know about threading.
3036	have to skip roughly seven (C<ld 100>) of these watchers.
3037		3612
3038	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3613	=item * one loop per thread is usually a good model.
3039		3614
3040	That means that changing a timer costs less than removing/adding them	3615	Doing this is almost never wrong, sometimes a better-performance model
3041	as only the relative motion in the event queue has to be paid for.	3616	exists, but it is always a good start.
3042		3617
3043	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3618	=item * other models exist, such as the leader/follower pattern, where one
		3619	loop is handed through multiple threads in a kind of round-robin fashion.
3044		3620
3045	These just add the watcher into an array or at the head of a list.	3621	Choosing a model is hard - look around, learn, know that usually you can do
		3622	better than you currently do :-)
3046		3623
3047	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3624	=item * often you need to talk to some other thread which blocks in the
		3625	event loop.
3048		3626
3049	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3627	C<ev_async> watchers can be used to wake them up from other threads safely
		3628	(or from signal contexts...).
3050		3629
3051	These watchers are stored in lists then need to be walked to find the	3630	An example use would be to communicate signals or other events that only
3052	correct watcher to remove. The lists are usually short (you don't usually	3631	work in the default loop by registering the signal watcher with the
3053	have many watchers waiting for the same fd or signal).	3632	default loop and triggering an C<ev_async> watcher from the default loop
3054		3633	watcher callback into the event loop interested in the signal.
3055	=item Finding the next timer in each loop iteration: O(1)
3056
3057	By virtue of using a binary heap, the next timer is always found at the
3058	beginning of the storage array.
3059
3060	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3061
3062	A change means an I/O watcher gets started or stopped, which requires
3063	libev to recalculate its status (and possibly tell the kernel, depending
3064	on backend and wether C<ev_io_set> was used).
3065
3066	=item Activating one watcher (putting it into the pending state): O(1)
3067
3068	=item Priority handling: O(number_of_priorities)
3069
3070	Priorities are implemented by allocating some space for each
3071	priority. When doing priority-based operations, libev usually has to
3072	linearly search all the priorities, but starting/stopping and activating
3073	watchers becomes O(1) w.r.t. priority handling.
3074
3075	=item Sending an ev_async: O(1)
3076
3077	=item Processing ev_async_send: O(number_of_async_watchers)
3078
3079	=item Processing signals: O(max_signal_number)
3080
3081	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3082	calls in the current loop iteration. Checking for async and signal events
3083	involves iterating over all running async watchers or all signal numbers.
3084		3634
3085	=back	3635	=back
3086		3636
		3637	=head3 COROUTINES
3087		3638
3088	=head1 Win32 platform limitations and workarounds	3639	Libev is very accommodating to coroutines ("cooperative threads"):
		3640	libev fully supports nesting calls to its functions from different
		3641	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3642	different coroutines, and switch freely between both coroutines running the
		3643	loop, as long as you don't confuse yourself). The only exception is that
		3644	you must not do this from C<ev_periodic> reschedule callbacks.
		3645
		3646	Care has been taken to ensure that libev does not keep local state inside
		3647	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3648	they do not call any callbacks.
		3649
		3650	=head2 COMPILER WARNINGS
		3651
		3652	Depending on your compiler and compiler settings, you might get no or a
		3653	lot of warnings when compiling libev code. Some people are apparently
		3654	scared by this.
		3655
		3656	However, these are unavoidable for many reasons. For one, each compiler
		3657	has different warnings, and each user has different tastes regarding
		3658	warning options. "Warn-free" code therefore cannot be a goal except when
		3659	targeting a specific compiler and compiler-version.
		3660
		3661	Another reason is that some compiler warnings require elaborate
		3662	workarounds, or other changes to the code that make it less clear and less
		3663	maintainable.
		3664
		3665	And of course, some compiler warnings are just plain stupid, or simply
		3666	wrong (because they don't actually warn about the condition their message
		3667	seems to warn about). For example, certain older gcc versions had some
		3668	warnings that resulted an extreme number of false positives. These have
		3669	been fixed, but some people still insist on making code warn-free with
		3670	such buggy versions.
		3671
		3672	While libev is written to generate as few warnings as possible,
		3673	"warn-free" code is not a goal, and it is recommended not to build libev
		3674	with any compiler warnings enabled unless you are prepared to cope with
		3675	them (e.g. by ignoring them). Remember that warnings are just that:
		3676	warnings, not errors, or proof of bugs.
		3677
		3678
		3679	=head2 VALGRIND
		3680
		3681	Valgrind has a special section here because it is a popular tool that is
		3682	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3683
		3684	If you think you found a bug (memory leak, uninitialised data access etc.)
		3685	in libev, then check twice: If valgrind reports something like:
		3686
		3687	==2274== definitely lost: 0 bytes in 0 blocks.
		3688	==2274== possibly lost: 0 bytes in 0 blocks.
		3689	==2274== still reachable: 256 bytes in 1 blocks.
		3690
		3691	Then there is no memory leak, just as memory accounted to global variables
		3692	is not a memleak - the memory is still being referenced, and didn't leak.
		3693
		3694	Similarly, under some circumstances, valgrind might report kernel bugs
		3695	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3696	although an acceptable workaround has been found here), or it might be
		3697	confused.
		3698
		3699	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3700	make it into some kind of religion.
		3701
		3702	If you are unsure about something, feel free to contact the mailing list
		3703	with the full valgrind report and an explanation on why you think this
		3704	is a bug in libev (best check the archives, too :). However, don't be
		3705	annoyed when you get a brisk "this is no bug" answer and take the chance
		3706	of learning how to interpret valgrind properly.
		3707
		3708	If you need, for some reason, empty reports from valgrind for your project
		3709	I suggest using suppression lists.
		3710
		3711
		3712	=head1 PORTABILITY NOTES
		3713
		3714	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3089		3715
3090	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3716	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3091	requires, and its I/O model is fundamentally incompatible with the POSIX	3717	requires, and its I/O model is fundamentally incompatible with the POSIX
3092	model. Libev still offers limited functionality on this platform in	3718	model. Libev still offers limited functionality on this platform in
3093	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3719	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3094	descriptors. This only applies when using Win32 natively, not when using	3720	descriptors. This only applies when using Win32 natively, not when using
3095	e.g. cygwin.	3721	e.g. cygwin.
3096		3722
		3723	Lifting these limitations would basically require the full
		3724	re-implementation of the I/O system. If you are into these kinds of
		3725	things, then note that glib does exactly that for you in a very portable
		3726	way (note also that glib is the slowest event library known to man).
		3727
3097	There is no supported compilation method available on windows except	3728	There is no supported compilation method available on windows except
3098	embedding it into other applications.	3729	embedding it into other applications.
3099		3730
		3731	Not a libev limitation but worth mentioning: windows apparently doesn't
		3732	accept large writes: instead of resulting in a partial write, windows will
		3733	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3734	so make sure you only write small amounts into your sockets (less than a
		3735	megabyte seems safe, but this apparently depends on the amount of memory
		3736	available).
		3737
3100	Due to the many, low, and arbitrary limits on the win32 platform and the	3738	Due to the many, low, and arbitrary limits on the win32 platform and
3101	abysmal performance of winsockets, using a large number of sockets is not	3739	the abysmal performance of winsockets, using a large number of sockets
3102	recommended (and not reasonable). If your program needs to use more than	3740	is not recommended (and not reasonable). If your program needs to use
3103	a hundred or so sockets, then likely it needs to use a totally different	3741	more than a hundred or so sockets, then likely it needs to use a totally
3104	implementation for windows, as libev offers the POSIX model, which cannot	3742	different implementation for windows, as libev offers the POSIX readiness
3105	be implemented efficiently on windows (microsoft monopoly games).	3743	notification model, which cannot be implemented efficiently on windows
		3744	(Microsoft monopoly games).
		3745
		3746	A typical way to use libev under windows is to embed it (see the embedding
		3747	section for details) and use the following F<evwrap.h> header file instead
		3748	of F<ev.h>:
		3749
		3750	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3751	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3752
		3753	#include "ev.h"
		3754
		3755	And compile the following F<evwrap.c> file into your project (make sure
		3756	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3757
		3758	#include "evwrap.h"
		3759	#include "ev.c"
3106		3760
3107	=over 4	3761	=over 4
3108		3762
3109	=item The winsocket select function	3763	=item The winsocket select function
3110		3764
3111	The winsocket C<select> function doesn't follow POSIX in that it requires	3765	The winsocket C<select> function doesn't follow POSIX in that it
3112	socket I<handles> and not socket I<file descriptors>. This makes select	3766	requires socket I<handles> and not socket I<file descriptors> (it is
3113	very inefficient, and also requires a mapping from file descriptors	3767	also extremely buggy). This makes select very inefficient, and also
3114	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3768	requires a mapping from file descriptors to socket handles (the Microsoft
3115	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3769	C runtime provides the function C<_open_osfhandle> for this). See the
3116	symbols for more info.	3770	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3771	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3117		3772
3118	The configuration for a "naked" win32 using the microsoft runtime	3773	The configuration for a "naked" win32 using the Microsoft runtime
3119	libraries and raw winsocket select is:	3774	libraries and raw winsocket select is:
3120		3775
3121	#define EV_USE_SELECT 1	3776	#define EV_USE_SELECT 1
3122	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3777	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3123		3778
3124	Note that winsockets handling of fd sets is O(n), so you can easily get a	3779	Note that winsockets handling of fd sets is O(n), so you can easily get a
3125	complexity in the O(n²) range when using win32.	3780	complexity in the O(n²) range when using win32.
3126		3781
3127	=item Limited number of file descriptors	3782	=item Limited number of file descriptors
3128		3783
3129	Windows has numerous arbitrary (and low) limits on things. Early versions	3784	Windows has numerous arbitrary (and low) limits on things.
3130	of winsocket's select only supported waiting for a max. of C<64> handles	3785
		3786	Early versions of winsocket's select only supported waiting for a maximum
3131	(probably owning to the fact that all windows kernels can only wait for	3787	of C<64> handles (probably owning to the fact that all windows kernels
3132	C<64> things at the same time internally; microsoft recommends spawning a	3788	can only wait for C<64> things at the same time internally; Microsoft
3133	chain of threads and wait for 63 handles and the previous thread in each).	3789	recommends spawning a chain of threads and wait for 63 handles and the
		3790	previous thread in each. Great).
3134		3791
3135	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3792	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3136	to some high number (e.g. C<2048>) before compiling the winsocket select	3793	to some high number (e.g. C<2048>) before compiling the winsocket select
3137	call (which might be in libev or elsewhere, for example, perl does its own	3794	call (which might be in libev or elsewhere, for example, perl does its own
3138	select emulation on windows).	3795	select emulation on windows).
3139		3796
3140	Another limit is the number of file descriptors in the microsoft runtime	3797	Another limit is the number of file descriptors in the Microsoft runtime
3141	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3798	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3142	or something like this inside microsoft). You can increase this by calling	3799	or something like this inside Microsoft). You can increase this by calling
3143	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3800	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3144	arbitrary limit), but is broken in many versions of the microsoft runtime	3801	arbitrary limit), but is broken in many versions of the Microsoft runtime
3145	libraries.	3802	libraries.
3146		3803
3147	This might get you to about C<512> or C<2048> sockets (depending on	3804	This might get you to about C<512> or C<2048> sockets (depending on
3148	windows version and/or the phase of the moon). To get more, you need to	3805	windows version and/or the phase of the moon). To get more, you need to
3149	wrap all I/O functions and provide your own fd management, but the cost of	3806	wrap all I/O functions and provide your own fd management, but the cost of
3150	calling select (O(n²)) will likely make this unworkable.	3807	calling select (O(n²)) will likely make this unworkable.
3151		3808
3152	=back	3809	=back
3153		3810
		3811	=head2 PORTABILITY REQUIREMENTS
		3812
		3813	In addition to a working ISO-C implementation and of course the
		3814	backend-specific APIs, libev relies on a few additional extensions:
		3815
		3816	=over 4
		3817
		3818	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3819	calling conventions regardless of C<ev_watcher_type *>.
		3820
		3821	Libev assumes not only that all watcher pointers have the same internal
		3822	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3823	assumes that the same (machine) code can be used to call any watcher
		3824	callback: The watcher callbacks have different type signatures, but libev
		3825	calls them using an C<ev_watcher *> internally.
		3826
		3827	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3828
		3829	The type C<sig_atomic_t volatile> (or whatever is defined as
		3830	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3831	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3832	believed to be sufficiently portable.
		3833
		3834	=item C<sigprocmask> must work in a threaded environment
		3835
		3836	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3837	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3838	pthread implementations will either allow C<sigprocmask> in the "main
		3839	thread" or will block signals process-wide, both behaviours would
		3840	be compatible with libev. Interaction between C<sigprocmask> and
		3841	C<pthread_sigmask> could complicate things, however.
		3842
		3843	The most portable way to handle signals is to block signals in all threads
		3844	except the initial one, and run the default loop in the initial thread as
		3845	well.
		3846
		3847	=item C<long> must be large enough for common memory allocation sizes
		3848
		3849	To improve portability and simplify its API, libev uses C<long> internally
		3850	instead of C<size_t> when allocating its data structures. On non-POSIX
		3851	systems (Microsoft...) this might be unexpectedly low, but is still at
		3852	least 31 bits everywhere, which is enough for hundreds of millions of
		3853	watchers.
		3854
		3855	=item C<double> must hold a time value in seconds with enough accuracy
		3856
		3857	The type C<double> is used to represent timestamps. It is required to
		3858	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3859	enough for at least into the year 4000. This requirement is fulfilled by
		3860	implementations implementing IEEE 754 (basically all existing ones).
		3861
		3862	=back
		3863
		3864	If you know of other additional requirements drop me a note.
		3865
		3866
		3867	=head1 ALGORITHMIC COMPLEXITIES
		3868
		3869	In this section the complexities of (many of) the algorithms used inside
		3870	libev will be documented. For complexity discussions about backends see
		3871	the documentation for C<ev_default_init>.
		3872
		3873	All of the following are about amortised time: If an array needs to be
		3874	extended, libev needs to realloc and move the whole array, but this
		3875	happens asymptotically rarer with higher number of elements, so O(1) might
		3876	mean that libev does a lengthy realloc operation in rare cases, but on
		3877	average it is much faster and asymptotically approaches constant time.
		3878
		3879	=over 4
		3880
		3881	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3882
		3883	This means that, when you have a watcher that triggers in one hour and
		3884	there are 100 watchers that would trigger before that, then inserting will
		3885	have to skip roughly seven (C<ld 100>) of these watchers.
		3886
		3887	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3888
		3889	That means that changing a timer costs less than removing/adding them,
		3890	as only the relative motion in the event queue has to be paid for.
		3891
		3892	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3893
		3894	These just add the watcher into an array or at the head of a list.
		3895
		3896	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3897
		3898	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3899
		3900	These watchers are stored in lists, so they need to be walked to find the
		3901	correct watcher to remove. The lists are usually short (you don't usually
		3902	have many watchers waiting for the same fd or signal: one is typical, two
		3903	is rare).
		3904
		3905	=item Finding the next timer in each loop iteration: O(1)
		3906
		3907	By virtue of using a binary or 4-heap, the next timer is always found at a
		3908	fixed position in the storage array.
		3909
		3910	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3911
		3912	A change means an I/O watcher gets started or stopped, which requires
		3913	libev to recalculate its status (and possibly tell the kernel, depending
		3914	on backend and whether C<ev_io_set> was used).
		3915
		3916	=item Activating one watcher (putting it into the pending state): O(1)
		3917
		3918	=item Priority handling: O(number_of_priorities)
		3919
		3920	Priorities are implemented by allocating some space for each
		3921	priority. When doing priority-based operations, libev usually has to
		3922	linearly search all the priorities, but starting/stopping and activating
		3923	watchers becomes O(1) with respect to priority handling.
		3924
		3925	=item Sending an ev_async: O(1)
		3926
		3927	=item Processing ev_async_send: O(number_of_async_watchers)
		3928
		3929	=item Processing signals: O(max_signal_number)
		3930
		3931	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3932	calls in the current loop iteration. Checking for async and signal events
		3933	involves iterating over all running async watchers or all signal numbers.
		3934
		3935	=back
		3936
3154		3937
3155	=head1 AUTHOR	3938	=head1 AUTHOR
3156		3939
3157	Marc Lehmann <libev@schmorp.de>.	3940	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3158		3941

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