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Revision 1.136 by root, Thu Mar 13 13:06:16 2008 UTC vs.
Revision 1.200 by root, Thu Oct 23 07:33:45 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	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	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	68	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		70
71	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	73	these event sources and provide your program with events.
74		74
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	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	107	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	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
157	not a problem.	178	not a problem.
158		179
159	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	215	recommended ones.
195		216
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
205	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
206		230
207	You could override this function in high-availability programs to, say,	231	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,	232	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.	233	or even to sleep a while and retry until some memory is available.
210		234
211	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	236	retries (example requires a standards-compliant C<realloc>).
213		237
214	static void *	238	static void *
215	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
216	{	240	{
217	for (;;)	241	for (;;)
…		…
226	}	250	}
227		251
228	...	252	...
229	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
230		254
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		256
233	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
234	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	259	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	260	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	261	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	262	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	263	(such as abort).
240		264
241	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
252		276
253	=back	277	=back
254		278
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		280
257	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
258	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
259	events, and dynamically created loops which do not.	283	I<function>).
260		284
261	If you use threads, a common model is to run the default event loop	285	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	286	supports signals and child events, and dynamically created loops which do
263	create, you also create another event loop. Libev itself does no locking	287	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		288
268	=over 4	289	=over 4
269		290
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		292
…		…
275	flags. If that is troubling you, check C<ev_backend ()> afterwards).	296	flags. If that is troubling you, check C<ev_backend ()> afterwards).
276		297
277	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
278	function.	299	function.
279		300
		301	Note that this function is I<not> thread-safe, so if you want to use it
		302	from multiple threads, you have to lock (note also that this is unlikely,
		303	as loops cannot bes hared easily between threads anyway).
		304
280	The default loop is the only loop that can handle C<ev_signal> and	305	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	306	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	307	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	308	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	309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	310	C<ev_default_init>.
286		311
287	The flags argument can be used to specify special behaviour or specific	312	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	321	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	322	thing, believe me).
298		323
299	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
300		325
301	If this flag bit is ored into the flag value (or the program runs setuid	326	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	327	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	329	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	330	useful to try out specific backends to test their performance, or to work
306	around bugs.	331	around bugs.
…		…
313		338
314	This works by calling C<getpid ()> on every iteration of the loop,	339	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	340	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	341	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	342	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	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
320		345
321	The big advantage of this flag is that you can forget about fork (and	346	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	347	forget about forgetting to tell libev about forking) when you use this
323	flag.	348	flag.
324		349
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	351	environment variable.
327		352
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		354
330	This is your standard select(2) backend. Not I<completely> standard, as	355	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	357	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	358	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.	359	usually the fastest backend for a low number of (low-numbered :) fds.
335		360
336	To get good performance out of this backend you need a high amount of	361	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	362	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	363	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	364	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	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readyness notifications you get per iteration.	366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
342		371
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		373
345	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	375	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	376	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,	377	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	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	379	performance tips.
351		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		385
354	For few fds, this backend is a bit little slower than poll and select,	386	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	387	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),	388	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	389	epoll scales either O(1) or O(active_fds). The epoll design has a number
358	of shortcomings, such as silently dropping events in some hard-to-detect	390	of shortcomings, such as silently dropping events in some hard-to-detect
359	cases and rewiring a syscall per fd change, no fork support and bad	391	cases and requiring a system call per fd change, no fork support and bad
360	support for dup.	392	support for dup.
361		393
362	While stopping, setting and starting an I/O watcher in the same iteration	394	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	395	will result in some caching, there is still a system call per such incident
364	(because the fd could point to a different file description now), so its	396	(because the fd could point to a different file description now), so its
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	397	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	398	very well if you register events for both fds.
367		399
368	Please note that epoll sometimes generates spurious notifications, so you	400	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	401	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.	402	(or space) is available.
371		403
372	Best performance from this backend is achieved by not unregistering all	404	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.	405	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	406	i.e. keep at least one watcher active per fd at all times. Stopping and
		407	starting a watcher (without re-setting it) also usually doesn't cause
		408	extra overhead.
375		409
376	While nominally embeddeble in other event loops, this feature is broken in	410	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	411	all kernel versions tested so far.
378		412
		413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		414	C<EVBACKEND_POLL>.
		415
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		417
381	Kqueue deserves special mention, as at the time of this writing, it	418	Kqueue deserves special mention, as at the time of this writing, it was
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	419	broken on all BSDs except NetBSD (usually it doesn't work reliably with
383	with anything but sockets and pipes, except on Darwin, where of course	420	anything but sockets and pipes, except on Darwin, where of course it's
384	it's completely useless). For this reason it's not being "autodetected"	421	completely useless). For this reason it's not being "auto-detected" unless
385	unless you explicitly specify it explicitly in the flags (i.e. using	422	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	423	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
387	system like NetBSD.
388		424
389	You still can embed kqueue into a normal poll or select backend and use it	425	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	426	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.	427	the target platform). See C<ev_embed> watchers for more info.
392		428
393	It scales in the same way as the epoll backend, but the interface to the	429	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	430	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	431	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	432	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	433	two event changes per incident. Support for C<fork ()> is very bad and it
398	drops fds silently in similarly hard-to-detect cases.	434	drops fds silently in similarly hard-to-detect cases.
399		435
400	This backend usually performs well under most conditions.	436	This backend usually performs well under most conditions.
401		437
402	While nominally embeddable in other event loops, this doesn't work	438	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	439	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	440	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	441	(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	442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	443	using it only for sockets.
		444
		445	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		446	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		447	C<NOTE_EOF>.
408		448
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	449	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		450
411	This is not implemented yet (and might never be, unless you send me an	451	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	452	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	456	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		457
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	458	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)).	459	it's really slow, but it still scales very well (O(active_fds)).
420		460
421	Please note that solaris event ports can deliver a lot of spurious	461	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	462	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	463	blocking when no data (or space) is available.
424		464
425	While this backend scales well, it requires one system call per active	465	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	466	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	467	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	468	might perform better.
429		469
430	On the positive side, ignoring the spurious readyness notifications, this	470	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	471	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	472	in all tests and is fully embeddable, which is a rare feat among the
		473	OS-specific backends.
		474
		475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		476	C<EVBACKEND_POLL>.
433		477
434	=item C<EVBACKEND_ALL>	478	=item C<EVBACKEND_ALL>
435		479
436	Try all backends (even potentially broken ones that wouldn't be tried	480	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	481	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		483
440	It is definitely not recommended to use this flag.	484	It is definitely not recommended to use this flag.
441		485
442	=back	486	=back
443		487
444	If one or more of these are ored into the flags value, then only these	488	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	489	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.	490	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		491
448	The most typical usage is like this:	492	Example: This is the most typical usage.
449		493
450	if (!ev_default_loop (0))	494	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		496
453	Restrict libev to the select and poll backends, and do not allow	497	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	498	environment settings to be taken into account:
455		499
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	500	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		501
458	Use whatever libev has to offer, but make sure that kqueue is used if	502	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	503	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):	504	private event loop and only if you know the OS supports your types of
		505	fds):
461		506
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		508
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	509	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		510
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	511	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	512	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	513	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).	514	undefined behaviour (or a failed assertion if assertions are enabled).
470		515
		516	Note that this function I<is> thread-safe, and the recommended way to use
		517	libev with threads is indeed to create one loop per thread, and using the
		518	default loop in the "main" or "initial" thread.
		519
471	Example: Try to create a event loop that uses epoll and nothing else.	520	Example: Try to create a event loop that uses epoll and nothing else.
472		521
473	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	522	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
474	if (!epoller)	523	if (!epoller)
475	fatal ("no epoll found here, maybe it hides under your chair");	524	fatal ("no epoll found here, maybe it hides under your chair");
476		525
477	=item ev_default_destroy ()	526	=item ev_default_destroy ()
478		527
479	Destroys the default loop again (frees all memory and kernel state	528	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	529	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	530	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>	531	responsibility to either stop all watchers cleanly yourself I<before>
483	calling this function, or cope with the fact afterwards (which is usually	532	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	533	the easiest thing, you can just ignore the watchers and/or C<free ()> them
485	for example).	534	for example).
486		535
487	Note that certain global state, such as signal state, will not be freed by	536	Note that certain global state, such as signal state, will not be freed by
…		…
519		568
520	=item ev_loop_fork (loop)	569	=item ev_loop_fork (loop)
521		570
522	Like C<ev_default_fork>, but acts on an event loop created by	571	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	572	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.	573	after fork that you want to re-use in the child, and how you do this is
		574	entirely your own problem.
525		575
526	=item int ev_is_default_loop (loop)	576	=item int ev_is_default_loop (loop)
527		577
528	Returns true when the given loop actually is the default loop, false otherwise.	578	Returns true when the given loop is, in fact, the default loop, and false
		579	otherwise.
529		580
530	=item unsigned int ev_loop_count (loop)	581	=item unsigned int ev_loop_count (loop)
531		582
532	Returns the count of loop iterations for the loop, which is identical to	583	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	584	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	599	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	600	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	601	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).	602	event occurring (or more correctly, libev finding out about it).
552		603
		604	=item ev_now_update (loop)
		605
		606	Establishes the current time by querying the kernel, updating the time
		607	returned by C<ev_now ()> in the progress. This is a costly operation and
		608	is usually done automatically within C<ev_loop ()>.
		609
		610	This function is rarely useful, but when some event callback runs for a
		611	very long time without entering the event loop, updating libev's idea of
		612	the current time is a good idea.
		613
		614	See also "The special problem of time updates" in the C<ev_timer> section.
		615
553	=item ev_loop (loop, int flags)	616	=item ev_loop (loop, int flags)
554		617
555	Finally, this is it, the event handler. This function usually is called	618	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	619	after you initialised all your watchers and you want to start handling
557	events.	620	events.
…		…
559	If the flags argument is specified as C<0>, it will not return until	622	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.	623	either no event watchers are active anymore or C<ev_unloop> was called.
561		624
562	Please note that an explicit C<ev_unloop> is usually better than	625	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	626	relying on all watchers to be stopped when deciding when a program has
564	finished (especially in interactive programs), but having a program that	627	finished (especially in interactive programs), but having a program
565	automatically loops as long as it has to and no longer by virtue of	628	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.	629	of relying on its watchers stopping correctly, that is truly a thing of
		630	beauty.
567		631
568	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	632	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	633	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.	634	process in case there are no events and will return after one iteration of
		635	the loop.
571		636
572	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	637	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	638	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	639	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	640	be an event internal to libev itself, so there is no guarentee that a
576	external event in conjunction with something not expressible using other	641	user-registered callback will be called), and will return after one
		642	iteration of the loop.
		643
		644	This is useful if you are waiting for some external event in conjunction
		645	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	646	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.	647	usually a better approach for this kind of thing.
579		648
580	Here are the gory details of what C<ev_loop> does:	649	Here are the gory details of what C<ev_loop> does:
581		650
582	- Before the first iteration, call any pending watchers.	651	- Before the first iteration, call any pending watchers.
583	* If EVFLAG_FORKCHECK was used, check for a fork.	652	* If EVFLAG_FORKCHECK was used, check for a fork.
584	- If a fork was detected, queue and call all fork watchers.	653	- If a fork was detected (by any means), queue and call all fork watchers.
585	- Queue and call all prepare watchers.	654	- Queue and call all prepare watchers.
586	- If we have been forked, recreate the kernel state.	655	- If we have been forked, detach and recreate the kernel state
		656	as to not disturb the other process.
587	- Update the kernel state with all outstanding changes.	657	- Update the kernel state with all outstanding changes.
588	- Update the "event loop time".	658	- Update the "event loop time" (ev_now ()).
589	- Calculate for how long to sleep or block, if at all	659	- Calculate for how long to sleep or block, if at all
590	(active idle watchers, EVLOOP_NONBLOCK or not having	660	(active idle watchers, EVLOOP_NONBLOCK or not having
591	any active watchers at all will result in not sleeping).	661	any active watchers at all will result in not sleeping).
592	- Sleep if the I/O and timer collect interval say so.	662	- Sleep if the I/O and timer collect interval say so.
593	- Block the process, waiting for any events.	663	- Block the process, waiting for any events.
594	- Queue all outstanding I/O (fd) events.	664	- Queue all outstanding I/O (fd) events.
595	- Update the "event loop time" and do time jump handling.	665	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
596	- Queue all outstanding timers.	666	- Queue all expired timers.
597	- Queue all outstanding periodics.	667	- Queue all expired periodics.
598	- If no events are pending now, queue all idle watchers.	668	- Unless any events are pending now, queue all idle watchers.
599	- Queue all check watchers.	669	- Queue all check watchers.
600	- Call all queued watchers in reverse order (i.e. check watchers first).	670	- 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	671	Signals and child watchers are implemented as I/O watchers, and will
602	be handled here by queueing them when their watcher gets executed.	672	be handled here by queueing them when their watcher gets executed.
603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	673	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
608	anymore.	678	anymore.
609		679
610	... queue jobs here, make sure they register event watchers as long	680	... 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..)	681	... as they still have work to do (even an idle watcher will do..)
612	ev_loop (my_loop, 0);	682	ev_loop (my_loop, 0);
613	... jobs done. yeah!	683	... jobs done or somebody called unloop. yeah!
614		684
615	=item ev_unloop (loop, how)	685	=item ev_unloop (loop, how)
616		686
617	Can be used to make a call to C<ev_loop> return early (but only after it	687	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	688	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	689	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.	690	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
621		691
622	This "unloop state" will be cleared when entering C<ev_loop> again.	692	This "unloop state" will be cleared when entering C<ev_loop> again.
623		693
		694	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		695
624	=item ev_ref (loop)	696	=item ev_ref (loop)
625		697
626	=item ev_unref (loop)	698	=item ev_unref (loop)
627		699
628	Ref/unref can be used to add or remove a reference count on the event	700	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	701	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	702	count is nonzero, C<ev_loop> will not return on its own.
		703
631	a watcher you never unregister that should not keep C<ev_loop> from	704	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	705	from returning, call ev_unref() after starting, and ev_ref() before
		706	stopping it.
		707
633	example, libev itself uses this for its internal signal pipe: It is not	708	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	709	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	710	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	711	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>	712	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,	713	(but only if the watcher wasn't active before, or was active before,
639	respectively).	714	respectively).
640		715
641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
642	running when nothing else is active.	717	running when nothing else is active.
643		718
644	struct ev_signal exitsig;	719	ev_signal exitsig;
645	ev_signal_init (&exitsig, sig_cb, SIGINT);	720	ev_signal_init (&exitsig, sig_cb, SIGINT);
646	ev_signal_start (loop, &exitsig);	721	ev_signal_start (loop, &exitsig);
647	evf_unref (loop);	722	evf_unref (loop);
648		723
649	Example: For some weird reason, unregister the above signal handler again.	724	Example: For some weird reason, unregister the above signal handler again.
650		725
651	ev_ref (loop);	726	ev_ref (loop);
652	ev_signal_stop (loop, &exitsig);	727	ev_signal_stop (loop, &exitsig);
653		728
654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	729	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
655		730
656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	731	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
657		732
658	These advanced functions influence the time that libev will spend waiting	733	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	734	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.	735	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		736	latency.
661		737
662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	738	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	739	allows libev to delay invocation of I/O and timer/periodic callbacks
664	increase efficiency of loop iterations.	740	to increase efficiency of loop iterations (or to increase power-saving
		741	opportunities).
665		742
666	The background is that sometimes your program runs just fast enough to	743	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	744	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	745	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	746	events, especially with backends like C<select ()> which have a high
670	overhead for the actual polling but can deliver many events at once.	747	overhead for the actual polling but can deliver many events at once.
671		748
672	By setting a higher I<io collect interval> you allow libev to spend more	749	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,	750	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	752	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.	753	introduce an additional C<ev_sleep ()> call into most loop iterations.
677		754
678	Likewise, by setting a higher I<timeout collect interval> you allow libev	755	Likewise, by setting a higher I<timeout collect interval> you allow libev
679	to spend more time collecting timeouts, at the expense of increased	756	to spend more time collecting timeouts, at the expense of increased
680	latency (the watcher callback will be called later). C<ev_io> watchers	757	latency/jitter/inexactness (the watcher callback will be called
681	will not be affected. Setting this to a non-null value will not introduce	758	later). C<ev_io> watchers will not be affected. Setting this to a non-null
682	any overhead in libev.	759	value will not introduce any overhead in libev.
683		760
684	Many (busy) programs can usually benefit by setting the io collect	761	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	762	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	763	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>,	764	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.	765	as this approaches the timing granularity of most systems.
		766
		767	Setting the I<timeout collect interval> can improve the opportunity for
		768	saving power, as the program will "bundle" timer callback invocations that
		769	are "near" in time together, by delaying some, thus reducing the number of
		770	times the process sleeps and wakes up again. Another useful technique to
		771	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		772	they fire on, say, one-second boundaries only.
		773
		774	=item ev_loop_verify (loop)
		775
		776	This function only does something when C<EV_VERIFY> support has been
		777	compiled in, which is the default for non-minimal builds. It tries to go
		778	through all internal structures and checks them for validity. If anything
		779	is found to be inconsistent, it will print an error message to standard
		780	error and call C<abort ()>.
		781
		782	This can be used to catch bugs inside libev itself: under normal
		783	circumstances, this function will never abort as of course libev keeps its
		784	data structures consistent.
689		785
690	=back	786	=back
691		787
692		788
693	=head1 ANATOMY OF A WATCHER	789	=head1 ANATOMY OF A WATCHER
		790
		791	In the following description, uppercase C<TYPE> in names stands for the
		792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		793	watchers and C<ev_io_start> for I/O watchers.
694		794
695	A watcher is a structure that you create and register to record your	795	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	796	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:	797	become readable, you would create an C<ev_io> watcher for that:
698		798
699	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	799	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
700	{	800	{
701	ev_io_stop (w);	801	ev_io_stop (w);
702	ev_unloop (loop, EVUNLOOP_ALL);	802	ev_unloop (loop, EVUNLOOP_ALL);
703	}	803	}
704		804
705	struct ev_loop *loop = ev_default_loop (0);	805	struct ev_loop *loop = ev_default_loop (0);
		806
706	struct ev_io stdin_watcher;	807	ev_io stdin_watcher;
		808
707	ev_init (&stdin_watcher, my_cb);	809	ev_init (&stdin_watcher, my_cb);
708	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
709	ev_io_start (loop, &stdin_watcher);	811	ev_io_start (loop, &stdin_watcher);
		812
710	ev_loop (loop, 0);	813	ev_loop (loop, 0);
711		814
712	As you can see, you are responsible for allocating the memory for your	815	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,	816	watcher structures (and it is I<usually> a bad idea to do this on the
714	although this can sometimes be quite valid).	817	stack).
		818
		819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
715		821
716	Each watcher structure must be initialised by a call to C<ev_init	822	Each watcher structure must be initialised by a call to C<ev_init
717	(watcher *, callback)>, which expects a callback to be provided. This	823	(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	824	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	825	watchers, each time the event loop detects that the file descriptor given
720	is readable and/or writable).	826	is readable and/or writable).
721		827
722	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	828	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	829	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	830	is also a macro to combine initialisation and setting in one call: C<<
725	(watcher *, callback, ...) >>.	831	ev_TYPE_init (watcher *, callback, ...) >>.
726		832
727	To make the watcher actually watch out for events, you have to start it	833	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	834	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	835	*) >>), and you can stop watching for events at any time by calling the
730	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	836	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
731		837
732	As long as your watcher is active (has been started but not stopped) you	838	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	839	must not touch the values stored in it. Most specifically you must never
734	reinitialise it or call its C<set> macro.	840	reinitialise it or call its C<ev_TYPE_set> macro.
735		841
736	Each and every callback receives the event loop pointer as first, the	842	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	843	registered watcher structure as second, and a bitset of received events as
738	third argument.	844	third argument.
739		845
…		…
799		905
800	The given async watcher has been asynchronously notified (see C<ev_async>).	906	The given async watcher has been asynchronously notified (see C<ev_async>).
801		907
802	=item C<EV_ERROR>	908	=item C<EV_ERROR>
803		909
804	An unspecified error has occured, the watcher has been stopped. This might	910	An unspecified error has occurred, the watcher has been stopped. This might
805	happen because the watcher could not be properly started because libev	911	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	912	ran out of memory, a file descriptor was found to be closed or any other
		913	problem. Libev considers these application bugs.
		914
807	problem. You best act on it by reporting the problem and somehow coping	915	You best act on it by reporting the problem and somehow coping with the
808	with the watcher being stopped.	916	watcher being stopped. Note that well-written programs should not receive
		917	an error ever, so when your watcher receives it, this usually indicates a
		918	bug in your program.
809		919
810	Libev will usually signal a few "dummy" events together with an error,	920	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	921	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	922	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	923	the error from read() or write(). This will not work in multi-threaded
814	programs, though, so beware.	924	programs, though, as the fd could already be closed and reused for another
		925	thing, so beware.
815		926
816	=back	927	=back
817		928
818	=head2 GENERIC WATCHER FUNCTIONS	929	=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		930
823	=over 4	931	=over 4
824		932
825	=item C<ev_init> (ev_TYPE *watcher, callback)	933	=item C<ev_init> (ev_TYPE *watcher, callback)
826		934
…		…
832	which rolls both calls into one.	940	which rolls both calls into one.
833		941
834	You can reinitialise a watcher at any time as long as it has been stopped	942	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.	943	(or never started) and there are no pending events outstanding.
836		944
837	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	945	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
838	int revents)>.	946	int revents)>.
		947
		948	Example: Initialise an C<ev_io> watcher in two steps.
		949
		950	ev_io w;
		951	ev_init (&w, my_cb);
		952	ev_io_set (&w, STDIN_FILENO, EV_READ);
839		953
840	=item C<ev_TYPE_set> (ev_TYPE *, [args])	954	=item C<ev_TYPE_set> (ev_TYPE *, [args])
841		955
842	This macro initialises the type-specific parts of a watcher. You need to	956	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	957	call C<ev_init> at least once before you call this macro, but you can
…		…
846	difference to the C<ev_init> macro).	960	difference to the C<ev_init> macro).
847		961
848	Although some watcher types do not have type-specific arguments	962	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.	963	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
850		964
		965	See C<ev_init>, above, for an example.
		966
851	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	967	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
852		968
853	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	969	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	970	calls into a single call. This is the most convenient method to initialise
855	a watcher. The same limitations apply, of course.	971	a watcher. The same limitations apply, of course.
		972
		973	Example: Initialise and set an C<ev_io> watcher in one step.
		974
		975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
856		976
857	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
858		978
859	Starts (activates) the given watcher. Only active watchers will receive	979	Starts (activates) the given watcher. Only active watchers will receive
860	events. If the watcher is already active nothing will happen.	980	events. If the watcher is already active nothing will happen.
861		981
		982	Example: Start the C<ev_io> watcher that is being abused as example in this
		983	whole section.
		984
		985	ev_io_start (EV_DEFAULT_UC, &w);
		986
862	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
863		988
864	Stops the given watcher again (if active) and clears the pending	989	Stops the given watcher if active, and clears the pending status (whether
		990	the watcher was active or not).
		991
865	status. It is possible that stopped watchers are pending (for example,	992	It is possible that stopped watchers are pending - for example,
866	non-repeating timers are being stopped when they become pending), but	993	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	994	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	995	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.	996	therefore a good idea to always call its C<ev_TYPE_stop> function.
870		997
871	=item bool ev_is_active (ev_TYPE *watcher)	998	=item bool ev_is_active (ev_TYPE *watcher)
872		999
873	Returns a true value iff the watcher is active (i.e. it has been started	1000	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	1001	and not yet been stopped). As long as a watcher is active you must not modify
…		…
922		1049
923	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
924		1051
925	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1052	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	1053	C<loop> nor C<revents> need to be valid as long as the watcher callback
927	can deal with that fact.	1054	can deal with that fact, as both are simply passed through to the
		1055	callback.
928		1056
929	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1057	=item int ev_clear_pending (loop, ev_TYPE *watcher)
930		1058
931	If the watcher is pending, this function returns clears its pending status	1059	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	1060	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>.	1061	watcher isn't pending it does nothing and returns C<0>.
934		1062
		1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1064	callback to be invoked, which can be accomplished with this function.
		1065
935	=back	1066	=back
936		1067
937		1068
938	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
939		1070
940	Each watcher has, by default, a member C<void *data> that you can change	1071	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	1072	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	1073	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	1074	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	1075	member, you can also "subclass" the watcher type and provide your own
945	data:	1076	data:
946		1077
947	struct my_io	1078	struct my_io
948	{	1079	{
949	struct ev_io io;	1080	ev_io io;
950	int otherfd;	1081	int otherfd;
951	void *somedata;	1082	void *somedata;
952	struct whatever *mostinteresting;	1083	struct whatever *mostinteresting;
953	}	1084	};
		1085
		1086	...
		1087	struct my_io w;
		1088	ev_io_init (&w.io, my_cb, fd, EV_READ);
954		1089
955	And since your callback will be called with a pointer to the watcher, you	1090	And since your callback will be called with a pointer to the watcher, you
956	can cast it back to your own type:	1091	can cast it back to your own type:
957		1092
958	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1093	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
959	{	1094	{
960	struct my_io *w = (struct my_io *)w_;	1095	struct my_io *w = (struct my_io *)w_;
961	...	1096	...
962	}	1097	}
963		1098
964	More interesting and less C-conformant ways of casting your callback type	1099	More interesting and less C-conformant ways of casting your callback type
965	instead have been omitted.	1100	instead have been omitted.
966		1101
967	Another common scenario is having some data structure with multiple	1102	Another common scenario is to use some data structure with multiple
968	watchers:	1103	embedded watchers:
969		1104
970	struct my_biggy	1105	struct my_biggy
971	{	1106	{
972	int some_data;	1107	int some_data;
973	ev_timer t1;	1108	ev_timer t1;
974	ev_timer t2;	1109	ev_timer t2;
975	}	1110	}
976		1111
977	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1112	In this case getting the pointer to C<my_biggy> is a bit more
978	you need to use C<offsetof>:	1113	complicated: Either you store the address of your C<my_biggy> struct
		1114	in the C<data> member of the watcher (for woozies), or you need to use
		1115	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1116	programmers):
979		1117
980	#include <stddef.h>	1118	#include <stddef.h>
981		1119
982	static void	1120	static void
983	t1_cb (EV_P_ struct ev_timer *w, int revents)	1121	t1_cb (EV_P_ ev_timer *w, int revents)
984	{	1122	{
985	struct my_biggy big = (struct my_biggy *	1123	struct my_biggy big = (struct my_biggy *
986	(((char *)w) - offsetof (struct my_biggy, t1));	1124	(((char *)w) - offsetof (struct my_biggy, t1));
987	}	1125	}
988		1126
989	static void	1127	static void
990	t2_cb (EV_P_ struct ev_timer *w, int revents)	1128	t2_cb (EV_P_ ev_timer *w, int revents)
991	{	1129	{
992	struct my_biggy big = (struct my_biggy *	1130	struct my_biggy big = (struct my_biggy *
993	(((char *)w) - offsetof (struct my_biggy, t2));	1131	(((char *)w) - offsetof (struct my_biggy, t2));
994	}	1132	}
995		1133
996		1134
997	=head1 WATCHER TYPES	1135	=head1 WATCHER TYPES
998		1136
999	This section describes each watcher in detail, but will not repeat	1137	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	1161	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	1162	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	1163	descriptors to non-blocking mode is also usually a good idea (but not
1026	required if you know what you are doing).	1164	required if you know what you are doing).
1027		1165
1028	If you must do this, then force the use of a known-to-be-good backend	1166	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	1167	known-to-be-good backend (at the time of this writing, this includes only
1030	C<EVBACKEND_POLL>).	1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1031		1169
1032	Another thing you have to watch out for is that it is quite easy to	1170	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	1171	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	1172	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	1173	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	1174	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	1175	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	1176	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.	1177	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1040		1178
1041	If you cannot run the fd in non-blocking mode (for example you should not	1179	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	1180	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	1181	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	1182	interface such as poll (fortunately in our Xlib example, Xlib already
1045	its own, so its quite safe to use).	1183	does this on its own, so its quite safe to use). Some people additionally
		1184	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1185	indefinitely.
		1186
		1187	But really, best use non-blocking mode.
1046		1188
1047	=head3 The special problem of disappearing file descriptors	1189	=head3 The special problem of disappearing file descriptors
1048		1190
1049	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1191	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,	1192	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	1193	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	1194	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	1195	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	1196	registered with libev, there is no efficient way to see that this is, in
1055	fact, a different file descriptor.	1197	fact, a different file descriptor.
1056		1198
…		…
1085	To support fork in your programs, you either have to call	1227	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,	1228	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	1229	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1088	C<EVBACKEND_POLL>.	1230	C<EVBACKEND_POLL>.
1089		1231
		1232	=head3 The special problem of SIGPIPE
		1233
		1234	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1235	when writing to a pipe whose other end has been closed, your program gets
		1236	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1237	this is sensible behaviour, for daemons, this is usually undesirable.
		1238
		1239	So when you encounter spurious, unexplained daemon exits, make sure you
		1240	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1241	somewhere, as that would have given you a big clue).
		1242
1090		1243
1091	=head3 Watcher-Specific Functions	1244	=head3 Watcher-Specific Functions
1092		1245
1093	=over 4	1246	=over 4
1094		1247
1095	=item ev_io_init (ev_io *, callback, int fd, int events)	1248	=item ev_io_init (ev_io *, callback, int fd, int events)
1096		1249
1097	=item ev_io_set (ev_io *, int fd, int events)	1250	=item ev_io_set (ev_io *, int fd, int events)
1098		1251
1099	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1252	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	1253	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.	1254	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1102		1255
1103	=item int fd [read-only]	1256	=item int fd [read-only]
1104		1257
1105	The file descriptor being watched.	1258	The file descriptor being watched.
1106		1259
…		…
1114		1267
1115	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1268	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	1269	readable, but only once. Since it is likely line-buffered, you could
1117	attempt to read a whole line in the callback.	1270	attempt to read a whole line in the callback.
1118		1271
1119	static void	1272	static void
1120	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1273	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1121	{	1274	{
1122	ev_io_stop (loop, w);	1275	ev_io_stop (loop, w);
1123	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1276	.. read from stdin here (or from w->fd) and handle any I/O errors
1124	}	1277	}
1125		1278
1126	...	1279	...
1127	struct ev_loop *loop = ev_default_init (0);	1280	struct ev_loop *loop = ev_default_init (0);
1128	struct ev_io stdin_readable;	1281	ev_io stdin_readable;
1129	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1130	ev_io_start (loop, &stdin_readable);	1283	ev_io_start (loop, &stdin_readable);
1131	ev_loop (loop, 0);	1284	ev_loop (loop, 0);
1132		1285
1133		1286
1134	=head2 C<ev_timer> - relative and optionally repeating timeouts	1287	=head2 C<ev_timer> - relative and optionally repeating timeouts
1135		1288
1136	Timer watchers are simple relative timers that generate an event after a	1289	Timer watchers are simple relative timers that generate an event after a
1137	given time, and optionally repeating in regular intervals after that.	1290	given time, and optionally repeating in regular intervals after that.
1138		1291
1139	The timers are based on real time, that is, if you register an event that	1292	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	1293	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	1294	year, it will still time out after (roughly) one hour. "Roughly" because
1142	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1143	monotonic clock option helps a lot here).	1296	monotonic clock option helps a lot here).
		1297
		1298	The callback is guaranteed to be invoked only I<after> its timeout has
		1299	passed, but if multiple timers become ready during the same loop iteration
		1300	then order of execution is undefined.
		1301
		1302	=head3 Be smart about timeouts
		1303
		1304	Many real-world problems involve some kind of timeout, usually for error
		1305	recovery. A typical example is an HTTP request - if the other side hangs,
		1306	you want to raise some error after a while.
		1307
		1308	What follows are some ways to handle this problem, from obvious and
		1309	inefficient to smart and efficient.
		1310
		1311	In the following, a 60 second activity timeout is assumed - a timeout that
		1312	gets reset to 60 seconds each time there is activity (e.g. each time some
		1313	data or other life sign was received).
		1314
		1315	=over 4
		1316
		1317	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1318
		1319	This is the most obvious, but not the most simple way: In the beginning,
		1320	start the watcher:
		1321
		1322	ev_timer_init (timer, callback, 60., 0.);
		1323	ev_timer_start (loop, timer);
		1324
		1325	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1326	and start it again:
		1327
		1328	ev_timer_stop (loop, timer);
		1329	ev_timer_set (timer, 60., 0.);
		1330	ev_timer_start (loop, timer);
		1331
		1332	This is relatively simple to implement, but means that each time there is
		1333	some activity, libev will first have to remove the timer from its internal
		1334	data structure and then add it again. Libev tries to be fast, but it's
		1335	still not a constant-time operation.
		1336
		1337	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1338
		1339	This is the easiest way, and involves using C<ev_timer_again> instead of
		1340	C<ev_timer_start>.
		1341
		1342	To implement this, configure an C<ev_timer> with a C<repeat> value
		1343	of C<60> and then call C<ev_timer_again> at start and each time you
		1344	successfully read or write some data. If you go into an idle state where
		1345	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1346	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1347
		1348	That means you can ignore both the C<ev_timer_start> function and the
		1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1350	member and C<ev_timer_again>.
		1351
		1352	At start:
		1353
		1354	ev_timer_init (timer, callback);
		1355	timer->repeat = 60.;
		1356	ev_timer_again (loop, timer);
		1357
		1358	Each time there is some activity:
		1359
		1360	ev_timer_again (loop, timer);
		1361
		1362	It is even possible to change the time-out on the fly, regardless of
		1363	whether the watcher is active or not:
		1364
		1365	timer->repeat = 30.;
		1366	ev_timer_again (loop, timer);
		1367
		1368	This is slightly more efficient then stopping/starting the timer each time
		1369	you want to modify its timeout value, as libev does not have to completely
		1370	remove and re-insert the timer from/into its internal data structure.
		1371
		1372	It is, however, even simpler than the "obvious" way to do it.
		1373
		1374	=item 3. Let the timer time out, but then re-arm it as required.
		1375
		1376	This method is more tricky, but usually most efficient: Most timeouts are
		1377	relatively long compared to the intervals between other activity - in
		1378	our example, within 60 seconds, there are usually many I/O events with
		1379	associated activity resets.
		1380
		1381	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1382	but remember the time of last activity, and check for a real timeout only
		1383	within the callback:
		1384
		1385	ev_tstamp last_activity; // time of last activity
		1386
		1387	static void
		1388	callback (EV_P_ ev_timer *w, int revents)
		1389	{
		1390	ev_tstamp now = ev_now (EV_A);
		1391	ev_tstamp timeout = last_activity + 60.;
		1392
		1393	// if last_activity + 60. is older than now, we did time out
		1394	if (timeout < now)
		1395	{
		1396	// timeout occured, take action
		1397	}
		1398	else
		1399	{
		1400	// callback was invoked, but there was some activity, re-arm
		1401	// the watcher to fire in last_activity + 60, which is
		1402	// guaranteed to be in the future, so "again" is positive:
		1403	w->again = timeout - now;
		1404	ev_timer_again (EV_A_ w);
		1405	}
		1406	}
		1407
		1408	To summarise the callback: first calculate the real timeout (defined
		1409	as "60 seconds after the last activity"), then check if that time has
		1410	been reached, which means something I<did>, in fact, time out. Otherwise
		1411	the callback was invoked too early (C<timeout> is in the future), so
		1412	re-schedule the timer to fire at that future time, to see if maybe we have
		1413	a timeout then.
		1414
		1415	Note how C<ev_timer_again> is used, taking advantage of the
		1416	C<ev_timer_again> optimisation when the timer is already running.
		1417
		1418	This scheme causes more callback invocations (about one every 60 seconds
		1419	minus half the average time between activity), but virtually no calls to
		1420	libev to change the timeout.
		1421
		1422	To start the timer, simply initialise the watcher and set C<last_activity>
		1423	to the current time (meaning we just have some activity :), then call the
		1424	callback, which will "do the right thing" and start the timer:
		1425
		1426	ev_timer_init (timer, callback);
		1427	last_activity = ev_now (loop);
		1428	callback (loop, timer, EV_TIMEOUT);
		1429
		1430	And when there is some activity, simply store the current time in
		1431	C<last_activity>, no libev calls at all:
		1432
		1433	last_actiivty = ev_now (loop);
		1434
		1435	This technique is slightly more complex, but in most cases where the
		1436	time-out is unlikely to be triggered, much more efficient.
		1437
		1438	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1439	callback :) - just change the timeout and invoke the callback, which will
		1440	fix things for you.
		1441
		1442	=item 4. Wee, just use a double-linked list for your timeouts.
		1443
		1444	If there is not one request, but many thousands (millions...), all
		1445	employing some kind of timeout with the same timeout value, then one can
		1446	do even better:
		1447
		1448	When starting the timeout, calculate the timeout value and put the timeout
		1449	at the I<end> of the list.
		1450
		1451	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1452	the list is expected to fire (for example, using the technique #3).
		1453
		1454	When there is some activity, remove the timer from the list, recalculate
		1455	the timeout, append it to the end of the list again, and make sure to
		1456	update the C<ev_timer> if it was taken from the beginning of the list.
		1457
		1458	This way, one can manage an unlimited number of timeouts in O(1) time for
		1459	starting, stopping and updating the timers, at the expense of a major
		1460	complication, and having to use a constant timeout. The constant timeout
		1461	ensures that the list stays sorted.
		1462
		1463	=back
		1464
		1465	So which method the best?
		1466
		1467	Method #2 is a simple no-brain-required solution that is adequate in most
		1468	situations. Method #3 requires a bit more thinking, but handles many cases
		1469	better, and isn't very complicated either. In most case, choosing either
		1470	one is fine, with #3 being better in typical situations.
		1471
		1472	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1473	rather complicated, but extremely efficient, something that really pays
		1474	off after the first million or so of active timers, i.e. it's usually
		1475	overkill :)
		1476
		1477	=head3 The special problem of time updates
		1478
		1479	Establishing the current time is a costly operation (it usually takes at
		1480	least two system calls): EV therefore updates its idea of the current
		1481	time only before and after C<ev_loop> collects new events, which causes a
		1482	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1483	lots of events in one iteration.
1144		1484
1145	The relative timeouts are calculated relative to the C<ev_now ()>	1485	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	1486	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	1487	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	1488	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:	1489	timeout on the current time, use something like this to adjust for this:
1150		1490
1151	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1491	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1152		1492
1153	The callback is guarenteed to be invoked only when its timeout has passed,	1493	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	1494	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1155	order of execution is undefined.	1495	()>.
1156		1496
1157	=head3 Watcher-Specific Functions and Data Members	1497	=head3 Watcher-Specific Functions and Data Members
1158		1498
1159	=over 4	1499	=over 4
1160		1500
1161	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1501	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1162		1502
1163	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1503	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1164		1504
1165	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1505	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	1506	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	1507	reached. If it is positive, then the timer will automatically be
1168	later, again, and again, until stopped manually.	1508	configured to trigger again C<repeat> seconds later, again, and again,
		1509	until stopped manually.
1169		1510
1170	The timer itself will do a best-effort at avoiding drift, that is, if you	1511	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	1512	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	1513	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	1514	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.	1515	do stuff) the timer will not fire more than once per event loop iteration.
1175		1516
1176	=item ev_timer_again (loop, ev_timer *)	1517	=item ev_timer_again (loop, ev_timer *)
1177		1518
1178	This will act as if the timer timed out and restart it again if it is	1519	This will act as if the timer timed out and restart it again if it is
1179	repeating. The exact semantics are:	1520	repeating. The exact semantics are:
1180		1521
1181	If the timer is pending, its pending status is cleared.	1522	If the timer is pending, its pending status is cleared.
1182		1523
1183	If the timer is started but nonrepeating, stop it (as if it timed out).	1524	If the timer is started but non-repeating, stop it (as if it timed out).
1184		1525
1185	If the timer is repeating, either start it if necessary (with the	1526	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.	1527	C<repeat> value), or reset the running timer to the C<repeat> value.
1187		1528
1188	This sounds a bit complicated, but here is a useful and typical	1529	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	1530	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		1531
1213	=item ev_tstamp repeat [read-write]	1532	=item ev_tstamp repeat [read-write]
1214		1533
1215	The current C<repeat> value. Will be used each time the watcher times out	1534	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),	1535	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.	1536	which is also when any modifications are taken into account.
1218		1537
1219	=back	1538	=back
1220		1539
1221	=head3 Examples	1540	=head3 Examples
1222		1541
1223	Example: Create a timer that fires after 60 seconds.	1542	Example: Create a timer that fires after 60 seconds.
1224		1543
1225	static void	1544	static void
1226	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1545	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1227	{	1546	{
1228	.. one minute over, w is actually stopped right here	1547	.. one minute over, w is actually stopped right here
1229	}	1548	}
1230		1549
1231	struct ev_timer mytimer;	1550	ev_timer mytimer;
1232	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1551	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1233	ev_timer_start (loop, &mytimer);	1552	ev_timer_start (loop, &mytimer);
1234		1553
1235	Example: Create a timeout timer that times out after 10 seconds of	1554	Example: Create a timeout timer that times out after 10 seconds of
1236	inactivity.	1555	inactivity.
1237		1556
1238	static void	1557	static void
1239	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1558	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1240	{	1559	{
1241	.. ten seconds without any activity	1560	.. ten seconds without any activity
1242	}	1561	}
1243		1562
1244	struct ev_timer mytimer;	1563	ev_timer mytimer;
1245	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1246	ev_timer_again (&mytimer); /* start timer */	1565	ev_timer_again (&mytimer); /* start timer */
1247	ev_loop (loop, 0);	1566	ev_loop (loop, 0);
1248		1567
1249	// and in some piece of code that gets executed on any "activity":	1568	// and in some piece of code that gets executed on any "activity":
1250	// reset the timeout to start ticking again at 10 seconds	1569	// reset the timeout to start ticking again at 10 seconds
1251	ev_timer_again (&mytimer);	1570	ev_timer_again (&mytimer);
1252		1571
1253		1572
1254	=head2 C<ev_periodic> - to cron or not to cron?	1573	=head2 C<ev_periodic> - to cron or not to cron?
1255		1574
1256	Periodic watchers are also timers of a kind, but they are very versatile	1575	Periodic watchers are also timers of a kind, but they are very versatile
1257	(and unfortunately a bit complex).	1576	(and unfortunately a bit complex).
1258		1577
1259	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1578	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	1579	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	1580	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 ()	1581	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	1582	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1583	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	1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1265	roughly 10 seconds later).	1585	roughly 10 seconds later as it uses a relative timeout).
1266		1586
1267	They can also be used to implement vastly more complex timers, such as	1587	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,	1588	such as triggering an event on each "midnight, local time", or other
1269	rules.	1589	complicated rules.
1270		1590
1271	As with timers, the callback is guarenteed to be invoked only when the	1591	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	1592	time (C<at>) has passed, but if multiple periodic timers become ready
1273	during the same loop iteration then order of execution is undefined.	1593	during the same loop iteration, then order of execution is undefined.
1274		1594
1275	=head3 Watcher-Specific Functions and Data Members	1595	=head3 Watcher-Specific Functions and Data Members
1276		1596
1277	=over 4	1597	=over 4
1278		1598
1279	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1280		1600
1281	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1282		1602
1283	Lots of arguments, lets sort it out... There are basically three modes of	1603	Lots of arguments, lets sort it out... There are basically three modes of
1284	operation, and we will explain them from simplest to complex:	1604	operation, and we will explain them from simplest to most complex:
1285		1605
1286	=over 4	1606	=over 4
1287		1607
1288	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1289		1609
1290	In this configuration the watcher triggers an event at the wallclock time	1610	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,	1611	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	1612	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.	1613	only run when the system clock reaches or surpasses this time.
1294		1614
1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1296		1616
1297	In this mode the watcher will always be scheduled to time out at the next	1617	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)	1618	C<at + N * interval> time (for some integer N, which can also be negative)
1299	and then repeat, regardless of any time jumps.	1619	and then repeat, regardless of any time jumps.
1300		1620
1301	This can be used to create timers that do not drift with respect to system	1621	This can be used to create timers that do not drift with respect to the
1302	time:	1622	system clock, for example, here is a C<ev_periodic> that triggers each
		1623	hour, on the hour:
1303		1624
1304	ev_periodic_set (&periodic, 0., 3600., 0);	1625	ev_periodic_set (&periodic, 0., 3600., 0);
1305		1626
1306	This doesn't mean there will always be 3600 seconds in between triggers,	1627	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	1628	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	1629	full hour (UTC), or more correctly, when the system time is evenly divisible
1309	by 3600.	1630	by 3600.
1310		1631
1311	Another way to think about it (for the mathematically inclined) is that	1632	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	1633	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.	1634	time where C<time = at (mod interval)>, regardless of any time jumps.
1314		1635
1315	For numerical stability it is preferable that the C<at> value is near	1636	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	1637	C<ev_now ()> (the current time), but there is no range requirement for
1317	this value.	1638	this value, and in fact is often specified as zero.
		1639
		1640	Note also that there is an upper limit to how often a timer can fire (CPU
		1641	speed for example), so if C<interval> is very small then timing stability
		1642	will of course deteriorate. Libev itself tries to be exact to be about one
		1643	millisecond (if the OS supports it and the machine is fast enough).
1318		1644
1319	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1320		1646
1321	In this mode the values for C<interval> and C<at> are both being	1647	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	1648	ignored. Instead, each time the periodic watcher gets scheduled, the
1323	reschedule callback will be called with the watcher as first, and the	1649	reschedule callback will be called with the watcher as first, and the
1324	current time as second argument.	1650	current time as second argument.
1325		1651
1326	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1652	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,	1653	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		1654
		1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1657	only event loop modification you are allowed to do).
		1658
1331	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1659	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1332	ev_tstamp now)>, e.g.:	1660	*w, ev_tstamp now)>, e.g.:
1333		1661
		1662	static ev_tstamp
1334	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1663	my_rescheduler (ev_periodic *w, ev_tstamp now)
1335	{	1664	{
1336	return now + 60.;	1665	return now + 60.;
1337	}	1666	}
1338		1667
1339	It must return the next time to trigger, based on the passed time value	1668	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	1669	(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	1670	will usually be called just before the callback will be triggered, but
1342	might be called at other times, too.	1671	might be called at other times, too.
1343		1672
1344	NOTE: I<< This callback must always return a time that is later than the	1673	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.	1674	equal to the passed C<now> value >>.
1346		1675
1347	This can be used to create very complex timers, such as a timer that	1676	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	1677	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	1678	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	1679	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).	1680	reason I omitted it as an example).
1352		1681
1353	=back	1682	=back
…		…
1357	Simply stops and restarts the periodic watcher again. This is only useful	1686	Simply stops and restarts the periodic watcher again. This is only useful
1358	when you changed some parameters or the reschedule callback would return	1687	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	1688	a different time than the last time it was called (e.g. in a crond like
1360	program when the crontabs have changed).	1689	program when the crontabs have changed).
1361		1690
		1691	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1692
		1693	When active, returns the absolute time that the watcher is supposed to
		1694	trigger next.
		1695
1362	=item ev_tstamp offset [read-write]	1696	=item ev_tstamp offset [read-write]
1363		1697
1364	When repeating, this contains the offset value, otherwise this is the	1698	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>).	1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1366		1700
…		…
1371		1705
1372	The current interval value. Can be modified any time, but changes only	1706	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	1707	take effect when the periodic timer fires or C<ev_periodic_again> is being
1374	called.	1708	called.
1375		1709
1376	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1710	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1377		1711
1378	The current reschedule callback, or C<0>, if this functionality is	1712	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	1713	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.	1714	the periodic timer fires or C<ev_periodic_again> is being called.
1381		1715
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	1716	=back
1388		1717
1389	=head3 Examples	1718	=head3 Examples
1390		1719
1391	Example: Call a callback every hour, or, more precisely, whenever the	1720	Example: Call a callback every hour, or, more precisely, whenever the
1392	system clock is divisible by 3600. The callback invocation times have	1721	system time is divisible by 3600. The callback invocation times have
1393	potentially a lot of jittering, but good long-term stability.	1722	potentially a lot of jitter, but good long-term stability.
1394		1723
1395	static void	1724	static void
1396	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1725	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1397	{	1726	{
1398	... its now a full hour (UTC, or TAI or whatever your clock follows)	1727	... its now a full hour (UTC, or TAI or whatever your clock follows)
1399	}	1728	}
1400		1729
1401	struct ev_periodic hourly_tick;	1730	ev_periodic hourly_tick;
1402	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1731	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1403	ev_periodic_start (loop, &hourly_tick);	1732	ev_periodic_start (loop, &hourly_tick);
1404		1733
1405	Example: The same as above, but use a reschedule callback to do it:	1734	Example: The same as above, but use a reschedule callback to do it:
1406		1735
1407	#include <math.h>	1736	#include <math.h>
1408		1737
1409	static ev_tstamp	1738	static ev_tstamp
1410	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1739	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1411	{	1740	{
1412	return fmod (now, 3600.) + 3600.;	1741	return now + (3600. - fmod (now, 3600.));
1413	}	1742	}
1414		1743
1415	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1744	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1416		1745
1417	Example: Call a callback every hour, starting now:	1746	Example: Call a callback every hour, starting now:
1418		1747
1419	struct ev_periodic hourly_tick;	1748	ev_periodic hourly_tick;
1420	ev_periodic_init (&hourly_tick, clock_cb,	1749	ev_periodic_init (&hourly_tick, clock_cb,
1421	fmod (ev_now (loop), 3600.), 3600., 0);	1750	fmod (ev_now (loop), 3600.), 3600., 0);
1422	ev_periodic_start (loop, &hourly_tick);	1751	ev_periodic_start (loop, &hourly_tick);
1423		1752
1424		1753
1425	=head2 C<ev_signal> - signal me when a signal gets signalled!	1754	=head2 C<ev_signal> - signal me when a signal gets signalled!
1426		1755
1427	Signal watchers will trigger an event when the process receives a specific	1756	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	1757	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	1758	will try it's best to deliver signals synchronously, i.e. as part of the
1430	normal event processing, like any other event.	1759	normal event processing, like any other event.
1431		1760
		1761	If you want signals asynchronously, just use C<sigaction> as you would
		1762	do without libev and forget about sharing the signal. You can even use
		1763	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1764
1432	You can configure as many watchers as you like per signal. Only when the	1765	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	1766	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	1767	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	1768	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	1769	the last signal watcher for a signal is stopped, libev will reset the
1437	SIG_DFL (regardless of what it was set to before).	1770	signal handler to SIG_DFL (regardless of what it was set to before).
1438		1771
1439	If possible and supported, libev will install its handlers with	1772	If possible and supported, libev will install its handlers with
1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1441	interrupted. If you have a problem with syscalls getting interrupted by	1774	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	1775	signals you can block all signals in an C<ev_check> watcher and unblock
1443	them in an C<ev_prepare> watcher.	1776	them in an C<ev_prepare> watcher.
1444		1777
1445	=head3 Watcher-Specific Functions and Data Members	1778	=head3 Watcher-Specific Functions and Data Members
1446		1779
…		…
1459		1792
1460	=back	1793	=back
1461		1794
1462	=head3 Examples	1795	=head3 Examples
1463		1796
1464	Example: Try to exit cleanly on SIGINT and SIGTERM.	1797	Example: Try to exit cleanly on SIGINT.
1465		1798
1466	static void	1799	static void
1467	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1800	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1468	{	1801	{
1469	ev_unloop (loop, EVUNLOOP_ALL);	1802	ev_unloop (loop, EVUNLOOP_ALL);
1470	}	1803	}
1471		1804
1472	struct ev_signal signal_watcher;	1805	ev_signal signal_watcher;
1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1474	ev_signal_start (loop, &sigint_cb);	1807	ev_signal_start (loop, &signal_watcher);
1475		1808
1476		1809
1477	=head2 C<ev_child> - watch out for process status changes	1810	=head2 C<ev_child> - watch out for process status changes
1478		1811
1479	Child watchers trigger when your process receives a SIGCHLD in response to	1812	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	1813	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	1814	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	1815	has been forked (which implies it might have already exited), as long
1483	loop isn't entered (or is continued from a watcher).	1816	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1817	forking and then immediately registering a watcher for the child is fine,
		1818	but forking and registering a watcher a few event loop iterations later is
		1819	not.
1484		1820
1485	Only the default event loop is capable of handling signals, and therefore	1821	Only the default event loop is capable of handling signals, and therefore
1486	you can only rgeister child watchers in the default event loop.	1822	you can only register child watchers in the default event loop.
1487		1823
1488	=head3 Process Interaction	1824	=head3 Process Interaction
1489		1825
1490	Libev grabs C<SIGCHLD> as soon as the default event loop is	1826	Libev grabs C<SIGCHLD> as soon as the default event loop is
1491	initialised. This is necessary to guarantee proper behaviour even if	1827	initialised. This is necessary to guarantee proper behaviour even if
1492	the first child watcher is started after the child exits. The occurance	1828	the first child watcher is started after the child exits. The occurrence
1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1829	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1494	synchronously as part of the event loop processing. Libev always reaps all	1830	synchronously as part of the event loop processing. Libev always reaps all
1495	children, even ones not watched.	1831	children, even ones not watched.
1496		1832
1497	=head3 Overriding the Built-In Processing	1833	=head3 Overriding the Built-In Processing
…		…
1501	handler, you can override it easily by installing your own handler for	1837	handler, you can override it easily by installing your own handler for
1502	C<SIGCHLD> after initialising the default loop, and making sure the	1838	C<SIGCHLD> after initialising the default loop, and making sure the
1503	default loop never gets destroyed. You are encouraged, however, to use an	1839	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	1840	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.	1841	that, so other libev users can use C<ev_child> watchers freely.
		1842
		1843	=head3 Stopping the Child Watcher
		1844
		1845	Currently, the child watcher never gets stopped, even when the
		1846	child terminates, so normally one needs to stop the watcher in the
		1847	callback. Future versions of libev might stop the watcher automatically
		1848	when a child exit is detected.
1506		1849
1507	=head3 Watcher-Specific Functions and Data Members	1850	=head3 Watcher-Specific Functions and Data Members
1508		1851
1509	=over 4	1852	=over 4
1510		1853
…		…
1539	=head3 Examples	1882	=head3 Examples
1540		1883
1541	Example: C<fork()> a new process and install a child handler to wait for	1884	Example: C<fork()> a new process and install a child handler to wait for
1542	its completion.	1885	its completion.
1543		1886
1544	ev_child cw;	1887	ev_child cw;
1545		1888
1546	static void	1889	static void
1547	child_cb (EV_P_ struct ev_child *w, int revents)	1890	child_cb (EV_P_ ev_child *w, int revents)
1548	{	1891	{
1549	ev_child_stop (EV_A_ w);	1892	ev_child_stop (EV_A_ w);
1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1893	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1551	}	1894	}
1552		1895
1553	pid_t pid = fork ();	1896	pid_t pid = fork ();
1554		1897
1555	if (pid < 0)	1898	if (pid < 0)
1556	// error	1899	// error
1557	else if (pid == 0)	1900	else if (pid == 0)
1558	{	1901	{
1559	// the forked child executes here	1902	// the forked child executes here
1560	exit (1);	1903	exit (1);
1561	}	1904	}
1562	else	1905	else
1563	{	1906	{
1564	ev_child_init (&cw, child_cb, pid, 0);	1907	ev_child_init (&cw, child_cb, pid, 0);
1565	ev_child_start (EV_DEFAULT_ &cw);	1908	ev_child_start (EV_DEFAULT_ &cw);
1566	}	1909	}
1567		1910
1568		1911
1569	=head2 C<ev_stat> - did the file attributes just change?	1912	=head2 C<ev_stat> - did the file attributes just change?
1570		1913
1571	This watches a filesystem path for attribute changes. That is, it calls	1914	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	1915	C<stat> regularly (or when the OS says it changed) and sees if it changed
1573	compared to the last time, invoking the callback if it did.	1916	compared to the last time, invoking the callback if it did.
1574		1917
1575	The path does not need to exist: changing from "path exists" to "path does	1918	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	1919	not exist" is a status change like any other. The condition "path does
…		…
1579	the stat buffer having unspecified contents.	1922	the stat buffer having unspecified contents.
1580		1923
1581	The path I<should> be absolute and I<must not> end in a slash. If it is	1924	The path I<should> be absolute and I<must not> end in a slash. If it is
1582	relative and your working directory changes, the behaviour is undefined.	1925	relative and your working directory changes, the behaviour is undefined.
1583		1926
1584	Since there is no standard to do this, the portable implementation simply	1927	Since there is no standard kernel interface to do this, the portable
1585	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1928	implementation simply calls C<stat (2)> regularly on the path to see if
1586	can specify a recommended polling interval for this case. If you specify	1929	it changed somehow. You can specify a recommended polling interval for
1587	a polling interval of C<0> (highly recommended!) then a I<suitable,	1930	this case. If you specify a polling interval of C<0> (highly recommended!)
1588	unspecified default> value will be used (which you can expect to be around	1931	then a I<suitable, unspecified default> value will be used (which
1589	five seconds, although this might change dynamically). Libev will also	1932	you can expect to be around five seconds, although this might change
1590	impose a minimum interval which is currently around C<0.1>, but thats	1933	dynamically). Libev will also impose a minimum interval which is currently
1591	usually overkill.	1934	around C<0.1>, but thats usually overkill.
1592		1935
1593	This watcher type is not meant for massive numbers of stat watchers,	1936	This watcher type is not meant for massive numbers of stat watchers,
1594	as even with OS-supported change notifications, this can be	1937	as even with OS-supported change notifications, this can be
1595	resource-intensive.	1938	resource-intensive.
1596		1939
1597	At the time of this writing, only the Linux inotify interface is	1940	At the time of this writing, the only OS-specific interface implemented
1598	implemented (implementing kqueue support is left as an exercise for the	1941	is the Linux inotify interface (implementing kqueue support is left as
1599	reader). Inotify will be used to give hints only and should not change the	1942	an exercise for the reader. Note, however, that the author sees no way
1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1943	of implementing C<ev_stat> semantics with kqueue).
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		1944
1605	=head3 Inotify	1945	=head3 ABI Issues (Largefile Support)
1606		1946
		1947	Libev by default (unless the user overrides this) uses the default
		1948	compilation environment, which means that on systems with large file
		1949	support disabled by default, you get the 32 bit version of the stat
		1950	structure. When using the library from programs that change the ABI to
		1951	use 64 bit file offsets the programs will fail. In that case you have to
		1952	compile libev with the same flags to get binary compatibility. This is
		1953	obviously the case with any flags that change the ABI, but the problem is
		1954	most noticeably disabled with ev_stat and large file support.
		1955
		1956	The solution for this is to lobby your distribution maker to make large
		1957	file interfaces available by default (as e.g. FreeBSD does) and not
		1958	optional. Libev cannot simply switch on large file support because it has
		1959	to exchange stat structures with application programs compiled using the
		1960	default compilation environment.
		1961
		1962	=head3 Inotify and Kqueue
		1963
1607	When C<inotify (7)> support has been compiled into libev (generally only	1964	When C<inotify (7)> support has been compiled into libev (generally
		1965	only available with Linux 2.6.25 or above due to bugs in earlier
1608	available on Linux) and present at runtime, it will be used to speed up	1966	implementations) and present at runtime, it will be used to speed up
1609	change detection where possible. The inotify descriptor will be created lazily	1967	change detection where possible. The inotify descriptor will be created
1610	when the first C<ev_stat> watcher is being started.	1968	lazily when the first C<ev_stat> watcher is being started.
1611		1969
1612	Inotify presense does not change the semantics of C<ev_stat> watchers	1970	Inotify presence does not change the semantics of C<ev_stat> watchers
1613	except that changes might be detected earlier, and in some cases, to avoid	1971	except that changes might be detected earlier, and in some cases, to avoid
1614	making regular C<stat> calls. Even in the presense of inotify support	1972	making regular C<stat> calls. Even in the presence of inotify support
1615	there are many cases where libev has to resort to regular C<stat> polling.	1973	there are many cases where libev has to resort to regular C<stat> polling,
		1974	but as long as the path exists, libev usually gets away without polling.
1616		1975
1617	(There is no support for kqueue, as apparently it cannot be used to	1976	There is no support for kqueue, as apparently it cannot be used to
1618	implement this functionality, due to the requirement of having a file	1977	implement this functionality, due to the requirement of having a file
1619	descriptor open on the object at all times).	1978	descriptor open on the object at all times, and detecting renames, unlinks
		1979	etc. is difficult.
1620		1980
1621	=head3 The special problem of stat time resolution	1981	=head3 The special problem of stat time resolution
1622		1982
1623	The C<stat ()> syscall only supports full-second resolution portably, and	1983	The C<stat ()> system call only supports full-second resolution portably, and
1624	even on systems where the resolution is higher, many filesystems still	1984	even on systems where the resolution is higher, most file systems still
1625	only support whole seconds.	1985	only support whole seconds.
1626		1986
1627	That means that, if the time is the only thing that changes, you might	1987	That means that, if the time is the only thing that changes, you can
1628	miss updates: on the first update, C<ev_stat> detects a change and calls	1988	easily miss updates: on the first update, C<ev_stat> detects a change and
1629	your callback, which does something. When there is another update within	1989	calls your callback, which does something. When there is another update
1630	the same second, C<ev_stat> will be unable to detect it.	1990	within the same second, C<ev_stat> will be unable to detect unless the
		1991	stat data does change in other ways (e.g. file size).
1631		1992
1632	The solution to this is to delay acting on a change for a second (or till	1993	The solution to this is to delay acting on a change for slightly more
1633	the next second boundary), using a roughly one-second delay C<ev_timer>	1994	than a second (or till slightly after the next full second boundary), using
1634	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1995	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1635	is added to work around small timing inconsistencies of some operating	1996	ev_timer_again (loop, w)>).
1636	systems.	1997
		1998	The C<.02> offset is added to work around small timing inconsistencies
		1999	of some operating systems (where the second counter of the current time
		2000	might be be delayed. One such system is the Linux kernel, where a call to
		2001	C<gettimeofday> might return a timestamp with a full second later than
		2002	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2003	update file times then there will be a small window where the kernel uses
		2004	the previous second to update file times but libev might already execute
		2005	the timer callback).
1637		2006
1638	=head3 Watcher-Specific Functions and Data Members	2007	=head3 Watcher-Specific Functions and Data Members
1639		2008
1640	=over 4	2009	=over 4
1641		2010
…		…
1647	C<path>. The C<interval> is a hint on how quickly a change is expected to	2016	C<path>. The C<interval> is a hint on how quickly a change is expected to
1648	be detected and should normally be specified as C<0> to let libev choose	2017	be detected and should normally be specified as C<0> to let libev choose
1649	a suitable value. The memory pointed to by C<path> must point to the same	2018	a suitable value. The memory pointed to by C<path> must point to the same
1650	path for as long as the watcher is active.	2019	path for as long as the watcher is active.
1651		2020
1652	The callback will be receive C<EV_STAT> when a change was detected,	2021	The callback will receive an C<EV_STAT> event when a change was detected,
1653	relative to the attributes at the time the watcher was started (or the	2022	relative to the attributes at the time the watcher was started (or the
1654	last change was detected).	2023	last change was detected).
1655		2024
1656	=item ev_stat_stat (loop, ev_stat *)	2025	=item ev_stat_stat (loop, ev_stat *)
1657		2026
1658	Updates the stat buffer immediately with new values. If you change the	2027	Updates the stat buffer immediately with new values. If you change the
1659	watched path in your callback, you could call this fucntion to avoid	2028	watched path in your callback, you could call this function to avoid
1660	detecting this change (while introducing a race condition). Can also be	2029	detecting this change (while introducing a race condition if you are not
1661	useful simply to find out the new values.	2030	the only one changing the path). Can also be useful simply to find out the
		2031	new values.
1662		2032
1663	=item ev_statdata attr [read-only]	2033	=item ev_statdata attr [read-only]
1664		2034
1665	The most-recently detected attributes of the file. Although the type is of	2035	The most-recently detected attributes of the file. Although the type is
1666	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2036	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1667	suitable for your system. If the C<st_nlink> member is C<0>, then there	2037	suitable for your system, but you can only rely on the POSIX-standardised
		2038	members to be present. If the C<st_nlink> member is C<0>, then there was
1668	was some error while C<stat>ing the file.	2039	some error while C<stat>ing the file.
1669		2040
1670	=item ev_statdata prev [read-only]	2041	=item ev_statdata prev [read-only]
1671		2042
1672	The previous attributes of the file. The callback gets invoked whenever	2043	The previous attributes of the file. The callback gets invoked whenever
1673	C<prev> != C<attr>.	2044	C<prev> != C<attr>, or, more precisely, one or more of these members
		2045	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2046	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1674		2047
1675	=item ev_tstamp interval [read-only]	2048	=item ev_tstamp interval [read-only]
1676		2049
1677	The specified interval.	2050	The specified interval.
1678		2051
1679	=item const char *path [read-only]	2052	=item const char *path [read-only]
1680		2053
1681	The filesystem path that is being watched.	2054	The file system path that is being watched.
1682		2055
1683	=back	2056	=back
1684		2057
1685	=head3 Examples	2058	=head3 Examples
1686		2059
1687	Example: Watch C</etc/passwd> for attribute changes.	2060	Example: Watch C</etc/passwd> for attribute changes.
1688		2061
1689	static void	2062	static void
1690	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2063	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1691	{	2064	{
1692	/* /etc/passwd changed in some way */	2065	/* /etc/passwd changed in some way */
1693	if (w->attr.st_nlink)	2066	if (w->attr.st_nlink)
1694	{	2067	{
1695	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2068	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1696	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2069	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1697	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2070	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1698	}	2071	}
1699	else	2072	else
1700	/* you shalt not abuse printf for puts */	2073	/* you shalt not abuse printf for puts */
1701	puts ("wow, /etc/passwd is not there, expect problems. "	2074	puts ("wow, /etc/passwd is not there, expect problems. "
1702	"if this is windows, they already arrived\n");	2075	"if this is windows, they already arrived\n");
1703	}	2076	}
1704		2077
1705	...	2078	...
1706	ev_stat passwd;	2079	ev_stat passwd;
1707		2080
1708	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2081	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1709	ev_stat_start (loop, &passwd);	2082	ev_stat_start (loop, &passwd);
1710		2083
1711	Example: Like above, but additionally use a one-second delay so we do not	2084	Example: Like above, but additionally use a one-second delay so we do not
1712	miss updates (however, frequent updates will delay processing, too, so	2085	miss updates (however, frequent updates will delay processing, too, so
1713	one might do the work both on C<ev_stat> callback invocation I<and> on	2086	one might do the work both on C<ev_stat> callback invocation I<and> on
1714	C<ev_timer> callback invocation).	2087	C<ev_timer> callback invocation).
1715		2088
1716	static ev_stat passwd;	2089	static ev_stat passwd;
1717	static ev_timer timer;	2090	static ev_timer timer;
1718		2091
1719	static void	2092	static void
1720	timer_cb (EV_P_ ev_timer *w, int revents)	2093	timer_cb (EV_P_ ev_timer *w, int revents)
1721	{	2094	{
1722	ev_timer_stop (EV_A_ w);	2095	ev_timer_stop (EV_A_ w);
1723		2096
1724	/* now it's one second after the most recent passwd change */	2097	/* now it's one second after the most recent passwd change */
1725	}	2098	}
1726		2099
1727	static void	2100	static void
1728	stat_cb (EV_P_ ev_stat *w, int revents)	2101	stat_cb (EV_P_ ev_stat *w, int revents)
1729	{	2102	{
1730	/* reset the one-second timer */	2103	/* reset the one-second timer */
1731	ev_timer_again (EV_A_ &timer);	2104	ev_timer_again (EV_A_ &timer);
1732	}	2105	}
1733		2106
1734	...	2107	...
1735	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2108	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1736	ev_stat_start (loop, &passwd);	2109	ev_stat_start (loop, &passwd);
1737	ev_timer_init (&timer, timer_cb, 0., 1.01);	2110	ev_timer_init (&timer, timer_cb, 0., 1.02);
1738		2111
1739		2112
1740	=head2 C<ev_idle> - when you've got nothing better to do...	2113	=head2 C<ev_idle> - when you've got nothing better to do...
1741		2114
1742	Idle watchers trigger events when no other events of the same or higher	2115	Idle watchers trigger events when no other events of the same or higher
1743	priority are pending (prepare, check and other idle watchers do not	2116	priority are pending (prepare, check and other idle watchers do not count
1744	count).	2117	as receiving "events").
1745		2118
1746	That is, as long as your process is busy handling sockets or timeouts	2119	That is, as long as your process is busy handling sockets or timeouts
1747	(or even signals, imagine) of the same or higher priority it will not be	2120	(or even signals, imagine) of the same or higher priority it will not be
1748	triggered. But when your process is idle (or only lower-priority watchers	2121	triggered. But when your process is idle (or only lower-priority watchers
1749	are pending), the idle watchers are being called once per event loop	2122	are pending), the idle watchers are being called once per event loop
…		…
1773	=head3 Examples	2146	=head3 Examples
1774		2147
1775	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2148	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1776	callback, free it. Also, use no error checking, as usual.	2149	callback, free it. Also, use no error checking, as usual.
1777		2150
1778	static void	2151	static void
1779	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2152	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1780	{	2153	{
1781	free (w);	2154	free (w);
1782	// now do something you wanted to do when the program has	2155	// now do something you wanted to do when the program has
1783	// no longer anything immediate to do.	2156	// no longer anything immediate to do.
1784	}	2157	}
1785		2158
1786	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1787	ev_idle_init (idle_watcher, idle_cb);	2160	ev_idle_init (idle_watcher, idle_cb);
1788	ev_idle_start (loop, idle_cb);	2161	ev_idle_start (loop, idle_cb);
1789		2162
1790		2163
1791	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1792		2165
1793	Prepare and check watchers are usually (but not always) used in tandem:	2166	Prepare and check watchers are usually (but not always) used in pairs:
1794	prepare watchers get invoked before the process blocks and check watchers	2167	prepare watchers get invoked before the process blocks and check watchers
1795	afterwards.	2168	afterwards.
1796		2169
1797	You I<must not> call C<ev_loop> or similar functions that enter	2170	You I<must not> call C<ev_loop> or similar functions that enter
1798	the current event loop from either C<ev_prepare> or C<ev_check>	2171	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1801	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2174	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1802	C<ev_check> so if you have one watcher of each kind they will always be	2175	C<ev_check> so if you have one watcher of each kind they will always be
1803	called in pairs bracketing the blocking call.	2176	called in pairs bracketing the blocking call.
1804		2177
1805	Their main purpose is to integrate other event mechanisms into libev and	2178	Their main purpose is to integrate other event mechanisms into libev and
1806	their use is somewhat advanced. This could be used, for example, to track	2179	their use is somewhat advanced. They could be used, for example, to track
1807	variable changes, implement your own watchers, integrate net-snmp or a	2180	variable changes, implement your own watchers, integrate net-snmp or a
1808	coroutine library and lots more. They are also occasionally useful if	2181	coroutine library and lots more. They are also occasionally useful if
1809	you cache some data and want to flush it before blocking (for example,	2182	you cache some data and want to flush it before blocking (for example,
1810	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2183	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1811	watcher).	2184	watcher).
1812		2185
1813	This is done by examining in each prepare call which file descriptors need	2186	This is done by examining in each prepare call which file descriptors
1814	to be watched by the other library, registering C<ev_io> watchers for	2187	need to be watched by the other library, registering C<ev_io> watchers
1815	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2188	for them and starting an C<ev_timer> watcher for any timeouts (many
1816	provide just this functionality). Then, in the check watcher you check for	2189	libraries provide exactly this functionality). Then, in the check watcher,
1817	any events that occured (by checking the pending status of all watchers	2190	you check for any events that occurred (by checking the pending status
1818	and stopping them) and call back into the library. The I/O and timer	2191	of all watchers and stopping them) and call back into the library. The
1819	callbacks will never actually be called (but must be valid nevertheless,	2192	I/O and timer callbacks will never actually be called (but must be valid
1820	because you never know, you know?).	2193	nevertheless, because you never know, you know?).
1821		2194
1822	As another example, the Perl Coro module uses these hooks to integrate	2195	As another example, the Perl Coro module uses these hooks to integrate
1823	coroutines into libev programs, by yielding to other active coroutines	2196	coroutines into libev programs, by yielding to other active coroutines
1824	during each prepare and only letting the process block if no coroutines	2197	during each prepare and only letting the process block if no coroutines
1825	are ready to run (it's actually more complicated: it only runs coroutines	2198	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1828	loop from blocking if lower-priority coroutines are active, thus mapping	2201	loop from blocking if lower-priority coroutines are active, thus mapping
1829	low-priority coroutines to idle/background tasks).	2202	low-priority coroutines to idle/background tasks).
1830		2203
1831	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2204	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1832	priority, to ensure that they are being run before any other watchers	2205	priority, to ensure that they are being run before any other watchers
		2206	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2207
1833	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2208	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1834	too) should not activate ("feed") events into libev. While libev fully	2209	activate ("feed") events into libev. While libev fully supports this, they
1835	supports this, they will be called before other C<ev_check> watchers	2210	might get executed before other C<ev_check> watchers did their job. As
1836	did their job. As C<ev_check> watchers are often used to embed other	2211	C<ev_check> watchers are often used to embed other (non-libev) event
1837	(non-libev) event loops those other event loops might be in an unusable	2212	loops those other event loops might be in an unusable state until their
1838	state until their C<ev_check> watcher ran (always remind yourself to	2213	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1839	coexist peacefully with others).	2214	others).
1840		2215
1841	=head3 Watcher-Specific Functions and Data Members	2216	=head3 Watcher-Specific Functions and Data Members
1842		2217
1843	=over 4	2218	=over 4
1844		2219
…		…
1846		2221
1847	=item ev_check_init (ev_check *, callback)	2222	=item ev_check_init (ev_check *, callback)
1848		2223
1849	Initialises and configures the prepare or check watcher - they have no	2224	Initialises and configures the prepare or check watcher - they have no
1850	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2225	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1851	macros, but using them is utterly, utterly and completely pointless.	2226	macros, but using them is utterly, utterly, utterly and completely
		2227	pointless.
1852		2228
1853	=back	2229	=back
1854		2230
1855	=head3 Examples	2231	=head3 Examples
1856		2232
1857	There are a number of principal ways to embed other event loops or modules	2233	There are a number of principal ways to embed other event loops or modules
1858	into libev. Here are some ideas on how to include libadns into libev	2234	into libev. Here are some ideas on how to include libadns into libev
1859	(there is a Perl module named C<EV::ADNS> that does this, which you could	2235	(there is a Perl module named C<EV::ADNS> that does this, which you could
1860	use for an actually working example. Another Perl module named C<EV::Glib>	2236	use as a working example. Another Perl module named C<EV::Glib> embeds a
1861	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2237	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1862	into the Glib event loop).	2238	Glib event loop).
1863		2239
1864	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2240	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1865	and in a check watcher, destroy them and call into libadns. What follows	2241	and in a check watcher, destroy them and call into libadns. What follows
1866	is pseudo-code only of course. This requires you to either use a low	2242	is pseudo-code only of course. This requires you to either use a low
1867	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2243	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1868	the callbacks for the IO/timeout watchers might not have been called yet.	2244	the callbacks for the IO/timeout watchers might not have been called yet.
1869		2245
1870	static ev_io iow [nfd];	2246	static ev_io iow [nfd];
1871	static ev_timer tw;	2247	static ev_timer tw;
1872		2248
1873	static void	2249	static void
1874	io_cb (ev_loop *loop, ev_io *w, int revents)	2250	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1875	{	2251	{
1876	}	2252	}
1877		2253
1878	// create io watchers for each fd and a timer before blocking	2254	// create io watchers for each fd and a timer before blocking
1879	static void	2255	static void
1880	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2256	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1881	{	2257	{
1882	int timeout = 3600000;	2258	int timeout = 3600000;
1883	struct pollfd fds [nfd];	2259	struct pollfd fds [nfd];
1884	// actual code will need to loop here and realloc etc.	2260	// actual code will need to loop here and realloc etc.
1885	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1886		2262
1887	/* the callback is illegal, but won't be called as we stop during check */	2263	/* the callback is illegal, but won't be called as we stop during check */
1888	ev_timer_init (&tw, 0, timeout * 1e-3);	2264	ev_timer_init (&tw, 0, timeout * 1e-3);
1889	ev_timer_start (loop, &tw);	2265	ev_timer_start (loop, &tw);
1890		2266
1891	// create one ev_io per pollfd	2267	// create one ev_io per pollfd
1892	for (int i = 0; i < nfd; ++i)	2268	for (int i = 0; i < nfd; ++i)
1893	{	2269	{
1894	ev_io_init (iow + i, io_cb, fds [i].fd,	2270	ev_io_init (iow + i, io_cb, fds [i].fd,
1895	((fds [i].events & POLLIN ? EV_READ : 0)	2271	((fds [i].events & POLLIN ? EV_READ : 0)
1896	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2272	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1897		2273
1898	fds [i].revents = 0;	2274	fds [i].revents = 0;
1899	ev_io_start (loop, iow + i);	2275	ev_io_start (loop, iow + i);
1900	}	2276	}
1901	}	2277	}
1902		2278
1903	// stop all watchers after blocking	2279	// stop all watchers after blocking
1904	static void	2280	static void
1905	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2281	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1906	{	2282	{
1907	ev_timer_stop (loop, &tw);	2283	ev_timer_stop (loop, &tw);
1908		2284
1909	for (int i = 0; i < nfd; ++i)	2285	for (int i = 0; i < nfd; ++i)
1910	{	2286	{
1911	// set the relevant poll flags	2287	// set the relevant poll flags
1912	// could also call adns_processreadable etc. here	2288	// could also call adns_processreadable etc. here
1913	struct pollfd *fd = fds + i;	2289	struct pollfd *fd = fds + i;
1914	int revents = ev_clear_pending (iow + i);	2290	int revents = ev_clear_pending (iow + i);
1915	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2291	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1916	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2292	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1917		2293
1918	// now stop the watcher	2294	// now stop the watcher
1919	ev_io_stop (loop, iow + i);	2295	ev_io_stop (loop, iow + i);
1920	}	2296	}
1921		2297
1922	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2298	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1923	}	2299	}
1924		2300
1925	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2301	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1926	in the prepare watcher and would dispose of the check watcher.	2302	in the prepare watcher and would dispose of the check watcher.
1927		2303
1928	Method 3: If the module to be embedded supports explicit event	2304	Method 3: If the module to be embedded supports explicit event
1929	notification (adns does), you can also make use of the actual watcher	2305	notification (libadns does), you can also make use of the actual watcher
1930	callbacks, and only destroy/create the watchers in the prepare watcher.	2306	callbacks, and only destroy/create the watchers in the prepare watcher.
1931		2307
1932	static void	2308	static void
1933	timer_cb (EV_P_ ev_timer *w, int revents)	2309	timer_cb (EV_P_ ev_timer *w, int revents)
1934	{	2310	{
1935	adns_state ads = (adns_state)w->data;	2311	adns_state ads = (adns_state)w->data;
1936	update_now (EV_A);	2312	update_now (EV_A);
1937		2313
1938	adns_processtimeouts (ads, &tv_now);	2314	adns_processtimeouts (ads, &tv_now);
1939	}	2315	}
1940		2316
1941	static void	2317	static void
1942	io_cb (EV_P_ ev_io *w, int revents)	2318	io_cb (EV_P_ ev_io *w, int revents)
1943	{	2319	{
1944	adns_state ads = (adns_state)w->data;	2320	adns_state ads = (adns_state)w->data;
1945	update_now (EV_A);	2321	update_now (EV_A);
1946		2322
1947	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2323	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1948	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2324	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1949	}	2325	}
1950		2326
1951	// do not ever call adns_afterpoll	2327	// do not ever call adns_afterpoll
1952		2328
1953	Method 4: Do not use a prepare or check watcher because the module you	2329	Method 4: Do not use a prepare or check watcher because the module you
1954	want to embed is too inflexible to support it. Instead, youc na override	2330	want to embed is not flexible enough to support it. Instead, you can
1955	their poll function. The drawback with this solution is that the main	2331	override their poll function. The drawback with this solution is that the
1956	loop is now no longer controllable by EV. The C<Glib::EV> module does	2332	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1957	this.	2333	this approach, effectively embedding EV as a client into the horrible
		2334	libglib event loop.
1958		2335
1959	static gint	2336	static gint
1960	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2337	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1961	{	2338	{
1962	int got_events = 0;	2339	int got_events = 0;
1963		2340
1964	for (n = 0; n < nfds; ++n)	2341	for (n = 0; n < nfds; ++n)
1965	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2342	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1966		2343
1967	if (timeout >= 0)	2344	if (timeout >= 0)
1968	// create/start timer	2345	// create/start timer
1969		2346
1970	// poll	2347	// poll
1971	ev_loop (EV_A_ 0);	2348	ev_loop (EV_A_ 0);
1972		2349
1973	// stop timer again	2350	// stop timer again
1974	if (timeout >= 0)	2351	if (timeout >= 0)
1975	ev_timer_stop (EV_A_ &to);	2352	ev_timer_stop (EV_A_ &to);
1976		2353
1977	// stop io watchers again - their callbacks should have set	2354	// stop io watchers again - their callbacks should have set
1978	for (n = 0; n < nfds; ++n)	2355	for (n = 0; n < nfds; ++n)
1979	ev_io_stop (EV_A_ iow [n]);	2356	ev_io_stop (EV_A_ iow [n]);
1980		2357
1981	return got_events;	2358	return got_events;
1982	}	2359	}
1983		2360
1984		2361
1985	=head2 C<ev_embed> - when one backend isn't enough...	2362	=head2 C<ev_embed> - when one backend isn't enough...
1986		2363
1987	This is a rather advanced watcher type that lets you embed one event loop	2364	This is a rather advanced watcher type that lets you embed one event loop
…		…
1993	prioritise I/O.	2370	prioritise I/O.
1994		2371
1995	As an example for a bug workaround, the kqueue backend might only support	2372	As an example for a bug workaround, the kqueue backend might only support
1996	sockets on some platform, so it is unusable as generic backend, but you	2373	sockets on some platform, so it is unusable as generic backend, but you
1997	still want to make use of it because you have many sockets and it scales	2374	still want to make use of it because you have many sockets and it scales
1998	so nicely. In this case, you would create a kqueue-based loop and embed it	2375	so nicely. In this case, you would create a kqueue-based loop and embed
1999	into your default loop (which might use e.g. poll). Overall operation will	2376	it into your default loop (which might use e.g. poll). Overall operation
2000	be a bit slower because first libev has to poll and then call kevent, but	2377	will be a bit slower because first libev has to call C<poll> and then
2001	at least you can use both at what they are best.	2378	C<kevent>, but at least you can use both mechanisms for what they are
		2379	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2002		2380
2003	As for prioritising I/O: rarely you have the case where some fds have	2381	As for prioritising I/O: under rare circumstances you have the case where
2004	to be watched and handled very quickly (with low latency), and even	2382	some fds have to be watched and handled very quickly (with low latency),
2005	priorities and idle watchers might have too much overhead. In this case	2383	and even priorities and idle watchers might have too much overhead. In
2006	you would put all the high priority stuff in one loop and all the rest in	2384	this case you would put all the high priority stuff in one loop and all
2007	a second one, and embed the second one in the first.	2385	the rest in a second one, and embed the second one in the first.
2008		2386
2009	As long as the watcher is active, the callback will be invoked every time	2387	As long as the watcher is active, the callback will be invoked every time
2010	there might be events pending in the embedded loop. The callback must then	2388	there might be events pending in the embedded loop. The callback must then
2011	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2012	their callbacks (you could also start an idle watcher to give the embedded	2390	their callbacks (you could also start an idle watcher to give the embedded
…		…
2020	interested in that.	2398	interested in that.
2021		2399
2022	Also, there have not currently been made special provisions for forking:	2400	Also, there have not currently been made special provisions for forking:
2023	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2024	but you will also have to stop and restart any C<ev_embed> watchers	2402	but you will also have to stop and restart any C<ev_embed> watchers
2025	yourself.	2403	yourself - but you can use a fork watcher to handle this automatically,
		2404	and future versions of libev might do just that.
2026		2405
2027	Unfortunately, not all backends are embeddable, only the ones returned by	2406	Unfortunately, not all backends are embeddable: only the ones returned by
2028	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2029	portable one.	2408	portable one.
2030		2409
2031	So when you want to use this feature you will always have to be prepared	2410	So when you want to use this feature you will always have to be prepared
2032	that you cannot get an embeddable loop. The recommended way to get around	2411	that you cannot get an embeddable loop. The recommended way to get around
2033	this is to have a separate variables for your embeddable loop, try to	2412	this is to have a separate variables for your embeddable loop, try to
2034	create it, and if that fails, use the normal loop for everything.	2413	create it, and if that fails, use the normal loop for everything.
2035		2414
		2415	=head3 C<ev_embed> and fork
		2416
		2417	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2418	automatically be applied to the embedded loop as well, so no special
		2419	fork handling is required in that case. When the watcher is not running,
		2420	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2421	as applicable.
		2422
2036	=head3 Watcher-Specific Functions and Data Members	2423	=head3 Watcher-Specific Functions and Data Members
2037		2424
2038	=over 4	2425	=over 4
2039		2426
2040	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2427	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2043		2430
2044	Configures the watcher to embed the given loop, which must be	2431	Configures the watcher to embed the given loop, which must be
2045	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2432	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2046	invoked automatically, otherwise it is the responsibility of the callback	2433	invoked automatically, otherwise it is the responsibility of the callback
2047	to invoke it (it will continue to be called until the sweep has been done,	2434	to invoke it (it will continue to be called until the sweep has been done,
2048	if you do not want thta, you need to temporarily stop the embed watcher).	2435	if you do not want that, you need to temporarily stop the embed watcher).
2049		2436
2050	=item ev_embed_sweep (loop, ev_embed *)	2437	=item ev_embed_sweep (loop, ev_embed *)
2051		2438
2052	Make a single, non-blocking sweep over the embedded loop. This works	2439	Make a single, non-blocking sweep over the embedded loop. This works
2053	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2440	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2054	apropriate way for embedded loops.	2441	appropriate way for embedded loops.
2055		2442
2056	=item struct ev_loop *other [read-only]	2443	=item struct ev_loop *other [read-only]
2057		2444
2058	The embedded event loop.	2445	The embedded event loop.
2059		2446
…		…
2061		2448
2062	=head3 Examples	2449	=head3 Examples
2063		2450
2064	Example: Try to get an embeddable event loop and embed it into the default	2451	Example: Try to get an embeddable event loop and embed it into the default
2065	event loop. If that is not possible, use the default loop. The default	2452	event loop. If that is not possible, use the default loop. The default
2066	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2453	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2067	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2454	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2068	used).	2455	used).
2069		2456
2070	struct ev_loop *loop_hi = ev_default_init (0);	2457	struct ev_loop *loop_hi = ev_default_init (0);
2071	struct ev_loop *loop_lo = 0;	2458	struct ev_loop *loop_lo = 0;
2072	struct ev_embed embed;	2459	ev_embed embed;
2073		2460
2074	// see if there is a chance of getting one that works	2461	// see if there is a chance of getting one that works
2075	// (remember that a flags value of 0 means autodetection)	2462	// (remember that a flags value of 0 means autodetection)
2076	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2463	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2077	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2464	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2078	: 0;	2465	: 0;
2079		2466
2080	// if we got one, then embed it, otherwise default to loop_hi	2467	// if we got one, then embed it, otherwise default to loop_hi
2081	if (loop_lo)	2468	if (loop_lo)
2082	{	2469	{
2083	ev_embed_init (&embed, 0, loop_lo);	2470	ev_embed_init (&embed, 0, loop_lo);
2084	ev_embed_start (loop_hi, &embed);	2471	ev_embed_start (loop_hi, &embed);
2085	}	2472	}
2086	else	2473	else
2087	loop_lo = loop_hi;	2474	loop_lo = loop_hi;
2088		2475
2089	Example: Check if kqueue is available but not recommended and create	2476	Example: Check if kqueue is available but not recommended and create
2090	a kqueue backend for use with sockets (which usually work with any	2477	a kqueue backend for use with sockets (which usually work with any
2091	kqueue implementation). Store the kqueue/socket-only event loop in	2478	kqueue implementation). Store the kqueue/socket-only event loop in
2092	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2479	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2093		2480
2094	struct ev_loop *loop = ev_default_init (0);	2481	struct ev_loop *loop = ev_default_init (0);
2095	struct ev_loop *loop_socket = 0;	2482	struct ev_loop *loop_socket = 0;
2096	struct ev_embed embed;	2483	ev_embed embed;
2097		2484
2098	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2485	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2099	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2486	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2100	{	2487	{
2101	ev_embed_init (&embed, 0, loop_socket);	2488	ev_embed_init (&embed, 0, loop_socket);
2102	ev_embed_start (loop, &embed);	2489	ev_embed_start (loop, &embed);
2103	}	2490	}
2104		2491
2105	if (!loop_socket)	2492	if (!loop_socket)
2106	loop_socket = loop;	2493	loop_socket = loop;
2107		2494
2108	// now use loop_socket for all sockets, and loop for everything else	2495	// now use loop_socket for all sockets, and loop for everything else
2109		2496
2110		2497
2111	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2498	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2112		2499
2113	Fork watchers are called when a C<fork ()> was detected (usually because	2500	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2157	is that the author does not know of a simple (or any) algorithm for a	2544	is that the author does not know of a simple (or any) algorithm for a
2158	multiple-writer-single-reader queue that works in all cases and doesn't	2545	multiple-writer-single-reader queue that works in all cases and doesn't
2159	need elaborate support such as pthreads.	2546	need elaborate support such as pthreads.
2160		2547
2161	That means that if you want to queue data, you have to provide your own	2548	That means that if you want to queue data, you have to provide your own
2162	queue. But at least I can tell you would implement locking around your	2549	queue. But at least I can tell you how to implement locking around your
2163	queue:	2550	queue:
2164		2551
2165	=over 4	2552	=over 4
2166		2553
2167	=item queueing from a signal handler context	2554	=item queueing from a signal handler context
2168		2555
2169	To implement race-free queueing, you simply add to the queue in the signal	2556	To implement race-free queueing, you simply add to the queue in the signal
2170	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2557	handler but you block the signal handler in the watcher callback. Here is
2171	some fictitiuous SIGUSR1 handler:	2558	an example that does that for some fictitious SIGUSR1 handler:
2172		2559
2173	static ev_async mysig;	2560	static ev_async mysig;
2174		2561
2175	static void	2562	static void
2176	sigusr1_handler (void)	2563	sigusr1_handler (void)
…		…
2243		2630
2244	=item ev_async_init (ev_async *, callback)	2631	=item ev_async_init (ev_async *, callback)
2245		2632
2246	Initialises and configures the async watcher - it has no parameters of any	2633	Initialises and configures the async watcher - it has no parameters of any
2247	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2248	believe me.	2635	trust me.
2249		2636
2250	=item ev_async_send (loop, ev_async *)	2637	=item ev_async_send (loop, ev_async *)
2251		2638
2252	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2253	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2254	C<ev_feed_event>, this call is safe to do in other threads, signal or	2641	C<ev_feed_event>, this call is safe to do from other threads, signal or
2255	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2256	section below on what exactly this means).	2643	section below on what exactly this means).
2257		2644
2258	This call incurs the overhead of a syscall only once per loop iteration,	2645	This call incurs the overhead of a system call only once per loop iteration,
2259	so while the overhead might be noticable, it doesn't apply to repeated	2646	so while the overhead might be noticeable, it doesn't apply to repeated
2260	calls to C<ev_async_send>.	2647	calls to C<ev_async_send>.
2261		2648
		2649	=item bool = ev_async_pending (ev_async *)
		2650
		2651	Returns a non-zero value when C<ev_async_send> has been called on the
		2652	watcher but the event has not yet been processed (or even noted) by the
		2653	event loop.
		2654
		2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2656	the loop iterates next and checks for the watcher to have become active,
		2657	it will reset the flag again. C<ev_async_pending> can be used to very
		2658	quickly check whether invoking the loop might be a good idea.
		2659
		2660	Not that this does I<not> check whether the watcher itself is pending, only
		2661	whether it has been requested to make this watcher pending.
		2662
2262	=back	2663	=back
2263		2664
2264		2665
2265	=head1 OTHER FUNCTIONS	2666	=head1 OTHER FUNCTIONS
2266		2667
…		…
2269	=over 4	2670	=over 4
2270		2671
2271	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2672	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2272		2673
2273	This function combines a simple timer and an I/O watcher, calls your	2674	This function combines a simple timer and an I/O watcher, calls your
2274	callback on whichever event happens first and automatically stop both	2675	callback on whichever event happens first and automatically stops both
2275	watchers. This is useful if you want to wait for a single event on an fd	2676	watchers. This is useful if you want to wait for a single event on an fd
2276	or timeout without having to allocate/configure/start/stop/free one or	2677	or timeout without having to allocate/configure/start/stop/free one or
2277	more watchers yourself.	2678	more watchers yourself.
2278		2679
2279	If C<fd> is less than 0, then no I/O watcher will be started and events	2680	If C<fd> is less than 0, then no I/O watcher will be started and the
2280	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2681	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2281	C<events> set will be craeted and started.	2682	the given C<fd> and C<events> set will be created and started.
2282		2683
2283	If C<timeout> is less than 0, then no timeout watcher will be	2684	If C<timeout> is less than 0, then no timeout watcher will be
2284	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2685	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2285	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2686	repeat = 0) will be started. C<0> is a valid timeout.
2286	dubious value.
2287		2687
2288	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2688	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2289	passed an C<revents> set like normal event callbacks (a combination of	2689	passed an C<revents> set like normal event callbacks (a combination of
2290	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2291	value passed to C<ev_once>:	2691	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2692	a timeout and an io event at the same time - you probably should give io
		2693	events precedence.
2292		2694
		2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2696
2293	static void stdin_ready (int revents, void *arg)	2697	static void stdin_ready (int revents, void *arg)
2294	{	2698	{
2295	if (revents & EV_TIMEOUT)
2296	/* doh, nothing entered */;
2297	else if (revents & EV_READ)	2699	if (revents & EV_READ)
2298	/* stdin might have data for us, joy! */;	2700	/* stdin might have data for us, joy! */;
		2701	else if (revents & EV_TIMEOUT)
		2702	/* doh, nothing entered */;
2299	}	2703	}
2300		2704
2301	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2302		2706
2303	=item ev_feed_event (ev_loop *, watcher *, int revents)	2707	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2304		2708
2305	Feeds the given event set into the event loop, as if the specified event	2709	Feeds the given event set into the event loop, as if the specified event
2306	had happened for the specified watcher (which must be a pointer to an	2710	had happened for the specified watcher (which must be a pointer to an
2307	initialised but not necessarily started event watcher).	2711	initialised but not necessarily started event watcher).
2308		2712
2309	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2310		2714
2311	Feed an event on the given fd, as if a file descriptor backend detected	2715	Feed an event on the given fd, as if a file descriptor backend detected
2312	the given events it.	2716	the given events it.
2313		2717
2314	=item ev_feed_signal_event (ev_loop *loop, int signum)	2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2315		2719
2316	Feed an event as if the given signal occured (C<loop> must be the default	2720	Feed an event as if the given signal occurred (C<loop> must be the default
2317	loop!).	2721	loop!).
2318		2722
2319	=back	2723	=back
2320		2724
2321		2725
…		…
2337		2741
2338	=item * Priorities are not currently supported. Initialising priorities	2742	=item * Priorities are not currently supported. Initialising priorities
2339	will fail and all watchers will have the same priority, even though there	2743	will fail and all watchers will have the same priority, even though there
2340	is an ev_pri field.	2744	is an ev_pri field.
2341		2745
		2746	=item * In libevent, the last base created gets the signals, in libev, the
		2747	first base created (== the default loop) gets the signals.
		2748
2342	=item * Other members are not supported.	2749	=item * Other members are not supported.
2343		2750
2344	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2751	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2345	to use the libev header file and library.	2752	to use the libev header file and library.
2346		2753
2347	=back	2754	=back
2348		2755
2349	=head1 C++ SUPPORT	2756	=head1 C++ SUPPORT
2350		2757
2351	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2758	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2352	you to use some convinience methods to start/stop watchers and also change	2759	you to use some convenience methods to start/stop watchers and also change
2353	the callback model to a model using method callbacks on objects.	2760	the callback model to a model using method callbacks on objects.
2354		2761
2355	To use it,	2762	To use it,
2356		2763
2357	#include <ev++.h>	2764	#include <ev++.h>
2358		2765
2359	This automatically includes F<ev.h> and puts all of its definitions (many	2766	This automatically includes F<ev.h> and puts all of its definitions (many
2360	of them macros) into the global namespace. All C++ specific things are	2767	of them macros) into the global namespace. All C++ specific things are
2361	put into the C<ev> namespace. It should support all the same embedding	2768	put into the C<ev> namespace. It should support all the same embedding
2362	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2769	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2429	your compiler is good :), then the method will be fully inlined into the	2836	your compiler is good :), then the method will be fully inlined into the
2430	thunking function, making it as fast as a direct C callback.	2837	thunking function, making it as fast as a direct C callback.
2431		2838
2432	Example: simple class declaration and watcher initialisation	2839	Example: simple class declaration and watcher initialisation
2433		2840
2434	struct myclass	2841	struct myclass
2435	{	2842	{
2436	void io_cb (ev::io &w, int revents) { }	2843	void io_cb (ev::io &w, int revents) { }
2437	}	2844	}
2438		2845
2439	myclass obj;	2846	myclass obj;
2440	ev::io iow;	2847	ev::io iow;
2441	iow.set <myclass, &myclass::io_cb> (&obj);	2848	iow.set <myclass, &myclass::io_cb> (&obj);
2442		2849
2443	=item w->set<function> (void *data = 0)	2850	=item w->set<function> (void *data = 0)
2444		2851
2445	Also sets a callback, but uses a static method or plain function as	2852	Also sets a callback, but uses a static method or plain function as
2446	callback. The optional C<data> argument will be stored in the watcher's	2853	callback. The optional C<data> argument will be stored in the watcher's
…		…
2448		2855
2449	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2856	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2450		2857
2451	See the method-C<set> above for more details.	2858	See the method-C<set> above for more details.
2452		2859
2453	Example:	2860	Example: Use a plain function as callback.
2454		2861
2455	static void io_cb (ev::io &w, int revents) { }	2862	static void io_cb (ev::io &w, int revents) { }
2456	iow.set <io_cb> ();	2863	iow.set <io_cb> ();
2457		2864
2458	=item w->set (struct ev_loop *)	2865	=item w->set (struct ev_loop *)
2459		2866
2460	Associates a different C<struct ev_loop> with this watcher. You can only	2867	Associates a different C<struct ev_loop> with this watcher. You can only
2461	do this when the watcher is inactive (and not pending either).	2868	do this when the watcher is inactive (and not pending either).
2462		2869
2463	=item w->set ([args])	2870	=item w->set ([arguments])
2464		2871
2465	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2872	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2466	called at least once. Unlike the C counterpart, an active watcher gets	2873	called at least once. Unlike the C counterpart, an active watcher gets
2467	automatically stopped and restarted when reconfiguring it with this	2874	automatically stopped and restarted when reconfiguring it with this
2468	method.	2875	method.
2469		2876
2470	=item w->start ()	2877	=item w->start ()
…		…
2494	=back	2901	=back
2495		2902
2496	Example: Define a class with an IO and idle watcher, start one of them in	2903	Example: Define a class with an IO and idle watcher, start one of them in
2497	the constructor.	2904	the constructor.
2498		2905
2499	class myclass	2906	class myclass
2500	{	2907	{
2501	ev::io io; void io_cb (ev::io &w, int revents);	2908	ev::io io ; void io_cb (ev::io &w, int revents);
2502	ev:idle idle void idle_cb (ev::idle &w, int revents);	2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2503		2910
2504	myclass (int fd)	2911	myclass (int fd)
2505	{	2912	{
2506	io .set <myclass, &myclass::io_cb > (this);	2913	io .set <myclass, &myclass::io_cb > (this);
2507	idle.set <myclass, &myclass::idle_cb> (this);	2914	idle.set <myclass, &myclass::idle_cb> (this);
2508		2915
2509	io.start (fd, ev::READ);	2916	io.start (fd, ev::READ);
2510	}	2917	}
2511	};	2918	};
2512		2919
2513		2920
2514	=head1 OTHER LANGUAGE BINDINGS	2921	=head1 OTHER LANGUAGE BINDINGS
2515		2922
2516	Libev does not offer other language bindings itself, but bindings for a	2923	Libev does not offer other language bindings itself, but bindings for a
2517	numbe rof languages exist in the form of third-party packages. If you know	2924	number of languages exist in the form of third-party packages. If you know
2518	any interesting language binding in addition to the ones listed here, drop	2925	any interesting language binding in addition to the ones listed here, drop
2519	me a note.	2926	me a note.
2520		2927
2521	=over 4	2928	=over 4
2522		2929
2523	=item Perl	2930	=item Perl
2524		2931
2525	The EV module implements the full libev API and is actually used to test	2932	The EV module implements the full libev API and is actually used to test
2526	libev. EV is developed together with libev. Apart from the EV core module,	2933	libev. EV is developed together with libev. Apart from the EV core module,
2527	there are additional modules that implement libev-compatible interfaces	2934	there are additional modules that implement libev-compatible interfaces
2528	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2935	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2529	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2936	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2937	and C<EV::Glib>).
2530		2938
2531	It can be found and installed via CPAN, its homepage is found at	2939	It can be found and installed via CPAN, its homepage is at
2532	L<http://software.schmorp.de/pkg/EV>.	2940	L<http://software.schmorp.de/pkg/EV>.
2533		2941
		2942	=item Python
		2943
		2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2945	seems to be quite complete and well-documented. Note, however, that the
		2946	patch they require for libev is outright dangerous as it breaks the ABI
		2947	for everybody else, and therefore, should never be applied in an installed
		2948	libev (if python requires an incompatible ABI then it needs to embed
		2949	libev).
		2950
2534	=item Ruby	2951	=item Ruby
2535		2952
2536	Tony Arcieri has written a ruby extension that offers access to a subset	2953	Tony Arcieri has written a ruby extension that offers access to a subset
2537	of the libev API and adds filehandle abstractions, asynchronous DNS and	2954	of the libev API and adds file handle abstractions, asynchronous DNS and
2538	more on top of it. It can be found via gem servers. Its homepage is at	2955	more on top of it. It can be found via gem servers. Its homepage is at
2539	L<http://rev.rubyforge.org/>.	2956	L<http://rev.rubyforge.org/>.
2540		2957
2541	=item D	2958	=item D
2542		2959
2543	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2544	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2545		2962
2546	=back	2963	=back
2547		2964
2548		2965
2549	=head1 MACRO MAGIC	2966	=head1 MACRO MAGIC
2550		2967
2551	Libev can be compiled with a variety of options, the most fundamantal	2968	Libev can be compiled with a variety of options, the most fundamental
2552	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2969	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2553	functions and callbacks have an initial C<struct ev_loop *> argument.	2970	functions and callbacks have an initial C<struct ev_loop *> argument.
2554		2971
2555	To make it easier to write programs that cope with either variant, the	2972	To make it easier to write programs that cope with either variant, the
2556	following macros are defined:	2973	following macros are defined:
…		…
2561		2978
2562	This provides the loop I<argument> for functions, if one is required ("ev	2979	This provides the loop I<argument> for functions, if one is required ("ev
2563	loop argument"). The C<EV_A> form is used when this is the sole argument,	2980	loop argument"). The C<EV_A> form is used when this is the sole argument,
2564	C<EV_A_> is used when other arguments are following. Example:	2981	C<EV_A_> is used when other arguments are following. Example:
2565		2982
2566	ev_unref (EV_A);	2983	ev_unref (EV_A);
2567	ev_timer_add (EV_A_ watcher);	2984	ev_timer_add (EV_A_ watcher);
2568	ev_loop (EV_A_ 0);	2985	ev_loop (EV_A_ 0);
2569		2986
2570	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2987	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2571	which is often provided by the following macro.	2988	which is often provided by the following macro.
2572		2989
2573	=item C<EV_P>, C<EV_P_>	2990	=item C<EV_P>, C<EV_P_>
2574		2991
2575	This provides the loop I<parameter> for functions, if one is required ("ev	2992	This provides the loop I<parameter> for functions, if one is required ("ev
2576	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2993	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2577	C<EV_P_> is used when other parameters are following. Example:	2994	C<EV_P_> is used when other parameters are following. Example:
2578		2995
2579	// this is how ev_unref is being declared	2996	// this is how ev_unref is being declared
2580	static void ev_unref (EV_P);	2997	static void ev_unref (EV_P);
2581		2998
2582	// this is how you can declare your typical callback	2999	// this is how you can declare your typical callback
2583	static void cb (EV_P_ ev_timer *w, int revents)	3000	static void cb (EV_P_ ev_timer *w, int revents)
2584		3001
2585	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3002	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2586	suitable for use with C<EV_A>.	3003	suitable for use with C<EV_A>.
2587		3004
2588	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3005	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2589		3006
2590	Similar to the other two macros, this gives you the value of the default	3007	Similar to the other two macros, this gives you the value of the default
2591	loop, if multiple loops are supported ("ev loop default").	3008	loop, if multiple loops are supported ("ev loop default").
		3009
		3010	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3011
		3012	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3013	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3014	is undefined when the default loop has not been initialised by a previous
		3015	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3016
		3017	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3018	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2592		3019
2593	=back	3020	=back
2594		3021
2595	Example: Declare and initialise a check watcher, utilising the above	3022	Example: Declare and initialise a check watcher, utilising the above
2596	macros so it will work regardless of whether multiple loops are supported	3023	macros so it will work regardless of whether multiple loops are supported
2597	or not.	3024	or not.
2598		3025
2599	static void	3026	static void
2600	check_cb (EV_P_ ev_timer *w, int revents)	3027	check_cb (EV_P_ ev_timer *w, int revents)
2601	{	3028	{
2602	ev_check_stop (EV_A_ w);	3029	ev_check_stop (EV_A_ w);
2603	}	3030	}
2604		3031
2605	ev_check check;	3032	ev_check check;
2606	ev_check_init (&check, check_cb);	3033	ev_check_init (&check, check_cb);
2607	ev_check_start (EV_DEFAULT_ &check);	3034	ev_check_start (EV_DEFAULT_ &check);
2608	ev_loop (EV_DEFAULT_ 0);	3035	ev_loop (EV_DEFAULT_ 0);
2609		3036
2610	=head1 EMBEDDING	3037	=head1 EMBEDDING
2611		3038
2612	Libev can (and often is) directly embedded into host	3039	Libev can (and often is) directly embedded into host
2613	applications. Examples of applications that embed it include the Deliantra	3040	applications. Examples of applications that embed it include the Deliantra
…		…
2620	libev somewhere in your source tree).	3047	libev somewhere in your source tree).
2621		3048
2622	=head2 FILESETS	3049	=head2 FILESETS
2623		3050
2624	Depending on what features you need you need to include one or more sets of files	3051	Depending on what features you need you need to include one or more sets of files
2625	in your app.	3052	in your application.
2626		3053
2627	=head3 CORE EVENT LOOP	3054	=head3 CORE EVENT LOOP
2628		3055
2629	To include only the libev core (all the C<ev_*> functions), with manual	3056	To include only the libev core (all the C<ev_*> functions), with manual
2630	configuration (no autoconf):	3057	configuration (no autoconf):
2631		3058
2632	#define EV_STANDALONE 1	3059	#define EV_STANDALONE 1
2633	#include "ev.c"	3060	#include "ev.c"
2634		3061
2635	This will automatically include F<ev.h>, too, and should be done in a	3062	This will automatically include F<ev.h>, too, and should be done in a
2636	single C source file only to provide the function implementations. To use	3063	single C source file only to provide the function implementations. To use
2637	it, do the same for F<ev.h> in all files wishing to use this API (best	3064	it, do the same for F<ev.h> in all files wishing to use this API (best
2638	done by writing a wrapper around F<ev.h> that you can include instead and	3065	done by writing a wrapper around F<ev.h> that you can include instead and
2639	where you can put other configuration options):	3066	where you can put other configuration options):
2640		3067
2641	#define EV_STANDALONE 1	3068	#define EV_STANDALONE 1
2642	#include "ev.h"	3069	#include "ev.h"
2643		3070
2644	Both header files and implementation files can be compiled with a C++	3071	Both header files and implementation files can be compiled with a C++
2645	compiler (at least, thats a stated goal, and breakage will be treated	3072	compiler (at least, thats a stated goal, and breakage will be treated
2646	as a bug).	3073	as a bug).
2647		3074
2648	You need the following files in your source tree, or in a directory	3075	You need the following files in your source tree, or in a directory
2649	in your include path (e.g. in libev/ when using -Ilibev):	3076	in your include path (e.g. in libev/ when using -Ilibev):
2650		3077
2651	ev.h	3078	ev.h
2652	ev.c	3079	ev.c
2653	ev_vars.h	3080	ev_vars.h
2654	ev_wrap.h	3081	ev_wrap.h
2655		3082
2656	ev_win32.c required on win32 platforms only	3083	ev_win32.c required on win32 platforms only
2657		3084
2658	ev_select.c only when select backend is enabled (which is enabled by default)	3085	ev_select.c only when select backend is enabled (which is enabled by default)
2659	ev_poll.c only when poll backend is enabled (disabled by default)	3086	ev_poll.c only when poll backend is enabled (disabled by default)
2660	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3087	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2661	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3088	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2662	ev_port.c only when the solaris port backend is enabled (disabled by default)	3089	ev_port.c only when the solaris port backend is enabled (disabled by default)
2663		3090
2664	F<ev.c> includes the backend files directly when enabled, so you only need	3091	F<ev.c> includes the backend files directly when enabled, so you only need
2665	to compile this single file.	3092	to compile this single file.
2666		3093
2667	=head3 LIBEVENT COMPATIBILITY API	3094	=head3 LIBEVENT COMPATIBILITY API
2668		3095
2669	To include the libevent compatibility API, also include:	3096	To include the libevent compatibility API, also include:
2670		3097
2671	#include "event.c"	3098	#include "event.c"
2672		3099
2673	in the file including F<ev.c>, and:	3100	in the file including F<ev.c>, and:
2674		3101
2675	#include "event.h"	3102	#include "event.h"
2676		3103
2677	in the files that want to use the libevent API. This also includes F<ev.h>.	3104	in the files that want to use the libevent API. This also includes F<ev.h>.
2678		3105
2679	You need the following additional files for this:	3106	You need the following additional files for this:
2680		3107
2681	event.h	3108	event.h
2682	event.c	3109	event.c
2683		3110
2684	=head3 AUTOCONF SUPPORT	3111	=head3 AUTOCONF SUPPORT
2685		3112
2686	Instead of using C<EV_STANDALONE=1> and providing your config in	3113	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2687	whatever way you want, you can also C<m4_include([libev.m4])> in your	3114	whatever way you want, you can also C<m4_include([libev.m4])> in your
2688	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3115	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2689	include F<config.h> and configure itself accordingly.	3116	include F<config.h> and configure itself accordingly.
2690		3117
2691	For this of course you need the m4 file:	3118	For this of course you need the m4 file:
2692		3119
2693	libev.m4	3120	libev.m4
2694		3121
2695	=head2 PREPROCESSOR SYMBOLS/MACROS	3122	=head2 PREPROCESSOR SYMBOLS/MACROS
2696		3123
2697	Libev can be configured via a variety of preprocessor symbols you have to define	3124	Libev can be configured via a variety of preprocessor symbols you have to
2698	before including any of its files. The default is not to build for multiplicity	3125	define before including any of its files. The default in the absence of
2699	and only include the select backend.	3126	autoconf is documented for every option.
2700		3127
2701	=over 4	3128	=over 4
2702		3129
2703	=item EV_STANDALONE	3130	=item EV_STANDALONE
2704		3131
…		…
2709	F<event.h> that are not directly supported by the libev core alone.	3136	F<event.h> that are not directly supported by the libev core alone.
2710		3137
2711	=item EV_USE_MONOTONIC	3138	=item EV_USE_MONOTONIC
2712		3139
2713	If defined to be C<1>, libev will try to detect the availability of the	3140	If defined to be C<1>, libev will try to detect the availability of the
2714	monotonic clock option at both compiletime and runtime. Otherwise no use	3141	monotonic clock option at both compile time and runtime. Otherwise no use
2715	of the monotonic clock option will be attempted. If you enable this, you	3142	of the monotonic clock option will be attempted. If you enable this, you
2716	usually have to link against librt or something similar. Enabling it when	3143	usually have to link against librt or something similar. Enabling it when
2717	the functionality isn't available is safe, though, although you have	3144	the functionality isn't available is safe, though, although you have
2718	to make sure you link against any libraries where the C<clock_gettime>	3145	to make sure you link against any libraries where the C<clock_gettime>
2719	function is hiding in (often F<-lrt>).	3146	function is hiding in (often F<-lrt>).
2720		3147
2721	=item EV_USE_REALTIME	3148	=item EV_USE_REALTIME
2722		3149
2723	If defined to be C<1>, libev will try to detect the availability of the	3150	If defined to be C<1>, libev will try to detect the availability of the
2724	realtime clock option at compiletime (and assume its availability at	3151	real-time clock option at compile time (and assume its availability at
2725	runtime if successful). Otherwise no use of the realtime clock option will	3152	runtime if successful). Otherwise no use of the real-time clock option will
2726	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3153	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2727	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3154	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2728	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3155	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2729		3156
2730	=item EV_USE_NANOSLEEP	3157	=item EV_USE_NANOSLEEP
2731		3158
2732	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3159	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2733	and will use it for delays. Otherwise it will use C<select ()>.	3160	and will use it for delays. Otherwise it will use C<select ()>.
2734		3161
		3162	=item EV_USE_EVENTFD
		3163
		3164	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3165	available and will probe for kernel support at runtime. This will improve
		3166	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3167	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3168	2.7 or newer, otherwise disabled.
		3169
2735	=item EV_USE_SELECT	3170	=item EV_USE_SELECT
2736		3171
2737	If undefined or defined to be C<1>, libev will compile in support for the	3172	If undefined or defined to be C<1>, libev will compile in support for the
2738	C<select>(2) backend. No attempt at autodetection will be done: if no	3173	C<select>(2) backend. No attempt at auto-detection will be done: if no
2739	other method takes over, select will be it. Otherwise the select backend	3174	other method takes over, select will be it. Otherwise the select backend
2740	will not be compiled in.	3175	will not be compiled in.
2741		3176
2742	=item EV_SELECT_USE_FD_SET	3177	=item EV_SELECT_USE_FD_SET
2743		3178
2744	If defined to C<1>, then the select backend will use the system C<fd_set>	3179	If defined to C<1>, then the select backend will use the system C<fd_set>
2745	structure. This is useful if libev doesn't compile due to a missing	3180	structure. This is useful if libev doesn't compile due to a missing
2746	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3181	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2747	exotic systems. This usually limits the range of file descriptors to some	3182	exotic systems. This usually limits the range of file descriptors to some
2748	low limit such as 1024 or might have other limitations (winsocket only	3183	low limit such as 1024 or might have other limitations (winsocket only
2749	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3184	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2750	influence the size of the C<fd_set> used.	3185	influence the size of the C<fd_set> used.
2751		3186
…		…
2775		3210
2776	=item EV_USE_EPOLL	3211	=item EV_USE_EPOLL
2777		3212
2778	If defined to be C<1>, libev will compile in support for the Linux	3213	If defined to be C<1>, libev will compile in support for the Linux
2779	C<epoll>(7) backend. Its availability will be detected at runtime,	3214	C<epoll>(7) backend. Its availability will be detected at runtime,
2780	otherwise another method will be used as fallback. This is the	3215	otherwise another method will be used as fallback. This is the preferred
2781	preferred backend for GNU/Linux systems.	3216	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3217	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2782		3218
2783	=item EV_USE_KQUEUE	3219	=item EV_USE_KQUEUE
2784		3220
2785	If defined to be C<1>, libev will compile in support for the BSD style	3221	If defined to be C<1>, libev will compile in support for the BSD style
2786	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3222	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2799	otherwise another method will be used as fallback. This is the preferred	3235	otherwise another method will be used as fallback. This is the preferred
2800	backend for Solaris 10 systems.	3236	backend for Solaris 10 systems.
2801		3237
2802	=item EV_USE_DEVPOLL	3238	=item EV_USE_DEVPOLL
2803		3239
2804	reserved for future expansion, works like the USE symbols above.	3240	Reserved for future expansion, works like the USE symbols above.
2805		3241
2806	=item EV_USE_INOTIFY	3242	=item EV_USE_INOTIFY
2807		3243
2808	If defined to be C<1>, libev will compile in support for the Linux inotify	3244	If defined to be C<1>, libev will compile in support for the Linux inotify
2809	interface to speed up C<ev_stat> watchers. Its actual availability will	3245	interface to speed up C<ev_stat> watchers. Its actual availability will
2810	be detected at runtime.	3246	be detected at runtime. If undefined, it will be enabled if the headers
		3247	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2811		3248
2812	=item EV_ATOMIC_T	3249	=item EV_ATOMIC_T
2813		3250
2814	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3251	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2815	access is atomic with respect to other threads or signal contexts. No such	3252	access is atomic with respect to other threads or signal contexts. No such
2816	type is easily found in the C language, so you can provide your own type	3253	type is easily found in the C language, so you can provide your own type
2817	that you know is safe for your purposes. It is used both for signal handler "locking"	3254	that you know is safe for your purposes. It is used both for signal handler "locking"
2818	as well as for signal and thread safety in C<ev_async> watchers.	3255	as well as for signal and thread safety in C<ev_async> watchers.
2819		3256
2820	In the absense of this define, libev will use C<sig_atomic_t volatile>	3257	In the absence of this define, libev will use C<sig_atomic_t volatile>
2821	(from F<signal.h>), which is usually good enough on most platforms.	3258	(from F<signal.h>), which is usually good enough on most platforms.
2822		3259
2823	=item EV_H	3260	=item EV_H
2824		3261
2825	The name of the F<ev.h> header file used to include it. The default if	3262	The name of the F<ev.h> header file used to include it. The default if
…		…
2864	When doing priority-based operations, libev usually has to linearly search	3301	When doing priority-based operations, libev usually has to linearly search
2865	all the priorities, so having many of them (hundreds) uses a lot of space	3302	all the priorities, so having many of them (hundreds) uses a lot of space
2866	and time, so using the defaults of five priorities (-2 .. +2) is usually	3303	and time, so using the defaults of five priorities (-2 .. +2) is usually
2867	fine.	3304	fine.
2868		3305
2869	If your embedding app does not need any priorities, defining these both to	3306	If your embedding application does not need any priorities, defining these
2870	C<0> will save some memory and cpu.	3307	both to C<0> will save some memory and CPU.
2871		3308
2872	=item EV_PERIODIC_ENABLE	3309	=item EV_PERIODIC_ENABLE
2873		3310
2874	If undefined or defined to be C<1>, then periodic timers are supported. If	3311	If undefined or defined to be C<1>, then periodic timers are supported. If
2875	defined to be C<0>, then they are not. Disabling them saves a few kB of	3312	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2882	code.	3319	code.
2883		3320
2884	=item EV_EMBED_ENABLE	3321	=item EV_EMBED_ENABLE
2885		3322
2886	If undefined or defined to be C<1>, then embed watchers are supported. If	3323	If undefined or defined to be C<1>, then embed watchers are supported. If
2887	defined to be C<0>, then they are not.	3324	defined to be C<0>, then they are not. Embed watchers rely on most other
		3325	watcher types, which therefore must not be disabled.
2888		3326
2889	=item EV_STAT_ENABLE	3327	=item EV_STAT_ENABLE
2890		3328
2891	If undefined or defined to be C<1>, then stat watchers are supported. If	3329	If undefined or defined to be C<1>, then stat watchers are supported. If
2892	defined to be C<0>, then they are not.	3330	defined to be C<0>, then they are not.
…		…
2902	defined to be C<0>, then they are not.	3340	defined to be C<0>, then they are not.
2903		3341
2904	=item EV_MINIMAL	3342	=item EV_MINIMAL
2905		3343
2906	If you need to shave off some kilobytes of code at the expense of some	3344	If you need to shave off some kilobytes of code at the expense of some
2907	speed, define this symbol to C<1>. Currently only used for gcc to override	3345	speed, define this symbol to C<1>. Currently this is used to override some
2908	some inlining decisions, saves roughly 30% codesize of amd64.	3346	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3347	much smaller 2-heap for timer management over the default 4-heap.
2909		3348
2910	=item EV_PID_HASHSIZE	3349	=item EV_PID_HASHSIZE
2911		3350
2912	C<ev_child> watchers use a small hash table to distribute workload by	3351	C<ev_child> watchers use a small hash table to distribute workload by
2913	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3352	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2920	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3359	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2921	usually more than enough. If you need to manage thousands of C<ev_stat>	3360	usually more than enough. If you need to manage thousands of C<ev_stat>
2922	watchers you might want to increase this value (I<must> be a power of	3361	watchers you might want to increase this value (I<must> be a power of
2923	two).	3362	two).
2924		3363
		3364	=item EV_USE_4HEAP
		3365
		3366	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3367	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3368	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3369	faster performance with many (thousands) of watchers.
		3370
		3371	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3372	(disabled).
		3373
		3374	=item EV_HEAP_CACHE_AT
		3375
		3376	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3377	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3378	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3379	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3380	but avoids random read accesses on heap changes. This improves performance
		3381	noticeably with many (hundreds) of watchers.
		3382
		3383	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3384	(disabled).
		3385
		3386	=item EV_VERIFY
		3387
		3388	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3389	be done: If set to C<0>, no internal verification code will be compiled
		3390	in. If set to C<1>, then verification code will be compiled in, but not
		3391	called. If set to C<2>, then the internal verification code will be
		3392	called once per loop, which can slow down libev. If set to C<3>, then the
		3393	verification code will be called very frequently, which will slow down
		3394	libev considerably.
		3395
		3396	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3397	C<0>.
		3398
2925	=item EV_COMMON	3399	=item EV_COMMON
2926		3400
2927	By default, all watchers have a C<void *data> member. By redefining	3401	By default, all watchers have a C<void *data> member. By redefining
2928	this macro to a something else you can include more and other types of	3402	this macro to a something else you can include more and other types of
2929	members. You have to define it each time you include one of the files,	3403	members. You have to define it each time you include one of the files,
2930	though, and it must be identical each time.	3404	though, and it must be identical each time.
2931		3405
2932	For example, the perl EV module uses something like this:	3406	For example, the perl EV module uses something like this:
2933		3407
2934	#define EV_COMMON \	3408	#define EV_COMMON \
2935	SV *self; /* contains this struct */ \	3409	SV *self; /* contains this struct */ \
2936	SV *cb_sv, *fh /* note no trailing ";" */	3410	SV *cb_sv, *fh /* note no trailing ";" */
2937		3411
2938	=item EV_CB_DECLARE (type)	3412	=item EV_CB_DECLARE (type)
2939		3413
2940	=item EV_CB_INVOKE (watcher, revents)	3414	=item EV_CB_INVOKE (watcher, revents)
2941		3415
…		…
2946	definition and a statement, respectively. See the F<ev.h> header file for	3420	definition and a statement, respectively. See the F<ev.h> header file for
2947	their default definitions. One possible use for overriding these is to	3421	their default definitions. One possible use for overriding these is to
2948	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3422	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2949	method calls instead of plain function calls in C++.	3423	method calls instead of plain function calls in C++.
2950		3424
		3425	=back
		3426
2951	=head2 EXPORTED API SYMBOLS	3427	=head2 EXPORTED API SYMBOLS
2952		3428
2953	If you need to re-export the API (e.g. via a dll) and you need a list of	3429	If you need to re-export the API (e.g. via a DLL) and you need a list of
2954	exported symbols, you can use the provided F<Symbol.*> files which list	3430	exported symbols, you can use the provided F<Symbol.*> files which list
2955	all public symbols, one per line:	3431	all public symbols, one per line:
2956		3432
2957	Symbols.ev for libev proper	3433	Symbols.ev for libev proper
2958	Symbols.event for the libevent emulation	3434	Symbols.event for the libevent emulation
2959		3435
2960	This can also be used to rename all public symbols to avoid clashes with	3436	This can also be used to rename all public symbols to avoid clashes with
2961	multiple versions of libev linked together (which is obviously bad in	3437	multiple versions of libev linked together (which is obviously bad in
2962	itself, but sometimes it is inconvinient to avoid this).	3438	itself, but sometimes it is inconvenient to avoid this).
2963		3439
2964	A sed command like this will create wrapper C<#define>'s that you need to	3440	A sed command like this will create wrapper C<#define>'s that you need to
2965	include before including F<ev.h>:	3441	include before including F<ev.h>:
2966		3442
2967	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3443	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
2984	file.	3460	file.
2985		3461
2986	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3462	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2987	that everybody includes and which overrides some configure choices:	3463	that everybody includes and which overrides some configure choices:
2988		3464
2989	#define EV_MINIMAL 1	3465	#define EV_MINIMAL 1
2990	#define EV_USE_POLL 0	3466	#define EV_USE_POLL 0
2991	#define EV_MULTIPLICITY 0	3467	#define EV_MULTIPLICITY 0
2992	#define EV_PERIODIC_ENABLE 0	3468	#define EV_PERIODIC_ENABLE 0
2993	#define EV_STAT_ENABLE 0	3469	#define EV_STAT_ENABLE 0
2994	#define EV_FORK_ENABLE 0	3470	#define EV_FORK_ENABLE 0
2995	#define EV_CONFIG_H <config.h>	3471	#define EV_CONFIG_H <config.h>
2996	#define EV_MINPRI 0	3472	#define EV_MINPRI 0
2997	#define EV_MAXPRI 0	3473	#define EV_MAXPRI 0
2998		3474
2999	#include "ev++.h"	3475	#include "ev++.h"
3000		3476
3001	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3477	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3002		3478
3003	#include "ev_cpp.h"	3479	#include "ev_cpp.h"
3004	#include "ev.c"	3480	#include "ev.c"
3005		3481
		3482	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3006		3483
3007	=head1 COMPLEXITIES	3484	=head2 THREADS AND COROUTINES
3008		3485
3009	In this section the complexities of (many of) the algorithms used inside	3486	=head3 THREADS
3010	libev will be explained. For complexity discussions about backends see the
3011	documentation for C<ev_default_init>.
3012		3487
3013	All of the following are about amortised time: If an array needs to be	3488	All libev functions are reentrant and thread-safe unless explicitly
3014	extended, libev needs to realloc and move the whole array, but this	3489	documented otherwise, but libev implements no locking itself. This means
3015	happens asymptotically never with higher number of elements, so O(1) might	3490	that you can use as many loops as you want in parallel, as long as there
3016	mean it might do a lengthy realloc operation in rare cases, but on average	3491	are no concurrent calls into any libev function with the same loop
3017	it is much faster and asymptotically approaches constant time.	3492	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3493	of course): libev guarantees that different event loops share no data
		3494	structures that need any locking.
		3495
		3496	Or to put it differently: calls with different loop parameters can be done
		3497	concurrently from multiple threads, calls with the same loop parameter
		3498	must be done serially (but can be done from different threads, as long as
		3499	only one thread ever is inside a call at any point in time, e.g. by using
		3500	a mutex per loop).
		3501
		3502	Specifically to support threads (and signal handlers), libev implements
		3503	so-called C<ev_async> watchers, which allow some limited form of
		3504	concurrency on the same event loop, namely waking it up "from the
		3505	outside".
		3506
		3507	If you want to know which design (one loop, locking, or multiple loops
		3508	without or something else still) is best for your problem, then I cannot
		3509	help you, but here is some generic advice:
3018		3510
3019	=over 4	3511	=over 4
3020		3512
3021	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3513	=item * most applications have a main thread: use the default libev loop
		3514	in that thread, or create a separate thread running only the default loop.
3022		3515
3023	This means that, when you have a watcher that triggers in one hour and	3516	This helps integrating other libraries or software modules that use libev
3024	there are 100 watchers that would trigger before that then inserting will	3517	themselves and don't care/know about threading.
3025	have to skip roughly seven (C<ld 100>) of these watchers.
3026		3518
3027	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3519	=item * one loop per thread is usually a good model.
3028		3520
3029	That means that changing a timer costs less than removing/adding them	3521	Doing this is almost never wrong, sometimes a better-performance model
3030	as only the relative motion in the event queue has to be paid for.	3522	exists, but it is always a good start.
3031		3523
3032	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3524	=item * other models exist, such as the leader/follower pattern, where one
		3525	loop is handed through multiple threads in a kind of round-robin fashion.
3033		3526
3034	These just add the watcher into an array or at the head of a list.	3527	Choosing a model is hard - look around, learn, know that usually you can do
		3528	better than you currently do :-)
3035		3529
3036	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3530	=item * often you need to talk to some other thread which blocks in the
		3531	event loop.
3037		3532
3038	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3533	C<ev_async> watchers can be used to wake them up from other threads safely
		3534	(or from signal contexts...).
3039		3535
3040	These watchers are stored in lists then need to be walked to find the	3536	An example use would be to communicate signals or other events that only
3041	correct watcher to remove. The lists are usually short (you don't usually	3537	work in the default loop by registering the signal watcher with the
3042	have many watchers waiting for the same fd or signal).	3538	default loop and triggering an C<ev_async> watcher from the default loop
3043		3539	watcher callback into the event loop interested in the signal.
3044	=item Finding the next timer in each loop iteration: O(1)
3045
3046	By virtue of using a binary heap, the next timer is always found at the
3047	beginning of the storage array.
3048
3049	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3050
3051	A change means an I/O watcher gets started or stopped, which requires
3052	libev to recalculate its status (and possibly tell the kernel, depending
3053	on backend and wether C<ev_io_set> was used).
3054
3055	=item Activating one watcher (putting it into the pending state): O(1)
3056
3057	=item Priority handling: O(number_of_priorities)
3058
3059	Priorities are implemented by allocating some space for each
3060	priority. When doing priority-based operations, libev usually has to
3061	linearly search all the priorities, but starting/stopping and activating
3062	watchers becomes O(1) w.r.t. priority handling.
3063
3064	=item Sending an ev_async: O(1)
3065
3066	=item Processing ev_async_send: O(number_of_async_watchers)
3067
3068	=item Processing signals: O(max_signal_number)
3069
3070	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3071	calls in the current loop iteration. Checking for async and signal events
3072	involves iterating over all running async watchers or all signal numbers.
3073		3540
3074	=back	3541	=back
3075		3542
		3543	=head3 COROUTINES
3076		3544
3077	=head1 Win32 platform limitations and workarounds	3545	Libev is very accommodating to coroutines ("cooperative threads"):
		3546	libev fully supports nesting calls to its functions from different
		3547	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3548	different coroutines, and switch freely between both coroutines running the
		3549	loop, as long as you don't confuse yourself). The only exception is that
		3550	you must not do this from C<ev_periodic> reschedule callbacks.
		3551
		3552	Care has been taken to ensure that libev does not keep local state inside
		3553	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3554	they do not clal any callbacks.
		3555
		3556	=head2 COMPILER WARNINGS
		3557
		3558	Depending on your compiler and compiler settings, you might get no or a
		3559	lot of warnings when compiling libev code. Some people are apparently
		3560	scared by this.
		3561
		3562	However, these are unavoidable for many reasons. For one, each compiler
		3563	has different warnings, and each user has different tastes regarding
		3564	warning options. "Warn-free" code therefore cannot be a goal except when
		3565	targeting a specific compiler and compiler-version.
		3566
		3567	Another reason is that some compiler warnings require elaborate
		3568	workarounds, or other changes to the code that make it less clear and less
		3569	maintainable.
		3570
		3571	And of course, some compiler warnings are just plain stupid, or simply
		3572	wrong (because they don't actually warn about the condition their message
		3573	seems to warn about). For example, certain older gcc versions had some
		3574	warnings that resulted an extreme number of false positives. These have
		3575	been fixed, but some people still insist on making code warn-free with
		3576	such buggy versions.
		3577
		3578	While libev is written to generate as few warnings as possible,
		3579	"warn-free" code is not a goal, and it is recommended not to build libev
		3580	with any compiler warnings enabled unless you are prepared to cope with
		3581	them (e.g. by ignoring them). Remember that warnings are just that:
		3582	warnings, not errors, or proof of bugs.
		3583
		3584
		3585	=head2 VALGRIND
		3586
		3587	Valgrind has a special section here because it is a popular tool that is
		3588	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3589
		3590	If you think you found a bug (memory leak, uninitialised data access etc.)
		3591	in libev, then check twice: If valgrind reports something like:
		3592
		3593	==2274== definitely lost: 0 bytes in 0 blocks.
		3594	==2274== possibly lost: 0 bytes in 0 blocks.
		3595	==2274== still reachable: 256 bytes in 1 blocks.
		3596
		3597	Then there is no memory leak, just as memory accounted to global variables
		3598	is not a memleak - the memory is still being refernced, and didn't leak.
		3599
		3600	Similarly, under some circumstances, valgrind might report kernel bugs
		3601	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3602	although an acceptable workaround has been found here), or it might be
		3603	confused.
		3604
		3605	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3606	make it into some kind of religion.
		3607
		3608	If you are unsure about something, feel free to contact the mailing list
		3609	with the full valgrind report and an explanation on why you think this
		3610	is a bug in libev (best check the archives, too :). However, don't be
		3611	annoyed when you get a brisk "this is no bug" answer and take the chance
		3612	of learning how to interpret valgrind properly.
		3613
		3614	If you need, for some reason, empty reports from valgrind for your project
		3615	I suggest using suppression lists.
		3616
		3617
		3618	=head1 PORTABILITY NOTES
		3619
		3620	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3078		3621
3079	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3622	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3080	requires, and its I/O model is fundamentally incompatible with the POSIX	3623	requires, and its I/O model is fundamentally incompatible with the POSIX
3081	model. Libev still offers limited functionality on this platform in	3624	model. Libev still offers limited functionality on this platform in
3082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3625	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3083	descriptors. This only applies when using Win32 natively, not when using	3626	descriptors. This only applies when using Win32 natively, not when using
3084	e.g. cygwin.	3627	e.g. cygwin.
3085		3628
		3629	Lifting these limitations would basically require the full
		3630	re-implementation of the I/O system. If you are into these kinds of
		3631	things, then note that glib does exactly that for you in a very portable
		3632	way (note also that glib is the slowest event library known to man).
		3633
3086	There is no supported compilation method available on windows except	3634	There is no supported compilation method available on windows except
3087	embedding it into other applications.	3635	embedding it into other applications.
3088		3636
		3637	Not a libev limitation but worth mentioning: windows apparently doesn't
		3638	accept large writes: instead of resulting in a partial write, windows will
		3639	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3640	so make sure you only write small amounts into your sockets (less than a
		3641	megabyte seems safe, but this apparently depends on the amount of memory
		3642	available).
		3643
3089	Due to the many, low, and arbitrary limits on the win32 platform and the	3644	Due to the many, low, and arbitrary limits on the win32 platform and
3090	abysmal performance of winsockets, using a large number of sockets is not	3645	the abysmal performance of winsockets, using a large number of sockets
3091	recommended (and not reasonable). If your program needs to use more than	3646	is not recommended (and not reasonable). If your program needs to use
3092	a hundred or so sockets, then likely it needs to use a totally different	3647	more than a hundred or so sockets, then likely it needs to use a totally
3093	implementation for windows, as libev offers the POSIX model, which cannot	3648	different implementation for windows, as libev offers the POSIX readiness
3094	be implemented efficiently on windows (microsoft monopoly games).	3649	notification model, which cannot be implemented efficiently on windows
		3650	(Microsoft monopoly games).
		3651
		3652	A typical way to use libev under windows is to embed it (see the embedding
		3653	section for details) and use the following F<evwrap.h> header file instead
		3654	of F<ev.h>:
		3655
		3656	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3657	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3658
		3659	#include "ev.h"
		3660
		3661	And compile the following F<evwrap.c> file into your project (make sure
		3662	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3663
		3664	#include "evwrap.h"
		3665	#include "ev.c"
3095		3666
3096	=over 4	3667	=over 4
3097		3668
3098	=item The winsocket select function	3669	=item The winsocket select function
3099		3670
3100	The winsocket C<select> function doesn't follow POSIX in that it requires	3671	The winsocket C<select> function doesn't follow POSIX in that it
3101	socket I<handles> and not socket I<file descriptors>. This makes select	3672	requires socket I<handles> and not socket I<file descriptors> (it is
3102	very inefficient, and also requires a mapping from file descriptors	3673	also extremely buggy). This makes select very inefficient, and also
3103	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3674	requires a mapping from file descriptors to socket handles (the Microsoft
3104	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3675	C runtime provides the function C<_open_osfhandle> for this). See the
3105	symbols for more info.	3676	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3677	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3106		3678
3107	The configuration for a "naked" win32 using the microsoft runtime	3679	The configuration for a "naked" win32 using the Microsoft runtime
3108	libraries and raw winsocket select is:	3680	libraries and raw winsocket select is:
3109		3681
3110	#define EV_USE_SELECT 1	3682	#define EV_USE_SELECT 1
3111	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3683	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3112		3684
3113	Note that winsockets handling of fd sets is O(n), so you can easily get a	3685	Note that winsockets handling of fd sets is O(n), so you can easily get a
3114	complexity in the O(n²) range when using win32.	3686	complexity in the O(n²) range when using win32.
3115		3687
3116	=item Limited number of file descriptors	3688	=item Limited number of file descriptors
3117		3689
3118	Windows has numerous arbitrary (and low) limits on things. Early versions	3690	Windows has numerous arbitrary (and low) limits on things.
3119	of winsocket's select only supported waiting for a max. of C<64> handles	3691
		3692	Early versions of winsocket's select only supported waiting for a maximum
3120	(probably owning to the fact that all windows kernels can only wait for	3693	of C<64> handles (probably owning to the fact that all windows kernels
3121	C<64> things at the same time internally; microsoft recommends spawning a	3694	can only wait for C<64> things at the same time internally; Microsoft
3122	chain of threads and wait for 63 handles and the previous thread in each).	3695	recommends spawning a chain of threads and wait for 63 handles and the
		3696	previous thread in each. Great).
3123		3697
3124	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3698	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3125	to some high number (e.g. C<2048>) before compiling the winsocket select	3699	to some high number (e.g. C<2048>) before compiling the winsocket select
3126	call (which might be in libev or elsewhere, for example, perl does its own	3700	call (which might be in libev or elsewhere, for example, perl does its own
3127	select emulation on windows).	3701	select emulation on windows).
3128		3702
3129	Another limit is the number of file descriptors in the microsoft runtime	3703	Another limit is the number of file descriptors in the Microsoft runtime
3130	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3704	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3131	or something like this inside microsoft). You can increase this by calling	3705	or something like this inside Microsoft). You can increase this by calling
3132	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3706	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3133	arbitrary limit), but is broken in many versions of the microsoft runtime	3707	arbitrary limit), but is broken in many versions of the Microsoft runtime
3134	libraries.	3708	libraries.
3135		3709
3136	This might get you to about C<512> or C<2048> sockets (depending on	3710	This might get you to about C<512> or C<2048> sockets (depending on
3137	windows version and/or the phase of the moon). To get more, you need to	3711	windows version and/or the phase of the moon). To get more, you need to
3138	wrap all I/O functions and provide your own fd management, but the cost of	3712	wrap all I/O functions and provide your own fd management, but the cost of
3139	calling select (O(n²)) will likely make this unworkable.	3713	calling select (O(n²)) will likely make this unworkable.
3140		3714
3141	=back	3715	=back
3142		3716
		3717	=head2 PORTABILITY REQUIREMENTS
		3718
		3719	In addition to a working ISO-C implementation and of course the
		3720	backend-specific APIs, libev relies on a few additional extensions:
		3721
		3722	=over 4
		3723
		3724	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3725	calling conventions regardless of C<ev_watcher_type *>.
		3726
		3727	Libev assumes not only that all watcher pointers have the same internal
		3728	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3729	assumes that the same (machine) code can be used to call any watcher
		3730	callback: The watcher callbacks have different type signatures, but libev
		3731	calls them using an C<ev_watcher *> internally.
		3732
		3733	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3734
		3735	The type C<sig_atomic_t volatile> (or whatever is defined as
		3736	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3737	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3738	believed to be sufficiently portable.
		3739
		3740	=item C<sigprocmask> must work in a threaded environment
		3741
		3742	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3743	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3744	pthread implementations will either allow C<sigprocmask> in the "main
		3745	thread" or will block signals process-wide, both behaviours would
		3746	be compatible with libev. Interaction between C<sigprocmask> and
		3747	C<pthread_sigmask> could complicate things, however.
		3748
		3749	The most portable way to handle signals is to block signals in all threads
		3750	except the initial one, and run the default loop in the initial thread as
		3751	well.
		3752
		3753	=item C<long> must be large enough for common memory allocation sizes
		3754
		3755	To improve portability and simplify its API, libev uses C<long> internally
		3756	instead of C<size_t> when allocating its data structures. On non-POSIX
		3757	systems (Microsoft...) this might be unexpectedly low, but is still at
		3758	least 31 bits everywhere, which is enough for hundreds of millions of
		3759	watchers.
		3760
		3761	=item C<double> must hold a time value in seconds with enough accuracy
		3762
		3763	The type C<double> is used to represent timestamps. It is required to
		3764	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3765	enough for at least into the year 4000. This requirement is fulfilled by
		3766	implementations implementing IEEE 754 (basically all existing ones).
		3767
		3768	=back
		3769
		3770	If you know of other additional requirements drop me a note.
		3771
		3772
		3773	=head1 ALGORITHMIC COMPLEXITIES
		3774
		3775	In this section the complexities of (many of) the algorithms used inside
		3776	libev will be documented. For complexity discussions about backends see
		3777	the documentation for C<ev_default_init>.
		3778
		3779	All of the following are about amortised time: If an array needs to be
		3780	extended, libev needs to realloc and move the whole array, but this
		3781	happens asymptotically rarer with higher number of elements, so O(1) might
		3782	mean that libev does a lengthy realloc operation in rare cases, but on
		3783	average it is much faster and asymptotically approaches constant time.
		3784
		3785	=over 4
		3786
		3787	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3788
		3789	This means that, when you have a watcher that triggers in one hour and
		3790	there are 100 watchers that would trigger before that, then inserting will
		3791	have to skip roughly seven (C<ld 100>) of these watchers.
		3792
		3793	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3794
		3795	That means that changing a timer costs less than removing/adding them,
		3796	as only the relative motion in the event queue has to be paid for.
		3797
		3798	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3799
		3800	These just add the watcher into an array or at the head of a list.
		3801
		3802	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3803
		3804	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3805
		3806	These watchers are stored in lists, so they need to be walked to find the
		3807	correct watcher to remove. The lists are usually short (you don't usually
		3808	have many watchers waiting for the same fd or signal: one is typical, two
		3809	is rare).
		3810
		3811	=item Finding the next timer in each loop iteration: O(1)
		3812
		3813	By virtue of using a binary or 4-heap, the next timer is always found at a
		3814	fixed position in the storage array.
		3815
		3816	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3817
		3818	A change means an I/O watcher gets started or stopped, which requires
		3819	libev to recalculate its status (and possibly tell the kernel, depending
		3820	on backend and whether C<ev_io_set> was used).
		3821
		3822	=item Activating one watcher (putting it into the pending state): O(1)
		3823
		3824	=item Priority handling: O(number_of_priorities)
		3825
		3826	Priorities are implemented by allocating some space for each
		3827	priority. When doing priority-based operations, libev usually has to
		3828	linearly search all the priorities, but starting/stopping and activating
		3829	watchers becomes O(1) with respect to priority handling.
		3830
		3831	=item Sending an ev_async: O(1)
		3832
		3833	=item Processing ev_async_send: O(number_of_async_watchers)
		3834
		3835	=item Processing signals: O(max_signal_number)
		3836
		3837	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3838	calls in the current loop iteration. Checking for async and signal events
		3839	involves iterating over all running async watchers or all signal numbers.
		3840
		3841	=back
		3842
3143		3843
3144	=head1 AUTHOR	3844	=head1 AUTHOR
3145		3845
3146	Marc Lehmann <libev@schmorp.de>.	3846	Marc Lehmann <libev@schmorp.de>.
3147		3847

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