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Revision 1.139 by root, Wed Apr 2 05:51:40 2008 UTC vs.
Revision 1.199 by root, Thu Oct 23 07:18:21 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<ev_loop *>. The library knows two
258	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
259	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
260
261	If you use threads, a common model is to run the default event loop
262	in your main thread (or in a separate thread) and for each thread you
263	create, you also create another event loop. Libev itself does no locking
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		284
268	=over 4	285	=over 4
269		286
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		288
…		…
281	from multiple threads, you have to lock (note also that this is unlikely,	298	from multiple threads, you have to lock (note also that this is unlikely,
282	as loops cannot bes hared easily between threads anyway).	299	as loops cannot bes hared easily between threads anyway).
283		300
284	The default loop is the only loop that can handle C<ev_signal> and	301	The default loop is the only loop that can handle C<ev_signal> and
285	C<ev_child> watchers, and to do this, it always registers a handler	302	C<ev_child> watchers, and to do this, it always registers a handler
286	for C<SIGCHLD>. If this is a problem for your app you can either	303	for C<SIGCHLD>. If this is a problem for your application you can either
287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
289	C<ev_default_init>.	306	C<ev_default_init>.
290		307
291	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
…		…
300	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
301	thing, believe me).	318	thing, believe me).
302		319
303	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
304		321
305	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
306	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
307	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
308	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
309	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
310	around bugs.	327	around bugs.
…		…
317		334
318	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
319	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
320	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
322	without a syscall and thus I<very> fast, but my GNU/Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
323	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
324		341
325	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
326	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
327	flag.	344	flag.
328		345
329	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
330	environment variable.	347	environment variable.
331		348
332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
333		350
334	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
336	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
337	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
338	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
339		356
340	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
341	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
342	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
343	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
344	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
345	readyness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
346		367
347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
348		369
349	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
350	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
351	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
352	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
353	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
354	performance tips.	375	performance tips.
355		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
356	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
357		381
358	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
359	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
360	like O(total_fds) where n is the total number of fds (or the highest fd),	384	like O(total_fds) where n is the total number of fds (or the highest fd),
361	epoll scales either O(1) or O(active_fds). The epoll design has a number	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
362	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
363	cases and rewiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
364	support for dup.	388	support for dup.
365		389
366	While stopping, setting and starting an I/O watcher in the same iteration	390	While stopping, setting and starting an I/O watcher in the same iteration
367	will result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
368	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
369	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
370	very well if you register events for both fds.	394	very well if you register events for both fds.
371		395
372	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
373	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
374	(or space) is available.	398	(or space) is available.
375		399
376	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
377	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible,
378	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
379		405
380	While nominally embeddeble in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
381	all kernel versions tested so far.	407	all kernel versions tested so far.
382		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
384		413
385	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
386	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
387	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
388	it's completely useless). For this reason it's not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
389	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
390	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
391	system like NetBSD.
392		420
393	You still can embed kqueue into a normal poll or select backend and use it	421	You still can embed kqueue into a normal poll or select backend and use it
394	only for sockets (after having made sure that sockets work with kqueue on	422	only for sockets (after having made sure that sockets work with kqueue on
395	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
396		424
397	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
398	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
399	course). While stopping, setting and starting an I/O watcher does never	427	course). While stopping, setting and starting an I/O watcher does never
400	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
401	two event changes per incident, support for C<fork ()> is very bad and it	429	two event changes per incident. Support for C<fork ()> is very bad and it
402	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
403		431
404	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
405		433
406	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
407	everywhere, so you might need to test for this. And since it is broken	435	everywhere, so you might need to test for this. And since it is broken
408	almost everywhere, you should only use it when you have a lot of sockets	436	almost everywhere, you should only use it when you have a lot of sockets
409	(for which it usually works), by embedding it into another event loop	437	(for which it usually works), by embedding it into another event loop
410	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
411	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
412		444
413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
414		446
415	This is not implemented yet (and might never be, unless you send me an	447	This is not implemented yet (and might never be, unless you send me an
416	implementation). According to reports, C</dev/poll> only supports sockets	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
421		453
422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
423	it's really slow, but it still scales very well (O(active_fds)).	455	it's really slow, but it still scales very well (O(active_fds)).
424		456
425	Please note that solaris event ports can deliver a lot of spurious	457	Please note that Solaris event ports can deliver a lot of spurious
426	notifications, so you need to use non-blocking I/O or other means to avoid	458	notifications, so you need to use non-blocking I/O or other means to avoid
427	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
428		460
429	While this backend scales well, it requires one system call per active	461	While this backend scales well, it requires one system call per active
430	file descriptor per loop iteration. For small and medium numbers of file	462	file descriptor per loop iteration. For small and medium numbers of file
431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
432	might perform better.	464	might perform better.
433		465
434	On the positive side, ignoring the spurious readyness notifications, this	466	On the positive side, with the exception of the spurious readiness
435	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
436	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
437		473
438	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
439		475
440	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
443		479
444	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
445		481
446	=back	482	=back
447		483
448	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
449	backends will be tried (in the reverse order as listed here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
450	specified, all backends in C<ev_recommended_backends ()> will be tried.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
451		487
452	The most typical usage is like this:	488	Example: This is the most typical usage.
453		489
454	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
456		492
457	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
458	environment settings to be taken into account:	494	environment settings to be taken into account:
459		495
460	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
461		497
462	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
463	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
464	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
465		502
466	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
467		504
468	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
469		506
470	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
471	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
…		…
476	libev with threads is indeed to create one loop per thread, and using the	513	libev with threads is indeed to create one loop per thread, and using the
477	default loop in the "main" or "initial" thread.	514	default loop in the "main" or "initial" thread.
478		515
479	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
480		517
481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
482	if (!epoller)	519	if (!epoller)
483	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
484		521
485	=item ev_default_destroy ()	522	=item ev_default_destroy ()
486		523
487	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
488	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
489	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
490	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
491	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
492	the easiest thing, you can just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
493	for example).	530	for example).
494		531
495	Note that certain global state, such as signal state, will not be freed by	532	Note that certain global state, such as signal state, will not be freed by
…		…
527		564
528	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
529		566
530	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
532	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
533		571
534	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
535		573
536	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
537		576
538	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
539		578
540	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
541	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
556	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
557	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
558	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
559	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
560		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
561	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
562		613
563	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
564	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
565	events.	616	events.
…		…
567	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
568	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
569		620
570	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
571	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
572	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
573	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
574	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
575		627
576	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
577	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
578	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
579		632
580	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
581	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
582	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
583	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
584	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
585	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
586	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
587		644
588	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
589		646
590	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
591	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
592	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
593	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
594	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
595	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
596	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
597	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
598	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
599	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
600	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
601	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
602	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
603	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
604	- Queue all outstanding timers.	662	- Queue all expired timers.
605	- Queue all outstanding periodics.	663	- Queue all expired periodics.
606	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
607	- Queue all check watchers.	665	- Queue all check watchers.
608	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
609	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
610	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
616	anymore.	674	anymore.
617		675
618	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
619	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
620	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
621	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
622		680
623	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
624		682
625	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
626	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
627	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
628	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
629		687
630	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
631		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
632	=item ev_ref (loop)	692	=item ev_ref (loop)
633		693
634	=item ev_unref (loop)	694	=item ev_unref (loop)
635		695
636	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
637	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
638	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
639	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
640	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
641	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
642	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
643	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
644	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
645	libraries. Just remember to I<unref after start> and I<ref before stop>	708	libraries. Just remember to I<unref after start> and I<ref before stop>
646	(but only if the watcher wasn't active before, or was active before,	709	(but only if the watcher wasn't active before, or was active before,
647	respectively).	710	respectively).
648		711
649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
650	running when nothing else is active.	713	running when nothing else is active.
651		714
652	struct ev_signal exitsig;	715	ev_signal exitsig;
653	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
654	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
655	evf_unref (loop);	718	evf_unref (loop);
656		719
657	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
658		721
659	ev_ref (loop);	722	ev_ref (loop);
660	ev_signal_stop (loop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
661		724
662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
663		726
664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
665		728
666	These advanced functions influence the time that libev will spend waiting	729	These advanced functions influence the time that libev will spend waiting
667	for events. Both are by default C<0>, meaning that libev will try to	730	for events. Both time intervals are by default C<0>, meaning that libev
668	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
669		733
670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
671	allows libev to delay invocation of I/O and timer/periodic callbacks to	735	allows libev to delay invocation of I/O and timer/periodic callbacks
672	increase efficiency of loop iterations.	736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
673		738
674	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
675	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
676	the program responsive, it also wastes a lot of CPU time to poll for new	741	program responsive, it also wastes a lot of CPU time to poll for new
677	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
678	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
679		744
680	By setting a higher I<io collect interval> you allow libev to spend more	745	By setting a higher I<io collect interval> you allow libev to spend more
681	time collecting I/O events, so you can handle more events per iteration,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
683	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	C<ev_timer>) will be not affected. Setting this to a non-null value will
684	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
685		750
686	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
687	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
688	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
689	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
690	any overhead in libev.	755	value will not introduce any overhead in libev.
691		756
692	Many (busy) programs can usually benefit by setting the io collect	757	Many (busy) programs can usually benefit by setting the I/O collect
693	interval to a value near C<0.1> or so, which is often enough for	758	interval to a value near C<0.1> or so, which is often enough for
694	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
695	usually doesn't make much sense to set it to a lower value than C<0.01>,	760	usually doesn't make much sense to set it to a lower value than C<0.01>,
696	as this approsaches the timing granularity of most systems.	761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
697		781
698	=back	782	=back
699		783
700		784
701	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
702		786
703	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
704	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
705	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
706		790
707	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
708	{	792	{
709	ev_io_stop (w);	793	ev_io_stop (w);
710	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
711	}	795	}
712		796
713	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
714	struct ev_io stdin_watcher;	798	ev_io stdin_watcher;
715	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
716	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
717	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
718	ev_loop (loop, 0);	802	ev_loop (loop, 0);
719		803
720	As you can see, you are responsible for allocating the memory for your	804	As you can see, you are responsible for allocating the memory for your
721	watcher structures (and it is usually a bad idea to do this on the stack,	805	watcher structures (and it is usually a bad idea to do this on the stack,
722	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
723		807
724	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
725	(watcher *, callback)>, which expects a callback to be provided. This	809	(watcher *, callback)>, which expects a callback to be provided. This
726	callback gets invoked each time the event occurs (or, in the case of io	810	callback gets invoked each time the event occurs (or, in the case of I/O
727	watchers, each time the event loop detects that the file descriptor given	811	watchers, each time the event loop detects that the file descriptor given
728	is readable and/or writable).	812	is readable and/or writable).
729		813
730	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
731	with arguments specific to this watcher type. There is also a macro	815	with arguments specific to this watcher type. There is also a macro
…		…
807		891
808	The given async watcher has been asynchronously notified (see C<ev_async>).	892	The given async watcher has been asynchronously notified (see C<ev_async>).
809		893
810	=item C<EV_ERROR>	894	=item C<EV_ERROR>
811		895
812	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
813	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
814	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
815	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
816	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
817		905
818	Libev will usually signal a few "dummy" events together with an error,	906	Libev will usually signal a few "dummy" events together with an error, for
819	for example it might indicate that a fd is readable or writable, and if	907	example it might indicate that a fd is readable or writable, and if your
820	your callbacks is well-written it can just attempt the operation and cope	908	callbacks is well-written it can just attempt the operation and cope with
821	with the error from read() or write(). This will not work in multithreaded	909	the error from read() or write(). This will not work in multi-threaded
822	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
823		912
824	=back	913	=back
825		914
826	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
827		916
…		…
840	which rolls both calls into one.	929	which rolls both calls into one.
841		930
842	You can reinitialise a watcher at any time as long as it has been stopped	931	You can reinitialise a watcher at any time as long as it has been stopped
843	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
844		933
845	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
846	int revents)>.	935	int revents)>.
		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
847		942
848	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
849		944
850	This macro initialises the type-specific parts of a watcher. You need to	945	This macro initialises the type-specific parts of a watcher. You need to
851	call C<ev_init> at least once before you call this macro, but you can	946	call C<ev_init> at least once before you call this macro, but you can
…		…
854	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
855		950
856	Although some watcher types do not have type-specific arguments	951	Although some watcher types do not have type-specific arguments
857	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
858		953
		954	See C<ev_init>, above, for an example.
		955
859	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
860		957
861	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
862	calls into a single call. This is the most convinient method to initialise	959	calls into a single call. This is the most convenient method to initialise
863	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
864		965
865	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
866		967
867	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
868	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
869		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
870	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
871		977
872	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
873	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
874	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
875	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
876	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
877	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
878		986
879	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
880		988
881	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
882	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
930		1038
931	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
932		1040
933	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
934	C<loop> nor C<revents> need to be valid as long as the watcher callback	1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
935	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
936		1045
937	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
938		1047
939	If the watcher is pending, this function returns clears its pending status	1048	If the watcher is pending, this function clears its pending status and
940	and returns its C<revents> bitset (as if its callback was invoked). If the	1049	returns its C<revents> bitset (as if its callback was invoked). If the
941	watcher isn't pending it does nothing and returns C<0>.	1050	watcher isn't pending it does nothing and returns C<0>.
942		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
943	=back	1055	=back
944		1056
945		1057
946	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
947		1059
948	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
949	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
950	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
951	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
952	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
953	data:	1065	data:
954		1066
955	struct my_io	1067	struct my_io
956	{	1068	{
957	struct ev_io io;	1069	ev_io io;
958	int otherfd;	1070	int otherfd;
959	void *somedata;	1071	void *somedata;
960	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
961	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
962		1078
963	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
964	can cast it back to your own type:	1080	can cast it back to your own type:
965		1081
966	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
967	{	1083	{
968	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
969	...	1085	...
970	}	1086	}
971		1087
972	More interesting and less C-conformant ways of casting your callback type	1088	More interesting and less C-conformant ways of casting your callback type
973	instead have been omitted.	1089	instead have been omitted.
974		1090
975	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
976	watchers:	1092	embedded watchers:
977		1093
978	struct my_biggy	1094	struct my_biggy
979	{	1095	{
980	int some_data;	1096	int some_data;
981	ev_timer t1;	1097	ev_timer t1;
982	ev_timer t2;	1098	ev_timer t2;
983	}	1099	}
984		1100
985	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1101	In this case getting the pointer to C<my_biggy> is a bit more
986	you need to use C<offsetof>:	1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
987		1106
988	#include <stddef.h>	1107	#include <stddef.h>
989		1108
990	static void	1109	static void
991	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ ev_timer *w, int revents)
992	{	1111	{
993	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
994	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
995	}	1114	}
996		1115
997	static void	1116	static void
998	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ ev_timer *w, int revents)
999	{	1118	{
1000	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
1001	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
1002	}	1121	}
1003		1122
1004		1123
1005	=head1 WATCHER TYPES	1124	=head1 WATCHER TYPES
1006		1125
1007	This section describes each watcher in detail, but will not repeat	1126	This section describes each watcher in detail, but will not repeat
…		…
1031	In general you can register as many read and/or write event watchers per	1150	In general you can register as many read and/or write event watchers per
1032	fd as you want (as long as you don't confuse yourself). Setting all file	1151	fd as you want (as long as you don't confuse yourself). Setting all file
1033	descriptors to non-blocking mode is also usually a good idea (but not	1152	descriptors to non-blocking mode is also usually a good idea (but not
1034	required if you know what you are doing).	1153	required if you know what you are doing).
1035		1154
1036	If you must do this, then force the use of a known-to-be-good backend	1155	If you cannot use non-blocking mode, then force the use of a
1037	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1156	known-to-be-good backend (at the time of this writing, this includes only
1038	C<EVBACKEND_POLL>).	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1039		1158
1040	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
1041	receive "spurious" readyness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
1042	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1043	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
1044	lot of those (for example solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
1045	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
1046	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1047	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1048		1167
1049	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
1050	play around with an Xlib connection), then you have to seperately re-test	1169	not play around with an Xlib connection), then you have to separately
1051	whether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
1052	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
1053	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
1054		1177
1055	=head3 The special problem of disappearing file descriptors	1178	=head3 The special problem of disappearing file descriptors
1056		1179
1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1058	descriptor (either by calling C<close> explicitly or by any other means,	1181	descriptor (either due to calling C<close> explicitly or any other means,
1059	such as C<dup>). The reason is that you register interest in some file	1182	such as C<dup2>). The reason is that you register interest in some file
1060	descriptor, but when it goes away, the operating system will silently drop	1183	descriptor, but when it goes away, the operating system will silently drop
1061	this interest. If another file descriptor with the same number then is	1184	this interest. If another file descriptor with the same number then is
1062	registered with libev, there is no efficient way to see that this is, in	1185	registered with libev, there is no efficient way to see that this is, in
1063	fact, a different file descriptor.	1186	fact, a different file descriptor.
1064		1187
…		…
1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1096	C<EVBACKEND_POLL>.	1219	C<EVBACKEND_POLL>.
1097		1220
1098	=head3 The special problem of SIGPIPE	1221	=head3 The special problem of SIGPIPE
1099		1222
1100	While not really specific to libev, it is easy to forget about SIGPIPE:	1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1101	when reading from a pipe whose other end has been closed, your program	1224	when writing to a pipe whose other end has been closed, your program gets
1102	gets send a SIGPIPE, which, by default, aborts your program. For most	1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
1103	programs this is sensible behaviour, for daemons, this is usually	1226	this is sensible behaviour, for daemons, this is usually undesirable.
1104	undesirable.
1105		1227
1106	So when you encounter spurious, unexplained daemon exits, make sure you	1228	So when you encounter spurious, unexplained daemon exits, make sure you
1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1108	somewhere, as that would have given you a big clue).	1230	somewhere, as that would have given you a big clue).
1109		1231
…		…
1115	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
1116		1238
1117	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
1118		1240
1119	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1120	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1242	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1121	C<EV_READ | EV_WRITE> to receive the given events.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1122		1244
1123	=item int fd [read-only]	1245	=item int fd [read-only]
1124		1246
1125	The file descriptor being watched.	1247	The file descriptor being watched.
1126		1248
…		…
1134		1256
1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1136	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
1137	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
1138		1260
1139	static void	1261	static void
1140	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1141	{	1263	{
1142	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
1143	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
1144	}	1266	}
1145		1267
1146	...	1268	...
1147	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
1148	struct ev_io stdin_readable;	1270	ev_io stdin_readable;
1149	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1150	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
1151	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
1152		1274
1153		1275
1154	=head2 C<ev_timer> - relative and optionally repeating timeouts	1276	=head2 C<ev_timer> - relative and optionally repeating timeouts
1155		1277
1156	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
1157	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
1158		1280
1159	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
1160	times out after an hour and you reset your system clock to last years	1282	times out after an hour and you reset your system clock to January last
1161	time, it will still time out after (roughly) and hour. "Roughly" because	1283	year, it will still time out after (roughly) one hour. "Roughly" because
1162	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1163	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
		1286
		1287	The callback is guaranteed to be invoked only I<after> its timeout has
		1288	passed, but if multiple timers become ready during the same loop iteration
		1289	then order of execution is undefined.
		1290
		1291	=head3 Be smart about timeouts
		1292
		1293	Many real-world problems involve some kind of timeout, usually for error
		1294	recovery. A typical example is an HTTP request - if the other side hangs,
		1295	you want to raise some error after a while.
		1296
		1297	What follows are some ways to handle this problem, from obvious and
		1298	inefficient to smart and efficient.
		1299
		1300	In the following, a 60 second activity timeout is assumed - a timeout that
		1301	gets reset to 60 seconds each time there is activity (e.g. each time some
		1302	data or other life sign was received).
		1303
		1304	=over 4
		1305
		1306	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1307
		1308	This is the most obvious, but not the most simple way: In the beginning,
		1309	start the watcher:
		1310
		1311	ev_timer_init (timer, callback, 60., 0.);
		1312	ev_timer_start (loop, timer);
		1313
		1314	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1315	and start it again:
		1316
		1317	ev_timer_stop (loop, timer);
		1318	ev_timer_set (timer, 60., 0.);
		1319	ev_timer_start (loop, timer);
		1320
		1321	This is relatively simple to implement, but means that each time there is
		1322	some activity, libev will first have to remove the timer from its internal
		1323	data structure and then add it again. Libev tries to be fast, but it's
		1324	still not a constant-time operation.
		1325
		1326	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1327
		1328	This is the easiest way, and involves using C<ev_timer_again> instead of
		1329	C<ev_timer_start>.
		1330
		1331	To implement this, configure an C<ev_timer> with a C<repeat> value
		1332	of C<60> and then call C<ev_timer_again> at start and each time you
		1333	successfully read or write some data. If you go into an idle state where
		1334	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1335	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1336
		1337	That means you can ignore both the C<ev_timer_start> function and the
		1338	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1339	member and C<ev_timer_again>.
		1340
		1341	At start:
		1342
		1343	ev_timer_init (timer, callback);
		1344	timer->repeat = 60.;
		1345	ev_timer_again (loop, timer);
		1346
		1347	Each time there is some activity:
		1348
		1349	ev_timer_again (loop, timer);
		1350
		1351	It is even possible to change the time-out on the fly, regardless of
		1352	whether the watcher is active or not:
		1353
		1354	timer->repeat = 30.;
		1355	ev_timer_again (loop, timer);
		1356
		1357	This is slightly more efficient then stopping/starting the timer each time
		1358	you want to modify its timeout value, as libev does not have to completely
		1359	remove and re-insert the timer from/into its internal data structure.
		1360
		1361	It is, however, even simpler than the "obvious" way to do it.
		1362
		1363	=item 3. Let the timer time out, but then re-arm it as required.
		1364
		1365	This method is more tricky, but usually most efficient: Most timeouts are
		1366	relatively long compared to the intervals between other activity - in
		1367	our example, within 60 seconds, there are usually many I/O events with
		1368	associated activity resets.
		1369
		1370	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1371	but remember the time of last activity, and check for a real timeout only
		1372	within the callback:
		1373
		1374	ev_tstamp last_activity; // time of last activity
		1375
		1376	static void
		1377	callback (EV_P_ ev_timer *w, int revents)
		1378	{
		1379	ev_tstamp now = ev_now (EV_A);
		1380	ev_tstamp timeout = last_activity + 60.;
		1381
		1382	// if last_activity + 60. is older than now, we did time out
		1383	if (timeout < now)
		1384	{
		1385	// timeout occured, take action
		1386	}
		1387	else
		1388	{
		1389	// callback was invoked, but there was some activity, re-arm
		1390	// the watcher to fire in last_activity + 60, which is
		1391	// guaranteed to be in the future, so "again" is positive:
		1392	w->again = timeout - now;
		1393	ev_timer_again (EV_A_ w);
		1394	}
		1395	}
		1396
		1397	To summarise the callback: first calculate the real timeout (defined
		1398	as "60 seconds after the last activity"), then check if that time has
		1399	been reached, which means something I<did>, in fact, time out. Otherwise
		1400	the callback was invoked too early (C<timeout> is in the future), so
		1401	re-schedule the timer to fire at that future time, to see if maybe we have
		1402	a timeout then.
		1403
		1404	Note how C<ev_timer_again> is used, taking advantage of the
		1405	C<ev_timer_again> optimisation when the timer is already running.
		1406
		1407	This scheme causes more callback invocations (about one every 60 seconds
		1408	minus half the average time between activity), but virtually no calls to
		1409	libev to change the timeout.
		1410
		1411	To start the timer, simply initialise the watcher and set C<last_activity>
		1412	to the current time (meaning we just have some activity :), then call the
		1413	callback, which will "do the right thing" and start the timer:
		1414
		1415	ev_timer_init (timer, callback);
		1416	last_activity = ev_now (loop);
		1417	callback (loop, timer, EV_TIMEOUT);
		1418
		1419	And when there is some activity, simply store the current time in
		1420	C<last_activity>, no libev calls at all:
		1421
		1422	last_actiivty = ev_now (loop);
		1423
		1424	This technique is slightly more complex, but in most cases where the
		1425	time-out is unlikely to be triggered, much more efficient.
		1426
		1427	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1428	callback :) - just change the timeout and invoke the callback, which will
		1429	fix things for you.
		1430
		1431	=item 4. Whee, use a double-linked list for your timeouts.
		1432
		1433	If there is not one request, but many thousands, all employing some kind
		1434	of timeout with the same timeout value, then one can do even better:
		1435
		1436	When starting the timeout, calculate the timeout value and put the timeout
		1437	at the I<end> of the list.
		1438
		1439	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1440	the list is expected to fire (for example, using the technique #3).
		1441
		1442	When there is some activity, remove the timer from the list, recalculate
		1443	the timeout, append it to the end of the list again, and make sure to
		1444	update the C<ev_timer> if it was taken from the beginning of the list.
		1445
		1446	This way, one can manage an unlimited number of timeouts in O(1) time for
		1447	starting, stopping and updating the timers, at the expense of a major
		1448	complication, and having to use a constant timeout. The constant timeout
		1449	ensures that the list stays sorted.
		1450
		1451	=back
		1452
		1453	So what method is the best?
		1454
		1455	The method #2 is a simple no-brain-required solution that is adequate in
		1456	most situations. Method #3 requires a bit more thinking, but handles many
		1457	cases better, and isn't very complicated either. In most case, choosing
		1458	either one is fine.
		1459
		1460	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1461	rather complicated, but extremely efficient, something that really pays
		1462	off after the first or so million of active timers, i.e. it's usually
		1463	overkill :)
		1464
		1465	=head3 The special problem of time updates
		1466
		1467	Establishing the current time is a costly operation (it usually takes at
		1468	least two system calls): EV therefore updates its idea of the current
		1469	time only before and after C<ev_loop> collects new events, which causes a
		1470	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1471	lots of events in one iteration.
1164		1472
1165	The relative timeouts are calculated relative to the C<ev_now ()>	1473	The relative timeouts are calculated relative to the C<ev_now ()>
1166	time. This is usually the right thing as this timestamp refers to the time	1474	time. This is usually the right thing as this timestamp refers to the time
1167	of the event triggering whatever timeout you are modifying/starting. If	1475	of the event triggering whatever timeout you are modifying/starting. If
1168	you suspect event processing to be delayed and you I<need> to base the timeout	1476	you suspect event processing to be delayed and you I<need> to base the
1169	on the current time, use something like this to adjust for this:	1477	timeout on the current time, use something like this to adjust for this:
1170		1478
1171	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1479	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1172		1480
1173	The callback is guarenteed to be invoked only when its timeout has passed,	1481	If the event loop is suspended for a long time, you can also force an
1174	but if multiple timers become ready during the same loop iteration then	1482	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1175	order of execution is undefined.	1483	()>.
1176		1484
1177	=head3 Watcher-Specific Functions and Data Members	1485	=head3 Watcher-Specific Functions and Data Members
1178		1486
1179	=over 4	1487	=over 4
1180		1488
1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1489	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1182		1490
1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1491	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1184		1492
1185	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1493	Configure the timer to trigger after C<after> seconds. If C<repeat>
1186	C<0.>, then it will automatically be stopped. If it is positive, then the	1494	is C<0.>, then it will automatically be stopped once the timeout is
1187	timer will automatically be configured to trigger again C<repeat> seconds	1495	reached. If it is positive, then the timer will automatically be
1188	later, again, and again, until stopped manually.	1496	configured to trigger again C<repeat> seconds later, again, and again,
		1497	until stopped manually.
1189		1498
1190	The timer itself will do a best-effort at avoiding drift, that is, if you	1499	The timer itself will do a best-effort at avoiding drift, that is, if
1191	configure a timer to trigger every 10 seconds, then it will trigger at	1500	you configure a timer to trigger every 10 seconds, then it will normally
1192	exactly 10 second intervals. If, however, your program cannot keep up with	1501	trigger at exactly 10 second intervals. If, however, your program cannot
1193	the timer (because it takes longer than those 10 seconds to do stuff) the	1502	keep up with the timer (because it takes longer than those 10 seconds to
1194	timer will not fire more than once per event loop iteration.	1503	do stuff) the timer will not fire more than once per event loop iteration.
1195		1504
1196	=item ev_timer_again (loop, ev_timer *)	1505	=item ev_timer_again (loop, ev_timer *)
1197		1506
1198	This will act as if the timer timed out and restart it again if it is	1507	This will act as if the timer timed out and restart it again if it is
1199	repeating. The exact semantics are:	1508	repeating. The exact semantics are:
1200		1509
1201	If the timer is pending, its pending status is cleared.	1510	If the timer is pending, its pending status is cleared.
1202		1511
1203	If the timer is started but nonrepeating, stop it (as if it timed out).	1512	If the timer is started but non-repeating, stop it (as if it timed out).
1204		1513
1205	If the timer is repeating, either start it if necessary (with the	1514	If the timer is repeating, either start it if necessary (with the
1206	C<repeat> value), or reset the running timer to the C<repeat> value.	1515	C<repeat> value), or reset the running timer to the C<repeat> value.
1207		1516
1208	This sounds a bit complicated, but here is a useful and typical	1517	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1209	example: Imagine you have a tcp connection and you want a so-called idle	1518	usage example.
1210	timeout, that is, you want to be called when there have been, say, 60
1211	seconds of inactivity on the socket. The easiest way to do this is to
1212	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1213	C<ev_timer_again> each time you successfully read or write some data. If
1214	you go into an idle state where you do not expect data to travel on the
1215	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1216	automatically restart it if need be.
1217
1218	That means you can ignore the C<after> value and C<ev_timer_start>
1219	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1220
1221	ev_timer_init (timer, callback, 0., 5.);
1222	ev_timer_again (loop, timer);
1223	...
1224	timer->again = 17.;
1225	ev_timer_again (loop, timer);
1226	...
1227	timer->again = 10.;
1228	ev_timer_again (loop, timer);
1229
1230	This is more slightly efficient then stopping/starting the timer each time
1231	you want to modify its timeout value.
1232		1519
1233	=item ev_tstamp repeat [read-write]	1520	=item ev_tstamp repeat [read-write]
1234		1521
1235	The current C<repeat> value. Will be used each time the watcher times out	1522	The current C<repeat> value. Will be used each time the watcher times out
1236	or C<ev_timer_again> is called and determines the next timeout (if any),	1523	or C<ev_timer_again> is called, and determines the next timeout (if any),
1237	which is also when any modifications are taken into account.	1524	which is also when any modifications are taken into account.
1238		1525
1239	=back	1526	=back
1240		1527
1241	=head3 Examples	1528	=head3 Examples
1242		1529
1243	Example: Create a timer that fires after 60 seconds.	1530	Example: Create a timer that fires after 60 seconds.
1244		1531
1245	static void	1532	static void
1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1533	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1247	{	1534	{
1248	.. one minute over, w is actually stopped right here	1535	.. one minute over, w is actually stopped right here
1249	}	1536	}
1250		1537
1251	struct ev_timer mytimer;	1538	ev_timer mytimer;
1252	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1539	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1253	ev_timer_start (loop, &mytimer);	1540	ev_timer_start (loop, &mytimer);
1254		1541
1255	Example: Create a timeout timer that times out after 10 seconds of	1542	Example: Create a timeout timer that times out after 10 seconds of
1256	inactivity.	1543	inactivity.
1257		1544
1258	static void	1545	static void
1259	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1546	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1260	{	1547	{
1261	.. ten seconds without any activity	1548	.. ten seconds without any activity
1262	}	1549	}
1263		1550
1264	struct ev_timer mytimer;	1551	ev_timer mytimer;
1265	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1552	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1266	ev_timer_again (&mytimer); /* start timer */	1553	ev_timer_again (&mytimer); /* start timer */
1267	ev_loop (loop, 0);	1554	ev_loop (loop, 0);
1268		1555
1269	// and in some piece of code that gets executed on any "activity":	1556	// and in some piece of code that gets executed on any "activity":
1270	// reset the timeout to start ticking again at 10 seconds	1557	// reset the timeout to start ticking again at 10 seconds
1271	ev_timer_again (&mytimer);	1558	ev_timer_again (&mytimer);
1272		1559
1273		1560
1274	=head2 C<ev_periodic> - to cron or not to cron?	1561	=head2 C<ev_periodic> - to cron or not to cron?
1275		1562
1276	Periodic watchers are also timers of a kind, but they are very versatile	1563	Periodic watchers are also timers of a kind, but they are very versatile
1277	(and unfortunately a bit complex).	1564	(and unfortunately a bit complex).
1278		1565
1279	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1566	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1280	but on wallclock time (absolute time). You can tell a periodic watcher	1567	but on wall clock time (absolute time). You can tell a periodic watcher
1281	to trigger "at" some specific point in time. For example, if you tell a	1568	to trigger after some specific point in time. For example, if you tell a
1282	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1569	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1283	+ 10.>) and then reset your system clock to the last year, then it will	1570	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1571	clock to January of the previous year, then it will take more than year
1284	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1572	to trigger the event (unlike an C<ev_timer>, which would still trigger
1285	roughly 10 seconds later).	1573	roughly 10 seconds later as it uses a relative timeout).
1286		1574
1287	They can also be used to implement vastly more complex timers, such as	1575	C<ev_periodic>s can also be used to implement vastly more complex timers,
1288	triggering an event on each midnight, local time or other, complicated,	1576	such as triggering an event on each "midnight, local time", or other
1289	rules.	1577	complicated rules.
1290		1578
1291	As with timers, the callback is guarenteed to be invoked only when the	1579	As with timers, the callback is guaranteed to be invoked only when the
1292	time (C<at>) has been passed, but if multiple periodic timers become ready	1580	time (C<at>) has passed, but if multiple periodic timers become ready
1293	during the same loop iteration then order of execution is undefined.	1581	during the same loop iteration, then order of execution is undefined.
1294		1582
1295	=head3 Watcher-Specific Functions and Data Members	1583	=head3 Watcher-Specific Functions and Data Members
1296		1584
1297	=over 4	1585	=over 4
1298		1586
1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1587	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1300		1588
1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1589	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1302		1590
1303	Lots of arguments, lets sort it out... There are basically three modes of	1591	Lots of arguments, lets sort it out... There are basically three modes of
1304	operation, and we will explain them from simplest to complex:	1592	operation, and we will explain them from simplest to most complex:
1305		1593
1306	=over 4	1594	=over 4
1307		1595
1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1596	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1309		1597
1310	In this configuration the watcher triggers an event at the wallclock time	1598	In this configuration the watcher triggers an event after the wall clock
1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1599	time C<at> has passed. It will not repeat and will not adjust when a time
1312	that is, if it is to be run at January 1st 2011 then it will run when the	1600	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1313	system time reaches or surpasses this time.	1601	only run when the system clock reaches or surpasses this time.
1314		1602
1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1603	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1316		1604
1317	In this mode the watcher will always be scheduled to time out at the next	1605	In this mode the watcher will always be scheduled to time out at the next
1318	C<at + N * interval> time (for some integer N, which can also be negative)	1606	C<at + N * interval> time (for some integer N, which can also be negative)
1319	and then repeat, regardless of any time jumps.	1607	and then repeat, regardless of any time jumps.
1320		1608
1321	This can be used to create timers that do not drift with respect to system	1609	This can be used to create timers that do not drift with respect to the
1322	time:	1610	system clock, for example, here is a C<ev_periodic> that triggers each
		1611	hour, on the hour:
1323		1612
1324	ev_periodic_set (&periodic, 0., 3600., 0);	1613	ev_periodic_set (&periodic, 0., 3600., 0);
1325		1614
1326	This doesn't mean there will always be 3600 seconds in between triggers,	1615	This doesn't mean there will always be 3600 seconds in between triggers,
1327	but only that the the callback will be called when the system time shows a	1616	but only that the callback will be called when the system time shows a
1328	full hour (UTC), or more correctly, when the system time is evenly divisible	1617	full hour (UTC), or more correctly, when the system time is evenly divisible
1329	by 3600.	1618	by 3600.
1330		1619
1331	Another way to think about it (for the mathematically inclined) is that	1620	Another way to think about it (for the mathematically inclined) is that
1332	C<ev_periodic> will try to run the callback in this mode at the next possible	1621	C<ev_periodic> will try to run the callback in this mode at the next possible
1333	time where C<time = at (mod interval)>, regardless of any time jumps.	1622	time where C<time = at (mod interval)>, regardless of any time jumps.
1334		1623
1335	For numerical stability it is preferable that the C<at> value is near	1624	For numerical stability it is preferable that the C<at> value is near
1336	C<ev_now ()> (the current time), but there is no range requirement for	1625	C<ev_now ()> (the current time), but there is no range requirement for
1337	this value.	1626	this value, and in fact is often specified as zero.
		1627
		1628	Note also that there is an upper limit to how often a timer can fire (CPU
		1629	speed for example), so if C<interval> is very small then timing stability
		1630	will of course deteriorate. Libev itself tries to be exact to be about one
		1631	millisecond (if the OS supports it and the machine is fast enough).
1338		1632
1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1633	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1340		1634
1341	In this mode the values for C<interval> and C<at> are both being	1635	In this mode the values for C<interval> and C<at> are both being
1342	ignored. Instead, each time the periodic watcher gets scheduled, the	1636	ignored. Instead, each time the periodic watcher gets scheduled, the
1343	reschedule callback will be called with the watcher as first, and the	1637	reschedule callback will be called with the watcher as first, and the
1344	current time as second argument.	1638	current time as second argument.
1345		1639
1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1640	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1347	ever, or make any event loop modifications>. If you need to stop it,	1641	ever, or make ANY event loop modifications whatsoever>.
1348	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1349	starting an C<ev_prepare> watcher, which is legal).
1350		1642
		1643	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1644	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1645	only event loop modification you are allowed to do).
		1646
1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1647	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1352	ev_tstamp now)>, e.g.:	1648	*w, ev_tstamp now)>, e.g.:
1353		1649
		1650	static ev_tstamp
1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1651	my_rescheduler (ev_periodic *w, ev_tstamp now)
1355	{	1652	{
1356	return now + 60.;	1653	return now + 60.;
1357	}	1654	}
1358		1655
1359	It must return the next time to trigger, based on the passed time value	1656	It must return the next time to trigger, based on the passed time value
1360	(that is, the lowest time value larger than to the second argument). It	1657	(that is, the lowest time value larger than to the second argument). It
1361	will usually be called just before the callback will be triggered, but	1658	will usually be called just before the callback will be triggered, but
1362	might be called at other times, too.	1659	might be called at other times, too.
1363		1660
1364	NOTE: I<< This callback must always return a time that is later than the	1661	NOTE: I<< This callback must always return a time that is higher than or
1365	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1662	equal to the passed C<now> value >>.
1366		1663
1367	This can be used to create very complex timers, such as a timer that	1664	This can be used to create very complex timers, such as a timer that
1368	triggers on each midnight, local time. To do this, you would calculate the	1665	triggers on "next midnight, local time". To do this, you would calculate the
1369	next midnight after C<now> and return the timestamp value for this. How	1666	next midnight after C<now> and return the timestamp value for this. How
1370	you do this is, again, up to you (but it is not trivial, which is the main	1667	you do this is, again, up to you (but it is not trivial, which is the main
1371	reason I omitted it as an example).	1668	reason I omitted it as an example).
1372		1669
1373	=back	1670	=back
…		…
1377	Simply stops and restarts the periodic watcher again. This is only useful	1674	Simply stops and restarts the periodic watcher again. This is only useful
1378	when you changed some parameters or the reschedule callback would return	1675	when you changed some parameters or the reschedule callback would return
1379	a different time than the last time it was called (e.g. in a crond like	1676	a different time than the last time it was called (e.g. in a crond like
1380	program when the crontabs have changed).	1677	program when the crontabs have changed).
1381		1678
		1679	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1680
		1681	When active, returns the absolute time that the watcher is supposed to
		1682	trigger next.
		1683
1382	=item ev_tstamp offset [read-write]	1684	=item ev_tstamp offset [read-write]
1383		1685
1384	When repeating, this contains the offset value, otherwise this is the	1686	When repeating, this contains the offset value, otherwise this is the
1385	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1687	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1386		1688
…		…
1391		1693
1392	The current interval value. Can be modified any time, but changes only	1694	The current interval value. Can be modified any time, but changes only
1393	take effect when the periodic timer fires or C<ev_periodic_again> is being	1695	take effect when the periodic timer fires or C<ev_periodic_again> is being
1394	called.	1696	called.
1395		1697
1396	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1698	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1397		1699
1398	The current reschedule callback, or C<0>, if this functionality is	1700	The current reschedule callback, or C<0>, if this functionality is
1399	switched off. Can be changed any time, but changes only take effect when	1701	switched off. Can be changed any time, but changes only take effect when
1400	the periodic timer fires or C<ev_periodic_again> is being called.	1702	the periodic timer fires or C<ev_periodic_again> is being called.
1401		1703
1402	=item ev_tstamp at [read-only]
1403
1404	When active, contains the absolute time that the watcher is supposed to
1405	trigger next.
1406
1407	=back	1704	=back
1408		1705
1409	=head3 Examples	1706	=head3 Examples
1410		1707
1411	Example: Call a callback every hour, or, more precisely, whenever the	1708	Example: Call a callback every hour, or, more precisely, whenever the
1412	system clock is divisible by 3600. The callback invocation times have	1709	system time is divisible by 3600. The callback invocation times have
1413	potentially a lot of jittering, but good long-term stability.	1710	potentially a lot of jitter, but good long-term stability.
1414		1711
1415	static void	1712	static void
1416	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1713	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1417	{	1714	{
1418	... its now a full hour (UTC, or TAI or whatever your clock follows)	1715	... its now a full hour (UTC, or TAI or whatever your clock follows)
1419	}	1716	}
1420		1717
1421	struct ev_periodic hourly_tick;	1718	ev_periodic hourly_tick;
1422	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1719	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1423	ev_periodic_start (loop, &hourly_tick);	1720	ev_periodic_start (loop, &hourly_tick);
1424		1721
1425	Example: The same as above, but use a reschedule callback to do it:	1722	Example: The same as above, but use a reschedule callback to do it:
1426		1723
1427	#include <math.h>	1724	#include <math.h>
1428		1725
1429	static ev_tstamp	1726	static ev_tstamp
1430	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1727	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1431	{	1728	{
1432	return fmod (now, 3600.) + 3600.;	1729	return now + (3600. - fmod (now, 3600.));
1433	}	1730	}
1434		1731
1435	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1732	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1436		1733
1437	Example: Call a callback every hour, starting now:	1734	Example: Call a callback every hour, starting now:
1438		1735
1439	struct ev_periodic hourly_tick;	1736	ev_periodic hourly_tick;
1440	ev_periodic_init (&hourly_tick, clock_cb,	1737	ev_periodic_init (&hourly_tick, clock_cb,
1441	fmod (ev_now (loop), 3600.), 3600., 0);	1738	fmod (ev_now (loop), 3600.), 3600., 0);
1442	ev_periodic_start (loop, &hourly_tick);	1739	ev_periodic_start (loop, &hourly_tick);
1443		1740
1444		1741
1445	=head2 C<ev_signal> - signal me when a signal gets signalled!	1742	=head2 C<ev_signal> - signal me when a signal gets signalled!
1446		1743
1447	Signal watchers will trigger an event when the process receives a specific	1744	Signal watchers will trigger an event when the process receives a specific
1448	signal one or more times. Even though signals are very asynchronous, libev	1745	signal one or more times. Even though signals are very asynchronous, libev
1449	will try it's best to deliver signals synchronously, i.e. as part of the	1746	will try it's best to deliver signals synchronously, i.e. as part of the
1450	normal event processing, like any other event.	1747	normal event processing, like any other event.
1451		1748
		1749	If you want signals asynchronously, just use C<sigaction> as you would
		1750	do without libev and forget about sharing the signal. You can even use
		1751	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1752
1452	You can configure as many watchers as you like per signal. Only when the	1753	You can configure as many watchers as you like per signal. Only when the
1453	first watcher gets started will libev actually register a signal watcher	1754	first watcher gets started will libev actually register a signal handler
1454	with the kernel (thus it coexists with your own signal handlers as long	1755	with the kernel (thus it coexists with your own signal handlers as long as
1455	as you don't register any with libev). Similarly, when the last signal	1756	you don't register any with libev for the same signal). Similarly, when
1456	watcher for a signal is stopped libev will reset the signal handler to	1757	the last signal watcher for a signal is stopped, libev will reset the
1457	SIG_DFL (regardless of what it was set to before).	1758	signal handler to SIG_DFL (regardless of what it was set to before).
1458		1759
1459	If possible and supported, libev will install its handlers with	1760	If possible and supported, libev will install its handlers with
1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1761	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1461	interrupted. If you have a problem with syscalls getting interrupted by	1762	interrupted. If you have a problem with system calls getting interrupted by
1462	signals you can block all signals in an C<ev_check> watcher and unblock	1763	signals you can block all signals in an C<ev_check> watcher and unblock
1463	them in an C<ev_prepare> watcher.	1764	them in an C<ev_prepare> watcher.
1464		1765
1465	=head3 Watcher-Specific Functions and Data Members	1766	=head3 Watcher-Specific Functions and Data Members
1466		1767
…		…
1479		1780
1480	=back	1781	=back
1481		1782
1482	=head3 Examples	1783	=head3 Examples
1483		1784
1484	Example: Try to exit cleanly on SIGINT and SIGTERM.	1785	Example: Try to exit cleanly on SIGINT.
1485		1786
1486	static void	1787	static void
1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1788	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1488	{	1789	{
1489	ev_unloop (loop, EVUNLOOP_ALL);	1790	ev_unloop (loop, EVUNLOOP_ALL);
1490	}	1791	}
1491		1792
1492	struct ev_signal signal_watcher;	1793	ev_signal signal_watcher;
1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1794	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1494	ev_signal_start (loop, &sigint_cb);	1795	ev_signal_start (loop, &signal_watcher);
1495		1796
1496		1797
1497	=head2 C<ev_child> - watch out for process status changes	1798	=head2 C<ev_child> - watch out for process status changes
1498		1799
1499	Child watchers trigger when your process receives a SIGCHLD in response to	1800	Child watchers trigger when your process receives a SIGCHLD in response to
1500	some child status changes (most typically when a child of yours dies). It	1801	some child status changes (most typically when a child of yours dies or
1501	is permissible to install a child watcher I<after> the child has been	1802	exits). It is permissible to install a child watcher I<after> the child
1502	forked (which implies it might have already exited), as long as the event	1803	has been forked (which implies it might have already exited), as long
1503	loop isn't entered (or is continued from a watcher).	1804	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1805	forking and then immediately registering a watcher for the child is fine,
		1806	but forking and registering a watcher a few event loop iterations later is
		1807	not.
1504		1808
1505	Only the default event loop is capable of handling signals, and therefore	1809	Only the default event loop is capable of handling signals, and therefore
1506	you can only rgeister child watchers in the default event loop.	1810	you can only register child watchers in the default event loop.
1507		1811
1508	=head3 Process Interaction	1812	=head3 Process Interaction
1509		1813
1510	Libev grabs C<SIGCHLD> as soon as the default event loop is	1814	Libev grabs C<SIGCHLD> as soon as the default event loop is
1511	initialised. This is necessary to guarantee proper behaviour even if	1815	initialised. This is necessary to guarantee proper behaviour even if
1512	the first child watcher is started after the child exits. The occurance	1816	the first child watcher is started after the child exits. The occurrence
1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1817	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1514	synchronously as part of the event loop processing. Libev always reaps all	1818	synchronously as part of the event loop processing. Libev always reaps all
1515	children, even ones not watched.	1819	children, even ones not watched.
1516		1820
1517	=head3 Overriding the Built-In Processing	1821	=head3 Overriding the Built-In Processing
…		…
1521	handler, you can override it easily by installing your own handler for	1825	handler, you can override it easily by installing your own handler for
1522	C<SIGCHLD> after initialising the default loop, and making sure the	1826	C<SIGCHLD> after initialising the default loop, and making sure the
1523	default loop never gets destroyed. You are encouraged, however, to use an	1827	default loop never gets destroyed. You are encouraged, however, to use an
1524	event-based approach to child reaping and thus use libev's support for	1828	event-based approach to child reaping and thus use libev's support for
1525	that, so other libev users can use C<ev_child> watchers freely.	1829	that, so other libev users can use C<ev_child> watchers freely.
		1830
		1831	=head3 Stopping the Child Watcher
		1832
		1833	Currently, the child watcher never gets stopped, even when the
		1834	child terminates, so normally one needs to stop the watcher in the
		1835	callback. Future versions of libev might stop the watcher automatically
		1836	when a child exit is detected.
1526		1837
1527	=head3 Watcher-Specific Functions and Data Members	1838	=head3 Watcher-Specific Functions and Data Members
1528		1839
1529	=over 4	1840	=over 4
1530		1841
…		…
1559	=head3 Examples	1870	=head3 Examples
1560		1871
1561	Example: C<fork()> a new process and install a child handler to wait for	1872	Example: C<fork()> a new process and install a child handler to wait for
1562	its completion.	1873	its completion.
1563		1874
1564	ev_child cw;	1875	ev_child cw;
1565		1876
1566	static void	1877	static void
1567	child_cb (EV_P_ struct ev_child *w, int revents)	1878	child_cb (EV_P_ ev_child *w, int revents)
1568	{	1879	{
1569	ev_child_stop (EV_A_ w);	1880	ev_child_stop (EV_A_ w);
1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1881	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1571	}	1882	}
1572		1883
1573	pid_t pid = fork ();	1884	pid_t pid = fork ();
1574		1885
1575	if (pid < 0)	1886	if (pid < 0)
1576	// error	1887	// error
1577	else if (pid == 0)	1888	else if (pid == 0)
1578	{	1889	{
1579	// the forked child executes here	1890	// the forked child executes here
1580	exit (1);	1891	exit (1);
1581	}	1892	}
1582	else	1893	else
1583	{	1894	{
1584	ev_child_init (&cw, child_cb, pid, 0);	1895	ev_child_init (&cw, child_cb, pid, 0);
1585	ev_child_start (EV_DEFAULT_ &cw);	1896	ev_child_start (EV_DEFAULT_ &cw);
1586	}	1897	}
1587		1898
1588		1899
1589	=head2 C<ev_stat> - did the file attributes just change?	1900	=head2 C<ev_stat> - did the file attributes just change?
1590		1901
1591	This watches a filesystem path for attribute changes. That is, it calls	1902	This watches a file system path for attribute changes. That is, it calls
1592	C<stat> regularly (or when the OS says it changed) and sees if it changed	1903	C<stat> regularly (or when the OS says it changed) and sees if it changed
1593	compared to the last time, invoking the callback if it did.	1904	compared to the last time, invoking the callback if it did.
1594		1905
1595	The path does not need to exist: changing from "path exists" to "path does	1906	The path does not need to exist: changing from "path exists" to "path does
1596	not exist" is a status change like any other. The condition "path does	1907	not exist" is a status change like any other. The condition "path does
…		…
1599	the stat buffer having unspecified contents.	1910	the stat buffer having unspecified contents.
1600		1911
1601	The path I<should> be absolute and I<must not> end in a slash. If it is	1912	The path I<should> be absolute and I<must not> end in a slash. If it is
1602	relative and your working directory changes, the behaviour is undefined.	1913	relative and your working directory changes, the behaviour is undefined.
1603		1914
1604	Since there is no standard to do this, the portable implementation simply	1915	Since there is no standard kernel interface to do this, the portable
1605	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1916	implementation simply calls C<stat (2)> regularly on the path to see if
1606	can specify a recommended polling interval for this case. If you specify	1917	it changed somehow. You can specify a recommended polling interval for
1607	a polling interval of C<0> (highly recommended!) then a I<suitable,	1918	this case. If you specify a polling interval of C<0> (highly recommended!)
1608	unspecified default> value will be used (which you can expect to be around	1919	then a I<suitable, unspecified default> value will be used (which
1609	five seconds, although this might change dynamically). Libev will also	1920	you can expect to be around five seconds, although this might change
1610	impose a minimum interval which is currently around C<0.1>, but thats	1921	dynamically). Libev will also impose a minimum interval which is currently
1611	usually overkill.	1922	around C<0.1>, but thats usually overkill.
1612		1923
1613	This watcher type is not meant for massive numbers of stat watchers,	1924	This watcher type is not meant for massive numbers of stat watchers,
1614	as even with OS-supported change notifications, this can be	1925	as even with OS-supported change notifications, this can be
1615	resource-intensive.	1926	resource-intensive.
1616		1927
1617	At the time of this writing, only the Linux inotify interface is	1928	At the time of this writing, the only OS-specific interface implemented
1618	implemented (implementing kqueue support is left as an exercise for the	1929	is the Linux inotify interface (implementing kqueue support is left as
1619	reader). Inotify will be used to give hints only and should not change the	1930	an exercise for the reader. Note, however, that the author sees no way
1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1931	of implementing C<ev_stat> semantics with kqueue).
1621	to fall back to regular polling again even with inotify, but changes are
1622	usually detected immediately, and if the file exists there will be no
1623	polling.
1624		1932
1625	=head3 ABI Issues (Largefile Support)	1933	=head3 ABI Issues (Largefile Support)
1626		1934
1627	Libev by default (unless the user overrides this) uses the default	1935	Libev by default (unless the user overrides this) uses the default
1628	compilation environment, which means that on systems with optionally	1936	compilation environment, which means that on systems with large file
1629	disabled large file support, you get the 32 bit version of the stat	1937	support disabled by default, you get the 32 bit version of the stat
1630	structure. When using the library from programs that change the ABI to	1938	structure. When using the library from programs that change the ABI to
1631	use 64 bit file offsets the programs will fail. In that case you have to	1939	use 64 bit file offsets the programs will fail. In that case you have to
1632	compile libev with the same flags to get binary compatibility. This is	1940	compile libev with the same flags to get binary compatibility. This is
1633	obviously the case with any flags that change the ABI, but the problem is	1941	obviously the case with any flags that change the ABI, but the problem is
1634	most noticably with ev_stat and largefile support.	1942	most noticeably disabled with ev_stat and large file support.
1635		1943
1636	=head3 Inotify	1944	The solution for this is to lobby your distribution maker to make large
		1945	file interfaces available by default (as e.g. FreeBSD does) and not
		1946	optional. Libev cannot simply switch on large file support because it has
		1947	to exchange stat structures with application programs compiled using the
		1948	default compilation environment.
1637		1949
		1950	=head3 Inotify and Kqueue
		1951
1638	When C<inotify (7)> support has been compiled into libev (generally only	1952	When C<inotify (7)> support has been compiled into libev (generally
		1953	only available with Linux 2.6.25 or above due to bugs in earlier
1639	available on Linux) and present at runtime, it will be used to speed up	1954	implementations) and present at runtime, it will be used to speed up
1640	change detection where possible. The inotify descriptor will be created lazily	1955	change detection where possible. The inotify descriptor will be created
1641	when the first C<ev_stat> watcher is being started.	1956	lazily when the first C<ev_stat> watcher is being started.
1642		1957
1643	Inotify presense does not change the semantics of C<ev_stat> watchers	1958	Inotify presence does not change the semantics of C<ev_stat> watchers
1644	except that changes might be detected earlier, and in some cases, to avoid	1959	except that changes might be detected earlier, and in some cases, to avoid
1645	making regular C<stat> calls. Even in the presense of inotify support	1960	making regular C<stat> calls. Even in the presence of inotify support
1646	there are many cases where libev has to resort to regular C<stat> polling.	1961	there are many cases where libev has to resort to regular C<stat> polling,
		1962	but as long as the path exists, libev usually gets away without polling.
1647		1963
1648	(There is no support for kqueue, as apparently it cannot be used to	1964	There is no support for kqueue, as apparently it cannot be used to
1649	implement this functionality, due to the requirement of having a file	1965	implement this functionality, due to the requirement of having a file
1650	descriptor open on the object at all times).	1966	descriptor open on the object at all times, and detecting renames, unlinks
		1967	etc. is difficult.
1651		1968
1652	=head3 The special problem of stat time resolution	1969	=head3 The special problem of stat time resolution
1653		1970
1654	The C<stat ()> syscall only supports full-second resolution portably, and	1971	The C<stat ()> system call only supports full-second resolution portably, and
1655	even on systems where the resolution is higher, many filesystems still	1972	even on systems where the resolution is higher, most file systems still
1656	only support whole seconds.	1973	only support whole seconds.
1657		1974
1658	That means that, if the time is the only thing that changes, you might	1975	That means that, if the time is the only thing that changes, you can
1659	miss updates: on the first update, C<ev_stat> detects a change and calls	1976	easily miss updates: on the first update, C<ev_stat> detects a change and
1660	your callback, which does something. When there is another update within	1977	calls your callback, which does something. When there is another update
1661	the same second, C<ev_stat> will be unable to detect it.	1978	within the same second, C<ev_stat> will be unable to detect unless the
		1979	stat data does change in other ways (e.g. file size).
1662		1980
1663	The solution to this is to delay acting on a change for a second (or till	1981	The solution to this is to delay acting on a change for slightly more
1664	the next second boundary), using a roughly one-second delay C<ev_timer>	1982	than a second (or till slightly after the next full second boundary), using
1665	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	1983	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1666	is added to work around small timing inconsistencies of some operating	1984	ev_timer_again (loop, w)>).
1667	systems.	1985
		1986	The C<.02> offset is added to work around small timing inconsistencies
		1987	of some operating systems (where the second counter of the current time
		1988	might be be delayed. One such system is the Linux kernel, where a call to
		1989	C<gettimeofday> might return a timestamp with a full second later than
		1990	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1991	update file times then there will be a small window where the kernel uses
		1992	the previous second to update file times but libev might already execute
		1993	the timer callback).
1668		1994
1669	=head3 Watcher-Specific Functions and Data Members	1995	=head3 Watcher-Specific Functions and Data Members
1670		1996
1671	=over 4	1997	=over 4
1672		1998
…		…
1678	C<path>. The C<interval> is a hint on how quickly a change is expected to	2004	C<path>. The C<interval> is a hint on how quickly a change is expected to
1679	be detected and should normally be specified as C<0> to let libev choose	2005	be detected and should normally be specified as C<0> to let libev choose
1680	a suitable value. The memory pointed to by C<path> must point to the same	2006	a suitable value. The memory pointed to by C<path> must point to the same
1681	path for as long as the watcher is active.	2007	path for as long as the watcher is active.
1682		2008
1683	The callback will be receive C<EV_STAT> when a change was detected,	2009	The callback will receive an C<EV_STAT> event when a change was detected,
1684	relative to the attributes at the time the watcher was started (or the	2010	relative to the attributes at the time the watcher was started (or the
1685	last change was detected).	2011	last change was detected).
1686		2012
1687	=item ev_stat_stat (loop, ev_stat *)	2013	=item ev_stat_stat (loop, ev_stat *)
1688		2014
1689	Updates the stat buffer immediately with new values. If you change the	2015	Updates the stat buffer immediately with new values. If you change the
1690	watched path in your callback, you could call this fucntion to avoid	2016	watched path in your callback, you could call this function to avoid
1691	detecting this change (while introducing a race condition). Can also be	2017	detecting this change (while introducing a race condition if you are not
1692	useful simply to find out the new values.	2018	the only one changing the path). Can also be useful simply to find out the
		2019	new values.
1693		2020
1694	=item ev_statdata attr [read-only]	2021	=item ev_statdata attr [read-only]
1695		2022
1696	The most-recently detected attributes of the file. Although the type is of	2023	The most-recently detected attributes of the file. Although the type is
1697	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2024	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1698	suitable for your system. If the C<st_nlink> member is C<0>, then there	2025	suitable for your system, but you can only rely on the POSIX-standardised
		2026	members to be present. If the C<st_nlink> member is C<0>, then there was
1699	was some error while C<stat>ing the file.	2027	some error while C<stat>ing the file.
1700		2028
1701	=item ev_statdata prev [read-only]	2029	=item ev_statdata prev [read-only]
1702		2030
1703	The previous attributes of the file. The callback gets invoked whenever	2031	The previous attributes of the file. The callback gets invoked whenever
1704	C<prev> != C<attr>.	2032	C<prev> != C<attr>, or, more precisely, one or more of these members
		2033	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2034	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1705		2035
1706	=item ev_tstamp interval [read-only]	2036	=item ev_tstamp interval [read-only]
1707		2037
1708	The specified interval.	2038	The specified interval.
1709		2039
1710	=item const char *path [read-only]	2040	=item const char *path [read-only]
1711		2041
1712	The filesystem path that is being watched.	2042	The file system path that is being watched.
1713		2043
1714	=back	2044	=back
1715		2045
1716	=head3 Examples	2046	=head3 Examples
1717		2047
1718	Example: Watch C</etc/passwd> for attribute changes.	2048	Example: Watch C</etc/passwd> for attribute changes.
1719		2049
1720	static void	2050	static void
1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2051	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1722	{	2052	{
1723	/* /etc/passwd changed in some way */	2053	/* /etc/passwd changed in some way */
1724	if (w->attr.st_nlink)	2054	if (w->attr.st_nlink)
1725	{	2055	{
1726	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2056	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1727	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2057	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1728	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2058	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1729	}	2059	}
1730	else	2060	else
1731	/* you shalt not abuse printf for puts */	2061	/* you shalt not abuse printf for puts */
1732	puts ("wow, /etc/passwd is not there, expect problems. "	2062	puts ("wow, /etc/passwd is not there, expect problems. "
1733	"if this is windows, they already arrived\n");	2063	"if this is windows, they already arrived\n");
1734	}	2064	}
1735		2065
1736	...	2066	...
1737	ev_stat passwd;	2067	ev_stat passwd;
1738		2068
1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2069	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1740	ev_stat_start (loop, &passwd);	2070	ev_stat_start (loop, &passwd);
1741		2071
1742	Example: Like above, but additionally use a one-second delay so we do not	2072	Example: Like above, but additionally use a one-second delay so we do not
1743	miss updates (however, frequent updates will delay processing, too, so	2073	miss updates (however, frequent updates will delay processing, too, so
1744	one might do the work both on C<ev_stat> callback invocation I<and> on	2074	one might do the work both on C<ev_stat> callback invocation I<and> on
1745	C<ev_timer> callback invocation).	2075	C<ev_timer> callback invocation).
1746		2076
1747	static ev_stat passwd;	2077	static ev_stat passwd;
1748	static ev_timer timer;	2078	static ev_timer timer;
1749		2079
1750	static void	2080	static void
1751	timer_cb (EV_P_ ev_timer *w, int revents)	2081	timer_cb (EV_P_ ev_timer *w, int revents)
1752	{	2082	{
1753	ev_timer_stop (EV_A_ w);	2083	ev_timer_stop (EV_A_ w);
1754		2084
1755	/* now it's one second after the most recent passwd change */	2085	/* now it's one second after the most recent passwd change */
1756	}	2086	}
1757		2087
1758	static void	2088	static void
1759	stat_cb (EV_P_ ev_stat *w, int revents)	2089	stat_cb (EV_P_ ev_stat *w, int revents)
1760	{	2090	{
1761	/* reset the one-second timer */	2091	/* reset the one-second timer */
1762	ev_timer_again (EV_A_ &timer);	2092	ev_timer_again (EV_A_ &timer);
1763	}	2093	}
1764		2094
1765	...	2095	...
1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2096	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1767	ev_stat_start (loop, &passwd);	2097	ev_stat_start (loop, &passwd);
1768	ev_timer_init (&timer, timer_cb, 0., 1.01);	2098	ev_timer_init (&timer, timer_cb, 0., 1.02);
1769		2099
1770		2100
1771	=head2 C<ev_idle> - when you've got nothing better to do...	2101	=head2 C<ev_idle> - when you've got nothing better to do...
1772		2102
1773	Idle watchers trigger events when no other events of the same or higher	2103	Idle watchers trigger events when no other events of the same or higher
1774	priority are pending (prepare, check and other idle watchers do not	2104	priority are pending (prepare, check and other idle watchers do not count
1775	count).	2105	as receiving "events").
1776		2106
1777	That is, as long as your process is busy handling sockets or timeouts	2107	That is, as long as your process is busy handling sockets or timeouts
1778	(or even signals, imagine) of the same or higher priority it will not be	2108	(or even signals, imagine) of the same or higher priority it will not be
1779	triggered. But when your process is idle (or only lower-priority watchers	2109	triggered. But when your process is idle (or only lower-priority watchers
1780	are pending), the idle watchers are being called once per event loop	2110	are pending), the idle watchers are being called once per event loop
…		…
1804	=head3 Examples	2134	=head3 Examples
1805		2135
1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2136	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1807	callback, free it. Also, use no error checking, as usual.	2137	callback, free it. Also, use no error checking, as usual.
1808		2138
1809	static void	2139	static void
1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2140	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1811	{	2141	{
1812	free (w);	2142	free (w);
1813	// now do something you wanted to do when the program has	2143	// now do something you wanted to do when the program has
1814	// no longer anything immediate to do.	2144	// no longer anything immediate to do.
1815	}	2145	}
1816		2146
1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2147	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1818	ev_idle_init (idle_watcher, idle_cb);	2148	ev_idle_init (idle_watcher, idle_cb);
1819	ev_idle_start (loop, idle_cb);	2149	ev_idle_start (loop, idle_cb);
1820		2150
1821		2151
1822	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2152	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1823		2153
1824	Prepare and check watchers are usually (but not always) used in tandem:	2154	Prepare and check watchers are usually (but not always) used in pairs:
1825	prepare watchers get invoked before the process blocks and check watchers	2155	prepare watchers get invoked before the process blocks and check watchers
1826	afterwards.	2156	afterwards.
1827		2157
1828	You I<must not> call C<ev_loop> or similar functions that enter	2158	You I<must not> call C<ev_loop> or similar functions that enter
1829	the current event loop from either C<ev_prepare> or C<ev_check>	2159	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1832	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2162	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1833	C<ev_check> so if you have one watcher of each kind they will always be	2163	C<ev_check> so if you have one watcher of each kind they will always be
1834	called in pairs bracketing the blocking call.	2164	called in pairs bracketing the blocking call.
1835		2165
1836	Their main purpose is to integrate other event mechanisms into libev and	2166	Their main purpose is to integrate other event mechanisms into libev and
1837	their use is somewhat advanced. This could be used, for example, to track	2167	their use is somewhat advanced. They could be used, for example, to track
1838	variable changes, implement your own watchers, integrate net-snmp or a	2168	variable changes, implement your own watchers, integrate net-snmp or a
1839	coroutine library and lots more. They are also occasionally useful if	2169	coroutine library and lots more. They are also occasionally useful if
1840	you cache some data and want to flush it before blocking (for example,	2170	you cache some data and want to flush it before blocking (for example,
1841	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2171	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1842	watcher).	2172	watcher).
1843		2173
1844	This is done by examining in each prepare call which file descriptors need	2174	This is done by examining in each prepare call which file descriptors
1845	to be watched by the other library, registering C<ev_io> watchers for	2175	need to be watched by the other library, registering C<ev_io> watchers
1846	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2176	for them and starting an C<ev_timer> watcher for any timeouts (many
1847	provide just this functionality). Then, in the check watcher you check for	2177	libraries provide exactly this functionality). Then, in the check watcher,
1848	any events that occured (by checking the pending status of all watchers	2178	you check for any events that occurred (by checking the pending status
1849	and stopping them) and call back into the library. The I/O and timer	2179	of all watchers and stopping them) and call back into the library. The
1850	callbacks will never actually be called (but must be valid nevertheless,	2180	I/O and timer callbacks will never actually be called (but must be valid
1851	because you never know, you know?).	2181	nevertheless, because you never know, you know?).
1852		2182
1853	As another example, the Perl Coro module uses these hooks to integrate	2183	As another example, the Perl Coro module uses these hooks to integrate
1854	coroutines into libev programs, by yielding to other active coroutines	2184	coroutines into libev programs, by yielding to other active coroutines
1855	during each prepare and only letting the process block if no coroutines	2185	during each prepare and only letting the process block if no coroutines
1856	are ready to run (it's actually more complicated: it only runs coroutines	2186	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1859	loop from blocking if lower-priority coroutines are active, thus mapping	2189	loop from blocking if lower-priority coroutines are active, thus mapping
1860	low-priority coroutines to idle/background tasks).	2190	low-priority coroutines to idle/background tasks).
1861		2191
1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2192	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1863	priority, to ensure that they are being run before any other watchers	2193	priority, to ensure that they are being run before any other watchers
		2194	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2195
1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2196	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1865	too) should not activate ("feed") events into libev. While libev fully	2197	activate ("feed") events into libev. While libev fully supports this, they
1866	supports this, they will be called before other C<ev_check> watchers	2198	might get executed before other C<ev_check> watchers did their job. As
1867	did their job. As C<ev_check> watchers are often used to embed other	2199	C<ev_check> watchers are often used to embed other (non-libev) event
1868	(non-libev) event loops those other event loops might be in an unusable	2200	loops those other event loops might be in an unusable state until their
1869	state until their C<ev_check> watcher ran (always remind yourself to	2201	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1870	coexist peacefully with others).	2202	others).
1871		2203
1872	=head3 Watcher-Specific Functions and Data Members	2204	=head3 Watcher-Specific Functions and Data Members
1873		2205
1874	=over 4	2206	=over 4
1875		2207
…		…
1877		2209
1878	=item ev_check_init (ev_check *, callback)	2210	=item ev_check_init (ev_check *, callback)
1879		2211
1880	Initialises and configures the prepare or check watcher - they have no	2212	Initialises and configures the prepare or check watcher - they have no
1881	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2213	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1882	macros, but using them is utterly, utterly and completely pointless.	2214	macros, but using them is utterly, utterly, utterly and completely
		2215	pointless.
1883		2216
1884	=back	2217	=back
1885		2218
1886	=head3 Examples	2219	=head3 Examples
1887		2220
1888	There are a number of principal ways to embed other event loops or modules	2221	There are a number of principal ways to embed other event loops or modules
1889	into libev. Here are some ideas on how to include libadns into libev	2222	into libev. Here are some ideas on how to include libadns into libev
1890	(there is a Perl module named C<EV::ADNS> that does this, which you could	2223	(there is a Perl module named C<EV::ADNS> that does this, which you could
1891	use for an actually working example. Another Perl module named C<EV::Glib>	2224	use as a working example. Another Perl module named C<EV::Glib> embeds a
1892	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2225	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1893	into the Glib event loop).	2226	Glib event loop).
1894		2227
1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2228	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1896	and in a check watcher, destroy them and call into libadns. What follows	2229	and in a check watcher, destroy them and call into libadns. What follows
1897	is pseudo-code only of course. This requires you to either use a low	2230	is pseudo-code only of course. This requires you to either use a low
1898	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2231	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1899	the callbacks for the IO/timeout watchers might not have been called yet.	2232	the callbacks for the IO/timeout watchers might not have been called yet.
1900		2233
1901	static ev_io iow [nfd];	2234	static ev_io iow [nfd];
1902	static ev_timer tw;	2235	static ev_timer tw;
1903		2236
1904	static void	2237	static void
1905	io_cb (ev_loop *loop, ev_io *w, int revents)	2238	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1906	{	2239	{
1907	}	2240	}
1908		2241
1909	// create io watchers for each fd and a timer before blocking	2242	// create io watchers for each fd and a timer before blocking
1910	static void	2243	static void
1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2244	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1912	{	2245	{
1913	int timeout = 3600000;	2246	int timeout = 3600000;
1914	struct pollfd fds [nfd];	2247	struct pollfd fds [nfd];
1915	// actual code will need to loop here and realloc etc.	2248	// actual code will need to loop here and realloc etc.
1916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2249	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1917		2250
1918	/* the callback is illegal, but won't be called as we stop during check */	2251	/* the callback is illegal, but won't be called as we stop during check */
1919	ev_timer_init (&tw, 0, timeout * 1e-3);	2252	ev_timer_init (&tw, 0, timeout * 1e-3);
1920	ev_timer_start (loop, &tw);	2253	ev_timer_start (loop, &tw);
1921		2254
1922	// create one ev_io per pollfd	2255	// create one ev_io per pollfd
1923	for (int i = 0; i < nfd; ++i)	2256	for (int i = 0; i < nfd; ++i)
1924	{	2257	{
1925	ev_io_init (iow + i, io_cb, fds [i].fd,	2258	ev_io_init (iow + i, io_cb, fds [i].fd,
1926	((fds [i].events & POLLIN ? EV_READ : 0)	2259	((fds [i].events & POLLIN ? EV_READ : 0)
1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2260	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1928		2261
1929	fds [i].revents = 0;	2262	fds [i].revents = 0;
1930	ev_io_start (loop, iow + i);	2263	ev_io_start (loop, iow + i);
1931	}	2264	}
1932	}	2265	}
1933		2266
1934	// stop all watchers after blocking	2267	// stop all watchers after blocking
1935	static void	2268	static void
1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2269	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1937	{	2270	{
1938	ev_timer_stop (loop, &tw);	2271	ev_timer_stop (loop, &tw);
1939		2272
1940	for (int i = 0; i < nfd; ++i)	2273	for (int i = 0; i < nfd; ++i)
1941	{	2274	{
1942	// set the relevant poll flags	2275	// set the relevant poll flags
1943	// could also call adns_processreadable etc. here	2276	// could also call adns_processreadable etc. here
1944	struct pollfd *fd = fds + i;	2277	struct pollfd *fd = fds + i;
1945	int revents = ev_clear_pending (iow + i);	2278	int revents = ev_clear_pending (iow + i);
1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2279	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2280	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1948		2281
1949	// now stop the watcher	2282	// now stop the watcher
1950	ev_io_stop (loop, iow + i);	2283	ev_io_stop (loop, iow + i);
1951	}	2284	}
1952		2285
1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2286	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1954	}	2287	}
1955		2288
1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2289	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1957	in the prepare watcher and would dispose of the check watcher.	2290	in the prepare watcher and would dispose of the check watcher.
1958		2291
1959	Method 3: If the module to be embedded supports explicit event	2292	Method 3: If the module to be embedded supports explicit event
1960	notification (adns does), you can also make use of the actual watcher	2293	notification (libadns does), you can also make use of the actual watcher
1961	callbacks, and only destroy/create the watchers in the prepare watcher.	2294	callbacks, and only destroy/create the watchers in the prepare watcher.
1962		2295
1963	static void	2296	static void
1964	timer_cb (EV_P_ ev_timer *w, int revents)	2297	timer_cb (EV_P_ ev_timer *w, int revents)
1965	{	2298	{
1966	adns_state ads = (adns_state)w->data;	2299	adns_state ads = (adns_state)w->data;
1967	update_now (EV_A);	2300	update_now (EV_A);
1968		2301
1969	adns_processtimeouts (ads, &tv_now);	2302	adns_processtimeouts (ads, &tv_now);
1970	}	2303	}
1971		2304
1972	static void	2305	static void
1973	io_cb (EV_P_ ev_io *w, int revents)	2306	io_cb (EV_P_ ev_io *w, int revents)
1974	{	2307	{
1975	adns_state ads = (adns_state)w->data;	2308	adns_state ads = (adns_state)w->data;
1976	update_now (EV_A);	2309	update_now (EV_A);
1977		2310
1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2311	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2312	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1980	}	2313	}
1981		2314
1982	// do not ever call adns_afterpoll	2315	// do not ever call adns_afterpoll
1983		2316
1984	Method 4: Do not use a prepare or check watcher because the module you	2317	Method 4: Do not use a prepare or check watcher because the module you
1985	want to embed is too inflexible to support it. Instead, youc na override	2318	want to embed is not flexible enough to support it. Instead, you can
1986	their poll function. The drawback with this solution is that the main	2319	override their poll function. The drawback with this solution is that the
1987	loop is now no longer controllable by EV. The C<Glib::EV> module does	2320	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1988	this.	2321	this approach, effectively embedding EV as a client into the horrible
		2322	libglib event loop.
1989		2323
1990	static gint	2324	static gint
1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2325	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1992	{	2326	{
1993	int got_events = 0;	2327	int got_events = 0;
1994		2328
1995	for (n = 0; n < nfds; ++n)	2329	for (n = 0; n < nfds; ++n)
1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2330	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1997		2331
1998	if (timeout >= 0)	2332	if (timeout >= 0)
1999	// create/start timer	2333	// create/start timer
2000		2334
2001	// poll	2335	// poll
2002	ev_loop (EV_A_ 0);	2336	ev_loop (EV_A_ 0);
2003		2337
2004	// stop timer again	2338	// stop timer again
2005	if (timeout >= 0)	2339	if (timeout >= 0)
2006	ev_timer_stop (EV_A_ &to);	2340	ev_timer_stop (EV_A_ &to);
2007		2341
2008	// stop io watchers again - their callbacks should have set	2342	// stop io watchers again - their callbacks should have set
2009	for (n = 0; n < nfds; ++n)	2343	for (n = 0; n < nfds; ++n)
2010	ev_io_stop (EV_A_ iow [n]);	2344	ev_io_stop (EV_A_ iow [n]);
2011		2345
2012	return got_events;	2346	return got_events;
2013	}	2347	}
2014		2348
2015		2349
2016	=head2 C<ev_embed> - when one backend isn't enough...	2350	=head2 C<ev_embed> - when one backend isn't enough...
2017		2351
2018	This is a rather advanced watcher type that lets you embed one event loop	2352	This is a rather advanced watcher type that lets you embed one event loop
…		…
2024	prioritise I/O.	2358	prioritise I/O.
2025		2359
2026	As an example for a bug workaround, the kqueue backend might only support	2360	As an example for a bug workaround, the kqueue backend might only support
2027	sockets on some platform, so it is unusable as generic backend, but you	2361	sockets on some platform, so it is unusable as generic backend, but you
2028	still want to make use of it because you have many sockets and it scales	2362	still want to make use of it because you have many sockets and it scales
2029	so nicely. In this case, you would create a kqueue-based loop and embed it	2363	so nicely. In this case, you would create a kqueue-based loop and embed
2030	into your default loop (which might use e.g. poll). Overall operation will	2364	it into your default loop (which might use e.g. poll). Overall operation
2031	be a bit slower because first libev has to poll and then call kevent, but	2365	will be a bit slower because first libev has to call C<poll> and then
2032	at least you can use both at what they are best.	2366	C<kevent>, but at least you can use both mechanisms for what they are
		2367	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2033		2368
2034	As for prioritising I/O: rarely you have the case where some fds have	2369	As for prioritising I/O: under rare circumstances you have the case where
2035	to be watched and handled very quickly (with low latency), and even	2370	some fds have to be watched and handled very quickly (with low latency),
2036	priorities and idle watchers might have too much overhead. In this case	2371	and even priorities and idle watchers might have too much overhead. In
2037	you would put all the high priority stuff in one loop and all the rest in	2372	this case you would put all the high priority stuff in one loop and all
2038	a second one, and embed the second one in the first.	2373	the rest in a second one, and embed the second one in the first.
2039		2374
2040	As long as the watcher is active, the callback will be invoked every time	2375	As long as the watcher is active, the callback will be invoked every time
2041	there might be events pending in the embedded loop. The callback must then	2376	there might be events pending in the embedded loop. The callback must then
2042	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2377	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2043	their callbacks (you could also start an idle watcher to give the embedded	2378	their callbacks (you could also start an idle watcher to give the embedded
…		…
2051	interested in that.	2386	interested in that.
2052		2387
2053	Also, there have not currently been made special provisions for forking:	2388	Also, there have not currently been made special provisions for forking:
2054	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2389	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2055	but you will also have to stop and restart any C<ev_embed> watchers	2390	but you will also have to stop and restart any C<ev_embed> watchers
2056	yourself.	2391	yourself - but you can use a fork watcher to handle this automatically,
		2392	and future versions of libev might do just that.
2057		2393
2058	Unfortunately, not all backends are embeddable, only the ones returned by	2394	Unfortunately, not all backends are embeddable: only the ones returned by
2059	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2395	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2060	portable one.	2396	portable one.
2061		2397
2062	So when you want to use this feature you will always have to be prepared	2398	So when you want to use this feature you will always have to be prepared
2063	that you cannot get an embeddable loop. The recommended way to get around	2399	that you cannot get an embeddable loop. The recommended way to get around
2064	this is to have a separate variables for your embeddable loop, try to	2400	this is to have a separate variables for your embeddable loop, try to
2065	create it, and if that fails, use the normal loop for everything.	2401	create it, and if that fails, use the normal loop for everything.
2066		2402
		2403	=head3 C<ev_embed> and fork
		2404
		2405	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2406	automatically be applied to the embedded loop as well, so no special
		2407	fork handling is required in that case. When the watcher is not running,
		2408	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2409	as applicable.
		2410
2067	=head3 Watcher-Specific Functions and Data Members	2411	=head3 Watcher-Specific Functions and Data Members
2068		2412
2069	=over 4	2413	=over 4
2070		2414
2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2415	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2074		2418
2075	Configures the watcher to embed the given loop, which must be	2419	Configures the watcher to embed the given loop, which must be
2076	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2420	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2077	invoked automatically, otherwise it is the responsibility of the callback	2421	invoked automatically, otherwise it is the responsibility of the callback
2078	to invoke it (it will continue to be called until the sweep has been done,	2422	to invoke it (it will continue to be called until the sweep has been done,
2079	if you do not want thta, you need to temporarily stop the embed watcher).	2423	if you do not want that, you need to temporarily stop the embed watcher).
2080		2424
2081	=item ev_embed_sweep (loop, ev_embed *)	2425	=item ev_embed_sweep (loop, ev_embed *)
2082		2426
2083	Make a single, non-blocking sweep over the embedded loop. This works	2427	Make a single, non-blocking sweep over the embedded loop. This works
2084	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2428	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2085	apropriate way for embedded loops.	2429	appropriate way for embedded loops.
2086		2430
2087	=item struct ev_loop *other [read-only]	2431	=item struct ev_loop *other [read-only]
2088		2432
2089	The embedded event loop.	2433	The embedded event loop.
2090		2434
…		…
2092		2436
2093	=head3 Examples	2437	=head3 Examples
2094		2438
2095	Example: Try to get an embeddable event loop and embed it into the default	2439	Example: Try to get an embeddable event loop and embed it into the default
2096	event loop. If that is not possible, use the default loop. The default	2440	event loop. If that is not possible, use the default loop. The default
2097	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2441	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2098	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2442	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2099	used).	2443	used).
2100		2444
2101	struct ev_loop *loop_hi = ev_default_init (0);	2445	struct ev_loop *loop_hi = ev_default_init (0);
2102	struct ev_loop *loop_lo = 0;	2446	struct ev_loop *loop_lo = 0;
2103	struct ev_embed embed;	2447	ev_embed embed;
2104		2448
2105	// see if there is a chance of getting one that works	2449	// see if there is a chance of getting one that works
2106	// (remember that a flags value of 0 means autodetection)	2450	// (remember that a flags value of 0 means autodetection)
2107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2451	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2452	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2109	: 0;	2453	: 0;
2110		2454
2111	// if we got one, then embed it, otherwise default to loop_hi	2455	// if we got one, then embed it, otherwise default to loop_hi
2112	if (loop_lo)	2456	if (loop_lo)
2113	{	2457	{
2114	ev_embed_init (&embed, 0, loop_lo);	2458	ev_embed_init (&embed, 0, loop_lo);
2115	ev_embed_start (loop_hi, &embed);	2459	ev_embed_start (loop_hi, &embed);
2116	}	2460	}
2117	else	2461	else
2118	loop_lo = loop_hi;	2462	loop_lo = loop_hi;
2119		2463
2120	Example: Check if kqueue is available but not recommended and create	2464	Example: Check if kqueue is available but not recommended and create
2121	a kqueue backend for use with sockets (which usually work with any	2465	a kqueue backend for use with sockets (which usually work with any
2122	kqueue implementation). Store the kqueue/socket-only event loop in	2466	kqueue implementation). Store the kqueue/socket-only event loop in
2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2467	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2124		2468
2125	struct ev_loop *loop = ev_default_init (0);	2469	struct ev_loop *loop = ev_default_init (0);
2126	struct ev_loop *loop_socket = 0;	2470	struct ev_loop *loop_socket = 0;
2127	struct ev_embed embed;	2471	ev_embed embed;
2128		2472
2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2473	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2474	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2131	{	2475	{
2132	ev_embed_init (&embed, 0, loop_socket);	2476	ev_embed_init (&embed, 0, loop_socket);
2133	ev_embed_start (loop, &embed);	2477	ev_embed_start (loop, &embed);
2134	}	2478	}
2135		2479
2136	if (!loop_socket)	2480	if (!loop_socket)
2137	loop_socket = loop;	2481	loop_socket = loop;
2138		2482
2139	// now use loop_socket for all sockets, and loop for everything else	2483	// now use loop_socket for all sockets, and loop for everything else
2140		2484
2141		2485
2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2486	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2143		2487
2144	Fork watchers are called when a C<fork ()> was detected (usually because	2488	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2188	is that the author does not know of a simple (or any) algorithm for a	2532	is that the author does not know of a simple (or any) algorithm for a
2189	multiple-writer-single-reader queue that works in all cases and doesn't	2533	multiple-writer-single-reader queue that works in all cases and doesn't
2190	need elaborate support such as pthreads.	2534	need elaborate support such as pthreads.
2191		2535
2192	That means that if you want to queue data, you have to provide your own	2536	That means that if you want to queue data, you have to provide your own
2193	queue. But at least I can tell you would implement locking around your	2537	queue. But at least I can tell you how to implement locking around your
2194	queue:	2538	queue:
2195		2539
2196	=over 4	2540	=over 4
2197		2541
2198	=item queueing from a signal handler context	2542	=item queueing from a signal handler context
2199		2543
2200	To implement race-free queueing, you simply add to the queue in the signal	2544	To implement race-free queueing, you simply add to the queue in the signal
2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2545	handler but you block the signal handler in the watcher callback. Here is
2202	some fictitiuous SIGUSR1 handler:	2546	an example that does that for some fictitious SIGUSR1 handler:
2203		2547
2204	static ev_async mysig;	2548	static ev_async mysig;
2205		2549
2206	static void	2550	static void
2207	sigusr1_handler (void)	2551	sigusr1_handler (void)
…		…
2274		2618
2275	=item ev_async_init (ev_async *, callback)	2619	=item ev_async_init (ev_async *, callback)
2276		2620
2277	Initialises and configures the async watcher - it has no parameters of any	2621	Initialises and configures the async watcher - it has no parameters of any
2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2622	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2279	believe me.	2623	trust me.
2280		2624
2281	=item ev_async_send (loop, ev_async *)	2625	=item ev_async_send (loop, ev_async *)
2282		2626
2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2627	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2628	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2285	C<ev_feed_event>, this call is safe to do in other threads, signal or	2629	C<ev_feed_event>, this call is safe to do from other threads, signal or
2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2630	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2287	section below on what exactly this means).	2631	section below on what exactly this means).
2288		2632
2289	This call incurs the overhead of a syscall only once per loop iteration,	2633	This call incurs the overhead of a system call only once per loop iteration,
2290	so while the overhead might be noticable, it doesn't apply to repeated	2634	so while the overhead might be noticeable, it doesn't apply to repeated
2291	calls to C<ev_async_send>.	2635	calls to C<ev_async_send>.
2292		2636
		2637	=item bool = ev_async_pending (ev_async *)
		2638
		2639	Returns a non-zero value when C<ev_async_send> has been called on the
		2640	watcher but the event has not yet been processed (or even noted) by the
		2641	event loop.
		2642
		2643	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2644	the loop iterates next and checks for the watcher to have become active,
		2645	it will reset the flag again. C<ev_async_pending> can be used to very
		2646	quickly check whether invoking the loop might be a good idea.
		2647
		2648	Not that this does I<not> check whether the watcher itself is pending, only
		2649	whether it has been requested to make this watcher pending.
		2650
2293	=back	2651	=back
2294		2652
2295		2653
2296	=head1 OTHER FUNCTIONS	2654	=head1 OTHER FUNCTIONS
2297		2655
…		…
2300	=over 4	2658	=over 4
2301		2659
2302	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2660	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2303		2661
2304	This function combines a simple timer and an I/O watcher, calls your	2662	This function combines a simple timer and an I/O watcher, calls your
2305	callback on whichever event happens first and automatically stop both	2663	callback on whichever event happens first and automatically stops both
2306	watchers. This is useful if you want to wait for a single event on an fd	2664	watchers. This is useful if you want to wait for a single event on an fd
2307	or timeout without having to allocate/configure/start/stop/free one or	2665	or timeout without having to allocate/configure/start/stop/free one or
2308	more watchers yourself.	2666	more watchers yourself.
2309		2667
2310	If C<fd> is less than 0, then no I/O watcher will be started and events	2668	If C<fd> is less than 0, then no I/O watcher will be started and the
2311	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2669	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2312	C<events> set will be craeted and started.	2670	the given C<fd> and C<events> set will be created and started.
2313		2671
2314	If C<timeout> is less than 0, then no timeout watcher will be	2672	If C<timeout> is less than 0, then no timeout watcher will be
2315	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2673	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2316	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2674	repeat = 0) will be started. C<0> is a valid timeout.
2317	dubious value.
2318		2675
2319	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2676	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2320	passed an C<revents> set like normal event callbacks (a combination of	2677	passed an C<revents> set like normal event callbacks (a combination of
2321	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2678	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2322	value passed to C<ev_once>:	2679	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2680	a timeout and an io event at the same time - you probably should give io
		2681	events precedence.
2323		2682
		2683	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2684
2324	static void stdin_ready (int revents, void *arg)	2685	static void stdin_ready (int revents, void *arg)
2325	{	2686	{
2326	if (revents & EV_TIMEOUT)
2327	/* doh, nothing entered */;
2328	else if (revents & EV_READ)	2687	if (revents & EV_READ)
2329	/* stdin might have data for us, joy! */;	2688	/* stdin might have data for us, joy! */;
		2689	else if (revents & EV_TIMEOUT)
		2690	/* doh, nothing entered */;
2330	}	2691	}
2331		2692
2332	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2693	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2333		2694
2334	=item ev_feed_event (ev_loop *, watcher *, int revents)	2695	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2335		2696
2336	Feeds the given event set into the event loop, as if the specified event	2697	Feeds the given event set into the event loop, as if the specified event
2337	had happened for the specified watcher (which must be a pointer to an	2698	had happened for the specified watcher (which must be a pointer to an
2338	initialised but not necessarily started event watcher).	2699	initialised but not necessarily started event watcher).
2339		2700
2340	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2701	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2341		2702
2342	Feed an event on the given fd, as if a file descriptor backend detected	2703	Feed an event on the given fd, as if a file descriptor backend detected
2343	the given events it.	2704	the given events it.
2344		2705
2345	=item ev_feed_signal_event (ev_loop *loop, int signum)	2706	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2346		2707
2347	Feed an event as if the given signal occured (C<loop> must be the default	2708	Feed an event as if the given signal occurred (C<loop> must be the default
2348	loop!).	2709	loop!).
2349		2710
2350	=back	2711	=back
2351		2712
2352		2713
…		…
2368		2729
2369	=item * Priorities are not currently supported. Initialising priorities	2730	=item * Priorities are not currently supported. Initialising priorities
2370	will fail and all watchers will have the same priority, even though there	2731	will fail and all watchers will have the same priority, even though there
2371	is an ev_pri field.	2732	is an ev_pri field.
2372		2733
		2734	=item * In libevent, the last base created gets the signals, in libev, the
		2735	first base created (== the default loop) gets the signals.
		2736
2373	=item * Other members are not supported.	2737	=item * Other members are not supported.
2374		2738
2375	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2739	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2376	to use the libev header file and library.	2740	to use the libev header file and library.
2377		2741
2378	=back	2742	=back
2379		2743
2380	=head1 C++ SUPPORT	2744	=head1 C++ SUPPORT
2381		2745
2382	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2746	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2383	you to use some convinience methods to start/stop watchers and also change	2747	you to use some convenience methods to start/stop watchers and also change
2384	the callback model to a model using method callbacks on objects.	2748	the callback model to a model using method callbacks on objects.
2385		2749
2386	To use it,	2750	To use it,
2387		2751
2388	#include <ev++.h>	2752	#include <ev++.h>
2389		2753
2390	This automatically includes F<ev.h> and puts all of its definitions (many	2754	This automatically includes F<ev.h> and puts all of its definitions (many
2391	of them macros) into the global namespace. All C++ specific things are	2755	of them macros) into the global namespace. All C++ specific things are
2392	put into the C<ev> namespace. It should support all the same embedding	2756	put into the C<ev> namespace. It should support all the same embedding
2393	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2757	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2460	your compiler is good :), then the method will be fully inlined into the	2824	your compiler is good :), then the method will be fully inlined into the
2461	thunking function, making it as fast as a direct C callback.	2825	thunking function, making it as fast as a direct C callback.
2462		2826
2463	Example: simple class declaration and watcher initialisation	2827	Example: simple class declaration and watcher initialisation
2464		2828
2465	struct myclass	2829	struct myclass
2466	{	2830	{
2467	void io_cb (ev::io &w, int revents) { }	2831	void io_cb (ev::io &w, int revents) { }
2468	}	2832	}
2469		2833
2470	myclass obj;	2834	myclass obj;
2471	ev::io iow;	2835	ev::io iow;
2472	iow.set <myclass, &myclass::io_cb> (&obj);	2836	iow.set <myclass, &myclass::io_cb> (&obj);
2473		2837
2474	=item w->set<function> (void *data = 0)	2838	=item w->set<function> (void *data = 0)
2475		2839
2476	Also sets a callback, but uses a static method or plain function as	2840	Also sets a callback, but uses a static method or plain function as
2477	callback. The optional C<data> argument will be stored in the watcher's	2841	callback. The optional C<data> argument will be stored in the watcher's
…		…
2479		2843
2480	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2844	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2481		2845
2482	See the method-C<set> above for more details.	2846	See the method-C<set> above for more details.
2483		2847
2484	Example:	2848	Example: Use a plain function as callback.
2485		2849
2486	static void io_cb (ev::io &w, int revents) { }	2850	static void io_cb (ev::io &w, int revents) { }
2487	iow.set <io_cb> ();	2851	iow.set <io_cb> ();
2488		2852
2489	=item w->set (struct ev_loop *)	2853	=item w->set (struct ev_loop *)
2490		2854
2491	Associates a different C<struct ev_loop> with this watcher. You can only	2855	Associates a different C<struct ev_loop> with this watcher. You can only
2492	do this when the watcher is inactive (and not pending either).	2856	do this when the watcher is inactive (and not pending either).
2493		2857
2494	=item w->set ([args])	2858	=item w->set ([arguments])
2495		2859
2496	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2860	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2497	called at least once. Unlike the C counterpart, an active watcher gets	2861	called at least once. Unlike the C counterpart, an active watcher gets
2498	automatically stopped and restarted when reconfiguring it with this	2862	automatically stopped and restarted when reconfiguring it with this
2499	method.	2863	method.
2500		2864
2501	=item w->start ()	2865	=item w->start ()
…		…
2525	=back	2889	=back
2526		2890
2527	Example: Define a class with an IO and idle watcher, start one of them in	2891	Example: Define a class with an IO and idle watcher, start one of them in
2528	the constructor.	2892	the constructor.
2529		2893
2530	class myclass	2894	class myclass
2531	{	2895	{
2532	ev::io io; void io_cb (ev::io &w, int revents);	2896	ev::io io ; void io_cb (ev::io &w, int revents);
2533	ev:idle idle void idle_cb (ev::idle &w, int revents);	2897	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2534		2898
2535	myclass (int fd)	2899	myclass (int fd)
2536	{	2900	{
2537	io .set <myclass, &myclass::io_cb > (this);	2901	io .set <myclass, &myclass::io_cb > (this);
2538	idle.set <myclass, &myclass::idle_cb> (this);	2902	idle.set <myclass, &myclass::idle_cb> (this);
2539		2903
2540	io.start (fd, ev::READ);	2904	io.start (fd, ev::READ);
2541	}	2905	}
2542	};	2906	};
2543		2907
2544		2908
2545	=head1 OTHER LANGUAGE BINDINGS	2909	=head1 OTHER LANGUAGE BINDINGS
2546		2910
2547	Libev does not offer other language bindings itself, but bindings for a	2911	Libev does not offer other language bindings itself, but bindings for a
2548	numbe rof languages exist in the form of third-party packages. If you know	2912	number of languages exist in the form of third-party packages. If you know
2549	any interesting language binding in addition to the ones listed here, drop	2913	any interesting language binding in addition to the ones listed here, drop
2550	me a note.	2914	me a note.
2551		2915
2552	=over 4	2916	=over 4
2553		2917
2554	=item Perl	2918	=item Perl
2555		2919
2556	The EV module implements the full libev API and is actually used to test	2920	The EV module implements the full libev API and is actually used to test
2557	libev. EV is developed together with libev. Apart from the EV core module,	2921	libev. EV is developed together with libev. Apart from the EV core module,
2558	there are additional modules that implement libev-compatible interfaces	2922	there are additional modules that implement libev-compatible interfaces
2559	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2923	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2560	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2924	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2925	and C<EV::Glib>).
2561		2926
2562	It can be found and installed via CPAN, its homepage is found at	2927	It can be found and installed via CPAN, its homepage is at
2563	L<http://software.schmorp.de/pkg/EV>.	2928	L<http://software.schmorp.de/pkg/EV>.
2564		2929
		2930	=item Python
		2931
		2932	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2933	seems to be quite complete and well-documented. Note, however, that the
		2934	patch they require for libev is outright dangerous as it breaks the ABI
		2935	for everybody else, and therefore, should never be applied in an installed
		2936	libev (if python requires an incompatible ABI then it needs to embed
		2937	libev).
		2938
2565	=item Ruby	2939	=item Ruby
2566		2940
2567	Tony Arcieri has written a ruby extension that offers access to a subset	2941	Tony Arcieri has written a ruby extension that offers access to a subset
2568	of the libev API and adds filehandle abstractions, asynchronous DNS and	2942	of the libev API and adds file handle abstractions, asynchronous DNS and
2569	more on top of it. It can be found via gem servers. Its homepage is at	2943	more on top of it. It can be found via gem servers. Its homepage is at
2570	L<http://rev.rubyforge.org/>.	2944	L<http://rev.rubyforge.org/>.
2571		2945
2572	=item D	2946	=item D
2573		2947
2574	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2948	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2575	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2949	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2576		2950
2577	=back	2951	=back
2578		2952
2579		2953
2580	=head1 MACRO MAGIC	2954	=head1 MACRO MAGIC
2581		2955
2582	Libev can be compiled with a variety of options, the most fundamantal	2956	Libev can be compiled with a variety of options, the most fundamental
2583	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2957	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2584	functions and callbacks have an initial C<struct ev_loop *> argument.	2958	functions and callbacks have an initial C<struct ev_loop *> argument.
2585		2959
2586	To make it easier to write programs that cope with either variant, the	2960	To make it easier to write programs that cope with either variant, the
2587	following macros are defined:	2961	following macros are defined:
…		…
2592		2966
2593	This provides the loop I<argument> for functions, if one is required ("ev	2967	This provides the loop I<argument> for functions, if one is required ("ev
2594	loop argument"). The C<EV_A> form is used when this is the sole argument,	2968	loop argument"). The C<EV_A> form is used when this is the sole argument,
2595	C<EV_A_> is used when other arguments are following. Example:	2969	C<EV_A_> is used when other arguments are following. Example:
2596		2970
2597	ev_unref (EV_A);	2971	ev_unref (EV_A);
2598	ev_timer_add (EV_A_ watcher);	2972	ev_timer_add (EV_A_ watcher);
2599	ev_loop (EV_A_ 0);	2973	ev_loop (EV_A_ 0);
2600		2974
2601	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2975	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2602	which is often provided by the following macro.	2976	which is often provided by the following macro.
2603		2977
2604	=item C<EV_P>, C<EV_P_>	2978	=item C<EV_P>, C<EV_P_>
2605		2979
2606	This provides the loop I<parameter> for functions, if one is required ("ev	2980	This provides the loop I<parameter> for functions, if one is required ("ev
2607	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2981	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2608	C<EV_P_> is used when other parameters are following. Example:	2982	C<EV_P_> is used when other parameters are following. Example:
2609		2983
2610	// this is how ev_unref is being declared	2984	// this is how ev_unref is being declared
2611	static void ev_unref (EV_P);	2985	static void ev_unref (EV_P);
2612		2986
2613	// this is how you can declare your typical callback	2987	// this is how you can declare your typical callback
2614	static void cb (EV_P_ ev_timer *w, int revents)	2988	static void cb (EV_P_ ev_timer *w, int revents)
2615		2989
2616	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2990	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2617	suitable for use with C<EV_A>.	2991	suitable for use with C<EV_A>.
2618		2992
2619	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2993	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2620		2994
2621	Similar to the other two macros, this gives you the value of the default	2995	Similar to the other two macros, this gives you the value of the default
2622	loop, if multiple loops are supported ("ev loop default").	2996	loop, if multiple loops are supported ("ev loop default").
		2997
		2998	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2999
		3000	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3001	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3002	is undefined when the default loop has not been initialised by a previous
		3003	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3004
		3005	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3006	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2623		3007
2624	=back	3008	=back
2625		3009
2626	Example: Declare and initialise a check watcher, utilising the above	3010	Example: Declare and initialise a check watcher, utilising the above
2627	macros so it will work regardless of whether multiple loops are supported	3011	macros so it will work regardless of whether multiple loops are supported
2628	or not.	3012	or not.
2629		3013
2630	static void	3014	static void
2631	check_cb (EV_P_ ev_timer *w, int revents)	3015	check_cb (EV_P_ ev_timer *w, int revents)
2632	{	3016	{
2633	ev_check_stop (EV_A_ w);	3017	ev_check_stop (EV_A_ w);
2634	}	3018	}
2635		3019
2636	ev_check check;	3020	ev_check check;
2637	ev_check_init (&check, check_cb);	3021	ev_check_init (&check, check_cb);
2638	ev_check_start (EV_DEFAULT_ &check);	3022	ev_check_start (EV_DEFAULT_ &check);
2639	ev_loop (EV_DEFAULT_ 0);	3023	ev_loop (EV_DEFAULT_ 0);
2640		3024
2641	=head1 EMBEDDING	3025	=head1 EMBEDDING
2642		3026
2643	Libev can (and often is) directly embedded into host	3027	Libev can (and often is) directly embedded into host
2644	applications. Examples of applications that embed it include the Deliantra	3028	applications. Examples of applications that embed it include the Deliantra
…		…
2651	libev somewhere in your source tree).	3035	libev somewhere in your source tree).
2652		3036
2653	=head2 FILESETS	3037	=head2 FILESETS
2654		3038
2655	Depending on what features you need you need to include one or more sets of files	3039	Depending on what features you need you need to include one or more sets of files
2656	in your app.	3040	in your application.
2657		3041
2658	=head3 CORE EVENT LOOP	3042	=head3 CORE EVENT LOOP
2659		3043
2660	To include only the libev core (all the C<ev_*> functions), with manual	3044	To include only the libev core (all the C<ev_*> functions), with manual
2661	configuration (no autoconf):	3045	configuration (no autoconf):
2662		3046
2663	#define EV_STANDALONE 1	3047	#define EV_STANDALONE 1
2664	#include "ev.c"	3048	#include "ev.c"
2665		3049
2666	This will automatically include F<ev.h>, too, and should be done in a	3050	This will automatically include F<ev.h>, too, and should be done in a
2667	single C source file only to provide the function implementations. To use	3051	single C source file only to provide the function implementations. To use
2668	it, do the same for F<ev.h> in all files wishing to use this API (best	3052	it, do the same for F<ev.h> in all files wishing to use this API (best
2669	done by writing a wrapper around F<ev.h> that you can include instead and	3053	done by writing a wrapper around F<ev.h> that you can include instead and
2670	where you can put other configuration options):	3054	where you can put other configuration options):
2671		3055
2672	#define EV_STANDALONE 1	3056	#define EV_STANDALONE 1
2673	#include "ev.h"	3057	#include "ev.h"
2674		3058
2675	Both header files and implementation files can be compiled with a C++	3059	Both header files and implementation files can be compiled with a C++
2676	compiler (at least, thats a stated goal, and breakage will be treated	3060	compiler (at least, thats a stated goal, and breakage will be treated
2677	as a bug).	3061	as a bug).
2678		3062
2679	You need the following files in your source tree, or in a directory	3063	You need the following files in your source tree, or in a directory
2680	in your include path (e.g. in libev/ when using -Ilibev):	3064	in your include path (e.g. in libev/ when using -Ilibev):
2681		3065
2682	ev.h	3066	ev.h
2683	ev.c	3067	ev.c
2684	ev_vars.h	3068	ev_vars.h
2685	ev_wrap.h	3069	ev_wrap.h
2686		3070
2687	ev_win32.c required on win32 platforms only	3071	ev_win32.c required on win32 platforms only
2688		3072
2689	ev_select.c only when select backend is enabled (which is enabled by default)	3073	ev_select.c only when select backend is enabled (which is enabled by default)
2690	ev_poll.c only when poll backend is enabled (disabled by default)	3074	ev_poll.c only when poll backend is enabled (disabled by default)
2691	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3075	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2692	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3076	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2693	ev_port.c only when the solaris port backend is enabled (disabled by default)	3077	ev_port.c only when the solaris port backend is enabled (disabled by default)
2694		3078
2695	F<ev.c> includes the backend files directly when enabled, so you only need	3079	F<ev.c> includes the backend files directly when enabled, so you only need
2696	to compile this single file.	3080	to compile this single file.
2697		3081
2698	=head3 LIBEVENT COMPATIBILITY API	3082	=head3 LIBEVENT COMPATIBILITY API
2699		3083
2700	To include the libevent compatibility API, also include:	3084	To include the libevent compatibility API, also include:
2701		3085
2702	#include "event.c"	3086	#include "event.c"
2703		3087
2704	in the file including F<ev.c>, and:	3088	in the file including F<ev.c>, and:
2705		3089
2706	#include "event.h"	3090	#include "event.h"
2707		3091
2708	in the files that want to use the libevent API. This also includes F<ev.h>.	3092	in the files that want to use the libevent API. This also includes F<ev.h>.
2709		3093
2710	You need the following additional files for this:	3094	You need the following additional files for this:
2711		3095
2712	event.h	3096	event.h
2713	event.c	3097	event.c
2714		3098
2715	=head3 AUTOCONF SUPPORT	3099	=head3 AUTOCONF SUPPORT
2716		3100
2717	Instead of using C<EV_STANDALONE=1> and providing your config in	3101	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2718	whatever way you want, you can also C<m4_include([libev.m4])> in your	3102	whatever way you want, you can also C<m4_include([libev.m4])> in your
2719	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3103	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2720	include F<config.h> and configure itself accordingly.	3104	include F<config.h> and configure itself accordingly.
2721		3105
2722	For this of course you need the m4 file:	3106	For this of course you need the m4 file:
2723		3107
2724	libev.m4	3108	libev.m4
2725		3109
2726	=head2 PREPROCESSOR SYMBOLS/MACROS	3110	=head2 PREPROCESSOR SYMBOLS/MACROS
2727		3111
2728	Libev can be configured via a variety of preprocessor symbols you have to define	3112	Libev can be configured via a variety of preprocessor symbols you have to
2729	before including any of its files. The default is not to build for multiplicity	3113	define before including any of its files. The default in the absence of
2730	and only include the select backend.	3114	autoconf is documented for every option.
2731		3115
2732	=over 4	3116	=over 4
2733		3117
2734	=item EV_STANDALONE	3118	=item EV_STANDALONE
2735		3119
…		…
2740	F<event.h> that are not directly supported by the libev core alone.	3124	F<event.h> that are not directly supported by the libev core alone.
2741		3125
2742	=item EV_USE_MONOTONIC	3126	=item EV_USE_MONOTONIC
2743		3127
2744	If defined to be C<1>, libev will try to detect the availability of the	3128	If defined to be C<1>, libev will try to detect the availability of the
2745	monotonic clock option at both compiletime and runtime. Otherwise no use	3129	monotonic clock option at both compile time and runtime. Otherwise no use
2746	of the monotonic clock option will be attempted. If you enable this, you	3130	of the monotonic clock option will be attempted. If you enable this, you
2747	usually have to link against librt or something similar. Enabling it when	3131	usually have to link against librt or something similar. Enabling it when
2748	the functionality isn't available is safe, though, although you have	3132	the functionality isn't available is safe, though, although you have
2749	to make sure you link against any libraries where the C<clock_gettime>	3133	to make sure you link against any libraries where the C<clock_gettime>
2750	function is hiding in (often F<-lrt>).	3134	function is hiding in (often F<-lrt>).
2751		3135
2752	=item EV_USE_REALTIME	3136	=item EV_USE_REALTIME
2753		3137
2754	If defined to be C<1>, libev will try to detect the availability of the	3138	If defined to be C<1>, libev will try to detect the availability of the
2755	realtime clock option at compiletime (and assume its availability at	3139	real-time clock option at compile time (and assume its availability at
2756	runtime if successful). Otherwise no use of the realtime clock option will	3140	runtime if successful). Otherwise no use of the real-time clock option will
2757	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3141	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2758	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3142	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2759	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3143	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2760		3144
2761	=item EV_USE_NANOSLEEP	3145	=item EV_USE_NANOSLEEP
2762		3146
2763	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3147	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2764	and will use it for delays. Otherwise it will use C<select ()>.	3148	and will use it for delays. Otherwise it will use C<select ()>.
2765		3149
		3150	=item EV_USE_EVENTFD
		3151
		3152	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3153	available and will probe for kernel support at runtime. This will improve
		3154	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3155	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3156	2.7 or newer, otherwise disabled.
		3157
2766	=item EV_USE_SELECT	3158	=item EV_USE_SELECT
2767		3159
2768	If undefined or defined to be C<1>, libev will compile in support for the	3160	If undefined or defined to be C<1>, libev will compile in support for the
2769	C<select>(2) backend. No attempt at autodetection will be done: if no	3161	C<select>(2) backend. No attempt at auto-detection will be done: if no
2770	other method takes over, select will be it. Otherwise the select backend	3162	other method takes over, select will be it. Otherwise the select backend
2771	will not be compiled in.	3163	will not be compiled in.
2772		3164
2773	=item EV_SELECT_USE_FD_SET	3165	=item EV_SELECT_USE_FD_SET
2774		3166
2775	If defined to C<1>, then the select backend will use the system C<fd_set>	3167	If defined to C<1>, then the select backend will use the system C<fd_set>
2776	structure. This is useful if libev doesn't compile due to a missing	3168	structure. This is useful if libev doesn't compile due to a missing
2777	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3169	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2778	exotic systems. This usually limits the range of file descriptors to some	3170	exotic systems. This usually limits the range of file descriptors to some
2779	low limit such as 1024 or might have other limitations (winsocket only	3171	low limit such as 1024 or might have other limitations (winsocket only
2780	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3172	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2781	influence the size of the C<fd_set> used.	3173	influence the size of the C<fd_set> used.
2782		3174
…		…
2806		3198
2807	=item EV_USE_EPOLL	3199	=item EV_USE_EPOLL
2808		3200
2809	If defined to be C<1>, libev will compile in support for the Linux	3201	If defined to be C<1>, libev will compile in support for the Linux
2810	C<epoll>(7) backend. Its availability will be detected at runtime,	3202	C<epoll>(7) backend. Its availability will be detected at runtime,
2811	otherwise another method will be used as fallback. This is the	3203	otherwise another method will be used as fallback. This is the preferred
2812	preferred backend for GNU/Linux systems.	3204	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3205	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2813		3206
2814	=item EV_USE_KQUEUE	3207	=item EV_USE_KQUEUE
2815		3208
2816	If defined to be C<1>, libev will compile in support for the BSD style	3209	If defined to be C<1>, libev will compile in support for the BSD style
2817	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3210	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2830	otherwise another method will be used as fallback. This is the preferred	3223	otherwise another method will be used as fallback. This is the preferred
2831	backend for Solaris 10 systems.	3224	backend for Solaris 10 systems.
2832		3225
2833	=item EV_USE_DEVPOLL	3226	=item EV_USE_DEVPOLL
2834		3227
2835	reserved for future expansion, works like the USE symbols above.	3228	Reserved for future expansion, works like the USE symbols above.
2836		3229
2837	=item EV_USE_INOTIFY	3230	=item EV_USE_INOTIFY
2838		3231
2839	If defined to be C<1>, libev will compile in support for the Linux inotify	3232	If defined to be C<1>, libev will compile in support for the Linux inotify
2840	interface to speed up C<ev_stat> watchers. Its actual availability will	3233	interface to speed up C<ev_stat> watchers. Its actual availability will
2841	be detected at runtime.	3234	be detected at runtime. If undefined, it will be enabled if the headers
		3235	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2842		3236
2843	=item EV_ATOMIC_T	3237	=item EV_ATOMIC_T
2844		3238
2845	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3239	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2846	access is atomic with respect to other threads or signal contexts. No such	3240	access is atomic with respect to other threads or signal contexts. No such
2847	type is easily found in the C language, so you can provide your own type	3241	type is easily found in the C language, so you can provide your own type
2848	that you know is safe for your purposes. It is used both for signal handler "locking"	3242	that you know is safe for your purposes. It is used both for signal handler "locking"
2849	as well as for signal and thread safety in C<ev_async> watchers.	3243	as well as for signal and thread safety in C<ev_async> watchers.
2850		3244
2851	In the absense of this define, libev will use C<sig_atomic_t volatile>	3245	In the absence of this define, libev will use C<sig_atomic_t volatile>
2852	(from F<signal.h>), which is usually good enough on most platforms.	3246	(from F<signal.h>), which is usually good enough on most platforms.
2853		3247
2854	=item EV_H	3248	=item EV_H
2855		3249
2856	The name of the F<ev.h> header file used to include it. The default if	3250	The name of the F<ev.h> header file used to include it. The default if
…		…
2895	When doing priority-based operations, libev usually has to linearly search	3289	When doing priority-based operations, libev usually has to linearly search
2896	all the priorities, so having many of them (hundreds) uses a lot of space	3290	all the priorities, so having many of them (hundreds) uses a lot of space
2897	and time, so using the defaults of five priorities (-2 .. +2) is usually	3291	and time, so using the defaults of five priorities (-2 .. +2) is usually
2898	fine.	3292	fine.
2899		3293
2900	If your embedding app does not need any priorities, defining these both to	3294	If your embedding application does not need any priorities, defining these
2901	C<0> will save some memory and cpu.	3295	both to C<0> will save some memory and CPU.
2902		3296
2903	=item EV_PERIODIC_ENABLE	3297	=item EV_PERIODIC_ENABLE
2904		3298
2905	If undefined or defined to be C<1>, then periodic timers are supported. If	3299	If undefined or defined to be C<1>, then periodic timers are supported. If
2906	defined to be C<0>, then they are not. Disabling them saves a few kB of	3300	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2913	code.	3307	code.
2914		3308
2915	=item EV_EMBED_ENABLE	3309	=item EV_EMBED_ENABLE
2916		3310
2917	If undefined or defined to be C<1>, then embed watchers are supported. If	3311	If undefined or defined to be C<1>, then embed watchers are supported. If
2918	defined to be C<0>, then they are not.	3312	defined to be C<0>, then they are not. Embed watchers rely on most other
		3313	watcher types, which therefore must not be disabled.
2919		3314
2920	=item EV_STAT_ENABLE	3315	=item EV_STAT_ENABLE
2921		3316
2922	If undefined or defined to be C<1>, then stat watchers are supported. If	3317	If undefined or defined to be C<1>, then stat watchers are supported. If
2923	defined to be C<0>, then they are not.	3318	defined to be C<0>, then they are not.
…		…
2933	defined to be C<0>, then they are not.	3328	defined to be C<0>, then they are not.
2934		3329
2935	=item EV_MINIMAL	3330	=item EV_MINIMAL
2936		3331
2937	If you need to shave off some kilobytes of code at the expense of some	3332	If you need to shave off some kilobytes of code at the expense of some
2938	speed, define this symbol to C<1>. Currently only used for gcc to override	3333	speed, define this symbol to C<1>. Currently this is used to override some
2939	some inlining decisions, saves roughly 30% codesize of amd64.	3334	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3335	much smaller 2-heap for timer management over the default 4-heap.
2940		3336
2941	=item EV_PID_HASHSIZE	3337	=item EV_PID_HASHSIZE
2942		3338
2943	C<ev_child> watchers use a small hash table to distribute workload by	3339	C<ev_child> watchers use a small hash table to distribute workload by
2944	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3340	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2951	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3347	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2952	usually more than enough. If you need to manage thousands of C<ev_stat>	3348	usually more than enough. If you need to manage thousands of C<ev_stat>
2953	watchers you might want to increase this value (I<must> be a power of	3349	watchers you might want to increase this value (I<must> be a power of
2954	two).	3350	two).
2955		3351
		3352	=item EV_USE_4HEAP
		3353
		3354	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3355	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3356	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3357	faster performance with many (thousands) of watchers.
		3358
		3359	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3360	(disabled).
		3361
		3362	=item EV_HEAP_CACHE_AT
		3363
		3364	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3365	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3366	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3367	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3368	but avoids random read accesses on heap changes. This improves performance
		3369	noticeably with many (hundreds) 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_VERIFY
		3375
		3376	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3377	be done: If set to C<0>, no internal verification code will be compiled
		3378	in. If set to C<1>, then verification code will be compiled in, but not
		3379	called. If set to C<2>, then the internal verification code will be
		3380	called once per loop, which can slow down libev. If set to C<3>, then the
		3381	verification code will be called very frequently, which will slow down
		3382	libev considerably.
		3383
		3384	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3385	C<0>.
		3386
2956	=item EV_COMMON	3387	=item EV_COMMON
2957		3388
2958	By default, all watchers have a C<void *data> member. By redefining	3389	By default, all watchers have a C<void *data> member. By redefining
2959	this macro to a something else you can include more and other types of	3390	this macro to a something else you can include more and other types of
2960	members. You have to define it each time you include one of the files,	3391	members. You have to define it each time you include one of the files,
2961	though, and it must be identical each time.	3392	though, and it must be identical each time.
2962		3393
2963	For example, the perl EV module uses something like this:	3394	For example, the perl EV module uses something like this:
2964		3395
2965	#define EV_COMMON \	3396	#define EV_COMMON \
2966	SV *self; /* contains this struct */ \	3397	SV *self; /* contains this struct */ \
2967	SV *cb_sv, *fh /* note no trailing ";" */	3398	SV *cb_sv, *fh /* note no trailing ";" */
2968		3399
2969	=item EV_CB_DECLARE (type)	3400	=item EV_CB_DECLARE (type)
2970		3401
2971	=item EV_CB_INVOKE (watcher, revents)	3402	=item EV_CB_INVOKE (watcher, revents)
2972		3403
…		…
2977	definition and a statement, respectively. See the F<ev.h> header file for	3408	definition and a statement, respectively. See the F<ev.h> header file for
2978	their default definitions. One possible use for overriding these is to	3409	their default definitions. One possible use for overriding these is to
2979	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3410	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2980	method calls instead of plain function calls in C++.	3411	method calls instead of plain function calls in C++.
2981		3412
		3413	=back
		3414
2982	=head2 EXPORTED API SYMBOLS	3415	=head2 EXPORTED API SYMBOLS
2983		3416
2984	If you need to re-export the API (e.g. via a dll) and you need a list of	3417	If you need to re-export the API (e.g. via a DLL) and you need a list of
2985	exported symbols, you can use the provided F<Symbol.*> files which list	3418	exported symbols, you can use the provided F<Symbol.*> files which list
2986	all public symbols, one per line:	3419	all public symbols, one per line:
2987		3420
2988	Symbols.ev for libev proper	3421	Symbols.ev for libev proper
2989	Symbols.event for the libevent emulation	3422	Symbols.event for the libevent emulation
2990		3423
2991	This can also be used to rename all public symbols to avoid clashes with	3424	This can also be used to rename all public symbols to avoid clashes with
2992	multiple versions of libev linked together (which is obviously bad in	3425	multiple versions of libev linked together (which is obviously bad in
2993	itself, but sometimes it is inconvinient to avoid this).	3426	itself, but sometimes it is inconvenient to avoid this).
2994		3427
2995	A sed command like this will create wrapper C<#define>'s that you need to	3428	A sed command like this will create wrapper C<#define>'s that you need to
2996	include before including F<ev.h>:	3429	include before including F<ev.h>:
2997		3430
2998	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3431	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3015	file.	3448	file.
3016		3449
3017	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3450	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3018	that everybody includes and which overrides some configure choices:	3451	that everybody includes and which overrides some configure choices:
3019		3452
3020	#define EV_MINIMAL 1	3453	#define EV_MINIMAL 1
3021	#define EV_USE_POLL 0	3454	#define EV_USE_POLL 0
3022	#define EV_MULTIPLICITY 0	3455	#define EV_MULTIPLICITY 0
3023	#define EV_PERIODIC_ENABLE 0	3456	#define EV_PERIODIC_ENABLE 0
3024	#define EV_STAT_ENABLE 0	3457	#define EV_STAT_ENABLE 0
3025	#define EV_FORK_ENABLE 0	3458	#define EV_FORK_ENABLE 0
3026	#define EV_CONFIG_H <config.h>	3459	#define EV_CONFIG_H <config.h>
3027	#define EV_MINPRI 0	3460	#define EV_MINPRI 0
3028	#define EV_MAXPRI 0	3461	#define EV_MAXPRI 0
3029		3462
3030	#include "ev++.h"	3463	#include "ev++.h"
3031		3464
3032	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3465	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3033		3466
3034	#include "ev_cpp.h"	3467	#include "ev_cpp.h"
3035	#include "ev.c"	3468	#include "ev.c"
3036		3469
		3470	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3037		3471
3038	=head1 COMPLEXITIES	3472	=head2 THREADS AND COROUTINES
3039		3473
3040	In this section the complexities of (many of) the algorithms used inside	3474	=head3 THREADS
3041	libev will be explained. For complexity discussions about backends see the
3042	documentation for C<ev_default_init>.
3043		3475
3044	All of the following are about amortised time: If an array needs to be	3476	All libev functions are reentrant and thread-safe unless explicitly
3045	extended, libev needs to realloc and move the whole array, but this	3477	documented otherwise, but libev implements no locking itself. This means
3046	happens asymptotically never with higher number of elements, so O(1) might	3478	that you can use as many loops as you want in parallel, as long as there
3047	mean it might do a lengthy realloc operation in rare cases, but on average	3479	are no concurrent calls into any libev function with the same loop
3048	it is much faster and asymptotically approaches constant time.	3480	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3481	of course): libev guarantees that different event loops share no data
		3482	structures that need any locking.
		3483
		3484	Or to put it differently: calls with different loop parameters can be done
		3485	concurrently from multiple threads, calls with the same loop parameter
		3486	must be done serially (but can be done from different threads, as long as
		3487	only one thread ever is inside a call at any point in time, e.g. by using
		3488	a mutex per loop).
		3489
		3490	Specifically to support threads (and signal handlers), libev implements
		3491	so-called C<ev_async> watchers, which allow some limited form of
		3492	concurrency on the same event loop, namely waking it up "from the
		3493	outside".
		3494
		3495	If you want to know which design (one loop, locking, or multiple loops
		3496	without or something else still) is best for your problem, then I cannot
		3497	help you, but here is some generic advice:
3049		3498
3050	=over 4	3499	=over 4
3051		3500
3052	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3501	=item * most applications have a main thread: use the default libev loop
		3502	in that thread, or create a separate thread running only the default loop.
3053		3503
3054	This means that, when you have a watcher that triggers in one hour and	3504	This helps integrating other libraries or software modules that use libev
3055	there are 100 watchers that would trigger before that then inserting will	3505	themselves and don't care/know about threading.
3056	have to skip roughly seven (C<ld 100>) of these watchers.
3057		3506
3058	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3507	=item * one loop per thread is usually a good model.
3059		3508
3060	That means that changing a timer costs less than removing/adding them	3509	Doing this is almost never wrong, sometimes a better-performance model
3061	as only the relative motion in the event queue has to be paid for.	3510	exists, but it is always a good start.
3062		3511
3063	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3512	=item * other models exist, such as the leader/follower pattern, where one
		3513	loop is handed through multiple threads in a kind of round-robin fashion.
3064		3514
3065	These just add the watcher into an array or at the head of a list.	3515	Choosing a model is hard - look around, learn, know that usually you can do
		3516	better than you currently do :-)
3066		3517
3067	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3518	=item * often you need to talk to some other thread which blocks in the
		3519	event loop.
3068		3520
3069	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3521	C<ev_async> watchers can be used to wake them up from other threads safely
		3522	(or from signal contexts...).
3070		3523
3071	These watchers are stored in lists then need to be walked to find the	3524	An example use would be to communicate signals or other events that only
3072	correct watcher to remove. The lists are usually short (you don't usually	3525	work in the default loop by registering the signal watcher with the
3073	have many watchers waiting for the same fd or signal).	3526	default loop and triggering an C<ev_async> watcher from the default loop
3074		3527	watcher callback into the event loop interested in the signal.
3075	=item Finding the next timer in each loop iteration: O(1)
3076
3077	By virtue of using a binary heap, the next timer is always found at the
3078	beginning of the storage array.
3079
3080	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3081
3082	A change means an I/O watcher gets started or stopped, which requires
3083	libev to recalculate its status (and possibly tell the kernel, depending
3084	on backend and wether C<ev_io_set> was used).
3085
3086	=item Activating one watcher (putting it into the pending state): O(1)
3087
3088	=item Priority handling: O(number_of_priorities)
3089
3090	Priorities are implemented by allocating some space for each
3091	priority. When doing priority-based operations, libev usually has to
3092	linearly search all the priorities, but starting/stopping and activating
3093	watchers becomes O(1) w.r.t. priority handling.
3094
3095	=item Sending an ev_async: O(1)
3096
3097	=item Processing ev_async_send: O(number_of_async_watchers)
3098
3099	=item Processing signals: O(max_signal_number)
3100
3101	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3102	calls in the current loop iteration. Checking for async and signal events
3103	involves iterating over all running async watchers or all signal numbers.
3104		3528
3105	=back	3529	=back
3106		3530
		3531	=head3 COROUTINES
3107		3532
3108	=head1 Win32 platform limitations and workarounds	3533	Libev is very accommodating to coroutines ("cooperative threads"):
		3534	libev fully supports nesting calls to its functions from different
		3535	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3536	different coroutines, and switch freely between both coroutines running the
		3537	loop, as long as you don't confuse yourself). The only exception is that
		3538	you must not do this from C<ev_periodic> reschedule callbacks.
		3539
		3540	Care has been taken to ensure that libev does not keep local state inside
		3541	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3542	they do not clal any callbacks.
		3543
		3544	=head2 COMPILER WARNINGS
		3545
		3546	Depending on your compiler and compiler settings, you might get no or a
		3547	lot of warnings when compiling libev code. Some people are apparently
		3548	scared by this.
		3549
		3550	However, these are unavoidable for many reasons. For one, each compiler
		3551	has different warnings, and each user has different tastes regarding
		3552	warning options. "Warn-free" code therefore cannot be a goal except when
		3553	targeting a specific compiler and compiler-version.
		3554
		3555	Another reason is that some compiler warnings require elaborate
		3556	workarounds, or other changes to the code that make it less clear and less
		3557	maintainable.
		3558
		3559	And of course, some compiler warnings are just plain stupid, or simply
		3560	wrong (because they don't actually warn about the condition their message
		3561	seems to warn about). For example, certain older gcc versions had some
		3562	warnings that resulted an extreme number of false positives. These have
		3563	been fixed, but some people still insist on making code warn-free with
		3564	such buggy versions.
		3565
		3566	While libev is written to generate as few warnings as possible,
		3567	"warn-free" code is not a goal, and it is recommended not to build libev
		3568	with any compiler warnings enabled unless you are prepared to cope with
		3569	them (e.g. by ignoring them). Remember that warnings are just that:
		3570	warnings, not errors, or proof of bugs.
		3571
		3572
		3573	=head2 VALGRIND
		3574
		3575	Valgrind has a special section here because it is a popular tool that is
		3576	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3577
		3578	If you think you found a bug (memory leak, uninitialised data access etc.)
		3579	in libev, then check twice: If valgrind reports something like:
		3580
		3581	==2274== definitely lost: 0 bytes in 0 blocks.
		3582	==2274== possibly lost: 0 bytes in 0 blocks.
		3583	==2274== still reachable: 256 bytes in 1 blocks.
		3584
		3585	Then there is no memory leak, just as memory accounted to global variables
		3586	is not a memleak - the memory is still being refernced, and didn't leak.
		3587
		3588	Similarly, under some circumstances, valgrind might report kernel bugs
		3589	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3590	although an acceptable workaround has been found here), or it might be
		3591	confused.
		3592
		3593	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3594	make it into some kind of religion.
		3595
		3596	If you are unsure about something, feel free to contact the mailing list
		3597	with the full valgrind report and an explanation on why you think this
		3598	is a bug in libev (best check the archives, too :). However, don't be
		3599	annoyed when you get a brisk "this is no bug" answer and take the chance
		3600	of learning how to interpret valgrind properly.
		3601
		3602	If you need, for some reason, empty reports from valgrind for your project
		3603	I suggest using suppression lists.
		3604
		3605
		3606	=head1 PORTABILITY NOTES
		3607
		3608	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3109		3609
3110	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3610	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3111	requires, and its I/O model is fundamentally incompatible with the POSIX	3611	requires, and its I/O model is fundamentally incompatible with the POSIX
3112	model. Libev still offers limited functionality on this platform in	3612	model. Libev still offers limited functionality on this platform in
3113	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3613	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3114	descriptors. This only applies when using Win32 natively, not when using	3614	descriptors. This only applies when using Win32 natively, not when using
3115	e.g. cygwin.	3615	e.g. cygwin.
3116		3616
		3617	Lifting these limitations would basically require the full
		3618	re-implementation of the I/O system. If you are into these kinds of
		3619	things, then note that glib does exactly that for you in a very portable
		3620	way (note also that glib is the slowest event library known to man).
		3621
3117	There is no supported compilation method available on windows except	3622	There is no supported compilation method available on windows except
3118	embedding it into other applications.	3623	embedding it into other applications.
3119		3624
		3625	Not a libev limitation but worth mentioning: windows apparently doesn't
		3626	accept large writes: instead of resulting in a partial write, windows will
		3627	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3628	so make sure you only write small amounts into your sockets (less than a
		3629	megabyte seems safe, but this apparently depends on the amount of memory
		3630	available).
		3631
3120	Due to the many, low, and arbitrary limits on the win32 platform and the	3632	Due to the many, low, and arbitrary limits on the win32 platform and
3121	abysmal performance of winsockets, using a large number of sockets is not	3633	the abysmal performance of winsockets, using a large number of sockets
3122	recommended (and not reasonable). If your program needs to use more than	3634	is not recommended (and not reasonable). If your program needs to use
3123	a hundred or so sockets, then likely it needs to use a totally different	3635	more than a hundred or so sockets, then likely it needs to use a totally
3124	implementation for windows, as libev offers the POSIX model, which cannot	3636	different implementation for windows, as libev offers the POSIX readiness
3125	be implemented efficiently on windows (microsoft monopoly games).	3637	notification model, which cannot be implemented efficiently on windows
		3638	(Microsoft monopoly games).
		3639
		3640	A typical way to use libev under windows is to embed it (see the embedding
		3641	section for details) and use the following F<evwrap.h> header file instead
		3642	of F<ev.h>:
		3643
		3644	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3645	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3646
		3647	#include "ev.h"
		3648
		3649	And compile the following F<evwrap.c> file into your project (make sure
		3650	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3651
		3652	#include "evwrap.h"
		3653	#include "ev.c"
3126		3654
3127	=over 4	3655	=over 4
3128		3656
3129	=item The winsocket select function	3657	=item The winsocket select function
3130		3658
3131	The winsocket C<select> function doesn't follow POSIX in that it requires	3659	The winsocket C<select> function doesn't follow POSIX in that it
3132	socket I<handles> and not socket I<file descriptors>. This makes select	3660	requires socket I<handles> and not socket I<file descriptors> (it is
3133	very inefficient, and also requires a mapping from file descriptors	3661	also extremely buggy). This makes select very inefficient, and also
3134	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3662	requires a mapping from file descriptors to socket handles (the Microsoft
3135	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3663	C runtime provides the function C<_open_osfhandle> for this). See the
3136	symbols for more info.	3664	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3665	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3137		3666
3138	The configuration for a "naked" win32 using the microsoft runtime	3667	The configuration for a "naked" win32 using the Microsoft runtime
3139	libraries and raw winsocket select is:	3668	libraries and raw winsocket select is:
3140		3669
3141	#define EV_USE_SELECT 1	3670	#define EV_USE_SELECT 1
3142	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3671	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3143		3672
3144	Note that winsockets handling of fd sets is O(n), so you can easily get a	3673	Note that winsockets handling of fd sets is O(n), so you can easily get a
3145	complexity in the O(n²) range when using win32.	3674	complexity in the O(n²) range when using win32.
3146		3675
3147	=item Limited number of file descriptors	3676	=item Limited number of file descriptors
3148		3677
3149	Windows has numerous arbitrary (and low) limits on things. Early versions	3678	Windows has numerous arbitrary (and low) limits on things.
3150	of winsocket's select only supported waiting for a max. of C<64> handles	3679
		3680	Early versions of winsocket's select only supported waiting for a maximum
3151	(probably owning to the fact that all windows kernels can only wait for	3681	of C<64> handles (probably owning to the fact that all windows kernels
3152	C<64> things at the same time internally; microsoft recommends spawning a	3682	can only wait for C<64> things at the same time internally; Microsoft
3153	chain of threads and wait for 63 handles and the previous thread in each).	3683	recommends spawning a chain of threads and wait for 63 handles and the
		3684	previous thread in each. Great).
3154		3685
3155	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3686	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3156	to some high number (e.g. C<2048>) before compiling the winsocket select	3687	to some high number (e.g. C<2048>) before compiling the winsocket select
3157	call (which might be in libev or elsewhere, for example, perl does its own	3688	call (which might be in libev or elsewhere, for example, perl does its own
3158	select emulation on windows).	3689	select emulation on windows).
3159		3690
3160	Another limit is the number of file descriptors in the microsoft runtime	3691	Another limit is the number of file descriptors in the Microsoft runtime
3161	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3692	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3162	or something like this inside microsoft). You can increase this by calling	3693	or something like this inside Microsoft). You can increase this by calling
3163	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3694	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3164	arbitrary limit), but is broken in many versions of the microsoft runtime	3695	arbitrary limit), but is broken in many versions of the Microsoft runtime
3165	libraries.	3696	libraries.
3166		3697
3167	This might get you to about C<512> or C<2048> sockets (depending on	3698	This might get you to about C<512> or C<2048> sockets (depending on
3168	windows version and/or the phase of the moon). To get more, you need to	3699	windows version and/or the phase of the moon). To get more, you need to
3169	wrap all I/O functions and provide your own fd management, but the cost of	3700	wrap all I/O functions and provide your own fd management, but the cost of
3170	calling select (O(n²)) will likely make this unworkable.	3701	calling select (O(n²)) will likely make this unworkable.
3171		3702
3172	=back	3703	=back
3173		3704
		3705	=head2 PORTABILITY REQUIREMENTS
		3706
		3707	In addition to a working ISO-C implementation and of course the
		3708	backend-specific APIs, libev relies on a few additional extensions:
		3709
		3710	=over 4
		3711
		3712	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3713	calling conventions regardless of C<ev_watcher_type *>.
		3714
		3715	Libev assumes not only that all watcher pointers have the same internal
		3716	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3717	assumes that the same (machine) code can be used to call any watcher
		3718	callback: The watcher callbacks have different type signatures, but libev
		3719	calls them using an C<ev_watcher *> internally.
		3720
		3721	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3722
		3723	The type C<sig_atomic_t volatile> (or whatever is defined as
		3724	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3725	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3726	believed to be sufficiently portable.
		3727
		3728	=item C<sigprocmask> must work in a threaded environment
		3729
		3730	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3731	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3732	pthread implementations will either allow C<sigprocmask> in the "main
		3733	thread" or will block signals process-wide, both behaviours would
		3734	be compatible with libev. Interaction between C<sigprocmask> and
		3735	C<pthread_sigmask> could complicate things, however.
		3736
		3737	The most portable way to handle signals is to block signals in all threads
		3738	except the initial one, and run the default loop in the initial thread as
		3739	well.
		3740
		3741	=item C<long> must be large enough for common memory allocation sizes
		3742
		3743	To improve portability and simplify its API, libev uses C<long> internally
		3744	instead of C<size_t> when allocating its data structures. On non-POSIX
		3745	systems (Microsoft...) this might be unexpectedly low, but is still at
		3746	least 31 bits everywhere, which is enough for hundreds of millions of
		3747	watchers.
		3748
		3749	=item C<double> must hold a time value in seconds with enough accuracy
		3750
		3751	The type C<double> is used to represent timestamps. It is required to
		3752	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3753	enough for at least into the year 4000. This requirement is fulfilled by
		3754	implementations implementing IEEE 754 (basically all existing ones).
		3755
		3756	=back
		3757
		3758	If you know of other additional requirements drop me a note.
		3759
		3760
		3761	=head1 ALGORITHMIC COMPLEXITIES
		3762
		3763	In this section the complexities of (many of) the algorithms used inside
		3764	libev will be documented. For complexity discussions about backends see
		3765	the documentation for C<ev_default_init>.
		3766
		3767	All of the following are about amortised time: If an array needs to be
		3768	extended, libev needs to realloc and move the whole array, but this
		3769	happens asymptotically rarer with higher number of elements, so O(1) might
		3770	mean that libev does a lengthy realloc operation in rare cases, but on
		3771	average it is much faster and asymptotically approaches constant time.
		3772
		3773	=over 4
		3774
		3775	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3776
		3777	This means that, when you have a watcher that triggers in one hour and
		3778	there are 100 watchers that would trigger before that, then inserting will
		3779	have to skip roughly seven (C<ld 100>) of these watchers.
		3780
		3781	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3782
		3783	That means that changing a timer costs less than removing/adding them,
		3784	as only the relative motion in the event queue has to be paid for.
		3785
		3786	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3787
		3788	These just add the watcher into an array or at the head of a list.
		3789
		3790	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3791
		3792	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3793
		3794	These watchers are stored in lists, so they need to be walked to find the
		3795	correct watcher to remove. The lists are usually short (you don't usually
		3796	have many watchers waiting for the same fd or signal: one is typical, two
		3797	is rare).
		3798
		3799	=item Finding the next timer in each loop iteration: O(1)
		3800
		3801	By virtue of using a binary or 4-heap, the next timer is always found at a
		3802	fixed position in the storage array.
		3803
		3804	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3805
		3806	A change means an I/O watcher gets started or stopped, which requires
		3807	libev to recalculate its status (and possibly tell the kernel, depending
		3808	on backend and whether C<ev_io_set> was used).
		3809
		3810	=item Activating one watcher (putting it into the pending state): O(1)
		3811
		3812	=item Priority handling: O(number_of_priorities)
		3813
		3814	Priorities are implemented by allocating some space for each
		3815	priority. When doing priority-based operations, libev usually has to
		3816	linearly search all the priorities, but starting/stopping and activating
		3817	watchers becomes O(1) with respect to priority handling.
		3818
		3819	=item Sending an ev_async: O(1)
		3820
		3821	=item Processing ev_async_send: O(number_of_async_watchers)
		3822
		3823	=item Processing signals: O(max_signal_number)
		3824
		3825	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3826	calls in the current loop iteration. Checking for async and signal events
		3827	involves iterating over all running async watchers or all signal numbers.
		3828
		3829	=back
		3830
3174		3831
3175	=head1 AUTHOR	3832	=head1 AUTHOR
3176		3833
3177	Marc Lehmann <libev@schmorp.de>.	3834	Marc Lehmann <libev@schmorp.de>.
3178		3835

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