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Revision 1.143 by root, Sun Apr 6 14:34:52 2008 UTC vs.
Revision 1.204 by root, Mon Oct 27 11:08:29 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
28		28
29	// this causes all nested ev_loop's to stop iterating	29	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
52		52
53	// initialise a timer watcher, then start it	53	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	54	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
57		57
58	// now wait for events to arrive	58	// now wait for events to arrive
59	ev_loop (loop, 0);	59	ev_loop (loop, 0);
60		60
61	// unloop was called, so exit	61	// unloop was called, so exit
62	return 0;	62	return 0;
63	}	63	}
64		64
65	=head1 DESCRIPTION	65	=head1 DESCRIPTION
66		66
67	The newest version of this document is also available as an html-formatted	67	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		70
71	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	73	these event sources and provide your program with events.
74		74
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	107	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	118	it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	119	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
121		142
122	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
123		144
124	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
125	library in any way.	146	library in any way.
…		…
134		155
135	=item ev_sleep (ev_tstamp interval)	156	=item ev_sleep (ev_tstamp interval)
136		157
137	Sleep for the given interval: The current thread will be blocked until	158	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	159	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	160	this is a sub-second-resolution C<sleep ()>.
140		161
141	=item int ev_version_major ()	162	=item int ev_version_major ()
142		163
143	=item int ev_version_minor ()	164	=item int ev_version_minor ()
144		165
…		…
157	not a problem.	178	not a problem.
158		179
159	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	181	version.
161		182
162	assert (("libev version mismatch",	183	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
165		186
166	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
167		188
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	192	a description of the set values.
172		193
173	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
175		196
176	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
178		199
179	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
180		201
181	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
187		208
188	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
189		210
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	215	recommended ones.
195		216
196	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
197		218
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		220
200	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
205	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
206		230
207	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
210		234
211	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	236	retries (example requires a standards-compliant C<realloc>).
213		237
214	static void *	238	static void *
215	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
216	{	240	{
217	for (;;)	241	for (;;)
…		…
226	}	250	}
227		251
228	...	252	...
229	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
230		254
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		256
233	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
234	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
236	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
237	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
238	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	263	(such as abort).
240		264
241	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
252		276
253	=back	277	=back
254		278
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		280
257	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
258	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
259	events, and dynamically created loops which do not.	283	I<function>).
260		284
261	If you use threads, a common model is to run the default event loop	285	The library knows two types of such loops, the I<default> loop, which
262	in your main thread (or in a separate thread) and for each thread you	286	supports signals and child events, and dynamically created loops which do
263	create, you also create another event loop. Libev itself does no locking	287	not.
264	whatsoever, so if you mix calls to the same event loop in different
265	threads, make sure you lock (this is usually a bad idea, though, even if
266	done correctly, because it's hideous and inefficient).
267		288
268	=over 4	289	=over 4
269		290
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		292
…		…
281	from multiple threads, you have to lock (note also that this is unlikely,	302	from multiple threads, you have to lock (note also that this is unlikely,
282	as loops cannot bes hared easily between threads anyway).	303	as loops cannot bes hared easily between threads anyway).
283		304
284	The default loop is the only loop that can handle C<ev_signal> and	305	The default loop is the only loop that can handle C<ev_signal> and
285	C<ev_child> watchers, and to do this, it always registers a handler	306	C<ev_child> watchers, and to do this, it always registers a handler
286	for C<SIGCHLD>. If this is a problem for your app you can either	307	for C<SIGCHLD>. If this is a problem for your application you can either
287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
289	C<ev_default_init>.	310	C<ev_default_init>.
290		311
291	The flags argument can be used to specify special behaviour or specific	312	The flags argument can be used to specify special behaviour or specific
…		…
300	The default flags value. Use this if you have no clue (it's the right	321	The default flags value. Use this if you have no clue (it's the right
301	thing, believe me).	322	thing, believe me).
302		323
303	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
304		325
305	If this flag bit is ored into the flag value (or the program runs setuid	326	If this flag bit is or'ed into the flag value (or the program runs setuid
306	or setgid) then libev will I<not> look at the environment variable	327	or setgid) then libev will I<not> look at the environment variable
307	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
308	override the flags completely if it is found in the environment. This is	329	override the flags completely if it is found in the environment. This is
309	useful to try out specific backends to test their performance, or to work	330	useful to try out specific backends to test their performance, or to work
310	around bugs.	331	around bugs.
…		…
317		338
318	This works by calling C<getpid ()> on every iteration of the loop,	339	This works by calling C<getpid ()> on every iteration of the loop,
319	and thus this might slow down your event loop if you do a lot of loop	340	and thus this might slow down your event loop if you do a lot of loop
320	iterations and little real work, but is usually not noticeable (on my	341	iterations and little real work, but is usually not noticeable (on my
321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
322	without a syscall and thus I<very> fast, but my GNU/Linux system also has	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
323	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
324		345
325	The big advantage of this flag is that you can forget about fork (and	346	The big advantage of this flag is that you can forget about fork (and
326	forget about forgetting to tell libev about forking) when you use this	347	forget about forgetting to tell libev about forking) when you use this
327	flag.	348	flag.
328		349
329	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
330	environment variable.	351	environment variable.
331		352
332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
333		354
334	This is your standard select(2) backend. Not I<completely> standard, as	355	This is your standard select(2) backend. Not I<completely> standard, as
…		…
336	but if that fails, expect a fairly low limit on the number of fds when	357	but if that fails, expect a fairly low limit on the number of fds when
337	using this backend. It doesn't scale too well (O(highest_fd)), but its	358	using this backend. It doesn't scale too well (O(highest_fd)), but its
338	usually the fastest backend for a low number of (low-numbered :) fds.	359	usually the fastest backend for a low number of (low-numbered :) fds.
339		360
340	To get good performance out of this backend you need a high amount of	361	To get good performance out of this backend you need a high amount of
341	parallelity (most of the file descriptors should be busy). If you are	362	parallelism (most of the file descriptors should be busy). If you are
342	writing a server, you should C<accept ()> in a loop to accept as many	363	writing a server, you should C<accept ()> in a loop to accept as many
343	connections as possible during one iteration. You might also want to have	364	connections as possible during one iteration. You might also want to have
344	a look at C<ev_set_io_collect_interval ()> to increase the amount of	365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
345	readyness notifications you get per iteration.	366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
346		371
347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
348		373
349	And this is your standard poll(2) backend. It's more complicated	374	And this is your standard poll(2) backend. It's more complicated
350	than select, but handles sparse fds better and has no artificial	375	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	376	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,	377	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	378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
354	performance tips.	379	performance tips.
355		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		383
356	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
357		385
358	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
359	but it scales phenomenally better. While poll and select usually scale	387	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),	388	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	389	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	390	of shortcomings, such as silently dropping events in some hard-to-detect
363	cases and requiring a syscall per fd change, no fork support and bad	391	cases and requiring a system call per fd change, no fork support and bad
364	support for dup.	392	support for dup.
365		393
		394	Epoll is also notoriously buggy - embedding epoll fds should work, but
		395	of course doesn't, and epoll just loves to report events for totally
		396	I<different> file descriptors (even already closed ones) than registered
		397	in the set (especially on SMP systems). Libev tries to counter these
		398	spurious notifications by employing an additional generation counter and
		399	comparing that against the events to filter out spurious ones.
		400
366	While stopping, setting and starting an I/O watcher in the same iteration	401	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	402	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	403	(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	404	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
370	very well if you register events for both fds.	405	very well if you register events for both fds.
371		406
372	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
374	(or space) is available.
375
376	Best performance from this backend is achieved by not unregistering all	407	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.	408	watchers for a file descriptor until it has been closed, if possible,
378	keep at least one watcher active per fd at all times.	409	i.e. keep at least one watcher active per fd at all times. Stopping and
		410	starting a watcher (without re-setting it) also usually doesn't cause
		411	extra overhead.
379		412
380	While nominally embeddeble in other event loops, this feature is broken in	413	While nominally embeddable in other event loops, this feature is broken in
381	all kernel versions tested so far.	414	all kernel versions tested so far.
382		415
		416	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		417	C<EVBACKEND_POLL>.
		418
383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	419	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
384		420
385	Kqueue deserves special mention, as at the time of this writing, it	421	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	422	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	423	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"	424	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	425	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)	426	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
391	system like NetBSD.
392		427
393	You still can embed kqueue into a normal poll or select backend and use it	428	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	429	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.	430	the target platform). See C<ev_embed> watchers for more info.
396		431
397	It scales in the same way as the epoll backend, but the interface to the	432	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	433	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	434	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	435	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	436	two event changes per incident. Support for C<fork ()> is very bad and it
402	drops fds silently in similarly hard-to-detect cases.	437	drops fds silently in similarly hard-to-detect cases.
403		438
404	This backend usually performs well under most conditions.	439	This backend usually performs well under most conditions.
405		440
406	While nominally embeddable in other event loops, this doesn't work	441	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	442	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	443	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	444	(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	445	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
411	sockets.	446	using it only for sockets.
		447
		448	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		449	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		450	C<NOTE_EOF>.
412		451
413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	452	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
414		453
415	This is not implemented yet (and might never be, unless you send me an	454	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	455	implementation). According to reports, C</dev/poll> only supports sockets
…		…
420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	459	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
421		460
422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	461	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)).	462	it's really slow, but it still scales very well (O(active_fds)).
424		463
425	Please note that solaris event ports can deliver a lot of spurious	464	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	465	notifications, so you need to use non-blocking I/O or other means to avoid
427	blocking when no data (or space) is available.	466	blocking when no data (or space) is available.
428		467
429	While this backend scales well, it requires one system call per active	468	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	469	file descriptor per loop iteration. For small and medium numbers of file
431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	470	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
432	might perform better.	471	might perform better.
433		472
434	On the positive side, ignoring the spurious readyness notifications, this	473	On the positive side, with the exception of the spurious readiness
435	backend actually performed to specification in all tests and is fully	474	notifications, this backend actually performed fully to specification
436	embeddable, which is a rare feat among the OS-specific backends.	475	in all tests and is fully embeddable, which is a rare feat among the
		476	OS-specific backends.
		477
		478	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		479	C<EVBACKEND_POLL>.
437		480
438	=item C<EVBACKEND_ALL>	481	=item C<EVBACKEND_ALL>
439		482
440	Try all backends (even potentially broken ones that wouldn't be tried	483	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	484	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
443		486
444	It is definitely not recommended to use this flag.	487	It is definitely not recommended to use this flag.
445		488
446	=back	489	=back
447		490
448	If one or more of these are ored into the flags value, then only these	491	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	492	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.	493	specified, all backends in C<ev_recommended_backends ()> will be tried.
451		494
452	The most typical usage is like this:	495	Example: This is the most typical usage.
453		496
454	if (!ev_default_loop (0))	497	if (!ev_default_loop (0))
455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	498	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
456		499
457	Restrict libev to the select and poll backends, and do not allow	500	Example: Restrict libev to the select and poll backends, and do not allow
458	environment settings to be taken into account:	501	environment settings to be taken into account:
459		502
460	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	503	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
461		504
462	Use whatever libev has to offer, but make sure that kqueue is used if	505	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	506	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):	507	private event loop and only if you know the OS supports your types of
		508	fds):
465		509
466	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	510	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
467		511
468	=item struct ev_loop *ev_loop_new (unsigned int flags)	512	=item struct ev_loop *ev_loop_new (unsigned int flags)
469		513
470	Similar to C<ev_default_loop>, but always creates a new event loop that is	514	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	515	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	520	libev with threads is indeed to create one loop per thread, and using the
477	default loop in the "main" or "initial" thread.	521	default loop in the "main" or "initial" thread.
478		522
479	Example: Try to create a event loop that uses epoll and nothing else.	523	Example: Try to create a event loop that uses epoll and nothing else.
480		524
481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	525	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
482	if (!epoller)	526	if (!epoller)
483	fatal ("no epoll found here, maybe it hides under your chair");	527	fatal ("no epoll found here, maybe it hides under your chair");
484		528
485	=item ev_default_destroy ()	529	=item ev_default_destroy ()
486		530
487	Destroys the default loop again (frees all memory and kernel state	531	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	532	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	533	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>	534	responsibility to either stop all watchers cleanly yourself I<before>
491	calling this function, or cope with the fact afterwards (which is usually	535	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	536	the easiest thing, you can just ignore the watchers and/or C<free ()> them
493	for example).	537	for example).
494		538
495	Note that certain global state, such as signal state, will not be freed by	539	Note that certain global state, such as signal state (and installed signal
496	this function, and related watchers (such as signal and child watchers)	540	handlers), will not be freed by this function, and related watchers (such
497	would need to be stopped manually.	541	as signal and child watchers) would need to be stopped manually.
498		542
499	In general it is not advisable to call this function except in the	543	In general it is not advisable to call this function except in the
500	rare occasion where you really need to free e.g. the signal handling	544	rare occasion where you really need to free e.g. the signal handling
501	pipe fds. If you need dynamically allocated loops it is better to use	545	pipe fds. If you need dynamically allocated loops it is better to use
502	C<ev_loop_new> and C<ev_loop_destroy>).	546	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
527		571
528	=item ev_loop_fork (loop)	572	=item ev_loop_fork (loop)
529		573
530	Like C<ev_default_fork>, but acts on an event loop created by	574	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	575	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.	576	after fork that you want to re-use in the child, and how you do this is
		577	entirely your own problem.
533		578
534	=item int ev_is_default_loop (loop)	579	=item int ev_is_default_loop (loop)
535		580
536	Returns true when the given loop actually is the default loop, false otherwise.	581	Returns true when the given loop is, in fact, the default loop, and false
		582	otherwise.
537		583
538	=item unsigned int ev_loop_count (loop)	584	=item unsigned int ev_loop_count (loop)
539		585
540	Returns the count of loop iterations for the loop, which is identical to	586	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	587	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	602	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	603	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	604	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).	605	event occurring (or more correctly, libev finding out about it).
560		606
		607	=item ev_now_update (loop)
		608
		609	Establishes the current time by querying the kernel, updating the time
		610	returned by C<ev_now ()> in the progress. This is a costly operation and
		611	is usually done automatically within C<ev_loop ()>.
		612
		613	This function is rarely useful, but when some event callback runs for a
		614	very long time without entering the event loop, updating libev's idea of
		615	the current time is a good idea.
		616
		617	See also "The special problem of time updates" in the C<ev_timer> section.
		618
561	=item ev_loop (loop, int flags)	619	=item ev_loop (loop, int flags)
562		620
563	Finally, this is it, the event handler. This function usually is called	621	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	622	after you initialised all your watchers and you want to start handling
565	events.	623	events.
…		…
567	If the flags argument is specified as C<0>, it will not return until	625	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.	626	either no event watchers are active anymore or C<ev_unloop> was called.
569		627
570	Please note that an explicit C<ev_unloop> is usually better than	628	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	629	relying on all watchers to be stopped when deciding when a program has
572	finished (especially in interactive programs), but having a program that	630	finished (especially in interactive programs), but having a program
573	automatically loops as long as it has to and no longer by virtue of	631	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.	632	of relying on its watchers stopping correctly, that is truly a thing of
		633	beauty.
575		634
576	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	635	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	636	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.	637	process in case there are no events and will return after one iteration of
		638	the loop.
579		639
580	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	640	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	641	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	642	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	643	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	644	user-registered callback will be called), and will return after one
		645	iteration of the loop.
		646
		647	This is useful if you are waiting for some external event in conjunction
		648	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	649	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.	650	usually a better approach for this kind of thing.
587		651
588	Here are the gory details of what C<ev_loop> does:	652	Here are the gory details of what C<ev_loop> does:
589		653
590	- Before the first iteration, call any pending watchers.	654	- Before the first iteration, call any pending watchers.
591	* If EVFLAG_FORKCHECK was used, check for a fork.	655	* If EVFLAG_FORKCHECK was used, check for a fork.
592	- If a fork was detected, queue and call all fork watchers.	656	- If a fork was detected (by any means), queue and call all fork watchers.
593	- Queue and call all prepare watchers.	657	- Queue and call all prepare watchers.
594	- If we have been forked, recreate the kernel state.	658	- If we have been forked, detach and recreate the kernel state
		659	as to not disturb the other process.
595	- Update the kernel state with all outstanding changes.	660	- Update the kernel state with all outstanding changes.
596	- Update the "event loop time".	661	- Update the "event loop time" (ev_now ()).
597	- Calculate for how long to sleep or block, if at all	662	- Calculate for how long to sleep or block, if at all
598	(active idle watchers, EVLOOP_NONBLOCK or not having	663	(active idle watchers, EVLOOP_NONBLOCK or not having
599	any active watchers at all will result in not sleeping).	664	any active watchers at all will result in not sleeping).
600	- Sleep if the I/O and timer collect interval say so.	665	- Sleep if the I/O and timer collect interval say so.
601	- Block the process, waiting for any events.	666	- Block the process, waiting for any events.
602	- Queue all outstanding I/O (fd) events.	667	- Queue all outstanding I/O (fd) events.
603	- Update the "event loop time" and do time jump handling.	668	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
604	- Queue all outstanding timers.	669	- Queue all expired timers.
605	- Queue all outstanding periodics.	670	- Queue all expired periodics.
606	- If no events are pending now, queue all idle watchers.	671	- Unless any events are pending now, queue all idle watchers.
607	- Queue all check watchers.	672	- Queue all check watchers.
608	- Call all queued watchers in reverse order (i.e. check watchers first).	673	- 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	674	Signals and child watchers are implemented as I/O watchers, and will
610	be handled here by queueing them when their watcher gets executed.	675	be handled here by queueing them when their watcher gets executed.
611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	676	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
616	anymore.	681	anymore.
617		682
618	... queue jobs here, make sure they register event watchers as long	683	... 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..)	684	... as they still have work to do (even an idle watcher will do..)
620	ev_loop (my_loop, 0);	685	ev_loop (my_loop, 0);
621	... jobs done. yeah!	686	... jobs done or somebody called unloop. yeah!
622		687
623	=item ev_unloop (loop, how)	688	=item ev_unloop (loop, how)
624		689
625	Can be used to make a call to C<ev_loop> return early (but only after it	690	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	691	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	692	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.	693	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
629		694
630	This "unloop state" will be cleared when entering C<ev_loop> again.	695	This "unloop state" will be cleared when entering C<ev_loop> again.
631		696
		697	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		698
632	=item ev_ref (loop)	699	=item ev_ref (loop)
633		700
634	=item ev_unref (loop)	701	=item ev_unref (loop)
635		702
636	Ref/unref can be used to add or remove a reference count on the event	703	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	704	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	705	count is nonzero, C<ev_loop> will not return on its own.
		706
639	a watcher you never unregister that should not keep C<ev_loop> from	707	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	708	from returning, call ev_unref() after starting, and ev_ref() before
		709	stopping it.
		710
641	example, libev itself uses this for its internal signal pipe: It is not	711	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	712	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	713	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	714	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>	715	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,	716	(but only if the watcher wasn't active before, or was active before,
647	respectively).	717	respectively).
648		718
649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	719	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
650	running when nothing else is active.	720	running when nothing else is active.
651		721
652	struct ev_signal exitsig;	722	ev_signal exitsig;
653	ev_signal_init (&exitsig, sig_cb, SIGINT);	723	ev_signal_init (&exitsig, sig_cb, SIGINT);
654	ev_signal_start (loop, &exitsig);	724	ev_signal_start (loop, &exitsig);
655	evf_unref (loop);	725	evf_unref (loop);
656		726
657	Example: For some weird reason, unregister the above signal handler again.	727	Example: For some weird reason, unregister the above signal handler again.
658		728
659	ev_ref (loop);	729	ev_ref (loop);
660	ev_signal_stop (loop, &exitsig);	730	ev_signal_stop (loop, &exitsig);
661		731
662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	732	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
663		733
664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	734	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
665		735
666	These advanced functions influence the time that libev will spend waiting	736	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	737	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.	738	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		739	latency.
669		740
670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	741	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	742	allows libev to delay invocation of I/O and timer/periodic callbacks
672	increase efficiency of loop iterations.	743	to increase efficiency of loop iterations (or to increase power-saving
		744	opportunities).
673		745
674	The background is that sometimes your program runs just fast enough to	746	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	747	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	748	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	749	events, especially with backends like C<select ()> which have a high
678	overhead for the actual polling but can deliver many events at once.	750	overhead for the actual polling but can deliver many events at once.
679		751
680	By setting a higher I<io collect interval> you allow libev to spend more	752	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,	753	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	755	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.	756	introduce an additional C<ev_sleep ()> call into most loop iterations.
685		757
686	Likewise, by setting a higher I<timeout collect interval> you allow libev	758	Likewise, by setting a higher I<timeout collect interval> you allow libev
687	to spend more time collecting timeouts, at the expense of increased	759	to spend more time collecting timeouts, at the expense of increased
688	latency (the watcher callback will be called later). C<ev_io> watchers	760	latency/jitter/inexactness (the watcher callback will be called
689	will not be affected. Setting this to a non-null value will not introduce	761	later). C<ev_io> watchers will not be affected. Setting this to a non-null
690	any overhead in libev.	762	value will not introduce any overhead in libev.
691		763
692	Many (busy) programs can usually benefit by setting the io collect	764	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	765	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	766	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>,	767	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.	768	as this approaches the timing granularity of most systems.
		769
		770	Setting the I<timeout collect interval> can improve the opportunity for
		771	saving power, as the program will "bundle" timer callback invocations that
		772	are "near" in time together, by delaying some, thus reducing the number of
		773	times the process sleeps and wakes up again. Another useful technique to
		774	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		775	they fire on, say, one-second boundaries only.
		776
		777	=item ev_loop_verify (loop)
		778
		779	This function only does something when C<EV_VERIFY> support has been
		780	compiled in, which is the default for non-minimal builds. It tries to go
		781	through all internal structures and checks them for validity. If anything
		782	is found to be inconsistent, it will print an error message to standard
		783	error and call C<abort ()>.
		784
		785	This can be used to catch bugs inside libev itself: under normal
		786	circumstances, this function will never abort as of course libev keeps its
		787	data structures consistent.
697		788
698	=back	789	=back
699		790
700		791
701	=head1 ANATOMY OF A WATCHER	792	=head1 ANATOMY OF A WATCHER
		793
		794	In the following description, uppercase C<TYPE> in names stands for the
		795	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		796	watchers and C<ev_io_start> for I/O watchers.
702		797
703	A watcher is a structure that you create and register to record your	798	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	799	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:	800	become readable, you would create an C<ev_io> watcher for that:
706		801
707	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	802	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
708	{	803	{
709	ev_io_stop (w);	804	ev_io_stop (w);
710	ev_unloop (loop, EVUNLOOP_ALL);	805	ev_unloop (loop, EVUNLOOP_ALL);
711	}	806	}
712		807
713	struct ev_loop *loop = ev_default_loop (0);	808	struct ev_loop *loop = ev_default_loop (0);
		809
714	struct ev_io stdin_watcher;	810	ev_io stdin_watcher;
		811
715	ev_init (&stdin_watcher, my_cb);	812	ev_init (&stdin_watcher, my_cb);
716	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	813	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
717	ev_io_start (loop, &stdin_watcher);	814	ev_io_start (loop, &stdin_watcher);
		815
718	ev_loop (loop, 0);	816	ev_loop (loop, 0);
719		817
720	As you can see, you are responsible for allocating the memory for your	818	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,	819	watcher structures (and it is I<usually> a bad idea to do this on the
722	although this can sometimes be quite valid).	820	stack).
		821
		822	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		823	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
723		824
724	Each watcher structure must be initialised by a call to C<ev_init	825	Each watcher structure must be initialised by a call to C<ev_init
725	(watcher *, callback)>, which expects a callback to be provided. This	826	(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	827	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	828	watchers, each time the event loop detects that the file descriptor given
728	is readable and/or writable).	829	is readable and/or writable).
729		830
730	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	831	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
731	with arguments specific to this watcher type. There is also a macro	832	macro to configure it, with arguments specific to the watcher type. There
732	to combine initialisation and setting in one call: C<< ev_<type>_init	833	is also a macro to combine initialisation and setting in one call: C<<
733	(watcher *, callback, ...) >>.	834	ev_TYPE_init (watcher *, callback, ...) >>.
734		835
735	To make the watcher actually watch out for events, you have to start it	836	To make the watcher actually watch out for events, you have to start it
736	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	837	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
737	*) >>), and you can stop watching for events at any time by calling the	838	*) >>), and you can stop watching for events at any time by calling the
738	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	839	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
739		840
740	As long as your watcher is active (has been started but not stopped) you	841	As long as your watcher is active (has been started but not stopped) you
741	must not touch the values stored in it. Most specifically you must never	842	must not touch the values stored in it. Most specifically you must never
742	reinitialise it or call its C<set> macro.	843	reinitialise it or call its C<ev_TYPE_set> macro.
743		844
744	Each and every callback receives the event loop pointer as first, the	845	Each and every callback receives the event loop pointer as first, the
745	registered watcher structure as second, and a bitset of received events as	846	registered watcher structure as second, and a bitset of received events as
746	third argument.	847	third argument.
747		848
…		…
807		908
808	The given async watcher has been asynchronously notified (see C<ev_async>).	909	The given async watcher has been asynchronously notified (see C<ev_async>).
809		910
810	=item C<EV_ERROR>	911	=item C<EV_ERROR>
811		912
812	An unspecified error has occured, the watcher has been stopped. This might	913	An unspecified error has occurred, the watcher has been stopped. This might
813	happen because the watcher could not be properly started because libev	914	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	915	ran out of memory, a file descriptor was found to be closed or any other
		916	problem. Libev considers these application bugs.
		917
815	problem. You best act on it by reporting the problem and somehow coping	918	You best act on it by reporting the problem and somehow coping with the
816	with the watcher being stopped.	919	watcher being stopped. Note that well-written programs should not receive
		920	an error ever, so when your watcher receives it, this usually indicates a
		921	bug in your program.
817		922
818	Libev will usually signal a few "dummy" events together with an error,	923	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	924	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	925	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	926	the error from read() or write(). This will not work in multi-threaded
822	programs, though, so beware.	927	programs, though, as the fd could already be closed and reused for another
		928	thing, so beware.
823		929
824	=back	930	=back
825		931
826	=head2 GENERIC WATCHER FUNCTIONS	932	=head2 GENERIC WATCHER FUNCTIONS
827
828	In the following description, C<TYPE> stands for the watcher type,
829	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
830		933
831	=over 4	934	=over 4
832		935
833	=item C<ev_init> (ev_TYPE *watcher, callback)	936	=item C<ev_init> (ev_TYPE *watcher, callback)
834		937
…		…
840	which rolls both calls into one.	943	which rolls both calls into one.
841		944
842	You can reinitialise a watcher at any time as long as it has been stopped	945	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.	946	(or never started) and there are no pending events outstanding.
844		947
845	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	948	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
846	int revents)>.	949	int revents)>.
		950
		951	Example: Initialise an C<ev_io> watcher in two steps.
		952
		953	ev_io w;
		954	ev_init (&w, my_cb);
		955	ev_io_set (&w, STDIN_FILENO, EV_READ);
847		956
848	=item C<ev_TYPE_set> (ev_TYPE *, [args])	957	=item C<ev_TYPE_set> (ev_TYPE *, [args])
849		958
850	This macro initialises the type-specific parts of a watcher. You need to	959	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	960	call C<ev_init> at least once before you call this macro, but you can
…		…
854	difference to the C<ev_init> macro).	963	difference to the C<ev_init> macro).
855		964
856	Although some watcher types do not have type-specific arguments	965	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.	966	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
858		967
		968	See C<ev_init>, above, for an example.
		969
859	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	970	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
860		971
861	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	972	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	973	calls into a single call. This is the most convenient method to initialise
863	a watcher. The same limitations apply, of course.	974	a watcher. The same limitations apply, of course.
		975
		976	Example: Initialise and set an C<ev_io> watcher in one step.
		977
		978	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
864		979
865	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	980	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
866		981
867	Starts (activates) the given watcher. Only active watchers will receive	982	Starts (activates) the given watcher. Only active watchers will receive
868	events. If the watcher is already active nothing will happen.	983	events. If the watcher is already active nothing will happen.
869		984
		985	Example: Start the C<ev_io> watcher that is being abused as example in this
		986	whole section.
		987
		988	ev_io_start (EV_DEFAULT_UC, &w);
		989
870	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	990	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
871		991
872	Stops the given watcher again (if active) and clears the pending	992	Stops the given watcher if active, and clears the pending status (whether
		993	the watcher was active or not).
		994
873	status. It is possible that stopped watchers are pending (for example,	995	It is possible that stopped watchers are pending - for example,
874	non-repeating timers are being stopped when they become pending), but	996	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	997	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	998	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.	999	therefore a good idea to always call its C<ev_TYPE_stop> function.
878		1000
879	=item bool ev_is_active (ev_TYPE *watcher)	1001	=item bool ev_is_active (ev_TYPE *watcher)
880		1002
881	Returns a true value iff the watcher is active (i.e. it has been started	1003	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	1004	and not yet been stopped). As long as a watcher is active you must not modify
…		…
924	The default priority used by watchers when no priority has been set is	1046	The default priority used by watchers when no priority has been set is
925	always C<0>, which is supposed to not be too high and not be too low :).	1047	always C<0>, which is supposed to not be too high and not be too low :).
926		1048
927	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1049	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
928	fine, as long as you do not mind that the priority value you query might	1050	fine, as long as you do not mind that the priority value you query might
929	or might not have been adjusted to be within valid range.	1051	or might not have been clamped to the valid range.
930		1052
931	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1053	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
932		1054
933	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1055	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	1056	C<loop> nor C<revents> need to be valid as long as the watcher callback
935	can deal with that fact.	1057	can deal with that fact, as both are simply passed through to the
		1058	callback.
936		1059
937	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1060	=item int ev_clear_pending (loop, ev_TYPE *watcher)
938		1061
939	If the watcher is pending, this function returns clears its pending status	1062	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	1063	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>.	1064	watcher isn't pending it does nothing and returns C<0>.
942		1065
		1066	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1067	callback to be invoked, which can be accomplished with this function.
		1068
943	=back	1069	=back
944		1070
945		1071
946	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1072	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
947		1073
948	Each watcher has, by default, a member C<void *data> that you can change	1074	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	1075	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	1076	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	1077	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	1078	member, you can also "subclass" the watcher type and provide your own
953	data:	1079	data:
954		1080
955	struct my_io	1081	struct my_io
956	{	1082	{
957	struct ev_io io;	1083	ev_io io;
958	int otherfd;	1084	int otherfd;
959	void *somedata;	1085	void *somedata;
960	struct whatever *mostinteresting;	1086	struct whatever *mostinteresting;
961	}	1087	};
		1088
		1089	...
		1090	struct my_io w;
		1091	ev_io_init (&w.io, my_cb, fd, EV_READ);
962		1092
963	And since your callback will be called with a pointer to the watcher, you	1093	And since your callback will be called with a pointer to the watcher, you
964	can cast it back to your own type:	1094	can cast it back to your own type:
965		1095
966	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1096	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
967	{	1097	{
968	struct my_io *w = (struct my_io *)w_;	1098	struct my_io *w = (struct my_io *)w_;
969	...	1099	...
970	}	1100	}
971		1101
972	More interesting and less C-conformant ways of casting your callback type	1102	More interesting and less C-conformant ways of casting your callback type
973	instead have been omitted.	1103	instead have been omitted.
974		1104
975	Another common scenario is having some data structure with multiple	1105	Another common scenario is to use some data structure with multiple
976	watchers:	1106	embedded watchers:
977		1107
978	struct my_biggy	1108	struct my_biggy
979	{	1109	{
980	int some_data;	1110	int some_data;
981	ev_timer t1;	1111	ev_timer t1;
982	ev_timer t2;	1112	ev_timer t2;
983	}	1113	}
984		1114
985	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1115	In this case getting the pointer to C<my_biggy> is a bit more
986	you need to use C<offsetof>:	1116	complicated: Either you store the address of your C<my_biggy> struct
		1117	in the C<data> member of the watcher (for woozies), or you need to use
		1118	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1119	programmers):
987		1120
988	#include <stddef.h>	1121	#include <stddef.h>
989		1122
990	static void	1123	static void
991	t1_cb (EV_P_ struct ev_timer *w, int revents)	1124	t1_cb (EV_P_ ev_timer *w, int revents)
992	{	1125	{
993	struct my_biggy big = (struct my_biggy *	1126	struct my_biggy big = (struct my_biggy *
994	(((char *)w) - offsetof (struct my_biggy, t1));	1127	(((char *)w) - offsetof (struct my_biggy, t1));
995	}	1128	}
996		1129
997	static void	1130	static void
998	t2_cb (EV_P_ struct ev_timer *w, int revents)	1131	t2_cb (EV_P_ ev_timer *w, int revents)
999	{	1132	{
1000	struct my_biggy big = (struct my_biggy *	1133	struct my_biggy big = (struct my_biggy *
1001	(((char *)w) - offsetof (struct my_biggy, t2));	1134	(((char *)w) - offsetof (struct my_biggy, t2));
1002	}	1135	}
1003		1136
1004		1137
1005	=head1 WATCHER TYPES	1138	=head1 WATCHER TYPES
1006		1139
1007	This section describes each watcher in detail, but will not repeat	1140	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	1164	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	1165	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	1166	descriptors to non-blocking mode is also usually a good idea (but not
1034	required if you know what you are doing).	1167	required if you know what you are doing).
1035		1168
1036	If you must do this, then force the use of a known-to-be-good backend	1169	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	1170	known-to-be-good backend (at the time of this writing, this includes only
1038	C<EVBACKEND_POLL>).	1171	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1039		1172
1040	Another thing you have to watch out for is that it is quite easy to	1173	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	1174	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	1175	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	1176	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	1177	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	1178	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	1179	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.	1180	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1048		1181
1049	If you cannot run the fd in non-blocking mode (for example you should not	1182	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	1183	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	1184	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	1185	interface such as poll (fortunately in our Xlib example, Xlib already
1053	its own, so its quite safe to use).	1186	does this on its own, so its quite safe to use). Some people additionally
		1187	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1188	indefinitely.
		1189
		1190	But really, best use non-blocking mode.
1054		1191
1055	=head3 The special problem of disappearing file descriptors	1192	=head3 The special problem of disappearing file descriptors
1056		1193
1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1194	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,	1195	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	1196	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	1197	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	1198	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	1199	registered with libev, there is no efficient way to see that this is, in
1063	fact, a different file descriptor.	1200	fact, a different file descriptor.
1064		1201
…		…
1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1232	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1096	C<EVBACKEND_POLL>.	1233	C<EVBACKEND_POLL>.
1097		1234
1098	=head3 The special problem of SIGPIPE	1235	=head3 The special problem of SIGPIPE
1099		1236
1100	While not really specific to libev, it is easy to forget about SIGPIPE:	1237	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	1238	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	1239	sent a SIGPIPE, which, by default, aborts your program. For most programs
1103	programs this is sensible behaviour, for daemons, this is usually	1240	this is sensible behaviour, for daemons, this is usually undesirable.
1104	undesirable.
1105		1241
1106	So when you encounter spurious, unexplained daemon exits, make sure you	1242	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	1243	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).	1244	somewhere, as that would have given you a big clue).
1109		1245
…		…
1115	=item ev_io_init (ev_io *, callback, int fd, int events)	1251	=item ev_io_init (ev_io *, callback, int fd, int events)
1116		1252
1117	=item ev_io_set (ev_io *, int fd, int events)	1253	=item ev_io_set (ev_io *, int fd, int events)
1118		1254
1119	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1255	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	1256	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.	1257	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1122		1258
1123	=item int fd [read-only]	1259	=item int fd [read-only]
1124		1260
1125	The file descriptor being watched.	1261	The file descriptor being watched.
1126		1262
…		…
1134		1270
1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1271	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	1272	readable, but only once. Since it is likely line-buffered, you could
1137	attempt to read a whole line in the callback.	1273	attempt to read a whole line in the callback.
1138		1274
1139	static void	1275	static void
1140	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1276	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1141	{	1277	{
1142	ev_io_stop (loop, w);	1278	ev_io_stop (loop, w);
1143	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1279	.. read from stdin here (or from w->fd) and handle any I/O errors
1144	}	1280	}
1145		1281
1146	...	1282	...
1147	struct ev_loop *loop = ev_default_init (0);	1283	struct ev_loop *loop = ev_default_init (0);
1148	struct ev_io stdin_readable;	1284	ev_io stdin_readable;
1149	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1285	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1150	ev_io_start (loop, &stdin_readable);	1286	ev_io_start (loop, &stdin_readable);
1151	ev_loop (loop, 0);	1287	ev_loop (loop, 0);
1152		1288
1153		1289
1154	=head2 C<ev_timer> - relative and optionally repeating timeouts	1290	=head2 C<ev_timer> - relative and optionally repeating timeouts
1155		1291
1156	Timer watchers are simple relative timers that generate an event after a	1292	Timer watchers are simple relative timers that generate an event after a
1157	given time, and optionally repeating in regular intervals after that.	1293	given time, and optionally repeating in regular intervals after that.
1158		1294
1159	The timers are based on real time, that is, if you register an event that	1295	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	1296	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	1297	year, it will still time out after (roughly) one hour. "Roughly" because
1162	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1298	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1163	monotonic clock option helps a lot here).	1299	monotonic clock option helps a lot here).
		1300
		1301	The callback is guaranteed to be invoked only I<after> its timeout has
		1302	passed, but if multiple timers become ready during the same loop iteration
		1303	then order of execution is undefined.
		1304
		1305	=head3 Be smart about timeouts
		1306
		1307	Many real-world problems involve some kind of timeout, usually for error
		1308	recovery. A typical example is an HTTP request - if the other side hangs,
		1309	you want to raise some error after a while.
		1310
		1311	What follows are some ways to handle this problem, from obvious and
		1312	inefficient to smart and efficient.
		1313
		1314	In the following, a 60 second activity timeout is assumed - a timeout that
		1315	gets reset to 60 seconds each time there is activity (e.g. each time some
		1316	data or other life sign was received).
		1317
		1318	=over 4
		1319
		1320	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1321
		1322	This is the most obvious, but not the most simple way: In the beginning,
		1323	start the watcher:
		1324
		1325	ev_timer_init (timer, callback, 60., 0.);
		1326	ev_timer_start (loop, timer);
		1327
		1328	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1329	and start it again:
		1330
		1331	ev_timer_stop (loop, timer);
		1332	ev_timer_set (timer, 60., 0.);
		1333	ev_timer_start (loop, timer);
		1334
		1335	This is relatively simple to implement, but means that each time there is
		1336	some activity, libev will first have to remove the timer from its internal
		1337	data structure and then add it again. Libev tries to be fast, but it's
		1338	still not a constant-time operation.
		1339
		1340	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1341
		1342	This is the easiest way, and involves using C<ev_timer_again> instead of
		1343	C<ev_timer_start>.
		1344
		1345	To implement this, configure an C<ev_timer> with a C<repeat> value
		1346	of C<60> and then call C<ev_timer_again> at start and each time you
		1347	successfully read or write some data. If you go into an idle state where
		1348	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1349	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1350
		1351	That means you can ignore both the C<ev_timer_start> function and the
		1352	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1353	member and C<ev_timer_again>.
		1354
		1355	At start:
		1356
		1357	ev_timer_init (timer, callback);
		1358	timer->repeat = 60.;
		1359	ev_timer_again (loop, timer);
		1360
		1361	Each time there is some activity:
		1362
		1363	ev_timer_again (loop, timer);
		1364
		1365	It is even possible to change the time-out on the fly, regardless of
		1366	whether the watcher is active or not:
		1367
		1368	timer->repeat = 30.;
		1369	ev_timer_again (loop, timer);
		1370
		1371	This is slightly more efficient then stopping/starting the timer each time
		1372	you want to modify its timeout value, as libev does not have to completely
		1373	remove and re-insert the timer from/into its internal data structure.
		1374
		1375	It is, however, even simpler than the "obvious" way to do it.
		1376
		1377	=item 3. Let the timer time out, but then re-arm it as required.
		1378
		1379	This method is more tricky, but usually most efficient: Most timeouts are
		1380	relatively long compared to the intervals between other activity - in
		1381	our example, within 60 seconds, there are usually many I/O events with
		1382	associated activity resets.
		1383
		1384	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1385	but remember the time of last activity, and check for a real timeout only
		1386	within the callback:
		1387
		1388	ev_tstamp last_activity; // time of last activity
		1389
		1390	static void
		1391	callback (EV_P_ ev_timer *w, int revents)
		1392	{
		1393	ev_tstamp now = ev_now (EV_A);
		1394	ev_tstamp timeout = last_activity + 60.;
		1395
		1396	// if last_activity + 60. is older than now, we did time out
		1397	if (timeout < now)
		1398	{
		1399	// timeout occured, take action
		1400	}
		1401	else
		1402	{
		1403	// callback was invoked, but there was some activity, re-arm
		1404	// the watcher to fire in last_activity + 60, which is
		1405	// guaranteed to be in the future, so "again" is positive:
		1406	w->again = timeout - now;
		1407	ev_timer_again (EV_A_ w);
		1408	}
		1409	}
		1410
		1411	To summarise the callback: first calculate the real timeout (defined
		1412	as "60 seconds after the last activity"), then check if that time has
		1413	been reached, which means something I<did>, in fact, time out. Otherwise
		1414	the callback was invoked too early (C<timeout> is in the future), so
		1415	re-schedule the timer to fire at that future time, to see if maybe we have
		1416	a timeout then.
		1417
		1418	Note how C<ev_timer_again> is used, taking advantage of the
		1419	C<ev_timer_again> optimisation when the timer is already running.
		1420
		1421	This scheme causes more callback invocations (about one every 60 seconds
		1422	minus half the average time between activity), but virtually no calls to
		1423	libev to change the timeout.
		1424
		1425	To start the timer, simply initialise the watcher and set C<last_activity>
		1426	to the current time (meaning we just have some activity :), then call the
		1427	callback, which will "do the right thing" and start the timer:
		1428
		1429	ev_timer_init (timer, callback);
		1430	last_activity = ev_now (loop);
		1431	callback (loop, timer, EV_TIMEOUT);
		1432
		1433	And when there is some activity, simply store the current time in
		1434	C<last_activity>, no libev calls at all:
		1435
		1436	last_actiivty = ev_now (loop);
		1437
		1438	This technique is slightly more complex, but in most cases where the
		1439	time-out is unlikely to be triggered, much more efficient.
		1440
		1441	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1442	callback :) - just change the timeout and invoke the callback, which will
		1443	fix things for you.
		1444
		1445	=item 4. Wee, just use a double-linked list for your timeouts.
		1446
		1447	If there is not one request, but many thousands (millions...), all
		1448	employing some kind of timeout with the same timeout value, then one can
		1449	do even better:
		1450
		1451	When starting the timeout, calculate the timeout value and put the timeout
		1452	at the I<end> of the list.
		1453
		1454	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1455	the list is expected to fire (for example, using the technique #3).
		1456
		1457	When there is some activity, remove the timer from the list, recalculate
		1458	the timeout, append it to the end of the list again, and make sure to
		1459	update the C<ev_timer> if it was taken from the beginning of the list.
		1460
		1461	This way, one can manage an unlimited number of timeouts in O(1) time for
		1462	starting, stopping and updating the timers, at the expense of a major
		1463	complication, and having to use a constant timeout. The constant timeout
		1464	ensures that the list stays sorted.
		1465
		1466	=back
		1467
		1468	So which method the best?
		1469
		1470	Method #2 is a simple no-brain-required solution that is adequate in most
		1471	situations. Method #3 requires a bit more thinking, but handles many cases
		1472	better, and isn't very complicated either. In most case, choosing either
		1473	one is fine, with #3 being better in typical situations.
		1474
		1475	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1476	rather complicated, but extremely efficient, something that really pays
		1477	off after the first million or so of active timers, i.e. it's usually
		1478	overkill :)
		1479
		1480	=head3 The special problem of time updates
		1481
		1482	Establishing the current time is a costly operation (it usually takes at
		1483	least two system calls): EV therefore updates its idea of the current
		1484	time only before and after C<ev_loop> collects new events, which causes a
		1485	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1486	lots of events in one iteration.
1164		1487
1165	The relative timeouts are calculated relative to the C<ev_now ()>	1488	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	1489	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	1490	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	1491	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:	1492	timeout on the current time, use something like this to adjust for this:
1170		1493
1171	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1494	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1172		1495
1173	The callback is guarenteed to be invoked only when its timeout has passed,	1496	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	1497	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1175	order of execution is undefined.	1498	()>.
1176		1499
1177	=head3 Watcher-Specific Functions and Data Members	1500	=head3 Watcher-Specific Functions and Data Members
1178		1501
1179	=over 4	1502	=over 4
1180		1503
1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1504	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1182		1505
1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1506	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1184		1507
1185	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1508	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	1509	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	1510	reached. If it is positive, then the timer will automatically be
1188	later, again, and again, until stopped manually.	1511	configured to trigger again C<repeat> seconds later, again, and again,
		1512	until stopped manually.
1189		1513
1190	The timer itself will do a best-effort at avoiding drift, that is, if you	1514	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	1515	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	1516	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	1517	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.	1518	do stuff) the timer will not fire more than once per event loop iteration.
1195		1519
1196	=item ev_timer_again (loop, ev_timer *)	1520	=item ev_timer_again (loop, ev_timer *)
1197		1521
1198	This will act as if the timer timed out and restart it again if it is	1522	This will act as if the timer timed out and restart it again if it is
1199	repeating. The exact semantics are:	1523	repeating. The exact semantics are:
1200		1524
1201	If the timer is pending, its pending status is cleared.	1525	If the timer is pending, its pending status is cleared.
1202		1526
1203	If the timer is started but nonrepeating, stop it (as if it timed out).	1527	If the timer is started but non-repeating, stop it (as if it timed out).
1204		1528
1205	If the timer is repeating, either start it if necessary (with the	1529	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.	1530	C<repeat> value), or reset the running timer to the C<repeat> value.
1207		1531
1208	This sounds a bit complicated, but here is a useful and typical	1532	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	1533	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		1534
1233	=item ev_tstamp repeat [read-write]	1535	=item ev_tstamp repeat [read-write]
1234		1536
1235	The current C<repeat> value. Will be used each time the watcher times out	1537	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),	1538	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.	1539	which is also when any modifications are taken into account.
1238		1540
1239	=back	1541	=back
1240		1542
1241	=head3 Examples	1543	=head3 Examples
1242		1544
1243	Example: Create a timer that fires after 60 seconds.	1545	Example: Create a timer that fires after 60 seconds.
1244		1546
1245	static void	1547	static void
1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1548	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1247	{	1549	{
1248	.. one minute over, w is actually stopped right here	1550	.. one minute over, w is actually stopped right here
1249	}	1551	}
1250		1552
1251	struct ev_timer mytimer;	1553	ev_timer mytimer;
1252	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1554	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1253	ev_timer_start (loop, &mytimer);	1555	ev_timer_start (loop, &mytimer);
1254		1556
1255	Example: Create a timeout timer that times out after 10 seconds of	1557	Example: Create a timeout timer that times out after 10 seconds of
1256	inactivity.	1558	inactivity.
1257		1559
1258	static void	1560	static void
1259	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1561	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1260	{	1562	{
1261	.. ten seconds without any activity	1563	.. ten seconds without any activity
1262	}	1564	}
1263		1565
1264	struct ev_timer mytimer;	1566	ev_timer mytimer;
1265	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1567	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1266	ev_timer_again (&mytimer); /* start timer */	1568	ev_timer_again (&mytimer); /* start timer */
1267	ev_loop (loop, 0);	1569	ev_loop (loop, 0);
1268		1570
1269	// and in some piece of code that gets executed on any "activity":	1571	// and in some piece of code that gets executed on any "activity":
1270	// reset the timeout to start ticking again at 10 seconds	1572	// reset the timeout to start ticking again at 10 seconds
1271	ev_timer_again (&mytimer);	1573	ev_timer_again (&mytimer);
1272		1574
1273		1575
1274	=head2 C<ev_periodic> - to cron or not to cron?	1576	=head2 C<ev_periodic> - to cron or not to cron?
1275		1577
1276	Periodic watchers are also timers of a kind, but they are very versatile	1578	Periodic watchers are also timers of a kind, but they are very versatile
1277	(and unfortunately a bit complex).	1579	(and unfortunately a bit complex).
1278		1580
1279	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1581	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	1582	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	1583	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 ()	1584	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	1585	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1586	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	1587	to trigger the event (unlike an C<ev_timer>, which would still trigger
1285	roughly 10 seconds later).	1588	roughly 10 seconds later as it uses a relative timeout).
1286		1589
1287	They can also be used to implement vastly more complex timers, such as	1590	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,	1591	such as triggering an event on each "midnight, local time", or other
1289	rules.	1592	complicated rules.
1290		1593
1291	As with timers, the callback is guarenteed to be invoked only when the	1594	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	1595	time (C<at>) has passed, but if multiple periodic timers become ready
1293	during the same loop iteration then order of execution is undefined.	1596	during the same loop iteration, then order of execution is undefined.
1294		1597
1295	=head3 Watcher-Specific Functions and Data Members	1598	=head3 Watcher-Specific Functions and Data Members
1296		1599
1297	=over 4	1600	=over 4
1298		1601
1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1602	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1300		1603
1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1604	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1302		1605
1303	Lots of arguments, lets sort it out... There are basically three modes of	1606	Lots of arguments, lets sort it out... There are basically three modes of
1304	operation, and we will explain them from simplest to complex:	1607	operation, and we will explain them from simplest to most complex:
1305		1608
1306	=over 4	1609	=over 4
1307		1610
1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1611	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1309		1612
1310	In this configuration the watcher triggers an event at the wallclock time	1613	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,	1614	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	1615	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.	1616	only run when the system clock reaches or surpasses this time.
1314		1617
1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1618	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1316		1619
1317	In this mode the watcher will always be scheduled to time out at the next	1620	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)	1621	C<at + N * interval> time (for some integer N, which can also be negative)
1319	and then repeat, regardless of any time jumps.	1622	and then repeat, regardless of any time jumps.
1320		1623
1321	This can be used to create timers that do not drift with respect to system	1624	This can be used to create timers that do not drift with respect to the
1322	time:	1625	system clock, for example, here is a C<ev_periodic> that triggers each
		1626	hour, on the hour:
1323		1627
1324	ev_periodic_set (&periodic, 0., 3600., 0);	1628	ev_periodic_set (&periodic, 0., 3600., 0);
1325		1629
1326	This doesn't mean there will always be 3600 seconds in between triggers,	1630	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	1631	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	1632	full hour (UTC), or more correctly, when the system time is evenly divisible
1329	by 3600.	1633	by 3600.
1330		1634
1331	Another way to think about it (for the mathematically inclined) is that	1635	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	1636	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.	1637	time where C<time = at (mod interval)>, regardless of any time jumps.
1334		1638
1335	For numerical stability it is preferable that the C<at> value is near	1639	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	1640	C<ev_now ()> (the current time), but there is no range requirement for
1337	this value.	1641	this value, and in fact is often specified as zero.
		1642
		1643	Note also that there is an upper limit to how often a timer can fire (CPU
		1644	speed for example), so if C<interval> is very small then timing stability
		1645	will of course deteriorate. Libev itself tries to be exact to be about one
		1646	millisecond (if the OS supports it and the machine is fast enough).
1338		1647
1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1648	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1340		1649
1341	In this mode the values for C<interval> and C<at> are both being	1650	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	1651	ignored. Instead, each time the periodic watcher gets scheduled, the
1343	reschedule callback will be called with the watcher as first, and the	1652	reschedule callback will be called with the watcher as first, and the
1344	current time as second argument.	1653	current time as second argument.
1345		1654
1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1655	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,	1656	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		1657
		1658	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1659	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1660	only event loop modification you are allowed to do).
		1661
1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1662	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1352	ev_tstamp now)>, e.g.:	1663	*w, ev_tstamp now)>, e.g.:
1353		1664
		1665	static ev_tstamp
1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1666	my_rescheduler (ev_periodic *w, ev_tstamp now)
1355	{	1667	{
1356	return now + 60.;	1668	return now + 60.;
1357	}	1669	}
1358		1670
1359	It must return the next time to trigger, based on the passed time value	1671	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	1672	(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	1673	will usually be called just before the callback will be triggered, but
1362	might be called at other times, too.	1674	might be called at other times, too.
1363		1675
1364	NOTE: I<< This callback must always return a time that is later than the	1676	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.	1677	equal to the passed C<now> value >>.
1366		1678
1367	This can be used to create very complex timers, such as a timer that	1679	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	1680	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	1681	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	1682	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).	1683	reason I omitted it as an example).
1372		1684
1373	=back	1685	=back
…		…
1377	Simply stops and restarts the periodic watcher again. This is only useful	1689	Simply stops and restarts the periodic watcher again. This is only useful
1378	when you changed some parameters or the reschedule callback would return	1690	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	1691	a different time than the last time it was called (e.g. in a crond like
1380	program when the crontabs have changed).	1692	program when the crontabs have changed).
1381		1693
		1694	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1695
		1696	When active, returns the absolute time that the watcher is supposed to
		1697	trigger next.
		1698
1382	=item ev_tstamp offset [read-write]	1699	=item ev_tstamp offset [read-write]
1383		1700
1384	When repeating, this contains the offset value, otherwise this is the	1701	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>).	1702	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1386		1703
…		…
1391		1708
1392	The current interval value. Can be modified any time, but changes only	1709	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	1710	take effect when the periodic timer fires or C<ev_periodic_again> is being
1394	called.	1711	called.
1395		1712
1396	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1713	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1397		1714
1398	The current reschedule callback, or C<0>, if this functionality is	1715	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	1716	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.	1717	the periodic timer fires or C<ev_periodic_again> is being called.
1401		1718
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	1719	=back
1408		1720
1409	=head3 Examples	1721	=head3 Examples
1410		1722
1411	Example: Call a callback every hour, or, more precisely, whenever the	1723	Example: Call a callback every hour, or, more precisely, whenever the
1412	system clock is divisible by 3600. The callback invocation times have	1724	system time is divisible by 3600. The callback invocation times have
1413	potentially a lot of jittering, but good long-term stability.	1725	potentially a lot of jitter, but good long-term stability.
1414		1726
1415	static void	1727	static void
1416	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1728	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1417	{	1729	{
1418	... its now a full hour (UTC, or TAI or whatever your clock follows)	1730	... its now a full hour (UTC, or TAI or whatever your clock follows)
1419	}	1731	}
1420		1732
1421	struct ev_periodic hourly_tick;	1733	ev_periodic hourly_tick;
1422	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1734	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1423	ev_periodic_start (loop, &hourly_tick);	1735	ev_periodic_start (loop, &hourly_tick);
1424		1736
1425	Example: The same as above, but use a reschedule callback to do it:	1737	Example: The same as above, but use a reschedule callback to do it:
1426		1738
1427	#include <math.h>	1739	#include <math.h>
1428		1740
1429	static ev_tstamp	1741	static ev_tstamp
1430	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1742	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1431	{	1743	{
1432	return fmod (now, 3600.) + 3600.;	1744	return now + (3600. - fmod (now, 3600.));
1433	}	1745	}
1434		1746
1435	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1747	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1436		1748
1437	Example: Call a callback every hour, starting now:	1749	Example: Call a callback every hour, starting now:
1438		1750
1439	struct ev_periodic hourly_tick;	1751	ev_periodic hourly_tick;
1440	ev_periodic_init (&hourly_tick, clock_cb,	1752	ev_periodic_init (&hourly_tick, clock_cb,
1441	fmod (ev_now (loop), 3600.), 3600., 0);	1753	fmod (ev_now (loop), 3600.), 3600., 0);
1442	ev_periodic_start (loop, &hourly_tick);	1754	ev_periodic_start (loop, &hourly_tick);
1443		1755
1444		1756
1445	=head2 C<ev_signal> - signal me when a signal gets signalled!	1757	=head2 C<ev_signal> - signal me when a signal gets signalled!
1446		1758
1447	Signal watchers will trigger an event when the process receives a specific	1759	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	1760	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	1761	will try it's best to deliver signals synchronously, i.e. as part of the
1450	normal event processing, like any other event.	1762	normal event processing, like any other event.
1451		1763
		1764	If you want signals asynchronously, just use C<sigaction> as you would
		1765	do without libev and forget about sharing the signal. You can even use
		1766	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1767
1452	You can configure as many watchers as you like per signal. Only when the	1768	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	1769	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	1770	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	1771	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	1772	the last signal watcher for a signal is stopped, libev will reset the
1457	SIG_DFL (regardless of what it was set to before).	1773	signal handler to SIG_DFL (regardless of what it was set to before).
1458		1774
1459	If possible and supported, libev will install its handlers with	1775	If possible and supported, libev will install its handlers with
1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1776	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1461	interrupted. If you have a problem with syscalls getting interrupted by	1777	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	1778	signals you can block all signals in an C<ev_check> watcher and unblock
1463	them in an C<ev_prepare> watcher.	1779	them in an C<ev_prepare> watcher.
1464		1780
1465	=head3 Watcher-Specific Functions and Data Members	1781	=head3 Watcher-Specific Functions and Data Members
1466		1782
…		…
1479		1795
1480	=back	1796	=back
1481		1797
1482	=head3 Examples	1798	=head3 Examples
1483		1799
1484	Example: Try to exit cleanly on SIGINT and SIGTERM.	1800	Example: Try to exit cleanly on SIGINT.
1485		1801
1486	static void	1802	static void
1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1803	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1488	{	1804	{
1489	ev_unloop (loop, EVUNLOOP_ALL);	1805	ev_unloop (loop, EVUNLOOP_ALL);
1490	}	1806	}
1491		1807
1492	struct ev_signal signal_watcher;	1808	ev_signal signal_watcher;
1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1809	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1494	ev_signal_start (loop, &sigint_cb);	1810	ev_signal_start (loop, &signal_watcher);
1495		1811
1496		1812
1497	=head2 C<ev_child> - watch out for process status changes	1813	=head2 C<ev_child> - watch out for process status changes
1498		1814
1499	Child watchers trigger when your process receives a SIGCHLD in response to	1815	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	1816	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	1817	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	1818	has been forked (which implies it might have already exited), as long
1503	loop isn't entered (or is continued from a watcher).	1819	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1820	forking and then immediately registering a watcher for the child is fine,
		1821	but forking and registering a watcher a few event loop iterations later is
		1822	not.
1504		1823
1505	Only the default event loop is capable of handling signals, and therefore	1824	Only the default event loop is capable of handling signals, and therefore
1506	you can only rgeister child watchers in the default event loop.	1825	you can only register child watchers in the default event loop.
1507		1826
1508	=head3 Process Interaction	1827	=head3 Process Interaction
1509		1828
1510	Libev grabs C<SIGCHLD> as soon as the default event loop is	1829	Libev grabs C<SIGCHLD> as soon as the default event loop is
1511	initialised. This is necessary to guarantee proper behaviour even if	1830	initialised. This is necessary to guarantee proper behaviour even if
1512	the first child watcher is started after the child exits. The occurance	1831	the first child watcher is started after the child exits. The occurrence
1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1832	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1514	synchronously as part of the event loop processing. Libev always reaps all	1833	synchronously as part of the event loop processing. Libev always reaps all
1515	children, even ones not watched.	1834	children, even ones not watched.
1516		1835
1517	=head3 Overriding the Built-In Processing	1836	=head3 Overriding the Built-In Processing
…		…
1521	handler, you can override it easily by installing your own handler for	1840	handler, you can override it easily by installing your own handler for
1522	C<SIGCHLD> after initialising the default loop, and making sure the	1841	C<SIGCHLD> after initialising the default loop, and making sure the
1523	default loop never gets destroyed. You are encouraged, however, to use an	1842	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	1843	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.	1844	that, so other libev users can use C<ev_child> watchers freely.
		1845
		1846	=head3 Stopping the Child Watcher
		1847
		1848	Currently, the child watcher never gets stopped, even when the
		1849	child terminates, so normally one needs to stop the watcher in the
		1850	callback. Future versions of libev might stop the watcher automatically
		1851	when a child exit is detected.
1526		1852
1527	=head3 Watcher-Specific Functions and Data Members	1853	=head3 Watcher-Specific Functions and Data Members
1528		1854
1529	=over 4	1855	=over 4
1530		1856
…		…
1559	=head3 Examples	1885	=head3 Examples
1560		1886
1561	Example: C<fork()> a new process and install a child handler to wait for	1887	Example: C<fork()> a new process and install a child handler to wait for
1562	its completion.	1888	its completion.
1563		1889
1564	ev_child cw;	1890	ev_child cw;
1565		1891
1566	static void	1892	static void
1567	child_cb (EV_P_ struct ev_child *w, int revents)	1893	child_cb (EV_P_ ev_child *w, int revents)
1568	{	1894	{
1569	ev_child_stop (EV_A_ w);	1895	ev_child_stop (EV_A_ w);
1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1896	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1571	}	1897	}
1572		1898
1573	pid_t pid = fork ();	1899	pid_t pid = fork ();
1574		1900
1575	if (pid < 0)	1901	if (pid < 0)
1576	// error	1902	// error
1577	else if (pid == 0)	1903	else if (pid == 0)
1578	{	1904	{
1579	// the forked child executes here	1905	// the forked child executes here
1580	exit (1);	1906	exit (1);
1581	}	1907	}
1582	else	1908	else
1583	{	1909	{
1584	ev_child_init (&cw, child_cb, pid, 0);	1910	ev_child_init (&cw, child_cb, pid, 0);
1585	ev_child_start (EV_DEFAULT_ &cw);	1911	ev_child_start (EV_DEFAULT_ &cw);
1586	}	1912	}
1587		1913
1588		1914
1589	=head2 C<ev_stat> - did the file attributes just change?	1915	=head2 C<ev_stat> - did the file attributes just change?
1590		1916
1591	This watches a filesystem path for attribute changes. That is, it calls	1917	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	1918	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.	1919	compared to the last time, invoking the callback if it did.
1594		1920
1595	The path does not need to exist: changing from "path exists" to "path does	1921	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	1922	not exist" is a status change like any other. The condition "path does
…		…
1599	the stat buffer having unspecified contents.	1925	the stat buffer having unspecified contents.
1600		1926
1601	The path I<should> be absolute and I<must not> end in a slash. If it is	1927	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.	1928	relative and your working directory changes, the behaviour is undefined.
1603		1929
1604	Since there is no standard to do this, the portable implementation simply	1930	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	1931	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	1932	it changed somehow. You can specify a recommended polling interval for
1607	a polling interval of C<0> (highly recommended!) then a I<suitable,	1933	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	1934	then a I<suitable, unspecified default> value will be used (which
1609	five seconds, although this might change dynamically). Libev will also	1935	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	1936	dynamically). Libev will also impose a minimum interval which is currently
1611	usually overkill.	1937	around C<0.1>, but thats usually overkill.
1612		1938
1613	This watcher type is not meant for massive numbers of stat watchers,	1939	This watcher type is not meant for massive numbers of stat watchers,
1614	as even with OS-supported change notifications, this can be	1940	as even with OS-supported change notifications, this can be
1615	resource-intensive.	1941	resource-intensive.
1616		1942
1617	At the time of this writing, only the Linux inotify interface is	1943	At the time of this writing, the only OS-specific interface implemented
1618	implemented (implementing kqueue support is left as an exercise for the	1944	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	1945	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	1946	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		1947
1625	=head3 ABI Issues (Largefile Support)	1948	=head3 ABI Issues (Largefile Support)
1626		1949
1627	Libev by default (unless the user overrides this) uses the default	1950	Libev by default (unless the user overrides this) uses the default
1628	compilation environment, which means that on systems with optionally	1951	compilation environment, which means that on systems with large file
1629	disabled large file support, you get the 32 bit version of the stat	1952	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	1953	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	1954	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	1955	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	1956	obviously the case with any flags that change the ABI, but the problem is
1634	most noticably with ev_stat and largefile support.	1957	most noticeably disabled with ev_stat and large file support.
1635		1958
1636	=head3 Inotify	1959	The solution for this is to lobby your distribution maker to make large
		1960	file interfaces available by default (as e.g. FreeBSD does) and not
		1961	optional. Libev cannot simply switch on large file support because it has
		1962	to exchange stat structures with application programs compiled using the
		1963	default compilation environment.
1637		1964
		1965	=head3 Inotify and Kqueue
		1966
1638	When C<inotify (7)> support has been compiled into libev (generally only	1967	When C<inotify (7)> support has been compiled into libev (generally
		1968	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	1969	implementations) and present at runtime, it will be used to speed up
1640	change detection where possible. The inotify descriptor will be created lazily	1970	change detection where possible. The inotify descriptor will be created
1641	when the first C<ev_stat> watcher is being started.	1971	lazily when the first C<ev_stat> watcher is being started.
1642		1972
1643	Inotify presense does not change the semantics of C<ev_stat> watchers	1973	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	1974	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	1975	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.	1976	there are many cases where libev has to resort to regular C<stat> polling,
		1977	but as long as the path exists, libev usually gets away without polling.
1647		1978
1648	(There is no support for kqueue, as apparently it cannot be used to	1979	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	1980	implement this functionality, due to the requirement of having a file
1650	descriptor open on the object at all times).	1981	descriptor open on the object at all times, and detecting renames, unlinks
		1982	etc. is difficult.
1651		1983
1652	=head3 The special problem of stat time resolution	1984	=head3 The special problem of stat time resolution
1653		1985
1654	The C<stat ()> syscall only supports full-second resolution portably, and	1986	The C<stat ()> system call only supports full-second resolution portably, and
1655	even on systems where the resolution is higher, many filesystems still	1987	even on systems where the resolution is higher, most file systems still
1656	only support whole seconds.	1988	only support whole seconds.
1657		1989
1658	That means that, if the time is the only thing that changes, you might	1990	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	1991	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	1992	calls your callback, which does something. When there is another update
1661	the same second, C<ev_stat> will be unable to detect it.	1993	within the same second, C<ev_stat> will be unable to detect unless the
		1994	stat data does change in other ways (e.g. file size).
1662		1995
1663	The solution to this is to delay acting on a change for a second (or till	1996	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>	1997	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>	1998	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	1999	ev_timer_again (loop, w)>).
1667	systems.	2000
		2001	The C<.02> offset is added to work around small timing inconsistencies
		2002	of some operating systems (where the second counter of the current time
		2003	might be be delayed. One such system is the Linux kernel, where a call to
		2004	C<gettimeofday> might return a timestamp with a full second later than
		2005	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2006	update file times then there will be a small window where the kernel uses
		2007	the previous second to update file times but libev might already execute
		2008	the timer callback).
1668		2009
1669	=head3 Watcher-Specific Functions and Data Members	2010	=head3 Watcher-Specific Functions and Data Members
1670		2011
1671	=over 4	2012	=over 4
1672		2013
…		…
1678	C<path>. The C<interval> is a hint on how quickly a change is expected to	2019	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	2020	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	2021	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.	2022	path for as long as the watcher is active.
1682		2023
1683	The callback will be receive C<EV_STAT> when a change was detected,	2024	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	2025	relative to the attributes at the time the watcher was started (or the
1685	last change was detected).	2026	last change was detected).
1686		2027
1687	=item ev_stat_stat (loop, ev_stat *)	2028	=item ev_stat_stat (loop, ev_stat *)
1688		2029
1689	Updates the stat buffer immediately with new values. If you change the	2030	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	2031	watched path in your callback, you could call this function to avoid
1691	detecting this change (while introducing a race condition). Can also be	2032	detecting this change (while introducing a race condition if you are not
1692	useful simply to find out the new values.	2033	the only one changing the path). Can also be useful simply to find out the
		2034	new values.
1693		2035
1694	=item ev_statdata attr [read-only]	2036	=item ev_statdata attr [read-only]
1695		2037
1696	The most-recently detected attributes of the file. Although the type is of	2038	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	2039	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	2040	suitable for your system, but you can only rely on the POSIX-standardised
		2041	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.	2042	some error while C<stat>ing the file.
1700		2043
1701	=item ev_statdata prev [read-only]	2044	=item ev_statdata prev [read-only]
1702		2045
1703	The previous attributes of the file. The callback gets invoked whenever	2046	The previous attributes of the file. The callback gets invoked whenever
1704	C<prev> != C<attr>.	2047	C<prev> != C<attr>, or, more precisely, one or more of these members
		2048	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2049	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1705		2050
1706	=item ev_tstamp interval [read-only]	2051	=item ev_tstamp interval [read-only]
1707		2052
1708	The specified interval.	2053	The specified interval.
1709		2054
1710	=item const char *path [read-only]	2055	=item const char *path [read-only]
1711		2056
1712	The filesystem path that is being watched.	2057	The file system path that is being watched.
1713		2058
1714	=back	2059	=back
1715		2060
1716	=head3 Examples	2061	=head3 Examples
1717		2062
1718	Example: Watch C</etc/passwd> for attribute changes.	2063	Example: Watch C</etc/passwd> for attribute changes.
1719		2064
1720	static void	2065	static void
1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2066	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1722	{	2067	{
1723	/* /etc/passwd changed in some way */	2068	/* /etc/passwd changed in some way */
1724	if (w->attr.st_nlink)	2069	if (w->attr.st_nlink)
1725	{	2070	{
1726	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2071	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1727	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2072	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1728	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2073	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1729	}	2074	}
1730	else	2075	else
1731	/* you shalt not abuse printf for puts */	2076	/* you shalt not abuse printf for puts */
1732	puts ("wow, /etc/passwd is not there, expect problems. "	2077	puts ("wow, /etc/passwd is not there, expect problems. "
1733	"if this is windows, they already arrived\n");	2078	"if this is windows, they already arrived\n");
1734	}	2079	}
1735		2080
1736	...	2081	...
1737	ev_stat passwd;	2082	ev_stat passwd;
1738		2083
1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2084	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1740	ev_stat_start (loop, &passwd);	2085	ev_stat_start (loop, &passwd);
1741		2086
1742	Example: Like above, but additionally use a one-second delay so we do not	2087	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	2088	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	2089	one might do the work both on C<ev_stat> callback invocation I<and> on
1745	C<ev_timer> callback invocation).	2090	C<ev_timer> callback invocation).
1746		2091
1747	static ev_stat passwd;	2092	static ev_stat passwd;
1748	static ev_timer timer;	2093	static ev_timer timer;
1749		2094
1750	static void	2095	static void
1751	timer_cb (EV_P_ ev_timer *w, int revents)	2096	timer_cb (EV_P_ ev_timer *w, int revents)
1752	{	2097	{
1753	ev_timer_stop (EV_A_ w);	2098	ev_timer_stop (EV_A_ w);
1754		2099
1755	/* now it's one second after the most recent passwd change */	2100	/* now it's one second after the most recent passwd change */
1756	}	2101	}
1757		2102
1758	static void	2103	static void
1759	stat_cb (EV_P_ ev_stat *w, int revents)	2104	stat_cb (EV_P_ ev_stat *w, int revents)
1760	{	2105	{
1761	/* reset the one-second timer */	2106	/* reset the one-second timer */
1762	ev_timer_again (EV_A_ &timer);	2107	ev_timer_again (EV_A_ &timer);
1763	}	2108	}
1764		2109
1765	...	2110	...
1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2111	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1767	ev_stat_start (loop, &passwd);	2112	ev_stat_start (loop, &passwd);
1768	ev_timer_init (&timer, timer_cb, 0., 1.01);	2113	ev_timer_init (&timer, timer_cb, 0., 1.02);
1769		2114
1770		2115
1771	=head2 C<ev_idle> - when you've got nothing better to do...	2116	=head2 C<ev_idle> - when you've got nothing better to do...
1772		2117
1773	Idle watchers trigger events when no other events of the same or higher	2118	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	2119	priority are pending (prepare, check and other idle watchers do not count
1775	count).	2120	as receiving "events").
1776		2121
1777	That is, as long as your process is busy handling sockets or timeouts	2122	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	2123	(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	2124	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	2125	are pending), the idle watchers are being called once per event loop
…		…
1804	=head3 Examples	2149	=head3 Examples
1805		2150
1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2151	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1807	callback, free it. Also, use no error checking, as usual.	2152	callback, free it. Also, use no error checking, as usual.
1808		2153
1809	static void	2154	static void
1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2155	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1811	{	2156	{
1812	free (w);	2157	free (w);
1813	// now do something you wanted to do when the program has	2158	// now do something you wanted to do when the program has
1814	// no longer anything immediate to do.	2159	// no longer anything immediate to do.
1815	}	2160	}
1816		2161
1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2162	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1818	ev_idle_init (idle_watcher, idle_cb);	2163	ev_idle_init (idle_watcher, idle_cb);
1819	ev_idle_start (loop, idle_cb);	2164	ev_idle_start (loop, idle_cb);
1820		2165
1821		2166
1822	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2167	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1823		2168
1824	Prepare and check watchers are usually (but not always) used in tandem:	2169	Prepare and check watchers are usually (but not always) used in pairs:
1825	prepare watchers get invoked before the process blocks and check watchers	2170	prepare watchers get invoked before the process blocks and check watchers
1826	afterwards.	2171	afterwards.
1827		2172
1828	You I<must not> call C<ev_loop> or similar functions that enter	2173	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>	2174	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,	2177	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	2178	C<ev_check> so if you have one watcher of each kind they will always be
1834	called in pairs bracketing the blocking call.	2179	called in pairs bracketing the blocking call.
1835		2180
1836	Their main purpose is to integrate other event mechanisms into libev and	2181	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	2182	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	2183	variable changes, implement your own watchers, integrate net-snmp or a
1839	coroutine library and lots more. They are also occasionally useful if	2184	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,	2185	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>	2186	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1842	watcher).	2187	watcher).
1843		2188
1844	This is done by examining in each prepare call which file descriptors need	2189	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	2190	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	2191	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	2192	libraries provide exactly this functionality). Then, in the check watcher,
1848	any events that occured (by checking the pending status of all watchers	2193	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	2194	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,	2195	I/O and timer callbacks will never actually be called (but must be valid
1851	because you never know, you know?).	2196	nevertheless, because you never know, you know?).
1852		2197
1853	As another example, the Perl Coro module uses these hooks to integrate	2198	As another example, the Perl Coro module uses these hooks to integrate
1854	coroutines into libev programs, by yielding to other active coroutines	2199	coroutines into libev programs, by yielding to other active coroutines
1855	during each prepare and only letting the process block if no coroutines	2200	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	2201	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	2204	loop from blocking if lower-priority coroutines are active, thus mapping
1860	low-priority coroutines to idle/background tasks).	2205	low-priority coroutines to idle/background tasks).
1861		2206
1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2207	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	2208	priority, to ensure that they are being run before any other watchers
		2209	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2210
1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2211	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	2212	activate ("feed") events into libev. While libev fully supports this, they
1866	supports this, they will be called before other C<ev_check> watchers	2213	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	2214	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	2215	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	2216	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1870	coexist peacefully with others).	2217	others).
1871		2218
1872	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
1873		2220
1874	=over 4	2221	=over 4
1875		2222
…		…
1877		2224
1878	=item ev_check_init (ev_check *, callback)	2225	=item ev_check_init (ev_check *, callback)
1879		2226
1880	Initialises and configures the prepare or check watcher - they have no	2227	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>	2228	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.	2229	macros, but using them is utterly, utterly, utterly and completely
		2230	pointless.
1883		2231
1884	=back	2232	=back
1885		2233
1886	=head3 Examples	2234	=head3 Examples
1887		2235
1888	There are a number of principal ways to embed other event loops or modules	2236	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	2237	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	2238	(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>	2239	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	2240	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1893	into the Glib event loop).	2241	Glib event loop).
1894		2242
1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2243	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	2244	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	2245	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	2246	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.	2247	the callbacks for the IO/timeout watchers might not have been called yet.
1900		2248
1901	static ev_io iow [nfd];	2249	static ev_io iow [nfd];
1902	static ev_timer tw;	2250	static ev_timer tw;
1903		2251
1904	static void	2252	static void
1905	io_cb (ev_loop *loop, ev_io *w, int revents)	2253	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1906	{	2254	{
1907	}	2255	}
1908		2256
1909	// create io watchers for each fd and a timer before blocking	2257	// create io watchers for each fd and a timer before blocking
1910	static void	2258	static void
1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2259	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1912	{	2260	{
1913	int timeout = 3600000;	2261	int timeout = 3600000;
1914	struct pollfd fds [nfd];	2262	struct pollfd fds [nfd];
1915	// actual code will need to loop here and realloc etc.	2263	// actual code will need to loop here and realloc etc.
1916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2264	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1917		2265
1918	/* the callback is illegal, but won't be called as we stop during check */	2266	/* the callback is illegal, but won't be called as we stop during check */
1919	ev_timer_init (&tw, 0, timeout * 1e-3);	2267	ev_timer_init (&tw, 0, timeout * 1e-3);
1920	ev_timer_start (loop, &tw);	2268	ev_timer_start (loop, &tw);
1921		2269
1922	// create one ev_io per pollfd	2270	// create one ev_io per pollfd
1923	for (int i = 0; i < nfd; ++i)	2271	for (int i = 0; i < nfd; ++i)
1924	{	2272	{
1925	ev_io_init (iow + i, io_cb, fds [i].fd,	2273	ev_io_init (iow + i, io_cb, fds [i].fd,
1926	((fds [i].events & POLLIN ? EV_READ : 0)	2274	((fds [i].events & POLLIN ? EV_READ : 0)
1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2275	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1928		2276
1929	fds [i].revents = 0;	2277	fds [i].revents = 0;
1930	ev_io_start (loop, iow + i);	2278	ev_io_start (loop, iow + i);
1931	}	2279	}
1932	}	2280	}
1933		2281
1934	// stop all watchers after blocking	2282	// stop all watchers after blocking
1935	static void	2283	static void
1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2284	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1937	{	2285	{
1938	ev_timer_stop (loop, &tw);	2286	ev_timer_stop (loop, &tw);
1939		2287
1940	for (int i = 0; i < nfd; ++i)	2288	for (int i = 0; i < nfd; ++i)
1941	{	2289	{
1942	// set the relevant poll flags	2290	// set the relevant poll flags
1943	// could also call adns_processreadable etc. here	2291	// could also call adns_processreadable etc. here
1944	struct pollfd *fd = fds + i;	2292	struct pollfd *fd = fds + i;
1945	int revents = ev_clear_pending (iow + i);	2293	int revents = ev_clear_pending (iow + i);
1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2294	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2295	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1948		2296
1949	// now stop the watcher	2297	// now stop the watcher
1950	ev_io_stop (loop, iow + i);	2298	ev_io_stop (loop, iow + i);
1951	}	2299	}
1952		2300
1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2301	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1954	}	2302	}
1955		2303
1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2304	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.	2305	in the prepare watcher and would dispose of the check watcher.
1958		2306
1959	Method 3: If the module to be embedded supports explicit event	2307	Method 3: If the module to be embedded supports explicit event
1960	notification (adns does), you can also make use of the actual watcher	2308	notification (libadns does), you can also make use of the actual watcher
1961	callbacks, and only destroy/create the watchers in the prepare watcher.	2309	callbacks, and only destroy/create the watchers in the prepare watcher.
1962		2310
1963	static void	2311	static void
1964	timer_cb (EV_P_ ev_timer *w, int revents)	2312	timer_cb (EV_P_ ev_timer *w, int revents)
1965	{	2313	{
1966	adns_state ads = (adns_state)w->data;	2314	adns_state ads = (adns_state)w->data;
1967	update_now (EV_A);	2315	update_now (EV_A);
1968		2316
1969	adns_processtimeouts (ads, &tv_now);	2317	adns_processtimeouts (ads, &tv_now);
1970	}	2318	}
1971		2319
1972	static void	2320	static void
1973	io_cb (EV_P_ ev_io *w, int revents)	2321	io_cb (EV_P_ ev_io *w, int revents)
1974	{	2322	{
1975	adns_state ads = (adns_state)w->data;	2323	adns_state ads = (adns_state)w->data;
1976	update_now (EV_A);	2324	update_now (EV_A);
1977		2325
1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2326	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2327	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1980	}	2328	}
1981		2329
1982	// do not ever call adns_afterpoll	2330	// do not ever call adns_afterpoll
1983		2331
1984	Method 4: Do not use a prepare or check watcher because the module you	2332	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	2333	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	2334	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	2335	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1988	this.	2336	this approach, effectively embedding EV as a client into the horrible
		2337	libglib event loop.
1989		2338
1990	static gint	2339	static gint
1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2340	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1992	{	2341	{
1993	int got_events = 0;	2342	int got_events = 0;
1994		2343
1995	for (n = 0; n < nfds; ++n)	2344	for (n = 0; n < nfds; ++n)
1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2345	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1997		2346
1998	if (timeout >= 0)	2347	if (timeout >= 0)
1999	// create/start timer	2348	// create/start timer
2000		2349
2001	// poll	2350	// poll
2002	ev_loop (EV_A_ 0);	2351	ev_loop (EV_A_ 0);
2003		2352
2004	// stop timer again	2353	// stop timer again
2005	if (timeout >= 0)	2354	if (timeout >= 0)
2006	ev_timer_stop (EV_A_ &to);	2355	ev_timer_stop (EV_A_ &to);
2007		2356
2008	// stop io watchers again - their callbacks should have set	2357	// stop io watchers again - their callbacks should have set
2009	for (n = 0; n < nfds; ++n)	2358	for (n = 0; n < nfds; ++n)
2010	ev_io_stop (EV_A_ iow [n]);	2359	ev_io_stop (EV_A_ iow [n]);
2011		2360
2012	return got_events;	2361	return got_events;
2013	}	2362	}
2014		2363
2015		2364
2016	=head2 C<ev_embed> - when one backend isn't enough...	2365	=head2 C<ev_embed> - when one backend isn't enough...
2017		2366
2018	This is a rather advanced watcher type that lets you embed one event loop	2367	This is a rather advanced watcher type that lets you embed one event loop
…		…
2024	prioritise I/O.	2373	prioritise I/O.
2025		2374
2026	As an example for a bug workaround, the kqueue backend might only support	2375	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	2376	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	2377	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	2378	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	2379	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	2380	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.	2381	C<kevent>, but at least you can use both mechanisms for what they are
		2382	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2033		2383
2034	As for prioritising I/O: rarely you have the case where some fds have	2384	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	2385	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	2386	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	2387	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.	2388	the rest in a second one, and embed the second one in the first.
2039		2389
2040	As long as the watcher is active, the callback will be invoked every time	2390	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	2391	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	2392	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	2393	their callbacks (you could also start an idle watcher to give the embedded
…		…
2051	interested in that.	2401	interested in that.
2052		2402
2053	Also, there have not currently been made special provisions for forking:	2403	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,	2404	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	2405	but you will also have to stop and restart any C<ev_embed> watchers
2056	yourself.	2406	yourself - but you can use a fork watcher to handle this automatically,
		2407	and future versions of libev might do just that.
2057		2408
2058	Unfortunately, not all backends are embeddable, only the ones returned by	2409	Unfortunately, not all backends are embeddable: only the ones returned by
2059	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2410	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2060	portable one.	2411	portable one.
2061		2412
2062	So when you want to use this feature you will always have to be prepared	2413	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	2414	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	2415	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.	2416	create it, and if that fails, use the normal loop for everything.
2066		2417
		2418	=head3 C<ev_embed> and fork
		2419
		2420	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2421	automatically be applied to the embedded loop as well, so no special
		2422	fork handling is required in that case. When the watcher is not running,
		2423	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2424	as applicable.
		2425
2067	=head3 Watcher-Specific Functions and Data Members	2426	=head3 Watcher-Specific Functions and Data Members
2068		2427
2069	=over 4	2428	=over 4
2070		2429
2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2430	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2074		2433
2075	Configures the watcher to embed the given loop, which must be	2434	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	2435	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	2436	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,	2437	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).	2438	if you do not want that, you need to temporarily stop the embed watcher).
2080		2439
2081	=item ev_embed_sweep (loop, ev_embed *)	2440	=item ev_embed_sweep (loop, ev_embed *)
2082		2441
2083	Make a single, non-blocking sweep over the embedded loop. This works	2442	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	2443	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2085	apropriate way for embedded loops.	2444	appropriate way for embedded loops.
2086		2445
2087	=item struct ev_loop *other [read-only]	2446	=item struct ev_loop *other [read-only]
2088		2447
2089	The embedded event loop.	2448	The embedded event loop.
2090		2449
…		…
2092		2451
2093	=head3 Examples	2452	=head3 Examples
2094		2453
2095	Example: Try to get an embeddable event loop and embed it into the default	2454	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	2455	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	2456	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	2457	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2099	used).	2458	used).
2100		2459
2101	struct ev_loop *loop_hi = ev_default_init (0);	2460	struct ev_loop *loop_hi = ev_default_init (0);
2102	struct ev_loop *loop_lo = 0;	2461	struct ev_loop *loop_lo = 0;
2103	struct ev_embed embed;	2462	ev_embed embed;
2104		2463
2105	// see if there is a chance of getting one that works	2464	// see if there is a chance of getting one that works
2106	// (remember that a flags value of 0 means autodetection)	2465	// (remember that a flags value of 0 means autodetection)
2107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2466	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2467	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2109	: 0;	2468	: 0;
2110		2469
2111	// if we got one, then embed it, otherwise default to loop_hi	2470	// if we got one, then embed it, otherwise default to loop_hi
2112	if (loop_lo)	2471	if (loop_lo)
2113	{	2472	{
2114	ev_embed_init (&embed, 0, loop_lo);	2473	ev_embed_init (&embed, 0, loop_lo);
2115	ev_embed_start (loop_hi, &embed);	2474	ev_embed_start (loop_hi, &embed);
2116	}	2475	}
2117	else	2476	else
2118	loop_lo = loop_hi;	2477	loop_lo = loop_hi;
2119		2478
2120	Example: Check if kqueue is available but not recommended and create	2479	Example: Check if kqueue is available but not recommended and create
2121	a kqueue backend for use with sockets (which usually work with any	2480	a kqueue backend for use with sockets (which usually work with any
2122	kqueue implementation). Store the kqueue/socket-only event loop in	2481	kqueue implementation). Store the kqueue/socket-only event loop in
2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2482	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2124		2483
2125	struct ev_loop *loop = ev_default_init (0);	2484	struct ev_loop *loop = ev_default_init (0);
2126	struct ev_loop *loop_socket = 0;	2485	struct ev_loop *loop_socket = 0;
2127	struct ev_embed embed;	2486	ev_embed embed;
2128		2487
2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2488	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2489	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2131	{	2490	{
2132	ev_embed_init (&embed, 0, loop_socket);	2491	ev_embed_init (&embed, 0, loop_socket);
2133	ev_embed_start (loop, &embed);	2492	ev_embed_start (loop, &embed);
2134	}	2493	}
2135		2494
2136	if (!loop_socket)	2495	if (!loop_socket)
2137	loop_socket = loop;	2496	loop_socket = loop;
2138		2497
2139	// now use loop_socket for all sockets, and loop for everything else	2498	// now use loop_socket for all sockets, and loop for everything else
2140		2499
2141		2500
2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2501	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2143		2502
2144	Fork watchers are called when a C<fork ()> was detected (usually because	2503	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	2547	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	2548	multiple-writer-single-reader queue that works in all cases and doesn't
2190	need elaborate support such as pthreads.	2549	need elaborate support such as pthreads.
2191		2550
2192	That means that if you want to queue data, you have to provide your own	2551	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	2552	queue. But at least I can tell you how to implement locking around your
2194	queue:	2553	queue:
2195		2554
2196	=over 4	2555	=over 4
2197		2556
2198	=item queueing from a signal handler context	2557	=item queueing from a signal handler context
2199		2558
2200	To implement race-free queueing, you simply add to the queue in the signal	2559	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	2560	handler but you block the signal handler in the watcher callback. Here is
2202	some fictitiuous SIGUSR1 handler:	2561	an example that does that for some fictitious SIGUSR1 handler:
2203		2562
2204	static ev_async mysig;	2563	static ev_async mysig;
2205		2564
2206	static void	2565	static void
2207	sigusr1_handler (void)	2566	sigusr1_handler (void)
…		…
2274		2633
2275	=item ev_async_init (ev_async *, callback)	2634	=item ev_async_init (ev_async *, callback)
2276		2635
2277	Initialises and configures the async watcher - it has no parameters of any	2636	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,	2637	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2279	believe me.	2638	trust me.
2280		2639
2281	=item ev_async_send (loop, ev_async *)	2640	=item ev_async_send (loop, ev_async *)
2282		2641
2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2642	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	2643	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	2644	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	2645	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2287	section below on what exactly this means).	2646	section below on what exactly this means).
2288		2647
2289	This call incurs the overhead of a syscall only once per loop iteration,	2648	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	2649	so while the overhead might be noticeable, it doesn't apply to repeated
2291	calls to C<ev_async_send>.	2650	calls to C<ev_async_send>.
2292		2651
2293	=item bool = ev_async_pending (ev_async *)	2652	=item bool = ev_async_pending (ev_async *)
2294		2653
2295	Returns a non-zero value when C<ev_async_send> has been called on the	2654	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2297	event loop.	2656	event loop.
2298		2657
2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2658	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2300	the loop iterates next and checks for the watcher to have become active,	2659	the loop iterates next and checks for the watcher to have become active,
2301	it will reset the flag again. C<ev_async_pending> can be used to very	2660	it will reset the flag again. C<ev_async_pending> can be used to very
2302	quickly check wether invoking the loop might be a good idea.	2661	quickly check whether invoking the loop might be a good idea.
2303		2662
2304	Not that this does I<not> check wether the watcher itself is pending, only	2663	Not that this does I<not> check whether the watcher itself is pending, only
2305	wether it has been requested to make this watcher pending.	2664	whether it has been requested to make this watcher pending.
2306		2665
2307	=back	2666	=back
2308		2667
2309		2668
2310	=head1 OTHER FUNCTIONS	2669	=head1 OTHER FUNCTIONS
…		…
2314	=over 4	2673	=over 4
2315		2674
2316	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2675	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2317		2676
2318	This function combines a simple timer and an I/O watcher, calls your	2677	This function combines a simple timer and an I/O watcher, calls your
2319	callback on whichever event happens first and automatically stop both	2678	callback on whichever event happens first and automatically stops both
2320	watchers. This is useful if you want to wait for a single event on an fd	2679	watchers. This is useful if you want to wait for a single event on an fd
2321	or timeout without having to allocate/configure/start/stop/free one or	2680	or timeout without having to allocate/configure/start/stop/free one or
2322	more watchers yourself.	2681	more watchers yourself.
2323		2682
2324	If C<fd> is less than 0, then no I/O watcher will be started and events	2683	If C<fd> is less than 0, then no I/O watcher will be started and the
2325	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2684	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2326	C<events> set will be craeted and started.	2685	the given C<fd> and C<events> set will be created and started.
2327		2686
2328	If C<timeout> is less than 0, then no timeout watcher will be	2687	If C<timeout> is less than 0, then no timeout watcher will be
2329	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2688	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2330	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2689	repeat = 0) will be started. C<0> is a valid timeout.
2331	dubious value.
2332		2690
2333	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2691	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2334	passed an C<revents> set like normal event callbacks (a combination of	2692	passed an C<revents> set like normal event callbacks (a combination of
2335	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2693	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2336	value passed to C<ev_once>:	2694	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2695	a timeout and an io event at the same time - you probably should give io
		2696	events precedence.
2337		2697
		2698	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2699
2338	static void stdin_ready (int revents, void *arg)	2700	static void stdin_ready (int revents, void *arg)
2339	{	2701	{
2340	if (revents & EV_TIMEOUT)
2341	/* doh, nothing entered */;
2342	else if (revents & EV_READ)	2702	if (revents & EV_READ)
2343	/* stdin might have data for us, joy! */;	2703	/* stdin might have data for us, joy! */;
		2704	else if (revents & EV_TIMEOUT)
		2705	/* doh, nothing entered */;
2344	}	2706	}
2345		2707
2346	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2708	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2347		2709
2348	=item ev_feed_event (ev_loop *, watcher *, int revents)	2710	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2349		2711
2350	Feeds the given event set into the event loop, as if the specified event	2712	Feeds the given event set into the event loop, as if the specified event
2351	had happened for the specified watcher (which must be a pointer to an	2713	had happened for the specified watcher (which must be a pointer to an
2352	initialised but not necessarily started event watcher).	2714	initialised but not necessarily started event watcher).
2353		2715
2354	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2716	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2355		2717
2356	Feed an event on the given fd, as if a file descriptor backend detected	2718	Feed an event on the given fd, as if a file descriptor backend detected
2357	the given events it.	2719	the given events it.
2358		2720
2359	=item ev_feed_signal_event (ev_loop *loop, int signum)	2721	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2360		2722
2361	Feed an event as if the given signal occured (C<loop> must be the default	2723	Feed an event as if the given signal occurred (C<loop> must be the default
2362	loop!).	2724	loop!).
2363		2725
2364	=back	2726	=back
2365		2727
2366		2728
…		…
2382		2744
2383	=item * Priorities are not currently supported. Initialising priorities	2745	=item * Priorities are not currently supported. Initialising priorities
2384	will fail and all watchers will have the same priority, even though there	2746	will fail and all watchers will have the same priority, even though there
2385	is an ev_pri field.	2747	is an ev_pri field.
2386		2748
		2749	=item * In libevent, the last base created gets the signals, in libev, the
		2750	first base created (== the default loop) gets the signals.
		2751
2387	=item * Other members are not supported.	2752	=item * Other members are not supported.
2388		2753
2389	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2754	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2390	to use the libev header file and library.	2755	to use the libev header file and library.
2391		2756
2392	=back	2757	=back
2393		2758
2394	=head1 C++ SUPPORT	2759	=head1 C++ SUPPORT
2395		2760
2396	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2761	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2397	you to use some convinience methods to start/stop watchers and also change	2762	you to use some convenience methods to start/stop watchers and also change
2398	the callback model to a model using method callbacks on objects.	2763	the callback model to a model using method callbacks on objects.
2399		2764
2400	To use it,	2765	To use it,
2401		2766
2402	#include <ev++.h>	2767	#include <ev++.h>
2403		2768
2404	This automatically includes F<ev.h> and puts all of its definitions (many	2769	This automatically includes F<ev.h> and puts all of its definitions (many
2405	of them macros) into the global namespace. All C++ specific things are	2770	of them macros) into the global namespace. All C++ specific things are
2406	put into the C<ev> namespace. It should support all the same embedding	2771	put into the C<ev> namespace. It should support all the same embedding
2407	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2772	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2474	your compiler is good :), then the method will be fully inlined into the	2839	your compiler is good :), then the method will be fully inlined into the
2475	thunking function, making it as fast as a direct C callback.	2840	thunking function, making it as fast as a direct C callback.
2476		2841
2477	Example: simple class declaration and watcher initialisation	2842	Example: simple class declaration and watcher initialisation
2478		2843
2479	struct myclass	2844	struct myclass
2480	{	2845	{
2481	void io_cb (ev::io &w, int revents) { }	2846	void io_cb (ev::io &w, int revents) { }
2482	}	2847	}
2483		2848
2484	myclass obj;	2849	myclass obj;
2485	ev::io iow;	2850	ev::io iow;
2486	iow.set <myclass, &myclass::io_cb> (&obj);	2851	iow.set <myclass, &myclass::io_cb> (&obj);
2487		2852
2488	=item w->set<function> (void *data = 0)	2853	=item w->set<function> (void *data = 0)
2489		2854
2490	Also sets a callback, but uses a static method or plain function as	2855	Also sets a callback, but uses a static method or plain function as
2491	callback. The optional C<data> argument will be stored in the watcher's	2856	callback. The optional C<data> argument will be stored in the watcher's
…		…
2493		2858
2494	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2859	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2495		2860
2496	See the method-C<set> above for more details.	2861	See the method-C<set> above for more details.
2497		2862
2498	Example:	2863	Example: Use a plain function as callback.
2499		2864
2500	static void io_cb (ev::io &w, int revents) { }	2865	static void io_cb (ev::io &w, int revents) { }
2501	iow.set <io_cb> ();	2866	iow.set <io_cb> ();
2502		2867
2503	=item w->set (struct ev_loop *)	2868	=item w->set (struct ev_loop *)
2504		2869
2505	Associates a different C<struct ev_loop> with this watcher. You can only	2870	Associates a different C<struct ev_loop> with this watcher. You can only
2506	do this when the watcher is inactive (and not pending either).	2871	do this when the watcher is inactive (and not pending either).
2507		2872
2508	=item w->set ([args])	2873	=item w->set ([arguments])
2509		2874
2510	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2875	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2511	called at least once. Unlike the C counterpart, an active watcher gets	2876	called at least once. Unlike the C counterpart, an active watcher gets
2512	automatically stopped and restarted when reconfiguring it with this	2877	automatically stopped and restarted when reconfiguring it with this
2513	method.	2878	method.
2514		2879
2515	=item w->start ()	2880	=item w->start ()
…		…
2539	=back	2904	=back
2540		2905
2541	Example: Define a class with an IO and idle watcher, start one of them in	2906	Example: Define a class with an IO and idle watcher, start one of them in
2542	the constructor.	2907	the constructor.
2543		2908
2544	class myclass	2909	class myclass
2545	{	2910	{
2546	ev::io io; void io_cb (ev::io &w, int revents);	2911	ev::io io ; void io_cb (ev::io &w, int revents);
2547	ev:idle idle void idle_cb (ev::idle &w, int revents);	2912	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2548		2913
2549	myclass (int fd)	2914	myclass (int fd)
2550	{	2915	{
2551	io .set <myclass, &myclass::io_cb > (this);	2916	io .set <myclass, &myclass::io_cb > (this);
2552	idle.set <myclass, &myclass::idle_cb> (this);	2917	idle.set <myclass, &myclass::idle_cb> (this);
2553		2918
2554	io.start (fd, ev::READ);	2919	io.start (fd, ev::READ);
2555	}	2920	}
2556	};	2921	};
2557		2922
2558		2923
2559	=head1 OTHER LANGUAGE BINDINGS	2924	=head1 OTHER LANGUAGE BINDINGS
2560		2925
2561	Libev does not offer other language bindings itself, but bindings for a	2926	Libev does not offer other language bindings itself, but bindings for a
2562	numbe rof languages exist in the form of third-party packages. If you know	2927	number of languages exist in the form of third-party packages. If you know
2563	any interesting language binding in addition to the ones listed here, drop	2928	any interesting language binding in addition to the ones listed here, drop
2564	me a note.	2929	me a note.
2565		2930
2566	=over 4	2931	=over 4
2567		2932
2568	=item Perl	2933	=item Perl
2569		2934
2570	The EV module implements the full libev API and is actually used to test	2935	The EV module implements the full libev API and is actually used to test
2571	libev. EV is developed together with libev. Apart from the EV core module,	2936	libev. EV is developed together with libev. Apart from the EV core module,
2572	there are additional modules that implement libev-compatible interfaces	2937	there are additional modules that implement libev-compatible interfaces
2573	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2938	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2574	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2939	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2940	and C<EV::Glib>).
2575		2941
2576	It can be found and installed via CPAN, its homepage is found at	2942	It can be found and installed via CPAN, its homepage is at
2577	L<http://software.schmorp.de/pkg/EV>.	2943	L<http://software.schmorp.de/pkg/EV>.
2578		2944
		2945	=item Python
		2946
		2947	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2948	seems to be quite complete and well-documented. Note, however, that the
		2949	patch they require for libev is outright dangerous as it breaks the ABI
		2950	for everybody else, and therefore, should never be applied in an installed
		2951	libev (if python requires an incompatible ABI then it needs to embed
		2952	libev).
		2953
2579	=item Ruby	2954	=item Ruby
2580		2955
2581	Tony Arcieri has written a ruby extension that offers access to a subset	2956	Tony Arcieri has written a ruby extension that offers access to a subset
2582	of the libev API and adds filehandle abstractions, asynchronous DNS and	2957	of the libev API and adds file handle abstractions, asynchronous DNS and
2583	more on top of it. It can be found via gem servers. Its homepage is at	2958	more on top of it. It can be found via gem servers. Its homepage is at
2584	L<http://rev.rubyforge.org/>.	2959	L<http://rev.rubyforge.org/>.
2585		2960
2586	=item D	2961	=item D
2587		2962
2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2963	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2589	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2964	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2965
		2966	=item Ocaml
		2967
		2968	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2969	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2590		2970
2591	=back	2971	=back
2592		2972
2593		2973
2594	=head1 MACRO MAGIC	2974	=head1 MACRO MAGIC
2595		2975
2596	Libev can be compiled with a variety of options, the most fundamantal	2976	Libev can be compiled with a variety of options, the most fundamental
2597	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2977	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2598	functions and callbacks have an initial C<struct ev_loop *> argument.	2978	functions and callbacks have an initial C<struct ev_loop *> argument.
2599		2979
2600	To make it easier to write programs that cope with either variant, the	2980	To make it easier to write programs that cope with either variant, the
2601	following macros are defined:	2981	following macros are defined:
…		…
2606		2986
2607	This provides the loop I<argument> for functions, if one is required ("ev	2987	This provides the loop I<argument> for functions, if one is required ("ev
2608	loop argument"). The C<EV_A> form is used when this is the sole argument,	2988	loop argument"). The C<EV_A> form is used when this is the sole argument,
2609	C<EV_A_> is used when other arguments are following. Example:	2989	C<EV_A_> is used when other arguments are following. Example:
2610		2990
2611	ev_unref (EV_A);	2991	ev_unref (EV_A);
2612	ev_timer_add (EV_A_ watcher);	2992	ev_timer_add (EV_A_ watcher);
2613	ev_loop (EV_A_ 0);	2993	ev_loop (EV_A_ 0);
2614		2994
2615	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2995	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2616	which is often provided by the following macro.	2996	which is often provided by the following macro.
2617		2997
2618	=item C<EV_P>, C<EV_P_>	2998	=item C<EV_P>, C<EV_P_>
2619		2999
2620	This provides the loop I<parameter> for functions, if one is required ("ev	3000	This provides the loop I<parameter> for functions, if one is required ("ev
2621	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3001	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2622	C<EV_P_> is used when other parameters are following. Example:	3002	C<EV_P_> is used when other parameters are following. Example:
2623		3003
2624	// this is how ev_unref is being declared	3004	// this is how ev_unref is being declared
2625	static void ev_unref (EV_P);	3005	static void ev_unref (EV_P);
2626		3006
2627	// this is how you can declare your typical callback	3007	// this is how you can declare your typical callback
2628	static void cb (EV_P_ ev_timer *w, int revents)	3008	static void cb (EV_P_ ev_timer *w, int revents)
2629		3009
2630	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3010	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2631	suitable for use with C<EV_A>.	3011	suitable for use with C<EV_A>.
2632		3012
2633	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3013	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2649		3029
2650	Example: Declare and initialise a check watcher, utilising the above	3030	Example: Declare and initialise a check watcher, utilising the above
2651	macros so it will work regardless of whether multiple loops are supported	3031	macros so it will work regardless of whether multiple loops are supported
2652	or not.	3032	or not.
2653		3033
2654	static void	3034	static void
2655	check_cb (EV_P_ ev_timer *w, int revents)	3035	check_cb (EV_P_ ev_timer *w, int revents)
2656	{	3036	{
2657	ev_check_stop (EV_A_ w);	3037	ev_check_stop (EV_A_ w);
2658	}	3038	}
2659		3039
2660	ev_check check;	3040	ev_check check;
2661	ev_check_init (&check, check_cb);	3041	ev_check_init (&check, check_cb);
2662	ev_check_start (EV_DEFAULT_ &check);	3042	ev_check_start (EV_DEFAULT_ &check);
2663	ev_loop (EV_DEFAULT_ 0);	3043	ev_loop (EV_DEFAULT_ 0);
2664		3044
2665	=head1 EMBEDDING	3045	=head1 EMBEDDING
2666		3046
2667	Libev can (and often is) directly embedded into host	3047	Libev can (and often is) directly embedded into host
2668	applications. Examples of applications that embed it include the Deliantra	3048	applications. Examples of applications that embed it include the Deliantra
…		…
2675	libev somewhere in your source tree).	3055	libev somewhere in your source tree).
2676		3056
2677	=head2 FILESETS	3057	=head2 FILESETS
2678		3058
2679	Depending on what features you need you need to include one or more sets of files	3059	Depending on what features you need you need to include one or more sets of files
2680	in your app.	3060	in your application.
2681		3061
2682	=head3 CORE EVENT LOOP	3062	=head3 CORE EVENT LOOP
2683		3063
2684	To include only the libev core (all the C<ev_*> functions), with manual	3064	To include only the libev core (all the C<ev_*> functions), with manual
2685	configuration (no autoconf):	3065	configuration (no autoconf):
2686		3066
2687	#define EV_STANDALONE 1	3067	#define EV_STANDALONE 1
2688	#include "ev.c"	3068	#include "ev.c"
2689		3069
2690	This will automatically include F<ev.h>, too, and should be done in a	3070	This will automatically include F<ev.h>, too, and should be done in a
2691	single C source file only to provide the function implementations. To use	3071	single C source file only to provide the function implementations. To use
2692	it, do the same for F<ev.h> in all files wishing to use this API (best	3072	it, do the same for F<ev.h> in all files wishing to use this API (best
2693	done by writing a wrapper around F<ev.h> that you can include instead and	3073	done by writing a wrapper around F<ev.h> that you can include instead and
2694	where you can put other configuration options):	3074	where you can put other configuration options):
2695		3075
2696	#define EV_STANDALONE 1	3076	#define EV_STANDALONE 1
2697	#include "ev.h"	3077	#include "ev.h"
2698		3078
2699	Both header files and implementation files can be compiled with a C++	3079	Both header files and implementation files can be compiled with a C++
2700	compiler (at least, thats a stated goal, and breakage will be treated	3080	compiler (at least, thats a stated goal, and breakage will be treated
2701	as a bug).	3081	as a bug).
2702		3082
2703	You need the following files in your source tree, or in a directory	3083	You need the following files in your source tree, or in a directory
2704	in your include path (e.g. in libev/ when using -Ilibev):	3084	in your include path (e.g. in libev/ when using -Ilibev):
2705		3085
2706	ev.h	3086	ev.h
2707	ev.c	3087	ev.c
2708	ev_vars.h	3088	ev_vars.h
2709	ev_wrap.h	3089	ev_wrap.h
2710		3090
2711	ev_win32.c required on win32 platforms only	3091	ev_win32.c required on win32 platforms only
2712		3092
2713	ev_select.c only when select backend is enabled (which is enabled by default)	3093	ev_select.c only when select backend is enabled (which is enabled by default)
2714	ev_poll.c only when poll backend is enabled (disabled by default)	3094	ev_poll.c only when poll backend is enabled (disabled by default)
2715	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3095	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2716	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3096	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2717	ev_port.c only when the solaris port backend is enabled (disabled by default)	3097	ev_port.c only when the solaris port backend is enabled (disabled by default)
2718		3098
2719	F<ev.c> includes the backend files directly when enabled, so you only need	3099	F<ev.c> includes the backend files directly when enabled, so you only need
2720	to compile this single file.	3100	to compile this single file.
2721		3101
2722	=head3 LIBEVENT COMPATIBILITY API	3102	=head3 LIBEVENT COMPATIBILITY API
2723		3103
2724	To include the libevent compatibility API, also include:	3104	To include the libevent compatibility API, also include:
2725		3105
2726	#include "event.c"	3106	#include "event.c"
2727		3107
2728	in the file including F<ev.c>, and:	3108	in the file including F<ev.c>, and:
2729		3109
2730	#include "event.h"	3110	#include "event.h"
2731		3111
2732	in the files that want to use the libevent API. This also includes F<ev.h>.	3112	in the files that want to use the libevent API. This also includes F<ev.h>.
2733		3113
2734	You need the following additional files for this:	3114	You need the following additional files for this:
2735		3115
2736	event.h	3116	event.h
2737	event.c	3117	event.c
2738		3118
2739	=head3 AUTOCONF SUPPORT	3119	=head3 AUTOCONF SUPPORT
2740		3120
2741	Instead of using C<EV_STANDALONE=1> and providing your config in	3121	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2742	whatever way you want, you can also C<m4_include([libev.m4])> in your	3122	whatever way you want, you can also C<m4_include([libev.m4])> in your
2743	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3123	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2744	include F<config.h> and configure itself accordingly.	3124	include F<config.h> and configure itself accordingly.
2745		3125
2746	For this of course you need the m4 file:	3126	For this of course you need the m4 file:
2747		3127
2748	libev.m4	3128	libev.m4
2749		3129
2750	=head2 PREPROCESSOR SYMBOLS/MACROS	3130	=head2 PREPROCESSOR SYMBOLS/MACROS
2751		3131
2752	Libev can be configured via a variety of preprocessor symbols you have to	3132	Libev can be configured via a variety of preprocessor symbols you have to
2753	define before including any of its files. The default in the absense of	3133	define before including any of its files. The default in the absence of
2754	autoconf is noted for every option.	3134	autoconf is documented for every option.
2755		3135
2756	=over 4	3136	=over 4
2757		3137
2758	=item EV_STANDALONE	3138	=item EV_STANDALONE
2759		3139
…		…
2764	F<event.h> that are not directly supported by the libev core alone.	3144	F<event.h> that are not directly supported by the libev core alone.
2765		3145
2766	=item EV_USE_MONOTONIC	3146	=item EV_USE_MONOTONIC
2767		3147
2768	If defined to be C<1>, libev will try to detect the availability of the	3148	If defined to be C<1>, libev will try to detect the availability of the
2769	monotonic clock option at both compiletime and runtime. Otherwise no use	3149	monotonic clock option at both compile time and runtime. Otherwise no use
2770	of the monotonic clock option will be attempted. If you enable this, you	3150	of the monotonic clock option will be attempted. If you enable this, you
2771	usually have to link against librt or something similar. Enabling it when	3151	usually have to link against librt or something similar. Enabling it when
2772	the functionality isn't available is safe, though, although you have	3152	the functionality isn't available is safe, though, although you have
2773	to make sure you link against any libraries where the C<clock_gettime>	3153	to make sure you link against any libraries where the C<clock_gettime>
2774	function is hiding in (often F<-lrt>).	3154	function is hiding in (often F<-lrt>).
2775		3155
2776	=item EV_USE_REALTIME	3156	=item EV_USE_REALTIME
2777		3157
2778	If defined to be C<1>, libev will try to detect the availability of the	3158	If defined to be C<1>, libev will try to detect the availability of the
2779	realtime clock option at compiletime (and assume its availability at	3159	real-time clock option at compile time (and assume its availability at
2780	runtime if successful). Otherwise no use of the realtime clock option will	3160	runtime if successful). Otherwise no use of the real-time clock option will
2781	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3161	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2782	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3162	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2783	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3163	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2784		3164
2785	=item EV_USE_NANOSLEEP	3165	=item EV_USE_NANOSLEEP
…		…
2796	2.7 or newer, otherwise disabled.	3176	2.7 or newer, otherwise disabled.
2797		3177
2798	=item EV_USE_SELECT	3178	=item EV_USE_SELECT
2799		3179
2800	If undefined or defined to be C<1>, libev will compile in support for the	3180	If undefined or defined to be C<1>, libev will compile in support for the
2801	C<select>(2) backend. No attempt at autodetection will be done: if no	3181	C<select>(2) backend. No attempt at auto-detection will be done: if no
2802	other method takes over, select will be it. Otherwise the select backend	3182	other method takes over, select will be it. Otherwise the select backend
2803	will not be compiled in.	3183	will not be compiled in.
2804		3184
2805	=item EV_SELECT_USE_FD_SET	3185	=item EV_SELECT_USE_FD_SET
2806		3186
2807	If defined to C<1>, then the select backend will use the system C<fd_set>	3187	If defined to C<1>, then the select backend will use the system C<fd_set>
2808	structure. This is useful if libev doesn't compile due to a missing	3188	structure. This is useful if libev doesn't compile due to a missing
2809	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3189	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2810	exotic systems. This usually limits the range of file descriptors to some	3190	exotic systems. This usually limits the range of file descriptors to some
2811	low limit such as 1024 or might have other limitations (winsocket only	3191	low limit such as 1024 or might have other limitations (winsocket only
2812	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3192	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2813	influence the size of the C<fd_set> used.	3193	influence the size of the C<fd_set> used.
2814		3194
…		…
2863	otherwise another method will be used as fallback. This is the preferred	3243	otherwise another method will be used as fallback. This is the preferred
2864	backend for Solaris 10 systems.	3244	backend for Solaris 10 systems.
2865		3245
2866	=item EV_USE_DEVPOLL	3246	=item EV_USE_DEVPOLL
2867		3247
2868	reserved for future expansion, works like the USE symbols above.	3248	Reserved for future expansion, works like the USE symbols above.
2869		3249
2870	=item EV_USE_INOTIFY	3250	=item EV_USE_INOTIFY
2871		3251
2872	If defined to be C<1>, libev will compile in support for the Linux inotify	3252	If defined to be C<1>, libev will compile in support for the Linux inotify
2873	interface to speed up C<ev_stat> watchers. Its actual availability will	3253	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2880	access is atomic with respect to other threads or signal contexts. No such	3260	access is atomic with respect to other threads or signal contexts. No such
2881	type is easily found in the C language, so you can provide your own type	3261	type is easily found in the C language, so you can provide your own type
2882	that you know is safe for your purposes. It is used both for signal handler "locking"	3262	that you know is safe for your purposes. It is used both for signal handler "locking"
2883	as well as for signal and thread safety in C<ev_async> watchers.	3263	as well as for signal and thread safety in C<ev_async> watchers.
2884		3264
2885	In the absense of this define, libev will use C<sig_atomic_t volatile>	3265	In the absence of this define, libev will use C<sig_atomic_t volatile>
2886	(from F<signal.h>), which is usually good enough on most platforms.	3266	(from F<signal.h>), which is usually good enough on most platforms.
2887		3267
2888	=item EV_H	3268	=item EV_H
2889		3269
2890	The name of the F<ev.h> header file used to include it. The default if	3270	The name of the F<ev.h> header file used to include it. The default if
…		…
2929	When doing priority-based operations, libev usually has to linearly search	3309	When doing priority-based operations, libev usually has to linearly search
2930	all the priorities, so having many of them (hundreds) uses a lot of space	3310	all the priorities, so having many of them (hundreds) uses a lot of space
2931	and time, so using the defaults of five priorities (-2 .. +2) is usually	3311	and time, so using the defaults of five priorities (-2 .. +2) is usually
2932	fine.	3312	fine.
2933		3313
2934	If your embedding app does not need any priorities, defining these both to	3314	If your embedding application does not need any priorities, defining these
2935	C<0> will save some memory and cpu.	3315	both to C<0> will save some memory and CPU.
2936		3316
2937	=item EV_PERIODIC_ENABLE	3317	=item EV_PERIODIC_ENABLE
2938		3318
2939	If undefined or defined to be C<1>, then periodic timers are supported. If	3319	If undefined or defined to be C<1>, then periodic timers are supported. If
2940	defined to be C<0>, then they are not. Disabling them saves a few kB of	3320	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2947	code.	3327	code.
2948		3328
2949	=item EV_EMBED_ENABLE	3329	=item EV_EMBED_ENABLE
2950		3330
2951	If undefined or defined to be C<1>, then embed watchers are supported. If	3331	If undefined or defined to be C<1>, then embed watchers are supported. If
2952	defined to be C<0>, then they are not.	3332	defined to be C<0>, then they are not. Embed watchers rely on most other
		3333	watcher types, which therefore must not be disabled.
2953		3334
2954	=item EV_STAT_ENABLE	3335	=item EV_STAT_ENABLE
2955		3336
2956	If undefined or defined to be C<1>, then stat watchers are supported. If	3337	If undefined or defined to be C<1>, then stat watchers are supported. If
2957	defined to be C<0>, then they are not.	3338	defined to be C<0>, then they are not.
…		…
2967	defined to be C<0>, then they are not.	3348	defined to be C<0>, then they are not.
2968		3349
2969	=item EV_MINIMAL	3350	=item EV_MINIMAL
2970		3351
2971	If you need to shave off some kilobytes of code at the expense of some	3352	If you need to shave off some kilobytes of code at the expense of some
2972	speed, define this symbol to C<1>. Currently only used for gcc to override	3353	speed, define this symbol to C<1>. Currently this is used to override some
2973	some inlining decisions, saves roughly 30% codesize of amd64.	3354	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3355	much smaller 2-heap for timer management over the default 4-heap.
2974		3356
2975	=item EV_PID_HASHSIZE	3357	=item EV_PID_HASHSIZE
2976		3358
2977	C<ev_child> watchers use a small hash table to distribute workload by	3359	C<ev_child> watchers use a small hash table to distribute workload by
2978	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3360	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2985	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3367	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2986	usually more than enough. If you need to manage thousands of C<ev_stat>	3368	usually more than enough. If you need to manage thousands of C<ev_stat>
2987	watchers you might want to increase this value (I<must> be a power of	3369	watchers you might want to increase this value (I<must> be a power of
2988	two).	3370	two).
2989		3371
		3372	=item EV_USE_4HEAP
		3373
		3374	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3375	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3376	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3377	faster performance with many (thousands) of watchers.
		3378
		3379	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3380	(disabled).
		3381
		3382	=item EV_HEAP_CACHE_AT
		3383
		3384	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3385	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3386	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3387	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3388	but avoids random read accesses on heap changes. This improves performance
		3389	noticeably with many (hundreds) of watchers.
		3390
		3391	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3392	(disabled).
		3393
		3394	=item EV_VERIFY
		3395
		3396	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3397	be done: If set to C<0>, no internal verification code will be compiled
		3398	in. If set to C<1>, then verification code will be compiled in, but not
		3399	called. If set to C<2>, then the internal verification code will be
		3400	called once per loop, which can slow down libev. If set to C<3>, then the
		3401	verification code will be called very frequently, which will slow down
		3402	libev considerably.
		3403
		3404	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3405	C<0>.
		3406
2990	=item EV_COMMON	3407	=item EV_COMMON
2991		3408
2992	By default, all watchers have a C<void *data> member. By redefining	3409	By default, all watchers have a C<void *data> member. By redefining
2993	this macro to a something else you can include more and other types of	3410	this macro to a something else you can include more and other types of
2994	members. You have to define it each time you include one of the files,	3411	members. You have to define it each time you include one of the files,
2995	though, and it must be identical each time.	3412	though, and it must be identical each time.
2996		3413
2997	For example, the perl EV module uses something like this:	3414	For example, the perl EV module uses something like this:
2998		3415
2999	#define EV_COMMON \	3416	#define EV_COMMON \
3000	SV *self; /* contains this struct */ \	3417	SV *self; /* contains this struct */ \
3001	SV *cb_sv, *fh /* note no trailing ";" */	3418	SV *cb_sv, *fh /* note no trailing ";" */
3002		3419
3003	=item EV_CB_DECLARE (type)	3420	=item EV_CB_DECLARE (type)
3004		3421
3005	=item EV_CB_INVOKE (watcher, revents)	3422	=item EV_CB_INVOKE (watcher, revents)
3006		3423
…		…
3011	definition and a statement, respectively. See the F<ev.h> header file for	3428	definition and a statement, respectively. See the F<ev.h> header file for
3012	their default definitions. One possible use for overriding these is to	3429	their default definitions. One possible use for overriding these is to
3013	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3430	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3014	method calls instead of plain function calls in C++.	3431	method calls instead of plain function calls in C++.
3015		3432
		3433	=back
		3434
3016	=head2 EXPORTED API SYMBOLS	3435	=head2 EXPORTED API SYMBOLS
3017		3436
3018	If you need to re-export the API (e.g. via a dll) and you need a list of	3437	If you need to re-export the API (e.g. via a DLL) and you need a list of
3019	exported symbols, you can use the provided F<Symbol.*> files which list	3438	exported symbols, you can use the provided F<Symbol.*> files which list
3020	all public symbols, one per line:	3439	all public symbols, one per line:
3021		3440
3022	Symbols.ev for libev proper	3441	Symbols.ev for libev proper
3023	Symbols.event for the libevent emulation	3442	Symbols.event for the libevent emulation
3024		3443
3025	This can also be used to rename all public symbols to avoid clashes with	3444	This can also be used to rename all public symbols to avoid clashes with
3026	multiple versions of libev linked together (which is obviously bad in	3445	multiple versions of libev linked together (which is obviously bad in
3027	itself, but sometimes it is inconvinient to avoid this).	3446	itself, but sometimes it is inconvenient to avoid this).
3028		3447
3029	A sed command like this will create wrapper C<#define>'s that you need to	3448	A sed command like this will create wrapper C<#define>'s that you need to
3030	include before including F<ev.h>:	3449	include before including F<ev.h>:
3031		3450
3032	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3451	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3049	file.	3468	file.
3050		3469
3051	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3470	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3052	that everybody includes and which overrides some configure choices:	3471	that everybody includes and which overrides some configure choices:
3053		3472
3054	#define EV_MINIMAL 1	3473	#define EV_MINIMAL 1
3055	#define EV_USE_POLL 0	3474	#define EV_USE_POLL 0
3056	#define EV_MULTIPLICITY 0	3475	#define EV_MULTIPLICITY 0
3057	#define EV_PERIODIC_ENABLE 0	3476	#define EV_PERIODIC_ENABLE 0
3058	#define EV_STAT_ENABLE 0	3477	#define EV_STAT_ENABLE 0
3059	#define EV_FORK_ENABLE 0	3478	#define EV_FORK_ENABLE 0
3060	#define EV_CONFIG_H <config.h>	3479	#define EV_CONFIG_H <config.h>
3061	#define EV_MINPRI 0	3480	#define EV_MINPRI 0
3062	#define EV_MAXPRI 0	3481	#define EV_MAXPRI 0
3063		3482
3064	#include "ev++.h"	3483	#include "ev++.h"
3065		3484
3066	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3485	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3067		3486
3068	#include "ev_cpp.h"	3487	#include "ev_cpp.h"
3069	#include "ev.c"	3488	#include "ev.c"
3070		3489
		3490	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3071		3491
3072	=head1 COMPLEXITIES	3492	=head2 THREADS AND COROUTINES
3073		3493
3074	In this section the complexities of (many of) the algorithms used inside	3494	=head3 THREADS
3075	libev will be explained. For complexity discussions about backends see the
3076	documentation for C<ev_default_init>.
3077		3495
3078	All of the following are about amortised time: If an array needs to be	3496	All libev functions are reentrant and thread-safe unless explicitly
3079	extended, libev needs to realloc and move the whole array, but this	3497	documented otherwise, but libev implements no locking itself. This means
3080	happens asymptotically never with higher number of elements, so O(1) might	3498	that you can use as many loops as you want in parallel, as long as there
3081	mean it might do a lengthy realloc operation in rare cases, but on average	3499	are no concurrent calls into any libev function with the same loop
3082	it is much faster and asymptotically approaches constant time.	3500	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3501	of course): libev guarantees that different event loops share no data
		3502	structures that need any locking.
		3503
		3504	Or to put it differently: calls with different loop parameters can be done
		3505	concurrently from multiple threads, calls with the same loop parameter
		3506	must be done serially (but can be done from different threads, as long as
		3507	only one thread ever is inside a call at any point in time, e.g. by using
		3508	a mutex per loop).
		3509
		3510	Specifically to support threads (and signal handlers), libev implements
		3511	so-called C<ev_async> watchers, which allow some limited form of
		3512	concurrency on the same event loop, namely waking it up "from the
		3513	outside".
		3514
		3515	If you want to know which design (one loop, locking, or multiple loops
		3516	without or something else still) is best for your problem, then I cannot
		3517	help you, but here is some generic advice:
3083		3518
3084	=over 4	3519	=over 4
3085		3520
3086	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3521	=item * most applications have a main thread: use the default libev loop
		3522	in that thread, or create a separate thread running only the default loop.
3087		3523
3088	This means that, when you have a watcher that triggers in one hour and	3524	This helps integrating other libraries or software modules that use libev
3089	there are 100 watchers that would trigger before that then inserting will	3525	themselves and don't care/know about threading.
3090	have to skip roughly seven (C<ld 100>) of these watchers.
3091		3526
3092	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3527	=item * one loop per thread is usually a good model.
3093		3528
3094	That means that changing a timer costs less than removing/adding them	3529	Doing this is almost never wrong, sometimes a better-performance model
3095	as only the relative motion in the event queue has to be paid for.	3530	exists, but it is always a good start.
3096		3531
3097	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3532	=item * other models exist, such as the leader/follower pattern, where one
		3533	loop is handed through multiple threads in a kind of round-robin fashion.
3098		3534
3099	These just add the watcher into an array or at the head of a list.	3535	Choosing a model is hard - look around, learn, know that usually you can do
		3536	better than you currently do :-)
3100		3537
3101	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3538	=item * often you need to talk to some other thread which blocks in the
		3539	event loop.
3102		3540
3103	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3541	C<ev_async> watchers can be used to wake them up from other threads safely
		3542	(or from signal contexts...).
3104		3543
3105	These watchers are stored in lists then need to be walked to find the	3544	An example use would be to communicate signals or other events that only
3106	correct watcher to remove. The lists are usually short (you don't usually	3545	work in the default loop by registering the signal watcher with the
3107	have many watchers waiting for the same fd or signal).	3546	default loop and triggering an C<ev_async> watcher from the default loop
3108		3547	watcher callback into the event loop interested in the signal.
3109	=item Finding the next timer in each loop iteration: O(1)
3110
3111	By virtue of using a binary heap, the next timer is always found at the
3112	beginning of the storage array.
3113
3114	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3115
3116	A change means an I/O watcher gets started or stopped, which requires
3117	libev to recalculate its status (and possibly tell the kernel, depending
3118	on backend and wether C<ev_io_set> was used).
3119
3120	=item Activating one watcher (putting it into the pending state): O(1)
3121
3122	=item Priority handling: O(number_of_priorities)
3123
3124	Priorities are implemented by allocating some space for each
3125	priority. When doing priority-based operations, libev usually has to
3126	linearly search all the priorities, but starting/stopping and activating
3127	watchers becomes O(1) w.r.t. priority handling.
3128
3129	=item Sending an ev_async: O(1)
3130
3131	=item Processing ev_async_send: O(number_of_async_watchers)
3132
3133	=item Processing signals: O(max_signal_number)
3134
3135	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3136	calls in the current loop iteration. Checking for async and signal events
3137	involves iterating over all running async watchers or all signal numbers.
3138		3548
3139	=back	3549	=back
3140		3550
		3551	=head3 COROUTINES
3141		3552
3142	=head1 Win32 platform limitations and workarounds	3553	Libev is very accommodating to coroutines ("cooperative threads"):
		3554	libev fully supports nesting calls to its functions from different
		3555	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3556	different coroutines, and switch freely between both coroutines running the
		3557	loop, as long as you don't confuse yourself). The only exception is that
		3558	you must not do this from C<ev_periodic> reschedule callbacks.
		3559
		3560	Care has been taken to ensure that libev does not keep local state inside
		3561	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3562	they do not clal any callbacks.
		3563
		3564	=head2 COMPILER WARNINGS
		3565
		3566	Depending on your compiler and compiler settings, you might get no or a
		3567	lot of warnings when compiling libev code. Some people are apparently
		3568	scared by this.
		3569
		3570	However, these are unavoidable for many reasons. For one, each compiler
		3571	has different warnings, and each user has different tastes regarding
		3572	warning options. "Warn-free" code therefore cannot be a goal except when
		3573	targeting a specific compiler and compiler-version.
		3574
		3575	Another reason is that some compiler warnings require elaborate
		3576	workarounds, or other changes to the code that make it less clear and less
		3577	maintainable.
		3578
		3579	And of course, some compiler warnings are just plain stupid, or simply
		3580	wrong (because they don't actually warn about the condition their message
		3581	seems to warn about). For example, certain older gcc versions had some
		3582	warnings that resulted an extreme number of false positives. These have
		3583	been fixed, but some people still insist on making code warn-free with
		3584	such buggy versions.
		3585
		3586	While libev is written to generate as few warnings as possible,
		3587	"warn-free" code is not a goal, and it is recommended not to build libev
		3588	with any compiler warnings enabled unless you are prepared to cope with
		3589	them (e.g. by ignoring them). Remember that warnings are just that:
		3590	warnings, not errors, or proof of bugs.
		3591
		3592
		3593	=head2 VALGRIND
		3594
		3595	Valgrind has a special section here because it is a popular tool that is
		3596	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3597
		3598	If you think you found a bug (memory leak, uninitialised data access etc.)
		3599	in libev, then check twice: If valgrind reports something like:
		3600
		3601	==2274== definitely lost: 0 bytes in 0 blocks.
		3602	==2274== possibly lost: 0 bytes in 0 blocks.
		3603	==2274== still reachable: 256 bytes in 1 blocks.
		3604
		3605	Then there is no memory leak, just as memory accounted to global variables
		3606	is not a memleak - the memory is still being refernced, and didn't leak.
		3607
		3608	Similarly, under some circumstances, valgrind might report kernel bugs
		3609	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3610	although an acceptable workaround has been found here), or it might be
		3611	confused.
		3612
		3613	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3614	make it into some kind of religion.
		3615
		3616	If you are unsure about something, feel free to contact the mailing list
		3617	with the full valgrind report and an explanation on why you think this
		3618	is a bug in libev (best check the archives, too :). However, don't be
		3619	annoyed when you get a brisk "this is no bug" answer and take the chance
		3620	of learning how to interpret valgrind properly.
		3621
		3622	If you need, for some reason, empty reports from valgrind for your project
		3623	I suggest using suppression lists.
		3624
		3625
		3626	=head1 PORTABILITY NOTES
		3627
		3628	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3143		3629
3144	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3630	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3145	requires, and its I/O model is fundamentally incompatible with the POSIX	3631	requires, and its I/O model is fundamentally incompatible with the POSIX
3146	model. Libev still offers limited functionality on this platform in	3632	model. Libev still offers limited functionality on this platform in
3147	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3633	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3148	descriptors. This only applies when using Win32 natively, not when using	3634	descriptors. This only applies when using Win32 natively, not when using
3149	e.g. cygwin.	3635	e.g. cygwin.
3150		3636
		3637	Lifting these limitations would basically require the full
		3638	re-implementation of the I/O system. If you are into these kinds of
		3639	things, then note that glib does exactly that for you in a very portable
		3640	way (note also that glib is the slowest event library known to man).
		3641
3151	There is no supported compilation method available on windows except	3642	There is no supported compilation method available on windows except
3152	embedding it into other applications.	3643	embedding it into other applications.
3153		3644
		3645	Not a libev limitation but worth mentioning: windows apparently doesn't
		3646	accept large writes: instead of resulting in a partial write, windows will
		3647	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3648	so make sure you only write small amounts into your sockets (less than a
		3649	megabyte seems safe, but this apparently depends on the amount of memory
		3650	available).
		3651
3154	Due to the many, low, and arbitrary limits on the win32 platform and the	3652	Due to the many, low, and arbitrary limits on the win32 platform and
3155	abysmal performance of winsockets, using a large number of sockets is not	3653	the abysmal performance of winsockets, using a large number of sockets
3156	recommended (and not reasonable). If your program needs to use more than	3654	is not recommended (and not reasonable). If your program needs to use
3157	a hundred or so sockets, then likely it needs to use a totally different	3655	more than a hundred or so sockets, then likely it needs to use a totally
3158	implementation for windows, as libev offers the POSIX model, which cannot	3656	different implementation for windows, as libev offers the POSIX readiness
3159	be implemented efficiently on windows (microsoft monopoly games).	3657	notification model, which cannot be implemented efficiently on windows
		3658	(Microsoft monopoly games).
		3659
		3660	A typical way to use libev under windows is to embed it (see the embedding
		3661	section for details) and use the following F<evwrap.h> header file instead
		3662	of F<ev.h>:
		3663
		3664	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3665	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3666
		3667	#include "ev.h"
		3668
		3669	And compile the following F<evwrap.c> file into your project (make sure
		3670	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3671
		3672	#include "evwrap.h"
		3673	#include "ev.c"
3160		3674
3161	=over 4	3675	=over 4
3162		3676
3163	=item The winsocket select function	3677	=item The winsocket select function
3164		3678
3165	The winsocket C<select> function doesn't follow POSIX in that it requires	3679	The winsocket C<select> function doesn't follow POSIX in that it
3166	socket I<handles> and not socket I<file descriptors>. This makes select	3680	requires socket I<handles> and not socket I<file descriptors> (it is
3167	very inefficient, and also requires a mapping from file descriptors	3681	also extremely buggy). This makes select very inefficient, and also
3168	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3682	requires a mapping from file descriptors to socket handles (the Microsoft
3169	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3683	C runtime provides the function C<_open_osfhandle> for this). See the
3170	symbols for more info.	3684	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3685	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3171		3686
3172	The configuration for a "naked" win32 using the microsoft runtime	3687	The configuration for a "naked" win32 using the Microsoft runtime
3173	libraries and raw winsocket select is:	3688	libraries and raw winsocket select is:
3174		3689
3175	#define EV_USE_SELECT 1	3690	#define EV_USE_SELECT 1
3176	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3691	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3177		3692
3178	Note that winsockets handling of fd sets is O(n), so you can easily get a	3693	Note that winsockets handling of fd sets is O(n), so you can easily get a
3179	complexity in the O(n²) range when using win32.	3694	complexity in the O(n²) range when using win32.
3180		3695
3181	=item Limited number of file descriptors	3696	=item Limited number of file descriptors
3182		3697
3183	Windows has numerous arbitrary (and low) limits on things. Early versions	3698	Windows has numerous arbitrary (and low) limits on things.
3184	of winsocket's select only supported waiting for a max. of C<64> handles	3699
		3700	Early versions of winsocket's select only supported waiting for a maximum
3185	(probably owning to the fact that all windows kernels can only wait for	3701	of C<64> handles (probably owning to the fact that all windows kernels
3186	C<64> things at the same time internally; microsoft recommends spawning a	3702	can only wait for C<64> things at the same time internally; Microsoft
3187	chain of threads and wait for 63 handles and the previous thread in each).	3703	recommends spawning a chain of threads and wait for 63 handles and the
		3704	previous thread in each. Great).
3188		3705
3189	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3706	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3190	to some high number (e.g. C<2048>) before compiling the winsocket select	3707	to some high number (e.g. C<2048>) before compiling the winsocket select
3191	call (which might be in libev or elsewhere, for example, perl does its own	3708	call (which might be in libev or elsewhere, for example, perl does its own
3192	select emulation on windows).	3709	select emulation on windows).
3193		3710
3194	Another limit is the number of file descriptors in the microsoft runtime	3711	Another limit is the number of file descriptors in the Microsoft runtime
3195	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3712	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3196	or something like this inside microsoft). You can increase this by calling	3713	or something like this inside Microsoft). You can increase this by calling
3197	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3714	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3198	arbitrary limit), but is broken in many versions of the microsoft runtime	3715	arbitrary limit), but is broken in many versions of the Microsoft runtime
3199	libraries.	3716	libraries.
3200		3717
3201	This might get you to about C<512> or C<2048> sockets (depending on	3718	This might get you to about C<512> or C<2048> sockets (depending on
3202	windows version and/or the phase of the moon). To get more, you need to	3719	windows version and/or the phase of the moon). To get more, you need to
3203	wrap all I/O functions and provide your own fd management, but the cost of	3720	wrap all I/O functions and provide your own fd management, but the cost of
3204	calling select (O(n²)) will likely make this unworkable.	3721	calling select (O(n²)) will likely make this unworkable.
3205		3722
3206	=back	3723	=back
3207		3724
		3725	=head2 PORTABILITY REQUIREMENTS
		3726
		3727	In addition to a working ISO-C implementation and of course the
		3728	backend-specific APIs, libev relies on a few additional extensions:
		3729
		3730	=over 4
		3731
		3732	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3733	calling conventions regardless of C<ev_watcher_type *>.
		3734
		3735	Libev assumes not only that all watcher pointers have the same internal
		3736	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3737	assumes that the same (machine) code can be used to call any watcher
		3738	callback: The watcher callbacks have different type signatures, but libev
		3739	calls them using an C<ev_watcher *> internally.
		3740
		3741	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3742
		3743	The type C<sig_atomic_t volatile> (or whatever is defined as
		3744	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3745	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3746	believed to be sufficiently portable.
		3747
		3748	=item C<sigprocmask> must work in a threaded environment
		3749
		3750	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3751	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3752	pthread implementations will either allow C<sigprocmask> in the "main
		3753	thread" or will block signals process-wide, both behaviours would
		3754	be compatible with libev. Interaction between C<sigprocmask> and
		3755	C<pthread_sigmask> could complicate things, however.
		3756
		3757	The most portable way to handle signals is to block signals in all threads
		3758	except the initial one, and run the default loop in the initial thread as
		3759	well.
		3760
		3761	=item C<long> must be large enough for common memory allocation sizes
		3762
		3763	To improve portability and simplify its API, libev uses C<long> internally
		3764	instead of C<size_t> when allocating its data structures. On non-POSIX
		3765	systems (Microsoft...) this might be unexpectedly low, but is still at
		3766	least 31 bits everywhere, which is enough for hundreds of millions of
		3767	watchers.
		3768
		3769	=item C<double> must hold a time value in seconds with enough accuracy
		3770
		3771	The type C<double> is used to represent timestamps. It is required to
		3772	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3773	enough for at least into the year 4000. This requirement is fulfilled by
		3774	implementations implementing IEEE 754 (basically all existing ones).
		3775
		3776	=back
		3777
		3778	If you know of other additional requirements drop me a note.
		3779
		3780
		3781	=head1 ALGORITHMIC COMPLEXITIES
		3782
		3783	In this section the complexities of (many of) the algorithms used inside
		3784	libev will be documented. For complexity discussions about backends see
		3785	the documentation for C<ev_default_init>.
		3786
		3787	All of the following are about amortised time: If an array needs to be
		3788	extended, libev needs to realloc and move the whole array, but this
		3789	happens asymptotically rarer with higher number of elements, so O(1) might
		3790	mean that libev does a lengthy realloc operation in rare cases, but on
		3791	average it is much faster and asymptotically approaches constant time.
		3792
		3793	=over 4
		3794
		3795	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3796
		3797	This means that, when you have a watcher that triggers in one hour and
		3798	there are 100 watchers that would trigger before that, then inserting will
		3799	have to skip roughly seven (C<ld 100>) of these watchers.
		3800
		3801	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3802
		3803	That means that changing a timer costs less than removing/adding them,
		3804	as only the relative motion in the event queue has to be paid for.
		3805
		3806	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3807
		3808	These just add the watcher into an array or at the head of a list.
		3809
		3810	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3811
		3812	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3813
		3814	These watchers are stored in lists, so they need to be walked to find the
		3815	correct watcher to remove. The lists are usually short (you don't usually
		3816	have many watchers waiting for the same fd or signal: one is typical, two
		3817	is rare).
		3818
		3819	=item Finding the next timer in each loop iteration: O(1)
		3820
		3821	By virtue of using a binary or 4-heap, the next timer is always found at a
		3822	fixed position in the storage array.
		3823
		3824	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3825
		3826	A change means an I/O watcher gets started or stopped, which requires
		3827	libev to recalculate its status (and possibly tell the kernel, depending
		3828	on backend and whether C<ev_io_set> was used).
		3829
		3830	=item Activating one watcher (putting it into the pending state): O(1)
		3831
		3832	=item Priority handling: O(number_of_priorities)
		3833
		3834	Priorities are implemented by allocating some space for each
		3835	priority. When doing priority-based operations, libev usually has to
		3836	linearly search all the priorities, but starting/stopping and activating
		3837	watchers becomes O(1) with respect to priority handling.
		3838
		3839	=item Sending an ev_async: O(1)
		3840
		3841	=item Processing ev_async_send: O(number_of_async_watchers)
		3842
		3843	=item Processing signals: O(max_signal_number)
		3844
		3845	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3846	calls in the current loop iteration. Checking for async and signal events
		3847	involves iterating over all running async watchers or all signal numbers.
		3848
		3849	=back
		3850
3208		3851
3209	=head1 AUTHOR	3852	=head1 AUTHOR
3210		3853
3211	Marc Lehmann <libev@schmorp.de>.	3854	Marc Lehmann <libev@schmorp.de>.
3212		3855

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