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Revision 1.158 by root, Wed May 21 12:51:38 2008 UTC vs.
Revision 1.194 by root, Mon Oct 20 16:08:36 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_ struct 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_ struct 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	struct 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
…		…
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 are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
203	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
229	}	250	}
230		251
231	...	252	...
232	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
233		254
234	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
235		256
236	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
237	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
238	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
239	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
240	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
241	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
242	(such as abort).	263	(such as abort).
243		264
244	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.
…		…
277	from multiple threads, you have to lock (note also that this is unlikely,	298	from multiple threads, you have to lock (note also that this is unlikely,
278	as loops cannot bes hared easily between threads anyway).	299	as loops cannot bes hared easily between threads anyway).
279		300
280	The default loop is the only loop that can handle C<ev_signal> and	301	The default loop is the only loop that can handle C<ev_signal> and
281	C<ev_child> watchers, and to do this, it always registers a handler	302	C<ev_child> watchers, and to do this, it always registers a handler
282	for C<SIGCHLD>. If this is a problem for your app you can either	303	for C<SIGCHLD>. If this is a problem for your application you can either
283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
285	C<ev_default_init>.	306	C<ev_default_init>.
286		307
287	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
…		…
296	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
297	thing, believe me).	318	thing, believe me).
298		319
299	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
300		321
301	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
302	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
303	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
304	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
305	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
306	around bugs.	327	around bugs.
…		…
313		334
314	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
315	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
316	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
318	without a syscall and thus I<very> fast, but my GNU/Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
319	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
320		341
321	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
322	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
323	flag.	344	flag.
324		345
325	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
326	environment variable.	347	environment variable.
327		348
328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
329		350
330	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
…		…
332	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
333	using this backend. It doesn't scale too well (O(highest_fd)), but its	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
334	usually the fastest backend for a low number of (low-numbered :) fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
335		356
336	To get good performance out of this backend you need a high amount of	357	To get good performance out of this backend you need a high amount of
337	parallelity (most of the file descriptors should be busy). If you are	358	parallelism (most of the file descriptors should be busy). If you are
338	writing a server, you should C<accept ()> in a loop to accept as many	359	writing a server, you should C<accept ()> in a loop to accept as many
339	connections as possible during one iteration. You might also want to have	360	connections as possible during one iteration. You might also want to have
340	a look at C<ev_set_io_collect_interval ()> to increase the amount of	361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
341	readiness notifications you get per iteration.	362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
342		367
343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
344		369
345	And this is your standard poll(2) backend. It's more complicated	370	And this is your standard poll(2) backend. It's more complicated
346	than select, but handles sparse fds better and has no artificial	371	than select, but handles sparse fds better and has no artificial
347	limit on the number of fds you can use (except it will slow down	372	limit on the number of fds you can use (except it will slow down
348	considerably with a lot of inactive fds). It scales similarly to select,	373	considerably with a lot of inactive fds). It scales similarly to select,
349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
350	performance tips.	375	performance tips.
351		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		379
352	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
353		381
354	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
355	but it scales phenomenally better. While poll and select usually scale	383	but it scales phenomenally better. While poll and select usually scale
356	like O(total_fds) where n is the total number of fds (or the highest fd),	384	like O(total_fds) where n is the total number of fds (or the highest fd),
357	epoll scales either O(1) or O(active_fds). The epoll design has a number	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
358	of shortcomings, such as silently dropping events in some hard-to-detect	386	of shortcomings, such as silently dropping events in some hard-to-detect
359	cases and requiring a syscall per fd change, no fork support and bad	387	cases and requiring a system call per fd change, no fork support and bad
360	support for dup.	388	support for dup.
361		389
362	While stopping, setting and starting an I/O watcher in the same iteration	390	While stopping, setting and starting an I/O watcher in the same iteration
363	will result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
364	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
366	very well if you register events for both fds.	394	very well if you register events for both fds.
367		395
368	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
369	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
370	(or space) is available.	398	(or space) is available.
371		399
372	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
373	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible,
374	keep at least one watcher active per fd at all times.	402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
375		405
376	While nominally embeddeble in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
377	all kernel versions tested so far.	407	all kernel versions tested so far.
378		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
380		413
381	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
382	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
383	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
384	it's completely useless). For this reason it's not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
385	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
387	system like NetBSD.
388		420
389	You still can embed kqueue into a normal poll or select backend and use it	421	You still can embed kqueue into a normal poll or select backend and use it
390	only for sockets (after having made sure that sockets work with kqueue on	422	only for sockets (after having made sure that sockets work with kqueue on
391	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
392		424
393	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
394	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
395	course). While stopping, setting and starting an I/O watcher does never	427	course). While stopping, setting and starting an I/O watcher does never
396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
397	two event changes per incident, support for C<fork ()> is very bad and it	429	two event changes per incident. Support for C<fork ()> is very bad and it
398	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
399		431
400	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
401		433
402	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
403	everywhere, so you might need to test for this. And since it is broken	435	everywhere, so you might need to test for this. And since it is broken
404	almost everywhere, you should only use it when you have a lot of sockets	436	almost everywhere, you should only use it when you have a lot of sockets
405	(for which it usually works), by embedding it into another event loop	437	(for which it usually works), by embedding it into another event loop
406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
407	sockets.	439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
408		444
409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
410		446
411	This is not implemented yet (and might never be, unless you send me an	447	This is not implemented yet (and might never be, unless you send me an
412	implementation). According to reports, C</dev/poll> only supports sockets	448	implementation). According to reports, C</dev/poll> only supports sockets
…		…
416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
417		453
418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
419	it's really slow, but it still scales very well (O(active_fds)).	455	it's really slow, but it still scales very well (O(active_fds)).
420		456
421	Please note that solaris event ports can deliver a lot of spurious	457	Please note that Solaris event ports can deliver a lot of spurious
422	notifications, so you need to use non-blocking I/O or other means to avoid	458	notifications, so you need to use non-blocking I/O or other means to avoid
423	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
424		460
425	While this backend scales well, it requires one system call per active	461	While this backend scales well, it requires one system call per active
426	file descriptor per loop iteration. For small and medium numbers of file	462	file descriptor per loop iteration. For small and medium numbers of file
427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
428	might perform better.	464	might perform better.
429		465
430	On the positive side, ignoring the spurious readiness notifications, this	466	On the positive side, with the exception of the spurious readiness
431	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
432	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
433		473
434	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
435		475
436	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
439		479
440	It is definitely not recommended to use this flag.	480	It is definitely not recommended to use this flag.
441		481
442	=back	482	=back
443		483
444	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
445	backends will be tried (in the reverse order as listed here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
446	specified, all backends in C<ev_recommended_backends ()> will be tried.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
447		487
448	The most typical usage is like this:	488	Example: This is the most typical usage.
449		489
450	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
452		492
453	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
454	environment settings to be taken into account:	494	environment settings to be taken into account:
455		495
456	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
457		497
458	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
459	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
460	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
461		502
462	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
463		504
464	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
465		506
466	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
467	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
…		…
472	libev with threads is indeed to create one loop per thread, and using the	513	libev with threads is indeed to create one loop per thread, and using the
473	default loop in the "main" or "initial" thread.	514	default loop in the "main" or "initial" thread.
474		515
475	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
476		517
477	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
478	if (!epoller)	519	if (!epoller)
479	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
480		521
481	=item ev_default_destroy ()	522	=item ev_default_destroy ()
482		523
483	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
484	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
485	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
486	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
487	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
488	the easiest thing, you can just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
489	for example).	530	for example).
490		531
491	Note that certain global state, such as signal state, will not be freed by	532	Note that certain global state, such as signal state, will not be freed by
…		…
523		564
524	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
525		566
526	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
527	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
528	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
529		571
530	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
531		573
532	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
533		576
534	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
535		578
536	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
537	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
552	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
553	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
554	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
555	event occurring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
556		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
		611
557	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
558		613
559	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
560	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
561	events.	616	events.
…		…
563	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
564	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
565		620
566	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
567	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
568	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
569	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
570	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
571		627
572	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
573	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
574	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
575		632
576	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
577	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
578	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
579	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
580	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
581	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
582	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
583		644
584	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
585		646
586	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
587	* If EVFLAG_FORKCHECK was used, check for a fork.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
588	- If a fork was detected, queue and call all fork watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
589	- Queue and call all prepare watchers.	650	- Queue and call all prepare watchers.
590	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
591	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
592	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
593	- Calculate for how long to sleep or block, if at all	655	- Calculate for how long to sleep or block, if at all
594	(active idle watchers, EVLOOP_NONBLOCK or not having	656	(active idle watchers, EVLOOP_NONBLOCK or not having
595	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
596	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
597	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
598	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
599	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
600	- Queue all outstanding timers.	662	- Queue all expired timers.
601	- Queue all outstanding periodics.	663	- Queue all expired periodics.
602	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
603	- Queue all check watchers.	665	- Queue all check watchers.
604	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
605	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
606	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
607	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
612	anymore.	674	anymore.
613		675
614	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
615	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
616	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
617	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
618		680
619	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
620		682
621	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
622	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
623	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
624	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
625		687
626	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
627		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
628	=item ev_ref (loop)	692	=item ev_ref (loop)
629		693
630	=item ev_unref (loop)	694	=item ev_unref (loop)
631		695
632	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
633	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
634	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
635	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
636	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
637	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
638	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
639	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
640	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
641	libraries. Just remember to I<unref after start> and I<ref before stop>	708	libraries. Just remember to I<unref after start> and I<ref before stop>
642	(but only if the watcher wasn't active before, or was active before,	709	(but only if the watcher wasn't active before, or was active before,
643	respectively).	710	respectively).
644		711
645	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
646	running when nothing else is active.	713	running when nothing else is active.
647		714
648	struct ev_signal exitsig;	715	struct ev_signal exitsig;
649	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
650	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
651	evf_unref (loop);	718	evf_unref (loop);
652		719
653	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
654		721
655	ev_ref (loop);	722	ev_ref (loop);
656	ev_signal_stop (loop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
657		724
658	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
659		726
660	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
661		728
662	These advanced functions influence the time that libev will spend waiting	729	These advanced functions influence the time that libev will spend waiting
663	for events. Both are by default C<0>, meaning that libev will try to	730	for events. Both time intervals are by default C<0>, meaning that libev
664	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
665		733
666	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
667	allows libev to delay invocation of I/O and timer/periodic callbacks to	735	allows libev to delay invocation of I/O and timer/periodic callbacks
668	increase efficiency of loop iterations.	736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
669		738
670	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
671	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
672	the program responsive, it also wastes a lot of CPU time to poll for new	741	program responsive, it also wastes a lot of CPU time to poll for new
673	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
674	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
675		744
676	By setting a higher I<io collect interval> you allow libev to spend more	745	By setting a higher I<io collect interval> you allow libev to spend more
677	time collecting I/O events, so you can handle more events per iteration,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
679	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	C<ev_timer>) will be not affected. Setting this to a non-null value will
680	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
681		750
682	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
683	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
684	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
685	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
686	any overhead in libev.	755	value will not introduce any overhead in libev.
687		756
688	Many (busy) programs can usually benefit by setting the io collect	757	Many (busy) programs can usually benefit by setting the I/O collect
689	interval to a value near C<0.1> or so, which is often enough for	758	interval to a value near C<0.1> or so, which is often enough for
690	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
691	usually doesn't make much sense to set it to a lower value than C<0.01>,	760	usually doesn't make much sense to set it to a lower value than C<0.01>,
692	as this approsaches the timing granularity of most systems.	761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
693		781
694	=back	782	=back
695		783
696		784
697	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
698		786
699	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
700	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
701	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
702		790
703	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
704	{	792	{
705	ev_io_stop (w);	793	ev_io_stop (w);
706	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
707	}	795	}
708		796
709	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
710	struct ev_io stdin_watcher;	798	struct ev_io stdin_watcher;
711	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
712	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
713	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
714	ev_loop (loop, 0);	802	ev_loop (loop, 0);
715		803
716	As you can see, you are responsible for allocating the memory for your	804	As you can see, you are responsible for allocating the memory for your
717	watcher structures (and it is usually a bad idea to do this on the stack,	805	watcher structures (and it is usually a bad idea to do this on the stack,
718	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
719		807
720	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
721	(watcher *, callback)>, which expects a callback to be provided. This	809	(watcher *, callback)>, which expects a callback to be provided. This
722	callback gets invoked each time the event occurs (or, in the case of io	810	callback gets invoked each time the event occurs (or, in the case of I/O
723	watchers, each time the event loop detects that the file descriptor given	811	watchers, each time the event loop detects that the file descriptor given
724	is readable and/or writable).	812	is readable and/or writable).
725		813
726	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
727	with arguments specific to this watcher type. There is also a macro	815	with arguments specific to this watcher type. There is also a macro
…		…
803		891
804	The given async watcher has been asynchronously notified (see C<ev_async>).	892	The given async watcher has been asynchronously notified (see C<ev_async>).
805		893
806	=item C<EV_ERROR>	894	=item C<EV_ERROR>
807		895
808	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
809	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
810	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
811	problem. You best act on it by reporting the problem and somehow coping	899	problem. You best act on it by reporting the problem and somehow coping
812	with the watcher being stopped.	900	with the watcher being stopped.
813		901
814	Libev will usually signal a few "dummy" events together with an error,	902	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	903	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	904	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	905	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	906	programs, though, as the fd could already be closed and reused for another
		907	thing, so beware.
819		908
820	=back	909	=back
821		910
822	=head2 GENERIC WATCHER FUNCTIONS	911	=head2 GENERIC WATCHER FUNCTIONS
823		912
…		…
839	(or never started) and there are no pending events outstanding.	928	(or never started) and there are no pending events outstanding.
840		929
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	931	int revents)>.
843		932
		933	Example: Initialise an C<ev_io> watcher in two steps.
		934
		935	ev_io w;
		936	ev_init (&w, my_cb);
		937	ev_io_set (&w, STDIN_FILENO, EV_READ);
		938
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	939	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		940
846	This macro initialises the type-specific parts of a watcher. You need to	941	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	942	call C<ev_init> at least once before you call this macro, but you can
848	call C<ev_TYPE_set> any number of times. You must not, however, call this	943	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
850	difference to the C<ev_init> macro).	945	difference to the C<ev_init> macro).
851		946
852	Although some watcher types do not have type-specific arguments	947	Although some watcher types do not have type-specific arguments
853	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	948	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		949
		950	See C<ev_init>, above, for an example.
		951
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	952	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		953
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	954	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	955	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	956	a watcher. The same limitations apply, of course.
		957
		958	Example: Initialise and set an C<ev_io> watcher in one step.
		959
		960	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		961
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	962	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		963
863	Starts (activates) the given watcher. Only active watchers will receive	964	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	965	events. If the watcher is already active nothing will happen.
		966
		967	Example: Start the C<ev_io> watcher that is being abused as example in this
		968	whole section.
		969
		970	ev_io_start (EV_DEFAULT_UC, &w);
865		971
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		973
868	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher again (if active) and clears the pending
869	status. It is possible that stopped watchers are pending (for example,	975	status. It is possible that stopped watchers are pending (for example,
…		…
926		1032
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1034
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1036	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1037	can deal with that fact, as both are simply passed through to the
		1038	callback.
932		1039
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1040	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1041
935	If the watcher is pending, this function returns clears its pending status	1042	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1043	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1044	watcher isn't pending it does nothing and returns C<0>.
938		1045
		1046	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1047	callback to be invoked, which can be accomplished with this function.
		1048
939	=back	1049	=back
940		1050
941		1051
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1052	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1053
944	Each watcher has, by default, a member C<void *data> that you can change	1054	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1055	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1056	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1057	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1058	member, you can also "subclass" the watcher type and provide your own
949	data:	1059	data:
950		1060
951	struct my_io	1061	struct my_io
952	{	1062	{
953	struct ev_io io;	1063	struct ev_io io;
954	int otherfd;	1064	int otherfd;
955	void *somedata;	1065	void *somedata;
956	struct whatever *mostinteresting;	1066	struct whatever *mostinteresting;
957	}	1067	};
		1068
		1069	...
		1070	struct my_io w;
		1071	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1072
959	And since your callback will be called with a pointer to the watcher, you	1073	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1074	can cast it back to your own type:
961		1075
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1076	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
963	{	1077	{
964	struct my_io *w = (struct my_io *)w_;	1078	struct my_io *w = (struct my_io *)w_;
965	...	1079	...
966	}	1080	}
967		1081
968	More interesting and less C-conformant ways of casting your callback type	1082	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1083	instead have been omitted.
970		1084
971	Another common scenario is having some data structure with multiple	1085	Another common scenario is to use some data structure with multiple
972	watchers:	1086	embedded watchers:
973		1087
974	struct my_biggy	1088	struct my_biggy
975	{	1089	{
976	int some_data;	1090	int some_data;
977	ev_timer t1;	1091	ev_timer t1;
978	ev_timer t2;	1092	ev_timer t2;
979	}	1093	}
980		1094
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1095	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1096	complicated: Either you store the address of your C<my_biggy> struct
		1097	in the C<data> member of the watcher (for woozies), or you need to use
		1098	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1099	programmers):
983		1100
984	#include <stddef.h>	1101	#include <stddef.h>
985		1102
986	static void	1103	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1104	t1_cb (EV_P_ struct ev_timer *w, int revents)
988	{	1105	{
989	struct my_biggy big = (struct my_biggy *	1106	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1107	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1108	}
992		1109
993	static void	1110	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1111	t2_cb (EV_P_ struct ev_timer *w, int revents)
995	{	1112	{
996	struct my_biggy big = (struct my_biggy *	1113	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1114	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1115	}
999		1116
1000		1117
1001	=head1 WATCHER TYPES	1118	=head1 WATCHER TYPES
1002		1119
1003	This section describes each watcher in detail, but will not repeat	1120	This section describes each watcher in detail, but will not repeat
…		…
1027	In general you can register as many read and/or write event watchers per	1144	In general you can register as many read and/or write event watchers per
1028	fd as you want (as long as you don't confuse yourself). Setting all file	1145	fd as you want (as long as you don't confuse yourself). Setting all file
1029	descriptors to non-blocking mode is also usually a good idea (but not	1146	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1147	required if you know what you are doing).
1031		1148
1032	If you must do this, then force the use of a known-to-be-good backend	1149	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1150	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1151	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1152
1036	Another thing you have to watch out for is that it is quite easy to	1153	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readiness notifications, that is your callback might	1154	receive "spurious" readiness notifications, that is your callback might
1038	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1155	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1039	because there is no data. Not only are some backends known to create a	1156	because there is no data. Not only are some backends known to create a
1040	lot of those (for example solaris ports), it is very easy to get into	1157	lot of those (for example Solaris ports), it is very easy to get into
1041	this situation even with a relatively standard program structure. Thus	1158	this situation even with a relatively standard program structure. Thus
1042	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1159	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1043	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1160	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1161
1045	If you cannot run the fd in non-blocking mode (for example you should not	1162	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1163	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1164	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1165	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1166	does this on its own, so its quite safe to use). Some people additionally
		1167	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1168	indefinitely.
		1169
		1170	But really, best use non-blocking mode.
1050		1171
1051	=head3 The special problem of disappearing file descriptors	1172	=head3 The special problem of disappearing file descriptors
1052		1173
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1174	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1175	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1176	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1177	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1178	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1179	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1180	fact, a different file descriptor.
1060		1181
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1212	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1213	C<EVBACKEND_POLL>.
1093		1214
1094	=head3 The special problem of SIGPIPE	1215	=head3 The special problem of SIGPIPE
1095		1216
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1217	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1218	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1219	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1220	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1221
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1222	So when you encounter spurious, unexplained daemon exits, make sure you
1103	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1223	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1104	somewhere, as that would have given you a big clue).	1224	somewhere, as that would have given you a big clue).
1105		1225
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1231	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1232
1113	=item ev_io_set (ev_io *, int fd, int events)	1233	=item ev_io_set (ev_io *, int fd, int events)
1114		1234
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1235	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1236	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1237	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1238
1119	=item int fd [read-only]	1239	=item int fd [read-only]
1120		1240
1121	The file descriptor being watched.	1241	The file descriptor being watched.
1122		1242
…		…
1130		1250
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1251	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1252	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1253	attempt to read a whole line in the callback.
1134		1254
1135	static void	1255	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1256	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1137	{	1257	{
1138	ev_io_stop (loop, w);	1258	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1259	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1260	}
1141		1261
1142	...	1262	...
1143	struct ev_loop *loop = ev_default_init (0);	1263	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1264	struct ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1266	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1267	ev_loop (loop, 0);
1148		1268
1149		1269
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1270	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1271
1152	Timer watchers are simple relative timers that generate an event after a	1272	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1273	given time, and optionally repeating in regular intervals after that.
1154		1274
1155	The timers are based on real time, that is, if you register an event that	1275	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to january last	1276	times out after an hour and you reset your system clock to January last
1157	year, it will still time out after (roughly) and hour. "Roughly" because	1277	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1279	monotonic clock option helps a lot here).
		1280
		1281	The callback is guaranteed to be invoked only I<after> its timeout has
		1282	passed, but if multiple timers become ready during the same loop iteration
		1283	then order of execution is undefined.
		1284
		1285	=head3 The special problem of time updates
		1286
		1287	Establishing the current time is a costly operation (it usually takes at
		1288	least two system calls): EV therefore updates its idea of the current
		1289	time only before and after C<ev_loop> collects new events, which causes a
		1290	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1291	lots of events in one iteration.
1160		1292
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1293	The relative timeouts are calculated relative to the C<ev_now ()>
1162	time. This is usually the right thing as this timestamp refers to the time	1294	time. This is usually the right thing as this timestamp refers to the time
1163	of the event triggering whatever timeout you are modifying/starting. If	1295	of the event triggering whatever timeout you are modifying/starting. If
1164	you suspect event processing to be delayed and you I<need> to base the timeout	1296	you suspect event processing to be delayed and you I<need> to base the
1165	on the current time, use something like this to adjust for this:	1297	timeout on the current time, use something like this to adjust for this:
1166		1298
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1299	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1300
1169	The callback is guarenteed to be invoked only after its timeout has passed,	1301	If the event loop is suspended for a long time, you can also force an
1170	but if multiple timers become ready during the same loop iteration then	1302	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1303	()>.
1172		1304
1173	=head3 Watcher-Specific Functions and Data Members	1305	=head3 Watcher-Specific Functions and Data Members
1174		1306
1175	=over 4	1307	=over 4
1176		1308
…		…
1195	This will act as if the timer timed out and restart it again if it is	1327	This will act as if the timer timed out and restart it again if it is
1196	repeating. The exact semantics are:	1328	repeating. The exact semantics are:
1197		1329
1198	If the timer is pending, its pending status is cleared.	1330	If the timer is pending, its pending status is cleared.
1199		1331
1200	If the timer is started but nonrepeating, stop it (as if it timed out).	1332	If the timer is started but non-repeating, stop it (as if it timed out).
1201		1333
1202	If the timer is repeating, either start it if necessary (with the	1334	If the timer is repeating, either start it if necessary (with the
1203	C<repeat> value), or reset the running timer to the C<repeat> value.	1335	C<repeat> value), or reset the running timer to the C<repeat> value.
1204		1336
1205	This sounds a bit complicated, but here is a useful and typical	1337	This sounds a bit complicated, but here is a useful and typical
1206	example: Imagine you have a tcp connection and you want a so-called idle	1338	example: Imagine you have a TCP connection and you want a so-called idle
1207	timeout, that is, you want to be called when there have been, say, 60	1339	timeout, that is, you want to be called when there have been, say, 60
1208	seconds of inactivity on the socket. The easiest way to do this is to	1340	seconds of inactivity on the socket. The easiest way to do this is to
1209	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1341	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1210	C<ev_timer_again> each time you successfully read or write some data. If	1342	C<ev_timer_again> each time you successfully read or write some data. If
1211	you go into an idle state where you do not expect data to travel on the	1343	you go into an idle state where you do not expect data to travel on the
…		…
1225	ev_timer_again (loop, timer);	1357	ev_timer_again (loop, timer);
1226		1358
1227	This is more slightly efficient then stopping/starting the timer each time	1359	This is more slightly efficient then stopping/starting the timer each time
1228	you want to modify its timeout value.	1360	you want to modify its timeout value.
1229		1361
		1362	Note, however, that it is often even more efficient to remember the
		1363	time of the last activity and let the timer time-out naturally. In the
		1364	callback, you then check whether the time-out is real, or, if there was
		1365	some activity, you reschedule the watcher to time-out in "last_activity +
		1366	timeout - ev_now ()" seconds.
		1367
1230	=item ev_tstamp repeat [read-write]	1368	=item ev_tstamp repeat [read-write]
1231		1369
1232	The current C<repeat> value. Will be used each time the watcher times out	1370	The current C<repeat> value. Will be used each time the watcher times out
1233	or C<ev_timer_again> is called and determines the next timeout (if any),	1371	or C<ev_timer_again> is called, and determines the next timeout (if any),
1234	which is also when any modifications are taken into account.	1372	which is also when any modifications are taken into account.
1235		1373
1236	=back	1374	=back
1237		1375
1238	=head3 Examples	1376	=head3 Examples
1239		1377
1240	Example: Create a timer that fires after 60 seconds.	1378	Example: Create a timer that fires after 60 seconds.
1241		1379
1242	static void	1380	static void
1243	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1381	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1244	{	1382	{
1245	.. one minute over, w is actually stopped right here	1383	.. one minute over, w is actually stopped right here
1246	}	1384	}
1247		1385
1248	struct ev_timer mytimer;	1386	struct ev_timer mytimer;
1249	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1250	ev_timer_start (loop, &mytimer);	1388	ev_timer_start (loop, &mytimer);
1251		1389
1252	Example: Create a timeout timer that times out after 10 seconds of	1390	Example: Create a timeout timer that times out after 10 seconds of
1253	inactivity.	1391	inactivity.
1254		1392
1255	static void	1393	static void
1256	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1394	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1257	{	1395	{
1258	.. ten seconds without any activity	1396	.. ten seconds without any activity
1259	}	1397	}
1260		1398
1261	struct ev_timer mytimer;	1399	struct ev_timer mytimer;
1262	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1263	ev_timer_again (&mytimer); /* start timer */	1401	ev_timer_again (&mytimer); /* start timer */
1264	ev_loop (loop, 0);	1402	ev_loop (loop, 0);
1265		1403
1266	// and in some piece of code that gets executed on any "activity":	1404	// and in some piece of code that gets executed on any "activity":
1267	// reset the timeout to start ticking again at 10 seconds	1405	// reset the timeout to start ticking again at 10 seconds
1268	ev_timer_again (&mytimer);	1406	ev_timer_again (&mytimer);
1269		1407
1270		1408
1271	=head2 C<ev_periodic> - to cron or not to cron?	1409	=head2 C<ev_periodic> - to cron or not to cron?
1272		1410
1273	Periodic watchers are also timers of a kind, but they are very versatile	1411	Periodic watchers are also timers of a kind, but they are very versatile
1274	(and unfortunately a bit complex).	1412	(and unfortunately a bit complex).
1275		1413
1276	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1414	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1277	but on wallclock time (absolute time). You can tell a periodic watcher	1415	but on wall clock time (absolute time). You can tell a periodic watcher
1278	to trigger after some specific point in time. For example, if you tell a	1416	to trigger after some specific point in time. For example, if you tell a
1279	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1417	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1280	+ 10.>, that is, an absolute time not a delay) and then reset your system	1418	+ 10.>, that is, an absolute time not a delay) and then reset your system
1281	clock to january of the previous year, then it will take more than year	1419	clock to January of the previous year, then it will take more than year
1282	to trigger the event (unlike an C<ev_timer>, which would still trigger	1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1283	roughly 10 seconds later as it uses a relative timeout).	1421	roughly 10 seconds later as it uses a relative timeout).
1284		1422
1285	C<ev_periodic>s can also be used to implement vastly more complex timers,	1423	C<ev_periodic>s can also be used to implement vastly more complex timers,
1286	such as triggering an event on each "midnight, local time", or other	1424	such as triggering an event on each "midnight, local time", or other
1287	complicated, rules.	1425	complicated rules.
1288		1426
1289	As with timers, the callback is guarenteed to be invoked only when the	1427	As with timers, the callback is guaranteed to be invoked only when the
1290	time (C<at>) has passed, but if multiple periodic timers become ready	1428	time (C<at>) has passed, but if multiple periodic timers become ready
1291	during the same loop iteration then order of execution is undefined.	1429	during the same loop iteration, then order of execution is undefined.
1292		1430
1293	=head3 Watcher-Specific Functions and Data Members	1431	=head3 Watcher-Specific Functions and Data Members
1294		1432
1295	=over 4	1433	=over 4
1296		1434
1297	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1298		1436
1299	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1300		1438
1301	Lots of arguments, lets sort it out... There are basically three modes of	1439	Lots of arguments, lets sort it out... There are basically three modes of
1302	operation, and we will explain them from simplest to complex:	1440	operation, and we will explain them from simplest to most complex:
1303		1441
1304	=over 4	1442	=over 4
1305		1443
1306	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1307		1445
1308	In this configuration the watcher triggers an event after the wallclock	1446	In this configuration the watcher triggers an event after the wall clock
1309	time C<at> has passed and doesn't repeat. It will not adjust when a time	1447	time C<at> has passed. It will not repeat and will not adjust when a time
1310	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1448	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1311	run when the system time reaches or surpasses this time.	1449	only run when the system clock reaches or surpasses this time.
1312		1450
1313	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1314		1452
1315	In this mode the watcher will always be scheduled to time out at the next	1453	In this mode the watcher will always be scheduled to time out at the next
1316	C<at + N * interval> time (for some integer N, which can also be negative)	1454	C<at + N * interval> time (for some integer N, which can also be negative)
1317	and then repeat, regardless of any time jumps.	1455	and then repeat, regardless of any time jumps.
1318		1456
1319	This can be used to create timers that do not drift with respect to system	1457	This can be used to create timers that do not drift with respect to the
1320	time, for example, here is a C<ev_periodic> that triggers each hour, on	1458	system clock, for example, here is a C<ev_periodic> that triggers each
1321	the hour:	1459	hour, on the hour:
1322		1460
1323	ev_periodic_set (&periodic, 0., 3600., 0);	1461	ev_periodic_set (&periodic, 0., 3600., 0);
1324		1462
1325	This doesn't mean there will always be 3600 seconds in between triggers,	1463	This doesn't mean there will always be 3600 seconds in between triggers,
1326	but only that the the callback will be called when the system time shows a	1464	but only that the callback will be called when the system time shows a
1327	full hour (UTC), or more correctly, when the system time is evenly divisible	1465	full hour (UTC), or more correctly, when the system time is evenly divisible
1328	by 3600.	1466	by 3600.
1329		1467
1330	Another way to think about it (for the mathematically inclined) is that	1468	Another way to think about it (for the mathematically inclined) is that
1331	C<ev_periodic> will try to run the callback in this mode at the next possible	1469	C<ev_periodic> will try to run the callback in this mode at the next possible
…		…
1333		1471
1334	For numerical stability it is preferable that the C<at> value is near	1472	For numerical stability it is preferable that the C<at> value is near
1335	C<ev_now ()> (the current time), but there is no range requirement for	1473	C<ev_now ()> (the current time), but there is no range requirement for
1336	this value, and in fact is often specified as zero.	1474	this value, and in fact is often specified as zero.
1337		1475
1338	Note also that there is an upper limit to how often a timer can fire (cpu	1476	Note also that there is an upper limit to how often a timer can fire (CPU
1339	speed for example), so if C<interval> is very small then timing stability	1477	speed for example), so if C<interval> is very small then timing stability
1340	will of course detoriate. Libev itself tries to be exact to be about one	1478	will of course deteriorate. Libev itself tries to be exact to be about one
1341	millisecond (if the OS supports it and the machine is fast enough).	1479	millisecond (if the OS supports it and the machine is fast enough).
1342		1480
1343	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1481	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1344		1482
1345	In this mode the values for C<interval> and C<at> are both being	1483	In this mode the values for C<interval> and C<at> are both being
…		…
1413	=back	1551	=back
1414		1552
1415	=head3 Examples	1553	=head3 Examples
1416		1554
1417	Example: Call a callback every hour, or, more precisely, whenever the	1555	Example: Call a callback every hour, or, more precisely, whenever the
1418	system clock is divisible by 3600. The callback invocation times have	1556	system time is divisible by 3600. The callback invocation times have
1419	potentially a lot of jittering, but good long-term stability.	1557	potentially a lot of jitter, but good long-term stability.
1420		1558
1421	static void	1559	static void
1422	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1560	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1423	{	1561	{
1424	... its now a full hour (UTC, or TAI or whatever your clock follows)	1562	... its now a full hour (UTC, or TAI or whatever your clock follows)
1425	}	1563	}
1426		1564
1427	struct ev_periodic hourly_tick;	1565	struct ev_periodic hourly_tick;
1428	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1429	ev_periodic_start (loop, &hourly_tick);	1567	ev_periodic_start (loop, &hourly_tick);
1430		1568
1431	Example: The same as above, but use a reschedule callback to do it:	1569	Example: The same as above, but use a reschedule callback to do it:
1432		1570
1433	#include <math.h>	1571	#include <math.h>
1434		1572
1435	static ev_tstamp	1573	static ev_tstamp
1436	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1437	{	1575	{
1438	return fmod (now, 3600.) + 3600.;	1576	return now + (3600. - fmod (now, 3600.));
1439	}	1577	}
1440		1578
1441	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1442		1580
1443	Example: Call a callback every hour, starting now:	1581	Example: Call a callback every hour, starting now:
1444		1582
1445	struct ev_periodic hourly_tick;	1583	struct ev_periodic hourly_tick;
1446	ev_periodic_init (&hourly_tick, clock_cb,	1584	ev_periodic_init (&hourly_tick, clock_cb,
1447	fmod (ev_now (loop), 3600.), 3600., 0);	1585	fmod (ev_now (loop), 3600.), 3600., 0);
1448	ev_periodic_start (loop, &hourly_tick);	1586	ev_periodic_start (loop, &hourly_tick);
1449		1587
1450		1588
1451	=head2 C<ev_signal> - signal me when a signal gets signalled!	1589	=head2 C<ev_signal> - signal me when a signal gets signalled!
1452		1590
1453	Signal watchers will trigger an event when the process receives a specific	1591	Signal watchers will trigger an event when the process receives a specific
1454	signal one or more times. Even though signals are very asynchronous, libev	1592	signal one or more times. Even though signals are very asynchronous, libev
1455	will try it's best to deliver signals synchronously, i.e. as part of the	1593	will try it's best to deliver signals synchronously, i.e. as part of the
1456	normal event processing, like any other event.	1594	normal event processing, like any other event.
1457		1595
		1596	If you want signals asynchronously, just use C<sigaction> as you would
		1597	do without libev and forget about sharing the signal. You can even use
		1598	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1599
1458	You can configure as many watchers as you like per signal. Only when the	1600	You can configure as many watchers as you like per signal. Only when the
1459	first watcher gets started will libev actually register a signal watcher	1601	first watcher gets started will libev actually register a signal handler
1460	with the kernel (thus it coexists with your own signal handlers as long	1602	with the kernel (thus it coexists with your own signal handlers as long as
1461	as you don't register any with libev). Similarly, when the last signal	1603	you don't register any with libev for the same signal). Similarly, when
1462	watcher for a signal is stopped libev will reset the signal handler to	1604	the last signal watcher for a signal is stopped, libev will reset the
1463	SIG_DFL (regardless of what it was set to before).	1605	signal handler to SIG_DFL (regardless of what it was set to before).
1464		1606
1465	If possible and supported, libev will install its handlers with	1607	If possible and supported, libev will install its handlers with
1466	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1608	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1467	interrupted. If you have a problem with syscalls getting interrupted by	1609	interrupted. If you have a problem with system calls getting interrupted by
1468	signals you can block all signals in an C<ev_check> watcher and unblock	1610	signals you can block all signals in an C<ev_check> watcher and unblock
1469	them in an C<ev_prepare> watcher.	1611	them in an C<ev_prepare> watcher.
1470		1612
1471	=head3 Watcher-Specific Functions and Data Members	1613	=head3 Watcher-Specific Functions and Data Members
1472		1614
…		…
1485		1627
1486	=back	1628	=back
1487		1629
1488	=head3 Examples	1630	=head3 Examples
1489		1631
1490	Example: Try to exit cleanly on SIGINT and SIGTERM.	1632	Example: Try to exit cleanly on SIGINT.
1491		1633
1492	static void	1634	static void
1493	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1635	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1494	{	1636	{
1495	ev_unloop (loop, EVUNLOOP_ALL);	1637	ev_unloop (loop, EVUNLOOP_ALL);
1496	}	1638	}
1497		1639
1498	struct ev_signal signal_watcher;	1640	struct ev_signal signal_watcher;
1499	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1500	ev_signal_start (loop, &sigint_cb);	1642	ev_signal_start (loop, &signal_watcher);
1501		1643
1502		1644
1503	=head2 C<ev_child> - watch out for process status changes	1645	=head2 C<ev_child> - watch out for process status changes
1504		1646
1505	Child watchers trigger when your process receives a SIGCHLD in response to	1647	Child watchers trigger when your process receives a SIGCHLD in response to
1506	some child status changes (most typically when a child of yours dies). It	1648	some child status changes (most typically when a child of yours dies or
1507	is permissible to install a child watcher I<after> the child has been	1649	exits). It is permissible to install a child watcher I<after> the child
1508	forked (which implies it might have already exited), as long as the event	1650	has been forked (which implies it might have already exited), as long
1509	loop isn't entered (or is continued from a watcher).	1651	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1652	forking and then immediately registering a watcher for the child is fine,
		1653	but forking and registering a watcher a few event loop iterations later is
		1654	not.
1510		1655
1511	Only the default event loop is capable of handling signals, and therefore	1656	Only the default event loop is capable of handling signals, and therefore
1512	you can only rgeister child watchers in the default event loop.	1657	you can only register child watchers in the default event loop.
1513		1658
1514	=head3 Process Interaction	1659	=head3 Process Interaction
1515		1660
1516	Libev grabs C<SIGCHLD> as soon as the default event loop is	1661	Libev grabs C<SIGCHLD> as soon as the default event loop is
1517	initialised. This is necessary to guarantee proper behaviour even if	1662	initialised. This is necessary to guarantee proper behaviour even if
1518	the first child watcher is started after the child exits. The occurance	1663	the first child watcher is started after the child exits. The occurrence
1519	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1664	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1520	synchronously as part of the event loop processing. Libev always reaps all	1665	synchronously as part of the event loop processing. Libev always reaps all
1521	children, even ones not watched.	1666	children, even ones not watched.
1522		1667
1523	=head3 Overriding the Built-In Processing	1668	=head3 Overriding the Built-In Processing
…		…
1527	handler, you can override it easily by installing your own handler for	1672	handler, you can override it easily by installing your own handler for
1528	C<SIGCHLD> after initialising the default loop, and making sure the	1673	C<SIGCHLD> after initialising the default loop, and making sure the
1529	default loop never gets destroyed. You are encouraged, however, to use an	1674	default loop never gets destroyed. You are encouraged, however, to use an
1530	event-based approach to child reaping and thus use libev's support for	1675	event-based approach to child reaping and thus use libev's support for
1531	that, so other libev users can use C<ev_child> watchers freely.	1676	that, so other libev users can use C<ev_child> watchers freely.
		1677
		1678	=head3 Stopping the Child Watcher
		1679
		1680	Currently, the child watcher never gets stopped, even when the
		1681	child terminates, so normally one needs to stop the watcher in the
		1682	callback. Future versions of libev might stop the watcher automatically
		1683	when a child exit is detected.
1532		1684
1533	=head3 Watcher-Specific Functions and Data Members	1685	=head3 Watcher-Specific Functions and Data Members
1534		1686
1535	=over 4	1687	=over 4
1536		1688
…		…
1565	=head3 Examples	1717	=head3 Examples
1566		1718
1567	Example: C<fork()> a new process and install a child handler to wait for	1719	Example: C<fork()> a new process and install a child handler to wait for
1568	its completion.	1720	its completion.
1569		1721
1570	ev_child cw;	1722	ev_child cw;
1571		1723
1572	static void	1724	static void
1573	child_cb (EV_P_ struct ev_child *w, int revents)	1725	child_cb (EV_P_ struct ev_child *w, int revents)
1574	{	1726	{
1575	ev_child_stop (EV_A_ w);	1727	ev_child_stop (EV_A_ w);
1576	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1577	}	1729	}
1578		1730
1579	pid_t pid = fork ();	1731	pid_t pid = fork ();
1580		1732
1581	if (pid < 0)	1733	if (pid < 0)
1582	// error	1734	// error
1583	else if (pid == 0)	1735	else if (pid == 0)
1584	{	1736	{
1585	// the forked child executes here	1737	// the forked child executes here
1586	exit (1);	1738	exit (1);
1587	}	1739	}
1588	else	1740	else
1589	{	1741	{
1590	ev_child_init (&cw, child_cb, pid, 0);	1742	ev_child_init (&cw, child_cb, pid, 0);
1591	ev_child_start (EV_DEFAULT_ &cw);	1743	ev_child_start (EV_DEFAULT_ &cw);
1592	}	1744	}
1593		1745
1594		1746
1595	=head2 C<ev_stat> - did the file attributes just change?	1747	=head2 C<ev_stat> - did the file attributes just change?
1596		1748
1597	This watches a filesystem path for attribute changes. That is, it calls	1749	This watches a file system path for attribute changes. That is, it calls
1598	C<stat> regularly (or when the OS says it changed) and sees if it changed	1750	C<stat> regularly (or when the OS says it changed) and sees if it changed
1599	compared to the last time, invoking the callback if it did.	1751	compared to the last time, invoking the callback if it did.
1600		1752
1601	The path does not need to exist: changing from "path exists" to "path does	1753	The path does not need to exist: changing from "path exists" to "path does
1602	not exist" is a status change like any other. The condition "path does	1754	not exist" is a status change like any other. The condition "path does
…		…
1605	the stat buffer having unspecified contents.	1757	the stat buffer having unspecified contents.
1606		1758
1607	The path I<should> be absolute and I<must not> end in a slash. If it is	1759	The path I<should> be absolute and I<must not> end in a slash. If it is
1608	relative and your working directory changes, the behaviour is undefined.	1760	relative and your working directory changes, the behaviour is undefined.
1609		1761
1610	Since there is no standard to do this, the portable implementation simply	1762	Since there is no standard kernel interface to do this, the portable
1611	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1763	implementation simply calls C<stat (2)> regularly on the path to see if
1612	can specify a recommended polling interval for this case. If you specify	1764	it changed somehow. You can specify a recommended polling interval for
1613	a polling interval of C<0> (highly recommended!) then a I<suitable,	1765	this case. If you specify a polling interval of C<0> (highly recommended!)
1614	unspecified default> value will be used (which you can expect to be around	1766	then a I<suitable, unspecified default> value will be used (which
1615	five seconds, although this might change dynamically). Libev will also	1767	you can expect to be around five seconds, although this might change
1616	impose a minimum interval which is currently around C<0.1>, but thats	1768	dynamically). Libev will also impose a minimum interval which is currently
1617	usually overkill.	1769	around C<0.1>, but thats usually overkill.
1618		1770
1619	This watcher type is not meant for massive numbers of stat watchers,	1771	This watcher type is not meant for massive numbers of stat watchers,
1620	as even with OS-supported change notifications, this can be	1772	as even with OS-supported change notifications, this can be
1621	resource-intensive.	1773	resource-intensive.
1622		1774
1623	At the time of this writing, only the Linux inotify interface is	1775	At the time of this writing, the only OS-specific interface implemented
1624	implemented (implementing kqueue support is left as an exercise for the	1776	is the Linux inotify interface (implementing kqueue support is left as
1625	reader, note, however, that the author sees no way of implementing ev_stat	1777	an exercise for the reader. Note, however, that the author sees no way
1626	semantics with kqueue). Inotify will be used to give hints only and should	1778	of implementing C<ev_stat> semantics with kqueue).
1627	not change the semantics of C<ev_stat> watchers, which means that libev
1628	sometimes needs to fall back to regular polling again even with inotify,
1629	but changes are usually detected immediately, and if the file exists there
1630	will be no polling.
1631		1779
1632	=head3 ABI Issues (Largefile Support)	1780	=head3 ABI Issues (Largefile Support)
1633		1781
1634	Libev by default (unless the user overrides this) uses the default	1782	Libev by default (unless the user overrides this) uses the default
1635	compilation environment, which means that on systems with optionally	1783	compilation environment, which means that on systems with large file
1636	disabled large file support, you get the 32 bit version of the stat	1784	support disabled by default, you get the 32 bit version of the stat
1637	structure. When using the library from programs that change the ABI to	1785	structure. When using the library from programs that change the ABI to
1638	use 64 bit file offsets the programs will fail. In that case you have to	1786	use 64 bit file offsets the programs will fail. In that case you have to
1639	compile libev with the same flags to get binary compatibility. This is	1787	compile libev with the same flags to get binary compatibility. This is
1640	obviously the case with any flags that change the ABI, but the problem is	1788	obviously the case with any flags that change the ABI, but the problem is
1641	most noticably with ev_stat and largefile support.	1789	most noticeably disabled with ev_stat and large file support.
1642		1790
1643	=head3 Inotify	1791	The solution for this is to lobby your distribution maker to make large
		1792	file interfaces available by default (as e.g. FreeBSD does) and not
		1793	optional. Libev cannot simply switch on large file support because it has
		1794	to exchange stat structures with application programs compiled using the
		1795	default compilation environment.
		1796
		1797	=head3 Inotify and Kqueue
1644		1798
1645	When C<inotify (7)> support has been compiled into libev (generally only	1799	When C<inotify (7)> support has been compiled into libev (generally only
1646	available on Linux) and present at runtime, it will be used to speed up	1800	available with Linux) and present at runtime, it will be used to speed up
1647	change detection where possible. The inotify descriptor will be created lazily	1801	change detection where possible. The inotify descriptor will be created lazily
1648	when the first C<ev_stat> watcher is being started.	1802	when the first C<ev_stat> watcher is being started.
1649		1803
1650	Inotify presence does not change the semantics of C<ev_stat> watchers	1804	Inotify presence does not change the semantics of C<ev_stat> watchers
1651	except that changes might be detected earlier, and in some cases, to avoid	1805	except that changes might be detected earlier, and in some cases, to avoid
1652	making regular C<stat> calls. Even in the presence of inotify support	1806	making regular C<stat> calls. Even in the presence of inotify support
1653	there are many cases where libev has to resort to regular C<stat> polling.	1807	there are many cases where libev has to resort to regular C<stat> polling,
		1808	but as long as the path exists, libev usually gets away without polling.
1654		1809
1655	(There is no support for kqueue, as apparently it cannot be used to	1810	There is no support for kqueue, as apparently it cannot be used to
1656	implement this functionality, due to the requirement of having a file	1811	implement this functionality, due to the requirement of having a file
1657	descriptor open on the object at all times).	1812	descriptor open on the object at all times, and detecting renames, unlinks
		1813	etc. is difficult.
1658		1814
1659	=head3 The special problem of stat time resolution	1815	=head3 The special problem of stat time resolution
1660		1816
1661	The C<stat ()> syscall only supports full-second resolution portably, and	1817	The C<stat ()> system call only supports full-second resolution portably, and
1662	even on systems where the resolution is higher, many filesystems still	1818	even on systems where the resolution is higher, most file systems still
1663	only support whole seconds.	1819	only support whole seconds.
1664		1820
1665	That means that, if the time is the only thing that changes, you can	1821	That means that, if the time is the only thing that changes, you can
1666	easily miss updates: on the first update, C<ev_stat> detects a change and	1822	easily miss updates: on the first update, C<ev_stat> detects a change and
1667	calls your callback, which does something. When there is another update	1823	calls your callback, which does something. When there is another update
1668	within the same second, C<ev_stat> will be unable to detect it as the stat	1824	within the same second, C<ev_stat> will be unable to detect unless the
1669	data does not change.	1825	stat data does change in other ways (e.g. file size).
1670		1826
1671	The solution to this is to delay acting on a change for slightly more	1827	The solution to this is to delay acting on a change for slightly more
1672	than a second (or till slightly after the next full second boundary), using	1828	than a second (or till slightly after the next full second boundary), using
1673	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1829	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1674	ev_timer_again (loop, w)>).	1830	ev_timer_again (loop, w)>).
…		…
1694	C<path>. The C<interval> is a hint on how quickly a change is expected to	1850	C<path>. The C<interval> is a hint on how quickly a change is expected to
1695	be detected and should normally be specified as C<0> to let libev choose	1851	be detected and should normally be specified as C<0> to let libev choose
1696	a suitable value. The memory pointed to by C<path> must point to the same	1852	a suitable value. The memory pointed to by C<path> must point to the same
1697	path for as long as the watcher is active.	1853	path for as long as the watcher is active.
1698		1854
1699	The callback will receive C<EV_STAT> when a change was detected, relative	1855	The callback will receive an C<EV_STAT> event when a change was detected,
1700	to the attributes at the time the watcher was started (or the last change	1856	relative to the attributes at the time the watcher was started (or the
1701	was detected).	1857	last change was detected).
1702		1858
1703	=item ev_stat_stat (loop, ev_stat *)	1859	=item ev_stat_stat (loop, ev_stat *)
1704		1860
1705	Updates the stat buffer immediately with new values. If you change the	1861	Updates the stat buffer immediately with new values. If you change the
1706	watched path in your callback, you could call this function to avoid	1862	watched path in your callback, you could call this function to avoid
…		…
1727		1883
1728	The specified interval.	1884	The specified interval.
1729		1885
1730	=item const char *path [read-only]	1886	=item const char *path [read-only]
1731		1887
1732	The filesystem path that is being watched.	1888	The file system path that is being watched.
1733		1889
1734	=back	1890	=back
1735		1891
1736	=head3 Examples	1892	=head3 Examples
1737		1893
1738	Example: Watch C</etc/passwd> for attribute changes.	1894	Example: Watch C</etc/passwd> for attribute changes.
1739		1895
1740	static void	1896	static void
1741	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1897	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1742	{	1898	{
1743	/* /etc/passwd changed in some way */	1899	/* /etc/passwd changed in some way */
1744	if (w->attr.st_nlink)	1900	if (w->attr.st_nlink)
1745	{	1901	{
1746	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1902	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1747	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1903	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1748	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1904	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1749	}	1905	}
1750	else	1906	else
1751	/* you shalt not abuse printf for puts */	1907	/* you shalt not abuse printf for puts */
1752	puts ("wow, /etc/passwd is not there, expect problems. "	1908	puts ("wow, /etc/passwd is not there, expect problems. "
1753	"if this is windows, they already arrived\n");	1909	"if this is windows, they already arrived\n");
1754	}	1910	}
1755		1911
1756	...	1912	...
1757	ev_stat passwd;	1913	ev_stat passwd;
1758		1914
1759	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1915	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1760	ev_stat_start (loop, &passwd);	1916	ev_stat_start (loop, &passwd);
1761		1917
1762	Example: Like above, but additionally use a one-second delay so we do not	1918	Example: Like above, but additionally use a one-second delay so we do not
1763	miss updates (however, frequent updates will delay processing, too, so	1919	miss updates (however, frequent updates will delay processing, too, so
1764	one might do the work both on C<ev_stat> callback invocation I<and> on	1920	one might do the work both on C<ev_stat> callback invocation I<and> on
1765	C<ev_timer> callback invocation).	1921	C<ev_timer> callback invocation).
1766		1922
1767	static ev_stat passwd;	1923	static ev_stat passwd;
1768	static ev_timer timer;	1924	static ev_timer timer;
1769		1925
1770	static void	1926	static void
1771	timer_cb (EV_P_ ev_timer *w, int revents)	1927	timer_cb (EV_P_ ev_timer *w, int revents)
1772	{	1928	{
1773	ev_timer_stop (EV_A_ w);	1929	ev_timer_stop (EV_A_ w);
1774		1930
1775	/* now it's one second after the most recent passwd change */	1931	/* now it's one second after the most recent passwd change */
1776	}	1932	}
1777		1933
1778	static void	1934	static void
1779	stat_cb (EV_P_ ev_stat *w, int revents)	1935	stat_cb (EV_P_ ev_stat *w, int revents)
1780	{	1936	{
1781	/* reset the one-second timer */	1937	/* reset the one-second timer */
1782	ev_timer_again (EV_A_ &timer);	1938	ev_timer_again (EV_A_ &timer);
1783	}	1939	}
1784		1940
1785	...	1941	...
1786	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1942	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1787	ev_stat_start (loop, &passwd);	1943	ev_stat_start (loop, &passwd);
1788	ev_timer_init (&timer, timer_cb, 0., 1.02);	1944	ev_timer_init (&timer, timer_cb, 0., 1.02);
1789		1945
1790		1946
1791	=head2 C<ev_idle> - when you've got nothing better to do...	1947	=head2 C<ev_idle> - when you've got nothing better to do...
1792		1948
1793	Idle watchers trigger events when no other events of the same or higher	1949	Idle watchers trigger events when no other events of the same or higher
1794	priority are pending (prepare, check and other idle watchers do not	1950	priority are pending (prepare, check and other idle watchers do not count
1795	count).	1951	as receiving "events").
1796		1952
1797	That is, as long as your process is busy handling sockets or timeouts	1953	That is, as long as your process is busy handling sockets or timeouts
1798	(or even signals, imagine) of the same or higher priority it will not be	1954	(or even signals, imagine) of the same or higher priority it will not be
1799	triggered. But when your process is idle (or only lower-priority watchers	1955	triggered. But when your process is idle (or only lower-priority watchers
1800	are pending), the idle watchers are being called once per event loop	1956	are pending), the idle watchers are being called once per event loop
…		…
1824	=head3 Examples	1980	=head3 Examples
1825		1981
1826	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1827	callback, free it. Also, use no error checking, as usual.	1983	callback, free it. Also, use no error checking, as usual.
1828		1984
1829	static void	1985	static void
1830	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1986	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1831	{	1987	{
1832	free (w);	1988	free (w);
1833	// now do something you wanted to do when the program has	1989	// now do something you wanted to do when the program has
1834	// no longer anything immediate to do.	1990	// no longer anything immediate to do.
1835	}	1991	}
1836		1992
1837	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1838	ev_idle_init (idle_watcher, idle_cb);	1994	ev_idle_init (idle_watcher, idle_cb);
1839	ev_idle_start (loop, idle_cb);	1995	ev_idle_start (loop, idle_cb);
1840		1996
1841		1997
1842	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1843		1999
1844	Prepare and check watchers are usually (but not always) used in tandem:	2000	Prepare and check watchers are usually (but not always) used in pairs:
1845	prepare watchers get invoked before the process blocks and check watchers	2001	prepare watchers get invoked before the process blocks and check watchers
1846	afterwards.	2002	afterwards.
1847		2003
1848	You I<must not> call C<ev_loop> or similar functions that enter	2004	You I<must not> call C<ev_loop> or similar functions that enter
1849	the current event loop from either C<ev_prepare> or C<ev_check>	2005	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1852	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2008	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1853	C<ev_check> so if you have one watcher of each kind they will always be	2009	C<ev_check> so if you have one watcher of each kind they will always be
1854	called in pairs bracketing the blocking call.	2010	called in pairs bracketing the blocking call.
1855		2011
1856	Their main purpose is to integrate other event mechanisms into libev and	2012	Their main purpose is to integrate other event mechanisms into libev and
1857	their use is somewhat advanced. This could be used, for example, to track	2013	their use is somewhat advanced. They could be used, for example, to track
1858	variable changes, implement your own watchers, integrate net-snmp or a	2014	variable changes, implement your own watchers, integrate net-snmp or a
1859	coroutine library and lots more. They are also occasionally useful if	2015	coroutine library and lots more. They are also occasionally useful if
1860	you cache some data and want to flush it before blocking (for example,	2016	you cache some data and want to flush it before blocking (for example,
1861	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2017	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1862	watcher).	2018	watcher).
1863		2019
1864	This is done by examining in each prepare call which file descriptors need	2020	This is done by examining in each prepare call which file descriptors
1865	to be watched by the other library, registering C<ev_io> watchers for	2021	need to be watched by the other library, registering C<ev_io> watchers
1866	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2022	for them and starting an C<ev_timer> watcher for any timeouts (many
1867	provide just this functionality). Then, in the check watcher you check for	2023	libraries provide exactly this functionality). Then, in the check watcher,
1868	any events that occured (by checking the pending status of all watchers	2024	you check for any events that occurred (by checking the pending status
1869	and stopping them) and call back into the library. The I/O and timer	2025	of all watchers and stopping them) and call back into the library. The
1870	callbacks will never actually be called (but must be valid nevertheless,	2026	I/O and timer callbacks will never actually be called (but must be valid
1871	because you never know, you know?).	2027	nevertheless, because you never know, you know?).
1872		2028
1873	As another example, the Perl Coro module uses these hooks to integrate	2029	As another example, the Perl Coro module uses these hooks to integrate
1874	coroutines into libev programs, by yielding to other active coroutines	2030	coroutines into libev programs, by yielding to other active coroutines
1875	during each prepare and only letting the process block if no coroutines	2031	during each prepare and only letting the process block if no coroutines
1876	are ready to run (it's actually more complicated: it only runs coroutines	2032	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1879	loop from blocking if lower-priority coroutines are active, thus mapping	2035	loop from blocking if lower-priority coroutines are active, thus mapping
1880	low-priority coroutines to idle/background tasks).	2036	low-priority coroutines to idle/background tasks).
1881		2037
1882	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2038	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1883	priority, to ensure that they are being run before any other watchers	2039	priority, to ensure that they are being run before any other watchers
		2040	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2041
1884	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2042	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1885	too) should not activate ("feed") events into libev. While libev fully	2043	activate ("feed") events into libev. While libev fully supports this, they
1886	supports this, they might get executed before other C<ev_check> watchers	2044	might get executed before other C<ev_check> watchers did their job. As
1887	did their job. As C<ev_check> watchers are often used to embed other	2045	C<ev_check> watchers are often used to embed other (non-libev) event
1888	(non-libev) event loops those other event loops might be in an unusable	2046	loops those other event loops might be in an unusable state until their
1889	state until their C<ev_check> watcher ran (always remind yourself to	2047	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1890	coexist peacefully with others).	2048	others).
1891		2049
1892	=head3 Watcher-Specific Functions and Data Members	2050	=head3 Watcher-Specific Functions and Data Members
1893		2051
1894	=over 4	2052	=over 4
1895		2053
…		…
1897		2055
1898	=item ev_check_init (ev_check *, callback)	2056	=item ev_check_init (ev_check *, callback)
1899		2057
1900	Initialises and configures the prepare or check watcher - they have no	2058	Initialises and configures the prepare or check watcher - they have no
1901	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2059	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1902	macros, but using them is utterly, utterly and completely pointless.	2060	macros, but using them is utterly, utterly, utterly and completely
		2061	pointless.
1903		2062
1904	=back	2063	=back
1905		2064
1906	=head3 Examples	2065	=head3 Examples
1907		2066
…		…
1916	and in a check watcher, destroy them and call into libadns. What follows	2075	and in a check watcher, destroy them and call into libadns. What follows
1917	is pseudo-code only of course. This requires you to either use a low	2076	is pseudo-code only of course. This requires you to either use a low
1918	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2077	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1919	the callbacks for the IO/timeout watchers might not have been called yet.	2078	the callbacks for the IO/timeout watchers might not have been called yet.
1920		2079
1921	static ev_io iow [nfd];	2080	static ev_io iow [nfd];
1922	static ev_timer tw;	2081	static ev_timer tw;
1923		2082
1924	static void	2083	static void
1925	io_cb (ev_loop *loop, ev_io *w, int revents)	2084	io_cb (ev_loop *loop, ev_io *w, int revents)
1926	{	2085	{
1927	}	2086	}
1928		2087
1929	// create io watchers for each fd and a timer before blocking	2088	// create io watchers for each fd and a timer before blocking
1930	static void	2089	static void
1931	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2090	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1932	{	2091	{
1933	int timeout = 3600000;	2092	int timeout = 3600000;
1934	struct pollfd fds [nfd];	2093	struct pollfd fds [nfd];
1935	// actual code will need to loop here and realloc etc.	2094	// actual code will need to loop here and realloc etc.
1936	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1937		2096
1938	/* the callback is illegal, but won't be called as we stop during check */	2097	/* the callback is illegal, but won't be called as we stop during check */
1939	ev_timer_init (&tw, 0, timeout * 1e-3);	2098	ev_timer_init (&tw, 0, timeout * 1e-3);
1940	ev_timer_start (loop, &tw);	2099	ev_timer_start (loop, &tw);
1941		2100
1942	// create one ev_io per pollfd	2101	// create one ev_io per pollfd
1943	for (int i = 0; i < nfd; ++i)	2102	for (int i = 0; i < nfd; ++i)
1944	{	2103	{
1945	ev_io_init (iow + i, io_cb, fds [i].fd,	2104	ev_io_init (iow + i, io_cb, fds [i].fd,
1946	((fds [i].events & POLLIN ? EV_READ : 0)	2105	((fds [i].events & POLLIN ? EV_READ : 0)
1947	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2106	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1948		2107
1949	fds [i].revents = 0;	2108	fds [i].revents = 0;
1950	ev_io_start (loop, iow + i);	2109	ev_io_start (loop, iow + i);
1951	}	2110	}
1952	}	2111	}
1953		2112
1954	// stop all watchers after blocking	2113	// stop all watchers after blocking
1955	static void	2114	static void
1956	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2115	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1957	{	2116	{
1958	ev_timer_stop (loop, &tw);	2117	ev_timer_stop (loop, &tw);
1959		2118
1960	for (int i = 0; i < nfd; ++i)	2119	for (int i = 0; i < nfd; ++i)
1961	{	2120	{
1962	// set the relevant poll flags	2121	// set the relevant poll flags
1963	// could also call adns_processreadable etc. here	2122	// could also call adns_processreadable etc. here
1964	struct pollfd *fd = fds + i;	2123	struct pollfd *fd = fds + i;
1965	int revents = ev_clear_pending (iow + i);	2124	int revents = ev_clear_pending (iow + i);
1966	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2125	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1967	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2126	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1968		2127
1969	// now stop the watcher	2128	// now stop the watcher
1970	ev_io_stop (loop, iow + i);	2129	ev_io_stop (loop, iow + i);
1971	}	2130	}
1972		2131
1973	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2132	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1974	}	2133	}
1975		2134
1976	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2135	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1977	in the prepare watcher and would dispose of the check watcher.	2136	in the prepare watcher and would dispose of the check watcher.
1978		2137
1979	Method 3: If the module to be embedded supports explicit event	2138	Method 3: If the module to be embedded supports explicit event
1980	notification (adns does), you can also make use of the actual watcher	2139	notification (libadns does), you can also make use of the actual watcher
1981	callbacks, and only destroy/create the watchers in the prepare watcher.	2140	callbacks, and only destroy/create the watchers in the prepare watcher.
1982		2141
1983	static void	2142	static void
1984	timer_cb (EV_P_ ev_timer *w, int revents)	2143	timer_cb (EV_P_ ev_timer *w, int revents)
1985	{	2144	{
1986	adns_state ads = (adns_state)w->data;	2145	adns_state ads = (adns_state)w->data;
1987	update_now (EV_A);	2146	update_now (EV_A);
1988		2147
1989	adns_processtimeouts (ads, &tv_now);	2148	adns_processtimeouts (ads, &tv_now);
1990	}	2149	}
1991		2150
1992	static void	2151	static void
1993	io_cb (EV_P_ ev_io *w, int revents)	2152	io_cb (EV_P_ ev_io *w, int revents)
1994	{	2153	{
1995	adns_state ads = (adns_state)w->data;	2154	adns_state ads = (adns_state)w->data;
1996	update_now (EV_A);	2155	update_now (EV_A);
1997		2156
1998	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2157	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1999	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2158	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2000	}	2159	}
2001		2160
2002	// do not ever call adns_afterpoll	2161	// do not ever call adns_afterpoll
2003		2162
2004	Method 4: Do not use a prepare or check watcher because the module you	2163	Method 4: Do not use a prepare or check watcher because the module you
2005	want to embed is too inflexible to support it. Instead, youc na override	2164	want to embed is not flexible enough to support it. Instead, you can
2006	their poll function. The drawback with this solution is that the main	2165	override their poll function. The drawback with this solution is that the
2007	loop is now no longer controllable by EV. The C<Glib::EV> module does	2166	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2008	this.	2167	this approach, effectively embedding EV as a client into the horrible
		2168	libglib event loop.
2009		2169
2010	static gint	2170	static gint
2011	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2171	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2012	{	2172	{
2013	int got_events = 0;	2173	int got_events = 0;
2014		2174
2015	for (n = 0; n < nfds; ++n)	2175	for (n = 0; n < nfds; ++n)
2016	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2176	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2017		2177
2018	if (timeout >= 0)	2178	if (timeout >= 0)
2019	// create/start timer	2179	// create/start timer
2020		2180
2021	// poll	2181	// poll
2022	ev_loop (EV_A_ 0);	2182	ev_loop (EV_A_ 0);
2023		2183
2024	// stop timer again	2184	// stop timer again
2025	if (timeout >= 0)	2185	if (timeout >= 0)
2026	ev_timer_stop (EV_A_ &to);	2186	ev_timer_stop (EV_A_ &to);
2027		2187
2028	// stop io watchers again - their callbacks should have set	2188	// stop io watchers again - their callbacks should have set
2029	for (n = 0; n < nfds; ++n)	2189	for (n = 0; n < nfds; ++n)
2030	ev_io_stop (EV_A_ iow [n]);	2190	ev_io_stop (EV_A_ iow [n]);
2031		2191
2032	return got_events;	2192	return got_events;
2033	}	2193	}
2034		2194
2035		2195
2036	=head2 C<ev_embed> - when one backend isn't enough...	2196	=head2 C<ev_embed> - when one backend isn't enough...
2037		2197
2038	This is a rather advanced watcher type that lets you embed one event loop	2198	This is a rather advanced watcher type that lets you embed one event loop
…		…
2044	prioritise I/O.	2204	prioritise I/O.
2045		2205
2046	As an example for a bug workaround, the kqueue backend might only support	2206	As an example for a bug workaround, the kqueue backend might only support
2047	sockets on some platform, so it is unusable as generic backend, but you	2207	sockets on some platform, so it is unusable as generic backend, but you
2048	still want to make use of it because you have many sockets and it scales	2208	still want to make use of it because you have many sockets and it scales
2049	so nicely. In this case, you would create a kqueue-based loop and embed it	2209	so nicely. In this case, you would create a kqueue-based loop and embed
2050	into your default loop (which might use e.g. poll). Overall operation will	2210	it into your default loop (which might use e.g. poll). Overall operation
2051	be a bit slower because first libev has to poll and then call kevent, but	2211	will be a bit slower because first libev has to call C<poll> and then
2052	at least you can use both at what they are best.	2212	C<kevent>, but at least you can use both mechanisms for what they are
		2213	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2053		2214
2054	As for prioritising I/O: rarely you have the case where some fds have	2215	As for prioritising I/O: under rare circumstances you have the case where
2055	to be watched and handled very quickly (with low latency), and even	2216	some fds have to be watched and handled very quickly (with low latency),
2056	priorities and idle watchers might have too much overhead. In this case	2217	and even priorities and idle watchers might have too much overhead. In
2057	you would put all the high priority stuff in one loop and all the rest in	2218	this case you would put all the high priority stuff in one loop and all
2058	a second one, and embed the second one in the first.	2219	the rest in a second one, and embed the second one in the first.
2059		2220
2060	As long as the watcher is active, the callback will be invoked every time	2221	As long as the watcher is active, the callback will be invoked every time
2061	there might be events pending in the embedded loop. The callback must then	2222	there might be events pending in the embedded loop. The callback must then
2062	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2063	their callbacks (you could also start an idle watcher to give the embedded	2224	their callbacks (you could also start an idle watcher to give the embedded
…		…
2071	interested in that.	2232	interested in that.
2072		2233
2073	Also, there have not currently been made special provisions for forking:	2234	Also, there have not currently been made special provisions for forking:
2074	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2075	but you will also have to stop and restart any C<ev_embed> watchers	2236	but you will also have to stop and restart any C<ev_embed> watchers
2076	yourself.	2237	yourself - but you can use a fork watcher to handle this automatically,
		2238	and future versions of libev might do just that.
2077		2239
2078	Unfortunately, not all backends are embeddable, only the ones returned by	2240	Unfortunately, not all backends are embeddable: only the ones returned by
2079	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2080	portable one.	2242	portable one.
2081		2243
2082	So when you want to use this feature you will always have to be prepared	2244	So when you want to use this feature you will always have to be prepared
2083	that you cannot get an embeddable loop. The recommended way to get around	2245	that you cannot get an embeddable loop. The recommended way to get around
2084	this is to have a separate variables for your embeddable loop, try to	2246	this is to have a separate variables for your embeddable loop, try to
2085	create it, and if that fails, use the normal loop for everything.	2247	create it, and if that fails, use the normal loop for everything.
2086		2248
		2249	=head3 C<ev_embed> and fork
		2250
		2251	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2252	automatically be applied to the embedded loop as well, so no special
		2253	fork handling is required in that case. When the watcher is not running,
		2254	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2255	as applicable.
		2256
2087	=head3 Watcher-Specific Functions and Data Members	2257	=head3 Watcher-Specific Functions and Data Members
2088		2258
2089	=over 4	2259	=over 4
2090		2260
2091	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2261	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2094		2264
2095	Configures the watcher to embed the given loop, which must be	2265	Configures the watcher to embed the given loop, which must be
2096	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2266	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2097	invoked automatically, otherwise it is the responsibility of the callback	2267	invoked automatically, otherwise it is the responsibility of the callback
2098	to invoke it (it will continue to be called until the sweep has been done,	2268	to invoke it (it will continue to be called until the sweep has been done,
2099	if you do not want thta, you need to temporarily stop the embed watcher).	2269	if you do not want that, you need to temporarily stop the embed watcher).
2100		2270
2101	=item ev_embed_sweep (loop, ev_embed *)	2271	=item ev_embed_sweep (loop, ev_embed *)
2102		2272
2103	Make a single, non-blocking sweep over the embedded loop. This works	2273	Make a single, non-blocking sweep over the embedded loop. This works
2104	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2274	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2105	apropriate way for embedded loops.	2275	appropriate way for embedded loops.
2106		2276
2107	=item struct ev_loop *other [read-only]	2277	=item struct ev_loop *other [read-only]
2108		2278
2109	The embedded event loop.	2279	The embedded event loop.
2110		2280
…		…
2112		2282
2113	=head3 Examples	2283	=head3 Examples
2114		2284
2115	Example: Try to get an embeddable event loop and embed it into the default	2285	Example: Try to get an embeddable event loop and embed it into the default
2116	event loop. If that is not possible, use the default loop. The default	2286	event loop. If that is not possible, use the default loop. The default
2117	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2287	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2118	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2119	used).	2289	used).
2120		2290
2121	struct ev_loop *loop_hi = ev_default_init (0);	2291	struct ev_loop *loop_hi = ev_default_init (0);
2122	struct ev_loop *loop_lo = 0;	2292	struct ev_loop *loop_lo = 0;
2123	struct ev_embed embed;	2293	struct ev_embed embed;
2124		2294
2125	// see if there is a chance of getting one that works	2295	// see if there is a chance of getting one that works
2126	// (remember that a flags value of 0 means autodetection)	2296	// (remember that a flags value of 0 means autodetection)
2127	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2128	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2129	: 0;	2299	: 0;
2130		2300
2131	// if we got one, then embed it, otherwise default to loop_hi	2301	// if we got one, then embed it, otherwise default to loop_hi
2132	if (loop_lo)	2302	if (loop_lo)
2133	{	2303	{
2134	ev_embed_init (&embed, 0, loop_lo);	2304	ev_embed_init (&embed, 0, loop_lo);
2135	ev_embed_start (loop_hi, &embed);	2305	ev_embed_start (loop_hi, &embed);
2136	}	2306	}
2137	else	2307	else
2138	loop_lo = loop_hi;	2308	loop_lo = loop_hi;
2139		2309
2140	Example: Check if kqueue is available but not recommended and create	2310	Example: Check if kqueue is available but not recommended and create
2141	a kqueue backend for use with sockets (which usually work with any	2311	a kqueue backend for use with sockets (which usually work with any
2142	kqueue implementation). Store the kqueue/socket-only event loop in	2312	kqueue implementation). Store the kqueue/socket-only event loop in
2143	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2144		2314
2145	struct ev_loop *loop = ev_default_init (0);	2315	struct ev_loop *loop = ev_default_init (0);
2146	struct ev_loop *loop_socket = 0;	2316	struct ev_loop *loop_socket = 0;
2147	struct ev_embed embed;	2317	struct ev_embed embed;
2148		2318
2149	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2150	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2151	{	2321	{
2152	ev_embed_init (&embed, 0, loop_socket);	2322	ev_embed_init (&embed, 0, loop_socket);
2153	ev_embed_start (loop, &embed);	2323	ev_embed_start (loop, &embed);
2154	}	2324	}
2155		2325
2156	if (!loop_socket)	2326	if (!loop_socket)
2157	loop_socket = loop;	2327	loop_socket = loop;
2158		2328
2159	// now use loop_socket for all sockets, and loop for everything else	2329	// now use loop_socket for all sockets, and loop for everything else
2160		2330
2161		2331
2162	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2332	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2163		2333
2164	Fork watchers are called when a C<fork ()> was detected (usually because	2334	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2208	is that the author does not know of a simple (or any) algorithm for a	2378	is that the author does not know of a simple (or any) algorithm for a
2209	multiple-writer-single-reader queue that works in all cases and doesn't	2379	multiple-writer-single-reader queue that works in all cases and doesn't
2210	need elaborate support such as pthreads.	2380	need elaborate support such as pthreads.
2211		2381
2212	That means that if you want to queue data, you have to provide your own	2382	That means that if you want to queue data, you have to provide your own
2213	queue. But at least I can tell you would implement locking around your	2383	queue. But at least I can tell you how to implement locking around your
2214	queue:	2384	queue:
2215		2385
2216	=over 4	2386	=over 4
2217		2387
2218	=item queueing from a signal handler context	2388	=item queueing from a signal handler context
2219		2389
2220	To implement race-free queueing, you simply add to the queue in the signal	2390	To implement race-free queueing, you simply add to the queue in the signal
2221	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2391	handler but you block the signal handler in the watcher callback. Here is
2222	some fictitiuous SIGUSR1 handler:	2392	an example that does that for some fictitious SIGUSR1 handler:
2223		2393
2224	static ev_async mysig;	2394	static ev_async mysig;
2225		2395
2226	static void	2396	static void
2227	sigusr1_handler (void)	2397	sigusr1_handler (void)
…		…
2294		2464
2295	=item ev_async_init (ev_async *, callback)	2465	=item ev_async_init (ev_async *, callback)
2296		2466
2297	Initialises and configures the async watcher - it has no parameters of any	2467	Initialises and configures the async watcher - it has no parameters of any
2298	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2299	believe me.	2469	trust me.
2300		2470
2301	=item ev_async_send (loop, ev_async *)	2471	=item ev_async_send (loop, ev_async *)
2302		2472
2303	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2304	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2305	C<ev_feed_event>, this call is safe to do in other threads, signal or	2475	C<ev_feed_event>, this call is safe to do from other threads, signal or
2306	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2307	section below on what exactly this means).	2477	section below on what exactly this means).
2308		2478
2309	This call incurs the overhead of a syscall only once per loop iteration,	2479	This call incurs the overhead of a system call only once per loop iteration,
2310	so while the overhead might be noticable, it doesn't apply to repeated	2480	so while the overhead might be noticeable, it doesn't apply to repeated
2311	calls to C<ev_async_send>.	2481	calls to C<ev_async_send>.
2312		2482
2313	=item bool = ev_async_pending (ev_async *)	2483	=item bool = ev_async_pending (ev_async *)
2314		2484
2315	Returns a non-zero value when C<ev_async_send> has been called on the	2485	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2317	event loop.	2487	event loop.
2318		2488
2319	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2489	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2320	the loop iterates next and checks for the watcher to have become active,	2490	the loop iterates next and checks for the watcher to have become active,
2321	it will reset the flag again. C<ev_async_pending> can be used to very	2491	it will reset the flag again. C<ev_async_pending> can be used to very
2322	quickly check wether invoking the loop might be a good idea.	2492	quickly check whether invoking the loop might be a good idea.
2323		2493
2324	Not that this does I<not> check wether the watcher itself is pending, only	2494	Not that this does I<not> check whether the watcher itself is pending, only
2325	wether it has been requested to make this watcher pending.	2495	whether it has been requested to make this watcher pending.
2326		2496
2327	=back	2497	=back
2328		2498
2329		2499
2330	=head1 OTHER FUNCTIONS	2500	=head1 OTHER FUNCTIONS
…		…
2334	=over 4	2504	=over 4
2335		2505
2336	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2506	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2337		2507
2338	This function combines a simple timer and an I/O watcher, calls your	2508	This function combines a simple timer and an I/O watcher, calls your
2339	callback on whichever event happens first and automatically stop both	2509	callback on whichever event happens first and automatically stops both
2340	watchers. This is useful if you want to wait for a single event on an fd	2510	watchers. This is useful if you want to wait for a single event on an fd
2341	or timeout without having to allocate/configure/start/stop/free one or	2511	or timeout without having to allocate/configure/start/stop/free one or
2342	more watchers yourself.	2512	more watchers yourself.
2343		2513
2344	If C<fd> is less than 0, then no I/O watcher will be started and events	2514	If C<fd> is less than 0, then no I/O watcher will be started and the
2345	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2515	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2346	C<events> set will be craeted and started.	2516	the given C<fd> and C<events> set will be created and started.
2347		2517
2348	If C<timeout> is less than 0, then no timeout watcher will be	2518	If C<timeout> is less than 0, then no timeout watcher will be
2349	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2519	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2350	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2520	repeat = 0) will be started. C<0> is a valid timeout.
2351	dubious value.
2352		2521
2353	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2522	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2354	passed an C<revents> set like normal event callbacks (a combination of	2523	passed an C<revents> set like normal event callbacks (a combination of
2355	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2524	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2356	value passed to C<ev_once>:	2525	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2526	a timeout and an io event at the same time - you probably should give io
		2527	events precedence.
2357		2528
		2529	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2530
2358	static void stdin_ready (int revents, void *arg)	2531	static void stdin_ready (int revents, void *arg)
2359	{	2532	{
2360	if (revents & EV_TIMEOUT)
2361	/* doh, nothing entered */;
2362	else if (revents & EV_READ)	2533	if (revents & EV_READ)
2363	/* stdin might have data for us, joy! */;	2534	/* stdin might have data for us, joy! */;
		2535	else if (revents & EV_TIMEOUT)
		2536	/* doh, nothing entered */;
2364	}	2537	}
2365		2538
2366	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2367		2540
2368	=item ev_feed_event (ev_loop *, watcher *, int revents)	2541	=item ev_feed_event (ev_loop *, watcher *, int revents)
2369		2542
2370	Feeds the given event set into the event loop, as if the specified event	2543	Feeds the given event set into the event loop, as if the specified event
2371	had happened for the specified watcher (which must be a pointer to an	2544	had happened for the specified watcher (which must be a pointer to an
…		…
2376	Feed an event on the given fd, as if a file descriptor backend detected	2549	Feed an event on the given fd, as if a file descriptor backend detected
2377	the given events it.	2550	the given events it.
2378		2551
2379	=item ev_feed_signal_event (ev_loop *loop, int signum)	2552	=item ev_feed_signal_event (ev_loop *loop, int signum)
2380		2553
2381	Feed an event as if the given signal occured (C<loop> must be the default	2554	Feed an event as if the given signal occurred (C<loop> must be the default
2382	loop!).	2555	loop!).
2383		2556
2384	=back	2557	=back
2385		2558
2386		2559
…		…
2415	=back	2588	=back
2416		2589
2417	=head1 C++ SUPPORT	2590	=head1 C++ SUPPORT
2418		2591
2419	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2592	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2420	you to use some convinience methods to start/stop watchers and also change	2593	you to use some convenience methods to start/stop watchers and also change
2421	the callback model to a model using method callbacks on objects.	2594	the callback model to a model using method callbacks on objects.
2422		2595
2423	To use it,	2596	To use it,
2424		2597
2425	#include <ev++.h>	2598	#include <ev++.h>
2426		2599
2427	This automatically includes F<ev.h> and puts all of its definitions (many	2600	This automatically includes F<ev.h> and puts all of its definitions (many
2428	of them macros) into the global namespace. All C++ specific things are	2601	of them macros) into the global namespace. All C++ specific things are
2429	put into the C<ev> namespace. It should support all the same embedding	2602	put into the C<ev> namespace. It should support all the same embedding
2430	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2603	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2497	your compiler is good :), then the method will be fully inlined into the	2670	your compiler is good :), then the method will be fully inlined into the
2498	thunking function, making it as fast as a direct C callback.	2671	thunking function, making it as fast as a direct C callback.
2499		2672
2500	Example: simple class declaration and watcher initialisation	2673	Example: simple class declaration and watcher initialisation
2501		2674
2502	struct myclass	2675	struct myclass
2503	{	2676	{
2504	void io_cb (ev::io &w, int revents) { }	2677	void io_cb (ev::io &w, int revents) { }
2505	}	2678	}
2506		2679
2507	myclass obj;	2680	myclass obj;
2508	ev::io iow;	2681	ev::io iow;
2509	iow.set <myclass, &myclass::io_cb> (&obj);	2682	iow.set <myclass, &myclass::io_cb> (&obj);
2510		2683
2511	=item w->set<function> (void *data = 0)	2684	=item w->set<function> (void *data = 0)
2512		2685
2513	Also sets a callback, but uses a static method or plain function as	2686	Also sets a callback, but uses a static method or plain function as
2514	callback. The optional C<data> argument will be stored in the watcher's	2687	callback. The optional C<data> argument will be stored in the watcher's
…		…
2516		2689
2517	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2690	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2518		2691
2519	See the method-C<set> above for more details.	2692	See the method-C<set> above for more details.
2520		2693
2521	Example:	2694	Example: Use a plain function as callback.
2522		2695
2523	static void io_cb (ev::io &w, int revents) { }	2696	static void io_cb (ev::io &w, int revents) { }
2524	iow.set <io_cb> ();	2697	iow.set <io_cb> ();
2525		2698
2526	=item w->set (struct ev_loop *)	2699	=item w->set (struct ev_loop *)
2527		2700
2528	Associates a different C<struct ev_loop> with this watcher. You can only	2701	Associates a different C<struct ev_loop> with this watcher. You can only
2529	do this when the watcher is inactive (and not pending either).	2702	do this when the watcher is inactive (and not pending either).
2530		2703
2531	=item w->set ([args])	2704	=item w->set ([arguments])
2532		2705
2533	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2706	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2534	called at least once. Unlike the C counterpart, an active watcher gets	2707	called at least once. Unlike the C counterpart, an active watcher gets
2535	automatically stopped and restarted when reconfiguring it with this	2708	automatically stopped and restarted when reconfiguring it with this
2536	method.	2709	method.
2537		2710
2538	=item w->start ()	2711	=item w->start ()
…		…
2562	=back	2735	=back
2563		2736
2564	Example: Define a class with an IO and idle watcher, start one of them in	2737	Example: Define a class with an IO and idle watcher, start one of them in
2565	the constructor.	2738	the constructor.
2566		2739
2567	class myclass	2740	class myclass
2568	{	2741	{
2569	ev::io io; void io_cb (ev::io &w, int revents);	2742	ev::io io ; void io_cb (ev::io &w, int revents);
2570	ev:idle idle void idle_cb (ev::idle &w, int revents);	2743	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2571		2744
2572	myclass (int fd)	2745	myclass (int fd)
2573	{	2746	{
2574	io .set <myclass, &myclass::io_cb > (this);	2747	io .set <myclass, &myclass::io_cb > (this);
2575	idle.set <myclass, &myclass::idle_cb> (this);	2748	idle.set <myclass, &myclass::idle_cb> (this);
2576		2749
2577	io.start (fd, ev::READ);	2750	io.start (fd, ev::READ);
2578	}	2751	}
2579	};	2752	};
2580		2753
2581		2754
2582	=head1 OTHER LANGUAGE BINDINGS	2755	=head1 OTHER LANGUAGE BINDINGS
2583		2756
2584	Libev does not offer other language bindings itself, but bindings for a	2757	Libev does not offer other language bindings itself, but bindings for a
2585	numbe rof languages exist in the form of third-party packages. If you know	2758	number of languages exist in the form of third-party packages. If you know
2586	any interesting language binding in addition to the ones listed here, drop	2759	any interesting language binding in addition to the ones listed here, drop
2587	me a note.	2760	me a note.
2588		2761
2589	=over 4	2762	=over 4
2590		2763
2591	=item Perl	2764	=item Perl
2592		2765
2593	The EV module implements the full libev API and is actually used to test	2766	The EV module implements the full libev API and is actually used to test
2594	libev. EV is developed together with libev. Apart from the EV core module,	2767	libev. EV is developed together with libev. Apart from the EV core module,
2595	there are additional modules that implement libev-compatible interfaces	2768	there are additional modules that implement libev-compatible interfaces
2596	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2769	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2597	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2770	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2771	and C<EV::Glib>).
2598		2772
2599	It can be found and installed via CPAN, its homepage is found at	2773	It can be found and installed via CPAN, its homepage is at
2600	L<http://software.schmorp.de/pkg/EV>.	2774	L<http://software.schmorp.de/pkg/EV>.
2601		2775
		2776	=item Python
		2777
		2778	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2779	seems to be quite complete and well-documented. Note, however, that the
		2780	patch they require for libev is outright dangerous as it breaks the ABI
		2781	for everybody else, and therefore, should never be applied in an installed
		2782	libev (if python requires an incompatible ABI then it needs to embed
		2783	libev).
		2784
2602	=item Ruby	2785	=item Ruby
2603		2786
2604	Tony Arcieri has written a ruby extension that offers access to a subset	2787	Tony Arcieri has written a ruby extension that offers access to a subset
2605	of the libev API and adds filehandle abstractions, asynchronous DNS and	2788	of the libev API and adds file handle abstractions, asynchronous DNS and
2606	more on top of it. It can be found via gem servers. Its homepage is at	2789	more on top of it. It can be found via gem servers. Its homepage is at
2607	L<http://rev.rubyforge.org/>.	2790	L<http://rev.rubyforge.org/>.
2608		2791
2609	=item D	2792	=item D
2610		2793
2611	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2612	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2795	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2613		2796
2614	=back	2797	=back
2615		2798
2616		2799
2617	=head1 MACRO MAGIC	2800	=head1 MACRO MAGIC
2618		2801
2619	Libev can be compiled with a variety of options, the most fundamantal	2802	Libev can be compiled with a variety of options, the most fundamental
2620	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2803	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2621	functions and callbacks have an initial C<struct ev_loop *> argument.	2804	functions and callbacks have an initial C<struct ev_loop *> argument.
2622		2805
2623	To make it easier to write programs that cope with either variant, the	2806	To make it easier to write programs that cope with either variant, the
2624	following macros are defined:	2807	following macros are defined:
…		…
2629		2812
2630	This provides the loop I<argument> for functions, if one is required ("ev	2813	This provides the loop I<argument> for functions, if one is required ("ev
2631	loop argument"). The C<EV_A> form is used when this is the sole argument,	2814	loop argument"). The C<EV_A> form is used when this is the sole argument,
2632	C<EV_A_> is used when other arguments are following. Example:	2815	C<EV_A_> is used when other arguments are following. Example:
2633		2816
2634	ev_unref (EV_A);	2817	ev_unref (EV_A);
2635	ev_timer_add (EV_A_ watcher);	2818	ev_timer_add (EV_A_ watcher);
2636	ev_loop (EV_A_ 0);	2819	ev_loop (EV_A_ 0);
2637		2820
2638	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2821	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2639	which is often provided by the following macro.	2822	which is often provided by the following macro.
2640		2823
2641	=item C<EV_P>, C<EV_P_>	2824	=item C<EV_P>, C<EV_P_>
2642		2825
2643	This provides the loop I<parameter> for functions, if one is required ("ev	2826	This provides the loop I<parameter> for functions, if one is required ("ev
2644	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2827	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2645	C<EV_P_> is used when other parameters are following. Example:	2828	C<EV_P_> is used when other parameters are following. Example:
2646		2829
2647	// this is how ev_unref is being declared	2830	// this is how ev_unref is being declared
2648	static void ev_unref (EV_P);	2831	static void ev_unref (EV_P);
2649		2832
2650	// this is how you can declare your typical callback	2833	// this is how you can declare your typical callback
2651	static void cb (EV_P_ ev_timer *w, int revents)	2834	static void cb (EV_P_ ev_timer *w, int revents)
2652		2835
2653	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2836	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2654	suitable for use with C<EV_A>.	2837	suitable for use with C<EV_A>.
2655		2838
2656	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2839	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2672		2855
2673	Example: Declare and initialise a check watcher, utilising the above	2856	Example: Declare and initialise a check watcher, utilising the above
2674	macros so it will work regardless of whether multiple loops are supported	2857	macros so it will work regardless of whether multiple loops are supported
2675	or not.	2858	or not.
2676		2859
2677	static void	2860	static void
2678	check_cb (EV_P_ ev_timer *w, int revents)	2861	check_cb (EV_P_ ev_timer *w, int revents)
2679	{	2862	{
2680	ev_check_stop (EV_A_ w);	2863	ev_check_stop (EV_A_ w);
2681	}	2864	}
2682		2865
2683	ev_check check;	2866	ev_check check;
2684	ev_check_init (&check, check_cb);	2867	ev_check_init (&check, check_cb);
2685	ev_check_start (EV_DEFAULT_ &check);	2868	ev_check_start (EV_DEFAULT_ &check);
2686	ev_loop (EV_DEFAULT_ 0);	2869	ev_loop (EV_DEFAULT_ 0);
2687		2870
2688	=head1 EMBEDDING	2871	=head1 EMBEDDING
2689		2872
2690	Libev can (and often is) directly embedded into host	2873	Libev can (and often is) directly embedded into host
2691	applications. Examples of applications that embed it include the Deliantra	2874	applications. Examples of applications that embed it include the Deliantra
…		…
2698	libev somewhere in your source tree).	2881	libev somewhere in your source tree).
2699		2882
2700	=head2 FILESETS	2883	=head2 FILESETS
2701		2884
2702	Depending on what features you need you need to include one or more sets of files	2885	Depending on what features you need you need to include one or more sets of files
2703	in your app.	2886	in your application.
2704		2887
2705	=head3 CORE EVENT LOOP	2888	=head3 CORE EVENT LOOP
2706		2889
2707	To include only the libev core (all the C<ev_*> functions), with manual	2890	To include only the libev core (all the C<ev_*> functions), with manual
2708	configuration (no autoconf):	2891	configuration (no autoconf):
2709		2892
2710	#define EV_STANDALONE 1	2893	#define EV_STANDALONE 1
2711	#include "ev.c"	2894	#include "ev.c"
2712		2895
2713	This will automatically include F<ev.h>, too, and should be done in a	2896	This will automatically include F<ev.h>, too, and should be done in a
2714	single C source file only to provide the function implementations. To use	2897	single C source file only to provide the function implementations. To use
2715	it, do the same for F<ev.h> in all files wishing to use this API (best	2898	it, do the same for F<ev.h> in all files wishing to use this API (best
2716	done by writing a wrapper around F<ev.h> that you can include instead and	2899	done by writing a wrapper around F<ev.h> that you can include instead and
2717	where you can put other configuration options):	2900	where you can put other configuration options):
2718		2901
2719	#define EV_STANDALONE 1	2902	#define EV_STANDALONE 1
2720	#include "ev.h"	2903	#include "ev.h"
2721		2904
2722	Both header files and implementation files can be compiled with a C++	2905	Both header files and implementation files can be compiled with a C++
2723	compiler (at least, thats a stated goal, and breakage will be treated	2906	compiler (at least, thats a stated goal, and breakage will be treated
2724	as a bug).	2907	as a bug).
2725		2908
2726	You need the following files in your source tree, or in a directory	2909	You need the following files in your source tree, or in a directory
2727	in your include path (e.g. in libev/ when using -Ilibev):	2910	in your include path (e.g. in libev/ when using -Ilibev):
2728		2911
2729	ev.h	2912	ev.h
2730	ev.c	2913	ev.c
2731	ev_vars.h	2914	ev_vars.h
2732	ev_wrap.h	2915	ev_wrap.h
2733		2916
2734	ev_win32.c required on win32 platforms only	2917	ev_win32.c required on win32 platforms only
2735		2918
2736	ev_select.c only when select backend is enabled (which is enabled by default)	2919	ev_select.c only when select backend is enabled (which is enabled by default)
2737	ev_poll.c only when poll backend is enabled (disabled by default)	2920	ev_poll.c only when poll backend is enabled (disabled by default)
2738	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2921	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2739	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2922	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2740	ev_port.c only when the solaris port backend is enabled (disabled by default)	2923	ev_port.c only when the solaris port backend is enabled (disabled by default)
2741		2924
2742	F<ev.c> includes the backend files directly when enabled, so you only need	2925	F<ev.c> includes the backend files directly when enabled, so you only need
2743	to compile this single file.	2926	to compile this single file.
2744		2927
2745	=head3 LIBEVENT COMPATIBILITY API	2928	=head3 LIBEVENT COMPATIBILITY API
2746		2929
2747	To include the libevent compatibility API, also include:	2930	To include the libevent compatibility API, also include:
2748		2931
2749	#include "event.c"	2932	#include "event.c"
2750		2933
2751	in the file including F<ev.c>, and:	2934	in the file including F<ev.c>, and:
2752		2935
2753	#include "event.h"	2936	#include "event.h"
2754		2937
2755	in the files that want to use the libevent API. This also includes F<ev.h>.	2938	in the files that want to use the libevent API. This also includes F<ev.h>.
2756		2939
2757	You need the following additional files for this:	2940	You need the following additional files for this:
2758		2941
2759	event.h	2942	event.h
2760	event.c	2943	event.c
2761		2944
2762	=head3 AUTOCONF SUPPORT	2945	=head3 AUTOCONF SUPPORT
2763		2946
2764	Instead of using C<EV_STANDALONE=1> and providing your config in	2947	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2765	whatever way you want, you can also C<m4_include([libev.m4])> in your	2948	whatever way you want, you can also C<m4_include([libev.m4])> in your
2766	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2949	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2767	include F<config.h> and configure itself accordingly.	2950	include F<config.h> and configure itself accordingly.
2768		2951
2769	For this of course you need the m4 file:	2952	For this of course you need the m4 file:
2770		2953
2771	libev.m4	2954	libev.m4
2772		2955
2773	=head2 PREPROCESSOR SYMBOLS/MACROS	2956	=head2 PREPROCESSOR SYMBOLS/MACROS
2774		2957
2775	Libev can be configured via a variety of preprocessor symbols you have to	2958	Libev can be configured via a variety of preprocessor symbols you have to
2776	define before including any of its files. The default in the absense of	2959	define before including any of its files. The default in the absence of
2777	autoconf is noted for every option.	2960	autoconf is documented for every option.
2778		2961
2779	=over 4	2962	=over 4
2780		2963
2781	=item EV_STANDALONE	2964	=item EV_STANDALONE
2782		2965
…		…
2787	F<event.h> that are not directly supported by the libev core alone.	2970	F<event.h> that are not directly supported by the libev core alone.
2788		2971
2789	=item EV_USE_MONOTONIC	2972	=item EV_USE_MONOTONIC
2790		2973
2791	If defined to be C<1>, libev will try to detect the availability of the	2974	If defined to be C<1>, libev will try to detect the availability of the
2792	monotonic clock option at both compiletime and runtime. Otherwise no use	2975	monotonic clock option at both compile time and runtime. Otherwise no use
2793	of the monotonic clock option will be attempted. If you enable this, you	2976	of the monotonic clock option will be attempted. If you enable this, you
2794	usually have to link against librt or something similar. Enabling it when	2977	usually have to link against librt or something similar. Enabling it when
2795	the functionality isn't available is safe, though, although you have	2978	the functionality isn't available is safe, though, although you have
2796	to make sure you link against any libraries where the C<clock_gettime>	2979	to make sure you link against any libraries where the C<clock_gettime>
2797	function is hiding in (often F<-lrt>).	2980	function is hiding in (often F<-lrt>).
2798		2981
2799	=item EV_USE_REALTIME	2982	=item EV_USE_REALTIME
2800		2983
2801	If defined to be C<1>, libev will try to detect the availability of the	2984	If defined to be C<1>, libev will try to detect the availability of the
2802	realtime clock option at compiletime (and assume its availability at	2985	real-time clock option at compile time (and assume its availability at
2803	runtime if successful). Otherwise no use of the realtime clock option will	2986	runtime if successful). Otherwise no use of the real-time clock option will
2804	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2987	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2805	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2988	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2806	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2989	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2807		2990
2808	=item EV_USE_NANOSLEEP	2991	=item EV_USE_NANOSLEEP
…		…
2819	2.7 or newer, otherwise disabled.	3002	2.7 or newer, otherwise disabled.
2820		3003
2821	=item EV_USE_SELECT	3004	=item EV_USE_SELECT
2822		3005
2823	If undefined or defined to be C<1>, libev will compile in support for the	3006	If undefined or defined to be C<1>, libev will compile in support for the
2824	C<select>(2) backend. No attempt at autodetection will be done: if no	3007	C<select>(2) backend. No attempt at auto-detection will be done: if no
2825	other method takes over, select will be it. Otherwise the select backend	3008	other method takes over, select will be it. Otherwise the select backend
2826	will not be compiled in.	3009	will not be compiled in.
2827		3010
2828	=item EV_SELECT_USE_FD_SET	3011	=item EV_SELECT_USE_FD_SET
2829		3012
2830	If defined to C<1>, then the select backend will use the system C<fd_set>	3013	If defined to C<1>, then the select backend will use the system C<fd_set>
2831	structure. This is useful if libev doesn't compile due to a missing	3014	structure. This is useful if libev doesn't compile due to a missing
2832	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3015	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2833	exotic systems. This usually limits the range of file descriptors to some	3016	exotic systems. This usually limits the range of file descriptors to some
2834	low limit such as 1024 or might have other limitations (winsocket only	3017	low limit such as 1024 or might have other limitations (winsocket only
2835	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3018	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2836	influence the size of the C<fd_set> used.	3019	influence the size of the C<fd_set> used.
2837		3020
…		…
2886	otherwise another method will be used as fallback. This is the preferred	3069	otherwise another method will be used as fallback. This is the preferred
2887	backend for Solaris 10 systems.	3070	backend for Solaris 10 systems.
2888		3071
2889	=item EV_USE_DEVPOLL	3072	=item EV_USE_DEVPOLL
2890		3073
2891	reserved for future expansion, works like the USE symbols above.	3074	Reserved for future expansion, works like the USE symbols above.
2892		3075
2893	=item EV_USE_INOTIFY	3076	=item EV_USE_INOTIFY
2894		3077
2895	If defined to be C<1>, libev will compile in support for the Linux inotify	3078	If defined to be C<1>, libev will compile in support for the Linux inotify
2896	interface to speed up C<ev_stat> watchers. Its actual availability will	3079	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2903	access is atomic with respect to other threads or signal contexts. No such	3086	access is atomic with respect to other threads or signal contexts. No such
2904	type is easily found in the C language, so you can provide your own type	3087	type is easily found in the C language, so you can provide your own type
2905	that you know is safe for your purposes. It is used both for signal handler "locking"	3088	that you know is safe for your purposes. It is used both for signal handler "locking"
2906	as well as for signal and thread safety in C<ev_async> watchers.	3089	as well as for signal and thread safety in C<ev_async> watchers.
2907		3090
2908	In the absense of this define, libev will use C<sig_atomic_t volatile>	3091	In the absence of this define, libev will use C<sig_atomic_t volatile>
2909	(from F<signal.h>), which is usually good enough on most platforms.	3092	(from F<signal.h>), which is usually good enough on most platforms.
2910		3093
2911	=item EV_H	3094	=item EV_H
2912		3095
2913	The name of the F<ev.h> header file used to include it. The default if	3096	The name of the F<ev.h> header file used to include it. The default if
…		…
2952	When doing priority-based operations, libev usually has to linearly search	3135	When doing priority-based operations, libev usually has to linearly search
2953	all the priorities, so having many of them (hundreds) uses a lot of space	3136	all the priorities, so having many of them (hundreds) uses a lot of space
2954	and time, so using the defaults of five priorities (-2 .. +2) is usually	3137	and time, so using the defaults of five priorities (-2 .. +2) is usually
2955	fine.	3138	fine.
2956		3139
2957	If your embedding app does not need any priorities, defining these both to	3140	If your embedding application does not need any priorities, defining these
2958	C<0> will save some memory and cpu.	3141	both to C<0> will save some memory and CPU.
2959		3142
2960	=item EV_PERIODIC_ENABLE	3143	=item EV_PERIODIC_ENABLE
2961		3144
2962	If undefined or defined to be C<1>, then periodic timers are supported. If	3145	If undefined or defined to be C<1>, then periodic timers are supported. If
2963	defined to be C<0>, then they are not. Disabling them saves a few kB of	3146	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2970	code.	3153	code.
2971		3154
2972	=item EV_EMBED_ENABLE	3155	=item EV_EMBED_ENABLE
2973		3156
2974	If undefined or defined to be C<1>, then embed watchers are supported. If	3157	If undefined or defined to be C<1>, then embed watchers are supported. If
2975	defined to be C<0>, then they are not.	3158	defined to be C<0>, then they are not. Embed watchers rely on most other
		3159	watcher types, which therefore must not be disabled.
2976		3160
2977	=item EV_STAT_ENABLE	3161	=item EV_STAT_ENABLE
2978		3162
2979	If undefined or defined to be C<1>, then stat watchers are supported. If	3163	If undefined or defined to be C<1>, then stat watchers are supported. If
2980	defined to be C<0>, then they are not.	3164	defined to be C<0>, then they are not.
…		…
2991		3175
2992	=item EV_MINIMAL	3176	=item EV_MINIMAL
2993		3177
2994	If you need to shave off some kilobytes of code at the expense of some	3178	If you need to shave off some kilobytes of code at the expense of some
2995	speed, define this symbol to C<1>. Currently this is used to override some	3179	speed, define this symbol to C<1>. Currently this is used to override some
2996	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3180	inlining decisions, saves roughly 30% code size on amd64. It also selects a
2997	much smaller 2-heap for timer management over the default 4-heap.	3181	much smaller 2-heap for timer management over the default 4-heap.
2998		3182
2999	=item EV_PID_HASHSIZE	3183	=item EV_PID_HASHSIZE
3000		3184
3001	C<ev_child> watchers use a small hash table to distribute workload by	3185	C<ev_child> watchers use a small hash table to distribute workload by
…		…
3012	two).	3196	two).
3013		3197
3014	=item EV_USE_4HEAP	3198	=item EV_USE_4HEAP
3015		3199
3016	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3200	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3017	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3201	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3018	to C<1>. The 4-heap uses more complicated (longer) code but has	3202	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3019	noticably faster performance with many (thousands) of watchers.	3203	faster performance with many (thousands) of watchers.
3020		3204
3021	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3205	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3022	(disabled).	3206	(disabled).
3023		3207
3024	=item EV_HEAP_CACHE_AT	3208	=item EV_HEAP_CACHE_AT
3025		3209
3026	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3210	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3027	timer and periodics heap, libev can cache the timestamp (I<at>) within	3211	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3028	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3212	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3029	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3213	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3030	but avoids random read accesses on heap changes. This improves performance	3214	but avoids random read accesses on heap changes. This improves performance
3031	noticably with with many (hundreds) of watchers.	3215	noticeably with many (hundreds) of watchers.
3032		3216
3033	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3217	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3034	(disabled).	3218	(disabled).
		3219
		3220	=item EV_VERIFY
		3221
		3222	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3223	be done: If set to C<0>, no internal verification code will be compiled
		3224	in. If set to C<1>, then verification code will be compiled in, but not
		3225	called. If set to C<2>, then the internal verification code will be
		3226	called once per loop, which can slow down libev. If set to C<3>, then the
		3227	verification code will be called very frequently, which will slow down
		3228	libev considerably.
		3229
		3230	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3231	C<0>.
3035		3232
3036	=item EV_COMMON	3233	=item EV_COMMON
3037		3234
3038	By default, all watchers have a C<void *data> member. By redefining	3235	By default, all watchers have a C<void *data> member. By redefining
3039	this macro to a something else you can include more and other types of	3236	this macro to a something else you can include more and other types of
3040	members. You have to define it each time you include one of the files,	3237	members. You have to define it each time you include one of the files,
3041	though, and it must be identical each time.	3238	though, and it must be identical each time.
3042		3239
3043	For example, the perl EV module uses something like this:	3240	For example, the perl EV module uses something like this:
3044		3241
3045	#define EV_COMMON \	3242	#define EV_COMMON \
3046	SV *self; /* contains this struct */ \	3243	SV *self; /* contains this struct */ \
3047	SV *cb_sv, *fh /* note no trailing ";" */	3244	SV *cb_sv, *fh /* note no trailing ";" */
3048		3245
3049	=item EV_CB_DECLARE (type)	3246	=item EV_CB_DECLARE (type)
3050		3247
3051	=item EV_CB_INVOKE (watcher, revents)	3248	=item EV_CB_INVOKE (watcher, revents)
3052		3249
…		…
3057	definition and a statement, respectively. See the F<ev.h> header file for	3254	definition and a statement, respectively. See the F<ev.h> header file for
3058	their default definitions. One possible use for overriding these is to	3255	their default definitions. One possible use for overriding these is to
3059	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3256	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3060	method calls instead of plain function calls in C++.	3257	method calls instead of plain function calls in C++.
3061		3258
		3259	=back
		3260
3062	=head2 EXPORTED API SYMBOLS	3261	=head2 EXPORTED API SYMBOLS
3063		3262
3064	If you need to re-export the API (e.g. via a dll) and you need a list of	3263	If you need to re-export the API (e.g. via a DLL) and you need a list of
3065	exported symbols, you can use the provided F<Symbol.*> files which list	3264	exported symbols, you can use the provided F<Symbol.*> files which list
3066	all public symbols, one per line:	3265	all public symbols, one per line:
3067		3266
3068	Symbols.ev for libev proper	3267	Symbols.ev for libev proper
3069	Symbols.event for the libevent emulation	3268	Symbols.event for the libevent emulation
3070		3269
3071	This can also be used to rename all public symbols to avoid clashes with	3270	This can also be used to rename all public symbols to avoid clashes with
3072	multiple versions of libev linked together (which is obviously bad in	3271	multiple versions of libev linked together (which is obviously bad in
3073	itself, but sometimes it is inconvinient to avoid this).	3272	itself, but sometimes it is inconvenient to avoid this).
3074		3273
3075	A sed command like this will create wrapper C<#define>'s that you need to	3274	A sed command like this will create wrapper C<#define>'s that you need to
3076	include before including F<ev.h>:	3275	include before including F<ev.h>:
3077		3276
3078	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3277	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3095	file.	3294	file.
3096		3295
3097	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3296	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3098	that everybody includes and which overrides some configure choices:	3297	that everybody includes and which overrides some configure choices:
3099		3298
3100	#define EV_MINIMAL 1	3299	#define EV_MINIMAL 1
3101	#define EV_USE_POLL 0	3300	#define EV_USE_POLL 0
3102	#define EV_MULTIPLICITY 0	3301	#define EV_MULTIPLICITY 0
3103	#define EV_PERIODIC_ENABLE 0	3302	#define EV_PERIODIC_ENABLE 0
3104	#define EV_STAT_ENABLE 0	3303	#define EV_STAT_ENABLE 0
3105	#define EV_FORK_ENABLE 0	3304	#define EV_FORK_ENABLE 0
3106	#define EV_CONFIG_H <config.h>	3305	#define EV_CONFIG_H <config.h>
3107	#define EV_MINPRI 0	3306	#define EV_MINPRI 0
3108	#define EV_MAXPRI 0	3307	#define EV_MAXPRI 0
3109		3308
3110	#include "ev++.h"	3309	#include "ev++.h"
3111		3310
3112	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3311	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3113		3312
3114	#include "ev_cpp.h"	3313	#include "ev_cpp.h"
3115	#include "ev.c"	3314	#include "ev.c"
3116		3315
		3316	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3117		3317
3118	=head1 THREADS AND COROUTINES	3318	=head2 THREADS AND COROUTINES
3119		3319
3120	=head2 THREADS	3320	=head3 THREADS
3121		3321
3122	Libev itself is completely threadsafe, but it uses no locking. This	3322	All libev functions are reentrant and thread-safe unless explicitly
		3323	documented otherwise, but libev implements no locking itself. This means
3123	means that you can use as many loops as you want in parallel, as long as	3324	that you can use as many loops as you want in parallel, as long as there
3124	only one thread ever calls into one libev function with the same loop	3325	are no concurrent calls into any libev function with the same loop
3125	parameter.	3326	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3327	of course): libev guarantees that different event loops share no data
		3328	structures that need any locking.
3126		3329
3127	Or put differently: calls with different loop parameters can be done in	3330	Or to put it differently: calls with different loop parameters can be done
3128	parallel from multiple threads, calls with the same loop parameter must be	3331	concurrently from multiple threads, calls with the same loop parameter
3129	done serially (but can be done from different threads, as long as only one	3332	must be done serially (but can be done from different threads, as long as
3130	thread ever is inside a call at any point in time, e.g. by using a mutex	3333	only one thread ever is inside a call at any point in time, e.g. by using
3131	per loop).	3334	a mutex per loop).
3132		3335
3133	If you want to know which design is best for your problem, then I cannot	3336	Specifically to support threads (and signal handlers), libev implements
		3337	so-called C<ev_async> watchers, which allow some limited form of
		3338	concurrency on the same event loop, namely waking it up "from the
		3339	outside".
		3340
		3341	If you want to know which design (one loop, locking, or multiple loops
		3342	without or something else still) is best for your problem, then I cannot
3134	help you but by giving some generic advice:	3343	help you, but here is some generic advice:
3135		3344
3136	=over 4	3345	=over 4
3137		3346
3138	=item * most applications have a main thread: use the default libev loop	3347	=item * most applications have a main thread: use the default libev loop
3139	in that thread, or create a seperate thread running only the default loop.	3348	in that thread, or create a separate thread running only the default loop.
3140		3349
3141	This helps integrating other libraries or software modules that use libev	3350	This helps integrating other libraries or software modules that use libev
3142	themselves and don't care/know about threading.	3351	themselves and don't care/know about threading.
3143		3352
3144	=item * one loop per thread is usually a good model.	3353	=item * one loop per thread is usually a good model.
3145		3354
3146	Doing this is almost never wrong, sometimes a better-performance model	3355	Doing this is almost never wrong, sometimes a better-performance model
3147	exists, but it is always a good start.	3356	exists, but it is always a good start.
3148		3357
3149	=item * other models exist, such as the leader/follower pattern, where one	3358	=item * other models exist, such as the leader/follower pattern, where one
3150	loop is handed through multiple threads in a kind of round-robbin fashion.	3359	loop is handed through multiple threads in a kind of round-robin fashion.
3151		3360
3152	Chosing a model is hard - look around, learn, know that usually you cna do	3361	Choosing a model is hard - look around, learn, know that usually you can do
3153	better than you currently do :-)	3362	better than you currently do :-)
3154		3363
3155	=item * often you need to talk to some other thread which blocks in the	3364	=item * often you need to talk to some other thread which blocks in the
		3365	event loop.
		3366
3156	event loop - C<ev_async> watchers can be used to wake them up from other	3367	C<ev_async> watchers can be used to wake them up from other threads safely
3157	threads safely (or from signal contexts...).	3368	(or from signal contexts...).
		3369
		3370	An example use would be to communicate signals or other events that only
		3371	work in the default loop by registering the signal watcher with the
		3372	default loop and triggering an C<ev_async> watcher from the default loop
		3373	watcher callback into the event loop interested in the signal.
3158		3374
3159	=back	3375	=back
3160		3376
3161	=head2 COROUTINES	3377	=head3 COROUTINES
3162		3378
3163	Libev is much more accomodating to coroutines ("cooperative threads"):	3379	Libev is very accommodating to coroutines ("cooperative threads"):
3164	libev fully supports nesting calls to it's functions from different	3380	libev fully supports nesting calls to its functions from different
3165	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3381	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3166	different coroutines and switch freely between both coroutines running the	3382	different coroutines, and switch freely between both coroutines running the
3167	loop, as long as you don't confuse yourself). The only exception is that	3383	loop, as long as you don't confuse yourself). The only exception is that
3168	you must not do this from C<ev_periodic> reschedule callbacks.	3384	you must not do this from C<ev_periodic> reschedule callbacks.
3169		3385
3170	Care has been invested into making sure that libev does not keep local	3386	Care has been taken to ensure that libev does not keep local state inside
3171	state inside C<ev_loop>, and other calls do not usually allow coroutine	3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3172	switches.	3388	they do not clal any callbacks.
3173		3389
		3390	=head2 COMPILER WARNINGS
3174		3391
3175	=head1 COMPLEXITIES	3392	Depending on your compiler and compiler settings, you might get no or a
		3393	lot of warnings when compiling libev code. Some people are apparently
		3394	scared by this.
3176		3395
3177	In this section the complexities of (many of) the algorithms used inside	3396	However, these are unavoidable for many reasons. For one, each compiler
3178	libev will be explained. For complexity discussions about backends see the	3397	has different warnings, and each user has different tastes regarding
3179	documentation for C<ev_default_init>.	3398	warning options. "Warn-free" code therefore cannot be a goal except when
		3399	targeting a specific compiler and compiler-version.
3180		3400
3181	All of the following are about amortised time: If an array needs to be	3401	Another reason is that some compiler warnings require elaborate
3182	extended, libev needs to realloc and move the whole array, but this	3402	workarounds, or other changes to the code that make it less clear and less
3183	happens asymptotically never with higher number of elements, so O(1) might	3403	maintainable.
3184	mean it might do a lengthy realloc operation in rare cases, but on average
3185	it is much faster and asymptotically approaches constant time.
3186		3404
3187	=over 4	3405	And of course, some compiler warnings are just plain stupid, or simply
		3406	wrong (because they don't actually warn about the condition their message
		3407	seems to warn about). For example, certain older gcc versions had some
		3408	warnings that resulted an extreme number of false positives. These have
		3409	been fixed, but some people still insist on making code warn-free with
		3410	such buggy versions.
3188		3411
3189	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3412	While libev is written to generate as few warnings as possible,
		3413	"warn-free" code is not a goal, and it is recommended not to build libev
		3414	with any compiler warnings enabled unless you are prepared to cope with
		3415	them (e.g. by ignoring them). Remember that warnings are just that:
		3416	warnings, not errors, or proof of bugs.
3190		3417
3191	This means that, when you have a watcher that triggers in one hour and
3192	there are 100 watchers that would trigger before that then inserting will
3193	have to skip roughly seven (C<ld 100>) of these watchers.
3194		3418
3195	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3419	=head2 VALGRIND
3196		3420
3197	That means that changing a timer costs less than removing/adding them	3421	Valgrind has a special section here because it is a popular tool that is
3198	as only the relative motion in the event queue has to be paid for.	3422	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3199		3423
3200	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3424	If you think you found a bug (memory leak, uninitialised data access etc.)
		3425	in libev, then check twice: If valgrind reports something like:
3201		3426
3202	These just add the watcher into an array or at the head of a list.	3427	==2274== definitely lost: 0 bytes in 0 blocks.
		3428	==2274== possibly lost: 0 bytes in 0 blocks.
		3429	==2274== still reachable: 256 bytes in 1 blocks.
3203		3430
3204	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3431	Then there is no memory leak, just as memory accounted to global variables
		3432	is not a memleak - the memory is still being refernced, and didn't leak.
3205		3433
3206	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3434	Similarly, under some circumstances, valgrind might report kernel bugs
		3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3436	although an acceptable workaround has been found here), or it might be
		3437	confused.
3207		3438
3208	These watchers are stored in lists then need to be walked to find the	3439	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3209	correct watcher to remove. The lists are usually short (you don't usually	3440	make it into some kind of religion.
3210	have many watchers waiting for the same fd or signal).
3211		3441
3212	=item Finding the next timer in each loop iteration: O(1)	3442	If you are unsure about something, feel free to contact the mailing list
		3443	with the full valgrind report and an explanation on why you think this
		3444	is a bug in libev (best check the archives, too :). However, don't be
		3445	annoyed when you get a brisk "this is no bug" answer and take the chance
		3446	of learning how to interpret valgrind properly.
3213		3447
3214	By virtue of using a binary or 4-heap, the next timer is always found at a	3448	If you need, for some reason, empty reports from valgrind for your project
3215	fixed position in the storage array.	3449	I suggest using suppression lists.
3216		3450
3217	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3218		3451
3219	A change means an I/O watcher gets started or stopped, which requires	3452	=head1 PORTABILITY NOTES
3220	libev to recalculate its status (and possibly tell the kernel, depending
3221	on backend and wether C<ev_io_set> was used).
3222		3453
3223	=item Activating one watcher (putting it into the pending state): O(1)	3454	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3224
3225	=item Priority handling: O(number_of_priorities)
3226
3227	Priorities are implemented by allocating some space for each
3228	priority. When doing priority-based operations, libev usually has to
3229	linearly search all the priorities, but starting/stopping and activating
3230	watchers becomes O(1) w.r.t. priority handling.
3231
3232	=item Sending an ev_async: O(1)
3233
3234	=item Processing ev_async_send: O(number_of_async_watchers)
3235
3236	=item Processing signals: O(max_signal_number)
3237
3238	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3239	calls in the current loop iteration. Checking for async and signal events
3240	involves iterating over all running async watchers or all signal numbers.
3241
3242	=back
3243
3244
3245	=head1 Win32 platform limitations and workarounds
3246		3455
3247	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3248	requires, and its I/O model is fundamentally incompatible with the POSIX	3457	requires, and its I/O model is fundamentally incompatible with the POSIX
3249	model. Libev still offers limited functionality on this platform in	3458	model. Libev still offers limited functionality on this platform in
3250	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3257	way (note also that glib is the slowest event library known to man).	3466	way (note also that glib is the slowest event library known to man).
3258		3467
3259	There is no supported compilation method available on windows except	3468	There is no supported compilation method available on windows except
3260	embedding it into other applications.	3469	embedding it into other applications.
3261		3470
		3471	Not a libev limitation but worth mentioning: windows apparently doesn't
		3472	accept large writes: instead of resulting in a partial write, windows will
		3473	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3474	so make sure you only write small amounts into your sockets (less than a
		3475	megabyte seems safe, but this apparently depends on the amount of memory
		3476	available).
		3477
3262	Due to the many, low, and arbitrary limits on the win32 platform and	3478	Due to the many, low, and arbitrary limits on the win32 platform and
3263	the abysmal performance of winsockets, using a large number of sockets	3479	the abysmal performance of winsockets, using a large number of sockets
3264	is not recommended (and not reasonable). If your program needs to use	3480	is not recommended (and not reasonable). If your program needs to use
3265	more than a hundred or so sockets, then likely it needs to use a totally	3481	more than a hundred or so sockets, then likely it needs to use a totally
3266	different implementation for windows, as libev offers the POSIX readiness	3482	different implementation for windows, as libev offers the POSIX readiness
3267	notification model, which cannot be implemented efficiently on windows	3483	notification model, which cannot be implemented efficiently on windows
3268	(microsoft monopoly games).	3484	(Microsoft monopoly games).
		3485
		3486	A typical way to use libev under windows is to embed it (see the embedding
		3487	section for details) and use the following F<evwrap.h> header file instead
		3488	of F<ev.h>:
		3489
		3490	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3491	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3492
		3493	#include "ev.h"
		3494
		3495	And compile the following F<evwrap.c> file into your project (make sure
		3496	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3497
		3498	#include "evwrap.h"
		3499	#include "ev.c"
3269		3500
3270	=over 4	3501	=over 4
3271		3502
3272	=item The winsocket select function	3503	=item The winsocket select function
3273		3504
3274	The winsocket C<select> function doesn't follow POSIX in that it requires	3505	The winsocket C<select> function doesn't follow POSIX in that it
3275	socket I<handles> and not socket I<file descriptors>. This makes select	3506	requires socket I<handles> and not socket I<file descriptors> (it is
3276	very inefficient, and also requires a mapping from file descriptors	3507	also extremely buggy). This makes select very inefficient, and also
3277	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3508	requires a mapping from file descriptors to socket handles (the Microsoft
3278	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3509	C runtime provides the function C<_open_osfhandle> for this). See the
3279	symbols for more info.	3510	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3511	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3280		3512
3281	The configuration for a "naked" win32 using the microsoft runtime	3513	The configuration for a "naked" win32 using the Microsoft runtime
3282	libraries and raw winsocket select is:	3514	libraries and raw winsocket select is:
3283		3515
3284	#define EV_USE_SELECT 1	3516	#define EV_USE_SELECT 1
3285	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3517	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3286		3518
3287	Note that winsockets handling of fd sets is O(n), so you can easily get a	3519	Note that winsockets handling of fd sets is O(n), so you can easily get a
3288	complexity in the O(n²) range when using win32.	3520	complexity in the O(n²) range when using win32.
3289		3521
3290	=item Limited number of file descriptors	3522	=item Limited number of file descriptors
3291		3523
3292	Windows has numerous arbitrary (and low) limits on things.	3524	Windows has numerous arbitrary (and low) limits on things.
3293		3525
3294	Early versions of winsocket's select only supported waiting for a maximum	3526	Early versions of winsocket's select only supported waiting for a maximum
3295	of C<64> handles (probably owning to the fact that all windows kernels	3527	of C<64> handles (probably owning to the fact that all windows kernels
3296	can only wait for C<64> things at the same time internally; microsoft	3528	can only wait for C<64> things at the same time internally; Microsoft
3297	recommends spawning a chain of threads and wait for 63 handles and the	3529	recommends spawning a chain of threads and wait for 63 handles and the
3298	previous thread in each. Great).	3530	previous thread in each. Great).
3299		3531
3300	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3532	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3301	to some high number (e.g. C<2048>) before compiling the winsocket select	3533	to some high number (e.g. C<2048>) before compiling the winsocket select
3302	call (which might be in libev or elsewhere, for example, perl does its own	3534	call (which might be in libev or elsewhere, for example, perl does its own
3303	select emulation on windows).	3535	select emulation on windows).
3304		3536
3305	Another limit is the number of file descriptors in the microsoft runtime	3537	Another limit is the number of file descriptors in the Microsoft runtime
3306	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3538	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3307	or something like this inside microsoft). You can increase this by calling	3539	or something like this inside Microsoft). You can increase this by calling
3308	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3309	arbitrary limit), but is broken in many versions of the microsoft runtime	3541	arbitrary limit), but is broken in many versions of the Microsoft runtime
3310	libraries.	3542	libraries.
3311		3543
3312	This might get you to about C<512> or C<2048> sockets (depending on	3544	This might get you to about C<512> or C<2048> sockets (depending on
3313	windows version and/or the phase of the moon). To get more, you need to	3545	windows version and/or the phase of the moon). To get more, you need to
3314	wrap all I/O functions and provide your own fd management, but the cost of	3546	wrap all I/O functions and provide your own fd management, but the cost of
3315	calling select (O(n²)) will likely make this unworkable.	3547	calling select (O(n²)) will likely make this unworkable.
3316		3548
3317	=back	3549	=back
3318		3550
3319
3320	=head1 PORTABILITY REQUIREMENTS	3551	=head2 PORTABILITY REQUIREMENTS
3321		3552
3322	In addition to a working ISO-C implementation, libev relies on a few	3553	In addition to a working ISO-C implementation and of course the
3323	additional extensions:	3554	backend-specific APIs, libev relies on a few additional extensions:
3324		3555
3325	=over 4	3556	=over 4
3326		3557
		3558	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3559	calling conventions regardless of C<ev_watcher_type *>.
		3560
		3561	Libev assumes not only that all watcher pointers have the same internal
		3562	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3563	assumes that the same (machine) code can be used to call any watcher
		3564	callback: The watcher callbacks have different type signatures, but libev
		3565	calls them using an C<ev_watcher *> internally.
		3566
3327	=item C<sig_atomic_t volatile> must be thread-atomic as well	3567	=item C<sig_atomic_t volatile> must be thread-atomic as well
3328		3568
3329	The type C<sig_atomic_t volatile> (or whatever is defined as	3569	The type C<sig_atomic_t volatile> (or whatever is defined as
3330	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3570	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3331	threads. This is not part of the specification for C<sig_atomic_t>, but is	3571	threads. This is not part of the specification for C<sig_atomic_t>, but is
3332	believed to be sufficiently portable.	3572	believed to be sufficiently portable.
3333		3573
3334	=item C<sigprocmask> must work in a threaded environment	3574	=item C<sigprocmask> must work in a threaded environment
3335		3575
…		…
3344	except the initial one, and run the default loop in the initial thread as	3584	except the initial one, and run the default loop in the initial thread as
3345	well.	3585	well.
3346		3586
3347	=item C<long> must be large enough for common memory allocation sizes	3587	=item C<long> must be large enough for common memory allocation sizes
3348		3588
3349	To improve portability and simplify using libev, libev uses C<long>	3589	To improve portability and simplify its API, libev uses C<long> internally
3350	internally instead of C<size_t> when allocating its data structures. On	3590	instead of C<size_t> when allocating its data structures. On non-POSIX
3351	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3591	systems (Microsoft...) this might be unexpectedly low, but is still at
3352	is still at least 31 bits everywhere, which is enough for hundreds of	3592	least 31 bits everywhere, which is enough for hundreds of millions of
3353	millions of watchers.	3593	watchers.
3354		3594
3355	=item C<double> must hold a time value in seconds with enough accuracy	3595	=item C<double> must hold a time value in seconds with enough accuracy
3356		3596
3357	The type C<double> is used to represent timestamps. It is required to	3597	The type C<double> is used to represent timestamps. It is required to
3358	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3598	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3362	=back	3602	=back
3363		3603
3364	If you know of other additional requirements drop me a note.	3604	If you know of other additional requirements drop me a note.
3365		3605
3366		3606
3367	=head1 VALGRIND	3607	=head1 ALGORITHMIC COMPLEXITIES
3368		3608
3369	Valgrind has a special section here because it is a popular tool that is	3609	In this section the complexities of (many of) the algorithms used inside
3370	highly useful, but valgrind reports are very hard to interpret.	3610	libev will be documented. For complexity discussions about backends see
		3611	the documentation for C<ev_default_init>.
3371		3612
3372	If you think you found a bug (memory leak, uninitialised data access etc.)	3613	All of the following are about amortised time: If an array needs to be
3373	in libev, then check twice: If valgrind reports something like:	3614	extended, libev needs to realloc and move the whole array, but this
		3615	happens asymptotically rarer with higher number of elements, so O(1) might
		3616	mean that libev does a lengthy realloc operation in rare cases, but on
		3617	average it is much faster and asymptotically approaches constant time.
3374		3618
3375	==2274== definitely lost: 0 bytes in 0 blocks.	3619	=over 4
3376	==2274== possibly lost: 0 bytes in 0 blocks.
3377	==2274== still reachable: 256 bytes in 1 blocks.
3378		3620
3379	then there is no memory leak. Similarly, under some circumstances,	3621	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3380	valgrind might report kernel bugs as if it were a bug in libev, or it
3381	might be confused (it is a very good tool, but only a tool).
3382		3622
3383	If you are unsure about something, feel free to contact the mailing list	3623	This means that, when you have a watcher that triggers in one hour and
3384	with the full valgrind report and an explanation on why you think this is	3624	there are 100 watchers that would trigger before that, then inserting will
3385	a bug in libev. However, don't be annoyed when you get a brisk "this is	3625	have to skip roughly seven (C<ld 100>) of these watchers.
3386	no bug" answer and take the chance of learning how to interpret valgrind
3387	properly.
3388		3626
3389	If you need, for some reason, empty reports from valgrind for your project	3627	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3390	I suggest using suppression lists.	3628
		3629	That means that changing a timer costs less than removing/adding them,
		3630	as only the relative motion in the event queue has to be paid for.
		3631
		3632	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3633
		3634	These just add the watcher into an array or at the head of a list.
		3635
		3636	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3637
		3638	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3639
		3640	These watchers are stored in lists, so they need to be walked to find the
		3641	correct watcher to remove. The lists are usually short (you don't usually
		3642	have many watchers waiting for the same fd or signal: one is typical, two
		3643	is rare).
		3644
		3645	=item Finding the next timer in each loop iteration: O(1)
		3646
		3647	By virtue of using a binary or 4-heap, the next timer is always found at a
		3648	fixed position in the storage array.
		3649
		3650	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3651
		3652	A change means an I/O watcher gets started or stopped, which requires
		3653	libev to recalculate its status (and possibly tell the kernel, depending
		3654	on backend and whether C<ev_io_set> was used).
		3655
		3656	=item Activating one watcher (putting it into the pending state): O(1)
		3657
		3658	=item Priority handling: O(number_of_priorities)
		3659
		3660	Priorities are implemented by allocating some space for each
		3661	priority. When doing priority-based operations, libev usually has to
		3662	linearly search all the priorities, but starting/stopping and activating
		3663	watchers becomes O(1) with respect to priority handling.
		3664
		3665	=item Sending an ev_async: O(1)
		3666
		3667	=item Processing ev_async_send: O(number_of_async_watchers)
		3668
		3669	=item Processing signals: O(max_signal_number)
		3670
		3671	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3672	calls in the current loop iteration. Checking for async and signal events
		3673	involves iterating over all running async watchers or all signal numbers.
		3674
		3675	=back
3391		3676
3392		3677
3393	=head1 AUTHOR	3678	=head1 AUTHOR
3394		3679
3395	Marc Lehmann <libev@schmorp.de>.	3680	Marc Lehmann <libev@schmorp.de>.

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