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Revision 1.157 by root, Tue May 20 23:49:41 2008 UTC vs.
Revision 1.197 by root, Tue Oct 21 20:52:30 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
		899	problem. Libev considers these application bugs.
		900
811	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
812	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
813		905
814	Libev will usually signal a few "dummy" events together with an error,	906	Libev will usually signal a few "dummy" events together with an error, for
815	for example it might indicate that a fd is readable or writable, and if	907	example it might indicate that a fd is readable or writable, and if your
816	your callbacks is well-written it can just attempt the operation and cope	908	callbacks is well-written it can just attempt the operation and cope with
817	with the error from read() or write(). This will not work in multithreaded	909	the error from read() or write(). This will not work in multi-threaded
818	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
819		912
820	=back	913	=back
821		914
822	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
823		916
…		…
839	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
840		933
841	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
842	int revents)>.	935	int revents)>.
843		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
		942
844	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
845		944
846	This macro initialises the type-specific parts of a watcher. You need to	945	This macro initialises the type-specific parts of a watcher. You need to
847	call C<ev_init> at least once before you call this macro, but you can	946	call C<ev_init> at least once before you call this macro, but you can
848	call C<ev_TYPE_set> any number of times. You must not, however, call this	947	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
850	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
851		950
852	Although some watcher types do not have type-specific arguments	951	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.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
854		953
		954	See C<ev_init>, above, for an example.
		955
855	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
856		957
857	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
858	calls into a single call. This is the most convinient method to initialise	959	calls into a single call. This is the most convenient method to initialise
859	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
860		965
861	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
862		967
863	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
864	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
865		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
866	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
867		977
868	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
869	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
870	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
871	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
872	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
873	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
874		986
875	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
876		988
877	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
878	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
926		1038
927	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
928		1040
929	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
930	C<loop> nor C<revents> need to be valid as long as the watcher callback	1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
931	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
932		1045
933	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
934		1047
935	If the watcher is pending, this function returns clears its pending status	1048	If the watcher is pending, this function clears its pending status and
936	and returns its C<revents> bitset (as if its callback was invoked). If the	1049	returns its C<revents> bitset (as if its callback was invoked). If the
937	watcher isn't pending it does nothing and returns C<0>.	1050	watcher isn't pending it does nothing and returns C<0>.
938		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
939	=back	1055	=back
940		1056
941		1057
942	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
943		1059
944	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
945	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
946	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
947	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
948	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
949	data:	1065	data:
950		1066
951	struct my_io	1067	struct my_io
952	{	1068	{
953	struct ev_io io;	1069	struct ev_io io;
954	int otherfd;	1070	int otherfd;
955	void *somedata;	1071	void *somedata;
956	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
957	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
958		1078
959	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
960	can cast it back to your own type:	1080	can cast it back to your own type:
961		1081
962	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
963	{	1083	{
964	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
965	...	1085	...
966	}	1086	}
967		1087
968	More interesting and less C-conformant ways of casting your callback type	1088	More interesting and less C-conformant ways of casting your callback type
969	instead have been omitted.	1089	instead have been omitted.
970		1090
971	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
972	watchers:	1092	embedded watchers:
973		1093
974	struct my_biggy	1094	struct my_biggy
975	{	1095	{
976	int some_data;	1096	int some_data;
977	ev_timer t1;	1097	ev_timer t1;
978	ev_timer t2;	1098	ev_timer t2;
979	}	1099	}
980		1100
981	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1101	In this case getting the pointer to C<my_biggy> is a bit more
982	you need to use C<offsetof>:	1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
983		1106
984	#include <stddef.h>	1107	#include <stddef.h>
985		1108
986	static void	1109	static void
987	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ struct ev_timer *w, int revents)
988	{	1111	{
989	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
990	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
991	}	1114	}
992		1115
993	static void	1116	static void
994	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ struct ev_timer *w, int revents)
995	{	1118	{
996	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
997	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
998	}	1121	}
999		1122
1000		1123
1001	=head1 WATCHER TYPES	1124	=head1 WATCHER TYPES
1002		1125
1003	This section describes each watcher in detail, but will not repeat	1126	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	1150	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	1151	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	1152	descriptors to non-blocking mode is also usually a good idea (but not
1030	required if you know what you are doing).	1153	required if you know what you are doing).
1031		1154
1032	If you must do this, then force the use of a known-to-be-good backend	1155	If you cannot use non-blocking mode, then force the use of a
1033	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1156	known-to-be-good backend (at the time of this writing, this includes only
1034	C<EVBACKEND_POLL>).	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1035		1158
1036	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
1037	receive "spurious" readiness notifications, that is your callback might	1160	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	1161	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	1162	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	1163	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	1164	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	1165	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.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1044		1167
1045	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
1046	play around with an Xlib connection), then you have to seperately re-test	1169	not play around with an Xlib connection), then you have to separately
1047	whether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
1048	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
1049	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
1050		1177
1051	=head3 The special problem of disappearing file descriptors	1178	=head3 The special problem of disappearing file descriptors
1052		1179
1053	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1054	descriptor (either by calling C<close> explicitly or by any other means,	1181	descriptor (either due to calling C<close> explicitly or any other means,
1055	such as C<dup>). The reason is that you register interest in some file	1182	such as C<dup2>). The reason is that you register interest in some file
1056	descriptor, but when it goes away, the operating system will silently drop	1183	descriptor, but when it goes away, the operating system will silently drop
1057	this interest. If another file descriptor with the same number then is	1184	this interest. If another file descriptor with the same number then is
1058	registered with libev, there is no efficient way to see that this is, in	1185	registered with libev, there is no efficient way to see that this is, in
1059	fact, a different file descriptor.	1186	fact, a different file descriptor.
1060		1187
…		…
1091	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1092	C<EVBACKEND_POLL>.	1219	C<EVBACKEND_POLL>.
1093		1220
1094	=head3 The special problem of SIGPIPE	1221	=head3 The special problem of SIGPIPE
1095		1222
1096	While not really specific to libev, it is easy to forget about SIGPIPE:	1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1097	when reading from a pipe whose other end has been closed, your program	1224	when writing to a pipe whose other end has been closed, your program gets
1098	gets send a SIGPIPE, which, by default, aborts your program. For most	1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
1099	programs this is sensible behaviour, for daemons, this is usually	1226	this is sensible behaviour, for daemons, this is usually undesirable.
1100	undesirable.
1101		1227
1102	So when you encounter spurious, unexplained daemon exits, make sure you	1228	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	1229	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).	1230	somewhere, as that would have given you a big clue).
1105		1231
…		…
1111	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
1112		1238
1113	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
1114		1240
1115	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1116	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1242	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1117	C<EV_READ | EV_WRITE> to receive the given events.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1118		1244
1119	=item int fd [read-only]	1245	=item int fd [read-only]
1120		1246
1121	The file descriptor being watched.	1247	The file descriptor being watched.
1122		1248
…		…
1130		1256
1131	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1132	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
1133	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
1134		1260
1135	static void	1261	static void
1136	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1137	{	1263	{
1138	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
1139	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
1140	}	1266	}
1141		1267
1142	...	1268	...
1143	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
1144	struct ev_io stdin_readable;	1270	struct ev_io stdin_readable;
1145	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1146	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
1147	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
1148		1274
1149		1275
1150	=head2 C<ev_timer> - relative and optionally repeating timeouts	1276	=head2 C<ev_timer> - relative and optionally repeating timeouts
1151		1277
1152	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
1153	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
1154		1280
1155	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
1156	times out after an hour and you reset your system clock to january last	1282	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	1283	year, it will still time out after (roughly) one hour. "Roughly" because
1158	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1159	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
		1286
		1287	The callback is guaranteed to be invoked only I<after> its timeout has
		1288	passed, but if multiple timers become ready during the same loop iteration
		1289	then order of execution is undefined.
		1290
		1291	=head3 The special problem of time updates
		1292
		1293	Establishing the current time is a costly operation (it usually takes at
		1294	least two system calls): EV therefore updates its idea of the current
		1295	time only before and after C<ev_loop> collects new events, which causes a
		1296	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1297	lots of events in one iteration.
1160		1298
1161	The relative timeouts are calculated relative to the C<ev_now ()>	1299	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	1300	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	1301	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	1302	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:	1303	timeout on the current time, use something like this to adjust for this:
1166		1304
1167	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1305	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1168		1306
1169	The callback is guarenteed to be invoked only after its timeout has passed,	1307	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	1308	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1171	order of execution is undefined.	1309	()>.
1172		1310
1173	=head3 Watcher-Specific Functions and Data Members	1311	=head3 Watcher-Specific Functions and Data Members
1174		1312
1175	=over 4	1313	=over 4
1176		1314
…		…
1195	This will act as if the timer timed out and restart it again if it is	1333	This will act as if the timer timed out and restart it again if it is
1196	repeating. The exact semantics are:	1334	repeating. The exact semantics are:
1197		1335
1198	If the timer is pending, its pending status is cleared.	1336	If the timer is pending, its pending status is cleared.
1199		1337
1200	If the timer is started but nonrepeating, stop it (as if it timed out).	1338	If the timer is started but non-repeating, stop it (as if it timed out).
1201		1339
1202	If the timer is repeating, either start it if necessary (with the	1340	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.	1341	C<repeat> value), or reset the running timer to the C<repeat> value.
1204		1342
1205	This sounds a bit complicated, but here is a useful and typical	1343	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	1344	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	1345	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	1346	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	1347	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	1348	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	1349	you go into an idle state where you do not expect data to travel on the
…		…
1225	ev_timer_again (loop, timer);	1363	ev_timer_again (loop, timer);
1226		1364
1227	This is more slightly efficient then stopping/starting the timer each time	1365	This is more slightly efficient then stopping/starting the timer each time
1228	you want to modify its timeout value.	1366	you want to modify its timeout value.
1229		1367
		1368	Note, however, that it is often even more efficient to remember the
		1369	time of the last activity and let the timer time-out naturally. In the
		1370	callback, you then check whether the time-out is real, or, if there was
		1371	some activity, you reschedule the watcher to time-out in "last_activity +
		1372	timeout - ev_now ()" seconds.
		1373
1230	=item ev_tstamp repeat [read-write]	1374	=item ev_tstamp repeat [read-write]
1231		1375
1232	The current C<repeat> value. Will be used each time the watcher times out	1376	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),	1377	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.	1378	which is also when any modifications are taken into account.
1235		1379
1236	=back	1380	=back
1237		1381
1238	=head3 Examples	1382	=head3 Examples
1239		1383
1240	Example: Create a timer that fires after 60 seconds.	1384	Example: Create a timer that fires after 60 seconds.
1241		1385
1242	static void	1386	static void
1243	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1387	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1244	{	1388	{
1245	.. one minute over, w is actually stopped right here	1389	.. one minute over, w is actually stopped right here
1246	}	1390	}
1247		1391
1248	struct ev_timer mytimer;	1392	struct ev_timer mytimer;
1249	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1393	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1250	ev_timer_start (loop, &mytimer);	1394	ev_timer_start (loop, &mytimer);
1251		1395
1252	Example: Create a timeout timer that times out after 10 seconds of	1396	Example: Create a timeout timer that times out after 10 seconds of
1253	inactivity.	1397	inactivity.
1254		1398
1255	static void	1399	static void
1256	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1400	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1257	{	1401	{
1258	.. ten seconds without any activity	1402	.. ten seconds without any activity
1259	}	1403	}
1260		1404
1261	struct ev_timer mytimer;	1405	struct ev_timer mytimer;
1262	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1406	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1263	ev_timer_again (&mytimer); /* start timer */	1407	ev_timer_again (&mytimer); /* start timer */
1264	ev_loop (loop, 0);	1408	ev_loop (loop, 0);
1265		1409
1266	// and in some piece of code that gets executed on any "activity":	1410	// and in some piece of code that gets executed on any "activity":
1267	// reset the timeout to start ticking again at 10 seconds	1411	// reset the timeout to start ticking again at 10 seconds
1268	ev_timer_again (&mytimer);	1412	ev_timer_again (&mytimer);
1269		1413
1270		1414
1271	=head2 C<ev_periodic> - to cron or not to cron?	1415	=head2 C<ev_periodic> - to cron or not to cron?
1272		1416
1273	Periodic watchers are also timers of a kind, but they are very versatile	1417	Periodic watchers are also timers of a kind, but they are very versatile
1274	(and unfortunately a bit complex).	1418	(and unfortunately a bit complex).
1275		1419
1276	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1420	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	1421	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	1422	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 ()	1423	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	1424	+ 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	1425	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	1426	to trigger the event (unlike an C<ev_timer>, which would still trigger
1283	roughly 10 seconds later as it uses a relative timeout).	1427	roughly 10 seconds later as it uses a relative timeout).
1284		1428
1285	C<ev_periodic>s can also be used to implement vastly more complex timers,	1429	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	1430	such as triggering an event on each "midnight, local time", or other
1287	complicated, rules.	1431	complicated rules.
1288		1432
1289	As with timers, the callback is guarenteed to be invoked only when the	1433	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	1434	time (C<at>) has passed, but if multiple periodic timers become ready
1291	during the same loop iteration then order of execution is undefined.	1435	during the same loop iteration, then order of execution is undefined.
1292		1436
1293	=head3 Watcher-Specific Functions and Data Members	1437	=head3 Watcher-Specific Functions and Data Members
1294		1438
1295	=over 4	1439	=over 4
1296		1440
1297	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1441	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1298		1442
1299	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1443	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1300		1444
1301	Lots of arguments, lets sort it out... There are basically three modes of	1445	Lots of arguments, lets sort it out... There are basically three modes of
1302	operation, and we will explain them from simplest to complex:	1446	operation, and we will explain them from simplest to most complex:
1303		1447
1304	=over 4	1448	=over 4
1305		1449
1306	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1450	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1307		1451
1308	In this configuration the watcher triggers an event after the wallclock	1452	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	1453	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	1454	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.	1455	only run when the system clock reaches or surpasses this time.
1312		1456
1313	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1457	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1314		1458
1315	In this mode the watcher will always be scheduled to time out at the next	1459	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)	1460	C<at + N * interval> time (for some integer N, which can also be negative)
1317	and then repeat, regardless of any time jumps.	1461	and then repeat, regardless of any time jumps.
1318		1462
1319	This can be used to create timers that do not drift with respect to system	1463	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	1464	system clock, for example, here is a C<ev_periodic> that triggers each
1321	the hour:	1465	hour, on the hour:
1322		1466
1323	ev_periodic_set (&periodic, 0., 3600., 0);	1467	ev_periodic_set (&periodic, 0., 3600., 0);
1324		1468
1325	This doesn't mean there will always be 3600 seconds in between triggers,	1469	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	1470	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	1471	full hour (UTC), or more correctly, when the system time is evenly divisible
1328	by 3600.	1472	by 3600.
1329		1473
1330	Another way to think about it (for the mathematically inclined) is that	1474	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	1475	C<ev_periodic> will try to run the callback in this mode at the next possible
1332	time where C<time = at (mod interval)>, regardless of any time jumps.	1476	time where C<time = at (mod interval)>, regardless of any time jumps.
1333		1477
1334	For numerical stability it is preferable that the C<at> value is near	1478	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	1479	C<ev_now ()> (the current time), but there is no range requirement for
1336	this value, and in fact is often specified as zero.	1480	this value, and in fact is often specified as zero.
		1481
		1482	Note also that there is an upper limit to how often a timer can fire (CPU
		1483	speed for example), so if C<interval> is very small then timing stability
		1484	will of course deteriorate. Libev itself tries to be exact to be about one
		1485	millisecond (if the OS supports it and the machine is fast enough).
1337		1486
1338	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1487	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1339		1488
1340	In this mode the values for C<interval> and C<at> are both being	1489	In this mode the values for C<interval> and C<at> are both being
1341	ignored. Instead, each time the periodic watcher gets scheduled, the	1490	ignored. Instead, each time the periodic watcher gets scheduled, the
…		…
1408	=back	1557	=back
1409		1558
1410	=head3 Examples	1559	=head3 Examples
1411		1560
1412	Example: Call a callback every hour, or, more precisely, whenever the	1561	Example: Call a callback every hour, or, more precisely, whenever the
1413	system clock is divisible by 3600. The callback invocation times have	1562	system time is divisible by 3600. The callback invocation times have
1414	potentially a lot of jittering, but good long-term stability.	1563	potentially a lot of jitter, but good long-term stability.
1415		1564
1416	static void	1565	static void
1417	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1566	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1418	{	1567	{
1419	... its now a full hour (UTC, or TAI or whatever your clock follows)	1568	... its now a full hour (UTC, or TAI or whatever your clock follows)
1420	}	1569	}
1421		1570
1422	struct ev_periodic hourly_tick;	1571	struct ev_periodic hourly_tick;
1423	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1572	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1424	ev_periodic_start (loop, &hourly_tick);	1573	ev_periodic_start (loop, &hourly_tick);
1425		1574
1426	Example: The same as above, but use a reschedule callback to do it:	1575	Example: The same as above, but use a reschedule callback to do it:
1427		1576
1428	#include <math.h>	1577	#include <math.h>
1429		1578
1430	static ev_tstamp	1579	static ev_tstamp
1431	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1580	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1432	{	1581	{
1433	return fmod (now, 3600.) + 3600.;	1582	return now + (3600. - fmod (now, 3600.));
1434	}	1583	}
1435		1584
1436	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1585	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1437		1586
1438	Example: Call a callback every hour, starting now:	1587	Example: Call a callback every hour, starting now:
1439		1588
1440	struct ev_periodic hourly_tick;	1589	struct ev_periodic hourly_tick;
1441	ev_periodic_init (&hourly_tick, clock_cb,	1590	ev_periodic_init (&hourly_tick, clock_cb,
1442	fmod (ev_now (loop), 3600.), 3600., 0);	1591	fmod (ev_now (loop), 3600.), 3600., 0);
1443	ev_periodic_start (loop, &hourly_tick);	1592	ev_periodic_start (loop, &hourly_tick);
1444		1593
1445		1594
1446	=head2 C<ev_signal> - signal me when a signal gets signalled!	1595	=head2 C<ev_signal> - signal me when a signal gets signalled!
1447		1596
1448	Signal watchers will trigger an event when the process receives a specific	1597	Signal watchers will trigger an event when the process receives a specific
1449	signal one or more times. Even though signals are very asynchronous, libev	1598	signal one or more times. Even though signals are very asynchronous, libev
1450	will try it's best to deliver signals synchronously, i.e. as part of the	1599	will try it's best to deliver signals synchronously, i.e. as part of the
1451	normal event processing, like any other event.	1600	normal event processing, like any other event.
1452		1601
		1602	If you want signals asynchronously, just use C<sigaction> as you would
		1603	do without libev and forget about sharing the signal. You can even use
		1604	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1605
1453	You can configure as many watchers as you like per signal. Only when the	1606	You can configure as many watchers as you like per signal. Only when the
1454	first watcher gets started will libev actually register a signal watcher	1607	first watcher gets started will libev actually register a signal handler
1455	with the kernel (thus it coexists with your own signal handlers as long	1608	with the kernel (thus it coexists with your own signal handlers as long as
1456	as you don't register any with libev). Similarly, when the last signal	1609	you don't register any with libev for the same signal). Similarly, when
1457	watcher for a signal is stopped libev will reset the signal handler to	1610	the last signal watcher for a signal is stopped, libev will reset the
1458	SIG_DFL (regardless of what it was set to before).	1611	signal handler to SIG_DFL (regardless of what it was set to before).
1459		1612
1460	If possible and supported, libev will install its handlers with	1613	If possible and supported, libev will install its handlers with
1461	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1614	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1462	interrupted. If you have a problem with syscalls getting interrupted by	1615	interrupted. If you have a problem with system calls getting interrupted by
1463	signals you can block all signals in an C<ev_check> watcher and unblock	1616	signals you can block all signals in an C<ev_check> watcher and unblock
1464	them in an C<ev_prepare> watcher.	1617	them in an C<ev_prepare> watcher.
1465		1618
1466	=head3 Watcher-Specific Functions and Data Members	1619	=head3 Watcher-Specific Functions and Data Members
1467		1620
…		…
1480		1633
1481	=back	1634	=back
1482		1635
1483	=head3 Examples	1636	=head3 Examples
1484		1637
1485	Example: Try to exit cleanly on SIGINT and SIGTERM.	1638	Example: Try to exit cleanly on SIGINT.
1486		1639
1487	static void	1640	static void
1488	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1641	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1489	{	1642	{
1490	ev_unloop (loop, EVUNLOOP_ALL);	1643	ev_unloop (loop, EVUNLOOP_ALL);
1491	}	1644	}
1492		1645
1493	struct ev_signal signal_watcher;	1646	struct ev_signal signal_watcher;
1494	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1495	ev_signal_start (loop, &sigint_cb);	1648	ev_signal_start (loop, &signal_watcher);
1496		1649
1497		1650
1498	=head2 C<ev_child> - watch out for process status changes	1651	=head2 C<ev_child> - watch out for process status changes
1499		1652
1500	Child watchers trigger when your process receives a SIGCHLD in response to	1653	Child watchers trigger when your process receives a SIGCHLD in response to
1501	some child status changes (most typically when a child of yours dies). It	1654	some child status changes (most typically when a child of yours dies or
1502	is permissible to install a child watcher I<after> the child has been	1655	exits). It is permissible to install a child watcher I<after> the child
1503	forked (which implies it might have already exited), as long as the event	1656	has been forked (which implies it might have already exited), as long
1504	loop isn't entered (or is continued from a watcher).	1657	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1658	forking and then immediately registering a watcher for the child is fine,
		1659	but forking and registering a watcher a few event loop iterations later is
		1660	not.
1505		1661
1506	Only the default event loop is capable of handling signals, and therefore	1662	Only the default event loop is capable of handling signals, and therefore
1507	you can only rgeister child watchers in the default event loop.	1663	you can only register child watchers in the default event loop.
1508		1664
1509	=head3 Process Interaction	1665	=head3 Process Interaction
1510		1666
1511	Libev grabs C<SIGCHLD> as soon as the default event loop is	1667	Libev grabs C<SIGCHLD> as soon as the default event loop is
1512	initialised. This is necessary to guarantee proper behaviour even if	1668	initialised. This is necessary to guarantee proper behaviour even if
1513	the first child watcher is started after the child exits. The occurance	1669	the first child watcher is started after the child exits. The occurrence
1514	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	1670	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1515	synchronously as part of the event loop processing. Libev always reaps all	1671	synchronously as part of the event loop processing. Libev always reaps all
1516	children, even ones not watched.	1672	children, even ones not watched.
1517		1673
1518	=head3 Overriding the Built-In Processing	1674	=head3 Overriding the Built-In Processing
…		…
1522	handler, you can override it easily by installing your own handler for	1678	handler, you can override it easily by installing your own handler for
1523	C<SIGCHLD> after initialising the default loop, and making sure the	1679	C<SIGCHLD> after initialising the default loop, and making sure the
1524	default loop never gets destroyed. You are encouraged, however, to use an	1680	default loop never gets destroyed. You are encouraged, however, to use an
1525	event-based approach to child reaping and thus use libev's support for	1681	event-based approach to child reaping and thus use libev's support for
1526	that, so other libev users can use C<ev_child> watchers freely.	1682	that, so other libev users can use C<ev_child> watchers freely.
		1683
		1684	=head3 Stopping the Child Watcher
		1685
		1686	Currently, the child watcher never gets stopped, even when the
		1687	child terminates, so normally one needs to stop the watcher in the
		1688	callback. Future versions of libev might stop the watcher automatically
		1689	when a child exit is detected.
1527		1690
1528	=head3 Watcher-Specific Functions and Data Members	1691	=head3 Watcher-Specific Functions and Data Members
1529		1692
1530	=over 4	1693	=over 4
1531		1694
…		…
1560	=head3 Examples	1723	=head3 Examples
1561		1724
1562	Example: C<fork()> a new process and install a child handler to wait for	1725	Example: C<fork()> a new process and install a child handler to wait for
1563	its completion.	1726	its completion.
1564		1727
1565	ev_child cw;	1728	ev_child cw;
1566		1729
1567	static void	1730	static void
1568	child_cb (EV_P_ struct ev_child *w, int revents)	1731	child_cb (EV_P_ struct ev_child *w, int revents)
1569	{	1732	{
1570	ev_child_stop (EV_A_ w);	1733	ev_child_stop (EV_A_ w);
1571	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1734	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1572	}	1735	}
1573		1736
1574	pid_t pid = fork ();	1737	pid_t pid = fork ();
1575		1738
1576	if (pid < 0)	1739	if (pid < 0)
1577	// error	1740	// error
1578	else if (pid == 0)	1741	else if (pid == 0)
1579	{	1742	{
1580	// the forked child executes here	1743	// the forked child executes here
1581	exit (1);	1744	exit (1);
1582	}	1745	}
1583	else	1746	else
1584	{	1747	{
1585	ev_child_init (&cw, child_cb, pid, 0);	1748	ev_child_init (&cw, child_cb, pid, 0);
1586	ev_child_start (EV_DEFAULT_ &cw);	1749	ev_child_start (EV_DEFAULT_ &cw);
1587	}	1750	}
1588		1751
1589		1752
1590	=head2 C<ev_stat> - did the file attributes just change?	1753	=head2 C<ev_stat> - did the file attributes just change?
1591		1754
1592	This watches a filesystem path for attribute changes. That is, it calls	1755	This watches a file system path for attribute changes. That is, it calls
1593	C<stat> regularly (or when the OS says it changed) and sees if it changed	1756	C<stat> regularly (or when the OS says it changed) and sees if it changed
1594	compared to the last time, invoking the callback if it did.	1757	compared to the last time, invoking the callback if it did.
1595		1758
1596	The path does not need to exist: changing from "path exists" to "path does	1759	The path does not need to exist: changing from "path exists" to "path does
1597	not exist" is a status change like any other. The condition "path does	1760	not exist" is a status change like any other. The condition "path does
…		…
1600	the stat buffer having unspecified contents.	1763	the stat buffer having unspecified contents.
1601		1764
1602	The path I<should> be absolute and I<must not> end in a slash. If it is	1765	The path I<should> be absolute and I<must not> end in a slash. If it is
1603	relative and your working directory changes, the behaviour is undefined.	1766	relative and your working directory changes, the behaviour is undefined.
1604		1767
1605	Since there is no standard to do this, the portable implementation simply	1768	Since there is no standard kernel interface to do this, the portable
1606	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1769	implementation simply calls C<stat (2)> regularly on the path to see if
1607	can specify a recommended polling interval for this case. If you specify	1770	it changed somehow. You can specify a recommended polling interval for
1608	a polling interval of C<0> (highly recommended!) then a I<suitable,	1771	this case. If you specify a polling interval of C<0> (highly recommended!)
1609	unspecified default> value will be used (which you can expect to be around	1772	then a I<suitable, unspecified default> value will be used (which
1610	five seconds, although this might change dynamically). Libev will also	1773	you can expect to be around five seconds, although this might change
1611	impose a minimum interval which is currently around C<0.1>, but thats	1774	dynamically). Libev will also impose a minimum interval which is currently
1612	usually overkill.	1775	around C<0.1>, but thats usually overkill.
1613		1776
1614	This watcher type is not meant for massive numbers of stat watchers,	1777	This watcher type is not meant for massive numbers of stat watchers,
1615	as even with OS-supported change notifications, this can be	1778	as even with OS-supported change notifications, this can be
1616	resource-intensive.	1779	resource-intensive.
1617		1780
1618	At the time of this writing, only the Linux inotify interface is	1781	At the time of this writing, the only OS-specific interface implemented
1619	implemented (implementing kqueue support is left as an exercise for the	1782	is the Linux inotify interface (implementing kqueue support is left as
1620	reader, note, however, that the author sees no way of implementing ev_stat	1783	an exercise for the reader. Note, however, that the author sees no way
1621	semantics with kqueue). Inotify will be used to give hints only and should	1784	of implementing C<ev_stat> semantics with kqueue).
1622	not change the semantics of C<ev_stat> watchers, which means that libev
1623	sometimes needs to fall back to regular polling again even with inotify,
1624	but changes are usually detected immediately, and if the file exists there
1625	will be no polling.
1626		1785
1627	=head3 ABI Issues (Largefile Support)	1786	=head3 ABI Issues (Largefile Support)
1628		1787
1629	Libev by default (unless the user overrides this) uses the default	1788	Libev by default (unless the user overrides this) uses the default
1630	compilation environment, which means that on systems with optionally	1789	compilation environment, which means that on systems with large file
1631	disabled large file support, you get the 32 bit version of the stat	1790	support disabled by default, you get the 32 bit version of the stat
1632	structure. When using the library from programs that change the ABI to	1791	structure. When using the library from programs that change the ABI to
1633	use 64 bit file offsets the programs will fail. In that case you have to	1792	use 64 bit file offsets the programs will fail. In that case you have to
1634	compile libev with the same flags to get binary compatibility. This is	1793	compile libev with the same flags to get binary compatibility. This is
1635	obviously the case with any flags that change the ABI, but the problem is	1794	obviously the case with any flags that change the ABI, but the problem is
1636	most noticably with ev_stat and largefile support.	1795	most noticeably disabled with ev_stat and large file support.
1637		1796
1638	=head3 Inotify	1797	The solution for this is to lobby your distribution maker to make large
		1798	file interfaces available by default (as e.g. FreeBSD does) and not
		1799	optional. Libev cannot simply switch on large file support because it has
		1800	to exchange stat structures with application programs compiled using the
		1801	default compilation environment.
1639		1802
		1803	=head3 Inotify and Kqueue
		1804
1640	When C<inotify (7)> support has been compiled into libev (generally only	1805	When C<inotify (7)> support has been compiled into libev (generally
		1806	only available with Linux 2.6.25 or above due to bugs in earlier
1641	available on Linux) and present at runtime, it will be used to speed up	1807	implementations) and present at runtime, it will be used to speed up
1642	change detection where possible. The inotify descriptor will be created lazily	1808	change detection where possible. The inotify descriptor will be created
1643	when the first C<ev_stat> watcher is being started.	1809	lazily when the first C<ev_stat> watcher is being started.
1644		1810
1645	Inotify presence does not change the semantics of C<ev_stat> watchers	1811	Inotify presence does not change the semantics of C<ev_stat> watchers
1646	except that changes might be detected earlier, and in some cases, to avoid	1812	except that changes might be detected earlier, and in some cases, to avoid
1647	making regular C<stat> calls. Even in the presence of inotify support	1813	making regular C<stat> calls. Even in the presence of inotify support
1648	there are many cases where libev has to resort to regular C<stat> polling.	1814	there are many cases where libev has to resort to regular C<stat> polling,
		1815	but as long as the path exists, libev usually gets away without polling.
1649		1816
1650	(There is no support for kqueue, as apparently it cannot be used to	1817	There is no support for kqueue, as apparently it cannot be used to
1651	implement this functionality, due to the requirement of having a file	1818	implement this functionality, due to the requirement of having a file
1652	descriptor open on the object at all times).	1819	descriptor open on the object at all times, and detecting renames, unlinks
		1820	etc. is difficult.
1653		1821
1654	=head3 The special problem of stat time resolution	1822	=head3 The special problem of stat time resolution
1655		1823
1656	The C<stat ()> syscall only supports full-second resolution portably, and	1824	The C<stat ()> system call only supports full-second resolution portably, and
1657	even on systems where the resolution is higher, many filesystems still	1825	even on systems where the resolution is higher, most file systems still
1658	only support whole seconds.	1826	only support whole seconds.
1659		1827
1660	That means that, if the time is the only thing that changes, you can	1828	That means that, if the time is the only thing that changes, you can
1661	easily miss updates: on the first update, C<ev_stat> detects a change and	1829	easily miss updates: on the first update, C<ev_stat> detects a change and
1662	calls your callback, which does something. When there is another update	1830	calls your callback, which does something. When there is another update
1663	within the same second, C<ev_stat> will be unable to detect it as the stat	1831	within the same second, C<ev_stat> will be unable to detect unless the
1664	data does not change.	1832	stat data does change in other ways (e.g. file size).
1665		1833
1666	The solution to this is to delay acting on a change for slightly more	1834	The solution to this is to delay acting on a change for slightly more
1667	than a second (or till slightly after the next full second boundary), using	1835	than a second (or till slightly after the next full second boundary), using
1668	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1836	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1669	ev_timer_again (loop, w)>).	1837	ev_timer_again (loop, w)>).
…		…
1689	C<path>. The C<interval> is a hint on how quickly a change is expected to	1857	C<path>. The C<interval> is a hint on how quickly a change is expected to
1690	be detected and should normally be specified as C<0> to let libev choose	1858	be detected and should normally be specified as C<0> to let libev choose
1691	a suitable value. The memory pointed to by C<path> must point to the same	1859	a suitable value. The memory pointed to by C<path> must point to the same
1692	path for as long as the watcher is active.	1860	path for as long as the watcher is active.
1693		1861
1694	The callback will receive C<EV_STAT> when a change was detected, relative	1862	The callback will receive an C<EV_STAT> event when a change was detected,
1695	to the attributes at the time the watcher was started (or the last change	1863	relative to the attributes at the time the watcher was started (or the
1696	was detected).	1864	last change was detected).
1697		1865
1698	=item ev_stat_stat (loop, ev_stat *)	1866	=item ev_stat_stat (loop, ev_stat *)
1699		1867
1700	Updates the stat buffer immediately with new values. If you change the	1868	Updates the stat buffer immediately with new values. If you change the
1701	watched path in your callback, you could call this function to avoid	1869	watched path in your callback, you could call this function to avoid
…		…
1722		1890
1723	The specified interval.	1891	The specified interval.
1724		1892
1725	=item const char *path [read-only]	1893	=item const char *path [read-only]
1726		1894
1727	The filesystem path that is being watched.	1895	The file system path that is being watched.
1728		1896
1729	=back	1897	=back
1730		1898
1731	=head3 Examples	1899	=head3 Examples
1732		1900
1733	Example: Watch C</etc/passwd> for attribute changes.	1901	Example: Watch C</etc/passwd> for attribute changes.
1734		1902
1735	static void	1903	static void
1736	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1904	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1737	{	1905	{
1738	/* /etc/passwd changed in some way */	1906	/* /etc/passwd changed in some way */
1739	if (w->attr.st_nlink)	1907	if (w->attr.st_nlink)
1740	{	1908	{
1741	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1909	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1742	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1910	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1743	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1911	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1744	}	1912	}
1745	else	1913	else
1746	/* you shalt not abuse printf for puts */	1914	/* you shalt not abuse printf for puts */
1747	puts ("wow, /etc/passwd is not there, expect problems. "	1915	puts ("wow, /etc/passwd is not there, expect problems. "
1748	"if this is windows, they already arrived\n");	1916	"if this is windows, they already arrived\n");
1749	}	1917	}
1750		1918
1751	...	1919	...
1752	ev_stat passwd;	1920	ev_stat passwd;
1753		1921
1754	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	1922	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1755	ev_stat_start (loop, &passwd);	1923	ev_stat_start (loop, &passwd);
1756		1924
1757	Example: Like above, but additionally use a one-second delay so we do not	1925	Example: Like above, but additionally use a one-second delay so we do not
1758	miss updates (however, frequent updates will delay processing, too, so	1926	miss updates (however, frequent updates will delay processing, too, so
1759	one might do the work both on C<ev_stat> callback invocation I<and> on	1927	one might do the work both on C<ev_stat> callback invocation I<and> on
1760	C<ev_timer> callback invocation).	1928	C<ev_timer> callback invocation).
1761		1929
1762	static ev_stat passwd;	1930	static ev_stat passwd;
1763	static ev_timer timer;	1931	static ev_timer timer;
1764		1932
1765	static void	1933	static void
1766	timer_cb (EV_P_ ev_timer *w, int revents)	1934	timer_cb (EV_P_ ev_timer *w, int revents)
1767	{	1935	{
1768	ev_timer_stop (EV_A_ w);	1936	ev_timer_stop (EV_A_ w);
1769		1937
1770	/* now it's one second after the most recent passwd change */	1938	/* now it's one second after the most recent passwd change */
1771	}	1939	}
1772		1940
1773	static void	1941	static void
1774	stat_cb (EV_P_ ev_stat *w, int revents)	1942	stat_cb (EV_P_ ev_stat *w, int revents)
1775	{	1943	{
1776	/* reset the one-second timer */	1944	/* reset the one-second timer */
1777	ev_timer_again (EV_A_ &timer);	1945	ev_timer_again (EV_A_ &timer);
1778	}	1946	}
1779		1947
1780	...	1948	...
1781	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	1949	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1782	ev_stat_start (loop, &passwd);	1950	ev_stat_start (loop, &passwd);
1783	ev_timer_init (&timer, timer_cb, 0., 1.02);	1951	ev_timer_init (&timer, timer_cb, 0., 1.02);
1784		1952
1785		1953
1786	=head2 C<ev_idle> - when you've got nothing better to do...	1954	=head2 C<ev_idle> - when you've got nothing better to do...
1787		1955
1788	Idle watchers trigger events when no other events of the same or higher	1956	Idle watchers trigger events when no other events of the same or higher
1789	priority are pending (prepare, check and other idle watchers do not	1957	priority are pending (prepare, check and other idle watchers do not count
1790	count).	1958	as receiving "events").
1791		1959
1792	That is, as long as your process is busy handling sockets or timeouts	1960	That is, as long as your process is busy handling sockets or timeouts
1793	(or even signals, imagine) of the same or higher priority it will not be	1961	(or even signals, imagine) of the same or higher priority it will not be
1794	triggered. But when your process is idle (or only lower-priority watchers	1962	triggered. But when your process is idle (or only lower-priority watchers
1795	are pending), the idle watchers are being called once per event loop	1963	are pending), the idle watchers are being called once per event loop
…		…
1819	=head3 Examples	1987	=head3 Examples
1820		1988
1821	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1989	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1822	callback, free it. Also, use no error checking, as usual.	1990	callback, free it. Also, use no error checking, as usual.
1823		1991
1824	static void	1992	static void
1825	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1993	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1826	{	1994	{
1827	free (w);	1995	free (w);
1828	// now do something you wanted to do when the program has	1996	// now do something you wanted to do when the program has
1829	// no longer anything immediate to do.	1997	// no longer anything immediate to do.
1830	}	1998	}
1831		1999
1832	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1833	ev_idle_init (idle_watcher, idle_cb);	2001	ev_idle_init (idle_watcher, idle_cb);
1834	ev_idle_start (loop, idle_cb);	2002	ev_idle_start (loop, idle_cb);
1835		2003
1836		2004
1837	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1838		2006
1839	Prepare and check watchers are usually (but not always) used in tandem:	2007	Prepare and check watchers are usually (but not always) used in pairs:
1840	prepare watchers get invoked before the process blocks and check watchers	2008	prepare watchers get invoked before the process blocks and check watchers
1841	afterwards.	2009	afterwards.
1842		2010
1843	You I<must not> call C<ev_loop> or similar functions that enter	2011	You I<must not> call C<ev_loop> or similar functions that enter
1844	the current event loop from either C<ev_prepare> or C<ev_check>	2012	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1847	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2015	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1848	C<ev_check> so if you have one watcher of each kind they will always be	2016	C<ev_check> so if you have one watcher of each kind they will always be
1849	called in pairs bracketing the blocking call.	2017	called in pairs bracketing the blocking call.
1850		2018
1851	Their main purpose is to integrate other event mechanisms into libev and	2019	Their main purpose is to integrate other event mechanisms into libev and
1852	their use is somewhat advanced. This could be used, for example, to track	2020	their use is somewhat advanced. They could be used, for example, to track
1853	variable changes, implement your own watchers, integrate net-snmp or a	2021	variable changes, implement your own watchers, integrate net-snmp or a
1854	coroutine library and lots more. They are also occasionally useful if	2022	coroutine library and lots more. They are also occasionally useful if
1855	you cache some data and want to flush it before blocking (for example,	2023	you cache some data and want to flush it before blocking (for example,
1856	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2024	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1857	watcher).	2025	watcher).
1858		2026
1859	This is done by examining in each prepare call which file descriptors need	2027	This is done by examining in each prepare call which file descriptors
1860	to be watched by the other library, registering C<ev_io> watchers for	2028	need to be watched by the other library, registering C<ev_io> watchers
1861	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2029	for them and starting an C<ev_timer> watcher for any timeouts (many
1862	provide just this functionality). Then, in the check watcher you check for	2030	libraries provide exactly this functionality). Then, in the check watcher,
1863	any events that occured (by checking the pending status of all watchers	2031	you check for any events that occurred (by checking the pending status
1864	and stopping them) and call back into the library. The I/O and timer	2032	of all watchers and stopping them) and call back into the library. The
1865	callbacks will never actually be called (but must be valid nevertheless,	2033	I/O and timer callbacks will never actually be called (but must be valid
1866	because you never know, you know?).	2034	nevertheless, because you never know, you know?).
1867		2035
1868	As another example, the Perl Coro module uses these hooks to integrate	2036	As another example, the Perl Coro module uses these hooks to integrate
1869	coroutines into libev programs, by yielding to other active coroutines	2037	coroutines into libev programs, by yielding to other active coroutines
1870	during each prepare and only letting the process block if no coroutines	2038	during each prepare and only letting the process block if no coroutines
1871	are ready to run (it's actually more complicated: it only runs coroutines	2039	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1874	loop from blocking if lower-priority coroutines are active, thus mapping	2042	loop from blocking if lower-priority coroutines are active, thus mapping
1875	low-priority coroutines to idle/background tasks).	2043	low-priority coroutines to idle/background tasks).
1876		2044
1877	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2045	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1878	priority, to ensure that they are being run before any other watchers	2046	priority, to ensure that they are being run before any other watchers
		2047	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2048
1879	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2049	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1880	too) should not activate ("feed") events into libev. While libev fully	2050	activate ("feed") events into libev. While libev fully supports this, they
1881	supports this, they might get executed before other C<ev_check> watchers	2051	might get executed before other C<ev_check> watchers did their job. As
1882	did their job. As C<ev_check> watchers are often used to embed other	2052	C<ev_check> watchers are often used to embed other (non-libev) event
1883	(non-libev) event loops those other event loops might be in an unusable	2053	loops those other event loops might be in an unusable state until their
1884	state until their C<ev_check> watcher ran (always remind yourself to	2054	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1885	coexist peacefully with others).	2055	others).
1886		2056
1887	=head3 Watcher-Specific Functions and Data Members	2057	=head3 Watcher-Specific Functions and Data Members
1888		2058
1889	=over 4	2059	=over 4
1890		2060
…		…
1892		2062
1893	=item ev_check_init (ev_check *, callback)	2063	=item ev_check_init (ev_check *, callback)
1894		2064
1895	Initialises and configures the prepare or check watcher - they have no	2065	Initialises and configures the prepare or check watcher - they have no
1896	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2066	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1897	macros, but using them is utterly, utterly and completely pointless.	2067	macros, but using them is utterly, utterly, utterly and completely
		2068	pointless.
1898		2069
1899	=back	2070	=back
1900		2071
1901	=head3 Examples	2072	=head3 Examples
1902		2073
…		…
1911	and in a check watcher, destroy them and call into libadns. What follows	2082	and in a check watcher, destroy them and call into libadns. What follows
1912	is pseudo-code only of course. This requires you to either use a low	2083	is pseudo-code only of course. This requires you to either use a low
1913	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2084	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1914	the callbacks for the IO/timeout watchers might not have been called yet.	2085	the callbacks for the IO/timeout watchers might not have been called yet.
1915		2086
1916	static ev_io iow [nfd];	2087	static ev_io iow [nfd];
1917	static ev_timer tw;	2088	static ev_timer tw;
1918		2089
1919	static void	2090	static void
1920	io_cb (ev_loop *loop, ev_io *w, int revents)	2091	io_cb (ev_loop *loop, ev_io *w, int revents)
1921	{	2092	{
1922	}	2093	}
1923		2094
1924	// create io watchers for each fd and a timer before blocking	2095	// create io watchers for each fd and a timer before blocking
1925	static void	2096	static void
1926	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2097	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1927	{	2098	{
1928	int timeout = 3600000;	2099	int timeout = 3600000;
1929	struct pollfd fds [nfd];	2100	struct pollfd fds [nfd];
1930	// actual code will need to loop here and realloc etc.	2101	// actual code will need to loop here and realloc etc.
1931	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2102	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1932		2103
1933	/* the callback is illegal, but won't be called as we stop during check */	2104	/* the callback is illegal, but won't be called as we stop during check */
1934	ev_timer_init (&tw, 0, timeout * 1e-3);	2105	ev_timer_init (&tw, 0, timeout * 1e-3);
1935	ev_timer_start (loop, &tw);	2106	ev_timer_start (loop, &tw);
1936		2107
1937	// create one ev_io per pollfd	2108	// create one ev_io per pollfd
1938	for (int i = 0; i < nfd; ++i)	2109	for (int i = 0; i < nfd; ++i)
1939	{	2110	{
1940	ev_io_init (iow + i, io_cb, fds [i].fd,	2111	ev_io_init (iow + i, io_cb, fds [i].fd,
1941	((fds [i].events & POLLIN ? EV_READ : 0)	2112	((fds [i].events & POLLIN ? EV_READ : 0)
1942	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2113	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1943		2114
1944	fds [i].revents = 0;	2115	fds [i].revents = 0;
1945	ev_io_start (loop, iow + i);	2116	ev_io_start (loop, iow + i);
1946	}	2117	}
1947	}	2118	}
1948		2119
1949	// stop all watchers after blocking	2120	// stop all watchers after blocking
1950	static void	2121	static void
1951	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2122	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1952	{	2123	{
1953	ev_timer_stop (loop, &tw);	2124	ev_timer_stop (loop, &tw);
1954		2125
1955	for (int i = 0; i < nfd; ++i)	2126	for (int i = 0; i < nfd; ++i)
1956	{	2127	{
1957	// set the relevant poll flags	2128	// set the relevant poll flags
1958	// could also call adns_processreadable etc. here	2129	// could also call adns_processreadable etc. here
1959	struct pollfd *fd = fds + i;	2130	struct pollfd *fd = fds + i;
1960	int revents = ev_clear_pending (iow + i);	2131	int revents = ev_clear_pending (iow + i);
1961	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2132	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1962	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2133	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1963		2134
1964	// now stop the watcher	2135	// now stop the watcher
1965	ev_io_stop (loop, iow + i);	2136	ev_io_stop (loop, iow + i);
1966	}	2137	}
1967		2138
1968	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2139	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1969	}	2140	}
1970		2141
1971	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2142	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1972	in the prepare watcher and would dispose of the check watcher.	2143	in the prepare watcher and would dispose of the check watcher.
1973		2144
1974	Method 3: If the module to be embedded supports explicit event	2145	Method 3: If the module to be embedded supports explicit event
1975	notification (adns does), you can also make use of the actual watcher	2146	notification (libadns does), you can also make use of the actual watcher
1976	callbacks, and only destroy/create the watchers in the prepare watcher.	2147	callbacks, and only destroy/create the watchers in the prepare watcher.
1977		2148
1978	static void	2149	static void
1979	timer_cb (EV_P_ ev_timer *w, int revents)	2150	timer_cb (EV_P_ ev_timer *w, int revents)
1980	{	2151	{
1981	adns_state ads = (adns_state)w->data;	2152	adns_state ads = (adns_state)w->data;
1982	update_now (EV_A);	2153	update_now (EV_A);
1983		2154
1984	adns_processtimeouts (ads, &tv_now);	2155	adns_processtimeouts (ads, &tv_now);
1985	}	2156	}
1986		2157
1987	static void	2158	static void
1988	io_cb (EV_P_ ev_io *w, int revents)	2159	io_cb (EV_P_ ev_io *w, int revents)
1989	{	2160	{
1990	adns_state ads = (adns_state)w->data;	2161	adns_state ads = (adns_state)w->data;
1991	update_now (EV_A);	2162	update_now (EV_A);
1992		2163
1993	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2164	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1994	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2165	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1995	}	2166	}
1996		2167
1997	// do not ever call adns_afterpoll	2168	// do not ever call adns_afterpoll
1998		2169
1999	Method 4: Do not use a prepare or check watcher because the module you	2170	Method 4: Do not use a prepare or check watcher because the module you
2000	want to embed is too inflexible to support it. Instead, youc na override	2171	want to embed is not flexible enough to support it. Instead, you can
2001	their poll function. The drawback with this solution is that the main	2172	override their poll function. The drawback with this solution is that the
2002	loop is now no longer controllable by EV. The C<Glib::EV> module does	2173	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2003	this.	2174	this approach, effectively embedding EV as a client into the horrible
		2175	libglib event loop.
2004		2176
2005	static gint	2177	static gint
2006	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2178	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2007	{	2179	{
2008	int got_events = 0;	2180	int got_events = 0;
2009		2181
2010	for (n = 0; n < nfds; ++n)	2182	for (n = 0; n < nfds; ++n)
2011	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2183	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2012		2184
2013	if (timeout >= 0)	2185	if (timeout >= 0)
2014	// create/start timer	2186	// create/start timer
2015		2187
2016	// poll	2188	// poll
2017	ev_loop (EV_A_ 0);	2189	ev_loop (EV_A_ 0);
2018		2190
2019	// stop timer again	2191	// stop timer again
2020	if (timeout >= 0)	2192	if (timeout >= 0)
2021	ev_timer_stop (EV_A_ &to);	2193	ev_timer_stop (EV_A_ &to);
2022		2194
2023	// stop io watchers again - their callbacks should have set	2195	// stop io watchers again - their callbacks should have set
2024	for (n = 0; n < nfds; ++n)	2196	for (n = 0; n < nfds; ++n)
2025	ev_io_stop (EV_A_ iow [n]);	2197	ev_io_stop (EV_A_ iow [n]);
2026		2198
2027	return got_events;	2199	return got_events;
2028	}	2200	}
2029		2201
2030		2202
2031	=head2 C<ev_embed> - when one backend isn't enough...	2203	=head2 C<ev_embed> - when one backend isn't enough...
2032		2204
2033	This is a rather advanced watcher type that lets you embed one event loop	2205	This is a rather advanced watcher type that lets you embed one event loop
…		…
2039	prioritise I/O.	2211	prioritise I/O.
2040		2212
2041	As an example for a bug workaround, the kqueue backend might only support	2213	As an example for a bug workaround, the kqueue backend might only support
2042	sockets on some platform, so it is unusable as generic backend, but you	2214	sockets on some platform, so it is unusable as generic backend, but you
2043	still want to make use of it because you have many sockets and it scales	2215	still want to make use of it because you have many sockets and it scales
2044	so nicely. In this case, you would create a kqueue-based loop and embed it	2216	so nicely. In this case, you would create a kqueue-based loop and embed
2045	into your default loop (which might use e.g. poll). Overall operation will	2217	it into your default loop (which might use e.g. poll). Overall operation
2046	be a bit slower because first libev has to poll and then call kevent, but	2218	will be a bit slower because first libev has to call C<poll> and then
2047	at least you can use both at what they are best.	2219	C<kevent>, but at least you can use both mechanisms for what they are
		2220	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2048		2221
2049	As for prioritising I/O: rarely you have the case where some fds have	2222	As for prioritising I/O: under rare circumstances you have the case where
2050	to be watched and handled very quickly (with low latency), and even	2223	some fds have to be watched and handled very quickly (with low latency),
2051	priorities and idle watchers might have too much overhead. In this case	2224	and even priorities and idle watchers might have too much overhead. In
2052	you would put all the high priority stuff in one loop and all the rest in	2225	this case you would put all the high priority stuff in one loop and all
2053	a second one, and embed the second one in the first.	2226	the rest in a second one, and embed the second one in the first.
2054		2227
2055	As long as the watcher is active, the callback will be invoked every time	2228	As long as the watcher is active, the callback will be invoked every time
2056	there might be events pending in the embedded loop. The callback must then	2229	there might be events pending in the embedded loop. The callback must then
2057	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2230	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2058	their callbacks (you could also start an idle watcher to give the embedded	2231	their callbacks (you could also start an idle watcher to give the embedded
…		…
2066	interested in that.	2239	interested in that.
2067		2240
2068	Also, there have not currently been made special provisions for forking:	2241	Also, there have not currently been made special provisions for forking:
2069	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2242	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2070	but you will also have to stop and restart any C<ev_embed> watchers	2243	but you will also have to stop and restart any C<ev_embed> watchers
2071	yourself.	2244	yourself - but you can use a fork watcher to handle this automatically,
		2245	and future versions of libev might do just that.
2072		2246
2073	Unfortunately, not all backends are embeddable, only the ones returned by	2247	Unfortunately, not all backends are embeddable: only the ones returned by
2074	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2248	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2075	portable one.	2249	portable one.
2076		2250
2077	So when you want to use this feature you will always have to be prepared	2251	So when you want to use this feature you will always have to be prepared
2078	that you cannot get an embeddable loop. The recommended way to get around	2252	that you cannot get an embeddable loop. The recommended way to get around
2079	this is to have a separate variables for your embeddable loop, try to	2253	this is to have a separate variables for your embeddable loop, try to
2080	create it, and if that fails, use the normal loop for everything.	2254	create it, and if that fails, use the normal loop for everything.
2081		2255
		2256	=head3 C<ev_embed> and fork
		2257
		2258	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2259	automatically be applied to the embedded loop as well, so no special
		2260	fork handling is required in that case. When the watcher is not running,
		2261	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2262	as applicable.
		2263
2082	=head3 Watcher-Specific Functions and Data Members	2264	=head3 Watcher-Specific Functions and Data Members
2083		2265
2084	=over 4	2266	=over 4
2085		2267
2086	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2268	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2089		2271
2090	Configures the watcher to embed the given loop, which must be	2272	Configures the watcher to embed the given loop, which must be
2091	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2273	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2092	invoked automatically, otherwise it is the responsibility of the callback	2274	invoked automatically, otherwise it is the responsibility of the callback
2093	to invoke it (it will continue to be called until the sweep has been done,	2275	to invoke it (it will continue to be called until the sweep has been done,
2094	if you do not want thta, you need to temporarily stop the embed watcher).	2276	if you do not want that, you need to temporarily stop the embed watcher).
2095		2277
2096	=item ev_embed_sweep (loop, ev_embed *)	2278	=item ev_embed_sweep (loop, ev_embed *)
2097		2279
2098	Make a single, non-blocking sweep over the embedded loop. This works	2280	Make a single, non-blocking sweep over the embedded loop. This works
2099	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2281	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2100	apropriate way for embedded loops.	2282	appropriate way for embedded loops.
2101		2283
2102	=item struct ev_loop *other [read-only]	2284	=item struct ev_loop *other [read-only]
2103		2285
2104	The embedded event loop.	2286	The embedded event loop.
2105		2287
…		…
2107		2289
2108	=head3 Examples	2290	=head3 Examples
2109		2291
2110	Example: Try to get an embeddable event loop and embed it into the default	2292	Example: Try to get an embeddable event loop and embed it into the default
2111	event loop. If that is not possible, use the default loop. The default	2293	event loop. If that is not possible, use the default loop. The default
2112	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2294	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2113	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2295	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2114	used).	2296	used).
2115		2297
2116	struct ev_loop *loop_hi = ev_default_init (0);	2298	struct ev_loop *loop_hi = ev_default_init (0);
2117	struct ev_loop *loop_lo = 0;	2299	struct ev_loop *loop_lo = 0;
2118	struct ev_embed embed;	2300	struct ev_embed embed;
2119		2301
2120	// see if there is a chance of getting one that works	2302	// see if there is a chance of getting one that works
2121	// (remember that a flags value of 0 means autodetection)	2303	// (remember that a flags value of 0 means autodetection)
2122	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2304	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2123	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2305	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2124	: 0;	2306	: 0;
2125		2307
2126	// if we got one, then embed it, otherwise default to loop_hi	2308	// if we got one, then embed it, otherwise default to loop_hi
2127	if (loop_lo)	2309	if (loop_lo)
2128	{	2310	{
2129	ev_embed_init (&embed, 0, loop_lo);	2311	ev_embed_init (&embed, 0, loop_lo);
2130	ev_embed_start (loop_hi, &embed);	2312	ev_embed_start (loop_hi, &embed);
2131	}	2313	}
2132	else	2314	else
2133	loop_lo = loop_hi;	2315	loop_lo = loop_hi;
2134		2316
2135	Example: Check if kqueue is available but not recommended and create	2317	Example: Check if kqueue is available but not recommended and create
2136	a kqueue backend for use with sockets (which usually work with any	2318	a kqueue backend for use with sockets (which usually work with any
2137	kqueue implementation). Store the kqueue/socket-only event loop in	2319	kqueue implementation). Store the kqueue/socket-only event loop in
2138	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2320	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2139		2321
2140	struct ev_loop *loop = ev_default_init (0);	2322	struct ev_loop *loop = ev_default_init (0);
2141	struct ev_loop *loop_socket = 0;	2323	struct ev_loop *loop_socket = 0;
2142	struct ev_embed embed;	2324	struct ev_embed embed;
2143		2325
2144	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2326	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2145	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2327	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2146	{	2328	{
2147	ev_embed_init (&embed, 0, loop_socket);	2329	ev_embed_init (&embed, 0, loop_socket);
2148	ev_embed_start (loop, &embed);	2330	ev_embed_start (loop, &embed);
2149	}	2331	}
2150		2332
2151	if (!loop_socket)	2333	if (!loop_socket)
2152	loop_socket = loop;	2334	loop_socket = loop;
2153		2335
2154	// now use loop_socket for all sockets, and loop for everything else	2336	// now use loop_socket for all sockets, and loop for everything else
2155		2337
2156		2338
2157	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2339	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2158		2340
2159	Fork watchers are called when a C<fork ()> was detected (usually because	2341	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2203	is that the author does not know of a simple (or any) algorithm for a	2385	is that the author does not know of a simple (or any) algorithm for a
2204	multiple-writer-single-reader queue that works in all cases and doesn't	2386	multiple-writer-single-reader queue that works in all cases and doesn't
2205	need elaborate support such as pthreads.	2387	need elaborate support such as pthreads.
2206		2388
2207	That means that if you want to queue data, you have to provide your own	2389	That means that if you want to queue data, you have to provide your own
2208	queue. But at least I can tell you would implement locking around your	2390	queue. But at least I can tell you how to implement locking around your
2209	queue:	2391	queue:
2210		2392
2211	=over 4	2393	=over 4
2212		2394
2213	=item queueing from a signal handler context	2395	=item queueing from a signal handler context
2214		2396
2215	To implement race-free queueing, you simply add to the queue in the signal	2397	To implement race-free queueing, you simply add to the queue in the signal
2216	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2398	handler but you block the signal handler in the watcher callback. Here is
2217	some fictitiuous SIGUSR1 handler:	2399	an example that does that for some fictitious SIGUSR1 handler:
2218		2400
2219	static ev_async mysig;	2401	static ev_async mysig;
2220		2402
2221	static void	2403	static void
2222	sigusr1_handler (void)	2404	sigusr1_handler (void)
…		…
2289		2471
2290	=item ev_async_init (ev_async *, callback)	2472	=item ev_async_init (ev_async *, callback)
2291		2473
2292	Initialises and configures the async watcher - it has no parameters of any	2474	Initialises and configures the async watcher - it has no parameters of any
2293	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2475	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2294	believe me.	2476	trust me.
2295		2477
2296	=item ev_async_send (loop, ev_async *)	2478	=item ev_async_send (loop, ev_async *)
2297		2479
2298	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2480	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2299	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2481	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2300	C<ev_feed_event>, this call is safe to do in other threads, signal or	2482	C<ev_feed_event>, this call is safe to do from other threads, signal or
2301	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	2483	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2302	section below on what exactly this means).	2484	section below on what exactly this means).
2303		2485
2304	This call incurs the overhead of a syscall only once per loop iteration,	2486	This call incurs the overhead of a system call only once per loop iteration,
2305	so while the overhead might be noticable, it doesn't apply to repeated	2487	so while the overhead might be noticeable, it doesn't apply to repeated
2306	calls to C<ev_async_send>.	2488	calls to C<ev_async_send>.
2307		2489
2308	=item bool = ev_async_pending (ev_async *)	2490	=item bool = ev_async_pending (ev_async *)
2309		2491
2310	Returns a non-zero value when C<ev_async_send> has been called on the	2492	Returns a non-zero value when C<ev_async_send> has been called on the
…		…
2312	event loop.	2494	event loop.
2313		2495
2314	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2496	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2315	the loop iterates next and checks for the watcher to have become active,	2497	the loop iterates next and checks for the watcher to have become active,
2316	it will reset the flag again. C<ev_async_pending> can be used to very	2498	it will reset the flag again. C<ev_async_pending> can be used to very
2317	quickly check wether invoking the loop might be a good idea.	2499	quickly check whether invoking the loop might be a good idea.
2318		2500
2319	Not that this does I<not> check wether the watcher itself is pending, only	2501	Not that this does I<not> check whether the watcher itself is pending, only
2320	wether it has been requested to make this watcher pending.	2502	whether it has been requested to make this watcher pending.
2321		2503
2322	=back	2504	=back
2323		2505
2324		2506
2325	=head1 OTHER FUNCTIONS	2507	=head1 OTHER FUNCTIONS
…		…
2329	=over 4	2511	=over 4
2330		2512
2331	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2513	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2332		2514
2333	This function combines a simple timer and an I/O watcher, calls your	2515	This function combines a simple timer and an I/O watcher, calls your
2334	callback on whichever event happens first and automatically stop both	2516	callback on whichever event happens first and automatically stops both
2335	watchers. This is useful if you want to wait for a single event on an fd	2517	watchers. This is useful if you want to wait for a single event on an fd
2336	or timeout without having to allocate/configure/start/stop/free one or	2518	or timeout without having to allocate/configure/start/stop/free one or
2337	more watchers yourself.	2519	more watchers yourself.
2338		2520
2339	If C<fd> is less than 0, then no I/O watcher will be started and events	2521	If C<fd> is less than 0, then no I/O watcher will be started and the
2340	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2522	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2341	C<events> set will be craeted and started.	2523	the given C<fd> and C<events> set will be created and started.
2342		2524
2343	If C<timeout> is less than 0, then no timeout watcher will be	2525	If C<timeout> is less than 0, then no timeout watcher will be
2344	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2526	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2345	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2527	repeat = 0) will be started. C<0> is a valid timeout.
2346	dubious value.
2347		2528
2348	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2529	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2349	passed an C<revents> set like normal event callbacks (a combination of	2530	passed an C<revents> set like normal event callbacks (a combination of
2350	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2531	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2351	value passed to C<ev_once>:	2532	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2533	a timeout and an io event at the same time - you probably should give io
		2534	events precedence.
2352		2535
		2536	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2537
2353	static void stdin_ready (int revents, void *arg)	2538	static void stdin_ready (int revents, void *arg)
2354	{	2539	{
2355	if (revents & EV_TIMEOUT)
2356	/* doh, nothing entered */;
2357	else if (revents & EV_READ)	2540	if (revents & EV_READ)
2358	/* stdin might have data for us, joy! */;	2541	/* stdin might have data for us, joy! */;
		2542	else if (revents & EV_TIMEOUT)
		2543	/* doh, nothing entered */;
2359	}	2544	}
2360		2545
2361	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2362		2547
2363	=item ev_feed_event (ev_loop *, watcher *, int revents)	2548	=item ev_feed_event (ev_loop *, watcher *, int revents)
2364		2549
2365	Feeds the given event set into the event loop, as if the specified event	2550	Feeds the given event set into the event loop, as if the specified event
2366	had happened for the specified watcher (which must be a pointer to an	2551	had happened for the specified watcher (which must be a pointer to an
…		…
2371	Feed an event on the given fd, as if a file descriptor backend detected	2556	Feed an event on the given fd, as if a file descriptor backend detected
2372	the given events it.	2557	the given events it.
2373		2558
2374	=item ev_feed_signal_event (ev_loop *loop, int signum)	2559	=item ev_feed_signal_event (ev_loop *loop, int signum)
2375		2560
2376	Feed an event as if the given signal occured (C<loop> must be the default	2561	Feed an event as if the given signal occurred (C<loop> must be the default
2377	loop!).	2562	loop!).
2378		2563
2379	=back	2564	=back
2380		2565
2381		2566
…		…
2410	=back	2595	=back
2411		2596
2412	=head1 C++ SUPPORT	2597	=head1 C++ SUPPORT
2413		2598
2414	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2599	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2415	you to use some convinience methods to start/stop watchers and also change	2600	you to use some convenience methods to start/stop watchers and also change
2416	the callback model to a model using method callbacks on objects.	2601	the callback model to a model using method callbacks on objects.
2417		2602
2418	To use it,	2603	To use it,
2419		2604
2420	#include <ev++.h>	2605	#include <ev++.h>
2421		2606
2422	This automatically includes F<ev.h> and puts all of its definitions (many	2607	This automatically includes F<ev.h> and puts all of its definitions (many
2423	of them macros) into the global namespace. All C++ specific things are	2608	of them macros) into the global namespace. All C++ specific things are
2424	put into the C<ev> namespace. It should support all the same embedding	2609	put into the C<ev> namespace. It should support all the same embedding
2425	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2610	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2492	your compiler is good :), then the method will be fully inlined into the	2677	your compiler is good :), then the method will be fully inlined into the
2493	thunking function, making it as fast as a direct C callback.	2678	thunking function, making it as fast as a direct C callback.
2494		2679
2495	Example: simple class declaration and watcher initialisation	2680	Example: simple class declaration and watcher initialisation
2496		2681
2497	struct myclass	2682	struct myclass
2498	{	2683	{
2499	void io_cb (ev::io &w, int revents) { }	2684	void io_cb (ev::io &w, int revents) { }
2500	}	2685	}
2501		2686
2502	myclass obj;	2687	myclass obj;
2503	ev::io iow;	2688	ev::io iow;
2504	iow.set <myclass, &myclass::io_cb> (&obj);	2689	iow.set <myclass, &myclass::io_cb> (&obj);
2505		2690
2506	=item w->set<function> (void *data = 0)	2691	=item w->set<function> (void *data = 0)
2507		2692
2508	Also sets a callback, but uses a static method or plain function as	2693	Also sets a callback, but uses a static method or plain function as
2509	callback. The optional C<data> argument will be stored in the watcher's	2694	callback. The optional C<data> argument will be stored in the watcher's
…		…
2511		2696
2512	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2697	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2513		2698
2514	See the method-C<set> above for more details.	2699	See the method-C<set> above for more details.
2515		2700
2516	Example:	2701	Example: Use a plain function as callback.
2517		2702
2518	static void io_cb (ev::io &w, int revents) { }	2703	static void io_cb (ev::io &w, int revents) { }
2519	iow.set <io_cb> ();	2704	iow.set <io_cb> ();
2520		2705
2521	=item w->set (struct ev_loop *)	2706	=item w->set (struct ev_loop *)
2522		2707
2523	Associates a different C<struct ev_loop> with this watcher. You can only	2708	Associates a different C<struct ev_loop> with this watcher. You can only
2524	do this when the watcher is inactive (and not pending either).	2709	do this when the watcher is inactive (and not pending either).
2525		2710
2526	=item w->set ([args])	2711	=item w->set ([arguments])
2527		2712
2528	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2713	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2529	called at least once. Unlike the C counterpart, an active watcher gets	2714	called at least once. Unlike the C counterpart, an active watcher gets
2530	automatically stopped and restarted when reconfiguring it with this	2715	automatically stopped and restarted when reconfiguring it with this
2531	method.	2716	method.
2532		2717
2533	=item w->start ()	2718	=item w->start ()
…		…
2557	=back	2742	=back
2558		2743
2559	Example: Define a class with an IO and idle watcher, start one of them in	2744	Example: Define a class with an IO and idle watcher, start one of them in
2560	the constructor.	2745	the constructor.
2561		2746
2562	class myclass	2747	class myclass
2563	{	2748	{
2564	ev::io io; void io_cb (ev::io &w, int revents);	2749	ev::io io ; void io_cb (ev::io &w, int revents);
2565	ev:idle idle void idle_cb (ev::idle &w, int revents);	2750	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2566		2751
2567	myclass (int fd)	2752	myclass (int fd)
2568	{	2753	{
2569	io .set <myclass, &myclass::io_cb > (this);	2754	io .set <myclass, &myclass::io_cb > (this);
2570	idle.set <myclass, &myclass::idle_cb> (this);	2755	idle.set <myclass, &myclass::idle_cb> (this);
2571		2756
2572	io.start (fd, ev::READ);	2757	io.start (fd, ev::READ);
2573	}	2758	}
2574	};	2759	};
2575		2760
2576		2761
2577	=head1 OTHER LANGUAGE BINDINGS	2762	=head1 OTHER LANGUAGE BINDINGS
2578		2763
2579	Libev does not offer other language bindings itself, but bindings for a	2764	Libev does not offer other language bindings itself, but bindings for a
2580	numbe rof languages exist in the form of third-party packages. If you know	2765	number of languages exist in the form of third-party packages. If you know
2581	any interesting language binding in addition to the ones listed here, drop	2766	any interesting language binding in addition to the ones listed here, drop
2582	me a note.	2767	me a note.
2583		2768
2584	=over 4	2769	=over 4
2585		2770
2586	=item Perl	2771	=item Perl
2587		2772
2588	The EV module implements the full libev API and is actually used to test	2773	The EV module implements the full libev API and is actually used to test
2589	libev. EV is developed together with libev. Apart from the EV core module,	2774	libev. EV is developed together with libev. Apart from the EV core module,
2590	there are additional modules that implement libev-compatible interfaces	2775	there are additional modules that implement libev-compatible interfaces
2591	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2776	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2592	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2777	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2778	and C<EV::Glib>).
2593		2779
2594	It can be found and installed via CPAN, its homepage is found at	2780	It can be found and installed via CPAN, its homepage is at
2595	L<http://software.schmorp.de/pkg/EV>.	2781	L<http://software.schmorp.de/pkg/EV>.
2596		2782
		2783	=item Python
		2784
		2785	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2786	seems to be quite complete and well-documented. Note, however, that the
		2787	patch they require for libev is outright dangerous as it breaks the ABI
		2788	for everybody else, and therefore, should never be applied in an installed
		2789	libev (if python requires an incompatible ABI then it needs to embed
		2790	libev).
		2791
2597	=item Ruby	2792	=item Ruby
2598		2793
2599	Tony Arcieri has written a ruby extension that offers access to a subset	2794	Tony Arcieri has written a ruby extension that offers access to a subset
2600	of the libev API and adds filehandle abstractions, asynchronous DNS and	2795	of the libev API and adds file handle abstractions, asynchronous DNS and
2601	more on top of it. It can be found via gem servers. Its homepage is at	2796	more on top of it. It can be found via gem servers. Its homepage is at
2602	L<http://rev.rubyforge.org/>.	2797	L<http://rev.rubyforge.org/>.
2603		2798
2604	=item D	2799	=item D
2605		2800
2606	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2801	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2607	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2802	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2608		2803
2609	=back	2804	=back
2610		2805
2611		2806
2612	=head1 MACRO MAGIC	2807	=head1 MACRO MAGIC
2613		2808
2614	Libev can be compiled with a variety of options, the most fundamantal	2809	Libev can be compiled with a variety of options, the most fundamental
2615	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	2810	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2616	functions and callbacks have an initial C<struct ev_loop *> argument.	2811	functions and callbacks have an initial C<struct ev_loop *> argument.
2617		2812
2618	To make it easier to write programs that cope with either variant, the	2813	To make it easier to write programs that cope with either variant, the
2619	following macros are defined:	2814	following macros are defined:
…		…
2624		2819
2625	This provides the loop I<argument> for functions, if one is required ("ev	2820	This provides the loop I<argument> for functions, if one is required ("ev
2626	loop argument"). The C<EV_A> form is used when this is the sole argument,	2821	loop argument"). The C<EV_A> form is used when this is the sole argument,
2627	C<EV_A_> is used when other arguments are following. Example:	2822	C<EV_A_> is used when other arguments are following. Example:
2628		2823
2629	ev_unref (EV_A);	2824	ev_unref (EV_A);
2630	ev_timer_add (EV_A_ watcher);	2825	ev_timer_add (EV_A_ watcher);
2631	ev_loop (EV_A_ 0);	2826	ev_loop (EV_A_ 0);
2632		2827
2633	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2828	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2634	which is often provided by the following macro.	2829	which is often provided by the following macro.
2635		2830
2636	=item C<EV_P>, C<EV_P_>	2831	=item C<EV_P>, C<EV_P_>
2637		2832
2638	This provides the loop I<parameter> for functions, if one is required ("ev	2833	This provides the loop I<parameter> for functions, if one is required ("ev
2639	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2834	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2640	C<EV_P_> is used when other parameters are following. Example:	2835	C<EV_P_> is used when other parameters are following. Example:
2641		2836
2642	// this is how ev_unref is being declared	2837	// this is how ev_unref is being declared
2643	static void ev_unref (EV_P);	2838	static void ev_unref (EV_P);
2644		2839
2645	// this is how you can declare your typical callback	2840	// this is how you can declare your typical callback
2646	static void cb (EV_P_ ev_timer *w, int revents)	2841	static void cb (EV_P_ ev_timer *w, int revents)
2647		2842
2648	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2843	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2649	suitable for use with C<EV_A>.	2844	suitable for use with C<EV_A>.
2650		2845
2651	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2846	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2667		2862
2668	Example: Declare and initialise a check watcher, utilising the above	2863	Example: Declare and initialise a check watcher, utilising the above
2669	macros so it will work regardless of whether multiple loops are supported	2864	macros so it will work regardless of whether multiple loops are supported
2670	or not.	2865	or not.
2671		2866
2672	static void	2867	static void
2673	check_cb (EV_P_ ev_timer *w, int revents)	2868	check_cb (EV_P_ ev_timer *w, int revents)
2674	{	2869	{
2675	ev_check_stop (EV_A_ w);	2870	ev_check_stop (EV_A_ w);
2676	}	2871	}
2677		2872
2678	ev_check check;	2873	ev_check check;
2679	ev_check_init (&check, check_cb);	2874	ev_check_init (&check, check_cb);
2680	ev_check_start (EV_DEFAULT_ &check);	2875	ev_check_start (EV_DEFAULT_ &check);
2681	ev_loop (EV_DEFAULT_ 0);	2876	ev_loop (EV_DEFAULT_ 0);
2682		2877
2683	=head1 EMBEDDING	2878	=head1 EMBEDDING
2684		2879
2685	Libev can (and often is) directly embedded into host	2880	Libev can (and often is) directly embedded into host
2686	applications. Examples of applications that embed it include the Deliantra	2881	applications. Examples of applications that embed it include the Deliantra
…		…
2693	libev somewhere in your source tree).	2888	libev somewhere in your source tree).
2694		2889
2695	=head2 FILESETS	2890	=head2 FILESETS
2696		2891
2697	Depending on what features you need you need to include one or more sets of files	2892	Depending on what features you need you need to include one or more sets of files
2698	in your app.	2893	in your application.
2699		2894
2700	=head3 CORE EVENT LOOP	2895	=head3 CORE EVENT LOOP
2701		2896
2702	To include only the libev core (all the C<ev_*> functions), with manual	2897	To include only the libev core (all the C<ev_*> functions), with manual
2703	configuration (no autoconf):	2898	configuration (no autoconf):
2704		2899
2705	#define EV_STANDALONE 1	2900	#define EV_STANDALONE 1
2706	#include "ev.c"	2901	#include "ev.c"
2707		2902
2708	This will automatically include F<ev.h>, too, and should be done in a	2903	This will automatically include F<ev.h>, too, and should be done in a
2709	single C source file only to provide the function implementations. To use	2904	single C source file only to provide the function implementations. To use
2710	it, do the same for F<ev.h> in all files wishing to use this API (best	2905	it, do the same for F<ev.h> in all files wishing to use this API (best
2711	done by writing a wrapper around F<ev.h> that you can include instead and	2906	done by writing a wrapper around F<ev.h> that you can include instead and
2712	where you can put other configuration options):	2907	where you can put other configuration options):
2713		2908
2714	#define EV_STANDALONE 1	2909	#define EV_STANDALONE 1
2715	#include "ev.h"	2910	#include "ev.h"
2716		2911
2717	Both header files and implementation files can be compiled with a C++	2912	Both header files and implementation files can be compiled with a C++
2718	compiler (at least, thats a stated goal, and breakage will be treated	2913	compiler (at least, thats a stated goal, and breakage will be treated
2719	as a bug).	2914	as a bug).
2720		2915
2721	You need the following files in your source tree, or in a directory	2916	You need the following files in your source tree, or in a directory
2722	in your include path (e.g. in libev/ when using -Ilibev):	2917	in your include path (e.g. in libev/ when using -Ilibev):
2723		2918
2724	ev.h	2919	ev.h
2725	ev.c	2920	ev.c
2726	ev_vars.h	2921	ev_vars.h
2727	ev_wrap.h	2922	ev_wrap.h
2728		2923
2729	ev_win32.c required on win32 platforms only	2924	ev_win32.c required on win32 platforms only
2730		2925
2731	ev_select.c only when select backend is enabled (which is enabled by default)	2926	ev_select.c only when select backend is enabled (which is enabled by default)
2732	ev_poll.c only when poll backend is enabled (disabled by default)	2927	ev_poll.c only when poll backend is enabled (disabled by default)
2733	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2928	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2734	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2929	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2735	ev_port.c only when the solaris port backend is enabled (disabled by default)	2930	ev_port.c only when the solaris port backend is enabled (disabled by default)
2736		2931
2737	F<ev.c> includes the backend files directly when enabled, so you only need	2932	F<ev.c> includes the backend files directly when enabled, so you only need
2738	to compile this single file.	2933	to compile this single file.
2739		2934
2740	=head3 LIBEVENT COMPATIBILITY API	2935	=head3 LIBEVENT COMPATIBILITY API
2741		2936
2742	To include the libevent compatibility API, also include:	2937	To include the libevent compatibility API, also include:
2743		2938
2744	#include "event.c"	2939	#include "event.c"
2745		2940
2746	in the file including F<ev.c>, and:	2941	in the file including F<ev.c>, and:
2747		2942
2748	#include "event.h"	2943	#include "event.h"
2749		2944
2750	in the files that want to use the libevent API. This also includes F<ev.h>.	2945	in the files that want to use the libevent API. This also includes F<ev.h>.
2751		2946
2752	You need the following additional files for this:	2947	You need the following additional files for this:
2753		2948
2754	event.h	2949	event.h
2755	event.c	2950	event.c
2756		2951
2757	=head3 AUTOCONF SUPPORT	2952	=head3 AUTOCONF SUPPORT
2758		2953
2759	Instead of using C<EV_STANDALONE=1> and providing your config in	2954	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2760	whatever way you want, you can also C<m4_include([libev.m4])> in your	2955	whatever way you want, you can also C<m4_include([libev.m4])> in your
2761	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2956	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2762	include F<config.h> and configure itself accordingly.	2957	include F<config.h> and configure itself accordingly.
2763		2958
2764	For this of course you need the m4 file:	2959	For this of course you need the m4 file:
2765		2960
2766	libev.m4	2961	libev.m4
2767		2962
2768	=head2 PREPROCESSOR SYMBOLS/MACROS	2963	=head2 PREPROCESSOR SYMBOLS/MACROS
2769		2964
2770	Libev can be configured via a variety of preprocessor symbols you have to	2965	Libev can be configured via a variety of preprocessor symbols you have to
2771	define before including any of its files. The default in the absense of	2966	define before including any of its files. The default in the absence of
2772	autoconf is noted for every option.	2967	autoconf is documented for every option.
2773		2968
2774	=over 4	2969	=over 4
2775		2970
2776	=item EV_STANDALONE	2971	=item EV_STANDALONE
2777		2972
…		…
2782	F<event.h> that are not directly supported by the libev core alone.	2977	F<event.h> that are not directly supported by the libev core alone.
2783		2978
2784	=item EV_USE_MONOTONIC	2979	=item EV_USE_MONOTONIC
2785		2980
2786	If defined to be C<1>, libev will try to detect the availability of the	2981	If defined to be C<1>, libev will try to detect the availability of the
2787	monotonic clock option at both compiletime and runtime. Otherwise no use	2982	monotonic clock option at both compile time and runtime. Otherwise no use
2788	of the monotonic clock option will be attempted. If you enable this, you	2983	of the monotonic clock option will be attempted. If you enable this, you
2789	usually have to link against librt or something similar. Enabling it when	2984	usually have to link against librt or something similar. Enabling it when
2790	the functionality isn't available is safe, though, although you have	2985	the functionality isn't available is safe, though, although you have
2791	to make sure you link against any libraries where the C<clock_gettime>	2986	to make sure you link against any libraries where the C<clock_gettime>
2792	function is hiding in (often F<-lrt>).	2987	function is hiding in (often F<-lrt>).
2793		2988
2794	=item EV_USE_REALTIME	2989	=item EV_USE_REALTIME
2795		2990
2796	If defined to be C<1>, libev will try to detect the availability of the	2991	If defined to be C<1>, libev will try to detect the availability of the
2797	realtime clock option at compiletime (and assume its availability at	2992	real-time clock option at compile time (and assume its availability at
2798	runtime if successful). Otherwise no use of the realtime clock option will	2993	runtime if successful). Otherwise no use of the real-time clock option will
2799	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2994	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2800	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2995	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2801	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2996	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2802		2997
2803	=item EV_USE_NANOSLEEP	2998	=item EV_USE_NANOSLEEP
…		…
2814	2.7 or newer, otherwise disabled.	3009	2.7 or newer, otherwise disabled.
2815		3010
2816	=item EV_USE_SELECT	3011	=item EV_USE_SELECT
2817		3012
2818	If undefined or defined to be C<1>, libev will compile in support for the	3013	If undefined or defined to be C<1>, libev will compile in support for the
2819	C<select>(2) backend. No attempt at autodetection will be done: if no	3014	C<select>(2) backend. No attempt at auto-detection will be done: if no
2820	other method takes over, select will be it. Otherwise the select backend	3015	other method takes over, select will be it. Otherwise the select backend
2821	will not be compiled in.	3016	will not be compiled in.
2822		3017
2823	=item EV_SELECT_USE_FD_SET	3018	=item EV_SELECT_USE_FD_SET
2824		3019
2825	If defined to C<1>, then the select backend will use the system C<fd_set>	3020	If defined to C<1>, then the select backend will use the system C<fd_set>
2826	structure. This is useful if libev doesn't compile due to a missing	3021	structure. This is useful if libev doesn't compile due to a missing
2827	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3022	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2828	exotic systems. This usually limits the range of file descriptors to some	3023	exotic systems. This usually limits the range of file descriptors to some
2829	low limit such as 1024 or might have other limitations (winsocket only	3024	low limit such as 1024 or might have other limitations (winsocket only
2830	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3025	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2831	influence the size of the C<fd_set> used.	3026	influence the size of the C<fd_set> used.
2832		3027
…		…
2881	otherwise another method will be used as fallback. This is the preferred	3076	otherwise another method will be used as fallback. This is the preferred
2882	backend for Solaris 10 systems.	3077	backend for Solaris 10 systems.
2883		3078
2884	=item EV_USE_DEVPOLL	3079	=item EV_USE_DEVPOLL
2885		3080
2886	reserved for future expansion, works like the USE symbols above.	3081	Reserved for future expansion, works like the USE symbols above.
2887		3082
2888	=item EV_USE_INOTIFY	3083	=item EV_USE_INOTIFY
2889		3084
2890	If defined to be C<1>, libev will compile in support for the Linux inotify	3085	If defined to be C<1>, libev will compile in support for the Linux inotify
2891	interface to speed up C<ev_stat> watchers. Its actual availability will	3086	interface to speed up C<ev_stat> watchers. Its actual availability will
…		…
2898	access is atomic with respect to other threads or signal contexts. No such	3093	access is atomic with respect to other threads or signal contexts. No such
2899	type is easily found in the C language, so you can provide your own type	3094	type is easily found in the C language, so you can provide your own type
2900	that you know is safe for your purposes. It is used both for signal handler "locking"	3095	that you know is safe for your purposes. It is used both for signal handler "locking"
2901	as well as for signal and thread safety in C<ev_async> watchers.	3096	as well as for signal and thread safety in C<ev_async> watchers.
2902		3097
2903	In the absense of this define, libev will use C<sig_atomic_t volatile>	3098	In the absence of this define, libev will use C<sig_atomic_t volatile>
2904	(from F<signal.h>), which is usually good enough on most platforms.	3099	(from F<signal.h>), which is usually good enough on most platforms.
2905		3100
2906	=item EV_H	3101	=item EV_H
2907		3102
2908	The name of the F<ev.h> header file used to include it. The default if	3103	The name of the F<ev.h> header file used to include it. The default if
…		…
2947	When doing priority-based operations, libev usually has to linearly search	3142	When doing priority-based operations, libev usually has to linearly search
2948	all the priorities, so having many of them (hundreds) uses a lot of space	3143	all the priorities, so having many of them (hundreds) uses a lot of space
2949	and time, so using the defaults of five priorities (-2 .. +2) is usually	3144	and time, so using the defaults of five priorities (-2 .. +2) is usually
2950	fine.	3145	fine.
2951		3146
2952	If your embedding app does not need any priorities, defining these both to	3147	If your embedding application does not need any priorities, defining these
2953	C<0> will save some memory and cpu.	3148	both to C<0> will save some memory and CPU.
2954		3149
2955	=item EV_PERIODIC_ENABLE	3150	=item EV_PERIODIC_ENABLE
2956		3151
2957	If undefined or defined to be C<1>, then periodic timers are supported. If	3152	If undefined or defined to be C<1>, then periodic timers are supported. If
2958	defined to be C<0>, then they are not. Disabling them saves a few kB of	3153	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2965	code.	3160	code.
2966		3161
2967	=item EV_EMBED_ENABLE	3162	=item EV_EMBED_ENABLE
2968		3163
2969	If undefined or defined to be C<1>, then embed watchers are supported. If	3164	If undefined or defined to be C<1>, then embed watchers are supported. If
2970	defined to be C<0>, then they are not.	3165	defined to be C<0>, then they are not. Embed watchers rely on most other
		3166	watcher types, which therefore must not be disabled.
2971		3167
2972	=item EV_STAT_ENABLE	3168	=item EV_STAT_ENABLE
2973		3169
2974	If undefined or defined to be C<1>, then stat watchers are supported. If	3170	If undefined or defined to be C<1>, then stat watchers are supported. If
2975	defined to be C<0>, then they are not.	3171	defined to be C<0>, then they are not.
…		…
2986		3182
2987	=item EV_MINIMAL	3183	=item EV_MINIMAL
2988		3184
2989	If you need to shave off some kilobytes of code at the expense of some	3185	If you need to shave off some kilobytes of code at the expense of some
2990	speed, define this symbol to C<1>. Currently this is used to override some	3186	speed, define this symbol to C<1>. Currently this is used to override some
2991	inlining decisions, saves roughly 30% codesize of amd64. It also selects a	3187	inlining decisions, saves roughly 30% code size on amd64. It also selects a
2992	much smaller 2-heap for timer management over the default 4-heap.	3188	much smaller 2-heap for timer management over the default 4-heap.
2993		3189
2994	=item EV_PID_HASHSIZE	3190	=item EV_PID_HASHSIZE
2995		3191
2996	C<ev_child> watchers use a small hash table to distribute workload by	3192	C<ev_child> watchers use a small hash table to distribute workload by
…		…
3007	two).	3203	two).
3008		3204
3009	=item EV_USE_4HEAP	3205	=item EV_USE_4HEAP
3010		3206
3011	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3207	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3012	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3208	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3013	to C<1>. The 4-heap uses more complicated (longer) code but has	3209	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3014	noticably faster performance with many (thousands) of watchers.	3210	faster performance with many (thousands) of watchers.
3015		3211
3016	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3017	(disabled).	3213	(disabled).
3018		3214
3019	=item EV_HEAP_CACHE_AT	3215	=item EV_HEAP_CACHE_AT
3020		3216
3021	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3217	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3022	timer and periodics heap, libev can cache the timestamp (I<at>) within	3218	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3023	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3219	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3024	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3220	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3025	but avoids random read accesses on heap changes. This improves performance	3221	but avoids random read accesses on heap changes. This improves performance
3026	noticably with with many (hundreds) of watchers.	3222	noticeably with many (hundreds) of watchers.
3027		3223
3028	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3224	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3029	(disabled).	3225	(disabled).
		3226
		3227	=item EV_VERIFY
		3228
		3229	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3230	be done: If set to C<0>, no internal verification code will be compiled
		3231	in. If set to C<1>, then verification code will be compiled in, but not
		3232	called. If set to C<2>, then the internal verification code will be
		3233	called once per loop, which can slow down libev. If set to C<3>, then the
		3234	verification code will be called very frequently, which will slow down
		3235	libev considerably.
		3236
		3237	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3238	C<0>.
3030		3239
3031	=item EV_COMMON	3240	=item EV_COMMON
3032		3241
3033	By default, all watchers have a C<void *data> member. By redefining	3242	By default, all watchers have a C<void *data> member. By redefining
3034	this macro to a something else you can include more and other types of	3243	this macro to a something else you can include more and other types of
3035	members. You have to define it each time you include one of the files,	3244	members. You have to define it each time you include one of the files,
3036	though, and it must be identical each time.	3245	though, and it must be identical each time.
3037		3246
3038	For example, the perl EV module uses something like this:	3247	For example, the perl EV module uses something like this:
3039		3248
3040	#define EV_COMMON \	3249	#define EV_COMMON \
3041	SV *self; /* contains this struct */ \	3250	SV *self; /* contains this struct */ \
3042	SV *cb_sv, *fh /* note no trailing ";" */	3251	SV *cb_sv, *fh /* note no trailing ";" */
3043		3252
3044	=item EV_CB_DECLARE (type)	3253	=item EV_CB_DECLARE (type)
3045		3254
3046	=item EV_CB_INVOKE (watcher, revents)	3255	=item EV_CB_INVOKE (watcher, revents)
3047		3256
…		…
3052	definition and a statement, respectively. See the F<ev.h> header file for	3261	definition and a statement, respectively. See the F<ev.h> header file for
3053	their default definitions. One possible use for overriding these is to	3262	their default definitions. One possible use for overriding these is to
3054	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3263	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3055	method calls instead of plain function calls in C++.	3264	method calls instead of plain function calls in C++.
3056		3265
		3266	=back
		3267
3057	=head2 EXPORTED API SYMBOLS	3268	=head2 EXPORTED API SYMBOLS
3058		3269
3059	If you need to re-export the API (e.g. via a dll) and you need a list of	3270	If you need to re-export the API (e.g. via a DLL) and you need a list of
3060	exported symbols, you can use the provided F<Symbol.*> files which list	3271	exported symbols, you can use the provided F<Symbol.*> files which list
3061	all public symbols, one per line:	3272	all public symbols, one per line:
3062		3273
3063	Symbols.ev for libev proper	3274	Symbols.ev for libev proper
3064	Symbols.event for the libevent emulation	3275	Symbols.event for the libevent emulation
3065		3276
3066	This can also be used to rename all public symbols to avoid clashes with	3277	This can also be used to rename all public symbols to avoid clashes with
3067	multiple versions of libev linked together (which is obviously bad in	3278	multiple versions of libev linked together (which is obviously bad in
3068	itself, but sometimes it is inconvinient to avoid this).	3279	itself, but sometimes it is inconvenient to avoid this).
3069		3280
3070	A sed command like this will create wrapper C<#define>'s that you need to	3281	A sed command like this will create wrapper C<#define>'s that you need to
3071	include before including F<ev.h>:	3282	include before including F<ev.h>:
3072		3283
3073	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3284	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3090	file.	3301	file.
3091		3302
3092	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3303	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3093	that everybody includes and which overrides some configure choices:	3304	that everybody includes and which overrides some configure choices:
3094		3305
3095	#define EV_MINIMAL 1	3306	#define EV_MINIMAL 1
3096	#define EV_USE_POLL 0	3307	#define EV_USE_POLL 0
3097	#define EV_MULTIPLICITY 0	3308	#define EV_MULTIPLICITY 0
3098	#define EV_PERIODIC_ENABLE 0	3309	#define EV_PERIODIC_ENABLE 0
3099	#define EV_STAT_ENABLE 0	3310	#define EV_STAT_ENABLE 0
3100	#define EV_FORK_ENABLE 0	3311	#define EV_FORK_ENABLE 0
3101	#define EV_CONFIG_H <config.h>	3312	#define EV_CONFIG_H <config.h>
3102	#define EV_MINPRI 0	3313	#define EV_MINPRI 0
3103	#define EV_MAXPRI 0	3314	#define EV_MAXPRI 0
3104		3315
3105	#include "ev++.h"	3316	#include "ev++.h"
3106		3317
3107	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3318	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3108		3319
3109	#include "ev_cpp.h"	3320	#include "ev_cpp.h"
3110	#include "ev.c"	3321	#include "ev.c"
3111		3322
		3323	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3112		3324
3113	=head1 THREADS AND COROUTINES	3325	=head2 THREADS AND COROUTINES
3114		3326
3115	=head2 THREADS	3327	=head3 THREADS
3116		3328
3117	Libev itself is completely threadsafe, but it uses no locking. This	3329	All libev functions are reentrant and thread-safe unless explicitly
		3330	documented otherwise, but libev implements no locking itself. This means
3118	means that you can use as many loops as you want in parallel, as long as	3331	that you can use as many loops as you want in parallel, as long as there
3119	only one thread ever calls into one libev function with the same loop	3332	are no concurrent calls into any libev function with the same loop
3120	parameter.	3333	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3334	of course): libev guarantees that different event loops share no data
		3335	structures that need any locking.
3121		3336
3122	Or put differently: calls with different loop parameters can be done in	3337	Or to put it differently: calls with different loop parameters can be done
3123	parallel from multiple threads, calls with the same loop parameter must be	3338	concurrently from multiple threads, calls with the same loop parameter
3124	done serially (but can be done from different threads, as long as only one	3339	must be done serially (but can be done from different threads, as long as
3125	thread ever is inside a call at any point in time, e.g. by using a mutex	3340	only one thread ever is inside a call at any point in time, e.g. by using
3126	per loop).	3341	a mutex per loop).
3127		3342
3128	If you want to know which design is best for your problem, then I cannot	3343	Specifically to support threads (and signal handlers), libev implements
		3344	so-called C<ev_async> watchers, which allow some limited form of
		3345	concurrency on the same event loop, namely waking it up "from the
		3346	outside".
		3347
		3348	If you want to know which design (one loop, locking, or multiple loops
		3349	without or something else still) is best for your problem, then I cannot
3129	help you but by giving some generic advice:	3350	help you, but here is some generic advice:
3130		3351
3131	=over 4	3352	=over 4
3132		3353
3133	=item * most applications have a main thread: use the default libev loop	3354	=item * most applications have a main thread: use the default libev loop
3134	in that thread, or create a seperate thread running only the default loop.	3355	in that thread, or create a separate thread running only the default loop.
3135		3356
3136	This helps integrating other libraries or software modules that use libev	3357	This helps integrating other libraries or software modules that use libev
3137	themselves and don't care/know about threading.	3358	themselves and don't care/know about threading.
3138		3359
3139	=item * one loop per thread is usually a good model.	3360	=item * one loop per thread is usually a good model.
3140		3361
3141	Doing this is almost never wrong, sometimes a better-performance model	3362	Doing this is almost never wrong, sometimes a better-performance model
3142	exists, but it is always a good start.	3363	exists, but it is always a good start.
3143		3364
3144	=item * other models exist, such as the leader/follower pattern, where one	3365	=item * other models exist, such as the leader/follower pattern, where one
3145	loop is handed through multiple threads in a kind of round-robbin fashion.	3366	loop is handed through multiple threads in a kind of round-robin fashion.
3146		3367
3147	Chosing a model is hard - look around, learn, know that usually you cna do	3368	Choosing a model is hard - look around, learn, know that usually you can do
3148	better than you currently do :-)	3369	better than you currently do :-)
3149		3370
3150	=item * often you need to talk to some other thread which blocks in the	3371	=item * often you need to talk to some other thread which blocks in the
		3372	event loop.
		3373
3151	event loop - C<ev_async> watchers can be used to wake them up from other	3374	C<ev_async> watchers can be used to wake them up from other threads safely
3152	threads safely (or from signal contexts...).	3375	(or from signal contexts...).
		3376
		3377	An example use would be to communicate signals or other events that only
		3378	work in the default loop by registering the signal watcher with the
		3379	default loop and triggering an C<ev_async> watcher from the default loop
		3380	watcher callback into the event loop interested in the signal.
3153		3381
3154	=back	3382	=back
3155		3383
3156	=head2 COROUTINES	3384	=head3 COROUTINES
3157		3385
3158	Libev is much more accomodating to coroutines ("cooperative threads"):	3386	Libev is very accommodating to coroutines ("cooperative threads"):
3159	libev fully supports nesting calls to it's functions from different	3387	libev fully supports nesting calls to its functions from different
3160	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3388	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3161	different coroutines and switch freely between both coroutines running the	3389	different coroutines, and switch freely between both coroutines running the
3162	loop, as long as you don't confuse yourself). The only exception is that	3390	loop, as long as you don't confuse yourself). The only exception is that
3163	you must not do this from C<ev_periodic> reschedule callbacks.	3391	you must not do this from C<ev_periodic> reschedule callbacks.
3164		3392
3165	Care has been invested into making sure that libev does not keep local	3393	Care has been taken to ensure that libev does not keep local state inside
3166	state inside C<ev_loop>, and other calls do not usually allow coroutine	3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3167	switches.	3395	they do not clal any callbacks.
3168		3396
		3397	=head2 COMPILER WARNINGS
3169		3398
3170	=head1 COMPLEXITIES	3399	Depending on your compiler and compiler settings, you might get no or a
		3400	lot of warnings when compiling libev code. Some people are apparently
		3401	scared by this.
3171		3402
3172	In this section the complexities of (many of) the algorithms used inside	3403	However, these are unavoidable for many reasons. For one, each compiler
3173	libev will be explained. For complexity discussions about backends see the	3404	has different warnings, and each user has different tastes regarding
3174	documentation for C<ev_default_init>.	3405	warning options. "Warn-free" code therefore cannot be a goal except when
		3406	targeting a specific compiler and compiler-version.
3175		3407
3176	All of the following are about amortised time: If an array needs to be	3408	Another reason is that some compiler warnings require elaborate
3177	extended, libev needs to realloc and move the whole array, but this	3409	workarounds, or other changes to the code that make it less clear and less
3178	happens asymptotically never with higher number of elements, so O(1) might	3410	maintainable.
3179	mean it might do a lengthy realloc operation in rare cases, but on average
3180	it is much faster and asymptotically approaches constant time.
3181		3411
3182	=over 4	3412	And of course, some compiler warnings are just plain stupid, or simply
		3413	wrong (because they don't actually warn about the condition their message
		3414	seems to warn about). For example, certain older gcc versions had some
		3415	warnings that resulted an extreme number of false positives. These have
		3416	been fixed, but some people still insist on making code warn-free with
		3417	such buggy versions.
3183		3418
3184	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3419	While libev is written to generate as few warnings as possible,
		3420	"warn-free" code is not a goal, and it is recommended not to build libev
		3421	with any compiler warnings enabled unless you are prepared to cope with
		3422	them (e.g. by ignoring them). Remember that warnings are just that:
		3423	warnings, not errors, or proof of bugs.
3185		3424
3186	This means that, when you have a watcher that triggers in one hour and
3187	there are 100 watchers that would trigger before that then inserting will
3188	have to skip roughly seven (C<ld 100>) of these watchers.
3189		3425
3190	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3426	=head2 VALGRIND
3191		3427
3192	That means that changing a timer costs less than removing/adding them	3428	Valgrind has a special section here because it is a popular tool that is
3193	as only the relative motion in the event queue has to be paid for.	3429	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3194		3430
3195	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3431	If you think you found a bug (memory leak, uninitialised data access etc.)
		3432	in libev, then check twice: If valgrind reports something like:
3196		3433
3197	These just add the watcher into an array or at the head of a list.	3434	==2274== definitely lost: 0 bytes in 0 blocks.
		3435	==2274== possibly lost: 0 bytes in 0 blocks.
		3436	==2274== still reachable: 256 bytes in 1 blocks.
3198		3437
3199	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3438	Then there is no memory leak, just as memory accounted to global variables
		3439	is not a memleak - the memory is still being refernced, and didn't leak.
3200		3440
3201	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3441	Similarly, under some circumstances, valgrind might report kernel bugs
		3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3443	although an acceptable workaround has been found here), or it might be
		3444	confused.
3202		3445
3203	These watchers are stored in lists then need to be walked to find the	3446	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3204	correct watcher to remove. The lists are usually short (you don't usually	3447	make it into some kind of religion.
3205	have many watchers waiting for the same fd or signal).
3206		3448
3207	=item Finding the next timer in each loop iteration: O(1)	3449	If you are unsure about something, feel free to contact the mailing list
		3450	with the full valgrind report and an explanation on why you think this
		3451	is a bug in libev (best check the archives, too :). However, don't be
		3452	annoyed when you get a brisk "this is no bug" answer and take the chance
		3453	of learning how to interpret valgrind properly.
3208		3454
3209	By virtue of using a binary or 4-heap, the next timer is always found at a	3455	If you need, for some reason, empty reports from valgrind for your project
3210	fixed position in the storage array.	3456	I suggest using suppression lists.
3211		3457
3212	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3213		3458
3214	A change means an I/O watcher gets started or stopped, which requires	3459	=head1 PORTABILITY NOTES
3215	libev to recalculate its status (and possibly tell the kernel, depending
3216	on backend and wether C<ev_io_set> was used).
3217		3460
3218	=item Activating one watcher (putting it into the pending state): O(1)	3461	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3219
3220	=item Priority handling: O(number_of_priorities)
3221
3222	Priorities are implemented by allocating some space for each
3223	priority. When doing priority-based operations, libev usually has to
3224	linearly search all the priorities, but starting/stopping and activating
3225	watchers becomes O(1) w.r.t. priority handling.
3226
3227	=item Sending an ev_async: O(1)
3228
3229	=item Processing ev_async_send: O(number_of_async_watchers)
3230
3231	=item Processing signals: O(max_signal_number)
3232
3233	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3234	calls in the current loop iteration. Checking for async and signal events
3235	involves iterating over all running async watchers or all signal numbers.
3236
3237	=back
3238
3239
3240	=head1 Win32 platform limitations and workarounds
3241		3462
3242	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3463	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3243	requires, and its I/O model is fundamentally incompatible with the POSIX	3464	requires, and its I/O model is fundamentally incompatible with the POSIX
3244	model. Libev still offers limited functionality on this platform in	3465	model. Libev still offers limited functionality on this platform in
3245	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3466	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3252	way (note also that glib is the slowest event library known to man).	3473	way (note also that glib is the slowest event library known to man).
3253		3474
3254	There is no supported compilation method available on windows except	3475	There is no supported compilation method available on windows except
3255	embedding it into other applications.	3476	embedding it into other applications.
3256		3477
		3478	Not a libev limitation but worth mentioning: windows apparently doesn't
		3479	accept large writes: instead of resulting in a partial write, windows will
		3480	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3481	so make sure you only write small amounts into your sockets (less than a
		3482	megabyte seems safe, but this apparently depends on the amount of memory
		3483	available).
		3484
3257	Due to the many, low, and arbitrary limits on the win32 platform and	3485	Due to the many, low, and arbitrary limits on the win32 platform and
3258	the abysmal performance of winsockets, using a large number of sockets	3486	the abysmal performance of winsockets, using a large number of sockets
3259	is not recommended (and not reasonable). If your program needs to use	3487	is not recommended (and not reasonable). If your program needs to use
3260	more than a hundred or so sockets, then likely it needs to use a totally	3488	more than a hundred or so sockets, then likely it needs to use a totally
3261	different implementation for windows, as libev offers the POSIX readiness	3489	different implementation for windows, as libev offers the POSIX readiness
3262	notification model, which cannot be implemented efficiently on windows	3490	notification model, which cannot be implemented efficiently on windows
3263	(microsoft monopoly games).	3491	(Microsoft monopoly games).
		3492
		3493	A typical way to use libev under windows is to embed it (see the embedding
		3494	section for details) and use the following F<evwrap.h> header file instead
		3495	of F<ev.h>:
		3496
		3497	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3498	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3499
		3500	#include "ev.h"
		3501
		3502	And compile the following F<evwrap.c> file into your project (make sure
		3503	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3504
		3505	#include "evwrap.h"
		3506	#include "ev.c"
3264		3507
3265	=over 4	3508	=over 4
3266		3509
3267	=item The winsocket select function	3510	=item The winsocket select function
3268		3511
3269	The winsocket C<select> function doesn't follow POSIX in that it requires	3512	The winsocket C<select> function doesn't follow POSIX in that it
3270	socket I<handles> and not socket I<file descriptors>. This makes select	3513	requires socket I<handles> and not socket I<file descriptors> (it is
3271	very inefficient, and also requires a mapping from file descriptors	3514	also extremely buggy). This makes select very inefficient, and also
3272	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	3515	requires a mapping from file descriptors to socket handles (the Microsoft
3273	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	3516	C runtime provides the function C<_open_osfhandle> for this). See the
3274	symbols for more info.	3517	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3518	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3275		3519
3276	The configuration for a "naked" win32 using the microsoft runtime	3520	The configuration for a "naked" win32 using the Microsoft runtime
3277	libraries and raw winsocket select is:	3521	libraries and raw winsocket select is:
3278		3522
3279	#define EV_USE_SELECT 1	3523	#define EV_USE_SELECT 1
3280	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3524	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3281		3525
3282	Note that winsockets handling of fd sets is O(n), so you can easily get a	3526	Note that winsockets handling of fd sets is O(n), so you can easily get a
3283	complexity in the O(n²) range when using win32.	3527	complexity in the O(n²) range when using win32.
3284		3528
3285	=item Limited number of file descriptors	3529	=item Limited number of file descriptors
3286		3530
3287	Windows has numerous arbitrary (and low) limits on things.	3531	Windows has numerous arbitrary (and low) limits on things.
3288		3532
3289	Early versions of winsocket's select only supported waiting for a maximum	3533	Early versions of winsocket's select only supported waiting for a maximum
3290	of C<64> handles (probably owning to the fact that all windows kernels	3534	of C<64> handles (probably owning to the fact that all windows kernels
3291	can only wait for C<64> things at the same time internally; microsoft	3535	can only wait for C<64> things at the same time internally; Microsoft
3292	recommends spawning a chain of threads and wait for 63 handles and the	3536	recommends spawning a chain of threads and wait for 63 handles and the
3293	previous thread in each. Great).	3537	previous thread in each. Great).
3294		3538
3295	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3539	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3296	to some high number (e.g. C<2048>) before compiling the winsocket select	3540	to some high number (e.g. C<2048>) before compiling the winsocket select
3297	call (which might be in libev or elsewhere, for example, perl does its own	3541	call (which might be in libev or elsewhere, for example, perl does its own
3298	select emulation on windows).	3542	select emulation on windows).
3299		3543
3300	Another limit is the number of file descriptors in the microsoft runtime	3544	Another limit is the number of file descriptors in the Microsoft runtime
3301	libraries, which by default is C<64> (there must be a hidden I<64> fetish	3545	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3302	or something like this inside microsoft). You can increase this by calling	3546	or something like this inside Microsoft). You can increase this by calling
3303	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3547	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3304	arbitrary limit), but is broken in many versions of the microsoft runtime	3548	arbitrary limit), but is broken in many versions of the Microsoft runtime
3305	libraries.	3549	libraries.
3306		3550
3307	This might get you to about C<512> or C<2048> sockets (depending on	3551	This might get you to about C<512> or C<2048> sockets (depending on
3308	windows version and/or the phase of the moon). To get more, you need to	3552	windows version and/or the phase of the moon). To get more, you need to
3309	wrap all I/O functions and provide your own fd management, but the cost of	3553	wrap all I/O functions and provide your own fd management, but the cost of
3310	calling select (O(n²)) will likely make this unworkable.	3554	calling select (O(n²)) will likely make this unworkable.
3311		3555
3312	=back	3556	=back
3313		3557
3314
3315	=head1 PORTABILITY REQUIREMENTS	3558	=head2 PORTABILITY REQUIREMENTS
3316		3559
3317	In addition to a working ISO-C implementation, libev relies on a few	3560	In addition to a working ISO-C implementation and of course the
3318	additional extensions:	3561	backend-specific APIs, libev relies on a few additional extensions:
3319		3562
3320	=over 4	3563	=over 4
3321		3564
		3565	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3566	calling conventions regardless of C<ev_watcher_type *>.
		3567
		3568	Libev assumes not only that all watcher pointers have the same internal
		3569	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3570	assumes that the same (machine) code can be used to call any watcher
		3571	callback: The watcher callbacks have different type signatures, but libev
		3572	calls them using an C<ev_watcher *> internally.
		3573
3322	=item C<sig_atomic_t volatile> must be thread-atomic as well	3574	=item C<sig_atomic_t volatile> must be thread-atomic as well
3323		3575
3324	The type C<sig_atomic_t volatile> (or whatever is defined as	3576	The type C<sig_atomic_t volatile> (or whatever is defined as
3325	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3577	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3326	threads. This is not part of the specification for C<sig_atomic_t>, but is	3578	threads. This is not part of the specification for C<sig_atomic_t>, but is
3327	believed to be sufficiently portable.	3579	believed to be sufficiently portable.
3328		3580
3329	=item C<sigprocmask> must work in a threaded environment	3581	=item C<sigprocmask> must work in a threaded environment
3330		3582
…		…
3339	except the initial one, and run the default loop in the initial thread as	3591	except the initial one, and run the default loop in the initial thread as
3340	well.	3592	well.
3341		3593
3342	=item C<long> must be large enough for common memory allocation sizes	3594	=item C<long> must be large enough for common memory allocation sizes
3343		3595
3344	To improve portability and simplify using libev, libev uses C<long>	3596	To improve portability and simplify its API, libev uses C<long> internally
3345	internally instead of C<size_t> when allocating its data structures. On	3597	instead of C<size_t> when allocating its data structures. On non-POSIX
3346	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3598	systems (Microsoft...) this might be unexpectedly low, but is still at
3347	is still at least 31 bits everywhere, which is enough for hundreds of	3599	least 31 bits everywhere, which is enough for hundreds of millions of
3348	millions of watchers.	3600	watchers.
3349		3601
3350	=item C<double> must hold a time value in seconds with enough accuracy	3602	=item C<double> must hold a time value in seconds with enough accuracy
3351		3603
3352	The type C<double> is used to represent timestamps. It is required to	3604	The type C<double> is used to represent timestamps. It is required to
3353	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3605	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3357	=back	3609	=back
3358		3610
3359	If you know of other additional requirements drop me a note.	3611	If you know of other additional requirements drop me a note.
3360		3612
3361		3613
3362	=head1 VALGRIND	3614	=head1 ALGORITHMIC COMPLEXITIES
3363		3615
3364	Valgrind has a special section here because it is a popular tool that is	3616	In this section the complexities of (many of) the algorithms used inside
3365	highly useful, but valgrind reports are very hard to interpret.	3617	libev will be documented. For complexity discussions about backends see
		3618	the documentation for C<ev_default_init>.
3366		3619
3367	If you think you found a bug (memory leak, uninitialised data access etc.)	3620	All of the following are about amortised time: If an array needs to be
3368	in libev, then check twice: If valgrind reports something like:	3621	extended, libev needs to realloc and move the whole array, but this
		3622	happens asymptotically rarer with higher number of elements, so O(1) might
		3623	mean that libev does a lengthy realloc operation in rare cases, but on
		3624	average it is much faster and asymptotically approaches constant time.
3369		3625
3370	==2274== definitely lost: 0 bytes in 0 blocks.	3626	=over 4
3371	==2274== possibly lost: 0 bytes in 0 blocks.
3372	==2274== still reachable: 256 bytes in 1 blocks.
3373		3627
3374	then there is no memory leak. Similarly, under some circumstances,	3628	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3375	valgrind might report kernel bugs as if it were a bug in libev, or it
3376	might be confused (it is a very good tool, but only a tool).
3377		3629
3378	If you are unsure about something, feel free to contact the mailing list	3630	This means that, when you have a watcher that triggers in one hour and
3379	with the full valgrind report and an explanation on why you think this is	3631	there are 100 watchers that would trigger before that, then inserting will
3380	a bug in libev. However, don't be annoyed when you get a brisk "this is	3632	have to skip roughly seven (C<ld 100>) of these watchers.
3381	no bug" answer and take the chance of learning how to interpret valgrind
3382	properly.
3383		3633
3384	If you need, for some reason, empty reports from valgrind for your project	3634	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3385	I suggest using suppression lists.	3635
		3636	That means that changing a timer costs less than removing/adding them,
		3637	as only the relative motion in the event queue has to be paid for.
		3638
		3639	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3640
		3641	These just add the watcher into an array or at the head of a list.
		3642
		3643	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3644
		3645	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3646
		3647	These watchers are stored in lists, so they need to be walked to find the
		3648	correct watcher to remove. The lists are usually short (you don't usually
		3649	have many watchers waiting for the same fd or signal: one is typical, two
		3650	is rare).
		3651
		3652	=item Finding the next timer in each loop iteration: O(1)
		3653
		3654	By virtue of using a binary or 4-heap, the next timer is always found at a
		3655	fixed position in the storage array.
		3656
		3657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3658
		3659	A change means an I/O watcher gets started or stopped, which requires
		3660	libev to recalculate its status (and possibly tell the kernel, depending
		3661	on backend and whether C<ev_io_set> was used).
		3662
		3663	=item Activating one watcher (putting it into the pending state): O(1)
		3664
		3665	=item Priority handling: O(number_of_priorities)
		3666
		3667	Priorities are implemented by allocating some space for each
		3668	priority. When doing priority-based operations, libev usually has to
		3669	linearly search all the priorities, but starting/stopping and activating
		3670	watchers becomes O(1) with respect to priority handling.
		3671
		3672	=item Sending an ev_async: O(1)
		3673
		3674	=item Processing ev_async_send: O(number_of_async_watchers)
		3675
		3676	=item Processing signals: O(max_signal_number)
		3677
		3678	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3679	calls in the current loop iteration. Checking for async and signal events
		3680	involves iterating over all running async watchers or all signal numbers.
		3681
		3682	=back
3386		3683
3387		3684
3388	=head1 AUTHOR	3685	=head1 AUTHOR
3389		3686
3390	Marc Lehmann <libev@schmorp.de>.	3687	Marc Lehmann <libev@schmorp.de>.

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