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Revision 1.161 by root, Sat May 24 03:08:03 2008 UTC vs.
Revision 1.257 by root, Wed Jul 15 16:08:24 2009 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	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	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	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on 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	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
178	not a problem.	192	not a problem.
179		193
180	Example: Make sure we haven't accidentally been linked against the wrong	194	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	195	version.
182		196
183	assert (("libev version mismatch",	197	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	198	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	199	&& ev_version_minor () >= EV_VERSION_MINOR));
186		200
187	=item unsigned int ev_supported_backends ()	201	=item unsigned int ev_supported_backends ()
188		202
189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	203	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
190	value) compiled into this binary of libev (independent of their	204	value) compiled into this binary of libev (independent of their
…		…
192	a description of the set values.	206	a description of the set values.
193		207
194	Example: make sure we have the epoll method, because yeah this is cool and	208	Example: make sure we have the epoll method, because yeah this is cool and
195	a must have and can we have a torrent of it please!!!11	209	a must have and can we have a torrent of it please!!!11
196		210
197	assert (("sorry, no epoll, no sex",	211	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	212	ev_supported_backends () & EVBACKEND_EPOLL));
199		213
200	=item unsigned int ev_recommended_backends ()	214	=item unsigned int ev_recommended_backends ()
201		215
202	Return the set of all backends compiled into this binary of libev and also	216	Return the set of all backends compiled into this binary of libev and also
203	recommended for this platform. This set is often smaller than the one	217	recommended for this platform. This set is often smaller than the one
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	229	recommended ones.
216		230
217	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
218		232
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		234
221	Sets the allocation function to use (the prototype is similar - the	235	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	237	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	264	}
251		265
252	...	266	...
253	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
254		268
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		270
257	Set the callback function to call on a retryable system call error (such	271	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	272	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	273	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	274	callback is set, then libev will expect it to remedy the situation, no
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	377	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	378	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	379	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	380	readiness notifications you get per iteration.
363		381
		382	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		383	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		384	C<exceptfds> set on that platform).
		385
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	386	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		387
366	And this is your standard poll(2) backend. It's more complicated	388	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	389	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	390	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	391	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	392	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	393	performance tips.
372		394
		395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		397
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
374		399
375	For few fds, this backend is a bit little slower than poll and select,	400	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	402	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	403	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	404
380	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
382		421
383	While stopping, setting and starting an I/O watcher in the same iteration	422	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	423	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	424	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
388		427	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		428
393	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	430	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
396		440
397	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	442	all kernel versions tested so far.
		443
		444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		445	C<EVBACKEND_POLL>.
399		446
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		448
402	Kqueue deserves special mention, as at the time of this writing, it	449	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	451	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	457	system like NetBSD.
409		458
410	You still can embed kqueue into a normal poll or select backend and use it	459	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	460	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		462
414	It scales in the same way as the epoll backend, but the interface to the	463	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	464	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	465	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	467	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
420		470
421	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
422		472
423	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	474	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	475	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	476	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
		479
		480	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		482	C<NOTE_EOF>.
429		483
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	484	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		485
432	This is not implemented yet (and might never be, unless you send me an	486	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	487	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	500	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	501	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	503	might perform better.
450		504
451	On the positive side, ignoring the spurious readiness notifications, this	505	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
		509
		510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		511	C<EVBACKEND_POLL>.
454		512
455	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
456		514
457	Try all backends (even potentially broken ones that wouldn't be tried	515	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		522
465	If one or more of these are or'ed into the flags value, then only these	523	If one or more of these are or'ed into the flags value, then only these
466	backends will be tried (in the reverse order as listed here). If none are	524	backends will be tried (in the reverse order as listed here). If none are
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		526
469	The most typical usage is like this:	527	Example: This is the most typical usage.
470		528
471	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		531
474	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	533	environment settings to be taken into account:
476		534
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		536
479	Use whatever libev has to offer, but make sure that kqueue is used if	537	Example: Use whatever libev has to offer, but make sure that kqueue is
480	available (warning, breaks stuff, best use only with your own private	538	used if available (warning, breaks stuff, best use only with your own
481	event loop and only if you know the OS supports your types of fds):	539	private event loop and only if you know the OS supports your types of
		540	fds):
482		541
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		543
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		545
487	Similar to C<ev_default_loop>, but always creates a new event loop that is	546	Similar to C<ev_default_loop>, but always creates a new event loop that is
488	always distinct from the default loop. Unlike the default loop, it cannot	547	always distinct from the default loop. Unlike the default loop, it cannot
…		…
493	libev with threads is indeed to create one loop per thread, and using the	552	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.	553	default loop in the "main" or "initial" thread.
495		554
496	Example: Try to create a event loop that uses epoll and nothing else.	555	Example: Try to create a event loop that uses epoll and nothing else.
497		556
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	558	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	559	fatal ("no epoll found here, maybe it hides under your chair");
501		560
502	=item ev_default_destroy ()	561	=item ev_default_destroy ()
503		562
504	Destroys the default loop again (frees all memory and kernel state	563	Destroys the default loop again (frees all memory and kernel state
505	etc.). None of the active event watchers will be stopped in the normal	564	etc.). None of the active event watchers will be stopped in the normal
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	567	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	569	for example).
511		570
512	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
515		574
516	In general it is not advisable to call this function except in the	575	In general it is not advisable to call this function except in the
517	rare occasion where you really need to free e.g. the signal handling	576	rare occasion where you really need to free e.g. the signal handling
518	pipe fds. If you need dynamically allocated loops it is better to use	577	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		603
545	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
546		605
547	Like C<ev_default_fork>, but acts on an event loop created by	606	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
550		610
551	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
552		612
553	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
554		615
555	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
556		617
557	Returns the count of loop iterations for the loop, which is identical to	618	Returns the count of loop iterations for the loop, which is identical to
558	the number of times libev did poll for new events. It starts at C<0> and	619	the number of times libev did poll for new events. It starts at C<0> and
559	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
560		621
561	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
564		637
565	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
566		639
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	641	use.
…		…
573	received events and started processing them. This timestamp does not	646	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	647	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	648	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	649	event occurring (or more correctly, libev finding out about it).
577		650
		651	=item ev_now_update (loop)
		652
		653	Establishes the current time by querying the kernel, updating the time
		654	returned by C<ev_now ()> in the progress. This is a costly operation and
		655	is usually done automatically within C<ev_loop ()>.
		656
		657	This function is rarely useful, but when some event callback runs for a
		658	very long time without entering the event loop, updating libev's idea of
		659	the current time is a good idea.
		660
		661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
		688
578	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
579		690
580	Finally, this is it, the event handler. This function usually is called	691	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	692	after you initialised all your watchers and you want to start handling
582	events.	693	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	695	If the flags argument is specified as C<0>, it will not return until
585	either no event watchers are active anymore or C<ev_unloop> was called.	696	either no event watchers are active anymore or C<ev_unloop> was called.
586		697
587	Please note that an explicit C<ev_unloop> is usually better than	698	Please note that an explicit C<ev_unloop> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	699	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	701	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	702	of relying on its watchers stopping correctly, that is truly a thing of
		703	beauty.
592		704
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	706	those events and any already outstanding ones, but will not block your
595	case there are no events and will return after one iteration of the loop.	707	process in case there are no events and will return after one iteration of
		708	the loop.
596		709
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	711	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	712	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	713	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	714	user-registered callback will be called), and will return after one
		715	iteration of the loop.
		716
		717	This is useful if you are waiting for some external event in conjunction
		718	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	720	usually a better approach for this kind of thing.
604		721
605	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
606		723
607	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	725	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	726	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	727	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	728	- If we have been forked, detach and recreate the kernel state
		729	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	730	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	731	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	732	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	733	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	739	- Queue all expired timers.
622	- Queue all outstanding periodics.	740	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	742	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	743	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	744	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	745	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	746	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	751	anymore.
634		752
635	... queue jobs here, make sure they register event watchers as long	753	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	754	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	755	ev_loop (my_loop, 0);
638	... jobs done. yeah!	756	... jobs done or somebody called unloop. yeah!
639		757
640	=item ev_unloop (loop, how)	758	=item ev_unloop (loop, how)
641		759
642	Can be used to make a call to C<ev_loop> return early (but only after it	760	Can be used to make a call to C<ev_loop> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	761	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		764
647	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
648		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
649	=item ev_ref (loop)	769	=item ev_ref (loop)
650		770
651	=item ev_unref (loop)	771	=item ev_unref (loop)
652		772
653	Ref/unref can be used to add or remove a reference count on the event	773	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	774	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	775	count is nonzero, C<ev_loop> will not return on its own.
		776
656	a watcher you never unregister that should not keep C<ev_loop> from	777	If you have a watcher you never unregister that should not keep C<ev_loop>
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	778	from returning, call ev_unref() after starting, and ev_ref() before
		779	stopping it.
		780
658	example, libev itself uses this for its internal signal pipe: It is not	781	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	782	is not visible to the libev user and should not keep C<ev_loop> from
660	no event watchers registered by it are active. It is also an excellent	783	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	784	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	785	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	786	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
665		790
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	792	running when nothing else is active.
668		793
669	struct ev_signal exitsig;	794	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	797	evf_unref (loop);
673		798
674	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
675		800
676	ev_ref (loop);	801	ev_ref (loop);
677	ev_signal_stop (loop, &exitsig);	802	ev_signal_stop (loop, &exitsig);
678		803
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	804	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		805
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	806	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		807
683	These advanced functions influence the time that libev will spend waiting	808	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	809	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	810	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		811	latency.
686		812
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	813	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	814	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	815	to increase efficiency of loop iterations (or to increase power-saving
		816	opportunities).
690		817
691	The background is that sometimes your program runs just fast enough to	818	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	819	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	820	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	821	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	822	overhead for the actual polling but can deliver many events at once.
696		823
697	By setting a higher I<io collect interval> you allow libev to spend more	824	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	825	time collecting I/O events, so you can handle more events per iteration,
699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
702		831
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	836	value will not introduce any overhead in libev.
708		837
709	Many (busy) programs can usually benefit by setting the I/O collect	838	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	839	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
		847
		848	Setting the I<timeout collect interval> can improve the opportunity for
		849	saving power, as the program will "bundle" timer callback invocations that
		850	are "near" in time together, by delaying some, thus reducing the number of
		851	times the process sleeps and wakes up again. Another useful technique to
		852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		853	they fire on, say, one-second boundaries only.
		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
		861	=item ev_invoke_pending (loop)
		862
		863	This call will simply invoke all pending watchers while resetting their
		864	pending state. Normally, C<ev_loop> does this automatically when required,
		865	but when overriding the invoke callback this call comes handy.
		866
		867	=item int ev_pending_count (loop)
		868
		869	Returns the number of pending watchers - zero indicates that no watchers
		870	are pending.
		871
		872	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		873
		874	This overrides the invoke pending functionality of the loop: Instead of
		875	invoking all pending watchers when there are any, C<ev_loop> will call
		876	this callback instead. This is useful, for example, when you want to
		877	invoke the actual watchers inside another context (another thread etc.).
		878
		879	If you want to reset the callback, use C<ev_invoke_pending> as new
		880	callback.
		881
		882	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		883
		884	Sometimes you want to share the same loop between multiple threads. This
		885	can be done relatively simply by putting mutex_lock/unlock calls around
		886	each call to a libev function.
		887
		888	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		889	wait for it to return. One way around this is to wake up the loop via
		890	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		891	and I<acquire> callbacks on the loop.
		892
		893	When set, then C<release> will be called just before the thread is
		894	suspended waiting for new events, and C<acquire> is called just
		895	afterwards.
		896
		897	Ideally, C<release> will just call your mutex_unlock function, and
		898	C<acquire> will just call the mutex_lock function again.
		899
		900	While event loop modifications are allowed between invocations of
		901	C<release> and C<acquire> (that's their only purpose after all), no
		902	modifications done will affect the event loop, i.e. adding watchers will
		903	have no effect on the set of file descriptors being watched, or the time
		904	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		905	to take note of any changes you made.
		906
		907	In theory, threads executing C<ev_loop> will be async-cancel safe between
		908	invocations of C<release> and C<acquire>.
		909
		910	See also the locking example in the C<THREADS> section later in this
		911	document.
		912
		913	=item ev_set_userdata (loop, void *data)
		914
		915	=item ev_userdata (loop)
		916
		917	Set and retrieve a single C<void *> associated with a loop. When
		918	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		919	C<0.>
		920
		921	These two functions can be used to associate arbitrary data with a loop,
		922	and are intended solely for the C<invoke_pending_cb>, C<release> and
		923	C<acquire> callbacks described above, but of course can be (ab-)used for
		924	any other purpose as well.
714		925
715	=item ev_loop_verify (loop)	926	=item ev_loop_verify (loop)
716		927
717	This function only does something when C<EV_VERIFY> support has been	928	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	929	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	930	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	931	is found to be inconsistent, it will print an error message to standard
		932	error and call C<abort ()>.
721		933
722	This can be used to catch bugs inside libev itself: under normal	934	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	935	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	936	data structures consistent.
725		937
726	=back	938	=back
727		939
728		940
729	=head1 ANATOMY OF A WATCHER	941	=head1 ANATOMY OF A WATCHER
730		942
		943	In the following description, uppercase C<TYPE> in names stands for the
		944	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		945	watchers and C<ev_io_start> for I/O watchers.
		946
731	A watcher is a structure that you create and register to record your	947	A watcher is a structure that you create and register to record your
732	interest in some event. For instance, if you want to wait for STDIN to	948	interest in some event. For instance, if you want to wait for STDIN to
733	become readable, you would create an C<ev_io> watcher for that:	949	become readable, you would create an C<ev_io> watcher for that:
734		950
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	951	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	952	{
737	ev_io_stop (w);	953	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	954	ev_unloop (loop, EVUNLOOP_ALL);
739	}	955	}
740		956
741	struct ev_loop *loop = ev_default_loop (0);	957	struct ev_loop *loop = ev_default_loop (0);
		958
742	struct ev_io stdin_watcher;	959	ev_io stdin_watcher;
		960
743	ev_init (&stdin_watcher, my_cb);	961	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	962	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	963	ev_io_start (loop, &stdin_watcher);
		964
746	ev_loop (loop, 0);	965	ev_loop (loop, 0);
747		966
748	As you can see, you are responsible for allocating the memory for your	967	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	968	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	969	stack).
		970
		971	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		972	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		973
752	Each watcher structure must be initialised by a call to C<ev_init	974	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	975	(watcher *, callback)>, which expects a callback to be provided. This
754	callback gets invoked each time the event occurs (or, in the case of I/O	976	callback gets invoked each time the event occurs (or, in the case of I/O
755	watchers, each time the event loop detects that the file descriptor given	977	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	978	is readable and/or writable).
757		979
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	980	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	981	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	982	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	983	ev_TYPE_init (watcher *, callback, ...) >>.
762		984
763	To make the watcher actually watch out for events, you have to start it	985	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	986	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	987	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	988	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		989
768	As long as your watcher is active (has been started but not stopped) you	990	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	991	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	992	reinitialise it or call its C<ev_TYPE_set> macro.
771		993
772	Each and every callback receives the event loop pointer as first, the	994	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	995	registered watcher structure as second, and a bitset of received events as
774	third argument.	996	third argument.
775		997
…		…
833		1055
834	=item C<EV_ASYNC>	1056	=item C<EV_ASYNC>
835		1057
836	The given async watcher has been asynchronously notified (see C<ev_async>).	1058	The given async watcher has been asynchronously notified (see C<ev_async>).
837		1059
		1060	=item C<EV_CUSTOM>
		1061
		1062	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1063	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1064
838	=item C<EV_ERROR>	1065	=item C<EV_ERROR>
839		1066
840	An unspecified error has occurred, the watcher has been stopped. This might	1067	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	1068	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	1069	ran out of memory, a file descriptor was found to be closed or any other
		1070	problem. Libev considers these application bugs.
		1071
843	problem. You best act on it by reporting the problem and somehow coping	1072	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	1073	watcher being stopped. Note that well-written programs should not receive
		1074	an error ever, so when your watcher receives it, this usually indicates a
		1075	bug in your program.
845		1076
846	Libev will usually signal a few "dummy" events together with an error,	1077	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	1078	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	1079	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	1080	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	1081	programs, though, as the fd could already be closed and reused for another
		1082	thing, so beware.
851		1083
852	=back	1084	=back
853		1085
854	=head2 GENERIC WATCHER FUNCTIONS	1086	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		1087
859	=over 4	1088	=over 4
860		1089
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1090	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1091
…		…
868	which rolls both calls into one.	1097	which rolls both calls into one.
869		1098
870	You can reinitialise a watcher at any time as long as it has been stopped	1099	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1100	(or never started) and there are no pending events outstanding.
872		1101
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1102	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1103	int revents)>.
		1104
		1105	Example: Initialise an C<ev_io> watcher in two steps.
		1106
		1107	ev_io w;
		1108	ev_init (&w, my_cb);
		1109	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		1110
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1111	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		1112
878	This macro initialises the type-specific parts of a watcher. You need to	1113	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1114	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	1117	difference to the C<ev_init> macro).
883		1118
884	Although some watcher types do not have type-specific arguments	1119	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1120	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1121
		1122	See C<ev_init>, above, for an example.
		1123
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1124	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1125
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1126	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1127	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1128	a watcher. The same limitations apply, of course.
892		1129
		1130	Example: Initialise and set an C<ev_io> watcher in one step.
		1131
		1132	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1133
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1134	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		1135
895	Starts (activates) the given watcher. Only active watchers will receive	1136	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1137	events. If the watcher is already active nothing will happen.
897		1138
		1139	Example: Start the C<ev_io> watcher that is being abused as example in this
		1140	whole section.
		1141
		1142	ev_io_start (EV_DEFAULT_UC, &w);
		1143
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1144	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		1145
900	Stops the given watcher again (if active) and clears the pending	1146	Stops the given watcher if active, and clears the pending status (whether
		1147	the watcher was active or not).
		1148
901	status. It is possible that stopped watchers are pending (for example,	1149	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1150	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1151	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1152	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1153	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1154
907	=item bool ev_is_active (ev_TYPE *watcher)	1155	=item bool ev_is_active (ev_TYPE *watcher)
908		1156
909	Returns a true value iff the watcher is active (i.e. it has been started	1157	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1158	and not yet been stopped). As long as a watcher is active you must not modify
…		…
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1184	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1185	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1186	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1187	from being executed (except for C<ev_idle> watchers).
940		1188
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1189	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1190	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1191
949	You I<must not> change the priority of a watcher as long as it is active or	1192	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1193	pending.
951		1194
		1195	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1196	fine, as long as you do not mind that the priority value you query might
		1197	or might not have been clamped to the valid range.
		1198
952	The default priority used by watchers when no priority has been set is	1199	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1200	always C<0>, which is supposed to not be too high and not be too low :).
954		1201
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1202	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1203	priorities.
957	or might not have been adjusted to be within valid range.
958		1204
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1205	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1206
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1207	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1208	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1209	can deal with that fact, as both are simply passed through to the
		1210	callback.
964		1211
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1212	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1213
967	If the watcher is pending, this function returns clears its pending status	1214	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1215	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1216	watcher isn't pending it does nothing and returns C<0>.
970		1217
		1218	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1219	callback to be invoked, which can be accomplished with this function.
		1220
971	=back	1221	=back
972		1222
973		1223
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1224	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1225
976	Each watcher has, by default, a member C<void *data> that you can change	1226	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1227	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1228	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1229	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1230	member, you can also "subclass" the watcher type and provide your own
981	data:	1231	data:
982		1232
983	struct my_io	1233	struct my_io
984	{	1234	{
985	struct ev_io io;	1235	ev_io io;
986	int otherfd;	1236	int otherfd;
987	void *somedata;	1237	void *somedata;
988	struct whatever *mostinteresting;	1238	struct whatever *mostinteresting;
989	}	1239	};
		1240
		1241	...
		1242	struct my_io w;
		1243	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1244
991	And since your callback will be called with a pointer to the watcher, you	1245	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1246	can cast it back to your own type:
993		1247
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1248	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1249	{
996	struct my_io *w = (struct my_io *)w_;	1250	struct my_io *w = (struct my_io *)w_;
997	...	1251	...
998	}	1252	}
999		1253
1000	More interesting and less C-conformant ways of casting your callback type	1254	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1255	instead have been omitted.
1002		1256
1003	Another common scenario is having some data structure with multiple	1257	Another common scenario is to use some data structure with multiple
1004	watchers:	1258	embedded watchers:
1005		1259
1006	struct my_biggy	1260	struct my_biggy
1007	{	1261	{
1008	int some_data;	1262	int some_data;
1009	ev_timer t1;	1263	ev_timer t1;
1010	ev_timer t2;	1264	ev_timer t2;
1011	}	1265	}
1012		1266
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1267	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1268	complicated: Either you store the address of your C<my_biggy> struct
		1269	in the C<data> member of the watcher (for woozies), or you need to use
		1270	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1271	programmers):
1015		1272
1016	#include <stddef.h>	1273	#include <stddef.h>
1017		1274
1018	static void	1275	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1276	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1277	{
1021	struct my_biggy big = (struct my_biggy *	1278	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1279	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1280	}
1024		1281
1025	static void	1282	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1283	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1284	{
1028	struct my_biggy big = (struct my_biggy *	1285	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1286	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1287	}
		1288
		1289	=head2 WATCHER PRIORITY MODELS
		1290
		1291	Many event loops support I<watcher priorities>, which are usually small
		1292	integers that influence the ordering of event callback invocation
		1293	between watchers in some way, all else being equal.
		1294
		1295	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1296	description for the more technical details such as the actual priority
		1297	range.
		1298
		1299	There are two common ways how these these priorities are being interpreted
		1300	by event loops:
		1301
		1302	In the more common lock-out model, higher priorities "lock out" invocation
		1303	of lower priority watchers, which means as long as higher priority
		1304	watchers receive events, lower priority watchers are not being invoked.
		1305
		1306	The less common only-for-ordering model uses priorities solely to order
		1307	callback invocation within a single event loop iteration: Higher priority
		1308	watchers are invoked before lower priority ones, but they all get invoked
		1309	before polling for new events.
		1310
		1311	Libev uses the second (only-for-ordering) model for all its watchers
		1312	except for idle watchers (which use the lock-out model).
		1313
		1314	The rationale behind this is that implementing the lock-out model for
		1315	watchers is not well supported by most kernel interfaces, and most event
		1316	libraries will just poll for the same events again and again as long as
		1317	their callbacks have not been executed, which is very inefficient in the
		1318	common case of one high-priority watcher locking out a mass of lower
		1319	priority ones.
		1320
		1321	Static (ordering) priorities are most useful when you have two or more
		1322	watchers handling the same resource: a typical usage example is having an
		1323	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1324	timeouts. Under load, data might be received while the program handles
		1325	other jobs, but since timers normally get invoked first, the timeout
		1326	handler will be executed before checking for data. In that case, giving
		1327	the timer a lower priority than the I/O watcher ensures that I/O will be
		1328	handled first even under adverse conditions (which is usually, but not
		1329	always, what you want).
		1330
		1331	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1332	will only be executed when no same or higher priority watchers have
		1333	received events, they can be used to implement the "lock-out" model when
		1334	required.
		1335
		1336	For example, to emulate how many other event libraries handle priorities,
		1337	you can associate an C<ev_idle> watcher to each such watcher, and in
		1338	the normal watcher callback, you just start the idle watcher. The real
		1339	processing is done in the idle watcher callback. This causes libev to
		1340	continously poll and process kernel event data for the watcher, but when
		1341	the lock-out case is known to be rare (which in turn is rare :), this is
		1342	workable.
		1343
		1344	Usually, however, the lock-out model implemented that way will perform
		1345	miserably under the type of load it was designed to handle. In that case,
		1346	it might be preferable to stop the real watcher before starting the
		1347	idle watcher, so the kernel will not have to process the event in case
		1348	the actual processing will be delayed for considerable time.
		1349
		1350	Here is an example of an I/O watcher that should run at a strictly lower
		1351	priority than the default, and which should only process data when no
		1352	other events are pending:
		1353
		1354	ev_idle idle; // actual processing watcher
		1355	ev_io io; // actual event watcher
		1356
		1357	static void
		1358	io_cb (EV_P_ ev_io *w, int revents)
		1359	{
		1360	// stop the I/O watcher, we received the event, but
		1361	// are not yet ready to handle it.
		1362	ev_io_stop (EV_A_ w);
		1363
		1364	// start the idle watcher to ahndle the actual event.
		1365	// it will not be executed as long as other watchers
		1366	// with the default priority are receiving events.
		1367	ev_idle_start (EV_A_ &idle);
		1368	}
		1369
		1370	static void
		1371	idle_cb (EV_P_ ev_idle *w, int revents)
		1372	{
		1373	// actual processing
		1374	read (STDIN_FILENO, ...);
		1375
		1376	// have to start the I/O watcher again, as
		1377	// we have handled the event
		1378	ev_io_start (EV_P_ &io);
		1379	}
		1380
		1381	// initialisation
		1382	ev_idle_init (&idle, idle_cb);
		1383	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1384	ev_io_start (EV_DEFAULT_ &io);
		1385
		1386	In the "real" world, it might also be beneficial to start a timer, so that
		1387	low-priority connections can not be locked out forever under load. This
		1388	enables your program to keep a lower latency for important connections
		1389	during short periods of high load, while not completely locking out less
		1390	important ones.
1031		1391
1032		1392
1033	=head1 WATCHER TYPES	1393	=head1 WATCHER TYPES
1034		1394
1035	This section describes each watcher in detail, but will not repeat	1395	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1419	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1420	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1421	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1422	required if you know what you are doing).
1063		1423
1064	If you must do this, then force the use of a known-to-be-good backend	1424	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1425	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1426	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1427	descriptors for which non-blocking operation makes no sense (such as
		1428	files) - libev doesn't guarentee any specific behaviour in that case.
1067		1429
1068	Another thing you have to watch out for is that it is quite easy to	1430	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1431	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1432	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1433	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1434	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1435	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1436	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1437	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1438
1077	If you cannot run the fd in non-blocking mode (for example you should not	1439	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1440	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1441	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1442	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1443	does this on its own, so its quite safe to use). Some people additionally
		1444	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1445	indefinitely.
		1446
		1447	But really, best use non-blocking mode.
1082		1448
1083	=head3 The special problem of disappearing file descriptors	1449	=head3 The special problem of disappearing file descriptors
1084		1450
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1451	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1452	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1453	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1454	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1455	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1456	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1457	fact, a different file descriptor.
1092		1458
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1489	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1490	C<EVBACKEND_POLL>.
1125		1491
1126	=head3 The special problem of SIGPIPE	1492	=head3 The special problem of SIGPIPE
1127		1493
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1494	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1495	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1496	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1497	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1498
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1499	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1500	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1501	somewhere, as that would have given you a big clue).
1137		1502
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1508	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1509
1145	=item ev_io_set (ev_io *, int fd, int events)	1510	=item ev_io_set (ev_io *, int fd, int events)
1146		1511
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1512	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1513	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1514	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1515
1151	=item int fd [read-only]	1516	=item int fd [read-only]
1152		1517
1153	The file descriptor being watched.	1518	The file descriptor being watched.
1154		1519
…		…
1162		1527
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1528	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1529	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1530	attempt to read a whole line in the callback.
1166		1531
1167	static void	1532	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1533	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1534	{
1170	ev_io_stop (loop, w);	1535	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1536	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1537	}
1173		1538
1174	...	1539	...
1175	struct ev_loop *loop = ev_default_init (0);	1540	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1541	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1542	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1543	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1544	ev_loop (loop, 0);
1180		1545
1181		1546
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1547	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1548
1184	Timer watchers are simple relative timers that generate an event after a	1549	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1550	given time, and optionally repeating in regular intervals after that.
1186		1551
1187	The timers are based on real time, that is, if you register an event that	1552	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1553	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1554	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1555	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1556	monotonic clock option helps a lot here).
		1557
		1558	The callback is guaranteed to be invoked only I<after> its timeout has
		1559	passed (not I<at>, so on systems with very low-resolution clocks this
		1560	might introduce a small delay). If multiple timers become ready during the
		1561	same loop iteration then the ones with earlier time-out values are invoked
		1562	before ones of the same priority with later time-out values (but this is
		1563	no longer true when a callback calls C<ev_loop> recursively).
		1564
		1565	=head3 Be smart about timeouts
		1566
		1567	Many real-world problems involve some kind of timeout, usually for error
		1568	recovery. A typical example is an HTTP request - if the other side hangs,
		1569	you want to raise some error after a while.
		1570
		1571	What follows are some ways to handle this problem, from obvious and
		1572	inefficient to smart and efficient.
		1573
		1574	In the following, a 60 second activity timeout is assumed - a timeout that
		1575	gets reset to 60 seconds each time there is activity (e.g. each time some
		1576	data or other life sign was received).
		1577
		1578	=over 4
		1579
		1580	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1581
		1582	This is the most obvious, but not the most simple way: In the beginning,
		1583	start the watcher:
		1584
		1585	ev_timer_init (timer, callback, 60., 0.);
		1586	ev_timer_start (loop, timer);
		1587
		1588	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1589	and start it again:
		1590
		1591	ev_timer_stop (loop, timer);
		1592	ev_timer_set (timer, 60., 0.);
		1593	ev_timer_start (loop, timer);
		1594
		1595	This is relatively simple to implement, but means that each time there is
		1596	some activity, libev will first have to remove the timer from its internal
		1597	data structure and then add it again. Libev tries to be fast, but it's
		1598	still not a constant-time operation.
		1599
		1600	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1601
		1602	This is the easiest way, and involves using C<ev_timer_again> instead of
		1603	C<ev_timer_start>.
		1604
		1605	To implement this, configure an C<ev_timer> with a C<repeat> value
		1606	of C<60> and then call C<ev_timer_again> at start and each time you
		1607	successfully read or write some data. If you go into an idle state where
		1608	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1609	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1610
		1611	That means you can ignore both the C<ev_timer_start> function and the
		1612	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1613	member and C<ev_timer_again>.
		1614
		1615	At start:
		1616
		1617	ev_init (timer, callback);
		1618	timer->repeat = 60.;
		1619	ev_timer_again (loop, timer);
		1620
		1621	Each time there is some activity:
		1622
		1623	ev_timer_again (loop, timer);
		1624
		1625	It is even possible to change the time-out on the fly, regardless of
		1626	whether the watcher is active or not:
		1627
		1628	timer->repeat = 30.;
		1629	ev_timer_again (loop, timer);
		1630
		1631	This is slightly more efficient then stopping/starting the timer each time
		1632	you want to modify its timeout value, as libev does not have to completely
		1633	remove and re-insert the timer from/into its internal data structure.
		1634
		1635	It is, however, even simpler than the "obvious" way to do it.
		1636
		1637	=item 3. Let the timer time out, but then re-arm it as required.
		1638
		1639	This method is more tricky, but usually most efficient: Most timeouts are
		1640	relatively long compared to the intervals between other activity - in
		1641	our example, within 60 seconds, there are usually many I/O events with
		1642	associated activity resets.
		1643
		1644	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1645	but remember the time of last activity, and check for a real timeout only
		1646	within the callback:
		1647
		1648	ev_tstamp last_activity; // time of last activity
		1649
		1650	static void
		1651	callback (EV_P_ ev_timer *w, int revents)
		1652	{
		1653	ev_tstamp now = ev_now (EV_A);
		1654	ev_tstamp timeout = last_activity + 60.;
		1655
		1656	// if last_activity + 60. is older than now, we did time out
		1657	if (timeout < now)
		1658	{
		1659	// timeout occured, take action
		1660	}
		1661	else
		1662	{
		1663	// callback was invoked, but there was some activity, re-arm
		1664	// the watcher to fire in last_activity + 60, which is
		1665	// guaranteed to be in the future, so "again" is positive:
		1666	w->repeat = timeout - now;
		1667	ev_timer_again (EV_A_ w);
		1668	}
		1669	}
		1670
		1671	To summarise the callback: first calculate the real timeout (defined
		1672	as "60 seconds after the last activity"), then check if that time has
		1673	been reached, which means something I<did>, in fact, time out. Otherwise
		1674	the callback was invoked too early (C<timeout> is in the future), so
		1675	re-schedule the timer to fire at that future time, to see if maybe we have
		1676	a timeout then.
		1677
		1678	Note how C<ev_timer_again> is used, taking advantage of the
		1679	C<ev_timer_again> optimisation when the timer is already running.
		1680
		1681	This scheme causes more callback invocations (about one every 60 seconds
		1682	minus half the average time between activity), but virtually no calls to
		1683	libev to change the timeout.
		1684
		1685	To start the timer, simply initialise the watcher and set C<last_activity>
		1686	to the current time (meaning we just have some activity :), then call the
		1687	callback, which will "do the right thing" and start the timer:
		1688
		1689	ev_init (timer, callback);
		1690	last_activity = ev_now (loop);
		1691	callback (loop, timer, EV_TIMEOUT);
		1692
		1693	And when there is some activity, simply store the current time in
		1694	C<last_activity>, no libev calls at all:
		1695
		1696	last_actiivty = ev_now (loop);
		1697
		1698	This technique is slightly more complex, but in most cases where the
		1699	time-out is unlikely to be triggered, much more efficient.
		1700
		1701	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1702	callback :) - just change the timeout and invoke the callback, which will
		1703	fix things for you.
		1704
		1705	=item 4. Wee, just use a double-linked list for your timeouts.
		1706
		1707	If there is not one request, but many thousands (millions...), all
		1708	employing some kind of timeout with the same timeout value, then one can
		1709	do even better:
		1710
		1711	When starting the timeout, calculate the timeout value and put the timeout
		1712	at the I<end> of the list.
		1713
		1714	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1715	the list is expected to fire (for example, using the technique #3).
		1716
		1717	When there is some activity, remove the timer from the list, recalculate
		1718	the timeout, append it to the end of the list again, and make sure to
		1719	update the C<ev_timer> if it was taken from the beginning of the list.
		1720
		1721	This way, one can manage an unlimited number of timeouts in O(1) time for
		1722	starting, stopping and updating the timers, at the expense of a major
		1723	complication, and having to use a constant timeout. The constant timeout
		1724	ensures that the list stays sorted.
		1725
		1726	=back
		1727
		1728	So which method the best?
		1729
		1730	Method #2 is a simple no-brain-required solution that is adequate in most
		1731	situations. Method #3 requires a bit more thinking, but handles many cases
		1732	better, and isn't very complicated either. In most case, choosing either
		1733	one is fine, with #3 being better in typical situations.
		1734
		1735	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1736	rather complicated, but extremely efficient, something that really pays
		1737	off after the first million or so of active timers, i.e. it's usually
		1738	overkill :)
		1739
		1740	=head3 The special problem of time updates
		1741
		1742	Establishing the current time is a costly operation (it usually takes at
		1743	least two system calls): EV therefore updates its idea of the current
		1744	time only before and after C<ev_loop> collects new events, which causes a
		1745	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1746	lots of events in one iteration.
1192		1747
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1748	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1749	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1750	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1751	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1752	timeout on the current time, use something like this to adjust for this:
1198		1753
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1754	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1755
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1756	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1757	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1758	()>.
		1759
		1760	=head3 The special problems of suspended animation
		1761
		1762	When you leave the server world it is quite customary to hit machines that
		1763	can suspend/hibernate - what happens to the clocks during such a suspend?
		1764
		1765	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1766	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1767	to run until the system is suspended, but they will not advance while the
		1768	system is suspended. That means, on resume, it will be as if the program
		1769	was frozen for a few seconds, but the suspend time will not be counted
		1770	towards C<ev_timer> when a monotonic clock source is used. The real time
		1771	clock advanced as expected, but if it is used as sole clocksource, then a
		1772	long suspend would be detected as a time jump by libev, and timers would
		1773	be adjusted accordingly.
		1774
		1775	I would not be surprised to see different behaviour in different between
		1776	operating systems, OS versions or even different hardware.
		1777
		1778	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1779	time jump in the monotonic clocks and the realtime clock. If the program
		1780	is suspended for a very long time, and monotonic clock sources are in use,
		1781	then you can expect C<ev_timer>s to expire as the full suspension time
		1782	will be counted towards the timers. When no monotonic clock source is in
		1783	use, then libev will again assume a timejump and adjust accordingly.
		1784
		1785	It might be beneficial for this latter case to call C<ev_suspend>
		1786	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1787	deterministic behaviour in this case (you can do nothing against
		1788	C<SIGSTOP>).
1204		1789
1205	=head3 Watcher-Specific Functions and Data Members	1790	=head3 Watcher-Specific Functions and Data Members
1206		1791
1207	=over 4	1792	=over 4
1208		1793
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1817	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1818
1234	If the timer is repeating, either start it if necessary (with the	1819	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1820	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1821
1237	This sounds a bit complicated, but here is a useful and typical	1822	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1823	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246
1247	That means you can ignore the C<after> value and C<ev_timer_start>
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249
1250	ev_timer_init (timer, callback, 0., 5.);
1251	ev_timer_again (loop, timer);
1252	...
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258
1259	This is more slightly efficient then stopping/starting the timer each time
1260	you want to modify its timeout value.
1261		1824
1262	=item ev_tstamp repeat [read-write]	1825	=item ev_tstamp repeat [read-write]
1263		1826
1264	The current C<repeat> value. Will be used each time the watcher times out	1827	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	1828	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	1829	which is also when any modifications are taken into account.
1267		1830
1268	=back	1831	=back
1269		1832
1270	=head3 Examples	1833	=head3 Examples
1271		1834
1272	Example: Create a timer that fires after 60 seconds.	1835	Example: Create a timer that fires after 60 seconds.
1273		1836
1274	static void	1837	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1838	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1839	{
1277	.. one minute over, w is actually stopped right here	1840	.. one minute over, w is actually stopped right here
1278	}	1841	}
1279		1842
1280	struct ev_timer mytimer;	1843	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1844	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1845	ev_timer_start (loop, &mytimer);
1283		1846
1284	Example: Create a timeout timer that times out after 10 seconds of	1847	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1848	inactivity.
1286		1849
1287	static void	1850	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1851	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1852	{
1290	.. ten seconds without any activity	1853	.. ten seconds without any activity
1291	}	1854	}
1292		1855
1293	struct ev_timer mytimer;	1856	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1857	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1858	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1859	ev_loop (loop, 0);
1297		1860
1298	// and in some piece of code that gets executed on any "activity":	1861	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	1862	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	1863	ev_timer_again (&mytimer);
1301		1864
1302		1865
1303	=head2 C<ev_periodic> - to cron or not to cron?	1866	=head2 C<ev_periodic> - to cron or not to cron?
1304		1867
1305	Periodic watchers are also timers of a kind, but they are very versatile	1868	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	1869	(and unfortunately a bit complex).
1307		1870
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1871	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	1872	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	1873	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1874	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	1875	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	1876	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		1877
		1878	You can tell a periodic watcher to trigger after some specific point
		1879	in time: for example, if you tell a periodic watcher to trigger "in 10
		1880	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1881	not a delay) and then reset your system clock to January of the previous
		1882	year, then it will take a year or more to trigger the event (unlike an
		1883	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1884	it, as it uses a relative timeout).
		1885
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1886	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	1887	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	1888	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1889	those cannot react to time jumps.
1320		1890
1321	As with timers, the callback is guaranteed to be invoked only when the	1891	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	1892	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	1893	timers become ready during the same loop iteration then the ones with
		1894	earlier time-out values are invoked before ones with later time-out values
		1895	(but this is no longer true when a callback calls C<ev_loop> recursively).
1324		1896
1325	=head3 Watcher-Specific Functions and Data Members	1897	=head3 Watcher-Specific Functions and Data Members
1326		1898
1327	=over 4	1899	=over 4
1328		1900
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1901	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		1902
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1903	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		1904
1333	Lots of arguments, lets sort it out... There are basically three modes of	1905	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1906	operation, and we will explain them from simplest to most complex:
1335		1907
1336	=over 4	1908	=over 4
1337		1909
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1910	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		1911
1340	In this configuration the watcher triggers an event after the wall clock	1912	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	1913	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1914	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	1915	will be stopped and invoked when the system clock reaches or surpasses
		1916	this point in time.
1344		1917
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1918	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		1919
1347	In this mode the watcher will always be scheduled to time out at the next	1920	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	1921	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	1922	negative) and then repeat, regardless of any time jumps. The C<offset>
		1923	argument is merely an offset into the C<interval> periods.
1350		1924
1351	This can be used to create timers that do not drift with respect to system	1925	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	1926	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	1927	hour, on the hour (with respect to UTC):
1354		1928
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1929	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1930
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1931	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	1932	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	1933	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	1934	by 3600.
1361		1935
1362	Another way to think about it (for the mathematically inclined) is that	1936	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	1937	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	1938	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		1939
1366	For numerical stability it is preferable that the C<at> value is near	1940	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	1941	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	1942	this value, and in fact is often specified as zero.
1369		1943
1370	Note also that there is an upper limit to how often a timer can fire (CPU	1944	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	1945	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	1946	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	1947	millisecond (if the OS supports it and the machine is fast enough).
1374		1948
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1949	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		1950
1377	In this mode the values for C<interval> and C<at> are both being	1951	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	1952	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	1953	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	1954	current time as second argument.
1381		1955
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1956	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	1957	or make ANY other event loop modifications whatsoever, unless explicitly
		1958	allowed by documentation here>.
1384		1959
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1960	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1961	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1962	only event loop modification you are allowed to do).
1388		1963
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1964	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1965	*w, ev_tstamp now)>, e.g.:
1391		1966
		1967	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1968	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1969	{
1394	return now + 60.;	1970	return now + 60.;
1395	}	1971	}
1396		1972
1397	It must return the next time to trigger, based on the passed time value	1973	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	1993	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	1994	program when the crontabs have changed).
1419		1995
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	1996	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		1997
1422	When active, returns the absolute time that the watcher is supposed to	1998	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	1999	to trigger next. This is not the same as the C<offset> argument to
		2000	C<ev_periodic_set>, but indeed works even in interval and manual
		2001	rescheduling modes.
1424		2002
1425	=item ev_tstamp offset [read-write]	2003	=item ev_tstamp offset [read-write]
1426		2004
1427	When repeating, this contains the offset value, otherwise this is the	2005	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2006	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2007	although libev might modify this value for better numerical stability).
1429		2008
1430	Can be modified any time, but changes only take effect when the periodic	2009	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	2010	timer fires or C<ev_periodic_again> is being called.
1432		2011
1433	=item ev_tstamp interval [read-write]	2012	=item ev_tstamp interval [read-write]
1434		2013
1435	The current interval value. Can be modified any time, but changes only	2014	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	2015	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	2016	called.
1438		2017
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2018	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		2019
1441	The current reschedule callback, or C<0>, if this functionality is	2020	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	2021	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	2022	the periodic timer fires or C<ev_periodic_again> is being called.
1444		2023
1445	=back	2024	=back
1446		2025
1447	=head3 Examples	2026	=head3 Examples
1448		2027
1449	Example: Call a callback every hour, or, more precisely, whenever the	2028	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	2029	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	2030	potentially a lot of jitter, but good long-term stability.
1452		2031
1453	static void	2032	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2033	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	2034	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	2035	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	2036	}
1458		2037
1459	struct ev_periodic hourly_tick;	2038	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	2040	ev_periodic_start (loop, &hourly_tick);
1462		2041
1463	Example: The same as above, but use a reschedule callback to do it:	2042	Example: The same as above, but use a reschedule callback to do it:
1464		2043
1465	#include <math.h>	2044	#include <math.h>
1466		2045
1467	static ev_tstamp	2046	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2047	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	2048	{
1470	return fmod (now, 3600.) + 3600.;	2049	return now + (3600. - fmod (now, 3600.));
1471	}	2050	}
1472		2051
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		2053
1475	Example: Call a callback every hour, starting now:	2054	Example: Call a callback every hour, starting now:
1476		2055
1477	struct ev_periodic hourly_tick;	2056	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	2057	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	2058	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	2059	ev_periodic_start (loop, &hourly_tick);
1481		2060
1482		2061
1483	=head2 C<ev_signal> - signal me when a signal gets signalled!	2062	=head2 C<ev_signal> - signal me when a signal gets signalled!
1484		2063
1485	Signal watchers will trigger an event when the process receives a specific	2064	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	2065	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	2066	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	2067	normal event processing, like any other event.
1489		2068
		2069	If you want signals asynchronously, just use C<sigaction> as you would
		2070	do without libev and forget about sharing the signal. You can even use
		2071	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2072
1490	You can configure as many watchers as you like per signal. Only when the	2073	You can configure as many watchers as you like per signal. Only when the
1491	first watcher gets started will libev actually register a signal watcher	2074	first watcher gets started will libev actually register a signal handler
1492	with the kernel (thus it coexists with your own signal handlers as long	2075	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	2076	you don't register any with libev for the same signal). Similarly, when
1494	watcher for a signal is stopped libev will reset the signal handler to	2077	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	2078	signal handler to SIG_DFL (regardless of what it was set to before).
1496		2079
1497	If possible and supported, libev will install its handlers with	2080	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2081	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1499	interrupted. If you have a problem with system calls getting interrupted by	2082	interrupted. If you have a problem with system calls getting interrupted by
1500	signals you can block all signals in an C<ev_check> watcher and unblock	2083	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		2100
1518	=back	2101	=back
1519		2102
1520	=head3 Examples	2103	=head3 Examples
1521		2104
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	2105	Example: Try to exit cleanly on SIGINT.
1523		2106
1524	static void	2107	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2108	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	2109	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	2110	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	2111	}
1529		2112
1530	struct ev_signal signal_watcher;	2113	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2114	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	2115	ev_signal_start (loop, &signal_watcher);
1533		2116
1534		2117
1535	=head2 C<ev_child> - watch out for process status changes	2118	=head2 C<ev_child> - watch out for process status changes
1536		2119
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2120	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2121	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2122	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2123	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2124	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2125	forking and then immediately registering a watcher for the child is fine,
		2126	but forking and registering a watcher a few event loop iterations later or
		2127	in the next callback invocation is not.
1542		2128
1543	Only the default event loop is capable of handling signals, and therefore	2129	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2130	you can only register child watchers in the default event loop.
		2131
		2132	Due to some design glitches inside libev, child watchers will always be
		2133	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2134	libev)
1545		2135
1546	=head3 Process Interaction	2136	=head3 Process Interaction
1547		2137
1548	Libev grabs C<SIGCHLD> as soon as the default event loop is	2138	Libev grabs C<SIGCHLD> as soon as the default event loop is
1549	initialised. This is necessary to guarantee proper behaviour even if	2139	initialised. This is necessary to guarantee proper behaviour even if
…		…
1559	handler, you can override it easily by installing your own handler for	2149	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2150	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2151	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2152	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2153	that, so other libev users can use C<ev_child> watchers freely.
		2154
		2155	=head3 Stopping the Child Watcher
		2156
		2157	Currently, the child watcher never gets stopped, even when the
		2158	child terminates, so normally one needs to stop the watcher in the
		2159	callback. Future versions of libev might stop the watcher automatically
		2160	when a child exit is detected.
1564		2161
1565	=head3 Watcher-Specific Functions and Data Members	2162	=head3 Watcher-Specific Functions and Data Members
1566		2163
1567	=over 4	2164	=over 4
1568		2165
…		…
1597	=head3 Examples	2194	=head3 Examples
1598		2195
1599	Example: C<fork()> a new process and install a child handler to wait for	2196	Example: C<fork()> a new process and install a child handler to wait for
1600	its completion.	2197	its completion.
1601		2198
1602	ev_child cw;	2199	ev_child cw;
1603		2200
1604	static void	2201	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2202	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2203	{
1607	ev_child_stop (EV_A_ w);	2204	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2205	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2206	}
1610		2207
1611	pid_t pid = fork ();	2208	pid_t pid = fork ();
1612		2209
1613	if (pid < 0)	2210	if (pid < 0)
1614	// error	2211	// error
1615	else if (pid == 0)	2212	else if (pid == 0)
1616	{	2213	{
1617	// the forked child executes here	2214	// the forked child executes here
1618	exit (1);	2215	exit (1);
1619	}	2216	}
1620	else	2217	else
1621	{	2218	{
1622	ev_child_init (&cw, child_cb, pid, 0);	2219	ev_child_init (&cw, child_cb, pid, 0);
1623	ev_child_start (EV_DEFAULT_ &cw);	2220	ev_child_start (EV_DEFAULT_ &cw);
1624	}	2221	}
1625		2222
1626		2223
1627	=head2 C<ev_stat> - did the file attributes just change?	2224	=head2 C<ev_stat> - did the file attributes just change?
1628		2225
1629	This watches a file system path for attribute changes. That is, it calls	2226	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2227	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2228	and sees if it changed compared to the last time, invoking the callback if
		2229	it did.
1632		2230
1633	The path does not need to exist: changing from "path exists" to "path does	2231	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2232	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2233	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2234	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2235	least one) and all the other fields of the stat buffer having unspecified
		2236	contents.
1638		2237
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2238	The path I<must not> end in a slash or contain special components such as
		2239	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2240	your working directory changes, then the behaviour is undefined.
1641		2241
1642	Since there is no standard to do this, the portable implementation simply	2242	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2243	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2244	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2245	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2246	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2247	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2248	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2249	currently around C<0.1>, but that's usually overkill.
1650		2250
1651	This watcher type is not meant for massive numbers of stat watchers,	2251	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2252	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2253	resource-intensive.
1654		2254
1655	At the time of this writing, only the Linux inotify interface is	2255	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2256	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2257	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2258	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2259
1664	=head3 ABI Issues (Largefile Support)	2260	=head3 ABI Issues (Largefile Support)
1665		2261
1666	Libev by default (unless the user overrides this) uses the default	2262	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2263	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2264	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2265	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2266	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2267	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2268	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2269	most noticeably displayed with ev_stat and large file support.
1674		2270
1675	=head3 Inotify	2271	The solution for this is to lobby your distribution maker to make large
		2272	file interfaces available by default (as e.g. FreeBSD does) and not
		2273	optional. Libev cannot simply switch on large file support because it has
		2274	to exchange stat structures with application programs compiled using the
		2275	default compilation environment.
1676		2276
		2277	=head3 Inotify and Kqueue
		2278
1677	When C<inotify (7)> support has been compiled into libev (generally only	2279	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2280	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2281	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2282	watcher is being started.
1681		2283
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2284	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2285	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2286	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2287	there are many cases where libev has to resort to regular C<stat> polling,
		2288	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2289	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2290	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2291	xfs are fully working) libev usually gets away without polling.
1686		2292
1687	(There is no support for kqueue, as apparently it cannot be used to	2293	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2294	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2295	descriptor open on the object at all times, and detecting renames, unlinks
		2296	etc. is difficult.
		2297
		2298	=head3 C<stat ()> is a synchronous operation
		2299
		2300	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2301	the process. The exception are C<ev_stat> watchers - those call C<stat
		2302	()>, which is a synchronous operation.
		2303
		2304	For local paths, this usually doesn't matter: unless the system is very
		2305	busy or the intervals between stat's are large, a stat call will be fast,
		2306	as the path data is usually in memory already (except when starting the
		2307	watcher).
		2308
		2309	For networked file systems, calling C<stat ()> can block an indefinite
		2310	time due to network issues, and even under good conditions, a stat call
		2311	often takes multiple milliseconds.
		2312
		2313	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2314	paths, although this is fully supported by libev.
1690		2315
1691	=head3 The special problem of stat time resolution	2316	=head3 The special problem of stat time resolution
1692		2317
1693	The C<stat ()> system call only supports full-second resolution portably, and	2318	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2319	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2320	still only support whole seconds.
1696		2321
1697	That means that, if the time is the only thing that changes, you can	2322	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2323	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2324	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2325	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2326	stat data does change in other ways (e.g. file size).
1702		2327
1703	The solution to this is to delay acting on a change for slightly more	2328	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2329	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2330	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2331	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2351	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2352	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2353	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2354	path for as long as the watcher is active.
1730		2355
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2356	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2357	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2358	last change was detected).
1734		2359
1735	=item ev_stat_stat (loop, ev_stat *)	2360	=item ev_stat_stat (loop, ev_stat *)
1736		2361
1737	Updates the stat buffer immediately with new values. If you change the	2362	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2363	watched path in your callback, you could call this function to avoid
…		…
1767		2392
1768	=head3 Examples	2393	=head3 Examples
1769		2394
1770	Example: Watch C</etc/passwd> for attribute changes.	2395	Example: Watch C</etc/passwd> for attribute changes.
1771		2396
1772	static void	2397	static void
1773	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2398	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1774	{	2399	{
1775	/* /etc/passwd changed in some way */	2400	/* /etc/passwd changed in some way */
1776	if (w->attr.st_nlink)	2401	if (w->attr.st_nlink)
1777	{	2402	{
1778	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2403	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1779	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2404	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1780	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2405	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1781	}	2406	}
1782	else	2407	else
1783	/* you shalt not abuse printf for puts */	2408	/* you shalt not abuse printf for puts */
1784	puts ("wow, /etc/passwd is not there, expect problems. "	2409	puts ("wow, /etc/passwd is not there, expect problems. "
1785	"if this is windows, they already arrived\n");	2410	"if this is windows, they already arrived\n");
1786	}	2411	}
1787		2412
1788	...	2413	...
1789	ev_stat passwd;	2414	ev_stat passwd;
1790		2415
1791	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2416	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1792	ev_stat_start (loop, &passwd);	2417	ev_stat_start (loop, &passwd);
1793		2418
1794	Example: Like above, but additionally use a one-second delay so we do not	2419	Example: Like above, but additionally use a one-second delay so we do not
1795	miss updates (however, frequent updates will delay processing, too, so	2420	miss updates (however, frequent updates will delay processing, too, so
1796	one might do the work both on C<ev_stat> callback invocation I<and> on	2421	one might do the work both on C<ev_stat> callback invocation I<and> on
1797	C<ev_timer> callback invocation).	2422	C<ev_timer> callback invocation).
1798		2423
1799	static ev_stat passwd;	2424	static ev_stat passwd;
1800	static ev_timer timer;	2425	static ev_timer timer;
1801		2426
1802	static void	2427	static void
1803	timer_cb (EV_P_ ev_timer *w, int revents)	2428	timer_cb (EV_P_ ev_timer *w, int revents)
1804	{	2429	{
1805	ev_timer_stop (EV_A_ w);	2430	ev_timer_stop (EV_A_ w);
1806		2431
1807	/* now it's one second after the most recent passwd change */	2432	/* now it's one second after the most recent passwd change */
1808	}	2433	}
1809		2434
1810	static void	2435	static void
1811	stat_cb (EV_P_ ev_stat *w, int revents)	2436	stat_cb (EV_P_ ev_stat *w, int revents)
1812	{	2437	{
1813	/* reset the one-second timer */	2438	/* reset the one-second timer */
1814	ev_timer_again (EV_A_ &timer);	2439	ev_timer_again (EV_A_ &timer);
1815	}	2440	}
1816		2441
1817	...	2442	...
1818	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2443	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1819	ev_stat_start (loop, &passwd);	2444	ev_stat_start (loop, &passwd);
1820	ev_timer_init (&timer, timer_cb, 0., 1.02);	2445	ev_timer_init (&timer, timer_cb, 0., 1.02);
1821		2446
1822		2447
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2448	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2449
1825	Idle watchers trigger events when no other events of the same or higher	2450	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2451	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2452	as receiving "events").
1828		2453
1829	That is, as long as your process is busy handling sockets or timeouts	2454	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2455	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2456	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2457	are pending), the idle watchers are being called once per event loop
…		…
1843		2468
1844	=head3 Watcher-Specific Functions and Data Members	2469	=head3 Watcher-Specific Functions and Data Members
1845		2470
1846	=over 4	2471	=over 4
1847		2472
1848	=item ev_idle_init (ev_signal *, callback)	2473	=item ev_idle_init (ev_idle *, callback)
1849		2474
1850	Initialises and configures the idle watcher - it has no parameters of any	2475	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2476	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2477	believe me.
1853		2478
…		…
1856	=head3 Examples	2481	=head3 Examples
1857		2482
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2483	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2484	callback, free it. Also, use no error checking, as usual.
1860		2485
1861	static void	2486	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2487	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2488	{
1864	free (w);	2489	free (w);
1865	// now do something you wanted to do when the program has	2490	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2491	// no longer anything immediate to do.
1867	}	2492	}
1868		2493
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2494	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2495	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2496	ev_idle_start (loop, idle_watcher);
1872		2497
1873		2498
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2499	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2500
1876	Prepare and check watchers are usually (but not always) used in tandem:	2501	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2502	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2503	afterwards.
1879		2504
1880	You I<must not> call C<ev_loop> or similar functions that enter	2505	You I<must not> call C<ev_loop> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2506	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2509	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2510	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2511	called in pairs bracketing the blocking call.
1887		2512
1888	Their main purpose is to integrate other event mechanisms into libev and	2513	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2514	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2515	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2516	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2517	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2518	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2519	watcher).
1895		2520
1896	This is done by examining in each prepare call which file descriptors need	2521	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2522	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2523	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2524	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2525	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2526	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2527	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2528	nevertheless, because you never know, you know?).
1904		2529
1905	As another example, the Perl Coro module uses these hooks to integrate	2530	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2531	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2532	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2533	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2536	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2537	low-priority coroutines to idle/background tasks).
1913		2538
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2539	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2540	priority, to ensure that they are being run before any other watchers
		2541	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2542
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2543	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2544	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2545	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2546	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2547	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2548	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2549	others).
1923		2550
1924	=head3 Watcher-Specific Functions and Data Members	2551	=head3 Watcher-Specific Functions and Data Members
1925		2552
1926	=over 4	2553	=over 4
1927		2554
…		…
1929		2556
1930	=item ev_check_init (ev_check *, callback)	2557	=item ev_check_init (ev_check *, callback)
1931		2558
1932	Initialises and configures the prepare or check watcher - they have no	2559	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2560	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2561	macros, but using them is utterly, utterly, utterly and completely
		2562	pointless.
1935		2563
1936	=back	2564	=back
1937		2565
1938	=head3 Examples	2566	=head3 Examples
1939		2567
…		…
1948	and in a check watcher, destroy them and call into libadns. What follows	2576	and in a check watcher, destroy them and call into libadns. What follows
1949	is pseudo-code only of course. This requires you to either use a low	2577	is pseudo-code only of course. This requires you to either use a low
1950	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2578	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1951	the callbacks for the IO/timeout watchers might not have been called yet.	2579	the callbacks for the IO/timeout watchers might not have been called yet.
1952		2580
1953	static ev_io iow [nfd];	2581	static ev_io iow [nfd];
1954	static ev_timer tw;	2582	static ev_timer tw;
1955		2583
1956	static void	2584	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2585	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2586	{
1959	}	2587	}
1960		2588
1961	// create io watchers for each fd and a timer before blocking	2589	// create io watchers for each fd and a timer before blocking
1962	static void	2590	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2591	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2592	{
1965	int timeout = 3600000;	2593	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2594	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2595	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2596	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2597
1970	/* the callback is illegal, but won't be called as we stop during check */	2598	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2599	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2600	ev_timer_start (loop, &tw);
1973		2601
1974	// create one ev_io per pollfd	2602	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2603	for (int i = 0; i < nfd; ++i)
1976	{	2604	{
1977	ev_io_init (iow + i, io_cb, fds [i].fd,	2605	ev_io_init (iow + i, io_cb, fds [i].fd,
1978	((fds [i].events & POLLIN ? EV_READ : 0)	2606	((fds [i].events & POLLIN ? EV_READ : 0)
1979	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2607	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1980		2608
1981	fds [i].revents = 0;	2609	fds [i].revents = 0;
1982	ev_io_start (loop, iow + i);	2610	ev_io_start (loop, iow + i);
1983	}	2611	}
1984	}	2612	}
1985		2613
1986	// stop all watchers after blocking	2614	// stop all watchers after blocking
1987	static void	2615	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2616	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2617	{
1990	ev_timer_stop (loop, &tw);	2618	ev_timer_stop (loop, &tw);
1991		2619
1992	for (int i = 0; i < nfd; ++i)	2620	for (int i = 0; i < nfd; ++i)
1993	{	2621	{
1994	// set the relevant poll flags	2622	// set the relevant poll flags
1995	// could also call adns_processreadable etc. here	2623	// could also call adns_processreadable etc. here
1996	struct pollfd *fd = fds + i;	2624	struct pollfd *fd = fds + i;
1997	int revents = ev_clear_pending (iow + i);	2625	int revents = ev_clear_pending (iow + i);
1998	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2626	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1999	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2627	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
2000		2628
2001	// now stop the watcher	2629	// now stop the watcher
2002	ev_io_stop (loop, iow + i);	2630	ev_io_stop (loop, iow + i);
2003	}	2631	}
2004		2632
2005	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2633	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
2006	}	2634	}
2007		2635
2008	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2636	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
2009	in the prepare watcher and would dispose of the check watcher.	2637	in the prepare watcher and would dispose of the check watcher.
2010		2638
2011	Method 3: If the module to be embedded supports explicit event	2639	Method 3: If the module to be embedded supports explicit event
2012	notification (libadns does), you can also make use of the actual watcher	2640	notification (libadns does), you can also make use of the actual watcher
2013	callbacks, and only destroy/create the watchers in the prepare watcher.	2641	callbacks, and only destroy/create the watchers in the prepare watcher.
2014		2642
2015	static void	2643	static void
2016	timer_cb (EV_P_ ev_timer *w, int revents)	2644	timer_cb (EV_P_ ev_timer *w, int revents)
2017	{	2645	{
2018	adns_state ads = (adns_state)w->data;	2646	adns_state ads = (adns_state)w->data;
2019	update_now (EV_A);	2647	update_now (EV_A);
2020		2648
2021	adns_processtimeouts (ads, &tv_now);	2649	adns_processtimeouts (ads, &tv_now);
2022	}	2650	}
2023		2651
2024	static void	2652	static void
2025	io_cb (EV_P_ ev_io *w, int revents)	2653	io_cb (EV_P_ ev_io *w, int revents)
2026	{	2654	{
2027	adns_state ads = (adns_state)w->data;	2655	adns_state ads = (adns_state)w->data;
2028	update_now (EV_A);	2656	update_now (EV_A);
2029		2657
2030	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2658	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
2031	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2659	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
2032	}	2660	}
2033		2661
2034	// do not ever call adns_afterpoll	2662	// do not ever call adns_afterpoll
2035		2663
2036	Method 4: Do not use a prepare or check watcher because the module you	2664	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2665	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2666	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2667	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2668	this approach, effectively embedding EV as a client into the horrible
		2669	libglib event loop.
2041		2670
2042	static gint	2671	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2672	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2673	{
2045	int got_events = 0;	2674	int got_events = 0;
2046		2675
2047	for (n = 0; n < nfds; ++n)	2676	for (n = 0; n < nfds; ++n)
2048	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2677	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
2049		2678
2050	if (timeout >= 0)	2679	if (timeout >= 0)
2051	// create/start timer	2680	// create/start timer
2052		2681
2053	// poll	2682	// poll
2054	ev_loop (EV_A_ 0);	2683	ev_loop (EV_A_ 0);
2055		2684
2056	// stop timer again	2685	// stop timer again
2057	if (timeout >= 0)	2686	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2687	ev_timer_stop (EV_A_ &to);
2059		2688
2060	// stop io watchers again - their callbacks should have set	2689	// stop io watchers again - their callbacks should have set
2061	for (n = 0; n < nfds; ++n)	2690	for (n = 0; n < nfds; ++n)
2062	ev_io_stop (EV_A_ iow [n]);	2691	ev_io_stop (EV_A_ iow [n]);
2063		2692
2064	return got_events;	2693	return got_events;
2065	}	2694	}
2066		2695
2067		2696
2068	=head2 C<ev_embed> - when one backend isn't enough...	2697	=head2 C<ev_embed> - when one backend isn't enough...
2069		2698
2070	This is a rather advanced watcher type that lets you embed one event loop	2699	This is a rather advanced watcher type that lets you embed one event loop
…		…
2076	prioritise I/O.	2705	prioritise I/O.
2077		2706
2078	As an example for a bug workaround, the kqueue backend might only support	2707	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2708	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2709	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2710	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2711	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2712	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2713	C<kevent>, but at least you can use both mechanisms for what they are
		2714	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2715
2086	As for prioritising I/O: rarely you have the case where some fds have	2716	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2717	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2718	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2719	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2720	the rest in a second one, and embed the second one in the first.
2091		2721
2092	As long as the watcher is active, the callback will be invoked every time	2722	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2723	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2724	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2725	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2726	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2727	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2728
2100	As long as the watcher is started it will automatically handle events. The	2729	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2730	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2731
2105	Also, there have not currently been made special provisions for forking:	2732	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2733	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2734	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2735	C<ev_loop_fork> on the embedded loop.
2109		2736
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2737	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2738	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2739	portable one.
2113		2740
2114	So when you want to use this feature you will always have to be prepared	2741	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2742	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2743	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2744	create it, and if that fails, use the normal loop for everything.
		2745
		2746	=head3 C<ev_embed> and fork
		2747
		2748	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2749	automatically be applied to the embedded loop as well, so no special
		2750	fork handling is required in that case. When the watcher is not running,
		2751	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2752	as applicable.
2118		2753
2119	=head3 Watcher-Specific Functions and Data Members	2754	=head3 Watcher-Specific Functions and Data Members
2120		2755
2121	=over 4	2756	=over 4
2122		2757
…		…
2148	event loop. If that is not possible, use the default loop. The default	2783	event loop. If that is not possible, use the default loop. The default
2149	loop is stored in C<loop_hi>, while the embeddable loop is stored in	2784	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2785	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	2786	used).
2152		2787
2153	struct ev_loop *loop_hi = ev_default_init (0);	2788	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	2789	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	2790	ev_embed embed;
2156		2791
2157	// see if there is a chance of getting one that works	2792	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	2793	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2794	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2795	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2161	: 0;	2796	: 0;
2162		2797
2163	// if we got one, then embed it, otherwise default to loop_hi	2798	// if we got one, then embed it, otherwise default to loop_hi
2164	if (loop_lo)	2799	if (loop_lo)
2165	{	2800	{
2166	ev_embed_init (&embed, 0, loop_lo);	2801	ev_embed_init (&embed, 0, loop_lo);
2167	ev_embed_start (loop_hi, &embed);	2802	ev_embed_start (loop_hi, &embed);
2168	}	2803	}
2169	else	2804	else
2170	loop_lo = loop_hi;	2805	loop_lo = loop_hi;
2171		2806
2172	Example: Check if kqueue is available but not recommended and create	2807	Example: Check if kqueue is available but not recommended and create
2173	a kqueue backend for use with sockets (which usually work with any	2808	a kqueue backend for use with sockets (which usually work with any
2174	kqueue implementation). Store the kqueue/socket-only event loop in	2809	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2810	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		2811
2177	struct ev_loop *loop = ev_default_init (0);	2812	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	2813	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	2814	ev_embed embed;
2180		2815
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2816	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2817	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	2818	{
2184	ev_embed_init (&embed, 0, loop_socket);	2819	ev_embed_init (&embed, 0, loop_socket);
2185	ev_embed_start (loop, &embed);	2820	ev_embed_start (loop, &embed);
2186	}	2821	}
2187		2822
2188	if (!loop_socket)	2823	if (!loop_socket)
2189	loop_socket = loop;	2824	loop_socket = loop;
2190		2825
2191	// now use loop_socket for all sockets, and loop for everything else	2826	// now use loop_socket for all sockets, and loop for everything else
2192		2827
2193		2828
2194	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2829	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2195		2830
2196	Fork watchers are called when a C<fork ()> was detected (usually because	2831	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	2834	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	2835	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2836	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	2837	handlers will be invoked, too, of course.
2203		2838
		2839	=head3 The special problem of life after fork - how is it possible?
		2840
		2841	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2842	up/change the process environment, followed by a call to C<exec()>. This
		2843	sequence should be handled by libev without any problems.
		2844
		2845	This changes when the application actually wants to do event handling
		2846	in the child, or both parent in child, in effect "continuing" after the
		2847	fork.
		2848
		2849	The default mode of operation (for libev, with application help to detect
		2850	forks) is to duplicate all the state in the child, as would be expected
		2851	when I<either> the parent I<or> the child process continues.
		2852
		2853	When both processes want to continue using libev, then this is usually the
		2854	wrong result. In that case, usually one process (typically the parent) is
		2855	supposed to continue with all watchers in place as before, while the other
		2856	process typically wants to start fresh, i.e. without any active watchers.
		2857
		2858	The cleanest and most efficient way to achieve that with libev is to
		2859	simply create a new event loop, which of course will be "empty", and
		2860	use that for new watchers. This has the advantage of not touching more
		2861	memory than necessary, and thus avoiding the copy-on-write, and the
		2862	disadvantage of having to use multiple event loops (which do not support
		2863	signal watchers).
		2864
		2865	When this is not possible, or you want to use the default loop for
		2866	other reasons, then in the process that wants to start "fresh", call
		2867	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2868	the default loop will "orphan" (not stop) all registered watchers, so you
		2869	have to be careful not to execute code that modifies those watchers. Note
		2870	also that in that case, you have to re-register any signal watchers.
		2871
2204	=head3 Watcher-Specific Functions and Data Members	2872	=head3 Watcher-Specific Functions and Data Members
2205		2873
2206	=over 4	2874	=over 4
2207		2875
2208	=item ev_fork_init (ev_signal *, callback)	2876	=item ev_fork_init (ev_signal *, callback)
…		…
2240	is that the author does not know of a simple (or any) algorithm for a	2908	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	2909	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	2910	need elaborate support such as pthreads.
2243		2911
2244	That means that if you want to queue data, you have to provide your own	2912	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	2913	queue. But at least I can tell you how to implement locking around your
2246	queue:	2914	queue:
2247		2915
2248	=over 4	2916	=over 4
2249		2917
2250	=item queueing from a signal handler context	2918	=item queueing from a signal handler context
2251		2919
2252	To implement race-free queueing, you simply add to the queue in the signal	2920	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2921	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	2922	an example that does that for some fictitious SIGUSR1 handler:
2255		2923
2256	static ev_async mysig;	2924	static ev_async mysig;
2257		2925
2258	static void	2926	static void
2259	sigusr1_handler (void)	2927	sigusr1_handler (void)
…		…
2325	=over 4	2993	=over 4
2326		2994
2327	=item ev_async_init (ev_async *, callback)	2995	=item ev_async_init (ev_async *, callback)
2328		2996
2329	Initialises and configures the async watcher - it has no parameters of any	2997	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2998	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	2999	trust me.
2332		3000
2333	=item ev_async_send (loop, ev_async *)	3001	=item ev_async_send (loop, ev_async *)
2334		3002
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3003	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3004	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	3005	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3006	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	3007	section below on what exactly this means).
2340		3008
		3009	Note that, as with other watchers in libev, multiple events might get
		3010	compressed into a single callback invocation (another way to look at this
		3011	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3012	reset when the event loop detects that).
		3013
2341	This call incurs the overhead of a system call only once per loop iteration,	3014	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	3015	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	3016	repeated calls to C<ev_async_send> for the same event loop.
2344		3017
2345	=item bool = ev_async_pending (ev_async *)	3018	=item bool = ev_async_pending (ev_async *)
2346		3019
2347	Returns a non-zero value when C<ev_async_send> has been called on the	3020	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	3021	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3024	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	3025	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	3026	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	3027	quickly check whether invoking the loop might be a good idea.
2355		3028
2356	Not that this does I<not> check whether the watcher itself is pending, only	3029	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	3030	only whether it has been requested to make this watcher pending: there
		3031	is a time window between the event loop checking and resetting the async
		3032	notification, and the callback being invoked.
2358		3033
2359	=back	3034	=back
2360		3035
2361		3036
2362	=head1 OTHER FUNCTIONS	3037	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	3041	=over 4
2367		3042
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3043	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		3044
2370	This function combines a simple timer and an I/O watcher, calls your	3045	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	3046	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	3047	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	3048	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	3049	more watchers yourself.
2375		3050
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	3051	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3052	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	3053	the given C<fd> and C<events> set will be created and started.
2379		3054
2380	If C<timeout> is less than 0, then no timeout watcher will be	3055	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3056	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3057	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		3058
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3059	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2386	passed an C<revents> set like normal event callbacks (a combination of	3060	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3061	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2388	value passed to C<ev_once>:	3062	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3063	a timeout and an io event at the same time - you probably should give io
		3064	events precedence.
2389		3065
		3066	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3067
2390	static void stdin_ready (int revents, void *arg)	3068	static void stdin_ready (int revents, void *arg)
2391	{	3069	{
2392	if (revents & EV_TIMEOUT)
2393	/* doh, nothing entered */;
2394	else if (revents & EV_READ)	3070	if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;	3071	/* stdin might have data for us, joy! */;
		3072	else if (revents & EV_TIMEOUT)
		3073	/* doh, nothing entered */;
2396	}	3074	}
2397		3075
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3076	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		3077
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)	3078	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2401		3079
2402	Feeds the given event set into the event loop, as if the specified event	3080	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an	3081	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).	3082	initialised but not necessarily started event watcher).
2405		3083
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3084	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2407		3085
2408	Feed an event on the given fd, as if a file descriptor backend detected	3086	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	3087	the given events it.
2410		3088
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	3089	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2412		3090
2413	Feed an event as if the given signal occurred (C<loop> must be the default	3091	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	3092	loop!).
2415		3093
2416	=back	3094	=back
…		…
2452	you to use some convenience methods to start/stop watchers and also change	3130	you to use some convenience methods to start/stop watchers and also change
2453	the callback model to a model using method callbacks on objects.	3131	the callback model to a model using method callbacks on objects.
2454		3132
2455	To use it,	3133	To use it,
2456		3134
2457	#include <ev++.h>	3135	#include <ev++.h>
2458		3136
2459	This automatically includes F<ev.h> and puts all of its definitions (many	3137	This automatically includes F<ev.h> and puts all of its definitions (many
2460	of them macros) into the global namespace. All C++ specific things are	3138	of them macros) into the global namespace. All C++ specific things are
2461	put into the C<ev> namespace. It should support all the same embedding	3139	put into the C<ev> namespace. It should support all the same embedding
2462	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3140	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2529	your compiler is good :), then the method will be fully inlined into the	3207	your compiler is good :), then the method will be fully inlined into the
2530	thunking function, making it as fast as a direct C callback.	3208	thunking function, making it as fast as a direct C callback.
2531		3209
2532	Example: simple class declaration and watcher initialisation	3210	Example: simple class declaration and watcher initialisation
2533		3211
2534	struct myclass	3212	struct myclass
2535	{	3213	{
2536	void io_cb (ev::io &w, int revents) { }	3214	void io_cb (ev::io &w, int revents) { }
2537	}	3215	}
2538		3216
2539	myclass obj;	3217	myclass obj;
2540	ev::io iow;	3218	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3219	iow.set <myclass, &myclass::io_cb> (&obj);
		3220
		3221	=item w->set (object *)
		3222
		3223	This is an B<experimental> feature that might go away in a future version.
		3224
		3225	This is a variation of a method callback - leaving out the method to call
		3226	will default the method to C<operator ()>, which makes it possible to use
		3227	functor objects without having to manually specify the C<operator ()> all
		3228	the time. Incidentally, you can then also leave out the template argument
		3229	list.
		3230
		3231	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3232	int revents)>.
		3233
		3234	See the method-C<set> above for more details.
		3235
		3236	Example: use a functor object as callback.
		3237
		3238	struct myfunctor
		3239	{
		3240	void operator() (ev::io &w, int revents)
		3241	{
		3242	...
		3243	}
		3244	}
		3245
		3246	myfunctor f;
		3247
		3248	ev::io w;
		3249	w.set (&f);
2542		3250
2543	=item w->set<function> (void *data = 0)	3251	=item w->set<function> (void *data = 0)
2544		3252
2545	Also sets a callback, but uses a static method or plain function as	3253	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3254	callback. The optional C<data> argument will be stored in the watcher's
…		…
2548		3256
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3257	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3258
2551	See the method-C<set> above for more details.	3259	See the method-C<set> above for more details.
2552		3260
2553	Example:	3261	Example: Use a plain function as callback.
2554		3262
2555	static void io_cb (ev::io &w, int revents) { }	3263	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3264	iow.set <io_cb> ();
2557		3265
2558	=item w->set (struct ev_loop *)	3266	=item w->set (struct ev_loop *)
2559		3267
2560	Associates a different C<struct ev_loop> with this watcher. You can only	3268	Associates a different C<struct ev_loop> with this watcher. You can only
2561	do this when the watcher is inactive (and not pending either).	3269	do this when the watcher is inactive (and not pending either).
…		…
2594	=back	3302	=back
2595		3303
2596	Example: Define a class with an IO and idle watcher, start one of them in	3304	Example: Define a class with an IO and idle watcher, start one of them in
2597	the constructor.	3305	the constructor.
2598		3306
2599	class myclass	3307	class myclass
2600	{	3308	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3309	ev::io io ; void io_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3310	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3311
2604	myclass (int fd)	3312	myclass (int fd)
2605	{	3313	{
2606	io .set <myclass, &myclass::io_cb > (this);	3314	io .set <myclass, &myclass::io_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3315	idle.set <myclass, &myclass::idle_cb> (this);
2608		3316
2609	io.start (fd, ev::READ);	3317	io.start (fd, ev::READ);
2610	}	3318	}
2611	};	3319	};
2612		3320
2613		3321
2614	=head1 OTHER LANGUAGE BINDINGS	3322	=head1 OTHER LANGUAGE BINDINGS
2615		3323
2616	Libev does not offer other language bindings itself, but bindings for a	3324	Libev does not offer other language bindings itself, but bindings for a
…		…
2623	=item Perl	3331	=item Perl
2624		3332
2625	The EV module implements the full libev API and is actually used to test	3333	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3334	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3335	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3336	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3337	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3338	and C<EV::Glib>).
2630		3339
2631	It can be found and installed via CPAN, its homepage is found at	3340	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3341	L<http://software.schmorp.de/pkg/EV>.
		3342
		3343	=item Python
		3344
		3345	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3346	seems to be quite complete and well-documented.
2633		3347
2634	=item Ruby	3348	=item Ruby
2635		3349
2636	Tony Arcieri has written a ruby extension that offers access to a subset	3350	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds file handle abstractions, asynchronous DNS and	3351	of the libev API and adds file handle abstractions, asynchronous DNS and
2638	more on top of it. It can be found via gem servers. Its homepage is at	3352	more on top of it. It can be found via gem servers. Its homepage is at
2639	L<http://rev.rubyforge.org/>.	3353	L<http://rev.rubyforge.org/>.
2640		3354
		3355	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3356	makes rev work even on mingw.
		3357
		3358	=item Haskell
		3359
		3360	A haskell binding to libev is available at
		3361	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3362
2641	=item D	3363	=item D
2642		3364
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3365	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3366	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3367
		3368	=item Ocaml
		3369
		3370	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3371	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2645		3372
2646	=back	3373	=back
2647		3374
2648		3375
2649	=head1 MACRO MAGIC	3376	=head1 MACRO MAGIC
…		…
2661		3388
2662	This provides the loop I<argument> for functions, if one is required ("ev	3389	This provides the loop I<argument> for functions, if one is required ("ev
2663	loop argument"). The C<EV_A> form is used when this is the sole argument,	3390	loop argument"). The C<EV_A> form is used when this is the sole argument,
2664	C<EV_A_> is used when other arguments are following. Example:	3391	C<EV_A_> is used when other arguments are following. Example:
2665		3392
2666	ev_unref (EV_A);	3393	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	3394	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	3395	ev_loop (EV_A_ 0);
2669		3396
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3397	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	3398	which is often provided by the following macro.
2672		3399
2673	=item C<EV_P>, C<EV_P_>	3400	=item C<EV_P>, C<EV_P_>
2674		3401
2675	This provides the loop I<parameter> for functions, if one is required ("ev	3402	This provides the loop I<parameter> for functions, if one is required ("ev
2676	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3403	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2677	C<EV_P_> is used when other parameters are following. Example:	3404	C<EV_P_> is used when other parameters are following. Example:
2678		3405
2679	// this is how ev_unref is being declared	3406	// this is how ev_unref is being declared
2680	static void ev_unref (EV_P);	3407	static void ev_unref (EV_P);
2681		3408
2682	// this is how you can declare your typical callback	3409	// this is how you can declare your typical callback
2683	static void cb (EV_P_ ev_timer *w, int revents)	3410	static void cb (EV_P_ ev_timer *w, int revents)
2684		3411
2685	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3412	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2686	suitable for use with C<EV_A>.	3413	suitable for use with C<EV_A>.
2687		3414
2688	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3415	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
…		…
2704		3431
2705	Example: Declare and initialise a check watcher, utilising the above	3432	Example: Declare and initialise a check watcher, utilising the above
2706	macros so it will work regardless of whether multiple loops are supported	3433	macros so it will work regardless of whether multiple loops are supported
2707	or not.	3434	or not.
2708		3435
2709	static void	3436	static void
2710	check_cb (EV_P_ ev_timer *w, int revents)	3437	check_cb (EV_P_ ev_timer *w, int revents)
2711	{	3438	{
2712	ev_check_stop (EV_A_ w);	3439	ev_check_stop (EV_A_ w);
2713	}	3440	}
2714		3441
2715	ev_check check;	3442	ev_check check;
2716	ev_check_init (&check, check_cb);	3443	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	3444	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	3445	ev_loop (EV_DEFAULT_ 0);
2719		3446
2720	=head1 EMBEDDING	3447	=head1 EMBEDDING
2721		3448
2722	Libev can (and often is) directly embedded into host	3449	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	3450	applications. Examples of applications that embed it include the Deliantra
…		…
2737	=head3 CORE EVENT LOOP	3464	=head3 CORE EVENT LOOP
2738		3465
2739	To include only the libev core (all the C<ev_*> functions), with manual	3466	To include only the libev core (all the C<ev_*> functions), with manual
2740	configuration (no autoconf):	3467	configuration (no autoconf):
2741		3468
2742	#define EV_STANDALONE 1	3469	#define EV_STANDALONE 1
2743	#include "ev.c"	3470	#include "ev.c"
2744		3471
2745	This will automatically include F<ev.h>, too, and should be done in a	3472	This will automatically include F<ev.h>, too, and should be done in a
2746	single C source file only to provide the function implementations. To use	3473	single C source file only to provide the function implementations. To use
2747	it, do the same for F<ev.h> in all files wishing to use this API (best	3474	it, do the same for F<ev.h> in all files wishing to use this API (best
2748	done by writing a wrapper around F<ev.h> that you can include instead and	3475	done by writing a wrapper around F<ev.h> that you can include instead and
2749	where you can put other configuration options):	3476	where you can put other configuration options):
2750		3477
2751	#define EV_STANDALONE 1	3478	#define EV_STANDALONE 1
2752	#include "ev.h"	3479	#include "ev.h"
2753		3480
2754	Both header files and implementation files can be compiled with a C++	3481	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	3482	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	3483	as a bug).
2757		3484
2758	You need the following files in your source tree, or in a directory	3485	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	3486	in your include path (e.g. in libev/ when using -Ilibev):
2760		3487
2761	ev.h	3488	ev.h
2762	ev.c	3489	ev.c
2763	ev_vars.h	3490	ev_vars.h
2764	ev_wrap.h	3491	ev_wrap.h
2765		3492
2766	ev_win32.c required on win32 platforms only	3493	ev_win32.c required on win32 platforms only
2767		3494
2768	ev_select.c only when select backend is enabled (which is enabled by default)	3495	ev_select.c only when select backend is enabled (which is enabled by default)
2769	ev_poll.c only when poll backend is enabled (disabled by default)	3496	ev_poll.c only when poll backend is enabled (disabled by default)
2770	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3497	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2771	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3498	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2772	ev_port.c only when the solaris port backend is enabled (disabled by default)	3499	ev_port.c only when the solaris port backend is enabled (disabled by default)
2773		3500
2774	F<ev.c> includes the backend files directly when enabled, so you only need	3501	F<ev.c> includes the backend files directly when enabled, so you only need
2775	to compile this single file.	3502	to compile this single file.
2776		3503
2777	=head3 LIBEVENT COMPATIBILITY API	3504	=head3 LIBEVENT COMPATIBILITY API
2778		3505
2779	To include the libevent compatibility API, also include:	3506	To include the libevent compatibility API, also include:
2780		3507
2781	#include "event.c"	3508	#include "event.c"
2782		3509
2783	in the file including F<ev.c>, and:	3510	in the file including F<ev.c>, and:
2784		3511
2785	#include "event.h"	3512	#include "event.h"
2786		3513
2787	in the files that want to use the libevent API. This also includes F<ev.h>.	3514	in the files that want to use the libevent API. This also includes F<ev.h>.
2788		3515
2789	You need the following additional files for this:	3516	You need the following additional files for this:
2790		3517
2791	event.h	3518	event.h
2792	event.c	3519	event.c
2793		3520
2794	=head3 AUTOCONF SUPPORT	3521	=head3 AUTOCONF SUPPORT
2795		3522
2796	Instead of using C<EV_STANDALONE=1> and providing your configuration in	3523	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2797	whatever way you want, you can also C<m4_include([libev.m4])> in your	3524	whatever way you want, you can also C<m4_include([libev.m4])> in your
2798	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3525	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2799	include F<config.h> and configure itself accordingly.	3526	include F<config.h> and configure itself accordingly.
2800		3527
2801	For this of course you need the m4 file:	3528	For this of course you need the m4 file:
2802		3529
2803	libev.m4	3530	libev.m4
2804		3531
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3532	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3533
2807	Libev can be configured via a variety of preprocessor symbols you have to	3534	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absence of	3535	define before including any of its files. The default in the absence of
2809	autoconf is noted for every option.	3536	autoconf is documented for every option.
2810		3537
2811	=over 4	3538	=over 4
2812		3539
2813	=item EV_STANDALONE	3540	=item EV_STANDALONE
2814		3541
…		…
2816	keeps libev from including F<config.h>, and it also defines dummy	3543	keeps libev from including F<config.h>, and it also defines dummy
2817	implementations for some libevent functions (such as logging, which is not	3544	implementations for some libevent functions (such as logging, which is not
2818	supported). It will also not define any of the structs usually found in	3545	supported). It will also not define any of the structs usually found in
2819	F<event.h> that are not directly supported by the libev core alone.	3546	F<event.h> that are not directly supported by the libev core alone.
2820		3547
		3548	In stanbdalone mode, libev will still try to automatically deduce the
		3549	configuration, but has to be more conservative.
		3550
2821	=item EV_USE_MONOTONIC	3551	=item EV_USE_MONOTONIC
2822		3552
2823	If defined to be C<1>, libev will try to detect the availability of the	3553	If defined to be C<1>, libev will try to detect the availability of the
2824	monotonic clock option at both compile time and runtime. Otherwise no use	3554	monotonic clock option at both compile time and runtime. Otherwise no
2825	of the monotonic clock option will be attempted. If you enable this, you	3555	use of the monotonic clock option will be attempted. If you enable this,
2826	usually have to link against librt or something similar. Enabling it when	3556	you usually have to link against librt or something similar. Enabling it
2827	the functionality isn't available is safe, though, although you have	3557	when the functionality isn't available is safe, though, although you have
2828	to make sure you link against any libraries where the C<clock_gettime>	3558	to make sure you link against any libraries where the C<clock_gettime>
2829	function is hiding in (often F<-lrt>).	3559	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2830		3560
2831	=item EV_USE_REALTIME	3561	=item EV_USE_REALTIME
2832		3562
2833	If defined to be C<1>, libev will try to detect the availability of the	3563	If defined to be C<1>, libev will try to detect the availability of the
2834	real-time clock option at compile time (and assume its availability at	3564	real-time clock option at compile time (and assume its availability
2835	runtime if successful). Otherwise no use of the real-time clock option will	3565	at runtime if successful). Otherwise no use of the real-time clock
2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3566	option will be attempted. This effectively replaces C<gettimeofday>
2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3567	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3568	correctness. See the note about libraries in the description of
		3569	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3570	C<EV_USE_CLOCK_SYSCALL>.
		3571
		3572	=item EV_USE_CLOCK_SYSCALL
		3573
		3574	If defined to be C<1>, libev will try to use a direct syscall instead
		3575	of calling the system-provided C<clock_gettime> function. This option
		3576	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3577	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3578	programs needlessly. Using a direct syscall is slightly slower (in
		3579	theory), because no optimised vdso implementation can be used, but avoids
		3580	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3581	higher, as it simplifies linking (no need for C<-lrt>).
2839		3582
2840	=item EV_USE_NANOSLEEP	3583	=item EV_USE_NANOSLEEP
2841		3584
2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3585	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2843	and will use it for delays. Otherwise it will use C<select ()>.	3586	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2859		3602
2860	=item EV_SELECT_USE_FD_SET	3603	=item EV_SELECT_USE_FD_SET
2861		3604
2862	If defined to C<1>, then the select backend will use the system C<fd_set>	3605	If defined to C<1>, then the select backend will use the system C<fd_set>
2863	structure. This is useful if libev doesn't compile due to a missing	3606	structure. This is useful if libev doesn't compile due to a missing
2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3607	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2865	exotic systems. This usually limits the range of file descriptors to some	3608	on exotic systems. This usually limits the range of file descriptors to
2866	low limit such as 1024 or might have other limitations (winsocket only	3609	some low limit such as 1024 or might have other limitations (winsocket
2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3610	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2868	influence the size of the C<fd_set> used.	3611	configures the maximum size of the C<fd_set>.
2869		3612
2870	=item EV_SELECT_IS_WINSOCKET	3613	=item EV_SELECT_IS_WINSOCKET
2871		3614
2872	When defined to C<1>, the select backend will assume that	3615	When defined to C<1>, the select backend will assume that
2873	select/socket/connect etc. don't understand file descriptors but	3616	select/socket/connect etc. don't understand file descriptors but
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3727	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	3728	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	3729	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3730	fine.
2988		3731
2989	If your embedding application does not need any priorities, defining these both to	3732	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	3733	both to C<0> will save some memory and CPU.
2991		3734
2992	=item EV_PERIODIC_ENABLE	3735	=item EV_PERIODIC_ENABLE
2993		3736
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	3737	If undefined or defined to be C<1>, then periodic timers are supported. If
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	3738	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3002	code.	3745	code.
3003		3746
3004	=item EV_EMBED_ENABLE	3747	=item EV_EMBED_ENABLE
3005		3748
3006	If undefined or defined to be C<1>, then embed watchers are supported. If	3749	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.	3750	defined to be C<0>, then they are not. Embed watchers rely on most other
		3751	watcher types, which therefore must not be disabled.
3008		3752
3009	=item EV_STAT_ENABLE	3753	=item EV_STAT_ENABLE
3010		3754
3011	If undefined or defined to be C<1>, then stat watchers are supported. If	3755	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.	3756	defined to be C<0>, then they are not.
…		…
3022	defined to be C<0>, then they are not.	3766	defined to be C<0>, then they are not.
3023		3767
3024	=item EV_MINIMAL	3768	=item EV_MINIMAL
3025		3769
3026	If you need to shave off some kilobytes of code at the expense of some	3770	If you need to shave off some kilobytes of code at the expense of some
3027	speed, define this symbol to C<1>. Currently this is used to override some	3771	speed (but with the full API), define this symbol to C<1>. Currently this
3028	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3772	is used to override some inlining decisions, saves roughly 30% code size
3029	much smaller 2-heap for timer management over the default 4-heap.	3773	on amd64. It also selects a much smaller 2-heap for timer management over
		3774	the default 4-heap.
		3775
		3776	You can save even more by disabling watcher types you do not need
		3777	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3778	(C<-DNDEBUG>) will usually reduce code size a lot.
		3779
		3780	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3781	provide a bare-bones event library. See C<ev.h> for details on what parts
		3782	of the API are still available, and do not complain if this subset changes
		3783	over time.
3030		3784
3031	=item EV_PID_HASHSIZE	3785	=item EV_PID_HASHSIZE
3032		3786
3033	C<ev_child> watchers use a small hash table to distribute workload by	3787	C<ev_child> watchers use a small hash table to distribute workload by
3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3788	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3044	two).	3798	two).
3045		3799
3046	=item EV_USE_4HEAP	3800	=item EV_USE_4HEAP
3047		3801
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3802	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3803	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	3804	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	3805	faster performance with many (thousands) of watchers.
3052		3806
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3807	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3054	(disabled).	3808	(disabled).
3055		3809
3056	=item EV_HEAP_CACHE_AT	3810	=item EV_HEAP_CACHE_AT
3057		3811
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3812	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	3813	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3814	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3815	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	3816	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	3817	noticeably with many (hundreds) of watchers.
3064		3818
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3819	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3066	(disabled).	3820	(disabled).
3067		3821
3068	=item EV_VERIFY	3822	=item EV_VERIFY
…		…
3074	called once per loop, which can slow down libev. If set to C<3>, then the	3828	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	3829	verification code will be called very frequently, which will slow down
3076	libev considerably.	3830	libev considerably.
3077		3831
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3832	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3079	C<0.>	3833	C<0>.
3080		3834
3081	=item EV_COMMON	3835	=item EV_COMMON
3082		3836
3083	By default, all watchers have a C<void *data> member. By redefining	3837	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	3838	this macro to a something else you can include more and other types of
3085	members. You have to define it each time you include one of the files,	3839	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	3840	though, and it must be identical each time.
3087		3841
3088	For example, the perl EV module uses something like this:	3842	For example, the perl EV module uses something like this:
3089		3843
3090	#define EV_COMMON \	3844	#define EV_COMMON \
3091	SV *self; /* contains this struct */ \	3845	SV *self; /* contains this struct */ \
3092	SV *cb_sv, *fh /* note no trailing ";" */	3846	SV *cb_sv, *fh /* note no trailing ";" */
3093		3847
3094	=item EV_CB_DECLARE (type)	3848	=item EV_CB_DECLARE (type)
3095		3849
3096	=item EV_CB_INVOKE (watcher, revents)	3850	=item EV_CB_INVOKE (watcher, revents)
3097		3851
…		…
3102	definition and a statement, respectively. See the F<ev.h> header file for	3856	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	3857	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3858	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	3859	method calls instead of plain function calls in C++.
3106		3860
		3861	=back
		3862
3107	=head2 EXPORTED API SYMBOLS	3863	=head2 EXPORTED API SYMBOLS
3108		3864
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	3865	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	3866	exported symbols, you can use the provided F<Symbol.*> files which list
3111	all public symbols, one per line:	3867	all public symbols, one per line:
3112		3868
3113	Symbols.ev for libev proper	3869	Symbols.ev for libev proper
3114	Symbols.event for the libevent emulation	3870	Symbols.event for the libevent emulation
3115		3871
3116	This can also be used to rename all public symbols to avoid clashes with	3872	This can also be used to rename all public symbols to avoid clashes with
3117	multiple versions of libev linked together (which is obviously bad in	3873	multiple versions of libev linked together (which is obviously bad in
3118	itself, but sometimes it is inconvenient to avoid this).	3874	itself, but sometimes it is inconvenient to avoid this).
3119		3875
…		…
3140	file.	3896	file.
3141		3897
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3898	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3143	that everybody includes and which overrides some configure choices:	3899	that everybody includes and which overrides some configure choices:
3144		3900
3145	#define EV_MINIMAL 1	3901	#define EV_MINIMAL 1
3146	#define EV_USE_POLL 0	3902	#define EV_USE_POLL 0
3147	#define EV_MULTIPLICITY 0	3903	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	3904	#define EV_PERIODIC_ENABLE 0
3149	#define EV_STAT_ENABLE 0	3905	#define EV_STAT_ENABLE 0
3150	#define EV_FORK_ENABLE 0	3906	#define EV_FORK_ENABLE 0
3151	#define EV_CONFIG_H <config.h>	3907	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0	3908	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0	3909	#define EV_MAXPRI 0
3154		3910
3155	#include "ev++.h"	3911	#include "ev++.h"
3156		3912
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3913	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		3914
3159	#include "ev_cpp.h"	3915	#include "ev_cpp.h"
3160	#include "ev.c"	3916	#include "ev.c"
3161		3917
		3918	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		3919
3163	=head1 THREADS AND COROUTINES	3920	=head2 THREADS AND COROUTINES
3164		3921
3165	=head2 THREADS	3922	=head3 THREADS
3166		3923
3167	Libev itself is completely thread-safe, but it uses no locking. This	3924	All libev functions are reentrant and thread-safe unless explicitly
		3925	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	3926	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	3927	are no concurrent calls into any libev function with the same loop
3170	parameter.	3928	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3929	of course): libev guarantees that different event loops share no data
		3930	structures that need any locking.
3171		3931
3172	Or put differently: calls with different loop parameters can be done in	3932	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	3933	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	3934	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	3935	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	3936	a mutex per loop).
3177		3937
3178	If you want to know which design is best for your problem, then I cannot	3938	Specifically to support threads (and signal handlers), libev implements
		3939	so-called C<ev_async> watchers, which allow some limited form of
		3940	concurrency on the same event loop, namely waking it up "from the
		3941	outside".
		3942
		3943	If you want to know which design (one loop, locking, or multiple loops
		3944	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	3945	help you, but here is some generic advice:
3180		3946
3181	=over 4	3947	=over 4
3182		3948
3183	=item * most applications have a main thread: use the default libev loop	3949	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a separate thread running only the default loop.	3950	in that thread, or create a separate thread running only the default loop.
…		…
3196		3962
3197	Choosing a model is hard - look around, learn, know that usually you can do	3963	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	3964	better than you currently do :-)
3199		3965
3200	=item * often you need to talk to some other thread which blocks in the	3966	=item * often you need to talk to some other thread which blocks in the
		3967	event loop.
		3968
3201	event loop - C<ev_async> watchers can be used to wake them up from other	3969	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	3970	(or from signal contexts...).
		3971
		3972	An example use would be to communicate signals or other events that only
		3973	work in the default loop by registering the signal watcher with the
		3974	default loop and triggering an C<ev_async> watcher from the default loop
		3975	watcher callback into the event loop interested in the signal.
3203		3976
3204	=back	3977	=back
3205		3978
		3979	=head4 THREAD LOCKING EXAMPLE
		3980
		3981	Here is a fictitious example of how to run an event loop in a different
		3982	thread than where callbacks are being invoked and watchers are
		3983	created/added/removed.
		3984
		3985	For a real-world example, see the C<EV::Loop::Async> perl module,
		3986	which uses exactly this technique (which is suited for many high-level
		3987	languages).
		3988
		3989	The example uses a pthread mutex to protect the loop data, a condition
		3990	variable to wait for callback invocations, an async watcher to notify the
		3991	event loop thread and an unspecified mechanism to wake up the main thread.
		3992
		3993	First, you need to associate some data with the event loop:
		3994
		3995	typedef struct {
		3996	mutex_t lock; /* global loop lock */
		3997	ev_async async_w;
		3998	thread_t tid;
		3999	cond_t invoke_cv;
		4000	} userdata;
		4001
		4002	void prepare_loop (EV_P)
		4003	{
		4004	// for simplicity, we use a static userdata struct.
		4005	static userdata u;
		4006
		4007	ev_async_init (&u->async_w, async_cb);
		4008	ev_async_start (EV_A_ &u->async_w);
		4009
		4010	pthread_mutex_init (&u->lock, 0);
		4011	pthread_cond_init (&u->invoke_cv, 0);
		4012
		4013	// now associate this with the loop
		4014	ev_set_userdata (EV_A_ u);
		4015	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4016	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4017
		4018	// then create the thread running ev_loop
		4019	pthread_create (&u->tid, 0, l_run, EV_A);
		4020	}
		4021
		4022	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4023	solely to wake up the event loop so it takes notice of any new watchers
		4024	that might have been added:
		4025
		4026	static void
		4027	async_cb (EV_P_ ev_async *w, int revents)
		4028	{
		4029	// just used for the side effects
		4030	}
		4031
		4032	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4033	protecting the loop data, respectively.
		4034
		4035	static void
		4036	l_release (EV_P)
		4037	{
		4038	userdata *u = ev_userdata (EV_A);
		4039	pthread_mutex_unlock (&u->lock);
		4040	}
		4041
		4042	static void
		4043	l_acquire (EV_P)
		4044	{
		4045	userdata *u = ev_userdata (EV_A);
		4046	pthread_mutex_lock (&u->lock);
		4047	}
		4048
		4049	The event loop thread first acquires the mutex, and then jumps straight
		4050	into C<ev_loop>:
		4051
		4052	void *
		4053	l_run (void *thr_arg)
		4054	{
		4055	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4056
		4057	l_acquire (EV_A);
		4058	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4059	ev_loop (EV_A_ 0);
		4060	l_release (EV_A);
		4061
		4062	return 0;
		4063	}
		4064
		4065	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4066	signal the main thread via some unspecified mechanism (signals? pipe
		4067	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4068	have been called (in a while loop because a) spurious wakeups are possible
		4069	and b) skipping inter-thread-communication when there are no pending
		4070	watchers is very beneficial):
		4071
		4072	static void
		4073	l_invoke (EV_P)
		4074	{
		4075	userdata *u = ev_userdata (EV_A);
		4076
		4077	while (ev_pending_count (EV_A))
		4078	{
		4079	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4080	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4081	}
		4082	}
		4083
		4084	Now, whenever the main thread gets told to invoke pending watchers, it
		4085	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4086	thread to continue:
		4087
		4088	static void
		4089	real_invoke_pending (EV_P)
		4090	{
		4091	userdata *u = ev_userdata (EV_A);
		4092
		4093	pthread_mutex_lock (&u->lock);
		4094	ev_invoke_pending (EV_A);
		4095	pthread_cond_signal (&u->invoke_cv);
		4096	pthread_mutex_unlock (&u->lock);
		4097	}
		4098
		4099	Whenever you want to start/stop a watcher or do other modifications to an
		4100	event loop, you will now have to lock:
		4101
		4102	ev_timer timeout_watcher;
		4103	userdata *u = ev_userdata (EV_A);
		4104
		4105	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4106
		4107	pthread_mutex_lock (&u->lock);
		4108	ev_timer_start (EV_A_ &timeout_watcher);
		4109	ev_async_send (EV_A_ &u->async_w);
		4110	pthread_mutex_unlock (&u->lock);
		4111
		4112	Note that sending the C<ev_async> watcher is required because otherwise
		4113	an event loop currently blocking in the kernel will have no knowledge
		4114	about the newly added timer. By waking up the loop it will pick up any new
		4115	watchers in the next event loop iteration.
		4116
3206	=head2 COROUTINES	4117	=head3 COROUTINES
3207		4118
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	4119	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	4120	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4121	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	4122	different coroutines, and switch freely between both coroutines running
3212	loop, as long as you don't confuse yourself). The only exception is that	4123	the loop, as long as you don't confuse yourself). The only exception is
3213	you must not do this from C<ev_periodic> reschedule callbacks.	4124	that you must not do this from C<ev_periodic> reschedule callbacks.
3214		4125
3215	Care has been invested into making sure that libev does not keep local	4126	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	4127	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3217	switches.	4128	they do not call any callbacks.
3218		4129
		4130	=head2 COMPILER WARNINGS
3219		4131
3220	=head1 COMPLEXITIES	4132	Depending on your compiler and compiler settings, you might get no or a
		4133	lot of warnings when compiling libev code. Some people are apparently
		4134	scared by this.
3221		4135
3222	In this section the complexities of (many of) the algorithms used inside	4136	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	4137	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	4138	warning options. "Warn-free" code therefore cannot be a goal except when
		4139	targeting a specific compiler and compiler-version.
3225		4140
3226	All of the following are about amortised time: If an array needs to be	4141	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	4142	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	4143	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		4144
3232	=over 4	4145	And of course, some compiler warnings are just plain stupid, or simply
		4146	wrong (because they don't actually warn about the condition their message
		4147	seems to warn about). For example, certain older gcc versions had some
		4148	warnings that resulted an extreme number of false positives. These have
		4149	been fixed, but some people still insist on making code warn-free with
		4150	such buggy versions.
3233		4151
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4152	While libev is written to generate as few warnings as possible,
		4153	"warn-free" code is not a goal, and it is recommended not to build libev
		4154	with any compiler warnings enabled unless you are prepared to cope with
		4155	them (e.g. by ignoring them). Remember that warnings are just that:
		4156	warnings, not errors, or proof of bugs.
3235		4157
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		4158
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4159	=head2 VALGRIND
3241		4160
3242	That means that changing a timer costs less than removing/adding them	4161	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	4162	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		4163
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4164	If you think you found a bug (memory leak, uninitialised data access etc.)
		4165	in libev, then check twice: If valgrind reports something like:
3246		4166
3247	These just add the watcher into an array or at the head of a list.	4167	==2274== definitely lost: 0 bytes in 0 blocks.
		4168	==2274== possibly lost: 0 bytes in 0 blocks.
		4169	==2274== still reachable: 256 bytes in 1 blocks.
3248		4170
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4171	Then there is no memory leak, just as memory accounted to global variables
		4172	is not a memleak - the memory is still being referenced, and didn't leak.
3250		4173
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4174	Similarly, under some circumstances, valgrind might report kernel bugs
		4175	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4176	although an acceptable workaround has been found here), or it might be
		4177	confused.
3252		4178
3253	These watchers are stored in lists then need to be walked to find the	4179	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	4180	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		4181
3257	=item Finding the next timer in each loop iteration: O(1)	4182	If you are unsure about something, feel free to contact the mailing list
		4183	with the full valgrind report and an explanation on why you think this
		4184	is a bug in libev (best check the archives, too :). However, don't be
		4185	annoyed when you get a brisk "this is no bug" answer and take the chance
		4186	of learning how to interpret valgrind properly.
3258		4187
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	4188	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	4189	I suggest using suppression lists.
3261		4190
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		4191
3264	A change means an I/O watcher gets started or stopped, which requires	4192	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and whether C<ev_io_set> was used).
3267		4193
3268	=item Activating one watcher (putting it into the pending state): O(1)	4194	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3269
3270	=item Priority handling: O(number_of_priorities)
3271
3272	Priorities are implemented by allocating some space for each
3273	priority. When doing priority-based operations, libev usually has to
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276
3277	=item Sending an ev_async: O(1)
3278
3279	=item Processing ev_async_send: O(number_of_async_watchers)
3280
3281	=item Processing signals: O(max_signal_number)
3282
3283	Sending involves a system call I<iff> there were no other C<ev_async_send>
3284	calls in the current loop iteration. Checking for async and signal events
3285	involves iterating over all running async watchers or all signal numbers.
3286
3287	=back
3288
3289
3290	=head1 Win32 platform limitations and workarounds
3291		4195
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4196	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	4197	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	4198	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4199	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3302	way (note also that glib is the slowest event library known to man).	4206	way (note also that glib is the slowest event library known to man).
3303		4207
3304	There is no supported compilation method available on windows except	4208	There is no supported compilation method available on windows except
3305	embedding it into other applications.	4209	embedding it into other applications.
3306		4210
		4211	Sensible signal handling is officially unsupported by Microsoft - libev
		4212	tries its best, but under most conditions, signals will simply not work.
		4213
		4214	Not a libev limitation but worth mentioning: windows apparently doesn't
		4215	accept large writes: instead of resulting in a partial write, windows will
		4216	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4217	so make sure you only write small amounts into your sockets (less than a
		4218	megabyte seems safe, but this apparently depends on the amount of memory
		4219	available).
		4220
3307	Due to the many, low, and arbitrary limits on the win32 platform and	4221	Due to the many, low, and arbitrary limits on the win32 platform and
3308	the abysmal performance of winsockets, using a large number of sockets	4222	the abysmal performance of winsockets, using a large number of sockets
3309	is not recommended (and not reasonable). If your program needs to use	4223	is not recommended (and not reasonable). If your program needs to use
3310	more than a hundred or so sockets, then likely it needs to use a totally	4224	more than a hundred or so sockets, then likely it needs to use a totally
3311	different implementation for windows, as libev offers the POSIX readiness	4225	different implementation for windows, as libev offers the POSIX readiness
3312	notification model, which cannot be implemented efficiently on windows	4226	notification model, which cannot be implemented efficiently on windows
3313	(Microsoft monopoly games).	4227	(due to Microsoft monopoly games).
		4228
		4229	A typical way to use libev under windows is to embed it (see the embedding
		4230	section for details) and use the following F<evwrap.h> header file instead
		4231	of F<ev.h>:
		4232
		4233	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4234	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4235
		4236	#include "ev.h"
		4237
		4238	And compile the following F<evwrap.c> file into your project (make sure
		4239	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4240
		4241	#include "evwrap.h"
		4242	#include "ev.c"
3314		4243
3315	=over 4	4244	=over 4
3316		4245
3317	=item The winsocket select function	4246	=item The winsocket select function
3318		4247
3319	The winsocket C<select> function doesn't follow POSIX in that it	4248	The winsocket C<select> function doesn't follow POSIX in that it
3320	requires socket I<handles> and not socket I<file descriptors> (it is	4249	requires socket I<handles> and not socket I<file descriptors> (it is
3321	also extremely buggy). This makes select very inefficient, and also	4250	also extremely buggy). This makes select very inefficient, and also
3322	requires a mapping from file descriptors to socket handles. See the	4251	requires a mapping from file descriptors to socket handles (the Microsoft
		4252	C runtime provides the function C<_open_osfhandle> for this). See the
3323	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	4253	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3324	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	4254	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3325		4255
3326	The configuration for a "naked" win32 using the Microsoft runtime	4256	The configuration for a "naked" win32 using the Microsoft runtime
3327	libraries and raw winsocket select is:	4257	libraries and raw winsocket select is:
3328		4258
3329	#define EV_USE_SELECT 1	4259	#define EV_USE_SELECT 1
3330	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4260	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3331		4261
3332	Note that winsockets handling of fd sets is O(n), so you can easily get a	4262	Note that winsockets handling of fd sets is O(n), so you can easily get a
3333	complexity in the O(n²) range when using win32.	4263	complexity in the O(n²) range when using win32.
3334		4264
3335	=item Limited number of file descriptors	4265	=item Limited number of file descriptors
…		…
3338		4268
3339	Early versions of winsocket's select only supported waiting for a maximum	4269	Early versions of winsocket's select only supported waiting for a maximum
3340	of C<64> handles (probably owning to the fact that all windows kernels	4270	of C<64> handles (probably owning to the fact that all windows kernels
3341	can only wait for C<64> things at the same time internally; Microsoft	4271	can only wait for C<64> things at the same time internally; Microsoft
3342	recommends spawning a chain of threads and wait for 63 handles and the	4272	recommends spawning a chain of threads and wait for 63 handles and the
3343	previous thread in each. Great).	4273	previous thread in each. Sounds great!).
3344		4274
3345	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4275	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3346	to some high number (e.g. C<2048>) before compiling the winsocket select	4276	to some high number (e.g. C<2048>) before compiling the winsocket select
3347	call (which might be in libev or elsewhere, for example, perl does its own	4277	call (which might be in libev or elsewhere, for example, perl and many
3348	select emulation on windows).	4278	other interpreters do their own select emulation on windows).
3349		4279
3350	Another limit is the number of file descriptors in the Microsoft runtime	4280	Another limit is the number of file descriptors in the Microsoft runtime
3351	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4281	libraries, which by default is C<64> (there must be a hidden I<64>
3352	or something like this inside Microsoft). You can increase this by calling	4282	fetish or something like this inside Microsoft). You can increase this
3353	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4283	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3354	arbitrary limit), but is broken in many versions of the Microsoft runtime	4284	(another arbitrary limit), but is broken in many versions of the Microsoft
3355	libraries.
3356
3357	This might get you to about C<512> or C<2048> sockets (depending on	4285	runtime libraries. This might get you to about C<512> or C<2048> sockets
3358	windows version and/or the phase of the moon). To get more, you need to	4286	(depending on windows version and/or the phase of the moon). To get more,
3359	wrap all I/O functions and provide your own fd management, but the cost of	4287	you need to wrap all I/O functions and provide your own fd management, but
3360	calling select (O(n²)) will likely make this unworkable.	4288	the cost of calling select (O(n²)) will likely make this unworkable.
3361		4289
3362	=back	4290	=back
3363		4291
3364
3365	=head1 PORTABILITY REQUIREMENTS	4292	=head2 PORTABILITY REQUIREMENTS
3366		4293
3367	In addition to a working ISO-C implementation, libev relies on a few	4294	In addition to a working ISO-C implementation and of course the
3368	additional extensions:	4295	backend-specific APIs, libev relies on a few additional extensions:
3369		4296
3370	=over 4	4297	=over 4
3371		4298
		4299	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4300	calling conventions regardless of C<ev_watcher_type *>.
		4301
		4302	Libev assumes not only that all watcher pointers have the same internal
		4303	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4304	assumes that the same (machine) code can be used to call any watcher
		4305	callback: The watcher callbacks have different type signatures, but libev
		4306	calls them using an C<ev_watcher *> internally.
		4307
3372	=item C<sig_atomic_t volatile> must be thread-atomic as well	4308	=item C<sig_atomic_t volatile> must be thread-atomic as well
3373		4309
3374	The type C<sig_atomic_t volatile> (or whatever is defined as	4310	The type C<sig_atomic_t volatile> (or whatever is defined as
3375	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4311	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3376	threads. This is not part of the specification for C<sig_atomic_t>, but is	4312	threads. This is not part of the specification for C<sig_atomic_t>, but is
3377	believed to be sufficiently portable.	4313	believed to be sufficiently portable.
3378		4314
3379	=item C<sigprocmask> must work in a threaded environment	4315	=item C<sigprocmask> must work in a threaded environment
3380		4316
…		…
3389	except the initial one, and run the default loop in the initial thread as	4325	except the initial one, and run the default loop in the initial thread as
3390	well.	4326	well.
3391		4327
3392	=item C<long> must be large enough for common memory allocation sizes	4328	=item C<long> must be large enough for common memory allocation sizes
3393		4329
3394	To improve portability and simplify using libev, libev uses C<long>	4330	To improve portability and simplify its API, libev uses C<long> internally
3395	internally instead of C<size_t> when allocating its data structures. On	4331	instead of C<size_t> when allocating its data structures. On non-POSIX
3396	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4332	systems (Microsoft...) this might be unexpectedly low, but is still at
3397	is still at least 31 bits everywhere, which is enough for hundreds of	4333	least 31 bits everywhere, which is enough for hundreds of millions of
3398	millions of watchers.	4334	watchers.
3399		4335
3400	=item C<double> must hold a time value in seconds with enough accuracy	4336	=item C<double> must hold a time value in seconds with enough accuracy
3401		4337
3402	The type C<double> is used to represent timestamps. It is required to	4338	The type C<double> is used to represent timestamps. It is required to
3403	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4339	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3404	enough for at least into the year 4000. This requirement is fulfilled by	4340	enough for at least into the year 4000. This requirement is fulfilled by
3405	implementations implementing IEEE 754 (basically all existing ones).	4341	implementations implementing IEEE 754, which is basically all existing
		4342	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4343	2200.
3406		4344
3407	=back	4345	=back
3408		4346
3409	If you know of other additional requirements drop me a note.	4347	If you know of other additional requirements drop me a note.
3410		4348
3411		4349
3412	=head1 COMPILER WARNINGS	4350	=head1 ALGORITHMIC COMPLEXITIES
3413		4351
3414	Depending on your compiler and compiler settings, you might get no or a	4352	In this section the complexities of (many of) the algorithms used inside
3415	lot of warnings when compiling libev code. Some people are apparently	4353	libev will be documented. For complexity discussions about backends see
3416	scared by this.	4354	the documentation for C<ev_default_init>.
3417		4355
3418	However, these are unavoidable for many reasons. For one, each compiler	4356	All of the following are about amortised time: If an array needs to be
3419	has different warnings, and each user has different tastes regarding	4357	extended, libev needs to realloc and move the whole array, but this
3420	warning options. "Warn-free" code therefore cannot be a goal except when	4358	happens asymptotically rarer with higher number of elements, so O(1) might
3421	targeting a specific compiler and compiler-version.	4359	mean that libev does a lengthy realloc operation in rare cases, but on
		4360	average it is much faster and asymptotically approaches constant time.
3422		4361
3423	Another reason is that some compiler warnings require elaborate	4362	=over 4
3424	workarounds, or other changes to the code that make it less clear and less
3425	maintainable.
3426		4363
3427	And of course, some compiler warnings are just plain stupid, or simply	4364	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3428	wrong (because they don't actually warn about the condition their message
3429	seems to warn about).
3430		4365
3431	While libev is written to generate as few warnings as possible,	4366	This means that, when you have a watcher that triggers in one hour and
3432	"warn-free" code is not a goal, and it is recommended not to build libev	4367	there are 100 watchers that would trigger before that, then inserting will
3433	with any compiler warnings enabled unless you are prepared to cope with	4368	have to skip roughly seven (C<ld 100>) of these watchers.
3434	them (e.g. by ignoring them). Remember that warnings are just that:
3435	warnings, not errors, or proof of bugs.
3436		4369
		4370	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3437		4371
3438	=head1 VALGRIND	4372	That means that changing a timer costs less than removing/adding them,
		4373	as only the relative motion in the event queue has to be paid for.
3439		4374
3440	Valgrind has a special section here because it is a popular tool that is	4375	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3441	highly useful, but valgrind reports are very hard to interpret.
3442		4376
3443	If you think you found a bug (memory leak, uninitialised data access etc.)	4377	These just add the watcher into an array or at the head of a list.
3444	in libev, then check twice: If valgrind reports something like:
3445		4378
3446	==2274== definitely lost: 0 bytes in 0 blocks.	4379	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3447	==2274== possibly lost: 0 bytes in 0 blocks.
3448	==2274== still reachable: 256 bytes in 1 blocks.
3449		4380
3450	Then there is no memory leak. Similarly, under some circumstances,	4381	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3451	valgrind might report kernel bugs as if it were a bug in libev, or it
3452	might be confused (it is a very good tool, but only a tool).
3453		4382
3454	If you are unsure about something, feel free to contact the mailing list	4383	These watchers are stored in lists, so they need to be walked to find the
3455	with the full valgrind report and an explanation on why you think this is	4384	correct watcher to remove. The lists are usually short (you don't usually
3456	a bug in libev. However, don't be annoyed when you get a brisk "this is	4385	have many watchers waiting for the same fd or signal: one is typical, two
3457	no bug" answer and take the chance of learning how to interpret valgrind	4386	is rare).
3458	properly.
3459		4387
3460	If you need, for some reason, empty reports from valgrind for your project	4388	=item Finding the next timer in each loop iteration: O(1)
3461	I suggest using suppression lists.
3462		4389
		4390	By virtue of using a binary or 4-heap, the next timer is always found at a
		4391	fixed position in the storage array.
		4392
		4393	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4394
		4395	A change means an I/O watcher gets started or stopped, which requires
		4396	libev to recalculate its status (and possibly tell the kernel, depending
		4397	on backend and whether C<ev_io_set> was used).
		4398
		4399	=item Activating one watcher (putting it into the pending state): O(1)
		4400
		4401	=item Priority handling: O(number_of_priorities)
		4402
		4403	Priorities are implemented by allocating some space for each
		4404	priority. When doing priority-based operations, libev usually has to
		4405	linearly search all the priorities, but starting/stopping and activating
		4406	watchers becomes O(1) with respect to priority handling.
		4407
		4408	=item Sending an ev_async: O(1)
		4409
		4410	=item Processing ev_async_send: O(number_of_async_watchers)
		4411
		4412	=item Processing signals: O(max_signal_number)
		4413
		4414	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4415	calls in the current loop iteration. Checking for async and signal events
		4416	involves iterating over all running async watchers or all signal numbers.
		4417
		4418	=back
		4419
		4420
		4421	=head1 GLOSSARY
		4422
		4423	=over 4
		4424
		4425	=item active
		4426
		4427	A watcher is active as long as it has been started (has been attached to
		4428	an event loop) but not yet stopped (disassociated from the event loop).
		4429
		4430	=item application
		4431
		4432	In this document, an application is whatever is using libev.
		4433
		4434	=item callback
		4435
		4436	The address of a function that is called when some event has been
		4437	detected. Callbacks are being passed the event loop, the watcher that
		4438	received the event, and the actual event bitset.
		4439
		4440	=item callback invocation
		4441
		4442	The act of calling the callback associated with a watcher.
		4443
		4444	=item event
		4445
		4446	A change of state of some external event, such as data now being available
		4447	for reading on a file descriptor, time having passed or simply not having
		4448	any other events happening anymore.
		4449
		4450	In libev, events are represented as single bits (such as C<EV_READ> or
		4451	C<EV_TIMEOUT>).
		4452
		4453	=item event library
		4454
		4455	A software package implementing an event model and loop.
		4456
		4457	=item event loop
		4458
		4459	An entity that handles and processes external events and converts them
		4460	into callback invocations.
		4461
		4462	=item event model
		4463
		4464	The model used to describe how an event loop handles and processes
		4465	watchers and events.
		4466
		4467	=item pending
		4468
		4469	A watcher is pending as soon as the corresponding event has been detected,
		4470	and stops being pending as soon as the watcher will be invoked or its
		4471	pending status is explicitly cleared by the application.
		4472
		4473	A watcher can be pending, but not active. Stopping a watcher also clears
		4474	its pending status.
		4475
		4476	=item real time
		4477
		4478	The physical time that is observed. It is apparently strictly monotonic :)
		4479
		4480	=item wall-clock time
		4481
		4482	The time and date as shown on clocks. Unlike real time, it can actually
		4483	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4484	clock.
		4485
		4486	=item watcher
		4487
		4488	A data structure that describes interest in certain events. Watchers need
		4489	to be started (attached to an event loop) before they can receive events.
		4490
		4491	=item watcher invocation
		4492
		4493	The act of calling the callback associated with a watcher.
		4494
		4495	=back
3463		4496
3464	=head1 AUTHOR	4497	=head1 AUTHOR
3465		4498
3466	Marc Lehmann <libev@schmorp.de>.	4499	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3467		4500

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