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Revision 1.19 by root, Thu Nov 1 11:43:10 2007 UTC vs.
Revision 1.138 by root, Sun May 6 16:30:27 2012 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	EV - perl interface to libevent, monkey.org/~provos/libevent/	3	EV - perl interface to libev, a high performance full-featured event loop
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use EV;	7	use EV;
		8
		9	# TIMERS
		10
		11	my $w = EV::timer 2, 0, sub {
		12	warn "is called after 2s";
		13	};
		14
		15	my $w = EV::timer 2, 2, sub {
		16	warn "is called roughly every 2s (repeat = 2)";
		17	};
		18
		19	undef $w; # destroy event watcher again
		20
		21	my $w = EV::periodic 0, 60, 0, sub {
		22	warn "is called every minute, on the minute, exactly";
		23	};
		24
		25	# IO
		26
		27	my $w = EV::io *STDIN, EV::READ, sub {
		28	my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
		29	warn "stdin is readable, you entered: ", <STDIN>;
		30	};
		31
		32	# SIGNALS
		33
		34	my $w = EV::signal 'QUIT', sub {
		35	warn "sigquit received\n";
		36	};
		37
		38	# CHILD/PID STATUS CHANGES
8		39
9	# TIMER	40	my $w = EV::child 666, 0, sub {
		41	my ($w, $revents) = @_;
		42	my $status = $w->rstatus;
		43	};
10		44
11	my $w = EV::timer 2, 0, sub {	45	# STAT CHANGES
12	warn "is called after 2s";	46	my $w = EV::stat "/etc/passwd", 10, sub {
13	};
14
15	my $w = EV::timer 2, 1, sub {
16	warn "is called roughly every 2s (repeat = 1)";
17	};
18
19	undef $w; # destroy event watcher again
20
21	my $w = EV::timer_abs 0, 60, sub {
22	warn "is called every minute, on the minute, exactly";
23	};
24
25	# IO
26
27	my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub {
28	my ($w, $revents) = @_; # all callbacks get the watcher object and event mask
29	if ($revents & EV::TIMEOUT) {
30	warn "nothing received on stdin for 10 seconds, retrying";
31	} else {
32	warn "stdin is readable, you entered: ", <STDIN>;
33	}
34	};
35	$w->timeout (10);
36
37	my $w = EV::timed_io \*STDIN, EV::READ, 30, sub {
38	my ($w, $revents) = @_;	47	my ($w, $revents) = @_;
39	if ($revents & EV::TIMEOUT) {	48	warn $w->path, " has changed somehow.\n";
40	warn "nothing entered within 30 seconds, bye bye.\n";
41	$w->stop;
42	} else {
43	my $line = <STDIN>;
44	warn "you entered something, you again have 30 seconds.\n";
45	}
46	};	49	};
47		50
48	# SIGNALS
49
50	my $w = EV::signal 'QUIT', sub {
51	warn "sigquit received\n";
52	};
53
54	my $w = EV::signal 3, sub {
55	warn "sigquit received (this is GNU/Linux, right?)\n";
56	};
57
58	# CHILD/PID STATUS CHANGES
59
60	my $w = EV::child 666, sub {
61	my ($w, $revents, $status) = @_;
62	};
63
64	# MAINLOOP	51	# MAINLOOP
65	EV::dispatch; # loop as long as watchers are active	52	EV::run; # loop until EV::unloop is called or all watchers stop
66	EV::loop; # the same thing
67	EV::loop EV::LOOP_ONESHOT; # block until some events could be handles	53	EV::run EV::RUN_ONCE; # block until at least one event could be handled
68	EV::loop EV::LOOP_NONBLOCK; # check and handle some events, but do not wait	54	EV::run EV::RUN_NOWAIT; # try to handle same events, but do not block
		55
		56	=head1 BEFORE YOU START USING THIS MODULE
		57
		58	If you only need timer, I/O, signal, child and idle watchers and not the
		59	advanced functionality of this module, consider using L<AnyEvent> instead,
		60	specifically the simplified API described in L<AE>.
		61
		62	When used with EV as backend, the L<AE> API is as fast as the native L<EV>
		63	API, but your programs/modules will still run with many other event loops.
69		64
70	=head1 DESCRIPTION	65	=head1 DESCRIPTION
71		66
72	This module provides an interface to libev	67	This module provides an interface to libev
73	(L<http://software.schmorp.de/pkg/libev.html>). You probably should	68	(L<http://software.schmorp.de/pkg/libev.html>). While the documentation
74	acquaint yourself with its documentation and source code to be able to use	69	below is comprehensive, one might also consult the documentation of
75	this module fully.	70	libev itself (L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod> or
		71	F<perldoc EV::libev>) for more subtle details on watcher semantics or some
		72	discussion on the available backends, or how to force a specific backend
		73	with C<LIBEV_FLAGS>, or just about in any case because it has much more
		74	detailed information.
		75
		76	This module is very fast and scalable. It is actually so fast that you
		77	can use it through the L<AnyEvent> module, stay portable to other event
		78	loops (if you don't rely on any watcher types not available through it)
		79	and still be faster than with any other event loop currently supported in
		80	Perl.
		81
		82	=head2 PORTING FROM EV 3.X to 4.X
		83
		84	EV version 4 introduces a number of incompatible changes summarised
		85	here. According to the depreciation strategy used by libev, there is a
		86	compatibility layer in place so programs should continue to run unchanged
		87	(the XS interface lacks this layer, so programs using that one need to be
		88	updated).
		89
		90	This compatibility layer will be switched off in some future release.
		91
		92	All changes relevant to Perl are renames of symbols, functions and
		93	methods:
		94
		95	EV::loop => EV::run
		96	EV::LOOP_NONBLOCK => EV::RUN_NOWAIT
		97	EV::LOOP_ONESHOT => EV::RUN_ONCE
		98
		99	EV::unloop => EV::break
		100	EV::UNLOOP_CANCEL => EV::BREAK_CANCEL
		101	EV::UNLOOP_ONE => EV::BREAK_ONE
		102	EV::UNLOOP_ALL => EV::BREAK_ALL
		103
		104	EV::TIMEOUT => EV::TIMER
		105
		106	EV::loop_count => EV::iteration
		107	EV::loop_depth => EV::depth
		108	EV::loop_verify => EV::verify
		109
		110	The loop object methods corresponding to the functions above have been
		111	similarly renamed.
		112
		113	=head2 MODULE EXPORTS
		114
		115	This module does not export any symbols.
76		116
77	=cut	117	=cut
78		118
79	package EV;	119	package EV;
80		120
81	use strict;	121	use common::sense;
82		122
83	BEGIN {	123	BEGIN {
84	our $VERSION = '0.1';	124	our $VERSION = '4.11';
85	use XSLoader;	125	use XSLoader;
86	XSLoader::load "EV", $VERSION;	126	XSLoader::load "EV", $VERSION;
87	}	127	}
88		128
89	@EV::Io::ISA =	129	@EV::IO::ISA =
90	@EV::Timer::ISA =	130	@EV::Timer::ISA =
91	@EV::Periodic::ISA =	131	@EV::Periodic::ISA =
92	@EV::Signal::ISA =	132	@EV::Signal::ISA =
		133	@EV::Child::ISA =
		134	@EV::Stat::ISA =
93	@EV::Idle::ISA =	135	@EV::Idle::ISA =
94	@EV::Prepare::ISA =	136	@EV::Prepare::ISA =
95	@EV::Check::ISA =	137	@EV::Check::ISA =
96	@EV::Child::ISA = "EV::Watcher";	138	@EV::Embed::ISA =
		139	@EV::Fork::ISA =
		140	@EV::Async::ISA =
		141	"EV::Watcher";
		142
		143	@EV::Loop::Default::ISA = "EV::Loop";
		144
		145	=head1 EVENT LOOPS
		146
		147	EV supports multiple event loops: There is a single "default event loop"
		148	that can handle everything including signals and child watchers, and any
		149	number of "dynamic event loops" that can use different backends (with
		150	various limitations), but no child and signal watchers.
		151
		152	You do not have to do anything to create the default event loop: When
		153	the module is loaded a suitable backend is selected on the premise of
		154	selecting a working backend (which for example rules out kqueue on most
		155	BSDs). Modules should, unless they have "special needs" always use the
		156	default loop as this is fastest (perl-wise), best supported by other
		157	modules (e.g. AnyEvent or Coro) and most portable event loop.
		158
		159	For specific programs you can create additional event loops dynamically.
		160
		161	If you want to take advantage of kqueue (which often works properly for
		162	sockets only) even though the default loop doesn't enable it, you can
		163	I<embed> a kqueue loop into the default loop: running the default loop
		164	will then also service the kqueue loop to some extent. See the example in
		165	the section about embed watchers for an example on how to achieve that.
		166
		167	=over 4
		168
		169	=item $loop = new EV::Loop [$flags]
		170
		171	Create a new event loop as per the specified flags. Please refer to
		172	the C<ev_loop_new ()> function description in the libev documentation
		173	(L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTIONS>,
		174	or locally-installed as F<EV::libev> manpage) for more info.
		175
		176	The loop will automatically be destroyed when it is no longer referenced
		177	by any watcher and the loop object goes out of scope.
		178
		179	If you are not embedding the loop, then Using C<EV::FLAG_FORKCHECK>
		180	is recommended, as only the default event loop is protected by this
		181	module. If you I<are> embedding this loop in the default loop, this is not
		182	necessary, as C<EV::embed> automatically does the right thing on fork.
		183
		184	=item $loop->loop_fork
		185
		186	Must be called after a fork in the child, before entering or continuing
		187	the event loop. An alternative is to use C<EV::FLAG_FORKCHECK> which calls
		188	this function automatically, at some performance loss (refer to the libev
		189	documentation).
		190
		191	=item $loop->verify
		192
		193	Calls C<ev_verify> to make internal consistency checks (for debugging
		194	libev) and abort the program if any data structures were found to be
		195	corrupted.
		196
		197	=item $loop = EV::default_loop [$flags]
		198
		199	Return the default loop (which is a singleton object). Since this module
		200	already creates the default loop with default flags, specifying flags here
		201	will not have any effect unless you destroy the default loop first, which
		202	isn't supported. So in short: don't do it, and if you break it, you get to
		203	keep the pieces.
		204
		205	=back
		206
97		207
98	=head1 BASIC INTERFACE	208	=head1 BASIC INTERFACE
99		209
100	=over 4	210	=over 4
101		211
102	=item $EV::NPRI
103
104	How many priority levels are available.
105
106	=item $EV::DIED	212	=item $EV::DIED
107		213
108	Must contain a reference to a function that is called when a callback	214	Must contain a reference to a function that is called when a callback
109	throws an exception (with $@ containing thr error). The default prints an	215	throws an exception (with $@ containing the error). The default prints an
110	informative message and continues.	216	informative message and continues.
111		217
112	If this callback throws an exception it will be silently ignored.	218	If this callback throws an exception it will be silently ignored.
113		219
		220	=item $flags = EV::supported_backends
		221
		222	=item $flags = EV::recommended_backends
		223
		224	=item $flags = EV::embeddable_backends
		225
		226	Returns the set (see C<EV::BACKEND_*> flags) of backends supported by this
		227	instance of EV, the set of recommended backends (supposed to be good) for
		228	this platform and the set of embeddable backends (see EMBED WATCHERS).
		229
		230	=item EV::sleep $seconds
		231
		232	Block the process for the given number of (fractional) seconds.
		233
		234	=item $time = EV::time
		235
		236	Returns the current time in (fractional) seconds since the epoch.
		237
114	=item $time = EV::now	238	=item $time = EV::now
115		239
116	Returns the time in (fractional) seconds since the epoch.	240	=item $time = $loop->now
117		241
		242	Returns the time the last event loop iteration has been started. This
		243	is the time that (relative) timers are based on, and referring to it is
		244	usually faster then calling EV::time.
		245
		246	=item EV::now_update
		247
		248	=item $loop->now_update
		249
		250	Establishes the current time by querying the kernel, updating the time
		251	returned by C<EV::now> in the progress. This is a costly operation and
		252	is usually done automatically within C<EV::loop>.
		253
		254	This function is rarely useful, but when some event callback runs for a
		255	very long time without entering the event loop, updating libev's idea of
		256	the current time is a good idea.
		257
		258	=item EV::suspend
		259
		260	=item $loop->suspend
		261
		262	=item EV::resume
		263
		264	=item $loop->resume
		265
		266	These two functions suspend and resume a loop, for use when the loop is
		267	not used for a while and timeouts should not be processed.
		268
		269	A typical use case would be an interactive program such as a game: When
		270	the user presses C<^Z> to suspend the game and resumes it an hour later it
		271	would be best to handle timeouts as if no time had actually passed while
		272	the program was suspended. This can be achieved by calling C<suspend>
		273	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		274	C<resume> directly afterwards to resume timer processing.
		275
		276	Effectively, all C<timer> watchers will be delayed by the time spend
		277	between C<suspend> and C<resume>, and all C<periodic> watchers
		278	will be rescheduled (that is, they will lose any events that would have
		279	occured while suspended).
		280
		281	After calling C<suspend> you B<must not> call I<any> function on the given
		282	loop other than C<resume>, and you B<must not> call C<resume>
		283	without a previous call to C<suspend>.
		284
		285	Calling C<suspend>/C<resume> has the side effect of updating the event
		286	loop time (see C<now_update>).
		287
		288	=item $backend = EV::backend
		289
		290	=item $backend = $loop->backend
		291
		292	Returns an integer describing the backend used by libev (EV::BACKEND_SELECT
		293	or EV::BACKEND_EPOLL).
		294
		295	=item $active = EV::run [$flags]
		296
		297	=item $active = $loop->run ([$flags])
		298
		299	Begin checking for events and calling callbacks. It returns when a
		300	callback calls EV::unloop or the flasg are nonzero (in which case the
		301	return value is true) or when there are no active watchers which reference
		302	the loop (keepalive is true), in which case the return value will be
		303	false. The returnv alue can generally be interpreted as "if true, there is
		304	more work left to do".
		305
		306	The $flags argument can be one of the following:
		307
		308	0 as above
		309	EV::RUN_ONCE block at most once (wait, but do not loop)
		310	EV::RUN_NOWAIT do not block at all (fetch/handle events but do not wait)
		311
		312	=item EV::break [$how]
		313
		314	=item $loop->break ([$how])
		315
		316	When called with no arguments or an argument of EV::BREAK_ONE, makes the
		317	innermost call to EV::loop return.
		318
		319	When called with an argument of EV::BREAK_ALL, all calls to EV::loop will
		320	return as fast as possible.
		321
		322	When called with an argument of EV::BREAK_CANCEL, any pending break will
		323	be cancelled.
		324
118	=item $version = EV::version	325	=item $count = EV::iteration
119		326
120	=item $method = EV::method	327	=item $count = $loop->iteration
121		328
122	Return version string and event polling method used.	329	Return the number of times the event loop has polled for new
		330	events. Sometimes useful as a generation counter.
123		331
124	=item EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT	332	=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
125		333
126	=item EV::loopexit $after	334	=item $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
127		335
128	Exit any active loop or dispatch after C<$after> seconds or immediately if	336	This function rolls together an I/O and a timer watcher for a single
129	C<$after> is missing or zero.	337	one-shot event without the need for managing a watcher object.
130		338
131	=item EV::dispatch	339	If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events>
		340	must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ
		341	| EV::WRITE>, indicating the type of I/O event you want to wait for. If
		342	you do not want to wait for some I/O event, specify C<undef> for
		343	C<$fh_or_undef> and C<0> for C<$events>).
132		344
133	Same as C<EV::loop 0>.	345	If timeout is C<undef> or negative, then there will be no
		346	timeout. Otherwise a EV::timer with this value will be started.
134		347
135	=item EV::event $callback	348	When an error occurs or either the timeout or I/O watcher triggers, then
		349	the callback will be called with the received event set (in general
		350	you can expect it to be a combination of C<EV::ERROR>, C<EV::READ>,
		351	C<EV::WRITE> and C<EV::TIMER>).
136		352
137	Creates a new event watcher waiting for nothing, calling the given callback.	353	EV::once doesn't return anything: the watchers stay active till either
		354	of them triggers, then they will be stopped and freed, and the callback
		355	invoked.
138		356
		357	=item EV::feed_fd_event $fd, $revents
		358
		359	=item $loop->feed_fd_event ($fd, $revents)
		360
		361	Feed an event on a file descriptor into EV. EV will react to this call as
		362	if the readyness notifications specified by C<$revents> (a combination of
		363	C<EV::READ> and C<EV::WRITE>) happened on the file descriptor C<$fd>.
		364
		365	=item EV::feed_signal_event $signal
		366
		367	Feed a signal event into the default loop. EV will react to this call as
		368	if the signal specified by C<$signal> had occured.
		369
		370	=item EV::feed_signal $signal
		371
		372	Feed a signal event into EV - unlike C<EV::feed_signal_event>, this works
		373	regardless of which loop has registered the signal, and is mainly useful
		374	fro custom signal implementations.
		375
		376	=item EV::set_io_collect_interval $time
		377
		378	=item $loop->set_io_collect_interval ($time)
		379
		380	=item EV::set_timeout_collect_interval $time
		381
		382	=item $loop->set_timeout_collect_interval ($time)
		383
		384	These advanced functions set the minimum block interval when polling for I/O events and the minimum
		385	wait interval for timer events. See the libev documentation at
		386	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP>
		387	(locally installed as F<EV::libev>) for a more detailed discussion.
		388
		389	=item $count = EV::pending_count
		390
		391	=item $count = $loop->pending_count
		392
		393	Returns the number of currently pending watchers.
		394
		395	=item EV::invoke_pending
		396
		397	=item $loop->invoke_pending
		398
		399	Invoke all currently pending watchers.
		400
		401	=back
		402
		403
		404	=head1 WATCHER OBJECTS
		405
		406	A watcher is an object that gets created to record your interest in some
		407	event. For instance, if you want to wait for STDIN to become readable, you
		408	would create an EV::io watcher for that:
		409
		410	my $watcher = EV::io *STDIN, EV::READ, sub {
		411	my ($watcher, $revents) = @_;
		412	warn "yeah, STDIN should now be readable without blocking!\n"
		413	};
		414
		415	All watchers can be active (waiting for events) or inactive (paused). Only
		416	active watchers will have their callbacks invoked. All callbacks will be
		417	called with at least two arguments: the watcher and a bitmask of received
		418	events.
		419
		420	Each watcher type has its associated bit in revents, so you can use the
		421	same callback for multiple watchers. The event mask is named after the
		422	type, i.e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
		423	EV::periodic sets EV::PERIODIC and so on, with the exception of I/O events
		424	(which can set both EV::READ and EV::WRITE bits).
		425
		426	In the rare case where one wants to create a watcher but not start it at
		427	the same time, each constructor has a variant with a trailing C<_ns> in
		428	its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
		429
		430	Please note that a watcher will automatically be stopped when the watcher
		431	object is destroyed, so you I<need> to keep the watcher objects returned by
		432	the constructors.
		433
		434	Also, all methods changing some aspect of a watcher (->set, ->priority,
		435	->fh and so on) automatically stop and start it again if it is active,
		436	which means pending events get lost.
		437
		438	=head2 COMMON WATCHER METHODS
		439
		440	This section lists methods common to all watchers.
		441
		442	=over 4
		443
		444	=item $w->start
		445
		446	Starts a watcher if it isn't active already. Does nothing to an already
		447	active watcher. By default, all watchers start out in the active state
		448	(see the description of the C<_ns> variants if you need stopped watchers).
		449
		450	=item $w->stop
		451
		452	Stop a watcher if it is active. Also clear any pending events (events that
		453	have been received but that didn't yet result in a callback invocation),
		454	regardless of whether the watcher was active or not.
		455
		456	=item $bool = $w->is_active
		457
		458	Returns true if the watcher is active, false otherwise.
		459
		460	=item $current_data = $w->data
		461
		462	=item $old_data = $w->data ($new_data)
		463
		464	Queries a freely usable data scalar on the watcher and optionally changes
		465	it. This is a way to associate custom data with a watcher:
		466
		467	my $w = EV::timer 60, 0, sub {
		468	warn $_[0]->data;
		469	};
		470	$w->data ("print me!");
		471
		472	=item $current_cb = $w->cb
		473
		474	=item $old_cb = $w->cb ($new_cb)
		475
		476	Queries the callback on the watcher and optionally changes it. You can do
		477	this at any time without the watcher restarting.
		478
		479	=item $current_priority = $w->priority
		480
		481	=item $old_priority = $w->priority ($new_priority)
		482
		483	Queries the priority on the watcher and optionally changes it. Pending
		484	watchers with higher priority will be invoked first. The valid range of
		485	priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
		486	-2). If the priority is outside this range it will automatically be
		487	normalised to the nearest valid priority.
		488
		489	The default priority of any newly-created watcher is 0.
		490
		491	Note that the priority semantics have not yet been fleshed out and are
		492	subject to almost certain change.
		493
		494	=item $w->invoke ($revents)
		495
		496	Call the callback *now* with the given event mask.
		497
		498	=item $w->feed_event ($revents)
		499
		500	Feed some events on this watcher into EV. EV will react to this call as if
		501	the watcher had received the given C<$revents> mask.
		502
		503	=item $revents = $w->clear_pending
		504
		505	If the watcher is pending, this function clears its pending status and
		506	returns its C<$revents> bitset (as if its callback was invoked). If the
		507	watcher isn't pending it does nothing and returns C<0>.
		508
		509	=item $previous_state = $w->keepalive ($bool)
		510
		511	Normally, C<EV::loop> will return when there are no active watchers
		512	(which is a "deadlock" because no progress can be made anymore). This is
		513	convenient because it allows you to start your watchers (and your jobs),
		514	call C<EV::loop> once and when it returns you know that all your jobs are
		515	finished (or they forgot to register some watchers for their task :).
		516
		517	Sometimes, however, this gets in your way, for example when the module
		518	that calls C<EV::loop> (usually the main program) is not the same module
		519	as a long-living watcher (for example a DNS client module written by
		520	somebody else even). Then you might want any outstanding requests to be
		521	handled, but you would not want to keep C<EV::loop> from returning just
		522	because you happen to have this long-running UDP port watcher.
		523
		524	In this case you can clear the keepalive status, which means that even
		525	though your watcher is active, it won't keep C<EV::loop> from returning.
		526
		527	The initial value for keepalive is true (enabled), and you can change it
		528	any time.
		529
		530	Example: Register an I/O watcher for some UDP socket but do not keep the
		531	event loop from running just because of that watcher.
		532
		533	my $udp_socket = ...
		534	my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
		535	$udp_watcher->keepalive (0);
		536
		537	=item $loop = $w->loop
		538
		539	Return the loop that this watcher is attached to.
		540
		541	=back
		542
		543
		544	=head1 WATCHER TYPES
		545
		546	Each of the following subsections describes a single watcher type.
		547
		548	=head3 I/O WATCHERS - is this file descriptor readable or writable?
		549
		550	=over 4
		551
139	=item my $w = EV::io $fileno_or_fh, $eventmask, $callback	552	=item $w = EV::io $fileno_or_fh, $eventmask, $callback
140		553
141	=item my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback	554	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
		555
		556	=item $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
		557
		558	=item $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
142		559
143	As long as the returned watcher object is alive, call the C<$callback>	560	As long as the returned watcher object is alive, call the C<$callback>
144	when the events specified in C<$eventmask> happen. Initially, the timeout	561	when at least one of events specified in C<$eventmask> occurs.
145	is disabled.
146		562
147	You can additionall set a timeout to occur on the watcher, but note that
148	this timeout will not be reset when you get an I/O event in the EV::PERSIST
149	case, and reaching a timeout will always stop the watcher even in the
150	EV::PERSIST case.
151
152	If you want a timeout to occur only after a specific time of inactivity, set
153	a repeating timeout and do NOT use EV::PERSIST.
154
155	Eventmask can be one or more of these constants ORed together:	563	The $eventmask can be one or more of these constants ORed together:
156		564
157	EV::READ wait until read() wouldn't block anymore	565	EV::READ wait until read() wouldn't block anymore
158	EV::WRITE wait until write() wouldn't block anymore	566	EV::WRITE wait until write() wouldn't block anymore
159	EV::PERSIST stay active after a (non-timeout) event occured
160		567
161	The C<io_ns> variant doesn't add/start the newly created watcher.	568	The C<io_ns> variant doesn't start (activate) the newly created watcher.
162		569
163	=item my $w = EV::timed_io $fileno_or_fh, $eventmask, $timeout, $callback	570	=item $w->set ($fileno_or_fh, $eventmask)
164		571
165	=item my $w = EV::timed_io_ns $fileno_or_fh, $eventmask, $timeout, $callback	572	Reconfigures the watcher, see the constructor above for details. Can be
		573	called at any time.
166		574
167	Same as C<io> and C<io_ns>, but also specifies a timeout (as if there was	575	=item $current_fh = $w->fh
168	a call to C<< $w->timeout ($timout, 1) >>. The persist flag is not allowed
169	and will automatically be cleared. The watcher will be restarted after each event.
170		576
171	If the timeout is zero or undef, no timeout will be set, and a normal	577	=item $old_fh = $w->fh ($new_fh)
172	watcher (with the persist flag set!) will be created.
173		578
174	This has the effect of timing out after the specified period of inactivity	579	Returns the previously set filehandle and optionally set a new one.
175	has happened.
176		580
177	Due to the design of libevent, this is also relatively inefficient, having	581	=item $current_eventmask = $w->events
178	one or two io watchers and a separate timeout watcher that you reset on
179	activity (by calling its C<start> method) is usually more efficient.
180		582
		583	=item $old_eventmask = $w->events ($new_eventmask)
		584
		585	Returns the previously set event mask and optionally set a new one.
		586
		587	=back
		588
		589
		590	=head3 TIMER WATCHERS - relative and optionally repeating timeouts
		591
		592	=over 4
		593
181	=item my $w = EV::timer $after, $repeat, $callback	594	=item $w = EV::timer $after, $repeat, $callback
182		595
183	=item my $w = EV::timer_ns $after, $repeat, $callback	596	=item $w = EV::timer_ns $after, $repeat, $callback
184		597
185	Calls the callback after C<$after> seconds. If C<$repeat> is true, the	598	=item $w = $loop->timer ($after, $repeat, $callback)
186	timer will be restarted after the callback returns. This means that the
187	callback would be called roughly every C<$after> seconds, prolonged by the
188	time the callback takes.
189		599
		600	=item $w = $loop->timer_ns ($after, $repeat, $callback)
		601
		602	Calls the callback after C<$after> seconds (which may be fractional). If
		603	C<$repeat> is non-zero, the timer will be restarted (with the $repeat
		604	value as $after) after the callback returns.
		605
		606	This means that the callback would be called roughly after C<$after>
		607	seconds, and then every C<$repeat> seconds. The timer does his best not
		608	to drift, but it will not invoke the timer more often then once per event
		609	loop iteration, and might drift in other cases. If that isn't acceptable,
		610	look at EV::periodic, which can provide long-term stable timers.
		611
		612	The timer is based on a monotonic clock, that is, if somebody is sitting
		613	in front of the machine while the timer is running and changes the system
		614	clock, the timer will nevertheless run (roughly) the same time.
		615
190	The C<timer_ns> variant doesn't add/start the newly created watcher.	616	The C<timer_ns> variant doesn't start (activate) the newly created watcher.
191		617
192	=item my $w = EV::timer_abs $at, $interval, $callback	618	=item $w->set ($after, $repeat)
193		619
194	=item my $w = EV::timer_abs_ns $at, $interval, $callback	620	Reconfigures the watcher, see the constructor above for details. Can be called at
		621	any time.
195		622
196	Similar to EV::timer, but the time is given as an absolute point in time	623	=item $w->again
197	(C<$at>), plus an optional C<$interval>.
198		624
199	If the C<$interval> is zero, then the callback will be called at the time	625	Similar to the C<start> method, but has special semantics for repeating timers:
200	C<$at> if that is in the future, or as soon as possible if its in the
201	past. It will not automatically repeat.
202		626
203	If the C<$interval> is nonzero, then the watcher will always be scheduled	627	If the timer is active and non-repeating, it will be stopped.
204	to time out at the next C<$at + integer * $interval> time.
205		628
206	This can be used to schedule a callback to run at very regular intervals,	629	If the timer is active and repeating, reset the timeout to occur
207	as long as the processing time is less then the interval (otherwise	630	C<$repeat> seconds after now.
208	obviously events will be skipped).	631
		632	If the timer is inactive and repeating, start it using the repeat value.
		633
		634	Otherwise do nothing.
		635
		636	This behaviour is useful when you have a timeout for some IO
		637	operation. You create a timer object with the same value for C<$after> and
		638	C<$repeat>, and then, in the read/write watcher, run the C<again> method
		639	on the timeout.
		640
		641	=back
		642
		643
		644	=head3 PERIODIC WATCHERS - to cron or not to cron?
		645
		646	=over 4
		647
		648	=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
		649
		650	=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
		651
		652	=item $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
		653
		654	=item $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
		655
		656	Similar to EV::timer, but is not based on relative timeouts but on
		657	absolute times. Apart from creating "simple" timers that trigger "at" the
		658	specified time, it can also be used for non-drifting absolute timers and
		659	more complex, cron-like, setups that are not adversely affected by time
		660	jumps (i.e. when the system clock is changed by explicit date -s or other
		661	means such as ntpd). It is also the most complex watcher type in EV.
		662
		663	It has three distinct "modes":
		664
		665	=over 4
		666
		667	=item * absolute timer ($interval = $reschedule_cb = 0)
		668
		669	This time simply fires at the wallclock time C<$at> and doesn't repeat. It
		670	will not adjust when a time jump occurs, that is, if it is to be run
		671	at January 1st 2011 then it will run when the system time reaches or
		672	surpasses this time.
		673
		674	=item * repeating interval timer ($interval > 0, $reschedule_cb = 0)
		675
		676	In this mode the watcher will always be scheduled to time out at the
		677	next C<$at + N * $interval> time (for some integer N) and then repeat,
		678	regardless of any time jumps.
		679
		680	This can be used to create timers that do not drift with respect to system
		681	time:
		682
		683	my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
		684
		685	That doesn't mean there will always be 3600 seconds in between triggers,
		686	but only that the the clalback will be called when the system time shows a
		687	full hour (UTC).
209		688
210	Another way to think about it (for the mathematically inclined) is that	689	Another way to think about it (for the mathematically inclined) is that
211	C<timer_abs> will try to tun the callback at the next possible time where	690	EV::periodic will try to run the callback in this mode at the next
212	C<$time = $at (mod $interval)>, regardless of any time jumps.	691	possible time where C<$time = $at (mod $interval)>, regardless of any time
		692	jumps.
213		693
		694	=item * manual reschedule mode ($reschedule_cb = coderef)
		695
		696	In this mode $interval and $at are both being ignored. Instead, each
		697	time the periodic watcher gets scheduled, the reschedule callback
		698	($reschedule_cb) will be called with the watcher as first, and the current
		699	time as second argument.
		700
		701	I<This callback MUST NOT stop or destroy this or any other periodic
		702	watcher, ever, and MUST NOT call any event loop functions or methods>. If
		703	you need to stop it, return 1e30 and stop it afterwards. You may create
		704	and start a C<EV::prepare> watcher for this task.
		705
		706	It must return the next time to trigger, based on the passed time value
		707	(that is, the lowest time value larger than or equal to to the second
		708	argument). It will usually be called just before the callback will be
		709	triggered, but might be called at other times, too.
		710
		711	This can be used to create very complex timers, such as a timer that
		712	triggers on each midnight, local time (actually 24 hours after the last
		713	midnight, to keep the example simple. If you know a way to do it correctly
		714	in about the same space (without requiring elaborate modules), drop me a
		715	note :):
		716
		717	my $daily = EV::periodic 0, 0, sub {
		718	my ($w, $now) = @_;
		719
		720	use Time::Local ();
		721	my (undef, undef, undef, $d, $m, $y) = localtime $now;
		722	86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
		723	}, sub {
		724	print "it's midnight or likely shortly after, now\n";
		725	};
		726
		727	=back
		728
214	The C<timer_abs_ns> variant doesn't add/start the newly created watcher.	729	The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
215		730
		731	=item $w->set ($at, $interval, $reschedule_cb)
		732
		733	Reconfigures the watcher, see the constructor above for details. Can be called at
		734	any time.
		735
		736	=item $w->again
		737
		738	Simply stops and starts the watcher again.
		739
		740	=item $time = $w->at
		741
		742	Return the time that the watcher is expected to trigger next.
		743
		744	=back
		745
		746
		747	=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
		748
		749	=over 4
		750
216	=item my $w = EV::signal $signal, $callback	751	=item $w = EV::signal $signal, $callback
217		752
218	=item my $w = EV::signal_ns $signal, $callback	753	=item $w = EV::signal_ns $signal, $callback
219		754
		755	=item $w = $loop->signal ($signal, $callback)
		756
		757	=item $w = $loop->signal_ns ($signal, $callback)
		758
220	Call the callback when $signal is received (the signal can be specified	759	Call the callback when $signal is received (the signal can be specified by
221	by number or by name, just as with kill or %SIG). Signal watchers are	760	number or by name, just as with C<kill> or C<%SIG>).
222	persistent no natter what.	761
		762	Only one event loop can grab a given signal - attempting to grab the same
		763	signal from two EV loops will crash the program immediately or cause data
		764	corruption.
223		765
224	EV will grab the signal for the process (the kernel only allows one	766	EV will grab the signal for the process (the kernel only allows one
225	component to receive signals) when you start a signal watcher, and	767	component to receive a signal at a time) when you start a signal watcher,
226	removes it again when you stop it. Pelr does the same when you add/remove	768	and removes it again when you stop it. Perl does the same when you
227	callbacks to %SIG, so watch out.	769	add/remove callbacks to C<%SIG>, so watch out.
228		770
229	Unfortunately, only one handler can be registered per signal. Screw	771	You can have as many signal watchers per signal as you want.
230	libevent.
231		772
232	The C<signal_ns> variant doesn't add/start the newly created watcher.	773	The C<signal_ns> variant doesn't start (activate) the newly created watcher.
233		774
234	=back	775	=item $w->set ($signal)
235		776
236	=head1 THE EV::Event CLASS	777	Reconfigures the watcher, see the constructor above for details. Can be
		778	called at any time.
237		779
238	All EV functions creating an event watcher (designated by C<my $w =>
239	above) support the following methods on the returned watcher object:
240
241	=over 4
242
243	=item $w->add ($timeout)
244
245	Stops and (re-)starts the event watcher, setting the optional timeout to
246	the given value, or clearing the timeout if none is given.
247
248	=item $w->start
249
250	Stops and (re-)starts the event watcher without touching the timeout.
251
252	=item $w->del
253
254	=item $w->stop
255
256	Stop the event watcher if it was started.
257
258	=item $current_callback = $w->cb
259
260	=item $old_callback = $w->cb ($new_callback)
261
262	Return the previously set callback and optionally set a new one.
263
264	=item $current_fh = $w->fh
265
266	=item $old_fh = $w->fh ($new_fh)
267
268	Returns the previously set filehandle and optionally set a new one (also
269	clears the EV::SIGNAL flag when setting a filehandle).
270
271	=item $current_signal = $w->signal	780	=item $current_signum = $w->signal
272		781
273	=item $old_signal = $w->signal ($new_signal)	782	=item $old_signum = $w->signal ($new_signal)
274		783
		784	Returns the previously set signal (always as a number not name) and
		785	optionally set a new one.
		786
		787	=back
		788
		789
		790	=head3 CHILD WATCHERS - watch out for process status changes
		791
		792	=over 4
		793
		794	=item $w = EV::child $pid, $trace, $callback
		795
		796	=item $w = EV::child_ns $pid, $trace, $callback
		797
		798	=item $w = $loop->child ($pid, $trace, $callback)
		799
		800	=item $w = $loop->child_ns ($pid, $trace, $callback)
		801
		802	Call the callback when a status change for pid C<$pid> (or any pid
		803	if C<$pid> is 0) has been received (a status change happens when the
		804	process terminates or is killed, or, when trace is true, additionally when
		805	it is stopped or continued). More precisely: when the process receives
		806	a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
		807	changed/zombie children and call the callback.
		808
		809	It is valid (and fully supported) to install a child watcher after a child
		810	has exited but before the event loop has started its next iteration (for
		811	example, first you C<fork>, then the new child process might exit, and
		812	only then do you install a child watcher in the parent for the new pid).
		813
		814	You can access both exit (or tracing) status and pid by using the
		815	C<rstatus> and C<rpid> methods on the watcher object.
		816
		817	You can have as many pid watchers per pid as you want, they will all be
		818	called.
		819
		820	The C<child_ns> variant doesn't start (activate) the newly created watcher.
		821
		822	=item $w->set ($pid, $trace)
		823
		824	Reconfigures the watcher, see the constructor above for details. Can be called at
		825	any time.
		826
		827	=item $current_pid = $w->pid
		828
275	Returns the previously set signal number and optionally set a new one (also sets	829	Returns the previously set process id and optionally set a new one.
276	the EV::SIGNAL flag when setting a signal).
277		830
278	=item $current_eventmask = $w->events	831	=item $exit_status = $w->rstatus
279		832
280	=item $old_eventmask = $w->events ($new_eventmask)	833	Return the exit/wait status (as returned by waitpid, see the waitpid entry
		834	in perlfunc).
281		835
		836	=item $pid = $w->rpid
		837
		838	Return the pid of the awaited child (useful when you have installed a
		839	watcher for all pids).
		840
		841	=back
		842
		843
		844	=head3 STAT WATCHERS - did the file attributes just change?
		845
		846	=over 4
		847
		848	=item $w = EV::stat $path, $interval, $callback
		849
		850	=item $w = EV::stat_ns $path, $interval, $callback
		851
		852	=item $w = $loop->stat ($path, $interval, $callback)
		853
		854	=item $w = $loop->stat_ns ($path, $interval, $callback)
		855
		856	Call the callback when a file status change has been detected on
		857	C<$path>. The C<$path> does not need to exist, changing from "path exists"
		858	to "path does not exist" is a status change like any other.
		859
		860	The C<$interval> is a recommended polling interval for systems where
		861	OS-supported change notifications don't exist or are not supported. If
		862	you use C<0> then an unspecified default is used (which is highly
		863	recommended!), which is to be expected to be around five seconds usually.
		864
		865	This watcher type is not meant for massive numbers of stat watchers,
		866	as even with OS-supported change notifications, this can be
		867	resource-intensive.
		868
		869	The C<stat_ns> variant doesn't start (activate) the newly created watcher.
		870
		871	=item ... = $w->stat
		872
		873	This call is very similar to the perl C<stat> built-in: It stats (using
		874	C<lstat>) the path specified in the watcher and sets perls stat cache (as
		875	well as EV's idea of the current stat values) to the values found.
		876
		877	In scalar context, a boolean is return indicating success or failure of
		878	the stat. In list context, the same 13-value list as with stat is returned
		879	(except that the blksize and blocks fields are not reliable).
		880
		881	In the case of an error, errno is set to C<ENOENT> (regardless of the
		882	actual error value) and the C<nlink> value is forced to zero (if the stat
		883	was successful then nlink is guaranteed to be non-zero).
		884
		885	See also the next two entries for more info.
		886
		887	=item ... = $w->attr
		888
		889	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		890	the values most recently detected by EV. See the next entry for more info.
		891
		892	=item ... = $w->prev
		893
		894	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		895	the previous set of values, before the change.
		896
		897	That is, when the watcher callback is invoked, C<< $w->prev >> will be set
		898	to the values found I<before> a change was detected, while C<< $w->attr >>
		899	returns the values found leading to the change detection. The difference (if any)
		900	between C<prev> and C<attr> is what triggered the callback.
		901
		902	If you did something to the filesystem object and do not want to trigger
		903	yet another change, you can call C<stat> to update EV's idea of what the
		904	current attributes are.
		905
		906	=item $w->set ($path, $interval)
		907
		908	Reconfigures the watcher, see the constructor above for details. Can be
		909	called at any time.
		910
		911	=item $current_path = $w->path
		912
		913	=item $old_path = $w->path ($new_path)
		914
282	Returns the previously set event mask and optionally set a new one.	915	Returns the previously set path and optionally set a new one.
283		916
284	=item $w->timeout ($after, $repeat)	917	=item $current_interval = $w->interval
285		918
286	Resets the timeout (see C<EV::timer> for details).	919	=item $old_interval = $w->interval ($new_interval)
287		920
288	=item $w->timeout_abs ($at, $interval)	921	Returns the previously set interval and optionally set a new one. Can be
		922	used to query the actual interval used.
289		923
290	Resets the timeout (see C<EV::timer_abs> for details).
291
292	=item $w->priority_set ($priority)
293
294	Set the priority of the watcher to C<$priority> (0 <= $priority < $EV::NPRI).
295
296	=back	924	=back
297		925
		926
		927	=head3 IDLE WATCHERS - when you've got nothing better to do...
		928
		929	=over 4
		930
		931	=item $w = EV::idle $callback
		932
		933	=item $w = EV::idle_ns $callback
		934
		935	=item $w = $loop->idle ($callback)
		936
		937	=item $w = $loop->idle_ns ($callback)
		938
		939	Call the callback when there are no other pending watchers of the same or
		940	higher priority (excluding check, prepare and other idle watchers of the
		941	same or lower priority, of course). They are called idle watchers because
		942	when the watcher is the highest priority pending event in the process, the
		943	process is considered to be idle at that priority.
		944
		945	If you want a watcher that is only ever called when I<no> other events are
		946	outstanding you have to set the priority to C<EV::MINPRI>.
		947
		948	The process will not block as long as any idle watchers are active, and
		949	they will be called repeatedly until stopped.
		950
		951	For example, if you have idle watchers at priority C<0> and C<1>, and
		952	an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
		953	and the I/O watcher will always run when ready. Only when the idle watcher
		954	at priority C<1> is stopped and the I/O watcher at priority C<0> is not
		955	pending with the C<0>-priority idle watcher be invoked.
		956
		957	The C<idle_ns> variant doesn't start (activate) the newly created watcher.
		958
		959	=back
		960
		961
		962	=head3 PREPARE WATCHERS - customise your event loop!
		963
		964	=over 4
		965
		966	=item $w = EV::prepare $callback
		967
		968	=item $w = EV::prepare_ns $callback
		969
		970	=item $w = $loop->prepare ($callback)
		971
		972	=item $w = $loop->prepare_ns ($callback)
		973
		974	Call the callback just before the process would block. You can still
		975	create/modify any watchers at this point.
		976
		977	See the EV::check watcher, below, for explanations and an example.
		978
		979	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
		980
		981	=back
		982
		983
		984	=head3 CHECK WATCHERS - customise your event loop even more!
		985
		986	=over 4
		987
		988	=item $w = EV::check $callback
		989
		990	=item $w = EV::check_ns $callback
		991
		992	=item $w = $loop->check ($callback)
		993
		994	=item $w = $loop->check_ns ($callback)
		995
		996	Call the callback just after the process wakes up again (after it has
		997	gathered events), but before any other callbacks have been invoked.
		998
		999	This can be used to integrate other event-based software into the EV
		1000	mainloop: You register a prepare callback and in there, you create io and
		1001	timer watchers as required by the other software. Here is a real-world
		1002	example of integrating Net::SNMP (with some details left out):
		1003
		1004	our @snmp_watcher;
		1005
		1006	our $snmp_prepare = EV::prepare sub {
		1007	# do nothing unless active
		1008	$dispatcher->{_event_queue_h}
		1009	or return;
		1010
		1011	# make the dispatcher handle any outstanding stuff
		1012	... not shown
		1013
		1014	# create an I/O watcher for each and every socket
		1015	@snmp_watcher = (
		1016	(map { EV::io $_, EV::READ, sub { } }
		1017	keys %{ $dispatcher->{_descriptors} }),
		1018
		1019	EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
		1020	? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
		1021	0, sub { },
		1022	);
		1023	};
		1024
		1025	The callbacks are irrelevant (and are not even being called), the
		1026	only purpose of those watchers is to wake up the process as soon as
		1027	one of those events occurs (socket readable, or timer timed out). The
		1028	corresponding EV::check watcher will then clean up:
		1029
		1030	our $snmp_check = EV::check sub {
		1031	# destroy all watchers
		1032	@snmp_watcher = ();
		1033
		1034	# make the dispatcher handle any new stuff
		1035	... not shown
		1036	};
		1037
		1038	The callbacks of the created watchers will not be called as the watchers
		1039	are destroyed before this can happen (remember EV::check gets called
		1040	first).
		1041
		1042	The C<check_ns> variant doesn't start (activate) the newly created watcher.
		1043
		1044	=item EV::CHECK constant issues
		1045
		1046	Like all other watcher types, there is a bitmask constant for use in
		1047	C<$revents> and other places. The C<EV::CHECK> is special as it has
		1048	the same name as the C<CHECK> sub called by Perl. This doesn't cause
		1049	big issues on newer perls (beginning with 5.8.9), but it means thatthe
		1050	constant must be I<inlined>, i.e. runtime calls will not work. That means
		1051	that as long as you always C<use EV> and then C<EV::CHECK> you are on the
		1052	safe side.
		1053
		1054	=back
		1055
		1056
		1057	=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
		1058
		1059	Fork watchers are called when a C<fork ()> was detected. The invocation
		1060	is done before the event loop blocks next and before C<check> watchers
		1061	are being called, and only in the child after the fork.
		1062
		1063	=over 4
		1064
		1065	=item $w = EV::fork $callback
		1066
		1067	=item $w = EV::fork_ns $callback
		1068
		1069	=item $w = $loop->fork ($callback)
		1070
		1071	=item $w = $loop->fork_ns ($callback)
		1072
		1073	Call the callback before the event loop is resumed in the child process
		1074	after a fork.
		1075
		1076	The C<fork_ns> variant doesn't start (activate) the newly created watcher.
		1077
		1078	=back
		1079
		1080
		1081	=head3 EMBED WATCHERS - when one backend isn't enough...
		1082
		1083	This is a rather advanced watcher type that lets you embed one event loop
		1084	into another (currently only IO events are supported in the embedded
		1085	loop, other types of watchers might be handled in a delayed or incorrect
		1086	fashion and must not be used).
		1087
		1088	See the libev documentation at
		1089	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code_when_one_backend_>
		1090	(locally installed as F<EV::libev>) for more details.
		1091
		1092	In short, this watcher is most useful on BSD systems without working
		1093	kqueue to still be able to handle a large number of sockets:
		1094
		1095	my $socket_loop;
		1096
		1097	# check wether we use SELECT or POLL _and_ KQUEUE is supported
		1098	if (
		1099	(EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
		1100	&& (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
		1101	) {
		1102	# use kqueue for sockets
		1103	$socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
		1104	}
		1105
		1106	# use the default loop otherwise
		1107	$socket_loop ||= EV::default_loop;
		1108
		1109	=over 4
		1110
		1111	=item $w = EV::embed $otherloop[, $callback]
		1112
		1113	=item $w = EV::embed_ns $otherloop[, $callback]
		1114
		1115	=item $w = $loop->embed ($otherloop[, $callback])
		1116
		1117	=item $w = $loop->embed_ns ($otherloop[, $callback])
		1118
		1119	Call the callback when the embedded event loop (C<$otherloop>) has any
		1120	I/O activity. The C<$callback> is optional: if it is missing, then the
		1121	embedded event loop will be managed automatically (which is recommended),
		1122	otherwise you have to invoke C<sweep> yourself.
		1123
		1124	The C<embed_ns> variant doesn't start (activate) the newly created watcher.
		1125
		1126	=back
		1127
		1128	=head3 ASYNC WATCHERS - how to wake up another event loop
		1129
		1130	Async watchers are provided by EV, but have little use in perl directly,
		1131	as perl neither supports threads running in parallel nor direct access to
		1132	signal handlers or other contexts where they could be of value.
		1133
		1134	It is, however, possible to use them from the XS level.
		1135
		1136	Please see the libev documentation for further details.
		1137
		1138	=over 4
		1139
		1140	=item $w = EV::async $callback
		1141
		1142	=item $w = EV::async_ns $callback
		1143
		1144	=item $w = $loop->async ($callback)
		1145
		1146	=item $w = $loop->async_ns ($callback)
		1147
		1148	=item $w->send
		1149
		1150	=item $bool = $w->async_pending
		1151
		1152	=back
		1153
		1154	=head3 CLEANUP WATCHERS - how to clean up when the event loop goes away
		1155
		1156	Cleanup watchers are not supported on the Perl level, they can only be
		1157	used via XS currently.
		1158
		1159
		1160	=head1 PERL SIGNALS
		1161
		1162	While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
		1163	with EV is as the same as any other C library: Perl-signals will only be
		1164	handled when Perl runs, which means your signal handler might be invoked
		1165	only the next time an event callback is invoked.
		1166
		1167	The solution is to use EV signal watchers (see C<EV::signal>), which will
		1168	ensure proper operations with regards to other event watchers.
		1169
		1170	If you cannot do this for whatever reason, you can also force a watcher
		1171	to be called on every event loop iteration by installing a C<EV::check>
		1172	watcher:
		1173
		1174	my $async_check = EV::check sub { };
		1175
		1176	This ensures that perl gets into control for a short time to handle any
		1177	pending signals, and also ensures (slightly) slower overall operation.
		1178
298	=head1 THREADS	1179	=head1 ITHREADS
299		1180
300	Threads are not supported by this in any way. Perl pseudo-threads is evil	1181	Ithreads are not supported by this module in any way. Perl pseudo-threads
301	and must die.	1182	is evil stuff and must die. Real threads as provided by Coro are fully
		1183	supported (and enhanced support is available via L<Coro::EV>).
		1184
		1185	=head1 FORK
		1186
		1187	Most of the "improved" event delivering mechanisms of modern operating
		1188	systems have quite a few problems with fork(2) (to put it bluntly: it is
		1189	not supported and usually destructive). Libev makes it possible to work
		1190	around this by having a function that recreates the kernel state after
		1191	fork in the child.
		1192
		1193	On non-win32 platforms, this module requires the pthread_atfork
		1194	functionality to do this automatically for you. This function is quite
		1195	buggy on most BSDs, though, so YMMV. The overhead for this is quite
		1196	negligible, because everything the function currently does is set a flag
		1197	that is checked only when the event loop gets used the next time, so when
		1198	you do fork but not use EV, the overhead is minimal.
		1199
		1200	On win32, there is no notion of fork so all this doesn't apply, of course.
302		1201
303	=cut	1202	=cut
304		1203
305	our $DIED = sub {	1204	our $DIED = sub {
306	warn "EV: error in callback (ignoring): $@";	1205	warn "EV: error in callback (ignoring): $@";
307	};	1206	};
308		1207
309	init;	1208	default_loop
310		1209	or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?';
311	push @AnyEvent::REGISTRY, [EV => "EV::AnyEvent"];
312		1210
313	1;	1211	1;
314		1212
315	=head1 SEE ALSO	1213	=head1 SEE ALSO
316		1214
317	L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>.	1215	L<EV::MakeMaker> - MakeMaker interface to XS API, L<EV::ADNS>
318	L<EV::AnyEvent>.	1216	(asynchronous DNS), L<Glib::EV> (makes Glib/Gtk2 use EV as event
		1217	loop), L<EV::Glib> (embed Glib into EV), L<Coro::EV> (efficient thread
		1218	integration), L<Net::SNMP::EV> (asynchronous SNMP), L<AnyEvent> for
		1219	event-loop agnostic and portable event driven programming.
319		1220
320	=head1 AUTHOR	1221	=head1 AUTHOR
321		1222
322	Marc Lehmann <schmorp@schmorp.de>	1223	Marc Lehmann <schmorp@schmorp.de>
323	http://home.schmorp.de/	1224	http://home.schmorp.de/
324		1225
325	=cut	1226	=cut
326		1227

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