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Revision 1.15 by root, Wed Oct 31 18:28:00 2007 UTC vs.
Revision 1.135 by root, Mon Dec 12 16:32:24 2011 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, $events) = @_; # all callbacks get the watcher object and event mask
29	if ($events & 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, $events) = @_;	47	my ($w, $revents) = @_;
39	if ($_[1] & 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	# MAINLOOP	51	# MAINLOOP
59	EV::dispatch; # loop as long as watchers are active	52	EV::run; # loop until EV::unloop is called or all watchers stop
60	EV::loop; # the same thing
61	EV::loop EV::LOOP_ONCE; # block until some events could be handles	53	EV::run EV::RUN_ONCE; # block until at least one event could be handled
62	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.
63		64
64	=head1 DESCRIPTION	65	=head1 DESCRIPTION
65		66
66	This module provides an interface to libevent	67	This module provides an interface to libev
67	(L<http://monkey.org/~provos/libevent/>). You probably should acquaint	68	(L<http://software.schmorp.de/pkg/libev.html>). While the documentation
68	yourself with its documentation and source code to be able to use this	69	below is comprehensive, one might also consult the documentation of
69	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.
70		75
71	Please note thta this module disables the libevent EPOLL method by	76	This module is very fast and scalable. It is actually so fast that you
72	default, see BUGS, below, if you need to enable it.	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.
73		116
74	=cut	117	=cut
75		118
76	package EV;	119	package EV;
77		120
78	use strict;	121	use common::sense;
79		122
80	BEGIN {	123	BEGIN {
81	our $VERSION = '0.03';	124	our $VERSION = '4.03';
82	use XSLoader;	125	use XSLoader;
83	XSLoader::load "EV", $VERSION;	126	XSLoader::load "EV", $VERSION;
84	}	127	}
85		128
86	@EV::Io::ISA = "EV::Watcher";	129	@EV::IO::ISA =
87	@EV::Time::ISA = "EV::Watcher";
88	@EV::Timer::ISA = "EV::Time";	130	@EV::Timer::ISA =
89	@EV::Periodic::ISA = "EV::Time";	131	@EV::Periodic::ISA =
90	@EV::Signal::ISA = "EV::Watcher";	132	@EV::Signal::ISA =
91	@EV::Idle::ISA = "EV::Watcher";	133	@EV::Child::ISA =
92	@EV::Prepare::ISA = "EV::Watcher";	134	@EV::Stat::ISA =
93	@EV::Check::ISA = "EV::Watcher";	135	@EV::Idle::ISA =
		136	@EV::Prepare::ISA =
		137	@EV::Check::ISA =
		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
94		207
95	=head1 BASIC INTERFACE	208	=head1 BASIC INTERFACE
96		209
97	=over 4	210	=over 4
98		211
99	=item $EV::NPRI
100
101	How many priority levels are available.
102
103	=item $EV::DIED	212	=item $EV::DIED
104		213
105	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
106	throws an exception (with $@ containing thr error). The default prints an	215	throws an exception (with $@ containing the error). The default prints an
107	informative message and continues.	216	informative message and continues.
108		217
109	If this callback throws an exception it will be silently ignored.	218	If this callback throws an exception it will be silently ignored.
110		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
111	=item $time = EV::now	238	=item $time = EV::now
112		239
113	Returns the time in (fractional) seconds since the epoch.	240	=item $time = $loop->now
114		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 = $loop->backend
		291
		292	Returns an integer describing the backend used by libev (EV::BACKEND_SELECT
		293	or EV::BACKEND_EPOLL).
		294
		295	=item EV::run [$flags]
		296
		297	=item $loop->run ([$flags])
		298
		299	Begin checking for events and calling callbacks. It returns when a
		300	callback calls EV::unloop.
		301
		302	The $flags argument can be one of the following:
		303
		304	0 as above
		305	EV::RUN_ONCE block at most once (wait, but do not loop)
		306	EV::RUN_NOWAIT do not block at all (fetch/handle events but do not wait)
		307
		308	=item EV::break [$how]
		309
		310	=item $loop->break ([$how])
		311
		312	When called with no arguments or an argument of EV::BREAK_ONE, makes the
		313	innermost call to EV::loop return.
		314
		315	When called with an argument of EV::BREAK_ALL, all calls to EV::loop will
		316	return as fast as possible.
		317
		318	When called with an argument of EV::BREAK_CANCEL, any pending break will
		319	be cancelled.
		320
115	=item $version = EV::version	321	=item $count = EV::iteration
116		322
117	=item $method = EV::method	323	=item $count = $loop->iteration
118		324
119	Return version string and event polling method used.	325	Return the number of times the event loop has polled for new
		326	events. Sometimes useful as a generation counter.
120		327
121	=item EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT	328	=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
122		329
123	=item EV::loopexit $after	330	=item $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
124		331
125	Exit any active loop or dispatch after C<$after> seconds or immediately if	332	This function rolls together an I/O and a timer watcher for a single
126	C<$after> is missing or zero.	333	one-shot event without the need for managing a watcher object.
127		334
128	=item EV::dispatch	335	If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events>
		336	must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ
		337	| EV::WRITE>, indicating the type of I/O event you want to wait for. If
		338	you do not want to wait for some I/O event, specify C<undef> for
		339	C<$fh_or_undef> and C<0> for C<$events>).
129		340
130	Same as C<EV::loop 0>.	341	If timeout is C<undef> or negative, then there will be no
		342	timeout. Otherwise a EV::timer with this value will be started.
131		343
132	=item EV::event $callback	344	When an error occurs or either the timeout or I/O watcher triggers, then
		345	the callback will be called with the received event set (in general
		346	you can expect it to be a combination of C<EV::ERROR>, C<EV::READ>,
		347	C<EV::WRITE> and C<EV::TIMER>).
133		348
134	Creates a new event watcher waiting for nothing, calling the given callback.	349	EV::once doesn't return anything: the watchers stay active till either
		350	of them triggers, then they will be stopped and freed, and the callback
		351	invoked.
135		352
		353	=item EV::feed_fd_event $fd, $revents
		354
		355	=item $loop->feed_fd_event ($fd, $revents)
		356
		357	Feed an event on a file descriptor into EV. EV will react to this call as
		358	if the readyness notifications specified by C<$revents> (a combination of
		359	C<EV::READ> and C<EV::WRITE>) happened on the file descriptor C<$fd>.
		360
		361	=item EV::feed_signal_event $signal
		362
		363	Feed a signal event into the default loop. EV will react to this call as
		364	if the signal specified by C<$signal> had occured.
		365
		366	=item EV::feed_signal $signal
		367
		368	Feed a signal event into EV - unlike C<EV::feed_signal_event>, this works
		369	regardless of which loop has registered the signal, and is mainly useful
		370	fro custom signal implementations.
		371
		372	=item EV::set_io_collect_interval $time
		373
		374	=item $loop->set_io_collect_interval ($time)
		375
		376	=item EV::set_timeout_collect_interval $time
		377
		378	=item $loop->set_timeout_collect_interval ($time)
		379
		380	These advanced functions set the minimum block interval when polling for I/O events and the minimum
		381	wait interval for timer events. See the libev documentation at
		382	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP>
		383	(locally installed as F<EV::libev>) for a more detailed discussion.
		384
		385	=item $count = EV::pending_count
		386
		387	=item $count = $loop->pending_count
		388
		389	Returns the number of currently pending watchers.
		390
		391	=item EV::invoke_pending
		392
		393	=item $loop->invoke_pending
		394
		395	Invoke all currently pending watchers.
		396
		397	=back
		398
		399
		400	=head1 WATCHER OBJECTS
		401
		402	A watcher is an object that gets created to record your interest in some
		403	event. For instance, if you want to wait for STDIN to become readable, you
		404	would create an EV::io watcher for that:
		405
		406	my $watcher = EV::io *STDIN, EV::READ, sub {
		407	my ($watcher, $revents) = @_;
		408	warn "yeah, STDIN should now be readable without blocking!\n"
		409	};
		410
		411	All watchers can be active (waiting for events) or inactive (paused). Only
		412	active watchers will have their callbacks invoked. All callbacks will be
		413	called with at least two arguments: the watcher and a bitmask of received
		414	events.
		415
		416	Each watcher type has its associated bit in revents, so you can use the
		417	same callback for multiple watchers. The event mask is named after the
		418	type, i.e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
		419	EV::periodic sets EV::PERIODIC and so on, with the exception of I/O events
		420	(which can set both EV::READ and EV::WRITE bits).
		421
		422	In the rare case where one wants to create a watcher but not start it at
		423	the same time, each constructor has a variant with a trailing C<_ns> in
		424	its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
		425
		426	Please note that a watcher will automatically be stopped when the watcher
		427	object is destroyed, so you I<need> to keep the watcher objects returned by
		428	the constructors.
		429
		430	Also, all methods changing some aspect of a watcher (->set, ->priority,
		431	->fh and so on) automatically stop and start it again if it is active,
		432	which means pending events get lost.
		433
		434	=head2 COMMON WATCHER METHODS
		435
		436	This section lists methods common to all watchers.
		437
		438	=over 4
		439
		440	=item $w->start
		441
		442	Starts a watcher if it isn't active already. Does nothing to an already
		443	active watcher. By default, all watchers start out in the active state
		444	(see the description of the C<_ns> variants if you need stopped watchers).
		445
		446	=item $w->stop
		447
		448	Stop a watcher if it is active. Also clear any pending events (events that
		449	have been received but that didn't yet result in a callback invocation),
		450	regardless of whether the watcher was active or not.
		451
		452	=item $bool = $w->is_active
		453
		454	Returns true if the watcher is active, false otherwise.
		455
		456	=item $current_data = $w->data
		457
		458	=item $old_data = $w->data ($new_data)
		459
		460	Queries a freely usable data scalar on the watcher and optionally changes
		461	it. This is a way to associate custom data with a watcher:
		462
		463	my $w = EV::timer 60, 0, sub {
		464	warn $_[0]->data;
		465	};
		466	$w->data ("print me!");
		467
		468	=item $current_cb = $w->cb
		469
		470	=item $old_cb = $w->cb ($new_cb)
		471
		472	Queries the callback on the watcher and optionally changes it. You can do
		473	this at any time without the watcher restarting.
		474
		475	=item $current_priority = $w->priority
		476
		477	=item $old_priority = $w->priority ($new_priority)
		478
		479	Queries the priority on the watcher and optionally changes it. Pending
		480	watchers with higher priority will be invoked first. The valid range of
		481	priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
		482	-2). If the priority is outside this range it will automatically be
		483	normalised to the nearest valid priority.
		484
		485	The default priority of any newly-created watcher is 0.
		486
		487	Note that the priority semantics have not yet been fleshed out and are
		488	subject to almost certain change.
		489
		490	=item $w->invoke ($revents)
		491
		492	Call the callback *now* with the given event mask.
		493
		494	=item $w->feed_event ($revents)
		495
		496	Feed some events on this watcher into EV. EV will react to this call as if
		497	the watcher had received the given C<$revents> mask.
		498
		499	=item $revents = $w->clear_pending
		500
		501	If the watcher is pending, this function clears its pending status and
		502	returns its C<$revents> bitset (as if its callback was invoked). If the
		503	watcher isn't pending it does nothing and returns C<0>.
		504
		505	=item $previous_state = $w->keepalive ($bool)
		506
		507	Normally, C<EV::loop> will return when there are no active watchers
		508	(which is a "deadlock" because no progress can be made anymore). This is
		509	convenient because it allows you to start your watchers (and your jobs),
		510	call C<EV::loop> once and when it returns you know that all your jobs are
		511	finished (or they forgot to register some watchers for their task :).
		512
		513	Sometimes, however, this gets in your way, for example when the module
		514	that calls C<EV::loop> (usually the main program) is not the same module
		515	as a long-living watcher (for example a DNS client module written by
		516	somebody else even). Then you might want any outstanding requests to be
		517	handled, but you would not want to keep C<EV::loop> from returning just
		518	because you happen to have this long-running UDP port watcher.
		519
		520	In this case you can clear the keepalive status, which means that even
		521	though your watcher is active, it won't keep C<EV::loop> from returning.
		522
		523	The initial value for keepalive is true (enabled), and you can change it
		524	any time.
		525
		526	Example: Register an I/O watcher for some UDP socket but do not keep the
		527	event loop from running just because of that watcher.
		528
		529	my $udp_socket = ...
		530	my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
		531	$udp_watcher->keepalive (0);
		532
		533	=item $loop = $w->loop
		534
		535	Return the loop that this watcher is attached to.
		536
		537	=back
		538
		539
		540	=head1 WATCHER TYPES
		541
		542	Each of the following subsections describes a single watcher type.
		543
		544	=head3 I/O WATCHERS - is this file descriptor readable or writable?
		545
		546	=over 4
		547
136	=item my $w = EV::io $fileno_or_fh, $eventmask, $callback	548	=item $w = EV::io $fileno_or_fh, $eventmask, $callback
137		549
138	=item my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback	550	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
		551
		552	=item $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
		553
		554	=item $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
139		555
140	As long as the returned watcher object is alive, call the C<$callback>	556	As long as the returned watcher object is alive, call the C<$callback>
141	when the events specified in C<$eventmask> happen. Initially, the timeout	557	when at least one of events specified in C<$eventmask> occurs.
142	is disabled.
143		558
144	You can additionall set a timeout to occur on the watcher, but note that
145	this timeout will not be reset when you get an I/O event in the EV::PERSIST
146	case, and reaching a timeout will always stop the watcher even in the
147	EV::PERSIST case.
148
149	If you want a timeout to occur only after a specific time of inactivity, set
150	a repeating timeout and do NOT use EV::PERSIST.
151
152	Eventmask can be one or more of these constants ORed together:	559	The $eventmask can be one or more of these constants ORed together:
153		560
154	EV::READ wait until read() wouldn't block anymore	561	EV::READ wait until read() wouldn't block anymore
155	EV::WRITE wait until write() wouldn't block anymore	562	EV::WRITE wait until write() wouldn't block anymore
156	EV::PERSIST stay active after a (non-timeout) event occured
157		563
158	The C<io_ns> variant doesn't add/start the newly created watcher.	564	The C<io_ns> variant doesn't start (activate) the newly created watcher.
159		565
160	=item my $w = EV::timed_io $fileno_or_fh, $eventmask, $timeout, $callback	566	=item $w->set ($fileno_or_fh, $eventmask)
161		567
162	=item my $w = EV::timed_io_ns $fileno_or_fh, $eventmask, $timeout, $callback	568	Reconfigures the watcher, see the constructor above for details. Can be
		569	called at any time.
163		570
164	Same as C<io> and C<io_ns>, but also specifies a timeout (as if there was	571	=item $current_fh = $w->fh
165	a call to C<< $w->timeout ($timout, 1) >>. The persist flag is not allowed
166	and will automatically be cleared. The watcher will be restarted after each event.
167		572
168	If the timeout is zero or undef, no timeout will be set, and a normal	573	=item $old_fh = $w->fh ($new_fh)
169	watcher (with the persist flag set!) will be created.
170		574
171	This has the effect of timing out after the specified period of inactivity	575	Returns the previously set filehandle and optionally set a new one.
172	has happened.
173		576
174	Due to the design of libevent, this is also relatively inefficient, having	577	=item $current_eventmask = $w->events
175	one or two io watchers and a separate timeout watcher that you reset on
176	activity (by calling its C<start> method) is usually more efficient.
177		578
		579	=item $old_eventmask = $w->events ($new_eventmask)
		580
		581	Returns the previously set event mask and optionally set a new one.
		582
		583	=back
		584
		585
		586	=head3 TIMER WATCHERS - relative and optionally repeating timeouts
		587
		588	=over 4
		589
178	=item my $w = EV::timer $after, $repeat, $callback	590	=item $w = EV::timer $after, $repeat, $callback
179		591
180	=item my $w = EV::timer_ns $after, $repeat, $callback	592	=item $w = EV::timer_ns $after, $repeat, $callback
181		593
182	Calls the callback after C<$after> seconds. If C<$repeat> is true, the	594	=item $w = $loop->timer ($after, $repeat, $callback)
183	timer will be restarted after the callback returns. This means that the
184	callback would be called roughly every C<$after> seconds, prolonged by the
185	time the callback takes.
186		595
		596	=item $w = $loop->timer_ns ($after, $repeat, $callback)
		597
		598	Calls the callback after C<$after> seconds (which may be fractional). If
		599	C<$repeat> is non-zero, the timer will be restarted (with the $repeat
		600	value as $after) after the callback returns.
		601
		602	This means that the callback would be called roughly after C<$after>
		603	seconds, and then every C<$repeat> seconds. The timer does his best not
		604	to drift, but it will not invoke the timer more often then once per event
		605	loop iteration, and might drift in other cases. If that isn't acceptable,
		606	look at EV::periodic, which can provide long-term stable timers.
		607
		608	The timer is based on a monotonic clock, that is, if somebody is sitting
		609	in front of the machine while the timer is running and changes the system
		610	clock, the timer will nevertheless run (roughly) the same time.
		611
187	The C<timer_ns> variant doesn't add/start the newly created watcher.	612	The C<timer_ns> variant doesn't start (activate) the newly created watcher.
188		613
189	=item my $w = EV::timer_abs $at, $interval, $callback	614	=item $w->set ($after, $repeat)
190		615
191	=item my $w = EV::timer_abs_ns $at, $interval, $callback	616	Reconfigures the watcher, see the constructor above for details. Can be called at
		617	any time.
192		618
193	Similar to EV::timer, but the time is given as an absolute point in time	619	=item $w->again
194	(C<$at>), plus an optional C<$interval>.
195		620
196	If the C<$interval> is zero, then the callback will be called at the time	621	Similar to the C<start> method, but has special semantics for repeating timers:
197	C<$at> if that is in the future, or as soon as possible if its in the
198	past. It will not automatically repeat.
199		622
200	If the C<$interval> is nonzero, then the watcher will always be scheduled	623	If the timer is active and non-repeating, it will be stopped.
201	to time out at the next C<$at + integer * $interval> time.
202		624
203	This can be used to schedule a callback to run at very regular intervals,	625	If the timer is active and repeating, reset the timeout to occur
204	as long as the processing time is less then the interval (otherwise	626	C<$repeat> seconds after now.
205	obviously events will be skipped).	627
		628	If the timer is inactive and repeating, start it using the repeat value.
		629
		630	Otherwise do nothing.
		631
		632	This behaviour is useful when you have a timeout for some IO
		633	operation. You create a timer object with the same value for C<$after> and
		634	C<$repeat>, and then, in the read/write watcher, run the C<again> method
		635	on the timeout.
		636
		637	=back
		638
		639
		640	=head3 PERIODIC WATCHERS - to cron or not to cron?
		641
		642	=over 4
		643
		644	=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
		645
		646	=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
		647
		648	=item $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
		649
		650	=item $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
		651
		652	Similar to EV::timer, but is not based on relative timeouts but on
		653	absolute times. Apart from creating "simple" timers that trigger "at" the
		654	specified time, it can also be used for non-drifting absolute timers and
		655	more complex, cron-like, setups that are not adversely affected by time
		656	jumps (i.e. when the system clock is changed by explicit date -s or other
		657	means such as ntpd). It is also the most complex watcher type in EV.
		658
		659	It has three distinct "modes":
		660
		661	=over 4
		662
		663	=item * absolute timer ($interval = $reschedule_cb = 0)
		664
		665	This time simply fires at the wallclock time C<$at> and doesn't repeat. It
		666	will not adjust when a time jump occurs, that is, if it is to be run
		667	at January 1st 2011 then it will run when the system time reaches or
		668	surpasses this time.
		669
		670	=item * repeating interval timer ($interval > 0, $reschedule_cb = 0)
		671
		672	In this mode the watcher will always be scheduled to time out at the
		673	next C<$at + N * $interval> time (for some integer N) and then repeat,
		674	regardless of any time jumps.
		675
		676	This can be used to create timers that do not drift with respect to system
		677	time:
		678
		679	my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
		680
		681	That doesn't mean there will always be 3600 seconds in between triggers,
		682	but only that the the clalback will be called when the system time shows a
		683	full hour (UTC).
206		684
207	Another way to think about it (for the mathematically inclined) is that	685	Another way to think about it (for the mathematically inclined) is that
208	C<timer_abs> will try to tun the callback at the next possible time where	686	EV::periodic will try to run the callback in this mode at the next
209	C<$time = $at (mod $interval)>, regardless of any time jumps.	687	possible time where C<$time = $at (mod $interval)>, regardless of any time
		688	jumps.
210		689
		690	=item * manual reschedule mode ($reschedule_cb = coderef)
		691
		692	In this mode $interval and $at are both being ignored. Instead, each
		693	time the periodic watcher gets scheduled, the reschedule callback
		694	($reschedule_cb) will be called with the watcher as first, and the current
		695	time as second argument.
		696
		697	I<This callback MUST NOT stop or destroy this or any other periodic
		698	watcher, ever, and MUST NOT call any event loop functions or methods>. If
		699	you need to stop it, return 1e30 and stop it afterwards. You may create
		700	and start a C<EV::prepare> watcher for this task.
		701
		702	It must return the next time to trigger, based on the passed time value
		703	(that is, the lowest time value larger than or equal to to the second
		704	argument). It will usually be called just before the callback will be
		705	triggered, but might be called at other times, too.
		706
		707	This can be used to create very complex timers, such as a timer that
		708	triggers on each midnight, local time (actually 24 hours after the last
		709	midnight, to keep the example simple. If you know a way to do it correctly
		710	in about the same space (without requiring elaborate modules), drop me a
		711	note :):
		712
		713	my $daily = EV::periodic 0, 0, sub {
		714	my ($w, $now) = @_;
		715
		716	use Time::Local ();
		717	my (undef, undef, undef, $d, $m, $y) = localtime $now;
		718	86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
		719	}, sub {
		720	print "it's midnight or likely shortly after, now\n";
		721	};
		722
		723	=back
		724
211	The C<timer_abs_ns> variant doesn't add/start the newly created watcher.	725	The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
212		726
		727	=item $w->set ($at, $interval, $reschedule_cb)
		728
		729	Reconfigures the watcher, see the constructor above for details. Can be called at
		730	any time.
		731
		732	=item $w->again
		733
		734	Simply stops and starts the watcher again.
		735
		736	=item $time = $w->at
		737
		738	Return the time that the watcher is expected to trigger next.
		739
		740	=back
		741
		742
		743	=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
		744
		745	=over 4
		746
213	=item my $w = EV::signal $signal, $callback	747	=item $w = EV::signal $signal, $callback
214		748
215	=item my $w = EV::signal_ns $signal, $callback	749	=item $w = EV::signal_ns $signal, $callback
216		750
		751	=item $w = $loop->signal ($signal, $callback)
		752
		753	=item $w = $loop->signal_ns ($signal, $callback)
		754
217	Call the callback when $signal is received (the signal can be specified	755	Call the callback when $signal is received (the signal can be specified by
218	by number or by name, just as with kill or %SIG). Signal watchers are	756	number or by name, just as with C<kill> or C<%SIG>).
219	persistent no natter what.	757
		758	Only one event loop can grab a given signal - attempting to grab the same
		759	signal from two EV loops will crash the program immediately or cause data
		760	corruption.
220		761
221	EV will grab the signal for the process (the kernel only allows one	762	EV will grab the signal for the process (the kernel only allows one
222	component to receive signals) when you start a signal watcher, and	763	component to receive a signal at a time) when you start a signal watcher,
223	removes it again when you stop it. Pelr does the same when you add/remove	764	and removes it again when you stop it. Perl does the same when you
224	callbacks to %SIG, so watch out.	765	add/remove callbacks to C<%SIG>, so watch out.
225		766
226	Unfortunately, only one handler can be registered per signal. Screw	767	You can have as many signal watchers per signal as you want.
227	libevent.
228		768
229	The C<signal_ns> variant doesn't add/start the newly created watcher.	769	The C<signal_ns> variant doesn't start (activate) the newly created watcher.
230		770
231	=back	771	=item $w->set ($signal)
232		772
233	=head1 THE EV::Event CLASS	773	Reconfigures the watcher, see the constructor above for details. Can be
		774	called at any time.
234		775
235	All EV functions creating an event watcher (designated by C<my $w =>
236	above) support the following methods on the returned watcher object:
237
238	=over 4
239
240	=item $w->add ($timeout)
241
242	Stops and (re-)starts the event watcher, setting the optional timeout to
243	the given value, or clearing the timeout if none is given.
244
245	=item $w->start
246
247	Stops and (re-)starts the event watcher without touching the timeout.
248
249	=item $w->del
250
251	=item $w->stop
252
253	Stop the event watcher if it was started.
254
255	=item $current_callback = $w->cb
256
257	=item $old_callback = $w->cb ($new_callback)
258
259	Return the previously set callback and optionally set a new one.
260
261	=item $current_fh = $w->fh
262
263	=item $old_fh = $w->fh ($new_fh)
264
265	Returns the previously set filehandle and optionally set a new one (also
266	clears the EV::SIGNAL flag when setting a filehandle).
267
268	=item $current_signal = $w->signal	776	=item $current_signum = $w->signal
269		777
270	=item $old_signal = $w->signal ($new_signal)	778	=item $old_signum = $w->signal ($new_signal)
271		779
		780	Returns the previously set signal (always as a number not name) and
		781	optionally set a new one.
		782
		783	=back
		784
		785
		786	=head3 CHILD WATCHERS - watch out for process status changes
		787
		788	=over 4
		789
		790	=item $w = EV::child $pid, $trace, $callback
		791
		792	=item $w = EV::child_ns $pid, $trace, $callback
		793
		794	=item $w = $loop->child ($pid, $trace, $callback)
		795
		796	=item $w = $loop->child_ns ($pid, $trace, $callback)
		797
		798	Call the callback when a status change for pid C<$pid> (or any pid
		799	if C<$pid> is 0) has been received (a status change happens when the
		800	process terminates or is killed, or, when trace is true, additionally when
		801	it is stopped or continued). More precisely: when the process receives
		802	a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
		803	changed/zombie children and call the callback.
		804
		805	It is valid (and fully supported) to install a child watcher after a child
		806	has exited but before the event loop has started its next iteration (for
		807	example, first you C<fork>, then the new child process might exit, and
		808	only then do you install a child watcher in the parent for the new pid).
		809
		810	You can access both exit (or tracing) status and pid by using the
		811	C<rstatus> and C<rpid> methods on the watcher object.
		812
		813	You can have as many pid watchers per pid as you want, they will all be
		814	called.
		815
		816	The C<child_ns> variant doesn't start (activate) the newly created watcher.
		817
		818	=item $w->set ($pid, $trace)
		819
		820	Reconfigures the watcher, see the constructor above for details. Can be called at
		821	any time.
		822
		823	=item $current_pid = $w->pid
		824
272	Returns the previously set signal number and optionally set a new one (also sets	825	Returns the previously set process id and optionally set a new one.
273	the EV::SIGNAL flag when setting a signal).
274		826
275	=item $current_eventmask = $w->events	827	=item $exit_status = $w->rstatus
276		828
277	=item $old_eventmask = $w->events ($new_eventmask)	829	Return the exit/wait status (as returned by waitpid, see the waitpid entry
		830	in perlfunc).
278		831
		832	=item $pid = $w->rpid
		833
		834	Return the pid of the awaited child (useful when you have installed a
		835	watcher for all pids).
		836
		837	=back
		838
		839
		840	=head3 STAT WATCHERS - did the file attributes just change?
		841
		842	=over 4
		843
		844	=item $w = EV::stat $path, $interval, $callback
		845
		846	=item $w = EV::stat_ns $path, $interval, $callback
		847
		848	=item $w = $loop->stat ($path, $interval, $callback)
		849
		850	=item $w = $loop->stat_ns ($path, $interval, $callback)
		851
		852	Call the callback when a file status change has been detected on
		853	C<$path>. The C<$path> does not need to exist, changing from "path exists"
		854	to "path does not exist" is a status change like any other.
		855
		856	The C<$interval> is a recommended polling interval for systems where
		857	OS-supported change notifications don't exist or are not supported. If
		858	you use C<0> then an unspecified default is used (which is highly
		859	recommended!), which is to be expected to be around five seconds usually.
		860
		861	This watcher type is not meant for massive numbers of stat watchers,
		862	as even with OS-supported change notifications, this can be
		863	resource-intensive.
		864
		865	The C<stat_ns> variant doesn't start (activate) the newly created watcher.
		866
		867	=item ... = $w->stat
		868
		869	This call is very similar to the perl C<stat> built-in: It stats (using
		870	C<lstat>) the path specified in the watcher and sets perls stat cache (as
		871	well as EV's idea of the current stat values) to the values found.
		872
		873	In scalar context, a boolean is return indicating success or failure of
		874	the stat. In list context, the same 13-value list as with stat is returned
		875	(except that the blksize and blocks fields are not reliable).
		876
		877	In the case of an error, errno is set to C<ENOENT> (regardless of the
		878	actual error value) and the C<nlink> value is forced to zero (if the stat
		879	was successful then nlink is guaranteed to be non-zero).
		880
		881	See also the next two entries for more info.
		882
		883	=item ... = $w->attr
		884
		885	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		886	the values most recently detected by EV. See the next entry for more info.
		887
		888	=item ... = $w->prev
		889
		890	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		891	the previous set of values, before the change.
		892
		893	That is, when the watcher callback is invoked, C<< $w->prev >> will be set
		894	to the values found I<before> a change was detected, while C<< $w->attr >>
		895	returns the values found leading to the change detection. The difference (if any)
		896	between C<prev> and C<attr> is what triggered the callback.
		897
		898	If you did something to the filesystem object and do not want to trigger
		899	yet another change, you can call C<stat> to update EV's idea of what the
		900	current attributes are.
		901
		902	=item $w->set ($path, $interval)
		903
		904	Reconfigures the watcher, see the constructor above for details. Can be
		905	called at any time.
		906
		907	=item $current_path = $w->path
		908
		909	=item $old_path = $w->path ($new_path)
		910
279	Returns the previously set event mask and optionally set a new one.	911	Returns the previously set path and optionally set a new one.
280		912
281	=item $w->timeout ($after, $repeat)	913	=item $current_interval = $w->interval
282		914
283	Resets the timeout (see C<EV::timer> for details).	915	=item $old_interval = $w->interval ($new_interval)
284		916
285	=item $w->timeout_abs ($at, $interval)	917	Returns the previously set interval and optionally set a new one. Can be
		918	used to query the actual interval used.
286		919
287	Resets the timeout (see C<EV::timer_abs> for details).
288
289	=item $w->priority_set ($priority)
290
291	Set the priority of the watcher to C<$priority> (0 <= $priority < $EV::NPRI).
292
293	=back	920	=back
294		921
		922
		923	=head3 IDLE WATCHERS - when you've got nothing better to do...
		924
		925	=over 4
		926
		927	=item $w = EV::idle $callback
		928
		929	=item $w = EV::idle_ns $callback
		930
		931	=item $w = $loop->idle ($callback)
		932
		933	=item $w = $loop->idle_ns ($callback)
		934
		935	Call the callback when there are no other pending watchers of the same or
		936	higher priority (excluding check, prepare and other idle watchers of the
		937	same or lower priority, of course). They are called idle watchers because
		938	when the watcher is the highest priority pending event in the process, the
		939	process is considered to be idle at that priority.
		940
		941	If you want a watcher that is only ever called when I<no> other events are
		942	outstanding you have to set the priority to C<EV::MINPRI>.
		943
		944	The process will not block as long as any idle watchers are active, and
		945	they will be called repeatedly until stopped.
		946
		947	For example, if you have idle watchers at priority C<0> and C<1>, and
		948	an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
		949	and the I/O watcher will always run when ready. Only when the idle watcher
		950	at priority C<1> is stopped and the I/O watcher at priority C<0> is not
		951	pending with the C<0>-priority idle watcher be invoked.
		952
		953	The C<idle_ns> variant doesn't start (activate) the newly created watcher.
		954
		955	=back
		956
		957
		958	=head3 PREPARE WATCHERS - customise your event loop!
		959
		960	=over 4
		961
		962	=item $w = EV::prepare $callback
		963
		964	=item $w = EV::prepare_ns $callback
		965
		966	=item $w = $loop->prepare ($callback)
		967
		968	=item $w = $loop->prepare_ns ($callback)
		969
		970	Call the callback just before the process would block. You can still
		971	create/modify any watchers at this point.
		972
		973	See the EV::check watcher, below, for explanations and an example.
		974
		975	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
		976
		977	=back
		978
		979
		980	=head3 CHECK WATCHERS - customise your event loop even more!
		981
		982	=over 4
		983
		984	=item $w = EV::check $callback
		985
		986	=item $w = EV::check_ns $callback
		987
		988	=item $w = $loop->check ($callback)
		989
		990	=item $w = $loop->check_ns ($callback)
		991
		992	Call the callback just after the process wakes up again (after it has
		993	gathered events), but before any other callbacks have been invoked.
		994
		995	This can be used to integrate other event-based software into the EV
		996	mainloop: You register a prepare callback and in there, you create io and
		997	timer watchers as required by the other software. Here is a real-world
		998	example of integrating Net::SNMP (with some details left out):
		999
		1000	our @snmp_watcher;
		1001
		1002	our $snmp_prepare = EV::prepare sub {
		1003	# do nothing unless active
		1004	$dispatcher->{_event_queue_h}
		1005	or return;
		1006
		1007	# make the dispatcher handle any outstanding stuff
		1008	... not shown
		1009
		1010	# create an I/O watcher for each and every socket
		1011	@snmp_watcher = (
		1012	(map { EV::io $_, EV::READ, sub { } }
		1013	keys %{ $dispatcher->{_descriptors} }),
		1014
		1015	EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
		1016	? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
		1017	0, sub { },
		1018	);
		1019	};
		1020
		1021	The callbacks are irrelevant (and are not even being called), the
		1022	only purpose of those watchers is to wake up the process as soon as
		1023	one of those events occurs (socket readable, or timer timed out). The
		1024	corresponding EV::check watcher will then clean up:
		1025
		1026	our $snmp_check = EV::check sub {
		1027	# destroy all watchers
		1028	@snmp_watcher = ();
		1029
		1030	# make the dispatcher handle any new stuff
		1031	... not shown
		1032	};
		1033
		1034	The callbacks of the created watchers will not be called as the watchers
		1035	are destroyed before this can happen (remember EV::check gets called
		1036	first).
		1037
		1038	The C<check_ns> variant doesn't start (activate) the newly created watcher.
		1039
		1040	=item EV::CHECK constant issues
		1041
		1042	Like all other watcher types, there is a bitmask constant for use in
		1043	C<$revents> and other places. The C<EV::CHECK> is special as it has
		1044	the same name as the C<CHECK> sub called by Perl. This doesn't cause
		1045	big issues on newer perls (beginning with 5.8.9), but it means thatthe
		1046	constant must be I<inlined>, i.e. runtime calls will not work. That means
		1047	that as long as you always C<use EV> and then C<EV::CHECK> you are on the
		1048	safe side.
		1049
		1050	=back
		1051
		1052
		1053	=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
		1054
		1055	Fork watchers are called when a C<fork ()> was detected. The invocation
		1056	is done before the event loop blocks next and before C<check> watchers
		1057	are being called, and only in the child after the fork.
		1058
		1059	=over 4
		1060
		1061	=item $w = EV::fork $callback
		1062
		1063	=item $w = EV::fork_ns $callback
		1064
		1065	=item $w = $loop->fork ($callback)
		1066
		1067	=item $w = $loop->fork_ns ($callback)
		1068
		1069	Call the callback before the event loop is resumed in the child process
		1070	after a fork.
		1071
		1072	The C<fork_ns> variant doesn't start (activate) the newly created watcher.
		1073
		1074	=back
		1075
		1076
		1077	=head3 EMBED WATCHERS - when one backend isn't enough...
		1078
		1079	This is a rather advanced watcher type that lets you embed one event loop
		1080	into another (currently only IO events are supported in the embedded
		1081	loop, other types of watchers might be handled in a delayed or incorrect
		1082	fashion and must not be used).
		1083
		1084	See the libev documentation at
		1085	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code_when_one_backend_>
		1086	(locally installed as F<EV::libev>) for more details.
		1087
		1088	In short, this watcher is most useful on BSD systems without working
		1089	kqueue to still be able to handle a large number of sockets:
		1090
		1091	my $socket_loop;
		1092
		1093	# check wether we use SELECT or POLL _and_ KQUEUE is supported
		1094	if (
		1095	(EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
		1096	&& (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
		1097	) {
		1098	# use kqueue for sockets
		1099	$socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
		1100	}
		1101
		1102	# use the default loop otherwise
		1103	$socket_loop ||= EV::default_loop;
		1104
		1105	=over 4
		1106
		1107	=item $w = EV::embed $otherloop[, $callback]
		1108
		1109	=item $w = EV::embed_ns $otherloop[, $callback]
		1110
		1111	=item $w = $loop->embed ($otherloop[, $callback])
		1112
		1113	=item $w = $loop->embed_ns ($otherloop[, $callback])
		1114
		1115	Call the callback when the embedded event loop (C<$otherloop>) has any
		1116	I/O activity. The C<$callback> is optional: if it is missing, then the
		1117	embedded event loop will be managed automatically (which is recommended),
		1118	otherwise you have to invoke C<sweep> yourself.
		1119
		1120	The C<embed_ns> variant doesn't start (activate) the newly created watcher.
		1121
		1122	=back
		1123
		1124	=head3 ASYNC WATCHERS - how to wake up another event loop
		1125
		1126	Async watchers are provided by EV, but have little use in perl directly,
		1127	as perl neither supports threads running in parallel nor direct access to
		1128	signal handlers or other contexts where they could be of value.
		1129
		1130	It is, however, possible to use them from the XS level.
		1131
		1132	Please see the libev documentation for further details.
		1133
		1134	=over 4
		1135
		1136	=item $w = EV::async $callback
		1137
		1138	=item $w = EV::async_ns $callback
		1139
		1140	=item $w->send
		1141
		1142	=item $bool = $w->async_pending
		1143
		1144	=back
		1145
		1146
		1147	=head1 PERL SIGNALS
		1148
		1149	While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
		1150	with EV is as the same as any other C library: Perl-signals will only be
		1151	handled when Perl runs, which means your signal handler might be invoked
		1152	only the next time an event callback is invoked.
		1153
		1154	The solution is to use EV signal watchers (see C<EV::signal>), which will
		1155	ensure proper operations with regards to other event watchers.
		1156
		1157	If you cannot do this for whatever reason, you can also force a watcher
		1158	to be called on every event loop iteration by installing a C<EV::check>
		1159	watcher:
		1160
		1161	my $async_check = EV::check sub { };
		1162
		1163	This ensures that perl gets into control for a short time to handle any
		1164	pending signals, and also ensures (slightly) slower overall operation.
		1165
295	=head1 THREADS	1166	=head1 ITHREADS
296		1167
297	Threads are not supported by this in any way. Perl pseudo-threads is evil	1168	Ithreads are not supported by this module in any way. Perl pseudo-threads
298	and must die.	1169	is evil stuff and must die. Real threads as provided by Coro are fully
		1170	supported (and enhanced support is available via L<Coro::EV>).
299		1171
300	=head1 BUGS	1172	=head1 FORK
301		1173
302	Lots. Libevent itself isn't well tested and rather buggy, and this module	1174	Most of the "improved" event delivering mechanisms of modern operating
303	is quite new at the moment.	1175	systems have quite a few problems with fork(2) (to put it bluntly: it is
		1176	not supported and usually destructive). Libev makes it possible to work
		1177	around this by having a function that recreates the kernel state after
		1178	fork in the child.
304		1179
305	Please note that the epoll method is not, in general, reliable in programs	1180	On non-win32 platforms, this module requires the pthread_atfork
306	that use fork (even if no libveent calls are being made in the forked	1181	functionality to do this automatically for you. This function is quite
307	process). If your program behaves erratically, try setting the environment	1182	buggy on most BSDs, though, so YMMV. The overhead for this is quite
308	variable C<EVENT_NOEPOLL> first when running the program.	1183	negligible, because everything the function currently does is set a flag
		1184	that is checked only when the event loop gets used the next time, so when
		1185	you do fork but not use EV, the overhead is minimal.
309		1186
310	In general, if you fork, then you can only use the EV module in one of the	1187	On win32, there is no notion of fork so all this doesn't apply, of course.
311	children.
312		1188
313	=cut	1189	=cut
314		1190
315	our $DIED = sub {	1191	our $DIED = sub {
316	warn "EV: error in callback (ignoring): $@";	1192	warn "EV: error in callback (ignoring): $@";
317	};	1193	};
318		1194
319	init;	1195	default_loop
320		1196	or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?';
321	push @AnyEvent::REGISTRY, [EV => "EV::AnyEvent"];
322		1197
323	1;	1198	1;
324		1199
325	=head1 SEE ALSO	1200	=head1 SEE ALSO
326		1201
327	L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>.	1202	L<EV::MakeMaker> - MakeMaker interface to XS API, L<EV::ADNS>
328	L<EV::AnyEvent>.	1203	(asynchronous DNS), L<Glib::EV> (makes Glib/Gtk2 use EV as event
		1204	loop), L<EV::Glib> (embed Glib into EV), L<Coro::EV> (efficient thread
		1205	integration), L<Net::SNMP::EV> (asynchronous SNMP), L<AnyEvent> for
		1206	event-loop agnostic and portable event driven programming.
329		1207
330	=head1 AUTHOR	1208	=head1 AUTHOR
331		1209
332	Marc Lehmann <schmorp@schmorp.de>	1210	Marc Lehmann <schmorp@schmorp.de>
333	http://home.schmorp.de/	1211	http://home.schmorp.de/
334		1212
335	=cut	1213	=cut
336		1214

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