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Revision 1.16 by root, Wed Oct 31 20:10:17 2007 UTC vs.
Revision 1.152 by root, Sun Oct 28 23:40:32 2018 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::break 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 = '0.03';	124	our $VERSION = 4.22;
85	use XSLoader;	125	use XSLoader;
		126	local $^W = 0; # avoid spurious warning
86	XSLoader::load "EV", $VERSION;	127	XSLoader::load "EV", $VERSION;
87	}	128	}
88		129
89	@EV::Io::ISA = "EV::Watcher";	130	@EV::IO::ISA =
90	@EV::Time::ISA = "EV::Watcher";
91	@EV::Timer::ISA = "EV::Time";	131	@EV::Timer::ISA =
92	@EV::Periodic::ISA = "EV::Time";	132	@EV::Periodic::ISA =
93	@EV::Signal::ISA = "EV::Watcher";	133	@EV::Signal::ISA =
94	@EV::Idle::ISA = "EV::Watcher";	134	@EV::Child::ISA =
95	@EV::Prepare::ISA = "EV::Watcher";	135	@EV::Stat::ISA =
96	@EV::Check::ISA = "EV::Watcher";	136	@EV::Idle::ISA =
		137	@EV::Prepare::ISA =
		138	@EV::Check::ISA =
		139	@EV::Embed::ISA =
		140	@EV::Fork::ISA =
		141	@EV::Async::ISA =
		142	"EV::Watcher";
		143
		144	@EV::Loop::Default::ISA = "EV::Loop";
		145
		146	=head1 EVENT LOOPS
		147
		148	EV supports multiple event loops: There is a single "default event loop"
		149	that can handle everything including signals and child watchers, and any
		150	number of "dynamic event loops" that can use different backends (with
		151	various limitations), but no child and signal watchers.
		152
		153	You do not have to do anything to create the default event loop: When
		154	the module is loaded a suitable backend is selected on the premise of
		155	selecting a working backend (which for example rules out kqueue on most
		156	BSDs). Modules should, unless they have "special needs" always use the
		157	default loop as this is fastest (perl-wise), best supported by other
		158	modules (e.g. AnyEvent or Coro) and most portable event loop.
		159
		160	For specific programs you can create additional event loops dynamically.
		161
		162	If you want to take advantage of kqueue (which often works properly for
		163	sockets only) even though the default loop doesn't enable it, you can
		164	I<embed> a kqueue loop into the default loop: running the default loop
		165	will then also service the kqueue loop to some extent. See the example in
		166	the section about embed watchers for an example on how to achieve that.
		167
		168	=over 4
		169
		170	=item $loop = new EV::Loop [$flags]
		171
		172	Create a new event loop as per the specified flags. Please refer to
		173	the C<ev_loop_new ()> function description in the libev documentation
		174	(L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTIONS>,
		175	or locally-installed as F<EV::libev> manpage) for more info.
		176
		177	The loop will automatically be destroyed when it is no longer referenced
		178	by any watcher and the loop object goes out of scope.
		179
		180	If you are not embedding the loop, then Using C<EV::FLAG_FORKCHECK>
		181	is recommended, as only the default event loop is protected by this
		182	module. If you I<are> embedding this loop in the default loop, this is not
		183	necessary, as C<EV::embed> automatically does the right thing on fork.
		184
		185	=item $loop->loop_fork
		186
		187	Must be called after a fork in the child, before entering or continuing
		188	the event loop. An alternative is to use C<EV::FLAG_FORKCHECK> which calls
		189	this function automatically, at some performance loss (refer to the libev
		190	documentation).
		191
		192	=item $loop->verify
		193
		194	Calls C<ev_verify> to make internal consistency checks (for debugging
		195	libev) and abort the program if any data structures were found to be
		196	corrupted.
		197
		198	=item $loop = EV::default_loop [$flags]
		199
		200	Return the default loop (which is a singleton object). Since this module
		201	already creates the default loop with default flags, specifying flags here
		202	will not have any effect unless you destroy the default loop first, which
		203	isn't supported. So in short: don't do it, and if you break it, you get to
		204	keep the pieces.
		205
		206	=back
		207
97		208
98	=head1 BASIC INTERFACE	209	=head1 BASIC INTERFACE
99		210
100	=over 4	211	=over 4
101		212
102	=item $EV::NPRI
103
104	How many priority levels are available.
105
106	=item $EV::DIED	213	=item $EV::DIED
107		214
108	Must contain a reference to a function that is called when a callback	215	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	216	throws an exception (with $@ containing the error). The default prints an
110	informative message and continues.	217	informative message and continues.
111		218
112	If this callback throws an exception it will be silently ignored.	219	If this callback throws an exception it will be silently ignored.
113		220
		221	=item $flags = EV::supported_backends
		222
		223	=item $flags = EV::recommended_backends
		224
		225	=item $flags = EV::embeddable_backends
		226
		227	Returns the set (see C<EV::BACKEND_*> flags) of backends supported by this
		228	instance of EV, the set of recommended backends (supposed to be good) for
		229	this platform and the set of embeddable backends (see EMBED WATCHERS).
		230
		231	=item EV::sleep $seconds
		232
		233	Block the process for the given number of (fractional) seconds.
		234
		235	=item $time = EV::time
		236
		237	Returns the current time in (fractional) seconds since the epoch.
		238
114	=item $time = EV::now	239	=item $time = EV::now
115		240
116	Returns the time in (fractional) seconds since the epoch.	241	=item $time = $loop->now
117		242
		243	Returns the time the last event loop iteration has been started. This
		244	is the time that (relative) timers are based on, and referring to it is
		245	usually faster then calling EV::time.
		246
		247	=item EV::now_update
		248
		249	=item $loop->now_update
		250
		251	Establishes the current time by querying the kernel, updating the time
		252	returned by C<EV::now> in the progress. This is a costly operation and
		253	is usually done automatically within C<EV::loop>.
		254
		255	This function is rarely useful, but when some event callback runs for a
		256	very long time without entering the event loop, updating libev's idea of
		257	the current time is a good idea.
		258
		259	=item EV::suspend
		260
		261	=item $loop->suspend
		262
		263	=item EV::resume
		264
		265	=item $loop->resume
		266
		267	These two functions suspend and resume a loop, for use when the loop is
		268	not used for a while and timeouts should not be processed.
		269
		270	A typical use case would be an interactive program such as a game: When
		271	the user presses C<^Z> to suspend the game and resumes it an hour later it
		272	would be best to handle timeouts as if no time had actually passed while
		273	the program was suspended. This can be achieved by calling C<suspend>
		274	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		275	C<resume> directly afterwards to resume timer processing.
		276
		277	Effectively, all C<timer> watchers will be delayed by the time spend
		278	between C<suspend> and C<resume>, and all C<periodic> watchers
		279	will be rescheduled (that is, they will lose any events that would have
		280	occured while suspended).
		281
		282	After calling C<suspend> you B<must not> call I<any> function on the given
		283	loop other than C<resume>, and you B<must not> call C<resume>
		284	without a previous call to C<suspend>.
		285
		286	Calling C<suspend>/C<resume> has the side effect of updating the event
		287	loop time (see C<now_update>).
		288
		289	=item $backend = EV::backend
		290
		291	=item $backend = $loop->backend
		292
		293	Returns an integer describing the backend used by libev (EV::BACKEND_SELECT
		294	or EV::BACKEND_EPOLL).
		295
		296	=item $active = EV::run [$flags]
		297
		298	=item $active = $loop->run ([$flags])
		299
		300	Begin checking for events and calling callbacks. It returns when a
		301	callback calls EV::break or the flags are nonzero (in which case the
		302	return value is true) or when there are no active watchers which reference
		303	the loop (keepalive is true), in which case the return value will be
		304	false. The return value can generally be interpreted as "if true, there is
		305	more work left to do".
		306
		307	The $flags argument can be one of the following:
		308
		309	0 as above
		310	EV::RUN_ONCE block at most once (wait, but do not loop)
		311	EV::RUN_NOWAIT do not block at all (fetch/handle events but do not wait)
		312
		313	=item EV::break [$how]
		314
		315	=item $loop->break ([$how])
		316
		317	When called with no arguments or an argument of EV::BREAK_ONE, makes the
		318	innermost call to EV::loop return.
		319
		320	When called with an argument of EV::BREAK_ALL, all calls to EV::loop will
		321	return as fast as possible.
		322
		323	When called with an argument of EV::BREAK_CANCEL, any pending break will
		324	be cancelled.
		325
118	=item $version = EV::version	326	=item $count = EV::iteration
119		327
120	=item $method = EV::method	328	=item $count = $loop->iteration
121		329
122	Return version string and event polling method used.	330	Return the number of times the event loop has polled for new
		331	events. Sometimes useful as a generation counter.
123		332
124	=item EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT	333	=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
125		334
126	=item EV::loopexit $after	335	=item $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
127		336
128	Exit any active loop or dispatch after C<$after> seconds or immediately if	337	This function rolls together an I/O and a timer watcher for a single
129	C<$after> is missing or zero.	338	one-shot event without the need for managing a watcher object.
130		339
131	=item EV::dispatch	340	If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events>
		341	must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ
		342	| EV::WRITE>, indicating the type of I/O event you want to wait for. If
		343	you do not want to wait for some I/O event, specify C<undef> for
		344	C<$fh_or_undef> and C<0> for C<$events>).
132		345
133	Same as C<EV::loop 0>.	346	If timeout is C<undef> or negative, then there will be no
		347	timeout. Otherwise a EV::timer with this value will be started.
134		348
135	=item EV::event $callback	349	When an error occurs or either the timeout or I/O watcher triggers, then
		350	the callback will be called with the received event set (in general
		351	you can expect it to be a combination of C<EV::ERROR>, C<EV::READ>,
		352	C<EV::WRITE> and C<EV::TIMER>).
136		353
137	Creates a new event watcher waiting for nothing, calling the given callback.	354	EV::once doesn't return anything: the watchers stay active till either
		355	of them triggers, then they will be stopped and freed, and the callback
		356	invoked.
138		357
		358	=item EV::feed_fd_event $fd, $revents
		359
		360	=item $loop->feed_fd_event ($fd, $revents)
		361
		362	Feed an event on a file descriptor into EV. EV will react to this call as
		363	if the readyness notifications specified by C<$revents> (a combination of
		364	C<EV::READ> and C<EV::WRITE>) happened on the file descriptor C<$fd>.
		365
		366	=item EV::feed_signal_event $signal
		367
		368	Feed a signal event into the default loop. EV will react to this call as
		369	if the signal specified by C<$signal> had occured.
		370
		371	=item EV::feed_signal $signal
		372
		373	Feed a signal event into EV - unlike C<EV::feed_signal_event>, this works
		374	regardless of which loop has registered the signal, and is mainly useful
		375	fro custom signal implementations.
		376
		377	=item EV::set_io_collect_interval $time
		378
		379	=item $loop->set_io_collect_interval ($time)
		380
		381	=item EV::set_timeout_collect_interval $time
		382
		383	=item $loop->set_timeout_collect_interval ($time)
		384
		385	These advanced functions set the minimum block interval when polling for I/O events and the minimum
		386	wait interval for timer events. See the libev documentation at
		387	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP>
		388	(locally installed as F<EV::libev>) for a more detailed discussion.
		389
		390	=item $count = EV::pending_count
		391
		392	=item $count = $loop->pending_count
		393
		394	Returns the number of currently pending watchers.
		395
		396	=item EV::invoke_pending
		397
		398	=item $loop->invoke_pending
		399
		400	Invoke all currently pending watchers.
		401
		402	=back
		403
		404
		405	=head1 WATCHER OBJECTS
		406
		407	A watcher is an object that gets created to record your interest in some
		408	event. For instance, if you want to wait for STDIN to become readable, you
		409	would create an EV::io watcher for that:
		410
		411	my $watcher = EV::io *STDIN, EV::READ, sub {
		412	my ($watcher, $revents) = @_;
		413	warn "yeah, STDIN should now be readable without blocking!\n"
		414	};
		415
		416	All watchers can be active (waiting for events) or inactive (paused). Only
		417	active watchers will have their callbacks invoked. All callbacks will be
		418	called with at least two arguments: the watcher and a bitmask of received
		419	events.
		420
		421	Each watcher type has its associated bit in revents, so you can use the
		422	same callback for multiple watchers. The event mask is named after the
		423	type, i.e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
		424	EV::periodic sets EV::PERIODIC and so on, with the exception of I/O events
		425	(which can set both EV::READ and EV::WRITE bits).
		426
		427	In the rare case where one wants to create a watcher but not start it at
		428	the same time, each constructor has a variant with a trailing C<_ns> in
		429	its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
		430
		431	Please note that a watcher will automatically be stopped when the watcher
		432	object is destroyed, so you I<need> to keep the watcher objects returned by
		433	the constructors.
		434
		435	Also, all methods changing some aspect of a watcher (->set, ->priority,
		436	->fh and so on) automatically stop and start it again if it is active,
		437	which means pending events get lost.
		438
		439	=head2 COMMON WATCHER METHODS
		440
		441	This section lists methods common to all watchers.
		442
		443	=over 4
		444
		445	=item $w->start
		446
		447	Starts a watcher if it isn't active already. Does nothing to an already
		448	active watcher. By default, all watchers start out in the active state
		449	(see the description of the C<_ns> variants if you need stopped watchers).
		450
		451	=item $w->stop
		452
		453	Stop a watcher if it is active. Also clear any pending events (events that
		454	have been received but that didn't yet result in a callback invocation),
		455	regardless of whether the watcher was active or not.
		456
		457	=item $bool = $w->is_active
		458
		459	Returns true if the watcher is active, false otherwise.
		460
		461	=item $current_data = $w->data
		462
		463	=item $old_data = $w->data ($new_data)
		464
		465	Queries a freely usable data scalar on the watcher and optionally changes
		466	it. This is a way to associate custom data with a watcher:
		467
		468	my $w = EV::timer 60, 0, sub {
		469	warn $_[0]->data;
		470	};
		471	$w->data ("print me!");
		472
		473	=item $current_cb = $w->cb
		474
		475	=item $old_cb = $w->cb ($new_cb)
		476
		477	Queries the callback on the watcher and optionally changes it. You can do
		478	this at any time without the watcher restarting.
		479
		480	=item $current_priority = $w->priority
		481
		482	=item $old_priority = $w->priority ($new_priority)
		483
		484	Queries the priority on the watcher and optionally changes it. Pending
		485	watchers with higher priority will be invoked first. The valid range of
		486	priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
		487	-2). If the priority is outside this range it will automatically be
		488	normalised to the nearest valid priority.
		489
		490	The default priority of any newly-created watcher is 0.
		491
		492	Note that the priority semantics have not yet been fleshed out and are
		493	subject to almost certain change.
		494
		495	=item $w->invoke ($revents)
		496
		497	Call the callback *now* with the given event mask.
		498
		499	=item $w->feed_event ($revents)
		500
		501	Feed some events on this watcher into EV. EV will react to this call as if
		502	the watcher had received the given C<$revents> mask.
		503
		504	=item $revents = $w->clear_pending
		505
		506	If the watcher is pending, this function clears its pending status and
		507	returns its C<$revents> bitset (as if its callback was invoked). If the
		508	watcher isn't pending it does nothing and returns C<0>.
		509
		510	=item $previous_state = $w->keepalive ($bool)
		511
		512	Normally, C<EV::loop> will return when there are no active watchers
		513	(which is a "deadlock" because no progress can be made anymore). This is
		514	convenient because it allows you to start your watchers (and your jobs),
		515	call C<EV::loop> once and when it returns you know that all your jobs are
		516	finished (or they forgot to register some watchers for their task :).
		517
		518	Sometimes, however, this gets in your way, for example when the module
		519	that calls C<EV::loop> (usually the main program) is not the same module
		520	as a long-living watcher (for example a DNS client module written by
		521	somebody else even). Then you might want any outstanding requests to be
		522	handled, but you would not want to keep C<EV::loop> from returning just
		523	because you happen to have this long-running UDP port watcher.
		524
		525	In this case you can clear the keepalive status, which means that even
		526	though your watcher is active, it won't keep C<EV::loop> from returning.
		527
		528	The initial value for keepalive is true (enabled), and you can change it
		529	any time.
		530
		531	Example: Register an I/O watcher for some UDP socket but do not keep the
		532	event loop from running just because of that watcher.
		533
		534	my $udp_socket = ...
		535	my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
		536	$udp_watcher->keepalive (0);
		537
		538	=item $loop = $w->loop
		539
		540	Return the loop that this watcher is attached to.
		541
		542	=back
		543
		544
		545	=head1 WATCHER TYPES
		546
		547	Each of the following subsections describes a single watcher type.
		548
		549	=head3 I/O WATCHERS - is this file descriptor readable or writable?
		550
		551	=over 4
		552
139	=item my $w = EV::io $fileno_or_fh, $eventmask, $callback	553	=item $w = EV::io $fileno_or_fh, $eventmask, $callback
140		554
141	=item my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback	555	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
		556
		557	=item $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
		558
		559	=item $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
142		560
143	As long as the returned watcher object is alive, call the C<$callback>	561	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	562	when at least one of events specified in C<$eventmask> occurs.
145	is disabled.
146		563
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:	564	The $eventmask can be one or more of these constants ORed together:
156		565
157	EV::READ wait until read() wouldn't block anymore	566	EV::READ wait until read() wouldn't block anymore
158	EV::WRITE wait until write() wouldn't block anymore	567	EV::WRITE wait until write() wouldn't block anymore
159	EV::PERSIST stay active after a (non-timeout) event occured
160		568
161	The C<io_ns> variant doesn't add/start the newly created watcher.	569	The C<io_ns> variant doesn't start (activate) the newly created watcher.
162		570
163	=item my $w = EV::timed_io $fileno_or_fh, $eventmask, $timeout, $callback	571	=item $w->set ($fileno_or_fh, $eventmask)
164		572
165	=item my $w = EV::timed_io_ns $fileno_or_fh, $eventmask, $timeout, $callback	573	Reconfigures the watcher, see the constructor above for details. Can be
		574	called at any time.
166		575
167	Same as C<io> and C<io_ns>, but also specifies a timeout (as if there was	576	=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		577
171	If the timeout is zero or undef, no timeout will be set, and a normal	578	=item $old_fh = $w->fh ($new_fh)
172	watcher (with the persist flag set!) will be created.
173		579
174	This has the effect of timing out after the specified period of inactivity	580	Returns the previously set filehandle and optionally set a new one.
175	has happened.
176		581
177	Due to the design of libevent, this is also relatively inefficient, having	582	=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		583
		584	=item $old_eventmask = $w->events ($new_eventmask)
		585
		586	Returns the previously set event mask and optionally set a new one.
		587
		588	=back
		589
		590
		591	=head3 TIMER WATCHERS - relative and optionally repeating timeouts
		592
		593	=over 4
		594
181	=item my $w = EV::timer $after, $repeat, $callback	595	=item $w = EV::timer $after, $repeat, $callback
182		596
183	=item my $w = EV::timer_ns $after, $repeat, $callback	597	=item $w = EV::timer_ns $after, $repeat, $callback
184		598
185	Calls the callback after C<$after> seconds. If C<$repeat> is true, the	599	=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		600
		601	=item $w = $loop->timer_ns ($after, $repeat, $callback)
		602
		603	Calls the callback after C<$after> seconds (which may be fractional or
		604	negative). If C<$repeat> is non-zero, the timer will be restarted (with
		605	the $repeat value as $after) after the callback returns.
		606
		607	This means that the callback would be called roughly after C<$after>
		608	seconds, and then every C<$repeat> seconds. The timer does his best not
		609	to drift, but it will not invoke the timer more often then once per event
		610	loop iteration, and might drift in other cases. If that isn't acceptable,
		611	look at EV::periodic, which can provide long-term stable timers.
		612
		613	The timer is based on a monotonic clock, that is, if somebody is sitting
		614	in front of the machine while the timer is running and changes the system
		615	clock, the timer will nevertheless run (roughly) the same time.
		616
190	The C<timer_ns> variant doesn't add/start the newly created watcher.	617	The C<timer_ns> variant doesn't start (activate) the newly created watcher.
191		618
192	=item my $w = EV::timer_abs $at, $interval, $callback	619	=item $w->set ($after, $repeat = 0)
193		620
194	=item my $w = EV::timer_abs_ns $at, $interval, $callback	621	Reconfigures the watcher, see the constructor above for details. Can be called at
		622	any time.
195		623
196	Similar to EV::timer, but the time is given as an absolute point in time	624	=item $w->again
197	(C<$at>), plus an optional C<$interval>.
198		625
199	If the C<$interval> is zero, then the callback will be called at the time	626	=item $w->again ($repeat)
200	C<$at> if that is in the future, or as soon as possible if its in the
201	past. It will not automatically repeat.
202		627
203	If the C<$interval> is nonzero, then the watcher will always be scheduled	628	Similar to the C<start> method, but has special semantics for repeating timers:
204	to time out at the next C<$at + integer * $interval> time.
205		629
206	This can be used to schedule a callback to run at very regular intervals,	630	If the timer is active and non-repeating, it will be stopped.
207	as long as the processing time is less then the interval (otherwise	631
208	obviously events will be skipped).	632	If the timer is active and repeating, reset the timeout to occur
		633	C<$repeat> seconds after now.
		634
		635	If the timer is inactive and repeating, start it using the repeat value.
		636
		637	Otherwise do nothing.
		638
		639	This behaviour is useful when you have a timeout for some IO
		640	operation. You create a timer object with the same value for C<$after> and
		641	C<$repeat>, and then, in the read/write watcher, run the C<again> method
		642	on the timeout.
		643
		644	If called with a C<$repeat> argument, then it uses this a timer repeat
		645	value.
		646
		647	=item $after = $w->remaining
		648
		649	Calculates and returns the remaining time till the timer will fire.
		650
		651	=back
		652
		653
		654	=head3 PERIODIC WATCHERS - to cron or not to cron?
		655
		656	=over 4
		657
		658	=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
		659
		660	=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
		661
		662	=item $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
		663
		664	=item $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
		665
		666	Similar to EV::timer, but is not based on relative timeouts but on
		667	absolute times. Apart from creating "simple" timers that trigger "at" the
		668	specified time, it can also be used for non-drifting absolute timers and
		669	more complex, cron-like, setups that are not adversely affected by time
		670	jumps (i.e. when the system clock is changed by explicit date -s or other
		671	means such as ntpd). It is also the most complex watcher type in EV.
		672
		673	It has three distinct "modes":
		674
		675	=over 4
		676
		677	=item * absolute timer ($interval = $reschedule_cb = 0)
		678
		679	This time simply fires at the wallclock time C<$at> and doesn't repeat. It
		680	will not adjust when a time jump occurs, that is, if it is to be run
		681	at January 1st 2011 then it will run when the system time reaches or
		682	surpasses this time.
		683
		684	=item * repeating interval timer ($interval > 0, $reschedule_cb = 0)
		685
		686	In this mode the watcher will always be scheduled to time out at the
		687	next C<$at + N * $interval> time (for the lowest integer N) and then repeat,
		688	regardless of any time jumps. Note that, since C<N> can be negative, the
		689	first trigger can happen before C<$at>.
		690
		691	This can be used to create timers that do not drift with respect to system
		692	time:
		693
		694	my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
		695
		696	That doesn't mean there will always be 3600 seconds in between triggers,
		697	but only that the the callback will be called when the system time shows a
		698	full hour (UTC).
209		699
210	Another way to think about it (for the mathematically inclined) is that	700	Another way to think about it (for the mathematically inclined) is that
211	C<timer_abs> will try to tun the callback at the next possible time where	701	EV::periodic will try to run the callback in this mode at the next
212	C<$time = $at (mod $interval)>, regardless of any time jumps.	702	possible time where C<$time = $at (mod $interval)>, regardless of any time
		703	jumps.
213		704
		705	=item * manual reschedule mode ($reschedule_cb = coderef)
		706
		707	In this mode $interval and $at are both being ignored. Instead, each
		708	time the periodic watcher gets scheduled, the reschedule callback
		709	($reschedule_cb) will be called with the watcher as first, and the current
		710	time as second argument.
		711
		712	I<This callback MUST NOT stop or destroy this or any other periodic
		713	watcher, ever, and MUST NOT call any event loop functions or methods>. If
		714	you need to stop it, return 1e30 and stop it afterwards. You may create
		715	and start a C<EV::prepare> watcher for this task.
		716
		717	It must return the next time to trigger, based on the passed time value
		718	(that is, the lowest time value larger than or equal to to the second
		719	argument). It will usually be called just before the callback will be
		720	triggered, but might be called at other times, too.
		721
		722	This can be used to create very complex timers, such as a timer that
		723	triggers on each midnight, local time (actually one day after the last
		724	midnight, to keep the example simple):
		725
		726	my $daily = EV::periodic 0, 0, sub {
		727	my ($w, $now) = @_;
		728
		729	use Time::Local ();
		730	my (undef, undef, undef, $d, $m, $y) = localtime $now;
		731	Time::Local::timelocal_nocheck 0, 0, 0, $d + 1, $m, $y
		732	}, sub {
		733	print "it's midnight or likely shortly after, now\n";
		734	};
		735
		736	=back
		737
214	The C<timer_abs_ns> variant doesn't add/start the newly created watcher.	738	The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
215		739
		740	=item $w->set ($at, $interval, $reschedule_cb)
		741
		742	Reconfigures the watcher, see the constructor above for details. Can be called at
		743	any time.
		744
		745	=item $w->again
		746
		747	Simply stops and starts the watcher again.
		748
		749	=item $time = $w->at
		750
		751	Return the time that the watcher is expected to trigger next.
		752
		753	=back
		754
		755
		756	=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
		757
		758	=over 4
		759
216	=item my $w = EV::signal $signal, $callback	760	=item $w = EV::signal $signal, $callback
217		761
218	=item my $w = EV::signal_ns $signal, $callback	762	=item $w = EV::signal_ns $signal, $callback
219		763
		764	=item $w = $loop->signal ($signal, $callback)
		765
		766	=item $w = $loop->signal_ns ($signal, $callback)
		767
220	Call the callback when $signal is received (the signal can be specified	768	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	769	number or by name, just as with C<kill> or C<%SIG>).
222	persistent no natter what.	770
		771	Only one event loop can grab a given signal - attempting to grab the same
		772	signal from two EV loops will crash the program immediately or cause data
		773	corruption.
223		774
224	EV will grab the signal for the process (the kernel only allows one	775	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	776	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	777	and removes it again when you stop it. Perl does the same when you
227	callbacks to %SIG, so watch out.	778	add/remove callbacks to C<%SIG>, so watch out.
228		779
229	Unfortunately, only one handler can be registered per signal. Screw	780	You can have as many signal watchers per signal as you want.
230	libevent.
231		781
232	The C<signal_ns> variant doesn't add/start the newly created watcher.	782	The C<signal_ns> variant doesn't start (activate) the newly created watcher.
233		783
234	=back	784	=item $w->set ($signal)
235		785
236	=head1 THE EV::Event CLASS	786	Reconfigures the watcher, see the constructor above for details. Can be
		787	called at any time.
237		788
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	789	=item $current_signum = $w->signal
272		790
273	=item $old_signal = $w->signal ($new_signal)	791	=item $old_signum = $w->signal ($new_signal)
274		792
		793	Returns the previously set signal (always as a number not name) and
		794	optionally set a new one.
		795
		796	=back
		797
		798
		799	=head3 CHILD WATCHERS - watch out for process status changes
		800
		801	=over 4
		802
		803	=item $w = EV::child $pid, $trace, $callback
		804
		805	=item $w = EV::child_ns $pid, $trace, $callback
		806
		807	=item $w = $loop->child ($pid, $trace, $callback)
		808
		809	=item $w = $loop->child_ns ($pid, $trace, $callback)
		810
		811	Call the callback when a status change for pid C<$pid> (or any pid
		812	if C<$pid> is 0) has been received (a status change happens when the
		813	process terminates or is killed, or, when trace is true, additionally when
		814	it is stopped or continued). More precisely: when the process receives
		815	a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
		816	changed/zombie children and call the callback.
		817
		818	It is valid (and fully supported) to install a child watcher after a child
		819	has exited but before the event loop has started its next iteration (for
		820	example, first you C<fork>, then the new child process might exit, and
		821	only then do you install a child watcher in the parent for the new pid).
		822
		823	You can access both exit (or tracing) status and pid by using the
		824	C<rstatus> and C<rpid> methods on the watcher object.
		825
		826	You can have as many pid watchers per pid as you want, they will all be
		827	called.
		828
		829	The C<child_ns> variant doesn't start (activate) the newly created watcher.
		830
		831	=item $w->set ($pid, $trace)
		832
		833	Reconfigures the watcher, see the constructor above for details. Can be called at
		834	any time.
		835
		836	=item $current_pid = $w->pid
		837
275	Returns the previously set signal number and optionally set a new one (also sets	838	Returns the previously set process id and optionally set a new one.
276	the EV::SIGNAL flag when setting a signal).
277		839
278	=item $current_eventmask = $w->events	840	=item $exit_status = $w->rstatus
279		841
280	=item $old_eventmask = $w->events ($new_eventmask)	842	Return the exit/wait status (as returned by waitpid, see the waitpid entry
		843	in perlfunc).
281		844
		845	=item $pid = $w->rpid
		846
		847	Return the pid of the awaited child (useful when you have installed a
		848	watcher for all pids).
		849
		850	=back
		851
		852
		853	=head3 STAT WATCHERS - did the file attributes just change?
		854
		855	=over 4
		856
		857	=item $w = EV::stat $path, $interval, $callback
		858
		859	=item $w = EV::stat_ns $path, $interval, $callback
		860
		861	=item $w = $loop->stat ($path, $interval, $callback)
		862
		863	=item $w = $loop->stat_ns ($path, $interval, $callback)
		864
		865	Call the callback when a file status change has been detected on
		866	C<$path>. The C<$path> does not need to exist, changing from "path exists"
		867	to "path does not exist" is a status change like any other.
		868
		869	The C<$interval> is a recommended polling interval for systems where
		870	OS-supported change notifications don't exist or are not supported. If
		871	you use C<0> then an unspecified default is used (which is highly
		872	recommended!), which is to be expected to be around five seconds usually.
		873
		874	This watcher type is not meant for massive numbers of stat watchers,
		875	as even with OS-supported change notifications, this can be
		876	resource-intensive.
		877
		878	The C<stat_ns> variant doesn't start (activate) the newly created watcher.
		879
		880	=item ... = $w->stat
		881
		882	This call is very similar to the perl C<stat> built-in: It stats (using
		883	C<lstat>) the path specified in the watcher and sets perls stat cache (as
		884	well as EV's idea of the current stat values) to the values found.
		885
		886	In scalar context, a boolean is return indicating success or failure of
		887	the stat. In list context, the same 13-value list as with stat is returned
		888	(except that the blksize and blocks fields are not reliable).
		889
		890	In the case of an error, errno is set to C<ENOENT> (regardless of the
		891	actual error value) and the C<nlink> value is forced to zero (if the stat
		892	was successful then nlink is guaranteed to be non-zero).
		893
		894	See also the next two entries for more info.
		895
		896	=item ... = $w->attr
		897
		898	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		899	the values most recently detected by EV. See the next entry for more info.
		900
		901	=item ... = $w->prev
		902
		903	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		904	the previous set of values, before the change.
		905
		906	That is, when the watcher callback is invoked, C<< $w->prev >> will be set
		907	to the values found I<before> a change was detected, while C<< $w->attr >>
		908	returns the values found leading to the change detection. The difference (if any)
		909	between C<prev> and C<attr> is what triggered the callback.
		910
		911	If you did something to the filesystem object and do not want to trigger
		912	yet another change, you can call C<stat> to update EV's idea of what the
		913	current attributes are.
		914
		915	=item $w->set ($path, $interval)
		916
		917	Reconfigures the watcher, see the constructor above for details. Can be
		918	called at any time.
		919
		920	=item $current_path = $w->path
		921
		922	=item $old_path = $w->path ($new_path)
		923
282	Returns the previously set event mask and optionally set a new one.	924	Returns the previously set path and optionally set a new one.
283		925
284	=item $w->timeout ($after, $repeat)	926	=item $current_interval = $w->interval
285		927
286	Resets the timeout (see C<EV::timer> for details).	928	=item $old_interval = $w->interval ($new_interval)
287		929
288	=item $w->timeout_abs ($at, $interval)	930	Returns the previously set interval and optionally set a new one. Can be
		931	used to query the actual interval used.
289		932
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	933	=back
297		934
		935
		936	=head3 IDLE WATCHERS - when you've got nothing better to do...
		937
		938	=over 4
		939
		940	=item $w = EV::idle $callback
		941
		942	=item $w = EV::idle_ns $callback
		943
		944	=item $w = $loop->idle ($callback)
		945
		946	=item $w = $loop->idle_ns ($callback)
		947
		948	Call the callback when there are no other pending watchers of the same or
		949	higher priority (excluding check, prepare and other idle watchers of the
		950	same or lower priority, of course). They are called idle watchers because
		951	when the watcher is the highest priority pending event in the process, the
		952	process is considered to be idle at that priority.
		953
		954	If you want a watcher that is only ever called when I<no> other events are
		955	outstanding you have to set the priority to C<EV::MINPRI>.
		956
		957	The process will not block as long as any idle watchers are active, and
		958	they will be called repeatedly until stopped.
		959
		960	For example, if you have idle watchers at priority C<0> and C<1>, and
		961	an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
		962	and the I/O watcher will always run when ready. Only when the idle watcher
		963	at priority C<1> is stopped and the I/O watcher at priority C<0> is not
		964	pending with the C<0>-priority idle watcher be invoked.
		965
		966	The C<idle_ns> variant doesn't start (activate) the newly created watcher.
		967
		968	=back
		969
		970
		971	=head3 PREPARE WATCHERS - customise your event loop!
		972
		973	=over 4
		974
		975	=item $w = EV::prepare $callback
		976
		977	=item $w = EV::prepare_ns $callback
		978
		979	=item $w = $loop->prepare ($callback)
		980
		981	=item $w = $loop->prepare_ns ($callback)
		982
		983	Call the callback just before the process would block. You can still
		984	create/modify any watchers at this point.
		985
		986	See the EV::check watcher, below, for explanations and an example.
		987
		988	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
		989
		990	=back
		991
		992
		993	=head3 CHECK WATCHERS - customise your event loop even more!
		994
		995	=over 4
		996
		997	=item $w = EV::check $callback
		998
		999	=item $w = EV::check_ns $callback
		1000
		1001	=item $w = $loop->check ($callback)
		1002
		1003	=item $w = $loop->check_ns ($callback)
		1004
		1005	Call the callback just after the process wakes up again (after it has
		1006	gathered events), but before any other callbacks have been invoked.
		1007
		1008	This can be used to integrate other event-based software into the EV
		1009	mainloop: You register a prepare callback and in there, you create io and
		1010	timer watchers as required by the other software. Here is a real-world
		1011	example of integrating Net::SNMP (with some details left out):
		1012
		1013	our @snmp_watcher;
		1014
		1015	our $snmp_prepare = EV::prepare sub {
		1016	# do nothing unless active
		1017	$dispatcher->{_event_queue_h}
		1018	or return;
		1019
		1020	# make the dispatcher handle any outstanding stuff
		1021	... not shown
		1022
		1023	# create an I/O watcher for each and every socket
		1024	@snmp_watcher = (
		1025	(map { EV::io $_, EV::READ, sub { } }
		1026	keys %{ $dispatcher->{_descriptors} }),
		1027
		1028	EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
		1029	? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
		1030	0, sub { },
		1031	);
		1032	};
		1033
		1034	The callbacks are irrelevant (and are not even being called), the
		1035	only purpose of those watchers is to wake up the process as soon as
		1036	one of those events occurs (socket readable, or timer timed out). The
		1037	corresponding EV::check watcher will then clean up:
		1038
		1039	our $snmp_check = EV::check sub {
		1040	# destroy all watchers
		1041	@snmp_watcher = ();
		1042
		1043	# make the dispatcher handle any new stuff
		1044	... not shown
		1045	};
		1046
		1047	The callbacks of the created watchers will not be called as the watchers
		1048	are destroyed before this can happen (remember EV::check gets called
		1049	first).
		1050
		1051	The C<check_ns> variant doesn't start (activate) the newly created watcher.
		1052
		1053	=item EV::CHECK constant issues
		1054
		1055	Like all other watcher types, there is a bitmask constant for use in
		1056	C<$revents> and other places. The C<EV::CHECK> is special as it has
		1057	the same name as the C<CHECK> sub called by Perl. This doesn't cause
		1058	big issues on newer perls (beginning with 5.8.9), but it means thatthe
		1059	constant must be I<inlined>, i.e. runtime calls will not work. That means
		1060	that as long as you always C<use EV> and then C<EV::CHECK> you are on the
		1061	safe side.
		1062
		1063	=back
		1064
		1065
		1066	=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
		1067
		1068	Fork watchers are called when a C<fork ()> was detected. The invocation
		1069	is done before the event loop blocks next and before C<check> watchers
		1070	are being called, and only in the child after the fork.
		1071
		1072	=over 4
		1073
		1074	=item $w = EV::fork $callback
		1075
		1076	=item $w = EV::fork_ns $callback
		1077
		1078	=item $w = $loop->fork ($callback)
		1079
		1080	=item $w = $loop->fork_ns ($callback)
		1081
		1082	Call the callback before the event loop is resumed in the child process
		1083	after a fork.
		1084
		1085	The C<fork_ns> variant doesn't start (activate) the newly created watcher.
		1086
		1087	=back
		1088
		1089
		1090	=head3 EMBED WATCHERS - when one backend isn't enough...
		1091
		1092	This is a rather advanced watcher type that lets you embed one event loop
		1093	into another (currently only IO events are supported in the embedded
		1094	loop, other types of watchers might be handled in a delayed or incorrect
		1095	fashion and must not be used).
		1096
		1097	See the libev documentation at
		1098	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code_when_one_backend_>
		1099	(locally installed as F<EV::libev>) for more details.
		1100
		1101	In short, this watcher is most useful on BSD systems without working
		1102	kqueue to still be able to handle a large number of sockets:
		1103
		1104	my $socket_loop;
		1105
		1106	# check wether we use SELECT or POLL _and_ KQUEUE is supported
		1107	if (
		1108	(EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
		1109	&& (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
		1110	) {
		1111	# use kqueue for sockets
		1112	$socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
		1113	}
		1114
		1115	# use the default loop otherwise
		1116	$socket_loop ||= EV::default_loop;
		1117
		1118	=over 4
		1119
		1120	=item $w = EV::embed $otherloop[, $callback]
		1121
		1122	=item $w = EV::embed_ns $otherloop[, $callback]
		1123
		1124	=item $w = $loop->embed ($otherloop[, $callback])
		1125
		1126	=item $w = $loop->embed_ns ($otherloop[, $callback])
		1127
		1128	Call the callback when the embedded event loop (C<$otherloop>) has any
		1129	I/O activity. The C<$callback> is optional: if it is missing, then the
		1130	embedded event loop will be managed automatically (which is recommended),
		1131	otherwise you have to invoke C<sweep> yourself.
		1132
		1133	The C<embed_ns> variant doesn't start (activate) the newly created watcher.
		1134
		1135	=back
		1136
		1137	=head3 ASYNC WATCHERS - how to wake up another event loop
		1138
		1139	Async watchers are provided by EV, but have little use in perl directly,
		1140	as perl neither supports threads running in parallel nor direct access to
		1141	signal handlers or other contexts where they could be of value.
		1142
		1143	It is, however, possible to use them from the XS level.
		1144
		1145	Please see the libev documentation for further details.
		1146
		1147	=over 4
		1148
		1149	=item $w = EV::async $callback
		1150
		1151	=item $w = EV::async_ns $callback
		1152
		1153	=item $w = $loop->async ($callback)
		1154
		1155	=item $w = $loop->async_ns ($callback)
		1156
		1157	=item $w->send
		1158
		1159	=item $bool = $w->async_pending
		1160
		1161	=back
		1162
		1163	=head3 CLEANUP WATCHERS - how to clean up when the event loop goes away
		1164
		1165	Cleanup watchers are not supported on the Perl level, they can only be
		1166	used via XS currently.
		1167
		1168
		1169	=head1 PERL SIGNALS
		1170
		1171	While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
		1172	with EV is as the same as any other C library: Perl-signals will only be
		1173	handled when Perl runs, which means your signal handler might be invoked
		1174	only the next time an event callback is invoked.
		1175
		1176	The solution is to use EV signal watchers (see C<EV::signal>), which will
		1177	ensure proper operations with regards to other event watchers.
		1178
		1179	If you cannot do this for whatever reason, you can also force a watcher
		1180	to be called on every event loop iteration by installing a C<EV::check>
		1181	watcher:
		1182
		1183	my $async_check = EV::check sub { };
		1184
		1185	This ensures that perl gets into control for a short time to handle any
		1186	pending signals, and also ensures (slightly) slower overall operation.
		1187
298	=head1 THREADS	1188	=head1 ITHREADS
299		1189
300	Threads are not supported by this in any way. Perl pseudo-threads is evil	1190	Ithreads are not supported by this module in any way. Perl pseudo-threads
301	and must die.	1191	is evil stuff and must die. Real threads as provided by Coro are fully
		1192	supported (and enhanced support is available via L<Coro::EV>).
302		1193
303	=head1 BUGS	1194	=head1 FORK
304		1195
305	Lots. Libevent itself isn't well tested and rather buggy, and this module	1196	Most of the "improved" event delivering mechanisms of modern operating
306	is quite new at the moment.	1197	systems have quite a few problems with fork(2) (to put it bluntly: it is
		1198	not supported and usually destructive). Libev makes it possible to work
		1199	around this by having a function that recreates the kernel state after
		1200	fork in the child.
307		1201
308	Please note that the epoll method is not, in general, reliable in programs	1202	On non-win32 platforms, this module requires the pthread_atfork
309	that use fork (even if no libveent calls are being made in the forked	1203	functionality to do this automatically for you. This function is quite
310	process). If your program behaves erratically, try setting the environment	1204	buggy on most BSDs, though, so YMMV. The overhead for this is quite
311	variable C<EVENT_NOEPOLL> first when running the program.	1205	negligible, because everything the function currently does is set a flag
		1206	that is checked only when the event loop gets used the next time, so when
		1207	you do fork but not use EV, the overhead is minimal.
312		1208
313	In general, if you fork, then you can only use the EV module in one of the	1209	On win32, there is no notion of fork so all this doesn't apply, of course.
314	children.
315		1210
316	=cut	1211	=cut
317		1212
318	our $DIED = sub {	1213	our $DIED = sub {
319	warn "EV: error in callback (ignoring): $@";	1214	warn "EV: error in callback (ignoring): $@";
320	};	1215	};
321		1216
322	init;	1217	default_loop
323		1218	or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?';
324	push @AnyEvent::REGISTRY, [EV => "EV::AnyEvent"];
325		1219
326	1;	1220	1;
327		1221
328	=head1 SEE ALSO	1222	=head1 SEE ALSO
329		1223
330	L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>.	1224	L<EV::MakeMaker> - MakeMaker interface to XS API, L<EV::ADNS>
331	L<EV::AnyEvent>.	1225	(asynchronous DNS), L<Glib::EV> (makes Glib/Gtk2 use EV as event
		1226	loop), L<EV::Glib> (embed Glib into EV), L<Coro::EV> (efficient thread
		1227	integration), L<Net::SNMP::EV> (asynchronous SNMP), L<AnyEvent> for
		1228	event-loop agnostic and portable event driven programming.
332		1229
333	=head1 AUTHOR	1230	=head1 AUTHOR
334		1231
335	Marc Lehmann <schmorp@schmorp.de>	1232	Marc Lehmann <schmorp@schmorp.de>
336	http://home.schmorp.de/	1233	http://home.schmorp.de/
337		1234
338	=cut	1235	=cut
339		1236

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