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Revision 1.9 by root, Sun Oct 28 06:40:46 2007 UTC vs.
Revision 1.167 by root, Thu Oct 19 18:02:42 2023 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		8
9	# TIMER	9	# TIMERS
10		10
11	my $w = EV::timer 2, 0, sub {	11	my $w = EV::timer 2, 0, sub {
12	warn "is called after 2s";	12	warn "is called after 2s";
13	};	13	};
14		14
15	my $w = EV::timer 2, 1, sub {	15	my $w = EV::timer 2, 2, sub {
16	warn "is called roughly every 2s (repeat = 1)";	16	warn "is called roughly every 2s (repeat = 2)";
17	};	17	};
18		18
19	undef $w; # destroy event watcher again	19	undef $w; # destroy event watcher again
20		20
21	# IO
22
23	my $w = EV::timer_abs 0, 60, sub {	21	my $w = EV::periodic 0, 60, 0, sub {
24	warn "is called every minute, on the minute, exactly";	22	warn "is called every minute, on the minute, exactly";
25	};	23	};
26		24
		25	# IO
		26
27	my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub {	27	my $w = EV::io *STDIN, EV::READ, sub {
28	my ($w, $events) = @_; # all callbacks get the watcher object and event mask	28	my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
29	if ($events & EV::TIMEOUT) {
30	warn "nothign received on stdin for 10 seconds, retrying";
31	} else {
32	warn "stdin is readable, you entered: ", <STDIN>;	29	warn "stdin is readable, you entered: ", <STDIN>;
33	}	30	};
		31
		32	# SIGNALS
		33
		34	my $w = EV::signal 'QUIT', sub {
		35	warn "sigquit received\n";
34	};	36	};
35	$w->timeout (10);	37
36		38	# CHILD/PID STATUS CHANGES
		39
		40	my $w = EV::child 666, 0, sub {
		41	my ($w, $revents) = @_;
		42	my $status = $w->rstatus;
		43	};
		44
		45	# STAT CHANGES
		46	my $w = EV::stat "/etc/passwd", 10, sub {
		47	my ($w, $revents) = @_;
		48	warn $w->path, " has changed somehow.\n";
		49	};
		50
37	# MAINLOOP	51	# MAINLOOP
38	EV::dispatch; # loop as long as watchers are active	52	EV::run; # loop until EV::break is called or all watchers stop
39	EV::loop; # the same thing	53	EV::run EV::RUN_ONCE; # block until at least one event could be handled
40	EV::loop EV::LOOP_ONCE;	54	EV::run EV::RUN_NOWAIT; # try to handle same events, but do not block
41	EV::loop EV::LOOP_ONSHOT;	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.
42		64
43	=head1 DESCRIPTION	65	=head1 DESCRIPTION
44		66
45	This module provides an interface to libevent	67	This module provides an interface to libev
46	(L<http://monkey.org/~provos/libevent/>). You probably should acquaint	68	(L<http://software.schmorp.de/pkg/libev.html>). While the documentation
47	yourself with its documentation and source code to be able to use this	69	below is comprehensive, one might also consult the documentation of
48	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.
49		75
50	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
51	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.
52		116
53	=cut	117	=cut
54		118
55	package EV;	119	package EV;
56		120
57	use strict;	121	use common::sense;
58		122
59	BEGIN {	123	BEGIN {
60	our $VERSION = '0.02';	124	our $VERSION = '4.34';
61	use XSLoader;	125	use XSLoader;
		126	local $^W = 0; # avoid spurious warning
62	XSLoader::load "EV", $VERSION;	127	XSLoader::load "EV", $VERSION;
63	}	128	}
64		129
		130	@EV::IO::ISA =
		131	@EV::Timer::ISA =
		132	@EV::Periodic::ISA =
		133	@EV::Signal::ISA =
		134	@EV::Child::ISA =
		135	@EV::Stat::ISA =
		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
		208
65	=head1 BASIC INTERFACE	209	=head1 BASIC INTERFACE
66		210
67	=over 4	211	=over 4
68		212
69	=item $EV::NPRI
70
71	How many priority levels are available.
72
73	=item $EV::DIED	213	=item $EV::DIED
74		214
75	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
76	throws an exception (with $@ containing thr error). The default prints an	216	throws an exception (with $@ containing the error). The default prints an
77	informative message and continues.	217	informative message and continues.
78		218
79	If this callback throws an exception it will be silently ignored.	219	If this callback throws an exception it will be silently ignored.
80		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
81	=item $time = EV::now	239	=item $time = EV::now
82		240
83	Returns the time in (fractional) seconds since the epoch.	241	=item $time = $loop->now
84		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::run>.
		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::run return.
		319
		320	When called with an argument of EV::BREAK_ALL, all calls to EV::run 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
85	=item $version = EV::version	326	=item $count = EV::iteration
86		327
87	=item $method = EV::method	328	=item $count = $loop->iteration
88		329
89	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.
90		332
91	=item EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT	333	=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
92		334
93	=item EV::loopexit $after	335	=item $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
94		336
95	Exit any active loop or dispatch after C<$after> seconds or immediately if	337	This function rolls together an I/O and a timer watcher for a single
96	C<$after> is missing or zero.	338	one-shot event without the need for managing a watcher object.
97		339
98	=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>).
99		345
100	Same as C<EV::loop 0>.	346	If timeout is C<undef> or negative, then there will be no
		347	timeout. Otherwise an C<EV::timer> with this value will be started.
101		348
102	=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>).
103		353
104	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.
105		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	for 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::run> 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::run> 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::run> (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::run> 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::run> 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
106	=item my $w = EV::io $fileno_or_fh, $eventmask, $callback	553	=item $w = EV::io $fileno_or_fh, $eventmask, $callback
107		554
108	=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, $callback)
109		560
110	As long as the returned watcher object is alive, call the C<$callback>	561	As long as the returned watcher object is alive, call the C<$callback>
111	when the events specified in C<$eventmask> happen. Initially, the timeout	562	when at least one of events specified in C<$eventmask> occurs.
112	is disabled.
113		563
114	Youc an additionall set a timeout to occur on the watcher, but note that
115	this timeout will not be reset when you get an I/O event in the EV::PERSIST
116	case, and reaching a timeout will always stop the watcher even in the
117	EV::PERSIST case.
118
119	If you want a timeout to occur only after a specific time of inactivity, set
120	a repeating timeout and do NOT use EV::PERSIST.
121
122	Eventmask can be one or more of these constants ORed together:	564	The $eventmask can be one or more of these constants ORed together:
123		565
124	EV::READ wait until read() wouldn't block anymore	566	EV::READ wait until read() wouldn't block anymore
125	EV::WRITE wait until write() wouldn't block anymore	567	EV::WRITE wait until write() wouldn't block anymore
126	EV::PERSIST stay active after a (non-timeout) event occured
127		568
128	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.
129		570
		571	=item $w->set ($fileno_or_fh, $eventmask)
		572
		573	Reconfigures the watcher, see the constructor above for details. Can be
		574	called at any time.
		575
		576	=item $current_fh = $w->fh
		577
		578	=item $old_fh = $w->fh ($new_fh)
		579
		580	Returns the previously set filehandle and optionally set a new one.
		581
		582	=item $current_eventmask = $w->events
		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
130	=item my $w = EV::timer $after, $repeat, $callback	595	=item $w = EV::timer $after, $repeat, $callback
131		596
132	=item my $w = EV::timer_ns $after, $repeat, $callback	597	=item $w = EV::timer_ns $after, $repeat, $callback
133		598
134	Calls the callback after C<$after> seconds. If C<$repeat> is true, the	599	=item $w = $loop->timer ($after, $repeat, $callback)
135	timer will be restarted after the callback returns. This means that the
136	callback would be called roughly every C<$after> seconds, prolonged by the
137	time the callback takes.
138		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
139	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.
140		618
141	=item my $w = EV::timer_abs $at, $interval, $callback	619	=item $w->set ($after, $repeat = 0)
142		620
143	=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.
144		623
145	Similar to EV::timer, but the time is given as an absolute point in time	624	=item $w->again
146	(C<$at>), plus an optional C<$interval>.
147		625
148	If the C<$interval> is zero, then the callback will be called at the time	626	=item $w->again ($repeat)
149	C<$at> if that is in the future, or as soon as possible if its in the
150	past. It will not automatically repeat.
151		627
152	If the C<$interval> is nonzero, then the watcher will always be scheduled	628	Similar to the C<start> method, but has special semantics for repeating timers:
153	to time out at the next C<$at + integer * $interval> time.
154		629
155	This can be used to schedule a callback to run at very regular intervals,	630	If the timer is active and non-repeating, it will be stopped.
156	as long as the processing time is less then the interval (otherwise	631
157	obviously events will be skipped).	632	If the timer is active and repeating, reset the timeout to occur
		633	C<$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	=item $repeat = $w->repeat
		652
		653	=item $old_repeat = $w->repeat ($new_repeat)
		654
		655	Returns the current value of the repeat attribute and optionally sets a
		656	new one. Setting the new one will not restart the watcher - if the watcher
		657	is active, the new repeat value is used whenever it expires next.
		658
		659	=back
		660
		661
		662	=head3 PERIODIC WATCHERS - to cron or not to cron?
		663
		664	=over 4
		665
		666	=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
		667
		668	=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
		669
		670	=item $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
		671
		672	=item $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
		673
		674	Similar to EV::timer, but is not based on relative timeouts but on
		675	absolute times. Apart from creating "simple" timers that trigger "at" the
		676	specified time, it can also be used for non-drifting absolute timers and
		677	more complex, cron-like, setups that are not adversely affected by time
		678	jumps (i.e. when the system clock is changed by explicit date -s or other
		679	means such as ntpd). It is also the most complex watcher type in EV.
		680
		681	It has three distinct "modes":
		682
		683	=over 4
		684
		685	=item * absolute timer ($interval = $reschedule_cb = 0)
		686
		687	This time simply fires at the wallclock time C<$at> and doesn't repeat. It
		688	will not adjust when a time jump occurs, that is, if it is to be run
		689	at January 1st 2011 then it will run when the system time reaches or
		690	surpasses this time.
		691
		692	=item * repeating interval timer ($interval > 0, $reschedule_cb = 0)
		693
		694	In this mode the watcher will always be scheduled to time out at the
		695	next C<$at + N * $interval> time (for the lowest integer N) and then repeat,
		696	regardless of any time jumps. Note that, since C<N> can be negative, the
		697	first trigger can happen before C<$at>.
		698
		699	This can be used to create timers that do not drift with respect to system
		700	time:
		701
		702	my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
		703
		704	That doesn't mean there will always be 3600 seconds in between triggers,
		705	but only that the the callback will be called when the system time shows a
		706	full hour (UTC).
158		707
159	Another way to think about it (for the mathematically inclined) is that	708	Another way to think about it (for the mathematically inclined) is that
160	C<timer_abs> will try to tun the callback at the next possible time where	709	EV::periodic will try to run the callback in this mode at the next
161	C<$time = $at (mod $interval)>, regardless of any time jumps.	710	possible time where C<$time = $at (mod $interval)>, regardless of any time
		711	jumps.
162		712
		713	=item * manual reschedule mode ($reschedule_cb = coderef)
		714
		715	In this mode $interval and $at are both being ignored. Instead, each
		716	time the periodic watcher gets scheduled, the reschedule callback
		717	($reschedule_cb) will be called with the watcher as first, and the current
		718	time as second argument.
		719
		720	I<This callback MUST NOT stop or destroy this or any other periodic
		721	watcher, ever, and MUST NOT call any event loop functions or methods>. If
		722	you need to stop it, return 1e30 and stop it afterwards. You may create
		723	and start an C<EV::prepare> watcher for this task.
		724
		725	It must return the next time to trigger, based on the passed time value
		726	(that is, the lowest time value larger than or equal to to the second
		727	argument). It will usually be called just before the callback will be
		728	triggered, but might be called at other times, too.
		729
		730	This can be used to create very complex timers, such as a timer that
		731	triggers on each midnight, local time (actually one day after the last
		732	midnight, to keep the example simple):
		733
		734	my $daily = EV::periodic 0, 0, sub {
		735	my ($w, $now) = @_;
		736
		737	use Time::Local ();
		738	my (undef, undef, undef, $d, $m, $y) = localtime $now;
		739	Time::Local::timelocal_nocheck 0, 0, 0, $d + 1, $m, $y
		740	}, sub {
		741	print "it's midnight or likely shortly after, now\n";
		742	};
		743
		744	=back
		745
163	The C<timer_abs_ns> variant doesn't add/start the newly created watcher.	746	The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
164		747
		748	=item $w->set ($at, $interval, $reschedule_cb)
		749
		750	Reconfigures the watcher, see the constructor above for details. Can be called at
		751	any time.
		752
		753	=item $w->again
		754
		755	Simply stops and starts the watcher again.
		756
		757	=item $time = $w->at
		758
		759	Return the time that the watcher is expected to trigger next.
		760
		761	=item $offset = $w->offset
		762
		763	=item $old_offset = $w->offset ($new_offset)
		764
		765	Returns the current value of the offset attribute and optionally sets a
		766	new one. Setting the new one will not restart the watcher - if the watcher
		767	is active, the new offset value is used whenever it expires next.
		768
		769	=item $interval = $w->interval
		770
		771	=item $old_interval = $w->interval ($new_interval)
		772
		773	See above, for the interval attribute.
		774
		775	=item $reschedule_cb = $w->reschedule_cb
		776
		777	=item $old_reschedule_cb = $w->reschedule_cb ($new_reschedule_cb)
		778
		779	See above, for the reschedule callback.
		780
		781	=back
		782
		783
		784	=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
		785
		786	=over 4
		787
165	=item my $w = EV::signal $signum, $callback	788	=item $w = EV::signal $signal, $callback
166		789
167	=item my $w = EV::signal_ns $signum, $callback	790	=item $w = EV::signal_ns $signal, $callback
168		791
169	Call the callback when signal $signum is received.	792	=item $w = $loop->signal ($signal, $callback)
170		793
		794	=item $w = $loop->signal_ns ($signal, $callback)
		795
		796	Call the callback when $signal is received (the signal can be specified by
		797	number or by name, just as with C<kill> or C<%SIG>).
		798
		799	Only one event loop can grab a given signal - attempting to grab the same
		800	signal from two EV loops will crash the program immediately or cause data
		801	corruption.
		802
		803	EV will grab the signal for the process (the kernel only allows one
		804	component to receive a signal at a time) when you start a signal watcher,
		805	and removes it again when you stop it. Perl does the same when you
		806	add/remove callbacks to C<%SIG>, so watch out.
		807
		808	You can have as many signal watchers per signal as you want.
		809
171	The C<signal_ns> variant doesn't add/start the newly created watcher.	810	The C<signal_ns> variant doesn't start (activate) the newly created watcher.
172		811
173	=back	812	=item $w->set ($signal)
174		813
175	=head1 THE EV::Event CLASS	814	Reconfigures the watcher, see the constructor above for details. Can be
		815	called at any time.
176		816
177	All EV functions creating an event watcher (designated by C<my $w =>	817	=item $current_signum = $w->signal
178	above) support the following methods on the returned watcher object:
179		818
180	=over 4	819	=item $old_signum = $w->signal ($new_signal)
181		820
182	=item $w->add ($timeout)	821	Returns the previously set signal (always as a number not name) and
		822	optionally set a new one.
183		823
184	Stops and (re-)starts the event watcher, setting the optional timeout to	824	=back
185	the given value, or clearing the timeout if none is given.
186		825
		826
		827	=head3 CHILD WATCHERS - watch out for process status changes
		828
		829	=over 4
		830
		831	=item $w = EV::child $pid, $trace, $callback
		832
		833	=item $w = EV::child_ns $pid, $trace, $callback
		834
		835	=item $w = $loop->child ($pid, $trace, $callback)
		836
		837	=item $w = $loop->child_ns ($pid, $trace, $callback)
		838
		839	Call the callback when a status change for pid C<$pid> (or any pid
		840	if C<$pid> is 0) has been received (a status change happens when the
		841	process terminates or is killed, or, when trace is true, additionally when
		842	it is stopped or continued). More precisely: when the process receives
		843	a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
		844	changed/zombie children and call the callback.
		845
		846	It is valid (and fully supported) to install a child watcher after a child
		847	has exited but before the event loop has started its next iteration (for
		848	example, first you C<fork>, then the new child process might exit, and
		849	only then do you install a child watcher in the parent for the new pid).
		850
		851	You can access both exit (or tracing) status and pid by using the
		852	C<rstatus> and C<rpid> methods on the watcher object.
		853
		854	You can have as many pid watchers per pid as you want, they will all be
		855	called.
		856
		857	The C<child_ns> variant doesn't start (activate) the newly created watcher.
		858
		859	=item $w->set ($pid, $trace)
		860
		861	Reconfigures the watcher, see the constructor above for details. Can be called at
		862	any time.
		863
		864	=item $current_pid = $w->pid
		865
		866	Returns the previously set process id and optionally set a new one.
		867
		868	=item $exit_status = $w->rstatus
		869
		870	Return the exit/wait status (as returned by waitpid, see the waitpid entry
		871	in perlfunc).
		872
		873	=item $pid = $w->rpid
		874
		875	Return the pid of the awaited child (useful when you have installed a
		876	watcher for all pids).
		877
		878	=item EV::Child::reinit [EXPERIMENTAL]
		879
		880	Internally, libev installs a signal handler for C<SIGCHLD>. Unfortunately,
		881	a lot of Perl code does soemthing like C<< local $SIG{CHLD} >>, which,
		882	unfortunately, is broken and will not restore the signal handler.
		883
		884	If this has happened, you can call this function to stop/rrestart the
		885	internal libev watcher, which will reset the signal handler.
		886
		887	Note that this is an experimental function, whose interface might change.
		888
		889	=back
		890
		891
		892	=head3 STAT WATCHERS - did the file attributes just change?
		893
		894	=over 4
		895
		896	=item $w = EV::stat $path, $interval, $callback
		897
		898	=item $w = EV::stat_ns $path, $interval, $callback
		899
		900	=item $w = $loop->stat ($path, $interval, $callback)
		901
		902	=item $w = $loop->stat_ns ($path, $interval, $callback)
		903
		904	Call the callback when a file status change has been detected on
		905	C<$path>. The C<$path> does not need to exist, changing from "path exists"
		906	to "path does not exist" is a status change like any other.
		907
		908	The C<$interval> is a recommended polling interval for systems where
		909	OS-supported change notifications don't exist or are not supported. If
		910	you use C<0> then an unspecified default is used (which is highly
		911	recommended!), which is to be expected to be around five seconds usually.
		912
		913	This watcher type is not meant for massive numbers of stat watchers,
		914	as even with OS-supported change notifications, this can be
		915	resource-intensive.
		916
		917	The C<stat_ns> variant doesn't start (activate) the newly created watcher.
		918
187	=item $w->start	919	=item ... = $w->stat
188		920
189	Stops and (re-)starts the event watcher without touching the timeout.	921	This call is very similar to the perl C<stat> built-in: It stats (using
		922	C<lstat>) the path specified in the watcher and sets perls stat cache (as
		923	well as EV's idea of the current stat values) to the values found.
190		924
191	=item $w->del	925	In scalar context, a boolean is return indicating success or failure of
		926	the stat. In list context, the same 13-value list as with stat is returned
		927	(except that the blksize and blocks fields are not reliable).
192		928
193	=item $w->stop	929	In the case of an error, errno is set to C<ENOENT> (regardless of the
		930	actual error value) and the C<nlink> value is forced to zero (if the stat
		931	was successful then nlink is guaranteed to be non-zero).
194		932
195	Stop the event watcher if it was started.	933	See also the next two entries for more info.
196		934
197	=item $current_callback = $w->cb	935	=item ... = $w->attr
198		936
199	=item $old_callback = $w->cb ($new_callback)	937	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		938	the values most recently detected by EV. See the next entry for more info.
200		939
		940	=item ... = $w->prev
		941
		942	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		943	the previous set of values, before the change.
		944
		945	That is, when the watcher callback is invoked, C<< $w->prev >> will be set
		946	to the values found I<before> a change was detected, while C<< $w->attr >>
		947	returns the values found leading to the change detection. The difference (if any)
		948	between C<prev> and C<attr> is what triggered the callback.
		949
		950	If you did something to the filesystem object and do not want to trigger
		951	yet another change, you can call C<stat> to update EV's idea of what the
		952	current attributes are.
		953
		954	=item $w->set ($path, $interval)
		955
		956	Reconfigures the watcher, see the constructor above for details. Can be
		957	called at any time.
		958
		959	=item $current_path = $w->path
		960
		961	=item $old_path = $w->path ($new_path)
		962
201	Return the previously set callback and optionally set a new one.	963	Returns the previously set path and optionally set a new one.
202		964
203	=item $current_fh = $w->fh	965	=item $current_interval = $w->interval
204		966
205	=item $old_fh = $w->fh ($new_fh)	967	=item $old_interval = $w->interval ($new_interval)
206		968
207	Returns the previously set filehandle and optionally set a new one.
208
209	=item $current_eventmask = $w->events
210
211	=item $old_eventmask = $w->events ($new_eventmask)
212
213	Returns the previously set event mask and optionally set a new one.	969	Returns the previously set interval and optionally set a new one. Can be
		970	used to query the actual interval used.
214		971
215	=item $w->timeout ($after, $repeat)
216
217	Resets the timeout (see C<EV::timer> for details).
218
219	=item $w->timeout_abs ($at, $interval)
220
221	Resets the timeout (see C<EV::timer_abs> for details).
222
223	=item $w->priority_set ($priority)
224
225	Set the priority of the watcher to C<$priority> (0 <= $priority < $EV::NPRI).
226
227	=back	972	=back
228		973
229	=head1 BUGS
230		974
231	Lots. Libevent itself isn't well tested and rather buggy, and this module	975	=head3 IDLE WATCHERS - when you've got nothing better to do...
232	is quite new at the moment.
233		976
234	Please note that the epoll method is not, in general, reliable in programs	977	=over 4
235	that use fork (even if no libveent calls are being made in the forked
236	process). If your program behaves erratically, try setting the environment
237	variable C<EVENT_NOEPOLL> first when running the program.
238		978
239	In general, if you fork, then you can only use the EV module in one of the	979	=item $w = EV::idle $callback
240	children.	980
		981	=item $w = EV::idle_ns $callback
		982
		983	=item $w = $loop->idle ($callback)
		984
		985	=item $w = $loop->idle_ns ($callback)
		986
		987	Call the callback when there are no other pending watchers of the same or
		988	higher priority (excluding check, prepare and other idle watchers of the
		989	same or lower priority, of course). They are called idle watchers because
		990	when the watcher is the highest priority pending event in the process, the
		991	process is considered to be idle at that priority.
		992
		993	If you want a watcher that is only ever called when I<no> other events are
		994	outstanding you have to set the priority to C<EV::MINPRI>.
		995
		996	The process will not block as long as any idle watchers are active, and
		997	they will be called repeatedly until stopped.
		998
		999	For example, if you have idle watchers at priority C<0> and C<1>, and
		1000	an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
		1001	and the I/O watcher will always run when ready. Only when the idle watcher
		1002	at priority C<1> is stopped and the I/O watcher at priority C<0> is not
		1003	pending with the C<0>-priority idle watcher be invoked.
		1004
		1005	The C<idle_ns> variant doesn't start (activate) the newly created watcher.
		1006
		1007	=back
		1008
		1009
		1010	=head3 PREPARE WATCHERS - customise your event loop!
		1011
		1012	=over 4
		1013
		1014	=item $w = EV::prepare $callback
		1015
		1016	=item $w = EV::prepare_ns $callback
		1017
		1018	=item $w = $loop->prepare ($callback)
		1019
		1020	=item $w = $loop->prepare_ns ($callback)
		1021
		1022	Call the callback just before the process would block. You can still
		1023	create/modify any watchers at this point.
		1024
		1025	See the EV::check watcher, below, for explanations and an example.
		1026
		1027	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
		1028
		1029	=back
		1030
		1031
		1032	=head3 CHECK WATCHERS - customise your event loop even more!
		1033
		1034	=over 4
		1035
		1036	=item $w = EV::check $callback
		1037
		1038	=item $w = EV::check_ns $callback
		1039
		1040	=item $w = $loop->check ($callback)
		1041
		1042	=item $w = $loop->check_ns ($callback)
		1043
		1044	Call the callback just after the process wakes up again (after it has
		1045	gathered events), but before any other callbacks have been invoked.
		1046
		1047	This can be used to integrate other event-based software into the EV
		1048	mainloop: You register a prepare callback and in there, you create io and
		1049	timer watchers as required by the other software. Here is a real-world
		1050	example of integrating Net::SNMP (with some details left out):
		1051
		1052	our @snmp_watcher;
		1053
		1054	our $snmp_prepare = EV::prepare sub {
		1055	# do nothing unless active
		1056	$dispatcher->{_event_queue_h}
		1057	or return;
		1058
		1059	# make the dispatcher handle any outstanding stuff
		1060	... not shown
		1061
		1062	# create an I/O watcher for each and every socket
		1063	@snmp_watcher = (
		1064	(map { EV::io $_, EV::READ, sub { } }
		1065	keys %{ $dispatcher->{_descriptors} }),
		1066
		1067	EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
		1068	? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
		1069	0, sub { },
		1070	);
		1071	};
		1072
		1073	The callbacks are irrelevant (and are not even being called), the
		1074	only purpose of those watchers is to wake up the process as soon as
		1075	one of those events occurs (socket readable, or timer timed out). The
		1076	corresponding EV::check watcher will then clean up:
		1077
		1078	our $snmp_check = EV::check sub {
		1079	# destroy all watchers
		1080	@snmp_watcher = ();
		1081
		1082	# make the dispatcher handle any new stuff
		1083	... not shown
		1084	};
		1085
		1086	The callbacks of the created watchers will not be called as the watchers
		1087	are destroyed before this can happen (remember EV::check gets called
		1088	first).
		1089
		1090	The C<check_ns> variant doesn't start (activate) the newly created watcher.
		1091
		1092	=item EV::CHECK constant issues
		1093
		1094	Like all other watcher types, there is a bitmask constant for use in
		1095	C<$revents> and other places. The C<EV::CHECK> is special as it has
		1096	the same name as the C<CHECK> sub called by Perl. This doesn't cause
		1097	big issues on newer perls (beginning with 5.8.9), but it means thatthe
		1098	constant must be I<inlined>, i.e. runtime calls will not work. That means
		1099	that as long as you always C<use EV> and then C<EV::CHECK> you are on the
		1100	safe side.
		1101
		1102	=back
		1103
		1104
		1105	=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
		1106
		1107	Fork watchers are called when a C<fork ()> was detected. The invocation
		1108	is done before the event loop blocks next and before C<check> watchers
		1109	are being called, and only in the child after the fork.
		1110
		1111	=over 4
		1112
		1113	=item $w = EV::fork $callback
		1114
		1115	=item $w = EV::fork_ns $callback
		1116
		1117	=item $w = $loop->fork ($callback)
		1118
		1119	=item $w = $loop->fork_ns ($callback)
		1120
		1121	Call the callback before the event loop is resumed in the child process
		1122	after a fork.
		1123
		1124	The C<fork_ns> variant doesn't start (activate) the newly created watcher.
		1125
		1126	=back
		1127
		1128
		1129	=head3 EMBED WATCHERS - when one backend isn't enough...
		1130
		1131	This is a rather advanced watcher type that lets you embed one event loop
		1132	into another (currently only IO events are supported in the embedded
		1133	loop, other types of watchers might be handled in a delayed or incorrect
		1134	fashion and must not be used).
		1135
		1136	See the libev documentation at
		1137	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code_when_one_backend_>
		1138	(locally installed as F<EV::libev>) for more details.
		1139
		1140	In short, this watcher is most useful on BSD systems without working
		1141	kqueue to still be able to handle a large number of sockets:
		1142
		1143	my $socket_loop;
		1144
		1145	# check wether we use SELECT or POLL _and_ KQUEUE is supported
		1146	if (
		1147	(EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
		1148	&& (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
		1149	) {
		1150	# use kqueue for sockets
		1151	$socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
		1152	}
		1153
		1154	# use the default loop otherwise
		1155	$socket_loop ||= EV::default_loop;
		1156
		1157	=over 4
		1158
		1159	=item $w = EV::embed $otherloop[, $callback]
		1160
		1161	=item $w = EV::embed_ns $otherloop[, $callback]
		1162
		1163	=item $w = $loop->embed ($otherloop[, $callback])
		1164
		1165	=item $w = $loop->embed_ns ($otherloop[, $callback])
		1166
		1167	Call the callback when the embedded event loop (C<$otherloop>) has any
		1168	I/O activity. The C<$callback> is optional: if it is missing, then the
		1169	embedded event loop will be managed automatically (which is recommended),
		1170	otherwise you have to invoke C<sweep> yourself.
		1171
		1172	The C<embed_ns> variant doesn't start (activate) the newly created watcher.
		1173
		1174	=back
		1175
		1176	=head3 ASYNC WATCHERS - how to wake up another event loop
		1177
		1178	Async watchers are provided by EV, but have little use in perl directly,
		1179	as perl neither supports threads running in parallel nor direct access to
		1180	signal handlers or other contexts where they could be of value.
		1181
		1182	It is, however, possible to use them from the XS level.
		1183
		1184	Please see the libev documentation for further details.
		1185
		1186	=over 4
		1187
		1188	=item $w = EV::async $callback
		1189
		1190	=item $w = EV::async_ns $callback
		1191
		1192	=item $w = $loop->async ($callback)
		1193
		1194	=item $w = $loop->async_ns ($callback)
		1195
		1196	=item $w->send
		1197
		1198	=item $bool = $w->async_pending
		1199
		1200	=back
		1201
		1202	=head3 CLEANUP WATCHERS - how to clean up when the event loop goes away
		1203
		1204	Cleanup watchers are not supported on the Perl level, they can only be
		1205	used via XS currently.
		1206
		1207
		1208	=head1 PERL SIGNALS
		1209
		1210	While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
		1211	with EV is as the same as any other C library: Perl-signals will only be
		1212	handled when Perl runs, which means your signal handler might be invoked
		1213	only the next time an event callback is invoked.
		1214
		1215	The solution is to use EV signal watchers (see C<EV::signal>), which will
		1216	ensure proper operations with regards to other event watchers.
		1217
		1218	If you cannot do this for whatever reason, you can also force a watcher
		1219	to be called on every event loop iteration by installing a C<EV::check>
		1220	watcher:
		1221
		1222	my $async_check = EV::check sub { };
		1223
		1224	This ensures that perl gets into control for a short time to handle any
		1225	pending signals, and also ensures (slightly) slower overall operation.
		1226
		1227	=head1 ITHREADS
		1228
		1229	Ithreads are not supported by this module in any way. Perl pseudo-threads
		1230	is evil stuff and must die. Real threads as provided by Coro are fully
		1231	supported (and enhanced support is available via L<Coro::EV>).
		1232
		1233	=head1 FORK
		1234
		1235	Most of the "improved" event delivering mechanisms of modern operating
		1236	systems have quite a few problems with fork(2) (to put it bluntly: it is
		1237	not supported and usually destructive). Libev makes it possible to work
		1238	around this by having a function that recreates the kernel state after
		1239	fork in the child.
		1240
		1241	On non-win32 platforms, this module requires the pthread_atfork
		1242	functionality to do this automatically for you. This function is quite
		1243	buggy on most BSDs, though, so YMMV. The overhead for this is quite
		1244	negligible, because everything the function currently does is set a flag
		1245	that is checked only when the event loop gets used the next time, so when
		1246	you do fork but not use EV, the overhead is minimal.
		1247
		1248	On win32, there is no notion of fork so all this doesn't apply, of course.
241		1249
242	=cut	1250	=cut
243		1251
244	our $DIED = sub {	1252	our $DIED = sub {
245	warn "EV: error in callback (ignoring): $@";	1253	warn "EV: error in callback (ignoring): $@";
246	};	1254	};
247		1255
248	our $NPRI = 4;	1256	default_loop
249	our $BASE = init;	1257	or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?';
250	priority_init $NPRI;
251
252	push @AnyEvent::REGISTRY, [EV => "EV::AnyEvent"];
253		1258
254	1;	1259	1;
255		1260
256	=head1 SEE ALSO	1261	=head1 SEE ALSO
257		1262
258	L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>.	1263	L<EV::MakeMaker> - MakeMaker interface to XS API, L<EV::ADNS>
259	L<EV::AnyEvent>.	1264	(asynchronous DNS), L<Glib::EV> (makes Glib/Gtk2 use EV as event
		1265	loop), L<EV::Glib> (embed Glib into EV), L<Coro::EV> (efficient thread
		1266	integration), L<Net::SNMP::EV> (asynchronous SNMP), L<AnyEvent> for
		1267	event-loop agnostic and portable event driven programming.
260		1268
261	=head1 AUTHOR	1269	=head1 AUTHOR
262		1270
263	Marc Lehmann <schmorp@schmorp.de>	1271	Marc Lehmann <schmorp@schmorp.de>
264	http://home.schmorp.de/	1272	http://home.schmorp.de/
265		1273
266	=cut	1274	=cut
267		1275

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