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Revision 1.19 by root, Sun Dec 10 23:59:15 2006 UTC vs.
Revision 1.333 by root, Tue Oct 12 06:47:54 2010 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	Event, Coro, Glib, Tk, Perl - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores wether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	There is a mailinglist for discussing all things AnyEvent, and an IRC
		52	channel, too.
		53
		54	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		55	Repository>, at L<http://anyevent.schmorp.de>, for more info.
		56
		57	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		58
		59	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		60	nowadays. So what is different about AnyEvent?
		61
		62	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		63	policy> and AnyEvent is I<small and efficient>.
		64
		65	First and foremost, I<AnyEvent is not an event model> itself, it only
		66	interfaces to whatever event model the main program happens to use, in a
		67	pragmatic way. For event models and certain classes of immortals alike,
		68	the statement "there can only be one" is a bitter reality: In general,
		69	only one event loop can be active at the same time in a process. AnyEvent
		70	cannot change this, but it can hide the differences between those event
		71	loops.
		72
		73	The goal of AnyEvent is to offer module authors the ability to do event
		74	programming (waiting for I/O or timer events) without subscribing to a
		75	religion, a way of living, and most importantly: without forcing your
		76	module users into the same thing by forcing them to use the same event
		77	model you use.
		78
		79	For modules like POE or IO::Async (which is a total misnomer as it is
		80	actually doing all I/O I<synchronously>...), using them in your module is
		81	like joining a cult: After you join, you are dependent on them and you
		82	cannot use anything else, as they are simply incompatible to everything
		83	that isn't them. What's worse, all the potential users of your
		84	module are I<also> forced to use the same event loop you use.
		85
		86	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		87	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		88	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
		89	your module uses one of those, every user of your module has to use it,
		90	too. But if your module uses AnyEvent, it works transparently with all
		91	event models it supports (including stuff like IO::Async, as long as those
		92	use one of the supported event loops. It is easy to add new event loops
		93	to AnyEvent, too, so it is future-proof).
		94
		95	In addition to being free of having to use I<the one and only true event
		96	model>, AnyEvent also is free of bloat and policy: with POE or similar
		97	modules, you get an enormous amount of code and strict rules you have to
		98	follow. AnyEvent, on the other hand, is lean and to the point, by only
		99	offering the functionality that is necessary, in as thin as a wrapper as
		100	technically possible.
		101
		102	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		103	of useful functionality, such as an asynchronous DNS resolver, 100%
		104	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		105	such as Windows) and lots of real-world knowledge and workarounds for
		106	platform bugs and differences.
		107
		108	Now, if you I<do want> lots of policy (this can arguably be somewhat
		109	useful) and you want to force your users to use the one and only event
		110	model, you should I<not> use this module.
22		111
23	=head1 DESCRIPTION	112	=head1 DESCRIPTION
24		113
25	L<AnyEvent> provides an identical interface to multiple event loops. This	114	L<AnyEvent> provides a uniform interface to various event loops. This
26	allows module authors to utilise an event loop without forcing module	115	allows module authors to use event loop functionality without forcing
27	users to use the same event loop (as only a single event loop can coexist	116	module users to use a specific event loop implementation (since more
28	peacefully at any one time).	117	than one event loop cannot coexist peacefully).
29		118
30	The interface itself is vaguely similar but not identical to the Event	119	The interface itself is vaguely similar, but not identical to the L<Event>
31	module.	120	module.
32		121
33	On the first call of any method, the module tries to detect the currently	122	During the first call of any watcher-creation method, the module tries
34	loaded event loop by probing wether any of the following modules is	123	to detect the currently loaded event loop by probing whether one of the
35	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	124	following modules is already loaded: L<EV>, L<AnyEvent::Impl::Perl>,
36	used. If none is found, the module tries to load these modules in the	125	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
37	order given. The first one that could be successfully loaded will be	126	found is used. If none are detected, the module tries to load the first
38	used. If still none could be found, AnyEvent will fall back to a pure-perl	127	four modules in the order given; but note that if L<EV> is not
39	event loop, which is also not very efficient.	128	available, the pure-perl L<AnyEvent::Impl::Perl> should always work, so
		129	the other two are not normally tried.
40		130
41	Because AnyEvent first checks for modules that are already loaded, loading	131	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	132	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	133	that model the default. For example:
44		134
45	use Tk;	135	use Tk;
46	use AnyEvent;	136	use AnyEvent;
47		137
48	# .. AnyEvent will likely default to Tk	138	# .. AnyEvent will likely default to Tk
49		139
		140	The I<likely> means that, if any module loads another event model and
		141	starts using it, all bets are off - this case should be very rare though,
		142	as very few modules hardcode event loops without announcing this very
		143	loudly.
		144
50	The pure-perl implementation of AnyEvent is called	145	The pure-perl implementation of AnyEvent is called
51	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	146	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52	explicitly.	147	explicitly and enjoy the high availability of that event loop :)
53		148
54	=head1 WATCHERS	149	=head1 WATCHERS
55		150
56	AnyEvent has the central concept of a I<watcher>, which is an object that	151	AnyEvent has the central concept of a I<watcher>, which is an object that
57	stores relevant data for each kind of event you are waiting for, such as	152	stores relevant data for each kind of event you are waiting for, such as
58	the callback to call, the filehandle to watch, etc.	153	the callback to call, the file handle to watch, etc.
59		154
60	These watchers are normal Perl objects with normal Perl lifetime. After	155	These watchers are normal Perl objects with normal Perl lifetime. After
61	creating a watcher it will immediately "watch" for events and invoke	156	creating a watcher it will immediately "watch" for events and invoke the
		157	callback when the event occurs (of course, only when the event model
		158	is in control).
		159
		160	Note that B<callbacks must not permanently change global variables>
		161	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		162	callbacks must not C<die> >>. The former is good programming practice in
		163	Perl and the latter stems from the fact that exception handling differs
		164	widely between event loops.
		165
62	the callback. To disable the watcher you have to destroy it (e.g. by	166	To disable a watcher you have to destroy it (e.g. by setting the
63	setting the variable that stores it to C<undef> or otherwise deleting all	167	variable you store it in to C<undef> or otherwise deleting all references
64	references to it).	168	to it).
65		169
66	All watchers are created by calling a method on the C<AnyEvent> class.	170	All watchers are created by calling a method on the C<AnyEvent> class.
67		171
		172	Many watchers either are used with "recursion" (repeating timers for
		173	example), or need to refer to their watcher object in other ways.
		174
		175	One way to achieve that is this pattern:
		176
		177	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		178	# you can use $w here, for example to undef it
		179	undef $w;
		180	});
		181
		182	Note that C<my $w; $w => combination. This is necessary because in Perl,
		183	my variables are only visible after the statement in which they are
		184	declared.
		185
68	=head2 IO WATCHERS	186	=head2 I/O WATCHERS
69		187
		188	$w = AnyEvent->io (
		189	fh => <filehandle_or_fileno>,
		190	poll => <"r" or "w">,
		191	cb => <callback>,
		192	);
		193
70	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	194	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71	the following mandatory arguments:	195	with the following mandatory key-value pairs as arguments:
72		196
73	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	197	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		198	for events (AnyEvent might or might not keep a reference to this file
		199	handle). Note that only file handles pointing to things for which
		200	non-blocking operation makes sense are allowed. This includes sockets,
		201	most character devices, pipes, fifos and so on, but not for example files
		202	or block devices.
		203
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	204	C<poll> must be a string that is either C<r> or C<w>, which creates a
75	a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback	205	watcher waiting for "r"eadable or "w"ritable events, respectively.
76	to invoke everytime the filehandle becomes ready.
77		206
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	207	C<cb> is the callback to invoke each time the file handle becomes ready.
79	a socket you can have one r + one w, not any more (limitation comes from
80	Tk - if you are sure you are not using Tk this limitation is gone).
81		208
82	Filehandles will be kept alive, so as long as the watcher exists, the	209	Although the callback might get passed parameters, their value and
83	filehandle exists, too.	210	presence is undefined and you cannot rely on them. Portable AnyEvent
		211	callbacks cannot use arguments passed to I/O watcher callbacks.
84		212
85	Example:	213	The I/O watcher might use the underlying file descriptor or a copy of it.
		214	You must not close a file handle as long as any watcher is active on the
		215	underlying file descriptor.
86		216
		217	Some event loops issue spurious readiness notifications, so you should
		218	always use non-blocking calls when reading/writing from/to your file
		219	handles.
		220
87	# wait for readability of STDIN, then read a line and disable the watcher	221	Example: wait for readability of STDIN, then read a line and disable the
		222	watcher.
		223
88	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	224	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89	chomp (my $input = <STDIN>);	225	chomp (my $input = <STDIN>);
90	warn "read: $input\n";	226	warn "read: $input\n";
91	undef $w;	227	undef $w;
92	});	228	});
93		229
94	=head2 TIME WATCHERS	230	=head2 TIME WATCHERS
95		231
		232	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		233
		234	$w = AnyEvent->timer (
		235	after => <fractional_seconds>,
		236	interval => <fractional_seconds>,
		237	cb => <callback>,
		238	);
		239
96	You can create a time watcher by calling the C<< AnyEvent->timer >>	240	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	241	method with the following mandatory arguments:
98		242
99	C<after> after how many seconds (fractions are supported) should the timer	243	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	244	supported) the callback should be invoked. C<cb> is the callback to invoke
		245	in that case.
101		246
102	The timer callback will be invoked at most once: if you want a repeating	247	Although the callback might get passed parameters, their value and
103	timer you have to create a new watcher (this is a limitation by both Tk	248	presence is undefined and you cannot rely on them. Portable AnyEvent
104	and Glib).	249	callbacks cannot use arguments passed to time watcher callbacks.
105		250
106	Example:	251	The callback will normally be invoked only once. If you specify another
		252	parameter, C<interval>, as a strictly positive number (> 0), then the
		253	callback will be invoked regularly at that interval (in fractional
		254	seconds) after the first invocation. If C<interval> is specified with a
		255	false value, then it is treated as if it were not specified at all.
107		256
		257	The callback will be rescheduled before invoking the callback, but no
		258	attempt is made to avoid timer drift in most backends, so the interval is
		259	only approximate.
		260
108	# fire an event after 7.7 seconds	261	Example: fire an event after 7.7 seconds.
		262
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	263	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	264	warn "timeout\n";
111	});	265	});
112		266
113	# to cancel the timer:	267	# to cancel the timer:
114	undef $w	268	undef $w;
115		269
116	=head2 CONDITION WATCHERS	270	Example 2: fire an event after 0.5 seconds, then roughly every second.
117		271
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	272	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
119	method without any arguments.	273	warn "timeout\n";
		274	};
120		275
121	A condition watcher watches for a condition - precisely that the C<<	276	=head3 TIMING ISSUES
122	->broadcast >> method has been called.
123		277
124	The watcher has only two methods:	278	There are two ways to handle timers: based on real time (relative, "fire
		279	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		280	o'clock").
		281
		282	While most event loops expect timers to specified in a relative way, they
		283	use absolute time internally. This makes a difference when your clock
		284	"jumps", for example, when ntp decides to set your clock backwards from
		285	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		286	fire "after a second" might actually take six years to finally fire.
		287
		288	AnyEvent cannot compensate for this. The only event loop that is conscious
		289	of these issues is L<EV>, which offers both relative (ev_timer, based
		290	on true relative time) and absolute (ev_periodic, based on wallclock time)
		291	timers.
		292
		293	AnyEvent always prefers relative timers, if available, matching the
		294	AnyEvent API.
		295
		296	AnyEvent has two additional methods that return the "current time":
125		297
126	=over 4	298	=over 4
127		299
128	=item $cv->wait	300	=item AnyEvent->time
129		301
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	302	This returns the "current wallclock time" as a fractional number of
131	called on c<$cv>, while servicing other watchers normally.	303	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		304	return, and the result is guaranteed to be compatible with those).
132		305
133	Not all event models support a blocking wait - some die in that case, so	306	It progresses independently of any event loop processing, i.e. each call
134	if you are using this from a module, never require a blocking wait, but	307	will check the system clock, which usually gets updated frequently.
135	let the caller decide wether the call will block or not (for example,
136	by coupling condition variables with some kind of request results and
137	supporting callbacks so the caller knows that getting the result will not
138	block, while still suppporting blockign waits if the caller so desires).
139		308
140	You can only wait once on a condition - additional calls will return	309	=item AnyEvent->now
141	immediately.
142		310
143	=item $cv->broadcast	311	This also returns the "current wallclock time", but unlike C<time>, above,
		312	this value might change only once per event loop iteration, depending on
		313	the event loop (most return the same time as C<time>, above). This is the
		314	time that AnyEvent's timers get scheduled against.
144		315
145	Flag the condition as ready - a running C<< ->wait >> and all further	316	I<In almost all cases (in all cases if you don't care), this is the
146	calls to C<wait> will return after this method has been called. If nobody	317	function to call when you want to know the current time.>
147	is waiting the broadcast will be remembered..
148		318
149	Example:	319	This function is also often faster then C<< AnyEvent->time >>, and
		320	thus the preferred method if you want some timestamp (for example,
		321	L<AnyEvent::Handle> uses this to update its activity timeouts).
150		322
151	# wait till the result is ready	323	The rest of this section is only of relevance if you try to be very exact
152	my $result_ready = AnyEvent->condvar;	324	with your timing; you can skip it without a bad conscience.
153		325
154	# do something such as adding a timer	326	For a practical example of when these times differ, consider L<Event::Lib>
155	# or socket watcher the calls $result_ready->broadcast	327	and L<EV> and the following set-up:
156	# when the "result" is ready.
157		328
158	$result_ready->wait;	329	The event loop is running and has just invoked one of your callbacks at
		330	time=500 (assume no other callbacks delay processing). In your callback,
		331	you wait a second by executing C<sleep 1> (blocking the process for a
		332	second) and then (at time=501) you create a relative timer that fires
		333	after three seconds.
		334
		335	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		336	both return C<501>, because that is the current time, and the timer will
		337	be scheduled to fire at time=504 (C<501> + C<3>).
		338
		339	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		340	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		341	last event processing phase started. With L<EV>, your timer gets scheduled
		342	to run at time=503 (C<500> + C<3>).
		343
		344	In one sense, L<Event::Lib> is more exact, as it uses the current time
		345	regardless of any delays introduced by event processing. However, most
		346	callbacks do not expect large delays in processing, so this causes a
		347	higher drift (and a lot more system calls to get the current time).
		348
		349	In another sense, L<EV> is more exact, as your timer will be scheduled at
		350	the same time, regardless of how long event processing actually took.
		351
		352	In either case, if you care (and in most cases, you don't), then you
		353	can get whatever behaviour you want with any event loop, by taking the
		354	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		355	account.
		356
		357	=item AnyEvent->now_update
		358
		359	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		360	the current time for each loop iteration (see the discussion of L<<
		361	AnyEvent->now >>, above).
		362
		363	When a callback runs for a long time (or when the process sleeps), then
		364	this "current" time will differ substantially from the real time, which
		365	might affect timers and time-outs.
		366
		367	When this is the case, you can call this method, which will update the
		368	event loop's idea of "current time".
		369
		370	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		371	when mod_perl executes the script, then the event loop will have the wrong
		372	idea about the "current time" (being potentially far in the past, when the
		373	script ran the last time). In that case you should arrange a call to C<<
		374	AnyEvent->now_update >> each time the web server process wakes up again
		375	(e.g. at the start of your script, or in a handler).
		376
		377	Note that updating the time I<might> cause some events to be handled.
159		378
160	=back	379	=back
161		380
162	=head2 SIGNAL WATCHERS	381	=head2 SIGNAL WATCHERS
163		382
		383	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		384
164	You can listen for signals using a signal watcher, C<signal> is the signal	385	You can watch for signals using a signal watcher, C<signal> is the signal
165	I<name> without any C<SIG> prefix.	386	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
		387	callback to be invoked whenever a signal occurs.
166		388
167	These watchers might use C<%SIG>, so programs overwriting those signals	389	Although the callback might get passed parameters, their value and
168	directly will likely not work correctly.	390	presence is undefined and you cannot rely on them. Portable AnyEvent
		391	callbacks cannot use arguments passed to signal watcher callbacks.
		392
		393	Multiple signal occurrences can be clumped together into one callback
		394	invocation, and callback invocation will be synchronous. Synchronous means
		395	that it might take a while until the signal gets handled by the process,
		396	but it is guaranteed not to interrupt any other callbacks.
		397
		398	The main advantage of using these watchers is that you can share a signal
		399	between multiple watchers, and AnyEvent will ensure that signals will not
		400	interrupt your program at bad times.
		401
		402	This watcher might use C<%SIG> (depending on the event loop used),
		403	so programs overwriting those signals directly will likely not work
		404	correctly.
169		405
170	Example: exit on SIGINT	406	Example: exit on SIGINT
171		407
172	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	408	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
173		409
174	=head1 GLOBALS	410	=head3 Restart Behaviour
		411
		412	While restart behaviour is up to the event loop implementation, most will
		413	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		414	pure perl implementation).
		415
		416	=head3 Safe/Unsafe Signals
		417
		418	Perl signals can be either "safe" (synchronous to opcode handling) or
		419	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		420	latter might corrupt your memory.
		421
		422	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		423	i.e. they will not interrupt your running perl program but will only be
		424	called as part of the normal event handling (just like timer, I/O etc.
		425	callbacks, too).
		426
		427	=head3 Signal Races, Delays and Workarounds
		428
		429	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		430	callbacks to signals in a generic way, which is a pity, as you cannot
		431	do race-free signal handling in perl, requiring C libraries for
		432	this. AnyEvent will try to do its best, which means in some cases,
		433	signals will be delayed. The maximum time a signal might be delayed is
		434	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		435	variable can be changed only before the first signal watcher is created,
		436	and should be left alone otherwise. This variable determines how often
		437	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		438	will cause fewer spurious wake-ups, which is better for power and CPU
		439	saving.
		440
		441	All these problems can be avoided by installing the optional
		442	L<Async::Interrupt> module, which works with most event loops. It will not
		443	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		444	(and not with L<POE> currently, as POE does its own workaround with
		445	one-second latency). For those, you just have to suffer the delays.
		446
		447	=head2 CHILD PROCESS WATCHERS
		448
		449	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		450
		451	You can also watch for a child process exit and catch its exit status.
		452
		453	The child process is specified by the C<pid> argument (on some backends,
		454	using C<0> watches for any child process exit, on others this will
		455	croak). The watcher will be triggered only when the child process has
		456	finished and an exit status is available, not on any trace events
		457	(stopped/continued).
		458
		459	The callback will be called with the pid and exit status (as returned by
		460	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		461	callback arguments.
		462
		463	This watcher type works by installing a signal handler for C<SIGCHLD>,
		464	and since it cannot be shared, nothing else should use SIGCHLD or reap
		465	random child processes (waiting for specific child processes, e.g. inside
		466	C<system>, is just fine).
		467
		468	There is a slight catch to child watchers, however: you usually start them
		469	I<after> the child process was created, and this means the process could
		470	have exited already (and no SIGCHLD will be sent anymore).
		471
		472	Not all event models handle this correctly (neither POE nor IO::Async do,
		473	see their AnyEvent::Impl manpages for details), but even for event models
		474	that I<do> handle this correctly, they usually need to be loaded before
		475	the process exits (i.e. before you fork in the first place). AnyEvent's
		476	pure perl event loop handles all cases correctly regardless of when you
		477	start the watcher.
		478
		479	This means you cannot create a child watcher as the very first
		480	thing in an AnyEvent program, you I<have> to create at least one
		481	watcher before you C<fork> the child (alternatively, you can call
		482	C<AnyEvent::detect>).
		483
		484	As most event loops do not support waiting for child events, they will be
		485	emulated by AnyEvent in most cases, in which the latency and race problems
		486	mentioned in the description of signal watchers apply.
		487
		488	Example: fork a process and wait for it
		489
		490	my $done = AnyEvent->condvar;
		491
		492	my $pid = fork or exit 5;
		493
		494	my $w = AnyEvent->child (
		495	pid => $pid,
		496	cb => sub {
		497	my ($pid, $status) = @_;
		498	warn "pid $pid exited with status $status";
		499	$done->send;
		500	},
		501	);
		502
		503	# do something else, then wait for process exit
		504	$done->recv;
		505
		506	=head2 IDLE WATCHERS
		507
		508	$w = AnyEvent->idle (cb => <callback>);
		509
		510	This will repeatedly invoke the callback after the process becomes idle,
		511	until either the watcher is destroyed or new events have been detected.
		512
		513	Idle watchers are useful when there is a need to do something, but it
		514	is not so important (or wise) to do it instantly. The callback will be
		515	invoked only when there is "nothing better to do", which is usually
		516	defined as "all outstanding events have been handled and no new events
		517	have been detected". That means that idle watchers ideally get invoked
		518	when the event loop has just polled for new events but none have been
		519	detected. Instead of blocking to wait for more events, the idle watchers
		520	will be invoked.
		521
		522	Unfortunately, most event loops do not really support idle watchers (only
		523	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		524	will simply call the callback "from time to time".
		525
		526	Example: read lines from STDIN, but only process them when the
		527	program is otherwise idle:
		528
		529	my @lines; # read data
		530	my $idle_w;
		531	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		532	push @lines, scalar <STDIN>;
		533
		534	# start an idle watcher, if not already done
		535	$idle_w ||= AnyEvent->idle (cb => sub {
		536	# handle only one line, when there are lines left
		537	if (my $line = shift @lines) {
		538	print "handled when idle: $line";
		539	} else {
		540	# otherwise disable the idle watcher again
		541	undef $idle_w;
		542	}
		543	});
		544	});
		545
		546	=head2 CONDITION VARIABLES
		547
		548	$cv = AnyEvent->condvar;
		549
		550	$cv->send (<list>);
		551	my @res = $cv->recv;
		552
		553	If you are familiar with some event loops you will know that all of them
		554	require you to run some blocking "loop", "run" or similar function that
		555	will actively watch for new events and call your callbacks.
		556
		557	AnyEvent is slightly different: it expects somebody else to run the event
		558	loop and will only block when necessary (usually when told by the user).
		559
		560	The tool to do that is called a "condition variable", so called because
		561	they represent a condition that must become true.
		562
		563	Now is probably a good time to look at the examples further below.
		564
		565	Condition variables can be created by calling the C<< AnyEvent->condvar
		566	>> method, usually without arguments. The only argument pair allowed is
		567	C<cb>, which specifies a callback to be called when the condition variable
		568	becomes true, with the condition variable as the first argument (but not
		569	the results).
		570
		571	After creation, the condition variable is "false" until it becomes "true"
		572	by calling the C<send> method (or calling the condition variable as if it
		573	were a callback, read about the caveats in the description for the C<<
		574	->send >> method).
		575
		576	Since condition variables are the most complex part of the AnyEvent API, here are
		577	some different mental models of what they are - pick the ones you can connect to:
175		578
176	=over 4	579	=over 4
177		580
		581	=item * Condition variables are like callbacks - you can call them (and pass them instead
		582	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		583
		584	=item * Condition variables are signals - one side can emit or send them,
		585	the other side can wait for them, or install a handler that is called when
		586	the signal fires.
		587
		588	=item * Condition variables are like "Merge Points" - points in your program
		589	where you merge multiple independent results/control flows into one.
		590
		591	=item * Condition variables represent a transaction - functions that start
		592	some kind of transaction can return them, leaving the caller the choice
		593	between waiting in a blocking fashion, or setting a callback.
		594
		595	=item * Condition variables represent future values, or promises to deliver
		596	some result, long before the result is available.
		597
		598	=back
		599
		600	Condition variables are very useful to signal that something has finished,
		601	for example, if you write a module that does asynchronous http requests,
		602	then a condition variable would be the ideal candidate to signal the
		603	availability of results. The user can either act when the callback is
		604	called or can synchronously C<< ->recv >> for the results.
		605
		606	You can also use them to simulate traditional event loops - for example,
		607	you can block your main program until an event occurs - for example, you
		608	could C<< ->recv >> in your main program until the user clicks the Quit
		609	button of your app, which would C<< ->send >> the "quit" event.
		610
		611	Note that condition variables recurse into the event loop - if you have
		612	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		613	lose. Therefore, condition variables are good to export to your caller, but
		614	you should avoid making a blocking wait yourself, at least in callbacks,
		615	as this asks for trouble.
		616
		617	Condition variables are represented by hash refs in perl, and the keys
		618	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		619	easy (it is often useful to build your own transaction class on top of
		620	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		621	its C<new> method in your own C<new> method.
		622
		623	There are two "sides" to a condition variable - the "producer side" which
		624	eventually calls C<< -> send >>, and the "consumer side", which waits
		625	for the send to occur.
		626
		627	Example: wait for a timer.
		628
		629	# condition: "wait till the timer is fired"
		630	my $timer_fired = AnyEvent->condvar;
		631
		632	# create the timer - we could wait for, say
		633	# a handle becomign ready, or even an
		634	# AnyEvent::HTTP request to finish, but
		635	# in this case, we simply use a timer:
		636	my $w = AnyEvent->timer (
		637	after => 1,
		638	cb => sub { $timer_fired->send },
		639	);
		640
		641	# this "blocks" (while handling events) till the callback
		642	# calls ->send
		643	$timer_fired->recv;
		644
		645	Example: wait for a timer, but take advantage of the fact that condition
		646	variables are also callable directly.
		647
		648	my $done = AnyEvent->condvar;
		649	my $delay = AnyEvent->timer (after => 5, cb => $done);
		650	$done->recv;
		651
		652	Example: Imagine an API that returns a condvar and doesn't support
		653	callbacks. This is how you make a synchronous call, for example from
		654	the main program:
		655
		656	use AnyEvent::CouchDB;
		657
		658	...
		659
		660	my @info = $couchdb->info->recv;
		661
		662	And this is how you would just set a callback to be called whenever the
		663	results are available:
		664
		665	$couchdb->info->cb (sub {
		666	my @info = $_[0]->recv;
		667	});
		668
		669	=head3 METHODS FOR PRODUCERS
		670
		671	These methods should only be used by the producing side, i.e. the
		672	code/module that eventually sends the signal. Note that it is also
		673	the producer side which creates the condvar in most cases, but it isn't
		674	uncommon for the consumer to create it as well.
		675
		676	=over 4
		677
		678	=item $cv->send (...)
		679
		680	Flag the condition as ready - a running C<< ->recv >> and all further
		681	calls to C<recv> will (eventually) return after this method has been
		682	called. If nobody is waiting the send will be remembered.
		683
		684	If a callback has been set on the condition variable, it is called
		685	immediately from within send.
		686
		687	Any arguments passed to the C<send> call will be returned by all
		688	future C<< ->recv >> calls.
		689
		690	Condition variables are overloaded so one can call them directly (as if
		691	they were a code reference). Calling them directly is the same as calling
		692	C<send>.
		693
		694	=item $cv->croak ($error)
		695
		696	Similar to send, but causes all calls to C<< ->recv >> to invoke
		697	C<Carp::croak> with the given error message/object/scalar.
		698
		699	This can be used to signal any errors to the condition variable
		700	user/consumer. Doing it this way instead of calling C<croak> directly
		701	delays the error detection, but has the overwhelming advantage that it
		702	diagnoses the error at the place where the result is expected, and not
		703	deep in some event callback with no connection to the actual code causing
		704	the problem.
		705
		706	=item $cv->begin ([group callback])
		707
		708	=item $cv->end
		709
		710	These two methods can be used to combine many transactions/events into
		711	one. For example, a function that pings many hosts in parallel might want
		712	to use a condition variable for the whole process.
		713
		714	Every call to C<< ->begin >> will increment a counter, and every call to
		715	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		716	>>, the (last) callback passed to C<begin> will be executed, passing the
		717	condvar as first argument. That callback is I<supposed> to call C<< ->send
		718	>>, but that is not required. If no group callback was set, C<send> will
		719	be called without any arguments.
		720
		721	You can think of C<< $cv->send >> giving you an OR condition (one call
		722	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		723	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		724
		725	Let's start with a simple example: you have two I/O watchers (for example,
		726	STDOUT and STDERR for a program), and you want to wait for both streams to
		727	close before activating a condvar:
		728
		729	my $cv = AnyEvent->condvar;
		730
		731	$cv->begin; # first watcher
		732	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		733	defined sysread $fh1, my $buf, 4096
		734	or $cv->end;
		735	});
		736
		737	$cv->begin; # second watcher
		738	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		739	defined sysread $fh2, my $buf, 4096
		740	or $cv->end;
		741	});
		742
		743	$cv->recv;
		744
		745	This works because for every event source (EOF on file handle), there is
		746	one call to C<begin>, so the condvar waits for all calls to C<end> before
		747	sending.
		748
		749	The ping example mentioned above is slightly more complicated, as the
		750	there are results to be passwd back, and the number of tasks that are
		751	begun can potentially be zero:
		752
		753	my $cv = AnyEvent->condvar;
		754
		755	my %result;
		756	$cv->begin (sub { shift->send (\%result) });
		757
		758	for my $host (@list_of_hosts) {
		759	$cv->begin;
		760	ping_host_then_call_callback $host, sub {
		761	$result{$host} = ...;
		762	$cv->end;
		763	};
		764	}
		765
		766	$cv->end;
		767
		768	This code fragment supposedly pings a number of hosts and calls
		769	C<send> after results for all then have have been gathered - in any
		770	order. To achieve this, the code issues a call to C<begin> when it starts
		771	each ping request and calls C<end> when it has received some result for
		772	it. Since C<begin> and C<end> only maintain a counter, the order in which
		773	results arrive is not relevant.
		774
		775	There is an additional bracketing call to C<begin> and C<end> outside the
		776	loop, which serves two important purposes: first, it sets the callback
		777	to be called once the counter reaches C<0>, and second, it ensures that
		778	C<send> is called even when C<no> hosts are being pinged (the loop
		779	doesn't execute once).
		780
		781	This is the general pattern when you "fan out" into multiple (but
		782	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		783	the callback and ensure C<end> is called at least once, and then, for each
		784	subrequest you start, call C<begin> and for each subrequest you finish,
		785	call C<end>.
		786
		787	=back
		788
		789	=head3 METHODS FOR CONSUMERS
		790
		791	These methods should only be used by the consuming side, i.e. the
		792	code awaits the condition.
		793
		794	=over 4
		795
		796	=item $cv->recv
		797
		798	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		799	>> methods have been called on C<$cv>, while servicing other watchers
		800	normally.
		801
		802	You can only wait once on a condition - additional calls are valid but
		803	will return immediately.
		804
		805	If an error condition has been set by calling C<< ->croak >>, then this
		806	function will call C<croak>.
		807
		808	In list context, all parameters passed to C<send> will be returned,
		809	in scalar context only the first one will be returned.
		810
		811	Note that doing a blocking wait in a callback is not supported by any
		812	event loop, that is, recursive invocation of a blocking C<< ->recv
		813	>> is not allowed, and the C<recv> call will C<croak> if such a
		814	condition is detected. This condition can be slightly loosened by using
		815	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		816	any thread that doesn't run the event loop itself.
		817
		818	Not all event models support a blocking wait - some die in that case
		819	(programs might want to do that to stay interactive), so I<if you are
		820	using this from a module, never require a blocking wait>. Instead, let the
		821	caller decide whether the call will block or not (for example, by coupling
		822	condition variables with some kind of request results and supporting
		823	callbacks so the caller knows that getting the result will not block,
		824	while still supporting blocking waits if the caller so desires).
		825
		826	You can ensure that C<< ->recv >> never blocks by setting a callback and
		827	only calling C<< ->recv >> from within that callback (or at a later
		828	time). This will work even when the event loop does not support blocking
		829	waits otherwise.
		830
		831	=item $bool = $cv->ready
		832
		833	Returns true when the condition is "true", i.e. whether C<send> or
		834	C<croak> have been called.
		835
		836	=item $cb = $cv->cb ($cb->($cv))
		837
		838	This is a mutator function that returns the callback set and optionally
		839	replaces it before doing so.
		840
		841	The callback will be called when the condition becomes "true", i.e. when
		842	C<send> or C<croak> are called, with the only argument being the
		843	condition variable itself. If the condition is already true, the
		844	callback is called immediately when it is set. Calling C<recv> inside
		845	the callback or at any later time is guaranteed not to block.
		846
		847	=back
		848
		849	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		850
		851	The available backend classes are (every class has its own manpage):
		852
		853	=over 4
		854
		855	=item Backends that are autoprobed when no other event loop can be found.
		856
		857	EV is the preferred backend when no other event loop seems to be in
		858	use. If EV is not installed, then AnyEvent will fall back to its own
		859	pure-perl implementation, which is available everywhere as it comes with
		860	AnyEvent itself.
		861
		862	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		863	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		864
		865	=item Backends that are transparently being picked up when they are used.
		866
		867	These will be used if they are already loaded when the first watcher
		868	is created, in which case it is assumed that the application is using
		869	them. This means that AnyEvent will automatically pick the right backend
		870	when the main program loads an event module before anything starts to
		871	create watchers. Nothing special needs to be done by the main program.
		872
		873	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		874	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		875	AnyEvent::Impl::Tk based on Tk, very broken.
		876	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		877	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		878	AnyEvent::Impl::Irssi used when running within irssi.
		879
		880	=item Backends with special needs.
		881
		882	Qt requires the Qt::Application to be instantiated first, but will
		883	otherwise be picked up automatically. As long as the main program
		884	instantiates the application before any AnyEvent watchers are created,
		885	everything should just work.
		886
		887	AnyEvent::Impl::Qt based on Qt.
		888
		889	Support for IO::Async can only be partial, as it is too broken and
		890	architecturally limited to even support the AnyEvent API. It also
		891	is the only event loop that needs the loop to be set explicitly, so
		892	it can only be used by a main program knowing about AnyEvent. See
		893	L<AnyEvent::Impl::IOAsync> for the gory details.
		894
		895	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		896
		897	=item Event loops that are indirectly supported via other backends.
		898
		899	Some event loops can be supported via other modules:
		900
		901	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		902
		903	B<WxWidgets> has no support for watching file handles. However, you can
		904	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		905	polls 20 times per second, which was considered to be too horrible to even
		906	consider for AnyEvent.
		907
		908	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		909	backend, so it can be supported through POE.
		910
		911	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		912	load L<POE> when detecting them, in the hope that POE will pick them up,
		913	in which case everything will be automatic.
		914
		915	=back
		916
		917	=head1 GLOBAL VARIABLES AND FUNCTIONS
		918
		919	These are not normally required to use AnyEvent, but can be useful to
		920	write AnyEvent extension modules.
		921
		922	=over 4
		923
178	=item $AnyEvent::MODEL	924	=item $AnyEvent::MODEL
179		925
180	Contains C<undef> until the first watcher is being created. Then it	926	Contains C<undef> until the first watcher is being created, before the
		927	backend has been autodetected.
		928
181	contains the event model that is being used, which is the name of the	929	Afterwards it contains the event model that is being used, which is the
182	Perl class implementing the model. This class is usually one of the	930	name of the Perl class implementing the model. This class is usually one
183	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	931	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
184	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	932	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
185		933	will be C<urxvt::anyevent>).
186	The known classes so far are:
187
188	AnyEvent::Impl::Coro based on Coro::Event, best choise.
189	AnyEvent::Impl::Event based on Event, also best choice :)
190	AnyEvent::Impl::Glib based on Glib, second-best choice.
191	AnyEvent::Impl::Tk based on Tk, very bad choice.
192	AnyEvent::Impl::Perl pure-perl implementation, inefficient.
193		934
194	=item AnyEvent::detect	935	=item AnyEvent::detect
195		936
196	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	937	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
197	necessary. You should only call this function right before you would have	938	if necessary. You should only call this function right before you would
198	created an AnyEvent watcher anyway, that is, very late at runtime.	939	have created an AnyEvent watcher anyway, that is, as late as possible at
		940	runtime, and not e.g. during initialisation of your module.
		941
		942	If you need to do some initialisation before AnyEvent watchers are
		943	created, use C<post_detect>.
		944
		945	=item $guard = AnyEvent::post_detect { BLOCK }
		946
		947	Arranges for the code block to be executed as soon as the event model is
		948	autodetected (or immediately if that has already happened).
		949
		950	The block will be executed I<after> the actual backend has been detected
		951	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		952	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		953	other initialisations - see the sources of L<AnyEvent::Strict> or
		954	L<AnyEvent::AIO> to see how this is used.
		955
		956	The most common usage is to create some global watchers, without forcing
		957	event module detection too early, for example, L<AnyEvent::AIO> creates
		958	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		959	avoid autodetecting the event module at load time.
		960
		961	If called in scalar or list context, then it creates and returns an object
		962	that automatically removes the callback again when it is destroyed (or
		963	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		964	a case where this is useful.
		965
		966	Example: Create a watcher for the IO::AIO module and store it in
		967	C<$WATCHER>, but do so only do so after the event loop is initialised.
		968
		969	our WATCHER;
		970
		971	my $guard = AnyEvent::post_detect {
		972	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		973	};
		974
		975	# the ||= is important in case post_detect immediately runs the block,
		976	# as to not clobber the newly-created watcher. assigning both watcher and
		977	# post_detect guard to the same variable has the advantage of users being
		978	# able to just C<undef $WATCHER> if the watcher causes them grief.
		979
		980	$WATCHER ||= $guard;
		981
		982	=item @AnyEvent::post_detect
		983
		984	If there are any code references in this array (you can C<push> to it
		985	before or after loading AnyEvent), then they will be called directly
		986	after the event loop has been chosen.
		987
		988	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		989	if it is defined then the event loop has already been detected, and the
		990	array will be ignored.
		991
		992	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		993	it, as it takes care of these details.
		994
		995	This variable is mainly useful for modules that can do something useful
		996	when AnyEvent is used and thus want to know when it is initialised, but do
		997	not need to even load it by default. This array provides the means to hook
		998	into AnyEvent passively, without loading it.
		999
		1000	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1001	together, you could put this into Coro (this is the actual code used by
		1002	Coro to accomplish this):
		1003
		1004	if (defined $AnyEvent::MODEL) {
		1005	# AnyEvent already initialised, so load Coro::AnyEvent
		1006	require Coro::AnyEvent;
		1007	} else {
		1008	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1009	# as soon as it is
		1010	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1011	}
199		1012
200	=back	1013	=back
201		1014
202	=head1 WHAT TO DO IN A MODULE	1015	=head1 WHAT TO DO IN A MODULE
203		1016
204	As a module author, you should "use AnyEvent" and call AnyEvent methods	1017	As a module author, you should C<use AnyEvent> and call AnyEvent methods
205	freely, but you should not load a specific event module or rely on it.	1018	freely, but you should not load a specific event module or rely on it.
206		1019
207	Be careful when you create watchers in the module body - Anyevent will	1020	Be careful when you create watchers in the module body - AnyEvent will
208	decide which event module to use as soon as the first method is called, so	1021	decide which event module to use as soon as the first method is called, so
209	by calling AnyEvent in your module body you force the user of your module	1022	by calling AnyEvent in your module body you force the user of your module
210	to load the event module first.	1023	to load the event module first.
211		1024
		1025	Never call C<< ->recv >> on a condition variable unless you I<know> that
		1026	the C<< ->send >> method has been called on it already. This is
		1027	because it will stall the whole program, and the whole point of using
		1028	events is to stay interactive.
		1029
		1030	It is fine, however, to call C<< ->recv >> when the user of your module
		1031	requests it (i.e. if you create a http request object ad have a method
		1032	called C<results> that returns the results, it may call C<< ->recv >>
		1033	freely, as the user of your module knows what she is doing. Always).
		1034
212	=head1 WHAT TO DO IN THE MAIN PROGRAM	1035	=head1 WHAT TO DO IN THE MAIN PROGRAM
213		1036
214	There will always be a single main program - the only place that should	1037	There will always be a single main program - the only place that should
215	dictate which event model to use.	1038	dictate which event model to use.
216		1039
217	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1040	If the program is not event-based, it need not do anything special, even
218	do anything special and let AnyEvent decide which implementation to chose.	1041	when it depends on a module that uses an AnyEvent. If the program itself
		1042	uses AnyEvent, but does not care which event loop is used, all it needs
		1043	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1044	available loop implementation.
219		1045
220	If the main program relies on a specific event model (for example, in Gtk2	1046	If the main program relies on a specific event model - for example, in
221	programs you have to rely on either Glib or Glib::Event), you should load	1047	Gtk2 programs you have to rely on the Glib module - you should load the
222	it before loading AnyEvent or any module that uses it, generally, as early	1048	event module before loading AnyEvent or any module that uses it: generally
223	as possible. The reason is that modules might create watchers when they	1049	speaking, you should load it as early as possible. The reason is that
224	are loaded, and AnyEvent will decide on the event model to use as soon as	1050	modules might create watchers when they are loaded, and AnyEvent will
225	it creates watchers, and it might chose the wrong one unless you load the	1051	decide on the event model to use as soon as it creates watchers, and it
226	correct one yourself.	1052	might choose the wrong one unless you load the correct one yourself.
227		1053
228	You can chose to use a rather inefficient pure-perl implementation by	1054	You can chose to use a pure-perl implementation by loading the
229	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	1055	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
230	generally better.	1056	everywhere, but letting AnyEvent chose the model is generally better.
		1057
		1058	=head2 MAINLOOP EMULATION
		1059
		1060	Sometimes (often for short test scripts, or even standalone programs who
		1061	only want to use AnyEvent), you do not want to run a specific event loop.
		1062
		1063	In that case, you can use a condition variable like this:
		1064
		1065	AnyEvent->condvar->recv;
		1066
		1067	This has the effect of entering the event loop and looping forever.
		1068
		1069	Note that usually your program has some exit condition, in which case
		1070	it is better to use the "traditional" approach of storing a condition
		1071	variable somewhere, waiting for it, and sending it when the program should
		1072	exit cleanly.
		1073
		1074
		1075	=head1 OTHER MODULES
		1076
		1077	The following is a non-exhaustive list of additional modules that use
		1078	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1079	modules and other event loops in the same program. Some of the modules
		1080	come as part of AnyEvent, the others are available via CPAN.
		1081
		1082	=over 4
		1083
		1084	=item L<AnyEvent::Util>
		1085
		1086	Contains various utility functions that replace often-used blocking
		1087	functions such as C<inet_aton> with event/callback-based versions.
		1088
		1089	=item L<AnyEvent::Socket>
		1090
		1091	Provides various utility functions for (internet protocol) sockets,
		1092	addresses and name resolution. Also functions to create non-blocking tcp
		1093	connections or tcp servers, with IPv6 and SRV record support and more.
		1094
		1095	=item L<AnyEvent::Handle>
		1096
		1097	Provide read and write buffers, manages watchers for reads and writes,
		1098	supports raw and formatted I/O, I/O queued and fully transparent and
		1099	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1100
		1101	=item L<AnyEvent::DNS>
		1102
		1103	Provides rich asynchronous DNS resolver capabilities.
		1104
		1105	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1106
		1107	Implement event-based interfaces to the protocols of the same name (for
		1108	the curious, IGS is the International Go Server and FCP is the Freenet
		1109	Client Protocol).
		1110
		1111	=item L<AnyEvent::Handle::UDP>
		1112
		1113	Here be danger!
		1114
		1115	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1116	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1117	its use of a stream-based API with a protocol that isn't streamable, that
		1118	the only way to improve it is to delete it.
		1119
		1120	It features data corruption (but typically only under load) and general
		1121	confusion. On top, the author is not only clueless about UDP but also
		1122	fact-resistant - some gems of his understanding: "connect doesn't work
		1123	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1124	packets", "I don't need to implement proper error checking as UDP doesn't
		1125	support error checking" and so on - he doesn't even understand what's
		1126	wrong with his module when it is explained to him.
		1127
		1128	=item L<AnyEvent::DBI>
		1129
		1130	Executes L<DBI> requests asynchronously in a proxy process for you,
		1131	notifying you in an event-based way when the operation is finished.
		1132
		1133	=item L<AnyEvent::AIO>
		1134
		1135	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1136	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1137	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1138	file I/O, and much more.
		1139
		1140	=item L<AnyEvent::HTTPD>
		1141
		1142	A simple embedded webserver.
		1143
		1144	=item L<AnyEvent::FastPing>
		1145
		1146	The fastest ping in the west.
		1147
		1148	=item L<Coro>
		1149
		1150	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1151
		1152	=back
231		1153
232	=cut	1154	=cut
233		1155
234	package AnyEvent;	1156	package AnyEvent;
235		1157
236	no warnings;	1158	# basically a tuned-down version of common::sense
237	use strict;	1159	sub common_sense {
		1160	# from common:.sense 3.3
		1161	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf3\x0f\xc0\xf0\xfc\x33\x00";
		1162	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1163	$^H |= 0x00000600;
		1164	}
		1165
		1166	BEGIN { AnyEvent::common_sense }
		1167
238	use Carp;	1168	use Carp ();
239		1169
240	our $VERSION = '2.5';	1170	our $VERSION = '5.271';
241	our $MODEL;	1171	our $MODEL;
242		1172
243	our $AUTOLOAD;	1173	our $AUTOLOAD;
244	our @ISA;	1174	our @ISA;
245		1175
246	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
247
248	our @REGISTRY;	1176	our @REGISTRY;
249		1177
		1178	our $VERBOSE;
		1179
		1180	BEGIN {
		1181	require "AnyEvent/constants.pl";
		1182
		1183	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1184
		1185	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1186	if ${^TAINT};
		1187
		1188	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1189
		1190	}
		1191
		1192	our $MAX_SIGNAL_LATENCY = 10;
		1193
		1194	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1195
		1196	{
		1197	my $idx;
		1198	$PROTOCOL{$_} = ++$idx
		1199	for reverse split /\s*,\s*/,
		1200	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1201	}
		1202
250	my @models = (	1203	my @models = (
251	[Coro::Event:: => AnyEvent::Impl::Coro::],	1204	[EV:: => AnyEvent::Impl::EV:: , 1],
		1205	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1206	# everything below here will not (normally) be autoprobed
		1207	# as the pureperl backend should work everywhere
		1208	# and is usually faster
252	[Event:: => AnyEvent::Impl::Event::],	1209	[Event:: => AnyEvent::Impl::Event::, 1],
253	[Glib:: => AnyEvent::Impl::Glib::],	1210	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1211	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1212	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1213	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1214	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1215	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
254	[Tk:: => AnyEvent::Impl::Tk::],	1216	[Wx:: => AnyEvent::Impl::POE::],
255	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1217	[Prima:: => AnyEvent::Impl::POE::],
		1218	# IO::Async is just too broken - we would need workarounds for its
		1219	# byzantine signal and broken child handling, among others.
		1220	# IO::Async is rather hard to detect, as it doesn't have any
		1221	# obvious default class.
		1222	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1223	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1224	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1225	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
256	);	1226	);
257		1227
258	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1228	our %method = map +($_ => 1),
		1229	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1230
		1231	our @post_detect;
		1232
		1233	sub post_detect(&) {
		1234	my ($cb) = @_;
		1235
		1236	push @post_detect, $cb;
		1237
		1238	defined wantarray
		1239	? bless \$cb, "AnyEvent::Util::postdetect"
		1240	: ()
		1241	}
		1242
		1243	sub AnyEvent::Util::postdetect::DESTROY {
		1244	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1245	}
259		1246
260	sub detect() {	1247	sub detect() {
		1248	# free some memory
		1249	*detect = sub () { $MODEL };
		1250
		1251	local $!; # for good measure
		1252	local $SIG{__DIE__};
		1253
		1254	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1255	my $model = "AnyEvent::Impl::$1";
		1256	if (eval "require $model") {
		1257	$MODEL = $model;
		1258	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1259	} else {
		1260	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1261	}
		1262	}
		1263
		1264	# check for already loaded models
261	unless ($MODEL) {	1265	unless ($MODEL) {
262	no strict 'refs';
263
264	# check for already loaded models
265	for (@REGISTRY, @models) {	1266	for (@REGISTRY, @models) {
266	my ($package, $model) = @$_;	1267	my ($package, $model) = @$_;
267	if (${"$package\::VERSION"} > 0) {	1268	if (${"$package\::VERSION"} > 0) {
268	if (eval "require $model") {	1269	if (eval "require $model") {
269	$MODEL = $model;	1270	$MODEL = $model;
270	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1271	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
271	last;	1272	last;
272	}	1273	}
273	}	1274	}
274	}	1275	}
275		1276
276	unless ($MODEL) {	1277	unless ($MODEL) {
277	# try to load a model	1278	# try to autoload a model
278
279	for (@REGISTRY, @models) {	1279	for (@REGISTRY, @models) {
280	my ($package, $model) = @$_;	1280	my ($package, $model, $autoload) = @$_;
		1281	if (
		1282	$autoload
		1283	and eval "require $package"
		1284	and ${"$package\::VERSION"} > 0
281	if (eval "require $model") {	1285	and eval "require $model"
		1286	) {
282	$MODEL = $model;	1287	$MODEL = $model;
283	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	1288	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
284	last;	1289	last;
285	}	1290	}
286	}	1291	}
287		1292
288	$MODEL	1293	$MODEL
289	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";	1294	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
290	}	1295	}
291
292	unshift @ISA, $MODEL;
293	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
294	}	1296	}
		1297
		1298	@models = (); # free probe data
		1299
		1300	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1301	unshift @ISA, $MODEL;
		1302
		1303	# now nuke some methods that are overriden by the backend.
		1304	# SUPER is not allowed.
		1305	for (qw(time signal child idle)) {
		1306	undef &{"AnyEvent::Base::$_"}
		1307	if defined &{"$MODEL\::$_"};
		1308	}
		1309
		1310	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1311
		1312	(shift @post_detect)->() while @post_detect;
		1313
		1314	*post_detect = sub(&) {
		1315	shift->();
		1316
		1317	undef
		1318	};
295		1319
296	$MODEL	1320	$MODEL
297	}	1321	}
298		1322
299	sub AUTOLOAD {	1323	sub AUTOLOAD {
300	(my $func = $AUTOLOAD) =~ s/.*://;	1324	(my $func = $AUTOLOAD) =~ s/.*://;
301		1325
302	$method{$func}	1326	$method{$func}
303	or croak "$func: not a valid method for AnyEvent objects";	1327	or Carp::croak "$func: not a valid AnyEvent class method";
304		1328
305	detect unless $MODEL;	1329	detect;
306		1330
307	my $class = shift;	1331	my $class = shift;
308	$class->$func (@_);	1332	$class->$func (@_);
309	}	1333	}
310		1334
		1335	# utility function to dup a filehandle. this is used by many backends
		1336	# to support binding more than one watcher per filehandle (they usually
		1337	# allow only one watcher per fd, so we dup it to get a different one).
		1338	sub _dupfh($$;$$) {
		1339	my ($poll, $fh, $r, $w) = @_;
		1340
		1341	# cygwin requires the fh mode to be matching, unix doesn't
		1342	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1343
		1344	open my $fh2, $mode, $fh
		1345	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1346
		1347	# we assume CLOEXEC is already set by perl in all important cases
		1348
		1349	($fh2, $rw)
		1350	}
		1351
		1352	=head1 SIMPLIFIED AE API
		1353
		1354	Starting with version 5.0, AnyEvent officially supports a second, much
		1355	simpler, API that is designed to reduce the calling, typing and memory
		1356	overhead by using function call syntax and a fixed number of parameters.
		1357
		1358	See the L<AE> manpage for details.
		1359
		1360	=cut
		1361
		1362	package AE;
		1363
		1364	our $VERSION = $AnyEvent::VERSION;
		1365
		1366	# fall back to the main API by default - backends and AnyEvent::Base
		1367	# implementations can overwrite these.
		1368
		1369	sub io($$$) {
		1370	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1371	}
		1372
		1373	sub timer($$$) {
		1374	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1375	}
		1376
		1377	sub signal($$) {
		1378	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1379	}
		1380
		1381	sub child($$) {
		1382	AnyEvent->child (pid => $_[0], cb => $_[1])
		1383	}
		1384
		1385	sub idle($) {
		1386	AnyEvent->idle (cb => $_[0])
		1387	}
		1388
		1389	sub cv(;&) {
		1390	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1391	}
		1392
		1393	sub now() {
		1394	AnyEvent->now
		1395	}
		1396
		1397	sub now_update() {
		1398	AnyEvent->now_update
		1399	}
		1400
		1401	sub time() {
		1402	AnyEvent->time
		1403	}
		1404
311	package AnyEvent::Base;	1405	package AnyEvent::Base;
312		1406
		1407	# default implementations for many methods
		1408
		1409	sub time {
		1410	eval q{ # poor man's autoloading {}
		1411	# probe for availability of Time::HiRes
		1412	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1413	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1414	*AE::time = \&Time::HiRes::time;
		1415	# if (eval "use POSIX (); (POSIX::times())...
		1416	} else {
		1417	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1418	*AE::time = sub (){ time }; # epic fail
		1419	}
		1420
		1421	*time = sub { AE::time }; # different prototypes
		1422	};
		1423	die if $@;
		1424
		1425	&time
		1426	}
		1427
		1428	*now = \&time;
		1429
		1430	sub now_update { }
		1431
		1432	# default implementation for ->condvar
		1433
		1434	sub condvar {
		1435	eval q{ # poor man's autoloading {}
		1436	*condvar = sub {
		1437	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1438	};
		1439
		1440	*AE::cv = sub (;&) {
		1441	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1442	};
		1443	};
		1444	die if $@;
		1445
		1446	&condvar
		1447	}
		1448
313	# default implementation for signal	1449	# default implementation for ->signal
314		1450
315	our %SIG_CB;	1451	our $HAVE_ASYNC_INTERRUPT;
		1452
		1453	sub _have_async_interrupt() {
		1454	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1455	&& eval "use Async::Interrupt 1.02 (); 1")
		1456	unless defined $HAVE_ASYNC_INTERRUPT;
		1457
		1458	$HAVE_ASYNC_INTERRUPT
		1459	}
		1460
		1461	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1462	our (%SIG_ASY, %SIG_ASY_W);
		1463	our ($SIG_COUNT, $SIG_TW);
		1464
		1465	# install a dummy wakeup watcher to reduce signal catching latency
		1466	# used by Impls
		1467	sub _sig_add() {
		1468	unless ($SIG_COUNT++) {
		1469	# try to align timer on a full-second boundary, if possible
		1470	my $NOW = AE::now;
		1471
		1472	$SIG_TW = AE::timer
		1473	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1474	$MAX_SIGNAL_LATENCY,
		1475	sub { } # just for the PERL_ASYNC_CHECK
		1476	;
		1477	}
		1478	}
		1479
		1480	sub _sig_del {
		1481	undef $SIG_TW
		1482	unless --$SIG_COUNT;
		1483	}
		1484
		1485	our $_sig_name_init; $_sig_name_init = sub {
		1486	eval q{ # poor man's autoloading {}
		1487	undef $_sig_name_init;
		1488
		1489	if (_have_async_interrupt) {
		1490	*sig2num = \&Async::Interrupt::sig2num;
		1491	*sig2name = \&Async::Interrupt::sig2name;
		1492	} else {
		1493	require Config;
		1494
		1495	my %signame2num;
		1496	@signame2num{ split ' ', $Config::Config{sig_name} }
		1497	= split ' ', $Config::Config{sig_num};
		1498
		1499	my @signum2name;
		1500	@signum2name[values %signame2num] = keys %signame2num;
		1501
		1502	*sig2num = sub($) {
		1503	$_[0] > 0 ? shift : $signame2num{+shift}
		1504	};
		1505	*sig2name = sub ($) {
		1506	$_[0] > 0 ? $signum2name[+shift] : shift
		1507	};
		1508	}
		1509	};
		1510	die if $@;
		1511	};
		1512
		1513	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1514	sub sig2name($) { &$_sig_name_init; &sig2name }
316		1515
317	sub signal {	1516	sub signal {
		1517	eval q{ # poor man's autoloading {}
		1518	# probe for availability of Async::Interrupt
		1519	if (_have_async_interrupt) {
		1520	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1521
		1522	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1523	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1524
		1525	} else {
		1526	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1527
		1528	if (AnyEvent::WIN32) {
		1529	require AnyEvent::Util;
		1530
		1531	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1532	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1533	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1534	} else {
		1535	pipe $SIGPIPE_R, $SIGPIPE_W;
		1536	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1537	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1538
		1539	# not strictly required, as $^F is normally 2, but let's make sure...
		1540	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1541	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1542	}
		1543
		1544	$SIGPIPE_R
		1545	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1546
		1547	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1548	}
		1549
		1550	*signal = $HAVE_ASYNC_INTERRUPT
		1551	? sub {
318	my (undef, %arg) = @_;	1552	my (undef, %arg) = @_;
319		1553
		1554	# async::interrupt
320	my $signal = uc $arg{signal}	1555	my $signal = sig2num $arg{signal};
321	or Carp::croak "required option 'signal' is missing";
322
323	my $w = bless [$signal, $arg{cb}], "AnyEvent::Base::Signal";
324
325	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1556	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1557
		1558	$SIG_ASY{$signal} ||= new Async::Interrupt
		1559	cb => sub { undef $SIG_EV{$signal} },
		1560	signal => $signal,
		1561	pipe => [$SIGPIPE_R->filenos],
		1562	pipe_autodrain => 0,
		1563	;
		1564
		1565	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1566	}
		1567	: sub {
		1568	my (undef, %arg) = @_;
		1569
		1570	# pure perl
		1571	my $signal = sig2name $arg{signal};
		1572	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1573
326	$SIG{$signal} ||= sub {	1574	$SIG{$signal} ||= sub {
		1575	local $!;
		1576	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1577	undef $SIG_EV{$signal};
		1578	};
		1579
		1580	# can't do signal processing without introducing races in pure perl,
		1581	# so limit the signal latency.
		1582	_sig_add;
		1583
		1584	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1585	}
		1586	;
		1587
		1588	*AnyEvent::Base::signal::DESTROY = sub {
		1589	my ($signal, $cb) = @{$_[0]};
		1590
		1591	_sig_del;
		1592
		1593	delete $SIG_CB{$signal}{$cb};
		1594
		1595	$HAVE_ASYNC_INTERRUPT
		1596	? delete $SIG_ASY{$signal}
		1597	: # delete doesn't work with older perls - they then
		1598	# print weird messages, or just unconditionally exit
		1599	# instead of getting the default action.
		1600	undef $SIG{$signal}
		1601	unless keys %{ $SIG_CB{$signal} };
		1602	};
		1603
		1604	*_signal_exec = sub {
		1605	$HAVE_ASYNC_INTERRUPT
		1606	? $SIGPIPE_R->drain
		1607	: sysread $SIGPIPE_R, (my $dummy), 9;
		1608
		1609	while (%SIG_EV) {
		1610	for (keys %SIG_EV) {
		1611	delete $SIG_EV{$_};
327	$_->() for values %{ $SIG_CB{$signal} };	1612	$_->() for values %{ $SIG_CB{$_} || {} };
		1613	}
		1614	}
		1615	};
328	};	1616	};
		1617	die if $@;
329		1618
330	$w	1619	&signal
331	}	1620	}
332		1621
333	sub AnyEvent::Base::Signal::DESTROY {	1622	# default implementation for ->child
		1623
		1624	our %PID_CB;
		1625	our $CHLD_W;
		1626	our $CHLD_DELAY_W;
		1627	our $WNOHANG;
		1628
		1629	# used by many Impl's
		1630	sub _emit_childstatus($$) {
		1631	my (undef, $rpid, $rstatus) = @_;
		1632
		1633	$_->($rpid, $rstatus)
		1634	for values %{ $PID_CB{$rpid} || {} },
		1635	values %{ $PID_CB{0} || {} };
		1636	}
		1637
		1638	sub child {
		1639	eval q{ # poor man's autoloading {}
		1640	*_sigchld = sub {
		1641	my $pid;
		1642
		1643	AnyEvent->_emit_childstatus ($pid, $?)
		1644	while ($pid = waitpid -1, $WNOHANG) > 0;
		1645	};
		1646
		1647	*child = sub {
		1648	my (undef, %arg) = @_;
		1649
		1650	defined (my $pid = $arg{pid} + 0)
		1651	or Carp::croak "required option 'pid' is missing";
		1652
		1653	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
		1654
		1655	# WNOHANG is almost cetrainly 1 everywhere
		1656	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1657	? 1
		1658	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
		1659
		1660	unless ($CHLD_W) {
		1661	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1662	# child could be a zombie already, so make at least one round
		1663	&_sigchld;
		1664	}
		1665
		1666	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
		1667	};
		1668
		1669	*AnyEvent::Base::child::DESTROY = sub {
334	my ($signal, $cb) = @{$_[0]};	1670	my ($pid, $cb) = @{$_[0]};
335		1671
336	delete $SIG_CB{$signal}{$cb};	1672	delete $PID_CB{$pid}{$cb};
		1673	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
337		1674
338	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1675	undef $CHLD_W unless keys %PID_CB;
		1676	};
		1677	};
		1678	die if $@;
		1679
		1680	&child
339	}	1681	}
		1682
		1683	# idle emulation is done by simply using a timer, regardless
		1684	# of whether the process is idle or not, and not letting
		1685	# the callback use more than 50% of the time.
		1686	sub idle {
		1687	eval q{ # poor man's autoloading {}
		1688	*idle = sub {
		1689	my (undef, %arg) = @_;
		1690
		1691	my ($cb, $w, $rcb) = $arg{cb};
		1692
		1693	$rcb = sub {
		1694	if ($cb) {
		1695	$w = _time;
		1696	&$cb;
		1697	$w = _time - $w;
		1698
		1699	# never use more then 50% of the time for the idle watcher,
		1700	# within some limits
		1701	$w = 0.0001 if $w < 0.0001;
		1702	$w = 5 if $w > 5;
		1703
		1704	$w = AE::timer $w, 0, $rcb;
		1705	} else {
		1706	# clean up...
		1707	undef $w;
		1708	undef $rcb;
		1709	}
		1710	};
		1711
		1712	$w = AE::timer 0.05, 0, $rcb;
		1713
		1714	bless \\$cb, "AnyEvent::Base::idle"
		1715	};
		1716
		1717	*AnyEvent::Base::idle::DESTROY = sub {
		1718	undef $${$_[0]};
		1719	};
		1720	};
		1721	die if $@;
		1722
		1723	&idle
		1724	}
		1725
		1726	package AnyEvent::CondVar;
		1727
		1728	our @ISA = AnyEvent::CondVar::Base::;
		1729
		1730	# only to be used for subclassing
		1731	sub new {
		1732	my $class = shift;
		1733	bless AnyEvent->condvar (@_), $class
		1734	}
		1735
		1736	package AnyEvent::CondVar::Base;
		1737
		1738	#use overload
		1739	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1740	# fallback => 1;
		1741
		1742	# save 300+ kilobytes by dirtily hardcoding overloading
		1743	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1744	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1745	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1746	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1747
		1748	our $WAITING;
		1749
		1750	sub _send {
		1751	# nop
		1752	}
		1753
		1754	sub send {
		1755	my $cv = shift;
		1756	$cv->{_ae_sent} = [@_];
		1757	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1758	$cv->_send;
		1759	}
		1760
		1761	sub croak {
		1762	$_[0]{_ae_croak} = $_[1];
		1763	$_[0]->send;
		1764	}
		1765
		1766	sub ready {
		1767	$_[0]{_ae_sent}
		1768	}
		1769
		1770	sub _wait {
		1771	$WAITING
		1772	and !$_[0]{_ae_sent}
		1773	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1774
		1775	local $WAITING = 1;
		1776	AnyEvent->one_event while !$_[0]{_ae_sent};
		1777	}
		1778
		1779	sub recv {
		1780	$_[0]->_wait;
		1781
		1782	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1783	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1784	}
		1785
		1786	sub cb {
		1787	my $cv = shift;
		1788
		1789	@_
		1790	and $cv->{_ae_cb} = shift
		1791	and $cv->{_ae_sent}
		1792	and (delete $cv->{_ae_cb})->($cv);
		1793
		1794	$cv->{_ae_cb}
		1795	}
		1796
		1797	sub begin {
		1798	++$_[0]{_ae_counter};
		1799	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1800	}
		1801
		1802	sub end {
		1803	return if --$_[0]{_ae_counter};
		1804	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1805	}
		1806
		1807	# undocumented/compatibility with pre-3.4
		1808	*broadcast = \&send;
		1809	*wait = \&_wait;
		1810
		1811	=head1 ERROR AND EXCEPTION HANDLING
		1812
		1813	In general, AnyEvent does not do any error handling - it relies on the
		1814	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1815	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1816	checking of all AnyEvent methods, however, which is highly useful during
		1817	development.
		1818
		1819	As for exception handling (i.e. runtime errors and exceptions thrown while
		1820	executing a callback), this is not only highly event-loop specific, but
		1821	also not in any way wrapped by this module, as this is the job of the main
		1822	program.
		1823
		1824	The pure perl event loop simply re-throws the exception (usually
		1825	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1826	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1827	so on.
		1828
		1829	=head1 ENVIRONMENT VARIABLES
		1830
		1831	The following environment variables are used by this module or its
		1832	submodules.
		1833
		1834	Note that AnyEvent will remove I<all> environment variables starting with
		1835	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1836	enabled.
		1837
		1838	=over 4
		1839
		1840	=item C<PERL_ANYEVENT_VERBOSE>
		1841
		1842	By default, AnyEvent will be completely silent except in fatal
		1843	conditions. You can set this environment variable to make AnyEvent more
		1844	talkative.
		1845
		1846	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1847	conditions, such as not being able to load the event model specified by
		1848	C<PERL_ANYEVENT_MODEL>.
		1849
		1850	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1851	model it chooses.
		1852
		1853	When set to C<8> or higher, then AnyEvent will report extra information on
		1854	which optional modules it loads and how it implements certain features.
		1855
		1856	=item C<PERL_ANYEVENT_STRICT>
		1857
		1858	AnyEvent does not do much argument checking by default, as thorough
		1859	argument checking is very costly. Setting this variable to a true value
		1860	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1861	check the arguments passed to most method calls. If it finds any problems,
		1862	it will croak.
		1863
		1864	In other words, enables "strict" mode.
		1865
		1866	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		1867	>>, it is definitely recommended to keep it off in production. Keeping
		1868	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1869	can be very useful, however.
		1870
		1871	=item C<PERL_ANYEVENT_MODEL>
		1872
		1873	This can be used to specify the event model to be used by AnyEvent, before
		1874	auto detection and -probing kicks in. It must be a string consisting
		1875	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1876	and the resulting module name is loaded and if the load was successful,
		1877	used as event model. If it fails to load AnyEvent will proceed with
		1878	auto detection and -probing.
		1879
		1880	This functionality might change in future versions.
		1881
		1882	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1883	could start your program like this:
		1884
		1885	PERL_ANYEVENT_MODEL=Perl perl ...
		1886
		1887	=item C<PERL_ANYEVENT_PROTOCOLS>
		1888
		1889	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1890	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1891	of auto probing).
		1892
		1893	Must be set to a comma-separated list of protocols or address families,
		1894	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1895	used, and preference will be given to protocols mentioned earlier in the
		1896	list.
		1897
		1898	This variable can effectively be used for denial-of-service attacks
		1899	against local programs (e.g. when setuid), although the impact is likely
		1900	small, as the program has to handle conenction and other failures anyways.
		1901
		1902	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1903	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1904	- only support IPv4, never try to resolve or contact IPv6
		1905	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1906	IPv6, but prefer IPv6 over IPv4.
		1907
		1908	=item C<PERL_ANYEVENT_EDNS0>
		1909
		1910	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1911	for DNS. This extension is generally useful to reduce DNS traffic, but
		1912	some (broken) firewalls drop such DNS packets, which is why it is off by
		1913	default.
		1914
		1915	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1916	EDNS0 in its DNS requests.
		1917
		1918	=item C<PERL_ANYEVENT_MAX_FORKS>
		1919
		1920	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1921	will create in parallel.
		1922
		1923	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1924
		1925	The default value for the C<max_outstanding> parameter for the default DNS
		1926	resolver - this is the maximum number of parallel DNS requests that are
		1927	sent to the DNS server.
		1928
		1929	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1930
		1931	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1932	configuration) in the default resolver. When set to the empty string, no
		1933	default config will be used.
		1934
		1935	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1936
		1937	When neither C<ca_file> nor C<ca_path> was specified during
		1938	L<AnyEvent::TLS> context creation, and either of these environment
		1939	variables exist, they will be used to specify CA certificate locations
		1940	instead of a system-dependent default.
		1941
		1942	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1943
		1944	When these are set to C<1>, then the respective modules are not
		1945	loaded. Mostly good for testing AnyEvent itself.
		1946
		1947	=back
340		1948
341	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1949	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1950
		1951	This is an advanced topic that you do not normally need to use AnyEvent in
		1952	a module. This section is only of use to event loop authors who want to
		1953	provide AnyEvent compatibility.
342		1954
343	If you need to support another event library which isn't directly	1955	If you need to support another event library which isn't directly
344	supported by AnyEvent, you can supply your own interface to it by	1956	supported by AnyEvent, you can supply your own interface to it by
345	pushing, before the first watcher gets created, the package name of	1957	pushing, before the first watcher gets created, the package name of
346	the event module and the package name of the interface to use onto	1958	the event module and the package name of the interface to use onto
347	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	1959	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
348	AnyEvent.	1960	AnyEvent, so it is reasonably cheap.
349		1961
350	Example:	1962	Example:
351		1963
352	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	1964	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
353		1965
354	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	1966	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
355	package/class when it finds the C<urxvt> package/module is loaded. When	1967	package/class when it finds the C<urxvt> package/module is already loaded.
		1968
356	AnyEvent is loaded and asked to find a suitable event model, it will	1969	When AnyEvent is loaded and asked to find a suitable event model, it
357	first check for the presence of urxvt.	1970	will first check for the presence of urxvt by trying to C<use> the
		1971	C<urxvt::anyevent> module.
358		1972
359	The class should provide implementations for all watcher types (see	1973	The class should provide implementations for all watcher types. See
360	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	1974	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
361	(Source code) and so on for actual examples, use C<perldoc -m	1975	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
362	AnyEvent::Impl::Glib> to see the sources).	1976	see the sources.
363		1977
		1978	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		1979	provide suitable (hopefully) replacements.
		1980
364	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	1981	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
365	uses the above line as-is. An interface isn't included in AnyEvent	1982	terminal emulator uses the above line as-is. An interface isn't included
366	because it doesn't make sense outside the embedded interpreter inside	1983	in AnyEvent because it doesn't make sense outside the embedded interpreter
367	I<rxvt-unicode>, and it is updated and maintained as part of the	1984	inside I<rxvt-unicode>, and it is updated and maintained as part of the
368	I<rxvt-unicode> distribution.	1985	I<rxvt-unicode> distribution.
369		1986
370	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1987	I<rxvt-unicode> also cheats a bit by not providing blocking access to
371	condition variables: code blocking while waiting for a condition will	1988	condition variables: code blocking while waiting for a condition will
372	C<die>. This still works with most modules/usages, and blocking calls must	1989	C<die>. This still works with most modules/usages, and blocking calls must
373	not be in an interactive appliation, so it makes sense.	1990	not be done in an interactive application, so it makes sense.
374		1991
375	=head1 ENVIRONMENT VARIABLES
376
377	The following environment variables are used by this module:
378
379	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
380	model gets used.
381
382	=head1 EXAMPLE	1992	=head1 EXAMPLE PROGRAM
383		1993
384	The following program uses an io watcher to read data from stdin, a timer	1994	The following program uses an I/O watcher to read data from STDIN, a timer
385	to display a message once per second, and a condvar to exit the program	1995	to display a message once per second, and a condition variable to quit the
386	when the user enters quit:	1996	program when the user enters quit:
387		1997
388	use AnyEvent;	1998	use AnyEvent;
389		1999
390	my $cv = AnyEvent->condvar;	2000	my $cv = AnyEvent->condvar;
391		2001
392	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	2002	my $io_watcher = AnyEvent->io (
		2003	fh => \*STDIN,
		2004	poll => 'r',
		2005	cb => sub {
393	warn "io event <$_[0]>\n"; # will always output <r>	2006	warn "io event <$_[0]>\n"; # will always output <r>
394	chomp (my $input = <STDIN>); # read a line	2007	chomp (my $input = <STDIN>); # read a line
395	warn "read: $input\n"; # output what has been read	2008	warn "read: $input\n"; # output what has been read
396	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2009	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		2010	},
		2011	);
		2012
		2013	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
		2014	warn "timeout\n"; # print 'timeout' at most every second
397	});	2015	});
398		2016
399	my $time_watcher; # can only be used once
400
401	sub new_timer {
402	$timer = AnyEvent->timer (after => 1, cb => sub {
403	warn "timeout\n"; # print 'timeout' about every second
404	&new_timer; # and restart the time
405	});
406	}
407
408	new_timer; # create first timer
409
410	$cv->wait; # wait until user enters /^q/i	2017	$cv->recv; # wait until user enters /^q/i
411		2018
412	=head1 REAL-WORLD EXAMPLE	2019	=head1 REAL-WORLD EXAMPLE
413		2020
414	Consider the L<Net::FCP> module. It features (among others) the following	2021	Consider the L<Net::FCP> module. It features (among others) the following
415	API calls, which are to freenet what HTTP GET requests are to http:	2022	API calls, which are to freenet what HTTP GET requests are to http:
…		…
465	syswrite $txn->{fh}, $txn->{request}	2072	syswrite $txn->{fh}, $txn->{request}
466	or die "connection or write error";	2073	or die "connection or write error";
467	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2074	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
468		2075
469	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2076	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
470	result and signals any possible waiters that the request ahs finished:	2077	result and signals any possible waiters that the request has finished:
471		2078
472	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2079	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
473		2080
474	if (end-of-file or data complete) {	2081	if (end-of-file or data complete) {
475	$txn->{result} = $txn->{buf};	2082	$txn->{result} = $txn->{buf};
476	$txn->{finished}->broadcast;	2083	$txn->{finished}->send;
477	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2084	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
478	}	2085	}
479		2086
480	The C<result> method, finally, just waits for the finished signal (if the	2087	The C<result> method, finally, just waits for the finished signal (if the
481	request was already finished, it doesn't wait, of course, and returns the	2088	request was already finished, it doesn't wait, of course, and returns the
482	data:	2089	data:
483		2090
484	$txn->{finished}->wait;	2091	$txn->{finished}->recv;
485	return $txn->{result};	2092	return $txn->{result};
486		2093
487	The actual code goes further and collects all errors (C<die>s, exceptions)	2094	The actual code goes further and collects all errors (C<die>s, exceptions)
488	that occured during request processing. The C<result> method detects	2095	that occurred during request processing. The C<result> method detects
489	wether an exception as thrown (it is stored inside the $txn object)	2096	whether an exception as thrown (it is stored inside the $txn object)
490	and just throws the exception, which means connection errors and other	2097	and just throws the exception, which means connection errors and other
491	problems get reported tot he code that tries to use the result, not in a	2098	problems get reported to the code that tries to use the result, not in a
492	random callback.	2099	random callback.
493		2100
494	All of this enables the following usage styles:	2101	All of this enables the following usage styles:
495		2102
496	1. Blocking:	2103	1. Blocking:
497		2104
498	my $data = $fcp->client_get ($url);	2105	my $data = $fcp->client_get ($url);
499		2106
500	2. Blocking, but parallelizing:	2107	2. Blocking, but running in parallel:
501		2108
502	my @datas = map $_->result,	2109	my @datas = map $_->result,
503	map $fcp->txn_client_get ($_),	2110	map $fcp->txn_client_get ($_),
504	@urls;	2111	@urls;
505		2112
506	Both blocking examples work without the module user having to know	2113	Both blocking examples work without the module user having to know
507	anything about events.	2114	anything about events.
508		2115
509	3a. Event-based in a main program, using any support Event module:	2116	3a. Event-based in a main program, using any supported event module:
510		2117
511	use Event;	2118	use EV;
512		2119
513	$fcp->txn_client_get ($url)->cb (sub {	2120	$fcp->txn_client_get ($url)->cb (sub {
514	my $txn = shift;	2121	my $txn = shift;
515	my $data = $txn->result;	2122	my $data = $txn->result;
516	...	2123	...
517	});	2124	});
518		2125
519	Event::loop;	2126	EV::loop;
520		2127
521	3b. The module user could use AnyEvent, too:	2128	3b. The module user could use AnyEvent, too:
522		2129
523	use AnyEvent;	2130	use AnyEvent;
524		2131
525	my $quit = AnyEvent->condvar;	2132	my $quit = AnyEvent->condvar;
526		2133
527	$fcp->txn_client_get ($url)->cb (sub {	2134	$fcp->txn_client_get ($url)->cb (sub {
528	...	2135	...
529	$quit->broadcast;	2136	$quit->send;
530	});	2137	});
531		2138
532	$quit->wait;	2139	$quit->recv;
		2140
		2141
		2142	=head1 BENCHMARKS
		2143
		2144	To give you an idea of the performance and overheads that AnyEvent adds
		2145	over the event loops themselves and to give you an impression of the speed
		2146	of various event loops I prepared some benchmarks.
		2147
		2148	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2149
		2150	Here is a benchmark of various supported event models used natively and
		2151	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2152	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2153	which it is), lets them fire exactly once and destroys them again.
		2154
		2155	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2156	distribution. It uses the L<AE> interface, which makes a real difference
		2157	for the EV and Perl backends only.
		2158
		2159	=head3 Explanation of the columns
		2160
		2161	I<watcher> is the number of event watchers created/destroyed. Since
		2162	different event models feature vastly different performances, each event
		2163	loop was given a number of watchers so that overall runtime is acceptable
		2164	and similar between tested event loop (and keep them from crashing): Glib
		2165	would probably take thousands of years if asked to process the same number
		2166	of watchers as EV in this benchmark.
		2167
		2168	I<bytes> is the number of bytes (as measured by the resident set size,
		2169	RSS) consumed by each watcher. This method of measuring captures both C
		2170	and Perl-based overheads.
		2171
		2172	I<create> is the time, in microseconds (millionths of seconds), that it
		2173	takes to create a single watcher. The callback is a closure shared between
		2174	all watchers, to avoid adding memory overhead. That means closure creation
		2175	and memory usage is not included in the figures.
		2176
		2177	I<invoke> is the time, in microseconds, used to invoke a simple
		2178	callback. The callback simply counts down a Perl variable and after it was
		2179	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2180	signal the end of this phase.
		2181
		2182	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2183	watcher.
		2184
		2185	=head3 Results
		2186
		2187	name watchers bytes create invoke destroy comment
		2188	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2189	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2190	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2191	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2192	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2193	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2194	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2195	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2196	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2197	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2198	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2199	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2200
		2201	=head3 Discussion
		2202
		2203	The benchmark does I<not> measure scalability of the event loop very
		2204	well. For example, a select-based event loop (such as the pure perl one)
		2205	can never compete with an event loop that uses epoll when the number of
		2206	file descriptors grows high. In this benchmark, all events become ready at
		2207	the same time, so select/poll-based implementations get an unnatural speed
		2208	boost.
		2209
		2210	Also, note that the number of watchers usually has a nonlinear effect on
		2211	overall speed, that is, creating twice as many watchers doesn't take twice
		2212	the time - usually it takes longer. This puts event loops tested with a
		2213	higher number of watchers at a disadvantage.
		2214
		2215	To put the range of results into perspective, consider that on the
		2216	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2217	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2218	cycles with POE.
		2219
		2220	C<EV> is the sole leader regarding speed and memory use, which are both
		2221	maximal/minimal, respectively. When using the L<AE> API there is zero
		2222	overhead (when going through the AnyEvent API create is about 5-6 times
		2223	slower, with other times being equal, so still uses far less memory than
		2224	any other event loop and is still faster than Event natively).
		2225
		2226	The pure perl implementation is hit in a few sweet spots (both the
		2227	constant timeout and the use of a single fd hit optimisations in the perl
		2228	interpreter and the backend itself). Nevertheless this shows that it
		2229	adds very little overhead in itself. Like any select-based backend its
		2230	performance becomes really bad with lots of file descriptors (and few of
		2231	them active), of course, but this was not subject of this benchmark.
		2232
		2233	The C<Event> module has a relatively high setup and callback invocation
		2234	cost, but overall scores in on the third place.
		2235
		2236	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2237	when using its pure perl backend.
		2238
		2239	C<Glib>'s memory usage is quite a bit higher, but it features a
		2240	faster callback invocation and overall ends up in the same class as
		2241	C<Event>. However, Glib scales extremely badly, doubling the number of
		2242	watchers increases the processing time by more than a factor of four,
		2243	making it completely unusable when using larger numbers of watchers
		2244	(note that only a single file descriptor was used in the benchmark, so
		2245	inefficiencies of C<poll> do not account for this).
		2246
		2247	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2248	more than 2000 watchers is a big setback, however, as correctness takes
		2249	precedence over speed. Nevertheless, its performance is surprising, as the
		2250	file descriptor is dup()ed for each watcher. This shows that the dup()
		2251	employed by some adaptors is not a big performance issue (it does incur a
		2252	hidden memory cost inside the kernel which is not reflected in the figures
		2253	above).
		2254
		2255	C<POE>, regardless of underlying event loop (whether using its pure perl
		2256	select-based backend or the Event module, the POE-EV backend couldn't
		2257	be tested because it wasn't working) shows abysmal performance and
		2258	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2259	as EV watchers, and 10 times as much memory as Event (the high memory
		2260	requirements are caused by requiring a session for each watcher). Watcher
		2261	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2262	implementation.
		2263
		2264	The design of the POE adaptor class in AnyEvent can not really account
		2265	for the performance issues, though, as session creation overhead is
		2266	small compared to execution of the state machine, which is coded pretty
		2267	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2268	using multiple sessions is not a good approach, especially regarding
		2269	memory usage, even the author of POE could not come up with a faster
		2270	design).
		2271
		2272	=head3 Summary
		2273
		2274	=over 4
		2275
		2276	=item * Using EV through AnyEvent is faster than any other event loop
		2277	(even when used without AnyEvent), but most event loops have acceptable
		2278	performance with or without AnyEvent.
		2279
		2280	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2281	the actual event loop, only with extremely fast event loops such as EV
		2282	adds AnyEvent significant overhead.
		2283
		2284	=item * You should avoid POE like the plague if you want performance or
		2285	reasonable memory usage.
		2286
		2287	=back
		2288
		2289	=head2 BENCHMARKING THE LARGE SERVER CASE
		2290
		2291	This benchmark actually benchmarks the event loop itself. It works by
		2292	creating a number of "servers": each server consists of a socket pair, a
		2293	timeout watcher that gets reset on activity (but never fires), and an I/O
		2294	watcher waiting for input on one side of the socket. Each time the socket
		2295	watcher reads a byte it will write that byte to a random other "server".
		2296
		2297	The effect is that there will be a lot of I/O watchers, only part of which
		2298	are active at any one point (so there is a constant number of active
		2299	fds for each loop iteration, but which fds these are is random). The
		2300	timeout is reset each time something is read because that reflects how
		2301	most timeouts work (and puts extra pressure on the event loops).
		2302
		2303	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2304	(1%) are active. This mirrors the activity of large servers with many
		2305	connections, most of which are idle at any one point in time.
		2306
		2307	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2308	distribution. It uses the L<AE> interface, which makes a real difference
		2309	for the EV and Perl backends only.
		2310
		2311	=head3 Explanation of the columns
		2312
		2313	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2314	each server has a read and write socket end).
		2315
		2316	I<create> is the time it takes to create a socket pair (which is
		2317	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2318
		2319	I<request>, the most important value, is the time it takes to handle a
		2320	single "request", that is, reading the token from the pipe and forwarding
		2321	it to another server. This includes deleting the old timeout and creating
		2322	a new one that moves the timeout into the future.
		2323
		2324	=head3 Results
		2325
		2326	name sockets create request
		2327	EV 20000 62.66 7.99
		2328	Perl 20000 68.32 32.64
		2329	IOAsync 20000 174.06 101.15 epoll
		2330	IOAsync 20000 174.67 610.84 poll
		2331	Event 20000 202.69 242.91
		2332	Glib 20000 557.01 1689.52
		2333	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2334
		2335	=head3 Discussion
		2336
		2337	This benchmark I<does> measure scalability and overall performance of the
		2338	particular event loop.
		2339
		2340	EV is again fastest. Since it is using epoll on my system, the setup time
		2341	is relatively high, though.
		2342
		2343	Perl surprisingly comes second. It is much faster than the C-based event
		2344	loops Event and Glib.
		2345
		2346	IO::Async performs very well when using its epoll backend, and still quite
		2347	good compared to Glib when using its pure perl backend.
		2348
		2349	Event suffers from high setup time as well (look at its code and you will
		2350	understand why). Callback invocation also has a high overhead compared to
		2351	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2352	uses select or poll in basically all documented configurations.
		2353
		2354	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2355	clearly fails to perform with many filehandles or in busy servers.
		2356
		2357	POE is still completely out of the picture, taking over 1000 times as long
		2358	as EV, and over 100 times as long as the Perl implementation, even though
		2359	it uses a C-based event loop in this case.
		2360
		2361	=head3 Summary
		2362
		2363	=over 4
		2364
		2365	=item * The pure perl implementation performs extremely well.
		2366
		2367	=item * Avoid Glib or POE in large projects where performance matters.
		2368
		2369	=back
		2370
		2371	=head2 BENCHMARKING SMALL SERVERS
		2372
		2373	While event loops should scale (and select-based ones do not...) even to
		2374	large servers, most programs we (or I :) actually write have only a few
		2375	I/O watchers.
		2376
		2377	In this benchmark, I use the same benchmark program as in the large server
		2378	case, but it uses only eight "servers", of which three are active at any
		2379	one time. This should reflect performance for a small server relatively
		2380	well.
		2381
		2382	The columns are identical to the previous table.
		2383
		2384	=head3 Results
		2385
		2386	name sockets create request
		2387	EV 16 20.00 6.54
		2388	Perl 16 25.75 12.62
		2389	Event 16 81.27 35.86
		2390	Glib 16 32.63 15.48
		2391	POE 16 261.87 276.28 uses POE::Loop::Event
		2392
		2393	=head3 Discussion
		2394
		2395	The benchmark tries to test the performance of a typical small
		2396	server. While knowing how various event loops perform is interesting, keep
		2397	in mind that their overhead in this case is usually not as important, due
		2398	to the small absolute number of watchers (that is, you need efficiency and
		2399	speed most when you have lots of watchers, not when you only have a few of
		2400	them).
		2401
		2402	EV is again fastest.
		2403
		2404	Perl again comes second. It is noticeably faster than the C-based event
		2405	loops Event and Glib, although the difference is too small to really
		2406	matter.
		2407
		2408	POE also performs much better in this case, but is is still far behind the
		2409	others.
		2410
		2411	=head3 Summary
		2412
		2413	=over 4
		2414
		2415	=item * C-based event loops perform very well with small number of
		2416	watchers, as the management overhead dominates.
		2417
		2418	=back
		2419
		2420	=head2 THE IO::Lambda BENCHMARK
		2421
		2422	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2423	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2424	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2425	shouldn't come as a surprise to anybody). As such, the benchmark is
		2426	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2427	very optimal. But how would AnyEvent compare when used without the extra
		2428	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2429
		2430	The benchmark itself creates an echo-server, and then, for 500 times,
		2431	connects to the echo server, sends a line, waits for the reply, and then
		2432	creates the next connection. This is a rather bad benchmark, as it doesn't
		2433	test the efficiency of the framework or much non-blocking I/O, but it is a
		2434	benchmark nevertheless.
		2435
		2436	name runtime
		2437	Lambda/select 0.330 sec
		2438	+ optimized 0.122 sec
		2439	Lambda/AnyEvent 0.327 sec
		2440	+ optimized 0.138 sec
		2441	Raw sockets/select 0.077 sec
		2442	POE/select, components 0.662 sec
		2443	POE/select, raw sockets 0.226 sec
		2444	POE/select, optimized 0.404 sec
		2445
		2446	AnyEvent/select/nb 0.085 sec
		2447	AnyEvent/EV/nb 0.068 sec
		2448	+state machine 0.134 sec
		2449
		2450	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2451	benchmarks actually make blocking connects and use 100% blocking I/O,
		2452	defeating the purpose of an event-based solution. All of the newly
		2453	written AnyEvent benchmarks use 100% non-blocking connects (using
		2454	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2455	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2456	generally require a lot more bookkeeping and event handling than blocking
		2457	connects (which involve a single syscall only).
		2458
		2459	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2460	offers similar expressive power as POE and IO::Lambda, using conventional
		2461	Perl syntax. This means that both the echo server and the client are 100%
		2462	non-blocking, further placing it at a disadvantage.
		2463
		2464	As you can see, the AnyEvent + EV combination even beats the
		2465	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2466	backend easily beats IO::Lambda and POE.
		2467
		2468	And even the 100% non-blocking version written using the high-level (and
		2469	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2470	higher level ("unoptimised") abstractions by a large margin, even though
		2471	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2472
		2473	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2474	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2475	part of the IO::Lambda distribution and were used without any changes.
		2476
		2477
		2478	=head1 SIGNALS
		2479
		2480	AnyEvent currently installs handlers for these signals:
		2481
		2482	=over 4
		2483
		2484	=item SIGCHLD
		2485
		2486	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2487	emulation for event loops that do not support them natively. Also, some
		2488	event loops install a similar handler.
		2489
		2490	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2491	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2492
		2493	=item SIGPIPE
		2494
		2495	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2496	when AnyEvent gets loaded.
		2497
		2498	The rationale for this is that AnyEvent users usually do not really depend
		2499	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2500	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2501	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2502	some random socket.
		2503
		2504	The rationale for installing a no-op handler as opposed to ignoring it is
		2505	that this way, the handler will be restored to defaults on exec.
		2506
		2507	Feel free to install your own handler, or reset it to defaults.
		2508
		2509	=back
		2510
		2511	=cut
		2512
		2513	undef $SIG{CHLD}
		2514	if $SIG{CHLD} eq 'IGNORE';
		2515
		2516	$SIG{PIPE} = sub { }
		2517	unless defined $SIG{PIPE};
		2518
		2519	=head1 RECOMMENDED/OPTIONAL MODULES
		2520
		2521	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2522	its built-in modules) are required to use it.
		2523
		2524	That does not mean that AnyEvent won't take advantage of some additional
		2525	modules if they are installed.
		2526
		2527	This section explains which additional modules will be used, and how they
		2528	affect AnyEvent's operation.
		2529
		2530	=over 4
		2531
		2532	=item L<Async::Interrupt>
		2533
		2534	This slightly arcane module is used to implement fast signal handling: To
		2535	my knowledge, there is no way to do completely race-free and quick
		2536	signal handling in pure perl. To ensure that signals still get
		2537	delivered, AnyEvent will start an interval timer to wake up perl (and
		2538	catch the signals) with some delay (default is 10 seconds, look for
		2539	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2540
		2541	If this module is available, then it will be used to implement signal
		2542	catching, which means that signals will not be delayed, and the event loop
		2543	will not be interrupted regularly, which is more efficient (and good for
		2544	battery life on laptops).
		2545
		2546	This affects not just the pure-perl event loop, but also other event loops
		2547	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2548
		2549	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2550	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2551	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2552	does nothing for those backends.
		2553
		2554	=item L<EV>
		2555
		2556	This module isn't really "optional", as it is simply one of the backend
		2557	event loops that AnyEvent can use. However, it is simply the best event
		2558	loop available in terms of features, speed and stability: It supports
		2559	the AnyEvent API optimally, implements all the watcher types in XS, does
		2560	automatic timer adjustments even when no monotonic clock is available,
		2561	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2562	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2563	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2564
		2565	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2566	then this module will do nothing for you.
		2567
		2568	=item L<Guard>
		2569
		2570	The guard module, when used, will be used to implement
		2571	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2572	lot less memory), but otherwise doesn't affect guard operation much. It is
		2573	purely used for performance.
		2574
		2575	=item L<JSON> and L<JSON::XS>
		2576
		2577	One of these modules is required when you want to read or write JSON data
		2578	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2579	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2580
		2581	=item L<Net::SSLeay>
		2582
		2583	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2584	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2585	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2586
		2587	=item L<Time::HiRes>
		2588
		2589	This module is part of perl since release 5.008. It will be used when the
		2590	chosen event library does not come with a timing source of its own. The
		2591	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2592	try to use a monotonic clock for timing stability.
		2593
		2594	=back
		2595
		2596
		2597	=head1 FORK
		2598
		2599	Most event libraries are not fork-safe. The ones who are usually are
		2600	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2601	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2602	are usually badly thought-out hacks that are incompatible with fork in
		2603	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2604	continue event-processing in both parent and child (or both, if you know
		2605	what you are doing).
		2606
		2607	This means that, in general, you cannot fork and do event processing in
		2608	the child if the event library was initialised before the fork (which
		2609	usually happens when the first AnyEvent watcher is created, or the library
		2610	is loaded).
		2611
		2612	If you have to fork, you must either do so I<before> creating your first
		2613	watcher OR you must not use AnyEvent at all in the child OR you must do
		2614	something completely out of the scope of AnyEvent.
		2615
		2616	The problem of doing event processing in the parent I<and> the child
		2617	is much more complicated: even for backends that I<are> fork-aware or
		2618	fork-safe, their behaviour is not usually what you want: fork clones all
		2619	watchers, that means all timers, I/O watchers etc. are active in both
		2620	parent and child, which is almost never what you want. USing C<exec>
		2621	to start worker children from some kind of manage rprocess is usually
		2622	preferred, because it is much easier and cleaner, at the expense of having
		2623	to have another binary.
		2624
		2625
		2626	=head1 SECURITY CONSIDERATIONS
		2627
		2628	AnyEvent can be forced to load any event model via
		2629	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2630	execute arbitrary code or directly gain access, it can easily be used to
		2631	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2632	will not be active when the program uses a different event model than
		2633	specified in the variable.
		2634
		2635	You can make AnyEvent completely ignore this variable by deleting it
		2636	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2637
		2638	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2639
		2640	use AnyEvent;
		2641
		2642	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2643	be used to probe what backend is used and gain other information (which is
		2644	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2645	$ENV{PERL_ANYEVENT_STRICT}.
		2646
		2647	Note that AnyEvent will remove I<all> environment variables starting with
		2648	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2649	enabled.
		2650
		2651
		2652	=head1 BUGS
		2653
		2654	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2655	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2656	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2657	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2658	pronounced).
		2659
533		2660
534	=head1 SEE ALSO	2661	=head1 SEE ALSO
535		2662
536	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	2663	Utility functions: L<AnyEvent::Util>.
537		2664
538	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	2665	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2666	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
539		2667
540	Nontrivial usage example: L<Net::FCP>.	2668	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2669	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2670	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2671	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
541		2672
542	=head1	2673	Non-blocking file handles, sockets, TCP clients and
		2674	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2675
		2676	Asynchronous DNS: L<AnyEvent::DNS>.
		2677
		2678	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2679	L<Coro::Event>,
		2680
		2681	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2682	L<AnyEvent::HTTP>.
		2683
		2684
		2685	=head1 AUTHOR
		2686
		2687	Marc Lehmann <schmorp@schmorp.de>
		2688	http://home.schmorp.de/
543		2689
544	=cut	2690	=cut
545		2691
546	1	2692	1
547		2693

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