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Revision 1.49 by root, Mon Apr 14 19:11:15 2008 UTC vs.
Revision 1.387 by root, Sat Oct 1 22:39:29 2011 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	FLTK 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	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		58
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		60
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
27		63
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	65	policy> and AnyEvent is I<small and efficient>.
30		66
31	First and foremost, I<AnyEvent is not an event model> itself, it only	67	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	68	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	69	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality, and AnyEvent	70	the statement "there can only be one" is a bitter reality: In general,
35	helps hiding the differences.	71	only one event loop can be active at the same time in a process. AnyEvent
		72	cannot change this, but it can hide the differences between those event
		73	loops.
36		74
37	The goal of AnyEvent is to offer module authors the ability to do event	75	The goal of AnyEvent is to offer module authors the ability to do event
38	programming (waiting for I/O or timer events) without subscribing to a	76	programming (waiting for I/O or timer events) without subscribing to a
39	religion, a way of living, and most importantly: without forcing your	77	religion, a way of living, and most importantly: without forcing your
40	module users into the same thing by forcing them to use the same event	78	module users into the same thing by forcing them to use the same event
41	model you use.	79	model you use.
42		80
43	For modules like POE or IO::Async (which is actually doing all I/O	81	For modules like POE or IO::Async (which is a total misnomer as it is
44	I<synchronously>...), using them in your module is like joining a	82	actually doing all I/O I<synchronously>...), using them in your module is
45	cult: After you joined, you are dependent on them and you cannot use	83	like joining a cult: After you join, you are dependent on them and you
46	anything else, as it is simply incompatible to everything that isn't	84	cannot use anything else, as they are simply incompatible to everything
47	itself.	85	that isn't them. What's worse, all the potential users of your
		86	module are I<also> forced to use the same event loop you use.
48		87
49	AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	works fine etc. etc. but none of these work together with the rest: POE	89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51	+ IO::Async? no go. Tk + Event? no go. If your module uses one of	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
52	those, every user of your module has to use it, too. If your module	91	uses one of those, every user of your module has to use it, too. But if
53	uses AnyEvent, it works transparently with all event models it supports	92	your module uses AnyEvent, it works transparently with all event models it
54	(including stuff like POE and IO::Async).	93	supports (including stuff like IO::Async, as long as those use one of the
		94	supported event loops. It is easy to add new event loops to AnyEvent, too,
		95	so it is future-proof).
55		96
56	In addition of being free of having to use I<the one and only true event	97	In addition to being free of having to use I<the one and only true event
57	model>, AnyEvent also is free of bloat and policy: with POE or similar	98	model>, AnyEvent also is free of bloat and policy: with POE or similar
58	modules, you get an enourmous amount of code and strict rules you have	99	modules, you get an enormous amount of code and strict rules you have to
59	to follow. AnyEvent, on the other hand, is lean and to the point by only	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
60	offering the functionality that is useful, in as thin as a wrapper as	101	offering the functionality that is necessary, in as thin as a wrapper as
61	technically possible.	102	technically possible.
62		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
63	Of course, if you want lots of policy (this can arguably be somewhat	110	Now, if you I<do want> lots of policy (this can arguably be somewhat
64	useful) and you want to force your users to use the one and only event	111	useful) and you want to force your users to use the one and only event
65	model, you should I<not> use this module.	112	model, you should I<not> use this module.
66		113
67
68	=head1 DESCRIPTION	114	=head1 DESCRIPTION
69		115
70	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
71	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
72	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
73	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
74		120
75	The interface itself is vaguely similar but not identical to the Event	121	The interface itself is vaguely similar, but not identical to the L<Event>
76	module.	122	module.
77		123
78	On the first call of any method, the module tries to detect the currently	124	During the first call of any watcher-creation method, the module tries
79	loaded event loop by probing wether any of the following modules is	125	to detect the currently loaded event loop by probing whether one of the
80	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
81	used. If none is found, the module tries to load these modules in the	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
82	order given. The first one that could be successfully loaded will be	128	found is used. If none are detected, the module tries to load the first
83	used. If still none could be found, AnyEvent will fall back to a pure-perl	129	four modules in the order given; but note that if L<EV> is not
84	event loop, which is also not very efficient.	130	available, the pure-perl L<AnyEvent::Loop> should always work, so
		131	the other two are not normally tried.
85		132
86	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
87	an Event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
88	that model the default. For example:	135	that model the default. For example:
89		136
90	use Tk;	137	use Tk;
91	use AnyEvent;	138	use AnyEvent;
92		139
93	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
94		141
		142	The I<likely> means that, if any module loads another event model and
		143	starts using it, all bets are off - this case should be very rare though,
		144	as very few modules hardcode event loops without announcing this very
		145	loudly.
		146
95	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
96	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	other event modules you can load it explicitly and enjoy the high
97	explicitly.	149	availability of that event loop :)
98		150
99	=head1 WATCHERS	151	=head1 WATCHERS
100		152
101	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
102	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
103	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
104		156
105	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
106	creating a watcher it will immediately "watch" for events and invoke	158	creating a watcher it will immediately "watch" for events and invoke the
		159	callback when the event occurs (of course, only when the event model
		160	is in control).
		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
107	the callback. To disable the watcher you have to destroy it (e.g. by	168	To disable a watcher you have to destroy it (e.g. by setting the
108	setting the variable that stores it to C<undef> or otherwise deleting all	169	variable you store it in to C<undef> or otherwise deleting all references
109	references to it).	170	to it).
110		171
111	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
112		173
		174	Many watchers either are used with "recursion" (repeating timers for
		175	example), or need to refer to their watcher object in other ways.
		176
		177	One way to achieve that is this pattern:
		178
		179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		180	# you can use $w here, for example to undef it
		181	undef $w;
		182	});
		183
		184	Note that C<my $w; $w => combination. This is necessary because in Perl,
		185	my variables are only visible after the statement in which they are
		186	declared.
		187
113	=head2 IO WATCHERS	188	=head2 I/O WATCHERS
114		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
115	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
116	the following mandatory arguments:	197	with the following mandatory key-value pairs as arguments:
117		198
118	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
119	events. C<poll> must be a string that is either C<r> or C<w>, that creates	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
120	a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
121	to invoke everytime the filehandle becomes ready.
122		208
123	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	209	C<cb> is the callback to invoke each time the file handle becomes ready.
124	a socket you can have one r + one w, not any more (limitation comes from
125	Tk - if you are sure you are not using Tk this limitation is gone).
126		210
127	Filehandles will be kept alive, so as long as the watcher exists, the	211	Although the callback might get passed parameters, their value and
128	filehandle exists, too.	212	presence is undefined and you cannot rely on them. Portable AnyEvent
		213	callbacks cannot use arguments passed to I/O watcher callbacks.
129		214
130	Example:	215	The I/O watcher might use the underlying file descriptor or a copy of it.
		216	You must not close a file handle as long as any watcher is active on the
		217	underlying file descriptor.
131		218
		219	Some event loops issue spurious readiness notifications, so you should
		220	always use non-blocking calls when reading/writing from/to your file
		221	handles.
		222
132	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
133	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
134	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
135	warn "read: $input\n";	228	warn "read: $input\n";
136	undef $w;	229	undef $w;
137	});	230	});
138		231
139	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
140		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
141	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
142	method with the following mandatory arguments:	243	method with the following mandatory arguments:
143		244
144	C<after> after how many seconds (fractions are supported) should the timer	245	C<after> specifies after how many seconds (fractional values are
145	activate. C<cb> the callback to invoke.	246	supported) the callback should be invoked. C<cb> is the callback to invoke
		247	in that case.
146		248
147	The timer callback will be invoked at most once: if you want a repeating	249	Although the callback might get passed parameters, their value and
148	timer you have to create a new watcher (this is a limitation by both Tk	250	presence is undefined and you cannot rely on them. Portable AnyEvent
149	and Glib).	251	callbacks cannot use arguments passed to time watcher callbacks.
150		252
151	Example:	253	The callback will normally be invoked only once. If you specify another
		254	parameter, C<interval>, as a strictly positive number (> 0), then the
		255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
152		258
		259	The callback will be rescheduled before invoking the callback, but no
		260	attempt is made to avoid timer drift in most backends, so the interval is
		261	only approximate.
		262
153	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
154	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
155	warn "timeout\n";	266	warn "timeout\n";
156	});	267	});
157		268
158	# to cancel the timer:	269	# to cancel the timer:
159	undef $w;	270	undef $w;
160		271
161	=head2 CONDITION WATCHERS	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
162		273
163	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
164	method without any arguments.	275	warn "timeout\n";
		276	};
165		277
166	A condition watcher watches for a condition - precisely that the C<<	278	=head3 TIMING ISSUES
167	->broadcast >> method has been called.
168		279
169	Note that condition watchers recurse into the event loop - if you have	280	There are two ways to handle timers: based on real time (relative, "fire
170	two watchers that call C<< ->wait >> in a round-robbin fashion, you	281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
171	lose. Therefore, condition watchers are good to export to your caller, but	282	o'clock").
172	you should avoid making a blocking wait, at least in callbacks, as this
173	usually asks for trouble.
174		283
175	The watcher has only two methods:	284	While most event loops expect timers to specified in a relative way, they
		285	use absolute time internally. This makes a difference when your clock
		286	"jumps", for example, when ntp decides to set your clock backwards from
		287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		288	fire "after a second" might actually take six years to finally fire.
		289
		290	AnyEvent cannot compensate for this. The only event loop that is conscious
		291	of these issues is L<EV>, which offers both relative (ev_timer, based
		292	on true relative time) and absolute (ev_periodic, based on wallclock time)
		293	timers.
		294
		295	AnyEvent always prefers relative timers, if available, matching the
		296	AnyEvent API.
		297
		298	AnyEvent has two additional methods that return the "current time":
176		299
177	=over 4	300	=over 4
178		301
		302	=item AnyEvent->time
		303
		304	This returns the "current wallclock time" as a fractional number of
		305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
		307
		308	It progresses independently of any event loop processing, i.e. each call
		309	will check the system clock, which usually gets updated frequently.
		310
		311	=item AnyEvent->now
		312
		313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
		317
		318	I<In almost all cases (in all cases if you don't care), this is the
		319	function to call when you want to know the current time.>
		320
		321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update its activity timeouts).
		324
		325	The rest of this section is only of relevance if you try to be very exact
		326	with your timing; you can skip it without a bad conscience.
		327
		328	For a practical example of when these times differ, consider L<Event::Lib>
		329	and L<EV> and the following set-up:
		330
		331	The event loop is running and has just invoked one of your callbacks at
		332	time=500 (assume no other callbacks delay processing). In your callback,
		333	you wait a second by executing C<sleep 1> (blocking the process for a
		334	second) and then (at time=501) you create a relative timer that fires
		335	after three seconds.
		336
		337	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		338	both return C<501>, because that is the current time, and the timer will
		339	be scheduled to fire at time=504 (C<501> + C<3>).
		340
		341	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		342	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		343	last event processing phase started. With L<EV>, your timer gets scheduled
		344	to run at time=503 (C<500> + C<3>).
		345
		346	In one sense, L<Event::Lib> is more exact, as it uses the current time
		347	regardless of any delays introduced by event processing. However, most
		348	callbacks do not expect large delays in processing, so this causes a
		349	higher drift (and a lot more system calls to get the current time).
		350
		351	In another sense, L<EV> is more exact, as your timer will be scheduled at
		352	the same time, regardless of how long event processing actually took.
		353
		354	In either case, if you care (and in most cases, you don't), then you
		355	can get whatever behaviour you want with any event loop, by taking the
		356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		357	account.
		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Loop>) cache the current
		362	time for each loop iteration (see the discussion of L<< AnyEvent->now >>,
		363	above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
		381	=back
		382
		383	=head2 SIGNAL WATCHERS
		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
		387	You can watch for signals using a signal watcher, C<signal> is the signal
		388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
		389	callback to be invoked whenever a signal occurs.
		390
		391	Although the callback might get passed parameters, their value and
		392	presence is undefined and you cannot rely on them. Portable AnyEvent
		393	callbacks cannot use arguments passed to signal watcher callbacks.
		394
		395	Multiple signal occurrences can be clumped together into one callback
		396	invocation, and callback invocation will be synchronous. Synchronous means
		397	that it might take a while until the signal gets handled by the process,
		398	but it is guaranteed not to interrupt any other callbacks.
		399
		400	The main advantage of using these watchers is that you can share a signal
		401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
		403
		404	This watcher might use C<%SIG> (depending on the event loop used),
		405	so programs overwriting those signals directly will likely not work
		406	correctly.
		407
		408	Example: exit on SIGINT
		409
		410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling)
		421	or "unsafe" (asynchronous) - the former might delay signal delivery
		422	indefinitely, the latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support
		432	attaching callbacks to signals in a generic way, which is a pity,
		433	as you cannot do race-free signal handling in perl, requiring
		434	C libraries for this. AnyEvent will try to do its best, which
		435	means in some cases, signals will be delayed. The maximum time
		436	a signal might be delayed is 10 seconds by default, but can
		437	be overriden via C<$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY}> or
		438	C<$AnyEvent::MAX_SIGNAL_LATENCY> - see the Ö<ENVIRONMENT VARIABLES>
		439	section for details.
		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). For those, you just have to suffer the
		445	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 case the latency and race
		486	problems 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:
		578
		579	=over 4
		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
179	=item $cv->wait	708	=item $cv->end
180		709
181	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	710	These two methods can be used to combine many transactions/events into
182	called on c<$cv>, while servicing other watchers normally.	711	one. For example, a function that pings many hosts in parallel might want
		712	to use a condition variable for the whole process.
183		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
184	You can only wait once on a condition - additional calls will return	802	You can only wait once on a condition - additional calls are valid but
185	immediately.	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.
186		817
187	Not all event models support a blocking wait - some die in that case	818	Not all event models support a blocking wait - some die in that case
188	(programs might want to do that so they stay interactive), so I<if you	819	(programs might want to do that to stay interactive), so I<if you are
189	are using this from a module, never require a blocking wait>, but let the	820	using this from a module, never require a blocking wait>. Instead, let the
190	caller decide wether the call will block or not (for example, by coupling	821	caller decide whether the call will block or not (for example, by coupling
191	condition variables with some kind of request results and supporting	822	condition variables with some kind of request results and supporting
192	callbacks so the caller knows that getting the result will not block,	823	callbacks so the caller knows that getting the result will not block,
193	while still suppporting blocking waits if the caller so desires).	824	while still supporting blocking waits if the caller so desires).
194		825
195	Another reason I<never> to C<< ->wait >> in a module is that you cannot	826	You can ensure that C<< ->recv >> never blocks by setting a callback and
196	sensibly have two C<< ->wait >>'s in parallel, as that would require	827	only calling C<< ->recv >> from within that callback (or at a later
197	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	828	time). This will work even when the event loop does not support blocking
198	can supply (the coroutine-aware backends C<Coro::EV> and C<Coro::Event>	829	waits otherwise.
199	explicitly support concurrent C<< ->wait >>'s from different coroutines,
200	however).
201		830
202	=item $cv->broadcast	831	=item $bool = $cv->ready
203		832
204	Flag the condition as ready - a running C<< ->wait >> and all further	833	Returns true when the condition is "true", i.e. whether C<send> or
205	calls to C<wait> will return after this method has been called. If nobody	834	C<croak> have been called.
206	is waiting the broadcast will be remembered..
207		835
208	Example:	836	=item $cb = $cv->cb ($cb->($cv))
209		837
210	# wait till the result is ready	838	This is a mutator function that returns the callback set and optionally
211	my $result_ready = AnyEvent->condvar;	839	replaces it before doing so.
212		840
213	# do something such as adding a timer	841	The callback will be called when the condition becomes "true", i.e. when
214	# or socket watcher the calls $result_ready->broadcast	842	C<send> or C<croak> are called, with the only argument being the
215	# when the "result" is ready.	843	condition variable itself. If the condition is already true, the
216		844	callback is called immediately when it is set. Calling C<recv> inside
217	$result_ready->wait;	845	the callback or at any later time is guaranteed not to block.
218		846
219	=back	847	=back
220		848
221	=head2 SIGNAL WATCHERS	849	=head1 SUPPORTED EVENT LOOPS/BACKENDS
222		850
223	You can listen for signals using a signal watcher, C<signal> is the signal	851	The available backend classes are (every class has its own manpage):
224	I<name> without any C<SIG> prefix. Multiple signals events can be clumped
225	together into one callback invocation, and callback invocation might or
226	might not be asynchronous.
227
228	These watchers might use C<%SIG>, so programs overwriting those signals
229	directly will likely not work correctly.
230
231	Example: exit on SIGINT
232
233	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
234
235	=head2 CHILD PROCESS WATCHERS
236
237	You can also listen for the status of a child process specified by the
238	C<pid> argument (or any child if the pid argument is 0). The watcher will
239	trigger as often as status change for the child are received. This works
240	by installing a signal handler for C<SIGCHLD>. The callback will be called with
241	the pid and exit status (as returned by waitpid).
242
243	Example: wait for pid 1333
244
245	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
246
247	=head1 GLOBALS
248		852
249	=over 4	853	=over 4
250		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 AnyEvent::Loop, 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	AnyEvent::Impl::IOAsync based on IO::Async.
		880	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		881	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		882
		883	=item Backends with special needs.
		884
		885	Qt requires the Qt::Application to be instantiated first, but will
		886	otherwise be picked up automatically. As long as the main program
		887	instantiates the application before any AnyEvent watchers are created,
		888	everything should just work.
		889
		890	AnyEvent::Impl::Qt based on Qt.
		891
		892	=item Event loops that are indirectly supported via other backends.
		893
		894	Some event loops can be supported via other modules:
		895
		896	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		897
		898	B<WxWidgets> has no support for watching file handles. However, you can
		899	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		900	polls 20 times per second, which was considered to be too horrible to even
		901	consider for AnyEvent.
		902
		903	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		904	backend, so it can be supported through POE.
		905
		906	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		907	load L<POE> when detecting them, in the hope that POE will pick them up,
		908	in which case everything will be automatic.
		909
		910	=back
		911
		912	=head1 GLOBAL VARIABLES AND FUNCTIONS
		913
		914	These are not normally required to use AnyEvent, but can be useful to
		915	write AnyEvent extension modules.
		916
		917	=over 4
		918
251	=item $AnyEvent::MODEL	919	=item $AnyEvent::MODEL
252		920
253	Contains C<undef> until the first watcher is being created. Then it	921	Contains C<undef> until the first watcher is being created, before the
		922	backend has been autodetected.
		923
254	contains the event model that is being used, which is the name of the	924	Afterwards it contains the event model that is being used, which is the
255	Perl class implementing the model. This class is usually one of the	925	name of the Perl class implementing the model. This class is usually one
256	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	926	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
257	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	927	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
258		928	will be C<urxvt::anyevent>).
259	The known classes so far are:
260
261	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
262	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
263	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
264	AnyEvent::Impl::Event based on Event, also second best choice :)
265	AnyEvent::Impl::Glib based on Glib, third-best choice.
266	AnyEvent::Impl::Tk based on Tk, very bad choice.
267	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
268		929
269	=item AnyEvent::detect	930	=item AnyEvent::detect
270		931
271	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	932	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
272	necessary. You should only call this function right before you would have	933	if necessary. You should only call this function right before you would
273	created an AnyEvent watcher anyway, that is, very late at runtime.	934	have created an AnyEvent watcher anyway, that is, as late as possible at
		935	runtime, and not e.g. during initialisation of your module.
		936
		937	The effect of calling this function is as if a watcher had been created
		938	(specifically, actions that happen "when the first watcher is created"
		939	happen when calling detetc as well).
		940
		941	If you need to do some initialisation before AnyEvent watchers are
		942	created, use C<post_detect>.
		943
		944	=item $guard = AnyEvent::post_detect { BLOCK }
		945
		946	Arranges for the code block to be executed as soon as the event model is
		947	autodetected (or immediately if that has already happened).
		948
		949	The block will be executed I<after> the actual backend has been detected
		950	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		951	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		952	other initialisations - see the sources of L<AnyEvent::Strict> or
		953	L<AnyEvent::AIO> to see how this is used.
		954
		955	The most common usage is to create some global watchers, without forcing
		956	event module detection too early, for example, L<AnyEvent::AIO> creates
		957	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		958	avoid autodetecting the event module at load time.
		959
		960	If called in scalar or list context, then it creates and returns an object
		961	that automatically removes the callback again when it is destroyed (or
		962	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		963	a case where this is useful.
		964
		965	Example: Create a watcher for the IO::AIO module and store it in
		966	C<$WATCHER>, but do so only do so after the event loop is initialised.
		967
		968	our WATCHER;
		969
		970	my $guard = AnyEvent::post_detect {
		971	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		972	};
		973
		974	# the ||= is important in case post_detect immediately runs the block,
		975	# as to not clobber the newly-created watcher. assigning both watcher and
		976	# post_detect guard to the same variable has the advantage of users being
		977	# able to just C<undef $WATCHER> if the watcher causes them grief.
		978
		979	$WATCHER ||= $guard;
		980
		981	=item @AnyEvent::post_detect
		982
		983	If there are any code references in this array (you can C<push> to it
		984	before or after loading AnyEvent), then they will be called directly
		985	after the event loop has been chosen.
		986
		987	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		988	if it is defined then the event loop has already been detected, and the
		989	array will be ignored.
		990
		991	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		992	it, as it takes care of these details.
		993
		994	This variable is mainly useful for modules that can do something useful
		995	when AnyEvent is used and thus want to know when it is initialised, but do
		996	not need to even load it by default. This array provides the means to hook
		997	into AnyEvent passively, without loading it.
		998
		999	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1000	together, you could put this into Coro (this is the actual code used by
		1001	Coro to accomplish this):
		1002
		1003	if (defined $AnyEvent::MODEL) {
		1004	# AnyEvent already initialised, so load Coro::AnyEvent
		1005	require Coro::AnyEvent;
		1006	} else {
		1007	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1008	# as soon as it is
		1009	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1010	}
		1011
		1012	=item AnyEvent::postpone { BLOCK }
		1013
		1014	Arranges for the block to be executed as soon as possible, but not before
		1015	the call itself returns. In practise, the block will be executed just
		1016	before the event loop polls for new events, or shortly afterwards.
		1017
		1018	This function never returns anything (to make the C<return postpone { ...
		1019	}> idiom more useful.
		1020
		1021	To understand the usefulness of this function, consider a function that
		1022	asynchronously does something for you and returns some transaction
		1023	object or guard to let you cancel the operation. For example,
		1024	C<AnyEvent::Socket::tcp_connect>:
		1025
		1026	# start a conenction attempt unless one is active
		1027	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1028	delete $self->{connect_guard};
		1029	...
		1030	};
		1031
		1032	Imagine that this function could instantly call the callback, for
		1033	example, because it detects an obvious error such as a negative port
		1034	number. Invoking the callback before the function returns causes problems
		1035	however: the callback will be called and will try to delete the guard
		1036	object. But since the function hasn't returned yet, there is nothing to
		1037	delete. When the function eventually returns it will assign the guard
		1038	object to C<< $self->{connect_guard} >>, where it will likely never be
		1039	deleted, so the program thinks it is still trying to connect.
		1040
		1041	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1042	callback directly on error:
		1043
		1044	$cb->(undef), return # signal error to callback, BAD!
		1045	if $some_error_condition;
		1046
		1047	It should use C<postpone>:
		1048
		1049	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1050	if $some_error_condition;
		1051
		1052	=item AnyEvent::log $level, $msg[, @args]
		1053
		1054	Log the given C<$msg> at the given C<$level>.
		1055
		1056	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1057	to see whether the message will be logged. If the test succeeds it will
		1058	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1059	the L<AnyEvent::Log> documentation for details.
		1060
		1061	If the test fails it will simply return. Right now this happens when a
		1062	numerical loglevel is used and it is larger than the level specified via
		1063	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1064
		1065	If you want to sprinkle loads of logging calls around your code, consider
		1066	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1067	which can reduce typing, codesize and can reduce the logging overhead
		1068	enourmously.
274		1069
275	=back	1070	=back
276		1071
277	=head1 WHAT TO DO IN A MODULE	1072	=head1 WHAT TO DO IN A MODULE
278		1073
279	As a module author, you should "use AnyEvent" and call AnyEvent methods	1074	As a module author, you should C<use AnyEvent> and call AnyEvent methods
280	freely, but you should not load a specific event module or rely on it.	1075	freely, but you should not load a specific event module or rely on it.
281		1076
282	Be careful when you create watchers in the module body - Anyevent will	1077	Be careful when you create watchers in the module body - AnyEvent will
283	decide which event module to use as soon as the first method is called, so	1078	decide which event module to use as soon as the first method is called, so
284	by calling AnyEvent in your module body you force the user of your module	1079	by calling AnyEvent in your module body you force the user of your module
285	to load the event module first.	1080	to load the event module first.
286		1081
		1082	Never call C<< ->recv >> on a condition variable unless you I<know> that
		1083	the C<< ->send >> method has been called on it already. This is
		1084	because it will stall the whole program, and the whole point of using
		1085	events is to stay interactive.
		1086
		1087	It is fine, however, to call C<< ->recv >> when the user of your module
		1088	requests it (i.e. if you create a http request object ad have a method
		1089	called C<results> that returns the results, it may call C<< ->recv >>
		1090	freely, as the user of your module knows what she is doing. Always).
		1091
287	=head1 WHAT TO DO IN THE MAIN PROGRAM	1092	=head1 WHAT TO DO IN THE MAIN PROGRAM
288		1093
289	There will always be a single main program - the only place that should	1094	There will always be a single main program - the only place that should
290	dictate which event model to use.	1095	dictate which event model to use.
291		1096
292	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1097	If the program is not event-based, it need not do anything special, even
293	do anything special and let AnyEvent decide which implementation to chose.	1098	when it depends on a module that uses an AnyEvent. If the program itself
		1099	uses AnyEvent, but does not care which event loop is used, all it needs
		1100	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1101	available loop implementation.
294		1102
295	If the main program relies on a specific event model (for example, in Gtk2	1103	If the main program relies on a specific event model - for example, in
296	programs you have to rely on either Glib or Glib::Event), you should load	1104	Gtk2 programs you have to rely on the Glib module - you should load the
297	it before loading AnyEvent or any module that uses it, generally, as early	1105	event module before loading AnyEvent or any module that uses it: generally
298	as possible. The reason is that modules might create watchers when they	1106	speaking, you should load it as early as possible. The reason is that
299	are loaded, and AnyEvent will decide on the event model to use as soon as	1107	modules might create watchers when they are loaded, and AnyEvent will
300	it creates watchers, and it might chose the wrong one unless you load the	1108	decide on the event model to use as soon as it creates watchers, and it
301	correct one yourself.	1109	might choose the wrong one unless you load the correct one yourself.
302		1110
303	You can chose to use a rather inefficient pure-perl implementation by	1111	You can chose to use a pure-perl implementation by loading the
304	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	1112	C<AnyEvent::Loop> module, which gives you similar behaviour
305	generally better.	1113	everywhere, but letting AnyEvent chose the model is generally better.
		1114
		1115	=head2 MAINLOOP EMULATION
		1116
		1117	Sometimes (often for short test scripts, or even standalone programs who
		1118	only want to use AnyEvent), you do not want to run a specific event loop.
		1119
		1120	In that case, you can use a condition variable like this:
		1121
		1122	AnyEvent->condvar->recv;
		1123
		1124	This has the effect of entering the event loop and looping forever.
		1125
		1126	Note that usually your program has some exit condition, in which case
		1127	it is better to use the "traditional" approach of storing a condition
		1128	variable somewhere, waiting for it, and sending it when the program should
		1129	exit cleanly.
		1130
		1131
		1132	=head1 OTHER MODULES
		1133
		1134	The following is a non-exhaustive list of additional modules that use
		1135	AnyEvent as a client and can therefore be mixed easily with other
		1136	AnyEvent modules and other event loops in the same program. Some of the
		1137	modules come as part of AnyEvent, the others are available via CPAN (see
		1138	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1139	a longer non-exhaustive list), and the list is heavily biased towards
		1140	modules of the AnyEvent author himself :)
		1141
		1142	=over 4
		1143
		1144	=item L<AnyEvent::Util>
		1145
		1146	Contains various utility functions that replace often-used blocking
		1147	functions such as C<inet_aton> with event/callback-based versions.
		1148
		1149	=item L<AnyEvent::Socket>
		1150
		1151	Provides various utility functions for (internet protocol) sockets,
		1152	addresses and name resolution. Also functions to create non-blocking tcp
		1153	connections or tcp servers, with IPv6 and SRV record support and more.
		1154
		1155	=item L<AnyEvent::Handle>
		1156
		1157	Provide read and write buffers, manages watchers for reads and writes,
		1158	supports raw and formatted I/O, I/O queued and fully transparent and
		1159	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1160
		1161	=item L<AnyEvent::DNS>
		1162
		1163	Provides rich asynchronous DNS resolver capabilities.
		1164
		1165	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1166
		1167	Implement event-based interfaces to the protocols of the same name (for
		1168	the curious, IGS is the International Go Server and FCP is the Freenet
		1169	Client Protocol).
		1170
		1171	=item L<AnyEvent::AIO>
		1172
		1173	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1174	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1175	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1176	file I/O, and much more.
		1177
		1178	=item L<AnyEvent::Filesys::Notify>
		1179
		1180	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1181	path changes (e.g. "watch this directory for new files", "watch this
		1182	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1183	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1184	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1185	fall back to blocking scans at regular intervals transparently on other
		1186	platforms, so it's about as portable as it gets.
		1187
		1188	(I haven't used it myself, but I haven't heard anybody complaining about
		1189	it yet).
		1190
		1191	=item L<AnyEvent::DBI>
		1192
		1193	Executes L<DBI> requests asynchronously in a proxy process for you,
		1194	notifying you in an event-based way when the operation is finished.
		1195
		1196	=item L<AnyEvent::HTTPD>
		1197
		1198	A simple embedded webserver.
		1199
		1200	=item L<AnyEvent::FastPing>
		1201
		1202	The fastest ping in the west.
		1203
		1204	=item L<Coro>
		1205
		1206	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1207	to simply invert the flow control - don't call us, we will call you:
		1208
		1209	async {
		1210	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1211	print "5 seconds later!\n";
		1212
		1213	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1214	my $line = <STDIN>; # works for ttys
		1215
		1216	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1217	my ($body, $hdr) = Coro::rouse_wait;
		1218	};
		1219
		1220	=back
306		1221
307	=cut	1222	=cut
308		1223
309	package AnyEvent;	1224	package AnyEvent;
310		1225
311	no warnings;	1226	# basically a tuned-down version of common::sense
312	use strict;	1227	sub common_sense {
		1228	# from common:.sense 3.4
		1229	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1230	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1231	$^H |= 0x00000600;
		1232	}
313		1233
		1234	BEGIN { AnyEvent::common_sense }
		1235
314	use Carp;	1236	use Carp ();
315		1237
316	our $VERSION = '3.0';	1238	our $VERSION = '6.02';
317	our $MODEL;	1239	our $MODEL;
318
319	our $AUTOLOAD;
320	our @ISA;	1240	our @ISA;
321
322	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
323
324	our @REGISTRY;	1241	our @REGISTRY;
		1242	our $VERBOSE;
		1243	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1244	our $MAX_SIGNAL_LATENCY = $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} || 10; # executes after the BEGIN block below (tainting!)
325		1245
		1246	BEGIN {
		1247	require "AnyEvent/constants.pl";
		1248
		1249	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1250
		1251	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1252	if ${^TAINT};
		1253
		1254	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1255	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1256
		1257	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1258	if ${^TAINT};
		1259
		1260	# $ENV{PERL_ANYEVENT_xxx} now valid
		1261
		1262	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 4;
		1263
		1264	my $idx;
		1265	$PROTOCOL{$_} = ++$idx
		1266	for reverse split /\s*,\s*/,
		1267	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1268	}
		1269
		1270	our @post_detect;
		1271
		1272	sub post_detect(&) {
		1273	my ($cb) = @_;
		1274
		1275	push @post_detect, $cb;
		1276
		1277	defined wantarray
		1278	? bless \$cb, "AnyEvent::Util::postdetect"
		1279	: ()
		1280	}
		1281
		1282	sub AnyEvent::Util::postdetect::DESTROY {
		1283	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1284	}
		1285
		1286	our $POSTPONE_W;
		1287	our @POSTPONE;
		1288
		1289	sub _postpone_exec {
		1290	undef $POSTPONE_W;
		1291
		1292	&{ shift @POSTPONE }
		1293	while @POSTPONE;
		1294	}
		1295
		1296	sub postpone(&) {
		1297	push @POSTPONE, shift;
		1298
		1299	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1300
		1301	()
		1302	}
		1303
		1304	sub log($$;@) {
		1305	# only load the big bloated module when we actually are about to log something
		1306	if ($_[0] <= ($VERBOSE || 1)) { # also catches non-numeric levels(!) and fatal
		1307	require AnyEvent::Log; # among other things, sets $VERBOSE to 9
		1308	# AnyEvent::Log overwrites this function
		1309	goto &log;
		1310	}
		1311
		1312	0 # not logged
		1313	}
		1314
		1315	sub logger($;$) {
		1316	package AnyEvent::Log;
		1317
		1318	my ($level, $renabled) = @_;
		1319
		1320	$$renabled = $level <= $VERBOSE;
		1321
		1322	my $pkg = (caller)[0];
		1323
		1324	my $logger = [$pkg, $level, $renabled];
		1325
		1326	our %LOGGER;
		1327	$LOGGER{$logger+0} = $logger;
		1328
		1329	require AnyEvent::Util;
		1330	my $guard = AnyEvent::Util::guard (sub {
		1331	# "clean up"
		1332	delete $LOGGER{$logger+0};
		1333	});
		1334
		1335	sub {
		1336	return 0 unless $$renabled;
		1337
		1338	$guard if 0; # keep guard alive, but don't cause runtime overhead
		1339	require AnyEvent::Log unless $AnyEvent::Log::VERSION;
		1340	package AnyEvent::Log;
		1341	_log ($logger->[0], $level, @_) # logger->[0] has been converted at load time
		1342	}
		1343	}
		1344
		1345	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1346	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1347	}
		1348
326	my @models = (	1349	our @models = (
327	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
328	[EV:: => AnyEvent::Impl::EV::],	1350	[EV:: => AnyEvent::Impl::EV::],
329	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],	1351	[AnyEvent::Loop:: => AnyEvent::Impl::Perl::],
		1352	# everything below here will not (normally) be autoprobed
		1353	# as the pure perl backend should work everywhere
		1354	# and is usually faster
		1355	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package, so msut be near the top
330	[Event:: => AnyEvent::Impl::Event::],	1356	[Event:: => AnyEvent::Impl::Event::], # slow, stable
331	[Glib:: => AnyEvent::Impl::Glib::],	1357	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1358	# everything below here should not be autoloaded
		1359	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1360	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1361	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1362	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
332	[Tk:: => AnyEvent::Impl::Tk::],	1363	[Wx:: => AnyEvent::Impl::POE::],
333	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1364	[Prima:: => AnyEvent::Impl::POE::],
		1365	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
		1366	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
		1367	[FLTK:: => AnyEvent::Impl::FLTK::],
334	);	1368	);
335		1369
336	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1370	our @isa_hook;
		1371
		1372	sub _isa_set {
		1373	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1374
		1375	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1376	for 1 .. $#pkg;
		1377
		1378	grep $_ && $_->[1], @isa_hook
		1379	and AE::_reset ();
		1380	}
		1381
		1382	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1383	sub _isa_hook($$;$) {
		1384	my ($i, $pkg, $reset_ae) = @_;
		1385
		1386	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1387
		1388	_isa_set;
		1389	}
		1390
		1391	# all autoloaded methods reserve the complete glob, not just the method slot.
		1392	# due to bugs in perls method cache implementation.
		1393	our @methods = qw(io timer time now now_update signal child idle condvar);
337		1394
338	sub detect() {	1395	sub detect() {
		1396	return $MODEL if $MODEL; # some programs keep references to detect
		1397
		1398	# IO::Async::Loop::AnyEvent is extremely evil, refuse to work with it
		1399	# the author knows about the problems and what it does to AnyEvent as a whole
		1400	# (and the ability of others to use AnyEvent), but simply wants to abuse AnyEvent
		1401	# anyway.
		1402	AnyEvent::log fatal => "AnyEvent: IO::Async::Loop::AnyEvent detected - this module is broken by design,\n"
		1403	. "abuses internals and breaks AnyEvent, will not continue."
		1404	if exists $INC{"IO/Async/Loop/AnyEvent.pm"};
		1405
		1406	local $!; # for good measure
		1407	local $SIG{__DIE__}; # we use eval
		1408
		1409	# free some memory
		1410	*detect = sub () { $MODEL };
		1411	# undef &func doesn't correctly update the method cache. grmbl.
		1412	# so we delete the whole glob. grmbl.
		1413	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1414	# a glob with an active sub. hrm. i hope it works, but perl is
		1415	# usually buggy in this department. sigh.
		1416	delete @{"AnyEvent::"}{@methods};
		1417	undef @methods;
		1418
		1419	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1420	my $model = $1;
		1421	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1422	if (eval "require $model") {
		1423	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1424	$MODEL = $model;
		1425	} else {
		1426	AnyEvent::log 4 => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1427	}
		1428	}
		1429
		1430	# check for already loaded models
339	unless ($MODEL) {	1431	unless ($MODEL) {
340	no strict 'refs';
341
342	# check for already loaded models
343	for (@REGISTRY, @models) {	1432	for (@REGISTRY, @models) {
344	my ($package, $model) = @$_;	1433	my ($package, $model) = @$_;
345	if (${"$package\::VERSION"} > 0) {	1434	if (${"$package\::VERSION"} > 0) {
346	if (eval "require $model") {	1435	if (eval "require $model") {
		1436	AnyEvent::log 7 => "autodetected model '$model', using it.";
347	$MODEL = $model;	1437	$MODEL = $model;
348	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;
349	last;	1438	last;
350	}	1439	}
351	}	1440	}
352	}	1441	}
353		1442
354	unless ($MODEL) {	1443	unless ($MODEL) {
355	# try to load a model	1444	# try to autoload a model
356
357	for (@REGISTRY, @models) {	1445	for (@REGISTRY, @models) {
358	my ($package, $model) = @$_;	1446	my ($package, $model) = @$_;
		1447	if (
359	if (eval "require $package"	1448	eval "require $package"
360	and ${"$package\::VERSION"} > 0	1449	and ${"$package\::VERSION"} > 0
361	and eval "require $model") {	1450	and eval "require $model"
		1451	) {
		1452	AnyEvent::log 7 => "autoloaded model '$model', using it.";
362	$MODEL = $model;	1453	$MODEL = $model;
363	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
364	last;	1454	last;
365	}	1455	}
366	}	1456	}
367		1457
368	$MODEL	1458	$MODEL
369	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event), Glib or Tk.";	1459	or AnyEvent::log fatal => "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
370	}	1460	}
371
372	unshift @ISA, $MODEL;
373	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
374	}	1461	}
375		1462
		1463	# free memory only needed for probing
		1464	undef @models;
		1465	undef @REGISTRY;
		1466
		1467	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1468
		1469	# now nuke some methods that are overridden by the backend.
		1470	# SUPER usage is not allowed in these.
		1471	for (qw(time signal child idle)) {
		1472	undef &{"AnyEvent::Base::$_"}
		1473	if defined &{"$MODEL\::$_"};
		1474	}
		1475
		1476	_isa_set;
		1477
		1478	# we're officially open!
		1479
		1480	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1481	require AnyEvent::Strict;
		1482	}
		1483
		1484	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1485	require AnyEvent::Debug;
		1486	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1487	}
		1488
		1489	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1490	require AnyEvent::Socket;
		1491	require AnyEvent::Debug;
		1492
		1493	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1494	$shell =~ s/\$\$/$$/g;
		1495
		1496	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1497	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1498	}
		1499
		1500	# now the anyevent environment is set up as the user told us to, so
		1501	# call the actual user code - post detects
		1502
		1503	(shift @post_detect)->() while @post_detect;
		1504	undef @post_detect;
		1505
		1506	*post_detect = sub(&) {
		1507	shift->();
		1508
		1509	undef
		1510	};
		1511
376	$MODEL	1512	$MODEL
377	}	1513	}
378		1514
379	sub AUTOLOAD {	1515	for my $name (@methods) {
380	(my $func = $AUTOLOAD) =~ s/.*://;	1516	*$name = sub {
381		1517	detect;
382	$method{$func}	1518	# we use goto because
383	or croak "$func: not a valid method for AnyEvent objects";	1519	# a) it makes the thunk more transparent
384		1520	# b) it allows us to delete the thunk later
385	detect unless $MODEL;	1521	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
386		1522	};
387	my $class = shift;
388	$class->$func (@_);
389	}	1523	}
		1524
		1525	# utility function to dup a filehandle. this is used by many backends
		1526	# to support binding more than one watcher per filehandle (they usually
		1527	# allow only one watcher per fd, so we dup it to get a different one).
		1528	sub _dupfh($$;$$) {
		1529	my ($poll, $fh, $r, $w) = @_;
		1530
		1531	# cygwin requires the fh mode to be matching, unix doesn't
		1532	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1533
		1534	open my $fh2, $mode, $fh
		1535	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1536
		1537	# we assume CLOEXEC is already set by perl in all important cases
		1538
		1539	($fh2, $rw)
		1540	}
		1541
		1542	=head1 SIMPLIFIED AE API
		1543
		1544	Starting with version 5.0, AnyEvent officially supports a second, much
		1545	simpler, API that is designed to reduce the calling, typing and memory
		1546	overhead by using function call syntax and a fixed number of parameters.
		1547
		1548	See the L<AE> manpage for details.
		1549
		1550	=cut
		1551
		1552	package AE;
		1553
		1554	our $VERSION = $AnyEvent::VERSION;
		1555
		1556	sub _reset() {
		1557	eval q{
		1558	# fall back to the main API by default - backends and AnyEvent::Base
		1559	# implementations can overwrite these.
		1560
		1561	sub io($$$) {
		1562	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1563	}
		1564
		1565	sub timer($$$) {
		1566	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1567	}
		1568
		1569	sub signal($$) {
		1570	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1571	}
		1572
		1573	sub child($$) {
		1574	AnyEvent->child (pid => $_[0], cb => $_[1])
		1575	}
		1576
		1577	sub idle($) {
		1578	AnyEvent->idle (cb => $_[0]);
		1579	}
		1580
		1581	sub cv(;&) {
		1582	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1583	}
		1584
		1585	sub now() {
		1586	AnyEvent->now
		1587	}
		1588
		1589	sub now_update() {
		1590	AnyEvent->now_update
		1591	}
		1592
		1593	sub time() {
		1594	AnyEvent->time
		1595	}
		1596
		1597	*postpone = \&AnyEvent::postpone;
		1598	*log = \&AnyEvent::log;
		1599	};
		1600	die if $@;
		1601	}
		1602
		1603	BEGIN { _reset }
390		1604
391	package AnyEvent::Base;	1605	package AnyEvent::Base;
392		1606
		1607	# default implementations for many methods
		1608
		1609	sub time {
		1610	eval q{ # poor man's autoloading {}
		1611	# probe for availability of Time::HiRes
		1612	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1613	*time = sub { Time::HiRes::time () };
		1614	*AE::time = \& Time::HiRes::time ;
		1615	*now = \&time;
		1616	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy.";
		1617	# if (eval "use POSIX (); (POSIX::times())...
		1618	} else {
		1619	*time = sub { CORE::time };
		1620	*AE::time = sub (){ CORE::time };
		1621	*now = \&time;
		1622	AnyEvent::log 3 => "using built-in time(), WARNING, no sub-second resolution!";
		1623	}
		1624	};
		1625	die if $@;
		1626
		1627	&time
		1628	}
		1629
		1630	*now = \&time;
		1631	sub now_update { }
		1632
		1633	sub _poll {
		1634	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1635	}
		1636
393	# default implementation for ->condvar, ->wait, ->broadcast	1637	# default implementation for ->condvar
		1638	# in fact, the default should not be overwritten
394		1639
395	sub condvar {	1640	sub condvar {
396	bless \my $flag, "AnyEvent::Base::CondVar"	1641	eval q{ # poor man's autoloading {}
397	}	1642	*condvar = sub {
		1643	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1644	};
398		1645
399	sub AnyEvent::Base::CondVar::broadcast {	1646	*AE::cv = sub (;&) {
400	${$_[0]}++;	1647	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
401	}	1648	};
		1649	};
		1650	die if $@;
402		1651
403	sub AnyEvent::Base::CondVar::wait {	1652	&condvar
404	AnyEvent->one_event while !${$_[0]};
405	}	1653	}
406		1654
407	# default implementation for ->signal	1655	# default implementation for ->signal
408		1656
409	our %SIG_CB;	1657	our $HAVE_ASYNC_INTERRUPT;
		1658
		1659	sub _have_async_interrupt() {
		1660	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1661	&& eval "use Async::Interrupt 1.02 (); 1")
		1662	unless defined $HAVE_ASYNC_INTERRUPT;
		1663
		1664	$HAVE_ASYNC_INTERRUPT
		1665	}
		1666
		1667	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1668	our (%SIG_ASY, %SIG_ASY_W);
		1669	our ($SIG_COUNT, $SIG_TW);
		1670
		1671	# install a dummy wakeup watcher to reduce signal catching latency
		1672	# used by Impls
		1673	sub _sig_add() {
		1674	unless ($SIG_COUNT++) {
		1675	# try to align timer on a full-second boundary, if possible
		1676	my $NOW = AE::now;
		1677
		1678	$SIG_TW = AE::timer
		1679	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1680	$MAX_SIGNAL_LATENCY,
		1681	sub { } # just for the PERL_ASYNC_CHECK
		1682	;
		1683	}
		1684	}
		1685
		1686	sub _sig_del {
		1687	undef $SIG_TW
		1688	unless --$SIG_COUNT;
		1689	}
		1690
		1691	our $_sig_name_init; $_sig_name_init = sub {
		1692	eval q{ # poor man's autoloading {}
		1693	undef $_sig_name_init;
		1694
		1695	if (_have_async_interrupt) {
		1696	*sig2num = \&Async::Interrupt::sig2num;
		1697	*sig2name = \&Async::Interrupt::sig2name;
		1698	} else {
		1699	require Config;
		1700
		1701	my %signame2num;
		1702	@signame2num{ split ' ', $Config::Config{sig_name} }
		1703	= split ' ', $Config::Config{sig_num};
		1704
		1705	my @signum2name;
		1706	@signum2name[values %signame2num] = keys %signame2num;
		1707
		1708	*sig2num = sub($) {
		1709	$_[0] > 0 ? shift : $signame2num{+shift}
		1710	};
		1711	*sig2name = sub ($) {
		1712	$_[0] > 0 ? $signum2name[+shift] : shift
		1713	};
		1714	}
		1715	};
		1716	die if $@;
		1717	};
		1718
		1719	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1720	sub sig2name($) { &$_sig_name_init; &sig2name }
410		1721
411	sub signal {	1722	sub signal {
		1723	eval q{ # poor man's autoloading {}
		1724	# probe for availability of Async::Interrupt
		1725	if (_have_async_interrupt) {
		1726	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling.";
		1727
		1728	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1729	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1730
		1731	} else {
		1732	AnyEvent::log 8 => "using emulated perl signal handling with latency timer.";
		1733
		1734	if (AnyEvent::WIN32) {
		1735	require AnyEvent::Util;
		1736
		1737	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1738	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1739	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1740	} else {
		1741	pipe $SIGPIPE_R, $SIGPIPE_W;
		1742	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1743	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1744
		1745	# not strictly required, as $^F is normally 2, but let's make sure...
		1746	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1747	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1748	}
		1749
		1750	$SIGPIPE_R
		1751	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1752
		1753	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1754	}
		1755
		1756	*signal = $HAVE_ASYNC_INTERRUPT
		1757	? sub {
412	my (undef, %arg) = @_;	1758	my (undef, %arg) = @_;
413		1759
		1760	# async::interrupt
414	my $signal = uc $arg{signal}	1761	my $signal = sig2num $arg{signal};
415	or Carp::croak "required option 'signal' is missing";
416
417	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1762	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1763
		1764	$SIG_ASY{$signal} ||= new Async::Interrupt
		1765	cb => sub { undef $SIG_EV{$signal} },
		1766	signal => $signal,
		1767	pipe => [$SIGPIPE_R->filenos],
		1768	pipe_autodrain => 0,
		1769	;
		1770
		1771	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1772	}
		1773	: sub {
		1774	my (undef, %arg) = @_;
		1775
		1776	# pure perl
		1777	my $signal = sig2name $arg{signal};
		1778	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1779
418	$SIG{$signal} ||= sub {	1780	$SIG{$signal} ||= sub {
		1781	local $!;
		1782	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1783	undef $SIG_EV{$signal};
		1784	};
		1785
		1786	# can't do signal processing without introducing races in pure perl,
		1787	# so limit the signal latency.
		1788	_sig_add;
		1789
		1790	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1791	}
		1792	;
		1793
		1794	*AnyEvent::Base::signal::DESTROY = sub {
		1795	my ($signal, $cb) = @{$_[0]};
		1796
		1797	_sig_del;
		1798
		1799	delete $SIG_CB{$signal}{$cb};
		1800
		1801	$HAVE_ASYNC_INTERRUPT
		1802	? delete $SIG_ASY{$signal}
		1803	: # delete doesn't work with older perls - they then
		1804	# print weird messages, or just unconditionally exit
		1805	# instead of getting the default action.
		1806	undef $SIG{$signal}
		1807	unless keys %{ $SIG_CB{$signal} };
		1808	};
		1809
		1810	*_signal_exec = sub {
		1811	$HAVE_ASYNC_INTERRUPT
		1812	? $SIGPIPE_R->drain
		1813	: sysread $SIGPIPE_R, (my $dummy), 9;
		1814
		1815	while (%SIG_EV) {
		1816	for (keys %SIG_EV) {
		1817	delete $SIG_EV{$_};
419	$_->() for values %{ $SIG_CB{$signal} || {} };	1818	&$_ for values %{ $SIG_CB{$_} || {} };
		1819	}
		1820	}
		1821	};
420	};	1822	};
		1823	die if $@;
421		1824
422	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1825	&signal
423	}
424
425	sub AnyEvent::Base::Signal::DESTROY {
426	my ($signal, $cb) = @{$_[0]};
427
428	delete $SIG_CB{$signal}{$cb};
429
430	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
431	}	1826	}
432		1827
433	# default implementation for ->child	1828	# default implementation for ->child
434		1829
435	our %PID_CB;	1830	our %PID_CB;
436	our $CHLD_W;	1831	our $CHLD_W;
437	our $CHLD_DELAY_W;	1832	our $CHLD_DELAY_W;
438	our $PID_IDLE;
439	our $WNOHANG;
440		1833
441	sub _child_wait {	1834	# used by many Impl's
442	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1835	sub _emit_childstatus($$) {
		1836	my (undef, $rpid, $rstatus) = @_;
		1837
		1838	$_->($rpid, $rstatus)
443	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1839	for values %{ $PID_CB{$rpid} || {} },
444	(values %{ $PID_CB{0} || {} });	1840	values %{ $PID_CB{0} || {} };
		1841	}
		1842
		1843	sub child {
		1844	eval q{ # poor man's autoloading {}
		1845	*_sigchld = sub {
		1846	my $pid;
		1847
		1848	AnyEvent->_emit_childstatus ($pid, $?)
		1849	while ($pid = waitpid -1, WNOHANG) > 0;
		1850	};
		1851
		1852	*child = sub {
		1853	my (undef, %arg) = @_;
		1854
		1855	my $pid = $arg{pid};
		1856	my $cb = $arg{cb};
		1857
		1858	$PID_CB{$pid}{$cb+0} = $cb;
		1859
		1860	unless ($CHLD_W) {
		1861	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1862	# child could be a zombie already, so make at least one round
		1863	&_sigchld;
		1864	}
		1865
		1866	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1867	};
		1868
		1869	*AnyEvent::Base::child::DESTROY = sub {
		1870	my ($pid, $icb) = @{$_[0]};
		1871
		1872	delete $PID_CB{$pid}{$icb};
		1873	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1874
		1875	undef $CHLD_W unless keys %PID_CB;
		1876	};
		1877	};
		1878	die if $@;
		1879
		1880	&child
		1881	}
		1882
		1883	# idle emulation is done by simply using a timer, regardless
		1884	# of whether the process is idle or not, and not letting
		1885	# the callback use more than 50% of the time.
		1886	sub idle {
		1887	eval q{ # poor man's autoloading {}
		1888	*idle = sub {
		1889	my (undef, %arg) = @_;
		1890
		1891	my ($cb, $w, $rcb) = $arg{cb};
		1892
		1893	$rcb = sub {
		1894	if ($cb) {
		1895	$w = AE::time;
		1896	&$cb;
		1897	$w = AE::time - $w;
		1898
		1899	# never use more then 50% of the time for the idle watcher,
		1900	# within some limits
		1901	$w = 0.0001 if $w < 0.0001;
		1902	$w = 5 if $w > 5;
		1903
		1904	$w = AE::timer $w, 0, $rcb;
		1905	} else {
		1906	# clean up...
		1907	undef $w;
		1908	undef $rcb;
		1909	}
		1910	};
		1911
		1912	$w = AE::timer 0.05, 0, $rcb;
		1913
		1914	bless \\$cb, "AnyEvent::Base::idle"
		1915	};
		1916
		1917	*AnyEvent::Base::idle::DESTROY = sub {
		1918	undef $${$_[0]};
		1919	};
		1920	};
		1921	die if $@;
		1922
		1923	&idle
		1924	}
		1925
		1926	package AnyEvent::CondVar;
		1927
		1928	our @ISA = AnyEvent::CondVar::Base::;
		1929
		1930	# only to be used for subclassing
		1931	sub new {
		1932	my $class = shift;
		1933	bless AnyEvent->condvar (@_), $class
		1934	}
		1935
		1936	package AnyEvent::CondVar::Base;
		1937
		1938	#use overload
		1939	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1940	# fallback => 1;
		1941
		1942	# save 300+ kilobytes by dirtily hardcoding overloading
		1943	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1944	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1945	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1946	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1947
		1948	our $WAITING;
		1949
		1950	sub _send {
		1951	# nop
		1952	}
		1953
		1954	sub _wait {
		1955	AnyEvent->_poll until $_[0]{_ae_sent};
		1956	}
		1957
		1958	sub send {
		1959	my $cv = shift;
		1960	$cv->{_ae_sent} = [@_];
		1961	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1962	$cv->_send;
		1963	}
		1964
		1965	sub croak {
		1966	$_[0]{_ae_croak} = $_[1];
		1967	$_[0]->send;
		1968	}
		1969
		1970	sub ready {
		1971	$_[0]{_ae_sent}
		1972	}
		1973
		1974	sub recv {
		1975	unless ($_[0]{_ae_sent}) {
		1976	$WAITING
		1977	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1978
		1979	local $WAITING = 1;
		1980	$_[0]->_wait;
445	}	1981	}
446		1982
447	undef $PID_IDLE;	1983	$_[0]{_ae_croak}
448	}	1984	and Carp::croak $_[0]{_ae_croak};
449		1985
450	sub _sigchld {	1986	wantarray
451	# make sure we deliver these changes "synchronous" with the event loop.	1987	? @{ $_[0]{_ae_sent} }
452	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1988	: $_[0]{_ae_sent}[0]
453	undef $CHLD_DELAY_W;
454	&_child_wait;
455	});
456	}	1989	}
457		1990
458	sub child {	1991	sub cb {
459	my (undef, %arg) = @_;	1992	my $cv = shift;
460		1993
461	defined (my $pid = $arg{pid} + 0)	1994	@_
462	or Carp::croak "required option 'pid' is missing";	1995	and $cv->{_ae_cb} = shift
		1996	and $cv->{_ae_sent}
		1997	and (delete $cv->{_ae_cb})->($cv);
463		1998
464	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1999	$cv->{_ae_cb}
465
466	unless ($WNOHANG) {
467	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
468	}
469
470	unless ($CHLD_W) {
471	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
472	# child could be a zombie already, so make at least one round
473	&_sigchld;
474	}
475
476	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
477	}	2000	}
478		2001
479	sub AnyEvent::Base::Child::DESTROY {	2002	sub begin {
480	my ($pid, $cb) = @{$_[0]};	2003	++$_[0]{_ae_counter};
481		2004	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
482	delete $PID_CB{$pid}{$cb};
483	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
484
485	undef $CHLD_W unless keys %PID_CB;
486	}	2005	}
		2006
		2007	sub end {
		2008	return if --$_[0]{_ae_counter};
		2009	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		2010	}
		2011
		2012	# undocumented/compatibility with pre-3.4
		2013	*broadcast = \&send;
		2014	*wait = \&recv;
		2015
		2016	=head1 ERROR AND EXCEPTION HANDLING
		2017
		2018	In general, AnyEvent does not do any error handling - it relies on the
		2019	caller to do that if required. The L<AnyEvent::Strict> module (see also
		2020	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		2021	checking of all AnyEvent methods, however, which is highly useful during
		2022	development.
		2023
		2024	As for exception handling (i.e. runtime errors and exceptions thrown while
		2025	executing a callback), this is not only highly event-loop specific, but
		2026	also not in any way wrapped by this module, as this is the job of the main
		2027	program.
		2028
		2029	The pure perl event loop simply re-throws the exception (usually
		2030	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		2031	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		2032	so on.
		2033
		2034	=head1 ENVIRONMENT VARIABLES
		2035
		2036	AnyEvent supports a number of environment variables that tune the
		2037	runtime behaviour. They are usually evaluated when AnyEvent is
		2038	loaded, initialised, or a submodule that uses them is loaded. Many of
		2039	them also cause AnyEvent to load additional modules - for example,
		2040	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2041	loaded.
		2042
		2043	All the environment variables documented here start with
		2044	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2045	namespace. Other modules are encouraged (but by no means required) to use
		2046	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2047	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2048	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2049	variables starting with C<AE_>, see below).
		2050
		2051	All variables can also be set via the C<AE_> prefix, that is, instead
		2052	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2053	case there is a clash btween anyevent and another program that uses
		2054	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2055	variable to the empty string, as those variables take precedence.
		2056
		2057	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2058	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2059	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2060	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2061	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2062	is set).
		2063
		2064	The exact algorithm is currently:
		2065
		2066	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2067	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2068	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2069
		2070	This ensures that child processes will not see the C<AE_> variables.
		2071
		2072	The following environment variables are currently known to AnyEvent:
		2073
		2074	=over 4
		2075
		2076	=item C<PERL_ANYEVENT_VERBOSE>
		2077
		2078	By default, AnyEvent will only log messages with loglevel C<3>
		2079	(C<critical>) or higher (see L<AnyEvent::Log>). You can set this
		2080	environment variable to a numerical loglevel to make AnyEvent more (or
		2081	less) talkative.
		2082
		2083	If you want to do more than just set the global logging level
		2084	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2085	complex specifications.
		2086
		2087	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2088	the default logging settings.
		2089
		2090	When set to C<5> or higher (C<warn>), causes AnyEvent to warn about
		2091	unexpected conditions, such as not being able to load the event model
		2092	specified by C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an
		2093	exception - this is the minimum recommended level.
		2094
		2095	When set to C<7> or higher (info), cause AnyEvent to report which event model it
		2096	chooses.
		2097
		2098	When set to C<8> or higher (debug), then AnyEvent will report extra information on
		2099	which optional modules it loads and how it implements certain features.
		2100
		2101	=item C<PERL_ANYEVENT_LOG>
		2102
		2103	Accepts rather complex logging specifications. For example, you could log
		2104	all C<debug> messages of some module to stderr, warnings and above to
		2105	stderr, and errors and above to syslog, with:
		2106
		2107	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2108
		2109	For the rather extensive details, see L<AnyEvent::Log>.
		2110
		2111	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2112	so will take effect even before AnyEvent has initialised itself.
		2113
		2114	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2115	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2116	using the latter saves a few hundred kB of memory until the first message
		2117	is being logged.
		2118
		2119	=item C<PERL_ANYEVENT_STRICT>
		2120
		2121	AnyEvent does not do much argument checking by default, as thorough
		2122	argument checking is very costly. Setting this variable to a true value
		2123	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2124	check the arguments passed to most method calls. If it finds any problems,
		2125	it will croak.
		2126
		2127	In other words, enables "strict" mode.
		2128
		2129	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2130	>>, it is definitely recommended to keep it off in production. Keeping
		2131	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2132	can be very useful, however.
		2133
		2134	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2135
		2136	If this env variable is nonempty, then its contents will be interpreted by
		2137	C<AnyEvent::Socket::parse_hostport> and C<AnyEvent::Debug::shell> (after
		2138	replacing every occurance of C<$$> by the process pid). The shell object
		2139	is saved in C<$AnyEvent::Debug::SHELL>.
		2140
		2141	This happens when the first watcher is created.
		2142
		2143	For example, to bind a debug shell on a unix domain socket in
		2144	F<< /tmp/debug<pid>.sock >>, you could use this:
		2145
		2146	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2147	# connect with e.g.: socat readline /tmp/debug123.sock
		2148
		2149	Or to bind to tcp port 4545 on localhost:
		2150
		2151	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		2152	# connect with e.g.: telnet localhost 4545
		2153
		2154	Note that creating sockets in F</tmp> or on localhost is very unsafe on
		2155	multiuser systems.
		2156
		2157	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2158
		2159	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2160	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2161
		2162	=item C<PERL_ANYEVENT_MODEL>
		2163
		2164	This can be used to specify the event model to be used by AnyEvent, before
		2165	auto detection and -probing kicks in.
		2166
		2167	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2168	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2169	resulting module name is loaded and - if the load was successful - used as
		2170	event model backend. If it fails to load then AnyEvent will proceed with
		2171	auto detection and -probing.
		2172
		2173	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2174	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2175	the end of a string designates a module name and quotes it appropriately).
		2176
		2177	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2178	could start your program like this:
		2179
		2180	PERL_ANYEVENT_MODEL=Perl perl ...
		2181
		2182	=item C<PERL_ANYEVENT_PROTOCOLS>
		2183
		2184	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2185	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2186	of auto probing).
		2187
		2188	Must be set to a comma-separated list of protocols or address families,
		2189	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2190	used, and preference will be given to protocols mentioned earlier in the
		2191	list.
		2192
		2193	This variable can effectively be used for denial-of-service attacks
		2194	against local programs (e.g. when setuid), although the impact is likely
		2195	small, as the program has to handle conenction and other failures anyways.
		2196
		2197	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2198	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2199	- only support IPv4, never try to resolve or contact IPv6
		2200	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2201	IPv6, but prefer IPv6 over IPv4.
		2202
		2203	=item C<PERL_ANYEVENT_HOSTS>
		2204
		2205	This variable, if specified, overrides the F</etc/hosts> file used by
		2206	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2207	from that file instead.
		2208
		2209	=item C<PERL_ANYEVENT_EDNS0>
		2210
		2211	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2212	DNS. This extension is generally useful to reduce DNS traffic, especially
		2213	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2214	packets, which is why it is off by default.
		2215
		2216	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2217	EDNS0 in its DNS requests.
		2218
		2219	=item C<PERL_ANYEVENT_MAX_FORKS>
		2220
		2221	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2222	will create in parallel.
		2223
		2224	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2225
		2226	The default value for the C<max_outstanding> parameter for the default DNS
		2227	resolver - this is the maximum number of parallel DNS requests that are
		2228	sent to the DNS server.
		2229
		2230	=item C<PERL_ANYEVENT_MAX_SIGNAL_LATENCY>
		2231
		2232	Perl has inherently racy signal handling (you can basically choose between
		2233	losing signals and memory corruption) - pure perl event loops (including
		2234	C<AnyEvent::Loop>, when C<Async::Interrupt> isn't available) therefore
		2235	have to poll regularly to avoid losing signals.
		2236
		2237	Some event loops are racy, but don't poll regularly, and some event loops
		2238	are written in C but are still racy. For those event loops, AnyEvent
		2239	installs a timer that regularly wakes up the event loop.
		2240
		2241	By default, the interval for this timer is C<10> seconds, but you can
		2242	override this delay with this environment variable (or by setting
		2243	the C<$AnyEvent::MAX_SIGNAL_LATENCY> variable before creating signal
		2244	watchers).
		2245
		2246	Lower values increase CPU (and energy) usage, higher values can introduce
		2247	long delays when reaping children or waiting for signals.
		2248
		2249	The L<AnyEvent::Async> module, if available, will be used to avoid this
		2250	polling (with most event loops).
		2251
		2252	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2253
		2254	The absolute path to a F<resolv.conf>-style file to use instead of
		2255	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2256	resolver, or the empty string to select the default configuration.
		2257
		2258	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2259
		2260	When neither C<ca_file> nor C<ca_path> was specified during
		2261	L<AnyEvent::TLS> context creation, and either of these environment
		2262	variables are nonempty, they will be used to specify CA certificate
		2263	locations instead of a system-dependent default.
		2264
		2265	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2266
		2267	When these are set to C<1>, then the respective modules are not
		2268	loaded. Mostly good for testing AnyEvent itself.
		2269
		2270	=back
487		2271
488	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2272	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		2273
		2274	This is an advanced topic that you do not normally need to use AnyEvent in
		2275	a module. This section is only of use to event loop authors who want to
		2276	provide AnyEvent compatibility.
489		2277
490	If you need to support another event library which isn't directly	2278	If you need to support another event library which isn't directly
491	supported by AnyEvent, you can supply your own interface to it by	2279	supported by AnyEvent, you can supply your own interface to it by
492	pushing, before the first watcher gets created, the package name of	2280	pushing, before the first watcher gets created, the package name of
493	the event module and the package name of the interface to use onto	2281	the event module and the package name of the interface to use onto
494	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	2282	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
495	AnyEvent.	2283	AnyEvent, so it is reasonably cheap.
496		2284
497	Example:	2285	Example:
498		2286
499	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	2287	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
500		2288
501	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	2289	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
502	package/class when it finds the C<urxvt> package/module is loaded. When	2290	package/class when it finds the C<urxvt> package/module is already loaded.
		2291
503	AnyEvent is loaded and asked to find a suitable event model, it will	2292	When AnyEvent is loaded and asked to find a suitable event model, it
504	first check for the presence of urxvt.	2293	will first check for the presence of urxvt by trying to C<use> the
		2294	C<urxvt::anyevent> module.
505		2295
506	The class should provide implementations for all watcher types (see	2296	The class should provide implementations for all watcher types. See
507	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	2297	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
508	(Source code) and so on for actual examples, use C<perldoc -m	2298	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
509	AnyEvent::Impl::Glib> to see the sources).	2299	see the sources.
510		2300
		2301	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		2302	provide suitable (hopefully) replacements.
		2303
511	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	2304	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
512	uses the above line as-is. An interface isn't included in AnyEvent	2305	terminal emulator uses the above line as-is. An interface isn't included
513	because it doesn't make sense outside the embedded interpreter inside	2306	in AnyEvent because it doesn't make sense outside the embedded interpreter
514	I<rxvt-unicode>, and it is updated and maintained as part of the	2307	inside I<rxvt-unicode>, and it is updated and maintained as part of the
515	I<rxvt-unicode> distribution.	2308	I<rxvt-unicode> distribution.
516		2309
517	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2310	I<rxvt-unicode> also cheats a bit by not providing blocking access to
518	condition variables: code blocking while waiting for a condition will	2311	condition variables: code blocking while waiting for a condition will
519	C<die>. This still works with most modules/usages, and blocking calls must	2312	C<die>. This still works with most modules/usages, and blocking calls must
520	not be in an interactive application, so it makes sense.	2313	not be done in an interactive application, so it makes sense.
521		2314
522	=head1 ENVIRONMENT VARIABLES
523
524	The following environment variables are used by this module:
525
526	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
527	model gets used.
528
529	=head1 EXAMPLE	2315	=head1 EXAMPLE PROGRAM
530		2316
531	The following program uses an io watcher to read data from stdin, a timer	2317	The following program uses an I/O watcher to read data from STDIN, a timer
532	to display a message once per second, and a condvar to exit the program	2318	to display a message once per second, and a condition variable to quit the
533	when the user enters quit:	2319	program when the user enters quit:
534		2320
535	use AnyEvent;	2321	use AnyEvent;
536		2322
537	my $cv = AnyEvent->condvar;	2323	my $cv = AnyEvent->condvar;
538		2324
539	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	2325	my $io_watcher = AnyEvent->io (
		2326	fh => \*STDIN,
		2327	poll => 'r',
		2328	cb => sub {
540	warn "io event <$_[0]>\n"; # will always output <r>	2329	warn "io event <$_[0]>\n"; # will always output <r>
541	chomp (my $input = <STDIN>); # read a line	2330	chomp (my $input = <STDIN>); # read a line
542	warn "read: $input\n"; # output what has been read	2331	warn "read: $input\n"; # output what has been read
543	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2332	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		2333	},
		2334	);
		2335
		2336	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
		2337	warn "timeout\n"; # print 'timeout' at most every second
544	});	2338	});
545		2339
546	my $time_watcher; # can only be used once
547
548	sub new_timer {
549	$timer = AnyEvent->timer (after => 1, cb => sub {
550	warn "timeout\n"; # print 'timeout' about every second
551	&new_timer; # and restart the time
552	});
553	}
554
555	new_timer; # create first timer
556
557	$cv->wait; # wait until user enters /^q/i	2340	$cv->recv; # wait until user enters /^q/i
558		2341
559	=head1 REAL-WORLD EXAMPLE	2342	=head1 REAL-WORLD EXAMPLE
560		2343
561	Consider the L<Net::FCP> module. It features (among others) the following	2344	Consider the L<Net::FCP> module. It features (among others) the following
562	API calls, which are to freenet what HTTP GET requests are to http:	2345	API calls, which are to freenet what HTTP GET requests are to http:
…		…
612	syswrite $txn->{fh}, $txn->{request}	2395	syswrite $txn->{fh}, $txn->{request}
613	or die "connection or write error";	2396	or die "connection or write error";
614	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2397	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
615		2398
616	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2399	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
617	result and signals any possible waiters that the request ahs finished:	2400	result and signals any possible waiters that the request has finished:
618		2401
619	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2402	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
620		2403
621	if (end-of-file or data complete) {	2404	if (end-of-file or data complete) {
622	$txn->{result} = $txn->{buf};	2405	$txn->{result} = $txn->{buf};
623	$txn->{finished}->broadcast;	2406	$txn->{finished}->send;
624	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2407	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
625	}	2408	}
626		2409
627	The C<result> method, finally, just waits for the finished signal (if the	2410	The C<result> method, finally, just waits for the finished signal (if the
628	request was already finished, it doesn't wait, of course, and returns the	2411	request was already finished, it doesn't wait, of course, and returns the
629	data:	2412	data:
630		2413
631	$txn->{finished}->wait;	2414	$txn->{finished}->recv;
632	return $txn->{result};	2415	return $txn->{result};
633		2416
634	The actual code goes further and collects all errors (C<die>s, exceptions)	2417	The actual code goes further and collects all errors (C<die>s, exceptions)
635	that occured during request processing. The C<result> method detects	2418	that occurred during request processing. The C<result> method detects
636	wether an exception as thrown (it is stored inside the $txn object)	2419	whether an exception as thrown (it is stored inside the $txn object)
637	and just throws the exception, which means connection errors and other	2420	and just throws the exception, which means connection errors and other
638	problems get reported tot he code that tries to use the result, not in a	2421	problems get reported to the code that tries to use the result, not in a
639	random callback.	2422	random callback.
640		2423
641	All of this enables the following usage styles:	2424	All of this enables the following usage styles:
642		2425
643	1. Blocking:	2426	1. Blocking:
…		…
671		2454
672	my $quit = AnyEvent->condvar;	2455	my $quit = AnyEvent->condvar;
673		2456
674	$fcp->txn_client_get ($url)->cb (sub {	2457	$fcp->txn_client_get ($url)->cb (sub {
675	...	2458	...
676	$quit->broadcast;	2459	$quit->send;
677	});	2460	});
678		2461
679	$quit->wait;	2462	$quit->recv;
		2463
		2464
		2465	=head1 BENCHMARKS
		2466
		2467	To give you an idea of the performance and overheads that AnyEvent adds
		2468	over the event loops themselves and to give you an impression of the speed
		2469	of various event loops I prepared some benchmarks.
		2470
		2471	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2472
		2473	Here is a benchmark of various supported event models used natively and
		2474	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2475	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2476	which it is), lets them fire exactly once and destroys them again.
		2477
		2478	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2479	distribution. It uses the L<AE> interface, which makes a real difference
		2480	for the EV and Perl backends only.
		2481
		2482	=head3 Explanation of the columns
		2483
		2484	I<watcher> is the number of event watchers created/destroyed. Since
		2485	different event models feature vastly different performances, each event
		2486	loop was given a number of watchers so that overall runtime is acceptable
		2487	and similar between tested event loop (and keep them from crashing): Glib
		2488	would probably take thousands of years if asked to process the same number
		2489	of watchers as EV in this benchmark.
		2490
		2491	I<bytes> is the number of bytes (as measured by the resident set size,
		2492	RSS) consumed by each watcher. This method of measuring captures both C
		2493	and Perl-based overheads.
		2494
		2495	I<create> is the time, in microseconds (millionths of seconds), that it
		2496	takes to create a single watcher. The callback is a closure shared between
		2497	all watchers, to avoid adding memory overhead. That means closure creation
		2498	and memory usage is not included in the figures.
		2499
		2500	I<invoke> is the time, in microseconds, used to invoke a simple
		2501	callback. The callback simply counts down a Perl variable and after it was
		2502	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2503	signal the end of this phase.
		2504
		2505	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2506	watcher.
		2507
		2508	=head3 Results
		2509
		2510	name watchers bytes create invoke destroy comment
		2511	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2512	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2513	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2514	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2515	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2516	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2517	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2518	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2519	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2520	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2521	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2522	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2523
		2524	=head3 Discussion
		2525
		2526	The benchmark does I<not> measure scalability of the event loop very
		2527	well. For example, a select-based event loop (such as the pure perl one)
		2528	can never compete with an event loop that uses epoll when the number of
		2529	file descriptors grows high. In this benchmark, all events become ready at
		2530	the same time, so select/poll-based implementations get an unnatural speed
		2531	boost.
		2532
		2533	Also, note that the number of watchers usually has a nonlinear effect on
		2534	overall speed, that is, creating twice as many watchers doesn't take twice
		2535	the time - usually it takes longer. This puts event loops tested with a
		2536	higher number of watchers at a disadvantage.
		2537
		2538	To put the range of results into perspective, consider that on the
		2539	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2540	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2541	cycles with POE.
		2542
		2543	C<EV> is the sole leader regarding speed and memory use, which are both
		2544	maximal/minimal, respectively. When using the L<AE> API there is zero
		2545	overhead (when going through the AnyEvent API create is about 5-6 times
		2546	slower, with other times being equal, so still uses far less memory than
		2547	any other event loop and is still faster than Event natively).
		2548
		2549	The pure perl implementation is hit in a few sweet spots (both the
		2550	constant timeout and the use of a single fd hit optimisations in the perl
		2551	interpreter and the backend itself). Nevertheless this shows that it
		2552	adds very little overhead in itself. Like any select-based backend its
		2553	performance becomes really bad with lots of file descriptors (and few of
		2554	them active), of course, but this was not subject of this benchmark.
		2555
		2556	The C<Event> module has a relatively high setup and callback invocation
		2557	cost, but overall scores in on the third place.
		2558
		2559	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2560	when using its pure perl backend.
		2561
		2562	C<Glib>'s memory usage is quite a bit higher, but it features a
		2563	faster callback invocation and overall ends up in the same class as
		2564	C<Event>. However, Glib scales extremely badly, doubling the number of
		2565	watchers increases the processing time by more than a factor of four,
		2566	making it completely unusable when using larger numbers of watchers
		2567	(note that only a single file descriptor was used in the benchmark, so
		2568	inefficiencies of C<poll> do not account for this).
		2569
		2570	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2571	more than 2000 watchers is a big setback, however, as correctness takes
		2572	precedence over speed. Nevertheless, its performance is surprising, as the
		2573	file descriptor is dup()ed for each watcher. This shows that the dup()
		2574	employed by some adaptors is not a big performance issue (it does incur a
		2575	hidden memory cost inside the kernel which is not reflected in the figures
		2576	above).
		2577
		2578	C<POE>, regardless of underlying event loop (whether using its pure perl
		2579	select-based backend or the Event module, the POE-EV backend couldn't
		2580	be tested because it wasn't working) shows abysmal performance and
		2581	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2582	as EV watchers, and 10 times as much memory as Event (the high memory
		2583	requirements are caused by requiring a session for each watcher). Watcher
		2584	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2585	implementation.
		2586
		2587	The design of the POE adaptor class in AnyEvent can not really account
		2588	for the performance issues, though, as session creation overhead is
		2589	small compared to execution of the state machine, which is coded pretty
		2590	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2591	using multiple sessions is not a good approach, especially regarding
		2592	memory usage, even the author of POE could not come up with a faster
		2593	design).
		2594
		2595	=head3 Summary
		2596
		2597	=over 4
		2598
		2599	=item * Using EV through AnyEvent is faster than any other event loop
		2600	(even when used without AnyEvent), but most event loops have acceptable
		2601	performance with or without AnyEvent.
		2602
		2603	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2604	the actual event loop, only with extremely fast event loops such as EV
		2605	does AnyEvent add significant overhead.
		2606
		2607	=item * You should avoid POE like the plague if you want performance or
		2608	reasonable memory usage.
		2609
		2610	=back
		2611
		2612	=head2 BENCHMARKING THE LARGE SERVER CASE
		2613
		2614	This benchmark actually benchmarks the event loop itself. It works by
		2615	creating a number of "servers": each server consists of a socket pair, a
		2616	timeout watcher that gets reset on activity (but never fires), and an I/O
		2617	watcher waiting for input on one side of the socket. Each time the socket
		2618	watcher reads a byte it will write that byte to a random other "server".
		2619
		2620	The effect is that there will be a lot of I/O watchers, only part of which
		2621	are active at any one point (so there is a constant number of active
		2622	fds for each loop iteration, but which fds these are is random). The
		2623	timeout is reset each time something is read because that reflects how
		2624	most timeouts work (and puts extra pressure on the event loops).
		2625
		2626	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2627	(1%) are active. This mirrors the activity of large servers with many
		2628	connections, most of which are idle at any one point in time.
		2629
		2630	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2631	distribution. It uses the L<AE> interface, which makes a real difference
		2632	for the EV and Perl backends only.
		2633
		2634	=head3 Explanation of the columns
		2635
		2636	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2637	each server has a read and write socket end).
		2638
		2639	I<create> is the time it takes to create a socket pair (which is
		2640	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2641
		2642	I<request>, the most important value, is the time it takes to handle a
		2643	single "request", that is, reading the token from the pipe and forwarding
		2644	it to another server. This includes deleting the old timeout and creating
		2645	a new one that moves the timeout into the future.
		2646
		2647	=head3 Results
		2648
		2649	name sockets create request
		2650	EV 20000 62.66 7.99
		2651	Perl 20000 68.32 32.64
		2652	IOAsync 20000 174.06 101.15 epoll
		2653	IOAsync 20000 174.67 610.84 poll
		2654	Event 20000 202.69 242.91
		2655	Glib 20000 557.01 1689.52
		2656	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2657
		2658	=head3 Discussion
		2659
		2660	This benchmark I<does> measure scalability and overall performance of the
		2661	particular event loop.
		2662
		2663	EV is again fastest. Since it is using epoll on my system, the setup time
		2664	is relatively high, though.
		2665
		2666	Perl surprisingly comes second. It is much faster than the C-based event
		2667	loops Event and Glib.
		2668
		2669	IO::Async performs very well when using its epoll backend, and still quite
		2670	good compared to Glib when using its pure perl backend.
		2671
		2672	Event suffers from high setup time as well (look at its code and you will
		2673	understand why). Callback invocation also has a high overhead compared to
		2674	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2675	uses select or poll in basically all documented configurations.
		2676
		2677	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2678	clearly fails to perform with many filehandles or in busy servers.
		2679
		2680	POE is still completely out of the picture, taking over 1000 times as long
		2681	as EV, and over 100 times as long as the Perl implementation, even though
		2682	it uses a C-based event loop in this case.
		2683
		2684	=head3 Summary
		2685
		2686	=over 4
		2687
		2688	=item * The pure perl implementation performs extremely well.
		2689
		2690	=item * Avoid Glib or POE in large projects where performance matters.
		2691
		2692	=back
		2693
		2694	=head2 BENCHMARKING SMALL SERVERS
		2695
		2696	While event loops should scale (and select-based ones do not...) even to
		2697	large servers, most programs we (or I :) actually write have only a few
		2698	I/O watchers.
		2699
		2700	In this benchmark, I use the same benchmark program as in the large server
		2701	case, but it uses only eight "servers", of which three are active at any
		2702	one time. This should reflect performance for a small server relatively
		2703	well.
		2704
		2705	The columns are identical to the previous table.
		2706
		2707	=head3 Results
		2708
		2709	name sockets create request
		2710	EV 16 20.00 6.54
		2711	Perl 16 25.75 12.62
		2712	Event 16 81.27 35.86
		2713	Glib 16 32.63 15.48
		2714	POE 16 261.87 276.28 uses POE::Loop::Event
		2715
		2716	=head3 Discussion
		2717
		2718	The benchmark tries to test the performance of a typical small
		2719	server. While knowing how various event loops perform is interesting, keep
		2720	in mind that their overhead in this case is usually not as important, due
		2721	to the small absolute number of watchers (that is, you need efficiency and
		2722	speed most when you have lots of watchers, not when you only have a few of
		2723	them).
		2724
		2725	EV is again fastest.
		2726
		2727	Perl again comes second. It is noticeably faster than the C-based event
		2728	loops Event and Glib, although the difference is too small to really
		2729	matter.
		2730
		2731	POE also performs much better in this case, but is is still far behind the
		2732	others.
		2733
		2734	=head3 Summary
		2735
		2736	=over 4
		2737
		2738	=item * C-based event loops perform very well with small number of
		2739	watchers, as the management overhead dominates.
		2740
		2741	=back
		2742
		2743	=head2 THE IO::Lambda BENCHMARK
		2744
		2745	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2746	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2747	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2748	shouldn't come as a surprise to anybody). As such, the benchmark is
		2749	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2750	very optimal. But how would AnyEvent compare when used without the extra
		2751	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2752
		2753	The benchmark itself creates an echo-server, and then, for 500 times,
		2754	connects to the echo server, sends a line, waits for the reply, and then
		2755	creates the next connection. This is a rather bad benchmark, as it doesn't
		2756	test the efficiency of the framework or much non-blocking I/O, but it is a
		2757	benchmark nevertheless.
		2758
		2759	name runtime
		2760	Lambda/select 0.330 sec
		2761	+ optimized 0.122 sec
		2762	Lambda/AnyEvent 0.327 sec
		2763	+ optimized 0.138 sec
		2764	Raw sockets/select 0.077 sec
		2765	POE/select, components 0.662 sec
		2766	POE/select, raw sockets 0.226 sec
		2767	POE/select, optimized 0.404 sec
		2768
		2769	AnyEvent/select/nb 0.085 sec
		2770	AnyEvent/EV/nb 0.068 sec
		2771	+state machine 0.134 sec
		2772
		2773	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2774	benchmarks actually make blocking connects and use 100% blocking I/O,
		2775	defeating the purpose of an event-based solution. All of the newly
		2776	written AnyEvent benchmarks use 100% non-blocking connects (using
		2777	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2778	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2779	generally require a lot more bookkeeping and event handling than blocking
		2780	connects (which involve a single syscall only).
		2781
		2782	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2783	offers similar expressive power as POE and IO::Lambda, using conventional
		2784	Perl syntax. This means that both the echo server and the client are 100%
		2785	non-blocking, further placing it at a disadvantage.
		2786
		2787	As you can see, the AnyEvent + EV combination even beats the
		2788	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2789	backend easily beats IO::Lambda and POE.
		2790
		2791	And even the 100% non-blocking version written using the high-level (and
		2792	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2793	higher level ("unoptimised") abstractions by a large margin, even though
		2794	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2795
		2796	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2797	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2798	part of the IO::Lambda distribution and were used without any changes.
		2799
		2800
		2801	=head1 SIGNALS
		2802
		2803	AnyEvent currently installs handlers for these signals:
		2804
		2805	=over 4
		2806
		2807	=item SIGCHLD
		2808
		2809	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2810	emulation for event loops that do not support them natively. Also, some
		2811	event loops install a similar handler.
		2812
		2813	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2814	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2815
		2816	=item SIGPIPE
		2817
		2818	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2819	when AnyEvent gets loaded.
		2820
		2821	The rationale for this is that AnyEvent users usually do not really depend
		2822	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2823	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2824	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2825	some random socket.
		2826
		2827	The rationale for installing a no-op handler as opposed to ignoring it is
		2828	that this way, the handler will be restored to defaults on exec.
		2829
		2830	Feel free to install your own handler, or reset it to defaults.
		2831
		2832	=back
		2833
		2834	=cut
		2835
		2836	undef $SIG{CHLD}
		2837	if $SIG{CHLD} eq 'IGNORE';
		2838
		2839	$SIG{PIPE} = sub { }
		2840	unless defined $SIG{PIPE};
		2841
		2842	=head1 RECOMMENDED/OPTIONAL MODULES
		2843
		2844	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2845	its built-in modules) are required to use it.
		2846
		2847	That does not mean that AnyEvent won't take advantage of some additional
		2848	modules if they are installed.
		2849
		2850	This section explains which additional modules will be used, and how they
		2851	affect AnyEvent's operation.
		2852
		2853	=over 4
		2854
		2855	=item L<Async::Interrupt>
		2856
		2857	This slightly arcane module is used to implement fast signal handling: To
		2858	my knowledge, there is no way to do completely race-free and quick
		2859	signal handling in pure perl. To ensure that signals still get
		2860	delivered, AnyEvent will start an interval timer to wake up perl (and
		2861	catch the signals) with some delay (default is 10 seconds, look for
		2862	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2863
		2864	If this module is available, then it will be used to implement signal
		2865	catching, which means that signals will not be delayed, and the event loop
		2866	will not be interrupted regularly, which is more efficient (and good for
		2867	battery life on laptops).
		2868
		2869	This affects not just the pure-perl event loop, but also other event loops
		2870	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2871
		2872	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2873	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2874	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2875	does nothing for those backends.
		2876
		2877	=item L<EV>
		2878
		2879	This module isn't really "optional", as it is simply one of the backend
		2880	event loops that AnyEvent can use. However, it is simply the best event
		2881	loop available in terms of features, speed and stability: It supports
		2882	the AnyEvent API optimally, implements all the watcher types in XS, does
		2883	automatic timer adjustments even when no monotonic clock is available,
		2884	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2885	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2886	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2887
		2888	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2889	then this module will do nothing for you.
		2890
		2891	=item L<Guard>
		2892
		2893	The guard module, when used, will be used to implement
		2894	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2895	lot less memory), but otherwise doesn't affect guard operation much. It is
		2896	purely used for performance.
		2897
		2898	=item L<JSON> and L<JSON::XS>
		2899
		2900	One of these modules is required when you want to read or write JSON data
		2901	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2902	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2903
		2904	=item L<Net::SSLeay>
		2905
		2906	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2907	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2908	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2909
		2910	=item L<Time::HiRes>
		2911
		2912	This module is part of perl since release 5.008. It will be used when the
		2913	chosen event library does not come with a timing source of its own. The
		2914	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2915	try to use a monotonic clock for timing stability.
		2916
		2917	=back
		2918
		2919
		2920	=head1 FORK
		2921
		2922	Most event libraries are not fork-safe. The ones who are usually are
		2923	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2924	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2925	are usually badly thought-out hacks that are incompatible with fork in
		2926	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2927	continue event-processing in both parent and child (or both, if you know
		2928	what you are doing).
		2929
		2930	This means that, in general, you cannot fork and do event processing in
		2931	the child if the event library was initialised before the fork (which
		2932	usually happens when the first AnyEvent watcher is created, or the library
		2933	is loaded).
		2934
		2935	If you have to fork, you must either do so I<before> creating your first
		2936	watcher OR you must not use AnyEvent at all in the child OR you must do
		2937	something completely out of the scope of AnyEvent.
		2938
		2939	The problem of doing event processing in the parent I<and> the child
		2940	is much more complicated: even for backends that I<are> fork-aware or
		2941	fork-safe, their behaviour is not usually what you want: fork clones all
		2942	watchers, that means all timers, I/O watchers etc. are active in both
		2943	parent and child, which is almost never what you want. USing C<exec>
		2944	to start worker children from some kind of manage rprocess is usually
		2945	preferred, because it is much easier and cleaner, at the expense of having
		2946	to have another binary.
		2947
		2948
		2949	=head1 SECURITY CONSIDERATIONS
		2950
		2951	AnyEvent can be forced to load any event model via
		2952	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2953	execute arbitrary code or directly gain access, it can easily be used to
		2954	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2955	will not be active when the program uses a different event model than
		2956	specified in the variable.
		2957
		2958	You can make AnyEvent completely ignore this variable by deleting it
		2959	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2960
		2961	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2962
		2963	use AnyEvent;
		2964
		2965	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2966	be used to probe what backend is used and gain other information (which is
		2967	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2968	$ENV{PERL_ANYEVENT_STRICT}.
		2969
		2970	Note that AnyEvent will remove I<all> environment variables starting with
		2971	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2972	enabled.
		2973
		2974
		2975	=head1 BUGS
		2976
		2977	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2978	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2979	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2980	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2981	pronounced).
		2982
680		2983
681	=head1 SEE ALSO	2984	=head1 SEE ALSO
682		2985
683	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2986	Tutorial/Introduction: L<AnyEvent::Intro>.
684	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>.
685		2987
686	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2988	FAQ: L<AnyEvent::FAQ>.
		2989
		2990	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2991	(simply logging).
		2992
		2993	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2994	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2995
		2996	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2997	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2998	L<Qt>, L<POE>, L<FLTK>.
		2999
687	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	3000	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
688	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.	3001	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		3002	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		3003	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
		3004	L<AnyEvent::Impl::FLTK>.
689		3005
		3006	Non-blocking handles, pipes, stream sockets, TCP clients and
		3007	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		3008
		3009	Asynchronous DNS: L<AnyEvent::DNS>.
		3010
		3011	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		3012
690	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	3013	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		3014	L<AnyEvent::HTTP>.
691		3015
692	=head1	3016
		3017	=head1 AUTHOR
		3018
		3019	Marc Lehmann <schmorp@schmorp.de>
		3020	http://home.schmorp.de/
693		3021
694	=cut	3022	=cut
695		3023
696	1	3024	1
697		3025

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