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Revision 1.23 by root, Wed Mar 7 17:37:24 2007 UTC vs.
Revision 1.365 by root, Tue Aug 16 14:47:26 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	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.
		58
		59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		60
		61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		62	nowadays. So what is different about AnyEvent?
		63
		64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		65	policy> and AnyEvent is I<small and efficient>.
		66
		67	First and foremost, I<AnyEvent is not an event model> itself, it only
		68	interfaces to whatever event model the main program happens to use, in a
		69	pragmatic way. For event models and certain classes of immortals alike,
		70	the statement "there can only be one" is a bitter reality: In general,
		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.
		74
		75	The goal of AnyEvent is to offer module authors the ability to do event
		76	programming (waiting for I/O or timer events) without subscribing to a
		77	religion, a way of living, and most importantly: without forcing your
		78	module users into the same thing by forcing them to use the same event
		79	model you use.
		80
		81	For modules like POE or IO::Async (which is a total misnomer as it is
		82	actually doing all I/O I<synchronously>...), using them in your module is
		83	like joining a cult: After you join, you are dependent on them and you
		84	cannot use anything else, as they are simply incompatible to everything
		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.
		87
		88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
		91	uses one of those, every user of your module has to use it, too. But if
		92	your module uses AnyEvent, it works transparently with all event models it
		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).
		96
		97	In addition to being free of having to use I<the one and only true event
		98	model>, AnyEvent also is free of bloat and policy: with POE or similar
		99	modules, you get an enormous amount of code and strict rules you have to
		100	follow. AnyEvent, on the other hand, is lean and to the point, by only
		101	offering the functionality that is necessary, in as thin as a wrapper as
		102	technically possible.
		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
		110	Now, if you I<do want> lots of policy (this can arguably be somewhat
		111	useful) and you want to force your users to use the one and only event
		112	model, you should I<not> use this module.
22		113
23	=head1 DESCRIPTION	114	=head1 DESCRIPTION
24		115
25	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
26	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
27	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
28	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
29		120
30	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>
31	module.	122	module.
32		123
33	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
34	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
35	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>,
36	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
37	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
38	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
39	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.
40		132
41	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	135	that model the default. For example:
44		136
45	use Tk;	137	use Tk;
46	use AnyEvent;	138	use AnyEvent;
47		139
48	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
49		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
50	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
51	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
52	explicitly.	149	availability of that event loop :)
53		150
54	=head1 WATCHERS	151	=head1 WATCHERS
55		152
56	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
57	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
58	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
59		156
60	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
61	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
62	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
63	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
64	references to it).	170	to it).
65		171
66	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.
67		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
68	=head2 IO WATCHERS	188	=head2 I/O WATCHERS
69		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
70	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
71	the following mandatory arguments:	197	with the following mandatory key-value pairs as arguments:
72		198
73	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
74	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
75	a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
76	to invoke everytime the filehandle becomes ready.
77		208
78	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.
79	a socket you can have one r + one w, not any more (limitation comes from
80	Tk - if you are sure you are not using Tk this limitation is gone).
81		210
82	Filehandles will be kept alive, so as long as the watcher exists, the	211	Although the callback might get passed parameters, their value and
83	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.
84		214
85	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.
86		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
87	# 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
88	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
90	warn "read: $input\n";	228	warn "read: $input\n";
91	undef $w;	229	undef $w;
92	});	230	});
93		231
94	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
95		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
96	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 >>
97	method with the following mandatory arguments:	243	method with the following mandatory arguments:
98		244
99	C<after> after how many seconds (fractions are supported) should the timer	245	C<after> specifies after how many seconds (fractional values are
100	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.
101		248
102	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
103	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
104	and Glib).	251	callbacks cannot use arguments passed to time watcher callbacks.
105		252
106	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.
107		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
108	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	266	warn "timeout\n";
111	});	267	});
112		268
113	# to cancel the timer:	269	# to cancel the timer:
114	undef $w	270	undef $w;
115		271
116	=head2 CONDITION WATCHERS	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
117		273
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
119	method without any arguments.	275	warn "timeout\n";
		276	};
120		277
121	A condition watcher watches for a condition - precisely that the C<<	278	=head3 TIMING ISSUES
122	->broadcast >> method has been called.
123		279
124	The watcher has only two methods:	280	There are two ways to handle timers: based on real time (relative, "fire
		281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		282	o'clock").
		283
		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":
125		299
126	=over 4	300	=over 4
127		301
128	=item $cv->wait	302	=item AnyEvent->time
129		303
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	304	This returns the "current wallclock time" as a fractional number of
131	called on c<$cv>, while servicing other watchers normally.	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).
132		307
133	Not all event models support a blocking wait - some die in that case, so	308	It progresses independently of any event loop processing, i.e. each call
134	if you are using this from a module, never require a blocking wait, but	309	will check the system clock, which usually gets updated frequently.
135	let the caller decide wether the call will block or not (for example,
136	by coupling condition variables with some kind of request results and
137	supporting callbacks so the caller knows that getting the result will not
138	block, while still suppporting blockign waits if the caller so desires).
139		310
140	You can only wait once on a condition - additional calls will return	311	=item AnyEvent->now
141	immediately.
142		312
143	=item $cv->broadcast	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.
144		317
145	Flag the condition as ready - a running C<< ->wait >> and all further	318	I<In almost all cases (in all cases if you don't care), this is the
146	calls to C<wait> will return after this method has been called. If nobody	319	function to call when you want to know the current time.>
147	is waiting the broadcast will be remembered..
148		320
149	Example:	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).
150		324
151	# wait till the result is ready	325	The rest of this section is only of relevance if you try to be very exact
152	my $result_ready = AnyEvent->condvar;	326	with your timing; you can skip it without a bad conscience.
153		327
154	# do something such as adding a timer	328	For a practical example of when these times differ, consider L<Event::Lib>
155	# or socket watcher the calls $result_ready->broadcast	329	and L<EV> and the following set-up:
156	# when the "result" is ready.
157		330
158	$result_ready->wait;	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.
159		380
160	=back	381	=back
161		382
162	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
163		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
164	You can listen for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
165	I<name> without any C<SIG> prefix. Multiple signals events can be clumped	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
166	together into one callback invocation, and callback invocation might or	389	callback to be invoked whenever a signal occurs.
167	might not be asynchronous.
168		390
169	These watchers might use C<%SIG>, so programs overwriting those signals	391	Although the callback might get passed parameters, their value and
170	directly will likely not work correctly.	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.
171		407
172	Example: exit on SIGINT	408	Example: exit on SIGINT
173		409
174	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
175		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		437	variable can be changed only before the first signal watcher is created,
		438	and should be left alone otherwise. This variable determines how often
		439	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		440	will cause fewer spurious wake-ups, which is better for power and CPU
		441	saving.
		442
		443	All these problems can be avoided by installing the optional
		444	L<Async::Interrupt> module, which works with most event loops. It will not
		445	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		446	(and not with L<POE> currently, as POE does its own workaround with
		447	one-second latency). For those, you just have to suffer the delays.
		448
176	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
177		450
178	You can also listen for the status of a child process specified by the	451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
179	C<pid> argument. The watcher will only trigger once. This works by
180	installing a signal handler for C<SIGCHLD>.
181		452
182	Example: wait for pid 1333	453	You can also watch for a child process exit and catch its exit status.
183		454
184	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });	455	The child process is specified by the C<pid> argument (on some backends,
		456	using C<0> watches for any child process exit, on others this will
		457	croak). The watcher will be triggered only when the child process has
		458	finished and an exit status is available, not on any trace events
		459	(stopped/continued).
185		460
186	=head1 GLOBALS	461	The callback will be called with the pid and exit status (as returned by
		462	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		463	callback arguments.
		464
		465	This watcher type works by installing a signal handler for C<SIGCHLD>,
		466	and since it cannot be shared, nothing else should use SIGCHLD or reap
		467	random child processes (waiting for specific child processes, e.g. inside
		468	C<system>, is just fine).
		469
		470	There is a slight catch to child watchers, however: you usually start them
		471	I<after> the child process was created, and this means the process could
		472	have exited already (and no SIGCHLD will be sent anymore).
		473
		474	Not all event models handle this correctly (neither POE nor IO::Async do,
		475	see their AnyEvent::Impl manpages for details), but even for event models
		476	that I<do> handle this correctly, they usually need to be loaded before
		477	the process exits (i.e. before you fork in the first place). AnyEvent's
		478	pure perl event loop handles all cases correctly regardless of when you
		479	start the watcher.
		480
		481	This means you cannot create a child watcher as the very first
		482	thing in an AnyEvent program, you I<have> to create at least one
		483	watcher before you C<fork> the child (alternatively, you can call
		484	C<AnyEvent::detect>).
		485
		486	As most event loops do not support waiting for child events, they will be
		487	emulated by AnyEvent in most cases, in which case the latency and race
		488	problems mentioned in the description of signal watchers apply.
		489
		490	Example: fork a process and wait for it
		491
		492	my $done = AnyEvent->condvar;
		493
		494	my $pid = fork or exit 5;
		495
		496	my $w = AnyEvent->child (
		497	pid => $pid,
		498	cb => sub {
		499	my ($pid, $status) = @_;
		500	warn "pid $pid exited with status $status";
		501	$done->send;
		502	},
		503	);
		504
		505	# do something else, then wait for process exit
		506	$done->recv;
		507
		508	=head2 IDLE WATCHERS
		509
		510	$w = AnyEvent->idle (cb => <callback>);
		511
		512	This will repeatedly invoke the callback after the process becomes idle,
		513	until either the watcher is destroyed or new events have been detected.
		514
		515	Idle watchers are useful when there is a need to do something, but it
		516	is not so important (or wise) to do it instantly. The callback will be
		517	invoked only when there is "nothing better to do", which is usually
		518	defined as "all outstanding events have been handled and no new events
		519	have been detected". That means that idle watchers ideally get invoked
		520	when the event loop has just polled for new events but none have been
		521	detected. Instead of blocking to wait for more events, the idle watchers
		522	will be invoked.
		523
		524	Unfortunately, most event loops do not really support idle watchers (only
		525	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		526	will simply call the callback "from time to time".
		527
		528	Example: read lines from STDIN, but only process them when the
		529	program is otherwise idle:
		530
		531	my @lines; # read data
		532	my $idle_w;
		533	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		534	push @lines, scalar <STDIN>;
		535
		536	# start an idle watcher, if not already done
		537	$idle_w ||= AnyEvent->idle (cb => sub {
		538	# handle only one line, when there are lines left
		539	if (my $line = shift @lines) {
		540	print "handled when idle: $line";
		541	} else {
		542	# otherwise disable the idle watcher again
		543	undef $idle_w;
		544	}
		545	});
		546	});
		547
		548	=head2 CONDITION VARIABLES
		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
		554
		555	If you are familiar with some event loops you will know that all of them
		556	require you to run some blocking "loop", "run" or similar function that
		557	will actively watch for new events and call your callbacks.
		558
		559	AnyEvent is slightly different: it expects somebody else to run the event
		560	loop and will only block when necessary (usually when told by the user).
		561
		562	The tool to do that is called a "condition variable", so called because
		563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
		566
		567	Condition variables can be created by calling the C<< AnyEvent->condvar
		568	>> method, usually without arguments. The only argument pair allowed is
		569	C<cb>, which specifies a callback to be called when the condition variable
		570	becomes true, with the condition variable as the first argument (but not
		571	the results).
		572
		573	After creation, the condition variable is "false" until it becomes "true"
		574	by calling the C<send> method (or calling the condition variable as if it
		575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
		577
		578	Since condition variables are the most complex part of the AnyEvent API, here are
		579	some different mental models of what they are - pick the ones you can connect to:
187		580
188	=over 4	581	=over 4
189		582
		583	=item * Condition variables are like callbacks - you can call them (and pass them instead
		584	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		585
		586	=item * Condition variables are signals - one side can emit or send them,
		587	the other side can wait for them, or install a handler that is called when
		588	the signal fires.
		589
		590	=item * Condition variables are like "Merge Points" - points in your program
		591	where you merge multiple independent results/control flows into one.
		592
		593	=item * Condition variables represent a transaction - functions that start
		594	some kind of transaction can return them, leaving the caller the choice
		595	between waiting in a blocking fashion, or setting a callback.
		596
		597	=item * Condition variables represent future values, or promises to deliver
		598	some result, long before the result is available.
		599
		600	=back
		601
		602	Condition variables are very useful to signal that something has finished,
		603	for example, if you write a module that does asynchronous http requests,
		604	then a condition variable would be the ideal candidate to signal the
		605	availability of results. The user can either act when the callback is
		606	called or can synchronously C<< ->recv >> for the results.
		607
		608	You can also use them to simulate traditional event loops - for example,
		609	you can block your main program until an event occurs - for example, you
		610	could C<< ->recv >> in your main program until the user clicks the Quit
		611	button of your app, which would C<< ->send >> the "quit" event.
		612
		613	Note that condition variables recurse into the event loop - if you have
		614	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		615	lose. Therefore, condition variables are good to export to your caller, but
		616	you should avoid making a blocking wait yourself, at least in callbacks,
		617	as this asks for trouble.
		618
		619	Condition variables are represented by hash refs in perl, and the keys
		620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		621	easy (it is often useful to build your own transaction class on top of
		622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		623	its C<new> method in your own C<new> method.
		624
		625	There are two "sides" to a condition variable - the "producer side" which
		626	eventually calls C<< -> send >>, and the "consumer side", which waits
		627	for the send to occur.
		628
		629	Example: wait for a timer.
		630
		631	# condition: "wait till the timer is fired"
		632	my $timer_fired = AnyEvent->condvar;
		633
		634	# create the timer - we could wait for, say
		635	# a handle becomign ready, or even an
		636	# AnyEvent::HTTP request to finish, but
		637	# in this case, we simply use a timer:
		638	my $w = AnyEvent->timer (
		639	after => 1,
		640	cb => sub { $timer_fired->send },
		641	);
		642
		643	# this "blocks" (while handling events) till the callback
		644	# calls ->send
		645	$timer_fired->recv;
		646
		647	Example: wait for a timer, but take advantage of the fact that condition
		648	variables are also callable directly.
		649
		650	my $done = AnyEvent->condvar;
		651	my $delay = AnyEvent->timer (after => 5, cb => $done);
		652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
		670
		671	=head3 METHODS FOR PRODUCERS
		672
		673	These methods should only be used by the producing side, i.e. the
		674	code/module that eventually sends the signal. Note that it is also
		675	the producer side which creates the condvar in most cases, but it isn't
		676	uncommon for the consumer to create it as well.
		677
		678	=over 4
		679
		680	=item $cv->send (...)
		681
		682	Flag the condition as ready - a running C<< ->recv >> and all further
		683	calls to C<recv> will (eventually) return after this method has been
		684	called. If nobody is waiting the send will be remembered.
		685
		686	If a callback has been set on the condition variable, it is called
		687	immediately from within send.
		688
		689	Any arguments passed to the C<send> call will be returned by all
		690	future C<< ->recv >> calls.
		691
		692	Condition variables are overloaded so one can call them directly (as if
		693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
		695
		696	=item $cv->croak ($error)
		697
		698	Similar to send, but causes all calls to C<< ->recv >> to invoke
		699	C<Carp::croak> with the given error message/object/scalar.
		700
		701	This can be used to signal any errors to the condition variable
		702	user/consumer. Doing it this way instead of calling C<croak> directly
		703	delays the error detection, but has the overwhelming advantage that it
		704	diagnoses the error at the place where the result is expected, and not
		705	deep in some event callback with no connection to the actual code causing
		706	the problem.
		707
		708	=item $cv->begin ([group callback])
		709
		710	=item $cv->end
		711
		712	These two methods can be used to combine many transactions/events into
		713	one. For example, a function that pings many hosts in parallel might want
		714	to use a condition variable for the whole process.
		715
		716	Every call to C<< ->begin >> will increment a counter, and every call to
		717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		718	>>, the (last) callback passed to C<begin> will be executed, passing the
		719	condvar as first argument. That callback is I<supposed> to call C<< ->send
		720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
		722
		723	You can think of C<< $cv->send >> giving you an OR condition (one call
		724	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		725	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		726
		727	Let's start with a simple example: you have two I/O watchers (for example,
		728	STDOUT and STDERR for a program), and you want to wait for both streams to
		729	close before activating a condvar:
		730
		731	my $cv = AnyEvent->condvar;
		732
		733	$cv->begin; # first watcher
		734	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		735	defined sysread $fh1, my $buf, 4096
		736	or $cv->end;
		737	});
		738
		739	$cv->begin; # second watcher
		740	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		741	defined sysread $fh2, my $buf, 4096
		742	or $cv->end;
		743	});
		744
		745	$cv->recv;
		746
		747	This works because for every event source (EOF on file handle), there is
		748	one call to C<begin>, so the condvar waits for all calls to C<end> before
		749	sending.
		750
		751	The ping example mentioned above is slightly more complicated, as the
		752	there are results to be passwd back, and the number of tasks that are
		753	begun can potentially be zero:
		754
		755	my $cv = AnyEvent->condvar;
		756
		757	my %result;
		758	$cv->begin (sub { shift->send (\%result) });
		759
		760	for my $host (@list_of_hosts) {
		761	$cv->begin;
		762	ping_host_then_call_callback $host, sub {
		763	$result{$host} = ...;
		764	$cv->end;
		765	};
		766	}
		767
		768	$cv->end;
		769
		770	This code fragment supposedly pings a number of hosts and calls
		771	C<send> after results for all then have have been gathered - in any
		772	order. To achieve this, the code issues a call to C<begin> when it starts
		773	each ping request and calls C<end> when it has received some result for
		774	it. Since C<begin> and C<end> only maintain a counter, the order in which
		775	results arrive is not relevant.
		776
		777	There is an additional bracketing call to C<begin> and C<end> outside the
		778	loop, which serves two important purposes: first, it sets the callback
		779	to be called once the counter reaches C<0>, and second, it ensures that
		780	C<send> is called even when C<no> hosts are being pinged (the loop
		781	doesn't execute once).
		782
		783	This is the general pattern when you "fan out" into multiple (but
		784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		785	the callback and ensure C<end> is called at least once, and then, for each
		786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
		788
		789	=back
		790
		791	=head3 METHODS FOR CONSUMERS
		792
		793	These methods should only be used by the consuming side, i.e. the
		794	code awaits the condition.
		795
		796	=over 4
		797
		798	=item $cv->recv
		799
		800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		801	>> methods have been called on C<$cv>, while servicing other watchers
		802	normally.
		803
		804	You can only wait once on a condition - additional calls are valid but
		805	will return immediately.
		806
		807	If an error condition has been set by calling C<< ->croak >>, then this
		808	function will call C<croak>.
		809
		810	In list context, all parameters passed to C<send> will be returned,
		811	in scalar context only the first one will be returned.
		812
		813	Note that doing a blocking wait in a callback is not supported by any
		814	event loop, that is, recursive invocation of a blocking C<< ->recv
		815	>> is not allowed, and the C<recv> call will C<croak> if such a
		816	condition is detected. This condition can be slightly loosened by using
		817	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		818	any thread that doesn't run the event loop itself.
		819
		820	Not all event models support a blocking wait - some die in that case
		821	(programs might want to do that to stay interactive), so I<if you are
		822	using this from a module, never require a blocking wait>. Instead, let the
		823	caller decide whether the call will block or not (for example, by coupling
		824	condition variables with some kind of request results and supporting
		825	callbacks so the caller knows that getting the result will not block,
		826	while still supporting blocking waits if the caller so desires).
		827
		828	You can ensure that C<< ->recv >> never blocks by setting a callback and
		829	only calling C<< ->recv >> from within that callback (or at a later
		830	time). This will work even when the event loop does not support blocking
		831	waits otherwise.
		832
		833	=item $bool = $cv->ready
		834
		835	Returns true when the condition is "true", i.e. whether C<send> or
		836	C<croak> have been called.
		837
		838	=item $cb = $cv->cb ($cb->($cv))
		839
		840	This is a mutator function that returns the callback set and optionally
		841	replaces it before doing so.
		842
		843	The callback will be called when the condition becomes "true", i.e. when
		844	C<send> or C<croak> are called, with the only argument being the
		845	condition variable itself. If the condition is already true, the
		846	callback is called immediately when it is set. Calling C<recv> inside
		847	the callback or at any later time is guaranteed not to block.
		848
		849	=back
		850
		851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		852
		853	The available backend classes are (every class has its own manpage):
		854
		855	=over 4
		856
		857	=item Backends that are autoprobed when no other event loop can be found.
		858
		859	EV is the preferred backend when no other event loop seems to be in
		860	use. If EV is not installed, then AnyEvent will fall back to its own
		861	pure-perl implementation, which is available everywhere as it comes with
		862	AnyEvent itself.
		863
		864	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		865	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		866
		867	=item Backends that are transparently being picked up when they are used.
		868
		869	These will be used if they are already loaded when the first watcher
		870	is created, in which case it is assumed that the application is using
		871	them. This means that AnyEvent will automatically pick the right backend
		872	when the main program loads an event module before anything starts to
		873	create watchers. Nothing special needs to be done by the main program.
		874
		875	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		876	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		877	AnyEvent::Impl::Tk based on Tk, very broken.
		878	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		879	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		880	AnyEvent::Impl::Irssi used when running within irssi.
		881	AnyEvent::Impl::IOAsync based on IO::Async.
		882	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		883	AnyEvent::Impl::FLTK2 based on FLTK (fltk 2 binding).
		884
		885	=item Backends with special needs.
		886
		887	Qt requires the Qt::Application to be instantiated first, but will
		888	otherwise be picked up automatically. As long as the main program
		889	instantiates the application before any AnyEvent watchers are created,
		890	everything should just work.
		891
		892	AnyEvent::Impl::Qt based on Qt.
		893
		894	=item Event loops that are indirectly supported via other backends.
		895
		896	Some event loops can be supported via other modules:
		897
		898	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		899
		900	B<WxWidgets> has no support for watching file handles. However, you can
		901	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		902	polls 20 times per second, which was considered to be too horrible to even
		903	consider for AnyEvent.
		904
		905	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		906	backend, so it can be supported through POE.
		907
		908	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		909	load L<POE> when detecting them, in the hope that POE will pick them up,
		910	in which case everything will be automatic.
		911
		912	=back
		913
		914	=head1 GLOBAL VARIABLES AND FUNCTIONS
		915
		916	These are not normally required to use AnyEvent, but can be useful to
		917	write AnyEvent extension modules.
		918
		919	=over 4
		920
190	=item $AnyEvent::MODEL	921	=item $AnyEvent::MODEL
191		922
192	Contains C<undef> until the first watcher is being created. Then it	923	Contains C<undef> until the first watcher is being created, before the
		924	backend has been autodetected.
		925
193	contains the event model that is being used, which is the name of the	926	Afterwards it contains the event model that is being used, which is the
194	Perl class implementing the model. This class is usually one of the	927	name of the Perl class implementing the model. This class is usually one
195	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	928	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
196	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	929	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
197		930	will be C<urxvt::anyevent>).
198	The known classes so far are:
199
200	AnyEvent::Impl::Coro based on Coro::Event, best choise.
201	AnyEvent::Impl::Event based on Event, also best choice :)
202	AnyEvent::Impl::Glib based on Glib, second-best choice.
203	AnyEvent::Impl::Tk based on Tk, very bad choice.
204	AnyEvent::Impl::Perl pure-perl implementation, inefficient.
205		931
206	=item AnyEvent::detect	932	=item AnyEvent::detect
207		933
208	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	934	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
209	necessary. You should only call this function right before you would have	935	if necessary. You should only call this function right before you would
210	created an AnyEvent watcher anyway, that is, very late at runtime.	936	have created an AnyEvent watcher anyway, that is, as late as possible at
		937	runtime, and not e.g. during initialisation of your module.
		938
		939	The effect of calling this function is as if a watcher had been created
		940	(specifically, actions that happen "when the first watcher is created"
		941	happen when calling detetc as well).
		942
		943	If you need to do some initialisation before AnyEvent watchers are
		944	created, use C<post_detect>.
		945
		946	=item $guard = AnyEvent::post_detect { BLOCK }
		947
		948	Arranges for the code block to be executed as soon as the event model is
		949	autodetected (or immediately if that has already happened).
		950
		951	The block will be executed I<after> the actual backend has been detected
		952	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		953	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		954	other initialisations - see the sources of L<AnyEvent::Strict> or
		955	L<AnyEvent::AIO> to see how this is used.
		956
		957	The most common usage is to create some global watchers, without forcing
		958	event module detection too early, for example, L<AnyEvent::AIO> creates
		959	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		960	avoid autodetecting the event module at load time.
		961
		962	If called in scalar or list context, then it creates and returns an object
		963	that automatically removes the callback again when it is destroyed (or
		964	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		965	a case where this is useful.
		966
		967	Example: Create a watcher for the IO::AIO module and store it in
		968	C<$WATCHER>, but do so only do so after the event loop is initialised.
		969
		970	our WATCHER;
		971
		972	my $guard = AnyEvent::post_detect {
		973	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		974	};
		975
		976	# the ||= is important in case post_detect immediately runs the block,
		977	# as to not clobber the newly-created watcher. assigning both watcher and
		978	# post_detect guard to the same variable has the advantage of users being
		979	# able to just C<undef $WATCHER> if the watcher causes them grief.
		980
		981	$WATCHER ||= $guard;
		982
		983	=item @AnyEvent::post_detect
		984
		985	If there are any code references in this array (you can C<push> to it
		986	before or after loading AnyEvent), then they will be called directly
		987	after the event loop has been chosen.
		988
		989	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		990	if it is defined then the event loop has already been detected, and the
		991	array will be ignored.
		992
		993	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		994	it, as it takes care of these details.
		995
		996	This variable is mainly useful for modules that can do something useful
		997	when AnyEvent is used and thus want to know when it is initialised, but do
		998	not need to even load it by default. This array provides the means to hook
		999	into AnyEvent passively, without loading it.
		1000
		1001	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1002	together, you could put this into Coro (this is the actual code used by
		1003	Coro to accomplish this):
		1004
		1005	if (defined $AnyEvent::MODEL) {
		1006	# AnyEvent already initialised, so load Coro::AnyEvent
		1007	require Coro::AnyEvent;
		1008	} else {
		1009	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1010	# as soon as it is
		1011	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1012	}
		1013
		1014	=item AnyEvent::postpone { BLOCK }
		1015
		1016	Arranges for the block to be executed as soon as possible, but not before
		1017	the call itself returns. In practise, the block will be executed just
		1018	before the event loop polls for new events, or shortly afterwards.
		1019
		1020	This function never returns anything (to make the C<return postpone { ...
		1021	}> idiom more useful.
		1022
		1023	To understand the usefulness of this function, consider a function that
		1024	asynchronously does something for you and returns some transaction
		1025	object or guard to let you cancel the operation. For example,
		1026	C<AnyEvent::Socket::tcp_connect>:
		1027
		1028	# start a conenction attempt unless one is active
		1029	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1030	delete $self->{connect_guard};
		1031	...
		1032	};
		1033
		1034	Imagine that this function could instantly call the callback, for
		1035	example, because it detects an obvious error such as a negative port
		1036	number. Invoking the callback before the function returns causes problems
		1037	however: the callback will be called and will try to delete the guard
		1038	object. But since the function hasn't returned yet, there is nothing to
		1039	delete. When the function eventually returns it will assign the guard
		1040	object to C<< $self->{connect_guard} >>, where it will likely never be
		1041	deleted, so the program thinks it is still trying to connect.
		1042
		1043	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1044	callback directly on error:
		1045
		1046	$cb->(undef), return # signal error to callback, BAD!
		1047	if $some_error_condition;
		1048
		1049	It should use C<postpone>:
		1050
		1051	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1052	if $some_error_condition;
		1053
		1054	=item AnyEvent::log $level, $msg[, @args]
		1055
		1056	Log the given C<$msg> at the given C<$level>.
		1057
		1058	Loads AnyEvent::Log on first use and calls C<AnyEvent::Log::log> -
		1059	consequently, look at the L<AnyEvent::Log> documentation for details.
211		1060
212	=back	1061	=back
213		1062
214	=head1 WHAT TO DO IN A MODULE	1063	=head1 WHAT TO DO IN A MODULE
215		1064
216	As a module author, you should "use AnyEvent" and call AnyEvent methods	1065	As a module author, you should C<use AnyEvent> and call AnyEvent methods
217	freely, but you should not load a specific event module or rely on it.	1066	freely, but you should not load a specific event module or rely on it.
218		1067
219	Be careful when you create watchers in the module body - Anyevent will	1068	Be careful when you create watchers in the module body - AnyEvent will
220	decide which event module to use as soon as the first method is called, so	1069	decide which event module to use as soon as the first method is called, so
221	by calling AnyEvent in your module body you force the user of your module	1070	by calling AnyEvent in your module body you force the user of your module
222	to load the event module first.	1071	to load the event module first.
223		1072
		1073	Never call C<< ->recv >> on a condition variable unless you I<know> that
		1074	the C<< ->send >> method has been called on it already. This is
		1075	because it will stall the whole program, and the whole point of using
		1076	events is to stay interactive.
		1077
		1078	It is fine, however, to call C<< ->recv >> when the user of your module
		1079	requests it (i.e. if you create a http request object ad have a method
		1080	called C<results> that returns the results, it may call C<< ->recv >>
		1081	freely, as the user of your module knows what she is doing. Always).
		1082
224	=head1 WHAT TO DO IN THE MAIN PROGRAM	1083	=head1 WHAT TO DO IN THE MAIN PROGRAM
225		1084
226	There will always be a single main program - the only place that should	1085	There will always be a single main program - the only place that should
227	dictate which event model to use.	1086	dictate which event model to use.
228		1087
229	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1088	If the program is not event-based, it need not do anything special, even
230	do anything special and let AnyEvent decide which implementation to chose.	1089	when it depends on a module that uses an AnyEvent. If the program itself
		1090	uses AnyEvent, but does not care which event loop is used, all it needs
		1091	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1092	available loop implementation.
231		1093
232	If the main program relies on a specific event model (for example, in Gtk2	1094	If the main program relies on a specific event model - for example, in
233	programs you have to rely on either Glib or Glib::Event), you should load	1095	Gtk2 programs you have to rely on the Glib module - you should load the
234	it before loading AnyEvent or any module that uses it, generally, as early	1096	event module before loading AnyEvent or any module that uses it: generally
235	as possible. The reason is that modules might create watchers when they	1097	speaking, you should load it as early as possible. The reason is that
236	are loaded, and AnyEvent will decide on the event model to use as soon as	1098	modules might create watchers when they are loaded, and AnyEvent will
237	it creates watchers, and it might chose the wrong one unless you load the	1099	decide on the event model to use as soon as it creates watchers, and it
238	correct one yourself.	1100	might choose the wrong one unless you load the correct one yourself.
239		1101
240	You can chose to use a rather inefficient pure-perl implementation by	1102	You can chose to use a pure-perl implementation by loading the
241	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	1103	C<AnyEvent::Loop> module, which gives you similar behaviour
242	generally better.	1104	everywhere, but letting AnyEvent chose the model is generally better.
		1105
		1106	=head2 MAINLOOP EMULATION
		1107
		1108	Sometimes (often for short test scripts, or even standalone programs who
		1109	only want to use AnyEvent), you do not want to run a specific event loop.
		1110
		1111	In that case, you can use a condition variable like this:
		1112
		1113	AnyEvent->condvar->recv;
		1114
		1115	This has the effect of entering the event loop and looping forever.
		1116
		1117	Note that usually your program has some exit condition, in which case
		1118	it is better to use the "traditional" approach of storing a condition
		1119	variable somewhere, waiting for it, and sending it when the program should
		1120	exit cleanly.
		1121
		1122
		1123	=head1 OTHER MODULES
		1124
		1125	The following is a non-exhaustive list of additional modules that use
		1126	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1127	modules and other event loops in the same program. Some of the modules
		1128	come as part of AnyEvent, the others are available via CPAN.
		1129
		1130	=over 4
		1131
		1132	=item L<AnyEvent::Util>
		1133
		1134	Contains various utility functions that replace often-used blocking
		1135	functions such as C<inet_aton> with event/callback-based versions.
		1136
		1137	=item L<AnyEvent::Socket>
		1138
		1139	Provides various utility functions for (internet protocol) sockets,
		1140	addresses and name resolution. Also functions to create non-blocking tcp
		1141	connections or tcp servers, with IPv6 and SRV record support and more.
		1142
		1143	=item L<AnyEvent::Handle>
		1144
		1145	Provide read and write buffers, manages watchers for reads and writes,
		1146	supports raw and formatted I/O, I/O queued and fully transparent and
		1147	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1148
		1149	=item L<AnyEvent::DNS>
		1150
		1151	Provides rich asynchronous DNS resolver capabilities.
		1152
		1153	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1154
		1155	Implement event-based interfaces to the protocols of the same name (for
		1156	the curious, IGS is the International Go Server and FCP is the Freenet
		1157	Client Protocol).
		1158
		1159	=item L<AnyEvent::Handle::UDP>
		1160
		1161	Here be danger!
		1162
		1163	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1164	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1165	its use of a stream-based API with a protocol that isn't streamable, that
		1166	the only way to improve it is to delete it.
		1167
		1168	It features data corruption (but typically only under load) and general
		1169	confusion. On top, the author is not only clueless about UDP but also
		1170	fact-resistant - some gems of his understanding: "connect doesn't work
		1171	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1172	packets", "I don't need to implement proper error checking as UDP doesn't
		1173	support error checking" and so on - he doesn't even understand what's
		1174	wrong with his module when it is explained to him.
		1175
		1176	=item L<AnyEvent::DBI>
		1177
		1178	Executes L<DBI> requests asynchronously in a proxy process for you,
		1179	notifying you in an event-based way when the operation is finished.
		1180
		1181	=item L<AnyEvent::AIO>
		1182
		1183	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1184	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1185	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1186	file I/O, and much more.
		1187
		1188	=item L<AnyEvent::HTTPD>
		1189
		1190	A simple embedded webserver.
		1191
		1192	=item L<AnyEvent::FastPing>
		1193
		1194	The fastest ping in the west.
		1195
		1196	=item L<Coro>
		1197
		1198	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1199
		1200	=back
243		1201
244	=cut	1202	=cut
245		1203
246	package AnyEvent;	1204	package AnyEvent;
247		1205
248	no warnings;	1206	# basically a tuned-down version of common::sense
249	use strict;	1207	sub common_sense {
		1208	# from common:.sense 3.4
		1209	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1210	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1211	$^H |= 0x00000600;
		1212	}
		1213
		1214	BEGIN { AnyEvent::common_sense }
		1215
250	use Carp;	1216	use Carp ();
251		1217
252	our $VERSION = '2.52';	1218	our $VERSION = '6.01';
253	our $MODEL;	1219	our $MODEL;
254		1220
255	our $AUTOLOAD;
256	our @ISA;	1221	our @ISA;
257		1222
258	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
259
260	our @REGISTRY;	1223	our @REGISTRY;
261		1224
		1225	our $VERBOSE;
		1226
		1227	BEGIN {
		1228	require "AnyEvent/constants.pl";
		1229
		1230	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1231
		1232	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1233	if ${^TAINT};
		1234
		1235	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1236	}
		1237
		1238	our $MAX_SIGNAL_LATENCY = 10;
		1239
		1240	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1241
		1242	{
		1243	my $idx;
		1244	$PROTOCOL{$_} = ++$idx
		1245	for reverse split /\s*,\s*/,
		1246	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1247	}
		1248
		1249	our @post_detect;
		1250
		1251	sub post_detect(&) {
		1252	my ($cb) = @_;
		1253
		1254	push @post_detect, $cb;
		1255
		1256	defined wantarray
		1257	? bless \$cb, "AnyEvent::Util::postdetect"
		1258	: ()
		1259	}
		1260
		1261	sub AnyEvent::Util::postdetect::DESTROY {
		1262	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1263	}
		1264
		1265	our $POSTPONE_W;
		1266	our @POSTPONE;
		1267
		1268	sub _postpone_exec {
		1269	undef $POSTPONE_W;
		1270
		1271	&{ shift @POSTPONE }
		1272	while @POSTPONE;
		1273	}
		1274
		1275	sub postpone(&) {
		1276	push @POSTPONE, shift;
		1277
		1278	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1279
		1280	()
		1281	}
		1282
		1283	sub log($$;@) {
		1284	require AnyEvent::Log;
		1285	# AnyEvent::Log overwrites this function
		1286	goto &log;
		1287	}
		1288
262	my @models = (	1289	our @models = (
		1290	[EV:: => AnyEvent::Impl::EV:: , 1],
263	[Coro::Event:: => AnyEvent::Impl::Coro::],	1291	[AnyEvent::Loop:: => AnyEvent::Impl::Perl:: , 1],
		1292	# everything below here will not (normally) be autoprobed
		1293	# as the pure perl backend should work everywhere
		1294	# and is usually faster
264	[Event:: => AnyEvent::Impl::Event::],	1295	[Event:: => AnyEvent::Impl::Event::, 1],
265	[Glib:: => AnyEvent::Impl::Glib::],	1296	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1297	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1298	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1299	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1300	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1301	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
266	[Tk:: => AnyEvent::Impl::Tk::],	1302	[Wx:: => AnyEvent::Impl::POE::],
267	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1303	[Prima:: => AnyEvent::Impl::POE::],
		1304	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
		1305	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
		1306	[FLTK:: => AnyEvent::Impl::FLTK2::],
268	);	1307	);
269		1308
270	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1309	our @isa_hook;
		1310
		1311	sub _isa_set {
		1312	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1313
		1314	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1315	for 1 .. $#pkg;
		1316
		1317	grep $_ && $_->[1], @isa_hook
		1318	and AE::_reset ();
		1319	}
		1320
		1321	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1322	sub _isa_hook($$;$) {
		1323	my ($i, $pkg, $reset_ae) = @_;
		1324
		1325	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1326
		1327	_isa_set;
		1328	}
		1329
		1330	# all autoloaded methods reserve the complete glob, not just the method slot.
		1331	# due to bugs in perls method cache implementation.
		1332	our @methods = qw(io timer time now now_update signal child idle condvar);
271		1333
272	sub detect() {	1334	sub detect() {
		1335	return $MODEL if $MODEL; # some programs keep references to detect
		1336
		1337	local $!; # for good measure
		1338	local $SIG{__DIE__}; # we use eval
		1339
		1340	# free some memory
		1341	*detect = sub () { $MODEL };
		1342	# undef &func doesn't correctly update the method cache. grmbl.
		1343	# so we delete the whole glob. grmbl.
		1344	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1345	# a glob with an active sub. hrm. i hope it works, but perl is
		1346	# usually buggy in this department. sigh.
		1347	delete @{"AnyEvent::"}{@methods};
		1348	undef @methods;
		1349
		1350	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1351	my $model = $1;
		1352	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1353	if (eval "require $model") {
		1354	$MODEL = $model;
		1355	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it."
		1356	if $VERBOSE >= 7;
		1357	} else {
		1358	AnyEvent::log warn => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1359	}
		1360	}
		1361
		1362	# check for already loaded models
273	unless ($MODEL) {	1363	unless ($MODEL) {
274	no strict 'refs';
275
276	# check for already loaded models
277	for (@REGISTRY, @models) {	1364	for (@REGISTRY, @models) {
278	my ($package, $model) = @$_;	1365	my ($package, $model) = @$_;
279	if (${"$package\::VERSION"} > 0) {	1366	if (${"$package\::VERSION"} > 0) {
280	if (eval "require $model") {	1367	if (eval "require $model") {
281	$MODEL = $model;	1368	$MODEL = $model;
282	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1369	AnyEvent::log 7 => "autodetected model '$model', using it."
		1370	if $VERBOSE >= 7;
283	last;	1371	last;
284	}	1372	}
285	}	1373	}
286	}	1374	}
287		1375
288	unless ($MODEL) {	1376	unless ($MODEL) {
289	# try to load a model	1377	# try to autoload a model
290
291	for (@REGISTRY, @models) {	1378	for (@REGISTRY, @models) {
292	my ($package, $model) = @$_;	1379	my ($package, $model, $autoload) = @$_;
		1380	if (
		1381	$autoload
293	if (eval "require $package"	1382	and eval "require $package"
294	and ${"$package\::VERSION"} > 0	1383	and ${"$package\::VERSION"} > 0
295	and eval "require $model") {	1384	and eval "require $model"
		1385	) {
296	$MODEL = $model;	1386	$MODEL = $model;
297	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	1387	AnyEvent::log 7 => "autoloaded model '$model', using it."
		1388	if $VERBOSE >= 7;
298	last;	1389	last;
299	}	1390	}
300	}	1391	}
301		1392
302	$MODEL	1393	$MODEL
303	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";	1394	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
304	}	1395	}
305
306	unshift @ISA, $MODEL;
307	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
308	}	1396	}
309		1397
		1398	# free memory only needed for probing
		1399	undef @models;
		1400	undef @REGISTRY;
		1401
		1402	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1403
		1404	# now nuke some methods that are overridden by the backend.
		1405	# SUPER usage is not allowed in these.
		1406	for (qw(time signal child idle)) {
		1407	undef &{"AnyEvent::Base::$_"}
		1408	if defined &{"$MODEL\::$_"};
		1409	}
		1410
		1411	_isa_set;
		1412
		1413	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1414	require AnyEvent::Strict;
		1415	}
		1416
		1417	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1418	require AnyEvent::Debug;
		1419	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1420	}
		1421
		1422	if (exists $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1423	require AnyEvent::Socket;
		1424	require AnyEvent::Debug;
		1425
		1426	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1427	$shell =~ s/\$\$/$$/g;
		1428
		1429	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1430	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1431	}
		1432
		1433	(shift @post_detect)->() while @post_detect;
		1434	undef @post_detect;
		1435
		1436	*post_detect = sub(&) {
		1437	shift->();
		1438
		1439	undef
		1440	};
		1441
310	$MODEL	1442	$MODEL
311	}	1443	}
312		1444
313	sub AUTOLOAD {	1445	for my $name (@methods) {
314	(my $func = $AUTOLOAD) =~ s/.*://;	1446	*$name = sub {
315		1447	detect;
316	$method{$func}	1448	# we use goto because
317	or croak "$func: not a valid method for AnyEvent objects";	1449	# a) it makes the thunk more transparent
318		1450	# b) it allows us to delete the thunk later
319	detect unless $MODEL;	1451	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
320		1452	};
321	my $class = shift;
322	$class->$func (@_);
323	}	1453	}
		1454
		1455	# utility function to dup a filehandle. this is used by many backends
		1456	# to support binding more than one watcher per filehandle (they usually
		1457	# allow only one watcher per fd, so we dup it to get a different one).
		1458	sub _dupfh($$;$$) {
		1459	my ($poll, $fh, $r, $w) = @_;
		1460
		1461	# cygwin requires the fh mode to be matching, unix doesn't
		1462	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1463
		1464	open my $fh2, $mode, $fh
		1465	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1466
		1467	# we assume CLOEXEC is already set by perl in all important cases
		1468
		1469	($fh2, $rw)
		1470	}
		1471
		1472	=head1 SIMPLIFIED AE API
		1473
		1474	Starting with version 5.0, AnyEvent officially supports a second, much
		1475	simpler, API that is designed to reduce the calling, typing and memory
		1476	overhead by using function call syntax and a fixed number of parameters.
		1477
		1478	See the L<AE> manpage for details.
		1479
		1480	=cut
		1481
		1482	package AE;
		1483
		1484	our $VERSION = $AnyEvent::VERSION;
		1485
		1486	sub _reset() {
		1487	eval q{
		1488	# fall back to the main API by default - backends and AnyEvent::Base
		1489	# implementations can overwrite these.
		1490
		1491	sub io($$$) {
		1492	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1493	}
		1494
		1495	sub timer($$$) {
		1496	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1497	}
		1498
		1499	sub signal($$) {
		1500	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1501	}
		1502
		1503	sub child($$) {
		1504	AnyEvent->child (pid => $_[0], cb => $_[1])
		1505	}
		1506
		1507	sub idle($) {
		1508	AnyEvent->idle (cb => $_[0]);
		1509	}
		1510
		1511	sub cv(;&) {
		1512	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1513	}
		1514
		1515	sub now() {
		1516	AnyEvent->now
		1517	}
		1518
		1519	sub now_update() {
		1520	AnyEvent->now_update
		1521	}
		1522
		1523	sub time() {
		1524	AnyEvent->time
		1525	}
		1526
		1527	*postpone = \&AnyEvent::postpone;
		1528	*log = \&AnyEvent::log;
		1529	};
		1530	die if $@;
		1531	}
		1532
		1533	BEGIN { _reset }
324		1534
325	package AnyEvent::Base;	1535	package AnyEvent::Base;
326		1536
		1537	# default implementations for many methods
		1538
		1539	sub time {
		1540	eval q{ # poor man's autoloading {}
		1541	# probe for availability of Time::HiRes
		1542	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1543	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy."
		1544	if $AnyEvent::VERBOSE >= 8;
		1545	*time = sub { Time::HiRes::time () };
		1546	*AE::time = \& Time::HiRes::time ;
		1547	# if (eval "use POSIX (); (POSIX::times())...
		1548	} else {
		1549	AnyEvent::log critical => "using built-in time(), WARNING, no sub-second resolution!";
		1550	*time = sub { CORE::time };
		1551	*AE::time = sub (){ CORE::time };
		1552	}
		1553
		1554	*now = \&time;
		1555	};
		1556	die if $@;
		1557
		1558	&time
		1559	}
		1560
		1561	*now = \&time;
		1562	sub now_update { }
		1563
		1564	sub _poll {
		1565	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1566	}
		1567
327	# default implementation for ->condvar, ->wait, ->broadcast	1568	# default implementation for ->condvar
		1569	# in fact, the default should not be overwritten
328		1570
329	sub condvar {	1571	sub condvar {
330	bless \my $flag, "AnyEvent::Base::CondVar"	1572	eval q{ # poor man's autoloading {}
331	}	1573	*condvar = sub {
		1574	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1575	};
332		1576
333	sub AnyEvent::Base::CondVar::broadcast {	1577	*AE::cv = sub (;&) {
334	${$_[0]}++;	1578	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
335	}	1579	};
		1580	};
		1581	die if $@;
336		1582
337	sub AnyEvent::Base::CondVar::wait {	1583	&condvar
338	AnyEvent->one_event while !${$_[0]};
339	}	1584	}
340		1585
341	# default implementation for ->signal	1586	# default implementation for ->signal
342		1587
343	our %SIG_CB;	1588	our $HAVE_ASYNC_INTERRUPT;
		1589
		1590	sub _have_async_interrupt() {
		1591	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1592	&& eval "use Async::Interrupt 1.02 (); 1")
		1593	unless defined $HAVE_ASYNC_INTERRUPT;
		1594
		1595	$HAVE_ASYNC_INTERRUPT
		1596	}
		1597
		1598	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1599	our (%SIG_ASY, %SIG_ASY_W);
		1600	our ($SIG_COUNT, $SIG_TW);
		1601
		1602	# install a dummy wakeup watcher to reduce signal catching latency
		1603	# used by Impls
		1604	sub _sig_add() {
		1605	unless ($SIG_COUNT++) {
		1606	# try to align timer on a full-second boundary, if possible
		1607	my $NOW = AE::now;
		1608
		1609	$SIG_TW = AE::timer
		1610	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1611	$MAX_SIGNAL_LATENCY,
		1612	sub { } # just for the PERL_ASYNC_CHECK
		1613	;
		1614	}
		1615	}
		1616
		1617	sub _sig_del {
		1618	undef $SIG_TW
		1619	unless --$SIG_COUNT;
		1620	}
		1621
		1622	our $_sig_name_init; $_sig_name_init = sub {
		1623	eval q{ # poor man's autoloading {}
		1624	undef $_sig_name_init;
		1625
		1626	if (_have_async_interrupt) {
		1627	*sig2num = \&Async::Interrupt::sig2num;
		1628	*sig2name = \&Async::Interrupt::sig2name;
		1629	} else {
		1630	require Config;
		1631
		1632	my %signame2num;
		1633	@signame2num{ split ' ', $Config::Config{sig_name} }
		1634	= split ' ', $Config::Config{sig_num};
		1635
		1636	my @signum2name;
		1637	@signum2name[values %signame2num] = keys %signame2num;
		1638
		1639	*sig2num = sub($) {
		1640	$_[0] > 0 ? shift : $signame2num{+shift}
		1641	};
		1642	*sig2name = sub ($) {
		1643	$_[0] > 0 ? $signum2name[+shift] : shift
		1644	};
		1645	}
		1646	};
		1647	die if $@;
		1648	};
		1649
		1650	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1651	sub sig2name($) { &$_sig_name_init; &sig2name }
344		1652
345	sub signal {	1653	sub signal {
		1654	eval q{ # poor man's autoloading {}
		1655	# probe for availability of Async::Interrupt
		1656	if (_have_async_interrupt) {
		1657	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling."
		1658	if $AnyEvent::VERBOSE >= 8;
		1659
		1660	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1661	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1662
		1663	} else {
		1664	AnyEvent::log 8 => "using emulated perl signal handling with latency timer."
		1665	if $AnyEvent::VERBOSE >= 8;
		1666
		1667	if (AnyEvent::WIN32) {
		1668	require AnyEvent::Util;
		1669
		1670	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1671	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1672	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1673	} else {
		1674	pipe $SIGPIPE_R, $SIGPIPE_W;
		1675	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1676	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1677
		1678	# not strictly required, as $^F is normally 2, but let's make sure...
		1679	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1680	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1681	}
		1682
		1683	$SIGPIPE_R
		1684	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1685
		1686	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1687	}
		1688
		1689	*signal = $HAVE_ASYNC_INTERRUPT
		1690	? sub {
346	my (undef, %arg) = @_;	1691	my (undef, %arg) = @_;
347		1692
		1693	# async::interrupt
348	my $signal = uc $arg{signal}	1694	my $signal = sig2num $arg{signal};
349	or Carp::croak "required option 'signal' is missing";
350
351	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1695	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1696
		1697	$SIG_ASY{$signal} ||= new Async::Interrupt
		1698	cb => sub { undef $SIG_EV{$signal} },
		1699	signal => $signal,
		1700	pipe => [$SIGPIPE_R->filenos],
		1701	pipe_autodrain => 0,
		1702	;
		1703
		1704	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1705	}
		1706	: sub {
		1707	my (undef, %arg) = @_;
		1708
		1709	# pure perl
		1710	my $signal = sig2name $arg{signal};
		1711	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1712
352	$SIG{$signal} ||= sub {	1713	$SIG{$signal} ||= sub {
		1714	local $!;
		1715	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1716	undef $SIG_EV{$signal};
		1717	};
		1718
		1719	# can't do signal processing without introducing races in pure perl,
		1720	# so limit the signal latency.
		1721	_sig_add;
		1722
		1723	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1724	}
		1725	;
		1726
		1727	*AnyEvent::Base::signal::DESTROY = sub {
		1728	my ($signal, $cb) = @{$_[0]};
		1729
		1730	_sig_del;
		1731
		1732	delete $SIG_CB{$signal}{$cb};
		1733
		1734	$HAVE_ASYNC_INTERRUPT
		1735	? delete $SIG_ASY{$signal}
		1736	: # delete doesn't work with older perls - they then
		1737	# print weird messages, or just unconditionally exit
		1738	# instead of getting the default action.
		1739	undef $SIG{$signal}
		1740	unless keys %{ $SIG_CB{$signal} };
		1741	};
		1742
		1743	*_signal_exec = sub {
		1744	$HAVE_ASYNC_INTERRUPT
		1745	? $SIGPIPE_R->drain
		1746	: sysread $SIGPIPE_R, (my $dummy), 9;
		1747
		1748	while (%SIG_EV) {
		1749	for (keys %SIG_EV) {
		1750	delete $SIG_EV{$_};
353	$_->() for values %{ $SIG_CB{$signal} || {} };	1751	&$_ for values %{ $SIG_CB{$_} || {} };
		1752	}
		1753	}
		1754	};
354	};	1755	};
		1756	die if $@;
355		1757
356	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1758	&signal
357	}
358
359	sub AnyEvent::Base::Signal::DESTROY {
360	my ($signal, $cb) = @{$_[0]};
361
362	delete $SIG_CB{$signal}{$cb};
363
364	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
365	}	1759	}
366		1760
367	# default implementation for ->child	1761	# default implementation for ->child
368		1762
369	our %PID_CB;	1763	our %PID_CB;
370	our $CHLD_W;	1764	our $CHLD_W;
371	our $PID_IDLE;	1765	our $CHLD_DELAY_W;
372	our $WNOHANG;
373		1766
374	sub _child_wait {	1767	# used by many Impl's
375	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1768	sub _emit_childstatus($$) {
		1769	my (undef, $rpid, $rstatus) = @_;
		1770
		1771	$_->($rpid, $rstatus)
376	$_->() for values %{ (delete $PID_CB{$pid}) || {} };	1772	for values %{ $PID_CB{$rpid} || {} },
		1773	values %{ $PID_CB{0} || {} };
		1774	}
		1775
		1776	sub child {
		1777	eval q{ # poor man's autoloading {}
		1778	*_sigchld = sub {
		1779	my $pid;
		1780
		1781	AnyEvent->_emit_childstatus ($pid, $?)
		1782	while ($pid = waitpid -1, WNOHANG) > 0;
		1783	};
		1784
		1785	*child = sub {
		1786	my (undef, %arg) = @_;
		1787
		1788	my $pid = $arg{pid};
		1789	my $cb = $arg{cb};
		1790
		1791	$PID_CB{$pid}{$cb+0} = $cb;
		1792
		1793	unless ($CHLD_W) {
		1794	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1795	# child could be a zombie already, so make at least one round
		1796	&_sigchld;
		1797	}
		1798
		1799	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1800	};
		1801
		1802	*AnyEvent::Base::child::DESTROY = sub {
		1803	my ($pid, $icb) = @{$_[0]};
		1804
		1805	delete $PID_CB{$pid}{$icb};
		1806	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1807
		1808	undef $CHLD_W unless keys %PID_CB;
		1809	};
		1810	};
		1811	die if $@;
		1812
		1813	&child
		1814	}
		1815
		1816	# idle emulation is done by simply using a timer, regardless
		1817	# of whether the process is idle or not, and not letting
		1818	# the callback use more than 50% of the time.
		1819	sub idle {
		1820	eval q{ # poor man's autoloading {}
		1821	*idle = sub {
		1822	my (undef, %arg) = @_;
		1823
		1824	my ($cb, $w, $rcb) = $arg{cb};
		1825
		1826	$rcb = sub {
		1827	if ($cb) {
		1828	$w = AE::time;
		1829	&$cb;
		1830	$w = AE::time - $w;
		1831
		1832	# never use more then 50% of the time for the idle watcher,
		1833	# within some limits
		1834	$w = 0.0001 if $w < 0.0001;
		1835	$w = 5 if $w > 5;
		1836
		1837	$w = AE::timer $w, 0, $rcb;
		1838	} else {
		1839	# clean up...
		1840	undef $w;
		1841	undef $rcb;
		1842	}
		1843	};
		1844
		1845	$w = AE::timer 0.05, 0, $rcb;
		1846
		1847	bless \\$cb, "AnyEvent::Base::idle"
		1848	};
		1849
		1850	*AnyEvent::Base::idle::DESTROY = sub {
		1851	undef $${$_[0]};
		1852	};
		1853	};
		1854	die if $@;
		1855
		1856	&idle
		1857	}
		1858
		1859	package AnyEvent::CondVar;
		1860
		1861	our @ISA = AnyEvent::CondVar::Base::;
		1862
		1863	# only to be used for subclassing
		1864	sub new {
		1865	my $class = shift;
		1866	bless AnyEvent->condvar (@_), $class
		1867	}
		1868
		1869	package AnyEvent::CondVar::Base;
		1870
		1871	#use overload
		1872	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1873	# fallback => 1;
		1874
		1875	# save 300+ kilobytes by dirtily hardcoding overloading
		1876	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1877	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1878	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1879	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1880
		1881	our $WAITING;
		1882
		1883	sub _send {
		1884	# nop
		1885	}
		1886
		1887	sub _wait {
		1888	AnyEvent->_poll until $_[0]{_ae_sent};
		1889	}
		1890
		1891	sub send {
		1892	my $cv = shift;
		1893	$cv->{_ae_sent} = [@_];
		1894	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1895	$cv->_send;
		1896	}
		1897
		1898	sub croak {
		1899	$_[0]{_ae_croak} = $_[1];
		1900	$_[0]->send;
		1901	}
		1902
		1903	sub ready {
		1904	$_[0]{_ae_sent}
		1905	}
		1906
		1907	sub recv {
		1908	unless ($_[0]{_ae_sent}) {
		1909	$WAITING
		1910	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1911
		1912	local $WAITING = 1;
		1913	$_[0]->_wait;
377	}	1914	}
378		1915
379	undef $PID_IDLE;	1916	$_[0]{_ae_croak}
380	}	1917	and Carp::croak $_[0]{_ae_croak};
381		1918
382	sub child {	1919	wantarray
383	my (undef, %arg) = @_;	1920	? @{ $_[0]{_ae_sent} }
384		1921	: $_[0]{_ae_sent}[0]
385	my $pid = uc $arg{pid}
386	or Carp::croak "required option 'pid' is missing";
387
388	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
389
390	unless ($WNOHANG) {
391	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
392	}
393
394	unless ($CHLD_W) {
395	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_child_wait);
396	# child could be a zombie already
397	$PID_IDLE ||= AnyEvent->timer (after => 0, cb => \&_child_wait);
398	}
399
400	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
401	}	1922	}
402		1923
403	sub AnyEvent::Base::Child::DESTROY {	1924	sub cb {
404	my ($pid, $cb) = @{$_[0]};	1925	my $cv = shift;
405		1926
406	delete $PID_CB{$pid}{$cb};	1927	@_
407	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1928	and $cv->{_ae_cb} = shift
		1929	and $cv->{_ae_sent}
		1930	and (delete $cv->{_ae_cb})->($cv);
408		1931
409	undef $CHLD_W unless keys %PID_CB;	1932	$cv->{_ae_cb}
410	}	1933	}
		1934
		1935	sub begin {
		1936	++$_[0]{_ae_counter};
		1937	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1938	}
		1939
		1940	sub end {
		1941	return if --$_[0]{_ae_counter};
		1942	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1943	}
		1944
		1945	# undocumented/compatibility with pre-3.4
		1946	*broadcast = \&send;
		1947	*wait = \&recv;
		1948
		1949	=head1 ERROR AND EXCEPTION HANDLING
		1950
		1951	In general, AnyEvent does not do any error handling - it relies on the
		1952	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1953	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1954	checking of all AnyEvent methods, however, which is highly useful during
		1955	development.
		1956
		1957	As for exception handling (i.e. runtime errors and exceptions thrown while
		1958	executing a callback), this is not only highly event-loop specific, but
		1959	also not in any way wrapped by this module, as this is the job of the main
		1960	program.
		1961
		1962	The pure perl event loop simply re-throws the exception (usually
		1963	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1964	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1965	so on.
		1966
		1967	=head1 ENVIRONMENT VARIABLES
		1968
		1969	The following environment variables are used by this module or its
		1970	submodules.
		1971
		1972	Note that AnyEvent will remove I<all> environment variables starting with
		1973	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1974	enabled.
		1975
		1976	=over 4
		1977
		1978	=item C<PERL_ANYEVENT_VERBOSE>
		1979
		1980	By default, AnyEvent will be completely silent except in fatal
		1981	conditions. You can set this environment variable to make AnyEvent more
		1982	talkative.
		1983
		1984	When set to C<5> or higher, causes AnyEvent to warn about unexpected
		1985	conditions, such as not being able to load the event model specified by
		1986	C<PERL_ANYEVENT_MODEL>.
		1987
		1988	When set to C<7> or higher, cause AnyEvent to report to STDERR which event
		1989	model it chooses.
		1990
		1991	When set to C<8> or higher, then AnyEvent will report extra information on
		1992	which optional modules it loads and how it implements certain features.
		1993
		1994	=item C<PERL_ANYEVENT_STRICT>
		1995
		1996	AnyEvent does not do much argument checking by default, as thorough
		1997	argument checking is very costly. Setting this variable to a true value
		1998	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1999	check the arguments passed to most method calls. If it finds any problems,
		2000	it will croak.
		2001
		2002	In other words, enables "strict" mode.
		2003
		2004	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2005	>>, it is definitely recommended to keep it off in production. Keeping
		2006	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2007	can be very useful, however.
		2008
		2009	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2010
		2011	If this env variable is set, then its contents will be interpreted by
		2012	C<AnyEvent::Socket::parse_hostport> (after replacing every occurance of
		2013	C<$$> by the process pid) and an C<AnyEvent::Debug::shell> is bound on
		2014	that port. The shell object is saved in C<$AnyEvent::Debug::SHELL>.
		2015
		2016	This takes place when the first watcher is created.
		2017
		2018	For example, to bind a debug shell on a unix domain socket in
		2019	F<< /tmp/debug<pid>.sock >>, you could use this:
		2020
		2021	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2022
		2023	Note that creating sockets in F</tmp> is very unsafe on multiuser
		2024	systems.
		2025
		2026	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2027
		2028	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2029	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2030
		2031	=item C<PERL_ANYEVENT_MODEL>
		2032
		2033	This can be used to specify the event model to be used by AnyEvent, before
		2034	auto detection and -probing kicks in.
		2035
		2036	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2037	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2038	resulting module name is loaded and - if the load was successful - used as
		2039	event model backend. If it fails to load then AnyEvent will proceed with
		2040	auto detection and -probing.
		2041
		2042	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2043	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2044	the end of a string designates a module name and quotes it appropriately).
		2045
		2046	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2047	could start your program like this:
		2048
		2049	PERL_ANYEVENT_MODEL=Perl perl ...
		2050
		2051	=item C<PERL_ANYEVENT_PROTOCOLS>
		2052
		2053	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2054	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2055	of auto probing).
		2056
		2057	Must be set to a comma-separated list of protocols or address families,
		2058	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2059	used, and preference will be given to protocols mentioned earlier in the
		2060	list.
		2061
		2062	This variable can effectively be used for denial-of-service attacks
		2063	against local programs (e.g. when setuid), although the impact is likely
		2064	small, as the program has to handle conenction and other failures anyways.
		2065
		2066	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2067	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2068	- only support IPv4, never try to resolve or contact IPv6
		2069	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2070	IPv6, but prefer IPv6 over IPv4.
		2071
		2072	=item C<PERL_ANYEVENT_EDNS0>
		2073
		2074	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		2075	for DNS. This extension is generally useful to reduce DNS traffic, but
		2076	some (broken) firewalls drop such DNS packets, which is why it is off by
		2077	default.
		2078
		2079	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2080	EDNS0 in its DNS requests.
		2081
		2082	=item C<PERL_ANYEVENT_MAX_FORKS>
		2083
		2084	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2085	will create in parallel.
		2086
		2087	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2088
		2089	The default value for the C<max_outstanding> parameter for the default DNS
		2090	resolver - this is the maximum number of parallel DNS requests that are
		2091	sent to the DNS server.
		2092
		2093	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2094
		2095	The file to use instead of F</etc/resolv.conf> (or OS-specific
		2096	configuration) in the default resolver. When set to the empty string, no
		2097	default config will be used.
		2098
		2099	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2100
		2101	When neither C<ca_file> nor C<ca_path> was specified during
		2102	L<AnyEvent::TLS> context creation, and either of these environment
		2103	variables exist, they will be used to specify CA certificate locations
		2104	instead of a system-dependent default.
		2105
		2106	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2107
		2108	When these are set to C<1>, then the respective modules are not
		2109	loaded. Mostly good for testing AnyEvent itself.
		2110
		2111	=back
411		2112
412	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2113	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		2114
		2115	This is an advanced topic that you do not normally need to use AnyEvent in
		2116	a module. This section is only of use to event loop authors who want to
		2117	provide AnyEvent compatibility.
413		2118
414	If you need to support another event library which isn't directly	2119	If you need to support another event library which isn't directly
415	supported by AnyEvent, you can supply your own interface to it by	2120	supported by AnyEvent, you can supply your own interface to it by
416	pushing, before the first watcher gets created, the package name of	2121	pushing, before the first watcher gets created, the package name of
417	the event module and the package name of the interface to use onto	2122	the event module and the package name of the interface to use onto
418	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	2123	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
419	AnyEvent.	2124	AnyEvent, so it is reasonably cheap.
420		2125
421	Example:	2126	Example:
422		2127
423	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	2128	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
424		2129
425	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	2130	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
426	package/class when it finds the C<urxvt> package/module is loaded. When	2131	package/class when it finds the C<urxvt> package/module is already loaded.
		2132
427	AnyEvent is loaded and asked to find a suitable event model, it will	2133	When AnyEvent is loaded and asked to find a suitable event model, it
428	first check for the presence of urxvt.	2134	will first check for the presence of urxvt by trying to C<use> the
		2135	C<urxvt::anyevent> module.
429		2136
430	The class should provide implementations for all watcher types (see	2137	The class should provide implementations for all watcher types. See
431	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	2138	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
432	(Source code) and so on for actual examples, use C<perldoc -m	2139	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
433	AnyEvent::Impl::Glib> to see the sources).	2140	see the sources.
434		2141
		2142	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		2143	provide suitable (hopefully) replacements.
		2144
435	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	2145	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
436	uses the above line as-is. An interface isn't included in AnyEvent	2146	terminal emulator uses the above line as-is. An interface isn't included
437	because it doesn't make sense outside the embedded interpreter inside	2147	in AnyEvent because it doesn't make sense outside the embedded interpreter
438	I<rxvt-unicode>, and it is updated and maintained as part of the	2148	inside I<rxvt-unicode>, and it is updated and maintained as part of the
439	I<rxvt-unicode> distribution.	2149	I<rxvt-unicode> distribution.
440		2150
441	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2151	I<rxvt-unicode> also cheats a bit by not providing blocking access to
442	condition variables: code blocking while waiting for a condition will	2152	condition variables: code blocking while waiting for a condition will
443	C<die>. This still works with most modules/usages, and blocking calls must	2153	C<die>. This still works with most modules/usages, and blocking calls must
444	not be in an interactive appliation, so it makes sense.	2154	not be done in an interactive application, so it makes sense.
445		2155
446	=head1 ENVIRONMENT VARIABLES
447
448	The following environment variables are used by this module:
449
450	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
451	model gets used.
452
453	=head1 EXAMPLE	2156	=head1 EXAMPLE PROGRAM
454		2157
455	The following program uses an io watcher to read data from stdin, a timer	2158	The following program uses an I/O watcher to read data from STDIN, a timer
456	to display a message once per second, and a condvar to exit the program	2159	to display a message once per second, and a condition variable to quit the
457	when the user enters quit:	2160	program when the user enters quit:
458		2161
459	use AnyEvent;	2162	use AnyEvent;
460		2163
461	my $cv = AnyEvent->condvar;	2164	my $cv = AnyEvent->condvar;
462		2165
463	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	2166	my $io_watcher = AnyEvent->io (
		2167	fh => \*STDIN,
		2168	poll => 'r',
		2169	cb => sub {
464	warn "io event <$_[0]>\n"; # will always output <r>	2170	warn "io event <$_[0]>\n"; # will always output <r>
465	chomp (my $input = <STDIN>); # read a line	2171	chomp (my $input = <STDIN>); # read a line
466	warn "read: $input\n"; # output what has been read	2172	warn "read: $input\n"; # output what has been read
467	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2173	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		2174	},
		2175	);
		2176
		2177	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
		2178	warn "timeout\n"; # print 'timeout' at most every second
468	});	2179	});
469		2180
470	my $time_watcher; # can only be used once
471
472	sub new_timer {
473	$timer = AnyEvent->timer (after => 1, cb => sub {
474	warn "timeout\n"; # print 'timeout' about every second
475	&new_timer; # and restart the time
476	});
477	}
478
479	new_timer; # create first timer
480
481	$cv->wait; # wait until user enters /^q/i	2181	$cv->recv; # wait until user enters /^q/i
482		2182
483	=head1 REAL-WORLD EXAMPLE	2183	=head1 REAL-WORLD EXAMPLE
484		2184
485	Consider the L<Net::FCP> module. It features (among others) the following	2185	Consider the L<Net::FCP> module. It features (among others) the following
486	API calls, which are to freenet what HTTP GET requests are to http:	2186	API calls, which are to freenet what HTTP GET requests are to http:
…		…
536	syswrite $txn->{fh}, $txn->{request}	2236	syswrite $txn->{fh}, $txn->{request}
537	or die "connection or write error";	2237	or die "connection or write error";
538	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2238	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
539		2239
540	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2240	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
541	result and signals any possible waiters that the request ahs finished:	2241	result and signals any possible waiters that the request has finished:
542		2242
543	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2243	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
544		2244
545	if (end-of-file or data complete) {	2245	if (end-of-file or data complete) {
546	$txn->{result} = $txn->{buf};	2246	$txn->{result} = $txn->{buf};
547	$txn->{finished}->broadcast;	2247	$txn->{finished}->send;
548	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2248	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
549	}	2249	}
550		2250
551	The C<result> method, finally, just waits for the finished signal (if the	2251	The C<result> method, finally, just waits for the finished signal (if the
552	request was already finished, it doesn't wait, of course, and returns the	2252	request was already finished, it doesn't wait, of course, and returns the
553	data:	2253	data:
554		2254
555	$txn->{finished}->wait;	2255	$txn->{finished}->recv;
556	return $txn->{result};	2256	return $txn->{result};
557		2257
558	The actual code goes further and collects all errors (C<die>s, exceptions)	2258	The actual code goes further and collects all errors (C<die>s, exceptions)
559	that occured during request processing. The C<result> method detects	2259	that occurred during request processing. The C<result> method detects
560	wether an exception as thrown (it is stored inside the $txn object)	2260	whether an exception as thrown (it is stored inside the $txn object)
561	and just throws the exception, which means connection errors and other	2261	and just throws the exception, which means connection errors and other
562	problems get reported tot he code that tries to use the result, not in a	2262	problems get reported to the code that tries to use the result, not in a
563	random callback.	2263	random callback.
564		2264
565	All of this enables the following usage styles:	2265	All of this enables the following usage styles:
566		2266
567	1. Blocking:	2267	1. Blocking:
568		2268
569	my $data = $fcp->client_get ($url);	2269	my $data = $fcp->client_get ($url);
570		2270
571	2. Blocking, but parallelizing:	2271	2. Blocking, but running in parallel:
572		2272
573	my @datas = map $_->result,	2273	my @datas = map $_->result,
574	map $fcp->txn_client_get ($_),	2274	map $fcp->txn_client_get ($_),
575	@urls;	2275	@urls;
576		2276
577	Both blocking examples work without the module user having to know	2277	Both blocking examples work without the module user having to know
578	anything about events.	2278	anything about events.
579		2279
580	3a. Event-based in a main program, using any support Event module:	2280	3a. Event-based in a main program, using any supported event module:
581		2281
582	use Event;	2282	use EV;
583		2283
584	$fcp->txn_client_get ($url)->cb (sub {	2284	$fcp->txn_client_get ($url)->cb (sub {
585	my $txn = shift;	2285	my $txn = shift;
586	my $data = $txn->result;	2286	my $data = $txn->result;
587	...	2287	...
588	});	2288	});
589		2289
590	Event::loop;	2290	EV::loop;
591		2291
592	3b. The module user could use AnyEvent, too:	2292	3b. The module user could use AnyEvent, too:
593		2293
594	use AnyEvent;	2294	use AnyEvent;
595		2295
596	my $quit = AnyEvent->condvar;	2296	my $quit = AnyEvent->condvar;
597		2297
598	$fcp->txn_client_get ($url)->cb (sub {	2298	$fcp->txn_client_get ($url)->cb (sub {
599	...	2299	...
600	$quit->broadcast;	2300	$quit->send;
601	});	2301	});
602		2302
603	$quit->wait;	2303	$quit->recv;
		2304
		2305
		2306	=head1 BENCHMARKS
		2307
		2308	To give you an idea of the performance and overheads that AnyEvent adds
		2309	over the event loops themselves and to give you an impression of the speed
		2310	of various event loops I prepared some benchmarks.
		2311
		2312	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2313
		2314	Here is a benchmark of various supported event models used natively and
		2315	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2316	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2317	which it is), lets them fire exactly once and destroys them again.
		2318
		2319	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2320	distribution. It uses the L<AE> interface, which makes a real difference
		2321	for the EV and Perl backends only.
		2322
		2323	=head3 Explanation of the columns
		2324
		2325	I<watcher> is the number of event watchers created/destroyed. Since
		2326	different event models feature vastly different performances, each event
		2327	loop was given a number of watchers so that overall runtime is acceptable
		2328	and similar between tested event loop (and keep them from crashing): Glib
		2329	would probably take thousands of years if asked to process the same number
		2330	of watchers as EV in this benchmark.
		2331
		2332	I<bytes> is the number of bytes (as measured by the resident set size,
		2333	RSS) consumed by each watcher. This method of measuring captures both C
		2334	and Perl-based overheads.
		2335
		2336	I<create> is the time, in microseconds (millionths of seconds), that it
		2337	takes to create a single watcher. The callback is a closure shared between
		2338	all watchers, to avoid adding memory overhead. That means closure creation
		2339	and memory usage is not included in the figures.
		2340
		2341	I<invoke> is the time, in microseconds, used to invoke a simple
		2342	callback. The callback simply counts down a Perl variable and after it was
		2343	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2344	signal the end of this phase.
		2345
		2346	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2347	watcher.
		2348
		2349	=head3 Results
		2350
		2351	name watchers bytes create invoke destroy comment
		2352	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2353	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2354	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2355	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2356	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2357	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2358	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2359	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2360	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2361	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2362	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2363	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2364
		2365	=head3 Discussion
		2366
		2367	The benchmark does I<not> measure scalability of the event loop very
		2368	well. For example, a select-based event loop (such as the pure perl one)
		2369	can never compete with an event loop that uses epoll when the number of
		2370	file descriptors grows high. In this benchmark, all events become ready at
		2371	the same time, so select/poll-based implementations get an unnatural speed
		2372	boost.
		2373
		2374	Also, note that the number of watchers usually has a nonlinear effect on
		2375	overall speed, that is, creating twice as many watchers doesn't take twice
		2376	the time - usually it takes longer. This puts event loops tested with a
		2377	higher number of watchers at a disadvantage.
		2378
		2379	To put the range of results into perspective, consider that on the
		2380	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2381	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2382	cycles with POE.
		2383
		2384	C<EV> is the sole leader regarding speed and memory use, which are both
		2385	maximal/minimal, respectively. When using the L<AE> API there is zero
		2386	overhead (when going through the AnyEvent API create is about 5-6 times
		2387	slower, with other times being equal, so still uses far less memory than
		2388	any other event loop and is still faster than Event natively).
		2389
		2390	The pure perl implementation is hit in a few sweet spots (both the
		2391	constant timeout and the use of a single fd hit optimisations in the perl
		2392	interpreter and the backend itself). Nevertheless this shows that it
		2393	adds very little overhead in itself. Like any select-based backend its
		2394	performance becomes really bad with lots of file descriptors (and few of
		2395	them active), of course, but this was not subject of this benchmark.
		2396
		2397	The C<Event> module has a relatively high setup and callback invocation
		2398	cost, but overall scores in on the third place.
		2399
		2400	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2401	when using its pure perl backend.
		2402
		2403	C<Glib>'s memory usage is quite a bit higher, but it features a
		2404	faster callback invocation and overall ends up in the same class as
		2405	C<Event>. However, Glib scales extremely badly, doubling the number of
		2406	watchers increases the processing time by more than a factor of four,
		2407	making it completely unusable when using larger numbers of watchers
		2408	(note that only a single file descriptor was used in the benchmark, so
		2409	inefficiencies of C<poll> do not account for this).
		2410
		2411	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2412	more than 2000 watchers is a big setback, however, as correctness takes
		2413	precedence over speed. Nevertheless, its performance is surprising, as the
		2414	file descriptor is dup()ed for each watcher. This shows that the dup()
		2415	employed by some adaptors is not a big performance issue (it does incur a
		2416	hidden memory cost inside the kernel which is not reflected in the figures
		2417	above).
		2418
		2419	C<POE>, regardless of underlying event loop (whether using its pure perl
		2420	select-based backend or the Event module, the POE-EV backend couldn't
		2421	be tested because it wasn't working) shows abysmal performance and
		2422	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2423	as EV watchers, and 10 times as much memory as Event (the high memory
		2424	requirements are caused by requiring a session for each watcher). Watcher
		2425	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2426	implementation.
		2427
		2428	The design of the POE adaptor class in AnyEvent can not really account
		2429	for the performance issues, though, as session creation overhead is
		2430	small compared to execution of the state machine, which is coded pretty
		2431	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2432	using multiple sessions is not a good approach, especially regarding
		2433	memory usage, even the author of POE could not come up with a faster
		2434	design).
		2435
		2436	=head3 Summary
		2437
		2438	=over 4
		2439
		2440	=item * Using EV through AnyEvent is faster than any other event loop
		2441	(even when used without AnyEvent), but most event loops have acceptable
		2442	performance with or without AnyEvent.
		2443
		2444	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2445	the actual event loop, only with extremely fast event loops such as EV
		2446	does AnyEvent add significant overhead.
		2447
		2448	=item * You should avoid POE like the plague if you want performance or
		2449	reasonable memory usage.
		2450
		2451	=back
		2452
		2453	=head2 BENCHMARKING THE LARGE SERVER CASE
		2454
		2455	This benchmark actually benchmarks the event loop itself. It works by
		2456	creating a number of "servers": each server consists of a socket pair, a
		2457	timeout watcher that gets reset on activity (but never fires), and an I/O
		2458	watcher waiting for input on one side of the socket. Each time the socket
		2459	watcher reads a byte it will write that byte to a random other "server".
		2460
		2461	The effect is that there will be a lot of I/O watchers, only part of which
		2462	are active at any one point (so there is a constant number of active
		2463	fds for each loop iteration, but which fds these are is random). The
		2464	timeout is reset each time something is read because that reflects how
		2465	most timeouts work (and puts extra pressure on the event loops).
		2466
		2467	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2468	(1%) are active. This mirrors the activity of large servers with many
		2469	connections, most of which are idle at any one point in time.
		2470
		2471	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2472	distribution. It uses the L<AE> interface, which makes a real difference
		2473	for the EV and Perl backends only.
		2474
		2475	=head3 Explanation of the columns
		2476
		2477	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2478	each server has a read and write socket end).
		2479
		2480	I<create> is the time it takes to create a socket pair (which is
		2481	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2482
		2483	I<request>, the most important value, is the time it takes to handle a
		2484	single "request", that is, reading the token from the pipe and forwarding
		2485	it to another server. This includes deleting the old timeout and creating
		2486	a new one that moves the timeout into the future.
		2487
		2488	=head3 Results
		2489
		2490	name sockets create request
		2491	EV 20000 62.66 7.99
		2492	Perl 20000 68.32 32.64
		2493	IOAsync 20000 174.06 101.15 epoll
		2494	IOAsync 20000 174.67 610.84 poll
		2495	Event 20000 202.69 242.91
		2496	Glib 20000 557.01 1689.52
		2497	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2498
		2499	=head3 Discussion
		2500
		2501	This benchmark I<does> measure scalability and overall performance of the
		2502	particular event loop.
		2503
		2504	EV is again fastest. Since it is using epoll on my system, the setup time
		2505	is relatively high, though.
		2506
		2507	Perl surprisingly comes second. It is much faster than the C-based event
		2508	loops Event and Glib.
		2509
		2510	IO::Async performs very well when using its epoll backend, and still quite
		2511	good compared to Glib when using its pure perl backend.
		2512
		2513	Event suffers from high setup time as well (look at its code and you will
		2514	understand why). Callback invocation also has a high overhead compared to
		2515	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2516	uses select or poll in basically all documented configurations.
		2517
		2518	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2519	clearly fails to perform with many filehandles or in busy servers.
		2520
		2521	POE is still completely out of the picture, taking over 1000 times as long
		2522	as EV, and over 100 times as long as the Perl implementation, even though
		2523	it uses a C-based event loop in this case.
		2524
		2525	=head3 Summary
		2526
		2527	=over 4
		2528
		2529	=item * The pure perl implementation performs extremely well.
		2530
		2531	=item * Avoid Glib or POE in large projects where performance matters.
		2532
		2533	=back
		2534
		2535	=head2 BENCHMARKING SMALL SERVERS
		2536
		2537	While event loops should scale (and select-based ones do not...) even to
		2538	large servers, most programs we (or I :) actually write have only a few
		2539	I/O watchers.
		2540
		2541	In this benchmark, I use the same benchmark program as in the large server
		2542	case, but it uses only eight "servers", of which three are active at any
		2543	one time. This should reflect performance for a small server relatively
		2544	well.
		2545
		2546	The columns are identical to the previous table.
		2547
		2548	=head3 Results
		2549
		2550	name sockets create request
		2551	EV 16 20.00 6.54
		2552	Perl 16 25.75 12.62
		2553	Event 16 81.27 35.86
		2554	Glib 16 32.63 15.48
		2555	POE 16 261.87 276.28 uses POE::Loop::Event
		2556
		2557	=head3 Discussion
		2558
		2559	The benchmark tries to test the performance of a typical small
		2560	server. While knowing how various event loops perform is interesting, keep
		2561	in mind that their overhead in this case is usually not as important, due
		2562	to the small absolute number of watchers (that is, you need efficiency and
		2563	speed most when you have lots of watchers, not when you only have a few of
		2564	them).
		2565
		2566	EV is again fastest.
		2567
		2568	Perl again comes second. It is noticeably faster than the C-based event
		2569	loops Event and Glib, although the difference is too small to really
		2570	matter.
		2571
		2572	POE also performs much better in this case, but is is still far behind the
		2573	others.
		2574
		2575	=head3 Summary
		2576
		2577	=over 4
		2578
		2579	=item * C-based event loops perform very well with small number of
		2580	watchers, as the management overhead dominates.
		2581
		2582	=back
		2583
		2584	=head2 THE IO::Lambda BENCHMARK
		2585
		2586	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2587	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2588	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2589	shouldn't come as a surprise to anybody). As such, the benchmark is
		2590	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2591	very optimal. But how would AnyEvent compare when used without the extra
		2592	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2593
		2594	The benchmark itself creates an echo-server, and then, for 500 times,
		2595	connects to the echo server, sends a line, waits for the reply, and then
		2596	creates the next connection. This is a rather bad benchmark, as it doesn't
		2597	test the efficiency of the framework or much non-blocking I/O, but it is a
		2598	benchmark nevertheless.
		2599
		2600	name runtime
		2601	Lambda/select 0.330 sec
		2602	+ optimized 0.122 sec
		2603	Lambda/AnyEvent 0.327 sec
		2604	+ optimized 0.138 sec
		2605	Raw sockets/select 0.077 sec
		2606	POE/select, components 0.662 sec
		2607	POE/select, raw sockets 0.226 sec
		2608	POE/select, optimized 0.404 sec
		2609
		2610	AnyEvent/select/nb 0.085 sec
		2611	AnyEvent/EV/nb 0.068 sec
		2612	+state machine 0.134 sec
		2613
		2614	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2615	benchmarks actually make blocking connects and use 100% blocking I/O,
		2616	defeating the purpose of an event-based solution. All of the newly
		2617	written AnyEvent benchmarks use 100% non-blocking connects (using
		2618	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2619	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2620	generally require a lot more bookkeeping and event handling than blocking
		2621	connects (which involve a single syscall only).
		2622
		2623	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2624	offers similar expressive power as POE and IO::Lambda, using conventional
		2625	Perl syntax. This means that both the echo server and the client are 100%
		2626	non-blocking, further placing it at a disadvantage.
		2627
		2628	As you can see, the AnyEvent + EV combination even beats the
		2629	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2630	backend easily beats IO::Lambda and POE.
		2631
		2632	And even the 100% non-blocking version written using the high-level (and
		2633	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2634	higher level ("unoptimised") abstractions by a large margin, even though
		2635	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2636
		2637	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2638	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2639	part of the IO::Lambda distribution and were used without any changes.
		2640
		2641
		2642	=head1 SIGNALS
		2643
		2644	AnyEvent currently installs handlers for these signals:
		2645
		2646	=over 4
		2647
		2648	=item SIGCHLD
		2649
		2650	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2651	emulation for event loops that do not support them natively. Also, some
		2652	event loops install a similar handler.
		2653
		2654	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2655	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2656
		2657	=item SIGPIPE
		2658
		2659	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2660	when AnyEvent gets loaded.
		2661
		2662	The rationale for this is that AnyEvent users usually do not really depend
		2663	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2664	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2665	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2666	some random socket.
		2667
		2668	The rationale for installing a no-op handler as opposed to ignoring it is
		2669	that this way, the handler will be restored to defaults on exec.
		2670
		2671	Feel free to install your own handler, or reset it to defaults.
		2672
		2673	=back
		2674
		2675	=cut
		2676
		2677	undef $SIG{CHLD}
		2678	if $SIG{CHLD} eq 'IGNORE';
		2679
		2680	$SIG{PIPE} = sub { }
		2681	unless defined $SIG{PIPE};
		2682
		2683	=head1 RECOMMENDED/OPTIONAL MODULES
		2684
		2685	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2686	its built-in modules) are required to use it.
		2687
		2688	That does not mean that AnyEvent won't take advantage of some additional
		2689	modules if they are installed.
		2690
		2691	This section explains which additional modules will be used, and how they
		2692	affect AnyEvent's operation.
		2693
		2694	=over 4
		2695
		2696	=item L<Async::Interrupt>
		2697
		2698	This slightly arcane module is used to implement fast signal handling: To
		2699	my knowledge, there is no way to do completely race-free and quick
		2700	signal handling in pure perl. To ensure that signals still get
		2701	delivered, AnyEvent will start an interval timer to wake up perl (and
		2702	catch the signals) with some delay (default is 10 seconds, look for
		2703	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2704
		2705	If this module is available, then it will be used to implement signal
		2706	catching, which means that signals will not be delayed, and the event loop
		2707	will not be interrupted regularly, which is more efficient (and good for
		2708	battery life on laptops).
		2709
		2710	This affects not just the pure-perl event loop, but also other event loops
		2711	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2712
		2713	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2714	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2715	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2716	does nothing for those backends.
		2717
		2718	=item L<EV>
		2719
		2720	This module isn't really "optional", as it is simply one of the backend
		2721	event loops that AnyEvent can use. However, it is simply the best event
		2722	loop available in terms of features, speed and stability: It supports
		2723	the AnyEvent API optimally, implements all the watcher types in XS, does
		2724	automatic timer adjustments even when no monotonic clock is available,
		2725	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2726	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2727	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2728
		2729	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2730	then this module will do nothing for you.
		2731
		2732	=item L<Guard>
		2733
		2734	The guard module, when used, will be used to implement
		2735	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2736	lot less memory), but otherwise doesn't affect guard operation much. It is
		2737	purely used for performance.
		2738
		2739	=item L<JSON> and L<JSON::XS>
		2740
		2741	One of these modules is required when you want to read or write JSON data
		2742	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2743	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2744
		2745	=item L<Net::SSLeay>
		2746
		2747	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2748	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2749	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2750
		2751	=item L<Time::HiRes>
		2752
		2753	This module is part of perl since release 5.008. It will be used when the
		2754	chosen event library does not come with a timing source of its own. The
		2755	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2756	try to use a monotonic clock for timing stability.
		2757
		2758	=back
		2759
		2760
		2761	=head1 FORK
		2762
		2763	Most event libraries are not fork-safe. The ones who are usually are
		2764	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2765	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2766	are usually badly thought-out hacks that are incompatible with fork in
		2767	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2768	continue event-processing in both parent and child (or both, if you know
		2769	what you are doing).
		2770
		2771	This means that, in general, you cannot fork and do event processing in
		2772	the child if the event library was initialised before the fork (which
		2773	usually happens when the first AnyEvent watcher is created, or the library
		2774	is loaded).
		2775
		2776	If you have to fork, you must either do so I<before> creating your first
		2777	watcher OR you must not use AnyEvent at all in the child OR you must do
		2778	something completely out of the scope of AnyEvent.
		2779
		2780	The problem of doing event processing in the parent I<and> the child
		2781	is much more complicated: even for backends that I<are> fork-aware or
		2782	fork-safe, their behaviour is not usually what you want: fork clones all
		2783	watchers, that means all timers, I/O watchers etc. are active in both
		2784	parent and child, which is almost never what you want. USing C<exec>
		2785	to start worker children from some kind of manage rprocess is usually
		2786	preferred, because it is much easier and cleaner, at the expense of having
		2787	to have another binary.
		2788
		2789
		2790	=head1 SECURITY CONSIDERATIONS
		2791
		2792	AnyEvent can be forced to load any event model via
		2793	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2794	execute arbitrary code or directly gain access, it can easily be used to
		2795	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2796	will not be active when the program uses a different event model than
		2797	specified in the variable.
		2798
		2799	You can make AnyEvent completely ignore this variable by deleting it
		2800	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2801
		2802	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2803
		2804	use AnyEvent;
		2805
		2806	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2807	be used to probe what backend is used and gain other information (which is
		2808	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2809	$ENV{PERL_ANYEVENT_STRICT}.
		2810
		2811	Note that AnyEvent will remove I<all> environment variables starting with
		2812	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2813	enabled.
		2814
		2815
		2816	=head1 BUGS
		2817
		2818	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2819	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2820	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2821	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2822	pronounced).
		2823
604		2824
605	=head1 SEE ALSO	2825	=head1 SEE ALSO
606		2826
607	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	2827	Tutorial/Introduction: L<AnyEvent::Intro>.
608		2828
609	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	2829	FAQ: L<AnyEvent::FAQ>.
610		2830
611	Nontrivial usage example: L<Net::FCP>.	2831	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2832	(simply logging).
612		2833
613	=head1	2834	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2835	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2836
		2837	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2838	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2839	L<Qt>, L<POE>, L<FLTK>.
		2840
		2841	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2842	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2843	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2844	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
		2845	L<AnyEvent::Impl::FLTK>.
		2846
		2847	Non-blocking handles, pipes, stream sockets, TCP clients and
		2848	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2849
		2850	Asynchronous DNS: L<AnyEvent::DNS>.
		2851
		2852	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		2853
		2854	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2855	L<AnyEvent::HTTP>.
		2856
		2857
		2858	=head1 AUTHOR
		2859
		2860	Marc Lehmann <schmorp@schmorp.de>
		2861	http://home.schmorp.de/
614		2862
615	=cut	2863	=cut
616		2864
617	1	2865	1
618		2866

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