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Revision 1.367 by root, Wed Aug 17 02:14:17 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.
		1060
		1061	If you want to sprinkle loads of logging calls around your code, consider
		1062	creating a logger callback with the C<AnyEvent::Log::logger< function.
211		1063
212	=back	1064	=back
213		1065
214	=head1 WHAT TO DO IN A MODULE	1066	=head1 WHAT TO DO IN A MODULE
215		1067
216	As a module author, you should "use AnyEvent" and call AnyEvent methods	1068	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.	1069	freely, but you should not load a specific event module or rely on it.
218		1070
219	Be careful when you create watchers in the module body - Anyevent will	1071	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	1072	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	1073	by calling AnyEvent in your module body you force the user of your module
222	to load the event module first.	1074	to load the event module first.
223		1075
		1076	Never call C<< ->recv >> on a condition variable unless you I<know> that
		1077	the C<< ->send >> method has been called on it already. This is
		1078	because it will stall the whole program, and the whole point of using
		1079	events is to stay interactive.
		1080
		1081	It is fine, however, to call C<< ->recv >> when the user of your module
		1082	requests it (i.e. if you create a http request object ad have a method
		1083	called C<results> that returns the results, it may call C<< ->recv >>
		1084	freely, as the user of your module knows what she is doing. Always).
		1085
224	=head1 WHAT TO DO IN THE MAIN PROGRAM	1086	=head1 WHAT TO DO IN THE MAIN PROGRAM
225		1087
226	There will always be a single main program - the only place that should	1088	There will always be a single main program - the only place that should
227	dictate which event model to use.	1089	dictate which event model to use.
228		1090
229	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1091	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.	1092	when it depends on a module that uses an AnyEvent. If the program itself
		1093	uses AnyEvent, but does not care which event loop is used, all it needs
		1094	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1095	available loop implementation.
231		1096
232	If the main program relies on a specific event model (for example, in Gtk2	1097	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	1098	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	1099	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	1100	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	1101	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	1102	decide on the event model to use as soon as it creates watchers, and it
238	correct one yourself.	1103	might choose the wrong one unless you load the correct one yourself.
239		1104
240	You can chose to use a rather inefficient pure-perl implementation by	1105	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	1106	C<AnyEvent::Loop> module, which gives you similar behaviour
242	generally better.	1107	everywhere, but letting AnyEvent chose the model is generally better.
		1108
		1109	=head2 MAINLOOP EMULATION
		1110
		1111	Sometimes (often for short test scripts, or even standalone programs who
		1112	only want to use AnyEvent), you do not want to run a specific event loop.
		1113
		1114	In that case, you can use a condition variable like this:
		1115
		1116	AnyEvent->condvar->recv;
		1117
		1118	This has the effect of entering the event loop and looping forever.
		1119
		1120	Note that usually your program has some exit condition, in which case
		1121	it is better to use the "traditional" approach of storing a condition
		1122	variable somewhere, waiting for it, and sending it when the program should
		1123	exit cleanly.
		1124
		1125
		1126	=head1 OTHER MODULES
		1127
		1128	The following is a non-exhaustive list of additional modules that use
		1129	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1130	modules and other event loops in the same program. Some of the modules
		1131	come as part of AnyEvent, the others are available via CPAN.
		1132
		1133	=over 4
		1134
		1135	=item L<AnyEvent::Util>
		1136
		1137	Contains various utility functions that replace often-used blocking
		1138	functions such as C<inet_aton> with event/callback-based versions.
		1139
		1140	=item L<AnyEvent::Socket>
		1141
		1142	Provides various utility functions for (internet protocol) sockets,
		1143	addresses and name resolution. Also functions to create non-blocking tcp
		1144	connections or tcp servers, with IPv6 and SRV record support and more.
		1145
		1146	=item L<AnyEvent::Handle>
		1147
		1148	Provide read and write buffers, manages watchers for reads and writes,
		1149	supports raw and formatted I/O, I/O queued and fully transparent and
		1150	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1151
		1152	=item L<AnyEvent::DNS>
		1153
		1154	Provides rich asynchronous DNS resolver capabilities.
		1155
		1156	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1157
		1158	Implement event-based interfaces to the protocols of the same name (for
		1159	the curious, IGS is the International Go Server and FCP is the Freenet
		1160	Client Protocol).
		1161
		1162	=item L<AnyEvent::Handle::UDP>
		1163
		1164	Here be danger!
		1165
		1166	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1167	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1168	its use of a stream-based API with a protocol that isn't streamable, that
		1169	the only way to improve it is to delete it.
		1170
		1171	It features data corruption (but typically only under load) and general
		1172	confusion. On top, the author is not only clueless about UDP but also
		1173	fact-resistant - some gems of his understanding: "connect doesn't work
		1174	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1175	packets", "I don't need to implement proper error checking as UDP doesn't
		1176	support error checking" and so on - he doesn't even understand what's
		1177	wrong with his module when it is explained to him.
		1178
		1179	=item L<AnyEvent::DBI>
		1180
		1181	Executes L<DBI> requests asynchronously in a proxy process for you,
		1182	notifying you in an event-based way when the operation is finished.
		1183
		1184	=item L<AnyEvent::AIO>
		1185
		1186	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1187	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1188	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1189	file I/O, and much more.
		1190
		1191	=item L<AnyEvent::HTTPD>
		1192
		1193	A simple embedded webserver.
		1194
		1195	=item L<AnyEvent::FastPing>
		1196
		1197	The fastest ping in the west.
		1198
		1199	=item L<Coro>
		1200
		1201	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1202
		1203	=back
243		1204
244	=cut	1205	=cut
245		1206
246	package AnyEvent;	1207	package AnyEvent;
247		1208
248	no warnings;	1209	# basically a tuned-down version of common::sense
249	use strict;	1210	sub common_sense {
		1211	# from common:.sense 3.4
		1212	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1213	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1214	$^H |= 0x00000600;
		1215	}
		1216
		1217	BEGIN { AnyEvent::common_sense }
		1218
250	use Carp;	1219	use Carp ();
251		1220
252	our $VERSION = '2.52';	1221	our $VERSION = '6.01';
253	our $MODEL;	1222	our $MODEL;
254		1223
255	our $AUTOLOAD;
256	our @ISA;	1224	our @ISA;
257		1225
258	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
259
260	our @REGISTRY;	1226	our @REGISTRY;
261		1227
		1228	our $VERBOSE;
		1229
		1230	BEGIN {
		1231	require "AnyEvent/constants.pl";
		1232
		1233	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1234
		1235	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1236	if ${^TAINT};
		1237
		1238	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1239	}
		1240
		1241	our $MAX_SIGNAL_LATENCY = 10;
		1242
		1243	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1244
		1245	{
		1246	my $idx;
		1247	$PROTOCOL{$_} = ++$idx
		1248	for reverse split /\s*,\s*/,
		1249	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1250	}
		1251
		1252	our @post_detect;
		1253
		1254	sub post_detect(&) {
		1255	my ($cb) = @_;
		1256
		1257	push @post_detect, $cb;
		1258
		1259	defined wantarray
		1260	? bless \$cb, "AnyEvent::Util::postdetect"
		1261	: ()
		1262	}
		1263
		1264	sub AnyEvent::Util::postdetect::DESTROY {
		1265	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1266	}
		1267
		1268	our $POSTPONE_W;
		1269	our @POSTPONE;
		1270
		1271	sub _postpone_exec {
		1272	undef $POSTPONE_W;
		1273
		1274	&{ shift @POSTPONE }
		1275	while @POSTPONE;
		1276	}
		1277
		1278	sub postpone(&) {
		1279	push @POSTPONE, shift;
		1280
		1281	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1282
		1283	()
		1284	}
		1285
		1286	sub log($$;@) {
		1287	require AnyEvent::Log;
		1288	# AnyEvent::Log overwrites this function
		1289	goto &log;
		1290	}
		1291
262	my @models = (	1292	our @models = (
		1293	[EV:: => AnyEvent::Impl::EV:: , 1],
263	[Coro::Event:: => AnyEvent::Impl::Coro::],	1294	[AnyEvent::Loop:: => AnyEvent::Impl::Perl:: , 1],
		1295	# everything below here will not (normally) be autoprobed
		1296	# as the pure perl backend should work everywhere
		1297	# and is usually faster
264	[Event:: => AnyEvent::Impl::Event::],	1298	[Event:: => AnyEvent::Impl::Event::, 1],
265	[Glib:: => AnyEvent::Impl::Glib::],	1299	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1300	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1301	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1302	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1303	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1304	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
266	[Tk:: => AnyEvent::Impl::Tk::],	1305	[Wx:: => AnyEvent::Impl::POE::],
267	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1306	[Prima:: => AnyEvent::Impl::POE::],
		1307	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
		1308	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
		1309	[FLTK:: => AnyEvent::Impl::FLTK2::],
268	);	1310	);
269		1311
270	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1312	our @isa_hook;
		1313
		1314	sub _isa_set {
		1315	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1316
		1317	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1318	for 1 .. $#pkg;
		1319
		1320	grep $_ && $_->[1], @isa_hook
		1321	and AE::_reset ();
		1322	}
		1323
		1324	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1325	sub _isa_hook($$;$) {
		1326	my ($i, $pkg, $reset_ae) = @_;
		1327
		1328	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1329
		1330	_isa_set;
		1331	}
		1332
		1333	# all autoloaded methods reserve the complete glob, not just the method slot.
		1334	# due to bugs in perls method cache implementation.
		1335	our @methods = qw(io timer time now now_update signal child idle condvar);
271		1336
272	sub detect() {	1337	sub detect() {
		1338	return $MODEL if $MODEL; # some programs keep references to detect
		1339
		1340	local $!; # for good measure
		1341	local $SIG{__DIE__}; # we use eval
		1342
		1343	# free some memory
		1344	*detect = sub () { $MODEL };
		1345	# undef &func doesn't correctly update the method cache. grmbl.
		1346	# so we delete the whole glob. grmbl.
		1347	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1348	# a glob with an active sub. hrm. i hope it works, but perl is
		1349	# usually buggy in this department. sigh.
		1350	delete @{"AnyEvent::"}{@methods};
		1351	undef @methods;
		1352
		1353	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1354	my $model = $1;
		1355	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1356	if (eval "require $model") {
		1357	$MODEL = $model;
		1358	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it."
		1359	if $VERBOSE >= 7;
		1360	} else {
		1361	AnyEvent::log warn => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1362	}
		1363	}
		1364
		1365	# check for already loaded models
273	unless ($MODEL) {	1366	unless ($MODEL) {
274	no strict 'refs';
275
276	# check for already loaded models
277	for (@REGISTRY, @models) {	1367	for (@REGISTRY, @models) {
278	my ($package, $model) = @$_;	1368	my ($package, $model) = @$_;
279	if (${"$package\::VERSION"} > 0) {	1369	if (${"$package\::VERSION"} > 0) {
280	if (eval "require $model") {	1370	if (eval "require $model") {
281	$MODEL = $model;	1371	$MODEL = $model;
282	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1372	AnyEvent::log 7 => "autodetected model '$model', using it."
		1373	if $VERBOSE >= 7;
283	last;	1374	last;
284	}	1375	}
285	}	1376	}
286	}	1377	}
287		1378
288	unless ($MODEL) {	1379	unless ($MODEL) {
289	# try to load a model	1380	# try to autoload a model
290
291	for (@REGISTRY, @models) {	1381	for (@REGISTRY, @models) {
292	my ($package, $model) = @$_;	1382	my ($package, $model, $autoload) = @$_;
		1383	if (
		1384	$autoload
293	if (eval "require $package"	1385	and eval "require $package"
294	and ${"$package\::VERSION"} > 0	1386	and ${"$package\::VERSION"} > 0
295	and eval "require $model") {	1387	and eval "require $model"
		1388	) {
296	$MODEL = $model;	1389	$MODEL = $model;
297	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	1390	AnyEvent::log 7 => "autoloaded model '$model', using it."
		1391	if $VERBOSE >= 7;
298	last;	1392	last;
299	}	1393	}
300	}	1394	}
301		1395
302	$MODEL	1396	$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.";	1397	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
304	}	1398	}
305
306	unshift @ISA, $MODEL;
307	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
308	}	1399	}
309		1400
		1401	# free memory only needed for probing
		1402	undef @models;
		1403	undef @REGISTRY;
		1404
		1405	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1406
		1407	# now nuke some methods that are overridden by the backend.
		1408	# SUPER usage is not allowed in these.
		1409	for (qw(time signal child idle)) {
		1410	undef &{"AnyEvent::Base::$_"}
		1411	if defined &{"$MODEL\::$_"};
		1412	}
		1413
		1414	_isa_set;
		1415
		1416	# we're officially open!
		1417
		1418	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1419	require AnyEvent::Strict;
		1420	}
		1421
		1422	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1423	require AnyEvent::Debug;
		1424	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1425	}
		1426
		1427	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1428	require AnyEvent::Socket;
		1429	require AnyEvent::Debug;
		1430
		1431	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1432	$shell =~ s/\$\$/$$/g;
		1433
		1434	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1435	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1436	}
		1437
		1438	# now the anyevent environment is set up as the user told us to, so
		1439	# call the actual user code - post detects
		1440
		1441	(shift @post_detect)->() while @post_detect;
		1442	undef @post_detect;
		1443
		1444	*post_detect = sub(&) {
		1445	shift->();
		1446
		1447	undef
		1448	};
		1449
310	$MODEL	1450	$MODEL
311	}	1451	}
312		1452
313	sub AUTOLOAD {	1453	for my $name (@methods) {
314	(my $func = $AUTOLOAD) =~ s/.*://;	1454	*$name = sub {
315		1455	detect;
316	$method{$func}	1456	# we use goto because
317	or croak "$func: not a valid method for AnyEvent objects";	1457	# a) it makes the thunk more transparent
318		1458	# b) it allows us to delete the thunk later
319	detect unless $MODEL;	1459	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
320		1460	};
321	my $class = shift;
322	$class->$func (@_);
323	}	1461	}
		1462
		1463	# utility function to dup a filehandle. this is used by many backends
		1464	# to support binding more than one watcher per filehandle (they usually
		1465	# allow only one watcher per fd, so we dup it to get a different one).
		1466	sub _dupfh($$;$$) {
		1467	my ($poll, $fh, $r, $w) = @_;
		1468
		1469	# cygwin requires the fh mode to be matching, unix doesn't
		1470	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1471
		1472	open my $fh2, $mode, $fh
		1473	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1474
		1475	# we assume CLOEXEC is already set by perl in all important cases
		1476
		1477	($fh2, $rw)
		1478	}
		1479
		1480	=head1 SIMPLIFIED AE API
		1481
		1482	Starting with version 5.0, AnyEvent officially supports a second, much
		1483	simpler, API that is designed to reduce the calling, typing and memory
		1484	overhead by using function call syntax and a fixed number of parameters.
		1485
		1486	See the L<AE> manpage for details.
		1487
		1488	=cut
		1489
		1490	package AE;
		1491
		1492	our $VERSION = $AnyEvent::VERSION;
		1493
		1494	sub _reset() {
		1495	eval q{
		1496	# fall back to the main API by default - backends and AnyEvent::Base
		1497	# implementations can overwrite these.
		1498
		1499	sub io($$$) {
		1500	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1501	}
		1502
		1503	sub timer($$$) {
		1504	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1505	}
		1506
		1507	sub signal($$) {
		1508	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1509	}
		1510
		1511	sub child($$) {
		1512	AnyEvent->child (pid => $_[0], cb => $_[1])
		1513	}
		1514
		1515	sub idle($) {
		1516	AnyEvent->idle (cb => $_[0]);
		1517	}
		1518
		1519	sub cv(;&) {
		1520	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1521	}
		1522
		1523	sub now() {
		1524	AnyEvent->now
		1525	}
		1526
		1527	sub now_update() {
		1528	AnyEvent->now_update
		1529	}
		1530
		1531	sub time() {
		1532	AnyEvent->time
		1533	}
		1534
		1535	*postpone = \&AnyEvent::postpone;
		1536	*log = \&AnyEvent::log;
		1537	};
		1538	die if $@;
		1539	}
		1540
		1541	BEGIN { _reset }
324		1542
325	package AnyEvent::Base;	1543	package AnyEvent::Base;
326		1544
		1545	# default implementations for many methods
		1546
		1547	sub time {
		1548	eval q{ # poor man's autoloading {}
		1549	# probe for availability of Time::HiRes
		1550	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1551	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy."
		1552	if $AnyEvent::VERBOSE >= 8;
		1553	*time = sub { Time::HiRes::time () };
		1554	*AE::time = \& Time::HiRes::time ;
		1555	# if (eval "use POSIX (); (POSIX::times())...
		1556	} else {
		1557	AnyEvent::log critical => "using built-in time(), WARNING, no sub-second resolution!";
		1558	*time = sub { CORE::time };
		1559	*AE::time = sub (){ CORE::time };
		1560	}
		1561
		1562	*now = \&time;
		1563	};
		1564	die if $@;
		1565
		1566	&time
		1567	}
		1568
		1569	*now = \&time;
		1570	sub now_update { }
		1571
		1572	sub _poll {
		1573	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1574	}
		1575
327	# default implementation for ->condvar, ->wait, ->broadcast	1576	# default implementation for ->condvar
		1577	# in fact, the default should not be overwritten
328		1578
329	sub condvar {	1579	sub condvar {
330	bless \my $flag, "AnyEvent::Base::CondVar"	1580	eval q{ # poor man's autoloading {}
331	}	1581	*condvar = sub {
		1582	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1583	};
332		1584
333	sub AnyEvent::Base::CondVar::broadcast {	1585	*AE::cv = sub (;&) {
334	${$_[0]}++;	1586	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
335	}	1587	};
		1588	};
		1589	die if $@;
336		1590
337	sub AnyEvent::Base::CondVar::wait {	1591	&condvar
338	AnyEvent->one_event while !${$_[0]};
339	}	1592	}
340		1593
341	# default implementation for ->signal	1594	# default implementation for ->signal
342		1595
343	our %SIG_CB;	1596	our $HAVE_ASYNC_INTERRUPT;
		1597
		1598	sub _have_async_interrupt() {
		1599	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1600	&& eval "use Async::Interrupt 1.02 (); 1")
		1601	unless defined $HAVE_ASYNC_INTERRUPT;
		1602
		1603	$HAVE_ASYNC_INTERRUPT
		1604	}
		1605
		1606	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1607	our (%SIG_ASY, %SIG_ASY_W);
		1608	our ($SIG_COUNT, $SIG_TW);
		1609
		1610	# install a dummy wakeup watcher to reduce signal catching latency
		1611	# used by Impls
		1612	sub _sig_add() {
		1613	unless ($SIG_COUNT++) {
		1614	# try to align timer on a full-second boundary, if possible
		1615	my $NOW = AE::now;
		1616
		1617	$SIG_TW = AE::timer
		1618	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1619	$MAX_SIGNAL_LATENCY,
		1620	sub { } # just for the PERL_ASYNC_CHECK
		1621	;
		1622	}
		1623	}
		1624
		1625	sub _sig_del {
		1626	undef $SIG_TW
		1627	unless --$SIG_COUNT;
		1628	}
		1629
		1630	our $_sig_name_init; $_sig_name_init = sub {
		1631	eval q{ # poor man's autoloading {}
		1632	undef $_sig_name_init;
		1633
		1634	if (_have_async_interrupt) {
		1635	*sig2num = \&Async::Interrupt::sig2num;
		1636	*sig2name = \&Async::Interrupt::sig2name;
		1637	} else {
		1638	require Config;
		1639
		1640	my %signame2num;
		1641	@signame2num{ split ' ', $Config::Config{sig_name} }
		1642	= split ' ', $Config::Config{sig_num};
		1643
		1644	my @signum2name;
		1645	@signum2name[values %signame2num] = keys %signame2num;
		1646
		1647	*sig2num = sub($) {
		1648	$_[0] > 0 ? shift : $signame2num{+shift}
		1649	};
		1650	*sig2name = sub ($) {
		1651	$_[0] > 0 ? $signum2name[+shift] : shift
		1652	};
		1653	}
		1654	};
		1655	die if $@;
		1656	};
		1657
		1658	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1659	sub sig2name($) { &$_sig_name_init; &sig2name }
344		1660
345	sub signal {	1661	sub signal {
		1662	eval q{ # poor man's autoloading {}
		1663	# probe for availability of Async::Interrupt
		1664	if (_have_async_interrupt) {
		1665	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling."
		1666	if $AnyEvent::VERBOSE >= 8;
		1667
		1668	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1669	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1670
		1671	} else {
		1672	AnyEvent::log 8 => "using emulated perl signal handling with latency timer."
		1673	if $AnyEvent::VERBOSE >= 8;
		1674
		1675	if (AnyEvent::WIN32) {
		1676	require AnyEvent::Util;
		1677
		1678	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1679	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1680	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1681	} else {
		1682	pipe $SIGPIPE_R, $SIGPIPE_W;
		1683	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1684	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1685
		1686	# not strictly required, as $^F is normally 2, but let's make sure...
		1687	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1688	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1689	}
		1690
		1691	$SIGPIPE_R
		1692	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1693
		1694	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1695	}
		1696
		1697	*signal = $HAVE_ASYNC_INTERRUPT
		1698	? sub {
346	my (undef, %arg) = @_;	1699	my (undef, %arg) = @_;
347		1700
		1701	# async::interrupt
348	my $signal = uc $arg{signal}	1702	my $signal = sig2num $arg{signal};
349	or Carp::croak "required option 'signal' is missing";
350
351	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1703	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1704
		1705	$SIG_ASY{$signal} ||= new Async::Interrupt
		1706	cb => sub { undef $SIG_EV{$signal} },
		1707	signal => $signal,
		1708	pipe => [$SIGPIPE_R->filenos],
		1709	pipe_autodrain => 0,
		1710	;
		1711
		1712	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1713	}
		1714	: sub {
		1715	my (undef, %arg) = @_;
		1716
		1717	# pure perl
		1718	my $signal = sig2name $arg{signal};
		1719	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1720
352	$SIG{$signal} ||= sub {	1721	$SIG{$signal} ||= sub {
		1722	local $!;
		1723	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1724	undef $SIG_EV{$signal};
		1725	};
		1726
		1727	# can't do signal processing without introducing races in pure perl,
		1728	# so limit the signal latency.
		1729	_sig_add;
		1730
		1731	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1732	}
		1733	;
		1734
		1735	*AnyEvent::Base::signal::DESTROY = sub {
		1736	my ($signal, $cb) = @{$_[0]};
		1737
		1738	_sig_del;
		1739
		1740	delete $SIG_CB{$signal}{$cb};
		1741
		1742	$HAVE_ASYNC_INTERRUPT
		1743	? delete $SIG_ASY{$signal}
		1744	: # delete doesn't work with older perls - they then
		1745	# print weird messages, or just unconditionally exit
		1746	# instead of getting the default action.
		1747	undef $SIG{$signal}
		1748	unless keys %{ $SIG_CB{$signal} };
		1749	};
		1750
		1751	*_signal_exec = sub {
		1752	$HAVE_ASYNC_INTERRUPT
		1753	? $SIGPIPE_R->drain
		1754	: sysread $SIGPIPE_R, (my $dummy), 9;
		1755
		1756	while (%SIG_EV) {
		1757	for (keys %SIG_EV) {
		1758	delete $SIG_EV{$_};
353	$_->() for values %{ $SIG_CB{$signal} || {} };	1759	&$_ for values %{ $SIG_CB{$_} || {} };
		1760	}
		1761	}
		1762	};
354	};	1763	};
		1764	die if $@;
355		1765
356	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1766	&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	}	1767	}
366		1768
367	# default implementation for ->child	1769	# default implementation for ->child
368		1770
369	our %PID_CB;	1771	our %PID_CB;
370	our $CHLD_W;	1772	our $CHLD_W;
371	our $PID_IDLE;	1773	our $CHLD_DELAY_W;
372	our $WNOHANG;
373		1774
374	sub _child_wait {	1775	# used by many Impl's
375	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1776	sub _emit_childstatus($$) {
		1777	my (undef, $rpid, $rstatus) = @_;
		1778
		1779	$_->($rpid, $rstatus)
376	$_->() for values %{ (delete $PID_CB{$pid}) || {} };	1780	for values %{ $PID_CB{$rpid} || {} },
		1781	values %{ $PID_CB{0} || {} };
		1782	}
		1783
		1784	sub child {
		1785	eval q{ # poor man's autoloading {}
		1786	*_sigchld = sub {
		1787	my $pid;
		1788
		1789	AnyEvent->_emit_childstatus ($pid, $?)
		1790	while ($pid = waitpid -1, WNOHANG) > 0;
		1791	};
		1792
		1793	*child = sub {
		1794	my (undef, %arg) = @_;
		1795
		1796	my $pid = $arg{pid};
		1797	my $cb = $arg{cb};
		1798
		1799	$PID_CB{$pid}{$cb+0} = $cb;
		1800
		1801	unless ($CHLD_W) {
		1802	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1803	# child could be a zombie already, so make at least one round
		1804	&_sigchld;
		1805	}
		1806
		1807	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1808	};
		1809
		1810	*AnyEvent::Base::child::DESTROY = sub {
		1811	my ($pid, $icb) = @{$_[0]};
		1812
		1813	delete $PID_CB{$pid}{$icb};
		1814	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1815
		1816	undef $CHLD_W unless keys %PID_CB;
		1817	};
		1818	};
		1819	die if $@;
		1820
		1821	&child
		1822	}
		1823
		1824	# idle emulation is done by simply using a timer, regardless
		1825	# of whether the process is idle or not, and not letting
		1826	# the callback use more than 50% of the time.
		1827	sub idle {
		1828	eval q{ # poor man's autoloading {}
		1829	*idle = sub {
		1830	my (undef, %arg) = @_;
		1831
		1832	my ($cb, $w, $rcb) = $arg{cb};
		1833
		1834	$rcb = sub {
		1835	if ($cb) {
		1836	$w = AE::time;
		1837	&$cb;
		1838	$w = AE::time - $w;
		1839
		1840	# never use more then 50% of the time for the idle watcher,
		1841	# within some limits
		1842	$w = 0.0001 if $w < 0.0001;
		1843	$w = 5 if $w > 5;
		1844
		1845	$w = AE::timer $w, 0, $rcb;
		1846	} else {
		1847	# clean up...
		1848	undef $w;
		1849	undef $rcb;
		1850	}
		1851	};
		1852
		1853	$w = AE::timer 0.05, 0, $rcb;
		1854
		1855	bless \\$cb, "AnyEvent::Base::idle"
		1856	};
		1857
		1858	*AnyEvent::Base::idle::DESTROY = sub {
		1859	undef $${$_[0]};
		1860	};
		1861	};
		1862	die if $@;
		1863
		1864	&idle
		1865	}
		1866
		1867	package AnyEvent::CondVar;
		1868
		1869	our @ISA = AnyEvent::CondVar::Base::;
		1870
		1871	# only to be used for subclassing
		1872	sub new {
		1873	my $class = shift;
		1874	bless AnyEvent->condvar (@_), $class
		1875	}
		1876
		1877	package AnyEvent::CondVar::Base;
		1878
		1879	#use overload
		1880	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1881	# fallback => 1;
		1882
		1883	# save 300+ kilobytes by dirtily hardcoding overloading
		1884	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1885	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1886	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1887	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1888
		1889	our $WAITING;
		1890
		1891	sub _send {
		1892	# nop
		1893	}
		1894
		1895	sub _wait {
		1896	AnyEvent->_poll until $_[0]{_ae_sent};
		1897	}
		1898
		1899	sub send {
		1900	my $cv = shift;
		1901	$cv->{_ae_sent} = [@_];
		1902	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1903	$cv->_send;
		1904	}
		1905
		1906	sub croak {
		1907	$_[0]{_ae_croak} = $_[1];
		1908	$_[0]->send;
		1909	}
		1910
		1911	sub ready {
		1912	$_[0]{_ae_sent}
		1913	}
		1914
		1915	sub recv {
		1916	unless ($_[0]{_ae_sent}) {
		1917	$WAITING
		1918	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1919
		1920	local $WAITING = 1;
		1921	$_[0]->_wait;
377	}	1922	}
378		1923
379	undef $PID_IDLE;	1924	$_[0]{_ae_croak}
380	}	1925	and Carp::croak $_[0]{_ae_croak};
381		1926
382	sub child {	1927	wantarray
383	my (undef, %arg) = @_;	1928	? @{ $_[0]{_ae_sent} }
384		1929	: $_[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	}	1930	}
402		1931
403	sub AnyEvent::Base::Child::DESTROY {	1932	sub cb {
404	my ($pid, $cb) = @{$_[0]};	1933	my $cv = shift;
405		1934
406	delete $PID_CB{$pid}{$cb};	1935	@_
407	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1936	and $cv->{_ae_cb} = shift
		1937	and $cv->{_ae_sent}
		1938	and (delete $cv->{_ae_cb})->($cv);
408		1939
409	undef $CHLD_W unless keys %PID_CB;	1940	$cv->{_ae_cb}
410	}	1941	}
		1942
		1943	sub begin {
		1944	++$_[0]{_ae_counter};
		1945	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1946	}
		1947
		1948	sub end {
		1949	return if --$_[0]{_ae_counter};
		1950	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1951	}
		1952
		1953	# undocumented/compatibility with pre-3.4
		1954	*broadcast = \&send;
		1955	*wait = \&recv;
		1956
		1957	=head1 ERROR AND EXCEPTION HANDLING
		1958
		1959	In general, AnyEvent does not do any error handling - it relies on the
		1960	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1961	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1962	checking of all AnyEvent methods, however, which is highly useful during
		1963	development.
		1964
		1965	As for exception handling (i.e. runtime errors and exceptions thrown while
		1966	executing a callback), this is not only highly event-loop specific, but
		1967	also not in any way wrapped by this module, as this is the job of the main
		1968	program.
		1969
		1970	The pure perl event loop simply re-throws the exception (usually
		1971	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1972	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1973	so on.
		1974
		1975	=head1 ENVIRONMENT VARIABLES
		1976
		1977	The following environment variables are used by this module or its
		1978	submodules.
		1979
		1980	Note that AnyEvent will remove I<all> environment variables starting with
		1981	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1982	enabled.
		1983
		1984	=over 4
		1985
		1986	=item C<PERL_ANYEVENT_VERBOSE>
		1987
		1988	By default, AnyEvent will be completely silent except in fatal
		1989	conditions. You can set this environment variable to make AnyEvent more
		1990	talkative.
		1991
		1992	When set to C<5> or higher, causes AnyEvent to warn about unexpected
		1993	conditions, such as not being able to load the event model specified by
		1994	C<PERL_ANYEVENT_MODEL>.
		1995
		1996	When set to C<7> or higher, cause AnyEvent to report to STDERR which event
		1997	model it chooses.
		1998
		1999	When set to C<8> or higher, then AnyEvent will report extra information on
		2000	which optional modules it loads and how it implements certain features.
		2001
		2002	=item C<PERL_ANYEVENT_STRICT>
		2003
		2004	AnyEvent does not do much argument checking by default, as thorough
		2005	argument checking is very costly. Setting this variable to a true value
		2006	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2007	check the arguments passed to most method calls. If it finds any problems,
		2008	it will croak.
		2009
		2010	In other words, enables "strict" mode.
		2011
		2012	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2013	>>, it is definitely recommended to keep it off in production. Keeping
		2014	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2015	can be very useful, however.
		2016
		2017	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2018
		2019	If this env variable is set, then its contents will be interpreted by
		2020	C<AnyEvent::Socket::parse_hostport> (after replacing every occurance of
		2021	C<$$> by the process pid) and an C<AnyEvent::Debug::shell> is bound on
		2022	that port. The shell object is saved in C<$AnyEvent::Debug::SHELL>.
		2023
		2024	This takes place when the first watcher is created.
		2025
		2026	For example, to bind a debug shell on a unix domain socket in
		2027	F<< /tmp/debug<pid>.sock >>, you could use this:
		2028
		2029	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2030
		2031	Note that creating sockets in F</tmp> is very unsafe on multiuser
		2032	systems.
		2033
		2034	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2035
		2036	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2037	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2038
		2039	=item C<PERL_ANYEVENT_MODEL>
		2040
		2041	This can be used to specify the event model to be used by AnyEvent, before
		2042	auto detection and -probing kicks in.
		2043
		2044	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2045	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2046	resulting module name is loaded and - if the load was successful - used as
		2047	event model backend. If it fails to load then AnyEvent will proceed with
		2048	auto detection and -probing.
		2049
		2050	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2051	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2052	the end of a string designates a module name and quotes it appropriately).
		2053
		2054	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2055	could start your program like this:
		2056
		2057	PERL_ANYEVENT_MODEL=Perl perl ...
		2058
		2059	=item C<PERL_ANYEVENT_PROTOCOLS>
		2060
		2061	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2062	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2063	of auto probing).
		2064
		2065	Must be set to a comma-separated list of protocols or address families,
		2066	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2067	used, and preference will be given to protocols mentioned earlier in the
		2068	list.
		2069
		2070	This variable can effectively be used for denial-of-service attacks
		2071	against local programs (e.g. when setuid), although the impact is likely
		2072	small, as the program has to handle conenction and other failures anyways.
		2073
		2074	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2075	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2076	- only support IPv4, never try to resolve or contact IPv6
		2077	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2078	IPv6, but prefer IPv6 over IPv4.
		2079
		2080	=item C<PERL_ANYEVENT_EDNS0>
		2081
		2082	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		2083	for DNS. This extension is generally useful to reduce DNS traffic, but
		2084	some (broken) firewalls drop such DNS packets, which is why it is off by
		2085	default.
		2086
		2087	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2088	EDNS0 in its DNS requests.
		2089
		2090	=item C<PERL_ANYEVENT_MAX_FORKS>
		2091
		2092	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2093	will create in parallel.
		2094
		2095	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2096
		2097	The default value for the C<max_outstanding> parameter for the default DNS
		2098	resolver - this is the maximum number of parallel DNS requests that are
		2099	sent to the DNS server.
		2100
		2101	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2102
		2103	The file to use instead of F</etc/resolv.conf> (or OS-specific
		2104	configuration) in the default resolver. When set to the empty string, no
		2105	default config will be used.
		2106
		2107	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2108
		2109	When neither C<ca_file> nor C<ca_path> was specified during
		2110	L<AnyEvent::TLS> context creation, and either of these environment
		2111	variables exist, they will be used to specify CA certificate locations
		2112	instead of a system-dependent default.
		2113
		2114	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2115
		2116	When these are set to C<1>, then the respective modules are not
		2117	loaded. Mostly good for testing AnyEvent itself.
		2118
		2119	=back
411		2120
412	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2121	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		2122
		2123	This is an advanced topic that you do not normally need to use AnyEvent in
		2124	a module. This section is only of use to event loop authors who want to
		2125	provide AnyEvent compatibility.
413		2126
414	If you need to support another event library which isn't directly	2127	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	2128	supported by AnyEvent, you can supply your own interface to it by
416	pushing, before the first watcher gets created, the package name of	2129	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	2130	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	2131	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
419	AnyEvent.	2132	AnyEvent, so it is reasonably cheap.
420		2133
421	Example:	2134	Example:
422		2135
423	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	2136	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
424		2137
425	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	2138	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
426	package/class when it finds the C<urxvt> package/module is loaded. When	2139	package/class when it finds the C<urxvt> package/module is already loaded.
		2140
427	AnyEvent is loaded and asked to find a suitable event model, it will	2141	When AnyEvent is loaded and asked to find a suitable event model, it
428	first check for the presence of urxvt.	2142	will first check for the presence of urxvt by trying to C<use> the
		2143	C<urxvt::anyevent> module.
429		2144
430	The class should provide implementations for all watcher types (see	2145	The class should provide implementations for all watcher types. See
431	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	2146	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	2147	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
433	AnyEvent::Impl::Glib> to see the sources).	2148	see the sources.
434		2149
		2150	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		2151	provide suitable (hopefully) replacements.
		2152
435	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	2153	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	2154	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	2155	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	2156	inside I<rxvt-unicode>, and it is updated and maintained as part of the
439	I<rxvt-unicode> distribution.	2157	I<rxvt-unicode> distribution.
440		2158
441	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2159	I<rxvt-unicode> also cheats a bit by not providing blocking access to
442	condition variables: code blocking while waiting for a condition will	2160	condition variables: code blocking while waiting for a condition will
443	C<die>. This still works with most modules/usages, and blocking calls must	2161	C<die>. This still works with most modules/usages, and blocking calls must
444	not be in an interactive appliation, so it makes sense.	2162	not be done in an interactive application, so it makes sense.
445		2163
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	2164	=head1 EXAMPLE PROGRAM
454		2165
455	The following program uses an io watcher to read data from stdin, a timer	2166	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	2167	to display a message once per second, and a condition variable to quit the
457	when the user enters quit:	2168	program when the user enters quit:
458		2169
459	use AnyEvent;	2170	use AnyEvent;
460		2171
461	my $cv = AnyEvent->condvar;	2172	my $cv = AnyEvent->condvar;
462		2173
463	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	2174	my $io_watcher = AnyEvent->io (
		2175	fh => \*STDIN,
		2176	poll => 'r',
		2177	cb => sub {
464	warn "io event <$_[0]>\n"; # will always output <r>	2178	warn "io event <$_[0]>\n"; # will always output <r>
465	chomp (my $input = <STDIN>); # read a line	2179	chomp (my $input = <STDIN>); # read a line
466	warn "read: $input\n"; # output what has been read	2180	warn "read: $input\n"; # output what has been read
467	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2181	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		2182	},
		2183	);
		2184
		2185	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
		2186	warn "timeout\n"; # print 'timeout' at most every second
468	});	2187	});
469		2188
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	2189	$cv->recv; # wait until user enters /^q/i
482		2190
483	=head1 REAL-WORLD EXAMPLE	2191	=head1 REAL-WORLD EXAMPLE
484		2192
485	Consider the L<Net::FCP> module. It features (among others) the following	2193	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:	2194	API calls, which are to freenet what HTTP GET requests are to http:
…		…
536	syswrite $txn->{fh}, $txn->{request}	2244	syswrite $txn->{fh}, $txn->{request}
537	or die "connection or write error";	2245	or die "connection or write error";
538	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2246	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
539		2247
540	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2248	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:	2249	result and signals any possible waiters that the request has finished:
542		2250
543	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2251	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
544		2252
545	if (end-of-file or data complete) {	2253	if (end-of-file or data complete) {
546	$txn->{result} = $txn->{buf};	2254	$txn->{result} = $txn->{buf};
547	$txn->{finished}->broadcast;	2255	$txn->{finished}->send;
548	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2256	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
549	}	2257	}
550		2258
551	The C<result> method, finally, just waits for the finished signal (if the	2259	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	2260	request was already finished, it doesn't wait, of course, and returns the
553	data:	2261	data:
554		2262
555	$txn->{finished}->wait;	2263	$txn->{finished}->recv;
556	return $txn->{result};	2264	return $txn->{result};
557		2265
558	The actual code goes further and collects all errors (C<die>s, exceptions)	2266	The actual code goes further and collects all errors (C<die>s, exceptions)
559	that occured during request processing. The C<result> method detects	2267	that occurred during request processing. The C<result> method detects
560	wether an exception as thrown (it is stored inside the $txn object)	2268	whether an exception as thrown (it is stored inside the $txn object)
561	and just throws the exception, which means connection errors and other	2269	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	2270	problems get reported to the code that tries to use the result, not in a
563	random callback.	2271	random callback.
564		2272
565	All of this enables the following usage styles:	2273	All of this enables the following usage styles:
566		2274
567	1. Blocking:	2275	1. Blocking:
568		2276
569	my $data = $fcp->client_get ($url);	2277	my $data = $fcp->client_get ($url);
570		2278
571	2. Blocking, but parallelizing:	2279	2. Blocking, but running in parallel:
572		2280
573	my @datas = map $_->result,	2281	my @datas = map $_->result,
574	map $fcp->txn_client_get ($_),	2282	map $fcp->txn_client_get ($_),
575	@urls;	2283	@urls;
576		2284
577	Both blocking examples work without the module user having to know	2285	Both blocking examples work without the module user having to know
578	anything about events.	2286	anything about events.
579		2287
580	3a. Event-based in a main program, using any support Event module:	2288	3a. Event-based in a main program, using any supported event module:
581		2289
582	use Event;	2290	use EV;
583		2291
584	$fcp->txn_client_get ($url)->cb (sub {	2292	$fcp->txn_client_get ($url)->cb (sub {
585	my $txn = shift;	2293	my $txn = shift;
586	my $data = $txn->result;	2294	my $data = $txn->result;
587	...	2295	...
588	});	2296	});
589		2297
590	Event::loop;	2298	EV::loop;
591		2299
592	3b. The module user could use AnyEvent, too:	2300	3b. The module user could use AnyEvent, too:
593		2301
594	use AnyEvent;	2302	use AnyEvent;
595		2303
596	my $quit = AnyEvent->condvar;	2304	my $quit = AnyEvent->condvar;
597		2305
598	$fcp->txn_client_get ($url)->cb (sub {	2306	$fcp->txn_client_get ($url)->cb (sub {
599	...	2307	...
600	$quit->broadcast;	2308	$quit->send;
601	});	2309	});
602		2310
603	$quit->wait;	2311	$quit->recv;
		2312
		2313
		2314	=head1 BENCHMARKS
		2315
		2316	To give you an idea of the performance and overheads that AnyEvent adds
		2317	over the event loops themselves and to give you an impression of the speed
		2318	of various event loops I prepared some benchmarks.
		2319
		2320	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2321
		2322	Here is a benchmark of various supported event models used natively and
		2323	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2324	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2325	which it is), lets them fire exactly once and destroys them again.
		2326
		2327	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2328	distribution. It uses the L<AE> interface, which makes a real difference
		2329	for the EV and Perl backends only.
		2330
		2331	=head3 Explanation of the columns
		2332
		2333	I<watcher> is the number of event watchers created/destroyed. Since
		2334	different event models feature vastly different performances, each event
		2335	loop was given a number of watchers so that overall runtime is acceptable
		2336	and similar between tested event loop (and keep them from crashing): Glib
		2337	would probably take thousands of years if asked to process the same number
		2338	of watchers as EV in this benchmark.
		2339
		2340	I<bytes> is the number of bytes (as measured by the resident set size,
		2341	RSS) consumed by each watcher. This method of measuring captures both C
		2342	and Perl-based overheads.
		2343
		2344	I<create> is the time, in microseconds (millionths of seconds), that it
		2345	takes to create a single watcher. The callback is a closure shared between
		2346	all watchers, to avoid adding memory overhead. That means closure creation
		2347	and memory usage is not included in the figures.
		2348
		2349	I<invoke> is the time, in microseconds, used to invoke a simple
		2350	callback. The callback simply counts down a Perl variable and after it was
		2351	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2352	signal the end of this phase.
		2353
		2354	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2355	watcher.
		2356
		2357	=head3 Results
		2358
		2359	name watchers bytes create invoke destroy comment
		2360	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2361	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2362	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2363	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2364	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2365	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2366	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2367	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2368	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2369	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2370	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2371	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2372
		2373	=head3 Discussion
		2374
		2375	The benchmark does I<not> measure scalability of the event loop very
		2376	well. For example, a select-based event loop (such as the pure perl one)
		2377	can never compete with an event loop that uses epoll when the number of
		2378	file descriptors grows high. In this benchmark, all events become ready at
		2379	the same time, so select/poll-based implementations get an unnatural speed
		2380	boost.
		2381
		2382	Also, note that the number of watchers usually has a nonlinear effect on
		2383	overall speed, that is, creating twice as many watchers doesn't take twice
		2384	the time - usually it takes longer. This puts event loops tested with a
		2385	higher number of watchers at a disadvantage.
		2386
		2387	To put the range of results into perspective, consider that on the
		2388	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2389	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2390	cycles with POE.
		2391
		2392	C<EV> is the sole leader regarding speed and memory use, which are both
		2393	maximal/minimal, respectively. When using the L<AE> API there is zero
		2394	overhead (when going through the AnyEvent API create is about 5-6 times
		2395	slower, with other times being equal, so still uses far less memory than
		2396	any other event loop and is still faster than Event natively).
		2397
		2398	The pure perl implementation is hit in a few sweet spots (both the
		2399	constant timeout and the use of a single fd hit optimisations in the perl
		2400	interpreter and the backend itself). Nevertheless this shows that it
		2401	adds very little overhead in itself. Like any select-based backend its
		2402	performance becomes really bad with lots of file descriptors (and few of
		2403	them active), of course, but this was not subject of this benchmark.
		2404
		2405	The C<Event> module has a relatively high setup and callback invocation
		2406	cost, but overall scores in on the third place.
		2407
		2408	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2409	when using its pure perl backend.
		2410
		2411	C<Glib>'s memory usage is quite a bit higher, but it features a
		2412	faster callback invocation and overall ends up in the same class as
		2413	C<Event>. However, Glib scales extremely badly, doubling the number of
		2414	watchers increases the processing time by more than a factor of four,
		2415	making it completely unusable when using larger numbers of watchers
		2416	(note that only a single file descriptor was used in the benchmark, so
		2417	inefficiencies of C<poll> do not account for this).
		2418
		2419	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2420	more than 2000 watchers is a big setback, however, as correctness takes
		2421	precedence over speed. Nevertheless, its performance is surprising, as the
		2422	file descriptor is dup()ed for each watcher. This shows that the dup()
		2423	employed by some adaptors is not a big performance issue (it does incur a
		2424	hidden memory cost inside the kernel which is not reflected in the figures
		2425	above).
		2426
		2427	C<POE>, regardless of underlying event loop (whether using its pure perl
		2428	select-based backend or the Event module, the POE-EV backend couldn't
		2429	be tested because it wasn't working) shows abysmal performance and
		2430	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2431	as EV watchers, and 10 times as much memory as Event (the high memory
		2432	requirements are caused by requiring a session for each watcher). Watcher
		2433	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2434	implementation.
		2435
		2436	The design of the POE adaptor class in AnyEvent can not really account
		2437	for the performance issues, though, as session creation overhead is
		2438	small compared to execution of the state machine, which is coded pretty
		2439	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2440	using multiple sessions is not a good approach, especially regarding
		2441	memory usage, even the author of POE could not come up with a faster
		2442	design).
		2443
		2444	=head3 Summary
		2445
		2446	=over 4
		2447
		2448	=item * Using EV through AnyEvent is faster than any other event loop
		2449	(even when used without AnyEvent), but most event loops have acceptable
		2450	performance with or without AnyEvent.
		2451
		2452	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2453	the actual event loop, only with extremely fast event loops such as EV
		2454	does AnyEvent add significant overhead.
		2455
		2456	=item * You should avoid POE like the plague if you want performance or
		2457	reasonable memory usage.
		2458
		2459	=back
		2460
		2461	=head2 BENCHMARKING THE LARGE SERVER CASE
		2462
		2463	This benchmark actually benchmarks the event loop itself. It works by
		2464	creating a number of "servers": each server consists of a socket pair, a
		2465	timeout watcher that gets reset on activity (but never fires), and an I/O
		2466	watcher waiting for input on one side of the socket. Each time the socket
		2467	watcher reads a byte it will write that byte to a random other "server".
		2468
		2469	The effect is that there will be a lot of I/O watchers, only part of which
		2470	are active at any one point (so there is a constant number of active
		2471	fds for each loop iteration, but which fds these are is random). The
		2472	timeout is reset each time something is read because that reflects how
		2473	most timeouts work (and puts extra pressure on the event loops).
		2474
		2475	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2476	(1%) are active. This mirrors the activity of large servers with many
		2477	connections, most of which are idle at any one point in time.
		2478
		2479	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2480	distribution. It uses the L<AE> interface, which makes a real difference
		2481	for the EV and Perl backends only.
		2482
		2483	=head3 Explanation of the columns
		2484
		2485	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2486	each server has a read and write socket end).
		2487
		2488	I<create> is the time it takes to create a socket pair (which is
		2489	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2490
		2491	I<request>, the most important value, is the time it takes to handle a
		2492	single "request", that is, reading the token from the pipe and forwarding
		2493	it to another server. This includes deleting the old timeout and creating
		2494	a new one that moves the timeout into the future.
		2495
		2496	=head3 Results
		2497
		2498	name sockets create request
		2499	EV 20000 62.66 7.99
		2500	Perl 20000 68.32 32.64
		2501	IOAsync 20000 174.06 101.15 epoll
		2502	IOAsync 20000 174.67 610.84 poll
		2503	Event 20000 202.69 242.91
		2504	Glib 20000 557.01 1689.52
		2505	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2506
		2507	=head3 Discussion
		2508
		2509	This benchmark I<does> measure scalability and overall performance of the
		2510	particular event loop.
		2511
		2512	EV is again fastest. Since it is using epoll on my system, the setup time
		2513	is relatively high, though.
		2514
		2515	Perl surprisingly comes second. It is much faster than the C-based event
		2516	loops Event and Glib.
		2517
		2518	IO::Async performs very well when using its epoll backend, and still quite
		2519	good compared to Glib when using its pure perl backend.
		2520
		2521	Event suffers from high setup time as well (look at its code and you will
		2522	understand why). Callback invocation also has a high overhead compared to
		2523	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2524	uses select or poll in basically all documented configurations.
		2525
		2526	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2527	clearly fails to perform with many filehandles or in busy servers.
		2528
		2529	POE is still completely out of the picture, taking over 1000 times as long
		2530	as EV, and over 100 times as long as the Perl implementation, even though
		2531	it uses a C-based event loop in this case.
		2532
		2533	=head3 Summary
		2534
		2535	=over 4
		2536
		2537	=item * The pure perl implementation performs extremely well.
		2538
		2539	=item * Avoid Glib or POE in large projects where performance matters.
		2540
		2541	=back
		2542
		2543	=head2 BENCHMARKING SMALL SERVERS
		2544
		2545	While event loops should scale (and select-based ones do not...) even to
		2546	large servers, most programs we (or I :) actually write have only a few
		2547	I/O watchers.
		2548
		2549	In this benchmark, I use the same benchmark program as in the large server
		2550	case, but it uses only eight "servers", of which three are active at any
		2551	one time. This should reflect performance for a small server relatively
		2552	well.
		2553
		2554	The columns are identical to the previous table.
		2555
		2556	=head3 Results
		2557
		2558	name sockets create request
		2559	EV 16 20.00 6.54
		2560	Perl 16 25.75 12.62
		2561	Event 16 81.27 35.86
		2562	Glib 16 32.63 15.48
		2563	POE 16 261.87 276.28 uses POE::Loop::Event
		2564
		2565	=head3 Discussion
		2566
		2567	The benchmark tries to test the performance of a typical small
		2568	server. While knowing how various event loops perform is interesting, keep
		2569	in mind that their overhead in this case is usually not as important, due
		2570	to the small absolute number of watchers (that is, you need efficiency and
		2571	speed most when you have lots of watchers, not when you only have a few of
		2572	them).
		2573
		2574	EV is again fastest.
		2575
		2576	Perl again comes second. It is noticeably faster than the C-based event
		2577	loops Event and Glib, although the difference is too small to really
		2578	matter.
		2579
		2580	POE also performs much better in this case, but is is still far behind the
		2581	others.
		2582
		2583	=head3 Summary
		2584
		2585	=over 4
		2586
		2587	=item * C-based event loops perform very well with small number of
		2588	watchers, as the management overhead dominates.
		2589
		2590	=back
		2591
		2592	=head2 THE IO::Lambda BENCHMARK
		2593
		2594	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2595	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2596	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2597	shouldn't come as a surprise to anybody). As such, the benchmark is
		2598	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2599	very optimal. But how would AnyEvent compare when used without the extra
		2600	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2601
		2602	The benchmark itself creates an echo-server, and then, for 500 times,
		2603	connects to the echo server, sends a line, waits for the reply, and then
		2604	creates the next connection. This is a rather bad benchmark, as it doesn't
		2605	test the efficiency of the framework or much non-blocking I/O, but it is a
		2606	benchmark nevertheless.
		2607
		2608	name runtime
		2609	Lambda/select 0.330 sec
		2610	+ optimized 0.122 sec
		2611	Lambda/AnyEvent 0.327 sec
		2612	+ optimized 0.138 sec
		2613	Raw sockets/select 0.077 sec
		2614	POE/select, components 0.662 sec
		2615	POE/select, raw sockets 0.226 sec
		2616	POE/select, optimized 0.404 sec
		2617
		2618	AnyEvent/select/nb 0.085 sec
		2619	AnyEvent/EV/nb 0.068 sec
		2620	+state machine 0.134 sec
		2621
		2622	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2623	benchmarks actually make blocking connects and use 100% blocking I/O,
		2624	defeating the purpose of an event-based solution. All of the newly
		2625	written AnyEvent benchmarks use 100% non-blocking connects (using
		2626	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2627	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2628	generally require a lot more bookkeeping and event handling than blocking
		2629	connects (which involve a single syscall only).
		2630
		2631	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2632	offers similar expressive power as POE and IO::Lambda, using conventional
		2633	Perl syntax. This means that both the echo server and the client are 100%
		2634	non-blocking, further placing it at a disadvantage.
		2635
		2636	As you can see, the AnyEvent + EV combination even beats the
		2637	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2638	backend easily beats IO::Lambda and POE.
		2639
		2640	And even the 100% non-blocking version written using the high-level (and
		2641	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2642	higher level ("unoptimised") abstractions by a large margin, even though
		2643	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2644
		2645	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2646	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2647	part of the IO::Lambda distribution and were used without any changes.
		2648
		2649
		2650	=head1 SIGNALS
		2651
		2652	AnyEvent currently installs handlers for these signals:
		2653
		2654	=over 4
		2655
		2656	=item SIGCHLD
		2657
		2658	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2659	emulation for event loops that do not support them natively. Also, some
		2660	event loops install a similar handler.
		2661
		2662	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2663	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2664
		2665	=item SIGPIPE
		2666
		2667	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2668	when AnyEvent gets loaded.
		2669
		2670	The rationale for this is that AnyEvent users usually do not really depend
		2671	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2672	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2673	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2674	some random socket.
		2675
		2676	The rationale for installing a no-op handler as opposed to ignoring it is
		2677	that this way, the handler will be restored to defaults on exec.
		2678
		2679	Feel free to install your own handler, or reset it to defaults.
		2680
		2681	=back
		2682
		2683	=cut
		2684
		2685	undef $SIG{CHLD}
		2686	if $SIG{CHLD} eq 'IGNORE';
		2687
		2688	$SIG{PIPE} = sub { }
		2689	unless defined $SIG{PIPE};
		2690
		2691	=head1 RECOMMENDED/OPTIONAL MODULES
		2692
		2693	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2694	its built-in modules) are required to use it.
		2695
		2696	That does not mean that AnyEvent won't take advantage of some additional
		2697	modules if they are installed.
		2698
		2699	This section explains which additional modules will be used, and how they
		2700	affect AnyEvent's operation.
		2701
		2702	=over 4
		2703
		2704	=item L<Async::Interrupt>
		2705
		2706	This slightly arcane module is used to implement fast signal handling: To
		2707	my knowledge, there is no way to do completely race-free and quick
		2708	signal handling in pure perl. To ensure that signals still get
		2709	delivered, AnyEvent will start an interval timer to wake up perl (and
		2710	catch the signals) with some delay (default is 10 seconds, look for
		2711	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2712
		2713	If this module is available, then it will be used to implement signal
		2714	catching, which means that signals will not be delayed, and the event loop
		2715	will not be interrupted regularly, which is more efficient (and good for
		2716	battery life on laptops).
		2717
		2718	This affects not just the pure-perl event loop, but also other event loops
		2719	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2720
		2721	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2722	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2723	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2724	does nothing for those backends.
		2725
		2726	=item L<EV>
		2727
		2728	This module isn't really "optional", as it is simply one of the backend
		2729	event loops that AnyEvent can use. However, it is simply the best event
		2730	loop available in terms of features, speed and stability: It supports
		2731	the AnyEvent API optimally, implements all the watcher types in XS, does
		2732	automatic timer adjustments even when no monotonic clock is available,
		2733	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2734	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2735	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2736
		2737	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2738	then this module will do nothing for you.
		2739
		2740	=item L<Guard>
		2741
		2742	The guard module, when used, will be used to implement
		2743	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2744	lot less memory), but otherwise doesn't affect guard operation much. It is
		2745	purely used for performance.
		2746
		2747	=item L<JSON> and L<JSON::XS>
		2748
		2749	One of these modules is required when you want to read or write JSON data
		2750	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2751	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2752
		2753	=item L<Net::SSLeay>
		2754
		2755	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2756	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2757	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2758
		2759	=item L<Time::HiRes>
		2760
		2761	This module is part of perl since release 5.008. It will be used when the
		2762	chosen event library does not come with a timing source of its own. The
		2763	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2764	try to use a monotonic clock for timing stability.
		2765
		2766	=back
		2767
		2768
		2769	=head1 FORK
		2770
		2771	Most event libraries are not fork-safe. The ones who are usually are
		2772	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2773	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2774	are usually badly thought-out hacks that are incompatible with fork in
		2775	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2776	continue event-processing in both parent and child (or both, if you know
		2777	what you are doing).
		2778
		2779	This means that, in general, you cannot fork and do event processing in
		2780	the child if the event library was initialised before the fork (which
		2781	usually happens when the first AnyEvent watcher is created, or the library
		2782	is loaded).
		2783
		2784	If you have to fork, you must either do so I<before> creating your first
		2785	watcher OR you must not use AnyEvent at all in the child OR you must do
		2786	something completely out of the scope of AnyEvent.
		2787
		2788	The problem of doing event processing in the parent I<and> the child
		2789	is much more complicated: even for backends that I<are> fork-aware or
		2790	fork-safe, their behaviour is not usually what you want: fork clones all
		2791	watchers, that means all timers, I/O watchers etc. are active in both
		2792	parent and child, which is almost never what you want. USing C<exec>
		2793	to start worker children from some kind of manage rprocess is usually
		2794	preferred, because it is much easier and cleaner, at the expense of having
		2795	to have another binary.
		2796
		2797
		2798	=head1 SECURITY CONSIDERATIONS
		2799
		2800	AnyEvent can be forced to load any event model via
		2801	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2802	execute arbitrary code or directly gain access, it can easily be used to
		2803	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2804	will not be active when the program uses a different event model than
		2805	specified in the variable.
		2806
		2807	You can make AnyEvent completely ignore this variable by deleting it
		2808	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2809
		2810	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2811
		2812	use AnyEvent;
		2813
		2814	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2815	be used to probe what backend is used and gain other information (which is
		2816	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2817	$ENV{PERL_ANYEVENT_STRICT}.
		2818
		2819	Note that AnyEvent will remove I<all> environment variables starting with
		2820	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2821	enabled.
		2822
		2823
		2824	=head1 BUGS
		2825
		2826	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2827	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2828	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2829	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2830	pronounced).
		2831
604		2832
605	=head1 SEE ALSO	2833	=head1 SEE ALSO
606		2834
607	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	2835	Tutorial/Introduction: L<AnyEvent::Intro>.
608		2836
609	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	2837	FAQ: L<AnyEvent::FAQ>.
610		2838
611	Nontrivial usage example: L<Net::FCP>.	2839	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2840	(simply logging).
612		2841
613	=head1	2842	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2843	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2844
		2845	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2846	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2847	L<Qt>, L<POE>, L<FLTK>.
		2848
		2849	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2850	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2851	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2852	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
		2853	L<AnyEvent::Impl::FLTK>.
		2854
		2855	Non-blocking handles, pipes, stream sockets, TCP clients and
		2856	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2857
		2858	Asynchronous DNS: L<AnyEvent::DNS>.
		2859
		2860	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		2861
		2862	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2863	L<AnyEvent::HTTP>.
		2864
		2865
		2866	=head1 AUTHOR
		2867
		2868	Marc Lehmann <schmorp@schmorp.de>
		2869	http://home.schmorp.de/
614		2870
615	=cut	2871	=cut
616		2872
617	1	2873	1
618		2874

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