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Revision 1.32 by root, Sat Nov 3 09:29:51 2007 UTC vs.
Revision 1.279 by root, Sun Aug 9 16:05:11 2009 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	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores wether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
		53
		54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		55
		56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		57	nowadays. So what is different about AnyEvent?
		58
		59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		60	policy> and AnyEvent is I<small and efficient>.
		61
		62	First and foremost, I<AnyEvent is not an event model> itself, it only
		63	interfaces to whatever event model the main program happens to use, in a
		64	pragmatic way. For event models and certain classes of immortals alike,
		65	the statement "there can only be one" is a bitter reality: In general,
		66	only one event loop can be active at the same time in a process. AnyEvent
		67	cannot change this, but it can hide the differences between those event
		68	loops.
		69
		70	The goal of AnyEvent is to offer module authors the ability to do event
		71	programming (waiting for I/O or timer events) without subscribing to a
		72	religion, a way of living, and most importantly: without forcing your
		73	module users into the same thing by forcing them to use the same event
		74	model you use.
		75
		76	For modules like POE or IO::Async (which is a total misnomer as it is
		77	actually doing all I/O I<synchronously>...), using them in your module is
		78	like joining a cult: After you joined, you are dependent on them and you
		79	cannot use anything else, as they are simply incompatible to everything
		80	that isn't them. What's worse, all the potential users of your
		81	module are I<also> forced to use the same event loop you use.
		82
		83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
		86	your module uses one of those, every user of your module has to use it,
		87	too. But if your module uses AnyEvent, it works transparently with all
		88	event models it supports (including stuff like IO::Async, as long as those
		89	use one of the supported event loops. It is trivial to add new event loops
		90	to AnyEvent, too, so it is future-proof).
		91
		92	In addition to being free of having to use I<the one and only true event
		93	model>, AnyEvent also is free of bloat and policy: with POE or similar
		94	modules, you get an enormous amount of code and strict rules you have to
		95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
		96	offering the functionality that is necessary, in as thin as a wrapper as
		97	technically possible.
		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
		105	Now, if you I<do want> lots of policy (this can arguably be somewhat
		106	useful) and you want to force your users to use the one and only event
		107	model, you should I<not> use this module.
22		108
23	=head1 DESCRIPTION	109	=head1 DESCRIPTION
24		110
25	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
26	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
27	users to use the same event loop (as only a single event loop can coexist	113	users to use the same event loop (as only a single event loop can coexist
28	peacefully at any one time).	114	peacefully at any one time).
29		115
30	The interface itself is vaguely similar but not identical to the Event	116	The interface itself is vaguely similar, but not identical to the L<Event>
31	module.	117	module.
32		118
33	On the first call of any method, the module tries to detect the currently	119	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	120	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	121	following modules is already loaded: L<EV>,
36	used. If none is found, the module tries to load these modules in the	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
37	order given. The first one that could be successfully loaded will be	123	L<POE>. The first one found is used. If none are found, the module tries
38	used. If still none could be found, AnyEvent will fall back to a pure-perl	124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
39	event loop, which is also not very efficient.	125	adaptor should always succeed) in the order given. The first one that can
		126	be successfully loaded will be used. If, after this, still none could be
		127	found, AnyEvent will fall back to a pure-perl event loop, which is not
		128	very efficient, but should work everywhere.
40		129
41	Because AnyEvent first checks for modules that are already loaded, loading	130	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	131	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	132	that model the default. For example:
44		133
45	use Tk;	134	use Tk;
46	use AnyEvent;	135	use AnyEvent;
47		136
48	# .. AnyEvent will likely default to Tk	137	# .. AnyEvent will likely default to Tk
49		138
		139	The I<likely> means that, if any module loads another event model and
		140	starts using it, all bets are off. Maybe you should tell their authors to
		141	use AnyEvent so their modules work together with others seamlessly...
		142
50	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
51	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
53		146
54	=head1 WATCHERS	147	=head1 WATCHERS
55		148
56	AnyEvent has the central concept of a I<watcher>, which is an object that	149	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	150	stores relevant data for each kind of event you are waiting for, such as
58	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
59		152
60	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
61	creating a watcher it will immediately "watch" for events and invoke	154	creating a watcher it will immediately "watch" for events and invoke the
		155	callback when the event occurs (of course, only when the event model
		156	is in control).
		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
62	the callback. To disable the watcher you have to destroy it (e.g. by	164	To disable the 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	165	variable you store it in to C<undef> or otherwise deleting all references
64	references to it).	166	to it).
65		167
66	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
67		169
		170	Many watchers either are used with "recursion" (repeating timers for
		171	example), or need to refer to their watcher object in other ways.
		172
		173	An any way to achieve that is this pattern:
		174
		175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		176	# you can use $w here, for example to undef it
		177	undef $w;
		178	});
		179
		180	Note that C<my $w; $w => combination. This is necessary because in Perl,
		181	my variables are only visible after the statement in which they are
		182	declared.
		183
68	=head2 IO WATCHERS	184	=head2 I/O WATCHERS
69		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
70	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	192	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71	the following mandatory arguments:	193	with the following mandatory key-value pairs as arguments:
72		194
73	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	202	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	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
76	to invoke everytime the filehandle becomes ready.
77		204
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	205	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		206
82	Filehandles will be kept alive, so as long as the watcher exists, the	207	Although the callback might get passed parameters, their value and
83	filehandle exists, too.	208	presence is undefined and you cannot rely on them. Portable AnyEvent
		209	callbacks cannot use arguments passed to I/O watcher callbacks.
84		210
85	Example:	211	The I/O watcher might use the underlying file descriptor or a copy of it.
		212	You must not close a file handle as long as any watcher is active on the
		213	underlying file descriptor.
86		214
		215	Some event loops issue spurious readyness notifications, so you should
		216	always use non-blocking calls when reading/writing from/to your file
		217	handles.
		218
87	# wait for readability of STDIN, then read a line and disable the watcher	219	Example: wait for readability of STDIN, then read a line and disable the
		220	watcher.
		221
88	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
90	warn "read: $input\n";	224	warn "read: $input\n";
91	undef $w;	225	undef $w;
92	});	226	});
93		227
94	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
95		229
		230	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		231
		232	$w = AnyEvent->timer (
		233	after => <fractional_seconds>,
		234	interval => <fractional_seconds>,
		235	cb => <callback>,
		236	);
		237
96	You can create a time watcher by calling the C<< AnyEvent->timer >>	238	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	239	method with the following mandatory arguments:
98		240
99	C<after> after how many seconds (fractions are supported) should the timer	241	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	242	supported) the callback should be invoked. C<cb> is the callback to invoke
		243	in that case.
101		244
102	The timer callback will be invoked at most once: if you want a repeating	245	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	246	presence is undefined and you cannot rely on them. Portable AnyEvent
104	and Glib).	247	callbacks cannot use arguments passed to time watcher callbacks.
105		248
106	Example:	249	The callback will normally be invoked once only. If you specify another
		250	parameter, C<interval>, as a strictly positive number (> 0), then the
		251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
107		254
		255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
		258
108	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	262	warn "timeout\n";
111	});	263	});
112		264
113	# to cancel the timer:	265	# to cancel the timer:
114	undef $w	266	undef $w;
115		267
116	=head2 CONDITION WATCHERS	268	Example 2: fire an event after 0.5 seconds, then roughly every second.
117		269
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
119	method without any arguments.	271	warn "timeout\n";
		272	};
120		273
121	A condition watcher watches for a condition - precisely that the C<<	274	=head3 TIMING ISSUES
122	->broadcast >> method has been called.
123		275
124	The watcher has only two methods:	276	There are two ways to handle timers: based on real time (relative, "fire
		277	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		278	o'clock").
		279
		280	While most event loops expect timers to specified in a relative way, they
		281	use absolute time internally. This makes a difference when your clock
		282	"jumps", for example, when ntp decides to set your clock backwards from
		283	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		284	fire "after" a second might actually take six years to finally fire.
		285
		286	AnyEvent cannot compensate for this. The only event loop that is conscious
		287	about these issues is L<EV>, which offers both relative (ev_timer, based
		288	on true relative time) and absolute (ev_periodic, based on wallclock time)
		289	timers.
		290
		291	AnyEvent always prefers relative timers, if available, matching the
		292	AnyEvent API.
		293
		294	AnyEvent has two additional methods that return the "current time":
125		295
126	=over 4	296	=over 4
127		297
128	=item $cv->wait	298	=item AnyEvent->time
129		299
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	300	This returns the "current wallclock time" as a fractional number of
131	called on c<$cv>, while servicing other watchers normally.	301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
132		303
133	Not all event models support a blocking wait - some die in that case, so	304	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	305	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		306
140	You can only wait once on a condition - additional calls will return	307	=item AnyEvent->now
141	immediately.
142		308
143	=item $cv->broadcast	309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
144		313
145	Flag the condition as ready - a running C<< ->wait >> and all further	314	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	315	function to call when you want to know the current time.>
147	is waiting the broadcast will be remembered..
148		316
149	Example:	317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	Note that updating the time I<might> cause some events to be handled.
		369
		370	=back
		371
		372	=head2 SIGNAL WATCHERS
		373
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
		376	You can watch for signals using a signal watcher, C<signal> is the signal
		377	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
		378	callback to be invoked whenever a signal occurs.
		379
		380	Although the callback might get passed parameters, their value and
		381	presence is undefined and you cannot rely on them. Portable AnyEvent
		382	callbacks cannot use arguments passed to signal watcher callbacks.
		383
		384	Multiple signal occurrences can be clumped together into one callback
		385	invocation, and callback invocation will be synchronous. Synchronous means
		386	that it might take a while until the signal gets handled by the process,
		387	but it is guaranteed not to interrupt any other callbacks.
		388
		389	The main advantage of using these watchers is that you can share a signal
		390	between multiple watchers, and AnyEvent will ensure that signals will not
		391	interrupt your program at bad times.
		392
		393	This watcher might use C<%SIG> (depending on the event loop used),
		394	so programs overwriting those signals directly will likely not work
		395	correctly.
		396
		397	Example: exit on SIGINT
		398
		399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		400
		401	=head3 Signal Races, Delays and Workarounds
		402
		403	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		404	callbacks to signals in a generic way, which is a pity, as you cannot
		405	do race-free signal handling in perl, requiring C libraries for
		406	this. AnyEvent will try to do it's best, which means in some cases,
		407	signals will be delayed. The maximum time a signal might be delayed is
		408	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		409	variable can be changed only before the first signal watcher is created,
		410	and should be left alone otherwise. This variable determines how often
		411	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		412	will cause fewer spurious wake-ups, which is better for power and CPU
		413	saving.
		414
		415	All these problems can be avoided by installing the optional
		416	L<Async::Interrupt> module, which works with most event loops. It will not
		417	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		418	(and not with L<POE> currently, as POE does it's own workaround with
		419	one-second latency). For those, you just have to suffer the delays.
		420
		421	=head2 CHILD PROCESS WATCHERS
		422
		423	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		424
		425	You can also watch on a child process exit and catch its exit status.
		426
		427	The child process is specified by the C<pid> argument (one some backends,
		428	using C<0> watches for any child process exit, on others this will
		429	croak). The watcher will be triggered only when the child process has
		430	finished and an exit status is available, not on any trace events
		431	(stopped/continued).
		432
		433	The callback will be called with the pid and exit status (as returned by
		434	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		435	callback arguments.
		436
		437	This watcher type works by installing a signal handler for C<SIGCHLD>,
		438	and since it cannot be shared, nothing else should use SIGCHLD or reap
		439	random child processes (waiting for specific child processes, e.g. inside
		440	C<system>, is just fine).
		441
		442	There is a slight catch to child watchers, however: you usually start them
		443	I<after> the child process was created, and this means the process could
		444	have exited already (and no SIGCHLD will be sent anymore).
		445
		446	Not all event models handle this correctly (neither POE nor IO::Async do,
		447	see their AnyEvent::Impl manpages for details), but even for event models
		448	that I<do> handle this correctly, they usually need to be loaded before
		449	the process exits (i.e. before you fork in the first place). AnyEvent's
		450	pure perl event loop handles all cases correctly regardless of when you
		451	start the watcher.
		452
		453	This means you cannot create a child watcher as the very first
		454	thing in an AnyEvent program, you I<have> to create at least one
		455	watcher before you C<fork> the child (alternatively, you can call
		456	C<AnyEvent::detect>).
		457
		458	As most event loops do not support waiting for child events, they will be
		459	emulated by AnyEvent in most cases, in which the latency and race problems
		460	mentioned in the description of signal watchers apply.
		461
		462	Example: fork a process and wait for it
		463
		464	my $done = AnyEvent->condvar;
		465
		466	my $pid = fork or exit 5;
		467
		468	my $w = AnyEvent->child (
		469	pid => $pid,
		470	cb => sub {
		471	my ($pid, $status) = @_;
		472	warn "pid $pid exited with status $status";
		473	$done->send;
		474	},
		475	);
		476
		477	# do something else, then wait for process exit
		478	$done->recv;
		479
		480	=head2 IDLE WATCHERS
		481
		482	$w = AnyEvent->idle (cb => <callback>);
		483
		484	Sometimes there is a need to do something, but it is not so important
		485	to do it instantly, but only when there is nothing better to do. This
		486	"nothing better to do" is usually defined to be "no other events need
		487	attention by the event loop".
		488
		489	Idle watchers ideally get invoked when the event loop has nothing
		490	better to do, just before it would block the process to wait for new
		491	events. Instead of blocking, the idle watcher is invoked.
		492
		493	Most event loops unfortunately do not really support idle watchers (only
		494	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		495	will simply call the callback "from time to time".
		496
		497	Example: read lines from STDIN, but only process them when the
		498	program is otherwise idle:
		499
		500	my @lines; # read data
		501	my $idle_w;
		502	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		503	push @lines, scalar <STDIN>;
		504
		505	# start an idle watcher, if not already done
		506	$idle_w ||= AnyEvent->idle (cb => sub {
		507	# handle only one line, when there are lines left
		508	if (my $line = shift @lines) {
		509	print "handled when idle: $line";
		510	} else {
		511	# otherwise disable the idle watcher again
		512	undef $idle_w;
		513	}
		514	});
		515	});
		516
		517	=head2 CONDITION VARIABLES
		518
		519	$cv = AnyEvent->condvar;
		520
		521	$cv->send (<list>);
		522	my @res = $cv->recv;
		523
		524	If you are familiar with some event loops you will know that all of them
		525	require you to run some blocking "loop", "run" or similar function that
		526	will actively watch for new events and call your callbacks.
		527
		528	AnyEvent is slightly different: it expects somebody else to run the event
		529	loop and will only block when necessary (usually when told by the user).
		530
		531	The instrument to do that is called a "condition variable", so called
		532	because they represent a condition that must become true.
		533
		534	Now is probably a good time to look at the examples further below.
		535
		536	Condition variables can be created by calling the C<< AnyEvent->condvar
		537	>> method, usually without arguments. The only argument pair allowed is
		538	C<cb>, which specifies a callback to be called when the condition variable
		539	becomes true, with the condition variable as the first argument (but not
		540	the results).
		541
		542	After creation, the condition variable is "false" until it becomes "true"
		543	by calling the C<send> method (or calling the condition variable as if it
		544	were a callback, read about the caveats in the description for the C<<
		545	->send >> method).
		546
		547	Condition variables are similar to callbacks, except that you can
		548	optionally wait for them. They can also be called merge points - points
		549	in time where multiple outstanding events have been processed. And yet
		550	another way to call them is transactions - each condition variable can be
		551	used to represent a transaction, which finishes at some point and delivers
		552	a result. And yet some people know them as "futures" - a promise to
		553	compute/deliver something that you can wait for.
		554
		555	Condition variables are very useful to signal that something has finished,
		556	for example, if you write a module that does asynchronous http requests,
		557	then a condition variable would be the ideal candidate to signal the
		558	availability of results. The user can either act when the callback is
		559	called or can synchronously C<< ->recv >> for the results.
		560
		561	You can also use them to simulate traditional event loops - for example,
		562	you can block your main program until an event occurs - for example, you
		563	could C<< ->recv >> in your main program until the user clicks the Quit
		564	button of your app, which would C<< ->send >> the "quit" event.
		565
		566	Note that condition variables recurse into the event loop - if you have
		567	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		568	lose. Therefore, condition variables are good to export to your caller, but
		569	you should avoid making a blocking wait yourself, at least in callbacks,
		570	as this asks for trouble.
		571
		572	Condition variables are represented by hash refs in perl, and the keys
		573	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		574	easy (it is often useful to build your own transaction class on top of
		575	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		576	it's C<new> method in your own C<new> method.
		577
		578	There are two "sides" to a condition variable - the "producer side" which
		579	eventually calls C<< -> send >>, and the "consumer side", which waits
		580	for the send to occur.
		581
		582	Example: wait for a timer.
150		583
151	# wait till the result is ready	584	# wait till the result is ready
152	my $result_ready = AnyEvent->condvar;	585	my $result_ready = AnyEvent->condvar;
153		586
154	# do something such as adding a timer	587	# do something such as adding a timer
155	# or socket watcher the calls $result_ready->broadcast	588	# or socket watcher the calls $result_ready->send
156	# when the "result" is ready.	589	# when the "result" is ready.
		590	# in this case, we simply use a timer:
		591	my $w = AnyEvent->timer (
		592	after => 1,
		593	cb => sub { $result_ready->send },
		594	);
157		595
		596	# this "blocks" (while handling events) till the callback
		597	# calls -<send
158	$result_ready->wait;	598	$result_ready->recv;
		599
		600	Example: wait for a timer, but take advantage of the fact that condition
		601	variables are also callable directly.
		602
		603	my $done = AnyEvent->condvar;
		604	my $delay = AnyEvent->timer (after => 5, cb => $done);
		605	$done->recv;
		606
		607	Example: Imagine an API that returns a condvar and doesn't support
		608	callbacks. This is how you make a synchronous call, for example from
		609	the main program:
		610
		611	use AnyEvent::CouchDB;
		612
		613	...
		614
		615	my @info = $couchdb->info->recv;
		616
		617	And this is how you would just set a callback to be called whenever the
		618	results are available:
		619
		620	$couchdb->info->cb (sub {
		621	my @info = $_[0]->recv;
		622	});
		623
		624	=head3 METHODS FOR PRODUCERS
		625
		626	These methods should only be used by the producing side, i.e. the
		627	code/module that eventually sends the signal. Note that it is also
		628	the producer side which creates the condvar in most cases, but it isn't
		629	uncommon for the consumer to create it as well.
		630
		631	=over 4
		632
		633	=item $cv->send (...)
		634
		635	Flag the condition as ready - a running C<< ->recv >> and all further
		636	calls to C<recv> will (eventually) return after this method has been
		637	called. If nobody is waiting the send will be remembered.
		638
		639	If a callback has been set on the condition variable, it is called
		640	immediately from within send.
		641
		642	Any arguments passed to the C<send> call will be returned by all
		643	future C<< ->recv >> calls.
		644
		645	Condition variables are overloaded so one can call them directly (as if
		646	they were a code reference). Calling them directly is the same as calling
		647	C<send>.
		648
		649	=item $cv->croak ($error)
		650
		651	Similar to send, but causes all call's to C<< ->recv >> to invoke
		652	C<Carp::croak> with the given error message/object/scalar.
		653
		654	This can be used to signal any errors to the condition variable
		655	user/consumer. Doing it this way instead of calling C<croak> directly
		656	delays the error detetcion, but has the overwhelmign advantage that it
		657	diagnoses the error at the place where the result is expected, and not
		658	deep in some event clalback without connection to the actual code causing
		659	the problem.
		660
		661	=item $cv->begin ([group callback])
		662
		663	=item $cv->end
		664
		665	These two methods can be used to combine many transactions/events into
		666	one. For example, a function that pings many hosts in parallel might want
		667	to use a condition variable for the whole process.
		668
		669	Every call to C<< ->begin >> will increment a counter, and every call to
		670	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		671	>>, the (last) callback passed to C<begin> will be executed. That callback
		672	is I<supposed> to call C<< ->send >>, but that is not required. If no
		673	callback was set, C<send> will be called without any arguments.
		674
		675	You can think of C<< $cv->send >> giving you an OR condition (one call
		676	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		677	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		678
		679	Let's start with a simple example: you have two I/O watchers (for example,
		680	STDOUT and STDERR for a program), and you want to wait for both streams to
		681	close before activating a condvar:
		682
		683	my $cv = AnyEvent->condvar;
		684
		685	$cv->begin; # first watcher
		686	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		687	defined sysread $fh1, my $buf, 4096
		688	or $cv->end;
		689	});
		690
		691	$cv->begin; # second watcher
		692	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		693	defined sysread $fh2, my $buf, 4096
		694	or $cv->end;
		695	});
		696
		697	$cv->recv;
		698
		699	This works because for every event source (EOF on file handle), there is
		700	one call to C<begin>, so the condvar waits for all calls to C<end> before
		701	sending.
		702
		703	The ping example mentioned above is slightly more complicated, as the
		704	there are results to be passwd back, and the number of tasks that are
		705	begung can potentially be zero:
		706
		707	my $cv = AnyEvent->condvar;
		708
		709	my %result;
		710	$cv->begin (sub { $cv->send (\%result) });
		711
		712	for my $host (@list_of_hosts) {
		713	$cv->begin;
		714	ping_host_then_call_callback $host, sub {
		715	$result{$host} = ...;
		716	$cv->end;
		717	};
		718	}
		719
		720	$cv->end;
		721
		722	This code fragment supposedly pings a number of hosts and calls
		723	C<send> after results for all then have have been gathered - in any
		724	order. To achieve this, the code issues a call to C<begin> when it starts
		725	each ping request and calls C<end> when it has received some result for
		726	it. Since C<begin> and C<end> only maintain a counter, the order in which
		727	results arrive is not relevant.
		728
		729	There is an additional bracketing call to C<begin> and C<end> outside the
		730	loop, which serves two important purposes: first, it sets the callback
		731	to be called once the counter reaches C<0>, and second, it ensures that
		732	C<send> is called even when C<no> hosts are being pinged (the loop
		733	doesn't execute once).
		734
		735	This is the general pattern when you "fan out" into multiple (but
		736	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		737	the callback and ensure C<end> is called at least once, and then, for each
		738	subrequest you start, call C<begin> and for each subrequest you finish,
		739	call C<end>.
159		740
160	=back	741	=back
161		742
162	=head2 SIGNAL WATCHERS	743	=head3 METHODS FOR CONSUMERS
163		744
164	You can listen for signals using a signal watcher, C<signal> is the signal	745	These methods should only be used by the consuming side, i.e. the
165	I<name> without any C<SIG> prefix. Multiple signals events can be clumped	746	code awaits the condition.
166	together into one callback invocation, and callback invocation might or
167	might not be asynchronous.
168
169	These watchers might use C<%SIG>, so programs overwriting those signals
170	directly will likely not work correctly.
171
172	Example: exit on SIGINT
173
174	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
175
176	=head2 CHILD PROCESS WATCHERS
177
178	You can also listen for the status of a child process specified by the
179	C<pid> argument (or any child if the pid argument is 0). The watcher will
180	trigger as often as status change for the child are received. This works
181	by installing a signal handler for C<SIGCHLD>. The callback will be called with
182	the pid and exit status (as returned by waitpid).
183
184	Example: wait for pid 1333
185
186	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
187
188	=head1 GLOBALS
189		747
190	=over 4	748	=over 4
191		749
		750	=item $cv->recv
		751
		752	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		753	>> methods have been called on c<$cv>, while servicing other watchers
		754	normally.
		755
		756	You can only wait once on a condition - additional calls are valid but
		757	will return immediately.
		758
		759	If an error condition has been set by calling C<< ->croak >>, then this
		760	function will call C<croak>.
		761
		762	In list context, all parameters passed to C<send> will be returned,
		763	in scalar context only the first one will be returned.
		764
		765	Note that doing a blocking wait in a callback is not supported by any
		766	event loop, that is, recursive invocation of a blocking C<< ->recv
		767	>> is not allowed, and the C<recv> call will C<croak> if such a
		768	condition is detected. This condition can be slightly loosened by using
		769	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		770	any thread that doesn't run the event loop itself.
		771
		772	Not all event models support a blocking wait - some die in that case
		773	(programs might want to do that to stay interactive), so I<if you are
		774	using this from a module, never require a blocking wait>. Instead, let the
		775	caller decide whether the call will block or not (for example, by coupling
		776	condition variables with some kind of request results and supporting
		777	callbacks so the caller knows that getting the result will not block,
		778	while still supporting blocking waits if the caller so desires).
		779
		780	You can ensure that C<< -recv >> never blocks by setting a callback and
		781	only calling C<< ->recv >> from within that callback (or at a later
		782	time). This will work even when the event loop does not support blocking
		783	waits otherwise.
		784
		785	=item $bool = $cv->ready
		786
		787	Returns true when the condition is "true", i.e. whether C<send> or
		788	C<croak> have been called.
		789
		790	=item $cb = $cv->cb ($cb->($cv))
		791
		792	This is a mutator function that returns the callback set and optionally
		793	replaces it before doing so.
		794
		795	The callback will be called when the condition becomes (or already was)
		796	"true", i.e. when C<send> or C<croak> are called (or were called), with
		797	the only argument being the condition variable itself. Calling C<recv>
		798	inside the callback or at any later time is guaranteed not to block.
		799
		800	=back
		801
		802	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		803
		804	The available backend classes are (every class has its own manpage):
		805
		806	=over 4
		807
		808	=item Backends that are autoprobed when no other event loop can be found.
		809
		810	EV is the preferred backend when no other event loop seems to be in
		811	use. If EV is not installed, then AnyEvent will fall back to its own
		812	pure-perl implementation, which is available everywhere as it comes with
		813	AnyEvent itself.
		814
		815	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		816	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		817
		818	=item Backends that are transparently being picked up when they are used.
		819
		820	These will be used when they are currently loaded when the first watcher
		821	is created, in which case it is assumed that the application is using
		822	them. This means that AnyEvent will automatically pick the right backend
		823	when the main program loads an event module before anything starts to
		824	create watchers. Nothing special needs to be done by the main program.
		825
		826	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		827	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		828	AnyEvent::Impl::Tk based on Tk, very broken.
		829	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		830	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		831	AnyEvent::Impl::Irssi used when running within irssi.
		832
		833	=item Backends with special needs.
		834
		835	Qt requires the Qt::Application to be instantiated first, but will
		836	otherwise be picked up automatically. As long as the main program
		837	instantiates the application before any AnyEvent watchers are created,
		838	everything should just work.
		839
		840	AnyEvent::Impl::Qt based on Qt.
		841
		842	Support for IO::Async can only be partial, as it is too broken and
		843	architecturally limited to even support the AnyEvent API. It also
		844	is the only event loop that needs the loop to be set explicitly, so
		845	it can only be used by a main program knowing about AnyEvent. See
		846	L<AnyEvent::Impl::Async> for the gory details.
		847
		848	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		849
		850	=item Event loops that are indirectly supported via other backends.
		851
		852	Some event loops can be supported via other modules:
		853
		854	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		855
		856	B<WxWidgets> has no support for watching file handles. However, you can
		857	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		858	polls 20 times per second, which was considered to be too horrible to even
		859	consider for AnyEvent.
		860
		861	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		862	backend, so it can be supported through POE.
		863
		864	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		865	load L<POE> when detecting them, in the hope that POE will pick them up,
		866	in which case everything will be automatic.
		867
		868	=back
		869
		870	=head1 GLOBAL VARIABLES AND FUNCTIONS
		871
		872	These are not normally required to use AnyEvent, but can be useful to
		873	write AnyEvent extension modules.
		874
		875	=over 4
		876
192	=item $AnyEvent::MODEL	877	=item $AnyEvent::MODEL
193		878
194	Contains C<undef> until the first watcher is being created. Then it	879	Contains C<undef> until the first watcher is being created, before the
		880	backend has been autodetected.
		881
195	contains the event model that is being used, which is the name of the	882	Afterwards it contains the event model that is being used, which is the
196	Perl class implementing the model. This class is usually one of the	883	name of the Perl class implementing the model. This class is usually one
197	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	884	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
198	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	885	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
199		886	will be C<urxvt::anyevent>).
200	The known classes so far are:
201
202	EV::AnyEvent based on EV (an interface to libev, best choice)
203	AnyEvent::Impl::Coro based on Coro::Event, second best choice.
204	AnyEvent::Impl::Event based on Event, also second best choice :)
205	AnyEvent::Impl::Glib based on Glib, second-best choice.
206	AnyEvent::Impl::Tk based on Tk, very bad choice.
207	AnyEvent::Impl::Perl pure-perl implementation, inefficient.
208		887
209	=item AnyEvent::detect	888	=item AnyEvent::detect
210		889
211	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	890	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
212	necessary. You should only call this function right before you would have	891	if necessary. You should only call this function right before you would
213	created an AnyEvent watcher anyway, that is, very late at runtime.	892	have created an AnyEvent watcher anyway, that is, as late as possible at
		893	runtime, and not e.g. while initialising of your module.
		894
		895	If you need to do some initialisation before AnyEvent watchers are
		896	created, use C<post_detect>.
		897
		898	=item $guard = AnyEvent::post_detect { BLOCK }
		899
		900	Arranges for the code block to be executed as soon as the event model is
		901	autodetected (or immediately if this has already happened).
		902
		903	The block will be executed I<after> the actual backend has been detected
		904	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		905	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		906	other initialisations - see the sources of L<AnyEvent::Strict> or
		907	L<AnyEvent::AIO> to see how this is used.
		908
		909	The most common usage is to create some global watchers, without forcing
		910	event module detection too early, for example, L<AnyEvent::AIO> creates
		911	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		912	avoid autodetecting the event module at load time.
		913
		914	If called in scalar or list context, then it creates and returns an object
		915	that automatically removes the callback again when it is destroyed (or
		916	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		917	a case where this is useful.
		918
		919	Example: Create a watcher for the IO::AIO module and store it in
		920	C<$WATCHER>. Only do so after the event loop is initialised, though.
		921
		922	our WATCHER;
		923
		924	my $guard = AnyEvent::post_detect {
		925	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		926	};
		927
		928	# the ||= is important in case post_detect immediately runs the block,
		929	# as to not clobber the newly-created watcher. assigning both watcher and
		930	# post_detect guard to the same variable has the advantage of users being
		931	# able to just C<undef $WATCHER> if the watcher causes them grief.
		932
		933	$WATCHER ||= $guard;
		934
		935	=item @AnyEvent::post_detect
		936
		937	If there are any code references in this array (you can C<push> to it
		938	before or after loading AnyEvent), then they will called directly after
		939	the event loop has been chosen.
		940
		941	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		942	if it is defined then the event loop has already been detected, and the
		943	array will be ignored.
		944
		945	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		946	it,as it takes care of these details.
		947
		948	This variable is mainly useful for modules that can do something useful
		949	when AnyEvent is used and thus want to know when it is initialised, but do
		950	not need to even load it by default. This array provides the means to hook
		951	into AnyEvent passively, without loading it.
214		952
215	=back	953	=back
216		954
217	=head1 WHAT TO DO IN A MODULE	955	=head1 WHAT TO DO IN A MODULE
218		956
219	As a module author, you should "use AnyEvent" and call AnyEvent methods	957	As a module author, you should C<use AnyEvent> and call AnyEvent methods
220	freely, but you should not load a specific event module or rely on it.	958	freely, but you should not load a specific event module or rely on it.
221		959
222	Be careful when you create watchers in the module body - Anyevent will	960	Be careful when you create watchers in the module body - AnyEvent will
223	decide which event module to use as soon as the first method is called, so	961	decide which event module to use as soon as the first method is called, so
224	by calling AnyEvent in your module body you force the user of your module	962	by calling AnyEvent in your module body you force the user of your module
225	to load the event module first.	963	to load the event module first.
226		964
		965	Never call C<< ->recv >> on a condition variable unless you I<know> that
		966	the C<< ->send >> method has been called on it already. This is
		967	because it will stall the whole program, and the whole point of using
		968	events is to stay interactive.
		969
		970	It is fine, however, to call C<< ->recv >> when the user of your module
		971	requests it (i.e. if you create a http request object ad have a method
		972	called C<results> that returns the results, it should call C<< ->recv >>
		973	freely, as the user of your module knows what she is doing. always).
		974
227	=head1 WHAT TO DO IN THE MAIN PROGRAM	975	=head1 WHAT TO DO IN THE MAIN PROGRAM
228		976
229	There will always be a single main program - the only place that should	977	There will always be a single main program - the only place that should
230	dictate which event model to use.	978	dictate which event model to use.
231		979
232	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	980	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
233	do anything special and let AnyEvent decide which implementation to chose.	981	do anything special (it does not need to be event-based) and let AnyEvent
		982	decide which implementation to chose if some module relies on it.
234		983
235	If the main program relies on a specific event model (for example, in Gtk2	984	If the main program relies on a specific event model - for example, in
236	programs you have to rely on either Glib or Glib::Event), you should load	985	Gtk2 programs you have to rely on the Glib module - you should load the
237	it before loading AnyEvent or any module that uses it, generally, as early	986	event module before loading AnyEvent or any module that uses it: generally
238	as possible. The reason is that modules might create watchers when they	987	speaking, you should load it as early as possible. The reason is that
239	are loaded, and AnyEvent will decide on the event model to use as soon as	988	modules might create watchers when they are loaded, and AnyEvent will
240	it creates watchers, and it might chose the wrong one unless you load the	989	decide on the event model to use as soon as it creates watchers, and it
241	correct one yourself.	990	might chose the wrong one unless you load the correct one yourself.
242		991
243	You can chose to use a rather inefficient pure-perl implementation by	992	You can chose to use a pure-perl implementation by loading the
244	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	993	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
245	generally better.	994	everywhere, but letting AnyEvent chose the model is generally better.
		995
		996	=head2 MAINLOOP EMULATION
		997
		998	Sometimes (often for short test scripts, or even standalone programs who
		999	only want to use AnyEvent), you do not want to run a specific event loop.
		1000
		1001	In that case, you can use a condition variable like this:
		1002
		1003	AnyEvent->condvar->recv;
		1004
		1005	This has the effect of entering the event loop and looping forever.
		1006
		1007	Note that usually your program has some exit condition, in which case
		1008	it is better to use the "traditional" approach of storing a condition
		1009	variable somewhere, waiting for it, and sending it when the program should
		1010	exit cleanly.
		1011
		1012
		1013	=head1 OTHER MODULES
		1014
		1015	The following is a non-exhaustive list of additional modules that use
		1016	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1017	modules and other event loops in the same program. Some of the modules
		1018	come with AnyEvent, most are available via CPAN.
		1019
		1020	=over 4
		1021
		1022	=item L<AnyEvent::Util>
		1023
		1024	Contains various utility functions that replace often-used but blocking
		1025	functions such as C<inet_aton> by event-/callback-based versions.
		1026
		1027	=item L<AnyEvent::Socket>
		1028
		1029	Provides various utility functions for (internet protocol) sockets,
		1030	addresses and name resolution. Also functions to create non-blocking tcp
		1031	connections or tcp servers, with IPv6 and SRV record support and more.
		1032
		1033	=item L<AnyEvent::Handle>
		1034
		1035	Provide read and write buffers, manages watchers for reads and writes,
		1036	supports raw and formatted I/O, I/O queued and fully transparent and
		1037	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1038
		1039	=item L<AnyEvent::DNS>
		1040
		1041	Provides rich asynchronous DNS resolver capabilities.
		1042
		1043	=item L<AnyEvent::HTTP>
		1044
		1045	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1046	HTTP requests.
		1047
		1048	=item L<AnyEvent::HTTPD>
		1049
		1050	Provides a simple web application server framework.
		1051
		1052	=item L<AnyEvent::FastPing>
		1053
		1054	The fastest ping in the west.
		1055
		1056	=item L<AnyEvent::DBI>
		1057
		1058	Executes L<DBI> requests asynchronously in a proxy process.
		1059
		1060	=item L<AnyEvent::AIO>
		1061
		1062	Truly asynchronous I/O, should be in the toolbox of every event
		1063	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1064	together.
		1065
		1066	=item L<AnyEvent::BDB>
		1067
		1068	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1069	L<BDB> and AnyEvent together.
		1070
		1071	=item L<AnyEvent::GPSD>
		1072
		1073	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1074
		1075	=item L<AnyEvent::IRC>
		1076
		1077	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1078
		1079	=item L<AnyEvent::XMPP>
		1080
		1081	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1082	Net::XMPP2>.
		1083
		1084	=item L<AnyEvent::IGS>
		1085
		1086	A non-blocking interface to the Internet Go Server protocol (used by
		1087	L<App::IGS>).
		1088
		1089	=item L<Net::FCP>
		1090
		1091	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1092	of AnyEvent.
		1093
		1094	=item L<Event::ExecFlow>
		1095
		1096	High level API for event-based execution flow control.
		1097
		1098	=item L<Coro>
		1099
		1100	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1101
		1102	=back
246		1103
247	=cut	1104	=cut
248		1105
249	package AnyEvent;	1106	package AnyEvent;
250		1107
		1108	# basically a tuned-down version of common::sense
		1109	sub common_sense {
251	no warnings;	1110	# no warnings
252	use strict;	1111	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1112	# use strict vars subs
		1113	$^H |= 0x00000600;
		1114	}
253		1115
		1116	BEGIN { AnyEvent::common_sense }
		1117
254	use Carp;	1118	use Carp ();
255		1119
256	our $VERSION = '2.55';	1120	our $VERSION = '5.0';
257	our $MODEL;	1121	our $MODEL;
258		1122
259	our $AUTOLOAD;	1123	our $AUTOLOAD;
260	our @ISA;	1124	our @ISA;
261		1125
262	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
263
264	our @REGISTRY;	1126	our @REGISTRY;
265		1127
		1128	our $WIN32;
		1129
		1130	our $VERBOSE;
		1131
		1132	BEGIN {
		1133	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1134	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1135
		1136	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1137	if ${^TAINT};
		1138
		1139	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1140
		1141	}
		1142
		1143	our $MAX_SIGNAL_LATENCY = 10;
		1144
		1145	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1146
		1147	{
		1148	my $idx;
		1149	$PROTOCOL{$_} = ++$idx
		1150	for reverse split /\s*,\s*/,
		1151	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1152	}
		1153
266	my @models = (	1154	my @models = (
267	[Coro::Event:: => AnyEvent::Impl::Coro::],
268	[EV:: => EV::AnyEvent::],	1155	[EV:: => AnyEvent::Impl::EV:: , 1],
		1156	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1157	# everything below here will not (normally) be autoprobed
		1158	# as the pureperl backend should work everywhere
		1159	# and is usually faster
269	[Event:: => AnyEvent::Impl::Event::],	1160	[Event:: => AnyEvent::Impl::Event::, 1],
270	[Glib:: => AnyEvent::Impl::Glib::],	1161	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1162	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1163	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1164	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1165	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1166	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
271	[Tk:: => AnyEvent::Impl::Tk::],	1167	[Wx:: => AnyEvent::Impl::POE::],
272	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1168	[Prima:: => AnyEvent::Impl::POE::],
		1169	# IO::Async is just too broken - we would need workarounds for its
		1170	# byzantine signal and broken child handling, among others.
		1171	# IO::Async is rather hard to detect, as it doesn't have any
		1172	# obvious default class.
		1173	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1174	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1175	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1176	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
273	);	1177	);
274		1178
275	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1179	our %method = map +($_ => 1),
		1180	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1181
		1182	our @post_detect;
		1183
		1184	sub post_detect(&) {
		1185	my ($cb) = @_;
		1186
		1187	if ($MODEL) {
		1188	$cb->();
		1189
		1190	undef
		1191	} else {
		1192	push @post_detect, $cb;
		1193
		1194	defined wantarray
		1195	? bless \$cb, "AnyEvent::Util::postdetect"
		1196	: ()
		1197	}
		1198	}
		1199
		1200	sub AnyEvent::Util::postdetect::DESTROY {
		1201	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1202	}
276		1203
277	sub detect() {	1204	sub detect() {
278	unless ($MODEL) {	1205	unless ($MODEL) {
279	no strict 'refs';	1206	local $SIG{__DIE__};
		1207
		1208	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1209	my $model = "AnyEvent::Impl::$1";
		1210	if (eval "require $model") {
		1211	$MODEL = $model;
		1212	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1213	} else {
		1214	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1215	}
		1216	}
280		1217
281	# check for already loaded models	1218	# check for already loaded models
		1219	unless ($MODEL) {
282	for (@REGISTRY, @models) {	1220	for (@REGISTRY, @models) {
283	my ($package, $model) = @$_;	1221	my ($package, $model) = @$_;
284	if (${"$package\::VERSION"} > 0) {	1222	if (${"$package\::VERSION"} > 0) {
285	if (eval "require $model") {	1223	if (eval "require $model") {
286	$MODEL = $model;	1224	$MODEL = $model;
287	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1225	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
288	last;	1226	last;
		1227	}
289	}	1228	}
290	}	1229	}
		1230
		1231	unless ($MODEL) {
		1232	# try to autoload a model
		1233	for (@REGISTRY, @models) {
		1234	my ($package, $model, $autoload) = @$_;
		1235	if (
		1236	$autoload
		1237	and eval "require $package"
		1238	and ${"$package\::VERSION"} > 0
		1239	and eval "require $model"
		1240	) {
		1241	$MODEL = $model;
		1242	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
		1243	last;
		1244	}
		1245	}
		1246
		1247	$MODEL
		1248	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
		1249	}
291	}	1250	}
292		1251
293	unless ($MODEL) {	1252	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
294	# try to load a model
295
296	for (@REGISTRY, @models) {
297	my ($package, $model) = @$_;
298	if (eval "require $package"
299	and ${"$package\::VERSION"} > 0
300	and eval "require $model") {
301	$MODEL = $model;
302	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
303	last;
304	}
305	}
306
307	$MODEL
308	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";
309	}
310		1253
311	unshift @ISA, $MODEL;	1254	unshift @ISA, $MODEL;
312	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1255
		1256	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1257
		1258	(shift @post_detect)->() while @post_detect;
313	}	1259	}
314		1260
315	$MODEL	1261	$MODEL
316	}	1262	}
317		1263
318	sub AUTOLOAD {	1264	sub AUTOLOAD {
319	(my $func = $AUTOLOAD) =~ s/.*://;	1265	(my $func = $AUTOLOAD) =~ s/.*://;
320		1266
321	$method{$func}	1267	$method{$func}
322	or croak "$func: not a valid method for AnyEvent objects";	1268	or Carp::croak "$func: not a valid method for AnyEvent objects";
323		1269
324	detect unless $MODEL;	1270	detect unless $MODEL;
325		1271
326	my $class = shift;	1272	my $class = shift;
327	$class->$func (@_);	1273	$class->$func (@_);
328	}	1274	}
329		1275
		1276	# utility function to dup a filehandle. this is used by many backends
		1277	# to support binding more than one watcher per filehandle (they usually
		1278	# allow only one watcher per fd, so we dup it to get a different one).
		1279	sub _dupfh($$;$$) {
		1280	my ($poll, $fh, $r, $w) = @_;
		1281
		1282	# cygwin requires the fh mode to be matching, unix doesn't
		1283	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1284
		1285	open my $fh2, $mode, $fh
		1286	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1287
		1288	# we assume CLOEXEC is already set by perl in all important cases
		1289
		1290	($fh2, $rw)
		1291	}
		1292
		1293	=head1 SIMPLIFIED AE API
		1294
		1295	Starting with version 5.0, AnyEvent officially supports a second, much
		1296	simpler, API that is designed to reduce the calling, typing and memory
		1297	overhead.
		1298
		1299	See the L<AE> manpage for details.
		1300
		1301	=cut
		1302
		1303	package AE;
		1304
		1305	our $VERSION = $AnyEvent::VERSION;
		1306
		1307	sub io($$$) {
		1308	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1309	}
		1310
		1311	sub timer($$$) {
		1312	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1313	}
		1314
		1315	sub signal($$) {
		1316	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1317	}
		1318
		1319	sub child($$) {
		1320	AnyEvent->child (pid => $_[0], cb => $_[1])
		1321	}
		1322
		1323	sub idle($) {
		1324	AnyEvent->idle (cb => $_[0])
		1325	}
		1326
		1327	sub cv(;&) {
		1328	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1329	}
		1330
		1331	sub now() {
		1332	AnyEvent->now
		1333	}
		1334
		1335	sub now_update() {
		1336	AnyEvent->now_update
		1337	}
		1338
		1339	sub time() {
		1340	AnyEvent->time
		1341	}
		1342
330	package AnyEvent::Base;	1343	package AnyEvent::Base;
331		1344
		1345	# default implementations for many methods
		1346
		1347	sub _time {
		1348	# probe for availability of Time::HiRes
		1349	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1350	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1351	*_time = \&Time::HiRes::time;
		1352	# if (eval "use POSIX (); (POSIX::times())...
		1353	} else {
		1354	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1355	*_time = sub { time }; # epic fail
		1356	}
		1357
		1358	&_time
		1359	}
		1360
		1361	sub time { _time }
		1362	sub now { _time }
		1363	sub now_update { }
		1364
332	# default implementation for ->condvar, ->wait, ->broadcast	1365	# default implementation for ->condvar
333		1366
334	sub condvar {	1367	sub condvar {
335	bless \my $flag, "AnyEvent::Base::CondVar"	1368	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
336	}
337
338	sub AnyEvent::Base::CondVar::broadcast {
339	${$_[0]}++;
340	}
341
342	sub AnyEvent::Base::CondVar::wait {
343	AnyEvent->one_event while !${$_[0]};
344	}	1369	}
345		1370
346	# default implementation for ->signal	1371	# default implementation for ->signal
347		1372
348	our %SIG_CB;	1373	our $HAVE_ASYNC_INTERRUPT;
		1374
		1375	sub _have_async_interrupt() {
		1376	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1377	&& eval "use Async::Interrupt 1.0 (); 1")
		1378	unless defined $HAVE_ASYNC_INTERRUPT;
		1379
		1380	$HAVE_ASYNC_INTERRUPT
		1381	}
		1382
		1383	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1384	our (%SIG_ASY, %SIG_ASY_W);
		1385	our ($SIG_COUNT, $SIG_TW);
		1386
		1387	sub _signal_exec {
		1388	$HAVE_ASYNC_INTERRUPT
		1389	? $SIGPIPE_R->drain
		1390	: sysread $SIGPIPE_R, my $dummy, 9;
		1391
		1392	while (%SIG_EV) {
		1393	for (keys %SIG_EV) {
		1394	delete $SIG_EV{$_};
		1395	$_->() for values %{ $SIG_CB{$_} || {} };
		1396	}
		1397	}
		1398	}
		1399
		1400	# install a dummy wakeup watcher to reduce signal catching latency
		1401	sub _sig_add() {
		1402	unless ($SIG_COUNT++) {
		1403	# try to align timer on a full-second boundary, if possible
		1404	my $NOW = AE::now;
		1405
		1406	$SIG_TW = AE::timer
		1407	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1408	$MAX_SIGNAL_LATENCY,
		1409	sub { } # just for the PERL_ASYNC_CHECK
		1410	;
		1411	}
		1412	}
		1413
		1414	sub _sig_del {
		1415	undef $SIG_TW
		1416	unless --$SIG_COUNT;
		1417	}
		1418
		1419	our $_sig_name_init; $_sig_name_init = sub {
		1420	eval q{ # poor man's autoloading
		1421	undef $_sig_name_init;
		1422
		1423	if (_have_async_interrupt) {
		1424	*sig2num = \&Async::Interrupt::sig2num;
		1425	*sig2name = \&Async::Interrupt::sig2name;
		1426	} else {
		1427	require Config;
		1428
		1429	my %signame2num;
		1430	@signame2num{ split ' ', $Config::Config{sig_name} }
		1431	= split ' ', $Config::Config{sig_num};
		1432
		1433	my @signum2name;
		1434	@signum2name[values %signame2num] = keys %signame2num;
		1435
		1436	*sig2num = sub($) {
		1437	$_[0] > 0 ? shift : $signame2num{+shift}
		1438	};
		1439	*sig2name = sub ($) {
		1440	$_[0] > 0 ? $signum2name[+shift] : shift
		1441	};
		1442	}
		1443	};
		1444	die if $@;
		1445	};
		1446
		1447	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1448	sub sig2name($) { &$_sig_name_init; &sig2name }
349		1449
350	sub signal {	1450	sub signal {
		1451	eval q{ # poor man's autoloading {}
		1452	# probe for availability of Async::Interrupt
		1453	if (_have_async_interrupt) {
		1454	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1455
		1456	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1457	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1458
		1459	} else {
		1460	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1461
		1462	require Fcntl;
		1463
		1464	if (AnyEvent::WIN32) {
		1465	require AnyEvent::Util;
		1466
		1467	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1468	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1469	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1470	} else {
		1471	pipe $SIGPIPE_R, $SIGPIPE_W;
		1472	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1473	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1474
		1475	# not strictly required, as $^F is normally 2, but let's make sure...
		1476	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1477	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1478	}
		1479
		1480	$SIGPIPE_R
		1481	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1482
		1483	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1484	}
		1485
		1486	*signal = sub {
351	my (undef, %arg) = @_;	1487	my (undef, %arg) = @_;
352		1488
353	my $signal = uc $arg{signal}	1489	my $signal = uc $arg{signal}
354	or Carp::croak "required option 'signal' is missing";	1490	or Carp::croak "required option 'signal' is missing";
355		1491
		1492	if ($HAVE_ASYNC_INTERRUPT) {
		1493	# async::interrupt
		1494
		1495	$signal = sig2num $signal;
356	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1496	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1497
		1498	$SIG_ASY{$signal} ||= new Async::Interrupt
		1499	cb => sub { undef $SIG_EV{$signal} },
		1500	signal => $signal,
		1501	pipe => [$SIGPIPE_R->filenos],
		1502	pipe_autodrain => 0,
		1503	;
		1504
		1505	} else {
		1506	# pure perl
		1507
		1508	# AE::Util has been loaded in signal
		1509	$signal = sig2name $signal;
		1510	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1511
357	$SIG{$signal} ||= sub {	1512	$SIG{$signal} ||= sub {
358	$_->() for values %{ $SIG_CB{$signal} || {} };	1513	local $!;
		1514	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1515	undef $SIG_EV{$signal};
		1516	};
		1517
		1518	# can't do signal processing without introducing races in pure perl,
		1519	# so limit the signal latency.
		1520	_sig_add;
		1521	}
		1522
		1523	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1524	};
		1525
		1526	*AnyEvent::Base::signal::DESTROY = sub {
		1527	my ($signal, $cb) = @{$_[0]};
		1528
		1529	_sig_del;
		1530
		1531	delete $SIG_CB{$signal}{$cb};
		1532
		1533	$HAVE_ASYNC_INTERRUPT
		1534	? delete $SIG_ASY{$signal}
		1535	: # delete doesn't work with older perls - they then
		1536	# print weird messages, or just unconditionally exit
		1537	# instead of getting the default action.
		1538	undef $SIG{$signal}
		1539	unless keys %{ $SIG_CB{$signal} };
		1540	};
359	};	1541	};
360		1542	die if $@;
361	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1543	&signal
362	}
363
364	sub AnyEvent::Base::Signal::DESTROY {
365	my ($signal, $cb) = @{$_[0]};
366
367	delete $SIG_CB{$signal}{$cb};
368
369	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
370	}	1544	}
371		1545
372	# default implementation for ->child	1546	# default implementation for ->child
373		1547
374	our %PID_CB;	1548	our %PID_CB;
375	our $CHLD_W;	1549	our $CHLD_W;
376	our $PID_IDLE;	1550	our $CHLD_DELAY_W;
377	our $WNOHANG;	1551	our $WNOHANG;
378		1552
379	sub _child_wait {	1553	sub _emit_childstatus($$) {
380	while (0 <= (my $pid = waitpid -1, $WNOHANG)) {	1554	my (undef, $rpid, $rstatus) = @_;
		1555
		1556	$_->($rpid, $rstatus)
381	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1557	for values %{ $PID_CB{$rpid} || {} },
382	(values %{ $PID_CB{0} || {} });	1558	values %{ $PID_CB{0} || {} };
383	}	1559	}
384		1560
385	undef $PID_IDLE;	1561	sub _sigchld {
		1562	my $pid;
		1563
		1564	AnyEvent->_emit_childstatus ($pid, $?)
		1565	while ($pid = waitpid -1, $WNOHANG) > 0;
386	}	1566	}
387		1567
388	sub child {	1568	sub child {
389	my (undef, %arg) = @_;	1569	my (undef, %arg) = @_;
390		1570
391	defined (my $pid = $arg{pid} + 0)	1571	defined (my $pid = $arg{pid} + 0)
392	or Carp::croak "required option 'pid' is missing";	1572	or Carp::croak "required option 'pid' is missing";
393		1573
394	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1574	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
395		1575
396	unless ($WNOHANG) {	1576	# WNOHANG is almost cetrainly 1 everywhere
397	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1577	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1578	? 1
		1579	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
		1580
		1581	unless ($CHLD_W) {
		1582	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1583	# child could be a zombie already, so make at least one round
		1584	&_sigchld;
398	}	1585	}
399		1586
400	unless ($CHLD_W) {
401	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_child_wait);
402	# child could be a zombie already
403	$PID_IDLE ||= AnyEvent->timer (after => 0, cb => \&_child_wait);
404	}
405
406	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1587	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
407	}	1588	}
408		1589
409	sub AnyEvent::Base::Child::DESTROY {	1590	sub AnyEvent::Base::child::DESTROY {
410	my ($pid, $cb) = @{$_[0]};	1591	my ($pid, $cb) = @{$_[0]};
411		1592
412	delete $PID_CB{$pid}{$cb};	1593	delete $PID_CB{$pid}{$cb};
413	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1594	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
414		1595
415	undef $CHLD_W unless keys %PID_CB;	1596	undef $CHLD_W unless keys %PID_CB;
416	}	1597	}
417		1598
		1599	# idle emulation is done by simply using a timer, regardless
		1600	# of whether the process is idle or not, and not letting
		1601	# the callback use more than 50% of the time.
		1602	sub idle {
		1603	my (undef, %arg) = @_;
		1604
		1605	my ($cb, $w, $rcb) = $arg{cb};
		1606
		1607	$rcb = sub {
		1608	if ($cb) {
		1609	$w = _time;
		1610	&$cb;
		1611	$w = _time - $w;
		1612
		1613	# never use more then 50% of the time for the idle watcher,
		1614	# within some limits
		1615	$w = 0.0001 if $w < 0.0001;
		1616	$w = 5 if $w > 5;
		1617
		1618	$w = AE::timer $w, 0, $rcb;
		1619	} else {
		1620	# clean up...
		1621	undef $w;
		1622	undef $rcb;
		1623	}
		1624	};
		1625
		1626	$w = AE::timer 0.05, 0, $rcb;
		1627
		1628	bless \\$cb, "AnyEvent::Base::idle"
		1629	}
		1630
		1631	sub AnyEvent::Base::idle::DESTROY {
		1632	undef $${$_[0]};
		1633	}
		1634
		1635	package AnyEvent::CondVar;
		1636
		1637	our @ISA = AnyEvent::CondVar::Base::;
		1638
		1639	package AnyEvent::CondVar::Base;
		1640
		1641	#use overload
		1642	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1643	# fallback => 1;
		1644
		1645	# save 300+ kilobytes by dirtily hardcoding overloading
		1646	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1647	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1648	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1649	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1650
		1651	our $WAITING;
		1652
		1653	sub _send {
		1654	# nop
		1655	}
		1656
		1657	sub send {
		1658	my $cv = shift;
		1659	$cv->{_ae_sent} = [@_];
		1660	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1661	$cv->_send;
		1662	}
		1663
		1664	sub croak {
		1665	$_[0]{_ae_croak} = $_[1];
		1666	$_[0]->send;
		1667	}
		1668
		1669	sub ready {
		1670	$_[0]{_ae_sent}
		1671	}
		1672
		1673	sub _wait {
		1674	$WAITING
		1675	and !$_[0]{_ae_sent}
		1676	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1677
		1678	local $WAITING = 1;
		1679	AnyEvent->one_event while !$_[0]{_ae_sent};
		1680	}
		1681
		1682	sub recv {
		1683	$_[0]->_wait;
		1684
		1685	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1686	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1687	}
		1688
		1689	sub cb {
		1690	my $cv = shift;
		1691
		1692	@_
		1693	and $cv->{_ae_cb} = shift
		1694	and $cv->{_ae_sent}
		1695	and (delete $cv->{_ae_cb})->($cv);
		1696
		1697	$cv->{_ae_cb}
		1698	}
		1699
		1700	sub begin {
		1701	++$_[0]{_ae_counter};
		1702	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1703	}
		1704
		1705	sub end {
		1706	return if --$_[0]{_ae_counter};
		1707	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1708	}
		1709
		1710	# undocumented/compatibility with pre-3.4
		1711	*broadcast = \&send;
		1712	*wait = \&_wait;
		1713
		1714	=head1 ERROR AND EXCEPTION HANDLING
		1715
		1716	In general, AnyEvent does not do any error handling - it relies on the
		1717	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1718	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1719	checking of all AnyEvent methods, however, which is highly useful during
		1720	development.
		1721
		1722	As for exception handling (i.e. runtime errors and exceptions thrown while
		1723	executing a callback), this is not only highly event-loop specific, but
		1724	also not in any way wrapped by this module, as this is the job of the main
		1725	program.
		1726
		1727	The pure perl event loop simply re-throws the exception (usually
		1728	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1729	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1730	so on.
		1731
		1732	=head1 ENVIRONMENT VARIABLES
		1733
		1734	The following environment variables are used by this module or its
		1735	submodules.
		1736
		1737	Note that AnyEvent will remove I<all> environment variables starting with
		1738	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1739	enabled.
		1740
		1741	=over 4
		1742
		1743	=item C<PERL_ANYEVENT_VERBOSE>
		1744
		1745	By default, AnyEvent will be completely silent except in fatal
		1746	conditions. You can set this environment variable to make AnyEvent more
		1747	talkative.
		1748
		1749	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1750	conditions, such as not being able to load the event model specified by
		1751	C<PERL_ANYEVENT_MODEL>.
		1752
		1753	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1754	model it chooses.
		1755
		1756	When set to C<8> or higher, then AnyEvent will report extra information on
		1757	which optional modules it loads and how it implements certain features.
		1758
		1759	=item C<PERL_ANYEVENT_STRICT>
		1760
		1761	AnyEvent does not do much argument checking by default, as thorough
		1762	argument checking is very costly. Setting this variable to a true value
		1763	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1764	check the arguments passed to most method calls. If it finds any problems,
		1765	it will croak.
		1766
		1767	In other words, enables "strict" mode.
		1768
		1769	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1770	>>, it is definitely recommended to keep it off in production. Keeping
		1771	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1772	can be very useful, however.
		1773
		1774	=item C<PERL_ANYEVENT_MODEL>
		1775
		1776	This can be used to specify the event model to be used by AnyEvent, before
		1777	auto detection and -probing kicks in. It must be a string consisting
		1778	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1779	and the resulting module name is loaded and if the load was successful,
		1780	used as event model. If it fails to load AnyEvent will proceed with
		1781	auto detection and -probing.
		1782
		1783	This functionality might change in future versions.
		1784
		1785	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1786	could start your program like this:
		1787
		1788	PERL_ANYEVENT_MODEL=Perl perl ...
		1789
		1790	=item C<PERL_ANYEVENT_PROTOCOLS>
		1791
		1792	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1793	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1794	of auto probing).
		1795
		1796	Must be set to a comma-separated list of protocols or address families,
		1797	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1798	used, and preference will be given to protocols mentioned earlier in the
		1799	list.
		1800
		1801	This variable can effectively be used for denial-of-service attacks
		1802	against local programs (e.g. when setuid), although the impact is likely
		1803	small, as the program has to handle conenction and other failures anyways.
		1804
		1805	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1806	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1807	- only support IPv4, never try to resolve or contact IPv6
		1808	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1809	IPv6, but prefer IPv6 over IPv4.
		1810
		1811	=item C<PERL_ANYEVENT_EDNS0>
		1812
		1813	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1814	for DNS. This extension is generally useful to reduce DNS traffic, but
		1815	some (broken) firewalls drop such DNS packets, which is why it is off by
		1816	default.
		1817
		1818	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1819	EDNS0 in its DNS requests.
		1820
		1821	=item C<PERL_ANYEVENT_MAX_FORKS>
		1822
		1823	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1824	will create in parallel.
		1825
		1826	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1827
		1828	The default value for the C<max_outstanding> parameter for the default DNS
		1829	resolver - this is the maximum number of parallel DNS requests that are
		1830	sent to the DNS server.
		1831
		1832	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1833
		1834	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1835	configuration) in the default resolver. When set to the empty string, no
		1836	default config will be used.
		1837
		1838	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1839
		1840	When neither C<ca_file> nor C<ca_path> was specified during
		1841	L<AnyEvent::TLS> context creation, and either of these environment
		1842	variables exist, they will be used to specify CA certificate locations
		1843	instead of a system-dependent default.
		1844
		1845	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1846
		1847	When these are set to C<1>, then the respective modules are not
		1848	loaded. Mostly good for testing AnyEvent itself.
		1849
		1850	=back
		1851
418	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1852	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1853
		1854	This is an advanced topic that you do not normally need to use AnyEvent in
		1855	a module. This section is only of use to event loop authors who want to
		1856	provide AnyEvent compatibility.
419		1857
420	If you need to support another event library which isn't directly	1858	If you need to support another event library which isn't directly
421	supported by AnyEvent, you can supply your own interface to it by	1859	supported by AnyEvent, you can supply your own interface to it by
422	pushing, before the first watcher gets created, the package name of	1860	pushing, before the first watcher gets created, the package name of
423	the event module and the package name of the interface to use onto	1861	the event module and the package name of the interface to use onto
424	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	1862	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
425	AnyEvent.	1863	AnyEvent, so it is reasonably cheap.
426		1864
427	Example:	1865	Example:
428		1866
429	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	1867	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
430		1868
431	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	1869	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
432	package/class when it finds the C<urxvt> package/module is loaded. When	1870	package/class when it finds the C<urxvt> package/module is already loaded.
		1871
433	AnyEvent is loaded and asked to find a suitable event model, it will	1872	When AnyEvent is loaded and asked to find a suitable event model, it
434	first check for the presence of urxvt.	1873	will first check for the presence of urxvt by trying to C<use> the
		1874	C<urxvt::anyevent> module.
435		1875
436	The class should provide implementations for all watcher types (see	1876	The class should provide implementations for all watcher types. See
437	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	1877	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
438	(Source code) and so on for actual examples, use C<perldoc -m	1878	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
439	AnyEvent::Impl::Glib> to see the sources).	1879	see the sources.
440		1880
		1881	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		1882	provide suitable (hopefully) replacements.
		1883
441	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	1884	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
442	uses the above line as-is. An interface isn't included in AnyEvent	1885	terminal emulator uses the above line as-is. An interface isn't included
443	because it doesn't make sense outside the embedded interpreter inside	1886	in AnyEvent because it doesn't make sense outside the embedded interpreter
444	I<rxvt-unicode>, and it is updated and maintained as part of the	1887	inside I<rxvt-unicode>, and it is updated and maintained as part of the
445	I<rxvt-unicode> distribution.	1888	I<rxvt-unicode> distribution.
446		1889
447	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1890	I<rxvt-unicode> also cheats a bit by not providing blocking access to
448	condition variables: code blocking while waiting for a condition will	1891	condition variables: code blocking while waiting for a condition will
449	C<die>. This still works with most modules/usages, and blocking calls must	1892	C<die>. This still works with most modules/usages, and blocking calls must
450	not be in an interactive application, so it makes sense.	1893	not be done in an interactive application, so it makes sense.
451		1894
452	=head1 ENVIRONMENT VARIABLES
453
454	The following environment variables are used by this module:
455
456	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
457	model gets used.
458
459	=head1 EXAMPLE	1895	=head1 EXAMPLE PROGRAM
460		1896
461	The following program uses an io watcher to read data from stdin, a timer	1897	The following program uses an I/O watcher to read data from STDIN, a timer
462	to display a message once per second, and a condvar to exit the program	1898	to display a message once per second, and a condition variable to quit the
463	when the user enters quit:	1899	program when the user enters quit:
464		1900
465	use AnyEvent;	1901	use AnyEvent;
466		1902
467	my $cv = AnyEvent->condvar;	1903	my $cv = AnyEvent->condvar;
468		1904
469	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	1905	my $io_watcher = AnyEvent->io (
		1906	fh => \*STDIN,
		1907	poll => 'r',
		1908	cb => sub {
470	warn "io event <$_[0]>\n"; # will always output <r>	1909	warn "io event <$_[0]>\n"; # will always output <r>
471	chomp (my $input = <STDIN>); # read a line	1910	chomp (my $input = <STDIN>); # read a line
472	warn "read: $input\n"; # output what has been read	1911	warn "read: $input\n"; # output what has been read
473	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1912	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		1913	},
474	});	1914	);
475		1915
476	my $time_watcher; # can only be used once	1916	my $time_watcher; # can only be used once
477		1917
478	sub new_timer {	1918	sub new_timer {
479	$timer = AnyEvent->timer (after => 1, cb => sub {	1919	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
482	});	1922	});
483	}	1923	}
484		1924
485	new_timer; # create first timer	1925	new_timer; # create first timer
486		1926
487	$cv->wait; # wait until user enters /^q/i	1927	$cv->recv; # wait until user enters /^q/i
488		1928
489	=head1 REAL-WORLD EXAMPLE	1929	=head1 REAL-WORLD EXAMPLE
490		1930
491	Consider the L<Net::FCP> module. It features (among others) the following	1931	Consider the L<Net::FCP> module. It features (among others) the following
492	API calls, which are to freenet what HTTP GET requests are to http:	1932	API calls, which are to freenet what HTTP GET requests are to http:
…		…
542	syswrite $txn->{fh}, $txn->{request}	1982	syswrite $txn->{fh}, $txn->{request}
543	or die "connection or write error";	1983	or die "connection or write error";
544	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1984	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
545		1985
546	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1986	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
547	result and signals any possible waiters that the request ahs finished:	1987	result and signals any possible waiters that the request has finished:
548		1988
549	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1989	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
550		1990
551	if (end-of-file or data complete) {	1991	if (end-of-file or data complete) {
552	$txn->{result} = $txn->{buf};	1992	$txn->{result} = $txn->{buf};
553	$txn->{finished}->broadcast;	1993	$txn->{finished}->send;
554	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1994	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
555	}	1995	}
556		1996
557	The C<result> method, finally, just waits for the finished signal (if the	1997	The C<result> method, finally, just waits for the finished signal (if the
558	request was already finished, it doesn't wait, of course, and returns the	1998	request was already finished, it doesn't wait, of course, and returns the
559	data:	1999	data:
560		2000
561	$txn->{finished}->wait;	2001	$txn->{finished}->recv;
562	return $txn->{result};	2002	return $txn->{result};
563		2003
564	The actual code goes further and collects all errors (C<die>s, exceptions)	2004	The actual code goes further and collects all errors (C<die>s, exceptions)
565	that occured during request processing. The C<result> method detects	2005	that occurred during request processing. The C<result> method detects
566	wether an exception as thrown (it is stored inside the $txn object)	2006	whether an exception as thrown (it is stored inside the $txn object)
567	and just throws the exception, which means connection errors and other	2007	and just throws the exception, which means connection errors and other
568	problems get reported tot he code that tries to use the result, not in a	2008	problems get reported tot he code that tries to use the result, not in a
569	random callback.	2009	random callback.
570		2010
571	All of this enables the following usage styles:	2011	All of this enables the following usage styles:
572		2012
573	1. Blocking:	2013	1. Blocking:
574		2014
575	my $data = $fcp->client_get ($url);	2015	my $data = $fcp->client_get ($url);
576		2016
577	2. Blocking, but parallelizing:	2017	2. Blocking, but running in parallel:
578		2018
579	my @datas = map $_->result,	2019	my @datas = map $_->result,
580	map $fcp->txn_client_get ($_),	2020	map $fcp->txn_client_get ($_),
581	@urls;	2021	@urls;
582		2022
583	Both blocking examples work without the module user having to know	2023	Both blocking examples work without the module user having to know
584	anything about events.	2024	anything about events.
585		2025
586	3a. Event-based in a main program, using any support Event module:	2026	3a. Event-based in a main program, using any supported event module:
587		2027
588	use Event;	2028	use EV;
589		2029
590	$fcp->txn_client_get ($url)->cb (sub {	2030	$fcp->txn_client_get ($url)->cb (sub {
591	my $txn = shift;	2031	my $txn = shift;
592	my $data = $txn->result;	2032	my $data = $txn->result;
593	...	2033	...
594	});	2034	});
595		2035
596	Event::loop;	2036	EV::loop;
597		2037
598	3b. The module user could use AnyEvent, too:	2038	3b. The module user could use AnyEvent, too:
599		2039
600	use AnyEvent;	2040	use AnyEvent;
601		2041
602	my $quit = AnyEvent->condvar;	2042	my $quit = AnyEvent->condvar;
603		2043
604	$fcp->txn_client_get ($url)->cb (sub {	2044	$fcp->txn_client_get ($url)->cb (sub {
605	...	2045	...
606	$quit->broadcast;	2046	$quit->send;
607	});	2047	});
608		2048
609	$quit->wait;	2049	$quit->recv;
		2050
		2051
		2052	=head1 BENCHMARKS
		2053
		2054	To give you an idea of the performance and overheads that AnyEvent adds
		2055	over the event loops themselves and to give you an impression of the speed
		2056	of various event loops I prepared some benchmarks.
		2057
		2058	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2059
		2060	Here is a benchmark of various supported event models used natively and
		2061	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2062	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2063	which it is), lets them fire exactly once and destroys them again.
		2064
		2065	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2066	distribution. It uses the L<AE> interface, which makes a real difference
		2067	for the EV and Perl backends only.
		2068
		2069	=head3 Explanation of the columns
		2070
		2071	I<watcher> is the number of event watchers created/destroyed. Since
		2072	different event models feature vastly different performances, each event
		2073	loop was given a number of watchers so that overall runtime is acceptable
		2074	and similar between tested event loop (and keep them from crashing): Glib
		2075	would probably take thousands of years if asked to process the same number
		2076	of watchers as EV in this benchmark.
		2077
		2078	I<bytes> is the number of bytes (as measured by the resident set size,
		2079	RSS) consumed by each watcher. This method of measuring captures both C
		2080	and Perl-based overheads.
		2081
		2082	I<create> is the time, in microseconds (millionths of seconds), that it
		2083	takes to create a single watcher. The callback is a closure shared between
		2084	all watchers, to avoid adding memory overhead. That means closure creation
		2085	and memory usage is not included in the figures.
		2086
		2087	I<invoke> is the time, in microseconds, used to invoke a simple
		2088	callback. The callback simply counts down a Perl variable and after it was
		2089	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2090	signal the end of this phase.
		2091
		2092	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2093	watcher.
		2094
		2095	=head3 Results
		2096
		2097	name watchers bytes create invoke destroy comment
		2098	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2099	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2100	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2101	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2102	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2103	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2104	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2105	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2106	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2107	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2108	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2109	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2110
		2111	=head3 Discussion
		2112
		2113	The benchmark does I<not> measure scalability of the event loop very
		2114	well. For example, a select-based event loop (such as the pure perl one)
		2115	can never compete with an event loop that uses epoll when the number of
		2116	file descriptors grows high. In this benchmark, all events become ready at
		2117	the same time, so select/poll-based implementations get an unnatural speed
		2118	boost.
		2119
		2120	Also, note that the number of watchers usually has a nonlinear effect on
		2121	overall speed, that is, creating twice as many watchers doesn't take twice
		2122	the time - usually it takes longer. This puts event loops tested with a
		2123	higher number of watchers at a disadvantage.
		2124
		2125	To put the range of results into perspective, consider that on the
		2126	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2127	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2128	cycles with POE.
		2129
		2130	C<EV> is the sole leader regarding speed and memory use, which are both
		2131	maximal/minimal, respectively. When using the L<AE> API there is zero
		2132	overhead (when going through the AnyEvent API create is about 5-6 times
		2133	slower, with other times being equal, so still uses far less memory than
		2134	any other event loop and is still faster than Event natively).
		2135
		2136	The pure perl implementation is hit in a few sweet spots (both the
		2137	constant timeout and the use of a single fd hit optimisations in the perl
		2138	interpreter and the backend itself). Nevertheless this shows that it
		2139	adds very little overhead in itself. Like any select-based backend its
		2140	performance becomes really bad with lots of file descriptors (and few of
		2141	them active), of course, but this was not subject of this benchmark.
		2142
		2143	The C<Event> module has a relatively high setup and callback invocation
		2144	cost, but overall scores in on the third place.
		2145
		2146	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2147	when using its pure perl backend.
		2148
		2149	C<Glib>'s memory usage is quite a bit higher, but it features a
		2150	faster callback invocation and overall ends up in the same class as
		2151	C<Event>. However, Glib scales extremely badly, doubling the number of
		2152	watchers increases the processing time by more than a factor of four,
		2153	making it completely unusable when using larger numbers of watchers
		2154	(note that only a single file descriptor was used in the benchmark, so
		2155	inefficiencies of C<poll> do not account for this).
		2156
		2157	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2158	more than 2000 watchers is a big setback, however, as correctness takes
		2159	precedence over speed. Nevertheless, its performance is surprising, as the
		2160	file descriptor is dup()ed for each watcher. This shows that the dup()
		2161	employed by some adaptors is not a big performance issue (it does incur a
		2162	hidden memory cost inside the kernel which is not reflected in the figures
		2163	above).
		2164
		2165	C<POE>, regardless of underlying event loop (whether using its pure perl
		2166	select-based backend or the Event module, the POE-EV backend couldn't
		2167	be tested because it wasn't working) shows abysmal performance and
		2168	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2169	as EV watchers, and 10 times as much memory as Event (the high memory
		2170	requirements are caused by requiring a session for each watcher). Watcher
		2171	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2172	implementation.
		2173
		2174	The design of the POE adaptor class in AnyEvent can not really account
		2175	for the performance issues, though, as session creation overhead is
		2176	small compared to execution of the state machine, which is coded pretty
		2177	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2178	using multiple sessions is not a good approach, especially regarding
		2179	memory usage, even the author of POE could not come up with a faster
		2180	design).
		2181
		2182	=head3 Summary
		2183
		2184	=over 4
		2185
		2186	=item * Using EV through AnyEvent is faster than any other event loop
		2187	(even when used without AnyEvent), but most event loops have acceptable
		2188	performance with or without AnyEvent.
		2189
		2190	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2191	the actual event loop, only with extremely fast event loops such as EV
		2192	adds AnyEvent significant overhead.
		2193
		2194	=item * You should avoid POE like the plague if you want performance or
		2195	reasonable memory usage.
		2196
		2197	=back
		2198
		2199	=head2 BENCHMARKING THE LARGE SERVER CASE
		2200
		2201	This benchmark actually benchmarks the event loop itself. It works by
		2202	creating a number of "servers": each server consists of a socket pair, a
		2203	timeout watcher that gets reset on activity (but never fires), and an I/O
		2204	watcher waiting for input on one side of the socket. Each time the socket
		2205	watcher reads a byte it will write that byte to a random other "server".
		2206
		2207	The effect is that there will be a lot of I/O watchers, only part of which
		2208	are active at any one point (so there is a constant number of active
		2209	fds for each loop iteration, but which fds these are is random). The
		2210	timeout is reset each time something is read because that reflects how
		2211	most timeouts work (and puts extra pressure on the event loops).
		2212
		2213	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2214	(1%) are active. This mirrors the activity of large servers with many
		2215	connections, most of which are idle at any one point in time.
		2216
		2217	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2218	distribution. It uses the L<AE> interface, which makes a real difference
		2219	for the EV and Perl backends only.
		2220
		2221	=head3 Explanation of the columns
		2222
		2223	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2224	each server has a read and write socket end).
		2225
		2226	I<create> is the time it takes to create a socket pair (which is
		2227	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2228
		2229	I<request>, the most important value, is the time it takes to handle a
		2230	single "request", that is, reading the token from the pipe and forwarding
		2231	it to another server. This includes deleting the old timeout and creating
		2232	a new one that moves the timeout into the future.
		2233
		2234	=head3 Results
		2235
		2236	name sockets create request
		2237	EV 20000 62.66 7.99
		2238	Perl 20000 68.32 32.64
		2239	IOAsync 20000 174.06 101.15 epoll
		2240	IOAsync 20000 174.67 610.84 poll
		2241	Event 20000 202.69 242.91
		2242	Glib 20000 557.01 1689.52
		2243	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2244
		2245	=head3 Discussion
		2246
		2247	This benchmark I<does> measure scalability and overall performance of the
		2248	particular event loop.
		2249
		2250	EV is again fastest. Since it is using epoll on my system, the setup time
		2251	is relatively high, though.
		2252
		2253	Perl surprisingly comes second. It is much faster than the C-based event
		2254	loops Event and Glib.
		2255
		2256	IO::Async performs very well when using its epoll backend, and still quite
		2257	good compared to Glib when using its pure perl backend.
		2258
		2259	Event suffers from high setup time as well (look at its code and you will
		2260	understand why). Callback invocation also has a high overhead compared to
		2261	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2262	uses select or poll in basically all documented configurations.
		2263
		2264	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2265	clearly fails to perform with many filehandles or in busy servers.
		2266
		2267	POE is still completely out of the picture, taking over 1000 times as long
		2268	as EV, and over 100 times as long as the Perl implementation, even though
		2269	it uses a C-based event loop in this case.
		2270
		2271	=head3 Summary
		2272
		2273	=over 4
		2274
		2275	=item * The pure perl implementation performs extremely well.
		2276
		2277	=item * Avoid Glib or POE in large projects where performance matters.
		2278
		2279	=back
		2280
		2281	=head2 BENCHMARKING SMALL SERVERS
		2282
		2283	While event loops should scale (and select-based ones do not...) even to
		2284	large servers, most programs we (or I :) actually write have only a few
		2285	I/O watchers.
		2286
		2287	In this benchmark, I use the same benchmark program as in the large server
		2288	case, but it uses only eight "servers", of which three are active at any
		2289	one time. This should reflect performance for a small server relatively
		2290	well.
		2291
		2292	The columns are identical to the previous table.
		2293
		2294	=head3 Results
		2295
		2296	name sockets create request
		2297	EV 16 20.00 6.54
		2298	Perl 16 25.75 12.62
		2299	Event 16 81.27 35.86
		2300	Glib 16 32.63 15.48
		2301	POE 16 261.87 276.28 uses POE::Loop::Event
		2302
		2303	=head3 Discussion
		2304
		2305	The benchmark tries to test the performance of a typical small
		2306	server. While knowing how various event loops perform is interesting, keep
		2307	in mind that their overhead in this case is usually not as important, due
		2308	to the small absolute number of watchers (that is, you need efficiency and
		2309	speed most when you have lots of watchers, not when you only have a few of
		2310	them).
		2311
		2312	EV is again fastest.
		2313
		2314	Perl again comes second. It is noticeably faster than the C-based event
		2315	loops Event and Glib, although the difference is too small to really
		2316	matter.
		2317
		2318	POE also performs much better in this case, but is is still far behind the
		2319	others.
		2320
		2321	=head3 Summary
		2322
		2323	=over 4
		2324
		2325	=item * C-based event loops perform very well with small number of
		2326	watchers, as the management overhead dominates.
		2327
		2328	=back
		2329
		2330	=head2 THE IO::Lambda BENCHMARK
		2331
		2332	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2333	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2334	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2335	shouldn't come as a surprise to anybody). As such, the benchmark is
		2336	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2337	very optimal. But how would AnyEvent compare when used without the extra
		2338	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2339
		2340	The benchmark itself creates an echo-server, and then, for 500 times,
		2341	connects to the echo server, sends a line, waits for the reply, and then
		2342	creates the next connection. This is a rather bad benchmark, as it doesn't
		2343	test the efficiency of the framework or much non-blocking I/O, but it is a
		2344	benchmark nevertheless.
		2345
		2346	name runtime
		2347	Lambda/select 0.330 sec
		2348	+ optimized 0.122 sec
		2349	Lambda/AnyEvent 0.327 sec
		2350	+ optimized 0.138 sec
		2351	Raw sockets/select 0.077 sec
		2352	POE/select, components 0.662 sec
		2353	POE/select, raw sockets 0.226 sec
		2354	POE/select, optimized 0.404 sec
		2355
		2356	AnyEvent/select/nb 0.085 sec
		2357	AnyEvent/EV/nb 0.068 sec
		2358	+state machine 0.134 sec
		2359
		2360	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2361	benchmarks actually make blocking connects and use 100% blocking I/O,
		2362	defeating the purpose of an event-based solution. All of the newly
		2363	written AnyEvent benchmarks use 100% non-blocking connects (using
		2364	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2365	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2366	generally require a lot more bookkeeping and event handling than blocking
		2367	connects (which involve a single syscall only).
		2368
		2369	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2370	offers similar expressive power as POE and IO::Lambda, using conventional
		2371	Perl syntax. This means that both the echo server and the client are 100%
		2372	non-blocking, further placing it at a disadvantage.
		2373
		2374	As you can see, the AnyEvent + EV combination even beats the
		2375	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2376	backend easily beats IO::Lambda and POE.
		2377
		2378	And even the 100% non-blocking version written using the high-level (and
		2379	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2380	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2381	in a non-blocking way.
		2382
		2383	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2384	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2385	part of the IO::lambda distribution and were used without any changes.
		2386
		2387
		2388	=head1 SIGNALS
		2389
		2390	AnyEvent currently installs handlers for these signals:
		2391
		2392	=over 4
		2393
		2394	=item SIGCHLD
		2395
		2396	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2397	emulation for event loops that do not support them natively. Also, some
		2398	event loops install a similar handler.
		2399
		2400	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2401	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2402
		2403	=item SIGPIPE
		2404
		2405	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2406	when AnyEvent gets loaded.
		2407
		2408	The rationale for this is that AnyEvent users usually do not really depend
		2409	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2410	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2411	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2412	some random socket.
		2413
		2414	The rationale for installing a no-op handler as opposed to ignoring it is
		2415	that this way, the handler will be restored to defaults on exec.
		2416
		2417	Feel free to install your own handler, or reset it to defaults.
		2418
		2419	=back
		2420
		2421	=cut
		2422
		2423	undef $SIG{CHLD}
		2424	if $SIG{CHLD} eq 'IGNORE';
		2425
		2426	$SIG{PIPE} = sub { }
		2427	unless defined $SIG{PIPE};
		2428
		2429	=head1 RECOMMENDED/OPTIONAL MODULES
		2430
		2431	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2432	it's built-in modules) are required to use it.
		2433
		2434	That does not mean that AnyEvent won't take advantage of some additional
		2435	modules if they are installed.
		2436
		2437	This section epxlains which additional modules will be used, and how they
		2438	affect AnyEvent's operetion.
		2439
		2440	=over 4
		2441
		2442	=item L<Async::Interrupt>
		2443
		2444	This slightly arcane module is used to implement fast signal handling: To
		2445	my knowledge, there is no way to do completely race-free and quick
		2446	signal handling in pure perl. To ensure that signals still get
		2447	delivered, AnyEvent will start an interval timer to wake up perl (and
		2448	catch the signals) with some delay (default is 10 seconds, look for
		2449	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2450
		2451	If this module is available, then it will be used to implement signal
		2452	catching, which means that signals will not be delayed, and the event loop
		2453	will not be interrupted regularly, which is more efficient (And good for
		2454	battery life on laptops).
		2455
		2456	This affects not just the pure-perl event loop, but also other event loops
		2457	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2458
		2459	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2460	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2461	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2462	does nothing for those backends.
		2463
		2464	=item L<EV>
		2465
		2466	This module isn't really "optional", as it is simply one of the backend
		2467	event loops that AnyEvent can use. However, it is simply the best event
		2468	loop available in terms of features, speed and stability: It supports
		2469	the AnyEvent API optimally, implements all the watcher types in XS, does
		2470	automatic timer adjustments even when no monotonic clock is available,
		2471	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2472	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2473	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2474
		2475	=item L<Guard>
		2476
		2477	The guard module, when used, will be used to implement
		2478	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2479	lot less memory), but otherwise doesn't affect guard operation much. It is
		2480	purely used for performance.
		2481
		2482	=item L<JSON> and L<JSON::XS>
		2483
		2484	This module is required when you want to read or write JSON data via
		2485	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2486	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2487
		2488	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2489	installed.
		2490
		2491	=item L<Net::SSLeay>
		2492
		2493	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2494	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2495	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2496
		2497	=item L<Time::HiRes>
		2498
		2499	This module is part of perl since release 5.008. It will be used when the
		2500	chosen event library does not come with a timing source on it's own. The
		2501	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2502	try to use a monotonic clock for timing stability.
		2503
		2504	=back
		2505
		2506
		2507	=head1 FORK
		2508
		2509	Most event libraries are not fork-safe. The ones who are usually are
		2510	because they rely on inefficient but fork-safe C<select> or C<poll>
		2511	calls. Only L<EV> is fully fork-aware.
		2512
		2513	If you have to fork, you must either do so I<before> creating your first
		2514	watcher OR you must not use AnyEvent at all in the child OR you must do
		2515	something completely out of the scope of AnyEvent.
		2516
		2517
		2518	=head1 SECURITY CONSIDERATIONS
		2519
		2520	AnyEvent can be forced to load any event model via
		2521	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2522	execute arbitrary code or directly gain access, it can easily be used to
		2523	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2524	will not be active when the program uses a different event model than
		2525	specified in the variable.
		2526
		2527	You can make AnyEvent completely ignore this variable by deleting it
		2528	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2529
		2530	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2531
		2532	use AnyEvent;
		2533
		2534	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2535	be used to probe what backend is used and gain other information (which is
		2536	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2537	$ENV{PERL_ANYEVENT_STRICT}.
		2538
		2539	Note that AnyEvent will remove I<all> environment variables starting with
		2540	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2541	enabled.
		2542
		2543
		2544	=head1 BUGS
		2545
		2546	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2547	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2548	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2549	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2550	pronounced).
		2551
610		2552
611	=head1 SEE ALSO	2553	=head1 SEE ALSO
612		2554
613	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	2555	Utility functions: L<AnyEvent::Util>.
614		2556
615	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	2557	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2558	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
616		2559
617	Nontrivial usage example: L<Net::FCP>.	2560	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2561	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2562	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2563	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
618		2564
619	=head1	2565	Non-blocking file handles, sockets, TCP clients and
		2566	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2567
		2568	Asynchronous DNS: L<AnyEvent::DNS>.
		2569
		2570	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2571	L<Coro::Event>,
		2572
		2573	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2574	L<AnyEvent::HTTP>.
		2575
		2576
		2577	=head1 AUTHOR
		2578
		2579	Marc Lehmann <schmorp@schmorp.de>
		2580	http://home.schmorp.de/
620		2581
621	=cut	2582	=cut
622		2583
623	1	2584	1
624		2585

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