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Revision 1.370 by root, Wed Aug 17 02:50:35 2011 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	Event, Coro, Glib, Tk, Perl - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt,
		6	FLTK and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores wether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
		58
		59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		60
		61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		62	nowadays. So what is different about AnyEvent?
		63
		64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		65	policy> and AnyEvent is I<small and efficient>.
		66
		67	First and foremost, I<AnyEvent is not an event model> itself, it only
		68	interfaces to whatever event model the main program happens to use, in a
		69	pragmatic way. For event models and certain classes of immortals alike,
		70	the statement "there can only be one" is a bitter reality: In general,
		71	only one event loop can be active at the same time in a process. AnyEvent
		72	cannot change this, but it can hide the differences between those event
		73	loops.
		74
		75	The goal of AnyEvent is to offer module authors the ability to do event
		76	programming (waiting for I/O or timer events) without subscribing to a
		77	religion, a way of living, and most importantly: without forcing your
		78	module users into the same thing by forcing them to use the same event
		79	model you use.
		80
		81	For modules like POE or IO::Async (which is a total misnomer as it is
		82	actually doing all I/O I<synchronously>...), using them in your module is
		83	like joining a cult: After you join, you are dependent on them and you
		84	cannot use anything else, as they are simply incompatible to everything
		85	that isn't them. What's worse, all the potential users of your
		86	module are I<also> forced to use the same event loop you use.
		87
		88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
		91	uses one of those, every user of your module has to use it, too. But if
		92	your module uses AnyEvent, it works transparently with all event models it
		93	supports (including stuff like IO::Async, as long as those use one of the
		94	supported event loops. It is easy to add new event loops to AnyEvent, too,
		95	so it is future-proof).
		96
		97	In addition to being free of having to use I<the one and only true event
		98	model>, AnyEvent also is free of bloat and policy: with POE or similar
		99	modules, you get an enormous amount of code and strict rules you have to
		100	follow. AnyEvent, on the other hand, is lean and to the point, by only
		101	offering the functionality that is necessary, in as thin as a wrapper as
		102	technically possible.
		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
		110	Now, if you I<do want> lots of policy (this can arguably be somewhat
		111	useful) and you want to force your users to use the one and only event
		112	model, you should I<not> use this module.
22		113
23	=head1 DESCRIPTION	114	=head1 DESCRIPTION
24		115
25	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
26	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
27	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
28	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
29		120
30	The interface itself is vaguely similar but not identical to the Event	121	The interface itself is vaguely similar, but not identical to the L<Event>
31	module.	122	module.
32		123
33	On the first call of any method, the module tries to detect the currently	124	During the first call of any watcher-creation method, the module tries
34	loaded event loop by probing wether any of the following modules is	125	to detect the currently loaded event loop by probing whether one of the
35	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
36	used. If none is found, the module tries to load these modules in the	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
37	order given. The first one that could be successfully loaded will be	128	found is used. If none are detected, the module tries to load the first
38	used. If still none could be found, AnyEvent will fall back to a pure-perl	129	four modules in the order given; but note that if L<EV> is not
39	event loop, which is also not very efficient.	130	available, the pure-perl L<AnyEvent::Loop> should always work, so
		131	the other two are not normally tried.
40		132
41	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
42	an Event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
43	that model the default. For example:	135	that model the default. For example:
44		136
45	use Tk;	137	use Tk;
46	use AnyEvent;	138	use AnyEvent;
47		139
48	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
49		141
		142	The I<likely> means that, if any module loads another event model and
		143	starts using it, all bets are off - this case should be very rare though,
		144	as very few modules hardcode event loops without announcing this very
		145	loudly.
		146
50	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
51	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	other event modules you can load it explicitly and enjoy the high
52	explicitly.	149	availability of that event loop :)
53		150
54	=head1 WATCHERS	151	=head1 WATCHERS
55		152
56	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
57	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
58	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
59		156
60	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
61	creating a watcher it will immediately "watch" for events and invoke	158	creating a watcher it will immediately "watch" for events and invoke the
		159	callback when the event occurs (of course, only when the event model
		160	is in control).
		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
62	the callback. To disable the watcher you have to destroy it (e.g. by	168	To disable a watcher you have to destroy it (e.g. by setting the
63	setting the variable that stores it to C<undef> or otherwise deleting all	169	variable you store it in to C<undef> or otherwise deleting all references
64	references to it).	170	to it).
65		171
66	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
67		173
		174	Many watchers either are used with "recursion" (repeating timers for
		175	example), or need to refer to their watcher object in other ways.
		176
		177	One way to achieve that is this pattern:
		178
		179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		180	# you can use $w here, for example to undef it
		181	undef $w;
		182	});
		183
		184	Note that C<my $w; $w => combination. This is necessary because in Perl,
		185	my variables are only visible after the statement in which they are
		186	declared.
		187
68	=head2 IO WATCHERS	188	=head2 I/O WATCHERS
69		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
70	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71	the following mandatory arguments:	197	with the following mandatory key-value pairs as arguments:
72		198
73	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
74	events. C<poll> must be a string that is either C<r> or C<w>, that creates	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
75	a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
76	to invoke everytime the filehandle becomes ready.
77		208
78	Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on	209	C<cb> is the callback to invoke each time the file handle becomes ready.
79	a socket you can have one r + one w, not any more (limitation comes from
80	Tk - if you are sure you are not using Tk this limitation is gone).
81		210
82	Filehandles will be kept alive, so as long as the watcher exists, the	211	Although the callback might get passed parameters, their value and
83	filehandle exists, too.	212	presence is undefined and you cannot rely on them. Portable AnyEvent
		213	callbacks cannot use arguments passed to I/O watcher callbacks.
84		214
85	Example:	215	The I/O watcher might use the underlying file descriptor or a copy of it.
		216	You must not close a file handle as long as any watcher is active on the
		217	underlying file descriptor.
86		218
		219	Some event loops issue spurious readiness notifications, so you should
		220	always use non-blocking calls when reading/writing from/to your file
		221	handles.
		222
87	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
88	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
90	warn "read: $input\n";	228	warn "read: $input\n";
91	undef $w;	229	undef $w;
92	});	230	});
93		231
94	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
95		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
96	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	method with the following mandatory arguments:	243	method with the following mandatory arguments:
98		244
99	C<after> after how many seconds (fractions are supported) should the timer	245	C<after> specifies after how many seconds (fractional values are
100	activate. C<cb> the callback to invoke.	246	supported) the callback should be invoked. C<cb> is the callback to invoke
		247	in that case.
101		248
102	The timer callback will be invoked at most once: if you want a repeating	249	Although the callback might get passed parameters, their value and
103	timer you have to create a new watcher (this is a limitation by both Tk	250	presence is undefined and you cannot rely on them. Portable AnyEvent
104	and Glib).	251	callbacks cannot use arguments passed to time watcher callbacks.
105		252
106	Example:	253	The callback will normally be invoked only once. If you specify another
		254	parameter, C<interval>, as a strictly positive number (> 0), then the
		255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
107		258
		259	The callback will be rescheduled before invoking the callback, but no
		260	attempt is made to avoid timer drift in most backends, so the interval is
		261	only approximate.
		262
108	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
109	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
110	warn "timeout\n";	266	warn "timeout\n";
111	});	267	});
112		268
113	# to cancel the timer:	269	# to cancel the timer:
114	undef $w;	270	undef $w;
115		271
116	=head2 CONDITION WATCHERS	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
117		273
118	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
119	method without any arguments.	275	warn "timeout\n";
		276	};
120		277
121	A condition watcher watches for a condition - precisely that the C<<	278	=head3 TIMING ISSUES
122	->broadcast >> method has been called.
123		279
124	The watcher has only two methods:	280	There are two ways to handle timers: based on real time (relative, "fire
		281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		282	o'clock").
		283
		284	While most event loops expect timers to specified in a relative way, they
		285	use absolute time internally. This makes a difference when your clock
		286	"jumps", for example, when ntp decides to set your clock backwards from
		287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		288	fire "after a second" might actually take six years to finally fire.
		289
		290	AnyEvent cannot compensate for this. The only event loop that is conscious
		291	of these issues is L<EV>, which offers both relative (ev_timer, based
		292	on true relative time) and absolute (ev_periodic, based on wallclock time)
		293	timers.
		294
		295	AnyEvent always prefers relative timers, if available, matching the
		296	AnyEvent API.
		297
		298	AnyEvent has two additional methods that return the "current time":
125		299
126	=over 4	300	=over 4
127		301
128	=item $cv->wait	302	=item AnyEvent->time
129		303
130	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	304	This returns the "current wallclock time" as a fractional number of
131	called on c<$cv>, while servicing other watchers normally.	305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
132		307
133	Not all event models support a blocking wait - some die in that case, so	308	It progresses independently of any event loop processing, i.e. each call
134	if you are using this from a module, never require a blocking wait, but	309	will check the system clock, which usually gets updated frequently.
135	let the caller decide wether the call will block or not (for example,
136	by coupling condition variables with some kind of request results and
137	supporting callbacks so the caller knows that getting the result will not
138	block, while still suppporting blockign waits if the caller so desires).
139		310
140	You can only wait once on a condition - additional calls will return	311	=item AnyEvent->now
141	immediately.
142		312
143	=item $cv->broadcast	313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
144		317
145	Flag the condition as ready - a running C<< ->wait >> and all further	318	I<In almost all cases (in all cases if you don't care), this is the
146	calls to C<wait> will return after this method has been called. If nobody	319	function to call when you want to know the current time.>
147	is waiting the broadcast will be remembered..
148		320
149	Example:	321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update its activity timeouts).
150		324
151	# wait till the result is ready	325	The rest of this section is only of relevance if you try to be very exact
152	my $result_ready = AnyEvent->condvar;	326	with your timing; you can skip it without a bad conscience.
153		327
154	# do something such as adding a timer	328	For a practical example of when these times differ, consider L<Event::Lib>
155	# or socket watcher the calls $result_ready->broadcast	329	and L<EV> and the following set-up:
156	# when the "result" is ready.
157		330
158	$result_ready->wait;	331	The event loop is running and has just invoked one of your callbacks at
		332	time=500 (assume no other callbacks delay processing). In your callback,
		333	you wait a second by executing C<sleep 1> (blocking the process for a
		334	second) and then (at time=501) you create a relative timer that fires
		335	after three seconds.
		336
		337	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		338	both return C<501>, because that is the current time, and the timer will
		339	be scheduled to fire at time=504 (C<501> + C<3>).
		340
		341	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		342	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		343	last event processing phase started. With L<EV>, your timer gets scheduled
		344	to run at time=503 (C<500> + C<3>).
		345
		346	In one sense, L<Event::Lib> is more exact, as it uses the current time
		347	regardless of any delays introduced by event processing. However, most
		348	callbacks do not expect large delays in processing, so this causes a
		349	higher drift (and a lot more system calls to get the current time).
		350
		351	In another sense, L<EV> is more exact, as your timer will be scheduled at
		352	the same time, regardless of how long event processing actually took.
		353
		354	In either case, if you care (and in most cases, you don't), then you
		355	can get whatever behaviour you want with any event loop, by taking the
		356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		357	account.
		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Loop>) cache the current
		362	time for each loop iteration (see the discussion of L<< AnyEvent->now >>,
		363	above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
159		380
160	=back	381	=back
161		382
162	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
163		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
164	You can listen for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
165	I<name> without any C<SIG> prefix. Multiple signals events can be clumped	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
166	together into one callback invocation, and callback invocation might or	389	callback to be invoked whenever a signal occurs.
167	might not be asynchronous.
168		390
169	These watchers might use C<%SIG>, so programs overwriting those signals	391	Although the callback might get passed parameters, their value and
170	directly will likely not work correctly.	392	presence is undefined and you cannot rely on them. Portable AnyEvent
		393	callbacks cannot use arguments passed to signal watcher callbacks.
		394
		395	Multiple signal occurrences can be clumped together into one callback
		396	invocation, and callback invocation will be synchronous. Synchronous means
		397	that it might take a while until the signal gets handled by the process,
		398	but it is guaranteed not to interrupt any other callbacks.
		399
		400	The main advantage of using these watchers is that you can share a signal
		401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
		403
		404	This watcher might use C<%SIG> (depending on the event loop used),
		405	so programs overwriting those signals directly will likely not work
		406	correctly.
171		407
172	Example: exit on SIGINT	408	Example: exit on SIGINT
173		409
174	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
175		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		437	variable can be changed only before the first signal watcher is created,
		438	and should be left alone otherwise. This variable determines how often
		439	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		440	will cause fewer spurious wake-ups, which is better for power and CPU
		441	saving.
		442
		443	All these problems can be avoided by installing the optional
		444	L<Async::Interrupt> module, which works with most event loops. It will not
		445	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		446	(and not with L<POE> currently, as POE does its own workaround with
		447	one-second latency). For those, you just have to suffer the delays.
		448
176	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
177		450
178	You can also listen for the status of a child process specified by the	451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
179	C<pid> argument (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		452
184	Example: wait for pid 1333	453	You can also watch for a child process exit and catch its exit status.
185		454
186	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });	455	The child process is specified by the C<pid> argument (on some backends,
		456	using C<0> watches for any child process exit, on others this will
		457	croak). The watcher will be triggered only when the child process has
		458	finished and an exit status is available, not on any trace events
		459	(stopped/continued).
187		460
188	=head1 GLOBALS	461	The callback will be called with the pid and exit status (as returned by
		462	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		463	callback arguments.
		464
		465	This watcher type works by installing a signal handler for C<SIGCHLD>,
		466	and since it cannot be shared, nothing else should use SIGCHLD or reap
		467	random child processes (waiting for specific child processes, e.g. inside
		468	C<system>, is just fine).
		469
		470	There is a slight catch to child watchers, however: you usually start them
		471	I<after> the child process was created, and this means the process could
		472	have exited already (and no SIGCHLD will be sent anymore).
		473
		474	Not all event models handle this correctly (neither POE nor IO::Async do,
		475	see their AnyEvent::Impl manpages for details), but even for event models
		476	that I<do> handle this correctly, they usually need to be loaded before
		477	the process exits (i.e. before you fork in the first place). AnyEvent's
		478	pure perl event loop handles all cases correctly regardless of when you
		479	start the watcher.
		480
		481	This means you cannot create a child watcher as the very first
		482	thing in an AnyEvent program, you I<have> to create at least one
		483	watcher before you C<fork> the child (alternatively, you can call
		484	C<AnyEvent::detect>).
		485
		486	As most event loops do not support waiting for child events, they will be
		487	emulated by AnyEvent in most cases, in which case the latency and race
		488	problems mentioned in the description of signal watchers apply.
		489
		490	Example: fork a process and wait for it
		491
		492	my $done = AnyEvent->condvar;
		493
		494	my $pid = fork or exit 5;
		495
		496	my $w = AnyEvent->child (
		497	pid => $pid,
		498	cb => sub {
		499	my ($pid, $status) = @_;
		500	warn "pid $pid exited with status $status";
		501	$done->send;
		502	},
		503	);
		504
		505	# do something else, then wait for process exit
		506	$done->recv;
		507
		508	=head2 IDLE WATCHERS
		509
		510	$w = AnyEvent->idle (cb => <callback>);
		511
		512	This will repeatedly invoke the callback after the process becomes idle,
		513	until either the watcher is destroyed or new events have been detected.
		514
		515	Idle watchers are useful when there is a need to do something, but it
		516	is not so important (or wise) to do it instantly. The callback will be
		517	invoked only when there is "nothing better to do", which is usually
		518	defined as "all outstanding events have been handled and no new events
		519	have been detected". That means that idle watchers ideally get invoked
		520	when the event loop has just polled for new events but none have been
		521	detected. Instead of blocking to wait for more events, the idle watchers
		522	will be invoked.
		523
		524	Unfortunately, most event loops do not really support idle watchers (only
		525	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		526	will simply call the callback "from time to time".
		527
		528	Example: read lines from STDIN, but only process them when the
		529	program is otherwise idle:
		530
		531	my @lines; # read data
		532	my $idle_w;
		533	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		534	push @lines, scalar <STDIN>;
		535
		536	# start an idle watcher, if not already done
		537	$idle_w ||= AnyEvent->idle (cb => sub {
		538	# handle only one line, when there are lines left
		539	if (my $line = shift @lines) {
		540	print "handled when idle: $line";
		541	} else {
		542	# otherwise disable the idle watcher again
		543	undef $idle_w;
		544	}
		545	});
		546	});
		547
		548	=head2 CONDITION VARIABLES
		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
		554
		555	If you are familiar with some event loops you will know that all of them
		556	require you to run some blocking "loop", "run" or similar function that
		557	will actively watch for new events and call your callbacks.
		558
		559	AnyEvent is slightly different: it expects somebody else to run the event
		560	loop and will only block when necessary (usually when told by the user).
		561
		562	The tool to do that is called a "condition variable", so called because
		563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
		566
		567	Condition variables can be created by calling the C<< AnyEvent->condvar
		568	>> method, usually without arguments. The only argument pair allowed is
		569	C<cb>, which specifies a callback to be called when the condition variable
		570	becomes true, with the condition variable as the first argument (but not
		571	the results).
		572
		573	After creation, the condition variable is "false" until it becomes "true"
		574	by calling the C<send> method (or calling the condition variable as if it
		575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
		577
		578	Since condition variables are the most complex part of the AnyEvent API, here are
		579	some different mental models of what they are - pick the ones you can connect to:
189		580
190	=over 4	581	=over 4
191		582
		583	=item * Condition variables are like callbacks - you can call them (and pass them instead
		584	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		585
		586	=item * Condition variables are signals - one side can emit or send them,
		587	the other side can wait for them, or install a handler that is called when
		588	the signal fires.
		589
		590	=item * Condition variables are like "Merge Points" - points in your program
		591	where you merge multiple independent results/control flows into one.
		592
		593	=item * Condition variables represent a transaction - functions that start
		594	some kind of transaction can return them, leaving the caller the choice
		595	between waiting in a blocking fashion, or setting a callback.
		596
		597	=item * Condition variables represent future values, or promises to deliver
		598	some result, long before the result is available.
		599
		600	=back
		601
		602	Condition variables are very useful to signal that something has finished,
		603	for example, if you write a module that does asynchronous http requests,
		604	then a condition variable would be the ideal candidate to signal the
		605	availability of results. The user can either act when the callback is
		606	called or can synchronously C<< ->recv >> for the results.
		607
		608	You can also use them to simulate traditional event loops - for example,
		609	you can block your main program until an event occurs - for example, you
		610	could C<< ->recv >> in your main program until the user clicks the Quit
		611	button of your app, which would C<< ->send >> the "quit" event.
		612
		613	Note that condition variables recurse into the event loop - if you have
		614	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		615	lose. Therefore, condition variables are good to export to your caller, but
		616	you should avoid making a blocking wait yourself, at least in callbacks,
		617	as this asks for trouble.
		618
		619	Condition variables are represented by hash refs in perl, and the keys
		620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		621	easy (it is often useful to build your own transaction class on top of
		622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		623	its C<new> method in your own C<new> method.
		624
		625	There are two "sides" to a condition variable - the "producer side" which
		626	eventually calls C<< -> send >>, and the "consumer side", which waits
		627	for the send to occur.
		628
		629	Example: wait for a timer.
		630
		631	# condition: "wait till the timer is fired"
		632	my $timer_fired = AnyEvent->condvar;
		633
		634	# create the timer - we could wait for, say
		635	# a handle becomign ready, or even an
		636	# AnyEvent::HTTP request to finish, but
		637	# in this case, we simply use a timer:
		638	my $w = AnyEvent->timer (
		639	after => 1,
		640	cb => sub { $timer_fired->send },
		641	);
		642
		643	# this "blocks" (while handling events) till the callback
		644	# calls ->send
		645	$timer_fired->recv;
		646
		647	Example: wait for a timer, but take advantage of the fact that condition
		648	variables are also callable directly.
		649
		650	my $done = AnyEvent->condvar;
		651	my $delay = AnyEvent->timer (after => 5, cb => $done);
		652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
		670
		671	=head3 METHODS FOR PRODUCERS
		672
		673	These methods should only be used by the producing side, i.e. the
		674	code/module that eventually sends the signal. Note that it is also
		675	the producer side which creates the condvar in most cases, but it isn't
		676	uncommon for the consumer to create it as well.
		677
		678	=over 4
		679
		680	=item $cv->send (...)
		681
		682	Flag the condition as ready - a running C<< ->recv >> and all further
		683	calls to C<recv> will (eventually) return after this method has been
		684	called. If nobody is waiting the send will be remembered.
		685
		686	If a callback has been set on the condition variable, it is called
		687	immediately from within send.
		688
		689	Any arguments passed to the C<send> call will be returned by all
		690	future C<< ->recv >> calls.
		691
		692	Condition variables are overloaded so one can call them directly (as if
		693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
		695
		696	=item $cv->croak ($error)
		697
		698	Similar to send, but causes all calls to C<< ->recv >> to invoke
		699	C<Carp::croak> with the given error message/object/scalar.
		700
		701	This can be used to signal any errors to the condition variable
		702	user/consumer. Doing it this way instead of calling C<croak> directly
		703	delays the error detection, but has the overwhelming advantage that it
		704	diagnoses the error at the place where the result is expected, and not
		705	deep in some event callback with no connection to the actual code causing
		706	the problem.
		707
		708	=item $cv->begin ([group callback])
		709
		710	=item $cv->end
		711
		712	These two methods can be used to combine many transactions/events into
		713	one. For example, a function that pings many hosts in parallel might want
		714	to use a condition variable for the whole process.
		715
		716	Every call to C<< ->begin >> will increment a counter, and every call to
		717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		718	>>, the (last) callback passed to C<begin> will be executed, passing the
		719	condvar as first argument. That callback is I<supposed> to call C<< ->send
		720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
		722
		723	You can think of C<< $cv->send >> giving you an OR condition (one call
		724	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		725	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		726
		727	Let's start with a simple example: you have two I/O watchers (for example,
		728	STDOUT and STDERR for a program), and you want to wait for both streams to
		729	close before activating a condvar:
		730
		731	my $cv = AnyEvent->condvar;
		732
		733	$cv->begin; # first watcher
		734	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		735	defined sysread $fh1, my $buf, 4096
		736	or $cv->end;
		737	});
		738
		739	$cv->begin; # second watcher
		740	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		741	defined sysread $fh2, my $buf, 4096
		742	or $cv->end;
		743	});
		744
		745	$cv->recv;
		746
		747	This works because for every event source (EOF on file handle), there is
		748	one call to C<begin>, so the condvar waits for all calls to C<end> before
		749	sending.
		750
		751	The ping example mentioned above is slightly more complicated, as the
		752	there are results to be passwd back, and the number of tasks that are
		753	begun can potentially be zero:
		754
		755	my $cv = AnyEvent->condvar;
		756
		757	my %result;
		758	$cv->begin (sub { shift->send (\%result) });
		759
		760	for my $host (@list_of_hosts) {
		761	$cv->begin;
		762	ping_host_then_call_callback $host, sub {
		763	$result{$host} = ...;
		764	$cv->end;
		765	};
		766	}
		767
		768	$cv->end;
		769
		770	This code fragment supposedly pings a number of hosts and calls
		771	C<send> after results for all then have have been gathered - in any
		772	order. To achieve this, the code issues a call to C<begin> when it starts
		773	each ping request and calls C<end> when it has received some result for
		774	it. Since C<begin> and C<end> only maintain a counter, the order in which
		775	results arrive is not relevant.
		776
		777	There is an additional bracketing call to C<begin> and C<end> outside the
		778	loop, which serves two important purposes: first, it sets the callback
		779	to be called once the counter reaches C<0>, and second, it ensures that
		780	C<send> is called even when C<no> hosts are being pinged (the loop
		781	doesn't execute once).
		782
		783	This is the general pattern when you "fan out" into multiple (but
		784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		785	the callback and ensure C<end> is called at least once, and then, for each
		786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
		788
		789	=back
		790
		791	=head3 METHODS FOR CONSUMERS
		792
		793	These methods should only be used by the consuming side, i.e. the
		794	code awaits the condition.
		795
		796	=over 4
		797
		798	=item $cv->recv
		799
		800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		801	>> methods have been called on C<$cv>, while servicing other watchers
		802	normally.
		803
		804	You can only wait once on a condition - additional calls are valid but
		805	will return immediately.
		806
		807	If an error condition has been set by calling C<< ->croak >>, then this
		808	function will call C<croak>.
		809
		810	In list context, all parameters passed to C<send> will be returned,
		811	in scalar context only the first one will be returned.
		812
		813	Note that doing a blocking wait in a callback is not supported by any
		814	event loop, that is, recursive invocation of a blocking C<< ->recv
		815	>> is not allowed, and the C<recv> call will C<croak> if such a
		816	condition is detected. This condition can be slightly loosened by using
		817	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		818	any thread that doesn't run the event loop itself.
		819
		820	Not all event models support a blocking wait - some die in that case
		821	(programs might want to do that to stay interactive), so I<if you are
		822	using this from a module, never require a blocking wait>. Instead, let the
		823	caller decide whether the call will block or not (for example, by coupling
		824	condition variables with some kind of request results and supporting
		825	callbacks so the caller knows that getting the result will not block,
		826	while still supporting blocking waits if the caller so desires).
		827
		828	You can ensure that C<< ->recv >> never blocks by setting a callback and
		829	only calling C<< ->recv >> from within that callback (or at a later
		830	time). This will work even when the event loop does not support blocking
		831	waits otherwise.
		832
		833	=item $bool = $cv->ready
		834
		835	Returns true when the condition is "true", i.e. whether C<send> or
		836	C<croak> have been called.
		837
		838	=item $cb = $cv->cb ($cb->($cv))
		839
		840	This is a mutator function that returns the callback set and optionally
		841	replaces it before doing so.
		842
		843	The callback will be called when the condition becomes "true", i.e. when
		844	C<send> or C<croak> are called, with the only argument being the
		845	condition variable itself. If the condition is already true, the
		846	callback is called immediately when it is set. Calling C<recv> inside
		847	the callback or at any later time is guaranteed not to block.
		848
		849	=back
		850
		851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		852
		853	The available backend classes are (every class has its own manpage):
		854
		855	=over 4
		856
		857	=item Backends that are autoprobed when no other event loop can be found.
		858
		859	EV is the preferred backend when no other event loop seems to be in
		860	use. If EV is not installed, then AnyEvent will fall back to its own
		861	pure-perl implementation, which is available everywhere as it comes with
		862	AnyEvent itself.
		863
		864	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		865	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		866
		867	=item Backends that are transparently being picked up when they are used.
		868
		869	These will be used if they are already loaded when the first watcher
		870	is created, in which case it is assumed that the application is using
		871	them. This means that AnyEvent will automatically pick the right backend
		872	when the main program loads an event module before anything starts to
		873	create watchers. Nothing special needs to be done by the main program.
		874
		875	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		876	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		877	AnyEvent::Impl::Tk based on Tk, very broken.
		878	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		879	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		880	AnyEvent::Impl::Irssi used when running within irssi.
		881	AnyEvent::Impl::IOAsync based on IO::Async.
		882	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		883	AnyEvent::Impl::FLTK2 based on FLTK (fltk 2 binding).
		884
		885	=item Backends with special needs.
		886
		887	Qt requires the Qt::Application to be instantiated first, but will
		888	otherwise be picked up automatically. As long as the main program
		889	instantiates the application before any AnyEvent watchers are created,
		890	everything should just work.
		891
		892	AnyEvent::Impl::Qt based on Qt.
		893
		894	=item Event loops that are indirectly supported via other backends.
		895
		896	Some event loops can be supported via other modules:
		897
		898	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		899
		900	B<WxWidgets> has no support for watching file handles. However, you can
		901	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		902	polls 20 times per second, which was considered to be too horrible to even
		903	consider for AnyEvent.
		904
		905	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		906	backend, so it can be supported through POE.
		907
		908	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		909	load L<POE> when detecting them, in the hope that POE will pick them up,
		910	in which case everything will be automatic.
		911
		912	=back
		913
		914	=head1 GLOBAL VARIABLES AND FUNCTIONS
		915
		916	These are not normally required to use AnyEvent, but can be useful to
		917	write AnyEvent extension modules.
		918
		919	=over 4
		920
192	=item $AnyEvent::MODEL	921	=item $AnyEvent::MODEL
193		922
194	Contains C<undef> until the first watcher is being created. Then it	923	Contains C<undef> until the first watcher is being created, before the
		924	backend has been autodetected.
		925
195	contains the event model that is being used, which is the name of the	926	Afterwards it contains the event model that is being used, which is the
196	Perl class implementing the model. This class is usually one of the	927	name of the Perl class implementing the model. This class is usually one
197	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	928	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
198	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	929	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
199		930	will be C<urxvt::anyevent>).
200	The known classes so far are:
201
202	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
203	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
204	AnyEvent::Impl::Coro based on Coro::Event, second best choice.
205	AnyEvent::Impl::Event based on Event, also second best choice :)
206	AnyEvent::Impl::Glib based on Glib, second-best choice.
207	AnyEvent::Impl::Tk based on Tk, very bad choice.
208	AnyEvent::Impl::Perl pure-perl implementation, inefficient.
209		931
210	=item AnyEvent::detect	932	=item AnyEvent::detect
211		933
212	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	934	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
213	necessary. You should only call this function right before you would have	935	if necessary. You should only call this function right before you would
214	created an AnyEvent watcher anyway, that is, very late at runtime.	936	have created an AnyEvent watcher anyway, that is, as late as possible at
		937	runtime, and not e.g. during initialisation of your module.
		938
		939	The effect of calling this function is as if a watcher had been created
		940	(specifically, actions that happen "when the first watcher is created"
		941	happen when calling detetc as well).
		942
		943	If you need to do some initialisation before AnyEvent watchers are
		944	created, use C<post_detect>.
		945
		946	=item $guard = AnyEvent::post_detect { BLOCK }
		947
		948	Arranges for the code block to be executed as soon as the event model is
		949	autodetected (or immediately if that has already happened).
		950
		951	The block will be executed I<after> the actual backend has been detected
		952	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		953	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		954	other initialisations - see the sources of L<AnyEvent::Strict> or
		955	L<AnyEvent::AIO> to see how this is used.
		956
		957	The most common usage is to create some global watchers, without forcing
		958	event module detection too early, for example, L<AnyEvent::AIO> creates
		959	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		960	avoid autodetecting the event module at load time.
		961
		962	If called in scalar or list context, then it creates and returns an object
		963	that automatically removes the callback again when it is destroyed (or
		964	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		965	a case where this is useful.
		966
		967	Example: Create a watcher for the IO::AIO module and store it in
		968	C<$WATCHER>, but do so only do so after the event loop is initialised.
		969
		970	our WATCHER;
		971
		972	my $guard = AnyEvent::post_detect {
		973	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		974	};
		975
		976	# the ||= is important in case post_detect immediately runs the block,
		977	# as to not clobber the newly-created watcher. assigning both watcher and
		978	# post_detect guard to the same variable has the advantage of users being
		979	# able to just C<undef $WATCHER> if the watcher causes them grief.
		980
		981	$WATCHER ||= $guard;
		982
		983	=item @AnyEvent::post_detect
		984
		985	If there are any code references in this array (you can C<push> to it
		986	before or after loading AnyEvent), then they will be called directly
		987	after the event loop has been chosen.
		988
		989	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		990	if it is defined then the event loop has already been detected, and the
		991	array will be ignored.
		992
		993	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		994	it, as it takes care of these details.
		995
		996	This variable is mainly useful for modules that can do something useful
		997	when AnyEvent is used and thus want to know when it is initialised, but do
		998	not need to even load it by default. This array provides the means to hook
		999	into AnyEvent passively, without loading it.
		1000
		1001	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1002	together, you could put this into Coro (this is the actual code used by
		1003	Coro to accomplish this):
		1004
		1005	if (defined $AnyEvent::MODEL) {
		1006	# AnyEvent already initialised, so load Coro::AnyEvent
		1007	require Coro::AnyEvent;
		1008	} else {
		1009	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1010	# as soon as it is
		1011	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1012	}
		1013
		1014	=item AnyEvent::postpone { BLOCK }
		1015
		1016	Arranges for the block to be executed as soon as possible, but not before
		1017	the call itself returns. In practise, the block will be executed just
		1018	before the event loop polls for new events, or shortly afterwards.
		1019
		1020	This function never returns anything (to make the C<return postpone { ...
		1021	}> idiom more useful.
		1022
		1023	To understand the usefulness of this function, consider a function that
		1024	asynchronously does something for you and returns some transaction
		1025	object or guard to let you cancel the operation. For example,
		1026	C<AnyEvent::Socket::tcp_connect>:
		1027
		1028	# start a conenction attempt unless one is active
		1029	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1030	delete $self->{connect_guard};
		1031	...
		1032	};
		1033
		1034	Imagine that this function could instantly call the callback, for
		1035	example, because it detects an obvious error such as a negative port
		1036	number. Invoking the callback before the function returns causes problems
		1037	however: the callback will be called and will try to delete the guard
		1038	object. But since the function hasn't returned yet, there is nothing to
		1039	delete. When the function eventually returns it will assign the guard
		1040	object to C<< $self->{connect_guard} >>, where it will likely never be
		1041	deleted, so the program thinks it is still trying to connect.
		1042
		1043	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1044	callback directly on error:
		1045
		1046	$cb->(undef), return # signal error to callback, BAD!
		1047	if $some_error_condition;
		1048
		1049	It should use C<postpone>:
		1050
		1051	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1052	if $some_error_condition;
		1053
		1054	=item AnyEvent::log $level, $msg[, @args]
		1055
		1056	Log the given C<$msg> at the given C<$level>.
		1057
		1058	Loads AnyEvent::Log on first use and calls C<AnyEvent::Log::log> -
		1059	consequently, look at the L<AnyEvent::Log> documentation for details.
		1060
		1061	If you want to sprinkle loads of logging calls around your code, consider
		1062	creating a logger callback with the C<AnyEvent::Log::logger> function.
215		1063
216	=back	1064	=back
217		1065
218	=head1 WHAT TO DO IN A MODULE	1066	=head1 WHAT TO DO IN A MODULE
219		1067
220	As a module author, you should "use AnyEvent" and call AnyEvent methods	1068	As a module author, you should C<use AnyEvent> and call AnyEvent methods
221	freely, but you should not load a specific event module or rely on it.	1069	freely, but you should not load a specific event module or rely on it.
222		1070
223	Be careful when you create watchers in the module body - Anyevent will	1071	Be careful when you create watchers in the module body - AnyEvent will
224	decide which event module to use as soon as the first method is called, so	1072	decide which event module to use as soon as the first method is called, so
225	by calling AnyEvent in your module body you force the user of your module	1073	by calling AnyEvent in your module body you force the user of your module
226	to load the event module first.	1074	to load the event module first.
227		1075
		1076	Never call C<< ->recv >> on a condition variable unless you I<know> that
		1077	the C<< ->send >> method has been called on it already. This is
		1078	because it will stall the whole program, and the whole point of using
		1079	events is to stay interactive.
		1080
		1081	It is fine, however, to call C<< ->recv >> when the user of your module
		1082	requests it (i.e. if you create a http request object ad have a method
		1083	called C<results> that returns the results, it may call C<< ->recv >>
		1084	freely, as the user of your module knows what she is doing. Always).
		1085
228	=head1 WHAT TO DO IN THE MAIN PROGRAM	1086	=head1 WHAT TO DO IN THE MAIN PROGRAM
229		1087
230	There will always be a single main program - the only place that should	1088	There will always be a single main program - the only place that should
231	dictate which event model to use.	1089	dictate which event model to use.
232		1090
233	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1091	If the program is not event-based, it need not do anything special, even
234	do anything special and let AnyEvent decide which implementation to chose.	1092	when it depends on a module that uses an AnyEvent. If the program itself
		1093	uses AnyEvent, but does not care which event loop is used, all it needs
		1094	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1095	available loop implementation.
235		1096
236	If the main program relies on a specific event model (for example, in Gtk2	1097	If the main program relies on a specific event model - for example, in
237	programs you have to rely on either Glib or Glib::Event), you should load	1098	Gtk2 programs you have to rely on the Glib module - you should load the
238	it before loading AnyEvent or any module that uses it, generally, as early	1099	event module before loading AnyEvent or any module that uses it: generally
239	as possible. The reason is that modules might create watchers when they	1100	speaking, you should load it as early as possible. The reason is that
240	are loaded, and AnyEvent will decide on the event model to use as soon as	1101	modules might create watchers when they are loaded, and AnyEvent will
241	it creates watchers, and it might chose the wrong one unless you load the	1102	decide on the event model to use as soon as it creates watchers, and it
242	correct one yourself.	1103	might choose the wrong one unless you load the correct one yourself.
243		1104
244	You can chose to use a rather inefficient pure-perl implementation by	1105	You can chose to use a pure-perl implementation by loading the
245	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	1106	C<AnyEvent::Loop> module, which gives you similar behaviour
246	generally better.	1107	everywhere, but letting AnyEvent chose the model is generally better.
		1108
		1109	=head2 MAINLOOP EMULATION
		1110
		1111	Sometimes (often for short test scripts, or even standalone programs who
		1112	only want to use AnyEvent), you do not want to run a specific event loop.
		1113
		1114	In that case, you can use a condition variable like this:
		1115
		1116	AnyEvent->condvar->recv;
		1117
		1118	This has the effect of entering the event loop and looping forever.
		1119
		1120	Note that usually your program has some exit condition, in which case
		1121	it is better to use the "traditional" approach of storing a condition
		1122	variable somewhere, waiting for it, and sending it when the program should
		1123	exit cleanly.
		1124
		1125
		1126	=head1 OTHER MODULES
		1127
		1128	The following is a non-exhaustive list of additional modules that use
		1129	AnyEvent as a client and can therefore be mixed easily with other
		1130	AnyEvent modules and other event loops in the same program. Some of the
		1131	modules come as part of AnyEvent, the others are available via CPAN (see
		1132	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1133	a longer non-exhaustive list), and the list is heavily biased towards
		1134	modules of the AnyEvent author himself :)
		1135
		1136	=over 4
		1137
		1138	=item L<AnyEvent::Util>
		1139
		1140	Contains various utility functions that replace often-used blocking
		1141	functions such as C<inet_aton> with event/callback-based versions.
		1142
		1143	=item L<AnyEvent::Socket>
		1144
		1145	Provides various utility functions for (internet protocol) sockets,
		1146	addresses and name resolution. Also functions to create non-blocking tcp
		1147	connections or tcp servers, with IPv6 and SRV record support and more.
		1148
		1149	=item L<AnyEvent::Handle>
		1150
		1151	Provide read and write buffers, manages watchers for reads and writes,
		1152	supports raw and formatted I/O, I/O queued and fully transparent and
		1153	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1154
		1155	=item L<AnyEvent::DNS>
		1156
		1157	Provides rich asynchronous DNS resolver capabilities.
		1158
		1159	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1160
		1161	Implement event-based interfaces to the protocols of the same name (for
		1162	the curious, IGS is the International Go Server and FCP is the Freenet
		1163	Client Protocol).
		1164
		1165	=item L<AnyEvent::Handle::UDP>
		1166
		1167	Here be danger!
		1168
		1169	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1170	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1171	its use of a stream-based API with a protocol that isn't streamable, that
		1172	the only way to improve it is to delete it.
		1173
		1174	It features data corruption (but typically only under load) and general
		1175	confusion. On top, the author is not only clueless about UDP but also
		1176	fact-resistant - some gems of his understanding: "connect doesn't work
		1177	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1178	packets", "I don't need to implement proper error checking as UDP doesn't
		1179	support error checking" and so on - he doesn't even understand what's
		1180	wrong with his module when it is explained to him.
		1181
		1182	=item L<AnyEvent::DBI>
		1183
		1184	Executes L<DBI> requests asynchronously in a proxy process for you,
		1185	notifying you in an event-based way when the operation is finished.
		1186
		1187	=item L<AnyEvent::AIO>
		1188
		1189	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1190	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1191	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1192	file I/O, and much more.
		1193
		1194	=item L<AnyEvent::HTTPD>
		1195
		1196	A simple embedded webserver.
		1197
		1198	=item L<AnyEvent::FastPing>
		1199
		1200	The fastest ping in the west.
		1201
		1202	=item L<Coro>
		1203
		1204	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1205
		1206	=back
247		1207
248	=cut	1208	=cut
249		1209
250	package AnyEvent;	1210	package AnyEvent;
251		1211
252	no warnings;	1212	# basically a tuned-down version of common::sense
253	use strict;	1213	sub common_sense {
		1214	# from common:.sense 3.4
		1215	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1216	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1217	$^H |= 0x00000600;
		1218	}
254		1219
		1220	BEGIN { AnyEvent::common_sense }
		1221
255	use Carp;	1222	use Carp ();
256		1223
257	our $VERSION = '2.9';	1224	our $VERSION = '6.01';
258	our $MODEL;	1225	our $MODEL;
259		1226
260	our $AUTOLOAD;
261	our @ISA;	1227	our @ISA;
262		1228
263	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
264
265	our @REGISTRY;	1229	our @REGISTRY;
266		1230
		1231	our $VERBOSE;
		1232
		1233	BEGIN {
		1234	require "AnyEvent/constants.pl";
		1235
		1236	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1237
		1238	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1239	if ${^TAINT};
		1240
		1241	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1242	}
		1243
		1244	our $MAX_SIGNAL_LATENCY = 10;
		1245
		1246	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1247
		1248	{
		1249	my $idx;
		1250	$PROTOCOL{$_} = ++$idx
		1251	for reverse split /\s*,\s*/,
		1252	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1253	}
		1254
		1255	our @post_detect;
		1256
		1257	sub post_detect(&) {
		1258	my ($cb) = @_;
		1259
		1260	push @post_detect, $cb;
		1261
		1262	defined wantarray
		1263	? bless \$cb, "AnyEvent::Util::postdetect"
		1264	: ()
		1265	}
		1266
		1267	sub AnyEvent::Util::postdetect::DESTROY {
		1268	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1269	}
		1270
		1271	our $POSTPONE_W;
		1272	our @POSTPONE;
		1273
		1274	sub _postpone_exec {
		1275	undef $POSTPONE_W;
		1276
		1277	&{ shift @POSTPONE }
		1278	while @POSTPONE;
		1279	}
		1280
		1281	sub postpone(&) {
		1282	push @POSTPONE, shift;
		1283
		1284	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1285
		1286	()
		1287	}
		1288
		1289	sub log($$;@) {
		1290	require AnyEvent::Log;
		1291	# AnyEvent::Log overwrites this function
		1292	goto &log;
		1293	}
		1294
267	my @models = (	1295	our @models = (
268	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
269	[EV:: => AnyEvent::Impl::EV::],	1296	[EV:: => AnyEvent::Impl::EV:: , 1],
270	[Coro::Event:: => AnyEvent::Impl::Coro::],	1297	[AnyEvent::Loop:: => AnyEvent::Impl::Perl:: , 1],
		1298	# everything below here will not (normally) be autoprobed
		1299	# as the pure perl backend should work everywhere
		1300	# and is usually faster
271	[Event:: => AnyEvent::Impl::Event::],	1301	[Event:: => AnyEvent::Impl::Event::, 1],
272	[Glib:: => AnyEvent::Impl::Glib::],	1302	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1303	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1304	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1305	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1306	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1307	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
273	[Tk:: => AnyEvent::Impl::Tk::],	1308	[Wx:: => AnyEvent::Impl::POE::],
274	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1309	[Prima:: => AnyEvent::Impl::POE::],
		1310	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
		1311	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
		1312	[FLTK:: => AnyEvent::Impl::FLTK2::],
275	);	1313	);
276		1314
277	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1315	our @isa_hook;
		1316
		1317	sub _isa_set {
		1318	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1319
		1320	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1321	for 1 .. $#pkg;
		1322
		1323	grep $_ && $_->[1], @isa_hook
		1324	and AE::_reset ();
		1325	}
		1326
		1327	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1328	sub _isa_hook($$;$) {
		1329	my ($i, $pkg, $reset_ae) = @_;
		1330
		1331	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1332
		1333	_isa_set;
		1334	}
		1335
		1336	# all autoloaded methods reserve the complete glob, not just the method slot.
		1337	# due to bugs in perls method cache implementation.
		1338	our @methods = qw(io timer time now now_update signal child idle condvar);
278		1339
279	sub detect() {	1340	sub detect() {
		1341	return $MODEL if $MODEL; # some programs keep references to detect
		1342
		1343	local $!; # for good measure
		1344	local $SIG{__DIE__}; # we use eval
		1345
		1346	# free some memory
		1347	*detect = sub () { $MODEL };
		1348	# undef &func doesn't correctly update the method cache. grmbl.
		1349	# so we delete the whole glob. grmbl.
		1350	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1351	# a glob with an active sub. hrm. i hope it works, but perl is
		1352	# usually buggy in this department. sigh.
		1353	delete @{"AnyEvent::"}{@methods};
		1354	undef @methods;
		1355
		1356	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1357	my $model = $1;
		1358	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1359	if (eval "require $model") {
		1360	$MODEL = $model;
		1361	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it."
		1362	if $VERBOSE >= 7;
		1363	} else {
		1364	AnyEvent::log warn => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1365	}
		1366	}
		1367
		1368	# check for already loaded models
280	unless ($MODEL) {	1369	unless ($MODEL) {
281	no strict 'refs';
282
283	# check for already loaded models
284	for (@REGISTRY, @models) {	1370	for (@REGISTRY, @models) {
285	my ($package, $model) = @$_;	1371	my ($package, $model) = @$_;
286	if (${"$package\::VERSION"} > 0) {	1372	if (${"$package\::VERSION"} > 0) {
287	if (eval "require $model") {	1373	if (eval "require $model") {
288	$MODEL = $model;	1374	$MODEL = $model;
289	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1375	AnyEvent::log 7 => "autodetected model '$model', using it."
		1376	if $VERBOSE >= 7;
290	last;	1377	last;
291	}	1378	}
292	}	1379	}
293	}	1380	}
294		1381
295	unless ($MODEL) {	1382	unless ($MODEL) {
296	# try to load a model	1383	# try to autoload a model
297
298	for (@REGISTRY, @models) {	1384	for (@REGISTRY, @models) {
299	my ($package, $model) = @$_;	1385	my ($package, $model, $autoload) = @$_;
		1386	if (
		1387	$autoload
300	if (eval "require $package"	1388	and eval "require $package"
301	and ${"$package\::VERSION"} > 0	1389	and ${"$package\::VERSION"} > 0
302	and eval "require $model") {	1390	and eval "require $model"
		1391	) {
303	$MODEL = $model;	1392	$MODEL = $model;
304	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	1393	AnyEvent::log 7 => "autoloaded model '$model', using it."
		1394	if $VERBOSE >= 7;
305	last;	1395	last;
306	}	1396	}
307	}	1397	}
308		1398
309	$MODEL	1399	$MODEL
310	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event), Glib or Tk.";	1400	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
311	}	1401	}
312
313	unshift @ISA, $MODEL;
314	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
315	}	1402	}
316		1403
		1404	# free memory only needed for probing
		1405	undef @models;
		1406	undef @REGISTRY;
		1407
		1408	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1409
		1410	# now nuke some methods that are overridden by the backend.
		1411	# SUPER usage is not allowed in these.
		1412	for (qw(time signal child idle)) {
		1413	undef &{"AnyEvent::Base::$_"}
		1414	if defined &{"$MODEL\::$_"};
		1415	}
		1416
		1417	_isa_set;
		1418
		1419	# we're officially open!
		1420
		1421	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1422	require AnyEvent::Strict;
		1423	}
		1424
		1425	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1426	require AnyEvent::Debug;
		1427	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1428	}
		1429
		1430	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1431	require AnyEvent::Socket;
		1432	require AnyEvent::Debug;
		1433
		1434	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1435	$shell =~ s/\$\$/$$/g;
		1436
		1437	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1438	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1439	}
		1440
		1441	# now the anyevent environment is set up as the user told us to, so
		1442	# call the actual user code - post detects
		1443
		1444	(shift @post_detect)->() while @post_detect;
		1445	undef @post_detect;
		1446
		1447	*post_detect = sub(&) {
		1448	shift->();
		1449
		1450	undef
		1451	};
		1452
317	$MODEL	1453	$MODEL
318	}	1454	}
319		1455
320	sub AUTOLOAD {	1456	for my $name (@methods) {
321	(my $func = $AUTOLOAD) =~ s/.*://;	1457	*$name = sub {
322		1458	detect;
323	$method{$func}	1459	# we use goto because
324	or croak "$func: not a valid method for AnyEvent objects";	1460	# a) it makes the thunk more transparent
325		1461	# b) it allows us to delete the thunk later
326	detect unless $MODEL;	1462	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
327		1463	};
328	my $class = shift;
329	$class->$func (@_);
330	}	1464	}
		1465
		1466	# utility function to dup a filehandle. this is used by many backends
		1467	# to support binding more than one watcher per filehandle (they usually
		1468	# allow only one watcher per fd, so we dup it to get a different one).
		1469	sub _dupfh($$;$$) {
		1470	my ($poll, $fh, $r, $w) = @_;
		1471
		1472	# cygwin requires the fh mode to be matching, unix doesn't
		1473	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1474
		1475	open my $fh2, $mode, $fh
		1476	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1477
		1478	# we assume CLOEXEC is already set by perl in all important cases
		1479
		1480	($fh2, $rw)
		1481	}
		1482
		1483	=head1 SIMPLIFIED AE API
		1484
		1485	Starting with version 5.0, AnyEvent officially supports a second, much
		1486	simpler, API that is designed to reduce the calling, typing and memory
		1487	overhead by using function call syntax and a fixed number of parameters.
		1488
		1489	See the L<AE> manpage for details.
		1490
		1491	=cut
		1492
		1493	package AE;
		1494
		1495	our $VERSION = $AnyEvent::VERSION;
		1496
		1497	sub _reset() {
		1498	eval q{
		1499	# fall back to the main API by default - backends and AnyEvent::Base
		1500	# implementations can overwrite these.
		1501
		1502	sub io($$$) {
		1503	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1504	}
		1505
		1506	sub timer($$$) {
		1507	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1508	}
		1509
		1510	sub signal($$) {
		1511	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1512	}
		1513
		1514	sub child($$) {
		1515	AnyEvent->child (pid => $_[0], cb => $_[1])
		1516	}
		1517
		1518	sub idle($) {
		1519	AnyEvent->idle (cb => $_[0]);
		1520	}
		1521
		1522	sub cv(;&) {
		1523	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1524	}
		1525
		1526	sub now() {
		1527	AnyEvent->now
		1528	}
		1529
		1530	sub now_update() {
		1531	AnyEvent->now_update
		1532	}
		1533
		1534	sub time() {
		1535	AnyEvent->time
		1536	}
		1537
		1538	*postpone = \&AnyEvent::postpone;
		1539	*log = \&AnyEvent::log;
		1540	};
		1541	die if $@;
		1542	}
		1543
		1544	BEGIN { _reset }
331		1545
332	package AnyEvent::Base;	1546	package AnyEvent::Base;
333		1547
		1548	# default implementations for many methods
		1549
		1550	sub time {
		1551	eval q{ # poor man's autoloading {}
		1552	# probe for availability of Time::HiRes
		1553	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1554	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy."
		1555	if $AnyEvent::VERBOSE >= 8;
		1556	*time = sub { Time::HiRes::time () };
		1557	*AE::time = \& Time::HiRes::time ;
		1558	# if (eval "use POSIX (); (POSIX::times())...
		1559	} else {
		1560	AnyEvent::log critical => "using built-in time(), WARNING, no sub-second resolution!";
		1561	*time = sub { CORE::time };
		1562	*AE::time = sub (){ CORE::time };
		1563	}
		1564
		1565	*now = \&time;
		1566	};
		1567	die if $@;
		1568
		1569	&time
		1570	}
		1571
		1572	*now = \&time;
		1573	sub now_update { }
		1574
		1575	sub _poll {
		1576	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1577	}
		1578
334	# default implementation for ->condvar, ->wait, ->broadcast	1579	# default implementation for ->condvar
		1580	# in fact, the default should not be overwritten
335		1581
336	sub condvar {	1582	sub condvar {
337	bless \my $flag, "AnyEvent::Base::CondVar"	1583	eval q{ # poor man's autoloading {}
338	}	1584	*condvar = sub {
		1585	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1586	};
339		1587
340	sub AnyEvent::Base::CondVar::broadcast {	1588	*AE::cv = sub (;&) {
341	${$_[0]}++;	1589	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
342	}	1590	};
		1591	};
		1592	die if $@;
343		1593
344	sub AnyEvent::Base::CondVar::wait {	1594	&condvar
345	AnyEvent->one_event while !${$_[0]};
346	}	1595	}
347		1596
348	# default implementation for ->signal	1597	# default implementation for ->signal
349		1598
350	our %SIG_CB;	1599	our $HAVE_ASYNC_INTERRUPT;
		1600
		1601	sub _have_async_interrupt() {
		1602	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1603	&& eval "use Async::Interrupt 1.02 (); 1")
		1604	unless defined $HAVE_ASYNC_INTERRUPT;
		1605
		1606	$HAVE_ASYNC_INTERRUPT
		1607	}
		1608
		1609	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1610	our (%SIG_ASY, %SIG_ASY_W);
		1611	our ($SIG_COUNT, $SIG_TW);
		1612
		1613	# install a dummy wakeup watcher to reduce signal catching latency
		1614	# used by Impls
		1615	sub _sig_add() {
		1616	unless ($SIG_COUNT++) {
		1617	# try to align timer on a full-second boundary, if possible
		1618	my $NOW = AE::now;
		1619
		1620	$SIG_TW = AE::timer
		1621	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1622	$MAX_SIGNAL_LATENCY,
		1623	sub { } # just for the PERL_ASYNC_CHECK
		1624	;
		1625	}
		1626	}
		1627
		1628	sub _sig_del {
		1629	undef $SIG_TW
		1630	unless --$SIG_COUNT;
		1631	}
		1632
		1633	our $_sig_name_init; $_sig_name_init = sub {
		1634	eval q{ # poor man's autoloading {}
		1635	undef $_sig_name_init;
		1636
		1637	if (_have_async_interrupt) {
		1638	*sig2num = \&Async::Interrupt::sig2num;
		1639	*sig2name = \&Async::Interrupt::sig2name;
		1640	} else {
		1641	require Config;
		1642
		1643	my %signame2num;
		1644	@signame2num{ split ' ', $Config::Config{sig_name} }
		1645	= split ' ', $Config::Config{sig_num};
		1646
		1647	my @signum2name;
		1648	@signum2name[values %signame2num] = keys %signame2num;
		1649
		1650	*sig2num = sub($) {
		1651	$_[0] > 0 ? shift : $signame2num{+shift}
		1652	};
		1653	*sig2name = sub ($) {
		1654	$_[0] > 0 ? $signum2name[+shift] : shift
		1655	};
		1656	}
		1657	};
		1658	die if $@;
		1659	};
		1660
		1661	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1662	sub sig2name($) { &$_sig_name_init; &sig2name }
351		1663
352	sub signal {	1664	sub signal {
		1665	eval q{ # poor man's autoloading {}
		1666	# probe for availability of Async::Interrupt
		1667	if (_have_async_interrupt) {
		1668	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling."
		1669	if $AnyEvent::VERBOSE >= 8;
		1670
		1671	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1672	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1673
		1674	} else {
		1675	AnyEvent::log 8 => "using emulated perl signal handling with latency timer."
		1676	if $AnyEvent::VERBOSE >= 8;
		1677
		1678	if (AnyEvent::WIN32) {
		1679	require AnyEvent::Util;
		1680
		1681	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1682	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1683	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1684	} else {
		1685	pipe $SIGPIPE_R, $SIGPIPE_W;
		1686	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1687	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1688
		1689	# not strictly required, as $^F is normally 2, but let's make sure...
		1690	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1691	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1692	}
		1693
		1694	$SIGPIPE_R
		1695	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1696
		1697	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1698	}
		1699
		1700	*signal = $HAVE_ASYNC_INTERRUPT
		1701	? sub {
353	my (undef, %arg) = @_;	1702	my (undef, %arg) = @_;
354		1703
		1704	# async::interrupt
355	my $signal = uc $arg{signal}	1705	my $signal = sig2num $arg{signal};
356	or Carp::croak "required option 'signal' is missing";
357
358	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1706	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1707
		1708	$SIG_ASY{$signal} ||= new Async::Interrupt
		1709	cb => sub { undef $SIG_EV{$signal} },
		1710	signal => $signal,
		1711	pipe => [$SIGPIPE_R->filenos],
		1712	pipe_autodrain => 0,
		1713	;
		1714
		1715	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1716	}
		1717	: sub {
		1718	my (undef, %arg) = @_;
		1719
		1720	# pure perl
		1721	my $signal = sig2name $arg{signal};
		1722	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1723
359	$SIG{$signal} ||= sub {	1724	$SIG{$signal} ||= sub {
		1725	local $!;
		1726	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1727	undef $SIG_EV{$signal};
		1728	};
		1729
		1730	# can't do signal processing without introducing races in pure perl,
		1731	# so limit the signal latency.
		1732	_sig_add;
		1733
		1734	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1735	}
		1736	;
		1737
		1738	*AnyEvent::Base::signal::DESTROY = sub {
		1739	my ($signal, $cb) = @{$_[0]};
		1740
		1741	_sig_del;
		1742
		1743	delete $SIG_CB{$signal}{$cb};
		1744
		1745	$HAVE_ASYNC_INTERRUPT
		1746	? delete $SIG_ASY{$signal}
		1747	: # delete doesn't work with older perls - they then
		1748	# print weird messages, or just unconditionally exit
		1749	# instead of getting the default action.
		1750	undef $SIG{$signal}
		1751	unless keys %{ $SIG_CB{$signal} };
		1752	};
		1753
		1754	*_signal_exec = sub {
		1755	$HAVE_ASYNC_INTERRUPT
		1756	? $SIGPIPE_R->drain
		1757	: sysread $SIGPIPE_R, (my $dummy), 9;
		1758
		1759	while (%SIG_EV) {
		1760	for (keys %SIG_EV) {
		1761	delete $SIG_EV{$_};
360	$_->() for values %{ $SIG_CB{$signal} || {} };	1762	&$_ for values %{ $SIG_CB{$_} || {} };
		1763	}
		1764	}
		1765	};
361	};	1766	};
		1767	die if $@;
362		1768
363	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1769	&signal
364	}
365
366	sub AnyEvent::Base::Signal::DESTROY {
367	my ($signal, $cb) = @{$_[0]};
368
369	delete $SIG_CB{$signal}{$cb};
370
371	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
372	}	1770	}
373		1771
374	# default implementation for ->child	1772	# default implementation for ->child
375		1773
376	our %PID_CB;	1774	our %PID_CB;
377	our $CHLD_W;	1775	our $CHLD_W;
378	our $CHLD_DELAY_W;	1776	our $CHLD_DELAY_W;
379	our $PID_IDLE;
380	our $WNOHANG;
381		1777
382	sub _child_wait {	1778	# used by many Impl's
383	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1779	sub _emit_childstatus($$) {
		1780	my (undef, $rpid, $rstatus) = @_;
		1781
		1782	$_->($rpid, $rstatus)
384	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1783	for values %{ $PID_CB{$rpid} || {} },
385	(values %{ $PID_CB{0} || {} });	1784	values %{ $PID_CB{0} || {} };
		1785	}
		1786
		1787	sub child {
		1788	eval q{ # poor man's autoloading {}
		1789	*_sigchld = sub {
		1790	my $pid;
		1791
		1792	AnyEvent->_emit_childstatus ($pid, $?)
		1793	while ($pid = waitpid -1, WNOHANG) > 0;
		1794	};
		1795
		1796	*child = sub {
		1797	my (undef, %arg) = @_;
		1798
		1799	my $pid = $arg{pid};
		1800	my $cb = $arg{cb};
		1801
		1802	$PID_CB{$pid}{$cb+0} = $cb;
		1803
		1804	unless ($CHLD_W) {
		1805	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1806	# child could be a zombie already, so make at least one round
		1807	&_sigchld;
		1808	}
		1809
		1810	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1811	};
		1812
		1813	*AnyEvent::Base::child::DESTROY = sub {
		1814	my ($pid, $icb) = @{$_[0]};
		1815
		1816	delete $PID_CB{$pid}{$icb};
		1817	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1818
		1819	undef $CHLD_W unless keys %PID_CB;
		1820	};
		1821	};
		1822	die if $@;
		1823
		1824	&child
		1825	}
		1826
		1827	# idle emulation is done by simply using a timer, regardless
		1828	# of whether the process is idle or not, and not letting
		1829	# the callback use more than 50% of the time.
		1830	sub idle {
		1831	eval q{ # poor man's autoloading {}
		1832	*idle = sub {
		1833	my (undef, %arg) = @_;
		1834
		1835	my ($cb, $w, $rcb) = $arg{cb};
		1836
		1837	$rcb = sub {
		1838	if ($cb) {
		1839	$w = AE::time;
		1840	&$cb;
		1841	$w = AE::time - $w;
		1842
		1843	# never use more then 50% of the time for the idle watcher,
		1844	# within some limits
		1845	$w = 0.0001 if $w < 0.0001;
		1846	$w = 5 if $w > 5;
		1847
		1848	$w = AE::timer $w, 0, $rcb;
		1849	} else {
		1850	# clean up...
		1851	undef $w;
		1852	undef $rcb;
		1853	}
		1854	};
		1855
		1856	$w = AE::timer 0.05, 0, $rcb;
		1857
		1858	bless \\$cb, "AnyEvent::Base::idle"
		1859	};
		1860
		1861	*AnyEvent::Base::idle::DESTROY = sub {
		1862	undef $${$_[0]};
		1863	};
		1864	};
		1865	die if $@;
		1866
		1867	&idle
		1868	}
		1869
		1870	package AnyEvent::CondVar;
		1871
		1872	our @ISA = AnyEvent::CondVar::Base::;
		1873
		1874	# only to be used for subclassing
		1875	sub new {
		1876	my $class = shift;
		1877	bless AnyEvent->condvar (@_), $class
		1878	}
		1879
		1880	package AnyEvent::CondVar::Base;
		1881
		1882	#use overload
		1883	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1884	# fallback => 1;
		1885
		1886	# save 300+ kilobytes by dirtily hardcoding overloading
		1887	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1888	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1889	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1890	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1891
		1892	our $WAITING;
		1893
		1894	sub _send {
		1895	# nop
		1896	}
		1897
		1898	sub _wait {
		1899	AnyEvent->_poll until $_[0]{_ae_sent};
		1900	}
		1901
		1902	sub send {
		1903	my $cv = shift;
		1904	$cv->{_ae_sent} = [@_];
		1905	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1906	$cv->_send;
		1907	}
		1908
		1909	sub croak {
		1910	$_[0]{_ae_croak} = $_[1];
		1911	$_[0]->send;
		1912	}
		1913
		1914	sub ready {
		1915	$_[0]{_ae_sent}
		1916	}
		1917
		1918	sub recv {
		1919	unless ($_[0]{_ae_sent}) {
		1920	$WAITING
		1921	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1922
		1923	local $WAITING = 1;
		1924	$_[0]->_wait;
386	}	1925	}
387		1926
388	undef $PID_IDLE;	1927	$_[0]{_ae_croak}
389	}	1928	and Carp::croak $_[0]{_ae_croak};
390		1929
391	sub _sigchld {	1930	wantarray
392	# make sure we deliver these changes "synchronous" with the event loop.	1931	? @{ $_[0]{_ae_sent} }
393	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1932	: $_[0]{_ae_sent}[0]
394	undef $CHLD_DELAY_W;
395	&_child_wait;
396	});
397	}	1933	}
398		1934
399	sub child {	1935	sub cb {
400	my (undef, %arg) = @_;	1936	my $cv = shift;
401		1937
402	defined (my $pid = $arg{pid} + 0)	1938	@_
403	or Carp::croak "required option 'pid' is missing";	1939	and $cv->{_ae_cb} = shift
		1940	and $cv->{_ae_sent}
		1941	and (delete $cv->{_ae_cb})->($cv);
404		1942
405	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1943	$cv->{_ae_cb}
406
407	unless ($WNOHANG) {
408	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
409	}
410
411	unless ($CHLD_W) {
412	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
413	# child could be a zombie already, so make at least one round
414	&_sigchld;
415	}
416
417	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
418	}	1944	}
419		1945
420	sub AnyEvent::Base::Child::DESTROY {	1946	sub begin {
421	my ($pid, $cb) = @{$_[0]};	1947	++$_[0]{_ae_counter};
422		1948	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
423	delete $PID_CB{$pid}{$cb};
424	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
425
426	undef $CHLD_W unless keys %PID_CB;
427	}	1949	}
		1950
		1951	sub end {
		1952	return if --$_[0]{_ae_counter};
		1953	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1954	}
		1955
		1956	# undocumented/compatibility with pre-3.4
		1957	*broadcast = \&send;
		1958	*wait = \&recv;
		1959
		1960	=head1 ERROR AND EXCEPTION HANDLING
		1961
		1962	In general, AnyEvent does not do any error handling - it relies on the
		1963	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1964	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1965	checking of all AnyEvent methods, however, which is highly useful during
		1966	development.
		1967
		1968	As for exception handling (i.e. runtime errors and exceptions thrown while
		1969	executing a callback), this is not only highly event-loop specific, but
		1970	also not in any way wrapped by this module, as this is the job of the main
		1971	program.
		1972
		1973	The pure perl event loop simply re-throws the exception (usually
		1974	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1975	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1976	so on.
		1977
		1978	=head1 ENVIRONMENT VARIABLES
		1979
		1980	The following environment variables are used by this module or its
		1981	submodules.
		1982
		1983	Note that AnyEvent will remove I<all> environment variables starting with
		1984	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1985	enabled.
		1986
		1987	=over 4
		1988
		1989	=item C<PERL_ANYEVENT_VERBOSE>
		1990
		1991	By default, AnyEvent will be completely silent except in fatal
		1992	conditions. You can set this environment variable to make AnyEvent more
		1993	talkative.
		1994
		1995	When set to C<5> or higher, causes AnyEvent to warn about unexpected
		1996	conditions, such as not being able to load the event model specified by
		1997	C<PERL_ANYEVENT_MODEL>.
		1998
		1999	When set to C<7> or higher, cause AnyEvent to report to STDERR which event
		2000	model it chooses.
		2001
		2002	When set to C<8> or higher, then AnyEvent will report extra information on
		2003	which optional modules it loads and how it implements certain features.
		2004
		2005	=item C<PERL_ANYEVENT_STRICT>
		2006
		2007	AnyEvent does not do much argument checking by default, as thorough
		2008	argument checking is very costly. Setting this variable to a true value
		2009	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2010	check the arguments passed to most method calls. If it finds any problems,
		2011	it will croak.
		2012
		2013	In other words, enables "strict" mode.
		2014
		2015	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2016	>>, it is definitely recommended to keep it off in production. Keeping
		2017	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2018	can be very useful, however.
		2019
		2020	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2021
		2022	If this env variable is set, then its contents will be interpreted by
		2023	C<AnyEvent::Socket::parse_hostport> (after replacing every occurance of
		2024	C<$$> by the process pid) and an C<AnyEvent::Debug::shell> is bound on
		2025	that port. The shell object is saved in C<$AnyEvent::Debug::SHELL>.
		2026
		2027	This takes place when the first watcher is created.
		2028
		2029	For example, to bind a debug shell on a unix domain socket in
		2030	F<< /tmp/debug<pid>.sock >>, you could use this:
		2031
		2032	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2033
		2034	Note that creating sockets in F</tmp> is very unsafe on multiuser
		2035	systems.
		2036
		2037	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2038
		2039	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2040	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2041
		2042	=item C<PERL_ANYEVENT_MODEL>
		2043
		2044	This can be used to specify the event model to be used by AnyEvent, before
		2045	auto detection and -probing kicks in.
		2046
		2047	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2048	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2049	resulting module name is loaded and - if the load was successful - used as
		2050	event model backend. If it fails to load then AnyEvent will proceed with
		2051	auto detection and -probing.
		2052
		2053	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2054	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2055	the end of a string designates a module name and quotes it appropriately).
		2056
		2057	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2058	could start your program like this:
		2059
		2060	PERL_ANYEVENT_MODEL=Perl perl ...
		2061
		2062	=item C<PERL_ANYEVENT_PROTOCOLS>
		2063
		2064	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2065	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2066	of auto probing).
		2067
		2068	Must be set to a comma-separated list of protocols or address families,
		2069	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2070	used, and preference will be given to protocols mentioned earlier in the
		2071	list.
		2072
		2073	This variable can effectively be used for denial-of-service attacks
		2074	against local programs (e.g. when setuid), although the impact is likely
		2075	small, as the program has to handle conenction and other failures anyways.
		2076
		2077	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2078	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2079	- only support IPv4, never try to resolve or contact IPv6
		2080	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2081	IPv6, but prefer IPv6 over IPv4.
		2082
		2083	=item C<PERL_ANYEVENT_EDNS0>
		2084
		2085	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		2086	for DNS. This extension is generally useful to reduce DNS traffic, but
		2087	some (broken) firewalls drop such DNS packets, which is why it is off by
		2088	default.
		2089
		2090	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2091	EDNS0 in its DNS requests.
		2092
		2093	=item C<PERL_ANYEVENT_MAX_FORKS>
		2094
		2095	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2096	will create in parallel.
		2097
		2098	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2099
		2100	The default value for the C<max_outstanding> parameter for the default DNS
		2101	resolver - this is the maximum number of parallel DNS requests that are
		2102	sent to the DNS server.
		2103
		2104	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2105
		2106	The file to use instead of F</etc/resolv.conf> (or OS-specific
		2107	configuration) in the default resolver. When set to the empty string, no
		2108	default config will be used.
		2109
		2110	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2111
		2112	When neither C<ca_file> nor C<ca_path> was specified during
		2113	L<AnyEvent::TLS> context creation, and either of these environment
		2114	variables exist, they will be used to specify CA certificate locations
		2115	instead of a system-dependent default.
		2116
		2117	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2118
		2119	When these are set to C<1>, then the respective modules are not
		2120	loaded. Mostly good for testing AnyEvent itself.
		2121
		2122	=back
428		2123
429	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2124	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		2125
		2126	This is an advanced topic that you do not normally need to use AnyEvent in
		2127	a module. This section is only of use to event loop authors who want to
		2128	provide AnyEvent compatibility.
430		2129
431	If you need to support another event library which isn't directly	2130	If you need to support another event library which isn't directly
432	supported by AnyEvent, you can supply your own interface to it by	2131	supported by AnyEvent, you can supply your own interface to it by
433	pushing, before the first watcher gets created, the package name of	2132	pushing, before the first watcher gets created, the package name of
434	the event module and the package name of the interface to use onto	2133	the event module and the package name of the interface to use onto
435	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	2134	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
436	AnyEvent.	2135	AnyEvent, so it is reasonably cheap.
437		2136
438	Example:	2137	Example:
439		2138
440	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	2139	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
441		2140
442	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	2141	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
443	package/class when it finds the C<urxvt> package/module is loaded. When	2142	package/class when it finds the C<urxvt> package/module is already loaded.
		2143
444	AnyEvent is loaded and asked to find a suitable event model, it will	2144	When AnyEvent is loaded and asked to find a suitable event model, it
445	first check for the presence of urxvt.	2145	will first check for the presence of urxvt by trying to C<use> the
		2146	C<urxvt::anyevent> module.
446		2147
447	The class should provide implementations for all watcher types (see	2148	The class should provide implementations for all watcher types. See
448	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	2149	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
449	(Source code) and so on for actual examples, use C<perldoc -m	2150	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
450	AnyEvent::Impl::Glib> to see the sources).	2151	see the sources.
451		2152
		2153	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		2154	provide suitable (hopefully) replacements.
		2155
452	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	2156	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
453	uses the above line as-is. An interface isn't included in AnyEvent	2157	terminal emulator uses the above line as-is. An interface isn't included
454	because it doesn't make sense outside the embedded interpreter inside	2158	in AnyEvent because it doesn't make sense outside the embedded interpreter
455	I<rxvt-unicode>, and it is updated and maintained as part of the	2159	inside I<rxvt-unicode>, and it is updated and maintained as part of the
456	I<rxvt-unicode> distribution.	2160	I<rxvt-unicode> distribution.
457		2161
458	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2162	I<rxvt-unicode> also cheats a bit by not providing blocking access to
459	condition variables: code blocking while waiting for a condition will	2163	condition variables: code blocking while waiting for a condition will
460	C<die>. This still works with most modules/usages, and blocking calls must	2164	C<die>. This still works with most modules/usages, and blocking calls must
461	not be in an interactive application, so it makes sense.	2165	not be done in an interactive application, so it makes sense.
462		2166
463	=head1 ENVIRONMENT VARIABLES
464
465	The following environment variables are used by this module:
466
467	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
468	model gets used.
469
470	=head1 EXAMPLE	2167	=head1 EXAMPLE PROGRAM
471		2168
472	The following program uses an io watcher to read data from stdin, a timer	2169	The following program uses an I/O watcher to read data from STDIN, a timer
473	to display a message once per second, and a condvar to exit the program	2170	to display a message once per second, and a condition variable to quit the
474	when the user enters quit:	2171	program when the user enters quit:
475		2172
476	use AnyEvent;	2173	use AnyEvent;
477		2174
478	my $cv = AnyEvent->condvar;	2175	my $cv = AnyEvent->condvar;
479		2176
480	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	2177	my $io_watcher = AnyEvent->io (
		2178	fh => \*STDIN,
		2179	poll => 'r',
		2180	cb => sub {
481	warn "io event <$_[0]>\n"; # will always output <r>	2181	warn "io event <$_[0]>\n"; # will always output <r>
482	chomp (my $input = <STDIN>); # read a line	2182	chomp (my $input = <STDIN>); # read a line
483	warn "read: $input\n"; # output what has been read	2183	warn "read: $input\n"; # output what has been read
484	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2184	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		2185	},
		2186	);
		2187
		2188	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
		2189	warn "timeout\n"; # print 'timeout' at most every second
485	});	2190	});
486		2191
487	my $time_watcher; # can only be used once
488
489	sub new_timer {
490	$timer = AnyEvent->timer (after => 1, cb => sub {
491	warn "timeout\n"; # print 'timeout' about every second
492	&new_timer; # and restart the time
493	});
494	}
495
496	new_timer; # create first timer
497
498	$cv->wait; # wait until user enters /^q/i	2192	$cv->recv; # wait until user enters /^q/i
499		2193
500	=head1 REAL-WORLD EXAMPLE	2194	=head1 REAL-WORLD EXAMPLE
501		2195
502	Consider the L<Net::FCP> module. It features (among others) the following	2196	Consider the L<Net::FCP> module. It features (among others) the following
503	API calls, which are to freenet what HTTP GET requests are to http:	2197	API calls, which are to freenet what HTTP GET requests are to http:
…		…
553	syswrite $txn->{fh}, $txn->{request}	2247	syswrite $txn->{fh}, $txn->{request}
554	or die "connection or write error";	2248	or die "connection or write error";
555	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2249	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
556		2250
557	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2251	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
558	result and signals any possible waiters that the request ahs finished:	2252	result and signals any possible waiters that the request has finished:
559		2253
560	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2254	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
561		2255
562	if (end-of-file or data complete) {	2256	if (end-of-file or data complete) {
563	$txn->{result} = $txn->{buf};	2257	$txn->{result} = $txn->{buf};
564	$txn->{finished}->broadcast;	2258	$txn->{finished}->send;
565	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2259	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
566	}	2260	}
567		2261
568	The C<result> method, finally, just waits for the finished signal (if the	2262	The C<result> method, finally, just waits for the finished signal (if the
569	request was already finished, it doesn't wait, of course, and returns the	2263	request was already finished, it doesn't wait, of course, and returns the
570	data:	2264	data:
571		2265
572	$txn->{finished}->wait;	2266	$txn->{finished}->recv;
573	return $txn->{result};	2267	return $txn->{result};
574		2268
575	The actual code goes further and collects all errors (C<die>s, exceptions)	2269	The actual code goes further and collects all errors (C<die>s, exceptions)
576	that occured during request processing. The C<result> method detects	2270	that occurred during request processing. The C<result> method detects
577	wether an exception as thrown (it is stored inside the $txn object)	2271	whether an exception as thrown (it is stored inside the $txn object)
578	and just throws the exception, which means connection errors and other	2272	and just throws the exception, which means connection errors and other
579	problems get reported tot he code that tries to use the result, not in a	2273	problems get reported to the code that tries to use the result, not in a
580	random callback.	2274	random callback.
581		2275
582	All of this enables the following usage styles:	2276	All of this enables the following usage styles:
583		2277
584	1. Blocking:	2278	1. Blocking:
585		2279
586	my $data = $fcp->client_get ($url);	2280	my $data = $fcp->client_get ($url);
587		2281
588	2. Blocking, but parallelizing:	2282	2. Blocking, but running in parallel:
589		2283
590	my @datas = map $_->result,	2284	my @datas = map $_->result,
591	map $fcp->txn_client_get ($_),	2285	map $fcp->txn_client_get ($_),
592	@urls;	2286	@urls;
593		2287
594	Both blocking examples work without the module user having to know	2288	Both blocking examples work without the module user having to know
595	anything about events.	2289	anything about events.
596		2290
597	3a. Event-based in a main program, using any support Event module:	2291	3a. Event-based in a main program, using any supported event module:
598		2292
599	use Event;	2293	use EV;
600		2294
601	$fcp->txn_client_get ($url)->cb (sub {	2295	$fcp->txn_client_get ($url)->cb (sub {
602	my $txn = shift;	2296	my $txn = shift;
603	my $data = $txn->result;	2297	my $data = $txn->result;
604	...	2298	...
605	});	2299	});
606		2300
607	Event::loop;	2301	EV::loop;
608		2302
609	3b. The module user could use AnyEvent, too:	2303	3b. The module user could use AnyEvent, too:
610		2304
611	use AnyEvent;	2305	use AnyEvent;
612		2306
613	my $quit = AnyEvent->condvar;	2307	my $quit = AnyEvent->condvar;
614		2308
615	$fcp->txn_client_get ($url)->cb (sub {	2309	$fcp->txn_client_get ($url)->cb (sub {
616	...	2310	...
617	$quit->broadcast;	2311	$quit->send;
618	});	2312	});
619		2313
620	$quit->wait;	2314	$quit->recv;
		2315
		2316
		2317	=head1 BENCHMARKS
		2318
		2319	To give you an idea of the performance and overheads that AnyEvent adds
		2320	over the event loops themselves and to give you an impression of the speed
		2321	of various event loops I prepared some benchmarks.
		2322
		2323	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2324
		2325	Here is a benchmark of various supported event models used natively and
		2326	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2327	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2328	which it is), lets them fire exactly once and destroys them again.
		2329
		2330	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2331	distribution. It uses the L<AE> interface, which makes a real difference
		2332	for the EV and Perl backends only.
		2333
		2334	=head3 Explanation of the columns
		2335
		2336	I<watcher> is the number of event watchers created/destroyed. Since
		2337	different event models feature vastly different performances, each event
		2338	loop was given a number of watchers so that overall runtime is acceptable
		2339	and similar between tested event loop (and keep them from crashing): Glib
		2340	would probably take thousands of years if asked to process the same number
		2341	of watchers as EV in this benchmark.
		2342
		2343	I<bytes> is the number of bytes (as measured by the resident set size,
		2344	RSS) consumed by each watcher. This method of measuring captures both C
		2345	and Perl-based overheads.
		2346
		2347	I<create> is the time, in microseconds (millionths of seconds), that it
		2348	takes to create a single watcher. The callback is a closure shared between
		2349	all watchers, to avoid adding memory overhead. That means closure creation
		2350	and memory usage is not included in the figures.
		2351
		2352	I<invoke> is the time, in microseconds, used to invoke a simple
		2353	callback. The callback simply counts down a Perl variable and after it was
		2354	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2355	signal the end of this phase.
		2356
		2357	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2358	watcher.
		2359
		2360	=head3 Results
		2361
		2362	name watchers bytes create invoke destroy comment
		2363	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2364	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2365	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2366	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2367	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2368	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2369	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2370	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2371	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2372	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2373	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2374	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2375
		2376	=head3 Discussion
		2377
		2378	The benchmark does I<not> measure scalability of the event loop very
		2379	well. For example, a select-based event loop (such as the pure perl one)
		2380	can never compete with an event loop that uses epoll when the number of
		2381	file descriptors grows high. In this benchmark, all events become ready at
		2382	the same time, so select/poll-based implementations get an unnatural speed
		2383	boost.
		2384
		2385	Also, note that the number of watchers usually has a nonlinear effect on
		2386	overall speed, that is, creating twice as many watchers doesn't take twice
		2387	the time - usually it takes longer. This puts event loops tested with a
		2388	higher number of watchers at a disadvantage.
		2389
		2390	To put the range of results into perspective, consider that on the
		2391	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2392	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2393	cycles with POE.
		2394
		2395	C<EV> is the sole leader regarding speed and memory use, which are both
		2396	maximal/minimal, respectively. When using the L<AE> API there is zero
		2397	overhead (when going through the AnyEvent API create is about 5-6 times
		2398	slower, with other times being equal, so still uses far less memory than
		2399	any other event loop and is still faster than Event natively).
		2400
		2401	The pure perl implementation is hit in a few sweet spots (both the
		2402	constant timeout and the use of a single fd hit optimisations in the perl
		2403	interpreter and the backend itself). Nevertheless this shows that it
		2404	adds very little overhead in itself. Like any select-based backend its
		2405	performance becomes really bad with lots of file descriptors (and few of
		2406	them active), of course, but this was not subject of this benchmark.
		2407
		2408	The C<Event> module has a relatively high setup and callback invocation
		2409	cost, but overall scores in on the third place.
		2410
		2411	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2412	when using its pure perl backend.
		2413
		2414	C<Glib>'s memory usage is quite a bit higher, but it features a
		2415	faster callback invocation and overall ends up in the same class as
		2416	C<Event>. However, Glib scales extremely badly, doubling the number of
		2417	watchers increases the processing time by more than a factor of four,
		2418	making it completely unusable when using larger numbers of watchers
		2419	(note that only a single file descriptor was used in the benchmark, so
		2420	inefficiencies of C<poll> do not account for this).
		2421
		2422	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2423	more than 2000 watchers is a big setback, however, as correctness takes
		2424	precedence over speed. Nevertheless, its performance is surprising, as the
		2425	file descriptor is dup()ed for each watcher. This shows that the dup()
		2426	employed by some adaptors is not a big performance issue (it does incur a
		2427	hidden memory cost inside the kernel which is not reflected in the figures
		2428	above).
		2429
		2430	C<POE>, regardless of underlying event loop (whether using its pure perl
		2431	select-based backend or the Event module, the POE-EV backend couldn't
		2432	be tested because it wasn't working) shows abysmal performance and
		2433	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2434	as EV watchers, and 10 times as much memory as Event (the high memory
		2435	requirements are caused by requiring a session for each watcher). Watcher
		2436	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2437	implementation.
		2438
		2439	The design of the POE adaptor class in AnyEvent can not really account
		2440	for the performance issues, though, as session creation overhead is
		2441	small compared to execution of the state machine, which is coded pretty
		2442	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2443	using multiple sessions is not a good approach, especially regarding
		2444	memory usage, even the author of POE could not come up with a faster
		2445	design).
		2446
		2447	=head3 Summary
		2448
		2449	=over 4
		2450
		2451	=item * Using EV through AnyEvent is faster than any other event loop
		2452	(even when used without AnyEvent), but most event loops have acceptable
		2453	performance with or without AnyEvent.
		2454
		2455	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2456	the actual event loop, only with extremely fast event loops such as EV
		2457	does AnyEvent add significant overhead.
		2458
		2459	=item * You should avoid POE like the plague if you want performance or
		2460	reasonable memory usage.
		2461
		2462	=back
		2463
		2464	=head2 BENCHMARKING THE LARGE SERVER CASE
		2465
		2466	This benchmark actually benchmarks the event loop itself. It works by
		2467	creating a number of "servers": each server consists of a socket pair, a
		2468	timeout watcher that gets reset on activity (but never fires), and an I/O
		2469	watcher waiting for input on one side of the socket. Each time the socket
		2470	watcher reads a byte it will write that byte to a random other "server".
		2471
		2472	The effect is that there will be a lot of I/O watchers, only part of which
		2473	are active at any one point (so there is a constant number of active
		2474	fds for each loop iteration, but which fds these are is random). The
		2475	timeout is reset each time something is read because that reflects how
		2476	most timeouts work (and puts extra pressure on the event loops).
		2477
		2478	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2479	(1%) are active. This mirrors the activity of large servers with many
		2480	connections, most of which are idle at any one point in time.
		2481
		2482	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2483	distribution. It uses the L<AE> interface, which makes a real difference
		2484	for the EV and Perl backends only.
		2485
		2486	=head3 Explanation of the columns
		2487
		2488	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2489	each server has a read and write socket end).
		2490
		2491	I<create> is the time it takes to create a socket pair (which is
		2492	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2493
		2494	I<request>, the most important value, is the time it takes to handle a
		2495	single "request", that is, reading the token from the pipe and forwarding
		2496	it to another server. This includes deleting the old timeout and creating
		2497	a new one that moves the timeout into the future.
		2498
		2499	=head3 Results
		2500
		2501	name sockets create request
		2502	EV 20000 62.66 7.99
		2503	Perl 20000 68.32 32.64
		2504	IOAsync 20000 174.06 101.15 epoll
		2505	IOAsync 20000 174.67 610.84 poll
		2506	Event 20000 202.69 242.91
		2507	Glib 20000 557.01 1689.52
		2508	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2509
		2510	=head3 Discussion
		2511
		2512	This benchmark I<does> measure scalability and overall performance of the
		2513	particular event loop.
		2514
		2515	EV is again fastest. Since it is using epoll on my system, the setup time
		2516	is relatively high, though.
		2517
		2518	Perl surprisingly comes second. It is much faster than the C-based event
		2519	loops Event and Glib.
		2520
		2521	IO::Async performs very well when using its epoll backend, and still quite
		2522	good compared to Glib when using its pure perl backend.
		2523
		2524	Event suffers from high setup time as well (look at its code and you will
		2525	understand why). Callback invocation also has a high overhead compared to
		2526	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2527	uses select or poll in basically all documented configurations.
		2528
		2529	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2530	clearly fails to perform with many filehandles or in busy servers.
		2531
		2532	POE is still completely out of the picture, taking over 1000 times as long
		2533	as EV, and over 100 times as long as the Perl implementation, even though
		2534	it uses a C-based event loop in this case.
		2535
		2536	=head3 Summary
		2537
		2538	=over 4
		2539
		2540	=item * The pure perl implementation performs extremely well.
		2541
		2542	=item * Avoid Glib or POE in large projects where performance matters.
		2543
		2544	=back
		2545
		2546	=head2 BENCHMARKING SMALL SERVERS
		2547
		2548	While event loops should scale (and select-based ones do not...) even to
		2549	large servers, most programs we (or I :) actually write have only a few
		2550	I/O watchers.
		2551
		2552	In this benchmark, I use the same benchmark program as in the large server
		2553	case, but it uses only eight "servers", of which three are active at any
		2554	one time. This should reflect performance for a small server relatively
		2555	well.
		2556
		2557	The columns are identical to the previous table.
		2558
		2559	=head3 Results
		2560
		2561	name sockets create request
		2562	EV 16 20.00 6.54
		2563	Perl 16 25.75 12.62
		2564	Event 16 81.27 35.86
		2565	Glib 16 32.63 15.48
		2566	POE 16 261.87 276.28 uses POE::Loop::Event
		2567
		2568	=head3 Discussion
		2569
		2570	The benchmark tries to test the performance of a typical small
		2571	server. While knowing how various event loops perform is interesting, keep
		2572	in mind that their overhead in this case is usually not as important, due
		2573	to the small absolute number of watchers (that is, you need efficiency and
		2574	speed most when you have lots of watchers, not when you only have a few of
		2575	them).
		2576
		2577	EV is again fastest.
		2578
		2579	Perl again comes second. It is noticeably faster than the C-based event
		2580	loops Event and Glib, although the difference is too small to really
		2581	matter.
		2582
		2583	POE also performs much better in this case, but is is still far behind the
		2584	others.
		2585
		2586	=head3 Summary
		2587
		2588	=over 4
		2589
		2590	=item * C-based event loops perform very well with small number of
		2591	watchers, as the management overhead dominates.
		2592
		2593	=back
		2594
		2595	=head2 THE IO::Lambda BENCHMARK
		2596
		2597	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2598	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2599	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2600	shouldn't come as a surprise to anybody). As such, the benchmark is
		2601	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2602	very optimal. But how would AnyEvent compare when used without the extra
		2603	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2604
		2605	The benchmark itself creates an echo-server, and then, for 500 times,
		2606	connects to the echo server, sends a line, waits for the reply, and then
		2607	creates the next connection. This is a rather bad benchmark, as it doesn't
		2608	test the efficiency of the framework or much non-blocking I/O, but it is a
		2609	benchmark nevertheless.
		2610
		2611	name runtime
		2612	Lambda/select 0.330 sec
		2613	+ optimized 0.122 sec
		2614	Lambda/AnyEvent 0.327 sec
		2615	+ optimized 0.138 sec
		2616	Raw sockets/select 0.077 sec
		2617	POE/select, components 0.662 sec
		2618	POE/select, raw sockets 0.226 sec
		2619	POE/select, optimized 0.404 sec
		2620
		2621	AnyEvent/select/nb 0.085 sec
		2622	AnyEvent/EV/nb 0.068 sec
		2623	+state machine 0.134 sec
		2624
		2625	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2626	benchmarks actually make blocking connects and use 100% blocking I/O,
		2627	defeating the purpose of an event-based solution. All of the newly
		2628	written AnyEvent benchmarks use 100% non-blocking connects (using
		2629	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2630	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2631	generally require a lot more bookkeeping and event handling than blocking
		2632	connects (which involve a single syscall only).
		2633
		2634	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2635	offers similar expressive power as POE and IO::Lambda, using conventional
		2636	Perl syntax. This means that both the echo server and the client are 100%
		2637	non-blocking, further placing it at a disadvantage.
		2638
		2639	As you can see, the AnyEvent + EV combination even beats the
		2640	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2641	backend easily beats IO::Lambda and POE.
		2642
		2643	And even the 100% non-blocking version written using the high-level (and
		2644	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2645	higher level ("unoptimised") abstractions by a large margin, even though
		2646	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2647
		2648	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2649	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2650	part of the IO::Lambda distribution and were used without any changes.
		2651
		2652
		2653	=head1 SIGNALS
		2654
		2655	AnyEvent currently installs handlers for these signals:
		2656
		2657	=over 4
		2658
		2659	=item SIGCHLD
		2660
		2661	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2662	emulation for event loops that do not support them natively. Also, some
		2663	event loops install a similar handler.
		2664
		2665	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2666	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2667
		2668	=item SIGPIPE
		2669
		2670	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2671	when AnyEvent gets loaded.
		2672
		2673	The rationale for this is that AnyEvent users usually do not really depend
		2674	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2675	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2676	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2677	some random socket.
		2678
		2679	The rationale for installing a no-op handler as opposed to ignoring it is
		2680	that this way, the handler will be restored to defaults on exec.
		2681
		2682	Feel free to install your own handler, or reset it to defaults.
		2683
		2684	=back
		2685
		2686	=cut
		2687
		2688	undef $SIG{CHLD}
		2689	if $SIG{CHLD} eq 'IGNORE';
		2690
		2691	$SIG{PIPE} = sub { }
		2692	unless defined $SIG{PIPE};
		2693
		2694	=head1 RECOMMENDED/OPTIONAL MODULES
		2695
		2696	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2697	its built-in modules) are required to use it.
		2698
		2699	That does not mean that AnyEvent won't take advantage of some additional
		2700	modules if they are installed.
		2701
		2702	This section explains which additional modules will be used, and how they
		2703	affect AnyEvent's operation.
		2704
		2705	=over 4
		2706
		2707	=item L<Async::Interrupt>
		2708
		2709	This slightly arcane module is used to implement fast signal handling: To
		2710	my knowledge, there is no way to do completely race-free and quick
		2711	signal handling in pure perl. To ensure that signals still get
		2712	delivered, AnyEvent will start an interval timer to wake up perl (and
		2713	catch the signals) with some delay (default is 10 seconds, look for
		2714	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2715
		2716	If this module is available, then it will be used to implement signal
		2717	catching, which means that signals will not be delayed, and the event loop
		2718	will not be interrupted regularly, which is more efficient (and good for
		2719	battery life on laptops).
		2720
		2721	This affects not just the pure-perl event loop, but also other event loops
		2722	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2723
		2724	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2725	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2726	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2727	does nothing for those backends.
		2728
		2729	=item L<EV>
		2730
		2731	This module isn't really "optional", as it is simply one of the backend
		2732	event loops that AnyEvent can use. However, it is simply the best event
		2733	loop available in terms of features, speed and stability: It supports
		2734	the AnyEvent API optimally, implements all the watcher types in XS, does
		2735	automatic timer adjustments even when no monotonic clock is available,
		2736	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2737	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2738	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2739
		2740	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2741	then this module will do nothing for you.
		2742
		2743	=item L<Guard>
		2744
		2745	The guard module, when used, will be used to implement
		2746	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2747	lot less memory), but otherwise doesn't affect guard operation much. It is
		2748	purely used for performance.
		2749
		2750	=item L<JSON> and L<JSON::XS>
		2751
		2752	One of these modules is required when you want to read or write JSON data
		2753	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2754	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2755
		2756	=item L<Net::SSLeay>
		2757
		2758	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2759	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2760	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2761
		2762	=item L<Time::HiRes>
		2763
		2764	This module is part of perl since release 5.008. It will be used when the
		2765	chosen event library does not come with a timing source of its own. The
		2766	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2767	try to use a monotonic clock for timing stability.
		2768
		2769	=back
		2770
		2771
		2772	=head1 FORK
		2773
		2774	Most event libraries are not fork-safe. The ones who are usually are
		2775	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2776	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2777	are usually badly thought-out hacks that are incompatible with fork in
		2778	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2779	continue event-processing in both parent and child (or both, if you know
		2780	what you are doing).
		2781
		2782	This means that, in general, you cannot fork and do event processing in
		2783	the child if the event library was initialised before the fork (which
		2784	usually happens when the first AnyEvent watcher is created, or the library
		2785	is loaded).
		2786
		2787	If you have to fork, you must either do so I<before> creating your first
		2788	watcher OR you must not use AnyEvent at all in the child OR you must do
		2789	something completely out of the scope of AnyEvent.
		2790
		2791	The problem of doing event processing in the parent I<and> the child
		2792	is much more complicated: even for backends that I<are> fork-aware or
		2793	fork-safe, their behaviour is not usually what you want: fork clones all
		2794	watchers, that means all timers, I/O watchers etc. are active in both
		2795	parent and child, which is almost never what you want. USing C<exec>
		2796	to start worker children from some kind of manage rprocess is usually
		2797	preferred, because it is much easier and cleaner, at the expense of having
		2798	to have another binary.
		2799
		2800
		2801	=head1 SECURITY CONSIDERATIONS
		2802
		2803	AnyEvent can be forced to load any event model via
		2804	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2805	execute arbitrary code or directly gain access, it can easily be used to
		2806	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2807	will not be active when the program uses a different event model than
		2808	specified in the variable.
		2809
		2810	You can make AnyEvent completely ignore this variable by deleting it
		2811	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2812
		2813	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2814
		2815	use AnyEvent;
		2816
		2817	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2818	be used to probe what backend is used and gain other information (which is
		2819	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2820	$ENV{PERL_ANYEVENT_STRICT}.
		2821
		2822	Note that AnyEvent will remove I<all> environment variables starting with
		2823	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2824	enabled.
		2825
		2826
		2827	=head1 BUGS
		2828
		2829	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2830	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2831	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2832	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2833	pronounced).
		2834
621		2835
622	=head1 SEE ALSO	2836	=head1 SEE ALSO
623		2837
624	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.	2838	Tutorial/Introduction: L<AnyEvent::Intro>.
625		2839
626	Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.	2840	FAQ: L<AnyEvent::FAQ>.
627		2841
628	Nontrivial usage example: L<Net::FCP>.	2842	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2843	(simply logging).
629		2844
630	=head1	2845	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2846	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2847
		2848	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2849	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2850	L<Qt>, L<POE>, L<FLTK>.
		2851
		2852	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2853	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2854	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2855	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
		2856	L<AnyEvent::Impl::FLTK>.
		2857
		2858	Non-blocking handles, pipes, stream sockets, TCP clients and
		2859	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2860
		2861	Asynchronous DNS: L<AnyEvent::DNS>.
		2862
		2863	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		2864
		2865	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2866	L<AnyEvent::HTTP>.
		2867
		2868
		2869	=head1 AUTHOR
		2870
		2871	Marc Lehmann <schmorp@schmorp.de>
		2872	http://home.schmorp.de/
631		2873
632	=cut	2874	=cut
633		2875
634	1	2876	1
635		2877

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