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Revision 1.219 by root, Thu Jun 25 11:16:08 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
22		45
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	46	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		47
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	48	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	49	nowadays. So what is different about AnyEvent?
27		50
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	51	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	52	policy> and AnyEvent is I<small and efficient>.
30		53
31	First and foremost, I<AnyEvent is not an event model> itself, it only	54	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	55	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	56	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality, and AnyEvent	57	the statement "there can only be one" is a bitter reality: In general,
35	helps hiding the differences.	58	only one event loop can be active at the same time in a process. AnyEvent
		59	cannot change this, but it can hide the differences between those event
		60	loops.
36		61
37	The goal of AnyEvent is to offer module authors the ability to do event	62	The goal of AnyEvent is to offer module authors the ability to do event
38	programming (waiting for I/O or timer events) without subscribing to a	63	programming (waiting for I/O or timer events) without subscribing to a
39	religion, a way of living, and most importantly: without forcing your	64	religion, a way of living, and most importantly: without forcing your
40	module users into the same thing by forcing them to use the same event	65	module users into the same thing by forcing them to use the same event
41	model you use.	66	model you use.
42		67
43	For modules like POE or IO::Async (which is actually doing all I/O	68	For modules like POE or IO::Async (which is a total misnomer as it is
44	I<synchronously>...), using them in your module is like joining a	69	actually doing all I/O I<synchronously>...), using them in your module is
45	cult: After you joined, you are dependent on them and you cannot use	70	like joining a cult: After you joined, you are dependent on them and you
46	anything else, as it is simply incompatible to everything that isn't	71	cannot use anything else, as they are simply incompatible to everything
47	itself.	72	that isn't them. What's worse, all the potential users of your
		73	module are I<also> forced to use the same event loop you use.
48		74
49	AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk	75	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50	works fine etc. etc. but none of these work together with the rest: POE	76	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51	+ IO::Async? no go. Tk + Event? no go. If your module uses one of	77	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
52	those, every user of your module has to use it, too. If your module	78	your module uses one of those, every user of your module has to use it,
53	uses AnyEvent, it works transparently with all event models it supports	79	too. But if your module uses AnyEvent, it works transparently with all
54	(including stuff like POE and IO::Async).	80	event models it supports (including stuff like IO::Async, as long as those
		81	use one of the supported event loops. It is trivial to add new event loops
		82	to AnyEvent, too, so it is future-proof).
55		83
56	In addition of being free of having to use I<the one and only true event	84	In addition to being free of having to use I<the one and only true event
57	model>, AnyEvent also is free of bloat and policy: with POE or similar	85	model>, AnyEvent also is free of bloat and policy: with POE or similar
58	modules, you get an enourmous amount of code and strict rules you have	86	modules, you get an enormous amount of code and strict rules you have to
59	to follow. AnyEvent, on the other hand, is lean and to the point by only	87	follow. AnyEvent, on the other hand, is lean and up to the point, by only
60	offering the functionality that is useful, in as thin as a wrapper as	88	offering the functionality that is necessary, in as thin as a wrapper as
61	technically possible.	89	technically possible.
62		90
		91	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		92	of useful functionality, such as an asynchronous DNS resolver, 100%
		93	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		94	such as Windows) and lots of real-world knowledge and workarounds for
		95	platform bugs and differences.
		96
63	Of course, if you want lots of policy (this can arguably be somewhat	97	Now, if you I<do want> lots of policy (this can arguably be somewhat
64	useful) and you want to force your users to use the one and only event	98	useful) and you want to force your users to use the one and only event
65	model, you should I<not> use this module.	99	model, you should I<not> use this module.
66
67		100
68	=head1 DESCRIPTION	101	=head1 DESCRIPTION
69		102
70	L<AnyEvent> provides an identical interface to multiple event loops. This	103	L<AnyEvent> provides an identical interface to multiple event loops. This
71	allows module authors to utilise an event loop without forcing module	104	allows module authors to utilise an event loop without forcing module
72	users to use the same event loop (as only a single event loop can coexist	105	users to use the same event loop (as only a single event loop can coexist
73	peacefully at any one time).	106	peacefully at any one time).
74		107
75	The interface itself is vaguely similar but not identical to the Event	108	The interface itself is vaguely similar, but not identical to the L<Event>
76	module.	109	module.
77		110
78	On the first call of any method, the module tries to detect the currently	111	During the first call of any watcher-creation method, the module tries
79	loaded event loop by probing whether any of the following modules is	112	to detect the currently loaded event loop by probing whether one of the
80	loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, L<Event>, L<Glib>, L<Tk>. The	113	following modules is already loaded: L<EV>,
		114	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
81	first one found is used. If none are found, the module tries to load these	115	L<POE>. The first one found is used. If none are found, the module tries
82	modules in the order given. The first one that could be successfully	116	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
83	loaded will be used. If still none could be found, AnyEvent will fall back	117	adaptor should always succeed) in the order given. The first one that can
84	to a pure-perl event loop, which is also not very efficient.	118	be successfully loaded will be used. If, after this, still none could be
		119	found, AnyEvent will fall back to a pure-perl event loop, which is not
		120	very efficient, but should work everywhere.
85		121
86	Because AnyEvent first checks for modules that are already loaded, loading	122	Because AnyEvent first checks for modules that are already loaded, loading
87	an Event model explicitly before first using AnyEvent will likely make	123	an event model explicitly before first using AnyEvent will likely make
88	that model the default. For example:	124	that model the default. For example:
89		125
90	use Tk;	126	use Tk;
91	use AnyEvent;	127	use AnyEvent;
92		128
93	# .. AnyEvent will likely default to Tk	129	# .. AnyEvent will likely default to Tk
94		130
		131	The I<likely> means that, if any module loads another event model and
		132	starts using it, all bets are off. Maybe you should tell their authors to
		133	use AnyEvent so their modules work together with others seamlessly...
		134
95	The pure-perl implementation of AnyEvent is called	135	The pure-perl implementation of AnyEvent is called
96	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	136	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
97	explicitly.	137	explicitly and enjoy the high availability of that event loop :)
98		138
99	=head1 WATCHERS	139	=head1 WATCHERS
100		140
101	AnyEvent has the central concept of a I<watcher>, which is an object that	141	AnyEvent has the central concept of a I<watcher>, which is an object that
102	stores relevant data for each kind of event you are waiting for, such as	142	stores relevant data for each kind of event you are waiting for, such as
103	the callback to call, the filehandle to watch, etc.	143	the callback to call, the file handle to watch, etc.
104		144
105	These watchers are normal Perl objects with normal Perl lifetime. After	145	These watchers are normal Perl objects with normal Perl lifetime. After
106	creating a watcher it will immediately "watch" for events and invoke	146	creating a watcher it will immediately "watch" for events and invoke the
		147	callback when the event occurs (of course, only when the event model
		148	is in control).
		149
		150	Note that B<callbacks must not permanently change global variables>
		151	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		152	callbacks must not C<die> >>. The former is good programming practise in
		153	Perl and the latter stems from the fact that exception handling differs
		154	widely between event loops.
		155
107	the callback. To disable the watcher you have to destroy it (e.g. by	156	To disable the watcher you have to destroy it (e.g. by setting the
108	setting the variable that stores it to C<undef> or otherwise deleting all	157	variable you store it in to C<undef> or otherwise deleting all references
109	references to it).	158	to it).
110		159
111	All watchers are created by calling a method on the C<AnyEvent> class.	160	All watchers are created by calling a method on the C<AnyEvent> class.
112		161
		162	Many watchers either are used with "recursion" (repeating timers for
		163	example), or need to refer to their watcher object in other ways.
		164
		165	An any way to achieve that is this pattern:
		166
		167	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		168	# you can use $w here, for example to undef it
		169	undef $w;
		170	});
		171
		172	Note that C<my $w; $w => combination. This is necessary because in Perl,
		173	my variables are only visible after the statement in which they are
		174	declared.
		175
113	=head2 IO WATCHERS	176	=head2 I/O WATCHERS
114		177
115	You can create I/O watcher by calling the C<< AnyEvent->io >> method with	178	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
116	the following mandatory arguments:	179	with the following mandatory key-value pairs as arguments:
117		180
118	C<fh> the Perl I<filehandle> (not filedescriptor) to watch for	181	C<fh> is the Perl I<file handle> (I<not> file descriptor) to watch
		182	for events (AnyEvent might or might not keep a reference to this file
		183	handle). Note that only file handles pointing to things for which
		184	non-blocking operation makes sense are allowed. This includes sockets,
		185	most character devices, pipes, fifos and so on, but not for example files
		186	or block devices.
		187
119	events. C<poll> must be a string that is either C<r> or C<w>, that creates	188	C<poll> must be a string that is either C<r> or C<w>, which creates a
120	a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback	189	watcher waiting for "r"eadable or "w"ritable events, respectively.
121	to invoke everytime the filehandle becomes ready.
122		190
123	Filehandles will be kept alive, so as long as the watcher exists, the	191	C<cb> is the callback to invoke each time the file handle becomes ready.
124	filehandle exists, too.
125		192
126	Example:	193	Although the callback might get passed parameters, their value and
		194	presence is undefined and you cannot rely on them. Portable AnyEvent
		195	callbacks cannot use arguments passed to I/O watcher callbacks.
127		196
		197	The I/O watcher might use the underlying file descriptor or a copy of it.
		198	You must not close a file handle as long as any watcher is active on the
		199	underlying file descriptor.
		200
		201	Some event loops issue spurious readyness notifications, so you should
		202	always use non-blocking calls when reading/writing from/to your file
		203	handles.
		204
128	# wait for readability of STDIN, then read a line and disable the watcher	205	Example: wait for readability of STDIN, then read a line and disable the
		206	watcher.
		207
129	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	208	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
130	chomp (my $input = <STDIN>);	209	chomp (my $input = <STDIN>);
131	warn "read: $input\n";	210	warn "read: $input\n";
132	undef $w;	211	undef $w;
133	});	212	});
…		…
135	=head2 TIME WATCHERS	214	=head2 TIME WATCHERS
136		215
137	You can create a time watcher by calling the C<< AnyEvent->timer >>	216	You can create a time watcher by calling the C<< AnyEvent->timer >>
138	method with the following mandatory arguments:	217	method with the following mandatory arguments:
139		218
140	C<after> after how many seconds (fractions are supported) should the timer	219	C<after> specifies after how many seconds (fractional values are
141	activate. C<cb> the callback to invoke.	220	supported) the callback should be invoked. C<cb> is the callback to invoke
		221	in that case.
142		222
143	The timer callback will be invoked at most once: if you want a repeating	223	Although the callback might get passed parameters, their value and
144	timer you have to create a new watcher (this is a limitation by both Tk	224	presence is undefined and you cannot rely on them. Portable AnyEvent
145	and Glib).	225	callbacks cannot use arguments passed to time watcher callbacks.
146		226
147	Example:	227	The callback will normally be invoked once only. If you specify another
		228	parameter, C<interval>, as a strictly positive number (> 0), then the
		229	callback will be invoked regularly at that interval (in fractional
		230	seconds) after the first invocation. If C<interval> is specified with a
		231	false value, then it is treated as if it were missing.
148		232
		233	The callback will be rescheduled before invoking the callback, but no
		234	attempt is done to avoid timer drift in most backends, so the interval is
		235	only approximate.
		236
149	# fire an event after 7.7 seconds	237	Example: fire an event after 7.7 seconds.
		238
150	my $w = AnyEvent->timer (after => 7.7, cb => sub {	239	my $w = AnyEvent->timer (after => 7.7, cb => sub {
151	warn "timeout\n";	240	warn "timeout\n";
152	});	241	});
153		242
154	# to cancel the timer:	243	# to cancel the timer:
155	undef $w;	244	undef $w;
156		245
157	=head2 CONDITION WATCHERS	246	Example 2: fire an event after 0.5 seconds, then roughly every second.
158		247
159	Condition watchers can be created by calling the C<< AnyEvent->condvar >>	248	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
160	method without any arguments.	249	warn "timeout\n";
		250	};
161		251
162	A condition watcher watches for a condition - precisely that the C<<	252	=head3 TIMING ISSUES
163	->broadcast >> method has been called.
164		253
165	Note that condition watchers recurse into the event loop - if you have	254	There are two ways to handle timers: based on real time (relative, "fire
166	two watchers that call C<< ->wait >> in a round-robbin fashion, you	255	in 10 seconds") and based on wallclock time (absolute, "fire at 12
167	lose. Therefore, condition watchers are good to export to your caller, but	256	o'clock").
168	you should avoid making a blocking wait, at least in callbacks, as this
169	usually asks for trouble.
170		257
171	The watcher has only two methods:	258	While most event loops expect timers to specified in a relative way, they
		259	use absolute time internally. This makes a difference when your clock
		260	"jumps", for example, when ntp decides to set your clock backwards from
		261	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		262	fire "after" a second might actually take six years to finally fire.
		263
		264	AnyEvent cannot compensate for this. The only event loop that is conscious
		265	about these issues is L<EV>, which offers both relative (ev_timer, based
		266	on true relative time) and absolute (ev_periodic, based on wallclock time)
		267	timers.
		268
		269	AnyEvent always prefers relative timers, if available, matching the
		270	AnyEvent API.
		271
		272	AnyEvent has two additional methods that return the "current time":
172		273
173	=over 4	274	=over 4
174		275
		276	=item AnyEvent->time
		277
		278	This returns the "current wallclock time" as a fractional number of
		279	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		280	return, and the result is guaranteed to be compatible with those).
		281
		282	It progresses independently of any event loop processing, i.e. each call
		283	will check the system clock, which usually gets updated frequently.
		284
		285	=item AnyEvent->now
		286
		287	This also returns the "current wallclock time", but unlike C<time>, above,
		288	this value might change only once per event loop iteration, depending on
		289	the event loop (most return the same time as C<time>, above). This is the
		290	time that AnyEvent's timers get scheduled against.
		291
		292	I<In almost all cases (in all cases if you don't care), this is the
		293	function to call when you want to know the current time.>
		294
		295	This function is also often faster then C<< AnyEvent->time >>, and
		296	thus the preferred method if you want some timestamp (for example,
		297	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		298
		299	The rest of this section is only of relevance if you try to be very exact
		300	with your timing, you can skip it without bad conscience.
		301
		302	For a practical example of when these times differ, consider L<Event::Lib>
		303	and L<EV> and the following set-up:
		304
		305	The event loop is running and has just invoked one of your callback at
		306	time=500 (assume no other callbacks delay processing). In your callback,
		307	you wait a second by executing C<sleep 1> (blocking the process for a
		308	second) and then (at time=501) you create a relative timer that fires
		309	after three seconds.
		310
		311	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		312	both return C<501>, because that is the current time, and the timer will
		313	be scheduled to fire at time=504 (C<501> + C<3>).
		314
		315	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		316	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		317	last event processing phase started. With L<EV>, your timer gets scheduled
		318	to run at time=503 (C<500> + C<3>).
		319
		320	In one sense, L<Event::Lib> is more exact, as it uses the current time
		321	regardless of any delays introduced by event processing. However, most
		322	callbacks do not expect large delays in processing, so this causes a
		323	higher drift (and a lot more system calls to get the current time).
		324
		325	In another sense, L<EV> is more exact, as your timer will be scheduled at
		326	the same time, regardless of how long event processing actually took.
		327
		328	In either case, if you care (and in most cases, you don't), then you
		329	can get whatever behaviour you want with any event loop, by taking the
		330	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		331	account.
		332
		333	=item AnyEvent->now_update
		334
		335	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		336	the current time for each loop iteration (see the discussion of L<<
		337	AnyEvent->now >>, above).
		338
		339	When a callback runs for a long time (or when the process sleeps), then
		340	this "current" time will differ substantially from the real time, which
		341	might affect timers and time-outs.
		342
		343	When this is the case, you can call this method, which will update the
		344	event loop's idea of "current time".
		345
		346	Note that updating the time I<might> cause some events to be handled.
		347
		348	=back
		349
		350	=head2 SIGNAL WATCHERS
		351
		352	You can watch for signals using a signal watcher, C<signal> is the signal
		353	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
		354	callback to be invoked whenever a signal occurs.
		355
		356	Although the callback might get passed parameters, their value and
		357	presence is undefined and you cannot rely on them. Portable AnyEvent
		358	callbacks cannot use arguments passed to signal watcher callbacks.
		359
		360	Multiple signal occurrences can be clumped together into one callback
		361	invocation, and callback invocation will be synchronous. Synchronous means
		362	that it might take a while until the signal gets handled by the process,
		363	but it is guaranteed not to interrupt any other callbacks.
		364
		365	The main advantage of using these watchers is that you can share a signal
		366	between multiple watchers.
		367
		368	This watcher might use C<%SIG>, so programs overwriting those signals
		369	directly will likely not work correctly.
		370
		371	Example: exit on SIGINT
		372
		373	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		374
		375	=head2 CHILD PROCESS WATCHERS
		376
		377	You can also watch on a child process exit and catch its exit status.
		378
		379	The child process is specified by the C<pid> argument (if set to C<0>, it
		380	watches for any child process exit). The watcher will triggered only when
		381	the child process has finished and an exit status is available, not on
		382	any trace events (stopped/continued).
		383
		384	The callback will be called with the pid and exit status (as returned by
		385	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		386	callback arguments.
		387
		388	This watcher type works by installing a signal handler for C<SIGCHLD>,
		389	and since it cannot be shared, nothing else should use SIGCHLD or reap
		390	random child processes (waiting for specific child processes, e.g. inside
		391	C<system>, is just fine).
		392
		393	There is a slight catch to child watchers, however: you usually start them
		394	I<after> the child process was created, and this means the process could
		395	have exited already (and no SIGCHLD will be sent anymore).
		396
		397	Not all event models handle this correctly (neither POE nor IO::Async do,
		398	see their AnyEvent::Impl manpages for details), but even for event models
		399	that I<do> handle this correctly, they usually need to be loaded before
		400	the process exits (i.e. before you fork in the first place). AnyEvent's
		401	pure perl event loop handles all cases correctly regardless of when you
		402	start the watcher.
		403
		404	This means you cannot create a child watcher as the very first
		405	thing in an AnyEvent program, you I<have> to create at least one
		406	watcher before you C<fork> the child (alternatively, you can call
		407	C<AnyEvent::detect>).
		408
		409	Example: fork a process and wait for it
		410
		411	my $done = AnyEvent->condvar;
		412
		413	my $pid = fork or exit 5;
		414
		415	my $w = AnyEvent->child (
		416	pid => $pid,
		417	cb => sub {
		418	my ($pid, $status) = @_;
		419	warn "pid $pid exited with status $status";
		420	$done->send;
		421	},
		422	);
		423
		424	# do something else, then wait for process exit
		425	$done->recv;
		426
		427	=head2 IDLE WATCHERS
		428
		429	Sometimes there is a need to do something, but it is not so important
		430	to do it instantly, but only when there is nothing better to do. This
		431	"nothing better to do" is usually defined to be "no other events need
		432	attention by the event loop".
		433
		434	Idle watchers ideally get invoked when the event loop has nothing
		435	better to do, just before it would block the process to wait for new
		436	events. Instead of blocking, the idle watcher is invoked.
		437
		438	Most event loops unfortunately do not really support idle watchers (only
		439	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		440	will simply call the callback "from time to time".
		441
		442	Example: read lines from STDIN, but only process them when the
		443	program is otherwise idle:
		444
		445	my @lines; # read data
		446	my $idle_w;
		447	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		448	push @lines, scalar <STDIN>;
		449
		450	# start an idle watcher, if not already done
		451	$idle_w ||= AnyEvent->idle (cb => sub {
		452	# handle only one line, when there are lines left
		453	if (my $line = shift @lines) {
		454	print "handled when idle: $line";
		455	} else {
		456	# otherwise disable the idle watcher again
		457	undef $idle_w;
		458	}
		459	});
		460	});
		461
		462	=head2 CONDITION VARIABLES
		463
		464	If you are familiar with some event loops you will know that all of them
		465	require you to run some blocking "loop", "run" or similar function that
		466	will actively watch for new events and call your callbacks.
		467
		468	AnyEvent is different, it expects somebody else to run the event loop and
		469	will only block when necessary (usually when told by the user).
		470
		471	The instrument to do that is called a "condition variable", so called
		472	because they represent a condition that must become true.
		473
		474	Condition variables can be created by calling the C<< AnyEvent->condvar
		475	>> method, usually without arguments. The only argument pair allowed is
		476
		477	C<cb>, which specifies a callback to be called when the condition variable
		478	becomes true, with the condition variable as the first argument (but not
		479	the results).
		480
		481	After creation, the condition variable is "false" until it becomes "true"
		482	by calling the C<send> method (or calling the condition variable as if it
		483	were a callback, read about the caveats in the description for the C<<
		484	->send >> method).
		485
		486	Condition variables are similar to callbacks, except that you can
		487	optionally wait for them. They can also be called merge points - points
		488	in time where multiple outstanding events have been processed. And yet
		489	another way to call them is transactions - each condition variable can be
		490	used to represent a transaction, which finishes at some point and delivers
		491	a result.
		492
		493	Condition variables are very useful to signal that something has finished,
		494	for example, if you write a module that does asynchronous http requests,
		495	then a condition variable would be the ideal candidate to signal the
		496	availability of results. The user can either act when the callback is
		497	called or can synchronously C<< ->recv >> for the results.
		498
		499	You can also use them to simulate traditional event loops - for example,
		500	you can block your main program until an event occurs - for example, you
		501	could C<< ->recv >> in your main program until the user clicks the Quit
		502	button of your app, which would C<< ->send >> the "quit" event.
		503
		504	Note that condition variables recurse into the event loop - if you have
		505	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
		506	lose. Therefore, condition variables are good to export to your caller, but
		507	you should avoid making a blocking wait yourself, at least in callbacks,
		508	as this asks for trouble.
		509
		510	Condition variables are represented by hash refs in perl, and the keys
		511	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		512	easy (it is often useful to build your own transaction class on top of
		513	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		514	it's C<new> method in your own C<new> method.
		515
		516	There are two "sides" to a condition variable - the "producer side" which
		517	eventually calls C<< -> send >>, and the "consumer side", which waits
		518	for the send to occur.
		519
		520	Example: wait for a timer.
		521
		522	# wait till the result is ready
		523	my $result_ready = AnyEvent->condvar;
		524
		525	# do something such as adding a timer
		526	# or socket watcher the calls $result_ready->send
		527	# when the "result" is ready.
		528	# in this case, we simply use a timer:
		529	my $w = AnyEvent->timer (
		530	after => 1,
		531	cb => sub { $result_ready->send },
		532	);
		533
		534	# this "blocks" (while handling events) till the callback
		535	# calls send
		536	$result_ready->recv;
		537
		538	Example: wait for a timer, but take advantage of the fact that
		539	condition variables are also code references.
		540
		541	my $done = AnyEvent->condvar;
		542	my $delay = AnyEvent->timer (after => 5, cb => $done);
		543	$done->recv;
		544
		545	Example: Imagine an API that returns a condvar and doesn't support
		546	callbacks. This is how you make a synchronous call, for example from
		547	the main program:
		548
		549	use AnyEvent::CouchDB;
		550
		551	...
		552
		553	my @info = $couchdb->info->recv;
		554
		555	And this is how you would just ste a callback to be called whenever the
		556	results are available:
		557
		558	$couchdb->info->cb (sub {
		559	my @info = $_[0]->recv;
		560	});
		561
		562	=head3 METHODS FOR PRODUCERS
		563
		564	These methods should only be used by the producing side, i.e. the
		565	code/module that eventually sends the signal. Note that it is also
		566	the producer side which creates the condvar in most cases, but it isn't
		567	uncommon for the consumer to create it as well.
		568
		569	=over 4
		570
		571	=item $cv->send (...)
		572
		573	Flag the condition as ready - a running C<< ->recv >> and all further
		574	calls to C<recv> will (eventually) return after this method has been
		575	called. If nobody is waiting the send will be remembered.
		576
		577	If a callback has been set on the condition variable, it is called
		578	immediately from within send.
		579
		580	Any arguments passed to the C<send> call will be returned by all
		581	future C<< ->recv >> calls.
		582
		583	Condition variables are overloaded so one can call them directly
		584	(as a code reference). Calling them directly is the same as calling
		585	C<send>. Note, however, that many C-based event loops do not handle
		586	overloading, so as tempting as it may be, passing a condition variable
		587	instead of a callback does not work. Both the pure perl and EV loops
		588	support overloading, however, as well as all functions that use perl to
		589	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		590	example).
		591
		592	=item $cv->croak ($error)
		593
		594	Similar to send, but causes all call's to C<< ->recv >> to invoke
		595	C<Carp::croak> with the given error message/object/scalar.
		596
		597	This can be used to signal any errors to the condition variable
		598	user/consumer.
		599
		600	=item $cv->begin ([group callback])
		601
175	=item $cv->wait	602	=item $cv->end
176		603
177	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	604	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		605
		606	These two methods can be used to combine many transactions/events into
		607	one. For example, a function that pings many hosts in parallel might want
		608	to use a condition variable for the whole process.
		609
		610	Every call to C<< ->begin >> will increment a counter, and every call to
		611	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		612	>>, the (last) callback passed to C<begin> will be executed. That callback
		613	is I<supposed> to call C<< ->send >>, but that is not required. If no
		614	callback was set, C<send> will be called without any arguments.
		615
		616	Let's clarify this with the ping example:
		617
		618	my $cv = AnyEvent->condvar;
		619
		620	my %result;
		621	$cv->begin (sub { $cv->send (\%result) });
		622
		623	for my $host (@list_of_hosts) {
		624	$cv->begin;
		625	ping_host_then_call_callback $host, sub {
		626	$result{$host} = ...;
		627	$cv->end;
		628	};
		629	}
		630
		631	$cv->end;
		632
		633	This code fragment supposedly pings a number of hosts and calls
		634	C<send> after results for all then have have been gathered - in any
		635	order. To achieve this, the code issues a call to C<begin> when it starts
		636	each ping request and calls C<end> when it has received some result for
		637	it. Since C<begin> and C<end> only maintain a counter, the order in which
		638	results arrive is not relevant.
		639
		640	There is an additional bracketing call to C<begin> and C<end> outside the
		641	loop, which serves two important purposes: first, it sets the callback
		642	to be called once the counter reaches C<0>, and second, it ensures that
		643	C<send> is called even when C<no> hosts are being pinged (the loop
		644	doesn't execute once).
		645
		646	This is the general pattern when you "fan out" into multiple subrequests:
		647	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		648	is called at least once, and then, for each subrequest you start, call
		649	C<begin> and for each subrequest you finish, call C<end>.
		650
		651	=back
		652
		653	=head3 METHODS FOR CONSUMERS
		654
		655	These methods should only be used by the consuming side, i.e. the
		656	code awaits the condition.
		657
		658	=over 4
		659
		660	=item $cv->recv
		661
		662	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
178	called on c<$cv>, while servicing other watchers normally.	663	>> methods have been called on c<$cv>, while servicing other watchers
		664	normally.
179		665
180	You can only wait once on a condition - additional calls will return	666	You can only wait once on a condition - additional calls are valid but
181	immediately.	667	will return immediately.
		668
		669	If an error condition has been set by calling C<< ->croak >>, then this
		670	function will call C<croak>.
		671
		672	In list context, all parameters passed to C<send> will be returned,
		673	in scalar context only the first one will be returned.
182		674
183	Not all event models support a blocking wait - some die in that case	675	Not all event models support a blocking wait - some die in that case
184	(programs might want to do that so they stay interactive), so I<if you	676	(programs might want to do that to stay interactive), so I<if you are
185	are using this from a module, never require a blocking wait>, but let the	677	using this from a module, never require a blocking wait>, but let the
186	caller decide whether the call will block or not (for example, by coupling	678	caller decide whether the call will block or not (for example, by coupling
187	condition variables with some kind of request results and supporting	679	condition variables with some kind of request results and supporting
188	callbacks so the caller knows that getting the result will not block,	680	callbacks so the caller knows that getting the result will not block,
189	while still suppporting blocking waits if the caller so desires).	681	while still supporting blocking waits if the caller so desires).
190		682
191	Another reason I<never> to C<< ->wait >> in a module is that you cannot	683	Another reason I<never> to C<< ->recv >> in a module is that you cannot
192	sensibly have two C<< ->wait >>'s in parallel, as that would require	684	sensibly have two C<< ->recv >>'s in parallel, as that would require
193	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	685	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
194	can supply (the coroutine-aware backends C<Coro::EV> and C<Coro::Event>	686	can supply.
195	explicitly support concurrent C<< ->wait >>'s from different coroutines,
196	however).
197		687
198	=item $cv->broadcast	688	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		689	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		690	versions and also integrates coroutines into AnyEvent, making blocking
		691	C<< ->recv >> calls perfectly safe as long as they are done from another
		692	coroutine (one that doesn't run the event loop).
199		693
200	Flag the condition as ready - a running C<< ->wait >> and all further	694	You can ensure that C<< -recv >> never blocks by setting a callback and
201	calls to C<wait> will return after this method has been called. If nobody	695	only calling C<< ->recv >> from within that callback (or at a later
202	is waiting the broadcast will be remembered..	696	time). This will work even when the event loop does not support blocking
		697	waits otherwise.
203		698
204	Example:	699	=item $bool = $cv->ready
205		700
206	# wait till the result is ready	701	Returns true when the condition is "true", i.e. whether C<send> or
207	my $result_ready = AnyEvent->condvar;	702	C<croak> have been called.
208		703
209	# do something such as adding a timer	704	=item $cb = $cv->cb ($cb->($cv))
210	# or socket watcher the calls $result_ready->broadcast
211	# when the "result" is ready.
212		705
213	$result_ready->wait;	706	This is a mutator function that returns the callback set and optionally
		707	replaces it before doing so.
		708
		709	The callback will be called when the condition becomes "true", i.e. when
		710	C<send> or C<croak> are called, with the only argument being the condition
		711	variable itself. Calling C<recv> inside the callback or at any later time
		712	is guaranteed not to block.
214		713
215	=back	714	=back
216		715
217	=head2 SIGNAL WATCHERS	716	=head1 GLOBAL VARIABLES AND FUNCTIONS
218
219	You can listen for signals using a signal watcher, C<signal> is the signal
220	I<name> without any C<SIG> prefix. Multiple signals events can be clumped
221	together into one callback invocation, and callback invocation might or
222	might not be asynchronous.
223
224	These watchers might use C<%SIG>, so programs overwriting those signals
225	directly will likely not work correctly.
226
227	Example: exit on SIGINT
228
229	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
230
231	=head2 CHILD PROCESS WATCHERS
232
233	You can also listen for the status of a child process specified by the
234	C<pid> argument (or any child if the pid argument is 0). The watcher will
235	trigger as often as status change for the child are received. This works
236	by installing a signal handler for C<SIGCHLD>. The callback will be called with
237	the pid and exit status (as returned by waitpid).
238
239	Example: wait for pid 1333
240
241	my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
242
243	=head1 GLOBALS
244		717
245	=over 4	718	=over 4
246		719
247	=item $AnyEvent::MODEL	720	=item $AnyEvent::MODEL
248		721
…		…
252	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	725	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
253	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	726	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
254		727
255	The known classes so far are:	728	The known classes so far are:
256		729
257	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
258	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
259	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).	730	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
260	AnyEvent::Impl::Event based on Event, also second best choice :)	731	AnyEvent::Impl::Event based on Event, second best choice.
		732	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
261	AnyEvent::Impl::Glib based on Glib, third-best choice.	733	AnyEvent::Impl::Glib based on Glib, third-best choice.
262	AnyEvent::Impl::Tk based on Tk, very bad choice.	734	AnyEvent::Impl::Tk based on Tk, very bad choice.
263	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.	735	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		736	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		737	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		738
		739	# warning, support for IO::Async is only partial, as it is too broken
		740	# and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
		741	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
		742
		743	There is no support for WxWidgets, as WxWidgets has no support for
		744	watching file handles. However, you can use WxWidgets through the
		745	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		746	second, which was considered to be too horrible to even consider for
		747	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		748	it's adaptor.
		749
		750	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		751	autodetecting them.
264		752
265	=item AnyEvent::detect	753	=item AnyEvent::detect
266		754
267	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if	755	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
268	necessary. You should only call this function right before you would have	756	if necessary. You should only call this function right before you would
269	created an AnyEvent watcher anyway, that is, very late at runtime.	757	have created an AnyEvent watcher anyway, that is, as late as possible at
		758	runtime.
		759
		760	=item $guard = AnyEvent::post_detect { BLOCK }
		761
		762	Arranges for the code block to be executed as soon as the event model is
		763	autodetected (or immediately if this has already happened).
		764
		765	If called in scalar or list context, then it creates and returns an object
		766	that automatically removes the callback again when it is destroyed. See
		767	L<Coro::BDB> for a case where this is useful.
		768
		769	=item @AnyEvent::post_detect
		770
		771	If there are any code references in this array (you can C<push> to it
		772	before or after loading AnyEvent), then they will called directly after
		773	the event loop has been chosen.
		774
		775	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		776	if it contains a true value then the event loop has already been detected,
		777	and the array will be ignored.
		778
		779	Best use C<AnyEvent::post_detect { BLOCK }> instead.
270		780
271	=back	781	=back
272		782
273	=head1 WHAT TO DO IN A MODULE	783	=head1 WHAT TO DO IN A MODULE
274		784
275	As a module author, you should "use AnyEvent" and call AnyEvent methods	785	As a module author, you should C<use AnyEvent> and call AnyEvent methods
276	freely, but you should not load a specific event module or rely on it.	786	freely, but you should not load a specific event module or rely on it.
277		787
278	Be careful when you create watchers in the module body - Anyevent will	788	Be careful when you create watchers in the module body - AnyEvent will
279	decide which event module to use as soon as the first method is called, so	789	decide which event module to use as soon as the first method is called, so
280	by calling AnyEvent in your module body you force the user of your module	790	by calling AnyEvent in your module body you force the user of your module
281	to load the event module first.	791	to load the event module first.
282		792
		793	Never call C<< ->recv >> on a condition variable unless you I<know> that
		794	the C<< ->send >> method has been called on it already. This is
		795	because it will stall the whole program, and the whole point of using
		796	events is to stay interactive.
		797
		798	It is fine, however, to call C<< ->recv >> when the user of your module
		799	requests it (i.e. if you create a http request object ad have a method
		800	called C<results> that returns the results, it should call C<< ->recv >>
		801	freely, as the user of your module knows what she is doing. always).
		802
283	=head1 WHAT TO DO IN THE MAIN PROGRAM	803	=head1 WHAT TO DO IN THE MAIN PROGRAM
284		804
285	There will always be a single main program - the only place that should	805	There will always be a single main program - the only place that should
286	dictate which event model to use.	806	dictate which event model to use.
287		807
288	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	808	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
289	do anything special and let AnyEvent decide which implementation to chose.	809	do anything special (it does not need to be event-based) and let AnyEvent
		810	decide which implementation to chose if some module relies on it.
290		811
291	If the main program relies on a specific event model (for example, in Gtk2	812	If the main program relies on a specific event model - for example, in
292	programs you have to rely on either Glib or Glib::Event), you should load	813	Gtk2 programs you have to rely on the Glib module - you should load the
293	it before loading AnyEvent or any module that uses it, generally, as early	814	event module before loading AnyEvent or any module that uses it: generally
294	as possible. The reason is that modules might create watchers when they	815	speaking, you should load it as early as possible. The reason is that
295	are loaded, and AnyEvent will decide on the event model to use as soon as	816	modules might create watchers when they are loaded, and AnyEvent will
296	it creates watchers, and it might chose the wrong one unless you load the	817	decide on the event model to use as soon as it creates watchers, and it
297	correct one yourself.	818	might chose the wrong one unless you load the correct one yourself.
298		819
299	You can chose to use a rather inefficient pure-perl implementation by	820	You can chose to use a pure-perl implementation by loading the
300	loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is	821	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
301	generally better.	822	everywhere, but letting AnyEvent chose the model is generally better.
		823
		824	=head2 MAINLOOP EMULATION
		825
		826	Sometimes (often for short test scripts, or even standalone programs who
		827	only want to use AnyEvent), you do not want to run a specific event loop.
		828
		829	In that case, you can use a condition variable like this:
		830
		831	AnyEvent->condvar->recv;
		832
		833	This has the effect of entering the event loop and looping forever.
		834
		835	Note that usually your program has some exit condition, in which case
		836	it is better to use the "traditional" approach of storing a condition
		837	variable somewhere, waiting for it, and sending it when the program should
		838	exit cleanly.
		839
		840
		841	=head1 OTHER MODULES
		842
		843	The following is a non-exhaustive list of additional modules that use
		844	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		845	in the same program. Some of the modules come with AnyEvent, some are
		846	available via CPAN.
		847
		848	=over 4
		849
		850	=item L<AnyEvent::Util>
		851
		852	Contains various utility functions that replace often-used but blocking
		853	functions such as C<inet_aton> by event-/callback-based versions.
		854
		855	=item L<AnyEvent::Socket>
		856
		857	Provides various utility functions for (internet protocol) sockets,
		858	addresses and name resolution. Also functions to create non-blocking tcp
		859	connections or tcp servers, with IPv6 and SRV record support and more.
		860
		861	=item L<AnyEvent::Handle>
		862
		863	Provide read and write buffers, manages watchers for reads and writes,
		864	supports raw and formatted I/O, I/O queued and fully transparent and
		865	non-blocking SSL/TLS.
		866
		867	=item L<AnyEvent::DNS>
		868
		869	Provides rich asynchronous DNS resolver capabilities.
		870
		871	=item L<AnyEvent::HTTP>
		872
		873	A simple-to-use HTTP library that is capable of making a lot of concurrent
		874	HTTP requests.
		875
		876	=item L<AnyEvent::HTTPD>
		877
		878	Provides a simple web application server framework.
		879
		880	=item L<AnyEvent::FastPing>
		881
		882	The fastest ping in the west.
		883
		884	=item L<AnyEvent::DBI>
		885
		886	Executes L<DBI> requests asynchronously in a proxy process.
		887
		888	=item L<AnyEvent::AIO>
		889
		890	Truly asynchronous I/O, should be in the toolbox of every event
		891	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		892	together.
		893
		894	=item L<AnyEvent::BDB>
		895
		896	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		897	L<BDB> and AnyEvent together.
		898
		899	=item L<AnyEvent::GPSD>
		900
		901	A non-blocking interface to gpsd, a daemon delivering GPS information.
		902
		903	=item L<AnyEvent::IGS>
		904
		905	A non-blocking interface to the Internet Go Server protocol (used by
		906	L<App::IGS>).
		907
		908	=item L<AnyEvent::IRC>
		909
		910	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		911
		912	=item L<Net::XMPP2>
		913
		914	AnyEvent based XMPP (Jabber protocol) module family.
		915
		916	=item L<Net::FCP>
		917
		918	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		919	of AnyEvent.
		920
		921	=item L<Event::ExecFlow>
		922
		923	High level API for event-based execution flow control.
		924
		925	=item L<Coro>
		926
		927	Has special support for AnyEvent via L<Coro::AnyEvent>.
		928
		929	=item L<IO::Lambda>
		930
		931	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		932
		933	=back
302		934
303	=cut	935	=cut
304		936
305	package AnyEvent;	937	package AnyEvent;
306		938
307	no warnings;	939	no warnings;
308	use strict;	940	use strict qw(vars subs);
309		941
310	use Carp;	942	use Carp;
311		943
312	our $VERSION = '3.1';	944	our $VERSION = 4.412;
313	our $MODEL;	945	our $MODEL;
314		946
315	our $AUTOLOAD;	947	our $AUTOLOAD;
316	our @ISA;	948	our @ISA;
317		949
		950	our @REGISTRY;
		951
		952	our $WIN32;
		953
		954	BEGIN {
		955	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		956	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		957
		958	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		959	if ${^TAINT};
		960	}
		961
318	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	962	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
319		963
320	our @REGISTRY;	964	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		965
		966	{
		967	my $idx;
		968	$PROTOCOL{$_} = ++$idx
		969	for reverse split /\s*,\s*/,
		970	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		971	}
321		972
322	my @models = (	973	my @models = (
323	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
324	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
325	[EV:: => AnyEvent::Impl::EV::],	974	[EV:: => AnyEvent::Impl::EV::],
326	[Event:: => AnyEvent::Impl::Event::],	975	[Event:: => AnyEvent::Impl::Event::],
327	[Glib:: => AnyEvent::Impl::Glib::],
328	[Tk:: => AnyEvent::Impl::Tk::],
329	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	976	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		977	# everything below here will not be autoprobed
		978	# as the pureperl backend should work everywhere
		979	# and is usually faster
		980	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		981	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		982	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		983	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		984	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		985	[Wx:: => AnyEvent::Impl::POE::],
		986	[Prima:: => AnyEvent::Impl::POE::],
		987	# IO::Async is just too broken - we would need workaorunds for its
		988	# byzantine signal and broken child handling, among others.
		989	# IO::Async is rather hard to detect, as it doesn't have any
		990	# obvious default class.
		991	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		992	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		993	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
330	);	994	);
331		995
332	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	996	our %method = map +($_ => 1),
		997	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		998
		999	our @post_detect;
		1000
		1001	sub post_detect(&) {
		1002	my ($cb) = @_;
		1003
		1004	if ($MODEL) {
		1005	$cb->();
		1006
		1007	1
		1008	} else {
		1009	push @post_detect, $cb;
		1010
		1011	defined wantarray
		1012	? bless \$cb, "AnyEvent::Util::postdetect"
		1013	: ()
		1014	}
		1015	}
		1016
		1017	sub AnyEvent::Util::postdetect::DESTROY {
		1018	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1019	}
333		1020
334	sub detect() {	1021	sub detect() {
335	unless ($MODEL) {	1022	unless ($MODEL) {
336	no strict 'refs';	1023	no strict 'refs';
		1024	local $SIG{__DIE__};
		1025
		1026	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1027	my $model = "AnyEvent::Impl::$1";
		1028	if (eval "require $model") {
		1029	$MODEL = $model;
		1030	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		1031	} else {
		1032	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		1033	}
		1034	}
337		1035
338	# check for already loaded models	1036	# check for already loaded models
		1037	unless ($MODEL) {
339	for (@REGISTRY, @models) {	1038	for (@REGISTRY, @models) {
340	my ($package, $model) = @$_;	1039	my ($package, $model) = @$_;
341	if (${"$package\::VERSION"} > 0) {	1040	if (${"$package\::VERSION"} > 0) {
342	if (eval "require $model") {	1041	if (eval "require $model") {
343	$MODEL = $model;	1042	$MODEL = $model;
344	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1043	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
345	last;	1044	last;
		1045	}
346	}	1046	}
347	}	1047	}
		1048
		1049	unless ($MODEL) {
		1050	# try to load a model
		1051
		1052	for (@REGISTRY, @models) {
		1053	my ($package, $model) = @$_;
		1054	if (eval "require $package"
		1055	and ${"$package\::VERSION"} > 0
		1056	and eval "require $model") {
		1057	$MODEL = $model;
		1058	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		1059	last;
		1060	}
		1061	}
		1062
		1063	$MODEL
		1064	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
		1065	}
348	}	1066	}
349		1067
350	unless ($MODEL) {	1068	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
351	# try to load a model
352
353	for (@REGISTRY, @models) {
354	my ($package, $model) = @$_;
355	if (eval "require $package"
356	and ${"$package\::VERSION"} > 0
357	and eval "require $model") {
358	$MODEL = $model;
359	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
360	last;
361	}
362	}
363
364	$MODEL
365	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.";
366	}
367		1069
368	unshift @ISA, $MODEL;	1070	unshift @ISA, $MODEL;
369	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1071
		1072	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1073
		1074	(shift @post_detect)->() while @post_detect;
370	}	1075	}
371		1076
372	$MODEL	1077	$MODEL
373	}	1078	}
374		1079
…		…
382		1087
383	my $class = shift;	1088	my $class = shift;
384	$class->$func (@_);	1089	$class->$func (@_);
385	}	1090	}
386		1091
		1092	# utility function to dup a filehandle. this is used by many backends
		1093	# to support binding more than one watcher per filehandle (they usually
		1094	# allow only one watcher per fd, so we dup it to get a different one).
		1095	sub _dupfh($$;$$) {
		1096	my ($poll, $fh, $r, $w) = @_;
		1097
		1098	# cygwin requires the fh mode to be matching, unix doesn't
		1099	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		1100	: $poll eq "w" ? ($w, ">")
		1101	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		1102
		1103	open my $fh2, "$mode&" . fileno $fh
		1104	or die "cannot dup() filehandle: $!,";
		1105
		1106	# we assume CLOEXEC is already set by perl in all important cases
		1107
		1108	($fh2, $rw)
		1109	}
		1110
387	package AnyEvent::Base;	1111	package AnyEvent::Base;
388		1112
		1113	# default implementations for many methods
		1114
		1115	BEGIN {
		1116	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1117	*_time = \&Time::HiRes::time;
		1118	# if (eval "use POSIX (); (POSIX::times())...
		1119	} else {
		1120	*_time = sub { time }; # epic fail
		1121	}
		1122	}
		1123
		1124	sub time { _time }
		1125	sub now { _time }
		1126	sub now_update { }
		1127
389	# default implementation for ->condvar, ->wait, ->broadcast	1128	# default implementation for ->condvar
390		1129
391	sub condvar {	1130	sub condvar {
392	bless \my $flag, "AnyEvent::Base::CondVar"	1131	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
393	}
394
395	sub AnyEvent::Base::CondVar::broadcast {
396	${$_[0]}++;
397	}
398
399	sub AnyEvent::Base::CondVar::wait {
400	AnyEvent->one_event while !${$_[0]};
401	}	1132	}
402		1133
403	# default implementation for ->signal	1134	# default implementation for ->signal
404		1135
405	our %SIG_CB;	1136	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1137
		1138	sub _signal_exec {
		1139	sysread $SIGPIPE_R, my $dummy, 4;
		1140
		1141	while (%SIG_EV) {
		1142	for (keys %SIG_EV) {
		1143	delete $SIG_EV{$_};
		1144	$_->() for values %{ $SIG_CB{$_} || {} };
		1145	}
		1146	}
		1147	}
406		1148
407	sub signal {	1149	sub signal {
408	my (undef, %arg) = @_;	1150	my (undef, %arg) = @_;
409		1151
		1152	unless ($SIGPIPE_R) {
		1153	require Fcntl;
		1154
		1155	if (AnyEvent::WIN32) {
		1156	require AnyEvent::Util;
		1157
		1158	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1159	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1160	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1161	} else {
		1162	pipe $SIGPIPE_R, $SIGPIPE_W;
		1163	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1164	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1165
		1166	# not strictly required, as $^F is normally 2, but let's make sure...
		1167	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1168	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1169	}
		1170
		1171	$SIGPIPE_R
		1172	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1173
		1174	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1175	}
		1176
410	my $signal = uc $arg{signal}	1177	my $signal = uc $arg{signal}
411	or Carp::croak "required option 'signal' is missing";	1178	or Carp::croak "required option 'signal' is missing";
412		1179
413	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1180	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
414	$SIG{$signal} ||= sub {	1181	$SIG{$signal} ||= sub {
415	$_->() for values %{ $SIG_CB{$signal} || {} };	1182	local $!;
		1183	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1184	undef $SIG_EV{$signal};
416	};	1185	};
417		1186
418	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1187	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
419	}	1188	}
420		1189
421	sub AnyEvent::Base::Signal::DESTROY {	1190	sub AnyEvent::Base::signal::DESTROY {
422	my ($signal, $cb) = @{$_[0]};	1191	my ($signal, $cb) = @{$_[0]};
423		1192
424	delete $SIG_CB{$signal}{$cb};	1193	delete $SIG_CB{$signal}{$cb};
425		1194
		1195	# delete doesn't work with older perls - they then
		1196	# print weird messages, or just unconditionally exit
		1197	# instead of getting the default action.
426	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1198	undef $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
427	}	1199	}
428		1200
429	# default implementation for ->child	1201	# default implementation for ->child
430		1202
431	our %PID_CB;	1203	our %PID_CB;
432	our $CHLD_W;	1204	our $CHLD_W;
433	our $CHLD_DELAY_W;	1205	our $CHLD_DELAY_W;
434	our $PID_IDLE;
435	our $WNOHANG;	1206	our $WNOHANG;
436		1207
437	sub _child_wait {	1208	sub _sigchld {
438	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1209	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
439	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1210	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
440	(values %{ $PID_CB{0} || {} });	1211	(values %{ $PID_CB{0} || {} });
441	}	1212	}
442
443	undef $PID_IDLE;
444	}
445
446	sub _sigchld {
447	# make sure we deliver these changes "synchronous" with the event loop.
448	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
449	undef $CHLD_DELAY_W;
450	&_child_wait;
451	});
452	}	1213	}
453		1214
454	sub child {	1215	sub child {
455	my (undef, %arg) = @_;	1216	my (undef, %arg) = @_;
456		1217
457	defined (my $pid = $arg{pid} + 0)	1218	defined (my $pid = $arg{pid} + 0)
458	or Carp::croak "required option 'pid' is missing";	1219	or Carp::croak "required option 'pid' is missing";
459		1220
460	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1221	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
461		1222
462	unless ($WNOHANG) {
463	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1223	$WNOHANG ||= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
464	}
465		1224
466	unless ($CHLD_W) {	1225	unless ($CHLD_W) {
467	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1226	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
468	# child could be a zombie already, so make at least one round	1227	# child could be a zombie already, so make at least one round
469	&_sigchld;	1228	&_sigchld;
470	}	1229	}
471		1230
472	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1231	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
473	}	1232	}
474		1233
475	sub AnyEvent::Base::Child::DESTROY {	1234	sub AnyEvent::Base::child::DESTROY {
476	my ($pid, $cb) = @{$_[0]};	1235	my ($pid, $cb) = @{$_[0]};
477		1236
478	delete $PID_CB{$pid}{$cb};	1237	delete $PID_CB{$pid}{$cb};
479	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1238	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
480		1239
481	undef $CHLD_W unless keys %PID_CB;	1240	undef $CHLD_W unless keys %PID_CB;
482	}	1241	}
483		1242
		1243	# idle emulation is done by simply using a timer, regardless
		1244	# of whether the process is idle or not, and not letting
		1245	# the callback use more than 50% of the time.
		1246	sub idle {
		1247	my (undef, %arg) = @_;
		1248
		1249	my ($cb, $w, $rcb) = $arg{cb};
		1250
		1251	$rcb = sub {
		1252	if ($cb) {
		1253	$w = _time;
		1254	&$cb;
		1255	$w = _time - $w;
		1256
		1257	# never use more then 50% of the time for the idle watcher,
		1258	# within some limits
		1259	$w = 0.0001 if $w < 0.0001;
		1260	$w = 5 if $w > 5;
		1261
		1262	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1263	} else {
		1264	# clean up...
		1265	undef $w;
		1266	undef $rcb;
		1267	}
		1268	};
		1269
		1270	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1271
		1272	bless \\$cb, "AnyEvent::Base::idle"
		1273	}
		1274
		1275	sub AnyEvent::Base::idle::DESTROY {
		1276	undef $${$_[0]};
		1277	}
		1278
		1279	package AnyEvent::CondVar;
		1280
		1281	our @ISA = AnyEvent::CondVar::Base::;
		1282
		1283	package AnyEvent::CondVar::Base;
		1284
		1285	use overload
		1286	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1287	fallback => 1;
		1288
		1289	sub _send {
		1290	# nop
		1291	}
		1292
		1293	sub send {
		1294	my $cv = shift;
		1295	$cv->{_ae_sent} = [@_];
		1296	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1297	$cv->_send;
		1298	}
		1299
		1300	sub croak {
		1301	$_[0]{_ae_croak} = $_[1];
		1302	$_[0]->send;
		1303	}
		1304
		1305	sub ready {
		1306	$_[0]{_ae_sent}
		1307	}
		1308
		1309	sub _wait {
		1310	AnyEvent->one_event while !$_[0]{_ae_sent};
		1311	}
		1312
		1313	sub recv {
		1314	$_[0]->_wait;
		1315
		1316	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1317	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1318	}
		1319
		1320	sub cb {
		1321	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1322	$_[0]{_ae_cb}
		1323	}
		1324
		1325	sub begin {
		1326	++$_[0]{_ae_counter};
		1327	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1328	}
		1329
		1330	sub end {
		1331	return if --$_[0]{_ae_counter};
		1332	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1333	}
		1334
		1335	# undocumented/compatibility with pre-3.4
		1336	*broadcast = \&send;
		1337	*wait = \&_wait;
		1338
		1339	=head1 ERROR AND EXCEPTION HANDLING
		1340
		1341	In general, AnyEvent does not do any error handling - it relies on the
		1342	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1343	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1344	checking of all AnyEvent methods, however, which is highly useful during
		1345	development.
		1346
		1347	As for exception handling (i.e. runtime errors and exceptions thrown while
		1348	executing a callback), this is not only highly event-loop specific, but
		1349	also not in any way wrapped by this module, as this is the job of the main
		1350	program.
		1351
		1352	The pure perl event loop simply re-throws the exception (usually
		1353	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1354	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1355	so on.
		1356
		1357	=head1 ENVIRONMENT VARIABLES
		1358
		1359	The following environment variables are used by this module or its
		1360	submodules.
		1361
		1362	Note that AnyEvent will remove I<all> environment variables starting with
		1363	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1364	enabled.
		1365
		1366	=over 4
		1367
		1368	=item C<PERL_ANYEVENT_VERBOSE>
		1369
		1370	By default, AnyEvent will be completely silent except in fatal
		1371	conditions. You can set this environment variable to make AnyEvent more
		1372	talkative.
		1373
		1374	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1375	conditions, such as not being able to load the event model specified by
		1376	C<PERL_ANYEVENT_MODEL>.
		1377
		1378	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1379	model it chooses.
		1380
		1381	=item C<PERL_ANYEVENT_STRICT>
		1382
		1383	AnyEvent does not do much argument checking by default, as thorough
		1384	argument checking is very costly. Setting this variable to a true value
		1385	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1386	check the arguments passed to most method calls. If it finds any problems,
		1387	it will croak.
		1388
		1389	In other words, enables "strict" mode.
		1390
		1391	Unlike C<use strict>, it is definitely recommended to keep it off in
		1392	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1393	developing programs can be very useful, however.
		1394
		1395	=item C<PERL_ANYEVENT_MODEL>
		1396
		1397	This can be used to specify the event model to be used by AnyEvent, before
		1398	auto detection and -probing kicks in. It must be a string consisting
		1399	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1400	and the resulting module name is loaded and if the load was successful,
		1401	used as event model. If it fails to load AnyEvent will proceed with
		1402	auto detection and -probing.
		1403
		1404	This functionality might change in future versions.
		1405
		1406	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1407	could start your program like this:
		1408
		1409	PERL_ANYEVENT_MODEL=Perl perl ...
		1410
		1411	=item C<PERL_ANYEVENT_PROTOCOLS>
		1412
		1413	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1414	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1415	of auto probing).
		1416
		1417	Must be set to a comma-separated list of protocols or address families,
		1418	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1419	used, and preference will be given to protocols mentioned earlier in the
		1420	list.
		1421
		1422	This variable can effectively be used for denial-of-service attacks
		1423	against local programs (e.g. when setuid), although the impact is likely
		1424	small, as the program has to handle conenction and other failures anyways.
		1425
		1426	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1427	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1428	- only support IPv4, never try to resolve or contact IPv6
		1429	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1430	IPv6, but prefer IPv6 over IPv4.
		1431
		1432	=item C<PERL_ANYEVENT_EDNS0>
		1433
		1434	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1435	for DNS. This extension is generally useful to reduce DNS traffic, but
		1436	some (broken) firewalls drop such DNS packets, which is why it is off by
		1437	default.
		1438
		1439	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1440	EDNS0 in its DNS requests.
		1441
		1442	=item C<PERL_ANYEVENT_MAX_FORKS>
		1443
		1444	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1445	will create in parallel.
		1446
		1447	=back
		1448
484	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1449	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		1450
		1451	This is an advanced topic that you do not normally need to use AnyEvent in
		1452	a module. This section is only of use to event loop authors who want to
		1453	provide AnyEvent compatibility.
485		1454
486	If you need to support another event library which isn't directly	1455	If you need to support another event library which isn't directly
487	supported by AnyEvent, you can supply your own interface to it by	1456	supported by AnyEvent, you can supply your own interface to it by
488	pushing, before the first watcher gets created, the package name of	1457	pushing, before the first watcher gets created, the package name of
489	the event module and the package name of the interface to use onto	1458	the event module and the package name of the interface to use onto
490	C<@AnyEvent::REGISTRY>. You can do that before and even without loading	1459	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
491	AnyEvent.	1460	AnyEvent, so it is reasonably cheap.
492		1461
493	Example:	1462	Example:
494		1463
495	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];	1464	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
496		1465
497	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>	1466	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
498	package/class when it finds the C<urxvt> package/module is loaded. When	1467	package/class when it finds the C<urxvt> package/module is already loaded.
		1468
499	AnyEvent is loaded and asked to find a suitable event model, it will	1469	When AnyEvent is loaded and asked to find a suitable event model, it
500	first check for the presence of urxvt.	1470	will first check for the presence of urxvt by trying to C<use> the
		1471	C<urxvt::anyevent> module.
501		1472
502	The class should provide implementations for all watcher types (see	1473	The class should provide implementations for all watcher types. See
503	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>	1474	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
504	(Source code) and so on for actual examples, use C<perldoc -m	1475	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
505	AnyEvent::Impl::Glib> to see the sources).	1476	see the sources.
506		1477
		1478	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		1479	provide suitable (hopefully) replacements.
		1480
507	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)	1481	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
508	uses the above line as-is. An interface isn't included in AnyEvent	1482	terminal emulator uses the above line as-is. An interface isn't included
509	because it doesn't make sense outside the embedded interpreter inside	1483	in AnyEvent because it doesn't make sense outside the embedded interpreter
510	I<rxvt-unicode>, and it is updated and maintained as part of the	1484	inside I<rxvt-unicode>, and it is updated and maintained as part of the
511	I<rxvt-unicode> distribution.	1485	I<rxvt-unicode> distribution.
512		1486
513	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1487	I<rxvt-unicode> also cheats a bit by not providing blocking access to
514	condition variables: code blocking while waiting for a condition will	1488	condition variables: code blocking while waiting for a condition will
515	C<die>. This still works with most modules/usages, and blocking calls must	1489	C<die>. This still works with most modules/usages, and blocking calls must
516	not be in an interactive application, so it makes sense.	1490	not be done in an interactive application, so it makes sense.
517		1491
518	=head1 ENVIRONMENT VARIABLES
519
520	The following environment variables are used by this module:
521
522	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
523	model gets used.
524
525	=head1 EXAMPLE	1492	=head1 EXAMPLE PROGRAM
526		1493
527	The following program uses an io watcher to read data from stdin, a timer	1494	The following program uses an I/O watcher to read data from STDIN, a timer
528	to display a message once per second, and a condvar to exit the program	1495	to display a message once per second, and a condition variable to quit the
529	when the user enters quit:	1496	program when the user enters quit:
530		1497
531	use AnyEvent;	1498	use AnyEvent;
532		1499
533	my $cv = AnyEvent->condvar;	1500	my $cv = AnyEvent->condvar;
534		1501
535	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	1502	my $io_watcher = AnyEvent->io (
		1503	fh => \*STDIN,
		1504	poll => 'r',
		1505	cb => sub {
536	warn "io event <$_[0]>\n"; # will always output <r>	1506	warn "io event <$_[0]>\n"; # will always output <r>
537	chomp (my $input = <STDIN>); # read a line	1507	chomp (my $input = <STDIN>); # read a line
538	warn "read: $input\n"; # output what has been read	1508	warn "read: $input\n"; # output what has been read
539	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1509	$cv->send if $input =~ /^q/i; # quit program if /^q/i
		1510	},
540	});	1511	);
541		1512
542	my $time_watcher; # can only be used once	1513	my $time_watcher; # can only be used once
543		1514
544	sub new_timer {	1515	sub new_timer {
545	$timer = AnyEvent->timer (after => 1, cb => sub {	1516	$timer = AnyEvent->timer (after => 1, cb => sub {
…		…
548	});	1519	});
549	}	1520	}
550		1521
551	new_timer; # create first timer	1522	new_timer; # create first timer
552		1523
553	$cv->wait; # wait until user enters /^q/i	1524	$cv->recv; # wait until user enters /^q/i
554		1525
555	=head1 REAL-WORLD EXAMPLE	1526	=head1 REAL-WORLD EXAMPLE
556		1527
557	Consider the L<Net::FCP> module. It features (among others) the following	1528	Consider the L<Net::FCP> module. It features (among others) the following
558	API calls, which are to freenet what HTTP GET requests are to http:	1529	API calls, which are to freenet what HTTP GET requests are to http:
…		…
608	syswrite $txn->{fh}, $txn->{request}	1579	syswrite $txn->{fh}, $txn->{request}
609	or die "connection or write error";	1580	or die "connection or write error";
610	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1581	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
611		1582
612	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1583	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
613	result and signals any possible waiters that the request ahs finished:	1584	result and signals any possible waiters that the request has finished:
614		1585
615	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1586	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
616		1587
617	if (end-of-file or data complete) {	1588	if (end-of-file or data complete) {
618	$txn->{result} = $txn->{buf};	1589	$txn->{result} = $txn->{buf};
619	$txn->{finished}->broadcast;	1590	$txn->{finished}->send;
620	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1591	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
621	}	1592	}
622		1593
623	The C<result> method, finally, just waits for the finished signal (if the	1594	The C<result> method, finally, just waits for the finished signal (if the
624	request was already finished, it doesn't wait, of course, and returns the	1595	request was already finished, it doesn't wait, of course, and returns the
625	data:	1596	data:
626		1597
627	$txn->{finished}->wait;	1598	$txn->{finished}->recv;
628	return $txn->{result};	1599	return $txn->{result};
629		1600
630	The actual code goes further and collects all errors (C<die>s, exceptions)	1601	The actual code goes further and collects all errors (C<die>s, exceptions)
631	that occured during request processing. The C<result> method detects	1602	that occurred during request processing. The C<result> method detects
632	whether an exception as thrown (it is stored inside the $txn object)	1603	whether an exception as thrown (it is stored inside the $txn object)
633	and just throws the exception, which means connection errors and other	1604	and just throws the exception, which means connection errors and other
634	problems get reported tot he code that tries to use the result, not in a	1605	problems get reported tot he code that tries to use the result, not in a
635	random callback.	1606	random callback.
636		1607
…		…
667		1638
668	my $quit = AnyEvent->condvar;	1639	my $quit = AnyEvent->condvar;
669		1640
670	$fcp->txn_client_get ($url)->cb (sub {	1641	$fcp->txn_client_get ($url)->cb (sub {
671	...	1642	...
672	$quit->broadcast;	1643	$quit->send;
673	});	1644	});
674		1645
675	$quit->wait;	1646	$quit->recv;
		1647
		1648
		1649	=head1 BENCHMARKS
		1650
		1651	To give you an idea of the performance and overheads that AnyEvent adds
		1652	over the event loops themselves and to give you an impression of the speed
		1653	of various event loops I prepared some benchmarks.
		1654
		1655	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1656
		1657	Here is a benchmark of various supported event models used natively and
		1658	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1659	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1660	which it is), lets them fire exactly once and destroys them again.
		1661
		1662	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1663	distribution.
		1664
		1665	=head3 Explanation of the columns
		1666
		1667	I<watcher> is the number of event watchers created/destroyed. Since
		1668	different event models feature vastly different performances, each event
		1669	loop was given a number of watchers so that overall runtime is acceptable
		1670	and similar between tested event loop (and keep them from crashing): Glib
		1671	would probably take thousands of years if asked to process the same number
		1672	of watchers as EV in this benchmark.
		1673
		1674	I<bytes> is the number of bytes (as measured by the resident set size,
		1675	RSS) consumed by each watcher. This method of measuring captures both C
		1676	and Perl-based overheads.
		1677
		1678	I<create> is the time, in microseconds (millionths of seconds), that it
		1679	takes to create a single watcher. The callback is a closure shared between
		1680	all watchers, to avoid adding memory overhead. That means closure creation
		1681	and memory usage is not included in the figures.
		1682
		1683	I<invoke> is the time, in microseconds, used to invoke a simple
		1684	callback. The callback simply counts down a Perl variable and after it was
		1685	invoked "watcher" times, it would C<< ->send >> a condvar once to
		1686	signal the end of this phase.
		1687
		1688	I<destroy> is the time, in microseconds, that it takes to destroy a single
		1689	watcher.
		1690
		1691	=head3 Results
		1692
		1693	name watchers bytes create invoke destroy comment
		1694	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
		1695	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
		1696	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
		1697	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
		1698	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
		1699	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1700	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
		1701	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
		1702	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
		1703	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
		1704
		1705	=head3 Discussion
		1706
		1707	The benchmark does I<not> measure scalability of the event loop very
		1708	well. For example, a select-based event loop (such as the pure perl one)
		1709	can never compete with an event loop that uses epoll when the number of
		1710	file descriptors grows high. In this benchmark, all events become ready at
		1711	the same time, so select/poll-based implementations get an unnatural speed
		1712	boost.
		1713
		1714	Also, note that the number of watchers usually has a nonlinear effect on
		1715	overall speed, that is, creating twice as many watchers doesn't take twice
		1716	the time - usually it takes longer. This puts event loops tested with a
		1717	higher number of watchers at a disadvantage.
		1718
		1719	To put the range of results into perspective, consider that on the
		1720	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1721	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1722	cycles with POE.
		1723
		1724	C<EV> is the sole leader regarding speed and memory use, which are both
		1725	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1726	far less memory than any other event loop and is still faster than Event
		1727	natively.
		1728
		1729	The pure perl implementation is hit in a few sweet spots (both the
		1730	constant timeout and the use of a single fd hit optimisations in the perl
		1731	interpreter and the backend itself). Nevertheless this shows that it
		1732	adds very little overhead in itself. Like any select-based backend its
		1733	performance becomes really bad with lots of file descriptors (and few of
		1734	them active), of course, but this was not subject of this benchmark.
		1735
		1736	The C<Event> module has a relatively high setup and callback invocation
		1737	cost, but overall scores in on the third place.
		1738
		1739	C<Glib>'s memory usage is quite a bit higher, but it features a
		1740	faster callback invocation and overall ends up in the same class as
		1741	C<Event>. However, Glib scales extremely badly, doubling the number of
		1742	watchers increases the processing time by more than a factor of four,
		1743	making it completely unusable when using larger numbers of watchers
		1744	(note that only a single file descriptor was used in the benchmark, so
		1745	inefficiencies of C<poll> do not account for this).
		1746
		1747	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1748	more than 2000 watchers is a big setback, however, as correctness takes
		1749	precedence over speed. Nevertheless, its performance is surprising, as the
		1750	file descriptor is dup()ed for each watcher. This shows that the dup()
		1751	employed by some adaptors is not a big performance issue (it does incur a
		1752	hidden memory cost inside the kernel which is not reflected in the figures
		1753	above).
		1754
		1755	C<POE>, regardless of underlying event loop (whether using its pure perl
		1756	select-based backend or the Event module, the POE-EV backend couldn't
		1757	be tested because it wasn't working) shows abysmal performance and
		1758	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		1759	as EV watchers, and 10 times as much memory as Event (the high memory
		1760	requirements are caused by requiring a session for each watcher). Watcher
		1761	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1762	implementation.
		1763
		1764	The design of the POE adaptor class in AnyEvent can not really account
		1765	for the performance issues, though, as session creation overhead is
		1766	small compared to execution of the state machine, which is coded pretty
		1767	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1768	using multiple sessions is not a good approach, especially regarding
		1769	memory usage, even the author of POE could not come up with a faster
		1770	design).
		1771
		1772	=head3 Summary
		1773
		1774	=over 4
		1775
		1776	=item * Using EV through AnyEvent is faster than any other event loop
		1777	(even when used without AnyEvent), but most event loops have acceptable
		1778	performance with or without AnyEvent.
		1779
		1780	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1781	the actual event loop, only with extremely fast event loops such as EV
		1782	adds AnyEvent significant overhead.
		1783
		1784	=item * You should avoid POE like the plague if you want performance or
		1785	reasonable memory usage.
		1786
		1787	=back
		1788
		1789	=head2 BENCHMARKING THE LARGE SERVER CASE
		1790
		1791	This benchmark actually benchmarks the event loop itself. It works by
		1792	creating a number of "servers": each server consists of a socket pair, a
		1793	timeout watcher that gets reset on activity (but never fires), and an I/O
		1794	watcher waiting for input on one side of the socket. Each time the socket
		1795	watcher reads a byte it will write that byte to a random other "server".
		1796
		1797	The effect is that there will be a lot of I/O watchers, only part of which
		1798	are active at any one point (so there is a constant number of active
		1799	fds for each loop iteration, but which fds these are is random). The
		1800	timeout is reset each time something is read because that reflects how
		1801	most timeouts work (and puts extra pressure on the event loops).
		1802
		1803	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		1804	(1%) are active. This mirrors the activity of large servers with many
		1805	connections, most of which are idle at any one point in time.
		1806
		1807	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1808	distribution.
		1809
		1810	=head3 Explanation of the columns
		1811
		1812	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1813	each server has a read and write socket end).
		1814
		1815	I<create> is the time it takes to create a socket pair (which is
		1816	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1817
		1818	I<request>, the most important value, is the time it takes to handle a
		1819	single "request", that is, reading the token from the pipe and forwarding
		1820	it to another server. This includes deleting the old timeout and creating
		1821	a new one that moves the timeout into the future.
		1822
		1823	=head3 Results
		1824
		1825	name sockets create request
		1826	EV 20000 69.01 11.16
		1827	Perl 20000 73.32 35.87
		1828	Event 20000 212.62 257.32
		1829	Glib 20000 651.16 1896.30
		1830	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1831
		1832	=head3 Discussion
		1833
		1834	This benchmark I<does> measure scalability and overall performance of the
		1835	particular event loop.
		1836
		1837	EV is again fastest. Since it is using epoll on my system, the setup time
		1838	is relatively high, though.
		1839
		1840	Perl surprisingly comes second. It is much faster than the C-based event
		1841	loops Event and Glib.
		1842
		1843	Event suffers from high setup time as well (look at its code and you will
		1844	understand why). Callback invocation also has a high overhead compared to
		1845	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1846	uses select or poll in basically all documented configurations.
		1847
		1848	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1849	clearly fails to perform with many filehandles or in busy servers.
		1850
		1851	POE is still completely out of the picture, taking over 1000 times as long
		1852	as EV, and over 100 times as long as the Perl implementation, even though
		1853	it uses a C-based event loop in this case.
		1854
		1855	=head3 Summary
		1856
		1857	=over 4
		1858
		1859	=item * The pure perl implementation performs extremely well.
		1860
		1861	=item * Avoid Glib or POE in large projects where performance matters.
		1862
		1863	=back
		1864
		1865	=head2 BENCHMARKING SMALL SERVERS
		1866
		1867	While event loops should scale (and select-based ones do not...) even to
		1868	large servers, most programs we (or I :) actually write have only a few
		1869	I/O watchers.
		1870
		1871	In this benchmark, I use the same benchmark program as in the large server
		1872	case, but it uses only eight "servers", of which three are active at any
		1873	one time. This should reflect performance for a small server relatively
		1874	well.
		1875
		1876	The columns are identical to the previous table.
		1877
		1878	=head3 Results
		1879
		1880	name sockets create request
		1881	EV 16 20.00 6.54
		1882	Perl 16 25.75 12.62
		1883	Event 16 81.27 35.86
		1884	Glib 16 32.63 15.48
		1885	POE 16 261.87 276.28 uses POE::Loop::Event
		1886
		1887	=head3 Discussion
		1888
		1889	The benchmark tries to test the performance of a typical small
		1890	server. While knowing how various event loops perform is interesting, keep
		1891	in mind that their overhead in this case is usually not as important, due
		1892	to the small absolute number of watchers (that is, you need efficiency and
		1893	speed most when you have lots of watchers, not when you only have a few of
		1894	them).
		1895
		1896	EV is again fastest.
		1897
		1898	Perl again comes second. It is noticeably faster than the C-based event
		1899	loops Event and Glib, although the difference is too small to really
		1900	matter.
		1901
		1902	POE also performs much better in this case, but is is still far behind the
		1903	others.
		1904
		1905	=head3 Summary
		1906
		1907	=over 4
		1908
		1909	=item * C-based event loops perform very well with small number of
		1910	watchers, as the management overhead dominates.
		1911
		1912	=back
		1913
		1914	=head2 THE IO::Lambda BENCHMARK
		1915
		1916	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1917	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		1918	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		1919	shouldn't come as a surprise to anybody). As such, the benchmark is
		1920	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		1921	very optimal. But how would AnyEvent compare when used without the extra
		1922	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		1923
		1924	The benchmark itself creates an echo-server, and then, for 500 times,
		1925	connects to the echo server, sends a line, waits for the reply, and then
		1926	creates the next connection. This is a rather bad benchmark, as it doesn't
		1927	test the efficiency of the framework or much non-blocking I/O, but it is a
		1928	benchmark nevertheless.
		1929
		1930	name runtime
		1931	Lambda/select 0.330 sec
		1932	+ optimized 0.122 sec
		1933	Lambda/AnyEvent 0.327 sec
		1934	+ optimized 0.138 sec
		1935	Raw sockets/select 0.077 sec
		1936	POE/select, components 0.662 sec
		1937	POE/select, raw sockets 0.226 sec
		1938	POE/select, optimized 0.404 sec
		1939
		1940	AnyEvent/select/nb 0.085 sec
		1941	AnyEvent/EV/nb 0.068 sec
		1942	+state machine 0.134 sec
		1943
		1944	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1945	benchmarks actually make blocking connects and use 100% blocking I/O,
		1946	defeating the purpose of an event-based solution. All of the newly
		1947	written AnyEvent benchmarks use 100% non-blocking connects (using
		1948	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1949	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		1950	generally require a lot more bookkeeping and event handling than blocking
		1951	connects (which involve a single syscall only).
		1952
		1953	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		1954	offers similar expressive power as POE and IO::Lambda, using conventional
		1955	Perl syntax. This means that both the echo server and the client are 100%
		1956	non-blocking, further placing it at a disadvantage.
		1957
		1958	As you can see, the AnyEvent + EV combination even beats the
		1959	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1960	backend easily beats IO::Lambda and POE.
		1961
		1962	And even the 100% non-blocking version written using the high-level (and
		1963	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		1964	large margin, even though it does all of DNS, tcp-connect and socket I/O
		1965	in a non-blocking way.
		1966
		1967	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		1968	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		1969	part of the IO::lambda distribution and were used without any changes.
		1970
		1971
		1972	=head1 SIGNALS
		1973
		1974	AnyEvent currently installs handlers for these signals:
		1975
		1976	=over 4
		1977
		1978	=item SIGCHLD
		1979
		1980	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		1981	emulation for event loops that do not support them natively. Also, some
		1982	event loops install a similar handler.
		1983
		1984	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent will
		1985	reset it to default, to avoid losing child exit statuses.
		1986
		1987	=item SIGPIPE
		1988
		1989	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		1990	when AnyEvent gets loaded.
		1991
		1992	The rationale for this is that AnyEvent users usually do not really depend
		1993	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		1994	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		1995	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		1996	some random socket.
		1997
		1998	The rationale for installing a no-op handler as opposed to ignoring it is
		1999	that this way, the handler will be restored to defaults on exec.
		2000
		2001	Feel free to install your own handler, or reset it to defaults.
		2002
		2003	=back
		2004
		2005	=cut
		2006
		2007	undef $SIG{CHLD}
		2008	if $SIG{CHLD} eq 'IGNORE';
		2009
		2010	$SIG{PIPE} = sub { }
		2011	unless defined $SIG{PIPE};
		2012
		2013	=head1 FORK
		2014
		2015	Most event libraries are not fork-safe. The ones who are usually are
		2016	because they rely on inefficient but fork-safe C<select> or C<poll>
		2017	calls. Only L<EV> is fully fork-aware.
		2018
		2019	If you have to fork, you must either do so I<before> creating your first
		2020	watcher OR you must not use AnyEvent at all in the child.
		2021
		2022
		2023	=head1 SECURITY CONSIDERATIONS
		2024
		2025	AnyEvent can be forced to load any event model via
		2026	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2027	execute arbitrary code or directly gain access, it can easily be used to
		2028	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2029	will not be active when the program uses a different event model than
		2030	specified in the variable.
		2031
		2032	You can make AnyEvent completely ignore this variable by deleting it
		2033	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2034
		2035	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2036
		2037	use AnyEvent;
		2038
		2039	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2040	be used to probe what backend is used and gain other information (which is
		2041	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2042	$ENV{PERL_ANYEVENT_STRICT}.
		2043
		2044	Note that AnyEvent will remove I<all> environment variables starting with
		2045	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2046	enabled.
		2047
		2048
		2049	=head1 BUGS
		2050
		2051	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2052	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2053	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2054	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2055	pronounced).
		2056
676		2057
677	=head1 SEE ALSO	2058	=head1 SEE ALSO
678		2059
679	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2060	Utility functions: L<AnyEvent::Util>.
680	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>.
681		2061
682	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2062	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2063	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		2064
683	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	2065	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
684	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.	2066	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2067	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2068	L<AnyEvent::Impl::POE>.
685		2069
		2070	Non-blocking file handles, sockets, TCP clients and
		2071	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		2072
		2073	Asynchronous DNS: L<AnyEvent::DNS>.
		2074
		2075	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		2076
686	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2077	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
687		2078
688	=head1	2079
		2080	=head1 AUTHOR
		2081
		2082	Marc Lehmann <schmorp@schmorp.de>
		2083	http://home.schmorp.de/
689		2084
690	=cut	2085	=cut
691		2086
692	1	2087	1
693		2088

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