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Revision 1.133 by root, Sun May 25 03:44:03 2008 UTC vs.
Revision 1.282 by root, Tue Aug 11 01:18:27 2009 UTC

1	=head1 => NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
		37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	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	63	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,	64	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enormous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70		108
71	=head1 DESCRIPTION	109	=head1 DESCRIPTION
72		110
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	140	starts using it, all bets are off. Maybe you should tell their authors to
103	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
104		142
105	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
108		146
109	=head1 WATCHERS	147	=head1 WATCHERS
110		148
111	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
…		…
115	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
118	is in control).	156	is in control).
119		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
120	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
121	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	166	to it).
123		167
124	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
128		172
129	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
130		174
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
133	undef $w;	177	undef $w;
134	});	178	});
135		179
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
138	declared.	182	declared.
139		183
140	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
141		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	192	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
144		194
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
146	for events. C<poll> must be a string that is either C<r> or C<w>,	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
148	respectively. C<cb> is the callback to invoke each time the file handle	205	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		206
151	Although the callback might get passed parameters, their value and	207	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	208	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	209	callbacks cannot use arguments passed to I/O watcher callbacks.
154		210
…		…
158		214
159	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	216	always use non-blocking calls when reading/writing from/to your file
161	handles.	217	handles.
162		218
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	219	Example: wait for readability of STDIN, then read a line and disable the
		220	watcher.
		221
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	224	warn "read: $input\n";
169	undef $w;	225	undef $w;
170	});	226	});
171		227
172	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
173		229
		230	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		231
		232	$w = AnyEvent->timer (
		233	after => <fractional_seconds>,
		234	interval => <fractional_seconds>,
		235	cb => <callback>,
		236	);
		237
174	You can create a time watcher by calling the C<< AnyEvent->timer >>	238	You can create a time watcher by calling the C<< AnyEvent->timer >>
175	method with the following mandatory arguments:	239	method with the following mandatory arguments:
176		240
177	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	242	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		244
181	Although the callback might get passed parameters, their value and	245	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	246	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	247	callbacks cannot use arguments passed to time watcher callbacks.
184		248
185	The timer callback will be invoked at most once: if you want a repeating	249	The callback will normally be invoked once only. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	250	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
188		254
189	Example:	255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
190		258
191	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	262	warn "timeout\n";
194	});	263	});
195		264
196	# to cancel the timer:	265	# to cancel the timer:
197	undef $w;	266	undef $w;
198		267
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	268	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		269
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
207	};	272	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		273
212	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
213		275
214	There are two ways to handle timers: based on real time (relative, "fire	276	There are two ways to handle timers: based on real time (relative, "fire
215	in 10 seconds") and based on wallclock time (absolute, "fire at 12	277	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	289	timers.
228		290
229	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	292	AnyEvent API.
231		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	Note that updating the time I<might> cause some events to be handled.
		369
		370	=back
		371
232	=head2 SIGNAL WATCHERS	372	=head2 SIGNAL WATCHERS
233		373
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
234	You can watch for signals using a signal watcher, C<signal> is the signal	376	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	377	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
237		379
238	Although the callback might get passed parameters, their value and	380	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	381	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	382	callbacks cannot use arguments passed to signal watcher callbacks.
241		383
…		…
243	invocation, and callback invocation will be synchronous. Synchronous means	385	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	386	that it might take a while until the signal gets handled by the process,
245	but it is guaranteed not to interrupt any other callbacks.	387	but it is guaranteed not to interrupt any other callbacks.
246		388
247	The main advantage of using these watchers is that you can share a signal	389	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	390	between multiple watchers, and AnyEvent will ensure that signals will not
		391	interrupt your program at bad times.
249		392
250	This watcher might use C<%SIG>, so programs overwriting those signals	393	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	394	so programs overwriting those signals directly will likely not work
		395	correctly.
252		396
253	Example: exit on SIGINT	397	Example: exit on SIGINT
254		398
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		400
		401	=head3 Signal Races, Delays and Workarounds
		402
		403	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		404	callbacks to signals in a generic way, which is a pity, as you cannot
		405	do race-free signal handling in perl, requiring C libraries for
		406	this. AnyEvent will try to do it's best, which means in some cases,
		407	signals will be delayed. The maximum time a signal might be delayed is
		408	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		409	variable can be changed only before the first signal watcher is created,
		410	and should be left alone otherwise. This variable determines how often
		411	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		412	will cause fewer spurious wake-ups, which is better for power and CPU
		413	saving.
		414
		415	All these problems can be avoided by installing the optional
		416	L<Async::Interrupt> module, which works with most event loops. It will not
		417	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		418	(and not with L<POE> currently, as POE does it's own workaround with
		419	one-second latency). For those, you just have to suffer the delays.
		420
257	=head2 CHILD PROCESS WATCHERS	421	=head2 CHILD PROCESS WATCHERS
258		422
		423	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		424
259	You can also watch on a child process exit and catch its exit status.	425	You can also watch on a child process exit and catch its exit status.
260		426
261	The child process is specified by the C<pid> argument (if set to C<0>, it	427	The child process is specified by the C<pid> argument (one some backends,
262	watches for any child process exit). The watcher will trigger as often	428	using C<0> watches for any child process exit, on others this will
263	as status change for the child are received. This works by installing a	429	croak). The watcher will be triggered only when the child process has
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	430	finished and an exit status is available, not on any trace events
265	and exit status (as returned by waitpid), so unlike other watcher types,	431	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	432
		433	The callback will be called with the pid and exit status (as returned by
		434	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		435	callback arguments.
		436
		437	This watcher type works by installing a signal handler for C<SIGCHLD>,
		438	and since it cannot be shared, nothing else should use SIGCHLD or reap
		439	random child processes (waiting for specific child processes, e.g. inside
		440	C<system>, is just fine).
267		441
268	There is a slight catch to child watchers, however: you usually start them	442	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	443	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	444	have exited already (and no SIGCHLD will be sent anymore).
271		445
272	Not all event models handle this correctly (POE doesn't), but even for	446	Not all event models handle this correctly (neither POE nor IO::Async do,
		447	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	448	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	449	the process exits (i.e. before you fork in the first place). AnyEvent's
		450	pure perl event loop handles all cases correctly regardless of when you
		451	start the watcher.
275		452
276	This means you cannot create a child watcher as the very first thing in an	453	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	454	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	455	watcher before you C<fork> the child (alternatively, you can call
		456	C<AnyEvent::detect>).
		457
		458	As most event loops do not support waiting for child events, they will be
		459	emulated by AnyEvent in most cases, in which the latency and race problems
		460	mentioned in the description of signal watchers apply.
279		461
280	Example: fork a process and wait for it	462	Example: fork a process and wait for it
281		463
282	my $done = AnyEvent->condvar;	464	my $done = AnyEvent->condvar;
283		465
284	my $pid = fork or exit 5;	466	my $pid = fork or exit 5;
285		467
286	my $w = AnyEvent->child (	468	my $w = AnyEvent->child (
287	pid => $pid,	469	pid => $pid,
288	cb => sub {	470	cb => sub {
289	my ($pid, $status) = @_;	471	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	472	warn "pid $pid exited with status $status";
291	$done->send;	473	$done->send;
292	},	474	},
293	);	475	);
294		476
295	# do something else, then wait for process exit	477	# do something else, then wait for process exit
296	$done->recv;	478	$done->recv;
		479
		480	=head2 IDLE WATCHERS
		481
		482	$w = AnyEvent->idle (cb => <callback>);
		483
		484	Sometimes there is a need to do something, but it is not so important
		485	to do it instantly, but only when there is nothing better to do. This
		486	"nothing better to do" is usually defined to be "no other events need
		487	attention by the event loop".
		488
		489	Idle watchers ideally get invoked when the event loop has nothing
		490	better to do, just before it would block the process to wait for new
		491	events. Instead of blocking, the idle watcher is invoked.
		492
		493	Most event loops unfortunately do not really support idle watchers (only
		494	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		495	will simply call the callback "from time to time".
		496
		497	Example: read lines from STDIN, but only process them when the
		498	program is otherwise idle:
		499
		500	my @lines; # read data
		501	my $idle_w;
		502	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		503	push @lines, scalar <STDIN>;
		504
		505	# start an idle watcher, if not already done
		506	$idle_w ||= AnyEvent->idle (cb => sub {
		507	# handle only one line, when there are lines left
		508	if (my $line = shift @lines) {
		509	print "handled when idle: $line";
		510	} else {
		511	# otherwise disable the idle watcher again
		512	undef $idle_w;
		513	}
		514	});
		515	});
297		516
298	=head2 CONDITION VARIABLES	517	=head2 CONDITION VARIABLES
		518
		519	$cv = AnyEvent->condvar;
		520
		521	$cv->send (<list>);
		522	my @res = $cv->recv;
299		523
300	If you are familiar with some event loops you will know that all of them	524	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	525	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	526	will actively watch for new events and call your callbacks.
303		527
304	AnyEvent is different, it expects somebody else to run the event loop and	528	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	529	loop and will only block when necessary (usually when told by the user).
306		530
307	The instrument to do that is called a "condition variable", so called	531	The instrument to do that is called a "condition variable", so called
308	because they represent a condition that must become true.	532	because they represent a condition that must become true.
		533
		534	Now is probably a good time to look at the examples further below.
309		535
310	Condition variables can be created by calling the C<< AnyEvent->condvar	536	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	537	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	538	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	539	becomes true, with the condition variable as the first argument (but not
		540	the results).
314		541
315	After creation, the condition variable is "false" until it becomes "true"	542	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method (or calling the condition variable as if it	543	by calling the C<send> method (or calling the condition variable as if it
317	were a callback).	544	were a callback, read about the caveats in the description for the C<<
		545	->send >> method).
318		546
319	Condition variables are similar to callbacks, except that you can	547	Condition variables are similar to callbacks, except that you can
320	optionally wait for them. They can also be called merge points - points	548	optionally wait for them. They can also be called merge points - points
321	in time where multiple outstanding events have been processed. And yet	549	in time where multiple outstanding events have been processed. And yet
322	another way to call them is transactions - each condition variable can be	550	another way to call them is transactions - each condition variable can be
323	used to represent a transaction, which finishes at some point and delivers	551	used to represent a transaction, which finishes at some point and delivers
324	a result.	552	a result. And yet some people know them as "futures" - a promise to
		553	compute/deliver something that you can wait for.
325		554
326	Condition variables are very useful to signal that something has finished,	555	Condition variables are very useful to signal that something has finished,
327	for example, if you write a module that does asynchronous http requests,	556	for example, if you write a module that does asynchronous http requests,
328	then a condition variable would be the ideal candidate to signal the	557	then a condition variable would be the ideal candidate to signal the
329	availability of results. The user can either act when the callback is	558	availability of results. The user can either act when the callback is
…		…
363	after => 1,	592	after => 1,
364	cb => sub { $result_ready->send },	593	cb => sub { $result_ready->send },
365	);	594	);
366		595
367	# this "blocks" (while handling events) till the callback	596	# this "blocks" (while handling events) till the callback
368	# calls send	597	# calls -<send
369	$result_ready->recv;	598	$result_ready->recv;
370		599
371	Example: wait for a timer, but take advantage of the fact that	600	Example: wait for a timer, but take advantage of the fact that condition
372	condition variables are also code references.	601	variables are also callable directly.
373		602
374	my $done = AnyEvent->condvar;	603	my $done = AnyEvent->condvar;
375	my $delay = AnyEvent->timer (after => 5, cb => $done);	604	my $delay = AnyEvent->timer (after => 5, cb => $done);
376	$done->recv;	605	$done->recv;
		606
		607	Example: Imagine an API that returns a condvar and doesn't support
		608	callbacks. This is how you make a synchronous call, for example from
		609	the main program:
		610
		611	use AnyEvent::CouchDB;
		612
		613	...
		614
		615	my @info = $couchdb->info->recv;
		616
		617	And this is how you would just set a callback to be called whenever the
		618	results are available:
		619
		620	$couchdb->info->cb (sub {
		621	my @info = $_[0]->recv;
		622	});
377		623
378	=head3 METHODS FOR PRODUCERS	624	=head3 METHODS FOR PRODUCERS
379		625
380	These methods should only be used by the producing side, i.e. the	626	These methods should only be used by the producing side, i.e. the
381	code/module that eventually sends the signal. Note that it is also	627	code/module that eventually sends the signal. Note that it is also
…		…
394	immediately from within send.	640	immediately from within send.
395		641
396	Any arguments passed to the C<send> call will be returned by all	642	Any arguments passed to the C<send> call will be returned by all
397	future C<< ->recv >> calls.	643	future C<< ->recv >> calls.
398		644
399	Condition variables are overloaded so one can call them directly (as a	645	Condition variables are overloaded so one can call them directly (as if
400	code reference). Calling them directly is the same as calling C<send>.	646	they were a code reference). Calling them directly is the same as calling
		647	C<send>.
401		648
402	=item $cv->croak ($error)	649	=item $cv->croak ($error)
403		650
404	Similar to send, but causes all call's to C<< ->recv >> to invoke	651	Similar to send, but causes all call's to C<< ->recv >> to invoke
405	C<Carp::croak> with the given error message/object/scalar.	652	C<Carp::croak> with the given error message/object/scalar.
406		653
407	This can be used to signal any errors to the condition variable	654	This can be used to signal any errors to the condition variable
408	user/consumer.	655	user/consumer. Doing it this way instead of calling C<croak> directly
		656	delays the error detetcion, but has the overwhelmign advantage that it
		657	diagnoses the error at the place where the result is expected, and not
		658	deep in some event clalback without connection to the actual code causing
		659	the problem.
409		660
410	=item $cv->begin ([group callback])	661	=item $cv->begin ([group callback])
411		662
412	=item $cv->end	663	=item $cv->end
413
414	These two methods are EXPERIMENTAL and MIGHT CHANGE.
415		664
416	These two methods can be used to combine many transactions/events into	665	These two methods can be used to combine many transactions/events into
417	one. For example, a function that pings many hosts in parallel might want	666	one. For example, a function that pings many hosts in parallel might want
418	to use a condition variable for the whole process.	667	to use a condition variable for the whole process.
419		668
420	Every call to C<< ->begin >> will increment a counter, and every call to	669	Every call to C<< ->begin >> will increment a counter, and every call to
421	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	670	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
422	>>, the (last) callback passed to C<begin> will be executed. That callback	671	>>, the (last) callback passed to C<begin> will be executed, passing the
423	is I<supposed> to call C<< ->send >>, but that is not required. If no	672	condvar as first argument. That callback is I<supposed> to call C<< ->send
424	callback was set, C<send> will be called without any arguments.	673	>>, but that is not required. If no group callback was set, C<send> will
		674	be called without any arguments.
425		675
426	Let's clarify this with the ping example:	676	You can think of C<< $cv->send >> giving you an OR condition (one call
		677	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		678	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		679
		680	Let's start with a simple example: you have two I/O watchers (for example,
		681	STDOUT and STDERR for a program), and you want to wait for both streams to
		682	close before activating a condvar:
427		683
428	my $cv = AnyEvent->condvar;	684	my $cv = AnyEvent->condvar;
429		685
		686	$cv->begin; # first watcher
		687	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		688	defined sysread $fh1, my $buf, 4096
		689	or $cv->end;
		690	});
		691
		692	$cv->begin; # second watcher
		693	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		694	defined sysread $fh2, my $buf, 4096
		695	or $cv->end;
		696	});
		697
		698	$cv->recv;
		699
		700	This works because for every event source (EOF on file handle), there is
		701	one call to C<begin>, so the condvar waits for all calls to C<end> before
		702	sending.
		703
		704	The ping example mentioned above is slightly more complicated, as the
		705	there are results to be passwd back, and the number of tasks that are
		706	begung can potentially be zero:
		707
		708	my $cv = AnyEvent->condvar;
		709
430	my %result;	710	my %result;
431	$cv->begin (sub { $cv->send (\%result) });	711	$cv->begin (sub { shift->send (\%result) });
432		712
433	for my $host (@list_of_hosts) {	713	for my $host (@list_of_hosts) {
434	$cv->begin;	714	$cv->begin;
435	ping_host_then_call_callback $host, sub {	715	ping_host_then_call_callback $host, sub {
436	$result{$host} = ...;	716	$result{$host} = ...;
…		…
451	loop, which serves two important purposes: first, it sets the callback	731	loop, which serves two important purposes: first, it sets the callback
452	to be called once the counter reaches C<0>, and second, it ensures that	732	to be called once the counter reaches C<0>, and second, it ensures that
453	C<send> is called even when C<no> hosts are being pinged (the loop	733	C<send> is called even when C<no> hosts are being pinged (the loop
454	doesn't execute once).	734	doesn't execute once).
455		735
456	This is the general pattern when you "fan out" into multiple subrequests:	736	This is the general pattern when you "fan out" into multiple (but
457	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	737	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
458	is called at least once, and then, for each subrequest you start, call	738	the callback and ensure C<end> is called at least once, and then, for each
459	C<begin> and for each subrequest you finish, call C<end>.	739	subrequest you start, call C<begin> and for each subrequest you finish,
		740	call C<end>.
460		741
461	=back	742	=back
462		743
463	=head3 METHODS FOR CONSUMERS	744	=head3 METHODS FOR CONSUMERS
464		745
…		…
480	function will call C<croak>.	761	function will call C<croak>.
481		762
482	In list context, all parameters passed to C<send> will be returned,	763	In list context, all parameters passed to C<send> will be returned,
483	in scalar context only the first one will be returned.	764	in scalar context only the first one will be returned.
484		765
		766	Note that doing a blocking wait in a callback is not supported by any
		767	event loop, that is, recursive invocation of a blocking C<< ->recv
		768	>> is not allowed, and the C<recv> call will C<croak> if such a
		769	condition is detected. This condition can be slightly loosened by using
		770	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		771	any thread that doesn't run the event loop itself.
		772
485	Not all event models support a blocking wait - some die in that case	773	Not all event models support a blocking wait - some die in that case
486	(programs might want to do that to stay interactive), so I<if you are	774	(programs might want to do that to stay interactive), so I<if you are
487	using this from a module, never require a blocking wait>, but let the	775	using this from a module, never require a blocking wait>. Instead, let the
488	caller decide whether the call will block or not (for example, by coupling	776	caller decide whether the call will block or not (for example, by coupling
489	condition variables with some kind of request results and supporting	777	condition variables with some kind of request results and supporting
490	callbacks so the caller knows that getting the result will not block,	778	callbacks so the caller knows that getting the result will not block,
491	while still supporting blocking waits if the caller so desires).	779	while still supporting blocking waits if the caller so desires).
492		780
493	Another reason I<never> to C<< ->recv >> in a module is that you cannot
494	sensibly have two C<< ->recv >>'s in parallel, as that would require
495	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
496	can supply.
497
498	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
499	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
500	versions and also integrates coroutines into AnyEvent, making blocking
501	C<< ->recv >> calls perfectly safe as long as they are done from another
502	coroutine (one that doesn't run the event loop).
503
504	You can ensure that C<< -recv >> never blocks by setting a callback and	781	You can ensure that C<< -recv >> never blocks by setting a callback and
505	only calling C<< ->recv >> from within that callback (or at a later	782	only calling C<< ->recv >> from within that callback (or at a later
506	time). This will work even when the event loop does not support blocking	783	time). This will work even when the event loop does not support blocking
507	waits otherwise.	784	waits otherwise.
508		785
509	=item $bool = $cv->ready	786	=item $bool = $cv->ready
510		787
511	Returns true when the condition is "true", i.e. whether C<send> or	788	Returns true when the condition is "true", i.e. whether C<send> or
512	C<croak> have been called.	789	C<croak> have been called.
513		790
514	=item $cb = $cv->cb ([new callback])	791	=item $cb = $cv->cb ($cb->($cv))
515		792
516	This is a mutator function that returns the callback set and optionally	793	This is a mutator function that returns the callback set and optionally
517	replaces it before doing so.	794	replaces it before doing so.
518		795
519	The callback will be called when the condition becomes "true", i.e. when	796	The callback will be called when the condition becomes (or already was)
520	C<send> or C<croak> are called. Calling C<recv> inside the callback	797	"true", i.e. when C<send> or C<croak> are called (or were called), with
		798	the only argument being the condition variable itself. Calling C<recv>
521	or at any later time is guaranteed not to block.	799	inside the callback or at any later time is guaranteed not to block.
522		800
523	=back	801	=back
524		802
525	=head3 MAINLOOP EMULATION	803	=head1 SUPPORTED EVENT LOOPS/BACKENDS
526		804
527	Sometimes (often for short test scripts, or even standalone programs	805	The available backend classes are (every class has its own manpage):
528	who only want to use AnyEvent), you I<do> want your program to block
529	indefinitely in some event loop.
530		806
531	In that case, you cna use a condition variable like this:	807	=over 4
532		808
533	AnyEvent->condvar->recv;	809	=item Backends that are autoprobed when no other event loop can be found.
534		810
535	This has the effect of entering the event loop and looping forever.	811	EV is the preferred backend when no other event loop seems to be in
		812	use. If EV is not installed, then AnyEvent will fall back to its own
		813	pure-perl implementation, which is available everywhere as it comes with
		814	AnyEvent itself.
536		815
537	Note that usually your program has some exit condition, in which case	816	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
538	it is better to use the "traditional" approach of storing a condition	817	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
539	variable, waiting for it, and sending it when the program should exit
540	cleanly.
541		818
		819	=item Backends that are transparently being picked up when they are used.
		820
		821	These will be used when they are currently loaded when the first watcher
		822	is created, in which case it is assumed that the application is using
		823	them. This means that AnyEvent will automatically pick the right backend
		824	when the main program loads an event module before anything starts to
		825	create watchers. Nothing special needs to be done by the main program.
		826
		827	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		828	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		829	AnyEvent::Impl::Tk based on Tk, very broken.
		830	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		831	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		832	AnyEvent::Impl::Irssi used when running within irssi.
		833
		834	=item Backends with special needs.
		835
		836	Qt requires the Qt::Application to be instantiated first, but will
		837	otherwise be picked up automatically. As long as the main program
		838	instantiates the application before any AnyEvent watchers are created,
		839	everything should just work.
		840
		841	AnyEvent::Impl::Qt based on Qt.
		842
		843	Support for IO::Async can only be partial, as it is too broken and
		844	architecturally limited to even support the AnyEvent API. It also
		845	is the only event loop that needs the loop to be set explicitly, so
		846	it can only be used by a main program knowing about AnyEvent. See
		847	L<AnyEvent::Impl::Async> for the gory details.
		848
		849	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		850
		851	=item Event loops that are indirectly supported via other backends.
		852
		853	Some event loops can be supported via other modules:
		854
		855	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		856
		857	B<WxWidgets> has no support for watching file handles. However, you can
		858	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		859	polls 20 times per second, which was considered to be too horrible to even
		860	consider for AnyEvent.
		861
		862	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		863	backend, so it can be supported through POE.
		864
		865	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		866	load L<POE> when detecting them, in the hope that POE will pick them up,
		867	in which case everything will be automatic.
		868
		869	=back
542		870
543	=head1 GLOBAL VARIABLES AND FUNCTIONS	871	=head1 GLOBAL VARIABLES AND FUNCTIONS
544		872
		873	These are not normally required to use AnyEvent, but can be useful to
		874	write AnyEvent extension modules.
		875
545	=over 4	876	=over 4
546		877
547	=item $AnyEvent::MODEL	878	=item $AnyEvent::MODEL
548		879
549	Contains C<undef> until the first watcher is being created. Then it	880	Contains C<undef> until the first watcher is being created, before the
		881	backend has been autodetected.
		882
550	contains the event model that is being used, which is the name of the	883	Afterwards it contains the event model that is being used, which is the
551	Perl class implementing the model. This class is usually one of the	884	name of the Perl class implementing the model. This class is usually one
552	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	885	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
553	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	886	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
554		887	will be C<urxvt::anyevent>).
555	The known classes so far are:
556
557	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
558	AnyEvent::Impl::Event based on Event, second best choice.
559	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
560	AnyEvent::Impl::Glib based on Glib, third-best choice.
561	AnyEvent::Impl::Tk based on Tk, very bad choice.
562	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
563	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
564	AnyEvent::Impl::POE based on POE, not generic enough for full support.
565
566	There is no support for WxWidgets, as WxWidgets has no support for
567	watching file handles. However, you can use WxWidgets through the
568	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
569	second, which was considered to be too horrible to even consider for
570	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
571	it's adaptor.
572
573	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
574	autodetecting them.
575		888
576	=item AnyEvent::detect	889	=item AnyEvent::detect
577		890
578	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	891	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
579	if necessary. You should only call this function right before you would	892	if necessary. You should only call this function right before you would
580	have created an AnyEvent watcher anyway, that is, as late as possible at	893	have created an AnyEvent watcher anyway, that is, as late as possible at
581	runtime.	894	runtime, and not e.g. while initialising of your module.
		895
		896	If you need to do some initialisation before AnyEvent watchers are
		897	created, use C<post_detect>.
582		898
583	=item $guard = AnyEvent::post_detect { BLOCK }	899	=item $guard = AnyEvent::post_detect { BLOCK }
584		900
585	Arranges for the code block to be executed as soon as the event model is	901	Arranges for the code block to be executed as soon as the event model is
586	autodetected (or immediately if this has already happened).	902	autodetected (or immediately if this has already happened).
587		903
		904	The block will be executed I<after> the actual backend has been detected
		905	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		906	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		907	other initialisations - see the sources of L<AnyEvent::Strict> or
		908	L<AnyEvent::AIO> to see how this is used.
		909
		910	The most common usage is to create some global watchers, without forcing
		911	event module detection too early, for example, L<AnyEvent::AIO> creates
		912	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		913	avoid autodetecting the event module at load time.
		914
588	If called in scalar or list context, then it creates and returns an object	915	If called in scalar or list context, then it creates and returns an object
589	that automatically removes the callback again when it is destroyed. See	916	that automatically removes the callback again when it is destroyed (or
		917	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
590	L<Coro::BDB> for a case where this is useful.	918	a case where this is useful.
		919
		920	Example: Create a watcher for the IO::AIO module and store it in
		921	C<$WATCHER>. Only do so after the event loop is initialised, though.
		922
		923	our WATCHER;
		924
		925	my $guard = AnyEvent::post_detect {
		926	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		927	};
		928
		929	# the ||= is important in case post_detect immediately runs the block,
		930	# as to not clobber the newly-created watcher. assigning both watcher and
		931	# post_detect guard to the same variable has the advantage of users being
		932	# able to just C<undef $WATCHER> if the watcher causes them grief.
		933
		934	$WATCHER ||= $guard;
591		935
592	=item @AnyEvent::post_detect	936	=item @AnyEvent::post_detect
593		937
594	If there are any code references in this array (you can C<push> to it	938	If there are any code references in this array (you can C<push> to it
595	before or after loading AnyEvent), then they will called directly after	939	before or after loading AnyEvent), then they will called directly after
596	the event loop has been chosen.	940	the event loop has been chosen.
597		941
598	You should check C<$AnyEvent::MODEL> before adding to this array, though:	942	You should check C<$AnyEvent::MODEL> before adding to this array, though:
599	if it contains a true value then the event loop has already been detected,	943	if it is defined then the event loop has already been detected, and the
600	and the array will be ignored.	944	array will be ignored.
601		945
602	Best use C<AnyEvent::post_detect { BLOCK }> instead.	946	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		947	it,as it takes care of these details.
		948
		949	This variable is mainly useful for modules that can do something useful
		950	when AnyEvent is used and thus want to know when it is initialised, but do
		951	not need to even load it by default. This array provides the means to hook
		952	into AnyEvent passively, without loading it.
603		953
604	=back	954	=back
605		955
606	=head1 WHAT TO DO IN A MODULE	956	=head1 WHAT TO DO IN A MODULE
607		957
…		…
630		980
631	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	981	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
632	do anything special (it does not need to be event-based) and let AnyEvent	982	do anything special (it does not need to be event-based) and let AnyEvent
633	decide which implementation to chose if some module relies on it.	983	decide which implementation to chose if some module relies on it.
634		984
635	If the main program relies on a specific event model. For example, in	985	If the main program relies on a specific event model - for example, in
636	Gtk2 programs you have to rely on the Glib module. You should load the	986	Gtk2 programs you have to rely on the Glib module - you should load the
637	event module before loading AnyEvent or any module that uses it: generally	987	event module before loading AnyEvent or any module that uses it: generally
638	speaking, you should load it as early as possible. The reason is that	988	speaking, you should load it as early as possible. The reason is that
639	modules might create watchers when they are loaded, and AnyEvent will	989	modules might create watchers when they are loaded, and AnyEvent will
640	decide on the event model to use as soon as it creates watchers, and it	990	decide on the event model to use as soon as it creates watchers, and it
641	might chose the wrong one unless you load the correct one yourself.	991	might chose the wrong one unless you load the correct one yourself.
642		992
643	You can chose to use a rather inefficient pure-perl implementation by	993	You can chose to use a pure-perl implementation by loading the
644	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	994	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
645	behaviour everywhere, but letting AnyEvent chose is generally better.	995	everywhere, but letting AnyEvent chose the model is generally better.
		996
		997	=head2 MAINLOOP EMULATION
		998
		999	Sometimes (often for short test scripts, or even standalone programs who
		1000	only want to use AnyEvent), you do not want to run a specific event loop.
		1001
		1002	In that case, you can use a condition variable like this:
		1003
		1004	AnyEvent->condvar->recv;
		1005
		1006	This has the effect of entering the event loop and looping forever.
		1007
		1008	Note that usually your program has some exit condition, in which case
		1009	it is better to use the "traditional" approach of storing a condition
		1010	variable somewhere, waiting for it, and sending it when the program should
		1011	exit cleanly.
		1012
646		1013
647	=head1 OTHER MODULES	1014	=head1 OTHER MODULES
648		1015
649	The following is a non-exhaustive list of additional modules that use	1016	The following is a non-exhaustive list of additional modules that use
650	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1017	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
651	in the same program. Some of the modules come with AnyEvent, some are	1018	modules and other event loops in the same program. Some of the modules
652	available via CPAN.	1019	come with AnyEvent, most are available via CPAN.
653		1020
654	=over 4	1021	=over 4
655		1022
656	=item L<AnyEvent::Util>	1023	=item L<AnyEvent::Util>
657		1024
658	Contains various utility functions that replace often-used but blocking	1025	Contains various utility functions that replace often-used but blocking
659	functions such as C<inet_aton> by event-/callback-based versions.	1026	functions such as C<inet_aton> by event-/callback-based versions.
660
661	=item L<AnyEvent::Handle>
662
663	Provide read and write buffers and manages watchers for reads and writes.
664		1027
665	=item L<AnyEvent::Socket>	1028	=item L<AnyEvent::Socket>
666		1029
667	Provides various utility functions for (internet protocol) sockets,	1030	Provides various utility functions for (internet protocol) sockets,
668	addresses and name resolution. Also functions to create non-blocking tcp	1031	addresses and name resolution. Also functions to create non-blocking tcp
669	connections or tcp servers, with IPv6 and SRV record support and more.	1032	connections or tcp servers, with IPv6 and SRV record support and more.
670		1033
		1034	=item L<AnyEvent::Handle>
		1035
		1036	Provide read and write buffers, manages watchers for reads and writes,
		1037	supports raw and formatted I/O, I/O queued and fully transparent and
		1038	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1039
		1040	=item L<AnyEvent::DNS>
		1041
		1042	Provides rich asynchronous DNS resolver capabilities.
		1043
		1044	=item L<AnyEvent::HTTP>
		1045
		1046	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1047	HTTP requests.
		1048
671	=item L<AnyEvent::HTTPD>	1049	=item L<AnyEvent::HTTPD>
672		1050
673	Provides a simple web application server framework.	1051	Provides a simple web application server framework.
674		1052
675	=item L<AnyEvent::DNS>
676
677	Provides rich asynchronous DNS resolver capabilities.
678
679	=item L<AnyEvent::FastPing>	1053	=item L<AnyEvent::FastPing>
680		1054
681	The fastest ping in the west.	1055	The fastest ping in the west.
682		1056
		1057	=item L<AnyEvent::DBI>
		1058
		1059	Executes L<DBI> requests asynchronously in a proxy process.
		1060
		1061	=item L<AnyEvent::AIO>
		1062
		1063	Truly asynchronous I/O, should be in the toolbox of every event
		1064	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1065	together.
		1066
		1067	=item L<AnyEvent::BDB>
		1068
		1069	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1070	L<BDB> and AnyEvent together.
		1071
		1072	=item L<AnyEvent::GPSD>
		1073
		1074	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1075
683	=item L<Net::IRC3>	1076	=item L<AnyEvent::IRC>
684		1077
685	AnyEvent based IRC client module family.	1078	AnyEvent based IRC client module family (replacing the older Net::IRC3).
686		1079
687	=item L<Net::XMPP2>	1080	=item L<AnyEvent::XMPP>
688		1081
689	AnyEvent based XMPP (Jabber protocol) module family.	1082	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1083	Net::XMPP2>.
		1084
		1085	=item L<AnyEvent::IGS>
		1086
		1087	A non-blocking interface to the Internet Go Server protocol (used by
		1088	L<App::IGS>).
690		1089
691	=item L<Net::FCP>	1090	=item L<Net::FCP>
692		1091
693	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1092	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
694	of AnyEvent.	1093	of AnyEvent.
…		…
699		1098
700	=item L<Coro>	1099	=item L<Coro>
701		1100
702	Has special support for AnyEvent via L<Coro::AnyEvent>.	1101	Has special support for AnyEvent via L<Coro::AnyEvent>.
703		1102
704	=item L<AnyEvent::AIO>, L<IO::AIO>
705
706	Truly asynchronous I/O, should be in the toolbox of every event
707	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
708	together.
709
710	=item L<AnyEvent::BDB>, L<BDB>
711
712	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
713	IO::AIO and AnyEvent together.
714
715	=item L<IO::Lambda>
716
717	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
718
719	=back	1103	=back
720		1104
721	=cut	1105	=cut
722		1106
723	package AnyEvent;	1107	package AnyEvent;
724		1108
		1109	# basically a tuned-down version of common::sense
		1110	sub common_sense {
725	no warnings;	1111	# no warnings
726	use strict;	1112	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1113	# use strict vars subs
		1114	$^H |= 0x00000600;
		1115	}
727		1116
		1117	BEGIN { AnyEvent::common_sense }
		1118
728	use Carp;	1119	use Carp ();
729		1120
730	our $VERSION = '4.03';	1121	our $VERSION = '5.1';
731	our $MODEL;	1122	our $MODEL;
732		1123
733	our $AUTOLOAD;	1124	our $AUTOLOAD;
734	our @ISA;	1125	our @ISA;
735		1126
736	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
737
738	our @REGISTRY;	1127	our @REGISTRY;
739		1128
740	our %PROTOCOL; # (ipv4|ipv6) => (1|2)	1129	our $WIN32;
		1130
		1131	our $VERBOSE;
		1132
		1133	BEGIN {
		1134	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1135	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1136
		1137	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1138	if ${^TAINT};
		1139
		1140	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1141
		1142	}
		1143
		1144	our $MAX_SIGNAL_LATENCY = 10;
		1145
		1146	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
741		1147
742	{	1148	{
743	my $idx;	1149	my $idx;
744	$PROTOCOL{$_} = ++$idx	1150	$PROTOCOL{$_} = ++$idx
		1151	for reverse split /\s*,\s*/,
745	for split /\s*,\s*/, $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1152	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
746	}	1153	}
747		1154
748	my @models = (	1155	my @models = (
749	[EV:: => AnyEvent::Impl::EV::],	1156	[EV:: => AnyEvent::Impl::EV:: , 1],
		1157	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1158	# everything below here will not (normally) be autoprobed
		1159	# as the pureperl backend should work everywhere
		1160	# and is usually faster
750	[Event:: => AnyEvent::Impl::Event::],	1161	[Event:: => AnyEvent::Impl::Event::, 1],
		1162	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1163	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1164	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
751	[Tk:: => AnyEvent::Impl::Tk::],	1165	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1166	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1167	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
752	[Wx:: => AnyEvent::Impl::POE::],	1168	[Wx:: => AnyEvent::Impl::POE::],
753	[Prima:: => AnyEvent::Impl::POE::],	1169	[Prima:: => AnyEvent::Impl::POE::],
754	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1170	# IO::Async is just too broken - we would need workarounds for its
755	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1171	# byzantine signal and broken child handling, among others.
756	[Glib:: => AnyEvent::Impl::Glib::],	1172	# IO::Async is rather hard to detect, as it doesn't have any
757	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1173	# obvious default class.
758	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1174	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
759	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1175	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1176	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1177	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
760	);	1178	);
761		1179
762	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1180	our %method = map +($_ => 1),
		1181	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
763		1182
764	our @post_detect;	1183	our @post_detect;
765		1184
766	sub post_detect(&) {	1185	sub post_detect(&) {
767	my ($cb) = @_;	1186	my ($cb) = @_;
768		1187
769	if ($MODEL) {	1188	if ($MODEL) {
770	$cb->();	1189	$cb->();
771		1190
772	1	1191	undef
773	} else {	1192	} else {
774	push @post_detect, $cb;	1193	push @post_detect, $cb;
775		1194
776	defined wantarray	1195	defined wantarray
777	? bless \$cb, "AnyEvent::Util::PostDetect"	1196	? bless \$cb, "AnyEvent::Util::postdetect"
778	: ()	1197	: ()
779	}	1198	}
780	}	1199	}
781		1200
782	sub AnyEvent::Util::PostDetect::DESTROY {	1201	sub AnyEvent::Util::postdetect::DESTROY {
783	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1202	@post_detect = grep $_ != ${$_[0]}, @post_detect;
784	}	1203	}
785		1204
786	sub detect() {	1205	sub detect() {
787	unless ($MODEL) {	1206	unless ($MODEL) {
788	no strict 'refs';	1207	local $SIG{__DIE__};
789		1208
790	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1209	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
791	my $model = "AnyEvent::Impl::$1";	1210	my $model = "AnyEvent::Impl::$1";
792	if (eval "require $model") {	1211	if (eval "require $model") {
793	$MODEL = $model;	1212	$MODEL = $model;
794	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1213	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
795	} else {	1214	} else {
796	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1215	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
797	}	1216	}
798	}	1217	}
799		1218
800	# check for already loaded models	1219	# check for already loaded models
801	unless ($MODEL) {	1220	unless ($MODEL) {
802	for (@REGISTRY, @models) {	1221	for (@REGISTRY, @models) {
803	my ($package, $model) = @$_;	1222	my ($package, $model) = @$_;
804	if (${"$package\::VERSION"} > 0) {	1223	if (${"$package\::VERSION"} > 0) {
805	if (eval "require $model") {	1224	if (eval "require $model") {
806	$MODEL = $model;	1225	$MODEL = $model;
807	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1226	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
808	last;	1227	last;
809	}	1228	}
810	}	1229	}
811	}	1230	}
812		1231
813	unless ($MODEL) {	1232	unless ($MODEL) {
814	# try to load a model	1233	# try to autoload a model
815
816	for (@REGISTRY, @models) {	1234	for (@REGISTRY, @models) {
817	my ($package, $model) = @$_;	1235	my ($package, $model, $autoload) = @$_;
		1236	if (
		1237	$autoload
818	if (eval "require $package"	1238	and eval "require $package"
819	and ${"$package\::VERSION"} > 0	1239	and ${"$package\::VERSION"} > 0
820	and eval "require $model") {	1240	and eval "require $model"
		1241	) {
821	$MODEL = $model;	1242	$MODEL = $model;
822	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1243	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
823	last;	1244	last;
824	}	1245	}
825	}	1246	}
826		1247
827	$MODEL	1248	$MODEL
828	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1249	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
829	}	1250	}
830	}	1251	}
831		1252
		1253	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1254
832	unshift @ISA, $MODEL;	1255	unshift @ISA, $MODEL;
833	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1256
		1257	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
834		1258
835	(shift @post_detect)->() while @post_detect;	1259	(shift @post_detect)->() while @post_detect;
836	}	1260	}
837		1261
838	$MODEL	1262	$MODEL
…		…
840		1264
841	sub AUTOLOAD {	1265	sub AUTOLOAD {
842	(my $func = $AUTOLOAD) =~ s/.*://;	1266	(my $func = $AUTOLOAD) =~ s/.*://;
843		1267
844	$method{$func}	1268	$method{$func}
845	or croak "$func: not a valid method for AnyEvent objects";	1269	or Carp::croak "$func: not a valid method for AnyEvent objects";
846		1270
847	detect unless $MODEL;	1271	detect unless $MODEL;
848		1272
849	my $class = shift;	1273	my $class = shift;
850	$class->$func (@_);	1274	$class->$func (@_);
851	}	1275	}
852		1276
		1277	# utility function to dup a filehandle. this is used by many backends
		1278	# to support binding more than one watcher per filehandle (they usually
		1279	# allow only one watcher per fd, so we dup it to get a different one).
		1280	sub _dupfh($$;$$) {
		1281	my ($poll, $fh, $r, $w) = @_;
		1282
		1283	# cygwin requires the fh mode to be matching, unix doesn't
		1284	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1285
		1286	open my $fh2, $mode, $fh
		1287	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1288
		1289	# we assume CLOEXEC is already set by perl in all important cases
		1290
		1291	($fh2, $rw)
		1292	}
		1293
		1294	=head1 SIMPLIFIED AE API
		1295
		1296	Starting with version 5.0, AnyEvent officially supports a second, much
		1297	simpler, API that is designed to reduce the calling, typing and memory
		1298	overhead.
		1299
		1300	See the L<AE> manpage for details.
		1301
		1302	=cut
		1303
		1304	package AE;
		1305
		1306	our $VERSION = $AnyEvent::VERSION;
		1307
		1308	sub io($$$) {
		1309	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1310	}
		1311
		1312	sub timer($$$) {
		1313	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1314	}
		1315
		1316	sub signal($$) {
		1317	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1318	}
		1319
		1320	sub child($$) {
		1321	AnyEvent->child (pid => $_[0], cb => $_[1])
		1322	}
		1323
		1324	sub idle($) {
		1325	AnyEvent->idle (cb => $_[0])
		1326	}
		1327
		1328	sub cv(;&) {
		1329	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1330	}
		1331
		1332	sub now() {
		1333	AnyEvent->now
		1334	}
		1335
		1336	sub now_update() {
		1337	AnyEvent->now_update
		1338	}
		1339
		1340	sub time() {
		1341	AnyEvent->time
		1342	}
		1343
853	package AnyEvent::Base;	1344	package AnyEvent::Base;
854		1345
		1346	# default implementations for many methods
		1347
		1348	sub _time {
		1349	# probe for availability of Time::HiRes
		1350	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1351	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1352	*_time = \&Time::HiRes::time;
		1353	# if (eval "use POSIX (); (POSIX::times())...
		1354	} else {
		1355	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1356	*_time = sub { time }; # epic fail
		1357	}
		1358
		1359	&_time
		1360	}
		1361
		1362	sub time { _time }
		1363	sub now { _time }
		1364	sub now_update { }
		1365
855	# default implementation for ->condvar	1366	# default implementation for ->condvar
856		1367
857	sub condvar {	1368	sub condvar {
858	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1369	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
859	}	1370	}
860		1371
861	# default implementation for ->signal	1372	# default implementation for ->signal
862		1373
863	our %SIG_CB;	1374	our $HAVE_ASYNC_INTERRUPT;
		1375
		1376	sub _have_async_interrupt() {
		1377	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1378	&& eval "use Async::Interrupt 1.0 (); 1")
		1379	unless defined $HAVE_ASYNC_INTERRUPT;
		1380
		1381	$HAVE_ASYNC_INTERRUPT
		1382	}
		1383
		1384	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1385	our (%SIG_ASY, %SIG_ASY_W);
		1386	our ($SIG_COUNT, $SIG_TW);
		1387
		1388	sub _signal_exec {
		1389	$HAVE_ASYNC_INTERRUPT
		1390	? $SIGPIPE_R->drain
		1391	: sysread $SIGPIPE_R, my $dummy, 9;
		1392
		1393	while (%SIG_EV) {
		1394	for (keys %SIG_EV) {
		1395	delete $SIG_EV{$_};
		1396	$_->() for values %{ $SIG_CB{$_} || {} };
		1397	}
		1398	}
		1399	}
		1400
		1401	# install a dummy wakeup watcher to reduce signal catching latency
		1402	sub _sig_add() {
		1403	unless ($SIG_COUNT++) {
		1404	# try to align timer on a full-second boundary, if possible
		1405	my $NOW = AE::now;
		1406
		1407	$SIG_TW = AE::timer
		1408	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1409	$MAX_SIGNAL_LATENCY,
		1410	sub { } # just for the PERL_ASYNC_CHECK
		1411	;
		1412	}
		1413	}
		1414
		1415	sub _sig_del {
		1416	undef $SIG_TW
		1417	unless --$SIG_COUNT;
		1418	}
		1419
		1420	our $_sig_name_init; $_sig_name_init = sub {
		1421	eval q{ # poor man's autoloading
		1422	undef $_sig_name_init;
		1423
		1424	if (_have_async_interrupt) {
		1425	*sig2num = \&Async::Interrupt::sig2num;
		1426	*sig2name = \&Async::Interrupt::sig2name;
		1427	} else {
		1428	require Config;
		1429
		1430	my %signame2num;
		1431	@signame2num{ split ' ', $Config::Config{sig_name} }
		1432	= split ' ', $Config::Config{sig_num};
		1433
		1434	my @signum2name;
		1435	@signum2name[values %signame2num] = keys %signame2num;
		1436
		1437	*sig2num = sub($) {
		1438	$_[0] > 0 ? shift : $signame2num{+shift}
		1439	};
		1440	*sig2name = sub ($) {
		1441	$_[0] > 0 ? $signum2name[+shift] : shift
		1442	};
		1443	}
		1444	};
		1445	die if $@;
		1446	};
		1447
		1448	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1449	sub sig2name($) { &$_sig_name_init; &sig2name }
864		1450
865	sub signal {	1451	sub signal {
		1452	eval q{ # poor man's autoloading {}
		1453	# probe for availability of Async::Interrupt
		1454	if (_have_async_interrupt) {
		1455	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1456
		1457	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1458	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1459
		1460	} else {
		1461	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1462
		1463	require Fcntl;
		1464
		1465	if (AnyEvent::WIN32) {
		1466	require AnyEvent::Util;
		1467
		1468	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1469	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1470	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1471	} else {
		1472	pipe $SIGPIPE_R, $SIGPIPE_W;
		1473	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1474	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1475
		1476	# not strictly required, as $^F is normally 2, but let's make sure...
		1477	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1478	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1479	}
		1480
		1481	$SIGPIPE_R
		1482	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1483
		1484	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1485	}
		1486
		1487	*signal = sub {
866	my (undef, %arg) = @_;	1488	my (undef, %arg) = @_;
867		1489
868	my $signal = uc $arg{signal}	1490	my $signal = uc $arg{signal}
869	or Carp::croak "required option 'signal' is missing";	1491	or Carp::croak "required option 'signal' is missing";
870		1492
		1493	if ($HAVE_ASYNC_INTERRUPT) {
		1494	# async::interrupt
		1495
		1496	$signal = sig2num $signal;
871	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1497	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1498
		1499	$SIG_ASY{$signal} ||= new Async::Interrupt
		1500	cb => sub { undef $SIG_EV{$signal} },
		1501	signal => $signal,
		1502	pipe => [$SIGPIPE_R->filenos],
		1503	pipe_autodrain => 0,
		1504	;
		1505
		1506	} else {
		1507	# pure perl
		1508
		1509	# AE::Util has been loaded in signal
		1510	$signal = sig2name $signal;
		1511	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1512
872	$SIG{$signal} ||= sub {	1513	$SIG{$signal} ||= sub {
873	$_->() for values %{ $SIG_CB{$signal} || {} };	1514	local $!;
		1515	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1516	undef $SIG_EV{$signal};
		1517	};
		1518
		1519	# can't do signal processing without introducing races in pure perl,
		1520	# so limit the signal latency.
		1521	_sig_add;
		1522	}
		1523
		1524	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1525	};
		1526
		1527	*AnyEvent::Base::signal::DESTROY = sub {
		1528	my ($signal, $cb) = @{$_[0]};
		1529
		1530	_sig_del;
		1531
		1532	delete $SIG_CB{$signal}{$cb};
		1533
		1534	$HAVE_ASYNC_INTERRUPT
		1535	? delete $SIG_ASY{$signal}
		1536	: # delete doesn't work with older perls - they then
		1537	# print weird messages, or just unconditionally exit
		1538	# instead of getting the default action.
		1539	undef $SIG{$signal}
		1540	unless keys %{ $SIG_CB{$signal} };
		1541	};
874	};	1542	};
875		1543	die if $@;
876	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1544	&signal
877	}
878
879	sub AnyEvent::Base::Signal::DESTROY {
880	my ($signal, $cb) = @{$_[0]};
881
882	delete $SIG_CB{$signal}{$cb};
883
884	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
885	}	1545	}
886		1546
887	# default implementation for ->child	1547	# default implementation for ->child
888		1548
889	our %PID_CB;	1549	our %PID_CB;
890	our $CHLD_W;	1550	our $CHLD_W;
891	our $CHLD_DELAY_W;	1551	our $CHLD_DELAY_W;
892	our $PID_IDLE;
893	our $WNOHANG;	1552	our $WNOHANG;
894		1553
895	sub _child_wait {	1554	sub _emit_childstatus($$) {
896	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1555	my (undef, $rpid, $rstatus) = @_;
		1556
		1557	$_->($rpid, $rstatus)
897	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1558	for values %{ $PID_CB{$rpid} || {} },
898	(values %{ $PID_CB{0} || {} });	1559	values %{ $PID_CB{0} || {} };
899	}
900
901	undef $PID_IDLE;
902	}	1560	}
903		1561
904	sub _sigchld {	1562	sub _sigchld {
905	# make sure we deliver these changes "synchronous" with the event loop.	1563	my $pid;
906	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1564
907	undef $CHLD_DELAY_W;	1565	AnyEvent->_emit_childstatus ($pid, $?)
908	&_child_wait;	1566	while ($pid = waitpid -1, $WNOHANG) > 0;
909	});
910	}	1567	}
911		1568
912	sub child {	1569	sub child {
913	my (undef, %arg) = @_;	1570	my (undef, %arg) = @_;
914		1571
915	defined (my $pid = $arg{pid} + 0)	1572	defined (my $pid = $arg{pid} + 0)
916	or Carp::croak "required option 'pid' is missing";	1573	or Carp::croak "required option 'pid' is missing";
917		1574
918	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1575	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
919		1576
920	unless ($WNOHANG) {	1577	# WNOHANG is almost cetrainly 1 everywhere
921	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1578	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
922	}	1579	? 1
		1580	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
923		1581
924	unless ($CHLD_W) {	1582	unless ($CHLD_W) {
925	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1583	$CHLD_W = AE::signal CHLD => \&_sigchld;
926	# child could be a zombie already, so make at least one round	1584	# child could be a zombie already, so make at least one round
927	&_sigchld;	1585	&_sigchld;
928	}	1586	}
929		1587
930	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1588	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
931	}	1589	}
932		1590
933	sub AnyEvent::Base::Child::DESTROY {	1591	sub AnyEvent::Base::child::DESTROY {
934	my ($pid, $cb) = @{$_[0]};	1592	my ($pid, $cb) = @{$_[0]};
935		1593
936	delete $PID_CB{$pid}{$cb};	1594	delete $PID_CB{$pid}{$cb};
937	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1595	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
938		1596
939	undef $CHLD_W unless keys %PID_CB;	1597	undef $CHLD_W unless keys %PID_CB;
940	}	1598	}
941		1599
		1600	# idle emulation is done by simply using a timer, regardless
		1601	# of whether the process is idle or not, and not letting
		1602	# the callback use more than 50% of the time.
		1603	sub idle {
		1604	my (undef, %arg) = @_;
		1605
		1606	my ($cb, $w, $rcb) = $arg{cb};
		1607
		1608	$rcb = sub {
		1609	if ($cb) {
		1610	$w = _time;
		1611	&$cb;
		1612	$w = _time - $w;
		1613
		1614	# never use more then 50% of the time for the idle watcher,
		1615	# within some limits
		1616	$w = 0.0001 if $w < 0.0001;
		1617	$w = 5 if $w > 5;
		1618
		1619	$w = AE::timer $w, 0, $rcb;
		1620	} else {
		1621	# clean up...
		1622	undef $w;
		1623	undef $rcb;
		1624	}
		1625	};
		1626
		1627	$w = AE::timer 0.05, 0, $rcb;
		1628
		1629	bless \\$cb, "AnyEvent::Base::idle"
		1630	}
		1631
		1632	sub AnyEvent::Base::idle::DESTROY {
		1633	undef $${$_[0]};
		1634	}
		1635
942	package AnyEvent::CondVar;	1636	package AnyEvent::CondVar;
943		1637
944	our @ISA = AnyEvent::CondVar::Base::;	1638	our @ISA = AnyEvent::CondVar::Base::;
945		1639
946	package AnyEvent::CondVar::Base;	1640	package AnyEvent::CondVar::Base;
947		1641
948	use overload	1642	#use overload
949	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1643	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
950	fallback => 1;	1644	# fallback => 1;
		1645
		1646	# save 300+ kilobytes by dirtily hardcoding overloading
		1647	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1648	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1649	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1650	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1651
		1652	our $WAITING;
951		1653
952	sub _send {	1654	sub _send {
953	# nop	1655	# nop
954	}	1656	}
955		1657
…		…
968	sub ready {	1670	sub ready {
969	$_[0]{_ae_sent}	1671	$_[0]{_ae_sent}
970	}	1672	}
971		1673
972	sub _wait {	1674	sub _wait {
		1675	$WAITING
		1676	and !$_[0]{_ae_sent}
		1677	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1678
		1679	local $WAITING = 1;
973	AnyEvent->one_event while !$_[0]{_ae_sent};	1680	AnyEvent->one_event while !$_[0]{_ae_sent};
974	}	1681	}
975		1682
976	sub recv {	1683	sub recv {
977	$_[0]->_wait;	1684	$_[0]->_wait;
…		…
979	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1686	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
980	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1687	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
981	}	1688	}
982		1689
983	sub cb {	1690	sub cb {
984	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1691	my $cv = shift;
		1692
		1693	@_
		1694	and $cv->{_ae_cb} = shift
		1695	and $cv->{_ae_sent}
		1696	and (delete $cv->{_ae_cb})->($cv);
		1697
985	$_[0]{_ae_cb}	1698	$cv->{_ae_cb}
986	}	1699	}
987		1700
988	sub begin {	1701	sub begin {
989	++$_[0]{_ae_counter};	1702	++$_[0]{_ae_counter};
990	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1703	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
…		…
996	}	1709	}
997		1710
998	# undocumented/compatibility with pre-3.4	1711	# undocumented/compatibility with pre-3.4
999	*broadcast = \&send;	1712	*broadcast = \&send;
1000	*wait = \&_wait;	1713	*wait = \&_wait;
		1714
		1715	=head1 ERROR AND EXCEPTION HANDLING
		1716
		1717	In general, AnyEvent does not do any error handling - it relies on the
		1718	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1719	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1720	checking of all AnyEvent methods, however, which is highly useful during
		1721	development.
		1722
		1723	As for exception handling (i.e. runtime errors and exceptions thrown while
		1724	executing a callback), this is not only highly event-loop specific, but
		1725	also not in any way wrapped by this module, as this is the job of the main
		1726	program.
		1727
		1728	The pure perl event loop simply re-throws the exception (usually
		1729	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1730	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1731	so on.
		1732
		1733	=head1 ENVIRONMENT VARIABLES
		1734
		1735	The following environment variables are used by this module or its
		1736	submodules.
		1737
		1738	Note that AnyEvent will remove I<all> environment variables starting with
		1739	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1740	enabled.
		1741
		1742	=over 4
		1743
		1744	=item C<PERL_ANYEVENT_VERBOSE>
		1745
		1746	By default, AnyEvent will be completely silent except in fatal
		1747	conditions. You can set this environment variable to make AnyEvent more
		1748	talkative.
		1749
		1750	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1751	conditions, such as not being able to load the event model specified by
		1752	C<PERL_ANYEVENT_MODEL>.
		1753
		1754	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1755	model it chooses.
		1756
		1757	When set to C<8> or higher, then AnyEvent will report extra information on
		1758	which optional modules it loads and how it implements certain features.
		1759
		1760	=item C<PERL_ANYEVENT_STRICT>
		1761
		1762	AnyEvent does not do much argument checking by default, as thorough
		1763	argument checking is very costly. Setting this variable to a true value
		1764	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1765	check the arguments passed to most method calls. If it finds any problems,
		1766	it will croak.
		1767
		1768	In other words, enables "strict" mode.
		1769
		1770	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1771	>>, it is definitely recommended to keep it off in production. Keeping
		1772	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1773	can be very useful, however.
		1774
		1775	=item C<PERL_ANYEVENT_MODEL>
		1776
		1777	This can be used to specify the event model to be used by AnyEvent, before
		1778	auto detection and -probing kicks in. It must be a string consisting
		1779	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1780	and the resulting module name is loaded and if the load was successful,
		1781	used as event model. If it fails to load AnyEvent will proceed with
		1782	auto detection and -probing.
		1783
		1784	This functionality might change in future versions.
		1785
		1786	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1787	could start your program like this:
		1788
		1789	PERL_ANYEVENT_MODEL=Perl perl ...
		1790
		1791	=item C<PERL_ANYEVENT_PROTOCOLS>
		1792
		1793	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1794	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1795	of auto probing).
		1796
		1797	Must be set to a comma-separated list of protocols or address families,
		1798	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1799	used, and preference will be given to protocols mentioned earlier in the
		1800	list.
		1801
		1802	This variable can effectively be used for denial-of-service attacks
		1803	against local programs (e.g. when setuid), although the impact is likely
		1804	small, as the program has to handle conenction and other failures anyways.
		1805
		1806	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1807	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1808	- only support IPv4, never try to resolve or contact IPv6
		1809	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1810	IPv6, but prefer IPv6 over IPv4.
		1811
		1812	=item C<PERL_ANYEVENT_EDNS0>
		1813
		1814	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1815	for DNS. This extension is generally useful to reduce DNS traffic, but
		1816	some (broken) firewalls drop such DNS packets, which is why it is off by
		1817	default.
		1818
		1819	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1820	EDNS0 in its DNS requests.
		1821
		1822	=item C<PERL_ANYEVENT_MAX_FORKS>
		1823
		1824	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1825	will create in parallel.
		1826
		1827	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1828
		1829	The default value for the C<max_outstanding> parameter for the default DNS
		1830	resolver - this is the maximum number of parallel DNS requests that are
		1831	sent to the DNS server.
		1832
		1833	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1834
		1835	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1836	configuration) in the default resolver. When set to the empty string, no
		1837	default config will be used.
		1838
		1839	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1840
		1841	When neither C<ca_file> nor C<ca_path> was specified during
		1842	L<AnyEvent::TLS> context creation, and either of these environment
		1843	variables exist, they will be used to specify CA certificate locations
		1844	instead of a system-dependent default.
		1845
		1846	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1847
		1848	When these are set to C<1>, then the respective modules are not
		1849	loaded. Mostly good for testing AnyEvent itself.
		1850
		1851	=back
1001		1852
1002	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1853	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1003		1854
1004	This is an advanced topic that you do not normally need to use AnyEvent in	1855	This is an advanced topic that you do not normally need to use AnyEvent in
1005	a module. This section is only of use to event loop authors who want to	1856	a module. This section is only of use to event loop authors who want to
…		…
1039		1890
1040	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1891	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1041	condition variables: code blocking while waiting for a condition will	1892	condition variables: code blocking while waiting for a condition will
1042	C<die>. This still works with most modules/usages, and blocking calls must	1893	C<die>. This still works with most modules/usages, and blocking calls must
1043	not be done in an interactive application, so it makes sense.	1894	not be done in an interactive application, so it makes sense.
1044
1045	=head1 ENVIRONMENT VARIABLES
1046
1047	The following environment variables are used by this module:
1048
1049	=over 4
1050
1051	=item C<PERL_ANYEVENT_VERBOSE>
1052
1053	By default, AnyEvent will be completely silent except in fatal
1054	conditions. You can set this environment variable to make AnyEvent more
1055	talkative.
1056
1057	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1058	conditions, such as not being able to load the event model specified by
1059	C<PERL_ANYEVENT_MODEL>.
1060
1061	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1062	model it chooses.
1063
1064	=item C<PERL_ANYEVENT_MODEL>
1065
1066	This can be used to specify the event model to be used by AnyEvent, before
1067	auto detection and -probing kicks in. It must be a string consisting
1068	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1069	and the resulting module name is loaded and if the load was successful,
1070	used as event model. If it fails to load AnyEvent will proceed with
1071	auto detection and -probing.
1072
1073	This functionality might change in future versions.
1074
1075	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1076	could start your program like this:
1077
1078	PERL_ANYEVENT_MODEL=Perl perl ...
1079
1080	=item C<PERL_ANYEVENT_PROTOCOLS>
1081
1082	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1083	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1084	of auto probing).
1085
1086	Must be set to a comma-separated list of protocols or address families,
1087	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1088	used, and preference will be given to protocols mentioned earlier in the
1089	list.
1090
1091	This variable can effectively be used for denial-of-service attacks
1092	against local programs (e.g. when setuid), although the impact is likely
1093	small, as the program has to handle connection errors already-
1094
1095	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1096	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1097	- only support IPv4, never try to resolve or contact IPv6
1098	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1099	IPv6, but prefer IPv6 over IPv4.
1100
1101	=item C<PERL_ANYEVENT_EDNS0>
1102
1103	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1104	for DNS. This extension is generally useful to reduce DNS traffic, but
1105	some (broken) firewalls drop such DNS packets, which is why it is off by
1106	default.
1107
1108	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1109	EDNS0 in its DNS requests.
1110
1111	=back
1112		1895
1113	=head1 EXAMPLE PROGRAM	1896	=head1 EXAMPLE PROGRAM
1114		1897
1115	The following program uses an I/O watcher to read data from STDIN, a timer	1898	The following program uses an I/O watcher to read data from STDIN, a timer
1116	to display a message once per second, and a condition variable to quit the	1899	to display a message once per second, and a condition variable to quit the
…		…
1279	through AnyEvent. The benchmark creates a lot of timers (with a zero	2062	through AnyEvent. The benchmark creates a lot of timers (with a zero
1280	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2063	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1281	which it is), lets them fire exactly once and destroys them again.	2064	which it is), lets them fire exactly once and destroys them again.
1282		2065
1283	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2066	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1284	distribution.	2067	distribution. It uses the L<AE> interface, which makes a real difference
		2068	for the EV and Perl backends only.
1285		2069
1286	=head3 Explanation of the columns	2070	=head3 Explanation of the columns
1287		2071
1288	I<watcher> is the number of event watchers created/destroyed. Since	2072	I<watcher> is the number of event watchers created/destroyed. Since
1289	different event models feature vastly different performances, each event	2073	different event models feature vastly different performances, each event
…		…
1310	watcher.	2094	watcher.
1311		2095
1312	=head3 Results	2096	=head3 Results
1313		2097
1314	name watchers bytes create invoke destroy comment	2098	name watchers bytes create invoke destroy comment
1315	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2099	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1316	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2100	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1317	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2101	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1318	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2102	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1319	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2103	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1320	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2104	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2105	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2106	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1321	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2107	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1322	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2108	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1323	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2109	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1324	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2110	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1325		2111
1326	=head3 Discussion	2112	=head3 Discussion
1327		2113
1328	The benchmark does I<not> measure scalability of the event loop very	2114	The benchmark does I<not> measure scalability of the event loop very
1329	well. For example, a select-based event loop (such as the pure perl one)	2115	well. For example, a select-based event loop (such as the pure perl one)
…		…
1341	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2127	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1342	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2128	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1343	cycles with POE.	2129	cycles with POE.
1344		2130
1345	C<EV> is the sole leader regarding speed and memory use, which are both	2131	C<EV> is the sole leader regarding speed and memory use, which are both
1346	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2132	maximal/minimal, respectively. When using the L<AE> API there is zero
		2133	overhead (when going through the AnyEvent API create is about 5-6 times
		2134	slower, with other times being equal, so still uses far less memory than
1347	far less memory than any other event loop and is still faster than Event	2135	any other event loop and is still faster than Event natively).
1348	natively.
1349		2136
1350	The pure perl implementation is hit in a few sweet spots (both the	2137	The pure perl implementation is hit in a few sweet spots (both the
1351	constant timeout and the use of a single fd hit optimisations in the perl	2138	constant timeout and the use of a single fd hit optimisations in the perl
1352	interpreter and the backend itself). Nevertheless this shows that it	2139	interpreter and the backend itself). Nevertheless this shows that it
1353	adds very little overhead in itself. Like any select-based backend its	2140	adds very little overhead in itself. Like any select-based backend its
1354	performance becomes really bad with lots of file descriptors (and few of	2141	performance becomes really bad with lots of file descriptors (and few of
1355	them active), of course, but this was not subject of this benchmark.	2142	them active), of course, but this was not subject of this benchmark.
1356		2143
1357	The C<Event> module has a relatively high setup and callback invocation	2144	The C<Event> module has a relatively high setup and callback invocation
1358	cost, but overall scores in on the third place.	2145	cost, but overall scores in on the third place.
		2146
		2147	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2148	when using its pure perl backend.
1359		2149
1360	C<Glib>'s memory usage is quite a bit higher, but it features a	2150	C<Glib>'s memory usage is quite a bit higher, but it features a
1361	faster callback invocation and overall ends up in the same class as	2151	faster callback invocation and overall ends up in the same class as
1362	C<Event>. However, Glib scales extremely badly, doubling the number of	2152	C<Event>. However, Glib scales extremely badly, doubling the number of
1363	watchers increases the processing time by more than a factor of four,	2153	watchers increases the processing time by more than a factor of four,
…		…
1424	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100	2214	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1425	(1%) are active. This mirrors the activity of large servers with many	2215	(1%) are active. This mirrors the activity of large servers with many
1426	connections, most of which are idle at any one point in time.	2216	connections, most of which are idle at any one point in time.
1427		2217
1428	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2218	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1429	distribution.	2219	distribution. It uses the L<AE> interface, which makes a real difference
		2220	for the EV and Perl backends only.
1430		2221
1431	=head3 Explanation of the columns	2222	=head3 Explanation of the columns
1432		2223
1433	I<sockets> is the number of sockets, and twice the number of "servers" (as	2224	I<sockets> is the number of sockets, and twice the number of "servers" (as
1434	each server has a read and write socket end).	2225	each server has a read and write socket end).
…		…
1441	it to another server. This includes deleting the old timeout and creating	2232	it to another server. This includes deleting the old timeout and creating
1442	a new one that moves the timeout into the future.	2233	a new one that moves the timeout into the future.
1443		2234
1444	=head3 Results	2235	=head3 Results
1445		2236
1446	name sockets create request	2237	name sockets create request
1447	EV 20000 69.01 11.16	2238	EV 20000 62.66 7.99
1448	Perl 20000 73.32 35.87	2239	Perl 20000 68.32 32.64
1449	Event 20000 212.62 257.32	2240	IOAsync 20000 174.06 101.15 epoll
1450	Glib 20000 651.16 1896.30	2241	IOAsync 20000 174.67 610.84 poll
		2242	Event 20000 202.69 242.91
		2243	Glib 20000 557.01 1689.52
1451	POE 20000 349.67 12317.24 uses POE::Loop::Event	2244	POE 20000 341.54 12086.32 uses POE::Loop::Event
1452		2245
1453	=head3 Discussion	2246	=head3 Discussion
1454		2247
1455	This benchmark I<does> measure scalability and overall performance of the	2248	This benchmark I<does> measure scalability and overall performance of the
1456	particular event loop.	2249	particular event loop.
…		…
1458	EV is again fastest. Since it is using epoll on my system, the setup time	2251	EV is again fastest. Since it is using epoll on my system, the setup time
1459	is relatively high, though.	2252	is relatively high, though.
1460		2253
1461	Perl surprisingly comes second. It is much faster than the C-based event	2254	Perl surprisingly comes second. It is much faster than the C-based event
1462	loops Event and Glib.	2255	loops Event and Glib.
		2256
		2257	IO::Async performs very well when using its epoll backend, and still quite
		2258	good compared to Glib when using its pure perl backend.
1463		2259
1464	Event suffers from high setup time as well (look at its code and you will	2260	Event suffers from high setup time as well (look at its code and you will
1465	understand why). Callback invocation also has a high overhead compared to	2261	understand why). Callback invocation also has a high overhead compared to
1466	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2262	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1467	uses select or poll in basically all documented configurations.	2263	uses select or poll in basically all documented configurations.
…		…
1530	=item * C-based event loops perform very well with small number of	2326	=item * C-based event loops perform very well with small number of
1531	watchers, as the management overhead dominates.	2327	watchers, as the management overhead dominates.
1532		2328
1533	=back	2329	=back
1534		2330
		2331	=head2 THE IO::Lambda BENCHMARK
		2332
		2333	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2334	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2335	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2336	shouldn't come as a surprise to anybody). As such, the benchmark is
		2337	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2338	very optimal. But how would AnyEvent compare when used without the extra
		2339	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2340
		2341	The benchmark itself creates an echo-server, and then, for 500 times,
		2342	connects to the echo server, sends a line, waits for the reply, and then
		2343	creates the next connection. This is a rather bad benchmark, as it doesn't
		2344	test the efficiency of the framework or much non-blocking I/O, but it is a
		2345	benchmark nevertheless.
		2346
		2347	name runtime
		2348	Lambda/select 0.330 sec
		2349	+ optimized 0.122 sec
		2350	Lambda/AnyEvent 0.327 sec
		2351	+ optimized 0.138 sec
		2352	Raw sockets/select 0.077 sec
		2353	POE/select, components 0.662 sec
		2354	POE/select, raw sockets 0.226 sec
		2355	POE/select, optimized 0.404 sec
		2356
		2357	AnyEvent/select/nb 0.085 sec
		2358	AnyEvent/EV/nb 0.068 sec
		2359	+state machine 0.134 sec
		2360
		2361	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2362	benchmarks actually make blocking connects and use 100% blocking I/O,
		2363	defeating the purpose of an event-based solution. All of the newly
		2364	written AnyEvent benchmarks use 100% non-blocking connects (using
		2365	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2366	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2367	generally require a lot more bookkeeping and event handling than blocking
		2368	connects (which involve a single syscall only).
		2369
		2370	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2371	offers similar expressive power as POE and IO::Lambda, using conventional
		2372	Perl syntax. This means that both the echo server and the client are 100%
		2373	non-blocking, further placing it at a disadvantage.
		2374
		2375	As you can see, the AnyEvent + EV combination even beats the
		2376	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2377	backend easily beats IO::Lambda and POE.
		2378
		2379	And even the 100% non-blocking version written using the high-level (and
		2380	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2381	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2382	in a non-blocking way.
		2383
		2384	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2385	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2386	part of the IO::lambda distribution and were used without any changes.
		2387
		2388
		2389	=head1 SIGNALS
		2390
		2391	AnyEvent currently installs handlers for these signals:
		2392
		2393	=over 4
		2394
		2395	=item SIGCHLD
		2396
		2397	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2398	emulation for event loops that do not support them natively. Also, some
		2399	event loops install a similar handler.
		2400
		2401	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2402	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2403
		2404	=item SIGPIPE
		2405
		2406	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2407	when AnyEvent gets loaded.
		2408
		2409	The rationale for this is that AnyEvent users usually do not really depend
		2410	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2411	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2412	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2413	some random socket.
		2414
		2415	The rationale for installing a no-op handler as opposed to ignoring it is
		2416	that this way, the handler will be restored to defaults on exec.
		2417
		2418	Feel free to install your own handler, or reset it to defaults.
		2419
		2420	=back
		2421
		2422	=cut
		2423
		2424	undef $SIG{CHLD}
		2425	if $SIG{CHLD} eq 'IGNORE';
		2426
		2427	$SIG{PIPE} = sub { }
		2428	unless defined $SIG{PIPE};
		2429
		2430	=head1 RECOMMENDED/OPTIONAL MODULES
		2431
		2432	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2433	it's built-in modules) are required to use it.
		2434
		2435	That does not mean that AnyEvent won't take advantage of some additional
		2436	modules if they are installed.
		2437
		2438	This section epxlains which additional modules will be used, and how they
		2439	affect AnyEvent's operetion.
		2440
		2441	=over 4
		2442
		2443	=item L<Async::Interrupt>
		2444
		2445	This slightly arcane module is used to implement fast signal handling: To
		2446	my knowledge, there is no way to do completely race-free and quick
		2447	signal handling in pure perl. To ensure that signals still get
		2448	delivered, AnyEvent will start an interval timer to wake up perl (and
		2449	catch the signals) with some delay (default is 10 seconds, look for
		2450	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2451
		2452	If this module is available, then it will be used to implement signal
		2453	catching, which means that signals will not be delayed, and the event loop
		2454	will not be interrupted regularly, which is more efficient (And good for
		2455	battery life on laptops).
		2456
		2457	This affects not just the pure-perl event loop, but also other event loops
		2458	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2459
		2460	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2461	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2462	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2463	does nothing for those backends.
		2464
		2465	=item L<EV>
		2466
		2467	This module isn't really "optional", as it is simply one of the backend
		2468	event loops that AnyEvent can use. However, it is simply the best event
		2469	loop available in terms of features, speed and stability: It supports
		2470	the AnyEvent API optimally, implements all the watcher types in XS, does
		2471	automatic timer adjustments even when no monotonic clock is available,
		2472	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2473	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2474	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2475
		2476	=item L<Guard>
		2477
		2478	The guard module, when used, will be used to implement
		2479	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2480	lot less memory), but otherwise doesn't affect guard operation much. It is
		2481	purely used for performance.
		2482
		2483	=item L<JSON> and L<JSON::XS>
		2484
		2485	This module is required when you want to read or write JSON data via
		2486	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2487	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2488
		2489	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2490	installed.
		2491
		2492	=item L<Net::SSLeay>
		2493
		2494	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2495	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2496	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2497
		2498	=item L<Time::HiRes>
		2499
		2500	This module is part of perl since release 5.008. It will be used when the
		2501	chosen event library does not come with a timing source on it's own. The
		2502	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2503	try to use a monotonic clock for timing stability.
		2504
		2505	=back
		2506
1535		2507
1536	=head1 FORK	2508	=head1 FORK
1537		2509
1538	Most event libraries are not fork-safe. The ones who are usually are	2510	Most event libraries are not fork-safe. The ones who are usually are
1539	because they rely on inefficient but fork-safe C<select> or C<poll>	2511	because they rely on inefficient but fork-safe C<select> or C<poll>
1540	calls. Only L<EV> is fully fork-aware.	2512	calls. Only L<EV> is fully fork-aware.
1541		2513
1542	If you have to fork, you must either do so I<before> creating your first	2514	If you have to fork, you must either do so I<before> creating your first
1543	watcher OR you must not use AnyEvent at all in the child.	2515	watcher OR you must not use AnyEvent at all in the child OR you must do
		2516	something completely out of the scope of AnyEvent.
1544		2517
1545		2518
1546	=head1 SECURITY CONSIDERATIONS	2519	=head1 SECURITY CONSIDERATIONS
1547		2520
1548	AnyEvent can be forced to load any event model via	2521	AnyEvent can be forced to load any event model via
…		…
1553	specified in the variable.	2526	specified in the variable.
1554		2527
1555	You can make AnyEvent completely ignore this variable by deleting it	2528	You can make AnyEvent completely ignore this variable by deleting it
1556	before the first watcher gets created, e.g. with a C<BEGIN> block:	2529	before the first watcher gets created, e.g. with a C<BEGIN> block:
1557		2530
1558	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2531	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1559		2532
1560	use AnyEvent;	2533	use AnyEvent;
1561		2534
1562	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2535	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1563	be used to probe what backend is used and gain other information (which is	2536	be used to probe what backend is used and gain other information (which is
1564	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2537	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2538	$ENV{PERL_ANYEVENT_STRICT}.
		2539
		2540	Note that AnyEvent will remove I<all> environment variables starting with
		2541	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2542	enabled.
		2543
		2544
		2545	=head1 BUGS
		2546
		2547	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2548	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2549	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2550	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2551	pronounced).
1565		2552
1566		2553
1567	=head1 SEE ALSO	2554	=head1 SEE ALSO
1568		2555
1569	Utility functions: L<AnyEvent::Util>.	2556	Utility functions: L<AnyEvent::Util>.
…		…
1572	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2559	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1573		2560
1574	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2561	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1575	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2562	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1576	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2563	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1577	L<AnyEvent::Impl::POE>.	2564	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1578		2565
1579	Non-blocking file handles, sockets, TCP clients and	2566	Non-blocking file handles, sockets, TCP clients and
1580	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2567	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1581		2568
1582	Asynchronous DNS: L<AnyEvent::DNS>.	2569	Asynchronous DNS: L<AnyEvent::DNS>.
1583		2570
1584	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2571	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2572	L<Coro::Event>,
1585		2573
1586	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2574	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2575	L<AnyEvent::HTTP>.
1587		2576
1588		2577
1589	=head1 AUTHOR	2578	=head1 AUTHOR
1590		2579
1591	Marc Lehmann <schmorp@schmorp.de>	2580	Marc Lehmann <schmorp@schmorp.de>
1592	http://home.schmorp.de/	2581	http://home.schmorp.de/
1593		2582
1594	=cut	2583	=cut
1595		2584
1596	1	2585	1
1597		2586

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