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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 { ... });
12		14
		15	# one-shot or repeating timers
13	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
14	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
15		18
16	print AnyEvent->now; # prints current event loop time	19	print AnyEvent->now; # prints current event loop time
17	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
18		21
		22	# POSIX signal
19	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });	23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
20		24
		25	# child process exit
21	my $w = AnyEvent->child (pid => $pid, cb => sub {	26	my $w = AnyEvent->child (pid => $pid, cb => sub {
22	my ($pid, $status) = @_;	27	my ($pid, $status) = @_;
23	...	28	...
24	});	29	});
		30
		31	# called when event loop idle (if applicable)
		32	my $w = AnyEvent->idle (cb => sub { ... });
25		33
26	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
27	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
28	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
29	# use a condvar in callback mode:	37	# use a condvar in callback mode:
…		…
32	=head1 INTRODUCTION/TUTORIAL	40	=head1 INTRODUCTION/TUTORIAL
33		41
34	This manpage is mainly a reference manual. If you are interested	42	This manpage is mainly a reference manual. If you are interested
35	in a tutorial or some gentle introduction, have a look at the	43	in a tutorial or some gentle introduction, have a look at the
36	L<AnyEvent::Intro> manpage.	44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
37		53
38	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
39		55
40	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
41	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
…		…
137	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
138	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
139	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
140	is in control).	156	is in control).
141		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> 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
142	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
143	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
144	to it).	166	to it).
145		167
146	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.
…		…
159	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
160	declared.	182	declared.
161		183
162	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
163		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
164	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
165	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
166		194
167	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for events	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
168	(AnyEvent might or might not keep a reference to this file handle). C<poll>	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
169	must be a string that is either C<r> or C<w>, which creates a watcher	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
170	waiting for "r"eadable or "w"ritable events, respectively. C<cb> is the	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
171	callback to invoke each time the file handle becomes ready.	205	C<cb> is the callback to invoke each time the file handle becomes ready.
172		206
173	Although the callback might get passed parameters, their value and	207	Although the callback might get passed parameters, their value and
174	presence is undefined and you cannot rely on them. Portable AnyEvent	208	presence is undefined and you cannot rely on them. Portable AnyEvent
175	callbacks cannot use arguments passed to I/O watcher callbacks.	209	callbacks cannot use arguments passed to I/O watcher callbacks.
176		210
…		…
191	undef $w;	225	undef $w;
192	});	226	});
193		227
194	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
195		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
196	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 >>
197	method with the following mandatory arguments:	239	method with the following mandatory arguments:
198		240
199	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
200	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
…		…
308	In either case, if you care (and in most cases, you don't), then you	350	In either case, if you care (and in most cases, you don't), then you
309	can get whatever behaviour you want with any event loop, by taking the	351	can get whatever behaviour you want with any event loop, by taking the
310	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
311	account.	353	account.
312		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
313	=back	370	=back
314		371
315	=head2 SIGNAL WATCHERS	372	=head2 SIGNAL WATCHERS
		373
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
316		375
317	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
318	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl	377	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
319	callback to be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
320		379
…		…
326	invocation, and callback invocation will be synchronous. Synchronous means	385	invocation, and callback invocation will be synchronous. Synchronous means
327	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,
328	but it is guaranteed not to interrupt any other callbacks.	387	but it is guaranteed not to interrupt any other callbacks.
329		388
330	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
331	between multiple watchers.	390	between multiple watchers, and AnyEvent will ensure that signals will not
		391	interrupt your program at bad times.
332		392
333	This watcher might use C<%SIG>, so programs overwriting those signals	393	This watcher might use C<%SIG> (depending on the event loop used),
334	directly will likely not work correctly.	394	so programs overwriting those signals directly will likely not work
		395	correctly.
335		396
336	Example: exit on SIGINT	397	Example: exit on SIGINT
337		398
338	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
339		400
		401	=head3 Signal Races, Delays and Workarounds
		402
		403	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		404	callbacks to signals in a generic way, which is a pity, as you cannot
		405	do race-free signal handling in perl, requiring C libraries for
		406	this. AnyEvent will try to do it's best, which means in some cases,
		407	signals will be delayed. The maximum time a signal might be delayed is
		408	specified in C<$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
340	=head2 CHILD PROCESS WATCHERS	421	=head2 CHILD PROCESS WATCHERS
341		422
		423	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		424
342	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.
343		426
344	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,
345	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
346	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
347	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
348	and exit status (as returned by waitpid), so unlike other watcher types,	431	(stopped/continued).
349	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).
350		441
351	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
352	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
353	have exited already (and no SIGCHLD will be sent anymore).	444	have exited already (and no SIGCHLD will be sent anymore).
354		445
355	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
356	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
357	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.
358		452
359	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
360	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
361	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.
362		461
363	Example: fork a process and wait for it	462	Example: fork a process and wait for it
364		463
365	my $done = AnyEvent->condvar;	464	my $done = AnyEvent->condvar;
366		465
…		…
376	);	475	);
377		476
378	# do something else, then wait for process exit	477	# do something else, then wait for process exit
379	$done->recv;	478	$done->recv;
380		479
		480	=head2 IDLE WATCHERS
		481
		482	$w = AnyEvent->idle (cb => <callback>);
		483
		484	Sometimes there is a need to do something, but it is not so important
		485	to do it instantly, but only when there is nothing better to do. This
		486	"nothing better to do" is usually defined to be "no other events need
		487	attention by the event loop".
		488
		489	Idle watchers ideally get invoked when the event loop has nothing
		490	better to do, just before it would block the process to wait for new
		491	events. Instead of blocking, the idle watcher is invoked.
		492
		493	Most event loops unfortunately do not really support idle watchers (only
		494	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		495	will simply call the callback "from time to time".
		496
		497	Example: read lines from STDIN, but only process them when the
		498	program is otherwise idle:
		499
		500	my @lines; # read data
		501	my $idle_w;
		502	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		503	push @lines, scalar <STDIN>;
		504
		505	# start an idle watcher, if not already done
		506	$idle_w ||= AnyEvent->idle (cb => sub {
		507	# handle only one line, when there are lines left
		508	if (my $line = shift @lines) {
		509	print "handled when idle: $line";
		510	} else {
		511	# otherwise disable the idle watcher again
		512	undef $idle_w;
		513	}
		514	});
		515	});
		516
381	=head2 CONDITION VARIABLES	517	=head2 CONDITION VARIABLES
		518
		519	$cv = AnyEvent->condvar;
		520
		521	$cv->send (<list>);
		522	my @res = $cv->recv;
382		523
383	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
384	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
385	will actively watch for new events and call your callbacks.	526	will actively watch for new events and call your callbacks.
386		527
387	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
388	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).
389		530
390	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
391	because they represent a condition that must become true.	532	because they represent a condition that must become true.
392		533
		534	Now is probably a good time to look at the examples further below.
		535
393	Condition variables can be created by calling the C<< AnyEvent->condvar	536	Condition variables can be created by calling the C<< AnyEvent->condvar
394	>> method, usually without arguments. The only argument pair allowed is	537	>> method, usually without arguments. The only argument pair allowed is
395
396	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
397	becomes true, with the condition variable as the first argument (but not	539	becomes true, with the condition variable as the first argument (but not
398	the results).	540	the results).
399		541
400	After creation, the condition variable is "false" until it becomes "true"	542	After creation, the condition variable is "false" until it becomes "true"
…		…
405	Condition variables are similar to callbacks, except that you can	547	Condition variables are similar to callbacks, except that you can
406	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
407	in time where multiple outstanding events have been processed. And yet	549	in time where multiple outstanding events have been processed. And yet
408	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
409	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
410	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.
411		554
412	Condition variables are very useful to signal that something has finished,	555	Condition variables are very useful to signal that something has finished,
413	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,
414	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
415	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
…		…
449	after => 1,	592	after => 1,
450	cb => sub { $result_ready->send },	593	cb => sub { $result_ready->send },
451	);	594	);
452		595
453	# this "blocks" (while handling events) till the callback	596	# this "blocks" (while handling events) till the callback
454	# calls send	597	# calls -<send
455	$result_ready->recv;	598	$result_ready->recv;
456		599
457	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
458	condition variables are also code references.	601	variables are also callable directly.
459		602
460	my $done = AnyEvent->condvar;	603	my $done = AnyEvent->condvar;
461	my $delay = AnyEvent->timer (after => 5, cb => $done);	604	my $delay = AnyEvent->timer (after => 5, cb => $done);
462	$done->recv;	605	$done->recv;
463		606
…		…
469		612
470	...	613	...
471		614
472	my @info = $couchdb->info->recv;	615	my @info = $couchdb->info->recv;
473		616
474	And this is how you would just ste a callback to be called whenever the	617	And this is how you would just set a callback to be called whenever the
475	results are available:	618	results are available:
476		619
477	$couchdb->info->cb (sub {	620	$couchdb->info->cb (sub {
478	my @info = $_[0]->recv;	621	my @info = $_[0]->recv;
479	});	622	});
…		…
497	immediately from within send.	640	immediately from within send.
498		641
499	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
500	future C<< ->recv >> calls.	643	future C<< ->recv >> calls.
501		644
502	Condition variables are overloaded so one can call them directly	645	Condition variables are overloaded so one can call them directly (as if
503	(as a code reference). Calling them directly is the same as calling	646	they were a code reference). Calling them directly is the same as calling
504	C<send>. Note, however, that many C-based event loops do not handle	647	C<send>.
505	overloading, so as tempting as it may be, passing a condition variable
506	instead of a callback does not work. Both the pure perl and EV loops
507	support overloading, however, as well as all functions that use perl to
508	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
509	example).
510		648
511	=item $cv->croak ($error)	649	=item $cv->croak ($error)
512		650
513	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
514	C<Carp::croak> with the given error message/object/scalar.	652	C<Carp::croak> with the given error message/object/scalar.
515		653
516	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
517	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.
518		660
519	=item $cv->begin ([group callback])	661	=item $cv->begin ([group callback])
520		662
521	=item $cv->end	663	=item $cv->end
522
523	These two methods are EXPERIMENTAL and MIGHT CHANGE.
524		664
525	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
526	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
527	to use a condition variable for the whole process.	667	to use a condition variable for the whole process.
528		668
529	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
530	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
531	>>, 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
532	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
533	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.
534		675
535	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:
536		683
537	my $cv = AnyEvent->condvar;	684	my $cv = AnyEvent->condvar;
538		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
539	my %result;	710	my %result;
540	$cv->begin (sub { $cv->send (\%result) });	711	$cv->begin (sub { shift->send (\%result) });
541		712
542	for my $host (@list_of_hosts) {	713	for my $host (@list_of_hosts) {
543	$cv->begin;	714	$cv->begin;
544	ping_host_then_call_callback $host, sub {	715	ping_host_then_call_callback $host, sub {
545	$result{$host} = ...;	716	$result{$host} = ...;
…		…
560	loop, which serves two important purposes: first, it sets the callback	731	loop, which serves two important purposes: first, it sets the callback
561	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
562	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
563	doesn't execute once).	734	doesn't execute once).
564		735
565	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
566	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
567	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
568	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>.
569		741
570	=back	742	=back
571		743
572	=head3 METHODS FOR CONSUMERS	744	=head3 METHODS FOR CONSUMERS
573		745
…		…
589	function will call C<croak>.	761	function will call C<croak>.
590		762
591	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,
592	in scalar context only the first one will be returned.	764	in scalar context only the first one will be returned.
593		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
594	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
595	(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
596	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
597	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
598	condition variables with some kind of request results and supporting	777	condition variables with some kind of request results and supporting
599	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,
600	while still supporting blocking waits if the caller so desires).	779	while still supporting blocking waits if the caller so desires).
601		780
602	Another reason I<never> to C<< ->recv >> in a module is that you cannot
603	sensibly have two C<< ->recv >>'s in parallel, as that would require
604	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
605	can supply.
606
607	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
608	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
609	versions and also integrates coroutines into AnyEvent, making blocking
610	C<< ->recv >> calls perfectly safe as long as they are done from another
611	coroutine (one that doesn't run the event loop).
612
613	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
614	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
615	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
616	waits otherwise.	784	waits otherwise.
617		785
…		…
623	=item $cb = $cv->cb ($cb->($cv))	791	=item $cb = $cv->cb ($cb->($cv))
624		792
625	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
626	replaces it before doing so.	794	replaces it before doing so.
627		795
628	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)
629	C<send> or C<croak> are called, with the only argument being the condition	797	"true", i.e. when C<send> or C<croak> are called (or were called), with
630	variable itself. Calling C<recv> inside the callback or at any later time	798	the only argument being the condition variable itself. Calling C<recv>
631	is guaranteed not to block.	799	inside the callback or at any later time is guaranteed not to block.
632		800
633	=back	801	=back
634		802
		803	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		804
		805	The available backend classes are (every class has its own manpage):
		806
		807	=over 4
		808
		809	=item Backends that are autoprobed when no other event loop can be found.
		810
		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.
		815
		816	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		817	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		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
		870
635	=head1 GLOBAL VARIABLES AND FUNCTIONS	871	=head1 GLOBAL VARIABLES AND FUNCTIONS
636		872
		873	These are not normally required to use AnyEvent, but can be useful to
		874	write AnyEvent extension modules.
		875
637	=over 4	876	=over 4
638		877
639	=item $AnyEvent::MODEL	878	=item $AnyEvent::MODEL
640		879
641	Contains C<undef> until the first watcher is being created. Then it	880	Contains C<undef> until the first watcher is being created, before the
		881	backend has been autodetected.
		882
642	contains the event model that is being used, which is the name of the	883	Afterwards it contains the event model that is being used, which is the
643	Perl class implementing the model. This class is usually one of the	884	name of the Perl class implementing the model. This class is usually one
644	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	885	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
645	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	886	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
646		887	will be C<urxvt::anyevent>).
647	The known classes so far are:
648
649	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
650	AnyEvent::Impl::Event based on Event, second best choice.
651	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
652	AnyEvent::Impl::Glib based on Glib, third-best choice.
653	AnyEvent::Impl::Tk based on Tk, very bad choice.
654	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
655	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
656	AnyEvent::Impl::POE based on POE, not generic enough for full support.
657
658	There is no support for WxWidgets, as WxWidgets has no support for
659	watching file handles. However, you can use WxWidgets through the
660	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
661	second, which was considered to be too horrible to even consider for
662	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
663	it's adaptor.
664
665	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
666	autodetecting them.
667		888
668	=item AnyEvent::detect	889	=item AnyEvent::detect
669		890
670	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	891	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
671	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
672	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
673	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>.
674		898
675	=item $guard = AnyEvent::post_detect { BLOCK }	899	=item $guard = AnyEvent::post_detect { BLOCK }
676		900
677	Arranges for the code block to be executed as soon as the event model is	901	Arranges for the code block to be executed as soon as the event model is
678	autodetected (or immediately if this has already happened).	902	autodetected (or immediately if this has already happened).
679		903
		904	The block will be executed I<after> the actual backend has been detected
		905	(C<$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
680	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
681	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
682	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 ||= $guard;
683		935
684	=item @AnyEvent::post_detect	936	=item @AnyEvent::post_detect
685		937
686	If there are any code references in this array (you can C<push> to it	938	If there are any code references in this array (you can C<push> to it
687	before or after loading AnyEvent), then they will called directly after	939	before or after loading AnyEvent), then they will called directly after
688	the event loop has been chosen.	940	the event loop has been chosen.
689		941
690	You should check C<$AnyEvent::MODEL> before adding to this array, though:	942	You should check C<$AnyEvent::MODEL> before adding to this array, though:
691	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
692	and the array will be ignored.	944	array will be ignored.
693		945
694	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.
695		953
696	=back	954	=back
697		955
698	=head1 WHAT TO DO IN A MODULE	956	=head1 WHAT TO DO IN A MODULE
699		957
…		…
754		1012
755		1013
756	=head1 OTHER MODULES	1014	=head1 OTHER MODULES
757		1015
758	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
759	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
760	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
761	available via CPAN.	1019	come with AnyEvent, most are available via CPAN.
762		1020
763	=over 4	1021	=over 4
764		1022
765	=item L<AnyEvent::Util>	1023	=item L<AnyEvent::Util>
766		1024
…		…
775		1033
776	=item L<AnyEvent::Handle>	1034	=item L<AnyEvent::Handle>
777		1035
778	Provide read and write buffers, manages watchers for reads and writes,	1036	Provide read and write buffers, manages watchers for reads and writes,
779	supports raw and formatted I/O, I/O queued and fully transparent and	1037	supports raw and formatted I/O, I/O queued and fully transparent and
780	non-blocking SSL/TLS.	1038	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
781		1039
782	=item L<AnyEvent::DNS>	1040	=item L<AnyEvent::DNS>
783		1041
784	Provides rich asynchronous DNS resolver capabilities.	1042	Provides rich asynchronous DNS resolver capabilities.
785		1043
…		…
813		1071
814	=item L<AnyEvent::GPSD>	1072	=item L<AnyEvent::GPSD>
815		1073
816	A non-blocking interface to gpsd, a daemon delivering GPS information.	1074	A non-blocking interface to gpsd, a daemon delivering GPS information.
817		1075
		1076	=item L<AnyEvent::IRC>
		1077
		1078	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1079
		1080	=item L<AnyEvent::XMPP>
		1081
		1082	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1083	Net::XMPP2>.
		1084
818	=item L<AnyEvent::IGS>	1085	=item L<AnyEvent::IGS>
819		1086
820	A non-blocking interface to the Internet Go Server protocol (used by	1087	A non-blocking interface to the Internet Go Server protocol (used by
821	L<App::IGS>).	1088	L<App::IGS>).
822		1089
823	=item L<Net::IRC3>
824
825	AnyEvent based IRC client module family.
826
827	=item L<Net::XMPP2>
828
829	AnyEvent based XMPP (Jabber protocol) module family.
830
831	=item L<Net::FCP>	1090	=item L<Net::FCP>
832		1091
833	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1092	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
834	of AnyEvent.	1093	of AnyEvent.
835		1094
…		…
839		1098
840	=item L<Coro>	1099	=item L<Coro>
841		1100
842	Has special support for AnyEvent via L<Coro::AnyEvent>.	1101	Has special support for AnyEvent via L<Coro::AnyEvent>.
843		1102
844	=item L<IO::Lambda>
845
846	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
847
848	=back	1103	=back
849		1104
850	=cut	1105	=cut
851		1106
852	package AnyEvent;	1107	package AnyEvent;
853		1108
		1109	# basically a tuned-down version of common::sense
		1110	sub common_sense {
854	no warnings;	1111	# no warnings
855	use strict;	1112	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1113	# use strict vars subs
		1114	$^H |= 0x00000600;
		1115	}
856		1116
		1117	BEGIN { AnyEvent::common_sense }
		1118
857	use Carp;	1119	use Carp ();
858		1120
859	our $VERSION = 4.233;	1121	our $VERSION = '5.1';
860	our $MODEL;	1122	our $MODEL;
861		1123
862	our $AUTOLOAD;	1124	our $AUTOLOAD;
863	our @ISA;	1125	our @ISA;
864		1126
865	our @REGISTRY;	1127	our @REGISTRY;
866		1128
867	our $WIN32;	1129	our $WIN32;
868		1130
		1131	our $VERBOSE;
		1132
869	BEGIN {	1133	BEGIN {
870	my $win32 = ! ! ($^O =~ /mswin32/i);	1134	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
871	eval "sub WIN32(){ $win32 }";	1135	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
872	}
873		1136
		1137	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1138	if ${^TAINT};
		1139
874	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1140	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1141
		1142	}
		1143
		1144	our $MAX_SIGNAL_LATENCY = 10;
875		1145
876	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1146	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
877		1147
878	{	1148	{
879	my $idx;	1149	my $idx;
…		…
881	for reverse split /\s*,\s*/,	1151	for reverse split /\s*,\s*/,
882	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1152	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
883	}	1153	}
884		1154
885	my @models = (	1155	my @models = (
886	[EV:: => AnyEvent::Impl::EV::],	1156	[EV:: => AnyEvent::Impl::EV:: , 1],
887	[Event:: => AnyEvent::Impl::Event::],
888	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1157	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
889	# everything below here will not be autoprobed	1158	# everything below here will not (normally) be autoprobed
890	# as the pureperl backend should work everywhere	1159	# as the pureperl backend should work everywhere
891	# and is usually faster	1160	# and is usually faster
		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
892	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles	1165	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
893	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
894	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
895	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1166	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
896	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1167	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
897	[Wx:: => AnyEvent::Impl::POE::],	1168	[Wx:: => AnyEvent::Impl::POE::],
898	[Prima:: => AnyEvent::Impl::POE::],	1169	[Prima:: => AnyEvent::Impl::POE::],
		1170	# IO::Async is just too broken - we would need workarounds for its
		1171	# byzantine signal and broken child handling, among others.
		1172	# IO::Async is rather hard to detect, as it doesn't have any
		1173	# obvious default class.
		1174	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		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
899	);	1178	);
900		1179
901	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1180	our %method = map +($_ => 1),
		1181	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
902		1182
903	our @post_detect;	1183	our @post_detect;
904		1184
905	sub post_detect(&) {	1185	sub post_detect(&) {
906	my ($cb) = @_;	1186	my ($cb) = @_;
907		1187
908	if ($MODEL) {	1188	if ($MODEL) {
909	$cb->();	1189	$cb->();
910		1190
911	1	1191	undef
912	} else {	1192	} else {
913	push @post_detect, $cb;	1193	push @post_detect, $cb;
914		1194
915	defined wantarray	1195	defined wantarray
916	? bless \$cb, "AnyEvent::Util::PostDetect"	1196	? bless \$cb, "AnyEvent::Util::postdetect"
917	: ()	1197	: ()
918	}	1198	}
919	}	1199	}
920		1200
921	sub AnyEvent::Util::PostDetect::DESTROY {	1201	sub AnyEvent::Util::postdetect::DESTROY {
922	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1202	@post_detect = grep $_ != ${$_[0]}, @post_detect;
923	}	1203	}
924		1204
925	sub detect() {	1205	sub detect() {
926	unless ($MODEL) {	1206	unless ($MODEL) {
927	no strict 'refs';
928	local $SIG{__DIE__};	1207	local $SIG{__DIE__};
929		1208
930	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1209	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
931	my $model = "AnyEvent::Impl::$1";	1210	my $model = "AnyEvent::Impl::$1";
932	if (eval "require $model") {	1211	if (eval "require $model") {
933	$MODEL = $model;	1212	$MODEL = $model;
934	warn "AnyEvent: loaded model '$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 $VERBOSE >= 2;
935	} else {	1214	} else {
936	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1215	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
937	}	1216	}
938	}	1217	}
939		1218
940	# check for already loaded models	1219	# check for already loaded models
941	unless ($MODEL) {	1220	unless ($MODEL) {
942	for (@REGISTRY, @models) {	1221	for (@REGISTRY, @models) {
943	my ($package, $model) = @$_;	1222	my ($package, $model) = @$_;
944	if (${"$package\::VERSION"} > 0) {	1223	if (${"$package\::VERSION"} > 0) {
945	if (eval "require $model") {	1224	if (eval "require $model") {
946	$MODEL = $model;	1225	$MODEL = $model;
947	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1226	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
948	last;	1227	last;
949	}	1228	}
950	}	1229	}
951	}	1230	}
952		1231
953	unless ($MODEL) {	1232	unless ($MODEL) {
954	# try to load a model	1233	# try to autoload a model
955
956	for (@REGISTRY, @models) {	1234	for (@REGISTRY, @models) {
957	my ($package, $model) = @$_;	1235	my ($package, $model, $autoload) = @$_;
		1236	if (
		1237	$autoload
958	if (eval "require $package"	1238	and eval "require $package"
959	and ${"$package\::VERSION"} > 0	1239	and ${"$package\::VERSION"} > 0
960	and eval "require $model") {	1240	and eval "require $model"
		1241	) {
961	$MODEL = $model;	1242	$MODEL = $model;
962	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1243	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
963	last;	1244	last;
964	}	1245	}
965	}	1246	}
966		1247
967	$MODEL	1248	$MODEL
968	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1249	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
969	}	1250	}
970	}	1251	}
971		1252
972	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1253	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
973		1254
…		…
983		1264
984	sub AUTOLOAD {	1265	sub AUTOLOAD {
985	(my $func = $AUTOLOAD) =~ s/.*://;	1266	(my $func = $AUTOLOAD) =~ s/.*://;
986		1267
987	$method{$func}	1268	$method{$func}
988	or croak "$func: not a valid method for AnyEvent objects";	1269	or Carp::croak "$func: not a valid method for AnyEvent objects";
989		1270
990	detect unless $MODEL;	1271	detect unless $MODEL;
991		1272
992	my $class = shift;	1273	my $class = shift;
993	$class->$func (@_);	1274	$class->$func (@_);
994	}	1275	}
995		1276
996	# utility function to dup a filehandle. this is used by many backends	1277	# utility function to dup a filehandle. this is used by many backends
997	# to support binding more than one watcher per filehandle (they usually	1278	# to support binding more than one watcher per filehandle (they usually
998	# allow only one watcher per fd, so we dup it to get a different one).	1279	# allow only one watcher per fd, so we dup it to get a different one).
999	sub _dupfh($$$$) {	1280	sub _dupfh($$;$$) {
1000	my ($poll, $fh, $r, $w) = @_;	1281	my ($poll, $fh, $r, $w) = @_;
1001		1282
1002	require Fcntl;
1003
1004	# cygwin requires the fh mode to be matching, unix doesn't	1283	# cygwin requires the fh mode to be matching, unix doesn't
1005	my ($rw, $mode) = $poll eq "r" ? ($r, "<")	1284	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
1006	: $poll eq "w" ? ($w, ">")
1007	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
1008		1285
1009	open my $fh2, "$mode&" . fileno $fh	1286	open my $fh2, $mode, $fh
1010	or die "cannot dup() filehandle: $!";	1287	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
1011		1288
1012	# we assume CLOEXEC is already set by perl in all important cases	1289	# we assume CLOEXEC is already set by perl in all important cases
1013		1290
1014	($fh2, $rw)	1291	($fh2, $rw)
1015	}	1292	}
1016		1293
		1294	=head1 SIMPLIFIED AE API
		1295
		1296	Starting with version 5.0, AnyEvent officially supports a second, much
		1297	simpler, API that is designed to reduce the calling, typing and memory
		1298	overhead.
		1299
		1300	See the L<AE> manpage for details.
		1301
		1302	=cut
		1303
		1304	package AE;
		1305
		1306	our $VERSION = $AnyEvent::VERSION;
		1307
		1308	sub io($$$) {
		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
1017	package AnyEvent::Base;	1344	package AnyEvent::Base;
1018		1345
1019	# default implementation for now and time	1346	# default implementations for many methods
1020		1347
1021	use Time::HiRes ();	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	}
1022		1358
1023	sub time { Time::HiRes::time }	1359	&_time
1024	sub now { Time::HiRes::time }	1360	}
		1361
		1362	sub time { _time }
		1363	sub now { _time }
		1364	sub now_update { }
1025		1365
1026	# default implementation for ->condvar	1366	# default implementation for ->condvar
1027		1367
1028	sub condvar {	1368	sub condvar {
1029	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1369	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
1030	}	1370	}
1031		1371
1032	# default implementation for ->signal	1372	# default implementation for ->signal
1033		1373
1034	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 }
1035		1450
1036	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 {
1037	my (undef, %arg) = @_;	1488	my (undef, %arg) = @_;
1038		1489
1039	my $signal = uc $arg{signal}	1490	my $signal = uc $arg{signal}
1040	or Carp::croak "required option 'signal' is missing";	1491	or Carp::croak "required option 'signal' is missing";
1041		1492
		1493	if ($HAVE_ASYNC_INTERRUPT) {
		1494	# async::interrupt
		1495
		1496	$signal = sig2num $signal;
1042	$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
1043	$SIG{$signal} ||= sub {	1513	$SIG{$signal} ||= sub {
1044	$_->() 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	};
1045	};	1542	};
1046		1543	die if $@;
1047	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1544	&signal
1048	}
1049
1050	sub AnyEvent::Base::Signal::DESTROY {
1051	my ($signal, $cb) = @{$_[0]};
1052
1053	delete $SIG_CB{$signal}{$cb};
1054
1055	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
1056	}	1545	}
1057		1546
1058	# default implementation for ->child	1547	# default implementation for ->child
1059		1548
1060	our %PID_CB;	1549	our %PID_CB;
1061	our $CHLD_W;	1550	our $CHLD_W;
1062	our $CHLD_DELAY_W;	1551	our $CHLD_DELAY_W;
1063	our $PID_IDLE;
1064	our $WNOHANG;	1552	our $WNOHANG;
1065		1553
1066	sub _child_wait {	1554	sub _emit_childstatus($$) {
1067	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1555	my (undef, $rpid, $rstatus) = @_;
		1556
		1557	$_->($rpid, $rstatus)
1068	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1558	for values %{ $PID_CB{$rpid} || {} },
1069	(values %{ $PID_CB{0} || {} });	1559	values %{ $PID_CB{0} || {} };
1070	}
1071
1072	undef $PID_IDLE;
1073	}	1560	}
1074		1561
1075	sub _sigchld {	1562	sub _sigchld {
1076	# make sure we deliver these changes "synchronous" with the event loop.	1563	my $pid;
1077	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1564
1078	undef $CHLD_DELAY_W;	1565	AnyEvent->_emit_childstatus ($pid, $?)
1079	&_child_wait;	1566	while ($pid = waitpid -1, $WNOHANG) > 0;
1080	});
1081	}	1567	}
1082		1568
1083	sub child {	1569	sub child {
1084	my (undef, %arg) = @_;	1570	my (undef, %arg) = @_;
1085		1571
1086	defined (my $pid = $arg{pid} + 0)	1572	defined (my $pid = $arg{pid} + 0)
1087	or Carp::croak "required option 'pid' is missing";	1573	or Carp::croak "required option 'pid' is missing";
1088		1574
1089	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1575	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
1090		1576
1091	unless ($WNOHANG) {	1577	# WNOHANG is almost cetrainly 1 everywhere
		1578	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1579	? 1
1092	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1580	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1093	}
1094		1581
1095	unless ($CHLD_W) {	1582	unless ($CHLD_W) {
1096	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1583	$CHLD_W = AE::signal CHLD => \&_sigchld;
1097	# child could be a zombie already, so make at least one round	1584	# child could be a zombie already, so make at least one round
1098	&_sigchld;	1585	&_sigchld;
1099	}	1586	}
1100		1587
1101	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1588	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
1102	}	1589	}
1103		1590
1104	sub AnyEvent::Base::Child::DESTROY {	1591	sub AnyEvent::Base::child::DESTROY {
1105	my ($pid, $cb) = @{$_[0]};	1592	my ($pid, $cb) = @{$_[0]};
1106		1593
1107	delete $PID_CB{$pid}{$cb};	1594	delete $PID_CB{$pid}{$cb};
1108	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1595	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1109		1596
1110	undef $CHLD_W unless keys %PID_CB;	1597	undef $CHLD_W unless keys %PID_CB;
1111	}	1598	}
1112		1599
		1600	# idle emulation is done by simply using a timer, regardless
		1601	# of whether the process is idle or not, and not letting
		1602	# the callback use more than 50% of the time.
		1603	sub idle {
		1604	my (undef, %arg) = @_;
		1605
		1606	my ($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
1113	package AnyEvent::CondVar;	1636	package AnyEvent::CondVar;
1114		1637
1115	our @ISA = AnyEvent::CondVar::Base::;	1638	our @ISA = AnyEvent::CondVar::Base::;
1116		1639
1117	package AnyEvent::CondVar::Base;	1640	package AnyEvent::CondVar::Base;
1118		1641
1119	use overload	1642	#use overload
1120	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1643	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1121	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;
1122		1653
1123	sub _send {	1654	sub _send {
1124	# nop	1655	# nop
1125	}	1656	}
1126		1657
…		…
1139	sub ready {	1670	sub ready {
1140	$_[0]{_ae_sent}	1671	$_[0]{_ae_sent}
1141	}	1672	}
1142		1673
1143	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 $WAITING = 1;
1144	AnyEvent->one_event while !$_[0]{_ae_sent};	1680	AnyEvent->one_event while !$_[0]{_ae_sent};
1145	}	1681	}
1146		1682
1147	sub recv {	1683	sub recv {
1148	$_[0]->_wait;	1684	$_[0]->_wait;
…		…
1150	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1686	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
1151	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1687	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
1152	}	1688	}
1153		1689
1154	sub cb {	1690	sub cb {
1155	$_[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
1156	$_[0]{_ae_cb}	1698	$cv->{_ae_cb}
1157	}	1699	}
1158		1700
1159	sub begin {	1701	sub begin {
1160	++$_[0]{_ae_counter};	1702	++$_[0]{_ae_counter};
1161	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1703	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
…		…
1167	}	1709	}
1168		1710
1169	# undocumented/compatibility with pre-3.4	1711	# undocumented/compatibility with pre-3.4
1170	*broadcast = \&send;	1712	*broadcast = \&send;
1171	*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
1172		1852
1173	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1853	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1174		1854
1175	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
1176	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
…		…
1210		1890
1211	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
1212	condition variables: code blocking while waiting for a condition will	1892	condition variables: code blocking while waiting for a condition will
1213	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
1214	not be done in an interactive application, so it makes sense.	1894	not be done in an interactive application, so it makes sense.
1215
1216	=head1 ENVIRONMENT VARIABLES
1217
1218	The following environment variables are used by this module:
1219
1220	=over 4
1221
1222	=item C<PERL_ANYEVENT_VERBOSE>
1223
1224	By default, AnyEvent will be completely silent except in fatal
1225	conditions. You can set this environment variable to make AnyEvent more
1226	talkative.
1227
1228	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1229	conditions, such as not being able to load the event model specified by
1230	C<PERL_ANYEVENT_MODEL>.
1231
1232	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1233	model it chooses.
1234
1235	=item C<PERL_ANYEVENT_STRICT>
1236
1237	AnyEvent does not do much argument checking by default, as thorough
1238	argument checking is very costly. Setting this variable to a true value
1239	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
1240	check the arguments passed to most method calls. If it finds any problems
1241	it will croak.
1242
1243	In other words, enables "strict" mode.
1244
1245	Unlike C<use strict> it is definitely recommended ot keep it off in
1246	production.
1247
1248	=item C<PERL_ANYEVENT_MODEL>
1249
1250	This can be used to specify the event model to be used by AnyEvent, before
1251	auto detection and -probing kicks in. It must be a string consisting
1252	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1253	and the resulting module name is loaded and if the load was successful,
1254	used as event model. If it fails to load AnyEvent will proceed with
1255	auto detection and -probing.
1256
1257	This functionality might change in future versions.
1258
1259	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1260	could start your program like this:
1261
1262	PERL_ANYEVENT_MODEL=Perl perl ...
1263
1264	=item C<PERL_ANYEVENT_PROTOCOLS>
1265
1266	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1267	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1268	of auto probing).
1269
1270	Must be set to a comma-separated list of protocols or address families,
1271	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1272	used, and preference will be given to protocols mentioned earlier in the
1273	list.
1274
1275	This variable can effectively be used for denial-of-service attacks
1276	against local programs (e.g. when setuid), although the impact is likely
1277	small, as the program has to handle connection errors already-
1278
1279	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1280	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1281	- only support IPv4, never try to resolve or contact IPv6
1282	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1283	IPv6, but prefer IPv6 over IPv4.
1284
1285	=item C<PERL_ANYEVENT_EDNS0>
1286
1287	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1288	for DNS. This extension is generally useful to reduce DNS traffic, but
1289	some (broken) firewalls drop such DNS packets, which is why it is off by
1290	default.
1291
1292	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1293	EDNS0 in its DNS requests.
1294
1295	=item C<PERL_ANYEVENT_MAX_FORKS>
1296
1297	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1298	will create in parallel.
1299
1300	=back
1301		1895
1302	=head1 EXAMPLE PROGRAM	1896	=head1 EXAMPLE PROGRAM
1303		1897
1304	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
1305	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
…		…
1468	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
1469	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,
1470	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.
1471		2065
1472	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
1473	distribution.	2067	distribution. It uses the L<AE> interface, which makes a real difference
		2068	for the EV and Perl backends only.
1474		2069
1475	=head3 Explanation of the columns	2070	=head3 Explanation of the columns
1476		2071
1477	I<watcher> is the number of event watchers created/destroyed. Since	2072	I<watcher> is the number of event watchers created/destroyed. Since
1478	different event models feature vastly different performances, each event	2073	different event models feature vastly different performances, each event
…		…
1499	watcher.	2094	watcher.
1500		2095
1501	=head3 Results	2096	=head3 Results
1502		2097
1503	name watchers bytes create invoke destroy comment	2098	name watchers bytes create invoke destroy comment
1504	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
1505	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
1506	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
1507	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
1508	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
1509	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
1510	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
1511	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
1512	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
1513	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
1514		2111
1515	=head3 Discussion	2112	=head3 Discussion
1516		2113
1517	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
1518	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)
…		…
1530	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2127	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1531	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
1532	cycles with POE.	2129	cycles with POE.
1533		2130
1534	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
1535	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
1536	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).
1537	natively.
1538		2136
1539	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
1540	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
1541	interpreter and the backend itself). Nevertheless this shows that it	2139	interpreter and the backend itself). Nevertheless this shows that it
1542	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
1543	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
1544	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.
1545		2143
1546	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
1547	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.
1548		2149
1549	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
1550	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
1551	C<Event>. However, Glib scales extremely badly, doubling the number of	2152	C<Event>. However, Glib scales extremely badly, doubling the number of
1552	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,
…		…
1613	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
1614	(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
1615	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.
1616		2217
1617	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
1618	distribution.	2219	distribution. It uses the L<AE> interface, which makes a real difference
		2220	for the EV and Perl backends only.
1619		2221
1620	=head3 Explanation of the columns	2222	=head3 Explanation of the columns
1621		2223
1622	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
1623	each server has a read and write socket end).	2225	each server has a read and write socket end).
…		…
1630	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
1631	a new one that moves the timeout into the future.	2233	a new one that moves the timeout into the future.
1632		2234
1633	=head3 Results	2235	=head3 Results
1634		2236
1635	name sockets create request	2237	name sockets create request
1636	EV 20000 69.01 11.16	2238	EV 20000 62.66 7.99
1637	Perl 20000 73.32 35.87	2239	Perl 20000 68.32 32.64
1638	Event 20000 212.62 257.32	2240	IOAsync 20000 174.06 101.15 epoll
1639	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
1640	POE 20000 349.67 12317.24 uses POE::Loop::Event	2244	POE 20000 341.54 12086.32 uses POE::Loop::Event
1641		2245
1642	=head3 Discussion	2246	=head3 Discussion
1643		2247
1644	This benchmark I<does> measure scalability and overall performance of the	2248	This benchmark I<does> measure scalability and overall performance of the
1645	particular event loop.	2249	particular event loop.
…		…
1647	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
1648	is relatively high, though.	2252	is relatively high, though.
1649		2253
1650	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
1651	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.
1652		2259
1653	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
1654	understand why). Callback invocation also has a high overhead compared to	2261	understand why). Callback invocation also has a high overhead compared to
1655	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
1656	uses select or poll in basically all documented configurations.	2263	uses select or poll in basically all documented configurations.
…		…
1719	=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
1720	watchers, as the management overhead dominates.	2327	watchers, as the management overhead dominates.
1721		2328
1722	=back	2329	=back
1723		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
1724		2507
1725	=head1 FORK	2508	=head1 FORK
1726		2509
1727	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
1728	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>
1729	calls. Only L<EV> is fully fork-aware.	2512	calls. Only L<EV> is fully fork-aware.
1730		2513
1731	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
1732	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.
1733		2517
1734		2518
1735	=head1 SECURITY CONSIDERATIONS	2519	=head1 SECURITY CONSIDERATIONS
1736		2520
1737	AnyEvent can be forced to load any event model via	2521	AnyEvent can be forced to load any event model via
…		…
1749	use AnyEvent;	2533	use AnyEvent;
1750		2534
1751	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2535	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1752	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
1753	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and	2537	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
1754	$ENV{PERL_ANYEGENT_STRICT}.	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.
1755		2543
1756		2544
1757	=head1 BUGS	2545	=head1 BUGS
1758		2546
1759	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard	2547	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
1760	to work around. If you suffer from memleaks, first upgrade to Perl 5.10	2548	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
1761	and check wether the leaks still show up. (Perl 5.10.0 has other annoying	2549	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
1762	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as	2550	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
1763	pronounced).	2551	pronounced).
1764		2552
1765		2553
1766	=head1 SEE ALSO	2554	=head1 SEE ALSO
1767		2555
…		…
1771	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2559	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1772		2560
1773	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2561	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1774	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>,
1775	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2563	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1776	L<AnyEvent::Impl::POE>.	2564	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1777		2565
1778	Non-blocking file handles, sockets, TCP clients and	2566	Non-blocking file handles, sockets, TCP clients and
1779	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2567	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1780		2568
1781	Asynchronous DNS: L<AnyEvent::DNS>.	2569	Asynchronous DNS: L<AnyEvent::DNS>.
1782		2570
1783	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>,
1784		2573
1785	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>.
1786		2576
1787		2577
1788	=head1 AUTHOR	2578	=head1 AUTHOR
1789		2579
1790	Marc Lehmann <schmorp@schmorp.de>	2580	Marc Lehmann <schmorp@schmorp.de>

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