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Revision 1.147 by root, Fri May 30 21:43:26 2008 UTC vs.
Revision 1.263 by root, Wed Jul 29 12:39:21 2009 UTC

1	=head1 => NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
		37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	63	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enormous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
…		…
121	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
122	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
123	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
124	is in control).	156	is in control).
125		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
126	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
127	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
128	to it).	166	to it).
129		167
130	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.
…		…
132	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
133	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
134		172
135	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
136		174
137	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
138	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
139	undef $w;	177	undef $w;
140	});	178	});
141		179
142	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
143	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
144	declared.	182	declared.
145		183
146	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
147		185
148	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	186	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
149	with the following mandatory key-value pairs as arguments:	187	with the following mandatory key-value pairs as arguments:
150		188
151	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	189	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		190	for events (AnyEvent might or might not keep a reference to this file
		191	handle). Note that only file handles pointing to things for which
		192	non-blocking operation makes sense are allowed. This includes sockets,
		193	most character devices, pipes, fifos and so on, but not for example files
		194	or block devices.
		195
152	for events. C<poll> must be a string that is either C<r> or C<w>,	196	C<poll> must be a string that is either C<r> or C<w>, which creates a
153	which creates a watcher waiting for "r"eadable or "w"ritable events,	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
		198
154	respectively. C<cb> is the callback to invoke each time the file handle	199	C<cb> is the callback to invoke each time the file handle becomes ready.
155	becomes ready.
156		200
157	Although the callback might get passed parameters, their value and	201	Although the callback might get passed parameters, their value and
158	presence is undefined and you cannot rely on them. Portable AnyEvent	202	presence is undefined and you cannot rely on them. Portable AnyEvent
159	callbacks cannot use arguments passed to I/O watcher callbacks.	203	callbacks cannot use arguments passed to I/O watcher callbacks.
160		204
…		…
164		208
165	Some event loops issue spurious readyness notifications, so you should	209	Some event loops issue spurious readyness notifications, so you should
166	always use non-blocking calls when reading/writing from/to your file	210	always use non-blocking calls when reading/writing from/to your file
167	handles.	211	handles.
168		212
169	Example:
170
171	# wait for readability of STDIN, then read a line and disable the watcher	213	Example: wait for readability of STDIN, then read a line and disable the
		214	watcher.
		215
172	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
173	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
174	warn "read: $input\n";	218	warn "read: $input\n";
175	undef $w;	219	undef $w;
176	});	220	});
…		…
186		230
187	Although the callback might get passed parameters, their value and	231	Although the callback might get passed parameters, their value and
188	presence is undefined and you cannot rely on them. Portable AnyEvent	232	presence is undefined and you cannot rely on them. Portable AnyEvent
189	callbacks cannot use arguments passed to time watcher callbacks.	233	callbacks cannot use arguments passed to time watcher callbacks.
190		234
191	The timer callback will be invoked at most once: if you want a repeating	235	The callback will normally be invoked once only. If you specify another
192	timer you have to create a new watcher (this is a limitation by both Tk	236	parameter, C<interval>, as a strictly positive number (> 0), then the
193	and Glib).	237	callback will be invoked regularly at that interval (in fractional
		238	seconds) after the first invocation. If C<interval> is specified with a
		239	false value, then it is treated as if it were missing.
194		240
195	Example:	241	The callback will be rescheduled before invoking the callback, but no
		242	attempt is done to avoid timer drift in most backends, so the interval is
		243	only approximate.
196		244
197	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
198	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
199	warn "timeout\n";	248	warn "timeout\n";
200	});	249	});
201		250
202	# to cancel the timer:	251	# to cancel the timer:
203	undef $w;	252	undef $w;
204		253
205	Example 2:
206
207	# fire an event after 0.5 seconds, then roughly every second	254	Example 2: fire an event after 0.5 seconds, then roughly every second.
208	my $w;
209		255
210	my $cb = sub {
211	# cancel the old timer while creating a new one
212	$w = AnyEvent->timer (after => 1, cb => $cb);	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		257	warn "timeout\n";
213	};	258	};
214
215	# start the "loop" by creating the first watcher
216	$w = AnyEvent->timer (after => 0.5, cb => $cb);
217		259
218	=head3 TIMING ISSUES	260	=head3 TIMING ISSUES
219		261
220	There are two ways to handle timers: based on real time (relative, "fire	262	There are two ways to handle timers: based on real time (relative, "fire
221	in 10 seconds") and based on wallclock time (absolute, "fire at 12	263	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
294	In either case, if you care (and in most cases, you don't), then you	336	In either case, if you care (and in most cases, you don't), then you
295	can get whatever behaviour you want with any event loop, by taking the	337	can get whatever behaviour you want with any event loop, by taking the
296	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
297	account.	339	account.
298		340
		341	=item AnyEvent->now_update
		342
		343	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		344	the current time for each loop iteration (see the discussion of L<<
		345	AnyEvent->now >>, above).
		346
		347	When a callback runs for a long time (or when the process sleeps), then
		348	this "current" time will differ substantially from the real time, which
		349	might affect timers and time-outs.
		350
		351	When this is the case, you can call this method, which will update the
		352	event loop's idea of "current time".
		353
		354	Note that updating the time I<might> cause some events to be handled.
		355
299	=back	356	=back
300		357
301	=head2 SIGNAL WATCHERS	358	=head2 SIGNAL WATCHERS
302		359
303	You can watch for signals using a signal watcher, C<signal> is the signal	360	You can watch for signals using a signal watcher, C<signal> is the signal
304	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	361	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
305	be invoked whenever a signal occurs.	362	callback to be invoked whenever a signal occurs.
306		363
307	Although the callback might get passed parameters, their value and	364	Although the callback might get passed parameters, their value and
308	presence is undefined and you cannot rely on them. Portable AnyEvent	365	presence is undefined and you cannot rely on them. Portable AnyEvent
309	callbacks cannot use arguments passed to signal watcher callbacks.	366	callbacks cannot use arguments passed to signal watcher callbacks.
310		367
…		…
312	invocation, and callback invocation will be synchronous. Synchronous means	369	invocation, and callback invocation will be synchronous. Synchronous means
313	that it might take a while until the signal gets handled by the process,	370	that it might take a while until the signal gets handled by the process,
314	but it is guaranteed not to interrupt any other callbacks.	371	but it is guaranteed not to interrupt any other callbacks.
315		372
316	The main advantage of using these watchers is that you can share a signal	373	The main advantage of using these watchers is that you can share a signal
317	between multiple watchers.	374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
318		376
319	This watcher might use C<%SIG>, so programs overwriting those signals	377	This watcher might use C<%SIG> (depending on the event loop used),
320	directly will likely not work correctly.	378	so programs overwriting those signals directly will likely not work
		379	correctly.
321		380
322	Example: exit on SIGINT	381	Example: exit on SIGINT
323		382
324	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
325		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		392	seconds). This variable can be changed only before the first signal
		393	watcher is created, and should be left alone otherwise. Higher values
		394	will cause fewer spurious wake-ups, which is better for power and CPU
		395	saving. All these problems can be avoided by installing the optional
		396	L<Async::Interrupt> module. This will not work with inherently broken
		397	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		398	currently, as POE does it's own workaround with one-second latency). With
		399	those, you just have to suffer the delays.
		400
326	=head2 CHILD PROCESS WATCHERS	401	=head2 CHILD PROCESS WATCHERS
327		402
328	You can also watch on a child process exit and catch its exit status.	403	You can also watch on a child process exit and catch its exit status.
329		404
330	The child process is specified by the C<pid> argument (if set to C<0>, it	405	The child process is specified by the C<pid> argument (one some backends,
331	watches for any child process exit). The watcher will trigger as often	406	using C<0> watches for any child process exit, on others this will
332	as status change for the child are received. This works by installing a	407	croak). The watcher will be triggered only when the child process has
333	signal handler for C<SIGCHLD>. The callback will be called with the pid	408	finished and an exit status is available, not on any trace events
334	and exit status (as returned by waitpid), so unlike other watcher types,	409	(stopped/continued).
335	you I<can> rely on child watcher callback arguments.	410
		411	The callback will be called with the pid and exit status (as returned by
		412	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		413	callback arguments.
		414
		415	This watcher type works by installing a signal handler for C<SIGCHLD>,
		416	and since it cannot be shared, nothing else should use SIGCHLD or reap
		417	random child processes (waiting for specific child processes, e.g. inside
		418	C<system>, is just fine).
336		419
337	There is a slight catch to child watchers, however: you usually start them	420	There is a slight catch to child watchers, however: you usually start them
338	I<after> the child process was created, and this means the process could	421	I<after> the child process was created, and this means the process could
339	have exited already (and no SIGCHLD will be sent anymore).	422	have exited already (and no SIGCHLD will be sent anymore).
340		423
341	Not all event models handle this correctly (POE doesn't), but even for	424	Not all event models handle this correctly (neither POE nor IO::Async do,
		425	see their AnyEvent::Impl manpages for details), but even for event models
342	event models that I<do> handle this correctly, they usually need to be	426	that I<do> handle this correctly, they usually need to be loaded before
343	loaded before the process exits (i.e. before you fork in the first place).	427	the process exits (i.e. before you fork in the first place). AnyEvent's
		428	pure perl event loop handles all cases correctly regardless of when you
		429	start the watcher.
344		430
345	This means you cannot create a child watcher as the very first thing in an	431	This means you cannot create a child watcher as the very first
346	AnyEvent program, you I<have> to create at least one watcher before you	432	thing in an AnyEvent program, you I<have> to create at least one
347	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	433	watcher before you C<fork> the child (alternatively, you can call
		434	C<AnyEvent::detect>).
		435
		436	As most event loops do not support waiting for child events, they will be
		437	emulated by AnyEvent in most cases, in which the latency and race problems
		438	mentioned in the description of signal watchers apply.
348		439
349	Example: fork a process and wait for it	440	Example: fork a process and wait for it
350		441
351	my $done = AnyEvent->condvar;	442	my $done = AnyEvent->condvar;
352		443
353	my $pid = fork or exit 5;	444	my $pid = fork or exit 5;
354		445
355	my $w = AnyEvent->child (	446	my $w = AnyEvent->child (
356	pid => $pid,	447	pid => $pid,
357	cb => sub {	448	cb => sub {
358	my ($pid, $status) = @_;	449	my ($pid, $status) = @_;
359	warn "pid $pid exited with status $status";	450	warn "pid $pid exited with status $status";
360	$done->send;	451	$done->send;
361	},	452	},
362	);	453	);
363		454
364	# do something else, then wait for process exit	455	# do something else, then wait for process exit
365	$done->recv;	456	$done->recv;
		457
		458	=head2 IDLE WATCHERS
		459
		460	Sometimes there is a need to do something, but it is not so important
		461	to do it instantly, but only when there is nothing better to do. This
		462	"nothing better to do" is usually defined to be "no other events need
		463	attention by the event loop".
		464
		465	Idle watchers ideally get invoked when the event loop has nothing
		466	better to do, just before it would block the process to wait for new
		467	events. Instead of blocking, the idle watcher is invoked.
		468
		469	Most event loops unfortunately do not really support idle watchers (only
		470	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		471	will simply call the callback "from time to time".
		472
		473	Example: read lines from STDIN, but only process them when the
		474	program is otherwise idle:
		475
		476	my @lines; # read data
		477	my $idle_w;
		478	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		479	push @lines, scalar <STDIN>;
		480
		481	# start an idle watcher, if not already done
		482	$idle_w ||= AnyEvent->idle (cb => sub {
		483	# handle only one line, when there are lines left
		484	if (my $line = shift @lines) {
		485	print "handled when idle: $line";
		486	} else {
		487	# otherwise disable the idle watcher again
		488	undef $idle_w;
		489	}
		490	});
		491	});
366		492
367	=head2 CONDITION VARIABLES	493	=head2 CONDITION VARIABLES
368		494
369	If you are familiar with some event loops you will know that all of them	495	If you are familiar with some event loops you will know that all of them
370	require you to run some blocking "loop", "run" or similar function that	496	require you to run some blocking "loop", "run" or similar function that
371	will actively watch for new events and call your callbacks.	497	will actively watch for new events and call your callbacks.
372		498
373	AnyEvent is different, it expects somebody else to run the event loop and	499	AnyEvent is slightly different: it expects somebody else to run the event
374	will only block when necessary (usually when told by the user).	500	loop and will only block when necessary (usually when told by the user).
375		501
376	The instrument to do that is called a "condition variable", so called	502	The instrument to do that is called a "condition variable", so called
377	because they represent a condition that must become true.	503	because they represent a condition that must become true.
		504
		505	Now is probably a good time to look at the examples further below.
378		506
379	Condition variables can be created by calling the C<< AnyEvent->condvar	507	Condition variables can be created by calling the C<< AnyEvent->condvar
380	>> method, usually without arguments. The only argument pair allowed is	508	>> method, usually without arguments. The only argument pair allowed is
381	C<cb>, which specifies a callback to be called when the condition variable	509	C<cb>, which specifies a callback to be called when the condition variable
382	becomes true.	510	becomes true, with the condition variable as the first argument (but not
		511	the results).
383		512
384	After creation, the condition variable is "false" until it becomes "true"	513	After creation, the condition variable is "false" until it becomes "true"
385	by calling the C<send> method (or calling the condition variable as if it	514	by calling the C<send> method (or calling the condition variable as if it
386	were a callback, read about the caveats in the description for the C<<	515	were a callback, read about the caveats in the description for the C<<
387	->send >> method).	516	->send >> method).
…		…
389	Condition variables are similar to callbacks, except that you can	518	Condition variables are similar to callbacks, except that you can
390	optionally wait for them. They can also be called merge points - points	519	optionally wait for them. They can also be called merge points - points
391	in time where multiple outstanding events have been processed. And yet	520	in time where multiple outstanding events have been processed. And yet
392	another way to call them is transactions - each condition variable can be	521	another way to call them is transactions - each condition variable can be
393	used to represent a transaction, which finishes at some point and delivers	522	used to represent a transaction, which finishes at some point and delivers
394	a result.	523	a result. And yet some people know them as "futures" - a promise to
		524	compute/deliver something that you can wait for.
395		525
396	Condition variables are very useful to signal that something has finished,	526	Condition variables are very useful to signal that something has finished,
397	for example, if you write a module that does asynchronous http requests,	527	for example, if you write a module that does asynchronous http requests,
398	then a condition variable would be the ideal candidate to signal the	528	then a condition variable would be the ideal candidate to signal the
399	availability of results. The user can either act when the callback is	529	availability of results. The user can either act when the callback is
…		…
433	after => 1,	563	after => 1,
434	cb => sub { $result_ready->send },	564	cb => sub { $result_ready->send },
435	);	565	);
436		566
437	# this "blocks" (while handling events) till the callback	567	# this "blocks" (while handling events) till the callback
438	# calls send	568	# calls -<send
439	$result_ready->recv;	569	$result_ready->recv;
440		570
441	Example: wait for a timer, but take advantage of the fact that	571	Example: wait for a timer, but take advantage of the fact that condition
442	condition variables are also code references.	572	variables are also callable directly.
443		573
444	my $done = AnyEvent->condvar;	574	my $done = AnyEvent->condvar;
445	my $delay = AnyEvent->timer (after => 5, cb => $done);	575	my $delay = AnyEvent->timer (after => 5, cb => $done);
446	$done->recv;	576	$done->recv;
		577
		578	Example: Imagine an API that returns a condvar and doesn't support
		579	callbacks. This is how you make a synchronous call, for example from
		580	the main program:
		581
		582	use AnyEvent::CouchDB;
		583
		584	...
		585
		586	my @info = $couchdb->info->recv;
		587
		588	And this is how you would just set a callback to be called whenever the
		589	results are available:
		590
		591	$couchdb->info->cb (sub {
		592	my @info = $_[0]->recv;
		593	});
447		594
448	=head3 METHODS FOR PRODUCERS	595	=head3 METHODS FOR PRODUCERS
449		596
450	These methods should only be used by the producing side, i.e. the	597	These methods should only be used by the producing side, i.e. the
451	code/module that eventually sends the signal. Note that it is also	598	code/module that eventually sends the signal. Note that it is also
…		…
464	immediately from within send.	611	immediately from within send.
465		612
466	Any arguments passed to the C<send> call will be returned by all	613	Any arguments passed to the C<send> call will be returned by all
467	future C<< ->recv >> calls.	614	future C<< ->recv >> calls.
468		615
469	Condition variables are overloaded so one can call them directly	616	Condition variables are overloaded so one can call them directly (as if
470	(as a code reference). Calling them directly is the same as calling	617	they were a code reference). Calling them directly is the same as calling
471	C<send>. Note, however, that many C-based event loops do not handle	618	C<send>.
472	overloading, so as tempting as it may be, passing a condition variable
473	instead of a callback does not work. Both the pure perl and EV loops
474	support overloading, however, as well as all functions that use perl to
475	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
476	example).
477		619
478	=item $cv->croak ($error)	620	=item $cv->croak ($error)
479		621
480	Similar to send, but causes all call's to C<< ->recv >> to invoke	622	Similar to send, but causes all call's to C<< ->recv >> to invoke
481	C<Carp::croak> with the given error message/object/scalar.	623	C<Carp::croak> with the given error message/object/scalar.
482		624
483	This can be used to signal any errors to the condition variable	625	This can be used to signal any errors to the condition variable
484	user/consumer.	626	user/consumer. Doing it this way instead of calling C<croak> directly
		627	delays the error detetcion, but has the overwhelmign advantage that it
		628	diagnoses the error at the place where the result is expected, and not
		629	deep in some event clalback without connection to the actual code causing
		630	the problem.
485		631
486	=item $cv->begin ([group callback])	632	=item $cv->begin ([group callback])
487		633
488	=item $cv->end	634	=item $cv->end
489
490	These two methods are EXPERIMENTAL and MIGHT CHANGE.
491		635
492	These two methods can be used to combine many transactions/events into	636	These two methods can be used to combine many transactions/events into
493	one. For example, a function that pings many hosts in parallel might want	637	one. For example, a function that pings many hosts in parallel might want
494	to use a condition variable for the whole process.	638	to use a condition variable for the whole process.
495		639
…		…
497	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	641	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
498	>>, the (last) callback passed to C<begin> will be executed. That callback	642	>>, the (last) callback passed to C<begin> will be executed. That callback
499	is I<supposed> to call C<< ->send >>, but that is not required. If no	643	is I<supposed> to call C<< ->send >>, but that is not required. If no
500	callback was set, C<send> will be called without any arguments.	644	callback was set, C<send> will be called without any arguments.
501		645
502	Let's clarify this with the ping example:	646	You can think of C<< $cv->send >> giving you an OR condition (one call
		647	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		648	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		649
		650	Let's start with a simple example: you have two I/O watchers (for example,
		651	STDOUT and STDERR for a program), and you want to wait for both streams to
		652	close before activating a condvar:
		653
		654	my $cv = AnyEvent->condvar;
		655
		656	$cv->begin; # first watcher
		657	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		658	defined sysread $fh1, my $buf, 4096
		659	or $cv->end;
		660	});
		661
		662	$cv->begin; # second watcher
		663	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		664	defined sysread $fh2, my $buf, 4096
		665	or $cv->end;
		666	});
		667
		668	$cv->recv;
		669
		670	This works because for every event source (EOF on file handle), there is
		671	one call to C<begin>, so the condvar waits for all calls to C<end> before
		672	sending.
		673
		674	The ping example mentioned above is slightly more complicated, as the
		675	there are results to be passwd back, and the number of tasks that are
		676	begung can potentially be zero:
503		677
504	my $cv = AnyEvent->condvar;	678	my $cv = AnyEvent->condvar;
505		679
506	my %result;	680	my %result;
507	$cv->begin (sub { $cv->send (\%result) });	681	$cv->begin (sub { $cv->send (\%result) });
…		…
527	loop, which serves two important purposes: first, it sets the callback	701	loop, which serves two important purposes: first, it sets the callback
528	to be called once the counter reaches C<0>, and second, it ensures that	702	to be called once the counter reaches C<0>, and second, it ensures that
529	C<send> is called even when C<no> hosts are being pinged (the loop	703	C<send> is called even when C<no> hosts are being pinged (the loop
530	doesn't execute once).	704	doesn't execute once).
531		705
532	This is the general pattern when you "fan out" into multiple subrequests:	706	This is the general pattern when you "fan out" into multiple (but
533	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	707	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
534	is called at least once, and then, for each subrequest you start, call	708	the callback and ensure C<end> is called at least once, and then, for each
535	C<begin> and for each subrequest you finish, call C<end>.	709	subrequest you start, call C<begin> and for each subrequest you finish,
		710	call C<end>.
536		711
537	=back	712	=back
538		713
539	=head3 METHODS FOR CONSUMERS	714	=head3 METHODS FOR CONSUMERS
540		715
…		…
556	function will call C<croak>.	731	function will call C<croak>.
557		732
558	In list context, all parameters passed to C<send> will be returned,	733	In list context, all parameters passed to C<send> will be returned,
559	in scalar context only the first one will be returned.	734	in scalar context only the first one will be returned.
560		735
		736	Note that doing a blocking wait in a callback is not supported by any
		737	event loop, that is, recursive invocation of a blocking C<< ->recv
		738	>> is not allowed, and the C<recv> call will C<croak> if such a
		739	condition is detected. This condition can be slightly loosened by using
		740	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		741	any thread that doesn't run the event loop itself.
		742
561	Not all event models support a blocking wait - some die in that case	743	Not all event models support a blocking wait - some die in that case
562	(programs might want to do that to stay interactive), so I<if you are	744	(programs might want to do that to stay interactive), so I<if you are
563	using this from a module, never require a blocking wait>, but let the	745	using this from a module, never require a blocking wait>. Instead, let the
564	caller decide whether the call will block or not (for example, by coupling	746	caller decide whether the call will block or not (for example, by coupling
565	condition variables with some kind of request results and supporting	747	condition variables with some kind of request results and supporting
566	callbacks so the caller knows that getting the result will not block,	748	callbacks so the caller knows that getting the result will not block,
567	while still supporting blocking waits if the caller so desires).	749	while still supporting blocking waits if the caller so desires).
568		750
569	Another reason I<never> to C<< ->recv >> in a module is that you cannot
570	sensibly have two C<< ->recv >>'s in parallel, as that would require
571	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
572	can supply.
573
574	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
575	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
576	versions and also integrates coroutines into AnyEvent, making blocking
577	C<< ->recv >> calls perfectly safe as long as they are done from another
578	coroutine (one that doesn't run the event loop).
579
580	You can ensure that C<< -recv >> never blocks by setting a callback and	751	You can ensure that C<< -recv >> never blocks by setting a callback and
581	only calling C<< ->recv >> from within that callback (or at a later	752	only calling C<< ->recv >> from within that callback (or at a later
582	time). This will work even when the event loop does not support blocking	753	time). This will work even when the event loop does not support blocking
583	waits otherwise.	754	waits otherwise.
584		755
585	=item $bool = $cv->ready	756	=item $bool = $cv->ready
586		757
587	Returns true when the condition is "true", i.e. whether C<send> or	758	Returns true when the condition is "true", i.e. whether C<send> or
588	C<croak> have been called.	759	C<croak> have been called.
589		760
590	=item $cb = $cv->cb ([new callback])	761	=item $cb = $cv->cb ($cb->($cv))
591		762
592	This is a mutator function that returns the callback set and optionally	763	This is a mutator function that returns the callback set and optionally
593	replaces it before doing so.	764	replaces it before doing so.
594		765
595	The callback will be called when the condition becomes "true", i.e. when	766	The callback will be called when the condition becomes "true", i.e. when
596	C<send> or C<croak> are called. Calling C<recv> inside the callback	767	C<send> or C<croak> are called, with the only argument being the condition
597	or at any later time is guaranteed not to block.	768	variable itself. Calling C<recv> inside the callback or at any later time
		769	is guaranteed not to block.
598		770
599	=back	771	=back
600		772
		773	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		774
		775	The available backend classes are (every class has its own manpage):
		776
		777	=over 4
		778
		779	=item Backends that are autoprobed when no other event loop can be found.
		780
		781	EV is the preferred backend when no other event loop seems to be in
		782	use. If EV is not installed, then AnyEvent will try Event, and, failing
		783	that, will fall back to its own pure-perl implementation, which is
		784	available everywhere as it comes with AnyEvent itself.
		785
		786	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		787	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		788	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		789
		790	=item Backends that are transparently being picked up when they are used.
		791
		792	These will be used when they are currently loaded when the first watcher
		793	is created, in which case it is assumed that the application is using
		794	them. This means that AnyEvent will automatically pick the right backend
		795	when the main program loads an event module before anything starts to
		796	create watchers. Nothing special needs to be done by the main program.
		797
		798	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		799	AnyEvent::Impl::Tk based on Tk, very broken.
		800	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		801	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		802	AnyEvent::Impl::Irssi used when running within irssi.
		803
		804	=item Backends with special needs.
		805
		806	Qt requires the Qt::Application to be instantiated first, but will
		807	otherwise be picked up automatically. As long as the main program
		808	instantiates the application before any AnyEvent watchers are created,
		809	everything should just work.
		810
		811	AnyEvent::Impl::Qt based on Qt.
		812
		813	Support for IO::Async can only be partial, as it is too broken and
		814	architecturally limited to even support the AnyEvent API. It also
		815	is the only event loop that needs the loop to be set explicitly, so
		816	it can only be used by a main program knowing about AnyEvent. See
		817	L<AnyEvent::Impl::Async> for the gory details.
		818
		819	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		820
		821	=item Event loops that are indirectly supported via other backends.
		822
		823	Some event loops can be supported via other modules:
		824
		825	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		826
		827	B<WxWidgets> has no support for watching file handles. However, you can
		828	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		829	polls 20 times per second, which was considered to be too horrible to even
		830	consider for AnyEvent.
		831
		832	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		833	backend, so it can be supported through POE.
		834
		835	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		836	load L<POE> when detecting them, in the hope that POE will pick them up,
		837	in which case everything will be automatic.
		838
		839	=back
		840
601	=head1 GLOBAL VARIABLES AND FUNCTIONS	841	=head1 GLOBAL VARIABLES AND FUNCTIONS
602		842
		843	These are not normally required to use AnyEvent, but can be useful to
		844	write AnyEvent extension modules.
		845
603	=over 4	846	=over 4
604		847
605	=item $AnyEvent::MODEL	848	=item $AnyEvent::MODEL
606		849
607	Contains C<undef> until the first watcher is being created. Then it	850	Contains C<undef> until the first watcher is being created, before the
		851	backend has been autodetected.
		852
608	contains the event model that is being used, which is the name of the	853	Afterwards it contains the event model that is being used, which is the
609	Perl class implementing the model. This class is usually one of the	854	name of the Perl class implementing the model. This class is usually one
610	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	855	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
611	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	856	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
612		857	will be C<urxvt::anyevent>).
613	The known classes so far are:
614
615	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
616	AnyEvent::Impl::Event based on Event, second best choice.
617	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
618	AnyEvent::Impl::Glib based on Glib, third-best choice.
619	AnyEvent::Impl::Tk based on Tk, very bad choice.
620	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
621	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
622	AnyEvent::Impl::POE based on POE, not generic enough for full support.
623
624	There is no support for WxWidgets, as WxWidgets has no support for
625	watching file handles. However, you can use WxWidgets through the
626	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
627	second, which was considered to be too horrible to even consider for
628	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
629	it's adaptor.
630
631	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
632	autodetecting them.
633		858
634	=item AnyEvent::detect	859	=item AnyEvent::detect
635		860
636	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	861	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
637	if necessary. You should only call this function right before you would	862	if necessary. You should only call this function right before you would
638	have created an AnyEvent watcher anyway, that is, as late as possible at	863	have created an AnyEvent watcher anyway, that is, as late as possible at
639	runtime.	864	runtime, and not e.g. while initialising of your module.
		865
		866	If you need to do some initialisation before AnyEvent watchers are
		867	created, use C<post_detect>.
640		868
641	=item $guard = AnyEvent::post_detect { BLOCK }	869	=item $guard = AnyEvent::post_detect { BLOCK }
642		870
643	Arranges for the code block to be executed as soon as the event model is	871	Arranges for the code block to be executed as soon as the event model is
644	autodetected (or immediately if this has already happened).	872	autodetected (or immediately if this has already happened).
645		873
		874	The block will be executed I<after> the actual backend has been detected
		875	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		876	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		877	other initialisations - see the sources of L<AnyEvent::Strict> or
		878	L<AnyEvent::AIO> to see how this is used.
		879
		880	The most common usage is to create some global watchers, without forcing
		881	event module detection too early, for example, L<AnyEvent::AIO> creates
		882	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		883	avoid autodetecting the event module at load time.
		884
646	If called in scalar or list context, then it creates and returns an object	885	If called in scalar or list context, then it creates and returns an object
647	that automatically removes the callback again when it is destroyed. See	886	that automatically removes the callback again when it is destroyed (or
		887	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
648	L<Coro::BDB> for a case where this is useful.	888	a case where this is useful.
		889
		890	Example: Create a watcher for the IO::AIO module and store it in
		891	C<$WATCHER>. Only do so after the event loop is initialised, though.
		892
		893	our WATCHER;
		894
		895	my $guard = AnyEvent::post_detect {
		896	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		897	};
		898
		899	# the ||= is important in case post_detect immediately runs the block,
		900	# as to not clobber the newly-created watcher. assigning both watcher and
		901	# post_detect guard to the same variable has the advantage of users being
		902	# able to just C<undef $WATCHER> if the watcher causes them grief.
		903
		904	$WATCHER ||= $guard;
649		905
650	=item @AnyEvent::post_detect	906	=item @AnyEvent::post_detect
651		907
652	If there are any code references in this array (you can C<push> to it	908	If there are any code references in this array (you can C<push> to it
653	before or after loading AnyEvent), then they will called directly after	909	before or after loading AnyEvent), then they will called directly after
654	the event loop has been chosen.	910	the event loop has been chosen.
655		911
656	You should check C<$AnyEvent::MODEL> before adding to this array, though:	912	You should check C<$AnyEvent::MODEL> before adding to this array, though:
657	if it contains a true value then the event loop has already been detected,	913	if it is defined then the event loop has already been detected, and the
658	and the array will be ignored.	914	array will be ignored.
659		915
660	Best use C<AnyEvent::post_detect { BLOCK }> instead.	916	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		917	it,as it takes care of these details.
		918
		919	This variable is mainly useful for modules that can do something useful
		920	when AnyEvent is used and thus want to know when it is initialised, but do
		921	not need to even load it by default. This array provides the means to hook
		922	into AnyEvent passively, without loading it.
661		923
662	=back	924	=back
663		925
664	=head1 WHAT TO DO IN A MODULE	926	=head1 WHAT TO DO IN A MODULE
665		927
…		…
720		982
721		983
722	=head1 OTHER MODULES	984	=head1 OTHER MODULES
723		985
724	The following is a non-exhaustive list of additional modules that use	986	The following is a non-exhaustive list of additional modules that use
725	AnyEvent and can therefore be mixed easily with other AnyEvent modules	987	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
726	in the same program. Some of the modules come with AnyEvent, some are	988	modules and other event loops in the same program. Some of the modules
727	available via CPAN.	989	come with AnyEvent, most are available via CPAN.
728		990
729	=over 4	991	=over 4
730		992
731	=item L<AnyEvent::Util>	993	=item L<AnyEvent::Util>
732		994
733	Contains various utility functions that replace often-used but blocking	995	Contains various utility functions that replace often-used but blocking
734	functions such as C<inet_aton> by event-/callback-based versions.	996	functions such as C<inet_aton> by event-/callback-based versions.
735
736	=item L<AnyEvent::Handle>
737
738	Provide read and write buffers and manages watchers for reads and writes.
739		997
740	=item L<AnyEvent::Socket>	998	=item L<AnyEvent::Socket>
741		999
742	Provides various utility functions for (internet protocol) sockets,	1000	Provides various utility functions for (internet protocol) sockets,
743	addresses and name resolution. Also functions to create non-blocking tcp	1001	addresses and name resolution. Also functions to create non-blocking tcp
744	connections or tcp servers, with IPv6 and SRV record support and more.	1002	connections or tcp servers, with IPv6 and SRV record support and more.
745		1003
		1004	=item L<AnyEvent::Handle>
		1005
		1006	Provide read and write buffers, manages watchers for reads and writes,
		1007	supports raw and formatted I/O, I/O queued and fully transparent and
		1008	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1009
746	=item L<AnyEvent::DNS>	1010	=item L<AnyEvent::DNS>
747		1011
748	Provides rich asynchronous DNS resolver capabilities.	1012	Provides rich asynchronous DNS resolver capabilities.
749		1013
		1014	=item L<AnyEvent::HTTP>
		1015
		1016	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1017	HTTP requests.
		1018
750	=item L<AnyEvent::HTTPD>	1019	=item L<AnyEvent::HTTPD>
751		1020
752	Provides a simple web application server framework.	1021	Provides a simple web application server framework.
753		1022
754	=item L<AnyEvent::FastPing>	1023	=item L<AnyEvent::FastPing>
755		1024
756	The fastest ping in the west.	1025	The fastest ping in the west.
757		1026
		1027	=item L<AnyEvent::DBI>
		1028
		1029	Executes L<DBI> requests asynchronously in a proxy process.
		1030
		1031	=item L<AnyEvent::AIO>
		1032
		1033	Truly asynchronous I/O, should be in the toolbox of every event
		1034	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1035	together.
		1036
		1037	=item L<AnyEvent::BDB>
		1038
		1039	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1040	L<BDB> and AnyEvent together.
		1041
		1042	=item L<AnyEvent::GPSD>
		1043
		1044	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1045
758	=item L<Net::IRC3>	1046	=item L<AnyEvent::IRC>
759		1047
760	AnyEvent based IRC client module family.	1048	AnyEvent based IRC client module family (replacing the older Net::IRC3).
761		1049
762	=item L<Net::XMPP2>	1050	=item L<AnyEvent::XMPP>
763		1051
764	AnyEvent based XMPP (Jabber protocol) module family.	1052	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1053	Net::XMPP2>.
		1054
		1055	=item L<AnyEvent::IGS>
		1056
		1057	A non-blocking interface to the Internet Go Server protocol (used by
		1058	L<App::IGS>).
765		1059
766	=item L<Net::FCP>	1060	=item L<Net::FCP>
767		1061
768	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1062	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
769	of AnyEvent.	1063	of AnyEvent.
…		…
774		1068
775	=item L<Coro>	1069	=item L<Coro>
776		1070
777	Has special support for AnyEvent via L<Coro::AnyEvent>.	1071	Has special support for AnyEvent via L<Coro::AnyEvent>.
778		1072
779	=item L<AnyEvent::AIO>, L<IO::AIO>
780
781	Truly asynchronous I/O, should be in the toolbox of every event
782	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
783	together.
784
785	=item L<AnyEvent::BDB>, L<BDB>
786
787	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
788	IO::AIO and AnyEvent together.
789
790	=item L<IO::Lambda>
791
792	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
793
794	=back	1073	=back
795		1074
796	=cut	1075	=cut
797		1076
798	package AnyEvent;	1077	package AnyEvent;
799		1078
		1079	# basically a tuned-down version of common::sense
		1080	sub common_sense {
800	no warnings;	1081	# no warnings
801	use strict;	1082	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1083	# use strict vars subs
		1084	$^H |= 0x00000600;
		1085	}
802		1086
		1087	BEGIN { AnyEvent::common_sense }
		1088
803	use Carp;	1089	use Carp ();
804		1090
805	our $VERSION = 4.11;	1091	our $VERSION = 4.881;
806	our $MODEL;	1092	our $MODEL;
807		1093
808	our $AUTOLOAD;	1094	our $AUTOLOAD;
809	our @ISA;	1095	our @ISA;
810		1096
811	our @REGISTRY;	1097	our @REGISTRY;
812		1098
813	our $WIN32;	1099	our $WIN32;
814		1100
		1101	our $VERBOSE;
		1102
815	BEGIN {	1103	BEGIN {
816	my $win32 = ! ! ($^O =~ /mswin32/i);	1104	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
817	eval "sub WIN32(){ $win32 }";	1105	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
818	}
819		1106
		1107	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1108	if ${^TAINT};
		1109
820	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1110	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1111
		1112	}
		1113
		1114	our $MAX_SIGNAL_LATENCY = 10;
821		1115
822	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1116	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
823		1117
824	{	1118	{
825	my $idx;	1119	my $idx;
…		…
827	for reverse split /\s*,\s*/,	1121	for reverse split /\s*,\s*/,
828	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1122	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
829	}	1123	}
830		1124
831	my @models = (	1125	my @models = (
832	[EV:: => AnyEvent::Impl::EV::],	1126	[EV:: => AnyEvent::Impl::EV:: , 1],
833	[Event:: => AnyEvent::Impl::Event::],	1127	[Event:: => AnyEvent::Impl::Event::, 1],
834	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1128	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
835	# everything below here will not be autoprobed	1129	# everything below here will not (normally) be autoprobed
836	# as the pureperl backend should work everywhere	1130	# as the pureperl backend should work everywhere
837	# and is usually faster	1131	# and is usually faster
		1132	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1133	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1134	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
838	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles	1135	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
839	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
840	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
841	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1136	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
842	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1137	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
843	[Wx:: => AnyEvent::Impl::POE::],	1138	[Wx:: => AnyEvent::Impl::POE::],
844	[Prima:: => AnyEvent::Impl::POE::],	1139	[Prima:: => AnyEvent::Impl::POE::],
		1140	# IO::Async is just too broken - we would need workarounds for its
		1141	# byzantine signal and broken child handling, among others.
		1142	# IO::Async is rather hard to detect, as it doesn't have any
		1143	# obvious default class.
		1144	# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1145	# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1146	# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
845	);	1147	);
846		1148
847	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1149	our %method = map +($_ => 1),
		1150	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
848		1151
849	our @post_detect;	1152	our @post_detect;
850		1153
851	sub post_detect(&) {	1154	sub post_detect(&) {
852	my ($cb) = @_;	1155	my ($cb) = @_;
853		1156
854	if ($MODEL) {	1157	if ($MODEL) {
855	$cb->();	1158	$cb->();
856		1159
857	1	1160	undef
858	} else {	1161	} else {
859	push @post_detect, $cb;	1162	push @post_detect, $cb;
860		1163
861	defined wantarray	1164	defined wantarray
862	? bless \$cb, "AnyEvent::Util::PostDetect"	1165	? bless \$cb, "AnyEvent::Util::postdetect"
863	: ()	1166	: ()
864	}	1167	}
865	}	1168	}
866		1169
867	sub AnyEvent::Util::PostDetect::DESTROY {	1170	sub AnyEvent::Util::postdetect::DESTROY {
868	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1171	@post_detect = grep $_ != ${$_[0]}, @post_detect;
869	}	1172	}
870		1173
871	sub detect() {	1174	sub detect() {
872	unless ($MODEL) {	1175	unless ($MODEL) {
873	no strict 'refs';
874	local $SIG{__DIE__};	1176	local $SIG{__DIE__};
875		1177
876	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1178	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
877	my $model = "AnyEvent::Impl::$1";	1179	my $model = "AnyEvent::Impl::$1";
878	if (eval "require $model") {	1180	if (eval "require $model") {
879	$MODEL = $model;	1181	$MODEL = $model;
880	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1182	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
881	} else {	1183	} else {
882	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1184	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
883	}	1185	}
884	}	1186	}
885		1187
886	# check for already loaded models	1188	# check for already loaded models
887	unless ($MODEL) {	1189	unless ($MODEL) {
888	for (@REGISTRY, @models) {	1190	for (@REGISTRY, @models) {
889	my ($package, $model) = @$_;	1191	my ($package, $model) = @$_;
890	if (${"$package\::VERSION"} > 0) {	1192	if (${"$package\::VERSION"} > 0) {
891	if (eval "require $model") {	1193	if (eval "require $model") {
892	$MODEL = $model;	1194	$MODEL = $model;
893	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1195	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
894	last;	1196	last;
895	}	1197	}
896	}	1198	}
897	}	1199	}
898		1200
899	unless ($MODEL) {	1201	unless ($MODEL) {
900	# try to load a model	1202	# try to autoload a model
901
902	for (@REGISTRY, @models) {	1203	for (@REGISTRY, @models) {
903	my ($package, $model) = @$_;	1204	my ($package, $model, $autoload) = @$_;
		1205	if (
		1206	$autoload
904	if (eval "require $package"	1207	and eval "require $package"
905	and ${"$package\::VERSION"} > 0	1208	and ${"$package\::VERSION"} > 0
906	and eval "require $model") {	1209	and eval "require $model"
		1210	) {
907	$MODEL = $model;	1211	$MODEL = $model;
908	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1212	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
909	last;	1213	last;
910	}	1214	}
911	}	1215	}
912		1216
913	$MODEL	1217	$MODEL
914	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1218	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
915	}	1219	}
916	}	1220	}
917		1221
		1222	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1223
918	unshift @ISA, $MODEL;	1224	unshift @ISA, $MODEL;
919	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1225
		1226	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
920		1227
921	(shift @post_detect)->() while @post_detect;	1228	(shift @post_detect)->() while @post_detect;
922	}	1229	}
923		1230
924	$MODEL	1231	$MODEL
…		…
926		1233
927	sub AUTOLOAD {	1234	sub AUTOLOAD {
928	(my $func = $AUTOLOAD) =~ s/.*://;	1235	(my $func = $AUTOLOAD) =~ s/.*://;
929		1236
930	$method{$func}	1237	$method{$func}
931	or croak "$func: not a valid method for AnyEvent objects";	1238	or Carp::croak "$func: not a valid method for AnyEvent objects";
932		1239
933	detect unless $MODEL;	1240	detect unless $MODEL;
934		1241
935	my $class = shift;	1242	my $class = shift;
936	$class->$func (@_);	1243	$class->$func (@_);
937	}	1244	}
938		1245
		1246	# utility function to dup a filehandle. this is used by many backends
		1247	# to support binding more than one watcher per filehandle (they usually
		1248	# allow only one watcher per fd, so we dup it to get a different one).
		1249	sub _dupfh($$;$$) {
		1250	my ($poll, $fh, $r, $w) = @_;
		1251
		1252	# cygwin requires the fh mode to be matching, unix doesn't
		1253	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1254
		1255	open my $fh2, $mode, $fh
		1256	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1257
		1258	# we assume CLOEXEC is already set by perl in all important cases
		1259
		1260	($fh2, $rw)
		1261	}
		1262
939	package AnyEvent::Base;	1263	package AnyEvent::Base;
940		1264
941	# default implementation for now and time	1265	# default implementations for many methods
942		1266
943	use Time::HiRes ();	1267	sub _time {
		1268	# probe for availability of Time::HiRes
		1269	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1270	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1271	*_time = \&Time::HiRes::time;
		1272	# if (eval "use POSIX (); (POSIX::times())...
		1273	} else {
		1274	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1275	*_time = sub { time }; # epic fail
		1276	}
944		1277
945	sub time { Time::HiRes::time }	1278	&_time
946	sub now { Time::HiRes::time }	1279	}
		1280
		1281	sub time { _time }
		1282	sub now { _time }
		1283	sub now_update { }
947		1284
948	# default implementation for ->condvar	1285	# default implementation for ->condvar
949		1286
950	sub condvar {	1287	sub condvar {
951	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1288	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
952	}	1289	}
953		1290
954	# default implementation for ->signal	1291	# default implementation for ->signal
955		1292
956	our %SIG_CB;	1293	our $HAVE_ASYNC_INTERRUPT;
957		1294
		1295	sub _have_async_interrupt() {
		1296	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1297	&& eval "use Async::Interrupt 1.0 (); 1")
		1298	unless defined $HAVE_ASYNC_INTERRUPT;
		1299
		1300	$HAVE_ASYNC_INTERRUPT
		1301	}
		1302
		1303	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1304	our (%SIG_ASY, %SIG_ASY_W);
		1305	our ($SIG_COUNT, $SIG_TW);
		1306
		1307	sub _signal_exec {
		1308	$HAVE_ASYNC_INTERRUPT
		1309	? $SIGPIPE_R->drain
		1310	: sysread $SIGPIPE_R, my $dummy, 9;
		1311
		1312	while (%SIG_EV) {
		1313	for (keys %SIG_EV) {
		1314	delete $SIG_EV{$_};
		1315	$_->() for values %{ $SIG_CB{$_} || {} };
		1316	}
		1317	}
		1318	}
		1319
		1320	# install a dummy wakeup watcher to reduce signal catching latency
		1321	sub _sig_add() {
		1322	unless ($SIG_COUNT++) {
		1323	# try to align timer on a full-second boundary, if possible
		1324	my $NOW = AnyEvent->now;
		1325
		1326	$SIG_TW = AnyEvent->timer (
		1327	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1328	interval => $MAX_SIGNAL_LATENCY,
		1329	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1330	);
		1331	}
		1332	}
		1333
		1334	sub _sig_del {
		1335	undef $SIG_TW
		1336	unless --$SIG_COUNT;
		1337	}
		1338
		1339	our %SIGNAME2NUM;
		1340	our @SIGNUM2NAME;
		1341	our $_sig_name_init; $_sig_name_init = sub {
		1342	undef $_sig_name_init;
		1343
		1344	if (_have_async_interrupt) {
		1345	*sig2num = \&Async::Interrupt::sig2num;
		1346	*sig2name = \&Async::Interrupt::sig2name;
		1347	} else {
		1348	require Config;
		1349
		1350	@SIGNAME2NUM{ split ' ', $Config::Config{sig_name} }
		1351	= split ' ', $Config::Config{sig_num};
		1352	@SIGNUM2NAME[values %SIGNAME2NUM] = keys %SIGNAME2NUM;
		1353
		1354	*sig2num = sub($) {
		1355	$_[0] > 0 ? shift : $SIGNAME2NUM{+shift}
		1356	};
		1357	*sig2name = sub ($) {
		1358	$_[0] > 0 ? $SIGNUM2NAME[+shift] : shift
		1359	};
		1360	}
		1361	};
		1362
		1363	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1364	sub sig2name($) { &$_sig_name_init; &sig2name }
		1365
958	sub signal {	1366	sub _signal {
959	my (undef, %arg) = @_;	1367	my (undef, %arg) = @_;
960		1368
961	my $signal = uc $arg{signal}	1369	my $signal = uc $arg{signal}
962	or Carp::croak "required option 'signal' is missing";	1370	or Carp::croak "required option 'signal' is missing";
963		1371
		1372	if ($HAVE_ASYNC_INTERRUPT) {
		1373	# async::interrupt
		1374
		1375	$signal = sig2num $signal;
964	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1376	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1377
		1378	$SIG_ASY{$signal} ||= new Async::Interrupt
		1379	cb => sub { undef $SIG_EV{$signal} },
		1380	signal => $signal,
		1381	pipe => [$SIGPIPE_R->filenos],
		1382	pipe_autodrain => 0,
		1383	;
		1384
		1385	} else {
		1386	# pure perl
		1387
		1388	# AE::Util has been loaded in signal
		1389	$signal = sig2name $signal;
		1390	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1391
965	$SIG{$signal} ||= sub {	1392	$SIG{$signal} ||= sub {
966	$_->() for values %{ $SIG_CB{$signal} || {} };	1393	local $!;
		1394	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1395	undef $SIG_EV{$signal};
		1396	};
		1397
		1398	# can't do signal processing without introducing races in pure perl,
		1399	# so limit the signal latency.
		1400	_sig_add;
967	};	1401	}
968		1402
969	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1403	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
970	}	1404	}
971		1405
		1406	sub signal {
		1407	# probe for availability of Async::Interrupt
		1408	if (_have_async_interrupt) {
		1409	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1410
		1411	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1412	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1413
		1414	} else {
		1415	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1416
		1417	require Fcntl;
		1418
		1419	if (AnyEvent::WIN32) {
		1420	require AnyEvent::Util;
		1421
		1422	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1423	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1424	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1425	} else {
		1426	pipe $SIGPIPE_R, $SIGPIPE_W;
		1427	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1428	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1429
		1430	# not strictly required, as $^F is normally 2, but let's make sure...
		1431	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1432	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1433	}
		1434
		1435	$SIGPIPE_R
		1436	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1437
		1438	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1439	}
		1440
		1441	*signal = \&_signal;
		1442	&signal
		1443	}
		1444
972	sub AnyEvent::Base::Signal::DESTROY {	1445	sub AnyEvent::Base::signal::DESTROY {
973	my ($signal, $cb) = @{$_[0]};	1446	my ($signal, $cb) = @{$_[0]};
974		1447
		1448	_sig_del;
		1449
975	delete $SIG_CB{$signal}{$cb};	1450	delete $SIG_CB{$signal}{$cb};
976		1451
977	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1452	$HAVE_ASYNC_INTERRUPT
		1453	? delete $SIG_ASY{$signal}
		1454	: # delete doesn't work with older perls - they then
		1455	# print weird messages, or just unconditionally exit
		1456	# instead of getting the default action.
		1457	undef $SIG{$signal}
		1458	unless keys %{ $SIG_CB{$signal} };
978	}	1459	}
979		1460
980	# default implementation for ->child	1461	# default implementation for ->child
981		1462
982	our %PID_CB;	1463	our %PID_CB;
983	our $CHLD_W;	1464	our $CHLD_W;
984	our $CHLD_DELAY_W;	1465	our $CHLD_DELAY_W;
985	our $PID_IDLE;
986	our $WNOHANG;	1466	our $WNOHANG;
987		1467
988	sub _child_wait {	1468	sub _emit_childstatus($$) {
989	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1469	my (undef, $rpid, $rstatus) = @_;
		1470
		1471	$_->($rpid, $rstatus)
990	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1472	for values %{ $PID_CB{$rpid} || {} },
991	(values %{ $PID_CB{0} || {} });	1473	values %{ $PID_CB{0} || {} };
992	}
993
994	undef $PID_IDLE;
995	}	1474	}
996		1475
997	sub _sigchld {	1476	sub _sigchld {
998	# make sure we deliver these changes "synchronous" with the event loop.	1477	my $pid;
999	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1478
1000	undef $CHLD_DELAY_W;	1479	AnyEvent->_emit_childstatus ($pid, $?)
1001	&_child_wait;	1480	while ($pid = waitpid -1, $WNOHANG) > 0;
1002	});
1003	}	1481	}
1004		1482
1005	sub child {	1483	sub child {
1006	my (undef, %arg) = @_;	1484	my (undef, %arg) = @_;
1007		1485
1008	defined (my $pid = $arg{pid} + 0)	1486	defined (my $pid = $arg{pid} + 0)
1009	or Carp::croak "required option 'pid' is missing";	1487	or Carp::croak "required option 'pid' is missing";
1010		1488
1011	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1489	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
1012		1490
1013	unless ($WNOHANG) {	1491	# WNOHANG is almost cetrainly 1 everywhere
		1492	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1493	? 1
1014	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1494	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1015	}
1016		1495
1017	unless ($CHLD_W) {	1496	unless ($CHLD_W) {
1018	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1497	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
1019	# child could be a zombie already, so make at least one round	1498	# child could be a zombie already, so make at least one round
1020	&_sigchld;	1499	&_sigchld;
1021	}	1500	}
1022		1501
1023	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1502	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
1024	}	1503	}
1025		1504
1026	sub AnyEvent::Base::Child::DESTROY {	1505	sub AnyEvent::Base::child::DESTROY {
1027	my ($pid, $cb) = @{$_[0]};	1506	my ($pid, $cb) = @{$_[0]};
1028		1507
1029	delete $PID_CB{$pid}{$cb};	1508	delete $PID_CB{$pid}{$cb};
1030	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1509	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1031		1510
1032	undef $CHLD_W unless keys %PID_CB;	1511	undef $CHLD_W unless keys %PID_CB;
1033	}	1512	}
1034		1513
		1514	# idle emulation is done by simply using a timer, regardless
		1515	# of whether the process is idle or not, and not letting
		1516	# the callback use more than 50% of the time.
		1517	sub idle {
		1518	my (undef, %arg) = @_;
		1519
		1520	my ($cb, $w, $rcb) = $arg{cb};
		1521
		1522	$rcb = sub {
		1523	if ($cb) {
		1524	$w = _time;
		1525	&$cb;
		1526	$w = _time - $w;
		1527
		1528	# never use more then 50% of the time for the idle watcher,
		1529	# within some limits
		1530	$w = 0.0001 if $w < 0.0001;
		1531	$w = 5 if $w > 5;
		1532
		1533	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1534	} else {
		1535	# clean up...
		1536	undef $w;
		1537	undef $rcb;
		1538	}
		1539	};
		1540
		1541	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1542
		1543	bless \\$cb, "AnyEvent::Base::idle"
		1544	}
		1545
		1546	sub AnyEvent::Base::idle::DESTROY {
		1547	undef $${$_[0]};
		1548	}
		1549
1035	package AnyEvent::CondVar;	1550	package AnyEvent::CondVar;
1036		1551
1037	our @ISA = AnyEvent::CondVar::Base::;	1552	our @ISA = AnyEvent::CondVar::Base::;
1038		1553
1039	package AnyEvent::CondVar::Base;	1554	package AnyEvent::CondVar::Base;
1040		1555
1041	use overload	1556	#use overload
1042	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1557	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1043	fallback => 1;	1558	# fallback => 1;
		1559
		1560	# save 300+ kilobytes by dirtily hardcoding overloading
		1561	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1562	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1563	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1564	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1565
		1566	our $WAITING;
1044		1567
1045	sub _send {	1568	sub _send {
1046	# nop	1569	# nop
1047	}	1570	}
1048		1571
…		…
1061	sub ready {	1584	sub ready {
1062	$_[0]{_ae_sent}	1585	$_[0]{_ae_sent}
1063	}	1586	}
1064		1587
1065	sub _wait {	1588	sub _wait {
		1589	$WAITING
		1590	and !$_[0]{_ae_sent}
		1591	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1592
		1593	local $WAITING = 1;
1066	AnyEvent->one_event while !$_[0]{_ae_sent};	1594	AnyEvent->one_event while !$_[0]{_ae_sent};
1067	}	1595	}
1068		1596
1069	sub recv {	1597	sub recv {
1070	$_[0]->_wait;	1598	$_[0]->_wait;
…		…
1089	}	1617	}
1090		1618
1091	# undocumented/compatibility with pre-3.4	1619	# undocumented/compatibility with pre-3.4
1092	*broadcast = \&send;	1620	*broadcast = \&send;
1093	*wait = \&_wait;	1621	*wait = \&_wait;
		1622
		1623	=head1 ERROR AND EXCEPTION HANDLING
		1624
		1625	In general, AnyEvent does not do any error handling - it relies on the
		1626	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1627	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1628	checking of all AnyEvent methods, however, which is highly useful during
		1629	development.
		1630
		1631	As for exception handling (i.e. runtime errors and exceptions thrown while
		1632	executing a callback), this is not only highly event-loop specific, but
		1633	also not in any way wrapped by this module, as this is the job of the main
		1634	program.
		1635
		1636	The pure perl event loop simply re-throws the exception (usually
		1637	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1638	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1639	so on.
		1640
		1641	=head1 ENVIRONMENT VARIABLES
		1642
		1643	The following environment variables are used by this module or its
		1644	submodules.
		1645
		1646	Note that AnyEvent will remove I<all> environment variables starting with
		1647	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1648	enabled.
		1649
		1650	=over 4
		1651
		1652	=item C<PERL_ANYEVENT_VERBOSE>
		1653
		1654	By default, AnyEvent will be completely silent except in fatal
		1655	conditions. You can set this environment variable to make AnyEvent more
		1656	talkative.
		1657
		1658	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1659	conditions, such as not being able to load the event model specified by
		1660	C<PERL_ANYEVENT_MODEL>.
		1661
		1662	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1663	model it chooses.
		1664
		1665	When set to C<8> or higher, then AnyEvent will report extra information on
		1666	which optional modules it loads and how it implements certain features.
		1667
		1668	=item C<PERL_ANYEVENT_STRICT>
		1669
		1670	AnyEvent does not do much argument checking by default, as thorough
		1671	argument checking is very costly. Setting this variable to a true value
		1672	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1673	check the arguments passed to most method calls. If it finds any problems,
		1674	it will croak.
		1675
		1676	In other words, enables "strict" mode.
		1677
		1678	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1679	>>, it is definitely recommended to keep it off in production. Keeping
		1680	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1681	can be very useful, however.
		1682
		1683	=item C<PERL_ANYEVENT_MODEL>
		1684
		1685	This can be used to specify the event model to be used by AnyEvent, before
		1686	auto detection and -probing kicks in. It must be a string consisting
		1687	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1688	and the resulting module name is loaded and if the load was successful,
		1689	used as event model. If it fails to load AnyEvent will proceed with
		1690	auto detection and -probing.
		1691
		1692	This functionality might change in future versions.
		1693
		1694	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1695	could start your program like this:
		1696
		1697	PERL_ANYEVENT_MODEL=Perl perl ...
		1698
		1699	=item C<PERL_ANYEVENT_PROTOCOLS>
		1700
		1701	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1702	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1703	of auto probing).
		1704
		1705	Must be set to a comma-separated list of protocols or address families,
		1706	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1707	used, and preference will be given to protocols mentioned earlier in the
		1708	list.
		1709
		1710	This variable can effectively be used for denial-of-service attacks
		1711	against local programs (e.g. when setuid), although the impact is likely
		1712	small, as the program has to handle conenction and other failures anyways.
		1713
		1714	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1715	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1716	- only support IPv4, never try to resolve or contact IPv6
		1717	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1718	IPv6, but prefer IPv6 over IPv4.
		1719
		1720	=item C<PERL_ANYEVENT_EDNS0>
		1721
		1722	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1723	for DNS. This extension is generally useful to reduce DNS traffic, but
		1724	some (broken) firewalls drop such DNS packets, which is why it is off by
		1725	default.
		1726
		1727	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1728	EDNS0 in its DNS requests.
		1729
		1730	=item C<PERL_ANYEVENT_MAX_FORKS>
		1731
		1732	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1733	will create in parallel.
		1734
		1735	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1736
		1737	The default value for the C<max_outstanding> parameter for the default DNS
		1738	resolver - this is the maximum number of parallel DNS requests that are
		1739	sent to the DNS server.
		1740
		1741	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1742
		1743	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1744	configuration) in the default resolver. When set to the empty string, no
		1745	default config will be used.
		1746
		1747	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1748
		1749	When neither C<ca_file> nor C<ca_path> was specified during
		1750	L<AnyEvent::TLS> context creation, and either of these environment
		1751	variables exist, they will be used to specify CA certificate locations
		1752	instead of a system-dependent default.
		1753
		1754	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1755
		1756	When these are set to C<1>, then the respective modules are not
		1757	loaded. Mostly good for testing AnyEvent itself.
		1758
		1759	=back
1094		1760
1095	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1761	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1096		1762
1097	This is an advanced topic that you do not normally need to use AnyEvent in	1763	This is an advanced topic that you do not normally need to use AnyEvent in
1098	a module. This section is only of use to event loop authors who want to	1764	a module. This section is only of use to event loop authors who want to
…		…
1132		1798
1133	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1799	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1134	condition variables: code blocking while waiting for a condition will	1800	condition variables: code blocking while waiting for a condition will
1135	C<die>. This still works with most modules/usages, and blocking calls must	1801	C<die>. This still works with most modules/usages, and blocking calls must
1136	not be done in an interactive application, so it makes sense.	1802	not be done in an interactive application, so it makes sense.
1137
1138	=head1 ENVIRONMENT VARIABLES
1139
1140	The following environment variables are used by this module:
1141
1142	=over 4
1143
1144	=item C<PERL_ANYEVENT_VERBOSE>
1145
1146	By default, AnyEvent will be completely silent except in fatal
1147	conditions. You can set this environment variable to make AnyEvent more
1148	talkative.
1149
1150	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1151	conditions, such as not being able to load the event model specified by
1152	C<PERL_ANYEVENT_MODEL>.
1153
1154	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1155	model it chooses.
1156
1157	=item C<PERL_ANYEVENT_MODEL>
1158
1159	This can be used to specify the event model to be used by AnyEvent, before
1160	auto detection and -probing kicks in. It must be a string consisting
1161	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1162	and the resulting module name is loaded and if the load was successful,
1163	used as event model. If it fails to load AnyEvent will proceed with
1164	auto detection and -probing.
1165
1166	This functionality might change in future versions.
1167
1168	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1169	could start your program like this:
1170
1171	PERL_ANYEVENT_MODEL=Perl perl ...
1172
1173	=item C<PERL_ANYEVENT_PROTOCOLS>
1174
1175	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1176	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1177	of auto probing).
1178
1179	Must be set to a comma-separated list of protocols or address families,
1180	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1181	used, and preference will be given to protocols mentioned earlier in the
1182	list.
1183
1184	This variable can effectively be used for denial-of-service attacks
1185	against local programs (e.g. when setuid), although the impact is likely
1186	small, as the program has to handle connection errors already-
1187
1188	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1189	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1190	- only support IPv4, never try to resolve or contact IPv6
1191	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1192	IPv6, but prefer IPv6 over IPv4.
1193
1194	=item C<PERL_ANYEVENT_EDNS0>
1195
1196	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1197	for DNS. This extension is generally useful to reduce DNS traffic, but
1198	some (broken) firewalls drop such DNS packets, which is why it is off by
1199	default.
1200
1201	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1202	EDNS0 in its DNS requests.
1203
1204	=item C<PERL_ANYEVENT_MAX_FORKS>
1205
1206	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1207	will create in parallel.
1208
1209	=back
1210		1803
1211	=head1 EXAMPLE PROGRAM	1804	=head1 EXAMPLE PROGRAM
1212		1805
1213	The following program uses an I/O watcher to read data from STDIN, a timer	1806	The following program uses an I/O watcher to read data from STDIN, a timer
1214	to display a message once per second, and a condition variable to quit the	1807	to display a message once per second, and a condition variable to quit the
…		…
1408	watcher.	2001	watcher.
1409		2002
1410	=head3 Results	2003	=head3 Results
1411		2004
1412	name watchers bytes create invoke destroy comment	2005	name watchers bytes create invoke destroy comment
1413	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2006	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1414	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2007	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1415	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2008	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1416	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2009	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1417	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2010	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1418	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2011	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		2012	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		2013	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1419	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2014	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1420	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2015	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1421	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2016	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1422	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2017	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1423		2018
1424	=head3 Discussion	2019	=head3 Discussion
1425		2020
1426	The benchmark does I<not> measure scalability of the event loop very	2021	The benchmark does I<not> measure scalability of the event loop very
1427	well. For example, a select-based event loop (such as the pure perl one)	2022	well. For example, a select-based event loop (such as the pure perl one)
…		…
1452	performance becomes really bad with lots of file descriptors (and few of	2047	performance becomes really bad with lots of file descriptors (and few of
1453	them active), of course, but this was not subject of this benchmark.	2048	them active), of course, but this was not subject of this benchmark.
1454		2049
1455	The C<Event> module has a relatively high setup and callback invocation	2050	The C<Event> module has a relatively high setup and callback invocation
1456	cost, but overall scores in on the third place.	2051	cost, but overall scores in on the third place.
		2052
		2053	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2054	when using its pure perl backend.
1457		2055
1458	C<Glib>'s memory usage is quite a bit higher, but it features a	2056	C<Glib>'s memory usage is quite a bit higher, but it features a
1459	faster callback invocation and overall ends up in the same class as	2057	faster callback invocation and overall ends up in the same class as
1460	C<Event>. However, Glib scales extremely badly, doubling the number of	2058	C<Event>. However, Glib scales extremely badly, doubling the number of
1461	watchers increases the processing time by more than a factor of four,	2059	watchers increases the processing time by more than a factor of four,
…		…
1539	it to another server. This includes deleting the old timeout and creating	2137	it to another server. This includes deleting the old timeout and creating
1540	a new one that moves the timeout into the future.	2138	a new one that moves the timeout into the future.
1541		2139
1542	=head3 Results	2140	=head3 Results
1543		2141
1544	name sockets create request	2142	name sockets create request
1545	EV 20000 69.01 11.16	2143	EV 20000 69.01 11.16
1546	Perl 20000 73.32 35.87	2144	Perl 20000 73.32 35.87
		2145	IOAsync 20000 157.00 98.14 epoll
		2146	IOAsync 20000 159.31 616.06 poll
1547	Event 20000 212.62 257.32	2147	Event 20000 212.62 257.32
1548	Glib 20000 651.16 1896.30	2148	Glib 20000 651.16 1896.30
1549	POE 20000 349.67 12317.24 uses POE::Loop::Event	2149	POE 20000 349.67 12317.24 uses POE::Loop::Event
1550		2150
1551	=head3 Discussion	2151	=head3 Discussion
1552		2152
1553	This benchmark I<does> measure scalability and overall performance of the	2153	This benchmark I<does> measure scalability and overall performance of the
1554	particular event loop.	2154	particular event loop.
…		…
1556	EV is again fastest. Since it is using epoll on my system, the setup time	2156	EV is again fastest. Since it is using epoll on my system, the setup time
1557	is relatively high, though.	2157	is relatively high, though.
1558		2158
1559	Perl surprisingly comes second. It is much faster than the C-based event	2159	Perl surprisingly comes second. It is much faster than the C-based event
1560	loops Event and Glib.	2160	loops Event and Glib.
		2161
		2162	IO::Async performs very well when using its epoll backend, and still quite
		2163	good compared to Glib when using its pure perl backend.
1561		2164
1562	Event suffers from high setup time as well (look at its code and you will	2165	Event suffers from high setup time as well (look at its code and you will
1563	understand why). Callback invocation also has a high overhead compared to	2166	understand why). Callback invocation also has a high overhead compared to
1564	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2167	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1565	uses select or poll in basically all documented configurations.	2168	uses select or poll in basically all documented configurations.
…		…
1628	=item * C-based event loops perform very well with small number of	2231	=item * C-based event loops perform very well with small number of
1629	watchers, as the management overhead dominates.	2232	watchers, as the management overhead dominates.
1630		2233
1631	=back	2234	=back
1632		2235
		2236	=head2 THE IO::Lambda BENCHMARK
		2237
		2238	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2239	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2240	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2241	shouldn't come as a surprise to anybody). As such, the benchmark is
		2242	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2243	very optimal. But how would AnyEvent compare when used without the extra
		2244	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2245
		2246	The benchmark itself creates an echo-server, and then, for 500 times,
		2247	connects to the echo server, sends a line, waits for the reply, and then
		2248	creates the next connection. This is a rather bad benchmark, as it doesn't
		2249	test the efficiency of the framework or much non-blocking I/O, but it is a
		2250	benchmark nevertheless.
		2251
		2252	name runtime
		2253	Lambda/select 0.330 sec
		2254	+ optimized 0.122 sec
		2255	Lambda/AnyEvent 0.327 sec
		2256	+ optimized 0.138 sec
		2257	Raw sockets/select 0.077 sec
		2258	POE/select, components 0.662 sec
		2259	POE/select, raw sockets 0.226 sec
		2260	POE/select, optimized 0.404 sec
		2261
		2262	AnyEvent/select/nb 0.085 sec
		2263	AnyEvent/EV/nb 0.068 sec
		2264	+state machine 0.134 sec
		2265
		2266	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2267	benchmarks actually make blocking connects and use 100% blocking I/O,
		2268	defeating the purpose of an event-based solution. All of the newly
		2269	written AnyEvent benchmarks use 100% non-blocking connects (using
		2270	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2271	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2272	generally require a lot more bookkeeping and event handling than blocking
		2273	connects (which involve a single syscall only).
		2274
		2275	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2276	offers similar expressive power as POE and IO::Lambda, using conventional
		2277	Perl syntax. This means that both the echo server and the client are 100%
		2278	non-blocking, further placing it at a disadvantage.
		2279
		2280	As you can see, the AnyEvent + EV combination even beats the
		2281	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2282	backend easily beats IO::Lambda and POE.
		2283
		2284	And even the 100% non-blocking version written using the high-level (and
		2285	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2286	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2287	in a non-blocking way.
		2288
		2289	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2290	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2291	part of the IO::lambda distribution and were used without any changes.
		2292
		2293
		2294	=head1 SIGNALS
		2295
		2296	AnyEvent currently installs handlers for these signals:
		2297
		2298	=over 4
		2299
		2300	=item SIGCHLD
		2301
		2302	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2303	emulation for event loops that do not support them natively. Also, some
		2304	event loops install a similar handler.
		2305
		2306	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2307	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2308
		2309	=item SIGPIPE
		2310
		2311	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2312	when AnyEvent gets loaded.
		2313
		2314	The rationale for this is that AnyEvent users usually do not really depend
		2315	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2316	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2317	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2318	some random socket.
		2319
		2320	The rationale for installing a no-op handler as opposed to ignoring it is
		2321	that this way, the handler will be restored to defaults on exec.
		2322
		2323	Feel free to install your own handler, or reset it to defaults.
		2324
		2325	=back
		2326
		2327	=cut
		2328
		2329	undef $SIG{CHLD}
		2330	if $SIG{CHLD} eq 'IGNORE';
		2331
		2332	$SIG{PIPE} = sub { }
		2333	unless defined $SIG{PIPE};
		2334
		2335	=head1 RECOMMENDED/OPTIONAL MODULES
		2336
		2337	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2338	it's built-in modules) are required to use it.
		2339
		2340	That does not mean that AnyEvent won't take advantage of some additional
		2341	modules if they are installed.
		2342
		2343	This section epxlains which additional modules will be used, and how they
		2344	affect AnyEvent's operetion.
		2345
		2346	=over 4
		2347
		2348	=item L<Async::Interrupt>
		2349
		2350	This slightly arcane module is used to implement fast signal handling: To
		2351	my knowledge, there is no way to do completely race-free and quick
		2352	signal handling in pure perl. To ensure that signals still get
		2353	delivered, AnyEvent will start an interval timer to wake up perl (and
		2354	catch the signals) with some delay (default is 10 seconds, look for
		2355	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2356
		2357	If this module is available, then it will be used to implement signal
		2358	catching, which means that signals will not be delayed, and the event loop
		2359	will not be interrupted regularly, which is more efficient (And good for
		2360	battery life on laptops).
		2361
		2362	This affects not just the pure-perl event loop, but also other event loops
		2363	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2364
		2365	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2366	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2367	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2368	does nothing for those backends.
		2369
		2370	=item L<EV>
		2371
		2372	This module isn't really "optional", as it is simply one of the backend
		2373	event loops that AnyEvent can use. However, it is simply the best event
		2374	loop available in terms of features, speed and stability: It supports
		2375	the AnyEvent API optimally, implements all the watcher types in XS, does
		2376	automatic timer adjustments even when no monotonic clock is available,
		2377	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2378	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2379	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2380
		2381	=item L<Guard>
		2382
		2383	The guard module, when used, will be used to implement
		2384	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2385	lot less memory), but otherwise doesn't affect guard operation much. It is
		2386	purely used for performance.
		2387
		2388	=item L<JSON> and L<JSON::XS>
		2389
		2390	This module is required when you want to read or write JSON data via
		2391	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2392	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2393
		2394	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2395	installed.
		2396
		2397	=item L<Net::SSLeay>
		2398
		2399	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2400	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2401	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2402
		2403	=item L<Time::HiRes>
		2404
		2405	This module is part of perl since release 5.008. It will be used when the
		2406	chosen event library does not come with a timing source on it's own. The
		2407	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2408	try to use a monotonic clock for timing stability.
		2409
		2410	=back
		2411
1633		2412
1634	=head1 FORK	2413	=head1 FORK
1635		2414
1636	Most event libraries are not fork-safe. The ones who are usually are	2415	Most event libraries are not fork-safe. The ones who are usually are
1637	because they rely on inefficient but fork-safe C<select> or C<poll>	2416	because they rely on inefficient but fork-safe C<select> or C<poll>
1638	calls. Only L<EV> is fully fork-aware.	2417	calls. Only L<EV> is fully fork-aware.
1639		2418
1640	If you have to fork, you must either do so I<before> creating your first	2419	If you have to fork, you must either do so I<before> creating your first
1641	watcher OR you must not use AnyEvent at all in the child.	2420	watcher OR you must not use AnyEvent at all in the child OR you must do
		2421	something completely out of the scope of AnyEvent.
1642		2422
1643		2423
1644	=head1 SECURITY CONSIDERATIONS	2424	=head1 SECURITY CONSIDERATIONS
1645		2425
1646	AnyEvent can be forced to load any event model via	2426	AnyEvent can be forced to load any event model via
…		…
1651	specified in the variable.	2431	specified in the variable.
1652		2432
1653	You can make AnyEvent completely ignore this variable by deleting it	2433	You can make AnyEvent completely ignore this variable by deleting it
1654	before the first watcher gets created, e.g. with a C<BEGIN> block:	2434	before the first watcher gets created, e.g. with a C<BEGIN> block:
1655		2435
1656	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2436	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1657		2437
1658	use AnyEvent;	2438	use AnyEvent;
1659		2439
1660	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2440	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1661	be used to probe what backend is used and gain other information (which is	2441	be used to probe what backend is used and gain other information (which is
1662	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2442	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2443	$ENV{PERL_ANYEVENT_STRICT}.
		2444
		2445	Note that AnyEvent will remove I<all> environment variables starting with
		2446	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2447	enabled.
		2448
		2449
		2450	=head1 BUGS
		2451
		2452	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2453	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2454	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2455	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2456	pronounced).
1663		2457
1664		2458
1665	=head1 SEE ALSO	2459	=head1 SEE ALSO
1666		2460
1667	Utility functions: L<AnyEvent::Util>.	2461	Utility functions: L<AnyEvent::Util>.
…		…
1670	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2464	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1671		2465
1672	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2466	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1673	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2467	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1674	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2468	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1675	L<AnyEvent::Impl::POE>.	2469	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1676		2470
1677	Non-blocking file handles, sockets, TCP clients and	2471	Non-blocking file handles, sockets, TCP clients and
1678	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2472	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1679		2473
1680	Asynchronous DNS: L<AnyEvent::DNS>.	2474	Asynchronous DNS: L<AnyEvent::DNS>.
1681		2475
1682	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2476	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2477	L<Coro::Event>,
1683		2478
1684	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2479	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2480	L<AnyEvent::HTTP>.
1685		2481
1686		2482
1687	=head1 AUTHOR	2483	=head1 AUTHOR
1688		2484
1689	Marc Lehmann <schmorp@schmorp.de>	2485	Marc Lehmann <schmorp@schmorp.de>
1690	http://home.schmorp.de/	2486	http://home.schmorp.de/
1691		2487
1692	=cut	2488	=cut
1693		2489
1694	1	2490	1
1695		2491

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