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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 });
22		39
23	=head1 INTRODUCTION/TUTORIAL	40	=head1 INTRODUCTION/TUTORIAL
24		41
25	This manpage is mainly a reference manual. If you are interested	42	This manpage is mainly a reference manual. If you are interested
26	in a tutorial or some gentle introduction, have a look at the	43	in a tutorial or some gentle introduction, have a look at the
27	L<AnyEvent::Intro> manpage.	44	L<AnyEvent::Intro> manpage.
28		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.
		53
29	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
30		55
31	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
32	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
33		58
34	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
35	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
36		61
37	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
38	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
39	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
40	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,
41	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
42	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
43		69
44	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
45	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
46	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
47	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
48	model you use.	74	model you use.
49		75
50	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
51	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
52	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
53	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
54	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
55	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.
56		82
57	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
58	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
59	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
60	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,
61	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
62	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
63	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
64	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
65		91
66	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
67	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
68	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
69	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
…		…
127	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
128	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
129	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
130	is in control).	156	is in control).
131		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
132	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
133	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
134	to it).	166	to it).
135		167
136	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.
…		…
138	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
139	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.
140		172
141	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
142		174
143	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
144	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
145	undef $w;	177	undef $w;
146	});	178	});
147		179
148	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,
149	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
150	declared.	182	declared.
151		183
152	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
153		185
154	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
155	with the following mandatory key-value pairs as arguments:	187	with the following mandatory key-value pairs as arguments:
156		188
157	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
158	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
159	which creates a watcher waiting for "r"eadable or "w"ritable events,	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
		198
160	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.
161	becomes ready.
162		200
163	Although the callback might get passed parameters, their value and	201	Although the callback might get passed parameters, their value and
164	presence is undefined and you cannot rely on them. Portable AnyEvent	202	presence is undefined and you cannot rely on them. Portable AnyEvent
165	callbacks cannot use arguments passed to I/O watcher callbacks.	203	callbacks cannot use arguments passed to I/O watcher callbacks.
166		204
…		…
170		208
171	Some event loops issue spurious readyness notifications, so you should	209	Some event loops issue spurious readyness notifications, so you should
172	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
173	handles.	211	handles.
174		212
175	Example:
176
177	# 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
178	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
179	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
180	warn "read: $input\n";	218	warn "read: $input\n";
181	undef $w;	219	undef $w;
182	});	220	});
…		…
192		230
193	Although the callback might get passed parameters, their value and	231	Although the callback might get passed parameters, their value and
194	presence is undefined and you cannot rely on them. Portable AnyEvent	232	presence is undefined and you cannot rely on them. Portable AnyEvent
195	callbacks cannot use arguments passed to time watcher callbacks.	233	callbacks cannot use arguments passed to time watcher callbacks.
196		234
197	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
198	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
199	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.
200		240
201	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.
202		244
203	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
204	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
205	warn "timeout\n";	248	warn "timeout\n";
206	});	249	});
207		250
208	# to cancel the timer:	251	# to cancel the timer:
209	undef $w;	252	undef $w;
210		253
211	Example 2:
212
213	# 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.
214	my $w;
215		255
216	my $cb = sub {
217	# cancel the old timer while creating a new one
218	$w = AnyEvent->timer (after => 1, cb => $cb);	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		257	warn "timeout\n";
219	};	258	};
220
221	# start the "loop" by creating the first watcher
222	$w = AnyEvent->timer (after => 0.5, cb => $cb);
223		259
224	=head3 TIMING ISSUES	260	=head3 TIMING ISSUES
225		261
226	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
227	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
…		…
300	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
301	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
302	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
303	account.	339	account.
304		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
305	=back	356	=back
306		357
307	=head2 SIGNAL WATCHERS	358	=head2 SIGNAL WATCHERS
308		359
309	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
310	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
311	be invoked whenever a signal occurs.	362	callback to be invoked whenever a signal occurs.
312		363
313	Although the callback might get passed parameters, their value and	364	Although the callback might get passed parameters, their value and
314	presence is undefined and you cannot rely on them. Portable AnyEvent	365	presence is undefined and you cannot rely on them. Portable AnyEvent
315	callbacks cannot use arguments passed to signal watcher callbacks.	366	callbacks cannot use arguments passed to signal watcher callbacks.
316		367
…		…
318	invocation, and callback invocation will be synchronous. Synchronous means	369	invocation, and callback invocation will be synchronous. Synchronous means
319	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,
320	but it is guaranteed not to interrupt any other callbacks.	371	but it is guaranteed not to interrupt any other callbacks.
321		372
322	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
323	between multiple watchers.	374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
324		376
325	This watcher might use C<%SIG>, so programs overwriting those signals	377	This watcher might use C<%SIG> (depending on the event loop used),
326	directly will likely not work correctly.	378	so programs overwriting those signals directly will likely not work
		379	correctly.
327		380
328	Example: exit on SIGINT	381	Example: exit on SIGINT
329		382
330	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
331		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$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
332	=head2 CHILD PROCESS WATCHERS	401	=head2 CHILD PROCESS WATCHERS
333		402
334	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.
335		404
336	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,
337	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
338	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
339	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
340	and exit status (as returned by waitpid), so unlike other watcher types,	409	(stopped/continued).
341	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).
342		419
343	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
344	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
345	have exited already (and no SIGCHLD will be sent anymore).	422	have exited already (and no SIGCHLD will be sent anymore).
346		423
347	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
348	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
349	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.
350		430
351	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
352	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
353	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.
354		439
355	Example: fork a process and wait for it	440	Example: fork a process and wait for it
356		441
357	my $done = AnyEvent->condvar;	442	my $done = AnyEvent->condvar;
358		443
359	my $pid = fork or exit 5;	444	my $pid = fork or exit 5;
360		445
361	my $w = AnyEvent->child (	446	my $w = AnyEvent->child (
362	pid => $pid,	447	pid => $pid,
363	cb => sub {	448	cb => sub {
364	my ($pid, $status) = @_;	449	my ($pid, $status) = @_;
365	warn "pid $pid exited with status $status";	450	warn "pid $pid exited with status $status";
366	$done->send;	451	$done->send;
367	},	452	},
368	);	453	);
369		454
370	# do something else, then wait for process exit	455	# do something else, then wait for process exit
371	$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	});
372		492
373	=head2 CONDITION VARIABLES	493	=head2 CONDITION VARIABLES
374		494
375	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
376	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
377	will actively watch for new events and call your callbacks.	497	will actively watch for new events and call your callbacks.
378		498
379	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
380	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).
381		501
382	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
383	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.
384		506
385	Condition variables can be created by calling the C<< AnyEvent->condvar	507	Condition variables can be created by calling the C<< AnyEvent->condvar
386	>> method, usually without arguments. The only argument pair allowed is	508	>> method, usually without arguments. The only argument pair allowed is
387	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
388	becomes true.	510	becomes true, with the condition variable as the first argument (but not
		511	the results).
389		512
390	After creation, the condition variable is "false" until it becomes "true"	513	After creation, the condition variable is "false" until it becomes "true"
391	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
392	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<<
393	->send >> method).	516	->send >> method).
…		…
395	Condition variables are similar to callbacks, except that you can	518	Condition variables are similar to callbacks, except that you can
396	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
397	in time where multiple outstanding events have been processed. And yet	520	in time where multiple outstanding events have been processed. And yet
398	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
399	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
400	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.
401		525
402	Condition variables are very useful to signal that something has finished,	526	Condition variables are very useful to signal that something has finished,
403	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,
404	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
405	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
…		…
439	after => 1,	563	after => 1,
440	cb => sub { $result_ready->send },	564	cb => sub { $result_ready->send },
441	);	565	);
442		566
443	# this "blocks" (while handling events) till the callback	567	# this "blocks" (while handling events) till the callback
444	# calls send	568	# calls -<send
445	$result_ready->recv;	569	$result_ready->recv;
446		570
447	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
448	condition variables are also code references.	572	variables are also callable directly.
449		573
450	my $done = AnyEvent->condvar;	574	my $done = AnyEvent->condvar;
451	my $delay = AnyEvent->timer (after => 5, cb => $done);	575	my $delay = AnyEvent->timer (after => 5, cb => $done);
452	$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	});
453		594
454	=head3 METHODS FOR PRODUCERS	595	=head3 METHODS FOR PRODUCERS
455		596
456	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
457	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
…		…
470	immediately from within send.	611	immediately from within send.
471		612
472	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
473	future C<< ->recv >> calls.	614	future C<< ->recv >> calls.
474		615
475	Condition variables are overloaded so one can call them directly	616	Condition variables are overloaded so one can call them directly (as if
476	(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
477	C<send>. Note, however, that many C-based event loops do not handle	618	C<send>.
478	overloading, so as tempting as it may be, passing a condition variable
479	instead of a callback does not work. Both the pure perl and EV loops
480	support overloading, however, as well as all functions that use perl to
481	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
482	example).
483		619
484	=item $cv->croak ($error)	620	=item $cv->croak ($error)
485		621
486	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
487	C<Carp::croak> with the given error message/object/scalar.	623	C<Carp::croak> with the given error message/object/scalar.
488		624
489	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
490	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.
491		631
492	=item $cv->begin ([group callback])	632	=item $cv->begin ([group callback])
493		633
494	=item $cv->end	634	=item $cv->end
495
496	These two methods are EXPERIMENTAL and MIGHT CHANGE.
497		635
498	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
499	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
500	to use a condition variable for the whole process.	638	to use a condition variable for the whole process.
501		639
…		…
503	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
504	>>, 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
505	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
506	callback was set, C<send> will be called without any arguments.	644	callback was set, C<send> will be called without any arguments.
507		645
508	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:
509		677
510	my $cv = AnyEvent->condvar;	678	my $cv = AnyEvent->condvar;
511		679
512	my %result;	680	my %result;
513	$cv->begin (sub { $cv->send (\%result) });	681	$cv->begin (sub { $cv->send (\%result) });
…		…
533	loop, which serves two important purposes: first, it sets the callback	701	loop, which serves two important purposes: first, it sets the callback
534	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
535	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
536	doesn't execute once).	704	doesn't execute once).
537		705
538	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
539	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
540	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
541	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>.
542		711
543	=back	712	=back
544		713
545	=head3 METHODS FOR CONSUMERS	714	=head3 METHODS FOR CONSUMERS
546		715
…		…
562	function will call C<croak>.	731	function will call C<croak>.
563		732
564	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,
565	in scalar context only the first one will be returned.	734	in scalar context only the first one will be returned.
566		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
567	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
568	(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
569	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
570	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
571	condition variables with some kind of request results and supporting	747	condition variables with some kind of request results and supporting
572	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,
573	while still supporting blocking waits if the caller so desires).	749	while still supporting blocking waits if the caller so desires).
574		750
575	Another reason I<never> to C<< ->recv >> in a module is that you cannot
576	sensibly have two C<< ->recv >>'s in parallel, as that would require
577	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
578	can supply.
579
580	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
581	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
582	versions and also integrates coroutines into AnyEvent, making blocking
583	C<< ->recv >> calls perfectly safe as long as they are done from another
584	coroutine (one that doesn't run the event loop).
585
586	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
587	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
588	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
589	waits otherwise.	754	waits otherwise.
590		755
591	=item $bool = $cv->ready	756	=item $bool = $cv->ready
592		757
593	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
594	C<croak> have been called.	759	C<croak> have been called.
595		760
596	=item $cb = $cv->cb ([new callback])	761	=item $cb = $cv->cb ($cb->($cv))
597		762
598	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
599	replaces it before doing so.	764	replaces it before doing so.
600		765
601	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
…		…
603	variable itself. Calling C<recv> inside the callback or at any later time	768	variable itself. Calling C<recv> inside the callback or at any later time
604	is guaranteed not to block.	769	is guaranteed not to block.
605		770
606	=back	771	=back
607		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
608	=head1 GLOBAL VARIABLES AND FUNCTIONS	841	=head1 GLOBAL VARIABLES AND FUNCTIONS
609		842
		843	These are not normally required to use AnyEvent, but can be useful to
		844	write AnyEvent extension modules.
		845
610	=over 4	846	=over 4
611		847
612	=item $AnyEvent::MODEL	848	=item $AnyEvent::MODEL
613		849
614	Contains C<undef> until the first watcher is being created. Then it	850	Contains C<undef> until the first watcher is being created, before the
		851	backend has been autodetected.
		852
615	contains the event model that is being used, which is the name of the	853	Afterwards it contains the event model that is being used, which is the
616	Perl class implementing the model. This class is usually one of the	854	name of the Perl class implementing the model. This class is usually one
617	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	855	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
618	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	856	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
619		857	will be C<urxvt::anyevent>).
620	The known classes so far are:
621
622	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
623	AnyEvent::Impl::Event based on Event, second best choice.
624	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
625	AnyEvent::Impl::Glib based on Glib, third-best choice.
626	AnyEvent::Impl::Tk based on Tk, very bad choice.
627	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
628	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
629	AnyEvent::Impl::POE based on POE, not generic enough for full support.
630
631	There is no support for WxWidgets, as WxWidgets has no support for
632	watching file handles. However, you can use WxWidgets through the
633	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
634	second, which was considered to be too horrible to even consider for
635	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
636	it's adaptor.
637
638	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
639	autodetecting them.
640		858
641	=item AnyEvent::detect	859	=item AnyEvent::detect
642		860
643	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	861	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
644	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
645	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
646	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>.
647		868
648	=item $guard = AnyEvent::post_detect { BLOCK }	869	=item $guard = AnyEvent::post_detect { BLOCK }
649		870
650	Arranges for the code block to be executed as soon as the event model is	871	Arranges for the code block to be executed as soon as the event model is
651	autodetected (or immediately if this has already happened).	872	autodetected (or immediately if this has already happened).
652		873
		874	The block will be executed I<after> the actual backend has been detected
		875	(C<$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
653	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
654	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
655	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 ||= $guard;
656		905
657	=item @AnyEvent::post_detect	906	=item @AnyEvent::post_detect
658		907
659	If there are any code references in this array (you can C<push> to it	908	If there are any code references in this array (you can C<push> to it
660	before or after loading AnyEvent), then they will called directly after	909	before or after loading AnyEvent), then they will called directly after
661	the event loop has been chosen.	910	the event loop has been chosen.
662		911
663	You should check C<$AnyEvent::MODEL> before adding to this array, though:	912	You should check C<$AnyEvent::MODEL> before adding to this array, though:
664	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
665	and the array will be ignored.	914	array will be ignored.
666		915
667	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.
668		923
669	=back	924	=back
670		925
671	=head1 WHAT TO DO IN A MODULE	926	=head1 WHAT TO DO IN A MODULE
672		927
…		…
727		982
728		983
729	=head1 OTHER MODULES	984	=head1 OTHER MODULES
730		985
731	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
732	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
733	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
734	available via CPAN.	989	come with AnyEvent, most are available via CPAN.
735		990
736	=over 4	991	=over 4
737		992
738	=item L<AnyEvent::Util>	993	=item L<AnyEvent::Util>
739		994
740	Contains various utility functions that replace often-used but blocking	995	Contains various utility functions that replace often-used but blocking
741	functions such as C<inet_aton> by event-/callback-based versions.	996	functions such as C<inet_aton> by event-/callback-based versions.
742
743	=item L<AnyEvent::Handle>
744
745	Provide read and write buffers and manages watchers for reads and writes.
746		997
747	=item L<AnyEvent::Socket>	998	=item L<AnyEvent::Socket>
748		999
749	Provides various utility functions for (internet protocol) sockets,	1000	Provides various utility functions for (internet protocol) sockets,
750	addresses and name resolution. Also functions to create non-blocking tcp	1001	addresses and name resolution. Also functions to create non-blocking tcp
751	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.
752		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
753	=item L<AnyEvent::DNS>	1010	=item L<AnyEvent::DNS>
754		1011
755	Provides rich asynchronous DNS resolver capabilities.	1012	Provides rich asynchronous DNS resolver capabilities.
756		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
757	=item L<AnyEvent::HTTPD>	1019	=item L<AnyEvent::HTTPD>
758		1020
759	Provides a simple web application server framework.	1021	Provides a simple web application server framework.
760		1022
761	=item L<AnyEvent::FastPing>	1023	=item L<AnyEvent::FastPing>
762		1024
763	The fastest ping in the west.	1025	The fastest ping in the west.
764		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
765	=item L<Net::IRC3>	1046	=item L<AnyEvent::IRC>
766		1047
767	AnyEvent based IRC client module family.	1048	AnyEvent based IRC client module family (replacing the older Net::IRC3).
768		1049
769	=item L<Net::XMPP2>	1050	=item L<AnyEvent::XMPP>
770		1051
771	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>).
772		1059
773	=item L<Net::FCP>	1060	=item L<Net::FCP>
774		1061
775	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1062	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
776	of AnyEvent.	1063	of AnyEvent.
…		…
781		1068
782	=item L<Coro>	1069	=item L<Coro>
783		1070
784	Has special support for AnyEvent via L<Coro::AnyEvent>.	1071	Has special support for AnyEvent via L<Coro::AnyEvent>.
785		1072
786	=item L<AnyEvent::AIO>, L<IO::AIO>
787
788	Truly asynchronous I/O, should be in the toolbox of every event
789	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
790	together.
791
792	=item L<AnyEvent::BDB>, L<BDB>
793
794	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
795	IO::AIO and AnyEvent together.
796
797	=item L<IO::Lambda>
798
799	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
800
801	=back	1073	=back
802		1074
803	=cut	1075	=cut
804		1076
805	package AnyEvent;	1077	package AnyEvent;
806		1078
		1079	# basically a tuned-down version of common::sense
		1080	sub common_sense {
807	no warnings;	1081	# no warnings
808	use strict;	1082	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1083	# use strict vars subs
		1084	$^H |= 0x00000600;
		1085	}
809		1086
		1087	BEGIN { AnyEvent::common_sense }
		1088
810	use Carp;	1089	use Carp ();
811		1090
812	our $VERSION = 4.11;	1091	our $VERSION = 4.881;
813	our $MODEL;	1092	our $MODEL;
814		1093
815	our $AUTOLOAD;	1094	our $AUTOLOAD;
816	our @ISA;	1095	our @ISA;
817		1096
818	our @REGISTRY;	1097	our @REGISTRY;
819		1098
820	our $WIN32;	1099	our $WIN32;
821		1100
		1101	our $VERBOSE;
		1102
822	BEGIN {	1103	BEGIN {
823	my $win32 = ! ! ($^O =~ /mswin32/i);	1104	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
824	eval "sub WIN32(){ $win32 }";	1105	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
825	}
826		1106
		1107	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1108	if ${^TAINT};
		1109
827	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1110	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1111
		1112	}
		1113
		1114	our $MAX_SIGNAL_LATENCY = 10;
828		1115
829	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1116	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
830		1117
831	{	1118	{
832	my $idx;	1119	my $idx;
…		…
834	for reverse split /\s*,\s*/,	1121	for reverse split /\s*,\s*/,
835	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1122	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
836	}	1123	}
837		1124
838	my @models = (	1125	my @models = (
839	[EV:: => AnyEvent::Impl::EV::],	1126	[EV:: => AnyEvent::Impl::EV:: , 1],
840	[Event:: => AnyEvent::Impl::Event::],	1127	[Event:: => AnyEvent::Impl::Event::, 1],
841	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1128	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
842	# everything below here will not be autoprobed	1129	# everything below here will not (normally) be autoprobed
843	# as the pureperl backend should work everywhere	1130	# as the pureperl backend should work everywhere
844	# 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
845	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles	1135	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
846	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
847	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
848	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1136	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
849	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1137	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
850	[Wx:: => AnyEvent::Impl::POE::],	1138	[Wx:: => AnyEvent::Impl::POE::],
851	[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
852	);	1147	);
853		1148
854	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1149	our %method = map +($_ => 1),
		1150	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
855		1151
856	our @post_detect;	1152	our @post_detect;
857		1153
858	sub post_detect(&) {	1154	sub post_detect(&) {
859	my ($cb) = @_;	1155	my ($cb) = @_;
860		1156
861	if ($MODEL) {	1157	if ($MODEL) {
862	$cb->();	1158	$cb->();
863		1159
864	1	1160	undef
865	} else {	1161	} else {
866	push @post_detect, $cb;	1162	push @post_detect, $cb;
867		1163
868	defined wantarray	1164	defined wantarray
869	? bless \$cb, "AnyEvent::Util::PostDetect"	1165	? bless \$cb, "AnyEvent::Util::postdetect"
870	: ()	1166	: ()
871	}	1167	}
872	}	1168	}
873		1169
874	sub AnyEvent::Util::PostDetect::DESTROY {	1170	sub AnyEvent::Util::postdetect::DESTROY {
875	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1171	@post_detect = grep $_ != ${$_[0]}, @post_detect;
876	}	1172	}
877		1173
878	sub detect() {	1174	sub detect() {
879	unless ($MODEL) {	1175	unless ($MODEL) {
880	no strict 'refs';
881	local $SIG{__DIE__};	1176	local $SIG{__DIE__};
882		1177
883	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1178	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
884	my $model = "AnyEvent::Impl::$1";	1179	my $model = "AnyEvent::Impl::$1";
885	if (eval "require $model") {	1180	if (eval "require $model") {
886	$MODEL = $model;	1181	$MODEL = $model;
887	warn "AnyEvent: loaded model '$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 $VERBOSE >= 2;
888	} else {	1183	} else {
889	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1184	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
890	}	1185	}
891	}	1186	}
892		1187
893	# check for already loaded models	1188	# check for already loaded models
894	unless ($MODEL) {	1189	unless ($MODEL) {
895	for (@REGISTRY, @models) {	1190	for (@REGISTRY, @models) {
896	my ($package, $model) = @$_;	1191	my ($package, $model) = @$_;
897	if (${"$package\::VERSION"} > 0) {	1192	if (${"$package\::VERSION"} > 0) {
898	if (eval "require $model") {	1193	if (eval "require $model") {
899	$MODEL = $model;	1194	$MODEL = $model;
900	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1195	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
901	last;	1196	last;
902	}	1197	}
903	}	1198	}
904	}	1199	}
905		1200
906	unless ($MODEL) {	1201	unless ($MODEL) {
907	# try to load a model	1202	# try to autoload a model
908
909	for (@REGISTRY, @models) {	1203	for (@REGISTRY, @models) {
910	my ($package, $model) = @$_;	1204	my ($package, $model, $autoload) = @$_;
		1205	if (
		1206	$autoload
911	if (eval "require $package"	1207	and eval "require $package"
912	and ${"$package\::VERSION"} > 0	1208	and ${"$package\::VERSION"} > 0
913	and eval "require $model") {	1209	and eval "require $model"
		1210	) {
914	$MODEL = $model;	1211	$MODEL = $model;
915	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1212	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
916	last;	1213	last;
917	}	1214	}
918	}	1215	}
919		1216
920	$MODEL	1217	$MODEL
921	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1218	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
922	}	1219	}
923	}	1220	}
924		1221
		1222	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1223
925	unshift @ISA, $MODEL;	1224	unshift @ISA, $MODEL;
926	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1225
		1226	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
927		1227
928	(shift @post_detect)->() while @post_detect;	1228	(shift @post_detect)->() while @post_detect;
929	}	1229	}
930		1230
931	$MODEL	1231	$MODEL
…		…
933		1233
934	sub AUTOLOAD {	1234	sub AUTOLOAD {
935	(my $func = $AUTOLOAD) =~ s/.*://;	1235	(my $func = $AUTOLOAD) =~ s/.*://;
936		1236
937	$method{$func}	1237	$method{$func}
938	or croak "$func: not a valid method for AnyEvent objects";	1238	or Carp::croak "$func: not a valid method for AnyEvent objects";
939		1239
940	detect unless $MODEL;	1240	detect unless $MODEL;
941		1241
942	my $class = shift;	1242	my $class = shift;
943	$class->$func (@_);	1243	$class->$func (@_);
944	}	1244	}
945		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
946	package AnyEvent::Base;	1263	package AnyEvent::Base;
947		1264
948	# default implementation for now and time	1265	# default implementations for many methods
949		1266
950	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	}
951		1277
952	sub time { Time::HiRes::time }	1278	&_time
953	sub now { Time::HiRes::time }	1279	}
		1280
		1281	sub time { _time }
		1282	sub now { _time }
		1283	sub now_update { }
954		1284
955	# default implementation for ->condvar	1285	# default implementation for ->condvar
956		1286
957	sub condvar {	1287	sub condvar {
958	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1288	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
959	}	1289	}
960		1290
961	# default implementation for ->signal	1291	# default implementation for ->signal
962		1292
963	our %SIG_CB;	1293	our $HAVE_ASYNC_INTERRUPT;
		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 $_sig_name_init; $_sig_name_init = sub {
		1340	eval q{ # poor man's autoloading
		1341	undef $_sig_name_init;
		1342
		1343	if (_have_async_interrupt) {
		1344	*sig2num = \&Async::Interrupt::sig2num;
		1345	*sig2name = \&Async::Interrupt::sig2name;
		1346	} else {
		1347	require Config;
		1348
		1349	my %signame2num;
		1350	@signame2num{ split ' ', $Config::Config{sig_name} }
		1351	= split ' ', $Config::Config{sig_num};
		1352
		1353	my @signum2name;
		1354	@signum2name[values %signame2num] = keys %signame2num;
		1355
		1356	*sig2num = sub($) {
		1357	$_[0] > 0 ? shift : $signame2num{+shift}
		1358	};
		1359	*sig2name = sub ($) {
		1360	$_[0] > 0 ? $signum2name[+shift] : shift
		1361	};
		1362	}
		1363	};
		1364	die if $@;
		1365	};
		1366
		1367	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1368	sub sig2name($) { &$_sig_name_init; &sig2name }
964		1369
965	sub signal {	1370	sub signal {
		1371	eval q{ # poor man's autoloading {}
		1372	# probe for availability of Async::Interrupt
		1373	if (_have_async_interrupt) {
		1374	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1375
		1376	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1377	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1378
		1379	} else {
		1380	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1381
		1382	require Fcntl;
		1383
		1384	if (AnyEvent::WIN32) {
		1385	require AnyEvent::Util;
		1386
		1387	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1388	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1389	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1390	} else {
		1391	pipe $SIGPIPE_R, $SIGPIPE_W;
		1392	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1393	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1394
		1395	# not strictly required, as $^F is normally 2, but let's make sure...
		1396	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1397	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1398	}
		1399
		1400	$SIGPIPE_R
		1401	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1402
		1403	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1404	}
		1405
		1406	*signal = sub {
966	my (undef, %arg) = @_;	1407	my (undef, %arg) = @_;
967		1408
968	my $signal = uc $arg{signal}	1409	my $signal = uc $arg{signal}
969	or Carp::croak "required option 'signal' is missing";	1410	or Carp::croak "required option 'signal' is missing";
970		1411
		1412	if ($HAVE_ASYNC_INTERRUPT) {
		1413	# async::interrupt
		1414
		1415	$signal = sig2num $signal;
971	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1416	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1417
		1418	$SIG_ASY{$signal} ||= new Async::Interrupt
		1419	cb => sub { undef $SIG_EV{$signal} },
		1420	signal => $signal,
		1421	pipe => [$SIGPIPE_R->filenos],
		1422	pipe_autodrain => 0,
		1423	;
		1424
		1425	} else {
		1426	# pure perl
		1427
		1428	# AE::Util has been loaded in signal
		1429	$signal = sig2name $signal;
		1430	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1431
972	$SIG{$signal} ||= sub {	1432	$SIG{$signal} ||= sub {
973	$_->() for values %{ $SIG_CB{$signal} || {} };	1433	local $!;
		1434	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1435	undef $SIG_EV{$signal};
		1436	};
		1437
		1438	# can't do signal processing without introducing races in pure perl,
		1439	# so limit the signal latency.
		1440	_sig_add;
		1441	}
		1442
		1443	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1444	};
		1445
		1446	*AnyEvent::Base::signal::DESTROY = sub {
		1447	my ($signal, $cb) = @{$_[0]};
		1448
		1449	_sig_del;
		1450
		1451	delete $SIG_CB{$signal}{$cb};
		1452
		1453	$HAVE_ASYNC_INTERRUPT
		1454	? delete $SIG_ASY{$signal}
		1455	: # delete doesn't work with older perls - they then
		1456	# print weird messages, or just unconditionally exit
		1457	# instead of getting the default action.
		1458	undef $SIG{$signal}
		1459	unless keys %{ $SIG_CB{$signal} };
		1460	};
974	};	1461	};
975		1462	die if $@;
976	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1463	&signal
977	}
978
979	sub AnyEvent::Base::Signal::DESTROY {
980	my ($signal, $cb) = @{$_[0]};
981
982	delete $SIG_CB{$signal}{$cb};
983
984	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
985	}	1464	}
986		1465
987	# default implementation for ->child	1466	# default implementation for ->child
988		1467
989	our %PID_CB;	1468	our %PID_CB;
990	our $CHLD_W;	1469	our $CHLD_W;
991	our $CHLD_DELAY_W;	1470	our $CHLD_DELAY_W;
992	our $PID_IDLE;
993	our $WNOHANG;	1471	our $WNOHANG;
994		1472
995	sub _child_wait {	1473	sub _emit_childstatus($$) {
996	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1474	my (undef, $rpid, $rstatus) = @_;
		1475
		1476	$_->($rpid, $rstatus)
997	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1477	for values %{ $PID_CB{$rpid} || {} },
998	(values %{ $PID_CB{0} || {} });	1478	values %{ $PID_CB{0} || {} };
999	}
1000
1001	undef $PID_IDLE;
1002	}	1479	}
1003		1480
1004	sub _sigchld {	1481	sub _sigchld {
1005	# make sure we deliver these changes "synchronous" with the event loop.	1482	my $pid;
1006	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1483
1007	undef $CHLD_DELAY_W;	1484	AnyEvent->_emit_childstatus ($pid, $?)
1008	&_child_wait;	1485	while ($pid = waitpid -1, $WNOHANG) > 0;
1009	});
1010	}	1486	}
1011		1487
1012	sub child {	1488	sub child {
1013	my (undef, %arg) = @_;	1489	my (undef, %arg) = @_;
1014		1490
1015	defined (my $pid = $arg{pid} + 0)	1491	defined (my $pid = $arg{pid} + 0)
1016	or Carp::croak "required option 'pid' is missing";	1492	or Carp::croak "required option 'pid' is missing";
1017		1493
1018	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1494	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
1019		1495
1020	unless ($WNOHANG) {	1496	# WNOHANG is almost cetrainly 1 everywhere
		1497	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1498	? 1
1021	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1499	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1022	}
1023		1500
1024	unless ($CHLD_W) {	1501	unless ($CHLD_W) {
1025	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1502	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
1026	# child could be a zombie already, so make at least one round	1503	# child could be a zombie already, so make at least one round
1027	&_sigchld;	1504	&_sigchld;
1028	}	1505	}
1029		1506
1030	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1507	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
1031	}	1508	}
1032		1509
1033	sub AnyEvent::Base::Child::DESTROY {	1510	sub AnyEvent::Base::child::DESTROY {
1034	my ($pid, $cb) = @{$_[0]};	1511	my ($pid, $cb) = @{$_[0]};
1035		1512
1036	delete $PID_CB{$pid}{$cb};	1513	delete $PID_CB{$pid}{$cb};
1037	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1514	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1038		1515
1039	undef $CHLD_W unless keys %PID_CB;	1516	undef $CHLD_W unless keys %PID_CB;
1040	}	1517	}
1041		1518
		1519	# idle emulation is done by simply using a timer, regardless
		1520	# of whether the process is idle or not, and not letting
		1521	# the callback use more than 50% of the time.
		1522	sub idle {
		1523	my (undef, %arg) = @_;
		1524
		1525	my ($cb, $w, $rcb) = $arg{cb};
		1526
		1527	$rcb = sub {
		1528	if ($cb) {
		1529	$w = _time;
		1530	&$cb;
		1531	$w = _time - $w;
		1532
		1533	# never use more then 50% of the time for the idle watcher,
		1534	# within some limits
		1535	$w = 0.0001 if $w < 0.0001;
		1536	$w = 5 if $w > 5;
		1537
		1538	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1539	} else {
		1540	# clean up...
		1541	undef $w;
		1542	undef $rcb;
		1543	}
		1544	};
		1545
		1546	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1547
		1548	bless \\$cb, "AnyEvent::Base::idle"
		1549	}
		1550
		1551	sub AnyEvent::Base::idle::DESTROY {
		1552	undef $${$_[0]};
		1553	}
		1554
1042	package AnyEvent::CondVar;	1555	package AnyEvent::CondVar;
1043		1556
1044	our @ISA = AnyEvent::CondVar::Base::;	1557	our @ISA = AnyEvent::CondVar::Base::;
1045		1558
1046	package AnyEvent::CondVar::Base;	1559	package AnyEvent::CondVar::Base;
1047		1560
1048	use overload	1561	#use overload
1049	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1562	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1050	fallback => 1;	1563	# fallback => 1;
		1564
		1565	# save 300+ kilobytes by dirtily hardcoding overloading
		1566	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1567	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1568	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1569	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1570
		1571	our $WAITING;
1051		1572
1052	sub _send {	1573	sub _send {
1053	# nop	1574	# nop
1054	}	1575	}
1055		1576
…		…
1068	sub ready {	1589	sub ready {
1069	$_[0]{_ae_sent}	1590	$_[0]{_ae_sent}
1070	}	1591	}
1071		1592
1072	sub _wait {	1593	sub _wait {
		1594	$WAITING
		1595	and !$_[0]{_ae_sent}
		1596	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1597
		1598	local $WAITING = 1;
1073	AnyEvent->one_event while !$_[0]{_ae_sent};	1599	AnyEvent->one_event while !$_[0]{_ae_sent};
1074	}	1600	}
1075		1601
1076	sub recv {	1602	sub recv {
1077	$_[0]->_wait;	1603	$_[0]->_wait;
…		…
1096	}	1622	}
1097		1623
1098	# undocumented/compatibility with pre-3.4	1624	# undocumented/compatibility with pre-3.4
1099	*broadcast = \&send;	1625	*broadcast = \&send;
1100	*wait = \&_wait;	1626	*wait = \&_wait;
		1627
		1628	=head1 ERROR AND EXCEPTION HANDLING
		1629
		1630	In general, AnyEvent does not do any error handling - it relies on the
		1631	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1632	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1633	checking of all AnyEvent methods, however, which is highly useful during
		1634	development.
		1635
		1636	As for exception handling (i.e. runtime errors and exceptions thrown while
		1637	executing a callback), this is not only highly event-loop specific, but
		1638	also not in any way wrapped by this module, as this is the job of the main
		1639	program.
		1640
		1641	The pure perl event loop simply re-throws the exception (usually
		1642	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1643	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1644	so on.
		1645
		1646	=head1 ENVIRONMENT VARIABLES
		1647
		1648	The following environment variables are used by this module or its
		1649	submodules.
		1650
		1651	Note that AnyEvent will remove I<all> environment variables starting with
		1652	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1653	enabled.
		1654
		1655	=over 4
		1656
		1657	=item C<PERL_ANYEVENT_VERBOSE>
		1658
		1659	By default, AnyEvent will be completely silent except in fatal
		1660	conditions. You can set this environment variable to make AnyEvent more
		1661	talkative.
		1662
		1663	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1664	conditions, such as not being able to load the event model specified by
		1665	C<PERL_ANYEVENT_MODEL>.
		1666
		1667	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1668	model it chooses.
		1669
		1670	When set to C<8> or higher, then AnyEvent will report extra information on
		1671	which optional modules it loads and how it implements certain features.
		1672
		1673	=item C<PERL_ANYEVENT_STRICT>
		1674
		1675	AnyEvent does not do much argument checking by default, as thorough
		1676	argument checking is very costly. Setting this variable to a true value
		1677	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1678	check the arguments passed to most method calls. If it finds any problems,
		1679	it will croak.
		1680
		1681	In other words, enables "strict" mode.
		1682
		1683	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1684	>>, it is definitely recommended to keep it off in production. Keeping
		1685	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1686	can be very useful, however.
		1687
		1688	=item C<PERL_ANYEVENT_MODEL>
		1689
		1690	This can be used to specify the event model to be used by AnyEvent, before
		1691	auto detection and -probing kicks in. It must be a string consisting
		1692	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1693	and the resulting module name is loaded and if the load was successful,
		1694	used as event model. If it fails to load AnyEvent will proceed with
		1695	auto detection and -probing.
		1696
		1697	This functionality might change in future versions.
		1698
		1699	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1700	could start your program like this:
		1701
		1702	PERL_ANYEVENT_MODEL=Perl perl ...
		1703
		1704	=item C<PERL_ANYEVENT_PROTOCOLS>
		1705
		1706	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1707	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1708	of auto probing).
		1709
		1710	Must be set to a comma-separated list of protocols or address families,
		1711	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1712	used, and preference will be given to protocols mentioned earlier in the
		1713	list.
		1714
		1715	This variable can effectively be used for denial-of-service attacks
		1716	against local programs (e.g. when setuid), although the impact is likely
		1717	small, as the program has to handle conenction and other failures anyways.
		1718
		1719	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1720	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1721	- only support IPv4, never try to resolve or contact IPv6
		1722	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1723	IPv6, but prefer IPv6 over IPv4.
		1724
		1725	=item C<PERL_ANYEVENT_EDNS0>
		1726
		1727	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1728	for DNS. This extension is generally useful to reduce DNS traffic, but
		1729	some (broken) firewalls drop such DNS packets, which is why it is off by
		1730	default.
		1731
		1732	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1733	EDNS0 in its DNS requests.
		1734
		1735	=item C<PERL_ANYEVENT_MAX_FORKS>
		1736
		1737	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1738	will create in parallel.
		1739
		1740	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1741
		1742	The default value for the C<max_outstanding> parameter for the default DNS
		1743	resolver - this is the maximum number of parallel DNS requests that are
		1744	sent to the DNS server.
		1745
		1746	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1747
		1748	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1749	configuration) in the default resolver. When set to the empty string, no
		1750	default config will be used.
		1751
		1752	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1753
		1754	When neither C<ca_file> nor C<ca_path> was specified during
		1755	L<AnyEvent::TLS> context creation, and either of these environment
		1756	variables exist, they will be used to specify CA certificate locations
		1757	instead of a system-dependent default.
		1758
		1759	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1760
		1761	When these are set to C<1>, then the respective modules are not
		1762	loaded. Mostly good for testing AnyEvent itself.
		1763
		1764	=back
1101		1765
1102	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1766	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1103		1767
1104	This is an advanced topic that you do not normally need to use AnyEvent in	1768	This is an advanced topic that you do not normally need to use AnyEvent in
1105	a module. This section is only of use to event loop authors who want to	1769	a module. This section is only of use to event loop authors who want to
…		…
1139		1803
1140	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1804	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1141	condition variables: code blocking while waiting for a condition will	1805	condition variables: code blocking while waiting for a condition will
1142	C<die>. This still works with most modules/usages, and blocking calls must	1806	C<die>. This still works with most modules/usages, and blocking calls must
1143	not be done in an interactive application, so it makes sense.	1807	not be done in an interactive application, so it makes sense.
1144
1145	=head1 ENVIRONMENT VARIABLES
1146
1147	The following environment variables are used by this module:
1148
1149	=over 4
1150
1151	=item C<PERL_ANYEVENT_VERBOSE>
1152
1153	By default, AnyEvent will be completely silent except in fatal
1154	conditions. You can set this environment variable to make AnyEvent more
1155	talkative.
1156
1157	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1158	conditions, such as not being able to load the event model specified by
1159	C<PERL_ANYEVENT_MODEL>.
1160
1161	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1162	model it chooses.
1163
1164	=item C<PERL_ANYEVENT_MODEL>
1165
1166	This can be used to specify the event model to be used by AnyEvent, before
1167	auto detection and -probing kicks in. It must be a string consisting
1168	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1169	and the resulting module name is loaded and if the load was successful,
1170	used as event model. If it fails to load AnyEvent will proceed with
1171	auto detection and -probing.
1172
1173	This functionality might change in future versions.
1174
1175	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1176	could start your program like this:
1177
1178	PERL_ANYEVENT_MODEL=Perl perl ...
1179
1180	=item C<PERL_ANYEVENT_PROTOCOLS>
1181
1182	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1183	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1184	of auto probing).
1185
1186	Must be set to a comma-separated list of protocols or address families,
1187	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1188	used, and preference will be given to protocols mentioned earlier in the
1189	list.
1190
1191	This variable can effectively be used for denial-of-service attacks
1192	against local programs (e.g. when setuid), although the impact is likely
1193	small, as the program has to handle connection errors already-
1194
1195	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1196	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1197	- only support IPv4, never try to resolve or contact IPv6
1198	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1199	IPv6, but prefer IPv6 over IPv4.
1200
1201	=item C<PERL_ANYEVENT_EDNS0>
1202
1203	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1204	for DNS. This extension is generally useful to reduce DNS traffic, but
1205	some (broken) firewalls drop such DNS packets, which is why it is off by
1206	default.
1207
1208	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1209	EDNS0 in its DNS requests.
1210
1211	=item C<PERL_ANYEVENT_MAX_FORKS>
1212
1213	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1214	will create in parallel.
1215
1216	=back
1217		1808
1218	=head1 EXAMPLE PROGRAM	1809	=head1 EXAMPLE PROGRAM
1219		1810
1220	The following program uses an I/O watcher to read data from STDIN, a timer	1811	The following program uses an I/O watcher to read data from STDIN, a timer
1221	to display a message once per second, and a condition variable to quit the	1812	to display a message once per second, and a condition variable to quit the
…		…
1415	watcher.	2006	watcher.
1416		2007
1417	=head3 Results	2008	=head3 Results
1418		2009
1419	name watchers bytes create invoke destroy comment	2010	name watchers bytes create invoke destroy comment
1420	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2011	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1421	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2012	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1422	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2013	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1423	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2014	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1424	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2015	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1425	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2016	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		2017	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		2018	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1426	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2019	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1427	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2020	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1428	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2021	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1429	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2022	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1430		2023
1431	=head3 Discussion	2024	=head3 Discussion
1432		2025
1433	The benchmark does I<not> measure scalability of the event loop very	2026	The benchmark does I<not> measure scalability of the event loop very
1434	well. For example, a select-based event loop (such as the pure perl one)	2027	well. For example, a select-based event loop (such as the pure perl one)
…		…
1459	performance becomes really bad with lots of file descriptors (and few of	2052	performance becomes really bad with lots of file descriptors (and few of
1460	them active), of course, but this was not subject of this benchmark.	2053	them active), of course, but this was not subject of this benchmark.
1461		2054
1462	The C<Event> module has a relatively high setup and callback invocation	2055	The C<Event> module has a relatively high setup and callback invocation
1463	cost, but overall scores in on the third place.	2056	cost, but overall scores in on the third place.
		2057
		2058	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2059	when using its pure perl backend.
1464		2060
1465	C<Glib>'s memory usage is quite a bit higher, but it features a	2061	C<Glib>'s memory usage is quite a bit higher, but it features a
1466	faster callback invocation and overall ends up in the same class as	2062	faster callback invocation and overall ends up in the same class as
1467	C<Event>. However, Glib scales extremely badly, doubling the number of	2063	C<Event>. However, Glib scales extremely badly, doubling the number of
1468	watchers increases the processing time by more than a factor of four,	2064	watchers increases the processing time by more than a factor of four,
…		…
1546	it to another server. This includes deleting the old timeout and creating	2142	it to another server. This includes deleting the old timeout and creating
1547	a new one that moves the timeout into the future.	2143	a new one that moves the timeout into the future.
1548		2144
1549	=head3 Results	2145	=head3 Results
1550		2146
1551	name sockets create request	2147	name sockets create request
1552	EV 20000 69.01 11.16	2148	EV 20000 69.01 11.16
1553	Perl 20000 73.32 35.87	2149	Perl 20000 73.32 35.87
		2150	IOAsync 20000 157.00 98.14 epoll
		2151	IOAsync 20000 159.31 616.06 poll
1554	Event 20000 212.62 257.32	2152	Event 20000 212.62 257.32
1555	Glib 20000 651.16 1896.30	2153	Glib 20000 651.16 1896.30
1556	POE 20000 349.67 12317.24 uses POE::Loop::Event	2154	POE 20000 349.67 12317.24 uses POE::Loop::Event
1557		2155
1558	=head3 Discussion	2156	=head3 Discussion
1559		2157
1560	This benchmark I<does> measure scalability and overall performance of the	2158	This benchmark I<does> measure scalability and overall performance of the
1561	particular event loop.	2159	particular event loop.
…		…
1563	EV is again fastest. Since it is using epoll on my system, the setup time	2161	EV is again fastest. Since it is using epoll on my system, the setup time
1564	is relatively high, though.	2162	is relatively high, though.
1565		2163
1566	Perl surprisingly comes second. It is much faster than the C-based event	2164	Perl surprisingly comes second. It is much faster than the C-based event
1567	loops Event and Glib.	2165	loops Event and Glib.
		2166
		2167	IO::Async performs very well when using its epoll backend, and still quite
		2168	good compared to Glib when using its pure perl backend.
1568		2169
1569	Event suffers from high setup time as well (look at its code and you will	2170	Event suffers from high setup time as well (look at its code and you will
1570	understand why). Callback invocation also has a high overhead compared to	2171	understand why). Callback invocation also has a high overhead compared to
1571	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2172	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1572	uses select or poll in basically all documented configurations.	2173	uses select or poll in basically all documented configurations.
…		…
1635	=item * C-based event loops perform very well with small number of	2236	=item * C-based event loops perform very well with small number of
1636	watchers, as the management overhead dominates.	2237	watchers, as the management overhead dominates.
1637		2238
1638	=back	2239	=back
1639		2240
		2241	=head2 THE IO::Lambda BENCHMARK
		2242
		2243	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2244	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2245	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2246	shouldn't come as a surprise to anybody). As such, the benchmark is
		2247	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2248	very optimal. But how would AnyEvent compare when used without the extra
		2249	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2250
		2251	The benchmark itself creates an echo-server, and then, for 500 times,
		2252	connects to the echo server, sends a line, waits for the reply, and then
		2253	creates the next connection. This is a rather bad benchmark, as it doesn't
		2254	test the efficiency of the framework or much non-blocking I/O, but it is a
		2255	benchmark nevertheless.
		2256
		2257	name runtime
		2258	Lambda/select 0.330 sec
		2259	+ optimized 0.122 sec
		2260	Lambda/AnyEvent 0.327 sec
		2261	+ optimized 0.138 sec
		2262	Raw sockets/select 0.077 sec
		2263	POE/select, components 0.662 sec
		2264	POE/select, raw sockets 0.226 sec
		2265	POE/select, optimized 0.404 sec
		2266
		2267	AnyEvent/select/nb 0.085 sec
		2268	AnyEvent/EV/nb 0.068 sec
		2269	+state machine 0.134 sec
		2270
		2271	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2272	benchmarks actually make blocking connects and use 100% blocking I/O,
		2273	defeating the purpose of an event-based solution. All of the newly
		2274	written AnyEvent benchmarks use 100% non-blocking connects (using
		2275	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2276	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2277	generally require a lot more bookkeeping and event handling than blocking
		2278	connects (which involve a single syscall only).
		2279
		2280	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2281	offers similar expressive power as POE and IO::Lambda, using conventional
		2282	Perl syntax. This means that both the echo server and the client are 100%
		2283	non-blocking, further placing it at a disadvantage.
		2284
		2285	As you can see, the AnyEvent + EV combination even beats the
		2286	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2287	backend easily beats IO::Lambda and POE.
		2288
		2289	And even the 100% non-blocking version written using the high-level (and
		2290	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2291	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2292	in a non-blocking way.
		2293
		2294	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2295	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2296	part of the IO::lambda distribution and were used without any changes.
		2297
		2298
		2299	=head1 SIGNALS
		2300
		2301	AnyEvent currently installs handlers for these signals:
		2302
		2303	=over 4
		2304
		2305	=item SIGCHLD
		2306
		2307	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2308	emulation for event loops that do not support them natively. Also, some
		2309	event loops install a similar handler.
		2310
		2311	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2312	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2313
		2314	=item SIGPIPE
		2315
		2316	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2317	when AnyEvent gets loaded.
		2318
		2319	The rationale for this is that AnyEvent users usually do not really depend
		2320	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2321	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2322	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2323	some random socket.
		2324
		2325	The rationale for installing a no-op handler as opposed to ignoring it is
		2326	that this way, the handler will be restored to defaults on exec.
		2327
		2328	Feel free to install your own handler, or reset it to defaults.
		2329
		2330	=back
		2331
		2332	=cut
		2333
		2334	undef $SIG{CHLD}
		2335	if $SIG{CHLD} eq 'IGNORE';
		2336
		2337	$SIG{PIPE} = sub { }
		2338	unless defined $SIG{PIPE};
		2339
		2340	=head1 RECOMMENDED/OPTIONAL MODULES
		2341
		2342	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2343	it's built-in modules) are required to use it.
		2344
		2345	That does not mean that AnyEvent won't take advantage of some additional
		2346	modules if they are installed.
		2347
		2348	This section epxlains which additional modules will be used, and how they
		2349	affect AnyEvent's operetion.
		2350
		2351	=over 4
		2352
		2353	=item L<Async::Interrupt>
		2354
		2355	This slightly arcane module is used to implement fast signal handling: To
		2356	my knowledge, there is no way to do completely race-free and quick
		2357	signal handling in pure perl. To ensure that signals still get
		2358	delivered, AnyEvent will start an interval timer to wake up perl (and
		2359	catch the signals) with some delay (default is 10 seconds, look for
		2360	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2361
		2362	If this module is available, then it will be used to implement signal
		2363	catching, which means that signals will not be delayed, and the event loop
		2364	will not be interrupted regularly, which is more efficient (And good for
		2365	battery life on laptops).
		2366
		2367	This affects not just the pure-perl event loop, but also other event loops
		2368	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2369
		2370	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2371	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2372	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2373	does nothing for those backends.
		2374
		2375	=item L<EV>
		2376
		2377	This module isn't really "optional", as it is simply one of the backend
		2378	event loops that AnyEvent can use. However, it is simply the best event
		2379	loop available in terms of features, speed and stability: It supports
		2380	the AnyEvent API optimally, implements all the watcher types in XS, does
		2381	automatic timer adjustments even when no monotonic clock is available,
		2382	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2383	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2384	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2385
		2386	=item L<Guard>
		2387
		2388	The guard module, when used, will be used to implement
		2389	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2390	lot less memory), but otherwise doesn't affect guard operation much. It is
		2391	purely used for performance.
		2392
		2393	=item L<JSON> and L<JSON::XS>
		2394
		2395	This module is required when you want to read or write JSON data via
		2396	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2397	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2398
		2399	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2400	installed.
		2401
		2402	=item L<Net::SSLeay>
		2403
		2404	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2405	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2406	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2407
		2408	=item L<Time::HiRes>
		2409
		2410	This module is part of perl since release 5.008. It will be used when the
		2411	chosen event library does not come with a timing source on it's own. The
		2412	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2413	try to use a monotonic clock for timing stability.
		2414
		2415	=back
		2416
1640		2417
1641	=head1 FORK	2418	=head1 FORK
1642		2419
1643	Most event libraries are not fork-safe. The ones who are usually are	2420	Most event libraries are not fork-safe. The ones who are usually are
1644	because they rely on inefficient but fork-safe C<select> or C<poll>	2421	because they rely on inefficient but fork-safe C<select> or C<poll>
1645	calls. Only L<EV> is fully fork-aware.	2422	calls. Only L<EV> is fully fork-aware.
1646		2423
1647	If you have to fork, you must either do so I<before> creating your first	2424	If you have to fork, you must either do so I<before> creating your first
1648	watcher OR you must not use AnyEvent at all in the child.	2425	watcher OR you must not use AnyEvent at all in the child OR you must do
		2426	something completely out of the scope of AnyEvent.
1649		2427
1650		2428
1651	=head1 SECURITY CONSIDERATIONS	2429	=head1 SECURITY CONSIDERATIONS
1652		2430
1653	AnyEvent can be forced to load any event model via	2431	AnyEvent can be forced to load any event model via
…		…
1658	specified in the variable.	2436	specified in the variable.
1659		2437
1660	You can make AnyEvent completely ignore this variable by deleting it	2438	You can make AnyEvent completely ignore this variable by deleting it
1661	before the first watcher gets created, e.g. with a C<BEGIN> block:	2439	before the first watcher gets created, e.g. with a C<BEGIN> block:
1662		2440
1663	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2441	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1664		2442
1665	use AnyEvent;	2443	use AnyEvent;
1666		2444
1667	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2445	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1668	be used to probe what backend is used and gain other information (which is	2446	be used to probe what backend is used and gain other information (which is
1669	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2447	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2448	$ENV{PERL_ANYEVENT_STRICT}.
		2449
		2450	Note that AnyEvent will remove I<all> environment variables starting with
		2451	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2452	enabled.
		2453
		2454
		2455	=head1 BUGS
		2456
		2457	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2458	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2459	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2460	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2461	pronounced).
1670		2462
1671		2463
1672	=head1 SEE ALSO	2464	=head1 SEE ALSO
1673		2465
1674	Utility functions: L<AnyEvent::Util>.	2466	Utility functions: L<AnyEvent::Util>.
…		…
1677	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2469	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1678		2470
1679	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2471	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1680	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2472	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1681	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2473	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1682	L<AnyEvent::Impl::POE>.	2474	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1683		2475
1684	Non-blocking file handles, sockets, TCP clients and	2476	Non-blocking file handles, sockets, TCP clients and
1685	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2477	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1686		2478
1687	Asynchronous DNS: L<AnyEvent::DNS>.	2479	Asynchronous DNS: L<AnyEvent::DNS>.
1688		2480
1689	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2481	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2482	L<Coro::Event>,
1690		2483
1691	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2484	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2485	L<AnyEvent::HTTP>.
1692		2486
1693		2487
1694	=head1 AUTHOR	2488	=head1 AUTHOR
1695		2489
1696	Marc Lehmann <schmorp@schmorp.de>	2490	Marc Lehmann <schmorp@schmorp.de>
1697	http://home.schmorp.de/	2491	http://home.schmorp.de/
1698		2492
1699	=cut	2493	=cut
1700		2494
1701	1	2495	1
1702		2496

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