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Revision 1.118 by root, Sun May 11 18:08:36 2008 UTC vs.
Revision 1.329 by root, Sun Jul 11 05:44:22 2010 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	38	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
		40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	There is a mailinglist for discussing all things AnyEvent, and an IRC
		52	channel, too.
		53
		54	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		55	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		56
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	57	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		58
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	59	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	60	nowadays. So what is different about AnyEvent?
27		61
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	62	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	63	policy> and AnyEvent is I<small and efficient>.
30		64
31	First and foremost, I<AnyEvent is not an event model> itself, it only	65	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	66	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	67	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	68	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	69	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	70	cannot change this, but it can hide the differences between those event
		71	loops.
37		72
38	The goal of AnyEvent is to offer module authors the ability to do event	73	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	74	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	75	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	76	module users into the same thing by forcing them to use the same event
42	model you use.	77	model you use.
43		78
44	For modules like POE or IO::Async (which is a total misnomer as it is	79	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	80	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	81	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	82	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	83	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	84	module are I<also> forced to use the same event loop you use.
50		85
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	86	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	87	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	88	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	89	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	90	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	91	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	92	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	93	to AnyEvent, too, so it is future-proof).
59		94
60	In addition to being free of having to use I<the one and only true event	95	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	96	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	97	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	98	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	99	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	100	technically possible.
66		101
		102	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		103	of useful functionality, such as an asynchronous DNS resolver, 100%
		104	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		105	such as Windows) and lots of real-world knowledge and workarounds for
		106	platform bugs and differences.
		107
67	Of course, if you want lots of policy (this can arguably be somewhat	108	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	109	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	110	model, you should I<not> use this module.
70		111
71	=head1 DESCRIPTION	112	=head1 DESCRIPTION
72		113
…		…
97	use AnyEvent;	138	use AnyEvent;
98		139
99	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
100		141
101	The I<likely> means that, if any module loads another event model and	142	The I<likely> means that, if any module loads another event model and
102	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off - this case should be very rare though,
103	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
104		146
105	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	149	explicitly and enjoy the high availability of that event loop :)
108		150
109	=head1 WATCHERS	151	=head1 WATCHERS
110		152
111	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
114		156
115	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	158	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	159	callback when the event occurs (of course, only when the event model
118	is in control).	160	is in control).
119		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practise in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
120	To disable the watcher you have to destroy it (e.g. by setting the	168	To disable the watcher you have to destroy it (e.g. by setting the
121	variable you store it in to C<undef> or otherwise deleting all references	169	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	170	to it).
123		171
124	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	175	example), or need to refer to their watcher object in other ways.
128		176
129	An any way to achieve that is this pattern:	177	An any way to achieve that is this pattern:
130		178
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
133	undef $w;	181	undef $w;
134	});	182	});
135		183
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	184	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	185	my variables are only visible after the statement in which they are
138	declared.	186	declared.
139		187
140	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
141		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
144		198
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
146	for events. C<poll> must be a string that is either C<r> or C<w>,	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
148	respectively. C<cb> is the callback to invoke each time the file handle	209	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		210
151	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
154		214
…		…
158		218
159	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	220	always use non-blocking calls when reading/writing from/to your file
161	handles.	221	handles.
162		222
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	228	warn "read: $input\n";
169	undef $w;	229	undef $w;
170	});	230	});
171		231
172	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
173		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
174	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
175	method with the following mandatory arguments:	243	method with the following mandatory arguments:
176		244
177	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	246	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		248
181	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
184		252
185	The timer callback will be invoked at most once: if you want a repeating	253	The callback will normally be invoked once only. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	254	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were missing.
188		258
189	Example:	259	The callback will be rescheduled before invoking the callback, but no
		260	attempt is done to avoid timer drift in most backends, so the interval is
		261	only approximate.
190		262
191	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	266	warn "timeout\n";
194	});	267	});
195		268
196	# to cancel the timer:	269	# to cancel the timer:
197	undef $w;	270	undef $w;
198		271
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		273
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
207	};	276	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		277
212	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
213		279
214	There are two ways to handle timers: based on real time (relative, "fire	280	There are two ways to handle timers: based on real time (relative, "fire
215	in 10 seconds") and based on wallclock time (absolute, "fire at 12	281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	293	timers.
228		294
229	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	296	AnyEvent API.
231		297
		298	AnyEvent has two additional methods that return the "current time":
		299
		300	=over 4
		301
		302	=item AnyEvent->time
		303
		304	This returns the "current wallclock time" as a fractional number of
		305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
		307
		308	It progresses independently of any event loop processing, i.e. each call
		309	will check the system clock, which usually gets updated frequently.
		310
		311	=item AnyEvent->now
		312
		313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
		317
		318	I<In almost all cases (in all cases if you don't care), this is the
		319	function to call when you want to know the current time.>
		320
		321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		324
		325	The rest of this section is only of relevance if you try to be very exact
		326	with your timing, you can skip it without bad conscience.
		327
		328	For a practical example of when these times differ, consider L<Event::Lib>
		329	and L<EV> and the following set-up:
		330
		331	The event loop is running and has just invoked one of your callback at
		332	time=500 (assume no other callbacks delay processing). In your callback,
		333	you wait a second by executing C<sleep 1> (blocking the process for a
		334	second) and then (at time=501) you create a relative timer that fires
		335	after three seconds.
		336
		337	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		338	both return C<501>, because that is the current time, and the timer will
		339	be scheduled to fire at time=504 (C<501> + C<3>).
		340
		341	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		342	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		343	last event processing phase started. With L<EV>, your timer gets scheduled
		344	to run at time=503 (C<500> + C<3>).
		345
		346	In one sense, L<Event::Lib> is more exact, as it uses the current time
		347	regardless of any delays introduced by event processing. However, most
		348	callbacks do not expect large delays in processing, so this causes a
		349	higher drift (and a lot more system calls to get the current time).
		350
		351	In another sense, L<EV> is more exact, as your timer will be scheduled at
		352	the same time, regardless of how long event processing actually took.
		353
		354	In either case, if you care (and in most cases, you don't), then you
		355	can get whatever behaviour you want with any event loop, by taking the
		356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		357	account.
		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		362	the current time for each loop iteration (see the discussion of L<<
		363	AnyEvent->now >>, above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
		381	=back
		382
232	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
233		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
234	You can watch for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
237		390
238	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
241		394
242	Multiple signal occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	397	that it might take a while until the signal gets handled by the process,
245	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
246		399
247	The main advantage of using these watchers is that you can share a signal	400	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
249		403
250	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
252		407
253	Example: exit on SIGINT	408	Example: exit on SIGINT
254		409
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do it's best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		437	variable can be changed only before the first signal watcher is created,
		438	and should be left alone otherwise. This variable determines how often
		439	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		440	will cause fewer spurious wake-ups, which is better for power and CPU
		441	saving.
		442
		443	All these problems can be avoided by installing the optional
		444	L<Async::Interrupt> module, which works with most event loops. It will not
		445	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		446	(and not with L<POE> currently, as POE does it's own workaround with
		447	one-second latency). For those, you just have to suffer the delays.
		448
257	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
258		450
		451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		452
259	You can also watch on a child process exit and catch its exit status.	453	You can also watch on a child process exit and catch its exit status.
260		454
261	The child process is specified by the C<pid> argument (if set to C<0>, it	455	The child process is specified by the C<pid> argument (one some backends,
262	watches for any child process exit). The watcher will trigger as often	456	using C<0> watches for any child process exit, on others this will
263	as status change for the child are received. This works by installing a	457	croak). The watcher will be triggered only when the child process has
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	458	finished and an exit status is available, not on any trace events
265	and exit status (as returned by waitpid), so unlike other watcher types,	459	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	460
		461	The callback will be called with the pid and exit status (as returned by
		462	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		463	callback arguments.
		464
		465	This watcher type works by installing a signal handler for C<SIGCHLD>,
		466	and since it cannot be shared, nothing else should use SIGCHLD or reap
		467	random child processes (waiting for specific child processes, e.g. inside
		468	C<system>, is just fine).
267		469
268	There is a slight catch to child watchers, however: you usually start them	470	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	471	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	472	have exited already (and no SIGCHLD will be sent anymore).
271		473
272	Not all event models handle this correctly (POE doesn't), but even for	474	Not all event models handle this correctly (neither POE nor IO::Async do,
		475	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	476	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	477	the process exits (i.e. before you fork in the first place). AnyEvent's
		478	pure perl event loop handles all cases correctly regardless of when you
		479	start the watcher.
275		480
276	This means you cannot create a child watcher as the very first thing in an	481	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	482	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	483	watcher before you C<fork> the child (alternatively, you can call
		484	C<AnyEvent::detect>).
		485
		486	As most event loops do not support waiting for child events, they will be
		487	emulated by AnyEvent in most cases, in which the latency and race problems
		488	mentioned in the description of signal watchers apply.
279		489
280	Example: fork a process and wait for it	490	Example: fork a process and wait for it
281		491
282	my $done = AnyEvent->condvar;	492	my $done = AnyEvent->condvar;
283		493
284	my $pid = fork or exit 5;	494	my $pid = fork or exit 5;
285		495
286	my $w = AnyEvent->child (	496	my $w = AnyEvent->child (
287	pid => $pid,	497	pid => $pid,
288	cb => sub {	498	cb => sub {
289	my ($pid, $status) = @_;	499	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	500	warn "pid $pid exited with status $status";
291	$done->send;	501	$done->send;
292	},	502	},
293	);	503	);
294		504
295	# do something else, then wait for process exit	505	# do something else, then wait for process exit
296	$done->recv;	506	$done->recv;
		507
		508	=head2 IDLE WATCHERS
		509
		510	$w = AnyEvent->idle (cb => <callback>);
		511
		512	Repeatedly invoke the callback after the process becomes idle, until
		513	either the watcher is destroyed or new events have been detected.
		514
		515	Idle watchers are useful when there is a need to do something, but it
		516	is not so important (or wise) to do it instantly. The callback will be
		517	invoked only when there is "nothing better to do", which is usually
		518	defined as "all outstanding events have been handled and no new events
		519	have been detected". That means that idle watchers ideally get invoked
		520	when the event loop has just polled for new events but none have been
		521	detected. Instead of blocking to wait for more events, the idle watchers
		522	will be invoked.
		523
		524	Unfortunately, most event loops do not really support idle watchers (only
		525	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		526	will simply call the callback "from time to time".
		527
		528	Example: read lines from STDIN, but only process them when the
		529	program is otherwise idle:
		530
		531	my @lines; # read data
		532	my $idle_w;
		533	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		534	push @lines, scalar <STDIN>;
		535
		536	# start an idle watcher, if not already done
		537	$idle_w ||= AnyEvent->idle (cb => sub {
		538	# handle only one line, when there are lines left
		539	if (my $line = shift @lines) {
		540	print "handled when idle: $line";
		541	} else {
		542	# otherwise disable the idle watcher again
		543	undef $idle_w;
		544	}
		545	});
		546	});
297		547
298	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
299		554
300	If you are familiar with some event loops you will know that all of them	555	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	556	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	557	will actively watch for new events and call your callbacks.
303		558
304	AnyEvent is different, it expects somebody else to run the event loop and	559	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	560	loop and will only block when necessary (usually when told by the user).
306		561
307	The instrument to do that is called a "condition variable", so called	562	The tool to do that is called a "condition variable", so called because
308	because they represent a condition that must become true.	563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
309		566
310	Condition variables can be created by calling the C<< AnyEvent->condvar	567	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	568	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	569	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	570	becomes true, with the condition variable as the first argument (but not
		571	the results).
314		572
315	After creation, the conditon variable is "false" until it becomes "true"	573	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method.	574	by calling the C<send> method (or calling the condition variable as if it
		575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
317		577
318	Condition variables are similar to callbacks, except that you can	578	Since condition variables are the most complex part of the AnyEvent API, here are
319	optionally wait for them. They can also be called merge points - points	579	some different mental models of what they are - pick the ones you can connect to:
320	in time where multiple outstandign events have been processed. And yet	580
321	another way to call them is transations - each condition variable can be	581	=over 4
322	used to represent a transaction, which finishes at some point and delivers	582
323	a result.	583	=item * Condition variables are like callbacks - you can call them (and pass them instead
		584	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		585
		586	=item * Condition variables are signals - one side can emit or send them,
		587	the other side can wait for them, or install a handler that is called when
		588	the signal fires.
		589
		590	=item * Condition variables are like "Merge Points" - points in your program
		591	where you merge multiple independent results/control flows into one.
		592
		593	=item * Condition variables represent a transaction - function that start
		594	some kind of transaction can return them, leaving the caller the choice
		595	between waiting in a blocking fashion, or setting a callback.
		596
		597	=item * Condition variables represent future values, or promises to deliver
		598	some result, long before the result is available.
		599
		600	=back
324		601
325	Condition variables are very useful to signal that something has finished,	602	Condition variables are very useful to signal that something has finished,
326	for example, if you write a module that does asynchronous http requests,	603	for example, if you write a module that does asynchronous http requests,
327	then a condition variable would be the ideal candidate to signal the	604	then a condition variable would be the ideal candidate to signal the
328	availability of results. The user can either act when the callback is	605	availability of results. The user can either act when the callback is
…		…
332	you can block your main program until an event occurs - for example, you	609	you can block your main program until an event occurs - for example, you
333	could C<< ->recv >> in your main program until the user clicks the Quit	610	could C<< ->recv >> in your main program until the user clicks the Quit
334	button of your app, which would C<< ->send >> the "quit" event.	611	button of your app, which would C<< ->send >> the "quit" event.
335		612
336	Note that condition variables recurse into the event loop - if you have	613	Note that condition variables recurse into the event loop - if you have
337	two pieces of code that call C<< ->recv >> in a round-robbin fashion, you	614	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
338	lose. Therefore, condition variables are good to export to your caller, but	615	lose. Therefore, condition variables are good to export to your caller, but
339	you should avoid making a blocking wait yourself, at least in callbacks,	616	you should avoid making a blocking wait yourself, at least in callbacks,
340	as this asks for trouble.	617	as this asks for trouble.
341		618
342	Condition variables are represented by hash refs in perl, and the keys	619	Condition variables are represented by hash refs in perl, and the keys
…		…
347		624
348	There are two "sides" to a condition variable - the "producer side" which	625	There are two "sides" to a condition variable - the "producer side" which
349	eventually calls C<< -> send >>, and the "consumer side", which waits	626	eventually calls C<< -> send >>, and the "consumer side", which waits
350	for the send to occur.	627	for the send to occur.
351		628
352	Example:	629	Example: wait for a timer.
353		630
354	# wait till the result is ready	631	# condition: "wait till the timer is fired"
355	my $result_ready = AnyEvent->condvar;	632	my $timer_fired = AnyEvent->condvar;
356		633
357	# do something such as adding a timer	634	# create the timer - we could wait for, say
358	# or socket watcher the calls $result_ready->send	635	# a handle becomign ready, or even an
359	# when the "result" is ready.	636	# AnyEvent::HTTP request to finish, but
360	# in this case, we simply use a timer:	637	# in this case, we simply use a timer:
361	my $w = AnyEvent->timer (	638	my $w = AnyEvent->timer (
362	after => 1,	639	after => 1,
363	cb => sub { $result_ready->send },	640	cb => sub { $timer_fired->send },
364	);	641	);
365		642
366	# this "blocks" (while handling events) till the callback	643	# this "blocks" (while handling events) till the callback
367	# calls send	644	# calls ->send
368	$result_ready->recv;	645	$timer_fired->recv;
		646
		647	Example: wait for a timer, but take advantage of the fact that condition
		648	variables are also callable directly.
		649
		650	my $done = AnyEvent->condvar;
		651	my $delay = AnyEvent->timer (after => 5, cb => $done);
		652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
369		670
370	=head3 METHODS FOR PRODUCERS	671	=head3 METHODS FOR PRODUCERS
371		672
372	These methods should only be used by the producing side, i.e. the	673	These methods should only be used by the producing side, i.e. the
373	code/module that eventually sends the signal. Note that it is also	674	code/module that eventually sends the signal. Note that it is also
…		…
386	immediately from within send.	687	immediately from within send.
387		688
388	Any arguments passed to the C<send> call will be returned by all	689	Any arguments passed to the C<send> call will be returned by all
389	future C<< ->recv >> calls.	690	future C<< ->recv >> calls.
390		691
		692	Condition variables are overloaded so one can call them directly (as if
		693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
		695
391	=item $cv->croak ($error)	696	=item $cv->croak ($error)
392		697
393	Similar to send, but causes all call's to C<< ->recv >> to invoke	698	Similar to send, but causes all call's to C<< ->recv >> to invoke
394	C<Carp::croak> with the given error message/object/scalar.	699	C<Carp::croak> with the given error message/object/scalar.
395		700
396	This can be used to signal any errors to the condition variable	701	This can be used to signal any errors to the condition variable
397	user/consumer.	702	user/consumer. Doing it this way instead of calling C<croak> directly
		703	delays the error detetcion, but has the overwhelmign advantage that it
		704	diagnoses the error at the place where the result is expected, and not
		705	deep in some event clalback without connection to the actual code causing
		706	the problem.
398		707
399	=item $cv->begin ([group callback])	708	=item $cv->begin ([group callback])
400		709
401	=item $cv->end	710	=item $cv->end
402
403	These two methods are EXPERIMENTAL and MIGHT CHANGE.
404		711
405	These two methods can be used to combine many transactions/events into	712	These two methods can be used to combine many transactions/events into
406	one. For example, a function that pings many hosts in parallel might want	713	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	714	to use a condition variable for the whole process.
408		715
409	Every call to C<< ->begin >> will increment a counter, and every call to	716	Every call to C<< ->begin >> will increment a counter, and every call to
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411	>>, the (last) callback passed to C<begin> will be executed. That callback	718	>>, the (last) callback passed to C<begin> will be executed, passing the
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	719	condvar as first argument. That callback is I<supposed> to call C<< ->send
413	callback was set, C<send> will be called without any arguments.	720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
414		722
415	Let's clarify this with the ping example:	723	You can think of C<< $cv->send >> giving you an OR condition (one call
		724	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		725	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		726
		727	Let's start with a simple example: you have two I/O watchers (for example,
		728	STDOUT and STDERR for a program), and you want to wait for both streams to
		729	close before activating a condvar:
416		730
417	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
418		732
		733	$cv->begin; # first watcher
		734	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		735	defined sysread $fh1, my $buf, 4096
		736	or $cv->end;
		737	});
		738
		739	$cv->begin; # second watcher
		740	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		741	defined sysread $fh2, my $buf, 4096
		742	or $cv->end;
		743	});
		744
		745	$cv->recv;
		746
		747	This works because for every event source (EOF on file handle), there is
		748	one call to C<begin>, so the condvar waits for all calls to C<end> before
		749	sending.
		750
		751	The ping example mentioned above is slightly more complicated, as the
		752	there are results to be passwd back, and the number of tasks that are
		753	begung can potentially be zero:
		754
		755	my $cv = AnyEvent->condvar;
		756
419	my %result;	757	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	758	$cv->begin (sub { shift->send (\%result) });
421		759
422	for my $host (@list_of_hosts) {	760	for my $host (@list_of_hosts) {
423	$cv->begin;	761	$cv->begin;
424	ping_host_then_call_callback $host, sub {	762	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	763	$result{$host} = ...;
…		…
440	loop, which serves two important purposes: first, it sets the callback	778	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	779	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	780	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	781	doesn't execute once).
444		782
445	This is the general pattern when you "fan out" into multiple subrequests:	783	This is the general pattern when you "fan out" into multiple (but
446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	784	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
447	is called at least once, and then, for each subrequest you start, call	785	the callback and ensure C<end> is called at least once, and then, for each
448	C<begin> and for eahc subrequest you finish, call C<end>.	786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
449		788
450	=back	789	=back
451		790
452	=head3 METHODS FOR CONSUMERS	791	=head3 METHODS FOR CONSUMERS
453		792
…		…
469	function will call C<croak>.	808	function will call C<croak>.
470		809
471	In list context, all parameters passed to C<send> will be returned,	810	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	811	in scalar context only the first one will be returned.
473		812
		813	Note that doing a blocking wait in a callback is not supported by any
		814	event loop, that is, recursive invocation of a blocking C<< ->recv
		815	>> is not allowed, and the C<recv> call will C<croak> if such a
		816	condition is detected. This condition can be slightly loosened by using
		817	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		818	any thread that doesn't run the event loop itself.
		819
474	Not all event models support a blocking wait - some die in that case	820	Not all event models support a blocking wait - some die in that case
475	(programs might want to do that to stay interactive), so I<if you are	821	(programs might want to do that to stay interactive), so I<if you are
476	using this from a module, never require a blocking wait>, but let the	822	using this from a module, never require a blocking wait>. Instead, let the
477	caller decide whether the call will block or not (for example, by coupling	823	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	825	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
481
482	Another reason I<never> to C<< ->recv >> in a module is that you cannot
483	sensibly have two C<< ->recv >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply.
486
487	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
488	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
489	versions and also integrates coroutines into AnyEvent, making blocking
490	C<< ->recv >> calls perfectly safe as long as they are done from another
491	coroutine (one that doesn't run the event loop).
492		827
493	You can ensure that C<< -recv >> never blocks by setting a callback and	828	You can ensure that C<< -recv >> never blocks by setting a callback and
494	only calling C<< ->recv >> from within that callback (or at a later	829	only calling C<< ->recv >> from within that callback (or at a later
495	time). This will work even when the event loop does not support blocking	830	time). This will work even when the event loop does not support blocking
496	waits otherwise.	831	waits otherwise.
…		…
498	=item $bool = $cv->ready	833	=item $bool = $cv->ready
499		834
500	Returns true when the condition is "true", i.e. whether C<send> or	835	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	836	C<croak> have been called.
502		837
503	=item $cb = $cv->cb ([new callback])	838	=item $cb = $cv->cb ($cb->($cv))
504		839
505	This is a mutator function that returns the callback set and optionally	840	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	841	replaces it before doing so.
507		842
508	The callback will be called when the condition becomes "true", i.e. when	843	The callback will be called when the condition becomes (or already was)
509	C<send> or C<croak> are called. Calling C<recv> inside the callback	844	"true", i.e. when C<send> or C<croak> are called (or were called), with
		845	the only argument being the condition variable itself. Calling C<recv>
510	or at any later time is guaranteed not to block.	846	inside the callback or at any later time is guaranteed not to block.
511		847
512	=back	848	=back
513		849
		850	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		851
		852	The available backend classes are (every class has its own manpage):
		853
		854	=over 4
		855
		856	=item Backends that are autoprobed when no other event loop can be found.
		857
		858	EV is the preferred backend when no other event loop seems to be in
		859	use. If EV is not installed, then AnyEvent will fall back to its own
		860	pure-perl implementation, which is available everywhere as it comes with
		861	AnyEvent itself.
		862
		863	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		864	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		865
		866	=item Backends that are transparently being picked up when they are used.
		867
		868	These will be used when they are currently loaded when the first watcher
		869	is created, in which case it is assumed that the application is using
		870	them. This means that AnyEvent will automatically pick the right backend
		871	when the main program loads an event module before anything starts to
		872	create watchers. Nothing special needs to be done by the main program.
		873
		874	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		875	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		876	AnyEvent::Impl::Tk based on Tk, very broken.
		877	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		878	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		879	AnyEvent::Impl::Irssi used when running within irssi.
		880
		881	=item Backends with special needs.
		882
		883	Qt requires the Qt::Application to be instantiated first, but will
		884	otherwise be picked up automatically. As long as the main program
		885	instantiates the application before any AnyEvent watchers are created,
		886	everything should just work.
		887
		888	AnyEvent::Impl::Qt based on Qt.
		889
		890	Support for IO::Async can only be partial, as it is too broken and
		891	architecturally limited to even support the AnyEvent API. It also
		892	is the only event loop that needs the loop to be set explicitly, so
		893	it can only be used by a main program knowing about AnyEvent. See
		894	L<AnyEvent::Impl::Async> for the gory details.
		895
		896	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		897
		898	=item Event loops that are indirectly supported via other backends.
		899
		900	Some event loops can be supported via other modules:
		901
		902	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		903
		904	B<WxWidgets> has no support for watching file handles. However, you can
		905	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		906	polls 20 times per second, which was considered to be too horrible to even
		907	consider for AnyEvent.
		908
		909	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		910	backend, so it can be supported through POE.
		911
		912	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		913	load L<POE> when detecting them, in the hope that POE will pick them up,
		914	in which case everything will be automatic.
		915
		916	=back
		917
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	918	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		919
		920	These are not normally required to use AnyEvent, but can be useful to
		921	write AnyEvent extension modules.
		922
516	=over 4	923	=over 4
517		924
518	=item $AnyEvent::MODEL	925	=item $AnyEvent::MODEL
519		926
520	Contains C<undef> until the first watcher is being created. Then it	927	Contains C<undef> until the first watcher is being created, before the
		928	backend has been autodetected.
		929
521	contains the event model that is being used, which is the name of the	930	Afterwards it contains the event model that is being used, which is the
522	Perl class implementing the model. This class is usually one of the	931	name of the Perl class implementing the model. This class is usually one
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	932	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	933	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
525		934	will be C<urxvt::anyevent>).
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546		935
547	=item AnyEvent::detect	936	=item AnyEvent::detect
548		937
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	938	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	939	if necessary. You should only call this function right before you would
551	have created an AnyEvent watcher anyway, that is, as late as possible at	940	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	941	runtime, and not e.g. while initialising of your module.
		942
		943	If you need to do some initialisation before AnyEvent watchers are
		944	created, use C<post_detect>.
553		945
554	=item $guard = AnyEvent::post_detect { BLOCK }	946	=item $guard = AnyEvent::post_detect { BLOCK }
555		947
556	Arranges for the code block to be executed as soon as the event model is	948	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	949	autodetected (or immediately if this has already happened).
558		950
		951	The block will be executed I<after> the actual backend has been detected
		952	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		953	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		954	other initialisations - see the sources of L<AnyEvent::Strict> or
		955	L<AnyEvent::AIO> to see how this is used.
		956
		957	The most common usage is to create some global watchers, without forcing
		958	event module detection too early, for example, L<AnyEvent::AIO> creates
		959	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		960	avoid autodetecting the event module at load time.
		961
559	If called in scalar or list context, then it creates and returns an object	962	If called in scalar or list context, then it creates and returns an object
560	that automatically removes the callback again when it is destroyed. See	963	that automatically removes the callback again when it is destroyed (or
		964	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
561	L<Coro::BDB> for a case where this is useful.	965	a case where this is useful.
		966
		967	Example: Create a watcher for the IO::AIO module and store it in
		968	C<$WATCHER>. Only do so after the event loop is initialised, though.
		969
		970	our WATCHER;
		971
		972	my $guard = AnyEvent::post_detect {
		973	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		974	};
		975
		976	# the ||= is important in case post_detect immediately runs the block,
		977	# as to not clobber the newly-created watcher. assigning both watcher and
		978	# post_detect guard to the same variable has the advantage of users being
		979	# able to just C<undef $WATCHER> if the watcher causes them grief.
		980
		981	$WATCHER ||= $guard;
562		982
563	=item @AnyEvent::post_detect	983	=item @AnyEvent::post_detect
564		984
565	If there are any code references in this array (you can C<push> to it	985	If there are any code references in this array (you can C<push> to it
566	before or after loading AnyEvent), then they will called directly after	986	before or after loading AnyEvent), then they will called directly after
567	the event loop has been chosen.	987	the event loop has been chosen.
568		988
569	You should check C<$AnyEvent::MODEL> before adding to this array, though:	989	You should check C<$AnyEvent::MODEL> before adding to this array, though:
570	if it contains a true value then the event loop has already been detected,	990	if it is defined then the event loop has already been detected, and the
571	and the array will be ignored.	991	array will be ignored.
572		992
573	Best use C<AnyEvent::post_detect { BLOCK }> instead.	993	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		994	it, as it takes care of these details.
		995
		996	This variable is mainly useful for modules that can do something useful
		997	when AnyEvent is used and thus want to know when it is initialised, but do
		998	not need to even load it by default. This array provides the means to hook
		999	into AnyEvent passively, without loading it.
		1000
		1001	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1002	together, you could put this into Coro (this is the actual code used by
		1003	Coro to accomplish this):
		1004
		1005	if (defined $AnyEvent::MODEL) {
		1006	# AnyEvent already initialised, so load Coro::AnyEvent
		1007	require Coro::AnyEvent;
		1008	} else {
		1009	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1010	# as soon as it is
		1011	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1012	}
574		1013
575	=back	1014	=back
576		1015
577	=head1 WHAT TO DO IN A MODULE	1016	=head1 WHAT TO DO IN A MODULE
578		1017
…		…
601		1040
602	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1041	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
603	do anything special (it does not need to be event-based) and let AnyEvent	1042	do anything special (it does not need to be event-based) and let AnyEvent
604	decide which implementation to chose if some module relies on it.	1043	decide which implementation to chose if some module relies on it.
605		1044
606	If the main program relies on a specific event model. For example, in	1045	If the main program relies on a specific event model - for example, in
607	Gtk2 programs you have to rely on the Glib module. You should load the	1046	Gtk2 programs you have to rely on the Glib module - you should load the
608	event module before loading AnyEvent or any module that uses it: generally	1047	event module before loading AnyEvent or any module that uses it: generally
609	speaking, you should load it as early as possible. The reason is that	1048	speaking, you should load it as early as possible. The reason is that
610	modules might create watchers when they are loaded, and AnyEvent will	1049	modules might create watchers when they are loaded, and AnyEvent will
611	decide on the event model to use as soon as it creates watchers, and it	1050	decide on the event model to use as soon as it creates watchers, and it
612	might chose the wrong one unless you load the correct one yourself.	1051	might chose the wrong one unless you load the correct one yourself.
613		1052
614	You can chose to use a rather inefficient pure-perl implementation by	1053	You can chose to use a pure-perl implementation by loading the
615	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1054	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
616	behaviour everywhere, but letting AnyEvent chose is generally better.	1055	everywhere, but letting AnyEvent chose the model is generally better.
		1056
		1057	=head2 MAINLOOP EMULATION
		1058
		1059	Sometimes (often for short test scripts, or even standalone programs who
		1060	only want to use AnyEvent), you do not want to run a specific event loop.
		1061
		1062	In that case, you can use a condition variable like this:
		1063
		1064	AnyEvent->condvar->recv;
		1065
		1066	This has the effect of entering the event loop and looping forever.
		1067
		1068	Note that usually your program has some exit condition, in which case
		1069	it is better to use the "traditional" approach of storing a condition
		1070	variable somewhere, waiting for it, and sending it when the program should
		1071	exit cleanly.
		1072
617		1073
618	=head1 OTHER MODULES	1074	=head1 OTHER MODULES
619		1075
620	The following is a non-exhaustive list of additional modules that use	1076	The following is a non-exhaustive list of additional modules that use
621	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1077	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
622	in the same program. Some of the modules come with AnyEvent, some are	1078	modules and other event loops in the same program. Some of the modules
623	available via CPAN.	1079	come as part of AnyEvent, the others are available via CPAN.
624		1080
625	=over 4	1081	=over 4
626		1082
627	=item L<AnyEvent::Util>	1083	=item L<AnyEvent::Util>
628		1084
629	Contains various utility functions that replace often-used but blocking	1085	Contains various utility functions that replace often-used but blocking
630	functions such as C<inet_aton> by event-/callback-based versions.	1086	functions such as C<inet_aton> by event-/callback-based versions.
631		1087
		1088	=item L<AnyEvent::Socket>
		1089
		1090	Provides various utility functions for (internet protocol) sockets,
		1091	addresses and name resolution. Also functions to create non-blocking tcp
		1092	connections or tcp servers, with IPv6 and SRV record support and more.
		1093
632	=item L<AnyEvent::Handle>	1094	=item L<AnyEvent::Handle>
633		1095
634	Provide read and write buffers and manages watchers for reads and writes.	1096	Provide read and write buffers, manages watchers for reads and writes,
		1097	supports raw and formatted I/O, I/O queued and fully transparent and
		1098	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1099
		1100	=item L<AnyEvent::DNS>
		1101
		1102	Provides rich asynchronous DNS resolver capabilities.
		1103
		1104	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1105
		1106	Implement event-based interfaces to the protocols of the same name (for
		1107	the curious, IGS is the International Go Server and FCP is the Freenet
		1108	Client Protocol).
		1109
		1110	=item L<AnyEvent::Handle::UDP>
		1111
		1112	Here be danger!
		1113
		1114	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1115	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1116	it's use of a stream-based API with a protocol that isn't streamable, that
		1117	the only way to improve it is to delete it.
		1118
		1119	It features data corruption (but typically only under load) and general
		1120	confusion. On top, the author is not only clueless about UDP but also
		1121	fact-resistant - some gems of his understanding: "connect doesn't work
		1122	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1123	packets", "I don't need to implement proper error checking as UDP doesn't
		1124	support error checking" and so on - he doesn't even understand what's
		1125	wrong with his module when it is explained to him.
		1126
		1127	=item L<AnyEvent::DBI>
		1128
		1129	Executes L<DBI> requests asynchronously in a proxy process for you,
		1130	notifying you in an event-bnased way when the operation is finished.
		1131
		1132	=item L<AnyEvent::AIO>
		1133
		1134	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1135	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1136	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1137	file I/O, and much more.
635		1138
636	=item L<AnyEvent::HTTPD>	1139	=item L<AnyEvent::HTTPD>
637		1140
638	Provides a simple web application server framework.	1141	A simple embedded webserver.
639
640	=item L<AnyEvent::DNS>
641
642	Provides asynchronous DNS resolver capabilities, beyond what
643	L<AnyEvent::Util> offers.
644		1142
645	=item L<AnyEvent::FastPing>	1143	=item L<AnyEvent::FastPing>
646		1144
647	The fastest ping in the west.	1145	The fastest ping in the west.
648		1146
649	=item L<Net::IRC3>
650
651	AnyEvent based IRC client module family.
652
653	=item L<Net::XMPP2>
654
655	AnyEvent based XMPP (Jabber protocol) module family.
656
657	=item L<Net::FCP>
658
659	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
660	of AnyEvent.
661
662	=item L<Event::ExecFlow>
663
664	High level API for event-based execution flow control.
665
666	=item L<Coro>	1147	=item L<Coro>
667		1148
668	Has special support for AnyEvent via L<Coro::AnyEvent>.	1149	Has special support for AnyEvent via L<Coro::AnyEvent>.
669		1150
670	=item L<AnyEvent::AIO>, L<IO::AIO>
671
672	Truly asynchronous I/O, should be in the toolbox of every event
673	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
674	together.
675
676	=item L<AnyEvent::BDB>, L<BDB>
677
678	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
679	IO::AIO and AnyEvent together.
680
681	=item L<IO::Lambda>
682
683	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
684
685	=back	1151	=back
686		1152
687	=cut	1153	=cut
688		1154
689	package AnyEvent;	1155	package AnyEvent;
690		1156
691	no warnings;	1157	# basically a tuned-down version of common::sense
692	use strict;	1158	sub common_sense {
		1159	# from common:.sense 1.0
		1160	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x00";
		1161	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1162	$^H |= 0x00000600;
		1163	}
693		1164
		1165	BEGIN { AnyEvent::common_sense }
		1166
694	use Carp;	1167	use Carp ();
695		1168
696	our $VERSION = '3.41';	1169	our $VERSION = '5.271';
697	our $MODEL;	1170	our $MODEL;
698		1171
699	our $AUTOLOAD;	1172	our $AUTOLOAD;
700	our @ISA;	1173	our @ISA;
701		1174
702	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
703
704	our @REGISTRY;	1175	our @REGISTRY;
705		1176
		1177	our $VERBOSE;
		1178
		1179	BEGIN {
		1180	require "AnyEvent/constants.pl";
		1181
		1182	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1183
		1184	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1185	if ${^TAINT};
		1186
		1187	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1188
		1189	}
		1190
		1191	our $MAX_SIGNAL_LATENCY = 10;
		1192
		1193	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1194
		1195	{
		1196	my $idx;
		1197	$PROTOCOL{$_} = ++$idx
		1198	for reverse split /\s*,\s*/,
		1199	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1200	}
		1201
706	my @models = (	1202	my @models = (
707	[EV:: => AnyEvent::Impl::EV::],	1203	[EV:: => AnyEvent::Impl::EV:: , 1],
		1204	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1205	# everything below here will not (normally) be autoprobed
		1206	# as the pureperl backend should work everywhere
		1207	# and is usually faster
708	[Event:: => AnyEvent::Impl::Event::],	1208	[Event:: => AnyEvent::Impl::Event::, 1],
		1209	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1210	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1211	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
709	[Tk:: => AnyEvent::Impl::Tk::],	1212	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1213	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1214	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
710	[Wx:: => AnyEvent::Impl::POE::],	1215	[Wx:: => AnyEvent::Impl::POE::],
711	[Prima:: => AnyEvent::Impl::POE::],	1216	[Prima:: => AnyEvent::Impl::POE::],
712	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1217	# IO::Async is just too broken - we would need workarounds for its
713	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1218	# byzantine signal and broken child handling, among others.
714	[Glib:: => AnyEvent::Impl::Glib::],	1219	# IO::Async is rather hard to detect, as it doesn't have any
715	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1220	# obvious default class.
716	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1221	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
717	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1222	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1223	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1224	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
718	);	1225	);
719		1226
720	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1227	our %method = map +($_ => 1),
		1228	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
721		1229
722	our @post_detect;	1230	our @post_detect;
723		1231
724	sub post_detect(&) {	1232	sub post_detect(&) {
725	my ($cb) = @_;	1233	my ($cb) = @_;
726		1234
727	if ($MODEL) {
728	$cb->();
729
730	1
731	} else {
732	push @post_detect, $cb;	1235	push @post_detect, $cb;
733		1236
734	defined wantarray	1237	defined wantarray
735	? bless \$cb, "AnyEvent::Util::Guard"	1238	? bless \$cb, "AnyEvent::Util::postdetect"
736	: ()	1239	: ()
		1240	}
		1241
		1242	sub AnyEvent::Util::postdetect::DESTROY {
		1243	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1244	}
		1245
		1246	sub detect() {
		1247	# free some memory
		1248	*detect = sub () { $MODEL };
		1249
		1250	local $!; # for good measure
		1251	local $SIG{__DIE__};
		1252
		1253	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1254	my $model = "AnyEvent::Impl::$1";
		1255	if (eval "require $model") {
		1256	$MODEL = $model;
		1257	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1258	} else {
		1259	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1260	}
737	}	1261	}
738	}
739		1262
740	sub AnyEvent::Util::Guard::DESTROY {	1263	# check for already loaded models
741	@post_detect = grep $_ != ${$_[0]}, @post_detect;
742	}
743
744	sub detect() {
745	unless ($MODEL) {	1264	unless ($MODEL) {
746	no strict 'refs';	1265	for (@REGISTRY, @models) {
747		1266	my ($package, $model) = @$_;
748	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1267	if (${"$package\::VERSION"} > 0) {
749	my $model = "AnyEvent::Impl::$1";
750	if (eval "require $model") {	1268	if (eval "require $model") {
751	$MODEL = $model;	1269	$MODEL = $model;
752	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1270	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
753	} else {	1271	last;
754	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1272	}
755	}	1273	}
756	}	1274	}
757		1275
758	# check for already loaded models
759	unless ($MODEL) {	1276	unless ($MODEL) {
		1277	# try to autoload a model
760	for (@REGISTRY, @models) {	1278	for (@REGISTRY, @models) {
761	my ($package, $model) = @$_;	1279	my ($package, $model, $autoload) = @$_;
		1280	if (
		1281	$autoload
		1282	and eval "require $package"
762	if (${"$package\::VERSION"} > 0) {	1283	and ${"$package\::VERSION"} > 0
763	if (eval "require $model") {	1284	and eval "require $model"
		1285	) {
764	$MODEL = $model;	1286	$MODEL = $model;
765	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1287	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
766	last;	1288	last;
767	}
768	}	1289	}
769	}	1290	}
770		1291
771	unless ($MODEL) {
772	# try to load a model
773
774	for (@REGISTRY, @models) {
775	my ($package, $model) = @$_;
776	if (eval "require $package"
777	and ${"$package\::VERSION"} > 0
778	and eval "require $model") {
779	$MODEL = $model;
780	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
781	last;
782	}
783	}
784
785	$MODEL	1292	$MODEL
786	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1293	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
787	}
788	}	1294	}
789
790	unshift @ISA, $MODEL;
791	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
792
793	(shift @post_detect)->() while @post_detect;
794	}	1295	}
		1296
		1297	@models = (); # free probe data
		1298
		1299	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1300	unshift @ISA, $MODEL;
		1301
		1302	# now nuke some methods that are overriden by the backend.
		1303	# SUPER is not allowed.
		1304	for (qw(time signal child idle)) {
		1305	undef &{"AnyEvent::Base::$_"}
		1306	if defined &{"$MODEL\::$_"};
		1307	}
		1308
		1309	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1310
		1311	(shift @post_detect)->() while @post_detect;
		1312
		1313	*post_detect = sub(&) {
		1314	shift->();
		1315
		1316	undef
		1317	};
795		1318
796	$MODEL	1319	$MODEL
797	}	1320	}
798		1321
799	sub AUTOLOAD {	1322	sub AUTOLOAD {
800	(my $func = $AUTOLOAD) =~ s/.*://;	1323	(my $func = $AUTOLOAD) =~ s/.*://;
801		1324
802	$method{$func}	1325	$method{$func}
803	or croak "$func: not a valid method for AnyEvent objects";	1326	or Carp::croak "$func: not a valid AnyEvent class method";
804		1327
805	detect unless $MODEL;	1328	detect;
806		1329
807	my $class = shift;	1330	my $class = shift;
808	$class->$func (@_);	1331	$class->$func (@_);
809	}	1332	}
810		1333
		1334	# utility function to dup a filehandle. this is used by many backends
		1335	# to support binding more than one watcher per filehandle (they usually
		1336	# allow only one watcher per fd, so we dup it to get a different one).
		1337	sub _dupfh($$;$$) {
		1338	my ($poll, $fh, $r, $w) = @_;
		1339
		1340	# cygwin requires the fh mode to be matching, unix doesn't
		1341	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1342
		1343	open my $fh2, $mode, $fh
		1344	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1345
		1346	# we assume CLOEXEC is already set by perl in all important cases
		1347
		1348	($fh2, $rw)
		1349	}
		1350
		1351	=head1 SIMPLIFIED AE API
		1352
		1353	Starting with version 5.0, AnyEvent officially supports a second, much
		1354	simpler, API that is designed to reduce the calling, typing and memory
		1355	overhead by using function call syntax and a fixed number of parameters.
		1356
		1357	See the L<AE> manpage for details.
		1358
		1359	=cut
		1360
		1361	package AE;
		1362
		1363	our $VERSION = $AnyEvent::VERSION;
		1364
		1365	# fall back to the main API by default - backends and AnyEvent::Base
		1366	# implementations can overwrite these.
		1367
		1368	sub io($$$) {
		1369	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1370	}
		1371
		1372	sub timer($$$) {
		1373	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1374	}
		1375
		1376	sub signal($$) {
		1377	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1378	}
		1379
		1380	sub child($$) {
		1381	AnyEvent->child (pid => $_[0], cb => $_[1])
		1382	}
		1383
		1384	sub idle($) {
		1385	AnyEvent->idle (cb => $_[0])
		1386	}
		1387
		1388	sub cv(;&) {
		1389	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1390	}
		1391
		1392	sub now() {
		1393	AnyEvent->now
		1394	}
		1395
		1396	sub now_update() {
		1397	AnyEvent->now_update
		1398	}
		1399
		1400	sub time() {
		1401	AnyEvent->time
		1402	}
		1403
811	package AnyEvent::Base;	1404	package AnyEvent::Base;
812		1405
		1406	# default implementations for many methods
		1407
		1408	sub time {
		1409	eval q{ # poor man's autoloading {}
		1410	# probe for availability of Time::HiRes
		1411	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1412	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1413	*AE::time = \&Time::HiRes::time;
		1414	# if (eval "use POSIX (); (POSIX::times())...
		1415	} else {
		1416	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1417	*AE::time = sub (){ time }; # epic fail
		1418	}
		1419
		1420	*time = sub { AE::time }; # different prototypes
		1421	};
		1422	die if $@;
		1423
		1424	&time
		1425	}
		1426
		1427	*now = \&time;
		1428
		1429	sub now_update { }
		1430
813	# default implementation for ->condvar	1431	# default implementation for ->condvar
814		1432
815	sub condvar {	1433	sub condvar {
816	bless {}, AnyEvent::CondVar::	1434	eval q{ # poor man's autoloading {}
		1435	*condvar = sub {
		1436	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1437	};
		1438
		1439	*AE::cv = sub (;&) {
		1440	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1441	};
		1442	};
		1443	die if $@;
		1444
		1445	&condvar
817	}	1446	}
818		1447
819	# default implementation for ->signal	1448	# default implementation for ->signal
820		1449
821	our %SIG_CB;	1450	our $HAVE_ASYNC_INTERRUPT;
		1451
		1452	sub _have_async_interrupt() {
		1453	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1454	&& eval "use Async::Interrupt 1.02 (); 1")
		1455	unless defined $HAVE_ASYNC_INTERRUPT;
		1456
		1457	$HAVE_ASYNC_INTERRUPT
		1458	}
		1459
		1460	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1461	our (%SIG_ASY, %SIG_ASY_W);
		1462	our ($SIG_COUNT, $SIG_TW);
		1463
		1464	# install a dummy wakeup watcher to reduce signal catching latency
		1465	# used by Impls
		1466	sub _sig_add() {
		1467	unless ($SIG_COUNT++) {
		1468	# try to align timer on a full-second boundary, if possible
		1469	my $NOW = AE::now;
		1470
		1471	$SIG_TW = AE::timer
		1472	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1473	$MAX_SIGNAL_LATENCY,
		1474	sub { } # just for the PERL_ASYNC_CHECK
		1475	;
		1476	}
		1477	}
		1478
		1479	sub _sig_del {
		1480	undef $SIG_TW
		1481	unless --$SIG_COUNT;
		1482	}
		1483
		1484	our $_sig_name_init; $_sig_name_init = sub {
		1485	eval q{ # poor man's autoloading {}
		1486	undef $_sig_name_init;
		1487
		1488	if (_have_async_interrupt) {
		1489	*sig2num = \&Async::Interrupt::sig2num;
		1490	*sig2name = \&Async::Interrupt::sig2name;
		1491	} else {
		1492	require Config;
		1493
		1494	my %signame2num;
		1495	@signame2num{ split ' ', $Config::Config{sig_name} }
		1496	= split ' ', $Config::Config{sig_num};
		1497
		1498	my @signum2name;
		1499	@signum2name[values %signame2num] = keys %signame2num;
		1500
		1501	*sig2num = sub($) {
		1502	$_[0] > 0 ? shift : $signame2num{+shift}
		1503	};
		1504	*sig2name = sub ($) {
		1505	$_[0] > 0 ? $signum2name[+shift] : shift
		1506	};
		1507	}
		1508	};
		1509	die if $@;
		1510	};
		1511
		1512	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1513	sub sig2name($) { &$_sig_name_init; &sig2name }
822		1514
823	sub signal {	1515	sub signal {
		1516	eval q{ # poor man's autoloading {}
		1517	# probe for availability of Async::Interrupt
		1518	if (_have_async_interrupt) {
		1519	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1520
		1521	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1522	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1523
		1524	} else {
		1525	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1526
		1527	if (AnyEvent::WIN32) {
		1528	require AnyEvent::Util;
		1529
		1530	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1531	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1532	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1533	} else {
		1534	pipe $SIGPIPE_R, $SIGPIPE_W;
		1535	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1536	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1537
		1538	# not strictly required, as $^F is normally 2, but let's make sure...
		1539	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1540	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1541	}
		1542
		1543	$SIGPIPE_R
		1544	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1545
		1546	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1547	}
		1548
		1549	*signal = $HAVE_ASYNC_INTERRUPT
		1550	? sub {
824	my (undef, %arg) = @_;	1551	my (undef, %arg) = @_;
825		1552
		1553	# async::interrupt
826	my $signal = uc $arg{signal}	1554	my $signal = sig2num $arg{signal};
827	or Carp::croak "required option 'signal' is missing";
828
829	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1555	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1556
		1557	$SIG_ASY{$signal} ||= new Async::Interrupt
		1558	cb => sub { undef $SIG_EV{$signal} },
		1559	signal => $signal,
		1560	pipe => [$SIGPIPE_R->filenos],
		1561	pipe_autodrain => 0,
		1562	;
		1563
		1564	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1565	}
		1566	: sub {
		1567	my (undef, %arg) = @_;
		1568
		1569	# pure perl
		1570	my $signal = sig2name $arg{signal};
		1571	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1572
830	$SIG{$signal} ||= sub {	1573	$SIG{$signal} ||= sub {
		1574	local $!;
		1575	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1576	undef $SIG_EV{$signal};
		1577	};
		1578
		1579	# can't do signal processing without introducing races in pure perl,
		1580	# so limit the signal latency.
		1581	_sig_add;
		1582
		1583	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1584	}
		1585	;
		1586
		1587	*AnyEvent::Base::signal::DESTROY = sub {
		1588	my ($signal, $cb) = @{$_[0]};
		1589
		1590	_sig_del;
		1591
		1592	delete $SIG_CB{$signal}{$cb};
		1593
		1594	$HAVE_ASYNC_INTERRUPT
		1595	? delete $SIG_ASY{$signal}
		1596	: # delete doesn't work with older perls - they then
		1597	# print weird messages, or just unconditionally exit
		1598	# instead of getting the default action.
		1599	undef $SIG{$signal}
		1600	unless keys %{ $SIG_CB{$signal} };
		1601	};
		1602
		1603	*_signal_exec = sub {
		1604	$HAVE_ASYNC_INTERRUPT
		1605	? $SIGPIPE_R->drain
		1606	: sysread $SIGPIPE_R, (my $dummy), 9;
		1607
		1608	while (%SIG_EV) {
		1609	for (keys %SIG_EV) {
		1610	delete $SIG_EV{$_};
831	$_->() for values %{ $SIG_CB{$signal} || {} };	1611	$_->() for values %{ $SIG_CB{$_} || {} };
		1612	}
		1613	}
		1614	};
832	};	1615	};
		1616	die if $@;
833		1617
834	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1618	&signal
835	}
836
837	sub AnyEvent::Base::Signal::DESTROY {
838	my ($signal, $cb) = @{$_[0]};
839
840	delete $SIG_CB{$signal}{$cb};
841
842	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
843	}	1619	}
844		1620
845	# default implementation for ->child	1621	# default implementation for ->child
846		1622
847	our %PID_CB;	1623	our %PID_CB;
848	our $CHLD_W;	1624	our $CHLD_W;
849	our $CHLD_DELAY_W;	1625	our $CHLD_DELAY_W;
850	our $PID_IDLE;
851	our $WNOHANG;	1626	our $WNOHANG;
852		1627
853	sub _child_wait {	1628	# used by many Impl's
854	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1629	sub _emit_childstatus($$) {
		1630	my (undef, $rpid, $rstatus) = @_;
		1631
		1632	$_->($rpid, $rstatus)
855	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1633	for values %{ $PID_CB{$rpid} || {} },
856	(values %{ $PID_CB{0} || {} });	1634	values %{ $PID_CB{0} || {} };
857	}
858
859	undef $PID_IDLE;
860	}
861
862	sub _sigchld {
863	# make sure we deliver these changes "synchronous" with the event loop.
864	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
865	undef $CHLD_DELAY_W;
866	&_child_wait;
867	});
868	}	1635	}
869		1636
870	sub child {	1637	sub child {
		1638	eval q{ # poor man's autoloading {}
		1639	*_sigchld = sub {
		1640	my $pid;
		1641
		1642	AnyEvent->_emit_childstatus ($pid, $?)
		1643	while ($pid = waitpid -1, $WNOHANG) > 0;
		1644	};
		1645
		1646	*child = sub {
871	my (undef, %arg) = @_;	1647	my (undef, %arg) = @_;
872		1648
873	defined (my $pid = $arg{pid} + 0)	1649	defined (my $pid = $arg{pid} + 0)
874	or Carp::croak "required option 'pid' is missing";	1650	or Carp::croak "required option 'pid' is missing";
875		1651
876	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1652	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
877		1653
878	unless ($WNOHANG) {	1654	# WNOHANG is almost cetrainly 1 everywhere
879	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1655	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
880	}	1656	? 1
		1657	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
881		1658
882	unless ($CHLD_W) {	1659	unless ($CHLD_W) {
883	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1660	$CHLD_W = AE::signal CHLD => \&_sigchld;
884	# child could be a zombie already, so make at least one round	1661	# child could be a zombie already, so make at least one round
885	&_sigchld;	1662	&_sigchld;
886	}	1663	}
887		1664
888	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1665	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
889	}	1666	};
890		1667
891	sub AnyEvent::Base::Child::DESTROY {	1668	*AnyEvent::Base::child::DESTROY = sub {
892	my ($pid, $cb) = @{$_[0]};	1669	my ($pid, $cb) = @{$_[0]};
893		1670
894	delete $PID_CB{$pid}{$cb};	1671	delete $PID_CB{$pid}{$cb};
895	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1672	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
896		1673
897	undef $CHLD_W unless keys %PID_CB;	1674	undef $CHLD_W unless keys %PID_CB;
		1675	};
		1676	};
		1677	die if $@;
		1678
		1679	&child
		1680	}
		1681
		1682	# idle emulation is done by simply using a timer, regardless
		1683	# of whether the process is idle or not, and not letting
		1684	# the callback use more than 50% of the time.
		1685	sub idle {
		1686	eval q{ # poor man's autoloading {}
		1687	*idle = sub {
		1688	my (undef, %arg) = @_;
		1689
		1690	my ($cb, $w, $rcb) = $arg{cb};
		1691
		1692	$rcb = sub {
		1693	if ($cb) {
		1694	$w = _time;
		1695	&$cb;
		1696	$w = _time - $w;
		1697
		1698	# never use more then 50% of the time for the idle watcher,
		1699	# within some limits
		1700	$w = 0.0001 if $w < 0.0001;
		1701	$w = 5 if $w > 5;
		1702
		1703	$w = AE::timer $w, 0, $rcb;
		1704	} else {
		1705	# clean up...
		1706	undef $w;
		1707	undef $rcb;
		1708	}
		1709	};
		1710
		1711	$w = AE::timer 0.05, 0, $rcb;
		1712
		1713	bless \\$cb, "AnyEvent::Base::idle"
		1714	};
		1715
		1716	*AnyEvent::Base::idle::DESTROY = sub {
		1717	undef $${$_[0]};
		1718	};
		1719	};
		1720	die if $@;
		1721
		1722	&idle
898	}	1723	}
899		1724
900	package AnyEvent::CondVar;	1725	package AnyEvent::CondVar;
901		1726
902	our @ISA = AnyEvent::CondVar::Base::;	1727	our @ISA = AnyEvent::CondVar::Base::;
903		1728
904	package AnyEvent::CondVar::Base;	1729	package AnyEvent::CondVar::Base;
		1730
		1731	#use overload
		1732	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1733	# fallback => 1;
		1734
		1735	# save 300+ kilobytes by dirtily hardcoding overloading
		1736	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1737	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1738	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1739	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1740
		1741	our $WAITING;
905		1742
906	sub _send {	1743	sub _send {
907	# nop	1744	# nop
908	}	1745	}
909		1746
…		…
922	sub ready {	1759	sub ready {
923	$_[0]{_ae_sent}	1760	$_[0]{_ae_sent}
924	}	1761	}
925		1762
926	sub _wait {	1763	sub _wait {
		1764	$WAITING
		1765	and !$_[0]{_ae_sent}
		1766	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1767
		1768	local $WAITING = 1;
927	AnyEvent->one_event while !$_[0]{_ae_sent};	1769	AnyEvent->one_event while !$_[0]{_ae_sent};
928	}	1770	}
929		1771
930	sub recv {	1772	sub recv {
931	$_[0]->_wait;	1773	$_[0]->_wait;
…		…
933	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1775	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
934	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1776	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
935	}	1777	}
936		1778
937	sub cb {	1779	sub cb {
938	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1780	my $cv = shift;
		1781
		1782	@_
		1783	and $cv->{_ae_cb} = shift
		1784	and $cv->{_ae_sent}
		1785	and (delete $cv->{_ae_cb})->($cv);
		1786
939	$_[0]{_ae_cb}	1787	$cv->{_ae_cb}
940	}	1788	}
941		1789
942	sub begin {	1790	sub begin {
943	++$_[0]{_ae_counter};	1791	++$_[0]{_ae_counter};
944	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1792	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
945	}	1793	}
946		1794
947	sub end {	1795	sub end {
948	return if --$_[0]{_ae_counter};	1796	return if --$_[0]{_ae_counter};
949	&{ $_[0]{_ae_end_cb} } if $_[0]{_ae_end_cb};	1797	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
950	}	1798	}
951		1799
952	# undocumented/compatibility with pre-3.4	1800	# undocumented/compatibility with pre-3.4
953	*broadcast = \&send;	1801	*broadcast = \&send;
954	*wait = \&_wait;	1802	*wait = \&_wait;
		1803
		1804	=head1 ERROR AND EXCEPTION HANDLING
		1805
		1806	In general, AnyEvent does not do any error handling - it relies on the
		1807	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1808	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1809	checking of all AnyEvent methods, however, which is highly useful during
		1810	development.
		1811
		1812	As for exception handling (i.e. runtime errors and exceptions thrown while
		1813	executing a callback), this is not only highly event-loop specific, but
		1814	also not in any way wrapped by this module, as this is the job of the main
		1815	program.
		1816
		1817	The pure perl event loop simply re-throws the exception (usually
		1818	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1819	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1820	so on.
		1821
		1822	=head1 ENVIRONMENT VARIABLES
		1823
		1824	The following environment variables are used by this module or its
		1825	submodules.
		1826
		1827	Note that AnyEvent will remove I<all> environment variables starting with
		1828	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1829	enabled.
		1830
		1831	=over 4
		1832
		1833	=item C<PERL_ANYEVENT_VERBOSE>
		1834
		1835	By default, AnyEvent will be completely silent except in fatal
		1836	conditions. You can set this environment variable to make AnyEvent more
		1837	talkative.
		1838
		1839	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1840	conditions, such as not being able to load the event model specified by
		1841	C<PERL_ANYEVENT_MODEL>.
		1842
		1843	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1844	model it chooses.
		1845
		1846	When set to C<8> or higher, then AnyEvent will report extra information on
		1847	which optional modules it loads and how it implements certain features.
		1848
		1849	=item C<PERL_ANYEVENT_STRICT>
		1850
		1851	AnyEvent does not do much argument checking by default, as thorough
		1852	argument checking is very costly. Setting this variable to a true value
		1853	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1854	check the arguments passed to most method calls. If it finds any problems,
		1855	it will croak.
		1856
		1857	In other words, enables "strict" mode.
		1858
		1859	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1860	>>, it is definitely recommended to keep it off in production. Keeping
		1861	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1862	can be very useful, however.
		1863
		1864	=item C<PERL_ANYEVENT_MODEL>
		1865
		1866	This can be used to specify the event model to be used by AnyEvent, before
		1867	auto detection and -probing kicks in. It must be a string consisting
		1868	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1869	and the resulting module name is loaded and if the load was successful,
		1870	used as event model. If it fails to load AnyEvent will proceed with
		1871	auto detection and -probing.
		1872
		1873	This functionality might change in future versions.
		1874
		1875	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1876	could start your program like this:
		1877
		1878	PERL_ANYEVENT_MODEL=Perl perl ...
		1879
		1880	=item C<PERL_ANYEVENT_PROTOCOLS>
		1881
		1882	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1883	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1884	of auto probing).
		1885
		1886	Must be set to a comma-separated list of protocols or address families,
		1887	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1888	used, and preference will be given to protocols mentioned earlier in the
		1889	list.
		1890
		1891	This variable can effectively be used for denial-of-service attacks
		1892	against local programs (e.g. when setuid), although the impact is likely
		1893	small, as the program has to handle conenction and other failures anyways.
		1894
		1895	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1896	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1897	- only support IPv4, never try to resolve or contact IPv6
		1898	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1899	IPv6, but prefer IPv6 over IPv4.
		1900
		1901	=item C<PERL_ANYEVENT_EDNS0>
		1902
		1903	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1904	for DNS. This extension is generally useful to reduce DNS traffic, but
		1905	some (broken) firewalls drop such DNS packets, which is why it is off by
		1906	default.
		1907
		1908	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1909	EDNS0 in its DNS requests.
		1910
		1911	=item C<PERL_ANYEVENT_MAX_FORKS>
		1912
		1913	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1914	will create in parallel.
		1915
		1916	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1917
		1918	The default value for the C<max_outstanding> parameter for the default DNS
		1919	resolver - this is the maximum number of parallel DNS requests that are
		1920	sent to the DNS server.
		1921
		1922	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1923
		1924	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1925	configuration) in the default resolver. When set to the empty string, no
		1926	default config will be used.
		1927
		1928	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1929
		1930	When neither C<ca_file> nor C<ca_path> was specified during
		1931	L<AnyEvent::TLS> context creation, and either of these environment
		1932	variables exist, they will be used to specify CA certificate locations
		1933	instead of a system-dependent default.
		1934
		1935	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1936
		1937	When these are set to C<1>, then the respective modules are not
		1938	loaded. Mostly good for testing AnyEvent itself.
		1939
		1940	=back
955		1941
956	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1942	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
957		1943
958	This is an advanced topic that you do not normally need to use AnyEvent in	1944	This is an advanced topic that you do not normally need to use AnyEvent in
959	a module. This section is only of use to event loop authors who want to	1945	a module. This section is only of use to event loop authors who want to
…		…
993		1979
994	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1980	I<rxvt-unicode> also cheats a bit by not providing blocking access to
995	condition variables: code blocking while waiting for a condition will	1981	condition variables: code blocking while waiting for a condition will
996	C<die>. This still works with most modules/usages, and blocking calls must	1982	C<die>. This still works with most modules/usages, and blocking calls must
997	not be done in an interactive application, so it makes sense.	1983	not be done in an interactive application, so it makes sense.
998
999	=head1 ENVIRONMENT VARIABLES
1000
1001	The following environment variables are used by this module:
1002
1003	=over 4
1004
1005	=item C<PERL_ANYEVENT_VERBOSE>
1006
1007	By default, AnyEvent will be completely silent except in fatal
1008	conditions. You can set this environment variable to make AnyEvent more
1009	talkative.
1010
1011	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1012	conditions, such as not being able to load the event model specified by
1013	C<PERL_ANYEVENT_MODEL>.
1014
1015	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1016	model it chooses.
1017
1018	=item C<PERL_ANYEVENT_MODEL>
1019
1020	This can be used to specify the event model to be used by AnyEvent, before
1021	autodetection and -probing kicks in. It must be a string consisting
1022	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1023	and the resulting module name is loaded and if the load was successful,
1024	used as event model. If it fails to load AnyEvent will proceed with
1025	autodetection and -probing.
1026
1027	This functionality might change in future versions.
1028
1029	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1030	could start your program like this:
1031
1032	PERL_ANYEVENT_MODEL=Perl perl ...
1033
1034	=back
1035		1984
1036	=head1 EXAMPLE PROGRAM	1985	=head1 EXAMPLE PROGRAM
1037		1986
1038	The following program uses an I/O watcher to read data from STDIN, a timer	1987	The following program uses an I/O watcher to read data from STDIN, a timer
1039	to display a message once per second, and a condition variable to quit the	1988	to display a message once per second, and a condition variable to quit the
…		…
1052	warn "read: $input\n"; # output what has been read	2001	warn "read: $input\n"; # output what has been read
1053	$cv->send if $input =~ /^q/i; # quit program if /^q/i	2002	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1054	},	2003	},
1055	);	2004	);
1056		2005
1057	my $time_watcher; # can only be used once
1058
1059	sub new_timer {
1060	$timer = AnyEvent->timer (after => 1, cb => sub {	2006	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1061	warn "timeout\n"; # print 'timeout' about every second	2007	warn "timeout\n"; # print 'timeout' at most every second
1062	&new_timer; # and restart the time
1063	});	2008	});
1064	}
1065
1066	new_timer; # create first timer
1067		2009
1068	$cv->recv; # wait until user enters /^q/i	2010	$cv->recv; # wait until user enters /^q/i
1069		2011
1070	=head1 REAL-WORLD EXAMPLE	2012	=head1 REAL-WORLD EXAMPLE
1071		2013
…		…
1123	syswrite $txn->{fh}, $txn->{request}	2065	syswrite $txn->{fh}, $txn->{request}
1124	or die "connection or write error";	2066	or die "connection or write error";
1125	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2067	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1126		2068
1127	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2069	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1128	result and signals any possible waiters that the request ahs finished:	2070	result and signals any possible waiters that the request has finished:
1129		2071
1130	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2072	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1131		2073
1132	if (end-of-file or data complete) {	2074	if (end-of-file or data complete) {
1133	$txn->{result} = $txn->{buf};	2075	$txn->{result} = $txn->{buf};
…		…
1141		2083
1142	$txn->{finished}->recv;	2084	$txn->{finished}->recv;
1143	return $txn->{result};	2085	return $txn->{result};
1144		2086
1145	The actual code goes further and collects all errors (C<die>s, exceptions)	2087	The actual code goes further and collects all errors (C<die>s, exceptions)
1146	that occured during request processing. The C<result> method detects	2088	that occurred during request processing. The C<result> method detects
1147	whether an exception as thrown (it is stored inside the $txn object)	2089	whether an exception as thrown (it is stored inside the $txn object)
1148	and just throws the exception, which means connection errors and other	2090	and just throws the exception, which means connection errors and other
1149	problems get reported tot he code that tries to use the result, not in a	2091	problems get reported to the code that tries to use the result, not in a
1150	random callback.	2092	random callback.
1151		2093
1152	All of this enables the following usage styles:	2094	All of this enables the following usage styles:
1153		2095
1154	1. Blocking:	2096	1. Blocking:
…		…
1197	of various event loops I prepared some benchmarks.	2139	of various event loops I prepared some benchmarks.
1198		2140
1199	=head2 BENCHMARKING ANYEVENT OVERHEAD	2141	=head2 BENCHMARKING ANYEVENT OVERHEAD
1200		2142
1201	Here is a benchmark of various supported event models used natively and	2143	Here is a benchmark of various supported event models used natively and
1202	through anyevent. The benchmark creates a lot of timers (with a zero	2144	through AnyEvent. The benchmark creates a lot of timers (with a zero
1203	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2145	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1204	which it is), lets them fire exactly once and destroys them again.	2146	which it is), lets them fire exactly once and destroys them again.
1205		2147
1206	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2148	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1207	distribution.	2149	distribution. It uses the L<AE> interface, which makes a real difference
		2150	for the EV and Perl backends only.
1208		2151
1209	=head3 Explanation of the columns	2152	=head3 Explanation of the columns
1210		2153
1211	I<watcher> is the number of event watchers created/destroyed. Since	2154	I<watcher> is the number of event watchers created/destroyed. Since
1212	different event models feature vastly different performances, each event	2155	different event models feature vastly different performances, each event
…		…
1233	watcher.	2176	watcher.
1234		2177
1235	=head3 Results	2178	=head3 Results
1236		2179
1237	name watchers bytes create invoke destroy comment	2180	name watchers bytes create invoke destroy comment
1238	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2181	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1239	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2182	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1240	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2183	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1241	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2184	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1242	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2185	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1243	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2186	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2187	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2188	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1244	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2189	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1245	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2190	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1246	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2191	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1247	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2192	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1248		2193
1249	=head3 Discussion	2194	=head3 Discussion
1250		2195
1251	The benchmark does I<not> measure scalability of the event loop very	2196	The benchmark does I<not> measure scalability of the event loop very
1252	well. For example, a select-based event loop (such as the pure perl one)	2197	well. For example, a select-based event loop (such as the pure perl one)
…		…
1264	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2209	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1265	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2210	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1266	cycles with POE.	2211	cycles with POE.
1267		2212
1268	C<EV> is the sole leader regarding speed and memory use, which are both	2213	C<EV> is the sole leader regarding speed and memory use, which are both
1269	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2214	maximal/minimal, respectively. When using the L<AE> API there is zero
		2215	overhead (when going through the AnyEvent API create is about 5-6 times
		2216	slower, with other times being equal, so still uses far less memory than
1270	far less memory than any other event loop and is still faster than Event	2217	any other event loop and is still faster than Event natively).
1271	natively.
1272		2218
1273	The pure perl implementation is hit in a few sweet spots (both the	2219	The pure perl implementation is hit in a few sweet spots (both the
1274	constant timeout and the use of a single fd hit optimisations in the perl	2220	constant timeout and the use of a single fd hit optimisations in the perl
1275	interpreter and the backend itself). Nevertheless this shows that it	2221	interpreter and the backend itself). Nevertheless this shows that it
1276	adds very little overhead in itself. Like any select-based backend its	2222	adds very little overhead in itself. Like any select-based backend its
1277	performance becomes really bad with lots of file descriptors (and few of	2223	performance becomes really bad with lots of file descriptors (and few of
1278	them active), of course, but this was not subject of this benchmark.	2224	them active), of course, but this was not subject of this benchmark.
1279		2225
1280	The C<Event> module has a relatively high setup and callback invocation	2226	The C<Event> module has a relatively high setup and callback invocation
1281	cost, but overall scores in on the third place.	2227	cost, but overall scores in on the third place.
		2228
		2229	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2230	when using its pure perl backend.
1282		2231
1283	C<Glib>'s memory usage is quite a bit higher, but it features a	2232	C<Glib>'s memory usage is quite a bit higher, but it features a
1284	faster callback invocation and overall ends up in the same class as	2233	faster callback invocation and overall ends up in the same class as
1285	C<Event>. However, Glib scales extremely badly, doubling the number of	2234	C<Event>. However, Glib scales extremely badly, doubling the number of
1286	watchers increases the processing time by more than a factor of four,	2235	watchers increases the processing time by more than a factor of four,
…		…
1330		2279
1331	=back	2280	=back
1332		2281
1333	=head2 BENCHMARKING THE LARGE SERVER CASE	2282	=head2 BENCHMARKING THE LARGE SERVER CASE
1334		2283
1335	This benchmark atcually benchmarks the event loop itself. It works by	2284	This benchmark actually benchmarks the event loop itself. It works by
1336	creating a number of "servers": each server consists of a socketpair, a	2285	creating a number of "servers": each server consists of a socket pair, a
1337	timeout watcher that gets reset on activity (but never fires), and an I/O	2286	timeout watcher that gets reset on activity (but never fires), and an I/O
1338	watcher waiting for input on one side of the socket. Each time the socket	2287	watcher waiting for input on one side of the socket. Each time the socket
1339	watcher reads a byte it will write that byte to a random other "server".	2288	watcher reads a byte it will write that byte to a random other "server".
1340		2289
1341	The effect is that there will be a lot of I/O watchers, only part of which	2290	The effect is that there will be a lot of I/O watchers, only part of which
1342	are active at any one point (so there is a constant number of active	2291	are active at any one point (so there is a constant number of active
1343	fds for each loop iterstaion, but which fds these are is random). The	2292	fds for each loop iteration, but which fds these are is random). The
1344	timeout is reset each time something is read because that reflects how	2293	timeout is reset each time something is read because that reflects how
1345	most timeouts work (and puts extra pressure on the event loops).	2294	most timeouts work (and puts extra pressure on the event loops).
1346		2295
1347	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2296	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1348	(1%) are active. This mirrors the activity of large servers with many	2297	(1%) are active. This mirrors the activity of large servers with many
1349	connections, most of which are idle at any one point in time.	2298	connections, most of which are idle at any one point in time.
1350		2299
1351	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2300	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1352	distribution.	2301	distribution. It uses the L<AE> interface, which makes a real difference
		2302	for the EV and Perl backends only.
1353		2303
1354	=head3 Explanation of the columns	2304	=head3 Explanation of the columns
1355		2305
1356	I<sockets> is the number of sockets, and twice the number of "servers" (as	2306	I<sockets> is the number of sockets, and twice the number of "servers" (as
1357	each server has a read and write socket end).	2307	each server has a read and write socket end).
1358		2308
1359	I<create> is the time it takes to create a socketpair (which is	2309	I<create> is the time it takes to create a socket pair (which is
1360	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2310	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1361		2311
1362	I<request>, the most important value, is the time it takes to handle a	2312	I<request>, the most important value, is the time it takes to handle a
1363	single "request", that is, reading the token from the pipe and forwarding	2313	single "request", that is, reading the token from the pipe and forwarding
1364	it to another server. This includes deleting the old timeout and creating	2314	it to another server. This includes deleting the old timeout and creating
1365	a new one that moves the timeout into the future.	2315	a new one that moves the timeout into the future.
1366		2316
1367	=head3 Results	2317	=head3 Results
1368		2318
1369	name sockets create request	2319	name sockets create request
1370	EV 20000 69.01 11.16	2320	EV 20000 62.66 7.99
1371	Perl 20000 73.32 35.87	2321	Perl 20000 68.32 32.64
1372	Event 20000 212.62 257.32	2322	IOAsync 20000 174.06 101.15 epoll
1373	Glib 20000 651.16 1896.30	2323	IOAsync 20000 174.67 610.84 poll
		2324	Event 20000 202.69 242.91
		2325	Glib 20000 557.01 1689.52
1374	POE 20000 349.67 12317.24 uses POE::Loop::Event	2326	POE 20000 341.54 12086.32 uses POE::Loop::Event
1375		2327
1376	=head3 Discussion	2328	=head3 Discussion
1377		2329
1378	This benchmark I<does> measure scalability and overall performance of the	2330	This benchmark I<does> measure scalability and overall performance of the
1379	particular event loop.	2331	particular event loop.
…		…
1381	EV is again fastest. Since it is using epoll on my system, the setup time	2333	EV is again fastest. Since it is using epoll on my system, the setup time
1382	is relatively high, though.	2334	is relatively high, though.
1383		2335
1384	Perl surprisingly comes second. It is much faster than the C-based event	2336	Perl surprisingly comes second. It is much faster than the C-based event
1385	loops Event and Glib.	2337	loops Event and Glib.
		2338
		2339	IO::Async performs very well when using its epoll backend, and still quite
		2340	good compared to Glib when using its pure perl backend.
1386		2341
1387	Event suffers from high setup time as well (look at its code and you will	2342	Event suffers from high setup time as well (look at its code and you will
1388	understand why). Callback invocation also has a high overhead compared to	2343	understand why). Callback invocation also has a high overhead compared to
1389	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2344	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1390	uses select or poll in basically all documented configurations.	2345	uses select or poll in basically all documented configurations.
…		…
1437	speed most when you have lots of watchers, not when you only have a few of	2392	speed most when you have lots of watchers, not when you only have a few of
1438	them).	2393	them).
1439		2394
1440	EV is again fastest.	2395	EV is again fastest.
1441		2396
1442	Perl again comes second. It is noticably faster than the C-based event	2397	Perl again comes second. It is noticeably faster than the C-based event
1443	loops Event and Glib, although the difference is too small to really	2398	loops Event and Glib, although the difference is too small to really
1444	matter.	2399	matter.
1445		2400
1446	POE also performs much better in this case, but is is still far behind the	2401	POE also performs much better in this case, but is is still far behind the
1447	others.	2402	others.
…		…
1453	=item * C-based event loops perform very well with small number of	2408	=item * C-based event loops perform very well with small number of
1454	watchers, as the management overhead dominates.	2409	watchers, as the management overhead dominates.
1455		2410
1456	=back	2411	=back
1457		2412
		2413	=head2 THE IO::Lambda BENCHMARK
		2414
		2415	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2416	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2417	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2418	shouldn't come as a surprise to anybody). As such, the benchmark is
		2419	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2420	very optimal. But how would AnyEvent compare when used without the extra
		2421	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2422
		2423	The benchmark itself creates an echo-server, and then, for 500 times,
		2424	connects to the echo server, sends a line, waits for the reply, and then
		2425	creates the next connection. This is a rather bad benchmark, as it doesn't
		2426	test the efficiency of the framework or much non-blocking I/O, but it is a
		2427	benchmark nevertheless.
		2428
		2429	name runtime
		2430	Lambda/select 0.330 sec
		2431	+ optimized 0.122 sec
		2432	Lambda/AnyEvent 0.327 sec
		2433	+ optimized 0.138 sec
		2434	Raw sockets/select 0.077 sec
		2435	POE/select, components 0.662 sec
		2436	POE/select, raw sockets 0.226 sec
		2437	POE/select, optimized 0.404 sec
		2438
		2439	AnyEvent/select/nb 0.085 sec
		2440	AnyEvent/EV/nb 0.068 sec
		2441	+state machine 0.134 sec
		2442
		2443	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2444	benchmarks actually make blocking connects and use 100% blocking I/O,
		2445	defeating the purpose of an event-based solution. All of the newly
		2446	written AnyEvent benchmarks use 100% non-blocking connects (using
		2447	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2448	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2449	generally require a lot more bookkeeping and event handling than blocking
		2450	connects (which involve a single syscall only).
		2451
		2452	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2453	offers similar expressive power as POE and IO::Lambda, using conventional
		2454	Perl syntax. This means that both the echo server and the client are 100%
		2455	non-blocking, further placing it at a disadvantage.
		2456
		2457	As you can see, the AnyEvent + EV combination even beats the
		2458	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2459	backend easily beats IO::Lambda and POE.
		2460
		2461	And even the 100% non-blocking version written using the high-level (and
		2462	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2463	higher level ("unoptimised") abstractions by a large margin, even though
		2464	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2465
		2466	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2467	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2468	part of the IO::Lambda distribution and were used without any changes.
		2469
		2470
		2471	=head1 SIGNALS
		2472
		2473	AnyEvent currently installs handlers for these signals:
		2474
		2475	=over 4
		2476
		2477	=item SIGCHLD
		2478
		2479	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2480	emulation for event loops that do not support them natively. Also, some
		2481	event loops install a similar handler.
		2482
		2483	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2484	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2485
		2486	=item SIGPIPE
		2487
		2488	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2489	when AnyEvent gets loaded.
		2490
		2491	The rationale for this is that AnyEvent users usually do not really depend
		2492	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2493	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2494	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2495	some random socket.
		2496
		2497	The rationale for installing a no-op handler as opposed to ignoring it is
		2498	that this way, the handler will be restored to defaults on exec.
		2499
		2500	Feel free to install your own handler, or reset it to defaults.
		2501
		2502	=back
		2503
		2504	=cut
		2505
		2506	undef $SIG{CHLD}
		2507	if $SIG{CHLD} eq 'IGNORE';
		2508
		2509	$SIG{PIPE} = sub { }
		2510	unless defined $SIG{PIPE};
		2511
		2512	=head1 RECOMMENDED/OPTIONAL MODULES
		2513
		2514	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2515	it's built-in modules) are required to use it.
		2516
		2517	That does not mean that AnyEvent won't take advantage of some additional
		2518	modules if they are installed.
		2519
		2520	This section explains which additional modules will be used, and how they
		2521	affect AnyEvent's operation.
		2522
		2523	=over 4
		2524
		2525	=item L<Async::Interrupt>
		2526
		2527	This slightly arcane module is used to implement fast signal handling: To
		2528	my knowledge, there is no way to do completely race-free and quick
		2529	signal handling in pure perl. To ensure that signals still get
		2530	delivered, AnyEvent will start an interval timer to wake up perl (and
		2531	catch the signals) with some delay (default is 10 seconds, look for
		2532	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2533
		2534	If this module is available, then it will be used to implement signal
		2535	catching, which means that signals will not be delayed, and the event loop
		2536	will not be interrupted regularly, which is more efficient (and good for
		2537	battery life on laptops).
		2538
		2539	This affects not just the pure-perl event loop, but also other event loops
		2540	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2541
		2542	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2543	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2544	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2545	does nothing for those backends.
		2546
		2547	=item L<EV>
		2548
		2549	This module isn't really "optional", as it is simply one of the backend
		2550	event loops that AnyEvent can use. However, it is simply the best event
		2551	loop available in terms of features, speed and stability: It supports
		2552	the AnyEvent API optimally, implements all the watcher types in XS, does
		2553	automatic timer adjustments even when no monotonic clock is available,
		2554	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2555	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2556	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2557
		2558	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2559	then this module will do nothing for you.
		2560
		2561	=item L<Guard>
		2562
		2563	The guard module, when used, will be used to implement
		2564	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2565	lot less memory), but otherwise doesn't affect guard operation much. It is
		2566	purely used for performance.
		2567
		2568	=item L<JSON> and L<JSON::XS>
		2569
		2570	One of these modules is required when you want to read or write JSON data
		2571	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2572	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2573
		2574	=item L<Net::SSLeay>
		2575
		2576	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2577	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2578	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2579
		2580	=item L<Time::HiRes>
		2581
		2582	This module is part of perl since release 5.008. It will be used when the
		2583	chosen event library does not come with a timing source on it's own. The
		2584	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2585	try to use a monotonic clock for timing stability.
		2586
		2587	=back
		2588
1458		2589
1459	=head1 FORK	2590	=head1 FORK
1460		2591
1461	Most event libraries are not fork-safe. The ones who are usually are	2592	Most event libraries are not fork-safe. The ones who are usually are
1462	because they rely on inefficient but fork-safe C<select> or C<poll>	2593	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1463	calls. Only L<EV> is fully fork-aware.	2594	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2595	are usually badly thought-out hacks that are incompatible with fork in
		2596	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2597	continue event-processing in both parent and child (or both, if you know
		2598	what you are doing).
		2599
		2600	This means that, in general, you cannot fork and do event processing in
		2601	the child if the event library was initialised before the fork (which
		2602	usually happens when the first AnyEvent watcher is created, or the library
		2603	is loaded).
1464		2604
1465	If you have to fork, you must either do so I<before> creating your first	2605	If you have to fork, you must either do so I<before> creating your first
1466	watcher OR you must not use AnyEvent at all in the child.	2606	watcher OR you must not use AnyEvent at all in the child OR you must do
		2607	something completely out of the scope of AnyEvent.
		2608
		2609	The problem of doing event processing in the parent I<and> the child
		2610	is much more complicated: even for backends that I<are> fork-aware or
		2611	fork-safe, their behaviour is not usually what you want: fork clones all
		2612	watchers, that means all timers, I/O watchers etc. are active in both
		2613	parent and child, which is almost never what you want. USing C<exec>
		2614	to start worker children from some kind of manage rprocess is usually
		2615	preferred, because it is much easier and cleaner, at the expense of having
		2616	to have another binary.
1467		2617
1468		2618
1469	=head1 SECURITY CONSIDERATIONS	2619	=head1 SECURITY CONSIDERATIONS
1470		2620
1471	AnyEvent can be forced to load any event model via	2621	AnyEvent can be forced to load any event model via
…		…
1476	specified in the variable.	2626	specified in the variable.
1477		2627
1478	You can make AnyEvent completely ignore this variable by deleting it	2628	You can make AnyEvent completely ignore this variable by deleting it
1479	before the first watcher gets created, e.g. with a C<BEGIN> block:	2629	before the first watcher gets created, e.g. with a C<BEGIN> block:
1480		2630
1481	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2631	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1482		2632
1483	use AnyEvent;	2633	use AnyEvent;
1484		2634
1485	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2635	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1486	be used to probe what backend is used and gain other information (which is	2636	be used to probe what backend is used and gain other information (which is
1487	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2637	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2638	$ENV{PERL_ANYEVENT_STRICT}.
		2639
		2640	Note that AnyEvent will remove I<all> environment variables starting with
		2641	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2642	enabled.
		2643
		2644
		2645	=head1 BUGS
		2646
		2647	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2648	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2649	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2650	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2651	pronounced).
1488		2652
1489		2653
1490	=head1 SEE ALSO	2654	=head1 SEE ALSO
		2655
		2656	Utility functions: L<AnyEvent::Util>.
1491		2657
1492	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2658	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1493	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2659	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1494		2660
1495	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2661	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1496	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2662	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1497	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2663	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1498	L<AnyEvent::Impl::POE>.	2664	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1499		2665
		2666	Non-blocking file handles, sockets, TCP clients and
		2667	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2668
		2669	Asynchronous DNS: L<AnyEvent::DNS>.
		2670
1500	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2671	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2672	L<Coro::Event>,
1501		2673
1502	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2674	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2675	L<AnyEvent::HTTP>.
1503		2676
1504		2677
1505	=head1 AUTHOR	2678	=head1 AUTHOR
1506		2679
1507	Marc Lehmann <schmorp@schmorp.de>	2680	Marc Lehmann <schmorp@schmorp.de>
1508	http://home.schmorp.de/	2681	http://home.schmorp.de/
1509		2682
1510	=cut	2683	=cut
1511		2684
1512	1	2685	1
1513		2686

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