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Revision 1.118 by root, Sun May 11 18:08:36 2008 UTC vs.
Revision 1.327 by root, Sun Jun 6 10:13:57 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
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off. Maybe you should tell their authors to
103	use AnyEvent so their modules work together with others seamlessly...	144	use AnyEvent so their modules work together with others seamlessly...
104		145
105	The pure-perl implementation of AnyEvent is called	146	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	147	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	148	explicitly and enjoy the high availability of that event loop :)
108		149
109	=head1 WATCHERS	150	=head1 WATCHERS
110		151
111	AnyEvent has the central concept of a I<watcher>, which is an object that	152	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	153	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	154	the callback to call, the file handle to watch, etc.
114		155
115	These watchers are normal Perl objects with normal Perl lifetime. After	156	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	157	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	158	callback when the event occurs (of course, only when the event model
118	is in control).	159	is in control).
119		160
		161	Note that B<callbacks must not permanently change global variables>
		162	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		163	callbacks must not C<die> >>. The former is good programming practise in
		164	Perl and the latter stems from the fact that exception handling differs
		165	widely between event loops.
		166
120	To disable the watcher you have to destroy it (e.g. by setting the	167	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	168	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	169	to it).
123		170
124	All watchers are created by calling a method on the C<AnyEvent> class.	171	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	173	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	174	example), or need to refer to their watcher object in other ways.
128		175
129	An any way to achieve that is this pattern:	176	An any way to achieve that is this pattern:
130		177
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	178	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	179	# you can use $w here, for example to undef it
133	undef $w;	180	undef $w;
134	});	181	});
135		182
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	183	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	184	my variables are only visible after the statement in which they are
138	declared.	185	declared.
139		186
140	=head2 I/O WATCHERS	187	=head2 I/O WATCHERS
141		188
		189	$w = AnyEvent->io (
		190	fh => <filehandle_or_fileno>,
		191	poll => <"r" or "w">,
		192	cb => <callback>,
		193	);
		194
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	195	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	196	with the following mandatory key-value pairs as arguments:
144		197
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	198	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		199	for events (AnyEvent might or might not keep a reference to this file
		200	handle). Note that only file handles pointing to things for which
		201	non-blocking operation makes sense are allowed. This includes sockets,
		202	most character devices, pipes, fifos and so on, but not for example files
		203	or block devices.
		204
146	for events. C<poll> must be a string that is either C<r> or C<w>,	205	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,	206	watcher waiting for "r"eadable or "w"ritable events, respectively.
		207
148	respectively. C<cb> is the callback to invoke each time the file handle	208	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		209
151	Although the callback might get passed parameters, their value and	210	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	211	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	212	callbacks cannot use arguments passed to I/O watcher callbacks.
154		213
…		…
158		217
159	Some event loops issue spurious readyness notifications, so you should	218	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	219	always use non-blocking calls when reading/writing from/to your file
161	handles.	220	handles.
162		221
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	222	Example: wait for readability of STDIN, then read a line and disable the
		223	watcher.
		224
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	225	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	226	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	227	warn "read: $input\n";
169	undef $w;	228	undef $w;
170	});	229	});
171		230
172	=head2 TIME WATCHERS	231	=head2 TIME WATCHERS
173		232
		233	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		234
		235	$w = AnyEvent->timer (
		236	after => <fractional_seconds>,
		237	interval => <fractional_seconds>,
		238	cb => <callback>,
		239	);
		240
174	You can create a time watcher by calling the C<< AnyEvent->timer >>	241	You can create a time watcher by calling the C<< AnyEvent->timer >>
175	method with the following mandatory arguments:	242	method with the following mandatory arguments:
176		243
177	C<after> specifies after how many seconds (fractional values are	244	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	245	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		247
181	Although the callback might get passed parameters, their value and	248	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	249	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	250	callbacks cannot use arguments passed to time watcher callbacks.
184		251
185	The timer callback will be invoked at most once: if you want a repeating	252	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	253	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	254	callback will be invoked regularly at that interval (in fractional
		255	seconds) after the first invocation. If C<interval> is specified with a
		256	false value, then it is treated as if it were missing.
188		257
189	Example:	258	The callback will be rescheduled before invoking the callback, but no
		259	attempt is done to avoid timer drift in most backends, so the interval is
		260	only approximate.
190		261
191	# fire an event after 7.7 seconds	262	Example: fire an event after 7.7 seconds.
		263
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	264	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	265	warn "timeout\n";
194	});	266	});
195		267
196	# to cancel the timer:	268	# to cancel the timer:
197	undef $w;	269	undef $w;
198		270
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	271	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		272
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	273	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		274	warn "timeout\n";
207	};	275	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		276
212	=head3 TIMING ISSUES	277	=head3 TIMING ISSUES
213		278
214	There are two ways to handle timers: based on real time (relative, "fire	279	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	280	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	292	timers.
228		293
229	AnyEvent always prefers relative timers, if available, matching the	294	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	295	AnyEvent API.
231		296
		297	AnyEvent has two additional methods that return the "current time":
		298
		299	=over 4
		300
		301	=item AnyEvent->time
		302
		303	This returns the "current wallclock time" as a fractional number of
		304	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		305	return, and the result is guaranteed to be compatible with those).
		306
		307	It progresses independently of any event loop processing, i.e. each call
		308	will check the system clock, which usually gets updated frequently.
		309
		310	=item AnyEvent->now
		311
		312	This also returns the "current wallclock time", but unlike C<time>, above,
		313	this value might change only once per event loop iteration, depending on
		314	the event loop (most return the same time as C<time>, above). This is the
		315	time that AnyEvent's timers get scheduled against.
		316
		317	I<In almost all cases (in all cases if you don't care), this is the
		318	function to call when you want to know the current time.>
		319
		320	This function is also often faster then C<< AnyEvent->time >>, and
		321	thus the preferred method if you want some timestamp (for example,
		322	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		323
		324	The rest of this section is only of relevance if you try to be very exact
		325	with your timing, you can skip it without bad conscience.
		326
		327	For a practical example of when these times differ, consider L<Event::Lib>
		328	and L<EV> and the following set-up:
		329
		330	The event loop is running and has just invoked one of your callback at
		331	time=500 (assume no other callbacks delay processing). In your callback,
		332	you wait a second by executing C<sleep 1> (blocking the process for a
		333	second) and then (at time=501) you create a relative timer that fires
		334	after three seconds.
		335
		336	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		337	both return C<501>, because that is the current time, and the timer will
		338	be scheduled to fire at time=504 (C<501> + C<3>).
		339
		340	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		341	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		342	last event processing phase started. With L<EV>, your timer gets scheduled
		343	to run at time=503 (C<500> + C<3>).
		344
		345	In one sense, L<Event::Lib> is more exact, as it uses the current time
		346	regardless of any delays introduced by event processing. However, most
		347	callbacks do not expect large delays in processing, so this causes a
		348	higher drift (and a lot more system calls to get the current time).
		349
		350	In another sense, L<EV> is more exact, as your timer will be scheduled at
		351	the same time, regardless of how long event processing actually took.
		352
		353	In either case, if you care (and in most cases, you don't), then you
		354	can get whatever behaviour you want with any event loop, by taking the
		355	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		356	account.
		357
		358	=item AnyEvent->now_update
		359
		360	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		361	the current time for each loop iteration (see the discussion of L<<
		362	AnyEvent->now >>, above).
		363
		364	When a callback runs for a long time (or when the process sleeps), then
		365	this "current" time will differ substantially from the real time, which
		366	might affect timers and time-outs.
		367
		368	When this is the case, you can call this method, which will update the
		369	event loop's idea of "current time".
		370
		371	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		372	when mod_perl executes the script, then the event loop will have the wrong
		373	idea about the "current time" (being potentially far in the past, when the
		374	script ran the last time). In that case you should arrange a call to C<<
		375	AnyEvent->now_update >> each time the web server process wakes up again
		376	(e.g. at the start of your script, or in a handler).
		377
		378	Note that updating the time I<might> cause some events to be handled.
		379
		380	=back
		381
232	=head2 SIGNAL WATCHERS	382	=head2 SIGNAL WATCHERS
233		383
		384	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		385
234	You can watch for signals using a signal watcher, C<signal> is the signal	386	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	387	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	388	callback to be invoked whenever a signal occurs.
237		389
238	Although the callback might get passed parameters, their value and	390	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	391	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	392	callbacks cannot use arguments passed to signal watcher callbacks.
241		393
242	Multiple signal occurances can be clumped together into one callback	394	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	395	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	396	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.	397	but it is guaranteed not to interrupt any other callbacks.
246		398
247	The main advantage of using these watchers is that you can share a signal	399	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	400	between multiple watchers, and AnyEvent will ensure that signals will not
		401	interrupt your program at bad times.
249		402
250	This watcher might use C<%SIG>, so programs overwriting those signals	403	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	404	so programs overwriting those signals directly will likely not work
		405	correctly.
252		406
253	Example: exit on SIGINT	407	Example: exit on SIGINT
254		408
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	409	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		410
		411	=head3 Restart Behaviour
		412
		413	While restart behaviour is up to the event loop implementation, most will
		414	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		415	pure perl implementation).
		416
		417	=head3 Safe/Unsafe Signals
		418
		419	Perl signals can be either "safe" (synchronous to opcode handling) or
		420	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		421	latter might corrupt your memory.
		422
		423	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		424	i.e. they will not interrupt your running perl program but will only be
		425	called as part of the normal event handling (just like timer, I/O etc.
		426	callbacks, too).
		427
		428	=head3 Signal Races, Delays and Workarounds
		429
		430	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		431	callbacks to signals in a generic way, which is a pity, as you cannot
		432	do race-free signal handling in perl, requiring C libraries for
		433	this. AnyEvent will try to do it's best, which means in some cases,
		434	signals will be delayed. The maximum time a signal might be delayed is
		435	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		436	variable can be changed only before the first signal watcher is created,
		437	and should be left alone otherwise. This variable determines how often
		438	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		439	will cause fewer spurious wake-ups, which is better for power and CPU
		440	saving.
		441
		442	All these problems can be avoided by installing the optional
		443	L<Async::Interrupt> module, which works with most event loops. It will not
		444	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		445	(and not with L<POE> currently, as POE does it's own workaround with
		446	one-second latency). For those, you just have to suffer the delays.
		447
257	=head2 CHILD PROCESS WATCHERS	448	=head2 CHILD PROCESS WATCHERS
258		449
		450	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		451
259	You can also watch on a child process exit and catch its exit status.	452	You can also watch on a child process exit and catch its exit status.
260		453
261	The child process is specified by the C<pid> argument (if set to C<0>, it	454	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	455	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	456	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	457	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,	458	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	459
		460	The callback will be called with the pid and exit status (as returned by
		461	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		462	callback arguments.
		463
		464	This watcher type works by installing a signal handler for C<SIGCHLD>,
		465	and since it cannot be shared, nothing else should use SIGCHLD or reap
		466	random child processes (waiting for specific child processes, e.g. inside
		467	C<system>, is just fine).
267		468
268	There is a slight catch to child watchers, however: you usually start them	469	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	470	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	471	have exited already (and no SIGCHLD will be sent anymore).
271		472
272	Not all event models handle this correctly (POE doesn't), but even for	473	Not all event models handle this correctly (neither POE nor IO::Async do,
		474	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	475	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).	476	the process exits (i.e. before you fork in the first place). AnyEvent's
		477	pure perl event loop handles all cases correctly regardless of when you
		478	start the watcher.
275		479
276	This means you cannot create a child watcher as the very first thing in an	480	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	481	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>).	482	watcher before you C<fork> the child (alternatively, you can call
		483	C<AnyEvent::detect>).
		484
		485	As most event loops do not support waiting for child events, they will be
		486	emulated by AnyEvent in most cases, in which the latency and race problems
		487	mentioned in the description of signal watchers apply.
279		488
280	Example: fork a process and wait for it	489	Example: fork a process and wait for it
281		490
282	my $done = AnyEvent->condvar;	491	my $done = AnyEvent->condvar;
283		492
284	my $pid = fork or exit 5;	493	my $pid = fork or exit 5;
285		494
286	my $w = AnyEvent->child (	495	my $w = AnyEvent->child (
287	pid => $pid,	496	pid => $pid,
288	cb => sub {	497	cb => sub {
289	my ($pid, $status) = @_;	498	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	499	warn "pid $pid exited with status $status";
291	$done->send;	500	$done->send;
292	},	501	},
293	);	502	);
294		503
295	# do something else, then wait for process exit	504	# do something else, then wait for process exit
296	$done->recv;	505	$done->recv;
		506
		507	=head2 IDLE WATCHERS
		508
		509	$w = AnyEvent->idle (cb => <callback>);
		510
		511	Repeatedly invoke the callback after the process becomes idle, until
		512	either the watcher is destroyed or new events have been detected.
		513
		514	Idle watchers are useful when there is a need to do something, but it
		515	is not so important (or wise) to do it instantly. The callback will be
		516	invoked only when there is "nothing better to do", which is usually
		517	defined as "all outstanding events have been handled and no new events
		518	have been detected". That means that idle watchers ideally get invoked
		519	when the event loop has just polled for new events but none have been
		520	detected. Instead of blocking to wait for more events, the idle watchers
		521	will be invoked.
		522
		523	Unfortunately, most event loops do not really support idle watchers (only
		524	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		525	will simply call the callback "from time to time".
		526
		527	Example: read lines from STDIN, but only process them when the
		528	program is otherwise idle:
		529
		530	my @lines; # read data
		531	my $idle_w;
		532	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		533	push @lines, scalar <STDIN>;
		534
		535	# start an idle watcher, if not already done
		536	$idle_w ||= AnyEvent->idle (cb => sub {
		537	# handle only one line, when there are lines left
		538	if (my $line = shift @lines) {
		539	print "handled when idle: $line";
		540	} else {
		541	# otherwise disable the idle watcher again
		542	undef $idle_w;
		543	}
		544	});
		545	});
297		546
298	=head2 CONDITION VARIABLES	547	=head2 CONDITION VARIABLES
		548
		549	$cv = AnyEvent->condvar;
		550
		551	$cv->send (<list>);
		552	my @res = $cv->recv;
299		553
300	If you are familiar with some event loops you will know that all of them	554	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	555	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	556	will actively watch for new events and call your callbacks.
303		557
304	AnyEvent is different, it expects somebody else to run the event loop and	558	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	559	loop and will only block when necessary (usually when told by the user).
306		560
307	The instrument to do that is called a "condition variable", so called	561	The tool to do that is called a "condition variable", so called because
308	because they represent a condition that must become true.	562	they represent a condition that must become true.
		563
		564	Now is probably a good time to look at the examples further below.
309		565
310	Condition variables can be created by calling the C<< AnyEvent->condvar	566	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	567	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	568	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	569	becomes true, with the condition variable as the first argument (but not
		570	the results).
314		571
315	After creation, the conditon variable is "false" until it becomes "true"	572	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method.	573	by calling the C<send> method (or calling the condition variable as if it
		574	were a callback, read about the caveats in the description for the C<<
		575	->send >> method).
317		576
318	Condition variables are similar to callbacks, except that you can	577	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	578	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	579
321	another way to call them is transations - each condition variable can be	580	=over 4
322	used to represent a transaction, which finishes at some point and delivers	581
323	a result.	582	=item * Condition variables are like callbacks - you can call them (and pass them instead
		583	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		584
		585	=item * Condition variables are signals - one side can emit or send them,
		586	the other side can wait for them, or install a handler that is called when
		587	the signal fires.
		588
		589	=item * Condition variables are like "Merge Points" - points in your program
		590	where you merge multiple independent results/control flows into one.
		591
		592	=item * Condition variables represent a transaction - function that start
		593	some kind of transaction can return them, leaving the caller the choice
		594	between waiting in a blocking fashion, or setting a callback.
		595
		596	=item * Condition variables represent future values, or promises to deliver
		597	some result, long before the result is available.
		598
		599	=back
324		600
325	Condition variables are very useful to signal that something has finished,	601	Condition variables are very useful to signal that something has finished,
326	for example, if you write a module that does asynchronous http requests,	602	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	603	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	604	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	608	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	609	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.	610	button of your app, which would C<< ->send >> the "quit" event.
335		611
336	Note that condition variables recurse into the event loop - if you have	612	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	613	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	614	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,	615	you should avoid making a blocking wait yourself, at least in callbacks,
340	as this asks for trouble.	616	as this asks for trouble.
341		617
342	Condition variables are represented by hash refs in perl, and the keys	618	Condition variables are represented by hash refs in perl, and the keys
…		…
347		623
348	There are two "sides" to a condition variable - the "producer side" which	624	There are two "sides" to a condition variable - the "producer side" which
349	eventually calls C<< -> send >>, and the "consumer side", which waits	625	eventually calls C<< -> send >>, and the "consumer side", which waits
350	for the send to occur.	626	for the send to occur.
351		627
352	Example:	628	Example: wait for a timer.
353		629
354	# wait till the result is ready	630	# condition: "wait till the timer is fired"
355	my $result_ready = AnyEvent->condvar;	631	my $timer_fired = AnyEvent->condvar;
356		632
357	# do something such as adding a timer	633	# create the timer - we could wait for, say
358	# or socket watcher the calls $result_ready->send	634	# a handle becomign ready, or even an
359	# when the "result" is ready.	635	# AnyEvent::HTTP request to finish, but
360	# in this case, we simply use a timer:	636	# in this case, we simply use a timer:
361	my $w = AnyEvent->timer (	637	my $w = AnyEvent->timer (
362	after => 1,	638	after => 1,
363	cb => sub { $result_ready->send },	639	cb => sub { $timer_fired->send },
364	);	640	);
365		641
366	# this "blocks" (while handling events) till the callback	642	# this "blocks" (while handling events) till the callback
367	# calls send	643	# calls ->send
368	$result_ready->recv;	644	$timer_fired->recv;
		645
		646	Example: wait for a timer, but take advantage of the fact that condition
		647	variables are also callable directly.
		648
		649	my $done = AnyEvent->condvar;
		650	my $delay = AnyEvent->timer (after => 5, cb => $done);
		651	$done->recv;
		652
		653	Example: Imagine an API that returns a condvar and doesn't support
		654	callbacks. This is how you make a synchronous call, for example from
		655	the main program:
		656
		657	use AnyEvent::CouchDB;
		658
		659	...
		660
		661	my @info = $couchdb->info->recv;
		662
		663	And this is how you would just set a callback to be called whenever the
		664	results are available:
		665
		666	$couchdb->info->cb (sub {
		667	my @info = $_[0]->recv;
		668	});
369		669
370	=head3 METHODS FOR PRODUCERS	670	=head3 METHODS FOR PRODUCERS
371		671
372	These methods should only be used by the producing side, i.e. the	672	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	673	code/module that eventually sends the signal. Note that it is also
…		…
386	immediately from within send.	686	immediately from within send.
387		687
388	Any arguments passed to the C<send> call will be returned by all	688	Any arguments passed to the C<send> call will be returned by all
389	future C<< ->recv >> calls.	689	future C<< ->recv >> calls.
390		690
		691	Condition variables are overloaded so one can call them directly (as if
		692	they were a code reference). Calling them directly is the same as calling
		693	C<send>.
		694
391	=item $cv->croak ($error)	695	=item $cv->croak ($error)
392		696
393	Similar to send, but causes all call's to C<< ->recv >> to invoke	697	Similar to send, but causes all call's to C<< ->recv >> to invoke
394	C<Carp::croak> with the given error message/object/scalar.	698	C<Carp::croak> with the given error message/object/scalar.
395		699
396	This can be used to signal any errors to the condition variable	700	This can be used to signal any errors to the condition variable
397	user/consumer.	701	user/consumer. Doing it this way instead of calling C<croak> directly
		702	delays the error detetcion, but has the overwhelmign advantage that it
		703	diagnoses the error at the place where the result is expected, and not
		704	deep in some event clalback without connection to the actual code causing
		705	the problem.
398		706
399	=item $cv->begin ([group callback])	707	=item $cv->begin ([group callback])
400		708
401	=item $cv->end	709	=item $cv->end
402
403	These two methods are EXPERIMENTAL and MIGHT CHANGE.
404		710
405	These two methods can be used to combine many transactions/events into	711	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	712	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	713	to use a condition variable for the whole process.
408		714
409	Every call to C<< ->begin >> will increment a counter, and every call to	715	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	716	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	717	>>, 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	718	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.	719	>>, but that is not required. If no group callback was set, C<send> will
		720	be called without any arguments.
414		721
415	Let's clarify this with the ping example:	722	You can think of C<< $cv->send >> giving you an OR condition (one call
		723	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		724	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		725
		726	Let's start with a simple example: you have two I/O watchers (for example,
		727	STDOUT and STDERR for a program), and you want to wait for both streams to
		728	close before activating a condvar:
416		729
417	my $cv = AnyEvent->condvar;	730	my $cv = AnyEvent->condvar;
418		731
		732	$cv->begin; # first watcher
		733	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		734	defined sysread $fh1, my $buf, 4096
		735	or $cv->end;
		736	});
		737
		738	$cv->begin; # second watcher
		739	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		740	defined sysread $fh2, my $buf, 4096
		741	or $cv->end;
		742	});
		743
		744	$cv->recv;
		745
		746	This works because for every event source (EOF on file handle), there is
		747	one call to C<begin>, so the condvar waits for all calls to C<end> before
		748	sending.
		749
		750	The ping example mentioned above is slightly more complicated, as the
		751	there are results to be passwd back, and the number of tasks that are
		752	begung can potentially be zero:
		753
		754	my $cv = AnyEvent->condvar;
		755
419	my %result;	756	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	757	$cv->begin (sub { shift->send (\%result) });
421		758
422	for my $host (@list_of_hosts) {	759	for my $host (@list_of_hosts) {
423	$cv->begin;	760	$cv->begin;
424	ping_host_then_call_callback $host, sub {	761	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	762	$result{$host} = ...;
…		…
440	loop, which serves two important purposes: first, it sets the callback	777	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	778	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	779	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	780	doesn't execute once).
444		781
445	This is the general pattern when you "fan out" into multiple subrequests:	782	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>	783	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	784	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>.	785	subrequest you start, call C<begin> and for each subrequest you finish,
		786	call C<end>.
449		787
450	=back	788	=back
451		789
452	=head3 METHODS FOR CONSUMERS	790	=head3 METHODS FOR CONSUMERS
453		791
…		…
469	function will call C<croak>.	807	function will call C<croak>.
470		808
471	In list context, all parameters passed to C<send> will be returned,	809	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	810	in scalar context only the first one will be returned.
473		811
		812	Note that doing a blocking wait in a callback is not supported by any
		813	event loop, that is, recursive invocation of a blocking C<< ->recv
		814	>> is not allowed, and the C<recv> call will C<croak> if such a
		815	condition is detected. This condition can be slightly loosened by using
		816	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		817	any thread that doesn't run the event loop itself.
		818
474	Not all event models support a blocking wait - some die in that case	819	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	820	(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	821	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	822	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	823	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	824	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	825	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		826
493	You can ensure that C<< -recv >> never blocks by setting a callback and	827	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	828	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	829	time). This will work even when the event loop does not support blocking
496	waits otherwise.	830	waits otherwise.
…		…
498	=item $bool = $cv->ready	832	=item $bool = $cv->ready
499		833
500	Returns true when the condition is "true", i.e. whether C<send> or	834	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	835	C<croak> have been called.
502		836
503	=item $cb = $cv->cb ([new callback])	837	=item $cb = $cv->cb ($cb->($cv))
504		838
505	This is a mutator function that returns the callback set and optionally	839	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	840	replaces it before doing so.
507		841
508	The callback will be called when the condition becomes "true", i.e. when	842	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	843	"true", i.e. when C<send> or C<croak> are called (or were called), with
		844	the only argument being the condition variable itself. Calling C<recv>
510	or at any later time is guaranteed not to block.	845	inside the callback or at any later time is guaranteed not to block.
511		846
512	=back	847	=back
513		848
		849	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		850
		851	The available backend classes are (every class has its own manpage):
		852
		853	=over 4
		854
		855	=item Backends that are autoprobed when no other event loop can be found.
		856
		857	EV is the preferred backend when no other event loop seems to be in
		858	use. If EV is not installed, then AnyEvent will fall back to its own
		859	pure-perl implementation, which is available everywhere as it comes with
		860	AnyEvent itself.
		861
		862	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		863	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		864
		865	=item Backends that are transparently being picked up when they are used.
		866
		867	These will be used when they are currently loaded when the first watcher
		868	is created, in which case it is assumed that the application is using
		869	them. This means that AnyEvent will automatically pick the right backend
		870	when the main program loads an event module before anything starts to
		871	create watchers. Nothing special needs to be done by the main program.
		872
		873	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		874	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		875	AnyEvent::Impl::Tk based on Tk, very broken.
		876	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		877	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		878	AnyEvent::Impl::Irssi used when running within irssi.
		879
		880	=item Backends with special needs.
		881
		882	Qt requires the Qt::Application to be instantiated first, but will
		883	otherwise be picked up automatically. As long as the main program
		884	instantiates the application before any AnyEvent watchers are created,
		885	everything should just work.
		886
		887	AnyEvent::Impl::Qt based on Qt.
		888
		889	Support for IO::Async can only be partial, as it is too broken and
		890	architecturally limited to even support the AnyEvent API. It also
		891	is the only event loop that needs the loop to be set explicitly, so
		892	it can only be used by a main program knowing about AnyEvent. See
		893	L<AnyEvent::Impl::Async> for the gory details.
		894
		895	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		896
		897	=item Event loops that are indirectly supported via other backends.
		898
		899	Some event loops can be supported via other modules:
		900
		901	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		902
		903	B<WxWidgets> has no support for watching file handles. However, you can
		904	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		905	polls 20 times per second, which was considered to be too horrible to even
		906	consider for AnyEvent.
		907
		908	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		909	backend, so it can be supported through POE.
		910
		911	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		912	load L<POE> when detecting them, in the hope that POE will pick them up,
		913	in which case everything will be automatic.
		914
		915	=back
		916
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	917	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		918
		919	These are not normally required to use AnyEvent, but can be useful to
		920	write AnyEvent extension modules.
		921
516	=over 4	922	=over 4
517		923
518	=item $AnyEvent::MODEL	924	=item $AnyEvent::MODEL
519		925
520	Contains C<undef> until the first watcher is being created. Then it	926	Contains C<undef> until the first watcher is being created, before the
		927	backend has been autodetected.
		928
521	contains the event model that is being used, which is the name of the	929	Afterwards it contains the event model that is being used, which is the
522	Perl class implementing the model. This class is usually one of the	930	name of the Perl class implementing the model. This class is usually one
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	931	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	932	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
525		933	will be C<urxvt::anyevent>).
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546		934
547	=item AnyEvent::detect	935	=item AnyEvent::detect
548		936
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	937	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	938	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	939	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	940	runtime, and not e.g. while initialising of your module.
		941
		942	If you need to do some initialisation before AnyEvent watchers are
		943	created, use C<post_detect>.
553		944
554	=item $guard = AnyEvent::post_detect { BLOCK }	945	=item $guard = AnyEvent::post_detect { BLOCK }
555		946
556	Arranges for the code block to be executed as soon as the event model is	947	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	948	autodetected (or immediately if this has already happened).
558		949
		950	The block will be executed I<after> the actual backend has been detected
		951	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		952	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		953	other initialisations - see the sources of L<AnyEvent::Strict> or
		954	L<AnyEvent::AIO> to see how this is used.
		955
		956	The most common usage is to create some global watchers, without forcing
		957	event module detection too early, for example, L<AnyEvent::AIO> creates
		958	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		959	avoid autodetecting the event module at load time.
		960
559	If called in scalar or list context, then it creates and returns an object	961	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	962	that automatically removes the callback again when it is destroyed (or
		963	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
561	L<Coro::BDB> for a case where this is useful.	964	a case where this is useful.
		965
		966	Example: Create a watcher for the IO::AIO module and store it in
		967	C<$WATCHER>. Only do so after the event loop is initialised, though.
		968
		969	our WATCHER;
		970
		971	my $guard = AnyEvent::post_detect {
		972	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		973	};
		974
		975	# the ||= is important in case post_detect immediately runs the block,
		976	# as to not clobber the newly-created watcher. assigning both watcher and
		977	# post_detect guard to the same variable has the advantage of users being
		978	# able to just C<undef $WATCHER> if the watcher causes them grief.
		979
		980	$WATCHER ||= $guard;
562		981
563	=item @AnyEvent::post_detect	982	=item @AnyEvent::post_detect
564		983
565	If there are any code references in this array (you can C<push> to it	984	If there are any code references in this array (you can C<push> to it
566	before or after loading AnyEvent), then they will called directly after	985	before or after loading AnyEvent), then they will called directly after
567	the event loop has been chosen.	986	the event loop has been chosen.
568		987
569	You should check C<$AnyEvent::MODEL> before adding to this array, though:	988	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,	989	if it is defined then the event loop has already been detected, and the
571	and the array will be ignored.	990	array will be ignored.
572		991
573	Best use C<AnyEvent::post_detect { BLOCK }> instead.	992	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		993	it, as it takes care of these details.
		994
		995	This variable is mainly useful for modules that can do something useful
		996	when AnyEvent is used and thus want to know when it is initialised, but do
		997	not need to even load it by default. This array provides the means to hook
		998	into AnyEvent passively, without loading it.
		999
		1000	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1001	together, you could put this into Coro (this is the actual code used by
		1002	Coro to accomplish this):
		1003
		1004	if (defined $AnyEvent::MODEL) {
		1005	# AnyEvent already initialised, so load Coro::AnyEvent
		1006	require Coro::AnyEvent;
		1007	} else {
		1008	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1009	# as soon as it is
		1010	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1011	}
574		1012
575	=back	1013	=back
576		1014
577	=head1 WHAT TO DO IN A MODULE	1015	=head1 WHAT TO DO IN A MODULE
578		1016
…		…
601		1039
602	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1040	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	1041	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.	1042	decide which implementation to chose if some module relies on it.
605		1043
606	If the main program relies on a specific event model. For example, in	1044	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	1045	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	1046	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	1047	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	1048	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	1049	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.	1050	might chose the wrong one unless you load the correct one yourself.
613		1051
614	You can chose to use a rather inefficient pure-perl implementation by	1052	You can chose to use a pure-perl implementation by loading the
615	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1053	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
616	behaviour everywhere, but letting AnyEvent chose is generally better.	1054	everywhere, but letting AnyEvent chose the model is generally better.
		1055
		1056	=head2 MAINLOOP EMULATION
		1057
		1058	Sometimes (often for short test scripts, or even standalone programs who
		1059	only want to use AnyEvent), you do not want to run a specific event loop.
		1060
		1061	In that case, you can use a condition variable like this:
		1062
		1063	AnyEvent->condvar->recv;
		1064
		1065	This has the effect of entering the event loop and looping forever.
		1066
		1067	Note that usually your program has some exit condition, in which case
		1068	it is better to use the "traditional" approach of storing a condition
		1069	variable somewhere, waiting for it, and sending it when the program should
		1070	exit cleanly.
		1071
617		1072
618	=head1 OTHER MODULES	1073	=head1 OTHER MODULES
619		1074
620	The following is a non-exhaustive list of additional modules that use	1075	The following is a non-exhaustive list of additional modules that use
621	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1076	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	1077	modules and other event loops in the same program. Some of the modules
623	available via CPAN.	1078	come as part of AnyEvent, the others are available via CPAN.
624		1079
625	=over 4	1080	=over 4
626		1081
627	=item L<AnyEvent::Util>	1082	=item L<AnyEvent::Util>
628		1083
629	Contains various utility functions that replace often-used but blocking	1084	Contains various utility functions that replace often-used but blocking
630	functions such as C<inet_aton> by event-/callback-based versions.	1085	functions such as C<inet_aton> by event-/callback-based versions.
631		1086
		1087	=item L<AnyEvent::Socket>
		1088
		1089	Provides various utility functions for (internet protocol) sockets,
		1090	addresses and name resolution. Also functions to create non-blocking tcp
		1091	connections or tcp servers, with IPv6 and SRV record support and more.
		1092
632	=item L<AnyEvent::Handle>	1093	=item L<AnyEvent::Handle>
633		1094
634	Provide read and write buffers and manages watchers for reads and writes.	1095	Provide read and write buffers, manages watchers for reads and writes,
		1096	supports raw and formatted I/O, I/O queued and fully transparent and
		1097	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1098
		1099	=item L<AnyEvent::DNS>
		1100
		1101	Provides rich asynchronous DNS resolver capabilities.
		1102
		1103	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1104
		1105	Implement event-based interfaces to the protocols of the same name (for
		1106	the curious, IGS is the International Go Server and FCP is the Freenet
		1107	Client Protocol).
		1108
		1109	=item L<AnyEvent::Handle::UDP>
		1110
		1111	Here be danger!
		1112
		1113	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1114	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1115	it's use of a stream-based API with a protocol that isn't streamable, that
		1116	the only way to improve it is to delete it.
		1117
		1118	It features data corruption (but typically only under load) and general
		1119	confusion. On top, the author is not only clueless about UDP but also
		1120	fact-resistant - some gems of his understanding: "connect doesn't work
		1121	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1122	packets", "I don't need to implement proper error checking as UDP doesn't
		1123	support error checking" and so on - he doesn't even understand what's
		1124	wrong with his module when it is explained to him.
		1125
		1126	=item L<AnyEvent::DBI>
		1127
		1128	Executes L<DBI> requests asynchronously in a proxy process for you,
		1129	notifying you in an event-bnased way when the operation is finished.
		1130
		1131	=item L<AnyEvent::AIO>
		1132
		1133	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1134	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1135	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1136	file I/O, and much more.
635		1137
636	=item L<AnyEvent::HTTPD>	1138	=item L<AnyEvent::HTTPD>
637		1139
638	Provides a simple web application server framework.	1140	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		1141
645	=item L<AnyEvent::FastPing>	1142	=item L<AnyEvent::FastPing>
646		1143
647	The fastest ping in the west.	1144	The fastest ping in the west.
648		1145
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>	1146	=item L<Coro>
667		1147
668	Has special support for AnyEvent via L<Coro::AnyEvent>.	1148	Has special support for AnyEvent via L<Coro::AnyEvent>.
669		1149
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	1150	=back
686		1151
687	=cut	1152	=cut
688		1153
689	package AnyEvent;	1154	package AnyEvent;
690		1155
691	no warnings;	1156	# basically a tuned-down version of common::sense
692	use strict;	1157	sub common_sense {
		1158	# from common:.sense 1.0
		1159	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x00";
		1160	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1161	$^H |= 0x00000600;
		1162	}
693		1163
		1164	BEGIN { AnyEvent::common_sense }
		1165
694	use Carp;	1166	use Carp ();
695		1167
696	our $VERSION = '3.41';	1168	our $VERSION = '5.27';
697	our $MODEL;	1169	our $MODEL;
698		1170
699	our $AUTOLOAD;	1171	our $AUTOLOAD;
700	our @ISA;	1172	our @ISA;
701		1173
702	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
703
704	our @REGISTRY;	1174	our @REGISTRY;
705		1175
		1176	our $VERBOSE;
		1177
		1178	BEGIN {
		1179	require "AnyEvent/constants.pl";
		1180
		1181	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1182
		1183	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1184	if ${^TAINT};
		1185
		1186	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1187
		1188	}
		1189
		1190	our $MAX_SIGNAL_LATENCY = 10;
		1191
		1192	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1193
		1194	{
		1195	my $idx;
		1196	$PROTOCOL{$_} = ++$idx
		1197	for reverse split /\s*,\s*/,
		1198	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1199	}
		1200
706	my @models = (	1201	my @models = (
707	[EV:: => AnyEvent::Impl::EV::],	1202	[EV:: => AnyEvent::Impl::EV:: , 1],
		1203	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1204	# everything below here will not (normally) be autoprobed
		1205	# as the pureperl backend should work everywhere
		1206	# and is usually faster
708	[Event:: => AnyEvent::Impl::Event::],	1207	[Event:: => AnyEvent::Impl::Event::, 1],
		1208	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1209	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1210	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
709	[Tk:: => AnyEvent::Impl::Tk::],	1211	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1212	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1213	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
710	[Wx:: => AnyEvent::Impl::POE::],	1214	[Wx:: => AnyEvent::Impl::POE::],
711	[Prima:: => AnyEvent::Impl::POE::],	1215	[Prima:: => AnyEvent::Impl::POE::],
712	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1216	# 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	1217	# byzantine signal and broken child handling, among others.
714	[Glib:: => AnyEvent::Impl::Glib::],	1218	# IO::Async is rather hard to detect, as it doesn't have any
715	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1219	# obvious default class.
716	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1220	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
717	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1221	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1222	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1223	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
718	);	1224	);
719		1225
720	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1226	our %method = map +($_ => 1),
		1227	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
721		1228
722	our @post_detect;	1229	our @post_detect;
723		1230
724	sub post_detect(&) {	1231	sub post_detect(&) {
725	my ($cb) = @_;	1232	my ($cb) = @_;
726		1233
727	if ($MODEL) {
728	$cb->();
729
730	1
731	} else {
732	push @post_detect, $cb;	1234	push @post_detect, $cb;
733		1235
734	defined wantarray	1236	defined wantarray
735	? bless \$cb, "AnyEvent::Util::Guard"	1237	? bless \$cb, "AnyEvent::Util::postdetect"
736	: ()	1238	: ()
		1239	}
		1240
		1241	sub AnyEvent::Util::postdetect::DESTROY {
		1242	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1243	}
		1244
		1245	sub detect() {
		1246	# free some memory
		1247	*detect = sub () { $MODEL };
		1248
		1249	local $!; # for good measure
		1250	local $SIG{__DIE__};
		1251
		1252	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1253	my $model = "AnyEvent::Impl::$1";
		1254	if (eval "require $model") {
		1255	$MODEL = $model;
		1256	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1257	} else {
		1258	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1259	}
737	}	1260	}
738	}
739		1261
740	sub AnyEvent::Util::Guard::DESTROY {	1262	# check for already loaded models
741	@post_detect = grep $_ != ${$_[0]}, @post_detect;
742	}
743
744	sub detect() {
745	unless ($MODEL) {	1263	unless ($MODEL) {
746	no strict 'refs';	1264	for (@REGISTRY, @models) {
747		1265	my ($package, $model) = @$_;
748	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1266	if (${"$package\::VERSION"} > 0) {
749	my $model = "AnyEvent::Impl::$1";
750	if (eval "require $model") {	1267	if (eval "require $model") {
751	$MODEL = $model;	1268	$MODEL = $model;
752	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1269	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
753	} else {	1270	last;
754	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1271	}
755	}	1272	}
756	}	1273	}
757		1274
758	# check for already loaded models
759	unless ($MODEL) {	1275	unless ($MODEL) {
		1276	# try to autoload a model
760	for (@REGISTRY, @models) {	1277	for (@REGISTRY, @models) {
761	my ($package, $model) = @$_;	1278	my ($package, $model, $autoload) = @$_;
		1279	if (
		1280	$autoload
		1281	and eval "require $package"
762	if (${"$package\::VERSION"} > 0) {	1282	and ${"$package\::VERSION"} > 0
763	if (eval "require $model") {	1283	and eval "require $model"
		1284	) {
764	$MODEL = $model;	1285	$MODEL = $model;
765	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1286	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
766	last;	1287	last;
767	}
768	}	1288	}
769	}	1289	}
770		1290
771	unless ($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	1291	$MODEL
786	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1292	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
787	}
788	}	1293	}
789
790	unshift @ISA, $MODEL;
791	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
792
793	(shift @post_detect)->() while @post_detect;
794	}	1294	}
		1295
		1296	@models = (); # free probe data
		1297
		1298	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1299	unshift @ISA, $MODEL;
		1300
		1301	# now nuke some methods that are overriden by the backend.
		1302	# SUPER is not allowed.
		1303	for (qw(time signal child idle)) {
		1304	undef &{"AnyEvent::Base::$_"}
		1305	if defined &{"$MODEL\::$_"};
		1306	}
		1307
		1308	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1309
		1310	(shift @post_detect)->() while @post_detect;
		1311
		1312	*post_detect = sub(&) {
		1313	shift->();
		1314
		1315	undef
		1316	};
795		1317
796	$MODEL	1318	$MODEL
797	}	1319	}
798		1320
799	sub AUTOLOAD {	1321	sub AUTOLOAD {
800	(my $func = $AUTOLOAD) =~ s/.*://;	1322	(my $func = $AUTOLOAD) =~ s/.*://;
801		1323
802	$method{$func}	1324	$method{$func}
803	or croak "$func: not a valid method for AnyEvent objects";	1325	or Carp::croak "$func: not a valid AnyEvent class method";
804		1326
805	detect unless $MODEL;	1327	detect;
806		1328
807	my $class = shift;	1329	my $class = shift;
808	$class->$func (@_);	1330	$class->$func (@_);
809	}	1331	}
810		1332
		1333	# utility function to dup a filehandle. this is used by many backends
		1334	# to support binding more than one watcher per filehandle (they usually
		1335	# allow only one watcher per fd, so we dup it to get a different one).
		1336	sub _dupfh($$;$$) {
		1337	my ($poll, $fh, $r, $w) = @_;
		1338
		1339	# cygwin requires the fh mode to be matching, unix doesn't
		1340	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1341
		1342	open my $fh2, $mode, $fh
		1343	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1344
		1345	# we assume CLOEXEC is already set by perl in all important cases
		1346
		1347	($fh2, $rw)
		1348	}
		1349
		1350	=head1 SIMPLIFIED AE API
		1351
		1352	Starting with version 5.0, AnyEvent officially supports a second, much
		1353	simpler, API that is designed to reduce the calling, typing and memory
		1354	overhead by using function call syntax and a fixed number of parameters.
		1355
		1356	See the L<AE> manpage for details.
		1357
		1358	=cut
		1359
		1360	package AE;
		1361
		1362	our $VERSION = $AnyEvent::VERSION;
		1363
		1364	# fall back to the main API by default - backends and AnyEvent::Base
		1365	# implementations can overwrite these.
		1366
		1367	sub io($$$) {
		1368	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1369	}
		1370
		1371	sub timer($$$) {
		1372	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1373	}
		1374
		1375	sub signal($$) {
		1376	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1377	}
		1378
		1379	sub child($$) {
		1380	AnyEvent->child (pid => $_[0], cb => $_[1])
		1381	}
		1382
		1383	sub idle($) {
		1384	AnyEvent->idle (cb => $_[0])
		1385	}
		1386
		1387	sub cv(;&) {
		1388	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1389	}
		1390
		1391	sub now() {
		1392	AnyEvent->now
		1393	}
		1394
		1395	sub now_update() {
		1396	AnyEvent->now_update
		1397	}
		1398
		1399	sub time() {
		1400	AnyEvent->time
		1401	}
		1402
811	package AnyEvent::Base;	1403	package AnyEvent::Base;
812		1404
		1405	# default implementations for many methods
		1406
		1407	sub time {
		1408	eval q{ # poor man's autoloading {}
		1409	# probe for availability of Time::HiRes
		1410	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1411	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1412	*AE::time = \&Time::HiRes::time;
		1413	# if (eval "use POSIX (); (POSIX::times())...
		1414	} else {
		1415	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1416	*AE::time = sub (){ time }; # epic fail
		1417	}
		1418
		1419	*time = sub { AE::time }; # different prototypes
		1420	};
		1421	die if $@;
		1422
		1423	&time
		1424	}
		1425
		1426	*now = \&time;
		1427
		1428	sub now_update { }
		1429
813	# default implementation for ->condvar	1430	# default implementation for ->condvar
814		1431
815	sub condvar {	1432	sub condvar {
816	bless {}, AnyEvent::CondVar::	1433	eval q{ # poor man's autoloading {}
		1434	*condvar = sub {
		1435	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1436	};
		1437
		1438	*AE::cv = sub (;&) {
		1439	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1440	};
		1441	};
		1442	die if $@;
		1443
		1444	&condvar
817	}	1445	}
818		1446
819	# default implementation for ->signal	1447	# default implementation for ->signal
820		1448
821	our %SIG_CB;	1449	our $HAVE_ASYNC_INTERRUPT;
		1450
		1451	sub _have_async_interrupt() {
		1452	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1453	&& eval "use Async::Interrupt 1.02 (); 1")
		1454	unless defined $HAVE_ASYNC_INTERRUPT;
		1455
		1456	$HAVE_ASYNC_INTERRUPT
		1457	}
		1458
		1459	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1460	our (%SIG_ASY, %SIG_ASY_W);
		1461	our ($SIG_COUNT, $SIG_TW);
		1462
		1463	# install a dummy wakeup watcher to reduce signal catching latency
		1464	# used by Impls
		1465	sub _sig_add() {
		1466	unless ($SIG_COUNT++) {
		1467	# try to align timer on a full-second boundary, if possible
		1468	my $NOW = AE::now;
		1469
		1470	$SIG_TW = AE::timer
		1471	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1472	$MAX_SIGNAL_LATENCY,
		1473	sub { } # just for the PERL_ASYNC_CHECK
		1474	;
		1475	}
		1476	}
		1477
		1478	sub _sig_del {
		1479	undef $SIG_TW
		1480	unless --$SIG_COUNT;
		1481	}
		1482
		1483	our $_sig_name_init; $_sig_name_init = sub {
		1484	eval q{ # poor man's autoloading {}
		1485	undef $_sig_name_init;
		1486
		1487	if (_have_async_interrupt) {
		1488	*sig2num = \&Async::Interrupt::sig2num;
		1489	*sig2name = \&Async::Interrupt::sig2name;
		1490	} else {
		1491	require Config;
		1492
		1493	my %signame2num;
		1494	@signame2num{ split ' ', $Config::Config{sig_name} }
		1495	= split ' ', $Config::Config{sig_num};
		1496
		1497	my @signum2name;
		1498	@signum2name[values %signame2num] = keys %signame2num;
		1499
		1500	*sig2num = sub($) {
		1501	$_[0] > 0 ? shift : $signame2num{+shift}
		1502	};
		1503	*sig2name = sub ($) {
		1504	$_[0] > 0 ? $signum2name[+shift] : shift
		1505	};
		1506	}
		1507	};
		1508	die if $@;
		1509	};
		1510
		1511	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1512	sub sig2name($) { &$_sig_name_init; &sig2name }
822		1513
823	sub signal {	1514	sub signal {
		1515	eval q{ # poor man's autoloading {}
		1516	# probe for availability of Async::Interrupt
		1517	if (_have_async_interrupt) {
		1518	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1519
		1520	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1521	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1522
		1523	} else {
		1524	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1525
		1526	if (AnyEvent::WIN32) {
		1527	require AnyEvent::Util;
		1528
		1529	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1530	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1531	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1532	} else {
		1533	pipe $SIGPIPE_R, $SIGPIPE_W;
		1534	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1535	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1536
		1537	# not strictly required, as $^F is normally 2, but let's make sure...
		1538	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1539	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1540	}
		1541
		1542	$SIGPIPE_R
		1543	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1544
		1545	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1546	}
		1547
		1548	*signal = $HAVE_ASYNC_INTERRUPT
		1549	? sub {
824	my (undef, %arg) = @_;	1550	my (undef, %arg) = @_;
825		1551
		1552	# async::interrupt
826	my $signal = uc $arg{signal}	1553	my $signal = sig2num $arg{signal};
827	or Carp::croak "required option 'signal' is missing";
828
829	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1554	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1555
		1556	$SIG_ASY{$signal} ||= new Async::Interrupt
		1557	cb => sub { undef $SIG_EV{$signal} },
		1558	signal => $signal,
		1559	pipe => [$SIGPIPE_R->filenos],
		1560	pipe_autodrain => 0,
		1561	;
		1562
		1563	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1564	}
		1565	: sub {
		1566	my (undef, %arg) = @_;
		1567
		1568	# pure perl
		1569	my $signal = sig2name $arg{signal};
		1570	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1571
830	$SIG{$signal} ||= sub {	1572	$SIG{$signal} ||= sub {
		1573	local $!;
		1574	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1575	undef $SIG_EV{$signal};
		1576	};
		1577
		1578	# can't do signal processing without introducing races in pure perl,
		1579	# so limit the signal latency.
		1580	_sig_add;
		1581
		1582	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1583	}
		1584	;
		1585
		1586	*AnyEvent::Base::signal::DESTROY = sub {
		1587	my ($signal, $cb) = @{$_[0]};
		1588
		1589	_sig_del;
		1590
		1591	delete $SIG_CB{$signal}{$cb};
		1592
		1593	$HAVE_ASYNC_INTERRUPT
		1594	? delete $SIG_ASY{$signal}
		1595	: # delete doesn't work with older perls - they then
		1596	# print weird messages, or just unconditionally exit
		1597	# instead of getting the default action.
		1598	undef $SIG{$signal}
		1599	unless keys %{ $SIG_CB{$signal} };
		1600	};
		1601
		1602	*_signal_exec = sub {
		1603	$HAVE_ASYNC_INTERRUPT
		1604	? $SIGPIPE_R->drain
		1605	: sysread $SIGPIPE_R, (my $dummy), 9;
		1606
		1607	while (%SIG_EV) {
		1608	for (keys %SIG_EV) {
		1609	delete $SIG_EV{$_};
831	$_->() for values %{ $SIG_CB{$signal} || {} };	1610	$_->() for values %{ $SIG_CB{$_} || {} };
		1611	}
		1612	}
		1613	};
832	};	1614	};
		1615	die if $@;
833		1616
834	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1617	&signal
835	}
836
837	sub AnyEvent::Base::Signal::DESTROY {
838	my ($signal, $cb) = @{$_[0]};
839
840	delete $SIG_CB{$signal}{$cb};
841
842	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
843	}	1618	}
844		1619
845	# default implementation for ->child	1620	# default implementation for ->child
846		1621
847	our %PID_CB;	1622	our %PID_CB;
848	our $CHLD_W;	1623	our $CHLD_W;
849	our $CHLD_DELAY_W;	1624	our $CHLD_DELAY_W;
850	our $PID_IDLE;
851	our $WNOHANG;	1625	our $WNOHANG;
852		1626
853	sub _child_wait {	1627	# used by many Impl's
854	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1628	sub _emit_childstatus($$) {
		1629	my (undef, $rpid, $rstatus) = @_;
		1630
		1631	$_->($rpid, $rstatus)
855	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1632	for values %{ $PID_CB{$rpid} || {} },
856	(values %{ $PID_CB{0} || {} });	1633	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	}	1634	}
869		1635
870	sub child {	1636	sub child {
		1637	eval q{ # poor man's autoloading {}
		1638	*_sigchld = sub {
		1639	my $pid;
		1640
		1641	AnyEvent->_emit_childstatus ($pid, $?)
		1642	while ($pid = waitpid -1, $WNOHANG) > 0;
		1643	};
		1644
		1645	*child = sub {
871	my (undef, %arg) = @_;	1646	my (undef, %arg) = @_;
872		1647
873	defined (my $pid = $arg{pid} + 0)	1648	defined (my $pid = $arg{pid} + 0)
874	or Carp::croak "required option 'pid' is missing";	1649	or Carp::croak "required option 'pid' is missing";
875		1650
876	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1651	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
877		1652
878	unless ($WNOHANG) {	1653	# WNOHANG is almost cetrainly 1 everywhere
879	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1654	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
880	}	1655	? 1
		1656	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
881		1657
882	unless ($CHLD_W) {	1658	unless ($CHLD_W) {
883	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1659	$CHLD_W = AE::signal CHLD => \&_sigchld;
884	# child could be a zombie already, so make at least one round	1660	# child could be a zombie already, so make at least one round
885	&_sigchld;	1661	&_sigchld;
886	}	1662	}
887		1663
888	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1664	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
889	}	1665	};
890		1666
891	sub AnyEvent::Base::Child::DESTROY {	1667	*AnyEvent::Base::child::DESTROY = sub {
892	my ($pid, $cb) = @{$_[0]};	1668	my ($pid, $cb) = @{$_[0]};
893		1669
894	delete $PID_CB{$pid}{$cb};	1670	delete $PID_CB{$pid}{$cb};
895	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1671	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
896		1672
897	undef $CHLD_W unless keys %PID_CB;	1673	undef $CHLD_W unless keys %PID_CB;
		1674	};
		1675	};
		1676	die if $@;
		1677
		1678	&child
		1679	}
		1680
		1681	# idle emulation is done by simply using a timer, regardless
		1682	# of whether the process is idle or not, and not letting
		1683	# the callback use more than 50% of the time.
		1684	sub idle {
		1685	eval q{ # poor man's autoloading {}
		1686	*idle = sub {
		1687	my (undef, %arg) = @_;
		1688
		1689	my ($cb, $w, $rcb) = $arg{cb};
		1690
		1691	$rcb = sub {
		1692	if ($cb) {
		1693	$w = _time;
		1694	&$cb;
		1695	$w = _time - $w;
		1696
		1697	# never use more then 50% of the time for the idle watcher,
		1698	# within some limits
		1699	$w = 0.0001 if $w < 0.0001;
		1700	$w = 5 if $w > 5;
		1701
		1702	$w = AE::timer $w, 0, $rcb;
		1703	} else {
		1704	# clean up...
		1705	undef $w;
		1706	undef $rcb;
		1707	}
		1708	};
		1709
		1710	$w = AE::timer 0.05, 0, $rcb;
		1711
		1712	bless \\$cb, "AnyEvent::Base::idle"
		1713	};
		1714
		1715	*AnyEvent::Base::idle::DESTROY = sub {
		1716	undef $${$_[0]};
		1717	};
		1718	};
		1719	die if $@;
		1720
		1721	&idle
898	}	1722	}
899		1723
900	package AnyEvent::CondVar;	1724	package AnyEvent::CondVar;
901		1725
902	our @ISA = AnyEvent::CondVar::Base::;	1726	our @ISA = AnyEvent::CondVar::Base::;
903		1727
904	package AnyEvent::CondVar::Base;	1728	package AnyEvent::CondVar::Base;
		1729
		1730	#use overload
		1731	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1732	# fallback => 1;
		1733
		1734	# save 300+ kilobytes by dirtily hardcoding overloading
		1735	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1736	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1737	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1738	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1739
		1740	our $WAITING;
905		1741
906	sub _send {	1742	sub _send {
907	# nop	1743	# nop
908	}	1744	}
909		1745
…		…
922	sub ready {	1758	sub ready {
923	$_[0]{_ae_sent}	1759	$_[0]{_ae_sent}
924	}	1760	}
925		1761
926	sub _wait {	1762	sub _wait {
		1763	$WAITING
		1764	and !$_[0]{_ae_sent}
		1765	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1766
		1767	local $WAITING = 1;
927	AnyEvent->one_event while !$_[0]{_ae_sent};	1768	AnyEvent->one_event while !$_[0]{_ae_sent};
928	}	1769	}
929		1770
930	sub recv {	1771	sub recv {
931	$_[0]->_wait;	1772	$_[0]->_wait;
…		…
933	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1774	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
934	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1775	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
935	}	1776	}
936		1777
937	sub cb {	1778	sub cb {
938	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1779	my $cv = shift;
		1780
		1781	@_
		1782	and $cv->{_ae_cb} = shift
		1783	and $cv->{_ae_sent}
		1784	and (delete $cv->{_ae_cb})->($cv);
		1785
939	$_[0]{_ae_cb}	1786	$cv->{_ae_cb}
940	}	1787	}
941		1788
942	sub begin {	1789	sub begin {
943	++$_[0]{_ae_counter};	1790	++$_[0]{_ae_counter};
944	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1791	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
945	}	1792	}
946		1793
947	sub end {	1794	sub end {
948	return if --$_[0]{_ae_counter};	1795	return if --$_[0]{_ae_counter};
949	&{ $_[0]{_ae_end_cb} } if $_[0]{_ae_end_cb};	1796	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
950	}	1797	}
951		1798
952	# undocumented/compatibility with pre-3.4	1799	# undocumented/compatibility with pre-3.4
953	*broadcast = \&send;	1800	*broadcast = \&send;
954	*wait = \&_wait;	1801	*wait = \&_wait;
		1802
		1803	=head1 ERROR AND EXCEPTION HANDLING
		1804
		1805	In general, AnyEvent does not do any error handling - it relies on the
		1806	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1807	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1808	checking of all AnyEvent methods, however, which is highly useful during
		1809	development.
		1810
		1811	As for exception handling (i.e. runtime errors and exceptions thrown while
		1812	executing a callback), this is not only highly event-loop specific, but
		1813	also not in any way wrapped by this module, as this is the job of the main
		1814	program.
		1815
		1816	The pure perl event loop simply re-throws the exception (usually
		1817	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1818	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1819	so on.
		1820
		1821	=head1 ENVIRONMENT VARIABLES
		1822
		1823	The following environment variables are used by this module or its
		1824	submodules.
		1825
		1826	Note that AnyEvent will remove I<all> environment variables starting with
		1827	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1828	enabled.
		1829
		1830	=over 4
		1831
		1832	=item C<PERL_ANYEVENT_VERBOSE>
		1833
		1834	By default, AnyEvent will be completely silent except in fatal
		1835	conditions. You can set this environment variable to make AnyEvent more
		1836	talkative.
		1837
		1838	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1839	conditions, such as not being able to load the event model specified by
		1840	C<PERL_ANYEVENT_MODEL>.
		1841
		1842	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1843	model it chooses.
		1844
		1845	When set to C<8> or higher, then AnyEvent will report extra information on
		1846	which optional modules it loads and how it implements certain features.
		1847
		1848	=item C<PERL_ANYEVENT_STRICT>
		1849
		1850	AnyEvent does not do much argument checking by default, as thorough
		1851	argument checking is very costly. Setting this variable to a true value
		1852	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1853	check the arguments passed to most method calls. If it finds any problems,
		1854	it will croak.
		1855
		1856	In other words, enables "strict" mode.
		1857
		1858	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1859	>>, it is definitely recommended to keep it off in production. Keeping
		1860	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1861	can be very useful, however.
		1862
		1863	=item C<PERL_ANYEVENT_MODEL>
		1864
		1865	This can be used to specify the event model to be used by AnyEvent, before
		1866	auto detection and -probing kicks in. It must be a string consisting
		1867	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1868	and the resulting module name is loaded and if the load was successful,
		1869	used as event model. If it fails to load AnyEvent will proceed with
		1870	auto detection and -probing.
		1871
		1872	This functionality might change in future versions.
		1873
		1874	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1875	could start your program like this:
		1876
		1877	PERL_ANYEVENT_MODEL=Perl perl ...
		1878
		1879	=item C<PERL_ANYEVENT_PROTOCOLS>
		1880
		1881	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1882	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1883	of auto probing).
		1884
		1885	Must be set to a comma-separated list of protocols or address families,
		1886	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1887	used, and preference will be given to protocols mentioned earlier in the
		1888	list.
		1889
		1890	This variable can effectively be used for denial-of-service attacks
		1891	against local programs (e.g. when setuid), although the impact is likely
		1892	small, as the program has to handle conenction and other failures anyways.
		1893
		1894	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1895	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1896	- only support IPv4, never try to resolve or contact IPv6
		1897	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1898	IPv6, but prefer IPv6 over IPv4.
		1899
		1900	=item C<PERL_ANYEVENT_EDNS0>
		1901
		1902	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1903	for DNS. This extension is generally useful to reduce DNS traffic, but
		1904	some (broken) firewalls drop such DNS packets, which is why it is off by
		1905	default.
		1906
		1907	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1908	EDNS0 in its DNS requests.
		1909
		1910	=item C<PERL_ANYEVENT_MAX_FORKS>
		1911
		1912	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1913	will create in parallel.
		1914
		1915	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1916
		1917	The default value for the C<max_outstanding> parameter for the default DNS
		1918	resolver - this is the maximum number of parallel DNS requests that are
		1919	sent to the DNS server.
		1920
		1921	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1922
		1923	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1924	configuration) in the default resolver. When set to the empty string, no
		1925	default config will be used.
		1926
		1927	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1928
		1929	When neither C<ca_file> nor C<ca_path> was specified during
		1930	L<AnyEvent::TLS> context creation, and either of these environment
		1931	variables exist, they will be used to specify CA certificate locations
		1932	instead of a system-dependent default.
		1933
		1934	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1935
		1936	When these are set to C<1>, then the respective modules are not
		1937	loaded. Mostly good for testing AnyEvent itself.
		1938
		1939	=back
955		1940
956	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1941	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
957		1942
958	This is an advanced topic that you do not normally need to use AnyEvent in	1943	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	1944	a module. This section is only of use to event loop authors who want to
…		…
993		1978
994	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1979	I<rxvt-unicode> also cheats a bit by not providing blocking access to
995	condition variables: code blocking while waiting for a condition will	1980	condition variables: code blocking while waiting for a condition will
996	C<die>. This still works with most modules/usages, and blocking calls must	1981	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.	1982	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		1983
1036	=head1 EXAMPLE PROGRAM	1984	=head1 EXAMPLE PROGRAM
1037		1985
1038	The following program uses an I/O watcher to read data from STDIN, a timer	1986	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	1987	to display a message once per second, and a condition variable to quit the
…		…
1052	warn "read: $input\n"; # output what has been read	2000	warn "read: $input\n"; # output what has been read
1053	$cv->send if $input =~ /^q/i; # quit program if /^q/i	2001	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1054	},	2002	},
1055	);	2003	);
1056		2004
1057	my $time_watcher; # can only be used once
1058
1059	sub new_timer {
1060	$timer = AnyEvent->timer (after => 1, cb => sub {	2005	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1061	warn "timeout\n"; # print 'timeout' about every second	2006	warn "timeout\n"; # print 'timeout' at most every second
1062	&new_timer; # and restart the time
1063	});	2007	});
1064	}
1065
1066	new_timer; # create first timer
1067		2008
1068	$cv->recv; # wait until user enters /^q/i	2009	$cv->recv; # wait until user enters /^q/i
1069		2010
1070	=head1 REAL-WORLD EXAMPLE	2011	=head1 REAL-WORLD EXAMPLE
1071		2012
…		…
1123	syswrite $txn->{fh}, $txn->{request}	2064	syswrite $txn->{fh}, $txn->{request}
1124	or die "connection or write error";	2065	or die "connection or write error";
1125	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2066	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1126		2067
1127	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2068	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:	2069	result and signals any possible waiters that the request has finished:
1129		2070
1130	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2071	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1131		2072
1132	if (end-of-file or data complete) {	2073	if (end-of-file or data complete) {
1133	$txn->{result} = $txn->{buf};	2074	$txn->{result} = $txn->{buf};
…		…
1141		2082
1142	$txn->{finished}->recv;	2083	$txn->{finished}->recv;
1143	return $txn->{result};	2084	return $txn->{result};
1144		2085
1145	The actual code goes further and collects all errors (C<die>s, exceptions)	2086	The actual code goes further and collects all errors (C<die>s, exceptions)
1146	that occured during request processing. The C<result> method detects	2087	that occurred during request processing. The C<result> method detects
1147	whether an exception as thrown (it is stored inside the $txn object)	2088	whether an exception as thrown (it is stored inside the $txn object)
1148	and just throws the exception, which means connection errors and other	2089	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	2090	problems get reported to the code that tries to use the result, not in a
1150	random callback.	2091	random callback.
1151		2092
1152	All of this enables the following usage styles:	2093	All of this enables the following usage styles:
1153		2094
1154	1. Blocking:	2095	1. Blocking:
…		…
1197	of various event loops I prepared some benchmarks.	2138	of various event loops I prepared some benchmarks.
1198		2139
1199	=head2 BENCHMARKING ANYEVENT OVERHEAD	2140	=head2 BENCHMARKING ANYEVENT OVERHEAD
1200		2141
1201	Here is a benchmark of various supported event models used natively and	2142	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	2143	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,	2144	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.	2145	which it is), lets them fire exactly once and destroys them again.
1205		2146
1206	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2147	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1207	distribution.	2148	distribution. It uses the L<AE> interface, which makes a real difference
		2149	for the EV and Perl backends only.
1208		2150
1209	=head3 Explanation of the columns	2151	=head3 Explanation of the columns
1210		2152
1211	I<watcher> is the number of event watchers created/destroyed. Since	2153	I<watcher> is the number of event watchers created/destroyed. Since
1212	different event models feature vastly different performances, each event	2154	different event models feature vastly different performances, each event
…		…
1233	watcher.	2175	watcher.
1234		2176
1235	=head3 Results	2177	=head3 Results
1236		2178
1237	name watchers bytes create invoke destroy comment	2179	name watchers bytes create invoke destroy comment
1238	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2180	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	2181	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	2182	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	2183	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	2184	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	2185	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2186	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2187	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	2188	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	2189	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	2190	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	2191	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1248		2192
1249	=head3 Discussion	2193	=head3 Discussion
1250		2194
1251	The benchmark does I<not> measure scalability of the event loop very	2195	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)	2196	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	2208	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	2209	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1266	cycles with POE.	2210	cycles with POE.
1267		2211
1268	C<EV> is the sole leader regarding speed and memory use, which are both	2212	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	2213	maximal/minimal, respectively. When using the L<AE> API there is zero
		2214	overhead (when going through the AnyEvent API create is about 5-6 times
		2215	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	2216	any other event loop and is still faster than Event natively).
1271	natively.
1272		2217
1273	The pure perl implementation is hit in a few sweet spots (both the	2218	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	2219	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	2220	interpreter and the backend itself). Nevertheless this shows that it
1276	adds very little overhead in itself. Like any select-based backend its	2221	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	2222	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.	2223	them active), of course, but this was not subject of this benchmark.
1279		2224
1280	The C<Event> module has a relatively high setup and callback invocation	2225	The C<Event> module has a relatively high setup and callback invocation
1281	cost, but overall scores in on the third place.	2226	cost, but overall scores in on the third place.
		2227
		2228	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2229	when using its pure perl backend.
1282		2230
1283	C<Glib>'s memory usage is quite a bit higher, but it features a	2231	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	2232	faster callback invocation and overall ends up in the same class as
1285	C<Event>. However, Glib scales extremely badly, doubling the number of	2233	C<Event>. However, Glib scales extremely badly, doubling the number of
1286	watchers increases the processing time by more than a factor of four,	2234	watchers increases the processing time by more than a factor of four,
…		…
1330		2278
1331	=back	2279	=back
1332		2280
1333	=head2 BENCHMARKING THE LARGE SERVER CASE	2281	=head2 BENCHMARKING THE LARGE SERVER CASE
1334		2282
1335	This benchmark atcually benchmarks the event loop itself. It works by	2283	This benchmark actually benchmarks the event loop itself. It works by
1336	creating a number of "servers": each server consists of a socketpair, a	2284	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	2285	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	2286	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".	2287	watcher reads a byte it will write that byte to a random other "server".
1340		2288
1341	The effect is that there will be a lot of I/O watchers, only part of which	2289	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	2290	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	2291	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	2292	timeout is reset each time something is read because that reflects how
1345	most timeouts work (and puts extra pressure on the event loops).	2293	most timeouts work (and puts extra pressure on the event loops).
1346		2294
1347	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2295	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	2296	(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.	2297	connections, most of which are idle at any one point in time.
1350		2298
1351	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2299	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1352	distribution.	2300	distribution. It uses the L<AE> interface, which makes a real difference
		2301	for the EV and Perl backends only.
1353		2302
1354	=head3 Explanation of the columns	2303	=head3 Explanation of the columns
1355		2304
1356	I<sockets> is the number of sockets, and twice the number of "servers" (as	2305	I<sockets> is the number of sockets, and twice the number of "servers" (as
1357	each server has a read and write socket end).	2306	each server has a read and write socket end).
1358		2307
1359	I<create> is the time it takes to create a socketpair (which is	2308	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.	2309	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1361		2310
1362	I<request>, the most important value, is the time it takes to handle a	2311	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	2312	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	2313	it to another server. This includes deleting the old timeout and creating
1365	a new one that moves the timeout into the future.	2314	a new one that moves the timeout into the future.
1366		2315
1367	=head3 Results	2316	=head3 Results
1368		2317
1369	name sockets create request	2318	name sockets create request
1370	EV 20000 69.01 11.16	2319	EV 20000 62.66 7.99
1371	Perl 20000 73.32 35.87	2320	Perl 20000 68.32 32.64
1372	Event 20000 212.62 257.32	2321	IOAsync 20000 174.06 101.15 epoll
1373	Glib 20000 651.16 1896.30	2322	IOAsync 20000 174.67 610.84 poll
		2323	Event 20000 202.69 242.91
		2324	Glib 20000 557.01 1689.52
1374	POE 20000 349.67 12317.24 uses POE::Loop::Event	2325	POE 20000 341.54 12086.32 uses POE::Loop::Event
1375		2326
1376	=head3 Discussion	2327	=head3 Discussion
1377		2328
1378	This benchmark I<does> measure scalability and overall performance of the	2329	This benchmark I<does> measure scalability and overall performance of the
1379	particular event loop.	2330	particular event loop.
…		…
1381	EV is again fastest. Since it is using epoll on my system, the setup time	2332	EV is again fastest. Since it is using epoll on my system, the setup time
1382	is relatively high, though.	2333	is relatively high, though.
1383		2334
1384	Perl surprisingly comes second. It is much faster than the C-based event	2335	Perl surprisingly comes second. It is much faster than the C-based event
1385	loops Event and Glib.	2336	loops Event and Glib.
		2337
		2338	IO::Async performs very well when using its epoll backend, and still quite
		2339	good compared to Glib when using its pure perl backend.
1386		2340
1387	Event suffers from high setup time as well (look at its code and you will	2341	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	2342	understand why). Callback invocation also has a high overhead compared to
1389	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2343	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1390	uses select or poll in basically all documented configurations.	2344	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	2391	speed most when you have lots of watchers, not when you only have a few of
1438	them).	2392	them).
1439		2393
1440	EV is again fastest.	2394	EV is again fastest.
1441		2395
1442	Perl again comes second. It is noticably faster than the C-based event	2396	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	2397	loops Event and Glib, although the difference is too small to really
1444	matter.	2398	matter.
1445		2399
1446	POE also performs much better in this case, but is is still far behind the	2400	POE also performs much better in this case, but is is still far behind the
1447	others.	2401	others.
…		…
1453	=item * C-based event loops perform very well with small number of	2407	=item * C-based event loops perform very well with small number of
1454	watchers, as the management overhead dominates.	2408	watchers, as the management overhead dominates.
1455		2409
1456	=back	2410	=back
1457		2411
		2412	=head2 THE IO::Lambda BENCHMARK
		2413
		2414	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2415	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2416	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2417	shouldn't come as a surprise to anybody). As such, the benchmark is
		2418	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2419	very optimal. But how would AnyEvent compare when used without the extra
		2420	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2421
		2422	The benchmark itself creates an echo-server, and then, for 500 times,
		2423	connects to the echo server, sends a line, waits for the reply, and then
		2424	creates the next connection. This is a rather bad benchmark, as it doesn't
		2425	test the efficiency of the framework or much non-blocking I/O, but it is a
		2426	benchmark nevertheless.
		2427
		2428	name runtime
		2429	Lambda/select 0.330 sec
		2430	+ optimized 0.122 sec
		2431	Lambda/AnyEvent 0.327 sec
		2432	+ optimized 0.138 sec
		2433	Raw sockets/select 0.077 sec
		2434	POE/select, components 0.662 sec
		2435	POE/select, raw sockets 0.226 sec
		2436	POE/select, optimized 0.404 sec
		2437
		2438	AnyEvent/select/nb 0.085 sec
		2439	AnyEvent/EV/nb 0.068 sec
		2440	+state machine 0.134 sec
		2441
		2442	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2443	benchmarks actually make blocking connects and use 100% blocking I/O,
		2444	defeating the purpose of an event-based solution. All of the newly
		2445	written AnyEvent benchmarks use 100% non-blocking connects (using
		2446	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2447	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2448	generally require a lot more bookkeeping and event handling than blocking
		2449	connects (which involve a single syscall only).
		2450
		2451	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2452	offers similar expressive power as POE and IO::Lambda, using conventional
		2453	Perl syntax. This means that both the echo server and the client are 100%
		2454	non-blocking, further placing it at a disadvantage.
		2455
		2456	As you can see, the AnyEvent + EV combination even beats the
		2457	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2458	backend easily beats IO::Lambda and POE.
		2459
		2460	And even the 100% non-blocking version written using the high-level (and
		2461	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2462	higher level ("unoptimised") abstractions by a large margin, even though
		2463	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2464
		2465	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2466	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2467	part of the IO::Lambda distribution and were used without any changes.
		2468
		2469
		2470	=head1 SIGNALS
		2471
		2472	AnyEvent currently installs handlers for these signals:
		2473
		2474	=over 4
		2475
		2476	=item SIGCHLD
		2477
		2478	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2479	emulation for event loops that do not support them natively. Also, some
		2480	event loops install a similar handler.
		2481
		2482	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2483	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2484
		2485	=item SIGPIPE
		2486
		2487	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2488	when AnyEvent gets loaded.
		2489
		2490	The rationale for this is that AnyEvent users usually do not really depend
		2491	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2492	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2493	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2494	some random socket.
		2495
		2496	The rationale for installing a no-op handler as opposed to ignoring it is
		2497	that this way, the handler will be restored to defaults on exec.
		2498
		2499	Feel free to install your own handler, or reset it to defaults.
		2500
		2501	=back
		2502
		2503	=cut
		2504
		2505	undef $SIG{CHLD}
		2506	if $SIG{CHLD} eq 'IGNORE';
		2507
		2508	$SIG{PIPE} = sub { }
		2509	unless defined $SIG{PIPE};
		2510
		2511	=head1 RECOMMENDED/OPTIONAL MODULES
		2512
		2513	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2514	it's built-in modules) are required to use it.
		2515
		2516	That does not mean that AnyEvent won't take advantage of some additional
		2517	modules if they are installed.
		2518
		2519	This section explains which additional modules will be used, and how they
		2520	affect AnyEvent's operation.
		2521
		2522	=over 4
		2523
		2524	=item L<Async::Interrupt>
		2525
		2526	This slightly arcane module is used to implement fast signal handling: To
		2527	my knowledge, there is no way to do completely race-free and quick
		2528	signal handling in pure perl. To ensure that signals still get
		2529	delivered, AnyEvent will start an interval timer to wake up perl (and
		2530	catch the signals) with some delay (default is 10 seconds, look for
		2531	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2532
		2533	If this module is available, then it will be used to implement signal
		2534	catching, which means that signals will not be delayed, and the event loop
		2535	will not be interrupted regularly, which is more efficient (and good for
		2536	battery life on laptops).
		2537
		2538	This affects not just the pure-perl event loop, but also other event loops
		2539	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2540
		2541	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2542	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2543	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2544	does nothing for those backends.
		2545
		2546	=item L<EV>
		2547
		2548	This module isn't really "optional", as it is simply one of the backend
		2549	event loops that AnyEvent can use. However, it is simply the best event
		2550	loop available in terms of features, speed and stability: It supports
		2551	the AnyEvent API optimally, implements all the watcher types in XS, does
		2552	automatic timer adjustments even when no monotonic clock is available,
		2553	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2554	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2555	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2556
		2557	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2558	then this module will do nothing for you.
		2559
		2560	=item L<Guard>
		2561
		2562	The guard module, when used, will be used to implement
		2563	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2564	lot less memory), but otherwise doesn't affect guard operation much. It is
		2565	purely used for performance.
		2566
		2567	=item L<JSON> and L<JSON::XS>
		2568
		2569	One of these modules is required when you want to read or write JSON data
		2570	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2571	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2572
		2573	=item L<Net::SSLeay>
		2574
		2575	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2576	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2577	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2578
		2579	=item L<Time::HiRes>
		2580
		2581	This module is part of perl since release 5.008. It will be used when the
		2582	chosen event library does not come with a timing source on it's own. The
		2583	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2584	try to use a monotonic clock for timing stability.
		2585
		2586	=back
		2587
1458		2588
1459	=head1 FORK	2589	=head1 FORK
1460		2590
1461	Most event libraries are not fork-safe. The ones who are usually are	2591	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>	2592	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1463	calls. Only L<EV> is fully fork-aware.	2593	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2594	are usually badly thought-out hacks that are incompatible with fork in
		2595	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2596	continue event-processing in both parent and child (or both, if you know
		2597	what you are doing).
		2598
		2599	This means that, in general, you cannot fork and do event processing in
		2600	the child if the event library was initialised before the fork (which
		2601	usually happens when the first AnyEvent watcher is created, or the library
		2602	is loaded).
1464		2603
1465	If you have to fork, you must either do so I<before> creating your first	2604	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.	2605	watcher OR you must not use AnyEvent at all in the child OR you must do
		2606	something completely out of the scope of AnyEvent.
		2607
		2608	The problem of doing event processing in the parent I<and> the child
		2609	is much more complicated: even for backends that I<are> fork-aware or
		2610	fork-safe, their behaviour is not usually what you want: fork clones all
		2611	watchers, that means all timers, I/O watchers etc. are active in both
		2612	parent and child, which is almost never what you want. USing C<exec>
		2613	to start worker children from some kind of manage rprocess is usually
		2614	preferred, because it is much easier and cleaner, at the expense of having
		2615	to have another binary.
1467		2616
1468		2617
1469	=head1 SECURITY CONSIDERATIONS	2618	=head1 SECURITY CONSIDERATIONS
1470		2619
1471	AnyEvent can be forced to load any event model via	2620	AnyEvent can be forced to load any event model via
…		…
1476	specified in the variable.	2625	specified in the variable.
1477		2626
1478	You can make AnyEvent completely ignore this variable by deleting it	2627	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:	2628	before the first watcher gets created, e.g. with a C<BEGIN> block:
1480		2629
1481	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2630	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1482		2631
1483	use AnyEvent;	2632	use AnyEvent;
1484		2633
1485	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2634	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	2635	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).	2636	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2637	$ENV{PERL_ANYEVENT_STRICT}.
		2638
		2639	Note that AnyEvent will remove I<all> environment variables starting with
		2640	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2641	enabled.
		2642
		2643
		2644	=head1 BUGS
		2645
		2646	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2647	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2648	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2649	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2650	pronounced).
1488		2651
1489		2652
1490	=head1 SEE ALSO	2653	=head1 SEE ALSO
		2654
		2655	Utility functions: L<AnyEvent::Util>.
1491		2656
1492	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2657	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>.	2658	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1494		2659
1495	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2660	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1496	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2661	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1497	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2662	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1498	L<AnyEvent::Impl::POE>.	2663	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1499		2664
		2665	Non-blocking file handles, sockets, TCP clients and
		2666	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2667
		2668	Asynchronous DNS: L<AnyEvent::DNS>.
		2669
1500	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2670	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2671	L<Coro::Event>,
1501		2672
1502	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2673	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2674	L<AnyEvent::HTTP>.
1503		2675
1504		2676
1505	=head1 AUTHOR	2677	=head1 AUTHOR
1506		2678
1507	Marc Lehmann <schmorp@schmorp.de>	2679	Marc Lehmann <schmorp@schmorp.de>
1508	http://home.schmorp.de/	2680	http://home.schmorp.de/
1509		2681
1510	=cut	2682	=cut
1511		2683
1512	1	2684	1
1513		2685

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