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Revision 1.349 by root, Mon Jul 4 21:14:42 2011 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 });
22		42
23	=head1 INTRODUCTION/TUTORIAL	43	=head1 INTRODUCTION/TUTORIAL
24		44
25	This manpage is mainly a reference manual. If you are interested	45	This manpage is mainly a reference manual. If you are interested
26	in a tutorial or some gentle introduction, have a look at the	46	in a tutorial or some gentle introduction, have a look at the
27	L<AnyEvent::Intro> manpage.	47	L<AnyEvent::Intro> manpage.
28		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
		58
29	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
30		60
31	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
32	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
33		63
34	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
35	policy> and AnyEvent is I<small and efficient>.	65	policy> and AnyEvent is I<small and efficient>.
36		66
37	First and foremost, I<AnyEvent is not an event model> itself, it only	67	First and foremost, I<AnyEvent is not an event model> itself, it only
38	interfaces to whatever event model the main program happens to use in a	68	interfaces to whatever event model the main program happens to use, in a
39	pragmatic way. For event models and certain classes of immortals alike,	69	pragmatic way. For event models and certain classes of immortals alike,
40	the statement "there can only be one" is a bitter reality: In general,	70	the statement "there can only be one" is a bitter reality: In general,
41	only one event loop can be active at the same time in a process. AnyEvent	71	only one event loop can be active at the same time in a process. AnyEvent
42	helps hiding the differences between those event loops.	72	cannot change this, but it can hide the differences between those event
		73	loops.
43		74
44	The goal of AnyEvent is to offer module authors the ability to do event	75	The goal of AnyEvent is to offer module authors the ability to do event
45	programming (waiting for I/O or timer events) without subscribing to a	76	programming (waiting for I/O or timer events) without subscribing to a
46	religion, a way of living, and most importantly: without forcing your	77	religion, a way of living, and most importantly: without forcing your
47	module users into the same thing by forcing them to use the same event	78	module users into the same thing by forcing them to use the same event
48	model you use.	79	model you use.
49		80
50	For modules like POE or IO::Async (which is a total misnomer as it is	81	For modules like POE or IO::Async (which is a total misnomer as it is
51	actually doing all I/O I<synchronously>...), using them in your module is	82	actually doing all I/O I<synchronously>...), using them in your module is
52	like joining a cult: After you joined, you are dependent on them and you	83	like joining a cult: After you join, you are dependent on them and you
53	cannot use anything else, as it is simply incompatible to everything that	84	cannot use anything else, as they are simply incompatible to everything
54	isn't itself. What's worse, all the potential users of your module are	85	that isn't them. What's worse, all the potential users of your
55	I<also> forced to use the same event loop you use.	86	module are I<also> forced to use the same event loop you use.
56		87
57	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
58	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
59	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
60	your module uses one of those, every user of your module has to use it,	91	uses one of those, every user of your module has to use it, too. But if
61	too. But if your module uses AnyEvent, it works transparently with all	92	your module uses AnyEvent, it works transparently with all event models it
62	event models it supports (including stuff like POE and IO::Async, as long	93	supports (including stuff like IO::Async, as long as those use one of the
63	as those use one of the supported event loops. It is trivial to add new	94	supported event loops. It is easy to add new event loops to AnyEvent, too,
64	event loops to AnyEvent, too, so it is future-proof).	95	so it is future-proof).
65		96
66	In addition to being free of having to use I<the one and only true event	97	In addition to being free of having to use I<the one and only true event
67	model>, AnyEvent also is free of bloat and policy: with POE or similar	98	model>, AnyEvent also is free of bloat and policy: with POE or similar
68	modules, you get an enormous amount of code and strict rules you have to	99	modules, you get an enormous amount of code and strict rules you have to
69	follow. AnyEvent, on the other hand, is lean and up to the point, by only	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
70	offering the functionality that is necessary, in as thin as a wrapper as	101	offering the functionality that is necessary, in as thin as a wrapper as
71	technically possible.	102	technically possible.
72		103
73	Of course, AnyEvent comes with a big (and fully optional!) toolbox	104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
74	of useful functionality, such as an asynchronous DNS resolver, 100%	105	of useful functionality, such as an asynchronous DNS resolver, 100%
…		…
80	useful) and you want to force your users to use the one and only event	111	useful) and you want to force your users to use the one and only event
81	model, you should I<not> use this module.	112	model, you should I<not> use this module.
82		113
83	=head1 DESCRIPTION	114	=head1 DESCRIPTION
84		115
85	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
86	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
87	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
88	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
89		120
90	The interface itself is vaguely similar, but not identical to the L<Event>	121	The interface itself is vaguely similar, but not identical to the L<Event>
91	module.	122	module.
92		123
93	During the first call of any watcher-creation method, the module tries	124	During the first call of any watcher-creation method, the module tries
94	to detect the currently loaded event loop by probing whether one of the	125	to detect the currently loaded event loop by probing whether one of the
95	following modules is already loaded: L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Impl::Perl>,
96	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
97	L<POE>. The first one found is used. If none are found, the module tries	128	found is used. If none are detected, the module tries to load the first
98	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	129	four modules in the order given; but note that if L<EV> is not
99	adaptor should always succeed) in the order given. The first one that can	130	available, the pure-perl L<AnyEvent::Impl::Perl> should always work, so
100	be successfully loaded will be used. If, after this, still none could be	131	the other two are not normally tried.
101	found, AnyEvent will fall back to a pure-perl event loop, which is not
102	very efficient, but should work everywhere.
103		132
104	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
105	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
106	that model the default. For example:	135	that model the default. For example:
107		136
…		…
109	use AnyEvent;	138	use AnyEvent;
110		139
111	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
112		141
113	The I<likely> means that, if any module loads another event model and	142	The I<likely> means that, if any module loads another event model and
114	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off - this case should be very rare though,
115	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
116		146
117	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called
118	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
119	explicitly and enjoy the high availability of that event loop :)	149	explicitly and enjoy the high availability of that event loop :)
120		150
…		…
127	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
128	creating a watcher it will immediately "watch" for events and invoke the	158	creating a watcher it will immediately "watch" for events and invoke the
129	callback when the event occurs (of course, only when the event model	159	callback when the event occurs (of course, only when the event model
130	is in control).	160	is in control).
131		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
132	To disable the watcher you have to destroy it (e.g. by setting the	168	To disable a watcher you have to destroy it (e.g. by setting the
133	variable you store it in to C<undef> or otherwise deleting all references	169	variable you store it in to C<undef> or otherwise deleting all references
134	to it).	170	to it).
135		171
136	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
137		173
138	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
139	example), or need to refer to their watcher object in other ways.	175	example), or need to refer to their watcher object in other ways.
140		176
141	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
142		178
143	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
144	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
145	undef $w;	181	undef $w;
146	});	182	});
…		…
149	my variables are only visible after the statement in which they are	185	my variables are only visible after the statement in which they are
150	declared.	186	declared.
151		187
152	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
153		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
154	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
155	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
156		198
157	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
158	for events. C<poll> must be a string that is either C<r> or C<w>,	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
159	which creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
160	respectively. C<cb> is the callback to invoke each time the file handle	209	C<cb> is the callback to invoke each time the file handle becomes ready.
161	becomes ready.
162		210
163	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
164	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
165	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
166		214
167	The I/O watcher might use the underlying file descriptor or a copy of it.	215	The I/O watcher might use the underlying file descriptor or a copy of it.
168	You must not close a file handle as long as any watcher is active on the	216	You must not close a file handle as long as any watcher is active on the
169	underlying file descriptor.	217	underlying file descriptor.
170		218
171	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
172	always use non-blocking calls when reading/writing from/to your file	220	always use non-blocking calls when reading/writing from/to your file
173	handles.	221	handles.
174		222
175	Example: wait for readability of STDIN, then read a line and disable the	223	Example: wait for readability of STDIN, then read a line and disable the
176	watcher.	224	watcher.
…		…
181	undef $w;	229	undef $w;
182	});	230	});
183		231
184	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
185		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
186	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
187	method with the following mandatory arguments:	243	method with the following mandatory arguments:
188		244
189	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
190	supported) the callback should be invoked. C<cb> is the callback to invoke	246	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
192		248
193	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
194	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
195	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
196		252
197	The callback will normally be invoked once only. If you specify another	253	The callback will normally be invoked only once. If you specify another
198	parameter, C<interval>, as a positive number, then the callback will be	254	parameter, C<interval>, as a strictly positive number (> 0), then the
199	invoked regularly at that interval (in fractional seconds) after the first	255	callback will be invoked regularly at that interval (in fractional
200	invocation.	256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
201		258
202	The callback will be rescheduled before invoking the callback, but no	259	The callback will be rescheduled before invoking the callback, but no
203	attempt is done to avoid timer drift in most backends, so the interval is	260	attempt is made to avoid timer drift in most backends, so the interval is
204	only approximate.	261	only approximate.
205		262
206	Example: fire an event after 7.7 seconds.	263	Example: fire an event after 7.7 seconds.
207		264
208	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
226		283
227	While most event loops expect timers to specified in a relative way, they	284	While most event loops expect timers to specified in a relative way, they
228	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
229	"jumps", for example, when ntp decides to set your clock backwards from	286	"jumps", for example, when ntp decides to set your clock backwards from
230	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to	287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
231	fire "after" a second might actually take six years to finally fire.	288	fire "after a second" might actually take six years to finally fire.
232		289
233	AnyEvent cannot compensate for this. The only event loop that is conscious	290	AnyEvent cannot compensate for this. The only event loop that is conscious
234	about these issues is L<EV>, which offers both relative (ev_timer, based	291	of these issues is L<EV>, which offers both relative (ev_timer, based
235	on true relative time) and absolute (ev_periodic, based on wallclock time)	292	on true relative time) and absolute (ev_periodic, based on wallclock time)
236	timers.	293	timers.
237		294
238	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
239	AnyEvent API.	296	AnyEvent API.
…		…
261	I<In almost all cases (in all cases if you don't care), this is the	318	I<In almost all cases (in all cases if you don't care), this is the
262	function to call when you want to know the current time.>	319	function to call when you want to know the current time.>
263		320
264	This function is also often faster then C<< AnyEvent->time >>, and	321	This function is also often faster then C<< AnyEvent->time >>, and
265	thus the preferred method if you want some timestamp (for example,	322	thus the preferred method if you want some timestamp (for example,
266	L<AnyEvent::Handle> uses this to update it's activity timeouts).	323	L<AnyEvent::Handle> uses this to update its activity timeouts).
267		324
268	The rest of this section is only of relevance if you try to be very exact	325	The rest of this section is only of relevance if you try to be very exact
269	with your timing, you can skip it without bad conscience.	326	with your timing; you can skip it without a bad conscience.
270		327
271	For a practical example of when these times differ, consider L<Event::Lib>	328	For a practical example of when these times differ, consider L<Event::Lib>
272	and L<EV> and the following set-up:	329	and L<EV> and the following set-up:
273		330
274	The event loop is running and has just invoked one of your callback at	331	The event loop is running and has just invoked one of your callbacks at
275	time=500 (assume no other callbacks delay processing). In your callback,	332	time=500 (assume no other callbacks delay processing). In your callback,
276	you wait a second by executing C<sleep 1> (blocking the process for a	333	you wait a second by executing C<sleep 1> (blocking the process for a
277	second) and then (at time=501) you create a relative timer that fires	334	second) and then (at time=501) you create a relative timer that fires
278	after three seconds.	335	after three seconds.
279		336
…		…
297	In either case, if you care (and in most cases, you don't), then you	354	In either case, if you care (and in most cases, you don't), then you
298	can get whatever behaviour you want with any event loop, by taking the	355	can get whatever behaviour you want with any event loop, by taking the
299	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
300	account.	357	account.
301		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		362	the current time for each loop iteration (see the discussion of L<<
		363	AnyEvent->now >>, above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
302	=back	381	=back
303		382
304	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
305		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
306	You can watch for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
307	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
308	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
309		390
310	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
311	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
312	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
313		394
…		…
315	invocation, and callback invocation will be synchronous. Synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
316	that it might take a while until the signal gets handled by the process,	397	that it might take a while until the signal gets handled by the process,
317	but it is guaranteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
318		399
319	The main advantage of using these watchers is that you can share a signal	400	The main advantage of using these watchers is that you can share a signal
320	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
321		403
322	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
323	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
324		407
325	Example: exit on SIGINT	408	Example: exit on SIGINT
326		409
327	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
328		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		437	variable can be changed only before the first signal watcher is created,
		438	and should be left alone otherwise. This variable determines how often
		439	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		440	will cause fewer spurious wake-ups, which is better for power and CPU
		441	saving.
		442
		443	All these problems can be avoided by installing the optional
		444	L<Async::Interrupt> module, which works with most event loops. It will not
		445	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		446	(and not with L<POE> currently, as POE does its own workaround with
		447	one-second latency). For those, you just have to suffer the delays.
		448
329	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
330		450
		451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		452
331	You can also watch on a child process exit and catch its exit status.	453	You can also watch for a child process exit and catch its exit status.
332		454
333	The child process is specified by the C<pid> argument (if set to C<0>, it	455	The child process is specified by the C<pid> argument (on some backends,
334	watches for any child process exit). The watcher will trigger as often	456	using C<0> watches for any child process exit, on others this will
335	as status change for the child are received. This works by installing a	457	croak). The watcher will be triggered only when the child process has
336	signal handler for C<SIGCHLD>. The callback will be called with the pid	458	finished and an exit status is available, not on any trace events
337	and exit status (as returned by waitpid), so unlike other watcher types,	459	(stopped/continued).
338	you I<can> rely on child watcher callback arguments.	460
		461	The callback will be called with the pid and exit status (as returned by
		462	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		463	callback arguments.
		464
		465	This watcher type works by installing a signal handler for C<SIGCHLD>,
		466	and since it cannot be shared, nothing else should use SIGCHLD or reap
		467	random child processes (waiting for specific child processes, e.g. inside
		468	C<system>, is just fine).
339		469
340	There is a slight catch to child watchers, however: you usually start them	470	There is a slight catch to child watchers, however: you usually start them
341	I<after> the child process was created, and this means the process could	471	I<after> the child process was created, and this means the process could
342	have exited already (and no SIGCHLD will be sent anymore).	472	have exited already (and no SIGCHLD will be sent anymore).
343		473
344	Not all event models handle this correctly (POE doesn't), but even for	474	Not all event models handle this correctly (neither POE nor IO::Async do,
		475	see their AnyEvent::Impl manpages for details), but even for event models
345	event models that I<do> handle this correctly, they usually need to be	476	that I<do> handle this correctly, they usually need to be loaded before
346	loaded before the process exits (i.e. before you fork in the first place).	477	the process exits (i.e. before you fork in the first place). AnyEvent's
		478	pure perl event loop handles all cases correctly regardless of when you
		479	start the watcher.
347		480
348	This means you cannot create a child watcher as the very first thing in an	481	This means you cannot create a child watcher as the very first
349	AnyEvent program, you I<have> to create at least one watcher before you	482	thing in an AnyEvent program, you I<have> to create at least one
350	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	483	watcher before you C<fork> the child (alternatively, you can call
		484	C<AnyEvent::detect>).
		485
		486	As most event loops do not support waiting for child events, they will be
		487	emulated by AnyEvent in most cases, in which the latency and race problems
		488	mentioned in the description of signal watchers apply.
351		489
352	Example: fork a process and wait for it	490	Example: fork a process and wait for it
353		491
354	my $done = AnyEvent->condvar;	492	my $done = AnyEvent->condvar;
355		493
…		…
365	);	503	);
366		504
367	# do something else, then wait for process exit	505	# do something else, then wait for process exit
368	$done->recv;	506	$done->recv;
369		507
		508	=head2 IDLE WATCHERS
		509
		510	$w = AnyEvent->idle (cb => <callback>);
		511
		512	This will repeatedly invoke the callback after the process becomes idle,
		513	until either the watcher is destroyed or new events have been detected.
		514
		515	Idle watchers are useful when there is a need to do something, but it
		516	is not so important (or wise) to do it instantly. The callback will be
		517	invoked only when there is "nothing better to do", which is usually
		518	defined as "all outstanding events have been handled and no new events
		519	have been detected". That means that idle watchers ideally get invoked
		520	when the event loop has just polled for new events but none have been
		521	detected. Instead of blocking to wait for more events, the idle watchers
		522	will be invoked.
		523
		524	Unfortunately, most event loops do not really support idle watchers (only
		525	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		526	will simply call the callback "from time to time".
		527
		528	Example: read lines from STDIN, but only process them when the
		529	program is otherwise idle:
		530
		531	my @lines; # read data
		532	my $idle_w;
		533	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		534	push @lines, scalar <STDIN>;
		535
		536	# start an idle watcher, if not already done
		537	$idle_w ||= AnyEvent->idle (cb => sub {
		538	# handle only one line, when there are lines left
		539	if (my $line = shift @lines) {
		540	print "handled when idle: $line";
		541	} else {
		542	# otherwise disable the idle watcher again
		543	undef $idle_w;
		544	}
		545	});
		546	});
		547
370	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
371		554
372	If you are familiar with some event loops you will know that all of them	555	If you are familiar with some event loops you will know that all of them
373	require you to run some blocking "loop", "run" or similar function that	556	require you to run some blocking "loop", "run" or similar function that
374	will actively watch for new events and call your callbacks.	557	will actively watch for new events and call your callbacks.
375		558
376	AnyEvent is different, it expects somebody else to run the event loop and	559	AnyEvent is slightly different: it expects somebody else to run the event
377	will only block when necessary (usually when told by the user).	560	loop and will only block when necessary (usually when told by the user).
378		561
379	The instrument to do that is called a "condition variable", so called	562	The tool to do that is called a "condition variable", so called because
380	because they represent a condition that must become true.	563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
381		566
382	Condition variables can be created by calling the C<< AnyEvent->condvar	567	Condition variables can be created by calling the C<< AnyEvent->condvar
383	>> method, usually without arguments. The only argument pair allowed is	568	>> method, usually without arguments. The only argument pair allowed is
384	C<cb>, which specifies a callback to be called when the condition variable	569	C<cb>, which specifies a callback to be called when the condition variable
385	becomes true.	570	becomes true, with the condition variable as the first argument (but not
		571	the results).
386		572
387	After creation, the condition variable is "false" until it becomes "true"	573	After creation, the condition variable is "false" until it becomes "true"
388	by calling the C<send> method (or calling the condition variable as if it	574	by calling the C<send> method (or calling the condition variable as if it
389	were a callback, read about the caveats in the description for the C<<	575	were a callback, read about the caveats in the description for the C<<
390	->send >> method).	576	->send >> method).
391		577
392	Condition variables are similar to callbacks, except that you can	578	Since condition variables are the most complex part of the AnyEvent API, here are
393	optionally wait for them. They can also be called merge points - points	579	some different mental models of what they are - pick the ones you can connect to:
394	in time where multiple outstanding events have been processed. And yet	580
395	another way to call them is transactions - each condition variable can be	581	=over 4
396	used to represent a transaction, which finishes at some point and delivers	582
397	a result.	583	=item * Condition variables are like callbacks - you can call them (and pass them instead
		584	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		585
		586	=item * Condition variables are signals - one side can emit or send them,
		587	the other side can wait for them, or install a handler that is called when
		588	the signal fires.
		589
		590	=item * Condition variables are like "Merge Points" - points in your program
		591	where you merge multiple independent results/control flows into one.
		592
		593	=item * Condition variables represent a transaction - functions that start
		594	some kind of transaction can return them, leaving the caller the choice
		595	between waiting in a blocking fashion, or setting a callback.
		596
		597	=item * Condition variables represent future values, or promises to deliver
		598	some result, long before the result is available.
		599
		600	=back
398		601
399	Condition variables are very useful to signal that something has finished,	602	Condition variables are very useful to signal that something has finished,
400	for example, if you write a module that does asynchronous http requests,	603	for example, if you write a module that does asynchronous http requests,
401	then a condition variable would be the ideal candidate to signal the	604	then a condition variable would be the ideal candidate to signal the
402	availability of results. The user can either act when the callback is	605	availability of results. The user can either act when the callback is
…		…
415		618
416	Condition variables are represented by hash refs in perl, and the keys	619	Condition variables are represented by hash refs in perl, and the keys
417	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing	620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
418	easy (it is often useful to build your own transaction class on top of	621	easy (it is often useful to build your own transaction class on top of
419	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call	622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
420	it's C<new> method in your own C<new> method.	623	its C<new> method in your own C<new> method.
421		624
422	There are two "sides" to a condition variable - the "producer side" which	625	There are two "sides" to a condition variable - the "producer side" which
423	eventually calls C<< -> send >>, and the "consumer side", which waits	626	eventually calls C<< -> send >>, and the "consumer side", which waits
424	for the send to occur.	627	for the send to occur.
425		628
426	Example: wait for a timer.	629	Example: wait for a timer.
427		630
428	# wait till the result is ready	631	# condition: "wait till the timer is fired"
429	my $result_ready = AnyEvent->condvar;	632	my $timer_fired = AnyEvent->condvar;
430		633
431	# do something such as adding a timer	634	# create the timer - we could wait for, say
432	# or socket watcher the calls $result_ready->send	635	# a handle becomign ready, or even an
433	# when the "result" is ready.	636	# AnyEvent::HTTP request to finish, but
434	# in this case, we simply use a timer:	637	# in this case, we simply use a timer:
435	my $w = AnyEvent->timer (	638	my $w = AnyEvent->timer (
436	after => 1,	639	after => 1,
437	cb => sub { $result_ready->send },	640	cb => sub { $timer_fired->send },
438	);	641	);
439		642
440	# this "blocks" (while handling events) till the callback	643	# this "blocks" (while handling events) till the callback
441	# calls send	644	# calls ->send
442	$result_ready->recv;	645	$timer_fired->recv;
443		646
444	Example: wait for a timer, but take advantage of the fact that	647	Example: wait for a timer, but take advantage of the fact that condition
445	condition variables are also code references.	648	variables are also callable directly.
446		649
447	my $done = AnyEvent->condvar;	650	my $done = AnyEvent->condvar;
448	my $delay = AnyEvent->timer (after => 5, cb => $done);	651	my $delay = AnyEvent->timer (after => 5, cb => $done);
449	$done->recv;	652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
450		670
451	=head3 METHODS FOR PRODUCERS	671	=head3 METHODS FOR PRODUCERS
452		672
453	These methods should only be used by the producing side, i.e. the	673	These methods should only be used by the producing side, i.e. the
454	code/module that eventually sends the signal. Note that it is also	674	code/module that eventually sends the signal. Note that it is also
…		…
467	immediately from within send.	687	immediately from within send.
468		688
469	Any arguments passed to the C<send> call will be returned by all	689	Any arguments passed to the C<send> call will be returned by all
470	future C<< ->recv >> calls.	690	future C<< ->recv >> calls.
471		691
472	Condition variables are overloaded so one can call them directly	692	Condition variables are overloaded so one can call them directly (as if
473	(as a code reference). Calling them directly is the same as calling	693	they were a code reference). Calling them directly is the same as calling
474	C<send>. Note, however, that many C-based event loops do not handle	694	C<send>.
475	overloading, so as tempting as it may be, passing a condition variable
476	instead of a callback does not work. Both the pure perl and EV loops
477	support overloading, however, as well as all functions that use perl to
478	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
479	example).
480		695
481	=item $cv->croak ($error)	696	=item $cv->croak ($error)
482		697
483	Similar to send, but causes all call's to C<< ->recv >> to invoke	698	Similar to send, but causes all calls to C<< ->recv >> to invoke
484	C<Carp::croak> with the given error message/object/scalar.	699	C<Carp::croak> with the given error message/object/scalar.
485		700
486	This can be used to signal any errors to the condition variable	701	This can be used to signal any errors to the condition variable
487	user/consumer.	702	user/consumer. Doing it this way instead of calling C<croak> directly
		703	delays the error detection, but has the overwhelming advantage that it
		704	diagnoses the error at the place where the result is expected, and not
		705	deep in some event callback with no connection to the actual code causing
		706	the problem.
488		707
489	=item $cv->begin ([group callback])	708	=item $cv->begin ([group callback])
490		709
491	=item $cv->end	710	=item $cv->end
492
493	These two methods are EXPERIMENTAL and MIGHT CHANGE.
494		711
495	These two methods can be used to combine many transactions/events into	712	These two methods can be used to combine many transactions/events into
496	one. For example, a function that pings many hosts in parallel might want	713	one. For example, a function that pings many hosts in parallel might want
497	to use a condition variable for the whole process.	714	to use a condition variable for the whole process.
498		715
499	Every call to C<< ->begin >> will increment a counter, and every call to	716	Every call to C<< ->begin >> will increment a counter, and every call to
500	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
501	>>, the (last) callback passed to C<begin> will be executed. That callback	718	>>, the (last) callback passed to C<begin> will be executed, passing the
502	is I<supposed> to call C<< ->send >>, but that is not required. If no	719	condvar as first argument. That callback is I<supposed> to call C<< ->send
503	callback was set, C<send> will be called without any arguments.	720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
504		722
505	Let's clarify this with the ping example:	723	You can think of C<< $cv->send >> giving you an OR condition (one call
		724	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		725	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		726
		727	Let's start with a simple example: you have two I/O watchers (for example,
		728	STDOUT and STDERR for a program), and you want to wait for both streams to
		729	close before activating a condvar:
506		730
507	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
508		732
		733	$cv->begin; # first watcher
		734	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		735	defined sysread $fh1, my $buf, 4096
		736	or $cv->end;
		737	});
		738
		739	$cv->begin; # second watcher
		740	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		741	defined sysread $fh2, my $buf, 4096
		742	or $cv->end;
		743	});
		744
		745	$cv->recv;
		746
		747	This works because for every event source (EOF on file handle), there is
		748	one call to C<begin>, so the condvar waits for all calls to C<end> before
		749	sending.
		750
		751	The ping example mentioned above is slightly more complicated, as the
		752	there are results to be passwd back, and the number of tasks that are
		753	begun can potentially be zero:
		754
		755	my $cv = AnyEvent->condvar;
		756
509	my %result;	757	my %result;
510	$cv->begin (sub { $cv->send (\%result) });	758	$cv->begin (sub { shift->send (\%result) });
511		759
512	for my $host (@list_of_hosts) {	760	for my $host (@list_of_hosts) {
513	$cv->begin;	761	$cv->begin;
514	ping_host_then_call_callback $host, sub {	762	ping_host_then_call_callback $host, sub {
515	$result{$host} = ...;	763	$result{$host} = ...;
…		…
530	loop, which serves two important purposes: first, it sets the callback	778	loop, which serves two important purposes: first, it sets the callback
531	to be called once the counter reaches C<0>, and second, it ensures that	779	to be called once the counter reaches C<0>, and second, it ensures that
532	C<send> is called even when C<no> hosts are being pinged (the loop	780	C<send> is called even when C<no> hosts are being pinged (the loop
533	doesn't execute once).	781	doesn't execute once).
534		782
535	This is the general pattern when you "fan out" into multiple subrequests:	783	This is the general pattern when you "fan out" into multiple (but
536	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
537	is called at least once, and then, for each subrequest you start, call	785	the callback and ensure C<end> is called at least once, and then, for each
538	C<begin> and for each subrequest you finish, call C<end>.	786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
539		788
540	=back	789	=back
541		790
542	=head3 METHODS FOR CONSUMERS	791	=head3 METHODS FOR CONSUMERS
543		792
…		…
547	=over 4	796	=over 4
548		797
549	=item $cv->recv	798	=item $cv->recv
550		799
551	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
552	>> methods have been called on c<$cv>, while servicing other watchers	801	>> methods have been called on C<$cv>, while servicing other watchers
553	normally.	802	normally.
554		803
555	You can only wait once on a condition - additional calls are valid but	804	You can only wait once on a condition - additional calls are valid but
556	will return immediately.	805	will return immediately.
557		806
…		…
559	function will call C<croak>.	808	function will call C<croak>.
560		809
561	In list context, all parameters passed to C<send> will be returned,	810	In list context, all parameters passed to C<send> will be returned,
562	in scalar context only the first one will be returned.	811	in scalar context only the first one will be returned.
563		812
		813	Note that doing a blocking wait in a callback is not supported by any
		814	event loop, that is, recursive invocation of a blocking C<< ->recv
		815	>> is not allowed, and the C<recv> call will C<croak> if such a
		816	condition is detected. This condition can be slightly loosened by using
		817	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		818	any thread that doesn't run the event loop itself.
		819
564	Not all event models support a blocking wait - some die in that case	820	Not all event models support a blocking wait - some die in that case
565	(programs might want to do that to stay interactive), so I<if you are	821	(programs might want to do that to stay interactive), so I<if you are
566	using this from a module, never require a blocking wait>, but let the	822	using this from a module, never require a blocking wait>. Instead, let the
567	caller decide whether the call will block or not (for example, by coupling	823	caller decide whether the call will block or not (for example, by coupling
568	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
569	callbacks so the caller knows that getting the result will not block,	825	callbacks so the caller knows that getting the result will not block,
570	while still supporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
571		827
572	Another reason I<never> to C<< ->recv >> in a module is that you cannot
573	sensibly have two C<< ->recv >>'s in parallel, as that would require
574	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
575	can supply.
576
577	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
578	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
579	versions and also integrates coroutines into AnyEvent, making blocking
580	C<< ->recv >> calls perfectly safe as long as they are done from another
581	coroutine (one that doesn't run the event loop).
582
583	You can ensure that C<< -recv >> never blocks by setting a callback and	828	You can ensure that C<< ->recv >> never blocks by setting a callback and
584	only calling C<< ->recv >> from within that callback (or at a later	829	only calling C<< ->recv >> from within that callback (or at a later
585	time). This will work even when the event loop does not support blocking	830	time). This will work even when the event loop does not support blocking
586	waits otherwise.	831	waits otherwise.
587		832
588	=item $bool = $cv->ready	833	=item $bool = $cv->ready
589		834
590	Returns true when the condition is "true", i.e. whether C<send> or	835	Returns true when the condition is "true", i.e. whether C<send> or
591	C<croak> have been called.	836	C<croak> have been called.
592		837
593	=item $cb = $cv->cb ([new callback])	838	=item $cb = $cv->cb ($cb->($cv))
594		839
595	This is a mutator function that returns the callback set and optionally	840	This is a mutator function that returns the callback set and optionally
596	replaces it before doing so.	841	replaces it before doing so.
597		842
598	The callback will be called when the condition becomes "true", i.e. when	843	The callback will be called when the condition becomes "true", i.e. when
599	C<send> or C<croak> are called, with the only argument being the condition	844	C<send> or C<croak> are called, with the only argument being the
600	variable itself. Calling C<recv> inside the callback or at any later time	845	condition variable itself. If the condition is already true, the
601	is guaranteed not to block.	846	callback is called immediately when it is set. Calling C<recv> inside
		847	the callback or at any later time is guaranteed not to block.
602		848
603	=back	849	=back
604		850
		851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		852
		853	The available backend classes are (every class has its own manpage):
		854
		855	=over 4
		856
		857	=item Backends that are autoprobed when no other event loop can be found.
		858
		859	EV is the preferred backend when no other event loop seems to be in
		860	use. If EV is not installed, then AnyEvent will fall back to its own
		861	pure-perl implementation, which is available everywhere as it comes with
		862	AnyEvent itself.
		863
		864	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		865	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		866
		867	=item Backends that are transparently being picked up when they are used.
		868
		869	These will be used if they are already loaded when the first watcher
		870	is created, in which case it is assumed that the application is using
		871	them. This means that AnyEvent will automatically pick the right backend
		872	when the main program loads an event module before anything starts to
		873	create watchers. Nothing special needs to be done by the main program.
		874
		875	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		876	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		877	AnyEvent::Impl::Tk based on Tk, very broken.
		878	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		879	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		880	AnyEvent::Impl::Irssi used when running within irssi.
		881	AnyEvent::Impl::IOAsync based on IO::Async.
		882	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		883	AnyEvent::Impl::FLTK based on FLTK.
		884
		885	=item Backends with special needs.
		886
		887	Qt requires the Qt::Application to be instantiated first, but will
		888	otherwise be picked up automatically. As long as the main program
		889	instantiates the application before any AnyEvent watchers are created,
		890	everything should just work.
		891
		892	AnyEvent::Impl::Qt based on Qt.
		893
		894	=item Event loops that are indirectly supported via other backends.
		895
		896	Some event loops can be supported via other modules:
		897
		898	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		899
		900	B<WxWidgets> has no support for watching file handles. However, you can
		901	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		902	polls 20 times per second, which was considered to be too horrible to even
		903	consider for AnyEvent.
		904
		905	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		906	backend, so it can be supported through POE.
		907
		908	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		909	load L<POE> when detecting them, in the hope that POE will pick them up,
		910	in which case everything will be automatic.
		911
		912	=back
		913
605	=head1 GLOBAL VARIABLES AND FUNCTIONS	914	=head1 GLOBAL VARIABLES AND FUNCTIONS
606		915
		916	These are not normally required to use AnyEvent, but can be useful to
		917	write AnyEvent extension modules.
		918
607	=over 4	919	=over 4
608		920
609	=item $AnyEvent::MODEL	921	=item $AnyEvent::MODEL
610		922
611	Contains C<undef> until the first watcher is being created. Then it	923	Contains C<undef> until the first watcher is being created, before the
		924	backend has been autodetected.
		925
612	contains the event model that is being used, which is the name of the	926	Afterwards it contains the event model that is being used, which is the
613	Perl class implementing the model. This class is usually one of the	927	name of the Perl class implementing the model. This class is usually one
614	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	928	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
615	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	929	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
616		930	will be C<urxvt::anyevent>).
617	The known classes so far are:
618
619	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
620	AnyEvent::Impl::Event based on Event, second best choice.
621	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
622	AnyEvent::Impl::Glib based on Glib, third-best choice.
623	AnyEvent::Impl::Tk based on Tk, very bad choice.
624	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
625	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
626	AnyEvent::Impl::POE based on POE, not generic enough for full support.
627
628	There is no support for WxWidgets, as WxWidgets has no support for
629	watching file handles. However, you can use WxWidgets through the
630	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
631	second, which was considered to be too horrible to even consider for
632	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
633	it's adaptor.
634
635	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
636	autodetecting them.
637		931
638	=item AnyEvent::detect	932	=item AnyEvent::detect
639		933
640	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	934	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
641	if necessary. You should only call this function right before you would	935	if necessary. You should only call this function right before you would
642	have created an AnyEvent watcher anyway, that is, as late as possible at	936	have created an AnyEvent watcher anyway, that is, as late as possible at
643	runtime.	937	runtime, and not e.g. during initialisation of your module.
		938
		939	If you need to do some initialisation before AnyEvent watchers are
		940	created, use C<post_detect>.
644		941
645	=item $guard = AnyEvent::post_detect { BLOCK }	942	=item $guard = AnyEvent::post_detect { BLOCK }
646		943
647	Arranges for the code block to be executed as soon as the event model is	944	Arranges for the code block to be executed as soon as the event model is
648	autodetected (or immediately if this has already happened).	945	autodetected (or immediately if that has already happened).
		946
		947	The block will be executed I<after> the actual backend has been detected
		948	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		949	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		950	other initialisations - see the sources of L<AnyEvent::Strict> or
		951	L<AnyEvent::AIO> to see how this is used.
		952
		953	The most common usage is to create some global watchers, without forcing
		954	event module detection too early, for example, L<AnyEvent::AIO> creates
		955	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		956	avoid autodetecting the event module at load time.
649		957
650	If called in scalar or list context, then it creates and returns an object	958	If called in scalar or list context, then it creates and returns an object
651	that automatically removes the callback again when it is destroyed. See	959	that automatically removes the callback again when it is destroyed (or
		960	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
652	L<Coro::BDB> for a case where this is useful.	961	a case where this is useful.
		962
		963	Example: Create a watcher for the IO::AIO module and store it in
		964	C<$WATCHER>, but do so only do so after the event loop is initialised.
		965
		966	our WATCHER;
		967
		968	my $guard = AnyEvent::post_detect {
		969	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		970	};
		971
		972	# the ||= is important in case post_detect immediately runs the block,
		973	# as to not clobber the newly-created watcher. assigning both watcher and
		974	# post_detect guard to the same variable has the advantage of users being
		975	# able to just C<undef $WATCHER> if the watcher causes them grief.
		976
		977	$WATCHER ||= $guard;
653		978
654	=item @AnyEvent::post_detect	979	=item @AnyEvent::post_detect
655		980
656	If there are any code references in this array (you can C<push> to it	981	If there are any code references in this array (you can C<push> to it
657	before or after loading AnyEvent), then they will called directly after	982	before or after loading AnyEvent), then they will be called directly
658	the event loop has been chosen.	983	after the event loop has been chosen.
659		984
660	You should check C<$AnyEvent::MODEL> before adding to this array, though:	985	You should check C<$AnyEvent::MODEL> before adding to this array, though:
661	if it contains a true value then the event loop has already been detected,	986	if it is defined then the event loop has already been detected, and the
662	and the array will be ignored.	987	array will be ignored.
663		988
664	Best use C<AnyEvent::post_detect { BLOCK }> instead.	989	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		990	it, as it takes care of these details.
		991
		992	This variable is mainly useful for modules that can do something useful
		993	when AnyEvent is used and thus want to know when it is initialised, but do
		994	not need to even load it by default. This array provides the means to hook
		995	into AnyEvent passively, without loading it.
		996
		997	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		998	together, you could put this into Coro (this is the actual code used by
		999	Coro to accomplish this):
		1000
		1001	if (defined $AnyEvent::MODEL) {
		1002	# AnyEvent already initialised, so load Coro::AnyEvent
		1003	require Coro::AnyEvent;
		1004	} else {
		1005	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1006	# as soon as it is
		1007	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1008	}
665		1009
666	=back	1010	=back
667		1011
668	=head1 WHAT TO DO IN A MODULE	1012	=head1 WHAT TO DO IN A MODULE
669		1013
…		…
680	because it will stall the whole program, and the whole point of using	1024	because it will stall the whole program, and the whole point of using
681	events is to stay interactive.	1025	events is to stay interactive.
682		1026
683	It is fine, however, to call C<< ->recv >> when the user of your module	1027	It is fine, however, to call C<< ->recv >> when the user of your module
684	requests it (i.e. if you create a http request object ad have a method	1028	requests it (i.e. if you create a http request object ad have a method
685	called C<results> that returns the results, it should call C<< ->recv >>	1029	called C<results> that returns the results, it may call C<< ->recv >>
686	freely, as the user of your module knows what she is doing. always).	1030	freely, as the user of your module knows what she is doing. Always).
687		1031
688	=head1 WHAT TO DO IN THE MAIN PROGRAM	1032	=head1 WHAT TO DO IN THE MAIN PROGRAM
689		1033
690	There will always be a single main program - the only place that should	1034	There will always be a single main program - the only place that should
691	dictate which event model to use.	1035	dictate which event model to use.
692		1036
693	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1037	If the program is not event-based, it need not do anything special, even
694	do anything special (it does not need to be event-based) and let AnyEvent	1038	when it depends on a module that uses an AnyEvent. If the program itself
695	decide which implementation to chose if some module relies on it.	1039	uses AnyEvent, but does not care which event loop is used, all it needs
		1040	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1041	available loop implementation.
696		1042
697	If the main program relies on a specific event model - for example, in	1043	If the main program relies on a specific event model - for example, in
698	Gtk2 programs you have to rely on the Glib module - you should load the	1044	Gtk2 programs you have to rely on the Glib module - you should load the
699	event module before loading AnyEvent or any module that uses it: generally	1045	event module before loading AnyEvent or any module that uses it: generally
700	speaking, you should load it as early as possible. The reason is that	1046	speaking, you should load it as early as possible. The reason is that
701	modules might create watchers when they are loaded, and AnyEvent will	1047	modules might create watchers when they are loaded, and AnyEvent will
702	decide on the event model to use as soon as it creates watchers, and it	1048	decide on the event model to use as soon as it creates watchers, and it
703	might chose the wrong one unless you load the correct one yourself.	1049	might choose the wrong one unless you load the correct one yourself.
704		1050
705	You can chose to use a pure-perl implementation by loading the	1051	You can chose to use a pure-perl implementation by loading the
706	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour	1052	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
707	everywhere, but letting AnyEvent chose the model is generally better.	1053	everywhere, but letting AnyEvent chose the model is generally better.
708		1054
…		…
724		1070
725		1071
726	=head1 OTHER MODULES	1072	=head1 OTHER MODULES
727		1073
728	The following is a non-exhaustive list of additional modules that use	1074	The following is a non-exhaustive list of additional modules that use
729	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1075	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
730	in the same program. Some of the modules come with AnyEvent, some are	1076	modules and other event loops in the same program. Some of the modules
731	available via CPAN.	1077	come as part of AnyEvent, the others are available via CPAN.
732		1078
733	=over 4	1079	=over 4
734		1080
735	=item L<AnyEvent::Util>	1081	=item L<AnyEvent::Util>
736		1082
737	Contains various utility functions that replace often-used but blocking	1083	Contains various utility functions that replace often-used blocking
738	functions such as C<inet_aton> by event-/callback-based versions.	1084	functions such as C<inet_aton> with event/callback-based versions.
739		1085
740	=item L<AnyEvent::Socket>	1086	=item L<AnyEvent::Socket>
741		1087
742	Provides various utility functions for (internet protocol) sockets,	1088	Provides various utility functions for (internet protocol) sockets,
743	addresses and name resolution. Also functions to create non-blocking tcp	1089	addresses and name resolution. Also functions to create non-blocking tcp
…		…
745		1091
746	=item L<AnyEvent::Handle>	1092	=item L<AnyEvent::Handle>
747		1093
748	Provide read and write buffers, manages watchers for reads and writes,	1094	Provide read and write buffers, manages watchers for reads and writes,
749	supports raw and formatted I/O, I/O queued and fully transparent and	1095	supports raw and formatted I/O, I/O queued and fully transparent and
750	non-blocking SSL/TLS.	1096	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
751		1097
752	=item L<AnyEvent::DNS>	1098	=item L<AnyEvent::DNS>
753		1099
754	Provides rich asynchronous DNS resolver capabilities.	1100	Provides rich asynchronous DNS resolver capabilities.
755		1101
		1102	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1103
		1104	Implement event-based interfaces to the protocols of the same name (for
		1105	the curious, IGS is the International Go Server and FCP is the Freenet
		1106	Client Protocol).
		1107
		1108	=item L<AnyEvent::Handle::UDP>
		1109
		1110	Here be danger!
		1111
		1112	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1113	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1114	its use of a stream-based API with a protocol that isn't streamable, that
		1115	the only way to improve it is to delete it.
		1116
		1117	It features data corruption (but typically only under load) and general
		1118	confusion. On top, the author is not only clueless about UDP but also
		1119	fact-resistant - some gems of his understanding: "connect doesn't work
		1120	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1121	packets", "I don't need to implement proper error checking as UDP doesn't
		1122	support error checking" and so on - he doesn't even understand what's
		1123	wrong with his module when it is explained to him.
		1124
756	=item L<AnyEvent::HTTP>	1125	=item L<AnyEvent::DBI>
757		1126
758	A simple-to-use HTTP library that is capable of making a lot of concurrent	1127	Executes L<DBI> requests asynchronously in a proxy process for you,
759	HTTP requests.	1128	notifying you in an event-based way when the operation is finished.
		1129
		1130	=item L<AnyEvent::AIO>
		1131
		1132	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1133	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1134	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1135	file I/O, and much more.
760		1136
761	=item L<AnyEvent::HTTPD>	1137	=item L<AnyEvent::HTTPD>
762		1138
763	Provides a simple web application server framework.	1139	A simple embedded webserver.
764		1140
765	=item L<AnyEvent::FastPing>	1141	=item L<AnyEvent::FastPing>
766		1142
767	The fastest ping in the west.	1143	The fastest ping in the west.
768		1144
769	=item L<AnyEvent::DBI>
770
771	Executes L<DBI> requests asynchronously in a proxy process.
772
773	=item L<AnyEvent::AIO>
774
775	Truly asynchronous I/O, should be in the toolbox of every event
776	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
777	together.
778
779	=item L<AnyEvent::BDB>
780
781	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
782	L<BDB> and AnyEvent together.
783
784	=item L<AnyEvent::GPSD>
785
786	A non-blocking interface to gpsd, a daemon delivering GPS information.
787
788	=item L<AnyEvent::IGS>
789
790	A non-blocking interface to the Internet Go Server protocol (used by
791	L<App::IGS>).
792
793	=item L<Net::IRC3>
794
795	AnyEvent based IRC client module family.
796
797	=item L<Net::XMPP2>
798
799	AnyEvent based XMPP (Jabber protocol) module family.
800
801	=item L<Net::FCP>
802
803	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
804	of AnyEvent.
805
806	=item L<Event::ExecFlow>
807
808	High level API for event-based execution flow control.
809
810	=item L<Coro>	1145	=item L<Coro>
811		1146
812	Has special support for AnyEvent via L<Coro::AnyEvent>.	1147	Has special support for AnyEvent via L<Coro::AnyEvent>.
813		1148
814	=item L<IO::Lambda>
815
816	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
817
818	=back	1149	=back
819		1150
820	=cut	1151	=cut
821		1152
822	package AnyEvent;	1153	package AnyEvent;
823		1154
824	no warnings;	1155	# basically a tuned-down version of common::sense
825	use strict;	1156	sub common_sense {
		1157	# from common:.sense 3.4
		1158	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1159	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1160	$^H |= 0x00000600;
		1161	}
826		1162
		1163	BEGIN { AnyEvent::common_sense }
		1164
827	use Carp;	1165	use Carp ();
828		1166
829	our $VERSION = 4.2;	1167	our $VERSION = '5.34';
830	our $MODEL;	1168	our $MODEL;
831		1169
832	our $AUTOLOAD;	1170	our $AUTOLOAD;
833	our @ISA;	1171	our @ISA;
834		1172
835	our @REGISTRY;	1173	our @REGISTRY;
836		1174
837	our $WIN32;	1175	our $VERBOSE;
838		1176
839	BEGIN {	1177	BEGIN {
840	my $win32 = ! ! ($^O =~ /mswin32/i);	1178	require "AnyEvent/constants.pl";
841	eval "sub WIN32(){ $win32 }";
842	}
843		1179
		1180	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1181
		1182	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1183	if ${^TAINT};
		1184
844	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1185	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1186
		1187	}
		1188
		1189	our $MAX_SIGNAL_LATENCY = 10;
845		1190
846	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1191	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
847		1192
848	{	1193	{
849	my $idx;	1194	my $idx;
…		…
851	for reverse split /\s*,\s*/,	1196	for reverse split /\s*,\s*/,
852	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1197	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
853	}	1198	}
854		1199
855	my @models = (	1200	my @models = (
856	[EV:: => AnyEvent::Impl::EV::],	1201	[EV:: => AnyEvent::Impl::EV:: , 1],
857	[Event:: => AnyEvent::Impl::Event::],
858	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1202	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
859	# everything below here will not be autoprobed	1203	# everything below here will not (normally) be autoprobed
860	# as the pureperl backend should work everywhere	1204	# as the pureperl backend should work everywhere
861	# and is usually faster	1205	# and is usually faster
		1206	[Event:: => AnyEvent::Impl::Event::, 1],
		1207	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1208	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1209	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
862	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles	1210	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
863	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
864	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
865	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1211	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
866	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1212	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
867	[Wx:: => AnyEvent::Impl::POE::],	1213	[Wx:: => AnyEvent::Impl::POE::],
868	[Prima:: => AnyEvent::Impl::POE::],	1214	[Prima:: => AnyEvent::Impl::POE::],
		1215	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::],
		1216	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
		1217	[FLTK:: => AnyEvent::Impl::FLTK::],
869	);	1218	);
870		1219
871	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1220	our %method = map +($_ => 1),
		1221	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
872		1222
873	our @post_detect;	1223	our @post_detect;
874		1224
875	sub post_detect(&) {	1225	sub post_detect(&) {
876	my ($cb) = @_;	1226	my ($cb) = @_;
877		1227
878	if ($MODEL) {
879	$cb->();
880
881	1
882	} else {
883	push @post_detect, $cb;	1228	push @post_detect, $cb;
884		1229
885	defined wantarray	1230	defined wantarray
886	? bless \$cb, "AnyEvent::Util::PostDetect"	1231	? bless \$cb, "AnyEvent::Util::postdetect"
887	: ()	1232	: ()
		1233	}
		1234
		1235	sub AnyEvent::Util::postdetect::DESTROY {
		1236	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1237	}
		1238
		1239	sub detect() {
		1240	# free some memory
		1241	*detect = sub () { $MODEL };
		1242
		1243	local $!; # for good measure
		1244	local $SIG{__DIE__};
		1245
		1246	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1247	my $model = "AnyEvent::Impl::$1";
		1248	if (eval "require $model") {
		1249	$MODEL = $model;
		1250	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1251	} else {
		1252	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1253	}
888	}	1254	}
889	}
890		1255
891	sub AnyEvent::Util::PostDetect::DESTROY {	1256	# check for already loaded models
892	@post_detect = grep $_ != ${$_[0]}, @post_detect;
893	}
894
895	sub detect() {
896	unless ($MODEL) {	1257	unless ($MODEL) {
897	no strict 'refs';	1258	for (@REGISTRY, @models) {
898	local $SIG{__DIE__};	1259	my ($package, $model) = @$_;
899		1260	if (${"$package\::VERSION"} > 0) {
900	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
901	my $model = "AnyEvent::Impl::$1";
902	if (eval "require $model") {	1261	if (eval "require $model") {
903	$MODEL = $model;	1262	$MODEL = $model;
904	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1263	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
905	} else {	1264	last;
906	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1265	}
907	}	1266	}
908	}	1267	}
909		1268
910	# check for already loaded models
911	unless ($MODEL) {	1269	unless ($MODEL) {
		1270	# try to autoload a model
912	for (@REGISTRY, @models) {	1271	for (@REGISTRY, @models) {
913	my ($package, $model) = @$_;	1272	my ($package, $model, $autoload) = @$_;
		1273	if (
		1274	$autoload
		1275	and eval "require $package"
914	if (${"$package\::VERSION"} > 0) {	1276	and ${"$package\::VERSION"} > 0
915	if (eval "require $model") {	1277	and eval "require $model"
		1278	) {
916	$MODEL = $model;	1279	$MODEL = $model;
917	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1280	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
918	last;	1281	last;
919	}
920	}	1282	}
921	}	1283	}
922		1284
923	unless ($MODEL) {
924	# try to load a model
925
926	for (@REGISTRY, @models) {
927	my ($package, $model) = @$_;
928	if (eval "require $package"
929	and ${"$package\::VERSION"} > 0
930	and eval "require $model") {
931	$MODEL = $model;
932	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
933	last;
934	}
935	}
936
937	$MODEL	1285	$MODEL
938	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1286	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?\n";
939	}
940	}	1287	}
941
942	unshift @ISA, $MODEL;
943	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
944
945	(shift @post_detect)->() while @post_detect;
946	}	1288	}
		1289
		1290	@models = (); # free probe data
		1291
		1292	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1293	unshift @ISA, $MODEL;
		1294
		1295	# now nuke some methods that are overridden by the backend.
		1296	# SUPER is not allowed.
		1297	for (qw(time signal child idle)) {
		1298	undef &{"AnyEvent::Base::$_"}
		1299	if defined &{"$MODEL\::$_"};
		1300	}
		1301
		1302	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1303	eval { require AnyEvent::Strict };
		1304	warn "AnyEvent: cannot load AnyEvent::Strict: $@"
		1305	if $@ && $VERBOSE;
		1306	}
		1307
		1308	(shift @post_detect)->() while @post_detect;
		1309
		1310	*post_detect = sub(&) {
		1311	shift->();
		1312
		1313	undef
		1314	};
947		1315
948	$MODEL	1316	$MODEL
949	}	1317	}
950		1318
951	sub AUTOLOAD {	1319	sub AUTOLOAD {
952	(my $func = $AUTOLOAD) =~ s/.*://;	1320	(my $func = $AUTOLOAD) =~ s/.*://;
953		1321
954	$method{$func}	1322	$method{$func}
955	or croak "$func: not a valid method for AnyEvent objects";	1323	or Carp::croak "$func: not a valid AnyEvent class method";
956		1324
957	detect unless $MODEL;	1325	detect;
958		1326
959	my $class = shift;	1327	my $class = shift;
960	$class->$func (@_);	1328	$class->$func (@_);
961	}	1329	}
962		1330
		1331	# utility function to dup a filehandle. this is used by many backends
		1332	# to support binding more than one watcher per filehandle (they usually
		1333	# allow only one watcher per fd, so we dup it to get a different one).
		1334	sub _dupfh($$;$$) {
		1335	my ($poll, $fh, $r, $w) = @_;
		1336
		1337	# cygwin requires the fh mode to be matching, unix doesn't
		1338	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1339
		1340	open my $fh2, $mode, $fh
		1341	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1342
		1343	# we assume CLOEXEC is already set by perl in all important cases
		1344
		1345	($fh2, $rw)
		1346	}
		1347
		1348	=head1 SIMPLIFIED AE API
		1349
		1350	Starting with version 5.0, AnyEvent officially supports a second, much
		1351	simpler, API that is designed to reduce the calling, typing and memory
		1352	overhead by using function call syntax and a fixed number of parameters.
		1353
		1354	See the L<AE> manpage for details.
		1355
		1356	=cut
		1357
		1358	package AE;
		1359
		1360	our $VERSION = $AnyEvent::VERSION;
		1361
		1362	# fall back to the main API by default - backends and AnyEvent::Base
		1363	# implementations can overwrite these.
		1364
		1365	sub io($$$) {
		1366	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1367	}
		1368
		1369	sub timer($$$) {
		1370	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1371	}
		1372
		1373	sub signal($$) {
		1374	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1375	}
		1376
		1377	sub child($$) {
		1378	AnyEvent->child (pid => $_[0], cb => $_[1])
		1379	}
		1380
		1381	sub idle($) {
		1382	AnyEvent->idle (cb => $_[0])
		1383	}
		1384
		1385	sub cv(;&) {
		1386	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1387	}
		1388
		1389	sub now() {
		1390	AnyEvent->now
		1391	}
		1392
		1393	sub now_update() {
		1394	AnyEvent->now_update
		1395	}
		1396
		1397	sub time() {
		1398	AnyEvent->time
		1399	}
		1400
963	package AnyEvent::Base;	1401	package AnyEvent::Base;
964		1402
965	# default implementation for now and time	1403	# default implementations for many methods
966		1404
967	use Time::HiRes ();	1405	sub time {
		1406	eval q{ # poor man's autoloading {}
		1407	# probe for availability of Time::HiRes
		1408	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1409	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1410	*AE::time = \&Time::HiRes::time;
		1411	# if (eval "use POSIX (); (POSIX::times())...
		1412	} else {
		1413	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1414	*AE::time = sub (){ time }; # epic fail
		1415	}
968		1416
969	sub time { Time::HiRes::time }	1417	*time = sub { AE::time }; # different prototypes
970	sub now { Time::HiRes::time }	1418	};
		1419	die if $@;
		1420
		1421	&time
		1422	}
		1423
		1424	*now = \&time;
		1425
		1426	sub now_update { }
971		1427
972	# default implementation for ->condvar	1428	# default implementation for ->condvar
973		1429
974	sub condvar {	1430	sub condvar {
		1431	eval q{ # poor man's autoloading {}
		1432	*condvar = sub {
975	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1433	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1434	};
		1435
		1436	*AE::cv = sub (;&) {
		1437	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1438	};
		1439	};
		1440	die if $@;
		1441
		1442	&condvar
976	}	1443	}
977		1444
978	# default implementation for ->signal	1445	# default implementation for ->signal
979		1446
980	our %SIG_CB;	1447	our $HAVE_ASYNC_INTERRUPT;
		1448
		1449	sub _have_async_interrupt() {
		1450	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1451	&& eval "use Async::Interrupt 1.02 (); 1")
		1452	unless defined $HAVE_ASYNC_INTERRUPT;
		1453
		1454	$HAVE_ASYNC_INTERRUPT
		1455	}
		1456
		1457	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1458	our (%SIG_ASY, %SIG_ASY_W);
		1459	our ($SIG_COUNT, $SIG_TW);
		1460
		1461	# install a dummy wakeup watcher to reduce signal catching latency
		1462	# used by Impls
		1463	sub _sig_add() {
		1464	unless ($SIG_COUNT++) {
		1465	# try to align timer on a full-second boundary, if possible
		1466	my $NOW = AE::now;
		1467
		1468	$SIG_TW = AE::timer
		1469	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1470	$MAX_SIGNAL_LATENCY,
		1471	sub { } # just for the PERL_ASYNC_CHECK
		1472	;
		1473	}
		1474	}
		1475
		1476	sub _sig_del {
		1477	undef $SIG_TW
		1478	unless --$SIG_COUNT;
		1479	}
		1480
		1481	our $_sig_name_init; $_sig_name_init = sub {
		1482	eval q{ # poor man's autoloading {}
		1483	undef $_sig_name_init;
		1484
		1485	if (_have_async_interrupt) {
		1486	*sig2num = \&Async::Interrupt::sig2num;
		1487	*sig2name = \&Async::Interrupt::sig2name;
		1488	} else {
		1489	require Config;
		1490
		1491	my %signame2num;
		1492	@signame2num{ split ' ', $Config::Config{sig_name} }
		1493	= split ' ', $Config::Config{sig_num};
		1494
		1495	my @signum2name;
		1496	@signum2name[values %signame2num] = keys %signame2num;
		1497
		1498	*sig2num = sub($) {
		1499	$_[0] > 0 ? shift : $signame2num{+shift}
		1500	};
		1501	*sig2name = sub ($) {
		1502	$_[0] > 0 ? $signum2name[+shift] : shift
		1503	};
		1504	}
		1505	};
		1506	die if $@;
		1507	};
		1508
		1509	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1510	sub sig2name($) { &$_sig_name_init; &sig2name }
981		1511
982	sub signal {	1512	sub signal {
		1513	eval q{ # poor man's autoloading {}
		1514	# probe for availability of Async::Interrupt
		1515	if (_have_async_interrupt) {
		1516	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1517
		1518	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1519	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1520
		1521	} else {
		1522	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1523
		1524	if (AnyEvent::WIN32) {
		1525	require AnyEvent::Util;
		1526
		1527	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1528	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1529	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1530	} else {
		1531	pipe $SIGPIPE_R, $SIGPIPE_W;
		1532	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1533	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1534
		1535	# not strictly required, as $^F is normally 2, but let's make sure...
		1536	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1537	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1538	}
		1539
		1540	$SIGPIPE_R
		1541	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1542
		1543	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1544	}
		1545
		1546	*signal = $HAVE_ASYNC_INTERRUPT
		1547	? sub {
983	my (undef, %arg) = @_;	1548	my (undef, %arg) = @_;
984		1549
		1550	# async::interrupt
985	my $signal = uc $arg{signal}	1551	my $signal = sig2num $arg{signal};
986	or Carp::croak "required option 'signal' is missing";
987
988	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1552	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1553
		1554	$SIG_ASY{$signal} ||= new Async::Interrupt
		1555	cb => sub { undef $SIG_EV{$signal} },
		1556	signal => $signal,
		1557	pipe => [$SIGPIPE_R->filenos],
		1558	pipe_autodrain => 0,
		1559	;
		1560
		1561	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1562	}
		1563	: sub {
		1564	my (undef, %arg) = @_;
		1565
		1566	# pure perl
		1567	my $signal = sig2name $arg{signal};
		1568	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1569
989	$SIG{$signal} ||= sub {	1570	$SIG{$signal} ||= sub {
		1571	local $!;
		1572	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1573	undef $SIG_EV{$signal};
		1574	};
		1575
		1576	# can't do signal processing without introducing races in pure perl,
		1577	# so limit the signal latency.
		1578	_sig_add;
		1579
		1580	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1581	}
		1582	;
		1583
		1584	*AnyEvent::Base::signal::DESTROY = sub {
		1585	my ($signal, $cb) = @{$_[0]};
		1586
		1587	_sig_del;
		1588
		1589	delete $SIG_CB{$signal}{$cb};
		1590
		1591	$HAVE_ASYNC_INTERRUPT
		1592	? delete $SIG_ASY{$signal}
		1593	: # delete doesn't work with older perls - they then
		1594	# print weird messages, or just unconditionally exit
		1595	# instead of getting the default action.
		1596	undef $SIG{$signal}
		1597	unless keys %{ $SIG_CB{$signal} };
		1598	};
		1599
		1600	*_signal_exec = sub {
		1601	$HAVE_ASYNC_INTERRUPT
		1602	? $SIGPIPE_R->drain
		1603	: sysread $SIGPIPE_R, (my $dummy), 9;
		1604
		1605	while (%SIG_EV) {
		1606	for (keys %SIG_EV) {
		1607	delete $SIG_EV{$_};
990	$_->() for values %{ $SIG_CB{$signal} || {} };	1608	$_->() for values %{ $SIG_CB{$_} || {} };
		1609	}
		1610	}
		1611	};
991	};	1612	};
		1613	die if $@;
992		1614
993	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1615	&signal
994	}
995
996	sub AnyEvent::Base::Signal::DESTROY {
997	my ($signal, $cb) = @{$_[0]};
998
999	delete $SIG_CB{$signal}{$cb};
1000
1001	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
1002	}	1616	}
1003		1617
1004	# default implementation for ->child	1618	# default implementation for ->child
1005		1619
1006	our %PID_CB;	1620	our %PID_CB;
1007	our $CHLD_W;	1621	our $CHLD_W;
1008	our $CHLD_DELAY_W;	1622	our $CHLD_DELAY_W;
1009	our $PID_IDLE;
1010	our $WNOHANG;
1011		1623
1012	sub _child_wait {	1624	# used by many Impl's
1013	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1625	sub _emit_childstatus($$) {
		1626	my (undef, $rpid, $rstatus) = @_;
		1627
		1628	$_->($rpid, $rstatus)
1014	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1629	for values %{ $PID_CB{$rpid} || {} },
1015	(values %{ $PID_CB{0} || {} });	1630	values %{ $PID_CB{0} || {} };
1016	}
1017
1018	undef $PID_IDLE;
1019	}
1020
1021	sub _sigchld {
1022	# make sure we deliver these changes "synchronous" with the event loop.
1023	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
1024	undef $CHLD_DELAY_W;
1025	&_child_wait;
1026	});
1027	}	1631	}
1028		1632
1029	sub child {	1633	sub child {
		1634	eval q{ # poor man's autoloading {}
		1635	*_sigchld = sub {
		1636	my $pid;
		1637
		1638	AnyEvent->_emit_childstatus ($pid, $?)
		1639	while ($pid = waitpid -1, WNOHANG) > 0;
		1640	};
		1641
		1642	*child = sub {
1030	my (undef, %arg) = @_;	1643	my (undef, %arg) = @_;
1031		1644
1032	defined (my $pid = $arg{pid} + 0)	1645	defined (my $pid = $arg{pid} + 0)
1033	or Carp::croak "required option 'pid' is missing";	1646	or Carp::croak "required option 'pid' is missing";
1034		1647
1035	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1648	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
1036		1649
1037	unless ($WNOHANG) {
1038	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1039	}
1040
1041	unless ($CHLD_W) {	1650	unless ($CHLD_W) {
1042	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1651	$CHLD_W = AE::signal CHLD => \&_sigchld;
1043	# child could be a zombie already, so make at least one round	1652	# child could be a zombie already, so make at least one round
1044	&_sigchld;	1653	&_sigchld;
1045	}	1654	}
1046		1655
1047	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1656	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
1048	}	1657	};
1049		1658
1050	sub AnyEvent::Base::Child::DESTROY {	1659	*AnyEvent::Base::child::DESTROY = sub {
1051	my ($pid, $cb) = @{$_[0]};	1660	my ($pid, $cb) = @{$_[0]};
1052		1661
1053	delete $PID_CB{$pid}{$cb};	1662	delete $PID_CB{$pid}{$cb};
1054	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1663	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1055		1664
1056	undef $CHLD_W unless keys %PID_CB;	1665	undef $CHLD_W unless keys %PID_CB;
		1666	};
		1667	};
		1668	die if $@;
		1669
		1670	&child
		1671	}
		1672
		1673	# idle emulation is done by simply using a timer, regardless
		1674	# of whether the process is idle or not, and not letting
		1675	# the callback use more than 50% of the time.
		1676	sub idle {
		1677	eval q{ # poor man's autoloading {}
		1678	*idle = sub {
		1679	my (undef, %arg) = @_;
		1680
		1681	my ($cb, $w, $rcb) = $arg{cb};
		1682
		1683	$rcb = sub {
		1684	if ($cb) {
		1685	$w = _time;
		1686	&$cb;
		1687	$w = _time - $w;
		1688
		1689	# never use more then 50% of the time for the idle watcher,
		1690	# within some limits
		1691	$w = 0.0001 if $w < 0.0001;
		1692	$w = 5 if $w > 5;
		1693
		1694	$w = AE::timer $w, 0, $rcb;
		1695	} else {
		1696	# clean up...
		1697	undef $w;
		1698	undef $rcb;
		1699	}
		1700	};
		1701
		1702	$w = AE::timer 0.05, 0, $rcb;
		1703
		1704	bless \\$cb, "AnyEvent::Base::idle"
		1705	};
		1706
		1707	*AnyEvent::Base::idle::DESTROY = sub {
		1708	undef $${$_[0]};
		1709	};
		1710	};
		1711	die if $@;
		1712
		1713	&idle
1057	}	1714	}
1058		1715
1059	package AnyEvent::CondVar;	1716	package AnyEvent::CondVar;
1060		1717
1061	our @ISA = AnyEvent::CondVar::Base::;	1718	our @ISA = AnyEvent::CondVar::Base::;
1062		1719
		1720	# only to be used for subclassing
		1721	sub new {
		1722	my $class = shift;
		1723	bless AnyEvent->condvar (@_), $class
		1724	}
		1725
1063	package AnyEvent::CondVar::Base;	1726	package AnyEvent::CondVar::Base;
1064		1727
1065	use overload	1728	#use overload
1066	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1729	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1067	fallback => 1;	1730	# fallback => 1;
		1731
		1732	# save 300+ kilobytes by dirtily hardcoding overloading
		1733	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1734	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1735	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1736	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1737
		1738	our $WAITING;
1068		1739
1069	sub _send {	1740	sub _send {
1070	# nop	1741	# nop
1071	}	1742	}
1072		1743
…		…
1085	sub ready {	1756	sub ready {
1086	$_[0]{_ae_sent}	1757	$_[0]{_ae_sent}
1087	}	1758	}
1088		1759
1089	sub _wait {	1760	sub _wait {
		1761	$WAITING
		1762	and !$_[0]{_ae_sent}
		1763	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1764
		1765	local $WAITING = 1;
1090	AnyEvent->one_event while !$_[0]{_ae_sent};	1766	AnyEvent->one_event while !$_[0]{_ae_sent};
1091	}	1767	}
1092		1768
1093	sub recv {	1769	sub recv {
1094	$_[0]->_wait;	1770	$_[0]->_wait;
…		…
1096	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1772	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
1097	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1773	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
1098	}	1774	}
1099		1775
1100	sub cb {	1776	sub cb {
1101	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1777	my $cv = shift;
		1778
		1779	@_
		1780	and $cv->{_ae_cb} = shift
		1781	and $cv->{_ae_sent}
		1782	and (delete $cv->{_ae_cb})->($cv);
		1783
1102	$_[0]{_ae_cb}	1784	$cv->{_ae_cb}
1103	}	1785	}
1104		1786
1105	sub begin {	1787	sub begin {
1106	++$_[0]{_ae_counter};	1788	++$_[0]{_ae_counter};
1107	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1789	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
…		…
1113	}	1795	}
1114		1796
1115	# undocumented/compatibility with pre-3.4	1797	# undocumented/compatibility with pre-3.4
1116	*broadcast = \&send;	1798	*broadcast = \&send;
1117	*wait = \&_wait;	1799	*wait = \&_wait;
		1800
		1801	=head1 ERROR AND EXCEPTION HANDLING
		1802
		1803	In general, AnyEvent does not do any error handling - it relies on the
		1804	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1805	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1806	checking of all AnyEvent methods, however, which is highly useful during
		1807	development.
		1808
		1809	As for exception handling (i.e. runtime errors and exceptions thrown while
		1810	executing a callback), this is not only highly event-loop specific, but
		1811	also not in any way wrapped by this module, as this is the job of the main
		1812	program.
		1813
		1814	The pure perl event loop simply re-throws the exception (usually
		1815	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1816	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1817	so on.
		1818
		1819	=head1 ENVIRONMENT VARIABLES
		1820
		1821	The following environment variables are used by this module or its
		1822	submodules.
		1823
		1824	Note that AnyEvent will remove I<all> environment variables starting with
		1825	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1826	enabled.
		1827
		1828	=over 4
		1829
		1830	=item C<PERL_ANYEVENT_VERBOSE>
		1831
		1832	By default, AnyEvent will be completely silent except in fatal
		1833	conditions. You can set this environment variable to make AnyEvent more
		1834	talkative.
		1835
		1836	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1837	conditions, such as not being able to load the event model specified by
		1838	C<PERL_ANYEVENT_MODEL>.
		1839
		1840	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1841	model it chooses.
		1842
		1843	When set to C<8> or higher, then AnyEvent will report extra information on
		1844	which optional modules it loads and how it implements certain features.
		1845
		1846	=item C<PERL_ANYEVENT_STRICT>
		1847
		1848	AnyEvent does not do much argument checking by default, as thorough
		1849	argument checking is very costly. Setting this variable to a true value
		1850	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1851	check the arguments passed to most method calls. If it finds any problems,
		1852	it will croak.
		1853
		1854	In other words, enables "strict" mode.
		1855
		1856	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		1857	>>, it is definitely recommended to keep it off in production. Keeping
		1858	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1859	can be very useful, however.
		1860
		1861	=item C<PERL_ANYEVENT_MODEL>
		1862
		1863	This can be used to specify the event model to be used by AnyEvent, before
		1864	auto detection and -probing kicks in. It must be a string consisting
		1865	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1866	and the resulting module name is loaded and if the load was successful,
		1867	used as event model. If it fails to load AnyEvent will proceed with
		1868	auto detection and -probing.
		1869
		1870	This functionality might change in future versions.
		1871
		1872	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1873	could start your program like this:
		1874
		1875	PERL_ANYEVENT_MODEL=Perl perl ...
		1876
		1877	=item C<PERL_ANYEVENT_PROTOCOLS>
		1878
		1879	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1880	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1881	of auto probing).
		1882
		1883	Must be set to a comma-separated list of protocols or address families,
		1884	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1885	used, and preference will be given to protocols mentioned earlier in the
		1886	list.
		1887
		1888	This variable can effectively be used for denial-of-service attacks
		1889	against local programs (e.g. when setuid), although the impact is likely
		1890	small, as the program has to handle conenction and other failures anyways.
		1891
		1892	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1893	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1894	- only support IPv4, never try to resolve or contact IPv6
		1895	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1896	IPv6, but prefer IPv6 over IPv4.
		1897
		1898	=item C<PERL_ANYEVENT_EDNS0>
		1899
		1900	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1901	for DNS. This extension is generally useful to reduce DNS traffic, but
		1902	some (broken) firewalls drop such DNS packets, which is why it is off by
		1903	default.
		1904
		1905	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1906	EDNS0 in its DNS requests.
		1907
		1908	=item C<PERL_ANYEVENT_MAX_FORKS>
		1909
		1910	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1911	will create in parallel.
		1912
		1913	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1914
		1915	The default value for the C<max_outstanding> parameter for the default DNS
		1916	resolver - this is the maximum number of parallel DNS requests that are
		1917	sent to the DNS server.
		1918
		1919	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1920
		1921	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1922	configuration) in the default resolver. When set to the empty string, no
		1923	default config will be used.
		1924
		1925	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1926
		1927	When neither C<ca_file> nor C<ca_path> was specified during
		1928	L<AnyEvent::TLS> context creation, and either of these environment
		1929	variables exist, they will be used to specify CA certificate locations
		1930	instead of a system-dependent default.
		1931
		1932	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1933
		1934	When these are set to C<1>, then the respective modules are not
		1935	loaded. Mostly good for testing AnyEvent itself.
		1936
		1937	=back
1118		1938
1119	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1939	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1120		1940
1121	This is an advanced topic that you do not normally need to use AnyEvent in	1941	This is an advanced topic that you do not normally need to use AnyEvent in
1122	a module. This section is only of use to event loop authors who want to	1942	a module. This section is only of use to event loop authors who want to
…		…
1156		1976
1157	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1977	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1158	condition variables: code blocking while waiting for a condition will	1978	condition variables: code blocking while waiting for a condition will
1159	C<die>. This still works with most modules/usages, and blocking calls must	1979	C<die>. This still works with most modules/usages, and blocking calls must
1160	not be done in an interactive application, so it makes sense.	1980	not be done in an interactive application, so it makes sense.
1161
1162	=head1 ENVIRONMENT VARIABLES
1163
1164	The following environment variables are used by this module:
1165
1166	=over 4
1167
1168	=item C<PERL_ANYEVENT_VERBOSE>
1169
1170	By default, AnyEvent will be completely silent except in fatal
1171	conditions. You can set this environment variable to make AnyEvent more
1172	talkative.
1173
1174	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1175	conditions, such as not being able to load the event model specified by
1176	C<PERL_ANYEVENT_MODEL>.
1177
1178	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1179	model it chooses.
1180
1181	=item C<PERL_ANYEVENT_MODEL>
1182
1183	This can be used to specify the event model to be used by AnyEvent, before
1184	auto detection and -probing kicks in. It must be a string consisting
1185	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1186	and the resulting module name is loaded and if the load was successful,
1187	used as event model. If it fails to load AnyEvent will proceed with
1188	auto detection and -probing.
1189
1190	This functionality might change in future versions.
1191
1192	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1193	could start your program like this:
1194
1195	PERL_ANYEVENT_MODEL=Perl perl ...
1196
1197	=item C<PERL_ANYEVENT_PROTOCOLS>
1198
1199	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1200	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1201	of auto probing).
1202
1203	Must be set to a comma-separated list of protocols or address families,
1204	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1205	used, and preference will be given to protocols mentioned earlier in the
1206	list.
1207
1208	This variable can effectively be used for denial-of-service attacks
1209	against local programs (e.g. when setuid), although the impact is likely
1210	small, as the program has to handle connection errors already-
1211
1212	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1213	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1214	- only support IPv4, never try to resolve or contact IPv6
1215	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1216	IPv6, but prefer IPv6 over IPv4.
1217
1218	=item C<PERL_ANYEVENT_EDNS0>
1219
1220	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1221	for DNS. This extension is generally useful to reduce DNS traffic, but
1222	some (broken) firewalls drop such DNS packets, which is why it is off by
1223	default.
1224
1225	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1226	EDNS0 in its DNS requests.
1227
1228	=item C<PERL_ANYEVENT_MAX_FORKS>
1229
1230	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1231	will create in parallel.
1232
1233	=back
1234		1981
1235	=head1 EXAMPLE PROGRAM	1982	=head1 EXAMPLE PROGRAM
1236		1983
1237	The following program uses an I/O watcher to read data from STDIN, a timer	1984	The following program uses an I/O watcher to read data from STDIN, a timer
1238	to display a message once per second, and a condition variable to quit the	1985	to display a message once per second, and a condition variable to quit the
…		…
1251	warn "read: $input\n"; # output what has been read	1998	warn "read: $input\n"; # output what has been read
1252	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1999	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1253	},	2000	},
1254	);	2001	);
1255		2002
1256	my $time_watcher; # can only be used once
1257
1258	sub new_timer {
1259	$timer = AnyEvent->timer (after => 1, cb => sub {	2003	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1260	warn "timeout\n"; # print 'timeout' about every second	2004	warn "timeout\n"; # print 'timeout' at most every second
1261	&new_timer; # and restart the time
1262	});	2005	});
1263	}
1264
1265	new_timer; # create first timer
1266		2006
1267	$cv->recv; # wait until user enters /^q/i	2007	$cv->recv; # wait until user enters /^q/i
1268		2008
1269	=head1 REAL-WORLD EXAMPLE	2009	=head1 REAL-WORLD EXAMPLE
1270		2010
…		…
1343		2083
1344	The actual code goes further and collects all errors (C<die>s, exceptions)	2084	The actual code goes further and collects all errors (C<die>s, exceptions)
1345	that occurred during request processing. The C<result> method detects	2085	that occurred during request processing. The C<result> method detects
1346	whether an exception as thrown (it is stored inside the $txn object)	2086	whether an exception as thrown (it is stored inside the $txn object)
1347	and just throws the exception, which means connection errors and other	2087	and just throws the exception, which means connection errors and other
1348	problems get reported tot he code that tries to use the result, not in a	2088	problems get reported to the code that tries to use the result, not in a
1349	random callback.	2089	random callback.
1350		2090
1351	All of this enables the following usage styles:	2091	All of this enables the following usage styles:
1352		2092
1353	1. Blocking:	2093	1. Blocking:
…		…
1401	through AnyEvent. The benchmark creates a lot of timers (with a zero	2141	through AnyEvent. The benchmark creates a lot of timers (with a zero
1402	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2142	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1403	which it is), lets them fire exactly once and destroys them again.	2143	which it is), lets them fire exactly once and destroys them again.
1404		2144
1405	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2145	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1406	distribution.	2146	distribution. It uses the L<AE> interface, which makes a real difference
		2147	for the EV and Perl backends only.
1407		2148
1408	=head3 Explanation of the columns	2149	=head3 Explanation of the columns
1409		2150
1410	I<watcher> is the number of event watchers created/destroyed. Since	2151	I<watcher> is the number of event watchers created/destroyed. Since
1411	different event models feature vastly different performances, each event	2152	different event models feature vastly different performances, each event
…		…
1432	watcher.	2173	watcher.
1433		2174
1434	=head3 Results	2175	=head3 Results
1435		2176
1436	name watchers bytes create invoke destroy comment	2177	name watchers bytes create invoke destroy comment
1437	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2178	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1438	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2179	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1439	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2180	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1440	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2181	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1441	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2182	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1442	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2183	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2184	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2185	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1443	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2186	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1444	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2187	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1445	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2188	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1446	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2189	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1447		2190
1448	=head3 Discussion	2191	=head3 Discussion
1449		2192
1450	The benchmark does I<not> measure scalability of the event loop very	2193	The benchmark does I<not> measure scalability of the event loop very
1451	well. For example, a select-based event loop (such as the pure perl one)	2194	well. For example, a select-based event loop (such as the pure perl one)
…		…
1463	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2206	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1464	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2207	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1465	cycles with POE.	2208	cycles with POE.
1466		2209
1467	C<EV> is the sole leader regarding speed and memory use, which are both	2210	C<EV> is the sole leader regarding speed and memory use, which are both
1468	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2211	maximal/minimal, respectively. When using the L<AE> API there is zero
		2212	overhead (when going through the AnyEvent API create is about 5-6 times
		2213	slower, with other times being equal, so still uses far less memory than
1469	far less memory than any other event loop and is still faster than Event	2214	any other event loop and is still faster than Event natively).
1470	natively.
1471		2215
1472	The pure perl implementation is hit in a few sweet spots (both the	2216	The pure perl implementation is hit in a few sweet spots (both the
1473	constant timeout and the use of a single fd hit optimisations in the perl	2217	constant timeout and the use of a single fd hit optimisations in the perl
1474	interpreter and the backend itself). Nevertheless this shows that it	2218	interpreter and the backend itself). Nevertheless this shows that it
1475	adds very little overhead in itself. Like any select-based backend its	2219	adds very little overhead in itself. Like any select-based backend its
1476	performance becomes really bad with lots of file descriptors (and few of	2220	performance becomes really bad with lots of file descriptors (and few of
1477	them active), of course, but this was not subject of this benchmark.	2221	them active), of course, but this was not subject of this benchmark.
1478		2222
1479	The C<Event> module has a relatively high setup and callback invocation	2223	The C<Event> module has a relatively high setup and callback invocation
1480	cost, but overall scores in on the third place.	2224	cost, but overall scores in on the third place.
		2225
		2226	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2227	when using its pure perl backend.
1481		2228
1482	C<Glib>'s memory usage is quite a bit higher, but it features a	2229	C<Glib>'s memory usage is quite a bit higher, but it features a
1483	faster callback invocation and overall ends up in the same class as	2230	faster callback invocation and overall ends up in the same class as
1484	C<Event>. However, Glib scales extremely badly, doubling the number of	2231	C<Event>. However, Glib scales extremely badly, doubling the number of
1485	watchers increases the processing time by more than a factor of four,	2232	watchers increases the processing time by more than a factor of four,
…		…
1546	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100	2293	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1547	(1%) are active. This mirrors the activity of large servers with many	2294	(1%) are active. This mirrors the activity of large servers with many
1548	connections, most of which are idle at any one point in time.	2295	connections, most of which are idle at any one point in time.
1549		2296
1550	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2297	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1551	distribution.	2298	distribution. It uses the L<AE> interface, which makes a real difference
		2299	for the EV and Perl backends only.
1552		2300
1553	=head3 Explanation of the columns	2301	=head3 Explanation of the columns
1554		2302
1555	I<sockets> is the number of sockets, and twice the number of "servers" (as	2303	I<sockets> is the number of sockets, and twice the number of "servers" (as
1556	each server has a read and write socket end).	2304	each server has a read and write socket end).
…		…
1563	it to another server. This includes deleting the old timeout and creating	2311	it to another server. This includes deleting the old timeout and creating
1564	a new one that moves the timeout into the future.	2312	a new one that moves the timeout into the future.
1565		2313
1566	=head3 Results	2314	=head3 Results
1567		2315
1568	name sockets create request	2316	name sockets create request
1569	EV 20000 69.01 11.16	2317	EV 20000 62.66 7.99
1570	Perl 20000 73.32 35.87	2318	Perl 20000 68.32 32.64
1571	Event 20000 212.62 257.32	2319	IOAsync 20000 174.06 101.15 epoll
1572	Glib 20000 651.16 1896.30	2320	IOAsync 20000 174.67 610.84 poll
		2321	Event 20000 202.69 242.91
		2322	Glib 20000 557.01 1689.52
1573	POE 20000 349.67 12317.24 uses POE::Loop::Event	2323	POE 20000 341.54 12086.32 uses POE::Loop::Event
1574		2324
1575	=head3 Discussion	2325	=head3 Discussion
1576		2326
1577	This benchmark I<does> measure scalability and overall performance of the	2327	This benchmark I<does> measure scalability and overall performance of the
1578	particular event loop.	2328	particular event loop.
…		…
1580	EV is again fastest. Since it is using epoll on my system, the setup time	2330	EV is again fastest. Since it is using epoll on my system, the setup time
1581	is relatively high, though.	2331	is relatively high, though.
1582		2332
1583	Perl surprisingly comes second. It is much faster than the C-based event	2333	Perl surprisingly comes second. It is much faster than the C-based event
1584	loops Event and Glib.	2334	loops Event and Glib.
		2335
		2336	IO::Async performs very well when using its epoll backend, and still quite
		2337	good compared to Glib when using its pure perl backend.
1585		2338
1586	Event suffers from high setup time as well (look at its code and you will	2339	Event suffers from high setup time as well (look at its code and you will
1587	understand why). Callback invocation also has a high overhead compared to	2340	understand why). Callback invocation also has a high overhead compared to
1588	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2341	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1589	uses select or poll in basically all documented configurations.	2342	uses select or poll in basically all documented configurations.
…		…
1652	=item * C-based event loops perform very well with small number of	2405	=item * C-based event loops perform very well with small number of
1653	watchers, as the management overhead dominates.	2406	watchers, as the management overhead dominates.
1654		2407
1655	=back	2408	=back
1656		2409
		2410	=head2 THE IO::Lambda BENCHMARK
		2411
		2412	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2413	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2414	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2415	shouldn't come as a surprise to anybody). As such, the benchmark is
		2416	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2417	very optimal. But how would AnyEvent compare when used without the extra
		2418	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2419
		2420	The benchmark itself creates an echo-server, and then, for 500 times,
		2421	connects to the echo server, sends a line, waits for the reply, and then
		2422	creates the next connection. This is a rather bad benchmark, as it doesn't
		2423	test the efficiency of the framework or much non-blocking I/O, but it is a
		2424	benchmark nevertheless.
		2425
		2426	name runtime
		2427	Lambda/select 0.330 sec
		2428	+ optimized 0.122 sec
		2429	Lambda/AnyEvent 0.327 sec
		2430	+ optimized 0.138 sec
		2431	Raw sockets/select 0.077 sec
		2432	POE/select, components 0.662 sec
		2433	POE/select, raw sockets 0.226 sec
		2434	POE/select, optimized 0.404 sec
		2435
		2436	AnyEvent/select/nb 0.085 sec
		2437	AnyEvent/EV/nb 0.068 sec
		2438	+state machine 0.134 sec
		2439
		2440	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2441	benchmarks actually make blocking connects and use 100% blocking I/O,
		2442	defeating the purpose of an event-based solution. All of the newly
		2443	written AnyEvent benchmarks use 100% non-blocking connects (using
		2444	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2445	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2446	generally require a lot more bookkeeping and event handling than blocking
		2447	connects (which involve a single syscall only).
		2448
		2449	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2450	offers similar expressive power as POE and IO::Lambda, using conventional
		2451	Perl syntax. This means that both the echo server and the client are 100%
		2452	non-blocking, further placing it at a disadvantage.
		2453
		2454	As you can see, the AnyEvent + EV combination even beats the
		2455	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2456	backend easily beats IO::Lambda and POE.
		2457
		2458	And even the 100% non-blocking version written using the high-level (and
		2459	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2460	higher level ("unoptimised") abstractions by a large margin, even though
		2461	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2462
		2463	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2464	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2465	part of the IO::Lambda distribution and were used without any changes.
		2466
		2467
		2468	=head1 SIGNALS
		2469
		2470	AnyEvent currently installs handlers for these signals:
		2471
		2472	=over 4
		2473
		2474	=item SIGCHLD
		2475
		2476	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2477	emulation for event loops that do not support them natively. Also, some
		2478	event loops install a similar handler.
		2479
		2480	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2481	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2482
		2483	=item SIGPIPE
		2484
		2485	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2486	when AnyEvent gets loaded.
		2487
		2488	The rationale for this is that AnyEvent users usually do not really depend
		2489	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2490	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2491	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2492	some random socket.
		2493
		2494	The rationale for installing a no-op handler as opposed to ignoring it is
		2495	that this way, the handler will be restored to defaults on exec.
		2496
		2497	Feel free to install your own handler, or reset it to defaults.
		2498
		2499	=back
		2500
		2501	=cut
		2502
		2503	undef $SIG{CHLD}
		2504	if $SIG{CHLD} eq 'IGNORE';
		2505
		2506	$SIG{PIPE} = sub { }
		2507	unless defined $SIG{PIPE};
		2508
		2509	=head1 RECOMMENDED/OPTIONAL MODULES
		2510
		2511	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2512	its built-in modules) are required to use it.
		2513
		2514	That does not mean that AnyEvent won't take advantage of some additional
		2515	modules if they are installed.
		2516
		2517	This section explains which additional modules will be used, and how they
		2518	affect AnyEvent's operation.
		2519
		2520	=over 4
		2521
		2522	=item L<Async::Interrupt>
		2523
		2524	This slightly arcane module is used to implement fast signal handling: To
		2525	my knowledge, there is no way to do completely race-free and quick
		2526	signal handling in pure perl. To ensure that signals still get
		2527	delivered, AnyEvent will start an interval timer to wake up perl (and
		2528	catch the signals) with some delay (default is 10 seconds, look for
		2529	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2530
		2531	If this module is available, then it will be used to implement signal
		2532	catching, which means that signals will not be delayed, and the event loop
		2533	will not be interrupted regularly, which is more efficient (and good for
		2534	battery life on laptops).
		2535
		2536	This affects not just the pure-perl event loop, but also other event loops
		2537	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2538
		2539	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2540	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2541	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2542	does nothing for those backends.
		2543
		2544	=item L<EV>
		2545
		2546	This module isn't really "optional", as it is simply one of the backend
		2547	event loops that AnyEvent can use. However, it is simply the best event
		2548	loop available in terms of features, speed and stability: It supports
		2549	the AnyEvent API optimally, implements all the watcher types in XS, does
		2550	automatic timer adjustments even when no monotonic clock is available,
		2551	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2552	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2553	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2554
		2555	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2556	then this module will do nothing for you.
		2557
		2558	=item L<Guard>
		2559
		2560	The guard module, when used, will be used to implement
		2561	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2562	lot less memory), but otherwise doesn't affect guard operation much. It is
		2563	purely used for performance.
		2564
		2565	=item L<JSON> and L<JSON::XS>
		2566
		2567	One of these modules is required when you want to read or write JSON data
		2568	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2569	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2570
		2571	=item L<Net::SSLeay>
		2572
		2573	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2574	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2575	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2576
		2577	=item L<Time::HiRes>
		2578
		2579	This module is part of perl since release 5.008. It will be used when the
		2580	chosen event library does not come with a timing source of its own. The
		2581	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2582	try to use a monotonic clock for timing stability.
		2583
		2584	=back
		2585
1657		2586
1658	=head1 FORK	2587	=head1 FORK
1659		2588
1660	Most event libraries are not fork-safe. The ones who are usually are	2589	Most event libraries are not fork-safe. The ones who are usually are
1661	because they rely on inefficient but fork-safe C<select> or C<poll>	2590	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1662	calls. Only L<EV> is fully fork-aware.	2591	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2592	are usually badly thought-out hacks that are incompatible with fork in
		2593	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2594	continue event-processing in both parent and child (or both, if you know
		2595	what you are doing).
		2596
		2597	This means that, in general, you cannot fork and do event processing in
		2598	the child if the event library was initialised before the fork (which
		2599	usually happens when the first AnyEvent watcher is created, or the library
		2600	is loaded).
1663		2601
1664	If you have to fork, you must either do so I<before> creating your first	2602	If you have to fork, you must either do so I<before> creating your first
1665	watcher OR you must not use AnyEvent at all in the child.	2603	watcher OR you must not use AnyEvent at all in the child OR you must do
		2604	something completely out of the scope of AnyEvent.
		2605
		2606	The problem of doing event processing in the parent I<and> the child
		2607	is much more complicated: even for backends that I<are> fork-aware or
		2608	fork-safe, their behaviour is not usually what you want: fork clones all
		2609	watchers, that means all timers, I/O watchers etc. are active in both
		2610	parent and child, which is almost never what you want. USing C<exec>
		2611	to start worker children from some kind of manage rprocess is usually
		2612	preferred, because it is much easier and cleaner, at the expense of having
		2613	to have another binary.
1666		2614
1667		2615
1668	=head1 SECURITY CONSIDERATIONS	2616	=head1 SECURITY CONSIDERATIONS
1669		2617
1670	AnyEvent can be forced to load any event model via	2618	AnyEvent can be forced to load any event model via
…		…
1681		2629
1682	use AnyEvent;	2630	use AnyEvent;
1683		2631
1684	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2632	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1685	be used to probe what backend is used and gain other information (which is	2633	be used to probe what backend is used and gain other information (which is
1686	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2634	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2635	$ENV{PERL_ANYEVENT_STRICT}.
		2636
		2637	Note that AnyEvent will remove I<all> environment variables starting with
		2638	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2639	enabled.
1687		2640
1688		2641
1689	=head1 BUGS	2642	=head1 BUGS
1690		2643
1691	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard	2644	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
1692	to work around. If you suffer from memleaks, first upgrade to Perl 5.10	2645	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
1693	and check wether the leaks still show up. (Perl 5.10.0 has other annoying	2646	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
1694	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as	2647	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
1695	pronounced).	2648	pronounced).
1696		2649
1697		2650
1698	=head1 SEE ALSO	2651	=head1 SEE ALSO
		2652
		2653	Tutorial/Introduction: L<AnyEvent::Intro>.
		2654
		2655	FAQ: L<AnyEvent::FAQ>.
1699		2656
1700	Utility functions: L<AnyEvent::Util>.	2657	Utility functions: L<AnyEvent::Util>.
1701		2658
1702	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2659	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1703	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2660	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1704		2661
1705	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2662	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1706	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2663	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1707	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2664	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1708	L<AnyEvent::Impl::POE>.	2665	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1709		2666
1710	Non-blocking file handles, sockets, TCP clients and	2667	Non-blocking file handles, sockets, TCP clients and
1711	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2668	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1712		2669
1713	Asynchronous DNS: L<AnyEvent::DNS>.	2670	Asynchronous DNS: L<AnyEvent::DNS>.
1714		2671
1715	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2672	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
1716		2673
1717	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2674	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2675	L<AnyEvent::HTTP>.
1718		2676
1719		2677
1720	=head1 AUTHOR	2678	=head1 AUTHOR
1721		2679
1722	Marc Lehmann <schmorp@schmorp.de>	2680	Marc Lehmann <schmorp@schmorp.de>

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