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Revision 1.340 by root, Fri Dec 3 18:39:06 2010 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	38	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
		40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
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 + IO::Async? No go. Tk + Event? No go. Again: if
60	your module uses one of those, every user of your module has to use it,	91	your module uses one of those, every user of your module has to use it,
61	too. But if your module uses AnyEvent, it works transparently with all	92	too. But if your module uses AnyEvent, it works transparently with all
62	event models it supports (including stuff like POE and IO::Async, as long	93	event models it supports (including stuff like IO::Async, as long as those
63	as those use one of the supported event loops. It is trivial to add new	94	use one of the supported event loops. It is easy to add new event loops
64	event loops to AnyEvent, too, so it is future-proof).	95	to AnyEvent, too, 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 strictly positive number (> 0), then the	254	parameter, C<interval>, as a strictly positive number (> 0), then the
199	callback will be invoked regularly at that interval (in fractional	255	callback will be invoked regularly at that interval (in fractional
200	seconds) after the first invocation. If C<interval> is specified with a	256	seconds) after the first invocation. If C<interval> is specified with a
201	false value, then it is treated as if it were missing.	257	false value, then it is treated as if it were not specified at all.
202		258
203	The callback will be rescheduled before invoking the callback, but no	259	The callback will be rescheduled before invoking the callback, but no
204	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
205	only approximate.	261	only approximate.
206		262
207	Example: fire an event after 7.7 seconds.	263	Example: fire an event after 7.7 seconds.
208		264
209	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
227		283
228	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
229	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
230	"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
231	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
232	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.
233		289
234	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
235	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
236	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)
237	timers.	293	timers.
238		294
239	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
240	AnyEvent API.	296	AnyEvent API.
…		…
262	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
263	function to call when you want to know the current time.>	319	function to call when you want to know the current time.>
264		320
265	This function is also often faster then C<< AnyEvent->time >>, and	321	This function is also often faster then C<< AnyEvent->time >>, and
266	thus the preferred method if you want some timestamp (for example,	322	thus the preferred method if you want some timestamp (for example,
267	L<AnyEvent::Handle> uses this to update it's activity timeouts).	323	L<AnyEvent::Handle> uses this to update its activity timeouts).
268		324
269	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
270	with your timing, you can skip it without bad conscience.	326	with your timing; you can skip it without a bad conscience.
271		327
272	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>
273	and L<EV> and the following set-up:	329	and L<EV> and the following set-up:
274		330
275	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
276	time=500 (assume no other callbacks delay processing). In your callback,	332	time=500 (assume no other callbacks delay processing). In your callback,
277	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
278	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
279	after three seconds.	335	after three seconds.
280		336
…		…
298	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
299	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
300	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
301	account.	357	account.
302		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
303	=back	381	=back
304		382
305	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
306		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
307	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
308	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
309	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
310		390
311	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
312	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
313	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
314		394
…		…
316	invocation, and callback invocation will be synchronous. Synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
317	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,
318	but it is guaranteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
319		399
320	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
321	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
322		403
323	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
324	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
325		407
326	Example: exit on SIGINT	408	Example: exit on SIGINT
327		409
328	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
329		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$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
330	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
331		450
		451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		452
332	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.
333		454
334	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,
335	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
336	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
337	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
338	and exit status (as returned by waitpid), so unlike other watcher types,	459	(stopped/continued).
339	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).
340		469
341	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
342	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
343	have exited already (and no SIGCHLD will be sent anymore).	472	have exited already (and no SIGCHLD will be sent anymore).
344		473
345	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
346	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
347	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.
348		480
349	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
350	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
351	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.
352		489
353	Example: fork a process and wait for it	490	Example: fork a process and wait for it
354		491
355	my $done = AnyEvent->condvar;	492	my $done = AnyEvent->condvar;
356		493
…		…
366	);	503	);
367		504
368	# do something else, then wait for process exit	505	# do something else, then wait for process exit
369	$done->recv;	506	$done->recv;
370		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
371	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
372		554
373	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
374	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
375	will actively watch for new events and call your callbacks.	557	will actively watch for new events and call your callbacks.
376		558
377	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
378	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).
379		561
380	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
381	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.
382		566
383	Condition variables can be created by calling the C<< AnyEvent->condvar	567	Condition variables can be created by calling the C<< AnyEvent->condvar
384	>> method, usually without arguments. The only argument pair allowed is	568	>> method, usually without arguments. The only argument pair allowed is
385	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
386	becomes true.	570	becomes true, with the condition variable as the first argument (but not
		571	the results).
387		572
388	After creation, the condition variable is "false" until it becomes "true"	573	After creation, the condition variable is "false" until it becomes "true"
389	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
390	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<<
391	->send >> method).	576	->send >> method).
392		577
393	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
394	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:
395	in time where multiple outstanding events have been processed. And yet	580
396	another way to call them is transactions - each condition variable can be	581	=over 4
397	used to represent a transaction, which finishes at some point and delivers	582
398	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
399		601
400	Condition variables are very useful to signal that something has finished,	602	Condition variables are very useful to signal that something has finished,
401	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,
402	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
403	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
…		…
416		618
417	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
418	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
419	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
420	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
421	it's C<new> method in your own C<new> method.	623	its C<new> method in your own C<new> method.
422		624
423	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
424	eventually calls C<< -> send >>, and the "consumer side", which waits	626	eventually calls C<< -> send >>, and the "consumer side", which waits
425	for the send to occur.	627	for the send to occur.
426		628
427	Example: wait for a timer.	629	Example: wait for a timer.
428		630
429	# wait till the result is ready	631	# condition: "wait till the timer is fired"
430	my $result_ready = AnyEvent->condvar;	632	my $timer_fired = AnyEvent->condvar;
431		633
432	# do something such as adding a timer	634	# create the timer - we could wait for, say
433	# or socket watcher the calls $result_ready->send	635	# a handle becomign ready, or even an
434	# when the "result" is ready.	636	# AnyEvent::HTTP request to finish, but
435	# in this case, we simply use a timer:	637	# in this case, we simply use a timer:
436	my $w = AnyEvent->timer (	638	my $w = AnyEvent->timer (
437	after => 1,	639	after => 1,
438	cb => sub { $result_ready->send },	640	cb => sub { $timer_fired->send },
439	);	641	);
440		642
441	# this "blocks" (while handling events) till the callback	643	# this "blocks" (while handling events) till the callback
442	# calls send	644	# calls ->send
443	$result_ready->recv;	645	$timer_fired->recv;
444		646
445	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
446	condition variables are also code references.	648	variables are also callable directly.
447		649
448	my $done = AnyEvent->condvar;	650	my $done = AnyEvent->condvar;
449	my $delay = AnyEvent->timer (after => 5, cb => $done);	651	my $delay = AnyEvent->timer (after => 5, cb => $done);
450	$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	});
451		670
452	=head3 METHODS FOR PRODUCERS	671	=head3 METHODS FOR PRODUCERS
453		672
454	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
455	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
…		…
468	immediately from within send.	687	immediately from within send.
469		688
470	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
471	future C<< ->recv >> calls.	690	future C<< ->recv >> calls.
472		691
473	Condition variables are overloaded so one can call them directly	692	Condition variables are overloaded so one can call them directly (as if
474	(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
475	C<send>. Note, however, that many C-based event loops do not handle	694	C<send>.
476	overloading, so as tempting as it may be, passing a condition variable
477	instead of a callback does not work. Both the pure perl and EV loops
478	support overloading, however, as well as all functions that use perl to
479	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
480	example).
481		695
482	=item $cv->croak ($error)	696	=item $cv->croak ($error)
483		697
484	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
485	C<Carp::croak> with the given error message/object/scalar.	699	C<Carp::croak> with the given error message/object/scalar.
486		700
487	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
488	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.
489		707
490	=item $cv->begin ([group callback])	708	=item $cv->begin ([group callback])
491		709
492	=item $cv->end	710	=item $cv->end
493
494	These two methods are EXPERIMENTAL and MIGHT CHANGE.
495		711
496	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
497	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
498	to use a condition variable for the whole process.	714	to use a condition variable for the whole process.
499		715
500	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
501	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
502	>>, 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
503	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
504	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.
505		722
506	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:
507		730
508	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
509		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
510	my %result;	757	my %result;
511	$cv->begin (sub { $cv->send (\%result) });	758	$cv->begin (sub { shift->send (\%result) });
512		759
513	for my $host (@list_of_hosts) {	760	for my $host (@list_of_hosts) {
514	$cv->begin;	761	$cv->begin;
515	ping_host_then_call_callback $host, sub {	762	ping_host_then_call_callback $host, sub {
516	$result{$host} = ...;	763	$result{$host} = ...;
…		…
531	loop, which serves two important purposes: first, it sets the callback	778	loop, which serves two important purposes: first, it sets the callback
532	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
533	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
534	doesn't execute once).	781	doesn't execute once).
535		782
536	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
537	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
538	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
539	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>.
540		788
541	=back	789	=back
542		790
543	=head3 METHODS FOR CONSUMERS	791	=head3 METHODS FOR CONSUMERS
544		792
…		…
548	=over 4	796	=over 4
549		797
550	=item $cv->recv	798	=item $cv->recv
551		799
552	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
553	>> methods have been called on c<$cv>, while servicing other watchers	801	>> methods have been called on C<$cv>, while servicing other watchers
554	normally.	802	normally.
555		803
556	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
557	will return immediately.	805	will return immediately.
558		806
…		…
560	function will call C<croak>.	808	function will call C<croak>.
561		809
562	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,
563	in scalar context only the first one will be returned.	811	in scalar context only the first one will be returned.
564		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
565	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
566	(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
567	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
568	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
569	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
570	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,
571	while still supporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
572		827
573	Another reason I<never> to C<< ->recv >> in a module is that you cannot
574	sensibly have two C<< ->recv >>'s in parallel, as that would require
575	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
576	can supply.
577
578	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
579	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
580	versions and also integrates coroutines into AnyEvent, making blocking
581	C<< ->recv >> calls perfectly safe as long as they are done from another
582	coroutine (one that doesn't run the event loop).
583
584	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
585	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
586	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
587	waits otherwise.	831	waits otherwise.
588		832
589	=item $bool = $cv->ready	833	=item $bool = $cv->ready
590		834
591	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
592	C<croak> have been called.	836	C<croak> have been called.
593		837
594	=item $cb = $cv->cb ([new callback])	838	=item $cb = $cv->cb ($cb->($cv))
595		839
596	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
597	replaces it before doing so.	841	replaces it before doing so.
598		842
599	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
600	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
601	variable itself. Calling C<recv> inside the callback or at any later time	845	condition variable itself. If the condition is already true, the
602	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.
603		848
604	=back	849	=back
605		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
		882	=item Backends with special needs.
		883
		884	Qt requires the Qt::Application to be instantiated first, but will
		885	otherwise be picked up automatically. As long as the main program
		886	instantiates the application before any AnyEvent watchers are created,
		887	everything should just work.
		888
		889	AnyEvent::Impl::Qt based on Qt.
		890
		891	Support for IO::Async can only be partial, as it is too broken and
		892	architecturally limited to even support the AnyEvent API. It also
		893	is the only event loop that needs the loop to be set explicitly, so
		894	it can only be used by a main program knowing about AnyEvent. See
		895	L<AnyEvent::Impl::IOAsync> for the gory details.
		896
		897	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		898
		899	=item Event loops that are indirectly supported via other backends.
		900
		901	Some event loops can be supported via other modules:
		902
		903	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		904
		905	B<WxWidgets> has no support for watching file handles. However, you can
		906	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		907	polls 20 times per second, which was considered to be too horrible to even
		908	consider for AnyEvent.
		909
		910	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		911	backend, so it can be supported through POE.
		912
		913	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		914	load L<POE> when detecting them, in the hope that POE will pick them up,
		915	in which case everything will be automatic.
		916
		917	=back
		918
606	=head1 GLOBAL VARIABLES AND FUNCTIONS	919	=head1 GLOBAL VARIABLES AND FUNCTIONS
607		920
		921	These are not normally required to use AnyEvent, but can be useful to
		922	write AnyEvent extension modules.
		923
608	=over 4	924	=over 4
609		925
610	=item $AnyEvent::MODEL	926	=item $AnyEvent::MODEL
611		927
612	Contains C<undef> until the first watcher is being created. Then it	928	Contains C<undef> until the first watcher is being created, before the
		929	backend has been autodetected.
		930
613	contains the event model that is being used, which is the name of the	931	Afterwards it contains the event model that is being used, which is the
614	Perl class implementing the model. This class is usually one of the	932	name of the Perl class implementing the model. This class is usually one
615	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	933	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
616	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	934	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
617		935	will be C<urxvt::anyevent>).
618	The known classes so far are:
619
620	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
621	AnyEvent::Impl::Event based on Event, second best choice.
622	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
623	AnyEvent::Impl::Glib based on Glib, third-best choice.
624	AnyEvent::Impl::Tk based on Tk, very bad choice.
625	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
626	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
627	AnyEvent::Impl::POE based on POE, not generic enough for full support.
628
629	There is no support for WxWidgets, as WxWidgets has no support for
630	watching file handles. However, you can use WxWidgets through the
631	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
632	second, which was considered to be too horrible to even consider for
633	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
634	it's adaptor.
635
636	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
637	autodetecting them.
638		936
639	=item AnyEvent::detect	937	=item AnyEvent::detect
640		938
641	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	939	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
642	if necessary. You should only call this function right before you would	940	if necessary. You should only call this function right before you would
643	have created an AnyEvent watcher anyway, that is, as late as possible at	941	have created an AnyEvent watcher anyway, that is, as late as possible at
644	runtime.	942	runtime, and not e.g. during initialisation of your module.
		943
		944	If you need to do some initialisation before AnyEvent watchers are
		945	created, use C<post_detect>.
645		946
646	=item $guard = AnyEvent::post_detect { BLOCK }	947	=item $guard = AnyEvent::post_detect { BLOCK }
647		948
648	Arranges for the code block to be executed as soon as the event model is	949	Arranges for the code block to be executed as soon as the event model is
649	autodetected (or immediately if this has already happened).	950	autodetected (or immediately if that has already happened).
		951
		952	The block will be executed I<after> the actual backend has been detected
		953	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		954	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		955	other initialisations - see the sources of L<AnyEvent::Strict> or
		956	L<AnyEvent::AIO> to see how this is used.
		957
		958	The most common usage is to create some global watchers, without forcing
		959	event module detection too early, for example, L<AnyEvent::AIO> creates
		960	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		961	avoid autodetecting the event module at load time.
650		962
651	If called in scalar or list context, then it creates and returns an object	963	If called in scalar or list context, then it creates and returns an object
652	that automatically removes the callback again when it is destroyed. See	964	that automatically removes the callback again when it is destroyed (or
		965	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
653	L<Coro::BDB> for a case where this is useful.	966	a case where this is useful.
		967
		968	Example: Create a watcher for the IO::AIO module and store it in
		969	C<$WATCHER>, but do so only do so after the event loop is initialised.
		970
		971	our WATCHER;
		972
		973	my $guard = AnyEvent::post_detect {
		974	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		975	};
		976
		977	# the ||= is important in case post_detect immediately runs the block,
		978	# as to not clobber the newly-created watcher. assigning both watcher and
		979	# post_detect guard to the same variable has the advantage of users being
		980	# able to just C<undef $WATCHER> if the watcher causes them grief.
		981
		982	$WATCHER ||= $guard;
654		983
655	=item @AnyEvent::post_detect	984	=item @AnyEvent::post_detect
656		985
657	If there are any code references in this array (you can C<push> to it	986	If there are any code references in this array (you can C<push> to it
658	before or after loading AnyEvent), then they will called directly after	987	before or after loading AnyEvent), then they will be called directly
659	the event loop has been chosen.	988	after the event loop has been chosen.
660		989
661	You should check C<$AnyEvent::MODEL> before adding to this array, though:	990	You should check C<$AnyEvent::MODEL> before adding to this array, though:
662	if it contains a true value then the event loop has already been detected,	991	if it is defined then the event loop has already been detected, and the
663	and the array will be ignored.	992	array will be ignored.
664		993
665	Best use C<AnyEvent::post_detect { BLOCK }> instead.	994	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		995	it, as it takes care of these details.
		996
		997	This variable is mainly useful for modules that can do something useful
		998	when AnyEvent is used and thus want to know when it is initialised, but do
		999	not need to even load it by default. This array provides the means to hook
		1000	into AnyEvent passively, without loading it.
		1001
		1002	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1003	together, you could put this into Coro (this is the actual code used by
		1004	Coro to accomplish this):
		1005
		1006	if (defined $AnyEvent::MODEL) {
		1007	# AnyEvent already initialised, so load Coro::AnyEvent
		1008	require Coro::AnyEvent;
		1009	} else {
		1010	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1011	# as soon as it is
		1012	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1013	}
666		1014
667	=back	1015	=back
668		1016
669	=head1 WHAT TO DO IN A MODULE	1017	=head1 WHAT TO DO IN A MODULE
670		1018
…		…
681	because it will stall the whole program, and the whole point of using	1029	because it will stall the whole program, and the whole point of using
682	events is to stay interactive.	1030	events is to stay interactive.
683		1031
684	It is fine, however, to call C<< ->recv >> when the user of your module	1032	It is fine, however, to call C<< ->recv >> when the user of your module
685	requests it (i.e. if you create a http request object ad have a method	1033	requests it (i.e. if you create a http request object ad have a method
686	called C<results> that returns the results, it should call C<< ->recv >>	1034	called C<results> that returns the results, it may call C<< ->recv >>
687	freely, as the user of your module knows what she is doing. always).	1035	freely, as the user of your module knows what she is doing. Always).
688		1036
689	=head1 WHAT TO DO IN THE MAIN PROGRAM	1037	=head1 WHAT TO DO IN THE MAIN PROGRAM
690		1038
691	There will always be a single main program - the only place that should	1039	There will always be a single main program - the only place that should
692	dictate which event model to use.	1040	dictate which event model to use.
693		1041
694	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1042	If the program is not event-based, it need not do anything special, even
695	do anything special (it does not need to be event-based) and let AnyEvent	1043	when it depends on a module that uses an AnyEvent. If the program itself
696	decide which implementation to chose if some module relies on it.	1044	uses AnyEvent, but does not care which event loop is used, all it needs
		1045	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1046	available loop implementation.
697		1047
698	If the main program relies on a specific event model - for example, in	1048	If the main program relies on a specific event model - for example, in
699	Gtk2 programs you have to rely on the Glib module - you should load the	1049	Gtk2 programs you have to rely on the Glib module - you should load the
700	event module before loading AnyEvent or any module that uses it: generally	1050	event module before loading AnyEvent or any module that uses it: generally
701	speaking, you should load it as early as possible. The reason is that	1051	speaking, you should load it as early as possible. The reason is that
702	modules might create watchers when they are loaded, and AnyEvent will	1052	modules might create watchers when they are loaded, and AnyEvent will
703	decide on the event model to use as soon as it creates watchers, and it	1053	decide on the event model to use as soon as it creates watchers, and it
704	might chose the wrong one unless you load the correct one yourself.	1054	might choose the wrong one unless you load the correct one yourself.
705		1055
706	You can chose to use a pure-perl implementation by loading the	1056	You can chose to use a pure-perl implementation by loading the
707	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour	1057	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
708	everywhere, but letting AnyEvent chose the model is generally better.	1058	everywhere, but letting AnyEvent chose the model is generally better.
709		1059
…		…
725		1075
726		1076
727	=head1 OTHER MODULES	1077	=head1 OTHER MODULES
728		1078
729	The following is a non-exhaustive list of additional modules that use	1079	The following is a non-exhaustive list of additional modules that use
730	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1080	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
731	in the same program. Some of the modules come with AnyEvent, some are	1081	modules and other event loops in the same program. Some of the modules
732	available via CPAN.	1082	come as part of AnyEvent, the others are available via CPAN.
733		1083
734	=over 4	1084	=over 4
735		1085
736	=item L<AnyEvent::Util>	1086	=item L<AnyEvent::Util>
737		1087
738	Contains various utility functions that replace often-used but blocking	1088	Contains various utility functions that replace often-used blocking
739	functions such as C<inet_aton> by event-/callback-based versions.	1089	functions such as C<inet_aton> with event/callback-based versions.
740		1090
741	=item L<AnyEvent::Socket>	1091	=item L<AnyEvent::Socket>
742		1092
743	Provides various utility functions for (internet protocol) sockets,	1093	Provides various utility functions for (internet protocol) sockets,
744	addresses and name resolution. Also functions to create non-blocking tcp	1094	addresses and name resolution. Also functions to create non-blocking tcp
…		…
746		1096
747	=item L<AnyEvent::Handle>	1097	=item L<AnyEvent::Handle>
748		1098
749	Provide read and write buffers, manages watchers for reads and writes,	1099	Provide read and write buffers, manages watchers for reads and writes,
750	supports raw and formatted I/O, I/O queued and fully transparent and	1100	supports raw and formatted I/O, I/O queued and fully transparent and
751	non-blocking SSL/TLS.	1101	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
752		1102
753	=item L<AnyEvent::DNS>	1103	=item L<AnyEvent::DNS>
754		1104
755	Provides rich asynchronous DNS resolver capabilities.	1105	Provides rich asynchronous DNS resolver capabilities.
756		1106
		1107	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1108
		1109	Implement event-based interfaces to the protocols of the same name (for
		1110	the curious, IGS is the International Go Server and FCP is the Freenet
		1111	Client Protocol).
		1112
		1113	=item L<AnyEvent::Handle::UDP>
		1114
		1115	Here be danger!
		1116
		1117	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1118	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1119	its use of a stream-based API with a protocol that isn't streamable, that
		1120	the only way to improve it is to delete it.
		1121
		1122	It features data corruption (but typically only under load) and general
		1123	confusion. On top, the author is not only clueless about UDP but also
		1124	fact-resistant - some gems of his understanding: "connect doesn't work
		1125	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1126	packets", "I don't need to implement proper error checking as UDP doesn't
		1127	support error checking" and so on - he doesn't even understand what's
		1128	wrong with his module when it is explained to him.
		1129
757	=item L<AnyEvent::HTTP>	1130	=item L<AnyEvent::DBI>
758		1131
759	A simple-to-use HTTP library that is capable of making a lot of concurrent	1132	Executes L<DBI> requests asynchronously in a proxy process for you,
760	HTTP requests.	1133	notifying you in an event-based way when the operation is finished.
		1134
		1135	=item L<AnyEvent::AIO>
		1136
		1137	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1138	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1139	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1140	file I/O, and much more.
761		1141
762	=item L<AnyEvent::HTTPD>	1142	=item L<AnyEvent::HTTPD>
763		1143
764	Provides a simple web application server framework.	1144	A simple embedded webserver.
765		1145
766	=item L<AnyEvent::FastPing>	1146	=item L<AnyEvent::FastPing>
767		1147
768	The fastest ping in the west.	1148	The fastest ping in the west.
769		1149
770	=item L<AnyEvent::DBI>
771
772	Executes L<DBI> requests asynchronously in a proxy process.
773
774	=item L<AnyEvent::AIO>
775
776	Truly asynchronous I/O, should be in the toolbox of every event
777	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
778	together.
779
780	=item L<AnyEvent::BDB>
781
782	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
783	L<BDB> and AnyEvent together.
784
785	=item L<AnyEvent::GPSD>
786
787	A non-blocking interface to gpsd, a daemon delivering GPS information.
788
789	=item L<AnyEvent::IGS>
790
791	A non-blocking interface to the Internet Go Server protocol (used by
792	L<App::IGS>).
793
794	=item L<Net::IRC3>
795
796	AnyEvent based IRC client module family.
797
798	=item L<Net::XMPP2>
799
800	AnyEvent based XMPP (Jabber protocol) module family.
801
802	=item L<Net::FCP>
803
804	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
805	of AnyEvent.
806
807	=item L<Event::ExecFlow>
808
809	High level API for event-based execution flow control.
810
811	=item L<Coro>	1150	=item L<Coro>
812		1151
813	Has special support for AnyEvent via L<Coro::AnyEvent>.	1152	Has special support for AnyEvent via L<Coro::AnyEvent>.
814		1153
815	=item L<IO::Lambda>
816
817	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
818
819	=back	1154	=back
820		1155
821	=cut	1156	=cut
822		1157
823	package AnyEvent;	1158	package AnyEvent;
824		1159
825	no warnings;	1160	# basically a tuned-down version of common::sense
826	use strict;	1161	sub common_sense {
		1162	# from common:.sense 3.3
		1163	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf3\x0f\xc0\xf0\xfc\x33\x00";
		1164	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1165	$^H |= 0x00000600;
		1166	}
827		1167
		1168	BEGIN { AnyEvent::common_sense }
		1169
828	use Carp;	1170	use Carp ();
829		1171
830	our $VERSION = 4.2;	1172	our $VERSION = '5.29';
831	our $MODEL;	1173	our $MODEL;
832		1174
833	our $AUTOLOAD;	1175	our $AUTOLOAD;
834	our @ISA;	1176	our @ISA;
835		1177
836	our @REGISTRY;	1178	our @REGISTRY;
837		1179
838	our $WIN32;	1180	our $VERBOSE;
839		1181
840	BEGIN {	1182	BEGIN {
841	my $win32 = ! ! ($^O =~ /mswin32/i);	1183	require "AnyEvent/constants.pl";
842	eval "sub WIN32(){ $win32 }";
843	}
844		1184
		1185	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1186
		1187	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1188	if ${^TAINT};
		1189
845	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1190	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1191
		1192	}
		1193
		1194	our $MAX_SIGNAL_LATENCY = 10;
846		1195
847	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1196	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
848		1197
849	{	1198	{
850	my $idx;	1199	my $idx;
…		…
852	for reverse split /\s*,\s*/,	1201	for reverse split /\s*,\s*/,
853	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1202	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
854	}	1203	}
855		1204
856	my @models = (	1205	my @models = (
857	[EV:: => AnyEvent::Impl::EV::],	1206	[EV:: => AnyEvent::Impl::EV:: , 1],
858	[Event:: => AnyEvent::Impl::Event::],
859	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1207	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
860	# everything below here will not be autoprobed	1208	# everything below here will not (normally) be autoprobed
861	# as the pureperl backend should work everywhere	1209	# as the pureperl backend should work everywhere
862	# and is usually faster	1210	# and is usually faster
		1211	[Event:: => AnyEvent::Impl::Event::, 1],
		1212	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1213	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1214	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
863	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles	1215	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
864	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
865	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
866	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1216	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
867	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1217	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
868	[Wx:: => AnyEvent::Impl::POE::],	1218	[Wx:: => AnyEvent::Impl::POE::],
869	[Prima:: => AnyEvent::Impl::POE::],	1219	[Prima:: => AnyEvent::Impl::POE::],
		1220	# IO::Async is just too broken - we would need workarounds for its
		1221	# byzantine signal and broken child handling, among others.
		1222	# IO::Async is rather hard to detect, as it doesn't have any
		1223	# obvious default class.
		1224	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1225	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1226	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1227	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
870	);	1228	);
871		1229
872	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1230	our %method = map +($_ => 1),
		1231	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
873		1232
874	our @post_detect;	1233	our @post_detect;
875		1234
876	sub post_detect(&) {	1235	sub post_detect(&) {
877	my ($cb) = @_;	1236	my ($cb) = @_;
878		1237
879	if ($MODEL) {
880	$cb->();
881
882	1
883	} else {
884	push @post_detect, $cb;	1238	push @post_detect, $cb;
885		1239
886	defined wantarray	1240	defined wantarray
887	? bless \$cb, "AnyEvent::Util::PostDetect"	1241	? bless \$cb, "AnyEvent::Util::postdetect"
888	: ()	1242	: ()
		1243	}
		1244
		1245	sub AnyEvent::Util::postdetect::DESTROY {
		1246	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1247	}
		1248
		1249	sub detect() {
		1250	# free some memory
		1251	*detect = sub () { $MODEL };
		1252
		1253	local $!; # for good measure
		1254	local $SIG{__DIE__};
		1255
		1256	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1257	my $model = "AnyEvent::Impl::$1";
		1258	if (eval "require $model") {
		1259	$MODEL = $model;
		1260	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1261	} else {
		1262	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1263	}
889	}	1264	}
890	}
891		1265
892	sub AnyEvent::Util::PostDetect::DESTROY {	1266	# check for already loaded models
893	@post_detect = grep $_ != ${$_[0]}, @post_detect;
894	}
895
896	sub detect() {
897	unless ($MODEL) {	1267	unless ($MODEL) {
898	no strict 'refs';	1268	for (@REGISTRY, @models) {
899	local $SIG{__DIE__};	1269	my ($package, $model) = @$_;
900		1270	if (${"$package\::VERSION"} > 0) {
901	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
902	my $model = "AnyEvent::Impl::$1";
903	if (eval "require $model") {	1271	if (eval "require $model") {
904	$MODEL = $model;	1272	$MODEL = $model;
905	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1273	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
906	} else {	1274	last;
907	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1275	}
908	}	1276	}
909	}	1277	}
910		1278
911	# check for already loaded models
912	unless ($MODEL) {	1279	unless ($MODEL) {
		1280	# try to autoload a model
913	for (@REGISTRY, @models) {	1281	for (@REGISTRY, @models) {
914	my ($package, $model) = @$_;	1282	my ($package, $model, $autoload) = @$_;
		1283	if (
		1284	$autoload
		1285	and eval "require $package"
915	if (${"$package\::VERSION"} > 0) {	1286	and ${"$package\::VERSION"} > 0
916	if (eval "require $model") {	1287	and eval "require $model"
		1288	) {
917	$MODEL = $model;	1289	$MODEL = $model;
918	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1290	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
919	last;	1291	last;
920	}
921	}	1292	}
922	}	1293	}
923		1294
924	unless ($MODEL) {
925	# try to load a model
926
927	for (@REGISTRY, @models) {
928	my ($package, $model) = @$_;
929	if (eval "require $package"
930	and ${"$package\::VERSION"} > 0
931	and eval "require $model") {
932	$MODEL = $model;
933	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
934	last;
935	}
936	}
937
938	$MODEL	1295	$MODEL
939	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1296	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?\n";
940	}
941	}	1297	}
942
943	unshift @ISA, $MODEL;
944	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
945
946	(shift @post_detect)->() while @post_detect;
947	}	1298	}
		1299
		1300	@models = (); # free probe data
		1301
		1302	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1303	unshift @ISA, $MODEL;
		1304
		1305	# now nuke some methods that are overridden by the backend.
		1306	# SUPER is not allowed.
		1307	for (qw(time signal child idle)) {
		1308	undef &{"AnyEvent::Base::$_"}
		1309	if defined &{"$MODEL\::$_"};
		1310	}
		1311
		1312	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1313	eval { require AnyEvent::Strict };
		1314	warn "AnyEvent: cannot load AnyEvent::Strict: $@"
		1315	if $@ && $VERBOSE;
		1316	}
		1317
		1318	(shift @post_detect)->() while @post_detect;
		1319
		1320	*post_detect = sub(&) {
		1321	shift->();
		1322
		1323	undef
		1324	};
948		1325
949	$MODEL	1326	$MODEL
950	}	1327	}
951		1328
952	sub AUTOLOAD {	1329	sub AUTOLOAD {
953	(my $func = $AUTOLOAD) =~ s/.*://;	1330	(my $func = $AUTOLOAD) =~ s/.*://;
954		1331
955	$method{$func}	1332	$method{$func}
956	or croak "$func: not a valid method for AnyEvent objects";	1333	or Carp::croak "$func: not a valid AnyEvent class method";
957		1334
958	detect unless $MODEL;	1335	detect;
959		1336
960	my $class = shift;	1337	my $class = shift;
961	$class->$func (@_);	1338	$class->$func (@_);
962	}	1339	}
963		1340
		1341	# utility function to dup a filehandle. this is used by many backends
		1342	# to support binding more than one watcher per filehandle (they usually
		1343	# allow only one watcher per fd, so we dup it to get a different one).
		1344	sub _dupfh($$;$$) {
		1345	my ($poll, $fh, $r, $w) = @_;
		1346
		1347	# cygwin requires the fh mode to be matching, unix doesn't
		1348	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1349
		1350	open my $fh2, $mode, $fh
		1351	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1352
		1353	# we assume CLOEXEC is already set by perl in all important cases
		1354
		1355	($fh2, $rw)
		1356	}
		1357
		1358	=head1 SIMPLIFIED AE API
		1359
		1360	Starting with version 5.0, AnyEvent officially supports a second, much
		1361	simpler, API that is designed to reduce the calling, typing and memory
		1362	overhead by using function call syntax and a fixed number of parameters.
		1363
		1364	See the L<AE> manpage for details.
		1365
		1366	=cut
		1367
		1368	package AE;
		1369
		1370	our $VERSION = $AnyEvent::VERSION;
		1371
		1372	# fall back to the main API by default - backends and AnyEvent::Base
		1373	# implementations can overwrite these.
		1374
		1375	sub io($$$) {
		1376	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1377	}
		1378
		1379	sub timer($$$) {
		1380	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1381	}
		1382
		1383	sub signal($$) {
		1384	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1385	}
		1386
		1387	sub child($$) {
		1388	AnyEvent->child (pid => $_[0], cb => $_[1])
		1389	}
		1390
		1391	sub idle($) {
		1392	AnyEvent->idle (cb => $_[0])
		1393	}
		1394
		1395	sub cv(;&) {
		1396	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1397	}
		1398
		1399	sub now() {
		1400	AnyEvent->now
		1401	}
		1402
		1403	sub now_update() {
		1404	AnyEvent->now_update
		1405	}
		1406
		1407	sub time() {
		1408	AnyEvent->time
		1409	}
		1410
964	package AnyEvent::Base;	1411	package AnyEvent::Base;
965		1412
966	# default implementation for now and time	1413	# default implementations for many methods
967		1414
968	use Time::HiRes ();	1415	sub time {
		1416	eval q{ # poor man's autoloading {}
		1417	# probe for availability of Time::HiRes
		1418	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1419	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1420	*AE::time = \&Time::HiRes::time;
		1421	# if (eval "use POSIX (); (POSIX::times())...
		1422	} else {
		1423	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1424	*AE::time = sub (){ time }; # epic fail
		1425	}
969		1426
970	sub time { Time::HiRes::time }	1427	*time = sub { AE::time }; # different prototypes
971	sub now { Time::HiRes::time }	1428	};
		1429	die if $@;
		1430
		1431	&time
		1432	}
		1433
		1434	*now = \&time;
		1435
		1436	sub now_update { }
972		1437
973	# default implementation for ->condvar	1438	# default implementation for ->condvar
974		1439
975	sub condvar {	1440	sub condvar {
		1441	eval q{ # poor man's autoloading {}
		1442	*condvar = sub {
976	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1443	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1444	};
		1445
		1446	*AE::cv = sub (;&) {
		1447	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1448	};
		1449	};
		1450	die if $@;
		1451
		1452	&condvar
977	}	1453	}
978		1454
979	# default implementation for ->signal	1455	# default implementation for ->signal
980		1456
981	our %SIG_CB;	1457	our $HAVE_ASYNC_INTERRUPT;
		1458
		1459	sub _have_async_interrupt() {
		1460	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1461	&& eval "use Async::Interrupt 1.02 (); 1")
		1462	unless defined $HAVE_ASYNC_INTERRUPT;
		1463
		1464	$HAVE_ASYNC_INTERRUPT
		1465	}
		1466
		1467	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1468	our (%SIG_ASY, %SIG_ASY_W);
		1469	our ($SIG_COUNT, $SIG_TW);
		1470
		1471	# install a dummy wakeup watcher to reduce signal catching latency
		1472	# used by Impls
		1473	sub _sig_add() {
		1474	unless ($SIG_COUNT++) {
		1475	# try to align timer on a full-second boundary, if possible
		1476	my $NOW = AE::now;
		1477
		1478	$SIG_TW = AE::timer
		1479	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1480	$MAX_SIGNAL_LATENCY,
		1481	sub { } # just for the PERL_ASYNC_CHECK
		1482	;
		1483	}
		1484	}
		1485
		1486	sub _sig_del {
		1487	undef $SIG_TW
		1488	unless --$SIG_COUNT;
		1489	}
		1490
		1491	our $_sig_name_init; $_sig_name_init = sub {
		1492	eval q{ # poor man's autoloading {}
		1493	undef $_sig_name_init;
		1494
		1495	if (_have_async_interrupt) {
		1496	*sig2num = \&Async::Interrupt::sig2num;
		1497	*sig2name = \&Async::Interrupt::sig2name;
		1498	} else {
		1499	require Config;
		1500
		1501	my %signame2num;
		1502	@signame2num{ split ' ', $Config::Config{sig_name} }
		1503	= split ' ', $Config::Config{sig_num};
		1504
		1505	my @signum2name;
		1506	@signum2name[values %signame2num] = keys %signame2num;
		1507
		1508	*sig2num = sub($) {
		1509	$_[0] > 0 ? shift : $signame2num{+shift}
		1510	};
		1511	*sig2name = sub ($) {
		1512	$_[0] > 0 ? $signum2name[+shift] : shift
		1513	};
		1514	}
		1515	};
		1516	die if $@;
		1517	};
		1518
		1519	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1520	sub sig2name($) { &$_sig_name_init; &sig2name }
982		1521
983	sub signal {	1522	sub signal {
		1523	eval q{ # poor man's autoloading {}
		1524	# probe for availability of Async::Interrupt
		1525	if (_have_async_interrupt) {
		1526	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1527
		1528	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1529	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1530
		1531	} else {
		1532	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1533
		1534	if (AnyEvent::WIN32) {
		1535	require AnyEvent::Util;
		1536
		1537	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1538	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1539	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1540	} else {
		1541	pipe $SIGPIPE_R, $SIGPIPE_W;
		1542	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1543	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1544
		1545	# not strictly required, as $^F is normally 2, but let's make sure...
		1546	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1547	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1548	}
		1549
		1550	$SIGPIPE_R
		1551	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1552
		1553	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1554	}
		1555
		1556	*signal = $HAVE_ASYNC_INTERRUPT
		1557	? sub {
984	my (undef, %arg) = @_;	1558	my (undef, %arg) = @_;
985		1559
		1560	# async::interrupt
986	my $signal = uc $arg{signal}	1561	my $signal = sig2num $arg{signal};
987	or Carp::croak "required option 'signal' is missing";
988
989	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1562	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1563
		1564	$SIG_ASY{$signal} ||= new Async::Interrupt
		1565	cb => sub { undef $SIG_EV{$signal} },
		1566	signal => $signal,
		1567	pipe => [$SIGPIPE_R->filenos],
		1568	pipe_autodrain => 0,
		1569	;
		1570
		1571	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1572	}
		1573	: sub {
		1574	my (undef, %arg) = @_;
		1575
		1576	# pure perl
		1577	my $signal = sig2name $arg{signal};
		1578	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1579
990	$SIG{$signal} ||= sub {	1580	$SIG{$signal} ||= sub {
		1581	local $!;
		1582	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1583	undef $SIG_EV{$signal};
		1584	};
		1585
		1586	# can't do signal processing without introducing races in pure perl,
		1587	# so limit the signal latency.
		1588	_sig_add;
		1589
		1590	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1591	}
		1592	;
		1593
		1594	*AnyEvent::Base::signal::DESTROY = sub {
		1595	my ($signal, $cb) = @{$_[0]};
		1596
		1597	_sig_del;
		1598
		1599	delete $SIG_CB{$signal}{$cb};
		1600
		1601	$HAVE_ASYNC_INTERRUPT
		1602	? delete $SIG_ASY{$signal}
		1603	: # delete doesn't work with older perls - they then
		1604	# print weird messages, or just unconditionally exit
		1605	# instead of getting the default action.
		1606	undef $SIG{$signal}
		1607	unless keys %{ $SIG_CB{$signal} };
		1608	};
		1609
		1610	*_signal_exec = sub {
		1611	$HAVE_ASYNC_INTERRUPT
		1612	? $SIGPIPE_R->drain
		1613	: sysread $SIGPIPE_R, (my $dummy), 9;
		1614
		1615	while (%SIG_EV) {
		1616	for (keys %SIG_EV) {
		1617	delete $SIG_EV{$_};
991	$_->() for values %{ $SIG_CB{$signal} || {} };	1618	$_->() for values %{ $SIG_CB{$_} || {} };
		1619	}
		1620	}
		1621	};
992	};	1622	};
		1623	die if $@;
993		1624
994	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1625	&signal
995	}
996
997	sub AnyEvent::Base::Signal::DESTROY {
998	my ($signal, $cb) = @{$_[0]};
999
1000	delete $SIG_CB{$signal}{$cb};
1001
1002	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
1003	}	1626	}
1004		1627
1005	# default implementation for ->child	1628	# default implementation for ->child
1006		1629
1007	our %PID_CB;	1630	our %PID_CB;
1008	our $CHLD_W;	1631	our $CHLD_W;
1009	our $CHLD_DELAY_W;	1632	our $CHLD_DELAY_W;
1010	our $PID_IDLE;
1011	our $WNOHANG;	1633	our $WNOHANG;
1012		1634
1013	sub _child_wait {	1635	# used by many Impl's
1014	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1636	sub _emit_childstatus($$) {
		1637	my (undef, $rpid, $rstatus) = @_;
		1638
		1639	$_->($rpid, $rstatus)
1015	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1640	for values %{ $PID_CB{$rpid} || {} },
1016	(values %{ $PID_CB{0} || {} });	1641	values %{ $PID_CB{0} || {} };
1017	}
1018
1019	undef $PID_IDLE;
1020	}
1021
1022	sub _sigchld {
1023	# make sure we deliver these changes "synchronous" with the event loop.
1024	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
1025	undef $CHLD_DELAY_W;
1026	&_child_wait;
1027	});
1028	}	1642	}
1029		1643
1030	sub child {	1644	sub child {
		1645	eval q{ # poor man's autoloading {}
		1646	*_sigchld = sub {
		1647	my $pid;
		1648
		1649	AnyEvent->_emit_childstatus ($pid, $?)
		1650	while ($pid = waitpid -1, $WNOHANG) > 0;
		1651	};
		1652
		1653	*child = sub {
1031	my (undef, %arg) = @_;	1654	my (undef, %arg) = @_;
1032		1655
1033	defined (my $pid = $arg{pid} + 0)	1656	defined (my $pid = $arg{pid} + 0)
1034	or Carp::croak "required option 'pid' is missing";	1657	or Carp::croak "required option 'pid' is missing";
1035		1658
1036	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1659	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
1037		1660
1038	unless ($WNOHANG) {	1661	# WNOHANG is almost cetrainly 1 everywhere
		1662	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1663	? 1
1039	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1664	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1040	}
1041		1665
1042	unless ($CHLD_W) {	1666	unless ($CHLD_W) {
1043	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1667	$CHLD_W = AE::signal CHLD => \&_sigchld;
1044	# child could be a zombie already, so make at least one round	1668	# child could be a zombie already, so make at least one round
1045	&_sigchld;	1669	&_sigchld;
1046	}	1670	}
1047		1671
1048	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1672	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
1049	}	1673	};
1050		1674
1051	sub AnyEvent::Base::Child::DESTROY {	1675	*AnyEvent::Base::child::DESTROY = sub {
1052	my ($pid, $cb) = @{$_[0]};	1676	my ($pid, $cb) = @{$_[0]};
1053		1677
1054	delete $PID_CB{$pid}{$cb};	1678	delete $PID_CB{$pid}{$cb};
1055	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1679	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1056		1680
1057	undef $CHLD_W unless keys %PID_CB;	1681	undef $CHLD_W unless keys %PID_CB;
		1682	};
		1683	};
		1684	die if $@;
		1685
		1686	&child
		1687	}
		1688
		1689	# idle emulation is done by simply using a timer, regardless
		1690	# of whether the process is idle or not, and not letting
		1691	# the callback use more than 50% of the time.
		1692	sub idle {
		1693	eval q{ # poor man's autoloading {}
		1694	*idle = sub {
		1695	my (undef, %arg) = @_;
		1696
		1697	my ($cb, $w, $rcb) = $arg{cb};
		1698
		1699	$rcb = sub {
		1700	if ($cb) {
		1701	$w = _time;
		1702	&$cb;
		1703	$w = _time - $w;
		1704
		1705	# never use more then 50% of the time for the idle watcher,
		1706	# within some limits
		1707	$w = 0.0001 if $w < 0.0001;
		1708	$w = 5 if $w > 5;
		1709
		1710	$w = AE::timer $w, 0, $rcb;
		1711	} else {
		1712	# clean up...
		1713	undef $w;
		1714	undef $rcb;
		1715	}
		1716	};
		1717
		1718	$w = AE::timer 0.05, 0, $rcb;
		1719
		1720	bless \\$cb, "AnyEvent::Base::idle"
		1721	};
		1722
		1723	*AnyEvent::Base::idle::DESTROY = sub {
		1724	undef $${$_[0]};
		1725	};
		1726	};
		1727	die if $@;
		1728
		1729	&idle
1058	}	1730	}
1059		1731
1060	package AnyEvent::CondVar;	1732	package AnyEvent::CondVar;
1061		1733
1062	our @ISA = AnyEvent::CondVar::Base::;	1734	our @ISA = AnyEvent::CondVar::Base::;
1063		1735
		1736	# only to be used for subclassing
		1737	sub new {
		1738	my $class = shift;
		1739	bless AnyEvent->condvar (@_), $class
		1740	}
		1741
1064	package AnyEvent::CondVar::Base;	1742	package AnyEvent::CondVar::Base;
1065		1743
1066	use overload	1744	#use overload
1067	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1745	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1068	fallback => 1;	1746	# fallback => 1;
		1747
		1748	# save 300+ kilobytes by dirtily hardcoding overloading
		1749	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1750	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1751	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1752	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1753
		1754	our $WAITING;
1069		1755
1070	sub _send {	1756	sub _send {
1071	# nop	1757	# nop
1072	}	1758	}
1073		1759
…		…
1086	sub ready {	1772	sub ready {
1087	$_[0]{_ae_sent}	1773	$_[0]{_ae_sent}
1088	}	1774	}
1089		1775
1090	sub _wait {	1776	sub _wait {
		1777	$WAITING
		1778	and !$_[0]{_ae_sent}
		1779	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1780
		1781	local $WAITING = 1;
1091	AnyEvent->one_event while !$_[0]{_ae_sent};	1782	AnyEvent->one_event while !$_[0]{_ae_sent};
1092	}	1783	}
1093		1784
1094	sub recv {	1785	sub recv {
1095	$_[0]->_wait;	1786	$_[0]->_wait;
…		…
1097	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1788	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
1098	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1789	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
1099	}	1790	}
1100		1791
1101	sub cb {	1792	sub cb {
1102	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1793	my $cv = shift;
		1794
		1795	@_
		1796	and $cv->{_ae_cb} = shift
		1797	and $cv->{_ae_sent}
		1798	and (delete $cv->{_ae_cb})->($cv);
		1799
1103	$_[0]{_ae_cb}	1800	$cv->{_ae_cb}
1104	}	1801	}
1105		1802
1106	sub begin {	1803	sub begin {
1107	++$_[0]{_ae_counter};	1804	++$_[0]{_ae_counter};
1108	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1805	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
…		…
1114	}	1811	}
1115		1812
1116	# undocumented/compatibility with pre-3.4	1813	# undocumented/compatibility with pre-3.4
1117	*broadcast = \&send;	1814	*broadcast = \&send;
1118	*wait = \&_wait;	1815	*wait = \&_wait;
		1816
		1817	=head1 ERROR AND EXCEPTION HANDLING
		1818
		1819	In general, AnyEvent does not do any error handling - it relies on the
		1820	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1821	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1822	checking of all AnyEvent methods, however, which is highly useful during
		1823	development.
		1824
		1825	As for exception handling (i.e. runtime errors and exceptions thrown while
		1826	executing a callback), this is not only highly event-loop specific, but
		1827	also not in any way wrapped by this module, as this is the job of the main
		1828	program.
		1829
		1830	The pure perl event loop simply re-throws the exception (usually
		1831	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1832	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1833	so on.
		1834
		1835	=head1 ENVIRONMENT VARIABLES
		1836
		1837	The following environment variables are used by this module or its
		1838	submodules.
		1839
		1840	Note that AnyEvent will remove I<all> environment variables starting with
		1841	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1842	enabled.
		1843
		1844	=over 4
		1845
		1846	=item C<PERL_ANYEVENT_VERBOSE>
		1847
		1848	By default, AnyEvent will be completely silent except in fatal
		1849	conditions. You can set this environment variable to make AnyEvent more
		1850	talkative.
		1851
		1852	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1853	conditions, such as not being able to load the event model specified by
		1854	C<PERL_ANYEVENT_MODEL>.
		1855
		1856	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1857	model it chooses.
		1858
		1859	When set to C<8> or higher, then AnyEvent will report extra information on
		1860	which optional modules it loads and how it implements certain features.
		1861
		1862	=item C<PERL_ANYEVENT_STRICT>
		1863
		1864	AnyEvent does not do much argument checking by default, as thorough
		1865	argument checking is very costly. Setting this variable to a true value
		1866	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1867	check the arguments passed to most method calls. If it finds any problems,
		1868	it will croak.
		1869
		1870	In other words, enables "strict" mode.
		1871
		1872	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		1873	>>, it is definitely recommended to keep it off in production. Keeping
		1874	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1875	can be very useful, however.
		1876
		1877	=item C<PERL_ANYEVENT_MODEL>
		1878
		1879	This can be used to specify the event model to be used by AnyEvent, before
		1880	auto detection and -probing kicks in. It must be a string consisting
		1881	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1882	and the resulting module name is loaded and if the load was successful,
		1883	used as event model. If it fails to load AnyEvent will proceed with
		1884	auto detection and -probing.
		1885
		1886	This functionality might change in future versions.
		1887
		1888	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1889	could start your program like this:
		1890
		1891	PERL_ANYEVENT_MODEL=Perl perl ...
		1892
		1893	=item C<PERL_ANYEVENT_PROTOCOLS>
		1894
		1895	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1896	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1897	of auto probing).
		1898
		1899	Must be set to a comma-separated list of protocols or address families,
		1900	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1901	used, and preference will be given to protocols mentioned earlier in the
		1902	list.
		1903
		1904	This variable can effectively be used for denial-of-service attacks
		1905	against local programs (e.g. when setuid), although the impact is likely
		1906	small, as the program has to handle conenction and other failures anyways.
		1907
		1908	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1909	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1910	- only support IPv4, never try to resolve or contact IPv6
		1911	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1912	IPv6, but prefer IPv6 over IPv4.
		1913
		1914	=item C<PERL_ANYEVENT_EDNS0>
		1915
		1916	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1917	for DNS. This extension is generally useful to reduce DNS traffic, but
		1918	some (broken) firewalls drop such DNS packets, which is why it is off by
		1919	default.
		1920
		1921	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1922	EDNS0 in its DNS requests.
		1923
		1924	=item C<PERL_ANYEVENT_MAX_FORKS>
		1925
		1926	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1927	will create in parallel.
		1928
		1929	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1930
		1931	The default value for the C<max_outstanding> parameter for the default DNS
		1932	resolver - this is the maximum number of parallel DNS requests that are
		1933	sent to the DNS server.
		1934
		1935	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1936
		1937	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1938	configuration) in the default resolver. When set to the empty string, no
		1939	default config will be used.
		1940
		1941	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1942
		1943	When neither C<ca_file> nor C<ca_path> was specified during
		1944	L<AnyEvent::TLS> context creation, and either of these environment
		1945	variables exist, they will be used to specify CA certificate locations
		1946	instead of a system-dependent default.
		1947
		1948	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1949
		1950	When these are set to C<1>, then the respective modules are not
		1951	loaded. Mostly good for testing AnyEvent itself.
		1952
		1953	=back
1119		1954
1120	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1955	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1121		1956
1122	This is an advanced topic that you do not normally need to use AnyEvent in	1957	This is an advanced topic that you do not normally need to use AnyEvent in
1123	a module. This section is only of use to event loop authors who want to	1958	a module. This section is only of use to event loop authors who want to
…		…
1157		1992
1158	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1993	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1159	condition variables: code blocking while waiting for a condition will	1994	condition variables: code blocking while waiting for a condition will
1160	C<die>. This still works with most modules/usages, and blocking calls must	1995	C<die>. This still works with most modules/usages, and blocking calls must
1161	not be done in an interactive application, so it makes sense.	1996	not be done in an interactive application, so it makes sense.
1162
1163	=head1 ENVIRONMENT VARIABLES
1164
1165	The following environment variables are used by this module:
1166
1167	=over 4
1168
1169	=item C<PERL_ANYEVENT_VERBOSE>
1170
1171	By default, AnyEvent will be completely silent except in fatal
1172	conditions. You can set this environment variable to make AnyEvent more
1173	talkative.
1174
1175	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1176	conditions, such as not being able to load the event model specified by
1177	C<PERL_ANYEVENT_MODEL>.
1178
1179	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1180	model it chooses.
1181
1182	=item C<PERL_ANYEVENT_MODEL>
1183
1184	This can be used to specify the event model to be used by AnyEvent, before
1185	auto detection and -probing kicks in. It must be a string consisting
1186	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1187	and the resulting module name is loaded and if the load was successful,
1188	used as event model. If it fails to load AnyEvent will proceed with
1189	auto detection and -probing.
1190
1191	This functionality might change in future versions.
1192
1193	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1194	could start your program like this:
1195
1196	PERL_ANYEVENT_MODEL=Perl perl ...
1197
1198	=item C<PERL_ANYEVENT_PROTOCOLS>
1199
1200	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1201	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1202	of auto probing).
1203
1204	Must be set to a comma-separated list of protocols or address families,
1205	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1206	used, and preference will be given to protocols mentioned earlier in the
1207	list.
1208
1209	This variable can effectively be used for denial-of-service attacks
1210	against local programs (e.g. when setuid), although the impact is likely
1211	small, as the program has to handle connection errors already-
1212
1213	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1214	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1215	- only support IPv4, never try to resolve or contact IPv6
1216	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1217	IPv6, but prefer IPv6 over IPv4.
1218
1219	=item C<PERL_ANYEVENT_EDNS0>
1220
1221	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1222	for DNS. This extension is generally useful to reduce DNS traffic, but
1223	some (broken) firewalls drop such DNS packets, which is why it is off by
1224	default.
1225
1226	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1227	EDNS0 in its DNS requests.
1228
1229	=item C<PERL_ANYEVENT_MAX_FORKS>
1230
1231	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1232	will create in parallel.
1233
1234	=back
1235		1997
1236	=head1 EXAMPLE PROGRAM	1998	=head1 EXAMPLE PROGRAM
1237		1999
1238	The following program uses an I/O watcher to read data from STDIN, a timer	2000	The following program uses an I/O watcher to read data from STDIN, a timer
1239	to display a message once per second, and a condition variable to quit the	2001	to display a message once per second, and a condition variable to quit the
…		…
1252	warn "read: $input\n"; # output what has been read	2014	warn "read: $input\n"; # output what has been read
1253	$cv->send if $input =~ /^q/i; # quit program if /^q/i	2015	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1254	},	2016	},
1255	);	2017	);
1256		2018
1257	my $time_watcher; # can only be used once
1258
1259	sub new_timer {
1260	$timer = AnyEvent->timer (after => 1, cb => sub {	2019	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1261	warn "timeout\n"; # print 'timeout' about every second	2020	warn "timeout\n"; # print 'timeout' at most every second
1262	&new_timer; # and restart the time
1263	});	2021	});
1264	}
1265
1266	new_timer; # create first timer
1267		2022
1268	$cv->recv; # wait until user enters /^q/i	2023	$cv->recv; # wait until user enters /^q/i
1269		2024
1270	=head1 REAL-WORLD EXAMPLE	2025	=head1 REAL-WORLD EXAMPLE
1271		2026
…		…
1344		2099
1345	The actual code goes further and collects all errors (C<die>s, exceptions)	2100	The actual code goes further and collects all errors (C<die>s, exceptions)
1346	that occurred during request processing. The C<result> method detects	2101	that occurred during request processing. The C<result> method detects
1347	whether an exception as thrown (it is stored inside the $txn object)	2102	whether an exception as thrown (it is stored inside the $txn object)
1348	and just throws the exception, which means connection errors and other	2103	and just throws the exception, which means connection errors and other
1349	problems get reported tot he code that tries to use the result, not in a	2104	problems get reported to the code that tries to use the result, not in a
1350	random callback.	2105	random callback.
1351		2106
1352	All of this enables the following usage styles:	2107	All of this enables the following usage styles:
1353		2108
1354	1. Blocking:	2109	1. Blocking:
…		…
1402	through AnyEvent. The benchmark creates a lot of timers (with a zero	2157	through AnyEvent. The benchmark creates a lot of timers (with a zero
1403	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2158	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1404	which it is), lets them fire exactly once and destroys them again.	2159	which it is), lets them fire exactly once and destroys them again.
1405		2160
1406	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2161	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1407	distribution.	2162	distribution. It uses the L<AE> interface, which makes a real difference
		2163	for the EV and Perl backends only.
1408		2164
1409	=head3 Explanation of the columns	2165	=head3 Explanation of the columns
1410		2166
1411	I<watcher> is the number of event watchers created/destroyed. Since	2167	I<watcher> is the number of event watchers created/destroyed. Since
1412	different event models feature vastly different performances, each event	2168	different event models feature vastly different performances, each event
…		…
1433	watcher.	2189	watcher.
1434		2190
1435	=head3 Results	2191	=head3 Results
1436		2192
1437	name watchers bytes create invoke destroy comment	2193	name watchers bytes create invoke destroy comment
1438	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2194	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1439	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2195	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1440	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2196	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1441	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2197	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1442	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2198	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1443	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2199	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2200	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2201	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1444	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2202	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1445	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2203	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1446	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2204	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1447	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2205	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1448		2206
1449	=head3 Discussion	2207	=head3 Discussion
1450		2208
1451	The benchmark does I<not> measure scalability of the event loop very	2209	The benchmark does I<not> measure scalability of the event loop very
1452	well. For example, a select-based event loop (such as the pure perl one)	2210	well. For example, a select-based event loop (such as the pure perl one)
…		…
1464	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2222	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1465	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2223	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1466	cycles with POE.	2224	cycles with POE.
1467		2225
1468	C<EV> is the sole leader regarding speed and memory use, which are both	2226	C<EV> is the sole leader regarding speed and memory use, which are both
1469	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2227	maximal/minimal, respectively. When using the L<AE> API there is zero
		2228	overhead (when going through the AnyEvent API create is about 5-6 times
		2229	slower, with other times being equal, so still uses far less memory than
1470	far less memory than any other event loop and is still faster than Event	2230	any other event loop and is still faster than Event natively).
1471	natively.
1472		2231
1473	The pure perl implementation is hit in a few sweet spots (both the	2232	The pure perl implementation is hit in a few sweet spots (both the
1474	constant timeout and the use of a single fd hit optimisations in the perl	2233	constant timeout and the use of a single fd hit optimisations in the perl
1475	interpreter and the backend itself). Nevertheless this shows that it	2234	interpreter and the backend itself). Nevertheless this shows that it
1476	adds very little overhead in itself. Like any select-based backend its	2235	adds very little overhead in itself. Like any select-based backend its
1477	performance becomes really bad with lots of file descriptors (and few of	2236	performance becomes really bad with lots of file descriptors (and few of
1478	them active), of course, but this was not subject of this benchmark.	2237	them active), of course, but this was not subject of this benchmark.
1479		2238
1480	The C<Event> module has a relatively high setup and callback invocation	2239	The C<Event> module has a relatively high setup and callback invocation
1481	cost, but overall scores in on the third place.	2240	cost, but overall scores in on the third place.
		2241
		2242	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2243	when using its pure perl backend.
1482		2244
1483	C<Glib>'s memory usage is quite a bit higher, but it features a	2245	C<Glib>'s memory usage is quite a bit higher, but it features a
1484	faster callback invocation and overall ends up in the same class as	2246	faster callback invocation and overall ends up in the same class as
1485	C<Event>. However, Glib scales extremely badly, doubling the number of	2247	C<Event>. However, Glib scales extremely badly, doubling the number of
1486	watchers increases the processing time by more than a factor of four,	2248	watchers increases the processing time by more than a factor of four,
…		…
1547	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100	2309	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1548	(1%) are active. This mirrors the activity of large servers with many	2310	(1%) are active. This mirrors the activity of large servers with many
1549	connections, most of which are idle at any one point in time.	2311	connections, most of which are idle at any one point in time.
1550		2312
1551	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2313	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1552	distribution.	2314	distribution. It uses the L<AE> interface, which makes a real difference
		2315	for the EV and Perl backends only.
1553		2316
1554	=head3 Explanation of the columns	2317	=head3 Explanation of the columns
1555		2318
1556	I<sockets> is the number of sockets, and twice the number of "servers" (as	2319	I<sockets> is the number of sockets, and twice the number of "servers" (as
1557	each server has a read and write socket end).	2320	each server has a read and write socket end).
…		…
1564	it to another server. This includes deleting the old timeout and creating	2327	it to another server. This includes deleting the old timeout and creating
1565	a new one that moves the timeout into the future.	2328	a new one that moves the timeout into the future.
1566		2329
1567	=head3 Results	2330	=head3 Results
1568		2331
1569	name sockets create request	2332	name sockets create request
1570	EV 20000 69.01 11.16	2333	EV 20000 62.66 7.99
1571	Perl 20000 73.32 35.87	2334	Perl 20000 68.32 32.64
1572	Event 20000 212.62 257.32	2335	IOAsync 20000 174.06 101.15 epoll
1573	Glib 20000 651.16 1896.30	2336	IOAsync 20000 174.67 610.84 poll
		2337	Event 20000 202.69 242.91
		2338	Glib 20000 557.01 1689.52
1574	POE 20000 349.67 12317.24 uses POE::Loop::Event	2339	POE 20000 341.54 12086.32 uses POE::Loop::Event
1575		2340
1576	=head3 Discussion	2341	=head3 Discussion
1577		2342
1578	This benchmark I<does> measure scalability and overall performance of the	2343	This benchmark I<does> measure scalability and overall performance of the
1579	particular event loop.	2344	particular event loop.
…		…
1581	EV is again fastest. Since it is using epoll on my system, the setup time	2346	EV is again fastest. Since it is using epoll on my system, the setup time
1582	is relatively high, though.	2347	is relatively high, though.
1583		2348
1584	Perl surprisingly comes second. It is much faster than the C-based event	2349	Perl surprisingly comes second. It is much faster than the C-based event
1585	loops Event and Glib.	2350	loops Event and Glib.
		2351
		2352	IO::Async performs very well when using its epoll backend, and still quite
		2353	good compared to Glib when using its pure perl backend.
1586		2354
1587	Event suffers from high setup time as well (look at its code and you will	2355	Event suffers from high setup time as well (look at its code and you will
1588	understand why). Callback invocation also has a high overhead compared to	2356	understand why). Callback invocation also has a high overhead compared to
1589	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2357	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1590	uses select or poll in basically all documented configurations.	2358	uses select or poll in basically all documented configurations.
…		…
1653	=item * C-based event loops perform very well with small number of	2421	=item * C-based event loops perform very well with small number of
1654	watchers, as the management overhead dominates.	2422	watchers, as the management overhead dominates.
1655		2423
1656	=back	2424	=back
1657		2425
		2426	=head2 THE IO::Lambda BENCHMARK
		2427
		2428	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2429	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2430	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2431	shouldn't come as a surprise to anybody). As such, the benchmark is
		2432	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2433	very optimal. But how would AnyEvent compare when used without the extra
		2434	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2435
		2436	The benchmark itself creates an echo-server, and then, for 500 times,
		2437	connects to the echo server, sends a line, waits for the reply, and then
		2438	creates the next connection. This is a rather bad benchmark, as it doesn't
		2439	test the efficiency of the framework or much non-blocking I/O, but it is a
		2440	benchmark nevertheless.
		2441
		2442	name runtime
		2443	Lambda/select 0.330 sec
		2444	+ optimized 0.122 sec
		2445	Lambda/AnyEvent 0.327 sec
		2446	+ optimized 0.138 sec
		2447	Raw sockets/select 0.077 sec
		2448	POE/select, components 0.662 sec
		2449	POE/select, raw sockets 0.226 sec
		2450	POE/select, optimized 0.404 sec
		2451
		2452	AnyEvent/select/nb 0.085 sec
		2453	AnyEvent/EV/nb 0.068 sec
		2454	+state machine 0.134 sec
		2455
		2456	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2457	benchmarks actually make blocking connects and use 100% blocking I/O,
		2458	defeating the purpose of an event-based solution. All of the newly
		2459	written AnyEvent benchmarks use 100% non-blocking connects (using
		2460	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2461	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2462	generally require a lot more bookkeeping and event handling than blocking
		2463	connects (which involve a single syscall only).
		2464
		2465	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2466	offers similar expressive power as POE and IO::Lambda, using conventional
		2467	Perl syntax. This means that both the echo server and the client are 100%
		2468	non-blocking, further placing it at a disadvantage.
		2469
		2470	As you can see, the AnyEvent + EV combination even beats the
		2471	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2472	backend easily beats IO::Lambda and POE.
		2473
		2474	And even the 100% non-blocking version written using the high-level (and
		2475	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2476	higher level ("unoptimised") abstractions by a large margin, even though
		2477	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2478
		2479	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2480	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2481	part of the IO::Lambda distribution and were used without any changes.
		2482
		2483
		2484	=head1 SIGNALS
		2485
		2486	AnyEvent currently installs handlers for these signals:
		2487
		2488	=over 4
		2489
		2490	=item SIGCHLD
		2491
		2492	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2493	emulation for event loops that do not support them natively. Also, some
		2494	event loops install a similar handler.
		2495
		2496	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2497	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2498
		2499	=item SIGPIPE
		2500
		2501	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2502	when AnyEvent gets loaded.
		2503
		2504	The rationale for this is that AnyEvent users usually do not really depend
		2505	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2506	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2507	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2508	some random socket.
		2509
		2510	The rationale for installing a no-op handler as opposed to ignoring it is
		2511	that this way, the handler will be restored to defaults on exec.
		2512
		2513	Feel free to install your own handler, or reset it to defaults.
		2514
		2515	=back
		2516
		2517	=cut
		2518
		2519	undef $SIG{CHLD}
		2520	if $SIG{CHLD} eq 'IGNORE';
		2521
		2522	$SIG{PIPE} = sub { }
		2523	unless defined $SIG{PIPE};
		2524
		2525	=head1 RECOMMENDED/OPTIONAL MODULES
		2526
		2527	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2528	its built-in modules) are required to use it.
		2529
		2530	That does not mean that AnyEvent won't take advantage of some additional
		2531	modules if they are installed.
		2532
		2533	This section explains which additional modules will be used, and how they
		2534	affect AnyEvent's operation.
		2535
		2536	=over 4
		2537
		2538	=item L<Async::Interrupt>
		2539
		2540	This slightly arcane module is used to implement fast signal handling: To
		2541	my knowledge, there is no way to do completely race-free and quick
		2542	signal handling in pure perl. To ensure that signals still get
		2543	delivered, AnyEvent will start an interval timer to wake up perl (and
		2544	catch the signals) with some delay (default is 10 seconds, look for
		2545	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2546
		2547	If this module is available, then it will be used to implement signal
		2548	catching, which means that signals will not be delayed, and the event loop
		2549	will not be interrupted regularly, which is more efficient (and good for
		2550	battery life on laptops).
		2551
		2552	This affects not just the pure-perl event loop, but also other event loops
		2553	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2554
		2555	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2556	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2557	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2558	does nothing for those backends.
		2559
		2560	=item L<EV>
		2561
		2562	This module isn't really "optional", as it is simply one of the backend
		2563	event loops that AnyEvent can use. However, it is simply the best event
		2564	loop available in terms of features, speed and stability: It supports
		2565	the AnyEvent API optimally, implements all the watcher types in XS, does
		2566	automatic timer adjustments even when no monotonic clock is available,
		2567	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2568	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2569	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2570
		2571	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2572	then this module will do nothing for you.
		2573
		2574	=item L<Guard>
		2575
		2576	The guard module, when used, will be used to implement
		2577	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2578	lot less memory), but otherwise doesn't affect guard operation much. It is
		2579	purely used for performance.
		2580
		2581	=item L<JSON> and L<JSON::XS>
		2582
		2583	One of these modules is required when you want to read or write JSON data
		2584	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2585	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2586
		2587	=item L<Net::SSLeay>
		2588
		2589	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2590	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2591	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2592
		2593	=item L<Time::HiRes>
		2594
		2595	This module is part of perl since release 5.008. It will be used when the
		2596	chosen event library does not come with a timing source of its own. The
		2597	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2598	try to use a monotonic clock for timing stability.
		2599
		2600	=back
		2601
1658		2602
1659	=head1 FORK	2603	=head1 FORK
1660		2604
1661	Most event libraries are not fork-safe. The ones who are usually are	2605	Most event libraries are not fork-safe. The ones who are usually are
1662	because they rely on inefficient but fork-safe C<select> or C<poll>	2606	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1663	calls. Only L<EV> is fully fork-aware.	2607	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2608	are usually badly thought-out hacks that are incompatible with fork in
		2609	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2610	continue event-processing in both parent and child (or both, if you know
		2611	what you are doing).
		2612
		2613	This means that, in general, you cannot fork and do event processing in
		2614	the child if the event library was initialised before the fork (which
		2615	usually happens when the first AnyEvent watcher is created, or the library
		2616	is loaded).
1664		2617
1665	If you have to fork, you must either do so I<before> creating your first	2618	If you have to fork, you must either do so I<before> creating your first
1666	watcher OR you must not use AnyEvent at all in the child.	2619	watcher OR you must not use AnyEvent at all in the child OR you must do
		2620	something completely out of the scope of AnyEvent.
		2621
		2622	The problem of doing event processing in the parent I<and> the child
		2623	is much more complicated: even for backends that I<are> fork-aware or
		2624	fork-safe, their behaviour is not usually what you want: fork clones all
		2625	watchers, that means all timers, I/O watchers etc. are active in both
		2626	parent and child, which is almost never what you want. USing C<exec>
		2627	to start worker children from some kind of manage rprocess is usually
		2628	preferred, because it is much easier and cleaner, at the expense of having
		2629	to have another binary.
1667		2630
1668		2631
1669	=head1 SECURITY CONSIDERATIONS	2632	=head1 SECURITY CONSIDERATIONS
1670		2633
1671	AnyEvent can be forced to load any event model via	2634	AnyEvent can be forced to load any event model via
…		…
1682		2645
1683	use AnyEvent;	2646	use AnyEvent;
1684		2647
1685	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2648	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1686	be used to probe what backend is used and gain other information (which is	2649	be used to probe what backend is used and gain other information (which is
1687	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2650	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2651	$ENV{PERL_ANYEVENT_STRICT}.
		2652
		2653	Note that AnyEvent will remove I<all> environment variables starting with
		2654	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2655	enabled.
1688		2656
1689		2657
1690	=head1 BUGS	2658	=head1 BUGS
1691		2659
1692	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard	2660	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
1693	to work around. If you suffer from memleaks, first upgrade to Perl 5.10	2661	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
1694	and check wether the leaks still show up. (Perl 5.10.0 has other annoying	2662	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
1695	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as	2663	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
1696	pronounced).	2664	pronounced).
1697		2665
1698		2666
1699	=head1 SEE ALSO	2667	=head1 SEE ALSO
		2668
		2669	Tutorial/Introduction: L<AnyEvent::Intro>.
		2670
		2671	FAQ: L<AnyEvent::FAQ>.
1700		2672
1701	Utility functions: L<AnyEvent::Util>.	2673	Utility functions: L<AnyEvent::Util>.
1702		2674
1703	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2675	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1704	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2676	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1705		2677
1706	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2678	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1707	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2679	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1708	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2680	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1709	L<AnyEvent::Impl::POE>.	2681	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1710		2682
1711	Non-blocking file handles, sockets, TCP clients and	2683	Non-blocking file handles, sockets, TCP clients and
1712	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2684	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1713		2685
1714	Asynchronous DNS: L<AnyEvent::DNS>.	2686	Asynchronous DNS: L<AnyEvent::DNS>.
1715		2687
1716	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2688	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
1717		2689
1718	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2690	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2691	L<AnyEvent::HTTP>.
1719		2692
1720		2693
1721	=head1 AUTHOR	2694	=head1 AUTHOR
1722		2695
1723	Marc Lehmann <schmorp@schmorp.de>	2696	Marc Lehmann <schmorp@schmorp.de>

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