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Revision 1.55 by root, Wed Apr 23 11:25:42 2008 UTC vs.
Revision 1.343 by root, Wed Dec 29 04:27:53 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, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib - 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
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	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.
22		58
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		60
25	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
26	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
27		63
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	65	policy> and AnyEvent is I<small and efficient>.
30		66
31	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
32	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
33	pragmatic way. For event models and certain classes of immortals alike,	69	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	70	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	71	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	72	cannot change this, but it can hide the differences between those event
		73	loops.
37		74
38	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
39	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
40	religion, a way of living, and most importantly: without forcing your	77	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	78	module users into the same thing by forcing them to use the same event
42	model you use.	79	model you use.
43		80
44	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
45	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
46	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
47	cannot use anything else, as it is simply incompatible to everything that	84	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	85	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	86	module are I<also> forced to use the same event loop you use.
50		87
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	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
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
54	your module uses one of those, every user of your module has to use it,	91	uses one of those, every user of your module has to use it, too. But if
55	too. But if your module uses AnyEvent, it works transparently with all	92	your module uses AnyEvent, it works transparently with all event models it
56	event models it supports (including stuff like POE and IO::Async, as long	93	supports (including stuff like IO::Async, as long as those use one of the
57	as those use one of the supported event loops. It is trivial to add new	94	supported event loops. It is easy to add new event loops to AnyEvent, too,
58	event loops to AnyEvent, too, so it is future-proof).	95	so it is future-proof).
59		96
60	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
61	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
62	modules, you get an enourmous amount of code and strict rules you have to	99	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
64	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
65	technically possible.	102	technically possible.
66		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
67	Of course, if you want lots of policy (this can arguably be somewhat	110	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	111	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	112	model, you should I<not> use this module.
70		113
71
72	=head1 DESCRIPTION	114	=head1 DESCRIPTION
73		115
74	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
75	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
76	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
77	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
78		120
79	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>
80	module.	122	module.
81		123
82	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
83	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
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Impl::Perl>,
85	L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found,	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
86	the module tries to load these modules in the stated order. The first one	128	found is used. If none are detected, the module tries to load the first
87	that can be successfully loaded will be used. If, after this, still none	129	four modules in the order given; but note that if L<EV> is not
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	130	available, the pure-perl L<AnyEvent::Impl::Perl> should always work, so
89	is not very efficient, but should work everywhere.	131	the other two are not normally tried.
90		132
91	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	135	that model the default. For example:
94		136
…		…
96	use AnyEvent;	138	use AnyEvent;
97		139
98	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
99		141
100	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
101	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,
102	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
103		146
104	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called
105	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
106	explicitly.	149	explicitly and enjoy the high availability of that event loop :)
107		150
108	=head1 WATCHERS	151	=head1 WATCHERS
109		152
110	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
111	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
112	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
113		156
114	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
115	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
116	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
117	is in control).	160	is in control).
118		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
119	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
120	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
121	to it).	170	to it).
122		171
123	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.
124		173
125	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
126	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.
127		176
128	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
129		178
130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
132	undef $w;	181	undef $w;
133	});	182	});
134		183
135	Note that C<my $w; $w => combination. This is necessary because in Perl,	184	Note that C<my $w; $w => combination. This is necessary because in Perl,
136	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
137	declared.	186	declared.
138		187
139	=head2 IO WATCHERS	188	=head2 I/O WATCHERS
		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
140		195
141	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
142	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
143		198
144	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	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
145	events. C<poll> must be a string that is either C<r> or C<w>, which	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
146	creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
147	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.
148	becomes ready.
149		210
150	File handles will be kept alive, so as long as the watcher exists, the	211	Although the callback might get passed parameters, their value and
151	file handle exists, too.	212	presence is undefined and you cannot rely on them. Portable AnyEvent
		213	callbacks cannot use arguments passed to I/O watcher callbacks.
152		214
		215	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	216	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	217	underlying file descriptor.
155		218
156	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
157	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
158	handles.	221	handles.
159		222
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	228	warn "read: $input\n";
166	undef $w;	229	undef $w;
167	});	230	});
168		231
169	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
170		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
171	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 >>
172	method with the following mandatory arguments:	243	method with the following mandatory arguments:
173		244
174	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	246	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	247	in that case.
177		248
178	The timer callback will be invoked at most once: if you want a repeating	249	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	250	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	251	callbacks cannot use arguments passed to time watcher callbacks.
181		252
182	Example:	253	The callback will normally be invoked only once. If you specify another
		254	parameter, C<interval>, as a strictly positive number (> 0), then the
		255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
183		258
		259	The callback will be rescheduled before invoking the callback, but no
		260	attempt is made to avoid timer drift in most backends, so the interval is
		261	only approximate.
		262
184	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	266	warn "timeout\n";
187	});	267	});
188		268
189	# to cancel the timer:	269	# to cancel the timer:
190	undef $w;	270	undef $w;
191		271
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		273
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
200	};	276	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		277
205	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
206		279
207	There are two ways to handle timers: based on real time (relative, "fire	280	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	282	o'clock").
210		283
211	While most event loops expect timers to specified in a relative way, they use	284	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	285	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	286	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	288	fire "after a second" might actually take six years to finally fire.
216		289
217	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
218	about these issues is L<EV>, which offers both relative (ev_timer) and	291	of these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	292	on true relative time) and absolute (ev_periodic, based on wallclock time)
		293	timers.
220		294
221	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	296	AnyEvent API.
223		297
		298	AnyEvent has two additional methods that return the "current time":
		299
		300	=over 4
		301
		302	=item AnyEvent->time
		303
		304	This returns the "current wallclock time" as a fractional number of
		305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
		307
		308	It progresses independently of any event loop processing, i.e. each call
		309	will check the system clock, which usually gets updated frequently.
		310
		311	=item AnyEvent->now
		312
		313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
		317
		318	I<In almost all cases (in all cases if you don't care), this is the
		319	function to call when you want to know the current time.>
		320
		321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update its activity timeouts).
		324
		325	The rest of this section is only of relevance if you try to be very exact
		326	with your timing; you can skip it without a bad conscience.
		327
		328	For a practical example of when these times differ, consider L<Event::Lib>
		329	and L<EV> and the following set-up:
		330
		331	The event loop is running and has just invoked one of your callbacks at
		332	time=500 (assume no other callbacks delay processing). In your callback,
		333	you wait a second by executing C<sleep 1> (blocking the process for a
		334	second) and then (at time=501) you create a relative timer that fires
		335	after three seconds.
		336
		337	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		338	both return C<501>, because that is the current time, and the timer will
		339	be scheduled to fire at time=504 (C<501> + C<3>).
		340
		341	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		342	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		343	last event processing phase started. With L<EV>, your timer gets scheduled
		344	to run at time=503 (C<500> + C<3>).
		345
		346	In one sense, L<Event::Lib> is more exact, as it uses the current time
		347	regardless of any delays introduced by event processing. However, most
		348	callbacks do not expect large delays in processing, so this causes a
		349	higher drift (and a lot more system calls to get the current time).
		350
		351	In another sense, L<EV> is more exact, as your timer will be scheduled at
		352	the same time, regardless of how long event processing actually took.
		353
		354	In either case, if you care (and in most cases, you don't), then you
		355	can get whatever behaviour you want with any event loop, by taking the
		356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		357	account.
		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		362	the current time for each loop iteration (see the discussion of L<<
		363	AnyEvent->now >>, above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
		381	=back
		382
224	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
225		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
226	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
227	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
228	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
229		390
		391	Although the callback might get passed parameters, their value and
		392	presence is undefined and you cannot rely on them. Portable AnyEvent
		393	callbacks cannot use arguments passed to signal watcher callbacks.
		394
230	Multiple signals occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
232	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,
233	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
234		399
235	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
236	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
237		403
238	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
239	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
240		407
241	Example: exit on SIGINT	408	Example: exit on SIGINT
242		409
243	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
244		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$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
245	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
246		450
		451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		452
247	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.
248		454
249	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,
250	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
251	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
252	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
253	and exit status (as returned by waitpid).	459	(stopped/continued).
254		460
255	Example: wait for pid 1333	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.
256		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).
		469
		470	There is a slight catch to child watchers, however: you usually start them
		471	I<after> the child process was created, and this means the process could
		472	have exited already (and no SIGCHLD will be sent anymore).
		473
		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
		476	that I<do> handle this correctly, they usually need to be loaded before
		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.
		480
		481	This means you cannot create a child watcher as the very first
		482	thing in an AnyEvent program, you I<have> to create at least one
		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.
		489
		490	Example: fork a process and wait for it
		491
		492	my $done = AnyEvent->condvar;
		493
		494	my $pid = fork or exit 5;
		495
257	my $w = AnyEvent->child (	496	my $w = AnyEvent->child (
258	pid => 1333,	497	pid => $pid,
259	cb => sub {	498	cb => sub {
260	my ($pid, $status) = @_;	499	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	500	warn "pid $pid exited with status $status";
		501	$done->send;
262	},	502	},
263	);	503	);
		504
		505	# do something else, then wait for process exit
		506	$done->recv;
		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	});
264		547
265	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
266		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
		554
		555	If you are familiar with some event loops you will know that all of them
		556	require you to run some blocking "loop", "run" or similar function that
		557	will actively watch for new events and call your callbacks.
		558
		559	AnyEvent is slightly different: it expects somebody else to run the event
		560	loop and will only block when necessary (usually when told by the user).
		561
		562	The tool to do that is called a "condition variable", so called because
		563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
		566
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	567	Condition variables can be created by calling the C<< AnyEvent->condvar
268	method without any arguments.	568	>> method, usually without arguments. The only argument pair allowed is
		569	C<cb>, which specifies a callback to be called when the condition variable
		570	becomes true, with the condition variable as the first argument (but not
		571	the results).
269		572
270	A condition variable waits for a condition - precisely that the C<<	573	After creation, the condition variable is "false" until it becomes "true"
271	->broadcast >> method has been called.	574	by calling the C<send> method (or calling the condition variable as if it
		575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
272		577
273	They are very useful to signal that a condition has been fulfilled, for	578	Since condition variables are the most complex part of the AnyEvent API, here are
		579	some different mental models of what they are - pick the ones you can connect to:
		580
		581	=over 4
		582
		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
		601
		602	Condition variables are very useful to signal that something has finished,
274	example, if you write a module that does asynchronous http requests,	603	for example, if you write a module that does asynchronous http requests,
275	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
276	availability of results.	605	availability of results. The user can either act when the callback is
		606	called or can synchronously C<< ->recv >> for the results.
277		607
278	You can also use condition variables to block your main program until	608	You can also use them to simulate traditional event loops - for example,
279	an event occurs - for example, you could C<< ->wait >> in your main	609	you can block your main program until an event occurs - for example, you
280	program until the user clicks the Quit button in your app, which would C<<	610	could C<< ->recv >> in your main program until the user clicks the Quit
281	->broadcast >> the "quit" event.	611	button of your app, which would C<< ->send >> the "quit" event.
282		612
283	Note that condition variables recurse into the event loop - if you have	613	Note that condition variables recurse into the event loop - if you have
284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	614	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
285	lose. Therefore, condition variables are good to export to your caller, but	615	lose. Therefore, condition variables are good to export to your caller, but
286	you should avoid making a blocking wait yourself, at least in callbacks,	616	you should avoid making a blocking wait yourself, at least in callbacks,
287	as this asks for trouble.	617	as this asks for trouble.
288		618
289	This object has two methods:	619	Condition variables are represented by hash refs in perl, and the keys
		620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		621	easy (it is often useful to build your own transaction class on top of
		622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		623	its C<new> method in your own C<new> method.
		624
		625	There are two "sides" to a condition variable - the "producer side" which
		626	eventually calls C<< -> send >>, and the "consumer side", which waits
		627	for the send to occur.
		628
		629	Example: wait for a timer.
		630
		631	# condition: "wait till the timer is fired"
		632	my $timer_fired = AnyEvent->condvar;
		633
		634	# create the timer - we could wait for, say
		635	# a handle becomign ready, or even an
		636	# AnyEvent::HTTP request to finish, but
		637	# in this case, we simply use a timer:
		638	my $w = AnyEvent->timer (
		639	after => 1,
		640	cb => sub { $timer_fired->send },
		641	);
		642
		643	# this "blocks" (while handling events) till the callback
		644	# calls ->send
		645	$timer_fired->recv;
		646
		647	Example: wait for a timer, but take advantage of the fact that condition
		648	variables are also callable directly.
		649
		650	my $done = AnyEvent->condvar;
		651	my $delay = AnyEvent->timer (after => 5, cb => $done);
		652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
		670
		671	=head3 METHODS FOR PRODUCERS
		672
		673	These methods should only be used by the producing side, i.e. the
		674	code/module that eventually sends the signal. Note that it is also
		675	the producer side which creates the condvar in most cases, but it isn't
		676	uncommon for the consumer to create it as well.
290		677
291	=over 4	678	=over 4
292		679
		680	=item $cv->send (...)
		681
		682	Flag the condition as ready - a running C<< ->recv >> and all further
		683	calls to C<recv> will (eventually) return after this method has been
		684	called. If nobody is waiting the send will be remembered.
		685
		686	If a callback has been set on the condition variable, it is called
		687	immediately from within send.
		688
		689	Any arguments passed to the C<send> call will be returned by all
		690	future C<< ->recv >> calls.
		691
		692	Condition variables are overloaded so one can call them directly (as if
		693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
		695
		696	=item $cv->croak ($error)
		697
		698	Similar to send, but causes all calls to C<< ->recv >> to invoke
		699	C<Carp::croak> with the given error message/object/scalar.
		700
		701	This can be used to signal any errors to the condition variable
		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.
		707
		708	=item $cv->begin ([group callback])
		709
293	=item $cv->wait	710	=item $cv->end
294		711
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	712	These two methods can be used to combine many transactions/events into
296	called on c<$cv>, while servicing other watchers normally.	713	one. For example, a function that pings many hosts in parallel might want
		714	to use a condition variable for the whole process.
297		715
		716	Every call to C<< ->begin >> will increment a counter, and every call to
		717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		718	>>, the (last) callback passed to C<begin> will be executed, passing the
		719	condvar as first argument. That callback is I<supposed> to call C<< ->send
		720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
		722
		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:
		730
		731	my $cv = AnyEvent->condvar;
		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
		757	my %result;
		758	$cv->begin (sub { shift->send (\%result) });
		759
		760	for my $host (@list_of_hosts) {
		761	$cv->begin;
		762	ping_host_then_call_callback $host, sub {
		763	$result{$host} = ...;
		764	$cv->end;
		765	};
		766	}
		767
		768	$cv->end;
		769
		770	This code fragment supposedly pings a number of hosts and calls
		771	C<send> after results for all then have have been gathered - in any
		772	order. To achieve this, the code issues a call to C<begin> when it starts
		773	each ping request and calls C<end> when it has received some result for
		774	it. Since C<begin> and C<end> only maintain a counter, the order in which
		775	results arrive is not relevant.
		776
		777	There is an additional bracketing call to C<begin> and C<end> outside the
		778	loop, which serves two important purposes: first, it sets the callback
		779	to be called once the counter reaches C<0>, and second, it ensures that
		780	C<send> is called even when C<no> hosts are being pinged (the loop
		781	doesn't execute once).
		782
		783	This is the general pattern when you "fan out" into multiple (but
		784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		785	the callback and ensure C<end> is called at least once, and then, for each
		786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
		788
		789	=back
		790
		791	=head3 METHODS FOR CONSUMERS
		792
		793	These methods should only be used by the consuming side, i.e. the
		794	code awaits the condition.
		795
		796	=over 4
		797
		798	=item $cv->recv
		799
		800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		801	>> methods have been called on C<$cv>, while servicing other watchers
		802	normally.
		803
298	You can only wait once on a condition - additional calls will return	804	You can only wait once on a condition - additional calls are valid but
299	immediately.	805	will return immediately.
		806
		807	If an error condition has been set by calling C<< ->croak >>, then this
		808	function will call C<croak>.
		809
		810	In list context, all parameters passed to C<send> will be returned,
		811	in scalar context only the first one will be returned.
		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.
300		819
301	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
302	(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
303	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
304	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
305	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
306	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,
307	while still suppporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
308		827
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot	828	You can ensure that C<< ->recv >> never blocks by setting a callback and
310	sensibly have two C<< ->wait >>'s in parallel, as that would require	829	only calling C<< ->recv >> from within that callback (or at a later
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	830	time). This will work even when the event loop does not support blocking
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	831	waits otherwise.
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315		832
316	=item $cv->broadcast	833	=item $bool = $cv->ready
317		834
318	Flag the condition as ready - a running C<< ->wait >> and all further	835	Returns true when the condition is "true", i.e. whether C<send> or
319	calls to C<wait> will (eventually) return after this method has been	836	C<croak> have been called.
320	called. If nobody is waiting the broadcast will be remembered..	837
		838	=item $cb = $cv->cb ($cb->($cv))
		839
		840	This is a mutator function that returns the callback set and optionally
		841	replaces it before doing so.
		842
		843	The callback will be called when the condition becomes "true", i.e. when
		844	C<send> or C<croak> are called, with the only argument being the
		845	condition variable itself. If the condition is already true, the
		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.
321		848
322	=back	849	=back
323		850
324	Example:	851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
325		852
326	# wait till the result is ready	853	The available backend classes are (every class has its own manpage):
327	my $result_ready = AnyEvent->condvar;
328		854
329	# do something such as adding a timer	855	=over 4
330	# or socket watcher the calls $result_ready->broadcast
331	# when the "result" is ready.
332	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (
334	after => 1,
335	cb => sub { $result_ready->broadcast },
336	);
337		856
338	# this "blocks" (while handling events) till the watcher	857	=item Backends that are autoprobed when no other event loop can be found.
339	# calls broadcast	858
340	$result_ready->wait;	859	EV is the preferred backend when no other event loop seems to be in
		860	use. If EV is not installed, then AnyEvent will fall back to its own
		861	pure-perl implementation, which is available everywhere as it comes with
		862	AnyEvent itself.
		863
		864	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		865	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		866
		867	=item Backends that are transparently being picked up when they are used.
		868
		869	These will be used if they are already loaded when the first watcher
		870	is created, in which case it is assumed that the application is using
		871	them. This means that AnyEvent will automatically pick the right backend
		872	when the main program loads an event module before anything starts to
		873	create watchers. Nothing special needs to be done by the main program.
		874
		875	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		876	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		877	AnyEvent::Impl::Tk based on Tk, very broken.
		878	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		879	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		880	AnyEvent::Impl::Irssi used when running within irssi.
		881	AnyEvent::Impl::IOAsync based on IO::Async.
		882
		883	=item Backends with special needs.
		884
		885	Qt requires the Qt::Application to be instantiated first, but will
		886	otherwise be picked up automatically. As long as the main program
		887	instantiates the application before any AnyEvent watchers are created,
		888	everything should just work.
		889
		890	AnyEvent::Impl::Qt based on Qt.
		891
		892	=item Event loops that are indirectly supported via other backends.
		893
		894	Some event loops can be supported via other modules:
		895
		896	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		897
		898	B<WxWidgets> has no support for watching file handles. However, you can
		899	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		900	polls 20 times per second, which was considered to be too horrible to even
		901	consider for AnyEvent.
		902
		903	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		904	backend, so it can be supported through POE.
		905
		906	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		907	load L<POE> when detecting them, in the hope that POE will pick them up,
		908	in which case everything will be automatic.
		909
		910	=back
341		911
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	912	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		913
		914	These are not normally required to use AnyEvent, but can be useful to
		915	write AnyEvent extension modules.
		916
344	=over 4	917	=over 4
345		918
346	=item $AnyEvent::MODEL	919	=item $AnyEvent::MODEL
347		920
348	Contains C<undef> until the first watcher is being created. Then it	921	Contains C<undef> until the first watcher is being created, before the
		922	backend has been autodetected.
		923
349	contains the event model that is being used, which is the name of the	924	Afterwards it contains the event model that is being used, which is the
350	Perl class implementing the model. This class is usually one of the	925	name of the Perl class implementing the model. This class is usually one
351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	926	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	927	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
353		928	will be C<urxvt::anyevent>).
354	The known classes so far are:
355
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)
360	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
363	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
364		929
365	=item AnyEvent::detect	930	=item AnyEvent::detect
366		931
367	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	932	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
368	if necessary. You should only call this function right before you would	933	if necessary. You should only call this function right before you would
369	have created an AnyEvent watcher anyway, that is, as late as possible at	934	have created an AnyEvent watcher anyway, that is, as late as possible at
370	runtime.	935	runtime, and not e.g. during initialisation of your module.
		936
		937	If you need to do some initialisation before AnyEvent watchers are
		938	created, use C<post_detect>.
		939
		940	=item $guard = AnyEvent::post_detect { BLOCK }
		941
		942	Arranges for the code block to be executed as soon as the event model is
		943	autodetected (or immediately if that has already happened).
		944
		945	The block will be executed I<after> the actual backend has been detected
		946	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		947	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		948	other initialisations - see the sources of L<AnyEvent::Strict> or
		949	L<AnyEvent::AIO> to see how this is used.
		950
		951	The most common usage is to create some global watchers, without forcing
		952	event module detection too early, for example, L<AnyEvent::AIO> creates
		953	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		954	avoid autodetecting the event module at load time.
		955
		956	If called in scalar or list context, then it creates and returns an object
		957	that automatically removes the callback again when it is destroyed (or
		958	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		959	a case where this is useful.
		960
		961	Example: Create a watcher for the IO::AIO module and store it in
		962	C<$WATCHER>, but do so only do so after the event loop is initialised.
		963
		964	our WATCHER;
		965
		966	my $guard = AnyEvent::post_detect {
		967	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		968	};
		969
		970	# the ||= is important in case post_detect immediately runs the block,
		971	# as to not clobber the newly-created watcher. assigning both watcher and
		972	# post_detect guard to the same variable has the advantage of users being
		973	# able to just C<undef $WATCHER> if the watcher causes them grief.
		974
		975	$WATCHER ||= $guard;
		976
		977	=item @AnyEvent::post_detect
		978
		979	If there are any code references in this array (you can C<push> to it
		980	before or after loading AnyEvent), then they will be called directly
		981	after the event loop has been chosen.
		982
		983	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		984	if it is defined then the event loop has already been detected, and the
		985	array will be ignored.
		986
		987	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		988	it, as it takes care of these details.
		989
		990	This variable is mainly useful for modules that can do something useful
		991	when AnyEvent is used and thus want to know when it is initialised, but do
		992	not need to even load it by default. This array provides the means to hook
		993	into AnyEvent passively, without loading it.
		994
		995	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		996	together, you could put this into Coro (this is the actual code used by
		997	Coro to accomplish this):
		998
		999	if (defined $AnyEvent::MODEL) {
		1000	# AnyEvent already initialised, so load Coro::AnyEvent
		1001	require Coro::AnyEvent;
		1002	} else {
		1003	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1004	# as soon as it is
		1005	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1006	}
371		1007
372	=back	1008	=back
373		1009
374	=head1 WHAT TO DO IN A MODULE	1010	=head1 WHAT TO DO IN A MODULE
375		1011
…		…
379	Be careful when you create watchers in the module body - AnyEvent will	1015	Be careful when you create watchers in the module body - AnyEvent will
380	decide which event module to use as soon as the first method is called, so	1016	decide which event module to use as soon as the first method is called, so
381	by calling AnyEvent in your module body you force the user of your module	1017	by calling AnyEvent in your module body you force the user of your module
382	to load the event module first.	1018	to load the event module first.
383		1019
384	Never call C<< ->wait >> on a condition variable unless you I<know> that	1020	Never call C<< ->recv >> on a condition variable unless you I<know> that
385	the C<< ->broadcast >> method has been called on it already. This is	1021	the C<< ->send >> method has been called on it already. This is
386	because it will stall the whole program, and the whole point of using	1022	because it will stall the whole program, and the whole point of using
387	events is to stay interactive.	1023	events is to stay interactive.
388		1024
389	It is fine, however, to call C<< ->wait >> when the user of your module	1025	It is fine, however, to call C<< ->recv >> when the user of your module
390	requests it (i.e. if you create a http request object ad have a method	1026	requests it (i.e. if you create a http request object ad have a method
391	called C<results> that returns the results, it should call C<< ->wait >>	1027	called C<results> that returns the results, it may call C<< ->recv >>
392	freely, as the user of your module knows what she is doing. always).	1028	freely, as the user of your module knows what she is doing. Always).
393		1029
394	=head1 WHAT TO DO IN THE MAIN PROGRAM	1030	=head1 WHAT TO DO IN THE MAIN PROGRAM
395		1031
396	There will always be a single main program - the only place that should	1032	There will always be a single main program - the only place that should
397	dictate which event model to use.	1033	dictate which event model to use.
398		1034
399	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1035	If the program is not event-based, it need not do anything special, even
400	do anything special (it does not need to be event-based) and let AnyEvent	1036	when it depends on a module that uses an AnyEvent. If the program itself
401	decide which implementation to chose if some module relies on it.	1037	uses AnyEvent, but does not care which event loop is used, all it needs
		1038	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1039	available loop implementation.
402		1040
403	If the main program relies on a specific event model. For example, in	1041	If the main program relies on a specific event model - for example, in
404	Gtk2 programs you have to rely on the Glib module. You should load the	1042	Gtk2 programs you have to rely on the Glib module - you should load the
405	event module before loading AnyEvent or any module that uses it: generally	1043	event module before loading AnyEvent or any module that uses it: generally
406	speaking, you should load it as early as possible. The reason is that	1044	speaking, you should load it as early as possible. The reason is that
407	modules might create watchers when they are loaded, and AnyEvent will	1045	modules might create watchers when they are loaded, and AnyEvent will
408	decide on the event model to use as soon as it creates watchers, and it	1046	decide on the event model to use as soon as it creates watchers, and it
409	might chose the wrong one unless you load the correct one yourself.	1047	might choose the wrong one unless you load the correct one yourself.
410		1048
411	You can chose to use a rather inefficient pure-perl implementation by	1049	You can chose to use a pure-perl implementation by loading the
412	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1050	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
413	behaviour everywhere, but letting AnyEvent chose is generally better.	1051	everywhere, but letting AnyEvent chose the model is generally better.
		1052
		1053	=head2 MAINLOOP EMULATION
		1054
		1055	Sometimes (often for short test scripts, or even standalone programs who
		1056	only want to use AnyEvent), you do not want to run a specific event loop.
		1057
		1058	In that case, you can use a condition variable like this:
		1059
		1060	AnyEvent->condvar->recv;
		1061
		1062	This has the effect of entering the event loop and looping forever.
		1063
		1064	Note that usually your program has some exit condition, in which case
		1065	it is better to use the "traditional" approach of storing a condition
		1066	variable somewhere, waiting for it, and sending it when the program should
		1067	exit cleanly.
		1068
		1069
		1070	=head1 OTHER MODULES
		1071
		1072	The following is a non-exhaustive list of additional modules that use
		1073	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1074	modules and other event loops in the same program. Some of the modules
		1075	come as part of AnyEvent, the others are available via CPAN.
		1076
		1077	=over 4
		1078
		1079	=item L<AnyEvent::Util>
		1080
		1081	Contains various utility functions that replace often-used blocking
		1082	functions such as C<inet_aton> with event/callback-based versions.
		1083
		1084	=item L<AnyEvent::Socket>
		1085
		1086	Provides various utility functions for (internet protocol) sockets,
		1087	addresses and name resolution. Also functions to create non-blocking tcp
		1088	connections or tcp servers, with IPv6 and SRV record support and more.
		1089
		1090	=item L<AnyEvent::Handle>
		1091
		1092	Provide read and write buffers, manages watchers for reads and writes,
		1093	supports raw and formatted I/O, I/O queued and fully transparent and
		1094	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1095
		1096	=item L<AnyEvent::DNS>
		1097
		1098	Provides rich asynchronous DNS resolver capabilities.
		1099
		1100	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1101
		1102	Implement event-based interfaces to the protocols of the same name (for
		1103	the curious, IGS is the International Go Server and FCP is the Freenet
		1104	Client Protocol).
		1105
		1106	=item L<AnyEvent::Handle::UDP>
		1107
		1108	Here be danger!
		1109
		1110	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1111	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1112	its use of a stream-based API with a protocol that isn't streamable, that
		1113	the only way to improve it is to delete it.
		1114
		1115	It features data corruption (but typically only under load) and general
		1116	confusion. On top, the author is not only clueless about UDP but also
		1117	fact-resistant - some gems of his understanding: "connect doesn't work
		1118	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1119	packets", "I don't need to implement proper error checking as UDP doesn't
		1120	support error checking" and so on - he doesn't even understand what's
		1121	wrong with his module when it is explained to him.
		1122
		1123	=item L<AnyEvent::DBI>
		1124
		1125	Executes L<DBI> requests asynchronously in a proxy process for you,
		1126	notifying you in an event-based way when the operation is finished.
		1127
		1128	=item L<AnyEvent::AIO>
		1129
		1130	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1131	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1132	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1133	file I/O, and much more.
		1134
		1135	=item L<AnyEvent::HTTPD>
		1136
		1137	A simple embedded webserver.
		1138
		1139	=item L<AnyEvent::FastPing>
		1140
		1141	The fastest ping in the west.
		1142
		1143	=item L<Coro>
		1144
		1145	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1146
		1147	=back
414		1148
415	=cut	1149	=cut
416		1150
417	package AnyEvent;	1151	package AnyEvent;
418		1152
419	no warnings;	1153	# basically a tuned-down version of common::sense
420	use strict;	1154	sub common_sense {
		1155	# from common:.sense 3.3
		1156	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf3\x0f\xc0\xf0\xfc\x33\x00";
		1157	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1158	$^H |= 0x00000600;
		1159	}
421		1160
		1161	BEGIN { AnyEvent::common_sense }
		1162
422	use Carp;	1163	use Carp ();
423		1164
424	our $VERSION = '3.12';	1165	our $VERSION = '5.29';
425	our $MODEL;	1166	our $MODEL;
426		1167
427	our $AUTOLOAD;	1168	our $AUTOLOAD;
428	our @ISA;	1169	our @ISA;
429		1170
430	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
431
432	our @REGISTRY;	1171	our @REGISTRY;
433		1172
		1173	our $VERBOSE;
		1174
		1175	BEGIN {
		1176	require "AnyEvent/constants.pl";
		1177
		1178	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1179
		1180	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1181	if ${^TAINT};
		1182
		1183	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1184
		1185	}
		1186
		1187	our $MAX_SIGNAL_LATENCY = 10;
		1188
		1189	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1190
		1191	{
		1192	my $idx;
		1193	$PROTOCOL{$_} = ++$idx
		1194	for reverse split /\s*,\s*/,
		1195	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1196	}
		1197
434	my @models = (	1198	my @models = (
435	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
436	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
437	[EV:: => AnyEvent::Impl::EV::],	1199	[EV:: => AnyEvent::Impl::EV:: , 1],
		1200	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1201	# everything below here will not (normally) be autoprobed
		1202	# as the pureperl backend should work everywhere
		1203	# and is usually faster
438	[Event:: => AnyEvent::Impl::Event::],	1204	[Event:: => AnyEvent::Impl::Event::, 1],
439	[Glib:: => AnyEvent::Impl::Glib::],	1205	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1206	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1207	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1208	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1209	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1210	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
440	[Tk:: => AnyEvent::Impl::Tk::],	1211	[Wx:: => AnyEvent::Impl::POE::],
441	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1212	[Prima:: => AnyEvent::Impl::POE::],
442	[Event::Lib:: => AnyEvent::Impl::EventLib::],	1213	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::],
443	);	1214	);
444		1215
445	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1216	our %method = map +($_ => 1),
		1217	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1218
		1219	our @post_detect;
		1220
		1221	sub post_detect(&) {
		1222	my ($cb) = @_;
		1223
		1224	push @post_detect, $cb;
		1225
		1226	defined wantarray
		1227	? bless \$cb, "AnyEvent::Util::postdetect"
		1228	: ()
		1229	}
		1230
		1231	sub AnyEvent::Util::postdetect::DESTROY {
		1232	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1233	}
446		1234
447	sub detect() {	1235	sub detect() {
		1236	# free some memory
		1237	*detect = sub () { $MODEL };
		1238
		1239	local $!; # for good measure
		1240	local $SIG{__DIE__};
		1241
		1242	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1243	my $model = "AnyEvent::Impl::$1";
		1244	if (eval "require $model") {
		1245	$MODEL = $model;
		1246	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1247	} else {
		1248	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1249	}
		1250	}
		1251
		1252	# check for already loaded models
448	unless ($MODEL) {	1253	unless ($MODEL) {
449	no strict 'refs';	1254	for (@REGISTRY, @models) {
450		1255	my ($package, $model) = @$_;
451	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1256	if (${"$package\::VERSION"} > 0) {
452	my $model = "AnyEvent::Impl::$1";
453	if (eval "require $model") {	1257	if (eval "require $model") {
454	$MODEL = $model;	1258	$MODEL = $model;
455	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1259	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
		1260	last;
		1261	}
456	}	1262	}
457	}	1263	}
458		1264
459	# check for already loaded models
460	unless ($MODEL) {	1265	unless ($MODEL) {
		1266	# try to autoload a model
461	for (@REGISTRY, @models) {	1267	for (@REGISTRY, @models) {
462	my ($package, $model) = @$_;	1268	my ($package, $model, $autoload) = @$_;
		1269	if (
		1270	$autoload
		1271	and eval "require $package"
463	if (${"$package\::VERSION"} > 0) {	1272	and ${"$package\::VERSION"} > 0
464	if (eval "require $model") {	1273	and eval "require $model"
		1274	) {
465	$MODEL = $model;	1275	$MODEL = $model;
466	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1276	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
467	last;	1277	last;
468	}
469	}	1278	}
470	}	1279	}
471		1280
472	unless ($MODEL) {
473	# try to load a model
474
475	for (@REGISTRY, @models) {
476	my ($package, $model) = @$_;
477	if (eval "require $package"
478	and ${"$package\::VERSION"} > 0
479	and eval "require $model") {
480	$MODEL = $model;
481	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
482	last;
483	}
484	}
485
486	$MODEL	1281	$MODEL
487	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1282	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?\n";
488	}
489	}	1283	}
490
491	unshift @ISA, $MODEL;
492	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
493	}	1284	}
		1285
		1286	@models = (); # free probe data
		1287
		1288	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1289	unshift @ISA, $MODEL;
		1290
		1291	# now nuke some methods that are overridden by the backend.
		1292	# SUPER is not allowed.
		1293	for (qw(time signal child idle)) {
		1294	undef &{"AnyEvent::Base::$_"}
		1295	if defined &{"$MODEL\::$_"};
		1296	}
		1297
		1298	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1299	eval { require AnyEvent::Strict };
		1300	warn "AnyEvent: cannot load AnyEvent::Strict: $@"
		1301	if $@ && $VERBOSE;
		1302	}
		1303
		1304	(shift @post_detect)->() while @post_detect;
		1305
		1306	*post_detect = sub(&) {
		1307	shift->();
		1308
		1309	undef
		1310	};
494		1311
495	$MODEL	1312	$MODEL
496	}	1313	}
497		1314
498	sub AUTOLOAD {	1315	sub AUTOLOAD {
499	(my $func = $AUTOLOAD) =~ s/.*://;	1316	(my $func = $AUTOLOAD) =~ s/.*://;
500		1317
501	$method{$func}	1318	$method{$func}
502	or croak "$func: not a valid method for AnyEvent objects";	1319	or Carp::croak "$func: not a valid AnyEvent class method";
503		1320
504	detect unless $MODEL;	1321	detect;
505		1322
506	my $class = shift;	1323	my $class = shift;
507	$class->$func (@_);	1324	$class->$func (@_);
508	}	1325	}
509		1326
		1327	# utility function to dup a filehandle. this is used by many backends
		1328	# to support binding more than one watcher per filehandle (they usually
		1329	# allow only one watcher per fd, so we dup it to get a different one).
		1330	sub _dupfh($$;$$) {
		1331	my ($poll, $fh, $r, $w) = @_;
		1332
		1333	# cygwin requires the fh mode to be matching, unix doesn't
		1334	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1335
		1336	open my $fh2, $mode, $fh
		1337	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1338
		1339	# we assume CLOEXEC is already set by perl in all important cases
		1340
		1341	($fh2, $rw)
		1342	}
		1343
		1344	=head1 SIMPLIFIED AE API
		1345
		1346	Starting with version 5.0, AnyEvent officially supports a second, much
		1347	simpler, API that is designed to reduce the calling, typing and memory
		1348	overhead by using function call syntax and a fixed number of parameters.
		1349
		1350	See the L<AE> manpage for details.
		1351
		1352	=cut
		1353
		1354	package AE;
		1355
		1356	our $VERSION = $AnyEvent::VERSION;
		1357
		1358	# fall back to the main API by default - backends and AnyEvent::Base
		1359	# implementations can overwrite these.
		1360
		1361	sub io($$$) {
		1362	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1363	}
		1364
		1365	sub timer($$$) {
		1366	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1367	}
		1368
		1369	sub signal($$) {
		1370	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1371	}
		1372
		1373	sub child($$) {
		1374	AnyEvent->child (pid => $_[0], cb => $_[1])
		1375	}
		1376
		1377	sub idle($) {
		1378	AnyEvent->idle (cb => $_[0])
		1379	}
		1380
		1381	sub cv(;&) {
		1382	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1383	}
		1384
		1385	sub now() {
		1386	AnyEvent->now
		1387	}
		1388
		1389	sub now_update() {
		1390	AnyEvent->now_update
		1391	}
		1392
		1393	sub time() {
		1394	AnyEvent->time
		1395	}
		1396
510	package AnyEvent::Base;	1397	package AnyEvent::Base;
511		1398
		1399	# default implementations for many methods
		1400
		1401	sub time {
		1402	eval q{ # poor man's autoloading {}
		1403	# probe for availability of Time::HiRes
		1404	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1405	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1406	*AE::time = \&Time::HiRes::time;
		1407	# if (eval "use POSIX (); (POSIX::times())...
		1408	} else {
		1409	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1410	*AE::time = sub (){ time }; # epic fail
		1411	}
		1412
		1413	*time = sub { AE::time }; # different prototypes
		1414	};
		1415	die if $@;
		1416
		1417	&time
		1418	}
		1419
		1420	*now = \&time;
		1421
		1422	sub now_update { }
		1423
512	# default implementation for ->condvar, ->wait, ->broadcast	1424	# default implementation for ->condvar
513		1425
514	sub condvar {	1426	sub condvar {
515	bless \my $flag, "AnyEvent::Base::CondVar"	1427	eval q{ # poor man's autoloading {}
516	}	1428	*condvar = sub {
		1429	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1430	};
517		1431
518	sub AnyEvent::Base::CondVar::broadcast {	1432	*AE::cv = sub (;&) {
519	${$_[0]}++;	1433	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
520	}	1434	};
		1435	};
		1436	die if $@;
521		1437
522	sub AnyEvent::Base::CondVar::wait {	1438	&condvar
523	AnyEvent->one_event while !${$_[0]};
524	}	1439	}
525		1440
526	# default implementation for ->signal	1441	# default implementation for ->signal
527		1442
528	our %SIG_CB;	1443	our $HAVE_ASYNC_INTERRUPT;
		1444
		1445	sub _have_async_interrupt() {
		1446	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1447	&& eval "use Async::Interrupt 1.02 (); 1")
		1448	unless defined $HAVE_ASYNC_INTERRUPT;
		1449
		1450	$HAVE_ASYNC_INTERRUPT
		1451	}
		1452
		1453	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1454	our (%SIG_ASY, %SIG_ASY_W);
		1455	our ($SIG_COUNT, $SIG_TW);
		1456
		1457	# install a dummy wakeup watcher to reduce signal catching latency
		1458	# used by Impls
		1459	sub _sig_add() {
		1460	unless ($SIG_COUNT++) {
		1461	# try to align timer on a full-second boundary, if possible
		1462	my $NOW = AE::now;
		1463
		1464	$SIG_TW = AE::timer
		1465	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1466	$MAX_SIGNAL_LATENCY,
		1467	sub { } # just for the PERL_ASYNC_CHECK
		1468	;
		1469	}
		1470	}
		1471
		1472	sub _sig_del {
		1473	undef $SIG_TW
		1474	unless --$SIG_COUNT;
		1475	}
		1476
		1477	our $_sig_name_init; $_sig_name_init = sub {
		1478	eval q{ # poor man's autoloading {}
		1479	undef $_sig_name_init;
		1480
		1481	if (_have_async_interrupt) {
		1482	*sig2num = \&Async::Interrupt::sig2num;
		1483	*sig2name = \&Async::Interrupt::sig2name;
		1484	} else {
		1485	require Config;
		1486
		1487	my %signame2num;
		1488	@signame2num{ split ' ', $Config::Config{sig_name} }
		1489	= split ' ', $Config::Config{sig_num};
		1490
		1491	my @signum2name;
		1492	@signum2name[values %signame2num] = keys %signame2num;
		1493
		1494	*sig2num = sub($) {
		1495	$_[0] > 0 ? shift : $signame2num{+shift}
		1496	};
		1497	*sig2name = sub ($) {
		1498	$_[0] > 0 ? $signum2name[+shift] : shift
		1499	};
		1500	}
		1501	};
		1502	die if $@;
		1503	};
		1504
		1505	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1506	sub sig2name($) { &$_sig_name_init; &sig2name }
529		1507
530	sub signal {	1508	sub signal {
		1509	eval q{ # poor man's autoloading {}
		1510	# probe for availability of Async::Interrupt
		1511	if (_have_async_interrupt) {
		1512	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1513
		1514	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1515	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1516
		1517	} else {
		1518	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1519
		1520	if (AnyEvent::WIN32) {
		1521	require AnyEvent::Util;
		1522
		1523	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1524	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1525	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1526	} else {
		1527	pipe $SIGPIPE_R, $SIGPIPE_W;
		1528	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1529	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1530
		1531	# not strictly required, as $^F is normally 2, but let's make sure...
		1532	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1533	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1534	}
		1535
		1536	$SIGPIPE_R
		1537	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1538
		1539	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1540	}
		1541
		1542	*signal = $HAVE_ASYNC_INTERRUPT
		1543	? sub {
531	my (undef, %arg) = @_;	1544	my (undef, %arg) = @_;
532		1545
		1546	# async::interrupt
533	my $signal = uc $arg{signal}	1547	my $signal = sig2num $arg{signal};
534	or Carp::croak "required option 'signal' is missing";
535
536	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1548	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1549
		1550	$SIG_ASY{$signal} ||= new Async::Interrupt
		1551	cb => sub { undef $SIG_EV{$signal} },
		1552	signal => $signal,
		1553	pipe => [$SIGPIPE_R->filenos],
		1554	pipe_autodrain => 0,
		1555	;
		1556
		1557	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1558	}
		1559	: sub {
		1560	my (undef, %arg) = @_;
		1561
		1562	# pure perl
		1563	my $signal = sig2name $arg{signal};
		1564	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1565
537	$SIG{$signal} ||= sub {	1566	$SIG{$signal} ||= sub {
		1567	local $!;
		1568	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1569	undef $SIG_EV{$signal};
		1570	};
		1571
		1572	# can't do signal processing without introducing races in pure perl,
		1573	# so limit the signal latency.
		1574	_sig_add;
		1575
		1576	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1577	}
		1578	;
		1579
		1580	*AnyEvent::Base::signal::DESTROY = sub {
		1581	my ($signal, $cb) = @{$_[0]};
		1582
		1583	_sig_del;
		1584
		1585	delete $SIG_CB{$signal}{$cb};
		1586
		1587	$HAVE_ASYNC_INTERRUPT
		1588	? delete $SIG_ASY{$signal}
		1589	: # delete doesn't work with older perls - they then
		1590	# print weird messages, or just unconditionally exit
		1591	# instead of getting the default action.
		1592	undef $SIG{$signal}
		1593	unless keys %{ $SIG_CB{$signal} };
		1594	};
		1595
		1596	*_signal_exec = sub {
		1597	$HAVE_ASYNC_INTERRUPT
		1598	? $SIGPIPE_R->drain
		1599	: sysread $SIGPIPE_R, (my $dummy), 9;
		1600
		1601	while (%SIG_EV) {
		1602	for (keys %SIG_EV) {
		1603	delete $SIG_EV{$_};
538	$_->() for values %{ $SIG_CB{$signal} || {} };	1604	$_->() for values %{ $SIG_CB{$_} || {} };
		1605	}
		1606	}
		1607	};
539	};	1608	};
		1609	die if $@;
540		1610
541	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1611	&signal
542	}
543
544	sub AnyEvent::Base::Signal::DESTROY {
545	my ($signal, $cb) = @{$_[0]};
546
547	delete $SIG_CB{$signal}{$cb};
548
549	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
550	}	1612	}
551		1613
552	# default implementation for ->child	1614	# default implementation for ->child
553		1615
554	our %PID_CB;	1616	our %PID_CB;
555	our $CHLD_W;	1617	our $CHLD_W;
556	our $CHLD_DELAY_W;	1618	our $CHLD_DELAY_W;
557	our $PID_IDLE;
558	our $WNOHANG;
559		1619
560	sub _child_wait {	1620	# used by many Impl's
561	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1621	sub _emit_childstatus($$) {
		1622	my (undef, $rpid, $rstatus) = @_;
		1623
		1624	$_->($rpid, $rstatus)
562	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1625	for values %{ $PID_CB{$rpid} || {} },
563	(values %{ $PID_CB{0} || {} });	1626	values %{ $PID_CB{0} || {} };
564	}
565
566	undef $PID_IDLE;
567	}
568
569	sub _sigchld {
570	# make sure we deliver these changes "synchronous" with the event loop.
571	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
572	undef $CHLD_DELAY_W;
573	&_child_wait;
574	});
575	}	1627	}
576		1628
577	sub child {	1629	sub child {
		1630	eval q{ # poor man's autoloading {}
		1631	*_sigchld = sub {
		1632	my $pid;
		1633
		1634	AnyEvent->_emit_childstatus ($pid, $?)
		1635	while ($pid = waitpid -1, WNOHANG) > 0;
		1636	};
		1637
		1638	*child = sub {
578	my (undef, %arg) = @_;	1639	my (undef, %arg) = @_;
579		1640
580	defined (my $pid = $arg{pid} + 0)	1641	defined (my $pid = $arg{pid} + 0)
581	or Carp::croak "required option 'pid' is missing";	1642	or Carp::croak "required option 'pid' is missing";
582		1643
583	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1644	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
584		1645
585	unless ($WNOHANG) {
586	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
587	}
588
589	unless ($CHLD_W) {	1646	unless ($CHLD_W) {
590	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1647	$CHLD_W = AE::signal CHLD => \&_sigchld;
591	# child could be a zombie already, so make at least one round	1648	# child could be a zombie already, so make at least one round
592	&_sigchld;	1649	&_sigchld;
593	}	1650	}
594		1651
595	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1652	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
596	}	1653	};
597		1654
598	sub AnyEvent::Base::Child::DESTROY {	1655	*AnyEvent::Base::child::DESTROY = sub {
599	my ($pid, $cb) = @{$_[0]};	1656	my ($pid, $cb) = @{$_[0]};
600		1657
601	delete $PID_CB{$pid}{$cb};	1658	delete $PID_CB{$pid}{$cb};
602	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1659	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
603		1660
604	undef $CHLD_W unless keys %PID_CB;	1661	undef $CHLD_W unless keys %PID_CB;
		1662	};
		1663	};
		1664	die if $@;
		1665
		1666	&child
605	}	1667	}
		1668
		1669	# idle emulation is done by simply using a timer, regardless
		1670	# of whether the process is idle or not, and not letting
		1671	# the callback use more than 50% of the time.
		1672	sub idle {
		1673	eval q{ # poor man's autoloading {}
		1674	*idle = sub {
		1675	my (undef, %arg) = @_;
		1676
		1677	my ($cb, $w, $rcb) = $arg{cb};
		1678
		1679	$rcb = sub {
		1680	if ($cb) {
		1681	$w = _time;
		1682	&$cb;
		1683	$w = _time - $w;
		1684
		1685	# never use more then 50% of the time for the idle watcher,
		1686	# within some limits
		1687	$w = 0.0001 if $w < 0.0001;
		1688	$w = 5 if $w > 5;
		1689
		1690	$w = AE::timer $w, 0, $rcb;
		1691	} else {
		1692	# clean up...
		1693	undef $w;
		1694	undef $rcb;
		1695	}
		1696	};
		1697
		1698	$w = AE::timer 0.05, 0, $rcb;
		1699
		1700	bless \\$cb, "AnyEvent::Base::idle"
		1701	};
		1702
		1703	*AnyEvent::Base::idle::DESTROY = sub {
		1704	undef $${$_[0]};
		1705	};
		1706	};
		1707	die if $@;
		1708
		1709	&idle
		1710	}
		1711
		1712	package AnyEvent::CondVar;
		1713
		1714	our @ISA = AnyEvent::CondVar::Base::;
		1715
		1716	# only to be used for subclassing
		1717	sub new {
		1718	my $class = shift;
		1719	bless AnyEvent->condvar (@_), $class
		1720	}
		1721
		1722	package AnyEvent::CondVar::Base;
		1723
		1724	#use overload
		1725	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1726	# fallback => 1;
		1727
		1728	# save 300+ kilobytes by dirtily hardcoding overloading
		1729	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1730	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1731	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1732	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1733
		1734	our $WAITING;
		1735
		1736	sub _send {
		1737	# nop
		1738	}
		1739
		1740	sub send {
		1741	my $cv = shift;
		1742	$cv->{_ae_sent} = [@_];
		1743	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1744	$cv->_send;
		1745	}
		1746
		1747	sub croak {
		1748	$_[0]{_ae_croak} = $_[1];
		1749	$_[0]->send;
		1750	}
		1751
		1752	sub ready {
		1753	$_[0]{_ae_sent}
		1754	}
		1755
		1756	sub _wait {
		1757	$WAITING
		1758	and !$_[0]{_ae_sent}
		1759	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1760
		1761	local $WAITING = 1;
		1762	AnyEvent->one_event while !$_[0]{_ae_sent};
		1763	}
		1764
		1765	sub recv {
		1766	$_[0]->_wait;
		1767
		1768	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1769	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1770	}
		1771
		1772	sub cb {
		1773	my $cv = shift;
		1774
		1775	@_
		1776	and $cv->{_ae_cb} = shift
		1777	and $cv->{_ae_sent}
		1778	and (delete $cv->{_ae_cb})->($cv);
		1779
		1780	$cv->{_ae_cb}
		1781	}
		1782
		1783	sub begin {
		1784	++$_[0]{_ae_counter};
		1785	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1786	}
		1787
		1788	sub end {
		1789	return if --$_[0]{_ae_counter};
		1790	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1791	}
		1792
		1793	# undocumented/compatibility with pre-3.4
		1794	*broadcast = \&send;
		1795	*wait = \&_wait;
		1796
		1797	=head1 ERROR AND EXCEPTION HANDLING
		1798
		1799	In general, AnyEvent does not do any error handling - it relies on the
		1800	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1801	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1802	checking of all AnyEvent methods, however, which is highly useful during
		1803	development.
		1804
		1805	As for exception handling (i.e. runtime errors and exceptions thrown while
		1806	executing a callback), this is not only highly event-loop specific, but
		1807	also not in any way wrapped by this module, as this is the job of the main
		1808	program.
		1809
		1810	The pure perl event loop simply re-throws the exception (usually
		1811	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1812	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1813	so on.
		1814
		1815	=head1 ENVIRONMENT VARIABLES
		1816
		1817	The following environment variables are used by this module or its
		1818	submodules.
		1819
		1820	Note that AnyEvent will remove I<all> environment variables starting with
		1821	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1822	enabled.
		1823
		1824	=over 4
		1825
		1826	=item C<PERL_ANYEVENT_VERBOSE>
		1827
		1828	By default, AnyEvent will be completely silent except in fatal
		1829	conditions. You can set this environment variable to make AnyEvent more
		1830	talkative.
		1831
		1832	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1833	conditions, such as not being able to load the event model specified by
		1834	C<PERL_ANYEVENT_MODEL>.
		1835
		1836	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1837	model it chooses.
		1838
		1839	When set to C<8> or higher, then AnyEvent will report extra information on
		1840	which optional modules it loads and how it implements certain features.
		1841
		1842	=item C<PERL_ANYEVENT_STRICT>
		1843
		1844	AnyEvent does not do much argument checking by default, as thorough
		1845	argument checking is very costly. Setting this variable to a true value
		1846	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1847	check the arguments passed to most method calls. If it finds any problems,
		1848	it will croak.
		1849
		1850	In other words, enables "strict" mode.
		1851
		1852	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		1853	>>, it is definitely recommended to keep it off in production. Keeping
		1854	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1855	can be very useful, however.
		1856
		1857	=item C<PERL_ANYEVENT_MODEL>
		1858
		1859	This can be used to specify the event model to be used by AnyEvent, before
		1860	auto detection and -probing kicks in. It must be a string consisting
		1861	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1862	and the resulting module name is loaded and if the load was successful,
		1863	used as event model. If it fails to load AnyEvent will proceed with
		1864	auto detection and -probing.
		1865
		1866	This functionality might change in future versions.
		1867
		1868	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1869	could start your program like this:
		1870
		1871	PERL_ANYEVENT_MODEL=Perl perl ...
		1872
		1873	=item C<PERL_ANYEVENT_PROTOCOLS>
		1874
		1875	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1876	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1877	of auto probing).
		1878
		1879	Must be set to a comma-separated list of protocols or address families,
		1880	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1881	used, and preference will be given to protocols mentioned earlier in the
		1882	list.
		1883
		1884	This variable can effectively be used for denial-of-service attacks
		1885	against local programs (e.g. when setuid), although the impact is likely
		1886	small, as the program has to handle conenction and other failures anyways.
		1887
		1888	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1889	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1890	- only support IPv4, never try to resolve or contact IPv6
		1891	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1892	IPv6, but prefer IPv6 over IPv4.
		1893
		1894	=item C<PERL_ANYEVENT_EDNS0>
		1895
		1896	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1897	for DNS. This extension is generally useful to reduce DNS traffic, but
		1898	some (broken) firewalls drop such DNS packets, which is why it is off by
		1899	default.
		1900
		1901	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1902	EDNS0 in its DNS requests.
		1903
		1904	=item C<PERL_ANYEVENT_MAX_FORKS>
		1905
		1906	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1907	will create in parallel.
		1908
		1909	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1910
		1911	The default value for the C<max_outstanding> parameter for the default DNS
		1912	resolver - this is the maximum number of parallel DNS requests that are
		1913	sent to the DNS server.
		1914
		1915	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1916
		1917	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1918	configuration) in the default resolver. When set to the empty string, no
		1919	default config will be used.
		1920
		1921	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1922
		1923	When neither C<ca_file> nor C<ca_path> was specified during
		1924	L<AnyEvent::TLS> context creation, and either of these environment
		1925	variables exist, they will be used to specify CA certificate locations
		1926	instead of a system-dependent default.
		1927
		1928	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1929
		1930	When these are set to C<1>, then the respective modules are not
		1931	loaded. Mostly good for testing AnyEvent itself.
		1932
		1933	=back
606		1934
607	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1935	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
608		1936
609	This is an advanced topic that you do not normally need to use AnyEvent in	1937	This is an advanced topic that you do not normally need to use AnyEvent in
610	a module. This section is only of use to event loop authors who want to	1938	a module. This section is only of use to event loop authors who want to
…		…
645	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1973	I<rxvt-unicode> also cheats a bit by not providing blocking access to
646	condition variables: code blocking while waiting for a condition will	1974	condition variables: code blocking while waiting for a condition will
647	C<die>. This still works with most modules/usages, and blocking calls must	1975	C<die>. This still works with most modules/usages, and blocking calls must
648	not be done in an interactive application, so it makes sense.	1976	not be done in an interactive application, so it makes sense.
649		1977
650	=head1 ENVIRONMENT VARIABLES
651
652	The following environment variables are used by this module:
653
654	=over 4
655
656	=item C<PERL_ANYEVENT_VERBOSE>
657
658	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
659	model it chooses.
660
661	=item C<PERL_ANYEVENT_MODEL>
662
663	This can be used to specify the event model to be used by AnyEvent, before
664	autodetection and -probing kicks in. It must be a string consisting
665	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
666	and the resulting module name is loaded and if the load was successful,
667	used as event model. If it fails to load AnyEvent will proceed with
668	autodetection and -probing.
669
670	This functionality might change in future versions.
671
672	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
673	could start your program like this:
674
675	PERL_ANYEVENT_MODEL=Perl perl ...
676
677	=back
678
679	=head1 EXAMPLE PROGRAM	1978	=head1 EXAMPLE PROGRAM
680		1979
681	The following program uses an IO watcher to read data from STDIN, a timer	1980	The following program uses an I/O watcher to read data from STDIN, a timer
682	to display a message once per second, and a condition variable to quit the	1981	to display a message once per second, and a condition variable to quit the
683	program when the user enters quit:	1982	program when the user enters quit:
684		1983
685	use AnyEvent;	1984	use AnyEvent;
686		1985
…		…
691	poll => 'r',	1990	poll => 'r',
692	cb => sub {	1991	cb => sub {
693	warn "io event <$_[0]>\n"; # will always output <r>	1992	warn "io event <$_[0]>\n"; # will always output <r>
694	chomp (my $input = <STDIN>); # read a line	1993	chomp (my $input = <STDIN>); # read a line
695	warn "read: $input\n"; # output what has been read	1994	warn "read: $input\n"; # output what has been read
696	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1995	$cv->send if $input =~ /^q/i; # quit program if /^q/i
697	},	1996	},
698	);	1997	);
699		1998
700	my $time_watcher; # can only be used once
701
702	sub new_timer {
703	$timer = AnyEvent->timer (after => 1, cb => sub {	1999	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
704	warn "timeout\n"; # print 'timeout' about every second	2000	warn "timeout\n"; # print 'timeout' at most every second
705	&new_timer; # and restart the time
706	});	2001	});
707	}
708		2002
709	new_timer; # create first timer
710
711	$cv->wait; # wait until user enters /^q/i	2003	$cv->recv; # wait until user enters /^q/i
712		2004
713	=head1 REAL-WORLD EXAMPLE	2005	=head1 REAL-WORLD EXAMPLE
714		2006
715	Consider the L<Net::FCP> module. It features (among others) the following	2007	Consider the L<Net::FCP> module. It features (among others) the following
716	API calls, which are to freenet what HTTP GET requests are to http:	2008	API calls, which are to freenet what HTTP GET requests are to http:
…		…
766	syswrite $txn->{fh}, $txn->{request}	2058	syswrite $txn->{fh}, $txn->{request}
767	or die "connection or write error";	2059	or die "connection or write error";
768	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2060	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
769		2061
770	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2062	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
771	result and signals any possible waiters that the request ahs finished:	2063	result and signals any possible waiters that the request has finished:
772		2064
773	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2065	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
774		2066
775	if (end-of-file or data complete) {	2067	if (end-of-file or data complete) {
776	$txn->{result} = $txn->{buf};	2068	$txn->{result} = $txn->{buf};
777	$txn->{finished}->broadcast;	2069	$txn->{finished}->send;
778	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2070	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
779	}	2071	}
780		2072
781	The C<result> method, finally, just waits for the finished signal (if the	2073	The C<result> method, finally, just waits for the finished signal (if the
782	request was already finished, it doesn't wait, of course, and returns the	2074	request was already finished, it doesn't wait, of course, and returns the
783	data:	2075	data:
784		2076
785	$txn->{finished}->wait;	2077	$txn->{finished}->recv;
786	return $txn->{result};	2078	return $txn->{result};
787		2079
788	The actual code goes further and collects all errors (C<die>s, exceptions)	2080	The actual code goes further and collects all errors (C<die>s, exceptions)
789	that occured during request processing. The C<result> method detects	2081	that occurred during request processing. The C<result> method detects
790	whether an exception as thrown (it is stored inside the $txn object)	2082	whether an exception as thrown (it is stored inside the $txn object)
791	and just throws the exception, which means connection errors and other	2083	and just throws the exception, which means connection errors and other
792	problems get reported tot he code that tries to use the result, not in a	2084	problems get reported to the code that tries to use the result, not in a
793	random callback.	2085	random callback.
794		2086
795	All of this enables the following usage styles:	2087	All of this enables the following usage styles:
796		2088
797	1. Blocking:	2089	1. Blocking:
…		…
825		2117
826	my $quit = AnyEvent->condvar;	2118	my $quit = AnyEvent->condvar;
827		2119
828	$fcp->txn_client_get ($url)->cb (sub {	2120	$fcp->txn_client_get ($url)->cb (sub {
829	...	2121	...
830	$quit->broadcast;	2122	$quit->send;
831	});	2123	});
832		2124
833	$quit->wait;	2125	$quit->recv;
		2126
		2127
		2128	=head1 BENCHMARKS
		2129
		2130	To give you an idea of the performance and overheads that AnyEvent adds
		2131	over the event loops themselves and to give you an impression of the speed
		2132	of various event loops I prepared some benchmarks.
		2133
		2134	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2135
		2136	Here is a benchmark of various supported event models used natively and
		2137	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2138	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2139	which it is), lets them fire exactly once and destroys them again.
		2140
		2141	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2142	distribution. It uses the L<AE> interface, which makes a real difference
		2143	for the EV and Perl backends only.
		2144
		2145	=head3 Explanation of the columns
		2146
		2147	I<watcher> is the number of event watchers created/destroyed. Since
		2148	different event models feature vastly different performances, each event
		2149	loop was given a number of watchers so that overall runtime is acceptable
		2150	and similar between tested event loop (and keep them from crashing): Glib
		2151	would probably take thousands of years if asked to process the same number
		2152	of watchers as EV in this benchmark.
		2153
		2154	I<bytes> is the number of bytes (as measured by the resident set size,
		2155	RSS) consumed by each watcher. This method of measuring captures both C
		2156	and Perl-based overheads.
		2157
		2158	I<create> is the time, in microseconds (millionths of seconds), that it
		2159	takes to create a single watcher. The callback is a closure shared between
		2160	all watchers, to avoid adding memory overhead. That means closure creation
		2161	and memory usage is not included in the figures.
		2162
		2163	I<invoke> is the time, in microseconds, used to invoke a simple
		2164	callback. The callback simply counts down a Perl variable and after it was
		2165	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2166	signal the end of this phase.
		2167
		2168	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2169	watcher.
		2170
		2171	=head3 Results
		2172
		2173	name watchers bytes create invoke destroy comment
		2174	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2175	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2176	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2177	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2178	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2179	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2180	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2181	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2182	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2183	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2184	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2185	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2186
		2187	=head3 Discussion
		2188
		2189	The benchmark does I<not> measure scalability of the event loop very
		2190	well. For example, a select-based event loop (such as the pure perl one)
		2191	can never compete with an event loop that uses epoll when the number of
		2192	file descriptors grows high. In this benchmark, all events become ready at
		2193	the same time, so select/poll-based implementations get an unnatural speed
		2194	boost.
		2195
		2196	Also, note that the number of watchers usually has a nonlinear effect on
		2197	overall speed, that is, creating twice as many watchers doesn't take twice
		2198	the time - usually it takes longer. This puts event loops tested with a
		2199	higher number of watchers at a disadvantage.
		2200
		2201	To put the range of results into perspective, consider that on the
		2202	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2203	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2204	cycles with POE.
		2205
		2206	C<EV> is the sole leader regarding speed and memory use, which are both
		2207	maximal/minimal, respectively. When using the L<AE> API there is zero
		2208	overhead (when going through the AnyEvent API create is about 5-6 times
		2209	slower, with other times being equal, so still uses far less memory than
		2210	any other event loop and is still faster than Event natively).
		2211
		2212	The pure perl implementation is hit in a few sweet spots (both the
		2213	constant timeout and the use of a single fd hit optimisations in the perl
		2214	interpreter and the backend itself). Nevertheless this shows that it
		2215	adds very little overhead in itself. Like any select-based backend its
		2216	performance becomes really bad with lots of file descriptors (and few of
		2217	them active), of course, but this was not subject of this benchmark.
		2218
		2219	The C<Event> module has a relatively high setup and callback invocation
		2220	cost, but overall scores in on the third place.
		2221
		2222	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2223	when using its pure perl backend.
		2224
		2225	C<Glib>'s memory usage is quite a bit higher, but it features a
		2226	faster callback invocation and overall ends up in the same class as
		2227	C<Event>. However, Glib scales extremely badly, doubling the number of
		2228	watchers increases the processing time by more than a factor of four,
		2229	making it completely unusable when using larger numbers of watchers
		2230	(note that only a single file descriptor was used in the benchmark, so
		2231	inefficiencies of C<poll> do not account for this).
		2232
		2233	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2234	more than 2000 watchers is a big setback, however, as correctness takes
		2235	precedence over speed. Nevertheless, its performance is surprising, as the
		2236	file descriptor is dup()ed for each watcher. This shows that the dup()
		2237	employed by some adaptors is not a big performance issue (it does incur a
		2238	hidden memory cost inside the kernel which is not reflected in the figures
		2239	above).
		2240
		2241	C<POE>, regardless of underlying event loop (whether using its pure perl
		2242	select-based backend or the Event module, the POE-EV backend couldn't
		2243	be tested because it wasn't working) shows abysmal performance and
		2244	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2245	as EV watchers, and 10 times as much memory as Event (the high memory
		2246	requirements are caused by requiring a session for each watcher). Watcher
		2247	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2248	implementation.
		2249
		2250	The design of the POE adaptor class in AnyEvent can not really account
		2251	for the performance issues, though, as session creation overhead is
		2252	small compared to execution of the state machine, which is coded pretty
		2253	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2254	using multiple sessions is not a good approach, especially regarding
		2255	memory usage, even the author of POE could not come up with a faster
		2256	design).
		2257
		2258	=head3 Summary
		2259
		2260	=over 4
		2261
		2262	=item * Using EV through AnyEvent is faster than any other event loop
		2263	(even when used without AnyEvent), but most event loops have acceptable
		2264	performance with or without AnyEvent.
		2265
		2266	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2267	the actual event loop, only with extremely fast event loops such as EV
		2268	adds AnyEvent significant overhead.
		2269
		2270	=item * You should avoid POE like the plague if you want performance or
		2271	reasonable memory usage.
		2272
		2273	=back
		2274
		2275	=head2 BENCHMARKING THE LARGE SERVER CASE
		2276
		2277	This benchmark actually benchmarks the event loop itself. It works by
		2278	creating a number of "servers": each server consists of a socket pair, a
		2279	timeout watcher that gets reset on activity (but never fires), and an I/O
		2280	watcher waiting for input on one side of the socket. Each time the socket
		2281	watcher reads a byte it will write that byte to a random other "server".
		2282
		2283	The effect is that there will be a lot of I/O watchers, only part of which
		2284	are active at any one point (so there is a constant number of active
		2285	fds for each loop iteration, but which fds these are is random). The
		2286	timeout is reset each time something is read because that reflects how
		2287	most timeouts work (and puts extra pressure on the event loops).
		2288
		2289	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2290	(1%) are active. This mirrors the activity of large servers with many
		2291	connections, most of which are idle at any one point in time.
		2292
		2293	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2294	distribution. It uses the L<AE> interface, which makes a real difference
		2295	for the EV and Perl backends only.
		2296
		2297	=head3 Explanation of the columns
		2298
		2299	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2300	each server has a read and write socket end).
		2301
		2302	I<create> is the time it takes to create a socket pair (which is
		2303	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2304
		2305	I<request>, the most important value, is the time it takes to handle a
		2306	single "request", that is, reading the token from the pipe and forwarding
		2307	it to another server. This includes deleting the old timeout and creating
		2308	a new one that moves the timeout into the future.
		2309
		2310	=head3 Results
		2311
		2312	name sockets create request
		2313	EV 20000 62.66 7.99
		2314	Perl 20000 68.32 32.64
		2315	IOAsync 20000 174.06 101.15 epoll
		2316	IOAsync 20000 174.67 610.84 poll
		2317	Event 20000 202.69 242.91
		2318	Glib 20000 557.01 1689.52
		2319	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2320
		2321	=head3 Discussion
		2322
		2323	This benchmark I<does> measure scalability and overall performance of the
		2324	particular event loop.
		2325
		2326	EV is again fastest. Since it is using epoll on my system, the setup time
		2327	is relatively high, though.
		2328
		2329	Perl surprisingly comes second. It is much faster than the C-based event
		2330	loops Event and Glib.
		2331
		2332	IO::Async performs very well when using its epoll backend, and still quite
		2333	good compared to Glib when using its pure perl backend.
		2334
		2335	Event suffers from high setup time as well (look at its code and you will
		2336	understand why). Callback invocation also has a high overhead compared to
		2337	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2338	uses select or poll in basically all documented configurations.
		2339
		2340	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2341	clearly fails to perform with many filehandles or in busy servers.
		2342
		2343	POE is still completely out of the picture, taking over 1000 times as long
		2344	as EV, and over 100 times as long as the Perl implementation, even though
		2345	it uses a C-based event loop in this case.
		2346
		2347	=head3 Summary
		2348
		2349	=over 4
		2350
		2351	=item * The pure perl implementation performs extremely well.
		2352
		2353	=item * Avoid Glib or POE in large projects where performance matters.
		2354
		2355	=back
		2356
		2357	=head2 BENCHMARKING SMALL SERVERS
		2358
		2359	While event loops should scale (and select-based ones do not...) even to
		2360	large servers, most programs we (or I :) actually write have only a few
		2361	I/O watchers.
		2362
		2363	In this benchmark, I use the same benchmark program as in the large server
		2364	case, but it uses only eight "servers", of which three are active at any
		2365	one time. This should reflect performance for a small server relatively
		2366	well.
		2367
		2368	The columns are identical to the previous table.
		2369
		2370	=head3 Results
		2371
		2372	name sockets create request
		2373	EV 16 20.00 6.54
		2374	Perl 16 25.75 12.62
		2375	Event 16 81.27 35.86
		2376	Glib 16 32.63 15.48
		2377	POE 16 261.87 276.28 uses POE::Loop::Event
		2378
		2379	=head3 Discussion
		2380
		2381	The benchmark tries to test the performance of a typical small
		2382	server. While knowing how various event loops perform is interesting, keep
		2383	in mind that their overhead in this case is usually not as important, due
		2384	to the small absolute number of watchers (that is, you need efficiency and
		2385	speed most when you have lots of watchers, not when you only have a few of
		2386	them).
		2387
		2388	EV is again fastest.
		2389
		2390	Perl again comes second. It is noticeably faster than the C-based event
		2391	loops Event and Glib, although the difference is too small to really
		2392	matter.
		2393
		2394	POE also performs much better in this case, but is is still far behind the
		2395	others.
		2396
		2397	=head3 Summary
		2398
		2399	=over 4
		2400
		2401	=item * C-based event loops perform very well with small number of
		2402	watchers, as the management overhead dominates.
		2403
		2404	=back
		2405
		2406	=head2 THE IO::Lambda BENCHMARK
		2407
		2408	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2409	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2410	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2411	shouldn't come as a surprise to anybody). As such, the benchmark is
		2412	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2413	very optimal. But how would AnyEvent compare when used without the extra
		2414	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2415
		2416	The benchmark itself creates an echo-server, and then, for 500 times,
		2417	connects to the echo server, sends a line, waits for the reply, and then
		2418	creates the next connection. This is a rather bad benchmark, as it doesn't
		2419	test the efficiency of the framework or much non-blocking I/O, but it is a
		2420	benchmark nevertheless.
		2421
		2422	name runtime
		2423	Lambda/select 0.330 sec
		2424	+ optimized 0.122 sec
		2425	Lambda/AnyEvent 0.327 sec
		2426	+ optimized 0.138 sec
		2427	Raw sockets/select 0.077 sec
		2428	POE/select, components 0.662 sec
		2429	POE/select, raw sockets 0.226 sec
		2430	POE/select, optimized 0.404 sec
		2431
		2432	AnyEvent/select/nb 0.085 sec
		2433	AnyEvent/EV/nb 0.068 sec
		2434	+state machine 0.134 sec
		2435
		2436	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2437	benchmarks actually make blocking connects and use 100% blocking I/O,
		2438	defeating the purpose of an event-based solution. All of the newly
		2439	written AnyEvent benchmarks use 100% non-blocking connects (using
		2440	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2441	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2442	generally require a lot more bookkeeping and event handling than blocking
		2443	connects (which involve a single syscall only).
		2444
		2445	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2446	offers similar expressive power as POE and IO::Lambda, using conventional
		2447	Perl syntax. This means that both the echo server and the client are 100%
		2448	non-blocking, further placing it at a disadvantage.
		2449
		2450	As you can see, the AnyEvent + EV combination even beats the
		2451	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2452	backend easily beats IO::Lambda and POE.
		2453
		2454	And even the 100% non-blocking version written using the high-level (and
		2455	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2456	higher level ("unoptimised") abstractions by a large margin, even though
		2457	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2458
		2459	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2460	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2461	part of the IO::Lambda distribution and were used without any changes.
		2462
		2463
		2464	=head1 SIGNALS
		2465
		2466	AnyEvent currently installs handlers for these signals:
		2467
		2468	=over 4
		2469
		2470	=item SIGCHLD
		2471
		2472	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2473	emulation for event loops that do not support them natively. Also, some
		2474	event loops install a similar handler.
		2475
		2476	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2477	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2478
		2479	=item SIGPIPE
		2480
		2481	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2482	when AnyEvent gets loaded.
		2483
		2484	The rationale for this is that AnyEvent users usually do not really depend
		2485	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2486	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2487	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2488	some random socket.
		2489
		2490	The rationale for installing a no-op handler as opposed to ignoring it is
		2491	that this way, the handler will be restored to defaults on exec.
		2492
		2493	Feel free to install your own handler, or reset it to defaults.
		2494
		2495	=back
		2496
		2497	=cut
		2498
		2499	undef $SIG{CHLD}
		2500	if $SIG{CHLD} eq 'IGNORE';
		2501
		2502	$SIG{PIPE} = sub { }
		2503	unless defined $SIG{PIPE};
		2504
		2505	=head1 RECOMMENDED/OPTIONAL MODULES
		2506
		2507	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2508	its built-in modules) are required to use it.
		2509
		2510	That does not mean that AnyEvent won't take advantage of some additional
		2511	modules if they are installed.
		2512
		2513	This section explains which additional modules will be used, and how they
		2514	affect AnyEvent's operation.
		2515
		2516	=over 4
		2517
		2518	=item L<Async::Interrupt>
		2519
		2520	This slightly arcane module is used to implement fast signal handling: To
		2521	my knowledge, there is no way to do completely race-free and quick
		2522	signal handling in pure perl. To ensure that signals still get
		2523	delivered, AnyEvent will start an interval timer to wake up perl (and
		2524	catch the signals) with some delay (default is 10 seconds, look for
		2525	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2526
		2527	If this module is available, then it will be used to implement signal
		2528	catching, which means that signals will not be delayed, and the event loop
		2529	will not be interrupted regularly, which is more efficient (and good for
		2530	battery life on laptops).
		2531
		2532	This affects not just the pure-perl event loop, but also other event loops
		2533	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2534
		2535	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2536	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2537	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2538	does nothing for those backends.
		2539
		2540	=item L<EV>
		2541
		2542	This module isn't really "optional", as it is simply one of the backend
		2543	event loops that AnyEvent can use. However, it is simply the best event
		2544	loop available in terms of features, speed and stability: It supports
		2545	the AnyEvent API optimally, implements all the watcher types in XS, does
		2546	automatic timer adjustments even when no monotonic clock is available,
		2547	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2548	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2549	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2550
		2551	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2552	then this module will do nothing for you.
		2553
		2554	=item L<Guard>
		2555
		2556	The guard module, when used, will be used to implement
		2557	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2558	lot less memory), but otherwise doesn't affect guard operation much. It is
		2559	purely used for performance.
		2560
		2561	=item L<JSON> and L<JSON::XS>
		2562
		2563	One of these modules is required when you want to read or write JSON data
		2564	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2565	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2566
		2567	=item L<Net::SSLeay>
		2568
		2569	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2570	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2571	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2572
		2573	=item L<Time::HiRes>
		2574
		2575	This module is part of perl since release 5.008. It will be used when the
		2576	chosen event library does not come with a timing source of its own. The
		2577	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2578	try to use a monotonic clock for timing stability.
		2579
		2580	=back
		2581
834		2582
835	=head1 FORK	2583	=head1 FORK
836		2584
837	Most event libraries are not fork-safe. The ones who are usually are	2585	Most event libraries are not fork-safe. The ones who are usually are
838	because they are so inefficient. Only L<EV> is fully fork-aware.	2586	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2587	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2588	are usually badly thought-out hacks that are incompatible with fork in
		2589	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2590	continue event-processing in both parent and child (or both, if you know
		2591	what you are doing).
		2592
		2593	This means that, in general, you cannot fork and do event processing in
		2594	the child if the event library was initialised before the fork (which
		2595	usually happens when the first AnyEvent watcher is created, or the library
		2596	is loaded).
839		2597
840	If you have to fork, you must either do so I<before> creating your first	2598	If you have to fork, you must either do so I<before> creating your first
841	watcher OR you must not use AnyEvent at all in the child.	2599	watcher OR you must not use AnyEvent at all in the child OR you must do
		2600	something completely out of the scope of AnyEvent.
		2601
		2602	The problem of doing event processing in the parent I<and> the child
		2603	is much more complicated: even for backends that I<are> fork-aware or
		2604	fork-safe, their behaviour is not usually what you want: fork clones all
		2605	watchers, that means all timers, I/O watchers etc. are active in both
		2606	parent and child, which is almost never what you want. USing C<exec>
		2607	to start worker children from some kind of manage rprocess is usually
		2608	preferred, because it is much easier and cleaner, at the expense of having
		2609	to have another binary.
		2610
842		2611
843	=head1 SECURITY CONSIDERATIONS	2612	=head1 SECURITY CONSIDERATIONS
844		2613
845	AnyEvent can be forced to load any event model via	2614	AnyEvent can be forced to load any event model via
846	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	2615	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
850	specified in the variable.	2619	specified in the variable.
851		2620
852	You can make AnyEvent completely ignore this variable by deleting it	2621	You can make AnyEvent completely ignore this variable by deleting it
853	before the first watcher gets created, e.g. with a C<BEGIN> block:	2622	before the first watcher gets created, e.g. with a C<BEGIN> block:
854		2623
855	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2624	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
856		2625
857	use AnyEvent;	2626	use AnyEvent;
		2627
		2628	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2629	be used to probe what backend is used and gain other information (which is
		2630	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2631	$ENV{PERL_ANYEVENT_STRICT}.
		2632
		2633	Note that AnyEvent will remove I<all> environment variables starting with
		2634	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2635	enabled.
		2636
		2637
		2638	=head1 BUGS
		2639
		2640	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2641	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2642	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2643	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2644	pronounced).
		2645
858		2646
859	=head1 SEE ALSO	2647	=head1 SEE ALSO
860		2648
861	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2649	Tutorial/Introduction: L<AnyEvent::Intro>.
862	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
863	L<Event::Lib>.
864		2650
865	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2651	FAQ: L<AnyEvent::FAQ>.
		2652
		2653	Utility functions: L<AnyEvent::Util>.
		2654
		2655	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2656	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		2657
		2658	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2659	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2660	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
866	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2661	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
867	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>.
868		2662
		2663	Non-blocking file handles, sockets, TCP clients and
		2664	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2665
		2666	Asynchronous DNS: L<AnyEvent::DNS>.
		2667
		2668	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		2669
869	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2670	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2671	L<AnyEvent::HTTP>.
		2672
870		2673
871	=head1 AUTHOR	2674	=head1 AUTHOR
872		2675
873	Marc Lehmann <schmorp@schmorp.de>	2676	Marc Lehmann <schmorp@schmorp.de>
874	http://home.schmorp.de/	2677	http://home.schmorp.de/
875		2678
876	=cut	2679	=cut
877		2680
878	1	2681	1
879		2682

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