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Revision 1.388 by root, Sun Oct 2 01:22:01 2011 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt,
		6	FLTK 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 ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->send; # 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	=head1 DESCRIPTION	114	=head1 DESCRIPTION
72		115
73	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
74	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
75	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
76	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
77		120
78	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>
79	module.	122	module.
80		123
81	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
82	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
83	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
85	L<POE>. The first one found is used. If none are found, the module tries	128	found is used. If none are detected, the module tries to load the first
86	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	129	four modules in the order given; but note that if L<EV> is not
87	adaptor should always succeed) in the order given. The first one that can	130	available, the pure-perl L<AnyEvent::Loop> should always work, so
88	be successfully loaded will be used. If, after this, still none could be	131	the other two are not normally tried.
89	found, AnyEvent will fall back to a pure-perl event loop, which is not
90	very efficient, but should work everywhere.
91		132
92	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
93	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
94	that model the default. For example:	135	that model the default. For example:
95		136
…		…
97	use AnyEvent;	138	use AnyEvent;
98		139
99	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
100		141
101	The I<likely> means that, if any module loads another event model and	142	The I<likely> means that, if any module loads another event model and
102	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off - this case should be very rare though,
103	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
104		146
105	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	other event modules you can load it explicitly and enjoy the high
107	explicitly.	149	availability of that event loop :)
108		150
109	=head1 WATCHERS	151	=head1 WATCHERS
110		152
111	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
114		156
115	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	158	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	159	callback when the event occurs (of course, only when the event model
118	is in control).	160	is in control).
119		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
120	To disable the watcher you have to destroy it (e.g. by setting the	168	To disable a watcher you have to destroy it (e.g. by setting the
121	variable you store it in to C<undef> or otherwise deleting all references	169	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	170	to it).
123		171
124	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
125		173
126	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	175	example), or need to refer to their watcher object in other ways.
128		176
129	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
130		178
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
133	undef $w;	181	undef $w;
134	});	182	});
135		183
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	184	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	185	my variables are only visible after the statement in which they are
138	declared.	186	declared.
139		187
140	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
141		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
144		198
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
146	for events. C<poll> must be a string that is either C<r> or C<w>,	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
148	respectively. C<cb> is the callback to invoke each time the file handle	209	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		210
151	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
154		214
155	The I/O watcher might use the underlying file descriptor or a copy of it.	215	The I/O watcher might use the underlying file descriptor or a copy of it.
156	You must not close a file handle as long as any watcher is active on the	216	You must not close a file handle as long as any watcher is active on the
157	underlying file descriptor.	217	underlying file descriptor.
158		218
159	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	220	always use non-blocking calls when reading/writing from/to your file
161	handles.	221	handles.
162		222
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	228	warn "read: $input\n";
169	undef $w;	229	undef $w;
170	});	230	});
171		231
172	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
173		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
174	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
175	method with the following mandatory arguments:	243	method with the following mandatory arguments:
176		244
177	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	246	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		248
181	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
184		252
185	The timer callback will be invoked at most once: if you want a repeating	253	The callback will normally be invoked only once. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	254	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
188		258
189	Example:	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.
190		262
191	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	266	warn "timeout\n";
194	});	267	});
195		268
196	# to cancel the timer:	269	# to cancel the timer:
197	undef $w;	270	undef $w;
198		271
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		273
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
207	};	276	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		277
212	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
213		279
214	There are two ways to handle timers: based on real time (relative, "fire	280	There are two ways to handle timers: based on real time (relative, "fire
215	in 10 seconds") and based on wallclock time (absolute, "fire at 12	281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
217		283
218	While most event loops expect timers to specified in a relative way, they	284	While most event loops expect timers to specified in a relative way, they
219	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
220	"jumps", for example, when ntp decides to set your clock backwards from	286	"jumps", for example, when ntp decides to set your clock backwards from
221	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to	287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
222	fire "after" a second might actually take six years to finally fire.	288	fire "after a second" might actually take six years to finally fire.
223		289
224	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
225	about these issues is L<EV>, which offers both relative (ev_timer, based	291	of these issues is L<EV>, which offers both relative (ev_timer, based
226	on true relative time) and absolute (ev_periodic, based on wallclock time)	292	on true relative time) and absolute (ev_periodic, based on wallclock time)
227	timers.	293	timers.
228		294
229	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	296	AnyEvent API.
231		297
		298	AnyEvent has two additional methods that return the "current time":
		299
		300	=over 4
		301
		302	=item AnyEvent->time
		303
		304	This returns the "current wallclock time" as a fractional number of
		305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
		307
		308	It progresses independently of any event loop processing, i.e. each call
		309	will check the system clock, which usually gets updated frequently.
		310
		311	=item AnyEvent->now
		312
		313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
		317
		318	I<In almost all cases (in all cases if you don't care), this is the
		319	function to call when you want to know the current time.>
		320
		321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update 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::Loop>) cache the current
		362	time for each loop iteration (see the discussion of L<< AnyEvent->now >>,
		363	above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
		381	=back
		382
232	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
233		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
234	You can watch for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
237		390
238	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
241		394
242	Multiple signal occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	397	that it might take a while until the signal gets handled by the process,
245	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
246		399
247	The main advantage of using these watchers is that you can share a signal	400	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
249		403
250	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
252		407
253	Example: exit on SIGINT	408	Example: exit on SIGINT
254		409
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling)
		421	or "unsafe" (asynchronous) - the former might delay signal delivery
		422	indefinitely, the latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support
		432	attaching callbacks to signals in a generic way, which is a pity,
		433	as you cannot do race-free signal handling in perl, requiring
		434	C libraries for this. AnyEvent will try to do its best, which
		435	means in some cases, signals will be delayed. The maximum time
		436	a signal might be delayed is 10 seconds by default, but can
		437	be overriden via C<$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY}> or
		438	C<$AnyEvent::MAX_SIGNAL_LATENCY> - see the Ö<ENVIRONMENT VARIABLES>
		439	section for details.
		440
		441	All these problems can be avoided by installing the optional
		442	L<Async::Interrupt> module, which works with most event loops. It will not
		443	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		444	(and not with L<POE> currently). For those, you just have to suffer the
		445	delays.
		446
257	=head2 CHILD PROCESS WATCHERS	447	=head2 CHILD PROCESS WATCHERS
258		448
		449	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		450
259	You can also watch on a child process exit and catch its exit status.	451	You can also watch for a child process exit and catch its exit status.
260		452
261	The child process is specified by the C<pid> argument (if set to C<0>, it	453	The child process is specified by the C<pid> argument (on some backends,
262	watches for any child process exit). The watcher will trigger as often	454	using C<0> watches for any child process exit, on others this will
263	as status change for the child are received. This works by installing a	455	croak). The watcher will be triggered only when the child process has
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	456	finished and an exit status is available, not on any trace events
265	and exit status (as returned by waitpid), so unlike other watcher types,	457	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	458
		459	The callback will be called with the pid and exit status (as returned by
		460	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		461	callback arguments.
		462
		463	This watcher type works by installing a signal handler for C<SIGCHLD>,
		464	and since it cannot be shared, nothing else should use SIGCHLD or reap
		465	random child processes (waiting for specific child processes, e.g. inside
		466	C<system>, is just fine).
267		467
268	There is a slight catch to child watchers, however: you usually start them	468	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	469	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	470	have exited already (and no SIGCHLD will be sent anymore).
271		471
272	Not all event models handle this correctly (POE doesn't), but even for	472	Not all event models handle this correctly (neither POE nor IO::Async do,
		473	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	474	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	475	the process exits (i.e. before you fork in the first place). AnyEvent's
		476	pure perl event loop handles all cases correctly regardless of when you
		477	start the watcher.
275		478
276	This means you cannot create a child watcher as the very first thing in an	479	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	480	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	481	watcher before you C<fork> the child (alternatively, you can call
		482	C<AnyEvent::detect>).
		483
		484	As most event loops do not support waiting for child events, they will be
		485	emulated by AnyEvent in most cases, in which case the latency and race
		486	problems mentioned in the description of signal watchers apply.
279		487
280	Example: fork a process and wait for it	488	Example: fork a process and wait for it
281		489
282	my $done = AnyEvent->condvar;	490	my $done = AnyEvent->condvar;
283		491
284	AnyEvent::detect; # force event module to be initialised
285
286	my $pid = fork or exit 5;	492	my $pid = fork or exit 5;
287		493
288	my $w = AnyEvent->child (	494	my $w = AnyEvent->child (
289	pid => $pid,	495	pid => $pid,
290	cb => sub {	496	cb => sub {
291	my ($pid, $status) = @_;	497	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	498	warn "pid $pid exited with status $status";
293	$done->send;	499	$done->send;
294	},	500	},
295	);	501	);
296		502
297	# do something else, then wait for process exit	503	# do something else, then wait for process exit
298	$done->wait;	504	$done->recv;
		505
		506	=head2 IDLE WATCHERS
		507
		508	$w = AnyEvent->idle (cb => <callback>);
		509
		510	This will repeatedly invoke the callback after the process becomes idle,
		511	until either the watcher is destroyed or new events have been detected.
		512
		513	Idle watchers are useful when there is a need to do something, but it
		514	is not so important (or wise) to do it instantly. The callback will be
		515	invoked only when there is "nothing better to do", which is usually
		516	defined as "all outstanding events have been handled and no new events
		517	have been detected". That means that idle watchers ideally get invoked
		518	when the event loop has just polled for new events but none have been
		519	detected. Instead of blocking to wait for more events, the idle watchers
		520	will be invoked.
		521
		522	Unfortunately, most event loops do not really support idle watchers (only
		523	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		524	will simply call the callback "from time to time".
		525
		526	Example: read lines from STDIN, but only process them when the
		527	program is otherwise idle:
		528
		529	my @lines; # read data
		530	my $idle_w;
		531	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		532	push @lines, scalar <STDIN>;
		533
		534	# start an idle watcher, if not already done
		535	$idle_w ||= AnyEvent->idle (cb => sub {
		536	# handle only one line, when there are lines left
		537	if (my $line = shift @lines) {
		538	print "handled when idle: $line";
		539	} else {
		540	# otherwise disable the idle watcher again
		541	undef $idle_w;
		542	}
		543	});
		544	});
299		545
300	=head2 CONDITION VARIABLES	546	=head2 CONDITION VARIABLES
		547
		548	$cv = AnyEvent->condvar;
		549
		550	$cv->send (<list>);
		551	my @res = $cv->recv;
301		552
302	If you are familiar with some event loops you will know that all of them	553	If you are familiar with some event loops you will know that all of them
303	require you to run some blocking "loop", "run" or similar function that	554	require you to run some blocking "loop", "run" or similar function that
304	will actively watch for new events and call your callbacks.	555	will actively watch for new events and call your callbacks.
305		556
306	AnyEvent is different, it expects somebody else to run the event loop and	557	AnyEvent is slightly different: it expects somebody else to run the event
307	will only block when necessary (usually when told by the user).	558	loop and will only block when necessary (usually when told by the user).
308		559
309	The instrument to do that is called a "condition variable", so called	560	The tool to do that is called a "condition variable", so called because
310	because they represent a condition that must become true.	561	they represent a condition that must become true.
		562
		563	Now is probably a good time to look at the examples further below.
311		564
312	Condition variables can be created by calling the C<< AnyEvent->condvar	565	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	566	>> method, usually without arguments. The only argument pair allowed is
314	C<cb>, which specifies a callback to be called when the condition variable	567	C<cb>, which specifies a callback to be called when the condition variable
315	becomes true.	568	becomes true, with the condition variable as the first argument (but not
		569	the results).
316		570
317	After creation, the conditon variable is "false" until it becomes "true"	571	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	572	by calling the C<send> method (or calling the condition variable as if it
		573	were a callback, read about the caveats in the description for the C<<
		574	->send >> method).
319		575
320	Condition variables are similar to callbacks, except that you can	576	Since condition variables are the most complex part of the AnyEvent API, here are
321	optionally wait for them. They can also be called merge points - points	577	some different mental models of what they are - pick the ones you can connect to:
322	in time where multiple outstandign events have been processed. And yet	578
323	another way to call them is transations - each condition variable can be	579	=over 4
324	used to represent a transaction, which finishes at some point and delivers	580
325	a result.	581	=item * Condition variables are like callbacks - you can call them (and pass them instead
		582	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		583
		584	=item * Condition variables are signals - one side can emit or send them,
		585	the other side can wait for them, or install a handler that is called when
		586	the signal fires.
		587
		588	=item * Condition variables are like "Merge Points" - points in your program
		589	where you merge multiple independent results/control flows into one.
		590
		591	=item * Condition variables represent a transaction - functions that start
		592	some kind of transaction can return them, leaving the caller the choice
		593	between waiting in a blocking fashion, or setting a callback.
		594
		595	=item * Condition variables represent future values, or promises to deliver
		596	some result, long before the result is available.
		597
		598	=back
326		599
327	Condition variables are very useful to signal that something has finished,	600	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	601	for example, if you write a module that does asynchronous http requests,
329	then a condition variable would be the ideal candidate to signal the	602	then a condition variable would be the ideal candidate to signal the
330	availability of results. The user can either act when the callback is	603	availability of results. The user can either act when the callback is
331	called or can synchronously C<< ->wait >> for the results.	604	called or can synchronously C<< ->recv >> for the results.
332		605
333	You can also use them to simulate traditional event loops - for example,	606	You can also use them to simulate traditional event loops - for example,
334	you can block your main program until an event occurs - for example, you	607	you can block your main program until an event occurs - for example, you
335	could C<< ->wait >> in your main program until the user clicks the Quit	608	could C<< ->recv >> in your main program until the user clicks the Quit
336	button of your app, which would C<< ->send >> the "quit" event.	609	button of your app, which would C<< ->send >> the "quit" event.
337		610
338	Note that condition variables recurse into the event loop - if you have	611	Note that condition variables recurse into the event loop - if you have
339	two pieces of code that call C<< ->wait >> in a round-robbin fashion, you	612	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	613	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	614	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	615	as this asks for trouble.
343		616
344	Condition variables are represented by hash refs in perl, and the keys	617	Condition variables are represented by hash refs in perl, and the keys
345	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing	618	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
346	easy (it is often useful to build your own transaction class on top of	619	easy (it is often useful to build your own transaction class on top of
347	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call	620	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
348	it's C<new> method in your own C<new> method.	621	its C<new> method in your own C<new> method.
349		622
350	There are two "sides" to a condition variable - the "producer side" which	623	There are two "sides" to a condition variable - the "producer side" which
351	eventually calls C<< -> send >>, and the "consumer side", which waits	624	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	625	for the send to occur.
353		626
354	Example:	627	Example: wait for a timer.
355		628
356	# wait till the result is ready	629	# condition: "wait till the timer is fired"
357	my $result_ready = AnyEvent->condvar;	630	my $timer_fired = AnyEvent->condvar;
358		631
359	# do something such as adding a timer	632	# create the timer - we could wait for, say
360	# or socket watcher the calls $result_ready->send	633	# a handle becomign ready, or even an
361	# when the "result" is ready.	634	# AnyEvent::HTTP request to finish, but
362	# in this case, we simply use a timer:	635	# in this case, we simply use a timer:
363	my $w = AnyEvent->timer (	636	my $w = AnyEvent->timer (
364	after => 1,	637	after => 1,
365	cb => sub { $result_ready->send },	638	cb => sub { $timer_fired->send },
366	);	639	);
367		640
368	# this "blocks" (while handling events) till the callback	641	# this "blocks" (while handling events) till the callback
369	# calls send	642	# calls ->send
370	$result_ready->wait;	643	$timer_fired->recv;
		644
		645	Example: wait for a timer, but take advantage of the fact that condition
		646	variables are also callable directly.
		647
		648	my $done = AnyEvent->condvar;
		649	my $delay = AnyEvent->timer (after => 5, cb => $done);
		650	$done->recv;
		651
		652	Example: Imagine an API that returns a condvar and doesn't support
		653	callbacks. This is how you make a synchronous call, for example from
		654	the main program:
		655
		656	use AnyEvent::CouchDB;
		657
		658	...
		659
		660	my @info = $couchdb->info->recv;
		661
		662	And this is how you would just set a callback to be called whenever the
		663	results are available:
		664
		665	$couchdb->info->cb (sub {
		666	my @info = $_[0]->recv;
		667	});
371		668
372	=head3 METHODS FOR PRODUCERS	669	=head3 METHODS FOR PRODUCERS
373		670
374	These methods should only be used by the producing side, i.e. the	671	These methods should only be used by the producing side, i.e. the
375	code/module that eventually sends the signal. Note that it is also	672	code/module that eventually sends the signal. Note that it is also
…		…
378		675
379	=over 4	676	=over 4
380		677
381	=item $cv->send (...)	678	=item $cv->send (...)
382		679
383	Flag the condition as ready - a running C<< ->wait >> and all further	680	Flag the condition as ready - a running C<< ->recv >> and all further
384	calls to C<wait> will (eventually) return after this method has been	681	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	682	called. If nobody is waiting the send will be remembered.
386		683
387	If a callback has been set on the condition variable, it is called	684	If a callback has been set on the condition variable, it is called
388	immediately from within send.	685	immediately from within send.
389		686
390	Any arguments passed to the C<send> call will be returned by all	687	Any arguments passed to the C<send> call will be returned by all
391	future C<< ->wait >> calls.	688	future C<< ->recv >> calls.
		689
		690	Condition variables are overloaded so one can call them directly (as if
		691	they were a code reference). Calling them directly is the same as calling
		692	C<send>.
392		693
393	=item $cv->croak ($error)	694	=item $cv->croak ($error)
394		695
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	696	Similar to send, but causes all calls to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	697	C<Carp::croak> with the given error message/object/scalar.
397		698
398	This can be used to signal any errors to the condition variable	699	This can be used to signal any errors to the condition variable
399	user/consumer.	700	user/consumer. Doing it this way instead of calling C<croak> directly
		701	delays the error detection, but has the overwhelming advantage that it
		702	diagnoses the error at the place where the result is expected, and not
		703	deep in some event callback with no connection to the actual code causing
		704	the problem.
400		705
401	=item $cv->begin ([group callback])	706	=item $cv->begin ([group callback])
402		707
403	=item $cv->end	708	=item $cv->end
404		709
…		…
406	one. For example, a function that pings many hosts in parallel might want	711	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	712	to use a condition variable for the whole process.
408		713
409	Every call to C<< ->begin >> will increment a counter, and every call to	714	Every call to C<< ->begin >> will increment a counter, and every call to
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	715	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411	>>, the (last) callback passed to C<begin> will be executed. That callback	716	>>, the (last) callback passed to C<begin> will be executed, passing the
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	717	condvar as first argument. That callback is I<supposed> to call C<< ->send
413	callback was set, C<send> will be called without any arguments.	718	>>, but that is not required. If no group callback was set, C<send> will
		719	be called without any arguments.
414		720
415	Let's clarify this with the ping example:	721	You can think of C<< $cv->send >> giving you an OR condition (one call
		722	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		723	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		724
		725	Let's start with a simple example: you have two I/O watchers (for example,
		726	STDOUT and STDERR for a program), and you want to wait for both streams to
		727	close before activating a condvar:
416		728
417	my $cv = AnyEvent->condvar;	729	my $cv = AnyEvent->condvar;
418		730
		731	$cv->begin; # first watcher
		732	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		733	defined sysread $fh1, my $buf, 4096
		734	or $cv->end;
		735	});
		736
		737	$cv->begin; # second watcher
		738	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		739	defined sysread $fh2, my $buf, 4096
		740	or $cv->end;
		741	});
		742
		743	$cv->recv;
		744
		745	This works because for every event source (EOF on file handle), there is
		746	one call to C<begin>, so the condvar waits for all calls to C<end> before
		747	sending.
		748
		749	The ping example mentioned above is slightly more complicated, as the
		750	there are results to be passwd back, and the number of tasks that are
		751	begun can potentially be zero:
		752
		753	my $cv = AnyEvent->condvar;
		754
419	my %result;	755	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	756	$cv->begin (sub { shift->send (\%result) });
421		757
422	for my $host (@list_of_hosts) {	758	for my $host (@list_of_hosts) {
423	$cv->begin;	759	$cv->begin;
424	ping_host_then_call_callback $host, sub {	760	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	761	$result{$host} = ...;
…		…
440	loop, which serves two important purposes: first, it sets the callback	776	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	777	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	778	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	779	doesn't execute once).
444		780
445	This is the general pattern when you "fan out" into multiple subrequests:	781	This is the general pattern when you "fan out" into multiple (but
446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	782	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
447	is called at least once, and then, for each subrequest you start, call	783	the callback and ensure C<end> is called at least once, and then, for each
448	C<begin> and for eahc subrequest you finish, call C<end>.	784	subrequest you start, call C<begin> and for each subrequest you finish,
		785	call C<end>.
449		786
450	=back	787	=back
451		788
452	=head3 METHODS FOR CONSUMERS	789	=head3 METHODS FOR CONSUMERS
453		790
454	These methods should only be used by the consuming side, i.e. the	791	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	792	code awaits the condition.
456		793
457	=over 4	794	=over 4
458		795
459	=item $cv->wait	796	=item $cv->recv
460		797
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	798	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	799	>> methods have been called on C<$cv>, while servicing other watchers
463	normally.	800	normally.
464		801
465	You can only wait once on a condition - additional calls are valid but	802	You can only wait once on a condition - additional calls are valid but
466	will return immediately.	803	will return immediately.
467		804
…		…
469	function will call C<croak>.	806	function will call C<croak>.
470		807
471	In list context, all parameters passed to C<send> will be returned,	808	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	809	in scalar context only the first one will be returned.
473		810
		811	Note that doing a blocking wait in a callback is not supported by any
		812	event loop, that is, recursive invocation of a blocking C<< ->recv
		813	>> is not allowed, and the C<recv> call will C<croak> if such a
		814	condition is detected. This condition can be slightly loosened by using
		815	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		816	any thread that doesn't run the event loop itself.
		817
474	Not all event models support a blocking wait - some die in that case	818	Not all event models support a blocking wait - some die in that case
475	(programs might want to do that to stay interactive), so I<if you are	819	(programs might want to do that to stay interactive), so I<if you are
476	using this from a module, never require a blocking wait>, but let the	820	using this from a module, never require a blocking wait>. Instead, let the
477	caller decide whether the call will block or not (for example, by coupling	821	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	822	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	823	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	824	while still supporting blocking waits if the caller so desires).
481		825
482	Another reason I<never> to C<< ->wait >> in a module is that you cannot
483	sensibly have two C<< ->wait >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
486	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
487	from different coroutines, however).
488
489	You can ensure that C<< -wait >> never blocks by setting a callback and	826	You can ensure that C<< ->recv >> never blocks by setting a callback and
490	only calling C<< ->wait >> from within that callback (or at a later	827	only calling C<< ->recv >> from within that callback (or at a later
491	time). This will work even when the event loop does not support blocking	828	time). This will work even when the event loop does not support blocking
492	waits otherwise.	829	waits otherwise.
493		830
494	=item $bool = $cv->ready	831	=item $bool = $cv->ready
495		832
496	Returns true when the condition is "true", i.e. whether C<send> or	833	Returns true when the condition is "true", i.e. whether C<send> or
497	C<croak> have been called.	834	C<croak> have been called.
498		835
499	=item $cb = $cv->cb ([new callback])	836	=item $cb = $cv->cb ($cb->($cv))
500		837
501	This is a mutator function that returns the callback set and optionally	838	This is a mutator function that returns the callback set and optionally
502	replaces it before doing so.	839	replaces it before doing so.
503		840
504	The callback will be called when the condition becomes "true", i.e. when	841	The callback will be called when the condition becomes "true", i.e. when
505	C<send> or C<croak> are called. Calling C<wait> inside the callback	842	C<send> or C<croak> are called, with the only argument being the
		843	condition variable itself. If the condition is already true, the
		844	callback is called immediately when it is set. Calling C<recv> inside
506	or at any later time is guaranteed not to block.	845	the callback or at any later time is guaranteed not to block.
507		846
508	=back	847	=back
509		848
		849	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		850
		851	The available backend classes are (every class has its own manpage):
		852
		853	=over 4
		854
		855	=item Backends that are autoprobed when no other event loop can be found.
		856
		857	EV is the preferred backend when no other event loop seems to be in
		858	use. If EV is not installed, then AnyEvent will fall back to its own
		859	pure-perl implementation, which is available everywhere as it comes with
		860	AnyEvent itself.
		861
		862	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		863	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		864
		865	=item Backends that are transparently being picked up when they are used.
		866
		867	These will be used if they are already loaded when the first watcher
		868	is created, in which case it is assumed that the application is using
		869	them. This means that AnyEvent will automatically pick the right backend
		870	when the main program loads an event module before anything starts to
		871	create watchers. Nothing special needs to be done by the main program.
		872
		873	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		874	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		875	AnyEvent::Impl::Tk based on Tk, very broken.
		876	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		877	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		878	AnyEvent::Impl::Irssi used when running within irssi.
		879	AnyEvent::Impl::IOAsync based on IO::Async.
		880	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		881	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		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
		911
510	=head1 GLOBAL VARIABLES AND FUNCTIONS	912	=head1 GLOBAL VARIABLES AND FUNCTIONS
511		913
		914	These are not normally required to use AnyEvent, but can be useful to
		915	write AnyEvent extension modules.
		916
512	=over 4	917	=over 4
513		918
514	=item $AnyEvent::MODEL	919	=item $AnyEvent::MODEL
515		920
516	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
517	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
518	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
519	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
520	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
521		928	will be C<urxvt::anyevent>).
522	The known classes so far are:
523
524	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
525	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
526	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
527	AnyEvent::Impl::Event based on Event, second best choice.
528	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
529	AnyEvent::Impl::Glib based on Glib, third-best choice.
530	AnyEvent::Impl::Tk based on Tk, very bad choice.
531	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
532	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
533	AnyEvent::Impl::POE based on POE, not generic enough for full support.
534
535	There is no support for WxWidgets, as WxWidgets has no support for
536	watching file handles. However, you can use WxWidgets through the
537	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
538	second, which was considered to be too horrible to even consider for
539	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
540	it's adaptor.
541
542	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
543	autodetecting them.
544		929
545	=item AnyEvent::detect	930	=item AnyEvent::detect
546		931
547	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	932	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
548	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
549	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
550	runtime.	935	runtime, and not e.g. during initialisation of your module.
		936
		937	The effect of calling this function is as if a watcher had been created
		938	(specifically, actions that happen "when the first watcher is created"
		939	happen when calling detetc as well).
		940
		941	If you need to do some initialisation before AnyEvent watchers are
		942	created, use C<post_detect>.
		943
		944	=item $guard = AnyEvent::post_detect { BLOCK }
		945
		946	Arranges for the code block to be executed as soon as the event model is
		947	autodetected (or immediately if that has already happened).
		948
		949	The block will be executed I<after> the actual backend has been detected
		950	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		951	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		952	other initialisations - see the sources of L<AnyEvent::Strict> or
		953	L<AnyEvent::AIO> to see how this is used.
		954
		955	The most common usage is to create some global watchers, without forcing
		956	event module detection too early, for example, L<AnyEvent::AIO> creates
		957	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		958	avoid autodetecting the event module at load time.
		959
		960	If called in scalar or list context, then it creates and returns an object
		961	that automatically removes the callback again when it is destroyed (or
		962	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		963	a case where this is useful.
		964
		965	Example: Create a watcher for the IO::AIO module and store it in
		966	C<$WATCHER>, but do so only do so after the event loop is initialised.
		967
		968	our WATCHER;
		969
		970	my $guard = AnyEvent::post_detect {
		971	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		972	};
		973
		974	# the ||= is important in case post_detect immediately runs the block,
		975	# as to not clobber the newly-created watcher. assigning both watcher and
		976	# post_detect guard to the same variable has the advantage of users being
		977	# able to just C<undef $WATCHER> if the watcher causes them grief.
		978
		979	$WATCHER ||= $guard;
		980
		981	=item @AnyEvent::post_detect
		982
		983	If there are any code references in this array (you can C<push> to it
		984	before or after loading AnyEvent), then they will be called directly
		985	after the event loop has been chosen.
		986
		987	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		988	if it is defined then the event loop has already been detected, and the
		989	array will be ignored.
		990
		991	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		992	it, as it takes care of these details.
		993
		994	This variable is mainly useful for modules that can do something useful
		995	when AnyEvent is used and thus want to know when it is initialised, but do
		996	not need to even load it by default. This array provides the means to hook
		997	into AnyEvent passively, without loading it.
		998
		999	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1000	together, you could put this into Coro (this is the actual code used by
		1001	Coro to accomplish this):
		1002
		1003	if (defined $AnyEvent::MODEL) {
		1004	# AnyEvent already initialised, so load Coro::AnyEvent
		1005	require Coro::AnyEvent;
		1006	} else {
		1007	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1008	# as soon as it is
		1009	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1010	}
		1011
		1012	=item AnyEvent::postpone { BLOCK }
		1013
		1014	Arranges for the block to be executed as soon as possible, but not before
		1015	the call itself returns. In practise, the block will be executed just
		1016	before the event loop polls for new events, or shortly afterwards.
		1017
		1018	This function never returns anything (to make the C<return postpone { ...
		1019	}> idiom more useful.
		1020
		1021	To understand the usefulness of this function, consider a function that
		1022	asynchronously does something for you and returns some transaction
		1023	object or guard to let you cancel the operation. For example,
		1024	C<AnyEvent::Socket::tcp_connect>:
		1025
		1026	# start a conenction attempt unless one is active
		1027	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1028	delete $self->{connect_guard};
		1029	...
		1030	};
		1031
		1032	Imagine that this function could instantly call the callback, for
		1033	example, because it detects an obvious error such as a negative port
		1034	number. Invoking the callback before the function returns causes problems
		1035	however: the callback will be called and will try to delete the guard
		1036	object. But since the function hasn't returned yet, there is nothing to
		1037	delete. When the function eventually returns it will assign the guard
		1038	object to C<< $self->{connect_guard} >>, where it will likely never be
		1039	deleted, so the program thinks it is still trying to connect.
		1040
		1041	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1042	callback directly on error:
		1043
		1044	$cb->(undef), return # signal error to callback, BAD!
		1045	if $some_error_condition;
		1046
		1047	It should use C<postpone>:
		1048
		1049	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1050	if $some_error_condition;
		1051
		1052	=item AnyEvent::log $level, $msg[, @args]
		1053
		1054	Log the given C<$msg> at the given C<$level>.
		1055
		1056	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1057	to see whether the message will be logged. If the test succeeds it will
		1058	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1059	the L<AnyEvent::Log> documentation for details.
		1060
		1061	If the test fails it will simply return. Right now this happens when a
		1062	numerical loglevel is used and it is larger than the level specified via
		1063	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1064
		1065	If you want to sprinkle loads of logging calls around your code, consider
		1066	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1067	which can reduce typing, codesize and can reduce the logging overhead
		1068	enourmously.
551		1069
552	=back	1070	=back
553		1071
554	=head1 WHAT TO DO IN A MODULE	1072	=head1 WHAT TO DO IN A MODULE
555		1073
…		…
559	Be careful when you create watchers in the module body - AnyEvent will	1077	Be careful when you create watchers in the module body - AnyEvent will
560	decide which event module to use as soon as the first method is called, so	1078	decide which event module to use as soon as the first method is called, so
561	by calling AnyEvent in your module body you force the user of your module	1079	by calling AnyEvent in your module body you force the user of your module
562	to load the event module first.	1080	to load the event module first.
563		1081
564	Never call C<< ->wait >> on a condition variable unless you I<know> that	1082	Never call C<< ->recv >> on a condition variable unless you I<know> that
565	the C<< ->send >> method has been called on it already. This is	1083	the C<< ->send >> method has been called on it already. This is
566	because it will stall the whole program, and the whole point of using	1084	because it will stall the whole program, and the whole point of using
567	events is to stay interactive.	1085	events is to stay interactive.
568		1086
569	It is fine, however, to call C<< ->wait >> when the user of your module	1087	It is fine, however, to call C<< ->recv >> when the user of your module
570	requests it (i.e. if you create a http request object ad have a method	1088	requests it (i.e. if you create a http request object ad have a method
571	called C<results> that returns the results, it should call C<< ->wait >>	1089	called C<results> that returns the results, it may call C<< ->recv >>
572	freely, as the user of your module knows what she is doing. always).	1090	freely, as the user of your module knows what she is doing. Always).
573		1091
574	=head1 WHAT TO DO IN THE MAIN PROGRAM	1092	=head1 WHAT TO DO IN THE MAIN PROGRAM
575		1093
576	There will always be a single main program - the only place that should	1094	There will always be a single main program - the only place that should
577	dictate which event model to use.	1095	dictate which event model to use.
578		1096
579	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1097	If the program is not event-based, it need not do anything special, even
580	do anything special (it does not need to be event-based) and let AnyEvent	1098	when it depends on a module that uses an AnyEvent. If the program itself
581	decide which implementation to chose if some module relies on it.	1099	uses AnyEvent, but does not care which event loop is used, all it needs
		1100	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1101	available loop implementation.
582		1102
583	If the main program relies on a specific event model. For example, in	1103	If the main program relies on a specific event model - for example, in
584	Gtk2 programs you have to rely on the Glib module. You should load the	1104	Gtk2 programs you have to rely on the Glib module - you should load the
585	event module before loading AnyEvent or any module that uses it: generally	1105	event module before loading AnyEvent or any module that uses it: generally
586	speaking, you should load it as early as possible. The reason is that	1106	speaking, you should load it as early as possible. The reason is that
587	modules might create watchers when they are loaded, and AnyEvent will	1107	modules might create watchers when they are loaded, and AnyEvent will
588	decide on the event model to use as soon as it creates watchers, and it	1108	decide on the event model to use as soon as it creates watchers, and it
589	might chose the wrong one unless you load the correct one yourself.	1109	might choose the wrong one unless you load the correct one yourself.
590		1110
591	You can chose to use a rather inefficient pure-perl implementation by	1111	You can chose to use a pure-perl implementation by loading the
592	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1112	C<AnyEvent::Loop> module, which gives you similar behaviour
593	behaviour everywhere, but letting AnyEvent chose is generally better.	1113	everywhere, but letting AnyEvent chose the model is generally better.
		1114
		1115	=head2 MAINLOOP EMULATION
		1116
		1117	Sometimes (often for short test scripts, or even standalone programs who
		1118	only want to use AnyEvent), you do not want to run a specific event loop.
		1119
		1120	In that case, you can use a condition variable like this:
		1121
		1122	AnyEvent->condvar->recv;
		1123
		1124	This has the effect of entering the event loop and looping forever.
		1125
		1126	Note that usually your program has some exit condition, in which case
		1127	it is better to use the "traditional" approach of storing a condition
		1128	variable somewhere, waiting for it, and sending it when the program should
		1129	exit cleanly.
		1130
594		1131
595	=head1 OTHER MODULES	1132	=head1 OTHER MODULES
596		1133
597	The following is a non-exhaustive list of additional modules that use	1134	The following is a non-exhaustive list of additional modules that use
598	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1135	AnyEvent as a client and can therefore be mixed easily with other
599	in the same program. Some of the modules come with AnyEvent, some are	1136	AnyEvent modules and other event loops in the same program. Some of the
600	available via CPAN.	1137	modules come as part of AnyEvent, the others are available via CPAN (see
		1138	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1139	a longer non-exhaustive list), and the list is heavily biased towards
		1140	modules of the AnyEvent author himself :)
601		1141
602	=over 4	1142	=over 4
603		1143
604	=item L<AnyEvent::Util>	1144	=item L<AnyEvent::Util>
605		1145
606	Contains various utility functions that replace often-used but blocking	1146	Contains various utility functions that replace often-used blocking
607	functions such as C<inet_aton> by event-/callback-based versions.	1147	functions such as C<inet_aton> with event/callback-based versions.
		1148
		1149	=item L<AnyEvent::Socket>
		1150
		1151	Provides various utility functions for (internet protocol) sockets,
		1152	addresses and name resolution. Also functions to create non-blocking tcp
		1153	connections or tcp servers, with IPv6 and SRV record support and more.
608		1154
609	=item L<AnyEvent::Handle>	1155	=item L<AnyEvent::Handle>
610		1156
611	Provide read and write buffers and manages watchers for reads and writes.	1157	Provide read and write buffers, manages watchers for reads and writes,
		1158	supports raw and formatted I/O, I/O queued and fully transparent and
		1159	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
612		1160
613	=item L<AnyEvent::Socket>	1161	=item L<AnyEvent::DNS>
614		1162
615	Provides a means to do non-blocking connects, accepts etc.	1163	Provides rich asynchronous DNS resolver capabilities.
		1164
		1165	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1166
		1167	Implement event-based interfaces to the protocols of the same name (for
		1168	the curious, IGS is the International Go Server and FCP is the Freenet
		1169	Client Protocol).
		1170
		1171	=item L<AnyEvent::AIO>
		1172
		1173	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1174	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1175	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1176	file I/O, and much more.
		1177
		1178	=item L<AnyEvent::Filesys::Notify>
		1179
		1180	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1181	path changes (e.g. "watch this directory for new files", "watch this
		1182	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1183	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1184	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1185	fall back to blocking scans at regular intervals transparently on other
		1186	platforms, so it's about as portable as it gets.
		1187
		1188	(I haven't used it myself, but I haven't heard anybody complaining about
		1189	it yet).
		1190
		1191	=item L<AnyEvent::DBI>
		1192
		1193	Executes L<DBI> requests asynchronously in a proxy process for you,
		1194	notifying you in an event-based way when the operation is finished.
616		1195
617	=item L<AnyEvent::HTTPD>	1196	=item L<AnyEvent::HTTPD>
618		1197
619	Provides a simple web application server framework.	1198	A simple embedded webserver.
620
621	=item L<AnyEvent::DNS>
622
623	Provides asynchronous DNS resolver capabilities, beyond what
624	L<AnyEvent::Util> offers.
625		1199
626	=item L<AnyEvent::FastPing>	1200	=item L<AnyEvent::FastPing>
627		1201
628	The fastest ping in the west.	1202	The fastest ping in the west.
629		1203
630	=item L<Net::IRC3>
631
632	AnyEvent based IRC client module family.
633
634	=item L<Net::XMPP2>
635
636	AnyEvent based XMPP (Jabber protocol) module family.
637
638	=item L<Net::FCP>
639
640	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
641	of AnyEvent.
642
643	=item L<Event::ExecFlow>
644
645	High level API for event-based execution flow control.
646
647	=item L<Coro>	1204	=item L<Coro>
648		1205
649	Has special support for AnyEvent.	1206	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1207	to simply invert the flow control - don't call us, we will call you:
650		1208
651	=item L<IO::Lambda>	1209	async {
		1210	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1211	print "5 seconds later!\n";
652		1212
653	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.	1213	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1214	my $line = <STDIN>; # works for ttys
654		1215
655	=item L<IO::AIO>	1216	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
656		1217	my ($body, $hdr) = Coro::rouse_wait;
657	Truly asynchronous I/O, should be in the toolbox of every event	1218	};
658	programmer. Can be trivially made to use AnyEvent.
659
660	=item L<BDB>
661
662	Truly asynchronous Berkeley DB access. Can be trivially made to use
663	AnyEvent.
664		1219
665	=back	1220	=back
666		1221
667	=cut	1222	=cut
668		1223
669	package AnyEvent;	1224	package AnyEvent;
670		1225
671	no warnings;	1226	# basically a tuned-down version of common::sense
672	use strict;	1227	sub common_sense {
		1228	# from common:.sense 3.4
		1229	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1230	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1231	$^H |= 0x00000600;
		1232	}
673		1233
		1234	BEGIN { AnyEvent::common_sense }
		1235
674	use Carp;	1236	use Carp ();
675		1237
676	our $VERSION = '3.3';	1238	our $VERSION = '6.02';
677	our $MODEL;	1239	our $MODEL;
678
679	our $AUTOLOAD;
680	our @ISA;	1240	our @ISA;
681
682	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
683
684	our @REGISTRY;	1241	our @REGISTRY;
		1242	our $VERBOSE;
		1243	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1244	our $MAX_SIGNAL_LATENCY = $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} || 10; # executes after the BEGIN block below (tainting!)
685		1245
		1246	BEGIN {
		1247	require "AnyEvent/constants.pl";
		1248
		1249	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1250
		1251	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1252	if ${^TAINT};
		1253
		1254	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1255	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1256
		1257	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1258	if ${^TAINT};
		1259
		1260	# $ENV{PERL_ANYEVENT_xxx} now valid
		1261
		1262	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 4;
		1263
		1264	my $idx;
		1265	$PROTOCOL{$_} = ++$idx
		1266	for reverse split /\s*,\s*/,
		1267	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1268	}
		1269
		1270	our @post_detect;
		1271
		1272	sub post_detect(&) {
		1273	my ($cb) = @_;
		1274
		1275	push @post_detect, $cb;
		1276
		1277	defined wantarray
		1278	? bless \$cb, "AnyEvent::Util::postdetect"
		1279	: ()
		1280	}
		1281
		1282	sub AnyEvent::Util::postdetect::DESTROY {
		1283	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1284	}
		1285
		1286	our $POSTPONE_W;
		1287	our @POSTPONE;
		1288
		1289	sub _postpone_exec {
		1290	undef $POSTPONE_W;
		1291
		1292	&{ shift @POSTPONE }
		1293	while @POSTPONE;
		1294	}
		1295
		1296	sub postpone(&) {
		1297	push @POSTPONE, shift;
		1298
		1299	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1300
		1301	()
		1302	}
		1303
		1304	sub log($$;@) {
		1305	# only load the big bloated module when we actually are about to log something
		1306	if ($_[0] <= ($VERBOSE || 1)) { # also catches non-numeric levels(!) and fatal
		1307	local ($!, $@);
		1308	require AnyEvent::Log; # among other things, sets $VERBOSE to 9
		1309	# AnyEvent::Log overwrites this function
		1310	goto &log;
		1311	}
		1312
		1313	0 # not logged
		1314	}
		1315
		1316	sub logger($;$) {
		1317	package AnyEvent::Log;
		1318
		1319	my ($level, $renabled) = @_;
		1320
		1321	$$renabled = $level <= $VERBOSE;
		1322
		1323	my $pkg = (caller)[0];
		1324
		1325	my $logger = [$pkg, $level, $renabled];
		1326
		1327	our %LOGGER;
		1328	$LOGGER{$logger+0} = $logger;
		1329
		1330	return unless defined wantarray;
		1331
		1332	require AnyEvent::Util;
		1333	my $guard = AnyEvent::Util::guard (sub {
		1334	# "clean up"
		1335	delete $LOGGER{$logger+0};
		1336	});
		1337
		1338	sub {
		1339	return 0 unless $$renabled;
		1340
		1341	$guard if 0; # keep guard alive, but don't cause runtime overhead
		1342	require AnyEvent::Log unless $AnyEvent::Log::VERSION;
		1343	package AnyEvent::Log;
		1344	_log ($logger->[0], $level, @_) # logger->[0] has been converted at load time
		1345	}
		1346	}
		1347
		1348	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1349	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1350	}
		1351
686	my @models = (	1352	our @models = (
687	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
688	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
689	[EV:: => AnyEvent::Impl::EV::],	1353	[EV:: => AnyEvent::Impl::EV::],
		1354	[AnyEvent::Loop:: => AnyEvent::Impl::Perl::],
		1355	# everything below here will not (normally) be autoprobed
		1356	# as the pure perl backend should work everywhere
		1357	# and is usually faster
		1358	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package, so msut be near the top
690	[Event:: => AnyEvent::Impl::Event::],	1359	[Event:: => AnyEvent::Impl::Event::], # slow, stable
		1360	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1361	# everything below here should not be autoloaded
		1362	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
691	[Tk:: => AnyEvent::Impl::Tk::],	1363	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1364	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1365	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
692	[Wx:: => AnyEvent::Impl::POE::],	1366	[Wx:: => AnyEvent::Impl::POE::],
693	[Prima:: => AnyEvent::Impl::POE::],	1367	[Prima:: => AnyEvent::Impl::POE::],
694	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1368	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
695	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1369	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
696	[Glib:: => AnyEvent::Impl::Glib::],	1370	[FLTK:: => AnyEvent::Impl::FLTK::],
697	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
698	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
699	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
700	);	1371	);
701		1372
702	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1373	our @isa_hook;
		1374
		1375	sub _isa_set {
		1376	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1377
		1378	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1379	for 1 .. $#pkg;
		1380
		1381	grep $_ && $_->[1], @isa_hook
		1382	and AE::_reset ();
		1383	}
		1384
		1385	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1386	sub _isa_hook($$;$) {
		1387	my ($i, $pkg, $reset_ae) = @_;
		1388
		1389	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1390
		1391	_isa_set;
		1392	}
		1393
		1394	# all autoloaded methods reserve the complete glob, not just the method slot.
		1395	# due to bugs in perls method cache implementation.
		1396	our @methods = qw(io timer time now now_update signal child idle condvar);
703		1397
704	sub detect() {	1398	sub detect() {
		1399	return $MODEL if $MODEL; # some programs keep references to detect
		1400
		1401	# IO::Async::Loop::AnyEvent is extremely evil, refuse to work with it
		1402	# the author knows about the problems and what it does to AnyEvent as a whole
		1403	# (and the ability of others to use AnyEvent), but simply wants to abuse AnyEvent
		1404	# anyway.
		1405	AnyEvent::log fatal => "AnyEvent: IO::Async::Loop::AnyEvent detected - this module is broken by design,\n"
		1406	. "abuses internals and breaks AnyEvent, will not continue."
		1407	if exists $INC{"IO/Async/Loop/AnyEvent.pm"};
		1408
		1409	local $!; # for good measure
		1410	local $SIG{__DIE__}; # we use eval
		1411
		1412	# free some memory
		1413	*detect = sub () { $MODEL };
		1414	# undef &func doesn't correctly update the method cache. grmbl.
		1415	# so we delete the whole glob. grmbl.
		1416	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1417	# a glob with an active sub. hrm. i hope it works, but perl is
		1418	# usually buggy in this department. sigh.
		1419	delete @{"AnyEvent::"}{@methods};
		1420	undef @methods;
		1421
		1422	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1423	my $model = $1;
		1424	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1425	if (eval "require $model") {
		1426	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1427	$MODEL = $model;
		1428	} else {
		1429	AnyEvent::log 4 => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1430	}
		1431	}
		1432
		1433	# check for already loaded models
705	unless ($MODEL) {	1434	unless ($MODEL) {
706	no strict 'refs';	1435	for (@REGISTRY, @models) {
707		1436	my ($package, $model) = @$_;
708	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1437	if (${"$package\::VERSION"} > 0) {
709	my $model = "AnyEvent::Impl::$1";
710	if (eval "require $model") {	1438	if (eval "require $model") {
		1439	AnyEvent::log 7 => "autodetected model '$model', using it.";
711	$MODEL = $model;	1440	$MODEL = $model;
712	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1441	last;
713	} else {	1442	}
714	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
715	}	1443	}
716	}	1444	}
717		1445
718	# check for already loaded models
719	unless ($MODEL) {	1446	unless ($MODEL) {
		1447	# try to autoload a model
720	for (@REGISTRY, @models) {	1448	for (@REGISTRY, @models) {
721	my ($package, $model) = @$_;	1449	my ($package, $model) = @$_;
		1450	if (
		1451	eval "require $package"
722	if (${"$package\::VERSION"} > 0) {	1452	and ${"$package\::VERSION"} > 0
723	if (eval "require $model") {	1453	and eval "require $model"
		1454	) {
		1455	AnyEvent::log 7 => "autoloaded model '$model', using it.";
724	$MODEL = $model;	1456	$MODEL = $model;
725	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
726	last;	1457	last;
727	}
728	}	1458	}
729	}	1459	}
730		1460
731	unless ($MODEL) {	1461	$MODEL
732	# try to load a model	1462	or AnyEvent::log fatal => "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
		1463	}
		1464	}
733		1465
734	for (@REGISTRY, @models) {	1466	# free memory only needed for probing
735	my ($package, $model) = @$_;	1467	undef @models;
736	if (eval "require $package"	1468	undef @REGISTRY;
737	and ${"$package\::VERSION"} > 0	1469
738	and eval "require $model") {	1470	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
739	$MODEL = $model;	1471
740	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1472	# now nuke some methods that are overridden by the backend.
		1473	# SUPER usage is not allowed in these.
		1474	for (qw(time signal child idle)) {
		1475	undef &{"AnyEvent::Base::$_"}
		1476	if defined &{"$MODEL\::$_"};
		1477	}
		1478
		1479	_isa_set;
		1480
		1481	# we're officially open!
		1482
		1483	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1484	require AnyEvent::Strict;
		1485	}
		1486
		1487	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1488	require AnyEvent::Debug;
		1489	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1490	}
		1491
		1492	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1493	require AnyEvent::Socket;
		1494	require AnyEvent::Debug;
		1495
		1496	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1497	$shell =~ s/\$\$/$$/g;
		1498
		1499	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1500	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1501	}
		1502
		1503	# now the anyevent environment is set up as the user told us to, so
		1504	# call the actual user code - post detects
		1505
		1506	(shift @post_detect)->() while @post_detect;
		1507	undef @post_detect;
		1508
		1509	*post_detect = sub(&) {
		1510	shift->();
		1511
		1512	undef
		1513	};
		1514
		1515	$MODEL
		1516	}
		1517
		1518	for my $name (@methods) {
		1519	*$name = sub {
		1520	detect;
		1521	# we use goto because
		1522	# a) it makes the thunk more transparent
		1523	# b) it allows us to delete the thunk later
		1524	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1525	};
		1526	}
		1527
		1528	# utility function to dup a filehandle. this is used by many backends
		1529	# to support binding more than one watcher per filehandle (they usually
		1530	# allow only one watcher per fd, so we dup it to get a different one).
		1531	sub _dupfh($$;$$) {
		1532	my ($poll, $fh, $r, $w) = @_;
		1533
		1534	# cygwin requires the fh mode to be matching, unix doesn't
		1535	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1536
		1537	open my $fh2, $mode, $fh
		1538	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1539
		1540	# we assume CLOEXEC is already set by perl in all important cases
		1541
		1542	($fh2, $rw)
		1543	}
		1544
		1545	=head1 SIMPLIFIED AE API
		1546
		1547	Starting with version 5.0, AnyEvent officially supports a second, much
		1548	simpler, API that is designed to reduce the calling, typing and memory
		1549	overhead by using function call syntax and a fixed number of parameters.
		1550
		1551	See the L<AE> manpage for details.
		1552
		1553	=cut
		1554
		1555	package AE;
		1556
		1557	our $VERSION = $AnyEvent::VERSION;
		1558
		1559	sub _reset() {
		1560	eval q{
		1561	# fall back to the main API by default - backends and AnyEvent::Base
		1562	# implementations can overwrite these.
		1563
		1564	sub io($$$) {
		1565	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1566	}
		1567
		1568	sub timer($$$) {
		1569	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1570	}
		1571
		1572	sub signal($$) {
		1573	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1574	}
		1575
		1576	sub child($$) {
		1577	AnyEvent->child (pid => $_[0], cb => $_[1])
		1578	}
		1579
		1580	sub idle($) {
		1581	AnyEvent->idle (cb => $_[0]);
		1582	}
		1583
		1584	sub cv(;&) {
		1585	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1586	}
		1587
		1588	sub now() {
		1589	AnyEvent->now
		1590	}
		1591
		1592	sub now_update() {
		1593	AnyEvent->now_update
		1594	}
		1595
		1596	sub time() {
		1597	AnyEvent->time
		1598	}
		1599
		1600	*postpone = \&AnyEvent::postpone;
		1601	*log = \&AnyEvent::log;
		1602	};
		1603	die if $@;
		1604	}
		1605
		1606	BEGIN { _reset }
		1607
		1608	package AnyEvent::Base;
		1609
		1610	# default implementations for many methods
		1611
		1612	sub time {
		1613	eval q{ # poor man's autoloading {}
		1614	# probe for availability of Time::HiRes
		1615	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1616	*time = sub { Time::HiRes::time () };
		1617	*AE::time = \& Time::HiRes::time ;
		1618	*now = \&time;
		1619	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy.";
		1620	# if (eval "use POSIX (); (POSIX::times())...
		1621	} else {
		1622	*time = sub { CORE::time };
		1623	*AE::time = sub (){ CORE::time };
		1624	*now = \&time;
		1625	AnyEvent::log 3 => "using built-in time(), WARNING, no sub-second resolution!";
		1626	}
		1627	};
		1628	die if $@;
		1629
		1630	&time
		1631	}
		1632
		1633	*now = \&time;
		1634	sub now_update { }
		1635
		1636	sub _poll {
		1637	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1638	}
		1639
		1640	# default implementation for ->condvar
		1641	# in fact, the default should not be overwritten
		1642
		1643	sub condvar {
		1644	eval q{ # poor man's autoloading {}
		1645	*condvar = sub {
		1646	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1647	};
		1648
		1649	*AE::cv = sub (;&) {
		1650	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1651	};
		1652	};
		1653	die if $@;
		1654
		1655	&condvar
		1656	}
		1657
		1658	# default implementation for ->signal
		1659
		1660	our $HAVE_ASYNC_INTERRUPT;
		1661
		1662	sub _have_async_interrupt() {
		1663	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1664	&& eval "use Async::Interrupt 1.02 (); 1")
		1665	unless defined $HAVE_ASYNC_INTERRUPT;
		1666
		1667	$HAVE_ASYNC_INTERRUPT
		1668	}
		1669
		1670	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1671	our (%SIG_ASY, %SIG_ASY_W);
		1672	our ($SIG_COUNT, $SIG_TW);
		1673
		1674	# install a dummy wakeup watcher to reduce signal catching latency
		1675	# used by Impls
		1676	sub _sig_add() {
		1677	unless ($SIG_COUNT++) {
		1678	# try to align timer on a full-second boundary, if possible
		1679	my $NOW = AE::now;
		1680
		1681	$SIG_TW = AE::timer
		1682	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1683	$MAX_SIGNAL_LATENCY,
		1684	sub { } # just for the PERL_ASYNC_CHECK
		1685	;
		1686	}
		1687	}
		1688
		1689	sub _sig_del {
		1690	undef $SIG_TW
		1691	unless --$SIG_COUNT;
		1692	}
		1693
		1694	our $_sig_name_init; $_sig_name_init = sub {
		1695	eval q{ # poor man's autoloading {}
		1696	undef $_sig_name_init;
		1697
		1698	if (_have_async_interrupt) {
		1699	*sig2num = \&Async::Interrupt::sig2num;
		1700	*sig2name = \&Async::Interrupt::sig2name;
		1701	} else {
		1702	require Config;
		1703
		1704	my %signame2num;
		1705	@signame2num{ split ' ', $Config::Config{sig_name} }
		1706	= split ' ', $Config::Config{sig_num};
		1707
		1708	my @signum2name;
		1709	@signum2name[values %signame2num] = keys %signame2num;
		1710
		1711	*sig2num = sub($) {
		1712	$_[0] > 0 ? shift : $signame2num{+shift}
		1713	};
		1714	*sig2name = sub ($) {
		1715	$_[0] > 0 ? $signum2name[+shift] : shift
		1716	};
		1717	}
		1718	};
		1719	die if $@;
		1720	};
		1721
		1722	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1723	sub sig2name($) { &$_sig_name_init; &sig2name }
		1724
		1725	sub signal {
		1726	eval q{ # poor man's autoloading {}
		1727	# probe for availability of Async::Interrupt
		1728	if (_have_async_interrupt) {
		1729	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling.";
		1730
		1731	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1732	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1733
		1734	} else {
		1735	AnyEvent::log 8 => "using emulated perl signal handling with latency timer.";
		1736
		1737	if (AnyEvent::WIN32) {
		1738	require AnyEvent::Util;
		1739
		1740	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1741	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1742	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1743	} else {
		1744	pipe $SIGPIPE_R, $SIGPIPE_W;
		1745	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1746	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1747
		1748	# not strictly required, as $^F is normally 2, but let's make sure...
		1749	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1750	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1751	}
		1752
		1753	$SIGPIPE_R
		1754	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1755
		1756	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1757	}
		1758
		1759	*signal = $HAVE_ASYNC_INTERRUPT
		1760	? sub {
		1761	my (undef, %arg) = @_;
		1762
		1763	# async::interrupt
		1764	my $signal = sig2num $arg{signal};
		1765	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1766
		1767	$SIG_ASY{$signal} ||= new Async::Interrupt
		1768	cb => sub { undef $SIG_EV{$signal} },
		1769	signal => $signal,
		1770	pipe => [$SIGPIPE_R->filenos],
		1771	pipe_autodrain => 0,
		1772	;
		1773
		1774	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1775	}
		1776	: sub {
		1777	my (undef, %arg) = @_;
		1778
		1779	# pure perl
		1780	my $signal = sig2name $arg{signal};
		1781	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1782
		1783	$SIG{$signal} ||= sub {
741	last;	1784	local $!;
		1785	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1786	undef $SIG_EV{$signal};
742	}	1787	};
		1788
		1789	# can't do signal processing without introducing races in pure perl,
		1790	# so limit the signal latency.
		1791	_sig_add;
		1792
		1793	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1794	}
		1795	;
		1796
		1797	*AnyEvent::Base::signal::DESTROY = sub {
		1798	my ($signal, $cb) = @{$_[0]};
		1799
		1800	_sig_del;
		1801
		1802	delete $SIG_CB{$signal}{$cb};
		1803
		1804	$HAVE_ASYNC_INTERRUPT
		1805	? delete $SIG_ASY{$signal}
		1806	: # delete doesn't work with older perls - they then
		1807	# print weird messages, or just unconditionally exit
		1808	# instead of getting the default action.
		1809	undef $SIG{$signal}
		1810	unless keys %{ $SIG_CB{$signal} };
		1811	};
		1812
		1813	*_signal_exec = sub {
		1814	$HAVE_ASYNC_INTERRUPT
		1815	? $SIGPIPE_R->drain
		1816	: sysread $SIGPIPE_R, (my $dummy), 9;
		1817
		1818	while (%SIG_EV) {
		1819	for (keys %SIG_EV) {
		1820	delete $SIG_EV{$_};
		1821	&$_ for values %{ $SIG_CB{$_} || {} };
743	}	1822	}
744
745	$MODEL
746	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.";
747	}	1823	}
748	}	1824	};
749
750	unshift @ISA, $MODEL;
751	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
752	}
753
754	$MODEL
755	}
756
757	sub AUTOLOAD {
758	(my $func = $AUTOLOAD) =~ s/.*://;
759
760	$method{$func}
761	or croak "$func: not a valid method for AnyEvent objects";
762
763	detect unless $MODEL;
764
765	my $class = shift;
766	$class->$func (@_);
767	}
768
769	package AnyEvent::Base;
770
771	# default implementation for ->condvar, ->wait, ->broadcast
772
773	sub condvar {
774	bless \my $flag, "AnyEvent::Base::CondVar"
775	}
776
777	sub AnyEvent::Base::CondVar::broadcast {
778	${$_[0]}++;
779	}
780
781	sub AnyEvent::Base::CondVar::wait {
782	AnyEvent->one_event while !${$_[0]};
783	}
784
785	# default implementation for ->signal
786
787	our %SIG_CB;
788
789	sub signal {
790	my (undef, %arg) = @_;
791
792	my $signal = uc $arg{signal}
793	or Carp::croak "required option 'signal' is missing";
794
795	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
796	$SIG{$signal} ||= sub {
797	$_->() for values %{ $SIG_CB{$signal} || {} };
798	};	1825	};
		1826	die if $@;
799		1827
800	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1828	&signal
801	}
802
803	sub AnyEvent::Base::Signal::DESTROY {
804	my ($signal, $cb) = @{$_[0]};
805
806	delete $SIG_CB{$signal}{$cb};
807
808	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
809	}	1829	}
810		1830
811	# default implementation for ->child	1831	# default implementation for ->child
812		1832
813	our %PID_CB;	1833	our %PID_CB;
814	our $CHLD_W;	1834	our $CHLD_W;
815	our $CHLD_DELAY_W;	1835	our $CHLD_DELAY_W;
816	our $PID_IDLE;
817	our $WNOHANG;
818		1836
819	sub _child_wait {	1837	# used by many Impl's
820	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1838	sub _emit_childstatus($$) {
		1839	my (undef, $rpid, $rstatus) = @_;
		1840
		1841	$_->($rpid, $rstatus)
821	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1842	for values %{ $PID_CB{$rpid} || {} },
822	(values %{ $PID_CB{0} || {} });	1843	values %{ $PID_CB{0} || {} };
		1844	}
		1845
		1846	sub child {
		1847	eval q{ # poor man's autoloading {}
		1848	*_sigchld = sub {
		1849	my $pid;
		1850
		1851	AnyEvent->_emit_childstatus ($pid, $?)
		1852	while ($pid = waitpid -1, WNOHANG) > 0;
		1853	};
		1854
		1855	*child = sub {
		1856	my (undef, %arg) = @_;
		1857
		1858	my $pid = $arg{pid};
		1859	my $cb = $arg{cb};
		1860
		1861	$PID_CB{$pid}{$cb+0} = $cb;
		1862
		1863	unless ($CHLD_W) {
		1864	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1865	# child could be a zombie already, so make at least one round
		1866	&_sigchld;
		1867	}
		1868
		1869	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1870	};
		1871
		1872	*AnyEvent::Base::child::DESTROY = sub {
		1873	my ($pid, $icb) = @{$_[0]};
		1874
		1875	delete $PID_CB{$pid}{$icb};
		1876	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1877
		1878	undef $CHLD_W unless keys %PID_CB;
		1879	};
		1880	};
		1881	die if $@;
		1882
		1883	&child
		1884	}
		1885
		1886	# idle emulation is done by simply using a timer, regardless
		1887	# of whether the process is idle or not, and not letting
		1888	# the callback use more than 50% of the time.
		1889	sub idle {
		1890	eval q{ # poor man's autoloading {}
		1891	*idle = sub {
		1892	my (undef, %arg) = @_;
		1893
		1894	my ($cb, $w, $rcb) = $arg{cb};
		1895
		1896	$rcb = sub {
		1897	if ($cb) {
		1898	$w = AE::time;
		1899	&$cb;
		1900	$w = AE::time - $w;
		1901
		1902	# never use more then 50% of the time for the idle watcher,
		1903	# within some limits
		1904	$w = 0.0001 if $w < 0.0001;
		1905	$w = 5 if $w > 5;
		1906
		1907	$w = AE::timer $w, 0, $rcb;
		1908	} else {
		1909	# clean up...
		1910	undef $w;
		1911	undef $rcb;
		1912	}
		1913	};
		1914
		1915	$w = AE::timer 0.05, 0, $rcb;
		1916
		1917	bless \\$cb, "AnyEvent::Base::idle"
		1918	};
		1919
		1920	*AnyEvent::Base::idle::DESTROY = sub {
		1921	undef $${$_[0]};
		1922	};
		1923	};
		1924	die if $@;
		1925
		1926	&idle
		1927	}
		1928
		1929	package AnyEvent::CondVar;
		1930
		1931	our @ISA = AnyEvent::CondVar::Base::;
		1932
		1933	# only to be used for subclassing
		1934	sub new {
		1935	my $class = shift;
		1936	bless AnyEvent->condvar (@_), $class
		1937	}
		1938
		1939	package AnyEvent::CondVar::Base;
		1940
		1941	#use overload
		1942	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1943	# fallback => 1;
		1944
		1945	# save 300+ kilobytes by dirtily hardcoding overloading
		1946	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1947	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1948	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1949	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1950
		1951	our $WAITING;
		1952
		1953	sub _send {
		1954	# nop
		1955	}
		1956
		1957	sub _wait {
		1958	AnyEvent->_poll until $_[0]{_ae_sent};
		1959	}
		1960
		1961	sub send {
		1962	my $cv = shift;
		1963	$cv->{_ae_sent} = [@_];
		1964	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1965	$cv->_send;
		1966	}
		1967
		1968	sub croak {
		1969	$_[0]{_ae_croak} = $_[1];
		1970	$_[0]->send;
		1971	}
		1972
		1973	sub ready {
		1974	$_[0]{_ae_sent}
		1975	}
		1976
		1977	sub recv {
		1978	unless ($_[0]{_ae_sent}) {
		1979	$WAITING
		1980	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1981
		1982	local $WAITING = 1;
		1983	$_[0]->_wait;
823	}	1984	}
824		1985
825	undef $PID_IDLE;	1986	$_[0]{_ae_croak}
826	}	1987	and Carp::croak $_[0]{_ae_croak};
827		1988
828	sub _sigchld {	1989	wantarray
829	# make sure we deliver these changes "synchronous" with the event loop.	1990	? @{ $_[0]{_ae_sent} }
830	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1991	: $_[0]{_ae_sent}[0]
831	undef $CHLD_DELAY_W;
832	&_child_wait;
833	});
834	}	1992	}
835		1993
836	sub child {	1994	sub cb {
837	my (undef, %arg) = @_;	1995	my $cv = shift;
838		1996
839	defined (my $pid = $arg{pid} + 0)	1997	@_
840	or Carp::croak "required option 'pid' is missing";	1998	and $cv->{_ae_cb} = shift
		1999	and $cv->{_ae_sent}
		2000	and (delete $cv->{_ae_cb})->($cv);
841		2001
842	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	2002	$cv->{_ae_cb}
843
844	unless ($WNOHANG) {
845	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
846	}
847
848	unless ($CHLD_W) {
849	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
850	# child could be a zombie already, so make at least one round
851	&_sigchld;
852	}
853
854	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
855	}	2003	}
856		2004
857	sub AnyEvent::Base::Child::DESTROY {	2005	sub begin {
858	my ($pid, $cb) = @{$_[0]};	2006	++$_[0]{_ae_counter};
859		2007	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
860	delete $PID_CB{$pid}{$cb};
861	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
862
863	undef $CHLD_W unless keys %PID_CB;
864	}	2008	}
		2009
		2010	sub end {
		2011	return if --$_[0]{_ae_counter};
		2012	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		2013	}
		2014
		2015	# undocumented/compatibility with pre-3.4
		2016	*broadcast = \&send;
		2017	*wait = \&recv;
		2018
		2019	=head1 ERROR AND EXCEPTION HANDLING
		2020
		2021	In general, AnyEvent does not do any error handling - it relies on the
		2022	caller to do that if required. The L<AnyEvent::Strict> module (see also
		2023	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		2024	checking of all AnyEvent methods, however, which is highly useful during
		2025	development.
		2026
		2027	As for exception handling (i.e. runtime errors and exceptions thrown while
		2028	executing a callback), this is not only highly event-loop specific, but
		2029	also not in any way wrapped by this module, as this is the job of the main
		2030	program.
		2031
		2032	The pure perl event loop simply re-throws the exception (usually
		2033	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		2034	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		2035	so on.
		2036
		2037	=head1 ENVIRONMENT VARIABLES
		2038
		2039	AnyEvent supports a number of environment variables that tune the
		2040	runtime behaviour. They are usually evaluated when AnyEvent is
		2041	loaded, initialised, or a submodule that uses them is loaded. Many of
		2042	them also cause AnyEvent to load additional modules - for example,
		2043	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2044	loaded.
		2045
		2046	All the environment variables documented here start with
		2047	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2048	namespace. Other modules are encouraged (but by no means required) to use
		2049	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2050	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2051	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2052	variables starting with C<AE_>, see below).
		2053
		2054	All variables can also be set via the C<AE_> prefix, that is, instead
		2055	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2056	case there is a clash btween anyevent and another program that uses
		2057	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2058	variable to the empty string, as those variables take precedence.
		2059
		2060	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2061	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2062	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2063	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2064	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2065	is set).
		2066
		2067	The exact algorithm is currently:
		2068
		2069	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2070	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2071	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2072
		2073	This ensures that child processes will not see the C<AE_> variables.
		2074
		2075	The following environment variables are currently known to AnyEvent:
		2076
		2077	=over 4
		2078
		2079	=item C<PERL_ANYEVENT_VERBOSE>
		2080
		2081	By default, AnyEvent will only log messages with loglevel C<3>
		2082	(C<critical>) or higher (see L<AnyEvent::Log>). You can set this
		2083	environment variable to a numerical loglevel to make AnyEvent more (or
		2084	less) talkative.
		2085
		2086	If you want to do more than just set the global logging level
		2087	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2088	complex specifications.
		2089
		2090	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2091	the default logging settings.
		2092
		2093	When set to C<5> or higher (C<warn>), causes AnyEvent to warn about
		2094	unexpected conditions, such as not being able to load the event model
		2095	specified by C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an
		2096	exception - this is the minimum recommended level.
		2097
		2098	When set to C<7> or higher (info), cause AnyEvent to report which event model it
		2099	chooses.
		2100
		2101	When set to C<8> or higher (debug), then AnyEvent will report extra information on
		2102	which optional modules it loads and how it implements certain features.
		2103
		2104	=item C<PERL_ANYEVENT_LOG>
		2105
		2106	Accepts rather complex logging specifications. For example, you could log
		2107	all C<debug> messages of some module to stderr, warnings and above to
		2108	stderr, and errors and above to syslog, with:
		2109
		2110	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2111
		2112	For the rather extensive details, see L<AnyEvent::Log>.
		2113
		2114	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2115	so will take effect even before AnyEvent has initialised itself.
		2116
		2117	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2118	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2119	using the latter saves a few hundred kB of memory until the first message
		2120	is being logged.
		2121
		2122	=item C<PERL_ANYEVENT_STRICT>
		2123
		2124	AnyEvent does not do much argument checking by default, as thorough
		2125	argument checking is very costly. Setting this variable to a true value
		2126	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2127	check the arguments passed to most method calls. If it finds any problems,
		2128	it will croak.
		2129
		2130	In other words, enables "strict" mode.
		2131
		2132	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2133	>>, it is definitely recommended to keep it off in production. Keeping
		2134	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2135	can be very useful, however.
		2136
		2137	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2138
		2139	If this env variable is nonempty, then its contents will be interpreted by
		2140	C<AnyEvent::Socket::parse_hostport> and C<AnyEvent::Debug::shell> (after
		2141	replacing every occurance of C<$$> by the process pid). The shell object
		2142	is saved in C<$AnyEvent::Debug::SHELL>.
		2143
		2144	This happens when the first watcher is created.
		2145
		2146	For example, to bind a debug shell on a unix domain socket in
		2147	F<< /tmp/debug<pid>.sock >>, you could use this:
		2148
		2149	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2150	# connect with e.g.: socat readline /tmp/debug123.sock
		2151
		2152	Or to bind to tcp port 4545 on localhost:
		2153
		2154	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		2155	# connect with e.g.: telnet localhost 4545
		2156
		2157	Note that creating sockets in F</tmp> or on localhost is very unsafe on
		2158	multiuser systems.
		2159
		2160	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2161
		2162	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2163	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2164
		2165	=item C<PERL_ANYEVENT_MODEL>
		2166
		2167	This can be used to specify the event model to be used by AnyEvent, before
		2168	auto detection and -probing kicks in.
		2169
		2170	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2171	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2172	resulting module name is loaded and - if the load was successful - used as
		2173	event model backend. If it fails to load then AnyEvent will proceed with
		2174	auto detection and -probing.
		2175
		2176	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2177	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2178	the end of a string designates a module name and quotes it appropriately).
		2179
		2180	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2181	could start your program like this:
		2182
		2183	PERL_ANYEVENT_MODEL=Perl perl ...
		2184
		2185	=item C<PERL_ANYEVENT_PROTOCOLS>
		2186
		2187	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2188	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2189	of auto probing).
		2190
		2191	Must be set to a comma-separated list of protocols or address families,
		2192	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2193	used, and preference will be given to protocols mentioned earlier in the
		2194	list.
		2195
		2196	This variable can effectively be used for denial-of-service attacks
		2197	against local programs (e.g. when setuid), although the impact is likely
		2198	small, as the program has to handle conenction and other failures anyways.
		2199
		2200	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2201	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2202	- only support IPv4, never try to resolve or contact IPv6
		2203	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2204	IPv6, but prefer IPv6 over IPv4.
		2205
		2206	=item C<PERL_ANYEVENT_HOSTS>
		2207
		2208	This variable, if specified, overrides the F</etc/hosts> file used by
		2209	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2210	from that file instead.
		2211
		2212	=item C<PERL_ANYEVENT_EDNS0>
		2213
		2214	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2215	DNS. This extension is generally useful to reduce DNS traffic, especially
		2216	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2217	packets, which is why it is off by default.
		2218
		2219	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2220	EDNS0 in its DNS requests.
		2221
		2222	=item C<PERL_ANYEVENT_MAX_FORKS>
		2223
		2224	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2225	will create in parallel.
		2226
		2227	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2228
		2229	The default value for the C<max_outstanding> parameter for the default DNS
		2230	resolver - this is the maximum number of parallel DNS requests that are
		2231	sent to the DNS server.
		2232
		2233	=item C<PERL_ANYEVENT_MAX_SIGNAL_LATENCY>
		2234
		2235	Perl has inherently racy signal handling (you can basically choose between
		2236	losing signals and memory corruption) - pure perl event loops (including
		2237	C<AnyEvent::Loop>, when C<Async::Interrupt> isn't available) therefore
		2238	have to poll regularly to avoid losing signals.
		2239
		2240	Some event loops are racy, but don't poll regularly, and some event loops
		2241	are written in C but are still racy. For those event loops, AnyEvent
		2242	installs a timer that regularly wakes up the event loop.
		2243
		2244	By default, the interval for this timer is C<10> seconds, but you can
		2245	override this delay with this environment variable (or by setting
		2246	the C<$AnyEvent::MAX_SIGNAL_LATENCY> variable before creating signal
		2247	watchers).
		2248
		2249	Lower values increase CPU (and energy) usage, higher values can introduce
		2250	long delays when reaping children or waiting for signals.
		2251
		2252	The L<AnyEvent::Async> module, if available, will be used to avoid this
		2253	polling (with most event loops).
		2254
		2255	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2256
		2257	The absolute path to a F<resolv.conf>-style file to use instead of
		2258	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2259	resolver, or the empty string to select the default configuration.
		2260
		2261	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2262
		2263	When neither C<ca_file> nor C<ca_path> was specified during
		2264	L<AnyEvent::TLS> context creation, and either of these environment
		2265	variables are nonempty, they will be used to specify CA certificate
		2266	locations instead of a system-dependent default.
		2267
		2268	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2269
		2270	When these are set to C<1>, then the respective modules are not
		2271	loaded. Mostly good for testing AnyEvent itself.
		2272
		2273	=back
865		2274
866	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2275	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
867		2276
868	This is an advanced topic that you do not normally need to use AnyEvent in	2277	This is an advanced topic that you do not normally need to use AnyEvent in
869	a module. This section is only of use to event loop authors who want to	2278	a module. This section is only of use to event loop authors who want to
…		…
903		2312
904	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2313	I<rxvt-unicode> also cheats a bit by not providing blocking access to
905	condition variables: code blocking while waiting for a condition will	2314	condition variables: code blocking while waiting for a condition will
906	C<die>. This still works with most modules/usages, and blocking calls must	2315	C<die>. This still works with most modules/usages, and blocking calls must
907	not be done in an interactive application, so it makes sense.	2316	not be done in an interactive application, so it makes sense.
908
909	=head1 ENVIRONMENT VARIABLES
910
911	The following environment variables are used by this module:
912
913	=over 4
914
915	=item C<PERL_ANYEVENT_VERBOSE>
916
917	By default, AnyEvent will be completely silent except in fatal
918	conditions. You can set this environment variable to make AnyEvent more
919	talkative.
920
921	When set to C<1> or higher, causes AnyEvent to warn about unexpected
922	conditions, such as not being able to load the event model specified by
923	C<PERL_ANYEVENT_MODEL>.
924
925	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
926	model it chooses.
927
928	=item C<PERL_ANYEVENT_MODEL>
929
930	This can be used to specify the event model to be used by AnyEvent, before
931	autodetection and -probing kicks in. It must be a string consisting
932	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
933	and the resulting module name is loaded and if the load was successful,
934	used as event model. If it fails to load AnyEvent will proceed with
935	autodetection and -probing.
936
937	This functionality might change in future versions.
938
939	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
940	could start your program like this:
941
942	PERL_ANYEVENT_MODEL=Perl perl ...
943
944	=back
945		2317
946	=head1 EXAMPLE PROGRAM	2318	=head1 EXAMPLE PROGRAM
947		2319
948	The following program uses an I/O watcher to read data from STDIN, a timer	2320	The following program uses an I/O watcher to read data from STDIN, a timer
949	to display a message once per second, and a condition variable to quit the	2321	to display a message once per second, and a condition variable to quit the
…		…
958	poll => 'r',	2330	poll => 'r',
959	cb => sub {	2331	cb => sub {
960	warn "io event <$_[0]>\n"; # will always output <r>	2332	warn "io event <$_[0]>\n"; # will always output <r>
961	chomp (my $input = <STDIN>); # read a line	2333	chomp (my $input = <STDIN>); # read a line
962	warn "read: $input\n"; # output what has been read	2334	warn "read: $input\n"; # output what has been read
963	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2335	$cv->send if $input =~ /^q/i; # quit program if /^q/i
964	},	2336	},
965	);	2337	);
966		2338
967	my $time_watcher; # can only be used once
968
969	sub new_timer {
970	$timer = AnyEvent->timer (after => 1, cb => sub {	2339	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
971	warn "timeout\n"; # print 'timeout' about every second	2340	warn "timeout\n"; # print 'timeout' at most every second
972	&new_timer; # and restart the time
973	});	2341	});
974	}
975		2342
976	new_timer; # create first timer
977
978	$cv->wait; # wait until user enters /^q/i	2343	$cv->recv; # wait until user enters /^q/i
979		2344
980	=head1 REAL-WORLD EXAMPLE	2345	=head1 REAL-WORLD EXAMPLE
981		2346
982	Consider the L<Net::FCP> module. It features (among others) the following	2347	Consider the L<Net::FCP> module. It features (among others) the following
983	API calls, which are to freenet what HTTP GET requests are to http:	2348	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1033	syswrite $txn->{fh}, $txn->{request}	2398	syswrite $txn->{fh}, $txn->{request}
1034	or die "connection or write error";	2399	or die "connection or write error";
1035	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2400	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1036		2401
1037	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2402	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1038	result and signals any possible waiters that the request ahs finished:	2403	result and signals any possible waiters that the request has finished:
1039		2404
1040	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2405	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1041		2406
1042	if (end-of-file or data complete) {	2407	if (end-of-file or data complete) {
1043	$txn->{result} = $txn->{buf};	2408	$txn->{result} = $txn->{buf};
1044	$txn->{finished}->broadcast;	2409	$txn->{finished}->send;
1045	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2410	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1046	}	2411	}
1047		2412
1048	The C<result> method, finally, just waits for the finished signal (if the	2413	The C<result> method, finally, just waits for the finished signal (if the
1049	request was already finished, it doesn't wait, of course, and returns the	2414	request was already finished, it doesn't wait, of course, and returns the
1050	data:	2415	data:
1051		2416
1052	$txn->{finished}->wait;	2417	$txn->{finished}->recv;
1053	return $txn->{result};	2418	return $txn->{result};
1054		2419
1055	The actual code goes further and collects all errors (C<die>s, exceptions)	2420	The actual code goes further and collects all errors (C<die>s, exceptions)
1056	that occured during request processing. The C<result> method detects	2421	that occurred during request processing. The C<result> method detects
1057	whether an exception as thrown (it is stored inside the $txn object)	2422	whether an exception as thrown (it is stored inside the $txn object)
1058	and just throws the exception, which means connection errors and other	2423	and just throws the exception, which means connection errors and other
1059	problems get reported tot he code that tries to use the result, not in a	2424	problems get reported to the code that tries to use the result, not in a
1060	random callback.	2425	random callback.
1061		2426
1062	All of this enables the following usage styles:	2427	All of this enables the following usage styles:
1063		2428
1064	1. Blocking:	2429	1. Blocking:
…		…
1092		2457
1093	my $quit = AnyEvent->condvar;	2458	my $quit = AnyEvent->condvar;
1094		2459
1095	$fcp->txn_client_get ($url)->cb (sub {	2460	$fcp->txn_client_get ($url)->cb (sub {
1096	...	2461	...
1097	$quit->broadcast;	2462	$quit->send;
1098	});	2463	});
1099		2464
1100	$quit->wait;	2465	$quit->recv;
1101		2466
1102		2467
1103	=head1 BENCHMARKS	2468	=head1 BENCHMARKS
1104		2469
1105	To give you an idea of the performance and overheads that AnyEvent adds	2470	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1107	of various event loops I prepared some benchmarks.	2472	of various event loops I prepared some benchmarks.
1108		2473
1109	=head2 BENCHMARKING ANYEVENT OVERHEAD	2474	=head2 BENCHMARKING ANYEVENT OVERHEAD
1110		2475
1111	Here is a benchmark of various supported event models used natively and	2476	Here is a benchmark of various supported event models used natively and
1112	through anyevent. The benchmark creates a lot of timers (with a zero	2477	through AnyEvent. The benchmark creates a lot of timers (with a zero
1113	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2478	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1114	which it is), lets them fire exactly once and destroys them again.	2479	which it is), lets them fire exactly once and destroys them again.
1115		2480
1116	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2481	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1117	distribution.	2482	distribution. It uses the L<AE> interface, which makes a real difference
		2483	for the EV and Perl backends only.
1118		2484
1119	=head3 Explanation of the columns	2485	=head3 Explanation of the columns
1120		2486
1121	I<watcher> is the number of event watchers created/destroyed. Since	2487	I<watcher> is the number of event watchers created/destroyed. Since
1122	different event models feature vastly different performances, each event	2488	different event models feature vastly different performances, each event
…		…
1134	all watchers, to avoid adding memory overhead. That means closure creation	2500	all watchers, to avoid adding memory overhead. That means closure creation
1135	and memory usage is not included in the figures.	2501	and memory usage is not included in the figures.
1136		2502
1137	I<invoke> is the time, in microseconds, used to invoke a simple	2503	I<invoke> is the time, in microseconds, used to invoke a simple
1138	callback. The callback simply counts down a Perl variable and after it was	2504	callback. The callback simply counts down a Perl variable and after it was
1139	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2505	invoked "watcher" times, it would C<< ->send >> a condvar once to
1140	signal the end of this phase.	2506	signal the end of this phase.
1141		2507
1142	I<destroy> is the time, in microseconds, that it takes to destroy a single	2508	I<destroy> is the time, in microseconds, that it takes to destroy a single
1143	watcher.	2509	watcher.
1144		2510
1145	=head3 Results	2511	=head3 Results
1146		2512
1147	name watchers bytes create invoke destroy comment	2513	name watchers bytes create invoke destroy comment
1148	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2514	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1149	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2515	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1150	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2516	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1151	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2517	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1152	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2518	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1153	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2519	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2520	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2521	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1154	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2522	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1155	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2523	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1156	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2524	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1157	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2525	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1158		2526
1159	=head3 Discussion	2527	=head3 Discussion
1160		2528
1161	The benchmark does I<not> measure scalability of the event loop very	2529	The benchmark does I<not> measure scalability of the event loop very
1162	well. For example, a select-based event loop (such as the pure perl one)	2530	well. For example, a select-based event loop (such as the pure perl one)
…		…
1174	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2542	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1175	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2543	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1176	cycles with POE.	2544	cycles with POE.
1177		2545
1178	C<EV> is the sole leader regarding speed and memory use, which are both	2546	C<EV> is the sole leader regarding speed and memory use, which are both
1179	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2547	maximal/minimal, respectively. When using the L<AE> API there is zero
		2548	overhead (when going through the AnyEvent API create is about 5-6 times
		2549	slower, with other times being equal, so still uses far less memory than
1180	far less memory than any other event loop and is still faster than Event	2550	any other event loop and is still faster than Event natively).
1181	natively.
1182		2551
1183	The pure perl implementation is hit in a few sweet spots (both the	2552	The pure perl implementation is hit in a few sweet spots (both the
1184	constant timeout and the use of a single fd hit optimisations in the perl	2553	constant timeout and the use of a single fd hit optimisations in the perl
1185	interpreter and the backend itself). Nevertheless this shows that it	2554	interpreter and the backend itself). Nevertheless this shows that it
1186	adds very little overhead in itself. Like any select-based backend its	2555	adds very little overhead in itself. Like any select-based backend its
1187	performance becomes really bad with lots of file descriptors (and few of	2556	performance becomes really bad with lots of file descriptors (and few of
1188	them active), of course, but this was not subject of this benchmark.	2557	them active), of course, but this was not subject of this benchmark.
1189		2558
1190	The C<Event> module has a relatively high setup and callback invocation	2559	The C<Event> module has a relatively high setup and callback invocation
1191	cost, but overall scores in on the third place.	2560	cost, but overall scores in on the third place.
		2561
		2562	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2563	when using its pure perl backend.
1192		2564
1193	C<Glib>'s memory usage is quite a bit higher, but it features a	2565	C<Glib>'s memory usage is quite a bit higher, but it features a
1194	faster callback invocation and overall ends up in the same class as	2566	faster callback invocation and overall ends up in the same class as
1195	C<Event>. However, Glib scales extremely badly, doubling the number of	2567	C<Event>. However, Glib scales extremely badly, doubling the number of
1196	watchers increases the processing time by more than a factor of four,	2568	watchers increases the processing time by more than a factor of four,
…		…
1231	(even when used without AnyEvent), but most event loops have acceptable	2603	(even when used without AnyEvent), but most event loops have acceptable
1232	performance with or without AnyEvent.	2604	performance with or without AnyEvent.
1233		2605
1234	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	2606	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1235	the actual event loop, only with extremely fast event loops such as EV	2607	the actual event loop, only with extremely fast event loops such as EV
1236	adds AnyEvent significant overhead.	2608	does AnyEvent add significant overhead.
1237		2609
1238	=item * You should avoid POE like the plague if you want performance or	2610	=item * You should avoid POE like the plague if you want performance or
1239	reasonable memory usage.	2611	reasonable memory usage.
1240		2612
1241	=back	2613	=back
1242		2614
1243	=head2 BENCHMARKING THE LARGE SERVER CASE	2615	=head2 BENCHMARKING THE LARGE SERVER CASE
1244		2616
1245	This benchmark atcually benchmarks the event loop itself. It works by	2617	This benchmark actually benchmarks the event loop itself. It works by
1246	creating a number of "servers": each server consists of a socketpair, a	2618	creating a number of "servers": each server consists of a socket pair, a
1247	timeout watcher that gets reset on activity (but never fires), and an I/O	2619	timeout watcher that gets reset on activity (but never fires), and an I/O
1248	watcher waiting for input on one side of the socket. Each time the socket	2620	watcher waiting for input on one side of the socket. Each time the socket
1249	watcher reads a byte it will write that byte to a random other "server".	2621	watcher reads a byte it will write that byte to a random other "server".
1250		2622
1251	The effect is that there will be a lot of I/O watchers, only part of which	2623	The effect is that there will be a lot of I/O watchers, only part of which
1252	are active at any one point (so there is a constant number of active	2624	are active at any one point (so there is a constant number of active
1253	fds for each loop iterstaion, but which fds these are is random). The	2625	fds for each loop iteration, but which fds these are is random). The
1254	timeout is reset each time something is read because that reflects how	2626	timeout is reset each time something is read because that reflects how
1255	most timeouts work (and puts extra pressure on the event loops).	2627	most timeouts work (and puts extra pressure on the event loops).
1256		2628
1257	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2629	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1258	(1%) are active. This mirrors the activity of large servers with many	2630	(1%) are active. This mirrors the activity of large servers with many
1259	connections, most of which are idle at any one point in time.	2631	connections, most of which are idle at any one point in time.
1260		2632
1261	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2633	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1262	distribution.	2634	distribution. It uses the L<AE> interface, which makes a real difference
		2635	for the EV and Perl backends only.
1263		2636
1264	=head3 Explanation of the columns	2637	=head3 Explanation of the columns
1265		2638
1266	I<sockets> is the number of sockets, and twice the number of "servers" (as	2639	I<sockets> is the number of sockets, and twice the number of "servers" (as
1267	each server has a read and write socket end).	2640	each server has a read and write socket end).
1268		2641
1269	I<create> is the time it takes to create a socketpair (which is	2642	I<create> is the time it takes to create a socket pair (which is
1270	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2643	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1271		2644
1272	I<request>, the most important value, is the time it takes to handle a	2645	I<request>, the most important value, is the time it takes to handle a
1273	single "request", that is, reading the token from the pipe and forwarding	2646	single "request", that is, reading the token from the pipe and forwarding
1274	it to another server. This includes deleting the old timeout and creating	2647	it to another server. This includes deleting the old timeout and creating
1275	a new one that moves the timeout into the future.	2648	a new one that moves the timeout into the future.
1276		2649
1277	=head3 Results	2650	=head3 Results
1278		2651
1279	name sockets create request	2652	name sockets create request
1280	EV 20000 69.01 11.16	2653	EV 20000 62.66 7.99
1281	Perl 20000 73.32 35.87	2654	Perl 20000 68.32 32.64
1282	Event 20000 212.62 257.32	2655	IOAsync 20000 174.06 101.15 epoll
1283	Glib 20000 651.16 1896.30	2656	IOAsync 20000 174.67 610.84 poll
		2657	Event 20000 202.69 242.91
		2658	Glib 20000 557.01 1689.52
1284	POE 20000 349.67 12317.24 uses POE::Loop::Event	2659	POE 20000 341.54 12086.32 uses POE::Loop::Event
1285		2660
1286	=head3 Discussion	2661	=head3 Discussion
1287		2662
1288	This benchmark I<does> measure scalability and overall performance of the	2663	This benchmark I<does> measure scalability and overall performance of the
1289	particular event loop.	2664	particular event loop.
…		…
1291	EV is again fastest. Since it is using epoll on my system, the setup time	2666	EV is again fastest. Since it is using epoll on my system, the setup time
1292	is relatively high, though.	2667	is relatively high, though.
1293		2668
1294	Perl surprisingly comes second. It is much faster than the C-based event	2669	Perl surprisingly comes second. It is much faster than the C-based event
1295	loops Event and Glib.	2670	loops Event and Glib.
		2671
		2672	IO::Async performs very well when using its epoll backend, and still quite
		2673	good compared to Glib when using its pure perl backend.
1296		2674
1297	Event suffers from high setup time as well (look at its code and you will	2675	Event suffers from high setup time as well (look at its code and you will
1298	understand why). Callback invocation also has a high overhead compared to	2676	understand why). Callback invocation also has a high overhead compared to
1299	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2677	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1300	uses select or poll in basically all documented configurations.	2678	uses select or poll in basically all documented configurations.
…		…
1347	speed most when you have lots of watchers, not when you only have a few of	2725	speed most when you have lots of watchers, not when you only have a few of
1348	them).	2726	them).
1349		2727
1350	EV is again fastest.	2728	EV is again fastest.
1351		2729
1352	Perl again comes second. It is noticably faster than the C-based event	2730	Perl again comes second. It is noticeably faster than the C-based event
1353	loops Event and Glib, although the difference is too small to really	2731	loops Event and Glib, although the difference is too small to really
1354	matter.	2732	matter.
1355		2733
1356	POE also performs much better in this case, but is is still far behind the	2734	POE also performs much better in this case, but is is still far behind the
1357	others.	2735	others.
…		…
1363	=item * C-based event loops perform very well with small number of	2741	=item * C-based event loops perform very well with small number of
1364	watchers, as the management overhead dominates.	2742	watchers, as the management overhead dominates.
1365		2743
1366	=back	2744	=back
1367		2745
		2746	=head2 THE IO::Lambda BENCHMARK
		2747
		2748	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2749	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2750	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2751	shouldn't come as a surprise to anybody). As such, the benchmark is
		2752	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2753	very optimal. But how would AnyEvent compare when used without the extra
		2754	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2755
		2756	The benchmark itself creates an echo-server, and then, for 500 times,
		2757	connects to the echo server, sends a line, waits for the reply, and then
		2758	creates the next connection. This is a rather bad benchmark, as it doesn't
		2759	test the efficiency of the framework or much non-blocking I/O, but it is a
		2760	benchmark nevertheless.
		2761
		2762	name runtime
		2763	Lambda/select 0.330 sec
		2764	+ optimized 0.122 sec
		2765	Lambda/AnyEvent 0.327 sec
		2766	+ optimized 0.138 sec
		2767	Raw sockets/select 0.077 sec
		2768	POE/select, components 0.662 sec
		2769	POE/select, raw sockets 0.226 sec
		2770	POE/select, optimized 0.404 sec
		2771
		2772	AnyEvent/select/nb 0.085 sec
		2773	AnyEvent/EV/nb 0.068 sec
		2774	+state machine 0.134 sec
		2775
		2776	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2777	benchmarks actually make blocking connects and use 100% blocking I/O,
		2778	defeating the purpose of an event-based solution. All of the newly
		2779	written AnyEvent benchmarks use 100% non-blocking connects (using
		2780	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2781	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2782	generally require a lot more bookkeeping and event handling than blocking
		2783	connects (which involve a single syscall only).
		2784
		2785	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2786	offers similar expressive power as POE and IO::Lambda, using conventional
		2787	Perl syntax. This means that both the echo server and the client are 100%
		2788	non-blocking, further placing it at a disadvantage.
		2789
		2790	As you can see, the AnyEvent + EV combination even beats the
		2791	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2792	backend easily beats IO::Lambda and POE.
		2793
		2794	And even the 100% non-blocking version written using the high-level (and
		2795	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2796	higher level ("unoptimised") abstractions by a large margin, even though
		2797	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2798
		2799	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2800	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2801	part of the IO::Lambda distribution and were used without any changes.
		2802
		2803
		2804	=head1 SIGNALS
		2805
		2806	AnyEvent currently installs handlers for these signals:
		2807
		2808	=over 4
		2809
		2810	=item SIGCHLD
		2811
		2812	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2813	emulation for event loops that do not support them natively. Also, some
		2814	event loops install a similar handler.
		2815
		2816	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2817	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2818
		2819	=item SIGPIPE
		2820
		2821	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2822	when AnyEvent gets loaded.
		2823
		2824	The rationale for this is that AnyEvent users usually do not really depend
		2825	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2826	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2827	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2828	some random socket.
		2829
		2830	The rationale for installing a no-op handler as opposed to ignoring it is
		2831	that this way, the handler will be restored to defaults on exec.
		2832
		2833	Feel free to install your own handler, or reset it to defaults.
		2834
		2835	=back
		2836
		2837	=cut
		2838
		2839	undef $SIG{CHLD}
		2840	if $SIG{CHLD} eq 'IGNORE';
		2841
		2842	$SIG{PIPE} = sub { }
		2843	unless defined $SIG{PIPE};
		2844
		2845	=head1 RECOMMENDED/OPTIONAL MODULES
		2846
		2847	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2848	its built-in modules) are required to use it.
		2849
		2850	That does not mean that AnyEvent won't take advantage of some additional
		2851	modules if they are installed.
		2852
		2853	This section explains which additional modules will be used, and how they
		2854	affect AnyEvent's operation.
		2855
		2856	=over 4
		2857
		2858	=item L<Async::Interrupt>
		2859
		2860	This slightly arcane module is used to implement fast signal handling: To
		2861	my knowledge, there is no way to do completely race-free and quick
		2862	signal handling in pure perl. To ensure that signals still get
		2863	delivered, AnyEvent will start an interval timer to wake up perl (and
		2864	catch the signals) with some delay (default is 10 seconds, look for
		2865	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2866
		2867	If this module is available, then it will be used to implement signal
		2868	catching, which means that signals will not be delayed, and the event loop
		2869	will not be interrupted regularly, which is more efficient (and good for
		2870	battery life on laptops).
		2871
		2872	This affects not just the pure-perl event loop, but also other event loops
		2873	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2874
		2875	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2876	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2877	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2878	does nothing for those backends.
		2879
		2880	=item L<EV>
		2881
		2882	This module isn't really "optional", as it is simply one of the backend
		2883	event loops that AnyEvent can use. However, it is simply the best event
		2884	loop available in terms of features, speed and stability: It supports
		2885	the AnyEvent API optimally, implements all the watcher types in XS, does
		2886	automatic timer adjustments even when no monotonic clock is available,
		2887	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2888	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2889	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2890
		2891	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2892	then this module will do nothing for you.
		2893
		2894	=item L<Guard>
		2895
		2896	The guard module, when used, will be used to implement
		2897	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2898	lot less memory), but otherwise doesn't affect guard operation much. It is
		2899	purely used for performance.
		2900
		2901	=item L<JSON> and L<JSON::XS>
		2902
		2903	One of these modules is required when you want to read or write JSON data
		2904	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2905	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2906
		2907	=item L<Net::SSLeay>
		2908
		2909	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2910	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2911	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2912
		2913	=item L<Time::HiRes>
		2914
		2915	This module is part of perl since release 5.008. It will be used when the
		2916	chosen event library does not come with a timing source of its own. The
		2917	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2918	try to use a monotonic clock for timing stability.
		2919
		2920	=back
		2921
1368		2922
1369	=head1 FORK	2923	=head1 FORK
1370		2924
1371	Most event libraries are not fork-safe. The ones who are usually are	2925	Most event libraries are not fork-safe. The ones who are usually are
1372	because they rely on inefficient but fork-safe C<select> or C<poll>	2926	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1373	calls. Only L<EV> is fully fork-aware.	2927	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2928	are usually badly thought-out hacks that are incompatible with fork in
		2929	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2930	continue event-processing in both parent and child (or both, if you know
		2931	what you are doing).
		2932
		2933	This means that, in general, you cannot fork and do event processing in
		2934	the child if the event library was initialised before the fork (which
		2935	usually happens when the first AnyEvent watcher is created, or the library
		2936	is loaded).
1374		2937
1375	If you have to fork, you must either do so I<before> creating your first	2938	If you have to fork, you must either do so I<before> creating your first
1376	watcher OR you must not use AnyEvent at all in the child.	2939	watcher OR you must not use AnyEvent at all in the child OR you must do
		2940	something completely out of the scope of AnyEvent.
		2941
		2942	The problem of doing event processing in the parent I<and> the child
		2943	is much more complicated: even for backends that I<are> fork-aware or
		2944	fork-safe, their behaviour is not usually what you want: fork clones all
		2945	watchers, that means all timers, I/O watchers etc. are active in both
		2946	parent and child, which is almost never what you want. USing C<exec>
		2947	to start worker children from some kind of manage rprocess is usually
		2948	preferred, because it is much easier and cleaner, at the expense of having
		2949	to have another binary.
1377		2950
1378		2951
1379	=head1 SECURITY CONSIDERATIONS	2952	=head1 SECURITY CONSIDERATIONS
1380		2953
1381	AnyEvent can be forced to load any event model via	2954	AnyEvent can be forced to load any event model via
…		…
1386	specified in the variable.	2959	specified in the variable.
1387		2960
1388	You can make AnyEvent completely ignore this variable by deleting it	2961	You can make AnyEvent completely ignore this variable by deleting it
1389	before the first watcher gets created, e.g. with a C<BEGIN> block:	2962	before the first watcher gets created, e.g. with a C<BEGIN> block:
1390		2963
1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2964	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1392		2965
1393	use AnyEvent;	2966	use AnyEvent;
		2967
		2968	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2969	be used to probe what backend is used and gain other information (which is
		2970	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2971	$ENV{PERL_ANYEVENT_STRICT}.
		2972
		2973	Note that AnyEvent will remove I<all> environment variables starting with
		2974	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2975	enabled.
		2976
		2977
		2978	=head1 BUGS
		2979
		2980	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2981	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2982	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2983	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2984	pronounced).
1394		2985
1395		2986
1396	=head1 SEE ALSO	2987	=head1 SEE ALSO
1397		2988
1398	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2989	Tutorial/Introduction: L<AnyEvent::Intro>.
1399	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1400	L<Event::Lib>, L<Qt>, L<POE>.
1401		2990
1402	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2991	FAQ: L<AnyEvent::FAQ>.
		2992
		2993	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2994	(simply logging).
		2995
		2996	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2997	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2998
		2999	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		3000	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		3001	L<Qt>, L<POE>, L<FLTK>.
		3002
		3003	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		3004	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		3005	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1403	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	3006	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
1404	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	3007	L<AnyEvent::Impl::FLTK>.
1405	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1406		3008
		3009	Non-blocking handles, pipes, stream sockets, TCP clients and
		3010	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		3011
		3012	Asynchronous DNS: L<AnyEvent::DNS>.
		3013
		3014	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		3015
1407	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	3016	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		3017	L<AnyEvent::HTTP>.
1408		3018
1409		3019
1410	=head1 AUTHOR	3020	=head1 AUTHOR
1411		3021
1412	Marc Lehmann <schmorp@schmorp.de>	3022	Marc Lehmann <schmorp@schmorp.de>
1413	http://home.schmorp.de/	3023	http://home.schmorp.de/
1414		3024
1415	=cut	3025	=cut
1416		3026
1417	1	3027	1
1418		3028

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