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Revision 1.420 by root, Fri Sep 5 22:17:26 2014 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, UV, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
		6	Qt, 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 L<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	492	# this forks and immediately calls exit in the child. this
285		493	# normally has all sorts of bad consequences for your parent,
		494	# so take this as an example only. always fork and exec,
		495	# or call POSIX::_exit, in real code.
286	my $pid = fork or exit 5;	496	my $pid = fork or exit 5;
287		497
288	my $w = AnyEvent->child (	498	my $w = AnyEvent->child (
289	pid => $pid,	499	pid => $pid,
290	cb => sub {	500	cb => sub {
291	my ($pid, $status) = @_;	501	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	502	warn "pid $pid exited with status $status";
293	$done->send;	503	$done->send;
294	},	504	},
295	);	505	);
296		506
297	# do something else, then wait for process exit	507	# do something else, then wait for process exit
298	$done->wait;	508	$done->recv;
		509
		510	=head2 IDLE WATCHERS
		511
		512	$w = AnyEvent->idle (cb => <callback>);
		513
		514	This will repeatedly invoke the callback after the process becomes idle,
		515	until either the watcher is destroyed or new events have been detected.
		516
		517	Idle watchers are useful when there is a need to do something, but it
		518	is not so important (or wise) to do it instantly. The callback will be
		519	invoked only when there is "nothing better to do", which is usually
		520	defined as "all outstanding events have been handled and no new events
		521	have been detected". That means that idle watchers ideally get invoked
		522	when the event loop has just polled for new events but none have been
		523	detected. Instead of blocking to wait for more events, the idle watchers
		524	will be invoked.
		525
		526	Unfortunately, most event loops do not really support idle watchers (only
		527	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		528	will simply call the callback "from time to time".
		529
		530	Example: read lines from STDIN, but only process them when the
		531	program is otherwise idle:
		532
		533	my @lines; # read data
		534	my $idle_w;
		535	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		536	push @lines, scalar <STDIN>;
		537
		538	# start an idle watcher, if not already done
		539	$idle_w ||= AnyEvent->idle (cb => sub {
		540	# handle only one line, when there are lines left
		541	if (my $line = shift @lines) {
		542	print "handled when idle: $line";
		543	} else {
		544	# otherwise disable the idle watcher again
		545	undef $idle_w;
		546	}
		547	});
		548	});
299		549
300	=head2 CONDITION VARIABLES	550	=head2 CONDITION VARIABLES
		551
		552	$cv = AnyEvent->condvar;
		553
		554	$cv->send (<list>);
		555	my @res = $cv->recv;
301		556
302	If you are familiar with some event loops you will know that all of them	557	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	558	require you to run some blocking "loop", "run" or similar function that
304	will actively watch for new events and call your callbacks.	559	will actively watch for new events and call your callbacks.
305		560
306	AnyEvent is different, it expects somebody else to run the event loop and	561	AnyEvent is slightly different: it expects somebody else to run the event
307	will only block when necessary (usually when told by the user).	562	loop and will only block when necessary (usually when told by the user).
308		563
309	The instrument to do that is called a "condition variable", so called	564	The tool to do that is called a "condition variable", so called because
310	because they represent a condition that must become true.	565	they represent a condition that must become true.
		566
		567	Now is probably a good time to look at the examples further below.
311		568
312	Condition variables can be created by calling the C<< AnyEvent->condvar	569	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	570	>> method, usually without arguments. The only argument pair allowed is
314	C<cb>, which specifies a callback to be called when the condition variable	571	C<cb>, which specifies a callback to be called when the condition variable
315	becomes true.	572	becomes true, with the condition variable as the first argument (but not
		573	the results).
316		574
317	After creation, the conditon variable is "false" until it becomes "true"	575	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	576	by calling the C<send> method (or calling the condition variable as if it
		577	were a callback, read about the caveats in the description for the C<<
		578	->send >> method).
319		579
320	Condition variables are similar to callbacks, except that you can	580	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	581	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	582
323	another way to call them is transations - each condition variable can be	583	=over 4
324	used to represent a transaction, which finishes at some point and delivers	584
325	a result.	585	=item * Condition variables are like callbacks - you can call them (and pass them instead
		586	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		587
		588	=item * Condition variables are signals - one side can emit or send them,
		589	the other side can wait for them, or install a handler that is called when
		590	the signal fires.
		591
		592	=item * Condition variables are like "Merge Points" - points in your program
		593	where you merge multiple independent results/control flows into one.
		594
		595	=item * Condition variables represent a transaction - functions that start
		596	some kind of transaction can return them, leaving the caller the choice
		597	between waiting in a blocking fashion, or setting a callback.
		598
		599	=item * Condition variables represent future values, or promises to deliver
		600	some result, long before the result is available.
		601
		602	=back
326		603
327	Condition variables are very useful to signal that something has finished,	604	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	605	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	606	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	607	availability of results. The user can either act when the callback is
331	called or can synchronously C<< ->wait >> for the results.	608	called or can synchronously C<< ->recv >> for the results.
332		609
333	You can also use them to simulate traditional event loops - for example,	610	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	611	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	612	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.	613	button of your app, which would C<< ->send >> the "quit" event.
337		614
338	Note that condition variables recurse into the event loop - if you have	615	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	616	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	617	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,	618	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	619	as this asks for trouble.
343		620
344	Condition variables are represented by hash refs in perl, and the keys	621	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	622	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	623	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	624	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
348	it's C<new> method in your own C<new> method.	625	its C<new> method in your own C<new> method.
349		626
350	There are two "sides" to a condition variable - the "producer side" which	627	There are two "sides" to a condition variable - the "producer side" which
351	eventually calls C<< -> send >>, and the "consumer side", which waits	628	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	629	for the send to occur.
353		630
354	Example:	631	Example: wait for a timer.
355		632
356	# wait till the result is ready	633	# condition: "wait till the timer is fired"
357	my $result_ready = AnyEvent->condvar;	634	my $timer_fired = AnyEvent->condvar;
358		635
359	# do something such as adding a timer	636	# create the timer - we could wait for, say
360	# or socket watcher the calls $result_ready->send	637	# a handle becomign ready, or even an
361	# when the "result" is ready.	638	# AnyEvent::HTTP request to finish, but
362	# in this case, we simply use a timer:	639	# in this case, we simply use a timer:
363	my $w = AnyEvent->timer (	640	my $w = AnyEvent->timer (
364	after => 1,	641	after => 1,
365	cb => sub { $result_ready->send },	642	cb => sub { $timer_fired->send },
366	);	643	);
367		644
368	# this "blocks" (while handling events) till the callback	645	# this "blocks" (while handling events) till the callback
369	# calls send	646	# calls ->send
370	$result_ready->wait;	647	$timer_fired->recv;
		648
		649	Example: wait for a timer, but take advantage of the fact that condition
		650	variables are also callable directly.
		651
		652	my $done = AnyEvent->condvar;
		653	my $delay = AnyEvent->timer (after => 5, cb => $done);
		654	$done->recv;
		655
		656	Example: Imagine an API that returns a condvar and doesn't support
		657	callbacks. This is how you make a synchronous call, for example from
		658	the main program:
		659
		660	use AnyEvent::CouchDB;
		661
		662	...
		663
		664	my @info = $couchdb->info->recv;
		665
		666	And this is how you would just set a callback to be called whenever the
		667	results are available:
		668
		669	$couchdb->info->cb (sub {
		670	my @info = $_[0]->recv;
		671	});
371		672
372	=head3 METHODS FOR PRODUCERS	673	=head3 METHODS FOR PRODUCERS
373		674
374	These methods should only be used by the producing side, i.e. the	675	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	676	code/module that eventually sends the signal. Note that it is also
…		…
378		679
379	=over 4	680	=over 4
380		681
381	=item $cv->send (...)	682	=item $cv->send (...)
382		683
383	Flag the condition as ready - a running C<< ->wait >> and all further	684	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	685	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	686	called. If nobody is waiting the send will be remembered.
386		687
387	If a callback has been set on the condition variable, it is called	688	If a callback has been set on the condition variable, it is called
388	immediately from within send.	689	immediately from within send.
389		690
390	Any arguments passed to the C<send> call will be returned by all	691	Any arguments passed to the C<send> call will be returned by all
391	future C<< ->wait >> calls.	692	future C<< ->recv >> calls.
		693
		694	Condition variables are overloaded so one can call them directly (as if
		695	they were a code reference). Calling them directly is the same as calling
		696	C<send>.
392		697
393	=item $cv->croak ($error)	698	=item $cv->croak ($error)
394		699
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	700	Similar to send, but causes all calls to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	701	C<Carp::croak> with the given error message/object/scalar.
397		702
398	This can be used to signal any errors to the condition variable	703	This can be used to signal any errors to the condition variable
399	user/consumer.	704	user/consumer. Doing it this way instead of calling C<croak> directly
		705	delays the error detection, but has the overwhelming advantage that it
		706	diagnoses the error at the place where the result is expected, and not
		707	deep in some event callback with no connection to the actual code causing
		708	the problem.
400		709
401	=item $cv->begin ([group callback])	710	=item $cv->begin ([group callback])
402		711
403	=item $cv->end	712	=item $cv->end
404		713
…		…
406	one. For example, a function that pings many hosts in parallel might want	715	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	716	to use a condition variable for the whole process.
408		717
409	Every call to C<< ->begin >> will increment a counter, and every call to	718	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	719	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	720	>>, 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	721	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.	722	>>, but that is not required. If no group callback was set, C<send> will
		723	be called without any arguments.
414		724
415	Let's clarify this with the ping example:	725	You can think of C<< $cv->send >> giving you an OR condition (one call
		726	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		727	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		728
		729	Let's start with a simple example: you have two I/O watchers (for example,
		730	STDOUT and STDERR for a program), and you want to wait for both streams to
		731	close before activating a condvar:
416		732
417	my $cv = AnyEvent->condvar;	733	my $cv = AnyEvent->condvar;
418		734
		735	$cv->begin; # first watcher
		736	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		737	defined sysread $fh1, my $buf, 4096
		738	or $cv->end;
		739	});
		740
		741	$cv->begin; # second watcher
		742	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		743	defined sysread $fh2, my $buf, 4096
		744	or $cv->end;
		745	});
		746
		747	$cv->recv;
		748
		749	This works because for every event source (EOF on file handle), there is
		750	one call to C<begin>, so the condvar waits for all calls to C<end> before
		751	sending.
		752
		753	The ping example mentioned above is slightly more complicated, as the
		754	there are results to be passed back, and the number of tasks that are
		755	begun can potentially be zero:
		756
		757	my $cv = AnyEvent->condvar;
		758
419	my %result;	759	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	760	$cv->begin (sub { shift->send (\%result) });
421		761
422	for my $host (@list_of_hosts) {	762	for my $host (@list_of_hosts) {
423	$cv->begin;	763	$cv->begin;
424	ping_host_then_call_callback $host, sub {	764	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	765	$result{$host} = ...;
…		…
427	};	767	};
428	}	768	}
429		769
430	$cv->end;	770	$cv->end;
431		771
		772	...
		773
		774	my $results = $cv->recv;
		775
432	This code fragment supposedly pings a number of hosts and calls	776	This code fragment supposedly pings a number of hosts and calls
433	C<send> after results for all then have have been gathered - in any	777	C<send> after results for all then have have been gathered - in any
434	order. To achieve this, the code issues a call to C<begin> when it starts	778	order. To achieve this, the code issues a call to C<begin> when it starts
435	each ping request and calls C<end> when it has received some result for	779	each ping request and calls C<end> when it has received some result for
436	it. Since C<begin> and C<end> only maintain a counter, the order in which	780	it. Since C<begin> and C<end> only maintain a counter, the order in which
…		…
440	loop, which serves two important purposes: first, it sets the callback	784	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	785	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	786	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	787	doesn't execute once).
444		788
445	This is the general pattern when you "fan out" into multiple subrequests:	789	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>	790	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	791	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>.	792	subrequest you start, call C<begin> and for each subrequest you finish,
		793	call C<end>.
449		794
450	=back	795	=back
451		796
452	=head3 METHODS FOR CONSUMERS	797	=head3 METHODS FOR CONSUMERS
453		798
454	These methods should only be used by the consuming side, i.e. the	799	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	800	code awaits the condition.
456		801
457	=over 4	802	=over 4
458		803
459	=item $cv->wait	804	=item $cv->recv
460		805
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	806	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	807	>> methods have been called on C<$cv>, while servicing other watchers
463	normally.	808	normally.
464		809
465	You can only wait once on a condition - additional calls are valid but	810	You can only wait once on a condition - additional calls are valid but
466	will return immediately.	811	will return immediately.
467		812
…		…
469	function will call C<croak>.	814	function will call C<croak>.
470		815
471	In list context, all parameters passed to C<send> will be returned,	816	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	817	in scalar context only the first one will be returned.
473		818
		819	Note that doing a blocking wait in a callback is not supported by any
		820	event loop, that is, recursive invocation of a blocking C<< ->recv >> is
		821	not allowed and the C<recv> call will C<croak> if such a condition is
		822	detected. This requirement can be dropped by relying on L<Coro::AnyEvent>
		823	, which allows you to do a blocking C<< ->recv >> from any thread
		824	that doesn't run the event loop itself. L<Coro::AnyEvent> is loaded
		825	automatically when L<Coro> is used with L<AnyEvent>, so code does not need
		826	to do anything special to take advantage of that: any code that would
		827	normally block your program because it calls C<recv>, be executed in an
		828	C<async> thread instead without blocking other threads.
		829
474	Not all event models support a blocking wait - some die in that case	830	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	831	(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	832	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	833	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	834	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	835	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	836	while still supporting blocking waits if the caller so desires).
481		837
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	838	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	839	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	840	time). This will work even when the event loop does not support blocking
492	waits otherwise.	841	waits otherwise.
493		842
494	=item $bool = $cv->ready	843	=item $bool = $cv->ready
495		844
496	Returns true when the condition is "true", i.e. whether C<send> or	845	Returns true when the condition is "true", i.e. whether C<send> or
497	C<croak> have been called.	846	C<croak> have been called.
498		847
499	=item $cb = $cv->cb ([new callback])	848	=item $cb = $cv->cb ($cb->($cv))
500		849
501	This is a mutator function that returns the callback set and optionally	850	This is a mutator function that returns the callback set and optionally
502	replaces it before doing so.	851	replaces it before doing so.
503		852
504	The callback will be called when the condition becomes "true", i.e. when	853	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	854	C<send> or C<croak> are called, with the only argument being the
		855	condition variable itself. If the condition is already true, the
		856	callback is called immediately when it is set. Calling C<recv> inside
506	or at any later time is guaranteed not to block.	857	the callback or at any later time is guaranteed not to block.
507		858
508	=back	859	=back
509		860
		861	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		862
		863	The available backend classes are (every class has its own manpage):
		864
		865	=over 4
		866
		867	=item Backends that are autoprobed when no other event loop can be found.
		868
		869	EV is the preferred backend when no other event loop seems to be in
		870	use. If EV is not installed, then AnyEvent will fall back to its own
		871	pure-perl implementation, which is available everywhere as it comes with
		872	AnyEvent itself.
		873
		874	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		875	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		876
		877	=item Backends that are transparently being picked up when they are used.
		878
		879	These will be used if they are already loaded when the first watcher
		880	is created, in which case it is assumed that the application is using
		881	them. This means that AnyEvent will automatically pick the right backend
		882	when the main program loads an event module before anything starts to
		883	create watchers. Nothing special needs to be done by the main program.
		884
		885	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		886	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		887	AnyEvent::Impl::Tk based on Tk, very broken.
		888	AnyEvent::Impl::UV based on UV, innovated square wheels.
		889	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		890	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		891	AnyEvent::Impl::Irssi used when running within irssi.
		892	AnyEvent::Impl::IOAsync based on IO::Async.
		893	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		894	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		895
		896	=item Backends with special needs.
		897
		898	Qt requires the Qt::Application to be instantiated first, but will
		899	otherwise be picked up automatically. As long as the main program
		900	instantiates the application before any AnyEvent watchers are created,
		901	everything should just work.
		902
		903	AnyEvent::Impl::Qt based on Qt.
		904
		905	=item Event loops that are indirectly supported via other backends.
		906
		907	Some event loops can be supported via other modules:
		908
		909	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		910
		911	B<WxWidgets> has no support for watching file handles. However, you can
		912	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		913	polls 20 times per second, which was considered to be too horrible to even
		914	consider for AnyEvent.
		915
		916	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		917	backend, so it can be supported through POE.
		918
		919	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		920	load L<POE> when detecting them, in the hope that POE will pick them up,
		921	in which case everything will be automatic.
		922
		923	=back
		924
510	=head1 GLOBAL VARIABLES AND FUNCTIONS	925	=head1 GLOBAL VARIABLES AND FUNCTIONS
511		926
		927	These are not normally required to use AnyEvent, but can be useful to
		928	write AnyEvent extension modules.
		929
512	=over 4	930	=over 4
513		931
514	=item $AnyEvent::MODEL	932	=item $AnyEvent::MODEL
515		933
516	Contains C<undef> until the first watcher is being created. Then it	934	Contains C<undef> until the first watcher is being created, before the
		935	backend has been autodetected.
		936
517	contains the event model that is being used, which is the name of the	937	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	938	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	939	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>).	940	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
521		941	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		942
545	=item AnyEvent::detect	943	=item AnyEvent::detect
546		944
547	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	945	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
548	if necessary. You should only call this function right before you would	946	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	947	have created an AnyEvent watcher anyway, that is, as late as possible at
550	runtime.	948	runtime, and not e.g. during initialisation of your module.
		949
		950	The effect of calling this function is as if a watcher had been created
		951	(specifically, actions that happen "when the first watcher is created"
		952	happen when calling detetc as well).
		953
		954	If you need to do some initialisation before AnyEvent watchers are
		955	created, use C<post_detect>.
		956
		957	=item $guard = AnyEvent::post_detect { BLOCK }
		958
		959	Arranges for the code block to be executed as soon as the event model is
		960	autodetected (or immediately if that has already happened).
		961
		962	The block will be executed I<after> the actual backend has been detected
		963	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		964	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		965	other initialisations - see the sources of L<AnyEvent::Strict> or
		966	L<AnyEvent::AIO> to see how this is used.
		967
		968	The most common usage is to create some global watchers, without forcing
		969	event module detection too early, for example, L<AnyEvent::AIO> creates
		970	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		971	avoid autodetecting the event module at load time.
		972
		973	If called in scalar or list context, then it creates and returns an object
		974	that automatically removes the callback again when it is destroyed (or
		975	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		976	a case where this is useful.
		977
		978	Example: Create a watcher for the IO::AIO module and store it in
		979	C<$WATCHER>, but do so only do so after the event loop is initialised.
		980
		981	our WATCHER;
		982
		983	my $guard = AnyEvent::post_detect {
		984	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		985	};
		986
		987	# the ||= is important in case post_detect immediately runs the block,
		988	# as to not clobber the newly-created watcher. assigning both watcher and
		989	# post_detect guard to the same variable has the advantage of users being
		990	# able to just C<undef $WATCHER> if the watcher causes them grief.
		991
		992	$WATCHER ||= $guard;
		993
		994	=item @AnyEvent::post_detect
		995
		996	If there are any code references in this array (you can C<push> to it
		997	before or after loading AnyEvent), then they will be called directly
		998	after the event loop has been chosen.
		999
		1000	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		1001	if it is defined then the event loop has already been detected, and the
		1002	array will be ignored.
		1003
		1004	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		1005	it, as it takes care of these details.
		1006
		1007	This variable is mainly useful for modules that can do something useful
		1008	when AnyEvent is used and thus want to know when it is initialised, but do
		1009	not need to even load it by default. This array provides the means to hook
		1010	into AnyEvent passively, without loading it.
		1011
		1012	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1013	together, you could put this into Coro (this is the actual code used by
		1014	Coro to accomplish this):
		1015
		1016	if (defined $AnyEvent::MODEL) {
		1017	# AnyEvent already initialised, so load Coro::AnyEvent
		1018	require Coro::AnyEvent;
		1019	} else {
		1020	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1021	# as soon as it is
		1022	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1023	}
		1024
		1025	=item AnyEvent::postpone { BLOCK }
		1026
		1027	Arranges for the block to be executed as soon as possible, but not before
		1028	the call itself returns. In practise, the block will be executed just
		1029	before the event loop polls for new events, or shortly afterwards.
		1030
		1031	This function never returns anything (to make the C<return postpone { ...
		1032	}> idiom more useful.
		1033
		1034	To understand the usefulness of this function, consider a function that
		1035	asynchronously does something for you and returns some transaction
		1036	object or guard to let you cancel the operation. For example,
		1037	C<AnyEvent::Socket::tcp_connect>:
		1038
		1039	# start a connection attempt unless one is active
		1040	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1041	delete $self->{connect_guard};
		1042	...
		1043	};
		1044
		1045	Imagine that this function could instantly call the callback, for
		1046	example, because it detects an obvious error such as a negative port
		1047	number. Invoking the callback before the function returns causes problems
		1048	however: the callback will be called and will try to delete the guard
		1049	object. But since the function hasn't returned yet, there is nothing to
		1050	delete. When the function eventually returns it will assign the guard
		1051	object to C<< $self->{connect_guard} >>, where it will likely never be
		1052	deleted, so the program thinks it is still trying to connect.
		1053
		1054	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1055	callback directly on error:
		1056
		1057	$cb->(undef), return # signal error to callback, BAD!
		1058	if $some_error_condition;
		1059
		1060	It should use C<postpone>:
		1061
		1062	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1063	if $some_error_condition;
		1064
		1065	=item AnyEvent::log $level, $msg[, @args]
		1066
		1067	Log the given C<$msg> at the given C<$level>.
		1068
		1069	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1070	to see whether the message will be logged. If the test succeeds it will
		1071	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1072	the L<AnyEvent::Log> documentation for details.
		1073
		1074	If the test fails it will simply return. Right now this happens when a
		1075	numerical loglevel is used and it is larger than the level specified via
		1076	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1077
		1078	If you want to sprinkle loads of logging calls around your code, consider
		1079	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1080	which can reduce typing, codesize and can reduce the logging overhead
		1081	enourmously.
551		1082
552	=back	1083	=back
553		1084
554	=head1 WHAT TO DO IN A MODULE	1085	=head1 WHAT TO DO IN A MODULE
555		1086
…		…
559	Be careful when you create watchers in the module body - AnyEvent will	1090	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	1091	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	1092	by calling AnyEvent in your module body you force the user of your module
562	to load the event module first.	1093	to load the event module first.
563		1094
564	Never call C<< ->wait >> on a condition variable unless you I<know> that	1095	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	1096	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	1097	because it will stall the whole program, and the whole point of using
567	events is to stay interactive.	1098	events is to stay interactive.
568		1099
569	It is fine, however, to call C<< ->wait >> when the user of your module	1100	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	1101	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 >>	1102	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).	1103	freely, as the user of your module knows what she is doing. Always).
573		1104
574	=head1 WHAT TO DO IN THE MAIN PROGRAM	1105	=head1 WHAT TO DO IN THE MAIN PROGRAM
575		1106
576	There will always be a single main program - the only place that should	1107	There will always be a single main program - the only place that should
577	dictate which event model to use.	1108	dictate which event model to use.
578		1109
579	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1110	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	1111	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.	1112	uses AnyEvent, but does not care which event loop is used, all it needs
		1113	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1114	available loop implementation.
582		1115
583	If the main program relies on a specific event model. For example, in	1116	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	1117	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	1118	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	1119	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	1120	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	1121	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.	1122	might choose the wrong one unless you load the correct one yourself.
590		1123
591	You can chose to use a rather inefficient pure-perl implementation by	1124	You can chose to use a pure-perl implementation by loading the
592	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1125	C<AnyEvent::Loop> module, which gives you similar behaviour
593	behaviour everywhere, but letting AnyEvent chose is generally better.	1126	everywhere, but letting AnyEvent chose the model is generally better.
		1127
		1128	=head2 MAINLOOP EMULATION
		1129
		1130	Sometimes (often for short test scripts, or even standalone programs who
		1131	only want to use AnyEvent), you do not want to run a specific event loop.
		1132
		1133	In that case, you can use a condition variable like this:
		1134
		1135	AnyEvent->condvar->recv;
		1136
		1137	This has the effect of entering the event loop and looping forever.
		1138
		1139	Note that usually your program has some exit condition, in which case
		1140	it is better to use the "traditional" approach of storing a condition
		1141	variable somewhere, waiting for it, and sending it when the program should
		1142	exit cleanly.
		1143
594		1144
595	=head1 OTHER MODULES	1145	=head1 OTHER MODULES
596		1146
597	The following is a non-exhaustive list of additional modules that use	1147	The following is a non-exhaustive list of additional modules that use
598	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1148	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	1149	AnyEvent modules and other event loops in the same program. Some of the
600	available via CPAN.	1150	modules come as part of AnyEvent, the others are available via CPAN (see
		1151	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1152	a longer non-exhaustive list), and the list is heavily biased towards
		1153	modules of the AnyEvent author himself :)
601		1154
602	=over 4	1155	=over 4
603		1156
604	=item L<AnyEvent::Util>	1157	=item L<AnyEvent::Util> (part of the AnyEvent distribution)
605		1158
606	Contains various utility functions that replace often-used but blocking	1159	Contains various utility functions that replace often-used blocking
607	functions such as C<inet_aton> by event-/callback-based versions.	1160	functions such as C<inet_aton> with event/callback-based versions.
608		1161
609	=item L<AnyEvent::Handle>	1162	=item L<AnyEvent::Socket> (part of the AnyEvent distribution)
610		1163
		1164	Provides various utility functions for (internet protocol) sockets,
		1165	addresses and name resolution. Also functions to create non-blocking tcp
		1166	connections or tcp servers, with IPv6 and SRV record support and more.
		1167
		1168	=item L<AnyEvent::Handle> (part of the AnyEvent distribution)
		1169
611	Provide read and write buffers and manages watchers for reads and writes.	1170	Provide read and write buffers, manages watchers for reads and writes,
		1171	supports raw and formatted I/O, I/O queued and fully transparent and
		1172	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
612		1173
613	=item L<AnyEvent::Socket>	1174	=item L<AnyEvent::DNS> (part of the AnyEvent distribution)
614		1175
615	Provides a means to do non-blocking connects, accepts etc.	1176	Provides rich asynchronous DNS resolver capabilities.
616		1177
617	=item L<AnyEvent::HTTPD>	1178	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
618		1179
619	Provides a simple web application server framework.	1180	Implement event-based interfaces to the protocols of the same name (for
		1181	the curious, IGS is the International Go Server and FCP is the Freenet
		1182	Client Protocol).
620		1183
		1184	=item L<AnyEvent::AIO> (part of the AnyEvent distribution)
		1185
		1186	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1187	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1188	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1189	file I/O, and much more.
		1190
		1191	=item L<AnyEvent::Fork>, L<AnyEvent::Fork::RPC>, L<AnyEvent::Fork::Pool>, L<AnyEvent::Fork::Remote>
		1192
		1193	These let you safely fork new subprocesses, either locally or
		1194	remotely (e.g.v ia ssh), using some RPC protocol or not, without
		1195	the limitations normally imposed by fork (AnyEvent works fine for
		1196	example). Dynamically-resized worker pools are obviously included as well.
		1197
		1198	And they are quite tiny and fast as well - "abusing" L<AnyEvent::Fork>
		1199	just to exec external programs can easily beat using C<fork> and C<exec>
		1200	(or even C<system>) in most programs.
		1201
		1202	=item L<AnyEvent::Filesys::Notify>
		1203
		1204	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1205	path changes (e.g. "watch this directory for new files", "watch this
		1206	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1207	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1208	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1209	fall back to blocking scans at regular intervals transparently on other
		1210	platforms, so it's about as portable as it gets.
		1211
		1212	(I haven't used it myself, but it seems the biggest problem with it is
		1213	it quite bad performance).
		1214
621	=item L<AnyEvent::DNS>	1215	=item L<AnyEvent::DBI>
622		1216
623	Provides asynchronous DNS resolver capabilities, beyond what	1217	Executes L<DBI> requests asynchronously in a proxy process for you,
624	L<AnyEvent::Util> offers.	1218	notifying you in an event-based way when the operation is finished.
625		1219
626	=item L<AnyEvent::FastPing>	1220	=item L<AnyEvent::FastPing>
627		1221
628	The fastest ping in the west.	1222	The fastest ping in the west.
629		1223
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>	1224	=item L<Coro>
648		1225
649	Has special support for AnyEvent.	1226	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1227	to simply invert the flow control - don't call us, we will call you:
650		1228
651	=item L<IO::Lambda>	1229	async {
		1230	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1231	print "5 seconds later!\n";
652		1232
653	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.	1233	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1234	my $line = <STDIN>; # works for ttys
654		1235
655	=item L<IO::AIO>	1236	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
656		1237	my ($body, $hdr) = Coro::rouse_wait;
657	Truly asynchronous I/O, should be in the toolbox of every event	1238	};
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		1239
665	=back	1240	=back
666		1241
667	=cut	1242	=cut
668		1243
669	package AnyEvent;	1244	package AnyEvent;
670		1245
671	no warnings;	1246	BEGIN {
672	use strict;	1247	require "AnyEvent/constants.pl";
		1248	&AnyEvent::common_sense;
		1249	}
673		1250
674	use Carp;	1251	use Carp ();
675		1252
676	our $VERSION = '3.3';	1253	our $VERSION = '7.07';
677	our $MODEL;	1254	our $MODEL;
678
679	our $AUTOLOAD;
680	our @ISA;	1255	our @ISA;
681
682	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
683
684	our @REGISTRY;	1256	our @REGISTRY;
		1257	our $VERBOSE;
		1258	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1259	our $MAX_SIGNAL_LATENCY = $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} || 10; # executes after the BEGIN block below (tainting!)
685		1260
		1261	BEGIN {
		1262	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1263
		1264	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1265	if ${^TAINT};
		1266
		1267	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1268	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1269
		1270	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1271	if ${^TAINT};
		1272
		1273	# $ENV{PERL_ANYEVENT_xxx} now valid
		1274
		1275	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 4;
		1276
		1277	my $idx;
		1278	$PROTOCOL{$_} = ++$idx
		1279	for reverse split /\s*,\s*/,
		1280	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1281	}
		1282
		1283	our @post_detect;
		1284
		1285	sub post_detect(&) {
		1286	my ($cb) = @_;
		1287
		1288	push @post_detect, $cb;
		1289
		1290	defined wantarray
		1291	? bless \$cb, "AnyEvent::Util::postdetect"
		1292	: ()
		1293	}
		1294
		1295	sub AnyEvent::Util::postdetect::DESTROY {
		1296	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1297	}
		1298
		1299	our $POSTPONE_W;
		1300	our @POSTPONE;
		1301
		1302	sub _postpone_exec {
		1303	undef $POSTPONE_W;
		1304
		1305	&{ shift @POSTPONE }
		1306	while @POSTPONE;
		1307	}
		1308
		1309	sub postpone(&) {
		1310	push @POSTPONE, shift;
		1311
		1312	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1313
		1314	()
		1315	}
		1316
		1317	sub log($$;@) {
		1318	# only load the big bloated module when we actually are about to log something
		1319	if ($_[0] <= ($VERBOSE || 1)) { # also catches non-numeric levels(!) and fatal
		1320	local ($!, $@);
		1321	require AnyEvent::Log; # among other things, sets $VERBOSE to 9
		1322	# AnyEvent::Log overwrites this function
		1323	goto &log;
		1324	}
		1325
		1326	0 # not logged
		1327	}
		1328
		1329	sub _logger($;$) {
		1330	my ($level, $renabled) = @_;
		1331
		1332	$$renabled = $level <= $VERBOSE;
		1333
		1334	my $logger = [(caller)[0], $level, $renabled];
		1335
		1336	$AnyEvent::Log::LOGGER{$logger+0} = $logger;
		1337
		1338	# return unless defined wantarray;
		1339	#
		1340	# require AnyEvent::Util;
		1341	# my $guard = AnyEvent::Util::guard (sub {
		1342	# # "clean up"
		1343	# delete $LOGGER{$logger+0};
		1344	# });
		1345	#
		1346	# sub {
		1347	# return 0 unless $$renabled;
		1348	#
		1349	# $guard if 0; # keep guard alive, but don't cause runtime overhead
		1350	# require AnyEvent::Log unless $AnyEvent::Log::VERSION;
		1351	# package AnyEvent::Log;
		1352	# _log ($logger->[0], $level, @_) # logger->[0] has been converted at load time
		1353	# }
		1354	}
		1355
		1356	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1357	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1358	}
		1359
686	my @models = (	1360	our @models = (
687	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
688	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
689	[EV:: => AnyEvent::Impl::EV::],	1361	[EV:: => AnyEvent::Impl::EV::],
		1362	[AnyEvent::Loop:: => AnyEvent::Impl::Perl::],
		1363	# everything below here will not (normally) be autoprobed
		1364	# as the pure perl backend should work everywhere
		1365	# and is usually faster
		1366	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package, so msut be near the top
690	[Event:: => AnyEvent::Impl::Event::],	1367	[Event:: => AnyEvent::Impl::Event::], # slow, stable
		1368	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1369	# everything below here should not be autoloaded
		1370	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
691	[Tk:: => AnyEvent::Impl::Tk::],	1371	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1372	[UV:: => AnyEvent::Impl::UV::], # switched from libev, added back all bugs imaginable
		1373	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1374	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
692	[Wx:: => AnyEvent::Impl::POE::],	1375	[Wx:: => AnyEvent::Impl::POE::],
693	[Prima:: => AnyEvent::Impl::POE::],	1376	[Prima:: => AnyEvent::Impl::POE::],
694	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1377	[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	1378	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
696	[Glib:: => AnyEvent::Impl::Glib::],	1379	[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	);	1380	);
701		1381
702	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1382	our @isa_hook;
		1383
		1384	sub _isa_set {
		1385	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1386
		1387	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1388	for 1 .. $#pkg;
		1389
		1390	grep $_ && $_->[1], @isa_hook
		1391	and AE::_reset ();
		1392	}
		1393
		1394	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1395	sub _isa_hook($$;$) {
		1396	my ($i, $pkg, $reset_ae) = @_;
		1397
		1398	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1399
		1400	_isa_set;
		1401	}
		1402
		1403	# all autoloaded methods reserve the complete glob, not just the method slot.
		1404	# due to bugs in perls method cache implementation.
		1405	our @methods = qw(io timer time now now_update signal child idle condvar);
703		1406
704	sub detect() {	1407	sub detect() {
		1408	return $MODEL if $MODEL; # some programs keep references to detect
		1409
		1410	# IO::Async::Loop::AnyEvent is extremely evil, refuse to work with it
		1411	# the author knows about the problems and what it does to AnyEvent as a whole
		1412	# (and the ability of others to use AnyEvent), but simply wants to abuse AnyEvent
		1413	# anyway.
		1414	AnyEvent::log fatal => "IO::Async::Loop::AnyEvent detected - that module is broken by\n"
		1415	. "design, abuses internals and breaks AnyEvent - will not continue."
		1416	if exists $INC{"IO/Async/Loop/AnyEvent.pm"};
		1417
		1418	local $!; # for good measure
		1419	local $SIG{__DIE__}; # we use eval
		1420
		1421	# free some memory
		1422	*detect = sub () { $MODEL };
		1423	# undef &func doesn't correctly update the method cache. grmbl.
		1424	# so we delete the whole glob. grmbl.
		1425	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1426	# a glob with an active sub. hrm. i hope it works, but perl is
		1427	# usually buggy in this department. sigh.
		1428	delete @{"AnyEvent::"}{@methods};
		1429	undef @methods;
		1430
		1431	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1432	my $model = $1;
		1433	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1434	if (eval "require $model") {
		1435	AnyEvent::log 7 => "Loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1436	$MODEL = $model;
		1437	} else {
		1438	AnyEvent::log 4 => "Unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1439	}
		1440	}
		1441
		1442	# check for already loaded models
705	unless ($MODEL) {	1443	unless ($MODEL) {
706	no strict 'refs';	1444	for (@REGISTRY, @models) {
707		1445	my ($package, $model) = @$_;
708	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1446	if (${"$package\::VERSION"} > 0) {
709	my $model = "AnyEvent::Impl::$1";
710	if (eval "require $model") {	1447	if (eval "require $model") {
		1448	AnyEvent::log 7 => "Autodetected model '$model', using it.";
711	$MODEL = $model;	1449	$MODEL = $model;
712	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1450	last;
713	} else {	1451	} else {
714	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1452	AnyEvent::log 8 => "Detected event loop $package, but cannot load '$model', skipping: $@";
		1453	}
715	}	1454	}
716	}	1455	}
717		1456
718	# check for already loaded models
719	unless ($MODEL) {	1457	unless ($MODEL) {
		1458	# try to autoload a model
720	for (@REGISTRY, @models) {	1459	for (@REGISTRY, @models) {
721	my ($package, $model) = @$_;	1460	my ($package, $model) = @$_;
		1461	if (
		1462	eval "require $package"
722	if (${"$package\::VERSION"} > 0) {	1463	and ${"$package\::VERSION"} > 0
723	if (eval "require $model") {	1464	and eval "require $model"
		1465	) {
		1466	AnyEvent::log 7 => "Autoloaded model '$model', using it.";
724	$MODEL = $model;	1467	$MODEL = $model;
725	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
726	last;	1468	last;
727	}
728	}	1469	}
729	}	1470	}
730		1471
731	unless ($MODEL) {	1472	$MODEL
732	# try to load a model	1473	or AnyEvent::log fatal => "Backend autodetection failed - did you properly install AnyEvent?";
		1474	}
		1475	}
733		1476
734	for (@REGISTRY, @models) {	1477	# free memory only needed for probing
735	my ($package, $model) = @$_;	1478	undef @models;
736	if (eval "require $package"	1479	undef @REGISTRY;
737	and ${"$package\::VERSION"} > 0	1480
738	and eval "require $model") {	1481	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
739	$MODEL = $model;	1482
740	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1483	# now nuke some methods that are overridden by the backend.
		1484	# SUPER usage is not allowed in these.
		1485	for (qw(time signal child idle)) {
		1486	undef &{"AnyEvent::Base::$_"}
		1487	if defined &{"$MODEL\::$_"};
		1488	}
		1489
		1490	_isa_set;
		1491
		1492	# we're officially open!
		1493
		1494	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1495	require AnyEvent::Strict;
		1496	}
		1497
		1498	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1499	require AnyEvent::Debug;
		1500	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1501	}
		1502
		1503	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1504	require AnyEvent::Socket;
		1505	require AnyEvent::Debug;
		1506
		1507	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1508	$shell =~ s/\$\$/$$/g;
		1509
		1510	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1511	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1512	}
		1513
		1514	# now the anyevent environment is set up as the user told us to, so
		1515	# call the actual user code - post detects
		1516
		1517	(shift @post_detect)->() while @post_detect;
		1518	undef @post_detect;
		1519
		1520	*post_detect = sub(&) {
		1521	shift->();
		1522
		1523	undef
		1524	};
		1525
		1526	$MODEL
		1527	}
		1528
		1529	for my $name (@methods) {
		1530	*$name = sub {
		1531	detect;
		1532	# we use goto because
		1533	# a) it makes the thunk more transparent
		1534	# b) it allows us to delete the thunk later
		1535	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1536	};
		1537	}
		1538
		1539	# utility function to dup a filehandle. this is used by many backends
		1540	# to support binding more than one watcher per filehandle (they usually
		1541	# allow only one watcher per fd, so we dup it to get a different one).
		1542	sub _dupfh($$;$$) {
		1543	my ($poll, $fh, $r, $w) = @_;
		1544
		1545	# cygwin requires the fh mode to be matching, unix doesn't
		1546	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1547
		1548	open my $fh2, $mode, $fh
		1549	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1550
		1551	# we assume CLOEXEC is already set by perl in all important cases
		1552
		1553	($fh2, $rw)
		1554	}
		1555
		1556	=head1 SIMPLIFIED AE API
		1557
		1558	Starting with version 5.0, AnyEvent officially supports a second, much
		1559	simpler, API that is designed to reduce the calling, typing and memory
		1560	overhead by using function call syntax and a fixed number of parameters.
		1561
		1562	See the L<AE> manpage for details.
		1563
		1564	=cut
		1565
		1566	package AE;
		1567
		1568	our $VERSION = $AnyEvent::VERSION;
		1569
		1570	sub _reset() {
		1571	eval q{
		1572	# fall back to the main API by default - backends and AnyEvent::Base
		1573	# implementations can overwrite these.
		1574
		1575	sub io($$$) {
		1576	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1577	}
		1578
		1579	sub timer($$$) {
		1580	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1581	}
		1582
		1583	sub signal($$) {
		1584	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1585	}
		1586
		1587	sub child($$) {
		1588	AnyEvent->child (pid => $_[0], cb => $_[1])
		1589	}
		1590
		1591	sub idle($) {
		1592	AnyEvent->idle (cb => $_[0]);
		1593	}
		1594
		1595	sub cv(;&) {
		1596	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1597	}
		1598
		1599	sub now() {
		1600	AnyEvent->now
		1601	}
		1602
		1603	sub now_update() {
		1604	AnyEvent->now_update
		1605	}
		1606
		1607	sub time() {
		1608	AnyEvent->time
		1609	}
		1610
		1611	*postpone = \&AnyEvent::postpone;
		1612	*log = \&AnyEvent::log;
		1613	};
		1614	die if $@;
		1615	}
		1616
		1617	BEGIN { _reset }
		1618
		1619	package AnyEvent::Base;
		1620
		1621	# default implementations for many methods
		1622
		1623	sub time {
		1624	eval q{ # poor man's autoloading {}
		1625	# probe for availability of Time::HiRes
		1626	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1627	*time = sub { Time::HiRes::time () };
		1628	*AE::time = \& Time::HiRes::time ;
		1629	*now = \&time;
		1630	AnyEvent::log 8 => "using Time::HiRes for sub-second timing accuracy.";
		1631	# if (eval "use POSIX (); (POSIX::times())...
		1632	} else {
		1633	*time = sub { CORE::time };
		1634	*AE::time = sub (){ CORE::time };
		1635	*now = \&time;
		1636	AnyEvent::log 3 => "Using built-in time(), no sub-second resolution!";
		1637	}
		1638	};
		1639	die if $@;
		1640
		1641	&time
		1642	}
		1643
		1644	*now = \&time;
		1645	sub now_update { }
		1646
		1647	sub _poll {
		1648	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1649	}
		1650
		1651	# default implementation for ->condvar
		1652	# in fact, the default should not be overwritten
		1653
		1654	sub condvar {
		1655	eval q{ # poor man's autoloading {}
		1656	*condvar = sub {
		1657	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1658	};
		1659
		1660	*AE::cv = sub (;&) {
		1661	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1662	};
		1663	};
		1664	die if $@;
		1665
		1666	&condvar
		1667	}
		1668
		1669	# default implementation for ->signal
		1670
		1671	our $HAVE_ASYNC_INTERRUPT;
		1672
		1673	sub _have_async_interrupt() {
		1674	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1675	&& eval "use Async::Interrupt 1.02 (); 1")
		1676	unless defined $HAVE_ASYNC_INTERRUPT;
		1677
		1678	$HAVE_ASYNC_INTERRUPT
		1679	}
		1680
		1681	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1682	our (%SIG_ASY, %SIG_ASY_W);
		1683	our ($SIG_COUNT, $SIG_TW);
		1684
		1685	# install a dummy wakeup watcher to reduce signal catching latency
		1686	# used by Impls
		1687	sub _sig_add() {
		1688	unless ($SIG_COUNT++) {
		1689	# try to align timer on a full-second boundary, if possible
		1690	my $NOW = AE::now;
		1691
		1692	$SIG_TW = AE::timer
		1693	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1694	$MAX_SIGNAL_LATENCY,
		1695	sub { } # just for the PERL_ASYNC_CHECK
		1696	;
		1697	}
		1698	}
		1699
		1700	sub _sig_del {
		1701	undef $SIG_TW
		1702	unless --$SIG_COUNT;
		1703	}
		1704
		1705	our $_sig_name_init; $_sig_name_init = sub {
		1706	eval q{ # poor man's autoloading {}
		1707	undef $_sig_name_init;
		1708
		1709	if (_have_async_interrupt) {
		1710	*sig2num = \&Async::Interrupt::sig2num;
		1711	*sig2name = \&Async::Interrupt::sig2name;
		1712	} else {
		1713	require Config;
		1714
		1715	my %signame2num;
		1716	@signame2num{ split ' ', $Config::Config{sig_name} }
		1717	= split ' ', $Config::Config{sig_num};
		1718
		1719	my @signum2name;
		1720	@signum2name[values %signame2num] = keys %signame2num;
		1721
		1722	*sig2num = sub($) {
		1723	$_[0] > 0 ? shift : $signame2num{+shift}
		1724	};
		1725	*sig2name = sub ($) {
		1726	$_[0] > 0 ? $signum2name[+shift] : shift
		1727	};
		1728	}
		1729	};
		1730	die if $@;
		1731	};
		1732
		1733	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1734	sub sig2name($) { &$_sig_name_init; &sig2name }
		1735
		1736	sub signal {
		1737	eval q{ # poor man's autoloading {}
		1738	# probe for availability of Async::Interrupt
		1739	if (_have_async_interrupt) {
		1740	AnyEvent::log 8 => "Using Async::Interrupt for race-free signal handling.";
		1741
		1742	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1743	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1744
		1745	} else {
		1746	AnyEvent::log 8 => "Using emulated perl signal handling with latency timer.";
		1747
		1748	if (AnyEvent::WIN32) {
		1749	require AnyEvent::Util;
		1750
		1751	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1752	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1753	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1754	} else {
		1755	pipe $SIGPIPE_R, $SIGPIPE_W;
		1756	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1757	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1758
		1759	# not strictly required, as $^F is normally 2, but let's make sure...
		1760	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1761	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1762	}
		1763
		1764	$SIGPIPE_R
		1765	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1766
		1767	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1768	}
		1769
		1770	*signal = $HAVE_ASYNC_INTERRUPT
		1771	? sub {
		1772	my (undef, %arg) = @_;
		1773
		1774	# async::interrupt
		1775	my $signal = sig2num $arg{signal};
		1776	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1777
		1778	$SIG_ASY{$signal} ||= new Async::Interrupt
		1779	cb => sub { undef $SIG_EV{$signal} },
		1780	signal => $signal,
		1781	pipe => [$SIGPIPE_R->filenos],
		1782	pipe_autodrain => 0,
		1783	;
		1784
		1785	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1786	}
		1787	: sub {
		1788	my (undef, %arg) = @_;
		1789
		1790	# pure perl
		1791	my $signal = sig2name $arg{signal};
		1792	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1793
		1794	$SIG{$signal} ||= sub {
741	last;	1795	local $!;
		1796	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1797	undef $SIG_EV{$signal};
742	}	1798	};
		1799
		1800	# can't do signal processing without introducing races in pure perl,
		1801	# so limit the signal latency.
		1802	_sig_add;
		1803
		1804	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1805	}
		1806	;
		1807
		1808	*AnyEvent::Base::signal::DESTROY = sub {
		1809	my ($signal, $cb) = @{$_[0]};
		1810
		1811	_sig_del;
		1812
		1813	delete $SIG_CB{$signal}{$cb};
		1814
		1815	$HAVE_ASYNC_INTERRUPT
		1816	? delete $SIG_ASY{$signal}
		1817	: # delete doesn't work with older perls - they then
		1818	# print weird messages, or just unconditionally exit
		1819	# instead of getting the default action.
		1820	undef $SIG{$signal}
		1821	unless keys %{ $SIG_CB{$signal} };
		1822	};
		1823
		1824	*_signal_exec = sub {
		1825	$HAVE_ASYNC_INTERRUPT
		1826	? $SIGPIPE_R->drain
		1827	: sysread $SIGPIPE_R, (my $dummy), 9;
		1828
		1829	while (%SIG_EV) {
		1830	for (keys %SIG_EV) {
		1831	delete $SIG_EV{$_};
		1832	&$_ for values %{ $SIG_CB{$_} || {} };
743	}	1833	}
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	}	1834	}
748	}	1835	};
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	};	1836	};
		1837	die if $@;
799		1838
800	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1839	&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	}	1840	}
810		1841
811	# default implementation for ->child	1842	# default implementation for ->child
812		1843
813	our %PID_CB;	1844	our %PID_CB;
814	our $CHLD_W;	1845	our $CHLD_W;
815	our $CHLD_DELAY_W;	1846	our $CHLD_DELAY_W;
816	our $PID_IDLE;
817	our $WNOHANG;
818		1847
819	sub _child_wait {	1848	# used by many Impl's
820	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1849	sub _emit_childstatus($$) {
		1850	my (undef, $rpid, $rstatus) = @_;
		1851
		1852	$_->($rpid, $rstatus)
821	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1853	for values %{ $PID_CB{$rpid} || {} },
822	(values %{ $PID_CB{0} || {} });	1854	values %{ $PID_CB{0} || {} };
		1855	}
		1856
		1857	sub child {
		1858	eval q{ # poor man's autoloading {}
		1859	*_sigchld = sub {
		1860	my $pid;
		1861
		1862	AnyEvent->_emit_childstatus ($pid, $?)
		1863	while ($pid = waitpid -1, WNOHANG) > 0;
		1864	};
		1865
		1866	*child = sub {
		1867	my (undef, %arg) = @_;
		1868
		1869	my $pid = $arg{pid};
		1870	my $cb = $arg{cb};
		1871
		1872	$PID_CB{$pid}{$cb+0} = $cb;
		1873
		1874	unless ($CHLD_W) {
		1875	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1876	# child could be a zombie already, so make at least one round
		1877	&_sigchld;
		1878	}
		1879
		1880	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1881	};
		1882
		1883	*AnyEvent::Base::child::DESTROY = sub {
		1884	my ($pid, $icb) = @{$_[0]};
		1885
		1886	delete $PID_CB{$pid}{$icb};
		1887	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1888
		1889	undef $CHLD_W unless keys %PID_CB;
		1890	};
		1891	};
		1892	die if $@;
		1893
		1894	&child
		1895	}
		1896
		1897	# idle emulation is done by simply using a timer, regardless
		1898	# of whether the process is idle or not, and not letting
		1899	# the callback use more than 50% of the time.
		1900	sub idle {
		1901	eval q{ # poor man's autoloading {}
		1902	*idle = sub {
		1903	my (undef, %arg) = @_;
		1904
		1905	my ($cb, $w, $rcb) = $arg{cb};
		1906
		1907	$rcb = sub {
		1908	if ($cb) {
		1909	$w = AE::time;
		1910	&$cb;
		1911	$w = AE::time - $w;
		1912
		1913	# never use more then 50% of the time for the idle watcher,
		1914	# within some limits
		1915	$w = 0.0001 if $w < 0.0001;
		1916	$w = 5 if $w > 5;
		1917
		1918	$w = AE::timer $w, 0, $rcb;
		1919	} else {
		1920	# clean up...
		1921	undef $w;
		1922	undef $rcb;
		1923	}
		1924	};
		1925
		1926	$w = AE::timer 0.05, 0, $rcb;
		1927
		1928	bless \\$cb, "AnyEvent::Base::idle"
		1929	};
		1930
		1931	*AnyEvent::Base::idle::DESTROY = sub {
		1932	undef $${$_[0]};
		1933	};
		1934	};
		1935	die if $@;
		1936
		1937	&idle
		1938	}
		1939
		1940	package AnyEvent::CondVar;
		1941
		1942	our @ISA = AnyEvent::CondVar::Base::;
		1943
		1944	# only to be used for subclassing
		1945	sub new {
		1946	my $class = shift;
		1947	bless AnyEvent->condvar (@_), $class
		1948	}
		1949
		1950	package AnyEvent::CondVar::Base;
		1951
		1952	#use overload
		1953	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1954	# fallback => 1;
		1955
		1956	# save 300+ kilobytes by dirtily hardcoding overloading
		1957	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1958	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1959	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1960	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1961
		1962	our $WAITING;
		1963
		1964	sub _send {
		1965	# nop
		1966	}
		1967
		1968	sub _wait {
		1969	AnyEvent->_poll until $_[0]{_ae_sent};
		1970	}
		1971
		1972	sub send {
		1973	my $cv = shift;
		1974	$cv->{_ae_sent} = [@_];
		1975	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1976	$cv->_send;
		1977	}
		1978
		1979	sub croak {
		1980	$_[0]{_ae_croak} = $_[1];
		1981	$_[0]->send;
		1982	}
		1983
		1984	sub ready {
		1985	$_[0]{_ae_sent}
		1986	}
		1987
		1988	sub recv {
		1989	unless ($_[0]{_ae_sent}) {
		1990	$WAITING
		1991	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1992
		1993	local $WAITING = 1;
		1994	$_[0]->_wait;
823	}	1995	}
824		1996
825	undef $PID_IDLE;	1997	$_[0]{_ae_croak}
826	}	1998	and Carp::croak $_[0]{_ae_croak};
827		1999
828	sub _sigchld {	2000	wantarray
829	# make sure we deliver these changes "synchronous" with the event loop.	2001	? @{ $_[0]{_ae_sent} }
830	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	2002	: $_[0]{_ae_sent}[0]
831	undef $CHLD_DELAY_W;
832	&_child_wait;
833	});
834	}	2003	}
835		2004
836	sub child {	2005	sub cb {
837	my (undef, %arg) = @_;	2006	my $cv = shift;
838		2007
839	defined (my $pid = $arg{pid} + 0)	2008	@_
840	or Carp::croak "required option 'pid' is missing";	2009	and $cv->{_ae_cb} = shift
		2010	and $cv->{_ae_sent}
		2011	and (delete $cv->{_ae_cb})->($cv);
841		2012
842	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	2013	$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	}	2014	}
856		2015
857	sub AnyEvent::Base::Child::DESTROY {	2016	sub begin {
858	my ($pid, $cb) = @{$_[0]};	2017	++$_[0]{_ae_counter};
859		2018	$_[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	}	2019	}
		2020
		2021	sub end {
		2022	return if --$_[0]{_ae_counter};
		2023	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		2024	}
		2025
		2026	# undocumented/compatibility with pre-3.4
		2027	*broadcast = \&send;
		2028	*wait = \&recv;
		2029
		2030	=head1 ERROR AND EXCEPTION HANDLING
		2031
		2032	In general, AnyEvent does not do any error handling - it relies on the
		2033	caller to do that if required. The L<AnyEvent::Strict> module (see also
		2034	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		2035	checking of all AnyEvent methods, however, which is highly useful during
		2036	development.
		2037
		2038	As for exception handling (i.e. runtime errors and exceptions thrown while
		2039	executing a callback), this is not only highly event-loop specific, but
		2040	also not in any way wrapped by this module, as this is the job of the main
		2041	program.
		2042
		2043	The pure perl event loop simply re-throws the exception (usually
		2044	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		2045	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		2046	so on.
		2047
		2048	=head1 ENVIRONMENT VARIABLES
		2049
		2050	AnyEvent supports a number of environment variables that tune the
		2051	runtime behaviour. They are usually evaluated when AnyEvent is
		2052	loaded, initialised, or a submodule that uses them is loaded. Many of
		2053	them also cause AnyEvent to load additional modules - for example,
		2054	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2055	loaded.
		2056
		2057	All the environment variables documented here start with
		2058	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2059	namespace. Other modules are encouraged (but by no means required) to use
		2060	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2061	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2062	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2063	variables starting with C<AE_>, see below).
		2064
		2065	All variables can also be set via the C<AE_> prefix, that is, instead
		2066	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2067	case there is a clash btween anyevent and another program that uses
		2068	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2069	variable to the empty string, as those variables take precedence.
		2070
		2071	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2072	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2073	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2074	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2075	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2076	is set).
		2077
		2078	The exact algorithm is currently:
		2079
		2080	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2081	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2082	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2083
		2084	This ensures that child processes will not see the C<AE_> variables.
		2085
		2086	The following environment variables are currently known to AnyEvent:
		2087
		2088	=over 4
		2089
		2090	=item C<PERL_ANYEVENT_VERBOSE>
		2091
		2092	By default, AnyEvent will log messages with loglevel C<4> (C<error>) or
		2093	higher (see L<AnyEvent::Log>). You can set this environment variable to a
		2094	numerical loglevel to make AnyEvent more (or less) talkative.
		2095
		2096	If you want to do more than just set the global logging level
		2097	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2098	complex specifications.
		2099
		2100	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2101	everything else at defaults.
		2102
		2103	When set to C<5> or higher (C<warn>), AnyEvent warns about unexpected
		2104	conditions, such as not being able to load the event model specified by
		2105	C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an exception - this
		2106	is the minimum recommended level for use during development.
		2107
		2108	When set to C<7> or higher (info), AnyEvent reports which event model it
		2109	chooses.
		2110
		2111	When set to C<8> or higher (debug), then AnyEvent will report extra
		2112	information on which optional modules it loads and how it implements
		2113	certain features.
		2114
		2115	=item C<PERL_ANYEVENT_LOG>
		2116
		2117	Accepts rather complex logging specifications. For example, you could log
		2118	all C<debug> messages of some module to stderr, warnings and above to
		2119	stderr, and errors and above to syslog, with:
		2120
		2121	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2122
		2123	For the rather extensive details, see L<AnyEvent::Log>.
		2124
		2125	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2126	so will take effect even before AnyEvent has initialised itself.
		2127
		2128	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2129	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2130	using the latter saves a few hundred kB of memory unless a module
		2131	explicitly needs the extra features of AnyEvent::Log.
		2132
		2133	=item C<PERL_ANYEVENT_STRICT>
		2134
		2135	AnyEvent does not do much argument checking by default, as thorough
		2136	argument checking is very costly. Setting this variable to a true value
		2137	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2138	check the arguments passed to most method calls. If it finds any problems,
		2139	it will croak.
		2140
		2141	In other words, enables "strict" mode.
		2142
		2143	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2144	>>, it is definitely recommended to keep it off in production. Keeping
		2145	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2146	can be very useful, however.
		2147
		2148	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2149
		2150	If this env variable is nonempty, then its contents will be interpreted by
		2151	C<AnyEvent::Socket::parse_hostport> and C<AnyEvent::Debug::shell> (after
		2152	replacing every occurance of C<$$> by the process pid). The shell object
		2153	is saved in C<$AnyEvent::Debug::SHELL>.
		2154
		2155	This happens when the first watcher is created.
		2156
		2157	For example, to bind a debug shell on a unix domain socket in
		2158	F<< /tmp/debug<pid>.sock >>, you could use this:
		2159
		2160	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2161	# connect with e.g.: socat readline /tmp/debug123.sock
		2162
		2163	Or to bind to tcp port 4545 on localhost:
		2164
		2165	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		2166	# connect with e.g.: telnet localhost 4545
		2167
		2168	Note that creating sockets in F</tmp> or on localhost is very unsafe on
		2169	multiuser systems.
		2170
		2171	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2172
		2173	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2174	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2175
		2176	=item C<PERL_ANYEVENT_MODEL>
		2177
		2178	This can be used to specify the event model to be used by AnyEvent, before
		2179	auto detection and -probing kicks in.
		2180
		2181	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2182	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2183	resulting module name is loaded and - if the load was successful - used as
		2184	event model backend. If it fails to load then AnyEvent will proceed with
		2185	auto detection and -probing.
		2186
		2187	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2188	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2189	the end of a string designates a module name and quotes it appropriately).
		2190
		2191	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2192	could start your program like this:
		2193
		2194	PERL_ANYEVENT_MODEL=Perl perl ...
		2195
		2196	=item C<PERL_ANYEVENT_IO_MODEL>
		2197
		2198	The current file I/O model - see L<AnyEvent::IO> for more info.
		2199
		2200	At the moment, only C<Perl> (small, pure-perl, synchronous) and
		2201	C<IOAIO> (truly asynchronous) are supported. The default is C<IOAIO> if
		2202	L<AnyEvent::AIO> can be loaded, otherwise it is C<Perl>.
		2203
		2204	=item C<PERL_ANYEVENT_PROTOCOLS>
		2205
		2206	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2207	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2208	of auto probing).
		2209
		2210	Must be set to a comma-separated list of protocols or address families,
		2211	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2212	used, and preference will be given to protocols mentioned earlier in the
		2213	list.
		2214
		2215	This variable can effectively be used for denial-of-service attacks
		2216	against local programs (e.g. when setuid), although the impact is likely
		2217	small, as the program has to handle connection and other failures anyways.
		2218
		2219	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2220	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2221	- only support IPv4, never try to resolve or contact IPv6
		2222	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2223	IPv6, but prefer IPv6 over IPv4.
		2224
		2225	=item C<PERL_ANYEVENT_HOSTS>
		2226
		2227	This variable, if specified, overrides the F</etc/hosts> file used by
		2228	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2229	from that file instead.
		2230
		2231	=item C<PERL_ANYEVENT_EDNS0>
		2232
		2233	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2234	DNS. This extension is generally useful to reduce DNS traffic, especially
		2235	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2236	packets, which is why it is off by default.
		2237
		2238	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2239	EDNS0 in its DNS requests.
		2240
		2241	=item C<PERL_ANYEVENT_MAX_FORKS>
		2242
		2243	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2244	will create in parallel.
		2245
		2246	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2247
		2248	The default value for the C<max_outstanding> parameter for the default DNS
		2249	resolver - this is the maximum number of parallel DNS requests that are
		2250	sent to the DNS server.
		2251
		2252	=item C<PERL_ANYEVENT_MAX_SIGNAL_LATENCY>
		2253
		2254	Perl has inherently racy signal handling (you can basically choose between
		2255	losing signals and memory corruption) - pure perl event loops (including
		2256	C<AnyEvent::Loop>, when C<Async::Interrupt> isn't available) therefore
		2257	have to poll regularly to avoid losing signals.
		2258
		2259	Some event loops are racy, but don't poll regularly, and some event loops
		2260	are written in C but are still racy. For those event loops, AnyEvent
		2261	installs a timer that regularly wakes up the event loop.
		2262
		2263	By default, the interval for this timer is C<10> seconds, but you can
		2264	override this delay with this environment variable (or by setting
		2265	the C<$AnyEvent::MAX_SIGNAL_LATENCY> variable before creating signal
		2266	watchers).
		2267
		2268	Lower values increase CPU (and energy) usage, higher values can introduce
		2269	long delays when reaping children or waiting for signals.
		2270
		2271	The L<AnyEvent::Async> module, if available, will be used to avoid this
		2272	polling (with most event loops).
		2273
		2274	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2275
		2276	The absolute path to a F<resolv.conf>-style file to use instead of
		2277	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2278	resolver, or the empty string to select the default configuration.
		2279
		2280	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2281
		2282	When neither C<ca_file> nor C<ca_path> was specified during
		2283	L<AnyEvent::TLS> context creation, and either of these environment
		2284	variables are nonempty, they will be used to specify CA certificate
		2285	locations instead of a system-dependent default.
		2286
		2287	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2288
		2289	When these are set to C<1>, then the respective modules are not
		2290	loaded. Mostly good for testing AnyEvent itself.
		2291
		2292	=back
865		2293
866	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2294	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
867		2295
868	This is an advanced topic that you do not normally need to use AnyEvent in	2296	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	2297	a module. This section is only of use to event loop authors who want to
…		…
903		2331
904	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2332	I<rxvt-unicode> also cheats a bit by not providing blocking access to
905	condition variables: code blocking while waiting for a condition will	2333	condition variables: code blocking while waiting for a condition will
906	C<die>. This still works with most modules/usages, and blocking calls must	2334	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.	2335	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		2336
946	=head1 EXAMPLE PROGRAM	2337	=head1 EXAMPLE PROGRAM
947		2338
948	The following program uses an I/O watcher to read data from STDIN, a timer	2339	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	2340	to display a message once per second, and a condition variable to quit the
…		…
958	poll => 'r',	2349	poll => 'r',
959	cb => sub {	2350	cb => sub {
960	warn "io event <$_[0]>\n"; # will always output <r>	2351	warn "io event <$_[0]>\n"; # will always output <r>
961	chomp (my $input = <STDIN>); # read a line	2352	chomp (my $input = <STDIN>); # read a line
962	warn "read: $input\n"; # output what has been read	2353	warn "read: $input\n"; # output what has been read
963	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2354	$cv->send if $input =~ /^q/i; # quit program if /^q/i
964	},	2355	},
965	);	2356	);
966		2357
967	my $time_watcher; # can only be used once
968
969	sub new_timer {
970	$timer = AnyEvent->timer (after => 1, cb => sub {	2358	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
971	warn "timeout\n"; # print 'timeout' about every second	2359	warn "timeout\n"; # print 'timeout' at most every second
972	&new_timer; # and restart the time
973	});	2360	});
974	}
975		2361
976	new_timer; # create first timer
977
978	$cv->wait; # wait until user enters /^q/i	2362	$cv->recv; # wait until user enters /^q/i
979		2363
980	=head1 REAL-WORLD EXAMPLE	2364	=head1 REAL-WORLD EXAMPLE
981		2365
982	Consider the L<Net::FCP> module. It features (among others) the following	2366	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:	2367	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1033	syswrite $txn->{fh}, $txn->{request}	2417	syswrite $txn->{fh}, $txn->{request}
1034	or die "connection or write error";	2418	or die "connection or write error";
1035	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2419	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1036		2420
1037	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2421	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:	2422	result and signals any possible waiters that the request has finished:
1039		2423
1040	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2424	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1041		2425
1042	if (end-of-file or data complete) {	2426	if (end-of-file or data complete) {
1043	$txn->{result} = $txn->{buf};	2427	$txn->{result} = $txn->{buf};
1044	$txn->{finished}->broadcast;	2428	$txn->{finished}->send;
1045	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2429	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1046	}	2430	}
1047		2431
1048	The C<result> method, finally, just waits for the finished signal (if the	2432	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	2433	request was already finished, it doesn't wait, of course, and returns the
1050	data:	2434	data:
1051		2435
1052	$txn->{finished}->wait;	2436	$txn->{finished}->recv;
1053	return $txn->{result};	2437	return $txn->{result};
1054		2438
1055	The actual code goes further and collects all errors (C<die>s, exceptions)	2439	The actual code goes further and collects all errors (C<die>s, exceptions)
1056	that occured during request processing. The C<result> method detects	2440	that occurred during request processing. The C<result> method detects
1057	whether an exception as thrown (it is stored inside the $txn object)	2441	whether an exception as thrown (it is stored inside the $txn object)
1058	and just throws the exception, which means connection errors and other	2442	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	2443	problems get reported to the code that tries to use the result, not in a
1060	random callback.	2444	random callback.
1061		2445
1062	All of this enables the following usage styles:	2446	All of this enables the following usage styles:
1063		2447
1064	1. Blocking:	2448	1. Blocking:
…		…
1092		2476
1093	my $quit = AnyEvent->condvar;	2477	my $quit = AnyEvent->condvar;
1094		2478
1095	$fcp->txn_client_get ($url)->cb (sub {	2479	$fcp->txn_client_get ($url)->cb (sub {
1096	...	2480	...
1097	$quit->broadcast;	2481	$quit->send;
1098	});	2482	});
1099		2483
1100	$quit->wait;	2484	$quit->recv;
1101		2485
1102		2486
1103	=head1 BENCHMARKS	2487	=head1 BENCHMARKS
1104		2488
1105	To give you an idea of the performance and overheads that AnyEvent adds	2489	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1107	of various event loops I prepared some benchmarks.	2491	of various event loops I prepared some benchmarks.
1108		2492
1109	=head2 BENCHMARKING ANYEVENT OVERHEAD	2493	=head2 BENCHMARKING ANYEVENT OVERHEAD
1110		2494
1111	Here is a benchmark of various supported event models used natively and	2495	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	2496	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,	2497	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.	2498	which it is), lets them fire exactly once and destroys them again.
1115		2499
1116	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2500	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1117	distribution.	2501	distribution. It uses the L<AE> interface, which makes a real difference
		2502	for the EV and Perl backends only.
1118		2503
1119	=head3 Explanation of the columns	2504	=head3 Explanation of the columns
1120		2505
1121	I<watcher> is the number of event watchers created/destroyed. Since	2506	I<watcher> is the number of event watchers created/destroyed. Since
1122	different event models feature vastly different performances, each event	2507	different event models feature vastly different performances, each event
…		…
1134	all watchers, to avoid adding memory overhead. That means closure creation	2519	all watchers, to avoid adding memory overhead. That means closure creation
1135	and memory usage is not included in the figures.	2520	and memory usage is not included in the figures.
1136		2521
1137	I<invoke> is the time, in microseconds, used to invoke a simple	2522	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	2523	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	2524	invoked "watcher" times, it would C<< ->send >> a condvar once to
1140	signal the end of this phase.	2525	signal the end of this phase.
1141		2526
1142	I<destroy> is the time, in microseconds, that it takes to destroy a single	2527	I<destroy> is the time, in microseconds, that it takes to destroy a single
1143	watcher.	2528	watcher.
1144		2529
1145	=head3 Results	2530	=head3 Results
1146		2531
1147	name watchers bytes create invoke destroy comment	2532	name watchers bytes create invoke destroy comment
1148	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2533	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	2534	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	2535	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	2536	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	2537	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	2538	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2539	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2540	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	2541	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	2542	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	2543	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	2544	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1158		2545
1159	=head3 Discussion	2546	=head3 Discussion
1160		2547
1161	The benchmark does I<not> measure scalability of the event loop very	2548	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)	2549	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	2561	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	2562	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1176	cycles with POE.	2563	cycles with POE.
1177		2564
1178	C<EV> is the sole leader regarding speed and memory use, which are both	2565	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	2566	maximal/minimal, respectively. When using the L<AE> API there is zero
		2567	overhead (when going through the AnyEvent API create is about 5-6 times
		2568	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	2569	any other event loop and is still faster than Event natively).
1181	natively.
1182		2570
1183	The pure perl implementation is hit in a few sweet spots (both the	2571	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	2572	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	2573	interpreter and the backend itself). Nevertheless this shows that it
1186	adds very little overhead in itself. Like any select-based backend its	2574	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	2575	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.	2576	them active), of course, but this was not subject of this benchmark.
1189		2577
1190	The C<Event> module has a relatively high setup and callback invocation	2578	The C<Event> module has a relatively high setup and callback invocation
1191	cost, but overall scores in on the third place.	2579	cost, but overall scores in on the third place.
		2580
		2581	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2582	when using its pure perl backend.
1192		2583
1193	C<Glib>'s memory usage is quite a bit higher, but it features a	2584	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	2585	faster callback invocation and overall ends up in the same class as
1195	C<Event>. However, Glib scales extremely badly, doubling the number of	2586	C<Event>. However, Glib scales extremely badly, doubling the number of
1196	watchers increases the processing time by more than a factor of four,	2587	watchers increases the processing time by more than a factor of four,
…		…
1231	(even when used without AnyEvent), but most event loops have acceptable	2622	(even when used without AnyEvent), but most event loops have acceptable
1232	performance with or without AnyEvent.	2623	performance with or without AnyEvent.
1233		2624
1234	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	2625	=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	2626	the actual event loop, only with extremely fast event loops such as EV
1236	adds AnyEvent significant overhead.	2627	does AnyEvent add significant overhead.
1237		2628
1238	=item * You should avoid POE like the plague if you want performance or	2629	=item * You should avoid POE like the plague if you want performance or
1239	reasonable memory usage.	2630	reasonable memory usage.
1240		2631
1241	=back	2632	=back
1242		2633
1243	=head2 BENCHMARKING THE LARGE SERVER CASE	2634	=head2 BENCHMARKING THE LARGE SERVER CASE
1244		2635
1245	This benchmark atcually benchmarks the event loop itself. It works by	2636	This benchmark actually benchmarks the event loop itself. It works by
1246	creating a number of "servers": each server consists of a socketpair, a	2637	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	2638	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	2639	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".	2640	watcher reads a byte it will write that byte to a random other "server".
1250		2641
1251	The effect is that there will be a lot of I/O watchers, only part of which	2642	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	2643	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	2644	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	2645	timeout is reset each time something is read because that reflects how
1255	most timeouts work (and puts extra pressure on the event loops).	2646	most timeouts work (and puts extra pressure on the event loops).
1256		2647
1257	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2648	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	2649	(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.	2650	connections, most of which are idle at any one point in time.
1260		2651
1261	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2652	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1262	distribution.	2653	distribution. It uses the L<AE> interface, which makes a real difference
		2654	for the EV and Perl backends only.
1263		2655
1264	=head3 Explanation of the columns	2656	=head3 Explanation of the columns
1265		2657
1266	I<sockets> is the number of sockets, and twice the number of "servers" (as	2658	I<sockets> is the number of sockets, and twice the number of "servers" (as
1267	each server has a read and write socket end).	2659	each server has a read and write socket end).
1268		2660
1269	I<create> is the time it takes to create a socketpair (which is	2661	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.	2662	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1271		2663
1272	I<request>, the most important value, is the time it takes to handle a	2664	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	2665	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	2666	it to another server. This includes deleting the old timeout and creating
1275	a new one that moves the timeout into the future.	2667	a new one that moves the timeout into the future.
1276		2668
1277	=head3 Results	2669	=head3 Results
1278		2670
1279	name sockets create request	2671	name sockets create request
1280	EV 20000 69.01 11.16	2672	EV 20000 62.66 7.99
1281	Perl 20000 73.32 35.87	2673	Perl 20000 68.32 32.64
1282	Event 20000 212.62 257.32	2674	IOAsync 20000 174.06 101.15 epoll
1283	Glib 20000 651.16 1896.30	2675	IOAsync 20000 174.67 610.84 poll
		2676	Event 20000 202.69 242.91
		2677	Glib 20000 557.01 1689.52
1284	POE 20000 349.67 12317.24 uses POE::Loop::Event	2678	POE 20000 341.54 12086.32 uses POE::Loop::Event
1285		2679
1286	=head3 Discussion	2680	=head3 Discussion
1287		2681
1288	This benchmark I<does> measure scalability and overall performance of the	2682	This benchmark I<does> measure scalability and overall performance of the
1289	particular event loop.	2683	particular event loop.
…		…
1291	EV is again fastest. Since it is using epoll on my system, the setup time	2685	EV is again fastest. Since it is using epoll on my system, the setup time
1292	is relatively high, though.	2686	is relatively high, though.
1293		2687
1294	Perl surprisingly comes second. It is much faster than the C-based event	2688	Perl surprisingly comes second. It is much faster than the C-based event
1295	loops Event and Glib.	2689	loops Event and Glib.
		2690
		2691	IO::Async performs very well when using its epoll backend, and still quite
		2692	good compared to Glib when using its pure perl backend.
1296		2693
1297	Event suffers from high setup time as well (look at its code and you will	2694	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	2695	understand why). Callback invocation also has a high overhead compared to
1299	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2696	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1300	uses select or poll in basically all documented configurations.	2697	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	2744	speed most when you have lots of watchers, not when you only have a few of
1348	them).	2745	them).
1349		2746
1350	EV is again fastest.	2747	EV is again fastest.
1351		2748
1352	Perl again comes second. It is noticably faster than the C-based event	2749	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	2750	loops Event and Glib, although the difference is too small to really
1354	matter.	2751	matter.
1355		2752
1356	POE also performs much better in this case, but is is still far behind the	2753	POE also performs much better in this case, but is is still far behind the
1357	others.	2754	others.
…		…
1363	=item * C-based event loops perform very well with small number of	2760	=item * C-based event loops perform very well with small number of
1364	watchers, as the management overhead dominates.	2761	watchers, as the management overhead dominates.
1365		2762
1366	=back	2763	=back
1367		2764
		2765	=head2 THE IO::Lambda BENCHMARK
		2766
		2767	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2768	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2769	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2770	shouldn't come as a surprise to anybody). As such, the benchmark is
		2771	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2772	very optimal. But how would AnyEvent compare when used without the extra
		2773	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2774
		2775	The benchmark itself creates an echo-server, and then, for 500 times,
		2776	connects to the echo server, sends a line, waits for the reply, and then
		2777	creates the next connection. This is a rather bad benchmark, as it doesn't
		2778	test the efficiency of the framework or much non-blocking I/O, but it is a
		2779	benchmark nevertheless.
		2780
		2781	name runtime
		2782	Lambda/select 0.330 sec
		2783	+ optimized 0.122 sec
		2784	Lambda/AnyEvent 0.327 sec
		2785	+ optimized 0.138 sec
		2786	Raw sockets/select 0.077 sec
		2787	POE/select, components 0.662 sec
		2788	POE/select, raw sockets 0.226 sec
		2789	POE/select, optimized 0.404 sec
		2790
		2791	AnyEvent/select/nb 0.085 sec
		2792	AnyEvent/EV/nb 0.068 sec
		2793	+state machine 0.134 sec
		2794
		2795	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2796	benchmarks actually make blocking connects and use 100% blocking I/O,
		2797	defeating the purpose of an event-based solution. All of the newly
		2798	written AnyEvent benchmarks use 100% non-blocking connects (using
		2799	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2800	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2801	generally require a lot more bookkeeping and event handling than blocking
		2802	connects (which involve a single syscall only).
		2803
		2804	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2805	offers similar expressive power as POE and IO::Lambda, using conventional
		2806	Perl syntax. This means that both the echo server and the client are 100%
		2807	non-blocking, further placing it at a disadvantage.
		2808
		2809	As you can see, the AnyEvent + EV combination even beats the
		2810	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2811	backend easily beats IO::Lambda and POE.
		2812
		2813	And even the 100% non-blocking version written using the high-level (and
		2814	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2815	higher level ("unoptimised") abstractions by a large margin, even though
		2816	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2817
		2818	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2819	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2820	part of the IO::Lambda distribution and were used without any changes.
		2821
		2822
		2823	=head1 SIGNALS
		2824
		2825	AnyEvent currently installs handlers for these signals:
		2826
		2827	=over 4
		2828
		2829	=item SIGCHLD
		2830
		2831	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2832	emulation for event loops that do not support them natively. Also, some
		2833	event loops install a similar handler.
		2834
		2835	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2836	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2837
		2838	=item SIGPIPE
		2839
		2840	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2841	when AnyEvent gets loaded.
		2842
		2843	The rationale for this is that AnyEvent users usually do not really depend
		2844	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2845	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2846	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2847	some random socket.
		2848
		2849	The rationale for installing a no-op handler as opposed to ignoring it is
		2850	that this way, the handler will be restored to defaults on exec.
		2851
		2852	Feel free to install your own handler, or reset it to defaults.
		2853
		2854	=back
		2855
		2856	=cut
		2857
		2858	undef $SIG{CHLD}
		2859	if $SIG{CHLD} eq 'IGNORE';
		2860
		2861	$SIG{PIPE} = sub { }
		2862	unless defined $SIG{PIPE};
		2863
		2864	=head1 RECOMMENDED/OPTIONAL MODULES
		2865
		2866	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2867	its built-in modules) are required to use it.
		2868
		2869	That does not mean that AnyEvent won't take advantage of some additional
		2870	modules if they are installed.
		2871
		2872	This section explains which additional modules will be used, and how they
		2873	affect AnyEvent's operation.
		2874
		2875	=over 4
		2876
		2877	=item L<Async::Interrupt>
		2878
		2879	This slightly arcane module is used to implement fast signal handling: To
		2880	my knowledge, there is no way to do completely race-free and quick
		2881	signal handling in pure perl. To ensure that signals still get
		2882	delivered, AnyEvent will start an interval timer to wake up perl (and
		2883	catch the signals) with some delay (default is 10 seconds, look for
		2884	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2885
		2886	If this module is available, then it will be used to implement signal
		2887	catching, which means that signals will not be delayed, and the event loop
		2888	will not be interrupted regularly, which is more efficient (and good for
		2889	battery life on laptops).
		2890
		2891	This affects not just the pure-perl event loop, but also other event loops
		2892	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2893
		2894	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2895	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2896	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2897	does nothing for those backends.
		2898
		2899	=item L<EV>
		2900
		2901	This module isn't really "optional", as it is simply one of the backend
		2902	event loops that AnyEvent can use. However, it is simply the best event
		2903	loop available in terms of features, speed and stability: It supports
		2904	the AnyEvent API optimally, implements all the watcher types in XS, does
		2905	automatic timer adjustments even when no monotonic clock is available,
		2906	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2907	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2908	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2909
		2910	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2911	then this module will do nothing for you.
		2912
		2913	=item L<Guard>
		2914
		2915	The guard module, when used, will be used to implement
		2916	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2917	lot less memory), but otherwise doesn't affect guard operation much. It is
		2918	purely used for performance.
		2919
		2920	=item L<JSON> and L<JSON::XS>
		2921
		2922	One of these modules is required when you want to read or write JSON data
		2923	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2924	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2925
		2926	=item L<Net::SSLeay>
		2927
		2928	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2929	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2930	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2931
		2932	=item L<Time::HiRes>
		2933
		2934	This module is part of perl since release 5.008. It will be used when the
		2935	chosen event library does not come with a timing source of its own. The
		2936	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2937	try to use a monotonic clock for timing stability.
		2938
		2939	=item L<AnyEvent::AIO> (and L<IO::AIO>)
		2940
		2941	The default implementation of L<AnyEvent::IO> is to do I/O synchronously,
		2942	stopping programs while they access the disk, which is fine for a lot of
		2943	programs.
		2944
		2945	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it switch to
		2946	a true asynchronous implementation, so event processing can continue even
		2947	while waiting for disk I/O.
		2948
		2949	=back
		2950
1368		2951
1369	=head1 FORK	2952	=head1 FORK
1370		2953
1371	Most event libraries are not fork-safe. The ones who are usually are	2954	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>	2955	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1373	calls. Only L<EV> is fully fork-aware.	2956	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2957	are usually badly thought-out hacks that are incompatible with fork in
		2958	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2959	continue event-processing in both parent and child (or both, if you know
		2960	what you are doing).
		2961
		2962	This means that, in general, you cannot fork and do event processing in
		2963	the child if the event library was initialised before the fork (which
		2964	usually happens when the first AnyEvent watcher is created, or the library
		2965	is loaded).
1374		2966
1375	If you have to fork, you must either do so I<before> creating your first	2967	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.	2968	watcher OR you must not use AnyEvent at all in the child OR you must do
		2969	something completely out of the scope of AnyEvent (see below).
		2970
		2971	The problem of doing event processing in the parent I<and> the child
		2972	is much more complicated: even for backends that I<are> fork-aware or
		2973	fork-safe, their behaviour is not usually what you want: fork clones all
		2974	watchers, that means all timers, I/O watchers etc. are active in both
		2975	parent and child, which is almost never what you want. Using C<exec>
		2976	to start worker children from some kind of manage prrocess is usually
		2977	preferred, because it is much easier and cleaner, at the expense of having
		2978	to have another binary.
		2979
		2980	In addition to logical problems with fork, there are also implementation
		2981	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2982	code if a thread (I am talking of pthreads here) was ever created in the
		2983	process, and this is just the tip of the iceberg. In general, using fork
		2984	from Perl is difficult, and attempting to use fork without an exec to
		2985	implement some kind of parallel processing is almost certainly doomed.
		2986
		2987	To safely fork and exec, you should use a module such as
		2988	L<Proc::FastSpawn> that let's you safely fork and exec new processes.
		2989
		2990	If you want to do multiprocessing using processes, you can
		2991	look at the L<AnyEvent::Fork> module (and some related modules
		2992	such as L<AnyEvent::Fork::RPC>, L<AnyEvent::Fork::Pool> and
		2993	L<AnyEvent::Fork::Remote>). This module allows you to safely create
		2994	subprocesses without any limitations - you can use X11 toolkits or
		2995	AnyEvent in the children created by L<AnyEvent::Fork> safely and without
		2996	any special precautions.
1377		2997
1378		2998
1379	=head1 SECURITY CONSIDERATIONS	2999	=head1 SECURITY CONSIDERATIONS
1380		3000
1381	AnyEvent can be forced to load any event model via	3001	AnyEvent can be forced to load any event model via
…		…
1386	specified in the variable.	3006	specified in the variable.
1387		3007
1388	You can make AnyEvent completely ignore this variable by deleting it	3008	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:	3009	before the first watcher gets created, e.g. with a C<BEGIN> block:
1390		3010
1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	3011	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1392		3012
1393	use AnyEvent;	3013	use AnyEvent;
		3014
		3015	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		3016	be used to probe what backend is used and gain other information (which is
		3017	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		3018	$ENV{PERL_ANYEVENT_STRICT}.
		3019
		3020	Note that AnyEvent will remove I<all> environment variables starting with
		3021	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		3022	enabled.
		3023
		3024
		3025	=head1 BUGS
		3026
		3027	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		3028	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		3029	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		3030	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		3031	pronounced).
1394		3032
1395		3033
1396	=head1 SEE ALSO	3034	=head1 SEE ALSO
1397		3035
1398	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	3036	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		3037
1402	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	3038	FAQ: L<AnyEvent::FAQ>.
		3039
		3040	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		3041	(simply logging).
		3042
		3043	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		3044	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		3045
		3046	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		3047	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		3048	L<Qt>, L<POE>, L<FLTK>.
		3049
		3050	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		3051	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		3052	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1403	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	3053	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>,	3054	L<AnyEvent::Impl::FLTK>.
1405	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1406		3055
		3056	Non-blocking handles, pipes, stream sockets, TCP clients and
		3057	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		3058
		3059	Asynchronous File I/O: L<AnyEvent::IO>.
		3060
		3061	Asynchronous DNS: L<AnyEvent::DNS>.
		3062
		3063	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		3064
1407	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	3065	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		3066	L<AnyEvent::HTTP>.
1408		3067
1409		3068
1410	=head1 AUTHOR	3069	=head1 AUTHOR
1411		3070
1412	Marc Lehmann <schmorp@schmorp.de>	3071	Marc Lehmann <schmorp@schmorp.de>
1413	http://home.schmorp.de/	3072	http://anyevent.schmorp.de
1414		3073
1415	=cut	3074	=cut
1416		3075
1417	1	3076	1
1418		3077

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